bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion cyclotron resonance frequency heating in JET during initial operations with the ITER-like wall
Authors: Jacquet P. , Bobkov V. , Colas L. , Czarnecka A. , Lerche E. , Mayoral M.-L. , Monakhov I. , Van-Eester D. , Arnoux G. , Brezinsek S. , Brix M. , Campergue A.-L. , Devaux S. , Drewelow P. , Graham M. , Klepper C. C. , Meigs A. , Milanesio D. , Mlynar J. , Pütterich T. , Sirinelli A. ,   JET-EFDA Contributors
Published: June 2014

In 2011/12, JET started operation with its new ITER-Like Wall (ILW) made of a tungsten (W) divertor and a beryllium (Be) main chamber wall. The impact of the new wall materials on the JET Ion Cyclotron Resonance Frequency (ICRF) operation is assessed and some important properties of JET plasmas heated with ICRF are highlighted. A ∼ 20% reduction of the antenna coupling resistance is observed with the ILW as compared with the JET carbon (JET-C) wall. Heat-fluxes on the protecting limiters close the antennas, quantified using Infra-Red thermography (maximum 4.5 MW/m2 in current drive phasing), are within the wall power load handling capabilities. A simple RF sheath rectification model using the antenna near-fields calculated with the TOPICA code can reproduce the heat-flux pattern around the antennas. ICRF heating results in larger tungsten and nickel (Ni) contents in the plasma and in a larger core radiation when compared to Neutral Beam Injection (NBI) heating. The location of the tungsten ICRF specific source could not be identified but some experimental observations indicate that main-chamber W components could be an important impurity source: for example, the divertor W influx deduced from spectroscopy is comparable when using RF or NBI at same power and comparable divertor conditions, and Be evaporation in the main chamber results in a strong reduction of the impurity level. In L-mode plasmas, the ICRF specific high-Z impurity content decreased when operating at higher plasma density and when increasing the hydrogen concentration from 5% to 15%. Despite the higher plasma bulk radiation, ICRF exhibited overall good plasma heating performance; the power is typically deposited at the plasma centre while the radiation is mainly from the outer part of the plasma bulk. Application of ICRF heating in H-mode plasmas has started, and the beneficial effect of ICRF central electron heating to prevent W accumulation in the plasma core has been observed.
Characterization of the onset of ion cyclotron parametric decay instability of lower hybrid waves in a diverted tokamak
Authors: Baek S. G. , Parker R. R. , Shiraiwa S. , Wallace G. M. , Bonoli P. T. , Porkolab M. , Takase Y. , Brunner D. , Faust I. C. , Hubbard A. E. , LaBombard B. , Lau C.
Published: June 2014

The goal of the lower hybrid current drive (LHCD) program on Alcator C-Mod is to develop and optimize reactor-relevant steady-state plasmas by controlling current density profile. However, current drive efficiency precipitously decreases as the line averaged density (n¯e) increases above ∼1 × 1020 m−3. Previous simulations show that the observed loss of current drive efficiency in high density plasmas stems from the interactions of LH waves with edge/scrape-off layer plasmas [Wallace et al., Phys. Plasmas 19, 062505 (2012)]. A recent observation [Baek et al., Plasma Phys. Controlled Fusion 55, 052001 (2013)] shows that the configuration dependent ion cyclotron parametric decay instability (PDI) is excited in the density range where the discrepancy between the experiments and simulations remains. Comparing the observed spectra with the homogeneous growth rate spectra indicates that the observed ion cyclotron PDI can be excited not only at the low-field-side but also at the high-field-side (HFS) edge of the tokamak. The model analysis shows that a relevant PDI process to Alcator C-Mod LHCD experiments is decay into ion cyclotron quasi-mode driven by parallel coupling. The underlying cause of the observed onset of ion cyclotron PDI is likely due to the weaker radial penetration of the LH wave in high density plasmas, which can lead to enhanced convective growth. Configuration-dependent PDIs are found to be correlated with different edge density profiles in different magnetic configurations. While the HFS edge of the tokamak can be potentially susceptible to PDI, as evidenced by experimental observations and ray-tracing analyses, enhancing single-pass absorption is expected to help recover the LHCD efficiency at reactor-relevant densities because it could suppress several parasitic loss mechanisms that are exacerbated in multi-pass regimes.
Quantum coherent plasmon in silver nanowires: A real-time TDDFT study
Authors: Ding Feizhi , Guidez Emilie B. , Aikens Christine M. , Li Xiaosong
Published: June 2014

A plasmon-like phenomenon, arising from coinciding resonant excitations of different electronic characteristics in 1D silver nanowires, has been proposed based on theoretical linear absorption spectra. Such a molecular plasmon holds the potential for anisotropic nanoplasmonic applications. However, its dynamical nature remains unexplored. In this work, quantum dynamics of longitudinal and transverse excitations in 1D silver nanowires are carried out within the real-time time-dependent density functional theory framework. The anisotropic electron dynamics confirm that the transverse transitions of different electronic characteristics are collective in nature and oscillate in-phase with respect to each other. Analysis of the time evolutions of participating one-electron wave functions suggests that the transverse transitions form a coherent wave packet that gives rise to a strong plasmon resonance at the molecular level.
A study on laminated structures in Terfenol-D/Epoxy particulate composite with enhanced magnetostriction
Authors: Du Tian , Zhang Tianli , Meng Hao , Zhou Xiaoming , Jiang Chengbao
Published: June 2014

