bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Study of An A+B→C Reaction-Diffusion System in a Capillary: Crossovers from Reaction to Diffusion-Limited Regimes
Authors: Koo Yong-Eun , Kopelman Raoul , Yen Andrew , Lin Anna 
Published: March 2011

AbstractContinuing work on elementary A+B→C reactions in capillaries, we study the reaction front dynamics of xylanol orange with Cr3+ in an effectively one-dimentional system with initially separated reactants. This reaction, in contrast to previously studied systems, is not strictly in the diffusion limited regime. i.e. the probability of reaction between species is not unity. Anamalous behavior not seen in the diffusion-limited case has been observed experimentally for the reaction rate, boundary motion, reaction zone width, and local reaction rate. The observed behavior is consistent with recent theoretical studies.
Mechanisms which can Accelerate the Growth of Phase Separating Domains Near a Wall
Authors: Troian Sandra M. 
Published: March 2011

AbstractThough the dynamics of bulk phase separation during spinodal decomposition is fairly well understood nowadays, recent experiments have shown that the same process occuring near a wall introduces some surprisingly fast domain growth kinetics. Studies of both polymer mixtures and simple binary fluids at critical composition quenched into the unstable regime reveal the presence of a fast mode associated with domains coarsening at the wall. The scattering data indicates that while the bulk domains grow in time as t1/3, as dictated by usual diffusion driven dynamics, the surface domains coarsen with exponents ranging from about 1.1 to 1.5 depending on the quench depth. We construct a model in which the average size of domains in a binary mixture undergoing spinodal decomposition near a wall can achieve growth exponents much larger than 1/3. The accelerated growth is associated with the domains of the non-wetting phase coarsening anisotropically against a wall coated with the wetting phase.The faster growth evolves from coupling Lifshitz-Slyozov type coarsening for critical volume fractions, modified to include the geometric constraint of growth near a wall, the process of domain coalescence. Included are some predictions for experimental tests of these ideas.
Diffusion Mechanisms of Molecules on Structured Surfaces
Authors: Silverberg Marvin 
Published: March 2011

AbstractThe diffusion of ethane and n-pentane on metallic surfaces is studied by molecular dynamics simulations. On atomically smooth, faced centered cubic (111) crystal surfaces, n-pentane has several conformational states, each of which diffuses at a different rate. Diffusion barriers are distinct from intramolecular conformational isomerization barriers. Weak friction is observed. Hopping diffusion occurs near the diffusion threshold. As the temperature is raised, correlated barrier crossing and recrossing increases. n-Pentane slides, transverse to its axis, without changing its orientation with respect to the surface. Conformational changes occur on a longer time scale than diffusional barrier crossing and are restricted by the surface. Far above the diffusion threshold temperature, partial molecular desorption occurs and conformational isomerization is less restricted. The molecules slide, roll and tumble continuously across the surface. A similar pattern of temperature-dependent change in diffusion mechanisms occurs in ethane but without conformational changes.
Buckling of a Confined Colloidal Crystal
Authors: Chou T. , Nelson D. R. 
Published: March 2011

AbstractThe behavior of colloidal suspensions confined between two plates narrowly spaced is examined. When plate separations are small, only one layer of particles can be confined; however, as plate separation is increased, multiple layers will eventually form. These layers can exist in a variety of structures depending on the energetics of packing. We examine the unstable modes which form as a single layer buckles on its way to forming two layers. Three ordered states are found; which one is selected depends on the form of the interparticle and wall potentials.
Diffusion-Limited Binary Reactions: a Hierarchy of Non-Classical Regimes
Authors: Argyrakis Panos , Kopelman Raoul , Lindenberg Katja 
Published: March 2011

AbstractWe discuss the various regimes of kinetic behavior of the densities of reactants for the A + B → 0 reaction from initial to asymptotic times. Scaling arguments and Monte Carlo simulations demonstrate an unexpectedly rich hierarchy of cross-overs among time exponents ir the decay law ρ ˜ t−α. For instance, in one dimension possible time domains include classical (α = 1), A + A-type (α = 1/2), Zeldovich (α = 1/4), asymptotic correlated (α = 3/4) and finally nonalgebraic (exponential) finite size regimes. Simulation and theory are consistent with respect to both exponefits and cross-over times for one and two dimensions.
Nanoengineering with DNA
Authors: Seeman Nadrian C. 
Published: March 2011

