bluuebunny/crossref_metadata_2025 huggingface dataset:
Effectiveness of Mentoring Programs for Youth: A Meta‐Analytic Review
Authors: DuBois David L. , Holloway Bruce E. , Valentine Jeffrey C. , Cooper Harris
Published: December 2002

We used meta‐analysis to review 55 evaluations of the effects of mentoring programs on youth. Overall, findings provide evidence of only a modest or small benefit of program participation for the average youth. Program effects are enhanced significantly, however, when greater numbers of both theory‐based and empirically based “best practices” are utilized and when strong relationships are formed between mentors and youth. Youth from backgrounds of environmental risk and disadvantage appear most likely to benefit from participation in mentoring programs. Outcomes for youth at‐risk due to personal vulnerabilities have varied substantially in relation to program characteristics, with a noteworthy potential evident for poorly implemented programs to actually have an adverse effect on such youth. Recommendations include greater adherence to guidelines for the design and implementation of effective mentoring programs as well as more in‐depth assessment of relationship and contextual factors in the evaluation of programs.
The Nature of Adolescents' Relationships with Their “Very Important” Nonparental Adults
Authors: Beam Margaret R. , Chen Chuansheng , Greenberger Ellen
Published: December 2002

As part of a larger program of research on the nature of adolescents' relationships with very important nonparental adults (hereafter referred to as “VIPs”), a community sample of 243 eleventh graders (mean age = 16.6 years) was surveyed, and a subgroup of 55 adolescents and their VIPs were interviewed about the nature and quality of their relationships. Results showed that (a) adolescent–VIP relationships were a normative component of adolescent development, not a result of problems in adolescents' lives; (b) adolescent–VIP relationships were generally of high quality (e.g., high support, low conflict, and high mutuality); (c) there were significant differences between kin and nonkin VIPs in terms of the duration of relationships and frequency of contact, but not in the quality of relationships; and (d) VIPs whom adolescents designated as extremely important were distinguished from other VIPs in terms of providing a higher level of social support and a higher frequency of contact. Theoretical and practical implications of these findings are discussed.
17β-Estradiol Enhances the Flux of Cholesterol Through the Cholesteryl Ester Cycle in Human Macrophages
Authors: Napolitano Mariarosaria , Blotta Ida , Montali Anna , Bravo Elena
Published: December 2002

Estrogens have been shown to have many positive effects on the function of arterial wall, and recent evidence suggest that 17β-estradiol has a direct action in reducing the accumulation of cholesteryl ester in macrophages. The mechanisms underlying the effects of 17β-estradiol on foam cell formation, however are poorly understood. The aim of this study is to investigate the role of 17β-estradiol in the regulation of the cholesteryl ester cycle and cholesterol efflux in human macrophages. In addition, the influence of 17β-estradiol on apolipoprotein E (apoE) and lipoprotein lipase (LDL) secretion by the cells was also tested. Human Monocyte Derived Macrophages (HMDM), matured in the presence or the absence of 17β-estradiol, were loaded with [3H]-cholesteryl ester-labeled-acetyl LDL (low density lipoprotein) and the efflux of radioactivity into the medium was measured. The effect of 17β-estradiol on cellular activities of acyl coenzyme A: cholesterol acyl transferase (ACAT), and both neutral and acid cholesteryl ester hydrolase (CEH) and the secretion of apoE and LDL into the medium, were also studied. The results indicate that 17β-estradiol induces an increase in the amount of labeled cholesterol released from the cells and, the data obtained from the measurements of ACAT and CEH activities showed that, in estrogen-treated HMDM, the cholesteryl ester cycle favors the hydrolysis of lipoprotein cholesterol by CEH in comparison with its acylation by ACAT. In particular, for the first time a strong enhancement of neutral and acid CEH in human macrophages by 17β-estradiol, was demonstrated. ApoE and LDL secretion increased during the maturation of monocytes to macrophages, and was not modified by 17β-estradiol. In contrast, loading the cells with cholesterol by incubation in the presence of acetylated or oxidized LDL produced an increase in the levels of apoE secreted by both estrogen-treated and control macrophages. The activity of LPL found in the cell medium, on the other hand, in lipid loaded cells tended to be increased only in estrogen treated macrophages, suggesting that the effects of estrogen on unloaded macrophages are different from those produced on lipid-loaded macrophages. On the whole, the present findings suggest that one of the mechanisms by which 17β-estradiol acts to reduce cholesterol accumulation in macrophages is by increasing reverse cholesterol transport through the enhancement of the cholesteryl ester cycle, so that the generation of intracellular unesterified cholesterol for excretion from the cells is favored.
Diagnostic Value of Succinate Ubiquinone Reductase Activity in the Identification of Patients with Mitochondrial DNA Depletion
Authors: Hargreaves I. P. , Rahman S. , Guthrie P. , Taanman J‐W. , Leonard J. V. , Land J. M. , Heales S. J. R.
Published: December 2002

