bluuebunny/crossref_metadata_2025 huggingface dataset:
A simple dilute-and-shoot approach for the determination of ultra-trace levels of arsenic in biological fluids via ICP-MS using CH3F/He as a reaction gas
Authors: Flórez M. R. , García-Ruiz E. , Bolea-Fernández E. , Vanhaecke F. , Resano M.
Published: October 2015

This article demonstrates the potential of CH3F as a reaction gas for the interference-free monitoring of As by ICP-MS.
Protein nanorings organized by poly(styrene-block-ethylene oxide) self-assembled thin films
Authors: Malmström Jenny , Wason Akshita , Roache Fergus , Yewdall N. Amy , Radjainia Mazdak , Wei Shanghai , Higgins Michael J. , Williams David E. , Gerrard Juliet A. , Travas-Sejdic Jadranka
Published: October 2015

Illustration of the sample preparation process. Lsmα (top left) is mixed with PS-b-PEO (top right) and spin coated into thin films with the protein sequestered into the PEO domains.
The use of electrostatic association for rapid RAFT synthesis of histamine polyelectrolyte in aqueous solutions at and below 25 °C
Authors: Huang Tao , Cui Zhigang , Ding Yi , Lu Xinhua , Cai Yuanli
Published: October 2015

Electrostatic association for rapid and quantitative synthesis of well-defined polyelectrolytes in dilute aqueous solutions at and below 25 °C.
Nanostructured lipid carriers modified with PEGylated carboxymethylcellulose polymers for effective delivery of docetaxel
Authors: Jiang Weihua , Wang Ju , Yang Lei , Jiang Xuewei , Bai Zhaoshi , Wang Zheran , He Yunpeng , Wang Dongkai
Published: October 2015

An amphiphilic carboxymethylcellulose-graft-histidine/methoxypolyethylene glycol (CMP) copolymer was firstly synthesized to modify nanostructured lipid carriers (NLCs) for effective delivery of docetaxel.
Synthesis and controlled curcumin supramolecular complex release from pH-sensitive modified gum-arabic-based hydrogels
Authors: Gerola Adriana P. , Silva Danielle C. , Jesus Sandra , Carvalho Rui A. , Rubira Adley F. , Muniz Edvani C. , Borges Olga , Valente Artur J. M.
Published: October 2015

Delivery of a curcumin supramolecular complex from pH-responsive gum arabic-based hydrogels.
A facile approach for the synthesis of highly luminescent carbon dots using vitamin-based small organic molecules with benzene ring structure as precursors
Authors: Zheng Yawen , Yang Dan , Wu Xin , Yan Haoran , Zhao Yuancong , Feng Bo , Duan Ke , Weng Jie , Wang Jianxin
Published: October 2015

In this study, vitamin-based small organic molecules were used as precursors to synthesize carbon dots by means of a hydrothermal approach.
Ab initio study on optical properties of glycine sodium nitrate: a novel semiorganic nonlinear optical crystal
Authors: Dadsetani M. , Omidi A. R.
Published: October 2015

The electronic structure, and linear and nonlinear optical susceptibilities of crystalline glycine-sodium nitrate (GSN) has been studied using the full potential linear augmented plane wave method within density-functional theory.
Conversion of straw to nitrogen doped carbon for efficient oxygen reduction catalysts in microbial fuel cells
Authors: Liu Lang , Xiong Qi , Li Chungen , Feng Yan , Chen Shuiliang
Published: October 2015

Nitrogen-doped carbon with high nitrogen content was prepared from rice straw through a three-step process, including hydrothermal, freeze drying and heat-treatment in NH3, and was used as a high-efficient oxygen reduction reaction catalyst in MFCs.
Catalyst-free Friedel–Crafts hydroxyalkylation of imidazo[1,2-α]pyridines with ethyl trifluoropyruvate
Authors: Li Ke , Zhao Xue-Mei , Yang Fa-Liu , Hou Xiao-Han , Xu Yan , Guo Yan-Chun , Hao Xin-Qi , Song Mao-Ping
Published: October 2015

A catalyst free Friedel–Crafts (F–C) hydroxyalkylation of imidazo[1,2-α]pyridines with ethyl trifluoropyruvate is herein described using isopropyl ether as a solvent.
Bifunctional AlN:Tb semiconductor with luminescence and photocatalytic properties
Authors: Wang Wei , Zhang Peng , Wang Xiaobai , Lei Xiang , Ding Hong , Yang Hua
Published: October 2015

AlN doped with Tb semiconductors exhibit strong green emission and excellent photocatalytic property.
Influence of removal of organic matter and iron and manganese oxides on cadmium adsorption by red paddy soil aggregates
Authors: Li Zhongwu , Huang Bin , Huang Jinquan , Chen Guiqiu , Zhang Chang , Nie Xiaodong , Luo Ninglin , Yao Hongbo , Ma Wenming , Zeng Guangming
Published: October 2015

Different soil components in various aggregates were selectively removed for evaluating their influence on Cd adsorption.
Exploration of charge transfer and absorption spectra of porphyrin–polyoxometalate hybrids to search for high performance sensitizers
Authors: Wu Hanni , Zhang Ting , Yan Likai , Su Zhongmin
Published: October 2015

Lindqvist-, Keggin-, and Anderson-type polyoxometalate organic–inorganic hybrids were designed to investigate their charge transfer character and screen them as high performance p-type sensitizers.
Preparation of graphene–hafnium oxide composite for selective enrichment and analysis of phosphopeptides
Authors: Huang Xuan , Wang Junping , Wang Junying , Liu Cuicui , Wang Shuo
Published: October 2015

