bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biological Reaction to Electrically Polarized Hydroxyapatite
Authors: Sakai Tomoko , Ueshima Masato , Morita Sadao , Nakamura Satoshi , Yamashita Kimihiro 
Published: April 2011

AbstractWe have studied the polarized hydroxyapatite (HAp) whose surface was negatively or positively charged. In this study, we assessed the interfaces in vitro and in vivo periodically. As in vitro experiment, samples were immersed in simulated body fluid for 7 days and the surface was examined by scanning electron microscope (SEM). As in vivo experiments, cortical bone defects were created on the femoral trochanters and the condyles of the six Japanese white rabbits and the samples were implanted. The rabbits were sacrificed at 1, 2 and 4 W after the operation to analyze the surfaces by the SEM and the optical microscopy. In this study, a new thick apatite layer was formed on the negatively charged surface (N-surface) after 1week immersion in SBF in vitro. Besides, significant new bone formation was found at 2 weeks after the operation on N-surface in vivo, which was earlier than positively charged or non-polarized HAp surface. From this study negatively charged HAp surface by polarization accelerated the HAp crystal growth or the new bone formation. Thus, this N-surface will be promising for earlier fixation of the prosthesis or better recovery of the bone defect.
Using Indentation and Intra-Vascular Ultrasound to Measure Arterial Response
Authors: Anderson P.M. , Glaser E.N. , Veress A.I. , Pharr G.M. , Vince D.G. , Cornhill J.F. , Herderick E.E. 
Published: April 2011

AbstractTwo alternatives to standard tensile testing of arteries are discussed. The first involves inflation of arteries and simultaneous measurement of radial displacement with intra-vascular ultrasound (IVUS). The second involves the measurement of load versus displacement during micro-indentation of the intimal surface. The IVUS technique is used to study the nonlinear stiffening of porcine coronaries during inflation and, ultimately, it may provide a method to determine mechanical properties in vivo. Processing of the IVUS data relies on accurate determination of the luminal/intimal and medial/advential boundaries during inflation. The microindentation technique is used to study the effect of loading rate on tissue stiffness, recovery, and internal dissipation. Ultimately, this technique may provide a method to measure local mechanical properties in the vicinity of an atherosclerotic plaque, for example. Accurate determination of the initial contact point between the indenter and intima is required, however. The techniques appear to successfully capture significant, nonlinear, time-dependent properties of arterial tissue.
Controlled Release of Bone Growth Factors from Injectable, Biodegradable Polymer Scaffolds for Bone Tissue Engineering
Authors: Hedberg Elizabeth L. , Mikos Antonios G. 
Published: April 2011

AbstractThe objective of this research is to fabricate injectable, polymeric composites that will act as scaffolds for bone ingrowth as well as carriers for the controlled release of bone growth factors. To that end, the injectable polyester poly(propylene fumarate) (PPF) was loaded with poly(DLlactic-co-glycolic acid) (PLGA) microparticles carrying the model drug FITC-dextran. This preparation was then crosslinked with N-vinyl pyrrolidinone in the presence of benzoyl peroxide as initiator and sodium chloride (NaCl) as leachable porogen. The encapsulation of growth factors in microparticles is necessary to minimize their denaturation during scaffold crosslinking. PLGA microparticles (0.04 g microparticles/g PPF) were incorporated into PPF composites having variable NaCl weight percents (50 and 70 wt% NaCl) and the effect on FITC-dextran release kinetics was determined in vitro for cylinders of diameter 6.5 mm and height 13.0 mm. The FITC-dextran loaded microparticles alone exhibited a large initial burst effect, while the composite materials displayed a smaller burst effect and a longer linear region of release. At day 3, 54.6±2.1%, 5.1±0.9%, and 12.5±0.3% of loaded FITC-dextran was released into pH 7.4 phosphate buffered saline from the microparticles, the 50 wt% NaCl, and the 70 wt% NaCl composites, respectively. By day 28, 90.9±6.9%, 12.7±1.7%, and 34.4±0.4% of loaded FITC-dextran was released. Our results demonstrate that PLGA microparticles can be incorporated into PPF composites and that the release kinetics of FITC-dextran can be systematically manipulated through alteration of the composite initial salt content.
Admittance Spectroscopy on Polymer Light-Emitting Diodes
Authors: Blom P.W.M. , Martens H.C.F. , Brom H.B. , Huiberts J.N. 
Published: April 2011

