bluuebunny/crossref_metadata_2025 huggingface dataset:
The invasion of tobacco mosaic virus RNA induces endoplasmic reticulum stress-related autophagy in HeLa cells
Authors: Li Li , Wang Li , Xiao Ruijing , Zhu Guoguo , Li Yan , Liu Changxuan , Yang Ru , Tang Zhiqing , Li Jie , Huang Wei , Chen Lang , Zheng Xiaoling , He Yuling , Tan Jinquan
Published: July 2011

The ability of human cells to defend against viruses originating from distant species has long been ignored. Owing to the pressure of natural evolution and human exploration, some of these viruses may be able to invade human beings. If their ‘fresh’ host had no defences, the viruses could cause a serious pandemic, as seen with HIV, SARS (severe acute respiratory syndrome) and avian influenza virus that originated from chimpanzees, the common palm civet and birds, respectively. It is unknown whether the human immune system could tolerate invasion with a plant virus. To model such an alien virus invasion, we chose TMV (tobacco mosaic virus) and used human epithelial carcinoma cells (HeLa cells) as its ‘fresh’ host. We established a reliable system for transfecting TMV-RNA into HeLa cells and found that TMV-RNA triggered autophagy in HeLa cells as shown by the appearance of autophagic vacuoles, the conversion of LC3-I (light chain protein 3-I) to LC3-II, the up-regulated expression of Beclin1 and the accumulation of TMV protein on autophagosomal membranes. We observed suspected TMV virions in HeLa cells by TEM (transmission electron microscopy). Furthermore, we found that TMV-RNA was translated into CP (coat protein) in the ER (endoplasmic reticulum) and that TMV-positive RNA translocated from the cytoplasm to the nucleolus. Finally, we detected greatly increased expression of GRP78 (78 kDa glucose-regulated protein), a typical marker of ERS (ER stress) and found that the formation of autophagosomes was closely related to the expanded ER membrane. Taken together, our data indicate that HeLa cells used ERS and ERS-related autophagy to defend against TMV-RNA.
Electron beam tuning of carrier concentrations in oxide nanowires
Authors: Ji Hyunjin , Choi Jaewan , Cho Youngseung , Hwang In-Sung , Kim Sun-Jung , Lee Jong-Heun , Roth Siegmar , Kim Gyu-Tae
Published: July 2011

In spite of the attractive electrical properties of metal oxide nanowires, it is difficult to tune their surface states, notably the ionic adsorbents and oxygen vacancies, both of which can cause instability, degradation, and the irreproducibility or unrepeatable changes of the electrical characteristics. In order to control the surface states of the nanowires, electron beams were locally irradiated onto the channels of metal oxide nanowire field effect transistors. This high energy electron beam irradiation changed the electrical properties of the individual metal oxide nanowires, due to the removal of the negative adsorbents (O2-, O-). The detachment of the ionic adsorbents changes the charge states of the nanowires, resulting in the enhancement of the electrical conductance in n-type nanowires (ZnO, SnO2) and the degradation of the conductance in p-type nanowires (CuO). By investigating the changes in the electrical properties of nanowire devices in air or vacuum, with or without exposure to electron beams, the roles of the physisorbed water molecules or chemisorbed oxygen molecules can be independently understood. Unlike the electron beam irradiation, the vacuum enhanced the conductance of both n-type (ZnO, SnO2) and p-type (CuO) nanowires, due to the release of charges caused by the detachment of the polarized water molecules that were screening them from the surface of the nanowires, irrespective of the major carrier type. The electron beam irradiation technique has the potential to locally modulate the charge carriers in electronic nanowire devices, and the changes could be maintained with proper passivation for the long-term preservation of the device characteristics.
An integrated energy storage scheme for a dispatchable solar and wind powered energy system
Authors: Garrison Jared B. , Webber Michael E.
Published: July 2011

This research analyzed an integrated energy system that includes a novel configuration of wind and solar coupled with two storage methods to make both wind and solar sources dispatchable during peak demand, thereby enabling their broader use. Named DSWiSS for Dispatchable Solar and Wind Storage System, the proposed system utilizes compressed air energy storage (CAES) that is driven from wind energy and thermal storage supplied by concentrating solar thermal power (CSP) in order to achieve firm power from intermittent, renewable sources. Although DSWiSS mimics the operation of a typical CAES facility, the replacement of energy derived from fossil fuels with energy generated from renewable resources makes this system unique. West Texas is a useful geographical testbed for this system because it has abundant co-located wind and solar resources; it has competitive electricity markets, which give producers an economic incentive to store night-time wind energy in order to be sold during peak price times; and it has a significant number of locations with geological formations suitable for CAES. Through a thermodynamic and a levelized lifetime cost analysis, the power system performance and the cost of energy are estimated for this integrated wind-solar-storage system. We calculate that the combination of these components yields an energy efficiency of 46% for the CAES main power block, and the overall system cost is only slightly more expensive per unit of electricity generated than the current technologies employed today.
Circularly polarized emission from ensembles of InAs/GaAs quantum dots
Authors: Moskalenko E. S. , Larsson L. A. , Holtz P. O.
Published: July 2011

