bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties of Dielectric Thin Films Formed by Laser Evaporation
Authors: Sankur H. 
Published: March 2011

ABSTRACTThe technique of laser evaporation for the deposition of thin films has been applied to a large class of materials including oxides, fluorides and II-VI semiconductors. The evaporations were performed in high vacuum or under O2 pressures of 10−3 Torr, on several types of substrates, by using CO2 lasers in CW and pulse modes. The thin films thus obtained have been characterized for their structural, optical and electrical properties.Entire ranges of mixtures in several binary systems (e.g., SnO2-SiO2), have been obtained by coevaporation, using mirrors to steer the laser beam among sources.Conditions that affect the stoichiometry and structural properties (laser parameters, background pressure, evaporation rate, substrate temperature) have been established for each material system. Differences in the evaporation behavior of materials under CW and pulsed conditions have been investigated for the case of ZnO. Present and future applications of this technique in the optical devices field are also discussed.
Column IIIA Metal film Deposition by Laser Photoionization of Metal-Halide Molecules in the Vapor Phase
Authors: Geohegan D. B. , Mccown A. W. , Eden J. G. 
Published: March 2011

ABSTRACTFilms of Column IIIA metals (In, Tℓ and Aℓ) have been deposited on several different substrates (stainless steel, nickel and copper) by photoionizing the corresponding metal-iodide or bromide (such as TℓI, InI or AℓI3) in the vapor phase and in the presence of a uniform electric field. These experiments were prompted by the measurement of large photoionization cross-sections for ion production (i.e., MX + 2ħ ω → M+ + X + e- or MX + ħω → M+ + X-) in these molecules at 193 nm. The effective cross-sections for the photoionization of TℓI and InI at 193 nm have been measured to be 2.2·10−17 cm2 and < 7·10−18 cm2, respectively. Depletions of the metal-halide ground state greater than 60% have been observed for ArF peak laser intensities of only 5 MW − cm−2.
Theory of Nuclear Relaxation in Confining Systems. Application to Non Wetting Liquids in Porous Silica Glasses
Authors: Korb J.-P. , Delville A. , Xu Shu , Jonas J. 
Published: March 2011

AbstractThis work shows how the geometrical confinements enhances the nuclear relaxation of a non wetting liquid in a model porous systems. Application of the proposed theory is made to interpret the size and frequency dependences of the 1H relaxation of methylcyclohexane liquid in sol-gel porous silica glasses with narrow pore-size distribution.
NMR Relaxation of quadrupolar Nuclei as a Probe of the Motion of Guest Species in Sodalite Cavities
Authors: Jelinek R. , Ozin G. A. 
Published: March 2011

AbstractUseful information on interactions and motion of guest molecules in sodalite cavities is obtained by estimating the spin-lattice and spin-echo decay rates of encapsulated Br− ions. An extremely fast spin-lattice relaxation rate is observed for 81Br nuclei, adjacent to Br−-empty cages which contain rapidly tumbling water molecules. We detect a further significant different T1 of the 81Br in Na8Br2- sodalite and AgsBr2-sodalite, respectively, which probably indicates a less restricted motion within the cavities of the Ag+-exchanged material. Spin-echo decay experiments additionally indicate a difference between the dynamic properties of the Br− anion in the encapsulated Na4Br and Ag4Br clusters, respectively.
Computer Simulations of Diffusion in Monolayers Physisorbed in Model Pores
Authors: Bojan Mary J. , Steele William 
Published: March 2011

AbstractTwo types of model pore have been considered as sorbents of methane at 300 K: the first is a straight cylinder with atomically rough walls characteristic of an amorphous solid. Three cylinder radii plus the reference flat surface were taken for study. The second is a parallel-walled slit pore made up of graphite basal planes that had been modified by the insertion of sulfide atoms. Here, two values of sulfur loading were taken together with the reference pure graphite pore. Two values of the wall spacing were assumed for each sulfur loading. Thermodynamic and structural properties are presented elsewhere; here, the dependence of diffusion constants as a function of the monolayer density is presented for methane in the various model pores. It is shown that these diffusivities depend primarily on the methane-methane collisions in the monolayer films. There is a slight dependence upon the nature of the solid surface which is interpreted in terms of the hindrances produced by soft obstacles to molecular motion parallel to the surfaces.
Visualisation of Fractal Fingering Using NMR Imaging
Authors: Davies Eleanor S. , Carpenter T. Adrian , Hall Laurance D. , Hall Christopher 
Published: March 2011

