bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of visual feedback and register changes on sign language production: A kinematic study with deaf signers
Authors: EMMOREY KAREN , GERTSBERG NELLY , KORPICS FRANCO , WRIGHT CHARLES E.
Published: December 2008

Speakers monitor their speech output by listening to their own voice. However, signers do not look directly at their hands and cannot see their own face. We investigated the importance of a visual perceptual loop for sign language monitoring by examining whether changes in visual input alter sign production. Deaf signers produced American Sign Language (ASL) signs within a carrier phrase under five conditions: blindfolded, wearing tunnel-vision goggles, normal (citation) signing, shouting, and informal signing. Three-dimensional movement trajectories were obtained using an Optotrak Certus system. Informally produced signs were shorter with less vertical movement. Shouted signs were displaced forward and to the right and were produced within a larger volume of signing space, with greater velocity, greater distance traveled, and a longer duration. Tunnel vision caused signers to produce less movement within the vertical dimension of signing space, but blind and citation signing did not differ significantly on any measure, except duration. Thus, signers do not “sign louder” when they cannot see themselves, but they do alter their sign production when vision is restricted. We hypothesize that visual feedback serves primarily to fine-tune the size of signing space rather than as input to a comprehension-based monitor.
Overlapping self-affine sets of Kakeya type
Authors: KÄENMÄKI ANTTI , SHMERKIN PABLO
Published: December 2008

We compute the Minkowski dimension for a family of self-affine sets on ℝ2. Our result holds for every (rather than generic) set in the class. Moreover, we exhibit explicit open subsets of this class where we allow overlapping, and do not impose any conditions on the norms of the linear maps. The family under consideration was inspired by the theory of Kakeya sets.
Algebraic Properties of ModuloqComplete ℓ-Wide Families
Authors: FELSZEGHY BÁLINT , HEGEDŰS GÁBOR , RÓNYAI LAJOS
Published: December 2008

Letqbe a power of a primep, and letn,d, ℓ be integers such that 1 ≤n, 1 ≤ ℓ <q. Consider the moduloqcomplete ℓ-wide family:

We describe a Gröbner basis of the vanishing idealI() of the set of characteristic vectors ofover fields of characteristicp. It turns out that this set of polynomials is a Gröbner basis for all term orderings ≺, for which the order of the variables isxn≺xn−1≺ ⋅⋅⋅ ≺x1.

We compute the Hilbert function ofI(), which yields formulae for the moduloprank of certain inclusion matrices related to.

We apply our results to problems from extremal set theory. We prove a sharp upper bound of the cardinality of a moduloqℓ-wide family, which shatters only small sets. This is closely related to a conjecture of Frankl [13] on certain ℓ-antichains. The formula of the Hilbert function also allows us to obtain an upper bound on the size of a set system with certain restricted intersections, generalizing a bound proposed by Babai and Frankl [6].

The paper generalizes and extends the results of [15], [16] and [17].
The assessment of complexity in congenital cardiac surgery based on objective data
Authors: Clarke David R. , Lacour-Gayet Francois , Jacobs Jeffrey Phillip , Jacobs Marshall L. , Maruszewski Bohdan , Pizarro Christian , Edwards Fred H. , Mavroudis Constantine
Published: December 2008

When designed in 2000, the Aristotle Complexity Score was entirely based on subjective probability. This approach, based on the opinion of experts, was considered a good solution due to the limited amount of data available. In 2008, the next generation of the complexity score will be based on observed data available from over 100,000 congenital cardiac operations currently gathered in the congenital cardiac surgery databases of the Society of Thoracic Surgeons and the European Association for Cardio-Thoracic Surgery.

A mortality score is created based on 70,000 surgeries harvested in the congenital databases of The Society of Thoracic Surgeons and The European Association for Cardio-Thoracic Surgery. It is derived from 118 congenital cardiovascular operations, representing 91% of the operations and including 97% of the patients. This Mortality Index of the new Aristotle Complexity Score could further be stratified into 5 levels with minimal within-group variation and maximal between-group variation, and may contribute to the planned unification of the Aristotle Complexity Score with the Risk Adjustment for Congenital Heart Surgery system.

Similarly, a score quantifying morbidity risk is created. Due to the progress of congenital cardiac surgery, the mortality is today reduced to an average of 4%. No instrument currently exists to measure the quality of care delivered to the survivors representing 96% of the patients. An objective assessment of morbidity was needed. The Morbidity Index, based on 50,000 operations gathered in the congenital databases of The Society of Thoracic Surgeons and The European Association for Cardio-Thoracic Surgery, is derived from 117 congenital cardiovascular operations representing 90% of the operations and including 95% of the patients. This morbidity indicator is calculated on an algorithm based on length of stay in the hospital and time on the ventilator.

The mortality and morbidity indicators will be part of the next generation of the complexity score, which will be named the Aristotle Average Complexity Score. It will be based on the sum of mortality, morbidity, and subjective technical difficulty. The introduction of objective data in assessment of mortality and morbidity in congenital cardiac surgery is a significant step forward, which should allow a better evaluation of the complexity of the operations performed by a given centre or surgeon.
Dietary fibre intake of pregnant women attending general practices in southern Brazil – The ECCAGE Study
Authors: Buss Caroline , Nunes Maria Angélica , Camey Suzi , Manzolli Patricia , Soares Rafael Marques , Drehmer Michele , Giacomello Andressa , Duncan Bruce Bartholow , Schmidt Maria Inês
Published: December 2008

Background

Increase in fibre intake during pregnancy may reduce weight gain, glucose intolerance, dyslipidaemia, pre-eclampsia and constipation. Few studies have evaluated adequacy of fibre intake during pregnancy.

