bluuebunny/crossref_metadata_2025 huggingface dataset:
Designing a square invisibility cloak using metamaterials made of stacked positive-negative index slabs
Authors: Zhu Guanghao
Published: April 2013

We present a design of a square invisibility cloak based on triangular transformations. In triangular transformations, certain areas of the cloak are squeezed to be infinitesimal in the virtual space. This results in cloak materials whose constitutive parameters are singular. We show rigorously that these prescribed singular materials can be emulated by metamaterials made of stacked positive-negative index slabs. We use numerical simulations to demonstrate the conceived square cloak, which in principle can be constructed using only homogenous and non-singular materials. The proposed square invisibility cloak suggests another important application of negative index media.
Spectroscopic ellipsometry and multiphonon Raman spectroscopic study of excitonic effects in ZnO films
Authors: Singh Chaman , Rath Shyama
Published: April 2013

The optical properties and room temperature excitonic features of rf-sputtered ZnO films on Si substrates are studied using spectroscopic ellipsometry and multiphonon Raman scattering. The complex dielectric function ε(E) = ε1(E) + iε2(E) in the spectral region of 1.3 to 5.5 eV is measured using variable-angle spectroscopic ellipsometry and a Tauc-Lorentz multi-oscillator model is employed to fit the lineshape of the dielectric function. The values of the refractive index of the as-deposited and annealed samples are obtained. Excitonic features in the dielectric function are observed after thermal annealing of the films. Multiphonon Raman spectra up to 7 orders of the longitudinal-optic phonon mode are observed. The matching of the outgoing resonance condition with the exciton energy indicates a strong exciton-phonon coupling. The shape of the dielectric function as well as the intensities and widths of the multiphonon lines suggest the role of both discrete and continuum excitons in describing the optical properties. The observation of excitonic features and the values of the refractive index suggest the high optical quality of the films.
Electron beam physical vapor deposition of thin ruby films for remote temperature sensing
Authors: Li Wei , Coppens Zachary J. , Greg Walker D. , Valentine Jason G.
Published: April 2013

Thermographic phosphors (TGPs) possessing temperature-dependent photoluminescence properties have a wide range of uses in thermometry due to their remote access and large temperature sensitivity range. However, in most cases, phosphors are synthesized in powder form, which prevents their use in high resolution micro and nanoscale thermal microscopy. In the present study, we investigate the use of electron beam physical vapor deposition to fabricate thin films of chromium-doped aluminum oxide (Cr-Al2O3, ruby) thermographic phosphors. Although as-deposited films were amorphous and exhibited weak photoluminescence, the films regained the stoichiometry and α-Al2O3 crystal structure of the combustion synthesized source powder after thermal annealing. As a consequence, the annealed films exhibit both strong photoluminescence and a temperature-dependent lifetime that decreases from 2.9 ms at 298 K to 2.1 ms at 370 K. Ruby films were also deposited on multiple substrates. To ensure a continuous film with smooth surface morphology and strong photoluminescence, we use a sapphire substrate, which is thermal expansion coefficient and lattice matched to the film. These thin ruby films can potentially be used as remote temperature sensors for probing the local temperatures of micro and nanoscale structures.
Reentrant cluster glass behavior in La2CoMnO6 nanoparticles
Authors: Krishna Murthy J. , Venimadhav A.
Published: April 2013

Magnetic study on La2CoMnO6 nanoparticles revealed multiple magnetic transitions at 218 K, 135 K, and below 38 K and the nature of the low temperature transition was unclear [J. K. Murthy and A. Venimadhav, J. Appl. Phys. 111, 024102 (2012)]. Presence of mixed valence states of Co and Mn has been confirmed from the X-ray photoelectron spectroscopy measurement and its presence along with antisite disorder affects in reducing the saturation magnetization of the nanoparticles. The zero-field-cooled and field-cooled bifurcation in dc magnetization, relaxation in zero-field-cooled magnetization, and large enhancement in coercive field below the glassy temperature have been discussed. Frequency dependence of ac susceptibility using power law has revealed cluster glass behaviour. Further, the dc field superimposed on ac susceptibility and absence of memory effect in ac susceptibility have suggested the existence of non-interacting clusters comprising of competing interactions below 38 K. Competing magnetic interactions due to the presence of mixed valences and antisite disorder found to establish a reentered cluster glassy state in the nanoparticles.
Deep-ultraviolet tailored- and low-refractive index antireflection coatings for light-extraction enhancement of light emitting diodes
Authors: Yan Xing , Shatalov Max , Saxena Tanuj , Shur Michael S.
Published: April 2013

An omnidirectional antireflection (AR) coating for a deep-ultraviolet (UV) AR band is designed and fabricated on the sapphire substrate of a deep-UV flip-chip light-emitting diode (LED) device. The two-layer AR coating uses the tailored- and low-refractive index nanoporous alumina fabricated by glancing-angle deposition methodology. The AR coating effectively matches the refractive indices between the air and sapphire substrate. At close-to-normal angles of incidence, this AR coating almost completely eliminates the Fresnel reflection at the sapphire/air interface of the deep-UV LED device. The resulting improvement of the light-extraction efficiency by 8% is in good agreement with the simulation results. For a total thickness of 172 nm for the two-layer AR coating, extinction was negligible (<2%). The results show that nanoporous alumina thin films are excellent tailored- and low-refractive index thin film materials for high-performance deep-UV AR coating applications.
Relaxor ferro- and paraelectricity in anisotropically strained SrTiO3 films
Authors: Wördenweber R. , Schubert J. , Ehlig T. , Hollmann E.
Published: April 2013

