bluuebunny/crossref_metadata_2025 huggingface dataset:
Monitoring the greater San Pedro Bay region using autonomous underwater gliders during fall of 2006
Authors: Todd Robert E. , Rudnick Daniel L. , Davis Russ E.
Published: June 2009

Glider surveys of the greater San Pedro Bay region in the Southern California Bight during the fall of 2006 demonstrated the utility of autonomous underwater gliders in a coastal region with complex flow and significant anthropogenic inputs. Three Spray gliders repeatedly surveyed between Santa Catalina Island and the coast of Southern California collecting profiles of temperature, salinity, and chlorophyll fluorescence and estimates of vertically averaged currents. These observations provided context for shelf transport studies during the Huntington Beach 2006 experiment and showed the transition from summer to winter conditions. Vertically averaged currents were predominantly poleward following topography with horizontal scales of approximately 20 km. The gliders surveyed a small cyclonic eddy near Santa Catalina Island and provided a unique view of the structure of the eddy. Nitrate concentration within the euphotic zone was estimated to be 19% greater within the eddy and led to significantly elevated chlorophyll concentrations at the subsurface maximum. Glider observations of salinity reliably detected the distinctly fresh signature of the effluent plume from an ocean outfall near Huntington Beach, California. The salinity anomaly caused by the plume was used to track the spread of the plume as it was advected poleward and away from the coast while remaining subsurface.
Gravity wave propagation and dissipation from the stratosphere to the lower thermosphere
Authors: Lu Xian , Liu Alan Z. , Swenson Gary R. , Li Tao , Leblanc Thierry , McDermid I. Stuart
Published: June 2009

One‐night (28 October 2003) temperature and horizontal wind measurements by a resonance sodium (Na) wind/temperature lidar at Maui (20.7°N, 156.3°W) and temperature measurement by a Rayleigh lidar at Mauna Loa Observatory (MLO, 19.5°N, 155.6°W), Hawaii, were used to study gravity wave (GW) propagation from the lower stratosphere to the lower thermosphere. A dominant wave mode was identified from 35 to 103 km. The wave was partially dissipated and propagating upward with a scale height of temperature amplitude at ∼14 km. A damping layer was present around the stratopause where the wave amplitude was small, which also corresponded to a low static stability layer. The vertical wavelengths were larger in the mesosphere (12–13 km) than in the stratosphere (6–7 km), consistent with the decreasing static stability with altitude. Hodograph analysis of the Na lidar wind data showed that the wave was propagating northward and the horizontal wavelength was 2140 km and intrinsic period was 15 h in the region 84–103 km. The apparent period was ∼6 h and consistent with Doppler shift of the background wind. It is suggested that the convective zone over the equator to the south of Hawaii provided a constant GW source that is responsible for the observed GW throughout the night.
An updated simulation of particle fluxes and cosmogenic nuclide production in the Earth's atmosphere
Authors: Masarik J. , Beer J.
Published: June 2009

Since the publication of our first paper devoted to this subject, we have extended our model, using new cosmic ray and nuclear data. Therefore, we revised particle fluxes in the atmosphere and used them in concert with experimental or evaluated cross sections to calculate the production rates of 3H, 7Be, 10Be, 14C, and 36Cl. The dependencies of these production rates on solar activity and geomagnetic field intensity were investigated in detail. Our simulations cover a whole range of these two parameters observed in the past. Comparison of the production rates calculated from two of the most frequently used primary galactic cosmic ray spectra showed weak dependence on the shape of the spectra. Alpha particles were included in the simulations for the first time, and we showed that the previously used scheme for estimation of alpha particle contribution to the total production rates is more complicated and latitude dependent. The production rates obtained agree well with most published experimental values.
Structure of the nonmigrating semidiurnal tide above Antarctica observed from the TIMED Doppler Interferometer
Authors: Iimura H. , Palo S. E. , Wu Q. , Killeen T. L. , Solomon S. C. , Skinner W. R.
Published: June 2009

Spatial structure and temporal evolution of the nonmigrating semidiurnal tidal components over Antarctica are determined by analyzing horizontal wind measurements in the Mesosphere and Lower Thermosphere (MLT) collected using TIMED Doppler Interferometer (TIDI) on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite from 2002 to 2007. The data were organized into six specific intervals of approximately 60 days corresponding to the TIMED yaw periods. The results confirm the existence of a westward propagating zonal wave number 1 (W1) semidiurnal tidal component in the Antarctic MLT meridional wind field prior to the Austral summer solstice. This wave achieves a peak amplitude near 20 m s−1 at 90 km and is vertically stratified while extending latitudinally from the pole to 60°S. A similar structure is observed in the zonal wind field. However, the amplitude maximizes around the Austral summer solstice during the yaw period spanning 15 November to 15 January. In addition to a strong latitudinal gradient in amplitude, the W1 component also shows a vertical wavelength from 20 km near the pole to 40 km at 60°S. The amplitude and phase agree well with ground‐based meteor radar observations from the South Pole. Evidence for significant though weaker standing (S0) and W3 components is also found. These components diminish in the vicinity of the pole and appear during the winter months with latitudinally restricted structures. The vertical wavelength of the S0 component during the summer is 25 km, similar to the W1 component. During the winter the wavelength of the S0 component becomes nearly evanescent.
Optical properties of boreal region biomass burning aerosols in central Alaska and seasonal variation of aerosol optical depth at an Arctic coastal site
Authors: Eck T. F. , Holben B. N. , Reid J. S. , Sinyuk A. , Hyer E. J. , O'Neill N. T. , Shaw G. E. , Vande Castle J. R. , Chapin F. S. , Dubovik O. , Smirnov A. , Vermote E. , Schafer J. S. , Giles D. , Slutsker I. , Sorokine M. , Newcomb W. W.
Published: June 2009

