bluuebunny/crossref_metadata_2025 huggingface dataset:
1911: The Unanchored Chinese Revolution
Authors: Mitter Rana
Published: January 2012

One hundred years after the 1911 Revolution (Xinhai Revolution) in China, its meaning continues to be highly contested. Paradoxically, the more time that passes, the less certain either political actors or scholars seem to be about the significance of 1911 for the path of Chinese revolutionary history. This essay examines three phenomena: the appropriation of 1911 in contemporary political and popular culture; the use of 1911 as a metaphor for contemporary politics by PRC historians; and the changing meaning of 1911 over the past ten decades, particularly during the years of the war against Japan. The essay concludes that it is precisely the “unanchored” nature of 1911, separated from any one path of historical interpretation, that has kept its meaning simultaneously uncertain and potent.
The International Law Commission's Articles on the Responsibility of States for Internationally Wrongful Acts Adopted on Second Reading
Authors: Wittich Stephan
Published: January 2012

In 2001 the International Law Commission finally adopted on second reading the Draft Articles on Responsibility of States for Internationally Wrongful Acts and the commentaries thereto, thereby successfully concluding almost half a century of work on the topic by the ILC. Subsequent to the adoption, the General Assembly welcomed the conclusion of the work of the ILC. This article highlights the main changes made during the second reading 1998–2001, among them the issue of international crimes, the concept of injured state and countermeasures. While the 59 articles are the result of compromise, they undoubtedly are a major achievement in one of the most important and most sensitive areas of international law. Ultimately they may be a useful tool to promote the enforcement of community interests in the international legal system.
The ESEMeD-WMH project: strenghtening epidemiological research in Europe through the study of variation in prevalence estimates
Authors: de Girolamo Giovanni , Alonso Jordi , Vilagut Gemma
Published: January 2012

The European Study of the Epidemiology of Mental Disorders (ESEMeD) project is the first cross-national European survey to collect data on prevalence, risk factors, health-related quality of life and use of services associated with common mental disorders. Representative samples of the non-institutionalized populations of Belgium, France, Germany, Italy, the Netherlands and Spain were interviewed using the CIDI 3.0, totaling 21,425 adult individuals. There was important variation across countries in prevalence estimates of the disorders studied, with Belgium and France in the highest proportions and Italy and Spain the lowest. Comorbidity of mood and anxiety disorders was frequent in all countries. Use of services due to mental health is low in all European countries, but especially low in Italy. Remarkably, only about one in five participants with a mental disorder had consulted the health services in the prior year. We discuss about the possible explanations of cross-national differences in prevalence estimates of mental disorders, and some of the limitations of the data on alcohol abuse and dependence gathered in the study. We conclude that despite the advances in knowledge about determinants and treatment methods, the care of the mentally ill is rather limited in Europe.
A NOTE ON EXPECTATIONAL STABILITY UNDER NONZERO TREND INFLATION
Authors: Kobayashi Teruyoshi , Muto Ichiro
Published: January 2012

This study examines the expectational stability of rational expectations equilibria (REE) under alternative Taylor rules when trend inflation is nonzero. We find that when trend inflation is high, the REE is likely to be expectationally unstable. This result holds true regardless of the nature of the data (such as contemporaneous, forecast, or lagged data) introduced in the Taylor rule. Our results suggest that high macroeconomic volatility during the period of high trend inflation can be explained well by introducing the concept of expectational stability.
Diabetes-Induced Alterations in the Extracellular Matrix and Their Impact on Myocardial Function
Authors: Law Brittany , Fowlkes Vennece , Goldsmith Jack G. , Carver Wayne , Goldsmith Edie C.
Published: January 2012

Diabetes is an increasing public health problem that is expected to escalate in the future due to the growing incidence of obesity in the western world. While this disease is well known for its devastating effects on the kidneys and vascular system, diabetic individuals can develop cardiac dysfunction, termed diabetic cardiomyopathy, in the absence of other cardiovascular risk factors such as hypertension or atherosclerosis. While much effort has gone into understanding the effects of elevated glucose or altered insulin sensitivity on cellular components within the heart, significant changes in the cardiac extracellular matrix (ECM) have also been noted. In this review article we highlight what is currently known regarding the effects diabetes has on both the expression and chemical modification of proteins within the ECM and how the fibrotic response often observed as a consequence of this disease can contribute to reduced cardiac function.
Implications of the Doha market access proposals for developing countries
Authors: LABORDE DAVID , MARTIN WILL , VAN DER MENSBRUGGHE DOMINIQUE
Published: January 2012

This paper uses detailed data on bound and applied tariffs to assess the consequences of the WTO's December 2008 Modalities for tariffs levied and faced by developing countries, and the welfare implications of these reforms. We find that the tiered formula for agriculture would halve tariffs in industrial countries and lower them more modestly in developing countries. In non-agricultural market access (NAMA), the formulas would reduce the tariff peaks facing developing countries and cut average industrial country tariffs by more than a third. We use a political-economy framework to assess the implications of flexibilities for the size of the tariff cuts and find they are likely to substantially reduce the outcome. However, despite the flexibilities, there are likely to be worthwhile gains, with applied tariffs facing developing countries cut by about 20% in agriculture and 28% in NAMA, and sizeable cuts in tariffs facing industrial countries. The welfare impacts of reform are evaluated using a new approach to aggregation that improves on the traditional, flawed approach of weighted-average tariffs. This substantially increases the estimated benefits of an agreement along the lines of these modalities, with estimated global income gains of up to $160 billion per year from market access reform.
The Challenge of Democracy: Explorations in American Racial Politics
Authors: Pinderhughes Dianne
Published: January 2012

