bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of sulfonated graphene oxide on the performance enhancement of acid–base composite membranes for direct methanol fuel cells
Authors: Neelakandan S. , K Noel Jacob , Kanagaraj P. , Sabarathinam R. M. , Muthumeenal A. , Nagendran A.
Published: May 2016

Sulfonated poly(1,4-phenylene ether ether sulfone) (SPEES)/poly(ether imide) (PEI)/sulfonated graphene oxide (SGO) based proton exchange membranes (PEMs) were prepared by a solution casting method.
Optimization of matrix solid-phase dispersion coupled with high performance liquid chromatography for determination of selected antibiotics in municipal sewage sludge
Authors: Vosough Maryam , Onilghi Mahdieh Nazari , Salemi Amir
Published: May 2016

Two alternative matrix nano-solid phase dispersion approaches coupled with HPLC-DAD were developed for the determination of sulfadiazine, sulfamerazine and sulfamethoxazole in STP sludge samples.
A novel modified electrode based on terbium oxide and carbon nanotubes for the simultaneous determination of methyldopa and paracetamol
Authors: Baytak Aysegul Kutluay , Duzmen Sehriban , Teker Tugce , Aslanoglu Mehmet
Published: May 2016

A novel voltammetric sensing platform was prepared ultrasonically by modifying a glassy carbon electrode (GCE) with a composite of terbium oxide (Tb4O7NPs) nanoparticles and carbon nanotubes (CNTs) for the simultaneous determination of methyldopa (MD) and paracetamol (PR).
Magnetic and fluorescent carbon-based nanohybrids for multi-modal imaging and magnetic field/NIR light responsive drug carriers
Authors: Wang Hui , Zhou Shuiqin
Published: May 2016

This mini-review summarizes the latest developments and addresses the future perspectives of carbon-based magnetic and fluorescent nanohybrids in the biomedical field.
Tuning the basicity of ionic liquids for efficient synthesis of alkylidene carbonates from CO2 at atmospheric pressure
Authors: Chen Kaihong , Shi Guiling , Dao Rina , Mei Ke , Zhou Xiuyuan , Li Haoran , Wang Congmin
Published: May 2016

A method for the efficient synthesis of alkylidene carbonates from CO2 by tuning the basicity of ionic liquids was reported.
Accurate force fields and methods for modelling organic molecular crystals at finite temperatures
Authors: Nyman Jonas , Pundyke Orla Sheehan , Day Graeme M.
Published: May 2016

We assess a series of atom–atom force fields for lattice energy and free energy modelling of molecular organic crystals.
Unravelling the working junction of aqueous-processed polymer–nanocrystal solar cells towards improved performance
Authors: Chen Zhaolai , Du Xiaohang , Jin Gan , Zeng Qingsen , Liu Fangyuan , Yang Bai
Published: May 2016

We demonstrate that the working principle of hybrid solar cells based on water-soluble polymers and nanocrystals follows a p–n junction instead of a type-II heterojunction. An improved PCE of 5.41% is obtained by optimizing these cells.
Intermolecular electron transfer states of 1-methyl-3-(N-(1,8-naphthalimidyl)ethyl)imidazolium iodide obtained by constrained density functional theory
Authors: Otsuka Takao , Sumita Masato , Izawa Hironori , Morihashi Kenji
Published: May 2016

Nonradiative decay from the ET-excited state of MNEI-I is mediated by the interaction of the iodine atom with the 1,8-naphthalimide or imidazolium groups.
An organosilane self-assembled monolayer incorporated into polymer solar cells enabling interfacial coherence to improve charge transport
Authors: Li Zhiqi , Zhang Xinyuan , Zhang Zhihui , Li Shujun , Liu Chunyu , Shen Liang , Guo Wenbin , Ruan Shengping
Published: May 2016

An organosilane self-assembled monolayer is introduced onto a TiO2transporting layer to improve electron extraction for polymer solar cells.
Voltammetry of the aqueous complexation–dissociation coupled to transfer (ACDT) mechanism with charged ligands
Authors: Molina Ángela , Olmos José Manuel , Laborda Eduardo , Gómez-Gil José María , González Joaquín
Published: May 2016

The voltammetry of the ACDT mechanism shows different responses depending on whether the ligand species is neutral or charged. Analytical solutions are deduced to calculate the current–potential signal and gain insight into the physicochemical processes behind it.
Rh-catalysed [5 + 1] cycloaddition of allenylcyclopropanes and CO: reaction development and application to the formal synthesis of (−)-galanthamine
Authors: Liu Cheng-Hang , Yu Zhi-Xiang
Published: May 2016

A Rh-catalyzed [5 + 1] cycloaddition of allenylcyclopropanes and CO has been developed to synthesize functionalized 2-methylidene-3,4-cyclohexenones. This cycloaddition reaction has been utilized as a key step in the formal synthesis of natural product (−)-galanthamine.
A Cu-catalyzed four-component cascade reaction to construct β-ester-γ-amino ketones
Authors: Ling Jiayue , Zhang Jie , Zhao Yanwei , Xu Yudong , Wang Hanghang , Lv Yuanzheng , Ji Meishan , Ma Liang , Ma Meihua , Wan Xiaobing
Published: May 2016

Herein, a novel Cu-catalyzed four-component cascade reaction, which encompasses styrenes, diazo reagents, amines, and tert-butyl hydroperoxide (TBHP), was well developed toward β-ester-γ-amino ketones, which showed high chemoselectivity.
Total synthesis, biosynthesis and biological profiles of clavine alkaloids
Authors: McCabe Stephanie R. , Wipf Peter
Published: May 2016