Long‐term monitoring of aerosol optical properties at a boreal forest AERONET site in interior Alaska was performed from 1994 through 2008 (excluding winter). Large interannual variability was observed, with some years showing near background aerosol optical depth (AOD) levels (<0.1 at 500 nm) while 2004 and 2005 had August monthly means similar in magnitude to peak months at major tropical biomass burning regions. Single scattering albedo (ω0; 440 nm) at the boreal forest site ranged from ∼0.91 to 0.99 with an average of ∼0.96 for observations in 2004 and 2005. This suggests a significant amount of smoldering combustion of woody fuels and peat/soil layers that would result in relatively low black carbon mass fractions for smoke particles. The fine mode particle volume median radius during the heavy burning years was quite large, averaging ∼0.17 μm at AOD(440 nm) = 0.1 and increasing to ∼0.25 μm at AOD(440 nm) = 3.0. This large particle size for biomass burning aerosols results in a greater relative scattering component of extinction and, therefore, also contributes to higher ω0. Additionally, monitoring at an Arctic Ocean coastal site (Barrow, Alaska) suggested transport of smoke to the Arctic in summer resulting in individual events with much higher AOD than that occurring during typical spring Arctic haze. However, the springtime mean AOD(500 nm) is higher during late March through late May (∼0.150) than during summer months (∼0.085) at Barrow partly due to very few days with low background AOD levels in spring compared with many days with clean background conditions in summer.
Modeling of ionospheric perturbation by 2004 Sumatra tsunami
Authors: Mai Chao‐Lun , Kiang Jean‐Fu
Published: June 2009

A complete model is proposed to analyze the electron density perturbation caused by tsunami‐induced gravity waves. Loss mechanisms of thermal conduction, viscosity, and ion drag are considered in deriving the dispersion relation of the atmospheric gravity waves (AGWs). This model is then used to analyze the electron density perturbation in the ionosphere caused by the Sumatra tsunami on 26 December 2004. It is found that the AGWs move horizontally at the same speed with that of the tsunami and are trapped at about 400 km high. The simulation results well explain that about 13 min after the tsunami triggers AGWs, electron density perturbation in the ionosphere can be detected by satellites that pass over.
On statistical properties of bed load sediment concentration
Authors: Radice Alessio , Ballio Francesco , Nikora Vladimir
Published: June 2009

Data from a long‐duration laboratory experiment involving optical measurements of moving particles in a bed load layer are presented. The data analysis is focused on identification of (1) the effects of the spatial measuring scale on concentration estimates, (2) statistical and scaling properties of sediment concentration, and (3) relationships between near‐bed turbulent flow and sediment motion. The obtained results are integrated into a conceptual model that can be instrumental in studying statistical properties of solid transport rate, which, in most cases, can be linearly associated with the particle concentration.
The concept of comparative information yield curves and its application to risk‐based site characterization
Authors: de Barros Felipe P. J. , Rubin Yoram , Maxwell Reed M.
Published: June 2009

Defining rational and effective hydrogeological data acquisition strategies is of crucial importance as such efforts are always resource limited. Usually, strategies are developed with the goal of reducing uncertainty, but less often they are developed in the context of their impacts on uncertainty. This paper presents an approach for determining site characterization needs on the basis of human health risk. The main challenge is in striking a balance between reduction in uncertainty in hydrogeological, behavioral, and physiological parameters. Striking this balance can provide clear guidance on setting priorities for data acquisition and for better estimating adverse health effects in humans. This paper addresses this challenge through theoretical developments and numerical simulation. A wide range of factors that affect site characterization needs are investigated, including the dimensions of the contaminant plume and additional length scales that characterize the transport problem, as well as the model of human health risk. The concept of comparative information yield curves is used for investigating the relative impact of hydrogeological and physiological parameters in risk. Results show that characterization needs are dependent on the ratios between flow and transport scales within a risk‐driven approach. Additionally, the results indicate that human health risk becomes less sensitive to hydrogeological measurements for large plumes. This indicates that under near‐ergodic conditions, uncertainty reduction in human health risk may benefit from better understanding of the physiological component as opposed to a more detailed hydrogeological characterization.
Dust and smoke transport from Africa to South America: Lidar profiling over Cape Verde and the Amazon rainforest
Authors: Ansmann Albert , Baars Holger , Tesche Matthias , Müller Detlef , Althausen Dietrich , Engelmann Ronny , Pauliquevis Theotonio , Artaxo Paulo
Published: June 2009

