bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculations on Application of Nonlinear Opganic Materials in Integrated Optics
Authors: Heinamaki A. , Homkanen S. , Tervonen A. 
Published: March 2011

ABSTRACTThe apolicability of nonlinear organic materials in integrated optics is discussed theoretically. We have studied the properties of an optically linear waveguide covered with a nonlinear organic film. Optical switching, power limiting and thresholding in optical logic are potential applications of this structure.The field distribution and propagation constant are solved exactly. The field in the nonlinear film is written in terms of Jacobian elliptic functions, and a procedure to compute them is presented. The trial functions used here turn out to be flexible and useful because – in contrary to the approaches where hyperbolic functions are used – they lead to a solution for a variety of parameters and in the case of negligible nonlinearity it coincides well with the linear case.The method is applied to a Si3 N4 waveguide with an organic overlayer. The effect of device parameters like refractive indices, thickness of the layers, incident power and strength of the nonlinearity is studied. The intensity dependence of the wavevector is determined and the lower limit cutoff powers for some structures are calculated.
Alveolar Ridge Augmentation with Composite Implants of Hydroxylapatite and Plaster for Correction of Bony Defects, Deficiencies and Related Contour Abnormalities
Authors: Terry Bill C. , Baker Ronald D. , Tucker Myron R. , Hanker Jacob S. 
Published: March 2011

AbstractMethods have been devised for preparation of composite hydroxylapatite (HA)-plaster of Paris (PP) implants for augmentation of edentulous alveolar ridges. These implants may be used to correct bony defects, deficiencies, and related contour abnormalities. The HA-PP implants are customized to exactly conform to the underlying bony architecture. They can either be preformed and sterilized for later use or made directly or indirectly at surgery. In addition to maintaining the desirable biological, chemical and mechanical properties of HA, the HA-PP implant provides complete containment of the HA particles in the desired implant shape. The PP also contributes to an enhanced bony healing response and the HA-PP implant is very biocompatible.
Ceramic - Bone Composite Implant: a New Method of Augmentation for Bone Regeneration
Authors: Habal Mutaz B. 
Published: March 2011

AbstractBony defects in the alveolar bone, maxilla, paranasal region, and the floor of the nose were corrected in 75 consecutive patients with a composite bone graft. The composite bone graft is a mixture of a slurry of corticocancellous cranial bone, hydroxyapatite (R), and Bacitracin powder, and thrombin. The paste-like composite is used to pack the defect and correct the deformity. Complete bony immobilization, done externally or internally, is necessary during the healing phase of the bone composite. The patients were longitudinally evaluated, and the healing of the bone was assessed radiographically and clinically. Two major complications occurred during the healing phase at the recipient sites: one may have been indirectly related to the donor site, and the second was related to the age of the patient and the previous surgeries contributed to the partial loss. Composite bone grafts produce better results due to faster solidification of the grafts which acts acts as a strong inductive matrix. The graft is used in the alveolar ridge and in hard tissue augmentation of the bony structures in the maxilla. The prospectus for the future is to see more composites grafting, since it combines the advantages of the materials used.
Evaluation of Charge Injection Properties of Thin Film Redox Materials for use as Neural Stimulation Electrodes
Authors: Kelliher Ellen M. , Rose Timothy L. 
Published: March 2011

AbstractThe charge injection limits of a variety of thin film redox materials considered for use as neural stimulation electrodes were evaluated under standardized conditions. Materials tested included the oxides of Ni, Ir, Rh, Ru, and Mn as well as conductive polypyrrole films. Electrodes with geometric areas of, ∼10–4 cm2were tested in bicarbonate buffered saline of pH 7.3. An electrochemically “safe” potential window was determined for each material by cyclic voltammetry. Charge injection capabilities within that window are evaluated with constant current 0.2 msec pulses. Pulse modes include anodic first and cathodic first biphasic pulses and monophasic cathodal pulses applied to electrodes held at an anodic bias. Pulsing from the anodic bias increased the charge limits for all the materials, but the most dramatic improvement was for Rh oxide. The highest charge injection values were obtained with oxides of iridium and rhodium and were of comparable value for the anodic bias mode of pulsing. Where the effect of film thickness was examined, the charge injection limit leveled off at 2–4 mC/cm2geometric as the film thickness increased.
Tissue Tolerance and Antibacterial Effectiveness of Hydroxylapatite Silver Phosphate Ceramics
Authors: Eitenmülleri J. , Hangst K. , Peters G. , Golsong W. 
Published: March 2011

