bluuebunny/crossref_metadata_2025 huggingface dataset:
Assamese Language, Narrative and the Making of the North East Frontier of India: Beyond Regional Indian Literary Studies
Authors: BARUAH MANJEET
Published: November 2012

This paper is divided into two broad sections. The first section deals with the Brahmaputra Valley in Assam (north east India) and its transformation into a frontier in the nineteenth century. The section also deals with how this process was closely linked to the re-interpretation of the region's relationship with Indo-Gangetic culture, and the impact on development of the modern ‘Assamese’ language. The second section interprets modern Assamese novels in the light of the issues raised in the first section. It explores how issues such as indigeneity, the concept of India and modern Assamese language, share a relation of conflict in modern Assamese fiction. It is suggested in the conclusion that, due to such historical specificities, the language and narrative of the frontier require a specific regional approach, and should not be subsumed within larger frameworks such as ‘the nation’ or ‘South Asia’.
Amyloid imaging in dementia
Authors: Ashraf A , Mehta P , Edison P
Published: November 2012

A major advancement in the field of medicine has been the timely advent of amyloid imaging, which has allowed critical evaluation of the complex relationship between amyloid β peptide (Aβ) aggregation and Alzheimer's diseasein vivo. Most importantly, amyloid imaging has the potential to detect Aβ in mildly affected as well as asymptomatic individuals, when the therapeutic window of opportunity might still be open to pharmacological intervention. It also shows significant promise in differential diagnosis of mild cognitive impairment or atypical dementias. Amyloid imaging studies support a model in which amyloid aggregation is considered an early event on the path of dementia, beginning insidiously in cognitively healthy individuals being accompanied by subtle cognitive, functional and structural brain alterations suggestive of incipient AD. As individuals progress to dementia, clinical decline and neurodegeneration accelerate and might proceed independently of amyloid accumulation. In this review we focus on amyloid imaging with particular emphasis on [11C]PIB in AD, mild cognitive impairment and other dementias, and discuss the advances made in this perplexing field.
Prevalence of psychiatric disorders in older patients attending an Arab tertiary facility
Authors: Amr Mostafa , Amin Tarek Tawfik , Al-Rhaddad Dahoud , Sallam Khalid
Published: November 2012

The phenomenon of population aging which was defined as an increase in the median age of the population is already a major social and health problem in a developing country such as Saudi Arabia and represents a challenge to the psychiatric profession (Hafezet al., 2000).
A PDTB-styled end-to-end discourse parser
Authors: LIN ZIHENG , NG HWEE TOU , KAN MIN-YEN
Published: November 2012

Since the release of the large discourse-level annotation of the Penn Discourse Treebank (PDTB), research work has been carried out on certain subtasks of this annotation, such as disambiguating discourse connectives and classifying Explicit or Implicit relations. We see a need to construct a full parser on top of these subtasks and propose a way to evaluate the parser. In this work, we have designed and developed an end-to-end discourse parser-to-parse free texts in the PDTB style in a fully data-driven approach. The parser consists of multiple components joined in a sequential pipeline architecture, which includes a connective classifier, argument labeler, explicit classifier, non-explicit classifier, and attribution span labeler. Our trained parser first identifies all discourse and non-discourse relations, locates and labels their arguments, and then classifies the sense of the relation between each pair of arguments. For the identified relations, the parser also determines the attribution spans, if any, associated with them. We introduce novel approaches to locate and label arguments, and to identify attribution spans. We also significantly improve on the current state-of-the-art connective classifier. We propose and present a comprehensive evaluation from both component-wise and error-cascading perspectives, in which we illustrate how each component performs in isolation, as well as how the pipeline performs with errors propagated forward. The parser gives an overall system F1 score of 46.80 percent for partial matching utilizing gold standard parses, and 38.18 percent with full automation.
The game of active search for extra-terrestrial intelligence: breaking the ‘Great Silence’
Authors: de Vladar Harold P.
Published: November 2012

The search for extra-terrestrial intelligence (SETI) has been performed principally as a one-way survey, listening of radio frequencies across the Milky Way and other galaxies. However, scientists have engaged in an active messaging only rarely. This suggests the simple rationale that if other civilizations exist and take a similar approach to ours, namely listening but not broadcasting, the result is a silent universe. A simple game theoretical model, the prisoner's dilemma, explains this situation: each player (civilization) can passively search (defect), or actively search and broadcast (cooperate). In order to maximize the payoff (or, equivalently, minimize the risks) the best strategy is not to broadcast. In fact, the active search has been opposed on the basis that it might be dangerous to expose ourselves. However, most of these ideas have not been based on objective arguments, and ignore accounting of the possible gains and losses. Thus, the question stands: should we perform an active search? I develop a game-theoretical framework where civilizations can be of different types, and explicitly apply it to a situation where societies are either interested in establishing a two-way communication or belligerent and in urge to exploit ours. The framework gives a quantitative solution (a mixed-strategy), which is how frequent we should perform the active SETI. This frequency is roughly proportional to the inverse of the risk, and can be extremely small. However, given the immense amount of stars being scanned, it supports active SETI. The model is compared with simulations, and the possible actions are evaluated through the San Marino scale, measuring the risks of messaging.
Conflict-Specific Effects of Accessory Stimuli on Cognitive Control in the Stroop Task and the Simon Task
Authors: Soutschek Alexander , Müller Hermann J. , Schubert Torsten
Published: November 2012

