bluuebunny/crossref_metadata_2025 huggingface dataset:
Two Aromatic Ester Organoimido Derivatives of Hexa­molybdate: Syntheses, Crystal Structures, and Spectroscopic Studies
Authors: Wang Manxiang , Wang Dafei , Xu Huanhuan , Hao Jian , Li Qiang
Published: September 2013

Two alkylimido derivatives of hexamolybdate, (Bu4N)2[Mo6O18(≡N‐o‐COOCH3C6H4)] (1) and (Bu4N)2[Mo6O18(≡N‐o‐COOCH2CH3C6H4)] (2), were synthesized in high purity and good yields by the reaction of [(C4H9)4N]4[α‐Mo8O26] and methyl anthranilate or ethyl‐o‐aminobenzoate hydrochloride with N,N′‐dicyclohexylcarbodiimide (DCC) as a dehydrating agent in dry acetonitrile solution, which were characterized by elemental analyses, IR, UV/Vis, and 1H NMR spectroscopy as well as ESI‐MS, and single‐crystal X‐ray diffraction study. Compound 1 crystallizes in the monoclinic space group P21/n with one‐dimensional chain structure via intramolecular hydrogen bond. Compound 2 also crystallizes in the monoclinic space group P21/n with dimer structure by intramolecular hydrogen bonds and π–π interactions between the pairs of cluster anions.
Two‐step Synthesis of MoS2 Nanotubes using Shock Waves with Lead as Growth Promoter
Authors: Brontvein Olga , Jayaram Vishakantaiah , Reddy K. P. J. , Gordon Jeffrey M. , Tenne Reshef
Published: September 2013

A new two‐step procedure for the synthesis of MoS2 nanotubes using lead as a growth promoter is reported. In the first step, molybdenum suboxide nanowhiskers containing a small amount of lead atoms were created by exposing a pressed MoS2+Pb mixture to highly compressed shock‐heated argon gas, with estimated temperatures exceeding 9900 K. In the second step, these molybdenum suboxide nanowhiskers served as templates for the sulfidization of the oxide into MoS2 nanotubes (by using H2S gas in a reducing atmosphere at 820 °C). Unlike the case of WS2 nanotubes, the synthesis of a pure phase of MoS2 nanotubes from molybdenum oxide has proven challenging, due mostly to the volatile nature of the latter at the high requisite reaction temperatures (>800 °C). In contrast, the nature and apparent reaction mechanism of the method reported herein are amenable to future scale‐up. The high‐temperature shockwave system should also facilitate the synthesis of new nanostructures from other layered materials.
Exporting Poor Health: The Irish in England
Authors: Delaney Liam , Fernihough Alan , Smith James P.
Published: September 2013

In the twentieth century, the Irish-born population in England has typically been in worse health than both the native population and the Irish population in Ireland, a reversal of the commonly observed healthy migrant effect. Recent birth cohorts living in England and born in Ireland, however, are healthier than the English population. The substantial Irish migrant health penalty arises principally for cohorts born between 1920 and 1960. In this article, we attempt to understand the processes that generated these changing migrant health patterns for Irish migrants to England. Our results suggest a strong role for economic selection in driving the dynamics of health differences between Irish-born migrants and white English populations.
Preliminary investigation of the influence of long-term dietary isoflavone intake on puberty onset and oestrous cycles in domestic cats (Felis catus)
Authors: Whitehouse-Tedd Katherine M. , Cave Nicholas J. , Ugarte Claudia E. , Thomas David G.
Published: September 2013

Genistein and daidzein are isoflavones which are reported to influence the reproductive system in a variety of mammalian species. This pilot study aimed to determine if dietary isoflavones could potentially influence reproductive parameters in domestic cats, when consumed during the postnatal development period. Cats (n = 12) were maintained on either a treatment (150 µg/g DM genistein and 150 µg/g DM daidzein, n = 4) or control (isoflavone free, n = 8) diet from weaning, up to 414 (±17.2) days post-weaning. Vaginal smears were taken thrice weekly and examined for oestrogen-induced cellular degradation in all cats. Behavioural indicators of oestrous were routinely scored for the presence or absence of six key behaviours. Genistein and daidzein did not alter puberty onset or oestrous cycle parameters in these cats (P > 0.05). Behavioural scores were higher in cats in the treatment group than control. Incidence of apparent spontaneous ovulation (inferred from extended inter-oestrous periods) was greater in treated cats than control cats, although serum hormone profiles were not available to confirm this observation. Further testing is warranted.
Wall pressure coherence in supersonic turbulent boundary layers
Authors: Di Marco A. , Camussi R. , Bernardini M. , Pirozzoli S.
Published: September 2013

A numerical database (Bernardini & Pirozzoli, Phys. Fluids, vol. 23, 2011, 085102) is analysed to investigate cross-statistics of wall-pressure fluctuations induced by supersonic turbulent boundary layers developing over a rigid smooth wall without a pressure gradient. The Mach number spans from 2 to 4 and a relatively large range of Reynolds numbers is considered. It is shown, for the first time, that the cross-statistics of wall-pressure fluctuations at such high Mach numbers is very similar to that usually observed in incompressible flow conditions. Furthermore, it is demonstrated that theoretical predictions provided by the well-known Corcos and Efimtsov models continue to apply.
Americanism, Un-Americanism, and the Gay Rights Movement
Authors: HALL SIMON
Published: September 2013

