bluuebunny/crossref_metadata_2025 huggingface dataset:
Atypical visual and somatosensory adaptation in schizophrenia-spectrum disorders
Authors: Andrade G N , Butler J S , Peters G A , Molholm S , Foxe J J
Published: May 2016

Neurophysiological investigations in patients with schizophrenia consistently show early sensory processing deficits in the visual system. Importantly, comparable sensory deficits have also been established in healthy first-degree biological relatives of patients with schizophrenia and in first-episode drug-naive patients. The clear implication is that these measures are endophenotypic, related to the underlying genetic liability for schizophrenia. However, there is significant overlap between patient response distributions and those of healthy individuals without affected first-degree relatives. Here we sought to develop more sensitive measures of sensory dysfunction in this population, with an eye to establishing endophenotypic markers with better predictive capabilities. We used a sensory adaptation paradigm in which electrophysiological responses to basic visual and somatosensory stimuli presented at different rates (ranging from 250 to 2550 ms interstimulus intervals, in blocked presentations) were compared. Our main hypothesis was that adaptation would be substantially diminished in schizophrenia, and that this would be especially prevalent in the visual system. High-density event-related potential recordings showed amplitude reductions in sensory adaptation in patients with schizophrenia (N=15 Experiment 1, N=12 Experiment 2) compared with age-matched healthy controls (N=15 Experiment 1, N=12 Experiment 2), and this was seen for both sensory modalities. At the individual participant level, reduced adaptation was more robust for visual compared with somatosensory stimulation. These results point to significant impairments in short-term sensory plasticity across sensory modalities in schizophrenia. These simple-to-execute measures may prove valuable as candidate endophenotypes and will bear follow-up in future work.
Candidate gene networks and blood biomarkers of methamphetamine-associated psychosis: an integrative RNA-sequencing report
Authors: Breen M S , Uhlmann A , Nday C M , Glatt S J , Mitt M , Metsalpu A , Stein D J , Illing N
Published: May 2016

The clinical presentation, course and treatment of methamphetamine (METH)-associated psychosis (MAP) are similar to that observed in schizophrenia (SCZ) and subsequently MAP has been hypothesized as a pharmacological and environmental model of SCZ. However, several challenges currently exist in diagnosing MAP accurately at the molecular and neurocognitive level before the MAP model can contribute to the discovery of SCZ biomarkers. We directly assessed subcortical brain structural volumes and clinical parameters of MAP within the framework of an integrative genome-wide RNA-Seq blood transcriptome analysis of subjects diagnosed with MAP (N=10), METH dependency without psychosis (MA;N=10) and healthy controls (N=10). First, we identified discrete groups of co-expressed genes (that is, modules) and tested them for functional annotation and phenotypic relationships to brain structure volumes, life events and psychometric measurements. We discovered one MAP-associated module involved in ubiquitin-mediated proteolysis downregulation, enriched with 61 genes previously found implicated in psychosis and SCZ across independent blood and post-mortem brain studies using convergent functional genomic (CFG) evidence. This module demonstrated significant relationships with brain structure volumes including the anterior corpus callosum (CC) and the nucleus accumbens. Furthermore, a second MAP and psychoticism-associated module involved in circadian clock upregulation was also enriched with 39 CFG genes, further associated with the CC. Subsequently, a machine-learning analysis of differentially expressed genes identified single blood-based biomarkers able to differentiate controls from methamphetamine dependents with 87% accuracy and MAP from MA subjects with 95% accuracy. CFG evidence validated a significant proportion of these putative MAP biomarkers in independent studies includingCLN3,FBP1,TBC1D2andZNF821(RNA degradation),ELK3andSINA3(circadian clock) andPIGFandUHMK1(ubiquitin-mediated proteolysis). Finally, focusing analysis on brain structure volumes revealed significantly lower bilateral hippocampal volumes in MAP subjects. Overall, these results suggest similar molecular and neurocognitive mechanisms underlying the pathophysiology of psychosis and SCZ regardless of substance abuse and provide preliminary evidence supporting the MAP paradigm as an exemplar for SCZ biomarker discovery.
bcTol: a highly water-soluble biradical for efficient dynamic nuclear polarization of biomolecules
Authors: Jagtap Anil P. , Geiger Michel-Andreas , Stöppler Daniel , Orwick-Rydmark Marcella , Oschkinat Hartmut , Sigurdsson Snorri Th.
Published: May 2016

The crystalline spirocyclohexanolyl-derived nitroxide biradical bcTol was shown to have unprecedented solubility in glycerol/water mixtures and display a large DNP enhancement (244) for a sample of a microcrystalline SH3 protein by solid-state NMR.
Design and fabrication of clustered rugged ZnO nanotube films with condensate microdrop self-propelling function
Authors: Chen Ying , Jing Zhihong
Published: May 2016

We design and fabricate a type of condensate microdrop self-propelling (CMDSP) clustered rugged nanotube film, which is achieved by two-step electrodeposition and low-surface-energy silane modification.
Pharmaceutical cocrystals: walking the talk
Authors: Bolla Geetha , Nangia Ashwini
Published: May 2016

