bluuebunny/crossref_metadata_2025 huggingface dataset:
A prospective analysis of trauma exposure: The mediating role of PTSD symptomatology
Authors: Orcutt Holly K. , Erickson Darin J. , Wolfe Jessica
Published: December 2002

Trauma exposure has been associated with increased risk of exposure to additional traumatic events. Reactions to trauma exposure, specifically PTSD symptomatology, may mediate the link between trauma exposure and later traumatic events. Data from a longitudinal sample of Gulf War veterans (N= 2.949) were analyzed using a series of regression models. Higher levels of combat exposure were related to increased reports of PTSD symptomatology immediately upon return as well as increased reports of traumatic events in the 2 years following the Gulf War. PTSD symptomatology partially mediated the link between combat exposure and later trauma. Symptom clusters were also analyzed separately as potential mediators. Implications for the treatment of PTSD and prevention of exposure to multiple traumas are discussed.
Parental caring as a possible buffer against sexual revictimization in young adult survivors of child sexual abuse
Authors: Jankowski M. Kay , Leitenberg Harold , Henning Kris , Coffey Patricia
Published: December 2002

This study examined whether parental caring provided a buffer against the revictimization effect. Nine hundred and seventy‐four undergraduate women provided information about child sexual abuse, physical abuse, and whether they witnessed violence between their parents during childhood. They also reported whether they had ever been the victim of sexual assault in adulthood, and offered their perceptions of the degree of care they received as a child from each parent. Results indicated that women who had been sexually abused in childhood were twice as likely to be sexually assaulted in adulthood and that women with 2 or more types of childhood trauma were 3 times as likely to be sexually revictimized. Parental caring was not found to buffer against the revictimization effect.
Coping, functioning, and adjustment of rescue workers after the Oklahoma City bombing
Authors: North Carol S. , Tivis Laura , McMillen J. Curtis , Pfefferbaum Betty , Cox Jann , Spitznagel Edward L. , Bunch Kenneth , Schorr John , Smith Elizabeth M.
Published: December 2002

Studies have not previously considered postdisaster adjustment in the context of psychiatric disorders. After the Oklahoma City bombing, a volunteer sample of 181 firefighters who served as rescue and recovery workers was assessed with a structured diagnostic interview. The firefighters had relatively low rates of posttraumatic stress disorder (PTSD) and described little functional impairment, positive social adjustment, and high job satisfaction. PTSD was associated with reduced job satisfaction and functional impairment, providing diagnostic validity. Turning to social supports, seeking mental health treatment, and taking medication were not widely prevalent coping responses. Postdisaster alcohol use disorders and drinking to cope were significantly associated with indicators of poorer functioning. Surveillance for problem drinking after disaster exposure may identify useful directions for intervention.
Modulation by Leptin, Insulin and Corticosterone of Oleoyl-estrone Synthesis in Cultured 3T3 L1 Cells
Authors: Esteve M. , Savall P. , Virgilli J. , Fernández-López J.A. , Remesar X. , Alemany M.
Published: December 2002

Preadipocytes (3T3 L1) were used between 7 and 14 days after differentiation; they were incubated with 44 nM 3H-esterone. The medium was supplemented with 1 μM recombinant murine leptin, 10 nM recombinant human insulin, or 1 μM corticosterone for up to 72 hr. In a second series of experiments, cells were incubated for 48 hr with different concentrations of leptin, insulin or corticosterone, and compared with controls (plain medium). Cells were harvested, washed in buffer and homogenized, and protein was measured. Lipid extracts of cell homogenates were used for HPLC; the label distribution in free and acyl-estrone peaks was measured. Overall uptake of estrone (i.e., the sum of free and acyl-estrone) by cells was not affected by leptin or corticosterone, but strongly reduced by insulin. Leptin and corticosterone increased the synthesis of acyl-esterone in a dose- and time-dependent way. Insulin decreased acyl-estrone synthesis at low concentrations and with little change over time. The results suggest that control of oleoyl-estrone deposition in adipocytes is modulated in at least two distinct steps: (a) estrone uptake, affected by insulin in the physiological range; and (b) synthesis of oleoyl-estrone from cell estrone. The latter may be affected by insulin, but leptin and corticosterone enhance the process.
Uptake of Dimannoside Clusters and Oligomannosides by Human Dendritic Cells
Authors: Bédouet Laurent , Bousser Marie-Thérèse , Frison Natacha , Boccaccio Claire , Abastado Jean-Pierre , Marceau Philippe , Mayer Roger , Monsigny Michel , Roche Annie-Claude
Published: December 2002

Knowing that human blood monocyte-derived dendritic cells express cell-surface mannose-specific lectins, we prepared various mannoses containing glycoconjugates with the aim of developing highly specific synthetic carriers of oligonucleotides and genes. Conjugates were prepared from oligosaccharides obtained by hydrazinolysis of Saccharomyces cerevisiae invertase glycopeptides. The reducing saccharides were converted into glycosynthons, i.e., into glyco-amino acids. Fluorescein derivatives were obtained by coupling the free carboxyl group of oligosaccharyl-pyroglutamate to the α-amino group of ∊-fluoresceinyl-thiocarbamyl lysine methyl ester. It has been shown by others that glycosylated linear oligolysines containing up to six α-D-mannopyranosylphenylthiocarbamyl units have a high affinity for the human mannose receptor. In order to obtain fully biodegradable clusters and to improve both the specificity and the selectivity, disaccharides transformed into glycosynthons were coupled to pentalysine carriers (Lys5-Ala-Cys-NH2). Glycosylated pentalysyl cysteine conjugates were made fluorescent upon substitution of the cysteine thiol group with fluorescein iodoacetamide. As shown by flow cytofluorimetry, both the dimannoside clusters and yeast oligomannosides were very efficiently taken up by DC, conversely lactoside clusters were not.
One hundred consecutive hepatic biopsies in the workup of living donors for right lobe liver transplantation
Authors: Ryan Charlotte K. , Johnson Lesley A. , Germin Barbara I. , Marcos Amadeo
Published: December 2002

