bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of model age on children's reactions to advertising stimuli
Authors: Macklin M. Carole
Published: July 2007

Two studies are reported that explore the role of age of model as a nonverbal cue in advertising directed to children. Conventional advertising wisdom holds “older is better” when casting for commercials directed to children. The purpose of the current work is to focus on the merits of this wisdom. Three different age ranges of models were paired with either toys (Study 1) or foods (Study 2). Preschoolers' attitudinal (affective, evaluative, and behavioral intent) responses to the products were measured. Study 1 (n = 36) with toys suggested support for the conventional wisdom. Study 2 (n = 36) was a replication of procedures from the first study with substitution of food items for toys. Study 2 resulted in no statistical differences at the traditional .05 level, but a trend appeared on behalf of the older‐ and younger‐age models outperforming the same‐age ones. The second study's results suggested that the nature of the product may moderate the effects of the adage, “older is better.”
An inductively derived model of the motivation to shop
Authors: Lesser Jack A. , Kamal Pushp
Published: July 2007

The purpose of this article is to inductively determine the relationships which underlie the motivation to shop. Specifically, a variety of exploratory analyses which have been widely used to construct theory are sequentially applied to the relationships of 10 motivational variables. The outcome of the article is the development of a model of shopping motivation which appears to have been derived through a systematic series of inductive assessment analyses.
Role transitions in older adults: A marketing opportunity
Authors: Schewe Charles D. , Balazs Anne L.
Published: July 2007

Consumers act out roles throughout their lives. Marketers assist in this role playing by providing the wardrobes, props, and sets in the form of products and services. They also help people understand acceptable role behavior by portraying roles in their communication programs. Consumers assume new roles as they age. This article is designed to enhance understanding of the often‐ignored roles that accompany aging and provides examples of and suggestions for effective marketing for these role transitions.
Prediction of choice in a technically complex, essentially intangible, highly experiential, and rapidly evolving consumer product
Authors: Nataraajan Rajan
Published: July 2007

This study compares the effectiveness of the theory of reasoned action, the most well known attitudinal approach, with that of traditional conjoint analysis, the most popular utilitarian approach, in predicting choice among real brands of word processing software. Results suggest that traditional conjoint analysis has a significantly higher first choice hit rate than the theory of reasoned action. With products such as word processing software, a utilitarian approach may be better than an attitudinal approach for predicting consumer choice. © 1993 John Wiley & Sons, Inc.
The role of memory in understanding and encouraging recycling behavior
Authors: Heckler Susan E.
Published: July 2007

This article explores the role of memory processes in two aspects of recycling behavior. First, traditional research in cognitive psychology, communication, and consumer behavior is discussed briefly as it relates to understanding how people learn why to recycle. More importantly, a recently emerging stream of memory research, examining memory processes in real‐world contexts, is introduced as a conceptual basis for understanding how people remember when and how to recycle. Additionally, these ideas are integrated to help explain the results of past recycling research and to offer suggestions regarding future recycling programs. © 1994 John Wiley & Sons, Inc.
Advancing versus delaying payments and consumer time orientation: A personal selling experiment
Authors: Amyx Douglas , Mowen John C.
Published: July 2007

The authors propose that an individual's capacity to plan and delay consumer decisions may impact purchases within personal selling situations. An experiment was conducted to investigate the effects of postponing or expediting a payment for a car on purchase intentions. A scale, developed to categorize future‐ and present‐time oriented individuals, was employed as a moderating variable. The results indicate that a present‐time oriented person tends to prefer delayed payments over immediate payments. In contrast, a future‐time oriented person is more likely to prefer immediate payments than a present‐time oriented person. The results are discussed in relation to applications for developing adaptive selling strategies. © 1995 John Wiley & Sons, Inc.
Exploring the psychological foundations of ethical positions in marketing
Authors: McIntyre Roger P. , Capen Margaret M. , Minton Ann P.
Published: July 2007

While demographic variables may ease the exploration of marketing ethics, psychological variables may provide more insight into individual differences in making ethical judgments. This article uses path analysis to explore relationships among cognitive style as measured by the Myers‐Briggs Type Indicator, Forsyth's ethical ideologies, and perceptions of moral judgments about ethical behaviors in marketing. © 1995 John Wiley & Sons, Inc.
Efficiency of service delivery systems in large commercial banks
Authors: Hunter William C.
Published: July 2007

This article provides novel empirical evidence on the cross‐sectional variation of the productive efficiency of large banks relative to their service delivery systems. The analysis is conducted using data drawn from a sample of 118 large U.S. commercial banks for the years 1989 through 1991. The analysis reveals that centralized service delivery systems increase bank costs significantly. In no case was it found that centralized service delivery systems reduce costs, as is often envisioned by proponents of centralization. It is also found that centralized back‐office operations tend to reduce costs significantly and are consistent with the existence of scale economies in bank back‐office operations. © 1995 John Wiley & Sons, Inc.
Accurate calculation method for the capacitance of generalized circular structures
Authors: Tefiku Faton , Yamashita Eikichi
Published: July 2007

The generalized circular structures imply combinations of concentric strip rings with various potentials. The rectangular boundary division method is extended to estimate the total electric field energy from which the capacitance is effectively calculated. Numerical results based on this method are compared with other available numerical results and experimental data.
Singular value decomposition improves accuracy and reliability of T‐septum waveguide field‐matching analysis
Authors: Labay Vladimir A. , Bornemann Jens
Published: July 2007