Laminated structures in Terfenol-D/Epoxy particulate composite were obtained via dynamic orientation by oscillating magnetic field. The mechanism of this process was studied and was explained by magnetorheology. The influence of related factors on laminated structures was investigated, including oscillating frequency, magnetic field intensity, particle size, and viscosity of epoxy matrix. A numerical simulation was conducted to model the evolutional process of laminated structures formation, and results consistent with our experiments were obtained. The dynamically oriented composites demonstrated an increase of magnetostriction by up to 300 ppm compared with statically oriented composites.
Note: On-line weak signal detection via adaptive stochastic resonance
Authors: Lu Siliang , He Qingbo , Kong Fanrang
Published: June 2014

We design an instrument with a novel embedded adaptive stochastic resonance (SR) algorithm that consists of a SR module and a digital zero crossing detection module for on-line weak signal detection in digital signal processing applications. The two modules are responsible for noise filtering and adaptive parameter configuration, respectively. The on-line weak signal detection can be stably achieved in seconds. The prototype instrument exhibits an advance of 20 dB averaged signal-to-noise ratio and 5 times averaged adjust R-square as compared to the input noisy signal, in considering different driving frequencies and noise levels.
Simulation of aerosol nucleation and growth in a turbulent mixing layer
Authors: Zhou Kun , Attili Antonio , Alshaarawi Amjad , Bisetti Fabrizio
Published: June 2014

A large-scale simulation of aerosol nucleation and growth in a turbulent mixing layer is performed and analyzed with the aim of elucidating the key processes involved. A cold gaseous stream is mixed with a hot stream of vapor, nanometer sized droplets nucleate as the vapor becomes supersaturated, and subsequently grow as more vapor condenses on their surface. All length and time scales of fluid motion and mixing are resolved and the quadrature method of moments is used to describe the dynamics of the condensing, non-inertial droplets. The results show that a region of high nucleation rate is located near the cold, dry stream, while particles undergo intense growth via condensation on the hot, humid vapor side. Supersaturation and residence times are such that number densities are low and neither coagulation nor vapor scavenging due to condensation are significant. The difference in Schmidt numbers of aerosol particles (approximated as infinity) and temperature and vapor (near unity) causes a drift of the aerosol particles in scalar space and contributes to a large scatter in the conditional statistics of aerosol quantities. The spatial distribution of the aerosol reveals high volume fraction on the hot side of the mixing layer. This distribution is due to drift against the mean and is related to turbulent mixing, which displaces particles from the nucleation region (cold side) into the growth region (hot side). Such a mechanism is absent in laminar flows and is a distinct feature of turbulent condensing aerosols.
Tunable random telegraph noise in individual square permalloy dots
Authors: Endean Daniel E. , Weigelt C. T. , Victora R. H. , Dan Dahlberg E.
Published: June 2014

Magnetization fluctuations caused by thermal energies are poorly understood, yet they represent a fundamental limit for many magnetic technologies. Here, thermal fluctuations of the magnetization are quantitatively characterized. The model magnetic system is thin square magnetic dots (<10 nm) with side lengths down to 200 nm. The magnetic state and the fluctuations are determined in individual dots by measuring the anisotropic magnetoresistance. The magnetization exhibits random telegraph noise with a transition rate determined by the dot size, the applied magnetic field, and the sample temperature. An energy barrier model of the system explains the dependence of the magnetic fluctuations on these parameters and is supported by additional experiments unaffected by the magnetic fluctuations. This independent identification of the mechanism producing magnetic noise, and its agreement with micromagnetic simulations, demonstrates a microscopic understanding of noise extendable to more complex noise sources such as 1/f noise.
Electronic structure of nitinol surfaces oxidized by low-energy ion bombardment
Authors: Petravic M. , Varasanec M. , Peter R. , Kavre I. , Metikos-Hukovic M. , Yang Y.-W.
Published: June 2014

We have studied the electronic structure of nitinol exposed to low-energy oxygen-ion bombardment, using x-ray photoemission spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. XPS spectra reveal a gradual transformation of nitinol surfaces into TiO2 with increased dose of implanted oxygen. No oxidation of Ni atoms has been detected. NEXAFS spectra around O K-edge and Ti L2,3-edge, reflecting the element-specific partial density of empty electronic states, exhibit features, which can be attributed to the creation of molecular orbitals, crystal field splitting, and the absence of long-range order, characteristic of the amorphous TiO2. Based on these results, we discuss the oxidation kinetics of nitinol under low-energy oxygen-ion bombardment.
Trap densities and transport properties of pentacene metal-oxide-semiconductor transistors. I. Analytical modeling of time-dependent characteristics
Authors: Basile A. F. , Cramer T. , Kyndiah A. , Biscarini F. , Fraboni B.
Published: June 2014

