bluuebunny/crossref_metadata_2025 huggingface dataset:
In Search of Cultural Diversity, Revisited: Recent Publication Trends in Cross-Cultural and Ethnic Minority Psychology
Authors: Hartmann William E. , Kim Eric S. , Kim Jackie H. J. , Nguyen Teresa U. , Wendt Dennis C. , Nagata Donna K. , Gone Joseph P.
Published: August 2013

Given the increasing proportion of ethnic minority individuals in the United States and psychology's historical reliance on theories derived from Euro American populations, it is important to monitor the status of cultural diversity research. We conducted a 10-year follow-up to Hall and Maramba's (2001) report of cross-cultural (CC) and ethnic minority (EM) publication trends. Comparing data from 1993–1999 and 2003–2009, we found that research on CC and EM issues continues to be underrepresented in the literature, particularly in top-tier journals. The American Psychological Association and Association for Psychological Science journals mirrored this discouraging trend, and the absence of top CC and EM authors on their editorial boards may point to a structural barrier to broader inclusion of cultural diversity research. We also found that fewer top CC and EM researchers are employed in psychology departments than one might hope, reflecting predominant attitudes within psychology of CC and EM research as peripheral to the larger field. Although clear that few gains have been made despite numerous awareness-raising efforts, the precise deficits were somewhat obscured, because the CC and EM terminology employed by Hall and Maramba (2001) did not fully capture the breadth of cultural diversity research currently underway in psychology. Thus, future attempts to assess the field would benefit from wider-reaching search terms. Additionally, we suggest that attention to reorganization within the evolving fields of cultural diversity research and to developing new categories of inquiry for research on cultural diversity that maintain focus on minority statuses in the United States may be productive routes forward for psychology as a discipline.
Evaluation of an In Silico PBPK Post‐Bariatric Surgery Model through Simulating Oral Drug Bioavailability of Atorvastatin and Cyclosporine
Authors: Darwich AS , Pade D , Rowland‐Yeo K , Jamei M , Åsberg A , Christensen H , Ashcroft DM , Rostami‐Hodjegan A
Published: August 2013

An increasing prevalence of morbid obesity has led to dramatic increases in the number of bariatric surgeries performed. Altered gastrointestinal physiology following surgery can be associated with modified oral drug bioavailability (Foral). In the absence of clinical data, an indication of changes to Foral via systems pharmacology models would be of value in adjusting dose levels after surgery. A previously developed virtual “post‐bariatric surgery” population was evaluated through mimicking clinical investigations on cyclosporine and atorvastatin after bariatric surgery. Cyclosporine simulations displayed a reduced fraction absorbed through gut wall (fa) and Foral after surgery, consistent with reported observations. Simulated atorvastatin Foral postsurgery was broadly reflective of observed data with indications of counteracting interplay between reduced fa and an increased fraction escaping gut wall metabolism (FG). Inability to fully recover observed atorvastatin exposure after biliopancreatic diversion with duodenal switch highlights the current gap regarding the knowledge of associated biological changes.

CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e47; doi:10.1038/psp.2013.23; advance online publication 12 June 2013
Refined instrumental variable method for Hammerstein–Wiener continuous‐time model identification
Authors: Ni Boyi , Gilson Marion , Garnier Hugues
Published: August 2013

This study presents the first attempt of direct continuous‐time model identification using instrumental variable method for Hammerstein–Wiener systems from sampled data. Under the assumption of monotonic function for the Wiener part, the whole non‐linear model is first estimated as an augmented multiple‐input single‐output linear model, from which the model parameters are then extracted by singular value decomposition. A refined instrumental variable method is proposed to consistently identify this non‐linear system acting in a coloured noisy environment. Monte Carlo simulation analysis is presented to illustrate the effectiveness of the proposed method.
Robustness analysis of global exponential stability of non‐linear systems with time delays and neutral terms
Authors: Shen Yi , Wang Jun
Published: August 2013

The global stability of non‐linear dynamical systems has been investigated extensively in recent decades. It is well known that time delay and neutral term could derail the stability of non‐linear systems. This study presents new results on the robustness of the global exponential stability of non‐linear systems with respect to time delay and neutral term. Given globally exponentially stable non‐linear systems, the problems to be addressed herein are how much time delay and neutral term contraction coefficient are allowed so that the non‐linear systems can remain to be globally exponentially stable, in the presence of time delay and neutral term. Upper bounds of allowable time delay and neutral term contraction coefficient will be derived for non‐linear systems to sustain their global exponential stability. A numerical example is provided to illustrate the results.
Optimal output feedback H∞ ‐tracking control design for Takagi and Sugeno fuzzy systems with immeasurable premise variables
Authors: Esfahani Said Hoghoughi
Published: August 2013