AbstractFractal fingering is a well known phenomenon, ususally visualised using photography. Previous experiments have shown that the patterns can be visualised using NMR imaging, and in this paper we show that the fractal dimension of such a pattern can be easily calculated.
Interface Effect on Dipole-Dipole Interaction
Authors: Urbakh Michael , Klafter Joseph 
Published: March 2011

AbstractThe nature of the pair interaction between dipoles embedded in a liquid in the vicinity of a non-metallic interface is investigated in the continuum limit. It is shown that the dipole-dipole interaction can be significantly modified in the presence of a boundary in liquids characterized by a nonlocal dielectric function or in liquids whose dielectric properties change due to geometrical restrictions. Different limits are studied and relationships to experimental observables are discussed.
The Critical Thickness of the Dislocation-Free Stranski Krastanow Pattern of Growth.
Authors: Grinfeld Michael A. 
Published: March 2011

AbstractIt was demonstrated earlier [1,2] in the framework of equilibrium thermodynamics that the morphological stability of the free boundaries and interfaces in crystals is extremely sensitive to the presence of shear stresses. Relying on that idea we have established the formula H = μσ/τ2 of a critical thickness of solidifying He4 films and of the dislocation-free Stranski-Krastanow growth of epitaxial films (where σ – the coefficient of surface tension, μ - the shear module of the crystal, τ - the external or misfit stress). In this report we present certain facts pertaining to possible patterns of the growing corrugations and introduce the second critical thickness at which a symmetry change in the patterns has to occur.
Preparation of High-Conductive High-Temperature PTC Resistor Ba1-x SrxPb1+yO3+z
Authors: Nagamoto H. , Kagotani H. , Koya T. 
Published: March 2011

AbstractThe positive temperature coefficient of resistivity (PTCR) effect in Ba1-xSrxPb1+yO3+z has been systematically studied. The effect of the PTC resistivity was strongly influenced by the preparation condition. The PTCR effect in metallic-conducting BaPb1+yO3+z. is confirmed around 700 °C, and the temperature where the PTCR effect starts can be successfully shifted to higher temperature range by substituting strontium for the A-site barium. The magnitude of the PTCR effect was increased and the resistibility was reduced by the enhancement of the sintering. In addition to Pb(IV) in the perovskite structure, Pb(II) is detected at the grain boundary in the sintered body.
The Escape of Particles from a Confining Potential well
Authors: Lavine James P. , Banghart Edmund K. , Pimbley Joseph M. 
Published: March 2011

AbstractMany electron devices and chemical reactions depend on the escape rate of particles confined by potential wells. When the diffusion coefficient of the particle is small, the carrier continuity or the Smoluchowski equation is used to study the escape rate. This equation includes diffusion and field-aided drift. In this work solutions to the Smoluchowski equation are probed to show how the escape rate depends on the potential well shape and well depth. It is found that the escape rate varies by up to two orders of magnitude when the potential shape differs for a fixed well depth.
One-Diohliensilonall A + B = 0 Reactmion with One Immobile Species
Authors: Argyrakisa Panos , Kopelman Raoul 
Published: March 2011

AbstractThe elementary batch reaction A + B = 0 is re-examined via Monte-Carlo simulations on a one-dimensional lattice. The relative mobility of the A and B species is varied in this model, but the initial densities of the A and B are always the same. We calculate the rates, the density profiles, and the particle distribution functions. The rate power law is conserved, i.e., the well-known 1/4 behavior is established for all mobilities. The rate coefficient is the only mobility-dependent quantity. The interparticle distribution functions show that the aggregation depends on the relative mobility but the segregation does not. This subtle difference has no effect on the asymptotic reaction order, which is close to 5.
Non-Classfcal Kinetiics in Hydrogen-Deuterium Exchange Reaction on Metal Catalyst
Authors: Choi Inchan , Kopelman Raoul 
Published: March 2011

