bluuebunny/crossref_metadata_2025 huggingface dataset:
Insights on FXR selective modulation. Speculation on bile acid chemical space in the discovery of potent and selective agonists
Authors: Sepe Valentina , Festa Carmen , Renga Barbara , Carino Adriana , Cipriani Sabrina , Finamore Claudia , Masullo Dario , del Gaudio Federica , Monti Maria Chiara , Fiorucci Stefano , Zampella Angela
Published: January 2016

Bile acids are the endogenous modulators of the nuclear receptor FXR and the membrane receptor GPBAR1. FXR represents a promising pharmacological target for the treatment of cholestatic liver disorders. Currently available semisynthetic bile acid derivatives cover the same chemical space of bile acids and therefore they are poorly selective toward BA receptors, increasing patient risk for adverse side effects. In this report, we have investigated around the structure of CDCA describing the synthesis and the in vitro and in vivo pharmacological characterization of a novel family of compounds modified on the steroidal tetracyclic core and on the side chain. Pharmacological characterization resulted in the identification of several potent and selective FXR agonists. These novel agents might add utility in the treatment of cholestatic disorders by potentially mitigating side effects linked to unwanted activation of GPBAR1.
Reptile Toll-like receptor 5 unveils adaptive evolution of bacterial flagellin recognition
Authors: Voogdt Carlos G. P. , Bouwman Lieneke I. , Kik Marja J. L. , Wagenaar Jaap A. , van Putten Jos P. M.
Published: January 2016

Toll-like receptors (TLR) are ancient innate immune receptors crucial for immune homeostasis and protection against infection. TLRs are present in mammals, birds, amphibians and fish but have not been functionally characterized in reptiles despite the central position of this animal class in vertebrate evolution. Here we report the cloning, characterization and function of TLR5 of the reptile Anolis carolinensis (Green Anole lizard). The receptor (acTLR5) displays the typical TLR protein architecture with 22 extracellular leucine rich repeats flanked by a N- and C-terminal leucine rich repeat domain, a membrane-spanning region and an intracellular TIR domain. The receptor is phylogenetically most similar to TLR5 of birds and most distant to fish TLR5. Transcript analysis revealed acTLR5 expression in multiple lizard tissues. Stimulation of acTLR5 with TLR ligands demonstrated unique responsiveness towards bacterial flagellin in both reptile and human cells. Comparison of acTLR5 and human TLR5 using purified flagellins revealed differential sensitivity to Pseudomonas but not Salmonella flagellin, indicating development of species-specific flagellin recognition during the divergent evolution of mammals and reptiles. Our discovery of reptile TLR5 fills the evolutionary gap regarding TLR conservation across vertebrates and provides novel insights in functional evolution of host-microbe interactions.
Hydrogen bonding-induced conformational change in a crystalline sugar derivative
Authors: Pal Kumar Bhaskar , Sarkar Vikramjit , Mukhopadhyay Balaram
Published: January 2016

We report crystallographic evidence of the change of a regular chair conformation to a skew boat conformation in a partially protected sugar derivative.
σ Bond activation through tunneling: formation of the boron hydride cations BHn+ (n = 2, 4, 6)
Authors: Qiu Yudong , Wu Chia-Hua , Schaefer III Henry F. , Allen Wesley D. , Agarwal Jay
Published: January 2016

The network of H2 additions to B+ and subsequent insertion reactions serve as a tractable model for hydrogen storage in elementary boron-containing compounds.
Prediction of topological phase transition in X2–SiGe monolayers
Authors: Juarez-Mosqueda Rosalba , Ma Yandong , Heine Thomas
Published: January 2016

Quantum spin Hall (QSH) insulators exhibit a bulk insulting gap and metallic edge states characterized by nontrivial topology.
Atomic scale insights into urea–peptide interactions in solution
Authors: Steinke Nicola , Gillams Richard J. , Pardo Luis Carlos , Lorenz Christian D. , McLain Sylvia E.
Published: January 2016

Investigations on the β-turn forming peptide, GPG, suggest that urea denatures proteins by replacing water molecules and subsequently weakening the peptide bonds as a possible mechanism of protein denaturation by urea.
Investigation of sodium insertion into tetracyanoquinodimethane (TCNQ): results for a TCNQ thin film obtained by a surface science approach
Authors: Precht R. , Stolz S. , Mankel E. , Mayer T. , Jaegermann W. , Hausbrand R.
Published: January 2016

Tetracyanoquinodimethane (TCNQ) was exposed to sodium vapour resulting in three phases containing reduced TCNQ with different electronic structures and chemical compositions.
Stabilities and defect-mediated lithium-ion conduction in a ground state cubic Li3N structure
Authors: Nguyen Manh Cuong , Hoang Khang , Wang Cai-Zhuang , Ho Kai-Ming
Published: January 2016

A stable ground state structure with cubic symmetry of Li3N (c-Li3N) is found by an ab initio initially symmetric random-generated crystal structure search method.
Shrimp-shell derived carbon nanodots as carbon and nitrogen sources to fabricate three-dimensional N-doped porous carbon electrocatalysts for the oxygen reduction reaction
Authors: Liu Rongrong , Zhang Haimin , Liu Shengwen , Zhang Xian , Wu Tianxing , Ge Xiao , Zang Yipeng , Zhao Huijun , Wang Guozhong
Published: January 2016

