bluuebunny/crossref_metadata_2025 huggingface dataset:
Deciphering complex patterns of class‐I HLA–peptide cross‐reactivity via hierarchical grouping
Authors: Mukherjee Sumanta , Warwicker Jim , Chandra Nagasuma
Published: February 2015

T‐cell responses in humans are initiated by the binding of a peptide antigen to a human leukocyte antigen (HLA) molecule. The peptide–HLA complex then recruits an appropriate T cell, leading to cell‐mediated immunity. More than 2000 HLA class‐I alleles are known in humans, and they vary only in their peptide‐binding grooves. The polymorphism they exhibit enables them to bind a wide range of peptide antigens from diverse sources. HLA molecules and peptides present a complex molecular recognition pattern, as many peptides bind to a given allele and a given peptide can be recognized by many alleles. A powerful grouping scheme that not only provides an insightful classification, but is also capable of dissecting the physicochemical basis of recognition specificity is necessary to address this complexity. We present a hierarchical classification of 2010 class‐I alleles by using a systematic divisive clustering method. All‐pair distances of alleles were obtained by comparing binding pockets in the structural models. By varying the similarity thresholds, a multilevel classification was obtained, with 7 supergroups, each further subclassifying to yield 72 groups. An independent clustering performed based only on similarities in their epitope pools correlated highly with pocket‐based clustering. Physicochemical feature combinations that best explain the basis of clustering are identified. Mutual information calculated for the set of peptide ligands enables identification of binding site residues contributing to peptide specificity. The grouping of HLA molecules achieved here will be useful for rational vaccine design, understanding disease susceptibilities and predicting risk of organ transplants.
Ambipolar zinc-polyiodide electrolyte for a high-energy density aqueous redox flow battery
Authors: Li Bin , Nie Zimin , Vijayakumar M. , Li Guosheng , Liu Jun , Sprenkle Vincent , Wang Wei
Published: February 2015

Redox flow batteries are receiving wide attention for electrochemical energy storage due to their unique architecture and advantages, but progress has so far been limited by their low energy density (~25 Wh l−1). Here we report a high-energy density aqueous zinc-polyiodide flow battery. Using the highly soluble iodide/triiodide redox couple, a discharge energy density of 167 Wh l−1 is demonstrated with a near-neutral 5.0 M ZnI2 electrolyte. Nuclear magnetic resonance study and density functional theory-based simulation along with flow test data indicate that the addition of an alcohol (ethanol) induces ligand formation between oxygen on the hydroxyl group and the zinc ions, which expands the stable electrolyte temperature window to from −20 to 50 °C, while ameliorating the zinc dendrite. With the high-energy density and its benign nature free from strong acids and corrosive components, zinc-polyiodide flow battery is a promising candidate for various energy storage applications.
The genome of Leishmania panamensis: insights into genomics of the L. (Viannia) subgenus.
Authors: Llanes Alejandro , Restrepo Carlos Mario , Vecchio Gina Del , Anguizola Franklin José , Lleonart Ricardo
Published: February 2015

Kinetoplastid parasites of the Leishmania genus cause several forms of leishmaniasis. Leishmania species pathogenic to human are separated into two subgenera, Leishmania (Leishmania) and L. (Viannia). Species from the Viannia subgenus cause predominantly cutaneous leishmaniasis in Central and South America, occasionally leading to more severe clinical presentations. Although the genomes of several species of Leishmania have been sequenced to date, only one belongs to this rather different subgenus. Here we explore the unique features of the Viannia subgenus by sequencing and analyzing the genome of L. (Viannia) panamensis. Against a background of conservation in gene content and synteny, we found key differences at the genomic level that may explain the occurrence of molecular processes involving nucleic acid manipulation and differential modification of surface glycoconjugates. These differences may in part explain some phenotypic characteristics of the Viannia parasites, including their increased adaptive capacity and enhanced metastatic ability.
Genetic variants in the Hippo pathway predict biochemical recurrence after radical prostatectomy for localized prostate cancer
Authors: Huang Chao-Yuan , Huang Shu-Pin , Lin Victor C. , Yu Chia-Cheng , Chang Ta-Yuan , Juang Shin-Hun , Bao Bo-Ying
Published: February 2015

While localized prostate cancer is potentially curative, many patients still show biochemical recurrence (BCR) after curative treatments such as radical prostatectomy (RP). The Hippo pathway has recently been shown to be an evolutionarily conserved regulator of tissue growth and its perturbation can trigger tumorigenesis. We hypothesize that genetic variants of the Hippo pathway may influence clinical outcomes in localized prostate cancer patients. We genotyped 53 tagging single-nucleotide polymorphisms (SNPs) from seven core Hippo pathway genes in 246 localized prostate cancer patients treated with RP. Kaplan-Meier analysis and Cox proportional hazard models were utilized to identify significant SNPs that correlated with BCR. For replication, five associated SNPs were genotyped in an independent cohort of 212 patients. After adjusting for known clinicopathologic factors, the association between STK3 rs7827435 and BCR (P = 0.018) was replicated in the second stage (P = 0.026; Pcombined = 0.001). Additional integrated in silico analysis provided evidence that rs7827435 affects STK3 expression, which in turn is significantly correlated with tumor aggressiveness and patient prognosis. In conclusion, genetic variants of the Hippo pathway contribute to the variable outcomes of prostate cancer and the discovery of these biomarkers provides a molecular approach for prognostic risk assessment.
The catalytic role of the M2 metal ion in PP2Cα
Authors: Pan Chang , Tang Jun-yi , Xu Yun-fei , Xiao Peng , Liu Hong-da , Wang Hao-an , Wang Wen-bo , Meng Fan-guo , Yu Xiao , Sun Jin-peng
Published: February 2015