A novel graphene–hafnium oxide composite was prepared and applied to selective enrichment phosphopeptides from biosamples.
Chitosan-graft-PAMAM–alginate core–shell nanoparticles: a safe and promising oral insulin carrier in an animal model
Authors: Mukhopadhyay P. , Kundu P. P.
Published: October 2015

Calcium chloride cross-linked PAMAM grafted chitosan–alginate core–shell nanoparticles are demonstrated as potential low-toxicity carriers for oral insulin delivery.
High performance SERS active substrates fabricated by directly growing graphene on Ag nanoparticles
Authors: Xu Shicai , Wang Jihua , Zou Yan , Liu Hanping , Wang Guiying , Zhang Xiumei , Jiang Shouzhen , Li Zhen , Cao Dongyan , Tang Rongxia
Published: October 2015

An efficient surface enhanced Raman scattering (SERS) substrate of graphene-isolated Ag nanoparticle (G/AgNP) has been developed by using excimer laser to ablate the ordered pyrolytic graphite in high vacuum onto Ag nanoparticles.
Side chain position, length and odd/even effects on the 2D self-assembly of mono-substituted anthraquinone derivatives at the liquid/solid interface
Authors: Hu Yi , Miao Kai , Zha Bao , Miao Xinrui , Xu Li , Deng Wenli
Published: October 2015

This work provides efficient methods for regulating self-assembled structures by changing the position, length and odd/even properties of the side chains.
Retracted Article: Shape-specific silver nanoparticles prepared by microwave-assisted green synthesis using pomegranate juice for bacterial inactivation and removal
Authors: Roy Ekta , Patra Santanu , Saha Shubham , Madhuri Rashmi , Sharma Prashant K.
Published: October 2015

Green synthesis of different shaped-AgNPs & their antibacterial activity.
Selective and sensitive chromogenic and fluorogenic detection of sulfur mustard in organic, aqueous and gaseous medium
Authors: Kumar Vinod , Rana Hemlata
Published: October 2015

A chromogenic and fluorogenic system based on a squaraine dye (SQ) was used for the highly selective and sensitive detection of the chemical warfare agent sulfur mustard.
ZnO quantum dots and graphene based heterostructure for excellent photoelastic and highly sensitive ultraviolet photodetector
Authors: Boruah Buddha Deka , Misra Abha
Published: October 2015

Heterostructures comprised of zinc oxide quantum dots (ZnO QDs) and graphene are presented for ultraviolet photodetectors (UV PD).
Construction of 3,5-dinitrated 1,4-dihydropyridines modifiable at 1,4-positions by a reaction of β-formyl-β-nitroenamines with aldehydes
Authors: Asahara Haruyasu , Hamada Mai , Nakaike Yumi , Nishiwaki Nagatoshi
Published: October 2015

A novel and efficient method for the synthesis of 4-substituted 3,5-dinitro-1,4-dihydropyridines by a reaction of β-formyl-β-nitroenamines with aldehydes was developed.
Injectable conducting interpenetrating polymer network hydrogels from gelatin-graft-polyaniline and oxidized dextran with enhanced mechanical properties
Authors: Li Longchao , Ge Juan , Ma Peter X. , Guo Baolin
Published: October 2015

Injectable conducting interpenetrating polymer network hydrogels based on gelatin-graft-polyaniline, carboxymethyl-chitosan and oxidized dextran with enhanced mechanical properties and excellent biocompatibility.
Fabrication of silica nanoparticle based polymer nanocomposites via a combination of mussel inspired chemistry and SET-LRP
Authors: Heng Chunning , Liu Meiying , Wang Ke , Zheng Xiaoyan , Huang Hongye , Deng Fengjie , Hui Junfeng , Zhang Xiaoyong , Wei Yen
Published: October 2015

A facile and efficient strategy combination of mussel inspired chemistry and SET-LRP has been developed for the surface modification of silica nanoparticles.
Ruthenium(ii)-polypyridyl zirconium(iv) metal–organic frameworks as a new class of sensitized solar cells
Authors: Maza W. A. , Haring A. J. , Ahrenholtz S. R. , Epley C. C. , Lin S. Y. , Morris A. J.
Published: October 2015

Ruthenium(ii) polypyridyl-doped metal–organic framework sensitized films on TiO2 for photovoltaics reveal that the preparative method of dye doping/incorporation into the MOF is integral to the total solar cell efficiency.
Effect of lipid peroxidation on membrane permeability of cancer and normal cells subjected to oxidative stress
Authors: Van der Paal Jonas , Neyts Erik C. , Verlackt Christof C. W. , Bogaerts Annemie
Published: October 2015

Molecular dynamics simulations suggest that the cholesterol-induced stability of lipid membranes during lipid peroxidation offers an explanation for the observed selectivity of plasma treatments towards cancer cells.
A universal chemical potential for sulfur vapours
Authors: Jackson Adam J. , Tiana Davide , Walsh Aron
Published: October 2015

The equilibrium thermochemistry of mixed vapour-phase sulfur allotropes is computed and solved to obtain a single chemical potential function.
Controlled positioning of analytes and cells on a plasmonic platform for glycan sensing using surface enhanced Raman spectroscopy
Authors: Tabatabaei Mohammadali , Wallace Gregory Q. , Caetano Fabiana A. , Gillies Elizabeth R. , Ferguson Stephen S. G. , Lagugné-Labarthet François
Published: October 2015