AbstractDNA is a tractable medium for controlling the structure of matter on the nanometer scale. We have explored ligating together stable branched DNA molecules to form geometrical objects. By this means, we have assembled a 3-connected molecule whose helix axes have the connectivity of a cube. The construct is a hexacatenane, each of whose cyclic strands corresponds to a face of the object. Each of its twelve edges contains a unique recognition site for cleavage by a restriction enzyme; these sites are used to demonstrate the assembly of the object. The plectonemic structure of DNA also permits the directed synthesis of molecular knots. Recently, we have constructed trefoil knots from B-DNA and an amphichiral figure-8 knot whose helical domains contain both B-DNA and Z-DNA.We have developed a solid-support methodology for the synthesis of geometrical objects. This approach provides greater control over products and topological purity, and lends itself better to automation. Branched molecules containing 3–6 double helical arms can be formed from equimolar mixtures of their component strands, thereby enabling the construction of 3–6 connected networks. The goals of this work include the construction of periodic multiply-connected networks of DNA. The aims of these DNA constructions include using them as scaffolding to build periodic macromolecular arrays for diffraction purposes, as well as directing the assembly of molecular electronic devices. There are wellcharacterized molecular transformations of DNA that make nano-scale machines feasible to build in this molecular context. These materials are likely to be useful for understanding crystallization processes and structure-function relationships.
α-Helical Polypeptide Materials
Authors: Enriquez E. P. , Jin M. Y. , Jarnagin R. C. , Samulski E. T. 
Published: March 2011

AbstractPoly(γ-benzyl-L-glutamate) (PBLG) may be derivatized on its periphery by covalently attaching χ-active NLO chromophores at the termini of its sidechains and thereby give a new class of SHG materials. The inherent liquid crystalline properties of concentrated solutions of α-helical PBLG may be exploited to establish unique supramolecular structures prior to E-field poling. When PBLG is derivatized at its N-terminus with lipoic acid, it will self-assemble on gold to give a thin film. Angle-dependent XPS, ellipsometry, contact angle measurements, and grazing angle IR reflection-absorption spectroscopy give quantitative information about the orientation of the polypeptide α-helices relative to the substrate surface. Consequently, polypeptides, in particular, Merrifield-synthesized or recombinant DNA-expressed synthetic polypeptides, present a novel fabrication route to thin films wherein molecular-engineered functionalities (chemical, electrical, or optically active species) may be encoded into the macromolecule's primary structure and subsequently expressed spatially via the spontaneous self-organization of these rod-like polymers.
Mechanical Properties of Biopolymer Chains
Authors: Pachter Ruth , Haaland Peter D. , Crane Robert L. , Adams W. Wade 
Published: March 2011

AbstractMolecular simulations that predict the molecular mechanical response of alpha-helical biopolymers with a reinforcing intra-molecular hydrogen bonding network, viz,, a ‘spring-like’ behavior, are presented in this study. Mechanical properties of extended biopolymer strands based on naturally occurring amino acids, namely poly(L-A1a) and for comparison poly(LGlu), versus synthetic PPTA containing an amide bond, are compared to those assuming alpha-helical structures. Thus, the pivotal role of such motifs in biological systems utilizing superior compressive mechanical properties can be inferred.
Hydroxyapatite/Al2 O3 Composite Biomaterial Implant
Authors: Shaoxian Zeng , Zhixiong Yang , Ping Ling , Guanghong Xu , Wanpeng Cao 
Published: March 2011

AbstractA new type of composite biomaterial was developed and is described in this paper. The composite is based on a high strength Al2O3 ceramic substrate, sintered with a layer of hydroxyapatite. The layer was examined by x-ray diffraction and infrared spectroscopy. Animal experiment showed that the composite has good biocompatibility, and can form tight osteointegration with bone in 12 weeks. It is a bioactive material with a high strength.
Large Scale Thermally Synthesized Polyaspartate as a Biodegradable Substitute in Polymer Applications
Authors: Wheeler A.P. , Koskan L.P. 
Published: March 2011

