bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of peptides in human Hsp20 and Hsp27 that possess molecular chaperone and anti-apoptotic activities
Authors: Nahomi Rooban B. , DiMauro Michael A. , Wang Benlian , Nagaraj Ram H.
Published: October 2014

Previous studies have identified peptides in the ‘crystallin-domain’ of the small heat-shock protein (sHSP) α-crystallin with chaperone and anti-apoptotic activities. We found that peptides in heat-shock protein Hsp20 (G71HFSVLLDVKHFSPEEIAVK91) and Hsp27 (D93RWRVSLDVNHFAPDELTVK113) with sequence homology to α-crystallin also have robust chaperone and anti-apoptotic activities. Both peptides inhibited hyperthermic and chemically induced aggregation of client proteins. The scrambled peptides of Hsp20 and Hsp27 showed no such effects. The chaperone activities of the peptides were better than those from αA- and αB-crystallin. HeLa cells took up the FITC-conjugated Hsp20 peptide and, when the cells were thermally stressed, the peptide was translocated from the cytoplasm to the nucleus. The two peptides inhibited apoptosis in HeLa cells by blocking cytochrome c release from the mitochondria and caspase-3 activation. We found that scrambling the last four amino acids in the two peptides (KAIV in Hsp20 and KTLV in Hsp27) made them unable to enter cells and ineffective against stress-induced apoptosis. Intraperitoneal injection of the peptides prevented sodium-selenite-induced cataract formation in rats by inhibiting protein aggregation and oxidative stress. Our study has identified peptides from Hsp20 and Hsp27 that may have therapeutic benefit in diseases where protein aggregation and apoptosis are contributing factors.
Using the robust statistics for travel time estimation on highways
Authors: Pirc Jure , Turk Goran , Žura Marijan
Published: October 2014

Highway operators around the world are using automated vehicle identification (AVI)‐based techniques as a technological input for travel time estimation on highways. Various AVI technologies provide various travel time measurement samples: some of them are able to identify only personal cars (e.g. tolling tags), while others provide mixed samples of all vehicle classes (e.g. license plate matching). As the adequate information on travel times should concern the personal cars, the influence of heavy vehicles (HVs) should be eliminated from the samples, which is not feasible with the use of existing travel time estimation algorithms. It was observed that also during congestion travel times of personal cars and HVs remain dispersed. The motivation for the present study was to introduce an algorithm that would be able to exclude the influence of slower HVs in travel time estimation for technologies, providing mixed samples of travel time measurements. This was achieved by the use of robust statistics. The results of the study could be used by all highway agencies and operators who are encountering problems with unreasonably extended estimations of travel times because of the presence of slow HVs in the traffic flow.
Electromagnetic band gap‐dipole sub‐array antennas creating an enhanced tilted beams for future base station
Authors: Kim Ilkyu , Rahmat‐Samii Yahya
Published: October 2014

A novel customised electromagnetic band gap (EBG)‐dipole sub‐array antenna with a tilted beam for future base‐station applications is presented. An enhanced tilted beam for the base‐station antenna is one of the safest methods to increase radio coverage area adhering to the strict power requirements. An array of four dipole‐EBG elements is designed demonstrating the enhanced down‐tilt beam. Each single element consists of dipole antenna mounted on a customised EBG ground plane created by connecting several unit cells of the EBG. The proposed array radiates a tilted beam in order to achieve a high directivity at fixed down‐tilt angle. The array antennas are simulated, fabricated and measured. The directivity of 11 dB is measured at the angle of 28° at 3.5 GHz. This directivity is 1.9 dB higher than the reference case that uses the broadside single element. In addition, the EBG‐dipole array that can be mechanically tilted is designed. The proposed array antenna exhibits acceptable impedance matching across the operational frequency band.
Robustness and energy efficiency – a logical multi‐topology scheme for time‐varying traffic in IP networks
Authors: Wang Jin , Wang Sheng , Xu Shizhong
Published: October 2014

This study deals with a strategy to save energy in an Internet protocol (IP) network allowing different subsets of IP links to be put in the sleep mode during different traffic periods. The proposed solution involves a three‐phase algorithm. In the first phase, time‐varying critical traffic matrices from a large collection of real traffic matrices are obtained. In the second phase, a local search heuristic algorithm is utilised that is based on the link weight setting for the energy‐saving optimisation corresponding to the critical traffic matrices. In the last phase, the real traffic flows are routed with the corresponding logical topologies. According to the performance studies that are conducted in a synthetic network and actual IP networks, this approach can achieve significantly improved energy efficiency while certain max link utilisation performance specifications and requirements are satisfied.
Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses
Authors: Teng Yun , Li Lee , Liu Yun-Long , Liu Lun , Liu Minghai
Published: October 2014

This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm3, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.
Suppression of epidemic spreading in complex networks by local information based behavioral responses
Authors: Zhang Hai-Feng , Xie Jia-Rong , Tang Ming , Lai Ying-Cheng
Published: October 2014