This study is concerned with the problem of output feedback H ∞ ‐tracking control design for Takagi and Sugeno (T–S) fuzzy systems with immeasurable premise variables. In most of the existing results in the area of fuzzy H ∞ ‐tracking control design, it is assumed that the information of premise variables is accessible through the measurement equations. This assumption reduces the practical applications of these results. On the other hand, there exist some recent results for control of T–S fuzzy systems with immeasurable premise variables in the literature. By combining this approach with our previous scheme in the area of fuzzy H ∞ ‐tracking control, the authors succeed to design a single controller which leads to the stability of the closed‐loop system and guarantees the required H ∞ tracking error norm to some reference and bounded signals. This single controller can be found by a search over the solutions of two linear matrix inequalities. The authors also offer a simple numerical method to find the optimal H ∞ ‐tracking control law. One particular example is given to illustrate the effectiveness of the obtained results.
Dynamics and swing control of mobile boom cranes subject to wind disturbances
Authors: Huang Jie , Maleki Ehsan , Singhose William
Published: August 2013

Operating cranes is challenging because payloads can experience large and dangerous oscillations. The oscillations are induced by both intentional motions commanded by the human operator and by external disturbances. Although significant progress has been achieved by using command shaping to reduce operator‐induced vibration, less success has been achieved on reducing oscillations induced by external disturbances, such as wind. The disturbance‐rejection task is more challenging because it requires accurate sensing of the crane payload. This study presents a combined command shaping and feedback control architecture. The input shaper eliminates the payload oscillation caused by human‐operator commands, and the feedback controller reduces the effect of wind gusts. Simulations of a large range of motions are used to analyse the dynamic behaviour of boom cranes using the proposed controller. Experimental results obtained from a small‐scale boom crane validate the simulated dynamic behaviour and the effectiveness of the controller.
Reachability and controllability of linear switched impulsive systems
Authors: Liu Chao , Li Chuandong , Han Qi , Li Chaojie , Zhang Qun
Published: August 2013

This study investigates the reachability and controllability of linear switched impulsive systems in which impulsive component is independent of switching among different subsystems. Some crucial geometrical criteria are established. The authors present the fact that the reachable sets and the controllable sets may not be subspaces, if impulsive matrices are singular. While impulsive matrices are reversible, the reachable and controllable subspaces can be determined by two proposed subspace algorithms. The authors also point out that the reachable or controllable subspace is an invariant subspace of the considered systems. Finally, two simple corresponding examples are discussed to illustrate the correctness and effectiveness of the proposed theoretical results.
Robust disturbance rejection based on equivalent‐input‐disturbance approach
Authors: Liu Rui‐Juan , Liu Guo‐Ping , Wu Min , Xiao Fang‐Chun , She Jinhua
Published: August 2013

A robust disturbance rejection method for uncertain systems is presented in this study. It effectively rejects both matched and unmatched disturbances and guarantees robust stability of the system when there exist modelling uncertainties. First, the authors show the configuration of the system that is based on the idea of the equivalent input disturbance (EID). An EID estimator is designed to compensate disturbances without requiring their prior knowledge. Then, a robust stability condition and the method of the controller design are presented using a linear‐matrix‐inequality. Finally, the validity of the authors method and its superiority over a conventional control method and the sliding‐mode control method are demonstrated through the simulations of a numerical example and experiments of a rotational‐speed control system.
Structure identification of uncertain dynamical networks coupled with complex‐variable chaotic systems
Authors: Wu Zhaoyan , Fu Xinchu
Published: August 2013

Topological structures and node dynamics of dynamical networks have important influence on their dynamical behaviours. In practical applications, not all of them can be well determined beforehand; therefore this study investigates the structure identification of an uncertain dynamical network coupled with complex‐variable chaotic systems. Based on the Barbalat's lemma, corresponding network estimators are designed for identifying the unknown or uncertain topological structure and node dynamics. Notably, the node dynamics need not to be identical and the topological structure need not to be symmetric or irreducible. Furthermore, this method can also better monitor the switching topological structure of a dynamical network. Numerical simulations are provided to verify the correctness and effectiveness of the theoretical results.
Line-imaging velocimetry for observing spatially heterogeneous mechanical and chemical responses in plastic bonded explosives during impact
Authors: Bolme C. A. , Ramos K. J.
Published: August 2013

A line-imaging velocity interferometer was implemented on a single-stage light gas gun to probe the spatial heterogeneity of mechanical response, chemical reaction, and initiation of detonation in explosives. The instrument is described in detail, and then data are presented on several shock-compressed materials to demonstrate the instrument performance on both homogeneous and heterogeneous samples. The noise floor of this diagnostic was determined to be 0.24 rad with a shot on elastically compressed sapphire. The diagnostic was then applied to two heterogeneous plastic bonded explosives: 3,3′-diaminoazoxyfurazan (DAAF) and PBX 9501, where significant spatial velocity heterogeneity was observed during the build up to detonation. In PBX 9501, the velocity heterogeneity was consistent with the explosive grain size, however in DAAF, we observed heterogeneity on a much larger length scale than the grain size that was similar to the imaging resolution of the instrument.
Are structural properties of dendrimers sensitive to the symmetry of branching? Computer simulation of lysine dendrimers
Authors: Falkovich S. , Markelov D. , Neelov I. , Darinskii A.
Published: August 2013