The issue of “un-Americanism” was present at the creation of the gay rights movement. Indeed the movement emerged, at least in part, as a response to wide-ranging discriminatory policies and practices that were implemented by the federal government during the Cold War. Faced with claims that they constituted an existential threat to the United States, activists in the early gay rights movement worked hard to affirm their patriotism and appealed frequently to the nation's founding ideals of liberty and equality. At times, they also characterized those who discriminated against them as “un-American.” Fifty years later, debates about “Americanism” and “un-Americanism” have been centre stage in the battle to repeal Don't Ask, Don't Tell and to secure gay marriage rights. With conservative politicians, commentators and activists claiming that demands for gay marriage threaten the foundation of American civilization, the gay rights movement and its supporters have responded in kind. The increased willingness of gay rights activists to lay the charge of “un-American” is, at one level, a logical extension of the appeal to Americanism that has long been central to the movement's rhetorical and symbolic approach. But it also reflects both the greater empowerment of today's LGBT community compared with their McCarthy-era predecessors and the divisiveness of contemporary American political culture.
The impact of distinct culture media inLeishmania infantumbiology and infectivity
Authors: SANTARÉM NUNO , CUNHA JOANA , SILVESTRE RICARDO , SILVA CÁTIA , MOREIRA DIANA , OUELLETTE MARC , CORDEIRO-DA-SILVA ANABELA
Published: September 2013

An ideal culture medium forLeishmaniapromastigotes should retain the basic characteristics of promastigotes found in sandflies (morphology and infectivity). Furthermore, the media should not create a bias in experimental settings, thus enabling the proper extrapolation of results. To assess this we studied several established media for promastigote growth. We analysed morphology, viability, cell cycle progression, metacyclic profile, capacity to differentiate into axenic amastigotes and infectivity. Furthermore, using a rational approach from the evaluated media we developed a simple serum-free medium (cRPMI). We report that parasites growing in different media present different biological characteristics and distinctin vitroandin vivoinfectivities. The developed medium, cRPMI, proved to be a less expensive substitute for traditional serum-supplemented media for thein vitromaintenance of promastigotes. In fact, cRPMI is ideal for the maintenance of parasites in the laboratory, diminishing the expected loss of virulence over time typical of the parasite cultivation. Ultimately this report is a clear warning that the normalization of culture media should be a real concern in the field as media-specific phenomena are sufficient to induce biological bias with consequences in infectivity and general parasite biology.
A meta-analysis of neuropsychological markers of vulnerability to suicidal behavior in mood disorders
Authors: Richard-Devantoy S. , Berlim M. T. , Jollant F.
Published: September 2013

Background

Suicidal behavior results from a complex interplay between stressful events and vulnerability factors, including cognitive deficits. However, it is not clear which cognitive tests may best reveal this vulnerability. The objective was to identify neuropsychological tests of vulnerability to suicidal acts in patients with mood disorders.

Method

A search was made of Medline, EMBASE and PsycINFO databases, and article references. A total of 25 studies (2323 participants) met the selection criteria. A total of seven neuropsychological tests [Iowa gambling task (IGT), Stroop test, trail making test part B, Wisconsin card sorting test, category and semantic verbal fluencies, and continuous performance test] were used in at least three studies to be analysed.

Results

IGT and category verbal fluency performances were lower in suicide attempters than in patient controls [respectively,g = –0.47, 95% confidence interval (CI) –0.65 to –0.29 andg = –0.32, 95% CI –0.60 to –0.04] and healthy controls, with no difference between the last two groups. Stroop performance was lower in suicide attempters than in patient controls (g = 0.37, 95% CI 0.10–0.63) and healthy controls, with patient controls scoring lower than healthy controls. The four other tests were altered in both patient groupsversushealthy controls but did not differ between patient groups.

Conclusions

Deficits in decision-making, category verbal fluency and the Stroop interference test were associated with histories of suicidal behavior in patients with mood disorders. Altered value-based and cognitive control processes may be important factors of suicidal vulnerability. These tests may also have the potential of guiding therapeutic interventions and becoming part of future systematic assessment of suicide risk.
A village-based multidisciplinary study on factors affecting the intensity of cystic echinococcosis in an endemic region of the Tibetan plateau, China
Authors: HU H. H. , WU W. P. , GUAN Y. Y. , WANG L. Y. , WANG Q. , CAI H. X. , HUANG Y.
Published: September 2013

We investigated and quantified the factors which may affect the prevalence of cystic echinococcosis caused by Echinococcus granulosus in Rangtang County using a multidisciplinary approach. From a previously performed field survey, epidemiological data were linked with environmental data. Altitude and land surface temperature were extracted from remote-sensing images. Cumulative logistic regression models were used to identify and quantify the potential risk factors. The multiple regression models confirmed that yaks (χ2 = 4·0447, P = 0·0443), dogs (χ2 = 8·3455, P = 0·0039) and altitude (χ2 = 7·6223, P = 0·0058) were positively correlated with the prevalence of cystic echinococcosis, while land surface temperature may have a negative association. The findings showed that dogs and yaks play the most important role in the transmission of cystic echinococcosis, while altitude and land surface temperature may also be involved in the transmission.
The association of weather and bathing water quality on the incidence of gastrointestinal illness in the west of Scotland
Authors: EZE J. I. , SCOTT E. M. , POLLOCK K. G. , STIDSON R. , MILLER C. A. , LEE D.
Published: September 2013