The interplay between individual behaviors and epidemic dynamics in complex networks is a topic of recent interest. In particular, individuals can obtain different types of information about the disease and respond by altering their behaviors, and this can affect the spreading dynamics, possibly in a significant way. We propose a model where individuals' behavioral response is based on a generic type of local information, i.e., the number of neighbors that has been infected with the disease. Mathematically, the response can be characterized by a reduction in the transmission rate by a factor that depends on the number of infected neighbors. Utilizing the standard susceptible-infected-susceptible and susceptible-infected-recovery dynamical models for epidemic spreading, we derive a theoretical formula for the epidemic threshold and provide numerical verification. Our analysis lays on a solid quantitative footing the intuition that individual behavioral response can in general suppress epidemic spreading. Furthermore, we find that the hub nodes play the role of “double-edged sword” in that they can either suppress or promote outbreak, depending on their responses to the epidemic, providing additional support for the idea that these nodes are key to controlling epidemic spreading in complex networks.
Control of linear modes in cylindrical resistive magnetohydrodynamics with a resistive wall, plasma rotation, and complex gain
Authors: Brennan D. P. , Finn J. M.
Published: October 2014

Feedback stabilization of magnetohydrodynamic (MHD) modes in a tokamak is studied in a cylindrical model with a resistive wall, plasma resistivity, viscosity, and toroidal rotation. The control is based on a linear combination of the normal and tangential components of the magnetic field just inside the resistive wall. The feedback includes complex gain, for both the normal and for the tangential components, and it is known that the imaginary part of the feedback for the former is equivalent to plasma rotation [J. M. Finn and L. Chacon, Phys. Plasmas 11, 1866 (2004)]. The work includes (1) analysis with a reduced resistive MHD model for a tokamak with finite β and with stepfunction current density and pressure profiles, and (2) computations with a full compressible visco-resistive MHD model with smooth decreasing profiles of current density and pressure. The equilibria are stable for β = 0 and the marginal stability values βrp,rw < βrp,iw < βip,rw < βip,iw (resistive plasma, resistive wall; resistive plasma, ideal wall; ideal plasma, resistive wall; and ideal plasma, ideal wall) are computed for both models. The main results are: (a) imaginary gain with normal sensors or plasma rotation stabilizes below βrp,iw because rotation suppresses the diffusion of flux from the plasma out through the wall and, more surprisingly, (b) rotation or imaginary gain with normal sensors destabilizes above βrp,iw because it prevents the feedback flux from entering the plasma through the resistive wall to form a virtual wall. A method of using complex gain Gi to optimize in the presence of rotation in this regime with β > βrp,iw is presented. The effect of imaginary gain with tangential sensors is more complicated but essentially destabilizes above and below βrp,iw.
Non-stationary dynamics in the bouncing ball: A wavelet perspective
Authors: Behera Abhinna K. , Sekar Iyengar A. N. , Panigrahi Prasanta K.
Published: October 2014

The non-stationary dynamics of a bouncing ball, comprising both periodic as well as chaotic behavior, is studied through wavelet transform. The multi-scale characterization of the time series displays clear signatures of self-similarity, complex scaling behavior, and periodicity. Self-similar behavior is quantified by the generalized Hurst exponent, obtained through both wavelet based multi-fractal detrended fluctuation analysis and Fourier methods. The scale dependent variable window size of the wavelets aptly captures both the transients and non-stationary periodic behavior, including the phase synchronization of different modes. The optimal time-frequency localization of the continuous Morlet wavelet is found to delineate the scales corresponding to neutral turbulence, viscous dissipation regions, and different time varying periodic modulations.
Noise tolerant spatiotemporal chaos computing
Authors: Kia Behnam , Kia Sarvenaz , Lindner John F. , Sinha Sudeshna , Ditto William L.
Published: October 2014

We introduce and design a noise tolerant chaos computing system based on a coupled map lattice (CML) and the noise reduction capabilities inherent in coupled dynamical systems. The resulting spatiotemporal chaos computing system is more robust to noise than a single map chaos computing system. In this CML based approach to computing, under the coupled dynamics, the local noise from different nodes of the lattice diffuses across the lattice, and it attenuates each other's effects, resulting in a system with less noise content and a more robust chaos computing architecture.
Phase-locked regimes in delay-coupled oscillator networks
Authors: Punetha Nirmal , Prasad Awadhesh , Ramaswamy Ramakrishna
Published: October 2014

For an ensemble of globally coupled oscillators with time-delayed interactions, an explicit relation for the frequency of synchronized dynamics corresponding to different phase behaviors is obtained. One class of solutions corresponds to globally synchronized in-phase oscillations. The other class of solutions have mixed phases, and these can be either randomly distributed or can be a splay state, namely with phases distributed uniformly on a circle. In the strong coupling limit and for larger networks, the in-phase synchronized configuration alone remains. Upon variation of the coupling strength or the size of the system, the frequency can change discontinuously, when there is a transition from one class of solutions to another. This can be from the in-phase state to a mixed-phase state, but can also occur between two in-phase configurations of different frequency. Analytical and numerical results are presented for coupled Landau–Stuart oscillators, while numerical results are shown for Rössler and FitzHugh-Nagumo systems.
Generation of circularly polarized radiation from a compact plasma-based extreme ultraviolet light source for tabletop X-ray magnetic circular dichroism studies
Authors: Wilson Daniel , Rudolf Denis , Weier Christian , Adam Roman , Winkler Gerrit , Frömter Robert , Danylyuk Serhiy , Bergmann Klaus , Grützmacher Detlev , Schneider Claus M. , Juschkin Larissa
Published: October 2014