From Saridon to Entresto: the journey of pharmaceuticals from the first drug–drug combination of propyphenazone and pyrithyldione in 1937 (left) to the most recent monosodium sacubitril and disodium valsartan in 2015 (right).
Shrink wrapping redox-active crystals of polyoxometalate open frameworks with organic polymers via crystal induced polymerisation
Authors: Takashima Yohei , Miras Haralampos N. , Glatzel Stefan , Cronin Leroy
Published: May 2016

Redox active POM network, (C4H10NO)40[W72Mn12Ge7O268], induced the crystal surface polymerization, driven by Mn(iii) centres embedded on the framework. Guest-exchange or osmotically driven tube growth studies showed that the crystal surface modulation can finely tune the network's properties.
Internal conversion and intersystem crossing pathways in UV excited, isolated uracils and their implications in prebiotic chemistry
Authors: Yu Hui , Sanchez-Rodriguez Jose A. , Pollum Marvin , Crespo-Hernández Carlos E. , Mai Sebastian , Marquetand Philipp , González Leticia , Ullrich Susanne
Published: May 2016

The photodynamic properties of molecules determine their ability to survive in harsh radiation environments.
Correlating structure and electronic band-edge properties in organolead halide perovskites nanoparticles
Authors: Zhu Qiushi , Zheng Kaibo , Abdellah Mohamed , Generalov Alexander , Haase Dörthe , Carlson Stefan , Niu Yuran , Heimdal Jimmy , Engdahl Anders , Messing Maria E. , Pullerits Tonu , Canton Sophie E.
Published: May 2016

Lattice strain modifies the subtle stereochemical activity of the Pb2+ lone-pair in organolead halide perovskites (OHLP) nanoparticles.
Morphology-controlled syntheses of α-MnO2 for electrochemical energy storage
Authors: He Weidong , Yang Wenjin , Wang Chenggang , Deng Xiaolong , Liu Baodan , Xu Xijin
Published: May 2016

The morphological transformations of MnO2 and morphology-dependent electrochemical performance were systematically investigated.
A mononuclear nonheme cobalt(iii)–hydroperoxide complex with an amphoteric reactivity in electrophilic and nucleophilic oxidative reactions
Authors: Tcho Woon-Young , Wang Bin , Lee Yong-Min , Cho Kyung-Bin , Shearer Jason , Nam Wonwoo
Published: May 2016

A mononuclear nonheme cobalt(iii)–hydroperoxide complex bearing a tetramethylated cyclam ligand, which is synthesized by the protonation of its corresponding cobalt(iii)–peroxide complex, exhibits an amphoteric reactivity in electrophilic and nucleophilic oxidative reactions.
Binding of oxime group to uranyl ion
Authors: Tsantis Sokratis T. , Zagoraiou Eirini , Savvidou Aikaterini , Raptopoulou Catherine P. , Psycharis Vassilis , Szyrwiel Lukasz , Hołyńska Małgorzata , Perlepes Spyros P.
Published: May 2016

The reactions of uranyl sources with 2-pyridyl ketoximes give a variety of products; a common structural motif in the complexes containing the anionic ligands is the η2 coordination mode of the deprotonated oxime group and the non-participation of the pyridyl nitrogen in coordination.
Asymmetric axonal edge guidance: a new paradigm for building oriented neuronal networks
Authors: Renault Renaud , Durand Jean-Baptiste , Viovy Jean-Louis , Villard Catherine
Published: May 2016

We present a novel kind of directional axon guides for brain-on-a-chip applications. The axonal directional selectivity is created by rerouting axons growing in the unwanted direction back to their original compartment while leaving the other growth direction unaffected.
Imidazolylpyridine-In(OTf)3catalyzed enantioselective allylation of ketimines derived from isatins
Authors: Chen Tingting , Cai Chun
Published: May 2016

An enantioselective In(OTf)3-catalyzed allylation of ketimines derived from isatins in the presence of an imidazolylpyridine ligand is described.
First total synthesis of (+)-broussonetine W: glycosidase inhibition of natural product & analogs
Authors: Song Ying-Ying , Kinami Kyoko , Kato Atsushi , Jia Yue-Mei , Li Yi-Xian , Fleet George W. J. , Yu Chu-Yi
Published: May 2016

Broussonetine W and its 11 analogues have been first synthesized from cyclic nitrones and assayed as potential gycosidase inhibitors.
A series of dendronized hyperbranched polymers with dendritic chromophore moieties in the periphery: convenient synthesis and large nonlinear optical effects
Authors: Yang Haitao , Tang Runli , Wu Wenbo , Liu Wei , Guo Qing , Liu Yingliang , Xu Shengang , Cao Shaokui , Li Zhen
Published: May 2016

Excellent optical transparency and NLO coefficients were achieved by introducing dendritic chromophore moieties to the periphery of dendronized hyperbranched polymers.
Influence of regiochemistry in the selective dispersion of metallic carbon nanotubes using electron poor conjugated polymers
Authors: Bodnaryk W. J. , Rice N. A. , Adronov A.
Published: May 2016

Nitration of a poly(fluorene-co-phenylene) backbone influences its selectivity for semiconducting versus metallic single-walled carbon nanotubes, and the regiochemistry of the nitro group has a significant impact.
Is the oxygen atom static or dynamic? The effect of generating animations on students' mental models of atomic structure
Authors: Akaygun Sevil
Published: May 2016