Objective

To assess, through an FFQ, the dietary fibre intake of pregnant women receiving prenatal care from general public practices and compare it with current guidelines.

Design and setting

Cross-sectional analyses of a pregnancy cohort study (ECCAGE – Study of Food Intake and Eating Behaviour in Pregnancy) conducted in eighteen general practices in southern Brazil, from June 2006 to April 2007.

Subjects

Five hundred and seventy-eight pregnant women with mean (sd) age of 24·9 (6·5) years and mean gestational age of 24·5 (5·8) weeks.

Results

The mean energy intake was 11 615 kJ/d (2776 kcal/d). The mean total fibre intake (30·2 g/d) was slightly above the recommended value of 28g/d (P< 0·001), yet 50 % (95 % CI 46, 54) of the women failed to meet the recommendation. Whole-grain fibre constituted only 1 % of total fibre intake in the cereal group. In adjusted Poisson regression analyses, not meeting the recommendation for fibre intake was associated with alcohol intake (prevalence ratio 1·29; 95 % CI 1·11, 1·50) and absence of nutritional guidance (prevalence ratio 1·22; 95 % CI 1·05, 1·42) during pregnancy.

Conclusions

About half of the pregnant women failed to meet the recommended fibre intake, especially those not reporting nutritional guidance during pregnancy. For most women, whole-grain cereal intake was absent or trivial. Taken together, our data indicate the need, at least in this setting, for greater nutritional education in prenatal care.
Auswirkungen verschiedener therapeutischer Ansätze zur Behandlung von Depressionen auf das beobachtete partnerschaftliche Konfliktverhalten
Authors: Gabriel Barbara , Bodenmann Guy , Widmer Kathrin , Charvoz Linda , Schramm Elisabeth , Hautzinger Martin
Published: December 2008

Theoretischer Hintergrund: Bestehende Befunde verweisen auf klare Zusammenhänge zwischen dem partnerschaftlichen Kommunikationsverhalten und dem Verlauf von Depressionen. Untersuchungen zu den Auswirkungen von Therapieansätzen zur Behandlung von Depressionen auf die dyadische Kommunikation sind jedoch kaum vorhanden. Methode: Mittels Varianzanalysen wurden erstmals die Effekte (Prä-Post) der kognitiven Verhaltenstherapie KVT (n = 17 Paare), der interpersonellen Psychotherapie IPT (n = 13 Paare) und der bewältigungsorientierten Paartherapie BOI (n = 17 Paare) auf die beobachtete dyadische Konfliktkommunikation beider Partner bei Paaren mit einem depressiven Partner überprüft. Ergebnisse: Die drei Therapieansätze führten zu einer vergleichbaren Verbesserung der Depression bei den Patienten sowie einer Abnahme von Kritik/Defensivität bei den Patienten und ihren Partnern. Ansonsten zeigten sich in erster Linie Veränderungen bei den Partnern, welche zwischen den Therapiegruppen divergierten. Schlussfolgerung: In Anbetracht der Bedeutung der dyadischen Kommunikation für den Langzeitverlauf von Depressionen sowie der Paarbeziehung sprechen die vorliegenden Befunde für den potenziellen Nutzen der BOI sowie des Einbezuges der Partner in den Therapieprozess.
Gravity influenced brittle‐ductile deformation and growth faulting in the lithosphere during collision: Results from laboratory experiments
Authors: Schueller Sylvie , Davy Philippe
Published: December 2008

Because of the competition between brittle and ductile rheologies and their interplay with tectonic and buoyancy forces, lithospheric deformation results in very contrasting styles. In continental collision, especially with unconfined boundaries, deformation can be either homogeneously distributed or localized on complex fault patterns, and different deformation modes such as contraction, extension, and strike‐slip interfere. Using scaled lithospheric analog experiments made of dry sand, silicone putties, and dense honey, we investigate the mechanical parameters that control the deformation style in colliding systems, with a particular focus on the roles of buoyancy and brittle‐ductile coupling. The analysis of tens of experiments shows that the principal deformation features depend on two main parameters: a brittle‐to‐ductile strength ratio Γ, which controls deformation localization at the largest scale, and a buoyancy‐to‐strength ratio Ar, which fixes the relative amount of contractional, extensional, and strike‐slip structures. Strain localization occurs only for Γ larger than a critical value (∼0.5), and the range of Γ values, over which the transition from nonlocalized to localized deformation occurs, is small. The three main deformation regimes (contraction, strike‐slip, and extension), which coexist in most of the collision experiments, occur in relative proportions that depend mainly on Ar and on the nature of the boundary conditions.
Ozone profile retrieval from GOMOS limb scattering measurements
Authors: Taha Ghassan , Jaross Glen , Fussen Didier , Vanhellemont Filip , Kyrölä Erkki , McPeters Richard D.
Published: December 2008

