bluuebunny/crossref_metadata_2025 huggingface dataset:
The program animation system PASTIS
Authors: Müller Heinrich , Winckler Jörg , Grzybek Stefan , Otte Matthias , Stoll Bertram , Equoy Frederic , Higelin Nicolas
Published: November 2006

The software animation system PASTIS (Program Animation System with Interactive Solutions) for program animation with emphasis on the visualization of the dynamic behaviour of algorithms and data structures is presented. Its main properties are unmodified source code of the visualized program, concurrent multiple views on algorithms and data structures, and interactive alterations of views during run time. PASTIS is distinguished by high modularity and strict separation of its components. This makes it particularly suitable for distributed computing environments. The interface between program and animation is a relational data model. Animations are directed by a single tuple, or sets of tuples, called relations, or sets of relations, called networks. Animations can be nested hierarchically. A prototype of PASTIS was implemented under Unix

Unix is a trademark of AT&T.

using the GNU source level debugger gdb and the X‐window system.
Ballerinas generated by a personal computer
Authors: Yoshimoto S.
Published: November 2006

Beautiful 3‐D figures of ballerinas have been generated by a non‐professional artist using a personal computer with commercially available ray‐tracing software and metaballs. This paper describes how these beautiful artistic creations have been drawn using very limited computational tools.
Three‐dimensional texture generator supervised by a small number of parameters
Authors: Gourret J. P. , Afflard P.
Published: November 2006

In this paper we give a method for generating surface appearances with a maximum number of 15 supervising parameters. Surfaces are made up of fast spatial changes (high spatial frequencies) and slow spatial changes (low spatial frequencies). The generator is a mixture of several techniques generally used in image synthesis, image animation, in CAD and in signal processing.

A model for generating fish scales is actually under development. The flexibility of the method makes it suitable for many other applications, such as 3D regular patterns, tissue‐like texture, etc.
A cell‐transverse display algorithm for regular and rectilinear 3D grid data
Authors: Doi Akio , Koide Akio
Published: November 2006

This paper proposes an efficient direct imaging algorithm for constructing iso‐surfaces from regular and rectilinear 3D grid data in scientific and engineering visualization. The basic idea is to generate and draw polygons simultaneously by processing the cells spanned by grids in decreasing order of distance from the current viewpoint. Iso‐surfaces are generated in five or six tetrahedrons into which the cells are subdivided, and are sent to a graphics device or drawn into a frame buffer on the fly. The execution order of each of the tetrahedrons is identical and is determined by the current viewpoint. Since the algorithm does not need to store intermediate polyhedral data and does not require a depth buffer memory for hidden surface removal, it is applicable to a large quantity of data on a 3D grid, such as computed tomography (CT) data. It is also particularly powerful for semi‐transparent display, because transparency calculation can be reduced to image compositing operations if the polygons are drawn in order of their z‐depth from the current viewpoint.
Multilevel use of coherence for complex radiosity environments
Authors: Vilaplana Josep , Pueyo Xavier
Published: November 2006

The performance of radiosity algorithms has been improved in recent years by means of using coherence when evaluating the visibility function for form factor computation. We present here a brief characterization of the uses of coherence for this goal. The characterization includes both previously proposed techniques and unexplored ones. Afterwards we propose new uses of coherence for visibility computation in form factor determination and we discuss the results of its implementation.
Cuticular lipids of insects: II. Hydrocarbons of the cockroachesPeriplaneta australasiae, Periplaneta brunnea andPeriplaneta fuliginosa
Authors: Jackson Larry L.
Published: November 2006

The major cuticular hydrocarbons of the cockroachesPeriplaneta australasiae, Periplaneta brunnea andPeriplaneta fuliginosa aren‐tricosane,cis‐9‐tricosene, 3‐methyltricosane, 11‐methyltricosane and 13‐methylpentacosane. There are as yet unexplained quantitative differences between the hydrocarbon compositions of males and females ofP. australasiae andP. fuliginosa, cis‐9‐tricosene being a major hydrocarbon of the males only. A series of mono‐methyl internally branched hydrocarbons ranging in chain length from 23 to 26 carbons with the methyl branch on the 13th carbon from one end was observed. Minor quantities of other hydrocarbons have been identified.
Metabolic fate of epoxycholesterol in the rat
Authors: Fioriti J. A. , Kanuk M. J. , George M. , Sims R. J.
Published: November 2006

The rate of disappearance of intubated epoxycholesterol from the rat gastro‐intestinal tract has been determined. The loss of this sterol is accompanied by the appearance of a sterol metabolite. This was isolated by preparative GLC and TLC and identified by mass spectrometry as 5α‐cholestan‐3β‐5α, 6‐β‐triol.
The densities of three classes of marine lipids in relation to their possible role as hydrostatic agents
Authors: Lewis R. W.
Published: November 2006

Wax esters, diacyl glycerol ethers and triglycerides were isolated from marine oils by preparative thin layer chromatography. Their densities indicated that wax esters would nearly equal squalene in effectiveness as a bouyant agent and that diacyl glycerol ethers would surpass triglycerides. Their compositions were listed to permit comparison with lipids from other sources.
Metabolic studies in isolated rat liver cells: II. Biosynthesis of serum low density lipoproteins and its regulation
Authors: Capuzzi David M. , Margolis Simeon
Published: November 2006