PP2C family phosphatases (the type 2C family of protein phosphatases; or metal-dependent phosphatase, PPM) constitute an important class of signaling enzymes that regulate many fundamental life activities. All PP2C family members have a conserved binuclear metal ion active center that is essential for their catalysis. However, the catalytic role of each metal ion during catalysis remains elusive. In this study, we discovered that mutations in the structurally buried D38 residue of PP2Cα (PPM1A) redefined the water-mediated hydrogen network in the active site and selectively disrupted M2 metal ion binding. Using the D38A and D38K mutations of PP2Cα as specific tools in combination with enzymology analysis, our results demonstrated that the M2 metal ion determines the rate-limiting step of substrate hydrolysis, participates in dianion substrate binding and stabilizes the leaving group after P-O bond cleavage. The newly characterized catalytic role of the M2 metal ion in this family not only provides insight into how the binuclear metal centers of the PP2C phosphatases are organized for efficient catalysis but also helps increase our understanding of the function and substrate specificity of PP2C family members.
The TLR4 Agonist Fibronectin Extra Domain A is Cryptic, Exposed by Elastase-2; use in a fibrin matrix cancer vaccine
Authors: Julier Ziad , Martino Mikaël M. , de Titta Alexandre , Jeanbart Laura , Hubbell Jeffrey A.
Published: February 2015

Fibronectin (FN) is an extracellular matrix (ECM) protein including numerous fibronectin type III (FNIII) repeats with different functions. The alternatively spliced FN variant containing the extra domain A (FNIII EDA), located between FNIII 11 and FNIII 12, is expressed in sites of injury, chronic inflammation and solid tumors. Although its function is not well understood, FNIII EDA is known to agonize Toll-like receptor 4 (TLR4). Here, by producing various FN fragments containing FNIII EDA, we found that FNIII EDA's immunological activity depends upon its local intramolecular context within the FN chain. N-terminal extension of the isolated FNIII EDA with its neighboring FNIII repeats (FNIII 9-10-11) enhanced its activity in agonizing TLR4, while C-terminal extension with the native FNIII 12-13-14 heparin-binding domain abrogated it. In addition, we reveal that an elastase 2 cleavage site is present between FNIII EDA and FNIII 12. Activity of the C-terminally extended FNIII EDA could be restored after cleavage of the FNIII 12-13-14 domain by elastase 2. FN being naturally bound to the ECM, we immobilized FNIII EDA-containing FN fragments within a fibrin matrix model along with antigenic peptides. Such matrices were shown to stimulate cytotoxic CD8+ T cell responses in two murine cancer models.
Real-world carbon nanoparticle exposures induce brain and gonadal alterations in zebrafish (Danio rerio) as determined by biospectroscopy techniques
Authors: Li Junyi , Ying Guang-Guo , Jones Kevin C. , Martin Francis L.
Published: February 2015

Differential tissue-specific effects of nanoparticles: biospectroscopy as a toxicity-sensing tool.
Binding interactions between prazosin and α1A-adrenoceptor: investigation on the thermodynamic behaviors and the binding mechanism by high performance affinity chromatography
Authors: Wang Jing , Li Qian , Yang Lingjian , Zhang Yajun , Yu Jie , Zhao Xinfeng , Zheng Jianbin , Zhang Youyi , Zheng Xiaohui
Published: February 2015

The interactions of prazosin binding to immobilized α1A-adrenoceptor were studied by frontal analysis and molecular docking.
Design and development of novel reactive amine nanocontainers for a self-healing epoxy adhesive: self-repairing investigation using the lap shear test
Authors: Khoee Sepideh , Kachoei Zahra
Published: February 2015

Recovery of fracture toughness of a self-healing epoxy adhesive is achieved by using a novel amine nanocontainer.
Concentration quenching in cerium oxide dispersions via a Förster resonance energy transfer mechanism facilitates the identification of fatty acids
Authors: Krishnan Asha , Sreeremya Thadathil S. , Mohamed A. Peer , Hareesh Unnikrishnan Saraswathy , Ghosh Swapankumar
Published: February 2015

The distance dependence of FRET has been utilized, as a simple and novel analytical tool, for explaining the fluorescence quenching of cerium dioxide dispersions and in the prediction of the structure of fatty acids.
Non-covalent functionalization of reduced graphene oxide using sulfanilic acid azocromotrop and its application as a supercapacitor electrode material
Authors: Jana Milan , Saha Sanjit , Khanra Partha , Samanta Pranab , Koo Hyeyoung , Chandra Murmu Naresh , Kuila Tapas
Published: February 2015

Sulfanilic acid azocromotrop modified reduced graphene oxide was prepared by non-covalent functionalization of graphene oxide followed by post reduction using hydrazine monohydrate.
Detection of ethanol in Brazilian gasoline station attendants
Authors: Borille Bruna Tassi , Fiorentin Taís Regina , Coppe Bruna Claudia , Comiran Eloisa , Bemvenuti Jacques Ana Laura , Vieira Sousa Tanara Rosângela , Pasa Graciela Gema , Pechansky Flavio , Maris de Jezus Castro Stela , Limberger Renata Pereira
Published: February 2015

