bluuebunny/crossref_metadata_2025 huggingface dataset:
Racial Inequality and Segregation Measures: Some Evidence from the 2000 Census
Authors: Sethi Rajiv , Somanathan Rohini
Published: May 2009

How much of the observed segregation between black and white Americans can be attributed to income disparities between the two groups? We adopt an approach to the decomposition of segregation measures that combines the method of indirect standardization with the idea that some degree of segregation is the outcome of purely random processes. Using the dissimilarity index as a measure of segregation and data on race and income from US metropolitan areas for 2000, we find that the role played by racial income inequality in accounting for segregation is modest but varies significantly across cities.
The right to contraception and the wrongs of restrictive services
Authors: Edouard Lindsay
Published: May 2009

Rights come with responsibilities for individuals, service providers, and purveyors. The operationalization of the right to contraception, for universal access to a wide range of effective methods, necessitates very different but complementary interventions. A rights‐based approach should aim to respect, protect, and fulfill rights. The wishes of individuals concerning childbearing necessitate informed choice, access to services, and lack of prejudice. Equity should be addressed through the strengthening of health systems, especially primary health care, with emphasis on the needs of underserved populations. Official pronouncements on population issues necessitate commitments. A philosophy of rights is particularly useful for service implementation, including the introduction of new contraceptive methods, by addressing the responsibilities of duty bearers and the claims of right holders. With the rights to and overwhelming health benefits of contraception, it is imperative to reverse the wrongs of limited reproductive health services.
Beyond de Tocqueville: The roles of vertical and horizontal individualism and conservatism in the 2004 U.S. presidential election
Authors: Zhang Jing , Nelson Michelle R. , Mao En
Published: May 2009

Individualism is a fundamental value to U.S. culture and democracy. We differentiate the horizontal from vertical dimension of individualism to predict voting in the 2004 presidential election. Horizontal individualism (HI) values equality and uniqueness, whereas vertical individualism (VI) values competition and achievement. In line with the value‐expressive function of attitudes and voter–politician congruency principles, we show how and when HI and VI affect voters' attitudes and voting. A pilot study revealed that VI correlated with vote; those who scored higher on VI were more likely to vote for Bush. Study 1 replicated these findings with a broader sample and a regression approach. The influence of individualism was less predictive than VI in both studies. In Study 2, we proposed that the effect of VI and HI values on voting decisions is mediated by political conservatism, which in turn predicts voters' trait assessment of candidates and voting decision. Path analysis of the data from a national survey supported our expectation among respondents with high political involvement, the context in which value‐expressive attitudes are more pronounced. Taken together, these studies advance our theoretical understanding of HI, VI, and individualism, as well as the process underlying the effect of values on decisions.
Schadenfreudeas a consumption‐related emotion: Feeling happiness about the downfall of another's product
Authors: Sundie Jill M. , Ward James C. , Beal Daniel J. , Chin Wynne W. , Geiger‐Oneto Stephanie
Published: May 2009

Emotional antecedents ofschadenfreude—joy experienced when observing another's downfall—were investigated in a status consumption context. Across 3 studies, status product failure produced schadenfreude and led to intentions to spread negative word‐of‐mouth (studies 1, 2), and increased negative affect and overall negative attitudes toward the status brand (study 3). Furthermore, studies 1 and 2 suggest that envy (particularly of social attention) can lead to schadenfreude by transmuting into hostile emotions. Finally, these studies suggest that schadenfreude in a consumption context can be precipitated by factors such as degree of target advantage and flaunting of the status product.
Coupling hydrodynamic modeling and empirical measures of bed mobility to predict the risk of scour and fill of salmon redds in a large regulated river
Authors: May Christine L. , Pryor Bonnie , Lisle Thomas E. , Lang Margaret
Published: May 2009

In order to assess the risk of scour and fill of spawning redds during floods, an understanding of the relations among river discharge, bed mobility, and scour and fill depths in areas of the streambed heavily utilized by spawning salmon is needed. Our approach coupled numerical flow modeling and empirical data from the Trinity River, California, to quantify spatially explicit zones of differential bed mobility and to identify specific areas where scour and fill is deep enough to impact redd viability. Spatial patterns of bed mobility, based on model‐predicted Shields stress, indicate that a zone of full mobility was limited to a central core that expanded with increasing flow strength. The likelihood and maximum depth of measured scour increased with increasing modeled Shields stress. Because redds were preferentially located in coarse substrate in shallow areas with close proximity to the stream banks, they were less likely to become mobilized or to risk deep scour during high‐flow events but were more susceptible to sediment deposition.
Observed relationships of ozone air pollution with temperature and emissions
Authors: Bloomer Bryan J. , Stehr Jeffrey W. , Piety Charles A. , Salawitch Ross J. , Dickerson Russell R.
Published: May 2009

