bluuebunny/crossref_metadata_2025 huggingface dataset:
Architecture and Ritual in the Churches of Constantinople
Authors: Marinis Vasileios
Published: December 2013

This book examines the interchange of architecture and ritual in the Middle and Late Byzantine churches of Constantinople (ninth to fifteenth centuries). It employs archaeological and archival data, hagiographic and historical sources, liturgical texts and commentaries, and monastic typika and testaments to integrate the architecture of the medieval churches of Constantinople with liturgical and extra-liturgical practices and their continuously evolving social and cultural context. The book argues against the approach that has dominated Byzantine studies: that of functional determinism, the view that architectural form always follows liturgical function. Instead, proceeding chapter by chapter through the spaces of the Byzantine church, it investigates how architecture responded to the exigencies of the rituals, and how church spaces eventually acquired new uses. The church building is described in the context of the culture and people whose needs it was continually adapted to serve. Rather than viewing churches as frozen in time (usually the time when the last brick was laid), this study argues that they were social constructs and so were never finished, but continually evolving.
On the contact region of a diffusion-limited evaporating drop: a local analysis
Authors: Morris S. J. S.
Published: December 2013

Motivated by experiments showing that a sessile drop of volatile perfectly wetting liquid initially advances over the substrate, but then reverses, we formulate the problem describing the contact region at reversal. Assuming a separation of scales, so that the radial extent of this region is small compared with the instantaneous radius$a$of the apparent contact line, we show that the time scale characterizing the contact region is small compared with that on which the bulk drop is evolving. As a result, the contact region is governed by a boundary-value problem, rather than an initial-value problem: the contact region has no memory, and all its properties are determined by conditions at the instant of reversal. We conclude that the apparent contact angle$\theta $is a function of the instantaneous drop radius$a$, as found in the experiments. We then non-dimensionalize the boundary-value problem, and find that its solution depends on one parameter$\mathscr{L}$, a dimensionless surface tension. According to this formulation, the apparent contact angle is well-defined: at the outer edge of the contact region, the film slope approaches a limit that is independent of the curvature of bulk drop. In this, it differs from the dynamic contact angle observed during spreading of non-volatile drops. Next, we analyse the boundary-value problem assuming$\mathscr{L}$to be small. Though, for arbitrary$\mathscr{L}$, determining$\theta $requires solving the steady diffusion equation for the vapour, there is, for small$\mathscr{L}$, a further separation of scales within the contact region. As a result,$\theta $is now determined by solving an ordinary differential equation. We predict that$\theta $varies as${a}^{- 1/ 6} $, as found experimentally for small drops ($a\lt 1~\mathrm{mm} $). For these drops, predicted and measured angles agree to within 10–30 %. Because the discrepancy increases with$a$, but$\mathscr{L}$is a decreasing function of$a$, we infer that some process occurring outside the contact region is required to explain the observed behaviour of larger drops having$a\gt 1~\mathrm{mm} $.
Entrepreneurial judgment as empathic accuracy: a sequential decision-making approach to entrepreneurial action
Authors: MCMULLEN JEFFERY S.
Published: December 2013

Entrepreurship theory within economics has long touted the importance of judgment in entrepreneurial action. More recently, proponents have begun to advocate extension of this work to organization studies. However, critics of entrepreneurial judgment have responded by claiming that the construct is only meaningfulpost hocand vapid when examinedex ante. Instead, they claim that, if entrepreneurship theory is to progress, then judgment must be replaced by a process logic known as effectuation. This article examines their claims and redefines the judgment dilemma as one of scope rather than existence. Empathic accuracy is then introduced to offer a means of addressing their criticism without having to deny the existence of entrepreneurial judgment. Empathic accuracy is also shown to be capable of explaining some of the cognitive mechanisms necessary for effectuation and dynamic socio-economic order.
An unusual cobalt(ii)-based single-walled metal–organic nanotube
Authors: Tseng Tien-Wen , Luo Tzuoo-Tsair , Su Chong-Cheng , Hsu Hui-Huan , Yang Chen-I , Lu Kuang-Lieh
Published: December 2013

Self-adaption to the formation of an unusual cobalt(ii)-based single-walled metal–organic nanotube is reported. In addition, a pseudo-merohedral twinning problem encountered in the X-ray diffraction analysis was solved, which significantly improves the crystallographic results.
Dendritic CdS assemblies for removal of organic dye molecules
Authors: Yu Zhou , Qu Fengyu , Wu Xiang
Published: December 2013

In this paper, novel CdS 3D assemblies are prepared via a facile and effective hydrothermal route using dimethyl sulfoxide as the growth template.
Binding multidentate ligands to Ni2+: kinetic identification of preferential binding sites
Authors: Nartop Dilek , Clegg William , Harrington Ross W. , Henderson Richard A. , Wills Corinne Y.
Published: December 2013

Kinetic studies on binding of Ni2+ to various multidentate ligands indicates rates follow the order: NH > pyridyl N > phenolic OH ∼ imine N.
Robust fault‐tolerant control for uncertain delta operator switched systems
Authors: Hu Hao , Jiang Bin , Yang Hao
Published: December 2013

