bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient synthesis of size-controlled open-framework nanoparticles fabricated with a micro-mixer: route to the improvement of Cs adsorption performance
Authors: Takahashi Akira , Minami Nobutsugu , Tanaka Hisashi , Sue Kiwamu , Minami Kimitaka , Parajuli Durga , Lee Kyoung-Moo , Ohkoshi Shin-ichi , Kurihara Masato , Kawamoto Tohru
Published: June 2015

An efficient preparation of size-controlled nanoparticles of an open framework coordination polymer.
Efficient gas–liquid contact using microfluidic membrane devices with staggered herringbone mixers
Authors: Femmer Tim , Eggersdorfer Max L. , Kuehne Alexander J. C. , Wessling Matthias
Published: June 2015

A microfluidic membrane device with staggered herringbone mixers for improved mass transport and reduced pressure drop.
Engineering of a peptide probe for β-amyloid aggregates
Authors: Aoraha Edwin , Candreva Jason , Kim Jin Ryoun
Published: June 2015

A non-self-aggregating peptide ligand for β-amyloid aggregates created by simple point mutation of an β-amyloid-derived segment.
Arsenic(+3) and DNA methyltransferases, and arsenic speciation in tadpole and frog life stages of western clawed frogs (Silurana tropicalis) exposed to arsenate
Authors: Koch Iris , Zhang Jing , Button Mark , Gibson Laura A , Caumette Guilhem , Langlois Valerie S , Reimer Kenneth J , Cullen William R
Published: June 2015

Western clawed frog (Silurana tropicalis) embryos were exposed to control, low (nominally 0.5 mg L−1) and high (nominally 1 mg L−1) arsenate (AsV) culture water concentrations to investigate the effects of arsenic (As) on different life stages, namely tadpole (Nieuwkoop and Faber stage 56, NF56) and frog stages (NF66). The effects were assessed by measuring arsenic(+3) and DNA methyltransferases (AS3MT and DNMT1), as well as As speciation in the tissues. The As content in frog tissues increased with water As concentration. The As species observed by high performance liquid chromatography – inductively coupled plasma mass spectrometry (HPLC-ICPMS) were mostly inorganic, dimethylarsinic acid (DMA) and trimethylarsine oxide (TMAO). With solid state X-ray absorption near edge structure (XANES) analysis, arsenobetaine/tetramethylarsonium ion were also seen. AS3MT levels decreased upon low As exposure in NF56, rising again to control levels at the high As exposure. In NF66 tissues, on the other hand, AS3MT decreased only with NF66 high As exposure. DNMT1 increased with exposure, and this was statistically significant only for the high As exposure at both life stages. Thus these enzymes seem to be affected by the As exposure. Methylation of As to form monomethylarsonate (MMA), DMA and TMAO in the frogs appeared to be inversely related to AS3MT levels. A possible interpretation of this finding is that when AS3MT is higher, excretion of MMA + DMA + TMAO is more efficient, leaving lower concentrations in the tissues, with the opposite effect (less excretion) when AS3MT is lower; alternatively, other enzymes or linked genes may affect the methylation of As.
Anti-leishmanial activity of Ni(ii), Pd(ii) and Pt(ii) β-oxodithioester complexes
Authors: Yadav Manoj Kumar , Rajput Gunjan , Srivastava Khushboo , Singh Rakesh K. , Mishra Rajnikant , Drew Michael G. B. , Singh Nanhai
Published: June 2015

Twelve new β-oxodithioester complexes (1–12) of the type [M(L)2] (M = Ni, Pd, Pt) have been synthesized and fully characterized.7and9showed impressive anti-leishmanial activity.
Synthesis of BiVO4via oxidant peroxo-method: insights into the photocatalytic performance and degradation mechanism of pollutants
Authors: Lopes Osmando F. , Carvalho Kele T. G. , Macedo Gabriel K. , de Mendonça Vagner R. , Avansi Waldir , Ribeiro Caue
Published: June 2015

A new method was proposed to obtain monoclinic BiVO4 with high photoactivity under visible light and its mechanism of photodegradation was investigated.
Organotellurium scaffolds for mass cytometry reagent development
Authors: Park Hanuel , Edgar Landon J. , Lumba Matthew A. , Willis Lisa M. , Nitz Mark
Published: June 2015

Tellurophenes are promising biocompatible mass tags.
Thermal boundary resistance at Au/Ge/Ge and Au/Si/Ge interfaces
Authors: Zhan T. , Xu Y. , Goto M. , Tanaka Y. , Kato R. , Sasaki M.
Published: June 2015

Amorphous Ge (a-Ge), crystalline Ge (c-Ge), and amorphous Si (a-Si) thin films were deposited on a Ge substrate at different temperatures by magnetron sputtering.
Electrochemical characterization of Pt–Ru–Ni/C anode electrocatalyst for methanol electrooxidation in membraneless fuel cells
Authors: Arun A. , Gowdhamamoorthi M. , Ponmani K. , Kiruthika S. , Muthukumaran B.
Published: June 2015

In the present work, carbon-supported Pt–Ru, Pt–Ni and Pt–Ru–Ni electrocatalysts with different atomic ratios were synthesized by NaBH4 reduction method.
Comparison of BTSE-RGD with DOTA-RGD as a potential imaging agent for tumors
Authors: Varshney Raunak , Singh Sweta , Tiwari Anjani K. , Mathur Rashi , Singh Shivani , Panwar Puja , Yadav Neelam , Chutani Krishna , Singh B. , Mishra Anil K.
Published: June 2015