A singular value decomposition (SVD) is used to solve the characteristic matrix equation of 2 different field‐matching analyses as applied to T‐septum waveguide structures. It is demonstrated that SVD avoids the need for complicated numerical zero‐detection algorithms, eliminates the major disadvantages of the classical field‐matching technique, and hence, improves the accuracy and reliability of the computed results. The values obtained are in close agreement with available theoretical data and measurements.
Editorial
Authors: Gupta K. C. , Sarkar Tapan K. , Maricevic Zoran A. , Kahrizi Masoud
Published: July 2007

Various de‐embedding procedures exist for characterizing passive lossless devices where radiation does not play a major role. However, for open structures where higher‐order, leaky‐wave modes are known to exist, or for discontinuity problems where complex modes are known to exist, one may wonder about the utilization of conventional de‐embedding schemes which do not account for power loss due to radiation when transferring planes of references. In this article, the Matrix Pencil Approach is presented as a novel and accurate de‐embedding procedure. In this procedure, the s‐parameters are computed directly without requiring specific values for the characteristic impedance. This is because, in this procedure, the results are automatically normalized with respect to the characteristic impedances of the ports at the frequency of computation. Also, the lines need not be terminated in their characteristic impedances, zo, to evaluate the s‐parameters. Numerical results are presented to illustrate this Matrix Pencil Approach. © 1992 John Wiley & Sons, Inc.
Analysis of open microstrip lines by MOL
Authors: Chen R. S. , Fang D. G. , Li X. G.
Published: July 2007

In this article, the analysis of the characteristics of open planar microstrip by using the method of lines (MOL) is given as the limit case of open cylindrical substrate microstrip lines. Numerical examples of both cylindrical substrate and open planar microstrips are presented. The results are in good agreement with those in the literature; this fact supports the validity of this method. © 1993 John Wiley & Sons, Inc.
Microwave modeling of curved coplanar waveguides
Authors: Soghomonian M. S. , Robertson I. D.
Published: July 2007

In this article, curved coplanar waveguides with varying radii of curvature built on alumina substrate have been characterized and a lumped element model has been developed. The model is found to give close agreement with measured data and a simple design formula is introduced for future applications. © 1993 John Wiley & Sons, Inc.
A new method for the measurement and analysis of noise parameters for MESFETS and HEMTs (invited article)
Authors: Nishida Masao , Uda Hisanori , Harada Yasoo
Published: July 2007

We have developed a new method to measure noise parameters for GaAs MESFETs and HEMTs more accurately, quickly, and reproducibly than the conventional method. We also devised an improved method for automatically calculating a gate‐induced noise current, a drain‐noise current, and their correlation coefficient from the measurement noise and S‐parameters. © 1993 John Wiley & Sons, Inc.
Computer‐aided engineering for microwave and millimeter‐wave circuits using the FD‐TD technique of field simulations (invited article)
Authors: Shibata Tsugumichi , Kimura Hideaki
Published: July 2007

This article describes our techniques for the three‐dimensional full‐wave field simulation of the computer‐aided design of broad‐band circuits operating in the microwave and millimeter wave frequency region. After reviewing the numerical algorithm of the finite‐difference time‐domain approach, the concept of the lumped device model is introduced into the simulation. We then propose an efficient way of calculating the scattering parameters of passive elements that uses the lumped device model as a standard termination of the circuit port. The analysis of a nonlinear circuit directly combined with the field simulation is also presented, and finally, a method of simulating integrated circuits mounted in a package is discussed. © 1993 John Wiley & Sons, Inc.
Computation of hybrid modes in waveguides based on a surface integral formulation
Authors: Swaminathan Madhavan , Sarkar Tapan K. , Petre Peter
Published: July 2007

The interconnections in integrated circuits behave as waveguides at high frequencies. A complete solution to Maxwell's equations is therefore necessary to analyze these lines due to the hybrid nature of the modes propagating in the waveguide. This can be a difficult task for interconnections having complex geometries. A surface integral formulation has been used in this article to compute the dispersion characteristics of hybrid modes propagating in the waveguide. The technique used is an extension of previous work and is based on a method of moments procedure to reduce an integro‐differential equation into a matrix equation using equivalent surface electric and magnetic currents. © 1993 John Wiley & Sons, Inc.
A network model for the aperture coupled microstrip patch
Authors: Dich Mikael , Østergaard Allan , Gothelf Ulrich
Published: July 2007

A network model for an aperture coupled microstrip patch is developed. The derivation of the topology of the network model is based on electromagnetic arguments. The values of the components in the network model are found by optimization using input reflection coefficient data computed from a method of moments model. The topology of the network model is described together with a procedure for the determination of the values of its components. After the determination of the values of the components, the network model can be used in a CAD program for a large range of mechanical dimensions, without the need of additional method of moments calculations. © 1993 John Wiley & Sons, Inc.
Time‐domain analysis of electromagnetic coupling of three‐dimensional circuits involving through holes
Authors: Maeda Shuji , Kashiwa Tatsuya , Fukai Ichiro
Published: July 2007