Both the Stroop and the Simon paradigms are often used in research on cognitive control, however, there is evidence that dissociable control processes are involved in these tasks: While conflicts in the Stroop task may be resolved mainly by enhanced task-relevant stimulus processing, conflicts in the Simon task may be resolved rather by suppressing the influence of task-irrelevant information on response selection. In the present study, we show that these control mechanisms interact in different ways with the presentation of accessory stimuli. Accessory stimuli do not affect cognitive control in the Simon task, but they impair the efficiency of cross-trial control processes in the Stroop task. Our findings underline the importance of differentiating between different types of conflicts and mechanisms of cognitive control.
A Mixture Distribution of Spatial Attention
Authors: Feng Jing , Spence Ian
Published: November 2012

Although it may seem paradoxical, the unified-focus and multiple-foci theories of spatial selective attention are both well supported by experimental evidence. However, the apparent contradiction is illusory and the two competing views may be reconciled by a closer examination of the spatial mechanisms involved. We propose that the deployment of attention may be modeled as a mixture of individual distributions of attention and we tested this hypothesis in two experiments. Participants had to identify targets among distractors, with the targets presented at various distances from the cued locations. Experiment 1 confirmed that the distribution of attention may be described by a mixture of individual distributions, each centered at a cued location. Experiment 2 showed that cue separation is an important determinant of whether spatial attention is divided or not.
The Role of Hyphens at the Constituent Boundary in Compound Word Identification
Authors: Bertram Raymond , Hyönä Jukka
Published: November 2012

The current eye-movement study investigated whether a salient segmentation cue like the hyphen facilitates the identification of long and short compound words. The study was conducted in Finnish, where compound words exist in great abundance. The results showed that long hyphenated compounds (musiikki-ilta) are identified faster than concatenated ones (yllätystulos), but short hyphenated compounds (ilta-asu) are identified slower than their concatenated counterparts (kesäsää). This pattern of results is explained by the visual acuity principle ( Bertram & Hyönä, 2003 ): A long compound word does not fully fit in the foveal area, where visual acuity is at its best. Therefore, its identification begins with the access of the initial constituent and this sequential processing is facilitated by the hyphen. However, a short compound word fits in the foveal area, and consequently the hyphen slows down processing by encouraging sequential processing in cases where it is possible to extract and use information of the second constituent as well.
Primed Self-Construal, Culture, and Stages of Impression Formation
Authors: Saribay S. Adil , Rim SoYon , Uleman James S.
Published: November 2012

The effects of culture on impression formation are widely documented but poorly understood. Priming independent and interdependent self-construals, and focusing on particular stages of impression formation, could help remedy this because such self-construals differ across cultures. In three experiments, participants’ were primed with independent or interdependent self-construals before they formed spontaneous or intentional impressions of others. In Experiment 1, lexical decision reaction times showed that both traits and situational properties were activated spontaneously, but were unaffected by self-construal priming. In Experiment 2, a false-recognition paradigm showed that spontaneous trait inferences were bound to relevant actors’ faces, again regardless of self-construal priming. In Experiment 3, explicit ratings did show priming effects. Those primed with independent (but not interdependent) self-construal inferred traits more strongly than situational properties. Primed self-construals appear to affect intentional but not spontaneous stages of impression formation. The differences between effects of primed and chronic self-construals are discussed.
Information and Communication Technology and Cultural Change
Authors: Hansen Nina , Postmes Tom , van der Vinne Nikita , van Thiel Wendy
Published: November 2012

This paper studies whether and how information and communication technology (ICT) changes self-construal and cultural values in a developing country. Ethiopian children were given laptops in the context of an ICT for development scheme. We compared children who used laptops (n = 69) with a control group without laptops (n = 76) and a second control group of children whose laptop had broken down (n = 24). Results confirmed that after 1 year of laptop usage, the children’s self-concept had become more independent and children endorsed individualist values more strongly. Interestingly, the impact of laptop usage on cultural values was mediated by self-construal (moderated mediation). Importantly, modernization did not “crowd out” traditional culture: ICT usage was not associated with a reduction in traditional expressions (interdependent self-construal, collectivist values). Theoretical and practical implications are discussed.
Cultural Inertia
Authors: Quezada Stephanie A. , Shaw Moira P. , Zárate Michael A.
Published: November 2012

The Latino population in the United States is rapidly increasing. This increase produces cultural change, and the cultural inertia model suggests that cultural change is resisted if one’s cultural identity must change. The present study investigates the role of ethnic identification in Latinos’ reactions to pressures to assimilate to mainstream American culture. Perceptions of cultural change were manipulated and prejudice toward White Americans, support for pro-minority legislation, and individual differences in collective self-esteem and openness to cultural change were measured. When biased to believe that their culture will have to change, Latinos high in collective self-esteem expressed greater prejudice toward White Americans and stronger political advocacy for Latino culture. These results support the cultural inertia model and make recommendations for how to improve intergroup relations.
Top‐down inflation and deflation at the summit of Kīlauea Volcano, Hawai‘i observed with InSAR
Authors: Baker Scott , Amelung Falk
Published: November 2012