The associations with weather and bathing water quality on infectious intestinal disease (IID) were investigated using data from two Scottish NHS Board areas. Monthly counts of viral and non-viral gastrointestinal infections were modelled as a smooth function of temperature, relative humidity and average monthly counts of faecal indicator organisms, respectively, adjusting for season and long-term trend effects. Strong seasonal patterns were observed for each group of pathogens. Peak viral gastrointestinal infection was in May while that of non-viral gastrointestinal infections was in July. A statistically significant negative association existed between weather (temperature and humidity) and viral infection. Average levels of non-viral gastrointestinal infections increased as temperature and relative humidity increased. Increasing levels of faecal indicator organisms in bathing waters were also associated with an increase in the average number of viral and non-viral gastrointestinal infections at the ecological level. Future climate change and prolonged precipitation events may result in increasing levels of faecal indicator organisms in bathing waters leading to likely increases in IIDs.
Detection of phytoplankton blooms in Antarctic coastal water with an online mooring system during summer 2010/11
Authors: Ma Yuxin , Zhang Fang , Yang Haizhen , Lin Ling , He Jianfeng
Published: September 2013

In order to continuously monitor the phytoplankton growth in Antarctic coastal waters, an online mooring system was deployed in Great Wall Bay (unofficial name), King George Island, and both chlorophyll a (chl a) concentrations and environmental variables were monitored in a period between December 2010 and March 2011. Water temperatures showed a significant increasing trend (0.27–2.52°C), whereas the salinities displayed a decreasing trend (34.19–33.86). In general, phytoplankton biomass accumulated from mid-December and two significant blooms developed in January (3.18 μg l-1 and 4.75 μg l-1) and were then maintained at a relatively high level, with a transient bloom in late February (4.93 μg l-1). Sea-ice meltwater and terrestrial freshwater input caused by the increase of temperature played an important role in inducing phytoplankton blooms in early summer. The variation and stratification of temperature and salinity signals in different water layers, without total mixing, suggested lateral intrusion of oceanic waters with alternating levels of temperature and salinity and, presumably, phytoplankton as well. Meanwhile, chl a concentrations initially decreased with an increase in irradiance, indicating the shade-adapted characteristic of phytoplankton in early summer, and then gradually adapted to the increasing irradiance. Our results demonstrated the effectiveness and reliability of the online coastal mooring system for the monitoring of Antarctic coastal phytoplankton bloom and environmental conditions.
What do we think life is? A simple illustration and its consequences
Authors: Bains William
Published: September 2013

The conundrum of finding a ‘definition’ for life can be side-stepped by asking how people actually identify examples of life, and using this as the basis for life detection strategies. I illustrate how astrobiologists actually select things that are living from things that are not living with a simple exercise, and use this as the starting point to develop four characteristics that underlie their decisions: highly distinctive structure (physical or chemical), dynamic behaviour (physical or chemical), multiple instances of life forming a ‘natural group’ and that the structural and dynamic characteristics of the group are independent of the details of the substrate on which life is growing. I show that these all derive the role of a code in the dynamic maintenance and propagation of life. I argue that evolution is neither a useful nor a practical way of identifying life. I conclude with some specific ways that these general categories of the observable properties of life can be detected.
Examining Sources of DIF in Psychological and Educational Assessment Using Multilevel Logistic Regression
Authors: Balluerka Nekane , Plewis Ian , Gorostiaga Arantxa , Padilla José-Luis
Published: September 2013

In the last three decades, important progress has been made toward more efficient statistical techniques for detecting Differential Item Functioning (DIF). However, the findings are scant when it comes to explaining DIF. Multilevel regression models can expand the knowledge of DIF causes, specifying a DIF parameter that varies randomly over items and testing hypotheses on sources of DIF shared by item bundles. The present study uses multilevel logistic regression to identify the item characteristics that could explain the presence of DIF in short tests or questionnaires, which are usually used in psychological and educational assessment. The usefulness of the approach is tested on measurements of the attitudes toward science of Spanish and English pupils obtained from the OECD Programme for International Student Assessment database.
RecG and UvsW catalyse robust DNA rewinding critical for stalled DNA replication fork rescue
Authors: Manosas Maria , Perumal Senthil K. , Bianco Piero R. , Ritort Felix , Benkovic Stephen J. , Croquette Vincent
Published: September 2013

Helicases that both unwind and rewind DNA have central roles in DNA repair and genetic recombination. In contrast to unwinding, DNA rewinding by helicases has proved difficult to characterize biochemically because of its thermodynamically downhill nature. Here we use single-molecule assays to mechanically destabilize a DNA molecule and follow, in real time, unwinding and rewinding by two DNA repair helicases, bacteriophage T4 UvsW and Escherichia coli RecG. We find that both enzymes are robust rewinding enzymes, which can work against opposing forces as large as 35 pN, revealing their active character. The generation of work during the rewinding reaction allows them to couple rewinding to DNA unwinding and/or protein displacement reactions central to the rescue of stalled DNA replication forks. The overall results support a general mechanism for monomeric rewinding enzymes.
Direct calculation of the solid-liquid Gibbs free energy difference in a single equilibrium simulation
Authors: Pedersen Ulf R.
Published: September 2013