Generation of circularly polarized light in the extreme ultraviolet (EUV) spectral region (about 25 eV–250 eV) is highly desirable for applications in spectroscopy and microscopy but very challenging to achieve in a small-scale laboratory. We present a compact apparatus for generation of linearly and circularly polarized EUV radiation from a gas-discharge plasma light source between 50 eV and 70 eV photon energy. In this spectral range, the 3p absorption edges of Fe (54 eV), Co (60 eV), and Ni (67 eV) offer a high magnetic contrast often employed for magneto-optical and electron spectroscopy as well as for magnetic imaging. We simulated and designed an instrument for generation of linearly and circularly polarized EUV radiation and performed polarimetric measurements of the degree of linear and circular polarization. Furthermore, we demonstrate first measurements of the X-ray magnetic circular dichroism at the Co 3p absorption edge with a plasma-based EUV light source. Our approach opens the door for laboratory-based, element-selective spectroscopy of magnetic materials and spectro-microscopy of ferromagnetic domains.
Metal-insulator transitions in IZO, IGZO, and ITZO films
Authors: Makise Kazumasa , Hidaka Kazuya , Ezaki Syohei , Asano Takayuki , Shinozaki Bunju , Tomai Shigekazu , Yano Koki , Nakamura Hiroaki
Published: October 2014

In this study, we measured the low-temperature resistivity of amorphous two- and three-dimensional (2D and 3D) indium-zinc oxide, indium-gallium-zinc oxide, and indium-tin-zinc oxide films with a wide range of carrier densities. To determine their critical characteristics at the metal-insulator transition (MIT), we used the Ioffe–Regel criterion. We found that the MIT occurs in a narrow range between kFℓ = 0.13 and kFℓ = 0.25, where kF and ℓ are the Fermi wave number and electron mean free path, respectively. For films in the insulating region, we analyzed ρ(T) using a procedure proposed by Zabrodskii and Zinov'eva. This analysis confirmed the occurrence of Mott and Efros–Shklovskii (ES) variable-range hopping. The materials studied show crossover behavior from exp(TMott/T)1/4 or exp(TMott/T)1/3 for Mott hopping conduction to exp(TES/T)1/2 for ES hopping conduction with decreasing temperature. For both 2D and 3D materials, we found that the relationship between TMott and TES satisfies TES ∝ TMott2/3.
An efficient computational scheme for electronic excitation spectra of molecules in solution using the symmetry-adapted cluster–configuration interaction method: The accuracy of excitation energies and intuitive charge-transfer indices
Authors: Fukuda Ryoichi , Ehara Masahiro
Published: October 2014

Solvent effects on electronic excitation spectra are considerable in many situations; therefore, we propose an efficient and reliable computational scheme that is based on the symmetry-adapted cluster-configuration interaction (SAC-CI) method and the polarizable continuum model (PCM) for describing electronic excitations in solution. The new scheme combines the recently proposed first-order PCM SAC-CI method with the PTE (perturbation theory at the energy level) PCM SAC scheme. This is essentially equivalent to the usual SAC and SAC-CI computations with using the PCM Hartree-Fock orbital and integrals, except for the additional correction terms that represent solute-solvent interactions. The test calculations demonstrate that the present method is a very good approximation of the more costly iterative PCM SAC-CI method for excitation energies of closed-shell molecules in their equilibrium geometry. This method provides very accurate values of electric dipole moments but is insufficient for describing the charge-transfer (CT) indices in polar solvent. The present method accurately reproduces the absorption spectra and their solvatochromism of push-pull type 2,2′-bithiophene molecules. Significant solvent and substituent effects on these molecules are intuitively visualized using the CT indices. The present method is the simplest and theoretically consistent extension of SAC-CI method for including PCM environment, and therefore, it is useful for theoretical and computational spectroscopy.
Physics of puffing and microexplosion of emulsion fuel droplets
Authors: Shinjo J. , Xia J. , Ganippa L. C. , Megaritis A.
Published: October 2014

The physics of water-in-oil emulsion droplet microexplosion/puffing has been investigated using high-fidelity interface-capturing simulation. Varying the dispersed-phase (water) sub-droplet size/location and the initiation location of explosive boiling (bubble formation), the droplet breakup processes have been well revealed. The bubble growth leads to local and partial breakup of the parent oil droplet, i.e., puffing. The water sub-droplet size and location determine the after-puffing dynamics. The boiling surface of the water sub-droplet is unstable and evolves further. Finally, the sub-droplet is wrapped by boiled water vapor and detaches itself from the parent oil droplet. When the water sub-droplet is small, the detachment is quick, and the oil droplet breakup is limited. When it is large and initially located toward the parent droplet center, the droplet breakup is more extensive. For microexplosion triggered by the simultaneous growth of multiple separate bubbles, each explosion is local and independent initially, but their mutual interactions occur at a later stage. The degree of breakup can be larger due to interactions among multiple explosions. These findings suggest that controlling microexplosion/puffing is possible in a fuel spray, if the emulsion-fuel blend and the ambient flow conditions such as heating are properly designed. The current study also gives us an insight into modeling the puffing and microexplosion of emulsion droplets and sprays.
Effect of electrical stress on Au/Pb (Zr0.52Ti0.48) O3/TiOxNy/Si gate stack for reliability analysis of ferroelectric field effect transistors
Authors: Khosla Robin , Sharma Deepak K. , Mondal Kunal , Sharma Satinder K.
Published: October 2014