Quasi‐simultaneous vertically resolved multiwavelength aerosol Raman lidar observations were conducted in the near field (Praia, Cape Verde, 15°N, 23.5°W) and in the far field (Manaus, Amazon basin, Brazil, 2.5°S, 60°W) of the long‐range transport regime between West Africa and South America. Based on a unique data set (case study) of spectrally resolved backscatter and extinction coefficients, and of the depolarization ratio a detailed characterization of aerosol properties, vertical stratification, mixing, and aging behavior during the long‐distance travel in February 2008 (dry season in western Africa, wet season in the Amazon basin) is presented. While highly stratified aerosol layers of dust and smoke up to 5.5 km height were found close to Africa, the aerosol over Manaus was almost well‐mixed, reached up to 3.5 km, and mainly consisted of aged biomass burning smoke.
Decadal variability of twentieth‐century El Niño and La Niña occurrence from observations and IPCC AR4 coupled models
Authors: Wang Xin , Wang Dongxiao , Zhou Wen
Published: June 2009

This study investigates the decadal variability of El Niño and La Niña occurrence in observations and examines that variability in a set of 20th Century climate simulations (20C3M) of coupled general circulation models (CGCMs) in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4).Wavelet analysis reveals that the observed frequency of El Niño events displays significant decadal variability with a period of about 12 years during 1920–1940, whereas the frequency of La Niña events shows significant decadal variations with a spectral peak at 16 years throughout the 20th century. Moreover, the frequencies of El Niño and La Niña events are influenced by different factors that are responsible for planetary teleconnections. The frequency of El Niño events is related the Atlantic Multidecadal Oscillation (AMO), while that of the La Niña events is associated with the Pacific Decadal Oscillation (PDO). Among the 15 IPCC AR4 CGCMs surveyed, csiro and miroc_medres CGCMs can reproduce the decadal variability of ENSO activity, and simulate partly its relationship with the Pacific and north Atlantic SSTa. These results will help us to further understand the important roles of the North Atlantic and North Pacific in ENSO variations.
A 600‐year annual 10Be record from the NGRIP ice core, Greenland
Authors: Berggren A.‐M. , Beer J. , Possnert G. , Aldahan A. , Kubik P. , Christl M. , Johnsen S. J. , Abreu J. , Vinther B. M.
Published: June 2009

Despite the extensive use of 10Be as the most significant information source on past solar activity, there has been only one record (Dye‐3, Greenland) providing annual resolution over several centuries. Here we report a new annual resolution 10Be record spanning the period 1389–1994 AD, measured in an ice core from the NGRIP site in Greenland. NGRIP and Dye‐3 10Be exhibits similar long‐term variability, although occasional short term differences between the two sites indicate that at least two high resolution 10Be records are needed to assess local variations and to confidently reconstruct past solar activity. A comparison with sunspot and neutron records confirms that ice core 10Be reflects solar Schwabe cycle variations, and continued 10Be variability suggests cyclic solar activity throughout the Maunder and Spörer grand solar activity minima. Recent 10Be values are low; however, they do not indicate unusually high recent solar activity compared to the last 600 years.
Is Psychological Research Really as Good as Medical Research? Effect Size Comparisons between Psychology and Medicine
Authors: Ferguson Christopher J.
Published: June 2009

Researchers have looked at comparisons between medical epidemiological research and psychological research using effect size r in an effort to compare relative effects. Often the outcomes of such efforts have demonstrated comparatively low effects for medical epidemiology research in comparison with effect sizes seen in psychology. The conclusion has often been that relatively small effects seen in psychology research are as strong as those found in important epidemiological medical research. The author suggests that many of the calculated effect sizes from medical epidemiological research on which this conclusion has been based are flawed. Specifically, rather than calculating effect sizes for treatment, many results have been for a Treatment Effect × Disease Effect interaction that was irrelevant to the main study hypothesis. A technique for developing a “hypothesis-relevant” effect size r is proposed.
The Impact of Human Intuition in Psychology
Authors: Goddard Murray J.
Published: June 2009

An empirically valid outcome in psychology may differ in the degree to which the outcome does or does not conform to human intuition. The author provides a brief history of three psychological outcomes violating human intuition, notes the resemblance to the common sense revolution, and then discusses how human intuition may be detrimental to behaviorism and evolutionary perspectives of human nature. The role of human intuition in supernatural beliefs is considered and, finally, possible methods to improve the plausibility of counterintuitive outcomes are suggested.
You Say you Had a Revolution: Methodological Foundations of Closed-Loop Psychology
Authors: Marken Richard S.
Published: June 2009

To the extent that a scientific revolution represents a fundamental change in a discipline, the cognitive revolution in psychology was not particularly revolutionary. What changed least in this revolution was methodology. The experimental methods used in cognitive psychology are the same as those used in the behaviorism it overthrew. This methodological continuity results from the fact that both behaviorism and cognitive psychology are based on the same paradigm, which is also the basis of experimental psychology: the open-loop causal model of behavioral organization. A truly revolutionary approach to understanding the mind has been largely ignored because it is built on a paradigm that is inconsistent with conventional research methods. This new approach to psychology, called Perceptual Control Theory (PCT), is based on a closed-loop control model of behavioral organization that is tested using control engineering methods that are unfamiliar to most psychologists. This paper introduces the methodological foundations of closed-loop psychology, explains why the closed-loop revolution has not happened yet, and suggests what psychology might look like after the revolution has occurred.
An Empirical Assessment of Meta-Analytic Practice
Authors: Dieckmann Nathan F. , Malle Bertram F. , Bodner Todd E.
Published: June 2009

