bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructure of the Mineralized Tissue/Calcium Phosphate Interface in Vitro
Authors: de Bruijn Joost D. , Davies John E. , Flach Jim S. , de Groot Klaas , van Blitterswijk Clemens A. 
Published: March 2011

ABSTRACTAn in vitro rat bone marrow cell (RBMC) system was used to examine the structure of the interface established between calcium phosphates (Ca-P) and mineralized tissue. The Ca-P used, varied either in chemical structure or crystallinity. Therefore, not only the influence of chemical composition, but also the effect of degradation of Ca-P ceramics could be studied. The interfaces were examined with scanning and transmission electron microscopy (SEM and TEM).SEM showed that deposition of mineralized extracellular matrix on the different materials examined varied both in time and morphology. Mineralization started with the formation of afibrillar globules with which collagen fibres became integrated. With TEM, three distinctly different interfacial structural arrangements were observed which were dependent on the presence or absence of an electron dense layer and/or an amorphous zone. The former was considered to be at least partially caused by protein adsorption, which would precede biological mineralization events, whereas the latter was considered to represent partial degradation of the ceramic surfaces.The results of this study showed that interfacial reactions were not only influenced by the chemical structure, but also by the crystallinity of Ca-P ceramics. Thus, characterisation of Ca-P implant materials is of critical importance in achieving a better understanding of the phenomena that occur at the bone-biomaterial interface.
Developmental Study of Diopside for Use as Implant Material
Authors: Nonami Toru 
Published: March 2011

ABSTRACTDiopside was prepared sintering a powder compact of composition CaMgSi2O6 at 1573K for 2 hours. The bending strength of this sintered body was 300MPa and fracture toughness was 3.5MPam1/2. Diopside was soaked in a simulated body fluid at 309.5K. Three days later diopside formed hydroxyapatite (Hap) all over the surface [1]. Diopside implanted in rabbits came in close contact with the newly grown bone. EPMA spectral diagrams show a change of composition across the junction from the diopside to the newly grown bone [2].
Dielectric Response of a Chain of Disordered Polarizable Spheres: Numerical Simulation and Theory
Authors: VillaseiÑor-Gonzalez Pedro , Noguez Cecilia , Barrera Ruben G. 
Published: March 2011

ABSTRACTWe applied to a one-dimensional system (1D) a recently developed diagrammatic formalism, in order to calculate the effective dielectric response of a chain of polarizable spheres embeded in an homogeneous host. The effective response is calculated within the dipolar, quasi-static approximation, through the summation of selected classes of diagrams. We compared our results with a numerical simulation, where the position of each sphere was generated at random and the induced dipole moment of each sphere was calculated by solving a set of linear equations through matrix inversion and using periodic boundary conditions.
Effects of Multiple Scattering on Ultrasonic Velocity, Attenuation and Backscattering Noise in Polycrystals
Authors: Bruce Thompson R. , Rose James H. , Ahmed S. 
Published: March 2011

ABSTRACTUnderstanding the propagation of ultrasonic waves in polycrystals is important in nondestructive evaluation, both for the purpose of properly detecting or interpreting signals scattered from discrete flaws and for characterizing the microstructure itself. In this paper, the use of the unified theory for elastic wave propagation, developed by Stanke and Kino and based on the second order Keller approximation, is first discussed. After a brief review of the general formalism, recent extensions to the case of polycrystals with preferred grain orientation and elongation are presented. Particular attention is placed on a case commonly found in stainless steels in which the [001] crystallographic axes are aligned and the grains are elongated in the same direction. Techniques to predict the backscattered noise, based on single scattering approximation are then discussed and data motivating the need for extension to include multiple scattering is described. Finally, ways in which these theories can be used to provide improved characterizations of microstructures is indicated.
Variational. Principies for Fuil-Potentiai. Muiltiple Scattering Theory
Authors: Nesbet R. K. 
Published: March 2011

ABSTRACTThe variational principle of Kohn and Rostokcr (KR) implies that the determinant of a product of matrices vanishes at energy eigenvalues. The standard KKR method uses square matrices appropriate to a truncated spherical harmonic expansion, and sets the determinant of one matrix in this product to zero. For general nonspherical potentials in space-filling local cells, the KR variational principle requires these matrices to be rectangular, since the intermediate sum should extend over a complete set of solid harmonic functions. If extended in this way, the intermediate sum can be replaced by a Wronskian surface integral over the interfaces of adjacent space-filling atomic cells, as formulated in the variational principle of Schlosser and Marcus. E-quivalence of these two different variational principles is established here in the limit of completeness of the intermediate sum. The practical implication is that the standard KKR method is not well founded for the full-potential problem. Improved results for low-order basis function expansions can be obtained by including a Wronskian interface integral in full-potential ACO calculations, as a variational completion of the truncated intermediate K KR sum. A revision of CPA alloy theory is proposed that avoids dependence on this intermediate sum.
Alloy Theory Through the Ages
Authors: Gonis A. 
Published: March 2011

