bluuebunny/crossref_metadata_2025 huggingface dataset:
A facile approach to the synthesis of structurally diverse 6,8a-dihydropyrido[2,3-d]pyrimidine derivatives via a three-component domino reaction
Authors: Dommaraju Yuvaraj , Bora Shruti , Prajapati Dipak
Published: July 2015

A concise and efficient approach to the synthesis of structurally diverse 6,8a-dihydropyrido[2,3-d]pyrimidine derivatives has been accomplished for the first-time by a three-component reaction involving alkylsulfonyl acetonitrile, an aromatic aldehyde, and 6-aminouracil.
A ring-closure method for preparing cyclic polymers from unconjugated vinyl monomers
Authors: Tang Qingquan , Chen Jiqiang , Zhao Yang , Zhang Ke
Published: July 2015

A unique ring-closure method was developed specifically focusing on the preparation of cyclic polymers derived from unconjugated vinyl monomers by combining RAFT/MADIX living polymerization technique and UV-induced SPAAC click reaction.
Color-tunable emission in Ce3+, Tb3+co-doped Ca5(BO3)3F phosphor
Authors: Yi Liping , Zhang Jilin , Qiu Zhongxian , Zhou Wenli , Yu Liping , Lian Shixun
Published: July 2015

Broadening of excitation bands and color-tunable emission of Ce3+, Tb3+ co-doped Ca5(BO3)3F phosphors are reported.
Facile thermal annealing of graphite oxide in air for graphene with a higher C/O ratio
Authors: Tian Suyun , Sun Jing , Yang Siwei , He Peng , Ding Shengju , Ding Guqiao , Xie Xiaoming
Published: July 2015

The C/O ratio of reduced graphene oxide can be improved to 25.9 by simple two-step thermal annealing in air.
Optimized solid phase extraction methodology for separation, and spectrophotometric determination of boron using amberlite XAD-16 resin modified with 2-(2-benzothiazolylazo)-4-methoxyphenol
Authors: Amin Alaa S.
Published: July 2015

Absorption spectra of 100 ng mL−1B(iii) complexed with 5 × 10−4M BTAMP at pH 5.5 at the optimum experimental conditions.
Nickel(ii)-ethylenediamine tetraacetic acid sensitized silicon nanowire array: an efficient cocatalyst-free photocatalyst for photocatalytic hydrogen generation under simulated sunlight irradiation
Authors: Huang Cheng , Kang Shi-Zhao , Li Xiangqing , Wang Dong , Qin Lixia , Lu Deli , Mu Jin
Published: July 2015

The nickel(ii)-ethylenediamine tetraacetic acid sensitized silicon nanowire array was prepared. The as-prepared photocatalytic system possesses high activity for photocatalytic H2 evolution under sunlight irradiation.
The preparation of flowerlike ZnMn2O4 microspheres assembled with porous nanosheets and their lithium battery performance as anode materials
Authors: Zeng Xiangyun , Shi Liuxue , Li Linjie , Yang Jiao , Cheng Xi , Gao Meizhen
Published: July 2015

Hierarchical flowerlike ZnMn2O4 microspheres with high electrochemical performance as an anode material for Li-ion batteries have been fabricated by a facile solvothermal method.
One-step synthesis of a cobalt sulfide/reduced graphene oxide composite used as an electrode material for supercapacitors
Authors: Xu Liang , Lu Yun
Published: July 2015

The CoS/rGO composite electrode exhibit a rather high rate capability.
Determination of the kinetics and influence of the mercury ion on papain catalytic activity
Authors: Liu Xue-Ying , Zeng Hong-Yan , Liao Meng-Chen , Claude Alain Gohi Bi Foua , Feng Bo
Published: July 2015

The effect of the mercury ion on papain activity of the substrate casein and its mechanism were investigated.
Extractive desulfurization of dibenzothiophene by a mixed extractant of N,N-dimethylacetamide, N,N-dimethylformamide and tetramethylene sulfone: optimization by Box–Behnken design
Authors: Zhao Kun , Cheng Yan , Liu Hongyu , Yang Chunping , Qiu Lu , Zeng Guangming , He Huijun
Published: July 2015

In this paper, the performance of extractive desulfurization (EDS) from gasoline was studied using a mixed solvent, which consisted of N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF) and tetramethylenesulfone (TMS).
Label-free carbon quantum dots as photoluminescence probes for ultrasensitive detection of glucose
Authors: Qiao Shi , Li Haitao , Li Hao , Liu Juan , Kong Weiqian , Hu Qiaozhen , Huang Hui , Liu Yang , Kang Zhenhui
Published: July 2015

Carbon quantum dots were demonstrated to be easy-to-use photoluminescence probes for the detection of glucose with fluorescence enhancement.
Iodine catalysed intramolecular C(sp3)–H functionalization: synthesis of 2,5-disubstituted oxazoles from N-arylethylamides
Authors: Samanta Supravat , Donthiri Ramachandra Reddy , Dinda Milan , Adimurthy Subbarayappa
Published: July 2015

Iodine catalyzed synthesis of 2,5-substituted oxazoles from N-arylethylamides through intramolecular C(sp3)–H functionalization under metal-free conditions is described.
A novel Cu–Mn/Ca–Zr catalyst for the synthesis of methyl formate from syngas
Authors: Zhao Haijun , Lin Minggui , Fang Kegong , Zhou Juan , Liu Ziyu , Zeng Gaofeng , Sun Yuhan
Published: July 2015

