bluuebunny/crossref_metadata_2025 huggingface dataset:
Menstrual cycle phase does not influence gender differences in experimental pain sensitivity
Authors: Klatzkin Rebecca R. , Mechlin Beth , Girdler Susan S.
Published: February 2009

Influence of menstrual cycle phase on experimental pain sensitivity in women and on gender differences in pain sensitivity was examined in 48 men and 49 women in response to cold pressor, heat, and ischemic pain. Each woman was tested at three points in their menstrual cycle in randomized order, the early follicular, late follicular, and luteal phases, while men were also tested three times, controlling for number of days between test sessions. Cycle phase was confirmed via serum hormone levels. As expected, women were significantly more sensitive to cold pain (p < .01), to heat pain (p < .0001), and to ischemic pain (p < .01) than men. However, pain perception during each task was not influenced by the menstrual cycle in women, nor did the menstrual cycle influence the magnitude of the gender differences in pain sensitivity. These results indicate that although women are more sensitive to a variety of noxious stimuli than men, menstrual cycle phase does not appear to moderate those differences in healthy men and women.
Ab initio protein modelling reveals novel human MIT domains
Authors: Rigden Daniel J. , Liu Han , Hayes Sebastian D. , Urbé Sylvie , Clague Michael J.
Published: February 2009

CHMPs 1B 2A 2B 4C 6
Physical association of the catalytic and helper modules of a family‐9 glycoside hydrolase is essential for activity
Authors: Burstein Tal , Shulman Michal , Jindou Sadanari , Petkun Svetlana , Frolow Felix , Shoham Yuval , Bayer Edward A. , Lamed Raphael
Published: February 2009

Cel9I (uniprotkb:Q02934) binds (MI:0407) to Cel9I (uniprotkb:Q02934) by pull down (MI:0096)
Naturerfahrungsräume – ein Beitrag der Stadtplanung zur Prävention und Gesundheitsförderung
Authors: Schemel Hans-Joachim
Published: February 2009

Einleitung

Unbestritten ist die enorme Bedeutung von körperlicher Bewegung für die Prävention und Gesundheitsförderung von Kindern. Somit stellt sich die Frage: Wie kann im Interesse einer gesunden Entwicklung unserer Kinder das spontane Bedürfnis, sich im Freien zu bewegen, geweckt und gestärkt werden? Im Folgenden wird als Antwort auf diese Frage die Grünflächenkategorie „Städtischer Naturerfahrungsraum“ vorgestellt. Sie berücksichtigt die Bedürfnisse älterer Kinder nach vielfältigen und gestaltbaren Spielräumen.
WORD CLASS DISTINCTIONS IN SECOND LANGUAGE ACQUISITION
Authors: Zyzik Eve , Azevedo Clara
Published: February 2009

Although the problem of word class has been explored in numerous first language studies, relatively little is known about this process in SLA. The present study measures second language (L2) learners’ knowledge of word class distinctions (e.g., noun vs. adjective) in a variety of syntactic contexts. English-speaking learners of Spanish from third-semester and third-year courses (N= 240) completed a receptive task that presented contrasting forms belonging to the same word family (e.g.,feliz“happy” andfelicidad“happiness”). The results indicate that learners from both groups are often unable to distinguish among word classes. In particular, learners have significant difficulty in discriminating between adjectives and nouns. Although ambiguous surface morphology contributes to word class confusions, the results suggest that L2 learners do not always recognize derivational suffixes that clearly mark word class. These difficulties are interpreted as stemming from weak syntactic morphological knowledge as well as incomplete knowledge of L2 distributional regularities.
NATIVE SPEAKERS’ VERSUS L2 LEARNERS’ SENSITIVITY TO PARALLELISM IN VP-ELLIPSIS
Authors: Duffield Nigel G. , Matsuo Ayumi
Published: February 2009

This article examines sensitivity to structural parallelism in verb phrase ellipsis constructions in English native speakers as well as in three groups of advanced second language (L2) learners. The results of a set of experiments, based on those of Tanenhaus and Carlson (1990), reveal subtle but reliable differences among the various learner groups. These differences are interpreted as showing that some L2 learners can acquire sensitivity to parallelism in the absence of surface transfer. Furthermore, the results cast doubt on two conventional theoretical claims: that the parallelism effect has a syntactic basis and that it is uniquely linked to instances of surface anaphora (Hankamer & Sag, 1976).
Place of death of adolescents and young adults with cancer: First study in a French population
Authors: Montel Sebastien , Laurence Valerie , Copel Laure , Pacquement Helene , Flahault Cecile
Published: February 2009

Objective:

To improve the palliative care and more effectively meet the needs of young patients and their families at the end of life, the authors investigated the place of death of adolescents and young adults treated in their institution and identified some of the factors influencing the choice of place of death.

Methods:

The parents and/or partners of adolescents and young adults (15 to 25 years old) who died at Institut Curie (cancer center) between 2000 and 2003 were contacted. Twenty-one families agreed to participate in the interview between October 2005 and April 2006. Analysis of the interviews comprised a descriptive part and a thematic part.

Results:

Nineteen out of 21 (90%) families declared that they did not really choose their child's place of death due to lack of time. However, all families said that they preferred the hospital. No family attended a bereavement group after their child's death and only 3 families (14%) consulted a mental health care professional. Thematic analysis showed that representations and beliefs concerning life and death at least partly determined the family's capacity to discuss the place of death with their child.