Poly-L-lysine (PLL) dendrimers are promising systems for biomedical applications due to their biocompatibility. These dendrimers have a specific topology: two spacers of different lengths come out of each branching point and thus the branching is asymmetric. Because of this asymmetry terminal groups are located at branches of different lengths, unlike dendrimers with a symmetric branching. This paper presents the results of the first systematic molecular dynamics simulation of such asymmetric PLL dendrimers. It is shown that PLL dendrimers are porous molecules with all terminal groups equally accessible to water. We have found that in spite of an asymmetry of branching the general structural characteristics of PLL dendrimers are rather similar to those of dendrimers with symmetric branching. We have also found that the structural characteristics of PLL dendrimers obey the general laws for dendrimers and that their electrostatic properties agree with the predictions of a general analytic theory.
Asymmetric processing of a substrate protein in sequential allosteric cycles of AAA+ nanomachines
Authors: Kravats Andrea N. , Tonddast-Navaei Sam , Bucher Ryan J. , Stan George
Published: August 2013

Essential protein quality control includes mechanisms of substrate protein (SP) unfolding and translocation performed by powerful ring-shaped AAA+ (ATPases associated with various cellular activities) nanomachines. These SP remodeling actions are effected by mechanical forces imparted by AAA+ loops that protrude into the central channel. Sequential intra-ring allosteric motions, which underlie repetitive SP-loop interactions, have been proposed to comprise clockwise (CW), counterclockwise (CCW), or random (R) conformational transitions of individual AAA+ subunits. To probe the effect of these allosteric mechanisms on unfoldase and translocase functions, we perform Langevin dynamics simulations of a coarse-grained model of an all-alpha SP processed by the single-ring ClpY ATPase or by the double-ring p97 ATPase. We find that, in all three allosteric mechanisms, the SP undergoes conformational transitions along a common set of pathways, which reveals that the active work provided by the ClpY machine involves single loop-SP interactions. Nevertheless, the rates and yields of SP unfolding and translocation are controlled by mechanism-dependent loop-SP binding events, as illustrated by faster timescales of SP processing in CW allostery compared with CCW and R allostery. The distinct efficacy of allosteric mechanisms is due to the asymmetric collaboration of adjacent subunits, which involves CW-biased structural motions of AAA+ loops and results in CW-compatible torque applied onto the SP. Additional simulations of mutant ClpY rings, which render a subset of subunits catalytically-defective or reduce their SP binding affinity, reveal that subunit-based conformational transitions play the major role in SP remodeling. Based on these results we predict that the minimally functional AAA+ ring includes three active subunits, only two of which are adjacent.
Superhydrophilic graphite surfaces and water-dispersible graphite colloids by electrochemical exfoliation
Authors: Li Yueh-Feng , Chen Shih-Ming , Lai Wei-Hao , Sheng Yu-Jane , Tsao Heng-Kwong
Published: August 2013

Superhydrophilic graphite surfaces and water-dispersible graphite colloids are obtained by electrochemical exfoliation with hydrophobic graphite electrodes. Such counterintuitive characteristics are caused by partial oxidation and investigated by examining both graphite electrodes and exfoliated particles after electrolysis. The extent of surface oxidation can be explored through contact angle measurement, scanning electron microscope, electrical sheet resistance, x-ray photoelectron spectroscopy, zeta-potential analyzer, thermogravimetric analysis, UV-visible, and Raman spectroscopy. The degree of wettability of the graphite anode can be altered by the electrolytic current and time. The water contact angle declines generally with increasing the electrolytic current or time. After a sufficient time, the graphite anode becomes superhydrophilic and its hydrophobicity can be recovered by peeling with adhesive tape. This consequence reveals that the anodic graphite is oxidized by oxygen bubbles but the oxidation just occurs at the outer layers of the graphite sheet. Moreover, the characteristics of oxidation revealed by UV peak shift, peak ratio between D and G bands, and negative zeta-potential indicate the presence of graphite oxide on the outer shell of the exfoliated colloids. However, thermogravimetric analysis for the extent of decomposition of oxygen functional groups verifies that the amount of oxygen groups is significantly less than that of graphite oxide prepared via Hummer method. The structure of this partially oxidized graphite may consist of a graphite core covered with an oxidized shell. The properties of the exfoliated colloids are also influenced by pH of the electrolytic solution. As pH is increased, the extent of oxidation descends and the thickness of oxidized shell decreases. Those results reveal that the degree of oxidation of exfoliated nanoparticles can be manipulated simply by controlling pH.
Dust acoustic solitons in a charge varying dusty plasma in the presence of ion nonthermality and background nonextensivity
Authors: Benzekka Moufida , Tribeche Mouloud
Published: August 2013

Dust acoustic (DA) solitons are addressed in a charge varying dusty plasma in the presence of ion nonthermality and background nonextensivity. A physically meaningful nonthermal nonextensive ion distribution is outlined. The correct non-Maxwellian ion charging current is derived based on the orbit-limited motion theory. Under grain-current balance, the variable dust charge is expressed in terms of the Lambert function. It is found that nonthermality and its nonextensive nature may act concurrently and influence the restoring force and hence the soliton profile. Due to the flexibility provided by the nonextensive parameter, we think that our model should provide a better fit of the space observations.
Enhancing detection sensitivity of piezoelectric plate sensor by increasing transverse electromechanical coupling constant
Authors: Wu Wei , Shih Wan Y. , Shih Wei-Heng
Published: August 2013