This study addresses two issues of robust fault‐tolerant stabilisation with circular disk pole constraints for uncertain delta operator switched systems with actuator faults. The first computes the dwell time and proposes a state feedback controller design approach to stabilise the considered switched system. The second solves the 𝒟‐stabilisation problem based on state switching strategy. Finally, an illustrative example is provided to validate the feasibility and effectiveness of the proposed approaches.
Improved strain precision with high spatial resolution using nanobeam precession electron diffraction
Authors: Rouviere Jean-Luc , Béché Armand , Martin Yannick , Denneulin Thibaud , Cooper David
Published: December 2013

NanoBeam Electron Diffraction is a simple and efficient technique to measure strain in nanostructures. Here, we show that improved results can be obtained by precessing the electron beam while maintaining a few nanometer probe size, i.e., by doing Nanobeam Precession Electron Diffraction (N-PED). The precession of the beam makes the diffraction spots more uniform and numerous, making N-PED more robust and precise. In N-PED, smaller probe size and better precision are achieved by having diffraction disks instead of diffraction dots. Precision in the strain measurement better than 2 × 10−4 is obtained with a probe size approaching 1 nm in diameter.
Application of Floquet theory to the stability of liquid films on structured surfaces
Authors: Ajaev Vladimir S. , Gatapova Elizaveta Ya. , Kabov Oleg A.
Published: December 2013

We consider instability of a liquid film on a substrate structured by an array of gas-filled grooves. The instability is driven by disjoining pressure, while the effect of structuring on viscous flow in the film is modeled by a square-wave variation of the slip length along the substrate. Linear stability criteria are established analytically using Floquet theory and compared with the predictions of a straightforward numerical approach, all in the framework of a lubrication-type model. Then, stability is analyzed for a more general model based on Stokes flow approximation; validity of the lubrication-type approach is discussed. The structuring is found to enhance the instability for a wide range of conditions. Resonant interaction between the interfacial deformations and the substrate structuring pattern leads to discontinuities in the dispersion curves, a situation analogous to appearance of gaps in the energy spectra seen in the applications of Floquet theory in solid state physics.
A quasi-Bohmian approach for a homogeneous spherical solid body based on its geometric structure
Authors: Koupaei Jalaledin Yousefi , Golshani Mehdi
Published: December 2013

In this paper we express the space of rotation as a Riemannian space and try to generalize the classical equations of motion of a homogeneous spherical solid body in the domain of quantum mechanics. This is done within Bohm's view of quantum mechanics, but we do not use the Schrödinger equation. Instead, we assume that in addition to the classical potential there is an extra potential and try to obtain it. In doing this, we start from a classical picture based on Hamilton-Jacobi formalism and statistical mechanics but we use an interpretation which is different from the classical one. Then, we introduce a proper action and extremize it. This procedure gives us a mathematical identity for the extra potential that limits its form. The classical mechanics is a trivial solution of this method. In the simplest cases where the extra potential is not a constant, a mathematical identity determines it uniquely. In fact the first nontrivial potential, apart from some constant coefficients which are determined by experiment, is the usual Bohmian quantum potential.
Atomic scale investigations of the gate controlled tunneling effect in graphyne nanoribbon
Authors: Yang Wen , Wang Lu-Hao , Geng Yang , Sun Qing-Qing , Zhou Peng , Ding Shi-Jing , Wei Zhang David
Published: December 2013

Configuration and transport properties of zigzag graphyne nanoribbon (n = 2) are investigated by means of the first-principles calculations and non-equilibrium Green's function in this work. We demonstrated the controllability of the graphyne's conductivity by gate bias, and the tunneling behavior induced by gate and drain voltages was investigated systemically. The characteristics of Id-Vd, Id-Vg, as well as the evolutions of current with electron temperature elevation were explored. The device exhibits a tunneling ratio around 103, and the state art of tunneling operations of the tunneling field effect transistor in this split-new material was achieved.
A new semi-analytical solution for inertial waves in a rectangular parallelepiped
Authors: Nurijanyan S. , Bokhove O. , Maas L. R. M.
Published: December 2013

A study of inertial gyroscopic waves in a rotating homogeneous fluid is undertaken both theoretically and numerically. A novel approach is presented to construct a semi-analytical solution of a linear three-dimensional fluid flow in a rotating rectangular parallelepiped bounded by solid walls. The three-dimensional solution is expanded in vertical modes to reduce the dynamics to the horizontal plane. On this horizontal plane, the two dimensional solution is constructed via superposition of “inertial” analogs of surface Poincaré and Kelvin waves reflecting from the walls. The infinite sum of inertial Poincaré waves has to cancel the normal flow of two inertial Kelvin waves near the boundaries. The wave system corresponding to every vertical mode results in an eigenvalue problem. Corresponding computations for rotationally modified surface gravity waves are in agreement with numerical values obtained by Taylor [“Tidal oscillations in gulfs and basins,” Proc. London Math. Soc., Ser. 2 XX, 148–181 (1921)], Rao [“Free gravitational oscillations in rotating rectangular basins,” J. Fluid Mech. 25, 523–555 (1966)] and also, for inertial waves, by Maas [“On the amphidromic structure of inertial waves in a rectangular parallelepiped,” Fluid Dyn. Res. 33, 373–401 (2003)] upon truncation of an infinite matrix. The present approach enhances the currently available, structurally concise modal solution introduced by Maas. In contrast to Maas' approach, our solution does not have any convergence issues in the interior and does not suffer from Gibbs phenomenon at the boundaries. Additionally, an alternative finite element method is used to contrast these two semi-analytical solutions with a purely numerical one. The main differences are discussed for a particular example and one eigenfrequency.
Landau expansion parameters for BaTiO3
Authors: Lu Xiaoyan , Li Hui , Cao Wenwu
Published: December 2013