The ferroelectric properties of anisotropically strained SrTiO3 films are analyzed by detailed measurements of the complex dielectric constant as function of temperature, frequency, bias voltage, and electric field direction. At low temperatures, strain induces a relaxor-ferroelectric phase that persists up to room temperature. The transition temperature and characteristic parameters (e.g., Curie temperature, static freezing temperature, degree of diffuseness of the phase transition, activation energy) of the relaxor phase depend strongly on the orientation of the electric field and, therefore, on the amount of structural strain in the given electric field direction. Also above the ferroelectric transition temperature, a relaxation of the permittivity is visible, i.e., the strain causes a relaxor-paraelectric behavior. Only at high enough temperatures, the relaxation time constant tends to zero and the “classical” dielectric state is obtained. Frequency and time dependent relaxation experiments demonstrate an extremely large distribution of the relaxation rates in both relaxor states (ferroelectric and paraelectric), which is indicative for the large distribution in the mobility of polar SrTiO3 regions with randomly distributed directions of dipole moments in the film. The large distribution might be taken as an indication for a large distribution in size and orientation of nanosize domains in the anisotropically strained SrTiO3 film.
Efficient parametric excitation of silicon-on-insulator microcantilever beams by fringing electrostatic fields
Authors: Linzon Yoav , Ilic Bojan , Lulinsky Stella , Krylov Slava
Published: April 2013

Large amplitude flexural vibrations have been excited in single layer silicon-on-insulator micromechanical cantilever beams in ambient air environment. Our driving approach relies on a single co-planar electrode located symmetrically around the actuated grounded cantilever. Electrostatic forces are created via tailored asymmetries in the fringing fields of deformed mechanical states during their electric actuation, with strong restoring forces acting in a direction opposite to the deflection. This results in an effective increase in the structure stiffness in its elastic regime. The devices had been fabricated using deep reactive ion etching based process and their responses were characterized in a laser Doppler vibrometer under ambient conditions. Harmonic voltages applied to the electrode result in the periodic modulation of the effective stiffness and lead to strong parametric excitation of the structure. As opposed to close gap actuators, where high-amplitude drives are severely limited by pull-in instabilities, squeezed gas damping, and stiction, our resonators exhibit very large vibration amplitudes (up to 8 in terms of the amplitude to thickness ratio in the strong parametric regime), with no apparent damage, via the application of highly tunable distributed forces. A reduced order model, based on the Galerkin decomposition, captures the main dynamical features of the system, and is consistent with the observed beam characteristics.
Infrared dielectric anisotropy and phonon modes of rutile TiO2
Authors: Schöche S. , Hofmann T. , Korlacki R. , Tiwald T. E. , Schubert M.
Published: April 2013

Spectroscopic ellipsometry in the mid-infrared and far-infrared spectral range and generalized ellipsometry in the mid-infrared spectral range are used to investigate the anisotropic dielectric response of rutile TiO2. The ordinary and extraordinary dielectric function tensor components and all infrared active phonon mode parameters of single crystalline rutile TiO2 are determined with high accuracy for wavelengths from 3 μm to 83 μm. The data were acquired from samples of (001), (100), and (111) surfaces cut from bulk single crystals. A factorized model dielectric function is employed in order to determine the frequencies and damping parameters of the transverse and longitudinal phonon modes with A2u and Eu symmetries. The bands of total reflection of s- and p-polarized light in dependence of the angle of incidence for highly symmetric sample cuts and orientations are derived. Excellent agreement with phonon modes reported in literature is obtained. Introduction of two additional modes for ordinary as well as extraordinary component of the dielectric function tensor was necessary to most accurately match the experimental data. The spectral position of the additional modes is compared to the calculated phonon density of states. The low-frequency dielectric constants are calculated from the determined phonon mode parameters and the high-frequency dielectric constants by applying the Lyddanne-Sachs-Teller relation. The presented data revise existing infrared optical function data and will be suitable for interpretation of any kind of infrared spectra for bulk TiO2 single crystal substrates, thin films, and TiO2 nanostructures.
Efficient parametric amplification in micro-resonators with integrated piezoelectric actuation and sensing capabilities
Authors: Thomas O. , Mathieu F. , Mansfield W. , Huang C. , Trolier-McKinstry S. , Nicu L.
Published: April 2013

We report, in this work, on unprecedented levels of parametric amplification in microelectromechanical resonators, operated in air, with integrated piezoelectric actuation and sensing capabilities. The method relies on an analytical/numerical understanding of the influence of geometrical nonlinearities inherent to the bridge-like configuration of the resonators. We provide analytical formulae to predict the performances of the parametric amplifier below the nonlinearity threshold, in terms of gain and quality factor (Q) enhancement. The analysis explains how to overcome this nonlinearity threshold by controlling the drive signals. It predicts that in theory, any Q-factor enhancement can be achieved. Experimental validation demonstrates a Q-factor enhancement by up to a factor 14 in air.
Identifying low-dimensional dynamics in type-I edge-localised-mode processes in JET plasmas
Authors: Calderon F. A. , Dendy R. O. , Chapman S. C. , Webster A. J. , Alper B. , Nicol R. M. ,   JET EFDA Contributors
Published: April 2013