RGD and its analogues are very important compounds and can be used as potential tumor-targeting agents.
Numerical investigation of the interaction between homogeneous and heterogeneous reactions of fuel-lean hydrogen–air mixtures over platinum in planar micro-channels
Authors: Chen Junjie , Gao Xuhui , Xu Deguang
Published: June 2015

Relative importance and respective contributions of homogeneous and heterogeneous reactions of fuel-lean hydrogen–air mixture over platinum in catalytic micro-channels were performed with detailed chemical kinetic mechanisms.
Preferential 〈220〉 crystalline growth in nanocrystalline silicon films from 27.12 MHz SiH4 plasma for applications in solar cells
Authors: Mondal Praloy , Das Debajyoti
Published: June 2015

Si-ncs are generally of 〈111〉 crystal orientation from random nucleation within poly-H network at grain-boundary, while Si ultra-ncs preferably harvest 〈220〉 alignment due to thermodynamically preferred grain growth by mono-H bonding at the boundary.
Polyethyleneimine for copper absorption II: kinetics, selectivity and efficiency from seawater
Authors: Lindén Johan B. , Larsson Mikael , Kaur Simarpreet , Skinner William M. , Miklavcic Stanley J. , Nann Thomas , Kempson Ivan M. , Nydén Magnus
Published: June 2015

Nano-thin coatings of glutaraldehyde cross-linked polyethyleneimine effectively and selectively accumulated copper from natural seawater.
Sn–Co nanoparticles encapsulated in grid-shell carbon spheres, applied as a high-performance anode material for lithium-ion batteries
Authors: Zhang Bo , Li Xiao-Shan , Liu Chun-Ling , Liu Zong-Huai , Dong Wen-Sheng
Published: June 2015

The Sn–Co nanoparticles encapsulated in grid-shell carbon spheres showed high capacity, good rate performance and excellent capacity retention.
Synthesis and spectroscopic properties of propeller type 2,4,6-tri(anthracen-9-yl)-1,3,5-triazine
Authors: Xu Li , Wang Peng-Fei , Zhang Juan-Juan , Wu Wei , Shi Jian-Wu , Yuan Jing-Fang , Han Hui , Wang Hua
Published: June 2015

The novel propeller typed compound, 2,4,6-tri(anthracen-9-yl)-1,3,5-triazine was synthesized by using 9-anthryl lithium with 1,3,5-trichlorotriazine or 2-chloro-4,6-dimethoxy-1,3,5-triazine. It's interesting spectroscopic behaviors were also studied.
Synthesis of 7-hydroxy-6,7-dihydro-indole and 6′,7′-dihydro-3,7′-biindole derivatives from domino reactions of arylglyoxals or methyl ketones with enamines
Authors: Lu Xin-Mou , Cai Zhong-Jian , Li Jian , Wang Shun-Yi , Ji Shun-Jun
Published: June 2015

A series of interesting 7-hydroxy-2-aryl-6,7-dihydro-indol-4(5H)-ones 3 was successfully synthesized in moderate to good yields by the domino reactions of different arylglyoxals 1 with enamines 2 under catalyst-free conditions.
Water diffusion in atmospherically relevant α-pinene secondary organic material
Authors: Price Hannah C. , Mattsson Johan , Zhang Yue , Bertram Allan K. , Davies James F. , Grayson James W. , Martin Scot T. , O'Sullivan Daniel , Reid Jonathan P. , Rickards Andrew M. J. , Murray Benjamin J.
Published: June 2015

We report the first direct measurements of water diffusion coefficients in secondary organic aerosol.
Alkyl-nitrile adlayers as probes of plasmonically induced electric fields
Authors: Kwasnieski Daniel T. , Wang Hao , Schultz Zachary D.
Published: June 2015

Adsorbed mercaptoalkylnitriles show Stark shifts on plasmonic surfaces that provide a direct measurement of the induced electric field.
Wide bandgap OPV polymers based on pyridinonedithiophene unit with efficiency >5%
Authors: Schneider Alexander M. , Lu Luyao , Manley Eric F. , Zheng Tianyue , Sharapov Valerii , Xu Tao , Marks Tobin J. , Chen Lin X. , Yu Luping
Published: June 2015

We report the properties of a new series of wide band gap photovoltaic polymers based on the N-alkyl 2-pyridone dithiophene (PDT) unit.
A super biosorbent from dendrimer poly(amidoamine)-grafted cellulose nanofibril aerogels for effective removal of Cr(vi)
Authors: Zhao Jiangqi , Zhang Xiaofang , He Xu , Xiao Meijie , Zhang Wei , Lu Canhui
Published: June 2015

A dendrimer PAMAM-g-CNF aerogel with unique molecular and microscopic structures demonstrates outstanding performance in Cr(vi) removal.
Phenylboronic acid-modified magnetic nanoparticles as a platform for carbon dot conjugation and doxorubicin delivery
Authors: Fahmi Mochamad Zakki , Chen Jem-Kun , Huang Chih-Ching , Ling Yong-Chien , Chang Jia-Yaw
Published: June 2015

This paper reports the development of multifunctional nanoparticles as effective dual-modality molecular imaging probes and drug delivery agents for simultaneous cancer diagnosis and chemotherapy.
Mesoporous silica nanoparticles grafted with a light-responsive protein shell for highly cytotoxic antitumoral therapy
Authors: Martínez-Carmona Marina , Baeza Alejandro , Rodriguez-Milla Miguel A. , García-Castro Javier , Vallet-Regí Maria
Published: June 2015