We present a low-temperature micro-photoluminescence (μ-PL) study of ensembles of InAs/GaAs quantum dots (QDs) with respect to its circular polarization (ρc) for a manifold of experimental conditions such as single or dual laser excitation, different excitation energies (hυex), varying excitation powers (Pex) of both lasers, and with or without an external magnetic field (Bext). It is demonstrated that an essential ρc (≤ 40%) could be recorded depending on Pex, even at Bext = 0 for hυex exceeding the PL energy of the wetting layer (EWL), while ρc remains negligible for hυex < EWL. To explain the data obtained, a model is developed according to which a nuclear magnetic field (BN) is created in the QDs by spin-polarized electrons. The BN plays a crucial role in the preservation of the electron spin, which otherwise effectively relaxes due to the presence of the anisotropic electron-hole exchange interaction (ωex). The application of an additional infra-red laser gives rise to a population of excess holes in the QDs, thus producing positively charged excitons. In this case, ωex = 0 and accordingly, ρc ≈ 40% at Bext = 0 is recorded, even for excitation with hυex < EWL.
Tunable wideband bandstop acoustic filter based on two-dimensional multiphysical phenomena periodic systems
Authors: Romero-García V. , Sánchez-Pérez J. V. , Garcia-Raffi L. M.
Published: July 2011

The physical properties of a periodic distribution of absorbent resonators is used in this work to design a tunable wideband bandstop acoustic filter. Analytical and numerical simulations as well as experimental validations show that the control of the resonances and the absorption of the scatterers along with their periodic arrangement in air introduce high technological possibilities to control noise. Sound manipulation is perhaps the most obvious application of the structures presented in this work. We apply this methodology to develop a device as an alternative to the conventional acoustic barriers with several properties from the acoustical point of view but also with additional esthetic and constructive characteristics.
Temperature dependence of polarization switching properties of Bi3.15Nd0.85Ti3O12 ferroelectric thin film
Authors: Zhang Y. , Zhong X. L. , Chen Z. H. , Wang J. B. , Zhou Y. C.
Published: July 2011

The temperature dependences of the polarization switching properties of Bi3.15Nd0.85Ti3O12 (BNT) ferroelectric thin film in the range from 25 to 150°C have been investigated. With increasing temperature, the switchable polarization and switching time decrease. Meanwhile, the depolarization field due to the interfacial layer between the electrode and the BNT film increases with increasing temperature, which induces more domain back-switching. In addition, the local switching properties of BNT film have been studied using piezoresponse force microscopy, and it is found that the prepared BNT film has good local switching behaviors.
Shock-induced decomposition of a high density glass (ZF6)
Authors: Zhou Xianming , Liu Xun , Li Jiabo , Li Jun , Cao Xiuxia
Published: July 2011

The dynamic high-pressure behavior of a high density glass (ZF6) was investigated in this study. The Hugoniot data, shock temperature (TH) and release sound velocity (C) of ZF6 were measured by a time-resolved multi-channel pyrometer in the shock pressure (PH) range of 50–170 GPa. The Hugoniot data is in accord with the Los Alamos Scientific Laboratory (LASL) shock Hugoniot data and shows a good linearity over 21 GPa. Polymorphic phase transitions were identified by the kinks in the measured TH-PH and C-PH relationships. The onset pressures of the transformations are ∼75 and ∼128 GPa, respectively. A thermodynamic calculation suggests that the phase transition at 75 GPa is its disproportionation to massicot (high pressure phase of PbO) and melted silica while the transition at 128 GPa is from the melting of massicot.
Magnetocaloric effect in Ni-Mn-Ga thin films under concurrent magnetostructural and Curie transitions
Authors: Zhang Yuepeng , Hughes R. A. , Britten J. F. , Dube P. A. , Preston J. S. , Botton G. A. , Niewczas M.
Published: July 2011

An investigation of the magnetocaloric effect for Ni-Mn-Ga films with a composition chosen to yield the highly advantageous magnetostructural phase transition between the paramagnetic austenitic and the ferromagnetic martensitic phases is presented. The observed effect is particularly strong at low magnetic fields, yielding a maximum negative entropy change of −1.4 J/kg K for a field change of only 0.5 T. It is also observed that the cooling process yields a 40% larger entropy change compared to the heating process. Temperature dependent magnetic, structural, and transport measurements indicate that the entropy peak difference between cooling and heating cycles is associated with a stronger overlap of the Curie transition of the austenitic phase with the magnetostructural phase transition upon cooling. The observed behavior is significant to micro-length-scale spot cooling applications utilizing thin films and large-scale magnetic refrigeration applications where low magnetic fields are favorable.
Optical enhancement and losses of pyramid textured thin-film silicon solar cells
Authors: Dewan Rahul , Vasilev Ivaylo , Jovanov Vladislav , Knipp Dietmar
Published: July 2011

The optical enhancement and losses of microcrystalline thin-film silicon solar cells with periodic pyramid textures were investigated. Using a finite difference time domain algorithm, the optical wave propagation in the solar cell structure was calculated by rigorously solving the Maxwell’s equations. The influence of the profile dimensions (the period and height of the pyramid) and solar cell thickness on the quantum efficiency and short circuit current were analyzed. Furthermore, the influence of the solar cell thickness on the upper limit of the short circuit current was investigated. The numerically simulated short circuit currents were compared to fundamental light trapping limits based on geometric optics. Finally, optical losses in the solar cell were analyzed. After identifying these key losses, strategies for minimizing the losses can be discussed.
Study of spin-coated resist coverage on nanoscale topography using spectroscopic ellipsometry
Authors: Yu Zhaoning , Hwu Justin , Liu Yongdong , Gauzner Gene , Lee Kim , Kuo David
Published: July 2011

