bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion Beam Deposition: Damage and Epitaxy
Authors: Armour D G
Published: March 2011

The bombardment of solid surfaces with ions in the energy range below about 150 eV, depending on the ion-substrate combination, results in a net growth of material on the surface. An ion beam facility capable of producing highly uniform, low energy beams of current densities in the range 10-1 to 1 Am-1 has been developed to study the potential of this growth technique for the fabrication of thin epitaxial films at low temperatures.

The energy deposition associated with ion bombardment, which is considered to be responsible for the low temperature epitaxy capability, can also cause atomic displacements on the surface and near-surface regions of the substrate during initial growth and in the growing film. A study of the growth processes thus requires investigation of the damaging effects of low energy ion bombardment. In the present paper, fundamental aspects of the implantation and deposition of materials using very low energy ions will be discussed.
Performance Advantages of Submicron Silicon-On-Insulator Devices for ULSI
Authors: Sturm James C.
Published: March 2011

In this paper the various performance advantages of SOI and SOS structures for submicron ULSI circuits will be described. In addition to the traditional speed and radiation-hardness advantages, there are several significant advantages of thin-film SOI compared to bulk structures for the submicron scaling of MOS transistors. These advantages include short-channel threshold voltage stability, improved sub-threshold slope, increased saturation current, and reduced hot electron effects. Both theory and data from several groups will be presented to illustrate these effects. Since these advantages all fall in areas that are critical limits to device engineering and scaling in the submicron regime, the motivation for using SOI should be even stronger as devices are scaled to smaller dimensions in the future. Consideration of SOI or SOS on the ULSI scale will require a technology capable of low defect films with a film thickness of 1000 A or less, however.
The prospects for minority carrier devices such as bipolar transistors for BI-MOS will also be discussed. Both device structure (lateral vs. vertical) and material quality are issues that must be addressed.
Synthesis of Buried Silicon Compounds Using Ion Implantation
Authors: White Alice E. , Short K. T. , Dynes R. C. , Gibson J. M. , Hull R.
Published: March 2011

Ion implantation is widely used for doping semiconductors at low concentration, but, with the advent of a new generation of high current implanters, synthesizing new materials rather that simply doping them has become feasible. This technique has been successfully applied to fabricating silicon-on-insulator (SOI) structures with oxygen and nitrogen for several years. Since we are interested in understanding the mechanisms of formation of these layers, we have concentrated on sub-stoichiometric implantation doses of oxygen where it is easier to observe the coalescing layer. In order to determine whether this process of compound formation is more general, our studies were expanded to include implantation of the transition metals. Here, elevated substrate temperatures are necessary to minimize Si surface damage. The resulting disilicide layers are of remarkably high quality: they are single crystals in registry with the silicon wafer and they have better residual resistivities than comparable UHV-reacted suicides.
Substrate Annealing and the MBE Growth of Silicon on Sapphire.
Authors: Pellegrino Joe , Richmond Eliezer
Published: March 2011

The effect of predeposition substrate annealing has been investigated for MBE grown silicon films on sapphire substrates (SOS). Films of varying thickness were grown on substrates which had been annealed at either 1450°C or 900°C. The surface morphology and crystal1inity for each film were examined. The silicon thicknesses ranged from 65-400 angstroms and the anneal time for both temperatures was 30 minutes.

The results indicate that the predeposition anneal of the sapphire substrate has a dramatic effect on the growth characteristics of the silicon film. The high temperature anneal promotes island growth of the silicon film which is easily resolved in the SEM. These islands are roughly 800 angstroms wide for a 65A thick film and grow to approximately 2200 angstroms for a 250A film. On the other hsuxi, the lower temperature anneal did not result in island formation, when examined by SEM, at any of the film thicknesses. In addition, X ray analysis reveals that the silicon layers for the high temperature anneal are epitaxial with a (100) orientation.
Buried Insulators and/or Conductors in Singles-Crystal Silicon Using Porous Silicon Techniques
Authors: Tsao Sylvia S.
Published: March 2011

Porous silicon lends itself to a variety of applications due to its unique characteristics such as an interconnected pore network, large surface area, and dopant-dependent selectivity of formation. Although the best-known application of porous Si is for silicon-on-insulator (SOI) fabrication, the porous silicon technique also offers elegant approaches for silicon-on-conductor (SOC) fabrication.

In this paper, we present an overview of porous Si techniques for both SOI and SOC applications. Possible limitations of the oxidized porous silicon process, for SOI in particular, are discussed. We also consider novel and multilayered structures which might be obtained using porous silicon.
Wafer Bonding for Soi
Authors: Maszara W.P. , Goetz G. , Caviglia T. , Cserhati A. , Johnson G. , McKitterick J.B.
Published: March 2011

Bonding of 3 and 4 in. oxidized silicon wafers was investigated for SOI applications. The bonding was achieved by using a surface treatment procedure compatible with VLSI processing and by heating in an inert atmosphere a pair of wafers which had been contacted face-to-face. A quantitative method for the evaluation of the surface energy of the bond based on crack propagation was developed. The bond strength was found to increase with the bonding temperature from about 60-85 erg/cm2 at room temperature to ⋍2200 erg/cm2 at 1405°C, in good agreement with the surface energy of bulk quartz. The strength was essentially independent of the bond time for up to 1100°C. Electrical properties of the wet-oxide-to-wet-oxide bond were tested using MOS capacitors. The results were consistent with a negative interface charge density of approximately 1011cm−2 at the bond. A double etch-back procedure was used to thin the device wafer to the desired thickness within *20 nm across a 3in. wafer. The density of threading dislocations in the remaining silicon layer was smaller than 103 cm−3, and the residual dopant concentration less than 5×l015cm−3, both remnants of the etchstop layer. A discussion of the bonding mechanism will be presented.
Cavity Formation in Simox Structures
Authors: El-Ghor M. K. , Pennycook S. J. , Sjoreen T. P. , White C. W. , Narayan J.
Published: March 2011

