bluuebunny/crossref_metadata_2025 huggingface dataset:
Description of the Mechanical Properties of Viscoelastic Materials Using a Modified Anelastic Element
Authors: Hermida Élida B.
Published: July 2007

Quasi‐static and dynamical tests are employed to measure the modulus or the compliance of a material as a function of time or frequency, and to determine the respective distribution function in the case of a linear viscoelastic medium. The evolution of the mechanical properties, and consequently the distribution functions, are usually described by empirical expressions which cannot always be interpreted according to a physical model. Furthermore, as a rule these empirical distributions do not lead to closed expressions for all the viscoelastic functions. The mechanical properties of viscoelastic materials (amorphous polymers, metallic glasses, etc.) are described using a modified anelastic element (MAE). This modified element is analogous to the standard anelastic element, having a single characteristic time, τ, that is not a constant but a function of time or frequency. On considering a particular functional dependence of τ, it is demonstrated how several empirical viscoelastic functions are approximations of the mechanical properties of the MAE. Moreover, this functional dependence is related to the log‐normal distribution the statistical and physical meanings of which are discussed in detail.
Effects of Electron(Hole)–SO‐Phonon Coupling on the Ground Exciton State in Quantum Wires
Authors: Sheng Wei‐Dong , Gu Shi‐Wei
Published: July 2007

Taking account of electron(hole)–SO‐phonon coupling, the ground exciton state in free‐standing quantum‐well wires with circular cross‐section is studied in detail. Two unitary transformations are carried out, the SO‐phonon‐induced potential in ϱ‐direction and the SO‐phonon‐induced interaction between an electron and a hole in z‐direction as well as the effective Hamiltonian of the exciton–SO‐phonon systems are obtained. The ground exciton state binding energy is calculated from a trial wave function separable in spatial coordinates. An unexpected result is obtained: although the electron (hole)–SO‐phonon coupling is very strong in quantum wires, its influence on the exciton binding energy is not so notable as that in 3D or 2D exciton‐phonon systems.
Quadratic Crystal‐Field Effects on the J = 15/2 Manifold in Cubic Symmetry
Authors: Kornienko A. A. , Kaminskii A. A. , Dunina E. B.
Published: July 2007

The effects of electron correlation resulting from one‐particle operators in third order are investigated. These effects are presented by an effective Hamiltonian having the form of a “quadratic crystal‐field”. The fitting to the Stark structure of the J = 15/2 manifold by the “quadratic crystal‐field” Hamiltonian gives good agreement with experimental data. The “quadratic crystal‐field” Hamiltonian may be useful for the analysis of the energy‐level scheme of Pr3+ ions in LiYF4 crystal, where there are problems in describing the higher manifolds by an effective one‐electron Hamiltonian.
Practicable Method for Estimating Thermal Depths from Phonon‐Broadened Photoexcitation Cross‐Section Bands. III. Generalization for Charged Centres
Authors: Pässler R.
Published: July 2007

The zero‐phonon threshold behaviour of thermally broadened absorption cross‐sections σ(hv, T) is examined for deep traps retaining a non‐zero net charge after the carrier excitation processes in consideration. The influence of a corresponding attractive or repulsive Coulomb potential on threshold properties of these absorption cross‐sections is described within the framework of conventional Sommerfeld factors. Concerning the characteristic vertex positions of transformed excitation curves ϱ(hν, T) ≡ exp (‐ hν/2kT) σ(hν, T), we attain in simple ways to analytical expressions for upper and lower bounds representing the limiting regimes of extremely strong and vanishing electron‐phonon coupling. Specializations for alternative charge‐state regimes give average vertex‐position versus thermal‐depth shifts of (½ + f) 2kT for attraction and \documentclass{article}\pagestyle{empty}\begin{document}$\(\sqrt[3]{{\pi ^2 R/2kT}} + \frac{5}{{12}} + \frac{2}{3}f) $\end{document} 2kT for repulsion (where f = 0 or 1 in cases of allowed or forbidden transition and R is the relevant Coulomb‐barrier Rydberg energy). The absorption threshold behaviours of hole excitation curves due to a series of second donor levels in silicon can be well understood under the assumption of allowed transitions affected by a repulsiue barrier whose actual strength is determined just by the light hole band (R → 15 meV). From experimental σp(hν, T) curves given by Grimmeiss and Skarstam we detect hole ionization energies Jp(T → 0) of about 553 meV for Si : S and 572 meV for Si : Se. Assessing the experimental σp(hν, 77 K) curves given by Tilly et al. we come to hole ionization energies Jp (77 K) of about 251 meV in case of Si: Ti and 356 meV in case of Si: V. All these semiempirical Jp values are found to be in reasonable agreement with other available data.
Electric Field Gradient Calculations in Hexagonal Tungsten Bronze Type Fe3+ Fluorides: (H2O)0.33FeF3 and Anhydrous FeF3
Authors: Leduje D. , Teillet J.
Published: July 2007

The polarisahle point‐charge model is used to calculate the electric field gradient (EFG) tensor at the Fe site in the two compounds (H2O)0.33FeF3 and anhydrous FeF3. The results are consistent with experimental Mösshauer data for a fluorine polarizability of 8 × 10−4nm3. Calculations on (H2O)0.33 FeF3 provide two very close quadrupole splittings (ΔEQ = 0.62 and 0.65 mm s−1) whereas calculations on anhydrous FeF3 provide only one quadrupole splitting (ΔEQ = −0.38 mm s −1).
A Novel Mechanism for the Kossel Effect Due to Coherent X‐Ray Scattering in Periodic Amorphous Multilayers
Authors: Jianc Xiaoming , Metzger T. H. , Peisl J.
Published: July 2007