Higher temperatures caused by increasing greenhouse gas concentrations are predicted to exacerbate photochemical smog if precursor emissions remain constant. We perform a statistical analysis of 21 years of ozone and temperature observations across the rural eastern U.S. The climate penalty factor is defined as the slope of the ozone/temperature relationship. For two precursor emission regimes, before and after 2002, the climate penalty factor was consistent across the distribution of ozone observations. Prior to 2002, ozone increased by an average of ∼3.2 ppbv/°C. After 2002, power plant NOx emissions were reduced by 43%, ozone levels fell ∼10%, and the climate penalty factor dropped to ∼2.2 ppbv/°C. NOx controls are effective for reducing photochemical smog and might lessen the severity of projected climate change penalties. Air quality models should be evaluated against these observations, and the climate penalty factor metric may be useful for evaluating the response of ozone to climate change.
Magnetosheath fluctuations at Venus for two extreme orientations of the interplanetary magnetic field
Authors: Du J. , Zhang T. L. , Wang C. , Volwerk M. , Delva M. , Baumjohann W.
Published: May 2009

Using the magnetosheath crossings of Venus Express on two consecutive days, we investigate magnetic fluctuations in the same locations for two extreme interplanetary magnetic field orientations, i.e., nearly along and nearly perpendicular to the solar wind flow. It is shown that the properties of the fluctuations are drastically different at basically the same location of the spacecraft in the magnetosheath. The strength and properties of the fluctuations are strongly controlled by the types of the upstream bow shock. The magnetic fluctuations behind a quasi‐parallel bow shock are quite strong and turbulent, having a strongly variable angle αeB between maximum variance direction of the fluctuations and the direction of the magnetic field, which may be convected from the upstream waves in the foreshock. The magnetic fluctuations behind a quasi‐perpendicular bow shock are less intensive and wave‐like, showing a less perturbed angle αeB, which are probably generated locally.
Measurements of the momentum and current transport from tearing instability in the Madison Symmetric Torus reversed-field pinch
Authors: Kuritsyn A. , Fiksel G. , Almagri A. F. , Brower D. L. , Ding W. X. , Miller M. C. , Mirnov V. V. , Prager S. C. , Sarff J. S.
Published: May 2009

In this paper measurements of momentum and current transport caused by current driven tearing instability are reported. The measurements are done in the Madison Symmetric Torus reversed-field pinch [R. N. Dexter, D. W. Kerst, T. W. Lovell, S. C. Prager, and J. C. Sprott, Fusion Technol. 19, 131 (1991)] in a regime with repetitive bursts of tearing instability causing magnetic field reconnection. It is established that the plasma parallel momentum profile flattens during these reconnection events: The flow decreases in the core and increases at the edge. The momentum relaxation phenomenon is similar in nature to the well established relaxation of the parallel electrical current and could be a general feature of self-organized systems. The measured fluctuation-induced Maxwell and Reynolds stresses, which govern the dynamics of plasma flow, are large and almost balance each other such that their difference is approximately equal to the rate of change of plasma momentum. The Hall dynamo, which is directly related to the Maxwell stress, drives the parallel current profile relaxation at resonant surfaces at the reconnection events. These results qualitatively agree with analytical calculations and numerical simulations. It is plausible that current-driven instabilities can be responsible for momentum transport in other laboratory and astrophysical plasmas.
Comment on “Plasma ionization by annularly bounded helicon waves” [Phys. Plasmas 13, 063501 (2006)]
Authors: Johnson Robert W.
Published: May 2009

The neoclassical calculation of the helicon wave theory contains a fundamental flaw. Use is made of a proportional relationship between the magnetic field and its curl to derive the Helmholtz equation describing helicon wave propagation. However, by the fundamental theorem of Stokes, the curl of the magnetic field must be perpendicular to that portion of the field contributing to the local curl. Re-examination of the equations of motion indicates that only electromagnetic waves propagate through a stationary region of constant pressure in a fully ionized, neutral medium.
Energy storage and dispersion of surface acoustic waves trapped in a periodic array of mechanical resonators
Authors: Dühring Maria B. , Laude Vincent , Khelif Abdelkrim
Published: May 2009

It has been shown previously that surface acoustic waves can be efficiently trapped and slowed by steep ridges on a piezoelectric substrate, giving rise to two families of shear-horizontal and vertically polarized surface waves. The mechanisms of energy storage and dispersion are explored by using the finite element method to model surface acoustic waves generated by high aspect ratio electrodes. A periodic model is proposed including a perfectly matched layer to simulate radiation conditions away from the sources, from which the modal distributions are found. The ratio of the mechanical energy confined to the electrode as compared to the total mechanical energy is calculated and is found to be increasing for increasing aspect ratio and to tend to a definite limit for the two families of surface waves. This observation is in support of the interpretation that high aspect ratio electrodes act as resonators storing mechanical energy. These resonators are evanescently coupled by the surface. The dispersion diagram is presented and shows very low group velocities as the wave vector approaches the limit of the first Brillouin zone.
High performance laser linewidth broadening for stimulated Brillouin suppression with zero parasitic amplitude modulation
Authors: Mitchell P. , Janssen A. , Luo J. K.
Published: May 2009

