bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoreflectance Characterization of Inter facial Residual Strain in InGaAs/GaAs Strained Single Quantum Well Structure
Authors: Watanabe Kenji , Takamori Takeshi , Kamijoh Takeshi
Published: March 2014

Photoreflectance spectroscopy has been used to characterize interfacial residual strain of the barrier in In
x
Ga1-x
As/GaAs (x=0.2) strained single quantum well structure grown on a GaAs substrate with the well width being below the critical layer thickness. The spectral feature corresponding to the GaAs E
0 transition shows a complicated structure which requires three components of oscillator including a feature corresponding to the E
0 transition to be well fitted. The splitting of the spectral feature suggests that residual inter facial tensile strain (∼2×10-3) exists in the GaAs layer and removes the degeneracy of the valence band, even though the case of pseudomorphic growth.
Extreme Optical Anisotropy in (110) Quantum Wells Induced by [110] Uniaxial Stress
Authors: Kajikawa Yasutomo
Published: March 2014

The effects of [110] uniaxial stress on the energy levels as well as those on the optical anisotropy in (110) quantum wells have been theoretically investigated within an effective-mass approximation. The calculated result for a (110) GaAs/Al0.3Ga0.7As quantum well shows two types of anticrossing behavior regarding the compression dependence of the energy levels: One type is the anticrossing between two levels which have a common n in the absence of stress; the other is between levels which have different n's. It is shown that the (110) in-plane optical anisotropy of interband transitions is drastically enhanced near either type of anticrossing. At a critical stress the matrix element for [001] or [110] polarization completely vanishes.
Electron Capture on DX Centers near \varGamma-X Crossover in AlGaAs:Te
Authors: Itskevich Igor E.
Published: March 2014

Relaxation of the persistent photoconductivity in AlGaAs:Te has been studied directly, in the real time, under quasihydrostatic pressure up to 11 kbar. Effect of the capture barrier broadening on the relaxation rate is reduced significantly at low electron concentration. The relaxation equation used for capture kinetics description in the wide electron concentration range appears to be not valid near the Γ–X crossover.
Defect Symmetries and Structures of Oxygen-Related Donors in Silicon Studied by Stress Deep-Level Transient Spectroscopy
Authors: Kamiura Yoichi , Terao Hirobumi , Okada Joji , Hashimoto Fumio
Published: March 2014

We have studied the defect symmetries of two kinds of oxygen-related donors in Si, thermal donor (TD) and new thermal donor (NTD) by the combination of deep-level transient spectroscopy (DLTS) with the application of uniaxial stress. As to TD, the stresses parallel to <100> and <110> directions split the DLTS peak into two components with the intensity ratios of low- and high-temperature components being 2:1 and 1:2, respectively, while the <111> stress caused neither splitting nor shift. On the other hand, the DLTS peak of NTD was not split by the stresses along all the above directions, but was shifted to low temperatures. From these results, we have concluded that TD arises from a relatively small oxygen cluster with an anisotropic electronic state of D
2d
symmetry with a <100> primary axis, while NTD is due to a larger oxygen cluster, which takes a high symmetry, at least T

d
to minimize the strain energy at the interface between the cluster and the Si matrix.
Spectroscopic Investigation of Semimagnetic Semiconductors under High Pressure
Authors: Shen S. C. , Jiang S.
Published: March 2014

Absorption and photoluminescence properties for semimagnetic semiconductors Cd1-x
Mn
x
Te, Cd1-x
Mn
x
Se, Zn1-x
Mn
x
Se and related mixed crystals have been investigated under high pressure. Three different kinds of optical transitions and related phenomena have been observed and discussed in light of the theory of crystal fields, band structures, and their hybridization and shifts with pressure for different mixed crystals. The polarization measurement and X-ray diffraction analysis have been also used for the confirmation of the observed transitions.
High-Field Magneto-Luminescence in Cd0.9Mn0.1 Se under High Pressures at 4.2 K
Authors: Matsuda Yasuhiro , Kuroda Noritaka , Mogi Iwao , Kido Giyuu , Nishina Yuichiro , Nakagawa Yasuaki , Anderson J. R. , Giriat W.
Published: March 2014

The photoluminescence due to the A-exciton in a diluted magnetic semiconductor Cd0.9Mn0.1Se has been measured at 4.2 K under 1 atm, 0.26 GPa and 1.51 GPa in the presence of magnetic fields up to 15 T. Two samples, one being oriented as H∥c and the other being oriented as H⊥c, are sealed together in a diamond anvil cell, where H and c denote the applied field and the c-axis of the wurtzite structure, respectively. The simultaneous measurement of the luminescence from the two samples has enabled us to study the anisotropy of the giant Zeeman shift of the A-exciton under a given pressure. The results show that the anisotropy is reduced significantly by pressure, giving a spectroscopic evidence that a hydrostatic pressure enhances the hexagonal distortion of the Cd(Mn)Se lattice.
Fundamental Gap of Diamond under Hydrostatic Pressure
Authors: Trojan I. A. , Eremets M. I. , Korolik M. Yu. , Struzhkin V. V. , Utjuzh A. N.
Published: March 2014

