bluuebunny/crossref_metadata_2025 huggingface dataset:
Subcellular alteration of glyceraldehyde‐3‐phosphate dehydrogenase in Alzheimer's disease fibroblasts
Authors: Mazzola Jennifer L. , Sirover Michael A.
Published: December 2002

The regulation of glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) has been implicated both in age‐related neurodegenerative disease and in apoptosis. Previous in vitro studies suggest an interaction between GAPDH and the β‐amyloid precursor protein (β‐APP), a protein directly involved in Alzheimer's disease (AD). New studies indicate that GAPDH is a multidimensional protein with diverse membrane, cytoplasmic, and nuclear functions; each is distinct from its role in glycolysis. The nuclear functions of GAPDH include a role in apoptosis that requires its translocation to the nucleus. Accordingly, β‐APP–GAPDH interactions, altering GAPDH structure in vivo, may affect energy generation, inducing hypometabolism, a characteristic AD phenotype. Because GAPDH is a multifunctional protein, pleiotropic effects may also occur in a variety of fundamental cellular pathways in AD cells. This may include unique GAPDH–RNA interactions. We report here the identification of a high‐molecular‐weight (HMW) GAPDH species present exclusively in the postnuclear fraction of AD cells. The latter is characterized by reduced GAPDH activity. The HMW GAPDH species was not detected in postnuclear age‐matched control (AMC) fractions nor in AD whole‐cell preparations. Each is characterized by normal GAPDH activity. By definition, the preparation of whole‐cell extracts entails the destruction of subcellular structure. The latter findings indicate that the dissociation of the GAPDH protein from the HMW species restores its enzymatic activity. Thus, these results reveal a new, unique intracellular phenotype in AD cells. The functional consequences of subcellular alteration in GAPDH structure in AD cells are considered. © 2002 Wiley‐Liss, Inc.
Endogenous RGS proteins facilitate dopamine D2S receptor coupling to Gαo proteins and Ca2+ responses in CHO‐K1 cells
Authors: Boutet-Robinet Elisa A. , Finana Frederic , Wurch Thierry , Pauwels Petrus J. , De Vries Luc
Published: December 2002

The role of RGS proteins on dopaminergic D2S receptor (D2SR) signalling was investigated in Chinese hamster ovary (CHO)‐K1 cells, using recombinant RGS protein‐ and PTX‐insensitive Gαo proteins. Dopamine‐mediated [35S]GTPγS binding was attenuated by more than 60% in CHO‐K1 D2SR cells coexpressing a RGS protein‐ and PTX‐insensitive GαoGly184Ser:Cys351Ile protein versus cells coexpressing a similar amount of PTX‐insensitive GαoCys351Ile protein. Dopamine‐agonist‐mediated Ca2+ responses were dependent on the coexpression with a GαoCys351Ile protein and were fully abolished upon coexpression with a GαoGly184Ser:Cys351Ile protein. These results suggest that interactions between the Gαo protein and RGS proteins are involved in efficient D2SR signalling.
Engineering of Escherichia coli β‐galactosidase for solvent display of a functional scFv antibody fragment
Authors: Alcalá Pilar , Ferrer-Miralles Neus , Villaverde Antonio
Published: December 2002

Protein engineering allows the generation of hybrid polypeptides with functional domains from different origins and therefore exhibiting new biological properties. We have explored several permissive sites in Escherichia coli β‐galactosidase to generate functional hybrid enzymes displaying a mouse scFv antibody fragment. When this segment was placed at the amino‐terminus of the enzyme, the whole fusion protein was stable, maintained its specific activity and interacted specifically with the target antigen, a main antigenic determinant of foot‐and‐mouth disease virus. In addition, the antigen‐targeted enzyme was enzymatically active when bound to the antigen and therefore useful as a reagent in single‐step immunoassays. These results prove the flexibility of E. coli β‐galactosidase as a carrier for large‐sized functional domains with binding properties and prompt the further exploration of the biotechnological applicability of the scFv enzyme targeting principle for diagnosis or other biomedical applications involving antigen tagging.
Information Capacity of Symbol Sequences
Authors: Sadovsky M. G.
Published: December 2002

The information capacity of sequences is considered through the calculation of specific entropy of their frequency dictionary. The specific entropy was calculated against the reconstructed dictionary which bears the most probable continuations of shorter strings. The measure developed allows to distinguish the sequences both from the random ones, and those with high level of (rather simple) order. Some applications of the developed methodology to genetics, bioinformatics, and linguistics are discussed.
The aetiology of postpsychotic posttraumatic stress disorder following a psychotic episode
Authors: Shaw Katharine , McFarlane Alexander C. , Bookless Clara , Air Tracy
Published: December 2002

This paper examines the aetiology of postpsychotic posttraumatic stress disorder (PP/PTSD) symptoms in a sample of participants who had been hospitalized following a psychotic episode. Forty two people hospitalized for a psychotic illness were interviewed during recovery to investigate whether a psychotic episode was associated with PTSD symptomatology. All participants found psychosis and hospitalization highly distressing. PP/PTSD symptoms were not associated with demographic factors, previous trauma, treatment, or insight. The PP/PTSD group reported more distress and intrusive memories associated with illness and treatment experiences and had higher scores for anxiety and dissociative symptoms. The development of PP/PTSD phenomenology was associated with the psychological distress of the experience.
Norepinephrine Inhibits Energy Metabolism of Human Peripheral Blood Mononuclear Cells via Adrenergic Receptors
Authors: Lünemann Jan D. , Buttgereit Frank , Tripmacher Robert , Baerwald Christoph G. O. , Burmester Gerd-Rüdiger , Krause Andreas
Published: December 2002

