bluuebunny/crossref_metadata_2025 huggingface dataset:
Configurational entropy of interacting particles adsorbed on one-dimensional channels arranged in a triangular structure
Authors: Pasinetti P. M. , Riccardo J. L. , Ramirez-Pastor A. J.
Published: April 2005

The configurational entropy of interacting particles adsorbed on one-dimensional channels arranged in a triangular cross-sectional structure is studied by combining Monte Carlo simulation and thermodynamic integration method. Three different energies have been considered in the adsorption process: (1) ϵo, constant interaction energy between a monomer and an adsorption site; (2) wL, interaction energy between nearest-neighbor particles adsorbed along a single channel, and (3) wT, interaction energy between particles adsorbed across nearest-neighbor channels. Special attention is devoted to the case of repulsive transversal interactions (wT>0), for which a rich variety of ordered phases are observed in the adlayer, depending on the value of the parameters kBT∕wT (being kB the Boltzmann constant) and wL∕wT. The influence of each ordered structure on the configurational entropy of the adlayer has been analyzed and discussed in the context of the lattice-gas model.
Neutron spin echo scattering angle measurement (SESAME)
Authors: Pynn R. , Fitzsimmons M. R. , Fritzsche H. , Gierlings M. , Major J. , Jason A.
Published: April 2005

We describe experiments in which the neutron spin echo technique is used to measure neutron scattering angles. We have implemented the technique, dubbed spin echo scattering angle measurement (SESAME), using thin films of Permalloy electrodeposited on silicon wafers as sources of the magnetic fields within which neutron spins precess. With 30-μm-thick films we resolve neutron scattering angles to about 0.02° with neutrons of 4.66Å wavelength. This allows us to probe correlation lengths up to 200nm in an application to small angle neutron scattering. We also demonstrate that SESAME can be used to separate specular and diffuse neutron reflection from surfaces at grazing incidence. In both of these cases, SESAME can make measurements at higher neutron intensity than is available with conventional methods because the angular resolution achieved is independent of the divergence of the neutron beam. Finally, we discuss the conditions under which SESAME might be used to probe in-plane structure in thin films and show that the method has advantages for incident neutron angles close to the critical angle because multiple scattering is automatically accounted for.
Exchange-hole dipole moment and the dispersion interaction
Authors: Becke Axel D. , Johnson Erin R.
Published: April 2005

A simple model is presented in which the instantaneous dipole moment of the exchange hole is used to generate a dispersion interaction between nonoverlapping systems. The model is easy to implement, requiring no electron correlation (in the usual sense) or time dependence, and has been tested on various atomic and molecular pairs. The resulting C6 dispersion coefficients are remarkably accurate.
The kinetics of internal structural relaxation of metallic glasses probed with ion beams and resistivity measurements
Authors: Mayr S. G.
Published: April 2005

The kinetics of structural relaxations in glassy metal Zr65Al7.5Cu27.5 films are monitored using resistivity measurements. As-prepared samples irreversibly relax towards their metastable equilibrium or steady-state in close relation to co-occurring surface smoothing, when exposed to annealing and ion treatment. Vice versa, ion beams are used as a tool to probe the response to small structural disturbances which are found to relax thermally following a stretched exponential time dependence. A strongly decreasing Kohlrausch exponent with temperature indicates increasing dynamic heterogeneities during successive freezing out of relaxational modes.
Velocity-field characteristics in the multivalley model of gallium arsenide
Authors: Sharma Ankur , Arora Vijay K.
Published: April 2005

The drift-velocity response to an applied electric field is investigated in a model based on an anisotropic distribution function of electrons. The randomly oriented velocity vectors in equilibrium transform to streamlined velocity vectors in a very high electric field, thereby yielding a saturation drift velocity that is comparable to the thermal velocity in the nondegenerate approximation. A clear distinction is made between the density-of-states effective mass and the conductivity effective mass for ellipsoidal valleys in gallium arsenide (GaAs). The effective mean free path, and hence the effective mobility, degrades as the electric field is increased. It is shown that as the applied electric field increases, electrons tend to follow the velocity-field profiles of those valleys with a higher Ohmic mean free path. The results are shown to be in excellent agreement with experimental data and with empirical relations obtained from the Monte Carlo simulations.
Comment on “Exact solutions of cylindrical and spherical dust ion acoustic waves” [Phys. Plasmas 10, 4162 (2003)]
Authors: Tian Bo , Gao Yi-Tian
Published: April 2005

Dusty plasmas have been found almost everywhere in the Universe. Sahu and Roychoudhury [Phys. Plasmas 10, 4162 (2003)] have done their interesting analytic work on the cylindrical dust ion-acoustic waves, without enough guidance to the readers on other existing analytic results. Such lack of guidance turns out to be critical. We hereby try to make the story more complete in the sense that the model does have plenty of exact analytic solutions published already, and to present a brief review on some of them. For the dust-ion-acoustic and dust-acoustic modes supported by the space/laboratory dusty plasmas, we hereby picture out some possibly observable effects for the future experiments, featured by a solitonic pulse aboard the varying ambient field propagating with its varying velocity and amplitude.
Differential tunnel transparency of a rectangular heterostructural barrier for the terahertz frequency range
Authors: Gribnikov Z. S. , Haddad G. I.
Published: April 2005

