bluuebunny/crossref_metadata_2025_split huggingface dataset:
General Overview of Vibrational Spectroscopy of Layered Transition-Metal Oxides
Authors: Julien C. , Nazri G.A. 
Published: April 2011

ABSTRACTWe report the vibrational spectra of various layered transition-metal oxides, which are potential cathode materials for advanced Li-ion batteries. They provide high specific energy density, high voltage, and remarkable reversibility for lithium intercalation-deintercalation process. Studies were carried out by Raman and FTIR spectroscopies. Oxides such as LiMO2 (M=Co, Ni, Cr) layered compounds and their mixed compounds have been investigated. The local environment of cations against oxygen neighboring atoms has been determined by considering polyhedral units building the lattice. Structural modifications induced by intercalation-deintercalation process, by cation substitution, or by low-temperature preparation route are examined.
Synthesis and Chemical Properties of Dye-Doped Mesoporous Transition Metal Oxides
Authors: Honma I. , Zhou H.S. , Moon S.C. 
Published: April 2011

AbstractSelf-assembled functional dye molecules in mesoporous transition metal oxides have been synthesized directly by Pc (phthalocyanine) molecules doped within hexadecyltrimethylammonium bromide (C16TMA) micelles assembled with oxide frameworks such as Vanadia (VOX), FeOx, MoO3and WO3to produce Pc-doped mesostructured materials. The Pc molecules were heavily doped inside the mesoporous channels and dye's optical absorption were measured. Pc molecules in contact with mesoporous transition metal oxides interfaces are optically excited and provide reductive electrons to water molecules to decompose into hydrogen by visible light exposures.
Platinum Supported Catalysts Prepared from Metal Carbonyl Clusters for Hydrocarbons Conversion
Authors: Kolosov P.E. , Shitova N.B. , Smolikov M.D. , Drozdov V.A. , Moroz E.M. 
Published: April 2011

AbstractThe investigation of surface Pt/alumina, Pt/ carbon (Sibunit) and Pt/SiO2 species prepared by anchoring of Pt carbonyl clusters of various nuclearity as precursors for high dispersive and thermostable platinum supported catalysts for hydrocarbons conversion, using RDF (radial distribution functions) and chemisorption methods, has shown strong metal-support interaction with formation of Pt/alumina phase with highly dispersed (practically monoatomic) and homogeneously distributed Pt atoms onto alumina surface. The catalytic properties were studied in methane oxidation and cyclohexane dehydrogenation reactions.
Heteropoly Acids Supported on Sol-Gel Matrices and Their Catalytic Activity and Selectivity
Authors: Grandstaff D.E. , Paciolla M. D. , Sein L.T. , Jacob R. , Narielwala K. , John S. , Patel N. , Kashani M. , Doll K. , Wei Y. , Jansen S. A. 
Published: April 2011

AbstractHeteropoly acids (HPA) are well known solid acids as well as oxidation catalysts. They find application in both homogeneous and heterogeneous reactions. As catalysts, problems associated with surface area and instability are diminished by supporting the HPA. It has been reported that supporting these materials on oxide substrates or porous carbon materials has resulted in some degree of instability. It has also been shown that encapsulating HPA in sol-gel silica matrices has produced an increase in catalytic performance without compromising the catalytic activity of the HPA. In this work, we analyzed the activity of a silica sol-gel supported HPA catalyst. The reaction which was chosen to illustrate such issues was the oxidation/dehydration of 1-butanol. In addition, the specific role of the support in the catalytic process is described. In this work, we characterized the silica-sol gel supported HPA catalyst to try to understand the effect of preparation in the overall catalytic selectivity and activity.
Activation of Alkanes by Transition Metal Nitrides and Carbides
Authors: Bennett C. A. , Neylon M. K. , Kwon H. H. , Choi S. , Curry K. E. , Thompson L. T. 
Published: April 2011