A novel catalyst comprised of Cu–Mn mixed oxides and CaO–ZrO2 solid base has contributed to a high-performance methyl formate (MF) synthesis from syngas in a slurry reactor.
High capacity and rate capability of a layered Li2RuO3cathode utilized in hybrid Na+/Li+batteries
Authors: Yao Ye , Yang Peilei , Bie Xiaofei , Wang Chunzhong , Wei Yingjin , Chen Gang , Du Fei
Published: July 2015

A hybrid-ion battery is established using Li2RuO3as the cathode, which demonstrates superior rate capability and long-term cycle life.
Enhanced methanol electrooxidation at Pt skin@PdPt nanocrystals
Authors: Kakade Bhalchandra , Patil Indrajit , Lokanathan Moorthi , Swami Anita
Published: July 2015

Pt skin structures over PdPt bimetallic nanocrystals show unusual enhancement in the methanol electrooxidation with mass activity of 2000 mA mgPt−1 and better stability.
On the nature of niobium substitution in niobium doped titania thin films by AACVD and its impact on electrical and optical properties
Authors: Gardecka A. J. , Goh G. K. L. , Sankar G. , Parkin I. P.
Published: July 2015

Niobium doped TiO2 thin films were deposited on silica coated glass substrate using aerosol assisted chemical vapour deposition (AACVD) from hexane solution, at 500 °C.
Scalable synthesis of highly dispersed silicon nanospheres by RF thermal plasma and their use as anode materials for high-performance Li-ion batteries
Authors: Hou Guolin , Cheng Benli , Cao Yuebin , Yao Mingshui , Ding Fei , Hu Peng , Yuan Fangli
Published: July 2015

Highly dispersed Si nanospheres and silicon nanosphere/porous-carbon composites with super electrochemical performance are successfully synthesized via thermal plasma and ball-milling.
Photocatalytic activity of ZnO/GaP1−xNxfor water splitting
Authors: Oshima Chihiro , Nishiyama Hiroshi , Chatterjee Abhijit , Uchida Katsunori , Sato Kazunori , Inoue Yasunobu , Hisatomi Takashi , Domen Kazunari
Published: July 2015

High photocatalytic activity of nitride-phosphide for water splitting.
Synthesis and design of biologically inspired biocompatible iron oxide nanoparticles for biomedical applications
Authors: Demirer Gozde S. , Okur Aysu C. , Kizilel Seda
Published: July 2015

Synthesis and design of biologically inspired biocompatible iron oxide nanoparticles.
A novel organic–inorganic hybrid polyoxometalate for the selective adsorption/isolation of β-lactoglobulin
Authors: Chen Qing , Zhang Dan-Dan , Wang Meng-Meng , Chen Xu-Wei , Wang Jian-Hua
Published: July 2015

A novel polyoxometalate (POM)-based organic–inorganic hybrid is preparedviaa one-pot hydrothermal reaction between Keggin POM and a star-like N-donor ligand. The hybrid exhibits excellent adsorption performance towards β-lactoglobulin with a favorable sorption capacity.
Thermodynamic investigation of Ti doping in MgAl2O4 based on the first-principles method
Authors: Kim Yongseon , Lim Jaehyuk , Kang Shinhoo
Published: July 2015

The doping form of Ti in MgAl2O4 crystals was investigated using a theoretical thermodynamic approach, and a quantitative analysis model of the thermodynamic stability and probability was constructed.
High temperature thermoelectric properties of Zn-doped Eu5In2Sb6
Authors: Chanakian Sevan , Aydemir Umut , Zevalkink Alex , Gibbs Zachary M. , Fleurial Jean-Pierre , Bux Sabah , Jeffrey Snyder G.
Published: July 2015

The Zintl phase Eu5In2−xZnxSb6 (x = 0, 0.025, 0.05, 0.1, 0.2) with optimized p-type carrier concentration displays a zT of up to 0.4 at ∼660 K.
Mechanochemical synthesis and high temperature thermoelectric properties of calcium-doped lanthanum telluride La3−xCaxTe4
Authors: Ma James M. , Clarke Samantha M. , Zeier Wolfgang G. , Vo Trinh , Von Allmen Paul , Jeffrey Snyder G. , Kaner Richard B. , Fleurial Jean-Pierre , Bux Sabah K.
Published: July 2015

The thermoelectric properties from 300–1275 K of calcium-doped La3−xTe4 are reported.
Stable and efficient deep-blue terfluorenes functionalized with carbazole dendrons for solution-processed organic light-emitting diodes
Authors: Zhao Lei , Wang Shumeng , Shao Shiyang , Ding Junqiao , Wang Lixiang , Jing Xiabin , Wang Fosong
Published: July 2015

Deep-blue terfluorenes with highly spectral stability and device efficiency have been successfully developed by functionalizing the backbone with carbazole dendrons, showing a peak EQE of 2.02% and CIE coordinates of (0.16, 0.04) for solution-processed undoped OLEDs.
Investigation of Au–Hg amalgam formation on substrate-immobilized individual Au nanorods
Authors: Schopf Carola , Martín Alfonso , Schmidt Michael , Iacopino Daniela
Published: July 2015

Investigation of controlled amalgamation of gold nanorods with chemically reduced mercury in aqueous solution leading to dramatic optical and morphological changes in the nanorods.
Ternary donor–acceptor phosphine oxide hosts with peculiar high energy gap for efficient blue electroluminescence
Authors: Sun Mingzhi , Zhu Liping , Kan Wenjing , Wei Ying , Ma Dongge , Fan Xuefeng , Huang Wei , Xu Hui
Published: July 2015