This review highlights noteworthy synthetic and biological aspects of the clavine subfamily of ergot alkaloids.
Treatment of textile effluent containing recalcitrant dyes using MOF derived Fe-ZSM-5 heterogeneous catalyst
Authors: Ahmad Mushtaq , Abdul Raman Abdul Aziz , Basirun Wan Jefrey , Bhargava Suresh K.
Published: May 2016

Fe-ZSM-5 is synthesized through a newly established 2-step process. 82% yield of Fe-ZSM-5 catalyst is possible at low temperature and pressure. 100% degradation of dyes is achieved with lesser amounts of catalyst and H2O2.
A clean synthesis of bis(indolyl)methane and biscoumarin derivatives using P4VPy–CuO nanoparticles as a new, efficient and heterogeneous polymeric catalyst
Authors: Shirini Farhad , Fallah-Shojaei Abdollah , Samavi Laleh , Abedini Masoumeh
Published: May 2016

A mild, simple, and efficient procedure has been developed for the synthesis of bis(indolyl)methanes and 3,3′-(arylmethylene)-bis-(4-hydroxy coumarins) using P4VPy–CuO nanoparticles as a heterogeneous polymeric catalyst.
Stability and bonding of the multiply coordinated bimetallic boron cycles: B8M22−, B7NM2and B6C2M2with M = Sc and Ti
Authors: Pham Hung Tan , Tam Nguyen Minh , Pham-Ho My Phuong , Nguyen Minh Tho
Published: May 2016

A theoretical investigation of the geometry, stability and aromaticity of boron clusters doped by two Sc and Ti atoms was carried out using DFT calculations.
Effect of calcination on adsorption performance of Mg–Al layered double hydroxide prepared by a water-in-oil microemulsion method
Authors: Yan Zhaoxiong , Zhu Bicheng , Yu Jiaguo , Xu Zhihua
Published: May 2016

Calcined Mg–Al layered double hydroxides synthesized by water-in-oil microemulsion method exhibit an enhanced adsorption performance for orange II.
A novel C–C radical–radical coupling reaction promoted by visible light: facile synthesis of 6-substituted N-methyl 5,6-dihydrobenzophenanthridine alkaloids
Authors: Liu Zhaoying , Huang Yajun , Xie Hongqi , Liu Wei , Zeng Jianguo , Cheng Pi
Published: May 2016

A photoredox mediated radical–radical coupling ofN-methyl 5,6-dihydrobenzophenanthridine alkaloids with α-electron withdrawing group substituted bromoalkane has been developed.
Facile one-step synthesis of highly graphitized hierarchical porous carbon nanosheets with large surface area and high capacity for lithium storage
Authors: Yang Qi , Zhao Zongbin , Jia Yanbao , Dong Yanfeng , Yu Zhengfa , Wang Xuzhen , Qiu Jieshan
Published: May 2016

Hierarchical porous carbon nanosheets with both high graphitization degree and large specific surface area were prepared and applied as anode for lithium storage, exhibiting a high reversible discharge capacity.
Photofixation of atmospheric nitrogen to ammonia with a novel ternary metal sulfide catalyst under visible light
Authors: Cao Yuhui , Hu Shaozheng , Li Fayun , Fan Zhiping , Bai Jin , Lu Guang , Wang Qiong
Published: May 2016

The NH4+ generation rate over ternary metal sulfide catalysts are linearly related to the sulfur vacancies concentration, confirming the photofixation capacity of N2 over ternary metal sulfide are dependent on the amount of sulfur vacancies.
Radical polymerization of miniemulsions induced by compressed gases
Authors: Dong Siming , Suzuki Yoshi , Nik Hadzir Noor Hadzuin , Lucien Frank P. , Zetterlund Per B.
Published: May 2016

Pressurization of a macroemulsion comprising a vinyl monomer/water/surfactant can result in formation of a transparent miniemulsion without use of high energy mixing, suitable for synthesis of polymeric nanoparticlesviaminiemulsion polymerization.
Synthesis and characterization of benzilic alcohol metalloporphyrin and its nanocomposite with graphene oxide (GO–CoTHMP) and investigation of their efficiency in the removal of environmental pollutants
Authors: Ghafuri Hossein , Rahmani Shirin , Rahimi Rahmatollah , Mohammadiyan Esmaeel
Published: May 2016

5,10,15,20-Tetrakis-(4-hydroxymethylphenyl)porphyrin (THMP), metalloporphyrin [(Co(iii)THMP)] and its nanocomposites with graphene oxide (GO–CoTHMP) were synthesized for the first time.
Hierarchically porous carbon black/graphene hybrid fibers for high performance flexible supercapacitors
Authors: Ma Wujun , Chen Shaohua , Yang Shengyuan , Zhu Meifang
Published: May 2016

Porous carbon black/reduced graphene oxide hybrid fiber was fabricated by a scalable wet-spinning method and a flexible solid-state SC with excellent electrochemical performance was assembled using the hybrid fiber.
Improving detection sensitivity by oriented bioconjugation of antibodies to quantum dots with a flexible spacer arm for immunoassay
Authors: Zhang Bingbo , Yu Jiani , Liu Chang , Wang Jun , Han Huanxing , Zhang Pengfei , Shi Donglu
Published: May 2016

The impacts of conjugation method and spacer arm for antibody covalent coupling with quantum dots on their biodetection performance are experimentally disclosed.
Carboxyfullerene decorated titanium dioxide nanomaterials for reactive oxygen species scavenging activities
Authors: Yang Kai-Cheng , Zheng Jia-Huei , Chen Yen-Ling , Lee Kuen-Chan , Cho Er-Chieh
Published: May 2016

