bluuebunny/crossref_metadata_2025 huggingface dataset:
Filipino Health Care Aides and the Nursing Home Labour Market in Winnipeg
Authors: Novek Sheila
Published: September 2013

Les maisons de soins infirmiers au Canada sont devenues de plus en plus dépendante des aides soignants immigrants. Plus qu’aucun autre groupe ethnique, les femmes philippines sont surrépresentées parmi les aidants (aides soignantes) dans le système de soins de santé canadien. Cette étude qualitative a exploré les expériences d’emploi des aides soignants immigrantes dans les maisons de soins infirmiers, de leurs points de vues, ainsi que ceux des intervenants. Quatorze entrevues ont été menées à Winnipeg, au Manitoba, avec aides de soins de santé philippines et avec les intervenants de soins de longue durée. Les résultats indiquaient que les réseaux sociaux immigrants agissent comme des voies reliant les femmes immigrantes des opportunités d’emploi dans les maisons des soins infirmiers. La composition de la main-d’œuvre est également faconnée par les stratégies de gestion et les ajustements du marché du travail, qui répondent à et renforcent ces réseaux sociaux. Ces résultats ont des implications pour la planification de la main-d’œuvre et la qualité de la prestation de soins dans les maisons de soins infirmiers.
Expression analysis of seed-specific genes in four angiosperm species with an emphasis on the unconserved expression patterns of homologous genes
Authors: Ma Lichao , Wang Yanrong , Liu Wenxian , Liu Zhipeng
Published: September 2013

Medicago truncatula, soybean (Glycine max), Arabidopsis thaliana and rice (Oryza sativa) all belong to the core angiosperm group of plants. Seed-specific genes are important for seed formation and development in these angiosperms. The identification of genes specifically expressed in angiosperm seeds and the comparison of the expression patterns of homologous genes among different angiosperm species can provide novel insights into the functions of genes that control seed development and the evolution of angiosperms. We downloaded the sequences and expression data from the relevant databases, and the seed-specific expression of genes was identified with cut-offs of a gene expression level ratio ≥ 5 and a Z-score ≥ 6. The genes were analysed using local BLAST software with an E-value ≤ 1.0E − 505. A total of 605, 581, 778 and 722 genes showed specific expression in the seeds of Medicago, soybean, Arabidopsis and rice, respectively. Additionally, we compared the expression patterns of seed-specific genes from each species with their homologues in the other three species, and found that the degree of variation in the expression patterns of homologous genes was low among closely related species but higher among more distantly related ones. The discrepancy between the homologous gene expression patterns may be caused by the different characteristics of the cis-elements in the promoter regions of the homologous genes.
Anthropometry and physical activity level in the prediction of metabolic syndrome in children
Authors: Andaki Alynne Christian Ribeiro , Tinôco Adelson Luiz Araújo , Mendes Edmar Lacerda , Andaki Júnior Roberto , Hills Andrew P , Amorim Paulo Roberto S
Published: September 2013

Objective

To evaluate the effectiveness of anthropometric measures and physical activity level in the prediction of metabolic syndrome (MetS) in children.

Design

Cross-sectional study with children from public and private schools. Children underwent an anthropometric assessment, blood pressure measurement and biochemical evaluation of serum for determination of TAG, HDL-cholesterol and glucose. Physical activity level was calculated and number of steps per day obtained using a pedometer for seven consecutive days.

Setting

Viçosa, south-eastern Brazil.

Subjects

Boys and girls (n 187), mean age 9·90 (sd 0·7) years.

Results

Conicity index, sum of four skinfolds, physical activity level and number of steps per day were accurate in predicting MetS in boys. Anthropometric indicators were accurate in predicting MetS for girls, specifically BMI, waist circumference measured at the narrowest point and at the level of the umbilicus, four skinfold thickness measures evaluated separately, the sum of subscapular and triceps skinfold thickness, the sum of four skinfolds and body fat percentage.

Conclusions

The sum of four skinfolds was the most accurate method in predicting MetS in both genders.
Trends in thinness prevalence among adolescents in ten European countries and the USA (1998–2006): a cross-sectional survey
Authors: Lazzeri Giacomo , Rossi Stefania , Kelly Colette , Vereecken Carine , Ahluwalia Namanjeet , Giacchi Mariano V
Published: September 2013

Objective

To describe the prevalence of ‘graded thinness’ in children aged 11, 13 and 15 years in eleven developed countries and to identify trends in the prevalence of ‘thinness’ (BMI < 17 kg/m2at age 18 years) by age and gender.

Design

Cross-sectional study using data collected through self-reported questionnaires.

Setting

Data were taken from the 1997/1998, 2001/2002 and 2005/2006 surveys of the Health Behaviours in School-aged Children (HBSC) Study.

Subjects

Children and adolescents from ten European countries and the USA (n158 000).

Results

Prevalence of grades 1, 2 and 3 of thinness was higher among 11-year-old students compared with the 13- and 15-year-olds in all countries. A higher prevalence of thinness was observed in girls than in boys. Since 1998 the prevalence of thinness decreased steadily in Czech boys and girls, while it increased for French girls. In the total European sample of females, thinness decreased from 1998 to 2006 (χ2for trend,P< 0·01). Age-adjusted logistic regression analysis showed that Czech boys and girls, and Flemish and American girls were less likely to be thin in 2006 than in 1998; while a noteworthy increment, even if borderline significant, was observed for French girls with a 41 % increase in the likelihood to be thin.