Visualizing the chemical structure and dynamics of particles has been challenging for many students; therefore, various visualizations and tools have been used in chemistry education. For science educators, it has been important to understand how students visualize and represent particular phenomena –i.e., their mental models– to design more effective learning environments. This study aimed to investigate and compare students'staticand dynamic representations of mental models for a fundamental concept of chemistry, atomic structure. Static representations of mental models were expressed as drawings and explanations given on paper, withdynamicones being generated by using animation-developing software. This mixed-method study was implemented in three parts. A total of 523 10th (N= 277) and 11th (246) grade high school students participated in a workshop where they first learned how to use one of three animation-developing software programs (K-Sketch, Chemsense or Pencil;N= 162, 204, 157, respectively), and then prepared an animation of an oxygen atom using that program. Before and after creating the animation, students were asked to draw the structure of the atom and to storyboard the oxygen atom for three seconds. After students generated their animations they were asked to explain their animations in 2–3 minute interviews (N= 324). The static and dynamic representations of mental models were compared statistically by the Wilcoxon Signed Rank Test within each group, and they were compared by the Kruskall Wallis Test between the groups. The results of the analysis showed that in all the groups, a significant difference (p= 0.000) between the initial and final static representations of mental models suggested that students modified their mental models towards a more refined and accurate representation of the atomic structure. Regardless of the software program used, students included significantly more dynamic features (p= 0.000) in their static representations of mental models after generating animations than they did initially. No significant difference (p> 0.05) between any of the features was conveyed in static representations of mental models of students who worked with different software programs. In addition, student-generated animations revealed some misconceptions, such as the movement of the parts of the atom or the atom itself besides electrons, which were not detected on paper.
Organogel electrolyte for high-loading silicon batteries
Authors: Cho Yoon-Gyo , Park Hyungmin , Lee Jung-In , Hwang Chihyun , Jeon Yuju , Park Soojin , Song Hyun-Kon
Published: May 2016

A cyanoresin organogel electrolyte, characterized byin situgelation with no initiators or crosslinkers, was used for high-loading silicon batteries of 1.3 mgSicm−2(equivalent to 3.3 mA h cm−2).
An ultra-high-performance anode material for supercapacitors: self-assembled long Co3O4 hollow tube network with multiple heteroatom (C-, N- and S-) doping
Authors: Li Jiangfeng , Zan Guangtao , Wu Qingsheng
Published: May 2016

A novel self-assembled long Co3O4 hollow tube network with multiple heteroatom (C-, N- and S-) doping was prepared for the first time by the combination of hydrothermal and calcination techniques using the eggshell membrane as the template and dopant.
Growth and characterization of Cr doped SnO2 microtubes with resonant cavity modes
Authors: García-Tecedor Miguel , Maestre David , Cremades Ana , Piqueras Javier
Published: May 2016

Cr doped SnO2 microtubes have been fabricated by a thermal evaporation–deposition method.
Model‐independent approach for short‐term electric load forecasting with guaranteed error convergence
Authors: Shen Zhixi , Wu Xiaoqin , Guerrero Josep M. , Song Yongduan
Published: May 2016

High precision short‐term load forecasting is crucial for enhancing safe and effective operation of power systems. This study presents a new method for short‐term load forecasting using the concept of trajectory tracking. Unlike most existing forecasting methods, the proposed one is essentially model independent in that the corresponding forecasting algorithms are derived without the need for the specific load models. Furthermore, based upon Lyapunov stability theory, the prediction error of the proposed method is shown to converge with sufficient accuracy one gives rise to better forecasting performance.
A feminist genealogy of posthuman aesthetics in the visual arts
Authors: Ferrando Francesca
Published: May 2016

This article aims to reassemble a feminist genealogy of the posthuman in the arts, with a specific focus on the visual works conceived by female artists after the rise of what has been retrospectively defined as first-wave Feminism. Starting with the main avant-garde movements of the first half of the twentieth century—specifically, Futurism, Dadaism and Surrealism—this genealogy analyses the second-wave Feminism of the 1960s and 1970s, with its integral exploration of the body highlighted by performance art. Following this, it takes into account the third-wave Feminism of the 1990s and its radical re-elaboration of the self: from Cyberfeminism and its revisitation of technology, to the artistic insights offered, on the one side, by critical techno-orientalist readings of the futures, and on the other, by the political and social articulations of Afrofuturism and Chicanafuturism. Lastly, this genealogy accesses the ways contemporary female artists are dealing with gender, social media and the notion of embodiment, touching upon elements that will become of key importance in fourth-wave Feminism. This article is published as part of a collection dedicated to multi- and interdisciplinary perspectives on gender studies.
Science, technology and innovation indicators in policy-making: the Nigerian experience
Authors: Siyanbola Willie , Adeyeye Adedamola , Olaopa Olawale , Hassan Omowumi
Published: May 2016