Using spectroscopic ellipsometry and rigorous coupled wave analysis, we studied the spin-coated resist coverage on 72.6 nm pitch line-and-space patterns of various depths (from ∼20 to ∼130 nm). Within the margin of measurement error, we find the tested nano-patterns have no apparent effect on the spin-coated resist thickness. The result suggests that, during the spinning, the resist ceased to flow at a critical thickness much larger than the pattern depth, and the resist thinning afterwards was dominated by solvent evaporation. The methods and results demonstrated in this work can improve the characterization and process control in a number of applications where spin coating on high-density nano-scale topographies is required.
Cu-dependent phase transition in polycrystalline CuGaSe2 thin films grown by three-stage process
Authors: Islam M. M. , Yamada A. , Sakurai T. , Kubota M. , Ishizuka S. , Matsubara K. , Niki S. , Akimoto K.
Published: July 2011

The Cu-dependent phase transition in polycrystalline CuGaSe2 thin films has been studied by an electron probe micro-analyzer (EPMA) and the synchrotron x-ray diffraction method. A Cu-deficiency parameter, Z, defined as (1 − Cu/Ga) was used to study the phase transition. Upon increasing the Z-value, the composition of the films on the Cu2Se-Ga2Se3 pseudo binary tie line was found to shift from the stoichiometric CuGaSe2 (1:1:2) (Z = 0) to the Ga-rich composition through the formation of several ordered defect compounds.The structural modification in the Cu-poor CuGaSe2 film has been investigated by the synchrotron x-ray diffraction method. The existence of the Cu-poor surface phase over the near-stoichiometric bulk CuGaSe2 film was confirmed by the fitting of the accelerated voltage dependent EPMA data.
The Bain path of paramagnetic Fe-Cr based alloys
Authors: Al-Zoubi N. , Johansson B. , Nilson G. , Vitos L.
Published: July 2011

Employing the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, we calculated the total energy and local magnetic moments of paramagnetic Fe-Cr-M (M = Cr, Mn, Fe, Co, Ni) alloys along the tetragonal distortion (Bain) path connecting the body centered cubic (bcc) and the face centered cubic (fcc) structures. The paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all alloys, the local magnetic moments on Fe atoms decrease from the maximum value corresponding to the bcc phase toward the minimum value realized for the fcc phase. Cobalt atoms have non-vanishing local magnetic moments only for tetragonal lattices with c/a < 1.30, whereas the local magnetic moments of Mn show weak crystal structure dependence. We find that Cr stabilizes the bcc lattice and increases the energy barrier as going from the bcc toward the fcc phase. Both Co and Ni favor the fcc lattice and decrease the energy barrier relative to the bcc phase. On the other hand, the tetragonal distortion around the fcc phase is facilitated by Cr and to a somewhat lesser extent also by Ni, but strongly impeded by Co. Manganese has negligible effect on the structural energy difference as well as on the energy barrier along the Bain path. Our findings on the alloying induced softening or hardening of Fe-Cr based alloys against tetragonal distortions are important for understanding the interstitial driven martensitic transformations in alloy steels.
Fracture behaviors and strength of Cu6Sn5 intermetallic compounds by indentation testing
Authors: Zhang Q. K. , Tan J. , Zhang Z. F.
Published: July 2011

In this study, the shear fracture behaviors of the Cu6Sn5 grains at the Sn-4Ag/Cu interface were studied by indentation test; the fracture mechanisms and shear strength were characterized through analyzing the indentation curves and fracture morphologies. Experimental results reveal that shear fractures of the Cu6Sn5 grains occur at the foundation or the center portion, depending on their size and shape, and there are bursts on the force-depth curves corresponding to the fracture. The shear fracture strength of the Cu6Sn5 grains fractured at their center portion is close to the shear strength of the Cu6Sn5 intermetallic compounds, and its average value is about 670 MPa.
Photo-luminescence study of heterogeneous terahertz quantum cascade lasers
Authors: Freeman Joshua R. , Brewer Anthony , Beere Harvey E. , Ritchie David A.
Published: July 2011

We present a study of heterogeneous terahertz quantum cascade lasers using micro-probe photoluminescence. Simulations and experiments are first presented on a homogeneous terahertz quantum cascade laser; these indicate that the population of the upper laser level and the energy of laser transition can be tracked by this technique. We then focus on heterogeneous terahertz quantum cascade lasers and demonstrate the utility of micro-photoluminescence for these devices by measuring the state populations and energy separations for each sub-stack independently.
QM:QM embedding using electronic densities within an ONIOM framework: Energies and analytic gradients
Authors: Hratchian Hrant P. , Krukau Aliaksandr V. , Parandekar Priya V. , Frisch Michael J. , Raghavachari Krishnan
Published: July 2011

Accurate calculations of large systems remain a challenge in electronic structure theory. Hybrid energy techniques are a promising family of methods for treating such systems. Expanding on previous developments, we present a QM:QM electronic embedding model whereby the high-level region is polarized by the electron density of the low-level region within an ONIOM framework. A direct Coulomb embedding model as well a more computationally efficient model involving a density fitting expansion are considered. We also develop a generalized theory for the first derivatives of these classes of QM:QM electronic embedding schemes, which requires solution of a single set of self-consistent field response equations. Two initial test cases are presented and discussed.
Accurate explicitly correlated wave functions for two electrons in a square
Authors: Ryabinkin Ilya G. , Staroverov Viktor N.
Published: July 2011