Conclusions

Our findings suggest that thinness is an important overlooked phenomenon with wide variation in prevalence and trends across developed countries. It deserves further longitudinal studies in a multinational context that could increase the understanding of the factors associated with thinness and contribute to developing preventive and nutritional programmes targeted at controlling obesity and chronic diseases, while monitoring thinness.
Phylogenetic relationships of Palaeogene ziphodont eusuchians and the status ofPristichampsusGervais, 1853
Authors: Brochu Christopher A.
Published: September 2013

Eusuchians with deep snouts and labiolingually compressed teeth are known from the Palaeogene of Laurasia. These are usually referred to Pristichampsinae, but the type species,Pristichampsus rollinati, is based on insufficiently diagnostic material and should be treated as a nomen dubium. At least two Lutetian species formerly referred toPristichampsuscan be recognised –Boverisuchus magnifronsin Germany and possibly elsewhere in Europe, andBoverisuchus vorax, new combination, in western North America. Material from the middle Eocene of Italy and Texas may represent distinct species. A phylogenetic analysis confirms their close relationship and also supports a relationship with two Asian forms – early EocenePlanocrania datangensisand PalaeocenePlanocrania hengdongensis. The name Planocraniidae Li 1976 is applied to this group. A distinctive quadrate with a prominent dorsal peak between medial and lateral hemicondyles is known only inBoverisuchus, and although the teeth ofPlanocraniaare flattened, they are not serrated. Planocraniids maintain a phylogenetic position as the sister group to Crocodyloidea+Alligatoroidea, but this part of the tree is unstable and discovery of older, more primitive planocraniids will help resolve conflicts on the phylogenetic relationships of extant crocodylian lineages.
Social support in depression: structural and functional factors, perceived control and help-seeking
Authors: Kleinberg A. , Aluoja A. , Vasar V.
Published: September 2013

Aims.

This study examined the associations of social support, loneliness and locus of control with depression and help-seeking in persons with major depression.

Methods.

Twelve-month help-seeking for emotional problems was assessed in a cross-sectional 2006 Estonian Health Survey. Non-institutionalized individuals aged 18–84 years (n = 6105) were interviewed. A major depressive episode was assessed using the Mini-International Neuropsychiatric Interview. Factors describing social support, social and emotional loneliness and locus of control were assessed, and their associations with depression were analysed. The associations with reported help-seeking behaviour among people identified as having a major depressive episode (n = 343) were explored.

Results.

Low frequency of contacts with one's friends and parents, emotional loneliness, external locus of control and emotional dissatisfaction with couple relations were significant factors predicting depression in the multivariate model. External locus of control was associated with help-seeking in the depressed sample. Interactions of emotional loneliness, locus of control and frequency of contacts with parents significantly predicted help-seeking in the depressed sample.

Conclusions.

Depression is associated with structural and functional factors of social support and locus of control. Help-seeking of depressed persons depends on locus of control, interactions of emotional loneliness, locus of control and contacts with the parental family.
Statistical Analyses of Monozygotic and Dizygotic Twinning Rates
Authors: Fellman Johan
Published: September 2013

The French mathematician Bertillon reasoned that the number of dizygotic (DZ) pairs would equal twice the number of twin pairs of unlike sexes. The remaining twin pairs in a sample would presumably be monozygotic (MZ). Weinberg restated this idea and the calculation has come to be known as Weinberg's differential rule (WDR). The keystone of WDR is that DZ twin pairs should be equally likely to be of the same or the opposite sex. Although the probability of a male birth is greater than .5, the reliability of WDR's assumptions has never been conclusively verified or rejected. Let the probability for an opposite-sex (OS) twin maternity be pO, for a same-sex (SS) twin maternity pS and, consequently, the probability for other maternities 1 − pS − pO. The parameter estimates $\hat p_O$ and $\hat p_S$ are relative frequencies. Applying WDR, the MZ rate is m = pS − pO and the DZ rate is d = 2pO, but the estimates $\hat m$ and $\hat d$ are not relative frequencies. The maximum likelihood estimators $\hat p_S$ and $\hat p_O$ are unbiased, efficient, and asymptotically normal. The linear transformations $\hat m = \hat p_S - \hat p_O$ and ${\skew6\hat d} = 2\hat p_O$ are efficient and asymptotically normal. If WDR holds they are also unbiased. For the tests of a set of m and d rates, contingency tables cannot be used. Alternative tests are presented and the models are applied on published data.
Strategies for Promoting Proenvironmental Behavior
Authors: Schultz P. Wesley
Published: September 2013

Environmental problems have their origins in human behavior, and as a result, any solution to environmental issues will require changes in behavior. While many disciplines in the social and behavioral sciences offer important perspectives on the behaviors linked with environmental problems, the study of the individual brings a focus on cognitive, social, and motivational processes that provides insights into effective ways to promote change. Psychological research on proenvironmental behavior dates back nearly 40 years, and within this rich body of empirical research are a number of well-established findings. Strategies such as prompts, commitments, feedback, social norms, incentives, and convenience have all been shown to effectively promote proenvironmental behavior – at least in some contexts, for some behaviors, and for some individuals. This article begins with a brief overview of these research findings, and then proceeds to examine the less-explored question about when various strategies work. The article concludes with recommendations for selecting an appropriate strategy for promoting behavior change, along with fruitful areas for future research.
The Role of Public Trust During Pandemics
Authors: Siegrist Michael , Zingg Alexandra
Published: September 2013