3D N-doped porous carbon material was successfully fabricated by a simple template-assisted pyrolysis method, exhibiting superior ORR catalytic performance.
Plasmon resonances tailored by Fano profiles in silver-based core–shell nanoparticles
Authors: Pellarin Michel , Broyer Michel , Lermé Jean , Lebeault Marie-Ange , Ramade Julien , Cottancin Emmanuel
Published: January 2016

The generic optical absorption band of core–shell M@Ag nanoparticles observed in many experiments is rationalized through the formation of a Fano-like profile originating from the coupling between the silver shell LSPR and the core interband absorption continuum.
Association of defects in doped non-stoichiometric ceria from first principles
Authors: Grieshammer Steffen , Nakayama Masanobu , Martin Manfred
Published: January 2016

DFT+U and Monte Carlo simulations reveal that defect interaction in doped ceria leads to a decrease of the energy of reduction.
Novel nanoparticle catalysts for catalytic gas sensing
Authors: Morsbach Eva , Kunz Sebastian , Bäumer Marcus
Published: January 2016

Applications such as catalytic gas sensing require a high density of catalytically active sites at low total heat capacity. One way to achieve this goal is the molecular linkage of colloidal nanoparticles with bifunctional ligands resulting in 3D-porous networks. The catalytic properties of such structures were investigated in a thermoelectric hydrogen sensor.
The hydrothermal evolution of the phase and shape of ZnS nanostructures and their gas-sensing properties
Authors: Hu Pengfei , Gong Guodong , Zhan Fangyi , Zhang Yuan , Li Rong , Cao Yali
Published: January 2016

The evolution of the phase of ZnS was achieved by adjusting the hydrothermal holding time or the dosage of the surfactant.
The effects of recycling on the properties of carbon nanotube-filled polypropylene composites and worker exposures
Authors: Zhang Jinde , Panwar Artee , Bello Dhimiter , Jozokos Tim , Isaacs Jacqueline A. , Barry Carol , Mead Joey
Published: January 2016

With production of nanocomposites, the product life cycle, including recycling, becomes critical.
Adipose-derived stem cells increase angiogenesis through matrix metalloproteinase-dependent collagen remodeling
Authors: Song Young Hye , Shon Seung Hee , Shan Mengrou , Stroock Abraham D , Fischbach Claudia
Published: January 2016

Adipose-derived stem cells (ASCs) are key regulators of extracellular matrix remodeling that modulates neovascularization during tissue regeneration.
Catalytic performance of the in situ synthesized palladium–polymer nanocomposite
Authors: Choudhary Meenakshi , Siwal Samarjeet , Nandi Debkumar , Mallick Kaushik
Published: January 2016

Multifunctional catalytic performance of thein situsynthesized polymer supported palladium nanoparticles (Pd NP).
One-pot solvothermal synthesis of bimetallic yolk–shell Ni@PtNi nanocrystals supported on reduced graphene oxide and their excellent catalytic properties for p-nitrophenol reduction
Authors: Mei Li-Ping , Wang Rui , Song Pei , Feng Jiu-Ju , Wang Zhi-Gang , Chen Jian-Rong , Wang Ai-Jun
Published: January 2016

Bimetallic yolk–shell Ni@PtNi NC-rGO were facilely prepared by a one-pot solvothermal method, which exhibited enhanced catalytic performance for p-nitrophenol reduction.
Aligned platinum nanowire networks from surface-oriented lipid cubic phase templates
Authors: Richardson S. J. , Burton M. R. , Staniec P. A. , Nandhakumar I. S. , Terrill N. J. , Elliott J. M. , Squires A. M.
Published: January 2016

A new aligned platinum nanostructure features an Fd3m “single diamond” morphology oriented with the (111) plane parallel to the substrate.
Solution-phase synthesis and biological evaluation of triostin A and its analogues
Authors: Hattori Kozo , Koike Kota , Okuda Kensuke , Hirayama Tasuku , Ebihara Masahiro , Takenaka Mei , Nagasawa Hideko
Published: January 2016

We have accomplished preparative solution-phase total syntheses of triostin A (17.5% in 13 steps) and its analogues with high yields to demonstrate their significant inhibitory activities on HIF-1 activation and cell proliferation.
Using a biomimetic membrane surface experiment to investigate the activity of the magnetite biomineralisation protein Mms6
Authors: Bird Scott M. , Rawlings Andrea E. , Galloway Johanna M. , Staniland Sarah S.
Published: January 2016

Using a surface-based mimic of a magnetosome interior, the biomineralisation protein Mms6 was found to be a more effective nucleator than binder of magnetite nanoparticles, and performs better than its C-terminal region alone.
Surface functionalization of up-converting NaYF4 nanocrystals with chiral molecules
Authors: Wawrzyńczyk D.
Published: January 2016

The surface of up-converting NaYF4:2%Er,20%Yb NPs have been successfully functionalized with chiral molecules, with simultaneously preserved colloidal stability and intense up-conversion emission.
The effects of the main components of seawater on the tribological properties of Cu–9Al–5Ni–4Fe–Mn alloy sliding against AISI 52100 steel
Authors: Jin Kongjie , Qiao Zhuhui , Wang Shuai , Zhu Shengyu , Cheng Jun , Yang Jun , Liu Weimin
Published: January 2016