Electron wave tunneling through a rectangular heterostructural emitter barrier is considered in the case of a homogeneous high-frequency (hf) alternating electric field directed normal to the barrier interfaces. This hf field leads not only to the well-known increase in a stationary tunnel current through the emitter barrier, which is proportional to EB2 (where EB is the electric-field amplitude) but also to a linear (∼EB) increase in an alternating current (ac) through this barrier with the same frequency ω as the electric-field frequency. The ac is a sharp function of ω, which grows significantly with an increase in ω (typically in the terahertz range). In a certain intermediate current and frequency region, the above-mentioned increase in the ac is the dominating effect of the alternating field. Such an effect can be used to optimize tunnel barrier emitters for ballistic transit-time terahertz-range oscillators.
Effect of noise on defect chaos in a reaction–diffusion model
Authors: Wang Hongli , Ouyang Qi
Published: April 2005

The influence of noise on defect chaos due to breakup of spiral waves through Doppler and Eckhaus instabilities is investigated numerically with a modified Fitzhugh–Nagumo model. By numerical simulations we show that the noise can drastically enhance the creation and annihilation rates of topological defects. The noise-free probability distribution function for defects in this model is found not to fit with the previously reported squared-Poisson distribution. Under the influence of noise, the distributions are flattened, and can fit with the squared-Poisson or the modified-Poisson distribution. The defect lifetime and diffusive property of defects under the influence of noise are also checked in this model.
Impact of a shearless flow and cylindricity on interchange instability in magnetized plasma
Authors: Benilov E. S.
Published: April 2005

The stability of magnetically confined plasmas is sometimes examined using the so-called “slab” model, where the toroidal geometry of the problem is approximated locally by the Cartesian one. In the present paper, a (more accurate) cylindrical approximation is considered and shown to yield results which are qualitatively different from those of the slab model. In particular, if the slab model is applied to the outboard region of the tokamak (where the gradient of the plasma’s density and that of the magnetic field are of the same sign), disturbances remain unstable at all times. In the cylindrical model, on the other hand, the E×B flow carries disturbances around the cylinder and they alternate between the unstable and stable regions. Naturally, this reduces the growth rate of instability and makes it dependent on the angular velocity of the flow.
Experimental measurement of stress at a four-domain junction in lead zirconate titanate
Authors: MacLaren Ian , Schmitt Ljubomira A. , Fuess Hartmut , Kungl Hans , Hoffmann Michael J.
Published: April 2005

A junction between two lamellar bands of ferroelectric domains in a lead zirconate titanate ceramic is analyzed using Kikuchi diffraction patterns in the transmission electron microscope. Indexing of the diffraction patterns allowed the determination of the three-dimensional relative orientation of the four different domains at the junction and thus the characterization of the domain boundaries. The local c∕a ratio could also be determined from the misorientations at the domain boundaries. Analysis of the data showed that large stresses were concentrated at the junction, and that this is inevitable at such band junctions. Such stress concentrations could act as nuclei for cracking of the ceramic under additional loading in service, perhaps particularly as a consequence of extended electromechanical cycling. Moreover, the stresses would increase with increasing c∕a, making the issues all the more serious for Ti-rich compositions having larger c∕a ratios.
Ferroelectric properties of LaAlO3∕BaTiO3 superlattices prepared by laser molecular-beam epitaxy
Authors: Li Y. , Hao L. Z. , Deng H. , Chen F. G. , Li Y. R.
Published: April 2005

LaAl O 3 ∕ BaTi O 3 superlattices were obtained on (100)-oriented Nb-doped SrTiO3 substrates by laser molecular-beam epitaxy. The x-ray diffraction spectra indicated that the c-axis strain changed with the layer thickness of the superlattices. The relation of the ferroelectric properties to the strain was studied with the different stacking periodicity at a fixed periodic number. The results showed that the strains played an important role on remnant polarization. The maximum remanent polarization was obtained at the highest c-axis strain stacking periodicity of 4∕4. The use of a LaAlO3 cap layer enhanced the ferroelectric properties due to the restricted strain effect.
Bimetallic Pt–Ag and Pd–Ag nanoparticles
Authors: Lahiri Debdutta , Bunker Bruce , Mishra Bhoopesh , Zhang Zhenyuan , Meisel Dan , Doudna C. M. , Bertino M. F. , Blum Frank D. , Tokuhiro A. T. , Chattopadhyay Soma , Shibata Tomohiro , Terry Jeff
Published: April 2005

We report studies of bimetallic nanoparticles with 15%–16% atomic crystal parameters size mismatch. The degree of alloying was probed in a 2-nm Pt core (smallest attainable core size) of Pt–Ag nanoparticles (completely immiscible in bulk) and 20-nm-diameter Pd–Ag nanowires (completely miscible in bulk). Particles were synthesized radiolytically, and depending on the initial parameters, they assume spherical or cylindrical (nanowire) morphologies. In all cases, the metals are seen to follow their bulk alloying characteristics. Pt and Ag segregate in both spherical and wire forms, which indicates that strain due to crystallographic mismatch overcomes the excess surface free energy in the small particles. The Pd–Ag nanowires alloy similar to previously reported spherical Pd–Ag particles of similar diameter and composition.
Volume preserving integrators for solenoidal fields on a grid
Authors: Finn John M. , Chacón Luis
Published: April 2005

