bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular and epidemiological analysis of methicillin-resistant Staphylococcus aureus otorrhoea: hospital- or community-acquired?
Authors: Nassif R G , Soliman R , Edwards D H , Kara N , Hussain S S M
Published: June 2010

Objectives:

(1) To identify newly diagnosed cases of methicillin-resistant Staphylococcus aureus ear infection in our local population; (2) to determine the risk factors involved in these patients' clinical courses, and (3) to type the bacterial strains isolated and thus identify whether they were hospital- or community-acquired.

Design and setting:

Retrospective review of case notes, together with laboratory-based molecular studies in the departments of otolaryngology and medical microbiology in a university teaching hospital in Scotland, UK.

Subjects:

Over a two-year period, 35 patients were identified with ear swabs positive for methicillin-resistant Staphylococcus aureus infection. These cases came from both hospital and community settings.

Main outcome measures:

(1) Identification of primary methicillin-resistant Staphylococcus aureus otorrhoea in patients with no previously documented colonisation; and (2) molecular typing of the strains isolated, using spa technology, to identify whether they were hospital- or community-acquired.

Results:

Of the 35 positive patients, 27 were previously known carriers of methicillin-resistant Staphylococcus aureus. The eight patients with newly diagnosed methicillin-resistant Staphylococcus aureus otorrhoea presented initially in the community. All of these patients had had contact with hospital staff (as in-patients or out-patients) in the weeks preceding development of their ear infection. Using the spa technique for molecular typing, we identified hospital-acquired (‘epidemic’) methicillin-resistant Staphylococcus aureus type 15 in all eight patients' isolates. All were sensitive to topical gentamicin.

Conclusions:

In our cohort, hospital-acquired methicillin-resistant Staphylococcus aureus type 15 was the commonest cause of methicillin-resistant Staphylococcus aureus otorrhoea, despite the fact that these patients all first presented in the community. We believe that contact with hospital staff or health care workers is a risk factor for acquiring methicillin-resistant Staphylococcus aureus otorrhoea in the community.
Collimated proton beam generation from ultraintense laser-irradiated hole target
Authors: Yang X.H. , Ma Y.Y. , Shao F.Q. , Xu H. , Yu M.Y. , Gu Y.Q. , Yu T.P. , Yin Y. , Tian C.L. , Kawata S.
Published: June 2010

Collimated proton beams from laser interaction with a slab having a hole on its backside are investigated using particle-in-cell simulation. The hot target electrons driven by the laser expand rapidly into the hole. However, at the hole's corners the electrons are strongly compressed and an intense electron jet is emitted from each corner, tightly followed by the ions. The plasma jets focus and collimate along the axis of the hole and can propagate without divergence within the hole. The effect of the hole diameter on the collimated proton beam is considered.
Focusing of Hermite-cosh-Gaussian laser beams in collisionless magnetoplasma
Authors: Patil S.D. , Takale M.V. , Navare S.T. , Dongare M.B.
Published: June 2010

This paper presents an investigation of the focusing of Hermite-cosh-Gaussian laser beams in magneto-plasma by considering ponderomotive nonlinearity. The dynamics of the combined effects of nonlinearity and spatial diffraction is presented. To highlight the nature of focusing, plot of beam-width parameter vs. dimensionless distance of propagation has been obtained. The effect of mode index and decentered parameter on the self-focusing of the beams has been discussed.
Who Believes Propaganda? Media Effects during the Anti-Japanese Protests in Beijing
Authors: Stockmann Daniela
Published: June 2010

The Chinese media have undergone commercial liberalization during the reform era. Interviews with media practitioners reveal that media reform has brought about three different types of newspapers that differ with respect to their degree of commercial liberalization. Based on a natural experiment during the anti-Japanese protests in Beijing in 2005, this article shows that urban residents found more strongly commercialized newspapers more persuasive than less commercialized newspapers. Provided that the state can enforce press restrictions when needed, commercial liberalization promotes the ability of the state to influence public opinion through the means of the news media.
A Survey Report on Chinese Journalists in China
Authors: Lin Fen
Published: June 2010

This report presents a portrait of contemporary liberal Chinese journalists. Compared with the national average ten years ago, a typical journalist in Guangzhou is younger, better-educated and more likely to be female, and less likely to be a Communist Party member. The survey shows that the literati value coexists with both the modern professional and Party journalism value during the current journalistic professionalization. Such coexistence results in a complexity in journalists' attitude and behaviour. Journalists tend to be inactively liberal: possessing liberal attitudes but not engaging themselves in action. The survey also reports evidence on the contingency of journalistic behaviour logic. Professional logic shows its popularity when journalists encounter conflicts involving legal, economic and political concerns, but not in cases involving moral or cultural conflicts. Neither professional nor commercial logic is strong enough to oppose political logic when journalists are handling severe political issues.
Religious Affirmation and Historical Criticism in Heschel's Biblical Interpretation
Authors: Levenson Jon D.
Published: June 2010