The hydrostatic pressure dependence of the fundamental gap of diamond has been measured up to 7 GPa. dEg/dP = 6.9 meV/GPa, in good agreement both with other experiments and the theoretical work [Surh et al. Phys. Rev. B 45, 8239 (1992)] which has successfully accounted for the pressure dependence of the dielectric constant.
Hall Effect under Pressure in Low Dimensional Organic Superconductors
Authors: Murata Keizo , Fortune Nathanael A. , Takahashi Toshihiro , Kikuchi Koichi , Tokumoto Madoka , Anzai Hiroyuki , Ikemoto Isao
Published: March 2014

Hall coefficient, R

H
(T) of low-dimensional organic superconductors, (DMET)2X and (BEDT-TTF)2X have been examined systematically under pressure of 0 - 10 kbar with the interest of understanding the electronic states in relation to superconductivity and spin density wave in these materials. Even in the metallic states in these materials, R

H
(T) are found to be remarkably temperature-dependent. We show that at least some of these temperature dependence is related to phase transition or its precursor, which has not been paid attention previously, and which could be discussed with superconductivity.
High Pressure and EXAFS Studies of the Spin-Density Wave States in Chromium Doped with Si, Ge, and Sn
Authors: Hochheimer Hans D.
Published: March 2014

From the pressure dependence of the Néel temperature (TN) in Cr-Si, Cr-Ge, and Cr-Sn alloys, the antiferromagnetic transition is found to be to the commensurate state above a certain threshold concentration. An Extended X-Ray-Absorption-Fine-Structure (EXAFS) study of Cr-Ge alloys shows clearly that Ge goes substitutionally into the Cr-lattice. On the basis of a two-band
nesting model this can be understood only if the group IVa elements act as a electron donor to the d band of Cr. The applicability of the two-band nesting model will be discussed.
High Pressure Phases of KH2PO4
Authors: Kobayashi Yuki , Endo Shoichi
Published: March 2014

The phase transitions in KH2PO4 have been studied at high pressures up to 25 GPa and temperatures up to 310°C by X-ray diffraction experiments using a multianvil (energy dispersive diffractometry) and a diamond anvil cell (angle dispersive diffractometry). The high pressure phase V proposed by Rapoport using differential thermal analysis was confirmed by obtaining its X-ray diffraction pattern at pressure above ∼3 GPa and temperature above ∼200°C, while the existence of another high pressure phase IV was not confirmed. We have succeeded in observing a new higher pressure phase above 10 GPa at room temperature. A tentative P–T phase diagram of KH2PO4 is presented.
Thermoelectric-Power Measurements as an Effective Tool for High Pressure Studies of the Electronic Structure
Authors: Itskevich E. S.
Published: March 2014

The main purpose of this report is to show the relation of qualitative changes in electron spectra (the band structure) with kinetic parameters, mainly with thermoelectric-power. We consider the electron topological transitions taking place for metals and semiconductors under high pressure as examples of these changes.
Recently the similar relations were found also for systems with intermediate valency. The measurements of kinetic parameters for high temperature superconductors (HTSC) also show how the electron structure is affected by pressure.
Semiconductor Pressure Sensors as Seen by a Physicist
Authors: Trzeciakowski Witold , Litwin-Staszewska Elżbieta , Perlin Piotr
Published: March 2014

The effect of pressure on the electronic states in semiconductors is reviewed in order to point out the phenomena useful for the pressure calibration. Specific examples are discussed in more detail: the optical sensor based on the quantum-well luminescence, the InSb resistive gauge, the AlGaAs graded-gap sensor.
Structural Phase Transition of III-V Nitrides under High Pressure
Authors: Ueno Masaki , Yoshida Minoru , Onodera Akifumi , Shimomura Osamu , Takemura Kenichi
Published: March 2014

Structural phase transitions and pressure-volume relationships in nitrides of the III-V compounds have been investigated at high pressure using x-ray diffraction in a diamond-anvil cell. The nitrides studied were all in the wurtzite structure before compression. Phase transitions into the rocksalt structure take place in AlN and InN at 23 and 12 GPa, respectively. No transition was observed for BN up to 106 GPa. The trend of the transition pressure is discussed in terms of the ionicity.
GaAs/AlAs Superlattices under Pressure
Authors: Reimann K.
Published: March 2014

High-pressure, low temperature photoluminescence measurements have been performed on several [111]- and [311]-grown GaAs/AlAs superlattices, which have corrugated interfaces. It is found that the minimum of the conduction band is at the Γ point in the GaAs layer for thick layers, and at the X point in the AlAs layer for thin layers (<3.6 nm), independent of growth direction. The confinement energies are calculated with a variational method and the valence band offset is determined.
Optical Properties of Branched Silicon Polymers
Authors: Kishilda Hideo , Tachilbana Hiroaki , Matsumoto Mutsuyoshi , Tokura Yoshinori
Published: March 2014

Optical properties of the branched and network silicon polymers have been studied. By introduction of the branching points onto the polysilanes, the absorption spectrum, which is characterized by a sharp excitonic peak, changes gradually into the amorphous-like one, while the uv luminescence disappears immediately with branching and the broad visible luminescence shows up. The network polymers, in which all backbones atoms are coordinated by three other backbone atoms in the limit of branching, show amorphous-like absorption spectra. By Ge-substitution for Si atoms in the backbone of network polymers, an absorption edge as well as the luminescence peak shift to the lower energy side by c.a. 0.5eV.
Modeling of Electron Injection and Transport in Multiple Quantum Well Infrared Photodetectors
Authors: Ershov Maxim , Ryzhii Victor
Published: March 2014

