bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulation of Lateral Septum CRF2Receptors Promotes Anorexia and Stress-Like Behaviors: Functional Homology to CRF1Receptors in Basolateral Amygdala
Authors: Bakshi Vaishali P. , Newman Sarah M. , Smith-Roe Stephanie , Jochman Kimberly A. , Kalin Ned H.
Published: September 2007

The corticotropin-releasing factor (CRF) system is the primary central mediator of stress-like states, coordinating behavioral, endocrine, and autonomic responses to stress. Although induction of anorexia is a well documented effect of CRF receptor agonist administration, the central sites and behavioral processes underlying this phenomenon are poorly understood. The present studies addressed this question by examining the neuroanatomical, behavioral, and pharmacological mechanisms mediating decreases in feeding produced by the CRF1/CRF2receptor agonist urocortin. Separate groups of food-restricted male Sprague Dawley rats were given infusions of urocortin (0, 50, 125, 250 ng/0.5 μl) into the lateral septum (LS) and immediately afterward were rated on a wide array of behaviors (locomotion, rearing, grooming, stereotypies) including a microstructural analysis of ingestive behavior. Intra-LS urocortin infusion dose-dependently reduced feeding and drinking while concomitantly increasing grooming, stereotypies, and ethological plus traditional measures of anxiety-like responses in the elevated plus-maze. Urocortin infusion into neighboring sites (lateral ventricle, medial caudate) had no effects. Coinfusion into the LS of the mixed CRF1/CRF2receptor antagonistd-Phe-CRF(12–41)(0, 100, 1000 ng/0.5 μl) or the novel selective CRF2receptor antagonist Astressin2B (0, 500, 1000 ng/0.5 μl) blocked urocortin-induced effects, but the CRF1-selective antagonist NBI27914 (0, 500, 1000 ng/0.5 μl) had no effect, although it completely reversed the behavioral sequelae of CRF when infused into the basolateral amygdala. These results indicate that one of the modes through which the CRF system promotes anorexia is the recruitment of stress-like states after stimulation of CRF2receptors within the LS.
Vmat2Heterozygous Mutant Mice Display a Depressive-Like Phenotype
Authors: Fukui Masato , Rodriguiz Ramona M. , Zhou Jiechun , Jiang Sara X. , Phillips Lindsey E. , Caron Marc G. , Wetsel William C.
Published: September 2007

The vesicular monoamine transporter 2 (VMAT2) is localized primarily within the CNS and is responsible for transporting monoamines from the cytoplasm into secretory vesicles. Because reserpine (a VMAT inhibitor) can precipitate depressive-like symptoms in humans, we investigated whetherVmat2heterozygous (HET) mice present with depressive-like behaviors. The mutants showed locomotor and rearing retardation in the open field and appeared anhedonic to 1 and 1.5% sucrose solutions. Immobility times forVmat2heterozygotes were prolonged in forced swim and imipramine normalized this behavior. HET animals also showed enhanced immobility in tail suspension and this response was alleviated by fluoxetine, reboxetine, and bupropion. Stimulated GTPγS binding indicated that α2-adrenergic receptors in HET hippocampus were more sensitive to UK 14,304 (5-bromo-N-(4,5-dihydro-1-H-imidazol-2-yl)-6-quinoxalinamine) stimulation than in wild type (WT) mice. In learned helplessness, mice were exposed to a shuttle box for 4 d or were given inescapable foot-shocks for the same time period. On day 5, all animals were tested in shock escape. Failure rates and the latency to escape were similar for WT and HET mice that were only pre-exposed to the test apparatus. In foot-shock groups, learned helplessness was more robust in heterozygotes than in WT controls. Basal secretion of serum corticosterone was not distinguished by genotype; however, corticosterone levels in mutants were more responsive to stress. Anxiety-like responses of WT and HET animals in the open field, light-dark exploration, zero maze, and novelty-suppressed feeding tests were indistinguishable. Collectively, these findings suggest thatVmat2heterozygotes display a depressive-like phenotype that is devoid of anxiety-like behavior.
DFG Forschergruppe 500: Computergestützte Destruktion komplexer Tragwerke durch kontrollierte Sprengung (DFG Research Unit 500: Computer aided destruction of complex structures using controlled explosives)
Authors: Hartmann Dietrich , Breidt Michael , Nguyen Van Vinh , Stangenberg Friedhelm , Höhler Sebastian , Schweizerhof Karl , Blankenhorn Gunther , Möller Bernd , Graf Wolfgang , Liebscher Martin
Published: September 2007

Thema der laufenden DFG-Forschergruppe 500 „Computergestützte Destruktion komplexer Tragwerke durch Sprengung” ist die realitätsnahe Simulation von Bauwerkssprengungen unter Berücksichtigung der in der Praxis vorhandenen Unwägbarkeiten. Hauptziel der Forschungsarbeit ist die Auffindung einer abgesicherten und optimalen Sprengstrategie zur Planungsunterstützung. Im Hinblick auf die adressierte Leserschaft behandelt der Artikel insbesondere die Entwicklung des forschergruppenübergreifenden Softwaresystems für den Sprengabbruch, das in seinem Kern auf der Verwendung effizienter Mehrkörpersysteme beruht.
Monte Carlo Simulation of Kinetically Limited Electrodeposition on a Surface with Metal Seed Clusters
Authors: Drews Timothy O. , Braatz Richard D. , Alkire Richard C.
Published: September 2007

