bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of the V4+-Centre in 6H- and 4H-SIC by the Method of Spectral-Hole Burning
Authors: Hecht C. , Kummer R. , Winnacker A. 
Published: June 2019

ABSTRACTIn the context of spectral-hole burning experiments in 4H- and 6H-SiC doped with vanadium the energy positions of the V4+/5+ level in both polytypes were determined in order to resolve discrepancies in literature. From these numbers the band offset of 6H/4H-SiC is calculated by using the Langer-Heinrich rule, and found to be of staggered type II. Furthermore the experiments show that thermally stable electronic traps exist in both polytypes at room temperature and considerably above, which may result in longtime transient shifts of electronic properties.
Reduced Modulus Acrylic Bone Cement
Authors: Litsky Alan S. , Rose Robert M. , Rubin Clinton T. 
Published: June 2019

ABSTRACTLoosening is the dominant long-term problem facing joint replacement surgeons and patients. A probable cause of endoprosthesis loosening is the strain singularity at the material interfaces. The concentration of shear at the bone-cement interface leads to micromotion which precipitates a soft-tissue membrane and resorption of the cancellous bone.A more compliant cement would substantially reduce the interfacial stresses and serve as a “pillow” between the prosthetic stem and the cancellous bone. We have developed a surgically-workable formulation of a reduced modulus acrylic bone cement — polybutylmethylmethacrylate (PBMMA) — to test this hypothesis. Materials property testing and in vivo implantation are discussed.
Use of Bone Morphogenetic Protein (BMP) and Cancellous Graft for Porous-Surfaced Interface Voids
Authors: Kim W. C. , Rechl H. , Amstutz H. C. , Hermens K. , O'carroll P. F. , Kabo M. , Urist M. 
Published: June 2019

ABSTRACTIt is known that bony ingrowth implants without intimate apposition results in diminished ingrowth. In this study the use of bone morphogenetic protein (BMP) and cancellous bone graft to augment ingrowth in interface voids is investigated in the canine. Eight CoCr surface replacement hip implants of chamfered cylinder design with beaded CoCr porous layer were implanted in four adult canines and followed from 23 to 56 days. Prior to implantation, cylindrical defects 4mm diameter by 3mm deep were created in the femoral head and acetabular surfaces and filled with 10mg of BMP in one hip and cancellous bone graft in the contralateral hip. Animals were followed with serial radiographs to sacrifice after which microradiographs of ground sections and histologic specimens were analyzed. All defects were 100% filled with viable new bone without differences in density, organization, or ingrowth in the BMP and cancellous specimens. Femoral specimens uniformly showed unexpected seating gaps which were bridged to varying degrees with viable new organized bone. In five femoral cases seating defects of 2mm or more were completely bridged with ingrowth at the porous layer. In one acetabular case a 6mm gap was 90% bridged. No correlation of results was noted with time to sacrifice. It was concluded that new bone present in the seating gaps was most likely due to spillage of material from the cylindrical defects. Although the amount of ingrowth required for durable fixation is unknown, incongruencies of implant fit are common. As BMP showed no discernible advantage over cancellous graft in results of this study we advocate liberal use of readily available cancellous graft (from reamings or femoral head) to fill interface voids.
Ion Implantation as a Tool for Improving the Properties of Orthopardic Alloys
Authors: Higham P. A. 
Published: June 2019

ABSTRACTIon Implantation is emerging as a specialized surface treatment method by which orthopaedic alloys can be doped in order to modify for corrision, fatigue and wear properties.In this paper alterations in the corrosion and fatigue resistance of 316LVM stainless steel and Ti 6A1-4V ELI titanium alloy are considered. The effect of various variables was investigated; ion species, flux, accelerating voltage.Changes in corrosion resistance were monitored by performing anodic polarization studies in deaerated 0.1M NaCi solution at 22°C. The most effective species were found to be tantalum and boron for improvements to stainless steel.Fatigue properties were investigated using a Wohler type rotating bend test. Preliminary results show that nitrogen ion implantation improved the fatigue life for the steel but not the titanium alloy. Indications were found to suggest that time since implantation affect the fatigue properties.
Bioelectrodes for Neural Prostheses
Authors: Hambrecht F. Terry 
Published: June 2019