The nickel-aluminum bronze alloy exhibits different friction coefficients under different environments: seawater ﹤ divalent salts solution ﹤ monovalent salts solution ﹤ distilled water.
Comparative study of dG affinity vs. DNA methylation modulating properties of side chain derivatives of procainamide: insight into its DNA hypomethylating effect
Authors: Gawade R. L. , Chakravarty D. K. , Debgupta J. , Sangtani E. , Narwade S. , Gonnade R. G. , Puranik V. G. , Deobagkar D. D.
Published: January 2016

Structural features of side-chains govern the association of procainamide and its derivatives with dG base of CpG rich DNA, which may differentially hinder the activity of DNMT-1, thereby they act as DNA hypomethylating agents.
Effect of different fabrication methods on the chemo-physical properties of silk fibroin films and on their interaction with neural cells
Authors: Sagnella Anna , Pistone Assunta , Bonetti Simone , Donnadio Anna , Saracino Emanuela , Nocchetti Morena , Dionigi Chiara , Ruani Giampiero , Muccini Michele , Posati Tamara , Benfenati Valentina , Zamboni Roberto
Published: January 2016

In this study, we investigated the influence of processing methods on the chemo-physical properties of silk fibroin (SF) film and on their interaction with neural cells.
Preparation and characterization of titanium-based PbO2electrodes modified by ethylene glycol
Authors: Hao Xu , Wuqi Guo , Jia Wu , Jiangtao Feng , Honghui Yang , Wei Yan
Published: January 2016

The present work focused on studying the effect of ethylene glycol (EG) modification on the electrochemical properties of lead dioxide electrodes prepared by the electrochemical deposition method.
Highly selective and sensitive colorimetric chemosensors for Hg2+ based on novel diaminomaleonitrile derivatives
Authors: Huo Yanping , Wang Songying , Lu Tianhua , Pan Chengqiang , Lu Yujing , Yang Xianghua , Hu Dongping , Hu Sheng
Published: January 2016

Five novel soluble chemosensors in EtOH/H2O based on Schiff-base diaminomaleonitrile derivatives which were modified by different aromatic functional moieties have been synthesized.
Direct synthesis of graphene quantum dots from multilayer graphene flakes through grinding assisted co-solvent ultrasonication for all-printed resistive switching arrays
Authors: Ali Junaid , Siddiqui Ghayas-ud-din , Yang Young Jin , Lee Kang Taek , Um Kiju , Choi Kyung Hyun
Published: January 2016

Graphene quantum dots (GQD) with diameters as small as ∼2 nm were synthesized by an efficient chemo-mechanical technique.
Identification and distinction of non-small-cell lung cancer cells by intracellular SERS nanoprobes
Authors: Zhang Yuqing , Ye Xiaojia , Xu Gengxin , Jin Xiulong , Luan Mengmeng , Lou Jiatao , Wang Lin , Huang Chengjun , Ye Jian
Published: January 2016

Combination of surface enhanced Raman scattering and multivariate statistical method allows to identify and distinguish three subtypes of non-small-cell lung cancer cells and leukocytes on the single-cell level.
The molecular mechanism of secondary sodium symporters elucidated through the lens of the computational microscope
Authors: Bisha Ina , Magistrato Alessandra
Published: January 2016

Transport of molecules across cellular membranes is a key biological process for normal cell function. In this review we describe current state-of-the-art knowledge on molecular mechanism of secondary active transporters obtained by molecular simulations studies.
Polyethylenimine analogs for improved gene delivery: effect of the type of amino groups
Authors: Xun Miao-Miao , Zhang Ju-Hui , Liu Yan-Hong , Zhang Ji , Xiao Ya-Ping , Guo Qian , Li Shuo , Yu Xiao-Qi
Published: January 2016

The 1°, 2° and 3° amine composition of PEI analogs could be easily adjusted by special synthetic method, and their effects on the gene transfection were studied.
Effect of shape and bending modulus on the properties of nematic lyotropic liquid crystals
Authors: Ruiz-Fernández A. R. , López-Cascales J. J. , Giner-Casares J. J. , Araya-Maturana R. , Díaz-Baños F. G. , Muñoz-Gacitúa D. , Weiss-López B. E.
Published: January 2016

Variation in the structure of the molecular aggregate associated with the increase of the TTAC concentration in the liquid crystal.
Boundary lubricating properties of hydrophobically modified polyacrylamide
Authors: Su Heng , Wang Xiang , Du Miao , Song Yihu , Zheng Qiang
Published: January 2016

Intermolecular association rather than the robust adsorption layer plays a significant role in boundary lubrication.
Highly phosphorescent platinum(ii) emitters: photophysics, materials and biological applications
Authors: Li Kai , Ming Tong Glenna So , Wan Qingyun , Cheng Gang , Tong Wai-Yip , Ang Wai-Hung , Kwong Wai-Lun , Che Chi-Ming
Published: January 2016

The structural effects of ligands on the emission properties of Pt(ii) complexes and promising applications of luminescent Pt(ii) complexes in various areas are discussed.
Atomistic picture of conformational exchange in a T4 lysozyme cavity mutant: an experiment-guided molecular dynamics study
Authors: Vallurupalli Pramodh , Chakrabarti Nilmadhab , Pomès Régis , Kay Lewis E.
Published: January 2016