An explicitly correlated linear-r12 variational method is developed for a system of two electrons confined to a two-dimensional square well with infinite walls. The wave function is written as an expansion in products of non-negative integer powers of the relative and center-of-mass electronic coordinates and powers of r12 restricted to 0 and 1. This form indirectly includes higher powers of the interelectronic distance and exhibits a much faster convergence than a similar expansion without r12-dependent terms. The method is implemented using high-precision floating-point arithmetic. Ground-state total energies are reported with at least 12 accurate significant figures for squares with sides from 1 to 50 bohrs. The method can be used “as is” for excited states and for two-dimensional rectangular wells. We also show that wave functions for two electrons in a square and in a rectangle have a higher symmetry than can be accounted for by the point group of the system.
Instabilities in interaction of circularly polarized laser pulse and overdense target
Authors: Zhang Xiaomei , Shen Baifei , Ji Liangliang , Wang Wenpeng , Xu Jiancai , Yu Yahong , Wang Xiaofeng
Published: July 2011

Instabilities in the interaction of a normal intensity circularly polarized pulse and an overdense foil are investigated with two and three dimensional particle-in-cell simulations. Two typical instabilities were shown during the interaction. One is the Weibel-like instability induced by the current far above the Alfven limit, and the other is the boundary instability with ring structures spreading to the center from the boundary which is induced by the transverse boundaries of the target or the laser pulse. These instabilities are important to the proton acceleration by using moderate laser pulses at intensities accessible experimentally with existing laser systems.
Three-dimensional electromagnetic strong turbulence. II. Wave packet collapse and structure of wave packets during strong turbulence
Authors: Graham D. B. , Robinson P. A. , Cairns Iver H. , Skjaeraasen O.
Published: July 2011

Large-scale simulations of wave packet collapse are performed by numerically solving the three-dimensional (3D) electromagnetic Zakharov equations, focusing on individual wave packet collapses and on wave packets that form in continuously driven strong turbulence. The collapse threshold is shown to decrease as the electron thermal speed νe/c increases and as the temperature ratio Ti/Te of ions to electrons decreases. Energy lost during wave packet collapse and dissipation is shown to depend on νe/c. The dynamics of density perturbations after collapse are studied in 3D electromagnetic strong turbulence for a range of Ti/Te. The structures of the Langmuir, transverse, and total electric field components of wave packets during strong turbulence are investigated over a range of νe/c. For νe/c≲0.17, strong turbulence is approximately electrostatic and wave packets have very similar structure to purely electrostatic wave packets. For νe/c≳0.17, transverse modes become trapped in density wells and contribute significantly to the structure of the total electric field. At all νe/c, the Langmuir energy density contours of wave packets are predominantly oblate (pancake shaped). The transverse energy density contours of wave packets are predominantly prolate (sausage shaped), with the major axis being perpendicular to the major axes of the Langmuir component. This results in the wave packet becoming more nearly spherical as νe/c increases, and in turn generates more spherical density wells during collapse. The results obtained are compared with previous 3D electrostatic results and 2D electromagnetic results.
Kinetics and dynamics of the NH3 + H → NH2 + H2 reaction using transition state methods, quasi-classical trajectories, and quantum-mechanical scattering
Authors: Corchado Jose C. , Espinosa-Garcia Joaquin , Yang Minghui
Published: July 2011

On a recent analytical potential energy surface developed by two of the authors, an exhaustive kinetics study, using variational transition state theory with multidimensional tunneling effect, and dynamics study, using both quasi-classical trajectory and full-dimensional quantum scattering methods, was carried out to understand the reactivity of the NH3 + H → NH2 + H2 gas-phase reaction. Initial state-selected time-dependent wave packet calculations using a full-dimensional model were performed, where the total reaction probabilities were calculated for the initial ground vibrational state and for four excited vibrational states of ammonia. Thermal rate constants were calculated for the temperature range 200–2000 K using the three methods and compared with available experimental data. We found that (a) the total reaction probabilities are very small, (b) the symmetric and asymmetric N–H stretch excitations enhance the reactivity, (c) the quantum-mechanical calculated thermal rate constants are about one order of magnitude smaller than the transition state theory results, which reproduce the experimental evidence, and (d) quasi-classical trajectory calculations, which were performed with the main goal of analyzing the influence of the zero-point energy problem on the final dynamics results, reproduce the quantum scattering calculations on the same surface.
Selective adsorption of atomic hydrogen on a h-BN thin film
Authors: Koswattage Kaveenga Rasika , Shimoyama Iwao , Baba Yuji , Sekiguchi Tetsuhiro , Nakagawa Kazumichi
Published: July 2011