In this study, we examined how the materials’ properties of a lead magnesium niobate-lead titanate solid solution, [Pb(Mg1/3Nb2/3)O3]0.63[PbTiO3]0.37 (PMN-PT) piezoelectric plate sensor (PEPS) affected the enhancement of the relative detection resonance frequency shift, −Δf/f of the sensor, where f and Δf were the resonance frequency and resonance frequency shift of the sensor, respectively. Specifically, the electromechanical coupling constant, −k31, of the PMN-PT PEPS was varied by changing the grain size of the piezoelectric layer as well as by applying a bias direct current electric field. Detection of streptavidin at the same concentration was carried out with biotin covalently immobilized on the surface of PEPS. It is shown that the −Δf/f of the same streptavidin detection was increased by more than 2-fold when the −k31 increased from 0.285 to 0.391.
Quasi-analytical solution for the stable system of the multi-layer folded graphene wrinkles
Authors: Zhang Yancheng , Wei Ning , Zhao Junhua , Gong Yadong , Rabczuk Timon
Published: August 2013

A quasi-analytical solution on the minimum length and its corresponding system energy is proposed for the stable multi-layer folded graphene wrinkles (FGWs). The quasi-analytical solution shows that: (1) at a certain threshold height, a single-layer FGW becomes energetically favorable compared to a standing graphene wrinkle. (2) All the geometrical properties of single-layer FGW reproduce in the double-layer FGWs, which is considered as the typical configuration for predicting the multi-layer folded FGWs. (3) Parametric studies show that the increased bending stiffness per length promotes the minimum graphene length while the case is reversed for the increased adhesion energy density. Both of the increased bending stiffness per length and adhesion energy density lead to the decreased system energy for the stable folded structure, while the system energy is less sensitive to the variation of adhesion energy density compared to that of the bending stiffness per length. Besides, molecular mechanics simulation shows that the present model has high accuracy on evaluating the system energy and the configuration for multi-layer FGWs.
Fabrication of uniform multi-compartment particles using microfludic electrospray technology for cell co-culture studies
Authors: Liu Zhou , Shum Ho Cheung
Published: August 2013

In this work, we demonstrate a robust and reliable approach to fabricate multi-compartment particles for cell co-culture studies. By taking advantage of the laminar flow within our microfluidic nozzle, multiple parallel streams of liquids flow towards the nozzle without significant mixing. Afterwards, the multiple parallel streams merge into a single stream, which is sprayed into air, forming monodisperse droplets under an electric field with a high field strength. The resultant multi-compartment droplets are subsequently cross-linked in a calcium chloride solution to form calcium alginate micro-particles with multiple compartments. Each compartment of the particles can be used for encapsulating different types of cells or biological cell factors. These hydrogel particles with cross-linked alginate chains show similarity in the physical and mechanical environment as the extracellular matrix of biological cells. Thus, the multi-compartment particles provide a promising platform for cell studies and co-culture of different cells. In our study, cells are encapsulated in the multi-compartment particles and the viability of cells is quantified using a fluorescence microscope after the cells are stained for a live/dead assay. The high cell viability after encapsulation indicates the cytocompatibility and feasibility of our technique. Our multi-compartment particles have great potential as a platform for studying cell-cell interactions as well as interactions of cells with extracellular factors.
Continuous time random walk with linear force applied to hydrated proteins
Authors: Fa Kwok Sau
Published: August 2013

An integro-differential diffusion equation with linear force, based on the continuous time random walk model, is considered. The equation generalizes the ordinary and fractional diffusion equations. Analytical expressions for transition probability density, mean square displacement, and intermediate scattering function are presented. The mean square displacement and intermediate scattering function can fit well the simulation data of the temperature-dependent translational dynamics of nitrogen atoms of elastin for a wide range of temperatures and various scattering vectors. Moreover, the numerical results are also compared with those of a fractional diffusion equation.
Evolution of structural and magnetic properties of amorphous CoFeB film with thermal annealing
Authors: Gupta Ranjeeta , Gupta Ajay , Gupta Mukul , Rajput Parasmani , Wildes Andrew
Published: August 2013