Relaxation-dispersion NMR techniques and molecular dynamics simulations have been used to understand how a cavity mutant of T4 lysozyme interconverts between two compact conformations.
In situ incorporation of FeS nanoparticles/carbon nanosheets composite with an interconnected porous structure as a high-performance anode for lithium ion batteries
Authors: Xu Yuanxian , Li Wenyue , Zhang Fan , Zhang Xiaolong , Zhang Wenjun , Lee Chun-Sing , Tang Yongbing
Published: January 2016

FeS nanoparticles embedded in porous carbon matrix with unique structure was successfully synthesized and shows impressive lithium ion battery performances.
Osteoinduction and long-term osseointegration promoted by combined effects of nitrogen and manganese elements in high nitrogen nickel-free stainless steel
Authors: Yu Yiqiang , Ding Tingting , Xue Yang , Sun Jiao
Published: January 2016

High nitrogen nickel-free stainless steel promoted osteoinduction and long-term osseointegration of implants by combined effects of N and Mn elements.
Dephosphorylation of Tak1 at Ser412 greatly contributes to the spermatocyte-specific testis toxicity induced by (5R)-5-hydroxytriptolide in C57BL/6 mice
Authors: Qi Xinming , Li Chunzhu , Wu Chunyong , Yu Cunzhi , Liu Mingxia , Gao Man , Li Chenggang , Yan Hong , Ren Jin
Published: January 2016

(5R)-5-Hydroxytriptolide (LLDT-8), a novel triptolide derivative, will proceed to phase II clinical trials for the treatment of rheumatoid arthritis and cancer.
Fabrication of 45 nm high In component metamorphic In0.7Ga0.3As/In0.6Ga0.4As composite‐channel high electron‐mobility transistors on GaAs substrates
Authors: Kang Weihua , Zhang Xiaodong , Ji Xian , Cai Yong , Zhou Jiahui , Xu Wenjun , Li Qi , Xiao Gongli , Zhang Baoshun , Li Haiou
Published: January 2016

A 45 nm high In component metamorphic In0.7Ga0.3As/In0.6Ga0.4As composite‐channel high electron‐mobility transistor (mHEMT) on GaAs substrate with good DC and RF performance has been developed. The structure was grown by molecular beam epitaxy and exhibits a superior electron mobility of 10200 cm2/(V.s) and a sheet density of 3.5 × 1012 cm−2 at a room temperature. A combined optical and e‐beam lithography technology was used to achieve the nanometre mHEMT device. The mHEMT device shows an extrinsic transconductance of up to 990 mS/mm and a maximum current density of 910 mA/mm. The unity current gain cutoff frequency fT and the maximum oscillation frequency fmax are 187.94 and 258.62 GHz, respectively. These performances make the device well suited for millimetre‐wave applications.
Track before mitigate: aspect dependence‐based tracking method for multipath mitigation
Authors: Khalili A. , Soliman A.A.
Published: January 2016

People tracking is a key building block in many applications such as surveillance, abnormal activity detection and the monitoring of elderly persons or persons with restricted mobility. In this reported work, the problem of multipath signals, which is one of the main challenges in indoor and urban environments, is addressed. The proposed method integrates the aspect dependence feature of multipath signals into the tracking framework which allows making full use of more potentially useful information in the time domain in order to make more accurate decisions and to relax some constraints in the space domain such as the large number of antennas that are placed over a large area. An important feature of the proposed method is that it can suppress/mark the entire multipath track; furthermore, it does not assume any prior knowledge of the environment.
Robust speaker recognition using library of cross‐domain variation compensation transforms
Authors: Huang Houjun , Yao Shengyu , Zhou Ruohua , Yan Yonghong
Published: January 2016

Although the state‐of‐the‐art i‐vector‐based probabilistic linear discriminant analysis systems resulted in promising performances in the National Institute of Standards and Technology speaker recognition evaluations, the impact of domain mismatch when the system development data and the evaluation data are collected from different sources remains a challenging problem. This issue was a focus of the Johns Hopkins University 2013 speaker recognition workshop where a domain adaptation challenge (DAC13) corpus was created to address it. The cross‐domain variation compensation (CDVC) approach has been recently proposed to address it when in‐domain development data are available. The work reported by the present authors addresses this issue when in‐domain development data are unavailable using a library of CDVC transforms. This approach is evaluated on the DAC13 corpus and is shown to be more powerful than nuisance attribute projection‐based inter‐dataset variability compensation and the whitening library.
Intelligent digital redesign of fuzzy controller for non‐linear systems with packet losses
Authors: Bum Koo Geun , Bae Park Jin , Hoon Joo Young
Published: January 2016

In this study, a novel intelligent digital redesign (IDR) technique is proposed for the sampled‐data fuzzy controller of the non‐linear system with packet losses. For the IDR development, the non‐linear system is represented in the Takagi–Sugeno fuzzy model and the packet loss is assumed to be an independent, identically distributed Bernoulli random process. After introducing the traditional IDR technique, the closed‐loop system with state‐matching error and the state‐matching error cost function are achieved for the development of the novel IDR technique. In the discrete‐time Lyapunov sense, the exponential mean‐square stability is guaranteed while minimising the state‐matching error, and its sufficient condition is derived into linear matrix inequalities. Two examples are provided to verify the effectiveness of the proposed technique by comparison.
Quantum learning of classical stochastic processes: The completely positive realization problem
Authors: Monràs Alex , Winter Andreas
Published: January 2016

