bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced catalytic activity of palladium nanoparticles confined inside porous carbon in methanol electro-oxidation
Authors: Datta Abheek , Kapri Sutanu , Bhattacharyya Sayan
Published: December 2014

The confinement of Pd nanoparticles inside porous carbon leads to enhanced redox properties and high reusability in methanol electro-oxidation reaction.
On-chip cavity-enhanced absorption spectroscopy using a white light-emitting diode and polymer mirrors
Authors: Rushworth Cathy M. , Jones Gareth , Fischlechner Martin , Walton Emma , Morgan Hywel
Published: December 2014

We have integrated disposable polymer mirrors within a microfluidic chip to form a multi-pass cell, which increases the absorption path length by a maximum of 28 times, providing micromolar detection limits in a probed volume of 10 nL.
Metabolomic analysis reveals functional overlapping of three signal transduction proteins in regulating ethanol tolerance in cyanobacterium Synechocystis sp. PCC 6803
Authors: Zhu Ye , Pei Guangsheng , Niu Xiangfeng , Shi Mengliang , Zhang Mingyang , Chen Lei , Zhang Weiwen
Published: December 2014

Low ethanol tolerance is a crucial factor that restricts the feasibility of bioethanol production in renewable cyanobacterial systems.
Classification of lung cancer using ensemble-based feature selection and machine learning methods
Authors: Cai Zhihua , Xu Dong , Zhang Qing , Zhang Jiexia , Ngai Sai-Ming , Shao Jianlin
Published: December 2014

The ensemble-based feature selection method presents the merit of acquisition of more informative and compact features than those obtained by individual methods.
Synthesis and electro-optical properties of new conjugated hybrid polymers from EDOT end-capped dibenzothiophene and dibenzofuran
Authors: Lin Kaiwen , Zhen Shijie , Ming Shouli , Xu Jingkun , Lu Baoyang
Published: December 2014

Two novel EDOT end-capped dibenzo five-membered ring-heterocycle hybrid polymers were synthesised and their optoelectronic properties were explored.
Comprehensive studies of pharmacokinetics and biodistribution of indocyanine green and liposomal indocyanine green by multispectral optoacoustic tomography
Authors: Song Wantong , Tang Zhaohui , Zhang Dawei , Burton Neal , Driessen Wouter , Chen Xuesi
Published: December 2014

A real-time and continuous study of the pharmacokinetics and biodistribution of ICG and Lipo-ICG are performed by multispectral optoacoustic tomography.
Resin-immobilized pyrrolidine-based chiral organocatalysts for asymmetric Michael additions of ketones and aldehydes to nitroolefins
Authors: Zhang Richeng , Yin Guohui , Li Yang , Yan Xilong , Chen Ligong
Published: December 2014

Based on the electrostatic adsorption between acidic resins and organocatalysts, a series of resin-supported chiral organocatalysts were designed and synthesized.
MoO2Cl2(DMF)2 catalyzed microwave assisted reductive cyclisation of nitroaromatics into dibenzodiazepines
Authors: Siddiqui I. R. , Srivastava Anushree , Singh Archana , Shamim Shayna , Rai Pragati
Published: December 2014

Microwave induced, MoO2Cl2(DMF)2 catalyzed synthesis of novel dibenzodiazepine scaffolds with potential biocidal activity.
Biocatalyst development for lactic acid production at acidic pH using inter-generic protoplast fusion
Authors: Singhvi Mamata , Gurjar Gayatri , Gupta Vidya , Gokhale Digambar
Published: December 2014

Acid tolerance ofL. delbrueckiiMut Uc-3 has been improved using an inter-generic protoplast fusion approach. The fusant was further treated with UV mutagenesis which generated a mutant with improved lactic acid production in acidic environment.
Passive optical mapping of structural evolution in complex fluids
Authors: Guzman-Sepulveda Jose R. , Douglass Kyle M. , Amin Samiul , Lewis Neil E. , Dogariu Aristide
Published: December 2014

Low-coherence optical scattering allows probing the complex structure of self-assembling systems over extended ranges of the temperature and concentrations.
Porous zirconium alginate beads adsorbent for fluoride adsorption from aqueous solutions
Authors: Qiusheng Zhou , Xiaoyan Lin , Jin Qian , Jing Wang , Xuegang Luo
Published: December 2014

The porous adsorbent was prepared by loading with zirconium ions. A batch of adsorption experiments were carried under various conditions. The result suggested that the adsorbent showed well potential for defluorination.
Electrostatics of soft charged interfaces with pH-dependent charge density: effect of consideration of appropriate hydrogen ion concentration distribution
Authors: Chen Guang , Das Siddhartha
Published: December 2014

Explicit consideration of hydrogen ion concentration for describing the electrostatics of grafted polyelectrolyte layers with pH-dependent charge density exhibits the necessity of considering a non-uniform depth dependent monomer distribution.
Direct extraction of carbonyl from waste polycarbonate with amines under environmentally friendly conditions: scope of waste polycarbonate as a carbonylating agent in organic synthesis
Authors: Singh Sukhdeep , Lei Yong , Schober Andreas
Published: December 2014