Titanium dioxide nanomaterials offer superior protection for human skin against ultraviolet light.
Coordination polymer-derived mesoporous Co3O4 hollow nanospheres for high-performance lithium-ions batteries
Authors: Wu Renbing , Qian Xukun , Law Adrian Wing-Keung , Zhou Kun
Published: May 2016

A green and convenient coordination polymers-inspired approach was developed to synthesize porous Co3O4 hollow nanospheres. The electrodes made of such nanospheres exhibited excellent electrochemical performance in lithium-ion batteries.
Thermally stable ferrocene-α-cyanostilbenes as efficient materials for second order nonlinear optical polarizability
Authors: Dhoun Sugandha , Depotter Griet , Kaur Sarbjeet , Kaur Paramjit , Clays Koen , Singh Kamaljit
Published: May 2016

Thermally stable ferrocene-α-cyanostilbenes exhibit non-zero dipole moments as well as good structure dependent second order nonlinear optical response.
Chelate-induced formation of Li2MnSiO4 nanorods as a high capacity cathode material for Li-ion batteries
Authors: Pei Yi , Chen Qing , Xu Cheng-Yan , Wang Hui-Xin , Fang Hai-Tao , Zhou Chang , Zhen Liang , Cao Guozhong
Published: May 2016

Pure phase carbon-coated Li2MnSiO4 nanorods with excellent cyclic stability as cathode materials for LIBs were prepared via a facile chelating agent-assisted hydrothermal method together with subsequent calcination.
Exploration of the tight structural–mechanical relationship in mulberry and non-mulberry silkworm silks
Authors: Fang Guangqiang , Sapru Sunaina , Behera Sibaram , Yao Jinrong , Shao Zhengzhong , Kundu Subhas C. , Chen Xin
Published: May 2016

The mystery of the structural–mechanical relationship in mulberry and non-mulberry silkworm silks was explored using synchrotron radiation techniques.
Nuclear localizations of phosphatidylinositol 5-phosphate 4-kinases α and β are dynamic and independently regulated during starvation-induced stress
Authors: Droubi Alaa , Bulley Simon J. , Clarke Jonathan H. , Irvine Robin F.
Published: May 2016

The chicken B-cell line DT40 has two isoforms of phosphatidylinositol 5-phosphate 4-kinase (PI5P4K), α and β, which are likely to exist as a mixture of obligate homo- and hetero-dimers. Previous work has led us to speculate that an important role of the β isoform may be to target the more active PI5P4Kα isoform to the nucleus. In the present study we expand upon that work by genomically tagging the PI5P4Ks with fluorochromes in the presence or absence of stable or acute depletions of PI5P4Kβ. Consistent with our original hypothesis we find that PI5P4Kα is predominantly (possible entirely) cytoplasmic when PI5P4Kβ is stably deleted from cells. In contrast, when PI5P4Kβ is inducibly removed within 1 h PI5P4Kα retains its wild-type distribution of approximately 50:50 between cytoplasm and nucleus even through a number of cell divisions. This leads us to speculate that PI5P4Kα is chromatin-associated. We also find that when cells are in the exponential phase of growth PI5P4Kβ is primarily cytoplasmic but translocates to the nucleus upon growth into the stationary phase or upon serum starvation. Once again this is not accompanied by a change in PI5P4Kα localization and we show, using an in vitro model, that this is possible because the dimerization between the two isoforms is dynamic. Given this shift in PI5P4Kβ upon nutrient deprivation we explore the phenotype of PI5P4K B-null cells exposed to this stress and find that they can sustain a greater degree of nutrient deprivation than their wild-type counterparts possibly as a result of up-regulation of autophagy.
Serum Levels of IL-17, IL-6, TNF-α and Disease Activity in Patients with Rheumatoid Arthritis
Authors: Beyazal M. , Devrimsel G. , Cüre M. , Türkyılmaz A. , Çapkın E. , Karkucak M.
Published: May 2016

Objective: The aim of this study was to evaluate serum levels of interleukin (IL)-17, IL-6, and tumor necrosis factor alpha (TNF-α) in RA patients and to assess the correlation of these cytokines with clinical and laboratory parameters.

Materials and Methods: 48 patients with RA and 35 healthy volunteers were enrolled in the study. Disease activity was determined by disease activity score (DAS28) in patients with RA. Patients with RA were categorized as mild (DAS28≤3.2), moderate (3.2<DAS28≤5.1), and severe (5.1<DAS28) according to DAS28. The serum levels of IL-17, IL-6 and TNF-α cytokines were measured by enzyme-linked immuno sorbent assay.

Results: The mean serum IL-17 and TNF-α levels did not differ between RA patients and controls (P>0.05). Serum IL-6 levels were significantly elevated in RA patients compared with controls (P<0.001). The increasing trend in mean serum IL-6 levels across group with mild, moderate, and severe disease activity was significant (P<0.001, respectively). In RA patients, serum IL-6 concentrations were significantly correlated with ESR, CRP, DAS28, and VAS (r=0.371, P=0.009; r=0.519, P<0.001; r=0.536, P<0.001; r=0.539, P<0.001, respectively). Also, Serum IL-17 concentrations demonstrated significant correlations with ESR, CRP, but not DAS28 (r=0.349, P=0.015; r=0.299, P=0.039; r=0.274, P=0.060, respectively). Serum TNF-α showed no significant correlation with disease activity indices.

