bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonunear Absorption in Phthalocyanines and Naphthalocyanines
Authors: Shirk James S. , Flom Steven R. , Lindle J. R. , Bartoli F. J. , Snow Arthur W. , Boyle Michael E. 
Published: March 2011

ABSTRACTThe wavelength dependence of the nonlinear absorption for lead tetrakis (cumyl-phenoxy) phthalocyanine (PbPc(CP)4) and lead octa (α-pentoxy) napthalocyanine (PbNc(α-PO)8) are reported. The ground state absorption and the reverse saturable absorption are substantially red shifted in PbNc (α-PO)8 as expected. Such control over the reverse saturable absorption is crucial to design optical limiting materials for specific wavelength ranges.
Molecular Dynamics Simulation Of A Cyclic Siloxane Based Liquid Crystalline Material
Authors: Patnaik Soumya S. , Pachter Ruth , Plimpton Steve , WADE ADAMS W. 
Published: March 2011

ABSTRACTWe have used molecular dynamics (MD) to study the room temperature bulk phase behavior of a cyclic siloxane with a pentamethylcyclosiloxane core and biphenyl-4-allyloxybenzoate Mesogens (BCS). This Material exhibits thermotropic liquid crystalline behavior above 120 °C. Bonded and non-bonded interactions were considered and a Molecular Mechanics force field was used to model the structural anisotropy of the siloxane Molecules. Molecular clusters with and without periodic boundary conditions (pbc) were studied to investigate the effect of the finite system size on the time evolution of the molecular structure. The precise nature of the boundary conditions was found to be significant and simulations that exclude pbc were better able to model the molecular system. It was found that molecular shapes associated with low energy conformations were not cylindrically symmetric but more splayed like. An approximate measure of the shape of the mesogens was obtained by describing ellipsoids around the Mesogens, and estimating the molecular length, breadth, and width from the principal axes of the ellipsoids. The orientational order was then calculated by defining the molecular axis to be along the major principal axis.
Observations of Damage and Transport of Hydrogen in Ion Bombarded Polycrystalline Silicon
Authors: Sharp D. J. , Panitz J. K. G. , Seager C. H. 
Published: March 2011

ABSTRACTA combination of chemical etching and sheet resistivity measurements showed that intense (1.4 mA/cm2 ) low energy (1400 eV) ion beam hydrogenation of polycrystalline silicon having a columnar structure can produce electrical defect passivation to depths in the order of 100 μm. Transmission electron micrographs disclose surface and near-surface features resulting from the ion beam bombardment which suggest that one of the hydrogen transport mechanisms may be defect induced.
Display Quality SOI by Recrystallization of Bridged Silicon Islands on Quartz
Authors: Bak C. S. , Braatz P. O. , Margerum J. D. 
Published: March 2011

ABSTRACTArrays of single crystal thin film silicon islands were prepared on fused quartz substrates by a zone melting recrystallization of bridged island patterns of poly-Si. A scanning graphite strip heater technique was used, with the Si islands connected (“bridged”) in the scanning direction by narrow Si strips. These strips generated a self-seeding effect in the crystalline growth, and the recrystallized Si islands were good quality SOI with <100> orientation as shown by x-ray and etch-pit analysis. Protuberances, film cracking and impurity segregation were greatly suppressed in this bridged island SOI as compared to defects normally observed in recrystallized continuous Si films on quartz. MOSFETs were fabricated in the SOI islands, using n-channel enhancement mode devices with a gate length of 5μm and a gate width of 50μm. The average carrier mobility measured on these SOI devices was 470 ± 70 cm2/V.s, which was twice as high as the mobility measured in MOSFETs fabricated concurrently in SOS. Good MOSFETs in the SOI islands showed a switching ratio of about 107 at 6V and a leakage of less than 2pA/μm. These results indicate that high performance drive circuits for liquid crystal displays can be fabricated in SOI recrystallized from bridged island patterns on transparent quartz substrates.
CMOS/SOS VLSI Technology
Authors: Sato Tai , Iwamura Jun , Tango Hiroyuki , Doi Katsuyuki 
Published: March 2011

