bluuebunny/crossref_metadata_2025 huggingface dataset:
Junction Temperature Measurements in Deep-UV Light-Emitting Diodes
Authors: Xi Y. , Xi J.-Q. , Gessmann Th. , Shah J. M. , Kim J. K. , Schubert E. F. , Fischer A. J. , Crawford M. H. , Bogart K. H. A. , Allerman A. A.
Published: April 2011

The junction temperature of AlGaN/GaN ultraviolet (UV) Light-Emitting Diodes (LEDs) emitting at 295 nm is measured by using the temperature coefficients of the diode forward voltage and emission peak energy. The high-energy slope of the spectrum is explored to measure the carrier temperature. A linear relation between junction temperature and current is found. Analysis of the experimental methods reveals that the diode-forward voltage is the most accurate method (± 3 °C). A theoretical model for the dependence of the diode junction voltage (Vj) on junction temperature (T) is developed that takes into account the temperature dependence of the energy gap. A thermal resistance of 87.6 K/W is obtained with the AlGaN/GaN LED sample mounted with thermal paste on a heat sink.
Nitride-Based Light-Emitting Diodes Grown on Particular Substrates: ZrB2,(3038) 4H-SiC and r-faced Sapphire.
Authors: Kamiyama Satoshi , Iwaya Motoaki , Amano Hiroshi , Akasaki Isamu
Published: April 2011

New substrate materials; ZrB2,(3038) 4H-SiC and r-faced sapphire, are evaluated for use in nitride-based light-emitting diodes (LEDs). They are thought to be suitable for low-cost, short-wavelength, and highly efficient light-emitting devices. The ZrB2 substrate presents a high-quality nitride layers and a blue-violet LED with an excellent L-I curve. A vertical electrical transport is also possible due to its preferable work function and high electrical conductivity. Nitride layers tilted 54.7° from the c-plane can be grown on (3038) 4H-SiC. The LED grown on the (3038) 4H-SiC substrate shows a smaller blue shift of the EL peak wavelength with increasing driving current. Although the crystalline quality of nitride layers on r-faced sapphire was improved with the optimization of the misorientation angle, the performance of blue-violet LEDs is still low. Further work is needed to enable the practical application of r-faced sapphire to nitride-based LEDs.
Pressure dependence of elastic constants in wurtzite and zinc-blende nitrides and their influence on the optical pressure coefficients in nitride heterostructures
Authors: Łepkowski Sławomir P. , Majewski Jacek A.
Published: April 2011

We have studied the nonlinear elasticity effects in III-N compounds. Particularly, we have determined the pressure dependences of elastic constants in wurtzite and zinc-blende InN, GaN, and AlN by performing ab-initio calculations in the framework of plane-wave pseudopotential implementation of the density-functional theory. We have found that C11, C12 in zinc-blende phase and C11, C12, C13, C33 in wurtzite phase depend significantly and almost linearly on hydrostatic pressure, for all considered nitrides. Much weaker dependences on pressure have been observed for C44 in both wurtzite and zinc-blende phases. Further, we have examined the influence of pressure dependence of elastic constant on the pressure coefficient of light emission, dEE / dP, in wurtzite and cubic, InGaN/GaN and GaN/AlGaN quantum wells. We show that the pressure dependence of elastic constants results in significant reduction of dEE / dP in nitride quantum wells and essentially improves the agreement between experimental and theoretical values.
Relationship of basal plane and prismatic stacking faults in GaN to low temperature photoluminescence peaks at ∼3.4 eV and ∼3.2 eV
Authors: Bai J. , Dudley M. , Chen L. , Skromme B. J. , Hartlieb P. J. , Michaels E. , Kolis J. W. , Wagner B. , Davis R. F. , Chowdhury U. , Dupuis R. D.
Published: April 2011

