bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Evaluation of Simox Material and Integrated Devices
Authors: Cristoloveanu Sorin
Published: March 2011

Adequate techniques for the electrical characterization of SOI structures are reviewed and applied to reveal a coherent image of SIMOX material. Sheet resistance, low temperature Hall effect and photoconductivity measurements are analysed with respect to the processing conditions. Depth profiles are identified by spreading resistance, MOS-Hall devices and differential ellipsometry. After annealing at high temperature the activation of thermal donors, not new donors, is attenuated. The properties of front and buried interfaces are compared with each other and referred to implantation and annealing conditions. The measurements of the dynamic transconductance, charge pumping current and noise in MOSFET's are shown to provide easier and more relevant evaluation than conventional MOS capacitance techniques. The minority carrier generation is studied by separating the contributions of the volume, interfaces and sidewalk. Not only is the performance of transistors fabricated on SIMOX excellent, but additional gain is possible using the new concept of volume inversion.
A High Performance Submicrometer CMOS/SOI Technology Using Ultrathin Silicon Films on Simox
Authors: Vasudev P.K. , Terrill K.W. , Seymour S.
Published: March 2011

The use of ultrathin SIMOX wafers for fabricating submicrometer CMOS integrated circuits is described. It is demonstrated from ring oscillator speeds that properly designed devices can exhibit very high transconductance and performance superior to circuits using bulk Si.
The Structure of Silicon Thin Films Grown on Sapphire by MBE
Authors: Twigg M. E. , Pellegrino J. G. , Richmond E. D.
Published: March 2011

From a series of imaging experiments performed in the transmission electron microscope (TEM), it is apparent that for silicon grown on sapphire (SOS) by molecular beam epitaxy (MBE), silicon thin film growth on the (1012) sapphire plane resembles that observed for analogous films grown by chemical vapor deposition (CVD). At 900°C very thin (150A) silicon films grow as islands with either the (001) or (110) planes parallel to the (1012) plane; it is also found that most of the silicon grows as (001) rather than (110) islands, as is true for CVD-grown SOS. The orientation, however, of (110) islands occuring in this MBE-grown SOS sample differs from that of (110) islands occuring in CVD-grown SOS. By following this initial 150A of growth with 2500A of silicon deposited at. 750°C, a continuous (001) film was grown in which microtwins appear to be the predominant defect. The MBE-grown SOS also resembles that grown by CVD in that the microtwin densities associated with the “majority” and “minority” twinning systems are influenced by the orientation of the sapphire substrate.
Low Dislocation Soi by Oxygen Implantation
Authors: Van Ommen A.H.
Published: March 2011

Recent results on silicon on insulator structures formed by implantation of oxygen and subsequent high temperature annealing will be discussed. The resulting silicon on insulator structure has sharp interfaces and a dislocation density of less than 105 cm -2 in the top silicon film. This density of defects is several orders of magnitude lower than previously reported values. The relation between the microstructure after implantation and this relatively low defect density will be discussed. Silicon point defects will be shown to play an important role in the establishment of the microstructure during implantation. Relations between implantation conditions, point defect concentrations and microstructure will be discussed to come to the formulation of the boundary conditions for the formation of high quality silicon on insulator material by this method.
Microstructural Characterization of Porous Silicon SOI Structures
Authors: L'ecuyer J.D. , Loretto M.H. , Farr J.P.G. , Keen J.M. , Castledine J.G. , L'esperance G.
Published: March 2011

SOI structures up to 60nm wide have been produced using oxidized porous silicon formed by selective n/n+ anodizing. The microstructures of the islands were investigated using TEM in both the planar and cross-section geometries. Typical island thickness is about 0.15nm and the buried oxidized porous silicon about 0.65μm. Retention of the island geometry is excellent. Few defects (essentially dislocations) are associated with either the anodizing or oxidation treatments. The interface sharpness between the epitaxial silicon/oxidized porous silicon is 10-20nm, an order of magnitude sharper than the back interface between the oxidized porous silicon and the substrate.
Synthesis of Buried Layers of β Sic in Single Crystal Silicon
Authors: Reeson Karen J , Hemment Peter L F , Stoemenos John , Davis John R , Celler George K
Published: March 2011

It is demonstrated that buried layers of β SiC can be fabricated within single crystal silicon substrates by implanting high doses of energetic carbon ions. If the implantation temperature is sufficiently high >625°C then the β SiC grows epitaxially within the silicon, during implantation, using the substrate as a seed. During the subsequent high temperature anneal redistribution of the implanted species occurs to give a well defined buried layer of β SiC overlain by single crystal silicon.
Buried Silicon-Nitride by High Temperature Nitrogen Implantation
Authors: Bussmann U. , Meerbach F.H.J. , Kaat E.H. Te
Published: March 2011