To enable optimum network transmission, the ideal is to launch as high laser power as possible into the optical fiber, to overcome the effects of fiber attenuation and maintain an acceptable signal to noise ratio. Launching high powers into a fiber however, results in unwanted nonlinear effects. Stimulated Brillouin scattering (SBS) is one of the nonlinear effects which reflects a significant proportion of the transmitted optical power back to the transmitter, degrading the system severely. This paper reports the development of a digitally selected supermode distributed Bragg reflector monolithic laser chip which can provide significant linewidth broadening using a pure frequency modulation technique by application of a dither current. By modifying a small segment of the laser chip material refractive index, it produces a modulation of the longitudinal mode and hence laser frequency; the monolithic laser chip has reduced the effects of SBS significantly with very little parasitic amplitude modulation.
Hafnium oxide/germanium oxynitride gate stacks on germanium: Capacitance scaling and interface state density
Authors: Oshima Yasuhiro , Shandalov Michael , Sun Yun , Pianetta Piero , McIntyre Paul C.
Published: May 2009

The chemical state of Ge in HfO2/GeOxNy/Ge gate stacks and electrical property correlations are investigated to understand their capacitance scaling potential. We obtained gate stacks with low interface state density (Dit∼3×1011 cm−2 eV−1) and a small capacitance equivalent oxide thickness (CET) of ∼1.35 nm by nitridation of Ge (100) and atomic layer deposition of HfO2. The nitrogen content of the GeOxNy affects both the crystalline structure of the overlying HfO2 and Ge diffusion into the HfO2. Introduction of Ge impurity by forming gas anneal coincided with the formation of a higher-k HfO2 phase, consistent with CET reduction.
Carbothermal reduction vapor phase transport growth of ZnO nanostructures: Effects of various carbon sources
Authors: Biswas M. , McGlynn E. , Henry M. O. , McCann M. , Rafferty A.
Published: May 2009

ZnO nanostructures were grown via carbothermal reduction vapor phase transport with carbon black, activated carbon, and graphite powders. Nanostructures can be grown at significantly lower temperatures with carbon black and activated carbon, although with different morphologies compared to graphite. The surface areas of the carbon black and activated carbon are higher than those of graphite; this has been used previously to explain the origin of such growth and morphology differences. We use different ZnO∕graphite ratios to equalize surface areas compared to carbon black and eliminate this effect, but differences in nanostructure growth and morphology remain. We discuss the effects of thermodynamics and carbon purity and conclude that the high surface activities of the carbon black and activated carbon are the reason for our results.
Improved carrier-transport properties of passivated CdMnTe crystals
Authors: Kim K. H. , Camarda G. S. , Bolotnikov A. E. , James R. B. , Hong Jinki , Kim SunUng
Published: May 2009

By analyzing photoconductive decay curves, we compared the surface recombination velocities of semi-insulating CdMnTe:In crystals grown by the vertical Bridgman method with or without surface passivation. Sulfur passivation effectively prevents the formation of a conductive Te oxide layer on the CdMnTe surface and reduces the surface recombination velocities by about one third. We demonstrated, from IR observations of the distribution maps of Te precipitates, that their configuration affects the anomalous photoconductive decay curves and the gamma-ray spectrum in some areas of the CdMnTe crystal. Notably, not only the size but also the spatial configuration of the Te precipitates modulates the carrier-transport properties.
Quantum size effect dependent critical size cluster and finite size effects
Authors: Binz S. M. , Hupalo M. , Tringides M. C.
Published: May 2009

Pb nucleation on top of a unique Pb island grown on Si(7×7) (in the form of a “hub”-“moat”-ring) confirms that electron confinement causes large variations in critical size cluster ic with island height. Because of smaller radial dimensions (less than 20 nm), the large variation of the nucleated island density on different layers cannot be a result of differences in terrace diffusion coefficients but ic. These results have important implications on how adsorption can be dramatically modified by quantum size effects.
Nanoelectromechanical system-integrated detector with silicon nanomechanical resonator and silicon nanochannel field effect transistor
Authors: Wenzler Josef-Stefan , Dunn Tyler , Erramilli Shyamsunder , Mohanty Pritiraj
Published: May 2009

We demonstrate the fabrication and operation of an integrated device containing a nanoelectromechanical system and an integrated detector. This on-chip silicon nanochannel field effect transistor is used to measure the motion of a silicon nanomechanical resonator at room temperature. Furthermore, we describe the operation of the device as a silicon-based room-temperature on-chip amplifier for improved displacement detection of nanomechanical resonators.
Femtosecond laser-induced shockwave formation on ablated silicon surface
Authors: Panchatsharam Senthilnathan , Tan Bo , Venkatakrishnan Krishnan
Published: May 2009

This paper reports an experimental study of the vapor plume and shockwave propagation generated during femtosecond laser ablation. An Yb-doped fiber amplified/oscillator laser with 1030 nm wavelength and pulse repetition rate up to 26 MHz was used to ablate a blank silicon substrate in an ambient air environment. The interaction of internal and external shockwaves with the sample surface was found to cause raised spherical rims around the central ablation regime within the crater. Rims formed by primary and secondary shockwaves can be clearly observed. Analysis of the rim formation is studied in detail.
Preparation and spectroscopic characterization of Nd3+:Y2O3 nanocrystals suspended in polymethyl methacrylate
Authors: Sardar Dhiraj K. , Chandra Sreerenjini , Gruber John B. , Gorski Waldemar , Zhang Maogen , Shim Jun Ho
Published: May 2009