The 6th order Taylor expansion of the free energy in terms of the order parameter has been generally accepted to describe first order structural phase transitions. In recently years, some researchers added the 8th order terms in order to explain the two branches in dielectric loops observed in the BaTiO3 single crystal. We show that the Landau free energy terminated at the 6th orders is sufficient to fit the experimental observations if the rich information in the field-induced phase transitions is explored. By using the typical characteristics of ferroelectric and dielectric double loops above the Curie temperature Tc, the temperature-dependent expansion coefficients can be determined with high accuracy.
Monotonicity of a relative Rényi entropy
Authors: Frank Rupert L. , Lieb Elliott H.
Published: December 2013

We show that a recent definition of relative Rényi entropy is monotone under completely positive, trace preserving maps. This proves a recent conjecture of Müller-Lennert et al. [“On quantum Rényi entropies: A new definition, some properties,” J. Math. Phys. 54, 122203 (2013); e-print arXiv:1306.3142v1; see also e-print arXiv:1306.3142].
On quantum Rényi entropies: A new generalization and some properties
Authors: Müller-Lennert Martin , Dupuis Frédéric , Szehr Oleg , Fehr Serge , Tomamichel Marco
Published: December 2013

The Rényi entropies constitute a family of information measures that generalizes the well-known Shannon entropy, inheriting many of its properties. They appear in the form of unconditional and conditional entropies, relative entropies, or mutual information, and have found many applications in information theory and beyond. Various generalizations of Rényi entropies to the quantum setting have been proposed, most prominently Petz's quasi-entropies and Renner's conditional min-, max-, and collision entropy. However, these quantum extensions are incompatible and thus unsatisfactory. We propose a new quantum generalization of the family of Rényi entropies that contains the von Neumann entropy, min-entropy, collision entropy, and the max-entropy as special cases, thus encompassing most quantum entropies in use today. We show several natural properties for this definition, including data-processing inequalities, a duality relation, and an entropic uncertainty relation.
The relationship between local liquid density and force applied on a tip of atomic force microscope: A theoretical analysis for simple liquids
Authors: Amano Ken-ichi , Suzuki Kazuhiro , Fukuma Takeshi , Takahashi Ohgi , Onishi Hiroshi
Published: December 2013

The density of a liquid is not uniform when placed on a solid. The structured liquid pushes or pulls a probe employed in atomic force microscopy, as demonstrated in a number of experimental studies. In the present study, the relation between the force on a probe and the local density of a liquid is derived based on the statistical mechanics of simple liquids. When the probe is identical to a solvent molecule, the strength of the force is shown to be proportional to the vertical gradient of ln(ρDS) with the local liquid's density on a solid surface being ρDS. The intrinsic liquid's density on a solid is numerically calculated and compared with the density reconstructed from the force on a probe that is identical or not identical to the solvent molecule.
Fluid of Janus molecules between two walls: The solvation force
Authors: Patrykiejew A. , Sokołowski S. , Sokołowska Z. , Ilnytskyi Ja.
Published: December 2013

We apply a density functional theory to calculate the solvation force in the system involving Janus particles confined between two planar walls. Janus particles are modeled as spheres composed of attractive and repulsive parts and their orientation is described by the vectors representing internal degrees of freedom. We consider the cases of pores with identical walls, as well as the pores with competing walls (the so-called Janus-like pores). The density functional approach we employ combines fundamental measure theory with a mean-field approximation for the anisotropic interparticle interaction. We study how the solvation force and the orientational structure of confined particles depend on the competition between the surface field and the interactions between confined molecules and on the parameters of the model such as temperature and density. It is shown that the anisotropic interaction between the confined molecules and the character of the walls significantly influence the solvation force.
Life cycle greenhouse gas emissions from geothermal electricity production
Authors: Sullivan J. L. , Wang M. Q.
Published: December 2013

A life cycle analysis (LCA) is presented for greenhouse gas (GHG) emissions and fossil energy use associated with geothermal electricity production with a special focus on operational GHG emissions from hydrothermal flash and dry steam plants. The analysis includes results for both the plant and fuel cycle components of the total life cycle. The impact of recent changes to California's GHG reporting protocol for GHG emissions are discussed by comparing emission rate metrics derived from post and pre revision data sets. These metrics are running capacity weighted average GHG emission rates (g/kWh) and emission rate cumulative distribution functions. To complete our life cycle analysis, plant cycle results were extracted from our previous work and added to fuel cycle results. The resulting life cycle fossil energy and greenhouse gas emissions values are compared among a range of fossil, nuclear, and renewable power technologies, including geothermal.
Polymer defect states modulate open-circuit voltage in bulk-heterojunction solar cells
Authors: Ripolles Teresa S. , Guerrero Antonio , Garcia-Belmonte Germà
Published: December 2013

