bluuebunny/crossref_metadata_2025 huggingface dataset:
A low-cost low-maintenance ultraviolet lithography light source based on light-emitting diodes
Authors: Erickstad M. , Gutierrez E. , Groisman A.
Published: October 2014

An LED-based UV-light source producing collimated uniform illumination over a large area is built and used to fabricate PDMS microchannels with near-rectangular profiles and depths up to 300 μm.
Magnetofluidic platform for multidimensional magnetic and optical barcoding of droplets
Authors: Lin Gungun , Makarov Denys , Medina-Sánchez Mariana , Guix Maria , Baraban Larysa , Cuniberti Gianaurelio , Schmidt Oliver G.
Published: October 2014

A magnetofluidic platform with integrated GMR sensors is demonstrated for on-demand facile generation and high-throughput real-time decoding of droplet barcodes.
Polypharmacology modelling using proteochemometrics (PCM): recent methodological developments, applications to target families, and future prospects
Authors: Cortés-Ciriano Isidro , Ain Qurrat Ul , Subramanian Vigneshwari , Lenselink Eelke B. , Méndez-Lucio Oscar , IJzerman Adriaan P. , Wohlfahrt Gerd , Prusis Peteris , Malliavin Thérèse E. , van Westen Gerard J. P. , Bender Andreas
Published: October 2014

Proteochemometric (PCM) modelling is a computational method to model the bioactivity of multiple ligands against multiple related protein targets simultaneously.
Thioflavin-based molecular probes for application in Alzheimer's disease: from in silico to in vitro models
Authors: Rodríguez-Rodríguez C. , Telpoukhovskaia M. A. , Alí-Torres J. , Rodríguez-Santiago L. , Manso Y. , Bailey G. A. , Hidalgo J. , Sodupe M. , Orvig C.
Published: October 2014

The proposed ThT-based drug candidate series is validated as chemical tools for further in vivo development.
Series asymmetric supercapacitors based on free-standing inner-connection electrodes for high energy density and high output voltage
Authors: Tao Jiayou , Liu Nishuang , Rao Jiangyu , Ding Longwei , AL Bahrani Majid Raissan , Li Luying , Su Jun , Gao Yihua
Published: October 2014

A series-wound asymmetric supercapacitor with an inner-connection structure has a high output voltage of 4.0 V and can power two LEDs connected in series.
‘One-pot’ sequential deprotection/functionalisation of linear-dendritic hybrid polymers using a xanthate mediated thiol/Michael addition
Authors: Auty Sam E. R. , Andrén Oliver C. J. , Y. Hern Faye , Malkoch Michael , Rannard Steven P.
Published: October 2014

Xanthate functional dendritic ATRP macroinitiators, synthesised via a new orthogonal strategy, have been used to form a library of linear-dendritic hybrids via one-pot, post polymerisation, deprotection/acrylate Michael addition.
Development of a prokaryotic-like polycistronic expression system based on a virus-originated internal ribosome entry site (IRES) in industrial eukaryotic microorganisms
Authors: Xu Linlin , Wang Gang , Wang Wenya , Lv Xiaofeng , Li Qiang , Yan Aixia
Published: October 2014

A prokaryotic-like polycistronic expression system was developed inPichia pastorisandAcremonium chrysogenum.
New haptens synthesis, antibody production and comparative molecular field analysis for tetracyclines
Authors: Wang Zhanhui , Sheng Yajie , Duan Hongxia , Yu Qing , Shi Weimin , Zhang Suxia
Published: October 2014

In this work, two novel haptens of tetracycline (TC) were synthesized and used to produce a polyclonal antibody for TC.
Multi-scale theoretical investigation of molecular hydrogen adsorption over graphene: coronene as a case study
Authors: Yeamin Md Bin , Faginas-Lago N. , Albertí M. , Cuesta I. G. , Sánchez-Marín J. , Sánchez de Merás A. M. J.
Published: October 2014

Multiscale modeling and simulation (MMS) combining B97-D/TZV2P DFT calculations and molecular dynamics simulations are performed to investigate the adsorption of hydrogen over coronene as a model of graphene.
Synthesis and studies of electrochemical properties of lophine derivatives
Authors: Hariharasubramanian A. , Ravichandran Y. Dominic
Published: October 2014

A versatile series of lophine derivatives (1–13) were synthesized and characterized, Fourier transform infrared spectroscopy (FTIR), Liquid Chromatography-Mass Spectrometry (LC-MS), and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy.
Structure and nanomechanics of collagen fibrils in articular cartilage at different stages of osteoarthritis
Authors: Shao Jundong , Lin Lijun , Tang Bin , Du Chang
Published: October 2014

This study aimed to investigate the variation of structure and nanomechanical properties of human articular cartilage (AC) at different stages of osteoarthritis (OA).
ortho-Quinone methide (o-QM): a highly reactive, ephemeral and versatile intermediate in organic synthesis
Authors: Singh Maya Shankar , Nagaraju Anugula , Anand Namrata , Chowdhury Sushobhan
Published: October 2014

In this critical review, we provide a comprehensive view of the chemistry ofortho-quinone methides as versatile reactive intermediates in organic synthesis.
Microwave-assisted growth of In2O3 nanoparticles on WO3 nanoplates to improve H2S-sensing performance
Authors: Yin Li , Chen Deliang , Hu Mingxiang , Shi Haiyue , Yang Dewei , Fan Bingbing , Shao Gang , Zhang Rui , Shao Guosheng
Published: October 2014