We analyzed a set of Global Ozone Monitoring by Occultation of Stars (GOMOS) bright limb measurements with solar zenith angles less than 85° and within 150 km of Stratospheric Aerosol and Gas Experiment II (SAGE II) measurements. In order to perform any species retrieval, GOMOS measurements were first corrected for stray light contamination. GOMOS pointing was analyzed using scene‐based tangent height algorithms, and the best results were achieved using ∼350 nm (Rayleigh) pixels that were consistent with GOMOS known accurate pointing. In order to demonstrate GOMOS bright limb capabilities, ozone profile retrievals were performed using GOMOS measurements of limb‐scattered radiances with the Ozone Mapping and Profiler Suite limb profiler algorithm. The algorithm performs a simultaneous optimal estimation inversion of both Hartley‐Huggins and Chappuis band radiances. We restricted our GOMOS ozone retrievals to the range 25–53 km, a region of relatively constant measurement uncertainty. In this first look at GOMOS limb data, the retrieved ozone profiles agree with collocated SAGE II measurements on average to within 10–15% and with a standard deviation of 10%. Retrieval results were consistent for both upper and lower GOMOS detector bands.
Time series modeling and central European temperature impact assessment of phenological records over the last 250 years
Authors: Schleip Christoph , Rutishauser This , Luterbacher Jürg , Menzel Annette
Published: December 2008

Long‐term spring and autumn phenological observations from Switzerland and Burgundy (eastern France) as well as long‐term Swiss monthly and seasonal temperature measurements offer a unique possibility to evaluate plant phenological variability and temperature impacts over the last 250 years. We compare Pearson correlation coefficients and linear moving window trends of two different lengths with a Bayesian correlation and model comparison approach. The latter is applied to calculate model probabilities, change‐point probabilities, functional descriptions, and rates of change of three selected models with increasing complexity and temperature weights of single months. Both approaches, the moving window trends as well as the Bayesian analysis, detect major changes in long‐term phenological and temperature time series at the end of the 20th century. Especially for summer temperatures since the 1980s, Bayesian model‐averaged trends reveal a warming rate that increased from an almost zero rate of change to an unprecedented rate of change of 0.08°C/a in 2006. After 1900, temperature series of all seasons show positive model‐averaged trends. In response to this temperature increase, the onset of phenology advanced significantly. We assess the linear dependence of phenological variability by a linear Pearson correlation approach. In addition we apply the Bayesian correlation to account for nonlinearities within the time series. Grape harvest dates show the highest Bayesian correlations with June temperatures of the current year. Spring phenological phases are influenced by May temperatures of the current year and summer temperatures of the preceding growing season. For future work we suggest testing increasingly complex time series models such as multiple change‐point models.
Level set simulation of coupled advection‐diffusion and pore structure evolution due to mineral precipitation in porous media
Authors: Li Xiaoyi , Huang Hai , Meakin Paul
Published: December 2008

A pore‐scale simulation technique based on level set interface tracking has been developed for modeling coupled reactive flow and structure evolution in porous media and fracture apertures. Advection, diffusion, and mineral precipitation resulting in changes in pore geometries are treated simultaneously by solving fully coupled fluid flow and reactive solute transport equations. The reaction‐induced evolution of solid grain surfaces is captured using a level set method, and a subgrid representation of the interface based on the level set approach is used instead of a pixel representation of the interface often used in cellular automata and lattice‐Boltzmann simulations. Precipitation processes within a 2‐D porous medium represented by nonoverlapping discs were simulated under various flow conditions and reaction rates, and the resulting changes of pore geometry are discussed. The simulation results indicate that under reaction‐limited conditions, precipitation is nearly uniform over the grain surfaces. However, this is no longer true when reaction is relatively fast and diffusion is the dominant transport process. In such cases, precipitation occurs mostly near the throat inlet and results in rapid permeability reduction with only a small reduction of porosity. In the case of fast reaction with transport dominated by advection (which is mostly likely in engineered remediation applications), solute can be delivered deep into fracture apertures and precipitation occurs mostly along preferential flow paths. Quantitative relationships between permeability and porosity under various flow conditions and reaction rates are also reported.
Precise magnesium isotope measurements in core top planktic and benthic foraminifera
Authors: Pogge von Strandmann Philip A. E.
Published: December 2008

This study presents a new methodology to obtain highly precise measurements (±0.1‰) of magnesium isotope ratios in very small samples of foraminiferal carbonate (40–50 μg). Here this technique is used to examine Mg isotopic variation among different species of core top foraminifera over a range of different ambient conditions. Despite the high degree of temperature control on the abundance of elemental Mg incorporated into foraminiferal tests, analyses of surface dwelling Globigerinoides ruber and G. sacculifer from five cores, with associated sea surface temperatures ranging from 20 to 31°C, show no significant temperature‐dependent variations in their Mg isotope ratios. Analyses of different size fractions of G. sacculifer show an increase in Mg/Ca with test size but no variation of Mg isotope ratio. In all, nine planktic and benthic species were analyzed; all show identical Mg isotope ratios with a mean of δ26Mg = −4.72‰, apart from small differences in three species, namely O. universa, G. sacculifer (which are both ∼0.4‰ lighter than the average), and P. obliquiloculata (which is ∼0.4‰ heavier). These results highlight the constancy of foraminiferal Mg isotope ratios, despite changing environmental conditions which dominate Mg/Ca variation and arguably affect Ca isotope fractionation. This is an important observation which needs to be included in any model of foraminiferal calcification. The insusceptibility of δ26Mg values to external parameters makes Mg isotopes ideally suited to constraining past variations in the Mg isotope budget of the oceans and the information this carries about the history of oceanic dolomitization, continental weathering, and hydrothermal behavior.
A new height for the summer mesopause: Antarctica, December 2007
Authors: Kirkwood S. , Nilsson H. , Morris R. J. , Klekociuk A. R. , Holdsworth D. A. , Mitchell N. J.
Published: December 2008