We use interferometric synthetic aperture radar (InSAR) to study deformation of the summit caldera at Kīlauea Volcano during 2000–2008, which spanned both an east rift zone eruptive event in 2007 and the start of the ongoing summit eruption in 2008. The data set consists of small baseline subset (SBAS) time series generated from 270 acquisitions on three separate beam modes from the Radarsat‐1 satellite. We identify 12 time periods with distinct patterns of displacement that we attribute until late 2003 to secular tectonic‐driven deformation and from 2004 to 2008 to four different sources in the summit area. We model the shallow magmatic system as a spherical reservoir at 1.9 ± 0.1 km depth below the surface to the northeast of Halemaumau (source 1) and three vertically stacked sills at greater depths in the southern caldera area (source 2 at the southern edge of the caldera at 2.9 ± 0.2 km depth, source 3 to the south‐southeast of the caldera at 3.4 ± 0.5 km depth, and source 4 south of the caldera at 3.6 ± 0.4 km depth). The sequence for filling of and withdrawal from these reservoirs reveals a top‐down process, with sequences of both inflation and deflation initiating in the shallowest source. Inflation of source 3 is coincident with elevated seismic activity in the upper east rift zone in February 2006 and May 2007. Source 4 is elongated toward the southwest rift zone and also shows elevated seismicity that extends toward the southwest rift zone.
Radial gradients of phase space density in the inner electron radiation
Authors: Kim Kyung‐Chan , Shprits Yuri
Published: November 2012

While the outer radiation belt (3.5 < L < 8.0) is highly variable with respect to geomagnetic activity, the inner radiation belt (1.2 < L< 2.0) is relatively stable. Less attention has been paid to the inner electron belt in recent years. It has been generally accepted that the equilibrium structure of radiation belt electrons is explained by the slow inward radial diffusion from a source in the outer belt and losses by Coulomb collision and wave‐particle interaction. In this study, we examine this well accepted theory using the radial profiles of the phase space density (PSD), inferred from in situ measurements made by three different satellites: S3–3, CRRES, and POLAR. Our results show that electron PSD in the inner electron belt has a clear prominent local peak and negative radial gradient in the outer portion of the inner zone, i.e., decreasing PSD with increasingL‐value. A likely explanation for the peaks in PSD is acceleration due to energy diffusion produced by lightning‐generated and anthropogenic whistlers. These results indicate that either additional local acceleration mechanism is responsible for the formation of the inner electron belt or inner electron belt is formed by sporadic injections of electrons into the inner zone. The currently well accepted model of slow diffusion and losses will be further examined by the upcoming Radiation Belt Storm Probes (RBSP) mission.
On the retrieval of the specular reflection in GNSS carrier observations for ocean altimetry
Authors: Semmling A. M. , Schmidt T. , Wickert J. , Schön S. , Fabra F. , Cardellach E. , Rius A.
Published: November 2012

This paper presents an altimetric method for ocean monitoring by remote sensing. It uses carrier observations of reflected GNSS signals. The method is illustrated in a simulation study and applied to a long term experiment yielding an ocean tide spectrum. The altimetric concept is based on residual observations of Doppler frequency. A linear relation between Doppler residuals f0 and height departures ΔHfrom the surface level is derived. In contrast to existing phase‐based methods which are constrained by smooth ocean conditions, the frequency‐based retrieval here described holds good for rougher ocean conditions. Two retrievals of Doppler residuals are distinguished: Tracking Retrieval and Spectral Retrieval. A simulation study investigates the performance of Spectral Retrieval for a rough ocean surface with a noise‐like sea level deviationξ(t). Simulation settings were adjusted to reflection events in coastal experiments with an elevation range of [5…15] deg. In this range Tracking Retrieval tolerates a surface standard deviation σξ < 5 cm, whereas Spectral Retrieval tolerates σξ ≤ 30 cm. These limits correspond to significant wave heights of 20 cm for Tracking Retrieval and 1.2 m for Spectral Retrieval. The simulation results are confirmed by applying the altimetric method to the experimental data. The recovery of continuous phase tracks in experimental data is onerous and Tracking Retrieval only works for a period of smooth ocean conditions (162 events). By contrast, Spectral Retrieval yields altimetric estimates throughout the whole experiment (2607 events). The altimetric time series extends over more than 60 days and results in a tide spectrum that resolves diurnal (K1) and semidiurnal (M2, S2) constituents. The formal precision for these estimates lies in the decimeter range.
Log cabins and lab coats
Authors: Jacobs Howy
Published: November 2012

The case for science in the US is getting drowned out by other voices, notably on the right. Howy argues that to combat this worrying trend, scientists need to re‐engage politically in the Republican Party.
Redox-dependent stability of the γ-glutamylcysteine synthetase enzyme of Escherichia coli: a novel means of redox regulation
Authors: Kumar Shailesh , Kasturia Neha , Sharma Amit , Datt Manish , Bachhawat Anand K.
Published: November 2012