Among several tasks in Machine Learning, a specially important one is the problem of inferring the latent variables of a system and their causal relations with the observed behavior. A paradigmatic instance of this is the task of inferring the hidden Markov model underlying a given stochastic process. This is known as the positive realization problem (PRP), [L. Benvenuti and L. Farina, IEEE Trans. Autom. Control 49(5), 651–664 (2004)] and constitutes a central problem in machine learning. The PRP and its solutions have far-reaching consequences in many areas of systems and control theory, and is nowadays an important piece in the broad field of positive systems theory. We consider the scenario where the latent variables are quantum (i.e., quantum states of a finite-dimensional system) and the system dynamics is constrained only by physical transformations on the quantum system. The observable dynamics is then described by a quantum instrument, and the task is to determine which quantum instrument — if any — yields the process at hand by iterative application. We take as a starting point the theory of quasi-realizations, whence a description of the dynamics of the process is given in terms of linear maps on state vectors and probabilities are given by linear functionals on the state vectors. This description, despite its remarkable resemblance with the hidden Markov model, or the iterated quantum instrument, is however devoid of any stochastic or quantum mechanical interpretation, as said maps fail to satisfy any positivity conditions. The completely positive realization problem then consists in determining whether an equivalent quantum mechanical description of the same process exists. We generalize some key results of stochastic realization theory, and show that the problem has deep connections with operator systems theory, giving possible insight to the lifting problem in quotient operator systems. Our results have potential applications in quantum machine learning, device-independent characterization and reverse-engineering of stochastic processes and quantum processors, and more generally, of dynamical processes with quantum memory [M. Guţă, Phys. Rev. A 83(6), 062324 (2011); M. Guţă and N. Yamamoto, e-print arXiv:1303.3771(2013)].
Direct-to-indirect bandgap transitions in ⟨110⟩ silicon nanowires
Authors: Jensen I. J. T. , Ulyashin A. G. , Løvvik O. M.
Published: January 2016

The bandstructure of ⟨110⟩ silicon nano wires (SiNWs) with diameters (d) up to 6.1 nm were studied using density functional theory. Three types of surface termination were investigated: H, F, and OH; all giving quantum confinement induced direct bandgaps in the investigated size range. Comparison of the calculated results to reported experimental values showed that trends in the bandstructure behaviour were well reproduced. By studying the relative decrease of global and local minima in the conduction band minimum with increasing d, it was possible to predict a direct-to-indirect bandgap transition at d = 9.2, 9.5, and 11.4 nm for H, F, and OH terminated NWs, respectively.
Fast and local non-linear evolution of steep wave-groups on deep water: A comparison of approximate models to fully non-linear simulations
Authors: Adcock T. A. A. , Taylor P. H.
Published: January 2016

The non-linear Schrödinger equation and its higher order extensions are routinely used for analysis of extreme ocean waves. This paper compares the evolution of individual wave-packets modelled using non-linear Schrödinger type equations with packets modelled using fully non-linear potential flow models. The modified non-linear Schrödinger Equation accurately models the relatively large scale non-linear changes to the shape of wave-groups, with a dramatic contraction of the group along the mean propagation direction and a corresponding extension of the width of the wave-crests. In addition, as extreme wave form, there is a local non-linear contraction of the wave-group around the crest which leads to a localised broadening of the wave spectrum which the bandwidth limited non-linear Schrödinger Equations struggle to capture. This limitation occurs for waves of moderate steepness and a narrow underlying spectrum.
Surface conductivity of InAs/GaSb superlattice infrared detectors treated with thiolated self assembled monolayers
Authors: Henry Nathan C. , Brown Alexander , Knorr Daniel B. , Baril Neil , Nallon Eric , Lenhart Joseph L. , Tidrow Meimei , Bandara Sumith
Published: January 2016

The surface conductivity of InAs/GaSb based type II superlattice (T2SL) long wavelength infrared material following the deposition of thiolated self-assembled monolayers (SAMs) of cysteamine, octadecanethiol, dodecanethiol, and hexanethiol are reported. Quantitative mobility spectrum analysis (QMSA) was employed to study the mobility and to isolate and identify surface carriers following SAM treatments on planar samples. QMSA data collected following the deposition of the SAMs on InAs/GaSb material correlates well with dark current measurements, demonstrating the usefulness of QMSA as a tool for evaluating surface conductivity and predicting device performance. All samples displayed a reduction in surface conductivity and dark current density following thiol treatment. Dark current densities were reduced to 1.1 × 10−5, 1.3 × 10−5, 1.6 × 10−5, and 5 × 10−6 A/cm2 for hexanethiol, dodecanethiol, octadecanethiol, and cysteamine, respectively, from 5.7 × 10−4 A cm2 for unpassivated devices.
Spin-electron acoustic soliton and exchange interaction in separate spin evolution quantum plasmas
Authors: Andreev Pavel A.
Published: January 2016