The adsorption of atomic hydrogen on hexagonal boron nitride (h-BN) is studied using two element-specific spectroscopies, i.e., near-edge x-ray absorption fine structure (NEXAFS) spectroscopy and x-ray photoelectron spectroscopy (XPS). B K-edge NEXAFS spectra show a clear change in the energy region of the π* band before and after reaction with atomic deuterium. On the other hand, N K-edge NEXAFS spectra show only a little change. B 1s XPS spectra show a distinct component at the low binding energy side of a main component, while N 1s XPS spectra show peak broadening at the high binding energy side. These experimental results are analyzed by the discrete variational Xα method with a core-hole effect and are explained by a model in which hydrogen atoms are preferentially adsorbed on the B sites of h-BN. Based on the experimental and theoretical results, we propose a site-selective property of BN material on adsorption of atomic hydrogen.
Bistability in an injection locked two color laser with dual injection
Authors: Heinricht Patrycja , Wetzel Benjamin , O’Brien Stephen , Amann Andreas , Osborne Simon
Published: July 2011

A two color Fabry-Pérot laser subjected to optical injection in both modes is examined experimentally and theoretically. The theoretical analysis predicts a bistability between locked states due to a swallow-tail bifurcation, which is unique to the dual injection system. This bistability is confirmed experimentally and used as the basis for an all optical memory element with switching times below 500 ps.
A multigrid method for N-component nucleation
Authors: van Putten Dennis S. , Glazenborg Simon P. , Hagmeijer Rob , Venner Cornelis H.
Published: July 2011

A multigrid algorithm has been developed enabling more efficient solution of the cluster size distribution for N-component nucleation from the Becker-Döring equations. The theoretical derivation is valid for an arbitrary number of condensing components, making the simulation of many-component nucleating systems feasible. A steady state ternary nucleation problem is defined to demonstrate its efficiency. The results are used as a validation for existing nucleation theories. The non-steady state ternary problem provides useful insight into the initial stages of the nucleation process. We observe that for the ideal mixture the main nucleation flux bypasses the saddle point.
A fiber loop mirror temperature sensor demodulation technique using a long-period grating in a photonic crystal fiber and a band-pass filter
Authors: Wang Yunpeng , Zhao Chun-Liu , Dong Xinyong , Kang Juan , Jin Shangzhong
Published: July 2011

A fiber loop mirror (FLM) temperature sensor using a long-period grating (LPG) written in a photonic crystal fiber (PCF) and a band-pass filter as a demodulator is proposed. By utilizing the stable filtering function of the LPG in the PCF, the resonant wavelength variation of the FLM with temperature is transferred effectively to the intensity variation of the output light. By monitoring the light intensity of the band-pass of the filter, temperature applied on the FLM is deduced by an optical power meter. Experiment results show that the temperature sensitivity is high as ∼1.742 dB/ °C when a filter with a full width at half maximum 3 nm and the center at 1545 nm is used.
Simple preconditioning for time-dependent density functional perturbation theory
Authors: Lehtovaara Lauri , Marques Miguel A. L.
Published: July 2011

By far, the most common use of time-dependent density functional theory is in the linear-reponse regime, where it provides information about electronic excitations. Ideally, the linear-response equations should be solved by a method that avoids the use of the unoccupied Kohn-Sham states — such as the Sternheimer method — as this reduces the complexity and increases the precision of the calculation. However, the Sternheimer equation becomes ill-conditioned near and indefinite above the first resonant frequency, seriously hindering the use of efficient iterative solution methods. To overcome this serious limitation, and to improve the general convergence properties of the iterative techniques, we propose a simple preconditioning strategy. In our method, the Sternheimer equation is solved directly as a linear equation using an iterative Krylov subspace method, i.e., no self-consistent cycle is required. Furthermore, the preconditioner uses the information of just a few unoccupied states and requires simple and minimal modifications to existing implementations. In this way, convergence can be reached faster and in a considerably wider frequency range than the traditional approach.
Homogeneous nano-patterning using plasmon-assisted photolithography
Authors: Ueno Kosei , Takabatake Satoaki , Onishi Ko , Itoh Hiroko , Nishijima Yoshiaki , Misawa Hiroaki
Published: July 2011

We report an innovative lithography system appropriate for fabricating sharp-edged nanodot patterns with nanoscale accuracy using plasmon-assisted photolithography. The key technology is two-photon photochemical reactions of a photoresist induced by plasmonic near-field light and the scattering component of the light in a photoresist film. The scattering component of the light is a radiation mode from higher order localized surface plasmon resonances scattered by metallic nanostructures.
Tetracene thin film transistors with polymer gate dielectrics
Authors: Bertolazzi Simone , Wünsche Julia , Cicoira Fabio , Santato Clara
Published: July 2011

The use of polymer dielectrics is an important step towards large-area, flexible, and low-cost electronics. In this letter, we study the effect of the polymer dielectrics polystyrene and parylene C on the charge transport properties of tetracene thin films in transistor configuration. By using polymer dielectrics, the tetracene hole mobility increased by more than one order of magnitude, up to 0.2 cm2 V−1 s−1, as compared to bare silicon dioxide. We correlate this result to a favorable morphology of the tetracene films during the early stages of growth.
NiSi crystal structure, site preference, and partitioning behavior of palladium in NiSi(Pd)/Si(100) thin films: Experiments and calculations
Authors: Mao Zugang , Kim Yeong-Cheol , Lee Hi-Deok , Adusumilli Praneet , Seidman David N.
Published: July 2011