Kinetic Monte Carlo (KMC) simulations were carried out to simulate kinetic-limited electrodeposition of a metal (M) onto an array of pre-existing metal clusters on a substrate (S) of a second conducting material. Electrochemical reaction and surface diffusion were accounted for in a KMC code which tracked deposit growth with a (2+1)-dimensional approach. Beginning with various arrangements of ten-atom metal seed clusters on a substrate platform of 300 × 300 fcc lattice sites, KMC simulations were carried out to investigate the evolution of the surface morphology. The influence of the number (spacing) of pre-existing seed clusters, the applied potential, and the metal–substrate surface diffusion energy barrier were investigated. It was found that when 16 or fewer seed clusters were present on the surface prior to electrodeposition, the resulting nucleation distribution was dominated by secondary nuclei formed during deposition. For substrates with a metal–substrate surface diffusion energy barrier greater than 3.5 × 10-20 J, it was more difficult to control the uniform growth of the seed clusters owing to the nucleation of secondary clusters. At lower applied potentials it was found that larger nuclei could be grown with a more controlled size distribution because fewer secondary nuclei were formed. Furthermore, it was found that larger clusters with a more controlled size distribution can be grown when more clusters are seeded onto the surface because the deposited atoms were more likely to attach to existing clusters, than to form secondary nuclei.
Hydrogen Adsorption on Activated Platinum Electrodes – An Electrochemical Impedance Spectroscopy Study
Authors: Reiner A. , Kuhn H. , Wokaun A. , Scherer G. G.
Published: September 2007

On the way to prepare stable platinum electrodes for the characterization of the Hupd reaction by electrochemical impedance measurements, a novel, feather-like platinum surface modification was found and characterized. In addition, a precursor morphology was identified. Electrochemical impedance measurements at selected potentials in the Hupd potential region yield information on double layer capacity, adsorption capacity, and adsorption resistance of the Hupd reaction for these two electrode morphologies.
DFT Studies on the Nature of Coadsorbates on SO4
2-/Au(111)
Authors: Venkatachalam Sudha , Jacob Timo
Published: September 2007

Density Functional Theory (DFT) studies were performed on the adsorption of sulfate on Au(111). Focusing on the well-known (√3 × √7)R19.1° structure reported by various surface sensitive techniques, the coadsorption of H3O+ and/or H2O has been considered in different combinations. The calculated binding energies show that the coadsorption of a single H3O+ per sulfate is the most stable configuration, which is in agreement with experimental observations. Further, we find that in the case of coadsorption of both H3O+ and H2O along with sulfate, one of the protons of hydronium moves to sulfate, finally leading to bisulfate with two coadsorbed water molecules. Besides the morphology and energetics of the different configurations, we also discuss the nature of the surface bonds by analyzing the charge density distribution.
In Situ Scanning Tunnelling Microscopy in Ionic Liquids: Prospects and Challenges
Authors: Endres Frank , Zein El Abedin Sherif
Published: September 2007

In this paper devoted to Professor Dieter Kolb's 65th birthday the prospects and challenges of ionic liquids for fundamental investigations at the interface electrode/electrolyte are discussed. Ionic liquids consist solely of mainly organic cations and anions and they have wide electrochemical windows of up to 6 V (approximately ± 3 V vs. NHE) combined with wide thermal windows of up to 300ºC and extremely low vapour pressures between 10-11 and 10-10 mbar around room temperature. Thus, thermodynamically they give access to many elements and compounds at variable temperature which due to their reactivity cannot be electrodeposited in aqueous solutions. Apart from a discussion of electrochemical windows examples to be covered in this paper are the local probe deposition of silicon, aluminium and tantalum on Au(111). There is an incredibly high number of possible liquids (between 1012 and 1018 liquids, binary and ternary mixtures have been predicted) but also one major challenge for fundamental physicochemical studies, especially with the in situ STM: purity. It is tough to purify ionic liquids as hitherto they can neither be distilled with considerable rates without decomposition nor recrystallized nor sublimed. It will be shortly discussed that even apparently ultrapure ionic liquids can contain low amounts of inorganic impurities leading to inexpected behaviour on the single crystalline surface of Au(111). Due to their importance this paper focuses soleley on the third generation of ionic liquids, i.e. air and water stable ones.
Du discours à l'épistolaire: les échos du Pro Plancio dans la lettre de Cicéron à Lentulus Spinther (Fam. I, 9)
Authors: Bernard Jacques-Emmanuel
Published: September 2007

After the conference at Luca in 56 BC, where Caesar, Crassus, and Pompey renewed their Triumvirate, Cicero was forced to accept a compromise, which appears in the orations that he delivered to defend both the Triumvirs (De prouinciis consularibus) and his own enemies (defence of Vatinius and Gabinius). In a letter to Lentulus Spinther of December 54, Cicero justified his new political attitude toward the popular leaders. Designed as a plea, this letter, one of Cicero's longest, raises the question: “What similarity is there between a letter and a speech in court or at a public meeting?” (Fam.IX, 21, 1). Relying on the intertextuality of the letter to Lentulus with the oration Pro Plancio, delivered four months previously, this paper considers how Cicero adapts appropriateness and decorum to his addressee and displays a rhetoric that is half way between judicial eloquence and epistolary discourse.
Blair's Ideal Orator: Civic Rhetoric and Christian Politeness in Lectures 25-34
Authors: Walzer Arthur E.
Published: September 2007