Significance of results:

Although progress has been made over recent years in France, there is still considerable room for improvement of palliative care to more effectively meet the needs of young patients and their families at the end of life.
Morbidity, mortality, and parental grief: A review of the literature on the relationship between the death of a child and the subsequent health of parents
Authors: Hendrickson Karrie Cummings
Published: February 2009

Objective:

This review was undertaken to analyze the research to date and identify areas for future research regarding the associations between parental grief after the death of a child and the subsequent health of the parents, including both their mortality and morbidity risks.

Methods:

Relevant literature was identified through a search of OVID-Medline, CINAHL, and PsycINFO using variations of the terms “parental grief and bereaved parents” combined with “health,” “illness,” “morbidity,” and “mortality.” Additionally, bibliographies of selected articles were reviewed to identify additional sources. The final sample includes 17 articles.

Results:

The literature search revealed a paucity of publications on the topic. However, it also showed that the studies that have been done examining the relationship between parental grief and health outcomes have produced conflicting results in almost every disease state examined. Additionally, several concerns with the quality of existing studies came to light that may bring their results into question. Three primary areas of concern surfaced including lack of consistency in measurement for psychological variables and “soft” self-report health outcomes, questionable methodologies in bereavement research in general, and the lack of a uniform definition of bereaved parents.

Significance of results:

Based on these findings, it is clear that more methodologically sound research is necessary to clarify the relationship between parental grief after the death of a child and the parents' subsequent morbidity and mortality risks.
Die Entwicklung des strategischen Gedächtnisses im Laufe der Grundschulzeit
Authors: Hünnerkopf Michael , Kron-Sperl Veronika , Schneider Wolfgang
Published: February 2009

Zusammenfassung. Es werden Ergebnisse der Würzburger Längsschnittstudie dargestellt, in der der Entwicklungsverlauf des strategischen Gedächtnisses vom letzten Kindergartenjahr bis zum Ende der vierten Klasse in halbjährigem Abstand untersucht wurde. Für eine Stichprobe von ca. 100 Kindern konnte das in der Münchner LOGIK-Studie gefundene Muster des sprunghaften Strategieerwerbs für die Sortierstrategie bestätigt werden, während sich bei der Wiederholungsstrategie kein bedeutsamer Unterschied in der Art des Strategieerwerbs zeigte. Der kombinierte Gebrauch von Sortier- und Wiederholungsstrategie brachte Vorteile bei der Abrufleistung der Sort-Recall-Aufgabe, nicht aber der Serial Learning-Free-Recall-Aufgabe. Für zukünftige Forschungsarbeiten wird der Einsatz einer Aufgabe zur Untersuchung der Strategieentwicklung empfohlen.
Die Entwicklung von identitäts-stabilisierenden Prozessen im Jugendalter – das Beispiel „Immunisierung”
Authors: Greve Werner , Zimmermann Stefan , Meyer Tamara , Ackermann Julia , Hellmers Sabine , Pielniok Marianna
Published: February 2009

Zusammenfassung. Obwohl die Entwicklung und Festigung des Selbstkonzeptes die zentrale Entwicklungsaufgabe in der Adoleszenz ist, hat die Untersuchung der Entwicklung von Selbst-stabilisierenden Prozessen in dieser Altersgruppe bislang wenig Aufmerksamkeit auf sich gezogen. Allerdings ist der Aufbau Selbst-stabilisierender Prozesse deswegen eine komplexe Aufgabe, weil gerade im späten Jugend- und frühen Erwachsenenalter nicht nur ein differenziertes, sondern auch ein hinreichend realistisches Selbstbild aufgebaut werden muss. Als exemplarischer Mechanismus, der Realitätsadaptivität und Selbststabilisierung verbinden kann, wird die Selbst-Immunisierung vorgestellt, d.h. die Anpassung der individuellen Operationalisierung von Selbstkonzeptaspekten an das je eigene subjektive Fertigkeitsprofil. Es wird die Hypothese formuliert, dass sich zugleich mit der Etablierung von derartigen Mechanismen ihre Funktionalität entwickelt: Dienen sie im frühen Jugendalter zunächst allgemein der Stabilisierung und Verteidigung des globalen Selbstwertempfindens, so übernehmen sie mit wachsender Differenzierung des Selbstbildes und Verbreiterung des Repertoires von Stabilisierungsmechanismen zunehmend spezifischere Funktionen. In einer Pilotstudie mit einer Stichprobe von 1337 Jugendlichen im Alter von 12 bis 22 Jahren zeigte sich, dass Selbst-Immunisierung negative Effekte von Lebensbelastungen auf das globale Selbstwertempfinden in der frühen Adoleszenz stärker puffert als in der späteren. Abschließend werde mögliche Anschlusshypothesen und Implikationen für weitere Studien diskutiert.
Iterative solution of the electromagnetic inverse scattering problem from the transient scattered field
Authors: Dubois A. , Belkebir K. , Catapano I. , Saillard M.
Published: February 2009

