bluuebunny/crossref_metadata_2025 huggingface dataset:
Massively parallel implementations of coupled-cluster methods for electron spin resonance spectra. I. Isotropic hyperfine coupling tensors in large radicals
Authors: Verma Prakash , Perera Ajith , Morales Jorge A.
Published: November 2013

Coupled cluster (CC) methods provide highly accurate predictions of molecular properties, but their high computational cost has precluded their routine application to large systems. Fortunately, recent computational developments in the ACES III program by the Bartlett group [the OED/ERD atomic integral package, the super instruction processor, and the super instruction architecture language] permit overcoming that limitation by providing a framework for massively parallel CC implementations. In that scheme, we are further extending those parallel CC efforts to systematically predict the three main electron spin resonance (ESR) tensors (A-, g-, and D-tensors) to be reported in a series of papers. In this paper inaugurating that series, we report our new ACES III parallel capabilities that calculate isotropic hyperfine coupling constants in 38 neutral, cationic, and anionic radicals that include the 11B, 17O, 9Be, 19F, 1H, 13C, 35Cl, 33S,14N, 31P, and 67Zn nuclei. Present parallel calculations are conducted at the Hartree-Fock (HF), second-order many-body perturbation theory [MBPT(2)], CC singles and doubles (CCSD), and CCSD with perturbative triples [CCSD(T)] levels using Roos augmented double- and triple-zeta atomic natural orbitals basis sets. HF results consistently overestimate isotropic hyperfine coupling constants. However, inclusion of electron correlation effects in the simplest way via MBPT(2) provides significant improvements in the predictions, but not without occasional failures. In contrast, CCSD results are consistently in very good agreement with experimental results. Inclusion of perturbative triples to CCSD via CCSD(T) leads to small improvements in the predictions, which might not compensate for the extra computational effort at a non-iterative N7-scaling in CCSD(T). The importance of these accurate computations of isotropic hyperfine coupling constants to elucidate experimental ESR spectra, to interpret spin-density distributions, and to characterize and identify radical species is illustrated with our results from large organic radicals. Those include species relevant for organic chemistry, petroleum industry, and biochemistry, such as the cyclo-hexyl, 1-adamatyl, and Zn-porphycene anion radicals, inter alia.
A liquid-helium-free superconducting coil system forming a flat minimum-magnetic-field distribution of an electron cyclotron resonance ion source
Authors: Yoshida Ken-ichi , Nara Takayuki , Saitoh Yuichi , Yokota Watalu
Published: November 2013

A flat distribution of the minimum magnetic field (flat-Bmin) of an electron cyclotron resonance ion source (ECRIS) is expected to perform better in highly charged ion production than classical Bmin. To form a flat-Bmin structure with a liquid helium-free superconducting device, a coil system of seven coils with four current leads has been designed. The lead number was reduced by connecting the plural coils in series to maintain the flat-Bmin structure even when the coil currents are changed for adjustment. This coil system can be operated with a helium-free cryostat, since the estimation of heat from the leads to the coils is nearly equivalent to the existing superconducting ECRIS of a similar type.
Effect of confinement on the solid-liquid coexistence of Lennard-Jones Fluid
Authors: Das Chandan K. , Singh Jayant K.
Published: November 2013

The solid-liquid coexistence of a Lennard-Jones fluid confined in slit pores of variable pore size, H, is studied using molecular dynamics simulations. Three-stage pseudo-supercritical transformation path of Grochola [J. Chem. Phys. 120(5), 2122 (2004)] and multiple histogram reweighting are employed for the confined system, for various pore sizes ranging from 20 to 5 molecular diameters, to compute the solid-liquid coexistence. The Gibbs free energy difference is evaluated using thermodynamic integration method by connecting solid-liquid phases under confinement via one or more intermediate states without any first order phase transition among them. Thermodynamic melting temperature is found to oscillate with wall separation, which is in agreement with the behavior seen for kinetic melting temperature evaluated in an earlier study. However, thermodynamic melting temperature for almost all wall separations is higher than the bulk case, which is contrary to the behavior seen for the kinetic melting temperature. The oscillation founds to decay at around H = 12, and beyond that pore size dependency of the shift in melting point is well represented by the Gibbs-Thompson equation.
A multireference perturbation method using non-orthogonal Hartree-Fock determinants for ground and excited states
Authors: Yost Shane R. , Kowalczyk Tim , Van Voorhis Troy
Published: November 2013

In this article we propose the ΔSCF(2) framework, a multireference strategy based on second-order perturbation theory, for ground and excited electronic states. Unlike the complete active space family of methods, ΔSCF(2) employs a set of self-consistent Hartree-Fock determinants, also known as ΔSCF states. Each ΔSCF electronic state is modified by a first-order correction from Møller-Plesset perturbation theory and used to construct a Hamiltonian in a configuration interactions like framework. We present formulas for the resulting matrix elements between nonorthogonal states that scale as \documentclass[12pt]{minimal}\begin{document}$N_{\text{occ}}^2N_{\text{virt}}^3$\end{document}Nocc2Nvirt3. Unlike most active space methods, ΔSCF(2) treats the ground and excited state determinants even-handedly. We apply ΔSCF(2) to the H2, hydrogen fluoride, and H4 systems and show that the method provides accurate descriptions of ground- and excited-state potential energy surfaces with no single active space containing more than 10 ΔSCF states.
Stochastic dynamics of small ensembles of non-processive molecular motors: The parallel cluster model
Authors: Erdmann Thorsten , Albert Philipp J. , Schwarz Ulrich S.
Published: November 2013