Two VHF atmospheric radars operating in Antarctica during austral summer 2007/2008 found the Polar Mesosphere Summer Echo (PMSE) layer at 3–5 km higher altitude during the early season, compared to the late season, and to earlier seasons. Temperatures from the microwave limb sounder on the Aura satellite show that the height of the cold summer mesopause was ∼3 km higher than usual at the same time. The winter polar vortex over Antarctica did not break up until late December, so that eastward winds in the lower stratosphere were as strong as westward winds in the upper stratosphere during the early part of the austral summer. We find that a combination of limited gravity wave forcing from below in the same hemisphere and interhemisphere coupling between the winter stratosphere/mesosphere and the summer mesopause may explain the observations, and suggest a need for reappraisal of the formation mechanisms for the summer mesopause.
Global P, PP, and PKP wave microseisms observed from distant storms
Authors: Gerstoft Peter , Shearer Peter M. , Harmon Nick , Zhang Jian
Published: December 2008

Microseisms are the continuous background vibrations of the Earth observed between earthquakes. Most microseism studies have focused on low frequency energy (0.05–0.5 Hz) propagating as surface waves, but in the microseism spectrum there is also energy that propagates as body waves (P‐waves). Using array analysis on southern California stations we show that these body waves are generated in the ocean from distant storms and propagate deep within the Earth's mantle and core as P, PP and PKP phases. Comparisons with ocean wave hindcast data identify several distinct source regions in both the northern and southern hemispheres. Analyses of these body waves demonstrate that microseisms often have a strong P‐wave component originating from distant locations.
Small‐scale structures in flickering aurora
Authors: Whiter D. K. , Lanchester B. S. , Gustavsson B. , Ivchenko N. , Sullivan J. M. , Dahlgren H.
Published: December 2008

A state‐of‐the‐art multispectral imager has been used to study the flickering component of an auroral event at high spatial (40 m) and temporal (32 fps) resolution. Scale sizes for the flickering patches were found to be regularly smaller than 1 km. The typical flickering frequency observed was in the range 6–8 Hz, although flickering patches at both lower and higher frequencies were identified. The flickering structure was correlated with the coincident non‐flickering aurora, showing that although there is a temporal relationship between the two, there is no spatial correlation. These results support the theory that flickering structure is caused by interfering dispersive Alfvén waves.
Interpretation and evaluation of combined measurement techniques for soil CO2 efflux: Discrete surface chambers and continuous soil CO2 concentration probes
Authors: Riveros‐Iregui Diego A. , McGlynn Brian L. , Epstein Howard E. , Welsch Daniel L.
Published: December 2008

Soil CO2 efflux is a large respiratory flux from terrestrial ecosystems and a critical component of the global carbon (C) cycle. Lack of process understanding of the spatiotemporal controls on soil CO2 efflux limits our ability to extrapolate from fluxes measured at point scales to scales useful for corroboration with other ecosystem level measures of C exchange. Additional complications are introduced by the effects of soil water content seasonality and rainfall on the performance of measurement techniques. In this paper we present measurements of soil CO2 efflux made at two contrasting sites within a characteristic subalpine forest of the northern Rocky Mountains. Comparison of measurements between the soil respiration chamber technique and the soil CO2 profile technique over daily and seasonal time scales indicated that soil water content plays a major role in the magnitude and seasonality of soil CO2 efflux, especially after snowmelt or following summer rainfall. Agreement between both techniques was limited during high soil water content conditions and after summer rainfall. Differences in diel hysteresis patterns of soil CO2 efflux between sites were controlled by the effects of canopy cover and temporal differences in photosynthetic activity of vegetation. Our results indicate that an accurate parameterization of soil water content heterogeneity in space and time must be a critical component of realistic model representations of soil CO2 efflux from heterogeneous landscapes.
Neuropeptide Y Y2 receptor in health and disease
Authors: Parker S L , Balasubramaniam A
Published: December 2008

British Journal of Pharmacology (2008) 155, 1307; doi:10.1038/bjp.2008.376
Toward a Component-Based Design Framework of the International Information Technology Standardization Process
Authors: Ngosi Theodora , Braganza Ashley
Published: December 2008

This article is about a proposal to develop a component-based design (CBD) framework of the international information technology standardization (IITS) process. This process is criticized widely in information systems (IS) literatures for its complexity as a barrier to successful project development. These criticisms have not challenged this process itself or accede to proactive action toward positive changes. We stress the importance of reconstructing this process within a CBD framework, not only to reduce sources of complexity but also to give special prominence of project development. Primarily, our qualitative empirical case study of five projects is grounded in the organization information processing theory (OIPT) as a lens. Theorizing from the qualitative empirical evidence we define the IITS process, followed by its inductive analysis guided by OIPT as a lens through three levels: its environment, content and performance. Through this lens we articulate assumptions about IITS process complexity. From rich descriptions of this process, we combine selected dimensions of CBD and OIPT as a lens to develop the theoretical depth of concepts that add detail to our CBD framework. One implication for practice of this framework is for provisioning incisive IITS process change strategies drawing upon its dominating qualities. This article makes three contributions to the IS field: this CBD framework is a key contribution. We bridge the gap in knowledge by defining the IITS process, explicating its complexity toward proactive action. By using OIPT as a lens we extend its application.
Modulational instability in a purely nonlinear coupled complex Ginzburg–Landau equations through a nonlinear discrete transmission line
Authors: Ndzana Fabien II , Mohamadou Alidou , Kofané Timoléon C.
Published: December 2008