This paper deals with an iterative approach to solve the electromagnetic inverse scattering problem from single view transient data. The measurement configuration consists in illuminating a two‐dimensional scattering system with an electromagnetic transient source and in measuring the time domain response all around the investigated region. The aim is then to determine the electromagnetic properties of the target from the measurements. The problem is formulated in the frequency domain for a large number of frequencies, such that the incident pulse is accurately sampled, rather than in the time domain. The parameters of interest, namely, the relative permittivity and the conductivity profiles, are built up iteratively by minimizing a cost functional involving the discrepancy between the measured scattered fields and those that would be obtained via a forward model. Numerical examples are presented to prove the efficiency of the suggested method and its robustness against noise. The influence of the central frequency and of the bandwidth of the incident field on the achievable performances is also illustrated.
Swelling pressure of a divalent‐rich bentonite: Diffuse double‐layer theory revisited
Authors: Schanz Tom , Tripathy Snehasis
Published: February 2009

Physicochemical forces are responsible for the swelling pressure development in saturated bentonites. In this paper, the swelling pressures of several compacted bentonite specimens for a range of dry density of 1.10–1.73 Mg/m3were measured experimentally. The clay used was a divalent‐rich Ca‐Mg‐bentonite with 12% exchangeable Na+ions. The theoretical swelling pressure–dry density relationship for the bentonite was determined from the Gouy‐Chapman diffuse double‐layer theory. A comparison of experimental and theoretical results showed that the experimental swelling pressures are either smaller or greater than their theoretical counterparts within different dry density ranges. It is shown that for dry density of the clay less than about 1.55 Mg/m3, a possible dissociation of ions from the surface of the clay platelets contributed to the diffuse double‐layer repulsion. At higher dry densities, the adsorptive forces due to surface and ion hydration dominated the swelling pressures of the clay. A comparison of the modified diffuse double‐layer theory equations proposed in the literature to determine the swelling pressures of compacted bentonites and the experimental results for the clay in this study showed that the agreement between the calculated and experimental swelling pressure results is very good for dry densities less than 1.55 Mg/m3, whereas at higher dry densities the use of the equations was found to be limited.
Assimilation of satellite images into a sediment transport model of Lake Michigan
Authors: Stroud Jonathan R. , Lesht Barry M. , Schwab David J. , Beletsky Dmitry , Stein Michael L.
Published: February 2009

In this paper we develop and examine several schemes for combining daily images obtained from the Sea‐viewing Wide Field Spectrometer (SeaWiFS) with a two‐dimensional sediment transport model of Lake Michigan. We consider two data assimilation methods, direct insertion and a kriging‐based approach, and perform a forecasting study focused on a 2‐month period in spring 1998 when a large storm caused substantial amounts of sediment resuspension and horizontal sediment transport in the lake. By beginning with the simplest possible forecast method and sequentially adding complexity we are able to assess the improvements offered by combining the satellite data with the numerical model. In our application, we find that data assimilation schemes that include both the data and the lake dynamics improve forecast root mean square error by 40% over purely model‐based approaches and by 20% over purely data‐based approaches.
STEREO observations of upstream and downstream waves at low Mach number shocks
Authors: Russell C. T. , Jian L. K. , Blanco‐Cano X. , Luhmann J. G.
Published: February 2009

Early theories of upstream and downstream wave formation at laminar (low Mach number, low beta) shocks predicted that upstream waves would arise from phase‐standing whistlers, propagating upstream along the shock normal. Downstream waves were attributed to nearly perpendicular shocks where waves had a different dispersion than the whistler mode, allowing them to stand downstream. Observations of low‐Mach number shocks with STEREO reveal both upstream and downstream waves, but unlike the prediction of early theory, the downstream waves arise for a wide variety of shock conditions. These downstream waves appear to be compressional magnetosonic waves.
Sources of rotational signals in Saturn's magnetosphere
Authors: Khurana Krishan K. , Mitchell Donald G. , Arridge Christopher S. , Dougherty Michele K. , Russell Christopher T. , Paranicas Chris , Krupp Norbert , Coates Andrew J.
Published: February 2009

Saturn's internal magnetic field is exceptionally symmetric about its rotation axis. Yet local and remotely sensed observations of field and plasma in Saturn's magnetosphere display periodicities close to Saturn's rotation period. In this communication we provide evidence that Saturn's inner/middle magnetosphere contains semipermanent azimuthal anomalies in the ring current region in the fluxes of energetic charged particles, plasma density, magnetic field, and electrical current with a longitudinal wave number m = 1. We demonstrate that in the presence of these anomalies and a finite solar elevation angle, the solar wind lifts Saturn's magnetosphere asymmetrically in longitude, generating a tilt in the current sheet of Saturn. The current sheet tilt further produces periodicities in Saturn's middle and outer magnetosphere. The ubiquitous nature of the ring current region anomalies and their profound influence on the magnetospheric structure strongly suggest that the period of the Saturn kilometric radiation (SKR) wave power is controlled by them.
Analysis of subprotonospheric whistlers observed by DEMETER: A case study
Authors: Chum Jaroslav , Santolik Ondrej , Parrot Michel
Published: February 2009