Buried silicon nitride layers are formed by high temperature (600-800°C), high dose (0.3-1 x 1018 Ncm -2) nitrogen implantation into silicon. The nitride structure of as-implanted and annealed (6 h at 1200°C) samples is revealed by TEM-analysis. At implantation temperatures up to 600°C an amorphous SixN" layer is formed. At higher temperatures crystalline precipitates are found within an amorphous environment. They are identified as β-Si3N4 by electron diffraction. By subsequent annealing the previously amorphous material crystallizes to a-Si3N4, while the β-grains seem to be stable.
High Dose Carbon Ion Implantation Studies in Silicon
Authors: Srikanth K. , Chu M. , Ashok S. , Nguyen N. , Vedam K.
Published: March 2011

The electrical properties of crystalline Si (c-Si) subjected to high-dose (1E17 cm-2) implantation of C with varying post- anneal conditions have been investigated. The electrical barrier formation and carrier transport across the implanted layer have been studied using metal-implanted layer-Si structures. In the as-implanted samples, a Schottky diode-like behaviour is seen but with a very high diode ideality factor. The well-known influence of ion damage on the Si surface barrier is clearly evident, but in addition we see the domination of transport by a Si-C buried layer formed after annealing . Spectroscopic ellipsometry measurements and FTIR spectroscopy confirm the formation of buried Si-C.
Dislocation Reduction on Simox Substrates by Using Multiple Implants
Authors: Cheek Tom F. , Chen Daniel
Published: March 2011

A technique for dislocation density reduction in SIMOX (Separation by IMplantation of OXygen) substrates by using multiple implant and anneal cycles is described. This scheme produces SIMOX material with dislocation defect densities less than 1 x 105/cm2. This dislocation density value is three to four orders of magnitude lower than that of comparable single implant slices having the same total dose and anneal conditions.
Processing Simox Wafer Below the Critical Temperature
Authors: Sioshansi Piran , Namavar Fereydoon
Published: March 2011

The creation of SIMOX material by multiple step substoichiometry oxygen ion implantation of silicon wafers followed by high temperature annealing has already been demonstrated by different groups [1-4] This paper reports on the formation of SIMOX wafers at temperatures well below the critical temperature (500-550°C) specified for oxygen implantation of the SIMOX process. A multiple step procedure has been devised, each step consisting of oxygen ion implantation at doses of 2.5 and 3 x 1017 O+/cm2 followed by solid phase epitaxy at a temperature of 950°C for two hours. Non-destructive optical analysis and XTEM investigation of the wafers indicates the formation of a continuous buried oxide with good quality single crystal silicon on the surface after accumulated dose of 1.1x1018 O+/cm2 following high temperature annealing at 1300°C for six hours.

The processing of SIMOX material at a lower temperature will enable the utilization of a wide variety of ion implanters, will simplify the design of the end station of the new generation high current ion implanters, and will have an impact on the availability and economics of SIMOX wafers.
Formation of Buried Oxide in Mev Oxygen Implanted Silicon
Authors: Nieh C.W. , Xiong F. , Ahn C. C. , Zhou Z. , Jamieson D. N. , Vreeland T. , Fultz B. , Tombrello T. A.
Published: March 2011

We have studied the formation of buried oxide in MeV oxygen implanted Si. A continuous oxide layer is formed in the samples implanted with 2x1018/cm2 oxygen and annealed at 1300° C. The microstructures are studied by cross-sectional transmission electron microscopy and high resolution electron microscopy. Chemical information was obtained by electron energy loss spectroscopy. The effects of implantation temperature are studied. Implantation at a low substrate temperature leads to a well-defined buried SiO2 layer, inhibits the formation of oxide precipitates in the silicon, and reduces silicon inclusions in the SiO2.
Precipitate and Defect Formation in Oxygen Implanted Silicon-on-Insulator Material
Authors: Krause S.J. , Jung C.O. , Ravi T.S. , Wilson S.R. , Burke D.E.
Published: March 2011

