bluuebunny/crossref_metadata_2025 huggingface dataset:
Asset liability management for individual households ‐ Abstract of the London Discussion
Authors: Dempster Michael
Published: November 2011

This abstract relates to the following paper:

DempsterM.A.H. & MedovaE.A.Asset liability management for individual households. British Actuarial Journal, doi:10.1017/S135732171100016X
Cross-linguistic influence in French–English bilingual children's possessive constructions
Authors: NICOLADIS ELENA
Published: November 2011

The purpose of this article was to test the predictions of a speech production model of cross-linguistic influence in French–English bilingual children. A speech production model predicts bidirectional influence (i.e., bilinguals’ greater use of periphrastic constructions like the hat of the dog relative to monolinguals in English and reversed possessive constructions like *chien chapeau to refer to a dog's hat). In contrast, other explanations predict unidirectional influence from French to English. Possessive constructions were elicited from preschool French–English bilingual children as well as preschool French and English monolinguals within the same age range. The results showed bidirectional influence, consistent with a speech production model.
Chemical and Morphological Study of Gunshot Residue Persisting on the Shooter by Means of Scanning Electron Microscopy and Energy Dispersive X-Ray Spectrometry
Authors: Brożek-Mucha Zuzanna
Published: November 2011

Persistence of gunshot residue (GSR) simultaneously collected from hands, face and hair, and clothing of the shooting person was examined. Samples were collected from five shooters in nine time intervals after a single shoot with a Luger 9 mm pistol, in the range of 0–4 h and examined with scanning electron microscopy and energy dispersive X-ray spectrometry. Numbers of particles, frequencies of occurrence of certain compositions of particles, and their sizes in function of the time intervals were inspected. The greatest numbers of particles were observed in samples collected from hands right after shooting, but they decrease quickly with time. In samples collected from the face smaller initial numbers of particles were found, but they lasted at a similar level longer. The estimated half-life times of particles were less than 1 h for samples taken from the hands, over 1 h for clothing and about 2–3 h for the face. In samples collected at longer intervals after shooting, there were particles present of small sizes and irregular shapes. The results demonstrate that including evidence collected from the suspect's face and hair may increase the probability of detection of GSR in cases when the suspect has not been apprehended immediately after the investigated incident.
The location of reconnection at the magnetopause: Testing the maximum magnetic shear model with THEMIS observations
Authors: Trattner K. J. , Petrinec S. M. , Fuselier S. A. , Phan T. D.
Published: November 2011

Reconnection at the Earth's magnetopause is the mechanism by which magnetic fields in different regions change topology to create open magnetic field lines that allow energy and momentum to flow into the magnetosphere. One of the long‐standing open questions about magnetic reconnection is the location of the reconnection line. There are two reconnection scenarios discussed in the literature: (1) antiparallel reconnection where shear angles between the magnetospheric field and the interplanetary magnetic field (IMF) are near 180° and (2) component reconnection where a tilted reconnection line which crosses the magnetopause in the subsolar region at shear angles not near 180°. Early satellite observations were limited to the detection of accelerated ion beams in the magnetopause boundary layer to determine the general direction of the reconnection line location with respect to the satellite. An improved view of the reconnection location at the magnetopause was determined from ionospheric emissions observed by polar‐orbiting imagers which revealed that both scenarios occur. The time‐of‐flight effect of precipitating ions in the cusp in connection with the low‐velocity cutoff method pinpointed reconnection locations and their dependency on IMF conditions. These results are summarized by the maximum magnetic shear model. This study uses confirmed magnetic reconnection locations from the THEMIS mission to test the predictions of this reconnection location model. The results reveal that the maximum magnetic shear model predicts the observed reconnection locations for dominant IMF BY conditions very well but needs further improvement and modifications for dominant southward IMF conditions.
Analytical estimates of quasi‐linear diffusion coefficients and electron lifetimes in the inner radiation belt
Authors: Mourenas D. , Ripoll J.‐F.
Published: November 2011

The behavior of trapped electrons in the Earth's radiation belts can be described in terms of relativistic quasi‐linear diffusion by cyclotron‐resonant plasma waves. Multidimensional dynamical simulations of the full belts require rapid and accurate evaluations of the diffusion coefficients. Recently developed approximations already allow replacing the integration over the wave‐normal distribution by an evaluation at a carefully chosen point. An approximate, but useful, analytical formulation of diffusion coefficients is derived here in the particular limit of low frequency and moderately oblique waves. It accounts for both the integration over the wave‐normal distribution and the summation over all the relevant n‐harmonic resonances. Analytical estimates of the diffusion coefficients averaged over the bounce motion along a geomagnetic field line are also given. From them, a simplified analytical expression of the electron lifetimes is deduced. Detailed comparisons between the analytical formulas and the full numerical solutions are presented for different cases of resonant interactions of electrons with hiss waves inside the plasmasphere, demonstrating a fair agreement and providing a better understanding of the simulation results.
Titan's ionospheric composition and structure: Photochemical modeling of Cassini INMS data
Authors: Westlake J. H. , Waite J. H. , Mandt K. E. , Carrasco N. , Bell J. M. , Magee B. A. , Wahlund J.‐E.
Published: November 2011

