bluuebunny/crossref_metadata_2025 huggingface dataset:
Radial‐Profile Control of Cylindrical Plasma Source With Multiple Low‐Inductance Antenna Units
Authors: Takenaka Kosuke , Setsuhara Yuichi , Nishisaka Kazuaki , Ebe Akinori
Published: June 2009

Radial‐profile control of cylindrical plasma source with 500 mm in diameter has been carried out using multiple low‐inductance antenna (LIA) units. Measurements of ion saturation current in the cylindrical chamber demonstrated an excellent control capability of radial distribution by adjusting the power‐deposition profile. The non‐uniformity of radial distributions was improved from 8.3% to 5.4% with the plasma control technologies. The results indicate that the plasma control technologies with multiple LIA units are quite attractive as a plasma source for large‐area wafer processes over 450 mm in diameter, which inherently require excellent profile control capabilities.
Investigation of Synthesis‐Gas Production via CH4O2Ar Gas Mixture Using Microwave Plasma Torch
Authors: Yaghmaee Maziar S. , Shokri Babak , Khiabani Neda H. , Sarani Abdollah
Published: June 2009

In this study, a non‐thermal plasma reactor under atmospheric pressure instead of the usual catalytic processes was developed to produce synthesis‐gas (CO, H2) “syngas” from the CH4O2Ar system. Moreover, using the Gibbs free energy minimization method, the gas phase composition of plasma species was calculated as quantitative pre‐estimate for our analytical observations. In our experimental investigation, a plasma reactor consisting of a microwave plasma torch, gas tube, cooling section, and sampling part was used. The experiments have been carried out under atmospheric pressure with maximum 300 W microwave power. To analyze the produced gas, the gas chromatography (GC) and the Fourier transform infrared (FTIR) spectroscopy have been used. In order to optimize the production conditions, the effect of O2/CH4 gas flow rate and plasma power in the plasma chemistry phenomenon, CH4 conversion and CO selectivity have been investigated. Our experimental results confirm our simulations and they are in good agreement with existing literature data so far.
Negative Ion Density Measurements in Reactive Magnetron Sputtering
Authors: Dodd Robert , You ShaoDong , Bryant Paul M. , Bradley James W.
Published: June 2009

A combination of laser photo‐detachment and conventional Langmuir probing has been used to obtain the bulk negative ion density in both a DC and radio frequency (RF) sputter magnetron. The argon and oxygen discharges were operated at low powers and over a range of pressures. The photo‐detachment signal is expected to reach a limiting value; however, the signal continues to increase with laser energy density and this can be attributed to a laser ablation effect. In the RF magnetron the electron temperature (Te) in oxygen decreased with increasing pressure, whereas the electron density (Ne) increased from 0.53 to 8.6 × 1014 m−3. At around 12 mTorr, a sudden increase in Ne by 3.7 is accompanied by a small drop in Te. The negative ion density (N−) also increases with pressure reaching a maximum of 1.7 × 1014 m−3 between 5 and 10 mTorr. Under similar conditions, the DC magnetron negative ion fraction (N−/Ne) is estimated to be ∼0.01, being significantly lower than in the RF magnetron where N−/Ne ≈ 1.
SiOx‐Based Gas Barrier Coatings for Polymer Substrates by Atmospheric Pressure Plasma Jet Deposition
Authors: Scopece Paolo , Viaro Andrea , Sulcis Roberta , Kulyk Illya , Patelli Alessandro , Guglielmi Massimo
Published: June 2009

An efficient way to increase the gas barrier properties of polymers is the development of silica barrier coatings; in fact inorganic barrier layers like SiNx and SiOx, usually obtained by PECVD, can decrease the gas permeation through polymeric substrates by several orders of magnitude. Nevertheless, the known costs of vacuum systems and in‐line processing needs have generated increasing interest to develop atmospheric condition alternatives. In this work results on deposition of SiOx on thin layers obtained by an atmospheric plasma jet as well as results on the gas permeation behaviour are presented. Obtained results, on the thickness and composition of the coatings, are evaluated under several deposition conditions.
Optimization of an Atmospheric Pressure Plasma Copolymerization Process With a View to Nanopowder Functionalization
Authors: Hody Hubert , Choquet Patrick , Moreno Maryline , Pireaux Jean‐Jacques
Published: June 2009