Prediction of the mutual effects of the components involving through holes is essential for the design of multilayer circuits to operate at high frequencies. In this article, the characteristics of coupling between adjacent pairs of through holes and between a through hole and microstrip were analyzed using the finite‐difference time‐domain (FD‐TD) method. Numerical results in the time and frequency domains were compared with experimental results; these agreed well. Coupling coefficients were shown to depend on the orientation and distance of the microstrips or a through hole of the secondary from the primary through hole. The distribution of electric field intensity during through hole‐through hole coupling was also shown. The method described appears to hold great promise for substitution for the experimental process. © 1993 John Wiley & Sons, Inc.
Design of different configurations of finite microstrip arrays of circular patches
Authors: Kishk Ahmed A. , Ramaraju Swarajya L.
Published: July 2007

A computer code is written to analyze different configurations of finite microstrip arrays. This code will be used as an educational and design tool for students and industrial engineers. The code will be available on PC computers in an interactive graphic mode for the NSF/IEEE Center on Computer Applications in Electromagnetics Education (CAEME). The arrays are made of circular patches with coaxial feeds and exciting different modes. Mutual coupling between the elements and surface wave effects are considered. The conventional dual feed configuration is used to generate circular polarization. Also, circular polarization is realized by sequential feeding of linearly polarized elements. Different array configurations of fixed and scanned beams are analyzed.
Moments‐method analysis of a finite array of arbitrary shaped microstrip patch radiating elements
Authors: Notter Michael John , Parini Clive G.
Published: July 2007

A full‐wave model for the analysis of a finite array of arbitrary shaped, probe fed, microstrip elements is presented. The method of moments is used first to obtain a space‐domain solution to the mixed potential integral equation (MPIE) for the isolated element in terms of linear ramp basis functions over triangular subdomains. A second order matrix equation for the array problem is then set up using characteristic current modes as basis functions. These converge rapidly and have orthogonality properties such that only the intermode coupling between separated elements need be computed—a relatively simple operation. Predicted and measured performance characteristics for a 37‐element 8‐GHz array of dual‐mode patches are given which demonstrate the accuracy obtainable with this approach.
The GPI‐anchored CD52 antigen of the sperm surface interacts with semenogelin and participates in clot formation and liquefaction of human semen
Authors: Flori Federica , Ermini Leonardo , La Sala Giovanni Battista , Nicoli Alessia , Capone Antonietta , Focarelli Riccardo , Rosati Floriana , Giovampaola Cinzia Della
Published: July 2007

CD52 is a human glycosylphosphatidylinositol (GPI)‐anchored antigen exclusively expressed in leukocytes and epididymal cells. It is also present in sperm, being inserted in their plasma membrane as they pass through the epididymis. In a previous paper we identified a new CD52 form without GPI anchor by fast performance liquid chromatography (FPLC) fractionation of semen components. The form has a lower negative charge than the GPI‐anchored form and occurs as the only CD52 form in prostasome‐free seminal plasma. It was also found associated with the ejaculated sperm, but in contrast to the GPI‐anchored one, it is lost during the capacitation process. In this paper we indicate that (1) the GPI‐anchored CD52 of the sperm surface serves as receptor for semenogelin I during clot formation, (2) liquefaction involves cleavage of the GPI anchor from certain CD52 molecules, releasing sperm from the clot and the soluble antigen bound to semenogelin fragments into the seminal plasma and (3) the clot is a sponge‐like structure housing sperm. Soluble CD52 was immunopurified from the soluble CD52‐containing FPLC fraction using CAMPATH‐1G and was found to be complexed with a semenogelin‐derived peptide of the carboxyl terminal portion of semenogelin I, having the sequence SQTEKLVAGKQI and starting from amino acid 376. Immunoprecipitation and immunoblot analyses using CAMPATH‐1G and anti‐semenogelin as immunoprecipitating antibodies and anti‐gp20 and anti‐semenogelin as immunoblot detectors of the corresponding antigens, confirmed that the soluble CD52 formed a complex with semenogelin. The semenogelin‐CD52 soluble form was found to be a direct consequence of the liquefaction process since only the GPI‐anchored CD52 was recovered in uniquefied semen after recovering sperm and seminal plasma by urea solubilization of the clot. Mol. Reprod. Dev. 75: 326–335, 2008. © 2007 Wiley‐Liss, Inc.
Polyurethane/polyaniline and polyurethane‐poly(methyl methacrylate)/polyaniline conductive core‐shell particles: Preparation, morphology, and conductivity
Authors: Li Chien‐Yu , Chiu Wen‐Yen , Don Trong‐Ming
Published: July 2007

Polyurethane/polyaniline (PU/PANI) and polyurethane‐poly(methyl methacrylate)/polyaniline (PU‐PMMA/PANI) conductive core‐shell particles were synthesized by a two‐stage polymerization process. The first stage was to produce a core of PU or PU‐PMMA via miniemulsion polymerization using sodium dodecyl sulfate (SDS) as the surfactant. The second stage was to synthesize the shell of polyaniline over the surface of core particles. Hydrogen chloride (HCl) and dodecyl benzenesulfonic acid (DBSA) were used as the dopant agents. Ammonium persulfate (APS) was used as the oxidant for the polymerization of ANI. Different concentrations of HCl, DBSA, and SDS would cause different conformations of PANI chains and thus different morphologies of PANI particles. UV–visible spectra revealed that the polaron band was blue‐shifted because of the more coiled conformation of PANI chains by increasing the concentration of DBSA. Besides, with a high concentration of DBSA, both spherical‐ and rod‐shape PANI particles were observed by transmission electron microscope, and the coverage of PANI particles onto the core surfaces was improved. The key point of formation of rod‐type PANI particles was that DBSA was served with a high concentration accompanied with the existence of HCl or SDS. The better coverage of PANI particles over the core surfaces by charging higher DBSA concentrations resulted in a higher conductivity of hybrid particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3902–3911, 2007
Fractal Aspects of Powder Flow and Densification
Authors: Mihranyan Albert , Strømme Maria
Published: July 2007

