bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Properties of Tetravalent Neptunium in Lead Molybdate
Authors: Phillips William , Feldman J. M.
Published: January 2005

The optical properties of neptunium in single-crystal lead molybdate have been measured to determine the suitability of Np4+ ions for laser applications. It was found that neptunium enters the crystals predominantly in the tetravalent state, with Np4+ ions occupying Pb2+ lattice sites. Another ionization state, probably Np6+, also appears, but is eliminated by the presence of Na+ in the crystals. Optical absorption at wavelengths longer than 0.6 μ is due to transitions from the 4I9/2 ground state to the other members of the 4I multiplet. Fluorescence, arising from 4I11/2→4I9/2 transitions, is excited by pumping in the 0.6-to-1.3-μ region. The emission fills a band between 1.6 and 2.2 μ at room temperature, but at 77°K it is confined largely to five lines, the narrowest of which has a width of about 13 cm−1. The quantum efficiency at 77°K approaches unity. Laser threshold calculations for PbMoO4 containing 0.005 mole % Np4+ indicate a rather high pulsed threshold at 77°K. However, crystals containing 0.1 mole % at Np4+ would have thresholds low enough for cw operation. Concentrations of this magnitude are not realizable in PbMoO4, but this is not necessarily the case for the other scheelite-structured tungstates and molybdates.
Vibrational Relaxation in Liquid Dichloromethane
Authors: Hunter Joseph L. , Dardy Henry D.
Published: January 2005

Measurements of ultrasonic absorption have been conducted in liquid dichloromethane over a frequency range of 30 to 510 Mc/sec, and over a temperature range of −60° to 25°C. The relaxation is exceedingly strong. The experimental values are predictable by the assumption that the vibrational specific heat of the molecule is the chief cause of the absorption, if it is assumed that the first vibrational mode is inactive, as hypothesized by Andreae. The frequencies of relaxation, arrived at through a curve of best fit, are 171 Mc/sec at 25°C, 147 Mc/sec at 0°C, and 117 Mc/sec at −60°C. The measured velocity dispersion is in agreement with the magnitude of the relaxing specific heat of vibration.
Scattering from Coulomb-Like Potentials without Divergences or Cutoffs. I. Formalism: Generalized Lippmann-Schwinger Equations
Authors: West Geoffrey B.
Published: January 2005

We present a general method whereby integral equations, which govern the solution to the radial Schrödinger equation, can be derived. The equations are quite flexible and can be arranged so as to define divergenceless iterative procedures. They are therefore particularly useful for Coulombic and singular potentials, neither of which are normally covered by the standard theory. We have carefully examined the standard theory as applied to Coulombic potentials; this is generally characterized by logarithmic divergences. We show that the standard Lippmann-Schwinger equation is no longer applicable and must be replaced by the corresponding homogeneous integral equation. Furthermore, we demonstrate that the T matrix, as conventionally defined, vanishes. Upon application of our generalized integral equation, a perturbative result for the scattering amplitude is obtained without the appearance of divergences or cutoffs. In the case of a pure point Coulomb potential, this result agrees very favorably with the exact one. In the modified case, our expression, by virtue of the fact that it does not require knowledge of Coulomb wavefunctions, is much simpler for computational purposes than the standard expressions. One simple example of the application of this method to singular potentials is briefly discussed.
Criterion for Bose-Einstein Condensation and Representation of Canonical Commutation Relations
Authors: Ezawa Hiroshi , Luban Marshall
Published: January 2005

The existence of a Bose-Einstein condensation in an interacting many-boson system at T = 0°K is proved under certain conditions on the particle density and the interparticle potential. Starting with the tentative assumption that the condensation exists, we study the fluctuation in the occupation number of the condensate with due regard to its interactions (1) with particles outside the condensate as well as (2) with the fluctuation itself. If the condensate fluctuation has a normalizable ground state, then the assumed existence of the condensation is tenable. For the case of the pair-Hamiltonian model satisfying the conditions for condensation, the interactions of the second category are of no importance. In the limit of infinite volume, this Hamiltonian can be diagonalized in an irreducible representation of a Bose-field operatorφ(x), whereφ(x) has nonvanishing ground state expectation value, in accordance with the usual c-number replacement of creation and destruction operators for the condensate particles. The full Hamiltonian for a system of pairwise interacting bosons is studied only in a low-density limit. Bose-Einstein condensation exists when the over-all space integral of the interparticle potential is positive. In this case the interactions of the second category play an important role in ensuring a normalizable ground state for the condensate fluctuation. There is an indication that in the limit of infinite volume the Hamiltonian cannot be diagonalized in any irreducible representation of the field operatorφ. Yet the c-number replacement of the condensate operators is legitimate as far as states of particles outside the condensate are concerned. Some speculations are made as to what may happen for systems of moderate density.
Two-Body Orbitals for One-Dimensional Fermion Gas with Application to Repulsive δ-Function Interactions
Authors: Kapuy E. , March N. H.
Published: January 2005

