bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation on cation distribution and luminescence in spinel phase γ-Ga3−δO4 : Sm nanostructures using X-ray absorption spectroscopy
Authors: Sharma Aditya , Varshney Mayora , Shin Hyun-Joon , Chae Keun Hwa , Won Sung Ok
Published: November 2017

In this study, spectroscopic investigations are employed to quantify the Ga distribution over the tetrahedral/octahedral sites and to assimilate the luminescence properties in the barely reported γ-Ga2.67O4 : Sm nanoparticles.
BiOBr/BiOCl/carbon quantum dot microspheres with superior visible light-driven photocatalysis
Authors: Zhao Chenhui , Liang Ying , Li Wei , Tian Yi , Chen Xin , Yin Dezhong , Zhang Qiuyu
Published: November 2017

In this paper, BiOBr/BiOCl/CQDs heterostructure microspheres were successfully synthesized via a facile solvothermal method.
Preparation and properties of lambda-cyhalothrin/polyurethane drug-loaded nanoemulsions
Authors: Qin He , Zhang Hong , Li Lingxiao , Zhou Xiaoteng , Li Junpei , Kan Chengyou
Published: November 2017

A new lambda-cyhalothrin/castor oil-based polyurethane formulation with controlled-release behavior and good foliage adhesion properties is prepared.
SERS detection of microRNA biomarkers for cancer diagnosis using gold-coated paramagnetic nanoparticles to capture SERS-active gold nanoparticles
Authors: Zhang Hao , Yi Yu , Zhou Chunhui , Ying Guoqing , Zhou Xiangdong , Fu Chaopeng , Zhu Yifeng , Shen Youqing
Published: November 2017

A highly sensitive magnetic-capture SERS assay for detecting cancer-related microRNAs was developed by enhancing the formation of SERS “hot spots”.
A fluorenylidene-acridane that becomes dark in color upon grinding – ground state mechanochromism by conformational change
Authors: Suzuki Tsuyoshi , Okada Hiroshi , Nakagawa Takafumi , Komatsu Kazuki , Fujimoto Chikako , Kagi Hiroyuki , Matsuo Yutaka
Published: November 2017

We report mechanochromic color change controlled by conformational change (folded and twisted conformers) of fluorenylidene-acridanes (FAs).
Drying kinetics of water droplets stabilized by surfactant molecules or solid particles in a thin non-volatile oil layer
Authors: Miyazaki Hayato , Inasawa Susumu
Published: November 2017

Types of stabilizers, molecules or particles, hardly affect the drying kinetics of water droplets which is explained by water diffusion models.
Improved performance through tight coupling of redox cycles of sulfur and 2,6-polyanthraquinone in lithium–sulfur batteries
Authors: Lau Ka-Cheong , Shkrob Ilya A. , Dietz Rago Nancy L. , Connell Justin G. , Phelan Daniel , Hu Bin , Zhang Lu , Zhang Zhengcheng , Liao Chen
Published: November 2017

A redox-active polyanthraquinone suppresses polysulfide shuttling in lithium–sulfur batteries by coupling redox reactions of this polymer with the S redox cycle.
Design and synthesis of Janus-structured mutually doped SnO2–Co3O4hollow nanostructures as superior anode materials for lithium-ion batteries
Authors: Park Gi Dae , Lee Jung-Kul , Chan Kang Yun
Published: November 2017

Janus-structured materials are synthesized by spray pyrolysis and a subsequent oxidation process. The synergistic effect of mutual doping of hollow SnO2nanoplates and Co3O4polyhedra, and nanocatalysts of metallic Co resulted in excellent electrochemical performances of the Janus-structured SnO2–Co3O4composite.
The role of chemical structure in indacenodithienothiophene-alt-benzothiadiazole copolymers for high performance organic solar cells with improved photo-stability through minimization of burn-in loss
Authors: Chochos Christos L. , Leclerc Nicolas , Gasparini Nicola , Zimmerman Nicolas , Tatsi Elisavet , Katsouras Athanasios , Moschovas Dimitrios , Serpetzoglou Efthymis , Konidakis Ioannis , Fall Sadiara , Lévêque Patrick , Heiser Thomas , Spanos Michael , Gregoriou Vasilis G. , Stratakis Emmanuel , Ameri Tayebeh , Brabec Christoph J. , Avgeropoulos Apostolos
Published: November 2017

The organic solar cell initial burn-in loss is suppressed via the rational design of the polymer's chemical structure.
Computational biology: deep learning
Authors: Jones William , Alasoo Kaur , Fishman Dmytro , Parts Leopold
Published: November 2017

Deep learning is the trendiest tool in a computational biologist's toolbox. This exciting class of methods, based on artificial neural networks, quickly became popular due to its competitive performance in prediction problems. In pioneering early work, applying simple network architectures to abundant data already provided gains over traditional counterparts in functional genomics, image analysis, and medical diagnostics. Now, ideas for constructing and training networks and even off-the-shelf models have been adapted from the rapidly developing machine learning subfield to improve performance in a range of computational biology tasks. Here, we review some of these advances in the last 2 years.
Integrating the whole from the sum of the parts: vignettes in computational biology
Authors: Skolnick Jeffrey
Published: November 2017