Metal-Ferroelectric-Insulator-Semiconductor (MFIS) structure with 20 nm thin lead zirconate titanate (PZT) ferroelectric film and 6 nm ultrathin high-κ titanium oxynitride (TiOxNy) insulator layer on p-Si substrate were fabricated. Effect of constant voltage stress (CVS) on electrical characteristics of MFIS structure was investigated to study the reliability of fabricated devices. The experimental results showed trivial variation in memory window (ΔW) from 1.05 to 1 V under CVS of 0 to 15 V (5.76 MV/cm) at sweep voltage of ±5 V. Also, leakage current density (J) reduced from 5.57 to 1.94 μA/cm2 under CVS of 5.76 MV/cm, supported by energy band diagram. It signifies highly reliable TiOxNy buffer layer for Ferroelectric Random Access Memory. After programming at ±5 V, the high (CH) and low (CL) capacitances reliability remains distinguishable for 5000 s even if we extrapolate measured data to 15 years. Microstructures analysis of XRD reveals the formation of (100) and (111) orientation of PZT and TiOxNy, respectively. Thus, Au/PZT/TiOxNy/Si, MFIS gate stacks can be potential candidate for next generation reliable Ferroelectric Field Effect Transistors.
McMillan-Mayer theory of solutions revisited: Simplifications and extensions
Authors: Vafaei Shaghayegh , Tomberli Bruno , Gray C. G.
Published: October 2014

McMillan and Mayer (MM) proved two remarkable theorems in their paper on the equilibrium statistical mechanics of liquid solutions. They first showed that the grand canonical partition function for a solution can be reduced to one with an effectively solute-only form, by integrating out the solvent degrees of freedom. The total effective solute potential in the effective solute grand partition function can be decomposed into components which are potentials of mean force for isolated groups of one, two, three, etc., solute molecules. Second, from the first result, now assuming low solute concentration, MM derived an expansion for the osmotic pressure in powers of the solute concentration, in complete analogy with the virial expansion of gas pressure in powers of the density at low density. The molecular expressions found for the osmotic virial coefficients have exactly the same form as the corresponding gas virial coefficients, with potentials of mean force replacing vacuum potentials. In this paper, we restrict ourselves to binary liquid solutions with solute species A and solvent species B and do three things: (a) By working with a semi-grand canonical ensemble (grand with respect to solvent only) instead of the grand canonical ensemble used by MM, and avoiding graphical methods, we have greatly simplified the derivation of the first MM result, (b) by using a simple nongraphical method developed by van Kampen for gases, we have greatly simplified the derivation of the second MM result, i.e., the osmotic pressure virial expansion; as a by-product, we show the precise relation between MM theory and Widom potential distribution theory, and (c) we have extended MM theory by deriving virial expansions for other solution properties such as the enthalpy of mixing. The latter expansion is proving useful in analyzing ongoing isothermal titration calorimetry experiments with which we are involved. For the enthalpy virial expansion, we have also changed independent variables from semi-grand canonical, i.e., fixed \documentclass[12pt]{minimal}\begin{document}$\lbrace N_A,\mu _B,\mathcal {V},T\rbrace$\end{document}{NA,μB,V,T}, to those relevant to the experiment, i.e., fixed {NA, NB, p, T}, where μ denotes chemical potential, N the number of molecules, \documentclass[12pt]{minimal}\begin{document}$\mathcal {V}$\end{document}V the volume, p the pressure, and T the temperature.
Observation of optical second harmonic generation from suspended single-layer and bi-layer graphene
Authors: Lin Kung-Hsuan , Weng Shao-Wei , Lyu Po-Wei , Tsai Tsong-Ru , Su Wei-Bin
Published: October 2014

We have experimentally investigated the optical second harmonic generation (SHG) on suspended single-layer and bi-layer graphene sheets. By shining normally incident 800-nm light with polarization along the sample planes, the SHG intensities of single-layer and bi-layer graphene are found to be comparable to the one of polar GaAs with large second order susceptibility, which is unexpected because both have the centrosymmetric property. Our experimental results reveal that the strong SHG is not due to the defects breaking the symmetry. Instead, we suggest that the SHG signals result from the long-range curvature fluctuations on the suspended single-layer and bi-layer graphene sheets.
Thermal influence on charge carrier transport in solar cells based on GaAs PN junctions
Authors: Osses-Márquez Juan , Calderón-Muñoz Williams R.
Published: October 2014

The electron and hole one-dimensional transport in a solar cell based on a Gallium Arsenide (GaAs) PN junction and its dependency with electron and lattice temperatures are studied here. Electrons and heat transport are treated on an equal footing, and a cell operating at high temperatures using concentrators is considered. The equations of a two-temperature hydrodynamic model are written in terms of asymptotic expansions for the dependent variables with the electron Reynolds number as a perturbation parameter. The dependency of the electron and hole densities through the junction with the temperature is analyzed solving the steady-state model at low Reynolds numbers. Lattice temperature distribution throughout the device is obtained considering the change of kinetic energy of electrons due to interactions with the lattice and heat absorbed from sunlight. In terms of performance, higher values of power output are obtained with low lattice temperature and hot energy carriers. This modeling contributes to improve the design of heat exchange devices and thermal management strategies in photovoltaic technologies.
Mechanistic photodecarboxylation of pyruvic acid: Excited-state proton transfer and three-state intersection
Authors: Chang Xue-Ping , Fang Qiu , Cui Ganglong
Published: October 2014