Explicit strongly orthogonal two-body orbitals (geminals) are constructed from free-particle Wannier functions for the lowest singlet state of a one-dimensional homogeneous fermion gas. As an application of the method, the ground-state energy is evaluated for repulsive delta function interactions for a range of the coupling constant. For weak coupling, the present method yields a lower energy than that of the Overhauser state. Using second-order perturbation corrections as a means of comparison, it is found that, in the high-density limit, the strongly orthogonal geminal product gives only a fifth of the total correlation energy. In the strong coupling regime, the results are more favorable but it proves difficult to determine the asymptotic behavior.
Superposition of patterns in cross-linked liquid crystals
Authors: Stich N. , Kitzerow H.-S.
Published: January 2005

Patterns appearing in liquid crystals due to electrohydrodynamic convection can be permanently stored by in situ photopolymerization. After curing, the respective pattern is fixed in a glasslike state which is stable even if the entropy production becomes zero. If a small amount of photoreactive mesogenic monomers is dissolved in a cholesteric liquid crystal, the reaction can result in the formation of either separate polymer walls or a polymer film with a regularly modulated surface. The symmetry and the orientation of the pattern depend essentially on the ratio between the sample thickness and the helical pitch of the cholesteric phase, while the cross section of the polymer walls or the topography of the polymer film depend on the ultraviolet radiation and the concentration of the reactive monomer.
Heteronuclear dipolar recoupling in solid-state nuclear magnetic resonance by amplitude-, phase-, and frequency-modulated Lee–Goldburg cross-polarization
Authors: Dvinskikh Sergey V. , Zimmermann Herbert , Maliniak Arnold , Sandström Dick
Published: January 2005

This paper presents a theoretical, numerical, and experimental study of phase- and frequency-switched Lee–Goldburg cross-polarization (FSLG–CP) under magic-angle spinning conditions. It is shown that a well-defined amplitude modulation of one of the two radio-frequency (rf) fields in the FSLG–CP sequence results in highly efficient heteronuclear dipolar recoupling. The recoupled dipolar interaction is γ-encoded and, under ideal conditions, the effective spin Hamiltonian is equivalent to that in continuous-wave Lee–Goldburg CP. In practice, however, FSLG–CP is less susceptible to rf field mismatch and inhomogeneity, and provides better suppression of H1 spin diffusion. The performance of FSLG–CP is experimentally demonstrated on liquid-crystalline samples exhibiting motionally averaged dipolar couplings.
Direct observation of magnetization reversal in thin Nd2Fe14B film
Authors: Park H. S. , Park Y.-G. , Gao Y. , Shindo D. , Inoue M.
Published: January 2005

By utilizing a sharp magnetic needle made of a sintered Nd2Fe14B permanent magnet, we were able to produce a strong magnetic field of up to approximately 560kA∕m in a transmission electron microscope and succeeded in observing the magnetization reversal in a thin film of sintered Nd2Fe14B by in situ Lorentz microscopy. The increase in the magnetic field induced by the magnetic needle led to a pair of straight magnetic domain walls forming abruptly from the grain boundary. The successive nucleation in the neighboring grain started at the grain boundary adjacent to the magnetic domain wall formed first. Eventually, the magnetic domain walls in the neighboring grains connected and moved continuously and finally disappeared.
Structural and microstructural characterization of nanocrystalline silicon thin films obtained by radio-frequency magnetron sputtering
Authors: Morales M. , Leconte Y. , Rizk R. , Chateigner Daniel
Published: January 2005

Textured silicon thin films are deposited by reactive magnetron sputtering in hydrogen-rich plasma on (100)-Si and amorphous SiO2 substrates. We quantitatively determine, combining x-ray texture analysis, x-ray reflectivity, transmission electron microscopy, atomic force microscopy measurements, and Raman and Fourier transform infrared spectroscopy analyses, the structure (cell parameter and mean electron density) and microstructure (crystalline fraction, preferred orientations, anisotropic crystallite sizes, thicknesses, etc.) of these films. For both kinds of substrates, no perfect ⟨111⟩ orientation is observed whereas a systematic elongation of the anisotropic Si crystallites along one [111] direction is present. A small elongation of the Si cell parameter of the nanocrystals is found without internal stress. With the substrate to target distance, the crystalline fraction and mean electron density show an opposite behavior to that of the film porosity. The former increases and the latter decreases, and are correlated to the texture evolution. Preferred orientations are observed with texture strengths around two to three times a random distribution, with a tendency to achieve lower strengths for films grown on SiO2 substrates. The texture components are evolving with the substrate to target distance, with ⟨110⟩ and ⟨hhℓ⟩ (ℓ larger than 2) orientations favored for smaller and larger distances, respectively. All these microstructural properties are correlated with their optical properties and more particularly to their refractive index and their optical band gap.
Rayleigh–Taylor mixing rates for compressible flow
Authors: Jin H. , Liu X. F. , Lu T. , Cheng B. , Glimm J. , Sharp D. H.
Published: January 2005