Living donor liver transplantation allows an increasing number of patients with end-stage liver disease the opportunity for effective treatment in the face of a critical shortage of cadaveric organs. Hepatic steatosis decreases functional graft mass and may contribute to graft dysfunction. Screening liver biopsy allows accurate quantitation of hepatic fat, but is an invasive procedure that is not universally employed in the evaluation of living donors. We studied 100 consecutive prospective right lobe living donors, all evaluated with liver biopsy, imaging studies, and various clinical parameters. The accuracy and predictive value of body mass index (BMI) and imaging were compared with biopsy in determining the amount of hepatic fat. There were no complications to biopsy, with 33% showing some degree of steatosis. BMI correlated only weakly with biopsy, with 73% of overweight (BMI > 25) donors having little or no hepatic fat. Imaging was only 12% sensitive to small amounts (5% to 10%) of fat, with increasing sensitivity to more severe steatosis. Imaging diagnosed steatosis in 2 donors without hepatic fat and failed to identify a candidate denied with biopsy-proven 30% steatosis. Conversely, 9% of candidates with BMIs of 25 or less had 10% or greater steatosis. Moreover, three candidates were denied surgery because biopsy detected occult liver disease. Accurate quantification of hepatic fat is not afforded by BMI and imaging studies alone. Screening liver biopsy has a low complication rate and may serve to increase donor safety. Biopsy is essential in identifying donor grafts at risk for poor recipient outcome while maximizing the donor pool.
Calculation of the melting point of NaCl by molecular simulation
Authors: Anwar Jamshed , Frenkel Daan , Noro Massimo G.
Published: December 2002

We report a numerical calculation of the melting point of NaCl. The solid–liquid transition was located by determining the point where the chemical potentials of the solid and liquid phases intersect. To compute these chemical potentials, we made use of free energy calculations. For the solid phase the free energy was determined by thermodynamic integration from the Einstein crystal. For the liquid phase two distinct approaches were employed: one based on particle insertion and growth using the Kirkwood coupling parameter, and the other involving thermodynamic integration of the NaCl liquid to a Lennard-Jones fluid. The latter approach was found to be significantly more accurate. The coexistence point at 1074 K was characterized by a pressure of −30±40 MPa and a chemical potential of −97.9±0.2kβT. This result is remarkably good as the error bounds on the pressure enclose the expected coexistence pressure of about 0.1 MPa (ambient). Using the Clausius–Clapyron relation, we estimate that dP/dT≈3 MPa/K. This yields a melting point of 1064±14 K at ambient pressure, which encompasses the quoted range for the experimental melting point (1072.45–1074.4 K). The good agreement with the experimental melting-point data provides additional evidence that the Tosi–Fumi model for NaCl is quite accurate. Our study illustrates that the melting point of an ionic system can be calculated accurately by employing a judicious combination of free energy techniques. The techniques used in this work can be directly extended to more complex, charged systems.
Quantum real-space transfer in a heterostructure overgrown on the cleaved edge of a superlattice
Authors: Gribnikov Z. S. , Vagidov N. Z. , Bashirov R. R. , Mitin V. V. , Haddad G. I.
Published: December 2002

A dispersion relation for an electron in a two-layer (and also multilayer) quantum well (QW) is formed as a result of a certain combination of initial dispersion relations for each of the forming layers. Such a combination can be used to engineer new dispersion relations with desirable properties. The same relates to a two-dimensional electron gas (2DEG) induced in a multilayer medium. In this study, we consider first such a 2DEG in a specific two-layer structure where a superlattice (SL) plays the role of the second half-infinite layer, and electrons with large wave numbers along the SL vector spread from the first ordinary QW layer to this SL. As a result of such a quantum (dynamic) real-space transfer, electrons become heavier, and the dispersion relation achieves an additional negative effective mass (NEM) section. Such NEM dispersion relations were studied for several different material systems, including the two most interesting three-material systems: (1) an isomorphic Al0.15Ga0.85As//GaAs/Al0.5Ga0.5As structure and (2) a strained In0.53Ga0.47As//InxGa1−xAs/InyAl1−y As structure (x>0.53, y<0.52) with a strain-balanced InxGa1−xAs/InyAl1−yAs SL. Most of the results were verified using a simplified 1D model, but some of them were verified by more complicated 2D-model calculations.
Flow rate and interface roughness of zinc oxide thin films deposited by spray pyrolysis technique
Authors: Ebothé J. , El Hichou A. , Vautrot P. , Addou M.
Published: December 2002