This article provides a critical review of the process of formulating science, technology and innovation (STI) policy in Nigeria using scientific indicators. The attainment of development goals requires a painstaking process of policy-making based on scientific evidence derivable from relevant evidence. However, in many developing countries, there is a gap between policy and development priorities as most policies are not based on scientific facts either because they are unavailable or, where they exist, unreliable. Using a system analysis framework, the article brings into perspective the fundamental role played by STI indicators in providing scientific evidence for designing, formulating and implementing national innovation policy. This can serve as a framework for utilizing scientific evidence in policy-making in a developing country context. This article is published as part of a thematic collection on scientific advice to governments.
Perspective: Defining and quantifying the role of dynamics in enzyme catalysis
Authors: Warshel Arieh , Bora Ram Prasad
Published: May 2016

Enzymes control chemical reactions that are key to life processes, and allow them to take place on the time scale needed for synchronization between the relevant reaction cycles. In addition to general interest in their biological roles, these proteins present a fundamental scientific puzzle, since the origin of their tremendous catalytic power is still unclear. While many different hypotheses have been put forward to rationalize this, one of the proposals that has become particularly popular in recent years is the idea that dynamical effects contribute to catalysis. Here, we present a critical review of the dynamical idea, considering all reasonable definitions of what does and does not qualify as a dynamical effect. We demonstrate that no dynamical effect (according to these definitions) has ever been experimentally shown to contribute to catalysis. Furthermore, the existence of non-negligible dynamical contributions to catalysis is not supported by consistent theoretical studies. Our review is aimed, in part, at readers with a background in chemical physics and biophysics, and illustrates that despite a substantial body of experimental effort, there has not yet been any study that consistently established a connection between an enzyme’s conformational dynamics and a significant increase in the catalytic contribution of the chemical step. We also make the point that the dynamical proposal is not a semantic issue but a well-defined scientific hypothesis with well-defined conclusions.
Flow around a helically twisted elliptic cylinder
Authors: Kim Woojin , Lee Jungil , Choi Haecheon
Published: May 2016

In the present study, we conduct unsteady three-dimensional simulations of flows around a helically twisted elliptic (HTE) cylinder at the Reynolds numbers of 100 and 3900, based on the free-stream velocity and square root of the product of the lengths of its major and minor axes. A parametric study is conducted for Re = 100 by varying the aspect ratio (AR) of the elliptic cross section and the helical spanwise wavelength (λ). Depending on the values of AR and λ, the flow in the wake contains the characteristic wavelengths of λ, 2λ, 6λ, or even longer than 60λ, showing a wide diversity of flows in the wake due to the shape change. The drag on the optimal (i.e., having lowest drag) HTE cylinder (AR = 1.3 and λ = 3.5d) is lower by 18% than that of the circular cylinder, and its lift fluctuations are zero owing to complete suppression of vortex shedding in the wake. This optimal HTE configuration reduces the drag by 23% for Re = 3900 where the wake is turbulent, showing that the HTE cylinder reduces the mean drag and lift fluctuations for both laminar and turbulent flows.
Toward integrated multi-scale pedestal simulations including edge-localized-mode dynamics, evolution of edge-localized-mode cycles, and continuous fluctuations
Authors: Xu X. Q. , Xia T. Y. , Yan N. , Liu Z. X. , Kong D. F. , Diallo A. , Groebner R. J. , Hubbard A. E. , Hughes J. W.
Published: May 2016

The high-fidelity BOUT++ two-fluid code suite has demonstrated significant recent progress toward integrated multi-scale simulations of tokamak pedestal, including Edge-Localized-Mode (ELM) dynamics, evolution of ELM cycles, and continuous fluctuations, as observed in experiments. Nonlinear ELM simulations show three stages of an ELM event: (1) a linear growing phase; (2) a fast crash phase; and (3) a slow inward turbulence spreading phase lasting until the core heating flux balances the ELM energy loss and the ELM is terminated. A new coupling/splitting model has been developed to perform simulations of multi-scale ELM dynamics. Simulation tracks five ELM cycles for 10 000 Alfvén times for small ELMs. The temporal evolution of the pedestal pressure is similar to that of experimental measurements for the pedestal pressure profile collapses and recovers to a steep gradient during ELM cycles. To validate BOUT++ simulations against experimental data and develop physics understanding of the fluctuation characteristics for different tokamak operation regimes, both quasi-coherent fluctuations (QCFs) in ELMy H-modes and Weakly Coherent Modes in I-modes have been simulated using three dimensional 6-field 2-fluid electromagnetic model. The H-mode simulation results show that (1) QCFs are localized in the pedestal region having a predominant frequency at f≃300−400 kHz and poloidal wavenumber at kθ≃0.7 cm−1, and propagate in the electron diamagnetic direction in the laboratory frame. The overall signatures of simulation results for QCFs show good agreement with C-Mod and DIII-D measurements. (2) The pedestal profiles giving rise to QCFs are near the marginal instability threshold for ideal peeling-ballooning modes for both C-Mod and DIII-D, while the collisional electromagnetic drift-Alfvén wave appears to be dominant for DIII-D. (3) Particle diffusivity is either smaller than the heat diffusivity for DIII-D or similar to the heat diffusivity for C-Mod. Key I-mode simulation results are that (1) a strong instability exists at n≥20 for resistive ballooning mode and drift-Alfvén wave; (2) the frequency spectrum of nonlinear BOUT++ simulation features a peak around 300 kHz for the mode number n = 20, consistent with a reflectometer measurement at nearby position; (3) the calculated particle diffusivity is larger than the calculated heat diffusivity, which is consistent with a key feature of the I-mode pedestal with no particle barrier.
“Glass-like” thermal conductivity gradually induced in thermoelectric Sr8Ga16Ge30 clathrate by off-centered guest atoms
Authors: Christensen Sebastian , Schmøkel Mette Stokkebro , Borup Kasper Andersen , Madsen Georg K. H. , McIntyre Garry J. , Capelli Silvia C. , Christensen Mogens , Iversen Bo Brummerstedt
Published: May 2016