In the three decades after the publication of the first meta-analyses in the behavioral sciences, hundreds of articles and a number of technical guides have emerged concerning meta-analytic practice and reporting standards. The purpose of the present study is to review the practice and reporting standards of a random sample of published meta-analyses ( n = 100) in psychology and related disciplines in the decade from 1994 through 2004. We focus on practice and reporting at each stage of the meta-analytic process and explore differences between psychological subdisciplines. These findings suggest that the practice of meta-analysis in the last decade has not yet converged on a set of common standards, though some expert recommendations are beginning to be heeded. Authors should be attentive to proper procedure and reporting in light of the numerous threats to the validity of a meta-analysis. Ironically, even though meta-analysts often struggle with incomplete or inconsistent reporting in primary research they are themselves not entirely consistent in reporting their methods and results.
Shall we Really do it Again? The Powerful Concept of Replication is Neglected in the Social Sciences
Authors: Schmidt Stefan
Published: June 2009

Replication is one of the most important tools for the verification of facts within the empirical sciences. A detailed examination of the notion of replication reveals that there are many different meanings to this concept and the relevant procedures, but hardly any systematic literature. This paper analyzes the concept of replication from a theoretical point of view. It demonstrates that the theoretical demands are scarcely met in everyday work within the social sciences. Some demands are just not feasible, whereas others are constricted by restrictions relating to publication. A new classification scheme based on a functional approach that distinguishes between different types of replication is proposed. Next, it will be argued that replication addresses the important connection between existing and new knowledge. To do so it has to be applied explicitly and systematically. The paper ends with a description of procedures how this could be done and a set of recommendations how to handle the concept of replication in the future to exploit its potential to the full.
An Example of Psychological Science's Failure to Self-Correct
Authors: Kelley Lance P. , Blashfield Roger K.
Published: June 2009

This paper illustrates the impact of the human element in the scientific process by presenting the history of Broverman, Broverman, Clarkson, Rosenkrantz, and Vogel (1970) , one of the most highly cited papers in psychology. Broverman et al. stimulated remarkable interest in sex bias among mental health professionals. Several articles published in major psychology journals demonstrated the paper's fatal flaws in the 2 decades following its publication. Nonetheless, Broverman et al. was accepted with little resistance. Broverman et al. continues to be cited as empirical support for the sex bias hypothesis among mental health professionals.
What's Wrong with Research Literatures? And how to Make Them Right
Authors: Howard George S. , Hill Trey L. , Maxwell Scott E. , Baptista Telmo Mourinho , Farias Miguel H. , Coelho Claudia , Coulter-Kern Marcie , Coulter-Kern Russell
Published: June 2009

Meta-analysis is now the accepted procedure for summarizing research literatures in areas of applied psychology. Because of the bias for publishing statistically significant findings, while usually rejecting nonsignificant results, our research literatures yield misleading answers to important quantitative questions (e.g., How much better is the average psychotherapy patient relative to a comparable group of untreated controls? How much more aggressive are children who watch a great deal of violent TV than children who watch little or no violence on TV?). While all such research literatures provide overly optimistic meta-analytic estimates, exactly how practically important are these overestimates? Three studies testing the literature on implementation intentions finds only slightly elevated effectiveness estimates. Conversely, in three studies another growing research literature (the efficacy of remote intercessory prayer) is found to be misleading and is in all likelihood not a real effect (i.e., our three studies suggest the literature likely consists of Type I errors). Rules of thumb to predict which research literatures are likely invalid are offered. Finally, revised publication and data analysis procedures to generate unbiased research literatures in the future are examined.
Do Research Literatures Give Correct Answers?
Authors: Howard George S. , Lau Michael Y. , Maxwell Scott E. , Venter André , Lundy Rae , Sweeny Ryan M.
Published: June 2009

The rationale for insisting on properly designed studies is to ensure the construction of research literatures that are not influenced by biases of any sort. Once a literature is established, however, whatever answers it gives (usually via meta-analysis) are accepted as valid. The results of our favored statistical techniques are understood best when significant relationships are present while the meaning of null results are unclear. Thus, significant findings are more likely to be published. This file drawer problem has been known for many years. However, the effect that the file drawer has on research literatures has never been probed empirically. A new method is described that tests the impact a file drawer has on a research literature. The results of the file drawer on four separate psychological research literatures are presented.
A comparative assessment of octanol-water partitioning and distribution constant estimation methods for perfluoroalkyl carboxylates and sulfonates
Authors: Rayne Sierra , Forest Kaya
Published: June 2009