A new mechanism for the the excitation of the Kossel effect is observed in periodic amorphous multilayers, where the X‐rays, scattered coherntly from atoms in the amorphous state, act as the sources within the one‐dimensional periodic multilayer. The Kossel effect, which is well described by the distorted‐wave Born approximation, is manifested as intensity modulations whenever the exit angle of the scattered beam equals any Bragg angle of the multilayer diffraction. While it is initially surprising for an amorphous sample, this Kossel effect must be treated by dynamical theory and will only occur for sharp interfaces between W and C sublayers.
Velocity of Sound and Resistivity Measurements on Amorphous FeCrB, FeMnB, and FeNiB during Structural Relaxation
Authors: Riontino G. , Koebrugge G. W. , Baricco M. , Sietsma J.
Published: July 2007

The velocity of sound and the electrical resistivity of amorphous Fe75Cr5B20, Fe75Mn5B20, and Fe75Ni5B20, are measured during isothermal heat treatments. It is shown that different types of measurements are indeed necessary in order to reach sensible conclusions on relaxation mechanisms, since one measurement only is prone to multiple interpretation. Without reference to any specific model, the present study sheds some light on the nature of the atomic rearrangements involved in the structural relaxation processes, combining the results of two experimental techniques and three related compositions.
Computer Simulation of the 36.87° [001] {310} Symmetrical Tilt Grain Boundary Structure in B.C.C. Metals
Authors: Erhart J. , Trubelík I.
Published: July 2007

The stable atomic arrangements of the 36.87° [001] {310} symmetrical tilt grain boundary structure in b.c.c. metals are calculated using the method of molecular statics. Four different atomic structures, which differ in the energy, rigid body displacement of the grains, and the shift of the boundary plane, are found.
Vibrational Properties of Pd1−c Fec Disordered Binary Alloys
Authors: Upadhyaya S. C. , Prakash D. , Sharma D. K. , Shyam R. , Upadhyaya J. C.
Published: July 2007

The transition metal model potential of Animalu is applied to study the lattice dynamics of two f.c.c disordered alloys of Pd and Fe, namely Pd0.96Fe0.04 and Pd0.90Fe0.10 First the model potential is uscd to compute the radial and tangential force constants of Pd and Fe for the two alloys and also those of pure Pd up to ten sets of nearest neighbours. The concentration average of these force constants is used to determine the force constants of the two disordered alloys. Next, the dynamical matrix is constructed and the secular equation is solved to calculate the phonon dispersion curves and elastic constants of pure Pd and Pd0.96Fe0.04 and Pd0.90Fe0.10 alloys. In all the cases a reasonably good agreement is found between the computed and experimental results, when three‐body forces are incorporated in the interaction system. Phonon density of states and the temperature dependence of specific heat and Debye temperature of the two alloy systems are also computed and presented.
Electronic Structure of Aluminum Surfaces. Results from Empirical Tight‐Binding Scattering Theory
Authors: Würde K. , Mazur A. , Pollmann J.
Published: July 2007

The results of an empirical tight‐binding study of the electronic properties of Al surfaces are reported. The underlying bulk crystal is described by a realistic first‐nearest‐neighbour empirical tight‐binding Hamiltonian which includes s‐, p‐, and d‐orbitals. The electronic structure of the (OO1), (110), and (111) surfaces is calculated for semi‐infinite systems employing the scattering theoretical method. Our results are compared with the results of other calculations and with experimental data. For a few representative cases we analyse the origin and nature as well as the spatial localization of the surface states.
Core Hole Effect on the XAS Si K Edge Shape in α‐Quartz
Authors: Jollet F. , Noguera C.
Published: July 2007

The role of the core hole effect on the Si K X‐ray absorption spectrum of α‐quartz is established thanks to two electronic structure calculations: 1. a self‐consistent band structure approach at ambient pressure and under hydrostatic pressure, that accounts for the gap and the valence band shape, and that provides the empty density of states of α‐quartz, is shown to be unable to reproduce the experimental Si K edge shape; 2. on the opposite, a self‐consistent embedded cluster calculation, which allows to include the effect of thc core hole yields a local p density of states on an excited silicon atom which compares satisfactorily with the experimental spectrum.
Magnetic Susceptibility of Copper Oxide Based Antiferrornagnets in an Anisotropic Heisenberg Model
Authors: Singh R. P. , Tao Z. C. , Singh M.
Published: July 2007

The RPA Green's function theory is extended to study the magnetic properties of copper oxide based antiferromagnets in an anisotropic Heisenberg model. It is shown rather generally by the use of spectral representation that the magnetic properties of copper oxide based antiferromagnets have a crossover from 3D to quasi‐2D behavior near the temperature (≈ 2J∥ √2r/kB). Here J∥ is the intraplanar exchange coupling strength and r the ratio of interplanar to intraplanar coupling strengths. The magnetic susceptibility as a function of temperature is calculated numerically. Our numerical results are compared with experimental measurements of the magnetic susceptibility on La2CuO4_y compounds. It is found that the RPA magnetic susceptibility agrees reasonably well with experiments at high temperatures, but misses totally the peak near the temperature (≈2J∥/kB).
A Contribution to the Mean‐Field Analysis of Amorphous Magnets
Authors: Millev Y. , Fähnle M.
Published: July 2007