This work aims at optimizing a dielectric barrier discharge (DBD) process in a reactor designed for coating nanopowders. A copolymerization involving maleic anhydride and vinyltrimethoxysilane has been chosen to functionalize samples with carboxylic groups. Prior to any deposition on powder, an optimization of the process on flat substrates is required to allow a carboxyl functionalization independent of the position in the reactor. Accordingly, flat substrates have been placed along the reactor and subsequently analysed by XPS, SEM and Auger. From the results obtained, experimental conditions allowing batches of functionalized powder are deduced.
PVD Synthesis and Transfer into Water‐Based Solutions of Functionalized Gold Nanoparticles
Authors: Moreau Nicolas , Michiels Carine , Masereel Bernard , Feron Olivier , Gallez Bernard , Vander Borght Thierry , Lucas Stéphane
Published: June 2009

Large quantities of gold nanoparticles (Au NPs) were prepared by physical vapour deposition (PVD) technique. The produced nanoparticles were transferred into water solutions [containing 1% of carboxymethylcellulose (CMC)]. To achieve this resuspension, the Au NPs were embedded in a NaCl matrix, also deposited by PVD. In order to avoid the instantaneous and irreversible aggregation of the Au NPs, a surface modification needs to be performed, for example, by coating the metallic particles with plasma polymerized polymers. In this work, we present selected conditions allowing the production of aqueous solutions of Au NPs with small diameters (ca. 10 nm). The whole process is carried out thanks to a fully automatic plasma deposition system, allowing the production of high concentration of gold nanoparticles.
Gene flow from weedy red rice (Oryza sativa L.) to cultivated rice and fitness of hybrids
Authors: Shivrain Vinod K , Burgos Nilda R , Gealy David R , Sales Marites A , Smith Kenneth L
Published: June 2009

BACKGROUND: Gene transfer from weeds to crops could produce weedy individuals that might impact upon the evolutionary dynamics of weedy populations, the persistence of escaped genes in agroecosystems and approaches to weed management and containment of transgenic crops. The present aim was to quantify the gene flowrate from weedy red rice to cultivated rice, and evaluate the morphology, phenology and fecundity of resulting hybrids. Field experiments were conducted at Stuttgart and Rohwer, Arkansas, USA. Twelve red rice accessions and an imazethapyr‐resistant rice (Imi‐R; Clearfield™) were used.

RESULTS: Hybrids between Imi‐R rice × red rice were 138–150 cm tall and flowered 1–5 days later than the rice parent, regardless of the red rice parent. Hybrids produced 20–50% more seed than the rice parent, but had equivalent seed production to the majority of red rice parents. Seeds of all hybrids were red, pubescent and dehisced at maturity. For the majority of hybrids, seed germination was higher than that of the red rice parent. The gene flowrate from red rice to rice was 0.01–0.2% and differed by red rice biotype. The hybrids had higher fecundity and potential competitive ability than the rice parent, and in some cases also the red rice parent.

CONCLUSIONS: Red rice plants are vectors of gene flow back to cultivated rice and other weedy populations. The progeny of red rice hybrids from cultivated rice mother plants have higher chances of persistence than those from red rice mother plants. Gene flow mitigation strategies should consider this scenario. Copyright © 2009 Society of Chemical Industry
Substrate‐temperature effect on the microstructural and optical properties of ZnS thin films obtained by close‐spaced vacuum sublimation
Authors: Kurbatov D. , Opanasyuk A. , Khlyap H.
Published: June 2009

The effect of substrate temperature (Ts = 373–973 K) on the structural and optical properties of ZnS films obtained by a close‐spaced vacuum sublimation technique has been studied. Examination of layers morphology and structure was performed by scanning electron microscopy and X‐ray diffraction methods. The results of these studies enabled determination of the dependence of the main structural film parameters (texture, surface roughness, lattice parameters, grain and X‐ray scattering domain sizes, microstrain) on the growth conditions. Optical characteristics were studied in the range of wavelength near the “red edge” of ZnS photoconductivity. Spectral distributions of transmission coefficient T (λ), refractive index n (λ), extinction coefficient k (λ) and their dependence on the deposition temperature of ZnS films are obtained. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of substrate size on characteristics of carbon films deposited on glass plate substrates by thermal chemical vapor deposition
Authors: Chen Po‐Yu , Shiue Sham‐Tsong , Lin Hung‐Yi
Published: June 2009