ABSTRACTFrom admittance spectroscopy measurements on poly(p-phenylene vinylene) based light-emitting diodes various relaxation processes can be observed. At low bias inductive contributions due to the transit of charge carriers dominate, at high bias capacitive contributions as a result of charge redistribution appears. These processes reveal a transition from space-charge limited to recombination limited behavior, as is also indicated by the current-voltage characteristics.
Metal-to-Ligand Charge Transfer Excited States in π-Conjugated Systems
Authors: Li Yiting , Whittle C. Ed , Walters Keith A. , Ley Kevin D. , Schanze Kirk S. 
Published: April 2011

ABSTRACTThis paper overviews recent work that examined the optical properties of mono-disperse, PPE-based π-conjugated oligomers that contain a 2,2-bipyridine-5,5'-diyl metal coordinating unit. The photophysical properties of the free oligomers and metallated oligomers that contain the -Ru(bpy)22+ and -Re(CO)3Cl transition metal complexes coordinated to the bpy-diyl unit have been characterized by absorption, photoluminescence and transient absorption spectroscopy. In addition, we report the photophysics of a novel organometallic “square” that features “sides” consisting of a PPE-type π-conjugated oligomer and “corners” that consist of (dbubpy)PtII(acetylide)2 units (where dbubpy = 4,4'-di-tert-butyl-2,2'-bipyridine).
Approaches to Advanced Organic Light Emitting Diodes: Materials and Devices
Authors: Ikai Masamichi , Taga Yasunori 
Published: April 2011

ABSTRACTWe present our recent findings on the development of organic light emitting diodes (OLEDs). One of the keys to highly efficient phosphorescent emission in organic light-emitting diodes is to confine triplet excitons generated within the emitting layer. To confine triplet excitons, we employ perfluorinated phenylene dendrimers (C60F42) as a both hole- and exciton-block layer, and a hole-transport material (4,4',4”-tris(N-carbazolyl) triphenylamine [TCTA]) as a host for the phosphorescent dopant, Ir(ppy)3, in the emitting layer. The maximum external quantum efficiency reaches to 19.2%, and is over 15% even at high injection current densities of 10 to 20 mA/cm2, where the brightness of the device reaches to approximately 10,000 cd/m2.
A Mercury Selective Electrode
Authors: Scaggs Jon , Russell Dale D. , Duttagupta S. P. , Hill Michael W. 
Published: April 2011

ABSTRACTA novel mercury ion selective electrode has been constructed to have strongly coordinating macrocyclic ligand binding site covalently attached to polythiophene film using 1-1,4,10-trioxa-7,13-diazacyclopentadecane-1-thiophenylmethane (TDCD-thiophenylmethane) as a specific chelator. In amperometric mode, the current is proportional to mercury (II) concentrations down to 2 ppb. Reversible cyclic voltammetric waves show that both mercury (I) and mercury (II) are stabilized by the ligand. Monomethyl mercury and vapor phase elemental mercury are also electrochemically determined. Dissolved oxygen and heavy metal cations show no significant interference even at ten times the mercury concentration. The polymer surface shows robust performance for two years or longer. Fabrication strategies are being developed to optimize the probe performance. The variables under investigation include substrate surface roughness, the ratio of derivitized thiophene (TDCD-thiophenylmethane) to underivatized thiophene in the surface polymer, ratio of thiophene with two chelating rings to thiophene with only one, number and thickness of electrodeposited polymer layers, composition of polymer layers, and number of -CH2- units separating the chelating ring from the thiophene monomer units. The probe exhibits linear response to mercury concentration, and detects mercury in several forms.
The Relationship Between Molecular Structure and Spectroscopic Properties of a Series of Transition Metal-Containing Phenylacetylene Oligomers and Polymers
Authors: Cooper Thomas M. , McLean Daniel G , Rogers Joy E. 
Published: April 2011

ABSTRACTTo develop novel nonlinear dyes for photonic applications, we synthesized a series of transition metal-containing phenylacetylene oligomers and polymers. The optical properties of these compounds were measured by UV/Vis, fluorescence, and flash photolysis experiments. As the number of oligomer units increased, the transition energies decreased. A solvatochromism experiment suggested the fluorescing state was different from the absorbing state. As a group, the spectra of the polymeric versions of these complexes were red shifted from the spectra of the oligomers. The polymeric complexes had less clear trends relating the number of oligomer units to transition energies. A comparison of a low molecular weight and a high molecular weight polymer showed the degree of polymerization caused spectroscopic shifts comparable to the number of phenylacetylene units in the monomer unit.
Investigation of Morphology and Interface in Polymer Composite Thin Films
Authors: Chiang C. K. , Sung L. P. , Popielarz R. 
Published: April 2011