In Brazil, gasoline station attendants are regularly exposed to the ethanol contained in fuel, as well as the one used as the gasoline additive.
Co-crystals and molecular salts of carboxylic acid/pyridine complexes: can calculated pKa's predict proton transfer? A case study of nine complexes
Authors: Lemmerer Andreas , Govindraju Stefan , Johnston Marcelle , Motloung Xolani , Savig Kelsey L.
Published: February 2015

Prediction of proton transfer made only using the structural formula can predict at which range of calculated ΔpKa's a co-crystal or a molecular salt forms in a series of carboxylic acid/pyridine complexes.
A comprehensive understanding of the synthons involving C–H⋯F–C hydrogen bond(s) from structural and computational analyses
Authors: Kaur Gurpreet , Choudhury Angshuman Roy
Published: February 2015

The synthons involving C–H⋯F–C hydrogen bonds remain unaltered when more halogen (F/Cl/Br) atoms are added.
Photodissociation dynamics of ethanethiol in clusters: complementary information from velocity map imaging, mass spectrometry and calculations
Authors: Svrčková Pavla , Pysanenko Andriy , Lengyel Jozef , Rubovič Peter , Kočišek Jaroslav , Poterya Viktoriya , Slavíček Petr , Fárník Michal
Published: February 2015

We investigate the solvent effects on photodissociation dynamics of the S–H bond in ethanethiol CH3CH2SH (EtSH).
Multi-length-scale relationships between the polymer molecular structure and charge transport: the case of poly-naphthalene diimide bithiophene
Authors: Fazzi Daniele , Caironi Mario
Published: February 2015

Charge transport in organic polymer semiconductors is a complex phenomenon affected by structural and electronic properties ranging over different length scales, from the molecular one up to the macro-scale.
Hydrogen production by the water-gas shift reaction using CuNi/Fe2O3 catalyst
Authors: Jha Ajay , Jeong Dae-Woon , Shim Jae-Oh , Jang Won-Jun , Lee Yeol-Lim , Rode Chandrashekhar V. , Roh Hyun-Seog
Published: February 2015

Incorporation of both Cu and Ni together into the crystalline lattice of Fe2O3 results in a significant increase in the catalytic activity and also suppresses the methanation reaction in the high-temperature water-gas shift (HT-WGS) reaction.
Nickel complexes for catalytic C–H bond functionalization
Authors: Johnson S. A.
Published: February 2015

A search for fundamental understanding of how Ni complexes can be designed to undergo challenging C–H activation reactions provides an entry into unprecedented C–H functionalization reactions.
Protective effects of alisol B 23-acetate from edible botanical Rhizoma alismatis against carbon tetrachloride-induced hepatotoxicity in mice
Authors: Meng Qiang , Chen Xinli , Wang Changyuan , Liu Qi , Sun Huijun , Sun Pengyuan , Huo Xiaokui , Liu Zhihao , Liu Kexin
Published: February 2015

Alisol B 23-acetate protects against CCl4-induced hepatotoxicity via FXR and STAT3-mediated gene regulation in mice.
Research highlights: aptamers on a chip
Authors: Kim Donghyuk , Pushkarsky Ivan , Tay Andy , Di Carlo Dino
Published: February 2015

Array-based discovery of multivalent aptamers – Aptamers for electrochemical sensing of TGF-β1 release from liver cells – Maintenance-free aptamer biosensor.
5-Fluorouracil loaded thermosensitive PLGA–PEG–PLGA hydrogels for the prevention of postoperative tendon adhesion
Authors: Yuan Baoming , He Chaoliang , Dong Xiaoming , Wang Jincheng , Gao Zhongli , Wang Qian , Tian Huayu , Chen Xuesi
Published: February 2015

Thermosensitive PLGA–PEG–PLGA hydrogels containing 5-fluorouracil were applied to cover the sutured Achilles tendon of rats, leading to a significant reduction in adhesion formation during the tendon healing.
Tuning the photoluminescence and ultrasensitive trace detection properties of few-layer MoS2by decoration with gold nanoparticles
Authors: Singha Shib Shankar , Nandi Dipanjan , Singha Achintya
Published: February 2015

Tuning the optical properties and ultrasensitive molecular detection capabilities of Au nanoparticle-decorated MoS2.
Sulfur-based hyper cross-linked polymers
Authors: Monnereau Laure , Grandclaudon Charlotte , Muller Thierry , Bräse Stefan
Published: February 2015

The possibilities offered by sulphur-based chemistry to produce 3D-polymers based on a tetrakis(phenyl)methane core have been exploited: eight HCPs were generated by oxidation, nucleophilic substitution or thia-Michael additions.
Relation between molecular structure of smectite and liquefaction of mudstone
Authors: Li Guichen , Jiang Zuohan , Feng Xiaowei , Zhang Nong , Xu Xingliang
Published: February 2015

As the degrees of water soaking increase, breakage of the smectite microstructure will occur, and overall energy of the mode will dramatically decreases, resulting in mudstone with macroscopic phenomena such as argillization and liquefaction.
Photoluminescent nanoparticles in water with tunable emission for coating and ink-jet printing
Authors: Deng Chao , Yang Zhening , Zheng Zhicheng , Liu Na , Ling Jun
Published: February 2015