Metal-oxide-semiconductor (MOS) transistors fabricated with pentacene thin films were characterized by temperature-dependent current-voltage (I-V) characteristics, time-dependent current measurements, and admittance spectroscopy. The channel mobility shows almost linear variation with temperature, suggesting that only shallow traps are present in the semiconductor and at the oxide/semiconductor interface. The admittance spectra feature a broad peak, which can be modeled as the sum of a continuous distribution of relaxation times. The activation energy of this peak is comparable to the polaron binding energy in pentacene. The absence of trap signals in the admittance spectra confirmed that both the semiconductor and the oxide/semiconductor interface have negligible density of deep traps, likely owing to the passivation of SiO2 before pentacene growth. Nevertheless, current instabilities were observed in time-dependent current measurements following the application of gate-voltage pulses. The corresponding activation energy matches the energy of a hole trap in SiO2. We show that hole trapping in the oxide can explain both the temperature and the time dependences of the current instabilities observed in pentacene MOS transistors. The combination of these experimental techniques allows us to derive a comprehensive model for charge transport in hybrid architectures where trapping processes occur at various time and length scales.
Trap densities and transport properties of pentacene metal–oxide–semiconductor transistors: II—Numerical modeling of dc characteristics
Authors: Basile A. F. , Kyndiah A. , Biscarini F. , Fraboni B.
Published: June 2014

A numerical procedure to calculate the drain-current (ID) vs. gate-voltage (VG) characteristics from numerical solutions of the Poisson equation for organic Thin-Film Transistors (TFTs) is presented. Polaron transport is modeled as two-dimensional charge transport in a semiconductor having free-carrier density of states proportional to the density of molecules and traps with energy equal to the polaron-hopping barrier. The simulated ID-VG curves are proportional to the product of the density of free carriers, calculated as a function of VG, and the intrinsic mobility, assumed to be a constant independent of temperature. The presence of traps in the oxide was also taken into account in the model, which was applied to a TFT made with six monolayers of pentacene grown on an oxide substrate. The polaron-hopping barrier determines the temperature dependence of the simulated ID-VG curves, trapping in the oxide is responsible for current reduction at high bias and the slope of the characteristics near threshold is related to the metal-semiconductor work-function difference. The values of the model parameters yielding the best match between calculations and experiments are consistent with previous experimental results and theoretical predictions. Therefore, this model enables to extract both physical and technological properties of thin-film devices from the temperature-dependent dc characteristics.
Femtosecond single-electron diffraction
Authors: Lahme S. , Kealhofer C. , Krausz F. , Baum P.
Published: June 2014

Ultrafast electron diffraction allows the tracking of atomic motion in real time, but space charge effects within dense electron packets are a problem for temporal resolution. Here, we report on time-resolved pump-probe diffraction using femtosecond single-electron pulses that are free from intra-pulse Coulomb interactions over the entire trajectory from the source to the detector. Sufficient average electron current is achieved at repetition rates of hundreds of kHz. Thermal load on the sample is avoided by minimizing the pump-probe area and by maximizing heat diffusion. Time-resolved diffraction from fibrous graphite polycrystals reveals coherent acoustic phonons in a nanometer-thick grain ensemble with a signal-to-noise level comparable to conventional multi-electron experiments. These results demonstrate the feasibility of pump-probe diffraction in the single-electron regime, where simulations indicate compressibility of the pulses down to few-femtosecond and attosecond duration.
In-situ probing of metallic glass formation and crystallization upon heating and cooling via fast differential scanning calorimetry
Authors: Pogatscher S. , Uggowitzer P. J. , Löffler J. F.
Published: June 2014

The crystallization of small-scale Au-based metallic glass samples was investigated by fast differential scanning calorimetry. Rapid cooling and heating makes possible in-situ probing of glass formation from the supercooled liquid state or direct transition from the glassy state to the equilibrium liquid and, thereby, the determination of a critical cooling (Φc ∼ 600 Ks−1) and heating rate (Φh ∼ 6 × 103 Ks−1) for crystallization. Crystallization kinetics was studied in the whole supercooled liquid region by linear heating and isothermal calorimetry. We show that the temperature dependence of crystal growth is reflected in a “Kissinger plot” for Au49Ag5.5Pd2.3Cu26.9Si16.3 and compares well with a model for crystal growth in a glassy system. Linear heating and isothermal measurements after heating the glass show that its crystallization is always growth-controlled up to its temperature of melting. In contrast, for a low degree of direct undercooling from the equilibrium liquid isothermal crystallization is nucleation-controlled, whereas it is again growth-controlled at large undercooling. The overall crystallization behavior of the metallic glass is presented in a complete time-temperature-transformation map on cooling and, so far not accessible, on heating after various cooling procedures.
Nonlinear birefringence in plasmas: Polarization dynamics, vector modulational instability, and vector solitons
Authors: Borhanian Jafar
Published: June 2014

The propagation of an elliptically polarized intense laser pulse in an unmagnetized collisionless uniform plasma is considered. A multiple scale perturbation theory is employed to show that in a weakly relativistic regime, evolution of the components of vector potential is governed by two coherently coupled nonlinear Schrödinger (NLS) equations. A set of equations describing the evolution of Stokes parameters is derived within the continuous wave approximation and the dynamics of components of field amplitude is studied. The polarization dynamics of a pulse is investigated by means of numerical solution of the coupled NLS equations. A detailed analysis of vector modulational instability is presented and the possibility for occurrence of various kinds of vector solitary waves is addressed.
Transport driven plasma flows in the scrape-off layer of ADITYA Tokamak in different orientations of magnetic field
Authors: Sangwan Deepak , Jha Ratneshwar , Brotankova Jana , Gopalkrishna M. V.
Published: June 2014