The interface growth and topology of sprayed ZnO thin films are examined here using the spatial scaling approach to the film surface in relation with the effect of a spraying deposition flow rate, f, ranging between 1 and 8 mil min−1. This thermally activated process is performed at the optimal temperature of the material (T=723 K). Two different growth mechanisms are identified, each of them characteristic of a particular f region. These related regions are separated from each other at a critical growth rate value of fc=5 mil min−1. The mechanism evolved below fc leads to a Hurst exponent α=0.4 typical of simple ballistic deposition growth modes. The morphology evolution in this f region corresponds to smoothing of the film surface with an increase of the flow rate. The growth kinetic exponent n=0.9 obtained in this region could be assigned to the elimination of some groove. Beyond fc, the spraying process engenders duplicate roughness exponents. The first value relative to the lowest scan lengths increases with f from α1=0.40 until unity. The second one, always evaluated at α2=0.16, is free of the f value. The growth kinetic exponent obtained in this f region, n=1.6, confirms a change of the growth mechanism, the last probably linked to incorporation of Zn particles at the growing film surface.
Synthetic characteristics of large carbon cluster ions by laser ablation of polymers in vacuum
Authors: Shibagaki K. , Takada N. , Sasaki K. , Kadota K.
Published: December 2002

The synthetic characteristics of large carbon cluster ions by laser ablation of polymers in vacuum were investigated. Time-of-flight mass spectrometry was used for analyzing the masses of ionic species produced by laser ablation. We found that large carbon cluster ions Cn+ with n up to 400 were synthesized in vacuum when copolymer of ethylene and tetrafluoroethylene, polyvinyliden fluoride, and chlorotrifluoroethylene were employed as the target material. Since the synthesis of large cluster ions in vacuum is a surprising phenomenon, we examined the synthesis efficiency in various experimental conditions. By comparing mass spectra obtained from various polymers containing hydrogen and/or halogen atoms, the existence of both hydrogen and halogen atoms in polymers do not directly contribute to enhance the synthesis efficiency of large carbon clusters. In addition, microscopic observations of surface morphologies of laser-ablated polymers revealed that the clustering reactions in eroded craters had little correlation with the synthesis efficiency of large carbon clusters.
Temperature dependence of thermal expansion and elastic constants of single crystals of ZrB2 and the suitability of ZrB2 as a substrate for GaN film
Authors: Okamoto Norihiko L. , Kusakari Misato , Tanaka Katsushi , Inui Haruyuki , Yamaguchi Masaharu , Otani Shigeki
Published: December 2002

Coefficients of thermal expansion (CTE) and elastic constants of single crystals of ZrB2 have been determined in the temperature ranges from room temperature to 1073 K and from room temperature to 1373 K, respectively. The elastic constants of ZrB2 are best characterized by the large value of the Young modulus (as high as 500 GPa) and the small values of the Poisson ratio (0.13–0.15), indicating the high stiffness and hardness and the brittleness, respectively. The values of CTE along the a- and c-axis directions are 6.66×10−6 and 6.93×10−6 K−1, respectively, when averaged over the temperature range from room temperature to 1073 K. The CTE value along the a-axis direction of ZrB2 is only moderately larger than the corresponding value for GaN. This together with the small lattice mismatch along the a-axis direction between ZrB2 and GaN in the heteroepitaxial orientation relationship of (0001)GaN//(0001)ZrB2 and 〈112̄0〉GaN//〈112̄0〉ZrB2 indicate that only a small compressive stress develops in the GaN thin-film crystal grown on the (0001) surface of the ZrB2 substrate. The stresses developed in the GaN thin-film crystal are evaluated with the values of CTE and elastic constants of ZrB2 determined in the present study. The evaluation verifies the suitability of ZrB2 as a substrate for heteroepitaxial growth of GaN.
A discrete solvent reaction field model within density functional theory
Authors: Jensen Lasse , van Duijnen Piet Th. , Snijders Jaap G.
Published: December 2002

In this work we present theory and implementation for a discrete reaction field model within Density Functional Theory (DFT) for studying solvent effects on molecules. The model combines a quantum mechanical (QM) description of the solute and a classical description of the solvent molecules (MM). The solvent molecules are modeled by point charges representing the permanent electronic charge distribution, and distributed polarizabilities for describing the solvent polarization arising from many-body interactions. The QM/MM interactions are introduced into the Kohn–Sham equations, thereby allowing for the solute to be polarized by the solvent and vice versa. Here we present some initial results for water in aqueous solution. It is found that the inclusion of solvent polarization is essential for an accurate description of dipole and quadrupole moments in the liquid phase. We find a very good agreement between the liquid phase dipole and quadrupole moments obtained using the Local Density Approximation and results obtained with a similar model at the Coupled Cluster Singles and Doubles level of theory using the same water cluster structure. The influence of basis set and exchange correlation functional on the liquid phase properties was investigated and indicates that for an accurate description of the liquid phase properties using DFT a good description of the gas phase dipole moment and molecular polarizability are also needed.
Nonlinear effects caused by intense electromagnetic waves in an electron-positron-ion plasma
Authors: Shukla P. K. , Stenflo L. , Fedele R.
Published: December 2002

It is shown that intense radiation nonlinearly interacts with the acousticlike waves in an electron-positron-ion plasma at nonrelativistic temperatures. The interaction is governed by the electromagnetic wave equation including the relativistic electron and positron mass variations and the density changes associated with the acousticlike waves, and an equation for the latter in the presence of the radiation pressure. The governing nonlinear equations are analyzed to show the possibility of a novel modulational instability as well as the formation of light bullets and solitons.
p-type conduction in codoped ZnO thin films
Authors: Singh A. V. , Mehra R. M. , Wakahara A. , Yoshida A.
Published: December 2002

p-type conduction in ZnO thin films was realized by the codoping method. Types of conduction and carrier density in codoped ZnO films were found to be dependent on the oxygen partial pressure ratios in the sputtering gas mixture. The lowest room temperature resistivity was found to be 11.77 Ω cm with a hole density of 9.0×1016 cm−3 for the films deposited in 60% of oxygen partial pressure ratio. Codoped films were found to be c-oriented and highly transparent.
High-resolution x-ray diffraction for characterization and monitoring of silicon-on-insulator fabrication processes
Authors: Cohen G. M. , Mooney P. M. , Park H. , Cabral C. , Jones E. C.
Published: December 2002