Novel polyfluorene-containing copolymers with 2-(dimethylamino)ethyl methacrylate self-assemble into photoluminescent nanoparticles in aqueous solutions and act as an excellent scaffold for incorporating various pigments to emit tunable colors, including white, with high quantum yield up to 0.80.
Spaced Retrieval Training: 26 Years of Growth
Authors: Benigas Jeanette E.
Published: February 2015

Clinicians frequently use spaced retrieval training (SRT) to assist people with memory loss in retention and recall functional information. The body of literature surrounding SRT has made valuable additions, shown flexibility and extended the use of the strategy to other populations. The history and additions of SRT will be reviewed.
Algorithm for heart rate extraction in a novel wearable acoustic sensor
Authors: Chen Guangwei , Imtiaz Syed Anas , Aguilar–Pelaez Eduardo , Rodriguez–Villegas Esther
Published: February 2015

Phonocardiography is a widely used method of listening to the heart sounds and indicating the presence of cardiac abnormalities. Each heart cycle consists of two major sounds – S1 and S2 – that can be used to determine the heart rate. The conventional method of acoustic signal acquisition involves placing the sound sensor at the chest where this sound is most audible. Presented is a novel algorithm for the detection of S1 and S2 heart sounds and the use of them to extract the heart rate from signals acquired by a small sensor placed at the neck. This algorithm achieves an accuracy of 90.73 and 90.69%, with respect to heart rate value provided by two commercial devices, evaluated on more than 38 h of data acquired from ten different subjects during sleep in a pilot clinical study. This is the largest dataset for acoustic heart sound classification and heart rate extraction in the literature to date. The algorithm in this study used signals from a sensor designed to monitor breathing. This shows that the same sensor and signal can be used to monitor both breathing and heart rate, making it highly useful for long‐term wearable vital signs monitoring.
Lightweight wrist photoplethysmography for heavy exercise: motion robust heart rate monitoring algorithm
Authors: Lai Po‐Hsiang , Kim Insoo
Published: February 2015

The challenge of heart rate monitoring based on wrist photoplethysmography (PPG) during heavy exercise is addressed. PPG is susceptible to motion artefacts, which have to be mitigated for accurate heart rate estimation. Motion artefacts are particularly apparent for wrist devices, for example, a smart watch, because of the high mobility of the arms. Proposed is a low complexity highly accurate heart rate estimation method for continuous heart rate monitoring using wrist PPG. The proposed method achieved 2.57% mean absolute error in a test data set where subjects ran for a maximum speed of 17 km/h.
Sliding mode fault‐tolerant control of an octorotor using linear parameter varying‐based schemes
Authors: Alwi Halim , Edwards Christopher
Published: February 2015

This study presents two fault‐tolerant control (FTC) schemes for an octorotor UAV. The FTC schemes are based on an linear parameter varying system representation and utilises a combination of sliding‐mode ideas and control allocation (CA) in order to take full advantage of the available redundant rotors in the octorotor configuration. A detailed synthesis procedure for the design of the two FTC schemes in the presence of uncertainty, as well as faults/failures, is presented. The first scheme is based on an online CA methodology where knowledge of the rotor effectiveness level has been used to redistribute the control signals to the healthy rotors. The second scheme assumes that this information is not available and uses a fixed CA structure even in the event of faults/failures. Although the synthesis process for the two schemes is different and they use different strategies to redistribute the control signals when faults/failures occur, both schemes involved the same ‘baseline’ (sliding‐mode) controller which does not need to be reconfigured. The difference is in the final physical control law where the CA matrix is defined. Simulation results on the full non‐linear octorotor model are presented for the two different schemes in the presence of uncertainty, sensor noise as well as faults/failures. The simulation results for various fault/failure scenarios show no visible degradation in state tracking performance, highlighting the potential of the proposed schemes.
Diagnosis of solid insulation deterioration for power transformers with dissolved gas analysis‐based time series correlation
Authors: Wang Xuelei , Li Qingmin , Yang Rui , Li Chengrong , Zhang Ying
Published: February 2015

Dissolved gas analysis (DGA) is a prevailing methodology being widely used to detect incipient faults in power transformers. Although various methods have been developed to interpret DGA results, they may sometimes fail to diagnose precisely, especially when solid insulation deterioration is involved. This study presents a time series correlation technique, in which the sampled data of dissolved gases in the transformer oil are considered as a time series and the series correlation scheme in statistics is adopted to explore and manipulate the fault information. Both the constant and variable characteristic parameters are initially chosen based on analysis in terms of frequency histograms. With quantitative correlation analysis between the constant and variable characteristic parameters, a new criterion for solid insulation diagnosis is thereby proposed, which can be used to diagnose whether solid insulation deterioration is involved in a transformer fault, as well as further distinguish the electrical faults from the thermal ones. According to the proposed technique, explorative tests regarding two power transformers have shown promising results. With regard to the 91 fault samples collected from China Power Grid, the diagnosis accuracies for electrical and thermal faults were 86.5 and 77.7%, respectively, whereas it was 61.5% for the prevailing CO2/CO criterion.
Facile synthesis and characterisation of SiO2@PSS/Ag‐PPy using SiO2@PSS as template
Authors: Zhang Xiongzhi , Huang Yu , Huang Xiyan , Huang Chi , Li Houbin , Yi Shengping , Liu Xinghai
Published: February 2015