New experimental data is available in the literature regarding the octanol-water distribution behavior of representative straight chain perfluoroalkyl carboxylate (PFCA) and sulfonate (PFSA) congeners. The current study provides the first investigation into the predictive ability of various software programs for estimating the corresponding octanol-water partitioning (log P) and distribution (log D) constants of PFCAs and PFSAs. Wide predictive variation was found within and between the various methods. Several programs were able to accurately estimate the log P/D fragmental contributions of a -CF~2~- group for PFCAs, as well as the associated Gibbs free energies for partitioning into octanol from water due to the hydrophobic character of the perfluoroalkyl chain (Δ~hydrophobic~G~ow~). Only the SPARC log D method accurately predicted the electrostatic contributions of the carboxylate head group (Δ~electrostatic~G~ow~) towards octanol-water partitioning for PFCAs. Similar log D values and organic carbon normalized sediment-water partitioning coefficients (K~oc~) for PFCAs and PFSAs having equivalent perfluoroalkyl chain lengths suggests potentially equivalent Δ~electrostatic~G~ow~ and Δ~hydrophobic~G~ow~ contributions towards lipophilic partitioning for these two contaminant classes at near neutral pH values, regardless of head group identity. In contrast, there are potentially different Δ~electrostatic~G~ow~ and Δ~hydrophobic~G~ow~ contributions towards proteinophilic partitioning under biologically relevant conditions.
Zeroth order regular approximation approach to parity violating nuclear magnetic resonance shielding tensors
Authors: Nahrwold Sophie , Berger Robert
Published: June 2009

In this paper, a quasirelativistic two-component zeroth order regular approximation (ZORA) density functional theory (DFT) approach to the calculation of parity violating (PV) resonance frequency differences between the nuclear magnetic resonance (NMR) spectra of enantiomers is presented and the systematics of PV NMR shielding constants in C2-symmetric dihydrogen dichalcogenides (H2X2 with X=O17, S33, S77e, T125e, P209o) are investigated. The typical sin(2α)-like dependence of the PV NMR frequency splittings on the dihedral angle α is observed for the entire series. As for the scaling behavior of the effect with the nuclear charge Z of X, the previously reported Z2.5±0.5 scaling in the nonrelativistic limit is reproduced and a scaling of approximately Z3 for the paramagnetic and Z5 for the spin-orbit coupling contribution to the frequency splitting is observed in the relativistic framework. The paramagnetic and spin-orbit coupling contributions are typically of opposite sign for the molecular structures studied herein and the maximum scaling of the total ZORA frequency splitting (i.e., the sum of the two contributions) is Z3.9 for H2Po2. Thus, an earlier claim for a spin-orbit coupling contribution scaling with up to Z7 for H2Po2 and the erratic dihedral angle dependence obtained for this compound within a four-component Dirac–Hartree–Fock–Coulomb study is not confirmed at the DFT level. The maximum NMR frequency splitting reported here is of the order of 10 mHz for certain clamped conformations of H2Po2 inside a static magnetic field with magnetic flux density of 11.7 T. Frequency splittings of this size have been estimated to be detectable with present day NMR spectrometers. Thus, a NMR route toward molecular PV appears promising once suitable compounds have been identified.
Tungsten and barium transport in the internal plasma of hollow cathodes
Authors: Polk James E. , Mikellides Ioannis G. , Katz Ira , Capece Angela M.
Published: June 2009

The effect of tungsten erosion, transport, and redeposition on the operation of dispenser hollow cathodes was investigated in detailed examinations of the discharge cathode inserts from 8200 h and 30 352 h ion engine wear tests. Erosion and subsequent redeposition of tungsten in the electron emission zone at the downstream end of the insert reduce the porosity of the tungsten matrix, preventing the flow of barium from the interior. This inhibits the interfacial reactions of the barium-calcium-aluminate impregnant with the tungsten in the pores. A numerical model of barium transport in the internal xenon discharge plasma shows that the barium required to reduce the work function in the emission zone can be supplied from upstream through the gas phase. Barium that flows out of the pores of the tungsten insert is rapidly ionized in the xenon discharge and pushed back to the emitter surface by the electric field and drag from the xenon ion flow. This barium ion flux is sufficient to maintain a barium surface coverage at the downstream end greater than 0.6, even if local barium production at that point is inhibited by tungsten deposits. The model also shows that the neutral barium pressure exceeds the equilibrium vapor pressure of the impregnant decomposition reaction over much of the insert length, so the reactions are suppressed. Only a small region upstream of the zone blocked by tungsten deposits is active and supplies the required barium. These results indicate that hollow cathode failure models based on barium depletion rates in vacuum dispenser cathodes are very conservative.
O-regime dynamics and modeling in Tore Supra
Authors: Turco F. , Giruzzi G. , Imbeaux F. , Udintsev V. S. , Artaud J. F. , Barana O. , Dumont R. , Mazon D. , Ségui J.-L.
Published: June 2009