In2O3@WO3 composites, synthesized via a microwave-assisted method, show high sensitivity to H2S due to the synergistic effect of In2O3 and WO3.
Perovskite processing for photovoltaics: a spectro-thermal evaluation
Authors: Williams Alice E. , Holliman Peter J. , Carnie Matthew J. , Davies Matthew L. , Worsley David A. , Watson Trystan M.
Published: October 2014

A real-time analysis by STA-FTIR of changes occurring and volatiles evolved during processing of perovskites for PV technology. Solvent retention, presence of chemical species and decomposition of materials can be evaluated to gain insight into material composition.
Color temperature control of quantum dot white light emitting diodes by grafting organic fluorescent molecules
Authors: Kim Namhun , Lee Jongho , An Hyuncheol , Pang Changhyun , Cho Sung Min , Chae Heeyeop
Published: October 2014

White-light emitting single compounds were synthesized by grafting blue-fluorescent molecules onto yellow emitting CdSe/ZnS quantum dots and white light emitting diodes were demonstrated. Facile adjustment of color temperature was also demonstrated by controlling the size of quantum dots and the amount of grafted organic blue-emitting molecules.
Novel hole transport materials based on N,N′-disubstituted-dihydrophenazine derivatives for electroluminescent diodes
Authors: Zheng Zhiwen , Dong Qingchen , Gou Liao , Su Jian-Hua , Huang Jinhai
Published: October 2014

A series of novel hole transport materials for organic light-emitting diodes (OLEDs) based on 9,14-diphenyl-9,14-dihydrodibenzo[a,c]phenazine were synthesized and characterized by 1H NMR and 13C NMR, mass spectrometry and single crystal structure analysis methodologies.
Hollow nanocubes made of Ag–Au alloys for SERS detection with sensitivity of 10−8 M for melamine
Authors: Li Ju-Mei , Yang Yin , Qin Dong
Published: October 2014

Ag–Au hollow nanocubes were used for SERS detection with a sensitivity of 10−8 M for melamine.
Structural requirements for the collagenase and elastase activity of cathepsin K and its selective inhibition by an exosite inhibitor
Authors: Sharma Vidhu , Panwar Preety , O’Donoghue Anthony J. , Cui Haoran , Guido Rafael V. C. , Craik Charles S. , Brömme Dieter
Published: October 2014

Human cathepsin K (CatK) is a major drug target for the treatment of osteoporosis. Although its collagenase activity is unique, CatK also exerts a potent elastolytic activity that is shared with human cathepsins V and S. Other members of the cysteine cathepsin family, which are structurally similar, do not exhibit significant collagen and elastin degrading activities. This raises the question of the presence of specific structural elements, exosites, that are required for these activities. CatK has two exosites that control its collagenolytic and elastolytic activity. Modifications of exosites 1 and 2 block the elastase activity of CatK, whereas only exosite-1 alterations prevent collagenolysis. Neither exosite affects the catalytic activity, protease stability, subsite specificity of CatK or the degradation of other biological substrates by this protease. A low-molecular-mass inhibitor that docks into exosite-1 inhibits the elastase and collagenase activity of CatK without interfering with the degradation of other protein substrates. The identification of CatK exosites opens up the prospect of designing highly potent inhibitors that selectively inhibit the degradation of therapeutically relevant substrates by this multifunctional protease.
Structure-based design and functional studies of novel noroviral 3C protease chimaeras offer insights into substrate specificity
Authors: Herod Morgan R. , Prince Cynthia A. , Skilton Rachel J. , Ward Vernon K. , Cooper Jonathan B. , Clarke Ian N.
Published: October 2014

The norovirus NS6 protease is a key target for anti-viral drug development. Noroviruses encode a 2200 amino acid polyprotein which is cleaved by this critical protease at five defined boundary substrates into six mature non-structural (NS) proteins. Studies of the human norovirus (HNV) NS6 protease, in the context of a full ORF1 polyprotein, have been severely hampered because HNVs are not culturable. Thus, investigations into the HNV NS6 protease have been largely restricted to in vitro assays using Escherichia coli-expressed, purified enzyme. The NS6 protease is formed of two distinct domains joined by a linking loop. Structural data suggest that domain 2 of the protease possesses substantial substrate binding pockets which form the bulk of the interactions with the NS boundaries and largely dictate boundary specificity and cleavage. We have constructed chimaeric murine norovirus (MNV) genomes carrying individual domains from the HNV protease and demonstrated by cell transfection that chimaeric HNV proteases have functional activity in the context of the full-length ORF1 polyprotein. Although domain 2 primarily confers boundary specificity, our data suggest that an inter-domain interaction exists within HNV NS6 protease which influences cleavage of specific substrates. The present study also shows that chimaeric MNVs provide improved models for studying HNV protein function in the context of a full ORF1 polyprotein.
Quasi-linear analysis of the extraordinary electron wave destabilized by runaway electrons
Authors: Pokol G. I. , Kómár A. , Budai A. , Stahl A. , Fülöp T.
Published: October 2014

