FACULTY PUBLICATIONS

In this paper, we present emission line strengths, abundances, and element ratios (X/O for Ne, S, Cl, and Ar) for a sample of 38 Galactic disk planetary nebulae (PNe) consisting primarily of Peimbert classification Type I. Spectrophotometry for these PNe incorporates an extended optical/near-IR range of λλ3600–9600 Å including the [SIII] lines at 9069 Å and 9532 Å, setting this relatively large sample apart from typical spectral coverage. We have utilized Emission Line Spectrum Analyzer, a five-level atom abundance routine, to determine Te , Ne , ionization correction factors, and total element abundances, thereby continuing our work toward a uniformly processed set of data. With a compilation of data from >120 Milky Way PNe, we present results from our most recent analysis of abundance patterns in Galactic disk PNe. With a wide range of metallicities, galactocentric distances, and both Type I and non-Type I objects, we have examined the alpha elements against H II regions and blue compact galaxies (H2BCGs) to discern signatures of depletion or enhancement in PNe progenitor stars, particularly the destruction or production of O and Ne. We present evidence that many PNe have higher Ne/O and lower Ar/Ne ratios compared to H2BCGs within the range of 8.5–9.0 for 12 + log(O/H). This suggests that Ne is being synthesized in the low- and intermediate-mass progenitors. Sulfur abundances in PNe continue to show great scatter and are systematically lower than those found in H2BCG at a given metallicity. Although we find that PNe do show some distinction in alpha elements when compared to H2BCG, within the Peimbert classification types studied, PNe do not show significant differences in alpha elements amongst themselves, at least to an extent that would distinguish in situ nucleosynthesis from the observed dispersion in abundance ratios.

We discuss results stemming from observations of the white-light and [Fe XIV] emission corona during the total eclipse of the Sun of 2008 August 1, in Mongolia (Altaj region) and in Russia (Akademgorodok, Novosibirsk, Siberia). Corresponding to the current extreme solar minimum, the white-light corona, visible up to 20 solar radii, was of a transient type with well-pronounced helmet streamers situated above a chain of prominences at position angles 48°, 130°, 241° and 322°. A variety of coronal holes, filled with a number of thin polar plumes, were seen around the poles. Furthering an original method of image processing, stars up to 12 magnitude, a Kreutz-group comet (C/2008 O1), and a coronal mass ejection (CME) were also detected, with the smallest resolvable structures being of, and at some places even less than, 1 arcsec. Differences, presumably motions, in the corona and prominences are seen even with the 19-min time difference between our sites. In addition to the high-resolution coronal images, which show the continuum corona (K-corona) that results from electron scattering of photospheric light, images of the overlapping green-emission-line (530.3 nm, [Fe XIV]) corona were obtained with the help of two narrow-passband filters (centered on the line itself and for the continuum in the vicinity of 529.1 nm, respectively), each with FWHM of 0.15 nm. Through solar observations, on whose scheduling and details we consulted, with the Solar and Heliospheric Observatory, Hinode’s XRT and SOT, TRACE, and STEREO, as well as Wilcox Solar Observatory and SOHO/MDI magnetograms, we set our eclipse observations in the context of the current unusually low and prolonged solar minimum.

We amassed statistics for quiet-sun chromosphere spicules at the limb using ground-based observations from the Swedish 1-m Solar Telescope on La Palma and simultaneously from NASA’s Transition Region and Coronal Explorer (TRACE) spacecraft. The observations were obtained in July 2006. With the 0.2 arcsecond resolution obtained after maximizing the ground-based resolution with the Multi-Object Multi-Frame Blind Deconvolution (MOMFBD) program, we obtained specific statistics for sizes and motions of over two dozen individual spicules, based on movies compiled at 50-second cadence for the series of five wavelengths observed in a very narrow band at H-alpha, on-band and in the red and blue wings at 0.035 nm and 0.070 nm (10 s at each wavelength) using the SOUP filter, and had simultaneous observations in the 160 nm EUV continuum from TRACE. The MOMFBD restoration also automatically aligned the images, facilitating the making of Dopplergrams at each off-band pair. We studied 40 H-alpha spicules, and 14 EUV spicules that overlapped H-alpha spicules; we found that their dynamical and morphological properties fit into the framework of several previous studies. From a preliminary comparison with spicule theories, our observations are consistent with a reconnection mechanism for spicule generation, and with UV spicules being a sheath region surrounding the H-alpha spicules.

During the total solar eclipse at Akademgorodok, Siberia, Russia, on 1 August 2008, we imaged the flash spectrum with a slitless spectrograph. We have spectroscopically determined the duration of totality, the epoch of the 2nd and 3rd contacts and the duration of the flash spectrum. Here we compare the 2008 flash spectra with those that we similarly obtained from the total solar eclipse of 29 March 2006, at Kastellorizo, Greece. Any changes of the intensity of the coronal emission lines, in particularly those of [Fe X] and [Fe XIV], could give us valuable information about the temperature of the corona. The results show that the ionization state of the corona, as manifested especially by the [FeXIV] emission line, was much weaker during the 2008 eclipse, indicating that following the long, inactive period during the solar minimum, there was a drop in the overall temperature of the solar corona.

Elliot, J. L., M. J. Person, C.A. Zuluaga, A.S. Bosh, E.R. Adams, T.C. Brothers, A. A. S. Gulbis, S. E. Levine, M. Lockhart, A. M. Zangari, B. A. Babcock, K. DuPré, J. M. Pasachoff, S. P. Souza, W. Rosing, N. Secrest, L. Bright, E. W. Dunham, S. S. Sheppard, M. Kakkala, T. Tilleman, B. Berger, J. W. Briggs, G. Jacobson, P. Valleli, B. Volz, S. Rapoport, R. Hart, M. Brucker, R. Michel, A. Mattingly, L. Zambranno-Marin, A. W. Meyer, J. Wolf, E. V. Ryan, W. H. Ryan, K. Morzinsky, B. Grigsby, J. Brimacombe, D. Ragozzine, H. G. Montano, and A. Gilmore

The Kuiper belt is a collection of dwarf planets and other small bodies that lie beyond the orbit of Neptune. Believed to have formed contemporaneously with the planets (or soon thereafter), Kuiper belt objects (KBOs) offer clues, through their spatial distribution and physical properties, to conditions during the formation of the solar system. Unfortunately, due to their small size and great instance, few methods allow detailed investigations of these frigid bodies. Here we report the first multi-chord observations of a KBO stellar occultation, which occurred on 2009 October 9 (UT). We find that the KBO 55636 (2002 TX300), which is a member of the water-ice rich Haumea KBO collisional family, has a mean radius of 143 ± 5 km (circular solution). Allowing for possible elliptical shapes we find a geometric albedo 0.88 (+0.06, –0.14) in the V photometric band, which firmly establishes that 55636 is smaller than previously thought and, like its parent body Haumea, is among the most highly reflective objects in the Solar System. Dynamical calculations by two groups indicate that the collision that created 55636 occurred at least 1 Gyr ago, which raises the question of how such a small, ancient body can have a highly reflective surface.

With observations of a stellar occultation by a Kuiper belt object (KBO) from multiple stations, one could establish its radius with an accuracy of a few kilometers. Combining this radius with photometry would establish an accurate geometric albedo. For those KBOs with orbiting companions, these data will further provide highly accurate densities constraining material composition. Stellar occultation data also establish stringent upper limits on any atmospheres and probe for small, nearby companions. The difficulty in observing a KBO occultation has been in generating an accurate prediction so that observers can be deployed within the occultation shadow path. Current KBO ephemerides are at best accurate to a few tenths of an arcsecond, while angular radii of the largest bodies are less than 0.02 arcsec. To improve the ephemerides of the KBOs most promising for stellar occultations, we conduct astrometric observations of KBOs selected (i) for large angular radii, and (ii) in sky regions with large star densities. We have made bi-monthly observations with the Lowell 42-inch Hall telescope since Dec. 2004 and monthly to bi-monthly observations with the SMARTS 0.9 m at CTIO since May 2005. Approximately 1200 KBO astrometric measurements have been submitted to the Minor Planet Center. We use these data to establish ephemeris correction models with which we predict appulses by target KBOs. We observed three of these appulses to test our accuracy. The difference between the predicted and observed closest approach agrees within the formal error for two of the three appulses, but the errors are somewhat larger than the body’s radius. Hence our predictions are almost accurate enough to reliably place observers within the shadow path of a KBO occultation, and improving with each astrometric observation. This work is supported, in part, by USRA subcontract 8500-98-03 (Lowell Observatory) and NASA Grant NNX07AK73G (MIT).

We describe a portable imaging photometer for the observation of stellar occultation events by Kuiper Belt objects (KBOs) and other small bodies. The system is referred to as the Portable Instrument for Capturing Occultations (PICO). It is designed to be transportable to remote observing sites by a single observer. A GPS timing system is used to trigger exposures of a Finger Lakes Instrumentation ML261E-25 camera to facilitate the combination of observational results from multiple sites. The system weighs a total of 11 kg when packed into its single rigid 55.1×35.8×22.6-cm container, meeting current airline size and weight limits for carry-on baggage. Twelve such systems have been constructed. Nine systems were deployed for observation of a stellar occultation by Kuiper Belt object 55636 in October 2009 (Elliot et al. 2010). During the same month, one system was used to record a stellar occultation by minor planet 762 Pulcova.

BIOLOGY

CHEMISTRY

New ligands and compositions with bridged bis-aromatic ligands are disclosed that catalyze the polymerization of monomers into polymers. These catalysts with metal centers have high performance characteristics, including higher comonomer incorporation into ethylene/olefin copolymers, where such olefins are for example, 1-octene, propylene or styrene. The catalysts also polymerize propylene into isotactic polypropylene.

Polymer directed enzyme prodrug therapy (PDEPT), is a novel method of directing chemotherapy treatment towards tumors. PDEPT takes advantage of the enhanced permeability and retention effect, whereby macromolecules accumulate in cancerous tissue due to its leaky vasculature and poor lymphatic drainage systems. In this way, polymer-enzyme bioconjugates with high molecular weights (>40 kg/mol) or large diameters (>4 nm) can be selectively taken up and activate prodrugs within tumors.

Covalently attaching polymers to proteins indubitably affects their properties, as the protein is subjected to stresses of environmental changes, and perhaps even conformational changes. Thus, selection of an appropriate polymer and development of an effective conjugation technique are of paramount importance. PEG (polyethylene glycol) and its analog polyPEGA (polyethylene glycol methyl ether acrylate) are two potentially suitable polymers. Not only do they enhance the molecular weight and diameter on the model enzyme, trypsin, but certain polymer lengths can also enhance trypsin activity.

Typical enzymatic assays for trypsin rely on amide or ester bond cleavage to produce a single chromophore. Fluorescence based assays generally rely on fluorophore-quencher or matched donor-acceptor chromophore pairs for fluorescence resonance energy transfer. In this research, we are looking to take advantage of the increased sensitivity of fluorescence-based assays over UV, as well as to simplify the energy transfer system by using a self-quenching dye. When multiple fluorophores are attached to the same substrate, a decrease in intensity is observed due to internal energy transfer. In this system, Rhodamine-B fluorophores are attached via trypsin-cleavable lysine linkers to dendritic scaffolds derived from 2,2-bis(hydroxymethyl) propionic acid. Polyethylene glycol methyl ether was used as a water-solubilizing core. Cleavage of the lysine linkers should release fluorophore molecules and cause a detectable and corresponding increase in fluorescence activity. Fluorescence analysis of synthesized boc-protected substrates demonstrates that fluorescent activity decreases with increasing dendrimer generation.