Conclusions: This study showed that patients with RA had significantly increased cytokine level for IL-6, but not IL-17 and TNF-α and high level of serum IL-6 cytokine was associated with disease activity. However, further follow-up studies involving large samples are required to clarify precise role of these cytokines in disease development and progress.
Voluntary Use of Information Technology: An Analysis and Synthesis of the Literature
Authors: Tsai HsingYi , Compeau Deborah , Meister Darren
Published: May 2016

Voluntariness is recognized as an important influence on individual and collective technology acceptance. We conducted a comprehensive review of this literature and identified a rich set of voluntariness concepts and methods of operationalization. However, while considerable empirical evidence is reported in the literature, our review also revealed inconsistent results concerning the relationship between voluntariness and other concepts. Against that backdrop, we synthesized the literature into three types of voluntariness - perceived, intended and realizable voluntariness (RVOL), and showed how prior literature had not adequately accounted for RVOL. Moreover, we examined the multiple mechanisms that influence voluntariness and created a model to describe how to advance new knowledge about the important relationships among the three types of voluntariness and between voluntariness and user behavior. We argue that these concepts and relationships may help advance our knowledge of how a new technology is used individually and collectively in organizations.
“Marginalization” in third world feminism: its problematics and theoretical reconfiguration
Authors: Mansoor Asma
Published: May 2016

With the imposition of certain notions of agency and marginalization prescribed by first world feminist discourses, global feminism has cumulatively remained mired within a binaristic closure. This closure is based on the idea of an agentive Western feminist center and a passive third world feminism at the margin. This article endeavours to go beyond this closure to initiate debates regarding the operational praxis of a third world woman’s marginal placement as articulated in third world feminist discourses. It problematizes the idea of “disempowerment” that stems from a patriarchal model depicting man as the nucleus and a woman as a peripheral and centripetal entity, drawn within the mise en abyme of self-consolidating representations. Therefore, the argument presented here revisits the notion of the marginalization of third world women by subjecting the theoretical approaches regarding female marginalization and agency—as articulated by Spivak, Irigaray and Kristeva, et al.—to a deconstructive mode of analysis to explore the theoretical reconfiguration of a third world woman’s marginal placement. This article reconsiders the margin as discursively “limitrophic” so that the binaries between the margin/center, agency/disempowerment and third world feminism/first world feminism are re-scrutinized. The margin, thus, becomes an agentive plane for a third world woman as she uses it to direct her gaze away from any discursive center. In this way, a third world woman undermines the West-centric centripetal force despite being englobed within what Kristeva calls “supranational sociocultural ensembles” and sees her “self” as independent of any fixed center so that she redefines herself as an autonomous thinking woman able to dismantle the notion of a congealed subalternity. This article is published as part of a thematic collection on gender studies.
High-extinction virtually imaged phased array-based Brillouin spectroscopy of turbid biological media
Authors: Fiore Antonio , Zhang Jitao , Shao Peng , Yun Seok Hyun , Scarcelli Giuliano
Published: May 2016

Brillouin microscopy has recently emerged as a powerful technique to characterize the mechanical properties of biological tissue, cell, and biomaterials. However, the potential of Brillouin microscopy is currently limited to transparent samples, because Brillouin spectrometers do not have sufficient spectral extinction to reject the predominant non-Brillouin scattered light of turbid media. To overcome this issue, we combined a multi-pass Fabry-Perot interferometer with a two-stage virtually imaged phased array spectrometer. The Fabry-Perot etalon acts as an ultra-narrow band-pass filter for Brillouin light with high spectral extinction and low loss. We report background-free Brillouin spectra from Intralipid solutions and up to 100 μm deep within chicken muscle tissue.
Time-resolved pump and probe x-ray absorption fine structure spectroscopy at beamline P11 at PETRA III
Authors: Göries D. , Dicke B. , Roedig P. , Stübe N. , Meyer J. , Galler A. , Gawelda W. , Britz A. , Geßler P. , Sotoudi Namin H. , Beckmann A. , Schlie M. , Warmer M. , Naumova M. , Bressler C. , Rübhausen M. , Weckert E. , Meents A.
Published: May 2016

We report about the development and implementation of a new setup for time-resolved X-ray absorption fine structure spectroscopy at beamline P11 utilizing the outstanding source properties of the low-emittance PETRA III synchrotron storage ring in Hamburg. Using a high intensity micrometer-sized X-ray beam in combination with two positional feedback systems, measurements were performed on the transition metal complex fac-Tris[2-phenylpyridinato-C2,N]iridium(III) also referred to as fac-Ir(ppy)3. This compound is a representative of the phosphorescent iridium(III) complexes, which play an important role in organic light emitting diode (OLED) technology. The experiment could directly prove the anticipated photoinduced charge transfer reaction. Our results further reveal that the temporal resolution of the experiment is limited by the PETRA III X-ray bunch length of ∼103 ps full width at half maximum (FWHM).
Thermo-resistive disruptions and the tokamak density limit
Authors: Gates D. A. , Brennan D. P. , Delgado-Aparicio L. , Teng Q. , White R. B.
Published: May 2016

The physical mechanism behind the tokamak density limit scaling is described in terms of a non-linear theory of tearing mode growth in cylindrical geometry coupled to a model for thermal transport in the island. Important new physics features of the model include: (1) island asymmetry due to finite island width in cylindrical geometry, (2) a model of radiation based on local coronal equilibrium including impurity radiation, (3) current perturbations due the perturbed resistivity, and (4) numerical solution of the cylindrical eigenfunctions and Δ′. The semi-analytic cylindrical model is then solved for a wide range of current profiles, magnetic field values, and plasma currents using reasonable assumptions for impurity densities and the Greenwald limit [M. Greenwald et al., Nucl. Fusion 28, 2199 (1988)] is reproduced. The limit is shown to be only weakly dependent on variations in the assumed parameters.
Anomalous water drop bouncing on a nanotextured surface by the Leidenfrost levitation
Authors: Lee Doo Jin , Song Young Seok
Published: May 2016

