bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical and Structural Investigations on Mn-Ion States in MOCVD-grown Ga1−xMnxN
Authors: Martin Strassburg , Jayantha Senawiratne , Christoph Hums , Nikolaus Dietz , Matthew H. Kane , Ali Asghar , Christopher J. Summers , Ute Haboeck , Axel Hoffmann , Dmitry Azamat , Wolfgang Gehlhoff , Ian T. Ferguson 
Published: April 2011

ABSTRACTThe incorporation of Mn into GaMnN epilayers by MOCVD growth was investigated. Samples with high Mn concentrations lead to room temperature ferromagnetism. In addition an absorption band around 1.5 eV was observed. Intensity and linewidth of this band scaled with the Mn concentration and with the room temperature (RT) saturation magnetization. This band is assigned to the internal Mn3+ transition between the 5E and the partially filled 5T2 levels of the 5D state. The broadening of the absorption band is introduced by the high Mn concentration. Recharging of the Mn3+ to Mn2+ was found to effectively suppress these transitions resulting also in a significant reduction of the RT magnetization. The pronounced sensitivity of the relative position of the Fermi level and 1.5 eV absorption band can be used to predict the magnetization behavior of the Ga1−xMnxN epilayers. The absence of doping-induced strain was observed by Raman spectroscopy. The structural quality, the presence of Mn2+ ions were confirmed by EPR spectroscopy, meanwhile no Mn-Mn interactions were observed.
CMOS Compatible Erbium Coupled Si Nanocrystal Thin Films for Microphotonics
Authors: Stolfi M. , Dal Negro L. , Michel J. , Duan X. , Le Blanc J. , Haavisto J. , Kimerling L.C. 
Published: April 2011

ABSTRACTEr doped Si-rich SiO2 films were deposited through reactive RF magnetron co-sputtering and subjected to a single annealing step to simultaneously form silicon nanocrystals (Si-nc's) and activate the Er emission. Reference Er in stoichiometric SiO2 (Er:SiO2) films were deposited for comparison and the Er emission in the presence of Si-nc's was optimized with respect to the annealing temperature. The Er emission from Er in SiO2 containing Si-nc's (Er:SiO2+Si-nc) films is maximized at annealing temperatures between 600 °C and 800 °C, where the 1.54 μm emission is enhanced by more than two orders of magnitude relative to Er:SiO2 samples. Efficient energy coupling between Si-nc's and Er ions was demonstrated through excitation cross section measurements and non-resonant Er excitation experiments for samples annealed at temperatures as low as 600 °C. Since strong emission can be achieved from Er:SiO2+Si-nc films deposited through a standard CMOS process and annealed at temperatures below 700 °C, they can be used to fabricate CMOS compatible light
OPTICAL PROPERTIES OF Ge NANOWIRES GROWN ON SILICON (100) AND (111) SUBSTRATES
Authors: Sharma V. , Kamenev B. V. , Tsybeskov L. , Kamins T. I. 
Published: April 2011

ABSTRACTIn this paper, we report Raman Scattering (RS) and photoluminescence (PL) measurements of Ge nanowires (NWs) grown via vapor-liquid-solid (VLS) using chemical vapor deposition silicon substrates consisting of (100) and (111) crystallographic orientations. Ge NWs grown are ∼40 nm in diameter, approximately a micrometer in length, and a sharp narrow Raman peak at ∼300 cm−1 indicates single crystal quality. An absence of SiGe peak in the Raman spectra indicates that SiGe interdiffusion is insignificant for the NW volume. Low temperature PL-intensity-dependence spectra indicate that the observed emission originates at the Ge NW – Si substrate interface, where SiGe intermixing has been detected. This interface is formed differently for (111) and (100) oriented Si substrates due to the <111> preferential growth direction of Ge NWs.
Carrier Transport in One-dimensional Ge Nanowires/Si Substrate Heterojunctions
Authors: Lee Eun-Kyu , Kamenev Boris V. , Forsh Pavel A. , Kamins Ted I. , Tsybeskov Leonid 
Published: April 2011

ABSTRACTSamples of Ge Nanowires (Ge NWs) grown by chemical vapor deposition (CVD) on single crystal, (100) and (111) oriented Si substrates were studied with respect to their electrical properties. Using different contact geometries, direct current (DC) and alternating current (AC) electrical and photoelectrical measurements were carried out at room temperature. A rectifying junction behavior was observed indicating a low defect density at NWs/substrate heterointerface. AC conductance exhibits significant frequency dependence with a power law behavior, suggesting that carrier transport in Ge NW volume is associated with hopping processes.
Nanocomposite TiC/a-C coatings: structure and properties
Authors: De Hosson Jeff Th. M. , Pei Yutao , Galvan Damiano , Cavaleiro Albano 
Published: April 2011