We describe a method to fabricate polymethyl methacrylate (PMMA), a polymeric host, in which nanocrystals of Nd3+:Y2O3 are suspended. The spectroscopic properties of this material are analyzed using the standard Judd–Ofelt technique. The phenomenological Judd–Ofelt intensity parameters are used to calculate the radiative decay rates and the branching ratios of the F43/2→I4J (J=9/2, 11/2, 13/2, and 15/2) intermanifold transitions. The room temperature fluorescence lifetime has been measured for the most intense F43/2→I411/2 emission transition. Emission cross sections for the intense intermanifold transitions and peak emission cross sections for the intense inter-Stark transitions are also reported. Assignments to individual Stark levels of the I4J manifolds have been made and compared with the calculated splittings reported earlier. Finally, the spectroscopic properties of the Nd3+:Y2O3 nanocrystals suspended in PMMA are compared with those of Nd3+ doped in various host materials. Detailed optical analysis led to favorable values of fluorescence lifetime and emission cross section for the F43/2→I411/2 transition, which suggest that the Nd3+:Y2O3 nanocrystals embedded in PMMA would have potential for various photonic applications including laser systems and optical communication devices.
Photoluminescence study on heavily donor and acceptor impurity doped GaAs layers grown by molecular-beam epitaxy
Authors: Islam A. Z. M. Touhidul , Jung D. W. , Noh J. P. , Otsuka N.
Published: May 2009

Gallium arsenide layers doped with high concentrations of Be and Si by molecular-beam epitaxy are studied by photoluminescence (PL) spectroscopy. PL peaks from doped layers are observed at energies significantly lower than the band-gap of GaAs. The growth and doping conditions suggest that the origin of these peaks is different from that of low energy PL peaks, which were observed in earlier studies and attributed to impurity-vacancy complexes. The dependence of the peak energy on the temperature and the annealing is found to differ from that of the peaks attributed to impurity-vacancy complexes. On the basis of these observations, it is suggested that the low energy peaks are attributed to short range ordered arrangements of impurity ions. This possibility is examined by calculations of the PL spectra with models of pairs of acceptor and donor delta-doped layers and PL experiments of a superlattice of pairs of Be and Si delta-doped layers.
A statistical analysis of systematic errors in temperature and ram velocity estimates from satellite-borne retarding potential analyzers
Authors: Klenzing J. H. , Earle G. D. , Heelis R. A. , Coley W. R.
Published: May 2009

The use of biased grids as energy filters for charged particles is common in satellite-borne instruments such as a planar retarding potential analyzer (RPA). Planar RPAs are currently flown on missions such as the Communications/Navigation Outage Forecast System and the Defense Meteorological Satellites Program to obtain estimates of geophysical parameters including ion velocity and temperature. It has been shown previously that the use of biased grids in such instruments creates a nonuniform potential in the grid plane, which leads to inherent errors in the inferred parameters. A simulation of ion interactions with various configurations of biased grids has been developed using a commercial finite-element analysis software package. Using a statistical approach, the simulation calculates collected flux from Maxwellian ion distributions with three-dimensional drift relative to the instrument. Perturbations in the performance of flight instrumentation relative to expectations from the idealized RPA flux equation are discussed. Both single grid and dual-grid systems are modeled to investigate design considerations. Relative errors in the inferred parameters for each geometry are characterized as functions of ion temperature and drift velocity.
Diamagnetic measurements in the STOR-M tokamak by a flux loop system exterior to the vacuum vessel
Authors: Trembach Dallas , Xiao Chijin , Dreval Mykola , Hirose Akira
Published: May 2009

Diamagnetic measurements of poloidal beta have been performed in the STOR-M tokamak by a flux loop placed exterior to the vacuum chamber with compensation for the vacuum toroidal field using a nonenclosing coplanar coil, and vibrational compensation from auxiliary coils. It was found that in STOR-M conditions (20% toroidal magnetic field decay over discharge) there is significant influence on the diamagnetic flux measurements from strong residual signals, presumably from image currents being induced by the toroidal field coils, requiring further compensation. A blank (nonplasma) shot is used specifically to eliminate the residual component which is not proportional to the toroidal magnetic field. Data from normal Ohmic discharge operation is presented and calculations of poloidal beta from coil data (βθ∼0.5) is found to be in reasonable agreement with the values of poloidal beta obtained from measurements of electron density and Spitzer temperature with neoclassical corrections for trapped electrons. Contributions present in the blank shot (residual) signal and the limitations of this method are discussed.
Conformational properties of compact polymers
Authors: Bohn Manfred , Heermann Dieter W.
Published: May 2009