Computing phase diagrams of model systems is an essential part of computational condensed matter physics. In this paper, we discuss in detail the interface pinning (IP) method for calculation of the Gibbs free energy difference between a solid and a liquid. This is done in a single equilibrium simulation by applying a harmonic field that biases the system towards two-phase configurations. The Gibbs free energy difference between the phases is determined from the average force that the applied field exerts on the system. As a test system, we study the Lennard-Jones model. It is shown that the coexistence line can be computed efficiently to a high precision when the IP method is combined with the Newton-Raphson method for finding roots. Statistical and systematic errors are investigated. Advantages and drawbacks of the IP method are discussed. The high pressure part of the temperature-density coexistence region is outlined by isomorphs.
Transition from dislocation glide to creep controlled damage in fatigued thin Cu films
Authors: Trinks C. , Volkert C. A.
Published: September 2013

The ultra-high cycle fatigue behavior of supported Cu films with thicknesses between 40 and 360 nm has been investigated using a novel atomic force microscope (AFM)-based resonance method. The damage created under strain controlled fatigue loading is investigated as a function of applied strain, film thickness, and cycle numbers up to 5 × 1010. For films thicker than 100 nm, extrusions and boundary cracks limit the fatigue performance but only appear above a threshold in the applied strain amplitude which scales inversely with the square root of the film thickness. The extrusion formation is attributed to dislocation activation. The grain boundary cracks are replaced by grain boundary grooves in films of 100 nm and thinner. The grooves are believed to form by diffusion mediated creep processes, similar to observations at higher temperatures but here driven by cyclic stresses and capillarity, and become detectable once the accumulated plastic strain exceeds a critical value. These results indicate that due to creep processes, thinner films can be less resistant to fatigue than thicker films, particularly for large cycle numbers.
Ordered structures of diblock nanorods induced by diblock copolymers
Authors: Chai Aihua , Zhang Dong , Jiang Yangwei , He Linli , Zhang Linxi
Published: September 2013

The self-assembly of diblock copolymer (DBCP)/diblock nanorod (DBNR) mixtures are studied by using a dissipative particle dynamics simulation method. The microstructures of DBCP/DBNR blends depend on the type of DBCPs as well as the number of DBNRs. For the asymmetric DBCPs of A3B7, the morphological transition of DBCP/DBNR blends from cylinder phase to lamellar phase is observed for the DBNRs with suitable length and component. Meanwhile, for the symmetric DBCPs of A5B5, the lamellar morphologies of DBCP/DBNR blends can always maintain during the process of adding DBNRs to the blends except for the case of component length mismatch between the DBCPs and the DBNRs. On the other hand, DBCPs can also affect the orientation and the spatial distributions of DBNRs deeply, and the ordered structures of DBNRs are formed for the DBCP/DBNR blends with a large number of DBNRs. Comparisons with homopolymer/DBNR blends are made, and only the aggregation structures are observed in homopolymer/DBNR blends. This investigation can provide valuable assistance in exploring and designing complicated polymer/nanoparticle composites with the desired properties.
A novel forcing technique to simulate turbulent mixing in a decaying scalar field
Authors: Carroll Phares L. , Verma Siddhartha , Blanquart G.
Published: September 2013

To realize the full potential of Direct Numerical Simulation in turbulent mixing studies, it is necessary to develop numerical schemes capable of sustaining the flow physics of turbulent scalar quantities. In this work, a new scalar field forcing technique, termed “linear scalar forcing,” is presented and evaluated for passive scalars. It is compared to both the well-known mean scalar gradient forcing technique and a low waveshell spectral forcing technique. The proposed forcing is designed to capture the physics of one-time scalar variance injection and the subsequent self-similar turbulent scalar field decay, whereas the mean scalar gradient forcing and low waveshell forcing techniques are representative of continuous scalar variance injection. The linear scalar forcing technique is examined over a range of Schmidt numbers, and the behavior of the proposed scalar forcing is analyzed using single and two-point statistics. The proposed scalar forcing technique is found to be perfectly isotropic, preserving accepted scalar field statistics (fluxes) and distributions (scalar quantity, dissipation rate). Additionally, it is found that the spectra resulting from the three scalar forcing techniques are comparable for unity Schmidt number conditions, but differences manifest at high Schmidt numbers. These disparities are reminiscent of those reported between scaling arguments suggested by theoretical predictions and experimental results for the viscous-convective subrange.
Portable device for magnetic stimulation: Assessment survival and proliferation in human lymphocytes
Authors: Pérez H. , Cordova-Fraga T. , López-Briones S. , Martínez-Espinosa J. C. , Rosas E. F. , Espinoza A. , Villagómez-Castro J. C. , Sosa M. , Topsu S. , Bernal-Alvarado J. J.
Published: September 2013

A device's instrumentation for magnetic stimulation on human lymphocytes is presented. This is a new procedure to stimulate growing cells with ferrofluid in vortices of magnetic field. The stimulation of magnetic vortices was provided at five different frequencies, from 100 to 2500 Hz and intensities from 1.13 to 4.13 mT. To improve the stimulation effects, a paramagnetic ferrofluid was added on the cell culture medium. The results suggest that the frequency changes and the magnetic field variation produce an important increase in the number of proliferating cells as well as in the cellular viability. This new magnetic stimulation modality could trigger an intracellular mechanism to induce cell proliferation and cellular survival only on mitogen stimulated cells.
so(3) algebraic approach to the Morse potential
Authors: Zhang Hong-Biao , Yang Lin , Guo San-Xing
Published: September 2013