SUMMARYMan has always been fascinated with the quest to understand the inner workings of nature at a fundamental level. According to Embedocles[1], a philosopher in ancient Greece, all material things consist of four basic elements (he called them “roots”), namely earth, water, air, and fire. Modern mail's interpretation of that statement is that earth, water and air refer to the three states of matter, i.e., solids, liquids and gasses, with fire designating a process for transforming one of those states into the other. Be that as it may, Embedocles' statement could be conceived as the first attempt to construct an alloy theory, i.e., a predictive capability of the behavior of composite systems.
Real Space Multiple Scattering Description of Alloy Phase Stability
Authors: Turchi P. E. A. , Sluiter M. 
Published: March 2011

ABSTRACTWe present a brief overview of the advanced methodology which has been recently developed to study phase stability properties of substitutional alloys, including order-disorder phenomena and structural transformations. The approach is based on the real space version of the Generalized Perturbation Method, first introduced by Ducastelle and Gautier, within the Korringa-Kohn- Rostoker multiple scattering formulation of the Coherent Potential Approximation. Temperature effects are taken into account with a generalized meanfield approach, namely the Cluster Variation Method. The viability and the predictive power of such a scheme will be illustrated by a few examples, among them: (1) the ground state properties of alloys, in particular the ordering tendencies for a series of equiatomic bcc-based alloys, (2) the computation of alloy phase diagrams with the case of fcc and bcc-based Ni-Al alloys, (3) the calculation of antiphase boundary energies and interfacial energies, and (4) the stability of artificial ordered superlattices.
Ground State Searches in Fcc Intermetallics
Authors: Wolverton C. , Ceder G. , Fontaine D. De , Dreyssé H. 
Published: March 2011

ABSTRACTA cluster expansion is used to predict the fcc groutnd states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. TFile internetallic structures are not assumed, but derived rigorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearizedmuffin- tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration.
Comparison of Ni-Pt and Co-Pt Alloys Aided by Multiple-Scattering Calculations of Local Electronic Structure
Authors: Pisanty Alejandro , Martinez-Carrillo Miguel Angel , Amador Carlos 
Published: March 2011

ABSTRACTThe interaction between atomic and magnetic order is very strong in Ni-Pt alloys, whereas Co-Pt alloys show local magnetic properties which are independent of the composition and state of order of the system. A multiple-scattering calculation on Ni-Pt alloys is used in this paper, together with band structures for ordered compounds of both Ni-Pt and Co-Pt, to discuss the origin of the difference in properties between both alloy systems.
Phase Diagram of Ni-Pt from Linear Muffin-Tin Orbitals Total Energy Calculations
Authors: Amador C. , Lambrecht W. R. L. , Segall B. 
Published: March 2011

ABSTRACTProgress in the calculation of the phase diagram of the Ni-Pt compounds from "first-principles" is reported. Our procedure consists of: (1) calculating total energies for ordered structures as a function of volume and including internal relaxations by means of the linear muffin-tin orbitals method within the atomic sphere approximation; (2) mapping these results onto an Ising model with effective interaction parameters; and (3) calculating the phase diagram by means of the cluster variation method. We identify the elastic energy related to the difference in the Ni and Pt lattice constant as one of the major problems in this system and discuss the convergence of the cluster expansion of the energy.
Effective Cluster Interactions at Disordered Surfaces
Authors: Drchal V. , Kudrnovsky J. , Udvardi L. , Weinberger P. , Pasturel A. 
Published: March 2011

ABSTRACTEffective cluster interactions (ECI) at surfaces of substitutionally disordered alloys are determined using the generalization of the TB-LMTO-CPA method to inhomogeneous systems. Illustrative results are reported for the (Ag,Pd) alloy system.
Full—Potential Lmto Calculation of Brittle Fracture in Titanium Carbide
Authors: Price D.L. , Cooper B.R. 
Published: March 2011

ABSTRACTThe refractory transition metal—carbides commonly fail under stress by brittle fracture and the properties and nature of the fracture process are consequently of practical interest. We have calculated the fracture properties of titanium carbide under tensile stress using our full—potential LMTO method, a methodology which is closely related to multiple scattering theory (and includes a true interstitial region). The fracture calculation is accomplished by employing a repeated slab (or repeated cleavage separation) geometry. Within this geometry, the fracture process is simulated most simply by uniformly increasing the gap separation from zero to a distance on the order of a few atomic radii. A more sophisticated search for fracture instability involved stretching the ideal crystal and examining the separation energetics of the strained system.Results of these calculations will be reported both for the ideal, stoichiometric titanium carbide crystal and also for systems containing carbon vacancies. We will discuss therole of such defects in modifying the bonding behavior at the cleavage plane and the resulting effect on resistance to fracture.
Real-Space Multiple Scattering Theory Method: Formalism and Applications
Authors: Zhang X.-G. 
Published: March 2011