Runaway electrons with strongly anisotropic distributions present in post-disruption tokamak plasmas can destabilize the extraordinary electron (EXEL) wave. The present work investigates the dynamics of the quasi-linear evolution of the EXEL instability for a range of different plasma parameters using a model runaway distribution function valid for highly relativistic runaway electron beams produced primarily by the avalanche process. Simulations show a rapid pitch-angle scattering of the runaway electrons in the high energy tail on the 100–1000 μs time scale. Due to the wave-particle interaction, a modification to the synchrotron radiation spectrum emitted by the runaway electron population is foreseen, exposing a possible experimental detection method for such an interaction.
The two-loop sunrise graph in two space-time dimensions with arbitrary masses in terms of elliptic dilogarithms
Authors: Adams Luise , Bogner Christian , Weinzierl Stefan
Published: October 2014

We present the two-loop sunrise integral with arbitrary non-zero masses in two space-time dimensions in terms of elliptic dilogarithms. We find that the structure of the result is as simple and elegant as in the equal mass case, only the arguments of the elliptic dilogarithms are modified. These arguments have a nice geometric interpretation.
A quasiparticle-based multi-reference coupled-cluster method
Authors: Rolik Zoltán , Kállay Mihály
Published: October 2014

The purpose of this paper is to introduce a quasiparticle-based multi-reference coupled-cluster (MRCC) approach. The quasiparticles are introduced via a unitary transformation which allows us to represent a complete active space reference function and other elements of an orthonormal multi-reference (MR) basis in a determinant-like form. The quasiparticle creation and annihilation operators satisfy the fermion anti-commutation relations. On the basis of these quasiparticles, a generalization of the normal-ordered operator products for the MR case can be introduced as an alternative to the approach of Mukherjee and Kutzelnigg [Recent Prog. Many-Body Theor. 4, 127 (1995); Mukherjee and Kutzelnigg, J. Chem. Phys. 107, 432 (1997)]. Based on the new normal ordering any quasiparticle-based theory can be formulated using the well-known diagram techniques. Beyond the general quasiparticle framework we also present a possible realization of the unitary transformation. The suggested transformation has an exponential form where the parameters, holding exclusively active indices, are defined in a form similar to the wave operator of the unitary coupled-cluster approach. The definition of our quasiparticle-based MRCC approach strictly follows the form of the single-reference coupled-cluster method and retains several of its beneficial properties. Test results for small systems are presented using a pilot implementation of the new approach and compared to those obtained by other MR methods.
Quantum diffusion wave-function approach to two-dimensional vibronic spectroscopy
Authors: Wehner Johannes , Falge Mirjam , Strunz Walter T. , Engel Volker
Published: October 2014

We apply the quantum diffusion wavefunction approach to calculate vibronic two-dimensional (2D) spectra. As an example, we use a system consisting of two electronic states with harmonic oscillator potentials which are coupled to a bath and interact with three time-delayed laser pulses. The first- and second-order perturbative wave functions which enter into the expression for the third-order polarization are determined for a sufficient number of stochastic runs. The wave-packet approach, besides being an alternative technique to calculate the spectra, offers an intuitive insight into the dissipation dynamics and its relation to the 2D vibronic spectra.
Riemann–Hilbert problem approach for two-dimensional flow inverse scattering
Authors: Agaltsov A. D. , Novikov R. G.
Published: October 2014

We consider inverse scattering for the time-harmonic wave equation with first-order perturbation in two dimensions. This problem arises in particular in the acoustic tomography of moving fluid. We consider linearized and nonlinearized reconstruction algorithms for this problem of inverse scattering. Our nonlinearized reconstruction algorithm is based on the non-local Riemann–Hilbert problem approach. Comparisons with preceding results are given.
The formation mechanism and impact of streamwise vortices on NACA 0021 airfoil's performance with undulating leading edge modification
Authors: Rostamzadeh N. , Hansen K. L. , Kelso R. M. , Dally B. B.
Published: October 2014

Wings with tubercles have been shown to display advantageous loading behavior at high attack angles compared to their unmodified counterparts. In an earlier study by the authors, it was shown that an undulating leading-edge configuration, including but not limited to a tubercled model, induces a cyclic variation in circulation along the span that gives rise to the formation of counter-rotating streamwise vortices. While the aerodynamic benefits of full-span tubercled wings have been associated with the presence of such vortices, their formation mechanism and influence on wing performance are still in question. In the present work, experimental and numerical tests were conducted to further investigate the effect of tubercles on the flow structure over full-span modified wings based on the NACA 0021 profile, in the transitional flow regime. It is found that a skew-induced mechanism accounts for the formation of streamwise vortices whose development is accompanied by flow separation in delta-shaped regions near the trailing edge. The presence of vortices is detrimental to the performance of full-span wings pre-stall, however renders benefits post-stall as demonstrated by wind tunnel pressure measurement tests. Finally, primary and secondary vortices are identified post-stall that produce an enhanced momentum transfer effect that reduces flow separation, thus increasing the generated amount of lift.
Intermolecular interactions of trifluorohalomethanes with Lewis bases in the gas phase: An ab initio study
Authors: Wang Yi-Siang , Yin Chih-Chien , Chao Sheng D.
Published: October 2014