We construct so(3) algebra associated with the Morse potential and show that these operators obey so(3) commutation relations. A so(3) algebraic method is proposed in order to obtain the eigenvalues and eigenfunctions of the Morse potential. This method exhibits that Cartan operator \documentclass[12pt]{minimal}\begin{document}$\hat{J}_z$\end{document}Ĵz, the lowering operator \documentclass[12pt]{minimal}\begin{document}$\hat{J}_-$\end{document}Ĵ−, and the raising operator \documentclass[12pt]{minimal}\begin{document}$\hat{J}_+$\end{document}Ĵ+ determine successfully energy eigenvalues, the lowest energy eigenfunction, and excited energy eigenfunctions, respectively.
Modeling of wave modes on a vertical film of a viscous ferromagnetic fluid flowing down a cylindrical electric conductor
Authors: Tsvelodub O. Yu. , Rohlfs W. , Kneer R.
Published: September 2013

The present study considers axially symmetrical waves on the surface of a ferromagnetic viscous fluid film flowing down a cylindrical conductor with a non-constant current. In addition to the gravitational force, the film is affected by a uniform magnetic field. Using the long-wave approximation, a model equation is obtained for the evolution of the film thickness from its undisturbed value. By showing that solutions with and without a constant magnetic field are self-similar, scaling parameters are identified and presented. Numerical solutions of the time-dependent non-linear partial differential equation are presented when current in the conductor is described by a ramp function (i.e., magnetic field onset).
How a single aluminum atom makes a difference to gallium: First-principles simulations of bimetallic cluster melting
Authors: Ojha Udbhav , Steenbergen Krista G. , Gaston Nicola
Published: September 2013

First principles molecular dynamics simulations of Ga19Al+ have been performed in the microcanonical ensemble using parallel tempering. We perform a thorough investigation of the changes induced by the presence of an Al atom in the Ga dominated cluster. Dynamic analysis indicates that the Al atom prefers to occupy the internal sites of the cluster structure, at all temperatures, and above 450 K, the Al atom is less mobile than the central Ga atom throughout the simulation. Using the multiple histogram method, canonical specific heat curves are obtained that compare well with previous experimental measurements of the specific heat and equivalent simulations for the \documentclass[12pt]{minimal}\begin{document}${\rm Ga}_{20}^{+}$\end{document} Ga 20+ cluster. The first-principles melting temperature agrees well with the experimental value for Ga19Al+. Analysis of the root mean squared fluctuation in bond length, velocity auto-correlation function, and the corresponding power spectrum, confirms the solid-liquid-like phase transition in Ga19Al+, as for \documentclass[12pt]{minimal}\begin{document}${\rm Ga}_{20}^{+}$\end{document} Ga 20+.
Deformation properties between fluid and periodic circular obstacles in polydimethylsiloxane microchannels: Experimental and numerical investigations under various conditions
Authors: Kang ChanKyu , Overfelt Ruel A. , Roh Changhyun
Published: September 2013

Understanding the mechanical properties of optically transparent polydimethylsiloxane (PDMS) microchannels was essential to the design of polymer-based microdevices. In this experiment, PDMS microchannels were filled with a 100 μM solution of rhodamine 6G dye at very low Reynolds numbers (∼10−3). The deformation of PDMS microchannels created by pressure-driven flow was investigated by fluorescence microscopy and quantified the deformation by the linear relationship between dye layer thickness and intensity. A line scan across the channel determined the microchannel deformation at several channel positions. Scaling analysis widely used to justify PDMS bulging approximation was allowed when the applied flow rate was as high as 2.0 μl/min. The three physical parameters (i.e., flow rate, PDMS wall thickness, and mixing ratio) and the design parameter (i.e., channel aspect ratio = channel height/channel width) were considered as critical parameters and provided the different features of pressure distributions within polymer-based microchannel devices. The investigations of the four parameters performed on flexible materials were carried out by comparison of experiment and finite element method (FEM) results. The measured Young's modulus from PDMS tensile test specimens at various circumstances provided reliable results for the finite element method. A thin channel wall, less cross-linker, high flow rate, and low aspect ratio microchannel were inclined to have a significant PDMS bulging. Among them, various mixing ratios related to material property and aspect ratios were one of the significant factors to determine PDMS bulging properties. The measured deformations were larger than the numerical simulation but were within corresponding values predicted by the finite element method in most cases.
Modeling lower critical solution temperature behavior of associating polymer brushes with classical density functional theory
Authors: Gong Kai , Marshall Bennett D. , Chapman Walter G.
Published: September 2013

We study the lower critical solution temperature (LCST) behavior of associating polymer brushes (i.e., poly(N-isopropylacrylamide)) using classical density functional theory. Without using any empirical or temperature-dependent parameters, we find the phase transition of polymer brushes from extended to collapsed structure with increasing temperature, indicating the LCST behavior of polymer brushes. The LCST behavior of associating polymer brushes is attributed to the interplay of hydrogen bonding interactions and Lennard-Jones attractions in the system. The effect of grafting density and molecular weight on the phase behavior of associating polymer brushes has been also investigated. We find no LCST behavior at low grafting density or molecular weight. Moreover, increasing grafting density decreases the LCST and swelling ratio of polymer brushes. Similarly, increasing molecular weight decreases the LCST but increases the swelling ratio. At very high grafting density, a partial collapsed structure appears near the LCST. Qualitatively consistent with experiments, our results provide insight into the molecular mechanism of LCST behavior of associating polymer brushes.
Reversible patterning of poly(methylmethacrylate) doped with disperse Red 1 by laser scanning
Authors: Tuma J. , Lyutakov O. , Huttel I. , Slepicka P. , Svorcik V.
Published: September 2013