Defect states influence the operation of organic solar cells altering transport, recombination, and energetic mechanisms. This work investigates how processing conditions induce morphology-related, electrically active defects in the donor polymer of bulk-heterojunction solar cells. Structural order is inferred from absorption and X-ray diffraction data, while defect density is determined from capacitance methods. A correlation is observed between the polymer nanocrystallite size, the defect concentration, and the output voltage. For the case of poly(3-hexylthiophene), processing that promote crystallinity is beneficial for the device performance as it decreases the defect density (energy disorder) that finally enlarges the maximum achievable open-circuit voltage. Defect states within the effective bandgap modulate the downshift of the hole Fermi level upon illumination that in turn establishes the achievable open-circuit voltage.
Reorientation of the helix of the tryptophan-rich gp41W peptide from HIV-1 at interfaces
Authors: Matar Gladys , Benichou Emmanuel , Nasir Mehmet Nail , Harfouch Yara El , Brevet Pierre-François , Besson Françoise
Published: December 2013

The glycoprotein gp41 from the Human Immunodeficiency Virus type 1 (HIV-1) has an amino acid sequence enriched in tryptophan residues, the so-called gp41W peptide (i.e., KWASLWNWFNITNWLWYIK) and plays a crucial role in HIV-1 host cell infection. Using the coupling of Second Harmonic Generation targeting the tryptophan residues with lateral surface tension measurements, we investigate the interaction of gp41W with a neat air/water and a lipid/water interfaces. At the air/water interface, gp41W presents a well-defined orientation and this orientation is strongly modified at the lipid/water interface, depending on the surface pressure. These results show that this strategy is well suited to monitor tryptophan containing α-helices orientation at lipid/water interfaces.
Thermal resistance between crossed carbon nanotubes: Molecular dynamics simulations and analytical modeling
Authors: Hu Guo-Jie , Cao Bing-Yang
Published: December 2013

A nonequilibrium molecular dynamics (MD) method is used to calculate the thermal resistance between crossed carbon nanotubes (CNTs). The thermal resistance is predicted to be of the order of 109–1011 K/W. The effects of the crossing angle, nanotube length, and initial nanotube spacing on the thermal resistance are studied in detail with the fixed boundary condition applied in the axial direction of each CNT. The thermal resistance is found to increase with the increasing crossing angle while decrease with the increasing nanotube length and converge to a constant eventually. An increase in the thermal resistance is observed for nanotubes with larger initial spacing and the increase becomes abrupt as the initial spacing is increased to the van der Waals diameter. Between the crossed CNTs the phonon transport is constricted through the contact. The thermal resistance between the crossed CNTs calculated by MD is found to be close to the ballistic constriction resistance, which indicates that the constriction thermal resistance plays a major role in the inter-tube thermal resistance and the ballistic transport of phonons is dominant in the thermal transport between the crossed CNTs.
Multiexciton complex from extrinsic centers in AlGaAs epilayers on Ge and Si substrates
Authors: Sarti F. , Muñoz Matutano G. , Bauer D. , Dotti N. , Bietti S. , Isella G. , Vinattieri A. , Sanguinetti S. , Gurioli M.
Published: December 2013

The multiexciton properties of extrinsic centers from AlGaAs layers on Ge and Si substrates are addressed. The two photon cascade is found both in steady state and in time resolved experiments. Polarization analysis of the photoluminescence provides clearcut attribution to neutral biexciton complexes. Our findings demonstrate the prospect of exploiting extrinsic centers for generating entangled photon pairs on a Si based device.
Influence of excess Ba concentration on the dielectric nonlinearity in Mn and V-doped BaTiO3 multi layer ceramic capacitors
Authors: Yoon Seok-Hyun , Kim Sun-Jung , Kim Sang-Hyuk , Kim Doo-Young
Published: December 2013

The effect of excess Ba concentration on the dielectric nonlinearity was investigated in Mn and V-doped BaTiO3 multi layer ceramic capacitors (MLCC) under the same grain size condition, which was described by the Preisach model utilizing the first order reversal curve (FORC) distribution. The high-field dielectric constant and its ac field dependence dramatically changed increasing to a maximum and then decreasing with the increase of Ba concentration. The saturation polarization which scales to the magnitude of spontaneous polarization also showed similar behavior. These results indicate that the dependence of the dielectric constant on the Ba concentration is associated with the variation of both domain wall contribution and the magnitude of the spontaneous polarization, which could be correlated with the same dependence on the Ba concentration of the reversible FORC distribution at zero bias and the irreversible FORC distribution near origin. In the corresponding bulk specimens of the dielectrics of MLCC, almost the same amount of the Ba2TiSi2O8 second phases were detected irrespective of Ba concentration, which shows that the excess Ba incorporate into BaTiO3. Thus, low and high Ba concentration corresponds to Ba-deficient and Ba-rich or Ti-deficient BaTiO3, respectively, which results in a small spontaneous polarization and low domain wall density. The intermediate Ba concentration for the maximum dielectric constant is supposed to be near stoichiometric condition in the ABO3 structure corresponding to large spontaneous polarization and high domain wall density. The excess Ba concentration and its resultant A/B stoichiometry is a crucial factor controlling dielectric properties.
Current–voltage characteristics of the semiconductor nanowires under the metal-semiconductor-metal structure
Authors: Wen Jing , Zhang Xitian , Gao Hong , Wang Mingjiao
Published: December 2013