Non-processive molecular motors have to work together in ensembles in order to generate appreciable levels of force or movement. In skeletal muscle, for example, hundreds of myosin II molecules cooperate in thick filaments. In non-muscle cells, by contrast, small groups with few tens of non-muscle myosin II motors contribute to essential cellular processes such as transport, shape changes, or mechanosensing. Here we introduce a detailed and analytically tractable model for this important situation. Using a three-state crossbridge model for the myosin II motor cycle and exploiting the assumptions of fast power stroke kinetics and equal load sharing between motors in equivalent states, we reduce the stochastic reaction network to a one-step master equation for the binding and unbinding dynamics (parallel cluster model) and derive the rules for ensemble movement. We find that for constant external load, ensemble dynamics is strongly shaped by the catch bond character of myosin II, which leads to an increase of the fraction of bound motors under load and thus to firm attachment even for small ensembles. This adaptation to load results in a concave force-velocity relation described by a Hill relation. For external load provided by a linear spring, myosin II ensembles dynamically adjust themselves towards an isometric state with constant average position and load. The dynamics of the ensembles is now determined mainly by the distribution of motors over the different kinds of bound states. For increasing stiffness of the external spring, there is a sharp transition beyond which myosin II can no longer perform the power stroke. Slow unbinding from the pre-power-stroke state protects the ensembles against detachment.
Untilting BiFeO3: The influence of substrate boundary conditions in ultra-thin BiFeO3 on SrTiO3
Authors: Yang Yongsoo , Schlepütz Christian M. , Adamo Carolina , Schlom Darrell G. , Clarke Roy
Published: November 2013

We report on the role of oxygen octahedral tilting in the monoclinic-to-tetragonal phase transition in ultra-thin BiFeO3 films grown on (001) SrTiO3 substrates. Reciprocal space maps clearly show the disappearance of the integer-order Bragg peak splitting associated with the monoclinic phase when the film thickness decreases below 20 unit cells. This monoclinic-to-tetragonal transition is accompanied by the evolution of the half-order diffraction peaks, which reflects untilting of the oxygen octahedra around the [110] axis, proving that the octahedral tilting is closely correlated with the transition. This structural change is thickness-dependent, and different from a strain-induced transition in the conventional sense.
Water dissociation on Ni(100) and Ni(111): Effect of surface temperature on reactivity
Authors: Seenivasan H. , Tiwari Ashwani K.
Published: November 2013

Water adsorption and dissociation on Ni(100) and Ni(111) surfaces are studied using density functional theory calculations. Water adsorbs on top site on both the surfaces, while H and OH adsorb on four fold hollow and three fold hollow (fcc) sites on Ni(100) and Ni(111), respectively. Transition states (TS) on both surfaces are identified using climbing image-nudged elastic band method. It is found that the barrier to dissociation on Ni(100) surface is slightly lower than that on Ni(111) surface. Dissociation on both the surfaces is exothermic, while the exothermicity on Ni(100) is large. To study the effect of lattice motion on the energy barrier, TS calculations are performed for various values of Q (lattice atom coordinate along the surface normal) and the change in the barrier height and position is determined. Calculations show that the energy barrier to reaction decreases with increasing Q and increases with decreasing Q on both the surfaces. Dissociation probability values at different surface temperatures are computed using semi-classical approximation. Results show that the influence of surface temperature on dissociation probability on the Ni(100) is significantly larger compared to that of Ni(111). Moreover, on Ni(100), a dramatic shift in energy barrier to lower incident energy values is observed with increasing surface temperature, while the shift is smaller in the case of Ni(111).
Site-dependent Si KL23L23 resonant Auger electron spectra following inner-shell excitation of Cl3SiSi(CH3)3
Authors: Suzuki Isao H. , Endo Hikari , Nagai Kanae , Takahashi Osamu , Tamenori Yusuke , Nagaoka Shin-ichi
Published: November 2013

Spectator resonant Auger electron spectra with the Si 1s photoexcitation of Cl3SiSi(CH3)3 have been measured using an electron spectroscopic technique combined with undulator radiation. The transition with the highest intensity in the total ion yield (TIY) spectrum, coming from excitation of a Si 1s electron on the Cl-side into a vacant valence orbital, generates the resonant Auger decay in which the excited electron remains in this valence orbital. Photoexcitation of 1s electrons into some Rydberg orbitals induces Auger shake-down transitions, because higher-lying Rydberg orbitals in the two Si atoms closely positioned hold spatially overlapping considerably. A broad TIY peak slightly above the 1s ionization thresholds appreciably yields resonant Auger decays in which a slow photoelectron is re-captured into a higher-lying Rydberg orbital. The normal Auger peak shape at this photon energy is distorted due to a post-collision interaction effect. These findings provide a clear understanding on properties of the excited orbitals which are ambiguous in the measurement of the TIY only.
Effective slippage on superhydrophobic trapezoidal grooves
Authors: Zhou Jiajia , Asmolov Evgeny S. , Schmid Friederike , Vinogradova Olga I.
Published: November 2013