We report an anomalous liquid drop bouncing phenomenon that is generated by the Leidenfrost levitation due to a vapor layer reducing energy dissipation during the collision. The Leidenfrost levitation of water drops on both a hydrophobic surface and nanotextured Cassie surface is investigated. When the water drop is positioned onto the hydrophobic surface, a superhydrophobic feature is observed by the levitation effect due to the vapor film, which results in a slow evaporation of the drop due to the low thermal conductivity of the vapor layer that inhibits heat transfer between the heated surface and the water drop. In contrast, for the nanotextured surface, the water drop can bounce off after impact on the surface when it overcomes gravitational and adhesion forces. The spontaneous water drop bouncing on the nanotextured surface is powered by the combination effect of the Leidenfrost levitation and the non-wetting Cassie state.
Ultrafast time measurements by time-correlated single photon counting coupled with superconducting single photon detector
Authors: Shcheslavskiy V. , Morozov P. , Divochiy A. , Vakhtomin Yu. , Smirnov K. , Becker W.
Published: May 2016

Time resolution is one of the main characteristics of the single photon detectors besides quantum efficiency and dark count rate. We demonstrate here an ultrafast time-correlated single photon counting (TCSPC) setup consisting of a newly developed single photon counting board SPC-150NX and a superconducting NbN single photon detector with a sensitive area of 7 × 7 μm. The combination delivers a record instrument response function with a full width at half maximum of 17.8 ps and system quantum efficiency ∼15% at wavelength of 1560 nm. A calculation of the root mean square value of the timing jitter for channels with counts more than 1% of the peak value yielded about 7.6 ps. The setup has also good timing stability of the detector–TCSPC board.
Design and analysis of a high-accuracy flexure hinge
Authors: Liu Min , Zhang Xianmin , Fatikow Sergej
Published: May 2016

This paper designs and analyzes a new kind of flexure hinge obtained by using a topology optimization approach, namely, a quasi-V-shaped flexure hinge (QVFH). Flexure hinges are formed by three segments: the left and right segments with convex shapes and the middle segment with straight line. According to the results of topology optimization, the curve equations of profiles of the flexure hinges are developed by numerical fitting. The in-plane dimensionless compliance equations of the flexure hinges are derived based on Castigliano’s second theorem. The accuracy of rotation, which is denoted by the compliance of the center of rotation that deviates from the midpoint, is derived. The equations for evaluating the maximum stresses are also provided. These dimensionless equations are verified by finite element analysis and experimentation. The analytical results are within 8% uncertainty compared to the finite element analysis results and within 9% uncertainty compared to the experimental measurement data. Compared with the filleted V-shaped flexure hinge, the QVFH has a higher accuracy of rotation and better ability of preserving the center of rotation position but smaller compliance.
Anomalous dimensionality dependence of diffusion in a rugged energy landscape: How pathological is one dimension?
Authors: Seki Kazuhiko , Bagchi Kaushik , Bagchi Biman
Published: May 2016

Diffusion in one dimensional rugged energy landscape (REL) is predicted to be pathologically different (from any higher dimension) with a much larger chance of encountering broken ergodicity [D. L. Stein and C. M. Newman, AIP Conf. Proc. 1479, 620 (2012)]. However, no quantitative study of this difference has been reported, despite the prevalence of multidimensional physical models in the literature (like a high dimensional funnel guiding protein folding/unfolding). Paradoxically, some theoretical studies of these phenomena still employ a one dimensional diffusion description for analytical tractability. We explore the dimensionality dependent diffusion on REL by carrying out an effective medium approximation based analytical calculations and compare them with the available computer simulation results. We find that at an intermediate level of ruggedness (assumed to have a Gaussian distribution), where diffusion is well-defined, the value of the effective diffusion coefficient depends on dimensionality and changes (increases) by several factors (∼5-10) in going from 1d to 2d. In contrast, the changes in subsequent transitions (like 2d to 3d and 3d to 4d and so on) are far more modest, of the order of 10-20% only. When ruggedness is given by random traps with an exponential distribution of barrier heights, the mean square displacement (MSD) is sub-diffusive (a well-known result), but the growth of MSD is described by different exponents in one and higher dimensions. The reason for such strong ruggedness induced retardation in the case of one dimensional REL is discussed. We also discuss the special limiting case of infinite dimension (d = ∞) where the effective medium approximation becomes exact and where theoretical results become simple. We discuss, for the first time, the role of spatial correlation in the landscape on diffusion of a random walker.
Simulations on shifting medium and its application in wireless power transfer system to enhance magnetic coupling
Authors: Li Wenwen , Zhang Yingyi , Yao Chen , Tang Houjun
Published: May 2016

Shifting medium is a kind of an anisotropic but homogeneous metamaterial designed by transformation optics. An object or free space enclosed by the shifting medium could be moved to a certain distance away from the original position. In this paper, we propose a cone-shaped shifting medium shell to move an internal coil to the given position. In this way, the two coils in a wireless power transfer system could be equivalently moved closer; thus, their magnetic coupling is enhanced. The theoretical models and numerical simulations are presented and analyzed to validate the effects of the shifting medium shell. Both ohmic loss and magnetic loss are also considered for practical concerns. Finally, we discuss the simplification of such a shifting medium to facilitate its fabrication.
Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods
Authors: Segawa Takuya F. , Doppelbauer Maximilian , Garbuio Luca , Doll Andrin , Polyhach Yevhen O. , Jeschke Gunnar
Published: May 2016