The relationship between the optical properties and microstructure of GaN is of great interest due to the important optical and electronic applications of this material. Several different studies have been reported attempting to link the low temperature photoluminescence (PL) peak at ∼3.4 eV to the presence of various microstructural defects. However, no clear systematic studies have been reported establishing such a link for the PL peak observed at ∼3.2 eV. In this paper, we present evidence linking the ∼3.4 eV PL peak to the presence of a thin layer of cubic phase associated with basal plane stacking faults (BSF). This relationship is mainly established by studying a series of ammonothermally-grown GaN bulk crystals. The existence and strength of the ∼3.4 eV peak are found to be related to the I2 type BSF (RI2=1/3<1>) observed in these samples. To investigate the relationship between the ∼3.2 eV peak and structural defects, a series of GaN epilayers grown on either SiC or sapphire (of various off-cut angles) was investigated by TEM and PL spectroscopy. Samples grown on 3.5° off-cut SiC and 5° and 9° off-cut sapphire substrates exhibit PL peaks near ∼3.2 and ∼3.4 eV, which are absent in the on-axis SiC and sapphire cases. TEM shows that the former group of samples has defect configurations consisting of prismatic stacking faults (PSFs) folding back and forth between two different {1120} planes connected by stair rod dislocations, which in turn fold onto to I1 type BSFs again with stair rod dislocations at the fault intersections. The ∼3.2 eV PL peaks are proposed to possibly arise from transitions involving the PSFs and the stair rods associated with their mutual intersections and their intersections with the BSFs. The ∼3.4 eV peak is again attributed to the thin layer of cubic phase associated with the I1 type BSF (three bilayers as opposed to four bilayers for the I2 type BSF).
Direct AFM Observation of Strain Effects on MOCVD-Grown GaN Epilayer Surface Morphology
Authors: Florescu D.I. , Lee D.S. , Ramer J.C. , Merai V.N. , Parekh A. , Lu D. , Armour E.A. , Quinn W.E.
Published: April 2011

In this study, we investigate the dependence of GaN surface morphology on the absolute strain values for thin (<10 μm) epitaxial films grown by MOCVD on c-plane sapphire substrates of various miscut angles towards the m-plane. Results indicate an excellent correlation between the surface roughness observed employing an AFM tool and epilayer strain values. An overall increase of surface roughness (decrease of atomic terrace width) is found with decreasing compressive strain (epilayer vs. bulk value). In addition, sapphire substrates with increasing miscut angle (0.30 deg) appear to relax the inherent, built-in strain differently in the vertical (growth) direction when compared to just (0.00 deg) substrates. Strain relaxation by typical V-shaped, hexagonal pits is directly imaged through the comparison of surface features inside and outside of pits in the thin GaN epilayer films.
X-ray Excited Optical Luminescence Studies of InGaN and Rare-Earth Doped GaN Epilayers
Authors: Katchkanov V. , Mosselmans J.F.W. , O'Donnell K.P. , Poolton N.R.J. , Hernandez S.
Published: April 2011

A successful attempt to use X-ray Excited Optical Luminescence (XEOL) for the detection of Extended X-ray Absorption Fine Structure (EXAFS) in III-nitrides is reported. The samples studied were InGaN and rare-earth (RE) doped GaN epilayers. For the first time Ga K-edge EXAFS oscillations were measured by monitoring the well-known “yellow” emission of GaN at 560 nm. The analysis of Optically Detected (OD) EXAFS data confirmed the expected local structure for Ga in GaN. The intensity oscillation of the “yellow” band when X-ray energy was scanned across the Ga K-edge indicates that core excitation of Ga atom has a high probability of transfer to defects responsible for “yellow” emission.
Discrete Steps in the Capacitance-Voltage Characteristics of GaInN/GaN Light Emitting Diode Structures
Authors: Xia Y. , Williams E. , Park Y. , Yilmaz I. , Shah J.M. , Schubert E.F. , Wetzel C.
Published: April 2011

A detailed modeling of the electronic bandstructure of GaInN alloys and GaInN/GaN heterostructures typically used for high efficiency light emitting diodes is of high relevance for future improvements. Here we are exploring opportunities to accurately quantify the carrier dynamics under forward and reverse voltage bias. In GaInN/GaN LED-type heterostructures we observe distinct steps in the junction capacitance as a function of bias voltage within the depletion regime. Up to three individual steps can be identified that correspond to alternating ranges of capacitive and resistive impedances. Our analysis suggests that we are quantitatively monitoring the electron concentration in each individual quantum well. The pronounced clarity of the data reveals a high level of epitaxial perfection and spatial homogeneity across the entire area of the junction.
Impact of Manganese incorporation on the structural and magnetic properties of MOCVD-grown Ga1−xMnxN
Authors: Kane Matthew H. , Asghar Ali , Strassburg Martin , Song Qing , Payne Adam M. , Summers Christopher J. , John Zhang Z. , Dietz Nikolaus , Ferguson Ian T.
Published: April 2011