As is typical of contemporary cutting-edge interdisciplinary fields, computational biology touches and impacts many disciplines ranging from fundamental studies in the areas of genomics, proteomics transcriptomics, lipidomics to practical applications such as personalized medicine, drug discovery, and synthetic biology. This editorial examines the multifaceted role computational biology plays. Using the tools of deep learning, it can make powerful predictions of many biological variables, which may not provide a deep understanding of what factors contribute to the phenomena. Alternatively, it can provide the how and the why of biological processes. Most importantly, it can help guide and interpret what experiments and biological systems to study.
Community-Based Hearing Rehabilitation: Implementation and Outcome Evaluation
Authors: Thammaiah Spoorthi , Manchaiah Vinaya , Easwar Vijayalakshmi , Krishna Rajalakshmi , McPherson Bradley
Published: November 2017

Community-based rehabilitation (CBR) is a program designed to support persons with disabilities living in remote and rural areas. CBR primarily aims to provide required rehabilitation services to financially deprived persons with disabilities living in communities with limited access to such services. Today, globally, many organizations adhere to this approach to serve the rehabilitation needs of various disabilities. Recently, the CBR approach has started gaining interest in the rehabilitation sector concerned with hearing disabilities. This paper provides a general framework for the implementation and outcome evaluation of community-based hearing rehabilitation (CBHR) programs. The entire process is discussed with support of an existing CBHR program in India implemented by a non-governmental organization (NGO), Audiology India (AI). In addition, the paper highlights several of the challenges involved in such work and also explores future directions for CBHR-based intervention programs.
Real‐time eye tracking for the assessment of driver fatigue
Authors: Xu Junli , Min Jianliang , Hu Jianfeng
Published: November 2017

Eye‐tracking is an important approach to collect evidence regarding some participants’ driving fatigue. In this contribution, the authors present a non‐intrusive system for evaluating driver fatigue by tracking eye movement behaviours. A real‐time eye‐tracker was used to monitor participants’ eye state for collecting eye‐movement data. These data are useful to get insights into assessing participants’ fatigue state during monotonous driving. Ten healthy subjects performed continuous simulated driving for 1–2 h with eye state monitoring on a driving simulator in this study, and these measured features of the fixation time and the pupil area were recorded via using eye movement tracking device. For achieving a good cost‐performance ratio and fast computation time, the fuzzy K‐nearest neighbour was employed to evaluate and analyse the influence of different participants on the variations in the fixation duration and pupil area of drivers. The findings of this study indicated that there are significant differences in domain value distribution of the pupil area under the condition with normal and fatigue driving state. Result also suggests that the recognition accuracy by jackknife validation reaches to about 89% in average, implying that show a significant potential of real‐time applicability of the proposed approach and is capable of detecting driver fatigue.
Wind farm HVRT capability improvement based on coordinated reactive power control strategy
Authors: Zhang Yuandong , Li Qing , Zhang Jinping , Qin Shiyao
Published: November 2017

Voltage swells after grid fault clearance is one of the major causes of large‐scale wind power tripping accidents in China. In this study, reasons that led to overvoltage phenomena were researched, and factors that influence the grid overvoltage during grid fault were quantitatively analysed through simulation. A coordinated reactive power control strategy combined the control of wind turbines with reactive power compensation devices was proposed to prevent the occurrence of high voltage and improve the high‐voltage ride through capability of wind power plant. Finally, the effectiveness of the proposed control strategy was indicated by the simulation results in DIgSILENT/PowerFactory.
Atomistic modelling of thin film argon evaporation over different solid surfaces at different wetting conditions
Authors: Hasan Mohammad Nasim , Shavik Sheikh Mohammad , Mukut Khaled Mosharraf , Rabbi Kazi Fazle , Faisal A H M
Published: November 2017

In the present study, non‐equilibrium molecular dynamics (MD) simulations have been performed to reveal the effect of solid–liquid interfacial wettability on the evaporation characteristics of thin liquid argon film placed over the flat solid surface. The atomistic model considered herein comprises of a three‐phase simulation domain having a solid wall over which liquid argon and argon vapour co‐exist. Initially, the system is thermally equilibrated at 90 K for a while after which rapid increase in the solid wall temperature induces a phase change process, i.e. evaporation. Both hydrophilic and hydrophobic wetting conditions of the solid surface have been considered at an evaporation temperature of 130 K for three different surface materials such as platinum, silver, and aluminium. The simulation results show that both the surface wettability and surface material have a significant role in phase transition phenomena of thin liquid film, particularly the surface wettability for the present system configuration. The thermal transport phenomena between the wall and liquid thin film have been studied thoroughly and discussed in terms of wall heat flux, evaporative mass flux, upper bound of maximum possible heat flux etc. The results obtained in the present MD simulation study are compared with the macroscopic predictions based on classical thermodynamics. Interestingly, a very good agreement has been found indicating that macroscopic thermodynamics approach can predict the characteristic of phase change phenomena of nanoscale thin liquid film.
Fabrication of a flexible biomimetic film with spontaneously unidirectional water‐spreading property
Authors: Tang Longjun , Wang Xiaolin , Hong Wen , Sun Wenxi , Yang Bin , Chen Xiang , Liu Jingquan
Published: November 2017

