Showing papers by "Albion College published in 2009"

Obliquity-paced Pliocene West Antarctic ice sheet oscillations

Abstract: Thirty years after oxygen isotope records from microfossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth's orbital geometry control the ice ages, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles. Furthermore, an understanding of the behaviour of the marine-based West Antarctic ice sheet (WAIS) during the 'warmer-than-present' early-Pliocene epoch ( approximately 5-3 Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming. Here we present a marine glacial record from the upper 600 m of the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, approximately 40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth's axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to approximately 3 degrees C warmer than today and atmospheric CO(2) concentration was as high as approximately 400 p.p.m.v. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model that simulates fluctuations in Antarctic ice volume of up to +7 m in equivalent sea level associated with the loss of the WAIS and up to +3 m in equivalent sea level from the East Antarctic ice sheet, in response to ocean-induced melting paced by obliquity. During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt under conditions of elevated CO(2).

The stratigraphic signature of the late Cenozoic Antarctic Ice Sheets in the Ross Embayment

Abstract: A 1284.87-m-long sediment core (AND-1B) from beneath the McMurdo sector of the Ross Ice Shelf provides the most complete single section record to date of fluctuations of the Antarctic Ice Sheets over the last 13 Ma. The core contains a succession of subglacial, glacimarine, and marine sediments that comprise ∼58 depositional sequences of possible orbital-scale duration. These cycles are constrained by a chronology based on biostratigraphic, magnetostratigraphic, and 40 Ar/ 39 Ar isotopic ages. Each sequence represents a record of a grounded ice-sheet advance and retreat cycle over the AND-1B drill site, and all sediments represent subglacial or marine deposystems with no subaerial exposure surfaces or terrestrial deposits. On the basis of characteristic facies within these sequences, and through comparison with sedimentation in modern glacial environments from various climatic and glacial settings, we identify three facies associations or sequence “motifs” that are linked to major changes in ice-sheet volume, glacial thermal regime, and climate. Sequence motif 1 is documented in the late Pleistocene and in the early Late Miocene intervals of AND-1B, and it is dominated by diamictite of subglacial origin overlain by thin mudstones interpreted as ice-shelf deposits. Motif 1 sequences lack evidence of subglacial meltwater and represent glaciation under cold, “polar”-type conditions. Motif 2 sequences were deposited during the Pliocene and early Pleistocene section of AND-1B and are characterized by subglacial diamictite overlain by a relatively thin proglacial-marine succession of mudstone-rich facies deposited during glacial retreat. Glacial minima are represented by diatom-bearing mudstone, and diatomite. Motif 2 represents glacial retreat and advance under a “subpolar” to “polar” style of glaciation that was warmer than present, but that had limited amounts of subglacial meltwater. Sequence motif 3 consists of subglacial diamictite that grades upward into a 5- to 10-m-thick proglacial retreat succession of stratified diamictite, graded conglomerate and sandstone, graded sandstone, and/or rhythmically stratified mudstone. Thick mudstone intervals, rather than diatomite-dominated deposition during glacial minima, suggest increased input of meltwater from nearby terrestrial sources during glacial minima. Motif 3 represents Late Miocene “subpolar”-style glaciation with significant volumes of glacially derived meltwater.

Botnet Economics: Uncertainty Matters

Abstract: Botnets have become an increasing security concern in today’s Internet. Thus far the mitigation to botnet attacks is a never ending arms race focusing on technical approaches. In this chapter, we model botnet-related cybercrimes as a result of profit-maximizing decision-making from the perspectives of both botnet masters and renters/attackers. From this economic model, we can understand the effective rental size and the optimal botnet size that can maximize the profits of botnet masters and attackers. We propose the idea of using virtual bots (honeypots running on virtual machines) to create uncertainty in the level of botnet attacks. The uncertainty introduced by virtual bots has a deep impact on the profit gains on the botnet market. With decreasing profitability, botnet-related attacks such as DDoS are reduced if not eliminated from the root cause, i.e. economic incentives.

Symmetric and asymmetric mitotic segregation patterns influence Wolbachia distribution in host somatic tissue.