AbstractThe tissue compatibility of the hydroxylapatite silver phosphate ceramics could be demonstrated in the cortex of mongrel dogs. The assessment was done by histomorphometrical methods. The toxicity depends on the content of silver phosphate and the method of manufacture.- In treatment of an experimentally induced osteomyelitis in dogs, hydroxylapatite silver phosphate containing granules had better success than an autologous spongiosa graft or hydroxylapatite granules without the agent.
Hydroxylapatite Augmentation Evaluation Using Computergraphic Analysis of Pre- and Postaugmentation Casts
Authors: Molina A. , Nelson D. , Healey K. , Minsley G. , Hanker J. 
Published: March 2011

AbstractAnalysis of pre- and postoperative casts is essential in evaluating the efficacy of hydroxylapatite implant procedures for denture support. Computergraphics have been used to quantitate the changes in anatomic contour of occlusal surfaces of teeth and in the diagnosis and treatment of patients with craniofacial malformations. They may prove to be a useful adjunct in the planning and execution of preprosthetic oral and maxillofacial surgery for ridge augmentation. Thus computergraphics may be useful in surveying pre- and postaugmentation casts and evaluating clinical outcomes. In addition, computergraphics may also be useful in evaluating the utility of various surgical techniques used to augment ridges. In this study, pre- and postsurgical maxillary and mandibular casts were made from tissue displacing, irreversible hydrocolloid impressions. A comparison of pre- and postsurgical ridge contours, surface areas and volumes were derived from computer digitized two-dimensional tracing of casts sectioned in the frontal plane. This was accomplished using a three-dimensional computergraphics program that reconstructed digitized two-dimensional images into a three-dimensional image which displayed ridge contours, surface areas and volumes. The application of computergraphic technology may also prove useful in quantitating and mapping time-dependent morphological changes in ridges supporting the prostheses. Thus this technique may be useful in monitoring resorption patterns in underlying bone as well as in the revision and compaction of implanted materials.
Composite Hydroxylapatite/Plaster Implants for Complex Endodontic Periapical Defects and Lesions
Authors: Lewis R. D. , Carnavale R. A. , Giammara B. L. , Hanker J. S. 
Published: March 2011

AbstractImplantation of a malleable composite hydroxylapatite/plaster of Paris mixture moistened with calcium hydroxide solution was performed in periapical defects which could not be treated successfully by nonsurgical procedures. A 1.5:1 mixture of sintered hydroxylapatite particles (OrthoMatrix HA-500) and plaster of Paris (USC Medical Grade Calcium Sulfate Hemihydrate B) containing 0.85% K2 SO4 is moistened with Calcium Hydroxide Topical Solution, USP and formed into a malleable mass. This is placed into the surgical defect, shaped and covered with resorbable polyester mesh. The flap is replaced and pressure applied for 5 minutes before suturing. Sutures are removed in I week and x-rays are taken immediately after surgery and at six month intervals. In all types of defects in which the material was employed, the prognosis for postsurgical tooth retention was improved and short term success was 91%. The success achieved suggests that this implantation procedure should receive wider application for complex endodontic periapical osseous defects.
Low-Density Microcellular Polymer Foams: Applications in Biomaterials
Authors: Sylwester A. , Aubert J. , Rand P. 
Published: March 2011