A method is outlined to obtain explicit analytical solutions for Handrich's mean‐field model of amorphous ferromagnets for the general spin quantum number S and the structural disorder parameter δ. The explicit solutions are given for S = 1/2 and δ = 1/3 and 1/2.
The Magneto‐Optical Kerr Effect in Co‐Based Multilayered Structures
Authors: Zhou Shi‐Ming , Chen Liang‐Yao , Su Yi , Qian You‐Hua
Published: July 2007

In this paper calculated magneto‐optical Kerr rotation spectra of Co/Pd, Co/Pt, and Co/Cu multilayers are presented. For Co/Pd and Co/Pt multilayers with a top Co layer the size of Kerr rotation |θ|k increases with increasing modulation wavelength. For Co/Cu multilayers with a top Co layer |θ|k increases with modulation wavelength increasing to 40 nm and then decreases with the modulation wavelength further increasing to 60 nm. For all these multilayers with a top non‐magnetic layer |θ|k decreases with increasing modulation wavelength. The optical constant effect of the non‐magnetic sublayer is discussed.
A Spatial Characteristic Scheme for Multigroup Discrete Ordinates Electron Energy Deposition in Two Dimensions
Authors: Datta R. P. , Ray A. K.
Published: July 2007

Energy deposition calculations are performed due to an incident source of electrons in rectangular slab geometry using the method of discrete ordinates for directions and the multigroup treatment in energy. Using the restricted stopping power formalism to distinguish between large energy loss collisions (catastrophic) and small energy loss collisions (continuous), coupled with a second‐order differencing scheme in energy, an improved model of electron energy loss is incorporated in our computational model. Results are presented for isotropic and normal incident sources and compared with available results.
Reversibility of a Phase Transition in KDP under Uniaxial Stress
Authors: Melo F. E. A. , Moreira S. G. C. , Filho J. Mendes , Moreira J. E.
Published: July 2007

Raman spectra of KDP, taken at a temperature near the paraelectric‐ferroelectric transition and submitted to a uniaxial stress show two new phase transitions. The change of symmetry of the ion units due to these transitions is related to the spectroscopic results. The reversibility of the transitions when temperature and pressure are cycled around the transition lines is discussed.
Magnetic Properties of a Transverse Spin‐1 Ising Model with Longitudinal Crystal Field Interactions
Authors: Benyoussef A. , Ez‐Zahraouy H.
Published: July 2007

The three‐dimensional spin‐1 Ising model with crystal field interactions exhibits tricritical behaviour. Using an expansion technique for cluster identities of spin‐1 localized spin systems, the influence of transverse magnetic field on this behaviour is studied. Temperature‐crystal field phase diagrams are investigated for different values of transverse field. The longitudinal and transverse magnetizations, as well as the quadrupolar moments are calculated. General formulas applicable to structures with arbitrary coordination number N, are given.
Far Infrared Reflection Spectra of Sillenite Crystals and Their Solid Solutions
Authors: Senulienè D. , Babonas G.
Published: July 2007

The infrared reflection spectra of sillenite type crystals of Bi12MO20 (M :Si, Ge, Ti, Fe) are measured in the whole range of the first‐order phonon frequencies and analyzed using the Kramers‐Kronig relations. Two‐mode behavior is determined for several characteristic modes of Bi12Si1−xTixO20 and Bi12Ge1−xTixO20 solid solutions. The experimental data are discussed in the model of vibrating structural units. The vibration frequencies and the force constants for tetrahedra MO4 are calculated. The calculation results are in good agreement with experimental data for the modes with two‐mode behavior.
Crystal Structure and Phase Transitions in the A3B2X9 Family of Crystals
Authors: Tomaszewski P. E.
Published: July 2007

A schematic representation of several kinds of crystal structure motives in A3B2X9 compounds is presented. The search for regularities in the occurrence of each motive with respect to the chemical composition of about 200 phases is described. The phase transitions observed in several crystals from this family are also discussed. The presented data on possible symmetry changes could be used for further studies of phase transitions.
A Simple Analysis of the Magnetic Susceptibilities in Quantum Dots of Optoelectronic Materials in the Presence of a Parallel Magnetic Field
Authors: Ghatak K. P. , Bhattacharyya D.
Published: July 2007

An attempt is made to study the dia‐ and paramagnetic susceptibilities of electrons in quantum dots of optoelectronic materials in the presence of a parallel magnetic field, on the basis of a newly formulated electron dispersion law. It is found, taking n‐Hg1−xCdxTe and In1−xGaxAsyP1−y lattice‐matched InP as examples that both susceptibilities increase with increasing electron concentration in oscillatory manners and increase monotonically with decreasing film thickness in the electric quantum limit. In addition, the numerical values of the susceptibilities in quaternary materials are greater than in the ternary compounds.
The Surface Barrier of a Uniaxial Anisotropic Superconductor
Authors: Saif A. G.
Published: July 2007

The role of a transport current on the annihilation of the surface barrier for a high‐temperature type‐II superconducting infinite slab of arbitrary thickness as well as for a high‐temperature type‐II superconducting cylinder are investigated. The London penetrating field, the vortex fields, and the Gibbs potential are calculated. The barrier depends on the external field strength, the value of the transport current flowing through the sample, and the orientation of the external field. Agreement with previous results in some cases is found.
Silver Ion Conducting Borate Glass. Evidence of Ion Association from Temperature Dependent Mobility, Conductivity, and IR Spectral Studies
Authors: Shaju K. M. , Chandra S.
Published: July 2007