The regime of nonlinear temperature oscillations (O-regime), characteristic of noninductive discharges on Tore Supra [Équipe Tore Supra, Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, France, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 1, p. 9], is investigated in its triggering and suppressing mechanism. This regime can be described by two nonlinearly coupled equations for the current density j(r) and the electron temperature Te(r) where the equation coefficients are functions of j and Te themselves. Both the integrated modeling code CRONOS [V. Basiuk et al., Nucl. Fusion 43, 822 (2003)] and a two-patch predator-prey system with diffusion and noise have been used and results have been compared to the experimental observations of the O-regime. A database of discharges is analyzed which features monotonic, flat, and reversed safety factor (q) profiles in order to characterize the action of external actuators on the regime dynamics with the widest generality. Electron cyclotron current drive and neutral beam injections have been used in order to induce localized perturbations in the total current profile j(r) as well as to change the plasma confinement conditions in the central region. Magnetic shear perturbations and modifications of the heat transport turn out to be the central parameters governing the dynamics of the O-regime.
The role of static disorder in negative thermal expansion in ReO3
Authors: Rodriguez Efrain E. , Llobet Anna , Proffen Thomas , Melot Brent C. , Seshadri Ram , Littlewood Peter B. , Cheetham Anthony K.
Published: June 2009

Time-of-flight neutron powder diffraction and specific heat measurements were used to study the nature of thermal expansion in rhenium trioxide, an electrically conducting oxide with cubic symmetry. The temperature evolution of the lattice parameters shows that ReO3 can exhibit negative thermal expansion below room temperature and that the transition from negative to positive thermal expansion depends on sample preparation; the single crystal sample demonstrated the highest transition temperature, 294(19) K, and largest negative value for the coefficient of thermal expansion, α=−10(1)×10−7 K−1. For the oxygen atoms, the atomic displacement parameters are strongly anisotropic even at 15 K, indicative of a large contribution of static disorder to the displacement parameters. Further inspection of the temperature evolution of the oxygen displacement parameters for different samples reveals that the static disorder contribution is greater for the samples with diminished negative thermal expansion (NTE) behavior. In addition, specific heat measurements show that ReO3 lacks the low energy Einstein-type modes seen in other NTE oxides such as ZrW2O8. The thermal expansion behavior in other NTE materials such as ZrW2O8, cuprite-type oxides, and the Prussian blue cyanides are discussed and compared with that of our ReO3 samples.
Large reversible magnetocaloric effect in DyCuAl compound
Authors: Dong Q. Y. , Shen B. G. , Chen J. , Shen J. , Sun J. R.
Published: June 2009

Large reversible magnetocaloric effect, which is associated with a second-order magnetic transition at 28 K, has been observed in DyCuAl compound. The maximum values of magnetic entropy change −ΔSM and adiabatic temperature change ΔTad are 20.4 J kg−1 K−1 and 7.7 K for a field change of 0–5 T, respectively. Especially, the large values of −ΔSM (10.9 J kg−1 K−1) and ΔTad (3.6 K) with a considerable refrigerant capacity value of 150 J kg−1 are also obtained for a relatively low field change of 0–2 T, suggesting that DyCuAl compound could be considered as a good candidate for low-temperature magnetic refrigerant.
Neural network characterization of plasma-induced charging damage on thick oxide-based metal-oxide-semiconductor device
Authors: Kim Byungwhan , Kwon Sang Hee , Kwon Kwang Ho , Kang Sangwoo , Baek Kyu-Ha , Lee Jin Ho
Published: June 2009

Charging damage can critically degrade oxide reliability. Antenna-structured metal-oxide-semiconductor field-effect transistors were fabricated to examine the effect of process parameters on charging damage. Charging damage to threshold voltage (Vth) was investigated experimentally as well as by constructing a neural network model. For a systematic modeling, charging damage process was characterized by means of a face-centered Box–Wilson experiment. The prediction performance of neural network model was optimized by applying genetic algorithm. A radio frequency source power was identified as the most influential factor. This could be more ascertained by the insignificant impact of bias power or gas ratio. Using the model, implications of plasma nonuniformity and polymer deposition were examined under various plasma conditions.
“All-Heusler alloy” current-perpendicular-to-plane giant magnetoresistance
Authors: Nikolaev Konstantin , Kolbo Paul , Pokhil Taras , Peng Xilin , Chen Yonghua , Ambrose Thomas , Mryasov Oleg
Published: June 2009

A materials system of ternary full Heusler alloys exhibiting substantial current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) has been theoretically proposed and experimentally realized. Observed trends in magnetoresistance are broadly consistent with the modeling results. A CPP-GMR of 6.7% and ΔRA of 4 mΩ μm2 have been demonstrated in the bottom spin-valve configuration. The spin-stand testing of narrow-track recording heads confirmed compatibility of these materials with hard disk drive reader technology.
Understanding x-ray diffraction of nonpolar gallium nitride films
Authors: Moram M. A. , Johnston C. F. , Hollander J. L. , Kappers M. J. , Humphreys C. J.
Published: June 2009