When carbon films are prepared using thermal CVD, the properties of carbon films are affected by many factors, such as the precursor gas, deposition temperature, and working pressure. It is believed that the substrate size is also an important factor in preparing carbon films by thermal CVD. Hence, this study investigates the effect of substrate size on the properties of carbon coatings that are deposited on glass plate substrates in a quartz tube furnace using thermal CVD. Experimental results show that the deposition thickness decreases with increasing silica glass‐plate width, indicating that the deposition rate of carbon coatings decreases with increasing deposition area of the glass plate substrate. Meanwhile, the ordered degree and crystallite size of carbon films increase with increasing glass‐plate width, while the number and size of particles on carbon‐coating surfaces, surface roughness, and electrical resistivity of carbon films decrease. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of SiC diodes, power MOSFETs and intelligent power modules
Authors: Nakamura Takashi , Miura Mineo , Kawamoto Noriaki , Nakano Yuki , Otsuka Takukazu , Oku‐mura Keiji , Kamisawa Akira
Published: June 2009

Silicon carbide (SiC) power devices have been expected as next‐generation power‐saving devices. We succeeded in fabricating very large area (1 cm2) SiC Schottky barrier diodes (SBDs) with forward current of 300 A by inactivating areas including crystal defects. Heterojunction diodes with avalanche energy of over 2000 mJ/cm2were also developed. The reliability of gate oxide films of SiC DMOSFETs was enhanced to a level that is comparable to silicon power devices by improving oxidation techniques. We succeeded in fabricating SiC trench MOSFETs with low on‐resistance (1.7 mΩ cm2). 250 °C operation of intelligent power modules (IPMs) with SiC DMOSFETs was achieved by using a new attachment technology. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Broad gain spectra of single and multiple InGaAsN quantum well systems
Authors: Miloszewski Jacek M. , Wartak Marek S. , Weetman Philip
Published: June 2009

The optical gain of single and multiple quantum well systems fabricated from InGaAsN/GaAs was investigated. We performed a numerical analysis to find structures which would increase the gain bandwidth for application in semiconductor optical amplifiers and broadband tunable lasers. A 10‐band k · p Hamiltonian was used to calculate TE modal gain spectra. First, we calculated the gain spectra of a single quantum well for varying nitrogen compositions and well widths at fixed carrier density. Next, we calculated the gain spectra for two‐ and three‐quantum‐well systems which used the compositions and sizes of the previously analyzed single wells. The three‐quantum‐well system had an approximate 100% increase of gain bandwidth in comparison with a single quantum well. This increase is due to carefully selected different values of nitrogen compositions in various quantum wells. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure and optical properties of BiSeI crystal
Authors: Audzijonis A. , Gaigalas G. , Žigas L. , Sereika R. , Žaltauskas R. , Balnionis D. , Rėza A.
Published: June 2009

Electronic structure and optical properties of BiSeI were investigated with ab initio calculations based on density‐functional theory (DFT). The full potential linearized augmented plane wave (FP‐LAPW) method was used with the generalized gradient approximation (GGA). The complex dielectric function and optical constants, such as optical absorption coefficient, refractive index, extinction coefficient, energy‐loss spectrum and reflectivity, were calculated. It is shown that the p‐states of Bi, Se and I play an important role in absorption and reflectivity constants. The calculated optical constants of BiSeI exhibit anisotropy in two directions (x‐ and c‐axes). The experimental optical dielectric functions for single‐crystal BiSeI were determined using spectroscopic ellipsometry. The ellipsometry results were analyzed using the approximation of a pseudodielectric function (PDF). This method shows that experimental spectra consist of a four Lorentzian lines sum. The Lorentzian line parameters are obtained by minimization using the mean‐square method of the difference between the calculated and measured spectra of the dielectric constants. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On intrinsic point defect cluster formation during Czochralski crystal growth
Authors: Vanhellemont Jan , Spiewak Piotr , Sueoka Koji , Romandic Igor
Published: June 2009