AbstractMonte Carlo simulations of the A2 + B2→ P (with P = AA, AB, and BB) reaction on various monodisperse island systems provided various models for the reaction H2 + D2→ HD on alumina supported platinum catalysts. Anomalous reaction kinetics and reaction orders due to the effects of diffusion, reactant correlation, and ensemble character of the catalyst in low dimensional systems are observed not only at early time but also at steady state. Concentration effects and spillover studies indicate that surface diffusion and hydrogen spillover may be responsible for the anomalous behaviors.
Local Reaction Probability Effects in Non-Classical Kinetics: Batch and Steady State
Authors: Shi Zhong-You , Kopelman Raoul 
Published: March 2011

AbstractThe reaction A+A→0 is simulated in 1-D and 2-D square lattices with various local reaction probabilities, P. The effective reaction order, X, and the nearest neighbor distance distribution (NNDD), are evaluated in all these reactions. For batch reactions, sharp increases in X with increasing P occur at early times. Classical reaction limited kinetics is obtained at early times only when P→0. At long times, all reactions are in the non-classical, diffusion limited regime, regardless of P. For steady state reactions, our results demonstrate a similar behavior of X with P. The NNDD at steady state in 1-D media at P=1.0, i.e. diffusion limited reaction, follows the previously reported skewed exponential shape. This is no longer true for P<I. Finally, at P→0, as expected, an exponential (Poissonian) distribution is obtained for both reaction conditions.
Interfacial Dynamics of Water-in-Oil Dropliets: a Temperature-Jump Investigation
Authors: Alexandridis Paschalis , Holzwarth Josef F. , Hatton T. Alan 
Published: March 2011

AbstractThe dynamic response of water-in-oil AOT microemulsion droplets to perturbations caused by rapid energy transfer has been interpreted in terms of the surfactant interface bending rigidity. The Iodine Laser Temperature Jump technique was used to rapidly (1 μs) increase the microemulsion temperature and thus disturb the system equilibrium. The dynamic relaxation to the new equilibrium position was monitored by measuring the turbidity of the microemulsion over a I ms time interval immediately after the temperature jump. The rate and direction of the turbidity change depended on the initial temperature, size and salt content of the water droplets. We observed characteristic times of 2 to 10 μs and attributed them to the relaxation of the surfactant interface. A bending modulus of 0.4 kT was derived for the AOT interface, using a model for the shape perturbation of a spherical interface.
Numerircal Determination of Nucleatilon Parameters in Polymoriphic Crystalliization from Solutiions
Authors: Merlo M. , Santos A. , Duport L. Gago 
Published: March 2011

AbstractA numerical model based in nucleation and growth algorithms has been designed to compute the temporal sequences of precipitation and phase transformation kinetics in metastable solutions of polymorphic or hydrated substances. A outline of the model is made for the particular case of crystallization of several hydrated phases from nickel nitrate solutions
Picosecond Studies of Nonequilibrium Flux Dynamics in Superconductors
Authors: Freeman M. R. 
Published: March 2011

AbstractA fast time-domain magneto-optical technique is used to explore magnetic flux dynamics in the optically driven nonequilibrium state of Type I superconducting Pb films. It is found that the effective penetration of flux through the nonequilibrium intermediate state can be dramatically faster than through the normal metal. The system is probed through the application of rapid transient magnetic field pulses. Above the superconducting transition temperature, a direct measure of the diffusion coefficient of the magnetic field in the normal metal is obtained, on a time scale where the inhomogeneous spatial distribution of scattering sites is relevant. In the nonequilibrium superconductor the observations are dominated by coupling of the field transients to local motion of magnetic flux threading the normal domains. Studies as a function of how far the system is driven from equilibrium, and of the effect of a static applied magnetic field, indicate that the observations reflect the dynamics of normal/superconducting interfaces, and are strongly dependent on the microscopic arrangement of the intermediate state. By contrasting the response of pure Pb films to that of Pb1−xInx alloys, a comparison to Type II superconductivity is made.
Interfacial Properties of Isotropic Semi-Flexible Polymer Blends
Authors: Liu Andrea J. , Fredrickson Glenn H. 
Published: March 2011