We have investigated the effect of different implantation parameters on cavity formation in the top Si layer in SIMOX structures. Cavities were found to occur in the temperature range between 600 and 675°C. The nucleation and growth kinetics of cavities could be reasonably explained using classical theory, and showed a behavior similar to that of irradiation-induced voids in metals. A similar dependence on instantaneous current and beam scanning frequency was also observed. Post implantation annealing at a temperature of 1150°C for 80 min showed cavities starting to facet, and a threading dislocation density of < 105 cm2. SIMOX structures formed in (111) silicon are also presented.
The Importance of Treating Electron-Electron Interactions in the Calculation of Dynamic Third-Order Polarizabilities for Linear Conjugated Polyenes
Authors: Pierce Brian M.
Published: March 2011

The non-resonant electronic component of γ(-3ω ω, ω, ω) is calculated for ethylene, all-trans 1,3-butadiene, all-trans 1,3,5-hexatriene, and all-trans 1,3,5,7- octatetraene. The γ(-3ω; ω, ω, ω) is evaluated using the sum-over-states method and the all-valence-electron, semi-empirical INDO-SCF-MO procedure combined with single- and double-excitation configuration interaction (CI). The treatment of electron-electron interactions at the level of only single-excitation CI calculates negative values of γ(-3ω ω, ω, ω), which are in disagreement with measured positive values. The treatment of the interactions at the level of single- and double-excitation CI correctly calculates positive values for γ(-3ω ω, ω, ω). We conclude that the treatment of electron-electron interactions at least at the level of single- and double-excitation CI is needed to properly describe the dynamic thirdorder polarizabilities of linear conjugated polyenes, and related molecules with π-electron bonding networks.
Optimization of Second Order Nonlinear Optical Susceptibilities in Organic Materials
Authors: Katz H. E. , Dirk C. W. , Schilling M. L. , Singer K. D. , Sohn J. E.
Published: March 2011

Molecular second-order nonlinear optical susceptibilities (β) based on EFISH measurements in dimethylsulfoxide of selected donor-acceptor substituted organic compounds are reported. Enhanced values were noted for compounds containing highly ionizable substituents. Compounds possessing the highest susceptibilities were dissolved in polymer films and electric-field poled, leading to corresponding enhancements in the nonlinear optical coefficients. The data are consistent with molecular and thermodynamic models.
Theoretical Design of Polymeric Materials for Nonlinear Optics
Authors: Dory M. , Bodart V. P. , Delhalle J. , André J. M. , Brédas[a] J. L.
Published: March 2011

We present results of ab initio calculations on the electric response of oligomers representative of conjugated polymers of interest. We mainly focus on : (i) polyacetylenes, polyynes, polydiacetylenes, and polycumulenes; (ii) polyaromatic systems in both undoped and doped states; and (iii) polyaromatic vinylene compounds. Our aim is to find trends among related series of conjugated polymers in order to assess their potentialities for nonlinear optics applications and to help in designing materials with optimal characteristics.
Nonlinear Optical Waveguides Containing A Transition Metal-Based Dye Molecule
Authors: Cahill Paul A.
Published: March 2011

Two pentaammine malonitrile ruthenium dyes that show sharp and intense absorption maxima near 800 nm have been synthesized for use as nonlinear optical (NLO) dyes. Preliminary powder measurements of crystals of these dyes for second harmonic generation (SHG) are reported for incident 1064 nm light. The anomalous dispersion due to the location of the one-photon absorption maximum has interesting consequences for phase matching, and calculations for inherently phase-matched single-mode waveguides are presented.
Nonlinear Optical Properties of Chloronitroanilines
Authors: Gerbi D. J. , Boyd G. T. , Ender D. A. , Leung P. C. W.
Published: March 2011

A series of chloronitroaniline compounds were investigated as bulk crystals and in thin film form as potential nonlinear optical materials for use in electro-optic devices. Crystal structure determination and computational modelling were completed on 5- chloro-2-nitroaniline and electro-optic measurements were performed on crystals grown by physical vapor deposition. Second harmonic generation measurements were carried out on poled guest/host systems of 3-chloro-4-nitroaniline in poly(methylmethacrylate).
Strong Second Harmonic Generation in Poly(Oxyethylene)/p-Nitroaniline Complexes Crystallized under Electric Field.
Authors: Watanabe T. , Yoshinaga K. , Fichou D. , Chatani Y. , Miyata S.
Published: March 2011

Molecular doping of Poly(oxyethylene) by p-nitroaniline, followed by a crystallization under electric field, yields a material which exhibit strong second harmonic generation intensity such as 91 times that of urea.