ABSTRACTCMOS is considered as a prospective technology in the VLSI era because of its low power consumption and high driving capability. While ordinary bulk silicon CMOS devices are inferior to SOS CMOS devices in chip area, operation speed and latch-up problem due to the need for isolation wells. SOS is an inherent good partner of the CMOS circuits owing to the simple and perfect isolation. SOS technology, however, has the problem of high wafer cost. Consequently, SOS technology is best applied to high performance logic devices. Latest results of 8k-gate CMOS/SOS gate array and 16×16bit multipliers show 0.87ns 2-NAND gate delay and 27ns multiplication time, respectively, which compete with ECL devices. Application of SOS devices down to 1μm is also promising for very high speed operation. A 78ps gate delay is achieved by double solid phase epitaxy and 1μm technology. INTRO
Amorphous Si:H Linear Image Sensor Operated by a-Si:H TFT Array
Authors: Okumura F. , Kaneko S. 
Published: March 2011

ABSTRACTAn amorphous Si:H linear image sensor operated by a-Si:H TFT array has been proposed. This sensor consists of photodiode array, TFT array, matrix circuit, charge transfer capacitor, and external circuit. Mobility for TFT is 0.6 cm2/V.s and 5 μsec/bit read out time was obtained in the conventional matrix mode scanning. Moreover, a novel driving method is applied in order to improve the effective operation speed and an investigation for TFT noise was performed. Experimental data confirm the validity of the concept.
The Formation of Porous Silicon and its Applications to Dielectric Isolation
Authors: Frye R. C. 
Published: March 2011

ABSTRACTPorous silicon is formed by the anodic dissolution of p-type silicon in aqueous hydrofluoric acid. Because of its very high porosity, this material can be rapidly cKidized to form thick (˜10 μn) oxide layers with minimal stress on the underlying silicon wafer. A remarkable property of porous silicon is that preserves the crystalline orientation of the substrate despite removal of more than half of the silicon in the etched region, providing a suitable surface for the growth of epitaxial layers. Several schemes for dielectric isolation have been suggested which take advantage of these unique properties. In this paper, the mechanism of porous silicon formation will be presented and the relative advantages and disadvantages for practical device applications will be discussed.
Genetically-Engineered Protease-Activated Triggers in a Pore-Forming Protein
Authors: Walker Barbara , Walsh Nathan , Bayley Hagan 
Published: March 2011

ABSTRACTProtease-activated triggers have been introduced Into a pore-forming protein, staphylococcal a-hemolysin (αHL). The hemolysin was remodeled by genetic engineering to form two-chain constructs with redundant polypeptide sequences at the central loop, the Integrity of which Is crucial for efficient pore formation. The new hemolysins are activated when the polypeptide extensions are removed by proteases. By alterating the protease recognition sequence in the loop, selective activation by specified proteases can be obtained. Protease-triggered pore-forming proteins might be used for the selective destruction of cancer cells that bear tumor-associated proteases. When certain two-chain constructs are treated with proteases, a full-length polypeptide chain forms as the result of a protease-mediated transpeptidation reaction. This reaction might be used to produce chimeric hemolysins that are Inaccessible by conventional routes.
A Versatile Low Density Polysaccharide Matrix
Authors: Rohrbach Ronald P. , Unger P. D. 
Published: March 2011

ABSTRACTA material having the characteristics of very low density and high mechanical stability has been developed. This material is prepared by crosslinking the biopolymer alginic acid. Bulk densities as low as 0.15 g/cc have been obtained, while still possessing useful strength, 10% deformation at 347 psi. The physical properties can be varied by controlling the processing conditions, which affect pore volume, pore diameter, bulk density and surface area. Preparation of this material involves solvent exchange and subsequent crosslinking. The resin's minimum compressibility and physical strength allow this material to be considered for a number of applications including adsorbents, insulation and as a polymeric carrier for time release.
Failure And Energy-Absorbing Mechanisms of the Bessbeetle Cuticle
Authors: Thorp Katie E. G. , Gunderson Stephen L. 
Published: March 2011

ABSTRACTThe failure processes of the bessbeetle cuticle were studied through the use of scanning electron microscopy, light microscopy, and image analysis techniques. Specimens of elytra and pronotum were failed in tension under the light microscope. The failure process was documented in real time through the use of image analysis equipment and a video camera. Failure occurs primarily in a mixed-mode fashion due to the inherent curvature of the cuticle specimens and their complex hierarchical microstructure. A variety of energy-absorbing mechanisms were observed including remote microcracking, fiber pullout, and crack bridging. Damage accumulation around the failed region is extensive consisting of a significant amount of delamination, fiber-matrix disbonds, microcracking, and intra-fiber failure. The experimental methods and results will be discussed.
Precipitation in and on Polymers
Authors: Calvert Paul 
Published: March 2011