Separate spin evolution quantum hydrodynamics is generalized to include the Coulomb exchange interaction, which is considered as interaction between the spin-down electrons being in quantum states occupied by one electron. The generalized model is applied to study the non-linear spin-electron acoustic waves. Existence of the spin-electron acoustic soliton is demonstrated. Contributions of concentration, spin polarization, and exchange interaction to the properties of the spin electron acoustic soliton are studied.
Transient and periodic spatiotemporal structures in a reaction-diffusion-mechanics system
Authors: Kostin V. A. , Osipov G. V.
Published: January 2016

We study transient spatiotemporal structures induced by a weak space-time localized stimulus in an excitable contractile fiber within a two-component globally coupled reaction-diffusion model. The model which we develop allows us to analyze various regimes of excitation spreading and determine origin of the induced structures for various contraction types (defined by the fiber fixation) and global coupling strengths. One of the most notable effects we observed is the after-excitation effect. It leads to emergence of multiple excitation pulses excited by a single external stimulus and can result in long-lasting transient activity and appearance of new oscillatory attractor regimes, including the ones with multiple phase clusters.
Region-of-interest diffuse optical tomography system
Authors: Saikia Manob Jyoti , Kanhirodan Rajan
Published: January 2016

Diffuse optical tomography (DOT) using near-infrared light is a promising tool for non-invasive imaging of deep tissue. This technique is capable of quantitative reconstruction of absorption (μa) and scattering coefficient (μs) inhomogeneities in the tissue. The rationale for reconstructing the optical property map is that the absorption coefficient variation provides diagnostic information about metabolic and disease states of the tissue. The aim of DOT is to reconstruct the internal tissue cross section with good spatial resolution and contrast from noisy measurements non-invasively. We develop a region-of-interest scanning system based on DOT principles. Modulated light is injected into the phantom/tissue through one of the four light emitting diode sources. The light traversing through the tissue gets partially absorbed and scattered multiple times. The intensity and phase of the exiting light are measured using a set of photodetectors. The light transport through a tissue is diffusive in nature and is modeled using radiative transfer equation. However, a simplified model based on diffusion equation (DE) can be used if the system satisfies following conditions: (a) the optical parameter of the inhomogeneity is close to the optical property of the background, and (b) μs of the medium is much greater than μa (μs > > μa). The light transport through a highly scattering tissue satisfies both of these conditions. A discrete version of DE based on finite element method is used for solving the inverse problem. The depth of probing light inside the tissue depends on the wavelength of light, absorption, and scattering coefficients of the medium and the separation between the source and detector locations. Extensive simulation studies have been carried out and the results are validated using two sets of experimental measurements. The utility of the system can be further improved by using multiple wavelength light sources. In such a scheme, the spectroscopic variation of absorption coefficient in the tissue can be used to arrive at the oxygenation changes in the tissue.
Experimental determination of the viscous flow permeability of porous materials by measuring reflected low frequency acoustic waves
Authors: Berbiche A. , Sadouki M. , Fellah Z. E. A. , Ogam E. , Fellah M. , Mitri F. G. , Depollier C.
Published: January 2016

An acoustic reflectivity method is proposed for measuring the permeability or flow resistivity of air-saturated porous materials. In this method, a simplified expression of the reflection coefficient is derived in the Darcy's regime (low frequency range), which does not depend on frequency and porosity. Numerical simulations show that the reflection coefficient of a porous material can be approximated by its simplified expression obtained from its Taylor development to the first order. This approximation is good especially for resistive materials (of low permeability) and for the lower frequencies. The permeability is reconstructed by solving the inverse problem using waves reflected by plastic foam samples, at different frequency bandwidths in the Darcy regime. The proposed method has the advantage of being simple compared to the conventional methods that use experimental reflected data, and is complementary to the transmissivity method, which is more adapted to low resistive materials (high permeability).
Far infrared edge photoresponse and persistent edge transport in an inverted InAs/GaSb heterostructure
Authors: Dyer G. C. , Shi X. , Olson B. V. , Hawkins S. D. , Klem J. F. , Shaner E. A. , Pan W.
Published: January 2016

Direct current (DC) transport and far infrared photoresponse were studied an InAs/GaSb double quantum well with an inverted band structure. The DC transport depends systematically upon the DC bias configuration and operating temperature. Surprisingly, it reveals robust edge conduction despite prevalent bulk transport in our device of macroscopic size. Under 180 GHz far infrared illumination at oblique incidence, we measured a strong photovoltaic response. We conclude that quantum spin Hall edge transport produces the observed transverse photovoltages. Overall, our experimental results support a hypothesis that the photoresponse arises from direct coupling of the incident radiation field to edge states.
Spin-dependent and photon-assisted transmission enhancement and suppression in a magnetic-field tunable ZnSe/Zn1–x
Mn
x
Se heterostructure
Authors: Li Chun-Lei , Yuan Rui-Yang , Guo Yong
Published: January 2016