I address you on August 28, 2008, on the same evening as the Democratic nominee Barack Obama speaks at the Democratic National Convention in Denver, Colorado.
Why Cooperate? The Incentive to Supply Global Public Goods. By Scott Barrett. Oxford and New York: Oxford University Press, 2007. 280p. $45.00.
Authors: Whiteside Kerry
Published: January 2012

Public goods, as economists use the term, are “nonrival” (one person's consumption does not make it unavailable for others) and, typically, “nonexcludable” (if the good is provided to one person, others cannot be prevented from enjoying it as well). The classic example is the lighthouse, whose warning light goes out to and benefits all ships. Economists devote special attention to public goods because markets do not deliver them efficiently. Rational, self-interested actors realize that if anyone else provides this good, they can have it without paying for it. The incentives favor “free riding.” Others, however, see the same opportunity and so public goods go underprovided. There is thus a strong case for collective action to furnish public goods. Where collective benefits outweigh the costs of provision, government action can make society as a whole better-off.
Response to Kerry Whiteside's review of Why Cooperate? The Incentive to Supply Global Public Goods
Authors: Barrett Scott
Published: January 2012

I am grateful to Kerry Whiteside for reviewing my book, and wanted to respond to his two mildly critical comments.
Degassing history of Mars and the lifespan of its magnetic dynamo
Authors: Sandu Constantin , Kiefer Walter S.
Published: January 2012

The volcanic and magnetic activity on the surface of Mars is directly related to its thermal evolution and to the melting potential of its mantle. Mars does not have an internal magnetic field today but geologic evidence suggests a dynamo was active during the first 500 to 800 million years of Martian history. The existence of the magnetic field on the planet sets a lower bound on the vigor of convection within its liquid core. The vigor of core convection can be maintained by efficient cooling of the overlying mantle. An initially wet mantle will promote strong convection, rapid core cooling, and dynamo activity. Magmatic degassing and planetary cooling increases the mantle's viscosity, thus decreasing the rate of core cooling and possibly terminating dynamo activity. The timescale for ending core dynamo activity is controlled by the initial amount of water in the mantle and by the efficiency of the degassing process. This process is an alternative to recent models that postulate dynamo termination on Mars is controlled by impact heating of the mantle.
Anomalous ISR echoes preceding auroral breakup: Evidence for strong Langmuir turbulence
Authors: Akbari H. , Semeter J. L. , Dahlgren H. , Diaz M. , Zettergren M. , Strømme A. , Nicolls M. J. , Heinselman C.
Published: January 2012

Experimental results obtained with the 449‐MHz Poker Flat Incoherent Scatter Radar (PFISR) show unusual features in both the ion line and plasma line measurements during an auroral breakup event. The features are a greatly enhanced flat ion acoustic spectrum (believed to indicate the presence of an additional peak at zero Doppler), and two peaks in the plasma line spectrum. Similar spectral morphologies are observed during active HF ionospheric modification experiments and are considered unmistakable indications of Strong Langmuir Turbulence (SLT). In SLT theory, the central peak in ion acoustic spectrum is caused by Bragg scattering from non‐propagating density fluctuations (cavitons), and the two peaks in the plasma line spectrum are associated with (1) Langmuir waves trapped in the cavitons, at the cold plasma frequency, and (2) a “free mode” at the Langmuir frequency. Free modes are radiated Langmuir waves from collapsing cavitons that follow the linear dispersion relation. The observed turbulence was confined to a thin layer (∼10‐km) centered at ∼230 km altitude.
Modified two‐stream instability at perpendicular collisionless shocks: Full particle simulations
Authors: Umeda Takayuki , Kidani Yoshitaka , Matsukiyo Shuichi , Yamazaki Ryo
Published: January 2012

A full particle simulation study is carried out for studying microinstabilities generated in self‐consistently excited perpendicular collisionless shocks. The present two‐dimensional simulation with a high ion‐to‐electron mass ratio shows that the modified two‐stream instability can be generated by the interaction of incoming and reflected ions with electromagnetic whistler mode waves propagating in the direction quasi‐perpendicular to the ambient magnetic field. Properties of the excited whistler mode waves are consistent with the linear dispersion analysis based on the simulated velocity distribution functions. It is also found that the excited waves have an electron‐scale wavelength in the shock‐normal direction and an ion‐scale wavelength in the shock‐tangential direction, suggesting that the electron‐scale microturbulences and the ion‐scale shock structures are coupled with each other through the modified two‐stream instability.
The effect of orography and surface albedo on stratification in the summertime Saharan boundary layer: Dynamics and implications for dust transport
Authors: Birch Cathryn E. , Parker Douglas J. , Marsham John H. , Devine Gerard M.
Published: January 2012