Previous studies demonstrated that the adaptive response to stressors and inflammatory signals involves the activation of the automotic nervous system. Catecholamines have been shown to modulate the activity of various immune effector cells directly via membrane adrenergic receptors. Here, we investigated immediate effects of norepinephrine on energy metabolism of immune cells. Norepinephrine inhibits oxygen consumption of human peripheral blood mononuclear cells at concentrations that are relevant to its physiological range. The ?-adrenoreceptor antagonist propranolol, but not the ?-adrenoreceptor antagonist phentolamine reversed the norepinephrine induced inhibition in quiescent cells. Conversely, phentolamine but not propranolol is capable of blocking norepinephrine mediated effects in mitogen activated human peripheral blood mononuclear cells. Our data indicate that the sensitization of ?- and ?-adrenoreceptors on immune cells is differentially regulated, and that these processes depend on the activation state of these cells. These findings have important implications for the understanding of stress-induced suppression of immune function and may contribute to the elucidation of the pathogenesis of immunologically mediated diseases.
War exposure among children from Bosnia‐Hercegovina: Psychological adjustment in a community sample
Authors: Smith Patrick , Perrin Sean , Yule William , Hacam Berima , Stuvland Rune
Published: December 2002

As part of a United Nations Children's Fund (UNICEF) psychosocial programme during the war in Bosnia‐Hercegovina, data were collected from a community sample of 2,976 children aged between 9 and 14 years. Children completed standardized self‐report measures of posttraumatic stress symptoms, depression, anxiety, and grief, as well as a report of the amount of their own exposure to war‐related violence. Results showed that children reported high levels of posttraumatic stress symptoms and grief reactions However, their self‐reported levels of depression and anxiety were not raised. Levels of distress were related to children's amount and type of exposure. Girls reported more distress than boys, but there were few meaningful age effects within the age band studied. Results are discussed in the context of service development for children in war.
Diagnosis of Fructose‐1,6‐Bisphosphatase Deficiency Using Cultured Lymphocyte Fraction: A Secure and Noninvasive Alternative to Liver Biopsy
Authors: Kikawa Y. , Shin Y. S. , Inuzuka M. , Zammarchi E. , Mayumi M.
Published: December 2002

We report the result of enzymatic and molecular analyses, using cultured lymphocyte fractions (cultivated monocytes), of six Japanese patients (from five families) and one Italian patient with fructose‐1,6‐ bisphosphatase (FBPase) deficiency. Enzymatic analysis demonstrated FBPase deficiency in all seven patients, including the Italian patient whose fructose‐1,6‐bisphosphatase activity has been reported to be normal in leukocytes but deficient in liver. Molecular analysis of the FBPase gene identified pathogenic mutations in only 8 among the total 12 alleles of six families. We have thus demonstrated the validity of using cultured monocytes as a secure and noninvasive alternative to liver biopsy for accurate diagnosis of FBPase deficiency.
Tetrahydrobiopterin Responsiveness in Phenylketonuria. Two New Cases and a Review of Molecular Genetic Findings
Authors: Lässker U. , Zschocke J. , Blau N. , Santer R.
Published: December 2002

We report two new patients with tetrahydrobiopterin (BH4)‐responsive phenylketonuria and compare their phenylalanine hydroxylase (PAH) genotypes (A395P/IVS12+1g>a and R261Q/I65T, respectively) to those of previous cases from the literature. These case observations confirm earlier reports stating that BH4‐responsive patients are frequently carriers of a missense mutation within the DNA region coding for the catalytic domain of the enzyme. Interestingly, many of the PAH gene mutations detected in BH4‐responsive patients have been associated with an inconsistent phenotype in the past. Our case reports confirm that it is necessary to thoroughly examine individuals with increased phenylalanine levels, not only to detect BH4 deficiency, but also to identify patients with PAH deficiency who may benefit from BH4 treatment. In both of our patients, however, an effect of BH4 (7.5 mg/kg) on plasma phenylalanine levels was not seen in the newborn period. We therefore conclude that a normal neonatal BH4 test does not necessarily exclude BH4 responsiveness in all such patients.
Coping self‐efficacy perceptions as a mediator between acute stress response and long‐term distress following natural disasters
Authors: Benight Charles C. , Harper Michelle L.
Published: December 2002

The mediating effect of coping self‐efficacy (CSE) perceptions between acute stress responses (ASR) and 1 ‐year distress following two disasters was tested. Between 3 and 8 weeks after the second disaster and again at 1 year, 46 residents completed questionnaires. Posttraumatic Stress Disorder (PTSD) symptoms and global distress served as outcomes. Multiple regression demonstrated that ASR and Time 1 CSE were significant predictors of both Time 1 outcomes. Time 1 PTSD symptoms and Time 2 CSE were significant factors for Time 2 PTSD symptoms. Gender was significant for Time 2 PTSD symptoms, but not for Time 2 global distress. Longitudinally. Time 1 CSE predicted Time 2 PTSD symptoms, but not general distress. CSE mediated between ASR and both psychological outcomes at Time 2. Coping self‐efficacy perceptions provide a possible intervention target.
Transplantation for hepatocellular carcinoma and cirrhosis: Sensitivity of magnetic resonance imaging
Authors: Krinsky Glenn A. , Lee Vivian S. , Theise Neil D. , Weinreb Jeffrey C. , Morgan Glyn R. , Diflo Thomas , John Devon , Teperman Lewis W.
Published: December 2002

