bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure of Au/Ge/Au Multilayer Ohmic contacts to GaAs
Authors: Kim Tae-Il , Chung D. D. L. 
Published: March 2011

ABSTRACTThe presence of a 500 Å Ge layer in Au/Ge/Au ohmic contacts to GaAs was found to hinder the agglomeration of Au upon heating. An ohmic contact as uniform as the asdeposited metallization was achieved after heating at 300°C. Heating at 350–500°C resulted in various morphological entities in a Au-rich matrix. The microstructure changed from one with a Au-rich matrix to one with a GaAs-rich matrix and dendritic Au-rich islands at 525±25°C. Heating at 400°C or above resulted in Au-Ga phases with the epitaxial relationships α' (110) ‖ GaAs (100) and Au2Ga (112) ‖ GaAs (100).
Reaction Sintering Property of Green Compact of Si and TiC Mixed Powders in Nitrogen
Authors: Yasutomi Yoshiyuki , Sobue Masahisa , Shinozaki Shin-Ichi S. , Hangas John , Shinozaki Shin-Ichi S. 
Published: March 2011

ABSTRACTWe have developed a new type of near net shape sintering process using nitridation of Si and other inorganic powders. In this report, the sintering property of powder mixture compacts of TiC (10μm or 0.9μm) and Si (0.9μm) in a nitrogen atmosphere at 1350°C was investigated.A large portion of the Si formed Si3N4 on reaction with nitrogen, while TiC formed TiN and free carbon. A small portion of this free carbon was converted into β-SiC on reaction with Si and about 98% of the free carbon remained in the sintered body. Thus, composite ceramics having a composition of Si3N4·TiC·TiN·C·β-SiC were obtained. The porosity of this composite was much smaller than that of ordinary Si3N4 bonded ceramics, because of the large volume expansion for formation of free carbon. The pore size under 5μm can be got using TiC powder with an avarage size of 0.9μm.
Effect of Isostatic GAS Pressure on Optical Quality of MgAl2O4 Spinel
Authors: Hsu S.E. , Wang C.T. , Tsai D.S. , Yang S.J. 
Published: March 2011

ABSTRACTOptical transparent MgAl2O4 spinel is obtained by processing with high gas pressure to eliminate or reduce the residual pores. Both hot–pressed and sintered specimens are post–treated by the high argon hipping process here. The densities of all the specimens before hipping are over 99% theoretical density. In the high gas pressure process, the pressure ranges from 2000 to 30000psi at 1500°C for 2hrs. The transmittance from visible to IR are measured before and after gas pressure treatment. The transparency from visible to IR increases significantly with the HIP process. When applied pressure less than 6000psi, bulk density is proportional to the logarithm of the pressure and the logarithm of the absorption coefficient is proportional to the porosity. Bimodal grain–size distribution exists in the sintered and hipped specimens but is not observed in the uniaxial–hot–pressed–only samples. XRD analysis indicates the width of the diffraction peaks in the HIP specimens is less than that in UAHP specimens. The result illustrates the HIP process improves the spinel crystallinity.
High Active GAS (O2 or N2) Pressure Crystal Growth and Phase Diagram of YBaCuO Phases and GaN
Authors: Karpinski J. , Kaldis E. , Conder K. , Rusiecki S. , Jilek E. 
Published: March 2011

ABSTRACTA review of the phase diagram studies of the YBaCuO and GaN systems under high active gas (O2 or N2) pressure is given. The P,T equilibrium conditions for three superconducting phases existing in YBaCuO system vary as a function of Cu content. Application of high O2 pressure allows crystal growth of the 124 and 247 compounds and high N2 pressure alow crystal growth of GaN. We discuss also indications, that other YBaCuO compounds may exist.
The Role of Oxygen in the Hot Isostatic Pressing of High Tc Superconductors
Authors: Niska John V. , Loberg Bengt 
Published: March 2011