A microstructure inspired by the structure on the peristome of Nepenthes alata was prepared with parylene‐C through a sacrificial layer technology. The biomimetic microstructure on a flexible film exhibits high‐speed (>2.5 mm/s in average) and long‐distance (>20 mm for 4 μl water droplets) unidirectional water spreading. The wetting behaviour and the parameters that affect the anisotropic spreading behaviour were in‐depth investigated. The novel microstructure and fabrication methods in this work may provide new insights into liquid behaviours on rough surfaces, and new ideas for non‐power microfluidic platform.
Nano‐montmorillonite‐based porous material prepared by gel casting: structure and adsorption properties
Authors: E Tao , Li Ying , Yang Shuyi , Qian Jianhua , Liu Lin , Xing Jinjuan
Published: November 2017

Porous materials (P‐Mt) were prepared via gel casting method by nano‐montmorillonite (Nano‐Mt) powder. P‐Mt possessed adsorption capability to low concentration Cr3+ in tanning waste water. The initial concentration of Cr3+ was 10 mg/L (pH = 3 ± 0.1), its removal rate and adsorption quantity were 72.50% and 5.80 mg/g, respectively, when P‐Mt was sintered at 600°C. While sintering temperature was higher than 700°C, its adsorption capacity to Cr3+ was damped because crystal shape and lamellar structure of P‐Mt were significantly changed. It demonstrates that 600°C was a better sintering temperature at which P‐Mt could efficiently remove Cr3+ in tanning waste water. Moreover, the problem of easily aggregation and difficult recycle in liquid with Nano‐Mt powder was solved according to this method.
Preparation and magnetic properties of manganese silicide nanorods by a solid‐state reaction route
Authors: Lu Juanjuan , Wang Liangbiao , Zhang Junhao , Li Qianwen , Liu Weiqiao , Lou Zhengsong , Zheng Ao , Zhou Quanfa
Published: November 2017

Manganese silicide (Mn5Si3) nanorods were successfully prepared using manganese sesquioxide (Mn2O3), silicon (Si) and metallic magnesium (Mg) as starting materials via a solid‐state route in an autoclave. X‐ray powder diffraction pattern revealed that the obtained product was hexagonal phase Mn5Si3. Furthermore, the oxidation resistance and magnetic properties of the obtained Mn5Si3 nanorods were also investigated.
Double plasma resonance instability as a source of solar zebra emission
Authors: Benáček J. , Karlický M.
Published: November 2017

Context. The double plasma resonance (DPR) instability plays a basic role in the generation of solar radio zebras. In the plasma, consisting of the loss-cone type distribution of hot electrons and much denser and colder background plasma, this instability generates the upper-hybrid waves, which are then transformed into the electromagnetic waves and observed as radio zebras.

Aims. In the present paper we numerically study the double plasma resonance instability from the point of view of the zebra interpretation.

Methods. We use a 3-dimensional electromagnetic particle-in-cell (3D PIC) relativistic model. We use this model in two versions: (a) a spatially extended “multi-mode” model and (b) a spatially limited “specific-mode” model. While the multi-mode model is used for detailed computations and verifications of the results obtained by the “specific-mode” model, the specific-mode model is used for computations in a broad range of model parameters, which considerably save computational time. For an analysis of the computational results, we developed software tools in Python.

Results. First using the multi-mode model, we study details of the double plasma resonance instability. We show how the distribution function of hot electrons changes during this instability. Then we show that there is a very good agreement between results obtained by the multi-mode and specific-mode models, which is caused by a dominance of the wave with the maximal growth rate. Therefore, for computations in a broad range of model parameters, we use the specific-mode model. We compute the maximal growth rates of the double plasma resonance instability with a dependence on the ratio between the upper-hybrid ωUH and electron-cyclotron ωce frequency. We vary temperatures of both the hot and background plasma components and study their effects on the resulting growth rates. The results are compared with the analytical ones. We find a very good agreement between numerical and analytical growth rates. We also compute saturation energies of the upper-hybrid waves in a very broad range of parameters. We find that the saturation energies of the upper-hybrid waves show maxima and minima at almost the same values of ωUH∕ωce as the growth rates, but with a higher contrast between them than the growth rate maxima and minima. The contrast between saturation energy maxima and minima increases when the temperature of hot electrons increases. Furthermore, we find that the saturation energy of the upper-hybrid waves is proportional to the density of hot electrons. The maximum saturated energy can be up to one percent of the kinetic energy of hot electrons. Finally we find that the saturation energy maxima in the interval of ωUH∕ωce = 3–18 decrease according to the exponential function. All these findings can be used in the interpretation of solar radio zebras.
Stellar mass spectrum within massive collapsing clumps
Authors: Lee Yueh-Ning , Hennebelle Patrick
Published: November 2017

Context. Understanding the origin of the initial mass function (IMF) of stars is a major problem for the star formation process and beyond.

Aim. We investigate the dependence of the peak of the IMF on the physics of the so-called first Larson core, which corresponds to the point where the dust becomes opaque to its own radiation.

Methods. We performed numerical simulations of collapsing clouds of 1000 M⊙ for various gas equations of state (eos), paying great attention to the numerical resolution and convergence. The initial conditions of these numerical experiments are varied in the companion paper. We also develop analytical models that we compare to our numerical results.

Results. When an isothermal eos is used, we show that the peak of the IMF shifts to lower masses with improved numerical resolution. When an adiabatic eos is employed, numerical convergence is obtained. The peak position varies with the eos, and using an analytical model to infer the mass of the first Larson core, we find that the peak position is about ten times its value. By analyzing the stability of nonlinear density fluctuations in the vicinity of a point mass and then summing over a reasonable density distribution, we find that tidal forces exert a strong stabilizing effect and likely lead to a preferential mass several times higher than that of the first Larson core.