The present review examined the importance of trust when preparing for and during a pandemic. The reviewed literature suggests that trust in health agencies positively influenced people’s willingness to adopt recommended behavior. Most of these studies are atheoretical, and due to the lack of a common framework for trust and its antecedents, finding commonalities among the studies may seem difficult. The trust, confidence, and cooperation model was used to uncover the commonalities among the various studies on trust. This framework suggests that a distinction between values and past performance may be helpful to better understand the impact of trust on risk perception and behavior. Based on the reviewed literature, the following five recommendations relevant for crisis communication during pandemics were identified: A diverse set of experts should be used as communicators, medical personnel need to model the recommended behavior, a transparent information strategy should be used, the focus should be not only on trust but also on confidence, and establishing trust in health authorities before a pandemic occurs is important. Furthermore, research gaps were identified that should be addressed to better understand the role of trust when dealing with pandemics.
Microtubule‐stabilizing agents delay the onset of EAE through inhibition of migration
Authors: O'Sullivan David , Miller John H , Northcote Peter T , La Flamme Anne Camille
Published: September 2013

We have shown previously that microtubule‐stabilizing agents (MSA), a class of anti‐proliferative compounds, can delay disease onset and reduce cumulative disease in an experimental model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). To explore how MSA could alter EAE disease processes, we compared the effect of administering MSA before or after peak antigen‐specific proliferation and found that treatment before proliferation completely inhibited antigen‐specific responses in the spleen; whereas administration of an MSA such as paclitaxel or docetaxel after peak proliferation did not. Despite the presence of antigen‐specific responses in mice treated at the later time point, both treatment periods resulted in similar protection against EAE, suggesting that the protective effect of MSA in EAE could not be solely attributed to anti‐proliferative activity. Instead, using in vivo migration assays, it was shown that MSA inhibit immune cell infiltration into the central nervous system (CNS). Furthermore, we found that the efficacy of an MSA could be enhanced by administering low doses of two different MSA together, such as peloruside A and ixabepilone, indicating that these MSA synergize in vivo to suppress disease. Taken together, these data suggest that MSA can suppress EAE by at least two distinct mechanisms of action—prevention of proliferation and inhibition of migration into the CNS. Finally, we have shown that a combination treatment with synergizing MSA may provide enhanced protection at lower therapeutic doses.
C5a, but not C5a‐des Arg, induces upregulation of heteromer formation between complement C5a receptors C5aR and C5L2
Authors: Croker Daniel E , Halai Reena , Fairlie David P , Cooper Matthew A
Published: September 2013

Receptors for C5a have an important role in innate immunity and inflammation where their expression and activation is tightly regulated. There are two known receptors for C5a: the C5a receptor (C5aR) and the C5a receptor like‐2 (C5L2) receptor. Here we hypothesized that activation of C5aR might lead to heteromer formation with C5L2, as a downregulatory mechanism for C5aR signaling. To investigate this experimentally, bioluminescent resonance energy transfer (BRET) was implemented and supported by wide‐field microscopy to analyze receptor localization in transfected HEK293 cells and human monocyte‐derived macrophages (HMDM). BRET experiments indicated the presence of constitutive C5aR‐C5L2 heteromers, where C5a, but not C5a‐des Arg, was able to induce further heteromer formation, which was inhibited by a C5aR‐specific antagonist. The data obtained suggest that C5aR‐C5L2 can form heteromers in a process enhanced by C5a, but not by C5a‐des Arg. There was also a significant difference in the levels of the anti‐inflammatory cytokine IL‐10 detected in HMDM following exposure to C5a compared with that seen for C5a‐des Arg but no differences in the pro‐inflammatory cytokines TNFα and IL‐6. These subtle differences in C5a and C5a‐des Arg induced receptor function may be of benefit in understanding the regulation of C5a in acute inflammation.
Biomedically relevant circuit‐design strategies in mammalian synthetic biology
Authors: Bacchus William , Aubel Dominique , Fussenegger Martin
Published: September 2013

The development and progress in synthetic biology has been remarkable. Although still in its infancy, synthetic biology has achieved much during the past decade. Improvements in genetic circuit design have increased the potential for clinical applicability of synthetic biology research. What began as simple transcriptional gene switches has rapidly developed into a variety of complex regulatory circuits based on the transcriptional, translational and post‐translational regulation. Instead of compounds with potential pharmacologic side effects, the inducer molecules now used are metabolites of the human body and even members of native cell signaling pathways. In this review, we address recent progress in mammalian synthetic biology circuit design and focus on how novel designs push synthetic biology toward clinical implementation. Groundbreaking research on the implementation of optogenetics and intercellular communications is addressed, as particularly optogenetics provides unprecedented opportunities for clinical application. Along with an increase in synthetic network complexity, multicellular systems are now being used to provide a platform for next‐generation circuit design.
Dual lipidation of the brain-specific Cdc42 isoform regulates its functional properties
Authors: Wirth Alexander , Chen-Wacker Chen , Wu Yao-Wen , Gorinski Nataliya , Filippov Mikhail A. , Pandey Ghanshyam , Ponimaskin Evgeni
Published: September 2013