Titan's upper atmosphere produces an ionosphere at high altitudes from photoionization and electron impact that exhibits complex chemical processes in which hydrocarbons and nitrogen‐containing molecules are produced through ion‐molecule reactions. The structure and composition of Titan's ionosphere has been extensively investigated by the Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini spacecraft. We present a detailed study using linear correlation analysis, 1‐D photochemical modeling, and empirical modeling of Titan's dayside ionosphere constrained by Cassini measurements. The 1‐D photochemical model is found to reproduce the primary photoionization products of N2 and CH4. The major ions, CH5+, C2H5+, and HCNH+ are studied extensively to determine the primary processes controlling their production and loss. To further investigate the chemistry of Titan's ionosphere we present an empirical model of the ion densities that calculates the ion densities using the production and loss rates derived from the INMS data. We find that the chemistry included in our model sufficiently reproduces the hydrocarbon species as observed by the INMS. However, we find that the chemistry from previous models appears insufficient to accurately reproduce the nitrogen‐containing organic compound abundances observed by the INMS. The major ion, HCNH+, is found to be overproduced in both the empirical and 1‐D photochemical models. We analyze the processes producing and consuming HCNH+ in order to determine the cause of this discrepancy. We find that a significant chemical loss process is needed. We suggest that the loss process must be with one of the major components, namely C2H2, C2H4, or H2.
Controls on stream water dissolved mercury in three mid‐Appalachian forested headwater catchments
Authors: Riscassi Ami L. , Scanlon Todd M.
Published: November 2011

Determining the controls on dissolved mercury (HgD) transport is necessary to improve estimations of export from unmonitored watersheds and to forecast responses to changes in deposition and other environmental forcings. Stream water HgD and dissolved organic carbon (DOC) were evaluated over a range of discharge conditions in three streams within Shenandoah National Park, VA. Watersheds are distinguished by stream water pH (ranging from neutral to acidic) and soil size fractioning (ranging from clays to sands). At all sites, discharge was a significant but poor predictor of HgD concentrations (r2 from 0.13–0.52). HgD was strongly coupled with DOC at all sites (r2 from 0.74–0.89). UV absorbance at 254 nm (UV254), a proxy for DOC quantity and quality, slightly improved the predictions of HgD. Mean DOC quality differed between streams, with less aromatic DOC mobilized from the more acidic watershed. The site with less aromatic DOC and sandy soils mobilized more Hg to the stream for the same quantity and quality of DOC, likely due to the reduced capacity of the larger‐grained soils to retain Hg, leaving a greater fraction associated with the organic matter. A similar amount of 0.54 ng HgD/mg DOC is transported at all sites, suggesting the less aromatic DOC transports less Hg per unit DOC, offsetting the effects of soil type. This research demonstrates that soil composition and DOC quality influence HgDexport. We also provide evidence that soil organic carbon is a primary control on Hg‐DOC ratios (0.12–1.4 ng mg−1) observed across the U.S. and Sweden.
Dynamic measurements of mitochondrial hydrogen peroxide concentration and glutathione redox state in rat pancreatic β-cells using ratiometric fluorescent proteins: confounding effects of pH with HyPer but not roGFP1
Authors: Roma Leticia P. , Duprez Jessica , Takahashi Hilton K. , Gilon Patrick , Wiederkehr Andreas , Jonas Jean-Christophe
Published: November 2011

Using the ROS (reactive oxygen species)-sensitive fluorescent dyes dichlorodihydrofluorescein and dihydroethidine, previous studies yielded opposite results about the glucose regulation of oxidative stress in insulin-secreting pancreatic β-cells. In the present paper, we used the ratiometric fluorescent proteins HyPer and roGFP1 (redox-sensitive green fluorescent protein 1) targeted to mitochondria [mt-HyPer (mitochondrial HyPer)/mt-roGFP1 (mitochondrial roGFP1)] to monitor glucose-induced changes in mitochondrial hydrogen peroxide concentration and glutathione redox state in adenovirus-infected rat islet cell clusters. Because of the reported pH sensitivity of HyPer, the results were compared with those obtained with the mitochondrial pH sensors mt-AlpHi and mt-SypHer. The fluorescence ratio of the mitochondrial probes slowly decreased (mt-HyPer) or increased (mt-roGFP1) in the presence of 10 mmol/l glucose. Besides its expected sensitivity to H2O2, mt-HyPer was also highly pH sensitive. In agreement, changes in mitochondrial metabolism similarly affected mt-HyPer, mt-AlpHi and mt-SypHer fluorescence signals. In contrast, the mt-roGFP1 fluorescence ratio was only slightly affected by pH and reversibly increased when glucose was lowered from 10 to 2 mmol/l. This increase was abrogated by the catalytic antioxidant Mn(III) tetrakis (4-benzoic acid) porphyrin but not by N-acetyl-L-cysteine. In conclusion, due to its pH sensitivity, mt-HyPer is not a reliable indicator of mitochondrial H2O2 in β-cells. In contrast, the mt-roGFP1 fluorescence ratio monitors changes in β-cell mitochondrial glutathione redox state with little interference from pH changes. Our results also show that glucose acutely decreases rather than increases mitochondrial thiol oxidation in rat β-cells.
Three-Dimensional Magnetic Resonance Imaging of Velopharyngeal Structures
Authors: Bae Youkyung , Kuehn David P. , Sutton Bradley P. , Conway Charles A. , Perry Jamie L.
Published: November 2011

Purpose

To report the feasibility of using a 3-dimensional (3D) magnetic resonance imaging (MRI) protocol for examining velopharyngeal structures. Using collected 3D MRI data, the authors investigated the effect of sex on the midsagittal velopharyngeal structures and the levator veli palatini (levator) muscle configurations.