Progress in characterizing, understanding and controlling intrinsic point defect generation and clustering during Cz growth of single crystals is discussed. It is shown that intrinsic point defects in Si and Ge behave quite similar and that the observed clustering behaviour can be understood taking into account the impact of extrinsic point defects, doping and strain on the formation, recombination and diffusivity of the intrinsic point defects in both materials. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of defects in organic semiconductors by charge based Deep Level Transient Spectroscopy (Q‐DLTS)
Authors: Nguyen T. P. , Renaud C. , Rendu P. Le , Yang S. H.
Published: June 2009

We report the results of measurements of traps in light emitting devices using a new derivative of poly(phenylene vinylene) (PPV) as an active material by the charge based Deep Level Transient Spectroscopy (Q‐DLTS) technique. Diodes of structure Indium Tin Oxide (ITO)/PEDOT:PSS/poly(2‐ethylhexyl)surfanyl‐5‐methoxy phenylene vinylene (MEH‐S‐PPV)/M with M = Al and M = Ca/Al were investigated by measurements of current‐voltage‐luminance characteristics. From analysis of these characteristics, evidence of charge trapping in devices was demonstrated. The trap parameters were then determined from Q‐DLTS measurements, which were carried out on the samples as a function of the charging time, the applied voltage and the temperature. Five trap levels of activation energy in the range [0.3‐0.6 eV] and of density of order of 1017 cm–3 were identified in diodes with Ca/Al cathode. Electron (one level) and hole (four levels) traps were then clearly distinguished by performing measurements in hole‐only devices. Trapping processes are discussed and tentatively proposed to performance of the light emitting diodes studied. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of crystalline defects in silicon for SOI applications by means of light scattering tomography
Authors: Kononchuk Oleg , Monier Vanessa , Capello Luciana , Pichaud Bernard
Published: June 2009

Capabilities of LST technique to study defects in silicon wafers for SOI applications are reviewed. Hardware modifications required for quantitative defect size analysis are presented together with novel calibration procedure based on HF inspection of SOI wafers. Examples of LST sensitivity to different types of the defects are demonstrated. Theoretical predictions of dislocation light scattering dependence on polarization have been confirmed allowing determination of dislocation's Burger's vector from LST measurements. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dislocation nucleation in heteroepitaxial semiconducting films
Authors: Pichaud B. , Burle N. , Texier M. , Alfonso C. , Gailhanou M. , Thibault‐Pénisson J. , Fontaine C. , Vdovin V. I.
Published: June 2009

The nucleation of dislocation in semiconductors is still a matter of debate and especially in heteroepitaxial films. To understand this nucleation process the classical models of dislocation nucleation are presented and criticized. Two main points are then developed: emission of dislocations from surface steps and the role of point defects agglomeration on dislocation nucleation. Recent atomic simulation of half loops emission from surface steps and experimental evidences of anisotropic relaxation of GaInAs films deposited on vicinal (111) GaAs substrates strongly support surface steps as preferential sites for nucleation. In low temperature buffer layer structures (SiGe/Si) an original dislocation structure is observed which corresponds to the dislocation emission in different glide systems by a unique nucleation centre. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure, chemistry and electrical properties of extended defects in crystalline silicon for photovoltaics
Authors: Seibt M. , Abdelbarey D. , Kveder V. , Rudolf C. , Saring P. , Stolze L. , Voß O.
Published: June 2009