Not least among the bittersweet gifts of modernity to the Jews is the complication of dealing with the Bible both as sacred scripture and as a document subject to the same canons of inquiry as any other historical, or putatively historical, record. The problem goes far beyond the familiar one posed by narratives that ancient historians find doubtful or quite impossible. For historical critical research into the Tanakh (as into all other scriptures) also uncovers the processes of development of the worldviews within the literature and thus puts a painful question to those who wish to affirm Judaism as a contemporary reality. How can a literature so variegated and contradictory speak with a normative voice today? It is no wonder that so many biblical scholars avoid the normative theological questions altogether and content themselves with historical and philological description (which, of course, presupposes norms of its own). It is also no wonder that so many religious practitioners neglect the historical issues and treat their scriptures as representing a static, uniform, and unvarying worldview—not surprisingly, the worldview of their own, postbiblical affirmation.
Interdependence of episodic and semantic memory: Evidence from neuropsychology
Authors: GREENBERG DANIEL L. , VERFAELLIE MIEKE
Published: June 2010

Tulving’s (1972) theory of memory draws a distinction between general knowledge (semantic memory) and memory for events (episodic memory). Neuropsychological studies have generally examined each type of memory in isolation, but theorists have long argued that these two forms of memory are interdependent. Here we review several lines of neuropsychological research that have explored the interdependence of episodic and semantic memory. The studies show that these forms of memory can affect each other both at encoding and at retrieval. We suggest that theories of memory should be revised to account for all of the interdependencies between episodic and semantic memory; they should also incorporate forms of memory that do not fit neatly into either category. (JINS, 2010, 16, 748–753.)
Women, economy, war
Authors: Nordstrom Carolyn
Published: June 2010

Political violence amplifies contemporary trends occurring worldwide in the twenty-first century: globalization, an increasing reliance on the informal economy, a shift from twentieth-century manufacturing to resource and labour wildcatting, and the growth of complex international extra-legal trade networks. Women are central to all of these, though their roles both as leaders of development and victims of violence are often overlooked in mainstream analyses. To explain these invisibilities, this article introduces the concept of vanishing points – places where formal analyses and policy effectively cease, such as the dividing lines between formal and informal economies, and the violence associated with controlling extra-legal profits that is effectively invisible to the public at large. The realities of women's work amid political violence and postwar development, and across the spectrum of in/formality are explored. The conclusions serve to challenge established notions of power, profit, and economy, and the role of gender within these.
Short‐ and long‐timescale thermospheric variability as observed from OI 630.0 nm dayglow emissions from low latitudes
Authors: Pallamraju Duggirala , Das Uma , Chakrabarti Supriya
Published: June 2010

We carried out high‐cadence (5 min) and high‐spatial resolution (2° magnetic latitude) observations of daytime OI 630.0 nm airglow emission brightness from a low‐latitude station to understand the behavior of neutral dynamics in the daytime. The results indicate that the wave periodicities of 12–20 min, and 2 h exist over a wide spatial range of around 8°–12° magnetic latitudes. The 20–80 min periodicities in the dayglow seem to appear more often in the measurements closer to the magnetic equator and not at latitudes farther away. Further, periodicities in that range are found to be frequent in the variations of the equatorial electrojet (EEJ) strength as well. We show that wave periodicities due to the neutral dynamics, at least until around 8° magnetic latitude, are influenced by those that affect the EEJ strength variation as well. Furthermore, the average daily OI 630.0 nm emission brightness over 3 months varied in consonance with that of the sunspot numbers indicating a strong solar influence on the magnitudes of dayglow emissions.
Multiple equilibria in a cloud‐resolving model using the weak temperature gradient approximation
Authors: Sessions Sharon L. , Sugaya Satomi , Raymond David J. , Sobel Adam H.
Published: June 2010

Multiple equilibria corresponding to either a state with persistent, precipitating deep convection or a nonprecipitating state are shown to exist in a cloud‐resolving model employing the weak temperature gradient (WTG) approximation. WTG is important for the existence of both equilibria; numerical experiments show that a weak enforcement of WTG eliminates the dry nonprecipitating state. In situations which support both equilibria, we find that the dry equilibrium has a small or negative gross moist stability, while larger positive values of gross moist stability correspond to the precipitating equilibrium. Our simulations also show that the gross moist stability tends to become negative during times of rapid change in the atmospheric moisture, as occurs in the transient stages of convection.
Simulations of atmospheric phenomena at the Phoenix landing site with the Ames General Circulation Model
Authors: Nelli Steven M. , Renno Nilton O. , Murphy James R. , Feldman William C. , Bougher Stephen W.
Published: June 2010

Phoenix, the first NASA Mars Scout class mission, was designed to “follow the water” and study the polar region. Landing in late northern spring, Phoenix measured soil chemistry, near‐surface water ice, and studied numerous atmospheric properties and weather phenomena. Here, we use atmospheric measurements made by Phoenix to test and calibrate the Ames General Circulation Model (GCM) and start the process of analyzing and interpreting the vast data set provided by this groundbreaking mission. The GCM reproduces surface pressures and temperatures within the measured diurnal and seasonal ranges. It also reproduces measured water ice cloud profiles with ground fogs forming after Ls = 120° and a separate cloud deck between 3 km and 6 km above the surface. Near‐surface water vapor pressures have daytime maxima above 1 Pa in both the data and model. We find that frosts and fogs observed by Phoenix are correlated with the formation of high‐pressure weather systems over the landing site.
Further assembly required: construction and dynamics of the endoplasmic reticulum network
Authors: Park Seong H , Blackstone Craig
Published: June 2010