Conclusions. We propose that in a sufficiently massive and cold cloud, the peak of the IMF is determined by the thermodynamics of the high-density adiabatic gas as well as the stabilizing influence of tidal forces. The resulting characteristic mass is about ten times the mass of the first Larson core, which altogether leads to a few tenths of solar masses. Since these processes are not related to the large-scale physical conditions and to the environment, our results suggest a possible explanation for the apparent universality of the peak of the IMF.
Palaeoenvironmental control on primary fluids characteristics of lacustrine source rocks in the Autun Permian Basin (France)
Authors: Garel Sylvain , Behar Françoise , Schnyder Johann , Baudin François
Published: November 2017

The Autunian (Late Gzhelian-Sakmarian, ∼295 Ma) of the Autun Basin (Saône-et-Loire, France) is well known for its lacustrine oil-shales and boghead that were exploited during the 19th and 20th centuries. A study of the kerogen geochemistry, palynofacies, hydrocarbon (HC) distribution of pyrolysates and kinetics on these organic-rich sediments gave indications on the control of lacustrine primary fluid characteristics by palaeoenvironmental settings. Palynofacies results have shown a Botryococcus algae dominance in the boghead, whereas the oil-shales were dominated either by a mixing of terrestrial particles and lacustrine phytoplanktonic/bacterial organic matter (OM), or by a lacustrine OM that suffered biodegradation within the water column. During the Autunian, an increasing trend of degraded lacustrine OM concentration is observed in the successive oil-shales. Geochemical and kinetics analyses showed that, except for the boghead, hydrogen index values were < 700 mg/g TOC and activation energies diagram showed multi-energetic profiles, unexpected for such a lacustrine OM. Along with pyrolysates primary fluids ones, these results unraveled two groups of oil-shale samples. On the one hand, samples dominated by well-preserved lacustrine and terrestrial OM produced primary fluids dominated by n-alkanes with (n-C6-n-C14) /n-C14+ n-alkanes ratio depending on the proportion of terrestrial OM. They were only encountered in the three oldest oil-shales. On the other hand, the HC profile of fluids originating from samples dominated by degraded lacustrine OM, which was obtained for the first time in this study, show low n-alkanes concentrations and a relatively prominent hump. These samples were only present in the three youngest oil-shale levels. Finally, the boghead showed a link between strong concentration of the Pila genus of Botryococcus algae and a primary fluid dominated by n-C6-n-C14 n-alkanes.

By comparing these data with published palaeoenvironmental studies, it appears that the kind of dominant OM, and thus the HC distribution of primary fluids, is controlled by the lake level: a lower depth preventing the settlement of anoxic conditions in the bottom waters, and the subsequent good preservation of the OM. During the Autunian, the lake level decreased, consequence of a reduced tectonic activity and of the beginning of a dryer period. Finally, these changes will have caused a strong decrease of the nutrient influx to the lake, favoring the bloom of Botryococcus algae that accumulated to form the boghead.
Controlling factors on source rock development: implications from 3D stratigraphic modeling of Triassic deposits in the Western Canada Sedimentary Basin
Authors: Crombez Vincent , Rohais Sébastien , Baudin François , Chauveau Benoit , Euzen Tristan , Granjeon Didier
Published: November 2017

The recent development of unconventional resources has triggered a regain of interest for source-rocks. The presence of hydrocarbons in these unconventional systems is generally associated with organic-rich sediments. This study aims at better understanding the factors controlling the accumulation of marine organic matter at basin scale, using a process-based approach. This work focuses on the Montney, Doig and Halfway Formations (Lower and Middle Triassic, Alberta and British Columbia, Canada). Recent studies show that the Triassic strata of the Western Canada sedimentary basin can be considered as a transitional period between the Paleozoic passive margin and the Jurassic foreland basin. Based on a 3D regional stratigraphic architecture and on a description of the organic rich interval distribution, a process-based numerical model (DionisosFlow and DORS) has been used to simulate the stratigraphic evolution of the Montney, Doig and Halfway Formations and reproduce the organic distribution in these formations. This modeling approach allowed us to test different scenarios of primary productivity and basin restriction and discuss the regional controls on organic matter accumulation such as dynamic of anoxia or dilution of organic matter by detrital sediments. The reconstruction of the stratigraphic architecture emphasizes a major drop of the water discharge in the basin. In the absence of any evidence supporting a link with a climate change, the drop in water discharge suggests a major modification of the drainage area of the basin, potentially associated with the early stage of the cordilleran orogeny and foreland basin evolution. The numerical simulation also shows that the primary productivity rates in the Montney and Doig Formations are characteristic of a coastal area and that a basin restriction is required to account for the level of anoxia observed in the studied Formations. Lastly, this study investigates the regional controls on organic matter accumulation and emphasizes the impact of regional paleogeographic and geodynamic evolution on the dynamic of anoxia and on the dilution.
Small-scaled lateral variations of an organic-rich formation in a ramp-type depositional environment (the Late Jurassic of the Boulonnais, France): impact of the clastic supply
Authors: Hatem Ebraheem , Tribovillard Nicolas , Averbuch Olivier , Bout-Roumazeilles Viviane , Trentesaux Alain , Deconinck Jean-François , Baudin François , Adatte Thierry
Published: November 2017