ABSTRACTMineralized biological tissues form by growth of inorganic phases in or on polymers and membranes. This paper discusses the mechanisms for these processes from a bio-mimetic point of view. Mineralization within a polymer or gel can lead to very fine precipitates because particle agglomeration is prevented and solute diffusion rates are low.Localization of mineralization appears to occur in biology by activation of particular surfaces. The possibility is discussed that this may be due to a close lattice match between the spacing of groups on the polymer and the spacing of ions in the mineral. It is shown that this mechanism is unlikely and other possibilities are discussed.
Proliferation and Interactions of Several Cell Types Encapsulated Within Dense (Non-Porous) Protein-Permeable Polyurethane Membranes
Authors: Wang Albert Y. , Ward Robert S. , White Kathleen A. , Kuhn Robert W. , Taylor Julie E. , John Judith K. 
Published: March 2011

AbstractProtein-permeable dense (non-porous) urethane membranes have been evaluated forin vitrocell culture, and in vivo cell encapsulation. Polyurethane membranes were designed to exhibit permeability to proteins, gases, and nutrients without the existence of pores. The membranes are non-cytotoxic, angiogenic, and permeable to gases, nutrients, secretagogues and cell products via purely concentration-driven transport. Non-anchorage and anchorage dependent cells were grown encapsulated within the membrane and with the membrane as a growth substrate. Several non-anchorage dependent cell types proliferated within the membrane bothin-vitroandin-vivo. Anchorage-dependent cells were grown on the membranes as a substrate. Encapsulated cells have been maintained in culture for up to six months with nutrients supplied only by the external media. Immuno-isolation has been demonstrated with cells implanted into murine hosts. Explants of membrane encapsulated cells exhibited a high degree of vascularization, with little or no fibrous tissue. The ability to support cell growth and function, and the ability to protect xenogenic cells from immunologic rejection suggest that the membranes would be useful in the construction of hybrid artificial organs, devices for cell transplantation, and substrates for cell and tissue culture.
Novel Preparation of Poly(Vinyl Alcohol) Microparticles without Crosslinking Agent for Controlled Drug Delivery
Authors: Ficek Becky J. , Peppas Nicholas A. 
Published: March 2011

AbstractPoly(vinyl alcohol) microparticles were prepared by a novel freezing-thawing process in the absence of a crosslinking agent. An aqueous PVA solution to which 1.25 wt% sodium lauryl sulfate was added was dispersed in corn oil. The system was agitated and the ensuing suspended droplets of PVA solution were solidified by a cyclic freezing-thawing process. Key parameters of the process were the PVA to corn oil ratio, the amount of surfactant added, agitation speed, number of freeze cycles, temperatures of freezing and thawing, and presence of additional components.Crystallization was observed during the freezing-thawing process. The degree of crystallinity was measured with differential scanning calorimetry. Bovine serum albumin was incorporated into the particles by an absorption technique. Studies of BSA release from the microparticles in vitro showed that the release could be prolonged for up to 7 days. BSA diffusion coefficients were calculated from these data and the release mechanism was identified.
Bioactive Glass Templates for the Synthesis of Bone-Like TissueIn Vitro
Authors: Ei-Ghannam A. , Ducheyne P. , Shapiro I. M. 
Published: March 2011

AbstractPorous glass templates of pore size 75–200 14m and 20–30% porosity were synthesized. The glass disks were conditioned in a modified tris buffer (SBF) for 48 hrs and then treated with tissue culture medium (TCM) for 1 hr at 37°C. Other porous glass templates were treated with either SBF or TCM. The conditioned glass disks were seeded with 106neonatal rat calvaria osteoblasts and maintained in culture for 2, 5 or 7 days. It was found that the bioactive glass was rapidly invaded by cells which colonized the porous template. Morphological and biochemical analyses suggested that a bone-like tissue was formed inside templates conditioned with both SBF and TCM. By 7 days, the cells exhibited high alkaline phosphatase activity and synthesized osteocalcin. SDS-PAGE indicated the presence of type I collagen. SEM-EDAX analysis showed the formation of a bone-like tissue throughout the entire sample, while inspection of the Ca:P ratio indicated that the cells synthesized a mineral phase. Indeed, the FTIR spectra of the mineral confirmed that it was a biological hydroxyapatite. The rapid formation of the bone-like material within the templatein vitrosuggests that this template may be valuable clinically for the repair of bone lesions.
Use of a Multiple Lumen Cuff for Nerve Regeneration
Authors: Greer Raymond , Daniel John , Uemura Etsuro , Kudej Raymond , Chen Yueh-Sheng , Chung Chih-Hui 
Published: March 2011

