bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonlinear Optical Polymers for Electrooptical Devices
Authors: DeMartino R. , Haas D. , Khanarian G. , Leslie T. , Man H. T. , Riggs J. , Sansone M. , Stamatoff J. , Teng C. , Yoon H. 
Published: March 2011

ABSTRACTAlthough organic crystals may be used to experimentally verify the large nonlinearities and short response times of organics, such crystals are not acceptable for device applications due to significant fabrication difficulties. Further, the bulk material nonlinearity is a function of molecular orientation and symmetry which may not be controlled during the crystallization process.Nonlinear optical polymers have been synthesized at Hoechst Celanese for which the active NLO unit is attached to the polymer backbone as a pendant side chain. Control of orientation and symmetry of the unit is achieved by poling in an external electric field at elevated temperatures resulting in second order susceptibilities larger than inorganic crystals. The polymers have attractive secondary properties (i.e., optical transparency, high glass transition temperatures which are controlled by adjusting the side chain length and nature of the polymer backbone, low dielectric constants, and flat frequency respose). Further, single mode waveguides may be fabricated by spin coating. Deposition of electrodes on the waveguide permits application of an external field which changes the material's index of refraction due to the linear electrooptical effect. Thus, a host of electrooptical waveguide devices may be constructed which operate at low voltages and very high frequencies.
Effect of a Moderate Blood Exchange with Fluosol-Da 20% on the Disposition of Digoxin in the Dog
Authors: Hoke John F. , Ravis William R. 
Published: March 2011

AbstractThe effect of a perfluorochemical blood substitute (Fluosol-DA 20%) on the disposition kinetics of digoxin in the dog was studied. An intravenous dose of digoxin was administered at either 0.25 or 24 hours following a 30% blood exchange with the dog's own blood (SHAM group) or Fluosol-DA (treatment group). A significant change in the initial volume of distribution and mean residence time in the serum was noted when digoxin was administered 0.25 hours after the Fluosol-DA blood exchange. This volume of distribution change was not observed when digoxin was administered 24 hours after the Fluosol-DA blood exchange. No change in the t1/2, total body clearance, or volume of distribution at steady-state was observed in any of the treatments. No change in the partitioning of digoxin in the blood was noted following Fluosol-DA administration.
A Perspective on the FDA Premarket Approval Process
Authors: Ely John L. 
Published: March 2011

AbstractPremarket review processes as prescribed by the Medical Device Amendments of 1976 to the Food, Drug, and Cosmetic Act greatly affect the use of materials in medical products, especially for implantable devices. The premarket approval process can have a particularly important role in eventual commercial medical uses of materials. Managing the process properly is often critical to the success or failure of a product.A review of the law and regulations as they pertain to premarket approval is presented. Subjects included in this overview are prediction of process time and costs, examination of potential pitfalls in the process, recommendations on organizing for successful completion of the process and handling the relationship with FDA.Specific materials related issues that are likely to arise are noted.
Development of a Resorbable Tricalcium Phosphate (TCP) Amine Antibiotic Composite
Authors: Morris Lisa M. , Bajpai Praphyilla K. 
Published: March 2011

AbstractCalcium phosphate collagen composites are currently being used to rebuild bone. Commercial collagen preparations have been claimed to he hvpo-antigenic but none are non-antigenic. The collagen in calcium phosphate collagen composites is eventually degraded to its component amino acids. Two thirds of collagen consists of glvcine, hvdroxvproline, and proline. Since both tricalcium phosphate (TCP) and collagen are resorbable and both can he utilized to form bone, incorporation of amino acids into TCP-amino acid composites should nrovide the building blocks for formation of new bone. Stich composites should also be non-antigenic. Previous work conducted with composites of amino acids with aluminum calcium phosphorous oxide (ALCAP) ceramics, has shown that these composites can be uised to repair traumatized bone in rats. In our study, experiments conducted with TCP cysteine, Ivsine, or proline composites showed that the composites, after setting to hardness, degrade slowly and can he molded into different froms. Dissolution studies were conducted with composites of TCP with each of the above amino acids in Tris-MCl buffer (PH 7.4) at 37°C in vitro. Experiments conducted with antibiotics showed that antibiotics such as penicillin and ervthromvcin can be incorporated into the TCP amino acid composite. Subcutaneous implants of TCP amino acid composites in rats showed that most of the TCP-proline composite was degraded bv day 4, TCP-lvsine composite he day 7, and TCP-cysteine composite by day 21. Our results suggest that TCP amino acid composites are biocomnatible and can he used to repair experimentally traumatized bone.
Demonstration of the Bacterial-Biomaterial Interface in Implant Specimens
Authors: Dobbins J. J. , Giammara B. L. , Hanker J. S. , Yates P. E. , DeVries W. C. 
Published: March 2011