Cdc42 (cell division cycle 42) is a member of the Rho GTPase family which regulates a variety of cellular activities by controlling actin cytoskeleton and gene expression. Cdc42 is expressed in the form of two splice variants. The canonical Cdc42 isoform is prenylated (Cdc42-prenyl), whereas the brainspecific isoform can be palmitoylated (Cdc42-palm). In the present study we have demonstrated palmitoylation of endogenous Cdc42 in rodent and human brains and identified Cys188 and Cys189 as acylation sites of Cdc42-palm. Moreover, we have shown that Cys188 can also be prenylated. Analysis of acylation-deficient mutants revealed that lipidation of Cys188 is essential for proper membrane binding of Cdc42-palm as well as for Cdc42-mediated regulation of gene transcription and induction of densely packed filopodia in neuroblastoma cells. We also found that Cdc42-prenyl is a dominant splice variant in a wide range of commonly used cell lines as well as in the cerebellum, whereas Cdc42-palm is the main Cdc42 isoform in hippocampus, where it is critically involved in the formation of dendritic filopodia and spines. Replacement of endogenous Cdc42 by its acylation-deficient mutants revealed the importance of Cdc42-palm lipidation for its morphogenic and synaptogenic effects in neurons. These findings demonstrate that dual lipidation of Cdc42-palm represents an important regulator of morphogenic signalling in hippocampal neurons.
Intrinsic degrees of freedom for MIMO interference channel
Authors: Bai Xiaojuan
Published: September 2013

Intrinsic degrees of freedom (IDoF) which are the measure about the relative transmission ability of a channel from a transmitter to a receiver in the current transmit power at finite signal‐to‐noise power ratio are proposed. According to the IDoF of the subchannel in every dimension of channel space, the number of spatial dimensions allocated to the interferer by the interference avoiding technique, which is no more than the maximum number of subchannels associated with the decreasing IDoF of the transmission channel due to interference in the multiuser multi‐antennas interference channel, is given from an information‐theory perspective.
Distributed video coding with video analytics information for video surveillance application
Authors: Lee Myeong‐Jin
Published: September 2013

A lightweight distributed video coding scheme is presented for video surveillance applications. Background frames and foreground maps are generated using a video analytics module on the decoder side. Only sub‐frames containing foreground blocks are encoded using a transform‐domain Wyner‐Ziv codec. A decoded frame is synthesised with the reconstructed sub‐frames and the background frame. Through a simulation, the proposed scheme is shown to achieve better than state‐of‐the‐art coding efficiency while reducing coding complexity greatly both at the encoder and the decoder.
High‐speed direct modulation unidirectional emission microring lasers
Authors: Lv Xiao‐Meng , Huang Yong‐Zhen , Zou Ling‐Xiu , Long Heng , Xiao Jin‐Long , Yang Yue‐De , Du Yun
Published: September 2013

A InAlGaAs/InP microring laser with a ring width of 5 µm and an external radius of 10 µm, connected with a 2 µm‐wide output waveguide, is fabricated by the planar technology process. Continuous‐wave lasing operation is realised with a threshold current of 3 mA at 298 K, and 3 dB bandwidths of 10.8 and 8.7 GHz are obtained at the injection currents of 12 mA at 291 and 298 K, respectively.
Molecular nanonetwork channel model
Authors: Kabir M.H. , Kwak K.S.
Published: September 2013

Molecules serve as information carriers in molecular communications. Information bits are encoded by varying the concentration of molecules. The information bits thus encoded are conveyed to the receiver through molecular diffusion. A ligand‐receptor receiver measures the concentration of the molecules in order to retrieve the information. In this reported work, a memory channel using first‐order Markov chain is developed. A methodical approach to calculate channel capacity is followed. Also, a closed form capacity equation has been derived.
UWB monocycle pulse generation based on colourless silicon photonic integrated circuit
Authors: Xu Ke , Cheng Zhenzhou , Wong Chi Yan , Tsang Hon Ki
Published: September 2013

Ultra‐wideband monocycle pulse generation is experimentally demonstrated on a silicon photonic circuit with a monolithically integrated wavelength‐tunable phase‐intensity modulation converter and a waveguide germanium photodetector. A fractional bandwidth of 166% is achieved and modulation with a 2.5 Gbit/s test data pattern was demonstrated.
Circuit analysis of the memristive stateful implication gate
Authors: Fang Xudong , Tang Yuhua
Published: September 2013

A recently published memristive stateful implication (IMP) gate circuit is analysed with confirmation that it cannot achieve the full resistance switching of the output memristor in case both input memristors of the IMP gate are in the OFF resistance state. The initial parameter conditions for the IMP gate are derived, and the minimum resistance of the output memristor achievable is yielded. The HSPICE simulation confirms that a resistance refreshing scheme is indispensable for the IMP gate to function properly.
Knowledge‐aided robust adaptive beamforming with small snapshots
Authors: Gong C. , Huang L. , Xu D. , Ye Z.
Published: September 2013

A robust adaptive beamforming method is proposed to combat arbitrary array steering vector (SV) mismatches and small sample size. First, with the imprecise knowledge of the array manifold and angular sectors of the interferences, an a priori covariance matrix can be acquired. Secondly, a theoretically optimal covariance matrix can be obtained by combining an a priori covariance matrix with the sample covariance matrix. Finally, the mismatch vector between the actual and presumed SV can be estimated by solving a quadratic convex optimisation problem.
Tri‐band rectangle‐loaded monopole antenna with inverted‐L slot for WLAN/WiMAX applications
Authors: Chen H. , Yang X. , Yin Y.‐Z. , Wu J.‐J. , Cai Y.‐M.
Published: September 2013