In his Lectures on Rhetoric and Belles Lettres, Hugh Blair works within the tradition of Isocrates, Cicero, and Quintilian in presenting rhetoric as a school subject that forms character and educates in citizenship. But by the terms of his title, “Rhetoric” and “Belles Lettres,” Blair signals a commitment to two different ideals of character—the ideal of civic republicanism of Roman rhetoric, on the one hand, and that of a middleclass, polite culture, on the other. As Blair wrestles with the tensions inherent in his program to reconcile the two in lectures 25–34, he inadvertently dramatizes the transformation from a rhetorical culture to a modern, bourgeois one.
A Torontói Alexitímia Skála (TAS-20) magyar változata: megbízhatósága és faktorvaliditása egyetemista mintán
Authors: Cserjési Renáta , Luminet Olivier , Lénárd László
Published: September 2007

Az
alexitímia olyan személyiségjegy, amely magába foglalja az érzelmek azonosításának,
az emocionális arousal és a testi érzetek megkülönböztetésének, valamint az
érzelmek külvilág felétörténőkifejezésének zavarát. A 20 tételes Torontói
Alexitímia Skála (TAS-20) három faktor –az érzelmek azonosításának nehézsége, az érzelmek kifejezésének nehézsége
és a prag­matikus gondolkodás–mentén
ragadja meg az alexitímia konstruktumát. A TAS-20 magyar nyelvűváltozatát 275
egyetemi hallgató(172 nőés 103 férfi) töltötte ki a Pécsi Tudományegyetemen. A
más nyelvekre fordított változatokhoz hasonla
On the time delay of the photoplastic effect
Authors: Pellegrino Joseph , Galligan J. M.
Published: September 2007

Photoplasticity in mercury cadmium telluride, Hg1-x Cdx Te with x = 0.3, has been studied as a function of light frequency and deformation temperature. We show that there is an easily measurable time delay accompanying irradiation of the crystal and the change in stress. This time delay is temperature dependent, suggesting a diffusion of charge carriers, introduced by the light, to the interior of the crystal. A simple analysis is given of the observed temperature dependence that is consistent with the experiments.
Ceramic-to-metal welding by a pressurized combustion reaction
Authors: Miyamoto Yoshinari , Nakamoto Takashi , Koizumi Mitsue , Yamada Osamu
Published: September 2007

A new method of ceramic-to-metal welding has been developed using a pressurized combustion reaction to form Mo—TiB2—Mo and Mo—TiC—Mo couples. Mixtures of Ti powder with B or C between Mo disks were electrically ignited under 3 GPa pressure. The exothermic reaction of the powders resulted in the formation of TiB2 and TiC and reaction with Mo at the metal interface. Weld strengths of the Mo—TiB2—Mo and Mo—TiC—Mo couples were 20—40 MPa and ∼ 10 MPa, respectively.
Indexing of icosahedral quasiperiodic crystals
Authors: Cahn John W. , Shechtman Dan , Gratias Denis
Published: September 2007

Since the definition of quasiperiodicity is intimately connected to the indexing of a Fourier transform, for the case of an icosahedral solid, the step necessary to prove, using diffraction, that an object is quasiperiodic, is described. Various coordinate systems are discussed and reasons are given for choosing one aligned with a set of three orthogonal two-fold axes. Based on this coordinate system, the main crystallographic projections are presented and several analyzed single-crystal electron diffraction patterns are demonstrated. The extinction rules for three of the five icosahedral Bravais quasilattices are compared, and some simple relationships with the six-dimensional cut and projection crystallography are derived. This analysis leads to a simple application for indexing powder diffraction patterns.
Nucleation and growth in surface-melted crystalline and amorphous Fe40Ni40P14B6alloys
Authors: Wallace R. J. , Kaufmann E. N.
Published: September 2007

The well-known glass-forming alloy Fe40Ni40P14B6was surface melted by an electron beam traversing its surface at various velocities in an identical manner for both the crystalline and the amorphous state of the alloy. Cross-sectional optical metallography and numerical heat-flow analysis were used to show that (1) crystallization of the amorphous state does not occur during treatment around or in the regrown layer at the highest processing speeds, a behavior consistent with an extrapolation of isothermal nucleation and growth measurements; (2) initial resolidification of the molten layer is always crystalline when the melt pool contacts underlying crystalline material where nucleation is immediate; and (3) solidification front velocities greater than 5 ± 0. 5 cm/s exceed the maximum kinetic limit for growth of the crystalline phase and amorphous layers are formed, a result consistent with the eutectic nature of the alloy. Inconsistencies with the work of previous investigators of this system are discussed.
Chemical preparation and properties of high-field zinc oxide varistors
Authors: Dosch R. G. , Tuttle B. A. , Brooks R. A.
Published: September 2007

Chemical preparation methods were developed for high-field ZnO varistors which used precipitation techniques to prepare precursor powders. Varistors were made by sintering uniaxially pressed pellets in the range of 675°–740 °C in air. Properties of these varistors included electric fields (E) in the 10–100 kV/cm range at current densities (J) of 5 A/cm2, nonlinearity coefficients (α) greater than 30 for 2.5≤J≤5.O A/cm2, and densities in the range of 65%-99% of theoretical depending both on sintering temperature and composition.
Ion beam processing of LiNbO3
Authors: Appleton B. R. , Beardsley G. M. , Farlow G. C. , Christie W. H. , Ashley P. R.
Published: September 2007