Observations have shown that there are significant day‐to‐day variations in the stratification of the Saharan boundary layer, which is a control on regional dust transport and mixing. It has been suggested that the Hoggar Mountains, in the east part of the Sahara desert, act as an elevated heat source that injects air out of the convective boundary layer, induces subsidence, and inhibits the growth of the daytime convective boundary layer (CBL) over the western (remote) part of the Sahara. Here model experiments are performed for three case study periods: control cases and runs with the surface albedo and orographic variations in the Hoggar region removed. It is shown that plumes of hot air over the mountains can inject hot air (which may be dust laden) through the Saharan residual layer to altitudes of 8 km. The mountains and, to a lesser extent, the patches of low surface albedo produce a deeper and warmer CBL up to 400 km west of the main peaks. The model simulations also provide evidence that the mountains inhibit the daytime growth of the remote convective boundary layer, as postulated in earlier observational papers. However, the mechanism for this remote influence on the boundary layer is not subsidence induced by the mountains. Instead, the mountains act as an obstacle to the larger‐scale northeasterly flow and divert cooler air to the west and east of the mountain range. This cools the remote boundary layer and therefore reduces the depth of the daytime CBL.
Evaluation of multireanalysis products with in situ observations over the Tibetan Plateau
Authors: Wang Aihui , Zeng Xubin
Published: January 2012

As the highest plateau in the world, the Tibetan Plateau (TP) strongly affects regional weather and climate as well as global atmospheric circulations. Here six reanalysis products (i.e., MERRA, NCEP/NCAR‐1, CFSR, ERA‐40, ERA‐Interim, and GLDAS) are evaluated using in situ measurements at 63 weather stations over the TP from the Chinese Meteorological Administration (CMA) for 1992–2001 and at nine stations from field campaigns (CAMP/Tibet) for 2002–2004. The measurement variables include daily and monthly precipitation and air temperature at all CMA and CAMP/Tibet stations as well as radiation (downward and upward shortwave and longwave), wind speed, humidity, and surface pressure at CAMP stations. Four statistical quantities (correlation coefficient, ratio of standard deviations, standard deviation of differences, and bias) are computed, and a ranking approach is also utilized to quantify the relative performance of reanalyses with respect to each variable and each statistical quantity. Compared with measurements at the 63 CMA stations, ERA‐Interim has the best overall performance in both daily and monthly air temperatures, while MERRA has a high correlation with observations. GLDAS has the best overall performance in both daily and monthly precipitation because it is primarily based on the merged precipitation product from surface measurements and satellite remote sensing, while ERA‐40 and MERRA have the highest correlation coefficients for daily and monthly precipitation, respectively. Compared with measurements at the nine CAMP stations, CFSR shows the best overall performance, followed by GLDAS, although the best ranking scores are different for different variables. It is also found that NCEP/NCAR‐1 reanalysis shows the worst overall performance compared with both CMA and CAMP data. Since no reanalysis product is superior to others in all variables at both daily and monthly time scales, various reanalysis products should be combined for the study of weather and climate over the TP.
Benchmarking the performance of pairwise homogenization of surface temperatures in the United States
Authors: Williams Claude N. , Menne Matthew J. , Thorne Peter W.
Published: January 2012

Changes in the circumstances behind in situ temperature measurements often lead to biases in individual station records that, collectively, can also bias regional temperature trends. Since these biases are comparable in magnitude to climate change signals, homogeneity “corrections” are necessary to make the records suitable for climate analysis. To quantify the effectiveness of U.S. surface temperature homogenization, a randomized perturbed ensemble of the USHCN pairwise homogenization algorithm was run against a suite of benchmark analogs to real monthly temperature data. Results indicate that all randomized versions of the algorithm consistently produce homogenized data closer to the true climate signal in the presence of widespread systematic errors. When applied to the real‐world observations, the randomized ensemble reinforces previous understanding that the two dominant sources of bias in the U.S. temperature records are caused by changes to time of observation (spurious cooling in minimum and maximum) and conversion to electronic resistance thermometers (spurious cooling in maximum and warming in minimum). Error bounds defined by the ensemble output indicate that maximum temperature trends are positive for the past 30, 50 and 100 years, and that these maximums contain pervasive negative biases that cause the unhomogenized (raw) trends to fall below the lower limits of uncertainty. Moreover, because residual bias in the homogenized analogs is one‐tailed under biased errors, it is likely that maximum temperature trends have been underestimated in the USHCN. Trends for minimum temperature are also positive over the three periods, but the ensemble error bounds encompass trends from the unhomogenized data.
Estimation of the solar flare neutron worst‐case fluxes and fluences for missions traveling close to the Sun
Authors: Lario D.
Published: January 2012