We study the effective slippage on superhydrophobic grooves with trapezoidal cross-sections of various geometries (including the limiting cases of triangles and rectangular stripes), by using two complementary approaches. First, dissipative particle dynamics (DPD) simulations of a flow past such surfaces have been performed to validate an expression [E. S. Asmolov and O. I. Vinogradova, J. Fluid Mech. 706, 108 (2012)] that relates the eigenvalues of the effective slip-length tensor for one-dimensional textures. Second, we propose theoretical estimates for the effective slip length and calculate it numerically by solving the Stokes equation based on a collocation method. The comparison between the two approaches shows that they are in excellent agreement. Our results demonstrate that the effective slippage depends strongly on the area-averaged slip, the amplitude of the roughness, and on the fraction of solid in contact with the liquid. To interpret these results, we analyze flow singularities near slipping heterogeneities, and demonstrate that they inhibit the effective slip and enhance the anisotropy of the flow. Finally, we propose some guidelines to design optimal one-dimensional superhydrophobic surfaces, motivated by potential applications in microfluidics.
Linear stability analysis on supersonic streamwise vortices
Authors: Hiejima Toshihiko
Published: November 2013

In this study, the spatial growth rates of supersonic streamwise vortices were investigated by inviscid linear stability analysis. The freestream Mach numbers were 2.5, 5.0, and 7.5. In previous measurements taken to define the streamwise vortices, the stagnation temperature profile of supersonic flows is approximately uniform. This study found that the growth rate of vortices at the uniform stagnation temperature is smaller than that of isentropic vortices. The instability properties of the streamwise vortices can be explained by the ratio of the circulation to the axial velocity deficit, and also by the Mach number. Moreover, it is found that the compressibility effect, by which the instability reduces as the Mach number increases, is caused by the negative energy arising from the entropy gradient of supersonic vortices that accompanies the axial velocity deficit-like wake. From an energy perspective, the effect may reasonably be correlated with the large density perturbations in supersonic flows. This study also proposes a general convective Mach number for supersonic streamwise vortices. The normalized growth rates are shown to be a function of convective Mach number within the investigated range of ratio parameters.
The effect of undulating leading-edge modifications on NACA 0021 airfoil characteristics
Authors: Rostamzadeh N. , Kelso R. M. , Dally B. B. , Hansen K. L.
Published: November 2013

In spite of its mammoth physical size, the humpback whale's manoeuvrability in hunting has captured the attention of biologists as well as fluid mechanists. It has now been established that the protrusions on the leading-edges of the humpback's pectoral flippers, known as tubercles, account for this species’ agility and manoeuvrability. In the present work, Prandtl's nonlinear lifting-line theory was employed to propose a hypothesis that the favourable traits observed in the performance of tubercled lifting bodies are not exclusive to this form of leading-edge configuration. Accordingly, a novel alternative to tubercles was introduced and incorporated into the design of four airfoils that underwent wind tunnel force and pressure measurement tests in the transitional flow regime. In addition, a Computation Fluid Dynamics study was performed using the Shear Stress Transport transitional model in the context of unsteady Reynolds-Averaged Navier-Stokes at several attack angles. The results from the numerical investigation are in reasonable agreement with those of the experiments, and suggest the presence of features that are also observed in flows over tubercled foils, most notably a distinct pair of streamwise vortices for each wavelength of the tubercle-like feature.
Impurity effects on polaron-exciton formation in conjugated polymers
Authors: Ribeiro Luiz Antonio , da Cunha Wiliam Ferreira , de Oliveira Neto Pedro Henrique , Gargano Ricardo , e Silva Geraldo Magela
Published: November 2013

Combining the one-dimensional tight-binding Su-Schrieffer-Heeger model and the extended Hubbard model, the collision of two oppositely charged polarons is investigated under the influence of impurity effects using a non-adiabatic evolution method. Results show that electron-electron interactions have direct influence on the charge distribution coupled to the polaron-exciton lattice defect. Additionally, the presence of an impurity in the collisional process reduces the critical electric field for the polaron-exciton formation. In the small electric field regime, the impurity effects open three channels and are of fundamental importance to favor the polaron-exciton creation. The results indicate that the scattering between polarons in the presence of impurities can throw a new light on the description of electroluminescence in conjugated polymer systems.
Internal friction of hydrated soda-lime-silicate glasses
Authors: Reinsch S. , Müller R. , Deubener J. , Behrens H.
Published: November 2013

The internal friction of hydrated soda-lime-silica glasses with total water content (CW) up to 1.9 wt. % was studied by dynamic mechanical analysis (DMA) using temperature-frequency sweeps from 723 K to 273 K and from 1 s−1 to 50 s−1. Total water content and concentrations of H2O molecules ($C_{{\rm H}_2 {\rm O}}$CH2O) and OH groups (COH) in the DMA specimens were determined by infrared spectroscopy. For low water contents (CW ≈ COH < 0.25 wt. %) two discrete internal friction peaks below the glass transition (α relaxation) were assigned to the low-temperature motion of alkali ions (γ relaxation) and cooperative movements of dissimilar mobile species under participation of OH at higher temperature (βOH relaxation). For large water contents (CW > 1 wt. %), where significant amounts of molecular water are evident ($C_{{\rm H}_2 {\rm O}}$CH2O > 0.15 wt. %), however, internal friction spectra change unexpectedly: the βOH peak heights saturate and a low temperature shoulder appears on the β-relaxation peak. This emerging relaxation mode ($\beta _{{\rm H}_2 {\rm O}}$βH2O relaxation) was assigned to the motions of H2O molecules. $\beta _{{\rm H}_2 {\rm O}}$βH2O relaxation was found to be faster than βOH but slower than γ relaxation. Activation energy of the different relaxation modes increased in the order γ < $\beta _{{\rm H}_2 {\rm O}}$βH2O < βOH < α.
A gas gun based technique for studying the role of temperature in dynamic fracture and fragmentation
Authors: Jones D. R. , Chapman D. J. , Eakins D. E.
Published: November 2013

