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2009

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Articles 6241 - 6270 of 6337

Full-Text Articles in Physical Sciences and Mathematics

Measurement Of The W Boson Mass, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Jan 2009

Measurement Of The W Boson Mass, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present a measurement of the W boson mass in W → ev decays using 1 fb-1 of data collected with the D0 detector during Run II of the Fermilab Tevatron collider. With a sample of 499830 W → ev candidate events, we measure MW = 80.401 ± 0.043 GeV. This is the most precise measurement from a single experiment.

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Measurement Of Dijet Angular Distributions At √S = 1.96 Tev And Searches For Quark Compositeness And Extra Spatial Dimensions, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Jan 2009

Measurement Of Dijet Angular Distributions At √S = 1.96 Tev And Searches For Quark Compositeness And Extra Spatial Dimensions, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We present the first measurement of dijet angular distributions in pp collisions at √s = 1.96 TeV at the Fermilab Tevatron Collider. The measurement is based on a dataset corresponding to an integrated luminosity of 0:7 fb-1 collected with the D0 detector. Dijet angular distributions have been measured over a range of dijet masses, from 0.25 TeV to above 1.1 TeV. The data are in good agreement with the predictions of perturbative QCD and are used to constrain new physics models including quark compositeness, large extra dimensions, and TeV-1 scale extra dimensions. For all models considered, we …

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Direct Measurement Of The Mass Difference Between Top And Antitop Quarks, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Jan 2009

Direct Measurement Of The Mass Difference Between Top And Antitop Quarks, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present a measurement of the mass difference between t and t quarks in lepton + jets final states of tt events in 1 fb-1 of data collected with the D0 detector from Fermilab Tevatron Collider pp collisions at √s = 1.96 TeV. The measured mass difference of 3.8 ± 3.7 GeV is consistent with the equality of t and t masses. This is the first direct measurement of a mass difference between a quark and its antiquark partner.

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Search For The Standard Model Higgs Boson In Tau Final States, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Jan 2009

Search For The Standard Model Higgs Boson In Tau Final States, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present a search for the standard model Higgs boson using hadronically decaying tau leptons, in 1 fb-1 of data collected with the D0 detector at the Fermilab Tevatron pp collider. We select two final states: τ± plus missing transverse energy and b jets, and τ+τ- plus jets. These final states are sensitive to a combination of associated W/Z boson plus Higgs boson, vector boson fusion, and gluon-gluon fusion production processes. The observed ratio of the combined limit on the Higgs production cross section at the 95% C.L. to the standard model expectation is 29 …

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Search For Resonant Pair Production Of Neutral Long-Lived Particles Decaying To Bb In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Jan 2009

Search For Resonant Pair Production Of Neutral Long-Lived Particles Decaying To Bb In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We report on a first search for resonant pair production of neutral long-lived particles (NLLP) which each decay to a bb pair, using 3.6 fb-1 of data recorded with the D0 detector at the Fermilab Tevatron collider. We search for pairs of displaced vertices in the tracking detector at radii in the range 1.6–20 cm from the beam axis. No significant excess is observed above background, and upper limits are set on the production rate in a hidden-valley benchmark model for a range of Higgs boson masses and NLLP masses and lifetimes.

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Search For Next-To-Minimal Supersymmetric Higgs Bosons In The H → Aa → Μμμμ, Μμττ Channels Using Pp Collisions At √S = 1.96 Tev, V.M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Jan 2009

Search For Next-To-Minimal Supersymmetric Higgs Bosons In The H → Aa → Μμμμ, Μμττ Channels Using Pp Collisions At √S = 1.96 Tev, V.M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We report on a first search for production of the lightest neutral CP-even Higgs boson (h) in the next-to-minimal supersymmetric standard model, where h decays to a pair of neutral pseudoscalar Higgs bosons (a), using 4.2 fb-1 of data recorded with the D0 detector at Fermilab. The a bosons are required to either both decay to μ+μ- or one to μ+μ and the other to τ+τ. No significant signal is observed, and we set limits on its production as functions of Ma and Mh.