Powder flowability is affected by a number of particulate properties including particle size, surface area, and surface roughness. Surface irregularities play an important role in controlling powder flow properties. In the present work, a relationship was derived between the reactive fractal dimension – representing the fractallity of the part of the surface participating in particle‐particle interactions during powder flow – and the initial increase in density of a powder bed during densification. The reactive and true textural fractal dimensions for a model system comprised of silicified microcrystalline cellulose particles were also experimentally obtained. The concept of the reactive fractal dimension was shown to be helpful for a comprehensive description of the powder densification process. It indicates how rapidly the active interparticulate area involved in particle‐particle interactions grows with powder size reduction. It is suggested that the reactive fractal dimension can be used for describing powder flow behavior and to elucidate the sensitivity of powder flowability to particle size changes.
Hypoxia‐inducible factor‐1α (HIF‐1α) gene polymorphisms, circulating insulin‐like growth factor binding protein (IGFBP)‐3 levels and prostate cancer
Authors: Li Haojie , Bubley Glenn J. , Balk Stephen P. , Gaziano J. Michael , Pollak Michael , Stampfer Meir J. , Ma Jing
Published: July 2007

BACKGROUND

The Hypoxia‐inducible factor‐1 (HIF‐1) plays an important role in regulating angiogenesis in response to hypoxia. Two non‐synonymous polymorphisms (P582S C→T and A588T G→A) in the coding region of the subunit 1α (HIF‐1α) gene have been associated with enhanced stability of the protein and androgen‐independent prostate cancer (CaP). Insulin‐like growth factor binding protein (IGFBP)‐3 mRNA is more abundantly expressed in hypoxia‐related inflammatory angiogenesis and recent in vivo data suggest that IGFBP‐3 has direct, IGF‐independent inhibitory effects on angiogenesis.

METHODS

We examined the association of these polymorphisms with CaP among 1,072 incident cases and 1,271 controls, and further explored their joint associations with various prediagnostic plasma vascular endothelial growth factor (VEGF), IGF‐I, and IGFBP‐3 levels.

RESULTS

Neither the P582S nor the A588T polymorphism was associated with risk of overall or metastatic/fatal CaP. However, we found that, among men with the homozygous CC wild‐type (but not CT/TT) of the HIF‐1α P582S, higher IGFBP‐3 levels (≥ vs. <median) were associated with a 28% (95% CI, 0.55–0.95; Pinteraction = 0.01) lower risk of overall CaP and a 53% (0.25–0.88; Pinteraction = 0.11) lower risk of metastatic and fatal CaP. The A588T polymorphism was too rare to assess interactions.

CONCLUSIONS

The two HIF‐1α gene polymorphisms were not directly associated with CaP, but the interaction between the P582S polymorphism and IGFBP‐3 merits further evaluation in mechanistic studies. Prostate 67: 1354–1361, 2007. © 2007 Wiley‐Liss, Inc.
Shared‐care arrangements and the primary/secondary‐care interface
Authors: Khambh Jas , Barnick Christian
Published: July 2007

Specialist and high‐risk drugs are increasingly being prescribed in the community due to a shift in services from secondary to primary care. This article describes the shared‐care arrange ments that need to be in place to ensure safe and effective treatment. Copyright © 2007 Wiley Interface Ltd
Rayleigh‐debye scattering of light of anthracene crystals
Authors: Uzarczyk A. , Myja M. , Godlewski J.
Published: July 2007

Light scattering in pure solids is due to the extended discrete variation of the dielectric constant. To describe the scattering of light in anthracene crystals the Rayleigh‐Debye theory is used. A direct relation between the nature of structural defects in molecular solids and the spatial variation of the dielectric constant is found. On the basis of the relation, the form of the scattering correlation function is derived. Theoretical relations describing the intensity of light scattering in molecular crystals are applied to experimental data concerning the intensity of scattered light in anthracene crystals as a function of wavelength for small angles of scattering. It is found that the diameter of the scattering centres in anthracene is of the order of few μm with concentration about 108 cm−3.
Equation of State and Thermal Expansivity under the Effect of High Pressure and High Temperature
Authors: Kumar M. , Upadhyay S. P.
Published: July 2007

A simple method is developed to investigate interatomic separations and thermal expansion coefficients at pressures ranging from the atomspheric one up to the structural transition pressure, and temperatures ranging from RT to the melting temperature. The calculations are performed using an ionic model based on Harrison's quantum mechanical form for the overlap repulsive energy which takes into account the interactions up to second neighbours. The van der Waals dipole‐dipole and dipole‐quadrupole interactions evaluated from more accurate methods are also included in the model. The results depend sensitively on temperature and pressure. The thermal expansion coefficient increases with temperature, while this increase becomes rather slow as pressure is increased. A strong decline of the thermal expansion coefficient with pressure at a constant temperature is also obtained. The results are compared with available experimental data, and good agreement supports the validity of the method developed in the present work.
Structural Phase Stability in BaSe
Authors: Kalpana G. , Palanivel B. , Rajagopalan M.
Published: July 2007