We studied a potential petroleum source rock deposited in a clastic-dominated ramp environment: the Argiles de Châtillon Formation (Kimmeridgian-Tithonian, Boulonnais area, northern France). The formation was deposited along a proximal-distal gradient on this ramp affected by synsedimentary fault movements. A sedimentological, mineralogical and geochemical study was conducted to decipher the distribution patterns of sedimentary parameters along such a depth increase over the ramp. It comes out that smectite distribution unexpectedly mimics the lateral depth evolution despite the good floatability of the mineral. It is also observed that the Argiles de Châtillon could accumulate noticeable amounts of organic matter in spite of paleoenvironmental conditions that were not specifically prone to organic matter preservation and burial (sedimentation rate, mineral particle grain size, productivity, oxygenation level…). Conversely, reactive iron, when being present in limited abundance, must have allowed sulfide ions to react with organic molecules instead of forming iron sulfides, which fostered organic matter preservation and accumulation. This protecting role of organic sulfide incorporation (additional to other favorable factors) cannot exist if reactive iron is relatively abundant. Lastly, our results (still fragmentary) suggest that smectite minerals could carry reactive iron, which would have occasionally hampered organic-matter preservation.
Effects of Ni d-levels on the electronic band structure of NixCd1-xO semiconducting alloys
Authors: Francis Christopher A. , Jaquez Maribel , Sánchez-Royo Juan F. , Farahani Sepher K. V. , McConville Chris F. , Beeman Jeffrey , Ting Min , Yu Kin M. , Dubón Oscar D. , Walukiewicz Wladek
Published: November 2017

NixCd1-xO has a ∼3 eV band edge offset and bandgap varying from 2.2 to 3.6 eV, which is potentially important for transparent electronic and photovoltaic applications. We present a systematic study of the electronic band structure of NixCd1-xO alloys across the composition range. Ion irradiation of alloy samples leads to a saturation of the electron concentration associated with pinning of the Fermi level (EF) at the Fermi stabilization energy, the common energy reference located at 4.9 eV below the vacuum level. The composition dependence of the pinned EF allows determination of the conduction band minimum (CBM) energy relative to the vacuum level. The unusually strong deviation of the CBM energy observed from the virtual crystal approximation is explained by a band anticrossing interaction between localized 3d states of Ni and the extended states of the NixCd1-xO alloy host. The resulting band structure explains the dependence between the composition and the electrical and optical properties of the alloys—the rapid reduction of the electron mobility as well as previously observed positive band gap bowing parameter. X-ray photoelectron spectroscopy studies confirm that the L-point valence band maximum in the Cd-rich alloys are unaffected by the interaction with Ni d-states.
Tensor-structured coupled cluster theory
Authors: Schutski Roman , Zhao Jinmo , Henderson Thomas M. , Scuseria Gustavo E.
Published: November 2017

We derive and implement a new way of solving coupled cluster equations with lower computational scaling. Our method is based on the decomposition of both amplitudes and two electron integrals, using a combination of tensor hypercontraction and canonical polyadic decomposition. While the original theory scales as O(N6) with respect to the number of basis functions, we demonstrate numerically that we achieve sub-millihartree difference from the original theory with O(N4) scaling. This is accomplished by solving directly for the factors that decompose the cluster operator. The proposed scheme is quite general and can be easily extended to other many-body methods.
Tunable intersubband transitions in ZnO/ZnMgO multiple quantum wells in the mid infrared spectral range
Authors: Orphal Laura , Kalusniak Sascha , Benson Oliver , Sadofev Sergey
Published: November 2017

We report on controllable tuning of intersubband transitions in ZnO/Zn0.60Mg0.40O multiple quantum well structures grown by molecular beam epitaxy on sapphire. The transitions from the first to the second electronic energy state within the conduction band are directly observed by infrared spectroscopy. By variation of the quantum well width, the intersubband transition energies are tuned from 290 to 370 meV. The experimental results are in good agreement with theoretical calculations assuming the presence of internal electric fields of 2 MV·cm−1.
Temperature dependent frequency tuning of NbOx relaxation oscillators
Authors: Nandi Sanjoy Kumar , Li Shuai , Liu Xinjun , Elliman Robert G.
Published: November 2017

This study investigates the temperature dependence of current-controlled negative differential resistance (CC-NDR) in Pt/NbOx/TiN devices and its effect on the dynamics of associated Pearson-Anson relaxation oscillators. The voltage range over which CC-NDR is observed decreases with increasing temperature such that no NDR is observed for temperatures above ∼380 K. Up to this temperature, relaxation oscillators exhibit voltage and temperature dependent oscillation frequencies in the range of 1 to 13 MHz. Significantly, the sensitivity of the frequency to temperature changes was found to be voltage-dependent, ranging from 39.6 kHz/K at a source voltage of 2 V to 110 kHz/K at a source voltage of 3 V, in the temperature range of 296–328 K. Such a behaviour provides insights into temperature tolerance and tuning variability for environmentally sensitive neuromorphic computing.
Generation of high-power few-cycle lasers via Brillouin-based plasma amplification
Authors: Zhang Z. M. , Zhang B. , Hong W. , Deng Z. G. , Teng J. , He S. K. , Zhou W. M. , Gu Y. Q.
Published: November 2017