Mitochondrial DNA (mtDNA) depletion syndrome (McKusick 251880) is characterized by a progressive quantitative loss of mtDNA resulting in severe mitochondrial dysfunction. A diagnosis of mtDNA depletion can only be confirmed after Southern blot analysis of affected tissue. Only a limited number of centres have the facilities to offer this service, and this is frequently on an irregular basis. There is therefore a need for a test that can refine sample selection as well as complementing the molecular analysis. In this study we compared the activities of the nuclear‐encoded succinate ubiquinone reductase (complex II) to the activities of the combined mitochondrial and nuclear‐encoded mitochondrial electron transport chain (ETC) complexes; NADH:ubiquinone reductase (complex I), ubiquinol‐cytochrome‐c reductase (complex III), and cytochrome‐c oxidase (complex IV), in skeletal muscle biopsies from 7 patients with confirmed mtDNA depletion. In one patient there was no evidence of an ETC defect. However, the remaining 6 patients exhibited reduced complex I and IV activities. Five of these patients also displayed reduced complex II[ndash]III (succinate:cytochrome‐c reductase) activity. Individual measurement of complex II and complex III activities demonstrated normal levels of complex II activity compared to complex III, which was reduced in the 5 biopsies assayed. These findings suggest a possible diagnostic value for the detection of normal levels of complex II activity in conjunction with reduced complex I, III and IV activity in the identification of likely candidates for mtDNA depletion syndrome
Autobiographical memory specificity, intrusive memory, and general memory skills in Dutch–Indonesian survivors of the World War II Era
Authors: Wessel Ineke , Merckelbach Harald , Dekkers Theo
Published: December 2002

A lack of specific autobiographical memory may result from exposure to psychoiogical trauma, intrusive memories of adverse events, and/or a general memory deficit. This study explored the role of these variables in 25 patients with various psychiatric diagnoses and 15 healthy controls. All participants had been exposed to war atrocities during their childhood in Indonesia. Patients produced significantly less specific memories than did controls. In addition, rather than performance on general neuropsychological memory tests, the frequent occurrence of intrusive memories and the avoidance of reminders of trauma predicted less autobiographical memory specificity. These result‐ replicate and extend earlier findings on intrusive and nonspecific autobiographical memory in depressed samples to a group of people who experienced war atrocities in childhood.
Factors Contributing to the Survival of Self‐Help Groups
Authors: Wituk Scott A. , Shepherd Matthew D. , Warren Mary , Meissen Greg
Published: December 2002

Despite the growing utilization of self‐help groups, there have been only a handful of studies that have examined the factors that contribute to their survival. The purpose of this study was to explore the factors that contribute to self‐help group survival by examining their relationship with external sources (i.e., national and local self‐help organizations, professionals) and group organizational characteristics (i.e., leadership diversification, recruitment, attendance at group meetings). Representatives from 245 active and 94 recently disbanded self‐help groups were included in the analysis. Results indicated that the primary factors that discriminated between active and disbanded groups were the number of new people to attend a meeting, average group meeting attendance, length of existence, leadership diversification, outreach to potential group members, and support from national and local organizations. Results are discussed in terms of what national self‐help organizations, self‐help clearinghouses, and others who interact with self‐help groups can do to empower and support them.
Implications of Evidence‐Based Practice for Community Health
Authors: Hausman Alice J.
Published: December 2002

Evidence‐based practice, developed in clinical medicine, is being applied to community health programs. Barriers to implementation of evidence‐based practice noted in clinical medicine are likely to exist in community health settings and may be complicated by the nature of community health programs. These barriers include accessibility and availability of relevant data, social and political considerations of program decision‐making, and conflicting expectations for evaluation research. This paper discusses barriers to both amassing evidence for practice and using evidence for decision‐making in community health. The potential for conflict between practice goals set by evidence‐based thinking and those set by community health organizations is also discussed. Implications for evaluations of community health programs are raised and recommendations for improving access to and use of evaluation information are made.
A Poincaré–Birkhoff–Witt commutator lemma for Uq[gl(m|n)]
Authors: Wit David De
Published: December 2002

We present and prove in detail a Poincaré–Birkhoff–Witt commutator lemma for the quantum superalgebra Uq[gl(m|n)].
Impedance spectroscopy analysis of La-doped PbWO4 single crystals
Authors: Huang Hongwei , Feng Xiqi , Man Zhenyong , Tang Tong-Bor , Dong Ming , Ye Zuo-Guang
Published: December 2002

The effect of La doping on the scintillating properties of lead tungstate single crystal has been intensively investigated and was found to be dependent on the doping concentration. In this article a series of La-doped single crystals were measured and analyzed by the impedance spectroscopic technique. The experimental results show that the ac conductivities of PWO:La crystals follow Jonscher’s power law. The main carriers are oxygen vacancies with an approximate activation energy of 0.78 eV for ionic conduction of all the crystals. The effects of La doping on the conductivity and dielectric relaxation are interpreted in terms of a transition level in the range of 500 ppm–1 mol % for La doping. For low doping concentrations, positive charge caused by substitution of La3+ ions on the Pb2+ lattice are balanced by VPb, whereas it is by interstitial oxygen and La ions at W lattices for heavy doping.
Basis set and electron correlation effects on ab initio electronic and vibrational nonlinear optical properties of conjugated organic molecules
Authors: Torrent-Sucarrat Miquel , Solà Miquel , Duran Miquel , Luis Josep M. , Kirtman Bernard
Published: December 2002

We have studied how the calculation of electronic and vibrational contributions to nonlinear optical properties of three representative π-conjugated organic molecules is affected by the choice of basis set and the inclusion of electron correlation effects. The 6-31G basis does not always provide even qualitative accuracy. For semiquantitative accuracy a 6-31+G(d) basis is sufficient. Although, as compared to QCISD, a second-order Møller–Plesset (MP2) treatment often yields a substantial fraction of the electron correlation contribution, our MP2 results for the separate electronic and vibrational terms are not consistently of semiquantitative accuracy. Nevertheless, at the MP2 level the ratio between the vibrational and electronic contributions is satisfactorily reproduced.
Nonlinear inverse bremsstrahlung absorption in laser-fusion plasma corona
Authors: Sid A.
Published: December 2002