We study Rayleigh–Taylor instability in both the moderately compressible and weakly compressible regimes. For the two-dimensional single mode case, we find that the dimensionless terminal velocities (and associated Froude numbers) are nearly constant over most of this region of parameter space, as the thermodynamic parameters describing the equation of state are varied. The phenomenological drag coefficient which occurs in the single mode buoyancy-drag equation is directly related to the terminal velocities and has a similar behavior. Pressure differences and interface shape, however, display significant dependence on the equation of state parameters even for the weakly compressible flows. For three-dimensional multimode mixing, we expect accordingly that density stratification rather than drag will provide the leading compressibility effect. We develop an analytical model to account for density stratification effects in multimode self-similar mixing. Our theory is consistent with and extends numerically based conclusions developed earlier which also identify density stratification as the dominant compressibility effect for multimode three-dimensional mixing.
Extended-area optically induced organization of microparticles on a surface
Authors: Garcés-Chávez V. , Dholakia K. , Spalding G. C.
Published: January 2005

To extend beyond the limited field of view associated with optical tweezers, we implement a new geometry for lensless optical trapping (“LOT”). A Ronchi ruling is imaged at a sample interface beyond the critical angle for total internal reflection imposing local structure upon the optical fields. Due to the resulting transverse optical gradients, more than one thousand microparticles spanning 1mm2 were organized into microchannels that are entirely optical in origin. A generalized approach is presented, allowing for either guiding or stable trapping, as a function of the relative intensity of the counterpropagating surface waves.
Improved morphology of polymer-fullerene photovoltaic devices with thermally induced concentration gradients
Authors: Drees M. , Davis R. M. , Heflin J. R.
Published: January 2005

Gradient concentration profiles for efficient charge transfer and transport can be created in polymer-fullerene organic photovoltaics by thermally induced interdiffusion of an initial bilayer. Prior demonstrations with poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and C60 have been limited by the low miscibility of the two component materials. The morphology of the interdiffused films and resultant photovoltaic efficiency are improved by the use of the more miscible electron donor∕electron acceptor pair of poly(3-octylthiophene) and C60. The resultant concentration gradient profile is demonstrated by Auger spectroscopy and ion-beam milling. Increases in the short-circuit currents and fill factors relative to interdiffused MEH-PPV∕C60 devices lead to monochromatic power conversion efficiencies of 1.5% at 470nm.
Effect of stress and/or field annealing on the magnetic behavior of the (Co77Si13.5B9.5)90Fe7Nb3 amorphous alloy
Authors: Miguel C. , Zhukov A. P. , del Val J. J. , Ramírez de Arellano A. , González J.
Published: January 2005

Variations of coercive field, induced magnetic anisotropy, and saturation magnetostriction constant in (Co77Si13.5B9.5)90Fe7Nb3 amorphous ribbons submitted to stress and/or axial magnetic-field annealing are reported. The annealing was carried out by using the Joule-heating effect (average temperature values of the sample corresponding to the intensity of the electrical current were 273, 378, 409, and 445°C) and the applied stress and axial magnetic field during the thermal treatments were 500MPa and 750A∕m, respectively. As a result of these treatments, a uniaxial in-plane magnetic anisotropy, which affects drastically the soft magnetic character of the samples, was developed.
Electron conduction mechanism and band diagram of sputter-deposited Al∕ZrO2∕Si structure
Authors: Chiu Fu-Chien , Lin Zhi-Hong , Chang Che-Wei , Wang Chen-Chih , Chuang Kun-Fu , Huang Chih-Yao , Lee Joseph Ya-min , Hwang Huey-Liang
Published: January 2005

Metal-oxide-semiconductor capacitors that incorporate ZrO2 gate dielectrics were fabricated by radio frequency magnetron sputtering. In this work, the essential structures and electrical properties of ZrO2 thin films were investigated. C-V, energy dispersive x-ray spectrometry, and transmission electron microscopy analyses reveal that an interfacial layer was formed, subsequently reducing the k value of the annealed ZrO2 thin films. Additionally, the mechanisms of conduction of the Al∕ZrO2∕p-Si metal/zirconium oxide/semiconductor structure were studied with reference to plots of standard Schottky emission, modified Schottky emission, and Poole–Frenkel emission. According to those results, the dominant mechanisms at high temperatures (>425K) are Poole–Frenkel emission and Schottky emission in low electric fields (<0.6MV∕cm) and high electric fields (>1MV∕cm), respectively. Experimental results indicate that the Al∕ZrO2 barrier height is 0.92eV and the extracted trap level is about 1.1eV from the conduction band of ZrO2. The modified Schottky emission can be applied in an electric field to ensure that the electronic mean free path of the insulator is less than its thickness. According to the modified Schottky emission model, the extracted electronic mobility of ZrO2 thin films is around 13cm2∕Vs at 475K. The mean free path of transported electrons in ZrO2 thin films is between 16.2 and 17.4nm at high temperatures (425–∼475K).
Excessive Balmer line broadening in a plane cathode abnormal glow discharge in hydrogen
Authors: Cvetanović N. , Kuraica M. M. , Konjević N.
Published: January 2005

Results of a Doppler spectroscopy study of the hydrogen Balmer alpha line in an abnormal glow discharge operated in pure hydrogen are reported. Measurements of line shapes are performed side-on to the discharge axis in a low electric field region of negative glow. The excessive Balmer alpha broadening is detected and its presence and linewidth is related to the collisions of fast hydrogen atoms with molecular hydrogen. The collision model enabled also an estimation of effective cross section data from the Balmer alpha axial intensity decay curves. Large excessive Balmer alpha line broadening in pure hydrogen and its dependence upon the direction of observation with respect to the electric field is in contradiction to the resonance transfer model, proposed byMills et al. in several publications [see, e.g., IEEE Trans. Plasma Sci. 31, 338 (2003)].
Short-time aggregation dynamics of reversible light-induced cluster formation in ferrofluids
Authors: Kellner R. R. , Köhler W.
Published: January 2005