Ion implantation and ion beam mixing have been investigated as alternative techniques to hightemperature diffusion for introducing dopants into LiNbO3. Heavy ion bombardment at both 77 and 300 K initiated a near-surface decomposition causing Li to diffuse to the surface where it formed a nonuniform agglomerate. The damage and annealing characteristics of this effect were studied by ion scattering/channeling, secondary ion mass spectrometry, and optical microscopy. The origins of the surface decomposition are discussed along with possible solutions, and selected samples were evaluated for waveguide properties.
Optical absorption of rare-earth-doped BeF2 glasses
Authors: Tick P. A.
Published: September 2007

BeF2 glasses are potentially useful materials for light transmission in the near infrared region of the spectrum. While the intrinsic attenuation of BeF2 is thought to be much lower than silica, the optimum wavelength will be further in the infrared, near 2.1 μ. In this spectral region impurities other than transition metals may be important—rare earths, for example. The data required to estimate the contributions to attenuation are normally not available; hence it is the purpose of the present work to provide that information. Using a binary BeF2/ThF4 glass, the optical absorption spectra of a number of rare earths are measured. The experimental procedures, optical spectra, and absorption strength are described.
Growth of tetragonal BaTiO3 single crystal fibers
Authors: Saifi M. , Dubois B. , Vogel E.M. , Thiel F.A.
Published: September 2007

With the increasing use of optical fibers in the telecommunication network, there is need for fiber geometry compatible optical devices such as optical amplifiers, switches, couplers, and isolators. These active devices are based on field-dependent material properties, such as electrooptic and magneto-optic effects, which are stronger in single crystal than in amorphous materials. Single crystal fibers can be grown by the laser heated pedestal growth (LHPG) technique. In this paper we report the growth of single crystal fibers of ferroelectric barium titanate from sintered ceramic rods of stoichiometric barium titanate. Barium titanate is one of the most extensively investigated ferroelectric materials. However, its growth from stoichiometric melt always results in its hexagonal nonferroelectric phase. Using LHPG, single crystal strontium titanate seed, and sintered ceramic barium titanate rods, we have succeeded in growing single crystal fibers (∼ 100 μ m diameter) of pure barium titanate with tetragonal (ferroelectric) crystal structure. This paper discusses growth and characterization of these fibers.
Fabrication process, experimental results, and application for an elemental level vertically intergrated circuit (ELVIC)
Authors: Enomoto Tadayoshi
Published: September 2007

A new double-layered stacked LSI fabrication process has been developed for the purpose of realizing short fabrication turn-around time, high fabrication yield, and high integration density. This process, which is named “Elemental Level Vertical Integrated Circuit (ELVIC)” technology, puts two conventionally made LSI chips face to face and bonds them by thermal compression. The process includes, in addition to the conventional LSI fabrication process, vertical interconnection (VI) formation in the upper and lower LSI layers, planarization of both upper and lower layer surfaces, and inter-level connections using pressure and heat. In the experimental version, about 52 000 10X10μm2 Au-on-Ti VIs were connected on a 5×5 mm2 chip. Each pair of mated VIs was measured and had a tensile strength of 4 mg · force. A two-layer, 31-stage inter-CMOS/bulk ring oscillator consisting of p-channel MOSFETs on the upper layer and n-channel MOSFETs on the lower layer has been built. Propagation delay time per stage is 1.86 ns at the supply voltage of 5 V. ELVIC technology can produce a variety of benefits such as high production yield, doubling integration density, latchup-free CMOS LSIs, radiation-damage-free LSIs, multifunction, and complete mixing of bipolar, CMOS, and GaAs technologies.
Electrical and thermal transport properties of the Y1 − xMxCrO3system
Authors: Weber W.J. , Griffin C.W. , Bates J.L.
Published: September 2007

The effects of substituting divalent metal ions (Mg, Ca, Sr, Ba) for Y in YCrO3were investigated by electrical conductivity, Seebeck coefficient, and thermal conductivity measurements. The electrical conductivity results were consistent with the hopping-type conduction of a temperature-independent concentration of small polarons, with measured activation energies of 0.18-0.26 eV. The Seebeck coefficient increased nearly linearly with temperature and indicatedp-type conductivity. Both electrical conductivity and Seebeck coefficient results show a strong dependence on dopant size (ionic radius) and indicate that the highest carrier concentrations were associated with Ca as the dopant, which is attributed to the similar ionic radii of Ca2+and Y3+. The thermal conductivity decreased slightly with temperature and dopant concentration.
Effects of low-energy electron bombardment on the surface chemical structure and adhesive properties of polytetrafluoroethylene (PTFE)
Authors: Kelber J.A. , Rogers J.W. , Ward S.J.
Published: September 2007

The x-ray photoemission studies of polytetrafluoroethylene (PTFE) bombarded by lowenergy electrons in ultra-high vacuum conditions indicate that the major chemical changes induced by electron bombardment are defluorination of the surface and cross-linking of the polymer chains. The same electron bombardment process, when performed in the presence of 1×10−6 Torr ND3, also results in the adsorption of nitrogen-containing groups at the surface. The rate of nitrogen adsorption is linear for short electron bombardment times while the rates of defluorination and cross-linking are roughly exponential. However, at long bombardment times, the rates of nitrogen uptake, defluorination, and cross-linking become zero at the same time, indicating that defluorination of the surface is the rate-determining step in electron beam-induced adsorption of nitrogen-containing species. Regardless of whether the bombardment is carried out in ultra-high vacuum or in the presence of ND3, the maximum modification depth is less than 30 Å. Pull tests performed on PTFE samples bombarded by electrons in ultra-high vacuum, then removed into air and bonded to epoxy show epoxy-PTFE joint strengths of 280–360 1b/in.2 (psi), are compared to zero psi for untreated PTFE and ≃2000 psi for cohesive failure within the PTFE layer.
Crystal structure of intermetallic phase in Fe–20Cr–4Al–0.5Y alloy by convergent beam electron diffraction
Authors: Ayer Raghavan , Scanlon J. C. , Ramanarayanan T. A. , Mueller R. R. , Petkovic-Luton R. , Steeds J. W.
Published: September 2007