Subprotonospheric (SP) whistlers consist of a series of low‐dispersion components that result from repeated reflections between the base of the ionosphere and altitudes up to ∼1000 km. We have used wave‐normal angles and plasma characteristics measured by the DEMETER microsatellite as an input for a three‐dimensional ray tracing technique. For several SP whistlers we have also succeeded in finding the causative lightning located at relatively large distances from the satellite footprint along the geomagnetic field line. We show that the reflections and formation of the SP whistlers take place owing to an oblique propagation, with respect to the magnetic field, in the waveguide formed by a profile of the increasing lower hybrid resonance frequency in the upper ionosphere and the base of the ionosphere. We have observed propagation across the magnetic meridian planes. We conclude that the individual components of the SP whistler propagate along different raypaths. The reflected components enter the ionosphere at relatively large distances from the satellite footprint and experience a spread of wave‐normal angles during this entry. Depending on the initial wave‐normal angle, these waves undergo a different number of reflections before reaching the satellite, thus arriving with different time delays. However, the first component observed of a SP whistler is formed by waves entering the ionosphere at relatively small distances from the satellite footprint and at relatively small wave‐normal angles. These waves do not reflect above the satellite but propagate to the opposite hemisphere.
A quiet time empirical model of equatorial vertical plasma drift in the Peruvian sector based on 150 km echoes
Authors: Alken P.
Published: February 2009

Equatorial vertical plasma drift is an important consequence of the E and F region dynamos. Understanding the climatology of vertical drift can provide significant insight into many ionospheric phenomena. In this study we present the first empirical model of vertical plasma drifts at 150 km altitude, observed by the Jicamarca Unattended Long‐term studies of the Ionosphere and Atmosphere (JULIA) coherent scatter radar located in Peru. The model, called JULIA Vertical Drift Model (JVDM), describes the local time, seasonal, and solar flux behavior of the equatorial vertical drifts in the Peruvian sector. The model is valid from 0800 through 1600 local time, which is typically when JULIA makes vertical drift measurements. During very high solar flux conditions, however, the model is unreliable before 1000 local time owing to a lack of JULIA data. The model includes a climatology of the 150 km equatorial vertical drifts as well as an estimate of the day‐to‐day variability, which can be significant. The daytime drifts typically peak between 1000 and 1200 LT and have amplitudes of 25–30 m/s ± 10 m/s. The model has been validated against the global empirical model of Scherliess and Fejer, with a total rms difference of under 4 m/s for 1000 to 1600 LT. This model will allow researchers to study daily variations in the equatorial electric field by subtracting the climatological mean. Model coefficients and software are available online at http://geomag.org/models and http://www.earthref.org.
Joint inversion of multichannel seismic reflection and wide‐angle seismic data: Improved imaging and refined velocity model of the crustal structure of the north Ecuador–south Colombia convergent margin
Authors: Agudelo W. , Ribodetti A. , Collot J.‐Y. , Operto S.
Published: February 2009

Improving seismic imaging of the crust is essential for understanding the structural factors controlling subduction zones processes. We developed a processing work flow based on the combined analysis of multichannel seismic reflection (MCS) and wide angle (WA) reflection/refraction data to derive both shallow and deep velocities suitable for prestack depth migration and to construct a blocky velocity model integrating all identifiable seismic phases contained in MCS and WA data. We apply this strategy to the study of the north Ecuador–SW Colombia subduction margin to improve the imaging and geostructural interpretation of a splay fault and surrounding outer and inner margin wedges. Results show improvements over tomographic inversion of WA data only, such as (1) sediment velocity variation across the trench and margin slope that correlates with lateral lithologic changes, tectonic compaction and effect of mass wasting processes; (2) a two‐layer velocity structure of the inner wedge basement that is consistent with the crust of an oceanic plateau; (3) a complex velocity structure of the outer wedge basement that consists of a deep, high‐velocity (5.0–5.5 km s−1) core and a low‐velocity zone (3.8–5.0 km s−1) associated with the major splay fault; (4) a ∼1.3‐km‐thick, low‐velocity (3.5–4.0 km s−1) subduction channel that extends beneath the margin outer wedge. Both the splay fault and subduction channel are expected to direct fluid flows; and (5) downdip velocity increase (5–6 km s−1) in the subducting oceanic crust associated with a low (7.8 km s−1) upper mantle velocity, possibly reflecting changes in rock nature or properties.
Illuminating the near‐sonic rupture velocities of the intracontinental Kokoxili Mw 7.8 and Denali fault Mw 7.9 strike‐slip earthquakes with global P wave back projection imaging
Authors: Walker Kristoffer T. , Shearer Peter M.
Published: February 2009

The Denali and Kokoxili strike‐slip earthquakes are two of the longest recent intracontinental ruptures. Previous studies report a range of rupture velocities. Here we image these earthquakes by reverse time migration of the intermediate‐frequency P wave train recorded by global broadband seismometers. This technique permits a relatively direct measure of rupture velocity (speed and direction) as constrained by the radiated seismic energy, free from restrictive assumptions or rupture speed bounds placed on the solution. We compare our results with published seismic, GPS displacement, and surface slip inversion results. Both ruptures were initially subshear and transitioned over a distance no longer than 40 km to supershear speeds close to the P wave speed of ∼5.6 km/s. We investigate the accuracy of our results with synthetic data and experiment with using different imaging parameters and seismic subnetworks. These tests allow us to rule out the possibility of subshear speeds along the supershear segments. Although we cannot exclude supershear speeds of 4.5–6.5 km/s, our most reliable rupture velocities of ∼5.6 km/s are close to the local P wave speeds. We hypothesize that these intracontinental faults have weak shear strengths or high breakdown slips or crustal rigidities and experience at least moderate slip or slip rate weakening. Our observations and previous published results lead us to speculate that very long, surface‐extending faults with general homogeneity in prestress and fault strength, together with smaller adjacent fault segments to provide triggering, may be necessary ingredients for the sub‐Rayleigh to supershear rupture speed transition in strike‐slip earthquakes.
Instrument calibration and aerosol optical depth validation of the China Aerosol Remote Sensing Network
Authors: Che Huizheng , Zhang Xiaoye , Chen Hongbin , Damiri Bahaiddin , Goloub Philippe , Li Zhengqiang , Zhang Xiaochun , Wei Yao , Zhou Huaigang , Dong Fan , Li Deping , Zhou Tianming
Published: February 2009