Presented in this work is a new experimental technique to facilitate studies of materials under uniform radial expansion at rates of strain typically seen in ballistic and impact studies (103 to 105 s−1) at temperatures around 100–1000 K. Previous work places a right-cylinder polymer insert in a sample cylinder, into which a matching polymer projectile is launched using a gas gun. The impact and resulting deformation of the polymers imparts radial momentum to the cylinder. This work replaces the polymer insert with a steel ogive. A polycarbonate projectile deforms around the insert and drives radial expansion. The uniform radial expansion created has a less complex interface than previous work as only one material is driving the cylinder wall. As deformation of the insert is no longer necessary, the opportunity to heat or cool the cylinder prior to expansion is now available for studies into the effect of temperature on fracture and fragmentation behavior. This paper describes the design of this new impact configuration alongside how strain rate and expansion profile can be controlled. Validation experiment results with 6061-T6 aluminum and Ti-6Al-4V cylinders using a variety of diagnostics are compared with numerical modelling, where the benefits of this technique in assisting development of material strength and failure models are discussed with methods to control the sample temperature.
Quantum point contact displacement transducer for a mechanical resonator at sub-Kelvin temperatures
Authors: Okazaki Yuma , Mahboob Imran , Onomitsu Koji , Sasaki Satoshi , Yamaguchi Hiroshi
Published: November 2013

Highly sensitive displacement transduction of a 1.67 MHz mechanical resonator with a quantum point contact (QPC) formed in a GaAs heterostructure is demonstrated. By positioning the QPC at the point of maximum mechanical strain on the resonator and operating at 80 mK, a displacement responsivity of 3.81 A/m is measured, which represents a two order of magnitude improvement on the previous QPC based devices. By further analyzing the QPC transport characteristics, a sub-Poisson-noise-limited displacement sensitivity of 25 fm/Hz1∕2 is determined which corresponds to a position resolution that is 23 times the standard quantum limit.
Combined vertically correlated InAs and GaAsSb quantum dots separated by triangular GaAsSb barrier
Authors: Hospodková A. , Oswald J. , Pangrác J. , Zíková M. , Kubištová J. , Komninou Ph , Kioseoglou J. , Kuldová K. , Hulicius E.
Published: November 2013

The aim of this work is to offer new possibilities for quantum dot (QD) band structure engineering, which can be used for the design of QD structures for optoelectronic and single photon applications. Two types of QDs, InAs and GaAsSb, are combined in self assembled vertically correlated QD structures. The first QD layer is formed by InAs QDs and the second by vertically correlated GaAsSb QDs. Combined QD layers are separated by a triangular GaAsSb barrier. The structure can be prepared as type-I, with both electrons and holes confined in InAs QDs, exhibiting a strong photoluminescence, or type-II, with electrons confined in InAs QDs and holes in GaAsSb QDs. The presence of the thin triangular GaAsSb barrier enables the realization of different quantum level alignment between correlated InAs and GaAsSb QDs, which can be adjusted by structure parameters as type-I or type-II like for ground and excited states separately. The position of holes in this type of structure is influenced by the presence of the triangular barrier or by the size and composition of the GaAsSb QDs. The electron-hole wavefunction overlap and the photoluminescence intensity alike can also be controlled by structure engineering.
An optimization method of relativistic backward wave oscillator using particle simulation and genetic algorithms
Authors: Chen Zaigao , Wang Jianguo , Wang Yue , Qiao Hailiang , Zhang Dianhui , Guo Weijie
Published: November 2013

Optimal design method of high-power microwave source using particle simulation and parallel genetic algorithms is presented in this paper. The output power, simulated by the fully electromagnetic particle simulation code UNIPIC, of the high-power microwave device is given as the fitness function, and the float-encoding genetic algorithms are used to optimize the high-power microwave devices. Using this method, we encode the heights of non-uniform slow wave structure in the relativistic backward wave oscillators (RBWO), and optimize the parameters on massively parallel processors. Simulation results demonstrate that we can obtain the optimal parameters of non-uniform slow wave structure in the RBWO, and the output microwave power enhances 52.6% after the device is optimized.
On the structure of guide magnetic field in the inertia-driven magnetic reconnection with the presence of shear flow
Authors: Hosseinpour M. , Mohammadi M. A.
Published: November 2013