A method to estimate the total fluence of solar flare neutrons at a spacecraft traveling in the innermost part of the heliosphere (at heliocentric radial distances of <1 AU) is presented. The results of the neutron production and emissivity codes of Hua and Lingenfelter (1987a, 1987b) scaled to one of the largest solar neutron events ever observed at the Earth are used to derive a conservative estimate of the energy spectrum of neutrons emitted from the Sun after a large solar flare. By taking into account the survival probability of a neutron to reach a certain heliocentric distance, we evaluate the observed time‐integrated spectrum of solar neutrons as a function of the heliocentric distance of the observer. By considering (1) a working relationship between the soft X‐ray class of a flare and the flare's production of solar neutrons, and (2) the number and size of soft X‐ray flares that may occur during a mission traveling close to the Sun, we compute an upper limit for the total fluence of solar neutrons at energies >1 MeV, >10 MeV, >100 MeV and >1000 MeV to which such a mission may be exposed. We apply this method to the Solar Probe Plus mission. Although our method gives a conservative estimate of neutron fluxes, the predicted mission‐integrated fluence of solar neutrons at Solar Probe Plus is orders of magnitude below that of solar energetic protons.
The Q43L mutant of neuregulin 2β is a pan-ErbB receptor antagonist
Authors: Wilson Kristy J. , Mill Christopher P. , Gallo Richard M. , Cameron Elizabeth M. , VanBrocklin Henry , Settleman Jeffrey , Riese David J.
Published: January 2012

The ErbB4 receptor tyrosine kinase possesses both tumour suppressor and oncogenic activities. Thus pharmacological agents are needed to help elucidate ErbB4 functions. However, limitations of existing ErbB4 agonists and antagonists have led us to seek novel ErbB4 antagonists. The Q43L mutant of the ErbB4 agonist NRG2β (neuregulin 2β) stimulates ErbB4 tyrosine phosphorylation, yet fails to stimulate ErbB4 coupling to cell proliferation. Thus in the present paper we hypothesize that NRG2β/Q43L may be an ErbB4 antagonist. NRG2β/Q43L competitively antagonizes agonist stimulation of ErbB4 coupling to cell proliferation. NRG2β/Q43L stimulates less ErbB4 tyrosine phosphorylation than does NRG2β. In addition, NRG2β stimulation of cell proliferation requires PI3K (phosphoinositide 3-kinase) activity and NRG2β stimulates greater Akt phosphorylation than does NRG2β/Q43L. Moreover, EGFR [EGF (epidermal growth factor) receptor] kinase activity (but not that of ErbB4) is critical for coupling ErbB4 to proliferation. Experiments utilizing ErbB4 splicing isoforms and mutants suggest that NRG2β and NRG2β/Q43L may differentially stimulate ErbB4 coupling to the transcriptional co-regulator YAP (Yes-associated protein). Finally, NRG2β/Q43L competitively antagonizes agonist stimulation of EGFR and ErbB2/ErbB3, indicating that NRG2β/Q43L is a pan-ErbB antagonist. Thus we postulate that NRG2β/Q43L and other antagonistic ligands stimulate ErbB tyrosine phosphorylation on a set of residues distinct from that stimulated by agonists, thus suggesting a novel mechanism of ErbB receptor regulation. Moreover, NRG2β/Q43L and related ligand-based antagonists establish a paradigm for the discovery of anti-ErbB therapeutics.
The Speech Intelligibility Index and the Pure-Tone Average as Predictors of Lexical Ability in Children Fit With Hearing Aids
Authors: Stiles Derek J. , Bentler Ruth A. , McGregor Karla K.
Published: January 2012

Purpose

To determine whether a clinically obtainable measure of audibility, the aided Speech Intelligibility Index (SII; American National Standards Institute, 2007), is more sensitive than the pure-tone average (PTA) at predicting the lexical abilities of children who wear hearing aids (CHA).

Method

School-age CHA and age-matched children with normal hearing (CNH) repeated words and nonwords, learned novel words, and completed a standardized receptive vocabulary test. Analyses of covariance allowed comparison of the 2 groups. For CHA, regression analyses determined whether SII held predictive value over and beyond PTA.

Results

CHA demonstrated poorer performance than CNH on tests of word and nonword repetition and receptive vocabulary. Groups did not differ on word learning. Aided SII was a stronger predictor of word and nonword repetition and receptive vocabulary than PTA. After accounting for PTA, aided SII remained a significant predictor of nonword repetition and receptive vocabulary.

Conclusions

Despite wearing hearing aids, CHA performed more poorly on 3 of 4 lexical measures. Individual differences among CHA were predicted by aided SII. Unlike PTA, aided SII incorporates hearing aid amplification characteristics and speech-frequency weightings and may provide a more valid estimate of the child's access to and ability to learn from auditory input in real-world environments.
The divide-expand-consolidate family of coupled cluster methods: Numerical illustrations using second order Møller-Plesset perturbation theory
Authors: Høyvik Ida-Marie , Kristensen Kasper , Jansik Branislav , Jørgensen Poul
Published: January 2012

Previously, we have introduced the linear scaling coupled cluster (CC) divide-expand-consolidate (DEC) method, using an occupied space partitioning of the standard correlation energy. In this article, we show that the correlation energy may alternatively be expressed using a virtual space partitioning, and that the Lagrangian correlation energy may be partitioned using elements from both the occupied and virtual partitioning schemes. The partitionings of the correlation energy leads to atomic site and pair interaction energies which are term-wise invariant with respect to an orthogonal transformation among the occupied or the virtual orbitals. Evaluating the atomic site and pair interaction energies using local orbitals leads to a linear scaling algorithm and a distinction between Coulomb hole and dispersion energy contributions to the correlation energy. Further, a detailed error analysis is performed illustrating the error control imposed on all components of the energy by the chosen energy threshold. This error control is ultimately used to show how to reduce the computational cost for evaluating dispersion energy contributions in DEC.
Gaining insight into the physics of dynamic atomic force microscopy in complex environments using the VEDA simulator
Authors: Kiracofe Daniel , Melcher John , Raman Arvind
Published: January 2012