The band structure of BaSe in both Nad‐type (Bl) and CsCl‐type (B2) structures is determined using the self‐consistent linear muffin‐tin orbital method within the atomic sphere approximation (LMTO‐ASA). In agreement with the earlier observations, the band gap is found to be indirect in both Bl and B2 structures. The calculated values of the band gaps are compared with the experimental values. From the ASA total energy calculations, the structural phase stability of BaSe is studied. At ambient conditions BaSe is found to be stable in the Bl structure. It undergoes a structural transition to the B2 structure at about 55 × 108 Pa, associated with a volume reduction of 14.3%. The equilibrium lattice constants for both Bl and B2 structures and the transition pressure are compared with earlier experimental results.
Recombination of Alloy‐Trapped Excitons in Ternary Solid Solutions with Common Cation Components
Authors: Reznitsky A. , Baranovskii S. D. , Tsekoun A. , Klingshirn C.
Published: July 2007

A new analysis of absorption and photoluminescence (PL) spectra of CdS1−xSex and ZnSe1−xTex solid solutions at liquid helium temperature is presented. It is shown that the high‐energy side of the luminescence band of excitons trapped in the band tail can be fitted by a simple exponential function exp (ϵ/ϵPL), the parameter EPL being proportional to the Urbach parameter ϵ0 in the absorption spectra. This analysis provides the most direct evaluation of the concentration N0 of localized tail states. The values N0a3 = (4.5 ± 0.7) × 10−3 and (2.5± 0.5) × 10−3 are obtained for CdS1−xSex and ZnSe1−xTex respectively, which lead to the estimations N0≈1.5 × l019and ≈ 8 × 1018 cm−3 in these solid solutions, using the previously determined value a ≈ 0.7 nm. A new model for the energy relaxation of excitons through the localized tail states is suggested which takes into account exciton‐phonon interactions and non‐radiative recombination of excitons.
Galvanomagnetic Transport of the Two‐Dimensional Electron Gas in In0. 53Ga0. 47As Quantum Wells
Authors: Ghosh P. K. , Chattopadhyay D.
Published: July 2007

Galvanomagnetic coefficients of the two‐dimensional (2D) electron gas in In0.53Ga0. 47As quantum wells are studied for classical magnetic fields by an iterative solution of the Boltzmann equation considering the degeneracy of the distribution function. Scatterings from polar optic phonons, deformation potential acoustic and piezoelectric phonons, inonized impurities, and alloy disorder are considered. The magnetoresistance coefficient is found to be more sensitive than the Hall mobility and the Hall ratio to changes in temperature, 2D carrier concentration, channel width, ionized impurity concentration, and magnetic field.
X‐Ray Absorption Fine Structure Investigation of the High Pressure Phase of KBr and RbCl. Full Multiple Scattering Analysis
Authors: Soldatov A. V. , Ivanchenko T. S. , Stekhin I. E. , Bianconi A. , Ingalls R.
Published: July 2007

X‐ray absorption near edge structure (XANES) of the Br and Rb K edge of the high pressure (B2) phase of KBr and RbCl is analyzed. A full multiple scattering method is used to investigate the conduction band structure of KBr and RbCl. Theoretical K‐edge absorption spectra obtained over a large energy interval are used to analyze the experimental data. As in the case of the low pressure (B1) phase, XANES is found to be determined by multiple scattering of photoelectrons in a large‐size cluster (30 atoms or more). For the energy interval up to 50 eV above the main edge, the single scattering approximation seems to be less satisfactory. A comparative analysis of XANES of the two compounds in two different crystal phases makes it possible to conclude on the role of the local symmetry around the absorbing site and the characteristics of the surrounding atoms in the formation of XANES and conduction band of the compounds investigated.
Electronic Structure of Copper‐Oxide Based High‐Tc Superconductors and Related Compounds from KK Analysis of Reflectance
Authors: Ghosh B. , Neogy C. , Deb S. K. , Nag A.
Published: July 2007

It is demonstrated that Kramers‐Kronig (KK) analysis of reflectance data using various physically acceptable extrapolation formulae yields results which agree quantitatively when the parameters are obtained by suitable statistical methods. The absorption and Im (−1/ϵ) spectra obtained by the KK analysis of reflectance data (0.5 to 6.1 eV) of REBa2Cu3O7−x (RE = Y, Dy, Ce) and different combinations of CuO, BaO, and RE oxides strongly suggest that in these 123 layered cuprates superconductivity results when excitons (near 1.4eV) in the polarizable layers and carriers (hole or hole‐polarons) in the conducting layers are both present in sufficient number.
From Liquid to Solid: Residual Disorder in the Local Environment of Oxygen‐Coordinated Zirconium
Authors: Landron C. , Douy A. , Bazin D.
Published: July 2007

X‐ray absorption is used as a chemically specific structural probe to investigate the short‐range order around zirconium cations in various crystallized, amorphous, or vitreous systems containing oxygencoordinated zirconium in order to connect it to the disorder in the environment of this cation in the liquid solution from which they are produced. The comparison of the various analyses gives detailed information on the local structure around the zirconium atoms. The type and the level of randomness is discussed. The radial distribution functions of the various samples with disordered structure are compared with the corresponding crystalline functions. The effects of disorder on the first two coordination shells are derived for these samples.
On Carrier Ion Interaction in RbAg4I5
Authors: Takeuchi T.
Published: July 2007