AbstractGroup V and VI nitrides and carbides were synthesized by the temperature programmed reaction of metal oxides with ammonia or an equimolar mixture of methane/hydrogen. The synthesis protocols were developed using thermogravimetric techniques. The resulting nitrides and carbides were primarily mesoporous and possessed surface areas in the range of 11 – 81 m2/g. Their alkane activation rates were comparable to a Pt-Sn/AL20 3 dehydrogenation catalyst and the surface area normalized reaction rates decreased in the following order: Mo2N > W2C > WC > W2N > WC1−x > VCoa0.05N > MO2C > VN = VC > NbMo0.01 N > NbMo0.05 > NbN = NbC. The activities measured at 450°C ranged between 1011 – 1013 molecules/cm2/s for n-butane and 1012 – 1013 molecules/cm2/s for n-hexane. The Group VI nitrides and carbides were far more active than the Group V materials. The Group VI materials catalyzed the hydrogenolysis and dehydrogenation reactions with similar activities whereas the Group V materials were more than 98% selective to dehydrogenation. While the metal atom type had the most significant effect on the catalytic properties, the lattice structure of the material also played a role. In particular, we observed that WC (hex) was almost twice as active as WC1-x (fcc). Nitrides and carbides of the same metal and lattice structure possessed similar catalytic properties, implying that the effect of the non-metal atom type was minimal. The W2N catalyst was found to be highly selective towards n-butane isomerization. The multimetallic nitrides each demonstrated some form of synergy.
Synthesis Of Highly Ordered Macroporous Minerals: Extension of the Synthetic Method to Other Metal Oxides and Organic-Inorganic Composites
Authors: Blanford C.F. , Do T.N. , Holland B.T. , Stein A. 
Published: April 2011

AbstractThe facile synthesis of three-dimensional macroporous arrays of titania, zirconia and alumina was recently reported [1]. The synthesis of these materials has now been extended to the oxides of iron, tungsten, and antimony, as well as a mixed yttrium-zirconium system and organically modi- fied silicates. These materials were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray energy dispersive spectrometry (EDS), and powder X-ray diffraction (XRD). Ordered structures of iron, tungsten, and antimony were formed from alkoxide precursors as in the originally reported synthesis, but the template was removed at a lower temperature. Samples of vinyl- and 2-cyanoethyl-modified silicates were formed from a mixture of organotrialkoxysilane and tetraalkoxysilane precursors; the polystyrene template was removed by extraction with a THF/acetone mixture. These results show the ease of extending the original syn- thesis to a wide range of systems. Also, the ability to form homogenous mixed-metal oxides will be important for tailoring the dielectric and photonic properties of these materials.
A New Generation of Ceramic Foams With Small Pore Size
Authors: Butcher Kenneth R. , Pickrell Gary R. 
Published: April 2011

AbstractA new process, GPM, has been developed to produce low density ceramic articles in any ceramic composition. This new process can produce articles with densities as low as 5% of the theoretical density (95% void fraction). The modulus of rupture values for the GPM material are in general 3-4 times as strong as the same density and composition ceramic foam. Products made with this new process are finding wide applicability in the catalyst and catalyst support media, low mass kiln furniture, ceramic pre-forms for metal/polymer infiltration and insulation markets. The microstructure, pore size and interconnectivity, and the fluid absorption properties of the GPM material are discussed.
Generation of Monodisperse Protein Nanoparticles by Electrospray Drying
Authors: Gomez A. , Bingham D. , de Juan L. , Tang K. 
Published: April 2011

AbstractThe feasibility of producing relatively monodisperse and biologically active protein particles by electrospray drying is demonstrated. The process entails dissolving dry powder in an electrosprayable solution. The solution is then dispersed and, after solvent evaporation, dry residues can be collected on suitable deposition substrates. The process was demonstrated in the case of insulin. Particles were sized visually, using a scanning electron microscope (SEM), and aerodynamically, using an inertial impactor. When electrosprays of nearly saturated solutions were operated in the stable cone-jet mode, impactor data showed that the particle average aerodynamic diameter ranged from about 88 to 110 nm in diameter and the distributions were quasi-monodisperse with relative standard deviation estimated at approximately 10%. SEM observations for the same conditions showed average particle dimensions ranging from 98 to 117 nm, with predominantly doughnut shapes. Smaller particles can be generated by decreasing the insulin concentration and/or by spraying smaller liquid flow rates. The biological activity of the electrospray-processed insulin samples was confirmed by comparing binding properties on insulin receptors against a control sample. Although the maximum production rate for monodisperse insulin nanoparticles from a single cone-jet is low, at about 0.23 mg/hour, overall production can be increased by multiplexing the device with microfabrication techniques.
Novel three Dimensional Biodegradable Scaffolds for Bone Tissue Engineering
Authors: Marra Kacey G. , Campbell Phil G. , Dimilla Paul A. , Kumta Prashant N. , Mooney Mark P. , Szem Jeffrey W. , Weiss Lee E. 
Published: April 2011