The crystal structure of a NiSi thin-film on a Si substrate and Pd site-substitution in NiSi and the partitioning behavior of Pd for NiSi(Pd)/Si(100) are investigated by x-ray diffraction (XRD), first-principles calculations, and atom-probe tomography (APT). The NiSi layer is a distorted orthorhombic structure from XRD patterns via experiments and calculations. We find that Pd has a strong driving force, 0.72 eV atom−1, for partitioning from Si into the orthorhombic NiSi layer. The calculated substitutional energies of Pd in NiSi indicate that Pd has a strong preference for Ni sublattice-sites, which is in agreement with concentration profiles determined by APT.
Uracil on Cu(110): A quantitative structure determination by energy-scanned photoelectron diffraction
Authors: Duncan D. A. , Unterberger W. , Kreikemeyer-Lorenzo D. , Woodruff D. P.
Published: July 2011

The local adsorption site of the nucleobase uracil on Cu(110) has been determined quantitatively by energy-scanned photoelectron diffraction (PhD). Qualitative inspection of the O 1s and N 1s soft x-ray photoelectron spectra, PhD modulation spectra, and O K-edge near-edge x-ray adsorption fine structure indicate that uracil bonds to the surface through its nitrogen and oxygen constituent atoms, each in near atop sites, with the molecular plane essentially perpendicular to surface and aligned along the close packed $[1\overline 1 0]$[11¯0] azimuth. Multiple scattering simulations of the PhD spectra confirm and refine this geometry. The Cu-N bondlength is 1.96 ± 0.04 Å, while the Cu–O bondlengths of the two inequivalent O atoms are 1.93 ± 0.04 Å and 1.96 ± 0.04 Å, respectively. The molecule is twisted out of the $[1\overline 1 0]$[11¯0]direction by 11 ± 5°.
Resistance states dependence of photoluminescence in Ag/ZnO/Pt structures
Authors: Yalishev V. Sh. , Kim Y. S. , Park B. H. , Yuldashev Sh. U.
Published: July 2011

Optical and resistance switching properties in the Ag/ZnO/Pt structure were investigated. Two types of resistance switching (bipolar and monopolar) were observed. Photoluminescence measurements showed dissimilar emission spectra for the each type of switching that might be explained by different processes occurred during resistance switching. In case of the bipolar resistance switching, the change in the ultraviolet part of spectrum was observed and it was attributed to Ag+ ions migration. On the other hand, the monopolar switching demonstrated the changes in the visible luminescence emission that could be, in turn, interpreted by the generation/recovery of oxygen vacancies.
Gapless band structure of PbPdO2: A combined first principles calculation and experimental study
Authors: Chen S. W. , Huang S. C. , Guo G. Y. , Lee J. M. , Chiang S. , Chen W. C. , Liang Y. C. , Lu K. T. , Chen J. M.
Published: July 2011

We present experimental evidence of the gapless band structure of PbPdO2 by combined x-ray photoemission and x-ray absorption spectra complemented with first principles band structure calculations. The electronic structure near the Fermi level of PbPdO2 is mainly composed of O 2p and Pd 4d bands, constructing the conduction path along the Pd-O layer in PbPdO2. Pd deficiency in PbPdO2 causes decreased O 2p-Pd 4d and increased O 2p-Pb 6p hybridizations, thereby inducing a small band gap and hence reducing conductivity. Hall measurements indicate that PbPdO2 is a p-type gapless semiconductor with intrinsic hole carriers transporting in the Pd-O layers.
Highly efficient light emission from stacking faults intersecting nonpolar GaInN quantum wells
Authors: Jönen H. , Rossow U. , Bremers H. , Hoffmann L. , Brendel M. , Dräger A. D. , Schwaiger S. , Scholz F. , Thalmair J. , Zweck J. , Hangleiter A.
Published: July 2011

We report on the optical properties of m-plane GaInN/GaN quantum wells (QWs). We found that the emission energy of GaInN QWs grown on m-plane SiC is significantly lower than on non-polar bulk GaN, which we attribute to the high density of stacking faults. Temperature and power dependent photoluminescence reveals that the GaInN QWs on SiC have almost as large internal quantum efficiencies as on bulk GaN despite the much higher defect density. Our results indicate that quantum-wire-like features formed by stacking faults intersecting the quantum wells provide a highly efficient light emission completely dominating the optical properties of the structures.
Investigation of structural and electronic properties of graphene oxide
Authors: Saxena Sumit , Tyson Trevor A. , Shukla Shobha , Negusse Ezana , Chen Haiyan , Bai Jianming
Published: July 2011

The local atomic structure of graphene oxide has been probed using synchrotron radiations. Detailed investigations of recently proposed simplistic model of graphene oxide using x-ray absorption near edge spectroscopy have been performed. X-ray diffraction measurements and calculations indicate loss of coherence between graphene-like layers. However, larger in-plane structural coherence is understood to be present. Selected area electron diffraction measurements indicate the presence of graphitic regions in graphene oxide which is expected to produce interesting confinement effects in graphene oxide which could be important for the development of tunable electronic and photonic devices.
Utilizing n-type vanadium oxide films as hole-extracting layers for small molecule organic photovoltaics
Authors: Hancox I. , Rochford L. A. , Clare D. , Sullivan P. , Jones T. S.
Published: July 2011