A quantitative description of the aggregation kinetics in the recently discovered phenomenon of reversible light-induced cluster formation in ferrofluids is presented. A simple early stage aggregation model is developed and the short-time aggregation behavior is monitored using turbidity measurements. The volume fraction and power dependency of the Fuchs stability ratio W are determined.
Improved signal analysis for motional Stark effect data
Authors: Makowski M. A. , Allen S. L. , Ellis R. , Geer R. , Jayakumar R. J. , Moller J. M. , Rice B. W.
Published: January 2005

Nonideal effects in the optical train of the motional Stark effect diagnostic have been modeled using the Mueller matrix formalism. The effects examined are birefringence in the vacuum windows, an imperfect reflective mirror, and signal pollution due to the presence of a circularly polarized light component. Relations for the measured intensity ratio are developed for each case. These relations suggest fitting functions to more accurately model the calibration data. One particular function, termed the tangent offset model, is found to fit the data for all channels better than the currently used tangent slope function. Careful analysis of the calibration data with the fitting functions reveals that a nonideal effect is present in the edge array and is attributed to nonideal performance of a mirror in that system. The result of applying the fitting function to the analysis of our data has been to improve the equilibrium reconstruction.
Stopping power for arbitrary angle between test particle velocity and magnetic field
Authors: Cereceda Carlo , de Peretti Michel , Deutsch Claude
Published: January 2005

Using the longitudinal dielectric function derived previously for charged test particles in helical movement around magnetic field lines, the numerical convergence of the series involved is found and the double numerical integrations on wave vector components are performed yielding the stopping power for arbitrary angle between the test particle velocity and magnetic field. Calculations are performed for particle Larmor radius larger and shorter than Debye length, i.e., for protons in a cold magnetized plasma and for thermonuclear α particles in a dense, hot, and strongly magnetized plasma. A strong decrease is found for the energy loss as the angle varies from 0 to π∕2. The range of thermonuclear α particles as a function of the velocity angle with respect to the magnetic field is also given.
Co
-doped TiO2 nanowire electric field-effect transistors fabricated by suspended molecular template method
Authors: Lee Yun-Hi , Yoo Je-Min , Park Dong-hyuk , Kim D. H. , Ju B. K.
Published: January 2005

We report on the fabrication of Co 3.4 at. % doped TiO2 nanowire-based field-effect transistors with a back gate of heavily doped Si substrate and their electric field-effect functions. The TiO2:Co nanowire, which was fabricated utilizing a conventional magnetron sputtering technique on a suspended molecular template between electrodes, is a polycrystalline and consists of a chain of nanoparticles on a molecular template. The N-type field-effect transistors prepared from the suspended Co–TiO2 nanowire junction were exhibited on currents, transconductances, and a mobility of up to 0.1mA∕μm, 0.2μA∕V, and μe≈66cm2∕Vs, respectively, at room temperature. The unique structure of these inorganic-organic functional devices may enable the fabrication of flexible nanoelectrospin devices.
Photorefractive polymer-dispersed liquid crystal based on a photoconducting polysiloxane
Authors: Paelke Lutz , Kitzerow Heinz-S. , Strohriegl Peter
Published: January 2005

The photorefractive effect in a photoconducting polymer containing small liquid crystal droplets is studied. Two beam coupling experiments indicate a high optical gain at moderate field strength (>50cm−1 at 10 V∕μm). The writing of photorefractive gratings is reversible. The dynamic behavior can be described by a two step process of the grating formation, the faster time constants being of the order of 100 ms. Modulation of the external voltage indicates that the reorientation of the director in the liquid crystals droplets is faster than the rise and decay times of the space charge field.
Selective removal of electrons from a Penning trap for negative ion autodetachment studies
Authors: Suess L. , Liu Y. , Dunning F. B.
Published: January 2005

It is shown that free electrons can be selectively removed from a Penning trap used to store heavy autodetaching negative ions by application of a series of small positive extraction pulses to one of the end electrodes of sufficient amplitude to extract the electrons yet not significantly perturb the heavy ion motion. This minimizes reattachment in the trap and increases the level of detailed information regarding ion lifetimes (and other properties) that can be obtained by monitoring the time evolution of the trapped ion population.
Intense terahertz laser fields on a two-dimensional electron gas with Rashba spin–orbit coupling
Authors: Cheng J. L. , Wu M. W.
Published: January 2005

The spin-dependent density of states and the density of spin polarization of an InAs-based two-dimensional electron gas with the Rashba spin–orbit coupling under an intense terahertz laser field are investigated by utilizing the Floquet states to solve the time-dependent Schrödinger equation. It is found that both densities are strongly affected by the terahertz laser field. Especially a terahertz magnetic moment perpendicular to the external terahertz laser field in the electron gas is induced. This effect can be used to convert terahertz electric signals into terahertz magnetic ones efficiently.
Nanoscale device isolation of organic transistors via electron-beam lithography
Authors: Mattis Brian A. , Pei Yunan , Subramanian Vivek
Published: January 2005