The sensitivity of magnetic resonance imaging (MRI) in patients who undergo transplantation for hepatocellular carcinoma (HCC) and cirrhosis is not known. We prospectively evaluated 24 patients with known HCC who underwent MRI and subsequent transplantation within 60 days (mean, 20 days). Using a phased-array coil at 1.5T, breath-hold turbo STIR and T2-weighted MR images were performed. Dynamic gadolinium-enhanced MRI was performed using a two- or three-dimensional gradient echo pulse sequence with images obtained in the hepatic arterial, portal venous, and equilibrium phases. The prospective interpretation of the MR study was directly compared with thin-section pathology evaluation of the explanted livers. All 24 patients had at least one HCC, and MR diagnosed tumor in 21 (88%) of these patients. On a lesion-by-lesion basis, MRI depicted 39 of 118 HCC for an overall sensitivity of 33%. MRI detected five (100%) of five lesions >5 cm, 20 (100%) of 20 lesions >2 cm but not exceeding 5 cm, 11 (52%) of 21 lesions between 1 and 2 cm, and three (4%) of 72 lesions <1 cm. Of the nine patients with carcinomatosis (innumerable lesions less than 1 cm), MR detected three lesions in one patient. Of the 15 dysplastic nodules found at pathology, MRI depicted a single 1.8-cm high-grade lesion, for a sensitivity of 7%. In conclusion, MRI is sensitive for the detection of HCC measuring at least 2 cm in diameter but is insensitive for the diagnosis of small HCC (<2 cm) and carcinomatosis.
Effect of ischemic preconditioning on hepatic microcirculation and function in a rat model of ischemia reperfusion injury
Authors: Koti Rahul S. , Yang Wenxuan , Dashwood Michael R. , Davidson Brian R. , Seifalian Alexander M.
Published: December 2002

Ischemic preconditioning (IPC) may protect the liver from ischemia reperfusion injury by nitric oxide formation. This study has investigated the effect of ischemic preconditioning on hepatic microcirculation (HM), and the relationship between nitric oxide metabolism and HM in preconditioning. Rats were allocated to 5 groups: 1. sham laparotomy; 2. 45 minutes lobar ischemia followed by 2-hour reperfusion (IR); 3. IPC with 5 minutes ischemia and 10 minutes reperfusion before IR; 4. L-arginine before IR; and 5. L-NAME + IPC before IR. HM was monitored by laser Doppler flowmeter. Liver transaminases, adenosine triphosphate, nitrites + nitrates, and guanosine 3′5′-cyclic monophosphate (cGMP) were measured. Nitric oxide synthase (NOS) distribution was studied using nicotinamide adeninine dinucleotide phosphate (NADPH) diaphorase histochemistry. At the end of reperfusion phase, in the IR group, flow in the HM recovered partially to 25.8% of baseline (P < .05 versus sham), whereas IPC improved HM to 49.5% of baseline (P < .01 versus IR). With L-arginine treatment, HM was 31.6% of baseline (NS versus IR), showing no attenuation of liver injury. In the preconditioned group treated with L-NAME, HM declined to 10.2% of baseline, suggesting not only a blockade of the preconditioning effect, but also an exacerbated liver injury. Hepatocellular injury was reduced by IPC, and L-arginine and was increased by NO inhibition with L-NAME. IPC also increased nitrate + nitrate (NOx) and cGMP concentrations. NOS detected by NADPH diaphorase staining was associated with hepatocytes and vascular endothelium, and was induced by IPC. IPC induced NOS and attenuated HM impairment and hepatocellular injury. These data strongly suggest a role for nitric oxide in IPC.
Patterned low temperature copper-rich deposits using inkjet printing
Authors: Rozenberg Gregor G. , Bresler Eric , Speakman Stuart P. , Jeynes Chris , Steinke Joachim H. G.
Published: December 2002

A PZT piezoelectric ceramic research drop-on-demand inkjet print head operating in bend mode was used as a means of delivering a copper precursor, vinyltrimethylsilane copper (+1) hexafluoroacetylacetonate, in a controlled and placement accurate fashion. The reagent disproportionates at low temperature (<200 °C), to deposit copper on glass. These deposits are shown to be more than 90% copper by weight by electron probe microanalysis and microbeam Rutherford backscattering spectroscopy. Microscopy shows a deposit diameter and three-dimensional profile that suggests a complex deposition and conversion mechanism. Our findings represent an important step towards the manufacture of electronic devices by entirely nonlithographic means.
On two dimensional coupled bosons and fermions
Authors: Turgut O. Teoman
Published: December 2002

We study complex bosons and fermions coupled through a generalized Yukawa type coupling in the large-Nc limit following ideas of Rajeev [Int. J. Mod. Phys. A 9, 5583 (1994)]. We study a linear approximation to this model. We show that in this approximation we do not have boson–antiboson and fermion–antifermion bound states occuring together. There is a possibility of having only fermion–antifermion bound states. We support this claim by finding distributional solutions with energies lower than the two mass treshold in the fermion sector. This has implications from the point of view of scattering theory to this model. We discuss some aspects of the scattering above the two mass treshold of boson pairs and fermion pairs. We also briefly present a gauged version of the same model and write down the linearized equations of motion.
Noncommutative geometry of angular momentum space U(su(2))
Authors: Batista Eliezer , Majid Shahn
Published: December 2002