The endoplasmic reticulum (ER) is a continuous membrane system comprising the nuclear envelope, ribosome‐studded peripheral sheets and an interconnected network of smooth tubules extending throughout the cell. Although protein biosynthesis, transport and quality control in the ER have been studied extensively, mechanisms underlying the notably diverse architecture of the ER have only emerged recently; this review highlights these new findings and how they relate to ER functional specializations. Several protein families, including reticulons and DP1/REEPs/Yop1, harbour hydrophobic hairpin domains that shape high‐curvature ER tubules and mediate intramembrane protein interactions. Members of the atlastin/RHD3/Sey1 family of dynamin‐related GTPases mediate the formation of three‐way junctions that characterize the tubular ER network, and additional classes of hydrophobic hairpin‐containing ER proteins interact with and remodel the microtubule cytoskeleton. Flat ER sheets have a different complement of proteins implicated in shaping, cisternal stacking and microtubule interactions. Finally, several shaping proteins are mutated in hereditary spastic paraplegias, emphasizing the particular importance of proper ER morphology and distribution for highly polarized cells.
Role of calpain in the regulation of CFTR (cystic fibrosis transmembrane conductance regulator) turnover
Authors: Averna Monica , Stifanese Roberto , Grosso Raffaella , Pedrazzi Marco , De Tullio Roberta , Salamino Franca , Pontremoli Sandro , Melloni Edon
Published: June 2010

The level of the mature native 170 kDa form of CFTR (cystic fibrosis transmembrane conductance regulator) at the plasma membrane is under the control of a selective proteolysis catalysed by calpain. The product of this limited digestion, consisting of discrete fragments still associated by strong interactions, is removed from the plasma membrane and internalized in vesicles and subject to an additional degradation. This process can be monitored by visualizing the accumulation of a 100 kDa fragment in a proliferating human leukaemic T-cell line and in human circulating lymphocytes. In reconstructed systems, and in intact cells, the conversion of native CFTR into the 100 kDa fragment linearly correlated with calpain activation and was prevented by addition of synthetic calpain inhibitors. A reduction in Ca2+ influx, by blocking the NMDA (N-methyl-D-aspartate) receptor Ca2+ channel, inhibited the conversion of the native 170 kDa fragment into the 100 kDa fragment, whereas an endosome acidification blocker promoted accumulation of the digested 100 kDa CFTR form. An important role in calpain-mediated turnover of CFTR is exerted by HSP90 (heat-shock protein 90), which, via association with the protein channel, modulates the degradative effect of calpain through a selective protection. Taken together these results indicate that CFTR turnover is initiated by calpain activation, which is induced by an increased Ca2+ influx and, following internalization of the cleaved channel protein, and completed by the lysosomal proteases. These findings provide new insights into the molecular mechanisms responsible for the defective functions of ion channels in human pathologies.
Angiotensin II increases mRNA levels of all TGF‐β isoforms in quiescent and activated rat hepatic stellate cells
Authors: Moreno‐Alvarez Paola , Sosa‐Garrocho Marcela , Briones‐Orta Marco A. , González‐Espinosa Claudia , Medina‐Tamayo Jaciel , Molina‐Jijón Eduardo , Pedraza‐Chaverri José , Macías‐Silva Marina
Published: June 2010

AII (angiotensin II) is a vasoactive peptide that plays an important role in the development of liver fibrosis mainly by regulating profibrotic cytokine expression such as TGF‐β (transforming growth factor‐β). Activated HSCs (hepatic stellate cells) are the major cell type responsible for ECM (extracellular matrix) deposition during liver fibrosis and are also a target for AII and TGF‐β actions. Here, we studied the effect of AII on the mRNA levels of TGF‐β isoforms in primary cultures of rat HSCs. Both quiescent and activated HSCs were stimulated with AII for different time periods, and mRNA levels of TGF‐β1, TGF‐β2 and TGF‐β3 isoforms were evaluated using RNaseI protection assay. The mRNA levels of all TGF‐β isoforms, particularly TGF‐β2 and TGF‐β3, were increased after AII treatment in activated HSCs. In addition, activated HSCs were able to produce active TGF‐β protein after AII treatment. The mRNA expression of TGF‐β isoforms induced by AII required both ERK1/2 and Nox (NADPH oxidase) activation but not PKC (protein kinase C) participation. ERK1/2 activation induced by AII occurs via AT1 receptors, but independently of either PKC and Nox activation or EGFR (epidermal growth factor receptor) transactivation. Interestingly, AII has a similar effect on TGF‐β expression in quiescent HSCs, although it has a smaller but significant effect on ERK1/2 activation in these cells.
SEMO: A Framework for Customer Social Networks Analysis Based on Semantics
Authors: García-Crespo Ángel , Colomo-Palacios Ricardo , Gómez-Berbís Juan Miguel , Ruiz-Mezcua Belén
Published: June 2010