The temperature dependence of ionic mobility for a silver ion conducting borate glass with composition 55.5 AgI22.25 Ag2O22.25 B2O3 (in mol%) is reported along with conductivity. Subsequently the value of mobile carriers n is calculated. The value of n is found to decrease with increase in temperature. Two types of ion association mechanisms viz., (i) self association and (ii) network association are proposed to explain the results. The proposed ion associations are checked by optical microscopy and temperature dependent IR spectral studies.
Thermal Expansion of Isotopically Substituted Alkali Hydrides
Authors: Tyutyunnik V. I.
Published: July 2007

The effect of both temperature and isotope substitution on the distance between ions in alkali hydride crystals is investigated by means of the rigid‐ion model with only nearest‐neighbour interactions. It is shown that the thermal expansion may be described as a function of the Coulomb potential parameters and the cation‐anion reduced mass. For the first time, the thermal expansion data are calculated for Na, K, Rb, and Cs hydrides and deuterides. The calculation results are in agreement with experimental values.
Strain‐Induced Interaction of Substitutional Atoms in Cubic Metals
Authors: Blanter M. S.
Published: July 2007

The energies of strain‐induced (elastic) interaction of pairs of substitutional atoms and host atom displacements around a substitutional atom are calculated for Al, Ag, Au, Cu, Ni, Pd, Cr, αFe, Mo, Nb, Ta, V, and W taking into account the discrete atomic structure of the host lattice. The elastic constants, Born‐von Karman constants of the host lattice, and coefficients of the concentration expansion of the solid solution lattice due to substitutional atoms are the numerical parameters used. A computer calculation is carried out in the general form appropriate for any substitutional atoms in these metals. The energies of strain‐induced interaction of substitutional atoms are of the same order as the “chemical” interaction energy and should be taken into account during computer simulation of structure and properties of the substitutional solid solutions.
Optical Properties of Wide‐Gap II‐VI ZnTe Epilayers
Authors: Averous M. , Abounadi A. , Aulombard R. L. , Bouchara D. , Briot N. , Briot O. , Calas J. , Cloitre T. , Gil B.
Published: July 2007

The optical properties of ZnTe epilayers grown by low‐pressure metal organic vapour phase epitaxy on GaAs and GaSb substrates are studied. The layers are grown by using the halide‐free triethylamine dimethylzinc adduct and di‐isopropyl telluride as zinc and tellurium precursors, respectively. A detailed analysis of the residual strain is offered as a function of layer thickness and substrate nature via reflectivity measurements performed at pumped liquid helium temperature. This is completed by an extensive analysis of near‐band‐edge photoluminescence spectra in order to discriminate the contribution of residual impurities. Using these precursors ZnTe layers with extremely low contamination rates are obtained.
Impurity States and Optical Transitions in Uniaxially Deformed Narrow‐Gap Semiconductors
Authors: Strikha M. V. , Vasko F. T.
Published: July 2007

The effect of uniaxial deformation along cubic axis on the states of point defects in narrow‐gap semiconductors is studied. The energy dependence of the splitting of deep h‐states into two doubly degenerate h1 and h2 states on the deformation value and the semiconductor characteristics is calculated. Changes of optical transitions from deep 1‐c and h‐centres with deformation are also examined. It is shown, that the absorption coefficient in this case is essentially anisotropic and its spectral dependences essentially differ from those in the case without deformation.
Hyperfine Effects in X‐Ray Emission Spectra of Transition Elements in Antiferromagnets
Authors: Barinskii R. L. , Kulikova I. M.
Published: July 2007

According to experimental investigations of the width and energy shift of X‐ray Kα1, Lα1 lines Ti, V, Nb in antiferromagnetic compounds of transition (Fe, Mn, Cr) and rare‐earth elements (Ln) it is shown that the spin density on diamagnetic ions, Ti, V, Nb is due to the superexchange interaction with paramagnetic ions in the second coordination sphere via oxygen atoms. The magnitude of the spin density is a function of the number and total spin of paramagnetic ions and of the J component (Sj) of total spin (S) in the rare‐earth series in compounds LnVO4 and Ln(Ti, Nb)2O6. It is shown that the spin density on the rare‐earth ions is greatly influenced by the decrease in radial extension of the 4f shell for Ce to Sm.
Acoustohelicon Amplification in a Piezoelectric Semiconducting Plasma
Authors: Misra K. D. , Pandey M. K.
Published: July 2007

Acoustohelicon amplification in semiconducting plasmas having piezoelectric or deformation potential coupling or both (viz., n‐InSb) are investigated using the kinetic approach. The dispersion relation for phonon‐ helicon interaction is derived in slow wave approximation. In case of a convective instability the amplification occurs if the drift velocity exceeds the velocity of sound (i.e. if the electric field is greater than 102 Vm−1) while in case of an absolute instability amplification is observed if the drift velocity is smaller than the velocity of sound (electric field less than 102 Vm−1). At higher electric fields (>4.27 × 104 Vm−1) the amplification coefficient for acoustohelicon waves, obtained by the kinetic approach, shows a maximum and then starts attenuating, contrary to the hydrodynamic approach where it is always monotonously increasing. The dependence of the amplification coefficient on various plasma parameters is studied in detail.
Monte‐Carlo Simulation on Random Magnetic Mixture with Competing Anisotropy. Oblique Antiferromagnetism of CsMn1−xCoxCl3 · 2 H2O
Authors: Kato T.
Published: July 2007