The formation and structure of defects and precipitates in high-dose oxygen implanted silicon-on-insulator material was directly studied by weak beam and high resolution electron microscopy. In as-implanted material, the edge of the oxygen implant profile contained 1.5 nm diameter precipitates at a density of 1019 cm2. Defects, including micrctwins, stacking faults, and (311) defects, were present in as-implanted material but no threading or loop dislocations were observed. This suggests that threading dislocations are formed in the thermal ramping and annealing cycle. In material annealed for different times and temperatures precipitate size was much more dependent on peak temperature rather than time-at-temperature indicating that oxygen diffusion distance is less important than thermodynamic factors in controlling precipitate size. Annealing from 1150°C to 1250°C produced threading dislocations and possible dislocation dipoles which extended through the superficial layer. Transient annealing of very low dose oxygen implanted Si produced loop and threading dislocations. This suggests that a high heating rate during precipitation will generate excess Si interstitials at a rate high enough to create high stresses at precipitates and form dislocations. A qualitative model for dislocation formation is proposed and processing conditions for reducing dislocation density are suggested.
AB Initio Calculation of the Polarizability and Hyperpolarizabilrties of Infinite Periodic Polymers by the Sum-Overstates approach
Authors: Barbier Christian , Delhalle Joseph , Andre Jean-Marie
Published: March 2011

We investigate the applicability of the Genkin-Mednis perturbative approach to the ab initio calculation of the static (hyper)polarizabilities of infinite periodic polymers. Test calculations on molecular hydrogen and polyacetylene chains are presented to assess some of the computational problems inherent to the method.
Advances in Organic Electro-Optic Devices
Authors: Thackara John I. , Lipscomb G. F. , Lytel R. S. , Ticknor A. J.
Published: March 2011

We report initial experiments on the fabrication of active and passiveintegrated optic device structures based on poled polymer electro-optic buried channel waveguides. The process of channel waveguide definition and fabrication through electric field poling is described and experimental results are presented. The fabrication, theoretical performance modeling and experimental evaluation of several integrated optic device structures, including phase modulators, directional couplers and Y-branch interferometers, are also reported.
Femtosecond Dynamics and Nonlinear Optical Properties of Polyacetylene
Authors: Etemad S. , Baker G. L. , Rothberg L. , Kajzar F.
Published: March 2011

We discuss two important aspects of the nonlinear optical response of polyacetylene, the prototype conjugated polymer. In the subband gap region, χ(3) of polyacetylene has a rich spectral response and its magnitude is found to be the largest among semiconductors. In the superband gap region, absorption of photons leads to direct photogeneration of charged solitons on a femtosecond-time-scale. These results are discussed in the context of a one-dimensional, coupled electronlattice system, and are generalized to other conjugated polymers.
Quadratic Electro-Optical Characterization of Molecular Nonlinear optical Materials
Authors: Luong John C. , Borrelli N. F. , Olszeuski A. R.
Published: March 2011

A convenient method of measuring the nonlinear optical properties of molecular compounds is described. The method involves measuring the quadratic electro-optical coefficient of a polymer composite containing a variable concentration of the candidate NLO material. The X(3) (ω) value obtained by this low-frequency Kerr measurement, after local-field corrections, can be compared to the nonresonant third-order susceptibility measured by degenerate-four-wave-mixing technique on selective samples. We find that the choice of the polymer matrix dictates the contribution of second-order susceptibility to the Kerr coefficient. Therefore, our method can also be extended to the measurement of second-order susceptibility, analogous to the technique of field-induced second-harmonic-generation.
Synthesis Approaches For Improving the Nonlinear Optical Properties of Pbz Polymers
Authors: Wolfe James F. , Loo Bock H. , Sanderson Robert A. , Bitler Steven P.
Published: March 2011

The synthesis of three types of functionalized benzazole structures is described. A centrosymmetric dihydroxy-benzobisthiazole has been synthesized for incorporation in flexible polymers having rigid, conjugated, third order nlo active units in the main chain. Benzazole structures terminated with an N,N-dimethylamino group and a carboxyl group have been synthesized for use as second order nlo pendants with flexible polymers. Benzazole structures terminated with an N,N-dimethylamino group and an amino group have been synthesized as precursors to second order nlo guest molecules.
Synthesis and Characterization of New Electroactive Polymers
Authors: Dalton L. R.
Published: March 2011

A general scheme for the preparation of soluble electroactive polymers is reviewed with emphasis that polymers so prepared permit investigation of the effects of π-electron delocalization and lattice charge upon nonlinear optical activity. Particular attention is focused upon six membered ring polymer derivatized in 1,4 positions with vinylamine substituents. Such substituents influence rates of polymerization reactions and electronic properties as well as solubility. Preliminary measurement of χ(3) for as-synthesized polymers is effected by DFWM.
Four-Wave Mixing in Metal Poly-Ynes
Authors: Frazier C. C. , Chauchard E. A. , Cockerham M. P. , Porter P. L.
Published: March 2011