Dispersed rat liver cells were used for study of protein and serum lipoprotein synthesis. Cellular leucine incorporatein was tested in the presence of various cofactors, buffers and inhibitors.14C‐leucine was incorporated into cellular protein at an active rate for 1 hr. Incorporation was more rapid in the presence of succinate, MgCl2, phosphate and nicotinamide, but these cofactors were not absolutely required. The liver cells also incorporated labeled leucine into lower density lipoproteins (1DL) and released the newly labeled 1DL into the incubation medium. Puromycin strongly inhibited the production of cellular protein and 1DL. The mode of cellular regulation of 1DL synthesis was examined. The rate of 1DL production was selectively enhanced by short term alimentation with dietary triglyceride or by the addition of a mixture of lipogenic cofactors to incubated liver cells. The utility of isolated liver cells as a preparation for metabolic control studies is discussed.
Postnatal changes in the phospholipid composition of livers from young lambs
Authors: Noble R. C. , Steele W. , Moore J. H.
Published: November 2006

The total lipids were extracted from the livers of newborn lambs, from the livers of lambs during the first week after birth and from the livers of adult sheep. After separation from the nonphospholipids on columns of silicic acid the phospholipids were analyzed by thin layer chromatography and quantitative gas liquid chromatography. In all samples phosphatidyl choline and phosphatidyl ethanolamine together accounted for about 80% of the total liver phospholipids. The phosphatidyl choline‐phosphatidyl ethanolamine ratio in the livers of the newborn lambs was markedly less than the ratio in the livers of the adult sheep. Moreover there was a pronounced increase in the phosphatidyl cholinephosphatidyl ethanolamine ratio in the livers of the lambs during the first week after birth. In the liver phospholipids of the lambs the concentration of phosphatidyl inositol was lower and the concentrations of phosphatidyl serine and sphingomyelin were greater than the corresponding concentrations in the liver phospholipids of the adult sheep. It is proposed that the change in the phosphatidyl choline‐phosphatidyl ethanolamine ratio in the livers of the lambs during the first week after birth is due, at least in part, to the marked change that occurs in the linoleic acid‐arachidonic acid ratio in the tissues of the lamb during this period.
Stereospecific hydration of unsaturated fatty acids by bacteria
Authors: Wallen L. L. , Davis E. N. , Wu Y. V. , Rohwedder W. K.
Published: November 2006

Three new 10‐hydroxy fatty acids, all optically active, have been prepared by the anaerobic microbiological hydration of acis‐9 double bond. Substrates that formed these new hydroxy fatty acids are linoleic, linolenic, and ricinoleic acids. The hydroxyl group has the D configuration and the methyl esters are levorotatory. Infrared, mass spectral, specific rotation and ultraviolet data on these compounds were determined. There was no migration of the unreated double bonds at C12 and C15 in linoleic or linolenic acids. The presence of a double bond in the 10‐hydroxy fatty acids significantly increased the optical rotation of the methyl esters. The hydratase enzyme showed unusual specificity among Δ9 unsaturated acids. While it hydrates methylene interrupted and hydroxy unsaturated acids, it failed to hydrate either 9‐decenoic, 12,13‐epoxy‐ or 12‐keto‐cis‐9‐octadecenoic acids or sterculic acid.
Lipid monolayers: Mechanisms of protein penetration with regard to membrane models
Authors: Colacicco Giuseppe
Published: November 2006

The influence of lipid and protein on the properties of the air‐water interface is analyzed with the view to formulate a mechanism of interaction of protein with lipid monolayers. The increase in surface pressure (ΔΠ) and the quantity of protein incorporated in the lipid film after injection of protein under lipid monolayers were studied as a function of both lipid structure and protein structure. With rabbit γ‐globulin, the values of ΔΠ were cholesterol > phosphatidyl choline > sphingomyelin. Similar results were obtained with ribonuclease, lysozyme and serum albumin. The quantities of protein found in films of either cholesterol or phosphatidyl choline (egg lecithin) were much larger than those calculated from a geometric model in which a protein monolayer occupies the area made available by the compressed lipid. Arguments are produced against penetration based on simple mechanisms of compressibility of the lipid film. The mechanisms operating in the incorporation of protein into lipid monolayers are grouped into three categories: (a) free penetration, typical of lecithin; (b) binding‐mediated penetration, typical of cholesterol and some glycosphingolipids; and (c) binding‐inhibited penetration, typical of the albumin‐ganglioside system and a specific lipid hapten‐antibody system. A model is described in which nonspecific protein interacts with polymeric lecithin structures (surface micelles). In the sequence of events X»Y»Z, the globular protein X is activated into the expanded or extended form Y by contact with the lipid and then restructured into a compact form Z with release of water and free energy. The resulting lipid‐protein assembly has a mosaic structure in which lipid and protein polar surfaces are exposed to water. Accessibility of lecithin to phospholipase A is consistent with the model and with current views on the state of protein in biological membranes; according to such views, protein is more likely structured inside the lipid milieu and not simply denatured on the lipid‐water interface.
Lipoxygenase fromZea mays: 9‐d‐hydroperoxy‐trans‐10,cis‐12‐octadecadienoic acid from linoleic acid
Authors: Gardner H. W. , Weisleder D.
Published: November 2006

Lipoxygenase from the germ of corn,Zea mays, oxidized linoleic acid to primarily 9‐d‐hydroperoxy‐trans‐10,cis‐12‐octadecadienoic acid.
Reactions of dimethyl sulfoxide with sulfonate esters of fatty alcohols. I. Synthesis of higher saturated and unsaturated fatty aldehydes
Authors: Mahadevan V. , Phillips F. , Lundberg W. O.
Published: November 2006