Physical mechanisms responsible for the operation and performance of Multiple Quantum Well (MQW) infrared photodetectors are studied using computer modeling. It is shown that the operating mechanism of MQW infrared photodetectors is associated with the redistribution of the potential across an MQW structure under the influence of absorbing radiation, which, in turn, results in the stimulation of electron injection from the emitter contact into the MQW region. The distribution of the electric field under the applied bias is highly nonuniform, with two distinct domains of high field, which controls the electron injection, and low field, supporting the transport of the injected electrons.
Persistent Spectral Hole-Burning in CuCl Nanocrystals: Demonstration of Optical Data Storage
Authors: Okamoto Shinji , Masumoto Yasuaki
Published: March 2014

Our discovery of the persistent spectral hole-burning (PSHB) phenomenon in semiconductor nanocrystal systems implies that the systems are applicable not only to an optical nonlinear device but also to an optical memory device. We demonstrate the optical data storage and thermal erasing of the optical data in CuCl nanocrystals. In addition, we make hole-growth and thermal annealing hole-filling experiments to study the mechanism of the PSHB phenomena. The phenomena can be explained by the two-level-system model.
Second-Order Raman Spectra of Nanostructures
Authors: Sasaki Yoshiro , Horie Chuji
Published: March 2014

Phonon states of nanostructures such as porous Si layers and small Ge particles are studied by the second-order Raman scattering. The sizes of particles are estimated to be a few to ten nanometers. The damping of the 2TO band is much larger than the TO(Γ) line. Surface phonon lines are observed at frequencies close to the Lucas mode and the S
8/S
8' mode of flat crystalline surfaces. The high frequency edge of the 2TO band shifts by a few cm1 reflecting confinement of the bulk phonons into a small volume.
Nonlinear Optical Properties of CdTe Microcrystallites in CaF2 Thin Film
Authors: Shen Meng-Yan , Yano Satoshi , Goto Takenari , Sato Futami , Tanaka Michiyoshi
Published: March 2014

The nonlinear optical properties of CdTe microcrystallites embedded in CaF2 by pulsed laser beam and electron beam coevaporation method are investigated with pump-probe technique. Only bleaching effect around wavelength region corresponding to the larger size microcrystallites can be obtained. The bleaching spectra are simulated with a state filling model. The upper energy states of the quantum confinement microcrystallites are perhaps also important to the nonlinear optical properties of microcrystallites.
Effects of Hole Doping in Semimacroscopic Systems
Authors: Suzuki Suzuki , Masato Masato , Nitta Nitta , Hitoshi Hitoshi , Iida Iida , Takeshi Takeshi
Published: March 2014

A two-dimensional molecular crystal model is investigated. The effects of hole doping are clarified in the semiconductor mesoscopic systems that have a strong electron-phonon interaction. In this system, a mesoscopic-size semiconductor is embedded in a bulk semiconductor, whose Peierls-band-gap energies are different each other. Electron-phonon structures are clarified for various values of the doping concentration (=ρ). We calculate the adiabatic potential energy curves relevant to the interaction between the mesoscopic region and the bipolaron that is created on the outside of the domain. These curves give comprehensive understanding of the ρ dependence on the electron-phonon structures. The absorption spectra are also calculated, and we find that the natures of the holes constrained in the mesoscopic system bring about remarkable structures in the absorption spectra.
Measurement of Nonlinear Refractive Index and Nonlinear Absorption Coefficient Using Transmission Spectrum
Authors: Zhang X. Q. , Fan X. W. , Shen D. Z. , Chen L. C. , Yang A. H. , Lu Y. M. , Chen Y. M.
Published: March 2014

We present a simple, but highly sensitive, method for obtaining both the sign and magnitude of the nonlinear refractive index and the nonlinear absorption coefficient as a function of wavelength. It is shown theoretically that these parameters can be easily obtained from the linear and nonlinear transmission spectra of the medium as well as the laser intensity distribution on the frequency. This technique is demonstrated for ZnSe-ZnS multiple quantum wells on transparent CaF2 substrate at 77 K.
Phonon Interaction in the Luminescence of Porous Silicon
Authors: Murayama Kazuro , Komatsu Hitoshi , Miyazaki Seiichi , Hirosi Masataka
Published: March 2014

It is found that the band width of a Gaussian-like luminescence spectrum of porous Si depends strongly on chemical etching time after anodization of crystalline Si. The narrowest luminescence band observed could be explained in terms of the radiative recombination of localized excitons with strong phonon coupling, while the broader luminescence band arises from the inhomogeneous broadening due to size distribution of Si nanostructures in the porous Si.
Study of C60-TDCN Nanometer Scale Thin Films
Authors: Xue Z. Q. , Gao H. J. , Liu W. M. , Wu Q. D. , Chen H. Y. , Qiang D. , Pang S. J. , Liu N.
Published: March 2014

A novel polymer, toluylene 2, 4-dicarbamidonitrile (TDCN) with carbon-nitrogen conjugated backbones, has been synthesised in our Polymer Laboratory. The C60-TDCN thin films have been prepared by the ICB-TOFMS deposition system. The C60-TDCN thin films are very good crystalline and possess electric bistability.
Implication of Silicon Nanocrystallites from Combined Absorption and Luminescence Studies of Free-Standing Porous Silicon Films
Authors: Xie Ya-Hong , Hybertsen Mark S. , Wilson William L.
Published: March 2014