AbstractWe analyze interfacial behavior in binary blends of polymers with different flexibilities. Our starting point is a free energy functional calculated from a microscopic model of wormlike chains. We show how this functional can be used to calculate interfacial properties within the Cahn-Hilliard approach. Here we present preliminary results applicable to chains that are globally coil-like. At the interface between two isotropic phases, each rich in a different polymer, we find that the polymers tend to be extended parallel to the interface. Thus their shape is oblate rather than spherical at the interface.
Angular-Resolved ESCA Studies of Cadmium Arachidate Monolayers on Si (100): Inelastic Mean-Free Path and Depth Profile Analysis
Authors: Letellier Shelli R. , Vogel Viola , Ratner Buddy D. , Leach-Scampavia Deborah 
Published: March 2011

AbstractAngular-resolved ESCA was used to study single cadmium arachidate monolayers transferred to Si (100) wafers by the Langmuir-Blodgett technique. We find the monolayers to be of high integrity with respect to those defects which enhance the escape probability of substrate photoelectrons through the overlayer. The inelastic mean-free pathlengths of Si (2p) and C (1s) electrons were calculated to be 49±6 Å and 45±6 Å for the kinetic energies of 1388 eV and 1202 eV, respectively. The overall ordering of the hydrocarbon chains is less than for alkane thiols assembled on noble metals. We find that the precision of the Tyler algorithm to deconvolute angular-resolved ESCA data into depth profiles is accurate within 10% for predicting the thickness of the hydrocarbon overlayer but less precise for intermediate layers.
Biopolymer-Thin Film Interactions
Authors: Maloney K. M. , Grainger D. W. 
Published: March 2011

AbstractBiopolymer self assembly in heterogeneous lipid monolayers at the air-water interface was investigated. Fluorescence microscopy allowed the visualization of protein recognition and binding to these microstructured membranes. Mimicking proteininduced membrane microstructuring and protein docking was achieved in ternary mixed lipid monolayer systems.
Photovoltaic Effects and Charge Transport Studies in Phycobiliproteins
Authors: Beladakere N. N. , Ravindran T. , Bihari B. , Sengupta S. , Marx K. A. , Kumar J. , Tripathy S. K. , Wiley B. , Kaplan D. L. 
Published: March 2011

AbstractPhycobiliproteins form highly efficient light absorbing systems in certain algae. We have investigated the charge-transport phenomena in these proteins by analyzing the dark current-voltage and photocurrent characteristics obtained across Au-phycobiliprotein-Au samples. A photovoltaic effect was observed for Au-phycoerythrin-Au sample. At low intensity levels, the photocurrent closely follows Onsager's law of geminate recombination in three dimensions.
Sub-Micrometer Hydroxyapatite Bioceramics
Authors: Shaoxian Zeng , Jingkun Guo , Zhixiong Yang , Jie Cai , Wanpeng Cao 
Published: March 2011

AbstractWe studied the microstructures of hydroxyapatite (HA) ceramics which were sintered under three different conditions. It was found that all the ceramics were of sub-micrometer structure. The synthetic HA ceramics were also compared with human enamel. It is concluded that human enamel has higher strength because of its unique microstructure.
Assembly of α-Hemolysin: a Proteinaceous Pore with Potential Applications in Materials Synthesis
Authors: Bayley Hagan , Krishnasastry Musti , Walker Barbara , Kasianowicz John 
Published: March 2011

Abstractα-Hemolysin (αHL) is secreted by the bacteriumStaphylococcus aureusas a watersoluble polypeptide of 293 amino acid residues. When presented with lipid bilayers or the detergent deoxycholate (DOC), aHL assembles into hexameric cylindrical pores that each contain one channel ∼ 1 to 2 nm in Internal diameter. A long-term goal of this laboratory is to use wild-type or re-engineered αHL pores as components of nanoscale materials: for example, to confer novel permeability properties upon thin films. The implementation of this concept would be facilitated by a better understanding of the mechanism by which the pore assembles. Reviewed here are findings that have given us insight Into the assembly mechanism, including the results of recent mutagenesis experiments. A critical summary is given of knowledge about the conformation of the monomer In solution, the hexamerIc pore and two proposed intermediates in assembly (a membrane-bound monomer and an oligomeric pore precursor). Future directions are outlined Including the prospects of obtaining three-dimensional structural data on the αHL pore or its precursors, methods for obtaining better monolayer sheets and new experiments on the topography of the pore and its precursors. The role of membrane receptors in facilitating the assembly of αHL is also discussed. Finally, it is demonstrated that despite our rather rudimentary knowledge of the assembly process, the Information gained so far still allows the design of mutant (αHL polypeptides with useful properties. For example, αHL mutants whose pore-forming ability is activated by proteases have been made.
Properties And Prevention of Adhesions Applications of Bioelastic Materials
Authors: Urry D. W. , Gowda D. Channe , Cox Betty A. , Hoban Lynne D. , Mckee Adam , Williams Taffy 
Published: March 2011