Long‐chain saturated fatty aldehydes (C10 to C18), as well as the C18 unsaturated aldehydes (oleyl, linoleyl, and linolenyl), were synthesized in good yields by the selective oxidation of the sulfonate esters of the corresponding alcohols with dimethyl sulfoxide in the presence of sodium bicarbonate. Chromatographic procedures for the isolation of the pure aldehydes from the reaction mixtures are described. The purity of the aldehydes was ascertained by thin‐layer chromatography, melting points of their 2,4‐dinitrophenyl hydrazones, infrared spectra and other physical methods.
Stearyl CoA as a precursor of oleic acid and glycerolipids in mammary microsomes from lactating bovine: Possible regulatory step in milk triglyceride synthesis
Authors: Kinsella J. E.
Published: November 2006

The stearyl desaturase of lactating bovine mammary tissue is located in the microsomes and requires activated fatty acid and NADH for activity. Other enzymes, acyl‐transferase(s) and deacylase which apparently compete with the desaturase for substrate are also present. Both the substrate 1‐14C‐stearyl CoA and the oleic acid produced by desaturase are esterified into the various lipid classes. The oleic acid is preferentially acylated into positionsn‐3 of the triglycerides andsn‐2 of the phosphatidylcholine. Experimental conditions causing reduced desaturase activity depressed triglyceride synthesis, and stimulation of desaturation by NADH L−α GP, acidic pH, 5.6, was accompanied by increased incorporation of radioactive fatty acids into the triglycerides. These data indicated that desaturase and glyceride acyl transferase were located contiguously within the microsomal membranes. The possibility that desaturase activity might control triglyceride synthesis in vivo is discussed. It was observed that mammary tissue from nonlactating cows 1–2 weeks and 2 days prior to calving lacked or possessed very low stearyl desaturase activity.
Synergistic effects of pravastatin and pioglitazone in renal tubular epithelial cells induced by transforming growth factor‐β1
Authors: Wei Jia‐li , Ma Chun‐yang , Zhang Yang‐De , Li Yiming
Published: November 2006

Recent studies suggest that treatment with PPAR‐γ agonists and statins have beneficial effects on renal disease. However, the combined effects of PPAR‐γ agonists and statins in human renal epithelial cells are unknown. Our present study revealed that there were synergistic effects of pravastatin and pioglitazone in the expression of alpha‐smooth muscle actin (α‐SMA), connective tissue growth factor (CTGF), fibronectin (FN), plasminogen activator inhibitor‐1 (PAI‐1) and collagen 1 in human renal proximal tubular epithelial cells induced by transforming growth factor‐beta 1 (TGF‐β1). The beneficial effects of combined therapy against renal tubular epithelial cell injury are attributed, at least in part, to the inhibition of transdifferentiation, extracellular matrix deposition and cytokine production.
Internal photoemission of electrons at interfaces of metals with low-κ insulators
Authors: Shamuilia S. , Afanas’ev V. V. , Somers P. , Stesmans A. , Li Y.-L. , Tőkei Zs. , Groeseneken G. , Maex K.
Published: November 2006

Energy barriers for electrons at interfaces of several low-permittivity insulators with metals (Ta, TaNx, TiNx, Au, and Al) are characterized using internal photoemission spectroscopy. In sharp contrast to thermal SiO2, the barriers show little sensitivity to the Fermi energy of the metal, suggesting that the uppermost occupied electron revels at the interface are states localized in the near-interfacial insulator layer. Moreover, despite large differences in the defect spectrum of the studied low-κ materials as revealed by electron spin resonance, all the measured energy barriers are found to be close to 4.5eV. The latter indicates an extrinsic nature of the corresponding common electron state, which is tentatively ascribed to traces of moisture at the interface.
Calculation of circular dichroism spectra from optical rotatory dispersion, and vice versa, as complementary tools for theoretical studies of optical activity using time-dependent density functional theory
Authors: Krykunov Mykhaylo , Kundrat Matthew D. , Autschbach Jochen
Published: November 2006

A comparison of two theoretical methods based on time-dependent density functional theory for the calculation of the linear dispersive and absorptive properties of chiral molecules has been made. For this purpose, a recently proposed computational method for the calculation of circular dichroism (CD) spectra from the imaginary part of the optical rotation parameter has been applied to six rigid organic molecules. The results have been compared to the CD spectra obtained from the rotatory strengths and from the Kramers-Kronig transformation of optical rotatory dispersion (ORD) curves. We have also investigated a criterion based on the Kramers-Kronig integration formula to determine a number of excitations in truncated CD spectra which may yield a reasonable low frequency resonant ORD. It has been tested by calculating the ORD from the sum-over-states formula both in the nonresonant and resonant regions. Finally, we have applied these methods to model the resonant optical activity of proline at low pH.
Rovibrational resonance effects in collision-induced electronic energy transfer: I2(E,v=–2)+CF4
Authors: Hutchison J. Matthew , Carlisle Benjamin R. , Stephenson Thomas A.
Published: November 2006