Controlled analyte and cell positioning is enabled on a plasmonic platform with patterned fluorocarbon polymer thin films for SERS-based glycan sensing.
A wavelength-resolved ratiometric photoelectrochemical technique: design and sensing applications
Authors: Hao Qing , Shan Xiaonan , Lei Jianping , Zang Yang , Yang Qianhui , Ju Huangxian
Published: October 2015

A wavelength-resolved ratiometric photoelectrochemical technique was developed as a novel concept for designing ratiometric photoelectrochemical sensors.
Stabilization of volatile Ti(BH4)3 by nano-confinement in a metal–organic framework
Authors: Callini E. , Szilágyi P. Á. , Paskevicius M. , Stadie N. P. , Réhault J. , Buckley C. E. , Borgschulte A. , Züttel A.
Published: October 2015

Volatile Ti(BH4)3 molecules stabilized on the surface of a MOF.
Topochemical molten salt synthesis for functional perovskite compounds
Authors: Li Lihong , Deng Jinxia , Chen Jun , Xing Xianran
Published: October 2015

This report reviews various topochemical molten salt synthesis (TMSS) reactions and their applications in fulfilling the demand for the tunable morphology of perovskite materials.
An lcy-topology amino acid MOF as eco-friendly catalyst for cyclic carbonate synthesis from CO2: Structure-DFT corroborated study
Authors: Kathalikkattil Amal Cherian , Babu Robin , Roshan Roshith Kuruppathparambil , Lee Hankyul , Kim Hyungjun , Tharun Jose , Suresh Eringathodi , Park Dae-Won
Published: October 2015

A Zn(ii)-amino acid MOF catalyst and its use for CO2fixation are reported, in addition to corresponding structure-topology-DFT studies.
Integrating photonic bandgaps with surface plasmon resonance for the enhancement of visible-light photocatalytic performance
Authors: Meng Sugang , Li Danzhen , Fu Xianliang , Fu Xianzhi
Published: October 2015

A 3D Au/ZnO hybrid with an inverse opal structure was designed for addressing light harvesting and carrier separation problems through combining local surface plasmon resonance, photonic crystal effect and heterostructure.
Kinetic analysis of photoelectrochemical water oxidation by mesostructured Co-Pi/α-Fe2O3 photoanodes
Authors: Carroll Gerard M. , Gamelin Daniel R.
Published: October 2015

Kinetics measurements are used to clarify the effect of Co-Pi on solar water splitting by Co-Pi/α-Fe2O3 composite photoanodes.
Glycomaterials for immunomodulation, immunotherapy, and infection prophylaxis
Authors: Restuccia Antonietta , Fettis Margaret M. , Hudalla Gregory A.
Published: October 2015

Synthetic carbohydrate-modified materials that can engage the innate and adaptive immune systems are receiving increasing interest to confer protection against onset of future disease, such as pathogen infection, as well as to treat established diseases, such as autoimmunity and cancer.
Conserved phosphorylation sites in the activation loop of the Arabidopsis phytosulfokine receptor PSKR1 differentially affect kinase and receptor activity
Authors: Hartmann Jens , Linke Dennis , Bönniger Christine , Tholey Andreas , Sauter Margret
Published: October 2015

PSK (phytosulfokine) is a plant peptide hormone perceived by a leucine-rich repeat receptor kinase. Phosphosite mapping of epitope-tagged PSKR1 (phytosulfokine receptor 1) from Arabidopsis thaliana plants identified Ser696 and Ser698 in the JM (juxtamembrane) region and probably Ser886 and/or Ser893 in the AL (activation loop) as in planta phosphorylation sites. In vitro-expressed kinase was autophosphorylated at Ser717 in the JM, and at Ser733, Thr752, Ser783, Ser864, Ser911, Ser958 and Thr998 in the kinase domain. The LC–ESI–MS/MS spectra provided support that up to three sites (Thr890, Ser893 and Thr894) in the AL were likely to be phosphorylated in vitro. These sites are evolutionarily highly conserved in PSK receptors, indicative of a conserved function. Site-directed mutagenesis of the four conserved residues in the activation segment, Thr890, Ser893, Thr894 and Thr899, differentially altered kinase activity in vitro and growth-promoting activity in planta. The T899A and the quadruple-mutated TSTT-A (T890A/S893A/T894A/T899A) mutants were both kinase-inactive, but PSKR1(T899A) retained growth-promoting activity. The T890A and S893A/T894A substitutions diminished kinase activity and growth promotion. We hypothesize that phosphorylation within the AL activates kinase activity and receptor function in a gradual and distinctive manner that may be a means to modulate the PSK response.
Effect of capacitor position on radiation patterns of ground radiation antenna
Authors: Zhang Rui , Liu Yang , Kim Hyeongdong
Published: October 2015

The radiation‐pattern variations of a ground radiation antenna are investigated. The series capacitor connected in the antenna radiation loop is successively placed in two different positions while the radiation patterns are respectively observed. The simulation and experimental results indicate that the radiation patterns are significantly changed in accordance with the capacitor's position. This study can be applied to implementing a radiation‐pattern‐reconfigurable GPS antenna.
Particle filter for nonlinear systems with multiple step randomly delayed measurements
Authors: Huang Yulong , Zhang Yonggang , Li Ning , Zhao Lin
Published: October 2015