We study wave propagation in a nonlinear transmission line with dissipative elements. We show analytically that the telegraphers' equations of the electrical transmission line can be modeled by a pair of continuous coupled complex Ginzburg–Landau equations, coupled by purely nonlinear terms. Based on this system, we investigated both analytically and numerically the modulational instability (MI). We produce characteristics of the MI in the form of typical dependence of the instability growth rate on the wavenumbers and system parameters. Generic outcomes of the nonlinear development of the MI are investigated by dint of direct simulations of the underlying equations. We find that the initial modulated plane wave disintegrates into waves train. An apparently turbulent state takes place in the system during the propagation.
Turbulence, waves, and jets in a differentially heated rotating annulus experiment
Authors: Wordsworth R. D. , Read P. L. , Yamazaki Y. H.
Published: December 2008

We report an analog laboratory study of planetary-scale turbulence and jet formation. A rotating annulus was cooled and heated at its inner and outer walls, respectively, causing baroclinic instability to develop in the fluid inside. At high rotation rates and low temperature differences, the flow became chaotic and ultimately fully turbulent. The inclusion of sloping top and bottom boundaries caused turbulent eddies to behave like planetary waves at large scales, and eddy interaction with the zonal flow then led to the formation of several alternating jets at mid-depth. The jets did not scale with the Rhines length, and spectral analysis of the flow indicated a distinct separation between jets and eddies in wavenumber space, with direct energy transfer occurring nonlocally between them. Our results suggest that the traditional “turbulent cascade” picture of zonal jet formation may be an inappropriate one in the geophysically important case of large-scale flows forced by differential solar heating.
Composition and luminescence of AlInGaN layers grown by plasma-assisted molecular beam epitaxy
Authors: Bejtka K. , Edwards P. R. , Martin R. W. , Fernández-Garrido S. , Calleja E.
Published: December 2008

A study of AlInGaN epilayers, grown by plasma-assisted molecular beam epitaxy, was performed using spatially resolved x-ray microanalysis and luminescence spectroscopy in order to investigate competition between the incorporation of In, Al, and Ga as a function of the growth temperature in the 565–660 °C range and the nominal AlN mole fraction. The samples studied have AlN and InN mole fractions in the ranges of 4%–30% and 0%–16%, respectively. Composition measurements show the effect of decreasing temperature to be an increase in the incorporation of InN, accompanied by a small but discernible decrease in the ratio of GaN to AlN mole fractions. The incorporation of In is also shown to be significantly increased by decreasing the Al mole fraction. Optical emission peaks, observed by cathodoluminescence mapping and by photoluminescence, provide further information on the epilayer compositions as a function of substrate temperature, and the dependencies of peak energy and linewidth are plotted.
Dielectric responses of modified BaTiO3 ceramics in multilayer ceramic capacitors to the combined uniaxial stress and dc bias field
Authors: Yang Gang , Yue Zhenxing , Gui Zhilun , Li Longtu
Published: December 2008

Dielectric measurements of modified BaTiO3 in a multilayer ceramic capacitor (MLCC) show that the application of external uniaxial stress perpendicular to electric field in a MLCC can lead to a slight increase in the dielectric permittivity. The additional application of a dc bias results in a significantly suppressed dielectric permittivity in the temperature range from 228 to 453 K. These observations can be explained as a result of domain wall movements in grains with a core-shell structure, due to the combined stress and dc bias field. As the dc bias increased up to 5.6 MV/m, the Curie peak, which has diffuse phase transition characteristics in the absence of dc bias, becomes sharper, and two new peaks are induced at about 250 and 315 K. Furthermore, the first order paraelectric-ferroelectric phase transition of the modified BaTiO3 ceramic becomes stronger with increasing dc bias when a uniaxial stress is also applied.
Dielectric nonlinearity of stack piezoelectric actuator under the combined uniaxial mechanical and electric loads
Authors: Yang Gang , Yue Zhenxing , Ji Ye , Li Longtu
Published: December 2008

The dielectric nonlinearity of stack lead zirconium titanate (PZT) piezoelectric actuator was investigated under the combined uniaxial mechanical and electric loads. In the intermediate electric field region (Rayleigh region), the Rayleigh coefficient increases at less than 50 MPa, beyond which it declines. Similarly, the dielectric nonlinearity identified by P-E hysteresis loop, revealed by both the dielectric measurement and the Rayleigh law fitting, also shows an initial increase at less than 50 MPa and a subsequent decrease when stress is above 50 MPa. In the high electric field region, the dielectric nonlinearity declined continuously with increasing stress, which leads to a fact that a boundary between the Rayleigh region and high field region becomes smeared. These results could be interpreted as the influences of the applied stress on ferroelectric domain-related contributions to dielectric response, which is very important to the practical application of stack piezoelectric actuators.
Modeling of the evolution of dielectric loss with processing temperature in ferroelectric and dielectric thin oxide films
Authors: Zhu X. H. , Guigues B. , Defaÿ E. , Aïd M.
Published: December 2008