Method

Ten Caucasian healthy adults (5 women and 5 men) participated. A whole-head 3D MRI scan was obtained while participants were at rest in the supine position. Basic anatomic parameters of the velopharynx including midsagittal velopharyngeal structures and levator muscle configurations were compared between sexes.

Results

Detailed information on the 3D MRI protocol and data analysis method was introduced in the study. On the basis of the data, only the length of the levator muscle showed a statistically significant sex difference: Male participants had significantly longer levator muscles than those of female participants.

Conclusions

The present study successfully demonstrated the use of 3D MRI in quantifying major velopharyngeal structures and provided additional data on the anatomic variations that exist in healthy adult individuals.
Performance enhancement of blue light-emitting diodes with AlGaN barriers and a special designed electron-blocking layer
Authors: Zhang Yun-Yan , Yao Guang-Rui
Published: November 2011

In this study, the characteristics of the nitride-based blue light-emitting diode (LED) with AlGaN barriers are analyzed numerically and experimentally. The emission spectra, carrier concentrations in the quantum wells (QWs), energy band diagrams, electrostatic fields, and internal quantum efficiency are investigated. The results indicate that the LED with AlGaN barriers has a better hole-injection efficiency and an enhanced carrier confinement in its active region over the conventional counterpart with GaN barriers. The results also show that the AlGaN electron-blocking layer (EBL) with a gradual variation of Al mole fraction has a significantly enhanced electron blocking capability as well as a greatly improved hole-injection efficiency. When Al0.08Ga0.92N QW barriers and the special designed EBL are used, the electroluminescence emission intensity is increased greatly by 69% at 200 A/cm2 and the efficiency droop is reduced markedly to 8.7% from 85% at 400 A/cm2 compared with those of the conventional LED.
Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response
Authors: Ortiz Rocío , Quintana Iban , Etxarri Jon , Lejardi Ainhoa , Sarasua Jose-Ramon
Published: November 2011

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.
Characterization of metastabilities in Cu(In,Ga)Se2 thin-film solar cells by capacitance and current-voltage spectroscopy
Authors: Eisenbarth Tobias , Caballero Raquel , Nichterwitz Melanie , Kaufmann Christian A. , Schock Hans-Werner , Unold Thomas
Published: November 2011

Metastabilities in Cu(In,Ga)Se2 (CIGS)-based solar cells induced by red light illumination, blue light illumination, and voltage bias treatment are investigated by admittance spectroscopy, capacitance-voltage profiling, thermally stimulated capacitance, and temperature dependent current-voltage (IVT) measurements. It is found that the characteristic N1-admittance response exhibits changes in the activation energy after light soaking and forward bias treatment, whereas no significant change of the activation energy is observed after reverse bias treatment. A roll-over effect is observed in the IVT characteristics for conditions of the sample for which the N1-activation energy is larger than 100 meV. We show that these results are in good agreement with a recently proposed interpretation of admittance spectra, which relates the N1 signature to a back-contact barrier in CIGS solar cells. We also show that, within this model, the changes in the IV characteristics upon light soaking with blue light can be consistently explained with metastabilities in the CdS buffer layer. Furthermore, distinct activation energies for the relaxation dynamics of the red light soaking (Erel = 270 meV) and reverse bias effect (Erel = 730 meV) are observed, which indicates that both phenomena have different physical origins.
Coverage effects in the adsorption of H2 on Pd(100) studied by ab initio molecular dynamics simulations
Authors: Groß Axel
Published: November 2011

The interaction of hydrogen with palladium surfaces represents one of the model systems for the study of the adsorption and absorptionat metal surfaces. Theoretical gas-surface dynamics studies have usually concentrated on the adsorption dynamics on clean surfaces. Only recently it has become possible, based on advances in the electronic structure codes and improvements in the computer power, to address the much more complex problem of the adsorption dynamics on precovered surfaces. Here, I present ab initiomolecular dynamics (AIMD) simulations based on periodic density functional theory (DFT) calculations of the adsorption of H2 on hydrogen-precovered Pd(100) for a broad variety of different hydrogen coverage structures. The stability of the adsorbate structures and the adsorption dynamics are analyzed in detail. Calculated sticking probabilities are larger than expected for pure site-blocking consistent with experimental results. It turns out that the adsorption dynamics on the strongly corrugated surfaces depends sensitively on the dynamic response of the substrate atoms upon the impact of the impinging H2 molecules. In addition, for some structures the adsorption probability was evaluated as a function of the kinetic energy. Adsorbate structures corresponding to the same coverage but with different arrangements of the adsorbed atoms can lead to a qualitatively different dependence of the adsorption probability on the kinetic energy changing also the order of the preferred structures, as far as the adsorption is concerned, as a function of the kinetic energy. This indicates that dynamical effects such as steering and dynamical trapping play an important role in the adsorption on these precovered substrates.
Phase behaviors of cyclic diblock copolymers
Authors: Zhang Guojie , Fan Zhongyong , Yang Yuliang , Qiu Feng
Published: November 2011