We study the standard angular momentum algebra [xi,xj]=ıλεijkxk as a noncommutative manifold Rλ3. We show that there is a natural 4D differential calculus and obtain its cohomology and Hodge * operator. We solve the spin 0 wave equation and some aspects of the Maxwell or electromagnetic theory including solutions for a uniform electric current density, and we find a natural Dirac operator ∂/. We embed Rλ3 inside a 4D noncommutative space–time which is the limit q→1 of q-Minkowski space and show that Rλ3 has a natural quantum isometry group given by the quantum double C(SU(2))⋊U(su(2)) which is a singular limit of the q-Lorentz group. We view Rλ3 as a collection of all fuzzy spheres taken together. We also analyze the semiclassical limit via minimum uncertainty states |j,θ,φ〉 approximating classical positions in polar coordinates.
On the spectral and wave propagation properties of the surface Maryland model
Authors: Bentosela F. , Briet Ph. , Pastur L.
Published: December 2002

We study the discrete Schrödinger operator H in Zd with the surface potential of the form V(x)=gδ(x1)tan π(α⋅x2+ω), where for x∈Zd we write x=(x1,x2), x1∈Zd1, x2∈Zd2, α∈Rd2, ω∈[0,1). We first consider the case where the components of the vector α are rationally independent, i.e., the case of the quasi-periodic potential. We prove that the spectrum of H on the interval [−d,d] (coinciding with the spectrum of the discrete Laplacian) is absolutely continuous. Then we show that generalized eigenfunctions, corresponding to this interval, have the form of volume (bulk) waves, which are oscillating and nondecreasing (or slow decreasing) in all variables. They are the sum of the incident plane wave and of an infinite number of reflected or transmitted plane waves, scattered by the subspace Zd2. These eigenfunctions are orthogonal, complete and verify a natural analog of the Lippmann–Schwinger equation. We discuss also the case where d1=d2=1 and α=p/q is a rational number, i.e., a q-periodic surface potential. In this case we show that the spectrum is absolutely continuous and besides the volume (Bloch) waves there are also the surface waves, whose amplitude decays exponentially as |x1|→∞. The part of the spectrum corresponding to the surface waves consists of a finite number of bands. For large q the bands outside of [−d,d] are exponentially small in q, and converge in a natural sense to the pure point spectrum that was found [B. Khoruzhenko and L. Pastur, Phys. Rep. 288, 109–125 (1997)] in the case of the Diophantine α’s.
Fourier transforms of Lorentz invariant functions
Authors: Wurm Alexander , Krausz Nurit , DeWitt-Morette Cécile , Berg Marcus
Published: December 2002

Fourier transforms of Lorentz invariant functions in Minkowski space, with support on both the timelike and the spacelike domains are performed by means of direct integration. The cases of 1+1 and 1+2 dimensions are worked out in detail, and the results for 1+n dimensions are given.
Magnetocrystalline anisotropy and compositional order in Fe0.5Pt0.5: Calculations from an ab initio electronic model
Authors: Ostanin S. , Razee S. S. A. , Staunton J. B. , Ginatempo B. , Bruno Ezio
Published: December 2002

The magnetic properties of FePt samples, potential materials for high density recording media, depend sharply on the degree of chemical ordering produced during their preparation. This has prompted our investigation of the chemical order in both paramagnetic (P) and ferromagnetic (F) phases of a Fe0.5Pt0.5 solid solution and its effect upon the magnetocrystalline anisotropy (MAE) of the latter phase. Our “first-principles” theory uses density functional electronic structure calculations and a mean field treatment of both compositional and magnetic “local moment” fluctuations. We find both phases to be unstable to L10 (CuAu)-type order below temperatures of 1975 K (P) and 1565 K (F) which compares well with that found experimentally (≈1600 K) and our estimate of the Curie temperature as 575 K is also in fair agreement (710 K). For L10 order the calculated MAE is uniaxial with a simple form, υL10c(0,0,1)2 sin2 θ, where the coefficient υL10=9.7×108 erg/cm3, c(0,0,1) is the degree of order (between 0 and 0.5) and θ is the angle between the magnetization direction and the magnetic easy axis, which lies perpendicular to the layering of the L10 structure, also consistent with experimental data. Tetragonal distortions of the underlying face-centered-cubic lattice that occur as chemical order sets in are found to have a much smaller effect on the MAE.
Radio-frequency current drive theory in the presence of fluctuations
Authors: Taguchi M.
Published: December 2002

The effect of low-frequency fluctuations on the radio-frequency- (rf-) induced current has been investigated by using a renormalization technique of statistical dynamics. With the application of the functional integral method to a Fokker–Planck equation in the presence of fluctuations, a closed set of equations is derived for an ensemble-averaged distribution function and a response function to an infinitesimal external perturbation. The nonlinear terms in these equations, which describe the radial anomalous transport for resonant particles, have a nonlocal feature not only in time but also in configuration and momentum spaces. The local approximation to these nonlinear terms quite simplifies the governing equations. For a steady-state current drive in the presence of fluctuations, the rf-induced current profile and its radial width are studied with the use of the local approximation to the nonlinear terms. The nonlocal effect in momentum space is also discussed for the weak and strong turbulent limits. This effect on the current profile width is found to be important for the weak turbulence although it can be neglected for the strong turbulence.
Free energy model for hysteresis in magnetostrictive transducers
Authors: Smith Ralph C. , Dapino Marcelo J. , Seelecke Stefan
Published: December 2002

This article addresses the development of a free energy model for magnetostrictive transducers operating in hysteretic and nonlinear regimes. Such models are required both for material and system characterization and for model-based control design. The model is constructed in two steps. In the first, Helmholtz and Gibbs free energy relations are constructed for homogeneous materials with constant internal fields. In the second step, the effects of material nonhomogeneities and nonconstant effective fields are incorporated through the construction of appropriate stochastic distributions. Properties of the model are illustrated through comparison and prediction of data collected from a typical Terfenol-D transducer.
Control of vibrational ionization branching through feedback-optimized tailored femtosecond laser pulses
Authors: Hertz E. , Nersisyan G. , Papadogiannis N. A. , Charalambidis D.
Published: December 2002