AbstractPolyanionic proteins isolated from biominerals serve as models for the development of biodegradable surface-reactive commercial polymers. A simple model for the natural polyanions is polyaspartic acid. This polymer may be made on a large scale using thermal polymerization of dry aspartic acid. The immediate result of the reaction is polysuccinimide which is hydrolyzed with base to form the polypeptide. The overall process yields up to 99% conversion of aspartic acid to polyaspartate. The thermal polyaspartate (TPA) is a copolymer having 70% of the amide bonds formed from β-carboxyl groups and 30% from α-carboxyl groups. TPA is as effective as the commercial polyanion polyacrylate in mineral dispersion and growth inhibition assays. Biodegradation of the TPA has been established using standard BOD and CO2 evolution assays. In contrast, polyacrylates appear to be non-degradable. Modifications of the TPA have been made by reacting the succinimide with nucleophiles. Crosslinking of the polymer has been achieved, a process which results in absorbent gels. Because TPA can be produced in large scale, has similar activity to polyacrylate and is biodegradable, it seems a likely candidate for use in numerous applications in which non-degradable polyanions are employed. These applications include use as detergent additives, water treatment chemicals, dispersants for the paint and paper industry and as superabsorbents in health and sanitary products.
Engineered Proteins for Biomaterials
Authors: Stayton Patrick S. , Chilkoti Ashutosh , Long Cynthia J. , Pettit Dean K. , Tan Philip H. S. , Chen Guohua , Hoffman Allan S. 
Published: March 2011

AbstractA molecular adaptor for interfacing environmentally sensitive, soluble polymers and antibody molecules has been developed. The gene coding for the minimally sized, 55 amino acid IgG binding domain from protein G has been constructed by total gene synthesis. This domain is thermally stable, exhibits a highly reversible folding and unfolding equilibrium, and recognizes IgG and Fab molecules with high affinity. These properties make the protein G domain a potentially useful adaptor for non-covalent immobilization of antibodies to soluble polymers and hydrogels. Engineered single-chain Fv antibody fragments have also been constructed and a method for expanding the usefulness of the protein G adaptor to these molecules is proposed. The engineered antibodies also provide a model system for developing general immobilization strategies aimed at maximizing binding affinities and therapeutic responses. The overall goal is to develop optimized engineering designs for functionally optimized antibody-material hybrids.
In Situ Characterization of Interfacial and Bulk Properties of Lithium Polymer Batteries Using 4-Probe DC Techniques
Authors: Liu Meilin , Visco Steven J. , De Jonghe Lutgard C. 
Published: March 2011

AbstractThe use of transient and steady-state 4-probe techniques for the evaluation of the limitations to performance in solid-state electrochemical devices is described. The application of sequential, bipolar square-wave current pulses to a solid polymer cell with two internal reference electrodes allows separation of the polarization behavior of the various components of the cell, and indicates the rate limiting processes in the cell. Careful design of the experimental cell and appropriate selection of current pulse width allows evaluation of fundamental kinetic and transport properties, as well as activation parameters. Steady state constant-current measurements using 4-probe cells allows in situ observation of interface stability and/or polarization as a function of time as the cell is cycling.
Theory of Ionic Diffusion Across Material Interfaces
Authors: Balkanski M. , Nachev I. , Deppe J. , Wallis R. F. 
Published: March 2011

AbstractIon diffusion across material interfaces is considered in a sequence of approximations with increasing complexity. First, the one-dimensional lattice gas model of particle diffusion is generalized to include a finite width interface region, and the possible existence of an energy barrier at the interface. Overvoltage measurements on InSe, and dielectric loss measurements on B2O3 - 0.5Li20 - 0.15Li2SO4 are used to determine the field-free hopping rates in the two materials. It is shown that the energy barrier is a dominant parameter. This model is then modified by considering the disorder of the glass structure and the blocking effect resulting from the ion interaction. Next, a more rigorous treatment is presented by solving the Poisson equation with appropriate boundatry conditions, and a self-consistent theory of the ionic diffusion is proposed. To clarify this problem, an intermediate step and two additional models with increasing sophistication are considered: first, the potential φ(x) of the moving charge density n(x) is calculated and it is shown that φ(x) is not negligible. Then, a feed-back is provided by including this potential in the diffusion equation. This treatment is already self-consistent and more realistic but leads to long computations even for the simple one dimensional lattice-gas model. A remedy of this difficulty is proposed whereby the theory is reformulated in order to guarantee from the beginning the self-consistency of the solution of the non-linear diffusion problem. Straightforward extensions to the two-dimensional case are then possible. The results of the computations are illustrated with numerical examples for different values of the physical parameters.
A Cluster Modelling Study of Conductivity of Yttria-Stabilized Zirconia
Authors: Depero Laura E. , Zocchi Marcello , Parmigiani Fulvio 
Published: March 2011