Strong coupling stimulated Brillouin backscattering (sc-SBS) in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers. Here, we report on a new regime of brillouin-based plasma amplification, producing an amplified pulse with a duration of 5 fs and unfocused intensity of 6 × 1017 W/cm2. The results are obtained from 2D particle-in-cell simulations, using two circularly polarized pump and seed pulse with Gaussian transverse profile, both at an intensity of 2.74 × 1016 W/cm2, counter-propagating in a 0.3nc plasma. The significant compression of amplified seed is achieved as a result of sc-SBS amplification as well as additional compression by the interplay between self-phase modulation and negative group delay dispersion. We show that the amplified seed retains high beam qualities since the filamentation can be prevented due to the fast compression. This scheme may pave the way for few-cycle laser pulses to reach exawatt or even zetawatt regime.
A broadband antireflective nanostructure with Ag nanoparticles on SiO2 nanocolumns
Authors: Zhang Hao , Lou Chaogang , Huang Xiaodan , Yu Xiaojian , Yang Hua , Pribat Didier
Published: November 2017

A broadband antireflective nanostructure with Ag nanoparticles on SiO2 nanocolumns has been presented. Ag nanoparticles are located at the top of SiO2 nanocolumns which are deposited on Si substrates. SiO2 nanocolumns are fabricated by oblique angle deposition through electron beam evaporation, and Ag nanoparticles are fabricated by thermal evaporation. Experimental results show that the average reflection can reach 3.84% in the range of 400–700 nm and 5.75% in the range of 400–1100 nm, much lower than that of Ag islands on SiO2 thin films. The simulation shows that the broadband low reflection can be attributed to the localized surface plasmon resonance of Ag nanoparticles whose resonance wavelengths depends on the size of Ag nanoparticles. The different diameters of SiO2 nanocolumns determine the size distribution of Ag nanoparticles which resonate in a wide wavelength range and lead to a broadband low reflection. This provides a possible way to fabricate a broadband antireflection structure.
van der Waals epitaxy of Ge films on mica
Authors: Littlejohn A. J. , Xiang Y. , Rauch E. , Lu T.-M. , Wang G.-C.
Published: November 2017

To date, many materials have been successfully grown on substrates through van der Waals epitaxy without adhering to the constraint of lattice matching as is required for traditional chemical epitaxy. However, for elemental semiconductors such as Ge, this has been challenging and therefore it has not been achieved thus far. In this paper, we report the observation of Ge epitaxially grown on mica at a narrow substrate temperature range around 425 °C. Despite the large lattice mismatch (23%) and the lack of high in-plane symmetry in the mica surface, an epitaxial Ge film with [111] out-of-plane orientation is observed. Crystallinity and electrical properties degrade upon deviation from the ideal growth temperature, as shown by Raman spectroscopy, X-ray diffraction, and Hall effect measurements. X-ray pole figure analysis reveals that there exist multiple rotational domains in the epitaxial Ge film with dominant in-plane orientations between Ge1¯10 and mica[100] of (20n)°, where n = 0, 1, 2, 3, 4, 5. A superlattice area mismatch model was used to account for the likelihood of the in-plane orientation formation and was found to be qualitatively consistent with the observed dominant orientations. Our observation of Ge epitaxy with one out-of-plane growth direction through van der Waals forces is a step toward the growth of single crystal Ge films without the constraint in the lattice and symmetry matches with the substrates.
Helicon antenna radiation patterns in a high-density hydrogen linear plasma device
Authors: Caneses J. F. , Blackwell B. D. , Piotrowicz P.
Published: November 2017

Antenna radiation patterns in the vicinity of a helicon antenna are investigated in hydrogen plasmas produced in the MAGPIE linear plasma device. Using a uniform cold-plasma full-wave code, we model the wave physics in MAGPIE and find good agreement with experimental wave measurements. We show for the first time which antenna elements in a helicon device couple most strongly to the plasma and discuss the physical mechanism that determines this effect. Helicon wavefields in the near field of the antenna are best described in terms of the group velocity and ray direction, while far from the antenna, helicon wavefields behave like plane waves and are best described in terms of eigen-modes. In addition, we present recent 2D axis-symmetric full-wave simulations of the 120 kW helicon source in ProtoMPEX [Rapp et al., IEEE Trans. Plasma Sci. 44(12), 3456–3464 (2016); Caughman et al., J. Vac. Sci. Technol. Vac. Surf. Films 35, 03E114 (2017); and Goulding et al., Fusion Sci. Technol. 72(4), 588–594 (2017)] (ne∼ 5 × 1019 m−3, B0∼ 70 mT, and f= 13.56 MHz) where the antenna radiation patterns are evident, and we provide an interpretation of the numerical results using the ideas developed in this paper.
Explaining the T,V-dependent dynamics of glass forming liquids: The cooperative free volume model tested against new simulation results
Authors: White Ronald P. , Lipson Jane E. G.
Published: November 2017