We report increased cell performance for boron subphthalocyanine chloride (SubPc)/fullerene (C60) organic photovoltaic (OPV) cells when thermally evaporated vanadium oxide (V2OX) thin films are incorporated as a hole-extracting layer at the indium-tin oxide (ITO)/SubPc interface. Ultra-violet photoemission spectroscopy (UPS) studies of the V2OX films reveal highly n-type character, with a large work function of 6.8 eV. This correlates well with recently reported data for other metal oxide hole-extracting layers, such as molybdenum oxide and tungsten oxide, in contrast to the p-type character previously reported for V2OX films. There is significant improvement in energy level alignment for hole-extraction when cells utilise the V2OX layer at the ITO/SubPc interface, resulting in substantial increases in open circuit voltage (VOC) and power conversion efficiency (ηp).
Photoreflectance study of N- and Sb-related modifications of the energy gap and spin-orbit splitting in InNAsSb alloys
Authors: Kudrawiec R. , Latkowska M. , Misiewicz J. , Zhuang Q. , Godenir A. M. R. , Krier A.
Published: July 2011

Photoreflectance spectroscopy has been used to study the energy gap and spin-orbit splitting in InNAsSb alloys containing different amounts of nitrogen and antimony. It has been observed that nitrogen mainly affects the conduction band, without having any influence on the spin-orbit splitting, whereas antimony significantly modifies the spin-orbit splitting. The N- and Sb-related modifications to the band structure lead to alloys which have a spin orbit splitting larger than the energy gap. Consequently, InNAsSb alloys are very promising for use in optoelectronic devices since they offer a route towards the reduction of non-radiative Auger recombination.
Effect of the viscosity on the electrical response of a hydrosolution
Authors: Freire F. C. M. , Dascalu C. , Atasiei R. , Alexe-Ionescu A. L. , Barbero G.
Published: July 2011

The electric response of a hydrosolution is investigated. We show that our experimental data can be interpreted by means of the standard drift-diffusion model only if the frequency dependence of the viscosity of the hydrosolution is taken into account. From this result, it follows that measurements of impedance spectroscopy can give information on the non-newtonian character of complex fluids.
Better biomolecule thermodynamics from kinetics
Authors: Girdhar Kiran , Scott Gregory , Chemla Yann R. , Gruebele Martin
Published: July 2011

Protein stability is measured by denaturation: When solvent conditions are changed (e.g., temperature, denaturant concentration, or pH) the protein population switches between thermodynamic states. The resulting denaturation curves have baselines. If the baselines are steep, nonlinear, or incomplete, it becomes difficult to characterize protein denaturation. Baselines arise because the chromophore probing denaturation is sensitive to solvent conditions, or because the thermodynamic states evolve structurally when solvent conditions are changed, or because the barriers are very low (downhill folding). Kinetics can largely eliminate such baselines: Relaxation of chromophores, or within thermodynamic states, is much faster than the transition over activation barriers separating states. This separation of time scales disentangles population switching between states (desired signal) from chromophore or population relaxation within states (baselines). We derive simple formulas to extract unfolding thermodynamics from kinetics. The formulas are tested with model data and with a difficult experimental test case: the apparent two-state folder PI3K SH3 domain. Its melting temperature Tm can be extracted reliably by our “thermodynamics from kinetics approach,” even when conventional fitting is unreliable.
The effect of particle size on coercivity and crystallinity of SmCo5
Authors: Chen C. H. , Knutson S. J. , Shen Y. , Wheeler R. A. , Horwath J. C. , Barnes P. N.
Published: July 2011

It is observed a turning point in the particle size for which the coercivity Hci of a Sm-Co alloy reaches a peak. Using a broad size range from 20 nm to 5 mm, the turning point of the flake thickness for SmCo5 nanoflakes is determined in the range of 100–180 nm with Hci peak at ∼20 kOe. A lower coercivity at a particle size well below the turning point is likely related to a more detailed nanoscale morphology that controls coercivity. The effect of particle size on crystallinity for high energy milled powder is also discussed with four observations.
Ion adsorption and its influence on direct current electric field induced deformations of flexoelectric nematic layers
Authors: Derfel Grzegorz , Buczkowska Mariola
Published: July 2011

The influence of ion adsorption on the behavior of the nematic liquid crystal layers is studied numerically. The homeotropic flexoelectric layer subjected to the dc electric field is considered. Selective adsorption of positive ions is assumed. The analysis is based on the free energy formalism for ion adsorption. The distributions of director orientation angle, electric potential, and ion concentrations are calculated by numerical resolving of suitable torques equations and Poisson equation. The threshold voltages for the deformations are also determined. It was shown that adsorption affects the distributions of both cations and anions. Sufficiently large number of adsorbed ions leads to spontaneous deformation arising without any threshold if the total number of ions creates sufficiently strong electric field with significant field gradients in the neighborhood of electrodes. The spontaneous deformations are favored by strong flexoelectricity, large thickness, large ion concentrations, weak anchoring, and large adsorption energy.
Diagnosis of breast cancer recurrence using a microfluidic device featuring tethered cationic polymers
Authors: Chen Jem-Kun , Bai Bing-Jun , Chang Feng-Chih
Published: July 2011

In this study, we grafted pH-responsive poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) onto a Si substrate as the medium in a microfluidic device to detect breast cancer recurrence DNA (bcrDNA584) and a control human genomic DNA (hgDNA528) at extremely low concentrations (down to 0.15 ng/μl). The quantities of these two DNAs obtained through the capture and release from tethered PDMAEMA brushes under pH tuning conditions were sufficient for them to be amplified recognizably, suggesting that this approach could be used in miniaturized lab-on-a-chip cartridges for rapid disease diagnosis.
Hot carrier effect on gate-induced drain leakage current in high-k/metal gate n-channel metal-oxide-semiconductor field-effect transistors
Authors: Dai Chih-Hao , Chang Ting-Chang , Chu Ann-Kuo , Kuo Yuan-Jui , Ho Szu-Han , Hsieh Tien-Yu , Lo Wen-Hung , Chen Ching-En , Shih Jou-Miao , Chung Wan-Lin , Dai Bai-Shan , Chen Hua-Mao , Xia Guangrui , Cheng Osbert , Huang Cheng Tung
Published: July 2011