A novel phototriggered drug delivery nanocarrier, which exhibits very high tumor cytotoxicity against human tumoral cells, is presented.
Electrospun poly(l-lactide-co-caprolactone)–collagen–chitosan vascular graft in a canine femoral artery model
Authors: Wu Tong , Jiang Bojie , Wang Yuanfei , Yin Anlin , Huang Chen , Wang Sheng , Mo Xiumei
Published: June 2015

(P(LLA-CL)–COL–CS) composite vascular grafts could effectively improve patency rate, promote tissue regeneration, and enhance gene expression.
Formation and osteoblast behavior of HA nano-rod/fiber patterned coatings on tantalum in porous and compact forms
Authors: Wang Cuicui , Fan Zhibin , Han Yong
Published: June 2015

Osteoblast survival and proliferation are enhanced on quasi-upright HA nanorods but inhibited on paralleled HA nanofibers compared to Ta.
The role of breast cancer resistance protein (Bcrp/Abcg2) in triptolide-induced testis toxicity
Authors: Li Chunzhu , Xing Guozhen , Maeda Kazuya , Wu Chunyong , Gong Likun , Sugiyama Yuichi , Qi Xinming , Ren Jin , Wang Guangji
Published: June 2015

Triptolide possesses unique immunosuppressive and anti-tumor activities. However, its clinical use is limited by the cumulative toxicity in the testis and the mechanisms are poorly understood.
Joint optimisation of secret key capacity and sparse channel estimation based on pilot power allocation
Authors: Qi Chenhao , Nallanathan Arumugam , Wu Lenan
Published: June 2015

Pilot power allocation is investigated under the framework of physical layer secure communications in time‐division duplex systems, where the secret keys are generated from the estimates of sparse wireless channels. The joint optimisation of secret key capacity and sparse channel estimation performance based on pilot power allocation is formulated as a convex optimisation problem. Considering the fairness between these two sides, a scaling factor is introduced. Then, a scheme is proposed to fast solve the problem by looking up a table and using existing optimisation solvers. Simulation results show that a proper scaling factor can make a trade‐off between the secret key capacity and sparse channel estimation performance.
Asynchronous probabilistic neighbour discovery algorithm in mobile low‐duty‐cycle WSNs
Authors: Chen Liangyin , Wang Zhe , Cheng Hua , Zhang Jingyu , Cheng Yanhong , You Hongyue , Luo Qian , Liu Kai
Published: June 2015

For real‐time applications in mobile low‐duty‐cycle (DC) wireless sensor networks (WSNs), discovering neighbours needs to be achieved in both short average latency and high fraction of discoveries (FDs) with low energy consumption. A novel asynchronous probabilistic method is proposed, in which a node randomly chooses a prime, e.g. p, from a pre‐configured prime set and wakes up only at the first slot during every p continuous slot which is for a hyper‐cycle length, i.e. a fixed number continuous slots, determined by the prime sets, and then selects another prime for the next hyper cycle. For low‐DCs, especially <2%, one can flexibly configure different prime sets for the given DC, and the more the primes in the sets, the lower the average discovery latency (ADL) that is achieved. Simulations show that the proposed method can not only achieve a shorter ADL than SearchLight, but also obtain a shorter and smaller tail on FDs than Birthday.
Low‐complexity constant multiplication for layer processing in MIMO symbol detection
Authors: Kim Tae‐Hwan
Published: June 2015

A method to reduce the hardware complexity of the layer processing units for symbol detectors in multiple‐input–multiple‐output (MIMO) communication systems is presented. In the proposed method, the symbol constellation for each layer is modified virtually so as to reduce the hardware complexity of the constant multipliers required for the layer processing unit. For systems with 64‐quadrature‐amplitude modulation (QAM), the proposed method reduces the number of arithmetic units implementing constant multipliers by 42.9%, when compared with the conventional method.
Inkjet printing of resistively loaded FSS for microwave absorbers
Authors: Zabri S.N. , Cahill R. , Conway G. , Schuchinsky A.
Published: June 2015

Inkjet printing is proposed as a means to create the resistively loaded elements of a frequency selective surface (FSS) which suppresses radar backscatter when placed above a metal ground plane. Spectral transmission and reflection measurements from 9 to 18 GHz show that the dot density of the printed features and the volume ratio of an aqueous vehicle and nano‐silver (Ag) ink mixture can be selected to obtain surface resistances in the range 1.2–200 Ω/sq.
Influence and mitigation of long differential via stub on signal integrity
Authors: Wang Jun , Lu Jian‐Min , Chu Xiu‐Qin , Liu Yang , Lai Xin‐Quan , Li Yu‐Shan
Published: June 2015

How the long differential via stub influences the time‐domain response and the eye diagram of the signal trace in a thick multilayer printed circuit board is investigated. Then, it is proved that RL termination has the same efficiency as R and RC terminations on improving signal integrity and the eye diagram. Finally, a method is proposed to mitigate the influence of the via stub by combining mismatched R termination and reflection gain at the receiving end.
Eco‐driving strategies in battery electric vehicle use – how do drivers adapt over time?
Authors: Neumann Isabel , Franke Thomas , Cocron Peter , Bühler Franziska , Krems Josef F.
Published: June 2015