X-ray diffraction (XRD) is widely used for the rapid evaluation of the structural quality of thin films. In order to determine how defect densities relate to XRD data, we investigated a series of heteroepitaxial nonpolar a-plane GaN films with different densities of dislocations and basal plane stacking faults (determined by transmission electron microscopy). Factors influencing XRD data include surface roughness effects, limited lateral coherence lengths, lateral microstrain, mosaic tilt, and wafer curvature, in addition to the defects present. No direct correlation between defect densities and any measured XRD parameter was found. However, the structural imperfections dominating XRD data can be identified by specific analysis of each individual broadening factor. This reductive approach permits full explanation of the in-plane rotational anisotropy of symmetric ω-scan widths for both a-plane and m-plane films: in these samples, mosaic tilt is the dominant factor.
Efficient model for field-induced magnetization and magnetostriction of Galfenol
Authors: Evans P. G. , Dapino M. J.
Published: June 2009

A fully coupled, nonlinear model is presented that characterizes the three-dimensional (3D) strain and magnetization response to magnetic field at constant stress in cubic magnetostrictive materials. A multiscale thermodynamic approach is taken which accounts for nonlinear anisotropy, material texture, and hysteresis effects. The model is validated with measurements of textured polycrystalline Galfenol. The model provides an efficient framework for characterization, design, and control of Galfenol (Fe–Ga) devices with 3D functionality subjected to combined magnetic field and stress loading.
Tunable two-dimensional plasmon resonances in an InGaAs/InP high electron mobility transistor
Authors: Saxena H. , Peale R. E. , Buchwald W. R.
Published: June 2009

Voltage-tunable plasmon resonances in the two-dimensional electron gas (2DEG) of a high electron mobility transistor (HEMT) fabricated from the InGaAs/InP materials system are reported. The device was fabricated from a commercial HEMT wafer by depositing source and drain contacts using standard photolithography and a semitransparent gate contact that consisted of a 0.5 μm period transmission grating formed by electron-beam lithography. Narrow-band resonant absorption of terahertz radiation was observed in transmission in the frequency range of 10–50 cm−1. The resonance frequency depends on the gate-tuned sheet charge density of the 2DEG. The observed separation of resonance fundamental from its harmonics and their shift with gate bias are compared with theory.
Structural characterization and iron detection at Σ3 grain boundaries in multicrystalline silicon
Authors: Chen Bin , Chen Jun , Sekiguchi Takashi , Saito Mitsuhiro , Kimoto Koji
Published: June 2009

Transition-metal impurities gettered by grain boundaries (GBs) act as recombination centers of carriers and are regarded to be harmful defects in multicrystalline silicon (mc-Si) used for solar cell production. In this study, gettering of iron by Σ3 GBs in mc-Si was investigated by using transmission electron microscopy and annular dark-field (ADF) imaging. In the clean specimen, both straight Σ3{111} GB and zig-zag Σ3{110}, {112} GBs are not electrically active, whereas the zig-zag Σ3{110}, {112} GBs become electrically active when contaminated with iron. ADF images have shown that iron is preferentially gettered at the irregular parts of zig-zag Σ3{112} GB and exists in the form of clusters. The iron gettering abilities of these Σ3 GBs have been discussed.
Population inversion of G14 excited state of Tm3+ investigated by means of numerical solutions of the rate equations system in Yb:Tm:Nd:LiYF4 crystal
Authors: Librantz André Felipe Henriques , Gomes Laércio , Courrol Lilia Coronato , Ranieri Izilda Marcia , Baldochi Sonia Lícia
Published: June 2009

In this work we present the spectroscopic properties of LiYF4 (YLF) single crystals activated with thulium and codoped with ytterbium and neodymium ions. The most important processes that lead to the thulium upconversion emissions in the blue region were identified. A time-resolved luminescence spectroscopy technique was employed to measure the luminescence decays and to determine the most important mechanisms involved in the upconversion process that populates G14(Tm3+) excited state. Analysis of the energy transfer processes dynamics using selective pulsed laser excitations in Yb:Tm:Nd, Tm:Nd, and Tm:Yb YLF crystals shows that the energy transfer from Nd3+ to Yb3+ ions is the mechanism responsible for the enhancement in the blue upconversion efficiency in the Yb:Tm:Nd:YLF when compared with the Yb:Tm system. A study of the energy transfer processes in YLF:Yb:Tm:Nd crystal showed that the G14 excited level is mainly populated by a sequence of two nonradiative energy transfers that start well after the Nd3+ and Tm3+ excitations at 797 nm according to Nd3+(F43/2)→Yb3+(F27/2), followed by Yb3+(F25/2)→Tm(H34)→Tm3+(G14) . Results of numerical simulation of the rate equations system showed that a population inversion for 481.4 nm laser emission line is attained for a pumping rate threshold of 26 s−1, which is equivalent to an intensity of 880 W cm−2 for a continuous laser pumping at 797 nm. On the other hand, a population inversion was not observed for the case of 960 nm (Yb3+) pumping.
Role of vacancy-type defects in the formation of silicon nanocrystals
Authors: Mokry C. R. , Simpson P. J. , Knights A. P.
Published: June 2009