Monte Carlo simulations of coarse-grained polymers provide a useful tool to deepen the understanding of conformational and statistical properties of polymers both in physical as well as in biological systems. In this study we sample compact conformations on a cubic L×L×L lattice with different occupancy fractions by modifying a recently proposed algorithm. The system sizes studied extend up to N=256 000 monomers, going well beyond the limits of older publications on compact polymers. We analyze several conformational properties of these polymers, including segment correlations and screening of excluded volume. Most importantly we propose a scaling law for the end-to-end distance distribution and analyze the moments of this distribution. It shows universality with respect to different occupancy fractions, i.e., system densities. We further analyze the distance distribution between intrachain segments, which turns out to be of great importance for biological experiments. We apply these new findings to the problem of chromatin folding inside interphase nuclei and show that—although chromatin is in a compacted state—the classical theory of compact polymers does not explain recent experimental results.
Melting properties of a simple tight-binding model of transition metals. I. The region of half-filled d-band
Authors: Cazorla C. , Alfè D. , Gillan M. J.
Published: May 2009

We present calculations of the free energy, and hence the melting properties, of a simple tight-binding model for transition metals in the region of d-band filling near the middle of a d-series, the parameters of the model being designed to mimic molybdenum. The melting properties are calculated for pressures ranging from ambient to several megabars. The model is intended to be the simplest possible tight-binding representation of the two basic parts of the energy: first, the pairwise repulsion due to Fermi exclusion; and second, the d-band bonding energy described in terms of an electronic density of states that depends on structure. In addition to the number of d-electrons, the model contains four parameters, which are adjusted to fit the pressure dependent d-band-width and the zero-temperature pressure-volume relation of Mo. We show that the resulting model reproduces well the phonon dispersion relations of Mo in the body-centered-cubic structure, as well as the radial distribution function of the high-temperature solid and liquid given by earlier first-principles simulations. Our free energy calculations start from the free energy of the liquid and solid phases of the purely repulsive pair potential model, without d-band bonding. The free energy of the full tight-binding model is obtained from this by thermodynamic integration. The resulting melting properties of the model are quite close to those given by earlier first-principles work on Mo. An interpretation of these melting properties is provided by showing how they are related to those of the purely repulsive model.
Observation of two-dimensional electron gas in a Si quantum well with mobility of 1.6×106 cm2/Vs
Authors: Lu T. M. , Tsui D. C. , Lee C.-H. , Liu C. W.
Published: May 2009

We report the observation of a two-dimensional electron gas (2DEG) in a Si quantum well with mobility 1.6×106 cm2/Vs at carrier densities n≥1.5×1011/cm2. The 2DEG, which resides in an undoped Si/SiGe heterostructure, is capacitively induced using an insulated-gate field-effect transistor (IGFET) device structure; its mobility is determined from transport and quantum Hall effect measurements at 0.3 K. Our IGFET device makes it now possible to access by transport experiments the low electron density regime down to n∼1×1010/cm2.
Tunneling anisotropic magnetoresistance in epitaxial CoFe/n-GaAs junctions
Authors: Uemura Tetsuya , Imai Yosuke , Harada Masanobu , Matsuda Ken-ichi , Yamamoto Masafumi
Published: May 2009

Magnetic and transport properties of a fully epitaxial CoFe/n-GaAs junction were investigated. The CoFe film grown on the GaAs showed strong magnetic anisotropy in which uniaxial anisotropy with an easy axis of [11¯0] dominated with a slight cubic anisotropy having easy axes of [110] and [11¯0] superimposed. Tunneling anisotropic magnetoresistance (TAMR) was observed at 4.2 K in the CoFe/n-GaAs junction. Angular dependence of the tunnel resistance showed uniaxial-type anisotropic tunnel resistance between the [110] and [11¯0] directions in the (001) plane that varied strongly with a bias voltage. The observed TAMR effect can be explained by the anisotropic electronic structure due to Rashba and Dresselhaus spin-orbit interactions.
High power N-face GaN high electron mobility transistors grown by molecular beam epitaxy with optimization of AlN nucleation
Authors: Wong Man Hoi , Pei Yi , Speck James S. , Mishra Umesh K.
Published: May 2009

We investigated the effect of AlN nucleation layers (NLs) on the structural and electrical properties of N-face GaN grown on C-face 6H-SiC substrates by plasma-assisted molecular beam epitaxy. The GaN films were characterized by secondary ion mass spectroscopy, x-ray diffraction, and transistor electrical measurements. It was found that an AlN NL grown in the N-rich regime was essential for realizing highly resistive GaN buffers. The mosaic structure of the GaN epilayers was systematically correlated with the AlN nucleation conditions. N-face high electron mobility transistors fabricated on these low-leakage buffers demonstrated the highest output power density at 4 GHz to date of 8.1 W/mm with an associated power-added efficiency of 54%.
Dependence of depolarization temperature on cation vacancies and lattice distortion for lead-free 74(Bi1/2Na1/2)TiO3–20.8(Bi1/2K1/2)TiO3–5.2BaTiO3 ferroelectric ceramics
Authors: Zhu Mankang , Hu Hancheng , Lei Na , Hou Yudong , Yan Hui
Published: May 2009