The crystal structure and chemical composition of the intermetallic phase in a Fe-20%Cr-4%Al-0.5%Y (wt. %) alloy were investigated by electron microscopy. Convergent beam diffraction studies revealed that the intermetallic phase forms in three different crystal structures that could coexist in a single grain of the phase. The dominant crystal structure was shown to be hexagonal (a= 0.85,c= 0.84 nm) with a space group most likely to beP63/mmc. Within the hexagonal phase, regions of a rhombohedral crystal structure (a= 0.85,c= 1.26 nm) were observed that had grown in without an apparent phase boundary separating the two crystal structures. The third crystal structure was determined to be monoclinic (a= 0.97,b= 0.85,c= 1.07 nm, and beta = 97.3°) and formed by twinning on the {10$\overline 1$1} planes of the hexagonal phase. The chemical compositions of regions with different crystal structures were comparable and the stoichiometry of the intermetallic phase corresponds to (Fe,Cr)17(Al,Y)2. The relationship of the observed crystal structures to those previously reported is discussed.
The diffusion of hydrogen in silicon and mechanisms for “unintentional” hydrogenation during ion beam processing
Authors: Seager C. H. , Anderson R. A. , Panitz J. K. G.
Published: September 2007

Experiments are described in which hydrogen is injected into silicon by various techniques and detected by the neutralization of boron acceptor sites. Wet chemical etching is shown to inject protons several microns in a few seconds; this experiment is used to set a lower limit on the diffusivity of hydrogen of ⋍2⊠10−11 cm2/s at 300 K, a number in reasonable agreement with prior estimates deduced by Van Wieririgen and Warmholtz from high-temperature permeation measurements. A number of experiments are reported to elucidate the mechanism for “unintentional” hydrogenation occurring during argon ion bombardment. The data suggest that this effect is caused by bombardment-induced injection of hydrogen from surface H2O/hydrocarbon contaminants.
The role of diffusion in amorphous-phase formation and crystallization of amorphous Ni–Zr
Authors: Barbour J. C. , de Reus R. , van der Gon A. W. Denier , Saris F. W.
Published: September 2007

The Ni–Zr system is examined as a representative system for the formation of an amorphous phase by diffusion and for the crystallization of an amorphous phase by diffusion. High-resolution electron microscopy (HREM) is used to show that the amorphous phase grows by bulk diffusion through the amorphous material rather than by short-circuit diffusion. Also, the HREM shows that the amorphous phase formed by diffusion appears to be the same as the vapor-deposited amorphous phase. A correlation between crystallization temperatures (Tx) and the enthalpy of large-atom hole formation is given. This correlation predicts values of Tx that are lower than those predicted from the small-atom hole-formation model. The difference in hole-formation enthalpies for the large and small atoms is given as a criterion for amorphous-phase formation via diffusion.
The oriented growth of anatase in thin films of amorphous titania
Authors: Howitt D. G. , Harker A. B.
Published: September 2007

The growth of an oriented anatase grain structure from the post-deposition annealing of amorphous reactive ion-beam-deposited thin films of titanium oxide has been demonstrated. The transformation has been observed directly by electron microscopy and the crystallization of the films occurs only when their thicknesses are greater than about 50 nm. Substrate effects were not found to be significant to the crystallization, which could also be induced by annealing freestanding films. The transformation processes can be described in terms of existing theories of crystal growth where the amorphous film is described as a supercooled liquid.
Effect of material and design parameters on the life and operating voltage of a ZnO varistor
Authors: Gupta T. K.
Published: September 2007

A varistor's life has been defined as the time required to reach a limiting power density at which the power generated exceeds the power dissipated. Based on this concept, a working model for predicting the life of a ZnO varistor has been developed in terms of several critical material and design parameters. The model provides a direction as to whether these parameters should be maximized or minimized in order to enhance a varistor's life. Alternately, given a predetermined amount of the varistor's life, the model predicts a safe operating voltage under a given set of conditions.
Hydrogen concentration gradients in cathodically charged austenitic stainless steel
Authors: Ulmer D. G. , Altstetter C. J.
Published: September 2007

An x-ray diffraction technique has been developed to makein-situmeasurements of hydrogen concentration profiles from which diffusivity and solubility values are calculated. Hydrogen is supplied to the metal surface by cathodically polarizing it in a bath of 1N H2SO4electrolyte. The incident x-ray beam penetrates a thin layer of electrolyte solution at the surface of the sample, thus, x-ray diffraction profile changes can be recorded as a function of charging time and temperature. The applied potential prevents outgassing of the specimen during the measurement. The x-ray diffraction profiles are deconvoluted to remove the α1/α2doublet and noncompositional broadening effects. Composition-depth profiles are then obtained from an intensity band transformation of the deconvoluted data. A diffusion coefficient is determined by fitting a solution to Fick's second law to the concentration-depth profile. The technique described here was used to measure hydrogen diffusivity in stainless steel in the temperature range 20°–80°C.
Thin-film alloys of Bi1−x Sbx produced by ion-beam mixing and their thermoelectric properties
Authors: Ibrahim A. M. , Thompson D. A. , Davies J. A.
Published: September 2007