An efficient green method for converting polycarbonate into urea derivatives and bisphenol-A by sequestration of carbonyl from waste polycarbonate.
Insight into two antioxidants binding to the catalase NADPH binding site from traditional Chinese medicines
Authors: Huang Hung-Jin , Chen Hsin-Yi , Chang Yuan-Shiun , Chen Calvin Yu-Chian
Published: December 2014

The two TCM compounds, hesperidin and THSG, might help to keep catalase active during the decomposition of hydrogen peroxide.
Photophysics of lumichrome in anionic and cationic micellar media
Authors: Maity Banibrata , Chatterjee Aninda , Seth Debabrata
Published: December 2014

The photophysics of lumichrome in the presence of cationic and anionic micellar environments was reported in this article.
A comprehensive test set of epoxidation rate constants for iron(iv)–oxo porphyrin cation radical complexes
Authors: Sainna Mala A. , Kumar Suresh , Kumar Devesh , Fornarini Simonetta , Crestoni Maria Elisa , de Visser Sam P.
Published: December 2014

Trends in oxygen atom transfer to Compound I of the P450 models with an extensive test set have been studied and show a preferred regioselectivity of epoxidation over hydroxylation in the gas-phase for the first time.
Energy transfer within responsive pi-conjugated coassembled peptide-based nanostructures in aqueous environments
Authors: Ardoña Herdeline Ann M. , Tovar John D.
Published: December 2014

Energy transfer is demonstrated within a responsive donor–acceptor system which incorporates two different semiconducting units (oligo(p-phenylenevinylene and quaterthiophene) coassembled within peptide nanostructures in completely aqueous environments.
Methodological development of a specific tool for assessing acceptability of assistive systems of powered two‐wheeler‐riders
Authors: Füssl Elisabeth , Oberlader Manuel , Beanland Vanessa , Spyropoulou Ioanna , Lenné Michael G. , Joshi Somya , Rößger Lars , Leden Lars , Underwood Geoff , Carvalhais Jose
Published: December 2014

Research on the acceptability of assistive systems for improving the safety of powered two‐wheelers (PTWs) is a pressing issue. The use of safety‐enhancing assistive systems for motorised vehicles, including advanced driver assistance systems and in‐vehicle information systems is widespread in many countries. Yet, there is only a limited number of equivalent intelligent transport systems (ITS) for PTWs, namely advanced rider assistance systems and on‐bike information systems. This study describes the methodological development of a specific tool for assessing motorcyclists’ acceptability of ITS, as part of the motorcyclists’ profiling questionnaire (MOPROQ). There were three stages of development. First, a literature review was undertaken to assess the current state of the art regarding ITS for PTWs and to determine the most relevant facets of acceptability that should be measured. Second, a series of focus group interviews were conducted to explore riders’ attitudes towards ITS. Finally, the focus group results were used to develop a large‐scale survey (MOPROQ), which was administered to an initial sample of over 6000 riders internationally. The designed tool can be used as a basis for the determination of rider acceptability of ITS systems in the future.
Channel estimation and transmit power control in wireless body area networks
Authors: Di Franco Fabio , Tachtatzis Christos , Atkinson Robert C. , Tinnirello Ilenia , Glover Ian A.
Published: December 2014

Wireless body area networks have recently received much attention because of their application to assisted living and remote patient monitoring. For these applications, energy minimisation is a critical issue since, in many cases, batteries cannot be easily replaced or recharged. Reducing energy expenditure by avoiding unnecessary high transmission power and minimising frame retransmissions is therefore crucial. In this study, a transmit power control scheme suitable for IEEE 802.15.6 networks operating in beacon mode with superframe boundaries is proposed. The transmission power is modulated, frame‐by‐frame, according to a run‐time estimation of the channel conditions. Power measurements using the beacon frames are made periodically, providing reverse channel gain and an opportunistic fade margin, set on the basis of prior power fluctuations, is added. This approach allows tracking of the highly variable on‐body to on‐body propagation channel without the need to transmit additional probe frames. An experimental study based on test cases demonstrates the effectiveness of the scheme and compares its performance with alternative solutions presented in the literature.
Heat‐pump performance: voltage dip/sag, under‐voltage and over‐voltage
Authors: Heffernan William J.B. , Watson Neville R. , Watson Jeremy D.
Published: December 2014

Reverse cycle air‐source heat‐pumps are an increasingly significant load in New Zealand and in many other countries. This has raised concern over the impact wide‐spread use of heat‐pumps may have on the grid. The characteristics of the loads connected to the power system are changing because of heat‐pumps. Their performance during under‐voltage events such as voltage dips has the potential to compound the event and possibly cause voltage collapse. In this study, results from testing six heat‐pumps are presented to assess their performance at various voltages and hence their impact on voltage stability.
Resonant third harmonic generation of KrF laser in Ar gas
Authors: Rakowski R. , Barna A. , Suta T. , Bohus J. , Földes I. B. , Szatmári S. , Mikołajczyk J. , Bartnik A. , Fiedorowicz H. , Verona C. , Verona Rinati G. , Margarone D. , Nowak T. , Rosiński M. , Ryć L.
Published: December 2014