The electronic properties of present‐day multicrystalline silicon (mc‐Si) materials for photovoltaic applications are strongly influenced by point defects, their mutual interaction and their interaction with dislocations and grain boundaries. This paper presents results from fundamental investigations of metal impurity interaction with extended defects, namely a small‐angle grain boundary and bulk microdefects. It is shown that the distribution of copper silicide precipitates closely follows the density of bulk microdefects indicating the underlying physics of ‘good’ and ‘bad’ grains frequently observed in mc‐Si. Co‐precipitation of copper and nickel in the same samples leads to virtually the same distribution of multimetal silicide precipitates which according to light‐beam induced current measurements show the same recombination activity as single‐metal silicide particles. Transmission electron microscopy is used to show that for copper‐rich and nickel‐rich conditions two types of silicides co‐exist, i.e. Cu3Si precipitates containing a small amount of nickel and NiSi2 precipitates containing some copper. Finally, phosphorus‐diffusion gettering (PDG) is discussed as the main gettering process used in presentday silicon photovoltaics. Special emphasis is put on the effect of extended defects and their interaction with metal impurities on PDG kinetics. It is shown that different limiting processes will be simultaneously operative in mc‐Si as a result of inhomogeneous bulk defect distributions (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Can molecular quantum descriptors predict the butene selectivity in nickel(II) catalyzed ethylene dimerization? A QSPR study
Authors: Tognetti Vincent , Fayet Guillaume , Adamo Carlo
Published: June 2009

In this article, we assess the ability of common molecular descriptors issued from quantum chemistry calculations (geometrical parameters, atomic charges, isodesmic energies, polarizabilities, and descriptors from conceptual DFT) to predict the butene selectivity in the mixed (P,N)‐nickel(II) catalyzed ethylene dimerization process. To this aim, 29 active species are considered, characterized by different substitution patterns on the nitrogen and phosphorus atoms. For each of them, the Gibbs energy difference between the transition states for the third ethylene insertion and for the butene elimination is computed to characterize the selectivity. Our results show that, in contrast to previously reported catalysts, the studied descriptors did not show any significant correlations with the property to predict and their integration in a multivariate analysis was not more efficient for the considered catalytic systems. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Spatially ordered surfactant assemblies in the gas phase: negatively charged bis(2‐ethylhexyl)sulfosuccinate‐alkaline metal ion aggregates
Authors: Giorgi Gianluca , Giocaliere Elisa , Ceraulo Leopoldo , Ruggirello Angela , Liveri Vincenzo Turco
Published: June 2009

The formation and structural features of negatively charged aggregates of sodium bis(2‐ethylhexyl)sulfosuccinate (AOTNa) surfactant molecules in the gas phase have been investigated by electrospray ionization mass spectrometry (ESI‐MS) and density functional theory calculations. Mainly driven by the interactions of alkali metal ions both with the oxygen atoms of the sulfonate group and with the succinate moiety of the AOT− anion, spatially ordered supramolecular assemblies, characterized by an internal core composed of surfactant counterions and hydrophilic head groups surrounded by the surfactant alkyl chains pointing outwards, are formed. Calculations have shown that surfactant self‐organization in the gas phase is energetically favoured, the energy of formation of negatively charged aggregates from isolated AOTNa and AOT− being linearly related to the aggregation number. Information on the chelating properties of AOTNa towards clusters of inorganic salts was achieved by infusion of solutions at various AOTNa/metal salt (NaCl, NaBr, NaI, LiI, KCl, CsI, RbI) ratios in the ESI source of a mass spectrometer. A wide variety of negatively charged AOT‐metal aggregates, some of them also incorporating halide (X−) ions, has been observed. Calculations have shown that the capture of a halide anion to give the AOTMX− species is favoured but the energetics of the process depends on the alkali metal and halide types. The use of energy‐resolved mass spectrometry has allowed us to evaluate the stability of different complexes and to evaluate the role played by the metal ion. Overall, the present investigation supports the idea that, in the gas phase, mainly driven by electrostatic interactions, surfactant molecules are present as molecular aggregates characterized by a reverse micelle‐like organization with an internal core formed by the surfactant counterions and head groups surrounded by the surfactant alkyl chains. These peculiar aggregates are able to incorporate ionic clusters in their hydrophilic core. Copyright © 2009 John Wiley & Sons, Ltd.
Stable isotope ratio analysis to differentiate temporal diets of a free‐ranging herbivore
Authors: Walter W. D. , Leslie D. M.
Published: June 2009