Glutathione is a thiol-containing tripeptide that plays important roles in redox-related processes. The first step in glutathione biosynthesis is catalysed by γ-GCS (γ-glutamylcysteine synthetase). The crystal structure of Escherichia coli γ-GCS has revealed the presence of a disulfide bond. As the disulfide-bonding cysteine residues Cys372 and Cys395 are not well conserved among γ-GCS enzymes in this lineage, we have initiated a biochemical genetic strategy to investigate the functional importance of these and other cysteine residues. In a cysteine-free γ-GCS that was non-functional, suppressor analysis yielded combinations of cysteine and aromatic residues at the position of the disulfide bond, and one mutant that lacked any cysteine residues. Kinetic analysis of the wild-type and mutant enzymes revealed that the disulfide bond was not involved in determining the affinity of the enzyme towards its substrate, but had an important role in determining the stability of the protein, and its catalytic efficiency. We show that in vivo the γ-GCS enzyme can also exist in a reduced form and that the mutants lacking the disulfide bond show a decreased half-life. These results demonstrate a novel means of regulation of γ-GCS by the redox environment that works by an alteration in its stability.
Regulation of adipogenesis by cytoskeleton remodelling is facilitated by acetyltransferase MEC-17-dependent acetylation of α-tubulin
Authors: Yang Wulin , Guo Xiangxiang , Thein Shermaine , Xu Feng , Sugii Shigeki , Baas Peter W. , Radda George K. , Han Weiping
Published: November 2012

Cytoskeleton remodelling is a prerequisite step for the morphological transition from preadipocytes to mature adipocytes. Although microtubules play a pivotal role in organizing cellular structure, regulation of microtubule dynamics during adipogenesis remains unclear. In the present paper we show that acetylation of α-tubulin is up-regulated during adipogenesis, and adipocyte development is dependent on α-tubulin acetylation, as expression of an acetylation-resistant α-tubulin mutant significantly inhibits adipogenesis. Moreover, acetylation of α-tubulin is under the control of the acetyltransferase MEC-17 and deacetylases SIRT2 (Sirtuin 2) and HDAC6 (histone deacetylase 6). Adipocyte development is inhibited in MEC-17-knockdown cells, but enhanced in MEC-17-overexpressing cells. Finally, we show that katanin, a microtubule-severing protein with enhanced activity on acetylated α-tubulin, is actively involved in adipogenesis. We propose that co-ordinated up-regulation of α-tubulin acetylation initiates cytoskeleton remodelling by promoting α-tubulin severing by katanin which, in turn, allows expansion of lipid droplets and accelerates the morphological transition toward mature adipocytes.
Structural characterization of the mechanism through which human glutamic acid decarboxylase auto-activates
Authors: Langendorf Christopher G. , Tuck Kellie L. , Key Trevor L. G. , Fenalti Gustavo , Pike Robert N. , Rosado Carlos J. , Wong Anders S. M. , Buckle Ashley M. , Law Ruby H. P. , Whisstock James C.
Published: November 2012

Imbalances in GABA (γ-aminobutyric acid) homoeostasis underlie psychiatric and movement disorders. The ability of the 65 kDa isoform of GAD (glutamic acid decarboxylase), GAD65, to control synaptic GABA levels is influenced through its capacity to auto-inactivate. In contrast, the GAD67 isoform is constitutively active. Previous structural insights suggest that flexibility in the GAD65 catalytic loop drives enzyme inactivation. To test this idea, we constructed a panel of GAD65/67 chimaeras and compared the ability of these molecules to auto-inactivate. Together, our data reveal the important finding that the C-terminal domain of GAD plays a key role in controlling GAD65 auto-inactivation. In support of these findings, we determined the X-ray crystal structure of a GAD65/67 chimaera that reveals that the conformation of the catalytic loop is intimately linked to the C-terminal domain.
Investigation of Severe Craniomaxillofacial Battle Injuries Sustained by U.S. Service Members: A Case Series
Authors: Brown Baer Pamela R. , Wenke Joseph C. , Thomas Steven J. , Hale Colonel Robert G.
Published: November 2012

This case series describes craniomaxillofacial battle injuries, currently available surgical techniques, and the compromised outcomes of four service members who sustained severe craniomaxillofacial battle injuries in Iraq or Afghanistan. Demographic information, diagnostic evaluation, surgical procedures, and outcomes were collected and detailed with a follow-up of over 2 years. Reconstructive efforts with advanced, multidisciplinary, and multiple revision procedures were indicated; the full scope of conventional surgical options and resources were utilized. Patients experienced surgical complications, including postoperative wound dehiscence, infection, flap failure, inadequate mandibular healing, and failure of fixation. These complications required multiple revisions and salvage interventions. In addition, facial burns complicated reconstructive efforts by delaying treatment, decreasing surgical options, and increasing procedural numbers. All patients, despite multiple surgeries, continue to have functional and aesthetic deficits as a result of their injuries. Currently, no conventional treatments are available to satisfactorily reconstruct the face severely ravaged by explosive devices to an acceptable level, much less to natural form and function.
Low-frequency linear-mode regimes in the tokamak scrape-off layer
Authors: Mosetto Annamaria , Halpern Federico D. , Jolliet Sébastien , Ricci Paolo
Published: November 2012