Collisions of I2 in the E(0g+) electronic state with CF4 molecules induce electronic energy transfer to the nearby D, β, and D′ ion-pair states. Simulations of dispersed fluorescence spectra reveal collision-induced electronic energy transfer rate constants and final vibrational state distributions within each final electronic state. In comparison with earlier reports on I2(υE=0–2) collisions with He or Ar atoms, we find markedly different dynamics when I2, excited to the same rovibronic states, collides with CF4. Final vibrational state distributions agree with the associated Franck-Condon factors with the initially prepared state to a greater degree than those found with He or Ar collision partners and suggest that internal degrees of freedom in the CF4 molecule represent a substantial means for accepting the accompanying loss of I2 vibronic energy. Comparison of the E→D transfer of I2 excited to the J=23 and J=55 levels of the υE=0 state reveals the onset of specific, nonstatistical dynamics as the available energy is increased above the threshold for excitation of the low frequency ν2 bending mode of CF4.
Kinetic stability of the internal kink mode in ITER
Authors: Hu Bo , Betti R. , Manickam J.
Published: November 2006

The kinetic stability of the n=1, m=1 internal kink mode is analyzed for realistic equilibria typical of the standard operation scenario of ITER (the International Thermonuclear Experimental Reactor) [ITER Physics Basis Editors, Nucl. Fusion 39, 2137 (1999)]. The kinetic effects modify the inertia and the perturbed potential energy δW of the mode, the two key elements determining the mode stability. Numerical results are obtained for ITER-like equilibria with different q profiles. For moderate magnetic shear within the q=1 surface, the low frequency magnetohydrodynamic (MHD) branch is fully suppressed by the kinetic effects for the expected profiles and parameters up to twice the expected plasma β while the high frequency fishbone branch is found to be destabilized as the plasma β and the radius of the q=1 surface increase. The MHD branch can be destabilized at higher plasma β or larger radii of the q=1 surface only for q profiles with a low magnetic shear within the q=1 surface.
Efficient coupling of several broad area laser diodes into an optical fiber
Authors: McGinily Stephen J. , Abram Richard H. , Riis Erling , Ferguson Allister I.
Published: November 2006

A high brightness, fiber coupled optical pumping system is described based on readily available optical components. Operating at a wavelength of 670nm we have achieved an output of 1.25W from a 50μm core diameter fiber (0.22 NA) and 3.5W from a 100μm core diameter fiber (0.22 NA). This represents a six- to eightfold increase over commercially available systems at that wavelength. The design is generic and can immediately be implemented at other wavelengths, where high brightness pumping systems are not commercially available. The design and implementation are detailed.
Measurement of submilliwatt, picosecond terahertz emission from a femtosecond-laser-pumped solid-state dc to ac radiation converter based on a ZnSe crystal
Authors: Yugami Noboru , Ohata Nobuo , Yaegashi Kenta , Kawanago Hiroshi
Published: November 2006

We measured the terahertz pulse emission from a femtosecond-laser-pumped solid-state dc to ac radiation converter using a 150fs Ti:sapphire laser pulse for dense plasma diagnostics. The laser-produced ionization front was directly modulated from a periodic electrostatic field to pulsed emission. The central frequency of the emission was measured to be 0.13THz having a bandwidth of 0.1THz and a peak power of 0.2mW. This emission source is suitable for use in various novel diagnostic techniques, such as dense plasma diagnostics.
Non-Markovian modification of the golden rule rate expression
Authors: Basilevsky M. V. , Davidovich G. V. , Titov S. V. , Voronin A. I.
Published: November 2006

The reformulation of the standard golden rule approach considered in this paper for treating reactive tunneling reduces the computation of the reaction rate to a derivation of band shapes for energy levels of reactant and product states. This treatment is based on the assumption that the medium environment is actively involved as a partner in the energy exchange with the reactive subsystem but its reorganization effect is negligible. Starting from the quantum relaxation equation for the density matrix, the required band shapes are represented in terms of the spectral density function, exhibiting the continuum spectrum inherent to the interaction between the reactants and the medium in the total reactive system. The simplest Lorentzian spectral bands, obtained under Redfield approximation, proved to be unsatisfactory because they produced a divergent rate expression at low temperature. The problem is resolved by invoking a refined spectral band shape, which behaves as Lorentzian one at the band center but decays exponentially at its tails. The corresponding closed non-Markovian rate expression is derived and investigated taking as an example the photochemical H-transfer reaction between fluorene and acridine proceeding in the fluorene molecular crystal. The kinetics in this reactive system was thoroughly studied experimentally in a wide temperature range [B. Prass et al., Ber. Bunsenges. Phys. Chem. 102, 498 (1998)].
A new integrable equation with cuspons and W/M-shape-peaks solitons
Authors: Qiao Zhijun
Published: November 2006

In this paper, we propose a new completely integrable wave equation: mt+mx(u2−ux2)+2m2ux=0, m=u−uxx. The equation is derived from the two dimensional Euler equation and is proven to have Lax pair and bi-Hamiltonian structures. This equation possesses new cusp solitons—cuspons, instead of regular peakons ce−∣x−ct∣ with speed c. Through investigating the equation, we develop a new kind of soliton solutions—“W/M”-shape-peaks solitons. There exist no smooth solitons for this integrable water wave equation.
Linear scaling density fitting
Authors: Sodt Alex , Subotnik Joseph E. , Head-Gordon Martin
Published: November 2006