This strong activity arise from the new crystals possessing a noncentrosymmetric structure formed by the electric field crystallization.
Some Fundamental Aspects of the Thin Film Organization and Device – Structure Fabrication of Polydiacetylenes
Authors: Thakur M. , Verbeek B. , Chi G. C. , O'BRIEN K. J.
Published: March 2011

The utility of the Shear method in obtaining thin single crystal films of polydiacetylenes has been demonstrated previously. In this paper the principles of the Shear method are elucidated with analogy to the well-known L-B method. Both the methods, L-B and Shear, utilize the polar molecular interactions with the substrates as a control parameter for the molecular organization. The major difference between the two is that one (L-B) utilizes a liquid as the subphase while the other (Shear) uses solid substrates. Because of the nature of the interface the L-B approach leads to only one-dimensional organization and poor optical quality for the films while the Shear method provides 3-D organization and excellent optical quality.

Thin single crystal films of a specific polydiacetylene, PTS, are prepared on oxide coated silicon substrates by the Shear method. Waveguiding through the PTS films is demonstrated for the first time. Much progress is also made in the waveguide-structural fabrication of PTS films. The results are quite encouraging in terms of device applications of polydiacetylenes as optical switches and logic gates.
Nonlinear Organic Materials in Integrated Optics Structures
Authors: Stegeman G. I. , Zanoni R. , Seaton C. T.
Published: March 2011

Nonlinear organic materials, in conjunction with integrated optics structures, can potentially be used to perform a variety of all-optical operations on subpicosecond time scales. A number of potential devices are described and the material properties necessary to implement them are summarized. Progress in our laboratory toward these goals is detailed.
Nonlinear Optical Properties of Polyenes: Electron Correlation and Chain Conformation
Authors: Garito A. F. , Heflin J. R. , Wong K. Y. , Zamani-Khamiri O.
Published: March 2011

Using a recently developed many-electron theory of second and third order nonlinear optical susceptibilities, microscopic descriptions of γxxxx(-3ω;ω,ω,ω) are presented for two conformations of polyenes. The importance of electron correlations and the effects of variation in conformation and chain length are discussed.
Physiological Evaluation of Fluorocarbon Emulsions with Notes on F-Decalin and Pulmonary Inflation in the Rabbit
Authors: Clark Leland C. , Hoffmann Richard E. , Spokane Robert B. , Winston Pat E.
Published: March 2011

Continuing refinement of fluorocarbon blood substitutes depends upon perfection and application of methods to monitor oxygen transport in living animals. Methods involving chronic catheterization, electrode implantation and tissue sampling yield valuable basic information in animal experiments. The importance of blood lactate in assessing the adequacy of fluorocarbon oxygen transport is reported here. The preliminary observation of microbubble blockade in the pulmonary capillaries in rabbits receiving F-decalin (PP5) emulsion, resulting in lungs which remain noncollapsible for at least 79 days is also reported.
Effects of a Perfluorochenical Emulsion on Propranolol Binding by Alpha-I-Acid Glycoprotein
Authors: Fan H. F. , Parsons D. L.
Published: March 2011

The binding of propranolol by a perfluorochemical emulsion (PFCE), cXiacid glycoprotein (AGP), and their mixtures was examined by a dialysis exchange method at 37°C. A sedimentation method was used to verify propranolol binding by the PFCE. Binding of 100 and 500 ng/ml drug by 100, 75, 50 and 25% v/v concentrations of the PFCE or of 0.067% AGP was determined. Propranolol was highly bound by the PFCE with a percent free propranolol in undiluted PFCE of 13.1% at both 100 and 500 ng/ml propranolol. Propranolol was moderately bound by AGP. The percent free propranolol in 0.067% AGP was 31.4% and 32.4% for 100 and 500 ng/ml propranolol, respectively. The percent bound propranolol was not significantly different when the emulsion was diluted to 75 and 50% v/v with 0.067% AGP solution rather than buffer. When the PFCE was further diluted to 25% v/v with the 0.067% AGP solution the percent free propranolol was significantly lower than in the 25% v/v PFCE alone or 75% v/v protein solution alone. Thus, the PFCE has a relatively large affinity and capacity for propranolol. Propranolol did not partition from buffer to the PFC liquid. This indicates that propranolol bound by the PFCE is associated only with the emulsifiers.
The Effect of Varying Percentages of Fluosol-Da Hemodilution on Antipyrine Metabolism in the Rat
Authors: Shrewsbury Robert P. , Oliver Sharon R. , Anderson Wanda T. , Lewis Lee M. , White Lisa G.
Published: March 2011

Antipyrine disposition and metabolism in conscious, unrestrained Sprague-Dawley rats after 25% or 50% Fluosol hemodilution is reported. 25% hemodilution depressed antipyrine metabolism for 24 hours by primarily inhibiting cytochrome P-450. However, 50% hemodilution produced significant increases in the cytochrome P-450 activity after 48 hours. 25% hemodilution significantly reduced the antipyrine Vd at 0.5 and 72 hours. After 50% hemodilution, the Vd alternated between values greater and less than control throughout the 72hour study.
The Stability and Shelf-Life of Liposome Encapsulated Hemoglobin: A Potential Blood Substitute
Authors: Rudolph Alans , Stratton Lewis P. , Knoll Wayne K. , Bayne Sandra , Ligler Frances
Published: March 2011