Investigations of emission of harmonics from argon gas jet irradiated by 700 fs, 5 mJ pulses from a KrF laser are presented. Harmonics conversion was optimized by varying the experimental geometry and the nozzle size. For the collection of the harmonic radiation silicon and solar-blind diamond semiconductor detectors equipped with charge preamplifiers were applied. The possibility of using a single-crystal CVD diamond detector for separate measurement of the 3rd harmonic in the presence of a strong pumping radiation was explored. Our experiments show that the earlier suggested 0.7% conversion efficiency can really be obtained, but only in the case when phase matching is optimized with an elongated gas target length corresponding to the length of coherence.
Exploring the role of hydration and confinement in the aggregation of amyloidogenic peptides Aβ16−22 and Sup357−13 in AOT reverse micelles
Authors: Martinez Anna Victoria , Małolepsza Edyta , Rivera Eva , Lu Qing , Straub John E.
Published: December 2014

Knowledge of how intermolecular interactions of amyloid-forming proteins cause protein aggregation and how those interactions are affected by sequence and solution conditions is essential to our understanding of the onset of many degenerative diseases. Of particular interest is the aggregation of the amyloid-β (Aβ) peptide, linked to Alzheimer's disease, and the aggregation of the Sup35 yeast prion peptide, which resembles the mammalian prion protein linked to spongiform encephalopathies. To facilitate the study of these important peptides, experimentalists have identified small peptide congeners of the full-length proteins that exhibit amyloidogenic behavior, including the KLVFFAE sub-sequence, Aβ16−22, and the GNNQQNY subsequence, Sup357−13. In this study, molecular dynamics simulations were used to examine these peptide fragments encapsulated in reverse micelles (RMs) in order to identify the fundamental principles that govern how sequence and solution environment influence peptide aggregation. Aβ16−22 and Sup357−13 are observed to organize into anti-parallel and parallel β-sheet arrangements. Confinement in the sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles is shown to stabilize extended peptide conformations and enhance peptide aggregation. Substantial fluctuations in the reverse micelle shape are observed, in agreement with earlier studies. Shape fluctuations are found to facilitate peptide solvation through interactions between the peptide and AOT surfactant, including direct interaction between non-polar peptide residues and the aliphatic surfactant tails. Computed amide I IR spectra are compared with experimental spectra and found to reflect changes in the peptide structures induced by confinement in the RM environment. Furthermore, examination of the rotational anisotropy decay of water in the RM demonstrates that the water dynamics are sensitive to the presence of peptide as well as the peptide sequence. Overall, our results demonstrate that the RM is a complex confining environment where substantial direct interaction between the surfactant and peptides plays an important role in determining the resulting ensemble of peptide conformations. By extension the results suggest that similarly complex sequence-dependent interactions may determine conformational ensembles of amyloid-forming peptides in a cellular environment.
Effect of free surface roughness on the apparent glass transition temperature in thin polymer films measured by ellipsometry
Authors: Efremov Mikhail Yu.
Published: December 2014

Ellipsometry is one of the standard methods for observation of glass transition in thin polymer films. This work proposes that sensitivity of the method to surface morphology can complicate manifestation of the transition in a few nm thick samples. Two possible mechanisms of free surface roughening in the vicinity of glass transition are discussed: roughening due to lateral heterogeneity and roughening associated with thermal capillary waves. Both mechanisms imply an onset of surface roughness in the glass transition temperature range, which affects the experimental data in a way that shifts apparent glass transition temperature. Effective medium approximation models are used to introduce surface roughness into optical calculations. The results of the optical modeling for a 5 nm thick polystyrene film on silicon are presented.
Sensitivity of polarization fluctuations to the nature of protein-water interactions: Study of biological water in four different protein-water systems
Authors: Ghosh Rikhia , Banerjee Saikat , Hazra Milan , Roy Susmita , Bagchi Biman
Published: December 2014