We investigated the use of electron-beam lithography on pentacene and poly(3-hexylthiophene) field-effect transistors to achieve device isolation and enable the realization of nanoscale organic circuits. We determined the doses and exposure linewidths needed to suppress carrier transport, enabling direct patterning at the nanoscale. The precision limits were also studied through an analysis of proximity scattering effects. With an optimized pattern and exposure, we reduced off-currents by almost four orders of magnitude and gate leakage by three orders of magnitude on backgated devices. Our electron-beam isolation methods also increased the on/off ratio and drastically improved the subthreshold swing, thus attesting to the viability of this technique for patterning of organic circuits at the nanoscale.
High-mobility carbon-nanotube thin-film transistors on a polymeric substrate
Authors: Snow E. S. , Campbell P. M. , Ancona M. G. , Novak J. P.
Published: January 2005

We report the development of high-mobility carbon-nanotube thin-film transistors fabricated on a polymeric substrate. The active semiconducting channel in the devices is composed of a random two-dimensional network of single-walled carbon nanotubes (SWNTs). The devices exhibit a field-effect mobility of 150cm2∕Vs and a normalized transconductance of 0.5mS∕mm. The ratio of on-current (Ion) to off-current (Ioff) is ∼100 and is limited by metallic SWNTs in the network. With electronic purification of the SWNTs and improved gate capacitance we project that the transconductance can be increased to ∼10–100mS∕mm with a significantly higher value of Ion∕Ioff, thus approaching crystalline semiconductor-like performance on polymeric substrates.
Th
4
+
donor∕Mg2+ acceptor-cosubstituted (Bi,Nd)4Ti3O12 films with excellent ferroelectric properties
Authors: Chiou Tai-Yi , Kuo Dong-Hau
Published: January 2005

A -site Th4+ donor∕B-site Mg2+ acceptor-cosubstituted (Bi3.15Nd0.85)Ti3O12 or (Bi3.15Nd0.85−2xTh2x)(Ti3−xMgx)O12 ferroelectric thin films with x=0.003 were prepared at 600°C by a chemical route. A concept of the electrostatic interaction between the positively charged donor and the negatively charged acceptor were introduced for the purpose of enhancing electrical polarization. A (117)-preferred film growth occurred. The 15min annealed films performed the best with a low coercive field of 45kV∕cm, a large remanent polarization (2Pr) of 70μC∕cm2, and a nonvolatile charge of 58μC∕cm2 after 1010 switching cycles. The excellent ferroelectric properties can be related to the (117)-preferred growth and the tilting of the triple-layered TiO6 octahedral chains.
Experimental evidence for antiferromagnetic spin–spin interaction between carriers localized in coupled quantum dots
Authors: Lee S. , Lee H. S. , Lee J. Y. , Dobrowolska M. , Furdyna J. K.
Published: January 2005

A self-assembled quantum dot (QD) system consisting of adjacent CdSe and CdZnMnSe QD layers in a ZnSe matrix was investigated using polarization-selective magnetophotoluminescence (PL). We can unambiguously identify which QD peak originates from which material, because PL from CdZnMnSe (a diluted magnetic semiconductor) exhibits a large Zeeman shift in the presence of a magnetic field. Significant enhancement of the degree of σ− circular polarization emitted by the nonmagnetic CdSe QDs is observed in the double layer system, as compared to that observed in similar CdSe QDs without the influence of neighboring CdZnMnSe QDs. This behavior can be understood in terms of antiferromagnetic interaction between carrier spins localized in pairs of CdSe and CdZnMnSe QDs that are electronically coupled.
Enhanced room-temperature luminescence efficiency through carrier localization in AlxGa1−xN alloys
Authors: Collins C. J. , Sampath A. V. , Garrett G. A. , Sarney W. L. , Shen H. , Wraback M. , Nikiforov A. Yu. , Cargill G. S. , Dierolf V.
Published: January 2005

AlGaN samples grown by plasma-assisted molecular-beam epitaxy on sapphire (0001) substrates, with 20%–50% Al content and without the use of indium, show intense room-temperature photoluminescence that is significantly redshifted, 200–400meV, from band edge. This intense emission is characterized by a long room-temperature lifetime (∼375ps) comparable to that seen in low defect density (∼108cm−2) GaN. Room-temperature monochromatic cathodoluminescence images at the redshifted peak reveal spatially nonuniform emission similar to that observed in In(Al)GaN alloys and attributed to compositional inhomogeneity. These observations suggest that spatial localization enhances the luminescence efficiency despite the high defect density (>1010cm−2) of the films by inhibiting movement of carriers to nonradiative sites.
Prion protein NMR structures of cats, dogs, pigs, and sheep
Authors: Lysek Dominikus A. , Schorn Christian , Nivon Lucas G. , Esteve-Moya Vicent , Christen Barbara , Calzolai Luigi , von Schroetter Christine , Fiorito Francesco , Herrmann Torsten , Güntert Peter , Wüthrich Kurt
Published: January 2005