Motivated by the wide range of physical parameters characterizing the scrape-off layer (SOL) of existing tokamaks, the regimes of low-frequency linear instabilities in the SOL are identified by numerical and analytical calculations based on the linear, drift-reduced Braginskii equations, with cold ions. The focus is put on ballooning modes and drift wave instabilities, i.e., their resistive, inertial, and ideal branches. A systematic study of each instability is performed, and the parameter space region where they dominate is identified. It is found that the drift waves dominate at high R/Ln, while the ballooning modes at low R/Ln; the relative influence of resistive and inertial effects is discussed. Electromagnetic effects suppress the drift waves and, when the threshold for ideal stability is overcome, the ideal ballooning mode develops. Our analysis is a first stage tool for the understanding of turbulence in the tokamak SOL, necessary to interpret the results of non-linear simulations.
Fully developed contact angle change of a droplet in liquid actuated by dielectric force
Authors: Yang Chih-Cheng , Yang Lin , Gary Tsai C. , Hongchang Jou Patrick , Andrew Yeh J.
Published: November 2012

The non-saturation phenomenon of contact angle change of a nonconductive droplet in an immiscible dielectric liquid with iso-density is demonstrated using the dielectric force due to the difference of the two dielectric constants. The concentric electrode design permits the dielectric force exerted at various contact angles. The droplet fully develops from 22° to 176° (nearly spherical) in contact angle as the voltages tuned from 0 to 215 Vrms. The contact angle change was found to behave almost linearly with respect to voltage by experiments. The dielectric force in the liquid/liquid interface was further simulated at the aspects of energy distribution, force distribution, and electric fields, found in a good agreement with experimental results.
Band alignment of epitaxial ZnS/Zn3P2 heterojunctions
Authors: Bosco Jeffrey P. , Demers Steven B. , Kimball Gregory M. , Lewis Nathan S. , Atwater Harry A.
Published: November 2012

The energy-band alignment of epitaxial zb-ZnS(001)/α-Zn3P2(001) heterojunctions has been determined by measurement of shifts in the phosphorus 2p and sulfur 2p core-level binding energies for various thicknesses (0.6–2.2 nm) of ZnS grown by molecular beam epitaxy on Zn3P2. In addition, the position of the valence-band maximum for bulk ZnS and Zn3P2 films was estimated using density functional theory calculations of the valence-band density-of-states. The heterojunction was observed to be type I, with a valence-band offset, ΔEV, of −1.19 ± 0.07 eV, which is significantly different from the type II alignment based on electron affinities that is predicted by Anderson theory. n+-ZnS/p-Zn3P2 heterojunctions demonstrated open-circuit voltages of >750 mV, indicating passivation of the Zn3P2 surface due to the introduction of the ZnS overlayer. Carrier transport across the heterojunction devices was inhibited by the large conduction-band offset, which resulted in short-circuit current densities of <0.1 mA cm−2 under 1 Sun simulated illumination. Hence, constraints on the current density will likely limit the direct application of the ZnS/Zn3P2 heterojunction to photovoltaics, whereas metal-insulator-semiconductor structures that utilize an intrinsic ZnS insulating layer appear promising.
Time-dependent investigation of charge injection in a quantum dot containing one electron
Authors: de Sousa J. S. , Covaci L. , Peeters F. M. , Farias G. A.
Published: November 2012

The interaction of an injected electron towards a quantum dot (QD) containing a single confined electron is investigated using a flexible time-dependent quantum mechanics formalism, which allows both electrons to move and undergo quantum transitions. Different scenarios combining quantum dot dimensions, dielectric constant, injected wave packet energy, and width were explored, and our main results are: (i) due to the large characteristic transitions times between the confined state in the quantum dot and the delocalized state in the continuum, it is relatively difficult to ionize the occupied QD by Coulomb interaction solely and (ii) the charging state of the quantum dot can be sensed by direct injection of charges.
Morphology-influenced thermal conductivity of polyethylene single chains and crystalline fibers
Authors: Zhang Teng , Luo Tengfei
Published: November 2012

In this paper, the thermal conductivities of polyethylene (PE) single chains and aligned crystalline fibers are calculated using molecular dynamics simulations with the condensed-phase optimized molecular potentials for atomistic simulation studies potential. The segment disorder along the PE chains is found to play an important role in thermal transport in both single PE chains and crystalline PE fibers. In a crystalline PE, thermal conductivity decreases as temperature increases since thermal expansion creates space for chain segment rotation. A critical temperature around 400 K is identified where thermal conductivity decreases by about 90%. The results show that chain morphology is critical to the thermal transport in PE structures.
Diffusion in two-dimensional conical varying width channels: Comparison of analytical and numerical results
Authors: Pineda Inti , Alvarez-Ramirez José , Dagdug Leonardo
Published: November 2012