AbstractMicrocellular polymer foams are of interest as biomaterials for uses such as artificial skin, synthetic vascular replacements, artificial organs, and for use in permeable drug delivery systems. We wish to report the use of thermally - induced phase separation as a technology by which a variety of polymer foams can be prepared. This process permits control of foam morphology, cell size, and density. Importantly, the phase separation process results in fully open-celled foam structures. Additives such as small molecules and functionalized polymers have been incorporated into these microcellular foams resulting in polymer surfaces with controlled porosity and chemical modification. Microcellular polyurethane foams, with chemically modified surfaces, have potential application as small-diameter vascular replacements.
Current Status and Research Activity of Selected Oral Biomaterials
Authors: Brackett Susan E. , Duncanson Manville G. 
Published: March 2011

AbstractA brief review of the present consensus of the efficacy of two increasingly used oral biomaterials: castable ceramics and resin bonding agents is presented. The most challenging research problems will be discussed and current progress of the research in the areas reviewed. Some goals for future research will be suggested in light of the current research activity.
Static Mechanical Properties of Helically Constructed Polyurethane Vascular Grafts Before and after Implantation
Authors: Weygang Miranda L. , Lee J. Michael , Wilson Gregory J. , Klement Petr , Binnington Allen G. 
Published: March 2011

AbstractThe influence of mechanical properties on the acute and chronic success of vascular grafts remains the subject of considerable debate. It is widely held that the matching of some set of mechanical properties at the anastomosis between a natural vessel and a vascular graft will optimize the likelihood of clinical sucess. Investigations in this area have largely concentrated on compliance (defined as the percentage change in diameter per unit change in pressure) as the parameter to be matched across the anastomosis. However, compliance represents only one out of a set of candidate parameters (including elastic moduli, Poisson ratios, admittance, distensibility, and hydraulic impedance among others) and there is no definitive evidence that it is in any way the most important mechanical parameter to be considered. As well, the concentration on compliance has resulted in the failure to examine the importance of the longitudinal behavior of the vascular grafts. The longitudinal properties of any vessel can profoundly influence the observed circumferential behavior; however, this is, at best, only implicit in the onedimensional compliance parameter.
Surface Modification of Polymeric Materials and its Effect on Blood Compatibility
Authors: Wrobleski Debra A. , Cash David L. , Archuleta Thomas , Barthell Barry L. , Kossowsky Ram , London Jerry E. , Lehnert Bruce E. , Duchane David V. 
Published: March 2011

AbstractThe surfaces of commercially available polymeric materials have been modified through two techniques, the chemical infusion process and physical vapor deposition. The surfaces of poly(methylmethacrylate) (PMMA) have been modified through a chemical infusion process by treatment of the sample with a solution containing varying amounts of titanium(IV)isopropoxide and polyvinylpyrrolidone (PVP). The surfaces of silicone rubber samples have been coated with a thin coating of titanium dioxide with an ion beam sputtering technique. The treated samples were characterized by scanning electron microscopy, optical microscopy, and neutron activation analysis. The infused samples were evaluated for blood compatibility using two biological assays: 1) an adherence assay in which the adherence of human polymorphonuclear leukocytes to the samples was determined, and 2) a hemolysis assay using rat blood erythrocytes to determine the hemolytic activity of the samples. Based on the results of these assays, the PMMA samples treated with PVP alone resulted in an improvement in reactivity with the blood cells.
A Wear Evaluation of Artificial Joints Made of Ti Alloys in Vivo and in Vitro
Authors: Xiaozhong Zhang , Qin Ouyang 
Published: March 2011

AbstractThe results of wear tests of various Ti alloys are presented. The N+ implanted alloy, especially after solution treating and aging, shows a better wear resistance. Ti-trace element studies of prosthetic patients' hair or blood show a higher average Ti content after about 10 years of replacement over the control subjects.
Future of Artificial Organs; Therapeutic Artificial Organs
Authors: Nosé Yukihiko , Malchesky Paul S. 
Published: March 2011