Using the effective-mass approximation and Floquet theory, we theoretically investigate the terahertz photon-assisted transport through a ZnSe/Zn1−xMnxSe heterostructure under an external magnetic field, an electric field, and a spatially homogeneous oscillatory field. The results show that both amplitude and frequency of the oscillatory field can accurately manipulate the magnitude of the spin-dependent transmission probability and the positions of the Fano-type resonance due to photon absorption and emission processes. Transmission resonances can be enhanced to optimal resonances or drastically suppressed for spin-down electrons tunneling through the heterostructure and for spin-up ones tunneling through the same structure, resonances can also be enhanced or suppressed, but the intensity is less than the spin-down ones. Furthermore, it is important to note that transmission suppression can be clearly seen from both the spin-down component and the spin-up component of the current density at low magnetic field; at the larger magnetic field, however, the spin-down component is suppressed, and the spin-up component is enhanced. These interesting properties may provide an alternative method to develop multi-parameter modulation electron-polarized devices.
Crystal and magnetic structures of Cr1∕3NbSe2 from neutron diffraction
Authors: Gubkin A. F. , Proskurina E. P. , Kousaka Y. , Sherokalova E. M. , Selezneva N. V. , Miao P. , Lee S. , Zhang J. , Ishikawa Y. , Torii S. , Kamiyama T. , Campo J. , Akimitsu J. , Baranov N. V.
Published: January 2016

Neutron diffraction measurements of the Cr intercalated niobium diselenide Cr1∕3NbSe2 together with magnetization measurements have revealed that this compound exhibits ferromagnetic ordering below TC = 96 K unlike a chiral helimagnetic order observed in the sulfide compound Cr1∕3NbS2. As derived from neutron diffraction data, the Cr magnetic moments μCr = 2.83 ± 0.03 μB in Cr1∕3NbSe2 are aligned within basal plane. The discrepancy in the magnetic states of Cr1∕3NbS2 and Cr1∕3NbSe2 is ascribed to the difference in the preferential site occupation of Cr ions in crystal lattices. In Cr1∕3NbSe2, the Cr ions are predominantly distributed over 2b Wyckoff site, which determines a centrosymmetric character of the crystal structure unlike Cr1∕3NbS2, where the Cr ions are mainly located in 2c position and the crystal structure is non-centrosymmetric.
Oscillatory reaction cross sections caused by normal mode sampling in quasiclassical trajectory calculations
Authors: Nagy Tibor , Vikár Anna , Lendvay György
Published: January 2016

The quasiclassical trajectory (QCT) method is an efficient and important tool for studying the dynamics of bimolecular reactions. In this method, the motion of the atoms is simulated classically, and the only quantum effect considered is that the initial vibrational states of reactant molecules are semiclassically quantized. A sensible expectation is that the initial ensemble of classical molecular states generated this way should be stationary, similarly to the quantum state it is supposed to represent. The most widely used method for sampling the vibrational phase space of polyatomic molecules is based on the normal mode approximation. In the present work, it is demonstrated that normal mode sampling provides a nonstationary ensemble even for a simple molecule like methane, because real potential energy surfaces are anharmonic in the reactant domain. The consequences were investigated for reaction CH4 + H → CH3 + H2 and its various isotopologs and were found to be dramatic. Reaction probabilities and cross sections obtained from QCT calculations oscillate periodically as a function of the initial distance of the colliding partners and the excitation functions are erratic. The reason is that in the nonstationary ensemble of initial states, the mean bond length of the breaking C–H bond oscillates in time with the frequency of the symmetric stretch mode. We propose a simple method, one-period averaging, in which reactivity parameters are calculated by averaging over an entire period of the mean C–H bond length oscillation, which removes the observed artifacts and provides the physically most reasonable reaction probabilities and cross sections when the initial conditions for QCT calculations are generated by normal mode sampling.
Particle simulations of mode conversion between slow mode and fast mode in lower hybrid range of frequencies
Authors: Jia Guozhang , Xiang Nong , Wang Xueyi , Huang Yueheng , Lin Yu
Published: January 2016

The propagation and mode conversion of lower hybrid waves in an inhomogeneous plasma are investigated by using the nonlinear δf algorithm in a two-dimensional particle-in-cell simulation code based on the gyrokinetic electron and fully kinetic ion (GeFi) scheme [Lin et al., Plasma Phys. Controlled Fusion 47, 657 (2005)]. The characteristics of the simulated waves, such as wavelength, frequency, phase, and group velocities, agree well with the linear theoretical analysis. It is shown that a significant reflection component emerges in the conversion process between the slow mode and the fast mode when the scale length of the density variation is comparable to the local wavelength. The dependences of the reflection coefficient on the scale length of the density variation are compared with the results based on the linear full wave model for cold plasmas. It is indicated that the mode conversion for the waves with a frequency of 2.45 GHz (ω ∼ 3ωLH, where ωLH represents the lower hybrid resonance) and within Tokamak relevant amplitudes can be well described in the linear scheme. As the frequency decreases, the modification due to the nonlinear term becomes important. For the low-frequency waves (ω ∼ 1.3ωLH), the generations of the high harmonic modes and sidebands through nonlinear mode-mode coupling provide new power channels and thus could reduce the reflection significantly.
Terahertz emission from two-plasmon-decay induced transient currents in laser-solid interactions
Authors: Liao G.-Q. , Li Y.-T. , Li C. , Mondal S. , Hafez H. A. , Fareed M. A. , Ozaki T. , Wang W.-M. , Sheng Z.-M. , Zhang J.
Published: January 2016