ABSTRACTThe bismuth-based 2212 and 2223 superconductors and the yttrium-based 123 and 124 high Tc superconductors are oxide ceramics, so that oxidizing conditions must be maintained in the HIP to avoid oxygen loss and decomposition. This has been done in an argon gas HIP by using glass encapsulation, but internal gas pressure retards densification. The thermodynamics of the release of oxygen by the superconductive ceramics and the stability of the metal to oxygen can be shown on a free energy diagram (Ellingham diagram). The base metals (as Fe and Cu) are reactive with respect to superconductive ceramics but not silver.
Fabrication of Volumetric Dilatometer Using Buoyancy Under High Pressure Gas
Authors: Nanko Makoto , Sakayori W. , Ishizaki K. , Uehara K. , Ueda M. 
Published: March 2011

ABSTRACTSintering processes are monitored by dilatometry. A conventional dilatometer under high gas pressure (typical HIPping conditions) is constructed using graphite rods to examine linear thermal expansivity of one sample. This method has a few disadvantages, such as the pressure of graphite rods acting as a uniaxial hot press. The advantage of a HIP method, compared to a hot press sintering is the capacity to process many samples at a time. The graphite rod method is applicable for only one sample. A volumetric dilatometer was developed using buoyancy under high gas pressure, which can monitor HIP sintering processes of many samples and check for capsule failure.
Bimetallic Coatings for Twin - Screw Extruder Barrels
Authors: Archer G.F. , Stephenson D.J. 
Published: March 2011

ABSTRACTIn this paper the development of novel wear/corrosion resistant coatings for twin screw extruders used in the food industry is discussed. The conventional materials used for extruder applications are reviewed and their limitations highlighted. The requirements for a new surface engineering philosophy are introduced and utilised to develop a new manufacturing system for the coating of extruder barrels. These coatings are based on Ni/Cr/B/Si/Fe alloys containing WC particulate. The processing route combines conventional PM technology with consolidation of the coating by hot isostatic pressing (HIPping). The HIP cycle is tailored to optimise the coating/substrate adhesion and the coating microstructure. Examples are given which illustrate the superior performance of these HIPped bimetallic coatings compared to conventional surface treatments.
The Resorbable Bioglassceramics Based on Calcium Biophosphate
Authors: Chin Tsung-Shune , Wu D. C. , Liu H. S. , Hung M. P. , Wang C. P. 
Published: March 2011

ABSTRACTNovel resorbable bioglassceramic artificial tooth roots based on calcium biphosphate were synthesized, implanted into rabbits, and assessed. They were prepared by melting a glass composition of CaO/(CaO+P205) = 0.33, casting, crushing, loose powder sintering and crystallization annealing. The resultant porosity is 3 to 36 μm. The three point bending strength is 33 to 150 MPa depending on annealing treatment. The crystallized phases are β-Ca2P2O7 and CaP206. These porous implants show remarkable biocompatibility with the old bone and induce the growth of new bone within 30 days. The implants are partly resorbed after 90 days and replaced by new bone. The ingrowth of blood vessels into the implant is abundantly seen after 90 days despite a small original porosity, due probably to enlarged pores by preferential resorption of the implant material. The new ceramics are good candidates for resorbable bone bioimplant.
In Vivo Interactions with (Tissue Culture Pretreated) Dermal Sheep Collagen
Authors: van Wachem P. B. , van Wachem P. B. , Damink L. H. H. Olde , Dijkstra P. J. , Feijen J. , Nieuwenhuis P. 
Published: March 2011

ABSTRACTPretreatment in tissue culture (TC) was previously found to markedly reduce the in vitro cytotoxicity of two types of crosslinked dermal sheep collagens (DSC's). This in vivo study confirms our in vitro results, in that TC-pretreatment of crosslinked DSC's resulted in the marked reduction or elimination of cytotoxic effects, such as increased cell infiltration, a deviant neutrophil-morphology, lipid formation and cell death. TC-pretreatment affected the crosslinked state of both DSC's in a different way, which could be deduced from the differences in gelatin-formation and presence of giant cells from macrophage- or fibroblast-origin. The results are explained in view of the differences in crosslinking.
Develoapmet of a Tissue Analog for Cartilage Repair
Authors: Pachence J. M. , Frenkel S. R. , Lin H. 
Published: March 2011