A spectral method of self-consistent field theory has been applied to AB cyclic block copolymers. Phase behaviors of cyclic diblock copolymers, such as order-disorder transition, order-order transition, and domain spacing size, have been studied, showing good consistency with previous experimental and theoretical results. Compared to linear diblocks, cyclic diblocks are harder to phase separate due to the topological constraint of the ring structure. A direct disorder-to-cylinder transition window is observed in the phase diagram, which is significantly different from the mean field phase diagram of linear diblock copolymers. The domain spacing size ratio between cyclic and linear diblock copolymers is typically close to 0.707, indicating in segregation that the cyclic polymer can be considered to be made up of linear diblocks with half of the original chain length.
Ultrafast switching of ferroelastic nanodomains in bilayered ferroelectric thin films
Authors: Ehara Y. , Yasui S. , Nagata J. , Kan D. , Anbusathaiah V. , Yamada T. , Sakata O. , Funakubo H. , Nagarajan V.
Published: November 2011

The dynamic switching of ferroelastic nanodomains in ferroelectric PbZr0.3Ti0.7O3/PbZr0.7Ti0.3O3 bilayers was investigated. Synchrotron microdiffraction using a high-speed pulse generator reveals that electric field pulses as short as 200 ns can switch the ferroelastic domain. Multiples of random distribution analysis of the field-induced changes in diffraction peak intensities finds a dynamic strain change from 0.2 to 1% with increasing the pulse width. Raman spectroscopy shows considerable decreases in A1(1TO) soft mode intensity after applications of short pulses, confirming the ferroelastic switching. The results demonstrate that ferroelastic domains can indeed move at time scales of the order of hundreds of nanoseconds.
Barrier height determination of silicide-silicon contact by hybrid density functional simulation
Authors: Gao Qun , Guo Jing
Published: November 2011

Accurate prediction of the Schottky barrier heights (SBHs) from first principles is important for contact and device technologies. Ab initio simulations based on widely used local density approximation and generalized gradient approximation significantly underestimate the SBHs. By modeling CoSi2-Si and NiSi2-Si contacts using the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional calculations, we demonstrate that HSE hybrid functional simulations can predict the SBHs in agreement with experiments. Furthermore, the effects of interfacial dopants and metal induced gap states are examined by ab initio hybrid functional simulations.
Temperature dependent photoluminescence from porous silicon nanostructures: Quantum confinement and oxide related transitions
Authors: Ray Mallar , Ratan Bandyopadhyay Nil , Ghanta Ujjwal , Klie Robert F. , Kumar Pramanick Ashit , Das Samaresh , Ray Samit K. , Minhaz Hossain Syed
Published: November 2011

Temperature dependent photoluminescence (PL) spectroscopy along with structural investigations of luminescent porous Si enable us to experimentally distinguish between the relative contributions of band-to-band and oxide interface mediated electronic transitions responsible for light emission from these nanostructures. Porous Si samples formed using high current densities (J ≥ 80 mA/cm2) have large porosities (P ≥ 85%) and consequently smaller (∼1-6 nm) average crystallite sizes. The PL spectra of these high porosity samples are characterized by multiple peaks. Two dominant peaks—one in the blue regime and one in the yellow/orange regime, along with a very low intensity red/NIR peak, are observed for these samples. The high energy peak position is nearly independent of temperature, whereas the yellow/orange peak red-shifts with increasing temperature. Both the peaks blue shift with ageing and with increasing porosity. The intensity of the blue peak increases whereas the yellow/orange peak decreases with increasing temperature, while the intensity and peak position of the very low intensity red/NIR peak appears to be unaffected by temperature, porosity, and ageing. The low porosity samples (P ≤ 60%) on the other hand exhibit a single PL peak whose intensity decreases and exhibits a very small red spectral shift with increase in temperature. From the variation of intensity and PL peak positions, it is established that both quantum confinement of excitons and oxide related interfacial defect states play dominant role in light emission from porous Si and it is possible to qualitatively distinguish and assign their individual contributions.
Time-of-flight measurements and vertical transport in a high electron-mobility polymer
Authors: Blakesley James C , Schubert Marcel , Steyrleuthner Robert , Chen Zhihua , Facchetti Antonio , Neher Dieter
Published: November 2011