Edge localised mode (ELM) measurements from reproducibly similar plasmas in the Joint European Torus (JET) tokamak, which differ only in their gas puffing rate, are analysed in terms of the pattern in the sequence of inter-ELM time intervals. It is found that the category of ELM defined empirically as type I—typically more regular, less frequent, and having larger amplitude than other ELM types—embraces substantially different ELMing processes. By quantifying the structure in the sequence of inter-ELM time intervals using delay time plots, we reveal transitions between distinct phase space dynamics, implying transitions between distinct underlying physical processes. The control parameter for these transitions between these different ELMing processes is the gas puffing rate.
Enhanced nucleate boiling on horizontal hydrophobic-hydrophilic carbon nanotube coatings
Authors: Dai Xianming , Huang Xinyu , Yang Fanghao , Li Xiaodong , Sightler Joshua , Yang Yingchao , Li Chen
Published: April 2013

Ideal hydrophobic-hydrophilic composite cavities are highly desired to enhance nucleate boiling. However, it is challenging and costly to fabricate these types of cavities by conventional micro/nano fabrication techniques. In this study, a type of hydrophobic-hydrophilic composite interfaces were synthesized from functionalized multiwall carbon nanotubes by introducing hydrophilic functional groups on the pristine multiwall carbon nanotubes. This type of carbon nanotube enabled hydrophobic-hydrophilic composite interfaces were systematically characterized. Ideal cavities created by the interfaces were experimentally demonstrated to be the primary reason to substantially enhance nucleate boiling.
Mechanism behind self-sustained oscillations in direct current glow discharges and dusty plasmas
Authors: Nae Cho Sung
Published: April 2013

An alternative explanation to the mechanism behind self-sustained oscillations of ions in direct current (DC) glow discharges is provided. Such description is distinguished from the one provided by the fluid models, where oscillations are attributed to the positive feedback mechanism associated with photoionization of particles and photoemission of electrons from the cathode. Here, oscillations arise as consequence of interaction between an ion and the surface charges induced by it at the bounding electrodes. Such mechanism provides an elegant explanation to why self-sustained oscillations occur only in the negative resistance region of the voltage-current characteristic curve in the DC glow discharges. Furthermore, this alternative description provides an elegant explanation to the formation of plasma fireballs in the laboratory plasma. It has been found that oscillation frequencies increase with ion's surface charge density, but at the rate which is significantly slower than it does with the electric field. The presented mechanism also describes self-sustained oscillations of ions in dusty plasmas, which demonstrates that self-sustained oscillations in dusty plasmas and DC glow discharges involve common physical processes.
Effects of sodium incorporation in Co-evaporated Cu2ZnSnSe4 thin-film solar cells
Authors: Li Jian V. , Kuciauskas Darius , Young Matthew R. , Repins Ingrid L.
Published: April 2013

Sodium incorporation into Cu2ZnSnSe4 (CZTSe) substantially improves the device efficiency by enhancing the open-circuit voltage (VOC) and fill factor. Sodium increases hole density, makes the acceptor shallower, shifts the Fermi level lower, and leads to higher built-in voltage and, consequently, higher VOC. Sodium reduces the concentration of certain deep recombination centers, which further benefits VOC. The increase of hole density and mobility enhances the CZTSe conductivity leading to higher fill factor. Sodium causes smaller depletion width, hence, lower short-circuit current. The minority-carrier lifetime decreases slightly after sodium is incorporated via the Mo-coated soda-lime glass, although adding NaF provides some amelioration.
In-plane anisotropy control of the magnetic vortex gyrotropic mode
Authors: Roy P. E.
Published: April 2013

The effect of an in-plane induced uniaxial anisotropy on the magnetic vortex gyrotropic frequency is investigated by micromagnetic simulations, exemplified by the inverse magnetostriction in a uniaxially stressed circular dot. It is found that the gyrotropic frequency decreases with increasing magnitude of the induced uniaxial anisotropy. The results are analyzed by extracting the restoring forces from the vortex dynamical potential-well. The dominant contribution to the decreasing trend in frequency is found to be due to a softening of both the restoring force spring constants. This work offers an alternative method to control the gyrotropic frequency of a magnetic vortex.
Communication: Calibration of a strong-correlation density functional on transition-metal atoms
Authors: Becke Axel D.
Published: April 2013

In recent work [A. D. Becke, J. Chem. Phys. 138, 074109 (2013)10.1063/1.4790598], a suite of density functionals for static, dynamical, and strong correlation was introduced. The strong-correlation part is intended to describe dissociating chemical systems using symmetry-restricted orbitals, and was calibrated on spin- and spatially-symmetrized open-shell atoms of the first and second rows. This Communication extends the calibration of our functionals to transition-metal atoms by including all open-shell atoms through the third row. We find that the theory works well for transition-metal atoms also. The new concomitant parametrization will be applied to problems of chemical interest in upcoming work.
Analysis of rich inelastic electron tunneling spectra: Case study of terthiophene on Au(111)
Authors: Koslowski B. , Maurer N. , Stocker M. , Chulkov S. K. , Benoit D. M. , Ziemann P.
Published: April 2013