Since the time of Kirkwood, observed deviations in magnitude of the dielectric constant of aqueous protein solution from that of neat water (∼80) and slower decay of polarization have been subjects of enormous interest, controversy, and debate. Most of the common proteins have large permanent dipole moments (often more than 100 D) that can influence structure and dynamics of even distant water molecules, thereby affecting collective polarization fluctuation of the solution, which in turn can significantly alter solution's dielectric constant. Therefore, distance dependence of polarization fluctuation can provide important insight into the nature of biological water. We explore these aspects by studying aqueous solutions of four different proteins of different characteristics and varying sizes, chicken villin headpiece subdomain (HP-36), immunoglobulin binding domain protein G (GB1), hen-egg white lysozyme (LYS), and Myoglobin (MYO). We simulate fairly large systems consisting of single protein molecule and 20000–30000 water molecules (varied according to the protein size), providing a concentration in the range of ∼2–3 mM. We find that the calculated dielectric constant of the system shows a noticeable increment in all the cases compared to that of neat water. Total dipole moment auto time correlation function of water ⟨δMW(0)δMW(t)⟩ is found to be sensitive to the nature of the protein. Surprisingly, dipole moment of the protein and total dipole moment of the water molecules are found to be only weakly coupled. Shellwise decomposition of water molecules around protein reveals higher density of first layer compared to the succeeding ones. We also calculate heuristic effective dielectric constant of successive layers and find that the layer adjacent to protein has much lower value (∼50). However, progressive layers exhibit successive increment of dielectric constant, finally reaching a value close to that of bulk 4–5 layers away. We also calculate shellwise orientational correlation function and tetrahedral order parameter to understand the local dynamics and structural re-arrangement of water. Theoretical analysis providing simple method for calculation of shellwise local dielectric constant and implication of these findings are elaborately discussed in the present work.
Nucleation and crystal growth in a suspension of charged colloidal silica spheres with bi-modal size distribution studied by time-resolved ultra-small-angle X-ray scattering
Authors: Hornfeck Wolfgang , Menke Dirk , Forthaus Martin , Subatzus Sebastian , Franke Markus , Schöpe Hans-Joachim , Palberg Thomas , Perlich Jan , Herlach Dieter
Published: December 2014

A suspension of charged colloidal silica spheres exhibiting a bi-modal size distribution of particles, thereby mimicking a binary mixture, was studied using time-resolved ultra-small-angle synchrotron X-ray scattering (USAXS). The sample, consisting of particles of diameters dA = (104.7 ± 9.0)  nm and dB = (88.1 ± 7.8)  nm (dA/dB ≈ 1.2), and with an estimated composition A0.6(1)B0.4(1), was studied with respect to its phase behaviour in dependance of particle number density and interaction, of which the latter was modulated by varying amounts of added base (NaOH). Moreover, its short-range order in the fluid state and its eventual solidification into a long-range ordered colloidal crystal were observed in situ, allowing the measurement of the associated kinetics of nucleation and crystal growth. Key parameters of the nucleation kinetics such as crystallinity, crystallite number density, and nucleation rate density were extracted from the time-resolved scattering curves. By this means an estimate on the interfacial energy for the interface between the icosahedral short-range ordered fluid and a body-centered cubic colloidal crystal was obtained, comparable to previously determined values for single-component colloidal systems.
Electric field enhancement in a self-assembled 2D array of silver nanospheres
Authors: El-Khoury Patrick Z. , Khon Elena , Gong Yu , Joly Alan G. , Abellan Patricia , Evans James E. , Browning Nigel D. , Hu Dehong , Zamkov Mikhail , Hess Wayne P.
Published: December 2014

We investigate the plasmonic properties of a self-assembled 2D array of Ag nanospheres (average particle diameter/inter-particle separation distance of 9/3.7 nm). The structures of the individual particles and their assemblies are characterized using high-resolution transmission electron microscopy (HR-TEM). The plasmonic response of the nanoparticle network is probed using two-photon photoemission electron microscopy (TP-PEEM). HR-TEM and TP-PEEM statistics reveal the structure and plasmonic response of the network to be homogeneous on average. This translates into a relatively uniform surface-enhanced Raman scattering (SERS) response from biphenyl,4-4′-dithiol (BPDT) molecules adsorbed onto different sites of the network. Reproducible, bright, and low-background SERS spectra are recorded and assigned on the basis of density functional theory calculations in which BPDT is chemisorbed onto the vertex of a finite tetrahedral Ag cluster consisting of 20 Ag atoms. A notable agreement between experiment and theory allows us to rigorously account for the observable vibrational states of BPDT in the ∼200–2200 cm−1 region of the spectrum. Finite difference time domain simulations further reveal that physical enhancement factors on the order of 106 are attainable at the nanogaps formed between the silver nanospheres in the 2D array. Combined with modest chemical enhancement factors, this study paves the way for reproducible single molecule signals from an easily self-assembled SERS substrate.
Iso-flux tension propagation theory of driven polymer translocation: The role of initial configurations
Authors: Sarabadani Jalal , Ikonen Timo , Ala-Nissila Tapio
Published: December 2014

We investigate the dynamics of pore-driven polymer translocation by theoretical analysis and molecular dynamics (MD) simulations. Using the tension propagation theory within the constant flux approximation we derive an explicit equation of motion for the tension front. From this we derive a scaling relation for the average translocation time τ, which captures the asymptotic result \documentclass[12pt]{minimal}\begin{document}$\tau \propto N_0^{1+\nu }$\end{document}τ∝N01+ν, where N0 is the chain length and ν is the Flory exponent. In addition, we derive the leading correction-to-scaling term to τ and show that all terms of order \documentclass[12pt]{minimal}\begin{document}$N_0^{2\nu }$\end{document}N02ν exactly cancel out, leaving only a finite-chain length correction term due to the effective pore friction, which is linearly proportional to N0. We use the model to numerically include fluctuations in the initial configuration of the polymer chain in addition to thermal noise. We show that when the cis side fluctuations are properly accounted for, the model not only reproduces previously known results but also considerably improves the estimates of the monomer waiting time distribution and the time evolution of the translocation coordinate s(t), showing excellent agreement with MD simulations.
Shear-induced conformation change in α-crystalline nylon6
Authors: Arabnejad Saeid , Manzhos Sergei , He Chaobin , Shim V. P. W.
Published: December 2014