The effect of the inclusion of cation interaction in RbAg4I5 on the activation energy is discussed and found to be quite important.
Elastostatic Green's Function and Its Spatial Derivatives for Cubic Symmetry. Exactly Solvable Cases
Authors: Morawiec A.
Published: July 2007

The Green's function and its spatial derivatives for a cubic infinite medium in cases when they can be obtained in form of explicit analytic expressions are presented. It is known that the problem reduces to a sextic equation which, in general case, is unsolvable. Symbolic solutions, however, can be given in some special cases. New formulae for directions lying in (001) and (110) planes are given. Full solutions for [100] and [111] directions are presented as examples. First derivatives of the Green's function with respect to spatial coordinates are also expressed through the roots of the sextic equation and the solutions for the same special directions are given.
Electron Energy Spectrum and Wave Functions in Quantum Wells on the Base ofIV‐VI Narrow‐Gap Semiconductors
Authors: Dugaev V. K. , Petrov P. P.
Published: July 2007

The results of analytical calculations of the energy spectrum and wave functions of electrons localized within quantum wells grown on IV‐VI narrow‐gap semiconductors are presented. The eigenvalue equations determining the size‐quantized levels are in agreement with previous reports in literature, but some aspects concerning the symmetry of wave functions are elucidated. The wave functions for localized states are presented in explicit form. Using these wave functions as a new basis we obtain the effective Hamiltonian for electrons in quantum wells. The energy spectrum of electrons in the presence of a magnetic field is presented as well.
The Uniaxial Strain Effect on the Ternary Alloy Semiconductor Ga1−xAlxP
Authors: Badi N. , Abid H. , Soudini B. , Amrane N. , Driz M. , Dufour J. P. , Aourag H. , Khelifa B.
Published: July 2007

The effect of static uniaxial compression along the cubic direction 〈100〉 is studied. The empirical pseudo‐potential method (EPM) within the so‐called virtual crystal approximation (VCA) is used to compute the electronic charge densities at selected k‐points of the valence and the conduction band edges in Ga1−xAlxP. These charge densities are used to study the modification of the bonding and the electronic properties of the alloy with respect to the composition and the lattice constant variations along the 〈100〉 direction.
Magnetization and Critical Temperature of the Structurally Disordered s‐d Model
Authors: Ponedilok G. V. , Savenko V. P.
Published: July 2007

A disordered s‐d model is considered and applied for the description of amorphous ferromagnetic compounds. The partition function is obtained in the form of a functional integral over Bose fields. The thermodynamical potential is calculated in RPA. The magnetization and critical temperature of the “ferromagnetic‐paramagnetic” phase transition of amorphous compounds with liquid‐type disorder are studied.
Low Temperature EPR Spectra of the (Pr, RE)BaCuO Ceramics in the Orthorhombic Phase
Authors: Guskos N. , Likodimos V. , Patapis S. K. , Kuriata J. , Wabia M. , Sadlowski L. , Koufoudakis A. , Mitros C. , Gamari‐Seale H. , Psycharis V.
Published: July 2007

The EPR spectra of the members of the series Pr0.5RE0.5Ba2Cu3O6+x (RE = Pr, La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, Tm, Yb, and Lu) in the orthorhombic phase are investigated at low temperature. The EPR spectra arise from two different paramagnetic centers, one from divalent copper ions in orthorhombic local crystal field symmetry and another from exchange coupled pairs of copper ions whose origin is discussed. The EPR spectra essentially depend on the time exposition. The EPR spectra of some divalent and trivalent rare earth ions are recorded. The crystal field analysis is done for the trivalent ytterbium ions. The semiconducting behaviour of the dc conductivity can be attributed to thermally activated small polaron hopping motion.
Electron Paramagnetic Resonance and Superposition Model Analysis of Zero‐Field Splitting for Gd3+ in Eu2Co3(NO3)12·24H2O
Authors: Jain V. K.
Published: July 2007

Electron paramagnetic resonance of Gd3+ in Eu2Co3(NO3)12 24H2O single crystals is studied at ≈ 9.45 GHz and room temperature. Gd3+ substitutes for the Eu3+ site. In addition to the allowed fine structure lines some weak low field lines, identified as forbidden transitions (ΔM = ±2, ±3) are observed. The superposition model is applied to the zero‐field splitting parameter b for Gd3 + in Eu2Co3(NO3)12·24H2O, Ce2Mg3(NO3)12·24H2O, and La2Mg3(NO3)12·24H2O.
Mossbauer and Magnetic Investigations of Iron‐Rich FeNiZr Amorphous Alloys
Authors: Zatroch M. , Kováč J. , Rohr L. , Aubertin F. , Gonser U.
Published: July 2007

Mössbauer, high‐field susceptibility, and thermomagnetic measurements indicate a correlation between reentrant spin glass (RSG)‐like behaviour and the presence of a broad hyperfine magnetic field distribution of Fe92−xNixZr8 glasses. The pure iron area, in which the competition between antiferromagnetic and ferromagnetic exchange takes place, is probably responsible for both. There is a transition from collinear to noncollinear magnetic structure at low temperatures for x = 0, 2, 5 due to this competition. The substitution of Ni for Fe or the hydrogenation suppresses the RSG‐like behaviour.
Solitary Excitations in the Antiferromagnet KCuF3
Authors: Liu Wu‐Ming , Zhou Ben‐Lian , Guo Li‐Ming
Published: July 2007