Nonlinear inverse bremsstrahlung absorption (NLIBA) of laser energy by inhomogeneous hot plasmas has been studied using the kinetic theory. A general expression has been derived for the NLIBA coefficient. It has been shown that the electrons–ion (e–i) collision frequency and the local absorption coefficient depend on the scaling factor, Zv02/vt2, which is a nonlinear effect. It is due to the depletion of plasma, heated by laser beam, in slow electrons. This is interpreted as the flatness of the isotropic distribution function, f0, compared to the Maxwell’s function, fM. The IBA reduction rate by this nonlinearity is explicitly determined as a function of Zv02/vt2. This rate takes its maximum value, 45%, for Zv02l/vt2⩾4. The growth rate of Weibel modes excited by IBA is also reduced by this nonlinear effect.
Kinetic and mechanistic studies on the abstraction reactions of atomic O (3P) with (CH3)2SiH2 and (CH3)3SiH
Authors: Zhang Qingzhu , Gu Yueshu , Wang Shaokun
Published: December 2002

The reactions of atomic O (3P) with (CH3)2SiH2 and (CH3)3SiH have been studied theoretically using ab initio molecular orbital theory for the first time. Geometries have been optimized at the MP2 level with the 6-311G(d,p) and 6-311G(2d,2p) basis sets. The single-point energy calculations have been carried at the QCISD(T)/6-311+G(3df,2p) level. Theoretical analysis provides conclusive evidence that the main process occurring in each reaction is the hydrogen abstraction from the Si–H bonds leading to the formation of the H2 and silyl radical; the hydrogen abstraction from the C–H bonds has higher barrier and is difficult to react. Two nearly degenerate transition states of A″3 and A′3 symmetries have been located for each hydrogen abstraction reaction from the Si–H bonds. Changes of geometries, generalized normal-mode vibrational frequencies, and potential energies along the reaction paths are discussed and compared. The rate constants have been deduced over a wide temperature range of 200–3000 K using canonical variational transition-state theory (CVT) with small curvature tunneling effect (SCT). The calculated CVT/SCT rate constants exhibit typical non-Arrhenius behavior, three-parameter rate-temperature formulas are fitted as follows (in units of cm3 molecule−1 s−1): k1(T)=(3.41×10−16)T1.65exp(−411.72/T) and k2(T)=(1.85×10−15)T1.42 exp(−372.57/T) for the reactions of O (3P) with (CH3)2SiH2 and (CH3)3SiH, respectively. The calculated rate constants are compared with the available experimental values.
Dust acoustic solitary wave in the presence of dust streaming
Authors: Mahmood S. , Saleem H.
Published: December 2002

The effects of dust streaming on the nonlinear dust acoustic wave are studied in unmagnetized homogeneous dust-ion and dust-ion-electron plasmas. The numerical results are applied to Saturn’s F-ring for illustrative purpose.
Optimization of the tunability of barium strontium titanate films via epitaxial stresses
Authors: Ban Z.-G. , Alpay S. P.
Published: December 2002

The tunability of epitaxial barium strontium titanate films is analyzed theoretically using a phenomenological model. The relative dielectric constant of Ba0.5Sr0.5TiO3 (BST 50/50) films as a function of the applied external electric field is calculated and an electric field–misfit strain phase diagram is developed to assist in the interpretation of the behavior. On the basis of these results, the tunability of BST 50/50 films as a function of the misfit strain is provided and compared with the experimental data in the literature. Analysis shows that a high tunability can be achieved by adjusting the misfit strain especially in the vicinity of a structural phase transformation. The misfit strain in epitaxial films can be controlled with the selection of a substrate material or variations in the film thickness. The film thickness dependence is due to misfit dislocation formation at the film growth temperature. A critical thickness to attain the maximum tunability can be defined for BST 50/50 films on MgO (∼90 nm) and LaAlO3 (∼120 nm) substrates. It is suggested that the selection of the substrate and/or the film thickness can be chosen as design parameters to manipulate the strain state in the film to achieve optimum tunability.
Structural and electrical characteristics of chemical-solution-derived (Bi,La)4Ti3O12 thin films with various Bi2O3 template layers
Authors: Bao Dinghua , Chiu Te-Wei , Wakiya Naoki , Shinozaki Kazuo , Mizutani Nobuyasu
Published: December 2002

Ferroelectric (Bi,La)4Ti3O12 (BLT) thin films with different Bi2O3 template layers were prepared on Pt/Ti/SiO2/Si substrates by a chemical-solution deposition method. The BLT films with a thin Bi2O3 bottom layer and those with a thin Bi2O3 intermediate layer had a (117) preferentially oriented growth after annealing at 750 °C, while those with a thin Bi2O3 upper layer and those without a Bi2O3 template layer exhibited a high c-axis orientation. The surface morphologies changed with different preferential orientations. The electrical measurements showed that the use of Bi2O3 template layers improved significantly the P–E hysteresis loops of BLT thin films. The remanent polarization (2Pr) and coercive field (Ec) values of BLT films without a Bi2O3 template layer, with a Bi2O3 upper layer, with a Bi2O3 bottom layer, and with a Bi2O3 intermediate layer annealed at 750 °C were 10.8, 29.12, 26.17, and 19.67 μC/cm2; 79.0, 74.5, 75.5, and 76.3 kV/cm, respectively, at an applied electric field of 350 kV/cm. The dielectric constants and dissipation factors were 184, 303, 243, and 217; 0.036, 0.044, 0.039, and 0.039, respectively, at the frequency of 100 kHz, for these BLT films without a Bi2O3 template layer, with a Bi2O3 upper layer, with a Bi2O3 bottom layer, and with a Bi2O3 intermediate layer. All the capacitors with Bi2O3 template layers showed good polarization fatigue characteristics at least up to 3×1010 bipolar pulse cycles and excellent retention properties up to 3×104 s.
Pentacene thin film transistors on inorganic dielectrics: Morphology, structural properties, and electronic transport
Authors: Knipp D. , Street R. A. , Völkel A. , Ho J.
Published: December 2002