We have reported previously that metal poly-ynes have large thirdorder optical susceptibilities. Based on the four-wave mixing studies reported here, we conclude that strong two-photon absorptions in metal poly-ynes contribute significantly to the observed third-order nonlinearities of these materials. Hyperpolarizability/r.u. increases only slightly with chain length for tetrahydrofuran solutions of the metal poly-ynes. The possible influence of conformers on this behavior is discussed.
Calculations on Application of Nonlinear Opganic Materials in Integrated Optics
Authors: Heinamaki A. , Homkanen S. , Tervonen A.
Published: March 2011

The 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.
The Effect of Plasma Substitutes on Sedimentation Rates and Viscosity
Authors: Cerny Lawrence C. , Cerny Elaine L.
Published: March 2011

About twenty years ago, The National Academy of Science-National Research Council's Committee on Plasma and Plasma Substitute, Division of Medical Sciences sponsored the Third Conference on Artificial Colloidal Agents. At that time there was some concern about the stability of dextran. Therefore there was the need for a more suitable artificial colloidal plasma volume expander. At this meeting the results were presented in order to evaluate the feasibility of using solutions of hydroxyethyl starch (HES). This polymer is a derivative of amylopectin, a “waxy” starch, containing only branched chains of glycoside molecules devoid of a linear component. It is prepared by first reacting the starch to acid hydrolysis and then with ethylene oxide in an alkaline solution. There are two distinct advantages to using HES as a plasma substitute. The first is the wide range of molecular weights that are available and the second is the degree of molar substitution, which is defined as the average nunber of hydroxyethyl groups reacted per anhydroglucose residue. It is this unique combination that is the major determinant for the rate of amylase hydrolysis and the time of retention. The half-life concentration parameter, that is, the time required for the concentration of HES in the bloodstream, following intravenous injection, to fall to 50 percent of its initial peak value, has a range of times from 24–36 hours for a weight average molecular weight, Mw, of 450,000 and degree of molar substitution, M.S., of 0.7 to 2–4 hours for a Mw of 40,000 and M.S. of 0.55, respectively [1].
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

Methods 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

Bony 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

The 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.
Hydroxylapatite Silver Phosphate Ceramics: Production, Analysis and Biological Testing of their Antibacterial Effectiveness
Authors: Hangst K. , Eitenmüller J. , Weltin R. , Peters G.
Published: March 2011

One important, and perhaps the crucial reason for lack of success in permanent implants is their colonization by bacteria (ref. 1,2 ). There are various reports of bacteria lodging the surface implants and their success in escaping from the host's defense mechanisms. Quantitative studies of ecosystems have established that more than 99,9% of the bacteria within the system live in microcolonies within biofilms that are adherent to inert surfaces ( ref. 3,4 ). Many of the bacteria that colonize the surfaces of clinical biomaterials also grow in thick, adherent biofilms ( 10, 11 ). - They may be introduced when a biomaterial is implanted or they may be carried to the surface of the biomaterial by a transient bacteriemia. Once there, their adherence is probably a virulence factor and it may enhance their protection against both antibiotics and natural host defences. The adherence of bacteria in industrial systems protect them from chemical and biocides and antiseptics. Adherence of autochtonous bacteria to ephitelium protects them from surfactants, opsonizing antibodies and phagocytic macrophages ( 12,13,14,15,16,17 ). - Apparently what is needed is antibacterial protection confined to the surface of the implant to prevent bacterial invasion of the implant. Antimicrobial penetration into the surrounding tissues is probably unnecessary.
Tissue Tolerance and Antibacterial Effectiveness of Hydroxylapatite Silver Phosphate Ceramics
Authors: Eitenmülleri J. , Hangst K. , Peters G. , Golsong W.
Published: March 2011

The 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

Analysis 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

Implantation 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

Microcellular 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.
Two Ultrasonic Techniques to Evaluate Bone Remodeling About Femoral Prostheses
Authors: Zimmerman Mark C. , Meunier Alain , Christel Pascal , Sedel Laurent , Katz J. Lawrence
Published: March 2011

Ultrasonic techniques have been used extensively to measure the anisotropic elastic properties of calcified tissue [1–4]. Yoon and Katz [3] have derived the equations relating the elastic constants to the technical moduli: Young's modulus, shear modulus, and the bulk modulus. In order to make these calculations they assumed that bone was transversely isotropic (hexagonally symmetric). Abendschein and Hyatt [1] demonstrated that there was a good correlation between the longitudinal modulus (E3) of bone experimentally measured with ultrasound and mechanical techniques. Some investigators have even used these techniques to determine the different mechanical properties of pathological bone (osteopetrotic, osteoporotic) [4].
The Mechanical Behavior of Normal and Osteoporotic Bone: the Effects of Cemented and Noncemented Hemiarthroplasty in Dogs
Authors: Cook Stephen D. , Thomas Kevin A. , Kester Mark A. , Harding Amanda F.
Published: March 2011