Dynamic atomic force microscopy (dAFM) continues to grow in popularity among scientists in many different fields, and research on new methods and operating modes continues to expand the resolution, capabilities, and types of samples that can be studied. But many promising increases in capability are accompanied by increases in complexity. Indeed, interpreting modern dAFM data can be challenging, especially on complicated material systems, or in liquid environments where the behavior is often contrary to what is known in air or vacuum environments. Mathematical simulations have proven to be an effective tool in providing physical insight into these non-intuitive systems. In this article we describe recent developments in the VEDA (virtual environment for dynamic AFM) simulator, which is a suite of freely available, open-source simulation tools that are delivered through the cloud computing cyber-infrastructure of nanoHUB (www.nanohub.org). Here we describe three major developments. First, simulations in liquid environments are improved by enhancements in the modeling of cantilever dynamics, excitation methods, and solvation shell forces. Second, VEDA is now able to simulate many new advanced modes of operation (bimodal, phase-modulation, frequency-modulation, etc.). Finally, nineteen different tip-sample models are available to simulate the surface physics of a wide variety different material systems including capillary, specific adhesion, van der Waals, electrostatic, viscoelasticity, and hydration forces. These features are demonstrated through example simulations and validated against experimental data, in order to provide insight into practical problems in dynamic AFM.
Clusters in a mixture of an “amphiphilic” ionic liquid and a nonionic liquid: Theoretical study
Authors: Aerov Artem A. , Khokhlov Alexei R. , Potemkin Igor I.
Published: January 2012

A Flory-Huggins type lattice approach is used to describe theoretically a heterogeneous mixture composed of an ionic liquid (IL) and a nonionic liquid (nIL). It is analyzed, how the behavior of the system depends on the difference in the affinities of the cations and the anions to the neutral molecules (i.e., on the “amphiphilicity” of the IL with respect to the nIL). It is proved that if the difference in the affinities is not large, two macrophases coexist in the mixture; if the difference exceeds a certain threshold value, the mixture becomes microheterogeneous: depending on its composition, it can turn either into ion clusters dispersed over the phase having low concentration of ions, or into clusters of neutral molecules dispersed over the phase having high concentration of ions. If the system is not close to the critical point, the ion clusters can be only small: the maximal ratio of their diameter to an ion diameter is of the order of ten; however, the clusters of nonionic molecules can be large, if the difference in the affinities has a certain value. It is predicted also that cavities can nucleate inside an IL, and clusters of ions can appear in a saturated vapor of an IL.
Structure and electronic properties of a benzene-water solution
Authors: Mateus Margarida P. S. , Galamba Nuno , Cabral Benedito J. Costa
Published: January 2012

Electronic properties of benzene in water were investigated by a sequential quantum mechanical/molecular dynamics approach. Emphasis was placed on the analysis of the structure, polarization effects, and ionization spectrum. By adopting a polarizable model for both benzene and water the structure of the benzene-water solution is in good agreement with data from first principles molecular dynamics. Further, strong evidence that water molecules acquire enhanced orientational order near the benzene molecule is found. Upon hydration, the quadrupole moment of benzene is not significantly changed in comparison with the gas-phase value. We are also reporting results for the dynamic polarizability of benzene in water. Our results indicate that the low energy behaviour of the dynamic polarizability of gas-phase and hydrated benzene is quite similar. Outer valence Green's function calculations for benzene in liquid water show a splitting of the gas-phase energy levels associated with the 1e1g(π), 2e2g, and 2e1u orbitals upon hydration. Lifting of the orbitals degeneracy and redshift of the outer valence bands is related to symmetry breaking of the benzene structure in solution and polarization effects from the surrounding water molecules.
Role of negatively charged ions in plasma on the growth and field emission properties of spherical carbon nanotube tip
Authors: Tewari Aarti , Walia Ritu , Sharma Suresh C.
Published: January 2012

The role of negatively charged ions in plasma on growth (without catalyst) and field emission properties of spherical carbon nanotube (CNT) tip has been theoretically investigated. A theoretical model of charge neutrality, including the kinetics of electrons, negatively and positively charged ions, neutral atoms, and the energy balance of various species has been developed. Numerical calculations of the spherical CNT tip radius for different relative density of negatively charged ions ɛr(=nSF6-/nC+, where nSF6- and nC+ are the equilibrium densities of sulphur hexafluoride and carbon ions, respectively) have been carried out for the typical glow discharge plasma parameters. It is found that the spherical CNT tip radius decreases with ɛr and hence the field emission of electrons from the spherical CNT tip increases. Some of our theoretical results are in accordance with the existing experimental observations.
Anisotropy of strain relaxation in (100) and (110) Si/SiGe heterostructures
Authors: Trinkaus H. , Buca D. , Minamisawa R. A. , Holländer B. , Luysberg M. , Mantl S.
Published: January 2012