ABSTRACTNeural prostheses which are commercially available include cochlear implants for treating certain forms of deafness and urinary bladder evacuation prostheses for individuals with spinal cord disorders. In the future we can anticipate improvements in bioelectrodes and biomaterials which should permit more sophisticated devices such as visual prostheses for the blind and auditory prostheses for the deaf based on microstimulation of the central nervous system.
Electronic Materials in Biological Applications
Authors: Regnault William F. , Picciolo Grace Lee 
Published: June 2019

ABSTRACTDecisions concerning patient care, which are routinely made by the attending physician, based on experience and clinical laboratory analyses, will eventually be supplemented or even replaced by real-time, quantified, health assessments from cutaneous and indwelling multisensor probes. These probes will employ a multitude of technologies including optical and solid state techniques for the precise measurement of body analytes such as blood gases, electrolytes, pH, glucose, etc. In addition to clinical monitoring, these sensors will also be used to provide feed-back for closed-loop therapeutic systems.Currently, there are rapid advances being made in sensor technology and its application for the determination of various analytes. However, a major problem still remains at the device/body interface, especially when chronic implantation is required.
Effects of Relaxin on the Mechanical Properties of Collagen Rich Tissues
Authors: Dylewski John R. , Larkin L. H. , Beatty C. L. 
Published: June 2019

ABSTRACTA collagenous scar capsule forms around biomaterial implants and for deformable implants such as a breast prosthesis, this phenomenon of capsular scar contracture may lead to deformation and hardening of the implant. Relaxin, a peptide hormone of pregnancy which is known to affect collagen rich tissues, was given to mice in an attempt to eliminate or lessen this contracture. A short (8 day) study was performed to observe the effects of relaxin and estrogen on the mechanical properties of Skin and the interpubic ligament. A longer (27 day) study observed the effects of relaxin in estrogen primed mice containing implants. Changes in skin, interpubic ligament, scar capsule and contracture phenomenon were noted. Stress-strain characterization, dynamic mechanical spectroscopy and light microscopy were used to characterize the effects of relaxin and estradiol on the contracture phenomenon. Qualitatively, relaxin given to estrogen primed mice was shown to lessen implant contracture and deformability. Administration of relaxin produced the documented changes in the interpubic ligament, but differences were noted between the 8 and 27 day studies. Differences in the failure stress and strain and modulus for the long implant and short non-implant study were noted for the relaxin treated mice.
Chemical Composition and Morphology of Titanium Surface Oxides
Authors: Lausmaa J. , Mattsson L. , Rolander U. , Kasemo B. 
Published: June 2019

ABSTRACTTitanium has emerged as one of the most tissue-compatible metallic materials. The high degree of biocompatibility is intimately connected with the oxide that forms on the metal surface. In the present work a broad characterization has been made of titanium samples pretreated both by presently used clinical procedures (mechanical machining, ultrasonic cleaning and autoclaving) and by alternative preparation procedures such as electropolishing and anodic oxidation. The former samples are found to have a surface oxide of TiO2 which is 30–50 Å thick, with some trace element contamination and a relatively large carbon content (30–50 % of a monoatomic layer). The anodically oxidized samples also consist of TiO2 with an oxide thickness range of 50–2000 Å, but the morphology and crystallinity of the anodic oxides are found to depend on thickness and preparation conditions.The main methods of investigation used in the present study were ESCA, SIMS and transmission electron microscopy.
Biomaterials in Ophthalmology A Generalist's Overview
Authors: Lee J. Michael 
Published: June 2019