This study is devoted to the unbiased motion of a point-like Brownian particle in two-dimensional tilted asymmetric channels of varying width formed by straight walls. An effective one-dimensional description in terms of the generalized Fick-Jacobs equation is used to derive formulas that yield the particle's effective diffusion coefficient as a function of the geometric parameters of the channel. To such end, we use the formulas obtained by Bradley [Phys. Rev. E 80, 061142 (2009)10.1103/PhysRevE.80.061142] and by Dagdug and Pineda [J. Chem. Phys. 137, 024107 (2012)10.1063/1.4733394] to study two-dimensional diffusion in narrow and smoothly asymmetric channels of varying width. Comparison with Brownian dynamics simulation results allows us to establish the domain of applicability of both the one-dimensional description and the effective diffusion coefficient formulas.
Lattice-registered growth of GaSb on Si (211) with molecular beam epitaxy
Authors: Hosseini Vajargah S. , Ghanad-Tavakoli S. , Preston J. S. , Botton G. A. , Kleiman R. N.
Published: November 2012

A GaSb film was grown on a Si(211) substrate using molecular beam epitaxy indicating full lattice relaxation as well as full lattice registration and dislocation-free growth in the plane perpendicular to the [01 − 1]-direction. Heteroepitaxy of GaSb on a Si(211) substrate is dominated by numerous first order and multiple higher order micro-twins. The atomic-resolved structural study of GaSb films by high-angle annular dark-field scanning transmission electron microscopy reveals that slight tilt, along with twinning, favors the lattice registry to Si(211) substrates. Preferential bonding of impinging Ga and Sb atoms at the interface due to two distinctive bonding sites on the Si(211) surface enables growth that is sublattice-ordered and free of anti-phase boundaries. The role of the substrate orientation on the strain distribution of GaSb epilayers is further elucidated by investigating the local change in the lattice parameter using the geometric phase analysis method and hence effectiveness of the lattice tilting in reducing the interfacial strain was confirmed further.
Non-planar substrate effect on the interface trap capacitance of metal-oxide-semiconductor structures with ultra thin oxides
Authors: Tseng Po-Hao , Hwu Jenn-Gwo
Published: November 2012

Redistribution of interface trap capacitance (Cit) was observed in non-planar substrate metal-oxide-semiconductor (MOS) capacitors with ultra thin oxides. It was found that the behavior of Cit of non-planar substrate MOS capacitors is dependent on the non-planar portion. The non-planar devices exhibit two peaks distribution in Cit due to multiple surfaces effect. A Cit model combining uniform and non-uniform areas effect was proposed for the observation. The non-uniform substrate MOS capacitors exhibit significant non-uniform deep depletion behaviors and degradation in constant voltage stress reliability.
Excitons imaging in hybrid organic-inorganic films
Authors: Trigui Amani , Mlayah Adnen , Abid Younes , Zwick Antoine , Boughzala Habib
Published: November 2012

In this work we investigate the excitonic properties of (4-FC6H4C2H4NH3)2PbI4 hybrid organic/inorganic thin films. We first use a standard point-by-point photoluminescence mapping. The maps formed using the photoluminescence intensity, line width, and broadening reveal the presence of structural defects. Using a statistical treatment of the data we found that the spatial fluctuations of the photoluminescence peak wavelengths are rather small compared to the photoluminescence line width. Moreover, we report the first direct observation of spatially resolved excitonic photoluminescence in this type of materials using dark-field imaging of white-light pumped photoluminescence. Owing to the rapid acquisition time of the dark-field images, their temperature dependence was studied, and the thermal behavior of the photoluminescence was investigated using this technique. We show that photoluminescence mapping combined with dark-field imaging and spectroscopy provides valuable information on the excitonic properties of hybrid organic/inorganic thin films.
Light trapping in solar cells: When does a Lambertian scatterer scatter Lambertianly?
Authors: Battaglia Corsin , Boccard Mathieu , Haug Franz-Josef , Ballif Christophe
Published: November 2012

We derive scaling laws for the Rayleigh-Sommerfeld formulation we recently developed to describe light scattering from nanotextured interfaces. These scaling laws provide precious intuition on how to link scattering from different interfaces. In particular, we answer the question how to obtain a Lambertian scatterer into silicon, starting from a Lambertian scatterer into air relevant to the development of light trapping schemes in thin-film silicon solar cells. We also define a Lambertionality factor which measures how close an arbitrary scatterer approaches Lambertian scattering and extend the fundamental 4n2 light trapping limit to arbitrary scattering distributions.
Modeling and numerical simulations of growth and morphologies of three dimensional aggregated silver films
Authors: Davis L. J. , Boggess M. , Kodpuak E. , Deutsch M.
Published: November 2012

We report on a model for the deposition of three dimensional, aggregated nanocrystalline silver films, and an efficient numerical simulation method developed for visualizing such structures. We compare our results to a model system comprising chemically deposited silver films with morphologies ranging from dilute, uniform distributions of nanoparticles to highly porous aggregated networks. Disordered silver films grown in solution on silica substrates are characterized using digital image analysis of high resolution scanning electron micrographs. While the latter technique provides little volume information, plane-projected (two dimensional) island structure and surface coverage may be reliably determined. Three parameters governing film growth are evaluated using these data and used as inputs for the deposition model, greatly reducing computing requirements while still providing direct access to the complete (bulk) structure of the films throughout the growth process. We also show how valuable three dimensional characteristics of the deposited materials can be extracted using the simulated structures.
Pressure effect on Bi0.4Ca0.6Mn1−xRuxO3 manganite: Enhanced ferromagnetism and collapsed exchange bias
Authors: Fita I. , Markovich V. , Wisniewski A. , Puzniak R. , Mahendiran R. , Gorodetsky G.
Published: November 2012