In this paper, the off-morphotropic-phase-boundary 74(Bi1/2Na1/2)TiO3–20.8(Bi1/2K1/2)TiO3–5.2BaTiO3 ceramics were fabricated at different sintering temperatures. It was found out that as the sintering temperature increases, the volatilization of the A-site elements is aggravated, thus generating the oxygen vacancies; meanwhile, the tetragonality of the perovskite lattice reduces gradually. Besides, the temperature-dependent dielectric responses revealed that as the sintering temperature increases, the depolarization temperature Td decreases while the Curie–Weiss point TC increases. It is suggested that the lattice distortion, other than the oxygen vacancies, is the crucial factor in influencing the depolarization temperature.
Magnetic waves pervade the Sun’s corona
Authors: Day Charles
Published: May 2009

Alfvén waves manifest magnetism’s dominance of coronal dynamics. Whether they heat the Sun’s corona remains uncertain.
Recession blurs outlook for corporate research
Authors: Matthews Jermey N. A.
Published: May 2009

Companies are reducing costs by canceling high-risk R&D projects or moving them to alliances with academia, federal laboratories, and other companies.
The detection and characterization of exoplanets
Authors: Lunine Jonathan I. , Macintosh Bruce , Peale Stanton
Published: May 2009

The variety of methods by which planets beyond our solar system can be found will lead to the detection and eventual characterization of Earth-size bodies orbiting their stars at hospitable distances.
Follow the light: Ellipsometry and polarimetry
Authors: Arwin Hans , Aspnes David E.
Published: May 2009

By exploiting the polarization and wavelength dependence of optical responses, ellipsometers and polarimeters furnish accurate information about interfaces, materials, and even biological systems.
Mina Bissell: Context is everything
Authors: Short Ben
Published: May 2009

Bissell remains as passionate about science as ever.
The Virtual Kidney: an eScience interface and Grid portal
Authors: Harris Peter J. , Buyya Rajkumar , Chu Xingchen , Kobialka Tom , Kazmierczak Ed , Moss Robert , Appelbe William , Hunter Peter J. , Thomas S. Randall
Published: May 2009

The Virtual Kidney uses a web interface and distributed computing to provide experimental scientists and analysts with access to computational simulations and knowledge databases hosted in geographically separated laboratories. Users can explore a variety of complex models without requiring the specific programming environment in which applications have been developed.

This initiative exploits high-bandwidth communication networks for collaborative research and for shared access to knowledge resources. The Virtual Kidney has been developed within a specialist community of renal scientists but is transferable to other areas of research requiring interaction between published literature and databases, theoretical models and simulations and the formulation of effective experimental designs.

A web-based three-dimensional interface provides access to experimental data, a parameter database and mathematical models. A multi-scale kidney reconstruction includes blood vessels and serially sectioned nephrons. Selection of structures provides links to the database, returning parameter values and extracts from the literature.

Models are run locally or remotely with a Grid resource broker managing scheduling, monitoring and visualization of simulation results and application, credential and resource allocation. Simulation results are viewed graphically or as scaled colour gradients on the Virtual Kidney structures, allowing visual and quantitative appreciation of the effects of simulated parameter changes.
Alveolar duct expansion greatly enhances aerosol deposition: a three-dimensional computational fluid dynamics study
Authors: Darquenne C. , Harrington L. , Prisk G.K.
Published: May 2009

Obtaining
in vivo
data of particle transport in the human lung is often difficult, if not impossible. Computational fluid dynamics (CFD) can provide detailed information on aerosol transport in realistic airway geometries. This paper provides a review of the key CFD studies of aerosol transport in the acinar region of the human lung. It also describes the first ever three-dimensional model of a single fully alveolated duct with moving boundaries allowing for the cyclic expansion and contraction that occurs during breathing. Studies of intra-acinar aerosol transport performed in models with stationary walls (SWs) showed that flow patterns were influenced by the geometric characteristics of the alveolar aperture, the presence of the alveolar septa contributed to the penetration of the particles into the lung periphery and there were large inhomogeneities in deposition patterns within the acinar structure. Recent studies have now used acinar models with moving walls. In these cases, particles penetrate the alveolar cavities not only as a result of sedimentation and diffusion but also as a result of convective transport, resulting in a much higher deposition prediction than that in SW models. Thus, models that fail to incorporate alveolar wall motions probably underestimate aerosol deposition in the acinar region of the lung.
Modelling sarcoplasmic reticulum calcium ATPase and its regulation in cardiac myocytes
Authors: Koivumäki Jussi T. , Takalo Jouni , Korhonen Topi , Tavi Pasi , Weckström Matti
Published: May 2009