ABSTRACTThis contribution deals with fundamental and applied concepts in nano-structured coatings, in particular focusing on the characterization with high-resolution (transmission) electron microscopy. Both unbalanced and balanced magnetron sputtering systems were used to deposit nc-TiC/a-C nanocomposite coatings with hydrogenated or hydrogen-free amorphous carbon (a-C) matrix, respectively. The contents of Ti and C in the coatings have been varied over a wide range (7∼45 at.% Ti) by changing the flow rate of acetylene gas or the locations of substrates relative to the center of C/TiC targets. Different levels of bias voltage and deposition pressure were used to control the nanostructure. The nanocomposite coatings exhibit hardness of 5∼35 GPa, hardness/E-modulus ratio up to 0.15, wear rate of 4.8×10−17 m3/Nm, coefficient of friction of 0.04 under dry sliding and strong self-lubrication effects. The nanostructure and elemental distribution in the coatings have been characterized with cross-sectional and planar high-resolution transmission electron microscopy (HRTEM) and energy filtered TEM. The influences of the volume fraction and size distribution of nano-crystallites TiC (nc-TiC) on the coating properties were examined.
Characterization of Electrochemically Activated Surface on Rolled Commercial AA8006 Alumnium
Authors: Yu Yingda , Sævik Øystein , Nordlien Jan Halvor , Nisancioglu Kemal 
Published: April 2011

ABSTRACTCommercial alloy AA8006 (nominal composition in wt%1.5Fe, 0.4Mn, 0.2Si) exhibits electrochemical activation in chloride media as a result of annealing at temperatures above 350°C. Activation is manifested by a significant negative shift in the corrosion potential and a significant increase in the anodic current when polarized above the corrosion potential in aqueous chloride solution. This phenomenon was correlated with the enrichment of trace element Pb at the oxide-metal interface. For fixed annealing time, maximum activation and Pb-enrichment are obtained at an annealing temperature of 450 °C independent of the original surface condition. Reduced activation with increasing temperature is attributed to increasing density of the spinel crystalline phase to cause the passivity of the surface.
Laser induced hierarchical nano-composites in metallic multi-films: structural characterization
Authors: Daniel C. , Mücklich F. 
Published: April 2011

ABSTRACTBiological solutions to enhance strength and stability often use lateral and hierarchical composite structures from nano- to micro-scale. The effect does not consist of a large chemical variety but it is realized by structural composites (namely phase changes and orientations). A new developed bio-mimetic laser interference metallurgical technique uses this biological approach to optimize mechanical properties of surfaces and thin films. A hierarchical nano-composite is realized by both a vertical nm-scaled period of PVD-processed multi-films and a lateral μm-scaled period of laser interference metallurgy.In past, laser interference irradiated Ni/Al multi-films showed periodical properties in the range of interference period. The hardness and modulus could be varied periodically and the texture and stress situation could be significantly changed.In this work, the micro-structural evolution of irradiated Ni/Al multi-films is analyzed by TEM measurements to justify the properties change. The grain size can be obtained to be laterally oscillating between 5 to 10 nm and up to 100 nm and the layer interface to be semicoherent. Up to a certain depth, intermetallic compounds are found in the layer interface.
Electron Microscopy Analysis on the Worn Surface of a High-Chromium White Iron During Dry Sliding Contact
Authors: Bedolla-Jacuinde A. , Rainforth W. M. 
Published: April 2011

ABSTRACTA series of microstructural phenomena within a thickness of material (tribolayer) below the worn surface, have been developed during dry sliding wear of a high-chromium cast iron. The overall wear behavior of the alloy is determined by the properties of this tribolayer. From the present work, a transmission electron microscopy analysis has been undertaken on the different features developing at different distances below the worn surface following wear sliding tests of a 17%Cr white cast iron alloy, whose microstructure is composed by 25% eutectic M7C3 carbides within an austenitic matrix. The observed phenomena is an increase in the dislocation density, plastic deformation by twinning followed by severe shear banding along with carbides fracture, a mechanical mixture formed by iron oxide and carbide particles produced from large carbides comminution, and finally a flat iron oxide layer. Wear debris was apparently created from the oxide film detaching from the outermost surface where equivalent strain is maximum. No evidence of strain induced martensite was observed from the present work, which has been reported in some austenitic materials. The implications of the microstructural evolution are discussed in terms of the wear theories and behavior of metals at high strains levels.
A Novel Polymer-Synthesized Ceramic Composite Based System for Bone Repair: Osteoblast Growth on Scaffolds with Varied Calcium Phosphate Content
Authors: Khan Yusuf M. , Katti Dhirendra S. , Laurencin Cato T. 
Published: April 2011