For any viable blood substitute, questions of long-term storage and shelf-life must be addressed. Recently, we have made great progress in improving the stability of the blood substitute, liposome encapsulated hemoglobin (LEH). We have concentrated our efforts on protecting LEH in solution and in the long-term preservation of LEH by lyophilization. In particular, we have been able to retard and in some cases, reverse the oxidative process of metHb formation in solution by the addition of antioxidants such as NADH and glutathione. We have been able to regenerate Hb preparations with 60% metHb by the addition of 10 mM NADH and glutathione. In these preparations addition of these antioxidants results in a decrease of metHb levels from 62% to 15% over the course of 12.5 days at 4°C. We have also explored the use of protective solutes such as the disaccharide trehalose in the preservation of LEH in the freeze-dried state. Addition of increasing amounts of trehalose and other disaccharides results in the inhibition of lyophilization-induced fusion events and in the retention of hemoglobin within the unilamellar liposomal vesicles following rehydration.
Near Total Blood Exchange with Perfluorochemical Preparations
Authors: Geyer Robert P. , Taylor Kenneth , Eccles Robert , Zerbonne Therese , Gallagher Anna , Goodin Thomas , Williams Steven
Published: March 2011

Near total blood replacement in rats has been accomplished with perfluorochemical (PFC) preparations containing hydroxyethylstarch and electrolytes. F-dimethyladamantane (F-DMA) was used alone or mixed with F-N,N-dimethylcyclohexylmethylamine (F-CHA). These compounds were emulsified to yield particles approximately 150 to 250 nanometers in diameter. The nonionic surfactant, Pluronic F68, was used as the emulsifying agent. Over ninety percent of the rats survived when their hematocrits were taken to 3 volume percent or lower from a pre-perfusion value of about 44 volume percent. In spite of the reduction in total mixed venous oxygen concentration, the oxygen partial pressure rose. During the perfusion the rats breathed 100 percent oxygen, but during the subsequent period this was decreased 10 percent per day. Six to 7 days later the hematocrits had risen to 30 to 40 volume percent. Thereafter the animals continued to develop and grow.
Biocompatibility, Osteoconduction and Biodegradation of Porous Hydroxyapatite, Tricalcium Phosphate, Sintered Hydroxyapatite and Calcium Carbonate in Rabbit Bone Defects
Authors: Shors Edwin C. , White Eugene W. , Kopchok George
Published: March 2011

The biocompatibility, osteoconduction and biodegradation characteristics of calcium phosphate ceramics is controversial. Few comparative studies have controlled for material properties as well as biological influences. In this study, we compared the in-vivo response of implants made porous (500 μm pores) using the Replamineforu™ process and composed of hydroxyapatite (HA), sintered hydroxyapatite (SHA), tricalcium phosphate (TCP) or calcium carbonate (CC). In ten rabbits, rod-shaped implants (5mm d × 10m 1) of each material were randomly press-fit into two bilateral defects of either the bicortical iliac crest or unicortical proximal tibial metaphysis. Explants were harvested at 1 to 9 months, sectioned midsagitally with half embedded in plastic for qualitative histomorphometry, and the other half decalcified and stained for histology. The acute and chronic inflammatory response was minimal for all implants. The osteoconduction properties were similar for the calcium phosphate materials, resulting in repair of the cortical defects within three months with partial bony fill of the medullary canal. CC completely degraded by three months, causing incomplete defect closure in some cases. TCP partially degraded in the medullary canal, but remained when surrounded by bone in the cortex. HA and SHA did not degrade. In summary:
Factors Affecting Initial Strength Performance of a Hydroxylapatite-Calcium Sulfate Hemihydrate Composite
Authors: Devine Timothy R. , Johnson Keith A.
Published: March 2011

Hydroxylapatite (HA) has been shown to be an efficacious bio-implant material in a number of surgical procedures[l]. A problem in the use of this material is that of particle migration away from the implant site. One method to resolve this problem is to mix the HA with calcium sulfate hemihydrate, CaSO4·0.5H2O, and allow the material to set to a gypsum/HA composite monolith[2]. The gypsum is resorbed by the body over a period of weeks, leaving the hydroxylapatite surrounded by newly generated tissue.
Surface Properties, Efficacy and Biological Responses to Biomaterials
Authors: Lemons J. E.
Published: March 2011

Biological responses to synthetic materials used for the construction of surgical implants often determine device longevities. Over the past two decades, individuals from basic and applied disciplines have attempted to better understand the phenomena associated with biomaterial to tissue interfaces and to better control the surface and bulk properties of the synthetic substances for each area of device applications. Surface properties of metals, polymers, ceramics and composites are reviewed and where possible, correlated with tissue responses. Specific examples of solid and porous titanium and cobalt base alloys are presented to demonstrate the importance of surface and bulk properties with respect to biocompatibility.
Morphological Changes of Isolated Osteoclasts in Cell Culture Due to Different Biomaterials
Authors: Lambrecht J. Thomas , Ewers R. , Kerscher A. , Jentzsch R.
Published: March 2011

Osteoclasts have been isolated in primary cell culture using femoral bone of laying hens being fed on an eight day calcium free diet. Placing these cells on the surface of fixed cortico-femoral chicken bone provoked the feature of resorption pits proving that they are able to resorb bone.

After placing osteoclasts on different biomaterials (Aluminumoxide ceramics, teflon, carbon fibre reinforced polysulphone, polymethylmethacrylate, polydioxanone) scanning electron microscopy was performed. Different materials provoke different morphological features of these cells, probably due to functional variations as a response to the changing surfaces. Adhesion was feasible on all the surfaces, uptake of small surface particles was possible and cell fusion took place on most materials suggesting acceptance of the tested biomaterials by the cells.