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Search For Long-Lived Charged Massive Particles With The D0 Detector, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Jan 2009

Search For Long-Lived Charged Massive Particles With The D0 Detector, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We search for long-lived charged massive particles using 1.1 fb-1 of data collected by the D0 detector at the Fermilab Tevatron pp Collider. Time-of-flight information is used to search for pair produced long-lived tau sleptons, gauginolike charginos, and Higgsino-like charginos. We find no evidence of a signal and set 95% C.L. cross section upper limits for staus, which vary from 0.31 to 0.04 pb for stau masses between 60 and 300 GeV. We also set lower mass limits of 206 GeV (171 GeV) for pair produced charged gauginos (Higgsinos).

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Self-Assembly Of Magnetic Ni Nanoparticles Into 1d Arrays With Antiferromagnetic Order, Valery Bliznyuk, Srikanth Singamaneni, Sarbeswar Sahoo, Srinivas Polisetty, Xi He, Christian Binek Jan 2009

Self-Assembly Of Magnetic Ni Nanoparticles Into 1d Arrays With Antiferromagnetic Order, Valery Bliznyuk, Srikanth Singamaneni, Sarbeswar Sahoo, Srinivas Polisetty, Xi He, Christian Binek

Christian Binek Publications

In this paper, we report on the magnetic properties of isolated nanoparticles and interacting nanochains formed by the self-assembly of Ni nanoparticles. The magnetic properties were studied using superconducting quantum interference device (SQUID) magnetometry and magnetic force microscopy (MFM). We demonstrate that single-domain Ni nanoparticles spontaneously form one-dimensional (1D) chains under the influence of an external magnetic field. Furthermore, such magnetic field-driven self-assembly in conjunction with surface templating produces regular arrays of 1D nanochains with antiferromagnetic intra-chain order. The antiferromagnetic order, which is in striking contrast to what is found for non-interacting nanoparticle assemblies within the chains, can be evidenced …

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Simulation Of Boundary Layer Trajectory Dispersion Sensitivity To Soil Moisture Conditions: Mm5 And Noah-Based Investigation, Rezaul Mahmood Jan 2009

Simulation Of Boundary Layer Trajectory Dispersion Sensitivity To Soil Moisture Conditions: Mm5 And Noah-Based Investigation, Rezaul Mahmood

School of Natural Resources: Faculty Publications

No abstract provided.

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A System For Estimating Bowen Ratio And Evaporation From Waste Lagoons, Rezaul Mahmood Jan 2009

A System For Estimating Bowen Ratio And Evaporation From Waste Lagoons, Rezaul Mahmood

School of Natural Resources: Faculty Publications

No abstract provided.

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Near Surface Atmospheric Response To Simulated Changes In Land-Cover, Vegetation Fraction, And Soil Moisture Over Western Kentucky, Rezaul Mahmood Jan 2009

Near Surface Atmospheric Response To Simulated Changes In Land-Cover, Vegetation Fraction, And Soil Moisture Over Western Kentucky, Rezaul Mahmood

School of Natural Resources: Faculty Publications

No abstract provided.

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Dipole-Induced, Thermally Stable Lamellar Structure By Polar Aromatic Silane, Jinyue Jiang, Ocelio V. Lima, Yong Pei, Xiao Cheng Zeng, Li Tan, Eric Forsythe Jan 2009

Dipole-Induced, Thermally Stable Lamellar Structure By Polar Aromatic Silane, Jinyue Jiang, Ocelio V. Lima, Yong Pei, Xiao Cheng Zeng, Li Tan, Eric Forsythe

Xiao Cheng Zeng Publications

Lamellar structures, consisting of alternating inorganic layers separated by organic moieties, have attracted much attention over a wide range of applications, such as polymer-clay composites, rheology control, and optoelectronic devices. Organosilanes are ideal candidates for such efforts due to their ability to self-assemble and the intrinsic hybrid configuration of organic/inorganic moieties. Yet, the main emphasis has been focused on alkylsilane, where an alkyl group is linked with a silane terminal, i.e., R-SiX3 (R is alkane and X can be halogen or alkoxy). Construction of stacked monolayers of alkylsilane through chemisorption is possible. The demonstrated pathway usually takes place after …

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Materials Design Of Half-Metallic Graphene And Graphene Nanoribbons, Menghao Wu, Xiaojun Wu, Yi Gao, Xiao Cheng Zeng Jan 2009