AbstractBacterial infection can be a problem associated with biomaterial implants especially with the total artificial heart or other cardiovascular prostheses such as ventricular assist devices, intravenous catheters, ventriculo-atrial shunts, pacemaker electrodes and, rarely, prosthetic heart valves. Bacterial commensals such as Staphylococcus epidermidis, which is ordinarily non-infective in human skin and mucous membranes, is now recognized as an opportunistic pathogen of biomaterial implants, particularly cardiovascular prostheses. In these implantations the S. epidermidis undergoes transformation to produce mucoid or polysaccharide extracellular coating substances. The latter promote bacterial adherence to biomaterial surfaces and protect the bacteria to some extent against antibiotics and host defense mechanisms. The result is increased virulence of the slime-producing strains. A number of techniques have been developed in our laboratories which facilitate identification of such bacterial pathogens on biopsy or postmortem specimens. These light and analytical electron microscopic methodologies include special cytochemical staining and rapid drying and embedding methods. Their efficacy and accuracy have been verified by studies on cultured and subcultured pathogens which are more time consuming. It is of interest that the microscopic methods showed the presence of macrophages as well as neutrophils on the specimens.
Analytical and Structural Electron Microscopy of Metal-Cell Interactions.
Authors: Coombs Neil A. , Pilliar Robert M. , Weatherly George C. 
Published: March 2011

AbstractHuman gingival fibroblasts have been grown in culture on thin (10–50nm) substrates of nickel, chromium and titanium and examined by structural and analytical transmission electron microscopy. Cells grown on titanium show no signs of metal uptake and have morphologies very similar to controls grown on carbon substrates. However, cells grown on nickel and chromium show significant metal uptake and some structural abnormalities. The majority of the ingested nickel and chromium appears to be associated with nucleic acids.
Low Voltage Sen for Unique Surface Analysis of Prosthetic Devices
Authors: Goldberg Eugene P. , Yalon Moshe , Longo William E. 
Published: March 2011

AbstractSurgical manipulation of plastic prostheses using metal instruments is likely to produce surface damage and surface roughness which may compromise biocompatibility of implants due to tissue irritation and increased cellular or bacterial adhesion. There are virtually no data in the literature concerning the clinical occurrence and consequences of manipulative surface damage to implants. We have found that conventional high voltage scanning electron microscopy techniques (HVSEM) obscure surface defects on plastics due in large measure to beam energy “healing” by local melting. This paper reports the use of low voltage SEM (LVSEN) at low beam voltages (<1.5keV) and without the need for conductive carbon or Au/Pd coatings for examination of plastic device surfaces before and after normal surgical manipulation. Results for intraocular lens implants, a major human prosthesis, clearly demonstrate that standard surgical procedures can produce significant implant surface damage which may not be observed by normal SEN analysis. LVSEN has been shown to readily visualize such previously unobserved surface defects in model surgical manipulation experiments. These results have important implications for more reliable polymer surface characterization and for development of improved prosthetic devices, instruments, and implant surgery.
Cryopreserved Dermis is an Ideal Substrate for the Engraftment and Maturation of Human Epidermal Keratinocyte Cultures
Authors: Langdon Robert C. , Cuono Charles B. , Birchall Nicholas , Moellmann Gisela E. , Madri Joseph A. , McGuire Joseph 
Published: March 2011