A study of shear deformation of α-crystalline nylon6 is undertaken, using dispersion-corrected density functional theory. The shear stress-strain relationship and shear strength for interlayer shear deformation are computed. A conformation change induced by shear is identified along twinning deformation, whereby the conformation of chains, specifically the location of non-H-bonded hydrogen atoms, changes continuously. This paves a way for the modulation of properties of this group of materials by small shear deformation, if the non-H-bonded hydrogens are chemically substituted to form non-equivalent conformations when deformed.
Dual-sensor technique for characterization of carrier lifetime decay transients in semiconductors
Authors: Ahrenkiel R. K. , Johnston S. W. , Kuciauskas D. , Tynan Jerry
Published: December 2014

This work addresses the frequent discrepancy between transient photoconductive (PC) decay and transient photoluminescence (PL) decay. With this dual- sensor technique, one measures the transient PC and PL decay simultaneously with the same incident light pulse, removing injection-level uncertainty. Photoconductive decay measures the transient photoconductivity, Δσ(t). PCD senses carriers released from shallow traps as well as the photo-generated electron-hole pairs. In addition, variations in carrier mobility with injection level (and time) contribute to the decay time. PL decay senses only electron-hole recombination via photon emission. Theory and experiment will show that the time dependence of the two techniques can be quite different at high injection.
A chirped-pulse Fourier-transform microwave/pulsed uniform flow spectrometer. II. Performance and applications for reaction dynamics
Authors: Abeysekera Chamara , Zack Lindsay N. , Park G. Barratt , Joalland Baptiste , Oldham James M. , Prozument Kirill , Ariyasingha Nuwandi M. , Sims Ian R. , Field Robert W. , Suits Arthur G.
Published: December 2014

This second paper in a series of two reports on the performance of a new instrument for studying chemical reaction dynamics and kinetics at low temperatures. Our approach employs chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy to probe photolysis and bimolecular reaction products that are thermalized in pulsed uniform flows. Here we detail the development and testing of a new Ka-band CP-FTMW spectrometer in combination with the pulsed flow system described in Paper I [J. M. Oldham, C. Abeysekera, B. Joalland, L. N. Zack, K. Prozument, I. R. Sims, G. B. Park, R. W. Field, and A. G. Suits, J. Chem. Phys. 141, 154202 (2014)]. This combination delivers broadband spectra with MHz resolution and allows monitoring, on the μs timescale, of the appearance of transient reaction products. Two benchmark reactive systems are used to illustrate and characterize the performance of this new apparatus: the photodissociation of SO2 at 193 nm, for which the vibrational populations of the SO product are monitored, and the reaction between CN and C2H2, for which the HCCCN product is detected in its vibrational ground state. The results show that the combination of these two well-matched techniques, which we refer to as chirped-pulse in uniform flow, also provides insight into the vibrational and rotational relaxation kinetics of the nascent reaction products. Future directions are discussed, with an emphasis on exploring the low temperature chemistry of complex polyatomic systems.
Reactive HiPIMS deposition of SiO2/Ta2O5 optical interference filters
Authors: Hála Matěj , Vernhes Richard , Zabeida Oleg , Klemberg-Sapieha Jolanta-Ewa , Martinu Ludvik
Published: December 2014

In this contribution, based on the detailed understanding of the processes at the target during reactive high power impulse magnetron sputtering (HiPIMS), we demonstrate the deposition of both low- and high-index films and their implementation in optical interference filters with enhanced performance. We first investigate strategies for stabilizing the arc-free HiPIMS discharges above Si and Ta targets in the presence of oxygen. We show that hysteresis can be suppressed for these two target materials by suitable pulse-management strategies, ensuring good process stability without having to rely on any feedback control. Afterwards, we discuss the room temperature deposition of optically transparent SiO2 and Ta2O5 single layers as well as the fabrication of SiO2/Ta2O5 stacks such as 7 layer Bragg reflectors and 11 layer Fabry-Perot interference filters. We also analyze the optical and mechanical characteristics of these various coatings and compare them with their counterparts obtained by radio-frequency magnetron sputtering (RFMS). Among other findings, we observe that the coatings prepared by HiPIMS present higher refractive index and lower surface roughness values, suggesting a denser microstructure. In addition, the HiPIMS-deposited optical filters exhibit a better optical performance than their counterparts fabricated by RFMS, but it is especially with respect to the mechanical properties such as scratch resistance and low residual stress, that the coatings prepared by HiPIMS present the most dramatic improvements (up to 42% and 72% enhancement, respectively). Finally, we show that the stress values obtained for the HiPIMS-deposited SiO2 and Ta2O5 coatings are lower than for other deposition techniques commonly used in the fabrication of optical interference filters.
Controllable growth of copper-phthalocyanine thin film on rough graphene substrate
Authors: Dou Wei-Dong , Lee Chun-Sing
Published: December 2014