The result of a combined study of absorption and photoluminescence from high optical quality, free-standing, porous Si films is presented. With a scattering loss of less than 5%, these films allow unambiguous, detailed analysis of the optical absorption edge, and, in addition, enable us to correlate the optical absorption and emission behavior on the same sample. The main results of consistent energy position shift in both absorption and photoluminescence, together with the behavior of the emission lifetime versus the energy position shift, support the model that the observed optical processes derive from an ensemble of Si nanocrystallites.
Applicability of Local-Field Approximation to Harmonic Generation in H-Aggregate Dye Monolayers
Authors: Miyano Kenjiro , Tomioka Akihiro , Ui Hiroki
Published: March 2014

The local-field approximation has been tested for a system with strong molecular correlation, i.e. H-aggregate of a dye in Langmuir-Blodgett monolayers. Both microscopic and macroscopic aspects of the approximation have been examined and found that the approximation gives adequate description of the optical properties of the system both in the linear and second-harmonic generation processes.
Electron Dynamics in CdSe Microcrystallites in Porous Glass
Authors: Ikemoto Yuka , Shen Meng-Yan , Goto Takenari
Published: March 2014

We embedded CdSe nanocrstallites into a porous glass with a diffusion process. Using picosecond time resolved luminescence spectrum technique, we investigated the electron dynamics in the CdSe microcrystallites in porous glass. The luminescence decay of our sample has a fast component decay sensitive to temperature. For a sample of CdSe microcrystallites with an average size of 25 Å diameter, the fast decay is 50 ps at 77 K, and is 100 ps at 2 K. With a simple three level model, the luminescence decay is simulated. The temperature dependence of luminescence decay results from nonradiative process.
Optical Properties of Germanium Cluster-Based Nanostructured Film
Authors: Han Min , Gong Yanchun , Ma Jianxin , Liu Fengqi , Wang Guanghou
Published: March 2014

Germanium Cluster-based nanostructured films are prepared by inert gas evaporation. Their optical properties are analyzed by spectrophotometric measurement. Blue shift of the fundamental band gap is found to be as large as 2.0eV for the 10nm size cluster-based sample. Agreement is reached between the measurement and the theory of quantum confinement if the oxidation of the clusters is taken into account.
Luminescence of Silicon Nanocrystals and Porous Silicon
Authors: Brus Louis
Published: March 2014

Silicon nanocrystals have been made by a high temperature aerosol method. When passivated with 0.5-1 nm of oxide, the crystallites luminescence with ca. 5% quantum yield at room temperature, at visible wavelengths about 1 eV above the bulk silicon band gap. Spectroscopy shows that the nanocrystals behave as indirect gap semiconductors with phonon induced spectra. The quantum yield at room temperature is high, not because the nanocrystals are somewhat direct gap like, but because the fast radiationless processes which dominate carrier dynamics in bulk silicon are suppressed in nanocrystal silicon. The dynamics become molecule-like in nanocrystal silicon.
Nonlinear Properties of Nanometer-Sized Copper Clusters Embedded in LiF Medium
Authors: Wang Guanghou , Zhang Haiqian , Han Min , Ma Jianxing , Wang Qun , Zhao Jijun
Published: March 2014

Structures and optical properties of embedded copper clusters have been studied by EXAFS and optical absorption. The experiments demonstrate that (1) the interatomic distances contract and mean coordination number decreases as the cluster size decreases. (2) Optical resonances are greatly enhanced at visible region. These may be due to quantum size effect of the clusters themselves and the influence by its surrounding medium.
Rayleigh Scattering of Silica Glass and Silica Fibers with Heat Treatment
Authors: Sakaguchi Shigeki , Todoroki Shin-ichi
Published: March 2014

We investigated the effect of heat treatment on the Rayleigh scattering of silica glass and silica fibers in relation to the fictive temperature (Tf). The scattering intensity of silica glass changes in proportion to Tf which varies according to the condition of the heat treatment. As-drawn silica fibers exhibit Tf values close to 1600 °C. The scattering intensity of a fiber after heat treatment becomes 25 % less than that before treatment. On the assumption that a linear relation between Rayleigh scattering and Tf is valid for glasses and fibers, this result suggests that a further loss reduction can be expected in silica fibers by reducing Tf.
UV-Induced Structural Changes in Photosensitive Optical Fibres
Authors: Canning J. , Sceats M. G. , Carter A. L. G.
Published: March 2014

Changes in the scattering properties of optical fibres are observed with uv irradiation. In uniformly processed samples there is an increase in attenuation in the visible region which has a spectral edge that has a λ-4 dependency. Furthermore, when the fibre is processed periodically through a phase mask a large permanent increase in scattering is measured. This scattering arises from the interfaces between those regions which have undergone a change of state and those which have not.
Blue Light Generation by Cerenkov-type Second-Harmonic Generation in Thermally Poled Silicate Glass Thin Film Waveguide
Authors: Nakanishi Makoto , Ni Xuxiang , Sugihara Okihiro , Okamoto Naomichi , Suzuki Hideo
Published: March 2014