The characteristic hypothalamus square-wave secretion and its regulation of the pituitary are essential for the optimal functioning of the menstrual cycle. Here we consider two coupled models, where one mimics the square-wave secretion and the second, a self-replication chemical system, representing a regulated subsystem. We analyze the relation of the period and amplitude of the square-wave oscillations on the secondary oscillator, finding that both period and amplitude shape the secondary oscillations. Furthermore, a combined slow change of both period and amplitude are required for biologically suitable product concentrations of the secondary oscillator.

In ecological modeling, seasonality can be represented as a switching between different environmental conditions. This switching strategy can be related to the so-called Parrondian games, where the alternation of two losing games yield a winning game. Hence we can consider two dynamics that, by themselves, yield undesirable behaviors, but when alternated yield a desirable oscillatory behavior. In this case, we also consider a noisy switching strategy and find that the desirable oscillatory behavior prevails.

In any fossil site, dating the site is essential to understanding the site's significance, because chronological data permits comparisons with materials from other sites, and ultimately enables regional settlement patterns, migration or evolutionary rates to be determined. A dating method's ability to date significant fossil materials directly rather than just dating associated sedimentary or rock units adds to its archaeological and paleontological utility. Electron spin resonance (ESR) dating can provide chronometric ages for vertebrate teeth throughout the Pleistocene and late Pliocene. For mollusc shells and coral, ESR's effective dating range spans much of the Pleistocene. As such, ESR has been used to assess the evolutionary ranges for both hominids and their associated cultural materials and to solve specific geochronological problems. We discuss several examples where ESR has been used to date Neanderthal burials and skeletal materials, including Mezmaiskaya, Obi-Rakhmat, and Pradayrol, as well as dating for cultural materials from pebble tool cultures, Mousterian, and Middle Paleolithic sites. In each case, ESR has provided vital geochronological data, in some cases, where no other methods were applicable.

New chronological, sedimentary morphometric and diagenetic analyses were combined to determine sedimentation rates, relative humidity, and paleotemperatures for the Middle to Early Upper Paleolithic deposits at Divje Babe I, Slovenia's oldest archaeological site. Its thick archaeological sequence housed Mousterian artifacts, including hearths, a perforated ursid femur interpreted as a flute, bone tools, and ∼ 200,000 cave bear (Ursus spelaeus) skeletal remains (NISP).

Eleven archaeologically significant layers were dated by 42 independent standard ESR (electron spin resonance) analyses from 26 teeth. To calculate volumetrically averaged external dose rates, > 190 sedimentary component samples were analyzed by NAA. Sediment was also analyzed for grain size, geochemistry, cryoturbation, cataclasis, pre- and post-depositional corrosion, secondary cementation, and aggregate formation. Local paleotemperature estimates were verified by comparing with palynological determinations and then compared to global δ¹⁸O and palynological records.

Direct evidence for a systematic occupation of the African tropics during the early late Pleistocene is lacking. Here, we report a record of human occupation between 105–42 ka, based on results from a radiometrically-dated cave section from the Mozambican segment of the Niassa (Malawi/Nyasa) Rift called Ngalue. The sedimentary sequence from bottom to top has five units. We concentrate on the so-called ‘‘Middle Beds,’’ which contain a Middle Stone Age industry characterized by the use of the discoidal reduction technique. A significant typological feature is the presence of formal types such as points, scrapers, awls, and microliths. Special objects consist of grinders/core-axes covered by ochre. Ngalue is one of the few directly-dated Pleistocene sites located along the biogeographical corridor for modern human dispersals that links east, central, and southern Africa, and, with further study, may shed new light on hominin cave habitats during the late Pleistocene.

Barnacles have never been successfully dated by electron spin resonance (ESR). Living mainly in the intertidal zone, barnacles die when sea level changes cause their permanent exposure. Thus, dating the barnacles dates past sea level changes that occur due to ocean volume changes, crustal isostasy, and tectonics. By modifying the standard ESR method for molluscs to chemically dissolve 20 μm from off the shells, six barnacle samples from Norridgewock, Maine, and Khyex River, British Columbia, were tested for suitability for ESR dating. Due to Mn2 interference peaks, the four Maine barnacle samples were not datable by ESR. Two barnacles from BC, which lacked Mn2 interference, yielded a mean ESR age of 15.1 ±1.0 ka. These ages agree well with 14C dates on the barnacles themselves and wood in the overlying glaciomarine sediment. Although stability tests to calculate the mean dating signal lifetime and more ESR calibration tests against other barnacles of known age are needed to ensure the method’s accuracy, ESR can indeed date Balanus, and thus, sea level changes.

COMPUTER SCIENCE

Deploying, running, and maintaining applications running on a distributed set of resources is a challenging task. Distributed application management systems are designed to automate the process, and to help developers cope with the problems that arise. In this paper, we highlight the key features of Plush, an application management system for PlanetLab and ModelNet, and describe how Plush simplifies peer-to-peer system visualization and evaluation.

PlanetLab is a seasoned Internet testbed for distributed applications consisting of donated nodes located at more than 350 remote locations spread across the globe. It is particularly appropriate for peer-to-peer application research due its large-scale, distributed operation, and the availability of nodes with edge characteristics. This paper describes the basic testbed offering and suggests appropriate use-cases.

Deploying and controlling experiments running on a distributed set of resources is a challenging task. Software developers often spend a significant amount of time dealing with the complexities associated with resource configuration and management in these environments. Experiment control systems are designed to automate the process, and to ultimately help developers cope with the common problems that arise during the design, implementation, and evaluation of distributed systems. However, many of the existing control systems were designed with specific computing environments in mind, and thus do not provide support for heterogeneous resources in different testbeds. In this paper, we explore the functionality of Gush, an experiment control system, and discuss how it supports execution on three of the four GENI control frameworks.

Many undergraduate liberal arts institutions offer computer science majors. This article illustrates how quality computer science programs can be realized in a wide variety of liberal arts settings by describing and contrasting the actual programs at five liberal arts colleges: Williams College, Kalamazoo College, the State University of New York at Geneseo, Spelman College, and Calvin College. While the example programs differ in size, mission, and the nature of their home institutions, all take advantage of their liberal arts setting to offer rich computer science educations. Comparing these programs to each other and to the latest ACM/IEEE Computer Society computer science curriculum shows that the liberal arts programs are distinguishable from the ACM/Computer Society recommendations but at the same time are strong undergraduate majors.

Because of the growing importance of concurrent programming, many people are trying to figure out where in the curriculum to introduce students to concurrency. In this paper we discuss the use of concurrency in an introductory computer science course. This course, which has been taught for ten years, introduces concurrency in the context of event-driven programming. It also makes use of graphics and animations with the support of a library that reduces the syntactic overhead of using these constructs. Students learn to use separate threads in a way that enables them to write programs that match their intuitions of the world. While the separate threads do interact, programs are selected so that race conditions are generally not an issue.

Learning the relational structure of a domain is a fundamental problem in statistical relational learning. The deep transfer algorithm of Davis and Domingos attempts to improve structure learning in Markov logic networks by harnessing the power of transfer learning, using the second-order structural regularities of a source domain to bias the structure search process in a target domain. We propose that the clique-scoring process which discovers these second-order regularities constitutes a novel standalone method for learning the structure of Markov logic networks, and that this fact, rather than the transfer of structural knowledge across domains, accounts for much of the performance benefit observed via the deep transfer process. This claim is supported by experiments in which we find that clique scoring within a single domain often produces results equaling or surpassing the performance of deep transfer incorporating external knowledge, and also by explicit algorithmic similarities between deep transfer and other structure learning techniques.

Multithreaded programs are notoriously prone to race conditions, a problem exacerbated by the widespread adoption of multi-core processors with complex memory models and cache coherence protocols. Much prior work has focused on static and dynamic analyses for race detection, but these algorithms typically are unable to distinguish destructive races that cause erroneous behavior from benign races that do not. Performing this classification manually is difficult, timeconsuming, and error prone.

This paper presents a new dynamic analysis technique that uses adversarial memory to classify race conditions as destructive or benign on systems with relaxed memory models. Unlike a typical language implementation, which may only infrequently exhibit non-sequentially consistent behavior, our adversarial memory implementation exploits the full freedom of the memory model to return older, unexpected, or stale values for memory reads whenever possible, in an attempt to crash the target program (that is, to force the program to behave erroneously). A crashing execution provides concrete evidence of a destructive bug, and this bug can be strongly correlated with a specific race condition in the target program.

Experimental results with our Jumble prototype for Java demonstrate that adversarial memory is highly effective at identifying destructive race conditions, and in distinguishing them from race conditions that are real but benign. Adversarial memory can also reveal destructive races that would not be detected by traditional testing (even after thousands of runs) or by model checkers that assume sequential consistency

RoadRunner is a dynamic analysis framework designed to facilitate rapid prototyping and experimentation with dynamic analyses for concurrent Java programs. It provides a clean API for communicating an event stream to back-end analyses, where each event describes some operation of interest performed by the target program, such as accessing memory, synchronizing on a lock, forking a new thread, and so on. This API enables the developer to focus on the essential algorithmic issues of the dynamic analysis, rather than on orthogonal infrastructure complexities.

Each back-end analysis tool is expressed as a filter over the event stream, allowing easy composition of analyses into tool chains. This tool-chain architecture permits complex analyses to be described and implemented as a sequence of more simple, modular steps, and it facilitates experimentation with different tool compositions. Moreover, the ability to insert various monitoring tools into the tool chain facilitates debugging and performance tuning.

In this position paper we restrict attention to a basic prerequisite to effective integration. The study of programming languages provides a basis for teaching students how to express concurrent and parallel constructions, how to understand their semantics, and how to analyze properties of their programs. More concretely, we present recommendations stemming from recent SIGPLAN-sponsored activities regarding programming language curriculum development. As a first, but important step, toward best preparing students for the increasingly-concurrent landscape, we advocate their recommendation to include a common core of language and implementation concepts in all Computer Science and Software Engineering programs.

We consider the problem of finding minimum reset sequences in synchronizing automata. The well-known Cerny conjecture states that every n-state synchronizing automaton has a reset sequence with length at most (n-1)². While this conjecture gives an upper bound on the length of every reset sequence, it does not directly address the problem of finding the shortest reset sequence. We call this the minimum reset sequence (MRS) problem. We give an O(mn^k+ n^k+1)-time (n-1)/(k-1)-approximation for the MRS problem for any k ≥ 2. We also show that our analysis is tight. When k=2 our algorithm reduces to Eppstein's algorithm and yields an (n-1)-approximation. When k=n our algorithm is the familiar exponential-time, exact algorithm. We define a non-trivial class of MRS which we call stackcover. We show that stackcover naturally generalizes two classic optimization problems: min setcover and shortest common supersequence. Both these problems are known to be hard to approximate, although at present, setcover has a slightly stronger lower bound. In particular, it is NP-hard to approximate setcover to within a factor of c * log n for some c>0. Thus, the MRS problem is as least as hard to approximate as setcover. This improves the previous best lower bound which showed that it was NP-hard to approximate the MRS on binary alphabets to within any constant factor. Our result requires an alphabet of arbitrary size.