Even moderately small molecules like 2,2′:5′,2″-terthiophene exhibit quite rich vibrational spectra. Detection and assignment of vibronic transitions of such a single adsorbed molecule in inelastic electron tunneling spectroscopy (IETS) using scanning tunneling microscopy are notoriously hampered by noise and the low efficiency of inelastic channels of typically well below 1%. We demonstrate by a thorough statistical analysis that detection of almost all predicted transitions can be determined experimentally within the energy range 0–120 meV with an estimated detection limit for the efficiency of inelastic channels of ∼0.15%. The maximum accuracy of our transition energies is 2 meV and thus smaller than the thermal broadening at 5 K. On short time scales up to some hours, that accuracy appears to be limited by tunneling current noise. The present analysis confirms earlier results which showed that IETS obeys propensity rules rather than selection rules as observed for optical transitions. Furthermore, the previous indications that anharmonic components in the interaction potentials are important for calculating properties of molecular vibrations were corroborated.
Infrared nanosecond laser-metal ablation in atmosphere: Initial plasma during laser pulse and further expansion
Authors: Wu Jian , Wei Wenfu , Li Xingwen , Jia Shenli , Qiu Aici
Published: April 2013

We have investigated the dynamics of the nanosecond laser ablated plasma within and after the laser pulse irradiation using fast photography. A 1064 nm, 15 ns laser beam was focused onto a target made from various materials with an energy density in the order of J/mm2 in atmosphere. The plasma dynamics during the nanosecond laser pulse were observed, which could be divided into three stages: fast expansion, division into the primary plasma and the front plasma, and stagnation. After the laser terminated, a critical moment when the primary plasma expansion transited from the shock model to the drag model was resolved, and this phenomenon could be understood in terms of interactions between the primary and the front plasmas.
Polarization-sensitive microelectromechanical systems based tunable terahertz metamaterials using three dimensional electric split-ring resonator arrays
Authors: Ma Fusheng , Qian You , Lin Yu-Sheng , Liu Hongwei , Zhang Xinhai , Liu Zhen , Ming-Lin Tsai Julius , Lee Chengkuo
Published: April 2013

We present the design, simulation, fabrication, and characterization of structurally reconfigurable metamaterials showing terahertz frequency tunability with a polarization-sensitivity. The proposed metamaterial structures employ deformable microelectromechanical system based curved cantilevers for tuning the resonance frequency of the electric split-ring resonators. The resonance frequency is observed to be either tunable or non-tunable with the electric field of the incident wave, which is perpendicular or parallel to the split gap of the electric split-ring resonators. This polarization-sensitive characteristic has been demonstrated by both the electromagnetic simulation and the experimental measurement. The observed polarization-sensitive tunability could be used for the development of polarization sensitive and insensitive THz polarimetric devices.
Domain structure and magnetization of the permalloy/niobium bilayers
Authors: Uspenskaya L. S. , Tikhomirov O. A. , Bozhko S. I. , Egorov S. V. , Chugunov A. A.
Published: April 2013

Domain structure and kinetics of the magnetization reversal in the Py/Nb bilayers grown with lift-off lithography have been studied using visualization by magneto-optical indicator film technique. Various types of domain walls and switching behavior are observed depending both on film and substrate thickness. The observed transformations of the domain structure are in agreement with the model, which takes into account effective surface anisotropy governed by surface roughness, while influence of the misfit-induced elastic strain is found to be negligible.
Electromagnetically induced transparency of charge pumping in a triple-quantum-dots with Λ-type level structure
Authors: Guan Chun , Xing Yunhui , Zhang Chao , Ma Zhongshui
Published: April 2013

We demonstrate an electromagnetically induced electron transparency (EIET) in electron transport through a coupled triple-quantum-dots system under two radiation fields. The direct evidence of EIET is that an electron can travel from the left dot to the right dot without any effect from the center dot. The EIET (position, height, and symmetry) can be tuned by several controllable parameters of the radiation fields, such as the Rabi frequencies and detuning frequencies. The result offers a resonant transport tuning technique using radiation fields.
p-channel thin-film transistors based on spray-coated Cu2O films
Authors: Pattanasattayavong Pichaya , Thomas Stuart , Adamopoulos George , McLachlan Martyn A. , Anthopoulos Thomas D.
Published: April 2013

Thin films of cuprous oxide (Cu2O) were grown using solution-based spray pyrolysis in ambient air and incorporated into hole-transporting thin-film transistors. The phase of the oxide was confirmed by X-ray diffraction measurements while the optical band gap of the films was determined to be ∼2.57 eV from optical transmission measurements. Electrical characterization of Cu2O films was performed using bottom-gate, bottom-contact transistors based on SiO2 gate dielectric and gold source-drain electrodes. As-prepared devices show clear p-channel operation with field-effect hole mobilities in the range of 10−4–10−3 cm2 V−1 s−1 with some devices exhibiting values close to 1 × 10−2 cm2 V−1 s−1.
Switchable Schottky diode characteristics induced by electroforming process in Mn-doped ZnO thin films
Authors: Nam Yoonseung , Hwang Inrok , Oh Sungtaek , Lee Sangik , Lee Keundong , Hong Sahwan , Kim Jinsoo , Choi Taekjib , Ho Park Bae
Published: April 2013