Two modifications of the resolution of the identity (RI)/density fitting (DF) approximations are presented. First, we apply linear scaling and J-engine techniques to speed up traditional DF. Second, we develop an algorithm that produces local, accurate fits with effort that scales linearly with system size. The fits produced are continuous, differentiable, well-defined, and do not require preset fitting domains. This metric-independent technique for producing a priori local fits is shown to be accurate and robust even for large systems. Timings are presented for linear scaling RI/DF calculations on large one-, two-, and three-dimensional carbon systems.
Competition between double exchange and purely magnetic Heisenberg models in mixed valence systems: Application to half-doped manganites
Authors: Bastardis Roland , Guihéry Nathalie , Suaud Nicolas , de Graaf Coen
Published: November 2006

A truncated Hubbard model is developed for the description of the electronic structure of odd-electron TM–L–TM units (TM=transition metal and L=ligand). The model variationally treats both the double exchange and purely magnetic Heisenberg configurations. This Hubbard model can either be mapped on a purely magnetic Heisenber model in which the bridging oxygen is also magnetic or on a double exchange model owing to the hybridization of the magnetic and ligand or bitals. The purely magnetic Heisenberg model is analytically solved in the general case of two metals (having n magnetic orbitals) bridged by a magnetic oxygen. The comparison of the analytical expressions of the Heisenberg energies to those of the double exchange model reveals that the two model spectra are identical except for one state which does not belong to the model space of the double exchange Hamiltonian. Consequently, the fitting of the model spectra to accurate ab initio spectra does not discriminate between the physically different models. These concepts are illustrated for the Mn–O–Mn unit (or Zener polaron) found in the half-doped manganite Pr0.6Ca0.4MnO3. It is shown that in the present case the projections of the ab initio ground state wave function onto both model spaces are almost identical provided that one uses properly localized orbitals, proving that the magnetic description of the Zener polaron and the double exchange viewpoint of the electronic structure are equally valid.
Spectral convergence of the quadrature discretization method in the solution of the Schrödinger and Fokker-Planck equations: Comparison with sinc methods
Authors: Lo Joseph , Shizgal Bernie D.
Published: November 2006

Spectral methods based on nonclassical polynomials and Fourier basis functions or sinc interpolation techniques are compared for several eigenvalue problems for the Fokker-Planck and Schrödinger equations. A very rapid spectral convergence of the eigenvalues versus the number of quadrature points is obtained with the quadrature discretization method (QDM) and the appropriate choice of the weight function. The QDM is a pseudospectral method and the rate of convergence is compared with the sinc method reported by Wei [J. Chem. Phys., 110, 8930 (1999)]. In general, sinc methods based on Fourier basis functions with a uniform grid provide a much slower convergence. The paper considers Fokker-Planck equations (and analogous Schrödinger equations) for the thermalization of electrons in atomic moderators and for a quartic potential employed to model chemical reactions. The solution of the Schrödinger equation for the vibrational states of I2 with a Morse potential is also considered.
Structural characterization of ZnO films grown by molecular beam epitaxy on sapphire with MgO buffer
Authors: Pécz B. , El-Shaer A. , Bakin A. , Mofor A.-C. , Waag A. , Stoemenos J.
Published: November 2006

The structural characteristics of the ZnO film grown on sapphire substrate using a thin MgO buffer layer were studied using transmission electron microscopy and high-resolution x-ray diffraction. The growth was carried out in a modified plasma-molecular beam epitaxy system. The observed misfit dislocations were well confined at the sapphire overgrown interface exhibiting domain matching epitaxy, where the integral multiples of lattice constants match across the interface. The main extended defects in the ZnO film were the threading dislocations having a mean density of 4×109cm−2. The formation of the MgO buffer layer as well as the ZnO growth were monitored in situ by reflection high-energy electron diffraction. The very thin ∼1nm, MgO buffer layer can partially interdiffuse with the ZnO as well as react with the Al2O3 substrate forming an intermediate epitaxial layer having the spinel (MgO∕Al2O3) structure.
Thermoluminescence of ZrO2 doped with Yb2O3 following excitation with x rays
Authors: Lai Lee-Jene , Sheu Hwo-Shuenn , Lin Yao-Kwang , Hsu Ya-Chuan , Chu Tieh-Chi
Published: November 2006

This study examines the thermoluminescence (TL) of ytterbium oxide (Yb2O3)-doped zirconia (ZrO2) in response to ultraviolet (UV) and synchrotron x-ray excitations. Experimental results demonstrate that, as well as a strong TL peak at 105°C and a weak peak at 205°C, another small peak appears at 150°C. The TL peak at 150°C exhibits dopant concentration quenching. The intensity of the two small peaks, particularly that at 150°C, increases rapidly with the energy of the photons. However, increasing the doping concentration of Yb2O3 reduces the intensity of both TL peaks at 105 and 205°C, and reduces the ZrO2 content in the monoclinic phase. This finding indicates that the intensities of both TL peaks at 105 and 205°C are associated with the ZrO2 content in the monoclinic phase. Additionally, the TL glow remains clearly observed from both undoped and doped samples after 48h of storage. Doping ZrO2 with Yb2O3 reduces the rate of fading of TL from the undoped ZrO2 sample. The stable TL peak of the Yb2O3 dopant at 150°C indicates its greater effectiveness than pure ZrO2 in dosimetry. These observations and their implications are discussed.
Silicon nanoparticle formation by short pulse electrochemical etching in the transition regime
Authors: Nychyporuk T. , Lysenko V. , Gautier B. , Barbier D.
Published: November 2006