A new particle filter for nonlinear systems with multiple step randomly delayed measurements is proposed. In the proposed method, particles and their weights are updated in the Bayesian estimation framework by considering the multiple step randomly delayed measurement model. Simulation results show that the proposed method has higher estimation accuracy than existing methods.
Synthesis of coupled resonator‐based multiplexers with generalised structures using coupling matrix optimisation
Authors: Tubail D.A. , Skaik T.F.
Published: October 2015

Design techniques of coupled resonator circuits used in synthesising two port filters and three port diplexers are developed to synthesise N port multiplexers. Novel general structure is proposed and it can achieve an unlimited arbitrary number of channels, different responses and various properties and characteristics without extra resonators, external junctions or power distribution network in a compact size. The synthesis of the proposed multiplexers is based on optimisation approach where the coupling coefficients between resonators presented by coupling matrix are found from optimisation techniques by minimising a cost function.
Polarisation rotation Bragg grating with high diffraction efficiency using Si waveguide top surface groove grating
Authors: Okayama H. , Onawa Y. , Shimura D. , Yaegashi H. , Sasaki H.
Published: October 2015

Polarisation‐independent Bragg grating wavelength filter with high diffraction efficiency using silicon waveguide is reported. An antisymmetric grating structure with groove at the top surface of the waveguide is used to generate the polarisation rotation Bragg diffraction. The concept was verified by simulation. Polarisation‐independent bandpass filter consisting of 3 dB coupler and polarisation rotation Bragg diffraction was experimentally demonstrated.
High‐speed low‐power and low‐power supply voltage dynamic comparator
Authors: Xu Daiguo , Xu Shiliu , Chen Guangbing
Published: October 2015

A structure of a dynamic comparator with high‐speed low‐power and a low‐power supply voltage is proposed. The proposed comparator is compared with previous dynamic comparators. For the same size of input/output transistors and latch as well as load capacitance, it is more than 1.3 times faster with <85% power consumption. The proposed structure exhibits faster speed and lower power consumption at the same time. Moreover, it provides better performance regarding low‐power supply voltage, it also brings moderate input‐referred noise and offset among these structures.
Implementation of low‐power, non‐volatile latch utilising ferroelectric transistor
Authors: Mitchell C. , Hunt M.R. , McCartney C.L. , Ho F.D.
Published: October 2015

The implementation of a non‐volatile latch circuit developed with a metal–ferroelectric–semiconductor field‐effect transistor is presented. The circuit contains two inverter stages in order to create and rectify the desired waveform. The hysteresis properties of the ferroelectric transistor allow it to retain a polarisation state after an applied voltage at the gate is removed. This circuit has reduced power requirements because a constant power supply is not needed at all times; instead, a voltage is only needed at the gate of the ferroelectric transistor when storing a value, and the other components only need a power supply when reading the stored value from the circuit. The circuit is less complex than similar non‐volatile latches because only a single ferroelectric transistor is used and fewer overall transistors may be used. It also has the advantage of being radiation‐hardened for space applications.
Stability assessment of non‐Foster circuits based on time‐domain method
Authors: Elfrgani Aseim M. , Moussounda Renaud , Rojas Roberto G.
Published: October 2015

Non‐Foster circuits are attractive for microwave and antenna applications since they are not restricted by the gain‐bandwidth product. A persistent problem with these circuits is the potential instability (mainly unwanted oscillations) due to the presence of positive feedback. The stability properties of these circuits are discussed with a time‐domain technique that computes the largest (maximal) Lyapunov exponent (MLE) for time‐series signals within the circuit's structure as well as at its output to determine with confidence the circuit's stability. In case of instability, the circuit is stabilised with different controllers. A circuit or system is considered stable when the MLEs obtained from signals at multiple nodes are negative. Moreover, the effect of small DC bias variations on stability is also studied. The proposed stability analysis approach has been successfully applied to two known topologies: namely, negative impedance converters and inverters.
Design fabrication and characterisation of polyaniline and multiwall carbon nanotubes composites‐based patch antenna
Authors: Zahir Hamouda , Wojkiewicz Jean‐Luc , Alexander Pud , Kone Lamine , Belkacem Belaabed , Bergheul Said , Lasri Tuami
Published: October 2015

This study presents the conception, simulation, realisation and characterisation of a patch antenna made of a composite based on polyaniline (PANI) and multiwall carbon nanotubes (MWCNTs). The antenna is designed to operate at the frequency of 4.5 GHz; the dielectric substrate used is Rogers RT/Duroid® 5870 which has a dielectric permittivity of 2.33 and a loss tangent of 0.0012. The conductive polymer (PANI/MWCNTs) fabricated has a conductivity of 4500 S/m. The performance of the proposed antenna is investigated as a function of the thickness of the conductive polymer. The experimental results show an antenna gain of 5.18 dB for a PANI/MWCNTs thickness of 110 μm. The results obtained suggest that this kind of conductive polymers are good candidates for future applications based on organic electronics.
Control scheme for grid‐tied distributed generation inverter under unbalanced and distorted utility conditions with power quality ancillary services
Authors: Chilipi Rajasekharareddy , Al Sayari Naji , Al Hosani Khalifa , Beig Abdul Rahiman
Published: October 2015