We report the control of the ionization yield ratio to different vibrational levels of the electronic ground state of NO+ by feedback optimization of shaped ultra-short laser pulses. The nitric oxide NO molecule is excited by the second harmonic of a phase-shaped Ti:sapphire femtosecond laser. The optimization of pulse tailoring by a learning evolutionary algorithm leads to significant modifications of the vibrational ionic distribution observed by photoelectron spectroscopy. The control exerted over two groups of photoelectrons is robust and reveals some selectivity.
Reduced equations for electromagnetic turbulence in tokamaks
Authors: Hinton F. L. , Rosenbluth M. N. , Waltz R. E.
Published: December 2002

A set of reduced equations is derived for use in simulations of electromagnetic turbulence in tokamaks, in which the electron transit time scale is removed. The time step is not subject to a Courant condition depending on the electron thermal speed, but instead depends on the Alfvén speed. This allows significantly longer time steps in explicit numerical methods, for relevant values of the ratio of electron pressure to magnetic pressure.
Modification of Kolmogorov spectra of weakly turbulent shear Alfvén waves by dust grains
Authors: Onishchenko O. G. , Pokhotelov O. A. , Sagdeev R. Z. , Stenflo L. , Pavlenko V. P. , Shukla P. K. , Zolotukhin V. V.
Published: December 2002

Decay instabilities and Kolmogorov-type spectra of weakly turbulent shear-Alfvén waves in dusty plasmas are analyzed in the limit when the wave dispersion is produced solely by the dust grain density inhomogeneity. It is shown that the reduced equations for weakly nonlinear and dispersive waves possess two conservation laws for the wave energy and generalized enstrophy. It turns out that the weakly turbulent plasma Kolmogorov spectra associated with these conservation laws are nonlocal. It is found that the presence of a dust grain inhomogeneity leads to the formation of an Iroshnikov–Kraichnan type energy spectrum related to the energy conservation law. The possibility of the existence of such spectra in space plasmas is discussed. The specific features of the obtained energy spectra can be used for the identification of dust grains in the Earth’s ionosphere, the solar wind and the interstellar medium using the data collected by magnetometers onboard satellites.
Tailored nanoparticle films from monosized tin oxide nanocrystals: Particle synthesis, film formation, and size-dependent gas-sensing properties
Authors: Kennedy M. K. , Kruis F. E. , Fissan H. , Mehta B. R. , Stappert S. , Dumpich G.
Published: December 2002

In order to investigate the change of gas-sensitive properties of undoped tin oxide nanoparticle films depending on particle size, a thin film synthesis technique has been developed. Well-defined tin oxide nanoparticles have been prepared using a gas-phase condensation method. Pure SnO was used as starting material and was evaporated at T=820 °C. The resulting particles were sintered and crystallized in-flight at T=650 °C. Size-selected nanoparticles ranging from 10 to 35 nm were produced to form a nanoparticle film by means of electrostatic precipitation or low pressure impaction. The effect of in-flight oxidation, sintering, and crystallization on the structure, size, and size distribution of nanoparticles have been studied in detail. The samples show n-type semiconductors’ behavior like bulk SnO2. The influence of particle size on gas sensitivity and response behavior is investigated for C2H5OH at operating temperatures 200–300 °C using silicon substrates having an interdigitated contact pattern and an integrated heating system. In the range of 10–35 nm it has been shown unambiguously that decreasing the particle size of tin oxide particles leads to an increase of the sensitivity and a more rapid response on changing gas conditions. The effect is especially clear for films with a particle size of 20 nm or smaller.
Field strengths in oblique shock waves
Authors: Miyahara Seiji , Kawashima Takahiro , Ohsawa Yukiharu
Published: December 2002

Large-amplitude oblique shock waves are studied with theory and particle simulations, with particular attention paid to electric and magnetic field strengths. First, by use of a two-fluid model, field strengths in a shock wave propagating obliquely to an external magnetic field are analytically obtained as functions of the Alfvén speed, shock speed, and propagation angle. Then, one-dimensional, relativistic, electromagnetic particle simulations are performed to test the theoretical prediction. The theory and simulation are found to be in good agreement for a wide range of angles.
Effect of inserting a ferromagnetic layer on the giant magnetoresistance of spin-valve sandwiches
Authors: Xu Ming , Wang Yong , Xiong Gang , Liu Cuixiu , Mai Zhenhong
Published: December 2002

By extending a previous semi-classical model, we investigate the effects of inserting a second ferromagnetic material at the interface or in the interior of the ferromagnetic layer in NiFe/Cu/NiFe and/or Co/Cu/Co sandwiched structures on their giant magnetoresistance (GMR). The calculated GMR was found to be consistent with experimental results, indicating that our model is applicable even for complicated spin-valve multilayers. Moreover, some theoretical predictions are given in this letter that allow us to propose ways to optimize spin-valve structures.
Reflection high-energy electron diffraction experimental analysis of polycrystalline MgO films with grain size and orientation distributions
Authors: Brewer R. T. , Atwater Harry A. , Groves J. R. , Arendt P. N.
Published: December 2002