AbstractThe ideal replacement for skin damaged by full-thickness injury is the split-thickness autograft. In extensive burns, use of autograft is limited by the availability of uninjured donor skin. This limitation can be overcome by grafting viable cryopreserved cadaveric skin following escharectomy. To preclude immunologic rejection of the allograft, the epidermis is later removed by abrasion and replaced with autologous keratinocyte cultures. The cultures rapidly stratify and within 7 days form a differentiated epidermis of normal thickness. Over several weeks the basement membrane zone reconstitutes normally by several criteria including the presence of a lamina densa and of anchoring fibrils and immunohistochemical demonstration of type IV collagen and laminin. Melanocytes, which are present in small numbers in the keratinocyte cultures. assume their normal position and function in the epidermis of the composite graft. Langerhans cells migrate into the autologous cultured keratinocyte graft.Autologous keratinocytes can be greatly expanded in cell culture and used as grafts to resurface large areas. The functional quality of such grafts however is dependent on the ability of the dermal substrate to support the permanent engraftment of keratinocyte cultures through reconstitution of a normal basement membrane zone.
Collagenous Materials Enhance Healing of Chronic Skin Ulcers
Authors: Silver Frederick H. , Doillon Charles J. , Rojo Blas , Olson Robert M. , Kamath Chandrakala Y. , Berg Richard A. 
Published: March 2011

AbstractType I collagen in a porous sponge form attracts fibroblasts in culture and accelerates repair of animal wounds. This study examines the effect of type I collagen sponge and flakes on healing of chronic skin ulcers. Patients included in this study had skin ulcers.Patients included in this study had skin ulcers characterized by loss of dermis and epidermis without exposure of muscle, tendon or bone. Patients showing evidence of systemic infection or patients with ulcers that decreased in area during an initial three week observation period were excluded.Three out of seven patients treated with a collagen sponge and twelve out of fourteen patients treated with collagen flakes showed a 40% decrease in wound area after six weeks of treatment. In comparison, eighteen control patients showed no change in wound area over the same time interval. These results suggest that collagen flakes are effective in initiating healing of chronic skin ulcers.
Polymers as Ophthalmic Lubricating Agents
Authors: Kalachandra S. , Shah D. O. 
Published: March 2011

AbstractPhysio-chemical properties such as coefficients of friction between low energy surfaces (PMMA/PMMA), surface tension, contact angle and viscosity of various water soluble polymer solutions ( 3–62cp) were measured at ambient temperature. The results showed that the surface tension and the contact angle are independent of viscosity of each polymer. The analysis of the data revealed that the system is operating in a region of “Boundary Lubrication”. It is seen, beyond 30 cp viscosity of almost all polymer solutions, the coefficient friction has been found to be independent of viscosity.Polyvinyl alcohol appears to have better lubricity in the vicinity of 30 cp viscosity or lower values than the cellulose derivatives and dextran. Hydrophobic interaction between PMMA surface and vinyl backbone may be responsible for this observation.It appears that the coefficient of friction of these polymer solutions depends on the structure, conformation and adsorption characteristics of polymers as well as surface characteristics of sliding surfaces, load, speed and viscosity.
The Elastic Properties of Osteoporotic and Osteopetrotic Bone
Authors: Katz J. Lawrence , Yoon H. S. , Meunier A. , Christel P. 
Published: March 2011

AbstractWe have been involved in using several ultrasonic wave propagation techniques to study the relationship between the structure and the elastic properties of bone, both normal and pathological. Pulse through ultrasonic techniques have been used to measure the ultrasonic velocities in human, normal, osteoporotic and osteopetrotic femoral bones in vitro at 5 MHz and room temperature. An ultrasonic right-angle reflector technique has also been used on the same specimens at room temperature and 15 MHz (the third harmonic of a 5 MHz immersion type transducer). In addition, microhardness measurements have been made on the same bones from which the specimens for ultrasonic measurements were obtained.
The Influence of Biomechanical Factors at the Tissue-Biomaterial Interface
Authors: Brunski John B. , Hipp J. A. , Cochran G. V. B. 
Published: March 2011

AbstractWhen an implant is placed into bone, an interface is created. This interface has a critical biomechanical function: it must support the implant in bone. However, failure of implant fixation (i.e., implant “loosening”), continues to be a leading cause of implant failure [1,2]. While there are a number of factors involved in this problem, it is recognized that biomechanical factors play a role, and this paper reviews the more important factors, including relative motion and interfacial stresses and strains. Also, it presents results from a recent in vivo experiment on controlled loading of an interface.
Ion Beam Deposition of Calcium Hydroxyapatite
Authors: Barthell B. L. , Archuleta T. A. , Kossowsky Ram 
Published: March 2011