A novel method of integrating solenoidal flows given on a grid is developed. In three dimensions, the method involves splitting the flow into two or possibly three flows that are two dimensional and area preserving, and can therefore be integrated by Crank–Nicolson or a modified form of leapfrog, both of which exactly conserve area. The method involves an interpolation scheme which ensures the solenoidal nature of the field throughout the domain (on and off the grid) by means of tricubic splines. It is shown that the method is easily generalized to arbitrary curvilinear coordinates and also generalizes to higher dimensions. A method of integrating compressional three-dimensional flows given on a grid is outlined.
Determination of long-range correlations by quiet-time statistics
Authors: Lynch V. E. , Carreras B. A. , Sanchez R. , LaBombard B. , van Milligen B. Ph. , Newman D. E.
Published: April 2005

Quiet-time statistics is an approach to the analysis of fluctuation time series that, by measuring the duration of successive transport events and the quiet times between them, allows the extraction of information on the long-range correlations in the system. It provides information similar to that obtained from rescaled adjusted range (R∕S) statistics. However, when the data are contaminated by extraneous oscillations, it is difficult to effectively use R∕S statistics or standard quiet-time analysis. In this paper, quiet-time analysis is generalized so that time series contaminated by oscillations can be treated. This new technique is effective over a wide range of time scales.
Development of cold isostatic pressing graphite module for a heat-resistant lower hybrid current drive antenna
Authors: Maebara Sunao , Goniche Marc , Kazarian Fabienne , Seki Masami , Ikeda Yoshitaka , Imai Tsuyoshi , Beaumont Bertrand
Published: April 2005

Development of a plasma facing module using Cold Isostatic Pressing Graphite (CIPG) was successfully achieved for use in driving a heat-resistant Lower Hybrid Current Drive (LHCD) antenna. A thin stainless film (10μm), a molybdenum film (10μm), and a copper film (50μm) were overlaid on the CIPG materials, the CIPG surfaces were successfully coated with the Cu-layer by diffusion bonding method. This module whose length is 206mm, has four waveguides, and a water cooling channel. High rf-power long pulse operations with water cooling were successfully tested up to 250kW (125MW∕m2)∕700s, a stationary temperature and vacuum pressure was performed. But the maximum rf transmission power was limited to 47MW∕m2 for a plasma facing module using Carbon Fiber Composite (CFC) due to poor Cu-plating, a power density large by more than a factor 2.5 was achieved with the CIPG module. The rf power density which meets the requirement of the rf electric field of 5kV∕cm for a design of the LHCD antenna in International Thermonuclear Experimental Reactor (ITER) was successfully performed.
Gravimetric and volumetric approaches adapted for hydrogen sorption measurements with in situ conditioning on small sorbent samples
Authors: Poirier E. , Chahine R. , Tessier A. , Bose T. K.
Published: April 2005

We present high sensitivity (0 to 1 bar, 295 K) gravimetric and volumetric hydrogen sorption measurement systems adapted for in situ sample conditioning at high temperature and high vacuum. These systems are designed especially for experiments on sorbents available in small masses (mg) and requiring thorough degassing prior to sorption measurements. Uncertainty analysis from instrumental specifications and hydrogen absorption measurements on palladium are presented. The gravimetric and volumetric systems yield cross-checkable results within about 0.05 wt % on samples weighing from (3 to 25) mg. Hydrogen storage capacities of single-walled carbon nanotubes measured at 1 bar and 295 K with both systems are presented.
Electron prebunching in microwave magnetron by electric priming using anode shape modification
Authors: Kim J. I. , Won J. H. , Park G. S.
Published: April 2005

Electric priming is proposed for electron prebunching in a microwave magnetron and is demonstrated using a particle-in-cell code. When the N∕2-fold perturbation of the radial electric field using an anode shape modification is imposed in the interaction space of the N-cavity magnetron along the azimuthal direction, the electrons initially develop into the desired π-mode resulting in rapid startup. The startup is hastened from 3.2 to 1.2 ns when the radial variation of the protrusion and recession is 6.5% of the anode radius with the angular width of 6°.
Simple model for ac ionic conduction in solids
Authors: Bisquert J. , Halpern V. , Henn F.
Published: April 2005

We present a model for the ac conduction in ionically conducting solids that takes into account, in a simple way, the interaction between carriers. The Coulomb force forms an “ionic atmosphere” that exerts a restoring force on a central ion, whose motion corresponds to an overdamped oscillator. We consider the effect of the relaxation of the ionic atmosphere by introducing an additional equation for the displacement of the potential toward the particle position. The general behavior of the ac conductivity can be understood in terms of two types of motions: motion of the bound ion at high frequencies determined by microscopic friction, and a much slower motion coupled to the surrounding carriers relaxation at low frequencies.
Symmetric informationally complete–positive operator valued measures and the extended Clifford group
Authors: Appleby D. M.
Published: April 2005