The structural and transport properties of evaporated pentacene organic thin film transistors (TFTs) are reported, and they show the influence of the deposition conditions with different inorganic dielectrics. Dielectrics compatible with large area fabrication were explored to facilitate low cost electronics on glass or flexible plastic substrates. X-ray diffraction and atomic force microscopy show a clear correlation between the morphology and the structure of the highly polycrystalline films for all dielectrics investigated. The roughness of the dielectric has a distinct influence on the morphology and the structural properties, whereas the films on smooth thermal oxide are in general highly ordered and independent of the deposition conditions. The ordered films exhibit a “thin film” and a bulk phase, and the bulk phase volume fraction increases with the deposition temperature and the film thickness. Careful control of the deposition conditions gives virtually identical films on thermal oxide and silicon nitride dielectrics. The electronic properties of inverted staggered transistors show that the TFT mobility is correlated with the morphology and structure of the films. The TFTs exhibit very similar mobilities of ∼0.4 cm2/Vs and on/off ratios >108 on thermal oxide and silicon nitride. The impact of the dielectric on the device parameters of mobility, threshold voltage, and subthreshold voltage slope is discussed. Temperature dependent measurements of the mobility were performed to study the influence of traps on electronic transport. Bias stress experiments were carried out to investigate the stability of the TFTs, and to gain understanding of the transport mechanisms of thermally evaporated pentacene TFTs.
Intramolecular vibrational energy redistribution, mode specificity, and nonexponential unimolecular decay dynamics of vibrationally highly excited states of DCO (X̃ 2A′)
Authors: Renth F. , Temps F. , Tröllsch A.
Published: December 2002

The unimolecular dynamics of vibrationally highly excited states of DCO (X̃ 2A′) in the energy region up to Evib⩽9500 cm−1, beyond the D–CO (X̃) dissociation threshold, has been investigated using an effective polyad Hamiltonian obtained by fitting to the term energies from the measured B̃ 2A′←X̃ 2A′ stimulated emission pumping (SEP) spectra of the molecule [Stöck et al., J. Chem. Phys. 106, 5333 (1997); Temps and Tröllsch, Z. Phys. Chem. 215, 207 (2001)]. An added absorbing negative imaginary potential allowed for the unimolecular dissociation of the highly excited DCO via distinctive open reaction channels of the DC stretching vibration. The ensuing dynamics was explored using a wave packet propagation approach. Time profiles describing the intramolecular vibrational energy redistribution (IVR) and unimolecular decay kinetics were computed for the CO stretching zero-order basis states up to 6 quanta of excitation and the DCO bending zero-order basis states up to 12 quanta of excitation. The computed decay curves for the CO stretching zero-order basis states compare nicely with those of the respective coherent superposition states constructed directly from the measured SEP spectra (assuming the CO stretching mode as the Franck–Condon active bright zero-order mode that determines the observed transitions). A comparison of the decay curves with those of the almost isoenergetic DCO bending zero-order basis states in the respective polyads reveals large differences in the couplings of the two vibrational modes among each other and with the open dissociation channels. The obtained unimolecular decay profiles exhibit pronounced non-exponential kinetics. Comparison with statistically calculated decay rates shows a substantial degree of mode specificity of the dynamics, which can be attributed to a bottleneck in the IVR from the CO stretching vibration to the reaction coordinate. The model calculations explain the two-to-three orders of magnitude large difference between the measured eigenstate specific DCO (X̃) decay constants [Stöck et al.] and predictions by microcanonical statistical rate theories.
Molecular motors driven by laser pulses: Role of molecular chirality and photon helicity
Authors: Hoki Kunihito , Yamaki Masahiro , Koseki Shiro , Fujimura Yuichi
Published: December 2002

The results of a theoretical study on molecular motors driven by laser pulses are presented. The roles of molecular chirality and photon helicity in determination of their unidirectional rotation are clarified. An expression for an instantaneous angular momentum of motors driven by lasers in the density matrix formalism was derived. Assuming randomly oriented molecular motors, the initial distribution-averaged instantaneous angular momentum in the dipole approximation was obtained. Taking into account parity inversion symmetry of molecular motors in the averaged instantaneous angular momentum, it is shown that the directions of the averaged instantaneous angular momentum of (R)- and (S)-chiral molecular motors are opposite, but that the magnitudes are the same. This is independent of polarization of laser fields. That is, the chiral motors driven by a linearly polarized optical field creates a unidirectional motion in a molecular fixed frame. On the other hand, the direction of rotation in the laboratory fixed frame is decided by a circularly polarized laser regardless of its molecular chirality. A simple example of real chiral molecular motors is used to demonstrate the interplay of molecular chirality and photon helicity in determination of their unidirectional rotation. The internal rotation of the CHO group plays the role of the engine of the motor. The time evolution of the rotational wave packets of the molecular motors driven by linearly or circularly polarized laser pulses was numerically evaluated and the dynamical behaviors were analyzed. Effects of temperature on the instantaneous angular momentum of the molecular motors are presented as well.
A kinetic theory of homogeneous bubble nucleation
Authors: Shen Vincent K. , Debenedetti Pablo G.
Published: December 2002