The results show that morphological changes of isolated osteoclasts in cell culture can be detected due to different functional challenges of the surfaces of different biomaterials.
Stra Cor Membrane, a Bioplastic Skin Substitute
Authors: Widra Abe , Cohen M. N.
Published: March 2011

The historical background describing development of Stra Cor membranes is outlined. Wound healing is related to the properties desired in an ideal bridging cover. Results from clinical application of StraCor II membranes to wounds of the lower extremities are described.
An Introduction to Liposome Encapsulation of Bioactive Polyanions
Authors: Ottenbrite Raphael M. , Sunamoto Juno
Published: March 2011

Polyanionic polymers with differing molecular weight, lipophilicity, and charge density were synthesized and their ability to non-specifically “activate” macrophages was evaluated. The level of activation of test polymer-elicited macrophages was monitored by their tumoricidal capacity. In addition, the ability of test polymers to inhibit growth of Lewis lung in vivo was evaluated. We have determined that the activation of macrophages by test polymers differs from that of the conventional activating agents pyran and C. parvum.

We then found that these polycarboxylic acid copolymers could be encapsulated by liposomes and administered intravenously. Superoxide production by murine peritoneal exudate macrophages activated by the test polyanions encapsulated in liposomes was increased by 300% in the first 2 hours compared to macrophages activated by the free polymers.
Sustained Delivery of Bioactive Polypeptide by Compression in Lipid Admixture
Authors: Wang Paul Y.
Published: March 2011

Bioactive polypeptides are susceptible to inactivation by proteolytic enzymes in body fluids. Instead of many injections, these polypeptides may be specially formulated to prolong their action in vivo to several months by entrapment in a polymer mixture. In a recent fundamental study on implant for drug delivery, it was found in this laboratory that a polymer support component was not mandatory and pharmacologically active macromolecules could be readily delivered on a sustained basis. Consequently, when 10% insulin (Zn) was admixed with cholesterol and then compressed, the hormone action was extended to about 20 days when tested subcutaneously in Wistar rats with streptozotocin-induced diabetes. Evaluation of other lipids has shown that with palmitic acid as the excipient, the 8-hr action of insulin can be extended to about 40 days. The same type of sustained delivery implant containing insulin or pituitary growth hormone can enhance growth in normal Wistar rats. Since no synthetic materials were used, biocompatibility problem is not expected. Further, the fatty acid excipient is gradually eroded in vivo, and explantation of the implant will not be necessary as well. This approach shall be particularly useful in special formulations of other pharmaceutical proteins such as the rDNA-produced somatotropin analog used in growth enhancement of farm animals raised for consumer food products.
Medical-Grade Polyurethanes: Their Crucial Role in Artificial Hearts
Authors: Szycher Michael
Published: March 2011

One of the most crucial requirements since the inception of the artificial heart program has been the need to develop biomaterials specific to chronic implantation. Major problems include the propensity for thrombus formation at the blood-materials interface, long-term flexing reliability, and the tendency of the body to reject foreign objects.
Some Unique Properties of a Bilayer and Liposome Forming System
Authors: Macgregor Roderick D. , Taylor Noel , Hunt C. Anthony
Published: March 2011

The unique procedure developed for forming artificial red cells (Science 230, 1165, 1985) allows encapsulation of proteins to concentrations in excess of 20g%. The procedure requires a hypotonic starting solution, whereas the final suspension is equilibrated at 300 mOsm. Hemoglobin (Hb) was one of several proteins encapsulated. The procedure is based on emulsion formation and subsequent evaporation of the nonaqueous phase, a common liposome-formation procedure, but has unique features. The densities of the phases are matched by adding a Freon. The emulsion is formed using conditions that eliminate protein denaturation. This research was designed to evaluate the fine structure at each critical stage using thin section electron microscopy. The results revealed remarkable, previously unseen detail that raises questions about the variety of properties that can be engineered into lipid bilayer structures. The initial emulsion was nonclassical. Submicron particles in large relative numbers suggested a minimal surface tension difference between the two phases. After nearly complete evaporation of the nonaqueous phase, “microcapsule” particles were present but their architecture showed little in common with classical liposomes; there was no evidence of bilayer membranes. Following extrusion, a slow increase in the osmolality to 300 mOsm dramatically altered the architecture of the microcapsules: The encapsulated protein concentration increased, and lipid bilayer membranes were formed. The resulting “liposomes” were often chambered rather than having concentric bilayer structures. Two closely opposed bilayers surrounding a volume of protein solution was a common structure.
Concentiration Dependence of the Translational Diffusion of Monoclonal Antibodies Specifically Bound to Phospholipid Langmmuir-Blodgett Films
Authors: Wright Lois L. , Palmer Arthur G. , Thompson Nancy L.
Published: March 2011

The concentration dependence of protein diffusion in solution and in two-dimensional biological membranes is of current theoretical and experimental interest [1]. Langmuir-Blodgett films can be employed to measure protein diffusion coefficients in or on fluid phospholipid bilayers, as a function of protein concentration. Substrate-supported phospholipid monolayers and bilayers have been used extensively as models of immunological cell membranes, and are also of interest in fields other than membrane biophysics, including protein crystallography, medical technology, bioelectronics, optics, and surface science [2,3].
Alcap Delivery Devices and the Sustained Release of Difluoronethylornithine (DFNO) in Vitro and in Vivo Using Male Rats
Authors: Benghuzzi Haned A. , Bajpai Praphulla K.
Published: March 2011