A Monte‐Carlo simulation for a simplified model for CsMn1−xCoxCl3 · 2H2O which is a typical magnetic mixture with competing anisotropies is performed. From calculations for the magnetic moment of each atom and the magnetic susceptibilities, it is found that the characteristic features of the phase diagram are reproduced by the present model. That is, besides the CsMnCl3 · 2 H2O‐type antiferromagnetic phase and the CsCoCl3 · 2 H2O‐type one, an intermediate phase exists in between the two phases. In the intermediate concentration region two successive second‐order phase transitions occur with increasing temperature. The spin structure of the intermediate phase is consistent with the NMR result of Kubo et al., that is, there exist two perpendicular antiferromagnetic domains linked over the whole crystal, which are separated by domain walls.
Ion Beam Induced Luminescence of Alkali Halide Crystals
Authors: Suchańska M. , Bazhin A. I. , Konopelko E. I.
Published: July 2007

New experimental results bearing on luminescence induced by ion beam on pure and doped alkali halide crystals are reviewed. In the optical spectra besides activator luminescence bands new intrinsic luminescence bands are observed. The mechanism of the recombination of electrons from the conduction band with V2 hole centre is discussed.
Study of New Alkylammonium Hexachlorostannates and Their Phase Transitions by Differential Scanning Calorimetry and Infrared Spectroscopy
Authors: Čermák M. , Fuith A. , Vaněk P. , Silha J. , Málková Z.
Published: July 2007

Fourteen new structural phase transitions are detected in layer‐type monoalkylammonium hexachloro‐stannates (CnH2n+1NH3)2SnCl6 (n = 2 to 8) by means of differential scanning calorimetry. The basic thermodynamic data are determined for the transitions. The infrared spectra of the compounds are measured in the range of molecular vibrations (500 to 4000 cm−1) at room temperature and in dependence on temperature (77 to 298 K) by the method of nujol mull.
On the Mean Square Relative Atomic Displacements in Strongly Anharmonic Crystals
Authors: Zubov V. I. , Pascual M. F. , Rabelo J. N. Teixeira , de Faria A. C.
Published: July 2007

The correlative method of unsymmetrized self‐consistent field is used to study the mean square relative atomic displacements in crystals taking into account the strong anharmonicity and interatomic correlations. General expressions for these quantities in arbitrary crystal lattices are obtained. As an illustration, the mean square relative displacements between nearest, second, and third neighbours in a strongly anharmonic linear chain are calculated. The results are compared with those obtained with more rough approximations (harmonic, quasi‐harmonic, etc.). The influence of anharmonic effects is discussed.
Effect of Sb Additives on Electron Mobility in Amorphous Selenium
Authors: Mikla V. I. , Rubish V. M.
Published: July 2007

Time‐of‐flight drift mobility experiments are carried out on amorphous SbxSe100−x to investigate the charge transport mechanism in these films. Electron drift mobility‐temperature data indicate that electron transport in a‐SbxSe100−x alloys is controlled by a set of shallow traps at 0.33 eV below the conduction band edge. Although the trap depth remains unchanged with increasing Sb content, the effective drift mobilities of electrons decrease with the Sb content in SbxSe100−x amorphous films.
Far‐Infrared ATR from Surface Exciton Polaritons
Authors: Albuquerque E. L. , Fulco P.
Published: July 2007

The surface exciton polariton spectrum in superlattices made up of two alternating media A and B is reported, where one of the layers shows spatial dispersion in its frequency dependent dielectric function. A theoretical approach based on the effective medium theory to determine the surface exciton polariton dispersion relation is used. Also the attenuated total reflectivity (ATR) is calculated to probe the surface exciton polariton modes.
Magnetoresistance and Hall Effect of Some Magnetically Ordered CrxMn1−xSb Single Crystals
Authors: Kohnke H. J. , Dunkel H. , Schünemann J.‐W. , Bärner K. , Buzhinsky S.
Published: July 2007

The anomalous Hall effect ϱH and the magnetoresistance Δϱ/ϱ of CrxMn1−xSb single crystals with x = 0.4 are measured for 4.2 K < T < 300 K, 0 < H < 7T. The Hall effect appears to be determined by anisotropic (magnon) spin scattering while the (complex) magnetoresistance appears to be also spin‐dependent but is described using at least two different spin scattering contributions.
Infrared Properties of Metallic and Insulating La1−zXzCu1−xMnxO3−δ Compounds (X = Sr, Ba)
Authors: Tang Yi , Shaltout I. , Braunstein R. , Helmolt R. V. , Haupt L. , Bärner K.
Published: July 2007

The mixed crystal series La1−zXzCu1−xMnxO3‐δ with X = Sr, Ba include high‐Tc superconductors, ferromagnetic (double exchange coupled) metals as well as spin‐glass‐like semiconductors, and therefore are selected for comparative studies of their infrared spectra. Optical conductivity is obtained between 150 and 4000cm−1 through Kramers‐Kronig analysis of infrared and optical reflectivity data. The information on energy dependent interactions between electrons and other quasiparticles or elementary excitations are provided through the analysis involving extended Drude and polaron transport models. Distinctive frequency dependent electron‐phonon coupling is found in all cases which manifests itself through the appearance of different current carrying quasi‐particles. Also, two or three prominent optical phonons are observed which are not completely screened even in the normal state of the high‐Tc superconductors and do not change their positions appreciably within each series. Line narrowing is suggested to occur when the magnetic long‐range order is switched on.
X‐ray study of diffuse scattering in Ni–20 at% Cr
Authors: Schönfeld B. , Ice G. E. , Sparks C. J. , Haubold H.‐G. , Schweika W. , Shaffer L. B.
Published: July 2007