The increasing importance of the Internet in most domains has brought about a paradigm change in consumer relations. The influence of Social Networks has entered the Customer Relationship Management domain under the coined term CRM 2.0. In this context, the need to understand and classify the interactions of customers by means of new platforms has emerged as a challenge for both researchers and professionals worldwide. This is the perfect scenario for the use of SEMO, a platform for Customer Social Networks Analysis based on Semantics and emotion mining. The platform benefits from both semantic annotation and classification and text analysis, relying on techniques from the Natural Language Processing domain. The results of the evaluation of the experimental implementation of SEMO reveal a promising and viable platform from a technical perspective.
Understanding Information Disclosure Behaviour in Australian Facebook Users
Authors: Hey Tow William Newk-Fon , Dell Peter , Venable John
Published: June 2010

The advent of social networking websites presents further opportunities for criminals to obtain information for use in identity theft, cyber-stalking, and worse activities. This paper presents research investigating why users of social networking websites willingly disclose personal information and what sorts of information they provide (or not). The study employed an ethnographic approach of participation in the online community and interviews of community members, combined with a quantitative survey. The findings show that users are often simply not aware of the issues or feel that the risk to them personally is very low. The paper develops a preliminary theoretical model to explain the information disclosure phenomenon. It further recommends that government agencies or social networking websites themselves conduct campaigns to inform the public of these issues and that social networking websites consider removing some facilities. The study was conducted in an Australian context and focussed on the popular Facebook website.
Online Social Networks: Why We Disclose
Authors: Krasnova Hanna , Spiekermann Sarah , Koroleva Ksenia , Hildebrand Thomas
Published: June 2010

On online social networks such as Facebook, massive self-disclosure by users has attracted the attention of Industry players and policymakers worldwide. Despite the Impressive scope of this phenomenon, very little Is understood about what motivates users to disclose personal Information. Integrating focus group results Into a theoretical privacy calculus framework, we develop and empirically test a Structural Equation Model of self-disclosure with 259 subjects. We find that users are primarily motivated to disclose Information because of the convenience of maintaining and developing relationships and platform enjoyment. Countervailing these benefits, privacy risks represent a critical barrier to information disclosure. However, users’ perception of risk can be mitigated by their trust in the network provider and availability of control options. Based on these findings, we offer recommendations for network providers.
Exploring the Impact of Soclo-Technlcal Core-Periphery Structures in Open Source Software Development
Authors: Amrit Chintan , van Hillegersberg Jos
Published: June 2010

In this paper we apply the social network concept of core-periphery structure to the socio-technical structure of a software development team. We propose a socio-technical pattern that can be used to locate emerging coordination problems in Open Source projects. With the help of our tool and method called TESNA, we demonstrate a method to monitor the socio-technical core-periphery movement in Open Source projects. We then study the impact of different core-periphery movements on Open Source projects. We conclude that a steady core-periphery shift towards the core is beneficial to the project, whereas shifts away from the core are clearly not good. Furthermore, oscillatory shifts towards and away from the core can be considered as an Indication of the instability of the project. Such an analysis can provide developers with a good Insight into the health of an Open Source project. Researchers can gain from the pattern theory, and from the method we use to study the core-periphery movements.
Exploring Temporal Coordination of Events with Facebook.com
Authors: Khan Zuhair , Jarvenpaa Sirkka L.
Published: June 2010

The coordination of a social event requires a number of time-bounded tasks (exact time, location, activities of the event) to be determined prior to the event. On university campuses, Facebook is increasingly used to organize ad hoc physical gatherings within social groups. The coordination takes place via Facebook event pages and a ‘wall’ that represent online, shared, interactive spaces. This paper explores how such online interactive spaces facilitate the temporal coordination of social events. We content analyze Facebook's event pages and walls to understand how social group behavior is different from prevailing theories of group task progress and media use. The results suggest that, similar to many work groups, social groups exhibit differential interactive behaviors before and after the midpoint of when the event is created on Facebook and when the offline activity is going to happen. However, the results differ in the sense that the interactive behavior is highest before rather than after the midpoint. We also found that the involvement of the creator of the event pages is associated with higher interactive behavior of the social group. We discuss the findings and derive implications for the design of online tools for social event management.
Velocity-field characteristics of polycrystalline pentacene field-effect transistors
Authors: Cobb Brian , Wang Liang , Dunn Lawrence , Dodabalapur Ananth
Published: June 2010

In this article, we report on the carrier velocity of polycrystalline pentacene transistors as a function of lateral electric field in both quasistatic and nonquasistatic regimes. We performed a series of measurements on devices with a range of channel lengths. At moderate lateral electric fields (<5×105 V/cm), the characteristics are similar to those of disordered or amorphous organic semiconductors. The highest velocities we have measured are near 5×104 cm/s at room temperature. Additional dynamic measurements, using both step response and frequency response methods, correlate strongly to the quasistatic findings. These results fill an important void between experimental results that have been obtained with disordered/amorphous organic semiconductors and single crystals.
Microcavity effect on the nonlinear intersubband response of multiple-quantum-well structures: The strong-coupling-regime
Authors: Załużny M. , Nalewajko C.
Published: June 2010