Eco‐driving is of high importance when driving battery electric vehicles (BEVs) in terms of prolonging the vehicle's limited range. A longitudinal field study with 40 participants was conducted to examine which eco‐driving strategies users know before and after driving a BEV for 3 months. Furthermore, participant's knowledge regarding eco‐driving strategies with BEVs against internal combustion engine vehicles (ICEVs) was compared. After 3 months of BEV usage, a driving test was applied in order to investigate the strategies drivers apply to drive energy efficiently and to estimate the effectiveness of these strategies. Results reveal that reported eco‐driving strategies for BEVs and ICEVs differ significantly. Users reported significantly more BEV eco‐driving strategies after experiencing the BEV for 3 months than before. Furthermore, drivers were able to significantly reduce energy consumption by applying eco‐driving strategies in the driving test. Reported eco‐driving strategies proved to be effective. The results imply that eco‐driving strategies for ICEVs have to be adapted for BEV eco‐driving and that drivers gain a deeper understanding of factors that influence energy consumption by experiencing the BEV for a longer period of time. Based on the results, support of the driver through training or assistance systems is recommended.
Design and implementation of a robust switching strategy for DC–DC converters
Authors: Noori Abdollah , Farsi Milad , Mahboobi Esfanjani Reza
Published: June 2015

In this study, a novel robust switching rule is designed for DC–DC converters utilising switched systems’ theory. The converter dynamic is described in the form of linear switched affine systems with constant external input and then, sliding‐mode switching controller is developed to ensure robust asymptotic stability of the desired equilibrium point for the system. The inherent robustness of the sliding‐mode switching rule leads to efficient regulation of the output voltage under load variations. Simulation results of the buck converter are presented to demonstrate the superiority of the proposed method compared with some of existing schemes in the literature. Finally, experimental results from a laboratory buck circuit are reported to confirm the applicability of the introduced scheme.
A microfluidic device approach to generate hollow alginate microfibers with controlled wall thickness and inner diameter
Authors: Pham Uyen H. T. , Hanif Madiha , Asthana Amit , Iqbal Samir M.
Published: June 2015

Alginate is a natural polymer with inherent biocompatibility. A simple polydimethylsiloxane (PDMS) microfluidic device based self-assembled fabrication of alginate hollow microfibers is presented. The inner diameter as well as wall thickness of the microfibers were controlled effortlessly, by altering core and sheath flow rates in the microfluidic channels. The gelation/cross-linking occured while the solutions were ejected. The microfibers were generated spontaneously, extruding out of the outlet microchannel. It was observed that the outer diameter was independent of the flow rates, while the internal diameter and wall thickness of the hollow fibers were found to be functions of the core and sheath flow rates. At a constant sheath flow, with increasing core flow rates, the internal diameters increased and the wall thicknesses decreased. At a fixed core flow, when sheath flow rate increased, the internal diameters decreased and the wall thickness increased. The immobilization of enzymes in such hollow microfibers can be a potential application as microbioreactors.
Intrinsic dielectric properties of magnetodielectric La2CoMnO6
Authors: Silva R. X. , Moreira R. L. , Almeida R. M. , Paniago R. , Paschoal C. W. A.
Published: June 2015

Manganite with a double perovskite structure is an attractive material because of its interesting magnetoelectric and dielectric responses. In particular, colossal dielectric constant (CDC) behavior has been observed in La2CoMnO6 (LCMO) at radio frequencies and at room temperature. In this paper, we used infrared-reflectivity spectroscopy to study a LCMO ceramic obtained through a modified Pechini's method to determine the phonon contribution to the intrinsic dielectric response of the system and to investigate the CDC origin. The analysis of the main polar modes and of the obtained phonon parameters indicate that the CDC effect of LCMO is of pure extrinsic origin. In addition, we estimated the dielectric constant and the quality factor of the material in the microwave region to be ε′s ∼ 16 and Qu × f ∼ 124 THz, which verifies that LCMO is appropriate for application in microwave devices and circuitry.
Flow development and structural loading on dual step cylinders in laminar shedding regime
Authors: McClure J. , Morton C. , Yarusevych S.
Published: June 2015

The flow development over a dual step cylinder is investigated numerically at a Reynolds number (ReD) of 150 for a range of aspect ratios, 0.2 ≤ L/D ≤ 5, and diameter ratios, 1.1 ≤ D/d ≤ 4. The results reveal the following four distinct types of wake topology downstream of the larger diameter cylinder: (i) shedding of hairpin vortices, (ii) transient asymmetric shedding, (iii) primarily spanwise shedding, and (iv) no vortex shedding. Dominant vortex interactions are reconstructed for each regime. These interactions, involving half-loop vortex connections, vortex merging, and direct vortex connections are shown to occur periodically as the large and small cylinder structures undergo vortex dislocations. Topological schematics are introduced to relate the characteristic frequencies to the periodic vortex interactions. The observed types of wake topology are shown to produce distinctly different mean and fluctuating forces on the dual step cylinder. For lower aspect and diameter ratios (L/D ∼ 1 and D/d ∼ 1.5), a reduction in fluctuating lift of up to 80% can be achieved on the base cylinder with a minor reduction in mean drag (∼5%). The results indicate that similar performance improvements can be sustained by attaching multiple larger diameter cylinders to the base cylinder. The changes in the fluid forcing are shown to be related to the secondary flow produced by the downwash at the stepwise discontinuities. This process also involves the production of streamwise vorticity at the steps, which is shown to be associated with the deformation of the main spanwise vortical structures.
Three-dimensional kinetic Monte Carlo simulations of diamond chemical vapor deposition
Authors: Rodgers W. J. , May P. W. , Allan N. L. , Harvey J. N.
Published: June 2015