The NMR structures of the recombinant cellular form of the prion proteins (PrP
C
) of the cat (
Felis catus
), dog (
Canis familiaris
), and pig (
Sus scrofa
), and of two polymorphic forms of the prion protein from sheep (
Ovis aries
) are presented. In all of these species, PrP
C
consists of an N-terminal flexibly extended tail with ≈100 amino acid residues and a C-terminal globular domain of ≈100 residues with three α-helices and a short antiparallel β-sheet. Although this global architecture coincides with the previously reported murine, Syrian hamster, bovine, and human PrP
C
structures, there are local differences between the globular domains of the different species. Because the five newly determined PrP
C
structures originate from species with widely different transmissible spongiform encephalopathy records, the present data indicate previously uncharacterized possible correlations between local features in PrP
C
three-dimensional structures and susceptibility of different mammalian species to transmissible spongiform encephalopathies.
Prion protein NMR structures of chickens, turtles, and frogs
Authors: Calzolai Luigi , Lysek Dominikus A. , Pérez Daniel R. , Güntert Peter , Wüthrich Kurt
Published: January 2005

The NMR structures of the recombinant prion proteins from chicken (
Gallus gallus
; chPrP), the red-eared slider turtle (
Trachemys scripta
; tPrP), and the African clawed frog (
Xenopus laevis
; xlPrP) are presented. The amino acid sequences of these prion proteins show ≈30% identity with mammalian prion proteins. All three species form the same molecular architecture as mammalian PrP
C
, with a long, flexibly disordered tail attached to the N-terminal end of a globular domain. The globular domain in chPrP and tPrP contains three α-helices, one short 3
10
-helix, and a short antiparallel β-sheet. In xlPrP, the globular domain includes three α-helices and a somewhat longer β-sheet than in the other species. The spatial arrangement of these regular secondary structures coincides closely with that of the globular domain in mammalian prion proteins. Based on the low sequence identity to mammalian PrPs, comparison of chPrP, tPrP, and xlPrP with mammalian PrP
C
structures is used to identify a set of essential amino acid positions for the preservation of the same PrP
C
fold in birds, reptiles, amphibians, and mammals. There are additional conserved residues without apparent structural roles, which are of interest for the ongoing search for physiological functions of PrP
C
in healthy organisms.
Delay-Induced Super-Latent Inhibition as a Function of Order of Exposure to Two Flavours Prior to Compound Conditioning
Authors: De La Casa L. G. , Lubow R. E.
Published: January 2005

A number of recent conditioned taste aversion (CTA) experiments have demonstrated a super-latent inhibition (LI) effect—namely, a time-induced increase in the effects of stimulus preexposure when the interval between acquisition and test is spent in a context that is different from the other experimental contexts. Two CTA experiments with rats were conducted to examine the role of primacy in producing super-LI. In Experiment 1, one of two flavours was pre-exposed, following which a second flavour was preexposed. After the second preexposure, animals were conditioned by pairing a compound of the two preexposed flavours with LiCl. The test stage was conducted 1 or 21 days after conditioning, with the interval being spent in either the same or different contexts. In the test, animals were confronted with two bottles, each with one of the two preexposed flavours. Super-LI was obtained only for the first preexposed flavour in the 21-day delay group that spent the interval in a different context. Experiment 2 was designed to ensure that the effects in Experiment 1 represented LI, and to control for order of presentation of the flavours and time between preexposure and acquisition. The results replicated those of Experiment 1. The two experiments support the importance of primacy in the general super-LI experiment where CS-alone preexposure precedes CS–US.
Flavour Liking and Preference Conditioned by Caffeine in Humans
Authors: Yeomans Martin R. , Durlach Paula J. , Tinley Elizabeth M.
Published: January 2005

When caffeine consumers repeatedly experience a novel flavoured drink containing caffeine, the rated pleasantness of the drink flavour increases progressively. These results could be interpreted in terms of the flavour acting as a Pavlovian conditioned stimulus (CS) predicting the consequences of caffeine ingestion. However, all studies of this phenomenon to date have used between-subjects designs, and one criticism of this is that changes in pleasantness might have arisen from nonspecific effects. A more rigorous test is to examine changes in pleasantness for two drinks, a CS+ flavour paired with caffeine and CS− paired with placebo. Accordingly, 20 moderate caffeine consumers consumed both CS+ and CS− drinks in counterbalanced order over eight conditioning trials at breakfast, with hedonic and sensory characteristics evaluated on each trial. As predicted, the rated pleasantness of the CS+ drink increased whereas pleasantness of the CS− drink did not change. Despite this, participants did not have an overall preference for the CS+ flavour posttraining. However, both those who chose the CS+ and those who chose the CS− at the end showed the same direction and rate of change in pleasantness for the two drinks during training, but spurious differences in baseline preference obscured this effect in terms of an overall change in preference. Overall these data suggest that changes in pleasantness of drinks paired with caffeine delivery are best explained in terms of Pavlovian associations between drink flavour and the postingestive effects of caffeine.
The effect of journal title changes on impact factors
Authors: Tempest David
Published: January 2005

One of the most misunderstood aspects of journal management is the effect of journal title changes on the ThomsonScientific impact factor. This study analyses journals that changed their title in 1994 and 1995 and ascertains the period of time taken to recover the impact factor. Effects of subject classification and of the size of the journal are also investigated to see if recovery time depends on them. The analysis shows that recovery times are longer than predicted. Suggestions are made on how publishers may approach communication of journal title changes to minimize the effects on the impact factor.
A normal form for admissible characters in the sense of Lynch
Authors: Baur Karin
Published: January 2005