AbstractWe have constructed osteogenic scaffolds using solid freeform fabrication techniques. Blends of biodegradable polymers, polycaprolactone and poly(D,L-lactic-co-glycolic acid), have been examined as scaffolds for applications in bone tissue engineering. Hydroxyapatite granules were incorporated into the blends and porous discs were prepared. Mechanical properties and degradation rates of the composites were determined. The discs were seeded with rabbit bone marrow or cultured bone marrow stromal cells and in vitro studies were conducted. Electron microscopy and histological analysis revealed an osteogenic composite that supports bone cell growth not only on the surface but throughout the 1 mm thick scaffold as well. Seeded and unseeded discs were mechanically assembled in layers and implanted in a rabbit rectus abdominis muscle. Bone growth was evident after eight weeks in vivo. Electron microscopy and histological analyses indicate vascularization and primitive bone formation throughout the seeded composite, and also a “fusion” of the layers to form a single, solid construct. Finally, we have begun to incorporate the growth factor IGF-I into the scaffold to enhance osteogenicity and/or as an alternative to cell seeding.
An Approach to Classify Degradable Polymers
Authors: Burkersroda F. v. , Goepferich A. M. 
Published: April 2011

AbstractDespite tremendous progress towards a better understanding of polymer erosion, degradable polymers could so far not be classified according to their erosion behavior. It was the goal of this study to close this gap and to find those parameters that determine how a polymer erodes. Therefore, a dimensionless erosionnumber ε was defined, that can be calculated from the velocity of polymer degradation and water diffusion in the polymer bulk. s indicates whether erosion is a surface phenomenon (surface erosion) or whether it affects the complete polymer bulk bulk erosion). ε is characteristic for a polymer type and depends on the diffusivity of water inside polymer matrix, on the molecular weight of a polymer, and the dimensions of an eroding polymer matrix. The proposed erosion theory shows that ‘surface erosion’ and ‘bulk erosion’ are two potential erosion pathways that are open to any degradable polymer.
Cellular Adhesion and Spreading of Endothelial Cells Monitored in Real Time Using the Quartz Crystal Microbalance
Authors: Zhou Tiean , Braunhut Susan J. , Medeiros Diane , Marx Kenneth A. 
Published: April 2011

AbstractWe have applied the Quartz Crystal Microbalance (QCM) technique to continuously record the processes of endothelial cell (EC) adhesion, spreading and cellular mass distribution changes during initial cell to surface contact and homeostatic attachment. ECs (50,000) were layered onto a set volume of media in the QCM device and simultaneously in a mock cell used for photomicroscopy. As cells were observed in the mock cell device to contact and attach to the surface over 45-55 min, we measured in the QCM device a continuous decrease in frequency and continuous increase in resistance, achieving a maximum at about one hr (1400 Ω frequency change and 1400 Ω motional resistance change). These frequency and resistance values stabilized over the next 24 hrs and were unchanged out to 72 hr by QCM measurement (to ∼700 Hz, ∼700 Ω), as the cells were observed to spread in the mock device. Both bovine aortic (BAE) and bovine capillary (BCE) endothelial cells were studied and found to exhibit similar behavior. These studies demonstrate that QCM can be used to detect continuous changes in cell mass and viscoelastic behavior.
Artificial Protein Hydrogel Materials
Authors: Petka W. A. , Harden J. L. , Sakata J. K. , Tirrell D. A. 
Published: April 2011