We perform an ab initio computational study of molecular complexes with the general formula CF3X—B that involve one trifluorohalomethane CF3X (X = Cl or Br) and one of a series of Lewis bases B in the gas phase. The Lewis bases are so chosen that they provide a range of electron-donating abilities for comparison. Based on the characteristics of their electron pairs, we consider the Lewis bases with a single n-pair (NH3 and PH3), two n-pairs (H2O and H2S), two n-pairs with an unsaturated bond (H2CO and H2CS), and a single π-pair (C2H4) and two π-pairs (C2H2). The aim is to systematically investigate the influence of the electron pair characteristics and the central atom substitution effects on the geometries and energetics of the formed complexes. The counterpoise-corrected supermolecule MP2 and coupled-cluster single double with perturbative triple [CCSD(T)] levels of theory have been employed, together with a series of basis sets up to aug-cc-pVTZ. The angular and radial configurations, the binding energies, and the electrostatic potentials of the stable complexes have been compared and discussed as the Lewis base varies. For those complexes where halogen bonding plays a significant role, the calculated geometries and energetics are consistent with the σ-hole model. Upon formation of stable complexes, the C–X bond lengths shorten, while the C–X vibrational frequencies increase, thus rendering blueshifting halogen bonds. The central atom substitution usually enlarges the intermolecular bond distances while it reduces the net charge transfers, thus weakening the bond strengths. The analysis based on the σ-hole model is grossly reliable but requires suitable modifications incorporating the central atom substitution effects, in particular, when interaction components other than electrostatic contributions are involved.
Full-dimensional control of the radiationless decay in pyrazine using the dynamic Stark effect
Authors: Saab Mohamad , Sala Matthieu , Lasorne Benjamin , Gatti Fabien , Guérin Stéphane
Published: October 2014

We present a full quantum-mechanical study of the laser control of the radiationless decay between the B3u(nπ*) and B2u(ππ*) states of pyrazine using the dynamic Stark effect. In contrast to our previous study [Sala et al., J. Chem. Phys. 140, 194309 (2014)], where a four-dimensional model was used, all the 24 degrees of freedom are now included in order to test the robustness of the strategy of control. Using a vibronic coupling Hamiltonian model in a diabatic representation, the multi-layer version of the multi-configuration time-dependent Hartree method is exploited to propagate the corresponding wave packets. We still observe a trapping of the wavepacket on the B2u(ππ*) potential energy surface due to the Stark effect for a longer time than the “non-resonant field-free” B2u(ππ*) lifetime.
On the calculation of internal forces in mechanically stressed polyatomic molecules
Authors: Avdoshenko Stanislav M. , Konda Sai Sriharsha M. , Makarov Dmitrii E.
Published: October 2014

We discuss how to define and to compute internal forces in a molecule subjected to mechanical stress. Because of the inherently many-body character of intramolecular interactions, internal forces cannot be uniquely defined without specifying a set of internal coordinates used to describe the molecular structure. When such a set is comprised of 3N − 6 interactomic distances (N being the number of atoms) and includes the bond lengths of interest, we show that the associated forces, while satisfying the equation F = ∂V/∂R (where R is the bond length, F is the internal force in this bond, and V is the potential energy of the molecule), can be determined from the molecular geometry alone. We illustrate these ideas using several toy models ranging from small molecules to a graphene sheet and show that the magnitude of the internal force in a bond is not necessarily a good predictor of its strength in response to mechanical loading. At the same time, analysis of internal forces reveals interesting phenomena such as the force multiplication effect, where weak external forces may, e.g., be used to break strong bonds, and offers insight into the catch-bond phenomenon where chemical reactivity is suppressed through application of a force.
A technique for verifying the input response function of neutron time-of-flight scintillation detectors using cosmic rays
Authors: Bonura M. A. , Ruiz C. L. , Fehl D. L. , Cooper G. W. , Chandler G. , Hahn K. D. , Nelson A. J. , Styron J. D. , Torres J. A.
Published: October 2014

An accurate interpretation of DD or DT fusion neutron time-of-flight (nTOF) signals from current mode detectors employed at the Z-facility at Sandia National Laboratories requires that the instrument response functions (IRF’s) be deconvolved from the measured nTOF signals. A calibration facility that produces detectable sub-ns radiation pulses is typically used to measure the IRF of such detectors. This work, however, reports on a simple method that utilizes cosmic radiation to measure the IRF of nTOF detectors, operated in pulse-counting mode. The characterizing metrics reported here are the throughput delay and full-width-at-half-maximum. This simple approach yields consistent IRF results with the same detectors calibrated in 2007 at a LINAC bremsstrahlung accelerator (Idaho State University). In particular, the IRF metrics from these two approaches and their dependence on the photomultipliers bias agree to within a few per cent. This information may thus be used to verify if the IRF for a given nTOF detector employed at Z has changed since its original current-mode calibration and warrants re-measurement.
Effects of annealing and structural phase transformation on the Urbach absorption in thin silver sulphide films
Authors: Chattopadhyay P. , Guha Roy S.
Published: October 2014