This paper investigates the channel hot carrier stress (CHCS) effects on gate-induced drain leakage (GIDL) current in high-k/metal-gate n-type metal-oxide-semiconductor field effect transistors. It was found that the behavior of GIDL current during CHCS is dependent upon the interfacial layer (IL) oxide thickness of high-k/metal-gate stacks. For a thinner IL, the GIDL current gradually decreases during CHCS, a result contrary to that found in a device with thicker IL. Based on the variation of GIDL current at different stress conditions, the trap-assisted band-to-band hole injection model is proposed to explain the different behavior of GIDL current for different IL thicknesses.
Temperature performance of the edge emitting transistor laser
Authors: Liang Song , Zhu Hongliang , Kong Duanhua , Niu Bin , Zhao Lingjuan , Wang Wei
Published: July 2011

The characteristic temperature (T0) of the edge emitting transistor laser (TL) is studied numerically. For the deep-ridge TL, the common base (CB) mode characteristic temperature (T0,CB) is a lot lower than the common emitter (CE) mode characteristic temperature (T0,CE), which is comparable to a conventional laser. This is resulted from the increase of the emitter to base current gain with the base current, which amplifies the increase of the CB threshold current with temperature. For the shallow-ridge TL, the T0,CE is found to be also rather low and is only slightly higher than the T0,CB. This can be attributed to the large fraction of electron current in the total base current, which is related to the large thickness of base layer and the insertion of quantum wells in the TL.
Increment of the Extinction Illusion by Long Stimulation
Authors: Araragi Yukyu , Kitaoka Akiyoshi
Published: July 2011

We quantitatively examined the effect of stimulus duration on the extinction illusion. A white disc was presented or not presented at an intersection of a grey grid (intersection configuration) or on a homogeneous background (background configuration). The extinction illusion was quantified as the subtraction of no-disc responses in the background configuration (ie baseline) from no-disc responses in the intersection configuration, when the disc was presented. Experiment 1 showed a temporal effect: the extinction illusion increased as stimulus duration increased; this temporal effect was observed when the disc was presented at 9 deg from the fixation point and when the stimulus duration was 1000 – 6000 ms. Experiment 2 showed a visual field anisotropy: the extinction illusion occurred more frequently in the upper visual field than in the lower visual field, when the stimulus duration was 200 ms; the anisotropy was not observed when the stimulus duration was 6000 ms. Experiment 3 showed an alley-length effect: when the grid alley was long, the extinction illusion occurred more frequently in the 6000 ms condition than in the 200 ms condition; the temporal effect was not observed when the grid alley was short. These results suggest that the temporal effect of the extinction illusion might be due to perceptual filling-in of luminance information of the grid alley.
Haptic Object Recognition: How Important are Depth Cues and Plane Orientation?
Authors: Lawson Rebecca , Bracken Sarah
Published: July 2011

Raised-line drawings of familiar objects are very difficult to identify with active touch only. In contrast, haptically explored real 3-D objects are usually recognised efficiently, albeit slower and less accurately than with vision. Real 3-D objects have more depth information than outline drawings, but also extra information about identity (eg texture, hardness, temperature). Previous studies have not manipulated the availability of depth information in haptic object recognition whilst controlling for other information sources, so the importance of depth cues has not been assessed. In the present experiments, people named plastic small-scale models of familiar objects. Five versions of bilaterally symmetrical objects were produced. Versions varied only in the amount of depth information: minimal for cookie-cutter and filled-in outlines, partial for squashed and half objects, and full for 3-D models. Recognition was faster and much more accurate when more depth information was available, whether exploration was with both hands or just one finger. Novices found it almost impossible to recognise objects explored with two hand-held probes whereas experts succeeded using probes regardless of the amount of depth information. Surprisingly, plane misorientation did not impair recognition. Unlike with vision, depth information, but not object orientation, is extremely important for haptic object recognition.
Different Signals of Personality and Health from the Two Sides of the Face
Authors: Kramer Robin S S , Ward Robert
Published: July 2011

Previous studies demonstrate that people with different personality traits have different-looking faces. We investigated whether personality and health information are differently signalled by the two hemifaces. Using composite images created from women with high and low scores on health and personality dimensions, we investigated discrimination accuracy with original and mirrored hemifaces. By comparing discrimination accuracy for particular types of hemiface, we address issues regarding both the location of information signals and how these signals are conveyed. From the hemiface stimuli, participants could accurately identify three of the Big Five traits, along with health. We found differences in which hemiface could be more accurately identified, depending on the expressed trait. Emotional stability and health were more accurately discriminated from the right hemiface, while extraversion showed higher accuracy from the left hemiface. We found evidence for differences between hemifaces related to both directional asymmetries and to other information content. Finally, our results also address ongoing debate about which side of the face is more attractive, as we found attractiveness differences between hemifaces depended upon the personality trait most clearly expressed.