Sprague-Dawley albino male rats (25) were divided into five groups consisting of five rats each. Polymer (polylactic acid) impregnated ALCAP capsules filled with 40 mg DFMO were implanted subcutaneously (SC) or intraperitoneally (IP) in Group I and II rats respectively. Rats in Group III were implanted with empty polymer impregnated ALCAP capsules (ALCAP control). Group IV rats were administered orally 3% DFMO in drinking water. Rats in Group V served as controls. Blood samples were collected every week for nine weeks via the tail artery. The concentration of DFNO in the plasma was determined. Data obtained showed that the levels of DFMO in the serum of rats in groups I, I, and IV were 64.71 ±4.08. 219.18 ± 14.48, 16.71 ± 5.21 ug ml−1, respectively at the end of nine weeks. Body weights of the controls and DFMO treated rats were not significantly different (p<0.05). The diarrhea often noted in rats treated orally with DFHO was not observed in rats implanted with ALCAP or ALCAP capsules filled with DFMO. The results of this study suggest that: (1) polymer impregnated ALCAP ceramic implants can be used to deliver DFMO in vivo in a sustained manner for long durations of time, and (2) a ceramic system can be designed to deliver DFNO and drugs such as DFMO in a sustained manner over long durations of time in humans.
Fast Curing Epoxy and Episulfide Resins for Biomedical Applications
Authors: Hadjinikolaou Ioannis N. , Bell James P. , Spangberg Larz
Published: March 2011

Epoxy resins have physical properties that make them suitable for dental and orthopaedic applications such as adhesives and cements. However, it has been observed that epoxy resins harden too slowly for clinical use when mixed with conventional curing agents, e.g. amines and polyamides. A new epoxy - diepisulfide - polyamide system has been developed which gels in 5 to 20 minutes at room temperature. The system consists of two parts: a polyamide curing agent, and a blend of the diepisulfide analog of diglycidyl ether of bisphenol A [DGEBA] dissolved in a mixture of epoxies of the DGEBA type.
Rheology of Sodium Hyaluronate Solutions and Relevance to their Use as Medical Implants
Authors: Devore Dale P. , Loftus Sandra A. , MedChem B. S.
Published: March 2011

Hyaluronic acid is a high molecular weight, linear polysaccharide composed of repeating subunits of glucuronic acid and N-acetylglucosamine. The structure is shown in figure 1. In vertebrates, the polymer is widely distributed through all connective tissue and has been implicated in cell-cell interaction, cell matrix adhesion, cell mobility and extracellular matrix organization (1,2). NaHA is an important tissue lubricant (3,4) and has been shown to exert a facilitating influence on wound repair (5).
Effect of an Electromagtnetic Field Used for Bone Gwoth Stimulation on Corrosion of 316L Stainless Steel
Authors: Edwards Brian , Posey-Dowty Jessica , Highm Paul
Published: March 2011

A recent development in fracture treatment is that of electrical stimulation to enhance healing. Since the fractured limb receiving treatment may have been inmmbilized or fixed with 316L stainless steel (SS) internal fixation devices, there is an interest in docu.menting how the electromagnetic field affects corrosion of this alloy. The stimulator under investigation produces an electrcnagnetic field having a 3.5 ± IMV pulse height delivered at 75 Hz within the treatment coils. Corrosion, as quantified by analyzing test solutions for Ni and Cr levels, was measured for specimens in and out of the stimulator field.

Three-week in vitro corrosion tests were conducted at 37°C in 0.9% NaCl adjusted to pH levels of 7.4 and 4.0. Specimen were 316L SS rods with surfaces finished to 600 grit. 0-rings were added to form crevices in order to accelerate corrosion. Stimulation was continuous for test specimens. An equal number (ten for each pH) of control specimens received no stimulation.
A statistical comparison of the data reveals that at a 95% confidence level the stimulator field did not affect corrosion of the 316L SS.
Cast Co-Cr-Mo Alloy as a Substrate for Porous Coated Prosthetic Devices
Authors: Gustavson L. , Crippen T. , Dumbleton J. H. , Bushelow M.
Published: March 2011

The application of metallic porous coatings on hip prostheses stems has increased the need for evaluating the interrelationship of implant design, material properties, and manufacturing process relative to component fatigue resistance.

In testing the PCA®(porous-coated anatomical) hip a three phase approach was followed comparing Vitallium® and Ti-6AI-4V alloys. Material and component fatigue tests were conducted, followed by in vitro stress analysis. The results of these studies are discussed.
Permeability of CardiothanerR-51 (AvcothanerR-51) and SilasticR500–1 to Lipophilic Drugs
Authors: Bruck Stephen D. , Kojima M.
Published: March 2011

Sorption processes (adsorption, absorption, permeation) are of considerable importance in the physico-chemical and biological performance of polymeric biomaterials, especially in cardiovascular applications, and in various controlled drug release and drug carrier systems [1,2]. Transport of molecules of widely ranging molecular weights through synthetic as well as biologic membranes represents a basic process in the performance of many medical devices.
Indentation Fracture Toughness Testing of and Crack Propagation Mode in Dental Composites
Authors: Ferracane Jack L.
Published: March 2011

The use of a Vicker's indenter to measure the fracture resistance of dental composite resins was correlated to fracture toughness results obtained by bending of notched bars. There is a fair correlation between the methods, but many dental composites do not form cracks by the indentation technique, thereby limiting its usefulness. SEM micrographs reveal a crack propagation mode which is mostly through the matrix and along the filler/matrix interface, with evidence of particle fracture
Preparation and Analysis of Ti and Alloyed Ti Surfaces Used in the Evaluation of Biological Response
Authors: Lausmaa J. , Ask M. , Rolander U. , Kasemo B.
Published: March 2011