This paper introduced the calibration of the CE‐318 sunphotometer of the China Aerosol Remote Sensing Network (CARSNET) and the validation of aerosol optical depth (AOD) by AOD module of ASTPWin software compared with the simultaneous measurements of the Aerosol Robotic Network (AERONET)/Photométrie pour le Traitement Opérationnel de Normalization Satellitaire (PHOTONS) and PREDE skyradiometer. The results show that the CARSNET AOD measurements have the same accuracy as the AERONET/PHOTONS. On the basis of a comparison between CARSNET and AERONET, the AODs from CARSNET at 1020, 870, 670, and 440 nm are about 0.03, 0.01, 0.01, and 0.01 larger than those from AERONET, respectively. The aerosol optical properties over Beijing acquired through the CE‐318 sunphotometers of one AERONET/PHOTONS site and two CARSNET sites were analyzed on the basis of 4‐year measurements. It was obvious that the AOD of the Shangdianzi site (rural site) was lower than that of the two urban sites (the Institute of Atmospheric Physics (IAP) site (north urban site) and the Beijing Meteorological Observatory (BJO) site (south urban site)). The AOD of BJO was about 0.05, 0.04, 0.05, and 0.06 larger than that of IAP at 1020, 870, 670, and 440 nm, respectively, indicating that there is more local pollution in the south part of Beijing. The highest AOD was found in summer because of the stagnation planetary boundary layer and transport of pollutants from large pollution centers south of Beijing. The high temperature and relative humidity in summer also favor the production of aerosol precursor and the hygroscopic growth of the existing particles locally, which results in high AOD. In contrast, the lowest AOD at the two urban sites and one rural site in Beijing occurred in winter as the frequent cold air masses help pollutants diffuse easily.
Effects of soot‐induced snow albedo change on snowpack and hydrological cycle in western United States based on Weather Research and Forecasting chemistry and regional climate simulations
Authors: Qian Yun , Gustafson William I. , Leung L. Ruby , Ghan Steven J.
Published: February 2009

Radiative forcing induced by soot on snow is an important anthropogenic forcing affecting the global climate. In this study we simulated the deposition of soot aerosol on snow and the resulting impact on snowpack and the hydrological cycle in the western United States. A year‐long simulation was performed using the chemistry version of the Weather Research and Forecasting model (WRF‐Chem) to determine the soot deposition, followed by three simulations using WRF in meteorology‐only mode, with and without the soot‐induced snow albedo perturbations. The chemistry simulation shows large spatial variability in soot deposition that reflects the localized emissions and the influence of the complex terrain. The soot‐induced snow albedo perturbations increase the surface net solar radiation flux during late winter to early spring, increase the surface air temperature, and reduce the snow accumulation and spring snowmelt. These effects are stronger over the central Rockies and southern Alberta, where soot deposition and snowpack overlap the most. The indirect forcing of soot accelerates snowmelt and alters stream flows, including a trend toward earlier melt dates in the western United States. The soot‐induced albedo reduction initiates a positive feedback process whereby dirty snow absorbs more solar radiation, heating the surface and warming the air. This warming causes reduced snow depth and fraction, which further reduces the regional surface albedo for the snow‐covered regions. For a doubled snow albedo perturbation, the change to surface energy and temperature is around 50–80%; however, snowpack reduction is nonlinearly accelerated.
Basal mechanics of ice streams: Insights from the stick‐slip motion of Whillans Ice Stream, West Antarctica
Authors: Winberry J. Paul , Anandakrishnan Sridhar , Alley Richard B. , Bindschadler Robert A. , King Matt A.
Published: February 2009

The downstream portion of Whillans Ice Stream, West Antarctica, moves primarily by stick‐slip motion. The observation of stick‐slip motion suggests that the bed is governed by velocity‐weakening physics and that the basal physics is more unstable than suggested by laboratory studies. The stick‐slip cycle of Whillans Ice Plain exhibits substantial variability in both the duration of sticky periods and in slip magnitude. To understand this variability, we modeled the forces acting on the ice stream during the stick phase of the stick‐slip cycle. The ocean tides introduce changes in the rate at which stress is applied to the ice plain. Increased loading rates promote earlier failure and vice versa. Results show that the bed of Whillans Ice Stream strengthens over time (healing) during the quiescent intervals in the stick‐slip cycle, with the bed weakening during slip events. The time‐dependent strengthening of the ice plain bed following termination of slip events indicates that the strength of the bed may vary by up to 0.35 kPa during the course of a single day.
Monsoon versus ocean circulation controls on paleoenvironmental conditions off southern Sumatra during the past 300,000 years
Authors: Lückge Andreas , Mohtadi Mahyar , Rühlemann Carsten , Scheeder Georg , Vink Annemiek , Reinhardt Lutz , Wiedicke Michael
Published: February 2009