Ion-beam mixing in the Bi/Sb system using Ne+, Ar+, and Kr+ ions in the energy range 40–110 keV has been investigated by Rutherford backscattering analysis. The mixing is shown to be temperature independent in the region of 40–250 K; at higher temperatures the mixing per ion increases rapidly with temperature. Initially, a square-root dependence of the mixing on the ion dose was observed. At higher doses a saturation effect is obtained as the Sb becomes uniformly distributed in depth throughout the film. Also, the mixing was found to increase linearly with the energy deposited into atomic displacement collisions at the Bi/Sb interface. Alloys of Bi1−x Sbx (0<x<0.5) have been produced. The thermoelectric power of the fully mixed alloys reaches a maximum value at an alloy composition of Bi0.87 Sb0.13. The thermoelectric power for partially mixed alloys exhibits almost the same dependence on Ar+ dose as the amount of mixing.
Kinetic decomposition of Ni2SiO4 in oxygen potential gradients
Authors: Jacob K. T. , Shukla A. K.
Published: September 2007

Nickel orthosilicate (Ni2SiO4) has been found to decompose into its component binary oxides in oxygen potential gradients at 1373 K. Nickel oxide was formed at the high oxygen potential boundary, while silica was detected at the low oxygen potential side. Significant porosity and fissures were observed near the Ni2SiO4/SiO2 interface and the SiO2 layer. The critical oxygen partial pressure ratio required for decomposition varied from 1.63 to 2.15 as the oxygen pressures were altered from 1.01 ⊠ 105 to 2.7X 10−4 Pa, well above the dissociation pressure of Ni2SiO4. Platinum markers placed at the boundaries of the Ni2SiO4 sample indicated growth of NiO at the higher oxygen potential boundary, without any apparent transport of material to the low oxygen potential side. However, significant movement of the bulk Ni2SiO4 crystal with respect to the marker was not observed. The decomposition of the silicate occurs due to the unequal rates of transport of Ni and Si. The critical oxygen partial pressure ratio required for decomposition is related both to the thermodynamic stability of Ni2SiO4 with respect to component oxides and the ratio of diffusivities of nickel and silicon. Kinetic decomposition of multicomponent oxides, first discovered by Schmalzried, Laqua, and co-workers [H. Schmalzried, W. Laqua, and P. L. Lin, Z. Natur Forsch. Teil A 34, 192 (1979); H. Schmalzried and W. Laqua, Oxid. Met. 15, 339 (1981); W. Laqua and H. Schmalzried, Chemical Metallurgy—A Tribute to Carl Wagner (Metallurgical Society of the AIME, New York, 1981), p. 29] has important consequences for their use at high temperatures and in geochemistry.
Estimation of the infrared absorption of ZnCl2–KBr glass by molecular dynamics
Authors: Inoue Satoru , Tamaki Mitsuru , Kawazoe Hiroshi , Yamane Masayuki
Published: September 2007

Molecular dynamic calculations have been made on glasses in the ZnCl2–KBr system in order to estimate the infrared (IR) absorption of these glasses. Oxygen-free glass was estimated to be transparent up to 25 μm. Glasses containing oxygen impurities were estimated to be transparent only up to 16 μm, with a weak absorption band around 10.4 μm. This agrees with experimental results of glasses in the ZnCl2–KBr–PbBr2system.
Variation of the pressure dependence of the superconducting transition temperature with x in La1−xSrx CuO4
Authors: Schirber J. E. , Venturini E. L. , Kwak J. F. , Ginley D. S. , Morosin B.
Published: September 2007

Hydrostatic pressure measurements of the superconducting transition temperature were made as a function of x in La2−xSrx CuO4. A sharp change in the behavior occurs between x = 0.2 and 0.25 in that the pressure derivative goes from positive to essentially zero. This result is discussed in the context of band structure models.
Microstructural evolution in sintering of ALOOH gels
Authors: Yarbrough Walter A. , Roy Rustum
Published: September 2007

Materials derived by precipitation or polymerization chemistry (e.g., “sol-gel” methods) are usually obtained in noncrystalline or otherwise metastable phases, and transformation to more thermodynamically stable phases generally occurs by a nucleation and growth process. In a fully reconstructive transformation, such as occurs in the alumina system, the activation energy for nucleation may be higher than that for simple short-range diffusion. Hence nucleation frequency can be a controlling factor in the development of microstructurc. The efficacy of seeding as a method of microstructural and phase control in solution-derived or so-called sol-gel materials has been clearly demonstrated for the alumina system. The epitaxial nature of this phenomenon is explored, using the polarizing microscope to follow the crystallographic orientation of the transformed material as the transformation proceeds, showing that this is epitaxial in nature, and that the nucleation frequency in unseeded material is relatively low (∼ 1010 cm−3). The microscope was then used to demonstrate the effect on nucleation frequency of seeding with materials selected to be isostructural, isotypic, and having little or no similarity to the corundum structure. Using these and other methods, the seeding phenomenon in alumina gels is shown to result from epitaxial growth of the stable corundum phase on isostructural or isotypic nuclei in the solid state. This approach is applied to formulate hypotheses for the mechanisms by which some of the previously reported effects of seeding, e.g., enhanced densification and microstructural refinement, can be understood and to formulate a set of generalizations for its potential application to other systems.
Inhibition of tribo-oxidation preceding wear, by single-phased TiNx films formed by ion implantation into TiAl6V4
Authors: Pons F. , Pivin J. C. , Farges G.
Published: September 2007