Water accessibility is a key parameter for the understanding of the structure of biomolecules, especially membrane proteins. Several experimental techniques based on the combination of electron paramagnetic resonance (EPR) spectroscopy with site-directed spin labeling are currently available. Among those, we compare relaxation time measurements and electron spin echo envelope modulation (ESEEM) experiments using pulse EPR with Overhauser dynamic nuclear polarization (DNP) at X-band frequency and a magnetic field of 0.33 T. Overhauser DNP transfers the electron spin polarization to nuclear spins via cross-relaxation. The change in the intensity of the 1H NMR spectrum of H2O at a Larmor frequency of 14 MHz under a continuous-wave microwave irradiation of the nitroxide spin label contains information on the water accessibility of the labeled site. As a model system for a membrane protein, we use the hydrophobic α-helical peptide WALP23 in unilamellar liposomes of DOPC. Water accessibility measurements with all techniques are conducted for eight peptides with different spin label positions and low radical concentrations (10–20 μM). Consistently in all experiments, the water accessibility appears to be very low, even for labels positioned near the end of the helix. The best profile is obtained by Overhauser DNP, which is the only technique that succeeds in discriminating neighboring positions in WALP23. Since the concentration of the spin-labeled peptides varied, we normalized the DNP parameter ϵ, being the relative change of the NMR intensity, by the electron spin concentration, which was determined from a continuous-wave EPR spectrum.
Room temperature optically detected magnetic resonance (photoluminescence detected magnetic resonance) of radical ion pairs induced by vacuum ultraviolet in thin polymeric films
Authors: Verkhovlyuk V. N. , Fedotov K. Yu. , Anisimov O. A.
Published: May 2016

A setup for recording optically detected electron paramagnetic resonance spectra of radical ions involved in geminate recombination and generated by vacuum ultraviolet is described. The setup allows registration of EPR spectra from short-lived radical ions in polymeric films at room temperature by recombination fluorescence modulated by a resonance microwave field.
Performance improvements of wavelength-shifting-fiber neutron detectors using high-resolution positioning algorithms
Authors: Wang C. L.
Published: May 2016

Three high-resolution positioning methods based on the FluoroBancroft linear-algebraic method [S. B. Andersson, Opt. Express 16, 18714 (2008)] are proposed for wavelength-shifting fiber (WLSF) neutron detectors. Using a Gaussian or exponential-decay light-response function, the non-linear relation of photon-number profiles vs. x-pixels was linearized and neutron positions were determined. After taking the super-Poissonian photon noise into account, the proposed algorithms give an average of 0.03-0.08 pixel position error much smaller than that (0.29 pixel) from a traditional maximum photon algorithm (MPA). The new algorithms result in better detector uniformity, less position misassignment (ghosting), better spatial resolution, and an equivalent or better instrument resolution in powder diffraction than the MPA. These improvements will facilitate broader applications of WLSF detectors at time-of-flight neutron powder diffraction beamlines, including single-crystal diffraction and texture analysis.
Quantum selection rule dependent plasmonic enhancement in quantum dot infrared photodetectors
Authors: Zhang Yingjie , Vaillancourt Jarrod , Gu Guiru , Guo Wei , Lu Xuejun
Published: May 2016

In this paper, we analyze quantum selection rules of intersubband transitions in quantum dots (QDs) and determine their impact on plasmonic enhancement in quantum dot infrared photodetectors (QDIPs). Photoluminescence and photocurrent spectrum measurement were performed on QD samples with different doping levels to identify the QD energy levels and associate the photodetection peaks with the intersubband transitions. The quantum selection rules of the intersubband transitions are determined by the electric-dipole interaction. To determine the impact of quantum selection rules on the plasmonic enhancement, we fabricated metallic two-dimensional subwavelength hole array (2DSHA) plasmonic structures with different periods on QDIPs for specific plasmonic enhancement of individual intersubband transitions. We found that the plasmonic enhancement ratios of different intersubband transitions are not the same. The unequal enhancement ratios are attributed to the quantum selection rules in the intersubband transitions and the dominant electric field (E-field E→) vectors induced by the 2DSHA plasmonic structure.
Stress measurements of planar dielectric elastomer actuators
Authors: Osmani Bekim , Aeby Elise A. , Müller Bert
Published: May 2016

Dielectric elastomer actuator (DEA) micro- and nano-structures are referred to artificial muscles because of their specific continuous power and adequate time response. The bending measurement of an asymmetric, planar DEA is described. The asymmetric cantilevers consist of 1 or 5 μm-thin DEAs deposited on polyethylene naphthalate (PEN) substrates 16, 25, 38, or 50 μm thick. The application of a voltage to the DEA electrodes generates an electrostatic pressure in the sandwiched silicone elastomer layer, which causes the underlying PEN substrate to bend. Optical beam deflection enables the detection of the bending angle vs. applied voltage. Bending radii as large as 850 m were reproducibly detected. DEA tests with electric fields of up to 80 V/μm showed limitations in electrode’s conductivity and structure failures. The actuation measurement is essential for the quantitative characterization of nanometer-thin, low-voltage, single- and multi-layer DEAs, as foreseen for artificial sphincters to efficiently treat severe urinary and fecal incontinence.
Effect of Mach number on the efficiency of microwave energy deposition in supersonic flow
Authors: Lashkov V. A. , Karpenko A. G. , Khoronzhuk R. S. , Mashek I. Ch.
Published: May 2016