AbstractInitial studies using the rat sciatic nerve demonstrated the ability to adapt a multiple lumen cuff face to a nerve stump repair site. The neurons in the proximal stump grew through the individual conduits of the silicone rubber cuff, crossed a 5 mm gap, and continued into the distal stump. The effect of the cuff design on axonal regeneration was studied by comparing macroscopic and microstructural results for experimental groups of Sprague-Dawley rats with controls at 8, 12, 16, and 24 weeks post-implantation. The several individual nerve bundles which formed within the cuff lumens during these periods maintained their alignment on the distal side of the gap. The use of the multiple lumen system provided suitable scaffolding support and control of orientation and direction for fibers and established a sized, controlled environment for regeneration within each of the separate nerve cuff compartments.
Stabilizing Fiber-Based Cell Delivery Devices by Physically Bonding Adjacent Fibers
Authors: Mooney D. J. , Mazzoni C. L. , Organ G. M. , Puelacher W. C. , Vacanti J. P. , Langer R. 
Published: March 2011

AbstractNon-woven meshes of polyglycoiic acid (PGA) fibers are attractive candidates to transplant cells and engineer new tissue. However, these devices typically lack the structural stability to resist compressive forces, and collapse in vivo. To determine whether these devices could be stabilized by physically bonding adjacent PGA fibers, we have sprayed solutions of poly (L-lactic acid) (PLLA) and a 50/50 copolymer of poly (D,L-lactic-co-glycolic acid) (PLGA) dissolved in chloroform over PGA meshes formed into hollow tubes. After the chloroform evaporated, the PLLA and PLGA formed a coating over the PGA fibers and bonded adjacent fibers. The pattern and extent of fiber bonding was found to depend on both the concentration of polymer in the spraying solution, and the total mass of polymer sprayed on the device. The compression resistance of sprayed devices increased with increasing extent of bonding, and devices bonded with PLLA resisted compressive forces better than devices bonded with PLGA. For example, under a compressive force of 200 mN, devices sprayed with PLLA compressed approximately 20%, while devices sprayed with PLGA were completely crushed. To determine whether stabilized devices such as these can guide the development of neointestine and neocartilage by transplanted cells, intestinal cells and chondrocytes have been attached to PLLA bonded devices and transplanted into experimental animals.
Controlled Release of Trimaterene from Poly(DL-Lactide-Co-Glycolide) Microspheres
Authors: Ouellete Amy D. , Peppas Nicholas A. 
Published: March 2011

AbstractRelease of triamterene from 150–300 gm poly(DL-lactide-co-glycolide) (PLGA) microspheres was investigated in vitro as a function of lactic acid/glycolic acid (LA/GA) copolymer ratio and drug loading both with free microspheres and with microspheres embedded in a silicone matrix. Biphasic release consisting of diffusion controlled release followed by erosion controlled release corresponding to polymer degradation was observed in all samples. Drug release from PLGA 50:50 copolymer microspheres was three times faster than the release from PLGA 75:25 microspheres for the higher drug loading (20 wt%) and slightly faster for the lower drug loading (10 wt%). Release rates from spheres containing the higher drug loading were approximately one order of magnitude faster than release from spheres containing the lower drug loading for the same PLGA copolymer. The same qualitative results were observed for the spheres embedded in silicone matrices; however, the overall release was much slower. The results demonstrate that release behavior may be altered by changing LA/GA copolymer ratio, drug loading, and microsphere environment to obtain the desired release characteristics.
Double-Walled Microspheres for Drug Delivery
Authors: Pekarek Kathleen J. , Jacob Jules S. , Mathiowltz Edith 
Published: March 2011