We present a method to calculate the I-V characteristics of semiconductor nanowires under the metal-semiconductor-metal (MSM) structure. The carrier concentration as an important parameter is introduced into the expression of the current. The subband structure of the nanowire has been considered for associating it with the position of the Fermi level and circumventing the uncertainties of the contact areas in the contacts. The tunneling and thermionic emission currents in the two Schottky barriers at the two metal-semiconductor contacts are discussed. We find that the two barriers have different influences on the I-V characteristics of the MSM structure, one of which under the forward bias plays the role of threshold voltage if its barrier height is large and the applied voltage is small, and the other under the reverse bias controls the shapes of I-V curves. Our calculations show that the shapes of the I-V curves for the MSM structure are mainly determined by the barrier heights of the contacts and the carrier concentration. The nearly identical I-V characteristics can be obtained by using different values of the barrier heights and carrier concentration, which means that the contact type conversion can be ascribed not only to the changes of the barrier heights but also that of the carrier concentration. We also discuss the mechanisms of the ohmic-Schottky conversions and clarify the ambiguity in the literature. The possibility about the variation of the carrier concentration under the applied fields has been confirmed by experimental results.
Forces and torque on a pair of uncharged conducting spheres in an external electric field
Authors: Lekner John
Published: December 2013

Exact results are given for the forces acting on two conducting spheres in an applied electric field E. The torque acting on the two-sphere system is proportional to the difference between the longitudinal and transverse polarizabilities: τ=(αℓ−αt)E2 sinθ cosθ (θ is the angle between the applied field and the line-of-centers of the spheres). The forces acting on the two spheres are equal and opposite, and given by the derivatives of αℓ and αt with respect to the sphere separation. Simple analytic forms for the torque and forces are found at small and at large separations. At all separations, the torque always acts to align the line of centers of the spheres with the external field. Possible applications are to colloidal suspensions of spherical conducting particles.
Mn concentration dependent structural and optical properties of a-plane Zn0.99-xMnxNa0.01O
Authors: Lu B. , Zhou T. T. , Ma M. J. , Ye Y. H. , Ye Z. Z. , Lu J. G. , Pan X. H.
Published: December 2013

Non-polar a-plane (112¯0) Zn0.99−xMnxNa0.01O (x = 0, 0.02, 0.03, 0.04, and 0.05) thin films have been prepared on r-plane (112¯0) sapphire substrates by pulsed laser deposition (PLD). The influences of Mn content on the structural and optical properties of the films have been studied. It is indicated that moderate Mn doping facilitates the non-polar growth of ZnO, and all the doped films are single phase with a hexagonal wurtzite structure. The transmittance spectra suggested that all films are transparent in the visible region exhibiting a transmittance above 80%. Mn2+ doped Zn0.99Na0.01O shows an initial decrease of optical band gap (OBG) for small concentration of Mn, followed by a monotonic increase. The anomalous decrease in OBG for low concentrations of Mn is attributed to the strong exchange interaction present between the sp electrons of the host matrix and d electrons of Mn. Emission studies were also performed showing suppressed blue-shifted ultraviolet band and dominant violet-blue bands, which might originate from the zinc vacancy (VZn) and zinc interstitial (Zni) defects. The intensity of defect-related emission peaks is Mn doping-level-dependent as well and the results coincide well with that from the structural analyses.
Effect of wool and thermo-binder fibers on adhesion of alfa fibers in polyester composite
Authors: Omri Med. Amin , Triki A. , Guicha M. , Hassen Med. Ben , Arous M. , Ahmed El Hamzaoui H. , Bulou A.
Published: December 2013

Dielectric study was investigated in order to probe the interfacial region fibers/matrix of the polyester composite reinforced with alfa/wool/thermo-binder fibers. Dielectric spectra were measured in the frequency range from 10−1 Hz to 106 Hz, and temperature interval from 40 °C to 150 °C. This study revealed the presence of two dielectric relaxations in the composite. While the first one was attributed to the α mode relaxation associated with the glass transition of the matrix, the second was associated with the conductivity resulting from the carriers' charges diffusion noted for high temperature above glass transition and low frequencies. As this study did not show the presence of the interfacial polarization effect in the composite, it was accomplished with the vibrational study using the FT-IR and Raman techniques. A great compatibility between fibers and matrix was proven by a less hydrophilic character of the reinforcement giving rise to additional valence vibrations from wool fibers and hydrogen bonds.
First-principles DFT+U modeling of defect behaviors in anti-ferromagnetic uranium mononitride
Authors: Lan Jian-Hui , Zhao Zi-Chen , Wu Qiong , Zhao Yu-Liang , Chai Zhi-Fang , Shi Wei-Qun
Published: December 2013

A series of point defects in uranium mononitride (UN) have been studied by first-principles DFT+U calculations. The influence of intrinsic defects on the properties of UN was explored by considering the anti-ferromagnetic (AFM) order along the [001] direction. Our results show that all the point defects lead to obvious volume swelling of UN crystal. Energetically, the interstitial nitrogen defect is the most favorable one among single-point defects in UN crystal with the formation energy of 4.539 eV, while the N-Frenkel pair becomes the most preferable one among double-point defects. The AFM order induces obvious electron spin polarization of uranium towards neighboring uranium atoms with opposite spin orientations in UN crystal.
Self-frequency summing in quantum dot photonic crystal nanocavity lasers
Authors: Ota Yasutomo , Watanabe Katsuyuki , Iwamoto Satoshi , Arakawa Yasuhiko
Published: December 2013