Stable isotope ratio analysis (SIRA) of carbon (δ13C) and nitrogen (δ15N) in tissue samples of herbivores can identify photosynthetic pathways (C3 vs. C4) of plants consumed. We present results from free‐ranging Rocky Mountain elk (Cervus elaphus) that highlight the ability to differentiate diets using tissue δ13C and δ15N. The signatures of δ13C and δ15N differed in tissues of varying metabolic activity: muscle, a short‐term dietary indicator (i.e., 1–2 months) and hoof, a long‐term dietary indicator (i.e., 3–12 months). We also documented that δ13C and δ15N values along elk hooves (proximal, middle, distal sections) elucidated temporal shifts in dietary selection. The carbon isotopes of the composite hoof were similar to those of the middle section, but the composite hoof differed in δ13C from the distal and proximal sections. The δ13C and δ15N signatures also differed among elk populations, indicating temporal dietary shifts of individuals occupying disparate native range and human‐derived agricultural landscapes. Analyses of stable isotopes in various tissues highlighted carbon and nitrogen assimilation through time and differences in the foraging ecology of a rangeland herbivore. Published in 2009 by John Wiley & Sons, Ltd.
A communication efficient probabilistic algorithm for mining frequent itemsets from a peer‐to‐peer network
Authors: Datta Souptik , Kargupta Hillol
Published: June 2009

Data intensive large‐scale distributed systems like peer‐to‐peer (P2P) networks are becoming increasingly popular where centralization of data is impossible for mining and analysis. Unfortunately, most of the existing data mining algorithms work only when data can be accessed in its entirety. Finding all the network‐wide frequent itemsets is computationally difficult and usually has large communication overhead in such environment. This paper focuses on developing a communication efficient algorithm for discovering frequent itemsets from a P2P network. A sampling‐based approach is adopted to find approximate solution instead of an exact solution with probabilistic guarantee. The benefit of approximation technique is reflected in the low communication overhead in discovering majority of frequent itemsets with probabilistic guarantee. The main principal followed by the algorithm assumes that an independent and identically distributed (iid) sample of the entire data is available at one location to generate a set of candidate itemsets. Collecting iid sample from a P2P network is a challenging problem because of varying degrees of connectivity and sizes of data shared. The paper first addresses this issue and shows how an iid sample of nodes and data can be collected from a P2P network using random walk. It applies the proposed sampling technique to identify most of the frequent itemsets from a P2P network. Theoretical analysis shows how to decide about optimum sample size and minimize communication to compute the results. Experimental results show that the proposed algorithm discovers all of the network‐wide frequent itemsets using communication that scales sublinearly with network and datasize. © 2009 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 2: 48‐69, 2009
Meaning making through multiple modalities in a biology classroom: A multimodal semiotics discourse analysis
Authors: Jaipal Kamini
Published: June 2009

The teaching of science is a complex process, involving the use of multiple modalities. This paper illustrates the potential of a multimodal semiotics discourse analysis framework to illuminate meaning‐making possibilities during the teaching of a science concept. A multimodal semiotics analytical framework is developed and used to (1) analyze the semiotic and epistemological meanings communicated by multiple modalities during the teaching of a biology concept and (2) highlight features of semiotic modalities that extend meaning‐making opportunities in science classrooms. The classroom discourse of a Grade 11 biology teacher was analyzed during the teaching of the concept chemosynthesis. Data were drawn from lesson transcripts, observational fieldnotes, and informal interviews with the teacher. The findings showed that the multimodal semiotics framework was useful at illustrating how semiotic and epistemological functions of modalities compounded meanings. Most significantly, an emergent multimodal framework relating semiotic functions and science learning outcomes emerged that has the potential to (1) act as a metacognitive tool for teachers to select, sequence, and scaffold modalities and (2) act as an analytical framework for educational researchers to analyze meaning making in science teaching and learning. © 2009 Wiley Periodicals, Inc. Sci Ed 94:48–72, 2010
Swift heavy ion induced effects at Mo/Si interface and silicide formation
Authors: Agarwal Garima , Kulshrestha Vaibhav , Jain Rajkumar , Kabiraj D. , Sulania Indra , Kulriya Pawan , Jain I. P.
Published: June 2009