We investigated the asymmetric current-voltage (I-V) characteristics and accompanying unipolar resistive switching of pure ZnO and Mn(1%)-doped ZnO (Mn:ZnO) films sandwiched between Pt electrodes. After electroforming, a high resistance state of the Mn:ZnO capacitor revealed switchable diode characteristics whose forward direction was determined by the polarity of the electroforming voltage. Linear fitting of the I-V curves highlighted that the rectifying behavior was influenced by a Schottky barrier at the Pt/Mn:ZnO interface. Our results suggest that formation of conducting filaments from the cathode during the electroforming process resulted in a collapse of the Schottky barrier (near the cathode), and rectifying behaviors dominated by a remnant Schottky barrier near the anode.
Magnetoconduction in a two-dimensional system confined in wurtzite AlxGa1−xN/GaN heterostructure
Authors: Cangas R. , Hidalgo M. A.
Published: April 2013

The magnetoresistivity of a two dimensional electron system confined in a wurtzite Al0.22Ga0.78N/GaN heterostructure has been reproduced using a theoretical model based on a modified semiclassical theory. When an external magnetic field is applied, nodes appear on the beating pattern Subnikov-de Haas oscillations due to carriers with different spin orientations. The analysis of the magnetoresistivity experimental data with the model led us to know accurately the value of the spin-orbit coupling material parameters.
Large stable strain memory effect in poled Mn-doped Pb(Mn1/3Sb2/3)O3-Pb(Zr,Ti)O3 ceramics
Authors: Du Gang , Liang Ruihong , Wang Li , Li Kui , Zhang Wenbin , Wang Genshui , Dong Xianlin
Published: April 2013

Large strain memory effect was confirmed in the poled and aged Mn-doped 0.05Pb(Mn1/3Sb2/3)O3-0.50PbZrO3-0.45PbTiO3 ceramics due to the presence of asymmetric strain hysteresis curve with two stable strain states at zero electric field. This strain memory is two times larger than that of the unipolar strain output. Moreover, the large strain memory effect is quite stable at high electric field or down to 0.01 Hz and shows good stability even after 20 000 fatigue cycles. These results indicate that strain memory piezoelectric actuator, which could keep its output strain without any operating fields, may be fabricated using this kind of material.
Communication: Induced photoemission from nonadiabatic dynamics assisted by dynamical Stark effect
Authors: Arasaki Yasuki , Scheit Simona , Takatsuka Kazuo
Published: April 2013

Through nonadiabatic interaction due to electron transfer as that in alkali halides, vibrational dynamics on the ionic potential energy surface (large dipole moment) is coupled to that on the covalent surface (small dipole moment). Thus, population transfer between the states should cause long-range electron jump between two remote sites, which thereby leads to a sudden change of the large molecular dipole moment. Therefore, by making repeated use of the dynamical Stark effect, one may expect emission of photons from it. We show with coupled quantum wavepacket dynamics calculation that such photoemission can indeed occur and can be controlled by an external field. The present photoemission can offer an alternative scheme to study femtosecond and subfemtosecond vibrational and electronic dynamics and may serve as a unique optical source.
Flexible graphene woven fabrics for touch sensing
Authors: Lee Xiao , Yang Tingting , Li Xiao , Zhang Rujing , Zhu Miao , Zhang Hongze , Xie Dan , Wei Jinquan , Zhong Minlin , Wang Kunlin , Wu Dehai , Li Zhihong , Zhu Hongwei
Published: April 2013

Graphene woven fabric (GWF) prepared from chemical vapor deposition was used as smart self-sensing element to assemble piezoresistor through directly transferring onto the flexible substrate poly(dimethylsiloxane) (PDMS) with the deposited Ti/Au electrodes. A rational strategy was proposed to fabricate flexible touch sensors easily and effectively with the full usage of the mechanical and electrical properties of GWF, whose resistance is highly sensitive to macro-deformation or micro-defect. Compared to commercial and traditional touch sensing, the GWF-on-PDMS piezoresistor is structurally flexible that is demanded under special conditions and meanwhile makes the piezoresistor to have excellent durability.
Significant elastocaloric effect in a Fe-31.2Pd (at. %) single crystal
Authors: Xiao Fei , Fukuda Takashi , Kakeshita Tomoyuki
Published: April 2013

A significant elastocaloric effect was detected in a Fe-31.2Pd (at. %) single crystal when a compressive stress was applied in the [001]P direction of the parent phase at temperatures of 240-290 K. The temperature decrease caused by the removal of adiabatic stress was approximately 2 K and the refrigeration capacity was calculated to be 2 MJ/m3 under a stress of 100 MPa. This significant elastocaloric effect over a wide temperature range was caused by the remarkable temperature dependence of the Young's modulus in the [001]P direction.
Comparing the distribution of the electronic gap of an organic molecule with its photoluminescence spectrum
Authors: Milan D. C. , Villalvilla J. M. , Díaz-García M. A. , Untiedt C.
Published: April 2013