ABSTRACTDifferent forms of the real-space multiple scattering theory (RS-MST) formalism are compared in order to understand its convergence behavior with respect to truncation in the angular momentum expansions. In particular the so-called “folding method” or (1,n) mode is considered, in which the renormalized t-matrix T of the semi-infinite system has the dimension of n (n > 1) repeating units and the self-consistent equation for T is constructed by adding and contracting one such unit. It has been demonstrated in previous studies of layered structures that the folding method converges rapidly in both angular momentum (L) and site (n) indices and yields accurate results. The convergence behavior is an important factor to be considered in applying the various forms of the RS-MST method to layered structures as well as other systems with extended defects.
Scattering and Multiple Scattering in Disordered Materials, an Overview
Authors: Weaver Richard L. , Butler W. H. 
Published: March 2011

ABSTRACTThe papers papers in this section were presented at a joint session of symposium V on Applications of Multiple Scattering Theory and of Symposium P on Disordered Systems. They show that the ideas of scattering theory can help us to understand a very broad class ofphenomena.
Diffusing Wave Spectroscopy: The Dynamics of Multiply Scattering Media
Authors: Weitz D. A. , Pine D. J. , Durian D. J. , Zhu J. X. 
Published: March 2011

ABSTRACTWhen light is very strongly multiply scattered by a medium, its propagation can be well described by a diffusion approximation. This allows important, measurable quantities to be calculated theoretically and interpreted. Thus, for example the total light transmitted through a sample can be used to determine the transport mean free path which characterizes the diffusive transport of the light. In addition, the distribution of path lengths followed by the diffusing light can be determined. This distribution can in turn be used to interpret the temporal fluctuations of the scattered intensity that arise due to the motion of the scattering medium. Therefore, traditional quasielastic, or dynamic, light scattering can be extended to the strongly multiple scattering limit. This technique is called Diffusing Wave Spectroscopy (DWS), and allows useful information about the dynamics of the medium to be determined. Furthermore, new physical processes can be studiedusing DWS. For example, DWS is sensitive to very small motions of colloidal particles: motion of 1 pm diameter particles can be resolved on lengths of∼ 5 Å using light with a wavelength of 0.5 μm. New physical phenomena are probed when motion on these length scales is observed. In particular, the time evolution of the hydrodynamic interaction between concentrated colloidal particles can be resolved. In addition, DWScan also probe spatially rare events since the light paths sample a large volume of the sample. This allows DWS to probe very slow dynamics, making it useful for the study of materials such as foams. This talk reviews the fundamentals of DWS and highlights some ofits unique applications.
First-Principles Angle-Resolved Photoemission Intensity Calculations in Y Ba2Cu3O7
Authors: Lindroos M. , Bansil A. , Campuzano J. C. 
Published: March 2011

ABSTRACTWe discuss the application of the multiple scattering theory to obtain first-principles predictions of angle-resolved photoemission intensities (ARPES) in the high-Tc superconductors. In this connection, we have generalized and implemented the ‘one-step’ photoemission approach to treat systems with an arbitrary number of atoms in the layer unit cell. We illustrate the methodology with results for the r-S symmetry direction for the (001)-surface of orthorhombic YBa2Cu3O7. Our computations give insight into the effects of surface termination, and of polarization of incident light on photoemission intensities.
Hierarchical Structure of a Natural Composite: Insect Cuticle
Authors: Gunderson Stephen L. , Gunnison Katie E. , Sawvel John W. 
Published: March 2011

AbstractThe insect cuticle is an excellent example of a natural, fiber-reinforced, polymeric composite consisting of chitin fibers embedded in a protein matrix. Optical and electron microscopy have been used to examine the structure and interaction of the constituents of the bessbeetle (Odontotaenius disjunctus) cuticle from the molecular to the macroscopic levels.Molecular chains of the polysaccharide chitin (N-acetylglucosamine) are grouped together to form “fibrils” which are either dispersed throughout the matrix or combined to form larger “fibers”. The fibers are unidirectionally oriented within individual sheets or laminae which are stacked on top of one another at various angles forming a laminated structure.The protein matrix is ductile upon initial deposition but then undergoes a crosslinking process which increases its shear stiffness, thereby improving load transfer between fibers. The matrix is bound to the chitin via beta linkages holding it together at both the fibril and fiber levels. The matrix has a fibrous morphology which provides adequate toughness in spite of the high degree of crosslinking.Reference is made to designs observed in the bessbeetle cuticle which could be applied to man-made composites for improved performance primarily in the areas of damage tolerance and strength and stiffness coupled with low weight. For these designs to be implemented using synthetic materials, new or modified processing and fabrication methods are needed.
Self-Organization (Assembly) in Biosynthesis of Silk Fibers - A Hierarchical Problem
Authors: Kaplan David L. , Fossey Stephen , Viney Christopher , Muller Wayne 
Published: March 2011