Swift heavy ion (SHI) induced modification at metal/Si interfaces has emerged as an interesting field of research due to its large applications. In this study, we investigate SHI‐induced mixed molybdenum silicide film with ion fluences. The molybdenum thin films were deposited on silicon substrates using e‐beam evaporation at 10−8 torr vacuum. Thin films were irradiated with Au ions of energy 120 MeV to form molybdenum silicide. The samples were characterized by grazing incidence X‐ray diffraction (GIXRD) technique for the identification of phase formation at the interface. Rutherford backscattering spectrometry (RBS) was used to investigate the elemental distribution in the films. The mixing rate calculations were made and the diffusivity values obtained lead to a transient melt phase formation at the interface according to thermal spike model. Irradiation‐induced effects at surface have been observed and roughness variations at the surface were calculated using atomic force microscopy (AFM) technique. Copyright © 2009 John Wiley & Sons, Ltd.
Confined Assembly of Asymmetric Block‐Copolymer Nanofibers via Multiaxial Jet Electrospinning
Authors: Kalra Vibha , Lee Jung Hun , Park Jay Hoon , Marquez Manuel , Joo Yong Lak
Published: June 2009

Multiaxial (triaxial/coaxial) electrospinning is utilized to fabricate block copolymer (poly(styrene‐b‐isoprene), PS‐b‐PI) nanofibers covered with a silica shell. The thermally stable silica shell allows post‐fabrication annealing of the fibers to obtain equilibrium self‐assembly. For the case of coaxial nanofibers, block copolymers with different isoprene volume fractions are studied to understand the effect of physical confinement and interfacial interaction on self‐assembled structures. Various confined assemblies such as co‐existing cylinders and concentric lamellar rings are obtained with the styrene domain next to the silica shell. This confined assembly is then utilized as a template to guide the placement of functional nanoparticles such as magnetite selectively into the PI domain in self‐assembled nanofibers. To further investigate the effect of interfacial interaction and frustration due to the physically confined environment, triaxial configuration is used where the middle layer of the self‐assembling material is sandwiched between the innermost and outermost silica layers. The results reveal that confined block‐copolymer assembly is significantly altered by the presence and interaction with both inner and outer silica layers. When nanoparticles are incorporated into PS‐b‐PI and placed as the middle layer, the PI phase with magnetite nanoparticles migrates next to the silica layers. The migration of the PI phase to the silica layers is also observed for the blend of PS and PS‐b‐PI as the middle layer. These materials not only provide a platform to further study the effect of confinement and wall interactions on self‐assembly but can also help develop an approach to fabricate multilayered, multistructured nanofibers for high‐end applications such as drug delivery.
Increased expression of the NR2A NMDA receptor subunit in the prefrontal cortex of rats reared in isolation
Authors: Turnock‐Jones Julia J. , Jennings Carol A. , Robbins Melanie J. , Cluderay Jane E. , Cilia Jackie , Reid Juliet L. , Taylor Adam , Jones Declan N.C. , Emson Piers C. , Southam Eric
Published: June 2009

A hypofunction of the N‐methyl‐D‐aspartate (NMDA) receptor has been implicated in the pathophysiology of schizophrenia. Compelling evidence of altered NMDA receptor subunit expression in the schizophrenic brain has not, however, so far emerged. Rats reared in isolation exhibit several characteristics, including disturbed sensory gating, which resemble those seen in schizophrenia. To explore the possibility that NMDA receptor dysfunction may contribute to the behavioral and neurochemical consequences of rearing rats in isolation, we compared NMDA receptor subunit expression in brains of rats which were housed in isolation and which displayed a deficit in prepulse inhibition of the acoustic startle response with that of socially housed controls. An initial microarray analysis revealed a 1.26‐fold increase in NR2A transcript in the prefrontal cortex, but not in the nucleus accumbens, of rats reared in isolation compared with those housed socially. In contrast, NR1, NR2B, NR2C, NR2D, NR3A, and NR3B subunit expression was unchanged in either brain area. In a second cohort of animals, in situ hybridization revealed increased NR2A mRNA expression in the medial prefrontal cortex, an observation that was substantiated by increased [3H]CGP39653 binding suggesting that NR2A receptor subunit protein expression was also elevated in the medial prefrontal cortex of the same animals. No changes in expression of NR1 or NR2B subunits were observed at both mRNA and protein level. Altered NR2A subunit expression in the medial prefrontal cortex of rats reared in isolation suggests that NMDA receptor dysfunction may contribute to the underlying pathophysiology of this preclinical model of aspects of schizophrenia. Synapse 63:836–846, 2009. © 2009 Wiley‐Liss, Inc.
Learning about obligation, compassion, and global justice: The place of contemplative pedagogy
Authors: Kahane David
Published: June 2009