This study proposes a control scheme with a new fundamental sequence components extractor for grid interfaced distributed generation inverter under polluted grid conditions. The proposed sequence extractor is realised using third‐order sinusoidal signal integrator‐based frequency adaptive filters. It has an excellent ability to decompose the three‐phase voltage and current signals into positive and negative sequence components under distorted grid scenario. The proposed control scheme is immune to frequency variations and is capable of providing power quality ancillary services such as reactive power compensation and harmonics rejection in addition to basic power injection. The performance of the proposed system under various grid disturbances and loading conditions is evaluated through simulation and experimental studies.
Legendre sequences for periodic non‐coherent pulse compression
Authors: Baden John Michael
Published: October 2015

Perfect periodic cross‐correlation is achievable in non‐coherent pulse compression using Legendre sequences of any prime length. This paper briefly describes the (previously known) transmit and reference signals for the N = 4k − 1 case where N, the sequence length, is prime and k is a positive integer. It is then shown that a slight modification allows perfect periodic correlation with N = 4k − 3, doubling the number of available sequences.
Suppression of external quantum efficiency roll-off of nanopatterned organic-light emitting diodes at high current densities
Authors: Kuwae Hiroyuki , Nitta Atsushi , Yoshida Kou , Kasahara Takashi , Matsushima Toshinori , Inoue Munetomo , Shoji Shuichi , Mizuno Jun , Adachi Chihaya
Published: October 2015

We developed organic light-emitting diodes (OLEDs) with nanopatterned current flow regions using electron-beam lithography with the aim of suppressing singlet–polaron annihilation (SPA). Nanopatterns composed of lines and circles were used in the current flow regions of nano-line and nano-dot OLEDs, respectively. Excitons partially escape from the current flow regions where SPA takes place. As such, current densities where external quantum efficiencies were half of their initial values (J0) increased as line width and circle diameter were decreased to close to the exciton diffusion length. Circles were more efficient at enhancing exciton escape and increasing J0 than lines. The J0 increase in the nano-dot OLEDs containing nanopatterned circles with a diameter of 50 nm was approximately 41-fold that of a conventional OLED with a current flow region of 4 mm2. The dependence of J0 on the size and shape of the nanopatterns was well explained by an SPA model that considered exciton diffusion. Nanopatterning of OLEDs is a feasible method of obtaining large J0.
Compact RF ion source for industrial electrostatic ion accelerator
Authors: Kwon Hyeok-Jung , Park Sae-Hoon , Kim Dae-Il , Cho Yong-Sub
Published: October 2015

Korea Multi-purpose Accelerator Complex is developing a single-ended electrostatic ion accelerator to irradiate gaseous ions, such as hydrogen and nitrogen, on materials for industrial applications. ELV type high voltage power supply has been selected. Because of the limited space, electrical power, and robust operation, a 200 MHz RF ion source has been developed. In this paper, the accelerator system, test stand of the ion source, and its test results are described.
Strong influence of periodic boundary conditions on lateral diffusion in lipid bilayer membranes
Authors: Camley Brian A. , Lerner Michael G. , Pastor Richard W. , Brown Frank L. H.
Published: October 2015

The Saffman-Delbrück hydrodynamic model for lipid-bilayer membranes is modified to account for the periodic boundary conditions commonly imposed in molecular simulations. Predicted lateral diffusion coefficients for membrane-embedded solid bodies are sensitive to box shape and converge slowly to the limit of infinite box size, raising serious doubts for the prospects of using detailed simulations to accurately predict membrane-protein diffusivities and related transport properties. Estimates for the relative error associated with periodic boundary artifacts are 50% and higher for fully atomistic models in currently feasible simulation boxes. MARTINI simulations of LacY membrane protein diffusion and LacY dimer diffusion in DPPC membranes and lipid diffusion in pure DPPC bilayers support the underlying hydrodynamic model.
Optics of the NIFS negative ion source test stand by infrared calorimetry and numerical modelling
Authors: Veltri P. , Antoni V. , Agostinetti P. , Brombin M. , Ikeda K. , Kisaki M. , Nakano H. , Sartori E. , Serianni G. , Takeiri Y. , Tsumori K.
Published: October 2015

At National Institute for Fusion Science (NIFS), a multi-ampere negative ion source is used to support the R&D on H− production, extraction, and acceleration. In this contribution, we study the characteristics of the acceleration system of this source, in order to characterize the beam optics at different operational conditions. A dedicated experimental campaign was carried out at NIFS, using as main diagnostic the infra-red imaging of the beam profiles. The experimental measurements are also compared with 3D numerical simulations, in order to validate the codes and to assess their degree of reliability. The simulations show a satisfactory agreement with the experimental results.
Hydrophilic behavior of graphene and graphene-based materials
Authors: Accordino Sebastián R. , Montes de Oca Joan Manuel , Rodriguez Fris J. Ariel , Appignanesi Gustavo A.
Published: October 2015

Graphene and the graphene-based materials like graphite, carbon nanotubes, and fullerenes are not only usually regarded as hydrophobic but also have been widely employed as paradigms for the investigation of the behavior of water under nonpolar confinement, a question of major concern for fields ranging from biology to materials design. However, some experimental and theoretical insights seem to contradict, at least partially, such a picture. In this work, we will provide firm evidence for a neat hydrophilic nature of graphene surfaces. Our molecular dynamics studies will demonstrate that parallel graphene sheets present a strong tendency to remain fully hydrated for moderately long times (even when the equilibrium state is indeed the collapse of the plates), and thus, they are less prone to self-assembly than model hydrophobic surfaces we shall employ as control which readily undergo a hydrophobic collapse. Potential of mean force calculations will indeed make evident that the solvent exerts a repulsive contribution on the self-assembly of graphene surfaces. Moreover, we shall also quantify graphene hydrophilicity by means of the calculation of water density at two pressures and water density fluctuations. This latter study has never been performed on graphene and represents a means both to confirm and to quantify its neat hydrophilic behavior. We shall also make evident the relevance of the mildly attractive water-carbon interactions, since their artificial weakening will be shown to revert from typically hydrophilic to typically hydrophobic behavior.
Mean force on a finite-sized rigid particle, droplet, or bubble in a viscous compressible medium
Authors: Annamalai Subramanian , Balachandar S.
Published: October 2015