A three-dimensional kinetic Monte Carlo model has been developed to simulate the chemical vapor deposition of a diamond (100) surface under conditions used to grow single-crystal diamond (SCD), microcrystalline diamond (MCD), nanocrystalline diamond (NCD), and ultrananocrystalline diamond (UNCD) films. The model includes adsorption of CHx (x = 0, 3) species, insertion of CHy (y = 0-2) into surface dimer bonds, etching/desorption of both transient adsorbed species and lattice sidewalls, lattice incorporation, and surface migration but not defect formation or renucleation processes. A value of ∼200 kJ mol−1 for the activation Gibbs energy, ΔG‡etch, for etching an adsorbed CHx species reproduces the experimental growth rate accurately. SCD and MCD growths are dominated by migration and step-edge growth, whereas in NCD and UNCD growths, migration is less and species nucleate where they land. Etching of species from the lattice sidewalls has been modelled as a function of geometry and the number of bonded neighbors of each species. Choice of appropriate parameters for the relative decrease in etch rate as a function of number of neighbors allows flat-bottomed etch pits and/or sharp-pointed etch pits to be simulated, which resemble those seen when etching diamond in H2 or O2 atmospheres. Simulation of surface defects using unetchable, immobile species reproduces other observed growth phenomena, such as needles and hillocks. The critical nucleus for new layer growth is 2 adjacent surface carbons, irrespective of the growth regime. We conclude that twinning and formation of multiple grains rather than pristine single-crystals may be a result of misoriented growth islands merging, with each island forming a grain, rather than renucleation caused by an adsorbing defect species.
Critical magnetic fields of superconducting aluminum-substituted Ba8Si42Al4 clathrate
Authors: Li Yang , Garcia Jose , Franco Giovanni , Lu Junqiang , Lu Kejie , Rong Bo , Shafiq Basir , Chen Ning , Liu Yang , Liu Lihua , Song Bensheng , Wei Yuping , Johnson Shardai S. , Luo Zhiping , Feng Zhaosheng
Published: June 2015

In recent years, efforts have been made to explore the superconductivity of clathrates containing crystalline frameworks of group-IV elements. The superconducting silicon clathrate is unusual in that the structure is dominated by strong sp3 covalent bonds between silicon atoms, rather than the metallic bonding that is more typical of traditional superconductors. This paper reports on critical magnetic fields of superconducting Al-substituted silicon clathrates, which were investigated by transport, ac susceptibility, and dc magnetization measurements in magnetic fields up to 90 kOe. For the sample Ba8Si42Al4, the critical magnetic fields were measured to be HC1 = 40.2 Oe and HC2 = 66.4 kOe. The London penetration depth of 4360 Å and the coherence length 70 Å were obtained, whereas the estimated Ginzburg–Landau parameter of κ = 62 revealed that Ba8Si42Al4 is a strong type-II superconductor.
ALICE—An advanced reflectometer for static and dynamic experiments in magnetism at synchrotron radiation facilities
Authors: Abrudan R. , Brüssing F. , Salikhov R. , Meermann J. , Radu I. , Ryll H. , Radu F. , Zabel H.
Published: June 2015

We report on significant developments of a high vacuum reflectometer (diffractometer) and spectrometer for soft x-ray synchrotron experiments which allows conducting a wide range of static and dynamic experiments. Although the chamber named ALICE was designed for the analysis of magnetic hetero- and nanostructures via resonant magnetic x-ray scattering, the instrument is not limited to this technique. The versatility of the instrument was testified by a series of pilot experiments. Static measurements involve the possibility to use scattering and spectroscopy synchrotron based techniques (photon-in photon-out, photon-in electron-out, and coherent scattering). Dynamic experiments require either laser or magnetic field pulses to excite the spin system followed by x-ray probe in the time domain from nano- to femtosecond delay times. In this temporal range, the demagnetization/remagnetization dynamics and magnetization precession in a number of magnetic materials (metals, alloys, and magnetic multilayers) can be probed in an element specific manner. We demonstrate here the capabilities of the system to host a variety of experiments, featuring ALICE as one of the most versatile and demanded instruments at the Helmholtz Center in Berlin-BESSY II synchrotron center in Berlin, Germany.
Position sensitivity of graphene field effect transistors to X-rays
Authors: Cazalas Edward , Sarker Biddut K. , Moore Michael E. , Childres Isaac , Chen Yong P. , Jovanovic Igor
Published: June 2015

Device architectures that incorporate graphene to realize detection of electromagnetic radiation typically utilize the direct absorbance of radiation by graphene. This limits their effective area to the size of the graphene and their applicability to lower-energy, less penetrating forms of radiation. In contrast, graphene-based transistor architectures that utilize the field effect as the detection mechanism can be sensitive to interactions of radiation not only with graphene but also with the surrounding substrate. Here, we report the study of the position sensitivity and response of a graphene-based field effect transistor (GFET) to penetrating, well-collimated radiation (micro-beam X-rays), producing ionization in the substrate primarily away from graphene. It is found that responsivity and response speed are strongly dependent on the X-ray beam distance from graphene and the gate voltage applied to the GFET. To develop an understanding of the spatially dependent response, a model is developed that incorporates the volumetric charge generation, transport, and recombination. The model is in good agreement with the observed spatial response characteristics of the GFET and predicts a greater response potential of the GFET to radiation interacting near its surface. The study undertaken provides the necessary insight into the volumetric nature of the GFET response, essential for development of GFET-based detectors for more penetrating forms of ionizing radiation.
Helical Turing patterns in the Lengyel-Epstein model in thin cylindrical layers
Authors: Bánsági T. , Taylor A. F.
Published: June 2015