We describe the structure of the extended Clifford group [defined to be the group consisting of all operators, unitary and antiunitary, which normalize the generalized Pauli group (or Weyl–Heisenberg group as it is often called)]. We also obtain a number of results concerning the structure of the Clifford group proper (i.e., the group consisting just of the unitary operators which normalize the generalized Pauli group). We then investigate the action of the extended Clifford group operators on symmetric informationally complete–positive operator valued measures (or SIC–POVMs) covariant relative to the action of the generalized Pauli group. We show that each of the fiducial vectors which has been constructed so far (including all the vectors constructed numerically by Renes et al.) is an eigenvector of one of a special class of order 3 Clifford unitaries. This suggests a strengthening of a conjecture of Zauner’s. We give a complete characterization of the orbits and stability groups in dimensions 2–7. Finally, we show that the problem of constructing fiducial vectors may be expected to simplify in the infinite sequence of dimensions 7,13,19,21,31,… . We illustrate this point by constructing exact expressions for fiducial vectors in dimensions 7 and 19.
A practical extension of the 3ω method to multilayer structures
Authors: Olson Brandon W. , Graham Samuel , Chen Kuan
Published: April 2005

An improved data reduction method is used to extend the popular 3ω method to general layered geometries. This approach utilizes an unapproximated analytical solution, cast in terms of thermal impedance, to simultaneously measure thermal conductivity, thermal capacity, conductivity anisotropy, and interlayer contact resistance in multilayer planar structures. This method places no restrictions on the number or thickness of individual material layers, and it allows experimental measurements to be taken over a much wider range of frequencies than was previously possible. The search algorithm associated with the model is straightforward, robust, and requires no specialized software to compose. Experimental results are presented for a two-layer borosilicate glass/zeolite structure as well as a Si∕SiO2 structure. In both instances, the algorithm was able to simultaneously extract thermal conductivity and thermal diffusivity values using a single series of 3ω measurements.
Least-squares wave-front reconstruction of Shack-Hartmann sensors and shearing interferometers using multigrid techniques
Authors: Baker K. L.
Published: April 2005

This article details a multigrid algorithm that is suitable for least-squares wave-front reconstruction of Shack-Hartmann and shearing interferometer wave-front sensors. The algorithm detailed in this article is shown to scale with the number of subapertures in the same fashion as fast Fourier transform techniques, making it suitable for use in applications requiring a large number of subapertures and high Strehl ratio systems such as for high spatial frequency characterization of high-density plasmas, optics metrology, and multiconjugate and extreme adaptive optics systems.
Biomechanical hand-functionality measurement system
Authors: Paske William C. , Metzger Charles L. , Sutherland Jeffrey M.
Published: April 2005

Functional assessment of the hands may now be accomplished via a biomechanical handset designed to repeatably and reproducibly aid in the identification of fine motor performance issues which may be present in either or both hands of the test subject. The test is accomplished by monitoring the force triangle defined by the thumb (digit I), index finger (digit II), and small finger (digit V) as they maintain a grip on a hand sensor throughout several repetitive exercises. The sensor consists of three independent load cells built into a single block. The three independently applied forces are sampled every 4ms. These forces are evaluated as a function of time and test parameters are then derived for use as diagnostic aids.
Nuclear magnetic resonance magnet actively cooled by pulse tube refrigerator
Authors: Kirichek Oleg , Carr Philip , Johnson Chris , Atrey Milind
Published: April 2005

High field NMR spectrometers have been an essential tool for biomolecular scientists for many years. They have been instrumental in the pursuit of understanding of the structure, function and dynamics of proteins and other biological molecules. In addition, NMR is increasingly used for small molecule applications such as metabonomics, providing capabilities that aid drug discovery, as well as general organic and inorganic chemistry [M. Pellecchia et al., Nature Reviews Drug Discovery 1, 211 (2002)]. However, access to these systems is restricted due to the requirement to periodically refill them with liquid cryogens. This is both logistically demanding and expensive. A new system combining NMR spectrometry and Pulse Tube Refrigeration (PTR) has been developed and successfully tested. This approach eliminates the dependence on liquid cryogens, reduces spectrometer downtime, and also significantly reduces the size of the system. In the near future this new type of analytical tool may become ubiquitous in biomedical and chemical laboratories.
Atomic force microscope in liquid with a specially designed probe for practical application
Authors: Zhang Dongxian , Zhang Haijun , Lin Xiaofeng
Published: April 2005

An atomic force microscope (AFM) in liquid was developed. The specially designed AFM probe was composed of a tip attached to a cantilever, a cantilever-tip pedestal, a circular Plexiglas window, and a scanner which is made up of three perpendicular tube piezos. When the instrument works, the liquid level is between the upper and lower surface of the window, and a circular meniscus is established around the Plexiglas window, preventing the tip from being affected or destroyed by surface tension of the liquid. In this setup, the cantilever tip and the sample are completely immersed in fluid. Meanwhile, during the cantilever-tip scanning over the sample during measurement, this system has no restriction on the sample’s size and weight and has a high scanning speed, which can be up to 40lines∕s or 10s for a 400×400pixel image. Some experiments were carried out on the system to demonstrate the elegant performance. The results show that the AFM (i) enables the whole canitlever tip to dive into the fluid; (ii) the sample can also be totally immersed by the fluid; (iii) the size and weight of samples are not restricted, enabling the instrument to image comparatively large or heavy sample; (iv) it is capable of scanning over samples with high speed. All of these advantages indicate this AFM has a great prospect for practical applications.
Real-time monitoring of the origination of multimacroion domains in a polyelectrolyte solution
Authors: Sedlák Marián
Published: April 2005