The location and size distribution of silicon nanocrystals (Si-nc) formed in SiO2 by Si ion implantation and annealing were investigated. Transmission electron microscopy images revealed that the location and size distribution of the Si-nc are strongly correlated with the location of the vacancies produced in the SiO2 network by the implantation, as simulated by stopping and range of ions in matter and measured by positron annihilation spectroscopy (PAS). Simultaneous consideration of PAS and photoluminescence measurements suggest that the diffusion necessary for Ostwald ripening of Si-nc depends on the concentration and location of vacancy-type defects, and when the majority of these defects have been removed by annealing, the growth of the Si-nc slows dramatically or stops entirely. We demonstrate the capability for modification and enhancement of emission from Si-nc through the controlled introduction of defects into the oxide prior to annealing.
On the effect of the atmosphere on the evaporation of sessile droplets of water
Authors: Sefiane K. , Wilson S. K. , David S. , Dunn G. J. , Duffy B. R.
Published: June 2009

An experimental and theoretical study of the effect of the atmosphere on the evaporation of pinned sessile droplets of water is described. The experimental work investigated the evaporation rates of sessile droplets in atmospheres of three different ambient gases (namely, helium, nitrogen, and carbon dioxide) at reduced pressure (from 40 to 1000 mbars) using four different substrates (namely, aluminum, titanium, Macor, and polytetrafluoroethylene) with a wide range of thermal conductivities. Reducing the atmospheric pressure increases the diffusion coefficient of water vapor in the atmosphere and hence increases the evaporation rate. Changing the ambient gas also alters the diffusion coefficient and hence also affects the evaporation rate. A mathematical model that takes into account the effect of the atmospheric pressure and the nature of the ambient gas on the diffusion of water vapor in the atmosphere and the thermal conductivity of the substrate is developed, and its predictions are found to be in encouraging agreement with the experimental results.
Bond fluctuation model to describe physical aging in polymeric materials
Authors: Arnoult M. , Saiter J. M. , Pareige C. , Meseguer Dueñas J. M. , Gómez Ribelles J. L. , Molina Mateo J.
Published: June 2009

The thermal behavior of a polymeric material during a cooling ramp was simulated by means of the bond fluctuation model. By introducing both an intramolecular and an intermolecular potential, if the cooling rate is fast enough, the glass transition occurs, and the states attained at low temperatures can be characterized as disordered glasses. The evolution of the resulting amorphous systems was then studied during isothermal periods both for systems starting as an amorphous liquid and as an amorphous glass. The results show that after a very long annealing time at temperatures above the glass transition, an excess of energy loss appears in the system when compared to the usual glass theory. The Monte Carlo method was used to simulate the physical aging phenomena at long time scales.
The parent anion of the RGD tripeptide: Photoelectron spectroscopy and quantum chemistry calculations
Authors: Li Xiang , Wang Haopeng , Bowen Kit H. , Grégoire G. , Lecomte F. , Schermann Jean-Pierre , Desfrançois Charles
Published: June 2009

The gas-phase conformation of the intact (parent) unprotected RGD− peptide anion has been investigated using a combination of anion photoelectron spectroscopy and quantum chemistry calculations of its low-energy stable structures. The experimentally observed RGD− species correspond to a conformation in which the guanidinium group is protonated, the C-terminus is neutral, the aspartic acid carboxyl is deprotonated, and the anion’s excess electron orbital is localized on the protonated guanidinium. This structure is reminiscent of the RGD loop, which is the peptide motif recognized by trans-membrane integrins. The parent RGD− radical anion was generated using a unique infrared desorption-photoemission-helium jet ion source, whose ability to produce radical anions of peptides may also have analytical mass spectrometric implications.
Parasitic memory effect induced by high erasing pulses in metal-oxide-semiconductor field-effect transistor device containing silicon nanocrystals
Authors: Ang R. , Chen T. P. , Yi M. D. , Dao H. L. , Wong J. I.
Published: June 2009

The metal-oxide-semiconductor field-effect transistor (MOSFET) device containing silicon nanocrystals (nc-Si) is fabricated by an ion-beam technique. The parasitic effect in the subthreshold region is only observed by the application of high erasing pulses. By using the second derivative method, the formation of the parasitic transistor is confirmed. The parasitic transistor is only activated upon the trapping of holes into the nc-Si at the edge channel. In addition, electron or hole trapping in the nc-Si depend on the voltage polarity and magnitude, which lead to positive or negative shifts in the threshold voltage. This demonstrates the feasibility of memory applications in MOSFET device.
Young’s modulus of pulsed-laser deposited V6O13 thin films
Authors: Rúa Armando , Fernández Félix E. , Cabrera Rafmag , Sepúlveda Nelson
Published: June 2009

The mixed valence vanadium oxide V6O13 is an interesting material which exhibits an insulator-to-metal or semiconductor-to-semiconductor transition at low temperatures. It is also a much studied cathode material for lithium-based thin film batteries. However, there is little information available about its mechanical properties. Young’s modulus of pulsed-laser deposited V6O13 thin films has been determined by measuring the fundamental resonant frequency of silicon dioxide microcantilevers coated with V6O13. Laser deflection techniques were used to measure the cantilevers’ resonant frequencies. The films were further characterized by x-ray diffraction, atomic force microscopy, and resistivity measurements. The value of Young’s modulus associated with the direction along the material’s (001) planes was found to be approximately 100GPa. The values obtained for films ranging from 90to200nm were equal within experimental error.