Single-phased films of α-Ti1−x Nx, ∊-Ti2Nx, or δ-TiNx with a homogeneous composition on more than 400 nm were produced by ion implantation at several different energies in the TiAl6V4 alloy. Secondary ion mass spectroscopy (SIMS) profiles and ionic images recorded within the tracks after incremented cycles of friction against a 35NCD16 steel ball in air have shown that a Ti–O–C–N film is progressively formed on the surface of α solid solutions, while more concentrated nitride films resist oxidation. The friction and abrasion resistances of ∊ or δ nitride films are initially improved for a time lasting for as long as their N content increases, but they are finally self-destroying. On the contrary, the hardening effect of N in an α-Ti matrix keeps a really severe amount of abrasion from occurring during running in of the implanted surface, without suppressing the building up of a lubricant oxide hardened by N.
Selective electron-induced decomposition of CVD SiO2 overlayers on oxides
Authors: Okuhara T. , White J. M.
Published: September 2007

The electron-induced decomposition (EID) of SiO2 overlayers on various high surface area oxide substrates was studied using Auger electron analysis (AES). Bulk SiO2 was stable upon electron bombardment, but bulk Al2O3 decomposed readily to elemental Al when the primary electron beam energy was 2 keV and the beam current was 6–16 μA. On the other hand, SiO2 overlayers having an average thickness of about 10 Å on Al2O3 decomposed selectively under the same conditions. In contrast to Al2O3 substrates, SiO2 overlayers on TiO2, ZrO2, and MgO were quite stable to the same electron bombardment. Therefore it is concluded that Al2O3 accelerates the EID of SiO2 overlayers and the SiO2 overlayer suppresses EID of Al2O3 substrates.
Synthetic diamonds produce pressure of 125 GPa (1.25 Mbar)
Authors: Ruoff Arthur L. , Weir Samuel T. , Brister Keith E. , Vohra Yogesh K.
Published: September 2007

Synthetic gray-blue diamonds were used as anvils in a diamond anvil cell to produce a pressure of 125 GPa (1.25 Mbar) in a gasketed sample. Pressure was measured by x-ray diffraction methods by using gold and iron as a calibrant and also by optical methods based on the shift of the fluorescence peaks of ruby with pressure. The future potential of synthetic diamonds for ultrapressure research is discussed.
Thin-film interactions and their relevance to electronic packaging
Authors: Chang Chin-An
Published: September 2007

Thin-film interactions have been increasingly important to various aspects of electronic technologies, including devices and packaging. Extensive outdiffusion and alloy formation, for example, can be detrimental to the yield and reliability of the parts fabricated. Understanding such interactions, and their dependence on various factors, continues to be a challenge to thin-film scientists. Several aspects related to thin-film interactions are described in this paper: a review of the ambient effects that provides an understanding of the basic reaction mechanisms at the interface; an illustration of concerns upon choosing a diffusion barrier layer, and reaction across such a layer; and the effect of undesired outdiffusion on the solder spread related to joining.
Microstructural characterization of YBa2Cu3O7−x
Authors: Sarikaya M. , Thiel B. L. , Aksay I. A. , Weber W. J. , Frydrych W. S.
Published: September 2007

A detailed characterization study on polycrystalline specimens of YBa2Cu3Oy-x that were prepared by solid-state reaction techniques has been carried out. In the samples studied. magnetization and resistivity measurements indicate superconductivity onset temperatures of up to 89 K. Transmission electron microscopy (TEM) techniques have been used to facilitate direct microstructural characterization. It is shown that the planar defects on (001) planes form during the ion milling of the samples and are not directly connected with superconductivity. Laser Raman spectroscopy has revealed that these materials are sensitive to environmental degradation.
X-ray photoemission spectroscopy of the 90 K superconductor Ba2YCu3O7−δ
Authors: Iqbal Z. , Leone E. , Chin R. , Signorelli A. J. , Bose A. , Eckhardt H.
Published: September 2007

The x-ray photoemission spectroscopie (XPS) data from different pelletized samples of the 90 K superconductor Ba2YCu3O7−δ (where δ∼0.2) have been obtained. The valence band spectrum (recorded at 300 and 170 K), which is composed of contributions from both the Cu 3d and O 2p levels, is compared with the full potential linearized augmented plane wave (FLAPW) calculated electronic density-of-states (DOS) reported by Massidda et al. and Mattheiss and Hamann. The experimental data indicate a relatively low DOS at the Fermi level. Detailed measurements of the core level Cu 2p, O 1s, Ba 3d, 4d, and Y 3d spectra of the superconducting and related standard materials, are presented. Data for the superconducting material were recorded in the freshly prepared form as well as after scraping in situ. The Cu 2p core level, satellite, and Auger spectra for the various samples were carefully examined in order to assess the possibility of the presence of Cu3+ ions in Ba2YCu3O7-δ. It is observed that surface reaction in air to form carbonates and hydroxides occurs readily in the superconducting material.
Magnetic and electronic properties of M-Ba–Cu–O (M = Y, Er, Eu)
Authors: Jenny H. , Walz B. , Leeman G. , Geiser V. , Jost S. , Frey T. , Güntherodt H.-J.
Published: September 2007