AbstractThe origins, syntheses, variable composition and physical properties of bioelastic materials are discussed. The latter includes their capacity to undergo inverse temperature transitions to increased order on raising the temperature and to be designable to interconvert free energies involving the intensive variables of mechanical force, temperature, pressure, chemical potential, electrochemical potential and light.Bioelastic materials include analogues and other chemical variations of the viscoelastic polypeptide, poly(Val-Pro-Gly-Val-Gly), and cross-linked elastomeric matrices thereof. This parent material has been shown to be remarkably biocompatible; it can be minimally modified to vary the rate of hydrolytic breakdown; it can contain enzymatically reactive sites; and it can have cell attachment sites included which promote excellent cell adhesion, spreading and growth to confluence.One specific application is in the prevention of postoperative adhesion. There are some 30,000,000 per year surgical procedures in this country and a large portion of these would benefit if a suitable material were available for preventing adhesions. Bioelastic materials have been tested in a contaminated peritoneal model, and promising preliminary studies have been carried out in the rabbit eye model for strabismus surgery. In the peritoneal model, 90% of the 29 control animals exhibited significant adhesions; whereas, only 20% of the 29 animals using gas sterilized matrices had significant adhesions. On the basis of this data, it appears that cross-linked poly(VPGVG) is an effective physical barrier to adhesion formation in a trauma model with resulting hemorrhage and contamination.The potential use of bioelastic materials as a pericardial substitute following the more than 400,000 open heart surgeries per year in the U.S. is under development beginning with the use of bioelastic matrices to prevent adhesions to the total artificial heart being used as a bridge to heart transplantation such that the site will be less compromised when receiving the donor heart.
Nuts
Authors: Vincent Julian F. V. 
Published: March 2011

AbstractThe shell (pericarp) of nuts protects the seed from being eaten before it can germinate. It is presumably designed to resist fracture by external forces, and evolution will have optimised its design for this purpose. It appears that the material of larger shells, which will tend to be structurally more brittle, is tougher. However, the fracture mechanics theory for shells in compression is not available, nor the information on the biological selection pressures.
Structure and Composition of Rhinoceros Horn
Authors: Orden Ann Chidester Van , Daniel Joseph C. 
Published: March 2011

AbstractRhinoceros horn has been used medicinally and as a talisman in many cultures and animals are slaughtered to obtain the horn. With the dwindling populations of rhinos, and the limited number and breeding success of captive rhinos, there is a critical need to learn as much as is possible about their horns to find an adequate substitute. Examination of rhino horn was made using optical microscopy, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD). The structure of the horn is unusual and consists of two separate phases, one of hair-like filaments, built around a central core in circumferential layers and the other surrounding and filling in the spaces between the filaments as a matrix. Together, these two structures make up a biological composite, structurally similar to metal, ceramic or polymer based composites. The structural morphology, the dimensions of the structures, and the chemistry of the horn are discussed. Comparisons are made between horn, hoof, and hair of rhinos and hoof and hair from horses, their nearest living relatives.
Is the Tyrosine Rich Eggshell Protein of Schistosoma Mansoni an Electron Transport Chain?
Authors: Cordingley John S. , Thomson John A. , Middaugh C. Russell 
Published: March 2011

AbstractThe schistosome eggshell is composed of two kinds of cross-linked proteins. One is glycine rich and the other is extremely tyrosine rich and highly repetitive. The highly conserved sequence of the tyrosine residues in the tyrosine rich protein suggests that it may play a role as an electron transport chain during eggshell cross-linking. Studies using model synthetic peptides suggest that the tyrosine rich protein may adopt a left-handed structure, possibly a left-handed alpha-helix.