ABSTRACTPurified type I collagen was formed into matrices whose pore sizes were defined on the basis of previous results. The first series of in vitro studies measured the metabolism of chondrocytes grown in matrices with various pore sizes; results revealed that the growth rate was independent of the average matrix pore size, but that ckmdrocyte infiltration throughout the matrix was optimal for pore sizes of 100 to 150 un. In a second series of studies, type I collagen was combined with hyaluranic acid; the HyA/collagen matrices had little effect on chcrdrocyte cell growth versus the collagen matrices. A third set of in vitro studies used collagen matrices incorporating varying cornentrations of insulin-like growth factor. It was found that the IGF-1/collagen matrices can significantly effect the growth and metabolism of the clxrihrocytes. These experiments were vital in establishing the collagen matrix parameters which will be used in subsequent in vivo studies.
Tissue Fabrication: Reconstitution and Remodeling in Vitro
Authors: Bell Eugene , Scott Sumi 
Published: March 2011

ABSTRACTTwo approaches to the reconstitution of tissues and organs are reviewed. The first consists of imitating the architecture of actual tissues and organs by combining cultured specialized cells with extracellular matrix components to produce a connective tissue substrate on or in which epithelial, mesothelial or endothelial cells can be plated or seeded and subsequently differentiate into mono or multilayered tissues and other structures. The second consists of providing an acellular framework of extracellular matrix constituents that can be occupied by adjacent host tissues after implantation in vivo and be remodeled by them to resemble the host tissues it is designed to replace. A paradigm for events in vivo, designed to study the process of remodeling of acellular matrices in vitro has been developed. The living skin equivalent (LSE), an example of a product fabricated using the first approach to tissue engineering, has been adapted to study events of extracellular matrix remodeling, relevent to the second approach to tissue engineering. After creating a disc shaped wound bed in an LSE, the wound is filled with a collagen matrix with or without added supplements and the process of epidermal wound closure and associated events in the dermis are followed. It is shown that fibroblast conditioned medium or a simple molecule such as ascorbic acid, added with no additional growth factors to the collagen matrix used to fill the wound bed, strongly stimulates the process of repair. Dermal fibroblasts from the adjacent tissue invade the collagen lattice that forms in the wound bed, and keratinocytes recruited from the wound edge overgrow the new dermal tissue. The applicability of the paradigm to the repair of vascular and other tissues will be discussed and approaches to optimizing the composition of acellular constructs considered.
Reconstituted Collagen Produces Different Healing Reactions in Bony and Soft Tissue Compartments
Authors: Todescan Reynaldo , Davies Johne E. 
Published: March 2011

ABSTRACTUsing both in vivo and in vitro experiments we have demonstrated that: reconstituted collagen will undergo mineralization in a healing bony compartment; that this mineralization is the result of spontaneous precipitation of calcium salts due to the presence of alkaline phosphatase produced by the bone cells, and that once calcified, the collagen will undergo cellular resorption by tartrate-resistant multi-nucleate giant cells similar to osteoclasts. This sequence of events is quite different to that in the supra-bony soft-tissue compartment where no calcification of the collagen is apparent, the collagen matrix becomes infiltrated with fibroblast-like cells and little resorption of the matrix occurs during implantation.We conclude that reconstituted collagen may be employed as both a tissue barrier, enhancing guided tissue regeneration, and a bone-substitute material, which becomes replaced by natural bone tissue.
Surface Modification of Bio-Active Ceramic (Artificial Bone) by Ion Implantation
Authors: Takaoka G. H. , Tanaka R. , Usui H. , Koh S. K. , Current M. I. , Yamada I. , Akamatsu S. , Kokubo T. 
Published: March 2011

ABSTRACTGlass-ceramics (A-W) containing apatite and wollastonite phases have been developed that show good bio-compatibility and rapidly form chemical bonds with living bone. The glass-ceramic (A-W) was implanted with 200 keV Zr and Ar ions at doses of 1E15 to 1E17 ions/sq.cm. It was found that the Zr ion implantation was effective for obtaining high mechanical strength in simulated body fluid. The increase of the mechanical strength can be considered to be due to the formation of Zr and O bonds by ion implantation. The bioactivity of the implanted ceramics remained, and was improved after soaking in the simulated body fluid. In the case of Ar ion implantation, the fracture strength was not improved. However, the bioactivity was strong and improved with increase of the time soaked in the simulated body fluid.
Cellular Interaction with Biomaterials Modified by Arg-Gly-Asp Containing Peptides
Authors: Glass James R. , Craig William S. , Dickerson Ken , Pierschbacher Michael D 
Published: March 2011