In this article, we derive a rate model, the “cooperative free volume” (CFV) model, to explain relaxation dynamics in terms of a system’s free volume, Vfree, and its temperature, T, over widely varied pressure dependent conditions. In the CFV model, the rate a molecule moves a distance on the order of its own size is dependent on the cooperation of surrounding molecules to open up enough free space. To test CFV, we have generated extensive T,V dependent simulation data for structural relaxation times, τ, on a Kob and Andersen type Lennard-Jones (KA-LJ) fluid. The Vfree = V − Vhc values are obtained by estimating the limiting hard core volume, Vhc, through analysis of the KA-LJ PVT data. We provide the first simulation evidence that shows ln τ to be linearly proportional to 1/Vfree on isotherms, with T-dependent slopes, thus confirming our recent analysis of experimental systems. The linear relationship exhibited by the simulation data is further shown to occur at temperatures both above and below the transition to Arrhenius behavior. We also show that the gas kinetic T-dependent contribution is important in simulation results and that there can be a significant entropic contribution from lingering molecular hard-cores at high T. A key result is that non-Arrhenius relaxation behavior is always exhibited on isobars of the KA-LJ fluid, even at high T. The CFV model predicts all of this behavior over a surprisingly wide range of the KA-LJ T,V space, fitting it with just a single set of three parameters. The CFV approach leads to a framework wherein the number of cooperating particles, and thus, the process free energy of activation, is inversely proportional to Vfree, and this is the foundation for the form of the model’s volume contribution, a form that we find to hold for all systems and at all temperatures.
Porosity-enhanced solar powered hydrogen generation in GaN photoelectrodes
Authors: Hou Y. , Ahmed Syed Z. , Jiu L. , Bai J. , Wang T.
Published: November 2017

Two types of GaN based photoelectrodes using either horizontally aligned or vertically aligned nanopores have been fabricated by means of using an electrochemical etching approach. The photoelectrodes based on such nanostructures have demonstrated an up to 5-fold enhancement in applied bias photon-to-current efficiency and incident photon-to-current efficiency in comparison with their planar counterpart, leading to a high Faradaic conversion efficiency which approaches 1. The GaN photoelectrodes with these nanopores also show excellent chemical stability in HBr solution as an electrolyte. The results presented reveal that the gas diffusion in the nanopores plays an important role in water splitting processes, which should be taken into account when designing a GaN photoelectrode with a nanopore structure.
Particle reflection along the magnetic field in nonlinear magnetosonic pulses
Authors: Ohsawa Yukiharu
Published: November 2017

Reflection of electrons and positrons in oblique, nonlinear magnetosonic pulses is theoretically analyzed. With the use of the parallel pseudo potential F, which is the integral of the parallel electric field along the magnetic field, a simple equation for reflection conditions is derived, which shows that reflection along the magnetic field is caused by two forces: one arising from the parallel pseudo potential multiplied by the particle charge and the other from the magnetic mirror effect. The two forces push electrons in the opposite directions. In compressive solitons, in which the magnetic field is intensified, electrons with large magnetic moments can be reflected by the magnetic mirror effect, whereas in rarefactive solitons, in which the magnetic field is weaker than outside, electrons with small magnetic moments can be reflected by the parallel pseudo potential. Although F is basically positive and large in shock waves, it occasionally becomes negative in some regions behind the shock front in nonstationary wave evolution. These negative spikes of F can reflect electrons. In contrast to the case of electrons, the two forces push positrons in the same direction. For this reason, compressive solitons in an electron-positron-ion plasma reflect a large fraction of positrons compared with electrons, whereas rarefactive solitons will reflect no positrons. A shock wave can reflect a majority of positrons with its large F. However, in a pure electron-positron plasma, in which F becomes zero, positron reflection will rarely occur.
Transport modeling of convection dominated helicon discharges in Proto-MPEX with the B2.5-Eirene code
Authors: Owen L. W. , Rapp J. , Canik J. , Lore J. D.
Published: November 2017

Data-constrained interpretative analyses of plasma transport in convection dominated helicon discharges in the Proto-MPEX linear device, and predictive calculations with additional Electron Cyclotron Heating/Electron Bernstein Wave (ECH/EBW) heating, are reported. The B2.5-Eirene code, in which the multi-fluid plasma code B2.5 is coupled to the kinetic Monte Carlo neutrals code Eirene, is used to fit double Langmuir probe measurements and fast camera data in front of a stainless-steel target. The absorbed helicon and ECH power (11 kW) and spatially constant anomalous transport coefficients that are deduced from fitting of the probe and optical data are additionally used for predictive simulations of complete axial distributions of the densities, temperatures, plasma flow velocities, particle and energy fluxes, and possible effects of alternate fueling and pumping scenarios. The somewhat hollow electron density and temperature radial profiles from the probe data suggest that Trivelpiece-Gould wave absorption is the dominant helicon electron heating source in the discharges analyzed here. There is no external ion heating, but the corresponding calculated ion temperature radial profile is not hollow. Rather it reflects ion heating by the electron-ion equilibration terms in the energy balance equations and ion radial transport resulting from the hollow density profile. With the absorbed power and the transport model deduced from fitting the sheath limited discharge data, calculated conduction limited higher recycling conditions were produced by reducing the pumping and increasing the gas fueling rate, resulting in an approximate doubling of the target ion flux and reduction of the target heat flux.
Josephson parametric converter saturation and higher order effects
Authors: Liu G. , Chien T.-C. , Cao X. , Lanes O. , Alpern E. , Pekker D. , Hatridge M.
Published: November 2017