Plastic strain relaxation of SiGe layers of different crystal orientations is analytically analyzed and compared with experimental results. First, strain relaxation induced by ion implantation and annealing, considering dislocation loop punching and loop interactions with interfaces/surfaces is discussed. A flexible curved dislocation model is used to determine the relation of critical layer thickness with strain/stress. Specific critical conditions to be fulfilled, at both the start and end of the relaxation, are discussed by introducing a quality parameter for efficient strain relaxation, defined as the ratio of real to ideal critical thickness versus strain/stress. The anisotropy of the resolved shear stress is discussed for (001) and (011) crystal orientations in comparison with the experimentally observed anisotropy of strain relaxation for Si/SiGe heterostructures.
Solute rotation in polar liquids: Microscopic basis for the Stokes-Einstein-Debye model
Authors: Das Amit , Biswas Ranjit , Chakrabarti J.
Published: January 2012

Here, we develop a framework for a molecular level understanding of the celebrated Stokes-Einstein-Debye (SED) formula. In particular, we explore reasons behind the surprising success of the SED model in describing dipolar solute rotation in complex polar media. Relative importance of solvent viscosity and solute-solvent dipolar interaction is quantified via a self-consistent treatment for the total friction on a rotating solute where the hydrodynamic contribution is modified by the friction arising from the longer ranged solute-solvent dipolar interaction. Although the solute-solvent dipolar coupling is obtained via the Mori-Zwanzig formalism, the inclusion of solvent structure via the wave vector dependent viscosity in the hydrodynamic contribution incorporates solvent molecularity in the present theory. This approach satisfactorily describes the experimental rotation times measured using a dipolar solute, coumarin 153 (C153), in protic and aprotic polar liquids, and more importantly, provides microscopic explanation for insignificant contribution of electrical interactions on solute rotation, in contrast to the substantial role played by the translational dielectric friction in the context of ionic mobility. It is also discussed on how the present theory can be suitably extended to study the rotation of a realistic solute in media other than dipolar solvents.
Stress tensor dependence of the polarized Raman spectrum of tetragonal barium titanate
Authors: Pezzotti Giuseppe , Okai Keisuke , Zhu Wenliang
Published: January 2012

The stress tensor dependence of the polarized Raman spectrum of the barium titanate (BaTiO3) tetragonal structure has been theoretically elucidated and the phonon deformation potential (PDP) constants of its A1(TO) and E(TO) vibrational modes measured by means of a spectroscopic analysis of single-crystalline samples under controlled stress fields. Two types of stress field were employed: (i) A uniaxial (compressive) stress field generated with loading along different crystallographic axes and (ii) a biaxial (tensile) stress field stored at the tip of a surface crack propagated across the a-plane of the crystal. This latter stress field enabled us unfolding the full set of PDP values for the E(TO) vibrational mode. However, the highly graded (multiaxial) stress field stored at the crack tip required both rationalizing the dependence of oblique phonons on crystal orientation and applying a spatial deconvolution routine based on the three-dimensional response of the Raman probe. According to a combination of experimental and computational procedures, we quantitatively uncoupled the effects of crystallographic orientation and spatial convolution from the locally collected Raman spectra. Uniaxial compression and biaxial tensile stress calibrations led to consistent PDP values, thus allowing the establishment of a working algorithm for stress analysis in the technologically important class of perovskitic material. Finally, as an application of the newly developed procedure, a tensor-resolved stress analysis was performed to evaluate the unknown (elastic) magnitude of the residual stress components and the extent of the plastic deformation zone generated around a Vickers indentation print in BaTiO3 single crystal. The present findings open the way to tensor resolved Raman analysis of the complex strain fields stored in advanced ferroelectric devices.
Constrained adiabatic trajectory method: A global integrator for explicitly time-dependent Hamiltonians
Authors: Leclerc A. , Jolicard G. , Viennot D. , Killingbeck J. P.
Published: January 2012

The constrained adiabatic trajectory method (CATM) is reexamined as an integrator for the Schrödinger equation. An initial discussion places the CATM in the context of the different integrators used in the literature for time-independent or explicitly time-dependent Hamiltonians. The emphasis is put on adiabatic processes and within this adiabatic framework the interdependence between the CATM, the wave operator, the Floquet, and the (t, t′) theories is presented in detail. Two points are then more particularly analyzed and illustrated by a numerical calculation describing the \documentclass[12pt]{minimal}\begin{document}$\text{H}_2^+$\end{document}H2+ ion submitted to a laser pulse. The first point is the ability of the CATM to dilate the Hamiltonian spectrum and thus to make the perturbative treatment of the equations defining the wave function possible, possibly by using a Krylov subspace approach as a complement. The second point is the ability of the CATM to handle extremely complex time-dependencies, such as those which appear when interaction representations are used to integrate the system.
Theory of nitrogen doping of carbon nanoribbons: Edge effects
Authors: Jiang Jie , Turnbull Joseph , Lu Wenchang , Boguslawski Piotr , Bernholc J.
Published: January 2012