This paper introduces a new approximation algorithm for the near-field ambient occlusion problem. It combines known pieces in a new way to achieve substantially improved quality over fast methods and substantially improved performance compared to accurate methods. Intuitively, it computes the analog of a shadow volume for ambient light around each polygon, and then applies a tunable occlusion function within the region it encloses. The algorithm operates on dynamic triangle meshes and produces output that is comparable to ray traced occlusion for many scenes. The algorithm's performance on modern GPUs is largely independent of geometric complexity and is dominated by fill rate, as is the case with most deferred shading algorithms.

This paper presents a hybrid algorithm for rendering approximate motion and defocus blur with precise stochastic visibility evaluation. It demonstrates---for the first time, with a full stochastic technique---real-time performance on conventional GPU architectures for complex scenes at 1920x1080 HD resolution. The algorithm operates on dynamic triangle meshes for which per-vertex velocity or corresponding vertices from the previous frame are available. It leverages multisample antialiasing (MSAA) and a tight space-time-aperture convex hull to efficiently evaluate visibility independently of shading. For triangles that cross z=0, it fall backs to a 2D bounding box that we hypothesize but do not prove is conservative. The algorithm further reduces sample variance within primitives by integrating textures according to ray differentials in time and aperture.

Image Space Photon Mapping (ISPM) rasterizes a light-space bounce map of emitted photons surviving initial-bounce Russian roulette sampling on a GPU. It then traces photons conventionally on the CPU. Traditional photon mapping estimates final radiance by gathering photons from a k-d tree. ISPM instead scatters indirect illumination by rasterizing an array of photon volumes. Each volume bounds a filter kernel based on the a priori probability density of each photon path. These two steps exploit the fact that initial path segments from point lights and final ones into a pinhole camera each have a common center of projection. An optional step uses joint bilateral upsampling of irradiance to reduce the fill requirements of rasterizing photon volumes. ISPM preserves the accurate and physically-based nature of photon mapping, supports arbitrary BSDFs, and captures both high- and low-frequency illumination effects such as caustics and diffuse color interreflection.

The OptiX engine is a programmable ray tracing system designed for NVIDIA GPUs and other highly parallel architectures. OptiX builds on the key observation that most ray tracing algorithms can be implemented using a small set of programmable operations. Consequently, the core of OptiX is a domain-specific just-in-time compiler that generates custom ray tracing kernels by combining user-supplied programs for ray generation, material shading, object intersection, and scene traversal. This enables the implementation of a highly diverse set of ray tracing-based algorithms and applications, including interactive rendering, offline rendering, collision detection systems, artificial intelligence queries, and scientific simulations such as sound propagation. OptiX achieves high performance through a compact object model and application of several ray tracing-specific compiler optimizations. For ease of use it exposes a single-ray programming model with full support for recursion and a dynamic dispatch mechanism similar to virtual function calls.

GEOSCIENCES

During the last deglaciation, increases in atmospheric CO₂ coincided with a decrease in atmospheric Δ¹⁴C. One explanation is that this is the result of the ventilation of a long-accumulating CO₂-rich, ¹⁴C-poor deep-ocean reservoir. From a sediment core taken off the coast of Baja California, Marchitto et al. (2007) showed evidence of a deglacial water mass very depleted in ¹⁴C which they hypothesize may be from reservoir water that partially re-equilibrated in the Southern Ocean and spread northward at intermediate depth. We present results from an intermediate-depth core off northern New Zealand. We estimated late glacial intermediate water Δ¹⁴C from radiocarbon measurements of pairs of benthic and planktonic foraminifera from benthic abundance peaks. Our preliminary results show no sign of a ¹⁴C depleted water mass prior to 18300 BP and suggest that circulation at intermediate depth during the late glacial/early deglacial period was consistent with modern circulation.

In piston cores from the open subarctic Pacific and the Okhotsk Sea, diatom-bound δ¹⁵N (δ¹⁵N_db), biogenic opal, calcium carbonate, and barium were measured from coretop to the previous glacial maximum (MIS6). Glacial intervals are generally characterized by high δ¹⁵N_db (~8‰) and low productivity, whereas interglacial intervals have a lower δ¹⁵N_db (5.7–6.3‰) and indicate high biogenic productivity. These data extend the regional swath of evidence for nearly complete surface nutrient utilization during glacial maxima, consistent with stronger upper water column stratification throughout the subarctic region during colder intervals. An early deglacial decline in δ¹⁵N_db of 2‰ at ~17.5 ka, previously observed in the Bering Sea, is found here in the open subarctic Pacific record and arguably also in the Okhotsk, and a case can be made that a similar decrease in δ¹⁵N_db occurred in both regions at the previous deglaciation as well. The early deglacial δ¹⁵N_db decrease, best explained by a decrease in surface nutrient utilization, appears synchronous with southern hemisphere-associated deglacial changes and with the Heinrich 1 event in the North Atlantic. This δ¹⁵N_db decrease may signal the initial deglacial weakening in subarctic North Pacific stratification and/or a deglacial increase in shallow subsurface nitrate concentration. If the former, it would be the North Pacific analogue to the increase in vertical exchange inferred for the Southern Ocean at the time of Heinrich Event 1. In either case, the lack of any clear change in paleo-productivity proxies during this interval would seem to require an early deglacial decrease in the iron-to-nitrate ratio of subsurface nutrient supply or the predominance of light limitation of phytoplankton growth during the deglaciation prior to Bølling-Allerød warming.

The Bering Sea gateway between the Pacific and Arctic oceans impacts global climate when glacial- interglacial shifts in shore line position and ice coverage change regional albedo. Previous work has shown that during the last glacial termination and into the Holocene, sea level rises and sea ice coverage diminishes from perennial to absent. Yet, existing work has not quantified sea ice duration or sea surface temperatures (SST) during this transition. Here we combine diatom assemblages with the first alkenone record from the Bering Sea to provide a semiquantitative record of sea ice duration, SST, and productivity change since the Last Glacial Maximum (LGM). During the LGM, diatom assemblages indicate that sea ice covered the southeastern Bering Sea perennially. At 15.1 cal ka B.P., the diatom assemblage shifts to one more characteristic of seasonal sea ice and alkenones occur in the sediments in low concentrations. Deglaciation is characterized by laminated intervals with highly productive and diverse diatom assemblages and inferred high coccolithophorid production. At 11.3 cal ka B.P. the diatom assemblage shifts from one dominated by sea ice species to one dominated by a warmer water, North Pacific species. Simultaneously, the SST increases by 3°C and the southeastern Bering Sea becomes ice-free year-round. Productivity and temperature proxies are positively correlated with independently dated records from elsewhere in the Bering Sea, the Sea of Okhotsk, and the North Pacific, indicating that productivity and SST changes are coeval across the region.

Erosion via lavaka formation is widespread in Madagascar, but controls on why and where lavakas occur are not understood. GIS analysis reveals a spatial correlation between lavaka abundance and the frequency of seismic events: most lavakas occur in or near areas where earthquakes are most frequent. This correlation explains the unevenness of lavaka distribution in the Malagasy highlands, and highlights the importance of natural factors in lavaka formation. Seismic activity appears to pre-condition the landscape to lavaka formation, although the mechanism by which this happens is not yet known. Recognizing the connection, however, allows us to pinpoint areas prone to future lavaka development in zones of active deforestation. Areas with greatest frequency of seismic events are most at risk for high-density lavaka development.

Zircons in transport in the Amazon River vary in grain size by an order of magnitude (30-300 µm equivalent spherical diameter (ESD): coarse silt to medium sand), and range in age from a few Ma to 2.8 Ga. Age and size are not independent of one another. There is an overall trend toward decreasing average grain size with increasing age, but superimposed on this trend are two average-size maxima, at 100-300 Ma and 1000-1100 Ma. Mesozoic and Cenozoic grains, for example, have average ESD 122 µm (with standard error 42 µm); whereas grains older than 2000 Ma have average ESD about half that: 67 µm (± 14 µm). A full Wentworth size class (lower fine sand-upper coarse silt) separates the two average values, meaning that zircons in these age populations are hydraulically distinct.

Evidence for hydrodynamic fractionation of zircons comes from comparison of sand size with the sizes of co-transported zircons. Average grain size of host sands and incorporated zircons are correlated, but the best correlations are with specific sand-size fractions. Zircon size is positively correlated with percent medium sand, and inversely correlated with percent very fine sand (p<0.0001 in both cases). In samples with >50% medium sand, average zircon size is 100 µm, compared with 80 µm in samples with >50% very fine sand. This indicates that zircon deposition is not size-blind, and that zircons are tracking with hydraulically comparable sand grains.

Comparison of five samples taken from a single Amazon River dune reveals statistically significant differences among age spectra obtained from different hydrodynamic microenvironments. Samples from a single locality, with identical provenance, should have zircon age populations statistically indistinguishable from one another, but these samples show differences at the 2σ level, with several age populations occurring in only a subset of the samples. We conclude that hydrodynamic fractionation of zircons and zircon age populations does occur. Zircon size should therefore be taken into consideration in detrital zircon provenance analysis.

Chaos areas on Europa—regions where the surface has been disrupted, with rafts of remnant crust set in a hummocky matrix of slushy appearance—do not look like classic impacts; but several lines of evidence suggest they may be sites where impactors fully penetrated the ice crust. In this model, the matrix represents the boiled and refrozen surface of the underlying water layer, and the embedded plates are wreckage of the fragmented crust. The size and shape of chaos areas are significantly correlated. Large chaos areas tend to have complex, irregular borders whereas smaller ones are generally equidimensional with simpler boundaries. There is also a correlation between chaos shape and raft count: the more irregular the chaos shape, the more rafts it tends to have. These relationships match predictions from impact experiments into ice over water, which show a relationship between impact energy and the shape of the resultant hole. The large jagged openings reflect wide-field fragmentation of the ice crust above the water layer, which is greater at higher energy (or in thinner crust).

Chaos areas are concentrated at low latitude, consistent with the expectation for impacts on a tidally locked satellite. Almost 60% of chaos areas (653 of 1092 features imaged at 230 m/pixel or better) are clustered between 30° north and south. Likewise, the percent surface area occupied by chaos terrain is greatest at low latitudes, and decreases with distance from the equator. The chaos distribution echoes that of non-penetrating craters on Europa, which also show low-latitude clustering (14/28 craters > 4km diameter are within 30° of the equator, and only 5/28 are at >60°).

Existing data hint at some apex-antapex asymmetry, but we present this tentatively because longitudinal coverage in the Galileo data is limited. There are slightly more chaos areas (both absolutely and per degree longitude) in the leading hemisphere REGMAP strip than in the corresponding trailing hemisphere strip; and the area occupied by chaos is 11% in the trailing in comparison with 21% in the leading hemisphere strip. Although strong conclusions cannot be drawn because of the lack of body-wide coverage, these data are consistent with predicted impact asymmetry.