High-resolution x-ray diffraction (HRXRD) was used to monitor silicon-on-insulator (SOI) device fabrication processes. The use of HRXRD is attractive since it is nondestructive and can be applied directly to product wafers. We show the usefulness of this technique for the characterization of amorphizing implants for shallow junctions, solid phase recrystallization of implanted junctions, cobalt-silicide formation, and oxidation; all are critical processes for complementary metal oxide semiconductor device fabrication on SOI. We also found the technique applicable to multilayered SOI structures fabricated by wafer bonding, where the tilt and rotation of each SOI layer with respect to the handle substrate, allowed us to obtain independent measurements of each SOI film.
Correlated analysis of deep level transient spectroscopy and thermally stimulated current spectra
Authors: Menichelli David , Borchi Emilio
Published: December 2002

A method for the analysis of deep level spectra in semiconductors has been developed, which enables the determination of different trap signatures even when a large number of spectral peaks overalp. This procedure invokes the simultaneous analysis of thermally stimulated currents and deep level transient spectroscopy spectra by the numerical solution of the integral equations linking the full deep level populations to the measured signals. The method has been tested for a set of neutron irradiated silicon samples, giving very satisfactory results.
Comment on “Study on the quantum efficiency of resonant cavity enhanced GaAs far-infrared detectors” [J. Appl. Phys. 91, 5538 (2002)]
Authors: Korotkov A. L.
Published: December 2002

We point out that the reflection from the active-layer interfaces in multilayer GaAs far-infrared detectors should be taken into account for the proper analysis of optical efficiency in cases of a large number of emitter layers and low reflectivity of the top and bottom mirrors.
Microstructures of magnetic tunneling junctions
Authors: Li Lai-feng , Liu Xiaoyong , Xiao Gang
Published: December 2002

We have investigated the microstructures of magnetic tunneling junctions using high-resolution transmission electron microscopy (HRTEM). These junctions exhibit large magnetoresistance of 34% at room temperature and at tens of gauss. HRTEM reveals well-defined layered polycrystalline metallic structures. The important A12O3 tunneling barrier has an amorphous structure containing a few tiny crystalline inhomogeneties. Though the barrier is flat over large length scales, its interfaces with the neighboring electrodes are rough. We have characterized the roughness amplitude and wavelength, which are consistent with the magnitude of offset bias fields in measured hysteretic magnetoresistance curves.
Magnetorotational and Parker instabilities in magnetized plasma Dean flow as applied to centrifugally confined plasmas
Authors: Huang Yi-Min , Hassam A. B.
Published: December 2002

The ideal magnetohydrodynamics stability of a Dean flow plasma supported against centrifugal forces by an axial magnetic field is studied. Only axisymmetric perturbations are allowed for simplicity. Two distinct but coupled destabilization mechanisms are present: flow shear (magnetorotational instability) and magnetic buoyancy (Parker instability). It is shown that the flow shear alone is likely insufficient to destabilize the plasma, but the magnetic buoyancy instability could occur. For a high Mach number (MS), high Alfvén Mach number (MA) system with MSMA≳πR/a (R/a is the aspect ratio), the Parker instability is unstable for long axial wavelength modes. Implications for the centrifugal confinement approach to magnetic fusion are also discussed.
Characteristics of LaAlO3/Si(100) deposited under various oxygen pressures
Authors: Xiang Wenfeng , Lü Huibin , Yan Lei , Guo Haizhong , Liu Lifeng , Zhou Yueliang , Yang Guozhen , Jiang Jinchun , Cheng Huansheng , Chen Zhenghao
Published: December 2002

High-k dielectric LaAlO3 (LAO) thin films were deposited by laser molecular-beam epitaxy under various oxygen pressures. X-ray diffraction showed that the LAO films were amorphous. The chemical compositions and thickness of the LAO thin films were measured using Rutherford backscattering spectrometry. Al/LAO/Si metal–oxide–semiconductor capacitor structures were fabricated and measured. The leakage current density versus voltage curves showed that the leakage current of the LAO thin films decreased by increasing the oxygen pressure of the preparation. Specifically, when prepared under the active oxygen (containing atom oxygen), the leakage current of the LAO sample was lower than that prepared under the general oxygen. All of the capacitance–voltage curves have a positive shift along the voltage axis and the flatband voltage decreased with increasing oxygen pressures during the LAO thin-film preparation.
Identification of luminous region in porous silicon layers
Authors: Kim Y. Y. , Lee K. W. , Ahn E. J. , Shim S.
Published: December 2002

Photoluminescence spectra were measured experimentally and compared with the results of the optical model calculations in oder to identify the region of photoluminescence in a porous silicon layer. It is found that the upper surface region in the porous silicon layer contributes most of the luminescence, by analyzing the interference patterns of the photoluminescence spectra and those of reflectances. It is confirmed by comparing the results of a detailed computer simulation with the experiments, and by analyzing the photoluminescence characteristics of a free-standing porous silicon film. Analyses of the photoluminescence spectra measured using several different excitation wavelengths also support our conclusion.
Band-tail photoluminescence in hydrogenated amorphous silicon oxynitride and silicon nitride films
Authors: Kato Hiromitsu , Kashio Norihide , Ohki Yoshimichi , Seol Kwang Soo , Noma Takashi
Published: December 2002