ABSTRACTPolymer/ceramic composite matrices for bone tissue engineering were constructed by synthesizing a poorly crystalline calcium phosphate within poly(lactide-co-glycolide) microspheres that were subsequently fused together to form 3-dimensional structures. Calcium ion dissolution from the composite matrices in simulated body fluid was examined over a 24 hour period. The initial 4 hour period showed an increase in calcium ion concentration, whereas, a decrease in calcium ion concentration was noted thereafter. This decrease in concentration coincided with the precipitation of calcium phosphate on the surface of the matrices. Osteoblast proliferation studies on composite matrices showed statistically significant increases in cell number throughout the 21 day time period. These data together suggest that the composite matrix acts as both a calcium ion donor for reprecipitation of calcium phosphate that may enhance osteointegration of the implant, and a suitable surface for osteoblast proliferation.
Microfabricated 3D Scaffolds for Tissue Engineering Applications
Authors: Mata Alvaro , Fleischman Aaron J. , Roy Shuvo 
Published: April 2011

ABSTRACTMicrofabrication and soft lithographic techniques are combined to develop three-dimensional (3D) polydimethylsiloxane (PDMS) scaffolds comprising multiple levels of meandering pore geometry textured with 10 μm posts. Both micro-architecture and surface micro-textures have been shown to selectively stimulate cell and tissue behavior. To achieve a 3D scaffold with precise micro-architecture and surface micro-textures, 100 μm thick PDMS films were manufactured using a stacking technique to realize a 66% porous 3D structure with 200 × 400 μm horizontal through holes, 300 μm diameter vertical through holes and 71% surface coverage with 10 μm diameter and 10 μm high posts. Each PDMS porous film level was manufactured by the dual-sided molding of uncured PDMS between a three level SU-8 photoresist mold (of 200, 10, and 100 μm thick features) and a PDMS mold with 10 μm deep micro-textures. Dual-sided molding was achieved using a custom motion control mechanical jig that allowed relative mold alignment to within ∼ ±10 μm.
Microfluidic Cell Volume Biosensor for High Throughput Drug Screening
Authors: Ateya Daniel A. , Sachs Frederick , Hua Susan Z. 
Published: April 2011

ABSTRACTThe maintenance of cell volume is critical to health. Cell volume change reflects many biological and physiological processes. We have developed a lab-chip to measure cell volume change in real-time with high sensitivity and resolution, and applicable to both adherent and suspended cell populations. The volume change was detected by measuring the impedance of extra-cellular solution within a microfluidic chamber containing the cells. Using microfabrication to make precise chamber dimensions, volume change can be detected in response to an osmotic gradient <1mOsm. The sensor provides rapid screening of pharmaceutical agents affecting cell volume. We have screened for peptides that affect cell volume regulation and found one in spider venom that inhibits at ∼100pM.
A novel nanofiber scaffold by electrospinning and its utility in microvascular tissue engineering
Authors: Han Dong , Goldgraben Sara , Frame Mary D. , Gouma Pelagia-Irene 
Published: April 2011

ABSTRACTCellulose acetate (CA) thin, porous membranes were produced by electrospinning precursor polymer solutions in acetone at room temperature. During this process, CA nanofibers were produced when a high electric field of 12 kV was applied to the precursor solution. The diameters of fibers obtained varied from 100 nm to 1.2 μm while the average diameter was approximately 500 nm. The electrospinning parameters used to control the morphology of the fibers and their membranes are flow rate, the distance between the syringe needle that ejects fluid and the collector, and the voltage applied. These membranes were used as scaffolds for microvascular cells growth. The structure of the membranes that were produced mimic the topography and porosity of extracellular matrix (ECM) in two key ways. The fiber diameter mimics extracellular protein fiber diameter, thus enabling cellular attachment and facilitating cellular migration. The porosity mimics that of extracellular matrix such that microvascular capillary tube formation is enhanced. The non-woven fiber mats were examined by means of electron microscopy and the nanofibers were seen to be oriented randomly. The issue of strengthening the CA scaffold is currently studied by adding ceramic nano-structured component (carbon nanotubes) in the polymer membranes.
Biodistribution and Tumor-Targeting Potential of Poly(Ethylene Glycol)-Modified Gelatin Nanoparticles
Authors: Kaul Goldie , Amiji Mansoor 
Published: April 2011