The origin of the “glass-like” plateau in thermal conductivity of inorganic type I clathrates has been debated for more than a decade. Here, it is demonstrated that the low temperature thermal conductivity of Sr8Ga16Ge30 can be controlled by the synthesis method: A flux-grown sample has a “glass-like” plateau in thermal conductivity at low temperature, while a zone-melted sample instead has a crystalline peak. A combination of flux-growth and zone-melting produces an intermediate thermal conductivity. In a comprehensive study of three single crystal samples, it is shown by neutron diffraction that the transition from crystalline peak to “glass-like” plateau is related to an increase in Sr guest atom off-centering distance from 0.24 Å to 0.43 Å. By modifying ab initio calculated force constants for the guest atom to an isotropic model, we reproduce both measured heat capacity and inelastic neutron scattering data. The transition from peak to plateau in the thermal conductivity can be modeled by a combined increase of Rayleigh and disorder scattering. Measurement of heat capacity refutes simple models for tunneling of Sr between off-center sites. Furthermore, the electronic properties of the same samples are characterized by Hall carrier density, Seebeck coefficient, and resistivity. The present comprehensive analysis excludes tunneling and charge carrier scattering as dominant contributors to the “glass-like” plateau. The increased guest atom off-centering distance controlled by synthesis provides a possible microscopic mechanism for reducing the low temperature thermal conductivity of clathrates.
Some bifurcation routes to chaos of thermocapillary convection in two-dimensional liquid layers of finite extent
Authors: Li K. , Xun B. , Hu W. R.
Published: May 2016

As a part of the preliminary studies for the future space experiment (Zona-K) in the Russian module of the International Space Station, some bifurcation routes to chaos of thermocapillary convection in two-dimensional liquid layers filled with 10 cSt silicone oil have been numerically studied in this paper. As the laterally applied temperature difference is raised, variations in the spatial structure and temporal evolution of the thermocapillary convection and a complex sequence of transitions are observed. The results show that the finite extent of the liquid layer significantly influences the tempo-spatial evolution of the thermocapillary convection. Moreover, the bifurcation route of the thermocapillary convection changes very sensitively by the aspect ratio of the liquid layer. With the increasing Reynolds number (applied temperature difference), the steady thermocapillary convection experiences two consecutive transitions from periodic oscillatory state to quasi-periodic oscillatory state with frequency-locking before emergence of chaotic convection in a liquid layer of aspect ratio 14.25, and the thermocapillary convection undergoes period-doubling cascades leading to chaotic convection in a liquid layer of aspect ratio 13.0.
Path optimization by a variational reaction coordinate method. II. Improved computational efficiency through internal coordinates and surface interpolation
Authors: Birkholz Adam B. , Schlegel H. Bernhard
Published: May 2016

Reaction path optimization is being used more frequently as an alternative to the standard practice of locating a transition state and following the path downhill. The Variational Reaction Coordinate (VRC) method was proposed as an alternative to chain-of-states methods like nudged elastic band and string method. The VRC method represents the path using a linear expansion of continuous basis functions, allowing the path to be optimized variationally by updating the expansion coefficients to minimize the line integral of the potential energy gradient norm, referred to as the Variational Reaction Energy (VRE) of the path. When constraints are used to control the spacing of basis functions and to couple the minimization of the VRE with the optimization of one or more individual points along the path (representing transition states and intermediates), an approximate path as well as the converged geometries of transition states and intermediates along the path are determined in only a few iterations. This algorithmic efficiency comes at a high per-iteration cost due to numerical integration of the VRE derivatives. In the present work, methods for incorporating redundant internal coordinates and potential energy surface interpolation into the VRC method are described. With these methods, the per-iteration cost, in terms of the number of potential energy surface evaluations, of the VRC method is reduced while the high algorithmic efficiency is maintained.
Exact relativistic expressions for polarization of incoherent Thomson scattering
Authors: Mirnov V. V. , Den Hartog D. J. , Parke E.
Published: May 2016

We present a derivation of the degree of polarization for incoherent Thomson scattering (TS) using Mueller matrix formalism. An exact analytic solution is obtained for spectrum-integrated matrix elements. The solution is valid for the full range of incident polarizations, scattering angles, and electron thermal motion from non-relativistic to ultra-relativistic. It is based on a newly developed theoretical model, a finite transit time (FTT) correction to previous theoretical work on TS polarization. The Mueller matrix elements are substantially different from previous calculations without the FTT correction, even to the lowest linear order in Te/mec2≪1. Mathematically, the derivation is a unique example of fully analytical integration of the 3D scattering operator over a relativistic Maxwellian distribution function; experimentally, the results have application to the use of the polarization properties of Thomson scattered light as a method of electron temperature measurement. The results can also be used as a reliable tool for benchmarking and verification of numerical codes for frequency resolved properties of TS polarization.
Theory for the anomalous electron transport in Hall effect thrusters. I. Insights from particle-in-cell simulations
Authors: Lafleur T. , Baalrud S. D. , Chabert P.
Published: May 2016