The article is devoted to experimental and numerical studies of the efficiency of microwave energy deposition into a supersonic flow around the blunt cylinder at different Mach numbers. Identical conditions for energy deposition have been kept in the experiments, thus allowing to evaluate the pure effect of varying Mach number on the pressure drop. Euler equations are solved numerically to model the corresponding unsteady flow compressed gas. The results of numerical simulations are compared to the data obtained from the physical experiments. It is shown that the momentum, which the body receives during interaction of the gas domain modified by microwave discharge with a shock layer before the body, increases almost linearly with rising of Mach number and the efficiency of energy deposition also rises.
Particle dynamics in fluids with random interactions
Authors: Shagolsem Lenin S. , Rabin Yitzhak
Published: May 2016

We study the dynamics of particles in a multi-component 2d Lennard-Jones (LJ) fluid in the limiting case where all the particles are different (APD). The equilibrium properties of this APD system were studied in our earlier work [L. S. Shagolsem et al., J. Chem. Phys. 142, 051104 (2015).]. We use molecular dynamics simulations to investigate the statistical properties of particle trajectories in a temperature range covering both the fluid and the solid-fluid coexistence region. We calculate the mean-square displacement as well as displacement, angle, and waiting time distributions, and compare the results with those for one-component LJ fluid. As temperature is lowered, the dynamics of the APD system becomes increasingly complex, as the intrinsic difference between the particles is amplified by neighborhood identity ordering and by the inhomogeneous character of the solid-fluid coexistence region. The ramifications of our results for the analysis of protein tracking experiments in living cells are discussed.
Real-space visualization of conformation-independent oligothiophene electronic structure
Authors: Taber Benjamen N. , Kislitsyn Dmitry A. , Gervasi Christian F. , Mills Jon M. , Rosenfield Ariel E. , Zhang Lei , Mannsfeld Stefan C. B. , Prell James S. , Briseno Alejandro L. , Nazin George V.
Published: May 2016

We present scanning tunneling microscopy and spectroscopy (STM/STS) investigations of the electronic structures of different alkyl-substituted oligothiophenes on the Au(111) surface. STM imaging showed that on Au(111), oligothiophenes adopted distinct straight and bent conformations. By combining STS maps with STM images, we visualize, in real space, particle-in-a-box-like oligothiophene molecular orbitals. We demonstrate that different planar conformers with significant geometrical distortions of oligothiophene backbones surprisingly exhibit very similar electronic structures, indicating a low degree of conformation-induced electronic disorder. The agreement of these results with gas-phase density functional theory calculations implies that the oligothiophene interaction with the Au(111) surface is generally insensitive to molecular conformation.
InSb nanowire double quantum dots coupled to a superconducting microwave cavity
Authors: Wang R. , Deacon R. S. , Car D. , Bakkers E. P. A. M. , Ishibashi K.
Published: May 2016

By employing a micrometer precision mechanical transfer technique, we embed individual InSb nanowires into a superconducting coplanar waveguide resonator. We investigate the characteristics of a double quantum dot formed in an InSb nanowire interacting with a single mode microwave field. The charge stability diagram can be obtained from the amplitude and phase response of the resonator independently from the dc transport measurement. As the charge transits between dot-dot, or dot-lead, the change of resonator transmission is compared and the charge-cavity coupling strength is extracted to be in the magnitude of several MHz.
Automated force controller for amplitude modulation atomic force microscopy
Authors: Miyagi Atsushi , Scheuring Simon
Published: May 2016

Atomic Force Microscopy (AFM) is widely used in physics, chemistry, and biology to analyze the topography of a sample at nanometer resolution. Controlling precisely the force applied by the AFM tip to the sample is a prerequisite for faithful and reproducible imaging. In amplitude modulation (oscillating) mode AFM, the applied force depends on the free and the setpoint amplitudes of the cantilever oscillation. Therefore, for keeping the applied force constant, not only the setpoint amplitude but also the free amplitude must be kept constant. While the AFM user defines the setpoint amplitude, the free amplitude is typically subject to uncontrollable drift, and hence, unfortunately, the real applied force is permanently drifting during an experiment. This is particularly harmful in biological sciences where increased force destroys the soft biological matter. Here, we have developed a strategy and an electronic circuit that analyzes permanently the free amplitude of oscillation and readjusts the excitation to maintain the free amplitude constant. As a consequence, the real applied force is permanently and automatically controlled with picoNewton precision. With this circuit associated to a high-speed AFM, we illustrate the power of the development through imaging over long-duration and at various forces. The development is applicable for all AFMs and will widen the applicability of AFM to a larger range of samples and to a larger range of (non-specialist) users. Furthermore, from controlled force imaging experiments, the interaction strength between biomolecules can be analyzed.
A photoemission study of the effectiveness of nickel, manganese, and cobalt based corrosion barriers for silicon photo-anodes during water oxidation
Authors: O'Connor Robert , Bogan Justin , McCoy Anthony , Byrne Conor , Hughes Greg
Published: May 2016

Silicon is an attractive material for solar water splitting applications due to its abundance and its capacity to absorb a large fraction of incident solar radiation. However, it has not received as much attention as other materials due to its tendency to oxidize very quickly in aqueous environments, particularly when it is employed as the anode where it drives the oxygen evolution reaction. In recent years, several works have appeared in the literature examining the suitability of thin transition metal oxide films grown on top of the silicon to act as a corrosion barrier. The film should be transparent to solar radiation, allow hole transport from the silicon surface to the electrolyte, and stop the diffusion of oxygen from the electrolyte back to the silicon. In this work, we compare Mn-oxide, Co-oxide, and Ni-oxide thin films grown using physical vapor deposition in order to evaluate which material offers the best combination of photocurrent and corrosion protection. In addition to the electrochemical data, we also present a detailed before-and-after study of the surface chemistry of the films using x-ray photoelectron spectroscopy. This approach allows for a comprehensive analysis of the mechanisms by which the corrosion barriers protect the underlying silicon, and how they degrade during the water oxidation reaction.
Demonstration of large field effect in topological insulator films via a high-κ back gate
Authors: Wang C. Y. , Lin H. Y. , Yang S. R. , Chen K. H. M. , Lin Y. H. , Chen K. H. , Young L. B. , Cheng C. K. , Fanchiang Y. T. , Tseng S. C. , Hong M. , Kwo J.
Published: May 2016