Evolution of structural and magnetic properties of amorphous Co68Fe14B18 thin film with thermal annealing has been studied. Initially, the film exhibits a structural relaxation as evidenced by annihilation of excess free volume and an increase in topological short range order. Annealing at 473 K results in precipitation of primary phase followed by formation of boride phase at a still higher temperature of 598 K. Iron preferentially precipitates out in the primary phase, resulting in the formation of bcc Co58Fe41. This suggests an affinity of Co towards B. Such affinity between Co and B is evidenced even in the as-deposited film, using hard x-ray photoelectron spectroscopy (HAXPES) measurements. As-deposited film exhibits an in-plane uniaxial magnetic anisotropy which disappears at a temperature well beyond crystallization temperature, suggesting that the origin of anisotropy is mainly a chemical short range order in the system. Variation in the coercivity with thermal annealing can be understood in terms of random anisotropy model. Precise measurement of Fe self-diffusion using neutron reflectivity shows that diffusion length associated with annihilation of excess free volume in the film is about 0.5 nm. This agrees with the length scale of structural fluctuations in amorphous alloys. Secondary ion mass spectrometry measurements show that thermal annealing results in depletion of B in the region of the interface with the substrate, with associated faster Fe diffusion in this region. This faster diffusion of Fe may be a possible cause of preferential crystallization of the film in the interfacial region as seen in some earlier studies.
Light trapping efficiency of periodic and quasiperiodic back-reflectors for thin film solar cells: A comparative study
Authors: Micco A. , Ricciardi A. , Pisco M. , La Ferrara V. , Mercaldo L. V. , Delli Veneri P. , Cutolo A. , Cusano A.
Published: August 2013

Recently, great efforts have been carried out to design optimized metallic nano-grating back-reflectors to improve the light absorption in thin film solar cells. In this work, we compare the performances of deterministic aperiodic backreflectors in the form of 1-D nanogratings based on the generalized Fibonacci deterministic aperiodic sequence with a standard periodic one. The case of study here analyzed relies on a realistic solar cell model, where light absorption is evaluated only in the intrinsic region of an amorphous silicon P-I-N junction. We found that the results of comparison are strongly influenced by the amorphous silicon extinction coefficient within the near-infrared wavelength range, where most photonic-plasmonic modes (responsible for the light absorption enhancement typically observed when structured metal nanogratings are employed) are excited. In particular, with device-grade hydrogenated amorphous silicon, we demonstrate that Fibonacci-like backreflectors are able to provide an absorption enhancement of about 4% and 20% with respect to periodic and flat metallic backreflectors, respectively. We also found that aperiodic gratings guarantee better results in terms of robustness to the incident angle of the incoming radiation. Overall, our results confirm that aperiodic geometries are effectively able to offer some intriguing perspectives to enhance light trapping capability in thin film solar cells especially thanks to the large set of patterns employable to enable a proper design of resonant modes number and their spectral locations.
Enhanced electrical manipulation of magnetic susceptibility in ferromagnetic amorphous alloy and piezoelectric bimorph heterostructure
Authors: Liu Guoxi , Zhang Yuan , Ci Penghong , Dong Shuxiang
Published: August 2013

In this study, we report an enhanced electrical manipulation of magnetic susceptibility in ferromagnetic amorphous alloy ribbon using a piezoelectric bimorph actuator. Theoretically, the strain produced by the piezoelectric bimorph and then coupled into the amorphous alloy ribbon is larger than that of a single piezoelectric plate under an identical applied electric field, thus resulting in a stronger magnetoelectric (ME) coupling for electrically manipulating magnetic susceptibility. Our experimental results have shown that the initial susceptibility tunability of the amorphous alloy ribbon upon the tuning electric field applied on the piezoelectric bimorph ranging from 0 kV/cm to 5 kV/cm can reach up to 750% at low-frequency of 1 kHz and maintain 80% at 1 MHz. This study expands the structure design of ME smart devices, especially the electrically controllable magnetic devices.
Creation of a two-dimensional electron gas and conductivity switching of nanowires at the LaAlO3/SrTiO3 interface grown by 90o off-axis sputtering
Authors: Podkaminer J. P. , Hernandez T. , Huang M. , Ryu S. , Bark C. W. , Baek S. H. , Frederick J. C. , Kim T. H. , Cho K. H. , Levy J. , Rzchowski M. S. , Eom C. B.
Published: August 2013

Two-dimensional electron gas (2DEG) formed at the interface between two oxide band-insulators LaAlO3 and SrTiO3 raises the possibility to develop oxide nanoelectronics. Here, we report the creation of a 2DEG at the LaAlO3/SrTiO3 heterointerfaces grown by 90° off-axis sputtering which allows uniform films over a large area. The electrical transport properties of the LaAlO3/SrTiO3 heterointerface are similar to those grown by pulsed laser deposition. We also demonstrate room-temperature conductive probe-based switching of quasi-one-dimensional structures. This work demonstrates that a scalable growth process can be used to create the two-dimensional electron gas system at oxide heterointerfaces.
Nonlinear excitation of low-n harmonics in reduced magnetohydrodynamic simulations of edge-localized modes
Authors: Krebs I. , Hölzl M. , Lackner K. , Günter S.
Published: August 2013