A single crystal of Ni–20 at% Cr aged at 744 K for 480 h, similar to the case of a previous neutron scattering experiment, is investigated by diffuse X‐ray scattering using X‐rays at three different wavelengths, λ = 0.2075 nm (5975 eV), 0.1489 nm (8327.2 eV), and 0.1531 nm (8097 eV). The short‐range order and displacement scattering are separated based on the 3λ method recently introduced as well as on the Georgopoulos‐Cohen method. Both evaluation schemes yield similar Warren‐Cowley short‐range order parameters with less agreement in the individual static atomic displacements. The nearest‐neighbor displacement obtained by the 3A method for NiCr pairs, is consistent with a simple phenomenological model in which the Cr atoms expand the Ni lattice in a short‐range ordered alloy. Effective pair interactions calculated from model crystals using the inverse Monte Carlo method are found to be larger than previously deduced from neutron scattering experiments. If these pair interactions are used in Monte Carlo simulations to calculate the transition temperatureT0of Ni2Cr,T0is underestimated compared with direct experimental findings.
A model‐free approach to eliminate autocorrelation when testing for process capability
Authors: Vännman Kerstin , Kulahci Murat
Published: July 2007

There is an increasing use of on‐line data acquisition systems in industry. This usually leads to autocorrelated data and implies that the assumption of independent observations has to be re‐examined. Most decision procedures for capability analysis assume independent data. In this article we present a new way of performing capability analysis when data are autocorrelated. This method is based on what can be called the ‘iterative skipping’ strategy. In that, by skipping a pre‐determined number of observations, e.g. considering every fifth observation, the data set is divided into subsamples for which the independence assumption may be valid. For each such subsample of the data we estimate a capability index. Then traditional tests, assuming independence, can be performed based on each estimated
capability index from the subsamples. By combining the information from each test statistic based on the subsamples in a suitable way, a new and efficient decision procedure is obtained. We discuss different ways of combining the information from these individual tests. A main appeal of our proposed method is that no time‐series model is needed. Copyright © 2007 John Wiley & Sons, Ltd.
Quantitative Structure–Retention Relationship Study of a Variety of Compounds in Reversed‐Phase Liquid Chromatography: A PLS‐MLR‐STANN Approach
Authors: Jalali‐Heravi M. , Garkani‐Nejad Z. , Kyani A.
Published: July 2007

A quantitative structure–retention relationships model has been developed to study the retention behavior of 87 aliphatic and aromatic compounds in Reversed‐Phase Liquid Chromatography (RPLC) on five bonded‐phase columns differing in silanol group acidity. Six numerical descriptors of Molecular Mass (M), partial charge of the most negative atom (NPCH), partial charge of the most positive hydrogen (PCHH), van der Waals volume (VOLUME), Dipole Moment (DIMO), and Highest Occupied Molecular Orbital (HOMO) have been calculated for each compound. A separate Multiple Linear Regression (MLR) model has been developed using the six descriptors for each column. Partial Least Square (PLS) combined with MLR mean effects has been used for the mechanism interpretation. The descriptors of M, HOMO, and DIMO showed the largest PLS regression coefficients. It is found in the present work that solute size, n–π donor–acceptor and dipole–dipole interactions play a major role in the RPLC retention mechanism. Also, a self‐training artificial neural network was developed using the six descriptors as its inputs. The results obtained using this model are in good agreement with the experimental results of all five columns. Superiority of this model with low standard errors and high correlation coefficients for all five stationary phases reveals nonlinear characteristics of retention in RPLC. Successful application of the six descriptors in modeling of the retention behavior of different data sets using gas chromatography (previous work) and RPLC (present work) with different stationary phases reveals the robustness of the parameters.
QSAR Studies and Molecular Design of Phenanthrene‐based Tylophorine Derivatives with Anticancer Activity
Authors: Liao Si‐Yan , Chen Jin‐Can , Qian Li , Shen Yong , Zheng Kang‐Cheng
Published: July 2007

The Quantitative Structure–Activity Relationship (QSAR) of a series of novel phenanthrene‐based tylophorine derivatives with anticancer activity has been studied by using the Density Functional Theory (DFT), Molecular Mechanics (MM2), and statistical methods. The established model shows not only significant statistical quality, but also predictive ability, with the square of adjusted correlation coefficient (R2A=0.813) and the square of the cross‐validation coefficient (q2=0.748). We find that the anticancer activity expressed as pIC50, which is defined as the negative value of the logarithm of necessary molar concentration of this series of compounds to cause 50% growth inhibition against the human A549 lung cancer cell line, closely relates with the energy (EHOMO) of the Highest Occupied Molecular Orbital (HOMO), the net charge of the terminal H atom of substituent R2 ($\rm{ Q_{{\rm{HR}}_{\rm{2}} } }$), the hydrophobic coefficient of substituent R2 (log $\rm{ P_{{\rm{R}}_{\rm{2}} } }$), and the net charges of the first atom of substituent R1 ($\rm{ Q_{{\rm{FR}}_{\rm{1}} } }$). The same model was further applied to predict the pIC50 for six recently reported congeneric compounds as external test set, and the predicted pIC50 values are close to the experimental ones, and thus it further confirms that this QSAR model has high predictive ability. The theoretical results can offer some useful references for understanding the action mechanism and designing new compounds with anticancer activity. Based on this QSAR equation, ten new compounds with higher anticancer activity have been theoretically designed and are expecting the experimental confirmation.
Eleven theses of general systems theory (GST)
Authors: Waelchli Fred
Published: July 2007