Field and laboratory analysis of soils formed on saprolitic bedrock and on midslope colluvium in the Betasso catchment, suggests that granitic regolith weathers slowly along the dry eastern margin of the Front Range. The bedrock-derived soil contains primarily smectitic clays and Fe-oxides as secondary minerals, which extend into the underlying saprolite. At both slope positions, kaolinite is present only below 40 cm and in trace amounts (<2 wt %). The mid-slope soil is developed on colluvium, which lies above and below a buried soil. Bulk carbon from the A horizon of the paleosol gave calibrated ages of 9000 yr and 8640 yr. Most weathered samples from Betasso have bulk densities < 2.0 T m^-3 and soil horizons give values < 1.75 T m^-3. Bulk chemical changes from bedrock and colluvium to soils are relatively small, probably mediated by the relatively dry climate and the transformation of plagioclase and biotite to secondary minerals without major losses of silica, cations or minor elements. Downprofile changes in bulk chemistry are subtle, but regolith generally is enriched in constituents such as C and Zr and slightly depleted in base-metal cations such as Ca and Na with respect to bedrock. Apatite concentrations in soils and unweathered colluvial deposits range from 0.10 to 0.27 weight percent. Concentrations of apatite and plagioclase are lowest, and the smectite concentrations highest in the buried A and B horizons, which indicate that the paleosol is the most weathered material sampled. Apatite morphology does not appear to show depth-related trends, but total phosphorus concentrations increase in the buried soil profile where apatite concentrations decrease, suggesting that the high P concentrations were adsorbed on Fe-oxides during weathering of the paleosurface. Comparison to other chronosequences in the western USA suggests that the buried colluvial soil at Betasso likely accumulated clay and Fe-oxides for at least 50 to 150 kyr. The upper saprolite-derived soil represents at least 35 to 60 kyr of clay and Fe-oxide accumulation.

Worldwide flood basalt formations are considered promising targets for permanent CO₂ capture and storage. The evaluation of flood basalts for extensive geologic sequestration requires focused, small-scale studies to assess the porosity and permeability characteristics of basalt flows as well as these flows’ potential to react with and trap CO₂ within new, stable carbonate minerals. More than 14 laterally continuous, well-exposed 22 million year old basalt flows in the Black Gap (BG) volcanic field, east of Big Bend National Park (BBNP) in west Texas, are ideal for this type of study. Based on detailed field analysis of vesiculation patterns in the 2 – 6 meter thick BG flows, storage of CO₂ would occur in the porous, highly permeable, upper vesicular zone, which makes up 40-70% of the total flow thickness. The middle dense zone, with low permeability and porosity, would function as a cap between flows and limit CO₂ movement, allowing time for mineralization to occur. These distinct vesiculation patterns and other field evidence were used in my study to conclude that the dominant emplacement mechanism for these flows was inflation, also common in flood basalt formations. Another important aspect of my research was geochemical analysis of the BG flows. Based on collected data, I concluded that BG lavas are geochemically distinct from older rocks exposed in BBNP, suggesting the flows were derived from a different mantle source. Further geochemical research on BG basalt flows could constrain the possible in-situ carbonate mineralization rates in crystalline silicates, which would permanently stabilize dissolved CO₂.

Three main factors have been proposed as controls on seismic layering in ocean crust: igneous composition, porosity, and metamorphic grade. At IODP Hole 1256D, we compare the geologic and geophysical structure of a complete section of upper oceanic crust. Drilled into oceanic crust of the Cocos Plate at 07°N x 092°W, Hole 1256D is the first hole drilled continuously through sediments, basalts, dikes and into the uppermost gabbros of the oceanic crust (Teagle et al., 2006). The crust at Hole 1256D formed at the East Pacific Rise 15 Ma at a superfast spreading rate (~22 cm/y full spreading rate), faster than any modern spreading on Earth. By combining remote, in situ, and laboratory measurements of seafloor crustal rocks from one site, we take advantage of the first opportunity to determine controls on seismic layering of normal oceanic crust through extrusive flows, dikes, and into the gabbros.

Preliminary analysis of shipboard measurements of crustal P-wave velocities <6.5 km/s, determined that the present base of Hole 1256D (1507 mbsf) is within Layer 2. Downhole velocity measurements only reach the uppermost gabbro (1422 mbsf) drilled, and Swift et al. (2008) concluded these deepest downhole measurements were consistent with Layer 2: steep Vp gradients with depth and maximum Vp ~6.5 km/s. Regional seismic experiments conducted near Hole 1256D showed a Layer 2-3 transition at 1450 to 1750 meters below seafloor (mbsf), or 1200 to 1500 meters subbasement (msb). With additional samples and downhole data from IODP Hole 1256D, we further constrain seismic layers of the ocean crust and examine the lithologic and physical/chemical controls on seismic layering in detail.

Previously, the Layer 2-3 boundary has been both drilled and imaged only at ODP Hole 504B. The deepest hole drilled into oceanic crust to date is still Hole 504B, over 2 km deep, but it only reaches into the dikes. Previous efforts at ocean drilling have been successful at accessing basalts, dikes, and gabbros, but not all at a single location within normal oceanic crust. This work compares igneous composition, alteration, and porosity across major seismic boundaries in the upper oceanic crust: within Layer 2 and the Layer 2-3 boundary at a single location, and in the context of previously drilled ODP Hole 504B, which reached Layer 3 but not gabbros.

Seamounts are an important feature of the seafloor but relatively little is known about their internal structure. Previous work has examined seamount surface morphology via seafloor mapping and submersible observations, broad geophysical characteristics via remote methods and one-dimensional structure through drilling. However, to model the formation of seamounts we need a better understanding of two- and three-dimensional variations, which are difficult to study in any detail beyond the surface of the seafloor. Ophiolitic seamounts provide a unique window for studying these difficult to reach features. This study proposes a model for seamount formation using field observations and laboratory measurements of a seamount preserved in the subduction-related Cretaceous Franciscan formation of northern California.

The preserved seamount in our study site likely formed in water deeper than 1.5 km, reached over 1 km high, and may have been formed at or near a ridge axis, with some similarities to seamounts formed on or near the modern East Pacific Rise. The relative paucity of faulting and fractured shear zones throughout the field area indicates little or no rearrangement of units during emplacement of the seamount onto land. The dominant lava flow morphology is pillow lavas, which constitute roughly three-quarters of observed flows. Massive flows and hyaloclastite and pillow fragment (HPF) flows each represent about one-eighth of the total thickness of flows, and sheet and lobate flows are both relatively minor. Volcanic facies are further classified based on density, porosity, igneous and metamorphic petrography, and major and trace element geochemistry.

Based on variations in flow morphology and related physical properties, we generalize seamount formation into three phases. A first ‘basal’ stage is dominated by small, tightly packed, lower-porosity pillows, which form at greater water depths atop existing oceanic crust. A second ‘intermediate’ stage is represented by several individual flow sequences, with the number and thickness of flow sequences present dependent upon rate and duration of eruption at a specific seamount. A typical flow sequence includes massive flows at the base, followed by pillow lavas and capped by HPF flows. The pillow lavas of this stage are more vesicular than the basal stage pillows and have a relatively high fraction of inter-pillow hyaloclastite, in part because they are emplaced above the initial basal flows in shallower water. Hydrothermal alteration of the larger pillows and field relations imply the intermediate stage lavas at this site may have been emplaced within a collapsed caldera structure. Finally, a third ‘cap’ stage occurs on the upper edifice of a seamount, at the end of an eruptive period. This cap stage is not dominated by a single morphology, but instead includes significant variation in flow morphology and the increased presence of sheet and HPF flows. Our model has important implications for understanding the structure and formation of seamounts, and provides context for one-dimensional drill holes, surface observations, and regional-scale geophysical measurements of seamounts.

Student adoption of cognitive strategies such as good thinking and reasoning is either limited or promoted by affective factors such as motivation, attitudes, feelings and emotions. The GARNET (Geoscience Affective Research Network) project examines the connection between affective factors and geoscience learning outcomes. Participating instructors used the Motivated Strategies for Learning Questionnaire (MSLQ; Pintrich et al., 1993) to investigate how aspects of the affective domain varied for students and to identify variations with classroom instruction strategies and learning environments. Here we report baseline MSLQ data collected from 13 physical geology classes at six institutions during fall 2008 and spring 2009 semesters. These are the first data to compare a diverse array of student values, beliefs, and learning strategies across multiple general education geoscience courses.

The MSLQ is an 81-item scale divided into six motivation and cognitive subcategories containing 15 separate subscales. GARNET institutions included public research universities, a private liberal arts college, and a community college. We analyzed matched pre and post MSLQ surveys, demographic, and performance data for 340 students. In any one semester, there are no large differences in MSLQ pre-instruction scores between different classes (hence institutions), suggesting that students’ initial motivation and learning strategies are fairly similar across institutions. There are some significant differences in MSLQ pre-instruction scores between fall and spring populations, suggesting somewhat different student attitudes as a function of semester. Within individual classes, students generally report little change in the study strategies they adopt (e.g., rehearsal, critical thinking) over the length of the semester. Various subscale categories have different trends for high and low performing students. Factors such as self-efficacy, test anxiety, and peer learning, record significant pre/post changes (p<0.05) in multiple classes across both semesters. By the end of the semester, most students became less self-confident, less anxious in test situations, and were more likely to seek help from peers and instructors.

We examine how demographic characteristics relate to the motivation and learning strategies of students entering introductory geology. We use the Motivated Strategies for Learning Questionnaire (MSLQ; Pintrich et al., 1993) to investigate how motivations and strategies vary among students entering introductory geology. As a group, students enter these courses with a range of motivations (e.g., goal orientation and control beliefs) and learning strategies (e.g., study methods, critical thinking, metacognition). Compared to non-geology students from a prior study (VanderStoep et al., 1996), entering introductory geology students are more extrinsically than intrinsically motivated, and have a lower goal orientation (task value).

Preliminary analyses indicate differences in motivation and strategies by gender, age, ethnicity, teaching style preference, reason for taking the course, and experience and interest in science. Students reporting lower interest in science upon entering introductory geology assign a lower degree of intrinsic motivation, self-efficacy, elaboration, critical thinking, metacognition, effort regulation, and task value to their coursework. Students with prior experience in college science courses report more self-efficacy and control of learning. Critical thinking correlates with experience. Students who enroll in introductory geology primarily to fulfill a general education requirement report lower extrinsic motivation, critical thinking, and task value. Students who prefer dominantly lecture-style classes (in contrast with active learning classes) score slightly higher on most MSLQ subscales, indicating higher motivation and more positive attitudes towards learning introductory geology. With age, intrinsic motivation increases, extrinsic motivation decreases, and a preference for peer learning decreases dramatically. Students from under-represented ethnic groups report lower intrinsic and extrinsic motivation. Compared to other factors, gender has a small influence on motivation and attitude among incoming students.

We observed introductory geology classrooms in an attempt to characterize student motivations and attitudes in a variety of classes. We assessed classroom learning environments using the Reformed Teaching Observation Protocol (RTOP; Sawada et al, 2002), a 25-item instrument that yields a score of 0-100 for each class. In an effort to assure appropriate rating based on a college lecture classroom, the observers developed a rubric that led to interrater reliability of R2=0.95.