Nonlinear simulations of the early edge-localized mode (ELM) phase based on a typical type-I ELMy ASDEX Upgrade discharge have been carried out using the reduced MHD code JOREK. The analysis is focused on the evolution of the toroidal Fourier spectrum. It is found that during the nonlinear evolution, linearly subdominant low-n Fourier components, in particular the n = 1, grow to energies comparable with linearly dominant harmonics. A simple model is developed, based on the idea that energy is transferred among the toroidal harmonics via second order nonlinear interaction. The simple model reproduces and explains very well the early nonlinear evolution of the toroidal spectrum in the JOREK simulations. Furthermore, it is shown for the n = 1 harmonic, that its spatial structure changes significantly during the transition from linear to nonlinearly driven growth. The rigidly growing structure of the linearly barely unstable n = 1 reaches far into the plasma core. In contrast, the nonlinearly driven n = 1 has a rigidly growing structure localized at the plasma edge, where the dominant toroidal harmonics driving the n = 1 are maximal and in phase. The presented quadratic coupling model might explain the recent experimental observation of strong low-n components in magnetic measurements [Wenninger et al., “Non-linear magnetic perturbations during edge localized modes in TCV dominated by low n mode components,” Nucl. Fusion (submitted)].
Effects of excess silicon on the 1540 nm Er3+ luminescence in silicon rich oxynitride films
Authors: Xu Lingbo , Jin Lu , Li Dongsheng , Yang Deren
Published: August 2013

Indirect excitation of Er3+ ions via energy transfer from silicon nano-clusters (Si-NCs) is demonstrated in silicon rich oxynitride films with different Si excess concentrations. Excess Si shows competitive effects on Er3+ luminescence. It could enhance the Er3+ emission efficiency while it degrades the energy transfer efficiency and density of optically active Er3+ ions at the same time. Furthermore, coalescence of Si-NCs is observed in the samples with high Si excess concentrations, reducing the density of sensitizers and their coupling with Er.
Kinetic simulation studies of laser-triggering in the Z gas switch
Authors: Welch D. R. , Rose D. V. , Thoma C. , Clark R. E. , Miller C. , Madrid E. A. , Zimmerman W. R. , Rambo P. K. , Schwarz J. , Savage M. , Atherton B. W.
Published: August 2013

Advanced z-pinch accelerators require precise timing of multiple mega-ampere drivers to deliver terawatt power. The triggering of these drivers is now largely initiated by laser ionization of gas switches. In this paper, we discuss detailed fully kinetic simulation of the Z laser-triggered gas switch involving detailed finite-difference time-domain particle-in-cell Monte Carlo modeling of the trigger section of the switch. Other components of the accelerator from the Marx bank through the pulse-forming line are described as circuit elements. The simulations presented here build on a recently developed model of electro-negative gas breakdown and streamer propagation that included photons produced from de-excited neutrals. New effects include multi-photon ionization of the gas in a prescribed laser field. The simulations show the sensitivity of triggering to laser parameters including focal plane within the anode-cathode gap of the trigger section of the switch, intensity at focus, and laser pulse length. Detailed electromagnetic simulations of the trigger section with circuit modeling of the upstream and downstream components are largely in agreement with Z data and demonstrate a new capability.
Temperature-dependent structural relaxation of BeZnO alloys
Authors: Su Longxing , Zhu Yuan , Chen Mingming , Zhang Quanlin , Su Yuquan , Ji Xu , Wu Tianzhun , Gui Xuchun , Xiang Rong , Tang Zikang
Published: August 2013

The thermal stability of BeZnO was examined in this study. Structural relaxation and reconstruction of the Be0.4Zn0.6O alloy film started at 500 °C and came to a halt at 800 °C. Be atoms were found to be diffused out from the host position, and BeO-based second phase was formed. The bandgap of Be0.4Zn0.6O was reduced to the value of pure ZnO after annealing at 600 °C. Therefore, the thermodynamic solubility of BeO in ZnO is far below than that of MgO in ZnO. Finally, the long term stability of BeZnO at room temperature was verified after aged for one year.
Nanoindentation experiments with different loading rate distinguish the mechanism of incipient plasticity
Authors: Chrobak D. , Kim Kwang-Ho , Kurzydłowski K. J. , Nowak R.
Published: August 2013

Recent findings in nanodeformation of semiconductors posed a dilemma whether the nanoscale plasticity starts with phase transformation or nucleation of dislocations in a stressed nanovolume. In this letter we demonstrate the results of nanoindentation experiments with different loading rate, which enable us to conclude on a mechanism of incipient plasticity. The recorded nanodeformation response of GaAs and Si contrasts that observed for either GaN or metallic Fe crystal, which supports the phase transformation nature of the GaAs incipient plasticity. The derived relationship between the energy barrier for defect nucleation and applied stress served as a verification of the obtained results.
Step-flow growth mode instability of N-polar GaN under N-excess
Authors: Chèze C. , Sawicka M. , Siekacz M. , Turski H. , Cywiński G. , Smalc-Koziorowska J. , Weyher J. L. , Kryśko M. , Łucznik B. , Boćkowski M. , Skierbiszewski C.
Published: August 2013