We observe a second-order nonlinearity of poled Ge-doped silica thin film. The origin of nonlinearity and the stability of the nonlinearity against heat and intense laser light are investigated from poled glass thin film. We fabricate a frequency doubling device using the silicate thin film waveguide, and by Cerenkov-type frequency doubling blue light generation was realized.
Blue Upconversion Characteristics of Thulium-doped Silica Fiber with High Germania Content
Authors: Tanabe Setsuhisa , Snitzer Elias , Cole Brian
Published: March 2014

Intense blue upconversion luminescences were observed in a high-NA silica fiber doped with Tm3+ and 25mol% GeO2 by pumping with a 630-670nm laser. The intensities of two bands due to the 1D2 → 3F4 at 455nm and 1G4 → 3H6 transition at 480nm were changed with the pumping wavelength, power, and the fiber length. These phenomena were ascribed to the population inversion of the3F4 excited state to the ground state and large population of the 3H4, that are the intermediate excited levels for the 3G4 and 1D4 upconversions, respectively. The nonlinear power dependence of the population could be due to the relatively low-phonon-energy, high Tm3+-concentration and high pump-power density in the core of this high-NA fiber. The peak shift of the 480nm-band with the fiber length and a two-photon process of 1.2 µm luminescence band are also discussed.
Thin Film Retardation Plates of Silica Glass Fabricated by Oblique Depositions
Authors: Takeda Yasuhiko , Motohiro Tomoyoshi , Hioki Tatsumi , Niikura Hiroshi , Niisaka Shunsuke
Published: March 2014

We developed thin film retardation plates of silica glass which work with normally incident lights at a wavelength as short as 300 nm. By depositing silica from an oblique direction (70°° from the substrate surface-normal) onto substrates, unique microscopic columnar structures were obtained. The columns of approximately 20 nm in diameter were inclined to the deposition direction which cause birefringence. Although obliquely deposited thin films often become opaque because of coalescence of the columns enhanced by absorbing moisture after the deposition processes, the opacity was suppressed using stacked structures of obliquely deposited and normally deposited layers.
Fabrication of High Quality Superconducting Tunnel Junctions
Authors: Akoh Hiroshi , Nakagawa Hiroshi , Joosse Koen , Aoyagi Masahiro , Esposito Antonio , Maehata Keisuke , Ishibashi Kenji , Takada Susumu
Published: March 2014

High quality Nb/AlOx/Nb superconducting tunnel junctions (STJs) are fabricated for the radiation detection. The fabrication process includes a MgO thin film, an underlayer method, a control of critical current, a nitrogen plasma passivation, and a SiO2 insulating layer. Subgap current characteristics of STJs have been investigated in the temperature range of 0.35K to 4.2K in order to evaluate the junction quality for the radiation detection. The STJs fabricated by present process show extremely high quality junction characteristics with a leakage current density of 0.1 pA/µm2, a resistance ratio R

d
/R

n
of 6×106 for a 200×200–µm2 STJ with a critical current density of 200A/cm2.
Large-Area Tunnel Junction Exhibiting Two Operating Modes for X-ray Detection
Authors: Taino Tohru , Ishibashi Kenji , Maehata Keisuke , Yoshida Shin-ichi , Povinelli Michelle L. , Nakagawa Hiroshi , Akoh Hiroshi , Joosse Koen , Takada Susumu , Kishimoto Maki , Katagiri Masaki
Published: March 2014

High quality Nb-based tunnel junctions with surface areas of 100×100 µm2 and 200×200 µm2 were tested by irradiating x-rays. The 200×200 µm2 junction exhibited better x-ray response than that of the 100×100 µm2 one, due to better collection of quasiparticles. The junction detected 5.9-keV x-rays with an energy resolution (FWHM) of 93 eV and the energy required for single electron collection was 6.5 meV. In the operation of the 200×200 µm2 junction, two kinds of operation modes with different pulse heights were found by applying a magnetic field with different ramping speeds. The individual operation modes gave different current-voltage characteristics. The Sine-Gordon equation was employed to calculate the current-volt-age characteristics for the large junction. From calculated results, it was confirmed that the higher pulse height operation mode was related to a large reduction of dc current through the junction.
Role of Special Junction Configurations in the Detection Performances
Authors: Cristiano Roberto
Published: March 2014

Superconducting tunnel junctions (STJs) have been proposed as detectors in a variety of experiments in different fields of physics. The detector configuration was initially tailored for the detection of X-rays, emphasizing the high energy resolution that such detectors could achieve, their wide band capability and the absence of energy thresholds. Since then the use of STJs was also proposed for the detection of dark matter, optical photons, etc.. Although in all cases the detection mechanism is essentially the same, each application require an ad hoc configuration in terms of junction structure, materials, role of the substrate and its coupling with the STJ sensor. The configuration as well as the physical problems involved may deeply differ from one application to the other. The aim of this work is to point out the peculiarities of the various STJ detector configurations which are under development, emphasizing the differences and the common problems.
Characterization of Superconducting Tunnel Junction X-ray Detectors by Low Temperature Scanning Electron Microscopy
Authors: Ohkubo Masataka , Sakamoto Isao , Hayashi Nobuyuki , Martin Jens , Panteleit Friedhelm , Huebener Rudolf
Published: March 2014