ABSTRACTIn order to develop a safe and effective systemically-administered delivery system for solid tumors, the biodistribution of control gelatin and poly(ethylene-glycol) modified (PEGylated) gelatin nanoparticles was examined in Lewis lung carcinoma (LLC)-bearing female C57BL6 mice. Type B gelatin and PEGylated gelatin nanoparticles were radiolabeled (125I) for the in vivo biodistribution studies after intravenous (i.v.) administration through the tail vein in LLC-bearing mice. At various time intervals, the tumor-bearing mice were sacrificed and tumor, blood, and major organs were harvested for analysis of radioactivity corresponding to the localization of the nanoparticles. Percent recovered dose was determined and normalized to the weight of the tissue or fluid sample. Non-compartmental pharmacokinetic analysis was performed to determine the long-circulating property and preferential tumor targeting potential of PEGylated gelatin nanoparticles in vivo. From the radioactivity in plasma and various organs collected, it was evident that the majority of PEGylated nanoparticles were present either in the blood pool or taken up by the tumor mass and liver. For instance, after 3 hours, the PEGylated gelatin nanoparticles were almost 2-fold higher in the blood pool than the control gelatin nanoparticles. PEGylated gelatin nanoparticles remained in the blood pool for a longer period of time due to the steric repulsion effect of the PEG chains as compared to the control gelatin nanoparticles. In addition, approximately 4-5% of the recovered dose of PEGylated gelatin nanoparticles was present in the tumor mass for up to 12 hours. The plasma and the tumor half-lives, area-under-the-curve, and the mean residence time of the PEGylated gelatin nanoparticles were significantly greater than those of the control gelatin nanoparticles. The results of the study confirmed long-circulating property and preferential tumor targeting potential of PEGylated gelatin nanoparticles in a murine tumor model.
Self-assembling Peptide Detergent A6D Directly Associates with Bovine Rhodopsin and Forms Lipid-like Vesicles
Authors: Zhao Xiaojun , Nagai Yusuke , Zhang Shuguang 
Published: April 2011

ABSTRACTMembrane protein study critically depends on detergents, which are amphilhilic molecules containing a hydrophilic “head” and a hydrophobic “tail” to mimic biological lipid bilayers to stabilize membrane proteins. However, detergents are not fully equivalent to lipid bilayers and in fact they only partly mimic lipid bilayers function. Consequently, membrane proteins in detergent solution are more or less denatured because detergents can not effectively stabilize membrane protein structures. Therefore, it is urgent to develop new types of detergents for more effectively stabilizing membrane proteins. Previously, we have reported a new type of self-assembly peptide detergents containing a hydrophilic head composed of either a negatively charged aspartic acid or a positively charged lysine and a tail of hydrophobic amino acids of six connective alanines. This new peptide detergent has been shown to be more effective for protecting membrane protein PS I structure than that the conventional detergent does. However, what type of physical structures peptide detergent can form is unclear yet. Here we presented our AFM and DSL analysis of the peptide detergent A6D, which not only form mixed micelles with n-Octyl-beta-D-Glucoside (OG) to solubilize membrane protein rhodopsin, but also can mimic lipid bilayers to keep rhodopsin in lipid-like vesicles for its structure preservation.
Processing and Development of Nano-Scale HA coatings for Biomedical Application
Authors: Rabiei Afsaneh , Thomas Brent 
Published: April 2011

ABSTRACTFunctionally graded Hydroxyapatite coating with graded Crystallinity across the thickness of the film has been processed and tested as a more effective orthopedic/ dental implant coating. The present study aims to increase the service-life of an orthopedic/ dental implant by creating materials that form a strong, long lasting, bond with the Ti substrate as well as juxtaposed bone. The health relatedness of the new material is to increase bonding between an implant and juxtaposed bone so that a patient who has received joint or dental replacement surgery may quickly return to a normal active lifestyle. Cross-sectional transmission electron microscopy analysis displayed that the films have a graded crystal structure with the crystalline layer near the substrate and the amorphous layer at the top surface. Compositional analysis was performed using SEM-EDX at the top surface as well as STEM-EDX at the cross section of the film. The average calcium to phosphorous ratio at the surface is 1.46, obtained by SEM-EDX. The Ca/P ratios in the crystalline and amorphous layers of the film are 1.6 to 1.7, close to the ratio of 1.67 for HA.
Preparation of textured bismuth titanate ceramics through templated grain growth combined with spark plasma sintering
Authors: Nishio Keishi , Maeda Rena , Kihou Junsuke , Kogo Yasuo , Kineri Tohru , Yasumori Atsuo 
Published: April 2011