Parallel plasma flows in the scrape-off layer of ADITYA tokamak are measured in two orientations of total magnetic field. In each orientation, experiments are carried out by reversing the direction of the toroidal magnetic field and the plasma current. The transport-driven component is determined by averaging flow Mach numbers, measured in two directions of the toroidal magnetic field and the plasma current for the same orientation. It is observed that there is a significant transport-driven component in the measured flow and the component depends on the field orientation.
Conversion of above- and below-bandgap photons via InAs quantum dot media embedded into GaAs solar cell
Authors: Sablon K. , Little J. , Vagidov N. , Li Y. , Mitin V. , Sergeev A.
Published: June 2014

Quantum dots (QDs) provide photovoltaic conversion of below-bandgap photons due to multistep electron transitions. QDs also increase conversion efficiency of the above-bandgap photons due to extraction of electrons from QDs via Coulomb interaction with hot electrons excited by high-energy photons. Nanoscale potential profile (potential barriers) and nanoscale band engineering (AlGaAs atomically thin barriers) allow for suppression of photoelectron capture to QDs. To study these kinetic effects and to distinguish them from the absorption enhancement due to light scattering on QDs, we investigate long, 3-μm base GaAs devices with various InAs QD media with 20 and 40 QD layers. Quantum efficiency measurements show that, at least at low doping, the multistep processes in QD media are strongly affected by the wetting layer (WL). The QD media with WLs provide substantial conversion of below-bandgap photons and for devices with 40 QD layers the short circuit current reaches 29.2 mA/cm2. The QD media with band-engineered AlGaAs barriers and reduced wetting layers (RWL) enhance conversion of high-energy photons and decrease the relaxation (thermal) losses.
Plasmonic crystal enhanced refractive index sensing
Authors: Stein Benedikt , Devaux Eloïse , Genet Cyriaque , Ebbesen Thomas W.
Published: June 2014

We demonstrate experimentally how the local anisotropy of the dispersion relation of surface plasmon modes propagating over periodic metal gratings can lead to an enhancement of the figure of merit of refractive index sensors. Exploiting the possibility to acquire defocused images of the Fourier space of a highly stable leakage radiation microscope, we report a twofold increase in sensing sensitivity close to the band gap of a one-dimensional plasmonic crystal where the anisotropy of the band structure is the most important. A practical sensing resolution of O(10−6) refractive index units is demonstrated.
Modulated differential photoacoustic cell to study the gelatinization in a starch-water suspension
Authors: Villada J. A. , Herrera W. , Espinosa-Arbeláez D. G. , Mosquera J. C. , Rodríguez-García M. E.
Published: June 2014

In this paper the design and implementation of a novel Differential Photoacoustic Cell (DPC) system is presented. The system was used to study the thermo optic transition in water-starch suspension called gelatinization. The melting temperature of Gallium was used to calibrate the temperature of the system. Both temperature values for starch gelatinization and gallium melting were agreed with those obtained using differential scanning calorimetry (DSC). The results show that this system is suitable to study other thermal processes in food or any thermal transition at low temperature.
Magnetic particle imaging of blood coagulation
Authors: Murase Kenya , Song Ruixiao , Hiratsuka Samu
Published: June 2014

We investigated the feasibility of visualizing blood coagulation using a system for magnetic particle imaging (MPI). A magnetic field-free line is generated using two opposing neodymium magnets and transverse images are reconstructed from the third-harmonic signals received by a gradiometer coil, using the maximum likelihood-expectation maximization algorithm. Our MPI system was used to image the blood coagulation induced by adding CaCl2 to whole sheep blood mixed with magnetic nanoparticles (MNPs). The “MPI value” was defined as the pixel value of the transverse image reconstructed from the third-harmonic signals. MPI values were significantly smaller for coagulated blood samples than those without coagulation. We confirmed the rationale of these results by calculating the third-harmonic signals for the measured viscosities of samples, with an assumption that the magnetization and particle size distribution of MNPs obey the Langevin equation and log-normal distribution, respectively. We concluded that MPI can be useful for visualizing blood coagulation.
Ultrafast dark-field surface inspection with hybrid-dispersion laser scanning
Authors: Yazaki Akio , Kim Chanju , Chan Jacky , Mahjoubfar Ata , Goda Keisuke , Watanabe Masahiro , Jalali Bahram
Published: June 2014

High-speed surface inspection plays an important role in industrial manufacturing, safety monitoring, and quality control. It is desirable to go beyond the speed limitation of current technologies for reducing manufacturing costs and opening a new window onto a class of applications that require high-throughput sensing. Here, we report a high-speed dark-field surface inspector for detection of micrometer-sized surface defects that can travel at a record high speed as high as a few kilometers per second. This method is based on a modified time-stretch microscope that illuminates temporally and spatially dispersed laser pulses on the surface of a fast-moving object and detects scattered light from defects on the surface with a sensitive photodetector in a dark-field configuration. The inspector's ability to perform ultrafast dark-field surface inspection enables real-time identification of difficult-to-detect features on weakly reflecting surfaces and hence renders the method much more practical than in the previously demonstrated bright-field configuration. Consequently, our inspector provides nearly 1000 times higher scanning speed than conventional inspectors. To show our method's broad utility, we demonstrate real-time inspection of the surface of various objects (a non-reflective black film, transparent flexible film, and reflective hard disk) for detection of 10 μm or smaller defects on a moving target at 20 m/s within a scan width of 25 mm at a scan rate of 90.9 MHz. Our method holds promise for improving the cost and performance of organic light-emitting diode displays for next-generation smart phones, lithium-ion batteries for green electronics, and high-efficiency solar cells.
Indentation size effect and the plastic compressibility of glass
Authors: Smedskjaer Morten M.
Published: June 2014