When developing large-scale mathematical models of physiology, some reduction in complexity is necessarily required to maintain computational efficiency. A prime example of such an intricate cell is the cardiac myocyte. For the predictive power of the cardiomyocyte models, it is vital to accurately describe the calcium transport mechanisms, since they essentially link the electrical activation to contractility. The removal of calcium from the cytoplasm takes place mainly by the Na
+
/Ca
2+
exchanger, and the sarcoplasmic reticulum Ca
2+
ATPase (SERCA). In the present study, we review the properties of SERCA, its frequency-dependent and
β
-adrenergic regulation, and the approaches of mathematical modelling that have been used to investigate its function. Furthermore, we present novel theoretical considerations that might prove useful for the elucidation of the role of SERCA in cardiac function, achieving a reduction in model complexity, but at the same time retaining the central aspects of its function. Our results indicate that to faithfully predict the physiological properties of SERCA, we should take into account the calcium-buffering effect and reversible function of the pump. This ‘uncomplicated’ modelling approach could be useful to other similar transport mechanisms as well.
Coupling contraction, excitation, ventricular and coronary blood flow across scale and physics in the heart
Authors: Lee Jack , Niederer Steven , Nordsletten David , Le Grice Ian , Smail Bruce , Kay David , Smith Nicolas
Published: May 2009

In this study, we review the development and application of multi-physics and multi-scale coupling in the construction of whole-heart physiological models. Through an examination of recent computational modelling developments, we analyse the significance of coupling mechanisms for the increased understanding of cardiac function in the areas of excitation–contraction, coronary blood flow and ventricular fluid mechanical coupling. Within these physiological domains, we demonstrate and discuss the importance of model parametrization, imaging-based model anatomy and computational implementation.
Subject-specific, multiscale simulation of electrophysiology: a software pipeline for image-based models and application examples
Authors: MacLeod R.S. , Stinstra J.G. , Lew S. , Whitaker R.T. , Swenson D.J. , Cole M.J. , Krüger J. , Brooks D.H. , Johnson C.R.
Published: May 2009

Many simulation studies in biomedicine are based on a similar sequence of processing steps, starting from images and running through geometric model generation, assignment of tissue properties, numerical simulation and visualization of the results—a process known as image-based geometric modelling and simulation. We present an overview of software systems for implementing such a sequence both within highly integrated problem-solving environments and in the form of loosely integrated pipelines. Loose integration in this case indicates that individual programs function largely independently but communicate through files of a common format and support simple scripting, so as to automate multiple executions wherever possible. We then describe three specific applications of such pipelines to translational biomedical research in electrophysiology.
Generation of histo-anatomically representative models of the individual heart: tools and application
Authors: Plank Gernot , Burton Rebecca A.B. , Hales Patrick , Bishop Martin , Mansoori Tahir , Bernabeu Miguel O. , Garny Alan , Prassl Anton J. , Bollensdorff Christian , Mason Fleur , Mahmood Fahd , Rodriguez Blanca , Grau Vicente , Schneider Jürgen E. , Gavaghan David , Kohl Peter
Published: May 2009

This paper presents methods to build histo-anatomically detailed individualized cardiac models. The models are based on high-resolution three-dimensional anatomical and/or diffusion tensor magnetic resonance images, combined with serial histological sectioning data, and are used to investigate individualized cardiac function. The current state of the art is reviewed, and its limitations are discussed. We assess the challenges associated with the generation of histo-anatomically representative individualizedin silicomodels of the heart. The entire processing pipeline including image acquisition, image processing, mesh generation, model set-up and execution of computer simulations, and the underlying methods are described. The multifaceted challenges associated with these goals are highlighted, suitable solutions are proposed, and an important application of developed high-resolution structure–function models in elucidating the effect of individual structural heterogeneity upon wavefront dynamics is demonstrated.
Eco-evolutionary dynamics: disentangling phenotypic, environmental and population fluctuations
Authors: Ezard Thomas H.G. , Côté Steeve D. , Pelletier Fanie
Published: May 2009

Decomposing variation in population growth into contributions from both ecological and evolutionary processes is of fundamental concern, particularly in a world characterized by rapid responses to anthropogenic threats. Although the impact of ecological change on evolutionary response has long been acknowledged, the converse has predominantly been neglected, especially empirically. By applying a recently published conceptual framework, we assess and contrast the relative importance of phenotypic and environmental variability on annual population growth in five ungulate populations. In four of the five populations, the contribution of phenotypic variability was greater than the contribution of environmental variability, although not significantly so. The similarity in the contributions of environment and phenotype suggests that neither is worthy of neglect. Population growth is a consequence of multiple processes, which strengthens arguments advocating integrated approaches to assess how populations respond to their environments.
Can gene flow have negative demographic consequences? Mixed evidence from stream threespine stickleback
Authors: Moore Jean-Sébastien , Hendry Andrew P.
Published: May 2009

Dispersal and gene flow can have both positive and negative effects on population size, but little empirical support from nature exists for the negative effects. We test for such effects in a stream population of threespine stickleback (
Gasterosteus aculeatus
L.) that is subject to high gene flow from a lake and is thus maladapted to stream conditions. In this system, maladaptation increases with distance along the stream, and this increase is associated with decreasing population densities until stickleback are no longer present (2.5 km from the lake). We conducted field experiments to inform whether this association might reflect a negative role for gene flow in constraining population size and therefore causing a local range limit. We specifically tested predictions deriving from theory: peripheral populations should show partial local adaptation, be under strong selection and not simply be maintained by dispersal. First, a transplant experiment suggested a weak home-site advantage in the peripheral population. Second, a mark–recapture study showed directional selection for a stream-adapted phenotype in 1 of 2 years. Third, another mark–recapture experiment showed that dispersal is limited to the point that positive demographic effects of dispersal are probably minimal. We conclude that, although gene flow does constrain morphological maladaptation in the outlet stream population, the evidence for its contribution to population size and range limits is mixed. We discuss the implications of our work for the study of factors influencing the evolution of species' ranges.
MHC standing genetic variation and pathogen resistance in wild Atlantic salmon
Authors: Dionne Mélanie , Miller Kristina M. , Dodson Julian J. , Bernatchez Louis
Published: May 2009