AbstractRecombinant DNA methods were used to create a new class of artificial proteins that undergo reversible gelation in response to changes in pH or temperature. These proteins consist of terminal a-helical “leucine zipper” domains flanking a central, water-soluble polvelectrolyte segment. The formation of coiled-coil aggregates of the terminal domains in near-neutral pH solution triggers formation of a polymer hydrogel, with the central polyelectrolyte segment retaining solvent and preventing precipitation of the chains. Dissociation of the coiled-coil aggregates through elevation of pH or temperature causes dissolution of the gel and a return to the viscous behavior characteristic of a polymer solution. The pH and temperature range of the hydrogel state and its viscoelastic properties may be systematically varied through precise changes of the length, composition and charge density of the terminal and central blocks. Such control is of value in designing hydrogels with predetermined physical properties and makes these biosynthetic triblock copolymer systems attractive candidates for use in molecular and cellular encapsulation and in controlled reagent delivery.
Three Generations of Bile Acid Sequestrants
Authors: Mandeville W. Harry , Braunlin William , Dhal Pradeep , Guo Amy , Huval Chad , Miller Karen , Petersen John , Polomoscanik Steven , Rosenbaum David , Sacchiero Robert , Ward James , Holmes-Farley S. Randall 
Published: April 2011

AbstractCholestyramine, the first bile acid sequestrant to be marketed, has been in use for over 20 years. Despite its low potency, requiring 16-24 g of polymer to achieve 20% LDL cholesterol reduction in hypercholesterolemic individuals, only one other sequestrant, colestipol, has come to market in the ensuing period. GelTex Pharmaceuticals has been involved for over six years in the discovery and development of new, more potent polymeric sequestrants. Two binding mechanisms are presented — one that operates via an aggregate binding structure and one that is effective via a defined site binding structure. These two binding mechanisms are compared and contrasted through bile acid binding isotherms. The best of these new sequestrants bind bile acids through a combination of hydrophobicity and ion exchange. Optimization and balancing of each of these interactions led us to more potent materials. The first of these, colesevelam hydrochloride is expected to be three to four times more potent than cholestyramine. A third generation product is still in research at GelTex. With another twofold increase in potency possible, single tablet therapy may become a reality.
Resorbable Synthetic Bone Grafts Formed From a Silicon Stabilized Calcium Phosphate Bioceramic
Authors: Langstaff S. , Sayer M. , Smith T. , Pugh S. 
Published: April 2011

AbstractSynthetic bone grafts resistant to random dissolution at physiological pH, yet capable of being gradually resorbed in vitro by osteoclasts have been created. Bulk ceramics and ceramic coatings formed from an additive stabilized colloidal sol possess two characteristic features: a phase mixture of calcium hydroxyapatite (HA) and a silicon stabilized tricalcium phosphate, and a microporous morphology based on inter-connected particles (0.2-1.0 μm). The characteristic phase composition arises during sintering through substitution reactions where silicon enters the calcium phosphate lattice under conditions of high chemical reactivity. Evidence for in vitro resorption lacunae on bulk ceramics is presented.
Plasma Surface Modification of Medical-Grade Ultra-High Molecular Weight Polyethylene for Improved Tribological Properties
Authors: Klapperich C.M. , Komvopoulos K. , Pruitt L. 
Published: April 2011

AbstractUltra-high molecular weight polyethylene (UHMWPE) is the principal material used to replace damaged cartilage in total joint replacement surgeries. This publication presents preliminary results from a new class of surface treatments to modify the surface chemistry and microstructure of UHMWPE under controlled processing conditions. Radio frequency plasmas were used to lightly crosslink the subsurface of UHMWPE and to modify the surface chemical state through the attachment of low-surface-energy fluorocarbon groups. A pin-on-disk apparatus was used to slide CoCrWNi pins with spherical tips on polished disks of plasma- treated and untreated UHMWPE immersed in a bath of preserved bovine serum. The wear resistance and surface chemical composition of tested specimens were characterized by surface profilometry and X-ray photoelectron spectroscopy (XPS), respectively. Changes in the surface hydrophobicity due to plasma treatment were evaluated using contact angle measurements. The prospect of surface plasma treatment in orthopedic applications is elucidated in the context of the obtained friction, wear, distilled water contact angle, and XPS results.
Interspecies Uptake of Polymeric Microspheres
Authors: Thanos Chris , Sandor Maryellen , Jong Yong , Jacob Jules , Yip Kay-Pong , Harper James , Morrell Craig , Scherer Jennifer 
Published: April 2011