The sub-band gap optical absorption in silver sulphide thin films prepared by chemical conversion technique has been studied in the light of Urbach absorption law at different annealing temperatures. The study reveals the Urbach absorption parameters and band gap of the material are sensitive to annealing temperature. Interestingly, these parameters undergo a sudden change as the annealing temperature exceeds a certain critical value. The observed changes in the values of absorption parameters have been attributed to the structural phase transition and the modification of grain boundary interfaces and/or changes in the crystallographic orientation due to annealing.
Temperature dependent soft x-ray absorption spectroscopy of liquids
Authors: Meibohm Jan , Schreck Simon , Wernet Philippe
Published: October 2014

A novel sample holder is introduced which allows for temperature dependent soft x-ray absorption spectroscopy of liquids in transmission mode. The setup is based on sample cells with x-ray transmissive silicon nitride windows. A cooling circuit allows for temperature regulation of the sample liquid between −10 °C and +50 °C. The setup enables to record soft x-ray absorption spectra of liquids in transmission mode with a temperature resolution of 0.5 K and better. Reliability and reproducibility of the spectra are demonstrated by investigating the characteristic temperature-induced changes in the oxygen K-edge x-ray absorption spectrum of liquid water. These are compared to the corresponding changes in the oxygen K-edge spectra from x-ray Raman scattering.
Efficient rejection-based simulation of biochemical reactions with stochastic noise and delays
Authors: Thanh Vo Hong , Priami Corrado , Zunino Roberto
Published: October 2014

We propose a new exact stochastic rejection-based simulation algorithm for biochemical reactions and extend it to systems with delays. Our algorithm accelerates the simulation by pre-computing reaction propensity bounds to select the next reaction to perform. Exploiting such bounds, we are able to avoid recomputing propensities every time a (delayed) reaction is initiated or finished, as is typically necessary in standard approaches. Propensity updates in our approach are still performed, but only infrequently and limited for a small number of reactions, saving computation time and without sacrificing exactness. We evaluate the performance improvement of our algorithm by experimenting with concrete biological models.
A 15 MHz bandwidth, 60 Vpp, low distortion power amplifier for driving high power piezoelectric transducers
Authors: Capineri Lorenzo
Published: October 2014

This paper presents the design and the realization of a linear power amplifier with large bandwidth (15 MHz) capable of driving low impedance ultrasonic transducers. The output current driving capability (up to 5 A) and low distortion makes it suitable for new research applications using high power ultrasound in the medical and industrial fields. The electronic design approach is modular so that the characteristics can be scaled according to specific applications and implementation details for the circuit layout are reported. Finally the characterization of the power amplifier module is presented.
Magnetization reversal in ferromagnetic thin films induced by spin-orbit interaction with Slonczewski-like spin transfer torque
Authors: Li Jia
Published: October 2014

We theoretically investigate the dynamics of magnetization in ferromagnetic thin films induced by spin-orbit interaction with Slonczewski-like spin transfer torque. We reproduce the experimental results of perpendicular magnetic anisotropy films by micromagnetic simulation. Due to the spin-orbit interaction, the magnetization can be switched by changing the direction of the current with the assistant of magnetic field. By increasing the current amplitude, wider range of switching events can be achieved. Time evolution of magnetization has provided us a clear view of the process, and explained the role of minimum external field. Slonczewski-like spin transfer torque modifies the magnetization when current is present. The magnitude of the minimum external field is determined by the strength of the Slonczewski-like spin transfer torque. The investigations may provide potential applications in magnetic memories.
Methane activation using Kr and Xe in a dielectric barrier discharge reactor
Authors: Jo Sungkwon , Lee Dae Hoon , Kim Kwan-Tae , Kang Woo Seok , Song Young-Hoon
Published: October 2014

Methane has interested many researchers as a possible new energy source, but the high stability of methane causes a bottleneck in methane activation, limiting its practical utilization. To determine how to effectively activate methane using non-thermal plasma, the conversion of methane is measured in a planar-type dielectric barrier discharge reactor using three different noble gases—Ar, Kr, and Xe—as additives. In addition to the methane conversion results at various applied voltages, the discharge characteristics such as electron temperature and electron density were calculated through zero-dimensional calculations. Moreover, the threshold energies of excitation and ionization were used to distinguish the dominant particle for activating methane between electrons, excited atoms, and ionized atoms. From the experiments and calculations, the selection of the additive noble gas is found to affect not only the conversion of methane but also the selectivity of product gases even under similar electron temperature and electron density conditions.
Homoepitaxial AlN thin films deposited on m-plane (11¯00) AlN substrates by metalorganic chemical vapor deposition
Authors: Bryan Isaac , Bryan Zachary , Bobea Milena , Hussey Lindsay , Kirste Ronny , Collazo Ramón , Sitar Zlatko
Published: October 2014

AlN homoepitaxial films were grown by metalorganic chemical vapor deposition on chemo-mechanically polished (11¯00)-oriented single crystalline AlN substrates. The dependence of the surface morphology, structural quality, and unintentional impurity concentrations on the growth temperature was studied in order to determine the most appropriate growth conditions for high quality (11¯00) AlN epitaxial layers. Optically smooth surfaces (RMS roughness of 0.4 nm) and high crystalline quality, as demonstrated by the presence of FWHM values for (101¯0) rocking curves along [0001] of less than 25 arc·sec, were achieved for films grown above 1350 °C. Furthermore, sharp and intense near band edge luminescence was observed in these high quality films. A reduction in unintentional oxygen impurity levels was seen with an increase in growth temperature. These high crystalline quality films are suitable for device applications and hold great potential for providing an ideal platform for deep UV emitters with high Al content AlGaN without polarization related effects.
Dynamical stability of Mo under high pressure and high temperature
Authors: Zeng Zhao-Yi , Hu Cui-E , Zhang Wei , Niu Zhen-Wei , Cai Ling-Cang
Published: October 2014