One problem in superconducting tunnel junction x-ray detectors is that the two electrodes respond differently to monochromatic x-rays, and produce double peaks in energy spectra. To study the double peak phenomenon, Low Temperature Scanning Electron Microscope (LTSEM) is a versatile tool, since it is possible to analyze two electrodes separately. From the LTSEM analyses in combination with x-ray detection experiments, it has been revealed that the intrinsic charge output of the base electrode is higher than that of the counter electrode over a wide range of bias voltages in our Nb/Al polycrystalline junctions. The voltage dependence of charge output is considerably modified by flux quanta trapped in a terrestrial magnetic field.
Simulating the effect of centrifugal forces in Jupiter's magnetosphere
Authors: Vogt Marissa F. , Kivelson Margaret G. , Khurana Krishan K. , Walker Raymond J. , Ashour‐Abdalla Maha , Bunce Emma J.
Published: March 2014

Jupiter's large scale size and rapid planetary rotation period combine to produce the strong centrifugal force responsible for many unique properties of its magnetosphere. It was previously proposed that this centrifugal force and nonadiabatic field line stretching could cause the observed dawn‐dusk asymmetry of Jupiter's plasma sheet, which is thickest near dusk. As flux tubes rotate and stretch between noon and dusk, particles bouncing along the field gain parallel energy and create pressure anisotropy. Because bounce times can be long compared with the outward expansion timescale, particles may respond nonadiabatically, and the resulting pressure anisotropy can drive the plasma sheet to instability. We used a large‐scale kinetic simulation to follow a collection of rotating particles as they move in a time‐varying, rotating magnetic field designed to represent flux tube expansion in Jupiter's magnetosphere. The analysis quantifies the response of trapped particles by characterizing the pressure anisotropy and energy changes. We compare results of nonadiabatic and adiabatic outward expansions and find that the nonadiabatic case leads to a large pitch angle anisotropy and higher total energy than for adiabatic expansion. Although the calculation was not handled fully self‐consistently, the results support the proposition that plasma pressure changes lead to changes in the magnetic field structure with local time. Our findings are consistent with the idea that nonadiabatic effects in Jupiter's magnetosphere contribute to field dipolarization and the observed plasma sheet thickening between noon and dusk.
Changes of thermospheric composition and ionospheric density caused by quasi 2 day wave dissipation
Authors: Yue Jia , Wang Wenbin
Published: March 2014

Using the thermosphere‐ionosphere‐mesosphere electrodynamics–general circulation model, we investigate the effect of quasi 2 day wave (QTDW) dissipation on thermospheric composition (O/N2) and ionospheric electron density during solar minimum. The overall thermospheric and ionospheric changes induced by the QTDW are evaluated by running the model with and without QTDW forcing imposed at the model lower boundary. The dissipation of the westward propagating QTDW in the lower thermosphere causes westward mean wind acceleration and drives a poleward meridional circulation. The circulation induced by the QTDW, as determined by the difference between the mean wind patterns of a run with the QTDW and a base run without the QTDW, enhances the mixing of constituents in the lower thermosphere. Through molecular diffusion, the decrease of the O mixing ratio and the increase of the N2 and O2 mixing ratios propagate from the lower thermosphere into the upper thermosphere. As a result, the O/N2 ratio near the ionospheric F2 peak is reduced by about 16–20% at low and midlatitudes. This in turn produces an approximately 16–32% depletion in the F2 peak electron density at low and midlatitudes. The simulated decrease of electron density during a QTDW event is in quantitative agreement with published observations. This work suggests a new major pathway for the traveling planetary wave from the lower atmosphere to affect the thermosphere and ionosphere via dissipation and mean wind acceleration.
A Pressing Need for Gender Balance in AGU Honors Nominations
Authors: Ball Jessica
Published: March 2014

AGU thrives on the volunteer efforts of its scientists, which is how I found myself agreeing to be a member of AGU's Science for Solutions Award committee last year. The award is targeted specifically at students and postdoctoral scientists who use Earth and space science to solve societal problems, and it was an intriguing experience to go through the process of evaluating the nominees and selecting a winner. All across the Union, members of other honors committees were going through a similar process, and at the 2013 Fall Meeting, those award recipients selected by the committees were honored.
Understanding Planetesimals
Authors: Elkins‐Tanton Linda T.
Published: March 2014

Planetesimals represent turning points in planetary formation, when the materials required for building planets are first incorporated into bodies with radii from tens to hundreds of kilometers or larger, and are sometimes differentiated into metallic cores and silicate mantles. These early celestial bodies are the accretionary step between the dust of the planetary nebula and the cadre of rocky planets. Thus, planetesimals hold the keys to understanding how Earth was formed, when water was deposited on Earth, and why Earth and other rocky planets may differ in composition.
Climate Variability in Northwestern Mexico
Authors: Celaya Carlos Lizárraga , Adams David K. , Isaias Arturo Quintanar
Published: March 2014

At the First Meeting of Regional Climatology of Northwestern Mexico, 20 researchers from several Mexican universities and research institutions discussed the impact of climate variability on water resources and ecological sustainability in northwestern Mexico. This subtropical region has meteorological and climatological behaviors characteristic of both the mid‐latitudes and the tropics. Given the semiarid to arid nature of the climate, precipitation is quite variable and is projected to become more so in current climate change projections.
Ambassador Award Nominations Sought: Celebrate Work in Outreach and Societal Impact
Authors: Finn Carol
Published: March 2014