We theoretically discuss the nonlinear intersubband response of multiple-quantum-well structures embedded in microcavities with plane-wave approximation. We employ a semiclassical approach based on the transfer matrix formalism and the so-called sheet model. The linear absorptive losses are taken into account. It is shown that in the strong-coupling-regime the saturation effect leads to the evolution of the absorption spectra from a pair of simple harmonic oscillators to highly anharmonic ones. The usefulness of the simplified analytical approach, based on a standard multibeam interference analysis and the “mean-field” approximation is also demonstrated.
Generation of liquid metal structures of high aspect ratio by application of an ac magnetic field
Authors: Andreev Oleg , Pothérat Alban , Thess André
Published: June 2010

We study how the shape of parts obtained through the LASER cladding process can be controlled by application of an ac magnetic field by means of two simple physical models: a numerical and an experimental one. More specifically, we show that straight metallic joints of high aspect ratio can be obtained by using inductors of triangular cross-section that concentrate electromagnetic forces at the bottom of the joint. The effect is first demonstrated on a numerical model for an infinitely long joint such as: we illustrate how the joint shape can be controlled by varying the inclination of the inductor and for a magnetic Bond number Bom=60 (which measures the ratio of electromagnetic to capillary forces), we obtain a joint of aspect ratio up to 7.2. We further find that inductor angles in the range 15°–25° lead to joint side faces that are close to vertical. These findings are then verified experimentally by placing a liquid metal drop in a purpose built inductor of triangular cross-section. We find a good agreement between the theoretical prediction of our two-dimensional model and the real three-dimensional drop. For the highest magnetic Bond number our generator could deliver, Bom=20.19, we achieved a drop aspect ratio of 2.73.
Experimental studies of planar metamaterials with a tunable cylindrical TE01n mode cavity
Authors: Krupka Jerzy , Gwarek Wojciech , Hartnett John G.
Published: June 2010

Tunable cylindrical TE01n mode cavity has been used for the measurement of the dielectric and magnetic properties of planar anisotropic metamaterials as a function of frequency. Experiments have been performed on low loss dielectric samples covered with thin metal patterns consisting split-ring resonators (SRRs), creating a regular hexagonal lattice. In order to determine the two complex quantities, namely the effective permittivity in the plane of metamaterial and the effective permeability in the direction perpendicular to that plane, two metamaterial samples have been used—one small sample consisting of only seven SRRs at the center of the substrate and another large sample, with a diameter larger than the diameter of the cavity, completely covered with SRRs. It has been shown that determination of the effective permittivity and permeability, that are three-dimensional quantities, requires an assumption of the effective thickness of the metamaterial samples. The resonance behavior of the permittivity and permeability for metamaterials consisting of a SRR lattice has been experimentally confirmed.
Hydrogen generation under visible light using nitrogen doped titania anodes
Authors: Lin H. , Rumaiz A. K. , Schulz M. , Huang C. P. , Shah S. Ismat
Published: June 2010

Hydrogen is among several energy sources that will be needed to replace the quickly diminishing fossil fuels. Free hydrogen is not available naturally on earth and the current processes require a fossil fuel, methane, to generate hydrogen. Electrochemical splitting of water on titania proposed by Fujishima suffers from low efficiency. The efficiency could be enhanced if full sun spectrum can be utilized. Using pulsed laser deposition technique we synthesized nitrogen doped titanium dioxide (TiO2−xNx) thin films with improved visible light sensitivity. The photoactivity was found to be N concentration dependent. Hydrogen evolution was observed under visible light irradiation (wavelength>390 nm) without the presence of any organic electron donor.
Lifetime limiting recombination pathway in thin-film polycrystalline silicon on glass solar cells
Authors: Wong J. , Huang J. L. , Eggleston B. , Green M. A. , Kunz O. , Evans R. , Keevers M. , Egan R. J.
Published: June 2010

The minority carrier lifetimes of a variety of polycrystalline silicon solar cells are estimated from temperature-dependent quantum efficiency data. In most cases the lifetimes have Arrhenius temperature dependences with activation energies of 0.17–0.21 eV near room temperature. There is also a rough inverse relationship between lifetime and the base dopant concentration. Judging by this inverse law, the activation energies of the lifetimes, and the absence of plateau behavior in the lifetimes of the higher doped cells at low temperatures, it is inferred that the dominant recombination pathway involves the electronic transition between shallow states which are 0.05–0.07 eV below the conduction band and 0.06–0.09 eV above the valence band, respectively, consistent with the shallow bands in silicon dislocations. The modeled recombination behavior implies that deep levels do not significantly affect the lifetimes for most of the cells at and below room temperature.
Spectral line shape profile of rovibrational transitions of CO embedded in p-H2 crystals studied by high resolution IR diode laser spectroscopy
Authors: Toda Naoya , Mizoguchi Asao , Kanamori Hideto
Published: June 2010