Analysis of biaxial texture of MgO films grown by ion-beam-assisted deposition (IBAD) has been performed using a quantitative reflection high-energy electron diffraction (RHEED) based method. MgO biaxial texture is determined by analysis of diffraction spot shapes from single RHEED images, and by measuring the width of RHEED in-plane rocking curves for MgO films grown on amorphous Si3N4 by IBAD using 750 eV Ar+ ions, at 45° incidence angle, and MgO e-beam evaporation. RHEED-based biaxial texture measurement accuracy is verified by comparison with in-plane and out-of-plane orientation distribution measurements made using transmission electron microscopy and x-ray rocking curves. In situ RHEED measurements also enable the analysis of the evolution of the biaxial texture which narrows with increasing film thickness. RHEED-based measurements of IBAD MgO biaxial texture show that the minimum in-plane orientation distribution depends on the out-of-plane orientation distribution, and indicates that the minimum obtainable in-plane orientation on distribution is 2°.
Collapse or swelling dynamics of homopolymer rings: Self-consistent Hartree approach
Authors: Rostiashvili Vakhtang G. , Lee Nam-Kyung , Vilgis Thomas A.
Published: December 2002

We investigate by the use of the Martin–Siggia–Rose generating functional technique and the self-consistent Hartree approximation, the dynamics of the ring homopolymer collapse (swelling) following an instantaneous change into a poor (good) solvent condition. The equation of motion for the time-dependent monomer-to-monomer correlation function is systematically derived. It is argued that for describing the coarse-graining process (which neglects the capillary instability and the coalescence of “pearls”) the Rouse mode representation is very helpful, so that the resulting equations of motion can be simply solved numerically. In the case of the collapse there are two characteristic regimes. The earlier regime is analyzed in the framework of the hierarchically crumpled fractal picture, with crumples of successively growing scale along the chain. The presented numerical results are in line with the corresponding simple scaling argumentation which in particular shows that the characteristic collapse time of a segment of length g scales at this earlier stage as tcrump*∼ζ0g/τ (where ζ0 is a bare friction coefficient and τ is a depth of quench). The later regime is related with a rearrangement of a “fluid of thermal blobs” and can be described by de Gennes’ “sausage” model. In contrast to the collapse the globule swelling can be seen (in the case that topological effects are neglected) as a homogeneous expansion of the globule interior. The swelling of each Rouse mode as well as gyration radius Rg is discussed.
Time and space-resolved measurement of a gas-puff laser-plasma x-ray source
Authors: Suzuki Masayuki , Daido Hiroyuki , Choi Il Woo , Yu Wei , Nagai Keiji , Norimatsu Takayoshi , Mima Kunioki , Fiedorowicz Henryk
Published: December 2002

The dynamic interaction processes between a nano-second laser pulse and a gas-puff target, such as those of plasma formation, laser heating, and x-ray emission, have been investigated quantitatively. Time and space-resolved x-ray and optical measurement techniques were used in order to investigate time-resolved laser absorption and subsequent x-ray generation. Efficient absorption of the incident laser energy into the gas-puff target of 17%, 12%, 38%, and 91% for neon, argon, krypton, and xenon, respectively, was shown experimentally. It was found that the laser absorption starts and, simultaneously, soft x-ray emission occurs. The soft x-ray lasts much longer than the laser pulse due to the recombination. Temporal evolution of the soft x-ray emission region was analyzed by comparing the experimental results to the results of the model calculation, in which the laser light propagation through a gas-puff plasma was taken into account.
Hall magnetohydrodynamic ballooning instability in the magnetotail
Authors: Zhu P. , Bhattacharjee A. , Ma Z. W.
Published: December 2002

The ballooning stability of the magnetotail is considered within the framework of Hall magnetohydrodynamics (MHD). In particular, the extent to which Hall MHD effects modify ideal MHD ballooning modes is explored extensively. It is shown that Hall MHD effects primarily enter the stability analysis through changes introduced in the plasma compressibility. Hence, the incompressible ideal MHD modes are not affected, while the compressible ideal MHD modes are altered both quantitatively and qualitatively. In addition to modifying the growth rate of the compressible ideal MHD mode, Hall effects also introduce a new instability, called the entropy interchange instability, which is a variant of the ion temperature gradient instability, when the gradient ratio η≡d ln Ti/d ln ρ of the configuration becomes greater than 2/3, where Ti is the ion temperature and ρ is the plasma density. The theory is applied to two types of magnetotail configurations—analytic equilibria developed by Voigt [in Solar Wind-Magnetosphere Coupling, edited by Y. Kamide and J. A. Slavin (Terra Scientific, Tokyo, 1986), pp. 233–273], and more realistic magnetotail configurations containing thin current sheets obtained from Hall MHD simulations of substorm dynamics by Ma and Bhattacharjee [Geophys. Res. Lett. 25, 3277 (1998)].
Improved corrosion resistance of IrMn by Cr and Ru additions
Authors: Carey M. J. , Kellock A. , Baril L. , Childress J. R. , Le T. , Thompson T. , Gurney B. A.
Published: December 2002

The magnetic and corrosion properties of Ir16Mn84 with Ru and Cr additions have been studied. Spin valves with Ir16Mn84–Ru have slightly lower Hex and Tb than when pure Ir16Mn84 is used. The corrosion properties improve, Hex and Tb improve with 3 vol % Cr, but drop considerably with more Cr additions, losing 21% of the pure IrMn value by 12 vol % Cr. The corrosion current and potential are Ic=8 μA/cm2 and E0=−580 mV respectively, for Ir16Mn84 with 12 vol % Cr. This represents a significant improvement over pure Ir16Mn84, which has Ic=100 μA/cm2 and E0=−1300 mV. When Ru is used as the additive, Ic and E0 are 10 μA/cm2 and −100 mV, respectively, for 9 vol %. Cr is the superior additive, especially in small concentrations where it shows a significant decrease in the Ic without degrading the magnetic properties.
Counterpoise-corrected geometries and harmonic frequencies of N-body clusters: Application to (HF)n (n=3,4)
Authors: Salvador Pedro , Szczȩśniak Małgorzata M.
Published: December 2002