AbstractIn natural systems, structural macromolecules undergo prescribed recognition and assembly steps during synthesis and processing. These associations lead to more complex assemblies that exhibit useful multifunctional properties. Many of these processes are not well understood. Some aspects of these processes are presented using the fibrous protein polymer silk as an example. Issues such as polymer chain biosynthesis, chain interactions, processing into fibrils, and complex engineering into supra-assemblies are addressed and biochemical, spectroscopic and modeling studies are reviewed. Genetic level controls of chain composition, crystalline/amorphous domain distribution, chain aggregation, chain registry, silk I-silk II phase transitions, nematic liquid crystalline phase, loss of water, global molecular alignment, and solution spinning are some of the characteristics of this biological system that are addressed. Although some information is available at the molecular and macro-scale levels, a key issue is the paucity of information at the meso-scale level to fully understand the role of structural hierarchy in the silk fiber assembly process.
Hierarchical Structure and Light Scattering in the Cornea
Authors: Farrell R. A. , Freund D. E. , McCally R. L. 
Published: March 2011

AbstractThe complex hierarchical structure of the cornea of the eye as it is known from light and electron-microscopy is reviewed. Microscopy depicts the cornea as a layered structure with each layer parallel to the cornea's surfaces. The middle 90% of the cornea is a connective tissue layer called the stroma, which in turn is comprised of 2 μm thick sheets (lamellae) of collagen fibrils embedded in a ground substance. Fibrils within a given lamella have their axes parallel to one another, while fibril axes in adjacent lamellae make large angles with one another. Predictions of light scattering theory are then used to show how light scattering measurements made on fresh tissue can test these structures for possible artifacts due to preparative procedures. With unpolarized light, the total scattering cross-section depends on the fibrillar ultrastructure, but not on the lamellar structure. Angular scattering depends on both levels of hierarchical organization. The lamellar level of organization is especially significant for the propagation and scattering of polarized light. To date the structural implications of scattering measurements are in accord with structures seen in electron micrographs.
Eukaryotic Signal Transduction Pathways And Man-Made Systems Compared
Authors: Bayley Hagan 
Published: March 2011

AbstractThe components of biological signal transduction pathways have been compared with those of electronic circuits. Indeed, attempts are being made to incorporate biomolecules into electronic devices. However, man-made biomolecular devices do not yet mimic several important features of naturally occurring systems, especially those of eukaryotes. It is well known that the polypeptide components of biological signal transduction pathways include subunits of receptors, regulatory proteins, enzymes and channels. It is less well appreciated that each component often exists in many functionally related but not redundant forms. When proteins are hetero-oligomers, numerous combinations of these forms may be permitted yielding large arrays of signal transduction molecules with overlapping properties. Further, the organization of these molecules within the cell Is highly complex. Especially alien to the materials scientist are the findings that signal transductlon proteins can translocate between regions of cells in response to stimuli and change in concentration as a consequence of breakdown and resynthesis. These features, as well as the interactions between signal transduction pathways, produce far more complex and fluid signalling networks than those presently used in man-made devices. Is anything to be gained by mimicking such complexity or are we on the right track in designing relatively simple, structurally rigid devices using biomolecular components?
Characterization of the Complex Matrix of theMytilus EdulisShell and the Implications for Biomimetic Ceramics
Authors: Keith J. A. , Stockwell S. A. , Ball D. H. , Muller W. S. , Kaplan D. L. , Thannhauser T. W. , Sherwood R. W. 
Published: March 2011

AbstractThe macromolecular matrix present in the composite shell of the blue mussel,Mytilus edulis, accounts for less than 1% of the shell by weight but is theorized to play a significant role in controlling the growth, morphology, and orientation of the CaCO3that makes up the shell. The presence of several proteins in this matrix, only some of which have affinity for calcium, suggests a hierarchical structural model for the shell. Proteins were isolated under denaturing, reducing conditions and separated by centrifugation, gel electrophoresis, and high performance liquid chromatography. The major matrix proteins, both soluble and insoluble, were evaluated for amino acid composition, calcium binding, and glycosylation. Some N-terminal sequence data was collected. Non-proteinaceous components of the matrix were also analyzed. Comparison of the mussel shell matrix with the protein matrix of other molluscan systems suggests that this complexity is not unique to the mussel and may provide a key to the understanding of more generic biomineralization processes necessary for such applications as biomimetic ceramics.