Thin poly(methylmethacrylate) films doped by or covalently attached to disperse Red 1 acrylate (DR1) were patterned by laser scanning and simultaneous sample movement in confocal microscope. In both cases, periodical structure due to Marangoni effect is created. Modified polymers surfaces were analyzed by FTIR spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. After first stage of patterning, second stage with sample movement in perpendicular direction was applied. Depending on the method of DR1 dotation fishnet structure is obtained or pattern structure disappears. In the latter case, reversibility of pattern formation and erasure by laser scanning was studied.
Magnetic properties of room temperature grown epitaxial Co1−xRux-alloy films
Authors: Idigoras O. , Palomares U. , Suszka A. K. , Fallarino L. , Berger A.
Published: September 2013

Epitaxial CoRu-alloy films with (1010) surface orientation and varying stoichiometry have been grown at room temperature. In order to achieve good epitaxy independent from the alloy composition, we have devised an underlayer sequence, which utilized a CrRu-alloy film as template layer with individually optimized composition. All alloys in the composition range of 0–30 at. % Ru content exhibit hcp structure and thus uniaxial magneto-crystalline anisotropy. We observe an almost linear decrease of the saturation magnetization and Curie temperature with increasing Ru content. However, the magneto-crystalline anisotropy shows a non-monotonous behavior with a maximum near 15% Ru.
Stretch or contraction induced inversion of rectification in diblock molecular junctions
Authors: Zhang Guang-Ping , Hu Gui-Chao , Song Yang , Xie Zhen , Wang Chuan-Kui
Published: September 2013

Based on ab initio theory and nonequilibrium Green's function method, the effect of stretch or contraction on the rectification in diblock co-oligomer molecular diodes is investigated theoretically. Interestingly, an inversion of rectifying direction induced by stretching or contracting the molecular junctions, which is closely related to the number of the pyrimidinyl-phenyl units, is proposed. The analysis of the molecular projected self-consistent Hamiltonian and the evolution of the frontier molecular orbitals as well as transmission coefficients under external biases gives an inside view of the observed results. It reveals that the asymmetric molecular level shift and asymmetric evolution of orbital wave functions under biases are competitive mechanisms for rectification. The stretching or contracting induced inversion of the rectification is due to the conversion of the dominant mechanism. This work suggests a feasible technique to manipulate the rectification performance in molecular diodes by use of the mechanically controllable method.
Origin and enhancement of the 1.3 μm luminescence from GaAs treated by ion-implantation and flash lamp annealing
Authors: Gao Kun , Prucnal S. , Skorupa W. , Helm M. , Zhou Shengqiang
Published: September 2013

GaAs and GaAs based materials have outstanding optoelectronic properties and are widely used as light emitting media in devices. Many approaches have been applied to GaAs to generate luminescence at 0.88, 1.30, and 1.55 μm which are transmission windows of optical fibers. In this paper, we present the photoluminescence at 1.30 μm from deep level defects in GaAs treated by ion-implantation and flash lamp annealing (FLA). Such emission, which exhibits superior temperature stability, can be obtained from FLA treated virgin GaAs as well as doped GaAs. Indium-doping in GaAs can greatly enhance the luminescence. By photoluminescence, Raman measurements, and positron annihilation spectroscopy, we conclude that the origin of the 1.30 μm emission is from transitions between the VAs-donor and X-acceptor pairs.
Renormalized bands and low-temperature colossal thermopower induced by Ir doping in Ca3Co4O9 system
Authors: Huang Yanan , Zhao Bangchuan , Lin Shuai , Song Wenhai , Sun Yuping
Published: September 2013

The effects of Ir doping on the low-temperature thermal and electrical transport properties of Ca3Co4−xIrxO9 (0 ≤ x ≤ 0.4) have been investigated. As Ir ions are doped into the system, a low-temperature thermopower upturn is introduced, and the temperature corresponding to the minimum thermopower TSmin increases monotonously with increasing x. Moreover, a low-temperature colossal thermopower is observed in the Ir-doped samples, which is beneficial to the low-temperature thermoelectric refrigeration in superconducting devices. For the x = 0.4 sample, its maximum thermopower Smax at the lowest measured temperature ∼24 K reaches 1500 μV/K. The appearance of such a colossal thermopower phenomenon is suggested to be closely related to the variations of the transport mechanism and the band structure induced by 5d-Ir doping.
Temperature dependence of the single-photon sensitivity of a quantum dot, optically gated, field-effect transistor
Authors: Gansen E. J. , Rowe M. A. , Harrington S. D. , Nehls J. M. , Etzel S. M. , Nam S. W. , Mirin R. P.
Published: September 2013