Abstract: Wolbachia are maternally inherited bacterial endosymbionts that occupy many but not all tissues of adult insects. During the initial mitotic divisions in Drosophila embryogenesis, Wolbachia exhibit a symmetric pattern of segregation. Wolbachia undergo microtubule-dependent and cell-cycle-regulated movement between centrosomes. Symmetric segregation occurs during late anaphase when Wolbachia cluster around duplicated and separating centrosomes. This centrosome association is microtubule-dependent and promotes an even Wolbachia distribution throughout the host embryo. By contrast, during the later embryonic and larval neuroblast divisions, Wolbachia segregate asymmetrically with the apical self-renewing neuroblast. During these polarized asymmetric neuroblast divisions, Wolbachia colocalize with the apical centrosome and apically localized Par complex. This localization depends on microtubules, but not the cortical actin-based cytoskeleton. We also found that Wolbachia concentrate in specific regions of the adult brain, which might be a direct consequence of the asymmetric Wolbachia segregation in the earlier neuroblast divisions. Finally, we demonstrate that the fidelity of asymmetric segregation to the self-renewing neuroblast is lower in the virulent Popcorn strain of Wolbachia.

Strain Heterogeneity and Damage Nucleation at Grain Boundaries during Monotonic Deformation in Commercial Purity Titanium

Abstract: Heterogeneous strain was analyzed in polycrystalline, commercial-purity titanium using many experimental techniques that provide information about microstructure, dislocation arrangement, grain orientation, orientation gradients, surface topography, and local strain gradients. The recrystallized microstructure with 50–200 µm grains was extensively characterized before and after deformation using 4-point bending to strains between 2% and 15%. Extremely heterogeneous deformation occurred along some grain boundaries, leading to orientation gradients exceeding 10° over 10–20 µm. Patches of highly characterized micro-structure were modeled using crystal plasticity finite element (CPFE) analysis to simulate the deformation to evaluate the ability of the CPFE model to capture local deformation processes. Damage nucleation events were identified that are associated with twin interactions with grain boundaries. Progress toward identifying fracture initiation criteria based upon slip and twin interactions with grain boundaries is illustrated with related CPFE simulations of deformation in a TiAl alloy.

Life history phenology differences between southern and northern populations of the apple maggot fly, Rhagoletis pomonella

Abstract: The textbook version of sympatric host race formation in Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) features an ancestral hawthorn-infesting race and a derived apple race differing in life-history timing and response to host fruit odor. However, previous research has focused largely on northeastern North America. To investigate life-history timing in poorly studied southeastern North American populations with very diverse hosts, we performed common garden experiments on emergence time on six southern R. pomonella populations and four other R. pomonella species-group populations. Findings were: (1) the diverse adult emergence times of southern populations resulted largely from genetic differences; (2) some southern populations had bimodal emergence curves; (3) correlations of allozyme markers and emergence times were uncommon in southern populations; and (4) mean emergence times from common garden rearings and dates of field collection of the populations were strongly correlated.

Conservation of arthropod midline netrin accumulation revealed with a cross-reactive antibody provides evidence for midline cell homology.

Abstract: Although many similarities in arthropod CNS development exist, differences in axonogenesis and the formation of midline cells, which regulate axon growth, have been observed. For example, axon growth patterns in the ventral nerve cord of Artemia franciscana differ from that of Drosophila melanogaster. Despite such differences, conserved molecular marker expression at the midline of several arthropod species indicates that midline cells may be homologous in distantly related arthropods. However, data from additional species are needed to test this hypothesis. In this investigation, nerve cord formation and the putative homology of midline cells were examined in distantly related arthropods, including: long- and short-germ insects (D. melanogaster, Aedes aeygypti, and Tribolium castaneum), branchiopod crustaceans (A. franciscana and Triops longicauditus), and malacostracan crustaceans (Porcellio laevis and Parhyale hawaiensis). These comparative analyses were aided by a cross-reactive antibody generated against the Netrin (Net) protein, a midline cell marker and regulator of axonogenesis. The mechanism of nerve cord formation observed in Artemia is found in Triops, another branchiopod, but is not found in the other arthropods examined. Despite divergent mechanisms of midline cell formation and nerve cord development, Net accumulation is detected in a well-conserved subset of midline cells in branchiopod crustaceans, malacostracan crustaceans, and insects. Notably, the Net accumulation pattern is also conserved at the midline of the amphipod P. hawaiensis, which undergoes split germ-band development. Conserved Net accumulation patterns indicate that arthropod midline cells are homologous, and that Nets function to regulate commissure formation during CNS development of Tetraconata.