Nitrogen doping of a carbon nanoribbon is profoundly affected by its one-dimensional character, symmetry, and interaction with edge states. Using state-of-the-art ab initiocalculations, including hybrid exact-exchange density functional theory, we find that, for N-doped zigzag ribbons, the electronic properties are strongly dependent upon sublattice effects due to the non-equivalence of the two sublattices. For armchair ribbons, N-doping effects are different depending upon the ribbon family: for families 2 and 0, the N-induced levels are in the conduction band, while for family 1 the N levels are in the gap. In zigzag nanoribbons, nitrogen close to the edge is a deep center, while in armchair nanoribbons its behavior is close to an effective-mass-like donor with the ionization energy dependent on the value of the band gap. In chiral nanoribbons, we find strong dependence of the impurity level and formation energy upon the edge position of the dopant, while such site-specificity is not manifested in the magnitude of the magnetization.
Multi-scale modeling of diffusion-controlled reactions in polymers: Renormalisation of reactivity parameters
Authors: Everaers Ralf , Rosa Angelo
Published: January 2012

The quantitative description of polymeric systems requires hierarchical modeling schemes, which bridge the gap between the atomic scale, relevant to chemical or biomolecular reactions, and the macromolecular scale, where the longest relaxation modes occur. Here, we use the formalism for diffusion-controlled reactions in polymers developed by Wilemski, Fixman, and Doi to discuss the renormalisation of the reactivity parameters in polymer models with varying spatial resolution. In particular, we show that the adjustments are independent of chain length. As a consequence, it is possible to match reactions times between descriptions with different resolution for relatively short reference chains and to use the coarse-grained model to make quantitative predictions for longer chains. We illustrate our results by a detailed discussion of the classical problem of chain cyclization in the Rouse model, which offers the simplest example of a multi-scale descriptions, if we consider differently discretized Rouse models for the same physical system. Moreover, we are able to explore different combinations of compact and non-compact diffusion in the local and large-scale dynamics by varying the embedding dimension.
Size-dependent low-frequency dielectric properties in the BaTiO3/poly(vinylidene fluoride) nanocomposite films
Authors: Fan Ben-Hui , Zha Jun-Wei , Wang Dongrui , Zhao Jun , Dang Zhi-Min
Published: January 2012

Effects of inorganic nanoparticles size and thermal agitation on dielectric properties of BaTiO3/poly(vinylidene fluoride) (BT/PVDF) nanocomposite films at low frequency were studied. The dielectric properties of the BT/PVDF nanocomposite films with three kinds of diameters of BT nanoparticles loading at 50 vol. % were studied in a wide frequency range from 10−2 Hz to 107 Hz by two measured processes. A significant low-frequency dielectric permittivity increase and the difference in dielectric properties between two measured processes were discussed. Interfacial polarization, crystal phase effect, and thermal agitation are considered to analyze the significant increase and difference in dielectric behaviors.
Converse-piezoelectric effect on current-voltage characteristics of symmetric ferroelectric tunnel junctions
Authors: Lu Xiaoyan , Cao Wenwu , Jiang Wenhua , Li Hui
Published: January 2012

Current-voltage characteristics of symmetric ferroelectric tunnel junction were studied in an ultrathin ferroelectric barrier with the consideration of the thickness and strain dependent converse-piezoelectric effect. With proper boundary conditions, large piezoelectric strain can be achieved in the ferroelectric barrier when its thickness is in the vicinity of the critical thickness. Because of the exponential relationship between the tunneling current and the effective film thickness, tunneling current can be greatly enhanced by the external electric field and substrate induced strain.
Polarization reversal and jump-like domain wall motion in stoichiometric LiTaO3 produced by vapor transport equilibration
Authors: Shur V. Ya. , Akhmatkhanov A. R. , Baturin I. S. , Shishkina E. V.
Published: January 2012

The polarization reversal and domain structure evolution has been studied in stoichiometric lithium tantalate prepared by vapor transport equilibration process. The first in situ visualization of domain kinetics has demonstrated the jump-like motion of few strictly oriented plane domain walls, which leads to short isolated current pulses in the switching current data. The proposed model of jump-like domain wall motion caused by interaction with pinning centers representing the areas with increased value of the threshold field is based on the effect of retardation of bulk screening. The derived formulas were applied successfully for analysis of the field dependence of the total switching time. The durations of wall jumps and wall stays (rest times) extracted from the switching current data are analyzed separately. The deceleration of the wall motion velocity during jump is controlled by the trail of residual depolarization field produced by bound charges and screening charges in the area behind the wall. The duration of the rest time is governed by the bulk screening of residual depolarization field. The value of Hurst exponent 0.75 obtained by fractal analysis of the switching current data has confirmed the essential influence of prehistory on the domain wall motion. The measurements of the coercive field by switching in bipolar triangular pulses in wide range of the field ramp rate have allowed us to extract the record low value of coercive field 60 V/mm for quasi-static polarization reversal.
Particulate mixing in a turbulent serpentine duct
Authors: Huang X. , Durbin P. A.
Published: January 2012