Considering the phonon-phonon interactions, we obtain the high temperature phonons of Mo under high pressure. The dynamically stable regions of bcc and fcc Mo in the phase diagram are predicted. By comparing the anharmonic free energy, we determine the bcc-fcc boundary. The bcc Mo is the stable phase up to 700 GPa. Around 210 GPa, there is no bcc-fcc phase transition, which is different with the results from quasiharmonic approximation.
Temperature effects in first-principles solid state calculations of the chemical shielding tensor made simple
Authors: Monserrat Bartomeu , Needs Richard J. , Pickard Chris J.
Published: October 2014

We study the effects of atomic vibrations on the solid-state chemical shielding tensor using first principles density functional theory calculations. At the harmonic level, we use a Monte Carlo method and a perturbative expansion. The Monte Carlo method is accurate but computationally expensive, while the perturbative method is computationally more efficient, but approximate. We find excellent agreement between the two methods for both the isotropic shift and the shielding anisotropy. The effects of zero-point quantum mechanical nuclear motion are important up to relatively high temperatures: at 500 K they still represent about half of the overall vibrational contribution. We also investigate the effects of anharmonic vibrations, finding that their contribution to the zero-point correction to the chemical shielding tensor is small. We exemplify these ideas using magnesium oxide and the molecular crystals L-alanine and β-aspartyl-L-alanine. We therefore propose as the method of choice to incorporate the effects of temperature in solid state chemical shielding tensor calculations using the perturbative expansion within the harmonic approximation. This approach is accurate and requires a computational effort that is about an order of magnitude smaller than that of dynamical or Monte Carlo approaches, so these effects might be routinely accounted for.
Extended mode in blocked impurity band detectors for terahertz radiation detection
Authors: Liao K. S. , Li N. , Wang C. , Li L. , Jing Y. L. , Wen J. , Li M. Y. , Wang H. , Zhou X. H. , Li Z. F. , Lu W.
Published: October 2014

We demonstrate the existence of an interfacial barrier in blocked impurity band (BIB) detectors using temperature-dependent dark current and corresponding theoretical calculations. Considering the effects of the interfacial barrier, the calculated photoresponse is in good agreement with the experimental results. A dual-excitation model, including the direct excitation over the full barrier and excitation to the band minimum with subsequent tunneling into the blocking layer, is proposed to quantitatively explain the observed photoresponse extension. A concept of extended-mode detection is developed to suggest the option for some selective photoresponse in the terahertz region and open the possibility of extending BIB photoresponse to lower frequency.
Large tunable linear magnetoresistance in gold nanoparticle decorated graphene
Authors: Jia Zhenzhao , Zhang Rui , Han Qi , Yan Qiaojing , Zhu Rui , Yu Dapeng , Wu Xiaosong
Published: October 2014

We propose and demonstrate gold nanoparticle decorated graphene as an ideal system for studying carrier inhomogeneity induced magnetoresistance. Large linear magnetoresistance has been realized in the system and the magnitude can be tuned by a gate. By detailed study, we provide an empirical expression, which reveals the dependence of the magnetoresistance on density fluctuations and mobility. The induced magnetoresistance is temperature independent and can be strongly enhanced by the high mobility of graphene, hence offers potential for magnetic sensor applications.
A comparison between characteristics of atmospheric-pressure plasma jets sustained by nanosecond- and microsecond-pulse generators in helium
Authors: Zhang Cheng , Shao Tao , Wang Ruixue , Zhou Zhongsheng , Zhou Yixiao , Yan Ping
Published: October 2014

Power source is an important parameter that can affect the characteristics of atmospheric-pressure plasma jets (APPJs), because it can play a key role on the discharge characteristics and ionization process of APPJs. In this paper, the characteristics of helium APPJs sustained by both nanosecond-pulse and microsecond-pulse generators are compared from the aspects of plume length, discharge current, consumption power, energy, and optical emission spectrum. Experimental results showed that the pulsed APPJ was initiated near the high-voltage electrode with a small curvature radius, and then the stable helium APPJ could be observed when the applied voltage increased. Moreover, the discharge current of the nanosecond-pulse APPJ was larger than that of the microsecond-pulse APPJ. Furthermore, although the nanosecond-pulse generator consumed less energy than the microsecond-pulse generator, longer plume length, larger instantaneous power per pulse and stronger spectral line intensity could be obtained in the nanosecond-pulse excitation case. In addition, some discussion indicated that the rise time of the applied voltage could play a prominent role on the generation of APPJs.
Communication: Modeling charge-sign asymmetric solvation free energies with nonlinear boundary conditions
Authors: Bardhan Jaydeep P. , Knepley Matthew G.
Published: October 2014