A novel coplanar waveguide‐fed tri‐band monopole antenna with a compact radiator (10 × 23 mm2) for WLAN/WiMAX applications is presented. By etching properly an inverted‐L slot on the straight strip loaded with a rectangular tuning patch and further adjusting the dimensions and positions of these structures, three distinct wide bands can be achieved. The measured and simulated results show that the proposed antenna has 10 dB impedance bandwidth of 470 MHz (2.38–2.85 GHz), 360 MHz (3.36–3.72 GHz) and 890 MHz (4.98–5.87 GHz) to cover all the 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands. Also, the proposed antenna produces good dipole‐like radiation pattern over the covering bands.
Artificial immune K‐means grid‐density clustering algorithm for real‐time monitoring and analysis of urban traffic
Authors: Chen Chuan Ming , Pi Dechang , Fang Zhuoran
Published: September 2013

A novel clustering algorithm is presented for monitoring and analysing traffic conditions in real‐time and automatically. The existing methods concentrate on analysis of traffic flow based on historical information, and they cannot provide timely analysis of traffic conditions. Regarding the vehicles on the roads as data points, a K‐means grid‐density clustering algorithm is proposed based on an artificial immune network to partition the vehicles data into proper clusters, and marks the densities for monitoring and analysing the traffic conditions. Simulated experimental results show that the proposed algorithm obtains higher efficiency and stability than traditional methods.
Role of the early stages of Ni-Si interaction on the structural properties of the reaction products
Authors: Alberti Alessandra , La Magna Antonino
Published: September 2013

Nickel-silicon compounds, as most of the transition metal silicides, show peculiar thermodynamic and kinetic behaviours. The reason resides in the metastability of a rich variety of different phases, which are frequently favoured by the interaction with the substrate or by the limited amount of atoms available during the reactions (thin films). The large effort devoted to the comprehension of the phenomena governing Ni-Si interaction from the very beginning of the reaction process testifies the widespread interest in the field and it is driven by the need to push as far forward as possible the scaling down of micro/nano-electronics devices. Here, we provide a review on the crucial role of the early stages of the Ni-Si atomic interaction to show how this interaction has a huge impact on the reaction process and on the structural properties of the reaction products. The formation of a Ni-Si mixed layer at the deposition stage, its structure and its role in the further evolution of the reaction couple are discussed on [001] Si and amorphous Si substrates. Controlling the mixed layer properties becomes extremely important in a regime wherein kinetics upsets thermodynamic stability, i.e., in thin films interactions, and during low temperature and/or ultra-rapid thermal processes, as required by the scaling down of the devices. In the review, it is highlighted how the opportunity to control thickness and composition of the mixed (precursor) layer opens the field to tailor new materials possessing intriguing properties, such as the case of transrotational Ni-silicides. Compared to standard poly-Ni silicides, they offer large chemical and structural stability windows as well as a promising electrical behaviour.
Model of native point defect equilibrium in Cu2ZnSnS4 and application to one-zone annealing
Authors: Kosyak V. , Mortazavi Amiri N. B. , Postnikov A. V. , Scarpulla M. A.
Published: September 2013

We report a quasichemical model for point defect equilibrium in Cu2ZnSnS4 (CZTS). An ab initio calculation was used to estimate the changes in the phonon spectrum of CZTS due to trial point defects and further vibrational free energy, which in turn influences the final defect concentrations. We identify the dominant point defects and estimate the free carrier concentrations as functions of the Zn, Cu, and Sn chemical potentials, the sulfur chemical potential being set by the vapor-solid equilibrium with elemental S at the same temperature as the sample (one-zone annealing). As hinted by calculated low formation enthalpies, either the Cu vacancy (VCu−) or Cu on Zn antisite (CuZn−) acceptors are expected to dominate over a wide range of cation chemical potentials. However, the sulfur vacancy (VS2+) becomes a dominant compensating donor especially for one-zone annealing conditions. We also find that different native defects induce distinct perturbations to the vibrational free energy, resulting in non-trivial qualitative and quantitative shifts in the defect equilibrium. At typical annealing temperatures and Zn-rich conditions, this may introduce especially strong modulations in the concentrations of ZnSn2− and, contrary to enthalpic predictions, of ZnCu+ compensating donors. The modeling indicates that one-zone processing should result in CZTS, which is p-type but extremely compensated because native donor defects are stabilized by the low Fermi level and finite-temperature effects.
Single-molecule spectroscopy of the unexpected collapse of an unfolded protein at low pH
Authors: Hofmann Hagen , Nettels Daniel , Schuler Benjamin
Published: September 2013