This paper reports the impact of the Mn incorporation on the structural and magnetic properties of Ga1−xMnxN on the metal-organic vapor phase deposition (MOCVD). Crystalline quality and phase purity were determined by high-resolution X-ray diffraction and indicated that no macroscopic second phases are formed during growth. Atomic force microscopy revealed a 2-dimensional MOCVD step-flow growth pattern in the Mn-incorporated samples. Various annealing steps were applied to some of the samples to reduce compensating defects and to investigate the effects of post processing on the growth. SQUID measurements showed an apparent ferromagnetic hysteresis behavior. However, none of the requirements for room temperature ferromagnetism in the prevailing mean field DMS theories were found. Therefore, different origins of the ferromagnetic signal are discussed.
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

The 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

Er 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

In 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

Samples 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

This 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

Commercial 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

Biological 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

A 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

Polymer/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

Microfabrication 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

The 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

Cellulose 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

In 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

Membrane 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

Functionally 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

Textured 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

(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

Bi2-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

A 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.
Bimodal size distribution of gold nanoparticles in aqueous solution during pulsed laser irradiation
Authors: Inasawa Susumu , Sugiyama Masakazu , Yamaguchi Yukio
Published: April 2011

Size distribution of gold nanoparticles in aqueous solution during pulsed laser irradiation (Nd:YAG laser, wavelength of 355 nm, pulse width 30 ps) is observed by transmission electron microscope (TEM). Interestingly, we observed that a single peak distribution of gold nanoparticles sizes (initially centered around 25 nm) is gradually turned into a two-peaks one upon laser radiation. Initial particles reduced their sizes and smaller particles were formed, resulting in the bimodal size distribution. In these bimodal size distributions, two peaks are observed, one is at 6 nm, and another is at 24 nm.
Nanometer Material Processing Using NSOM-delivered Femtosecond Laser Pulses
Authors: Cheng Chen-Hsiung , Li Ming
Published: April 2011

Nanometer-scale surface topology modification has been demonstrated using NSOM (near-field scanning optical microscope) delivered femto-second pulses. The ablation laser has a pulse width of 150 femto-second and wavelength of 387-nm. The laser pulses are coupled into the free end of a multimode optical fiber that a nanometer-size NSOM probe was fabricated on the other end with small orifice. The transmitted laser pulses from the probe orifice illuminates and machines the substrate surface when the probe is in near-field range of the substrate surface. The produced feature on Silicon surface is as least 200-nm deep with hole diameter around 200-nm. Near-field coupling of the laser has the potential to achieve ablation of feature size less than diffraction limit. Using NSOM delivery method also allows us to take advantage of nanometer metrology in precision surface ablation or other type of preformed surface modification. The ability of monitoring surface topology of substrate in real time enables us to accomplish the in-situ surface processing. We have demonstrated the technique of drilling 200-nm air holes on a pre-formed 600-nm wide wave guide. This method can be used to fabricate one-dimensional photonic crystal on a waveguide in ambient environment. The experiment design and performance evaluation will be discussed.
Nanoporous Polymer Films from Immiscible Polymer Blends: Pore Size and Composition Dependence
Authors: Liu Tong , Ozisik Rahmi , Siegel Richard W.
Published: April 2011

Nanoporous polymer films have been prepared using immiscible blends of polyetherimide (PEI) and poly(caprolactone diol) (PCLD). The films were prepared by spin-coating from a common solvent — dichloromethane (DCM). To create the nanoporous films, PCLD was removed by immersing the films in acetone, which dissolves PCLD only. Field emission scanning electron microscopy was used to study the porous structure. The pore structure of the films was affected by many factors such as composition of the blend, molecular weight, and various processing parameters. The formation of nanometer size pores was mainly due to the fast phase separation process during spin-coating. The pore size and pore size distribution was found to depend on the blend composition.
The Distributional Impact of Climate Policy
Authors: Jorgenson Dale W , Goettle Richard , Ho Mun S , Slesnick Daniel T , Wilcoxen Peter J
Published: April 2011

The purpose of this paper is to present a new methodology for evaluating the distributional impacts of climate policy. This methodology builds directly on the framework introduced by Jorgenson, Slesnick, and Wilcoxen (1992), but generalizes it by including leisure time, as well as goods and services, in the measure of household welfare. We provide detailed results for 244 different types of households distinguished by demographic characteristics. In addition, we evaluate the overall impact of a cap-and-trade system, as represented in Energy Modeling Forum 22. While there is a wide range of outcomes for different demographic groups, the impact on economic welfare is regressive and generally negative but relatively small.
Can Repository Scientists and Social Scientists Work Together to Find Solutions to Nuclear Waste Management Problems? A Repository Scientist's Perspective
Authors: Bonano Evaristo , Swift Peter , Appel Gordon , Meacham Paul
Published: April 2011