The electronic gap structure of the organic molecule N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine, also known as TPD, has been studied by means of a Scanning Tunneling Microscope (STM) and by Photoluminescence (PL) analysis. Hundreds of current-voltage characteristics measured at different spots of the sample show the typical behavior of a semiconductor. The analysis of the curves allows to construct a gap distribution histogram which reassembles the PL spectrum of this compound. This analysis demonstrates that STM can give relevant information, not only related to the expected value of a semiconductor gap but also on its distribution which affects its physical properties such as its PL.
Single heterojunction solar cells on exfoliated flexible ∼25 μm thick mono-crystalline silicon substrates
Authors: Saha Sayan , Hilali Mohamed M. , Onyegam Emmanuel U. , Sarkar Dabraj , Jawarani Dharmesh , Rao Rajesh A. , Mathew Leo , Smith Ryan S. , Xu Dewei , Das Ujjwal K. , Sopori Bhushan , Banerjee Sanjay K.
Published: April 2013

Mono-crystalline silicon single heterojunction solar cells on flexible, ultra-thin (∼25 μm) substrates have been developed based on a kerf-less exfoliation method. Optical and electrical measurements demonstrate maintained structural integrity of these flexible substrates. Among several single heterojunction ∼25 μm thick solar cells fabricated with un-optimized processes, the highest open circuit voltage of 603 mV, short circuit current of 34.4 mA/cm2, and conversion efficiency of 14.9% are achieved separately on three different cells. Preliminary reliability test results that include thermal shock and highly accelerated stress tests are also shown to demonstrate compatibility of this technology for use in photovoltaic modules.
Magneto-intersubband oscillations of the kinetic coefficients of a two-dimensional system with a spin-orbit interaction
Authors: Novokshonov S. G.
Published: April 2013

The temperature dependence of the Shubnikov–de Haas oscillations of longitudinal magnetoresistance of a two-dimensional electron system with the Rashba spin-orbit interaction is analyzed by using the expression for conductivity derived by S. G. Novokshonov and A. G. Groshev, Phys. Rev. B 74, 245333 (2006). It is shown that in the above system there exist magneto-intersubband oscillations of the kinetic coefficients characteristic for multisubband conductors. The period of these oscillations is determined by the spin precession frequency at the Fermi level ΩBF. In the case under consideration, the intersubband spin splitting depends on electron energy. This results in a weak temperature dependence of the magneto-intersubband oscillation amplitude, which is determined by Λ* = (2π2kBT/ℏωc)ℏ ΩBF / εF. This dependence is considerably weaker in comparison to the temperature smoothing of the Shubnikov–de Haas oscillation amplitude due to a small parameter (ℏ ΩBF /εF ≪ 1).
Context-Dependent Categorical Perception of Surprise
Authors: Cheal Jenna L , Rutherford M D
Published: April 2013

Evidence regarding the categorical perception of surprise facial expressions has been equivocal. Surprise is inherently ambiguous with respect to valence: it could be positive or negative. If this ambiguity interferes with categorical perception, disambiguating the valence might facilitate categorical perception. Participants identified and discriminated images that were selected from expression continua: happy – fear, surprise – fear, happy – surprise. Half were presented with a context for the surprise expressions indicating positive or negative valence. Both groups had a typical identification curve, but discrimination performance was better predicted by identification in the context condition for happy – fear and surprise – fear continua, suggesting that categorical perception was facilitated by the disambiguating context.
A Between-Subjects Test of the Lower-Identification/Higher-Priming Paradox
Authors: Rubino I Alex , Rociola Giuseppe , Di Lorenzo Giorgio , Magni Valentina , Ribolsi Michele , Mancini Valentina , Saya Anna , Pezzarossa Bianca , Siracusano Alberto , Suslow Thomas
Published: April 2013

An under-recognised U-shaped model states that unconscious and conscious perceptual effects are functionally exclusive and that unconscious perceptual effects manifest themselves only at the objective detection threshold, when conscious perception is completely absent. We tested the U-shaped line model with a between-subjects paradigm. Angry, happy, neutral faces, or blank slides were flashed for 5.5 ms and 19.5 ms before Chinese ideographs in a darkened room. A group of volunteers ( n = 84) were asked to rate how much they liked each ideograph and performed an identification task. According to the median identification score two subgroups were composed; one with 50% or <50% identification scores ( n = 31), and one with above 50% identification scores ( n = 53). The hypothesised U-shaped line was confirmed by the findings. Affective priming was found only at the two extreme points: the 5.5 ms condition of the low-identification group (subliminal perception) and the 19.5 ms condition of the >50% high-identification group (supraliminal perception). The two intermediate points (19.5 ms of the low-identification group and 5.5 ms of the high-identification group) did not correspond to significant priming effects. These results confirm that a complete absence of conscious perception is the condition for the deployment of unconscious perceptual effects.
Virtual Slant Explains Perceived Slant, Distortion, and Motion in Pictorial Scenes
Authors: Erkelens Casper J
Published: April 2013

Virtual slants of obliquely viewed figures consisting of skewed grids, computed as a function of depicted slant and slant of the physical surface, were compared with perceived slants in both monocular and binocular viewing conditions. Computations were based on an assumption of parallelism. Perceived slant was well-correlated with virtual slant, even though slants were generally underestimated. The qualitative relationship between virtual slants and physical surface slants was variable, and liable to produce different degrees and directions of apparent rotation as well as of apparent compensation, depending on the depicted slant of the stimulus. Contributions of screen-related cues were small and mainly limited to small slants. Remarkably, binocular disparity did not have any effect on perceived slant. The results imply that many past findings of both transformation and (apparent) compensation in pictorial viewing may in principle be straightforwardly explained as a function of the virtual stimulus.
The Influence of Symmetry on Children's Judgments of Facial Attractiveness
Authors: Vingilis-Jaremko Larissa , Maurer Daphne
Published: April 2013