The biocompatibility of Ti and Ti alloys is closely associated with the passivating surface oxide which covers these materials. In this paper results are presented from a broad surface characterization of pure Ti and Ti6A14V alloy surface oxides prepared by thermal oxidation by machining, or by electrochemical procedures (electropolishing and anodic oxidation). The chemical composition of the surface oxide on both materials is mainly TiO2, as shown by XPS, AES, and SIMS analyses. Significant differences exist for both the thermal and anodic oxides, in that the alloying elements are present in the surface oxide of the alloy. TEM and STEM studies show that the microstructure of the anodic oxide films is rather heterogeneous with areas of different porosity which can be correlated with the grain structure of the bulk metals. Oxides on the alloy are even more heterogeneous than on Ti, due to the more complex (two-phase) microstructure of the bulk metal, and also differ in crystallinity. The differences in the surface oxide properties can be expected to lead to differences in the biological response to these two materials. With the alloy, one must consider the risk of Al and/or V dissolution into the biological system.
Sorbent Chemicals in Hemodialysis and Medicine
Authors: Ash Stephen R. , Carr David J. , Blake Donald E.
Published: March 2011

From a medical standpoint, sorbent chemicals can be thought of as the converse of drugs. Drugs are chemicals which are given in concentrated form, which distribute within body tissue, and which produce (hopefully) beneficial physiological effects. In medical use, sorbents are exposed to body fluids, accumulate drugs or physiological chemicals within them, and produce (hopefully) beneficial effects. For both sorbents and drugs, the speed of the physiological benefit is usually limited by the rate of distribution of chemicals within the body tissues.
Ionic Polyurethanes: Surface and Blood-Contacting Properties
Authors: Okkema Ann Z. , Giroux Thomas A. , Grasel Timothy G. , Cooper Stuart L.
Published: March 2011

Sulfonated polyetherurethanes, synthesized by the substitution of 0, 5, 10, 15, and 20% of the urethane nitrogens with propane sultone, were evaluated in this study. The water absorption properties are dramatically affected by the sulfonate content. The surface properties are also found to be influenced by the percentage of sulfonate incorporation. The blood-contacting properties, as determined by both an acute and chronic canine ex vivo experiment, show increased thromboresistance with increased propyl sulfonate incorporation. A unique characteristic of the highly sulfonated polymers is the negligible platelet activation and spreading observed using scanning electron microscopy.
The Effect of Alkali Metal Cations on The Structure of Dissolved Silicate Oligomers
Authors: McCormick Alon V. , Bell A. T. , Radke C. J.
Published: March 2011

By means of 29Si spectroscopy, it is established that the distribution of silicate anions in alkaline silicate solutions is a moderate function of base composition. At a fixed SiO2. concentration and silicate ratio, the proportion of Si present in oligomeric and cage-like structures increases in progressing from Li to Cs hydroxide. Interactions between alkali metal cations and silicate anions are investigated using NMR spectroscopy of the cations; in this way the concentration of ion pairs is measured as a function of cation size. As a result the silicate redistribution is ascribed to cation-silicate anion pairing and to a higher selectivity for ion pairing by large silicate anions as cation size increases.
High Resolution Electron Microscopic Study of the Growth of Denser Phases on Zeolite Y and Zeolite L.
Authors: Zandbergen H. W.
Published: March 2011

High resolution electron microscopy (HREM) is a powerful tool in materials research. This is especially true in the study of zeolites because most of the questions concerning the properties of zeolites require a detailed characterization of the local structure [1]. The potential of HREM is illustrated with studies on the growth of denser phases on Zeolite Y and Zeolite L.
Characterization of Erionites with A Supported Metallic Phase by TEM, IR,AEM and Auger Methods
Authors: Acosta D. R. , Salmones J. , Navarrete J. , Juarez G.
Published: March 2011

Catalytic isomerization of paraffines of low molecular weight is a very important process in petrochemical refination and zeolites like mordenites and erionites are used frequently as supports, due to acid properties, neccesary for a dual action in hydroisomerization processes(1–3). In the present work, we analyze the behavior of erionites interchanged with Pt at low weight concentrations, using test reaction for n-pentane hydrodesintegration. At several stages of the process, small quantities of the samples were studied using TEM,AEM, IR, ESCA and Auger methods.
Structure and Epitaxy of Silver/Gold Microclusters on MgO
Authors: Marks L. D. , Hong M. C. , Zhang H. , Teo B. K.
Published: March 2011

We report observations by high resolution electron microscopy of model catalysts produced by impregnating MgO smoke particles with inorganic clusters. With the use of very low beam currents the substrates are of sufficiently low noise that we have been able to image cleanly both single atoms and very small clusters of size l-2nm in sufficient detail to determine their atomic structure. Two types of metal structures are observed: single atoms decorating atomic steps and in a few cases two-dimensional surface rafts, and a population of mainly single crystal with a few multiply twinned particles. The single crystal particles are pseudomorphically epitaxed on the MgO substrates.
Raman Spectra of Ion Intercalated Vermiculites
Authors: Jiang H. X. , Solin S. A. , Kim H. , Pinnavaia T. J.
Published: March 2011