Photodissociation dynamics of pyruvic acid experimentally differs from that of commonly known ketones. We have employed the complete active space self-consistent field and its multi-state second-order perturbation methods to study its photodissociation mechanism in the S0, T1, and S1 states. We have uncovered four nonadiabatic photodecarboxylation paths. (i) The S1 system relaxes via an excited-state intramolecular proton transfer (ESIPT) to a hydrogen-transferred tautomer, near which an S1/S0 conical intersection funnels the S1 to S0 state. Then, some trajectories continue completing the decarboxylation reaction in the S0 state; the remaining trajectories via a reverse hydrogen transfer return to the S0 minimum, from which a thermal decarboxylation reaction occurs. (ii) Due to a small S1 −T1 energy gap and a large S1/T1 spin-orbit coupling, an efficient S1 → T1 intersystem crossing process happens again near this S1/S0 conical intersection. When decaying to T1 state, a direct photodecarboxylation proceeds. (iii) Prior to ESIPT, the S1 system first decays to the T1 state via an S1 → T1 intersystem crossing; then, the T1 system evolves to a hydrogen-transferred tautomer. Therefrom, an adiabatic T1 decarboxylation takes place due to a small barrier of 7.7 kcal/mol. (iv) Besides the aforementioned T1 ESIPT process, there also exists a comparable Norrish type I reaction in the T1 state, which forms the ground-state products of CH3CO and COOH. Finally, we have found that ESIPT plays an important role. It closes the S1-T1 and S1-S0 energy gaps, effecting an S1/T1/S0 three-state intersection region, and mediating nonadiabatic photodecarboxylation reactions of pyruvic acid.
Effective and tunable light trapping in bulk heterojunction organic solar cells by employing Au-Ag alloy nanoparticles
Authors: Xu Ming , Feng Jing , Liu Yu-Shan , Jin Yu , Wang Hai-Yu , Sun Hong-Bo
Published: October 2014

Effective and tunable light trapping in organic solar cells (OSCs) has been demonstrated by employing Au-Ag alloy nanoparticles (NPs). A simple vacuum thermal annealing method has been employed to fabricate the Au-Ag alloy NPs with tunable molar ratio, and thereafter tunable localized surface plasmon resonance (LSPR). The incorporation of the alloy NPs with an appropriate molar ratio into the OSCs structures supports amplification of the electric field near the particles surface through LSPR and results in an enhanced light absorption at the absorption wavelength region of the absorber owing to the near field coupling. The short-circuit photocurrent density of the alloy NPs-based OSCs is improved from 7.37 to 8.74 mA/cm2 compared to that of control OSCs, and the efficiency of 3.03% is obtained, which corresponds to an enhancement factor of 19%.
Computer tomography of large dust clouds in complex plasmas
Authors: Killer Carsten , Himpel Michael , Melzer André
Published: October 2014

The dust density is a central parameter of a dusty plasma. Here, a tomography setup for the determination of the three-dimensionally resolved density distribution of spatially extended dust clouds is presented. The dust clouds consist of micron-sized particles confined in a radio frequency argon plasma, where they fill almost the entire discharge volume. First, a line-of-sight integrated dust density is obtained from extinction measurements, where the incident light from an LED panel is scattered and absorbed by the dust. Performing these extinction measurements from many different angles allows the reconstruction of the 3D dust density distribution, analogous to a computer tomography in medical applications.
Magnetic, dielectric, and magneto-dielectric properties of rare-earth-substituted Aurivillius phase Bi6Fe1.4Co0.6Ti3O18
Authors: Zuo X. Z. , Yang J. , Song D. P. , Yuan B. , Tang X. W. , Zhang K. J. , Zhu X. B. , Song W. H. , Dai J. M. , Sun Y. P.
Published: October 2014

We investigate the magnetic, dielectric, and magnetodielectric properties of rare-earth-substituted Aurivillius phase Bi6Fe1.4Co0.6Ti3O18. The room-temperature ferromagnetic behavior is observed in all samples, and the rare-earth-substituted samples exhibit an enhanced magnetization. The weak ferromagnetism can be ascribed to the spin canting of the antiferromagnetic coupling of the Fe-based and Co-based sublattices via Dzyaloshinsky-Moriya interaction. The dielectric loss of all samples exhibits two dielectric relaxation peaks corresponding to two different relaxation mechanisms. One relaxation process with Ea = 0.5 eV is related to the hoping process of oxygen vacancies and the other one with Ea = 1.6 eV can be ascribed to the intrinsic conduction. The Gd-doped sample exhibits a remarkable magnetodielectric effect (9.4%) at RT implying this Aurivillius phase may be the potential candidate for magnetodielectric applications.
Grain growth and structural relaxation of nanocrystalline Bi2Te3
Authors: Humphry-Baker Samuel A. , Schuh Christopher A.
Published: October 2014