A triangle-shaped D–A–A moleculePCImbPOwith unusually high triplet energy of 3.0 eV, enhanced D–A electronic coupling and separated FMO and triplet locations is described.
Poly(ADP-ribose)polymerase 1 stimulates the AP-site cleavage activity of tyrosyl-DNA phosphodiesterase 1
Authors: Lebedeva Natalia A. , Anarbaev Rashid O. , Sukhanova Maria , Vasil’eva Inna A. , Rechkunova Nadejda I. , Lavrik Olga I.
Published: July 2015

The influence of poly(ADP-ribose)polymerase 1 (PARP1) on the apurinic/apyrimidinic (AP)-site cleavage activity of tyrosyl–DNA phosphodiesterase 1 (TDP1) and interaction of PARP1 and TDP1 were studied. The efficiency of single or clustered AP-site hydrolysis catalysed by TDP1 was estimated. It was shown that the efficiency of AP-site cleavage increases in the presence of an additional AP-site in the opposite DNA strand depending on its position. PARP1 stimulates TDP1; the stimulation effect was abolished in the presence of NAD+. The interaction of these two proteins was characterized quantitatively by measuring the dissociation constant for the TDP1–PARP1 complex using fluorescently-labelled proteins. The distance between the N-termini of the proteins within the complex was estimated using FRET. The data obtained suggest that PARP1 and TDP1 bind in an antiparallel orientation; the N-terminus of the former protein interacts with the C-terminal domain of the latter. The functional significance of PARP1 and TDP1 interaction in the process of DNA repair was demonstrated for the first time.
Insulin down-regulates the expression of ubiquitin E3 ligases partially by inhibiting the activity and expression of AMP-activated protein kinase in L6 myotubes
Authors: Deng Hu-Ping , Chai Jia-Ke , Shen Chuan-An , Zhang Xi-Bo , Ma Li , Sun Tian-Jun , Hu Qing-Gang , Chi Yun-Fei , Dong Ning
Published: July 2015

While insulin is an anabolic hormone, AMP-activated protein kinase (AMPK) is not only a key energy regulator, but it can also control substrate metabolism directly by inducing skeletal muscle protein degradation. The hypothesis of the present study was that insulin inhibits AMPK and thus down-regulates the expression of the ubiquitin E3 ligases, muscle atrophy F-box (MAFbx) and muscle RING finger 1 (MuRF1) in skeletal muscle cells. Differentiated L6 myotubes were treated with 5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR) and/or compound C to stimulate and/or block AMPK respectively. These treatments were also conducted in the presence or absence of insulin and the cells were analysed by western blot and quantitative real-time PCR. In addition, nuleotide levels were determined using HPLC. The activation of AMPK with AICAR enhanced the mRNA levels of MAFbx and MuRF1. Insulin reduced the phosphorylation and activity AMPK, which was accompanied by reduced MAFbx and MuRF1 mRNA levels. Using a protein kinase B (PKB/Akt) inhibitor, we found that insulin regulates AMPK through the activation of Akt. Furthermore, insulin down-regulated AMPK α2 mRNA. We conclude that insulin inhibits AMPK through Akt phosphorylation in L6 myotubes, which may serve as a possible signalling pathway for the down-regulation of protein degradation. In addition, decreased expression of AMPK α2 may partially participate in inhibiting the activity of AMPK.
Specific GFP-binding artificial proteins (αRep): a new tool for in vitro to live cell applications
Authors: Chevrel Anne , Urvoas Agathe , de la Sierra-Gallay Ines Li , Aumont-Nicaise Magali , Moutel Sandrine , Desmadril Michel , Perez Franck , Gautreau Alexis , van Tilbeurgh Herman , Minard Philippe , Valerio-Lepiniec Marie
Published: July 2015

A family of artificial proteins, named αRep, based on a natural family of helical repeat was previously designed. αRep members are efficiently expressed, folded and extremely stable proteins. A large αRep library was constructed creating proteins with a randomized interaction surface. In the present study, we show that the αRep library is an efficient source of tailor-made specific proteins with direct applications in biochemistry and cell biology. From this library, we selected by phage display αRep binders with nanomolar dissociation constants against the GFP. The structures of two independent αRep binders in complex with the GFP target were solved by X-ray crystallography revealing two totally different binding modes. The affinity of the selected αReps for GFP proved sufficient for practically useful applications such as pull-down experiments. αReps are disulfide free proteins and are efficiently and functionally expressed in eukaryotic cells: GFP-specific αReps are clearly sequestrated by their cognate target protein addressed to various cell compartments. These results suggest that αRep proteins with tailor-made specificity can be selected and used in living cells to track, modulate or interfere with intracellular processes.
Uncoupling protein 2 mediates resistance to gemcitabine-induced apoptosis in hepatocellular carcinoma cell lines
Authors: Yu Guangsheng , Liu Jun , Xu Kesen , Dong Jiahong
Published: July 2015

Oxidative stress induction is a common effector pathway for commonly used chemotherapeutic agents like gemcitabine (GEM) in hepatocellular carcinoma (HCC) patients. However, GEM alone or in combination with oxiplatin hardly renders any survival benefits to HCC patients. Mitochondrial uncoupling protein 2 (UCP2) is known to suppress mitochondrial reactive oxygen species (ROS) generation, thus mitigating oxidative stress-induced apoptosis. We demonstrate in the present study, using a panel of HCC cell lines that sensitivity to GEM in HCC well correlate with the endogenous level of UCP2 protein expression. Moreover, ectopic overexpression of UCP2 in a HCC cell line with low endogenous UCP2 expression, HLE, significantly decreased mitochondrial superoxide induction by the anti-cancer drug GEM. Conversely, UCP2 mRNA silencing by RNA interference in HCC cell lines with high endogenous UCP2 expression significantly enhanced GEM-induced mitochondrial superoxide generation and apoptosis. Cumulatively, our results suggest a critical role for mitochondrial uncoupling in GEM resistance in HCC cell lines. Hence, synergistic targeting of UCP2 in combination with other chemotherapeutic agents might be more potent in HCC patients.
Molecular determinants of ATP-sensitive potassium channel MgATPase activity: diabetes risk variants and diazoxide sensitivity
Authors: Fatehi Mohammad , Carter Chris R.J. , Youssef Nermeen , Hunter Beth E. , Holt Andrew , Light Peter E.
Published: July 2015