We investigate charge transport in a high-electron mobility polymer, poly(N,N-bis 2-octyldodecyl-naphthalene-1,4,5,8-bis dicarboximide-2,6-diyl-alt-5,5-2,2-bithiophene) [P(NDI2OD-T2), Polyera ActivInk™ N2200]. Time-of-flight measurements reveal electron mobilities approaching those measured in field-effect transistors, the highest ever recorded in a conjugated polymer using this technique. The modest temperature dependence and weak dispersion of the transients indicate low energetic disorder in this material. Steady-state electron-only current measurements reveal a barrier to injection of about 300 meV. We propose that this barrier is located within the P(NDI2OD-T2) film and arises from molecular orientation effects.
Study on the structural and physical properties of ZnO nanowire arrays grown via electrochemical and hydrothermal depositions
Authors: Laurent K. , Brouri T. , Capo-Chichi M. , Yu D. P. , Leprince-Wang Y.
Published: November 2011

We report here the systematic study of well controlled ZnO nanowire arrays grown via two different chemical ways: electrodeposition and hydrothermal method, which are frequently used for low cost synthesis of ZnO nanowire arrays. Both methods consist of two elaboration steps: a seed layer ZnO was first deposited on the substrate and then the growth of the ZnO nanowire arrays on the seed layer was performed. Scanning electron microscopy observations show a similar morphology, while x-ray diffraction (XRD) and Raman spectra revealed a preferred orientation of ZnO nanowires towards the c-axis. High resolution transmission electron microscopy analysis showed excellent monocrystallinity of the nanowire. A p-n junction structure based on above two kinds of nanowire arrays with a p-CuSCN layer was fabricated and their photoluminescence (PL) and conductance were measured in comparison. PL measurements demonstrated a higher defects concentration in ZnO nanowires obtained by hydrothermal method which leads to a very high current in the corresponding p-n junction with the p-CuSCN layer. This property is very important in prospective to future applications such as photovoltaic cell, nanogenerator, or gas sensor.
Influence of the wavelength on the spatial resolution of pulsed-laser atom probe
Authors: Gault B. , Chen Y. M. , Moody M. P. , Ohkubo T. , Hono K. , Ringer S. P.
Published: November 2011

Modern atom probes typically incorporate an ultrafast pulsed-laser source with wavelength ranging from infrared (IR) to ultraviolet (UV) depending on the specific instrument. In order to estimate the influence of the wavelength on the accuracy of the technique, the achievable in-depth spatial resolution has been measured for atom probe analyses of the same pure W specimen using three different wavelengths and across a range of laser pulse energies. UV illumination is shown to yield superior spatial resolution to both IR and visible (green) wavelengths. We propose that this improvement relates to a faster decay of temperature enabled by light absorption confined to the near apex region.
Absolute intensity calibration of flat-field space-resolved extreme ultraviolet spectrometer using radial profiles of visible and extreme ultraviolet bremsstrahlung continuum emitted from high-density plasmas in Large Helical Device
Authors: Dong Chunfeng , Morita Shigeru , Goto Motoshi , Wang Erhui
Published: November 2011

A precise absolute intensity calibration of a flat-field space-resolved extreme ultraviolet (EUV) spectrometer working in wavelength range of 60–400 Å is carried out using a new calibration technique based on radial profile measurement of the bremsstrahlung continuum in Large Helical Device. A peaked vertical profile of the EUV bremsstrahlung continuum has been successfully observed in high-density plasmas (ne ≥ 1014 cm−3) with hydrogen ice pellet injection. The absolute calibration can be done by comparing the EUV bremsstrahlung profile with the visible bremsstrahlung profile of which the absolute value has been already calibrated using a standard lamp. The line-integrated profile of measured visible bremsstrahlung continuum is firstly converted into the local emissivity profile by considering a magnetic surface distortion due to the plasma pressure, and the local emissivity profile of EUV bremsstrahlung is secondly calculated by taking into account the electron temperature profile and free-free gaunt factor. The line-integrated profile of the EUV bremsstrahlung continuum is finally calculated from the local emissivity profile in order to compare with measured EUV bremsstrahlung profile. The absolute intensity calibration can be done by comparing measured and calculated EUV bremsstrahlung profiles. The calibration factor is thus obtained as a function of wavelength with excellent accuracy. It is also found in the profile analysis that the grating reflectivity of EUV emissions is constant along the direction perpendicular to the wavelength dispersion. Uncertainties on the calibration factor determined with the present method are discussed including charge-coupled device operation modes.
Effect of ball milling and post treatment on crystal defects and transport properties of Bi2(Se,Te)3 compounds
Authors: Lin Sin-Shien , Liao Chien-Neng
Published: November 2011

Ionized point defects that act as electron donors or acceptors can strongly affect thermoelectric transport properties of bismuth telluride compounds. These crystal imperfections including antisite defects and vacancies can be generated or annihilated during material processing. Here, we reported the effect of ball milling, thermal annealing, and electrical stressing on defect population in the Bi2(Se,Te)3 prepared by powder metallurgy. The milling process can modulate the relative portion of antisite defects and vacancies in crystal, and the Bi2(Se,Te)3 made of the powders with extended milling time showed high electron concentration and poor carrier mobility. The crystal defects, Te vacancies in particular, were eliminated to some degree during subsequent thermal treatment. An electric-current assisted thermal treatment was found to be very efficient in eliminating crystal defects, which can improve transport properties of Bi2(Se,Te)3 without causing re-evaporation of volatile Te and Se elements during high-temperature annealing.
Effect of tin doping on oxygen- and carbon-related defects in Czochralski silicon
Authors: Chroneos A. , Londos C. A. , Sgourou E. N.
Published: November 2011