SummaryAfter 40 years of research on various types of artificial organs, artificial organs once considered to be impossible have now become realities. The implantation of total cardiac prostheses is now feasible and many patients have been successfully bridged to transplant with total and partial artificial hearts. The use of the artificial kidney is now widespread all over the world. Various surgical implants such as heart valves, vascular grafts, cardiac pacemakers, and ophthalmologic implants, orthopedic implants are now used routinely. With the current trend of an increasing older population and the extension of the average life span, the need of artificial organ technologies is increasing annually. Because prostheses or artificial organ applications are quite expensive, the expenses involved for these types of application are increasing at an alarming rate annually. In the past, the only traditional medical technologies applied were primarily drugs and surgery. There are still limitations today in preventing end stage organ failure despite the remarkable studies made in surgery, drug therapy and even more recently in biochemistry and immunology. Artificial organ technologies must not only be for end stage organ failure but they can be useful in prophylaxis.The role of artificial organ technologies in therapeutics is now being recognized. The removal of pathologic macromolecules by plasmapheresis technologies such as in various types of autoimmune diseases has been proven to slow down the disease processes and in some cases stop their progression. Studies on lipoprotein removal by extracorporeal technologies show that the process of atherosclerosis may be slowed or stopped and that regression of atherosclerotic lesions may be possible.It is believed that the future of artificial organs should not only be focused on the development of replacement organs, but also on the artificial organ technologies for therapeutic or preventative medicine. By applying aggressively these type of technologies, certainly the outcome of early end stage organ failure can be prevented and the needs for artificial hearts, artificial kidneys, orthopedic implants and various implantable artificial organs reduced.
Quantitative Evaluation of Catheter Radiopacity by Fiber Optic Scanning Densitometry
Authors: Solomon D. D. , Byron M. P. , Lipton M. J. 
Published: March 2011

AbstractA rapid accurate method has been developed utilizing fiber optic scanning densitometry to quantify the radiopacity of vascular catheters. The technique provides for computerized calculation of relative catheter radiopacity and an appropriate control standard. A densitometer with a 180 degree collection angle for diffuse transmission density measurements was selected based on the diffusing nature of x-ray film (Q-factor 1.80). A benchmark catheter and 2 mil thick brass shim stock were selected as control standards for evaluation of mono- and multilumen tubing using standard x-ray conditions and an aluminum block attenuator.Results from reproducibility studies show scan-to-scan repeatability is within ±1%, and day-to-day variability is less than 5%. Application studies demonstrated a linear relationship between percent barium sulfate loading and the radiopaqueness of 16 gauge monolumen tubing. Results were also obtained from a clinical chest x-ray film showing good in vivo/in vitro correlation. The amount of radiopaque filler, design and orientation of the radiopaque region of the catheter was found to be critical in obtaining optimum catheter radiopacity.This method provides a quantitative technique which permits precise evaluation of vascular access devices as compared to the qualitative evaluation provided by methods such as ASTM F 640.
Enameling of Alumina Implant Materials with Bioglasses:Behavior of These Enamels in Simulated Biological Environments.
Authors: Muster D. , Crovisier J. L. , Hamert J. M. 
Published: March 2011

AbstractFour glasses were tested as enamel seals between osseous and mucous media on alumina implants. It was found that a perfect enamel adherence on the aluminous substrate is obtained at 1400° C. During enameling the surface of the implant is dissolved in the glass, which leads to the formation of aluminosilicate crystals in the implant/enamel interface. A rapid cooling from 200 to 1°C in water does not provoke fissuring of the enamel for the four glasses tested, which illustrates the good mechanical resistance of the implant/enamel bond. The preliminary in vitro results indicate that hydroxyapatite forms directly within the leached layer developed in plasma (except for KG.X glass).
The Analysis of Vapor-Deposited Pd Particles Supported on Thin Oxides
Authors: Poppa Helmut , Rumpf F. , Moorhead R. D. , Henry C. 
Published: March 2011