Line profiles of rovibrational transitions of CO embedded in p-H2 crystals were studied by high resolution midinfrared diode laser spectroscopy. The line profile analysis for the R(0)∥, R(0)⊥, P(1)∥, and P(1)⊥ transitions shows that spectral line shapes are well reproduced by a convolution of Gaussian and Lorentzian functions. The temperature dependence of the Lorentzian ΓL(T) and Gaussian widths ΓG(T) shows that there is a nonzero linewidth contribution to each at the T=0 K limit. The main part of the Lorentzian width ΓL(T=0) shows anisotropy in the hcp structure and is explained by spontaneous decay of the rotational excited state energy to phonon modes. A smaller part of ΓL(T=0) is attributed to inhomogeneous broadening due to the point defects of other CO molecules in the crystal. On the other hand, the Gaussian width ΓG(T=0) is explained by inhomogeneous broadening due to dislocations. In the T>0 region, ΓL(T) shows strong temperature dependence but ΓG(T) does not. The center frequencies of the R(0)⊥ and P(1)∥ transitions show blueshifts and those of the R(0)∥ and P(1)⊥ transitions show redshifts with increasing temperature. This phenomenon is explained by a decrease in the anisotropy in the crystal field, which is caused by the averaging of thermal lattice fluctuations. Furthermore, the contribution of vibration and rotation to the linewidth is discussed.
Entropy, diffusivity and the energy landscape of a waterlike fluid
Authors: Barros de Oliveira Alan , Salcedo Evy , Chakravarty Charusita , Barbosa Marcia C.
Published: June 2010

Molecular dynamics simulations and instantaneous normal mode (INM) analysis of a fluid with core-softened pair interactions and waterlike liquid-state anomalies are performed to obtain an understanding of the relationship between thermodynamics, transport properties, and the potential energy landscape. Rosenfeld scaling of diffusivities with the thermodynamic excess and pair correlation entropy is demonstrated for this model. The INM spectra are shown to carry information about the dynamical consequences of the interplay between length scales characteristic of anomalous fluids, such as bimodality of the real and imaginary branches of the frequency distribution. The INM spectral information is used to partition the liquid entropy into two contributions associated with the real and imaginary frequency modes; only the entropy contribution from the imaginary branch captures the nonmonotonic behavior of the excess entropy and diffusivity in the anomalous regime of the fluid.
Measurements of the surface critical current of YBa2Cu3O7−δ thin films: Probing the nonuniformity of their superconducting critical temperature along the c-axis
Authors: Bernstein P. , Mosqueira J. , Siejka J. , Vidal F. , Thimont Y. , McLoughlin C. , Ferro G.
Published: June 2010

The existence of nonsuperconducting zones in YBa2Cu3O7−δ (YBCO) films below the transition temperature to the nonresistive state can limit the performances of YBCO devices. In this work, we present detailed measurements of the temperature dependence of the critical surface current density of c-axis oriented epitaxial YBCO films, that suggest that their superconducting critical temperature, Tc, is modulated along the c-axis. This nonuniformity of Tc, that could be present in all YBCO films, seems also to be supported by measurements of both the field cooled in-plane magnetic moment and the oxygen content (by non-Rutherford elastic resonance scattering) of some samples.
Study of active surface defects in Ti doped ZnO nanoparticles
Authors: Naeem M. , Qaseem S. , Gul I. H. , Maqsood A.
Published: June 2010

The effects of surface defects (oxygen vacancies) on the electronic structure and photoluminance properties of titanium doped ZnO nanoparticles are reported. Nanoparticles of different sizes ranging from 6 to 25 nm are characterized by x-ray diffraction, Transmission electron microscopy, x-ray photoemission spectroscopy, and photoluminescence (PL) spectra. Structural analysis indicates that Ti ions are substituted at Zn sites in ZnO matrix. Surface defects are systemically increasing with decreasing the particles size, which is also confirmed by Raman scattering measurements. The intensity of the visible peak in the PL spectra exhibits an apparent nonmonotonic change over the entire range of the particle size. The intensity is shown to be decreasing with increasing the particle size but then increasing above a typical particle size of 15 nm. This nonmonotonic profile of visible intensity could be explained via two different mechanisms such as: (i) hole-trapped tunneling in smaller size particles and (ii) surface depletion region containing a rich amount of doubly charged oxygen vacancy (VO2+) in the bigger size particle.
Replication of noise-sustained autocatalytic chemical structures
Authors: Izús Gonzalo G. , Deza Roberto R. , Sánchez Alejandro D.
Published: June 2010

Autocatalytic systems in a differential-flow reactor may undergo a differential-flow-induced chemical instability toward a convectively unstable regime, in which noise-sustained structures may appear. This is the case of a system with Gray–Scott kinetics in a packed-bed reactor, as reported in [B. von Haeften and G. Izús, Phys. Rev. E 67, 056207 (2003)]. In this work, two identical copies of such a system are coupled in master-slave configuration and submitted to independent spatiotemporal Gaussian white noise sources. Numerical simulation of two-dimensional reactors with uniform and Poiseuille flows reveals that the slave system replicates to a very high degree of precision and the convective patterns arising in the master one due to the presence of noise. The quality of this synchronization is assessed through several measures. A convective instability in the synchronization manifold is theoretically predicted and numerically confirmed.
Efficient simulation of electron trapping in laser and plasma wakefield acceleration
Authors: Morshed S. , Antonsen T. M. , Palastro J. P.
Published: June 2010