ABSTRACTLaser scanning confocal microscopy (LSCM) has been applied to examine the filler particles and their distribution in BaTiO3-polymer composite films. We have measured thin-slice images of the composite films at various depths from the film surface and visualized the submicron size particles and the polymer between them nondestructively. We have found that, although BaTiO3 particles appear to be uniformly dispersed in the composite films when observed under conventional microscope, the particles form clusters at low BaTiO3 concentrations. The lower the concentration the larger the cluster size. The particles appear to be better dispersed in the high concentration composites than at low concentrations.
Charge Transport in Pentacene Thin Film Transistors
Authors: Schön J. H. , Buchholz L. D. , Kloc Ch. , Batlogg B. 
Published: April 2011

ABSTRACTThe charge transport properties in polycrystalline pentacene thin film transistors is investigated. A potential barrier is formed at grain boundaries due charged trapping states. The influence of such grain boundaries on the hole mobility of the devices is analyzed for different grain sizes, trap concentrations, and carrier densities. The results reveal that room temperature mobilities exceeding 0.5 cm2/Vs can be obtained in thin films with large grains as well as in nanocrystalline material. Consequently, single crystal device limits can be reached also by polycrystalline pentacene thin film transistors.
A Comparative Study of the Photophysics in Polyfluorenes and Polyfluorenes with Polyphenylene Dendron Sidechains
Authors: List E. J. W. , Pogantsch A. , Wenzl F.P. , Kim C.-H. , Shinar J. , Loi M. A. , Bongiovanni G. , Mura A. , Setayesh S. , Grimsdale A. C. , Nothofer H.G. , Müllen K. , Scherf U. , Leising G. 
Published: April 2011

ABSTRACTThe cw absorption, steady state photoluminescence (PL), photoinduced absorption (PA), PL-detected magnetic resonance (PLDMR), and the time resolved PL of a novel polyfluorene (PF) prepared with bulky polyphenylene dendrimer substituents are compared with those of (PF) with ethyl-hexyl substituents. We show that the dendronic sidechains suppress the contribution from unwanted low energetic emission, yielding a polymer with pure blue emission. The sidechains also strongly alter the dynamics of the excited entities. In particular, the time-resolved PL and temperature-dependence of the cw PL from 20-320 K reveal distinct singlet exciton (SE) dynamics in the polymer films, while the behavior in solution is essentially the same. However, the PA results show that the dynamics of polarons and triplet excitons (TEs) are similar, and the PLDMR shows that the interaction between the SEs and polarons are also similar.
Structural Properties of Conjugated Molecular Crystals Under high Pressure
Authors: Heimel Georg , Zojer Egbert , Resel Roland , Pushning Peter , Weinmeier Kerstin , Ambrosch-Draxl Claudia 
Published: April 2011

ABSTRACTElectro-active organic materials based on conjugated molecules, showing promising optical features in the UV/Vis region combined with high electron mobility and fluorescence quantum yield, are of great interest for both, scientific and commercial use. Since the electro-optical properties of these materials are critically influenced by their the crystal and molecular structures, the goal of our work is to study the nature of the intermolecular interactions by applying hydrostatic pressure. X-Ray powder diffraction experimets were carried out to determine the lattice parameters. These experimental data then served as an input for an optimization of the atomic positions and molecular orientation based on total -energy and atomic-force computations within density functional theory.
Esr Investigations On Polyaniline-Polyvinylchloride Blends
Authors: Chipara M. , Goovaerts E. , Chipara Magdalena , Munteanu I. 
Published: April 2011

ABSTRACTElectron spin resonance (ESR) investigations on blends of polyaniline (PANI) and polyvinylchloride (PVC), containing different amounts of PANI, ranging from 0 to 40% (in weight), are reported. The temperature dependence of resonance line parameters, in the temperature range 150 K to 500K is analyzed. It is proved that the high spins bipolarons are not contributed to the ESR spectrum and that the resonance spectrum does not contain contributions due to extremely high conducting islands, with lengths of the order of at least 1micron. From the temperature dependence of the double integral of the resonance line, it is concluded that, the blends exhibit an almost pure paramagnetic behavior and that at short times physical processes control the behavior of these blends. At long times (102 to103 hours), the resonance spectrum is drastically reduced due to the consumption of free electrons in the chemical reactions involved by the degradation processes occurring mainly in PVC. A stationary value is reached for storage times of about 2500 hours, in air, at room temperature.
Solvent-enhanced Dye Diffusion in Polymer This-Films for OLED Application
Authors: Pschenitzka F. , Long K. , Sturm J. C. 
Published: April 2011