Thirteen different physical geology classrooms (community college, public universities, and private college) had RTOP scores ranging from 19-85. We identified three representative groups: high (64-68), medium (45-46) and low (20-24). In a high scoring classroom, lectures are rare, students are actively engaged, and drive the direction of the course. We characterize the middle scoring classroom as an active lecture environment (e.g., students are involved in discussions through clickers). A more traditional lecture format with the instructor dominating the conversation is characteristic of a low scored classroom.

We compared RTOP scores with the Motivated Strategies for Learning Questionnaire (MSLQ; Pintrich et al, 1993). The MSLQ characterizes student attitudes and motivations about a class. There are clear correlations between the RTOP and some components from the MSLQ. On average, RTOP scores had a weak positive correlation with extrinsic goals and use of rehearsal strategies, a strong negative correlation with control of learning and self-efficacy, and a strong positive correlation with test anxiety.

Most students perceive that they have less control of their learning, have less confidence about their ability to be successful and have greater test anxiety in an active learning physical geology course that requires them to take more responsibility for their own success. The highest performing students did not exhibit the same trends. As students become more aware of the factors that influence their learning, and are challenged intellectually, they may become more cognizant of their own abilities and limitations. Ultimately, students who become more aware of their own strengths and weaknesses in the classroom are more academically successful. This underscores the importance of helping students develop strong metacognitive skills.

We sought to determine whether students’ attitudes and learning strategies influence their performance in college-level physical geology courses. We administered pre- and post-course Motivated Strategies for Learning Questionnaires (MSLQ, Pintrich et al, 1993) in physical geology classes taught by 13 instructors at six colleges and universities and compared the results to final class grade. Preliminary analysis using step-wise multiple regression* of matched pairs of student responses to the MSLQ (n = 152 for fall 2008; n = 188 for spring 2009) reveals that grades cannot be predicted from pre-course MSLQ scores, but are significantly (p < 0.01) correlated with several subscales of the MSLQ administered near the end of the course. The strongest predictor of final class grade was the student’s score on the self-efficacy subscale. Students with high self-efficacy are confident that they can understand class material, do well on assignments and exams, and master the skills being taught in the course.

Other key subscales of the MSLQ had effects that varied by semester. In fall 2008, students’ scores on the peer learning (PL) and control of learning beliefs (CB) subscales each had a negative correlation with their performance. Students who score high on the peer learning subscale often study with peers. Those who score high on the control of learning beliefs subscale feel that their individual study efforts determine their academic performance. In spring 2009, students’ scores on the intrinsic goal (IG) subscale had a negative correlation with their performance, but students’ scores on the task value (TV) subscale had a positive correlation with their performance. Students who score high on the intrinsic goal subscale strive to thoroughly understand course content and they prefer course material that challenges them and arouses their curiosity. Students who score high on the task value subscale like the course content and find it useful.

More than 60% of the Earth’s surface is composed of oceanic crust. The formation of new oceanic crust at ridge axes and the reincorporation of old crust into the mantle or its accretion onto continental margins at subduction zones are perhaps the most fundamental components of the plate tectonic cycle. These processes control the physiography of the Earth and the chemical and thermal evolution of the crust and mantle. Seafloor volcanoes, including seamounts and mid-ocean ridges, are dynamic environments where globally significant chemical, biological, and heat fluxes occur between the lithosphere and hydrosphere. The focus of this project was a study of water-rock-microbial alteration of the ancient seafloor preserved in the Abitibi Greenstone Belt (AGB).

Greenstone belts such as the AGB are useful for understanding ancient seafloor processes that we cannot access directly. When we study modern oceanic crust it is generally either just on the very surface of the seafloor, in a one-dimensional hole drilled into the crust, or by some remote method that prohibits detailed mapping. Greenstone belts are not perfect analogs of normal ocean crust and are likely preserved because they may be atypical (e.g. Karson, 2002). However, seafloor volcanic rocks are not all generated at normal mid-ocean ridge settings, and seamounts, back-arc spreading, and oceanic plateaus represent a significant portion of volcanic rocks found on the seafloor.

Investigations of seafloor hydrothermal systems are inherently interdisciplinary, reflecting the complex linkages between geological, biological, chemical, and physical processes. In particular, the role of microorganisms in the alteration of oceanic crust has only recently been demonstrated (see Furnes et al., 2008 for a review). The temperature and depth limits of oceanic basement microbiological activity have yet to be explored, but microbial activity occurring in the sub-seafloor biosphere may have a profound impact on processes and chemical fluxes during water-rock reactions and possibly hold the key to the development of life on the Earth and other planets.

Shallow, semi-spherical borings occur in clusters with densities of 1-3.5/cm² in quartzite boulders and in vein quartz from the localized basal conglomerate of the Cambrian-Ordovician Deadwood Formation in the east-central Black Hills of South Dakota. Some borings are superimposed on primary but enigmatic semi-circular structures, 2.5 to 5 cm in diameter, which are soft-sediment trace fossils formed prior to lithification. The macroborings are the first to be recorded from quartzite and vein quartz. Host boulders were eroded from near vertically dipping Paleoproterozoic quartzites from several different stratigraphic units. The thin boulder conglomerate grades or abruptly changes to sandstone through a layer ≤ 2 m thick in the Marjuman transgression (regionally correlated to the Cedarina dakotaensis trilobite zone). This transgression occurred prior to the start of the globally recognized Upper Cambrian Paibian Stage. Physically similar rocky-shore settings are widely known from quartzite islands of Cambrian age in Wisconsin, Middle Ordovician age on Ontario’s Manitoulin Island, Ordovician-Silurian age in Manitoba, and Devonian age in Western Australia. Erosion of quartzite surf boulders of equal or larger size occurred in all those regions, but the Black Hills of South Dakota is the only region where borings in quartzite are documented.

Quaternary Intertidal Deposits Intercalated with Volcanic Rocks on Isla Sombrero Chino
in the Galápagos Islands, Ecuador

A stratigraphic succession composed of limestone intercalated with volcanic ash and basalt capped by a conglomerate of mixed limestone and basalt cobbles was deposited in a trough-shaped depression approximately 25 m wide and 50 m long to a thickness of 1.62 m on the southwest side of Isla Sombrero Chino in the Galápagos Islands of Ecuador. Two layers of well-cemented calcarenite up to 20 cm thick accumulated as beach deposits with bioclasts of gastropods dominated by the Galápagos Periwinkle (Nodilittorina galapagiensis), a representative of the Beaded Hoofshell (Hipponix grayanus), broken crab fragments, and bird bones. Crustacean remains most likely belong to the Sally Lightfoot Crab (Graspus graspus). The bird bones are attributed to Audubon’s Shearwater (Puffinus iherminieri). Distinctly intertidal in origin, such a mixed assemblage of invertebrates and vertebrates is unusual and the association with basalt flows is seldom met in the rock record. The pristine state of the volcanic cone on Sombrero Chino is consistent with a 3He exposure age of 13± 0.8 ka. The age of the basalt-limestone sequence is unknown, but must be younger than the 3He exposure age. The basalt-limestone sequence is elevated approximately 3 m to 4 m above current sea level. This implies that the intertidal limestone was deposited during an interval of higher sea level or, more likely, was uplifted by magmatic inflation. Such intertidal deposits, in conjunction with more precise dating, have the potential to constrain the history of relative sea-level change during island growth and isostatic subsidence related to volcanism and lithospheric cooling. Intertidal deposits of the kind reported here, also help to distinguish between monogenetic as opposed to polygenetic history for volcanic islands.

Structural geology students solve numerous 3-D spatial problems using 2-D projections, yet many have difficulty visualizing how the projections work. Thus, they may learn how to solve sample problems by a given set of operations, but they have difficulty extrapolating to novel problems. Well-drawn perspective diagrams can help some students understand how projections work, for example the stereographic projection, but their value is limited by their static nature.

3-D visualization can be dramatically enhanced with the aid of computer applications, which make it possible to construct accurate 3-D models that can be manipulated by the user to show how projections work. Google SketchUp, a free application, can be used to create a realistic model of the stereographic projection. The lower hemisphere, projection point, projection plane (complete with great and small circles), and planes or lines representing geologic features (all referenced to the center of the sphere) can be constructed accurately enough to measure angles within the 3-D model. The ability to rotate the model, and all of its elements, allows students to connect the 3-D spatial relationships with the 2-D stereographic projection. Once the model is rotated, it is easy for students to retain the 3-D perspective.

The three-point problem is a classic example of a 3-D problem that is solved by projecting ‘on the fly’ into a plane. ArcMap and ArcScene, commercially available GIS software, can be combined to produce precise 2-D and 3-D illustrations of the solution to this problem. Turning layers on sequentially permits an orderly demonstration of how the three initial points can be used to construct the plane and structure contours of a geologic contact. Rotation of the 3-D model shows how the intersections of the topographic and structure contours define the outcrop pattern, and how to determine the depth of a contact below the surface. These programs can also be used to show how to measure displacement across a fault and how to construct cross-sections from map data.

During the Ordovician Taconic orogeny, Neoproterozoic to Ordovician shale and siltstone from the Laurentian slope and rise were thrust over coeval shelf rocks. Flysch, eroded from the advancing thrust sheets, blanketed the shelf rocks, and was locally overridden by the thrust sheets. On Mount Greylock in MA graphitic and non-graphitic schist are indistinguishable except for their C content. The graphite-rich schist was mapped as flysch of the Walloomsac Fm (WF), and the contact that separates WF, from graphite-poor rocks of the Greylock Sch (GS) was interpreted as a thrust. This assumed that the present distribution of graphite reflects the primary preservation of organic material in sediments. Based on our mapping, the gradational contact between WF and GS is difficult to locate and we found no strain gradients near it. In contrast, a wide zone within the WF especially near the contact with the structurally lower marble is a zone of intense deformation and shares many characteristics of mélange.

The distinction between graphite-rich and graphite-poor rocks is not a reliable stratigraphic tool. Typically graphite-rich (1-2 wt %) and graphite-poor (0.1-0.2 wt%) rocks are interlayered on scales ranging from 10- to 100-m. Examination of 200 thin sections reveals that 55% of WF samples are graphite-rich, but 45% are graphite-poor. Although only 10% of the GS samples are graphite-rich, 55% contain plagioclase grains with abundant graphite inclusions surrounded by a graphite-poor matrix, indicating that graphite was removed from the matrix by aqueous fluids.

We suggest that C was widely and more evenly distributed throughout the pelitic schist, and that large-scale redistribution of graphite occurred during metamorphism and thrusting. Aqueous fluids dissolved C in large volumes of rock, which are now graphite-poor, but commonly contain plagioclase with abundant graphite inclusions. Faults focused fluid flow and retrograde reactions, commonly observed in fault zone rocks, consumed water and decreased C solubility. C precipitated from these fluids to produce graphite-rich schist. Graphite weakened fault zone rocks and created a positive feedback between faulting, fluid flow, and graphite precipitation. We map the main thrust between graphite-rich schist and marble and include all of the pelites in the hanging-wall.