First real-time monitoring of the origination of multimacroion domains in an initially homogeneous polyelectrolyte solution was performed. Domains were generated by pH-induced increase of macroion charge in solution of poly(methacrylic acid). Monitoring was performed by static and dynamic light scatterings, in which scattering contributions from individual polyions and growing multimacroion domains were separated, such that amplitudes of both modes were expressed in absolute units. Kinetic results also yield new information regarding the nature of multimacroion domains.
Ultranarrow AuPd and Al wires
Authors: Altomare Fabio , Chang Albert M. , Melloch Michael R. , Hong Yuguang , Tu Charles W.
Published: April 2005

In this letter, we discuss a versatile template technique aimed to the fabrication of sub-10nm wide wires. Using this technique, we have measured AuPd wires, 12nm wide and as long as 20μm. Even materials that form a strong superficial oxide, and thus not suited to be used in combination with other techniques, can be employed. In particular, we have measured Al wires, with lateral width smaller or comparable to 10nm, and length exceeding 10μm.
Laterally aligned, multiwalled carbon nanotube growth using Magnetospirillium magnetotacticum
Authors: Kumar Nitin , Curtis Wayne , Hahm Jong-in
Published: April 2005

In this Letter, we report a straightforward method to produce multiwalled carbon nanotubes using magnetic nanoparticles of Magnetospirillium magnetotacticum as catalysts. Carbon nanotube growth on these nanoparticles resulted in multiwalled carbon nanotubes of an average diameter of 13nm showing a narrow distribution in diameter. The magnetic character of the iron-containing catalysts was exploited to generate biased growth orientations of the multiwalled carbon nanotubes during their synthesis. This magnetic bacteria-based synthetic approach represents a step forward towards synthesis-directed assembly of carbon nanotubes which is needed for easy integration of these materials into nanoelectronic devices.
Inducing and monitoring photoelectrochemical reactions at surfaces and buried interfaces in Cu(In,Ga)(S,Se)2 thin-film solar cells
Authors: Reichardt J. , Bär M. , Grimm A. , Kötschau I. , Lauermann I. , Sokoll S. , Lux-Steiner M. C. , Fischer Ch.-H. , Heske C. , Weinhardt L. , Fuchs O. , Jung Ch. , Gudat W. , Niesen T. P. , Karg F.
Published: April 2005

We report the direct observation of a photoinduced oxidation process at the buried buffer/absorber interface in high-efficiency Zn(O,OH)∕Cu(In,Ga)(S,Se)2 thin-film solar cell structures by means of x-ray emission and photoelectron spectroscopy. We propose a reaction mechanism that involves the decomposition of a hydroxide compound in the buffer layer into water and an oxide and present evidence that this process also occurs with visible light excitation and after accelerated lifetime tests of nonencapsulated devices. This suggests a possible photoinduced aging effect in solar cell devices with other hydroxide containing buffer layers or under humid conditions.
Passivation of InAs∕(GaIn)Sb short-period superlattice photodiodes with 10μm cutoff wavelength by epitaxial overgrowth with AlxGa1−xAsySb1−y
Authors: Rehm Robert , Walther Martin , Fuchs Frank , Schmitz Johannes , Fleissner Joachim
Published: April 2005

An approach for the passivation of photodiodes based on compounds of the InAs∕GaSb∕AlSb materials family is presented. The passivation is realized by the overgrowth of patterned mesa devices with a quaternary AlxGa1−xAsySb1−y layer, lattice matched to the GaSb substrate. Proof of concept is demonstrated on infrared photodiodes based on InAs∕(GaIn)Sb superlattices with 10μm cutoff wavelength operating at 77 K where suppression of surface leakage currents is observed.
Effects of tensile stress induced by silicon nitride passivation on electrical characteristics of AlGaN∕GaN heterostructure field-effect transistors
Authors: Jeon Chang Min , Lee Jong-Lam
Published: April 2005

The effects of tensile stress induced by silicon nitride (Si3N4) passivation on electrical characteristics of AlGaN∕GaN heterostructure field-effect transistors (HFETs) were investigated. The biaxial tensile stress applied to the AlGaN layer was increased with the thickness of the Si3N4 passivation layer, leading to the increase of sheet charge density confined at the heterointerface. The stress-induced charge density was 1.75×1011e∕cm2 for 80-nm-thick Si3N4 and 6.74×1011e∕cm2 for 500-nm-thick Si3N4. The maximum drain current and transconductance of AlGaN∕GaN HFET increased from 769 to 858mA∕mm and from 146 to 155mS∕mm after passivation, respectively.
Luminescent silicon carbide nanocrystallites in 3C-SiC∕polystyrene films
Authors: Fan J. Y. , Wu X. L. , Kong F. , Qiu T. , Huang G. S.
Published: April 2005

We report optical emission of SiC nanocrystallite films, which clearly shows the quantum confinement effect. Bulk polycrystalline 3C-SiC was first electrochemically etched and then the fabricated porous silicon carbide was ultrasonically treated in water or toluene suspension to disperse into colloidal nanoparticles. Transmission electron microscopy images clearly show that the colloidal nanoparticles have 3C-SiC lattice structure with sizes varying from about 6nm down to below 1nm. The suspension of 3C-SiC nanocrystallites exhibits ultrabright emission with wavelengths ranging from 400to520nm when the excitation wavelength varies from 250to480nm, in accordance with the quantum confinement effect. By adding polystyrene to the toluene suspension containing SiC nanoparticles and coating the mixing solution onto a Si wafer, we obtain the SiC∕polystyrene films that luminesce.
Thermal conductivity of B–C–N and BN nanotubes
Authors: Chang C. W. , Han Wei-Qiang , Zettl A.
Published: April 2005