A force formulation to compute the axial acoustic mean second-order force on finite-sized compressible and rigid particles is presented. The flow inside and outside the spherical inclusion is considered viscous and compressible. Other than for volumetric pulsations of the bubble/droplet, the sphericity of the inclusion is maintained (taken to be unity). A far-field derivation approach has been used to compute the force due to standing and traveling waves; and the force is expressed as a multipole expansion (infinite series). In case of a bubble and a rigid particle, there exist three length scales that govern the mean second-order force: mean radius of the spherical inclusion (R0), wavelength of the incoming acoustics (λ), and the momentum diffusion thickness of the ambient fluid (δo). While R0 and λ are arbitrary, we assume the viscous length scale is negligibly small compared to the acoustic wavelength. In case of a droplet, however, the following additional parameters (inside to outside fluid ratios) also play a role: density ratio (ρ̃), viscosity ratio (μ̃), and speed of sound ratio (c̃). The force expression yields the correct behavior in several limiting cases considered: (i) inviscid bubble and droplets with R0/λ ≪ 1, (ii) inviscid bubbles with finite R0/λ, and (iii) finite size rigid immovable particles. In general, while the monopole alone is sufficient to capture the force for small bubbles, higher-order terms are found to be important when R0/λ ≥ 0.02. In addition to reporting similar behavior for droplets, we study the effect arising from ρ̃, μ̃, c̃, and δo/R0 on the mean second-order force.
Tunneling-percolation behavior of polydisperse prolate and oblate ellipsoids
Authors: Kale Sohan , Sabet Fereshteh A. , Jasiuk Iwona , Ostoja-Starzewski Martin
Published: October 2015

We report Monte Carlo simulations of systems of polydisperse prolate and oblate ellipsoids using the critical path based tunneling-percolation model. For polydisperse prolate ellipsoids, the critical percolation volume fraction ϕc is shown to have a quasi-universal dependence on weight-averaged aspect ratio. For polydisperse oblate ellipsoids, ϕc is shown to have a quasi-universal dependence on the apparent aspect ratio, which is a function of up to fourth moment of the size distribution, as given by the generalized connectedness percolation theory. The functions are observed to approach the theoretical predictions for higher volume fractions and higher aspect ratios. The model predictions are compared with experimental data available on polydisperse multi-walled nanotubes (prolate ellipsoids) and graphene nanoplatelets (oblate ellipsoids) to estimate the tunneling lengthscale which is found to be well within the expected range.
Guiding and focusing of fast electron beams produced by ultra-intense laser pulse using a double cone funnel target
Authors: Zhang Wen-shuai , Cai Hong-bo , Zhu Shao-ping
Published: October 2015

A novel double cone funnel target design aiming at efficiently guiding and focusing fast electron beams produced in high intensity (>1019 W/cm2) laser-solid interactions is investigated via two-dimensional particle-in-cell simulations. The forward-going fast electron beams are shown to be directed and focused to a smaller size in comparison with the incident laser spot size. This plasma funnel attached on the cone target guides and focuses electrons in a manner akin to the control of liquid by a plastic funnel. Such device has the potential to add substantial design flexibility and prevent inefficiencies for important applications such as fast ignition. Two reasons account for the collimation of fast electron beams. First, the sheath electric fields and quasistatic magnetic fields inside the vacuum gap of the double cone provide confinement of the fast electrons in the laser-plasma interaction region. Second, the interface magnetic fields inside the beam collimator further guide and focus the fast electrons during the transport. The application of this technique to cone-guided fast ignition is considered, and it is shown that it can enhance the laser energy deposition in the compressed fuel plasma by a factor of 2 in comparison with the single cone target case.
Physics of beam self-modulation in plasma wakefield accelerators
Authors: Lotov K. V.
Published: October 2015

The self-modulation instability is a key effect that makes possible the usage of nowadays proton beams as drivers for plasma wakefield acceleration. Development of the instability in uniform plasmas and in plasmas with a small density up-step is numerically studied with the focus at nonlinear stages of beam evolution. The step parameters providing the strongest established wakefield are found, and the mechanism of stable bunch train formation is identified.
Structure of the runaway electron loss during induced disruptions in TEXTOR
Authors: Wongrach K. , Finken K. H. , Abdullaev S. S. , Willi O. , Zeng L. , Xu Y.
Published: October 2015

The loss of runaway electrons during an induced disruption is recorded by a synchrotron imaging technique using a fast infrared CCD camera. The loss is predominantly diffuse. During the “spiky-loss phase”, when the runaway beam moves close to the wall, a narrow channel between the runaway column and a scintillator probe is formed and lasts until the runaway beam is terminated. In some cases, the processed images show a stripe pattern at the plasma edge. A comparison between the MHD dominated disruptions and the MHD-free disruption is performed. A new mechanism of plasma disruptions with the runaway electron generation and a novel model which reproduces many characteristic features of the plasma beam evolution during a disruption is briefly described.
Periodically sheared 2D Yukawa systems
Authors: Kovács Anikó Zsuzsa , Hartmann Peter , Donkó Zoltán
Published: October 2015