Controlled formation of a monolayer or doublelayer of laterally separated Si nanoparticles at the surface of Si wafers with the use of short pulse anodization in the transition regime is reported and compared with two other anodization regimes: nanopore formation and electropolishing. The initial stages of the dynamics of the nanoparticle formation are studied in detail by means of atomic force microscopy. Detailed structural analysis of the height and surface density of the nanoparticles with respect to anodization current density, electrolyte composition, and anodization time has been performed.
Effects of Mn doping on dielectric properties of Mg-doped BaTiO3
Authors: Cha Seon Ho , Han Young Ho
Published: November 2006

The motion of oxygen vacancy as a defect complex and the effects of Mn addition on the dielectric relaxation in the Ba(Ti1−x−yMgxMny)O3−δ system have been studied in the frequency range of 25–106Hz at various temperatures. The dielectric constants (k) of 0.5mol% Mg-doped BaTiO3 rapidly decreased with increasing frequency at <1kHz and 200°C. There was a slight decrease in k observed for the BaTiO3 codoped with Mg and Mn and no change in k for singly Mn-doped BaTiO3. Loss peaks (tanδ) shifted to lower frequencies as the Mn content was increased, and the peak moved to higher frequencies with increasing temperature. Activation energies for the relaxation process of the Ba(Ti0.995−yMg0.005Mny)O3−δ system for y=0, 0.005, and 0.01 at 150–300°C were 0.47, 0.69, and 0.62eV, respectively, and at higher temperatures of 400–500°C were 1.08, 1.28, and 1.47eV for each corresponding composition.
Features of ion generation using Nd-glass laser
Authors: Kondrashev S. , Kanesue T. , Okamura M. , Sakakibara K.
Published: November 2006

Charge state and energy distributions of ions generated by a 3J∕30ns Nd-glass laser were measured at a distance of 3.7m from the target for seven different elements of the Periodic Table and for two different laser power densities (of the order of 1011 and 1012W∕cm2). Two groups of elements were found: highly charged ions with ionization potentials in the range of 500–1000eV were registered for all elements between C12 and Fe56; at the same time, ions with about-one-order-less ionization potentials were registered for elements between Ge74 and Ta181. The most probable reason for such a big difference is the recombination losses of ions during laser-produced plasma expansion into vacuum. Verification of recombination losses in the case of Ta181 target has shown no losses at distances longer than 32.5cm from the target, so recombination processes should take place at shorter distances. Current densities, pulse durations, energy ranges, and numbers of ions with different charge states were found for all elements by normalizing charge state distributions to total ion currents. Two different ion groups exist for all elements and laser power densities used in experiments: the faster group has a very weak dependence of energy on ion charge state, and the energies of the slower group are proportional to the charge states with high accuracy.
In-plane magnetotransport properties of Permalloy∕gadolinium∕Permalloy trilayers
Authors: Ranchal R. , Aroca C. , López E.
Published: November 2006

In this work we report on the magnetic and electrical properties of Permalloy∕gadolinium∕Permalloy (Py∕Gd∕Py) trilayers at low temperatures. These results are complemented with a structural study and numerical calculations. The Py-Gd coupling field is derived from magnetoresistance measurements in the transverse configuration of the trilayer with a Permalloy thickness lower than its exchange correlation length. The coupling field obtained was low, likely due to the presence of low Curie temperature Gd1−xNix alloys at the Py∕Gd interfaces.
Concentration-dependent diffusion of hydrogen in vitreous silica
Authors: Rundgren J. , Dong Q. , Hultquist G.
Published: November 2006

We report diffusion experiments where hydrogen permeates through a 1mm wall of vitreous silica at 550°C with applied gas pressures of 70, 460, 840, and 1200mbars. For each pressure, and at steady state, the flux and the amount of hydrogen in the material are measured. Within the experimental accuracy we find that the flux is proportional to the pressure and that the hydrogen amount increases with a falling gradient with respect to pressure. The result is a relationship between flux and mean concentration. A careful evaluation of the flux versus concentration relationship by means of the steady-state diffusion equation shows that the hydrogen diffusivity in the silica wall is concentration dependent and increases linearly with local concentration.
Structural, electronic, and optical properties of ZrO2 from ab initio calculations
Authors: Garcia J. C. , Scolfaro L. M. R. , Lino A. T. , Freire V. N. , Farias G. A. , Silva C. C. , Alves H. W. Leite , Rodrigues S. C. P. , da Silva E. F.
Published: November 2006

Structural, electronic, and optical properties for the cubic, tetragonal, and monoclinic crystalline phases of ZrO2, as derived from ab initio full-relativistic calculations, are presented. The electronic structure calculations were carried out by means of the all-electron full-potential linear augmented plane wave method, within the framework of the density functional theory and the local density approximation. The calculated carrier effective masses are shown to be highly anisotropic. The results obtained for the real and imaginary parts of the dielectric function, the reflectivity, and the refraction index show good agreement with the available experimental results. In order to obtain the static dielectric constant of ZrO2, we added to the electronic part the optical phonon contribution, which leads to values of ϵ1(0)≃29.5,26.2,21.9, respectively, along the xx, yy, and zz directions, for the monoclinic phase, in excellent accordance with experiment. Relativistic effects, including the spin-orbit interaction, are demonstrated to be important for a better evaluation of the effective mass values and in the detailed structure of the frequency dependent complex dielectric function.
Observation of coherent nonlinear interactions in the ion velocity distribution function
Authors: Uzun-Kaymak Ilker Ü. , Skiff Frederick
Published: November 2006