ABSTRACTFor the biomaterials scientist, the eye presents unique problems, principally because the maintenance of optical function is paramount. This paper concentrates on some current challenges in the development of devices to be placed in the optical path: from air to tear film, cornea, aqueous humour, pupil, lens, vitreous humour, and finally to the retina. Optical clarity during contact lens wear depends on control of deposits from tear film components (by patient performed cleaning procedures) and on continuous oxygen supply to the cornea whose clarity depends on intact epithelial and endothelial cells. Intracorneal lenses of contact lens material are possible if intracorneal fluid flow is not compromised. Corneal integrity can also be affected by adhesive endothelial cell damage during intraocular lens implantation, a factor leading to the development of so-called visco-elastic media for anterior chamber use. The associated questions of photodegradation of materials and protection of the optical tissues from photo-toxicity are critical in the eye. Laser surgery is also uniquely valuable in ophthalmology since many procedures can be performed without invasive access. Finally, intraocular lenses can also incur protein adsorption, cellular adhesion, and opacification of the lens capsule which compromise optical performance.
Slow Crack Growth in Dental Composites
Authors: Montes-G. G. M. , Draughn R. A. , Simpson T. H. 
Published: June 2019

ABSTRACTThe fracture properties of selected commercial composite dental restorative materials and a model composite system were studied to determine the influences of the reinforcing phase, exposure to water, and particle/polymer adhesion on crack propagation. The content of inorganic fillers ranged from 36 to 62 volume percent. In the model system the polymer phase approximated that of the commercial products, a constant size distribution of quartz fillers was used, and polymer/particle adhesion was varied. The double torsion test method was employed to measure relationships between applied stress intensity factor and velocity of crack propagation during stable crack growth. In all systems, cracks propagated through regions of high stress concentration at the low end of the velocity range studied (10−7 m/sec to 10−3 m/sec). Wet materials fractured at lower stress intensities than dry materials at all velocities. At high velocities unstable (stick-slip) growth occurred in dry materials with strong filler/matrix interfaces and in wet specimens with initially strong interfaces and less than 41 volume percent filler. In wet conditions, materials with poorly bonded fillers fractured by slow crack growth at stress intensities 10% to 30% below the levels of composites with strong interfaces.
Degradation of Rocks, Through Cracking Caused by Differential Thermal Expansion, in Relation to Nuclear Waste Repositories
Authors: Mclaren J.R. , Davidge R.W. , Titchell I. , Sincock K. , Bromley A. 
Published: June 2019

ABSTRACTHeating to temperatures up to 500°C, gives a reduction in Young's modulus and increase in permeability of granitic rocks and it is likely that a major reason is grain boundary cracking. The cracking of grain boundary facets in polycrystalline multiphase materials showing anisotropic thermal expansion behaviour is controlled by several microstructural factors in addition to the intrinsic thermal and elastic properties. Of specific interest are the relative orientations of the two grains meeting at the facet, and the size of the facet; these factors thus introduce two statistical aspects to the problem and these are introduced to give quantitative data on crack density versus temperature. The theory is compared with experimental measurements of Young's modulus and permeability for various rocks as a function of temperature. There is good qualitative agreement, and the additional (mainly microstructural) data required for a quantitative comparison are defined.
On the Mechanical Integrity of Ultra Low Dielectric Constant Materials for Use in Ulsi Beol Structures
Authors: Shaffer E. O. , Howard K. E. , Mills M. E. , Townsend P.H. 
Published: June 2019

AbstractAdherence to the prescript of Moore's law continues to drive materials development for new and lower dielectric constant materials for use as back-end-of-line (BEOL) interlayer dielectric in advanced logic IC's. As is the case for the current generation of low-K materials (<3.0), these ultra-low K materials (<2.2) will need to meet the variety of integration and reliability requirements for successful product development. Excluding the incorporation of fluorine to lower the material polarity, further reductions of dielectric constant can only be achieved by reduced density. Based upon the industry's experience with the current class of full density dielectrics, process integration may be challenging for ultra-low K materials. This anticipated difficulty derives from the profound differences in material properties, e.g. mechanical integrity, as one lowers the material density, which in turn confounds existing manufacturing processes that have evolved over 35 years based on silicon dioxide.Minimizing these material and processing differences by extending leveraged learning from previous technology nodes is essential for timely and cost-efficient development cycles. As a result, material selection of a full density low-K is somewhat influenced by the ability of that material to be extended into future generations. Understanding how the material properties will change as its density is lowered is vital to this selection process. In this paper, we present a summary of models for calculating effective properties as a function of density and apply these to current low-K materials with emphasis on mechanical integrity. We will also review experimental methods for measuring the mechanical integrity of ultra-low K materials and compare the results to the various models described herein.
The Effect of Fatigue on the Adhesion and Subcritical Debonding of Benzocyclobutene/Silicon Dioxide Interfaces
Authors: Snodgrass Jeffrey M. , Dauskardt Reinhold H. 
Published: June 2019