A multiproxy record has been acquired from a piston core (SO139‐74KL) taken offshore southern Sumatra, an area which is situated in the southwestern sector of the tropical Indo‐Pacific Warm Pool. The high‐resolution data sets (X‐ray fluorescence, total organic carbon, and C37 alkenones) were used to track changes in paleoproductivity, freshwater budget, and sea surface temperature (SST) of the tropical climate system at orbital time scales over the past 300 ka. Our paleoclimatic data show that enhanced marine paleoproductivity was directly related to strengthening of coastal upwelling during periods of increased boreal summer insolation and associated SE monsoon strength with a precessional cyclicity. Changes in freshwater supply were primarily forced by precession‐controlled changes in boreal NW winter monsoon rainfall enclosing an additional sea level component. SST variations of 2°–5°C occurred at eccentricity and precessional cyclicity. We suggest that the sea surface temperature variability off southern Sumatra is predominantly related to three major causes: (1) variations in upwelling intensity; (2) an elevated freshwater input into the southern Makassar Strait leading to reduced supply of warmer surface waters from the western Pacific and increased subsurface water transport via the Indonesian Throughflow into the Indian Ocean; and (3) long‐term changes in the intensity or frequency of low‐latitude climate phenomena, such as El Niño–Southern Oscillation.
Cultural Considerations in Assessing and Treating African Americans Who Stutter
Authors: Tellis Glen
Published: February 2009

The purpose of this paper is to provide speech-language pathologists with information that addresses cultural perceptions about stuttering and suggestions for assessment and treatment of stuttering in African Americans. The psychometric properties of the Stuttering Inventory for African Americans are discussed. Results indicate that this scale is reliable and valid. Overall, African Americans had positive perceptions about stuttering. Suggestions for evaluation and treatment of stuttering are provided.
Low-temperature metamagnetic states in single crystal TbNi2B2C studied by torque magnetometry
Authors: Rathnayaka K. D. D. , Naugle D. G. , Belevtsev B. I. , Canfield P. C. , Budko S. L.
Published: February 2009

Metamagnetic transitions in single crystal TbNi2B2C have been studied at 1.9 K with a Quantum Design torque magnetometer. The critical fields for the transitions depend strongly on the angle between the applied field and the easy axis [100]. Torque measurements have been made while changing the angular direction of the magnetic field (parallel to basal tetragonal ab-planes) at fixed field magnitude and while changing the field magnitude at fixed angular direction over a wide angular range (more than two quadrants). Torque magnetometry (sensitive only to the component of magnetization perpendicular to the field) indicates not only a different sequence of metamagnetic phases for fields near the easy axis from those near the hard axis, but also the different natures of a principal metamagnetic phase near the hard axis. Comparison of the results with longitudinal magnetization measurements is presented.
Structural and transport properties of Bi-substituted Co2MnO4
Authors: Kumar Ravi , Arora S. K. , Shvets I. V. , Rajeevan N. E. , Pradyumnan P. P. , Shukla D. K.
Published: February 2009

We report the structural and transport properties of the Bi-substituted Co2MnO4 multiferroic materials. Samples synthesized using the solid state reaction route with the composition BixCo2−xMnO4 (<0x<0.3) exhibit a single phase behavior with a cubic spinel structure (space group Fd3m). The lattice parameter was found to increase with the Bi substitution. The dc-conductivity studies reveal that all the samples possess a semiconducting behavior. The resistivity was found to decrease with the increase in the Bi substitution. The dc- as well as ac-conductivity data were analyzed in the light of various conduction models. The dc-conductivity data are explained using the variable range hopping model. The ac conductivity calculated from the dielectric data as a function of temperature and frequency demonstrates the cross over from small polaron tunneling to correlated barrier hopping type conduction in these materials.
Anisotropic Sm-(Co,Fe) nanoparticles by surfactant-assisted ball milling
Authors: Akdogan Nilay G. , Hadjipanayis George C. , Sellmyer David J.
Published: February 2009

Magnetically hard Sm2(Co0.8Fe0.2)17 and SmCo5 nanoparticles have been produced by using surfactant-assisted low- and high-energy ball milling techniques. Surfactants prevent the rewelding of the crashed particles during the milling process. Heptane was used as the milling medium and oleic acid as the surfactant. High-energy ball milling experiments took place in a milling vial with carbon steel balls by using an SPEX 8000M high-energy ball milling machine. The coercivity was found to increase with milling time with values of 2.3 kOe for Sm2(Co0.8Fe0.2)17 and 18.6 kOe for SmCo5 after 4 h of milling. Transmission electron microscopy data showed that the milled powders consisted of nanoparticles with an average size of 5–6 nm and a narrow size distribution. Samples deposited on copper coated carbon grid showed self-assembled nanoparticles which could be further aligned when subjected to a magnetic field.
Anomalous stabilization in a spin-transfer system at high spin polarization
Authors: Sodemann Inti , Bazaliy Ya. B.
Published: February 2009

Switching diagrams of nanoscale ferromagnets driven by a spin-transfer torque are studied in the macrospin approximation. We consider a disk-shaped free layer with in-plane easy axis and external magnetic field directed in plane at 90° to that axis. It is shown that this configuration is sensitive to the angular dependence of the spin-transfer efficiency factor and can be used to experimentally distinguish between different forms of g(θ), in particular, between the original Slonczewski form and the constant g approximation. The difference in switching diagrams is especially pronounced at large spin polarizations, with the Slonczewski case exhibiting an anomalous region.
Statics and dynamics of colloid-polymer mixtures near their critical point of phase separation: A computer simulation study of a continuous Asakura–Oosawa model
Authors: Zausch Jochen , Virnau Peter , Binder Kurt , Horbach Jürgen , Vink Richard L.
Published: February 2009