Pressure effect on magnetic state of Ru-doped charge-ordered manganite Bi0.4Ca0.6Mn1 − xRuxO3 (x = 0.1, 0.2) was investigated by magnetization measurements in the temperature range of 5−315 K and under pressure up to ∼10 kbar. It was found that the x = 0.2 composition is basically ferromagnetic (FM) while the low-doped (x = 0.1) one exhibits a FM cluster glass behavior and exchange bias (EB) effect at low temperatures. Bi0.4Ca0.6Mn0.9Ru0.1O3 demonstrates a substantial pressure-enhanced ferromagnetism, evidenced by ∼70% increase in spontaneous magnetization at 10 K under 10.3 kbar. It appears that an applied pressure strongly increases the FM to antiferromagnetic (AFM) phase ratio in the sample, leading to a notable decrease in both coercive field HC and EB field HE (HC and HE at 10 K decrease under pressure of ∼10 kbar by about 40% and 50%, respectively). The pressure-induced changes are qualitatively described within the simple model for FM size-variable clusters embedded in an AFM matrix. It is argued that both Ru-doping and external pressure act similarly, leading to a growth of the FM phase volume.
Embedded fragmentation of vibrational energies
Authors: Sode Olaseni , Hirata So
Published: November 2012

Can the zero-point vibrational energies (ZPVE) of molecular clusters and crystals be evaluated as sums of ZPVE of constituent molecular fragments embedded in the cluster or crystal electrostatic environment? What is the appropriate unit of fragmentation: monomers or overlapping dimers? Can the contributions of acoustic phonons, which are fundamentally delocalized, be recuperated at satisfactory accuracy? These questions are answered by this study applying embedded monomer- and dimer-fragmentation methods to the harmonic ZPVE of hydrogen fluoride clusters, hydrogen fluoride crystal, and water clusters. Our findings are as follows: (1) ZPVE are reproduced accurately by both fragmentation schemes within a few percents of exact values or a few tenths of 1 kcal mol−1 per molecule even for crystalline hydrogen fluoride, which has acoustic phonons. (2) Both the monomer- and dimer-based fragmentation are nearly equally accurate and useful for the absolute values of ZPVE, but the latter is more reliable than the former in reproducing the relative ZPVE of cluster isomers of the same size. (3) The embedding field is essential as it renders nonzero frequencies to the translational and rotational motions of monomers and dimers, accounting for the pseudo-translational and librational motions of the entire clusters or crystals. (4) Some of these low-frequency modes of fragments are calculated to have imaginary frequencies because the fragments are not at their equilibrium geometries, causing ZPVE to be complex. The imaginary part of ZPVE, which is nonphysical and is guaranteed to vanish in the exact limit of the many-body expansion, is nonetheless a useful estimate of errors in the real part.
External noise control in inherently stochastic biological systems
Authors: Zheng Likun , Chen Meng , Nie Qing
Published: November 2012

Biological systems are often subject to external noise from signal stimuli and environmental perturbations, as well as noises in the intracellular signal transduction pathway. Can different stochastic fluctuations interact to give rise to new emerging behaviors? How can a system reduce noise effects while still being capable of detecting changes in the input signal? Here, we study analytically and computationally the role of nonlinear feedback systems in controlling external noise with the presence of large internal noise. In addition to noise attenuation, we analyze derivatives of Fano factor to study systems' capability of differentiating signal inputs. We find effects of internal noise and external noise may be separated in one slow positive feedback loop system; in particular, the slow loop can decrease external noise and increase robustness of signaling with respect to fluctuations in rate constants, while maintaining the signal output specific to the input. For two feedback loops, we demonstrate that the influence of external noise mainly depends on how the fast loop responds to fluctuations in the input and the slow loop plays a limited role in determining the signal precision. Furthermore, in a dual loop system of one positive feedback and one negative feedback, a slower positive feedback always leads to better noise attenuation; in contrast, a slower negative feedback may not be more beneficial. Our results reveal interesting stochastic effects for systems containing both extrinsic and intrinsic noises, suggesting novel noise filtering strategies in inherently stochastic systems.
A new boundary condition for the three-dimensional Navier-Stokes equation and the vanishing viscosity limit
Authors: Xiao Yuelong , Xin Zhouping
Published: November 2012

In this paper, we propose a new vorticity boundary condition for the three-dimensional incompressible Navier-Stokes equation for a general smooth domain in R3. This boundary condition is motivated by the generalized Navier-slip boundary condition involving the vorticity. It is shown first that such an initial boundary value problem is well-posed at least local in time. Furthermore, more importantly, we obtain some estimates on rate of convergence in C([0, T], H1(Ω)) and C([0, T], H2(Ω)) of the solutions to the corresponding solutions of the ideal Euler equations with the standard slip boundary condition.
Semiquantal molecular dynamics simulations of hydrogen-bond dynamics in liquid water using multi-dimensional Gaussian wave packets
Authors: Ono Junichi , Ando Koji
Published: November 2012