AbstractThe effect of fatigue loading on microelectronic thin film interfaces has until now been difficult to quantify. Most industrial fatigue testing uses HAST (Highly Accelerated Stress Testing) protocols, which inherently convolutes the effects of mechanical fatigue and the test environment. Our work focuses on isolating the deleterious effects of mechanical fatigue on interfaces, which we have found to be substantial. In this study, the integrity of a low-k polymer interface involving benzocyclobutene (BCB) and silica was examined under a variety of loading conditions. Critical (fast fracture) adhesion values were measured using standard interface fracture-mechanics geometries. Experiments were then conducted to measure the debond growth rate as a function of the applied strain energy release rate under both static and cyclic loading conditions. Our results show that even under room temperature conditions, debond growth rates measured under cyclic fatigue are considerably faster than those observed under static loading. Results are presented detailing the effects of interface chemistry (adhesion promoters), environmental moisture, and test temperature on the resistance of the interfaces to subcritical debonding. Strategies for increasing resistance of dielectric interfaces to fatigue debonding are outlined.
Tacticity and surface chemistry effects on the glass transition temperature of thin supported PMMA films.
Authors: Grohens Y. , Hamon L. , Carriere P. , Holl Y. , Schultz J. 
Published: June 2019

ABSTRACTThe glass transition temperature (Tg) of thin supported films of stereoregular poly(methyl methacrylate) on silicon has been investigated by ellipsometry in temperature. The Tg of the spin coated layers of isotactic PMMA increases for thickness lower than 100 nm whereas a depression of the Tg is observed for the syndiotactic PMMA. This opposite trend in the Tg variation in thin layer between the two isomers evidenced a fascinating effect of the chain organization at an interacting interface. Hydrofluric acid surface etching of the silicon wafer was shown to decrease the threshold thickness at which the change in Tg occurs for both PMMA isomers. The influence of the interfacial interactions along with the tacticity dependent characteristics of the polymer will be discussed.
Simulation of Interfacial Fracture in Highly Crosslinked Adhesives
Authors: Stevens Mark J. 
Published: June 2019

ABSTRACTThe fracture of highly-crosslinked networks is investigated by molecular dynamics simulations. The network is modeled as a bead-spring polymer network between two solid surfaces. The network is dynamically formed by crosslinking an equilibrated liquid mixture. Tensile pull fracture is simulated as a function of the number of interfacial bonds. The sequence of molecular structural deformations that lead to failure are determined, and the connectivity is found to strongly control the stress-strain response and failure modes. The failure strain is related to the minimal paths in the network that connect the two solid surfaces. The failure stress is a fraction of the ideal stress required to fracture all the interfacial bonds, and is linearly proportional to the number of interfacial bonds. By allowing only a single bond between a crosslinker and the surface, interfacial failure always occurs. Allowing up to half of the crosslinker's bonds to occur with the surface, cohesive failure can occur.
Adhesion Enhancement Via Crystalline-Embedded Entanglements in Melt-Processed Layered Structures
Authors: Cole Phillip J. , Macosko Christopher W. 
Published: June 2019