A new route for the in‐situ formation of silver‐polypyrrole (Ag‐PPy) on the layer of SiO2@poly(sodium styrene sulphonate) (SiO2@PSS/Ag‐PPy) composite particles, using SiO2@poly(sodium styrene sulphonate) (SiO2@PSS) particles as a template is presented. The template SiO2@PSS consisting of a SiO2 core and PSS on the surface was prepared by the ‘grafting from’ approach. SiO2@PSS/Ag‐PPy was characterised by transmission electron microscopy, X‐ray powder diffraction, energy‐dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopic analysis, thermo‐gravimetric analysis and differential thermal analysis. The results showed that the SiO2@PSS/Ag‐PPy composites consisting of a spherical structure with a diameter of about 80 nm were successfully fabricated.
Diastereoselective Synthesis of 3,3-Disubstituted Oxindoles from N-Aryl-3-Chlorooxindoles Bearing C–N Axial Chirality via Nucleo­philic Substitution
Authors: Nakazaki Atsuo , Miyagawa Keitaro , Nishikawa Toshio
Published: February 2015

Diastereoselective synthesis of 3,3-disubstituted oxindoles was examined using racemic N-aryl-3-chlorooxindoles bearing C–N axial chirality. The reaction involved the nucleophilic substitution of 3-chlorooxindoles via an ortho-azaxylylene intermediate in the presence of AgBF4 and MS 4 Å. High diastereoselectivities (up to >95:<5) were achieved in the formation of 3-alkyl-3-aryloxindole derivatives when electron-rich arenes were used.
New optimally technical sizing procedure of domestic photovoltaic panel/battery system
Authors: Salah Chokri Ben , Lamamra Kheireddine , Fatnassi Anis
Published: February 2015

This paper describes a new sizing system of a solar array and a battery in a standalone photovoltaic system. The method consists in a fuzzy logic system that reads the consumed energy and the monthly average of daily solar radiation of the region in the input and gives the photovoltaic panel surface and the battery capacity in the output. The simulation results are based on Matlab/Simulink. The system performance with different inputs has been verified by carrying out simulation studies using calculated outputs. The results demonstrate the effectiveness of this approach. In fact, an example of a domestic house is provided in this paper, where the simulation results show good performances.
Non-pairwise additivity of the leading-order dispersion energy
Authors: Hollett Joshua W.
Published: February 2015

The leading-order (i.e., dipole-dipole) dispersion energy is calculated for one-dimensional (1D) and two-dimensional (2D) infinite lattices, and an infinite 1D array of infinitely long lines, of doubly occupied locally harmonic wells. The dispersion energy is decomposed into pairwise and non-pairwise additive components. By varying the force constant and separation of the wells, the non-pairwise additive contribution to the dispersion energy is shown to depend on the overlap of density between neighboring wells. As well separation is increased, the non-pairwise additivity of the dispersion energy decays. The different rates of decay for 1D and 2D lattices of wells is explained in terms of a Jacobian effect that influences the number of nearest neighbors. For an array of infinitely long lines of wells spaced 5 bohrs apart, and an inter-well spacing of 3 bohrs within a line, the non-pairwise additive component of the leading-order dispersion energy is −0.11 kJ mol−1 well−1, which is 7% of the total. The polarizability of the wells and the density overlap between them are small in comparison to that of the atomic densities that arise from the molecular density partitioning used in post-density-functional theory (DFT) damped dispersion corrections, or DFT-D methods. Therefore, the nonadditivity of the leading-order dispersion observed here is a conservative estimate of that in molecular clusters.
Electron transfer statistics and thermal fluctuations in molecular junctions
Authors: Goswami Himangshu Prabal , Harbola Upendra
Published: February 2015

We derive analytical expressions for probability distribution function (PDF) for electron transport in a simple model of quantum junction in presence of thermal fluctuations. Our approach is based on the large deviation theory combined with the generating function method. For large number of electrons transferred, the PDF is found to decay exponentially in the tails with different rates due to applied bias. This asymmetry in the PDF is related to the fluctuation theorem. Statistics of fluctuations are analyzed in terms of the Fano factor. Thermal fluctuations play a quantitative role in determining the statistics of electron transfer; they tend to suppress the average current while enhancing the fluctuations in particle transfer. This gives rise to both bunching and antibunching phenomena as determined by the Fano factor. The thermal fluctuations and shot noise compete with each other and determine the net (effective) statistics of particle transfer. Exact analytical expression is obtained for delay time distribution. The optimal values of the delay time between successive electron transfers can be lowered below the corresponding shot noise values by tuning the thermal effects.
World-line instantons and the Schwinger effect as a Wentzel–Kramers–Brillouin exact path integral
Authors: Gordon James , Semenoff Gordon W.
Published: February 2015

A detailed study of the semiclassical expansion of the world line path integral for a charged relativistic particle in a constant external electric field is presented. We show that the Schwinger formula for charged particle pair production is reproduced exactly by the semiclassical expansion around classical instanton solutions when the leading order of fluctuations is taken into account. We prove that all corrections to this leading approximation vanish and that the WKB approximation to the world line path integral is exact.
Measuring droplet size distributions from overlapping interferometric particle images
Authors: Bocanegra Evans Humberto , Dam Nico , van der Voort Dennis , Bertens Guus , van de Water Willem
Published: February 2015