We have studied the generation of terahertz (THz) radiation via the interaction of intense femtosecond laser pulses with solid targets at a small incidence angle. It is found that preplasma with a moderate density gradient can enhance the emission. We also observe saturation of the THz output with the driving laser energy. We find that THz emission is closely related to the 3/2 harmonics of the driving laser. Particle-in-cell simulations indicate that under the present experimental conditions, the THz emission could be attributed to the transient currents at the plasma-vacuum interface, mainly formed by the two-plasmon-decay instability.
Coupling of erbium dopants to yttrium orthosilicate photonic crystal cavities for on-chip optical quantum memories
Authors: Miyazono Evan , Zhong Tian , Craiciu Ioana , Kindem Jonathan M. , Faraon Andrei
Published: January 2016

Erbium dopants in crystals exhibit highly coherent optical transitions well suited for solid-state optical quantum memories operating in the telecom band. Here, we demonstrate coupling of erbium dopant ions in yttrium orthosilicate to a photonic crystal cavity fabricated directly in the host crystal using focused ion beam milling. The coupling leads to reduction of the photoluminescence lifetime and enhancement of the optical depth in microns-long devices, which will enable on-chip quantum memories.
Controlled exfoliation of (100) GaAs-based devices by spalling fracture
Authors: Sweet Cassi A. , Schulte Kevin L. , Simon John D. , Steiner Myles A. , Jain Nikhil , Young David L. , Ptak Aaron J. , Packard Corinne E.
Published: January 2016

The importance of exfoliation techniques increases as the semiconductor industry progresses toward thinner devices as a way to reduce material costs and improve performance. The controlled spalling technique is a recently developed substrate removal process that utilizes the physics of fracture to create wafer cleavage parallel to the surface at a precise depth. In this letter, we apply principles of linear elastic fracture mechanics to predict the process conditions needed to exfoliate (100) GaAs of a desired thickness. Spalling can be initiated in a controllable manner, by depositing a stressor film of a residual stress value just below the threshold value to induce a spontaneous spall. Experimental data show process window requirements to controllably spall (100) GaAs. Additionally, experimental spall depth in (100) GaAs compares well to spalling mechanics predictions when the effects of wafer thickness and modulus are considered. To test spalled material quality, III-V single junction photovoltaic devices are lifted off of a (100)-GaAs substrate by spalling methods and electrical characteristics are recorded. No degradation is observed in the spalled device, illustrating the potential of this method to rapidly produce thin, high quality devices.
Probing off-Hugoniot states in Ta, Cu, and Al to 1000 GPa compression with magnetically driven liner implosions
Authors: Lemke R. W. , Dolan D. H. , Dalton D. G. , Brown J. L. , Tomlinson K. , Robertson G. R. , Knudson M. D. , Harding E. , Mattsson A. E. , Carpenter J. H. , Drake R. R. , Cochrane K. , Blue B. E. , Robinson A. C. , Mattsson T. R.
Published: January 2016

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as it implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ∼1000 GPa is achieved in all cases. These experiments exhibit unexpectedly softer behavior above 200 GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum.
Evolution of complementary resistive switching characteristics using IrOx/GdOx/Al2O3/TiN structure
Authors: Jana Debanjan , Samanta Subhranu , Maikap Siddheswar , Cheng Hsin-Ming
Published: January 2016

The complementary resistive switching (CRS) characteristics using an IrOx/GdOx/Al2O3/TiN single cell are observed whereas the bipolar resistive switching (BRS) characteristics are observed for the IrOx/GdOx/TiN structure. Transmission electron microscope and energy dispersive X-ray spectroscopy depth profile show crystalline GdOx film and the presence of higher amount of oxygen at both IrOx/GdOx interface and Al2O3 layer. Inserting thin Al2O3 layer, the BRS is changed to CRS. This CRS has hopping distance of 0.58 nm and Poole-Frenkel current conductions for the “0” and “1” states, respectively. A schematic model using oxygen vacancy filament formation/rupture at the TE/GdOx interface and Al2O3 layer has been illustrated. This CRS device has good endurance of 1000 cycles with a pulse width of 1 μs, which is very useful for future crossbar architecture.
Self-deformation in a direct current driven helium jet micro discharge
Authors: Xu S. F. , Zhong X. X.
Published: January 2016

We report on the experimental observation of three dimensional self-deformation in an atmospheric micro discharge of the helium microjet through a tube into the ambient air upon a water electrode. The geometry of the discharge system is axial symmetric. While decreasing the discharge current, three dimensional collective motion of plasma filaments is directly observed. The three dimensional configuration of the discharge self changed from an axial symmetrical horn to a rectangular horn when the water acts as a cathode.
Effects of uniaxial strain on electron effective mass and tunneling capability of direct gap Ge1−xSnx alloys
Authors: Liu Lei , Liang Renrong , Wang Jing , Xu Jun
Published: January 2016

Direct gap Ge1−xSnx alloys under [100] and [110] uniaxial strain are comprehensively investigated by theoretical calculations using the nonlocal empirical pseudopotential method (EPM). It is shown that [100] uniaxial tensile strain aids indirect-to-direct gap transition in Ge1−xSnx alloys. The Γ electron effective mass along the optimal direction under [110] uniaxial strain is smaller than those under [100] uniaxial strain and (001) biaxial strain. Additionally, the direct tunneling gap is smallest along the strain-perpendicular direction under [110] uniaxial tensile strain, resulting in a maximum direct band-to-band tunneling generation rate. An optimal [110] uniaxial tensile strain is favorable for high-performance direct gap Ge1−xSnx electronic devices.