The formation of Turing patterns was investigated in thin cylindrical layers using the Lengyel-Epstein model of the chlorine dioxide-iodine-malonic acid reaction. The influence of the width of the layer W and the diameter D of the inner cylinder on the pattern with intrinsic wavelength l were determined in simulations with initial random noise perturbations to the uniform state for W < l/2 and D ∼ l or lower. We show that the geometric constraints of the reaction domain may result in the formation of helical Turing patterns with parameters that give stripes (b = 0.2) or spots (b = 0.37) in two dimensions. For b = 0.2, the helices were composed of lamellae and defects were likely as the diameter of the cylinder increased. With b = 0.37, the helices consisted of semi-cylinders and the orientation of stripes on the outer surface (and hence winding number) increased with increasing diameter until a new stripe appeared.
Analysis and comparison of CVS-ADC approaches up to third order for the calculation of core-excited states
Authors: Wenzel Jan , Holzer Andre , Wormit Michael , Dreuw Andreas
Published: June 2015

The extended second order algebraic-diagrammatic construction (ADC(2)-x) scheme for the polarization operator in combination with core-valence separation (CVS) approximation is well known to be a powerful quantum chemical method for the calculation of core-excited states and the description of X-ray absorption spectra. For the first time, the implementation and results of the third order approach CVS-ADC(3) are reported. Therefore, the CVS approximation has been applied to the ADC(3) working equations and the resulting terms have been implemented efficiently in the adcman program. By treating the α and β spins separately from each other, the unrestricted variant CVS-UADC(3) for the treatment of open-shell systems has been implemented as well. The performance and accuracy of the CVS-ADC(3) method are demonstrated with respect to a set of small and middle-sized organic molecules. Therefore, the results obtained at the CVS-ADC(3) level are compared with CVS-ADC(2)-x values as well as experimental data by calculating complete basis set limits. The influence of basis sets is further investigated by employing a large set of different basis sets. Besides the accuracy of core-excitation energies and oscillator strengths, the importance of cartesian basis functions and the treatment of orbital relaxation effects are analyzed in this work as well as computational timings. It turns out that at the CVS-ADC(3) level, the results are not further improved compared to CVS-ADC(2)-x and experimental data, because the fortuitous error compensation inherent in the CVS-ADC(2)-x approach is broken. While CVS-ADC(3) overestimates the core excitation energies on average by 0.61% ± 0.31%, CVS-ADC(2)-x provides an averaged underestimation of −0.22% ± 0.12%. Eventually, the best agreement with experiments can be achieved using the CVS-ADC(2)-x method in combination with a diffuse cartesian basis set at least at the triple-ζ level.
Structural modification of nanocrystalline diamond films via positive/negative bias enhanced nucleation and growth processes for improving their electron field emission properties
Authors: Saravanan A. , Huang B. R. , Sankaran K. J. , Keiser G. , Kurian J. , Tai N. H. , Lin I. N.
Published: June 2015

Electron field emission (EFE) properties of nanocrystalline diamond (NCD) films synthesized by the bias-enhanced growth (beg) process under different bias voltages were investigated. The induction of the nanographitic phases is presumed to be the prime factor in enhancing the EFE properties of negative biased NCD films. Transmission electron microscopic investigations reveal that a negative bias voltage of −300 V increases the rate of growth for NCD films with the size of the grains changing from nano to ultranano size. This effect also is accompanied by the induction of nanographitic filaments in the grain boundaries of the films. The turn-on field (E0) for the EFE process then effectively gets reduced. The EFE process of the beg-NCD−300V films can be turned on at E0 = 3.86 V/μm, and the EFE current density achieved is 1.49 mA/cm2 at an applied field of 7.85 V/μm. On the other hand, though a positive-bias beg process (+200 V) results in the reduction of grain size, it does not induce sufficient nanographitic phases to lower the E0 value of the EFE process. Moreover, the optical emission spectroscopic investigation indicates that one of the primary causes that changes the granular structure of the NCD films is the increase in the proportion of C2 and CH species induced in the growing plasma. The polarity of the bias voltage is of less importance in the microstructural evolution of the films.
Development of an improved H-bridge cascaded static synchronous compensator in power system
Authors: Zhang Chao , Zhang Aimin , Zhang Hang , Bai Yunfei , Guo Chujia , Geng Yingsan
Published: June 2015

This paper presents a new configuration of H-bridge cascaded static synchronous compensator (STATCOM) based on auto disturbance rejection control and modulation wave shifting control intended for installation in industrial and utility power distribution systems. It proposes an improved controller that devotes itself not only to satisfying the requirement of dynamic reactive power compensation but also to achieving the balance of DC capacitor voltage. The new configuration is prominent in having no restriction on the number of power module. Simulation results show the proposed controller exhibits better performance in terms of response time and transient stability compared with the proportion integration controller. Two actual H-bridge cascaded STATCOMs are constructed at 10 kV, 2 MVA and 380 V, 6.5 kVA, respectively, and a series of verifications test are executed in 380 V, 6.5 kVA STATCOM experimental system. The experiment results further prove that H-bridge cascaded STATCOM with the proposed controller has excellent dynamic performance and strong robustness.
Analytical energy gradient for the two-component normalized elimination of the small component method
Authors: Zou Wenli , Filatov Michael , Cremer Dieter
Published: June 2015