The effect of equilibrium shear flow on the structure of out-of-plane magnetic field is analytically investigated in the two-fluid magnetohydrodynamic (MHD) regimes of the collisionless tearing instability, where the electron inertia breaks the frozen-in condition. Our scaling analysis reveals that the Alfvénic and sub-Alfvénic shear flows cannot significantly modify the linear regimes of applicability. In addition, we show that the structure of out-of-plane magnetic field can either be quadrupolar or non-quadrupolar in Hall-MHD regimes. In particular, both types of structures can dominate at β < 1 (β is the ratio of plasma kinetic pressure to the pressure in the magnetic field) depending on the value of the normalized ion inertial skin depth. This conclusion, however, is in contradiction to the claim presented by Rogers et al. [J. Geophys. Res. 108, A3 (2003)], which states that the quadrupolar structure cannot appear at β < 1. The reasons of this disagreement are discussed in our study.
Performance of phase change materials for heat storage thermoelectric harvesting
Authors: Kiziroglou M. E. , Elefsiniotis A. , Wright S. W. , Toh T. T. , Mitcheson P. D. , Becker Th. , Yeatman E. M.
Published: November 2013

Heat storage energy harvesting devices have promise as independent power sources for wireless aircraft sensors. These generate energy from the temperature variation in time during flight. Previously reported devices use the phase change of water for heat storage, hence restricting applicability to instances with ground temperature above 0 °C. Here, we examine the use of alternative phase change materials (PCMs). A recently introduced numerical model is extended to include phase change inhomogeneity, and a PCM characterization method is proposed. A prototype device is presented, and two cases with phase changes at approximately −9.5 °C and +9.5 °C are studied.
Photocarrier localization and recombination dynamics in Cu2ZnSnS4 single crystals
Authors: Quang Phuong Le , Okano Makoto , Yamada Yasuhiro , Nagaoka Akira , Yoshino Kenji , Kanemitsu Yoshihiko
Published: November 2013

We have studied the photocarrier localization and recombination dynamics in Cu2ZnSnS4 single crystals at room temperature. The band-gap energy and tail states below the band edge were evaluated by a combination of photoluminescence (PL), PL excitation, photocurrent, and femtosecond transient reflectivity spectroscopy. The photocarriers are rapidly localized to shallow tail states within a typical time constant of several picoseconds to a few tens of picoseconds. The sub-nanosecond PL decay dynamics indicate the importance of multiple carrier trapping processes in the shallow tail states. Therefore, it is concluded that the tail states dominate the optical responses of Cu2ZnSnS4 single crystals.
Thermal conductivity of Er+3:Y2O3 films grown by atomic layer deposition
Authors: Raeisi Fard Hafez , Becker Nicholas , Hess Andrew , Pashayi Kamyar , Proslier Thomas , Pellin Michael , Borca-Tasciuc Theodorian
Published: November 2013

Cross-plane thermal conductivity of 800, 458, and 110 nm erbium-doped crystalline yttria (Er+3:Y2O3) films deposited via atomic layer deposition was measured using the 3ω method at room temperature. Thermal conductivity results show 16-fold increase in thermal conductivity from 0.49 W m−1K−1 to 8 W m−1K−1 upon post deposition annealing, partially due to the suppression of the number of the -OH/H2O bonds in the films after annealing. Thermal conductivity of the annealed film was ∼70% lower than undoped bulk single crystal yttria. The cumulative interface thermal resistivity of substrate-Er+3:Y2O3-metal heater was determined to be ∼2.5 × 10−8 m2 K/W.
Coupling of channel conductance and gate-to-channel capacitance in electric double layer transistors
Authors: Liu Feilong , Xie Wei , Shi Sha , Daniel Frisbie C. , Paul Ruden P.
Published: November 2013

Electric double layer transistors (EDLTs) have unique impedance properties. As the transport of charge in the semiconductor and of ions in the electrolyte involve different time scales, the gate-to-channel equivalent capacitance changes dramatically with frequency. An important feature is the coupling between the capacitance and the channel conductance in the frequency range of interest due to the relatively large time constant of the charging process. This paper presents a systematic study of these EDLT properties. An equivalent-circuit model is proposed that provides reasonable physical explanations and shows good agreement with the experimental results.
Electroluminescence efficiencies of erbium in silicon-based hosts
Authors: Cueff Sébastien , Manel Ramírez Joan , Kurvits Jonathan A. , Berencén Yonder , Zia Rashid , Garrido Blas , Rizk Richard , Labbé Christophe
Published: November 2013

We report on room-temperature 1.5 μm electroluminescence from trivalent erbium (Er3+) ions embedded in three different CMOS-compatible silicon-based hosts: SiO2, Si3N4, and SiNx. We show that although the insertion of either nitrogen or excess silicon helps enhance electrical conduction and reduce the onset voltage for electroluminescence, it drastically decreases the external quantum efficiency of Er3+ ions from 2% in SiO2 to 0.001% and 0.0004% in SiNx and Si3N4, respectively. Furthermore, we present strong evidence that hot carrier injection is significantly more efficient than defect-assisted conduction for the electrical excitation of Er3+ ions. These results suggest strategies to optimize the engineering of on-chip electrically excited silicon-based nanophotonic light sources.
Large sensitivity enhancement in semiconducting organic field effect transistor sensors through incorporation of ultra-fine platinum nanoparticles
Authors: Zheng Haisheng , Ramalingam Balavinayagam , Korampally Venumadhav , Gangopadhyay Shubhra
Published: November 2013