We demonstrate self-frequency summing in photonic crystal nanocavity lasers with quantum dot gain. Two dipole modes and a hexapole mode, supported in the cavity, simultaneously showed lasing oscillation in the near infrared wavelength region under optical carrier injection. Meanwhile, within the same laser cavity, the internally generated three laser fields are up-converted to exhibit sharp visible emission lines via intra-cavity nonlinear frequency summing (and doubling) processes. This self-frequency summing process in active nanocavities will pave the way for developing nanoscale nonlinear optical light sources.
InAs/GaAs p-type quantum dot infrared photodetector with higher efficiency
Authors: Lao Yan-Feng , Wolde Seyoum , Unil Perera A. G. , Zhang Y. H. , Wang T. M. , Liu H. C. , Kim J. O. , Schuler-Sandy Ted , Tian Zhao-Bing , Krishna S. S.
Published: December 2013

An InAs/GaAs quantum dot infrared photodetector (QDIP) based on p-type valence-band intersublevel hole transitions as opposed to conventional electron transitions is reported. Two response bands observed at 1.5–3 and 3–10 μm are due to transitions from the heavy-hole to spin-orbit split-off QD level and from the heavy-hole to heavy-hole level, respectively. Without employing optimized structures (e.g., the dark current blocking layer), the demonstrated QDIP displays promising characteristics, including a specific detectivity of 1.8×109 cm·Hz1/2/W and a quantum efficiency of 17%, which is about 5% higher than that of present n-type QDIPs. This study shows the promise of utilizing hole transitions for developing QDIPs.
Direct evidence of correlations between relaxor behavior and polar nano-regions in relaxor ferroelectrics: A case study of lead-free piezoelectrics Na0.5Bi0.5TiO3-x%BaTiO3
Authors: Ge Wenwei , Luo Chengtao , Devreugd Christopher P. , Zhang Qinhui , Ren Yang , Li Jiefang , Luo Haosu , Viehland D.
Published: December 2013

Diffuse scattering and relaxor behavior in Na0.5Bi0.5TiO3 (NBT) and NBT-5.6 at. %BaTiO3 (NBT-5.6%BT) were investigated. X-ray diffraction revealed two types of diffuse scattering in NBT: (i) broad and (ii) asymmetric L-shaped. After modification with 5.6%BT, the broad diffuse scattering patterns became narrow, and the asymmetric L-shaped ones were replaced by symmetric ones. The symmetric diffuse scattering in NBT-5.6%BT disappeared with increasing dc electric field (E) for E ≥ 9.5 kV/cm where the frequency dispersion in the dielectric constant disappeared. These results demonstrate that the relaxor characteristics are directly correlated with the diffuse scattering and the presence polar nano-regions.
Enhanced absorption of solar light in Ge/Si core-sheath nanowires compared to Si/Ge core-sheath and Si1−xGex nanowires: A theoretical study
Authors: Kallel Houssem , Chehaidar Abdallah , Arbouet Arnaud , Paillard Vincent
Published: December 2013

Coaxial core-sheath semiconductor nanowires exhibit an improved light absorption efficiency, rendering them promising building blocks in photovoltaic devices. In the present theoretical work, we focus on the optical properties of Si/Ge and Ge/Si core-sheath nanowires, compared to Si1−xGex alloy variants (without coated shell) of the same composition in Si and Ge. Using the analytical Lorenz-Mie theory, we compute both the absorption and scattering efficiencies, with a particular attention devoted to the shell thickness influence. The leaky modes resonances, associated to the optical response enhancement, are investigated and compared for all core/sheath and alloy variants. The optical resonances are found to keep almost the same spectral positions regardless the nanowire structure. More interestingly, core-sheath nanowires absorb more efficiently visible to near-infrared light than Si1−xGex alloys. Finally, the integrated solar absorption Jsolar, which is a figure of merit proportional to the photocurrent generated in a nanowire, is more efficient in the case of Ge/Si core-sheath nanowires than in the two other structures.
Frequencies of the geodesic acoustic mode and Alfvén gap modes in high-q2β plasmas with non-circular cross section
Authors: Fesenyuk O. P. , Kolesnichenko Ya. I. , Yakovenko Yu. V.
Published: December 2013

This work generalizes recent results [O. P. Fesenyuk et al., Plasma Phys. Controlled Fusion 54, 085014 (2012)] to plasmas with elongated cross section. It suggests new expressions for the frequencies of the geodesic acoustic mode and Alfvén gap modes in tokamaks, with a large ratio of the plasma pressure to the magnetic field pressure and a large safety factor (q≫1, which takes place in discharges with reversed-shear configuration and, especially, in hollow-current discharges).
Theory of waves in pair-ion plasmas: Natural explanation of backward modes
Authors: Kono M. , Vranjes J. , Batool N.
Published: December 2013

Backward waves observed in the experiments by Oohara and Hatakeyama (Phys. Rev. Lett. 91, 205005 (2003)) are identified to be ion cyclotron harmonic waves inherent to the kinetic theory. The derived dispersion equation is based on exact solutions of the characteristic equations of the Vlasov equation in a bounded cylindrical coordinate system; it is different from its counterpart in unbounded plasmas, and it provides all the branches of the dispersion relations observed in the experiment. Positive and negative ions respond to a potential in the same time scale and cooperate to expose kinetic orbital behaviors to the macroscopic propagation characteristics. In addition, the experimental setting of the large Larmor radius makes higher harmonic ion cyclotron backward/forward waves observable. The large Larmor radius effects are naturally treated by a kinetic theory.
Note: In situ measurement of vacuum window birefringence by atomic spectroscopy
Authors: Steffen Andreas , Alt Wolfgang , Genske Maximilian , Meschede Dieter , Robens Carsten , Alberti Andrea
Published: December 2013