We have measured the temperature-dependent thermal conductivity κ(T) of boron–carbon–nitride (B–C–N) and boron nitride (BN) nanotube mats between room temperature and 20K. For both materials, κ(T) increases with increasing temperature, with no sign of saturation. We employ an analysis method to estimate the intrinsic κ(T) of BN nanotubes converted from B–C–N nanotubes, and find that at room temperature κ(T) of a multiwalled BN nanotube can be comparable to that of a multiwalled carbon nanotube and may exceed it if made isotopically pure. At low temperature, the functional form of κ(T) reflects dimensional confinement.
A mutation in T7 RNA polymerase that facilitates promoter clearance
Authors: Guillerez Jean , Lopez Pascal J. , Proux Florence , Launay Hélène , Dreyfus Marc
Published: April 2005

Like multisubunit RNA polymerases (RNAPs), T7 RNAP frequently releases its transcript over the initial 8-12 transcribed nucleotides, when it still contacts the promoter. This abortive cycling, which is most prominent with initial sequences that deviate from those of T7 late genes, eventually compromises productive transcription. Starting from an
in vivo
situation where transcription of a target gene by T7 RNAP is virtually abolished because of extensive abortive cycling, we have selected a mutation in RNAP that restores target gene expression.
In vitro
, this mutation (P266L) weakens promoter binding but markedly reduces abortive cycling over a variety of initial sequences by stabilizing the transcription complex at nucleotides 5-8. Other substitutions of P266 have similar effects. X-ray data show that during the transition from initial to elongation complex, the N-terminal region undergoes a major structural switch of which P266 constitutes one of the hinges. How the mutation might facilitate this switch is tentatively discussed. On the practical side, the mutation can significantly improve
in vitro
transcription, particularly from templates carrying unfavorable initial sequences.
Supramolecular blueprint approach to metal-coordinated capsules
Authors: McKinlay Robert M. , Cave Gareth W. V. , Atwood Jerry L.
Published: April 2005

An important problem in designing any large network is the assembly of systems that are resilient to change. From a chemical point of view, an analogy can be used where one requires supramolecular assemblies to maintain their dimensionality combined with limited structural perturbation in response to variation in its intermolecular framework. The identification of hydrogen-bonded framework patterns within experimentally known supramolecular assemblies that are structurally robust to disruption and selective hydrogen substitution are envisioned to act as a supramolecular blueprint or template for metal-ion retroinsertion. Here, we report the formation of a large neutral discrete pseudo-spherical coordination capsule assembled from 6 pyrogallol[4]arene ligands and 24 Cu(II) metal ions. Amazingly, this coordination capsule is structurally analogous to its hydrogen-bonded counterpart. This result shows a robust ability of pyrogallol[4]arene molecules to self-assemble into large hexameric cage structures from either the hydrogen-bonding or metal-ligand coordination process. The identification of robust supramolecular assemblies that conserve their structure in response to interchangeability between hydrogen-bonded networks for metal coordination, or inversely, represents an important advancement in supramolecular design.
Semipermeable lipid bilayers exhibit diastereoselectivity favoring ribose
Authors: Sacerdote M. G. , Szostak J. W.
Published: April 2005

Nutrient uptake by a primitive cell would have been limited by the permeability characteristics of its membrane. We measured the permeabilities of model protocellular membranes to water, five of the six pentoses, and selected aldohexoses, ketohexoses, and three to six carbon alditols by following volume changes of vesicles after the addition of solute to the external medium. Solute hydrophobicities correlated poorly with permeability coefficients within one structural class of compounds. The permeability coefficients of diastereomeric sugars differed by as much as a factor of 10, with ribose being the most permeable aldopentose. Flexible alditols and sugars, sugars biased toward or restricted to furanose forms, and sugars having anomers with hydrophobic faces permeated more quickly than compounds lacking these features. Among the aldopentoses, only ribose possesses all of these properties. Ribose permeated both fatty acid and phospholipid membranes more rapidly than the other aldopentoses or hexoses. The enhanced permeability conferred by the unique conformational preferences of ribose would have allowed faster assimilation of ribose by primitive cells as they passively absorbed materials from the environment. The kinetic advantage of ribose over the other aldopentoses in crossing membranes may therefore have been one factor that facilitated the emergence of the RNA world.
Breeding for organic and low-input farming systems: An evolutionary–participatory breeding method for inbred cereal grains
Authors: Murphy Kevin , Lammer Doug , Lyon Steve , Carter Brady , Jones Stephen S.
Published: April 2005