It was experimentally found that the evolution of dielectric loss with processing temperature displays a common trend in ferroelectric and dielectric thin oxide films; first an increase and then a decrease in dielectric loss when the processing temperature is gradually raised. Such a dielectric response of ferroelectric/dielectric thin films has been theoretically addressed in this work. We propose that at the initial stage of the crystallization process in thin films, the transformation from amorphous to crystalline phase should substantially increase the dielectric loss. Then, with further increase in the processing temperature, the coalescent growth of small crystalline grains into big ones could be helpful in reducing the dielectric loss by lowering grain boundary densities. The obtained experimental data for (Ba,Sr)TiO3 thin films 500 nm in thickness were analyzed in terms of the model developed and shown to be in reasonable agreement with the theoretical results.
Energy derivatives in quantum Monte Carlo involving the zero-variance property
Authors: Badinski A. , Trail J. R. , Needs R. J.
Published: December 2008

We give an exact expression for the nth derivative of the expectation value of the energy that satisfies the zero-variance (ZV) principle when the wave function and its first n derivatives are exact. The ZV principle was previously applied to the first energy derivative (“force”) within the variational Monte Carlo and mixed-estimator diffusion Monte Carlo methods. We present a new expression for the force in pure-estimator diffusion Monte Carlo that satisfies the ZV principle and can be evaluated much more efficiently than previous expressions while maintaining comparable accuracy. This expression is the sum of a pure expectation value and a variational expectation value, which separately satisfy the ZV principle. The bias in this force estimator is second order in the deviation of the trial wave function from the diffusion Monte Carlo wave function. Results for small molecules demonstrate the accuracy of the method and its statistical efficiency.
Internal energy of HCl upon photolysis of 2-chloropropene at 193 nm investigated with time-resolved Fourier-transform spectroscopy and quasiclassical trajectories
Authors: Chang Chih-Min , Huang Yu-Hsuan , Liu Suet-Yi , Lee Yuan-Pern , Pombar-Pérez Marta , Martínez-Núñez Emilio , Vázquez Saulo A.
Published: December 2008

Following photodissociation of 2-chloropropene (H2CCClCH3) at 193 nm, vibration-rotationally resolved emission spectra of HCl (υ≤6) in the spectral region of 1900–2900 cm−1 were recorded with a step-scan time-resolved Fourier-transform spectrometer. All vibrational levels show a small low-J component corresponding to ∼400 K and a major high-J component corresponding to 7100–18 700 K with average rotational energy of 39±311 kJ mol−1. The vibrational population of HCl is inverted at υ=2, and the average vibrational energy is 86±5 kJ mol−1. Two possible channels of molecular elimination producing HCl+propyne or HCl+allene cannot be distinguished positively based on the observed internal energy distribution of HCl. The observed rotational distributions fit qualitatively with the distributions of both channels obtained with quasiclassical trajectories (QCTs), but the QCT calculations predict negligible populations for states at small J. The observed vibrational distribution agrees satisfactorily with the total QCT distribution obtained as a weighted sum of contributions from both four-center elimination channels. Internal energy distributions of HCl from 2-chloropropene and vinyl chloride are compared.
Patterned backgating using single-sided mask aligners: Application to density-matched electron-hole bilayers
Authors: Croxall A. F. , Das Gupta K. , Nicoll C. A. , Thangaraj M. , Farrer I. , Ritchie D. A. , Pepper M.
Published: December 2008

We report our work on fabricating lithographically aligned patterned backgates on thin (50–60 μm) III-V semiconductor samples using single sided mask aligners only. Along with this we also present a way to photograph both sides of a thin patterned chip using inexpensive infrared light emitting diodes and an inexpensive (consumer) digital camera. A robust method of contacting both sides of a sample using an ultrasonic bonder is described. In addition we present a mathematical model to analyze the variation in the electrochemical potential through the doped layers and heterojunctions that are normally present in most GaAs based devices. We utilize the technique and the estimates from our model to fabricate an electron-hole bilayer device in which each layer is separately contacted and has tunable densities. The electron and hole layers are separated by barriers either 25 or 15 nm wide. In both cases, the densities can be matched by using appropriate bias voltages.
Electronic properties of zigzag and armchair carbon nanotubes under uniaxial strain
Authors: Chen Yi-Ray , Weng Cheng-I , Sun Shih-Jye
Published: December 2008