We present an in situ method to measure the birefringence of a single vacuum window by means of microwave spectroscopy on an ensemble of cold atoms. Stress-induced birefringence can cause an ellipticity in the polarization of an initially linearly polarized laser beam. The amount of ellipticity can be reconstructed by measuring the differential vector light shift of an atomic hyperfine transition. Measuring the ellipticity as a function of the linear polarization angle allows us to infer the amount of birefringence Δn at the level of 10−8 and identify the orientation of the optical axes. The key benefit of this method is the ability to separately characterize each vacuum window, allowing the birefringence to be precisely compensated in existing vacuum apparatuses.
Extracting strength from high pressure ramp-release experiments
Authors: Brown J. L. , Alexander C. S. , Asay J. R. , Vogler T. J. , Ding J. L.
Published: December 2013

Unloading from a plastically deformed state has long been recognized as a sensitive measure of a material's deviatoric response. In the case of a ramp compression and unload, time resolved particle velocity measurements of a sample/window interface may be used to gain insight into the sample material's strength. Unfortunately, measurements of this type are often highly perturbed by wave interactions associated with impedance mismatches. Additionally, wave attenuation, the finite pressure range over which the material elastically unloads, and rate effects further complicate the analysis. Here, we present a methodology that overcomes these shortcomings to accurately calculate a mean shear stress near peak compression for experiments of this type. A new interpretation of the self-consistent strength analysis is presented and then validated through the analysis of synthetic data sets on tantalum to 250 GPa. The synthetic analyses suggest that the calculated shear stresses are within 3% of the simulated values obtained using both rate-dependent and rate-independent constitutive models. Window effects are addressed by a new technique referred to as the transfer function approach, where numerical simulations are used to define a mapping to transform the experimental measurements to in situ velocities. The transfer function represents a robust methodology to account for complex wave interactions and a dramatic improvement over the incremental impedance matching methods traditionally used. The technique is validated using experiments performed on both lithium fluoride and tantalum ramp compressed to peak stresses of 10 and 15 GPa, respectively. In each case, various windows of different shock impedance are used to ensure consistency within the transfer function analysis. The data are found to be independent of the window used and in good agreement with previous results.
Temperature dependent junction capacitance-voltage characteristics of Ni embedded TiN/SiO2/p-Si metal–insulator–semiconductor structure
Authors: Panda J. , Chattopadhyay S. , Nath T. K.
Published: December 2013

This work presents the junction capacitance–voltage characteristics of highly textured/epitaxial Ni nanoparticle embedded in TiN matrix (TiN(Ni)) metal-insulator-semiconductor TiN(Ni)/SiO2/p-Si (100) heterojunction in the temperature range of 10–300 K. This heterojunction behaves as metal-semiconductor junction with unavoidable leakage through native oxide SiO2 layer. The clockwise hysteresis loop has been observed in the capacitance-voltage characteristics measured at various frequencies mainly due to presence of trap centers at the TiN(Ni)/SiO2 interface and these are temperature dependent. The spin-dependent trap charge effect at the interface influences the quadratic nature of the capacitance with magnetic field. The junction magnetocapacitance (JMC) is observed to be dependent on both temperature and frequency. The highest JMC of this heterojunction has been observed at 200 K at higher frequencies (100 kHz–1 MHz). It is found that there is not much effect of band structure modification under magnetic field causing the JMC.
Motion, collision and annihilation of polarization vortex pair in single crystalline BaTiO3 thin film
Authors: Tian Xianbao , Yang Xinhua , Wang Peng , Peng Di
Published: December 2013

Domain evolution of a single crystalline BaTiO3 thin film, initially possessing two vortex-antivortex pairs, placed under compressive displacement loading with a constant strain rate, is simulated using a molecular dynamics method based on the shell model. The evolution details, including the relative motion and collision between the vortices and antivortices and their annihilation, are carefully observed, and both the movement velocity and the equilibrium time after annihilation are estimated. When the vortex-antivortex pairs annihilate, the polarization configuration evolves into a 180° domain structure. These distinctive domain evolution characteristics could open up opportunities for designing ferroelectric nanodevices.
Nonlinear electron acoustic waves in presence of shear magnetic field
Authors: Dutta Manjistha , Ghosh Samiran , Khan Manoranjan , Chakrabarti Nikhil
Published: December 2013

Nonlinear electron acoustic waves are studied in a quasineutral plasma in the presence of a variable magnetic field. The fluid model is used to describe the dynamics of two temperature electron species in a stationary positively charged ion background. Linear analysis of the governing equations manifests dispersion relation of electron magneto sonic wave. Whereas, nonlinear wave dynamics is being investigated by introducing Lagrangian variable method in long wavelength limit. It is shown from finite amplitude analysis that the nonlinear wave characteristics are well depicted by KdV equation. The wave dispersion arising in quasineutral plasma is induced by transverse magnetic field component. The results are discussed in the context of plasma of Earth's magnetosphere.
Structural investigations of hydrogenated epitaxial graphene grown on 4H-SiC (0001)
Authors: Tokarczyk M. , Kowalski G. , Możdżonek M. , Borysiuk J. , Stępniewski R. , Strupiński W. , Ciepielewski P. , Baranowski J. M.
Published: December 2013