Experimental and theoretical techniques are used to investigate the impact of tin doping on the formation and the thermal stability of oxygen- and carbon-related defects in electron-irradiated Czochralski silicon. The results verify previous reports that Sn doping reduces the formation of the VO defect and suppresses its conversion to the VO2 defect. Within experimental accuracy, a small delay in the growth of the VO2 defect is observed. Regarding carbon-related defects, it is determined that Sn doping leads to a reduction in the formation of the CiOi, CiCs, and CiOi(SiI) defects although an increase in their thermal stability is observed. The impact of strain induced in the lattice by the larger tin substitutional atoms, as well as their association with intrinsic defects and carbon impurities, can be considered as an explanation to account for the above observations. The density functional theory calculations are used to study the interaction of tin with lattice vacancies and oxygen- and carbon-related clusters. Both experimental and theoretical results demonstrate that tin co-doping is an efficient defect engineering strategy to suppress detrimental effects because of the presence of oxygen- and carbon-related defect clusters in devices.
An alternate switching/non-switching behavior of a nanostructured magnetic thin film under sub-Stoner-Wohlfarth switching fields
Authors: Min Lee Jong , Lim S. H.
Published: November 2011

Dynamic magnetization switching can occur under sub-Stoner-Wohlfarth switching fields, and the switching behavior is well described by the switching phase diagram, showing the regions of non-switching, coherent, and incoherent switching. However, in the incoherent switching region, an alternate switching/non-switching behavior is observed under a strong bias field in the transverse direction, invalidating the usual switching phase diagram. This abnormal switching behavior is explained by a damped oscillation motion of the magnetization, which is restricted by the energy well at a given condition.
“Stubborn” triaminotrinitrobenzene: Unusually high chemical stability of a molecular solid to 150 GPa
Authors: Davidson Alistair J. , Dias Ranga P. , Dattelbaum Dana M. , Yoo Choong-Shik
Published: November 2011

We report an unexpectedly high chemical stability of molecular solid 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) under static high pressures. In contrast to the high-pressure behavior of the majority of molecular solids, TATB remains both chemically stable and an insulator to 150 GPa—well above the predicted metallization pressure of 120 GPa. Single crystal studies have shown that TATB exhibits pressure-induced Raman changes associated with two subtle structural phase transitions at 28 and 56 GPa. These phase transitions are accompanied by remarkable color changes, from yellow to orange and to dark red with increasing pressure. We suggest that the high-stability of TATB arises as a result of its hydrogen-bonded aromatic two-dimensional (2D) layered structure and highly repulsive interlayer interaction, hindering the formation of 3D networks or metallic states.
High-Q silica microcavities on a chip: From microtoroid to microsphere
Authors: Jager J.-B. , Calvo V. , Delamadeleine E. , Hadji E. , Noé P. , Ricart T. , Bucci D. , Morand A.
Published: November 2011

We report on the realization of high-quality silica optical microcavities on a chip. We show that a precise control of radii of both silica disk and silicon pillar defines the shape of molten microresonators from microtoroids to microspheres. These last ones advantageously combine small mode volumes in structures of very small radii (5 < r < 14 μm) which are fully compatible to wafer-based processing. The optical quality-factor of silica microsphere on a chip is as high as 7.5 × 107 at 1.55 μm. The losses sources in these microspheres are detailed and we show that measured quality-factors are limited by the radiative losses for the smallest ones.
Solid dye-sensitized solar cells prepared through a counter strategy for filling of solid hole transporter
Authors: Yang Zhenzhen , Powers Katherine C. , Liu Di-Jia , Ren Yang , Xu Tao
Published: November 2011

Efficient solid-state dye sensitized solar cells (DSSCs) require a tight filling of solid p-type semiconductors into the dye-sensitized nanoporous n-type semiconductor in order to form a good interfacial electrical contact. We report here a facile and unique counter-methodology that achieves compact contact between the sensitized TiO2 network and the solid p-type semiconductor for the assembling of solid DSSCs. The separated n-type TiO2 nanoparticles (NPs) are firstly dye sensitized before formation of the film, which is opposite to the conventional procedure of sintering the TiO2 NPs into a nanoparticulate film prior to dye sensitization. Next, a solution of p-type CuSCN is mixed with the sensitized TiO2 NPs, followed by the evaporation of the solvent to obtain the solid nanocomposition of sensitized TiO2 NPs wrapped with p-type CuSCN. The solid DSSCs are assembled by a series of film compressing and film transferring processes. The structures of the cells are characterized and the photovoltaic behaviors of the cells are also investigated and compared with cells prepared by conventional methods.
Simultaneous second-harmonic generation, third-harmonic generation, and four-wave mixing microscopy with single sub-8 fs laser pulses
Authors: Selm R. , Krauss G. , Leitenstorfer A. , Zumbusch A.
Published: November 2011