We show that charge-sign-dependent asymmetric hydration can be modeled accurately using linear Poisson theory after replacing the standard electric-displacement boundary condition with a simple nonlinear boundary condition. Using a single multiplicative scaling factor to determine atomic radii from molecular dynamics Lennard-Jones parameters, the new model accurately reproduces MD free-energy calculations of hydration asymmetries for: (i) monatomic ions, (ii) titratable amino acids in both their protonated and unprotonated states, and (iii) the Mobley “bracelet” and “rod” test problems [D. L. Mobley, A. E. Barber II, C. J. Fennell, and K. A. Dill, “Charge asymmetries in hydration of polar solutes,” J. Phys. Chem. B 112, 2405–2414 (2008)]. Remarkably, the model also justifies the use of linear response expressions for charging free energies. Our boundary-element method implementation demonstrates the ease with which other continuum-electrostatic solvers can be extended to include asymmetry.
Height control of self-assembled quantum dots by strain engineering during capping
Authors: Grossi D. F. , Smereka P. , Keizer J. G. , Ulloa J. M. , Koenraad P. M.
Published: October 2014

Strain engineering during the capping of III-V quantum dots has been explored as a means to control the height of strained self-assembled quantum dots. Results of Kinetic Monte Carlo simulations are confronted with cross-sectional Scanning Tunnel Microscopy (STM) measurements performed on InAs quantum dots grown by molecular beam epitaxy. We studied InAs quantum dots that are capped by InxGa(1−x)As layers of different indium compositions. Both from our realistic 3D kinetic Monte Carlo simulations and the X-STM measurements on real samples, a trend in the height of the capped quantum dot is found as a function of the lattice mismatch between the quantum dot material and the capping layer. Results obtained on additional material combinations show a generic role of the elastic energy in the control of the quantum dot morphology by strain engineering during capping.
Unique light-induced degradation in yellow-emitting K2SiF6:Mn2+ phosphor
Authors: Oyama Takuya , Adachi Sadao
Published: October 2014

Photo-induced luminescence intensity degradation in yellow-emitting K2SiF6:Mn2+ phosphor is studied using x-ray diffraction measurement, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, PL decay analysis, and electron spin resonance (ESR) measurement. The yellow-emitting K2SiF6:Mn2+ phosphor exhibits remarkable degradation in the PL intensity under Xe lamp exposure. Coherent laser irradiation also induces degradation and its degree is in the order of He–Cd (λ = 325 nm) > Ar+ (488 nm) > He–Ne laser (632.8 nm). The degradation mechanism is proposed to be due to change in the valence state of manganese ions from Mn2+ to Mn3+ by the photooxidation (Mn2+ → Mn3+) or disproportionation reaction (2Mn2+ → Mn+ + Mn3+). The ESR measurement confirms the decreased Mn2+ spin density in the sample exposed with Xe lamp. The PLE spectrum suggests that the excitation of Mn3+ ions occurs through energy transfer upon absorption of exciting radiation by the Mn2+ ions. Thermal annealing of the degraded samples at ≥200 °C causes a blueshift in the PL emission band with an appearance of the Mn4+-related sharp red emission lines.
Size effects on electromechanical coupling fields of a bending piezoelectric nanoplate due to surface effects and flexoelectricity
Authors: Zhang Zhengrong , Jiang Liying
Published: October 2014

Due to large surface to volume ratio and manifest strain gradients typically present in nanostructures, it is essential to incorporate both surface effects and flexoelectricity in studying the size-dependent electromechanical coupling behaviors of piezoelectric materials at the nano-scale. In the current work, a modified Kirchhoff plate model with the consideration of residual surface stress, surface elasticity, surface piezoelectricity, and flexoelectricity is developed to investigate the electroelastic responses and vibrational behaviors of a bending piezoelectric nanoplate (PNP). The governing equations and the corresponding boundary conditions accounting for both the surface effects and the flexoelectricity are derived by the variational principle. Ritz approximate solutions of the static bending and the free vibration indicate that these nano-scale features are more prominent for thinner plates with smaller thickness. The simulation results also reveal that the influence of the flexoelectricity and the surface effects upon the bending behaviors of the PNP depends on the applied electrical loading and the plate dimensions. Moreover, it is also observed that the frequency tuning of PNP-based nanoresonators by adjusting applied electrical load can be modified by both the flexoelectricity and the surface effects. The current work is expected to provide increased understanding on the theoretical basis for the design and applications of PNP-based nanodevices.
Calculation of combined diffusion coefficients in SF6-Cu mixtures
Authors: Zhong Linlin , Wang Xiaohua , Rong Mingzhe , Wu Yi , Murphy Anthony B.
Published: October 2014

Diffusion coefficients play an important role in the description of the transport of metal vapours in gas mixtures. This paper is devoted to the calculation of four combined diffusion coefficients, namely, the combined ordinary diffusion coefficient, combined electric field diffusion coefficient, combined temperature diffusion coefficient, and combined pressure diffusion coefficient in SF6-Cu mixtures at temperatures up to 30 000 K. These four coefficients describe diffusion due to composition gradients, applied electric fields, temperature gradients, and pressure gradients, respectively. The influence of copper fluoride and sulfide species on the diffusion coefficients is shown to be negligible. The effect of copper proportion and gas pressures on these diffusion coefficients is investigated. It is shown that increasing the proportion of copper generally increases the magnitude of the four diffusion coefficients, except for copper mole fractions of 90% or more. It is further found that increasing the pressure reduces the magnitude of the coefficients, except for the combined temperature diffusion coefficient, and shifts the maximum of all four coefficients towards higher temperatures. The results presented in this paper can be applied to the simulation of high-voltage circuit breaker arcs.
Electrical characteristics of field-effect transistors based on indium arsenide nanowire thinner than 10 nm
Authors: Fu Mengqi , Pan Dong , Yang Yingjun , Shi Tuanwei , Zhang Zhiyong , Zhao Jianhua , Xu H. Q. , Chen Qing
Published: October 2014