Interferometric particle imaging provides a simple way to measure the probability density function (PDF) of droplet sizes from out-focus images. The optical setup is straightforward, but the interpretation of the data is a problem when particle images overlap. We propose a new way to analyze the images. The emphasis is not on a precise identification of droplets, but on obtaining a good estimate of the PDF of droplet sizes in the case of overlapping particle images. The algorithm is tested using synthetic and experimental data. We next use these methods to measure the PDF of droplet sizes produced by spinning disk aerosol generators. The mean primary droplet diameter agrees with predictions from the literature, but we find a broad distribution of satellite droplet sizes.
Suppression of vortex-induced vibration using the rotary oscillation of a cylinder
Authors: Du Lin , Sun Xiaofeng
Published: February 2015

An active control method for suppressing the response of an elastically mounted cylinder by forcing rotary oscillation is presented. Vortex-induced vibration (VIV) of structures is related to the interaction between body and shedding vortex. In the synchronization/lock-in regime, when the vortex shedding frequency fs matches the natural frequency fN of the spring-mass system, large displacement amplitude in the transverse direction is observed. The effect of rotary oscillation on unsteady laminar flow past a freely vibrating cylinder has been investigated. In this study, the cylinder has two degrees of freedom: forced rotary oscillation and vortex induced vibration. The investigation is based on the solutions of flow equations by using the immersed boundary method at moderate Reynolds number. The present computational results indicate the rotary oscillation control can be implemented to suppress the response amplitude of VIV by locking the vortex shedding frequency fs at the forcing frequency fr in the “lock-on” region. The “lock-on” phenomenon occurs in the wake of a rotationally oscillating cylinder, which is free to vibrate in the transverse direction. The essence of the present active control method is to change the frequency of the vortex shedding, rather than suppress it. The response of an elastically mounted cylinder is drastically suppressed to less than 1% of the cylinder diameter, when proper frequency ratio fr/fN and rotational velocity are imposed. Detailed analyses of aerodynamic performance are given to interpret the mechanism of the suppression of response caused by forced rotary oscillation. The effects of mass ratio and velocity rate of rotary oscillation are also found to play an important role in the spring-mass system. The efficiency of the present method increases with Reynolds number.
Equations of state and transport properties of mixtures in the warm dense regime
Authors: Hou Yong , Dai Jiayu , Kang Dongdong , Ma Wen , Yuan Jianmin
Published: February 2015

We have performed average-atom molecular dynamics to simulate the CH and LiH mixtures in the warm dense regime, and obtained equations of state and the ionic transport properties. The electronic structures are calculated by using the modified average-atom model, which have included the broadening of energy levels, and the ion-ion pair potentials of mixtures are constructed based on the temperature-dependent density functional theory. The ionic transport properties, such as ionic diffusion and shear viscosity, are obtained through the ionic velocity correlation functions. The equations of state and transport properties for carbon, hydrogen and lithium, hydrogen mixtures in a wide region of density and temperature are calculated. Through our computing the average ionization degree, average ion-sphere diameter and transition properties in the mixture, it is shown that transport properties depend not only on the ionic mass but also on the average ionization degree.
The effect of slow spatial processes on emerging spatiotemporal patterns
Authors: Doelman A. , Sewalt L. , Zagaris A.
Published: February 2015

We consider a two-component system of evolutionary partial differential equations posed on a bounded domain. Our system is pattern forming, with a small stationary pattern bifurcating from the background state. It is also equipped with a multiscale structure, manifesting itself through the presence of spectrum close to the origin. Spatial processes are associated with long time scales and affect the nonlinear pattern dynamics strongly. To track these dynamics past the bifurcation, we develop an asymptotics-based method complementing and extending rigorous center manifold reduction. Using it, we obtain a complete analytic description of the pattern stability problem in terms of the linear stability of the background state. Through this procedure, we portray with precision how slow spatial processes can destabilize small patterns close to onset. We further illustrate our results on a model describing phytoplankton whose growth is co-limited by nutrient and light. Localized colonies forming at intermediate depths are found to be subject to oscillatory destabilization shortly after emergence, whereas boundary-layer type colonies at the bottom persist. These analytic results are in agreement with numerical simulations for the full model, which we also present.
Mechanisms of surface pressure distribution within a laminar separation bubble at different Reynolds numbers
Authors: Lee Donghwi , Kawai Soshi , Nonomura Taku , Anyoji Masayuki , Aono Hikaru , Oyama Akira , Asai Keisuke , Fujii Kozo
Published: February 2015

Mechanisms behind the pressure distribution and skin friction within a laminar separation bubble (LSB) are investigated by large-eddy simulations around a 5% thickness blunt flat plate at the chord length based Reynolds number 5.0 × 103, 6.1 × 103, 1.1 × 104, and 2.0 × 104. The characteristics inside the LSB change with the Reynolds number; a steady laminar separation bubble (LSB_S) at the Reynolds number 5.0 × 103 and 6.1 × 103, and a steady-fluctuating laminar separation bubble (LSB_SF) at the Reynolds number 1.1 × 104, and 2.0 × 104. Different characteristics of pressure and skin friction distributions are observed by increasing the Reynolds number, such that a gradual monotonous pressure recovery in the LSB_S and a plateau pressure distribution followed by a rapid pressure recovery region in the LSB_SF. The reasons behind the different characteristics of pressure distributions at different Reynolds numbers are discussed by deriving the Reynolds averaged pressure gradient equation. It is confirmed that the viscous stress distributions near the surface play an important role in determining the formation of different pressure distributions. Depending on the Reynolds numbers, the viscous stress distributions near the surface are affected by the development of a separated laminar shear layer or the Reynolds shear stress. In addition, we show that the same analyses can be applied to the flows around a NACA0012 airfoil.
Current transient spectroscopy for trapping analysis on Au-free AlGaN/GaN Schottky barrier diode
Authors: Hu J. , Stoffels S. , Lenci S. , Bakeroot B. , Venegas R. , Groeseneken G. , Decoutere S.
Published: February 2015