In experiment 1, we examined developmental changes in the influence of symmetry on judgments of attractiveness by showing adults and children pairs of individual faces in which one face was transformed 75% toward perfect symmetry, while the other face was transformed by exaggerating its asymmetries by 75%. Adults and 9-year-olds, but not 5-year-olds, rated the more symmetric faces as more attractive than the less symmetric faces, although the effect was stronger in adults than 9-year-olds. The preference for symmetry was stronger for male than female faces, and stronger for adults' than children's faces. In experiment 2, comparisons of the symmetry of the original male and female faces revealed no measured differences but lower ratings by adults of symmetry in the male faces. Overall, the results suggest that the influence of symmetry on attractiveness judgments emerges after the age of 5 years, and matures after the age of 9 years. The stronger effects for adult viewers may reflect an increase in sensitivity to symmetry as experience with faces increases and/or as the visual system matures. As well, attractiveness may become more salient after puberty, so that honest signals of mate quality, such as symmetry, have a stronger effect for adult viewers, especially when judging adult faces.
Sexual health of Indian immigrant men in Australia: an exploratory research on help-seeking attitudes
Authors: Ramanathan Vijayasarathi , Sitharthan Gomathi , Pepper Karen , Wylie Kevan
Published: April 2013

The help-seeking attitudes for sexual health of Indian men living in Australia was explored. Of all survey respondents (n = 225), many preferred to seek help from medical doctors. Young (18–25 years) Indian men were three times more likely to prefer a specialist medical doctor than older men. Ethnicity and gender of the medical doctor was ‘not important’ for the majority of men. Most men preferred to seek help from their regular general practitioner.
Misplaced helix slows down ultrafast pressure-jump protein folding
Authors: Prigozhin Maxim B. , Liu Yanxin , Wirth Anna Jean , Kapoor Shobhna , Winter Roland , Schulten Klaus , Gruebele Martin
Published: April 2013

Using a newly developed microsecond pressure-jump apparatus, we monitor the refolding kinetics of the helix-stabilized five-helix bundle proteinλ*YA, the Y22W/Q33Y/G46,48A mutant ofλ-repressor fragment 6–85, from 3 μs to 5 ms after a 1,200-barP-drop. In addition to a microsecond phase, we observe a slower 1.4-ms phase during refolding to the native state. Unlike temperature denaturation, pressure denaturation produces a highly reversible helix-coil-rich state. This difference highlights the importance of the denatured initial condition in folding experiments and leads us to assign a compact nonnative helical trap as the reason for slowerP-jump–induced refolding. To complement the experiments, we performed over 50 μs of all-atom molecular dynamicsP-drop refolding simulations with four different force fields. Two of the force fields yield compact nonnative states with misplaced α-helix content within a few microseconds of theP-drop. Our overall conclusion from experiment and simulation is that the pressure-denatured state ofλ*YA contains mainly residual helix and little β-sheet; following a fastP-drop, at least someλ*YA forms misplaced helical structure within microseconds. We hypothesize that nonnative helix at helix-turn interfaces traps the protein in compact nonnative conformations. These traps delay the folding of at least some of the population for 1.4 ms en route to the native state. Based on molecular dynamics, we predict specific mutations at the helix-turn interfaces that should speed up refolding from the pressure-denatured state, if this hypothesis is correct.
p63-expressing cells are the stem cells of developing prostate, bladder, and colorectal epithelia
Authors: Pignon Jean-Christophe , Grisanzio Chiara , Geng Yan , Song Jiaxi , Shivdasani Ramesh A. , Signoretti Sabina
Published: April 2013

The tumor protein p63 (p63), and more specifically the NH2-terminal truncated (ΔN) p63 isoform, is a marker of basal epithelial cells and is required for normal development of several epithelial tissues, including the bladder and prostate glands. Although p63-expressing cells are proposed to be the stem cells of the developing prostate epithelium and bladder urothelium, cell lineages in these endoderm-derived epithelia remain highly controversial, and rigorous lineage tracing studies are warranted. Here, we generated knock-in mice expressing Cre recombinase (Cre) under the control of the endogenous
ΔNp63
promoter. Heterozygote

ΔNp63
+/Cre

mice were phenotypically normal and fertile. Cre-mediated recombination in

ΔNp63
+/Cre
;ROSA26
EYFP

reporter mice faithfully recapitulated the pattern of ΔNp63 expression and were useful for genetic lineage tracing of ΔNp63-expressing cells of the caudal endoderm in vivo. We found that ΔNp63-positive cells of the urogenital sinus generated all epithelial lineages of the prostate and bladder, indicating that these cells represent the stem/progenitor cells of those epithelia during development. We also observed ΔNp63 expression in caudal gut endoderm and the contribution of ΔNp63-positive cells to the stem/progenitor compartment of adult colorectal epithelium. Because
p63
is a master regulator of stratified epithelial development, this finding provides a unique developmental insight into the cell of origin of squamous cell metaplasia and squamous cell carcinoma of the colon.
HOMECAT: consensus homologs mapping for interspecific knowledge transfer and functional genomic data integration
Authors: Zorzan Simone , Lorenzetto Erika , Ettorre Michele , Pontelli Valeria , Laudanna Carlo , Buffelli Mario
Published: April 2013

Motivation: Comparative studies are encouraged by the fast increase of data availability from the latest high-throughput techniques, in particular from functional genomic studies. Yet, the size of datasets, the challenge of complete orthologs findings and not last, the variety of identification formats, make information integration challenging. With HOMECAT, we aim to facilitate cross-species relationship identification and data mapping, by combining orthology predictions from several publicly available sources, a convenient interface for high-throughput data download and automatic identifier conversion into a Cytoscape plug-in, that provides both an integration with a large set of bioinformatics tools, as well as a user-friendly interface.