We report remarkable improvement in sensitivity of pentacene-based field effect transistor devices towards trace nitro-aromatic explosive vapors through the incorporation of high density, sub-2 nm platinum nanoparticles (NPs) within these structures. Exploiting the unique electronic properties of these NPs, we have demonstrated a detection limit of 56.6 parts per billion of 2,4-dinitrotoluene (DNT) vapor while control samples without any embedded NPs showed no observable sensitivity to DNT vapor. We attribute this remarkable enhancement in sensitivity to the ability of these NPs to function as discrete nodes, participating in the charge transfer with adsorbed nitro-aromatic molecules.
Porous silicon nanoparticles as sensitizers for ultrasonic hyperthermia
Authors: Sviridov A. P. , Andreev V. G. , Ivanova E. M. , Osminkina L. A. , Tamarov K. P. , Timoshenko V. Yu.
Published: November 2013

Aqueous suspensions of porous silicon nanoparticles (NPs) with average size ∼100 nm and concentration ∼1 g/L undergo significant heating as compared with pure water under therapeutic ultrasonic (US) irradiation with frequencies of 1–2.5 MHz and intensities of 1–20 W/cm2. This effect is explained by taking into account the efficient absorption of US energy by NPs. The observed US-induced heating of biodegradable NPs is promising for applications in ultrasonic hyperthermia of tumors.
Dual-phase self-biased magnetoelectric energy harvester
Authors: Zhou Yuan , Apo Daniel J. , Priya Shashank
Published: November 2013

We report a magnetoelectric energy harvester structure that can simultaneously scavenge magnetic and vibration energy in the absence of DC magnetic field. The structure consisted of a piezoelectric macro-fiber composite bonded to a Ni cantilever. Large magnetoelectric coefficient ∼50 V/cm Oe and power density ∼4.5 mW/cm3 (1 g acceleration) were observed at the resonance frequency. An additive effect was realized when the harvester operated under dual-phase mode. The increase in voltage output at the first three resonance frequencies under dual-phase mode was found to be 2.4%, 35.5%, and 360.7%. These results present significant advancement toward high energy density multimode energy harvesting system.
Modelling transport in nanoparticle organic solar cells using Monte Carlo methods
Authors: Feron K. , Ulum S. , Holmes N. P. , Kilcoyne A. L. D. , Belcher W. J. , Zhou X. , Fell C. J. , Dastoor P. C.
Published: November 2013

Water-based nanoparticle (NP) organic solar cells eliminate the need for harmful organic solvents during deposition. However, the core-shell NP structure should limit charge extraction resulting in poor performance. Here, we use dynamic Monte Carlo modelling to show that for optimised NP structures the core-shell character does not severely limit performance. Simulations further reveal that small NPs are more susceptible to extensive phase segregation, which diminishes charge carrier percolation pathways from the cores to the electrodes and thus inhibits charge extraction. Simulated performance behaviour was used to propose an explanation for the experimentally observed change in performance due to annealing.
Magnetic phase transition and magnetocaloric effect in Dy12Co7 compound
Authors: Dong Q. Y. , Chen J. , Zhang X. Q. , Zheng X. Q. , Sun J. R. , Shen B. G.
Published: November 2013

Magnetic and magnetocaloric properties of Dy12Co7 compound have been investigated by magnetization measurements. Its magnetization does not reach saturation even for 7 T at 2 K due to the crystalline field effect. Dy12Co7 undergoes a ferromagnetic-paramagnetic phase transition around Curie temperature TC = 64 K. The thermomagnetic irreversibility between the zero-field-cooling and field-cooling curves is detected below TC in low magnetic field, and it is attributed to the narrow domain wall pinning effect. Large magnetic entropy change of 10.0 J kg−1 K−1 and refrigerant capacity of 299 J kg−1 for a magnetic field change of 0–5 T are found around TC, resulting from the large change of magnetization during the magnetic phase transition. The nature of second-order phase transition for Dy12Co7 induces the complete reversibility of magnetic entropy change around TC, which is very favourable for the application of magnetic refrigeration.
Energy loss rate of a charged particle in HgTe/(HgTe, CdTe) quantum wells
Authors: Chen Qinjun , Sin Ang Yee , Wang Xiaolin , Lewis R. A. , Zhang Chao
Published: November 2013

The energy loss rate (ELR) of a charged particle in a HgTe/(HgTe, CdTe) quantum well is investigated. We consider scattering of a charged particle by the bulk insulating states in this type of topological insulator. It is found that the ELR characteristics due to the intraband excitation have a linear energy dependence while those due to interband excitation depend on the energy exponentially. An interesting quantitative result is that for a large range of the incident energy, the mean inelastic scattering rate is around a few terahertz.
A microfluidic chip for controlled release of drugs from microcapsules
Authors: Cheng Wen-Chuan , He Yuan , Chang An-Yi , Que Long
Published: November 2013

A new microfluidic device with liquid-droplet merging and droplet storage functions for the controlled release of drugs from microcapsules is reported. A switching channel is designed and integrated within the microfluidic device, facilitating the generation and capturing of uniform droplets by the storage chambers. The drug model is the MnCO3 microparticle, which is encapsulated by a microcapsule and fabricated using a simple layer-by-layer nanoassembly process. The merging function is used for dynamically adding the control solution into the droplets, which contain drugs within the microcapsules (DWμCs) and water. The storage chambers are used for collecting DWμCs-laden droplets so that the controlled-drug release in specific droplets can be monitored for an extended period of time, which has been experimentally implemented successfully. This technology could offer a promising technical platform for the long-term observation and studies of drug effects on specific cells in a controlled manner, which is especially useful for single cell analysis.
The Movement Advantage in Famous and Unfamiliar Faces: A Comparison of Point-Light Displays and Shape-Normalised Avatar Stimuli
Authors: Bennetts Rachel J , Kim Jeesun , Burke Darren , Brooks Kevin R , Lucey Simon , Saragih Jason , Robbins Rachel A
Published: November 2013