ABSTRACTImproving the adhesion of polyolefins to glassy polymers is complicated by the semicrystalline nature of the polyolefins. Traditional methods used in glassy polymers to increase the interlayer adhesion, including the addition of a diblock copolymer or the formation of a copolymer throughin situreaction, are still successful with semicrystalline polymers. However, melt miscibility of the adhesion promoting molecules is not the only consideration; co-crystallization can also be significant. Even when co-crystallization is achieved, the reactive method is shown to provide greater fracture toughness than the addition of a pre-made diblock copolymer. In the latter case, the formation of micelles limits the efficiency of the diblock copolymer. Finally, significant adhesion enhancement is attainable in reactive systems with contact times as short as 45 seconds as demonstrated through a multilayer coextrusion of amorphous nylon against a polypropylene-maleated polypropylene blend.
Switching of Surface Properties with Polymer Brushes
Authors: Stamm Manfred , Minko Sergiy , Goreshnik Evgeniy , Usov Denis , Sidorenko Alexander 
Published: June 2019

ABSTRACTSwitchable surfaces were fabricated by grafting of two different polymers: polystyrene (PS) and poly-2-vinylpyridine (PVP) onto the surface of Si-wafers. The binary brushes of various composition, molecular weight and grafting density were synthesized via free radical polymerization initiated by the azo-initiator covalently attached to the surface of Si-wafers. Investigations showed that the binary brushes are very sensitive to the surrounding media. After exposition to a solvent selective for PVP (ethanol, water + HCl) the surface becomes hydrophilic and the top of the layer is covered by PVP. After exposition to a solvent selective for PS (toluene) the surface becomes hydrophobic and the top of the layer is enriched with PS segments. Switching kinetics depends on grafting density and layer composition and varies from several seconds to several minutes at room temperature. Surface morphology of the layers switches as well as the wetting behavior. Results show that the layer reconstruction is reversible and can be repeated many times.
Surface-attached Polymer Networks
Authors: Prucker Oswald , Müller Kristin , Rühe Jürgen 
Published: June 2019

ABSTRACTIn this paper we present three novel routes for the preparation of surface-attached polymer networks. In one system the network is formed in situ at the surface by thermal polymerization in solution and from the surface. Another synthetic route starts with a surface that carries photoreactive groups. Onto this surface a polymer is deposited that also carries photoreactive groups and both the crosslinks of the network and the covalent bond to the surface are formed by UV illumination. The third approach start with the in situ formation of surface-attached copolymers that again carry photoreactive groups that are subsequently linked together by UV light. We present evidence for the successful synthesis of these networks and their superior adhesion on glass surfaces.
Low Temperature Shallow Junction Formation For 70nm Technology Node And Beyond
Authors: Borland John O. 
Published: June 2019

AbstractLow temperature shallow junction formation is an attractive activation technique for 70nm technology node and beyond as it can easily be integrated into device structures that are formed using disposable spacer (reverse source drain extension formation) or low power CMOS devices using high-k/metal gate stack structures. Therefore, this paper will first review the shallow junction requirements as stated in the 2001 ITRS (international technology roadmap for semiconductors) and it's interpretation to ion implantation shallow junction formation for various dopant activation and annealing techniques. First high temperature (>1000°C) RTA spike, flash or sub-melt laser annealing techniques with oxide or oxynitride/polysilicon electrode gate stack structures will be discussed and its limitations to >8E19/cm3 boron electrically active dopant level due to boron solid solubility limit in silicon satisfying only the 100nm technology node requirement (2003). Next, higher temperature laser melt annealing (1200°C to 1400°C) will be discussed and it's applicability beyond 70nm node technology (2006) to 25nm node (2016) where boron solid solubility limit is up to 5E20/cm3. However, if high-k (HfO) dielectric/metal electrode gate stack structures are to be used starting at sub-100nm node in 2005 for low power CMOS then low temperature (>700°C) annealing must be used for shallow junction formation to prevent recrystallization and dielectric constant degradation. Using low temperature SPE (solid phase epitaxial regrowth) annealing techniques in the 550°C to 750°C for short anneal times of >5mins., shallow & abrupt junctions 8.0nm deep, >2.0nm/decade with up to 2.5E20/cm3 boron electrical active dopant level can be achieved satisfying the 25nm technology node (2016) requirements.