AbstractPresent microsphere delivery system technology consisting of a single drug dispersed within a polymer matrix has several drawbacks. One is the problem of the so-called “burst effect”. By exploiting the phenomenon of phase separation between two immiscible polymers dissolved in a mutual solvent, a double-walled microsphere could be manufactured with the second polymer coating the polymer/drug matrix. This one-step process would give a consistent coating of even very small microspheres not achievable via normal, two-step coating processes and would help to smooth out the release curve by lessening the “burst effect”. Along with solving the problem of the “burst effect”, this concept of double-walled microspheres could be used to achieve constant release of the drug over long periods of time. So far, this has only been achieved with a limited number of geometric configurations. Since every polymer has its own characteristic release rate, the release could be kept much more constant by changing the polymer type and/or properties. By combining these layers so that the release rate of one layer would complement the slowing of release due to decreased surface area or increased diffusion distances.
Selective Growth of Diamond Films On Mirror-Polished Silicon Substrates
Authors: Mao M.Y. , Tan S.S. , Zhang X.K. , Wang W.Y. 
Published: March 2011

AbstractPolycrystalline diamond thin films have been selectively grown on mirror-polished silicon substrates using bias-enhanced microwave plasma chemical vapour deposition (MPCVD) to increase diamond nucleation density. A slight etching of Si02 mask was employed after the nucleation treatment to remove the diamond nuclei on the mask. Perfect diamond patterns with smooth surface (particle size <0.5µm) and sharp boundaries were obtained. The diamond film gears with 400µm in diameter and 5µm in thickness were first fabricated by this technique.
Real Time Control of III-V Semiconductor Surfaces During Movpe Growth by Reflectance Anisotropy Spectroscopy
Authors: Ploska K. , Richter W. , Reinhardt F. , JÖnsson J. , Rumberg J. , Zorn M. 
Published: March 2011

AbstractReflectance anisotropy spectroscopy (RAS) is presented as real time analytical tool for metalorganic vapourphase epitaxy (MOVPE) of III-V-semiconductors. This optical method derives its surface sensitivity from the anisotropy of surface structures. It is shown that it is possible to monitor with RAS the oxide desorption from the substrate and that the substrate surface conditions thereafter, still in the pregrowth stage, can be correlated with certain reconstructions of the (001)-surfaces of InP and GaAs. The latter is possible through simultaneous RAS and RHEED measurements during MBE (molecular beam epitaxy) or MOMBE (metalorganic molecular beam epitaxy). Characteristic spectral features are also observed for other binary or ternary III-V-semiconductors. Time resolved measurements during growth give monolayer resolution for the growth rate in the case of GaAs. In the study of heterointerface growth exchange reactions between As and P together with their corresponding reaction time constants can be monitored and conclusions for the epitaxial growth procedure can be drawn.
Kinetics of Low-Pressure Mocvd Of GaAs from Triethyl-Gallium and Arsine
Authors: Ingle N.K. , Theodoropoulos C. , Mountziaris T.J. , Wexler R.M. , Smith F.T.J. 
Published: March 2011

AbstractThe growth of undoped GaAs films from Ga(C2H5)3 (TEG) and AsH3 by Metalorganic Chemical Vapor Deposition (MOCVD) has been studied in a low-pressure reactor operating at 3 Torr. This precursor combination is known to produce GaAs films with very low carbon incorporation when compared to films grown from Ga(CH3)3 (TMG) and AsH3. A kinetic model of the growth process has been developed that includes both gas-phase and surface reactions based on reported decomposition mechanisms of TEG and AsH3. The kinetic model was coupled to a transport model describing flow, heat and mass transfer. Finite element simulations were performed to determine the rate constants of the growth reactions that provide the best fit between predicted and observed growth rates. Under typical operating conditions the surface reactions were found to dominate the growth process and a reduced surface kinetic model was identified by sensitivity analysis. The proposed reaction-transport models can successfully predict observed growth rates of GaAs films and they can be used for identifying optimal operating conditions in MOCVD reactors.
Tetraalkyldiarsines As Potential Precursors for Electronic Materials: Synthesis and Characterization Of Various Iso-Propyl Arsenic Compounds
Authors: Brough Lawrence F. , Gang Liu , Lipkovich Matthew A. , Colacot Thomas J. , Goedken Virgil L. , Rees William S. 
Published: March 2011

AbstractTetrakis(iso-propyl)diarsine was synthesized by the reaction of (i-Pr)2AsLi with (i-Pr)2AsI. The lithium salt of the secondary arsine was produced following deprotonation of (i-Pr)2AsH, obtained by reduction of (i-Pr)2AsI, which was prepared by the thermolysis of (i-Pr)3Asl2. The X-ray crystal structure of \(i-Pr)3AsI]\I] has been determined on the product of the reaction of (i-Pr)3As and 12. Compounds of the general form E=As(i-Pr)3 (E = O, S, Se) have been prepared.