Recovery and grain growth behavior is investigated systematically for the nanocrystalline thermoelectric compound bismuth telluride, synthesized by mechanical alloying. During annealing treatments at elevated temperatures, structural evolution is tracked using x-ray diffraction, electron microscopy and calorimetry. Below a homologous temperature of about 0.6Tm, grain growth occurs slowly with an activation energy of 89 kJ/mol. However above this temperature grain growth becomes more rampant with an activation energy of 242 kJ/mol. The transition is attributed to a shift from a relaxation or recovery process that includes some reordering of the grain boundary structure, to a more conventional diffusionally-limited grain growth process. By extrapolating the measured grain growth and microstrain evolution kinetics, a thermal budget map is constructed, permitting recommendations for improving the thermoelectric properties of nanocrystalline materials processed via a powder route.
Mode dependent lattice thermal conductivity of single layer graphene
Authors: Wei Zhiyong , Yang Juekuan , Bi Kedong , Chen Yunfei
Published: October 2014

Molecular dynamics simulation is performed to extract the phonon dispersion and phonon lifetime of single layer graphene. The mode dependent thermal conductivity is calculated from the phonon kinetic theory. The predicted thermal conductivity at room temperature exhibits important quantum effects due to the high Debye temperature of graphene. But the quantum effects are reduced significantly when the simulated temperature is as high as 1000 K. Our calculations show that out-of-plane modes contribute about 41.1% to the total thermal conductivity at room temperature. The relative contribution of out-of-plane modes has a little decrease with the increase of temperature. Contact with substrate can reduce both the total thermal conductivity of graphene and the relative contribution of out-of-plane modes, in agreement with previous experiments and theories. Increasing the coupling strength between graphene and substrate can further reduce the relative contribution of out-of-plane modes. The present investigations also show that the relative contribution of different mode phonons is not sensitive to the grain size of graphene. The obtained phonon relaxation time provides useful insight for understanding the phonon mean free path and the size effects in graphene.
Multi-vortex states in magnetic nanoparticles
Authors: Gan W. L. , Chandra Sekhar M. , Wong D. W. , Purnama I. , Chiam S. Y. , Wong L. M. , Lew W. S.
Published: October 2014

We demonstrate a fabrication technique to create cylindrical NiFe magnetic nanoparticles (MNPs) with controlled dimensions and composition. MNPs thicker than 200 nm can form a double vortex configuration, which consists of a pair of vortices with opposite chirality. When MNPs thicker than 300 nm are relaxed after saturation, it forms a frustrated triple vortex state which produces a higher net magnetization as verified by light transmissivity measurements. Therefore, a greater magnetic torque can be actuated on a MNP in the triple vortex state.
Energy matrices of the building by incorporating daylight concept for composite climate—An experimental study
Authors: Sudan Madhu , Tiwari G. N.
Published: October 2014

In this paper, an attempt has been made to implement the concept of daylighting to conserve conventional fuel in a building known as SODHA BERS COMPLEX (SBC) at Varanasi, UP, India. The performance has been analyzed in the context of energy conservation. The building SBC is designed to provide sufficient daylighting, ventilation, as well as thermal comfort to occupants with optimum use of available space for a residential area. The two uppermost rooms of the building have been studied under clear sky conditions. It has been observed that (i) over the lifetime of the building an average energy saving from daylighting is found to be 7933 kW h, which corresponds to 16.18 tons of CO2 mitigation, and (ii) an energy payback time, energy production factor , and life cycle conversion efficiency of SBC are observed to be 5.5 yr, 9.09, and 0.17, respectively.
Enhanced optical property in quaternary GaInAsSb/AlGaAsSb quantum wells
Authors: Lin Chien-Hung , Lee Chien-Ping
Published: October 2014

High quality GaInAsSb/AlGaAsSb quantum wells (QWs) have been grown by molecular beam epitaxy using proper interface treatments. By controlling the group-V elements at interfaces, we obtained excellent optical quality QWs, which were free from undesired localized trap states, which may otherwise severely affect the exciton recombination. Strong and highly efficient exciton emissions up to room temperature with a wavelength of 2.2 μm were observed. A comprehensive investigation on the QW quality was carried out using temperature dependent and power dependent photoluminescence (PL) measurements. The PL emission intensity remains nearly constant at low temperatures and is free from the PL quenching from the defect induced localized states. The temperature dependent emission energy had a bulk-like behavior, indicating high quality well/barrier interfaces. Because of the uniformity of the QWs and smooth interfaces, the low temperature limit of inhomogeneous line width broadening is as small as 5 meV.
Physical properties of AlxIn1−xN thin film alloys sputtered at low temperature
Authors: Besleaga C. , Galca A. C. , Miclea C. F. , Mercioniu I. , Enculescu M. , Stan G. E. , Mateescu A. O. , Dumitru V. , Costea S.
Published: October 2014

In this paper, we report on the structural, optical, and electrical properties of a wide compositional range of AlxIn1−xN thin layers deposited on glass and polyethylene terephthalate substrates. AlxIn1−xN layers of controlled composition were obtained by a simple reactive magnetron co-sputtering protocol, using a single aluminium target with indium insets, by varying the Al/In target surface area ratio, and the composition of the deposition atmosphere. The relevant physical properties were investigated and discussed. It is shown that the texture of the thin films is dependent on the cation ratio, while the bowing parameters of lattice constants and band gap values are larger than those of epitaxial layers.
Chains of quantum dot molecules grown on Si surface pre-patterned by ion-assisted nanoimprint lithography
Authors: Smagina Zh. V. , Stepina N. P. , Zinovyev V. A. , Novikov P. L. , Kuchinskaya P. A. , Dvurechenskii A. V.
Published: October 2014