We demonstrate a compact pulse compression scheme that offers flexible chirp control for improved conversion efficiencies in high resolution nonlinear optical microscopy. An Er:fiber laser combined with a highly nonlinear optical fiber yields pulses centered at 1100 nm with a bandwidth of 500 nm. The compressed pulses with a duration of 7.6 fs enable simultaneous second-harmonic generation, third-harmonic generation, and four-wave mixing microscopy. The spectrum is tailored for an ideal compromise between conversion efficiency and spectral discrimination between the three types of broadband nonlinear signals. Distinct differences in structural contrast obtained from the simultaneous read-out of the three nonlinear signals are demonstrated in a biological sample.
H2O and D2 mixtures under pressure: Spectroscopy and proton exchange kinetics
Authors: Borstad Gustav M. , Yoo Choong-Shik
Published: November 2011

We have investigated the pressure-induced spectral changes and the proton exchange reactions of D2-H2O mixtures to 64 GPa using micro-Raman spectroscopy. The results show the profound difference in the rotational and vibrational Raman spectra of hydrogen isotopes from those of the pure samples, showing the vibrational modes at higher frequencies and continuing to increase with pressure without apparent turnover. This indicates the repulsive nature of D2-H2O interaction without hydrogen bonds between the two and, thus, interstitial fillings of D2 molecules into the bcc-like ice lattice. The spectral analysis using the Morse potential yields a hydrogen bond distance of 0.734 Å at 6 GPa—slightly shorter than that in pure—attributed to the repulsive interaction. The pressure-dependent spectral changes suggest that the proton-ordering transition in the ice lattice occurs over a large pressure range between 28 and 50 GPa, which is substantially lower than that of pure ice (40–80 GPa). This again indicates the presence of high internal pressure arising from the repulsive interaction. The Raman spectra show evidences that the proton exchange occurs in various phases including in solid D2 and H2O mixtures. Based on the time-dependent spectral changes, we obtained the proton exchange rates of k ∼ 0.085 h−1 at 0.2 GPa in fluid D2 and water mixtures, k ∼ 0.03 h−1 and 0.003 h−1 at 2 GPa and 4 GPa, respectively, in fluid D2-ice mixtures, and k ∼ 10−3 h−1 at 8 GPa in solid D2 and ice mixtures.
Surprising temperature dependence of the dust particle growth rate in low pressure Ar/C2H2 plasmas
Authors: Beckers J. , Kroesen G. M. W.
Published: November 2011

We have experimentally monitored the growth rate of dust particles in a low pressure Ar/C2H2 radiofrequency discharge as a function of the gas temperature Tg and independent of the C2H radical density and the gas density. Used diagnostics are laser light scattering and measurements of the phase angle between the RF voltage and current. In contrast to most literature, we demonstrate that the growth rate is not a monotonically decreasing function of Tg but shows a maximum around Tg = 65 °C. In addition, we demonstrate that the phase angle is an accurate measure to monitor the particle growth rate.
Stability analysis of multiple nonequilibrium fixed points in self-consistent electron transport calculations
Authors: Dzhioev Alan A. , Kosov D. S.
Published: November 2011

We present a method to perform stability analysis of nonequilibrium fixed points appearing in self-consistent electron transport calculations. The nonequilibrium fixed points are given by the self-consistent solution of stationary, nonlinear kinetic equation for single-particle density matrix. We obtain the stability matrix by linearizing the kinetic equation around the fixed points and analyze the real part of its spectrum to assess the asymptotic time behavior of the fixed points. We derive expressions for the stability matrices within Hartree-Fock and linear response adiabatic time-dependent density functional theory. The stability analysis of multiple fixed points is performed within the nonequilibrium Hartree-Fock approximation for the electron transport through a molecule with a spin-degenerate single level with local Coulomb interaction.
InGaN/GaN quantum well structures with greatly enhanced performance on a-plane GaN grown using self-organized nano-masks
Authors: Xing K. , Gong Y. , Bai J. , Wang T.
Published: November 2011

Great improvement in crystal quality of a-plane (non-polar) GaN has been achieved using a simple but effective overgrowth technique based on self-organized nano-masks. This has been confirmed by a massive reduction in full width at half maximum of x-ray diffraction rocking curves measured along both symmetrical and asymmetrical directions. Taking the advantage of utilising the nano-masks, a quick coalescence with a thickness of less than 1 μm has been obtained, which is much less than that using any conventional overgrowth techniques. The dislocation density has been significantly reduced by more than one order magnitude compared with a standard a-plane GaN layer on sapphire. An InGaN/GaN multiple quantum well (MQW) structure grown on the high quality a-plane GaN has demonstrated an enhancement with a factor of 7 in optical efficiency, compared with a similar MQW structure grown on a standard c-plane GaN layer. The excitation-power dependent photoluminescence measurements have confirmed that the a-plane InGaN/GaN MQW structure does not suffer from quantum-confined Stark effect any more.
Compact pulse forming line using barium titanate ceramic material
Authors: Kumar Sharma Surender , Deb P. , Shukla R. , Prabaharan T. , Shyam A.
Published: November 2011