To suppress short channel effects, lower off-state leakage current and enhance gate coupling efficiency, InAs nanowires (NWs) with diameter smaller than 10 nm could be needed in field-effect transistors (FETs) as the channel length scales down to tens of nanometers to improve the performance and increase the integration. Here, we fabricate and study FETs based on ultrathin wurtzite-structured InAs NWs, with the smallest NW diameter being 7.2 nm. The FETs based on ultrathin NWs exhibit high Ion/Ioff ratios of up to 2 × 108, small subthreshold swings of down to 120 mV/decade, and operate in enhancement-mode. The performance of the devices changes as a function of the diameter of the InAs NWs. The advantages and challenges of the FETs based on ultrathin NWs are discussed.
Broad spectral response photodetector based on individual tin-doped CdS nanowire
Authors: Zhou Weichang , Peng Yuehua , Yin Yanling , Zhou Yong , Zhang Yong , Tang Dongsheng
Published: October 2014

High purity and tin-doped 1D CdS micro/nano-structures were synthesized by a convenient thermal evaporation method. SEM, EDS, XRD and TEM were used to examine the morphology, composition, phase structure and crystallinity of as-prepared samples. Raman spectrum was used to confirm tin doped into CdS effectively. The effect of impurity on the photoresponse properties of photodetectors made from these as-prepared pure and tin-doped CdS micro/nano-structures under excitation of light with different wavelength was investigated. Various photoconductive parameters such as responsivity, external quantum efficiency, response time and stability were analyzed to evaluate the advantage of doped nanowires and the feasibility for photodetector application. Comparison with pure CdS nanobelt, the tin-doped CdS nanowires response to broader spectral range while keep the excellect photoconductive parameters. Both trapped state induced by tin impurity and optical whispering gallery mode microcavity effect in the doped CdS nanowires contribute to the broader spectral response. The micro-photoluminescence was used to confirm the whispering gallery mode effect and deep trapped state in the doped CdS nanowires.
Fluorous 1,2,3-Triazol-4-ylmethyl Amines and Amine Derivatives for Novel Surfactant Applications
Authors: Francis Dominic V. , Harper Jason B. , Read Roger W.
Published: October 2014

A series of fluorous surfactants with additional functionality were generated through the attachment of substituents at the amino nitrogen atom of the surfactant moiety. Examples of molecules containing one and two triazole ring systems were synthesized through N-alkylation and N-acylation strategies.
Selection of crop cultivars suited to the location combined with astute management can reduce crop yield penalties in pasture cropping systems
Authors: Thomas Dean T. , Lawes Roger A. , Descheemaeker Katrien , Moore Andrew D.
Published: October 2014

Pasture cropping is an emerging farming-systems practice of southern Australia, in which winter grain crops are sown into an established stand of a winter-dormant, summer-growing perennial pasture. There is a pressing need to define times, locations and climates that are suitable for pasture cropping. To evaluate effects of management interventions, agro-environment, and possible interactions on crop and pasture productivity associated with pasture cropping, an AusFarm® simulation model was built to describe a pasture-cropping system based on annual crop and subtropical grass. The model was parameterised using data from field research on pasture cropping with barley cv. Buloke and a C4 subtropical grass, Gatton panic (Panicum maximum cv. Gatton), conducted at Moora, Western Australia. The simulation was run over 50 years using the historical climate data of five southern Australian locations (Cunderdin, Jerdacuttup, Mingenew, and Moora in Western Australia, and Karoonda in South Australia). Two wheat cultivars and one barley crop were considered for each location, to examine the impact of crop phenology on this farming system.
Jerdacuttup and Moora favoured pasture cropping, with average barley-yield penalties of 10 and 12%. These locations were characterised by colder growing seasons, more plant-available water at anthesis, and more winter–spring rain. The cereal crops did not rely on stored soil moisture, growing instead on incident rain. The winter–spring growth of the Gatton panic pasture was highest at Mingenew. This generated a high yield penalty, 38% loss under pasture cropping, compared with the other locations. Changing the efficacy of a herbicide application to the pasture when the crop was sown had a strong effect on yield. Yield penalties at Moora and Mingenew reduced to 7 and 29%, respectively, when the proportion of live biomass killed by the herbicide was doubled.
Utilisation of soil moisture by the Gatton panic pasture during summer and early autumn had little effect on subsequent grain yield, whereas reduced pasture growth during the winter–spring growing period had a substantial effect on crop yield. Pasture cropping can therefore succeed in agro-climatic regions where crops can be grown on incident rain and pasture growth is suppressed through low temperature or herbicide. Perennial pasture growth should be minimised during the crop growing period through the management of crop sowing date, nitrogen fertiliser application and C4 grass suppression to minimise the effect on stored soil water at crop anthesis.