The differences between three previously defined counterpoise (CP) schemes for removing the BSSE in molecular complexes formed by more than two subunits have been assessed by CP-corrected geometry optimizations and frequency calculations for the hydrogen fluoride trimer and tetramer. The types of the functional counterpoise (FC) procedures included the site–site (SSFC), pairwise additive, and hierarchical Valiron–Mayer (VMFC) schemes. The latter approach takes into account the basis set extension of the dimers in the trimer, dimers and trimers in the tetramer, etc. The number of different calculations required to apply this counterpoise scheme increases very rapidly with the cluster size. The symmetry of the chosen systems makes the test of this approach computationally feasible. All the optimizations and frequency calculations have been carried out automatically using a new program that generates the necessary input files and repeatedly calls a slightly modified version of a Gaussian link. The results show that geometrical parameters, zero-point vibrational energies, and redshifts computed on the CP-corrected potential energy surfaces differ considerably from those evaluated on the uncorrected surfaces. The structural and energetic properties obtained with the conventional SSFC procedure are almost identical to those predicted by the more costly and complex VMFC method. Hence, the former seems to be more appropriate in the present case. Furthermore, symmetry-adapted perturbation theory calculations show the importance of computing the interaction energies at the CP-corrected geometries.
Thermoelectric power of Na-doped La0.7Ca0.3−yNayMnO3 both in the presence and the absence of magnetic field
Authors: Bhattacharya Sayani , Banerjee Aritra , Pal S. , Mukherjee R. K. , Chaudhuri B. K.
Published: December 2002

Magnetic-field (B=0–1.5 T) dependent thermoelectric power (TEP) of the Na-doped La0.7Ca0.3−yNayMnO3 (0.0⩽y⩽0.3) system has been studied in the temperature range 80–300 K. X-ray diffraction studies indicate a rhombohedrally distorted perovskite structure of the samples. The observed sharp peak in the resistivity (ρ) versus temperature (T) curve falls and shifts to higher temperature with increasing Na concentration (y). In the low-temperature ferromagnetic (FM) regime, thermopower (Seebeck coefficient, S) obeys the expression S=S0+S1.5T1.5+S4T4 over the entire range of y. Electron-magnon scattering is found to dominate the low-temperature resistivity and TEP data. High-temperature TEP data can be well fitted with Mott’s small polaron hopping model. The activation energy (ES) and polaron hopping energy (WH) decrease with increasing Na content. Both ES and WH decrease while polaron radius (rp) increase with the application of a magnetic field. Field-dependent TEP data also indicate the suppression of spin fluctuations in the presence of a magnetic field. In the low-temperature FM region, both magnon drag and phonon drag effects coexist.
The extended Lotka–Volterra lattice and affine Jacobi varieties of spectral curves
Authors: Inoue Rei
Published: December 2002

Based on the work by Smirnov and Zeitlin, we study a simple realization of the matrix construction of the affine Jacobi varieties. We find that the realization is given by a classical integrable model, the extended Lotka–Volterra lattice. We investigate the integrable structure of the representative for the gauge equivalence class of matrices, which is isomorphic to the affine Jacobi variety, and make use of it to discuss the solvability of the model.
Effects of hydrogen atoms on postannealing of phosphorus-ion implanted silicon
Authors: Yamashita Yoshifumi , Kamiura Yoichi , Yamamoto Ikuhisa , Ishiyama Takeshi , Sato Yoshiyuki
Published: December 2002

The ion implantation process used in silicon device processing needs a postannealing at as high as 1000 °C to recover the damages induced by high-energy ion bombardment and to electrically activate implanted impurities. We developed a postannealing treatment using remote-hydrogen plasma to reduce the annealing temperature. We found that our postannealing treatment more greatly reduced the resistivity of the surface region, which was very high just after implantation. The dependence of resistivity-reduction rate on annealing temperature was weaker for the annealing with hydrogen plasma than for the normal annealing. Therefore the enhancing effect by hydrogen was remarkable at lower temperature in the range of 250–350 °C. The less the dose quantity was, the stronger the enhancing effect was observed. The postannealing using hydrogen plasma with the power of 50 W at 300 °C for 2 h showed almost the same performance as the usual rapid thermal annealing process at 1000 °C for 30 s.
Growth and characterization of epitaxial Si/(LaxY1−x)2O3/Si heterostructures
Authors: Narayanan Vijay , Guha Supratik , Bojarczuk Nestor A. , Ross Frances M.
Published: December 2002

We have studied the effect of growth temperature on the growth mode and defect density of (LaxY1−x)2O3/Si(111) and Si(111)/(LaxY1−x)2O3/Si(111) heterostructures by transmission electron microscopy. We have also investigated the epitaxial relationships between fluorite and bixbyite oxides on different Si surfaces in the framework of a model which suggests that the mismatch between the oxygen sublattice and the Si substrate is the most important criterion for establishing the epitaxial relation. In addition, during attempts to achieve perfect lattice matching between (LaxY1−x)2O3 and Si by incorporating lanthanum beyond the near-lattice matched composition, we observe the formation of a phase-separated microstructure. A strain energy argument is developed to explain this observation.
Molecular beam study of CH4 oxidation on a Pt(111)–(2×2)-O surface
Authors: Kondo Takahiro , Sasaki Takashi , Yamamoto Shigehiko
Published: December 2002