The dimensions of intrinsically disordered and unfolded proteins critically depend on the solution conditions, such as temperature, pH, ionic strength, and osmolyte or denarurant concentration. However, a quantitative understanding of how the complex combination of chain-chain and chain-solvent interactions is affected by the solvent is still missing. Here, we take a step towards this goal by investigating the combined effect of pH and denaturants on the dimensions of an unfolded protein. We use single-molecule fluorescence spectroscopy to extract the dimensions of unfolded cold shock protein (CspTm) in mixtures of the denaturants urea and guanidinium chloride (GdmCl) at neutral and acidic pH. Surprisingly, even though a change in pH from 7 to 2.9 increases the net charge of CspTm from −3.8 to +10.2, the radius of gyration of the chain is very similar under both conditions, indicating that protonation of acidic side chains at low pH results in additional hydrophobic interactions. We use a simple shared binding site model that describes the joint effect of urea and GdmCl, together with polyampholyte theory and an ion cloud model that includes the chemical free energy of counterion interactions and side chain protonation, to quantify this effect.
Nucleation of in-grown stacking faults and dislocation half-loops in 4H-SiC epitaxy
Authors: Abadier M. , Myers-Ward R. L. , Mahadik N. A. , Stahlbush R. E. , Wheeler V. D. , Nyakiti L. O. , Eddy C. R. , Gaskill D. K. , Song H. , Sudarshan T. S. , Picard Y. N. , Skowronski M.
Published: September 2013

Ultraviolet photoluminescence, transmission electron microscopy and KOH etching were used to characterize extended defects in 4H-SiC epilayers grown at high growth rates (18 μm/h). Layers exhibited high densities of in-grown stacking faults and dislocation half-loops. The stacking faults were 8H Shockley-type faults. The Burgers vector of the dislocation half-loops was in the (0001) basal plane. Both defects nucleate within the epilayer at early stages of growth. Defect nucleation is directly correlated with high initial growth rate and is not related to any defects/heterogeneities in the substrate or epilayer. Epilayer growth by nucleation of two-dimensional islands is proposed as a possible mechanism for the formation of both defects, through nucleation of faulted Si-C bilayers.
Intrinsic beam shaping mechanism in spatially modulated broad area semiconductor amplifiers
Authors: Radziunas Mindaugas , Botey Muriel , Herrero Ramon , Staliunas Kestutis
Published: September 2013

We investigate beam shaping in broad area semiconductor amplifiers induced by a 2-dimensional (longitudinal and lateral) periodic modulation of the pump on a scale of several microns. The study is performed by solving numerically a (2 + 1)-dimensional model for the semiconductor amplifier. We show that, under realistic conditions, the anisotropic gain induced by the pump periodicity can show narrow angular profile of enhanced gain of less than 1°, providing an intrinsic filtering mechanism and eventually improving the spatial beam quality.
Frozen rotor approximation in the mixed quantum/classical theory for collisional energy transfer: Application to ozone stabilization
Authors: Teplukhin Alexander , Ivanov Mikhail , Babikov Dmitri
Published: September 2013

A frozen-rotor approximation is formulated for the mixed quantum/classical theory of collisional energy transfer and ro-vibrational energy flow [M. Ivanov and D. Babikov, J. Chem. Phys. 134, 144107 (2011)]. Numerical tests are conducted to assess its efficiency and accuracy, compared to the original version of the method, where rotation of the molecule in space is treated explicitly and adiabatically. New approach is considerably faster and helps blocking the artificial ro-vibrational transitions at the pre- and post-collisional stages of the process. Although molecular orientation in space is fixed, the energy exchange between rotational, vibrational, and translational digresses of freedom still occurs, allowing to compute ro-vibrational excitation and quenching. Behavior of the energy transfer function through eight orders of magnitude range of values and in a broad range of ΔE is reproduced well. In the range of moderate −500 ⩽ ΔE ⩽ +500 cm−1 the approximate method is rather accurate. The absolute values of stabilization cross sections for scattering resonances trapped behind the centrifugal threshold are a factor 2-to-3 smaller (compared to the explicit-rotation approach). This performance is acceptable and similar to the well-known sudden-rotation approximation in the time-independent inelastic scattering methods.
A dynamic model of the electroosmotic droplet switch
Authors: Barz Dominik P. J. , Steen Paul H.
Published: September 2013

A capillary switch is a bi-stable system of liquid/gas interfaces with a trigger to toggle back and forth between the two stable equilibrium states. We use an electro-osmotic pump as trigger. The pump, consisting of two electrodes and a porous substrate arranged between the droplets, moves volume between the droplets. This bistable system is called an electro-osmotic droplet switch. With the pump off, for low total volumes, the stable states are a pair of identical sub-hemispherical droplets or, for large enough total volumes, a large-small droplet configuration (two mirror-symmetric states). With the pump on, these stationary states are shifted and, if the pump strength is too great, there are no stationary states at all. In this article, we report the pump-on behavior as a modification of the pump-off behavior. To build the dynamic model of the system, we first develop a characterization of the electro-osmotic pump in the spirit of the Blake-Kozeny correlation for viscous flow through a packed bed. The control-volume model is based on center-of-mass motion. Model predictions compare favorably to observation.
The hydraulic bump: The surface signature of a plunging jet
Authors: Labousse M. , Bush J. W. M.
Published: September 2013