We present a kinetic theory of homogeneous bubble nucleation based on explicit calculation of the single-molecule evaporation and condensation rates as a function of the size of the vapor embryo. The surface condensation rate is calculated from the kinetic theory of gases, and the surface evaporation rate is related to the rate of escape of molecules from a potential well in the field established by the liquid–vapor interface. Equality of these rates corresponds naturally to the critical bubble. While the interface plays a crucial role in this respect, the kinetic nucleation theory does not invoke an explicit surface tension. The nucleation rate is derived from a population balance and depends only on the ratio of the evaporation to condensation rates. In contrast to classical theory, a nontrivial trend captured by the present theory is the increase in nucleation rate with decreasing temperature at fixed degree of metastability. Comparison with classical nucleation theory reveals markedly different supersaturation dependencies of the nucleation rate, while the predicted sizes of the critical bubble are in good agreement.
On powers of Bessel functions
Authors: Bender Carl M. , Brody Dorje C. , Meister Bernhard K.
Published: December 2002

A formula for the Taylor series expansion of the rth power of the modified Bessel function [Iν(z)]r is derived for arbitrary r. The result is expressed in terms of a recursive formula for a class of polynomials, which facilitates the systematic construction of the expansion of [Iν(z)]r.
Computation of the polarization due to the ferroelectric layer in a stacked capacitor from Sawyer–Tower hysteresis measurements
Authors: Bouregba R. , Poullain G.
Published: December 2002

Reducing thickness of thin ferroelectric films typically comes with an apparent degradation of their dielectric and ferroelectric properties. In practice one observes a marked decrease of the linear dielectric constant and of remanent and maximum polarizations which may arise from the presence of passive layers at the film interfaces. We propose a numerical procedure which allows us to investigate the genuine behavior of switching domains in the ferroelectric layer of a stacked capacitor. This is achieved owing to the computation of the ferroelectric polarization from Sawyer–Tower hysteresis measurements. Moreover, the proposed procedure simultaneously allows us to remove the possible loop deformations through a numerical compensation acting as a modified Sawyer–Tower (ST) circuit. The method is based on a suitable formulation of the polarization taking place in the ferroelectric layer which corrects for both the passive layer effect and for the parasitics of the ST circuit. In addition, a fit procedure is described from which may be derived the linear dielectric constant of the ferroelectric layer, the resistivity, and the interfacial capacitance of the stacked capacitor.
Asymptotics of information entropies of some Toda-like potentials
Authors: Dehesa J. S. , Martı́nez-Finkelshtein A. , Sorokin V. N.
Published: December 2002

The spreading of the quantum probability density for the highly-excited states of a single-particle system with an exponential-type potential on the positive semiaxis is quantitatively determined in both position and momentum spaces by means of the Boltzmann–Shannon information entropy. This problem boils down to the calculation of the asymptotics of the entropy-like integrals of the modified Bessel function of the second kind (also called the Mcdonald function or Basset function). The dependence of the two physical entropies on the large quantum number n is given in detail. It is shown that the semiclassical (WKB) position–space entropy grows slower than the corresponding quantity of not only the harmonic oscillator but also the single-particle systems with any power-type potential of the form V(x)=x2k, x∈R and k∈N. The momentum–space entropy, calculated with a method based on the properties of the Mcdonald function, is rigorously found to have a behavior of the form −ln ln n, in strong contrast with the corresponding quantity of other one-dimensional systems known up to now (power-type potentials, infinite well).
The essential spectrum of Schrödinger operators with asymptotically constant magnetic fields on the Poincaré upper-half plane
Authors: Inahama Yuzuru , Shirai Shin-ichi
Published: December 2002

We study the essential spectrum of the magnetic Schrödinger operators on the Poincaré upper-half plane and establish a hyperbolic analog of Iwatsuka’s result [J. Math. Kyoto Univ. 23(3), 475–480 (1983)] on the stability of the essential spectrum under perturbations from constant magnetic fields.
Density inhomogeneities and electron mobility in supercritical xenon
Authors: Holroyd Richard A. , Itoh Kengo , Nishikawa Masaru
Published: December 2002

The low-field mobility of electrons in supercritical Xe has been measured isothermally as a function of density above the critical temperature (289.7 K). At 293 K the mobility varies from a high of 890 cm2/V s at 9.2×1021 atoms/cm3 to a minimum value of 4.6 cm2/V s at a density of 3.5×1021 atoms/cm3, which is just below the critical density. The density dependence of the mobility is reasonably well predicted by the deformation potential model if the adiabatic compressibility is used to characterize the electron–medium interactions. Approximate agreement indicates that electrons are quasifree in supercritical xenon.
Parametric decay instabilities in the HELIX helicon plasma source
Authors: Kline J. L. , Scime E. E.
Published: December 2002