ABSTRACTBecause cells can recognize and attach to short synthetic peptides containing the tripeptide sequence, arg-gly-asp (RGD), we have designed peptides which will spontaneously bind and present an active RGD sequence on biomaterial surfaces. We have analyzed a number of synthetic peptides and fully characterized one which fulfills this functional criteria. This peptide has been named PepTite-2000™. When biomaterials are placed in aqueous buffers containing PepTite-2000, the peptide rapidly binds to the surface and provides a site for cell attachment. Cell attachment occurs to PepTite-2000 coated materials by an RGD dependent mechanism using the αvβ3 integrin. This coating protocol is widely applicable, and the peptide will coat and promote cell attachment to all the commonly used biomaterials we have tested including dacron, teflon, titanium and silicone. Analysis of the soft tissue response to dacron implants coated with PepTite-2000 demonstrates that the coating results in more rapid tissue ingrowth and less giant cell recruitment around the implanted materials. These data demonstrate that PepTite-2000 can be used to modify biomaterial surfaces and present a more “natural” site for cell interactions.
Principles of Tissue Engineering and Reconstruction Using Polymer-Cell Constructs
Authors: Mooney David J. , Cima Linda , Langer Robert , Johnson Lynt , Hansen Linda K. , Ingber Donald E. , Vacant Joseph P. 
Published: March 2011

ABSTRACTThe fields of materials science, cell and molecular biology, and surgical reconstruction are merging to create new devices for surgical transplantation and reconstructive applications. The field of artificial devices for implantation has matured over the last 40 years. Likewise, the field of transplantation and tissue reconstruction has undergone enormous change and improvements over the last 30 years. It has been proposed that these fields merge to create new tissue substitutes for functional replacement, therapy or reconstructive applications. Over the last five years, our lab has experimented with the concept of using man-made, biodegradable polymer systems as scaffolding for cell implantation devices. They have been designed to maximize diffusion parameters allowing nutrient exchange, gas exchange, and waste exchange. Vascular ingrowth occurs in the implant with subsequent resorption of the original polymer. This leaves a permanently engrafted new tissue which is a chimera of donor cells for functional replacement and recipient mesenchymal elements including blood vessels and supporting tissue. We have experimented in several model systems including hepatocyte implants, chondrocyte implants for cartilage reconstruction, urethelial implants for urinary reconstruction, and more recently small bowel and bone. Across this broad front of tissue types, much new knowledge has been gained and there continues to be hope that this will achieve clinical application.
Biodegradable Cell Transplantation Devices for Tissue Regeneration
Authors: Mikos Antonios G. , Wald Heidi L. , Sarakinos Georgios , Leite Susan M. , Langer Robert 
Published: March 2011

ABSTRACTBiodegradable polymers can be utilized as templates for cell transplantation and regeneration of metabolic organs and structural tissues. Candidate materials must be adhesive substrates for cells, promote cell growth and allow for retention of cell function. However, the processing requirements of such materials into highly porous three-dimensional structures with large surface per volume and an interconnecting pore network limits their potential application for tissue regeneration. A new processing technique was developed to produce uniform, three-dimensional cell transplantation devices of poly(lactic-co-glycolic acid). The process involved the preparation of highly porous membranes by a solvent-casting and particulate-leaching technique followed by their lamination. The device structural and mechanical properties depended on those of their constituent membranes, as evaluated by mercury porosimetry, scanning electron microscopy, and thermomechanical analysis. Cells to be seeded into the devices were injected from catheters incorporated within their structure. In vitro studies with model suspensions of dyed microspheres allowed for visual evaluation of the internal pore structure of various layered devices. From these studies, numerous parameters of device design for cell seeding were determined including pore size and injection rate. The membrane lamination technique produced devices without interfaces between layers as determined by microsphere injection and scanning electron microscopy.
Two Methods for Analyzing Waves in Composites with Random Microstructure
Authors: Willis John R. 
Published: March 2011