Using a 1D particle-in-cell simulation with perpendicular electric, E0, and magnetic, B0, fields, and modelling the azimuthal direction (i.e., the E0 × B0 direction), we study the cross-field electron transport in Hall effect thrusters (HETs). For low plasma densities, the electron transport is found to be well described by classical electron-neutral collision theory, but at sufficiently high densities (representative of typical HETs), a strong instability is observed to significantly enhance the electron mobility, even in the absence of electron-neutral collisions. This instability is associated with correlated high-frequency (of the order of MHz) and short-wavelength (of the order of mm) fluctuations in both the electric field and the plasma density, which are shown to be the cause of the anomalous transport. Saturation of the instability is observed to occur due to a combination of ion-wave trapping in the E0 × B0 direction, and convection in the E0 direction.
Theory for the anomalous electron transport in Hall effect thrusters. II. Kinetic model
Authors: Lafleur T. , Baalrud S. D. , Chabert P.
Published: May 2016

In Paper I [T. Lafleur et al., Phys. Plasmas 23, 053502 (2016)], we demonstrated (using particle-in-cell simulations) the definite correlation between an anomalously high cross-field electron transport in Hall effect thrusters (HETs), and the presence of azimuthal electrostatic instabilities leading to enhanced electron scattering. Here, we present a kinetic theory that predicts the enhanced scattering rate and provides an electron cross-field mobility that is in good agreement with experiment. The large azimuthal electron drift velocity in HETs drives a strong instability that quickly saturates due to a combination of ion-wave trapping and wave-convection, leading to an enhanced mobility many orders of magnitude larger than that expected from classical diffusion theory. In addition to the magnetic field strength, B0, this enhanced mobility is a strong function of the plasma properties (such as the plasma density) and therefore does not, in general, follow simple 1/B02 or 1/B0 scaling laws.
An improved neoclassical drift-magnetohydrodynamical fluid model of helical magnetic island equilibria in tokamak plasmas
Authors: Fitzpatrick Richard
Published: May 2016

The effect of the perturbed ion polarization current on the stability of neoclassical tearing modes in tokamak plasmas is calculated using an improved, neoclassical, four-field, drift-magnetohydrodynamical model. The calculation involves the self-consistent determination of the pressure and scalar electric potential profiles in the vicinity of the associated magnetic island chain, which allows the chain's propagation velocity to be fixed. Two regimes are considered. First, a regime in which neoclassical ion poloidal flow damping is not strong enough to enhance the magnitude of the polarization current (relative to that found in slab geometry). Second, a regime in which neoclassical ion poloidal flow damping is strong enough to significantly enhance the magnitude of the polarization current. In both regimes, two types of solution are considered. First, a freely rotating solution (i.e., an island chain that is not interacting with a static, resonant, magnetic perturbation). Second, a locked solution (i.e., an island chain that has been brought to rest in the laboratory frame via interaction with a static, resonant, magnetic perturbation). In all cases, the polarization current is found to be either always stabilizing or stabilizing provided that ηi≡dlnTi/dlnne does not exceed some threshold value. In certain ranges of ηi, the polarization current is found to have a stabilizing effect on a freely rotating island, but a destabilizing effect on a corresponding locked island.
Non-perturbative measurement of cross-field thermal diffusivity reduction at the O-point of 2/1 neoclassical tearing mode islands in the DIII-D tokamak
Authors: Bardóczi L. , Rhodes T. L. , Carter T. A. , Crocker N. A. , Peebles W. A. , Grierson B. A.
Published: May 2016

Neoclassical tearing modes (NTMs) often lead to the decrease of plasma performance and can lead to disruptions, which makes them a major impediment in the development of operating scenarios in present toroidal fusion devices. Recent gyrokinetic simulations predict a decrease of plasma turbulence and cross-field transport at the O-point of the islands, which in turn affects the NTM dynamics. In this paper, a heat transport model of magnetic islands employing spatially non-uniform cross-field thermal diffusivity (χ⊥) is presented. This model is used to derive χ⊥ at the O-point from electron temperature data measured across 2/1 NTM islands in DIII-D. It was found that χ⊥ at the O-point is 1 to 2 orders of magnitude smaller than the background plasma transport, in qualitative agreement with gyrokinetic predictions. As the anomalously large values of χ⊥ are often attributed to turbulence driven transport, the reduction of the O-point χ⊥ is consistent with turbulence reduction found in recent experiments. Finally, the implication of reduced χ⊥ at the O-point on NTM dynamics was investigated using the modified Rutherford equation that predicts a significant effect of reduced χ⊥ at the O-point on NTM saturation.
Electron temperature and density measurements of laser induced germanium plasma
Authors: Shakeel Hira , Arshad Saboohi , Haq S. U. , Nadeem Ali
Published: May 2016