Facial movement may provide cues to identity, by supporting the extraction of face shape information via structure-from-motion, or via characteristic patterns of movement. Currently, it is unclear whether familiar and unfamiliar faces derive the same benefit from these mechanisms. This study examined the movement advantage by asking participants to match moving and static images of famous and unfamiliar faces to facial point-light displays (PLDs) or shape-normalised avatars in a same/different task (experiment 1). In experiment 2 we also used a same/different task, but participants matched from PLD to PLD or from avatar to avatar. In both experiments, unfamiliar face matching was more accurate for PLDs than for avatars, but there was no effect of stimulus type on famous faces. In experiment 1, there was no movement advantage, but in experiment 2, there was a significant movement advantage for famous and unfamiliar faces. There was no evidence that familiarity increased the movement advantage. For unfamiliar faces, results suggest that participants were relying on characteristic movement patterns to match the faces, and did not derive any extra benefit from the structure-from-motion cues in the PLDs. The results indicate that participants may use static and movement-based cues in a flexible manner when matching famous and unfamiliar faces.
A Cue-Free Method to Probe Human Lighting Biases
Authors: Mazzilli Giacomo , Schofield Andrew J
Published: November 2013

People readily perceive patterns of shading as 3-D shapes. Owing to the generalised bas-relief ambiguity when extracting shape from shading, people must simultaneously estimate the shape of the surface and the nature of the light source. In many cases cues in the image will be insufficient to resolve all of the ambiguities present, and in such cases the human visual system may employ one of a number of prior assumptions based on ecology and experience. One such assumption is the lighting-from-above prior. Here, in the absence of extrinsic cues to lighting direction, ambiguous shading patterns are interpreted as if lit by a light source that is above the observer's head. Studies of this prior typically use ambiguous stimuli and observe perceptual biases. A degree of cueing is inherent to such methods. Participants see the shaded stimuli repeatedly and are asked to make shape judgments about them regardless of whether or not they actually perceive any 3-D shape. We wanted to access people's lighting prior more directly by establishing the template they would employ to detect a shaded object in the absence of any visual cue to object shape. To this end, we adopted a classification image approach.
Can Looking at a Hand Make Your Skin Crawl? Peering into the Uncanny Valley for Hands
Authors: Poliakoff Ellen , Beach Natalie , Best Rebecca , Howard Toby , Gowen Emma
Published: November 2013

It is postulated that there is an uncanny valley, whereby human-like stimuli such as robots or animated characters that fall short of being fully human are perceived as eerie or unsettling. Previous research has explored the existence of this effect for faces and whole bodies, while here we explore responses to photographs of real and artificial hands. In keeping with the notion of an uncanny valley, prosthetic hands that were of intermediate human-likeness were given the highest ratings of eeriness. However, within the categories of hands, ratings of eeriness reduced as human-likeness increased, suggesting a more complex pattern. Further investigation of this effect will be of relevance to the design of prosthetic limbs and could be used to test theories of the uncanny valley and social perception with simple stimuli.
Follicle size and reproductive hormone profiles during a post-weaning altrenogest treatment in primiparous sows
Authors: van Leeuwen J. J. J. , Martens M. R. T. M. , Jourquin J. , Driancourt M. A. , Wagner A. , Kemp B. , Soede N. M.
Published: November 2013

This study investigated the endocrine background of follicle size changes during post-weaning altrenogest treatment. altrenogest-treated sows received a 20-mg dosage daily at 8.00 a.m. from Day –1 to Day 14 after weaning. On Day –1, only 3/13 altrenogest-treated sows showed LH pulses compared with 8/8 control sows (P = 0.001). On Day 0, control sows showed a typical high frequency–low amplitude LH pattern, indicative for recruitment of oestrogenic follicles. In altrenogest-treated animals on Day 0, half of the sows showed high frequency–high amplitude pulses from 4–5 h after weaning. In altrenogest-treated sows, average follicle size increased from 3.1 ± 0.5 mm on Day 0 to 4.4 ± 0.6 mm on Day 5, then decreased to 3.7 ± 0.5 mm on Day 7 and stabilised thereafter. FSH and oestradiol (E2) concentrations showed a distinct diurnal pattern; high at 7.00 a.m. and low at 3.00 p.m. E2 concentrations (7.00 a.m.) showed a 2.5-fold increase from Day –1 to Day 2, and subsequently a 2-fold decline to reach a plateau at Day 8. FSH concentrations reached maximum levels by Day 5 and slowly declined afterwards. In conclusion, once-daily administration of altrenogest starting one day before weaning delays the weaning-induced increase in LH pulses. Although FSH and follicle size increase until Day 5 after weaning, follicle E2 production already decreased from Day 2 after weaning. Post-weaning altrenogest treatment thus results in a follicular wave of follicles that lose oestrogenic competence at Day 2 after weaning, presumably related to the changed LH dynamics during altrenogest treatment.
Nocturnal distance sampling of a Mediterranean population of fallow deer is consistent with population projections
Authors: Focardi Stefano , Franzetti Barbara , Ronchi Francesca
Published: November 2013