The spintronics applications long anticipated for topological insulators (TIs) has been hampered due to the presence of high density intrinsic defects in the bulk states. In this work we demonstrate the back-gating effect on TIs by integrating Bi2Se3 films 6–10 quintuple layer (QL) thick with amorphous high-κ oxides of Al2O3 and Y2O3. Large gating effect of tuning the Fermi level EF to very close to the band gap was observed, with an applied bias of an order of magnitude smaller than those of the SiO2 back gate, and the modulation of film resistance can reach as high as 1200%. The dependence of the gating effect on the TI film thickness was investigated, and ΔN2D/ΔVg varies with TI film thickness as ∼t−0.75. To enhance the gating effect, a Y2O3 layer thickness 4 nm was inserted into Al2O3 gate stack to increase the total κ value to 13.2. A 1.4 times stronger gating effect is observed, and the increment of induced carrier numbers is in good agreement with additional charges accumulated in the higher κ oxides. Moreover, we have reduced the intrinsic carrier concentration in the TI film by doping Te to Bi2Se3 to form Bi2TexSe1−x. The observation of a mixed state of ambipolar field that both electrons and holes are present indicates that we have tuned the EF very close to the Dirac Point. These results have demonstrated that our capability of gating TIs with high-κ back gate to pave the way to spin devices of tunable EF for dissipationless spintronics based on well-established semiconductor technology.
Terahertz intersubband photodetectors based on semi-polar GaN/AlGaN heterostructures
Authors: Durmaz Habibe , Nothern Denis , Brummer Gordie , Moustakas Theodore D. , Paiella Roberto
Published: May 2016

Terahertz intersubband photodetectors are developed based on GaN/AlGaN quantum wells grown on a free-standing semi-polar (202¯1¯) GaN substrate. These quantum wells are nearly free of the polarization-induced internal electric fields that severely complicate the design of nitride intersubband devices on traditional c-plane substrates. As a result, a promising bound-to-quasi-bound THz photodetector design can be implemented. Pronounced photocurrent peaks at the design frequency near 10 THz are measured, covering frequencies that are fundamentally inaccessible to existing arsenide intersubband devices due to reststrahlen absorption. This materials system provides a favorable platform to utilize the intrinsic advantages of nitride semiconductors for THz optoelectronics.
Topological design of the film-coupled nanoparticle for the field intensity enhancement over the broadband visible spectrum
Authors: Seong H. K. , Yoo J.
Published: May 2016

An extremely high localized surface plasmon resonance (LSPR) is generated at the small gap between a gold (Au) nanoparticle and an Au thin film. The conventional LSPR of the film-coupled nanoparticle gives a narrow bandwidth, and it causes low efficiency from the energy harvesting point of view. In this study, we obtained a primary shape of the nanoparticle that works for the field enhancement in the broadband visible spectrum by using topology optimization combined with the concept of the probability density function. We confirmed that the derived elliptical hole and the thin layer at the lower nanoparticle part lead to a broad visible spectrum from blue to red range.
Impurity effects on charge transport and magnetoconductance in a single layer poly(3-hexyl-thiophene) device
Authors: Gu Hang , Chang Shankui , Lu Haizhou , Holford David F. , Zhang Tingting , Hu Jianxu , Gillin William P. , Kreouzis Theo
Published: May 2016

We have used the introduction of shallow hole traps in poly(3-hexyl-thiophene) to test one of the predictions of the bipolaron theory of magnetoconductance (MC). The results show that the introduction of shallow traps effectively increases the degree of energetic disorder in the transport states whilst not affecting the position of the Fermi level and that this results in an increase in the MC response. These results are demonstrated to be in qualitative agreement with the theory and suggest one mechanism through which trap states may affect the MC response of organic semiconductors. This work presents a controllable way of chemical doping to engineer a change in absolute current at a given bias depending on the choice of anodes. It also allows for tuning the magnitude of negative MC response and electroluminescence efficiency under different driving conditions.
Hexagonal phase-pure wide band gap ε-Ga2O3 films grown on 6H-SiC substrates by metal organic chemical vapor deposition
Authors: Xia Xiaochuan , Chen Yuanpeng , Feng Qiuju , Liang Hongwei , Tao Pengcheng , Xu Mengxiang , Du Guotong
Published: May 2016

In this paper, hexagonal structure phase-pure wide-band gap ε-Ga2O3 films were grown by metal organic chemical vapor deposition on 6H-SiC substrates. The ε-Ga2O3 films with good crystal quality were verified by high-resolution X-ray diffraction. The out-of-plane epitaxial relationship between ε-Ga2O3 films and 6H-SiC substrates is confirmed to be ε-Ga2O3 (0001)//6H-SiC (0001), and the in-plane epitaxial relationship is also confirmed to be ε-Ga2O3 ⟨112¯0⟩//6H-SiC ⟨112¯0⟩. The SEM and AFM images show that the ε-Ga2O3 films are uniform and flat. The ε-Ga2O3 films are thermally stable up to approximately 800 °C and begin to transform into β-phase Ga2O3 at 850 °C. Then, they are completely converted to β-Ga2O3 films under 900 °C. The high-quality ε-Ga2O3 films with hexagonal structure have potential application in the optoelectronic field.