Employing the Holstein‐Primakoff transformation, first the spin‐Hamiltonian is transformed into a boson Hamiltonian. Then, using a coherent state ansatz, a time‐dependent variational principle, and the continuum approximation, two nonlinear coupled equations are obtained. Finally, these equations of motion, which describe the dynamics of the system, are reduced to one nonlinear Schrodinger equation with localized envelope soliton solutions. Introducing the inverse scattering transformation, single‐, two‐, and N‐soliton solutions are obtained and the solitary excitations in the antiferromagnet KCuF3 are investigated.
Spectral‐Angular Distribution and Polarization of Surface Parametric Optical Radiation
Authors: Andriyanchik A. A. , Baryshevskii V. G. , Kaminskii A. N.
Published: July 2007

Surface parametric (quasi‐Cherenkov) optical radiation of a relativistic charged particle, moving close to the surface of a spatially periodic medium, is considered. The spectral‐angular distribution and polarization characteristics of the radiation are found. The possibility of experimental observation of the radiation described is discussed.
Ab Initio Calculation of Infrared and Raman Spectra for Hydrogenated Amorphous Silicon
Authors: Zou Xian‐Wu , Zhang Wen‐Bing , Zhuang Hong‐Zhang , Jin Zhun‐Zhi
Published: July 2007

The ab initio method with the STO‐3G basis set is used to calculate the infrared and Raman spectra of hydrogenated amorphous silicon. To remove the systematic deviation of the calculated frequencies due to the finite number of the basis functions and the small size of the cluster, a scaling method is used. The results are in good agreement with the experiments. The calculated results support that there are SiH, SiH2, SiH3, and (SiH2)n configurations in hydrogenated amorphous silicon. The doublet lines are associated with the SiH3 configuration.
Site‐Selective Upconversion Luminescence of Ho3+ ‐Doped CaF2 Crystals
Authors: Zhang Xiao , Jouart J.‐P. , Bouffard M. , Mary G.
Published: July 2007

With red dye laser excitation, site‐selective upconversion properties of three Ho3+ centres (C4v, C3v, and dimer) in CaF2, : 0.1 at% Ho3+ crystals are studied. The energy level diagrams for the three centres are deduced from the spectral data. The excited state absorption from the 5I7 level plays a very important role in the upconversion coming from C4v, and C3v centres, whereas the ground state absorption of 5I8, dominates for that from the dimer centre. The upconversion of C4v and C3v centres is explained by a sequential two‐photon excitation mechanism. For the dimer centre, the predominant upconversion mechanism is energy transfer.
Double Screening Problem in Dechanneling by Point Defects
Authors: Siddiqui A. M. , Harikumar V. , Pathak A. P.
Published: July 2007

A simple double screening model is used to calculate the interaction potential between an energetic channeled μ+ and an impurity (O) in an otherwise perfect single crystal (Ta). The twofold screening of the nuclear charge of the impurity is first due to the atomic electrons and second due to conduction electrons of the host crystal (Ta). Using this potential the dechanneling cross‐section of muons due to the oxygen impurity in the lattice of Ta along various planes is evaluated. Three charge states of the oxygen impurity are considered and the corresponding dechanneling cross‐sections are predicted.
Optical and Structural Properties of ZnTeZnS Strained‐Layer Superlattices
Authors: Guan Z. P. , Lu Y. M. , Chen L. C. , Yang B. J. , Fan X. W.
Published: July 2007

ZnTeZnS strained‐layer superlattices are grown by atmospheric pressure metalorganic chemical vapor deposition on transparent BaF2(111) and GaAs(100) substrates. With X‐ray diffraction measurements, multi‐order satellites are observed, which confirms the formation of a periodic structure of the superlattices. Photoluminescence and optical absorption measurements are carried out at 77 K and room temperature. The photoluminescence spectra under different excitations, time‐resolved and time‐delayed spectra are employed to study the band band recombination at 77 K. The band structure and strain effects are studied using the uniaxial stress and the linear combination of atomic orbital theory for such high mismatch ZnTeZnS strained‐layer superlattices. It is noticed that the energy disparity of ZnTeZnS superlattices is large with ZnTe or ZnS buffer layers. So the band‐band emission can be observed over a wide wavelength region for ZnTeZnS superlattices.
Dynamics of Double‐Barrier Resonant Tunnelling Structures
Authors: Pandey L. N. , Muratov L. S. , Stockman M. I. , George Th. F.
Published: July 2007

A time‐dependent Schrödinger equation is solved numerically for a double‐barrier, quantum‐well resonant tunnelling structure (RTS), such as modelling a semiconductor heterostructure, by the fast Fourier transform method. Results are shown for a resonance tunnelling structure with barriers doped by a negative δ‐function potential (δ‐potential) which broadens the widths of the resonances and in turn decrease the electron dwell times. The strength of the δ‐function can be such that it may form bound states in the barrier regions, but the states bound to the δ‐potential are very shallow. For this study, the δ‐potentials are replaced by equivalent barriers of different heights and widths. It is found that for a certain strength of the δ‐potential or parametric value of a barrier with an equivalent effect in the RTS, there are three resonance states very close together. The squares of the wave functions trapped in the well region for the states oscillate in time for a broad wave packet in k‐space, whereas the wave function trapped in the whole structure decays exponentially. The oscillating part resembles quantum beats.
Spin‐Glass Behavior in Semiconducting Single Crystalline ZnMn2As2
Authors: Laue I. , Vanacken J. , Nateprov A. N. , Herlach F. , von Ortenberg M. , Arushanov E. K.
Published: July 2007