The germanium plasma produced by the fundamental harmonics (1064 nm) of Nd:YAG laser in single and double pulse configurations have been studied spectroscopically. The plasma is characterized by measuring the electron temperature using the Boltzmann plot method for neutral and ionized species and electron number density as a function of laser irradiance, ambient pressure, and distance from the target surface. It is observed that the plasma parameters have an increasing trend with laser irradiance (9–33 GW/cm2) and with ambient pressure (8–250 mbar). However, a decreasing trend is observed along the plume length up to 4.5 mm. The electron temperature and electron number density are also determined using a double pulse configuration, and their behavior at fixed energy ratio and different interpulse delays is discussed.
Rebound of continuous droplet streams from an immiscible liquid pool
Authors: Doak William J. , Laiacona Danielle M. , German Guy K. , Chiarot Paul R.
Published: May 2016

We report on the rebound of high velocity continuous water droplet streams from the surface of an immiscible oil pool. The droplets have diameters and velocities of less than 90 μm and 15 m/s, respectively, and were created at frequencies up to 60 kHz. The impact and rebound of continuous droplet streams at this scale and velocity have been largely unexplored. This regime bridges the gap between single drop and jet impacts. The impinging droplets create a divot at the surface of the oil pool that had a common characteristic shape across a wide-range of droplet and oil properties. After impact, the reflected droplets maintain the same uniformity and periodicity of the incoming droplets but have significantly lower velocity and kinetic energy. This was solely attributed to the generation of a flow induced in the viscous oil pool by the impacting droplets. Unlike normally directed impact of millimeter-scale droplets with a solid surface, our results show that an air film does not appear to be maintained beneath the droplets during impact. This suggests direct contact between the droplets and the surface of the oil pool. A ballistic failure limit, correlated with the Weber number, was identified where the rebound was suppressed and the droplets were driven through the oil surface. A secondary failure mode was identified for aperiodic incoming streams. Startup effects and early time dynamics of the rebounding droplet stream were also investigated.
Spectra and probability distributions of thermal flux in turbulent Rayleigh-Bénard convection
Authors: Pharasi Hirdesh K. , Kumar Deepesh , Kumar Krishna , Bhattacharjee Jayanta K.
Published: May 2016

The spectra of turbulent heat flux H(k) in Rayleigh-Bénard convection with and without uniform rotation are presented. The spectrum H(k) scales with wave number k as ∼k−2. The scaling exponent is almost independent of the Taylor number Ta and Prandtl number Pr for higher values of the reduced Rayleigh number r (>103). The exponent, however, depends on Ta and Pr for smaller values of r (<103). The probability distribution functions of the local heat fluxes are non-Gaussian and have exponential tails.
Tight-binding approximations to time-dependent density functional theory — A fast approach for the calculation of electronically excited states
Authors: Rüger Robert , van Lenthe Erik , Heine Thomas , Visscher Lucas
Published: May 2016

We propose a new method of calculating electronically excited states that combines a density functional theory based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed time-dependent density functional theory TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive TD-DFT calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB.
Simulation of the single-vibronic-level emission spectra of HAsO and DAsO
Authors: Mok Daniel K. W. , Lee Edmond P. F. , Dyke John M.
Published: May 2016

The single-vibronic-level (SVL) emission spectra of HAsO and DAsO have been simulated by electronic structure/Franck-Condon factor calculations to confirm the spectral molecular carrier and to investigate the electronic states involved. Various multi-reference (MR) methods, namely, NEVPT2 (n-electron valence state second order perturbation theory), RSPT2-F12 (explicitly correlated Rayleigh-Schrodinger second order perturbation theory), and MRCI-F12 (explicitly correlated multi-reference configuration interaction) were employed to compute the geometries and relative electronic energies for the X̃1A′ and Ã1A″ states of HAsO. These are the highest level calculations on these states yet reported. The MRCI-F12 method gives computed T0 (adiabatic transition energy including zero-point energy correction) values, which agree well with the available experimental T0 value much better than previously computed values and values computed with other MR methods in this work. In addition, the potential energy surfaces of the X̃1A′ and Ã1A″ states of HAsO were computed using the MRCI-F12 method. Franck-Condon factors between the two states, which include anharmonicity and Duschinsky rotation, were then computed and used to simulate the recently reported SVL emission spectra of HAsO and DAsO [R. Grimminger and D. J. Clouthier, J. Chem. Phys. 135, 184308 (2011)]. Our simulated SVL emission spectra confirm the assignments of the molecular carrier, the electronic states involved, and the vibrational structures observed in the SVL emission spectra but suggest a loss of intensity in the reported experimental spectra at the low emission energy region almost certainly due to a loss of responsivity near the cutoff region (∼800 nm) of the detector used. Computed and experimentally derived re (equilibrium) and/or r0 {the (0,0,0) vibrational level} geometries of the two states of HAsO are discussed.
High-frequency sound wave propagation in binary gas mixtures flowing through microchannels
Authors: Bisi M. , Lorenzani S.
Published: May 2016