ATP-sensitive K+ (KATP) channels play an important role in insulin secretion. KATP channels possess intrinsic MgATPase activity that is important in regulating channel activity in response to metabolic changes, although the precise structural determinants are not clearly understood. Furthermore, the sulfonylurea receptor 1 (SUR1) S1369A diabetes risk variant increases MgATPase activity, but the molecular mechanisms remain to be determined. Therefore, we hypothesized that residue–residue interactions between 1369 and 1372, predicted from in silico modelling, influence MgATPase activity, as well as sensitivity to the clinically used drug diazoxide that is known to increase MgATPase activity. We employed a point mutagenic approach with patch-clamp and direct biochemical assays to determine interaction between residues 1369 and 1372. Mutations in residues 1369 and 1372 predicted to decrease the residue interaction elicited a significant increase in MgATPase activity, whereas mutations predicted to possess similar residue interactions to wild-type (WT) channels elicited no alterations in MgATPase activity. In contrast, mutations that were predicted to increase residue interactions resulted in significant decreases in MgATPase activity. We also determined that a single S1369K substitution in SUR1 caused MgATPase activity and diazoxide pharmacological profiles to resemble those of channels containing the SUR2A subunit isoform. Our results provide evidence, at the single residue level, for a molecular mechanism that may underlie the association of the S1369A variant with type 2 diabetes. We also show a single amino acid difference can account for the markedly different diazoxide sensitivities between channels containing either the SUR1 or SUR2A subunit isoforms.
Smartphone‐based WiFi access point localisation and propagation parameter estimation using crowdsourcing
Authors: Zhuang Y. , Li Y. , Lan H. , Syed Z. , El‐Sheimy N.
Published: July 2015

The locations of WiFi access points (APs) are important for WiFi positioning, especially when a propagation model is used. The parameters for the propagation model, such as the pathloss exponent and noise variance, usually are not available when localising APs in a new environment. A crowdsourcing‐based prototype system is introduced that automatically generates WiFi databases using the uploaded data during normal usage of smartphones. In this system, the adjustment algorithm is originally used for the estimation of AP localisation and propagation parameters. Preliminary experiments show that the average AP localisation error of the prototype system is about 4.0 m in a typical indoor environment with considerably reduced time and labour costs compared with traditional methods.
Transient interference excision and signal recovery in OTHR using robust principal component analysis
Authors: Ai Xiao‐Fan , Luo Yong‐Jiang , Zhao Guo‐Qing
Published: July 2015

The performance of high‐frequency wave over‐the‐horizon radar (OTHR) is affected by transient interference. Transient interference suppression results in the integrity of the target signal. Without suppressing on clutter before interference excision, a robust principal component analysis is applied to separate clutter and the target signal, and the target signal is recovered simultaneously. Experimental results show the effectiveness of the proposed method.
Transmit power allocation for asymmetric bi‐directional relay networks using channel statistics
Authors: Ji Xiaodong , Zhu Wei‐Ping , Massicotte Daniel
Published: July 2015

This study proposes a transmit power allocation (TPA) scheme for bi‐directional relay networks with an objective of minimising the total power consumption to meet both the service quality (i.e. the outage probability) and individual power requirements. This new scheme focuses on the amplify‐and‐forward protocol‐based multiple‐access broadcast mode with asymmetric network traffics where the bi‐directional relay channel (BDRC) statistics are assumed to be available at the transmitters. A two‐step method is devised to solve the optimisation problem pertaining to the total power minimisation. In the proposed method, the system outage probability is first minimised subject to both the individual and total power constraints, and then the total power consumption of the network is minimised subject to the given service quality constraint based on the preliminary solutions achieved in the first step. This two‐step optimisation mechanism leads to a novel TPA algorithm for the relay and two sources of the network. Simulation results are provided to validate the proposed algorithm, showing that the proposed new power allocation scheme can significantly reduce the total power consumption, especially when the BDRC or the network traffic is asymmetric.
Antipodal pilot tones in orthogonal frequency division multiplexing systems for carrier frequency offset estimation
Authors: Promsuwanna Nattaphat , Uthansakul Monthippa , Uthansakul Peerapong , Kaewkrad Aranya
Published: July 2015

The main factor to degrade the orthogonality of OFDM subcarriers is the carrier frequency offset (CFO) linked to the intercarrier interference problem. Hence, it is necessary to precisely estimate and suitably compensate the CFO. In this study, two pilot tones where their pilot symbols are antipodal to each other are proposed in order to provide the same benefit as being null when they are combined. Although in literature the null subcarrier technique was presented to obtain the null benefit, these pilot tones cannot be reused for other purposes. In contrast, the antipodal pilot tones can be utilised for channel estimations while null pilot tones are used for CFO estimation only. Thus, the subcarriers of the proposed technique become more useful than the null subcarrier technique. Moreover, the simulation results show that the technique using antipodal pilot tones provides a better performance than the null subcarrier technique.
Bayesian blind turbo equaliser with reduced complexity based on channel estimate monitoring
Authors: Alves João Paulo Luz , Guimarães Alberto Gaspar , Pinto Ernesto Leite
Published: July 2015