Materials Design Of Half-Metallic Graphene And Graphene Nanoribbons, Menghao Wu, Xiaojun Wu, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Through patterned chemical modification, we show that both graphene sheets and zigzag-edged graphene nanoribbons (ZGNRs) can be converted to half-metals as long as the unmodified carbon strip (or width of ZGNRs) is sufficiently wide. Periodically functionalized graphene can mimic electronic behavior of edge-modified ZGNRs as the edge-modified zigzag carbon chains effectively divide a graphene sheet into a series of identical ZGNRs.

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First-Principles Study Of Methane Dehydrogenation On A Bimetallic Cu/N(111) Surface, Wei An, Xiao Cheng Zeng, C. Heath Turner Jan 2009

First-Principles Study Of Methane Dehydrogenation On A Bimetallic Cu/N(111) Surface, Wei An, Xiao Cheng Zeng, C. Heath Turner

Xiao Cheng Zeng Publications

We present density-functional theory calculations of the dehydrogenation of methane and CHx (x = 1 – 3) on a Cu/Ni(111) surface, where Cu atoms are substituted on the Ni surface at a coverage of 1/4 monolayer.

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On The Phase Diagram Of Water With Density Functional Theory Potentials: The Melting Temperature Of Ice /H With The Perdew–Burke–Ernzerhof And Becke–Lee–Yang–Parr Functionals, Soohaeng Yoo, Xiao Cheng Zeng, Sotiris C. Xantheas Jan 2009

On The Phase Diagram Of Water With Density Functional Theory Potentials: The Melting Temperature Of Ice /H With The Perdew–Burke–Ernzerhof And Becke–Lee–Yang–Parr Functionals, Soohaeng Yoo, Xiao Cheng Zeng, Sotiris C. Xantheas

Xiao Cheng Zeng Publications

The melting temperature (Tm) of ice Ih was determined from constant enthalpy and pressure (NPH) Born–Oppenheimer molecular dynamics simulations to be 417±3 K for the Perdew–Burke– Ernzerhof and 411±4 K for the Becke–Lee–Yang–Parr density functionals using a coexisting ice (Ih)-liquid phase at constant pressures of P=2500 and 10 000 bar and a density p=1 g/cm3, respectively.

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Noncovalent Interactions In The Asymmetric Synthesis Of Rigid, Conjugated Helical Structures, Makoto Miyasaka, Maren Pink, Suchada Rajca, Andrzej Rajca Jan 2009

Noncovalent Interactions In The Asymmetric Synthesis Of Rigid, Conjugated Helical Structures, Makoto Miyasaka, Maren Pink, Suchada Rajca, Andrzej Rajca

Andrzej Rajca Publications

Helical supramolecular architecture, such as helical foldamers, supramolecular helicates and aggregates, helical molecules, macromolecules, and oligomers, is a fascinating topic of interest in chemistry and materials science. Although such supramolecular structures may provide advantages in the design of stimuli-responsive and functional materials, the weak nature of the noncovalent forces, as well as the dependency of the dynamic process on their local environments, may hinder their possible applications because of their limited structural stability and processibility. Stabilization of these supramolecular structures could be achieved by modification of the molecular backbone with specific functional groups that permit intramolecular cross-linking, in which covalent …

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Paleohydrology Of Kangerlussuaq (Søndre Strømfjord), West Greenland During The Last ~8,000 Years, Frank Aebly, Sherilyn C. Fritz Jan 2009

Paleohydrology Of Kangerlussuaq (Søndre Strømfjord), West Greenland During The Last ~8,000 Years, Frank Aebly, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Major fluctuations of hydroclimate in West Greenland are recorded in paleoshoreline terraces that encircle several lakes near Kangerlussuaq, Greenland (67°01’N, 50°40’W). Geomorphic and stratigraphic analyses were used to construct a lake-level curve for Hunde Sø, a large closed-basin lake in this region. Changes in lake volume associated with lake-level fluctuations were calculated, and a water-balance model was used to determine the primary factors influencing lake volume and the changes in those factors necessary to affect reconstructed lake-level change. Sensitivity tests suggest that mean annual precipitation and the relative proportion of summer versus winter precipitation are the primary climate drivers of …