Using laser induced fluorescence (LIF) and higher order spectral analysis, we present the first measurements of phase space resolved coherent nonlinear interactions among the components of low frequency density fluctuations, (ω⩽ωci), in a linearly magnetized device. The bicoherence calculations employing the two point correlation technique suggest that there are two different coherent nonlinear wave-wave interactions in the measured spectrum. The first one, having a short correlation length and existing for slow moving ions, for which ∣υi‖∣⩽∣υith∣, is an interaction between fluctuations below the electron drift frequency, ω*. The second one is the strongest for fast moving ions, for which ∣υi‖∣⩾∣υith∣, and is a mode coupling between the azimuthal drift wave modes, m=1 and m=2. Combining these bispectral results with earlier linear analysis based on the power spectra of the fluctuations, we suggest that the nonlinear coupling observed between the spectral components below ω* for the case of slow moving ions is associated with the anomalous kinetic component. For slow moving ions, as we increase the neutral collision frequencies, the nonlinear interaction observed for spectral components below ω* decreases and the harmonic mode coupling for ω* takes over.
Determination of equilibrium density distribution and temperature of a pure electron plasma confined in a Penning trap
Authors: Aoki J. , Kiwamoto Y. , Kawai Y.
Published: November 2006

A fast scheme is proposed for determining the three-dimensional density distribution of a pure electron plasma under the thermal relaxation in a Penning trap on the basis of the observation of the axially integrated density distribution. The analysis that includes the contribution of the conducting wall reveals the appearance of a halo distribution surrounding the core distribution around the midplane. The core is confirmed to approach the Penning-type equilibrium distribution. Also proposed is a new scheme of the temperature determination of the electrons by analyzing a radial profile of the particles extracted with energy selection. This method is available on the basis of the self-consistent potential distribution associated with the equilibrium density distribution. The application of the two schemes of data analysis shows that the electron temperature decreases well below 0.1eV with a 1∕e folding time of ≈4× cyclotron-cooling time in the trap kept at room temperature.
Structural basis for the fast phase change of Ge2Sb2Te5: Ring statistics analogy between the crystal and amorphous states
Authors: Kohara Shinji , Kato Kenichi , Kimura Shigeru , Tanaka Hitoshi , Usuki Takeshi , Suzuya Kentaro , Tanaka Hiroshi , Moritomo Yutaka , Matsunaga Toshiyuki , Yamada Noboru , Tanaka Yoshihito , Suematsu Hiroyoshi , Takata Masaki
Published: November 2006

The three-dimensional atomic configuration of amorphous Ge2Sb2Te5 and GeTe were derived by reverse Monte Carlo simulation with synchrotron-radiation x-ray diffraction data. The authors found that amorphous Ge2Sb2Te5 can be regarded as “even-numbered ring structure,” because the ring statistics is dominated by four- and six-fold rings analogous to the crystal phase. On the other hand, the formation of Ge–Ge homopolar bonds in amorphous GeTe constructs both odd- and even-numbered rings. They believe that the unusual ring statistics of amorphous Ge2Sb2Te5 is the key for the fast crystallization speed of the material.
The c-DAC: A novel cubic diamond anvil cell with large sample volume/area and multidirectional optics
Authors: Sterer Eran , Silvera Isaac F.
Published: November 2006

We report on a new high-pressure instrument that has important advantages over the conventional diamond anvil cell (DAC). Our design is basically a miniaturized cubic press, i.e., six trimmed pyramidal diamond anvils compressing a central sample in three orthogonal directions rather than uniaxially. This geometry has three advantages over the DAC: first, it provides a high quality of uniform pressure due to the six-sided load, with improved support of the diamonds; second, samples can have volumes several hundred times larger and areas an order of magnitude greater; and third, it allows multidirectional optical access to the sample, with important advantages for spectroscopic studies such as Raman and Brillouin scatterings. The c-DAC is about the size and weight of a DAC and its pressure can be varied remotely, for example, while in a cryostat. The highest pressure achieved in our ongoing research is currently 22.4GPa, but limitations were not fundamental and we believe that pressures in the megabar range can be achieved.
Investigation of background edge thermal transport in ELMing and ELM-suppressed H-modes in DIII-D
Authors: Stacey W. M. , Evans T. E.
Published: November 2006

Thermal diffusivities are inferred in the plasma edge of a matched pair of DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] high confinement mode discharges, one with edge localized modes (ELMs) present and the other with ELMs suppressed by resonant magnetic perturbations. These experimentally inferred thermal diffusivity profiles are compared with the predictions of a variety of thermal transport theories.
Nanocrystalline barium titanate films on flexible plastic substrates via pulsed laser annealing
Authors: Tsagarakis Evangelos D. , Lew Connie , Thompson Michael O. , Giannelis Emmanuel P.
Published: November 2006

The drive towards ubiquitous electronics requires fundamental shifts in our approach to microelectronic fabrication as well as advances in materials and processing technologies. For large area electronics, low cost manufacturing, including roll-to-roll and printing technologies, will be required. These techniques present continuing challenges to develop processing technologies compatible with the low thermal budgets required for flexible polymeric substrates. The authors report here the deposition and dielectric properties of nanocrystalline BaTiO3 films on polyethylene terephthalate utilizing laser annealing as part of their effort to develop methods and tools for depositing various functional coatings and films on flexible substrates.
Cryogenic sapphire oscillator with exceptionally high long-term frequency stability
Authors: Hartnett J. G. , Locke C. R. , Ivanov E. N. , Tobar M. E. , Stanwix P. L.
Published: November 2006