ABSTRACTA method of solvent-enhanced dye diffusion in polymer films for organic light-emitting diode (OLED) application is introduced. After an initial dye transfer from a dye source substrate into the top of the electractive polymer film, the device substrate is then exposed to solvent vapor. Due to solvent absorption by the polymer film, the glass transition temperature of the polymer is significantly decreased, which leads to greatly enhanced diffusion of the dye in the polymer film. Secondary ion mass spectroscopy shows that the temperature for dye diffusion can be decreased by 150 °C. OLEDs with 0.4% external quantum efficiency were demonstrated. The materials used are the polymer poly(9-vinylcarbazole) (PVK) combined with electron transport molecules (PBD), and the dyes coumarin 47, coumarin 6 and Nile red.
Transparent Conductive Oxide Semiconductor ZnO:Al Films Produced by Magnetron Reactive Sputtering
Authors: Meng Chen , Zhiliang Pei , Xi Wang , Cao Sun , Lishi Wen 
Published: April 2011

ABSTRACTZnO:Al (ZAO) films were deposited on quartz substrates by dc magnetron reactive sputtering from a Zn target mixed with Al. The effect of substrate temperature and Al doping content on the structural, electrical and optical properties of ZAO films were investigated. It was observed that the (002) peak position of all films shifts to lower angle comparable to that of bulk ZnO due to the residual stress change with deposition parameters. The dependences of electrical properties such as resistivity, carrier concentration and Hall mobility on substrate temperature and Al doping content were measured. The minimum resistivity is 4.23×10−4 ω.cm with the carrier concentration of 9.21×1020 cm−3 and Hall mobility of 16.0 cm2v−1s−1. The visible transmittance of above 80% was obtained. The optical band gap was observed to increase with increasing carrier concentration. The possible mechanisms are discussed.
Transparent Conductive Tin Doped Indium Oxide Thin Films with Silver Additive
Authors: Hultåker Annette , Lu Jun , Olsson Eva , Niklasson Gunnar A. , Granqvist Claes-Göran 
Published: April 2011

ABSTRACTThin films of intermixed layers of In2O3:Sn (denoted ITO) and silver were made by reactive dc magnetron sputtering. The silver to indium atomic ratio was 0 ≤ x ≥ 0.09 Films with x = 0.01 showed increased luminous transmittance Tlum after annealing at 100 or 200°C, whereas x > 0.01 yielded lowered Tlum. The optical properties could be reconciled with the Maxwell-Garnett effective medium theory assuming that a well-defined portion of the silver was occluded as spheroidal particles. Films with x ≤ 0.06 had enhanced electrical conductivity after annealing at 200 or 300°C. Transmission electron microscopy displayed columnar features whose character depended on x.
Doping Experiments in ZNO
Authors: Stauber R.E. , Parilla P.A. , Perkins J.D. , Cueto J.A. Del , Ginley D.S. 
Published: April 2011

ABSTRACTThis paper reports on attempts to fabricate transparent electrically conductive p-type ZnO by pulsed laser deposition (PLD) and sputtering using N2, N2O and NO gases. Expanding on the work of Kawai and coworkers [1,2], we used an ion source, rather than an ECR source in the PLD chamber to dissociate N2O gas, and explored the use of aluminum in addition to gallium as potential co-dopants. The most promising results have been obtained with DC reactive sputtering of gallium-doped zinc metal targets. A three to six order of magnitude reduction in n-type carrier density was observed when 2% of the argon sputtering gas was replaced with NO.
Thin Film Growth of Zinc Oxide by Vapor Phase Epitaxy
Authors: Ellis James A. , Seng William F. , Barnes Peter A. 
Published: April 2011