We present non-equilibrium molecular dynamics simulation studies on the dynamic (complex) shear viscosity of a 2D Yukawa system. We have identified a non-monotonic frequency dependence of the viscosity at high frequencies and shear rates, an energy absorption maximum (local resonance) at the Einstein frequency of the system at medium shear rates, an enhanced collective wave activity, when the excitation is near the plateau frequency of the longitudinal wave dispersion, and the emergence of significant configurational anisotropy at small frequencies and high shear rates.
Off-normal and failure condition analysis of the MITICA negative-ion accelerator
Authors: Chitarin Giuseppe , Agostinetti Piero , Aprile Daniele , Marconato Nicolò , Marcuzzi Diego , Serianni Gianluigi , Veltri Pierluigi , Zaccaria Pierluigi
Published: October 2015

The negative-ion accelerator for the MITICA neutral beam injector has been designed and optimized in order to reduce the thermo-mechanical stresses in all components below limits compatible with the required fatigue life. However, deviation from the expected beam performances can be caused by “off-normal” operating conditions of the accelerator. The purpose of the present work is to identify and analyse all the “off-normal” operating conditions, which could possibly become critical in terms of thermo-mechanical stresses or of degradation of the optical performances of the beam.
Electromagnetic fluctuations in magnetized plasmas II: Extension of the theory for parallel wave vectors
Authors: Schlickeiser R. , Ganz A. , Kolberg U. , Yoon P. H.
Published: October 2015

Starting from the recently derived general expressions for the electromagnetic fluctuation spectra (electric and magnetic field) from uncorrelated plasma particles in plasmas with an uniform magnetic field, the case of strictly parallel (k⊥=0) oriented wave vectors with the respect to the uniform magnetic field direction is investigated. To derive fluctuation spectra valid in the entire complex frequency plane, the relevant dispersion functions and form factors are analytically continued to negative values of the imaginary part of the frequency for arbitrary gyrotropic plasma particle distribution functions. The generalized fluctuation-dissipation theorems for non-collective fluctuations in isotropic equal-temperature thermal distribution functions for general complex values of the frequency of the fluctuations with parallel wave vectors are derived.
Study of breakdown in an ablative pulsed plasma thruster
Authors: Huang Tiankun , Wu Zhiwen , Liu Xiangyang , Xie Kan , Wang Ningfei , Cheng Yue
Published: October 2015

Breakdown in ablative pulsed plasma thrusters (APPTs) must be studied in order to design new types of APPTs and measure particular parameters. In this paper, we studied a parallel-plate ablative pulsed plasma thruster that used a coaxial semiconductor spark plug. By operating the APPT about 500 times with various capacitor voltages and electrode gaps, we measured and analyzed the voltage of the spark plug, the voltage between the electrodes, and the discharge current. These experiments revealed a time delay (∼1–10 μs) between spark plug ignition and capacitor discharge, which may affect the performance of high-pulsing-rate (>10 kHz) and double-discharge APPTs, and the measurements of some of the APPT parameters. The delay time decreased as the capacitor voltage increased, and it increased with an increasing electrode gap and increasing number of ignitions. We explain our results through a simple theoretical analysis.
The absorption and radiation of a tungsten plasma plume during nanosecond laser ablation
Authors: Moscicki T. , Hoffman J. , Chrzanowska J.
Published: October 2015

In this paper, the effect of absorption of the laser beam and subsequent radiation on the dynamics of a tungsten plasma plume during pulsed laser ablation is analyzed. Different laser wavelengths are taken into consideration. The absorption and emission coefficients of tungsten plasma in a pressure range of 0.1–100 MPa and temperature up to 70 000 K are presented. The shielding effects due to the absorption and radiation of plasma may have an impact on the course of ablation. The numerical model that describes the tungsten target heating and the formation of the plasma and its expansion were made for 355 nm and 1064 nm wavelengths of a Nd:YAG laser. The laser beam with a Gaussian profile was focused to a spot size of 0.055 mm2 with a power density of 1 × 109 W/cm2 (10 ns full width half maximum pulse duration). The plasma expands into air at ambient pressure of 1 mPa. The use of the shorter wavelength causes faster heating of the target, thus the higher ablation rate. The consequences of a higher ablation rate are slower expansion and smaller dimensions of the plasma plume. The higher plasma temperature in the case of 1064 nm is due to the lower density and lower plasma radiation. In the initial phase of propagation of the plasma plume, when both the temperature and pressure are very high, the dominant radiation is emission due to photo-recombination. However, for a 1064 nm laser wavelength after 100 ns of plasma expansion, the radiation of the spectral lines is up to 46.5% of the total plasma radiation and should not be neglected.
Identification of new turbulence contributions to plasma transport and confinement in spherical tokamak regime
Authors: Wang W. X. , Ethier S. , Ren Y. , Kaye S. , Chen J. , Startsev E. , Lu Z. , Li Z. Q.
Published: October 2015