We propose a new coarse-grained model for the description of liquid-vapor phase separation of colloid-polymer mixtures. The hard-sphere repulsion between colloids, and between colloids and polymers, which is used in the well-known Asakura–Oosawa (AO) model, is replaced with Weeks–Chandler–Andersen potentials. Similarly, a soft potential of height comparable to thermal energy is used for the polymer-polymer interaction, rather than treating polymers as ideal gas particles. It is shown by grand-canonical Monte Carlo simulations that this model leads to a coexistence curve that almost coincides with that of the AO model and that the Ising critical behavior of static quantities is reproduced. Then the main advantage of the model is exploited—its suitability for Molecular Dynamics simulations—to study the dynamics of mean square displacements of the particles, transport coefficients such as the self-diffusion and interdiffusion coefficients, and dynamic structure factors. While the self-diffusion of polymers increases slightly when the critical point is approached, the self-diffusion of colloids decreases and at criticality the colloid self-diffusion coefficient is about a factor of 10 smaller than that of the polymers. Critical slowing down of interdiffusion is observed, which is qualitatively similar to symmetric binary Lennard-Jones mixtures, for which no dynamic asymmetry of self-diffusion coefficients occurs.
Electric generator using a triangular diamagnetic levitating rotor system
Authors: Ho Joe Nhut , Wang Wei-Chih
Published: February 2009

This paper describes a feasibility study of creating a small low friction and low maintenance generator using a diamagnetically stabilized levitating rotor. The planar rotor described in this paper uses a triangular configuration of magnets that generates emf by passing over coils placed below the rotor. Equations were developed to predict the generated emf from coils with two different coil geometries. Additionally, this paper provides a method for estimating optimal coil size and position for the planar rotor presented for both segmental arc and circular coils to obtain maximum power output. Experiments demonstrated that the emf generated in the coils matches well with the predicted wave forms for each case, and the optimization theory gives good prediction to outcome of induced waveforms. For the segmental arc coil design, the induced emf was 1.7 mV at a radial frequency of 21.8 rad/s. For the circular coil design, the emf was 1.25 mV at a radial frequency of 28.1 rad/s.
Photoacoustic spectra of Au quantum dots adsorbed on nanostructured TiO2 electrodes together with the photoelectrochemical current characteristics
Authors: Toyoda Taro , Tsugawa Sae , Shen Qing
Published: February 2009

The optical absorption of Au quantum dots (QDs) was studied by applying the photoacoustic (PA) spectroscopic technique, which is useful for optically opaque samples. The characteristic bands of Au QDs were observed at around 2.4 eV for electrodes consisting of 15 nm TiO2 nanoparticles and at around 2.3 eV for those consisting of 37 nm ones, which correspond to the characteristic surface plasmon resonance bands in the visible region. The electrode thickness dependence of the PA signal intensity around the characteristic band showed a tendency toward saturation in both cases. There was a great difference in the saturation characteristics of the PA signal intensity between the electrodes made with different sized TiO2 nanoparticles, even though the preparation conditions for the Au QDs were the same. The saturation time for electrodes made with 37 nm TiO2 nanoparticles was shorter than those made with 15 nm particles, indicating that the penetration of the QDs into the electrodes made with 37 nm nanoparticles was less than those made with 15 nm nanoparticles, although the porous area observed was high. Also, the PA signal intensity around the peak of electrodes with 15 nm nanoparticles is larger than that with 37 nm ones, indicating a higher adsorption rate for the smaller nanoparticles due to the lower surface activation energy of larger nanoparticles. There was no photoelectrochemical current response although the characteristic optical absorption bands of the Au QDs were observed by surface plasmon resonance.
Structures and stabilities of Aln+, Aln, and Aln− (n=13–34) clusters
Authors: Aguado Andrés , López José M.
Published: February 2009

Putative global minima of neutral (Aln) and singly charged (Aln+ and Aln−) aluminum clusters with n=13–34 have been located from first-principles density functional theory structural optimizations. The calculations include spin polarization and employ the generalized gradient approximation of Perdew, Burke, and Ernzerhof to describe exchange-correlation electronic effects. Our results show that icosahedral growth dominates the structures of aluminum clusters for n=13–22. For n=23–34, there is a strong competition between decahedral structures, relaxed fragments of a fcc crystalline lattice (some of them including stacking faults), and hexagonal prismatic structures. For such small cluster sizes, there is no evidence yet for a clear establishment of the fcc atomic packing prevalent in bulk aluminum. The global minimum structure for a given number of atoms depends significantly on the cluster charge for most cluster sizes. An explicit comparison is made with previous theoretical results in the range n=13–30: for n=19, 22, 24, 25, 26, 29, 30 we locate a lower energy structure than previously reported. Sizes n=32, 33 are studied here for the first time by an ab initio technique.
Schmidt-number effects on the flow past a sphere moving vertically in a stratified diffusive fluid
Authors: Hanazaki H. , Konishi K. , Okamura T.
Published: February 2009