ABSTRACTThe problem of calculating the mean wave in a composite with random microstructure is addressed. Exact characterizations of the problem can be given, in the form of stochastic variational principles. Substitution of simple configuration-dependent trial fields into these generates approximations which are, in a sense, ‘optimal’. It is necessary in practice to employ only trial fields which will generate, in the variational principle, no more statistical information than is actually available. Trial fields that require knowledge of two-point statistics generate equations that can also be obtained directly, through use of the QCA. The same fields can be substituted into an alternative variational principle to yield an approximation that makes use of three-point statistics – this approximation is less easy to obtain by direct reasoning. When not even two-point information is available, some more elementary approximation is needed. One such approximation, which is simple and direct in its application, is an extension to dynamics of a “self-consistent embedding” scheme which is widely used in static problems. This is also discussed, together with some illustrative results for a matrix containing inclusions and for a polycrystal.
Effective Properties of Discrete Random Composites Wherein the Host and Inclusion Phases Obey Different Constitutive Relations
Authors: Varadan V V. , Apparao R. T. , Varadan V. K. 
Published: March 2011

ABSTRACTIn studying the effective medium theories, polarization is hardly given a consideration in deciding the effective properties of a composite where the host and inclusion phases follow different constitutive equations. A significant conclusion of this paper is that eventhough the composite has discrete inclusions, with the inclusion phase obeying different constitutive properties than the host, the effective medium shows a preference for the inclusion behavior rather than the host which is continuous. As an example, results on polarization study are detailed for the specific case of chiral composites. Application of similar principles is presently explored in more complex problems like the elastic wave propagation through piezoelectric composites and the acoustic wave propagation through sediments.
Multiply Scattered and Diffusing Ultrasound: Applications, Experiments, Theory
Authors: Weaver Richard L 
Published: March 2011

ABSTRACTThe study of ultrasonic waves in random media in a strong multiple scattering limit is becoming increasingly relevant to applied techniques of nondestructive characterization of material microstructures. This paper reviews the state of that art within the context of engineering applications and also reviews the evidence for the Anderson Localization of ultrasound.While ultrasound has long been employed as a nondestructive probe of material microstructure, it has usually been the rapidly attenuated coherent wave, and in particular, its speed and attenuation, which has been scrutinized for that purpose. The theory of such waves is discussed here. However, recent experiments and theory are increasingly addressing the diffuse speckle wave field. This small but growing body of work is also reviewed.While there has been much work recently on optical and microwave realizations for the study of the Anderson localization of classical waves, there has been little such investigation with sound waves. Recent work demonstrating the Anderson Localization of Ultrasound in two dimensions may be the first such for any classical waves in dimension greater than one.
Korringa-Kohn-Rostoker Electronic Structure Method for Space-Filling Cell Potentials
Authors: Gonis A. , Butler W. H. , Zhang X.-G. 
Published: March 2011

ABSTRACTThe multiple scattering theory (MST) method of Korringa, and of Kohn and Rostoker for determining the electronic structure of solids, originally developed in connection with potentials bounded by noa-overlapping spheres (Muffin-tin (MT) potentials), is generalized to the case of space-filling potential cells of arbitrary shape through the use of a variational formalism. This generalized version of MST retains the separability of structure and potential characteristic of the application of MST to MT potentials. However, in contrast to the MT case, different forms of MST exhibit different convergence rates for the energy and the wave function. Numerical results are presented which illustrate the differing convergence rates of the variational and nonvariatonal forms of MST for space-filling potentials.
A Full-Potential Kkr Green's Function Method for Impurities in Metals
Authors: Dederichs P.H. , Drittler B. , Zeller R. 
Published: March 2011

ABSTRACTWe have developed a full-potential extension of the KKR Green's function method for impurities. The crystal potential is split into a sum of non-overlapping, cellular potentials. The solution for the individual anisotropic potentials is constructed by an iteration procedure starting from the solution for the isotropic potential. We discuss some technical details of the method and its efficiency in applications to impurities in metals. As examples we choose: i) calculations of local moments and Friedel oscillations in metals, ii) calculations of vacancy formation energies, iii) calculations of forces based on the Hellmann-Feynman theorem. For these applications we discuss the importance of the inclusion of full-potentials in comparison to atomic-sphere potentials.