AbstractOn the basis of a previously described structural model for the Yttria-Stabilized Zirconia, the conductivity for this material can be calculated. A fixed number of clusters is generated in a structure of 70×28 polyhedra to simulate different Y contents in the structure. The results are compared with the experimental results obtained by others and discussed.
Ionic Properties of Hydrous Oxide Gels
Authors: Livage J. 
Published: March 2011

AbstractThe sol-gel process offers new opportunities for the synthesis of ionic materials, specially in the shape of thin films. Hydrous oxides are obtained which exhibit specific properties arising from strong interactions betwwen adsorbed water molecules and the oxide network. Sol-gel derived coatings are good candidates as electrode materials for lithium batteries or electrochromic devices. Their open structure allows easier diffusion of Li+ions in the liquid phase while electrons are delocalized through the oxide network. Moreover, water molecules favor the formation of ordered phases leading to the deposition of layers with preferred orientation. Electrochemical insertion can then be described as an intercalation process between solid particles.
Structure, Diffraction and Energetic Stability of the Spinel form of LiCoO2
Authors: Reimers J. N. , Li W. , Rossen E. , Dahn J. R. 
Published: March 2011

AbstractA recently reported new phase of LiCoO2, called LT-LiCoO2 (LT stands for Low Temperature) by the discoverers, was synthesized at 400°C and studied using X-ray diffraction and electrochemical de-intercalation of lithium. The first reports of LT-LiCoO2 give convincing evidence that the compound is layered with the same structure type as LiCoO2 prepared at 850°C (HT-LiCoO2). However, the electrochemical properties of LT and HT LiCoO2 are markedly different, which is hard to understand if the crystal structures are almost the same. A better understanding of the diffraction and electrochemical data is attained if the LT structure is assumed to be spinel related analogous to Li2Ti2O4. We show that the layered structure (with suitable lattice constants and layer spacings) and spinel structure give identical powder diffraction patterns. We also show that the formation energies of the layered and spinel structures are also identical using a lattice gas model with pair-wise atom-atom interactions.
Influence of the Metal/Ceramic Interface Characteristics on Conductivity Measurements of Na-β" Alumina by Impedance Spectroscopy
Authors: Schreiber M. , Butchereit E. , Lutz C. 
Published: March 2011

AbstractThe quality of the metal/ceramic interface of solid ionically conducting materials is an important when undertaking impedance spectroscopy measurements. One major concern is the contact area between the metal and the ceramic. This work focussed on the treatment of the ceramic to the metal application by utilizing a standard quality Na-β" alumina. Next, a number of different metals were applied to the ceramic surface by different techniques, i.e. sputtering and evaporation, to serve as blocking electrodes in impedance spectroscopy measurements. The impedance spectroscopy measurements were carried out at temperatures from 30 - 300°C over a frequency range from 1 to 5 ×105 Hertz. The results are discussed in terms of the various parameters of impedance plots. Surface analysis techniques were applied to investigate the metal/ceramic interface before and after impedance spectroscopy measurements.
Surface Oxygen Exchange Kinetics in Oxide-Ion Conducting Solids
Authors: Boukamp Bernard A. , Bouwmeester H.J.M. , Verweij H. , Burggraaf A.J. 
Published: March 2011