This paper chronicles an effort to distill and order (for purposes of discussion and elaboration) frequently mentioned and significant ideas encountered in the literature of General Systems theory (GST). The product is a set of eleven theses, representing the author's selection and collation of seminal and recurrent GST themes. The author argues that attention to theory could aid the effort to develop practical applications of systems thinking. (Remember that a thesis is a statement or assertion, offered originally without proof, as the basis for an argument, discussion, or empirical test.)
“General systems theory, cultural change, and a human science foundation for planning and design”
Authors: Motloch John L. , Woodfin Thomas
Published: July 2007

Abstract — This paper integrates the knowledge‐base concerning systems, their behavior and structure, and the management of complex systems ‐ to provide insight to physical planning and design in equilibrium and rapidly‐changing conditions. It contributes to the redefinition of the professions of physical planning and design; and the establishment of their human science foundations.
Gordon pask — a skeleton for an unofficial biography
Authors: Glanville Ranulph
Published: July 2007

Gordon Pask was born on June 28th, 1928, the son of Percy (who imported and exported fruits) and his wife Mary. He had two elder brothers, Alfred (a Methodist minister) and Edgar (who was a professor of anaesthesia whose studies of hypothermia in pilots surviving “prangs” in World War II contributed enormously, not just then, but since to the survival of burns patients and those who survive air crashes). He was educated at Rydal School in North Wales, and then obtained Diplomas in Geology and Mining Engineering from Bangor and Liverpool Technical Colleges. In 1952 he gained his BA from Downing College, Cambridge, with his MA following in 1954. He has a Ph D from University College, University of London (in psychology), and was awarded the first D Sc, in Cybernetics, by the Open University, in 1974.

He married Elizabeth Poole, in 1956, and they have two daughters: Amanda, born 1961, and Hermione, born 1967.

Elizabeth and Gordon Pask live in Clapham's Old Town, an ancient village in south west London.
For Gordon, with love
Authors: Beer Stafford
Published: July 2007

Abstract — This record was made some years ago, so that the quarter‐century referred to has become exactly forty years. Thus we are now dealing either with improper fractions or with expanded centuries of a hundred and twenty‐eight years; but in either case we are concerned with a second‐order regulator compensating for the intrusion of a regulator that was compensating for its own intrusion in the first place (which was not, you observe, here).
The wholeness of a cybernetician
Authors: Löfgren Lars
Published: July 2007

Abstract ‐ It is our impression that Gordon Pask's writings cover fundamentals for large parts of the widely expanding fields of Cybernetics and Systems Theory. Thereby, and by his lecturing activities, he has become a unique figure in maintaining a kind of unity of the field of Cybernetics, well in accord with Wiener's view (“control and communication in the animal and the machine”; cf[26]). And that, with fresh ideas, sometimes very personal, sometimes very general, and always very interesting.

In this subjective review of a fragment of Pask's writings, notably within cybernetics, we will, in part, try to account for some of his earlier insights into how we judge the behaviour of an artefact (machine) in relation to that of a living organism (animal). And, partly, for his later‐conceived conversation theory. Some problems revealed in the latter theory, like how we‐in‐a‐conversation can represent a real behaviour, may well connect back to Pask's earlier studies into the problem whether we can produce artefacts (including thought models) of our behaviours as living beings.
Educating symbiotic p‐individuals through multi‐level conversations. From the integrity of concepts to the symbiosis of cultures
Authors: Boyd Gary Mcintyre
Published: July 2007

Abstract ‐ Interbody and transbody autopoietic virtual organisms, which Gordon Pask named “p‐individuals”, are taken to be the essential entities involved in cultural transmission. It is asserted that their problematical accessibility to consciousness, their competitive, and especially their pre‐emptive dominative character, must be dealt with more directly in order to work educationally toward symbiosis among cultures and between cultures and the biosphere. Both kinds of symbiosis are necessary conditions for our happiness and survival. Some heuristic rules for the appropriate conduct of multi‐level, and multi‐modal (verbal/visual etc.) learning conversations is examined as a practicable way to cultivate such symbioses. Gordon Pask's formal Conversation Theory prescribes some necessary aspects of such intercourse. Here it is extended and reframed by situating Pask's three leveled CT conversations in the author's seven cybersystemic levels of communication and control.
Improvement and research. A paskian evolution
Authors: Zeeuw Gerard De
Published: July 2007

Abstract — Progress in the social sciences is not as slow as its critics are apt to aver. Enormous amounts of data have been collected and many patterns described. What has been slow is the systematic use and application of such results, that is, intervention. Intervening to improve social systems meets with many difficulties, one of them the fact that this often seems to invalidate previous research results. It is argued that this may be due to the kind of “scientific object” defined, that separates observation and use. The argument is linked to some of the work of Gordon Pask, especially his Interaction of Actors Theory, and to his participation in the Centre for Innovation and Co‐operative Technology. The argument is developed to include the case where observation and use are not separated. Some examples of such cases are described.
Fundamental theorem of system structure: An application t6 the study of community school organizations
Authors: Hough Robbin R.
Published: July 2007