An original approach based on the combination of nanoimprint lithography and ion irradiation through mask has been developed for fabrication of large-area periodical pattern on Si(100). Using the selective etching of regions amorphized by ion irradiation ordered structures with grooves and ridges were obtained. The shape and depth of the relief were governed by ion energy and by the number of etching stages as well. Laterally ordered chains of Ge quantum dots were fabricated by molecular beam epitaxy of Ge on the pre-patterned Si substrates. For small amount of Ge deposited chains contain separate quantum dot molecules. The increase of deposition amount leads to overlapping of quantum dot molecules with formation of dense homogeneous chains of quantum dots. It was shown that the residual irradiation-induced bulk defects underneath the grooves suppress nucleation of Ge islands at the bottom of grooves. On pre-patterned substrates with whole defect regions, etched quantum dots grow at the bottom of grooves. The observed location of Ge quantum dots is interpreted in terms of local strain-mediated surface chemical potential which controls the sites of islands nucleation. The local chemical potential is affected by additional strain formed by the residual defects. It was shown by molecular dynamics calculations that these defects form the compressive strain at the bottom of grooves.
Field induced rectification and memristive behavior of TlGaSe2 layered semiconductor
Authors: Seyidov MirHasan Yu. , Suleymanov R. A. , Balaban Ertan , Şale Y.
Published: October 2014

We report the internal electric field induced rectification in TlGaSe2 layered semiconductor. This built-in internal electric field was imprinted into the TlGaSe2 sample prior to the measurements while cooling the samples under the external electric field. We employ various pairs of metallic electrodes (In-In, Au-In, Au-Cu), which are deposited on a smooth mirror-like surfaces of TlGaSe2 crystal, respectively, and used to measure the current flow in two directions, parallel and perpendicular to the plane of layers. The current–voltage (I–V) characteristics were measured on the samples with imprinted internal electric field. The diode-like I–V characteristics was observed with the rectification polarity coinciding with the direction of the imprinted electric field. This effect was observed in both directions parallel and perpendicular to the plane of layers. Our results support that near the metal-TlGaSe2 interface the barrier is formed after the pretreatment of the sample in the electric field. So, the diode with a controlled rectification direction, which is achieved by changing the polarization direction using an external bias, is fabricated. The field induced motion of the charge, which piles up under the respective contact that forms a barrier is assumed. The memristive behavior with characteristic pinched hysteresis loop is also observed.
The study of the Poincare-Lighthill-Kuo method by using the particle-in-cell simulation method in a dusty plasma
Authors: Zhang Jie , Yang Yang , Xu Yan-Xia , Yang Lei , Qi Xin , Duan Wen-shan
Published: October 2014

The application scope of the Poincare-Lighthill-Kuo (PLK) method is suggested by using the Particle-in-cell (PIC) numerical method to study head-on collision of two solitary waves. Comparisons between the numerical results from PIC simulations and the analytical ones from the PLK method indicate that the both are in good agreement with each other. The dependence of the phase shifts after the head-on collision on both amplitudes of two solitary waves is given from our PIC method. It is found that the phase shifts depended on the amplitude of both waves. The maximum amplitude during the colliding process is approximately equal to the sum of both amplitudes for the small amplitude solitary waves.
Thin, relaxed Si1−xGex virtual substrates on Si grown using C-doped Ge buffers
Authors: Hsu William , Mantey Jason , Hsieh Cheng-Chih , Roy Anupam , Banerjee Sanjay K.
Published: October 2014

Ultrathin C-doped Ge (Ge:C) buffers are used as effective buffer layers to grow thin and smooth Si1−xGex relaxed virtual substrates on Si over a wide range of Ge content (x = 0.23, 0.38, 0.50, 0.65, 1) by ultrahigh vacuum chemical vapor deposition. High degree of relaxation (≥90%) in thin Si1−xGex films (∼50 nm thick) is demonstrated using this approach without additional annealing. Raman data suggest that the Ge:C buffers are still under compressive stress with the subsequent Si1−xGex layer growth. A low threading dislocation density of the order of ∼6 × 104 cm−2 is obtained from the relaxed 500-nm Si0.77Ge0.23 film grown using this method.
Efficient optical path folding by using multiple total internal reflections in a microcavity
Authors: Shinohara Susumu , Sunada Satoshi , Fukushima Takehiro , Harayama Takahisa , Arai Kenichi , Yoshimura Kazuyuki
Published: October 2014

We propose using an asymmetric resonant microcavity for the efficient generation of an optical path that is much longer than the diameter of the cavity. The path is formed along a star polygonal periodic orbit within the cavity, which is stable and confined by total internal reflection. We fabricated a semiconductor device based on this idea with an average diameter of 0.3 mm and achieved a path length of 2.79 mm experimentally.
Fluid interfacial nanoroughness measurement through the morphological characteristics of graphene
Authors: Yoon Hong Min , Lee Jung Shin , Yeo Jong-Souk , Lee Joon Sang
Published: October 2014