The Raman spectra of ion intercalated Vermiculites have been studied. The torsional mode frequencies exhibit a shift to higher energy with increasing basal spacing d. Using a van der Waals type force model, and the nearest neighbor approximation, we have successfully derived the formula for the torsional mode frequency as functions of basal spacing d and other physical parameters. The calculation results are quite consistent with the experimental observations.
Structural and Dynamical Properties of Intercalated Layered Silicates
Authors: Jin W. , Mahanti S. D. , Solin S. A. , Gupta H. C.
Published: March 2011

Structural and dynamical properties of intercalated solids in general [1], and layered silicates of the type AxB1−x -Vermiculite in particular, are of both fundamental and practical interest. In these systems, two types of ions A and B with different ionic radii occupy the space between two silicate layers. On the fundamental side, one is interested in studying the average interlayer spacing as a function of (1) the concentration x of the large ion, (2) sizes and compressibilities of the intercalated ions and (3) the transverse rigidity of the silicate layers. In addition, one is interested in the dynamic properties of these solids. On the practical side, when the size difference between the two intercalants is large, one obtains pillared clays which are characterized by widely spaced silicate layers that are propped apart by sparsely distributed larger interlayer cations (sometimes referred to as pillars) [2]. The enormous free volume of accessible interior space that is derived from such an open structure has significent practical application in the field of catalysis and sieving.
Characterization of Zeolites by Gas Adsorption at Low Pressures
Authors: Venero Agustin F. , Chiou J. N.
Published: March 2011

The nitrogen and argon adsorption isotherms of three different zeolites, calcium A, ZSM-5, and sodium Y were obtained at 77.3 and 87.5 K. Using a continuous volumetric technique high resolution data was obtained in the Henry's Law region of the isotherm at relative pressures below 10−1 P/Po. The data for the two adsorbates indicates that nitrogen, due to its quadrupole moment, shows a high degree of localized adsorption, which makes it difficult to differentiate among zeolites of different pore sizes. Argon, on the other hand, can be used to identify zeolites of different pore sizes. The argon data was used in conjunction with the Horvath-Kawazoe model to obtain a pore size distribution of the zeolite.
Structural Studies of Pillared Clays and Modified Pillared Clays
Authors: Carrado Kathleen A. , Thompson Arthur R. , Winans Randall E. , Botto Robert E.
Published: March 2011

The long-range order of pillared interlayered clays (PILCs) after acid activation with 0.05N HCl has been investigated by X-ray diffraction (XRD) methods. The data show that long-range order in PILCs decreases as AlCH-PB = ZrCH-PB » Zr/AlCH-PB - Cr/AlCH-PB (PB - pillared bentonite; MCH = metal chlorohydroxy pillaring agent, where M - Al, Zr or Cr). Apparently, pure oxide clusters are more stable than mixed oxide clusters. Treatment of PILCs with dilute HCI at 25°C is less damaging than at reflux temperature, and calcined PILCs are more stable than air-dried materials. More structural damage occurs with 3M sulfuric acid treatment than with dilute HCI. Treatment with a weak base also causes some degradation of the pillars. 27AI-MAS NMR has been used to study pillared hectorite (PH), as well as other clay systems. The large increase of the observable octahedral aluminum (AI(VI)) resonance seen after pillaring is explained by loss of water from the [Al13O4 (OH) 24 (H2O)12] 7 +(Al13 ) cation. 27A1 spectra of PILCs derived from different pillaring agents and exposed to various heat and acid treatments are remarkably similar.
A New Family of Photoactive Catalysts Based Upon Bismuth Oxide
Authors: Harriman Anthony , Thomas John M. , Zhou Wuzong , Jefferson David A.
Published: March 2011

Bismuth(III) oxide, which is pale yellow, functions as an amphoteric semiconductor, although it is relatively unstable upon illumination with UV light. The energy level positioning, corrosion limits and photoactivity of samples of n-type bismuth oxide have been determined by electrochemical techniques. It was found that this material is able to oxidise water to molecular oxygen upon illumination with UV light.

Bismuth oxide forms a wide range of well-defined solid solutions with many other oxides and, in particular, niobium oxide can be used to form several distinct structures, each based upon defective fluorite. Each of these structures will function as an n-type semiconductor, retaining the basic properties of undoped bismuth oxide. However, the exact composition of the solid solution determines the band-gap energy of the semiconductor. Low concentrations of niobium in the lattice induce a substantial lowering in the band-gap energy and give rise to orange coloured materials that can collect a higher fraction of the solar spectrum. Photoelectrochemical studies showed that the presence of niobium caused the valence band to move to lower potentials but had little effect upon the energy of the conduction band. The photochemical properties of these solid solutions were studied using the photooxidation of alcohols as a test system. The results are discussed in terms of the structure of the oxide.
The Role of [M+O−] Centers (M+– Group IA Ion) in the Activation of Methane on Metal Oxides
Authors: Lunsford J. H. , Lin C.-H. , Wang J.-X. , Campbell K. D.
Published: March 2011

If the ionic radii are compatible, alkali metal ions will substitute for the divalent metal ions in magnesium oxide, calcium oxide and zinc oxide. At high temperatures in the presence of molecular oxygen, centers of the type [M+O−] are formed, where MM+– Group IA ion. The O− ions in equilibrium with these centers are effective in H” abstraction from CH4, which is the first step in the oxidative dimerization reaction. At reaction temperatures >720°C alkali metal oxides formed on the catalytic surface may themselves become active centers. Alkali metal carbonates also may inhibit the activity of the host oxide and sinter the oxide, thereby eliminating corner sites which result in complete oxidation.