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Androgen-Stimulated Udp-Glucose Dehydrogenase Expression Limits Prostate Androgen Availability Without Impacting Hyaluronan Levels, Qin Wei, Robert Galbenus, Ashraf Raza, Ronald Cerny, Melanie A. Simpson Jan 2009

Androgen-Stimulated Udp-Glucose Dehydrogenase Expression Limits Prostate Androgen Availability Without Impacting Hyaluronan Levels, Qin Wei, Robert Galbenus, Ashraf Raza, Ronald Cerny, Melanie A. Simpson

Ronald Cerny Publications

UDP-glucose dehydrogenase (UGDH) oxidizes UDP-glucose to UDP-glucuronate, an essential precursor for production of hyaluronan (HA), proteoglycans, and xenobiotic glucuronides. High levels of HA turnover in prostate cancer are correlated with aggressive progression. UGDH expression is high in the normal prostate even though HA accumulation is virtually undetectable. Thus, its normal role in the prostate may be to provide precursors for glucuronosyltransferase enzymes, which inactivate and solubilize androgens by glucuronidation. In this report, we quantified androgen dependence of UGDH, glucuronosyltransferase, and HA synthase expression. Androgen dependent and independent human prostate cancer cell lines were used to test the effects of UGDH …

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Continuous And Smooth Potential Energy Surface For Conductorlike Screening Solvation Model Using Fixed Points With Variable Areas, Peifeng Su, Hui Li Jan 2009

Continuous And Smooth Potential Energy Surface For Conductorlike Screening Solvation Model Using Fixed Points With Variable Areas, Peifeng Su, Hui Li

Department of Chemistry: Faculty Publications

Rigorously continuous and smooth potential energy surfaces, as well as exact analytic gradients, are obtained for a conductorlike screening solvation model (CPCM, a variant of the general COSMO) with Hartree–Fock (RHF, ROHF, UHF, and MCSCF) and density functional theory (R-DFT, RO-DFT, and U-DFT) methods using a new tessellation scheme, fixed points with variable areas (FIXPVA). In FIXPVA, spheres centered at atoms are used to define the molecular cavity and surface. The surface of each sphere is divided into 60, 240, or 960 tesserae, which have positions fixed relative to the sphere center and areas scaled by switching functions of their …

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Smooth Potential Energy Surface For Cavitation, Dispersion, And Repulsion Free Energies In Polarizable Continuum Model, Yali Wang, Hui Li Jan 2009

Smooth Potential Energy Surface For Cavitation, Dispersion, And Repulsion Free Energies In Polarizable Continuum Model, Yali Wang, Hui Li

Department of Chemistry: Faculty Publications

The fixed points with variable areas [FIXPVA (Ref. 1)] tessellation scheme is used to obtain smooth potential energy surfaces for the cavitation Gcav, dispersion Gdis, and repulsion Grep free energies in the polarizable continuum model (PCM). It is shown that FIXPVA can reproduce the standard GEPOL (Ref. 4) results to within 1 kcal/mol.

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A New Peroxide Fragmentation: Efficient Chemical Generation Of 1O2 In Organic Media, Patrick Dussault, Prasanta Ghorai Jan 2009

A New Peroxide Fragmentation: Efficient Chemical Generation Of 1O2 In Organic Media, Patrick Dussault, Prasanta Ghorai

Department of Chemistry: Faculty Publications

Monoactivated derivatives of 1,1-dihydroperoxides undergo an unprecedented base-promoted fragmentation to efficiently generate singlet oxygen (1O2) in anhydrous organic solvents.