Microwave parametric amplifiers based on Josephson junctions have become indispensable components of many quantum information experiments. One key limitation which has not been well predicted by theory is the gain saturation behavior which limits the amplifier's ability to process large amplitude signals. The typical explanation for this behavior in phase-preserving amplifiers based on three-wave mixing, such as the Josephson Parametric Converter, is pump depletion, in which the consumption of pump photons to produce amplification results in a reduction in gain. However, in this work, we present experimental data and theoretical calculations showing that the fourth-order Kerr nonlinearities inherent in Josephson junctions are the dominant factor. The Kerr-based theory has the unusual property of causing saturation to both lower and higher gains, depending on bias conditions. This work presents an efficient methodology for optimizing device performance in the presence of Kerr nonlinearities while retaining device tunability and points to the necessity of controlling higher-order Hamiltonian terms to make further improvements in parametric devices.
In-situ analysis of microwave conductivity and impedance spectroscopy for evaluation of charge carrier dynamics at interfaces
Authors: Choi Wookjin , Inoue Junichi , Tsutsui Yusuke , Sakurai Tsuneaki , Seki Shu
Published: November 2017

A unique concerted analysis comprising non-contact microwave conductivity measurements and impedance spectroscopy was developed to simultaneously assess the charge carrier mobility and injection barriers. The frequency dependence of the microwave conductivity as well as the electrical current was analyzed by applying sinusoidal voltage to determine the equivalent circuit parameters. Based on the temperature dependence of the circuit parameters, the energy of the injection barrier was estimated to be 0.4 eV with the Richardson–Schottky model, and the band-like transport was confirmed with the negative temperature coefficient with the β value of 1.4 in the intra-layer conduction of C8-BTBT. In contrast, the increase in the resistance of the C8-BTBT layer with decreasing temperature implied the occurrence of hopping-like transport in the inter-layer conduction of C8-BTBT.
Role of phase synchronisation in turbulence
Authors: Moradi Sara , Teaca Bogdan , Anderson Johan
Published: November 2017

The role of the phase dynamics in turbulence is investigated. As a demonstration of the importance of the phase dynamics, a simplified system is used, namely the one-dimensional Burgers equation, which is evolved numerically. The system is forced via a known external force, with two components that are added into the evolution equations of the amplitudes and the phase of the Fourier modes, separately. In this way, we are able to control the impact of the force on the dynamics of the phases. In the absence of the direct forcing in the phase equation, it is observed that the phases are not stochastic as assumed in the Random Phase Approximation (RPA) models, and in contrast, the non-linear couplings result in intermittent locking of the phases to ± π/2. The impact of the force, applied purely on the phases, is to increase the occurrence of the phase locking events in which the phases of the modes in a wide k range are now locked to ± π/2, leading to a change in the dynamics of both phases and amplitudes, with a significant localization of the real space flow structures.
Minority carrier diffusion length for electrons in an extended SWIR InAs/AlSb type-II superlattice photodiode
Authors: Cohen-Elias D. , Snapi N. , Klin O. , Weiss E. , Shusterman S. , Meir T. , Katz M.
Published: November 2017

We fabricated and characterized InAs/AlSb Type II superlattice photodetectors for the short wave infrared region with λcutoff close to 2.5 μm. Using C-V and quantum efficiency measurements, we extracted the carrier diffusion lengths, Ldiff, and at 220 K and 300 K, they were 0.94 μm and 1.9 μm, respectively. In addition, I-V and detectivity measurements were carried out. The quantum efficiencies at λ = 2.18 μm, −50 mV, 300 K, and 200 K were 29% and 16% and the detectivities were above 1010 and 2 × 1011 cm Hz1/2/Watt, respectively. At a bias of −50 mV, the dark current densities at 300 K and 200 K were 4 mA/cm2 and 2.3 × 10−6 A/cm2 and the resistance-areas were 16 Ω cm2 and 38 kΩ cm2, respectively.
Pulse discharge properties of PLZST antiferroelectric ceramics compared with ferroelectric and linear dielectrics
Authors: Xu Chenhong , Liu Zhen , Chen Xuefeng , Yan Shiguang , Cao Fei , Dong Xianlin , Wang Genshui
Published: November 2017

The pulse discharge properties of lead lanthanum zirconate stannate titanate (PLZST) antiferroelectric (AFE) ceramics, ferroelectric (FE) dielectrics, and linear dielectrics were compared in this paper. It is found that as the voltage increases, those three types of dielectrics display three different voltage-dependent regularities: the peak current (Imax) of linear dielectrics increases linearly with increasing voltage; the Imax of FE dielectrics rises up with a gradually declined increase rate; the Imax of PLZST AFE ceramics presents a three-stage growth and during the third stage, the regularity is similar with that of FE dielectrics. Furthermore, three advantages of PLZST AFE ceramics for pulse discharge can be determined: a large increase rate of Imax due the field-forced AFE-FE phase transition, a great enhanced power density and a relatively short discharge period time. These results would pave the way for understanding and utilizing AFE ceramics in pulse power application.
Ion and electron sheath characteristics in a low density and low temperature plasma
Authors: Borgohain Binita , Bailung H.
Published: November 2017

Ion and electron sheath characteristics in a low electron temperature (Te ∼ 0.25–0.40 eV) and density (ne ∼ 106–107 cm−3) plasma are described. The plasma is produced in the experimental volume through diffusion from a hot cathode discharge plasma source by using a magnetic filter. The electron energy distribution function in the experimental plasma volume is measured to be a narrow Maxwellian distribution indicating the absence of primary and energetic electrons which are decoupled in the source side by the cusp magnetic field near the filter. An emissive probe is used to measure the sheath potential profiles in front of a metal plate biased negative and positive with respect to the plasma potential. For a positive plate bias, the electron density decreases considerably and the electron sheath expands with a longer presheath region compared to the ion sheath. The sheath potential structures are found to follow the Debye sheath model.