AbstractCalcium hydroxyapatite has been sputtered on glass and Ti-6Al-4V substrates using a 1.5-kV argon ion beam. The films have been examined by x-ray diffraction analysis, energy dispersive spectroscopy, scanning electron microscopy, and adhesion testing. Results of this experimentation are presented.
Glycocalyx Enhances Prosthetic Vascular Graft Infection
Authors: Evers B. Mark , Giammara Beverly L. , Jubenville Denise , Malangoni Mark A. 
Published: March 2011

AbstractCoagulase-negative staphylococci are major pathogens in prosthetic implant infections, and the capability of certain strains to produce glycocalyx enhances their infectivity. We investigated the importance of glycocalyx in an animal model of prosthetic vascular graft infection. Coagulasenegative staphylococci (5×108) and 1 cm2pieces of Dacron or polytetrafluoroethylene (PTFE) grafts were placed in subcutaneous pockets of adult Sprague-Dawley rats. Two strains of bacteria were used, one producing and the other not producing glycocalyx. At 5 days, uninfected grafts were incorporated into the surrounding tissues whereas infected grafts were surrounded by fluid. Grafts were excised and adherent bacteria dislodged by sonication and quantitated. Scanning electron microscopy confirmed the presence of bacteria and glycocalyx, and the efficiency of bacterial dislodgement by sonication. The bacterial adherence (CFU/cm2mean ± SE) of glycocalyx-producing staphylococci was 3.7±1.1×107and 3.5±1.0×105to Dacron and PTFE, respectively (both < 0.05). Nonglycocalyx producing bacteria had decreased adherence to both Dacron (1.4±0.8×104) and PTFE (0.9±0.4±104). Antibiotic administration reduced the adherence of the nonglycocalyx producing strain by one log to both materials (p<0.05) but did not affect the glycocalyx-producing strain. These data demonstrate that glycocalyx production enhances the adherence of coagulase-negative staphylococci to prosthetic vascular graft materials. Prophylactic antibiotic administration does little to inhibit the adherence of glycocalyxproducing bacteria but does affect nonglycocalyx producing strains.
A Study of the Mass Transport Resistance of Glucose Across Rat Capsular Membranes
Authors: Freeman C. L. , Mayhan K. G. , Picha G. J. , Colton C. K. 
Published: March 2011

The interaction between a polymer or other foreign surface and soft tissue is determined by a variety of materials and tissue factors. After failing to engulf the foreign body, the classical response is to wall it off. First the site is invaded by macrophages and giant cells and then fibrous connective tissue is laid down. This fibrous connective tissue gradually replaces the cellular matrix and forms the capsule. The composition is mostly collagen and mucopolysaccharides with few cells in the mature capsule. It contains 75–80% water.When the implant surface represents a sensor and the transport of low molecular weight species across the capsule is necessary for meaningful measurement and response time, the mass transport resistance of the capsule may become a critical factor. This study represents an initial attempt to characterize the diffusion of glucose through fibrous capsules grown around silicone elastomer implants in a rat. Specifically, the study was designed to develop techniques to measure mass transport properties of tissue capsules, to use these techniques to determine effective glucose transport properties at two weeks, four weeks, and ten weeks after implant; and, to use these results along with histological examinations to gain an understanding of the factors which influence mass transport.
On the Propagation of Twin-Fault-Induced Stress in Platelet Fau-Framework Zeolites
Authors: Treacy M. M. J. , Newsam J. M. , Vaughan D. E. W. , Beyerlein R. A. , Rice S. B. , De Gruyter C. B. 
Published: March 2011