Availability: HOMECAT and the Supplementary Materials are freely available at http://www.cbmc.it/homecat/.

Contact:  simone.zorzan@univr.it

Supplementary information:  Supplementary data are available at Bioinformatics online.
RSVSim: an R/Bioconductor package for the simulation of structural variations
Authors: Bartenhagen Christoph , Dugas Martin
Published: April 2013

Summary: RSVSim is a tool for the simulation of deletions, insertions, inversions, tandem duplications and translocations of various sizes in any genome available as FASTA-file or data package in R. The structural variations can be generated randomly, based on user-supplied genomic coordinates or associated to various kinds of repeats. The package further comprises functions to estimate the distribution of structural variation sizes from real datasets.

Availability: RSVSim is implemented in R and available at http://www.bioconductor.org. A vignette with detailed descriptions of the functions and examples is included.

Contact: christoph.bartenhagen@uni-muenster.de
The Prevalence of Disclosure of HIV Status to HIV-Infected Children in Western Kenya
Authors: Turissini Matthew L. , Nyandiko Winstone M. , Ayaya Samuel O. , Marete Irene , Mwangi Ann , Chemboi Victor , Warui Lucy , Vreeman Rachel C.
Published: April 2013

Background

As antiretroviral therapy (ART) allows the world's 2.3 million human immunodeficiency virus (HIV)–infected children to grow and thrive, these children need to be informed of their HIV status. Neither the prevalence of disclosure to children nor its impact has been evaluated in most resource-limited settings.

Methods

We conducted a prospective assessment of a random sample of HIV-infected children ages 6–14 years enrolled in HIV care at a large referral clinic in Eldoret, Kenya. Clinicians administered questionnaires to children and caregivers independently at routine clinic visits to assess disclosure status, ART adherence, stigma, and depression. Children's demographic and clinical characteristics were extracted from chart review. We calculated descriptive statistics and performed logistic regression to assess the association between disclosure and other characteristics.

Results

Two hundred seventy children–caregiver dyads completed questionnaires. The mean child age was 9.3 years (standard deviation 2.6); 49% were male, and 42% were orphans. 11.1% of children had been informed of their HIV status (N = 30). Of those under 10 years, 3.3% knew their status, whereas 9.2% of 10- to 12-year-olds and 39.5% of 13- to 14-year-olds knew they had HIV. Only age was significantly associated with disclosure status in both bivariate analyses (P < .0001) and multiple logistic regression (odds ratio 1.67, 95% confidence interval 1.36–2.05) when considering social demographics, disease stage variables, adherence, stigma measures, and depression.

Conclusions

Rates of informing children in western Kenya of their HIV status are low, even among older children. Guiding families through developmentally appropriate disclosure processes should be a key facet of long-term pediatric HIV management.
Identification and characterization of a new cell surface protein possessing factor H-binding activity in the swine pathogen and zoonotic agent Streptococcus suis
Authors: Vaillancourt Katy , Bonifait Laetitia , Grignon Louis , Frenette Michel , Gottschalk Marcelo , Grenier Daniel
Published: April 2013

Streptococcus suis is a major swine pathogen and an emerging zoonotic agent. The ability of pathogenic bacteria to bind the complement regulator factor H on their cell surface may allow them to avoid complement attack and phagocytosis. The aim of this study was to characterize a new cell surface protein possessing factor H-binding activity in S. suis serotype 2. The capacity of S. suis to bind the complement regulator factor H on its surface was demonstrated by ELISA. Using a factor I–cofactor assay, it was found that the functional activity of factor H bound to S. suis was kept. Since the product of gene SSU0186 in S. suis P1/7 shared similarity with a Streptococcus pneumoniae protein (named PspC) possessing factor H-binding activity, it was proposed as a putative factor H receptor in S. suis. SSU0186 has a 1686 bp open reading frame encoding a 561 amino acid protein containing the Gram-positive cell wall anchoring motif (LPXTG) at the carboxy-terminal, an amino-terminal signal sequence, an α-helix domain, a proline-rich region and a G5 domain. The SSU0186 gene was cloned in Escherichia coli and the purified recombinant factor H-binding protein showed a molecular mass of 95 kDa, as determined by SDS-PAGE. The protein possessed the functional property of binding factor H. Sera from S. suis-infected pigs reacted with the recombinant factor H receptor, suggesting that it is produced during the course of infections. In conclusion, we identified a novel S. suis cell surface protein that binds the complement factor H. This cell surface protein may help S. suis to resist complement attack and phagocytosis and contribute to pathogenesis.