Parametric decay of the electromagnetic helicon pump wave into two electrostatic waves, thought to be a lower hybrid wave and an ion acoustic wave, is observed. The parametric excitation of the electrostatic waves is strongest near the axis of the helicon source. The parametrically excited wave amplitudes can be as large as 8% of the pump wave amplitude. Thus, efficient coupling between the parametrically excited waves and plasma particles (ions and electrons) can lead to enhanced plasma densities, electron temperatures, and ion temperatures. A correlation between the lower hybrid wave and electron temperatures and a correlation between the ion acoustic wave and ion temperatures near the antenna are observed.
Generalized Langmuir waves in a magnetized plasma with a Maxwellian–Lorentzian distribution
Authors: Mace R. L. , Hellberg M. A.
Published: December 2002

The generalized Langmuir modes in a magnetized plasma whose electrons have a hybrid kappa-Maxwellian velocity distribution are investigated in both the strongly and weakly magnetized regimes. It is found that the kappa distribution significantly alters both the dispersion relation and the Landau damping of the waves from what is ordinarily accepted based on the Maxwellian distribution. In general, the kappa distribution decreases the damping rate of the generalized Langmuir modes in the short wavelength region, but enhances it at the longest wavelengths. The spectral index of the distribution affects the real part of the dispersion relation also, but usually to a somewhat lesser extent. The modifications to both the real and imaginary parts of the dispersion relation are discussed in detail and the implications for plasma waves in space plasmas are briefly noted.
Equation-of-state measurements for aluminum, copper, and tantalum in the pressure range 80–440 GPa (0.8–4.4 Mbar)
Authors: Nellis W. J. , Mitchell A. C. , Young D. A.
Published: December 2002

Off-Hugoniot equation-of-state (EOS) measurements were performed on Al, Cu, and Ta shocked to pressures in the range 62–430 GPa and double-shocked or released isentropically to pressures in the range 80–440 GPa. Calculated temperatures of the off-Hugoniot states are in the range 2 400–14 500 K. All these off-Hugoniot data are in good agreement with approximating the double-shock and isentropic release curves with the mirror reflection in P−up space of the principal Hugoniot about the vertical axis through particle velocity up1 of the first-shock state. Effective Grüneisen γ’s of Al are in good agreement with the scaling relationship γ=γ0(V/V0). The high accuracy of EOS data of Al, Cu, and Ta, both on and off the principal Hugoniot, and their simple behaviors, including the absence of any observed phase transitions, qualifies these metals as EOS standards for use as anvils in shock-compression experiments.
Determination of absolute indium content in InGaN/GaN multiple quantum wells using anomalous x-ray scattering
Authors: Lee H. H. , Yi M. S. , Jang H. W. , Moon Y.-T. , Park S.-J. , Noh D. Y. , Tang M. , Liang K. S.
Published: December 2002

We have determined the absolute indium content incorporated in the crystalline lattice of InGaN films and InGaN/GaN multiple quantum wells using anomalous x-ray scattering (AXS). AXS spectra were obtained near the In K absorption edge at the InGaN (0006) Bragg peak where the InGaN Bragg reflection is well-resolved from the GaN reflections. By comparing the indium composition obtained by AXS to regular x-ray scattering results, which are also sensitive to the lattice strain, we determine the Poisson ratio of InGaN to be ν≈0.23. The AXS method can be effective in determining absolute chemical composition of InGaN independent of the lattice strain, which is especially valuable for InGaN multiple quantum wells.
Wafer-scale integration of GaAs optoelectronic devices with standard Si integrated circuits using a low-temperature bonding procedure
Authors: Georgakilas A. , Deligeorgis G. , Aperathitis E. , Cengher D. , Hatzopoulos Z. , Alexe M. , Dragoi V. , Gösele U. , Kyriakis-Bitzaros E. D. , Minoglou K. , Halkias G.
Published: December 2002

A methodology for the heterogeneous integration of epitaxial GaAs wafers with fully processed standard bipolar complementary metal-oxide-semiconductor Si wafers is presented. The complete low-temperature wafer bonding process flow, including procedures for the Si wafer planarization and GaAs substrate removal, has been developed and evaluated. The implementation of an in-plane optical link, consisting of an edge-emitting laser diode, a waveguide and a photodiode, is demonstrated.
Tip-gating effect in scanning impedance microscopy of nanoelectronic devices
Authors: Kalinin Sergei V. , Bonnell Dawn A. , Freitag Marcus , Johnson A. T.
Published: December 2002

Electronic transport in semiconducting single-walled carbon nanotubes is studied by combined scanning gate microscopy and scanning impedance microscopy (SIM). Depending on the probe potential, SIM can be performed in both invasive and noninvasive modes. High-resolution imaging of the defects is achieved when the probe acts as a local gate and simultaneously as an electrostatic probe of local potential. A class of weak defects becomes observable even if they are located in the vicinity of strong defects. The imaging mechanism of tip-gating scanning impedance microscopy is discussed.
InP-based two-dimensional photonic crystal on silicon: In-plane Bloch mode laser
Authors: Monat C. , Seassal C. , Letartre X. , Regreny P. , Rojo-Romeo P. , Viktorovitch P. , Le Vassor d’Yerville M. , Cassagne D. , Albert J. P. , Jalaguier E. , Pocas S. , Aspar B.
Published: December 2002

Defectless two-dimensional photonic crystal structures have been fabricated by drilling holes in a thin multi-quantum-well InP-based heterostructure transferred onto a silicon host wafer. Extremely low group velocity modes, which correspond to the predicted photonic valence band edge, have been observed for different filling factors. Under pulsed optical pumping, room temperature laser operation around 1.5 μm has been achieved on these structures with a threshold in the milliwatt range.
Design of semiconductor-waveguide-type optical isolators using the nonreciprocal loss/gain in the magneto-optical waveguides having MnAs nanoclusters
Authors: Shimizu H. , Tanaka M.
Published: December 2002