AbstractA model describing the propagation of a rhombohedral distortion in platelet CSZ–1 zeolites is presented. It is proposed that internal stress gradients grown into CSZ–1 platelets at synthesis are responsible for this distortion of the cubic FAU framework, where the spacings of 111 planes parallel to the platelet surfaces are elongated relative to the {111} planes. The presence of inhomogeneities is suggested by the presence of thin bands of twin faults which are invariably observed near the central layers of each platelet. Elastic modelling confirms that the effects of any stress associated with such twin faults will be most pronounced in the thinnest platelets, where the effects of elastic relaxation are minimal, and where the width of the fault zone relative to the platelet thickness is maximal. Platelet CSZ–3 and Y-type zeolites, which are considerably thicker, are therefore not expected to show significant rhombohedral distortion despite the presence of similar twin fault bands.
Composition Variation Between Cu-Ni Crystallites using TEM and EDS
Authors: Sinha Pankaj K. , Cale Timothy S. 
Published: March 2011

AbstractThe distribution of nickel and copper between crystallites supported on high surface area silica (Cabosil HS5) has been studied using a Philips 400 series transmission electron microscope equipped with super twin lenses, a field emission gun and EDAX energy dispersive X-ray spectroscope. The same Ni-Cu catalysts have previously been characterized and used in cyclopropane hydrogenolysis kinetics. The good intercrystallite homogeneity found in a well reduced sample having 31% nominal copper validates a critical assumption made in these previous studies. Limited data on unreduced and partially reduced samples also highlight the need to carefully control the degree of reduction in kinetic and characterization studies.
Three-State Lattice-Gas Model of H-S on Pt(111)
Authors: Rikvold Per Arne , Collins Joseph B. , Hansen G. D. , Gunton J. D. , Gawlinski E. T. 
Published: March 2011

AbstractWe consider a three-state lattice-gas with nearest-neighbor interactions on a triangular lattice as a model for multicomponent chemi- and physisorption. By varying the lateral interaction constants between the adsorbate particles, this model can be made to exhibit either enhanced adsorption or poisoning (inhibited adsorption). We discuss here the conditions on the interaction constants that lead to poisoning. We present the results of a ground-state calculation and detailed numerical study of the phase diagram for a set of interactions that exhibits poisoning. We calculate the phase diagrams and adsorption isotherms by the finite-size scaling transfer-matrix method. We consider the result as a simple model for the coadsorption of Sulphur and Hydrogen on a Platinum (111) surface, with interaction constants estimated from experimental data. The resulting adsorption isotherms are in good agreement with experimental results.
Characterization by XRD High Resolution Electron Microscopy of Hydrodesulfuration Catalysts
Authors: Cruz J. , Avalos-Borja M. , Fuentes S. , Diaz G. 
Published: March 2011

AbstractRecently a lot of work has attempted to correlate the activity of Co and Mo sulfide catalysts with observations of high resolution electron microscopy. Hydrodesulfuration (HDS) bulk sulfide catalysts are specially suited for this type of study. We prepared unsupported molybdenum sulfide by three methods: the homogeneous sulfide precipitation (HSP) (1), co-maceration (CM) (2), and impregnated thiosalt decomposition (ITD) (3). Pure cobalt sulfide was prepared only by HSP, and two Co-Mo sulfides in the ratios of 0.3 and 0.5 at. % were prepared by HSP and ITD. The samples were treated with a mixture of 20% H2S/H2 for 4 hrs. at 400 C. In all Co/Co+Mo mixtures the presence of Co9S8 and MoS2 was identified in both, ESP and ITD treatments. Characterization was done by high resolutibn electron microscopy. The ITD method can be considered a better method, as opposed to ESP for the preparation of mixed catalysts. This method produces poorly crystalline specimens that are usually associated to higher chemical activity.
Characterization of HDS and Syngas Catalysts Derived from Heterobimetallic Clusters
Authors: Curtis M. D. , Schwank J. , Penner-Hahn J. , Thompson L. , Baralt O. , Waldo G. 
Published: March 2011

AbstractDiscrete, organometallic clusters containing S, Mo, and Fe or Co have been deposited intact on metal oxide supports. These supported clusters are subjected to temperature programmed decomposition (TPDE) which causes loss of the organic ligands and produces catalysts active for CO hydrogenation and thiophene hydrodesulfurization (HDS). In-situ Mossbauer spectra reveal that the surface is remarkably uniform and that high spin ferrous iron is the predominate species (ca. 90%) under catalytic reaction conditions. EXAFS and XANES spectra show that the clusters are irreversibly oxidized by the surface at ca. 400 K under H2.