The overall concern of the present paper is with system performance. The sections which follow will: (1) present a brief overview of the fundamental theorem of system structure; (2) develop and test a very simple model of school district pegormancekhange and statistically examine key structural features following the outlines of the theorem; (3) estimate the resource requirements for a program which would optimize the performance of the districts under study; and (4) set forth several conclusions and suggestions for further research.
Intermedity ‐ basic state of social systems?
Authors: Davydov A. A.
Published: July 2007

It has been proved on the wide empirical material that social systems of various levels are in the state of intermedity between order and chaos. It has been shown that various phenomena in social systems (power dependences of variables, quasiperiodical variations, hyperbolic distributions of elements, avalanche‐like processes, etc.) are caused by the state of intermedity.
Criticizing a collaborative standard system: The step standard data access interface
Authors: Van Geuns J. S. , Kerckhoffs E. J. H.
Published: July 2007

The suitability of the Standard Data Access Interface (SDAI) as a basis for a collaborative modelling environment is evaluated through the development of a prototype implementation. Problems are reported and possible solutions suggested. A conclusion is formulated about the SDAI and recommendations concerning its future use are given.
On responsibility and authority
Authors: Ahaus Cees , van de Water Henny
Published: July 2007

Defining authorities is a topic of current interest in quality management. One of the conditions in the ISO 9000‐series deals with this topic. In this paper we will first examine the concepts of authority and responsibility, which are not at all univocally defined in organization literature. We will pay attention to the distinction between formal and factual authority and to various possible forms of overlap of authorities. We illustrate a management method in the use of convergence of factual to formal authority and responsebility. Finally we pose some questions on the relationship between authority and responsibility to various types of organizations in order to get a first idea to what extent it is desirable or possible to equalize factual and formal authorities.
Understanding the nature of system change: An interdisciplinary approach
Authors: Stickland Francis , Reavill Lawrence P.
Published: July 2007

The paper seeks to open up a debate on the nature of change at a conceptual and theoretical level. It argues that the abundance of methodologies and strategies for managing system change belies an acute lack of any clear understanding of the very nature and essence of change itself, whether it be institutional, technological, environmental or organizational. The paper calls for a greater comprehension of the fundamental dynamics of change, and highlights the considerable need for a solid theoretical basis from which to explore the complexities of system change. A cross‐discipline approach is suggested, involving the analysis of change phenomena drawn from across the natural and physical sciences, deriving common characteristics and principles for abstraction into a general change framework. Several examples of the approach are described briefly, using change phenomenon taken from a range of disciplines. The paper concludes by outlining other subject areas which contain conceptually useful change phenomena worth investigating.
An appreciation of Kenneth Boulding
Authors: Henderson Hazel
Published: July 2007

In this appreciation of Kenneth Boulding, Hazel Henderson pays special tribute to him as ‘a towering intellectual figure of the twentieth century who did more than most to open windows to the twenty‐first Century’. Following an introduction in which she touchingly talks of Kenneth and Elise Boulding, she shares with us her reviews of Boulding's Ecodynamics.
Heating induces aggregation and decreases detection of serotonin transporter protein on western blots
Authors: McLane Michael W. , Hatzidimitriou George , Yuan Jie , McCann Una , Ricaurte George
Published: July 2007

In recent years, there has been growing interest in the use of Western blot analysis to monitor changes in the abundance of the serotonin transporter (SERT) protein. In the Western blot procedure, heat denaturation is a common, early step. We now report that heating samples to 90°C decreases the abundance of the SERT protein band and causes dispersion of a majority of the SERT signal to a high molecular weight smear. These observations are in keeping with the fact that heating can influence the electrophoretic behavior of some proteins. By omitting the heat denaturation step in the Western blot procedure, better detection of the SERT protein is achieved. Synapse 61:875–876, 2007. © 2007 Wiley‐Liss, Inc.
The Voting Rights Act and the Election of Nonwhite
Officials
Authors: Lien Pei-te , Pinderhughes Dianne M. , Hardy-Fanta Carol , Sierra Christine M.
Published: July 2007

The Voting Rights Act (VRA) is one of the most important—if not
the most important—public policies developed
over the last half century to increase access to the U.S. political
system for people of color. The VRA also provides an important
context for understanding the ascension of nonwhite groups into the
elected leadership of the nation (Browning, Marshall, and Tabb 1984; Davidson and Grofman 1994; Menifield 2001; McClain and Stewart 2002; Segura and Bowler 2005;
Bositis 2006). This essay assesses the
present-day significance of the VRA for the political representation
of communities of color by examining the implications of
majority-minority districts and other key provisions in the VRA for
the election of nonwhite officials in the beginning years of the
twenty-first century.
Ranking Departments: A Comparison of Alternative
Approaches
Authors: Masuoka Natalie , Grofman Bernard , Feld Scott L.
Published: July 2007

There are many different ways to develop rankings of Ph.D.-granting
academic departments. Perhaps the most common method is
reputational: we simply ask knowledgeable scholars in the discipline
to provide their rankings and aggregate these in some fashion. Other
ways involve more “objective indicators.” But, of course,
departments have multiple attributes, e.g., we might be interested
in how good a department is as a place to get a Ph.D., or we might
be interested simply in the research record of its faculty, etc.
Thus, we might want to use different indicators to measure different
aspects of the department.