The two-dimensional quasistatic simulation code WAKE [P. Mora and T. Antonsen, Phys. Plasmas 4, 217 (1997)] used to model laser pulse propagation in tenuous plasma is modified to describe the dynamics of energetic particles. In the original code, all particles were assumed to satisfy the quasistatic approximation, which assumes that the driver and its wakefields are undisturbed during the transit time of plasma electrons through the pulse. Here, WAKE is modified to include the effects of electron trapping and beam loading by introducing a population of beam electrons, which are no longer subject to the quasistatic approximation. Algorithms for populating the group of beam particles are considered and are benchmarked to the full particle-in-cell simulations and experimental results. These modifications to WAKE provide a tool for simulating GeV laser or plasma wakefield acceleration on desktop computers.
Two- and three-body interatomic dispersion energy contributions to binding in molecules and solids
Authors: Anatole von Lilienfeld O. , Tkatchenko Alexandre
Published: June 2010

We present numerical estimates of the leading two- and three-body dispersion energy terms in van der Waals interactions for a broad variety of molecules and solids. The calculations are based on London and Axilrod–Teller–Muto expressions where the required interatomic dispersion energy coefficients, C6 and C9, are computed “on the fly” from the electron density. Inter- and intramolecular energy contributions are obtained using the Tang–Toennies (TT) damping function for short interatomic distances. The TT range parameters are equally extracted on the fly from the electron density using their linear relationship to van der Waals radii. This relationship is empiricially determined for all the combinations of He–Xe rare gas dimers, as well as for the He and Ar trimers. The investigated systems include the S22 database of noncovalent interactions, Ar, benzene and ice crystals, bilayer graphene, C60 dimer, a peptide (Ala10), an intercalated drug-DNA model [ellipticine-d(CG)2], 42 DNA base pairs, a protein (DHFR, 2616 atoms), double stranded DNA (1905 atoms), and 12 molecular crystal polymorphs from crystal structure prediction blind test studies. The two- and three-body interatomic dispersion energies are found to contribute significantly to binding and cohesive energies, for bilayer graphene the latter reaches 50% of experimentally derived binding energy. These results suggest that interatomic three-body dispersion potentials should be accounted for in atomistic simulations when modeling bulky molecules or condensed phase systems.
Rayleigh–Taylor instability in dielectric fluids
Authors: Joshi Amey , Radhakrishna M. C. , Rudraiah N.
Published: June 2010

Force on dielectric fluids in the presence of a nonuniform electric field is shown to reduce their specific weights. An appropriately chosen field gradient makes the specific weights of superposed fluids equal and prevents Rayleigh–Taylor instability. We derive the dispersion relation for perturbation at the interface of superposed dielectric fluids, within limits of linear theory, successively for ideal, Newtonian, and those with stratified viscosity. A dimensionless dielectric number is shown to determine the stability of the arrangement.
Solvatochromic shift of phenol blue in water from a combined Car–Parrinello molecular dynamics hybrid quantum mechanics-molecular mechanics and ZINDO approach
Authors: Murugan N. Arul , Jha Prakash Chandra , Rinkevicius Z. , Ruud Kenneth , Ågren Hans
Published: June 2010

The present work addresses the solvatochromic shift of phenol blue (PB) dye. For this purpose the results of Car–Parrinello molecular dynamics (CPMD) simulations for PB in gas phase are compared with results obtained for PB in water from CPMD hybrid quantum mechanics-molecular mechanics (CPMD-QM/MM) calculations. The absorption spectra were obtained using the intermediate neglect of differential overlap/spectroscopic-configuration interaction (INDO/CIS) method and were calculated for a multitude of configurations of the trajectory. The calculated λmax for PB in gas phase was found to be about 535 nm, which is considerably lower than the λmax reported for PB in nonpolar solvents. Different solvation shells for PB in water have been defined based on the solute-all-atoms and solvent center of mass radial distribution function (g(rX–O)). The electronic excitation energies for PB computed in the presence of solvent molecules in an increasing number of solvation shells were calculated in a systematic way to evaluate their contributions to the solvatochrmic shift. The inclusion of solvent molecules in the hydration shell yields a λmax of 640 nm, which contributes to almost 78% of the solvatochromic shift. The inclusion of solvent molecules up to 10 Å in the g(rX–O) rdf yields a λmax of 670 nm which is in good agreement with the experimentally reported value of 654–684 nm. Overall, the present study suggests that the combined CPMD-QM/MM and INDO-CIS approach can be used successfully to model solvatochromic shifts of organic dye molecules.
Study of piezoresistance under unixial stress for technologically relevant III-V semiconductors using wafer bending experiments
Authors: Nainani Aneesh , Yum Jung , Barnett Joel , Hill Richard , Goel Niti , Huang Jeff , Majhi Prashant , Jammy Raj , Saraswat Krishna C.
Published: June 2010

In this work, effect of uniaxial stress is studied by wafer bending on p/n-channel candidates for III-V based complimentary logic. p-GaSb has 2× higher piezoresistance (π) coefficient than p-In0.53Ga0.47As, which combined with high hole-mobility in GaSb makes it an attractive candidate for III-V p-metal-oxide-semiconductor-field-effect-transistor. Limitation on maximum stress introduced by wafer bending is improved when the III-V channel is grown epitaxially on silicon. 250 MPa of stress is achieved by wafer bending on III-V channel grown on silicon substrate, which is 5× higher than maximum stress achieved on III-V substrate.
Frequency stabilization of a radio frequency excited CO2 laser using the photoacoustic effect
Authors: Choi Jongwoon
Published: June 2010