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A Multi-Step Nmr Screen For The Identification And Evaluation Of Chemical Leads For Drug Discovery, Kelly A. Mercier, Matthew D. Shortridge, Robert Powers Jan 2009

A Multi-Step Nmr Screen For The Identification And Evaluation Of Chemical Leads For Drug Discovery, Kelly A. Mercier, Matthew D. Shortridge, Robert Powers

Department of Chemistry: Faculty Publications

A multi-step NMR based screening assay is described for identifying and evaluating chemical leads for their ability to bind a target protein. The multi-step NMR assay provides structure-related information while being an integral part of a structure based drug discovery and design program. The fundamental principle of the multi-step NMR assay is to combine distinct 1D and 2D NMR techniques, in such a manner, that the inherent strengths and weakness associated with each technique is complementary to each other in the screen. By taking advantage of the combined strengths of 1D and 2D NMR experiments, it is possible to minimize …

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Anhydrous Fluoride Salts And Reagents And Methods For Their Production, Stephen G. Dimagno, Haoran Sun Jan 2009

Anhydrous Fluoride Salts And Reagents And Methods For Their Production, Stephen G. Dimagno, Haoran Sun

Department of Chemistry: Faculty Publications

Anhydrous organic fluoride salts and reagents prepared by a method comprising the nucleophilic Substitution of a fluorinated aromatic or fluorinated unsaturated organic compound with a salt having the formula: [QnM]x+Ax- in an inert polar, aprotic solvent; wherein M is an atom capable of supporting a formal positive charge, the n groups Q are independently varied organic moieties, n is an integer such that the [QnM] carries at least one formal positive charge, x is an integer defining the number of formal positive charge(s), +, carried by the [QnM], A- …

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Energy Gradients In Combined Fragment Molecular Orbital And Polarizable Continuum Model (Fmo/Pcm) Calculation, Hui Li, Dmitri G. Federov, Takeshi Nagata, Kazuo Kitaura, Jan H. Jensen, Mark S. Gordon Jan 2009

Energy Gradients In Combined Fragment Molecular Orbital And Polarizable Continuum Model (Fmo/Pcm) Calculation, Hui Li, Dmitri G. Federov, Takeshi Nagata, Kazuo Kitaura, Jan H. Jensen, Mark S. Gordon

Hui Li Publications

The analytic energy gradients for the combined fragment molecular orbital and polarizable continuum model (FMO/PCM) method are derived and implemented. Applications of FMO/PCM geometry optimization to polyalanine show that the structures obtained with the FMO/PCM method are very close to those obtained with the corresponding full ab initio PCM methods. FMO/PCM (RHF/6-31G* level) is used to optimize the solution structure of the 304-atom Trp-cage miniprotein and the result is in agreement with NMR experiments. The key factors determining the relative stability of the a-helix, b-turn and the extended form in solution are elucidated for polyalanine.

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Panarchy: Discontinuities Reveal Similarities In The Dynamic System Structure Of Ecological And Social Systems, Ahjond S. Garmestani, Craig R. Allen, Lance Gunderson Jan 2009

Panarchy: Discontinuities Reveal Similarities In The Dynamic System Structure Of Ecological And Social Systems, Ahjond S. Garmestani, Craig R. Allen, Lance Gunderson

School of Natural Resources: Faculty Publications

In this paper, we review the empirical evidence of discontinuous distributions in complex systems within the context of panarchy theory and discuss the significance of discontinuities for understanding emergent properties such as resilience. Over specific spatial-temporal scale ranges, complex systems can configure in a variety of regimes, each defined by a characteristic set of self-organized structures and processes. A system may remain within a regime or dramatically shift to another regime. Understanding the drivers of regime shifts has provided critical insight into system structure and resilience. Although analyses of regime shifts have tended to focus on the system level, new …

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Scaling Up Of Co2 Fluxes From Leaf To Canopy In Maize-Based Agroecosystems, Timothy J. Arkebauer, Elizabeth A. Walter-Shea, Mark A. Mesarch, Andrew E. Suyker, Shashi Verma Jan 2009

Scaling Up Of Co2 Fluxes From Leaf To Canopy In Maize-Based Agroecosystems, Timothy J. Arkebauer, Elizabeth A. Walter-Shea, Mark A. Mesarch, Andrew E. Suyker, Shashi Verma

School of Natural Resources: Faculty Publications

Carbon dioxide fluxes are being measured in three maize-based agroecosystems in eastern Nebraska in an effort to better understand the potential for these systems to sequester carbon in the soil. Landscape-level fluxes of carbon, water and energy were measured using tower eddy covariance systems. In order to better understand the landscape-level results, measurements at smaller scales, using techniques promoted by John Norman, were made and scaled up to the landscape-level. Single leaf gas exchange properties (CO2 assimilation rate and stomatal conductance) and optical properties, direct and diffuse radiation incident on the canopy, and photosynthetically active radiation (PAR) reflected and …