The authors report on the development of a sapphire cryogenic microwave resonator oscillator with long-term fractional frequency stability of 2×10−17√τ for integration times τ>103s and a negative drift of about 2.2×10−15∕day. The short-term frequency instability of the oscillator is highly reproducible and also state of the art: 5.6×10−16 for an integration time of τ≈20s.
Terahertz-wave near-field imaging with subwavelength resolution using surface-wave-assisted bow-tie aperture
Authors: Ishihara Kunihiko , Ohashi Keishi , Ikari Tomofumi , Minamide Hiroaki , Yokoyama Hiroyuki , Shikata Jun-ichi , Ito Hiromasa
Published: November 2006

We demonstrate the terahertz-wave near-field imaging with subwavelength resolution using a bow-tie shaped aperture surrounded by concentric periodic structures in a metal film. A subwavelength aperture with concentric periodic grooves, which are known as a bull’s eye structure, shows extremely large enhanced transmission beyond the diffraction limit caused by the resonant excitation of surface waves. Additionally, a bow-tie aperture exhibits extraordinary field enhancement at the sharp tips of the metal, which enhances the transmission and the subwavelength spatial resolution. We introduced a bow-tie aperture to the bull’s eye structure and achieved high spatial resolution (∼λ∕17) in the near-field region. The terahertz-wave near-field image of the subwavelength metal pattern (pattern width=20μm) was obtained for the wavelength of 207μm.
One-dimensional and two-dimensional arrays of nanoholes generated by laser in the semiconfined configuration
Authors: Lugomer S. , Maksimović A. , Peto G. , Toth A. , Horvath E.
Published: November 2006

We have shown that nanoporosity can be generated on metal surfaces by nanosecond laser-matter interactions in the semiconfined configuration. The scanning electron microscope analysis has shown that nanoholes of ∼25–50nm in diameter, arranged in one-dimensional (1D) and two-dimensional (2D) irregular and regular arrays, have been formed. The interpretation is based on the generation of a dispersive, dissipative system of nonlinear solitary plasma waves (humps) that leave temperature/pressure fingerprints on the metal surface. It has been shown that the 1D irregular array of nanoholes can be interpreted as a result of the irregular string of solitary humps obtained by numerical simulation based on the Benney pd equation with the Gaussian perturbation. The 2D random array of nanoholes can be interpreted as a result of random solitary humps that can be obtained by numerical simulation from the Benney equation with the periodic perturbation. The regular string of nanoholes has been shown to appear as a result of breather modes (bound state of solitons), the numerical simulation of which has been based on the Boussinesq equation. The regular 2D array of nanoholes has been interpreted as fingerprints of breather modes, in agreement with the result of the numerical simulation of Tajiri and Murakami, [J. Math. Phys. 34, 2400 (1993)], based on the Kadomtsev-Petviashvili equation.
The effect of hydrogen on Cu3N thin films deposited by radio frequency magnetron sputtering
Authors: Wang J. , Chen J. T. , Miao B. B. , Zhang F. , Yan P. X.
Published: November 2006

The Cu3N films were synthesized at room temperature by radio frequency magnetron sputtering in various H2+N2 mixture atmosphere on a glass substrate. The introduction of hydrogen promoted the crystallization of Cu3N distinctly, and the optimized growth of (100) plane was strong. Compared to the films with no hydrogen introduced, the electrical resistivity decreased by several magnitudes and the optical energy gap decreased notably too. A conspicuous improvement of electrical and optical properties was achieved, but the surface morphology did not gain any modification; on the contrary, the introduction of hydrogen engendered the protuberances on the surface of the films. The thermal stability was investigated by heating the films in vacuum chamber at different temperatures. The films decomposed at 150°C initially and at 250°C entirely; the thermal stability is not as good as Cu3N films with no hydrogen included. The films were characterized by x-ray diffraction, UV-visible spectrum, four-point probe, and field emission scanning electron microscope method.
Thermally actuated untethered impact-driven locomotive microdevices
Authors: Sul O. J. , Falvo M. R. , Taylor R. M. , Washburn S. , Superfine R.
Published: November 2006

The authors have developed steerable locomotive devices as small as 30μm using the inertial impact drive as the thrust method. The devices consist of three-legged, thin-metal-film bimorphs designed to rest on three sharp tips with the device body curved up off the surface. Rapid, thermally induced curvature of one leg leads to stepwise translation on a low friction surface. A focused laser was used to supply energy and its parameters controlled the velocity and direction of motion of the device.
Time-dependent quantum transport and nonquasistatic effects in carbon nanotube transistors
Authors: Chen Yupeng , Ouyang Yijian , Guo Jing , Wu Thomas X.
Published: November 2006

Nonquasistatic effects in ac characteristics of carbon nanotube field-effect transistors are examined by solving a full time-dependent, open-boundary Schrödinger equation. The nonquasistatic characteristics, such as the finite channel charging time, and the dependence of small signal transconductance and gate capacitance on the frequency, are explored. The validity of the widely used quasistatic approximation is examined. The results show that the quasistatic approximation overestimates the transconductance and gate capacitance at high frequencies, but gives a more accurate value for the intrinsic cutoff frequency over a wide range of bias conditions.