The interfacial nanoroughness of liquid plays an important role in the reliability of liquid lenses, capillary waves, and mass transfer in biological cells [Grilli et al., Opt. Express 16, 8084 (2008), Wang et al., IEEE Photon. Technol. Lett. 18, 2650 (2006), and T. Fukuma et al., 92, 3603 (2007)]. However, the nanoroughness of liquid is hard to visualize or measure due to the instability and dynamics of the liquid-gas interface. In this study, we blanket a liquid water surface with monolayer graphene to project the nanoroughness of the liquid surface. Monolayer graphene can project the surface roughness because of the extremely high flexibility attributed to its one atomic thickness. The interface of graphene and water is successfully mimicked by the molecular dynamics method. The nanoroughness of graphene and water is defined based on density distribution. The correlation among the roughness of graphene and water is developed within a certain temperature range (298–390 K). The results show that the roughness of water surface is successfully transferred to graphene surface. Surface tension is also calculated with a simple water slab. The rise of temperature increased the roughness and decreased the surface tension. Finally, the relationship between graphene roughness and surface tension is fitted with a second-order polynomial equation.
Strain dependent ultrafast carrier dynamics in EuTiO3 films
Authors: Li Zhong-guo , Zhao Run , Li Weiwei , Wang Haiyan , Yang Hao , Song Ying-lin
Published: October 2014

The photocarrier relaxation dynamics of EuTiO3 films have been investigated using femtosecond transient absorption spectroscopy. Two kinds of EuTiO3 films, with and without strain, have been included. In both films, the decay dynamics of 2p-3dt2g transition has a fast (∼2 ps) and slow (ns) components which are independent of the strain. Remarkably, the transient photobleaching of 4f-3dt2g transition is found to be enhanced considerably in the strained film, accompanied with a subnanosecond carrier lifetime. This behavior can be linked to the strain induced band structure modulation. Our results reveal the dynamical interactions in EuTiO3, identifying the critical roles of strain in photo induced phenomena.
Ring waveguides for gigahertz acoustic waves on silicon
Authors: Boucher P. , Rauwerdink S. , Tahraoui A. , Wenger C. , Yamamoto Y. , Santos P. V.
Published: October 2014

We demonstrate a ring resonator for gigahertz surface acoustic waves (SAWs) consisting of a Ge waveguide on a silicon chip. SAWs generated by interdigital transducers on a section of the waveguide are guided over a curved path and detected by a second interdigital transducers. The structure of the GHz waveguide modes mapped using high resolution interferometry compares well with elastic calculations. The acoustic propagation properties as well as the potential applications of these semiconductor-based resonators are discussed.
Cyclic voltammetry on sputter-deposited films of electrochromic Ni oxide: Power-law decay of the charge density exchange
Authors: Wen Rui-Tao , Granqvist Claes G. , Niklasson Gunnar A.
Published: October 2014

Ni-oxide-based thin films were produced by reactive direct-current magnetron sputtering and were characterized by X-ray diffraction and Rutherford backscattering spectroscopy. Intercalation of Li+ ions was accomplished by cyclic voltammetry (CV) in an electrolyte of LiClO4 in propylene carbonate, and electrochromism was documented by spectrophotometry. The charge density exchange, and hence the optical modulation span, decayed gradually upon repeated cycling. This phenomenon was accurately described by an empirical power law, which was valid for at least 104 cycles when the applied voltage was limited to 4.1 V vs Li/Li+. Our results allow lifetime assessments for one of the essential components in an electrochromic device such as a “smart window” for energy-efficient buildings.
Fe-based bulk metallic glasses: Brittle or ductile?
Authors: Guo S. F. , Qiu J. L. , Yu P. , Xie S. H. , Chen W.
Published: October 2014

Fe-based bulk metallic glasses (BMGs) typically exhibit ultrahigh strength but a poor ductility. Here, an Fe62Ni18P13C7 BMG with a super large plasticity of above 50% is reported. Such a discovery is guided by understanding a composition-strength-ductility map, in which most of Fe-based BMGs are classified into three types: FeC(B)-based, FeB-based, and FeP(C)-based. We demonstrate that the mechanical properties of the different types of BMGs are linked with their different physical properties. Among the three types of BMGs, the FeP(C)-based BMGs often possess a lower glass transition temperature, a lower shear modulus, and a higher Poisson's ratio, resulting in a lower shear flow barrier and a higher plasticity. Our findings provide a guideline in understanding the mechanical behavior of Fe-based BMGs.
Domain wall pinning and interaction in rough cylindrical nanowires
Authors: Dolocan Voicu O.
Published: October 2014

Interactions between pairs of magnetic domain walls (DW) and pinning by radial constrictions were studied in cylindrical nanowires with surface roughness. It was found that a radial constriction creates a symmetric pinning potential well, with a change of slope when the DW is situated outside the notch. Surface deformation induces an asymmetry in the pinning potential as well as dynamical pinning. The depinning fields of the domain walls were found generally to decrease with increasing surface roughness. A DW pinned at a radial constriction creates a pinning potential well for a free DW in a parallel wire. We determined that trapped bound DW states appear above the depinning threshold and that the surface roughness facilitates the trapped bound DW states in parallel wires.