A seismologist who starts giving talks at her local library and city's chamber of commerce about her work gradually becomes a go‐to resource for her entire community on natural hazards preparation and safety. A professor at a community college creates an ambitious teaching initiative that supports hands‐on research experiences for students who have never before been given the chance to conduct experiments. An Arctic ecologist assembles and leads a state‐wide group of colleagues whose regular communication with legislators helps inform policy decisions and long‐term regional planning. A heliophysicist steps up and coordinates new space weather research collaborations whose participants cross continents and disciplines.
Science, Technology, Engineering, and Math: AGU's Commitment to the Next Generation
Authors: Howard Claire
Published: March 2014

AGU is committed to the progress of science, technology, engineering, and math (STEM) educational programming for the next generation of scientists. STEM ensures the future of science and technology by providing academic and professional support to students in these fields.
Curiosity rover finds evidence of Martian atmospheric loss
Authors: Schultz Colin
Published: March 2014

Researchers think that roughly 4 billion years ago, the atmosphere of Mars started to wither away, blasted into space by the solar wind and other forces. This atmospheric loss transformed Mars from a warmer and wetter planet to its current cold, arid state. As time progressed, Mars lost at least half but probably as much as 95% of its atmosphere.
Quantitative Analysis and Visualized Evidence for High Charge Separation Efficiency in a Solid‐Liquid Bulk Heterojunction
Authors: Zhao Xin , Luo Wenjun , Feng Jianyong , Li Mingxue , Li Zhaosheng , Yu Tao , Zou Zhigang
Published: March 2014

In the past few decades, some novel low‐cost nanostructured devices have been explored for converting solar energy into electrical or chemical energy, such as organic photovoltaic cells, photoelectrochemical solar cells, and solar water splitting cells. Generally, higher light absorption and/or charge separation efficiency are considered as the main reasons for improved performance in a nanostructured device versus a planar structure. However, quantitative analysis and definite experimental evidence remain elusive. Here, using BiVO4 as an example, comparable samples with porous and dense structures have been prepared by a simple method. The porous and dense films are assembled into a solid‐electrolyte bulk and planar heterojunction, respectively. Some quantitative results are obtained by decoupling photon absorption, interfacial charge transfer, and charge separation processes. These results suggest that higher charge separation efficiency is mainly responsible for enhanced performance in a solid‐electrolyte bulk heterojunction. Moreover, we also present visualized evidence to show higher charge separation efficiency comes from a shorter photo‐generated hole diffusion distance in a bulk heterojunction. These results can deepen understanding charge transfer in a bulk heterojunction and offer guidance to design a more efficient low‐cost device for solar conversion and storage.
Integration of Photosystem I with Graphene Oxide for Photocurrent Enhancement
Authors: LeBlanc Gabriel , Winter Kevin M. , Crosby William B. , Jennings G. Kane , Cliffel David E.
Published: March 2014

Photosystem I is a photoactive membrane protein used in nature to photo‐excite electrons with nearly unit internal quantum efficiency, sparking interest in using this biomaterial for solar energy conversion. Films of PSI deposited on p‐doped silicon have previously demonstrated significant photocurrents with an electrochemical mediator; however, improvement in electron transfer is needed. Here, it is investigated how PSI can be combined with graphene oxide (GO) or reduced graphene oxide (RGO) to generate composite films capable of improved photoelectrochemical performance. It is found that both composite films outperformed the PSI film alone, and the PSI‐GO composite film is found to perform the best. The enhancement is attributed to the decreased impedance and shift in the onset potential of the composite films.
Prepotent Response Inhibition and Interference Control in Autism Spectrum Disorders: Two Meta‐Analyses
Authors: Geurts Hilde M. , van den Bergh Sanne F. W. M. , Ruzzano Laura
Published: March 2014

There is a substantial amount of data providing evidence for, but also against the hypothesis that individuals with autism spectrum disorders (ASD) encounter inhibitory control deficits. ASD is often associated with interference control deficits rather than prepotent response inhibition. Moreover, the developmental trajectory for these inhibitory control processes is hypothesized to differ in ASD as compared to typical development. In efforts to gain a more comprehensive perspective of inhibition in ASD, separate quantitative analysis for prepotent response inhibition studies and interference control studies were conducted. Together, these two meta‐analyses included 41 studies with a combined sample size of 1,091 people with ASD (M age 14.8 years), and 1,306 typically developing (TD) controls (M age 13.8 years).The meta‐analyses indicated that individuals with ASD show increased difficulties in prepotent response inhibition (effect size 0.55) and in interference control (effect size 0.31). In addition, age was a relevant moderator for prepotent response inhibition but not for interference control. Exploratory analyses revealed that when IQ was taken into account, heterogeneity considerably decreased among interference control studies but not among prepotent response inhibition. In contrast to the general belief, both prepotent response inhibition and interference control problems were observed in individuals with ASD. However, a large variation between studies was also found. Therefore, there remain factors beyond inhibition type, age, or IQ that significantly influence inhibitory control performance among individuals with ASD. Autism Res 2014, 7: 407–420. © 2014 International Society for Autism Research, Wiley Periodicals, Inc.
Intramuscular innervation patterns of the brachialis muscle
Authors: Won Sung‐Yoon , Cho Young‐Hoon , Choi You‐Jin , Favero Vittorio , Woo Hee‐Soon , Chang Ki‐Yeon , Hu Kyung‐Seok , Kim Hee‐Jin
Published: March 2014