GaN layers were grown on N-polar GaN substrates by plasma-assisted molecular beam epitaxy under different III/V ratios. Ga-rich conditions assure step-flow growth with atomically flat surface covered by doubly-bunched steps, as for Ga-polar GaN. Growth under N-excess however leads to an unstable step-flow morphology. Particularly, for substrates slightly miscut towards ⟨101¯0⟩, interlacing fingers are covered by atomic steps pinned on both sides by small hexagonal pits. In contrast, a three-dimensional island morphology is observed on the Ga-polar equivalent sample. We attribute this result to lower diffusion barriers on N-polar compared to Ga-polar GaN under N-rich conditions.
Embedded graphene for large-area silicon-based devices
Authors: Gluba M. A. , Amkreutz D. , Troppenz G. V. , Rappich J. , Nickel N. H.
Published: August 2013

Macroscopic graphene films buried below amorphous and crystalline silicon capping layers are studied by Raman backscattering spectroscopy and Hall-effect measurements. The graphene films are grown by chemical vapor deposition on copper foil and transferred to glass substrates. Uncapped films possess charge-carrier mobilities of 2030 cm2/Vs at hole concentrations of 3.6 × 1012 cm−2. Graphene withstands the deposition and subsequent crystallization of silicon capping layers. However, the crystallinity of the silicon cap has large influence on the field-induced doping of graphene. Temperature dependent Hall-effect measurements reveal that the mobility of embedded graphene is limited by charged-impurity and phonon-assisted scattering.
Onion-like carbon and carbon nanotube film antennas
Authors: Vacirca Nicholas A. , McDonough John K. , Jost Kristy , Gogotsi Yury , Kurzweg Timothy P.
Published: August 2013

In this paper, radiating dipole antennas have been fabricated from rolled carbon films, which are typically used for supercapacitor electrodes. Return loss and radiation pattern measurements for onion-like carbon (OLC) and multi-walled carbon nanotubes (MWCNTs) antenna samples are presented and compared to a copper standard. The OLC antenna's radiation pattern measurements show a peak gain of −1.48 dBi, just less than 3 dB of a copper dipole antenna. Compared to antennas made from MWCNT films, the OLC samples show better radiation performance despite a lower measured conductivity.
Impact of annealing induced structural relaxation on the electrical properties and the crystallization kinetics of amorphous GeTe films
Authors: Privitera S. , Mio A. M. , D'Arrigo G. , Carria E. , Rimini E.
Published: August 2013

The electrical properties of amorphous GeTe films deposited at room temperature, ion implanted, and melt-quenched have been studied. The activation energy for the mobility gap varies from 0.64, in the melt-quenched, to 0.74 eV, in the as deposited film. In all the types of amorphous, pre-annealing at temperatures below crystallization induces relaxation, increasing the resistance and the mobility gap. Pre-annealing also reduces the nucleation rate for crystallization by a factor up to 4. A model is proposed, describing the competing processes of structural relaxation and crystallization, as governed by a population of sub-critical nuclei formed by medium range ordered regions.
A paramagnetic neutral VAlON center in wurtzite AlN for spin qubit application
Authors: Tu Y. , Tang Z. , Zhao X. G. , Chen Y. , Zhu Z. Q. , Chu J. H. , Fang J. C.
Published: August 2013

Spin-polarized electronic structures of VAlON centers consisting of an aluminum vacancy and a substitutional oxygen in AlN with different charge states are studied by first-principles calculations. It is observed that a paramagnetic neutral VAlON center is stable in p-type AlN. The defect center possesses a triplet ground state and a spin-conserved excited state with rather low excitation energy and its spin coherence time is in an order of second at T = 0 estimated by using a mean-field-based scheme. The results indicate that the neutral VAlON center is a promising candidate for spin coherent manipulation and qubit operation.
Fragmentation and Drought Legacy Correlate with Distribution of Burrhead Chub in Subtropical Streams of North America
Authors: Perkin Joshuah S. , Shattuck Zachary R. , Gerken Joseph E. , Bonner Timothy H.
Published: August 2013

Burrhead Chub Macrhybopsis marconis is a species of special concern endemic to subtropical streams in south Texas. We documented life history attributes and historical patterns in abundance and distribution to aid in understanding range‐wide declines of the species among the Colorado and Guadalupe‐San Antonio River systems. Life history results suggest Burrhead Chub lives for 2 years, reaches sexual maturity at age‐1, and spawns multiple clutches during March–September. Review of museum vouchers revealed Burrhead Chub is now missing from 26% of its historical range, including most impounded stream segments. There was a significant difference in the size of stream fragments for which Burrhead Chub is missing or still persists. Timing of many extirpations occurred after fragmentation and coincided with a record drought (1949–1959) when range‐wide stream flows were exceedingly low during the Burrhead Chub reproductive season. Furthermore, extensive historical collections taken during 1950–1961 in the Guadalupe River revealed a decline in relative abundance in upstream reaches as the drought continued. Based on these data, we hypothesize that Burrhead Chub experienced range‐wide declines associated with historical drought conditions in desiccated stream fragments. Following the drought, stream flows recovered but recolonization by Burrhead Chub was blocked by impoundments in many fragments. These findings support previous linkages between stream connectivity, flow magnitude, and the persistence of fish populations while providing insight into the mechanisms driving freshwater fish declines in the plains of North America.
Sport and exercise psychology research and Olympic success: An analytical and correlational investigation
Authors: Szabo Attila
Published: August 2013