Film growth behavior of copper-phthalocyanine (CuPc) on rough graphene (RG) and smooth graphene (SG) substrates was investigated experimentally. Both the RG and the SG are single layer graphene on metal substrates. The RG samples were prepared on copper foils and show rough surfaces; whereas, the SG samples prepared on Ni(111) substrates are characterized with much smoother surfaces. While CuPc molecules deposited on the two graphene substrates show similar molecular alignment, morphologies of the deposited films show considerable differences. On the SG substrate, CuPc molecules form two-dimensional islands with large size and sharp edges. While on the RG substrate, CuPc nucleates into particle-like grains without regular shapes. The high density of topographical defects on the RG substrate is believed to be a primary factor which leads to the formation of the smaller grains. The variation of thin film structures of CuPc with respect to the substrate temperature was also studied. Films with good crystallinity can still be obtained on the RG substrates when the substrate temperature is 80 °C or higher.
Evolution of linear moduli and remnant state variables during polarization reversal in a lead zirconate rectangular parallelpiped at room and high temperatures
Authors: Ji Dae Won , Kim Sang-Joo
Published: December 2014

A poled lead titanate zirconate rectangular parallelepiped is subjected to electric field pulses with gradually increasing magnitude at room and high temperatures. From measured electric displacement and strain responses, permittivity and piezoelectric coefficients are estimated and plotted with respect to remnant polarization. Equations for piezoelectric coefficients are proposed as functions of relative remnant polarization and temperature. The so-called reference remnant polarization and strains are calculated from measured remnant polarization and strains. Reference remnant strains are plotted with respect to reference remnant polarization, and their evolutions during polarization reversal are analyzed and compared.
Graphics processing unit accelerated three-dimensional model for the simulation of pulsed low-temperature plasmas
Authors: Fierro Andrew , Dickens James , Neuber Andreas
Published: December 2014

A 3-dimensional particle-in-cell/Monte Carlo collision simulation that is fully implemented on a graphics processing unit (GPU) is described and used to determine low-temperature plasma characteristics at high reduced electric field, E/n, in nitrogen gas. Details of implementation on the GPU using the NVIDIA Compute Unified Device Architecture framework are discussed with respect to efficient code execution. The software is capable of tracking around 10 × 106 particles with dynamic weighting and a total mesh size larger than 108 cells. Verification of the simulation is performed by comparing the electron energy distribution function and plasma transport parameters to known Boltzmann Equation (BE) solvers. Under the assumption of a uniform electric field and neglecting the build-up of positive ion space charge, the simulation agrees well with the BE solvers. The model is utilized to calculate plasma characteristics of a pulsed, parallel plate discharge. A photoionization model provides the simulation with additional electrons after the initial seeded electron density has drifted towards the anode. Comparison of the performance benefits between the GPU-implementation versus a CPU-implementation is considered, and a speed-up factor of 13 for a 3D relaxation Poisson solver is obtained. Furthermore, a factor 60 speed-up is realized for parallelization of the electron processes.
Growth control of the oxidation state in vanadium oxide thin films
Authors: Lee Shinbuhm , Meyer Tricia L. , Park Sungkyun , Egami Takeshi , Lee Ho Nyung
Published: December 2014

Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research but also technological applications that utilize the subtle change in the physical properties originating from the metal-insulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V2+3O3, V+4O2, and V2+5O5. A well pronounced MIT was only observed in VO2 films grown in a very narrow range of oxygen partial pressure P(O2). The films grown either in lower (<10 mTorr) or higher P(O2) (>25 mTorr) result in V2O3 and V2O5 phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO2 thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an improved MIT behavior.
Materials selection for oxide-based resistive random access memories
Authors: Guo Yuzheng , Robertson John
Published: December 2014

The energies of atomic processes in resistive random access memories (RRAMs) are calculated for four typical oxides, HfO2, TiO2, Ta2O5, and Al2O3, to define a materials selection process. O vacancies have the lowest defect formation energy in the O-poor limit and dominate the processes. A band diagram defines the operating Fermi energy and O chemical potential range. It is shown how the scavenger metal can be used to vary the O vacancy formation energy, via controlling the O chemical potential, and the mean Fermi energy. The high endurance of Ta2O5 RRAM is related to its more stable amorphous phase and the adaptive lattice rearrangements of its O vacancy.
Tuning the g-factor of neutral and charged excitons confined to self-assembled (Al,Ga)As shell quantum dots
Authors: Corfdir P. , Fontana Y. , Van Hattem B. , Russo-Averchi E. , Heiss M. , Fontcuberta i Morral A. , Phillips R. T.
Published: December 2014