AbstractParticle uptake into intestinal tissue has seen increasing attention due to its implications in drug delivery. We attempted to observe a delivery system in vivo and examine uptake in different species. Microspheres were fabricated from polymers including polyanhydrides and delivered to an isolated loop of intestine in several species. The microspheres contained a dye either conjugated to a protein or incorporated freely and were used to qualitatively detect and locate the spheres in the villi of the length of the small intestine. Microspheres were dispersed, sized by a Coulter particle size analyzer, and characterized by confocal and cross-polarized light microscopy, FTIR and SEM. Coulter analysis revealed microspheres to be generally less than 5 microns in diameter. SEM typically showed homogeneous morphology among groups of microspheres. In vivo uptake experiments were performed in rodents, pigs, and ruminants using various microsphere formulations. Microspheres were delivered into the proximal end of the jejunum of anesthetized animals and allowed adequate transit time to be taken up. Animals were euthanized at various time points for explantation of tissue and sampling of blood. Excised samples were embedded inq polyvinyl alcohol, frozen, and cut into sections ranging between 7 and 14 μm in thickness. Our method of incorporating dyes allowed for simultaneous visualization by visible light microscopy and confocal laser scanning microscopy. Two-fluorochrome fluorescence of the microspheres and optical sectioning confirmed the presence of microspheres within intestinal tissue. The amount of uptake depended on the animal model, the duration of the experiment, and the composition of the microsphere. An assay for either the fluorescent dye, the protein attached to it, or the polymer encapsulating it may enable us to determine intracellular concentrations of mierospheres for the quantification of uptake.
Experimental Measurements of Nucleation Frequency and Crystal Growth Rate in Pd-Cu-Ni-P Metallic Glass
Authors: Nishiyama Nobuyuki , Inoue Akihisa 
Published: April 2011

AbstractCrystallization mechanism and kinetics of a Pd40Cu30Ni10P20 glass was investigated in a wide temperature range from 603 (near the glass transition temperature) to 764 K (near the equilibrium melting temperature) by using an isothermal annealing treatment for nucleation and growth. The nucleus density (nv) is about 5 × 1013 nuclei/m3 and is independent of annealing temperature. Therefore, it is assumed that the crystallization of the alloy was dominated by heterogeneous nucleation due to “quenched-in nuclei”. On the other hand, the crystal growth rate (Uc) increases from 1.07 × 10− to 5.68 × 10−5 m/s with rising annealing temperature from 603 to 764 K. These values of Uc are 2–3 orders of magnitude larger than the calculated Uc on the basis of Classical Nucleation and Growth Theory (CNT). Furthermore, the glass-forming ability of the alloy will be discussed in the framework of the present results.
Phase Equilibria in the Zr-Cu-Al System: Implications for Bulk Metallic Glass Formation
Authors: Syed S. A. , Swenson D. 
Published: April 2011

AbstractPreliminary phase equilibrium relationships have been established in the Zr-Cu-Al system at 800 °C, using a combination of X-ray diffraction and electron probe microanalysis. These results are similar to previous investigations that have been reported in the literature. Several ternary phases are found to exist in this system, many of which lie within the gross compositional vicinity of interest to bulk amorphous alloy formation. The equilibrium phases present in the alloy Zr65Cu27.5A17.5, which exhibits a particularly high Tx-Tg in the amorphous state, are Zr2Cu and minor amounts of two additional phases: Zr3Al and what may be a ternary phase with a composition near Zr6CuAl3. When the 800 °C phase diagram isotherm is correlated with the known glass forming composition range of the Zr-Cu-Al system, it is found that the best glass forming behavior is confined to those regions of the diagram in which all equilibria include Zr-Cu constituent binary phases and Al-poor ternary phases. This may suggest that difficulties in the nucleation of these binary phases plays a role in the glass forming ability of Zr-Cu-Al and related higher order alloys.