Molecular dynamics simulations and quantum transport theory are employed to study the electronic properties of various zigzag and armchair carbon nanotubes (CNTs) under uniaxial compressive and tensile strains. It is found that the transfer integral decreases as the tensional strain increases. Furthermore, in the (3N+1,0) and (3N,0) zigzag nanotubes, the current induced by the application of a suitable bias voltage varies linearly with the magnitude of the applied strain. Thus, these particular zigzag CNTs are suitable for use as nanoscale strain sensors. Furthermore, the wider detected ranges occur in the smaller diameter of (3N,0) and (3N+1,0) tubes. However, in (11,0) zigzag nanotube and (5,5) armchair nanotube, the variation in current is not in accordance with Ohm’s law with respect to variations in the applied strain. Specifically, the electronic resistance decreases with increasing strain in (11,0) zigzag nanotube, while the current variations in different strains show the irregular and small perturbation in (5,5) armchair nanotube. Accordingly, neither the (11,0) zigzag nanotube nor the (5,5) armchair nanotube is suitable for strain sensing applications, but the (5,5) armchair nanotube has a current with the stable property for a conducting wire.
A planar organic near infrared light detector based on bulk heterojunction of a heteroquaterphenoquinone and poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1, 4-phenylene vinylene]
Authors: Agostinelli T. , Caironi M. , Natali D. , Sampietro M. , Dassa G. , Canesi E. V. , Bertarelli C. , Zerbi G. , Cabanillas-Gonzalez J. , De Silvestri S. , Lanzani G.
Published: December 2008

Planar organic detectors for the near infrared region of the light spectrum have been realized, processing from solution the quinoid molecule 5,5′-bis(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadiene-1-ylidene)-5,5′-dihydro-2,2′-bithiophene (QBT), which shows a peculiar absorption at 680 nm. Sensitization of the active material was obtained by creating a bulk donor-acceptor interface with poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene], which acts as hole acceptor. Photoexcitation and relaxation dynamics in pristine materials and bulk heterojunction have been investigated by means of pump-probe measurements, revealing charge transfer from QBT to polymer and efficient energy transfer the other way round.
Te doping of GaAs using metalorganic vapor phase epitaxy: Volatile versus nonvolatile behavior
Authors: Galiana Beatriz , Rey-Stolle Ignacio , Algora Carlos , García Iván
Published: December 2008

The incorporation of Te into the crystal lattice, when it is used as an n-type dopant for GaAs grown by metalorganic vapor phase epitaxy, is studied. For this purpose, several growth temperatures, total pressures, growth rates, and substrate misorientations have been analyzed, from which it is concluded that depending on the substrate misorientation and total pressure used, the Te behaves like a volatile dopant or a nonvolatile dopant as result of the enhancement or minimization of its adsorption onto the growth surface.
Hydrodynamic loading of microcantilevers oscillating near rigid walls
Authors: Tung Ryan C. , Jana Anirban , Raman Arvind
Published: December 2008

The vibrations of microcantilevers in atomic force microscopes (AFMs) or radio frequency (RF) switches are strongly influenced by the viscous hydrodynamics of the surrounding fluid in the vicinity of a rigid wall. While prior efforts to model this hydrodynamic loading have focused on squeeze film damping effects at high Knudsen and squeeze numbers, the regimes of low Knudsen and squeeze numbers are also very important for which squeeze film models need to be discarded in favor of unsteady Stokes hydrodynamics. We extend the work of Green and Sader [Phys Fluids 17, 073102 (2005); J. Appl. Phys. 98, 114913 (2005)] and present compact semianalytical formulas for the unsteady viscous hydrodynamic function of slender microbeams oscillating near rigid walls, in terms of key nondimensional numbers. Using these closed-form expressions, it becomes possible to predict easily the wet natural frequencies and quality factors of multiple modes of microcantilevers near rigid walls in diverse applications ranging from AFM in liquids to RF microswitches under ambient conditions. The semianalytical formulas are extensively validated by comparing their predicted wet natural frequencies and quality factors with those based on three-dimensional, transient flow-structure interaction simulations, as well as previous experiments performed in the field by other researchers.
Nonuniform threshold voltage profile in a-Si:H thin film transistor stressed under both gate and drain biases
Authors: Wie C. R. , Tang Z. , Park M. S.
Published: December 2008

In this paper we show that an a-Si:H thin film transistor (TFT) stressed with bias temperature stress (BTS) under both gate bias and drain bias produces a nonuniform threshold voltage profile which can be obtained from the quasi-Fermi potential profile and the threshold voltage (Vt)-shift data of BTS under the gate bias only. The transfer and output characteristics calculated with this nonuniform Vt-profile agreed well with the measured data, where the calculation was performed using both the gradual-channel approximation and independently the AIM Spice simulation with its level-15 a-Si TFT model. It is shown that local threshold voltage is high at the source and decreases toward the drain. Due to the nonuniform Vt-profile in the channel, the drain current level is higher in the forward direction, where the source and drain electrodes are the same between measurement and BTS, than in the reverse direction, where source and drain electrodes are interchanged. The forward and reverse I-V characteristics are somewhat similar to those of metal-oxide-semiconductor field-effect transistors with nonuniform channel doping.
Comment on “Model calculation for enhancement factor of a gated field emission nanotube” [J. Appl. Phys. 102, 114503 (2007)]
Authors: Roumeliotis J. A. , Xanthakis J. P.
Published: December 2008

In a recent publication Lei et al.1 calculated the enhancement factor of a gated open nanotube (NT) simulated as a cylindrically folded, zero-thickness sheet of metal. In this comment we argue that (a) the form of the tube (zero thickness) leads to unphysical results and (b) the method of calculation of the enhancement factor is wrong both physically and mathematically, leading to totally irrelevant information about the strength of the tunneling barrier of an electron emitted from the NT.
Response to “Comment on ‘Model calculation for enhancement factor of a gated field emission nanotube’ ” [J. Appl. Phys. 104, 116103 (2008)]
Authors: Lei D. , Zeng L. Y. , Wang W. B.
Published: December 2008