Organic and low-input farmers often plant seed varieties that have been selected under conventional practices, traditionally including high inputs of artificial fertilizers, crop protection chemicals and/or water. In addition, these crops are often selected in environments that may or may not represent the local environment of the farmer. An evolutionary participatory breeding (EPB) method emphasizes the utilization of natural selection in combination with site-specific farmer selection in early segregating generations of a heterogeneous crop population. EPB is a combination of two specific breeding methods, evolutionary breeding and participatory plant breeding. Evolutionary breeding has been shown to increase yield, disease resistance, genetic diversity and adaptability of a crop population over time. It is based on a mass selection technique used by farmers for over 10,000 years of crop improvement. Participatory plant breeding programs originated in developing countries to meet the needs of low-input, small-scale farmers in marginal environments who were often overlooked by conventional crop breeders. The EPB method is an efficient breeding system uniquely suited to improving crop varieties for the low-input and organic farmer. The EPB method utilizes the skills and knowledge of both breeders and farmers to develop heterogeneous landrace populations, and is an effective breeding method for both traditional and modern farmers throughout the world.
Molecular Epidemiology of Severe Acute Respiratory Syndrome–Associated Coronavirus Infections in Taiwan
Authors: Lan Yu-Ching , Liu Tze-Tze , Yang Jyh-Yuan , Lee Cheng-Ming , Chen Yen-Ju , Chan Yu-Jiun , Lu Jang-Jih , Liu Hsin-Fu , Hsiung Chao A. , Ho Mei-Shang , Hsiao Kwang-Jen , Chen Hour-Young , Chen Yi-Ming Arthur
Published: April 2005

Background In 2003, Taiwan experienced a series of outbreaks of severe acute respiratory syndrome (SARS) and 1 laboratory-contamination accident. Here we describe a new phylogenetic analytical method to study the sources and dissemination paths of SARS-associated coronavirus (SARS-CoV) infections in Taiwan

Methods A phylogenetic analytical tool for combining nucleotide sequences from 6 variable regions of a SARS-CoV genome was developed by use of 20 published SARS-CoV sequences; and this method was validated by use of 80 published SARS-CoV sequences. Subsequently, this new tool was applied to provide a better understanding of the entire complement of Taiwanese SARS-CoV isolates, including 20 previously published and 19 identified in this study. The epidemiological data were integrated with the results from the phylogenetic tree and from the nucleotide-signature pattern

Results The topologies of phylogenetic trees generated by the new and the conventional strategies were similar, with the former having better robustness than the latter, especially in comparison with the maximum-likelihood trees: the new strategy revealed that during 2003 there were 5 waves of epidemic SARS-CoV infection, which belonged to 3 phylogenetic clusters in Taiwan

Conclusions The new strategy is more efficient than its conventional counterparts. The outbreaks of SARS in Taiwan originated from multiple sources
WUSCHEL is a primary target for transcriptional regulation by SPLAYED in dynamic control of stem cell fate in Arabidopsis
Authors: Kwon Chang Seob , Chen Changbin , Wagner Doris
Published: April 2005

SNF2 chromatin-remodeling ATPases play an important role in ensuring proper development in higher eukaryotes by controlling accessibility of cis-regulatory DNA regions to transcription factors and to the transcriptional machinery. However, the biological targets controlled by these ATPases are largely unknown. Using genetic and molecular analyses we have identified WUSCHEL (WUS) as a biologically important target of the SNF2-class ATPase SPLAYED (SYD) in the shoot apical meristem of Arabidopsis. We present evidence that SYD is recruited to the WUS promoter and that it is involved in regulation of the stem cell pool maintenance via direct transcriptional control of this master regulator.
Genome-wide identification of Isw2 chromatin-remodeling targets by localization of a catalytically inactive mutant
Authors: Gelbart Marnie E. , Bachman Nurjana , Delrow Jeffrey , Boeke Jef D. , Tsukiyama Toshio
Published: April 2005

Isw2 ATP-dependent chromatin-remodeling activity is targeted to early meiotic andMATa-specific gene promoters inSaccharomyces cerevisiae. Unexpectedly, preferential cross-linking of wild-type Isw2p was not detected at these loci. Instead, the catalytically inactive Isw2p-K215R mutant is enriched at Isw2 targets, suggesting that Isw2p-K215R, but not wild-type Isw2p, is a sensitive chromatin immunoprecipitation (ChIP) reagent for marking sites of Isw2 activity in vivo. Genome-wide ChIP analyses confirmed this conclusion and identified tRNA genes (tDNAs) as a new class of Isw2 targets. Loss of Isw2p disrupted the periodic pattern of Ty1 integration upstream of tDNAs, but did not affect transcription of tDNAs or the associated Ty1 retrotransposons. In addition to identifying new Isw2 targets, our localization studies have important implications for the mechanism of Isw2 association with chromatin in vivo. Target-specific enrichment of Isw2p-K215R, not wild-type Isw2p, suggests that Isw2 is recruited transiently to remodel chromatin structure at these sites. In contrast, we found no evidence for Isw2 function at sites preferentially enriched by wild-type Isw2p, leading to our proposal that wild-type Isw2p cross-linking reveals a scanning mode of the complex as it surveys the genome for its targets.
Metal-responsive transcription factor (MTF-1) handles both extremes, copper load and copper starvation, by activating different genes
Authors: Selvaraj Anand , Balamurugan Kuppusamy , Yepiskoposyan Hasmik , Zhou Hao , Egli Dieter , Georgiev Oleg , Thiele Dennis J. , Schaffner Walter
Published: April 2005