A semiquantal (SQ) molecular dynamics (MD) simulation method based on an extended Hamiltonian formulation has been developed using multi-dimensional thawed Gaussian wave packets (WPs), and applied to an analysis of hydrogen-bond (H-bond) dynamics in liquid water. A set of Hamilton's equations of motion in an extended phase space, which includes variance-covariance matrix elements as auxiliary coordinates representing anisotropic delocalization of the WPs, is derived from the time-dependent variational principle. The present theory allows us to perform real-time and real-space SQMD simulations and analyze nuclear quantum effects on dynamics in large molecular systems in terms of anisotropic fluctuations of the WPs. Introducing the Liouville operator formalism in the extended phase space, we have also developed an explicit symplectic algorithm for the numerical integration, which can provide greater stability in the long-time SQMD simulations. The application of the present theory to H-bond dynamics in liquid water is carried out under a single-particle approximation in which the variance-covariance matrix and the corresponding canonically conjugate matrix are reduced to block-diagonal structures by neglecting the interparticle correlations. As a result, it is found that the anisotropy of the WPs is indispensable for reproducing the disordered H-bond network compared to the classical counterpart with the use of the potential model providing competing quantum effects between intra- and intermolecular zero-point fluctuations. In addition, the significant WP delocalization along the out-of-plane direction of the jumping hydrogen atom associated with the concerted breaking and forming of H-bonds has been detected in the H-bond exchange mechanism. The relevance of the dynamical WP broadening to the relaxation of H-bond number fluctuations has also been discussed. The present SQ method provides the novel framework for investigating nuclear quantum dynamics in the many-body molecular systems in which the local anisotropic fluctuations of nuclear WPs play an essential role.
Control of resonance enhanced multi-photon ionization photoelectron spectroscopy by phase-shaped femtosecond laser pulse
Authors: Zhang Shian , Lu Chenhui , Jia Tianqing , Qiu Jianrong , Sun Zhenrong
Published: November 2012

In this paper, we theoretically demonstrate that the (2+1+1) resonance enhanced multi-photon ionization photoelectron spectroscopy in sodium atom can be effectively controlled by shaping femtosecond laser pulse with a π phase step modulation in weak laser field, involving its total photoelectron energy, maximal photoelectron intensity, and spectroscopic bandwidth. Our results show that the total photoelectron energy can be suppressed but not enhanced, the maximal photoelectron intensity can be enhanced and also suppressed, and the photoelectron spectroscopy can be tremendously narrowed. These theoretical results can provide a feasible scheme to achieve the high-resolution photoelectron spectroscopy and study the excited state structure in atomic and molecular systems.
Attraction between neutral dielectrics mediated by multivalent ions in an asymmetric ionic fluid
Authors: Kanduč Matej , Naji Ali , Forsman Jan , Podgornik Rudolf
Published: November 2012

We study the interaction between two neutral plane-parallel dielectric bodies in the presence of a highly asymmetric ionic fluid, containing multivalent as well as monovalent (salt) ions. Image charge interactions, due to dielectric discontinuities at the boundaries, as well as effects from ion confinement in the slit region between the surfaces are taken fully into account, leading to image-generated depletion attraction, ion correlation attraction, and steric-like repulsive interactions. We investigate these effects by employing a combination of Monte Carlo simulation methods, including explicit-ion simulations (where all electrostatic interactions are simulated explicitly) and implicit-ion simulations (where monovalent ions are replaced by an effective screened electrostatic potential between multivalent ions), as well as an approximate analytical theory. The latter incorporates strong ion-image charge correlations, which develop in the presence of high valency ions in the mixture. We show that the implicit-ion simulations and the proposed analytical theory can describe the explicit simulation results on a qualitative level, while excellent quantitative agreement can be obtained for sufficiently large monovalent salt concentrations. The resultant attractive interaction between the neutral surfaces is shown to be significant, as compared with the usual van der Waals interactions between semi-infinite dielectrics, and can thus play an important role at the nano scale.
A scanning AC calorimetry technique for the analysis of nano-scale quantities of materials
Authors: Xiao Kechao , Gregoire John M. , McCluskey Patrick J. , Vlassak Joost J.
Published: November 2012

We present a scanning AC nanocalorimetry method that enables calorimetry measurements at heating and cooling rates that vary from isothermal to 2 × 103 K/s, thus bridging the gap between traditional scanning calorimetry of bulk materials and nanocalorimetry. The method relies on a micromachined nanocalorimetry sensor with a serpentine heating element that is sensitive enough to make measurements on thin-film samples and composition libraries. The ability to perform calorimetry over such a broad range of scanning rates makes it an ideal tool to characterize the kinetics of phase transformations or to explore the behavior of materials far from equilibrium. We demonstrate the technique by performing measurements on thin-film samples of Sn, In, and Bi with thicknesses ranging from 100 to 300 nm. The experimental heat capacities and melting temperatures agree well with literature values. The measured heat capacities are insensitive to the applied AC frequency, scan rate, and heat loss to the environment over a broad range of experimental parameters.