The loss of bone mass and consequently bone strength in persons aged forty and beyond is a continuing problem to the orthopaedic community. This progressive loss has been documented by various means such as radiographs, autopsy materials, CAT scans, and single or dual photon absorptiometrv. Orthopaedic problems arising from osteoporosis include fractures of the lumbar spine, distal radius and the femoral neck. Likewise, this age group represents the fraction of the population that will require prosthetic replacement of a joint. Unfortunately, little information is available concerning the mechanical properties of osteoporotic bones and its interaction with prosthetic devices.
Current Status and Research Activity of Selected Oral Biomaterials
Authors: Brackett Susan E. , Duncanson Manville G.
Published: March 2011

A 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

The 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

The 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

The 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

After 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

A 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

Four 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

Problems 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

High 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

The 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 and High Resolution Studies Of B-Zeolite Catalysts Using TEM and Fourier Transform Processing Techniques
Authors: Jóse-Yacamán Miguel , Pérez-Ramírez J. G. , Acosta D. R. , Gilson J. P. , Edwards G. C.
Published: March 2011

Zeolite Beta, synthesized in 1967 (1), is the first example of a large pore, high silica zeolite (SiO2O3 > 20) prepared in the presence of an organic template (Tetraethylammonium Hydroxide). Zeolite NU-2, whose synthesis has been reported in 1982 (2) seems to be related to the zeolite Beta. Although Zeolite Beta has been claimed as useful catalyst in hydrocracking (3), cracking (4), dewaxing (5), hydrotreating (6), shale oil (7) and Fisher-Tropsh products (B) conversions and as a selective adsorbent in the separation of alkylaromatics (9); this zeolite has not been extensively characterized in the open literature.
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

Pt 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

Re-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

Diffusion 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.
Molybdate Catalysts
Authors: Ueda Wataru
Published: March 2011

It is possible to classify the solid state catalyst systems into two categories; structure static catalyst and structure dynamic catalyst. The former is the catalyst in which the original structural circumstances of surface active center, such as coordinatively unsaturated state of active element, length and order of metal-ligand bond or of a bond between structural component, and their bond angle, are maintained unchanged during catalysis. The example is molybdenum sulfid which is a good catalyst for the isomerization and hydrogenation of olefins. On the contrary, the catalysts, in which the above circumstances of surface active center are changing dynamically during catalysis, are classified into the latter category. Molybdate catalysts for olefin oxidation by molecular oxygen at high temperature belong to this category. Main difference between two categories is whether the originally coordinated ligand on metal cation, such as sulfur anion of molybdenum sulfid and oxygen anion of metal molybdate, can participate in the catalysis directly or not. When the coordinated ligand is involved in the reaction, resulting abnormal coordinatively unsaturated state of surface active center must be sustained by the dynamic structure changes of both surface and bulk for the steady state catalysis. The bulk structure, therefore, affects strongly the properties of structure dynamic catalysts, whereas the properties of structure static catalysts depend on the surface structure like coner and edge mainly. The relationship between catalytic properties and structural stability of molybdate catalysts in the selective oxidation of propylene was discussed on the basis of18O tracer study.
A New Polymer-Based Hydrogen Getter
Authors: Gilliom Laura R.
Published: March 2011

Styrene-butadiene triblock copolymer PS-PB-PS was hydrogenated in the bulk using the Crabtree catalyst [Ir(COD)(py)(tcyp)]PF6(COD = 1,5-cyclooctadiene, py = pyridene, tcyp = tricyclohexylphosphine). Since this polymer/catalyst mixture reacts rapidly with hydrogen at ambient temperature and low hydrogen pressures, it should act as an effective hydrogen getter.
Auger Electron Spectroscopy of Amorphous Cu-30 at.% ZR Activated for Catalysis
Authors: Vanini Fabiano , Erbudak Mebmet , Kostorz Gernot , Baiker Alfons
Published: March 2011

Amorphous Cu70Zr30 ribbons heat treated at 473 K in a hydrogen atmosphere yield a very active catalyst for the hydrogenation of ethene and buta-diene. The catalytic activity is due to finely dispersed Cu particles formed on a surface containing numerous cracks. Auger depth profiles and scanning electron micrographs reveal details of the surface chemistry and morphology. The observations are related to the free-energy curve of bulk amorphous Cu-Zr.