We present a systematic study of the temperature dependence of the electrical noise in a quantum dot, optically gated, field-effect transistor (QDOGFET) and detail how the noise influences the sensitivity of these novel single-photon detectors. Previous studies have shown that when cooled to 4 K, QDOGFETs exhibit single-photon sensitivity and photon-number-resolving capabilities; however, there has been no systematic study of how operating temperature affects their performance. Here, we measure the noise spectra of a device for a range of sample temperatures between 7 K and 60 K. We use the noise data to determine the signal-to-noise ratio of the optical responses of the devices for various temperatures and detection rates. Our analysis indicates that QDOGFETs can operate over a broad range of temperatures, where increased operating temperature can be traded for decreased sensitivity.
Low-dilution limit of Zn1−xMnxGeAs2: Electrical and magnetic properties
Authors: Kilanski L. , Szałowski K. , Szymczak R. , Górska M. , Dynowska E. , Aleshkevych P. , Podgórni A. , Avdonin A. , Dobrowolski W. , Fedorchenko I. V. , Marenkin S. F.
Published: September 2013

We present the studies of electrical transport and magnetic interactions in Zn1−xMnxGeAs2 crystals with low Mn content 0≤x≤0.042. We show that the ionic-acceptor defects are mainly responsible for the strong p-type conductivity of our samples. We found that the negative magnetoresistance with maximum values of about −50% is related to the weak localization phenomena. The magnetic properties of Zn1−xMnxGeAs2 samples show that the random Mn-distribution in the cation sites of the host lattice occurs only for the sample with the lowest Mn-content, x = 0.003. The samples with higher Mn-content show a high level of magnetic frustration. Nonzero Curie-Weiss temperature observed in all our samples indicates that weak ferromagnetic (for x = 0.003) or antiferromagnetic (for x>0.005) interactions with the Curie-Weiss temperature, |Θ|<3 K, are present in this system. The Ruderman-Kittel-Kasuya-Yosida model, used to estimate the Mn-hole exchange integral Jpd for the diluted Zn0.997Mn0.003GeAs2 sample, makes possible to estimate the value of Jpd=(0.75 ± 0.09) eV.
Vibration analysis of nanomechanical mass sensor using double-layered graphene sheets resonators
Authors: Natsuki Toshiaki , Shi Jin-Xing , Ni Qing-Qing
Published: September 2013

Graphene sheets (GSs) are two-dimensional material with extremely favorable mass sensor properties. In the study, we examined the potential of nanoscale mass sensor based on simply supported double-layered graphene sheets (DLGSs) attached nanoparticles. Using the continuum elasticity theory, the influences of the attached mass and position of the nanoparticles on the frequency shifts of DLGSs are investigated in detail. The result shows that the frequency shift in DLGSs is much higher than that of the single-layered graphene sheets (SLGSs). The DLGSs based nanomechanical resonator could provide higher sensitivity than SLGSs.
Beneficial roles of Al back reflectors in optical absorption of Si nanowire array solar cells
Authors: Lee Eunsongyi , Zhou Keya , Gwon Minji , Jung Jin-Young , Lee Jung-Ho , Kim Dong-Wook
Published: September 2013

We investigate the influence of Al back reflectors on the optical absorption spectra of Si nanowire (NW) arrays by using the finite-difference time-domain simulation method. A flat Al layer enhances the absorption in the NW array due to not only the reflection-induced optical path length enlargement but also reflection of light between NWs and localized surface plasmon induced optical field confinement. An Al underlayer with a grating structure allows grating-coupled surface plasmon polariton excitation and raise the optical absorption in the Si NWs. Interplay among all these factors on the optical absorption and expected solar cell performance of the NW arrays is discussed.
Predicting magnetostructural trends in FeRh-based ternary systems
Authors: Barua Radhika , Jiménez-Villacorta Félix , Lewis L. H.
Published: September 2013

Correlations between magnetic transition temperatures and the average weighted valence band electron concentration ((s + d) electrons/atom) have led to the development of a phenomenological model that predicts the influence of elemental substitution on the magnetostructural response of bulk B2-ordered Fe(Rh1−xMx) or (Fe1−xMx)Rh alloys (M = transition elements; x < 6 at. %). Validation of this model is provided through synthesis and characterization of FeRh with Cu and Au additions. The data and associated trends indicate that the lattice and electronic free energies are both equally important in driving the magnetostructural transition in the bulk FeRh system.
Cryogenic nanoindentation size effect in [0 0 1]-oriented face-centered cubic and body-centered cubic single crystals
Authors: Lee Seok-Woo , Meza Lucas , Greer Julia R.
Published: September 2013

Cryogenic nanoindentation experiments performed on [0 0 1]-oriented single crystalline Nb, W, Al, and Au in an in situ nanomechanical instrument with customized cryogenic testing capability revealed temperature dependence on nanoindentation size effect. The Nix-Gao model, commonly used to capture indentation size effect at room temperature, does not take into account thermal effects and hence is not able to explain these experimental results where both hardness at infinite indentation depth and characteristic material length scale were found to be strong functions of temperature. Physical attributes are critically examined in the framework of intrinsic lattice resistance and dislocation cross-slip probability.
Integrated system modeling analysis of a cryogenic multi-cell deflecting-mode cavity resonator
Authors: Shin Young-Min , Church Michael
Published: September 2013