The authors recall the application of fixed‐lag particle smoothing (FLPS) to perform blind turbo equalisation under a Bayesian framework, assuming that the noise variance is unknown. This approach has been successfully applied in previous works, at the price of increasing equaliser computational complexity. This study's main contribution is to propose a strategy to monitor, along the iterations, the quality of channel estimate and soft information about the coded symbols, to switch from FLPS to the BCJR algorithm when performing soft‐input soft‐output equalisation. This approach allows saving significant computational effort without affecting bit error rate performance. Simulation results and a careful computational complexity analysis show the effectiveness of the techniques herein presented.
Demand for intelligent vehicle safety systems in Europe
Authors: Öörni Risto
Published: July 2015

The demand for four intelligent vehicle safety systems (IVSSs) – emergency braking, speed alert, blind spot monitoring and lane keeping support – is analysed by constructing their demand curves (demand as a function of product price) based on data available from user interviews and a literature study. The study also provides a method for constructing linear and exponential demand curves of the systems from data gathered from user interviews. The estimated linear and exponential demand curves were tested by least‐squares fitting to the data collected from user interviews. The mean absolute error was consistently larger for all of the systems studied here when using the linear instead of exponential model. This suggests that the exponential model reflects more accurately the demand for IVSSs than does the linear model.
The joy of transient chaos
Authors: Tél Tamás
Published: July 2015

We intend to show that transient chaos is a very appealing, but still not widely appreciated, subfield of nonlinear dynamics. Besides flashing its basic properties and giving a brief overview of the many applications, a few recent transient-chaos-related subjects are introduced in some detail. These include the dynamics of decision making, dispersion, and sedimentation of volcanic ash, doubly transient chaos of undriven autonomous mechanical systems, and a dynamical systems approach to energy absorption or explosion.
Modular apparatus for electrostatic actuation of common atomic force microscope cantilevers
Authors: Long Christian J. , Cannara Rachel J.
Published: July 2015

Piezoelectric actuation of atomic force microscope (AFM) cantilevers often suffers from spurious mechanical resonances in the loop between the signal driving the cantilever and the actual tip motion. These spurious resonances can reduce the accuracy of AFM measurements and in some cases completely obscure the cantilever response. To address these limitations, we developed a specialized AFM cantilever holder for electrostatic actuation of AFM cantilevers. The holder contains electrical contacts for the AFM cantilever chip, as well as an electrode (or electrodes) that may be precisely positioned with respect to the back of the cantilever. By controlling the voltages on the AFM cantilever and the actuation electrode(s), an electrostatic force is applied directly to the cantilever, providing a near-ideal transfer function from drive signal to tip motion. We demonstrate both static and dynamic actuations, achieved through the application of direct current and alternating current voltage schemes, respectively. As an example application, we explore contact resonance atomic force microscopy, which is a technique for measuring the mechanical properties of surfaces on the sub-micron length scale. Using multiple electrodes, we also show that the torsional resonances of the AFM cantilever may be excited electrostatically, opening the door for advanced dynamic lateral force measurements with improved accuracy and precision.
Using multi-dimensional Smolyak interpolation to make a sum-of-products potential
Authors: Avila Gustavo , Carrington Tucker
Published: July 2015

We propose a new method for obtaining potential energy surfaces in sum-of-products (SOP) form. If the number of terms is small enough, a SOP potential surface significantly reduces the cost of quantum dynamics calculations by obviating the need to do multidimensional integrals by quadrature. The method is based on a Smolyak interpolation technique and uses polynomial-like or spectral basis functions and 1D Lagrange-type functions. When written in terms of the basis functions from which the Lagrange-type functions are built, the Smolyak interpolant has only a modest number of terms. The ideas are tested for HONO (nitrous acid).
Full potential of radial junction Si thin film solar cells with advanced junction materials and design
Authors: Qian Shengyi , Misra Soumyadeep , Lu Jiawen , Yu Zhongwei , Yu Linwei , Xu Jun , Wang Junzhuan , Xu Ling , Shi Yi , Chen Kunji , Roca i Cabarrocas Pere
Published: July 2015

Combining advanced materials and junction design in nanowire-based thin film solar cells requires a different thinking of the optimization strategy, which is critical to fulfill the potential of nano-structured photovoltaics. Based on a comprehensive knowledge of the junction materials involved in the multilayer stack, we demonstrate here, in both experimental and theoretical manners, the potential of hydrogenated amorphous Si (a-Si:H) thin film solar cells in a radial junction (RJ) configuration. Resting upon a solid experimental basis, we also assess a more advanced tandem RJ structure with radially stacking a-Si:H/nanocrystalline Si (nc-Si:H) PIN junctions, and show that a balanced photo-current generation with a short circuit current density of Jsc = 14.2 mA/cm2 can be achieved in a tandem RJ cell, while reducing the expensive nc-Si:H absorber thickness from 1–3 μ m (in planar tandem cells) to only 120 nm. These results provide a clearly charted route towards a high performance Si thin film photovoltaics.
Experimental measurement of the Melnikov function
Authors: Meunier Patrice , Huck Peter , Nobili Clément , Villermaux Emmanuel
Published: July 2015