The R_f–Φ method is a powerful graphical approach for estimating finite strain of deformed elliptical objects, but one that students commonly find difficult to understand. We developed a program that allows users to explore visually how deforming a set of elliptical objects appears on R_f–Φ plots. A user creates or loads the ellipses and then deforms them by simple shear, pure shear, or rigid rotation. As the ratio of the long to short axis of the ellipses (R_f) and long-axis orientations (Φ) change in one window, the R_f–Φ plot continuously and instantaneously updates in another. Users can save snapshots of the deformed elliptical objects and the Rf–Φ plots to record graphical experiments. The program provides both R_f vs. Φ and polar ln(R_f) vs. 2(Φ) plots. The user can ‘undeform’ ellipses quickly and easily, making it possible to inspect the ‘original’ shapes and orientations of objects, and to evaluate the plausibility of the determined strain values. Users can export information about the pebbles' shape and orientation to spreadsheets for rigorous statistical analysis. This program is written in Java and so can run on virtually any operating system. Both the source code and the application will be freely available for academic purposes.

The New England Appalachians contain two north-south trending sets of gneiss domes. The western belt, which includes the Chester dome, contains thirteen domes that expose either 1 Ga Laurentian basement rocks or approximately 475 Ma rocks of the Shelburne Falls arc. The eastern belt contains twenty-one gneiss domes cored by either 600 Ma crust of possible Gondwanan affinity or approximately 450 Ma rocks of the Bronson Hill arc. Domes in both belts are surrounded by Silurian and Early Devonian metasedimentary rocks, which were deposited in two north-south trending basins before the Acadian orogeny. The Chester dome in southeastern Vermont, the main focus of this study, is an intensively studied, classic example of a mantled gneiss dome. Lower Paleozoic units around the Chester dome are dramatically thinner than they are elsewhere in southern Vermont, and are locally absent. A strong spatial correlation between the highly attenuated mantling units and highly strained, mylonitic rocks suggests the presence of a ductile, normal-sense shear zone. Garnet-bearing rocks in the core of the dome record metamorphism during decompression of 2 to 3 kbar, whereas rocks above the high-strain zone were metamorphosed during nearly isobaric conditions. Strain markers and kinematic indicators suggest that extension occurred during northward extrusion of lower to middle crustal wedges of Proterozoic and Ordovician quartz-feldspar-rich gneisses below and up into a thick tectonic cover of Silurian mica-rich metasediments that had been transported westward in large-scale nappes. If the ductile, normal-sense shear zone is responsible for syn-metamorphic decompression, as we propose, extrusion occurred at approximately 380 Ma.

This Geological Society of America Memoir contains thirty-six new articles tracing the geologic history of eastern North America from 1200 to 200 million years ago. It includes summary articles written by leading experts, which describe major tectonic events in the eastern North America, and specialized research papers describing recent progress in reconstructing Paleozoic mountain building processes in the Appalachians.

T. Nelson Dale is known not so much as a teacher but as one of the most important and productive early contributors to the geological study of the Northeast. With virtually no formal education beyond preparatory school (though he yearned to attend Yale), he embarked on a professional career that spanned seven decades, four of them with the U.S. Geological Survey, resulting in 60 geological publications (including 20 U.S.G.S. bulletins and 7 papers in the American Journal of Science). He became an expert—perhaps the expert of his time—on the geology of western New England and on the commercial building stones (granite, slate, marble) of the United States. His field studies in New England involved over 12,000 miles of hiking and more of driving the primitive roads; according to one of his grandsons, he was “a tiny...dynamo of a man who walked as far and fast as he was able for as long as he lived.”

The record of his early schooling by remarkable tutors, his travels in Europe, and the fortunate acquaintances who helped him on his unconventional career path is followed by a chronological narrative of his geological field work in Europe and the U.S. The account of his explorations is accompanied by wonderful vignettes of the places he visited and the people he met. A philosophical man of firm religious convictions, his stories are laced with Biblical references and character judgments from which not even the most casual acquaintances are immune. In his later years he wrote and spoke widely about philosophy, education, and religion.

The Keck Geology Consortium is an 18-college collaboration focused on enriching undergraduate education through development of high-quality geoscience research experiences for undergraduate students and faculty participants. The consortium projects are year-long research experiences that extend from summer project design and fieldwork through collection of laboratory data and analysis during the academic year, to the culminating presentation of research results at the annual spring symposium. The Keck experience incorporates all the characteristics of high-quality undergraduate research. Students are involved in original research, are stakeholders and retain intellectual ownership of their research, experience the excitement of working in group and independent contexts, discuss and publish their findings, and engage in the scientific process from conception to completion. Since 1987, 1094 students (1175 slots, 81 repeats) and over 121 faculty (410 slots, multiple repeats) have participated in 137 projects, providing a substantial data set for studying the impact of undergraduate research and field experiences on geoscience students. Over 56% of the students have been women, and since 1996, 34% of the project faculty have been women. There are now 45 Keck alumni in academic teaching and research positions, a matriculation rate three times the average of U.S. geoscience undergraduates. Twenty-two of these new faculty are women, indicating remarkable success in attracting women to and retaining women in academic geoscience careers.

The timescale of pluton construction and the relationship between granite plutons and rhyolitic volcanic complexes remain elusive problems that limit our understanding of crustal magmatism. High-precision geochronology of plutons associated with related volcanic rocks, such as the Silurian Vinalhaven Intrusive Complex (VHIC) on the coast of Maine, provide an ideal opportunity to constrain the timescale of pluton construction and establish the temporal relationship needed to examine the connection between subvolcanic rocks and associated volcanic rocks.

The VHIC is an excellent locality for such a study because the spatially-associated volcanic rocks, including flow-banded rhyolite domes mantled by block-and-ash-flow breccia deposits, almost certainly erupted from the intrusion. However, high-precision CA-TIMS U-Pb zircon ages of five granite samples from the intrusion indicate that the exposed level of the intrusion was constructed over at least 0.7 m.y. (419.9 ± 0.1 Ma to 419.2 ± 0.1 Ma), and two rhyolite tuff samples from the volcanic section indicate that the preserved volcanic rocks are 1.3 m.y. older than the intrusion. We believe this gap in time reflects both the poor preservation of the volcanic sequence and the level of exposure of the intrusion, a conclusion supported by a recent microgravity study of the VHIC, rather than a lack of consanguinity.

Two additional lines of evidence support this conclusion. First, granite samples from the intrusion yielded magmatic zircon crystals, with U-Pb ages that span the gap in time between the VHIC and the volcanic rocks. Given field evidence for rejuvenation of crystal mush during magma replenishment, these older zircon crystals represent antecrysts. Second, the Vinalhaven diabase (VHD), which occurs beneath the oldest block-and-ash flow breccias, contains ubiquitous quartz xenocrysts and rare xenoliths of granite. Together with whole rock major and trace element compositions, these observations suggest that the VHD formed by bulk mixing of gabbro and granite early in the history of the VHIC. Zircon xenocrysts in the VHD are similar in habit, size, color, and zoning characteristics to zircons from the VHIC granite, were almost certainly derived from the VHIC, and must be 421.2 Ma or older. Thus, we believe the pluton was constructed over about 2 m.y.

MATHEMATICS AND STATISTICS

The stick index of a knot K is defined to be the least number of line segments needed to construct a polygonal embedding of K. We define the projection stick index of K to be the least number of line segments in any projection of a polygonal embedding of K. In this paper, we establish bounds on the projection stick index for various torus knots. We then show that the stick index of a (p,2p+1)-torus knot is 4p, and the projection stick index is 2p+1. This provides examples of knots such that the projection stick index is one greater than half the stick index. We show that for all other torus knots for which the stick index is known, the projection stick index is larger than this. We conjecture that a projection stick index of half the stick index is unattainable for any knot.

The relationship between a local ring and its completion has long been known to be important and mysterious. One way of studying this relationship is to examine the dimensions of the formal fiber rings. In this paper, we answer the question; if A is an excellent local integral domain such that the dimension of the formal fiber ring of (0) is positive, then must the set of height-one prime ideals p such that the dimension of the formal fiber ring at (0) is the same as the dimension of the formal fiber ring at p be finite? Since excellent rings behave well, the intuition is that the answer to this question should be yes. We show, however, that there do exist excellent local integral domains such that the set described above is infinite, confirming that in many ways, excellent local rings do not behave as nicely has one might hope.

The Katz-Sarnak conjectures state that the behavior of zeros in families of L-functions are well-modeled by the eigenvalues of a classical compact group. We show we may attach a symmetry constant to many families of L-functions that identifies the corresponding classical compact group. Further, we identify a nice group structure, namely the symmetry constant of the Rankin-Selberg convolution of two families is the product of the symmetry constants. This allows us to predict the associated classical compact group in many new cases, which we then prove.

Auditors are required to use analytical procedures to identify the existence of unusual transactions, events, and trends. Benford's Law gives the expected patterns of the digits in numerical data, and has been advocated as a test for the authenticity and reliability of transaction level accounting data. This paper describes a new second-order test that calculates the digit frequencies of the differences between the ordered ranked) values in a data set. These digit frequencies approximate the frequencies of Benford's Law for most data sets. In the study the second-order test is applied to four sets of transactional data. The second-order test detected errors in data downloads, rounded data, data generated by statistical procedures, and the inaccurate ordering of data. The test can be applied to any data set and nonconformity usually signals some issue related to data integrity that might not have been easily detectable using traditional analytical procedures.

We investigate the relationship between the sizes of the sum and difference sets attached to a subset of {0,1,...,N}, chosen randomly according to a binomial model with parameter p(N), with N^{-1} = o(p(N)). We show that the random subset is almost surely difference dominated, as N --> ∞ for any choice of p(N) tending to zero, thus confirming a conjecture of Martin and O'Bryant. Furthermore, we exhibit a threshold phenomenon regarding the ratio of the size of the difference to the sumset. We also extend our results to the comparison of the generalized difference sets attached to an arbitrary pair of binary linear forms. The heart of our approach involves using different tools to obtain strong concentration of the sizes of the sum and difference sets about their mean values, for various ranges of the parameter p.

In this article, we discuss the remarkable connection between two very different fields, number theory and nuclear physics. We describe the essential aspects of these fields, the quantities studied, and how insights in one have been fruitfully applied in the other. The exciting branch of modern mathematics – random matrix theory – provides the connection between the two fields. We assume no detailed knowledge of number theory, nuclear physics, or random matrix theory; all that is required is some familiarity with linear algebra and probability theory, as well as some results from complex analysis. Our goal is to provide the inquisitive reader with a sound overview of the subjects, placing them in their historical context in a way that is not traditionally given in the popular and technical surveys.

This paper describes a model that generates weekly movie schedules in a multiplex movie theater. A movie schedule specifies within each day of the week, on which screen(s) different movies will be played, and at which time(s). The model consists of two parts: (i) conditional forecasts of the number of visitors per show for any possible starting time; and (ii) an optimization procedure that quickly finds an almost optimal schedule (which can be demonstrated to be close to the optimal schedule). To generate this schedule we formulate the so-called movie scheduling problem as a generalized set partitioning problem. The latter is solved with an algorithm based on column generation techniques. We have applied this combined demand forecasting /schedule optimization procedure to a multiplex in Amsterdam where we supported the scheduling of fourteen movie weeks. The proposed model not only makes movie scheduling easier and less time consuming, but also generates schedules that would attract more visitors than the current ‘intuition-based’ schedules.