Highly distinct features of spherical tokamaks (ST), such as National Spherical Torus eXperiment (NSTX) and NSTX-U, result in a different fusion plasma regime with unique physics properties compared to conventional tokamaks. Nonlinear global gyrokinetic simulations critical for addressing turbulence and transport physics in the ST regime have led to new insights. The drift wave Kelvin-Helmholtz (KH) instability characterized by intrinsic mode asymmetry is identified in strongly rotating NSTX L-mode plasmas. While the strong E×B shear associated with the rotation leads to a reduction in KH/ion temperature gradient turbulence, the remaining fluctuations can produce a significant ion thermal transport that is comparable to the experimental level in the outer core region (with no “transport shortfall”). The other new, important turbulence source identified in NSTX is the dissipative trapped electron mode (DTEM), which is believed to play little role in conventional tokamak regime. Due to the high fraction of trapped electrons, long wavelength DTEMs peaking around kθρs∼0.1 are destabilized in NSTX collisionality regime by electron density and temperature gradients achieved there. Surprisingly, the E×B shear stabilization effect on DTEM is remarkably weak, which makes it a major turbulence source in the ST regime dominant over collisionless TEM (CTEM). The latter, on the other hand, is subject to strong collisional and E×B shear suppression in NSTX. DTEM is shown to produce significant particle, energy and toroidal momentum transport, in agreement with experimental levels in NSTX H-modes. Moreover, DTEM-driven transport in NSTX parametric regime is found to increase with electron collision frequency, providing one possible source for the scaling of confinement time observed in NSTX H-modes. Most interestingly, the existence of a turbulence-free regime in the collision-induced CTEM to DTEM transition, corresponding to a minimum plasma transport in advanced ST collisionality regime, is predicted.
Existence of topological vortices in an Abelian Chern–Simons model
Authors: Guo Boling , Li Fangfang
Published: October 2015

In this paper, we prove the existence of topological vortices by variational method applied on an Abelian Chern–Simons model with a generic renormalizable potential. We also establish some properties of the solutions.
Note: Vibration suppression using tunable vibration absorber based on stiffness variable magneto-rheological gel
Authors: Shin Beom-Cheol , Yoon Jung-Hwan , Kim Young-Keun , Kim Kyung-Soo
Published: October 2015

This paper proposes a novel adaptive tunable vibration absorber (TVA) based on a smart material the magnetorheological gel (MRG) to achieve a wide range of tonal vibration suppression on the primary system to protect any connected sensitive device. The vibration suppression performance of the MRG TVA was analyzed by conducting a modal test of the primary system under different magnetic fields. The experiment verified that the proposed MRG TVA can be controlled to produce 379% of stiffness change or 115% of tuning frequency under just 200 mT magnetic field. The proposed MRG TVA was found to possess a wider tuning frequency range than the TVA based on other smart material such as magnetorheological elastomer.
Resummation of divergent perturbation series: Application to the vibrational states of H2CO molecule
Authors: Duchko A. N. , Bykov A. D.
Published: October 2015

Large-order Rayleigh–Schrödinger perturbation theory (RSPT) is applied to the calculation of anharmonic vibrational energy levels of H2CO molecule. We use the model of harmonic oscillators perturbed by anharmonic terms of potential energy. Since the perturbation series typically diverge due to strong couplings, we apply the algebraic approximation technique because of its effectiveness shown earlier by Goodson and Sergeev [J. Chem. Phys. 110, 8205 (1999); ibid. 124, 094111 (2006)] and in our previous articles [A. D. Bykov et al. Opt. Spectrosc. 114, 396 (2013); ibid. 116, 598 (2014)]. To facilitate the resummation of terms contributing to perturbed states, when resonance mixing between states is especially strong and perturbation series diverge very quick, we used repartition of the Hamiltonian by shifting the normal mode frequencies. Energy levels obtained by algebraic approximants were compared with the results of variational calculation. It was found that for low energy states (up to ∼5000 cm−1), algebraic approximants gave accurate values of energy levels, which were in excellent agreement with the variational method. For highly excited states, strong and multiple resonances complicate series resummation, but a suitable change of normal mode frequencies allows one to reduce the resonance mixing and to get accurate energy levels. The theoretical background of the problem of RSPT series divergence is discussed along with its numerical analysis. For these purposes, the vibrational energy is considered as a function of a complex perturbation parameter. Layout and classification of its singularities allow us to model the asymptotic behavior of the perturbation series and prove the robustness of the algorithm.
A new wide band gap thermoelectric quaternary selenide Cu2MgSnSe4
Authors: Pavan Kumar V. , Guilmeau Emmanuel , Raveau Bernard , Caignaert Vincent , Varadaraju U. V.
Published: October 2015

Cu2MgSnSe4 based compounds composed of high earth abundant elements have been identified to exhibit good thermoelectric performance in the mid-temperature range. The pristine phase shows a band gap of 1.7 eV, which is slightly higher than similar ternary and quaternary copper based stannite compounds. Cu2MgSnSe4 crystallizes in the tetragonal I4¯2m space group. Substitution of In at Sn site tends to decrease the tetragonal distortion toward the cubic symmetry. The electrical and thermal transport properties of Cu and In–doped Cu2MgSnSe4 in the temperature range of 300 K–700 K are studied. The substitution of In3+ for Sn4+ and Cu2+ for Mg2+ induces charge carriers as holes, which in turn lead to improvement in thermoelectric efficiency. The role of mass fluctuations and structural disorder in the evolution of the thermal conductivity of the doped selenides is discussed. A maximum ZT of 0.42 is attained for Cu2MgSn0.925In0.075Se4 around 700 K, and this value is comparable to that of Cu2ZnSnSe4.