We study the transport properties of a genuine two-dimensional flow with a large mean velocity perturbed periodically in time by means of an original experimental technique. The flow generated by the co-rotation of two cylinders is both stratified with a linear density gradient using salted water and viscous in order to prevent Ekman pumping and centrifugal instabilities. Thus, the mean flow contains a hyperbolic point with a homoclinic streamline, which we perturb periodically by an extra oscillation. A blob of scalar injected close to the stagnation point contracts on the stable manifold and stretches in the unstable direction. The distance between the stable and the unstable manifolds is measured as the distance between the maximum and the minimum of the dye undulating pattern and is recorded as a function of the perturbation frequency. This distance, also called the Melnikov function, presents a maximum when the residence time of a fluid particle in the mean flow is about half a perturbation period. This resonance criterion is recovered with good quantitative agreement by the theoretical prediction of the Melnikov function computed for this flow.
Recombination of H atoms on the dust in fusion plasmas
Authors: Bakhtiyari-Ramezani M. , Mahmoodi J. , Alinejad N.
Published: July 2015

We survey a model for theoretical study of the interaction of hydrogen and dust surface and apply our results for dusty plasmas to fusion devices. In this model, considering the mobility of ad-atoms from one physisorbed, or chemisorbed site, to other one by thermal diffusion, we describe the formation of H2 on grain surfaces. Finally, we calculate the formation rate on the high temperature dust surfaces for a range of temperature and density in typical conditions of divertor of tokamak.
Structures of the 2-nitrophenol alkali complexes in solution and the solid state
Authors: Reichelt Hendrik , Faunce Chester A. , Paradies Henrich H.
Published: July 2015

The materials studied in this investigation were aqueous solutions (0.02-25.0 mM) of the salts of alkali metal ion (Me+) and 2-nitrophenol (2-NP). In the investigation, small-angle X-ray scattering, wide-angle X-ray scattering, and membrane-pressure osmometry were used to study the 2-NP-Me+ molecular salt structures and the onset of crystallization as a function of concentration and temperature. The experimental methods used to examine the 2-NP-Me+ molecular salt complexes provided corroborative evidence for the existence of spherical clusters with hydrodynamic diameters between ∼12 Å (Li) and 14 Å (Cs). Guinier plots of the zero-angle scattering peak were characteristic of the scattering from lamellae-like shapes with thicknesses of ∼290 Å. Tetramer and pentamer 2-NP-Me+ molecular clusters for Me+ = Li, Na, K, and Rb were assembled from four or five 2-NP molecules bound to a central alkali metal ion. The coordination symmetry around the six coordinated Li+, Na+, and K+ ions was that of a trigonal prism (D3h), with an octahedral arrangement (D2h). The Rb+ also revealed six-coordinate geometry and the central Rb+ ion adopted an octahedral arrangement (D2h). The eight-coordinated Cs+ ions with six 2-NP ligands were characteristic of a square antiprism (D4d). The square antiprism was the outcome of leaving two o-nitro groups and two phenolic oxygens being left intermolecularly uncoordinated to the Cs+ ion. The 2-NP residues were strictly planar and contained short non-bonded intramolecular distances. van der Waals forces were present between the adjacently stacked phenyl rings. No water molecules were involved as ligands for any of the 2-nitrophenol-Me+ complexes.
Inverse patchy colloids with two and three patches. Analytical and numerical study
Authors: Kalyuzhnyi Y. V. , Vasilyev O. A. , Cummings P. T.
Published: July 2015

We propose an analytical solution of the multi-density Ornstein-Zernike equation supplemented by the associative Percus-Yevick closure relations specifically designed to describe the equilibrium properties of the novel class of patchy colloidal particles represented by the inverse patchy colloids with arbitrary number of patches. Using Baxter’s factorization method, we reduce solution of the problem to the solution of one nonlinear algebraic equation for the fraction of the particles with one non-bonded patch. We present closed-form expressions for the structure (structure factor) and thermodynamic (internal energy) properties of the system in terms of this fraction (and parameters of the model). We perform computer simulation studies and compare theoretical and computer simulation predictions for the pair distribution function, internal energy, and number of single and double bonds formed in the system, for two versions of the model, each with two and three patches. We consider the models with formation of the double bonds blocked by the patch-patch repulsion and the models without patch-patch repulsion. In general very good agreement between theoretical and computer simulation results is observed.
Legendre submanifolds in contact manifolds as attractors and geometric nonequilibrium thermodynamics
Authors: Goto Shin-itiro
Published: July 2015

It has been proposed that equilibrium thermodynamics is described on Legendre submanifolds in contact geometry. It is shown in this paper that Legendre submanifolds embedded in a contact manifold can be expressed as attractors in phase space for a certain class of contact Hamiltonian vector fields. By giving a physical interpretation that points outside the Legendre submanifold can represent nonequilibrium states of thermodynamic variables, in addition to that points of a given Legendre submanifold can represent equilibrium states of the variables, this class of contact Hamiltonian vector fields is physically interpreted as a class of relaxation processes, in which thermodynamic variables achieve an equilibrium state from a nonequilibrium state through a time evolution, a typical nonequilibrium phenomenon. Geometric properties of such vector fields on contact manifolds are characterized after introducing a metric tensor field on a contact manifold. It is also shown that a contact manifold and a strictly convex function induce a lower dimensional dually flat space used in information geometry where a geometrization of equilibrium statistical mechanics is constructed. Legendre duality on contact manifolds is explicitly stated throughout.
Driven synchronization in random networks of oscillators
Authors: Hindes Jason , Myers Christopher R.
Published: July 2015