AbstractThe surface oxygen exchange on oxides with high oxygen ion mobility is modelled with a two step reaction with adsorbed mono-atomic oxygen species as intermediate. Interpretation of the Po2 dependence of the exchange rates, following from this model, indicates that these adsorbed oxygen atoms are singly charged.For the stabilized δ-Bi2O3 solid electrolyte a good agreement has been found between the isotope exchange model and the electrochemical study of the oxygen exchange using gold electrodes. For the mixed La-Sr cobaltite perovskite a change in the surface exchange reaction is observed going from room temperature to 600°C. Indications are that above 450°C the bulk exchange is rate limiting with a (Po2)−1 dependence while below this temperature it is assumed that the dissociative adsorption is rate limiting with a (Po2)1/2 dependence.
The Structure and Ionic Conduction in Fluorite-Type Solid Solutions
Authors: Ito Yoshiaki 
Published: March 2011

AbstractThe crystal structure of β-Pb0.9Bi0.1F2.1 has been investigated in the temperature range 294 to 710K by single crystal X-ray diffraction method. Phase transition is observed at about 700K and the mean square displacements (MSD) of metal and fluorine ions show a rapid increase near the transition temperature. The fluorine ions do not show anharmonic thermal vibrations in the regular site in the temperature range.
Crystal Phase Effects in Electrochromic WO3
Authors: Klein J. D. , Yen A. 
Published: March 2011

AbstractThe electrochromic behavior of crystalline WO3 thin films of two different crystal structures was investigated. The films were deposited on ITO-coated Coming 7059 glass and transparent single crystal sapphire substrates by electron beam evaporation. The usual monoclinic crystal structure was obtained by post-annealing films deposited at low substrate temperatures. An alternative phase was generated by in-situ growth of crystalline films at high substrate temperatures. The reversible electrochemical insertion of Li was demonstrated by cyclic voltammetry. Optical switching was observed by comparing visible transmittance, visible reflectance, and infrared reflectance spectra of films before and after Li intercalation. The two film types assumed similar crystal structures upon lithiation. High infrared reflectance in the monoclinic phase was described well by an elementary freeelectron plasma edge model. However, the high-Ts. film exhibited significantly poorer reflectance in the infrared when lithiated.
Lithium Intercalation in Oxides: EMF Related to Structure and Chemistry
Authors: West K. , Zachau-Christiansen B. , Jacobsen T. , Skaarup S. 
Published: March 2011

AbstractExperimental results for a number of oxide host materials as electrodes in lithium batteries are compared in order to obtain a better understanding of the factors influencing the emf-composition relationships. These factors are divided into two main groups: Those that are consequences of the structure of the host lattice, and those who follow from the chemistry of the host material. Series of materials with the same structure, but different chemical composition (spinels and MO2(B)) are compared, as well as series of materials with the same chemical composition, LixV2O5, but different structure. These data show that the potential level is mainly determined by the host chemistry, although destabilisation of the host can also give a significant contribution. The host structure will determine the width of the composition interval as well as the inflexions on the emf-curve. The possibility for tailoring the emf by using mixtures of transition metals in the host lattice is discussed.
Insertion Reactions in Materials with Water-Containing Galleries
Authors: Huggins R. A. , Wohlfahrt-Mehrens M. , JÖrissen L. 
Published: March 2011

AbstractThe microscopic mechanism of the operation of the well - known “nickel” electrode involves the transport of protons through an outer layer of the Ni(OH)2 phase to the two-phase Ni(OH)2/NiOOH boundary, where the electrochemical reaction takes place. This boundary is displaced as the reaction proceeds. When it reaches the outer surface so that the NiOOH phase is in contact with the electrolyte, an additional process takes place, resulting in the rapid evolution of gaseous oxygen. Interpretation of the available thermodynamic data in terms of ternary phase equilibria shows that the equilibrium electrode potential should be more positive than that for the decomposition of water, as is experimentally observed.
Conductivity Vs Nmr Correlation Times, and Decoupled Cation Motion in Polymer-In-Salt Electrolytes
Authors: Fan Jiang , Marzke R.F. , Angeill C.A. 
Published: March 2011

AbstractWe report 7Li spin lattice relaxation times at 12.82 MHz over a range of temperatures for liquid electrolytes of various salt:polymer ratios, and compare the NMR correlation time obtained at the temperature of the T1 minimum with the conductivity relaxation time at the same temperature. We find that at low salt contents the two relaxation times have the same value, but beyond the “salt-inpolymer to polymer-in-salt transition” zone at the Tg maximum, the two times increasingly separate. This is taken as evidence for the onset of cation-matrix mobility decoupling, which maximizes at the pure salt extreme.