We have theoretically analyzed semiconductor-waveguide-type optical isolators, which are based on the nonreciprocal loss/gain in the magneto-optical waveguide having MnAs nanoclusters embedded in an InAlAs matrix. The whole device structure is grown on an InP substrate and the operation wavelength is 1.55 μm. In the TM mode, more than 119 dB/cm of isolation is predicted and the optimum device structure is discussed. Furthermore, we proposed and theoretically analyzed a semiconductor-waveguide-type optical isolator for the TE mode, which can realize 36 dB/cm of isolation. Since our waveguide-type optical isolators are composed of all semiconductor-based materials, they can be easily integrated with III–V based optoelectronic devices such as edge-emitting laser diodes.
Mitigation of transverse domain growth in two-dimensional polarization switching of lithium niobate
Authors: Peng L.-H. , Shih Y.-C. , Tsan S.-M. , Hsu C.-C.
Published: December 2002

This letter reports a charge control mechanism to mitigate the growth of transverse domain in the two-dimensional periodical polarization switching of Z-cut congruent-grown lithium niobate. This mechanism is established in a two-step procedure consisting of a first high temperature treatment followed by pulsed field poling. The ferroelectric χ(2) nonlinear photonic crystal thus formed exhibits a domain size as small as 3.3 μm and can emit an array of second harmonic green lasers when pumped by a Nd:yttritium–aluminum–garnet laser. These observations are ascribed to the (i) selective 180° domain nucleation underneath the oxidized electrode, and (ii) confinement of transverse domain motion to the positively charged boundary formed by the heat treatment.
Morphological and mechanical properties of carbon-nanotube-reinforced semicrystalline and amorphous polymer composites
Authors: Cadek M. , Coleman J. N. , Barron V. , Hedicke K. , Blau W. J.
Published: December 2002

In this work, multiwalled carbon nanotubes were investigated as potential mechanical reinforcement agents in two hosts, polyvinyl alcohol (PVA) and poly(9-vinyl carbazole) (PVK). It was found that, by adding various concentrations of nanotubes, both Young’s modulus and hardness increased by factors of 1.8 and 1.6 at 1 wt % in PVA and 2.8 and 2.0 at 8 wt % in PVK, in reasonable agreement with the Halpin–Tsai theory. Furthermore, the presence of the nanotubes was found to nucleate crystallization of the PVA. This crystal growth is thought to enhance matrix-nanotube stress transfer. In addition, microscopy studies suggest extremely strong interfacial bonding in the PVA-based composite. This is manifested by the fracture of the polymer rather that the polymer-nanotube interface.
A glow-discharge approach for functionalization of carbon nanotubes
Authors: Khare Bishun N. , Meyyappan M. , Kralj Joel , Wilhite Patrick , Sisay Metagus , Imanaka Hiroshi , Koehne Jessica , Baushchlicher Charles W.
Published: December 2002

We demonstrate the functionalization of single-walled carbon nanotubes (SWNTs) using a glow discharge for generating atomic or molecular radicals. A 30-s exposure to a cold plasma of H2 results in near-saturation coverage of SWNT with atomic hydrogen. Functionalization of SWNTs with atomic hydrogen is confirmed by an infrared band at 2924 cm−1, characteristic of C–H stretching mode. A corresponding decrease in the ultraviolet absorption is also observed, which is due to a loss of some conjugated C–C π bonds in hydrogen covered SWNTs.
Kinetic roughening study of perylene on glass and Au substrates
Authors: Zorba Serkan , Yan Li , Watkins Neil J. , Gao Yongli
Published: December 2002

We have investigated the growth kinetics of perylene, an organic semiconductor with high carrier mobility, on glass and Au substrates grown side-by-side by vapor deposition using atomic force microscopy. Our results show that kinetic roughening theory can reveal a wealth of information about polycrystalline growth. Higher order height–height correlation functions have been calculated for the perylene thin films on glass and Au. These results show that the height–height correlation function and the Hurst exponent saturate once the nominal perylene film thickness reaches the critical value of 40 Å on glass, and 100 Å on Au. After these thicknesses, overhang structures develop and dynamic scaling analysis becomes inappropriate. In addition, we have observed a complex, multiaffine behavior on both substrates evidenced by order dependence of the Hurst exponent. Grain size distribution and shape analysis were also performed on our films.
Analysis of Electrochemical and Thermal Behavior of Li-Ion Cells
Authors: Srinivasan Venkat , Wang C. Y.
Published: December 2002

This paper seeks to gain a better understanding of the thermal behavior of Li-ion cells using a previously developed two-dimensional, first principles-based thermal-electrochemical modeling approach. The model incorporates the reversible, irreversible, and ohmic heats in the matrix and solution phases, and the temperature dependence of the various transport, kinetic, and mass-transfer parameters based on Arrhenius expressions. Experimental data on the entropic contribution for the manganese oxide spinal and carbon electrodes, recently published in the literature, are also incorporated into the model in order to gauge the importance of this term in the overall heat generation. Simulations were used to estimate the thermal and electrical energy and the active material utilization at various rates in order to understand the effect of temperature on the electrochemistry and vice versa. In addition, the methodology of using experimental data, instead of an electrochemical model, to determine the heat-generation rate is examined by considering the differences between the local and lumped thermal models, and the assumption of using heat generation rate determined at a particular thermal environment under other conditions. Model simulations are used to gain insight into the appropriateness of various approximations in developing comprehensive thermal models for Li-ion cells. © 2002 The Electrochemical Society. All rights reserved.
Prolonged Single-Agent Versus Combination Chemotherapy in Indolent Follicular Lymphomas: A Study of the Cancer and Leukemia Group B
Authors: Peterson Bruce A. , Petroni Gina R. , Frizzera Glauco , Barcos Maurice , Bloomfield Clara D. , Nissen Nis I. , Hurd David D. , Henderson Edward S. , Sartiano George P. , Johnson Jeffrey L. , Holland James F. , Gottlieb Arlan J.
Published: December 2002