Photoluminescence (PL) measurements were performed on a series of hydrogenated amorphous silicon oxynitride and silicon nitride films with different nitrogen contents deposited by plasma-enhanced chemical-vapor deposition. From the PL and PL excitation spectra, the Urbach energy of the sample is found to be proportional to its PL half-maximum width, regardless of whether the sample is silicon oxynitride or silicon nitride. Time-resolved PL measurements showed that PL peak energy varies with time after the excitation, showing a systematic dependence on the chemical composition in the two materials. That the PLs observed in the two materials have very similar characteristics regardless of the presence of oxygen strongly indicates that the PLs result from the same chemical structure, more specifically Si–N bonds, and that the two materials have similar band-tail states associated with the static disorder. In the two materials, it is found that the electrons and holes photoexcited into such band-tail states recombine first through an excitonlike recombination process and then through a radiative tunneling recombination process.
Photoluminescent and electroluminescent properties of Mn-doped ZnS nanocrystals
Authors: Yang Heesun , Holloway Paul H. , Ratna Banahalli B.
Published: December 2002

ZnS:Mn nanocrystals with sizes between 3 and 4 nm were synthesized via a competitive reaction chemistry method, where the surface capping organic species (p-thiocresol) is used as an inhibitor of the crystal growth. The x-ray diffraction and photoluminescent (PL) properties of ZnS:Mn bulk and nanocrystals were compared. A direct current electroluminescent (EL) device having a hybrid organic/inorganic multilayer structure, indium tin oxide/poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT-PSS)/PVK/ZnS:Mn NC/Al, was tested. In this multilayer EL device structure, the PEDOT-PSS leads to enhanced hole injection, while the poly(N-vinylcarbazole) (PVK) serves as a passivation layer between the PEDOT-PSS and nanocrystal layers. Electron–hole recombination was not confined to the ZnS:Mn nanocrystal layer, but also occurred in the PVK layer. The result was emission from both the blue-emitting PVK and yellow-emitting ZnS:Mn nanocrystals. The EL emission spectrum was dependent upon the voltage, showing an increasing ratio of PVK emission to nanocrystal emission with increased voltage. The dependence of PL and EL emissions on Mn concentration (0.40 to 2.14 mol %) is also reported.
Influence of Cr concentration on the structural and magnetic properties of the diluted magnetic semiconductor Hg1−xCrxSe
Authors: Prozorovskiı̆ V. D. , Reshidova I. Yu. , Puzynya A. I. , Paranchych S. Yu. , Romanyuk V. R.
Published: December 2002

The results of a study of the structural and magnetic properties of single-crystal samples of the diluted magnetic semiconductor Hg1−xCrxSe with different concentrations of chromium ions (0<x⩽0.07) in the temperature interval 50–300 K are reported. It is found that the boundary of the existence region of the homogeneous solid solution lies at chromium concentrations x<0.05. In samples with x⩾0.05 the sharp growth of the magnetic susceptibility in the region of the phase transition temperature is due not only to a transition to a phase similar to a spin-glass phase, which is observed in all the samples studied, but also to a ferromagnetic contribution from ferromagnetic inclusions of HgCr2Se4 and CrSe in those samples.
Growth of Au-catalyzed ordered GaAs nanowire arrays by molecular-beam epitaxy
Authors: Wu Z. H. , Mei X. Y. , Kim D. , Blumin M. , Ruda H. E.
Published: December 2002

Ordered gallium arsenide (GaAs) nanowires are grown by molecular-beam epitaxy on GaAs (111)B substrates using Au-catalyzed vapor–liquid–solid growth defined by nanochannel alumina (NCA) templates. Field-emission scanning electron microscope images show highly ordered nanowires with a growth direction perpendicular to the substrate. The size (i.e., diameter) distribution of the wires is drastically narrowed by depositing the gold catalyst through an NCA template mask; this narrows the size distribution of the gold dots and arranges them in a well-ordered array, as defined by the NCA template. The nanowire diameter distribution full width at half maximum on the masked substrate is 5.1 nm, compared with 15.7 nm on an unmasked substrate.
Acoustic barriers based on periodic arrays of scatterers
Authors: Sanchez-Perez Juan V. , Rubio Constanza , Martinez-Sala Rosa , Sanchez-Grandia Rafael , Gomez Vicente
Published: December 2002

It is well known that certain periodic structures built by repetition of elements produce sound attenuation effects as a consequence of the destructive interference of the scattered waves by these elements. The sound attenuation results that we got from transmission experiments with these kind of structures, so-called sonic crystals (SCs), led us to think that SCs could be used as an acoustic barrier. Until now, most of the transmission experiments with these periodic arrays of scatterers have been performed under controlled conditions, so how they would behave outdoors is still not well known. In this letter we present outdoor-experimental results for two-dimensional SCs and from these it can be concluded that periodic arrays of scatterers are a suitable device to reduce noise in free-field conditions.
Weekly High-Dose Calcitriol and Docetaxel in Metastatic Androgen-Independent Prostate Cancer
Authors: Beer Tomasz M. , Eilers Kristine M. , Garzotto Mark , Egorin Merrill J. , Lowe Bruce A. , Henner W. David
Published: December 2002

Purpose: To determine the safety and efficacy of weekly high-dose oral calcitriol (Rocaltrol, Roche Pharmaceuticals, Basel, Switzerland) and docetaxel (Taxotere, Aventis Pharmaceuticals, Bridgewater, NJ) in patients with metastatic androgen-independent prostate cancer (AIPC).