Context Precise and accurate methods are essential to assess wildlife populations for sound management. We surveyed a managed population of fallow deer (Dama dama) in a Mediterranean environment in Italy, where this non-native ungulate has a negative impact on biodiversity. Aims We compare nocturnal distance-sampling (deer are detected by thermal imagery at night) population estimates with demographic projections of the same population. Methods We estimated natural survival in fawns (0.86), yearlings (0.83), adult males (0.70) and adult females (0.90) using capture–mark–recapture. By integrating survival estimates with population structure, reproductive traits and harvest data, we performed demographic projections. We performed nocturnal distance sampling on foot by using a thermal imagery once a year (in autumn) from 2001 to 2005. We walked 75–77 km (71 transects) per each survey. Key results We showed that our survey design met distance-sampling assumptions. Distance sampling and demographic projections yielded similar and precise (12.6% < CV <24.1%) population estimates, showing a decreasing (–164.64 deer year–1) population trend from 2755 deer in 2001 to 1877 in 2005. Conclusions We showed that nocturnal distance sampling is useful to monitor wild deer populations in forests effectively and that it represents a cost-effective tool to develop sounded management policy for this non-native species. We also provided, for the first time, a comprehensive stochastic population model for fallow deer in a Mediterranean environment. Using these population estimates, managers could reduce fallow deer population size to a level compatible with the conservation of the endangered Italian roe deer and improve forest regeneration. Implications Nocturnal distance sampling can be used to assess ungulate population living in dense forested habitats effectively and efficiently.
Syntaxin binding mechanism and disease-causing mutations in Munc18-2
Authors: Hackmann Yvonne , Graham Stephen C. , Ehl Stephan , Höning Stefan , Lehmberg Kai , Aricò Maurizio , Owen David J. , Griffiths Gillian M.
Published: November 2013

Significance

Understanding the molecular mechanisms that control secretion from cytotoxic T lymphocytes (CTL) and natural killer (NK) cells is the key for understanding how these cells destroy virally infected and tumourigenic cells. Precisely how mutations in Munc18-2 and syntaxin 11 (Stx11) give rise to loss of CTL and NK function and severe immunodeficiency is poorly understood. In this study we present a crystal structure of human Munc18-2 and analyze the disease-causing mutations. Our findings reveal a mechanism that allows Munc18-2 to selectively bind Stx11 and identify potential surrogate binding partners, which could restore Munc18-Stx function upon IL-2 activation.
Recruitment of TLR adapter TRIF to TLR4 signaling complex is mediated by the second helical region of TRIF TIR domain
Authors: Piao Wenji , Ru Lisa W. , Piepenbrink Kurt H. , Sundberg Eric J. , Vogel Stefanie N. , Toshchakov Vladimir Y.
Published: November 2013

Significance

This study sheds light on the mechanisms of Toll-like receptor 4 (TLR4) signaling complex assembly. Particularly, the interaction site that mediates Toll/IL-1R resistance (TIR) domain–containing adapter-inducing IFN-β (TRIF) recruitment to the TLR4 signaling complex is identified within the second helical region of the TRIF TIR domain. This finding is significant because “a mimic” of this site potently inhibits TLR4 signaling in cells by a competitive mechanism and decreases LPS-induced mortality in mice by more than 80%.
Regional variability of imaging biomarkers in autosomal dominant Alzheimer’s disease
Authors: Benzinger Tammie L. S. , Blazey Tyler , Jack Clifford R. , Koeppe Robert A. , Su Yi , Xiong Chengjie , Raichle Marcus E. , Snyder Abraham Z. , Ances Beau M. , Bateman Randall J. , Cairns Nigel J. , Fagan Anne M. , Goate Alison , Marcus Daniel S. , Aisen Paul S. , Christensen Jon J. , Ercole Lindsay , Hornbeck Russ C. , Farrar Angela M. , Aldea Patricia , Jasielec Mateusz S. , Owen Christopher J. , Xie Xianyun , Mayeux Richard , Brickman Adam , McDade Eric , Klunk William , Mathis Chester A. , Ringman John , Thompson Paul M. , Ghetti Bernardino , Saykin Andrew J. , Sperling Reisa A. , Johnson Keith A. , Salloway Stephen , Correia Stephen , Schofield Peter R. , Masters Colin L. , Rowe Christopher , Villemagne Victor L. , Martins Ralph , Ourselin Sebastien , Rossor Martin N. , Fox Nick C. , Cash David M. , Weiner Michael W. , Holtzman David M. , Buckles Virginia D. , Moulder Krista , Morris John C.
Published: November 2013

Significance

Beta-amyloid plaque accumulation, glucose hypometabolism, and neuronal atrophy are hallmarks of Alzheimer’s disease. However, the regional ordering of these biomarkers prior to dementia remains untested. In a cohort with Alzheimer’s disease mutations, we performed an integrated whole-brain analysis of three major imaging techniques: amyloid PET, [
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F]fluro-deoxyglucose PET, and structural MRI. We found that most gray-matter structures with amyloid plaques later have hypometabolism followed by atrophy. Critically, however, not all regions lose metabolic function, and not all regions atrophy, even when there is significant amyloid deposition. These regional disparities have important implications for clinical trials of disease-modifying therapies.