A frequency and a power of rf excited CO2 laser are stabilized using the photoacoustic effect generated from the laser itself. As the radiation intensity in a laser resonator changed, the pressure of laser medium gas changed due to its photoacoustic effect. A condenser microphone built in the resonator is used to convert delicate variations in the pressure into voltage signals to be used as input signals for lock-in stabilizer. As a result of stabilizing the frequency and power of the laser oscillated from P(20) line, at the apex of gain curve, the relative stability of the optical frequency and the rate of change in laser power are 5.57×10−8 and 9.3%, respectively.
Anisotropic shock response of columnar nanocrystalline Cu
Authors: Luo Sheng-Nian , Germann Timothy C. , Desai Tapan G. , Tonks Davis L. , An Qi
Published: June 2010

We perform molecular dynamics simulations to investigate the shock response of idealized hexagonal columnar nanocrystalline Cu, including plasticity, local shear, and spall damage during dynamic compression, release, and tension. Shock loading (one-dimensional strain) is applied along three principal directions of the columnar Cu sample, one longitudinal (along the column axis) and two transverse directions, exhibiting a strong anisotropy in the response to shock loading and release. Grain boundaries (GBs) serve as the nucleation sites for crystal plasticity and voids, due to the GB weakening effect as well as stress and shear concentrations. Stress gradients induce GB sliding which is pronounced for the transverse loading. The flow stress and GB sliding are the lowest but the spall strength is the highest, for longitudinal loading. For the grain size and loading conditions explored, void nucleation occurs at the peak shear deformation sites (GBs, and particularly triple junctions); spall damage is entirely intergranular for the transverse loading, while it may extend into grain interiors for the longitudinal loading. Crystal plasticity assists the void growth at the early stage but the growth is mainly achieved via GB separation at later stages for the transverse loading. Our simulations reveal such deformation mechanisms as GB sliding, stress, and shear concentration, GB-initiated crystal plasticity, and GB separation in nanocrystalline solids under shock wave loading.
Crystal nucleation rate isotherms in Lennard-Jones liquids
Authors: Baidakov Vladimir G. , Tipeev Azat O. , Bobrov Konstantin S. , Ionov Gennady V.
Published: June 2010

We present the results of molecular dynamics simulations of the crystal nucleation rate in a supercooled Lennard-Jones liquid. The nucleation rate as a function of the pressure has been calculated by the method of determining the expectation time for liquid crystallization at temperatures higher than that of the triple point (T∗=0.865), close to the temperature of the terminal critical point of the metastable extension of the melting curve (T∗=0.55) and below this temperature (T∗=0.4). In computer experiments the nucleation rate varied from 1032 to 1035 s−1 m−3. The dimensions of critical nuclei and the pressure inside them, the surface free energy at a critical crystal nucleus-liquid interface, the height of the nucleation barrier, and the Zeldovich factor have been determined from the results of molecular dynamics simulations and their comparison with classical homogeneous nucleation theory. It is shown that the surface free energy at a curved crystal-liquid interface, as distinct from a flat interface, has also been determined at temperatures lower than the temperature of the terminal critical point of the melting curve and is a monotonically increasing function of the temperature.
Kinetic Alfvén wave instability driven by electron temperature anisotropy in high-β plasmas
Authors: Chen L. , Wu D. J.
Published: June 2010

Based on the kinetic dispersion equation in the low-frequency condition of ω<Ωi (the ion cyclotron frequency), the instability driven by the electron temperature anisotropy in high-β plasmas, which is associated with kinetic Alfvén waves in the wave vector range of k∥λI⪡1 and k⊥ρi⪡1 (where λI and ρi are the ion inertial length and gyroradius, respectively), is investigated. The results show that the structures of both the growth rate and the real frequency are different from those driven by the ion temperature anisotropy. The growth rate is larger than that driven by the ion anisotropy. The critical instability condition is modified dramatically, in which the electron driven growth rate does not vanish at the classical critical point and its deviation from zero increases with the kinetic effect due to the short-wavelength modification.
First-principles study of Ru atoms and clusters adsorbed outside and inside carbon nanotubes
Authors: Gao Haili , Zhao Jijun
Published: June 2010

First-principles calculations were performed to investigate the binding energies, geometric structures, and electronic properties of 4d transition metal (TM) (particularly, Ru), atoms, and clusters adsorbed outside/inside the single-walled or double-walled carbon nanotubes. The equilibrium adsorption structures of the TM atoms depend on the valence electron configuration of the metal atoms. Due to curvature effect, all TM atoms adsorbed inside and outside (6, 6) carbon nanotubes donate different amounts of electrons to the nanotube, with a nearly constant difference of about 0.5 electrons/TM atom. The analysis of electronic density of states revealed hybridization between the p electrons from C and the d electrons from Ru, which results in charge transfer from metal to carbon. The amount of charge transfer shows systematical trend with the electronegativity of 4d TMs. When Ru atom or cluster adsorbs on double-walled nanotubes, the effect of charge transfer is slightly enhanced with regard to the single-walled nanotubes.