The propagation of high-frequency sound waves in binary gas mixtures flowing through microchannels is investigated by using the linearized Boltzmann equation based on a Bhatnagar-Gross-Krook (BGK)-type approach and diffuse reflection boundary conditions. The results presented refer to mixtures whose constituents have comparable molecular mass (like Ne-Ar) as well as to disparate-mass gas mixtures (composed of very heavy plus very light molecules, like He-Xe). The sound wave propagation model considered in the present paper allows to analyze the precise nature of the forced-sound modes excited in different gas mixtures.
Non-linear theory of a cavitated plasma wake in a plasma channel for special applications and control
Authors: Thomas Johannes , Kostyukov Igor Yu. , Pronold Jari , Golovanov Anton , Pukhov Alexander
Published: May 2016

We introduce a complete semi-analytical model for a cavitated electron wake driven by an electron beam in a radially inhomogeneous plasma. The electron response to the driver, dynamics of electrons in a thin sheath surrounding the cavity, as well as accelerating and focusing fields inside the cavity are calculated in the quasistatic approximation. Our theory holds for arbitrary radial density profiles and reduces to known models in the limit of a homogeneous plasma. A free-propagating blow-out in an evacuated channel experiences longitudinal squeezing, qualitatively the same as observed in particle-in-cell simulations for the laser pulse-driven case [Pukhov et al., Phys. Rev. Lett. 113, 245003 (2014)]. Our model also permits qualitative interpretation of the earlier observed cancellation of the focusing gradient in the cavity [Pukhov et al., Phys. Rev. Lett. 113, 245003 (2014)]. In this work, we show the underlying mechanism that causes the radial fields in the vacuum part of a channel to become defocussing.
The effect of electron inertia in Hall-driven magnetic field penetration in electron-magnetohydrodynamics
Authors: Richardson A. S. , Angus J. R. , Swanekamp S. B. , Rittersdorf I. M. , Ottinger P. F. , Schumer J. W.
Published: May 2016

Magnetic field penetration in electron-magnetohydrodynamics (EMHD) can be driven by density gradients through the Hall term [Kingsep et al., Sov. J. Plasma Phys. 10, 495 (1984)]. Particle-in-cell simulations have shown that a magnetic front can go unstable and break into vortices in the Hall-driven EMHD regime. In order to understand these results, a new fluid model had been derived from the Ly/Ln≪1 limit of EMHD, where Ly is the length scale along the front and Ln is the density gradient length scale. This model is periodic in the direction along the magnetic front, which allows the dynamics of the front to be studied independently of electrode boundary effects that could otherwise dominate the dynamics. Numerical solutions of this fluid model are presented that show for the first time the relation between Hall-driven EMHD, electron inertia, the Kelvin-Helmholtz (KH) instability, and the formation of magnetic vortices. These solutions show that a propagating magnetic front is unstable to the same KH mode predicted for a uniform plasma. This instability causes the electron flow to break up into vortices that are then driven into the plasma with a speed that is proportional to the Hall speed. This demonstrates that, in two-dimensional geometry with sufficiently low collisionality [collision rate ν ≲ vHall/(4δe)], Hall-driven magnetic penetration occurs not as a uniform shock front but rather as vortex-dominated penetration. Once the vortices form, the penetration speed is found to be nearly a factor of two larger than the redicted speed (vHall/2) obtained from Burgers' equation in the one-dimensional limit.
Electric-field-induced magnetization switching in CoFeB/MgO magnetic tunnel junctions with high junction resistance
Authors: Kanai S. , Matsukura F. , Ohno H.
Published: May 2016

We show the electric-field induced magnetization switching for CoFeB/MgO magnetic tunnel junctions with thick MgO barrier layer of 2.8 nm, whose resistance-area product is 176 kΩ μm2, and achieve the small switching energy of 6.3 fJ/bit. The increase of the junction resistance is expected to suppress the energy consumption due to the Joule heating during the switching; however, the energy is still dominated by the Joule energy rather than the charging energy. This is because the junction resistance decreases more rapidly for junctions with thicker MgO as bias voltage increases.
Tunnelling magnetoresistance of the half-metallic compensated ferrimagnet Mn2RuxGa
Authors: Borisov K. , Betto D. , Lau Y.-C. , Fowley C. , Titova A. , Thiyagarajah N. , Atcheson G. , Lindner J. , Deac A. M. , Coey J. M. D. , Stamenov P. , Rode K.
Published: May 2016

Tunnel magnetoresistance ratios of up to 40% are measured between 10 K and 300 K when the highly spin-polarized compensated ferrimagnet, Mn2RuxGa, is integrated into MgO-based perpendicular magnetic tunnel junctions. Temperature and bias dependences of the tunnel magnetoresistance effect, with a sign change near −0.2 V, reflect the structure of the Mn2RuxGa interface density of states. Despite magnetic moment vanishing at a compensation temperature of 200 K for x≈0.8, the tunnel magnetoresistance ratio remains non-zero throughout the compensation region, demonstrating that the spin-transport is governed by one of the Mn sub-lattices only. Broad temperature range magnetic field immunity of at least 0.5 T is demonstrated in the same sample. The high spin polarization and perpendicular magnetic anisotropy make Mn2RuxGa suitable for applications in both non-volatile magnetic random access memory cells and terahertz spin-transfer oscillators.