Patients and Methods: Thirty-seven patients were treated with oral calcitriol (0.5 μg/kg) on day 1 followed by docetaxel (36 mg/m2) on day 2, repeated weekly for 6 weeks of an 8-week cycle. Patients maintained a reduced calcium diet and increased oral hydration. Prostate-specific antigen (PSA) response was the primary end point, which was defined as a 50% reduction in PSA level confirmed 4 weeks later.

Results: Thirty of 37 patients (81%; 95% confidence interval [CI], 68% to 94%) achieved a PSA response. Twenty-two patients (59%; 95% CI, 43% to 75%) had a confirmed > 75% reduction in PSA. Eight of the 15 patients with measurable disease (53%; 95% CI, 27% to 79%) had a confirmed partial response. Median time to progression was 11.4 months (95% CI, 8.7 to 14 months), and median survival was 19.5 months (95% CI, 15.3 months to incalculable). Overall survival at 1 year was 89% (95% CI, 74% to 95%). Treatment-related toxicity was generally similar to that expected with single-agent docetaxel. Pharmacokinetics of either calcitriol or docetaxel were not affected by the presence of its companion drug in an exploratory substudy.

Conclusion: The combination of weekly oral high-dose calcitriol and weekly docetaxel is a well-tolerated regimen for AIPC. PSA and measurable disease response rates as well as time to progression and survival are promising when compared with contemporary phase II studies of single-agent docetaxel in AIPC. Further study of this regimen is warranted.
Biochemical characterization of two (C300F, P425T) arylsulfatase a missense mutations
Authors: Marcão Ana , Simonis Heidi , Schestag Frank , Sá Miranda M. Clara , Gieselmann Volkmar
Published: December 2002

Metachromatic leukodystrophy (OMIM 250100) is a lysosomal storage disease caused by the deficiency of arylsulfatase A (ARSA, EC 3.1.6.8). This disease affects mainly the nervous system, because patients cannot degrade 3‐O‐sulfo‐galactosylceramide (sulfatide), a major myelin lipid. Here we describe the characterization of the biochemical effects of two arylsulfatase A missense mutations, P425T and C300F. Transfection experiments demonstrate the expression of residual ARSA enzyme activity for P425T, but not for C300F substituted ARSA. Relative specific activity determination showed that the P425T substituted enzyme has retained about 12% of specific enzyme activity, whereas the C300F substituted enzyme is reduced to less than 1%. Pulse‐chase experiments reveal that both mutant proteins are unstable, with a half life of less than 6 hr. Increased secretion upon addition of NH4Cl indicates that the mutant proteins can pass the Golgi apparatus and thus are not degraded in the endoplasmic reticulum (ER), but in the lysosomes. This is supported by experiments, which demonstrate the presence of mannose‐6‐phosphate residues on the oligosaccharide side chains of the mutant proteins. Addition of the cysteine protease inhibitor leupeptin increases the amount of ARSA activity in cells expressing the P425T substituted enzyme, whereas no increase in activity was seen with C300F substituted ARSA. © 2002 Wiley‐Liss, Inc.
After the Omagh bomb: Posttraumatic stress disorder in health service staff
Authors: Luce Anna , Firth‐Cozens Jenny , Midgley Simon , Burges Clive
Published: December 2002

In this postal survey of 1064 health service staff working closest to the Omagh bombing in Northern Ireland, approximately half reported having professional or civilian involvement. Types of involvement and posttraumatic stress disorder (PTSD) levels varied between staff groups. Staff involved both professionally and as a civilian, particularly those who witnessed the trauma, or those who had experienced previous emotional problems and trauma, had the highest levels of symptomatology. Although staff with higher PTSD symptoms were more likely to seek professional help, only a minority contacted professionals for support.
Peritraumatic dissociative experiences, trauma narratives, and trauma pathology
Authors: Zoellner Lori A. , Alvarez‐Conrad Jennifer , Foa Edna B.
Published: December 2002

Peritraumatic dissociation, i.e., dissociation during or immediately after a traumatic event, has been associated with persistence of trauma‐related pathology. Peritraumatic dissociation may interfere with encoding of traumatic memories and this style may impede recovery. This study examines this hypothesis by analyzing trauma narratives from 28 female sexual and nonsexual assault victims who reported either high or low peritraumatic dissociation. Participants were asked to recount their assault. Narratives were videotaped, transcribed, and coded. Narratives of individuals with high peritraumatic dissociation had higher grade levels and a trend toward lower reading ease than those with low peritraumatic dissociation. Both higher grade levels and lower reading ease of prethreat sections of trauma narratives were related to posttreatment reexperiencing and anxiety symptoms.
Partners' ratings of combat veterans' anger
Authors: Calhoun Patrick S. , Beckham Jean C. , Feldman Michelle E. , Barefoot John C. , Haney Thom , Bosworth Hayden B.
Published: December 2002