ABSTRACTZinc Oxide is a potentially valuable semiconductor with photoconducting, piezoelectric, optoelectronic, and optical waveguide applications. A technique for the growth of ZnO epitaxial layers is necessary for improved device fabrication. Previously, attempts at ZnO epitaxial growth were constrained to sapphire substrates using sputtering as the preferred preparation technique. However, with the present availability of single crystal ZnO substrates the hope of high quality epitaxial layers exists. The authors will discuss several possibilities for growth precursors, and the resulting chemical reactions required for the formation of ZnO. This presentation discusses the growth of ZnO epitaxial layers by chemical vapor deposition without using metal-organic compounds. The thermodynamics and predicted growth rates for several reactions are presented as well as the preliminary growth results. The preliminary growths are characterized with the aid of Hall Effect measurements, providing information on resistivity, Hall mobility, and carrier concentration.
Transparent p-n Heterojunction Thin Film Diodes
Authors: Jayaraj M. K. , Draeseke A. D. , Tate J. , Hoffman R. L. , Wager J. F. 
Published: April 2011

ABSTRACTTransparent p-n heterojunction diodes are fabricated using p-type CuYO2:Ca and n-type ZnO:Al thin films on a glass substrate coated with indium-tin oxide (ITO). The contact between the n-ZnO:Al / p-CuYO2:Ca heterojunction is found to be rectifying, while the ITO / ZnO:Al contact is ohmic. The typical ratio of forward to reverse current is 15 in the range -3 to 3V. The diode current-voltage characteristics are dominated by the flow of space charge limited current, which is ascribed to the existence of an insulating ZnO interfacial layer. The diode structure has a total thickness of 0.85 μm and an optical transmission of 40%-50% in the visible region.
Prospects for the Mott Transition Field Effect Transistor
Authors: Misewich J.A. , Schrott A.G. 
Published: April 2011

ABSTRACTWe have been investigating the potential for a channel transistor which utilizes a perovskite oxide capable of undergoing the Mott metal-insulator transition as the channel material. Our experiments have identified three limitations to the performance of the oxide devices: contact resistance to the channel, mobility limitations due to polycrystalline channels, and inadequate field induced surface charge density. In this paper we review progress we have made in oxide electrodes and in improving channel growth conditions which have mitigated the limitations due to contact resistance and polycrystalline channels. We conclude with an outline of our approach to improving the field induced surface charge density.
Structural and Electrical Properties of Y2O3 Buffer Layer Prepared by Two Step Process
Authors: Lim Dong-Gun , Jang Bum-Sik , Moon Sang-Il , Jang Dong-Min , Heo Jinhee , Yi Junsin 
Published: April 2011

ABSTRACTIn this paper we investigated a feasibility of Y2O3 films as a buffer layer of MFIS (metal ferroelectric insulator semiconductor) type capacitor. Buffer layers were prepared by two-step process of a low temperature film growth and subsequent RTA treatment. Investigated parameters are given as substrate temperature, O2 partial pressure, post-annealing temperature, and suppression method of interfacial SiO2layer generation. By employing an ultra thin Y pre-metal layer, unwanted SiO2 layer generation was successfully suppressed at an interface between the buffer layer and Si substrate. By using two-step process, we improved the leakage current density of Y2O3 films by 2 orders and the Dit as low as 8.72×1010 cm−2eV−1. For a substrate temperature above 400°C and O2 partial pressure of 20%, we observed cubic Y2O3 phase domination in XRD spectra. We achieved 1.75% lattice mismatch between Y2O3 film and silicon substrate. Y2O3 buffer layer for a single transistor FRAM exhibited optimal properties when it was grown at 400°C with 20% O2 partial pressure then RTA treatment at 900°C in oxygen ambient.
Application of ultraviolet radiation to minimize interfacial layer formation during the growth of alternate high-k gate dielectrics on Si
Authors: Craciun V. , Bassim N. D. , Howard J. M. , Spear J. , Bates S. , Singh R. K. 
Published: April 2011

ABSTRACTYttrium oxide and barium strontium titanate (BST) thin films were grown directly on Si substrates by the pulsed laser deposition (PLD) technique. Because the optimum oxygen pressure during PLD process is of the order of 10 mTorr, some of the oxygen atoms are trapped inside the grown films and contribute to the growth of a silicon oxide interfacial layer. The use of an UV source during the growth resulted in the reduction of the optimum oxygen pressure and, as a consequence, the amount of trapped oxygen and thickness of the interfacial layer. In addition to that, UV radiation influenced the film morphologies and electrical properties. A further reduction of the interfacial layer was obtained on substrates that were exposed prior to deposition to NH3 for short periods of time under UV radiation.