We explicitly construct infinite families of MSTD (more sums than differences) sets. There are enough of these sets to prove that there exists a constant C such that at least C/r⁴ of the 2^r subsets of {1, ..., r} are MSTD sets; thus our family is significantly denser than previous constructions (whose densities are at most f(r)=2r=2 for some polynomial f(r)). We conclude by generalizing our method to compare linear forms.

We test the predictions of (a weakened version of) the L-functions Ratios Conjecture for the family of cuspidal newforms of weight k and level N, with either k fixed and N tending to infinity through the primes or N = 1 and k tending to infinity. We study the main and lower order terms in the 1-level density. We provide evidence for the Ratios Conjecture by computing and confirming its predictions up to a power savings in the family’s cardinality, at least for test functions whose Fourier transforms are supported in (-2; 2). We do this both for the weighted and unweighted 1-level density (where in the weighted case we use the Petersson weights), thus showing that either formulation may be used. These two 1-level densities differ by a term of size 1= log(k²n). Finally, we show that there is another way of extending the sums arising in the Ratios Conjecture, leading to a different answer (although the answer is such a lower order term that it is hopeless to observe which is correct).

Much is known about the divisibility of class numbers of both number fields and function fields, but the question of indivisibility of class numbers has proven far more intractable. Almost all previous results are for quadratic fields only, and the fields desired are not constructed explicitly. In this paper, we construct infinitely many function fields of degree m (3 not dividing m) over the rational function field with class number indivisible by 3.

We examine some of the properties of uniformly rigid transformations, and analyze the compatibility of uniform rigidity and (measurable) weak mixing along with some of their asymptotic convergence properties. We show that on Cantor space, there does not exist a finite measure-preserving, totally ergodic, uniformly rigid transformation. We briefly discuss general group actions and show that (measurable) weak mixing and uniform rigidity can coexist in a more general setting.

We define a class of discrete Abelian group extensions of rank-one transformations and establish necessary and sufficient conditions for these extensions to be power weakly mixing. We show that all members of this class are multiply recurrent. We then study conditions sufficient for showing that Cartesian products of transformations are conservative for a class of invertible infinite measure-preserving transformations and provide examples of these transformations.

PHYSICS

The reliability of RNA secondary structure predictions is subject to the accuracy of the underlying free energy model. Mfold and other RNA folding algorithms are based on the Turner model, whose weakest part is its formulation of loop free energies, particularly for multibranch loops. RNA loops contain single-strand and helix-crossing segments, so we develop an enhanced two-length freely jointed chain theory and revise it for self-avoidance. Our resulting universal formula for RNA loop entropy has fewer parameters than the Turner/Mfold model, and yet simulations show that the standard errors for multibranch loop free energies are reduced by an order of magnitude. We further note that coaxial stacking decreases the effective length of multibranch loops and provides, surprisingly, an entropic stabilization of the ordered configuration in addition to the enthalpic contribution of helix stacking. Our formula is in good agreement with measured hairpin free energies. We find that it also improves the accuracy of folding predictions.

We propose a simple physical mechanism to explain the ultrafast first step of vision, a photoinduced cis to trans rotation of retinal. In the ground state, the torsional stability of π bonds is countered by Coulomb interactions acting between the π lobes; the torsional dependence for Coulomb interactions is absent in the often-used Ohno approximation, but restored with our formula. After photoexcitation, the bonding weakens causing the destabilizing terms to dominate. The twist in the ground state due to steric interactions surrounding the 11-cis bond increases the initial torque and thus the speed of the reaction.

We present experimental results showing that quantum correlated light can be produced using non-degenerate, off-resonant, four-wave mixing (4WM) on both the D1 (795 nm) and D2 (780 nm) lines of 85Rb and 87Rb, extending earlier work on the D1 line of 85Rb. Using this 4WM process in a hot vapor cell to produce bright twin beams, we characterize the degree of intensity-difference noise reduction below the standard quantum limit for each of the four systems. Although each system approximates a double-lambda configuration, differences in details of the actual level structure lead to varying degrees of noise reduction. The observation of quantum correlations on light produced using all four of these systems, regardless of their substructure, suggests that it should be possible to use other systems with similar level structures in order to produce narrow frequency, non-classical beams at a particular wavelength.

We present an experimental realization of a low-noise, phase-insensitive optical amplifier using a four-wave mixing interaction in hot Rb vapor. Performance near the quantum limit for a range of amplifier gains, including near unity, can be achieved. Such low-noise amplifiers are essential for so-called quantum cloning machines and are useful in quantum information networks and protocols. We demonstrate that amplification and “cloning” of one half of a two mode squeezed state is possible while preserving entanglement. The inseparability criterion between the two original modes remains satisfied for small to large gains, while the EPR criterion is satisfied for a smaller range. This amplification of quantum correlations paves the way for optimal cloning of a bipartite entangled state.

Using a two-step, two-color laser spectroscopy technique, we have completed a measurement of the hyperfine structure within the 5s26p 2P_3/2 excited state in 115In I=9/2. A frequency stabilized GaN diode laser at 410 nm is locked to the 5P_1/2→6S_1/2 ground-state transition and a second 1291 nm diode laser is scanned over the 6S_1/2→6P_3/2transition to produce hyperfine spectra for the 6P_3/2F=3,4,5,6 manifold. We find the hyperfine splittings of consecutive sublevels to be as follows: 4−3=275.2542 MHz, 5−4=384.0571 MHz, and 6−5=517.4844 MHz. The magnetic dipole, electric quadrupole, and magnetic octupole hyperfine coupling constants derived from these three splittings are, respectively, a=79.337 MHz, b=62.55 MHz, and c=−0.044 MHz. The measured value of the dipole constant, a, agrees to within 2% with a recent theoretical prediction.

Superconducting quantum circuits, such as the superconducting phase qubit, have multiple quantum states that can interfere with ideal qubit operation. The use of multiple frequency control pulses, resonant with the energy differences of the multi-state system, is theoretically explored. An analytical method to design such control pulses is developed, using a generalization of the Floquet method to multiple frequency controls. This method is applicable to optimizing the control of both superconducting qubits and qudits, and is found to be in excellent agreement with time-dependent numerical simulations.

We present a method to synthesize an arbitrary quantum state of two superconducting resonators. This state-synthesis algorithm utilizes a coherent interaction of each resonator with a tunable artificial atom to create entangled quantum superpositions of photon number (Fock) states in the resonators. We theoretically analyze this approach, showing that it can efficiently synthesize NOON states, with large photon numbers, using existing technology.

We build upon work by C. K. Law [Phys. Rev. A 71, 034306 (2005)] to show in general that the entanglement between two fermions largely determines the extent to which the pair behaves like an elementary boson. Specifically, we derive upper and lower bounds on a quantity χ_N+1/χ_N that governs the bosonic character of a pair of fermions when N such pairs approximately share the same wavefunction. Our bounds depend on the purity of the single-particle density matrix, an indicator of entanglement, and demonstrate that if the entanglement is sufficiently strong, the quantity χ_N+1/χ_N approaches its ideal bosonic value.

PSYCHOLOGY

The defense use of participants in the Berkeley Guidance Study, Intergenerational Studies, University of California, Berkeley, was traced longitudinally from pre-adolescence (n = 130) to early adulthood (n = 120). As coded from their TAT stories using the Defense Mechanism Manual (DMM: Cramer, 1991a), the results showed change in defense use at adulthood. Consistent with previous findings, the defense of Projection was used more frequently than Denial at both ages. However, in adulthood there was a decline in the salience of Identification and an increase in the salience of Denial. This change in defense use between pre-adolescence and early adulthood was predicted by both childhood IQ and social class.

A longitudinal study of change in undercontrol, and its relation to the use of defense mechanisms, was studied with participants from the Berkeley Guidance Study of the Institute of Human Development, University of California, Berkeley. It was predicted that use of the immature defense of Denial, but not Projection or Identification, would be related at early adolescence to an increase in undercontrol as assessed from two independent measures. The assessment of Ego Undercontrol indicated that the majority of children decreased with age, but for those who increased at early adolescence, the increase was significantly related to the use of Denial. Similarly, assessment of Externalizing Behavior Problems at early adolescence indicated that an increase in Externalizing Problems was related to the use of Denial. It is suggested that in addition to indicating psychological immaturity, the use of Denial prevents these children from recognizing the negative impact of their undercontrolled behavior.

This chapter demonstrates how the experience of self-doubt may result in an increased use of defense mechanisms. In contrast to other more conscious strategies for protecting the self, defense mechanisms operate outside of awareness. In fact, awareness of their functioning may render them ineffective. In this essay, we focus on three defenses – denial, projection, and identification – that represent a hierarchy of defense development. Whether demonstrated by the observed relation between self-doubt and defense use, as in correlational studies, or shown by experimental studies in which a controlled intervention was used to create self-doubt, there is convincing evidence that the use of defense mechanisms is yet one more way in which the self is protected.

Most theories of inequity focus on relative inequity. In contrast, this paper provides evidence that individuals infer what people should have (i.e. an absolute standard) from the way inequity is described. In the reported experiment, participants give more to a subordinate actor when inequity is described in terms of “less than” rather than “more than,” and take more from a dominant actor when inequity is described in terms of “more than” rather than “less than,” even though the magnitude of inequity is constant. Mediational analyses suggest that these differences are driven by changes in individuals’ perceptions of what the actors should have (i.e. the standard). We conclude by discussing the implications for motivated perceptions of inequity and redistributive policy attitudes.

The relations among infant anger reactivity, approach behavior, and frontal electroencephalogram (EEG) asymmetry, and their relations to inhibitory control and behavior problems in early childhood were examined within the context of a longitudinal study of temperament. Two hundred nine infants' anger expressions to arm restraint were observed at 4 months of age. Infants' approach behaviors during play with an unpredictable toy and baseline frontal EEG asymmetry were assessed at 9 months of age. Inhibitory control during a Go/No-Go task and parent report of behavior problems were evaluated at 4 years of age. High anger-prone infants with left, but not right, frontal EEG asymmetry showed significantly more approach behaviors and less inhibitory control relative to less anger-prone infants. Although a link between anger proneness in infancy and behavior problems in early childhood was not found, a combination of low approach behaviors and poor inhibitory control was predictive of internalizing behaviors.

The temporal stability of delay-discount rates for monetary rewards was assessed using a monetary choice questionnaire (Kirby & Marakovic, 1996). Of 100 undergraduate participants who completed the questionnaire at the initial session, 81 returned 5 weeks later and 46 returned 57 weeks later for subsequent sessions. The 5-week test–retest stability of discount rates was .77 (95% confidence interval 5 .67–.85), the 1-year stability was .71 (.50–.84), and the 57-week stability was .63 (.41–.77). Thus, at least when similar testing situations are reinstated, discount rates as individual differences have 1-year stabilities in the range that is typically obtained for personality traits. Discount rates index an attribute of the person that is relatively stable over time but that is moderated by aspects of the situation, such as reward type and deprivational state.