AbstractProblems of analyzing by TEM and TPD (Temperature Programmed Desorption) the structure and micromorphology of small Pd particles vapor deposited in UHV onto clean oxide supports are discussed. Particle changes induced during extended exposures to high intensity electron irradiation of a number of electron transparent support materials such as Al2O3, SiO2, TiO2, MgO, and mica are examined. Different damage mechanisms are evaluated and experimental means of reducing the damage are explored. The possibility of extracting particle morphology information from a detailed analysis of CO thermal desorption spectra is also investigated. Evidence suggests that it may be possible to obtain micromorphology information down to very small particle sizes from TPD measurements if the effects of intrinsic particle morphology can be separated from the influence of diffusion of support species.
The Chemistry of Detrital Aluminum in Zeolites Studied by Multinuclear NMR Spectroscopy and Other Techniques
Authors: Jarman Richard H. 
Published: March 2011

AbstractHigh resolution 27Al NMR spectroscopy has been used to study the dealumination of the A-type zeolite ZK4. The aluminum removed from the lattice during calcination undergoes reversible changes in coordination when treated in acidic and basic media. 2 5 Si NMR spectroscopy reveals that the changes are confined to the detrital aluminum species and do not affect the zeolite framework. Thermogravimetric analysis data combined with compositional data available from 29Si NMR spectra have been used to probe the state of charge of the detrital aluminum species and the nature of defects present in the lattice.
Electron Microscopy Study of Morphology and Composition of a Ferrisilicate Catalyst
Authors: Csencsits Roseann , Gronsky Ronald , Nair Vinayan , Szostak Rosemarie 
Published: March 2011

AbstractThe effects of various synthesis conditions on the structure and composition of ferrisilicate analogs of zeolite ZSM-5 were considered. Scanning electron microscopy (SEM) was used to determine the particles size distributions and morphologies. Particle sizes vary from tenths of a micron to several microns, depending on degree of agitation during crystal growth, while morphology is additionally dependent on the concentration of iron in the gel during crystallization.X-ray emissive spectroscopy (XES) performed in the transmission electron microscope (TEM) was used to determine their composition variation. The distribution of iron amongst the crystals is more homogeneous if the gel is stirred and it does not depend on particle size.
Structural Transformations in Platinum Supported on y-Alumina Studied by X-Ray Absorption Spectroscopy
Authors: Robota H. J. , Cohn M. J. , Ringwelski A. Z. , Eades R. A. 
Published: March 2011

AbstractPt particles in a highly dispersed Pt/γ-A12O3 catalyst have been found to undergo ordering following the removal of chemisorbed oxygen with hydrogen at room temperature. The very small Pt particles are found to be disordered following an initial reduction at 500°C. Treating the ordered phase of Pt at 500°C in hydrogen is found to restore the disordered phase.
Structure of Supported Metal Catalysts Derived from Molecular Bimetallic Clusters
Authors: Kelley M. J. , Fung A. S. , McDevitt M. R. , Tooley P. A. , Gates B. C. 
Published: March 2011

AbstractRe-containing molecular bimetallic clusters were used as precursors for gamma alumina supported catalysts. Characterization by XPS and XAS after hydrogen reduction showed Re valence states in the order Re monometallic > Re-Os bimetallic > Re-Pt bimetallic > zero. These results suggest that industrial bimetallic catalysts are not best understood in terms of alloys, but rather as multifunctional, with each element contributing its own activity.
Computer Simulations of Diffusion, Adsorption and Reaction of Organic Molecules in Pillared Clays
Authors: Sahimi Muhammad , Tsotsis Theodore T. , Occelli Mario L. 
Published: March 2011

AbstractDiffusion and reaction of large organic molecules in pillared clays, a new class of catalysts capable of converting gas oil into transportation fluids, is investigated. We first discuss some recent experimental data and point out the possible difficulties for obtaining accurate data. We, then, discuss a new model for describing diffusion and reaction of large organic molecules in pillared clays. The model employs stochastic and random walk concepts to model the diffusion process, and a dynamic Monte Carlo method for predicting various properties of interest, such as the effective diffusivity of the molecules.