Pathogens are increasingly emerging in human-altered environments as a serious threat to biodiversity. In this context of rapid environmental changes, improving our knowledge on the interaction between ecology and evolution is critical. The objective of this study was to evaluate the influence of an immunocompetence gene, the major histocompatibility complex (MHC) class IIβ, on the pathogen infection levels in wild Atlantic salmon populations,Salmo salar, and identify selective agents involved in contemporary coevolution. MHC variability and bacterial infection rate were determined throughout the summer in juvenile salmon from six rivers belonging to different genetic and ecological regions in Québec, Canada. A total of 13 different pathogens were identified in kidney by DNA sequence analysis, including a predominant myxozoa, most probably recently introduced in North America. Infection rates were the highest in southern rivers at the beginning of the summer (average 47.6±6.3% infected fish). One MHC allele conferred a 2.9 times greater chance of being resistant to myxozoa, while another allele increased susceptibility by 3.4 times. The decrease in frequency of the susceptibility allele but not other MHC or microsatellite alleles during summer was suggestive of a mortality event from myxozoa infection. These results supported the hypothesis of pathogen-driven selection in the wild by means of frequency-dependent selection or change in selection through time and space rather than heterozygous advantage, and underline the importance of MHC standing genetic variation for facing pathogens in a changing environment.
Eco-evolutionary feedbacks in community and ecosystem ecology: interactions between the ecological theatre and the evolutionary play
Authors: Post David M. , Palkovacs Eric P.
Published: May 2009

Interactions between natural selection and environmental change are well recognized and sit at the core of ecology and evolutionary biology. Reciprocal interactions between ecology and evolution, eco-evolutionary feedbacks, are less well studied, even though they may be critical for understanding the evolution of biological diversity, the structure of communities and the function of ecosystems. Eco-evolutionary feedbacks require that populations alter their environment (niche construction) and that those changes in the environment feed back to influence the subsequent evolution of the population. There is strong evidence that organisms influence their environment through predation, nutrient excretion and habitat modification, and that populations evolve in response to changes in their environment at time-scales congruent with ecological change (contemporary evolution). Here, we outline how the niche construction and contemporary evolution interact to alter the direction of evolution and the structure and function of communities and ecosystems. We then present five empirical systems that highlight important characteristics of eco-evolutionary feedbacks: rotifer–algae chemostats; alewife–zooplankton interactions in lakes; guppy life-history evolution and nutrient cycling in streams; avian seed predators and plants; and tree leaf chemistry and soil processes. The alewife–zooplankton system provides the most complete evidence for eco-evolutionary feedbacks, but other systems highlight the potential for eco-evolutionary feedbacks in a wide variety of natural systems.
Experimental evaluation of evolution and coevolution as agents of ecosystem change in Trinidadian streams
Authors: Palkovacs Eric P. , Marshall Michael C. , Lamphere Brad A. , Lynch Benjamin R. , Weese Dylan J. , Fraser Douglas F. , Reznick David N. , Pringle Catherine M. , Kinnison Michael T.
Published: May 2009

Evolution has been shown to be a critical determinant of ecological processes in some systems, but its importance relative to traditional ecological effects is not well known. In addition, almost nothing is known about the role of coevolution in shaping ecosystem function. Here, we experimentally evaluated the relative effects of species invasion (a traditional ecological effect), evolution and coevolution on ecosystem processes in Trinidadian streams. We manipulated the presence and population-of-origin of two common fish species, the guppy (Poecilia reticulata) and the killifish (Rivulus hartii). We measured epilithic algal biomass and accrual, aquatic invertebrate biomass, and detrital decomposition. Our results show that, for some ecosystem responses, the effects of evolution and coevolution were larger than the effects of species invasion. Guppy evolution in response to alternative predation regimes significantly influenced algal biomass and accrual rates. Guppies from a high-predation site caused an increase in algae relative to guppies from a low-predation site; algae effects were probably shaped by observed divergence in rates of nutrient excretion and algae consumption.Rivulus–guppy coevolution significantly influenced the biomass of aquatic invertebrates. Locally coevolved populations reduced invertebrate biomass relative to non-coevolved populations. These results challenge the general assumption that intraspecific diversity is a less critical determinant of ecosystem function than is interspecific diversity. Given existing evidence for contemporary evolution in these fish species, our findings suggest considerable potential for eco-evolutionary feedbacks to operate as populations adapt to natural or anthropogenic perturbations.