Structural investigations of hydrogenated epitaxial graphene grown on SiC(0001) are presented. It is shown that hydrogen plays a dual role. In addition to contributing to the well-known removal of the buffer layer, it goes between the graphene planes, resulting in an increase of the interlayer spacing to 3.6 Å–3.8 Å. It is explained by the intercalation of molecular hydrogen between carbon planes, which is followed by H2 dissociation, resulting in negatively charged hydrogen atoms trapped between the graphene layers, with some addition of covalent bonding to carbon atoms. Negatively charged hydrogen may be responsible for p-doping observed in hydrogenated multilayer graphene.
Direct measurement of band offset at the interface between CdS and Cu2ZnSnS4 using hard X-ray photoelectron spectroscopy
Authors: Tajima Shin , Kataoka Keita , Takahashi Naoko , Kimoto Yasuji , Fukano Tatsuo , Hasegawa Masaki , Hazama Hirofumi
Published: December 2013

We directly and non-destructively measured the valence band offset at the interface between CdS and Cu2ZnSnS4 (CZTS) using hard X-ray photoelectron spectroscopy (HAXPES), which can measure the electron state of the buried interface because of its large analysis depth. These measurements were made using the following real devices; CZTS(t = 700 nm), CdS(t = 100 nm)/CZTS(t = 700 nm), and CdS(t = 5 nm)/CZTS(t = 700 nm) films formed on Mo coated glass. The valence band spectra were measured by HAXPES using an X-ray photon energy of 8 keV. The value of the valence band offset at the interface between CdS and CZTS was estimated as 1.0 eV by fitting the spectra. The conduction band offset could be deduced as 0.0 eV from the obtained valence band offset and the band gap energies of CdS and CZTS.
An assessment of global Ocean Thermal Energy Conversion resources under broad geographical constraints
Authors: Rajagopalan Krishnakumar , Nihous Gérard C.
Published: December 2013

Rates of Ocean Thermal Energy Conversion (OTEC) are assessed with a high-resolution (1° × 1°) ocean general circulation model when broad geographical restrictions are imposed on the OTEC implementation area. This may correspond to practical or legal limitations, such as the cost of long submarine power cables or the extent of Exclusive Economic Zones. Because some environmental effects predicted under large-scale OTEC scenarios exhibit a strong asymmetry among major oceanic basins, numerical experiments where the OTEC domain is restricted to such specific areas are also conducted. Results suggest that in all cases, a rate of about 0.2 TW per Sverdrup of OTEC deep cold seawater is sustained when overall OTEC net power peaks. At that juncture, temperature profiles in the OTEC implementation areas are affected in similar ways, while the strength of the Thermohaline Circulation roughly doubles. Overall geographical constraints simply defined by distance to shore, given the model's 1° horizontal resolution, produce global OTEC net power maxima of 12–14 TW. In such cases, OTEC net power density approximately increases in inverse proportion to the OTEC implementation area. Limiting OTEC development to the Indo-Pacific yields results similar to the global case with a maximum proportional to the implementation area (12 TW), but simulations restricted to the Atlantic behave quite differently. In the latter case, OTEC net power peaks a little over 5 TW. It is estimated that producing half the predicted power maxima would substantially limit large-scale environmental temperature changes in each case.
Temperature-dependent perpendicular magnetic anisotropy of Co-Pt on Cr2O3 antiferromagnetic oxide
Authors: Nozaki T. , Oida M. , Ashida T. , Shimomura N. , Sahashi M.
Published: December 2013

We clarify the origin of the interface perpendicular magnetic anisotropy (PMA) at the Cr2O3/ferromagnet interface by investigating the temperature dependence of the magnetic properties of Cr2O3/Co-Pt. We observed positive large interface PMA both above and below the blocking temperature of Cr2O3, with the PMA being less sensitive to temperature. Our results indicate that the effect of the metal/oxide interface, as well as that of the MgO/CoFeB interface, contributes strongly to the PMA at the Cr2O3/Co-Pt interface, although the effect of perpendicular exchange coupling might also slightly contribute to the interface PMA.
Identification of secreted bacterial proteins by noncanonical amino acid tagging
Authors: Mahdavi Alborz , Szychowski Janek , Ngo John T. , Sweredoski Michael J. , Graham Robert L. J. , Hess Sonja , Schneewind Olaf , Mazmanian Sarkis K. , Tirrell David A.
Published: December 2013

Significance

Microbial pathogens use complex secretion systems to deliver virulence factors into host cells, where they disrupt host cell function. Understanding these systems is essential to the development of new treatments for infectious disease. A challenge in such studies arises from the abundance of host cell proteins, which interfere with detection of microbial effectors. Here we describe a metabolic labeling strategy that allows selective enrichment of microbial proteins from the host cell cytoplasm. The method enables efficient identification of microbial proteins that have been delivered to the host, identifies distinct secretion profiles for intracellular and extracellular bacteria, and allows for determination of the order of injection of microbial proteins into host cells.