Purpose: The array of options for the initial management of follicular small cleaved lymphoma (FSCL) and follicular mixed lymphoma (FML) ranges from little or no therapy to the use of intensive combinations of drugs. The Cancer and Leukemia Group B (CALGB) compared two contrasting approaches: a single agent, and combination chemotherapy capable of curing diffuse aggressive lymphomas.

Patients and Methods: A total of 228 patients with stage III or IV FSCL or FML were randomized to cyclophosphamide or the combination of cyclophosphamide, doxorubicin, vincristine, prednisone, and bleomycin (CHOP-B). Treatment was continued in responders for 2 years beyond maximal response. The primary end point was survival in the most common subtype, FSCL.

Results: Ninety-one percent of all patients responded; complete responses were seen in 66% of those treated with cyclophosphamide and in 60% treated with CHOP-B (P = .36). At 10 years with either cyclophosphamide or CHOP-B, respectively, overall time to failure (25% failure free v 33%; P = .107) and survival (44% alive v 46%; P = .79) were similar by treatment. Outcomes in FSCL also were similar. In 46 patients with FML, at 10 years the combination was associated with better failure-free (9% v 48%; P = .005) and overall (25% v 61%; P = .024) survival. Acute toxic effects were more common with combination chemotherapy. Second malignancies, which might be attributed to treatment, were seen with both approaches.

Conclusion: There is no advantage to the initial use of the relatively intensive combination, CHOP-B, for patients with FSCL compared with the less toxic single agent, cyclophosphamide. However, in an unplanned subgroup analysis, patients with FML who received the combination experienced improved disease control and survival.
Phase II, Randomized Trial Comparing Bevacizumab Plus Fluorouracil (FU)/Leucovorin (LV) With FU/LV Alone in Patients With Metastatic Colorectal Cancer
Authors: Kabbinavar Fairooz , Hurwitz Herbert I. , Fehrenbacher Louis , Meropol Neal J. , Novotny William F. , Lieberman Grazyna , Griffing Susan , Bergsland Emily
Published: December 2002

Purpose: This phase II trial investigated the safety and efficacy of two doses of bevacizumab, a monoclonal antibody to vascular endothelial growth factor, plus fluorouracil (FU)/leucovorin (LV) versus FU/LV alone in patients with metastatic colorectal cancer.

Patients and Methods: One hundred four previously untreated patients with measurable metastatic colorectal cancer were randomly assigned to one of the following three treatment groups: 36 to FU (500 mg/m2)/LV (500 mg/m2) alone, 35 to FU/LV + low-dose bevacizumab (5 mg/kg every 2 weeks), and 33 to FU/LV + high-dose bevacizumab (10 mg/kg every 2 weeks). FU/LV was given weekly for the first 6 weeks of each 8-week cycle.

Results: Compared with the FU/LV control arm, treatment with bevacizumab (at both dose levels) plus FU/LV resulted in higher response rates (control arm, 17%, 95% confidence interval [CI], 7% to 34%; low-dose arm, 40%, 95% CI, 24% to 58%; high-dose arm, 24%, 95% CI, 12% to 43%), longer median time to disease progression (control arm, 5.2 months, 95% CI, 3.5 to 5.6 months; low-dose arm, 9.0 months, 95% CI, 5.8 to 10.9 months; high-dose arm, 7.2 months, 95% CI, 3.8 to 9.2 months), and longer median survival (control arm, 13.8 months; 95% CI, 9.1 to 23.0 months; low-dose arm, 21.5 months, 95% CI, 17.3 to undetermined; high-dose arm, 16.1 months; 95% CI, 11.0 to 20.7 months). After cross-over, two of 22 patients had a partial response to bevacizumab alone. Thrombosis was the most significant adverse event and was fatal in one patient. Hypertension, proteinuria, and epistaxis were other potential safety concerns.

Conclusion: The encouraging results of this randomized trial support further study of bevacizumab 5 mg/kg plus chemotherapy as first-line therapy for metastatic colorectal cancer.
The importance of being earnest: displayed emotions and witness credibility
Authors: Kaufmann Geir , Drevland Guri C. B. , Wessel Ellen , Overskeid Geir , Magnussen Svein
Published: December 2002

Participants viewed one of six video‐recorded versions of a rape victim's testimony, role‐played by a professional actress in one of six versions: Two versions of the testimony, representing a strong and a less strong rape scenario, were given in a free‐recall manner with one of three kinds of emotions displayed, termed congruent, neutral and incongruent emotional expressions. Credibility judgements were strongly influenced by the emotions displayed, but not by the content of the story. When video watching was compared to reading a transcript of the testimony, results indicated that perceived credibility was reduced when the witness displayed neutral or incongruent emotions. Story content and displayed emotion contributed equally to estimates of the probability of a guilty verdict. We conclude that perception of credibility is strongly influenced by social stereotypes regarding appropriate emotional expression. Copyright © 2002 John Wiley & Sons, Ltd.