When a falling jet of fluid strikes a horizontal fluid layer, a hydraulic jump arises downstream of the point of impact, provided a critical flow rate is exceeded. We here examine a phenomenon that arises below this jump threshold, a circular deflection of relatively small amplitude on the free surface that we call the hydraulic bump. The form of the circular bump can be simply understood in terms of the underlying vortex structure and its height simply deduced with Bernoulli arguments. As the incoming flux increases, a breaking of axial symmetry leads to polygonal hydraulic bumps. The relation between this polygonal instability and that arising in the hydraulic jump is discussed. The coexistence of hydraulic jumps and bumps can give rise to striking nested structures with polygonal jumps bound within polygonal bumps. The absence of a pronounced surface signature on the hydraulic bump indicates the dominant influence of the subsurface vorticity on its instability.
Municipal wastewater utilization for biomass and biodiesel production by Scenedesmus obliquus HM103382 and Micractinium reisseri JN169781
Authors: Abou-Shanab Reda A. I. , Kim Seong-Heon , Ji Min-Kyu , Lee Sang-Hun , Roh Hyun-Seog , Jeon Byong-Hun
Published: September 2013

Municipal wastewater is a major problem due to its high concentration of nutrients, which can cause eutrophication of the surrounding water, resulting in serious disturbance in health and ecosystem. Microalgae can utilize nitrogen and phosphorus in wastewater as a potential source of cost effective and sustainable means for biodiesel production. Two microalgal species including Scenedesmus obliquus HM103382 and Micractinium reisseri JN169781 were cultivated in domestic wastewater (influent and effluent) that was pretreated and supplemented with 15% CO2 in order to accomplish simultaneous nutrient removal and lipid production from wastewater. The biomass yield and lipid production were relatively high using either autoclaved or filter-sterilized wastewater compared to using either UV-irradiated or unsterilized wastewater (control). M. reisseri and S. obliquus grown in the autoclaved influent showed high biomass yield (0.41 ± 0.01 and 0.26 ± 0.03 g dry wt. l−1) and lipid content (22% and 19%), respectively. The highest removal rates of nitrogen (97%), phosphorus (98%), and inorganic carbon (77%) were achieved by M. reisseri cultivated in the autoclaved influent. The saturated fatty acids fractions accounted for 66% and 60% of the total fatty acids accumulated in M. reisseri grown in the filter-sterilized influent and the autoclaved effluent, respectively, which is desirable for good quality biodiesel.
Dynamics in thermo-responsive nanogel crystals undergoing melting
Authors: Joshi R. G. , Tata B. V. R. , Brijitta J.
Published: September 2013

We report here the dynamics in thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) nanogel crystals undergoing melting/freezing and verify the applicability of the dynamical criterion for melting/freezing proposed by Löwen et al. [Phys. Rev. Lett. 70, 1557 (1993)]. According to this criterion the ratio of long time diffusion coefficient (DL) to short time diffusion coefficients (DS) is ∼0.1 for colloidal particles in suspension undergoing melting/freezing. Static and dynamic light scattering techniques have been employed to identify the melting/freezing transition of PNIPAM nanogel colloidal crystals of two different volume fractions ϕ = 0.49 and 0.79 and to measure DL and DS across the melting. In dense PNIPAM nanogel crystals undergoing melting, the ratio DL/DS is found to be less than 0.1 for the first time and this deviation is higher in the suspension with higher ϕ. We also show that the deviation is genuine by measuring DL/DS on shear melted charged silica colloidal liquid undergoing freezing. The mean square displacement at shorter times, close to the melting, shows subdiffusive behavior. The subdiffusive behavior, arising due to the overlap of the dangling polymer chains between shells of the neighboring particles, is argued to be the reason for the observed deviation.
Sorption and diffusion of carbon dioxide and nitrogen in poly(methyl methacrylate)
Authors: Eslami Hossein , Kesik Melis , Karimi-Varzaneh Hossein Ali , Müller-Plathe Florian
Published: September 2013

Molecular dynamics simulations are performed to determine the solubility and diffusion coefficient of carbon dioxide and nitrogen in poly(methyl methacrylate) (PMMA). The solubilities of CO2 in the polymer are calculated employing our grand canonical ensemble simulation method, fixing the target excess chemical potential of CO2 in the polymer and varying the number of CO2 molecules in the polymer matrix till establishing equilibrium. It is shown that the calculated sorption isotherms of CO2 in PMMA, employing this method well agrees with experiment. Our results on the diffusion coefficients of CO2 and N2 in PMMA are shown to obey a common hopping mechanism. It is shown that the higher solubility of CO2 than that of N2 is a consequence of more attractive interactions between the carbonyl group of polymer and the sorbent. While the residence time of CO2 beside the carbonyl group of polymer is about three times higher than that of N2, the diffusion coefficient of CO2 in PMMA is higher than that of N2. The higher diffusion coefficient of CO2, compared to N2, in PMMA is shown to be due to the higher (≈3 times) swelling of polymer upon CO2 uptake.
The glassy and supercooled state of elemental sulfur: Vibrational modes, structure metastability, and polymer content
Authors: Andrikopoulos K. S. , Kalampounias A. G. , Falagara O. , Yannopoulos S. N.
Published: September 2013