Spouse reports may serve as an important source of collateral information in the assessment of posttraumatic stress disorder (PTSD) and associated behavioral problems. This study examined the concordance of anger reports among 94 combat veterans and their partners. Veterans' scores on subscales of the Multidimensional Anger Inventory were compared with scores on a parallel version completed by partners to assess veterans' anger symptomatology. The study examined whether the concordance between veteran and partner‐reported anger is moderated by whether the veteran suffers from PTSD. There was moderate agreement between veterans and their partners on reports of anger and little evidence to suggest that PTSD diagnosis affected the convergence between partner and veteran scores.
Exogenous Sphingosine Enters Xenopus Laevis Embryos Grown in Petri Dishes and It Is Metabolized
Authors: Rizzo Angela Mario , Rossi Federica , Guerra Anna , Berra Bruno , Gornati Rosalba , Bernardini Giovanni , Sonnino Sandro
Published: December 2002

Xenopus embryos of different developmental stages were exposed to 0.1 μM [1-3H]sphingosine. Labeled sphingosine was quickly absorbed by Xenopus embryos. The amount of radioactivity absorbed increased with embryo age and appeared to be linearly correlated (R=0.97) to the embryo surface area. About 45% of the total radioactivity associated to the embryos was found in the skin, 22% in the intestine, 15% in the heart, 12% in the liver and 6% in the brain.

A portion of [1-3H]sphingosine entered very rapidly the biosynthetic pathway of sphingolipids; after 30 min of incubation, in fact, only a small amount of free radioactive sphingosine could be detected. Sphingomyelin was the main radioactive sphingolipid synthesized; radioactive ceramide, galactosylceramide and lactosylceramide could also be recognized and quantified. On the contrary, the amount of radioactive gangliosides was hardly detectable.

A portion of [1-3H]sphinogosine absorbed by Xenopus embryos (30 to 60% depending on the developmental stage) entered the catabolic pathway producing radioactive phosphoethanolamine that was recycled for the biosynthesis of radioactive phosphatidylethanolamine. This phospholipid was produced mainly in the intestine and in the skin, while sphingomyelin was the main radioactive lipid in the heart, liver and brain.
Effect of Hydrogen Ion Concentration and Buffer Composition on Ligand Binding Characteristics and Polymerization of Cow's Milk Folate Binding Protein
Authors: Holm Jan , Hansen Steen Ingemann
Published: December 2002

The ligand binding and aggregation behavior of cow's milk folate binding protein depends on hydrogen ion concentration and buffer composition. At pH 5.0, the protein polymerizes in Tris-HCl subsequent to ligand binding. No polymerization occurs in acetate, and binding is markedly weaker in acetate or citrate buffers as compared to Tris-HCl. Polymerization of ligand-bound protein was far more pronounced at pH 7.4 as compared to pH 5.0 regardless of buffer composition. Binding affinity increased with decreasing concentration of protein both at pH 7.4 and 5.0. At pH 5.0 this effect seemed to level off at a protein concentration of 10−6 M which is 100–1000 fold higher than at pH 7.4. The data can be interpreted in terms of complex models for ligand binding systems polymerizing both in the absence or presence of ligand (pH 7.4) as well as only subsequent to ligand binding (pH 5.0).
Hyposmotically-Activated Efflux of L-Carnitine from a Human Mammary Cancer Cell Line
Authors: Shennan D.B.
Published: December 2002

Cell-swelling, induced by a hyposmotic challenge, stimulated the efflux of L-carnitine from a human mammary cancer cell line, MDA-MB-231. The response was dependent upon the extent of the osmotic shock. Hyposmotically-activated L-carnitine efflux was inhibited by the anion transport blocker diiodosalicylate. The efflux of taurine from MDA-MB-231 cells was also stimulated by a hyposmotic shock via a pathway sensitive to diiodosalicylate. L-carnitine efflux from MDA-MB-231 cells was stimulated by isosmotic swelling in a manner which was inhibited by diiodosalicylate. The results suggest that L-carnitine may exit cells via a volume-sensitive pathway: it is possible that L-carnitine efflux may utilize the same pathway as amino acids. The efflux of L-carnitine via this route could have a major effect on the intracellular concentration of L-carnitine and could facilitate transepithelial L-carnitine transport.
Specular reflectivity of plasma mirrors as a function of intensity, pulse duration, and angle of incidence
Authors: Ziener Ch. , Foster P. S. , Divall E. J. , Hooker C. J. , Hutchinson M. H. R. , Langley A. J. , Neely D.
Published: December 2002

The specular reflectivity of plasma mirrors formed by subpicosecond pulses from a titanium:sapphire laser has been measured for different angles of incidence and for two different pulse lengths as a function of the laser intensity. Laser pulses with energies up to 250 mJ and pulse durations of 90 and 500 fs were focused onto a fused silica substrate. For angles of incidence between 6° and 45° the specular reflectivity increases to values of about 80% for intensities above a certain threshold intensity. The threshold intensity varies with the pulse length but is nearly independent of the angle of incidence. For very high intensities the specular reflectivity drops again to values of only a few percent.
Compressional waves in complex (dusty) plasmas under microgravity conditions
Authors: Khrapak S. , Samsonov D. , Morfill G. , Thomas H. , Yaroshenko V. , Rothermel H. , Hagl T. , Fortov V. , Nefedov A. , Molotkov V. , Petrov O. , Lipaev A. , Ivanov A. , Baturin Y.
Published: December 2002