Oxide glasses exhibit significant densification under an applied isostatic pressure at the glass transition temperature. The glass compressibility is correlated with the chemical composition and atomic packing density, e.g., borate glasses with planar triangular BO3 units are more disposed for densification than silicate glasses with tetrahedral units. We here show that there is a direct relation between the plastic compressibility following hot isostatic compression and the extent of the indentation size effect (ISE), which is the decrease of hardness with indentation load exhibited by most materials. This could suggest that the ISE is correlated with indentation-induced shear bands, which should form in greater density when the glass network is more adaptable to volume changes through structural and topological rearrangements under an applied pressure.
Electron spin-lattice relaxation of low-symmetry Ni2+ centers in LiF
Authors: Azamat D. V. , Badalyan A. G. , Dejneka A. , Jastrabik L. , Lančok J.
Published: June 2014

The spin-lattice relaxation times of charge-compensated Ni2+ centers in LiF single crystals were measured using the electron spin echo technique. An analysis of the results revealed a very high relaxation rate with a linear dependence on temperature within the intermediate temperature range of 5–15 K. This acceleration of the relaxation rate was found to be due to the inhomogeneous distribution of Ni2+ ions in the LiF lattice. It seems that the effective cross-relaxation mechanism through the exchange-coupled clusters of Ni2+ ions can play a dominant role. Two-phonon Raman type relaxation dominates at higher temperatures involving the Debye phonon spectrum of the LiF lattice.
Initiation time of near-infrared laser-induced slip on the surface of silicon wafers
Authors: Choi Sungho , Jhang Kyung-Young
Published: June 2014

We have determined the initiation time of laser-induced slip on a silicon wafer surface subjected to a near-infrared continuous-wave laser by numerical simulations and experiments. First, numerical analysis was performed based on the heat transfer and thermoelasticity model to calculate the resolved shear stress and the temperature-dependent yield stress. Slip initiation time was predicted by finding the time at which the resolved shear stress reached the yield stress. Experimentally, the slip initiation time was measured by using a laser scattering technique that collects scattered light from the silicon wafer surface and detects strong scattering when the surface slip is initiated. The surface morphology of the silicon wafer surface after laser irradiation was also observed using an optical microscope to confirm the occurrence of slip. The measured slip initiation times agreed well with the numerical predictions.
Phonon and thermal transport properties of the misfit-layered oxide thermoelectric Ca3Co4O9 from first principles
Authors: Rébola Alejandro , Klie Robert F. , Zapol Peter , Öğüt Serdar
Published: June 2014

The full phonon spectra of two rational approximants to the incommensurate thermoelectric oxide material Ca3Co4O9 (CCO) are calculated from first principles within density functional theory (DFT) and its DFT + U extension. The computed phonon dispersion curves are then used to evaluate the constant volume heat capacity, as well as the full and partial (subsystem-projected) lattice thermal conductivity of CCO. The results are discussed in terms of the effects of the Hubbard U on the computed properties, the size of the rational approximants used to model CCO, the relative contributions of the two subsystems that comprise the misfit-layered material, and the anisotropic nature of the computed thermal conductivity. We obtain good agreement with available experimental data.
High-efficiency graphene nanomesh magnets realized by controlling mono-hydrogenation of pore edges
Authors: Kato T. , Nakamura T. , Kamijyo J. , Kobayashi T. , Yagi Y. , Haruyama J.
Published: June 2014

We demonstrate a drastic improvement in the efficiency of rare-element-free graphene nanomesh (GNM) magnets with saturation magnetization values as large as ∼10−4 emu/mm2, which are 10–100 times greater than those in previous GNM magnets hydrogenated by only annealing under a hydrogen molecule (H2) atmosphere, even at room temperature. This improvement is realized by a significant increase in the area of the mono-H-terminated pore edges by using hydrogen silsesquioxane resist treatment with electron beam irradiation, which can produce mono-H by detaching H-silicon (Si) bonds. This result must open the door for industrial applications of graphene magnets to rare-element-free magnetic and spintronic systems.
Study on neutron emission from 2.2 kJ plasma focus device
Authors: Talukdar N. , Neog N. K. , Borthakur T. K.
Published: June 2014

The neutron emission from a low energy (2.2 kJ) plasma focus device operated in deuterium medium has been investigated by employing photo-multiplier tube (PMT) and bubble dosimeter. The neutron emission is found to be pressure dependent and anisotropic in nature. In most cases of plasma focus shots, the PMT signal shows double pulses of neutron emission with different intensities and widths. An interesting relation between intensity of hard X-ray and neutron emission is also observed.
End-to-end and side-by-side assemblies of gold nanorods induced by dithiol poly(ethylene glycol)
Authors: Liu Jinsheng , Kan Caixia , Li Yuling , Xu Haiying , Ni Yuan , Shi Daning
Published: June 2014