Synchronization is a universal phenomenon found in many non-equilibrium systems. Much recent interest in this area has overlapped with the study of complex networks, where a major focus is determining how a system's connectivity patterns affect the types of behavior that it can produce. Thus far, modeling efforts have focused on the tendency of networks of oscillators to mutually synchronize themselves, with less emphasis on the effects of external driving. In this work, we discuss the interplay between mutual and driven synchronization in networks of phase oscillators of the Kuramoto type, and explore how the structure and emergence of such states depend on the underlying network topology for simple random networks with a given degree distribution. We find a variety of interesting dynamical behaviors, including bifurcations and bistability patterns that are qualitatively different for heterogeneous and homogeneous networks, and which are separated by a Takens-Bogdanov-Cusp singularity in the parameter region where the coupling strength between oscillators is weak. Our analysis is connected to the underlying dynamics of oscillator clusters for important states and transitions.
Studies of kinetic processes in a concentrated 3He-4He solution using an oscillating tuning fork
Authors: Bakhvalova V. A. , Gritsenko I. A. , Rudavskii E. Ya. , Chagovets V. K. , Sheshin G. A.
Published: July 2015

The dissipative processes causing the damping of quartz tuning fork vibrations in a solution of 15% 3He in 4He, are studied in a temperature range of 0.5–2.3 K. The resonance curves of the tuning forks are measured in the laminar flow region of the liquid, and their width is determined by the width of the dissipative processes. We examined tuning forks with a resonance frequency of 32 kHz, located inside a flask (“enclosed”) and tuning forks without a flask (“unenclosed”). The results of the experiment are compared to existing theories. It was found that a significant contribution to the damping of tuning fork oscillations for a solution, as opposed to pure 4He, is from the second sound radiation, the contribution of which exceeds the input of viscous dissipation at low temperatures. The radiation of the first sound does not contribute to the damping of the oscillations of the “enclosed” fork due to the small size of the cell versus the wavelength. In the case of the “unenclosed” fork, the damping is determined by three processes: viscous dissipation and radiation of the first and second sounds.
The regulation mechanism of yitJ and metF riboswitches
Authors: Gong Sha , Wang Yujie , Zhang Wenbing
Published: July 2015

Riboswitches which function at the transcriptional level are sensitive to cotranscriptional folding. Based on the recently proposed theory of cotranscriptional folding, we developed a transition node approximation method to effectively decrease the conformation space of long RNA chains. Our results indicate that this approximation is reliable for calculating the cotranscriptional folding kinetics of long mRNA chains. We theoretically studied the cotranscriptional folding behavior of the yitJ and metF riboswitches in the absence/presence of S-adenosylmethionine. Although the two S-box riboswitches have similar OFF-state structures and share common features of riboswitches operated at the transcriptional level, their regulation mechanisms are different. The yitJ riboswitch is regulated by a combination of thermodynamic and kinetic mechanisms, while the metF riboswitch is solely kinetically controlled. For the yitJ riboswitch, transcriptional pausing at the U-stretch directly following the terminator decreases the amount of ligand required to trigger the switch. The different regulation mechanisms and binding affinities of the two riboswitches result from the different lengths of the anti-terminator helix, which in yitJ is short and only disrupts helix P1 of the riboswitch aptamer, but in metF is long and breaks both the helices P1 and P4.
Diffusion approximations to the chemical master equation only have a consistent stochastic thermodynamics at chemical equilibrium
Authors: Horowitz Jordan M.
Published: July 2015

The stochastic thermodynamics of a dilute, well-stirred mixture of chemically reacting species is built on the stochastic trajectories of reaction events obtained from the chemical master equation. However, when the molecular populations are large, the discrete chemical master equation can be approximated with a continuous diffusion process, like the chemical Langevin equation or low noise approximation. In this paper, we investigate to what extent these diffusion approximations inherit the stochastic thermodynamics of the chemical master equation. We find that a stochastic-thermodynamic description is only valid at a detailed-balanced, equilibrium steady state. Away from equilibrium, where there is no consistent stochastic thermodynamics, we show that one can still use the diffusive solutions to approximate the underlying thermodynamics of the chemical master equation.
Magnetic anisotropy and magnetic domain structure in C-doped Mn5Ge3
Authors: Michez L.-A. , Virot F. , Petit M. , Hayn R. , Notin L. , Fruchart O. , Heresanu V. , Jamet M. , Le Thanh V.
Published: July 2015

Magnetic properties of Mn5Ge3C0.7 thin films grown by molecular beam epitaxy have been studied. SQUID-VSM measurements and magnetic force microscopy have been used to probe the magnetic state and determine the relevant magnetic parameters. The results are supported by a combination of improved Saito's and Kittel's models. The moderate perpendicular magnetic anisotropy (Qexp=2Kuμ0MSat2≈0.2) leads to a stripe domain structure for film thicknesses above 28 nm. For thinner films, the magnetization lies in-plane. The uniaxial magnetocrystalline constant has been found to be much weaker than in Mn5Ge3 and is assigned to hybridization effect between the Mn and C atoms.
Spin orbit coupling for molecular ab initio density matrix renormalization group calculations: Application to g-tensors
Authors: Roemelt Michael
Published: July 2015