Complex plasmas consist of electrons, ions and charged microparticles, with typical charge-to-mass ratios 1:10−5:10−13. The interest in these systems has grown explosively, because they can be investigated at the kinetic level (the microparticles). However, on Earth the supporting forces (against gravity) are of the same order as the electrostatic interparticle forces—and hence only strongly compressed systems can be investigated. Under microgravity conditions these “body forces” are a factor 102 smaller which allows the experimental investigation of weakly compressed three-dimensional complex plasmas. One way to study these systems is by the controlled excitation of low-frequency compressional waves. The first such experiments, conducted with the PKE-Nefedov laboratory on the International Space Station is reported. The waves were excited by modulating the voltage on the rf electrodes. By varying the modulation frequency the dispersion relation was measured. The results are compared with existing theoretical models.
CF A 2Σ+–X 2Π and B 2Δ–X 2Π study by broadband absorption spectroscopy in a plasma etch reactor: Determination of transition probabilities, CF X 2Π concentrations, and gas temperatures
Authors: Luque Jorge , Hudson Eric A. , Booth Jean-Paul
Published: December 2002

Broadband absorption spectroscopy was applied to study the CF A 2Σ+–X 2Π and B 2Δ–X 2Π transitions in a plasma etch reactor. We report a previously unobserved band, which is assigned as CF A 2Σ+–X 2Π (3,0). This band is significantly broadened by predissociation, and we estimate the average collision-free lifetime of the CF A 2Σ+ v′=3 level to be 0.30±0.08 ps. Experimental relative oscillator strength measurements, together with ab initio calculations, Rydberg–Klein–Rees-based wave functions and experimental lifetimes were used to calculate a full set of transition probabilities for the CF A 2Σ+–X 2Π and B 2Δ–X 2Π bands. The maximum observed number densities of CF X 2Π were ∼2×1013 cm−3 with sensitivity to measure to 1010 cm−3. The excited state and ground state temperatures were determined by comparing the spectra to simulations. The ground state rotational temperature was 450±30 K and the vibrational temperature was 850±80 K near the substrate surface. The CF B 2Δ excited state rotational temperatures are higher than those of the ground state. We show that this absorption technique is practical for determining gas temperatures and absolute concentrations in plasma etch reactors.
Control of the morphology transition for the growth of cubic GaN/AlN nanostructures
Authors: Martinez-Guerrero E. , Chabuel F. , Daudin B. , Rouvière J. L. , Mariette H.
Published: December 2002

The Stransky–Krastanow growth mode of strained layers which gives rise to a morphology transition from two-dimensional layer to three-dimensional islands is studied in details for the cubic gallium nitride on cubic aluminum nitride (GaN/AlN) system grown by molecular beam epitaxy. Besides the lattice parameter mismatch which governs this transition, we evidence the importance of two other parameters, namely the substrate temperature and the III/V flux ratio. Tuning each of these two parameters enables to control the strain relaxation mechanism of a GaN deposited onto AlN, leading to the growth of either quantum wells or quantum dots.
Mechanism of vortex switching in magnetic nanodots under a circular magnetic field. I. Resonance action of the field on the nanodot eigenmodes
Authors: Kovalev A. S. , Prilepsky J. E.
Published: December 2002

The resonance activation of the eigenmodes of a two-dimensional easy-plane ferromagnet of finite size by a circular magnetic field is considered as a basis for theoretical explanation of the mechanism of vortex switching in magnetic nanodots under the influence of such a field. It is shown analytically that in the case of weak easy-plane anisotropy, when the vortex has a nonzero polarization (a total magnetization along the hard axis), the influence of the field on the eigenmodes of the system is of a complicated nature. A circular field acts in a resonance manner on the azimuthal modes of the system, in which the magnetization depends on the azimuthal coordinate (in the form of a direct resonance at the eigenfrequencies of the azimuthal modes). The coupling of the azimuthal and symmetric (independent of the azimuthal coordinate) modes via the external field gives rise to complex parametric resonances at sum frequencies. The results obtained are compared with the data of previous numerical studies.
Staged work hardening of polycrystalline titanium at low temperatures and its relation to substructure evolution
Authors: Moskalenko V. A. , Smirnov A. R. , Kovaleva V. N. , Natsik V. D.
Published: December 2002

Tensile test diagrams of commercial-grade polycrystalline titanium foil are obtained in the temperature range 10–373 K, and the corresponding work hardening curves are plotted as stress versus plastic deformation, σ(εp). It is shown that the hardening curves consist of two (at low temperatures) or three (at high temperatures) fragments or stages, which are approximated by the equation σ=const+hεpn with constant rheological parameters n and h within each stage, and the empirical values of these parameters are determined over the investigated temperature range. The behavior of the hardening curves is compared with the features of the substructure evolution of the polycrystalline titanium at different stages of the plastic deformation, which are revealed by methods of electron and optical microscopy. The presence of correlations between the individual stages of the hardening and the structural states formed in the samples in the process of deformation is established. The effectiveness of the different types of substructures—ensembles of randomly distributed dislocations, reorientation bands, and twins—in the hardening of polycrystalline titanium is discussed.
Acoustic field in a thermoacoustic Stirling engine having a looped tube and resonator
Authors: Ueda Yuki , Biwa Tetsushi , Mizutani Uichiro , Yazaki Taichi
Published: December 2002

S. Backhaus and G. W. Swift [Nature 399, 335(1999)] have built a prototype thermoacoustic Stirling engine based on traveling wave energy conversions, and demonstrated that its efficiency reached above 40% of the Carnot efficiency. We experimentally investigate an acoustic field in the engine through simultaneous measurements of velocity U and pressure P. By focusing on the phase lead Φ of U relative to P in its regenerator, we find that the engine can achieve such a high efficiency by the negative Φ about −20° rather than a traveling wave phase (Φ=0).