The dc magnetization of single crystalline ZnMn2As2 is studied using an rf‐SQUID. It is found that the crystals are anisotropic, show a ferromagnetic transition around T = 310 K, a helical magnetic phase below T = 110 K, and there is evidence of a strong spin‐glass behavior below T = 33 K. The spin‐glass phase is studied from zero‐field cooled (ZFC) and rémanent magnetization experiments. An irreversibility line (de Almeida‐Thouless line) is clearly observed for both principal orientations of the crystal and a comparison is made between the magnetic moment relaxation measured using the ZFC and the rémanent methods.
Cherenkov Effect in the Context of Scanning Tunneling Microscopy
Authors: Smolyaninov I. I. , Keller O.
Published: July 2007

The intensity of the light emission from the STM tunneling junction between two metals is shown to depend exponentially on the tunneling distance. Assuming the exponential decay constant to be equal to the mean wave vector of the surface plasmons excited by the tunneling electrons, the plasmon phase velocity is estimated to be two times smaller than the Fermi velocity of the electrons. A new theoretical description of the light emission phenomenon based on a Cherenkov‐like resonant interaction between the tunneling electrons and the surface plasmons is developed.
Time‐Resolved Luminescence of Exciton‐Polaritons in Solid Xenon
Authors: Varding D. , Reimand I. , Zimmerer G.
Published: July 2007

The decay of excitons in solid Xe is investigated with time and spectrally resolved luminescence as a function of temperature and photon energy of excitation. The luminescence of free excitons exceeds the self‐trapped exciton luminescence by a factor of 50 (peak‐to‐peak). The FE‐decay curves yield a non‐exponential behaviour. They can be reproduced with Monte‐Carlo simulations of the exciton‐polariton transport to the sample/vacuum interface, taking into account phonon scattering and trapping. A new upper limit for the intrinsic self‐trapping rate in the lower 107 s−1 range and a surprisingly large experimental value for the scattering length ( ≈ 100 nm at T = 5 K) are deduced. It is indispensable to discuss the decay of excitons in solid Xe in terms of the exciton‐polariton model.
Isobaric Specific Heat and Thermal Expansion of Solids in the Debye Approximation
Authors: Askerov B. M. , Cankurtaran M.
Published: July 2007

A theoretical study in the Debye approximation is made of the isobaric specific heat (CP) and thermal expansion of solids with a Bravais lattice. Analytical expressions are obtained for the variations of CP and the linear thermal expansion coefficient (xp) with temperature. The temperature dependence of CP is determined by two characteristic parameters of the solid: the Debye temperature θand the Gruneisen parameter yc. It is shown that the difference CPCv between the calculated isobaric and isochoric specific heat capacities is very small at low temperatures (T≪θ) and increases markedly at higher temperatures. In the range T≫θ, CP is almost independent of temperature and is.determined solely by γG. This provides a technique to estimate the Gruneisen parameter γG from the measurements of isobaric specific heat at high temperatures. The results obtained for αP, in the low‐ and high‐temperature limits, are in agreement with those in literature.
Electrical Piezoeffect in Semiconducting BiSb Alloys due to Anisotropy of Electron Mobility
Authors: Tolutis R.
Published: July 2007

The strong electrical piezoeffect caused by the deformation induced anisotropy of electron mobility in Bi1−xSbx semiconducting samples is described. Attention is drawn to the piezoeffect voltage, high in undoped samples, its nonsymmetric change under tensile and compressive deformation, and its sign inversion at small magnetic fields. All these effects are explained in terms of electron intervalley repopulation and scattering. Possible applications are discussed.
Two‐Photon Absorption in an Indirect‐Gap Semiconductor Quantum Well System. II. Excitonic Transitions
Authors: Hassan A. R.
Published: July 2007

A theory of phonon‐assisted two‐photon exciton transitions in indirect‐band‐gap semiconductor layered quantum wells (QW) and quantum well wires (QWW) is developed. The expressions for the two‐photon absorption coefficients in one‐dimensional (1D), α,2D, α, and (bulk), α, respectively, are calculated. The spectral dependence of these expressions, the vicinity of the band edge, are found to obey the law (2ℏω ± ℏΩ – EG + E)β, where ℏω (ℏΩ) is the photon (phonon) energy, EG the effective indirect gap, and Ek the exciton binding energy. The values of β vary from – ½ up to ½ depending on the dimension of the system and the type of the coupling matrix element involved in each transition process. Before the edge, the final exciton states are of s‐ or p‐symmetry according to the photon polarizations with respect to the confinement directions in the QWs and to the selection rules allowed by the momentum matrix elements. A numerical estimation for the case Si0.5Ge0.5 shows that α for both photon polarizations (parallel and perpendicular to the confinement direction of the QW's) is enhanced over the values of α and α (allowed and forbidden transitions). Furthermore α is also enhanced over the α values of bulk materials. This behaviour of the αex's is interpreted as due to (i) the additional confinement of the carriers which occur going from 3D → 2D → 1D systems, (ii) the photon polarization configurations with respect to the confinement directions, and (iii) the coupling matrix elements.