Dialogue : Shrimp aquaculture in Thailand : A response to Vandergeest, Flaherty, and Miller

Abstract: Les AA. apportent une reponse critique a un precedent article de Vandergeest, Flaherty et Miller concernant l'aquaculture de la crevette en Thailande. Ils contestent notamment le rapport etabli entre les fermes d'aquaculture et les complexes industriels agro-alimentaires, et s'interrogent sur la pertinence de l'approche de l'ecologie politique dans ce champ de recherche

Apollo 17 regolith, 71501,262: A record of impact events and mare volcanism in lunar glasses

Abstract: Thirteen glasses from Apollo 17 regolith 71501,262 have been chemically analyzed by electron microprobe and isotopically dated with the 40Ar/39Ar dating method We report here the first isotopic age obtained for the Apollo 17 very low titanium (VLT) volcanic glasses, 3630 ± 40 Ma Twelve impact glasses that span a wide compositional range have been found to record ages ranging from 102 ± 20 Ma to 3740 ± 50 Ma The compositions of these impact glasses show that some have been produced by impact events within the Apollo 17 region, whereas others appear to be exotic to the landing site As the data sets that include compositions and ages of lunar impact glasses increase, the impact history in the Earth-Moon system will become better constrained

Field-scale cleanup of atrazine and cyanazine contaminated soil with a combined chemical-biological approach.

Abstract: A former agrichemical dealership in western Nebraska was suspected of having contaminated soil. Our objective was to characterize and remediate the contaminated site by a combined chemical-biological approach. This was accomplished by creating contour maps of the on-site contamination, placing the top 60 cm of contaminated soil in windrows and mixing with a mechanical high-speed mixer. Homogenized soil containing both atrazine [6-chloro-N-ethyl-N'-isopropyl-1,3,5-triazine-2,4-diamine] and cyanazine {2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl] amino]-2-methylpropanenitrile} was then used in laboratory investigations to determine optimum treatments for pesticide destruction. Iron suspension experiments verified that zerovalent iron (Fe(0)) plus ferrous sulfate (FeSO(4).7H(2)O) removed more than 90% of both atrazine and cyanazine within 14 d. Liquid chromatography/mass spectrometry (LC/MS) analysis of the atrazine solution after treating with Fe(0) and ferrous sulfate identified several degradation products commonly associated with biodegradation (i.e., deethlyatrazine (DEA), deisopropylatrazine (DIA), hydroxyatrazine (HA), and ammelines). Biological treatment evaluated emulsified soybean [Glycine max (L.) Merr.] oil (EOS) as a carbon source to stimulate biodegradation in static soil microcosms. Combining emulsified soybean oil with the chemical amendments resulted in higher destruction efficiencies (80-85%) and reduced the percentage of FeSO(4) needed. This chemical-biological treatment (Fe(0) + FeSO(4) + EOS, EOS Remediation, Raleigh, NC) was then applied with water to 275 m(3) of contaminated soil in the field. Windrows were tightly covered with clear plastic to increase soil temperature and maintain soil water content. Temporal sampling (0-342 d) revealed atrazine and cyanazine concentrations decreased by 79 to 91%. These results provide evidence that a combined chemical-biological approach can be used for on-site, field-scale treatment of pesticide-contaminated soil.

Spatio-temporal differences in the use of agricultural fields by male and female wood turtles (Glyptemys insculpta) inhabiting an agri-forest mosaic.

Abstract: —Recent studies have highlighted negative effects of agricultural activity on populations of the Wood Turtle (Glyptemys insculpta). Mitigating effects of agriculture on this imperiled species will require a thorough understanding of sexual and spatio-temporal differences in the use of fields by turtles. We investigated these factors using radio-telemetry data collected at the north-eastern limit of the species’ range in Nova Scotia, Canada. Males used hayfields more frequently and for a greater proportion of the active season than did females, exposing them to greater risk of machineryrelated mortality. Maintaining 43 m riparian buffer zones would protect males 95% of the time, although such buffers would encompass less than 65% of female movements. The only two mortalities recorded in our study were males. Perhaps more importantly, these males were killed during the second harvest, illustrating that the recommendations of a previous study, which suggested that disc mower blades be raised only during the first harvest, might not apply throughout the species’ range. Possible strategies for conserving Wood Turtles within agricultural landscapes are discussed.