One of the exigent issues moving towards the development and implementation of acceptable and enduring nuclear waste management solutions is ensuring that the attendant social, economic, and political factors are given due consideration as part of the process of evaluating and eventually selecting a preferred alternative. To date, the relevant literature on the subject of social and political aspects of nuclear waste management has, by and large, presented social scientists' perspectives, and only rarely represented the perspective of the physical scientists that have been involved in addressing the technical aspects of nuclear waste management. We present the perspective of a small subset of repository scientists that individually and collectively have many years of experience in geologic repository programs. We offer our view on how repository scientists and social scientists can work together constructively. As observed by both repository scientists and social scientists, issues related to social and political concerns have been a major contributor to the lack of progress in implementing an acceptable solution to the disposal of nuclear wastes. Therefore, it is critically important that repository scientists and social scientists work together towards finding solutions that can be demonstrated to provide the requisite level of safety and be socially and politically acceptable. Current U.S. circumstances influencing the management of nuclear wastes will likely result in a new or revised national policy. We assume that some kind of geologic disposal of nuclear wastes will be needed independent of what new options may be implemented for the nuclear fuel cycle. Implementation of a new or revised policy will present ample opportunities for repository scientists and social scientists to collaborate towards the common goal of finding technically and socially responsible solutions. This paper presents some suggestions using a fairly narrow set of circumstances as a means for starting the dialog on how to forge a workable relationship between the two groups.
Does Comprehensive Emergency Management Work? A Longitudinal Study in The Commonwealth of The Bahamas
Authors: Hughey Erin P. , Bell Heather M.
Published: April 2011

Disaster risk cannot be wholly eliminated and communities will continue to be affected by hazards. While governments, organizations and individuals work to limit exposure and reduce susceptibility to the negative social, economic, and environmental impacts of disasters, effective emergency response capabilities must also be developed and exercised, in order to reduce losses, better cope with impacts that do occur, and facilitate recovery. In 2002, the nation of The Bahamas established a comprehensive emergency management (CEM) system intended to improve disaster response capabilities. This paper describes the application of Quarantelli's methodology (1997) in evaluating response operations associated with six hurricanes that affected The Bahamas from 1992 to 2005. The research presented here is part of a 9 year longitudinal study begun in 2001 and designed to examine the influence of CEM on emergency response in an island nation. Results indicated that the implementation of a CEM system improved disaster response in several key areas, providing evidence that CEM is an effective strategy for an archipelagic nation.
Effects of mandibular incisor intrusion obtained using a conventional utility arch vs bone anchorage
Authors: Aydoğdu Esen , Özsoy Ömür Polat
Published: April 2011

Objective:

To compare the dentofacial effects of mandibular incisor intrusion using mini-implants with those of a conventional incisor intrusion mechanic, the utility arch.

Materials and Methods:

Twenty-six deep-bite patients were enrolled to one of the two groups. In group 1 the mandibular incisors were intruded using a 0.16 × 0.22–inch stainless-steel segmental wire connected to two mini-implants. In group 2 the mandibular incisor intrusion was performed using a conventional utility arch. Conventional lateral cephalometric radiographs were taken at pretreatment and at the end of intrusion. Thirty landmarks were identified to measure 23 linear and 20 angular measurements. Intragroup comparisons were made using a paired t-test or a Wilcoxon test. Intergroup comparisons were made using a Student's t-test or a Mann-Whitney U-test.

Results:

The duration of intrusion was 5 months for group 1 and 4 months for group 2. In the implant group, the mean amount of change was 0.4 mm/mo for the incisor tip and 0.3 mm/mo for the center of resistance, and in the utility arch group, the mean amount of change was 0.25 mm/mo for the incisor tip and 0.2 mm/mo for the center of resistance. The mandibular incisors showed an average protrusion of 7° in the implant group and 8° in the utility arch group.

Conclusions:

Incisor intrusion that was achieved using an implant-supported segmented archwire was no different than the movement achieved with a conventional intrusion utility arch. The only difference between the two methods was in the molar movement.
Capecitabine or Infusional 5-fluorouracil for Gastroesophageal Cancer: A Cost–Consequence Analysis
Authors: Horgan A.M. , Knox J.J. , Liu G. , Sahi C. , Bradbury P.A. , Leighl Natasha
Published: April 2011