Parabolic subalgebras

p

\mathfrak {p}

of semisimple Lie algebras define a

Z

\mathbb {Z}

-grading of the Lie algebra. If there exists a nilpotent element in the first graded part of

g

\mathfrak {g}

on which the adjoint group of

p

\mathfrak {p}

acts with a dense orbit, the parabolic subalgebra is said to be nice. The corresponding nilpotent element is also called admissible. Nice parabolic subalgebras of simple Lie algebras have been classified. In the case of Borel subalgebras a Richardson element of

g

1

\mathfrak {g}_1

is exactly one that involves all simple root spaces. It is, however, difficult to write down such nilpotent elements for general parabolic subalgebras. In this paper we give an explicit construction of admissible elements in

g

1

\mathfrak {g}_1

that uses as few root spaces as possible.
Un univers mécanique: la machine chez Alfred Jarry
Authors: Dubbelboer Marieke
Published: January 2005

Dans l'œuvre d'Alfred Jarry, notamment dans son roman
Le Surmâle
(1902), figurent un grand nombre de machines. Cet article essaie de montrer non seulement les idées et les fascinations qui s'expriment dans cette représentation de la machine, mais aussi l'originalité de cette représentation dans l'histoire littéraire. Au dix-neuvième siècle une exploitation dichotomique du thème est à remarquer dans laquelle la machine symbolise un progrès voulu ou non voulu. Dans son œuvre, Jarry monte de différentes machines, réelles et imaginaires, par lesquelles il exprime certains motifs importants: dynamisme, vitesse, sexualité, mort. En analysant ces motifs, cet article montre l'originalité de Jarry. En comparant Jarry à ses contemporains
fin-de-siècle
et aux mouvements d'avant-garde (futurisme, surréalisme, dadaïsme), il se révèle que la machine chez Jarry est plutôt détachée de toute idéologie. Il se distancie de l'exploitation dichotomique du thème et se sert du thème de façon humoriste. Ce qui reste est un rapport imaginaire et ludique avec la machine.
Nathalie Sarraute's Accent: The Poetry of
Tropismes
Authors: Kawakami Akane
Published: January 2005

This article explores the basis for Nathalie Sarraute's insistence that her work be classified as poetry rather than prose. The article shows that the roots of this preference can be found in her theoretical writings, which are put into practice in her creative works. Their ‘poetic’ quality is analysed using the tools of prosody, specifically on extracts from her collection of prose poems,
Tropismes
. This exercise throws up interesting theoretical resemblances between Sarraute and Proust: they share an extreme sensitivity to the aural aspect of written texts. The prosodic analysis also offers a new method of exploring the Sarrautean tropism, that is to say in terms of poetic accent: the nature of the tropism is reconsidered in the context of late nineteenth-century theories of speech rhythms, and compared with the notion of the ‘accent d'impulsion’.
Dietary CDP-choline supplementation prevents memory impairment caused by impoverished environmental conditions in rats
Authors: Teather Lisa A. , Wurtman Richard J.
Published: January 2005

We previously showed that dietary cytidine (5′)-diphosphocholine
(CDP-choline) supplementation could protect against the development of memory
deficits in aging rats. In the present study, younger rats exposed to
impoverished environmental conditions and manifesting hippocampal-dependent
memory impairments similar to those observed in the aging rodents were given
CDP-choline, and its effects on this cognitive deficit were assessed. Male
Sprague-Dawley rats reared for 3 mo in impoverished (IC) or enriched
environmental (EC) conditions concurrently received either a control diet or a
diet supplemented with CDP-choline (∼500 mg/kg/d). After 3 mo, rats were
trained to perform spatial and cued versions of the Morris water maze, and
their rates of acquisition and retention were compared. Impoverished rats
exhibited a selective deficit in hippocampal-dependent spatial memory which
could be ameliorated by feeding them CDP-choline. The CDP-choline had no
memory-enhancing effect in enriched rats, nor did it prevent the memory
impairment of impoverished rats if the animals consumed it for the initial or
final months instead of for the entire 3-mo period. These findings indicate
that long-term dietary CDP-choline supplementation can ameliorate the
hippocampal-dependent memory impairment caused by impoverished environmental
conditions in rats, and suggest that its actions result, in part, from a
long-term effect such as enhanced membrane phosphatide synthesis, an effect
shown to require long-term dietary supplementation with CDP-choline.
Socioeconomic resources, gender traditionalism, and wife abuse in urban Russian couples
Authors: Cubbins Lisa A. , Vannoy Dana
Published: January 2005

Until recently, Soviet data restrictions led to limited knowledge about wife abuse in Russia. This study adds to emerging research on Russian domestic violence by testing hypotheses derived from resource theory on the effects on wife abuse of husband's absolute resources versus spouses’ relative resources. Analysis of data from the 1996 National Survey of Russian Marriages (N= 664) shows support only for the influence of husband's absolute socioeconomic resources (education, employment status, and occupational rank). As in U.S. studies, intergenerational patterns of wife abuse and husband's alcohol use have notable effects on wife abuse. The findings suggest that although resource theory may partly explain wife abuse in urban Russia, spouses’ relative resources and husband's gender traditionalism currently have little influence.
“His” and “her” marriage expectations: Determinants and consequences
Authors: Waller Maureen R. , McLanahan Sara S.
Published: January 2005