The response addressed the comments of Roumeliotis and Xanthakis on our article [J. Appl. Phys. 102, 114503 (2007)]. The experimental results showed that the choice of the nanotube shape was true.
Ion-acoustic vortices in a nonuniform, dissipative quantum magnetoplasma with sheared ion flows
Authors: Masood W. , Mirza Arshad M. , Nargis Shahida
Published: December 2008

By employing the quantum hydrodynamic model, linear and nonlinear properties of quantum ion-acoustic waves are studied in a nonuniform, dissipative quantum plasma with sheared ion flow parallel to the ambient magnetic field. It is shown that the shear flow parallel to the magnetic field can drive the quantum ion-acoustic wave unstable. Stationary solutions of the nonlinear equations that govern the quantum ion-acoustic waves are also obtained. It is found that electrostatic monopolar, dipolar, and vortex street type solutions can appear in such a plasma. It is observed that the inclusion of the quantum statistical and Bohm potential terms significantly modify the scalelengths of these structures. The present work may have relevance in the dense astrophysical environments where quantum effects are expected to play a significant role.
A collective scattering system for measuring electron gyroscale fluctuations on the National Spherical Torus Experiment
Authors: Smith D. R. , Mazzucato E. , Lee W. , Park H. K. , Domier C. W. , Luhmann N. C.
Published: December 2008

A collective scattering system has been installed on the National Spherical Torus Experiment (NSTX) to measure electron gyroscale fluctuations in NSTX plasmas. The system measures fluctuations with k⊥ρe≲0.6 and k⊥≲20 cm−1. Up to five distinct wavenumbers are measured simultaneously, and the large toroidal curvature of NSTX plasmas provides enhanced spatial localization. Steerable optics can position the scattering volume throughout the plasma from the magnetic axis to the outboard edge. Initial measurements indicate rich turbulent dynamics on the electron gyroscale. The system will be a valuable tool for investigating the connection between electron temperature gradient turbulence and electron thermal transport in NSTX plasmas.
Photonic integration in k-space: Enhancing the performance of photonic crystal dye lasers
Authors: Christiansen Mads Brøkner , Kristensen Anders , Xiao Sanshui , Mortensen Niels Asger
Published: December 2008

We demonstrate how two optical functionalities can be implemented in a single photonic crystal structure by carefully engineering dispersion in several different bands at several different wavelengths. We use the concept for optically pumped dye doped hybrid polymer band edge lasers and show how a rectangular photonic crystal lattice imprinted into the surface can provide both feedback for in-plane band edge lasing and couple pump light into the device plane, thus increasing the emitted intensity and lowering the lasing threshold by more than an order of magnitude.
Genetic modification for bimaternal embryo development
Authors: Kono Tomohiro
Published: December 2008

Full mammalian development typically requires genomes from both the oocyte and spermatozoon. Biparental reproduction is necessary because of parent-specific epigenetic modification of the genome during gametogenesis; that is, a maternal methylation imprint imposed during the oocyte growth period and a paternal methylation imprint imposed in pregonadal gonocytes. This leads to unequivalent expression of imprinted genes from the maternal and paternal alleles in embryos and individuals. It is possible to hypothesise that the maternal methylation imprint is necessary to prevent parthenogenesis, which extinguishes the opportunity for having descendents, whereas the paternal methylation imprint prevents parthenogenesis, ensuring that a paternal contribution is obligatory for any descendants. To date, there are several lines of direct evidence that the epigenetic modifications that occur during oocyte growth have a decisive effect on mammalian development. Using bimaternal embryos with two sets of maternal genomes, the present paper illustrates how parental methylation imprints are an obstacle to the progression of parthenogenesis.
103 MASS SPECTROMETRY ANALYSIS OF UTERUS ENDOMETRIUM DURING PREGNANCY IN THE PIG
Authors: Chae J.-I. , Cho Y. K. , Cho S.-K. , Lee K.-K. , Koo D.-B.
Published: December 2008

In general, many important molecular events occur within the female reproductive tract, especially within the uterine endometrium, during periods of pregnancy. The endometrium includes a mucosal lining of the uterus, which functions to provide a suitable site for implantation and development of a fertilized egg and fetus. To date, developmental integrity involves molecular cascades whose interrelationships are not fully understood within the endometrium during pregnancy in pigs. In this study, we explored the functional regulated proteins in endometrium during periods of pregnancy periods (Day 40, n = 6; Day 70, n = 7; Day 90, n = 6 of pregnancy; and nonpregnancy, n = 1) using 2-dimensional gel electrophoresis (2-DE) and Western blotting. The functional regulated proteins were identified and discovered from differentially expressed proteins in the endometrium during pregnancy. In the proteomic analysis of the endometrium, 820 protein spots were matched on 2-DE gels. With 98 proteins regulated differentially among nonpregnant and pregnant tissues (matched and unmatched spots), 63 up- or down-regulated proteins have been identified. Interestingly, 6 of these 63 proteins were endothelial growth factor-associated proteins such as transgelin, transferrin, galectin-1, tropomyosin alpha, protein DJ-1, and beta-defensin. We also confirmed the expression levels of these proteins in the endometrium during pregnancy by using Western blotting. Our results suggest that the expressions of these genes involved in endometrial function and development from early to late gestation are associated with the regulation of endothelial growth factor.