Background: In patients with advanced gastroesophageal cancer, the phase III Randomized ECF for Advanced and Locally Advanced Esophagogastric Cancer 2 (REAL-2) trial demonstrated equivalent clinical efficacy when capecitabine (x) was substituted for 5-fluorouracil (5FU) in the epirubicin–cisplatin–5FU (ECF) regimen. Methods: The present analysis compares the direct medical costs associated with both regimens. This cost–consequence analysis of direct medical costs took resource utilization data from the REAL-2 trial where available. Direct medical costs were derived from the perspective of the Canadian public health care system in 2008 Canadian dollars. Mean cost per patient on each treatment arm was calculated. Results: Drug costs from start of treatment until first progression, including pre- and post-chemotherapy medications and administration costs, totalled $5,344 for ECX as compared with $3,187 for ECF. Costs for treatment of adverse events were estimated at $2,621 for ECX as compared with $3,397 for ECF. An additional cost of $873 was associated with insertion of an implanted venous access. Total incremental cost of ECX over ECF was $508. Conclusions: In advanced gastroesophageal cancer, capecitabine is an attractive alternative to 5FU. Although the drug cost per se is greater, use of capecitabine is associated with decreased consumption of hospital resources. Not only does capecitabine fit with patient preference for oral therapy, it also avoids the inconvenience and complications of central venous access.
Ghrelin Protects against the Detrimental Consequences ofPorphyromonas gingivalis-Induced Akt Inactivation through S-Nitrosylation on Salivary Mucin Synthesis
Authors: Slomiany Bronislaw L. , Slomiany Amalia
Published: April 2011

Disturbances in nitric oxide synthase isozyme system and the impairment in salivary mucin synthesis are well-recognized features associated with oral mucosal inflammatory responses to periodontopathic bacterium,P. gingivalis. In this study, using rat sublingual gland acinar cells, we report thatP. gingivalisLPS-induced impairment in mucin synthesis and associated suppression in Akt kinase activity were accompanied by a decrease in constitutive nitric oxide synthase (cNOS) activity and an induction in inducible nitric oxide synthase (iNOS) expression. The LPS effect on Akt inactivation was manifested in the kinase S-nitrosylation and a decrease in its phosphorylation at Ser473. Further, we demonstrate that a peptide hormone, ghrelin, countered the LPS-induced impairment in mucin synthesis. This effect of ghrelin was reflected in the suppression of iNOS and the increase in Akt activation, associated with the loss in S-nitrosylation and the increase in phosphorylation, as well as cNOS activation through phosphorylation. Our findings suggest that induction in iNOS expression byP. gingivalis-LPS leads to Akt kinase inactivation through S-nitrosylation that detrimentally impacts cNOS activation through phosphorylation as well as mucin synthesis. We also show that the countering effect of ghrelin onP. gingivalis-induced impairment in mucin synthesis is associated with Akt activation through phosphorylation.
From Matrix to Operator Inequalities
Authors: Loring Terry A.
Published: April 2011

We generalize Löwner's method for proving that matrix monotone functions are operator monotone. The relation x ≤ y on bounded operators is our model for a definition of C*-relations being residually finite dimensional.

Our main result is a meta-theorem about theorems involving relations on bounded operators. If we can show there are residually finite dimensional relations involved and verify a technical condition, then such a theorem will follow from its restriction to matrices.

Applications are shown regarding norms of exponentials, the norms of commutators, and “positive” noncommutative ∗-polynomials.
Characterisation of corona-generated ions used in a Neutral cluster and Air Ion Spectrometer (NAIS)
Authors: Manninen H. E. , Franchin A. , Schobesberger S. , Hirsikko A. , Hakala J. , Skromulis A. , Kangasluoma J. , Ehn M. , Junninen H. , Mirme A. , Mirme S. , Sipilä M. , Petäjä T. , Worsnop D. R. , Kulmala M.
Published: April 2011

Abstract. We characterized size and chemical composition of ions generated by a corona-needle charger of a Neutral cluster and Air Ion Spectrometer (NAIS) by using a high resolution differential mobility analyzer and a time-of-flight mass spectrometer. Our study is crucial to verify the role of corona-generated ions in the particle size spectra measured with the NAIS, in which a corona charger is used to charge aerosol particles down to the size range overlapping with the size of generated ions. The size and concentration of ions produced by the corona discharging process depend both on corona voltage and on properties and composition of carrier gas. Negative ions were <1.6 nm (0.8 cm2 V−1 s−1 in mobility) in all tested gas mixtures (nitrogen, air with variable mixing ratios of water vapour), whereas positive ions were <1.7 nm (0.7 cm2 V−1 s−1. Electrical filtering of the corona-generated ions and not removing all charged particles plays an important role in determining the lowest detection limit. Based on our experiments, the lowest detection limit for the NAIS in the particle mode is between 2 and 3 nm.