Ceramic material has very high relative permittivity, so compact pulse forming line can be made using these materials. Barium titanate (BaTiO3) has a relative permittivity of 1200 so it is used for making compact pulse forming line (PFL). Barium titanate also has piezoelectric effects so it cracks during high voltages discharges due to stresses developed in it. Barium titanate is mixed with rubber which absorbs the piezoelectric stresses when the PFL is charged and regain its original shape after the discharge. A composite mixture of barium titanate with the neoprene rubber is prepared. The relative permittivity of the composite mixture is measured to be 85. A coaxial pulse forming line of inner diameter 120 mm, outer diameter 240 mm, and length 350 mm is made and the composite mixture of barium titanate and neoprene rubber is filled between the inner and outer cylinders. The PFL is charged up to 120 kV and discharged into 5 Ω load. The voltage pulse of 70 kV, 21 ns is measured across the load. The conventional PFL is made up of oil or plastics dielectrics with the relative permittivity of 2–10 [D. R. Linde, CRC Handbook of Chemistry and Physics, 90th ed. (CRC, 2009); Xia et al., Rev. Sci. Instrum. 79, 086113 (2008); Yang et al., Rev. Sci. Instrum. 81, 43303 (2010)], which increases the length of PFL. We have reported the compactness in length achieved due to increase in relative permittivity of composite mixture by adding barium titanate in neoprene rubber.
Effects of B-site chemistry on BiFeO3-containing enhanced tetragonality systems
Authors: Stein David M. , Davies Peter K.
Published: November 2011

The ternary perovskite systems PbTiO3-BiFeO3-Bi(Mg1/2Ti1/2)O3 and PbTiO3-BiFeO3-BiScO3 were investigated to clarify the relationship between the observance of multiple dielectric transitions and B-site chemistry. Multiple dielectric transitions were observed for a range of compositions in the Bi(Mg1/2Ti1/2)O3-containing system. A temperature-dependent diffraction study confirmed the existence of a cubic and tetragonal co-existence region at temperatures between the two transitions. No similar dielectric behavior was observed in the PbTiO3-BiFeO3-BiScO3 system.
Observation of ultra-narrow band plasmon induced transparency based on large-area hybrid plasmon-waveguide systems
Authors: Zhang Jing , Bai Wenli , Cai Likang , Xu Yun , Song Guofeng , Gan Qiaoqiang
Published: November 2011

We report the observation of an ultra-narrow band plasmon induced transparency resonance which is realized in a large area hybrid plasmon-waveguide system consisting of a gold nanowire array embedded in a slab waveguide. Due to the destructive interference between optical modes supported by the hybrid system, an ultra-narrow plasmon induced transparency resonance with a bandwidth of 8 nm at the wavelength of 966 nm was obtained (i.e., ∼1/120 of the peak wavelength at the incident angle of 60°). The group velocity is estimated to be ∼76, which is promising for miniaturized slow-light components.
Experimental and theoretical investigation of thermal stress relief during epitaxial growth of Ge on Si using air-gapped SiO2 nanotemplates
Authors: Ghosh Swapnadip , Leonhardt Darin , Han Sang M.
Published: November 2011

We demonstrate that SiO2 nanotemplates embedded in epitaxial Ge grown on Si relieve the stress caused by the thermal expansion mismatch between Ge and Si. The templates also filter threading dislocations propagating from the underlying Ge-Si interface, reducing the density from 9.8 × 108 to 1.6 × 107 cm−2. However, we observe that twin defects form upon Ge coalescence over the template, and the density is approximately 2.8 × 107 cm−2. The coalescence occurs without direct contact with SiO2, leaving a void between Ge and SiO2 that further reduces the thermal stress. The stress obtained from finite element modeling corroborates the experimental observation.
Solid state photovoltaic cells based on localized surface plasmon-induced charge separation
Authors: Takahashi Yukina , Tatsuma Tetsu
Published: November 2011

Charge separation induced by localized surface plasmon resonance (LSPR) of gold and silver nanoparticles (AuNPs and AgNPs) are applied to various devices and photoelectrochemical functionalities. Here, we develop all solid state In/TiO2/MNPs/ITO photovoltaic cells (MNP = AuNP or AgNP) by using two-dimensional MNP ensembles. Their quantum efficiencies are higher than those of previously reported solid state cells with hole-transport materials (HTMs) (ITO/TiO2/AuNPs/HTM/Au). The photoresponses from cells without HTMs suggest that the photovoltage generates at the TiO2-MNP interface.
A compact, broadband slot waveguide polarization rotator
Authors: Fan Jiahua , Huang Chenguang , Zhu Lin
Published: November 2011

We demonstrate a chip-scale compact, broadband polarization rotator on a silicon substrate. Unlike previously demonstrated waveguide polarization rotators, our approach relies on the adiabatic mode evolution in a single horizontal slot-waveguide, which results in a simple design and one-mask fabrication process.The structure is designed to rotate the TM-polarized input by 90 degree while be transparent with the TE-polarized input. The fabricated device has a total length of 100μm. Transmission spectra show the average polarization extinction ratios of 20 dB and 15 dB for TE and TM -polarized inputs, respectively.