From insects to mammals, metallothionein genes are induced in response to heavy metal load by the transcription factor MTF-1, which binds to short DNA sequence motifs, termed metal response elements (MREs). Here we describe a novel and seemingly paradoxical role for MTF-1 in Drosophila in that it also mediates transcriptional activation of Ctr1B, a copper importer, upon copper depletion. Activation depends on the same type of MRE motifs in the upstream region of the Ctr1B gene as are normally required for metal induction. Thus, a single transcription factor, MTF-1, plays a direct role in both copper detoxification and acquisition by inducing the expression of metallothioneins and of a copper importer, respectively.
Macro and Micro Industrial Change
Authors: Pope Joseph
Published: April 2005

Provides a personal view of the future of the UK manufacturing
sector in a time of social and technological change. Discusses
communication between industry and society, the power of capital,
industry and unemployment, the need for stability within organizations,
and the aspirations of individuals within organizations. Summarizes that
industry problems should be viewed in a wider context, both socially and
internationally, to ensure the right priorities are selected.
Work Study in West Germany
Authors: Gencoglu Mehmet
Published: April 2005

Discusses the approach to work study used in West Germany. Examines
the nature and functions of the body that is responsible for providing a
framework for work study practice – REFA – as well as the
organization of training and instruction that is offered. Surmises that
work study practice in West Germany differs from that of other countries
by being more formal and structured, and that this has been used to
deliver numerous benefits.
Office Automation: Myth or Reality?
Authors: Beaumont John R.
Published: April 2005

Explores the misconception of information handling needs in
offices, leading to too great an emphasis on automation at the expense
of office staff. Describes information in terms of numbers text image
and voice data, and the information handling needs of the office in
terms of this. Concludes that there is a need to shift discussions of
office automation from a technical outlook to a management outlook.
Evaluate your Work‐at‐Home Potential
Authors: Jizba Barbara , Kleiner Brian H.
Published: April 2005

Examines the possibilities and requirements of home‐based work
arrangements. Considers personal work style, home environment and job
requisites as deciding factors about the suitability of working at home.
Concludes that whether working at home suits an individual depends on
their preferences and requirements, although this segment of the
workforce is likely to persist in the future as the population ages and
retirees continue their professional interests at home.
Building a Culture of Quality and Service: A Strategic
Approach to Success through Customer Service
Authors: Clark Andy
Published: April 2005

Considers the adoption of customer care by both public and private
sector organizations as a means of gaining a longer‐term competitive
edge. Examines ways of avoiding “charm‐school training”, the
concept of the internal customer, the challenges of quality service, and
a total approach to quality. Summarizes that if the “total
approach” is compatible with business style, short‐term enthusiasm
can be converted into long‐term and sustainable results.
Contracting – In or Out
Authors: Pitt Eddie
Published: April 2005

Describes approaches to potential cost savings that can be gained
by contracting in or out through an external service agency. Examines
the distinction between contracting in and the more permanent
contracting out, in the light of some of the advantages of contracting.
Concludes that with careful analysis it should be possible to select a
range of services that can be handed to service agencies, leaving the
organization to concentrate on its core functions.
Planning the Personal Use of Time
Authors: Littlewood Alan
Published: April 2005

Discusses methods and procedure for achieving effective personal
time management. Highlights the identification of problems, the
prioritization of objectives, and the breaking down of these objectives
into smaller tasks as stages in managing time effectively. Concludes
that the principle of time management is simple, and that with forward
planning and a clear purpose, it should be simple to achieve.
Retail Technology
Authors: Baines George
Published: April 2005

Discusses the reasons behind the drive for increased technology in
the retail industry. Considers the shift from supplier‐led to
marketing‐led operation, increased opening hours, increased product
ranges, more sophisticated layouts, and the need for more detailed sales
data as factors in the adoption of technology to satisfy information
needs. Concludes that the problems of the retail industry are providing
rich opportunities for EPoS system suppliers, especially those who link
EPoS into retail management and control systems.
Effective Report Presentation
Authors: Wilde Edwin
Published: April 2005

Examines the need for better report writing and presentation skills
to gain positive results. Establishes guidelines about how the report is
constructed: preliminary steps, report make‐up, content referencing, and
ease of reading. Concludes that it is essential that report writing
skills achieve a certain standard, because presentation affects the
subsequent value of the report.
Computer‐aided Manufacturing in the US
Authors: Corbo Anthony , Kleiner Brian H.
Published: April 2005

Discusses the adoption of CADCAM techniques by US manufacturers in
the struggle for business survival with reference to case examples.
Argues that CADCAM software offers valuable advantages over traditional
design/manufacturing methods, principally lack of mistakes in initial
production, and the reduction of both decision and design times by
drastic amounts. Concludes that the attribute of speed which makes
CADCAM such an advance is what is required by US companies to stay
alive.
Performance Indicators
Authors: Daniels Barrie
Published: April 2005

Discusses the need for measurement within the management process,
specifically the need for performance indicators. Examines the
management process relating to performance to construct an action plan
for defining performance indicators. Surmises that the important thing
is to construct performance measures which are recognized as fair and
enable the organization to look for improvements and evaluate progress.
Quality – A Belief and Awareness
Authors: King Terry
Published: April 2005

Discusses the introduction of the Crosby quality system into Dairy
Crest. Examines the 12 quality steps of the systems with reference to
staff training and reactions, information gathering, and individual
involvement, citing examples of aiming for zero errors and zero
sickness. Concludes that the quality system enhances management
responsiveness and commitment, employee pay and conditions, and
information flow – although belief in the system is needed.