Various high-Tc superconductors of the La–(Ba,Sr)–Cu–O and the M–Ba–Cu–O systems with M = Y, Er, and Eu have been prepared by the solid-state reaction method. Single-phase samples with no additional diffraction peaks as verified by x-ray diffraction (XRD) measurements have been obtained. Measurements of the electrical resistivity and of the magnetization showed sharp superconducting transitions with a width of 1 K. The measurements of the magnetic susceptibility have been extended above room temperature up to 770 K. There is clear evidence for the formation of a magnetic moment in all M–Ba–Cu–O samples. Monochromated x-ray photoelectron spectroscopy (MXPS) valence band and x-ray photoelectron spectroscopy (XPS) core level spectra have been measured on various samples at room temperature and at liquid nitrogen temperature.
Elastic constants and Debye temperature of polycrystalline Y1Ba2Cu3O7−x
Authors: Ledbetter H. M. , Austin M. W. , Kim S. A. , Lei Ming
Published: September 2007

Using ultrasonic methods, the quasi-isotropic elastic stiffnesses of void-containing Y1Ba2Cu3O7−x were determined By a composite-material model, these were corrected to the void-free state. From these, the Debye characteristic temperature was calculated. All the elastic stiffnesses fall well below those of polycrystalline BaTiO3, an approximate crystalstructural building block of Y1Ba2Cu3O7−x. The low apparent stiffness may result from oxygen vacancies, which soften interionic forces. Also, it may result from microcracks, which reduce elastic stiffness without lowering mass density.
Mechanisms of high-Tc superconductivity in low-dimensional materials
Authors: Kresin Vladimir Z.
Published: September 2007

High-Tc superconductivity is due to the action of two mechanisms: (1) plasmon mechanism, i.e., exchange of two-dimensional (2-D) plasmons and (2) strong electron-phonon coupling. The low dimensionality and the small value of the carrier concentration make the plasmon mechanism favorable. The small value of the coherence length leads to a unique opportunity to observe a multigap structure. The proximity effect can be used in order to increase Tc of A-15 compounds.
Erosion of amorphous nickel-phosphorus
Authors: Goretta K. C. , Routbort J. L. , Mayer A. , Schwarz R. B.
Published: September 2007

The steady-state erosion rate of electrodeposited amorphous Ni80P20 by angular alumina particles has been measured as a function of impingement angle from 15°–90°, particle velocity from 50–100 m/s, and average particle diameter from 40–390 μm. The erosion rate can be described by a power law in velocity and particle size. The erosion rates in Ni80P20 were compared to those measured for electrodeposited pure crystalline nickel. For all experimental conditions the erosion rate in the amorphous alloy exceeded that of nickel. The material removal in amorphous Ni80P20 is attributed to formation of plastic shear bands below the impact areas. For the most energetic particles the erosion leads to the formation of melt, which seems to be a consequence of the localized shear.
Growth mechanism of vapor-deposited diamond
Authors: Frenklach Michael , Spear Karl E.
Published: September 2007

An elementary-reaction mechanism of diamond growth by a vapor deposition process is proposed. The central postulate is that the main monomer growth species is acetylene. The mechanism basically consists of two alternating steps: surface activation by H abstraction of a hydrogen atom from a surface carbon and the addition of one or two acetylene molecules. During the addition reaction cycle a number of solid C–C bonds is formed and hydrogen atoms migrate from a lower to an upper surface layer. The mechanism is in general agreement with the macroscopic views of the Russian researchers and is consistent with the numerous experimental observations reported in the literature.
Nucleation of a new phase from the interaction of two adjacent phases: Some silicides
Authors: d'Heurle F. M.
Published: September 2007

The reactions of metal layers with their silicon substrates resulting in the formation of various silicides are considered generally not only as phenomena common to all diffusion couples where new phases are formed, but also as typical of all transitions from two to three phases. The conditions under which such transitions will display the same characteristics as encountered in the usual one-to-two phase transitions (condensation, crystallization, boiling) are analyzed by comparison to the classical theory of nucleation. Because of the lack of knowledge about the exact values of the relevant parameters, the discussion is carried out mostly in descriptive thermodynamic terms. Although nucleation effects are analyzed in general terms, the main focus of attention is a class of reactions where nucleation dominates the formation of a new phase; a salient feature of these reactions is the absence of any equilibrium temperature, although the nucleation temperatures are relatively well defined within narrow limits. Nucleation effects are correlated to such material characteristics as the stability of the nucleated phases, and to such kinetic characteristics as the sequence of phase formation. The modification of the energy levels of the different phases brought about by stress, ion bombardment, or the replacement of usual phases by metastable ones, are considered with respect to their effect on nucleation processes. The nearly total absence of literature references to nucleation in metal-metal diffusion couples is discussed with respect to some specific aspects of the metal-silicon reactions.
Growth of a coherent precipitate from a supersaturated solution
Authors: Laraia V. J. , Johnson William C. , Voorhees P. W.
Published: September 2007

A treatment of diffusion limited growth of a coherent spherical precipitate into supersaturated solution is presented. It is found that the growth kinetics are affected by dilatational coherency strains and by compositionally induced strains in the matrix phase. Numerical solutions to the time-dependent problem are obtained and are compared to the quasistationary solution. The parabolic growth coefficient is a function of the transformation strain, partial molar volumes of the components, elastic constants in each phase, interfacial compositions and far-field composition while, in contrast, the growth coefficient in the absence of stress is a function only of the reduced supersaturation. Elastic effects shift the interfacial concentration of the matrix in the direction of the far-field concentration, reducing the effective driving force for growth. At the same time, compositionally induced strains increase the diffusive flux, increasing the growth rate.