The analytical gradient for the two-component Normalized Elimination of the Small Component (2c-NESC) method is presented. The 2c-NESC is a Dirac-exact method that employs the exact two-component one-electron Hamiltonian and thus leads to exact Dirac spin-orbit (SO) splittings for one-electron atoms. For many-electron atoms and molecules, the effect of the two-electron SO interaction is modeled by a screened nucleus potential using effective nuclear charges as proposed by Boettger [Phys. Rev. B 62, 7809 (2000)]. The effect of spin-orbit coupling (SOC) on molecular geometries is analyzed utilizing the properties of the frontier orbitals and calculated SO couplings. It is shown that bond lengths can either be lengthened or shortened under the impact of SOC where in the first case the influence of low lying excited states with occupied antibonding orbitals plays a role and in the second case the jj-coupling between occupied antibonding and unoccupied bonding orbitals dominates. In general, the effect of SOC on bond lengths is relatively small (≤5% of the scalar relativistic changes in the bond length). However, large effects are found for van der Waals complexes Hg2 and Cn2, which are due to the admixture of more bonding character to the highest occupied spinors.
Non-vacuum growth of graphene films using solid carbon source
Authors: Nguyen Ba-Son , Lin Jen-Fin , Perng Dung-Ching
Published: June 2015

This study demonstrates that air annealing can grow high-quality graphene films on the surface of polycrystalline nickel film with the help of an effective SiO2 capping layer. The number of graphene layers can be modulated by the amount of carbon embedded in the Ni film before annealing. Raman analysis results, transmission electron microscopy images, and electron diffraction patterns of the samples confirm that graphene films can be grown in air with an oxygen blocking layer and a 10 °C/s cooling rate in an open-vented rapid thermal annealing chamber or an open tube furnace. The high-quality low-defect air-annealing grown graphene is comparable to commercially available graphene grown via chemical vapor deposition. The proposed graphene growth using air annealing technique is simple and low-cost, making it highly attractive for mass production. It is transfer-free to a silicon substrate and can speed up graphene development, opening up new applications.
First-principles study on the effect of alloying elements on the elastic deformation response in β-titanium alloys
Authors: Gouda Mohammed K. , Nakamura Koichi , A. H. Gepreel Mohamed
Published: June 2015

Theoretical deformation response of hypothetical β-titanium alloys was investigated using first-principles calculation technique under periodic boundary conditions. Simulation was carried out on hypothetical 54-atom supercell of Ti–X (X = Cr, Mn, Fe, Zr, Nb, Mo, Al, and Sn) binary alloys. The results showed that the strength of Ti increases by alloying, except for Cr. The most effective alloying elements are Nb, Zr, and Mo in the current simulation. The mechanism of bond breaking was revealed by studying the local structure around the alloying element atom with respect to volume change. Moreover, the effect of alloying elements on bulk modulus and admissible strain was investigated. It was found that Zr, Nb, and Mo have a significant effect to enhance the admissible strain of Ti without change in bulk modulus.
Percolation-like phase transitions in network models of protein dynamics
Authors: Weber Jeffrey K. , Pande Vijay S.
Published: June 2015

In broad terms, percolation theory describes the conditions under which clusters of nodes are fully connected in a random network. A percolation phase transition occurs when, as edges are added to a network, its largest connected cluster abruptly jumps from insignificance to complete dominance. In this article, we apply percolation theory to meticulously constructed networks of protein folding dynamics called Markov state models. As rare fluctuations are systematically repressed (or reintroduced), we observe percolation-like phase transitions in protein folding networks: whole sets of conformational states switch from nearly complete isolation to complete connectivity in a rapid fashion. We analyze the general and critical properties of these phase transitions in seven protein systems and discuss how closely dynamics on protein folding landscapes relate to percolation on random lattices.
Ferromagnetism in Cr-doped topological insulator TlSbTe2
Authors: Wang Zhiwei , Segawa Kouji , Sasaki Satoshi , Taskin A. A. , Ando Yoichi
Published: June 2015

We have synthesized a new ferromagnetic topological insulator by doping Cr to the ternary topological-insulator material TlSbTe2. Single crystals of Tl1−xCrxSbTe2 were grown by a melting method and it was found that Cr can be incorporated into the TlSbTe2 matrix only within the solubility limit of about 1%. The Curie temperature θC was found to increase with the Cr content but remained relatively low, with the maximum value of about 4 K. The easy axis was identified to be the c-axis and the saturation moment was 2.8 μB (Bohr magneton) at 1.8 K. The in-plane resistivity of all the samples studied showed metallic behavior with p-type carriers. Shubnikov-de Hass oscillations were observed in samples with the Cr-doping level of up to 0.76%. We also tried to induce ferromagnetism in TlBiTe2 by doping Cr, but no ferromagnetism was observed in Cr-doped TlBiTe2 crystals within the solubility limit of Cr which turned out to be also about 1%.
Deformed oscillator algebra approach of some quantum superintegrable Lissajous systems on the sphere and of their rational extensions
Authors: Marquette Ian , Quesne Christiane
Published: June 2015

We extend the construction of 2D superintegrable Hamiltonians with separation of variables in spherical coordinates using combinations of shift, ladder, and supercharge operators to models involving rational extensions of the two-parameter Lissajous systems on the sphere. These new families of superintegrable systems with integrals of arbitrary order are connected with Jacobi exceptional orthogonal polynomials of type I (or II) and supersymmetric quantum mechanics. Moreover, we present an algebraic derivation of the degenerate energy spectrum for the one- and two-parameter Lissajous systems and the rationally extended models. These results are based on finitely generated polynomial algebras, Casimir operators, realizations as deformed oscillator algebras, and finite-dimensional unitary representations. Such results have only been established so far for 2D superintegrable systems separable in Cartesian coordinates, which are related to a class of polynomial algebras that display a simpler structure. We also point out how the structure function of these deformed oscillator algebras is directly related with the generalized Heisenberg algebras spanned by the nonpolynomial integrals.
Magnetoelastic coupling in A2FeReO6 (A = Ba and Ca) probed by elastic constants and magnetostriction measurements
Authors: Li Ling , Koehler Michael R. , Bredeson Isaac , He Jian , Mandrus David , Keppens Veerle
Published: June 2015