A deflecting mode cavity is the integral element for six-dimensional phase-space beam control in bunch compressors and emittance transformers at high energy beam test facilities. RF performance of a high-Q device is, however, highly sensitive to operational conditions, in particular in a cryo-cooling environment. Using analytic calculations and RF simulations, we examined cavity parameters and deflecting characteristics of TM110,π mode of a 5 cell resonator in a liquid nitrogen cryostat, which has long been used at the Fermilab A0 Photoinjector (A0PI). The sensitivity analysis indicated that the cavity could lose 30%–40% of deflecting force due to defective input power coupling accompanying non-uniform field distribution across the cells with 40 ∼ 50 MeV electron beam and 70–80 kW klystron power. Vacuum-cryomodules of the 5 cell cavity are planned to be installed at the Fermilab Advanced Superconducting Test Accelerator facility. Comprehensive modeling analysis integrated with multi-physics simulation tools showed that RF loading of 1 ms can cause a ∼5 K maximum temperature increase, corresponding to a ∼4.3 μm/ms deformation and a 1.32 MHz/K maximum frequency shift. The integrated system modeling analysis will improve design process of a high-Q cavity with more accurate prediction of cryogenic RF performance under a high power pulse operation.
Effect of collision parameters in electronegative plasma sheath with two species of positive ions
Authors: Moulick R. , Mahanta M. K. , Goswami K. S.
Published: September 2013

The effect of ion neutral collision is shown for two species of positive ions in electronegative plasma. The ion neutral collision is modeled using power law of collision cross section. It is a usual case for processing plasma to have two species of positive ions and hence we attempt to study the dynamics of the two species of ions inside the collisional sheath of electronegative plasma.
Note: A new angle-resolved proton energy spectrometer
Authors: Zheng Y. , Su L. N. , Liu M. , Liu B. C. , Shen Z. W. , Fan H. T. , Li Y. T. , Chen L. M. , Lu X. , Ma J. L. , Wang W. M. , Wang Z. H. , Wei Z. Y. , Zhang J.
Published: September 2013

In typical laser-driven proton acceleration experiments Thomson parabola proton spectrometers are used to measure the proton spectra with very small acceptance angle in specific directions. Stacks composed of CR-39 nuclear track detectors, imaging plates, or radiochromic films are used to measure the angular distributions of the proton beams, respectively. In this paper, a new proton spectrometer, which can measure the spectra and angular distributions simultaneously, has been designed. Proton acceleration experiments performed on the Xtreme light III laser system demonstrates that the spectrometer can give angle-resolved spectra with a large acceptance angle. This will be conductive to revealing the acceleration mechanisms, optimization, and applications of laser-driven proton beams.
Effects of matrix layer composition on the structural and optical properties of self-organized InGaN quantum dots
Authors: Li Z. C. , Liu J. P. , Feng M. X. , Zhou K. , Zhang S. M. , Wang H. , Li D. Y. , Zhang L. Q. , Sun Q. , Jiang D. S. , Wang H. B. , Yang H.
Published: September 2013

Self-organized InGaN quantum dots (QDs) with emission wavelength from green to red range have been grown on GaN templated c-plane sapphire substrates by metal-organic chemical vapor deposition (MOCVD). The effects of matrix layer composition on the structural and optical properties of InGaN QDs have been investigated. A continued growth of QDs is observed during the growth of In0.1Ga0.9N matrix layer, which results in an increase of the QDs' size. By using In0.1Ga0.9N matrix layer instead of GaN one, the annealing induced blue-shift in emission energy of the InGaN QDs can be suppressed. After the growth of top GaN cap layer, a larger red-shift caused by the quantum confined Stark effect is observed in the sample with In0.1Ga0.9N matrix layer. Employing this method, InGaN QD sample emitting at 615 nm with an internal quantum efficiency of 24.3% has been grown. The significance of this method is that it allows a higher growth temperature of InGaN QDs with emission wavelength in the green range to improve the crystalline quality, which is beneficial to enhance the efficiency of green InGaN QD light-emitting-diodes and laser diodes.
Sample manuscript for an optical readout infrared imaging system based on polarization to eliminate stray light
Authors: Zhang Zhigang , Cheng Teng , Zhang Qingchuan , Mao Liang , Gao Jie , Wu Xiaoping
Published: September 2013

In the optical readout uncooled infrared imaging technology, the stray light produced by the reflection of the optical component surfaces is acquired together with the effective signal light by the charge coupled device (CCD, the dynamic range of CCD is limited), which reduces the dynamic range of the effective signal light. In this paper, we present a polarized optical readout system to eliminate the stray light. Shading experiments show that, in the new system, the stray light is filtered out up to 86% and the dynamic range of the effective signal light significantly increase by 50%. Infrared Imaging experiments show that the noise equipment temperature difference value decreases by 35%, and the infrared imaging performance is greatly improved.
Morphology of a graphene nanoribbon encapsulated in a carbon nanotube
Authors: Furuhashi F. , Shintani K.
Published: September 2013

The morphologies of graphene nanoribbons (GNRs) encapsulated in single-walled carbon nanotubes (SWNTs) are investigated using molecular-dynamics (MD) simulation. The GNRs are assumed to be hydrogen-terminated and formed by connecting polycyclic aromatic hydrocarbons, perylene or coronene molecules. The combined structures consisting of a GNR and an encapsulating SWNT are equilibrated at room temperature. It is shown that if the diameter of a SWNT is larger than the sum of the width of the GNR and twice the length of a C-H bond, a twisted GNR is obtained, whereas if the diameter of a SWNT is smaller than the sum of the two, the cross section of the SWNT cannot maintain its original circular shape and elliptically distorts, and a non-twisted GNR or a twisted GNR of long pitch is obtained. The estimated pitch of a regularly-twisted GNR agrees with the experimentally observed one in order of magnitude.