The interaction of CH4 with a Pt(111)–(2×2)-O surface has been investigated by a supersonic molecular beam scattering technique. CH4 irradiation is found to completely remove oxygen atoms from the surface via CH4 oxidation reaction, CH4+O→CO+H2. The reaction is found to be translationally activated. The oxidation probability of CH4 on Pt(111)–(2×2)-O is found roughly an order of magnitude greater than the initial dissociative chemisorption probability of CH4 on Pt(111), especially under a low incident kinetic energy condition. From the angular intensity distribution and the time-of-flight distribution measurements of scattered CH4, no significant difference in the collision dynamics of CH4 both on Pt(111) and on Pt(111)–(2×2)-O is recognized.
Dynamic characteristics of dislocations in Ge-doped and (Ge+B) codoped silicon
Authors: Yonenaga I. , Taishi T. , Huang X. , Hoshikawa K.
Published: December 2002

The dynamic behavior of dislocations in heavily germanium (Ge)-doped silicon (Si) crystals with concentrations up to 2.5×1020 cm−3, and Ge and boron (B) codoped Si crystals with concentrations of 4×1019 and 9×1018 cm−3, respectively, is investigated using the etch pit technique in comparison with that in undoped and B-doped Si crystals. Strong suppression of the generation of dislocations from a surface scratch is found for Ge and B codoped Si in comparison with that observed for Ge-doped and B-doped Si. The velocity of dislocations in Ge and B codoped Si crystals is found to be lower than that of dislocations in B-doped, Ge-doped, and undoped Si. The coexistence of Ge and B impurities in Si is considered to be effective at immobilizing and retarding the velocity of dislocations in Si.
Voltage distributions and nonoptical catastrophic mirror degradation in high power InGaAs/AlGaAs/GaAs lasers studied by Kelvin probe force microscopy
Authors: Ankudinov A. V. , Evtikhiev V. P. , Kotelnikov E. Yu. , Titkov A. N. , Laiho R.
Published: December 2002

Kelvin probe force microscopy is used to observe the bulk potential redistribution across the high power InGaAs/AlGaAs/GaAs separate confinement heterostructure quantum-well laser diodes for a wide range of injection currents, including the lasing regime. By increasing the injection current, the development of a parasitic voltage drop is detected at initial calibration layers and the buffer layer of the laser structure. Catastrophic degradation of the laser mirror was observed at the level of injection current ∼19 times the threshold value. Atomic force microscopy images of the mirror revealed a 100 nm deep crater of maximum width ∼2.5 μm in the vicinity of the buffer/emitter interface. By combining the surface morphology results of the destructed mirror with those of Kelvin probe force microscopy in operating devices, it is concluded that the parasitic voltage drop is responsible for a substantial energy dissipation and the nonoptical degradation of the laser mirror.
Second-order optical nonlinearities in thermally poled phosphate glasses
Authors: Thamboon Prissana , Krol Denise M.
Published: December 2002

Second-order optical nonlinearities (χ(2)) were induced in commercial phosphate glasses (Schott, IOG-1) by the thermal poling technique. Maker fringe experiments were used to characterize the induced nonlinear regions. The results show that a near-anodic surface and a bulk χ(2) are formed that are opposite in sign. The strength of the near-anodic surface χ(2) is greater than that of the bulk. The overall magnitude of the induced χ(2), as well as the surface to bulk ratio, increases as the applied voltage and poling temperature increase. A single-charge-carrier model and a nonblocking cathode describe the main features of the induced χ(2) profile.
Modification of the bonded interface in silicon-on-insulator structures under thermal treatment in hydrogen ambient
Authors: Antonova I. V. , Naumova O. V. , Popov V. P. , Stano J. , Skuratov V. A.
Published: December 2002

Results of a comparative charge deep-level transient spectroscopy study of Si/SiO2 interfaces in silicon-on-insulator structures prepared by wafer bonding and hydrogen slicing, and subsequently annealed in a hydrogen ambient in the temperature range of 430 to 670 °C are described. The trap transformations at the bonded interface are strongly discriminated from passivation of traps at the Si/thermal SiO2 interface. The nature of traps at the bonded interface is found to differ from that of traps at the Si/thermal SiO2 interface. Heat treatments at T>430 °C are shown to induce significant changes in virgin spectra of traps at bonded interfaces due to the generation of traps.
On certain geometric aspects of CPN harmonic maps
Authors: Grundland A. M. , Zakrzewski W. J.
Published: December 2002

A Weierstrass-type system of equations corresponding to CPN harmonic maps is presented. It constitutes a generalization of the previously constructed systems for CP1 and CP2 fields. From the linear spectral problem for the CPN model a set of conserved quantities is derived and used for a construction of a generalized Weierstrass representation for conformally parametrized surfaces immersed in multidimensional Euclidean spaces. Based on this representation a possible geometrical interpretation of CPN harmonic maps is discussed.
Central limit theorems for large graphs: Method of quantum decomposition
Authors: Hashimoto Yukihiro , Hora Akihito , Obata Nobuaki
Published: December 2002

A new method is proposed for investigating spectral distribution of the combinatorial Laplacian (adjacency matrix) of a large regular graph on the basis of quantum decomposition and quantum central limit theorem. General results are proved for Cayley graphs of discrete groups and for distance-regular graphs. The Coxeter groups and the Johnson graphs are discussed in detail by way of illustration. In particular, the limit distributions obtained from the Johnson graphs are characterized by the Meixner polynomials which form a one-parameter deformation of the Laguerre polynomials