Double perovskites A2FeReO6 (A = Ba, Ca) have been synthesized and studied using a combination of resonant ultrasound spectroscopy, magnetization, and magnetostriction measurements. A large softening in C44 over a wide temperature range is observed for Ba2FeReO6 below its Curie temperature (TC ≈ 311 K), which is indicative of a structural distortion. This softening is partially suppressed upon application of a low magnetic field. For Ca2FeReO6, both the longitudinal and shear moduli show a softening starting at T ≈ 160 K. In addition, magnetoelastic coupling constants have been estimated from elastic constants and magnetostriction data, which provide direct evidence of pronounced coupling between magnetism and the lattice degrees of freedom present in both compounds.
Superconducting molybdenum-rhenium electrodes for single-molecule transport studies
Authors: Gaudenzi R. , Island J. O. , de Bruijckere J. , Burzurí E. , Klapwijk T. M. , van der Zant H. S. J.
Published: June 2015

We demonstrate that electronic transport through single molecules or molecular ensembles, commonly based on gold (Au) electrodes, can be extended to superconducting electrodes by combining gold with molybdenum-rhenium (MoRe). This combination induces proximity-effect superconductivity in the gold to temperatures of at least 4.6 K and magnetic fields of 6 T, improving on previously reported aluminum based superconducting nanojunctions. As a proof of concept, we show three-terminal superconductive transport measurements through an individual Fe4 single-molecule magnet.
Mechanism of charge transfer and its impacts on Fermi-level pinning for gas molecules adsorbed on monolayer WS2
Authors: Zhou Changjie , Yang Weihuang , Zhu Huili
Published: June 2015

Density functional theory calculations were performed to assess changes in the geometric and electronic structures of monolayer WS2 upon adsorption of various gas molecules (H2, O2, H2O, NH3, NO, NO2, and CO). The most stable configuration of the adsorbed molecules, the adsorption energy, and the degree of charge transfer between adsorbate and substrate were determined. All evaluated molecules were physisorbed on monolayer WS2 with a low degree of charge transfer and accept charge from the monolayer, except for NH3, which is a charge donor. Band structure calculations showed that the valence and conduction bands of monolayer WS2 are not significantly altered upon adsorption of H2, H2O, NH3, and CO, whereas the lowest unoccupied molecular orbitals of O2, NO, and NO2 are pinned around the Fermi-level when these molecules are adsorbed on monolayer WS2. The phenomenon of Fermi-level pinning was discussed in light of the traditional and orbital mixing charge transfer theories. The impacts of the charge transfer mechanism on Fermi-level pinning were confirmed for the gas molecules adsorbed on monolayer WS2. The proposed mechanism governing Fermi-level pinning is applicable to the systems of adsorbates on recently developed two-dimensional materials, such as graphene and transition metal dichalcogenides.
Enhanced room temperature ferromagnetism in electrodeposited Co-doped ZnO nanostructured thin films by controlling the oxygen vacancy defects
Authors: Simimol A. , Anappara Aji A. , Greulich-Weber S. , Chowdhury Prasanta , Barshilia Harish C.
Published: June 2015

We report the growth of un-doped and cobalt doped ZnO nanostructures fabricated on FTO coated glass substrates using electrodeposition method. A detailed study on the effects of dopant concentration on morphology, structural, optical, and magnetic properties of the ZnO nanostructures has been carried out systematically by varying the Co concentration (c.Co) from 0.01 to 1 mM. For c.Co ≤ 0.2 mM, h-wurtzite phase with no secondary phases of Co were present in the ZnO nanostructures. For c.Co ≤ 0.2 mM, the photoluminescence spectra exhibited a decrease in the intensity of ultraviolet emission as well as band-gap narrowing with an increase in dopant concentration. All the doped samples displayed a broad emission in the visible range and its intensity increased with an increase in Co concentration. It was found that the defect centers such as oxygen vacancies and zinc interstitials were the source of the visible emission. The X-ray photoelectron spectroscopy studies revealed, Co was primarily in the divalent state, replacing the Zn ion inside the tetrahedral crystal site of ZnO without forming any cluster or secondary phases of Co. The un-doped ZnO nanorods exhibited diamagnetic behavior and it remained up to a c.Co of 0.05 mM, while for c.Co > 0.05 mM, the ZnO nanostructures exhibited ferromagnetic behavior at room temperature. The coercivity increased to 695 G for 0.2 mM Co-doped sample and then it decreased for c.Co > 0.2 mM. Our results illustrate that up to a threshold concentration of 0.2 mM, the strong ferromagnetism is due to the oxygen vacancy defects centers, which exist in the Co-doped ZnO nanostructures. The origin of strong ferromagnetism at room temperature in Co-doped ZnO nanostructures is attributed to the s-d exchange interaction between the localized spin moments resulting from the oxygen vacancies and d electrons of Co2+ ions. Our findings provide a new insight for tuning the defect density by precisely controlling the dopant concentration in order to get the desired magnetic behavior at room temperature.
Influence of the floating potential on micro-hollow cathode operation
Authors: Levko D. , Bliokh Y. P. , Krasik Ya. E.
Published: June 2015

The influence of a keeper electrode with a floating potential on the operation of a micro-hollow cathode is studied using the two-dimensional particle-in-cell Monte Carlo collisions model. The floating potential is determined self-consistently, taking into account the electron and ion charges collected by the keeper and the potential induced by the plasma non-compensated space charge. It is shown that the parameters of the micro-hollow cathode operation vary significantly, according to whether the keeper potential is floating or has a specified constant value.