The aim of this study was to provide accurate anatomical descriptions of the patterns of innervation of the brachialis muscle by the musculocutaneous, radial, and median nerves. Sihler's staining method was applied to 20 brachialis muscles from 10 cadavers to reveal the intramuscular distribution patterns of the musculocutaneous, radial, and median nerves. Three patterns of innervation of the brachialis muscle by the three studied nerves were found: single, double, and triple. These innervation patterns were categorized into four types: Type I—only the musculocutaneous nerve; Type II—double innervation by the musculocutaneous and radial nerves; Type III—double innervation by the musculocutaneous and median nerves; and Type IV—triple innervation by all three nerves. Single, double, and triple innervation patterns occurred 25%, 70% (Type II, 55%; Type III, 15%), and 5% of the samples, respectively. The brachialis muscle is not solely innervated by the musculocutaneous nerve but also by the radial and median nerves, thus making it a potentially triply innervated muscle. Double innervation of this muscle with either the musculocutaneous and median nerve or the musculocutaneous and radial nerves was also observed. Clin. Anat. 28:123–127, 2015. © 2014 Wiley Periodicals, Inc.
Perturbations of Smooth Actions with Nontrivial Cohomology
Authors: Damjanović Danijela
Published: March 2014

We prove a general perturbation result for smooth Lie group actions with nontrivial finite‐dimensional cohomology. It describes sufficient conditions on cohomology over an action which imply that the action lies in a finite‐dimensional family of actions such that any small perturbation of the family intersects the smooth conjugacy class of the given action. We cast the classical KAM result on perturbations of Diophantine vector fields on tori into this general setup, and we address a few applications and potential applications of this result to homogeneous Lie group actions with finite‐dimensional first cohomology. © 2014 Wiley Periodicals, Inc.
Questions on therapy with DPP‐4 inhibitors and bone homeostasis
Authors: Napoli Nicola
Published: March 2014

A recent study from Gallagher et al. aimed to investigate the effect of a new depeptidyl‐peptidase‐4 inhibitor, MK‐0626, on bone turnover in a mouse model developing insulin resistance and diabetes (MKR mice). Authors have found that treatment with MK‐0626 did not affect either MKR mice fasting glucose or parameters of bone metabolism. These data are not in accordance with previous findings, raising questions on the possible protective effect of depeptidyl‐peptidase‐4 inhibitors on bone loss. Given the negative effects on the bone caused by some antidiabetic drugs, results from this study may be disappointing, but a neutral effect on the bone is still reassuring. However, some aspects of this study should be considered in order to explain these results, and more studies are needed to better understand the effect of this class of drugs on the bone health in humans. Copyright © 2014 John Wiley & Sons, Ltd.
Equalizer technology followed by DIGE‐based proteomics for detection of cellular proteins in artificial peritoneal dialysis effluents
Authors: Lichtenauer Anton Michael , Herzog Rebecca , Tarantino Silvia , Aufricht Christoph , Kratochwill Klaus
Published: March 2014

Peritoneal dialysis effluent (PDE) represents a rich pool of potential biomarkers for monitoring disease and therapy. Until now, proteomic studies have been hindered by the plasma‐like composition of the PDE. Beads covered with a peptide library are a promising approach to remove high abundant proteins and concentrate the sample in one step. In this study, a novel approach for proteomic biomarker identification in PDEs consisting of a depletion and concentration step followed by 2D gel based protein quantification was established. To prove this experimental concept a model system of artificial PDEs was established by spiking unused peritoneal dialysis (PD) fluids with cellular proteins reflecting control conditions or cell stress. Using this procedure, we were able to reduce the amount of high abundant plasma proteins and concentrate low abundant proteins while preserving changes in abundance of proteins with cellular origin. The alterations in abundance of the investigated marker for cell stress, the heat shock proteins, showed similar abundance profiles in the artificial PDE as in pure cell culture samples. Our results demonstrate the efficacy of this system in detecting subtle changes in cellular protein expression triggered by unphysiological stress stimuli typical in PD, which could serve as biomarkers. Further studies using patients’ PDE will be necessary to prove the concept in clinical PD and to assess whether this technique is also informative regarding enriching low abundant plasma derived protein biomarker in the PDE.
Improving the accuracy of discontinuous Galerkin schemes at boundary layers
Authors: Hindenlang Florian J. , Gassner Gregor J. , Munz Claus‐Dieter
Published: March 2014

The resolution of boundary layers typically requires fine grids in the wall normal direction, which leads to anisotropic elements being refined towards the wall. Best practice guidelines for the mesh generation of stretched boundary layer grids exist for the finite volume or finite difference discretizations. A similar resolution of boundary layers with DG schemes can be achieved with a coarser grid because of the subgrid resolution of the DG scheme. High order schemes incorporate the possibility of high order element mappings, resulting in different resolution properties inside the element. In this paper, we show that the use of an internal element mapping in combination with a stretched grid can be used to reduce the error of the boundary layer approximation by an order of magnitude in comparison with the classical linear internal element mapping. The boundary layer is modeled by a one‐dimensional singular perturbation problem. In addition, we discuss the construction of the element mappings by interpolation and investigate the limits of the stretching function such that the resulting element Jacobian remains positive. A parameter study shows the influence of the element mapping for different polynomial degrees on the solution. Copyright © 2014 John Wiley & Sons, Ltd.