The aim of the current inquiry was to identify the national origin of scholars who lead the work in the area of Sport and Exercise Psychology, and to examine whether their research output is connected to the Olympic success of their national athletes. Consequently, the two specialised journals with the highest impact factors in this field were examined for the origin of publications throughout 11 years for authors' national affiliations. Subsequently, the link between national research output and Olympic medals was examined. The results revealed that over 50% of the publications originate from Canada, the UK and the USA. National research output in Sport and Exercise Psychology was correlated with the number of Olympic medals; the proportion of shared variance was 42% and 57%, respectively, in the two journals. Nevertheless, it is posited that the observed link is primarily due to other factors that ought to be examined in future research.
Effects of exploitation on an overabundant species: the lesser snow goose predicament
Authors: Koons David N. , Rockwell Robert F. , Aubry Lise M.
Published: August 2013

Invasive and overabundant species are an increasing threat to biodiversity and ecosystem functioning world‐wide. As such, large amounts of money are spent each year on attempts to control them. These efforts can, however, be thwarted if exploitation is compensated demographically or if populations simply become too numerous for management to elicit an effective and rapid functional response.

We examined the influence of these mechanisms on cause‐specific mortality in lesser snow geese using multistate capture–reencounter methods. The abundance and destructive foraging behaviours of snow geese have created a trophic cascade that reduces (sub‐)Arctic plant, insect and avian biodiversity, bestowing them the status of ‘overabundant’.

Historically, juvenile snow geese suffered from density‐related degradation of their saltmarsh brood‐rearing habitat. This allowed harvest mortality to be partially compensated by non‐harvest mortality (process correlation between mortality sources:ρ = −0·47; 90%BCI: −0·72 to −0·04). Snow goose family groups eventually responded to their own degradation of habitat by dispersing to non‐degraded areas. This relaxed the pressure of density dependence on juvenile birds, but without this mechanism for compensation, harvest began to have an additive effect on overall mortality (ρ = 0·60; 90%BCI: −0·06 to 0·81). In adults, harvest had an additive effect on overall mortality throughout the 42‐year study (ρ = 0·24; 90%BCI: −0·59 to 0·67).

With the aim of controlling overabundant snow geese, theConservationOrder amendment to theInternationalMigratoryBirdTreaty was implemented inFebruary of 1999 to allow for harvest regulations that had not been allowed since the early 1900s (e.g. a spring harvest season, high or unlimited bag limits and use of electronic calls and unplugged shotguns). Although harvest mortality momentarily increased following these actions, the increasing abundance of snow geese has since induced a state of satiation in harvest that has driven harvest rates below the long‐term average. More aggressive actions will thus be needed to halt the growth and spread of the devastating trophic cascade that snow geese have triggered.

Our approach to investigating the impacts of population control efforts on cause‐specific mortality will help guide more effective management of invasive and overabundant species world‐wide.
Plant β‐diversity in fragmented rain forests: testing floristic homogenization and differentiation hypotheses
Authors: Arroyo‐Rodríguez Víctor , Rös Matthias , Escobar Federico , Melo Felipe P. L. , Santos Bráulio A. , Tabarelli Marcelo , Chazdon Robin
Published: August 2013

Land‐use change is the main driver of global biodiversity loss, but its relative impact on species turnover (β‐diversity) across multiple spatial scales remains unclear. Plant communities in fragmented rain forests can undergo declines (floristic homogenization) or increases (floristic differentiation) in β‐diversity.

We tested these alternative hypotheses analysing a large vegetation data base from a hierarchically nested sampling design (450 plots in 45 forest patches in 3 landscapes with different deforestation levels) at Los Tuxtlas rain forest, Mexico. Differences in β‐diversity across spatial scales (i.e. among plots, among patches, and among landscapes) were analysed using multiplicative diversity decompositions of Hill numbers.

Plant β‐diversity among plots within forest patches decreased in landscapes with higher deforestation levels, leading to floristic homogenization within patches. This homogenization process can be explained by the loss of rare and shade‐tolerant plant species, and the recruitment and dominance of disturbance‐adapted species, and can limit the accumulation of species (γ‐diversity) in landscapes with higher deforestation.

Nevertheless, the landscape with the highest deforestation level showed the highest floristic differentiation among patches. This landscape showed the greatest isolation distances between patches; a landscape spatial pattern that can limit the interchange of seeds (and species) between patches. Because the study patches are undergoing secondary succession following disturbances (e.g. logging, edge effects), different disturbance regimes and increased distance among patches could lead to higher β‐diversity.

Synthesis. These findings indicate that patterns of floristic homogenization and differentiation depend on the landscape configuration and on the spatial scale of analysis. At the landscape scale, our results suggest that, in accordance with non‐equilibrium dynamics and the landscape‐divergence hypothesis, patches located in landscapes with different forest cover and different connectivity can experience contrasting successional pathways due to increasing levels of compositional differentiation between patches. These novel findings add further uncertainties to the maintenance of biodiversity in severely deforested tropical landscapes and have key ecological implications for biodiversity conservation planning.