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Impact Of Empire Expansion On Household Diet: The Inka In Northern Chile’S Atacama Desert, Sheila D. Vinton, Linda Perry, Karl J. Reinhard, Calogero M. Santoro, Isabel Teixeira-Santos Jan 2009

Impact Of Empire Expansion On Household Diet: The Inka In Northern Chile’S Atacama Desert, Sheila D. Vinton, Linda Perry, Karl J. Reinhard, Calogero M. Santoro, Isabel Teixeira-Santos

School of Natural Resources: Faculty Publications

The impact of expanding civilization on the health of American indigenous societies has long been studied. Most studies have focused on infections and malnutrition that occurred when less complex societies were incorporated into more complex civilizations. The details of dietary change, however, have rarely been explored. Using the analysis of starch residues recovered from coprolites, here we evaluate the dietary adaptations of indigenous farmers in northern Chile’s Atacama Desert during the time that the Inka Empire incorporated these communities into their economic system. This system has been described as ‘‘complementarity’’ because it involves interaction and trade in goods produced at …

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Semiclassical Propagation Method For Tunneling Ionization, Ilya I. Fabrikant, Gordon A. Gallup Jan 2009

Semiclassical Propagation Method For Tunneling Ionization, Ilya I. Fabrikant, Gordon A. Gallup

Gordon Gallup Publications

We apply the semiclassical propagation technique to tunneling ionization in atomic and molecular systems. Semiclassical wave functions and the tunneling flux are calculated from the solution of the classical equations of motion in the complex time plane. We illustrate this method by rederiving the known result for the decay rate of a negative ion in a weak electric field. We then obtain numerical results for atomic hydrogen, H2+, H2, and Ar, and compare them with the results of the asymptotic [Ammosov-Delone-Krainov (ADK)] theory. The asymptotic theory gives surprisingly good results for the atomic and molecular …

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Spatial Variations In Local Switching Parameters Of Ferroelectric Random Access Memory Capacitors, D. Wu, I. Kunishima, S. Roberts, Alexei Gruverman Jan 2009

Spatial Variations In Local Switching Parameters Of Ferroelectric Random Access Memory Capacitors, D. Wu, I. Kunishima, S. Roberts, Alexei Gruverman

Alexei Gruverman Publications

Spatially resolved studies of the switching behavior of micrometer scale Pb(Zr,Ti)O3 capacitors have been performed by piezoresponse force microscopy (PFM). PFM spectroscopy and bias-dependent imaging of domain patterns have been used to investigate variability in local switching parameters and address the capacitor scaling effect on switching. It was found that average coercive voltage and imprint bias are independent of capacitor size and are similar to the corresponding parameters obtained by polarization hysteresis measurements. This can be attributed to the slow switching kinetics during quasistatic PFM measurements. The obtained results demonstrate a possibility of testing the submicron capacitors in real …

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Development Of A Source Of Quasi-Monochromatic Mev Energy Photons, Donald Umstadter, Sudeep Banerjee, Viswanathan Ramanathan, Nathan D. Powers, Nathaniel Cunningham, Nathan A. Chandler-Smith Jan 2009

Development Of A Source Of Quasi-Monochromatic Mev Energy Photons, Donald Umstadter, Sudeep Banerjee, Viswanathan Ramanathan, Nathan D. Powers, Nathaniel Cunningham, Nathan A. Chandler-Smith

Donald Umstadter Publications

We report current progress on a project to develop an all-optically-driven x-ray photon source. A laser pulse with 40-50 TW of peak power is focused on a supersonic helium nozzle to drive a relativistic plasma wave. Electron beams with energies of 320 MeV (+/- 28 MeV) are accelerated by means of laser wakefield acceleration. Remarkably, the acceleration region is only 3 mm in length. This accelerator is currently being employed to demonstrate the generation of MeV- energy x-ray by means of all-optical Thomson scattering. By this mechanism, a lower power, laser pulse (from the same laser system) is focused onto …

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