The hierarchical structure of 95 self-reported impulsivity items, along with delay–discount rates for money, was examined. A large sample of college students participated in the study (N = 407). Items rep- resented every previously proposed dimension of self-reported impulsivity. Exploratory PCA yielded at least seven interpretable components: Prepared/Careful, Impetuous, Divertible, Thrill and Risk Seeking, Happy-Go-Lucky, Impatiently Pleasure Seeking, and Reserved. Discount rates loaded on Impatiently Plea- sure Seeking, and correlated with the impulsiveness and venturesomeness scales from the I7 (Eysenck, Pearson, Easting, & Allsopp, 1985). The hierarchical emergence of the components was explored, and we show how this hierarchical structure may help organize conflicting dimensions found in previous analyses. Finally, we argue that the discounting model (Ainslie, 1975) provides a qualitative framework for understanding the dimensions of impulsivity.

It has long been assumed that metacognition—thinking about one's own thoughts—is a uniquely human ability. Yet a decade of research suggests that, like humans, other animals can differentiate between what they know and what they do not know. They opt out of difficult trials; they avoid tests they are unlikely to answer correctly; and they make riskier "bets" when their memories are accurate than they do when their memories are inaccurate. These feats are simultaneously impressive and, by human standards, somewhat limited; new evidence suggests, however, that animals can generalize metacognitive judgments to new contexts and seek more information when they are unsure. Metacognition is intriguing, in part, because of parallels with self-reflection and conscious awareness. Consciousness appears to be consistent with, but not required by, the abilities animals have demonstrated thus far.

The spacing effect - that is, the benefit of spacing learning events apart rather than massing them together - has been demonstrated in hundreds of experiments, but is not well known to educators or learners. I investigated the spacing effect in the realistic context of flashcard use. Learners often divide flashcards into relatively small stacks, but compared to a large stack, small stacks decrease the spacing between study trials. In three experiments, participants used a web-based study programme to learn GRE-type word pairs. Studying one large stack of flashcards (i.e. spacing) was more effective than studying four smaller stacks of flashcards separately (i.e. massing). Spacing was also more effective than cramming - that is, massing study on the last day before the test. Across experiments, spacing was more effective than massing for 90% of the participants, yet after the first study session, 72% of the participants believed that massing had been more effective than spacing.

The dynamics of human memory are complex and often unintuitive, but certain features—such as the fact that studying results in learning—seem like common knowledge. In 12 experiments, however, participants who were told they would be allowed to study a list of word pairs between 1 and 4 times and then take a cued-recall test predicted little or no learning across trials, notwithstanding their large increases in actual learning. When queried directly, the participants espoused the belief that studying results in learning, but they showed little evidence of that belief in the actual task. These findings, when combined with A. Koriat, R. A. Bjork, L. Sheffer, and S. K. Bar’s (2004) research on judgments of forgetting, suggest a stability bias in human memory—that is, a tendency to assume that the accessibility of one’s memories will remain relatively stable over time rather than benefiting from future learning or suffering from future forgetting.

Taking tests enhances learning. But what happens when one cannot answer a test question—does an unsuccessful retrieval attempt impede future learning or enhance it? The authors examined this question using materials that ensured that retrieval attempts would be unsuccessful. In Experiments 1 and 2, participants were asked fictional general-knowledge questions (e.g., “What peace treaty ended the Calumet War?”). In Experiments 3–6, participants were shown a cue word (e.g., whale) and were asked to guess a weak associate (e.g., mammal); the rare trials on which participants guessed the correct response were excluded from the analyses. In the test condition, participants attempted to answer the question before being shown the answer; in the read-only condition, the question and answer were presented together. Unsuccessful retrieval attempts enhanced learning with both types of materials. These results demonstrate that retrieval attempts enhance future learning; they also suggest that taking challenging tests—instead of avoiding errors—may be one key to effective learning.

Students have to make scores of practical decisions when they study. We investigated the effectiveness of, and beliefs underlying, one such practical decision: the decision to test oneself while studying. Using a flashcards-like procedure, participants studied lists of word pairs. On the second of two study trials, participants either saw the entire pair again (pair mode) or saw the cue and attempted to generate the target (test mode). Participants were asked either to rate the effectiveness of each study mode (Experiment 1) or to choose between the two modes (Experiment 2). The results demonstrated a mismatch between metacognitive beliefs and study choices: Participants (incorrectly) judged that the pair mode resulted in the most learning, but chose the test mode most frequently. A post-experimental questionnaire suggested that self-testing was motivated by a desire to diagnose learning rather than a desire to improve learning.

We investigated whether the superior memory performance sometimes seen with delayed rather than immediate feedback was attributable to the shorter retention interval (or lag to test) from the last presentation of the correct information in the delayed condition. Whether lag to test was controlled or not, delayed feedback produced better final test performance than did immediate feedback, which in turn produced better performance than did no feedback at all, when we tested Grade 6 children learning school-relevant vocabulary. With college students learning GRE-level words, however, delayed feedback produced better performance than did immediate feedback (and both were better than no feedback) when lag to test was uncontrolled, but there was no difference between the delayed and immediate feedback conditions when the lag to test was controlled

Testing previously studied information enhances long-term memory, particularly when the information is successfully retrieved from memory. The authors examined the effect of unsuccessful retrieval attempts on learning. Participants in 5 experiments read an essay about vision. In the test condition, they were asked about embedded concepts before reading the passage; in the extended study condition, they were given a longer time to read the passage. To distinguish the effects of testing from attention direction, the authors emphasized the tested concepts in both conditions, using italics or bolded keywords or, in Experiment 5, by presenting the questions but not asking participants to answer them before reading the passage. Posttest performance was better in the test condition than in the extended study condition in all experiments—a pretesting effect—even though only items that were not successfully retrieved on the pretest were analyzed. The testing effect appears to be attributable, in part, to the role unsuccessful tests play in enhancing future learning.

Learners of all ages face complex decisions about how to study effectively. Here we investigated three such decisions made in concert—time allocation, ordering, and spacing. First, college students were presented with, and made judgments of learning about, 16 word-synonym pairs. Then, when presented with all 16 pairs, they created their own study schedule by choosing when and how long to study each item. The results indicated that (a) the most study time was allocated to difficult items, (b) relatively easy items tended to be studied first, and (c) participants spaced their study at a rate significantly greater than chance. The spacing data, which are of particular interest, differ from previous findings that have suggested that people, including adults, believe massing is more effective than spacing.

Recent DNA exonerations have shed light on the problem that people sometimes confess to crimes they did not commit. Drawing on police practices, laws concerning the admissibility of confession evidence, core principles of psychology, and forensic studies involving multiple methodologies, this White Paper summarizes what is known about police-induced confessions. In this review, we identify suspect characteristics (e.g., adolescence; intellectual disability; mental illness, and certain personality traits), interrogation tactics (e.g., excessive interrogation time; presentations of false evidence; minimization), and the phenomenology of innocence (e.g., the tendency to waive Miranda rights) that influence confessions, as well as their effects on judges and juries. This article concludes with a strong recommendation for the mandatory electronic recording of interrogations and considers other possibilities for the reform of interrogation practices and the protection of vulnerable suspect populations. [This is an official White Paper of the American Psychology-Law Society)

Reviewing the literature on police-induced confessions, we identified suspect characteristics and interrogation tactics that influence confessions and their effects on juries. We concluded with a call for the mandatory electronic recording of interrogations and a consideration of other possible reforms. The preceding commentaries make important substantive points that can lead us forward—on the effects of videotaping of interrogations on case dispositions; on the study of non-custodial methods, such as the controversial Mr. Big technique; and on an analysis of why confessions, once withdrawn, elicit such intractable responses compared to statements given by child and adult victims. Toward these ends, we hope that this issue provides a platform for future research aimed at improving the diagnostic value of confession evidence.

Crime suspects in the U.S. are typically questioned in a two-step process aimed, first, at behavioral lie detection during a pre-interrogation interview, followed by the elicitation of a confession during the interrogation itself (in Great Britain, the practice of investigative interviewing does not make this sharp distinction). Research conducted on the first step shows that police investigators often target innocent people for interrogation because of erroneous but confident judgments of deception. Research on the second step shows that innocent people are sometimes induced to confess to crimes they did not commit as a function of certain dispositional vulnerabilities or the use of overly persuasive interrogation tactics. Citing recent studies, this paper proposes that laboratory paradigms be used to help build more diagnostic models of interrogation. Substantively, we suggest that the British PEACE approach to investigative interviewing may provide a potentially effective alternative to the classic American interrogation. As a matter of policy, we suggest that the videotaping of entire interrogations from a balanced camera perspective is necessary to improve the fact finding accuracy of judges and juries who must evaluate confession evidence in court.

A confession is potent evidence, persuasive to judges and juries. Is it possible that a confession can also affect other evidence? The present study tested the hypothesis that a confession will alter eyewitness identification decisions. Two days after witnessing a theft and making an identification decision from a blank lineup, participants were told that certain lineup members had confessed or denied guilt during a subsequent interrogation. Among those who had made a selection but were told that another lineup member confessed, 61% changed their identifications—and did so with confidence. Among those who had not made an identification, 50% went on to select the confessor when his identity was known. These findings challenge the presumption in law that different forms of evidence are independent and suggest an important overlooked mechanism by which innocent confessors are wrongfully convicted—namely, that potentially exculpatory evidence is corrupted by the confession itself.

The anxiolytic neurosteroid allopregnanolone (3α-hydroxy-5α-pregnan-20-one or 3α,5α-THP) has been proposed to play a developmental role in emergent neural regulation of affective behavior. This experiment examined whether allopregnanolone administered during the last week of gestation in rats would alter neonatal and adult offspring behaviors in the selectively-bred High vocalizing line, who have low levels of allopregnanolone and high levels of anxious/depressive behaviors. Dams were injected twice a day with the neurosteroid or vehicle, or handled as controls, and were tested on the elevated plus maze just before parturition. Maternal behavior was assessed throughout the first week of life, and affective behavior in the offspring was tested at one week of age (ultrasonic vocalizations test) and as adults (plus maze and forced swim tests). Offspring prenatally exposed to allopregnanolone were less anxious as neonates and less depressed as adults compared to both control groups. Only male adult offspring, however, revealed less anxious behavior on the plus maze. Neither prenatal anxiety nor postnatal maternal behavior was affected by gestational allopregnanolone, suggesting that this prenatal exposure had a direct, long-lasting effect on the developing fetal brain independent of mediating maternal factors. These results are discussed in light of new evidence about the developmental role of the GABA-A receptor prenatally.

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Quaternary Intertidal Deposits Intercalated with Volcanic Rocks on Isla Sombrero Chino
in the Galápagos Islands, Ecuador

MATHEMATICS AND STATISTICS

PHYSICS

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FACULTY PUBLICATIONS

ASTRONOMY

BIOLOGY

CHEMISTRY

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GEOSCIENCES

Quaternary Intertidal Deposits Intercalated with Volcanic Rocks on Isla Sombrero Chino in the Galápagos Islands, Ecuador

MATHEMATICS AND STATISTICS

PHYSICS

PSYCHOLOGY

Quaternary Intertidal Deposits Intercalated with Volcanic Rocks on Isla Sombrero Chino
in the Galápagos Islands, Ecuador