ABSTRACTTextured bismuth titanate (Bi4Ti3O12), the simplest and best known compound among the bismuth layer-structure ferroelectrics is interesting because of its peculiar switching behavior which results from a small c-axis component of the spontaneous polarization and a small coercive force. We prepared Bi4Ti3O12 ceramics through the templated grain growth (TGG) method combined with the spark plasma sintering (SPS) method. The TGG method was developed to provide a simpler way of creating textured ceramic microstructures. The SPS method enables a compact powder to be sintered under uniform heating to a high density at relative low temperatures and with much shorter sintering periods than with conventional sintering.We obtained a Bi4Ti3O12 precursor powder through a co-precipitation method with Ti alkoxide and Bi oxide as raw materials. Platelet Bi4Ti3O12 was synthesized from the precursor powder through a flux method using NaCl and KCl. The obtained platelet Bi4Ti3O12 had a high aspect ratio. The ceramics were prepared by SPS treatment using a mixture of the platelet Bi4Ti3O12 and the amorphous precursor powder. As a result, dense ceramics could be easily obtained without crystalline amorphous precursors and grain growth was not observed during the sintering. After heat treatment of the ceramics, we obtained highly textured, high density Bi4Ti3O12 ceramics. The ceramics showed high orientation, above 70%, for the c-axis direction and high density of over 85%.
Growth of Yb:Y2O3 single crystals by the micro-pulling-down method
Authors: Novoselov A. , Mun J. H. , Yoshikawa A. , Boulon G. , Fukuda T. 
Published: April 2011

ABSTRACT(Ybx Y1-x)2O3 (x = 0.0, 0.005, 0.05, 0.08 and 0.15) promising single crystal laser rods of 4.2 mm in diameter and 15–20 mm in length have been grown from the rhenium crucible by the micro-pulling-down method in Ar + H2(3–4%) atmosphere. Linear decrease of lattice constant with the increase of Yb3+-content was observed. High homogeneity of the Yb3+-dopant distribution has been demonstrated. Absorption, emission and Raman spectra have been recorded and decay time was approximated.
Internal oxidation in solid solutions Bi2.1-xPbxSr2-yCa1-zRy+zCu2O8+d (R = Y, Nd or La).
Authors: Garshev A.V. , Knotko A.V. , Pulkin M.N. , Kirdyankin D.I. , Geyer A.V. , Putlayev V.I. 
Published: April 2011

ABSTRACTBi2-xPbxSr2CaCu2O8+d solid solutions with substitution of Sr or Ca by Y, Nd or La were fabricated at 760 - 79°C in N2-flow. The as-synthesized solutions were oxidized in air under isothermal condition and tested with XRD, TGA chemical analysis, TEM, XANES. Effect of rare-earth element content on oxidation kinetics and microstructure of the product is discussed.
Preparation of Boron Carbide Nanoparticles by Carbothermal Reduction Method
Authors: Chang Baohe , Gersten Bonnie , Adams Jane W. , Szewczyk Steve 
Published: April 2011

ABSTRACTA carbothermal reaction process was employed to synthesize nano-sized boron carbide particles. The reactions were carried out by heating a mixture of boric oxide powder and amorphous carbon reactant under a flow of argon atmosphere in a conventional high temperature tube furnace at 1350–1700 °C for 1–4 h. In order to obtain stoichiometric powder product, additional pure boron powder was added to the reaction mixture to compensate for the boron loss in the form of B2O2/B2O3vapor during the reaction. The effect of the structure and morphology of the precursor materials on that of the products was also investigated. X-ray diffraction (XRD) studies indicated that the powdered product prepared under optimized reaction conditions was crystalline boron carbide. Transmission electron microscopy (TEM) observations showed that the product nanoparticles ranged from 50 nm to 250 nm with the average size between 100 nm and 150 nm depending on the reaction conditions. Some boron carbide particles were as small as 50 nm. Energy dispersive spectroscopy (EDS) was also used to determine the stoichiometry of the boron carbide nanoparticle products.