The assemblies of gold nanorods (Au NRs) exhibit unique properties distinct from the isolated Au NR. We report an effective and simple method for the end-to-end (E-E) and side-by-side (S-S) assemblies of Au NRs with a molecularly defined nanogap (1–2 nm) only in the presence of dithiol poly(ethylene glycol) (HS-PEG-SH). The assembled methods need neither the pH value adjustments nor the addition of other organic solvent. With increasing amount of dithiol molecules, assembled modes of Au NRs experience an interesting procedure, changing from E-E to S-S orientation. The experimental results indicate that when the concentration of HS-PEG-SH is less than 0.25 μM, electrostatic repulsion of positive-charged CTA+ is stronger than the affinity of the Au-S binding, resulting in the E-E oriented assembly. Otherwise, the S-S oriented mode is predominated. The current assembled method will be potentially useful for the optoelectronics and biomedical engineering.
Graphene-assisted near-field radiative heat transfer between corrugated polar materials
Authors: Liu X. L. , Zhang Z. M.
Published: June 2014

Graphene has attracted great attention in nanoelectronics, optics, and energy harvesting. Here, the near-field radiative heat transfer between graphene-covered corrugated silica is investigated based on the exact scattering theory. It is found that graphene can improve the radiative heat flux between silica gratings by more than one order of magnitude and alleviate the performance sensitivity to lateral shift. The underlying mechanism is mainly attributed to the improved photon tunneling of modes away from phonon resonances. Besides, coating with graphene leads to nonlocal radiative transfer that breaks Derjaguin's proximity approximation and enables corrugated silica to outperform bulk silica in near-field radiation.
Enhanced memory effect via quantum confinement in 16 nm InN nanoparticles embedded in ZnO charge trapping layer
Authors: El-Atab Nazek , Cimen Furkan , Alkis Sabri , Ortaç Bülend , Alevli Mustafa , Dietz Nikolaus , Okyay Ali K. , Nayfeh Ammar
Published: June 2014

In this work, the fabrication of charge trapping memory cells with laser-synthesized indium-nitride nanoparticles (InN-NPs) embedded in ZnO charge trapping layer is demonstrated. Atomic layer deposited Al2O3 layers are used as tunnel and blocking oxides. The gate contacts are sputtered using a shadow mask which eliminates the need for any lithography steps. High frequency C-Vgate measurements show that a memory effect is observed, due to the charging of the InN-NPs. With a low operating voltage of 4 V, the memory shows a noticeable threshold voltage (Vt) shift of 2 V, which indicates that InN-NPs act as charge trapping centers. Without InN-NPs, the observed memory hysteresis is negligible. At higher programming voltages of 10 V, a memory window of 5 V is achieved and the Vt shift direction indicates that electrons tunnel from channel to charge storage layer.
Strong electroluminescence from SiO2-Tb2O3-Al2O3 mixed layers fabricated by atomic layer deposition
Authors: Rebohle L. , Braun M. , Wutzler R. , Liu B. , Sun J. M. , Helm M. , Skorupa W.
Published: June 2014

We report on the bright green electroluminescence (EL) with power efficiencies up to 0.15% of SiO2-Tb2O3-mixed layers fabricated by atomic layer deposition and partly co-doped with Al2O3. The electrical, EL, and breakdown behavior is investigated as a function of the Tb and the Al concentration. Special attention has been paid to the beneficial role of Al2O3 co-doping which improves important device parameters. In detail, it increases the maximum EL power efficiency and EL decay time, it nearly doubles the fraction of excitable Tb3+ ions, it shifts the region of high EL power efficiencies to higher injection currents, and it reduces the EL quenching over the device lifetime by an approximate factor of two. It is assumed that the presence of Al2O3 interferes the formation of Tb clusters and related defects. Therefore, the system SiO2-Tb2O3-Al2O3 represents a promising alternative for integrated, Si-based light emitters.
Multi-scale quantum point contact model for filamentary conduction in resistive random access memories devices
Authors: Lian Xiaojuan , Cartoixà Xavier , Miranda Enrique , Perniola Luca , Rurali Riccardo , Long Shibing , Liu Ming , Suñé Jordi
Published: June 2014

We depart from first-principle simulations of electron transport along paths of oxygen vacancies in HfO2 to reformulate the Quantum Point Contact (QPC) model in terms of a bundle of such vacancy paths. By doing this, the number of model parameters is reduced and a much clearer link between the microscopic structure of the conductive filament (CF) and its electrical properties can be provided. The new multi-scale QPC model is applied to two different HfO2-based devices operated in the unipolar and bipolar resistive switching (RS) modes. Extraction of the QPC model parameters from a statistically significant number of CFs allows revealing significant structural differences in the CF of these two types of devices and RS modes.
Monolithically integrated Helmholtz coils by 3-dimensional printing
Authors: Li Longguang , Abedini-Nassab Roozbeh , Yellen Benjamin B.
Published: June 2014