Spin Orbit Coupling (SOC) is introduced to molecular ab initio density matrix renormalization group (DMRG) calculations. In the presented scheme, one first approximates the electronic ground state and a number of excited states of the Born-Oppenheimer (BO) Hamiltonian with the aid of the DMRG algorithm. Owing to the spin-adaptation of the algorithm, the total spin S is a good quantum number for these states. After the non-relativistic DMRG calculation is finished, all magnetic sublevels of the calculated states are constructed explicitly, and the SOC operator is expanded in the resulting basis. To this end, spin orbit coupled energies and wavefunctions are obtained as eigenvalues and eigenfunctions of the full Hamiltonian matrix which is composed of the SOC operator matrix and the BO Hamiltonian matrix. This treatment corresponds to a quasi-degenerate perturbation theory approach and can be regarded as the molecular equivalent to atomic Russell-Saunders coupling. For the evaluation of SOC matrix elements, the full Breit-Pauli SOC Hamiltonian is approximated by the widely used spin-orbit mean field operator. This operator allows for an efficient use of the second quantized triplet replacement operators that are readily generated during the non-relativistic DMRG algorithm, together with the Wigner-Eckart theorem. With a set of spin-orbit coupled wavefunctions at hand, the molecular g-tensors are calculated following the scheme proposed by Gerloch and McMeeking. It interprets the effective molecular g-values as the slope of the energy difference between the lowest Kramers pair with respect to the strength of the applied magnetic field. Test calculations on a chemically relevant Mo complex demonstrate the capabilities of the presented method.
A high time resolution x-ray diagnostic on the Madison Symmetric Torus
Authors: DuBois Ami M. , Lee John David , Almagri Abdulgadar F.
Published: July 2015

A new high time resolution x-ray detector has been installed on the Madison Symmetric Torus (MST) to make measurements around sawtooth events. The detector system is comprised of a silicon avalanche photodiode, a 20 ns Gaussian shaping amplifier, and a 500 MHz digitizer with 14-bit sampling resolution. The fast shaping time diminishes the need to restrict the amount of x-ray flux reaching the detector, limiting the system dead-time. With a much higher time resolution than systems currently in use in high temperature plasma physics experiments, this new detector has the versatility to be used in a variety of discharges with varying flux and the ability to study dynamics on both slow and fast time scales. This paper discusses the new fast x-ray detector recently installed on MST and the improved time resolution capabilities compared to the existing soft and hard x-ray diagnostics. In addition to the detector hardware, improvements to the detector calibration and x-ray pulse identification software, such as additional fitting parameters and a more sophisticated fitting routine are discussed. Finally, initial data taken in both high confinement and standard reversed-field pinch plasma discharges are compared.
Velocimetry of cathode particles in a magnetoplasmadynamic thruster discharge plasma
Authors: Walker J. , Langendorf S. , Walker M. , Polzin K. , Kimberlin A.
Published: July 2015

With high-speed imaging, it is possible to directly observe the time-evolution of the macroscopic behavior of the discharge plasma in a magnetoplasmadynamic thruster (MPDT). By utilizing direct high-speed imaging capable of capturing many images over the course of a single discharge, the velocity of the cathode erosion particles can be measured, opening the possibility of a novel, noninvasive technique for discharge plasma flow field velocimetry. In this work, an 8 kA argon MPDT discharge is imaged at 26 173 fps utilizing a 0.9 neutral density filter. The camera is aligned with thruster centerline 4 m downstream of the thruster exit plane. By tracking visible particles appearing in the multiple images, the particle motion in the radial and azimuthal directions is directly imaged. Through the use of traditional techniques in digital particle image velocimetry, the cathode particles emanating from the discharge are measured to have a mean radial velocity of 44.6 ± 6.0 m/s with a 95% confidence interval and a statistically insignificant azimuthal velocity. The setup and analysis employed permits measurement of the particle velocity in orthogonal direction to the image sensor plane using a single camera. By combining a background removal subtraction technique and knowledge of the optical focal plane, the estimated mean axial velocity of the particles is 1.59 km/s. This investigation ends with a discussion of important factors to consider for future MPDT high-speed imaging particle velocimetry, such as frame-rate, image size, spatial resolution, optics, and data handling selections.
Synthesis of fluorescent core-shell nanomaterials and strategies to generate white light
Authors: Singh Amandeep , Kaur Ramanjot , Pandey O. P. , Wei Xueyong , Sharma Manoj
Published: July 2015

In this work, cadmium free core-shell ZnS:X/ZnS (X = Mn, Cu) nanoparticles have been synthesized and used for white light generation. First, the doping concentration of Manganese (Mn) was varied from 1% to 4% to optimize the dopant related emission and its optimal value was found to be 1%. Then, ZnS shell was grown over ZnS:Mn(1%) core to passivate the surface defects. Similarly, the optimal concentration of Copper (Cu) was found to be 0.8% in the range varied from 0.6% to 1.2%. In order to obtain an emission in the whole visible spectrum, dual doping of Mn and Cu was done in the core and the shell, respectively. A solid-solid mixing in different ratios of separately doped quantum dots (QDs) emitting in the blue green and the orange region was performed. Results show that the optimum mixture of QDs excited at 300 nm gives Commission Internationale del'Éclairage color coordinates of (0.35, 0.36), high color rendering index of 88, and correlated color temperature of 4704 K with minimum self-absorption.
Nonlinear optical conductivity of bilayer graphene with Rashba spin-orbit interaction in the terahertz regime
Authors: Liu Zheng , Sanderson Matthew , Zhang Chao , Cao J. C.
Published: July 2015

The effect of Rashba spin-orbit coupling on the nonlinear optical conductivity in a bilayer graphene is investigated. We demonstrate the very different role played by the Rashba term and interlayer hopping; in some cases, the two roles can be quite opposite. It is found that the Rashba term can either enhance or suppress the nonlinear effect in a bilayer graphene, depending on the strength of the interlayer hopping. For a weak interlayer hopping, the Rashba term can significantly enhance the nonlinear effect. An analytical result was derived, showing the interplay of the Rashba effect and the interlayer hopping effect.