Need for Cognition and Conscientiousness as Predictors of Political Interest and Voting Strategy1

Abstract: Participants (N = 251) used an Internet-based information board to learn about fictional U.S. presidential candidates in a voting simulation task. Need for cognition and conscientiousness interacted to predict political interest. Participants high in need for cognition and participants high in conscientiousness, regardless of the magnitude of the other construct, exhibited high political interest. Participants low in need for cognition and conscientiousness exhibited low political interest. Additionally, participants high in need for cognition or low in conscientiousness preferred an issue-based voting strategy, whereas those low in need for cognition or high in conscientiousness preferred a candidate-based voting strategy. These findings have important implications for how political information should be disseminated to voters through Internet means, such as political websites.

Text from Truchet Tiles

Abstract: A way to create text with Truchet tiles is presented where each letter is represented by a particular grouping of Truchet tiles. The resulting text is rendered in a surprisin gly and visually appealing manner within a tiled region.

A Palatable Introduction to and Demonstration of Statistical Main Effects and Interactions

Abstract: Because concrete explanations in a familiar context facilitate understanding, we illustrate the concept of an interaction via a baking analogy to provide students with food for thought. The demonstration initially introduces the concepts of independent and dependent variables using a chocolate chip cookie recipe. The demonstration provides an opportunity to distinguish between the main effect of an ingredient and the interactions between ingredients on taste perception. Student performance on exam questions suggests that this demonstration effectively helps students understand the concept and interpretation of an interaction.

Using Semiotics to Teach Rational Numbers to Prospective Elementary School Teachers

Abstract: Prospective elementary mathematics teachers should be able to understand how their future students understand number concepts. A difficult concept is that of rational numbers. Rational numbers often have complicated means of representation, signifiers and signifieds, making them difficult for students to understand and teach. In this paper, we describe how one teacher integrates a theory of semiotics when instructing prospective elementary school teachers about rational numbers. We propose that by teaching prospective teachers about semiotics, connections between signs and units are made explicit and prospective teachers will be more equipped to approach the instruction of rational numbers to future students.

Isotope Effects in Low Energy Ion-Atom Collisions

Abstract: Isotope effects for charge transfer processes have recently received increased attention. The ion-atom merged-beams apparatus at Oak Ridge National Laboratory is used to measure charge transfer for low energy collisions of multi-charged ions with H and D and is therefore well suited to investigate isotope effects. The apparatus has been relocated and upgraded to accept high velocity beams from the 250 kV High Voltage Platform at the Multi-Charged Ion Research Facility. The intense higher velocity multi-charged ion beams allow, for the first time, measurements with both H and D from keV/u down to meV/u collision energies in the center-of-mass frame. When charge transfer occurs at relatively large inter-nuclear distances (via radial couplings) the ion-induced dipole attraction can lead to trajectory effects, causing differences in the charge transfer cross sections for H and D. A strong isotope effect (nearly a factor of two) has been observed in the cross section for Si4+ + H(D) below 0.1 eV/u. However, little or no difference is observed for N2+ + H(D). Recently, strong effects have been predicted for the fundamental system He2+ + H(D,T) at collision energies below 200 eV/u where charge transfer occurs primarily through united-atom rotational coupling. We are currently exploring systemsmore » where rotational coupling is important and isotopic differences in the cross section can be observed.« less

Information game of public firewall rules

Abstract: Firewalls are among the most important components in network security. Traditionally, the rules of the firewall are kept private under the assumption that privacy of the ruleset makes attacks on the network more difficult. We posit that this assumption is no longer valid in the Internet of today due to two factors: the emergence of botnets reducing probing difficulty and second, the emergence of distributed applications where private rules increase the difficulty of troubleshooting. We argue that the enforcement of the policy is the key, not the secrecy of the policy itself. In this paper, we demonstrate through the application of game theory that public firewall rules when coupled with false information (lying) are not only viable but actually better.

Production, Characterization, and Measurement of H(D) Beams on the ORNL Merged-Beams Experiment

Abstract: Total cross section measurements of electron capture processes are being studied for low‐energy, Aq++H(D) collisions using the Ion‐Atom Merged‐Beams apparatus at the Multicharged Ion Research Facility (MIRF) at Oak Ridge National Laboratory (ORNL). On this apparatus, a modified Faraday cup detector is used to measure the intensity of the neutral beam. The conversion of the measured electrical current to the true neutral particle beam current is necessary to accurately determine the true cross section values. Inherent in this conversion process is the number of secondary electrons (γ) emitted from the surface of the detector upon impact of an atom. The method employed to determine γ and its role in the absolute electron capture measurements at ORNL‐MIRF are presented. With a recent upgrade to the apparatus, the neutral beam H(D) production technique has been improved and is discussed in detail in this paper.