3D printing technology is of great interest for the monolithic fabrication of integrated systems; however, it is a challenge to introduce metallic components into 3D printed molds to enable broader device functionality. Here, we develop a technique for constructing a multi-axial Helmholtz coil by injecting a eutectic liquid metal Gallium Indium alloy (EGaIn) into helically shaped orthogonal cavities constructed in a 3D printed block. The tri-axial solenoids each carry up to 3.6 A of electrical current and produce magnetic field up to 70 G. Within the central section of the coil, the field variation is less than 1% and is in agreement with theory. The flow rates and critical pressures required to fill the 3D cavities with liquid metal also agree with theoretical predictions and provide scaling trends for filling the 3D printed parts. These monolithically integrated solenoids may find future applications in electronic cell culture platforms, atomic traps, and miniaturized chemical analysis systems based on nuclear magnetic resonance.
Note: An approach to measurement of low frequency oscillation amplitude of discharge current of in-orbit Hall thruster
Authors: Han Liang , Ding Yongjie , Wei Liqiu , Yu Daren
Published: June 2014

This paper provides a method to measure the amplitude of low frequency oscillation under the on-track working condition, and realizes the sampling by means of adding the circuit design of sampling, low pass filtering by 3 dB at 48.2 kHz, detection and integrating in the filtering unit. The experimental results prove that the measuring device of merely 0.8 g can quantitatively reflect the amplitude of low frequency oscillation in Hall thruster and the maximum deviation of experiment data and theory data is 10% FS.
Caputo standard α-family of maps: Fractional difference vs. fractional
Authors: Edelman M.
Published: June 2014

In this paper, the author compares behaviors of systems which can be described by fractional differential and fractional difference equations using the fractional and fractional difference Caputo standard α-Families of maps as examples. The author shows that properties of fractional difference maps (systems with falling factorial-law memory) are similar to the properties of fractional maps (systems with power-law memory). The similarities (types of attractors, power-law convergence of trajectories, existence of cascade of bifurcations and intermittent cascade of bifurcations type trajectories, and dependence of properties on the memory parameter α) and differences in properties of falling factorial- and power-law memory maps are investigated.
Influence of carbon/nitrogen ratio on the anaerobic fermentative hydrogen production with cow dung compost
Authors: Li Ruixue , Zhi Zelun , Wang Hui
Published: June 2014

In the anaerobic fermentation process, the carbon/nitrogen (C/N) ratio in the medium is a critical factor representing nutrient balance, which is important for cell synthesis, growth, and metabolism. The cow dung compost was co-digested, respectively, with glucose and apple pomace (AP) in the batch experiments to investigate the effects of C/N ratio on fermentative hydrogen production. For the co-digestion of glucose and cow dung compost, the cumulative hydrogen yield (CHY) peaked with 1232.7 ml/L-culture at a C/N ratio of 9.3, and the concentrations of glucose and cow dung compost were 5.0 g/l and 180.0 g/l, respectively. However, the maximum CHY reached 1398.0 ml/L-culture for the co-digestion of cow dung compost and AP, and the C/N ratio was 10.6. In addition, when we used glucose as the single substrate and the microorganisms existing in the electrode of pH meter as bacteria source which was from previous hydrogen production with cow dung compost, at a C/N ratio of 10.3, the CHY peaked with 945.7 ml/L-culture, and the concentration of glucose was 10.0 g/l. Meanwhile, at the optimum C/N ratio, the main component of liquid end-products was butyrate.
Long-range hybrid ridge and trench plasmonic waveguides
Authors: Bian Yusheng , Gong Qihuang
Published: June 2014

We report a class of long-range hybrid plasmon polariton waveguides capable of simultaneously achieving low propagation loss and tight field localization at telecommunication wavelength. The symmetric (quasi-symmetric) hybrid configurations featuring high-refractive-index-contrast near the non-uniform metallic nanostructures enable significantly improved optical performance over conventional hybrid waveguides, exhibiting considerably longer propagation distances and dramatically enhanced figure of merits for similar degrees of confinement. Compared to their traditional long-range plasmonic counterparts, the proposed hybrid waveguides put much less stringent requirements on index-matching conditions, demonstrating nice performance under a wide range of physical dimensions and robust characteristics against certain fabrication imperfections. Studies concerning crosstalk between adjacent identical waveguides further reveal their potential for photonic integrations. In addition, alternative configurations with comparable guiding properties to the structures in our case studies are also proposed, which can potentially serve as attractive prototypes for numerous high-performance nanophotonic components.
Cross sections for electron capture and excitation in collisions of Liq+ (q=1, 2, 3) with atomic hydrogen
Authors: Liu L. , Li X. Y. , Wang J. G. , Janev R. K.
Published: June 2014

The two-center atomic orbital close-coupling method is employed to study electron capture and excitation reactions in collisions of Liq+ (q = 1-3) ions with ground state atomic hydrogen in the ion energy range from 0.1 keV/u to 300 keV/u, where u is the atomic mass unit. The interaction of the active electron with the projectile ions (Li+, Li2+) is represented by a model potential. Total and state-selective cross sections for charge transfer and excitation processes are calculated and compared with data from other sources when available.
Mobile Places, Relational Spaces: Conceptualizing Change in Sydney's LGBTQ Neighborhoods
Authors: Gorman-Murray Andrew , Nash Catherine Jean
Published: June 2014