This article uses couple‐level data from the Fragile Families and Child Wellbeing Study (N= 2,263) to investigate factors associated with unmarried parents’ expectations about marriage and the association between their expectations and subsequent union transitions. In most couples, both partners expect to marry, and their shared expectations are the strongest predictor of marriage and separation following their child's birth. Although men's expectations are somewhat more consequential for union transitions, marriage and relationship stability are more likely when at least one parent expects to marry. Factors such as children from previous relationships, distrust, conflict, and shared activities are also associated with union transitions. Findings about how expectations and other factors relate to marriage and separation may inform new marriage promotion initiatives.
Gender and marital satisfaction early in marriage: A growth curve approach
Authors: Kurdek Lawrence A.
Published: January 2005

The purpose of this study is to assess differences between husbands and wives (N= 526 couples at the first assessment) on (a) growth curves over the first 4 years of marriage for psychological distress, marriage‐specific appraisals, spousal interactions, social support, and marital satisfaction; (b) the strength of intraspouse links and cross‐spouse links involving the initial assessment of the first four variables and the growth curve for marital satisfaction; and (c) differences between spouses headed for divorce versus spouses in stable marriages on the growth curves for all five variables. On the basis of evidence that interspouse differences were largely nonsignificant, there was little support for the view that there are his and her versions of the processes that affect marital outcomes.
A family process model of problem behaviors in adolescents
Authors: Vandewater Elizabeth A. , Lansford Jennifer E.
Published: January 2005

This study examines the ways in which different family processes and personal experiences of social contexts are related to the adjustment of adolescents in a subsample of 755 mother‐child dyads drawn from the National Survey of Families and Households. Structural equation modeling was employed to examine a model in which joint family contexts (socioeconomic resources), mothers’ and adolescents’ experiences of outside‐family contexts (perceived social network quality and experience of school stress, respectively), and individual characteristics of mothers (distress) were expected to relate to adolescents’ externalizing and internalizing behaviors through their association with within‐family contexts (mother‐adolescent conflict, family warmth). This conceptual model was supported by the data. Pathways were consistent for boys and girls.
The long reach of divorce: Divorce and child well‐being across three generations
Authors: Amato Paul R. , Cheadle Jacob
Published: January 2005

We used data from the study of Marital Instability Over the Life Course to examine links between divorce in the grandparent generation and outcomes in the grandchild generation (N= 691). Divorce in the first (G1) generation was associated with lower education, more marital discord, weaker ties with mothers, and weaker ties with fathers in the third (G3) generation. These associations were mediated by family characteristics in the middle (G2) generation, including lower education, more marital discord, more divorce, and greater tension in early parent‐child relationships. In supplementary analyses, we found no evidence that the estimated effects of divorce differed by offspring gender or became weaker over time. Our results suggest that divorce has consequences for subsequent generations, including individuals who were not yet born at the time of the original divorce.
Fathering in intact and divorced families: Ethnic differences in retrospective reports
Authors: Schwartz Seth J. , Finley Gordon E.
Published: January 2005

The present study was designed to investigate whether ethnicity moderates the effects of divorce on young adults’ retrospective reports of fathering. An ethnically diverse sample of 1,989 university students completed measures of nurturant fathering, reported father involvement, and desired father involvement. Compared with participants from intact families, those from divorced families indicated lower levels of nurturant fathering and reported father involvement. These differences varied considerably by ethnicity. Reported fathering differences between participants from intact and divorced families were greatest in African Americans, Caribbean Islanders, and foreign‐born Cubans. These differences were smallest in non‐Hispanic Whites and Asians. Participants from divorced families reported greater levels of desired father involvement than did participants from intact families. These differences were not moderated by ethnicity.
Women's employment patterns during early parenthood: A group‐based trajectory analysis
Authors: Hynes Kathryn , Clarkberg Marin
Published: January 2005

Research on women's employment and parenthood frequently focuses on the correlates and consequences of decisions at a particular time, such as a birth. This article applies a group‐based trajectory method to examine women's employment trajectories across the period of early parenthood using the National Longitudinal Survey of Youth 1979 (N= 2,093). We find that throughout early parenthood, women exhibit significant movement into and out of the labor force. Factors that typically predict women's employment status, such as age at first birth and education, are also good predictors of women's employment patterns. We discuss the implications of these findings for future research, particularly on the use of a static measure of women's or couples’ employment status.
Gender, lineage, and fertility‐related outcomes in Ghana
Authors: Takyi Baffour K. , Nii‐Amoo Dodoo F.
Published: January 2005

A growing literature examines the empirical relationship between the joint reproductive preferences of marital partners and reproductive outcomes in Africa. Less explored is how spousal power in decision making may be influenced by lineage type. Using pooled data from Ghana, we investigate how lineage affects gendered reproductive decision outcomes and find some evidence that matrilineal women are more able than nonmatrilineal women to translate their reproductive preferences into action consistent with their goals.