Direct numerical simulations of particles in a serpentine duct were conducted at bulk flow Stokes numbers between 0.125 and 6. The geometrical curvature causes particles to depart direction from the mean flow. Above a Stokes number of about unity, a reflection layer forms along the outer curve of the bend. Reflectional mixing creates regions of nearly uniform particle mean velocity and kinetic energy. Particles leave the inner bend in a plume that separates from the inner wall at low Stokes number. At higher Stokes number, the plume splits in two, adding an upper part consisting of ballistic particles, that do not follow the geometrical curvature. When the Stokes number is low, the instantaneous 3-D distribution of particles visualizes wall streaks. But at higher Stokes number, particles disperse out of the reflection layer and form large scale puffs in the central portion of the duct.
Mediation of resonance energy transfer by a third molecule
Authors: Salam A.
Published: January 2012

The influence of a third molecule on the rate of resonance energy transfer is studied using diagrammatic perturbation theory within the framework of molecular quantum electrodynamics. Two distinct mechanisms are identified. One corresponds to direct transfer between donor and acceptor while the other involves relay of energy by the third species. Fermi Golden rule transition rates valid for all separation distances beyond wave function overlap are evaluated for these two processes as well as for the interference term between direct and indirect exchange, thereby extending previous work which was limited to the near-zone only. Short- and long-range limits are also obtained in each case. It is found that in the near-zone the indirect rate contribution exhibits inverse sixth power dependence on relative distances of emitter and absorber relative to the third body, in contrast to its far-zone counterpart, which exhibits inverse square behavior. The interference term, however, displays inverse cubic dependence on all three distance vectors at short-range and inverse behavior in the far-zone. Interestingly, for a collinear arrangement of the three molecules in the near-zone, the interference term is negative, reducing the overall rate of energy transfer. The results obtained are interpreted in terms of microscopic and macroscopic pictures of transfer occurring within a surrounding medium.
Optical pumping and reversal of hole spin in InAs/GaAs quantum dots
Authors: Fras F. , Eble B. , Bernardot F. , Testelin C. , Chamarro M. , Miard A. , Lemaître A.
Published: January 2012

We have obtained the optical pumping of hole spins, in p-doped InAs/GaAs quantum dots, via the generation of an intermediate trion state by a train of circularly polarized pulses. We show that we can optically control the orientation of the initialized hole spin, independently of the orientation of the intermediate trion state, by choosing the excitation energy of the circularly polarized light. This brings a supplementary degree of freedom for hole-spin manipulations in quantum dots.
Electric dipole moment in KH2PO4 systematically modified by proton irradiation
Authors: Jung Kweon Jin , Eui Lee Cheol , Noh S. J. , Kim H. S.
Published: January 2012

We have carried out an impedance spectroscopy study on a series of proton-irradiated KH2PO4 (KDP) systems. A systematic modification was observed in the transverse dipole moment of the proton-irradiated KDP systems, associated with hydrogen-ion displacements, as obtained from dielectric constant measurements by using a mean-field approximation. Besides, intercorrelation of the charge transport with the dielectric properties was revealed, both having closely to do with the hydrogen-bond modification.
Reducing vortex losses in superconducting microwave resonators with microsphere patterned antidot arrays
Authors: Bothner D. , Clauss C. , Koroknay E. , Kemmler M. , Gaber T. , Jetter M. , Scheffler M. , Michler P. , Dressel M. , Koelle D. , Kleiner R.
Published: January 2012

We experimentally investigate the vortex induced energy losses in niobium coplanar waveguide resonators with and without quasihexagonal arrays of nanoholes (antidots), where large-area antidot patterns have been fabricated using self-assembling microsphere lithography. We perform transmission spectroscopy experiments around 6.25 GHz in magnetic field cooling and zero field cooling procedures with perpendicular magnetic fields up to B = 27 mT at a temperature T = 4.2 K. We find that the introduction of antidot arrays into resonators reduces vortex induced losses by more than one order of magnitude.
Engineering magnetic domains in manganite thin films by laser interference
Authors: Bakaul S. R. , Lin W. , Wu T.
Published: January 2012

We report on the laser interference (LI) aided conversion from maze-like to stripe-like magnetic domains in La1−xSrxMnO3 (x ∼ 0.3) thin films grown on LaAlO3 substrates. This conversion is attributed to the periodic, local, and rapid heating by LI which facilitates the reconfiguration of magnetic domains without damaging the film structures. By annealing the sample, the stripe-like domains can be converted back to the maze-like state. Our result represents a non-magnetic scheme for reversible magnetic domain engineering in ferromagnetic thin films.
Band offsets in HfO2/InGaZnO4 heterojunctions
Authors: Cho Hyun , Douglas E. A. , Gila B. P. , Craciun V. , Lambers E. S. , Ren Fan , Pearton S. J.
Published: January 2012

The valence band discontinuity (ΔEV) of sputter deposited HfO2/InZnGaO4 (IGZO) heterostructures was obtained from x-ray photoelectron spectroscopy measurements. The HfO2 exhibited a bandgap of 6.07 eV from absorption measurements. A value of ΔEV = 0.48 ± 0.025 eV was obtained by using the Ga 2p3/2, Zn 2p3/2, and In 3d5/2 energy levels as references. This implies a conduction band offset ΔEC of 2.39 eV in HfO2/InGaZnO4 heterostructures and a nested interface band alignment.