We study the neutral exciton (X) and charged exciton (CX) transitions from (Al,Ga)As shell quantum dots located in core-shell nanowires, in the presence of a magnetic field. The g-factors and the diamagnetic coefficients of both the X and the CX depend on the orientation of the field with respect to the nanowire axis. The aspect ratio of the X wavefunction is quantified based on the anisotropy of the diamagnetic coefficient. For specific orientations of the magnetic field, it is possible to cancel the g-factor of the bright states of the X and the CX by means of an inversion of the sign of the hole's g-factor, which is promising for quantum information processing applications.
Interface structure and magnetism of CoFe/A1-FePt films with perpendicular magnetic anisotropy
Authors: Guan X. W. , Cheng X. M. , Huang T. , Miao X. S.
Published: December 2014

In this work, we investigated the strong perpendicular magnetic anisotropy (PMA) in CoFe/A1-FePt films. In our experiment, after rapid thermal annealing at a low temperature, CoFe (5 nm)/A1-FePt (3 nm) films present an effective PMA energy density up to 7.50 × 106 erg/cm3. The PMA diminishes when the A1-FePt film thickness increases, indicating that the magnetic anisotropy mainly originates in the interface region of CoFe/A1-FePt films. Moreover, the calculated PMA energy density by first principles is more than 5.51 × 106 erg/cm3 which is consistent with our experimental results. The calculated results further suggest an enhanced PMA and a lower saturation magnetization of CoFe/A1-FePt films would be obtained by introducing proper strain at the CoFe/A1-FePt interface region. The CoFe/A1-FePt films have the potential to be applied in low-power and thermally stable perpendicular spintronic devices.
Simulation and design of feedback control on resistive wall modes in Keda Torus eXperiment
Authors: Li Chenguang , Liu Wandong , Li Hong
Published: December 2014

The feedback control of resistive wall modes (RWMs) in Keda Torus eXperiment (KTX) (Liu et al., Plasma Phys. Controlled Fusion 56, 094009 (2014)) is investigated by simulation. A linear model is built to describe the growth of the unstable modes in the absence of feedback and the resulting mode suppression due to feedback, given the typical reversed field pinch plasma equilibrium. The layout of KTX with two shell structures (the vacuum vessel and the stabilizing shell) is taken into account. The feedback performance is explored both in the scheme of “clean mode control” (Zanca et al., Nucl. Fusion 47, 1425 (2007)) and “raw mode control.” The discrete time control model with specific characteristic times will mimic the real feedback control action and lead to the favored control cycle. Moreover, the conceptual design of feedback control system is also presented, targeting on both RWMs and tearing modes.
Continuously tunable temperature coefficient of resistivity in antiperovskite AgN1−xCxMn3 (0 ≤ x ≤ 0.15)
Authors: Lin J. C. , Tong P. , Lin S. , Wang B. S. , Song W. H. , Sun Y. P.
Published: December 2014

The antiperovskite intermetallic compounds AgN1−xCxMn3 (0 ≤ x ≤ 0.15) have been synthesized. As x increases, the temperature coefficient of resistivity (TCR) above room temperature decreases monotonically and finally changes the sign from positive to negative above x = 0.1. Meanwhile, the temperature range is gradually broadened. For x = 0.07, TCR is ∼3.1 ppm/K between 280 K and 375 K. Both the resistivity and its slope are insensitive to the external magnetic field, indicating an insignificant contribution from magnetic scattering or short-range magnetic ordering to the observed low-TCR. As manifested by the Hall effect, the charge carrier density in the paramagnetic state for x = 0.15 is reduced by an order of magnitude in comparison with that for x = 0. The reduction of carrier density and the enhancive disorders when x increases was proposed to be responsible for the decrease in TCR and its sign switch.
Integrated experimental and computational studies of deformation of single crystal copper at high strain rates
Authors: Rawat S. , Chandra S. , Chavan V. M. , Sharma S. , Warrier M. , Chaturvedi S. , Patel R. J.
Published: December 2014

Quasi-static (0.0033 s−1) and dynamic (103 s−1) compression experiments were performed on single crystal copper along ⟨100⟩ and ⟨110⟩ directions and best-fit parameters for the Johnson-Cook (JC) material model, which is an important input to hydrodynamic simulations for shock induced fracture, have been obtained. The deformation of single crystal copper along the ⟨110⟩ direction showed high yield strength, more strain hardening, and less strain rate sensitivity as compared to the ⟨100⟩ direction. Although the JC model at the macro-scale is easy to apply and describes a general response of material deformation, it lacks physical mechanisms that describe the influence of texture and initial orientation on the material response. Hence, a crystal plasticity model based on the theory of thermally activated motion of dislocations was used at the meso-scale, in which the evolution equations permit one to study and quantify the influence of initial orientation on the material response. Hardening parameters of the crystal plasticity model show less strain rate sensitivity along the ⟨110⟩ orientation as compared to the ⟨100⟩ orientation, as also shown by the JC model. Since the deformation process is inherently multiscale in nature, the shape changes observed in the experiments due to loading along ⟨100⟩ and ⟨110⟩ directions are also validated by molecular dynamics simulations at the nano-scale.
Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism
Authors: Jamer M. E. , Assaf B. A. , Sterbinsky G. E. , Arena D. A. , Heiman D.
Published: December 2014

Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. The results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.
Switchable diode effect in ferroelectric thin film: High dependence on poling process and temperature
Authors: Li Z. X. , Liu X. L. , Chen W. J. , Zhang X. Y. , Wang Ying , Xiong W. M. , Zheng Yue
Published: December 2014

Pb(Zr0.53Ti0.47)O3 (PZT) thin film was fabricated on Pt/Ti/SiO2/Si substrate by chemical solution deposition method. Our results show a very great switchable ferroelectric diode effect (SFDE) in Pt-PZT-Au structure, which is more obvious and controllable than that in other ferroelectric thin films. The electrical conduction exhibits high rectifying behavior after pre-poling and the polarity of ferroelectric diode can be switched by changing the orientation of polarization in ferroelectric thin film. Our results also indicate that the SFDE in PZT film is highly dependent on remanent polarization and temperature. With the increase of remanent polarization, the forward current of bistable rectifying behavior observably reduces. Therefore, our measurement indicated that the biggest rectification ratio can reach about 220, which is found in 250K after +10V poling. By analyzing the conduction data, it is found that the dominant conduction mechanism of the SFDE in this sample is due to the space-charge-limited bulk conduction (SCLC), and Schottky emission (SE) may play subordinate role in forward bias voltage. Our observation demonstrates that SFDE may be general characteristic in ferroelectrics as long as proper electrodes chosen.
Win–win strategies for high beef quality, consumer satisfaction, and farm efficiency, low environmental impacts and improved animal welfare
Authors: Hocquette J. F. , Botreau R. , Legrand I. , Polkinghorne R. , Pethick D. W. , Lherm M. , Picard B. , Doreau M. , Terlouw E. M. C.
Published: December 2014

Meat quality includes intrinsic qualities (the characteristics of the product itself) and extrinsic qualities (e.g. animal health and welfare, environmental impacts, price). There is still a high level of variability in beef palatability, which induces consumer dissatisfaction. We also observe a general trend towards an increasing importance of healthiness and safety (intrinsic) and environmental issues and animal welfare (extrinsic). Most grading systems describe carcasses using only animal traits (e.g. weight, conformation, fatness, animal age and sex). In North American and Asian countries, emphasis has been put on maturity and marbling. The European system is mainly based on yield estimation. The Meat Standards Australia grading scheme, which predicts beef palatability for each cut, proved to be effective in predicting beef palatability in many other countries. Some genetic markers are available to improve beef quality. In addition, gene and protein expression profiling of the bovine muscle revealed that the expression level of many genes and the abundance of many proteins may be potential indicators of muscle mass, tenderness, flavour or marbling of meat. The integration of all these parameters is likely to predict better beef palatability. The integration of extrinsic qualities in the prediction model increases the difficulty of achieving a global evaluation of overall meat quality. For instance, with respect to environmental issues, each feeding system has its own advantages and disadvantages. Despite this, win–win strategies have been identified. For example, animals that were less stressed at slaughter also produced more tender meat, and in some studies the most economically efficient farms had the lowest environmental impact. In other cases, there are trade-offs among and between intrinsic and extrinsic qualities. In any case, the combination of the different integrative approaches appears promising to improve the prediction of overall beef quality. A relevant combination of indicators related to sensory and nutritional quality, social and environmental considerations (such as e.g. carbon footprint, animal welfare, grassland biodiversity, rural development) and economic efficiency (income of farmers and of other stakeholders of the supply chain, etc.) will allow the prediction of the overall quality of beef mainly for consumers but also for any stakeholder in the supply chain.
Application of the Wood model to analyse lactation curves of organic dairy sheep farming
Authors: Hernández Juan Carlos Ángeles , Ortega Octavio Castelán , Portillo Benito Albarrán , Montaldo Hugo H. , Ronquillo Manuel González
Published: December 2014

The aim of the present study was to evaluate the performance of the Wood model to describe the characteristics of lactation curves of dairy ewes under organic management in Mexico. In total, 4861 weekly test-day milk yield records from 194 lactations of crossbred dairy ewes were analysed to assess the performance of an empirical model to fit their lactation curve. We used the mathematical model proposed by Wood. The evaluation criteria were the correlation coefficient (r) between the values of total milk yield observed and estimated, the coefficient of determination (R2), and the mean square prediction error (MSPE). In addition, the peak yield (PYest) and time at peak yield (PTest) were calculated. The Wood model showed adequate goodness of fit (r = 0.95, R2 = 0.92 and MSPE = 0.024). The Wood model detected that 52.06% of lactation curves had a continuously decreasing shape (atypical curve), probably as a consequence of the characteristic management of the organic system, mainly due to the genotype used and the nutritional management. Residuals were greater for atypical curves than for typical ones, indicating differences in the ability of the Wood model to fit the two types of shapes. In typical curves, the Wood model showed adequate estimates of total milk yield and time at peak yield. The peak yield was underestimated both in typical and atypical curves. The Wood model in atypical curves underestimated the time at peak yield and milk yields in late lactation. The Wood model showed a reasonable fit of lactation curve in dairy sheep in organic systems but presented deficiencies of fit in atypical curves; therefore, estimates should be interpreted carefully.