The flow generated by a sphere moving vertically in a uniformly stratified fluid is investigated numerically for typical Schmidt numbers (or Prandtl numbers) which would be usually realized. For a high Schmidt number of Sc=700 typical to salt stratification, strong vertical round jet is formed in the lee of the sphere as has been demonstrated previously. On the other hand, with larger molecular diffusion typical to the heat conductivity in the water (Sc=7) and that in the air (Sc=0.7), the jet becomes much broader and the vertical velocity significantly decreases. This shows that the formation of the vertical jet is controlled by the diffusion processes of stratifying agents. Indeed, the thickness of the diffusive boundary layer along the obstacle surface determines the radius of the jet which becomes broader with larger molecular diffusion. The results demonstrate that a strong vertical jet is most likely generated in the high Schmidt-number fluid such as the sea water, suggesting that this phenomenon would be most intimately related to the phenomena in the ocean, such as the vertical movement of zooplanktons and buoys used for the ocean observation.
Bosonic oscillator in the presence of minimal length
Authors: Falek M. , Merad M.
Published: February 2009

We present an exact solution of the one-dimensional Bosonic oscillator for spin 1 and spin 0, in the momentum space with the presence of minimal length uncertainty, the energy eigenvalues, and eigenfunctions are then determined for both cases.
Ba
[
(
Fe
0.9
Al
0.1
)
0.5
Ta
0.5
]
O
3
ceramics with extended giant dielectric constant step and reduced dielectric loss
Authors: Wang Z. , Chen X. M. , Liu X. Q.
Published: February 2009

Structure and dielectric characteristics of Ba[(Fe0.9Al0.1)0.5Ta0.5]O3 solid solution were investigated. The cubic crystal structure in space group Pm3¯m(221) was confirmed in the Al-substituted Ba(Fe0.5Ta0.5)O3 ceramics. The extended giant dielectric constant step and the significantly reduced room-temperature dielectric loss were obtained in the Al-substituted Ba(Fe0.5Ta0.5)O3 ceramics. These improvements of dielectric characteristics have great scientific significance for potential application of giant dielectric constant materials. XPS analysis results confirmed that the low-temperature dielectric relaxation originated from the mixed-valent structure of Fe2+/Fe3+ and the hopping of the charge carriers between them, and the improvements of dielectric characteristics in the Al-substituted Ba(Fe0.5Ta0.5)O3 ceramics were attributed to the modification of such mixed-valent structure of Fe2+/Fe3+.
Extension of lattice cluster theory to strongly interacting, self-assembling polymeric systems
Authors: Freed Karl F.
Published: February 2009

A new extension of the lattice cluster theory is developed to describe the influence of monomer structure and local correlations on the free energy of strongly interacting and self-assembling polymer systems. This extension combines a systematic high dimension (1/d) and high temperature expansion (that is appropriate for weakly interacting systems) with a direct treatment of strong interactions. The general theory is illustrated for a binary polymer blend whose two components contain “sticky” donor and acceptor groups, respectively. The free energy is determined as an explicit function of the donor-acceptor contact probabilities that depend, in turn, on the local structure and both the strong and weak interactions.
Dielectric relaxations and dielectric response in multiferroic BiFeO3 ceramics
Authors: Hunpratub Sitchai , Thongbai Prasit , Yamwong Teerapon , Yimnirun Rattikorn , Maensiri Santi
Published: February 2009

Single-phase multiferroic BiFeO3 ceramics were fabricated using pure precipitation-prepared BiFeO3 powder. Dielectric response of BiFeO3 ceramics was investigated over a wide range of temperature and frequency. Our results reveal that the BiFeO3 ceramic sintered at 700 °C exhibited high dielectric permittivity, and three dielectric relaxations were observed. A Debye-type dielectric relaxation at low temperatures (−50 to 20 °C) is attributed to the carrier hopping process between Fe2+ and Fe3+. The other two dielectric relaxations at the temperature ranges 30–130 °C and 140–200 °C could be due to the grain boundary effect and the defect ordering and/or the conductivity, respectively.
AlN/AlGaN short-period superlattice sacrificial layers in laser lift-off for vertical-type AlGaN-based deep ultraviolet light emitting diodes
Authors: Takeuchi Misaichi , Maegawa Tomohiro , Shimizu Hiroshi , Ooishi Shin , Ohtsuka Takumi , Aoyagi Yoshinobu
Published: February 2009

Large-area (∼1 cm2) laser lift-off (LLO) wafer separation of Al0.45Ga0.55N layers from AlN/sapphire templates has been demonstrated by using 200-period AlN/Al0.22Ga0.78N short-period superlattice (SPSL) sacrificial layers instead of conventional GaN photoabsorbing layers. The SPSL functions as the photoabsorbing and mechanically weakened layer in the LLO process. This SPSL-assisted LLO technique promises future progress of vertical-type deep ultraviolet light emitting diodes and freestanding AlN–AlGaN bulk substrates.
Superlinear photovoltaic effect in Si nanocrystals based metal-insulator-semiconductor devices
Authors: Prezioso S. , Hossain S. M. , Anopchenko A. , Pavesi L. , Wang M. , Pucker G. , Bellutti P.
Published: February 2009

Superlinear-variation in short circuit photocurrent with increasing incident optical power has been observed in metal-insulator-semiconductor structures having a silicon rich oxinitride active layer containing silicon nanocrystals. A model has been elaborated where an internal gain mechanism explains the superlinear photovoltaic effect. The internal gain mechanism is due to secondary carrier generation (SCG) from sub-bandgap levels in the nanocrystal. SCG is caused by impact excitation from the photogenerated conduction band electrons. The sub-bandgap levels are associated to traps formed at the dielectric/Si-nanocrystals interface.