Since the 1950s neighborhoods associated with lesbian, gay, bisexual, trans, and queer (LGBTQ) subjects and communities have become part of the urban landscape in many cities of the Global North. In Australia this is evident in Sydney, where particular inner-city suburbs are bracketed with ‘gay’, ‘lesbian’, and ‘queer’ sexualities. These sexual-spatial relations are multiple and changing, with current fears about the decline of ‘traditional’ gay village spaces coinciding with the emergence of alternative LGBTQ neighborhoods. This paper reinterprets these transformations, departing from notions of the ‘demise’ of gay spaces, (re)conceptualizing Sydney's LGBTQ neighborhoods as mobile and relational moorings that are not fixed and immutable but repeatedly reconstructed and regrounded from flows of people, knowledge, and capital. Moreover, such mobile practices and representations connect places, symbolically and materially constructing them in relation to each other. Consequently, rather than reading through narratives of ‘demise’ and ‘emergence’, we suggest Sydney's LGBTQ landscapes are embedded in, and (re)constituted through, a ‘politics of mobility’. We examine the physical displacement, representations of mobility, and embodied mobile practices underpinning these changes in inner-city Sydney. In doing so, our purpose is to make conceptual and practical connections between the significance of ‘place making’ and ‘mobility’ to LGBTQ lives, communities, and politics. This discussion encourages geographers of sexualities to consider the multiplicity of LGBTQ mobilities, and equally prompts mobilities scholars to be cognizant of sexual and gender politics in processes and outcomes of mobilities.
Gifted Places: The Inalienable Nature of Belonging in Place
Authors: Bennett Julia
Published: June 2014

This paper focuses on the importance of historic, social, and material connections in belonging to place. Mauss's anthropological concept of a ‘gift’ is deployed to understand how places are cared for by a community over time. The development of tangible and intangible connections between past, present, and future people and places is explored. On the basis of in-depth, qualitative research with a group of people who have long-standing connections to their local place, memories and life-narratives are unravelled to explore the social and material relationships that place embodies. An understanding of place as an inalienable gift may create a moral duty to nurture and pass on places to subsequent generations. The research takes a phenomenological approach in order to illuminate the largely unconsidered associations between personal biographies and material places. After a brief discussion of the data collection methods used, notably photo diaries, some empirical examples are put forward to demonstrate how the research participants act as current custodians of places. The paper concludes by bringing together the different aspects of belonging in place illustrated by these vignettes and shows how they contribute to belonging in place as a moral way of being-in-the-world; that is, what I term ‘an ontological belonging’.
Integrating Shape Cues of Adiposity and Color Information When Judging Facial Health and Attractiveness
Authors: Fisher Claire I , Hahn Amanda C , DeBruine Lisa M , Jones Benedict C
Published: June 2014

Facial cues of adiposity play an important role in social perceptions, such as health and attractiveness judgments. Although relatively low levels of adiposity are generally associated with good health, low levels of adiposity are also a symptom of many communicable diseases. Consequently, it may be important to distinguish between individuals displaying low levels of facial adiposity because they are in good physical condition and those displaying low levels of facial adiposity because they are ill. Integrating information from facial cues of adiposity with information from other health cues, such as facial coloration, may facilitate such distinctions. Here, participants rated the health and attractiveness of face images experimentally manipulated to vary in shape cues of adiposity and color cues associated with perceived health. As we had predicted, the extent to which faces with low levels of adiposity were rated more positively than faces with relatively high levels of adiposity was greater for faces with healthy color cues than it was for faces with unhealthy color cues. Such interactions highlight the integrative processes that allow us to distinguish between healthy and unhealthy individuals during social interactions, potentially reducing the likelihood of contracting infectious diseases.
Effects of varying doses of β-nerve growth factor on the timing of ovulation, plasma progesterone concentration and corpus luteum size in female alpacas (Vicugna pacos)
Authors: Stuart C. C. , Vaughan J. L. , Kershaw-Young C. M. , Wilkinson J. , Bathgate R. , de Graaf S. P.
Published: June 2014

Ovulation in camelids is induced by the seminal plasma protein ovulation-inducing factor (OIF), recently identified as β-nerve growth factor (β-NGF). The present study measured the total protein concentration in alpaca seminal plasma using a bicinchoninic acid (BCA) protein quantification assay and found it to be 22.2 ± 2.0 mg mL–1. To measure the effects of varying doses of β-NGF on the incidence and timing of ovulation, corpus luteum (CL) size and plasma progesterone concentration, 24 female alpacas were synchronised and treated with either: (1) 1 mL 0.9% saline (n = 5); (2) 4 µg buserelin (n = 5); (3) 1 mg β-NGF protein (n = 5); (4) 0.1 mg β-NGF (n = 5); or (5) 0.01 mg β-NGF (n = 4). Females were examined by transrectal ultrasonography at 1–2-h intervals between 20 and 45 h after treatment or until ovulation occurred, as well as on Day 8 to observe the size of the CL, at which time blood was collected to measure plasma progesterone concentrations. Ovulation was detected in 0/5, 5/5, 5/5, 3/5 and 0/4 female alpacas treated with saline, buserelin, 1, 0.1 and 0.01 mg β-NGF, respectively. Mean ovulation interval (P = 0.76), CL diameter (P = 0.96) and plasma progesterone concentration (P = 0.96) did not differ between treatments. Mean ovulation interval overall was 26.2 ± 1.0 h. In conclusion, buserelin and 1 mg β-NGF are equally effective at inducing ovulation in female alpacas, but at doses ≤0.1 mg, β-NGF is not a reliable method for the induction of ovulation.