This paper presents a combined technique of high voltage off-state stress and current transient measurements to investigate the trapping/de-trapping characteristics of Au-free AlGaN/GaN Schottky barrier diodes. The device features a symmetric three-terminal structure with a central anode contact surrounded by two separate cathodes. Under the diode off-state stress conditions, the two separate cathodes were electrically shorted. The de-trapping dynamics was studied by monitoring the recovery of the two-dimensional electron gas (2DEG) current at different temperatures by applying 0.5 V at cathode 2 while grounding cathode 1. During the recovery, the anode contact acts as a sensor of changes in diode leakage current. This leakage variation was found to be mainly due to the barrier height variation. With this method, the energy level and capture cross section of different traps in the AlGaN/GaN Schottky barrier diode can be extracted. Furthermore, the physical location of different trapping phenomena is indicated by studying the variation of the diode leakage current during the recovery. We have identified two distinct trapping mechanisms: (i) electron trapping at the AlGaN surface in the vicinity of the Schottky contact which results in the leakage reduction (barrier height ϕB increase) together with RON degradation; (ii) the electron trapping in the GaN channel layer which partially depletes the 2DEG. The physical origin of the two different traps is discussed in the text.
Effect of leakage current and shunt resistance on the light intensity dependence of organic solar cells
Authors: Proctor Christopher M. , Nguyen Thuc-Quyen
Published: February 2015

In this report, we demonstrate that parasitic leakage currents dominate the current voltage characteristics of organic solar cells measured under illumination intensities less than one sun when the device shunt resistance is too low (<106 Ω cm2). The implications of such effects on common interpretations of the light intensity dependence of the solar cell open circuit voltage, fill factor, short circuit current, and power conversion efficiency are discussed in detail.
Exchange spring in A1/L1 FePt composite and its application in magnetic force microscope
Authors: Li Guoqing , Zhu Yanyan , Zhang Yong , Zhao Hujun , Zeng Daofu , Li Yuhui , Lu Wei
Published: February 2015

This paper reported fabrication of FexPt100-x films with (001) epitaxy on MgO(100) substrates. The atomic percentage of Fe was changed within the range of x = 10–85 in order to search the optimal atomic ratio for achieving both high and isotropic-like coercivity. It was found that the Fe60Pt40 film exhibited large coercivities exceeding 5 kOe along both in-plane and out-of-plane directions due to the formation of A1/L10 FePt composite. A penta-domain model for hard/soft/hard exchange spring system was proposed to interpret the anomalous magnetization behaviors observed in Fe60Pt40 sample. By using Fe60Pt40 as the magnetic coating layer on a probe of magnetic force microscope, the flux changes at a linear density of 1000 kfci could be readily observed at a resolution of ∼13 nm.
Growth and properties of rare-earth arsenide InGaAs nanocomposites for terahertz generation
Authors: Salas R. , Guchhait S. , Sifferman S. D. , McNicholas K. M. , Dasika V. D. , Krivoy E. M. , Jung D. , Lee M. L. , Bank S. R.
Published: February 2015

We explore the electrical, optical, and structural properties of fast photoconductors of In0.53Ga0.47As containing a number of different rare-earth arsenide nanostructures. The rare-earth species provides a route to tailor the properties of the photoconductive materials. LuAs, GdAs, and LaAs nanostructures were embedded into InGaAs in a superlattice structure and compared to the relatively well-studied ErAs:InGaAs system. LaAs:InGaAs was found to have the highest dark resistivities, while GdAs:InGaAs had the lowest carrier lifetimes and highest carrier mobility at moderate depositions. The quality of the InGaAs overgrowth appears to have the most significant effect on the properties of these candidate fast photoconductors.
Refractometric sensing of Li salt with visible-light Si3N4 microdisk resonators
Authors: Doolin C. , Doolin P. , Lewis B. C. , Davis J. P.
Published: February 2015

We demonstrate aqueous refractive index sensing with 15–30 μm diameter silicon nitride microdisk resonators to detect small concentrations of Li salt. A dimpled-tapered fiber is used to couple 780 nm visible light to the microdisks, in order to perform spectroscopy on their optical resonances. The dimpled fiber probe allows testing of multiple devices on a chip in a single experiment. This sensing system is versatile and easy to use, while remaining competitive with other refractometric sensors. For example, from a 20 μm diameter device we measure a sensitivity of 230 ± 20 nm/refractive index units (RIU) with a loaded quality factor of 1.5 × 104, and a limit of detection down to (1.3 ± 0.1) × 10−6 RIU.
The energy barrier at noble metal/TiO2 junctions
Authors: Hossein-Babaei F. , Lajvardi Mehdi M. , Alaei-Sheini Navid
Published: February 2015