We report a detailed investigation of vibrational modes, structure, and dynamics of elemental sulfur in the glassy and the supercooled state, using Raman scattering and ab initio calculations. Polarized Raman spectra are recorded – for sulfur quenched from 473 K – over a broad temperature range from 93 K to 273 K where the supercooled liquid crystallized. The temperature induced shifts of the majority of the vibrational modes are determined and compared with the corresponding ones of crystalline sulfur. Analysis of the reduced isotropic spectra showed that the structure of the quenched product is composed of eight member rings (S8) and polymeric chains (Sμ) with a relative fraction comparable to that of the parent liquid at 473 K. Low temperature spectra, where spectral line broadening due to thermal effects is limited, revealed that two different polymeric species are present in the glass with distinct vibrational frequencies. Their interpretation was assisted by ab initio calculations used to simulate the vibrational frequencies of polymeric chains S8k (k = 1, …, 7). Theoretical results exhibit an increasing breathing mode frequency for sulfur chains up to k = 2, although it remains constant beyond the above value. The polymeric content is metastable; heating the glass above its glass transition temperature, Tg, destabilizes the chains and drives them back to the more thermodynamically stable rings. This bond interchange mechanism provides the structural origin of a secondary relaxation process in supercooled sulfur reported long ago, which has been also considered as a complication in the correct fragility estimation of this material. Finally, the Boson peak of the glass was found to exhibit strong temperature dependence even at temperatures below Tg.
Strong oxygen pressure dependence of ferroelectricity in BaTiO3/SrRuO3/SrTiO3 epitaxial heterostructures
Authors: Chen A. P. , Khatkhatay F. , Zhang W. , Jacob C. , Jiao L. , Wang H.
Published: September 2013

The oxygen pressure effect on the structural and ferroelectric properties have been studied in epitaxial BaTiO3 (BTO)/SrRuO3/SrTiO3 (001) heterostructures grown by pulsed laser deposition. It is found that oxygen pressure is a sensitive parameter, which can influence the characteristics of oxide films in many aspects. The out-of-plane lattice parameter, tetragonality, (c/a) and Ti/Ba ratio monotonously decrease as the oxygen pressure increases from 5 mTorr to 200 mTorr. Microstructural study shows that the growth of BaTiO3 varies from a dense large grained structure with a smooth surface to a small columnar grain structure with rough surface as the deposition pressure increases. Electrical measurements show that the 40 mTorr deposited BTO films present maximum remanent polarization (Pr) (14 μC/cm2) and saturation polarization (Ps) (27 μC/cm2) due to the stoichiometric cation ratio, very smooth surface, and low leakage current. These results demonstrate that the controlling of cation stoichiometry, surface morphology, and leakage current by oxygen pressure is one of very important prerequisites for device applications in the BaTiO3 films.
Passive resonators for wireless passive sensor readout enhancement
Authors: Sanz Diego A. , Mitrosbaras Costantino , Unigarro Edgar A. , Segura-Quijano Fredy
Published: September 2013

A scheme to enhance a wireless passive sensor's readout is presented. This alternative consists of the addition of a passive inductive-capacitive resonator placed between the sensor and readout antenna. A discrete model is proposed and used in simulations to study the effects of the resonator in the sensor-antenna interaction. A resonator was fabricated at 28 MHz to test the enhancement of the sensor's signal. Increases in the sensor's signal and the power transmitted to the sensor were always obtained for frequencies below 28 MHz. All experimental results were consistent with the simulation outcomes.
The effect of titanium doping on the structure and phase change characteristics of Sb4Te
Authors: Zhu Min , Wu Liangcai , Rao Feng , Song Zhitang , Ji Xinglong , Yao Dongning , Cheng Yan , Lv Shilong , Song Sannian , Liu Bo , Xu Ling
Published: September 2013

As a growth-dominated phase change material, Sb4Te (ST) has fast crystallization speed while thermal stability is very poor, which makes it unsuitable for application in phase change random access memory (PCRAM). After doping Ti, the crystallization temperature is greatly improved to 210.33 °C, which is much higher than that of conventional Ge2Sb2Te5 (∼150 °C), and the melting point is reduced to 540.27 °C. In addition, grain size of crystalline Ti-doped Sb4Te (TST) film is significantly decreased to nanoscale. Ti atom is believed to occupy the lattice site of Sb atom in TST. With good thermal stability, TST-based PCRAM cell also has fast crystallization rate of 6 ns. Furthermore, the energy consumption is also lower than that of Ge2Sb2Te5-based one. Endurance of exceeding 2E5 cycles is obtained with a resistance ratio of one order of magnitude. Therefore, Ti doping seems to be a good way to solve the contradiction between thermal stability and fast crystallization speed of Sb-Te alloys.
The effect of slip length on vortex rebound from a rigid boundary
Authors: Sutherland D. , Macaskill C. , Dritschel D. G.
Published: September 2013

The problem of a dipole incident normally on a rigid boundary, for moderate to large Reynolds numbers, has recently been treated numerically using a volume penalisation method by Nguyen van yen, Farge, and Schneider [Phys. Rev. Lett. 106, 184502 (2011)]. Their results indicate that energy dissipating structures persist in the inviscid limit. They found that the use of penalisation methods intrinsically introduces some slip at the boundary wall, where the slip approaches zero as the Reynolds number goes to infinity, so reducing to the no-slip case in this limit. We study the same problem, for both no-slip and partial slip cases, using compact differences on a Chebyshev grid in the direction normal to the wall and Fourier methods in the direction along the wall. We find that for the no-slip case there is no indication of the persistence of energy dissipating structures in the limit as viscosity approaches zero and that this also holds for any fixed slip length. However, when the slip length is taken to vary inversely with Reynolds number then the results of Nguyen van yen et al. are regained. It therefore appears that the prediction that energy dissipating structures persist in the inviscid limit follows from the two limits of wall slip length going to zero, and viscosity going to zero, not being treated independently in their use of the volume penalisation method.