Nobel metal/TiO2 structures are used as catalysts in chemical reactors, active components in TiO2-based electronic devices, and connections between such devices and the outside circuitry. Here, we investigate the energy barrier at the junctions between vacuum-deposited Ag, Au, and Pt thin films and TiO2 layers by recording their electrical current vs. voltage diagrams and spectra of optical responses. Deposited Au/, Pt/, and Ag/TiO2 behave like contacts with zero junction energy barriers, but the thermal annealing of the reverse-biased devices for an hour at 523 K in air converts them to Schottky diodes with high junction energy barriers, decreasing their reverse electric currents up to 106 times. Similar thermal processing in vacuum or pure argon proved ineffective. The highest energy barrier and the lowest reverse current among the devices examined belong to the annealed Ag/TiO2 contacts. The observed electronic features are described based on the physicochemical parameters of the constituting materials. The formation of higher junction barriers with rutile than with anatase is demonstrated.
Competitive interfacial charge transfer to graphene from the electrode contacts and surface adsorbates
Authors: Nouchi Ryo , Tanigaki Katsumi
Published: February 2015

Charge transfer (CT) at metal-graphene contacts induces a potential variation from the contact edges that extend to ∼1 μm. Potential variations with a similar length should be observed around charge-transferring surface adsorbates. Thus, it is expected that a competition exists between these two CT sources when one source is within ∼1 μm from the other. In this letter, weakly coupled Ni contacts and 7,7,8,8-tetracyanoquinodimethan molecules are employed as the CT sources to investigate their possible competition. The CT from the molecules adsorbed only in the channel region change the charge density of the graphene in the under-contact regions. The extent of the CT effect in the under-contact region is as long as ∼4 μm. The considerably long CT is ascribed to the high effective dielectric constant of the graphene under the contacts, resulting from a thin interfacial NiOx layer containing carbon impurities acquired from the graphene.
Parallel-plate submicron gap formed by micromachined low-density pillars for near-field radiative heat transfer
Authors: Ito Kota , Miura Atsushi , Iizuka Hideo , Toshiyoshi Hiroshi
Published: February 2015

Near-field radiative heat transfer has been a subject of great interest due to the applicability to thermal management and energy conversion. In this letter, a submicron gap between a pair of diced fused quartz substrates is formed by using micromachined low-density pillars to obtain both the parallelism and small parasitic heat conduction. The gap uniformity is validated by the optical interferometry at four corners of the substrates. The heat flux across the gap is measured in a steady-state and is no greater than twice of theoretically predicted radiative heat flux, which indicates that the parasitic heat conduction is suppressed to the level of the radiative heat transfer or less. The heat conduction through the pillars is modeled, and it is found to be limited by the thermal contact resistance between the pillar top and the opposing substrate surface. The methodology to form and evaluate the gap promotes the near-field radiative heat transfer to various applications such as thermal rectification, thermal modulation, and thermophotovoltaics.
Coupling quantum dots to optical fiber: Low pump threshold laser in the red with a near top hat beam profile
Authors: Cheng H. , Mironov A. E. , Ni J. H. , Yang H. J. , Chen W. W. , Dai Z. , Dragic P. D. , Dong J. , Park S.-J. , Eden J. G.
Published: February 2015

Direct coupling of the optical field in a ∼244 nm thick, CdSe/ZnS quantum dot film to an optical fiber has yielded lasing in the red (λ ∼ 644 nm) with a threshold pump energy density < 2.6 mJ cm−2. Comprising 28–31 layers of ∼8 nm diameter quantum dots deposited onto the exterior surface of a 125 μm diameter coreless silica fiber, this free-running oscillator produces 134 nJ in 3.6 ns FWHM pulses which correspond to 37 W of peak power from an estimated gain volume of ∼4.5 × 10−7 cm3. Lasing was confirmed by narrowing of the output optical radiation in both the spectral and temporal domains, and the laser beam intensity profile approximates a top hat.
Mixed convection radiative flow of three dimensional Maxwell fluid over an inclined stretching sheet in presence of thermophoresis and convective condition
Authors: Ashraf M. Bilal , Hayat T. , Shehzad S. A. , Alsaedi A.
Published: February 2015

Three dimensional radiative flow of Maxwell fluid over an inclined stretching surface with convective boundary condition is investigated. Heat and mass transfer analysis is taken into account with thermophoresis effects. Similarity transformations are utilized to reduce the partial differential equations into ordinary differential equations. Series solutions of velocity, temperature and concentration are developed. Influence of different parameters Biot number, therrmophoretic parameter, Deborah number, ratio parameter, inclined stretching angle, radiation parameter, mixed convection parameter and concentration buoyancy parameter on the non-dimensional velocity components, temperature and concentration are plotted and discussed in detail. Physical quantities of interests are tabulated and examined.
Growth of high-density carbon nanotube forests on conductive TiSiN supports
Authors: Yang Junwei , Esconjauregui Santiago , Robertson Alex W. , Guo Yuzheng , Hallam Toby , Sugime Hisashi , Zhong Guofang , Duesberg Georg S. , Robertson John
Published: February 2015

We grow vertically aligned carbon nanotube forests on refractory conductive films of TiSiN and achieve area densities of (5.1 ± 0.1) × 1012 tubes cm−2 and mass densities of about 0.3 g cm−3. The TiSiN films act as diffusion barriers limiting catalyst diffusion into the bulk of the support, and their low surface energy favours catalyst de-wetting, inducing forests to grow by the root growth mechanism. The nanotube area density is maximised by an additional discontinuous AlOx layer, which inhibits catalyst nanoparticle sintering by lateral surface diffusion. The forests and the TiSiN support show ohmic conduction. These results suggest that TiSiN is the favoured substrate for nanotube forest growth on conductors and liable of finding real applications in microelectronics.