Contemplative techniques like meditation can help students to go beyond a merely cognitive understanding of their responsibilities as global citizens, and to find an authentic motivation to serve.
Avulsion of the Hamstring Muscle Group: A Follow‐Up of 6 Adult Non‐Athletes with Early Operative Treatment: A Brief Report
Authors: Mica Ladislav , Schwaller Adrian , Stoupis Christoferos , Penka Igor , Vomela Jindřich , Vollenweider Andreas
Published: June 2009

Background

Complete proximal avulsions of the hamstring muscle group may cause significant morbidity and loss of function. These pelvis‐near musculoskeletal injuries are mostly acquired during sports activities in a hip flexion and knee extension. Here we present a study group of 6 middle‐aged to elderly patients suffering a complete proximal hamstring avulsion and following early surgical refixation. Early surgical refixation leads to complete resumption of the activities of daily life without loss of function.

Materials and methods

The 6 patients (3 men and 3 women) included in this study had an average age of 59.07 ± 4.47 years at the time of injury. All of them suffered a complete avulsion of the hamstring muscle group. Surgical refixation was accomplished with the corkscrew anchor refixation system (Arthrex Manufacturing, Inc., Naples, FL). The cases were retrospectively analyzed using a hip joint evaluation system, the Harris Hip Score, and radiological follow‐up by magnetic resonance imaging (MRI). Data are given as mean ± SEM. Student’s t‐test was used for normal distribution of the data.

Results

The mean follow‐up time was 31.83 ± 18.9 months (range: 10–118 months). All patients were rated not to have a significant difference in function compared with the uninjured side. None of the patients suffered any handicaps resulting from surgery or the injury. A complete consolidation in all patients was observed in the follow‐up MRI.

Conclusions

Early surgical intervention and subsequent therapy in a complete hamstring avulsion injury may prevent loss of hip‐joint stability and prevent the sequalae of degradative hip or vertebral events.
Parental Engagement and Barriers to Participation in a Community‐Based Preventive Intervention
Authors: Mendez Julia L. , Carpenter Johanna L. , LaForett Doré R. , Cohen Jeremy S.
Published: June 2009

This study examined parent characteristics and barriers to participation in a community‐based preventive intervention with a sample of 201 parents from low‐income and predominantly ethnic minority backgrounds. Person‐centered analyses revealed five subgroups of parents who demonstrated variability in their parent characteristics, which included psychological resources and level of parental involvement in education. Group membership was associated with differences in school involvement and use of the psychoeducational intervention at home, after accounting for the number of barriers to engagement. For the intervention attendance variable, greater number of barriers was associated with decreased attendance only for parents in the resilient subgroup and the psychologically distressed subgroup. Attendance remained constant across levels of barriers for the other three subgroups of parents. The results of the study inform theory and practice regarding how to tailor preventive interventions to accommodate subgroups of parents within populations that experience barriers to accessing mental health services.
The Role of Lay Health Advisors in Cardiovascular Risk Reduction: A Review
Authors: Fleury Julie , Keller Colleen , Perez Adriana , Lee Sarah M.
Published: June 2009

Interventions are needed to reduce the negative impact of cardiovascular disease. The combination of health risks for disease, disability, and mortality, particularly among underserved populations, might be best addressed with programs designed to enhance awareness and development of resources within a context of community support. The objectives of this review were to: (1) provide a comprehensive review and evaluation of the roles, evaluation, and effectiveness of LHA in community‐based programs with an emphasis on cardiovascular risk reduction; and (2) provide recommendations for future research involving LHA in such programs. Computer and manual searches were conducted of articles in the English‐language literature from 1980 to 2007. Twenty articles were evaluated, which emphasized the role of the LHA in cardiovascular risk reduction. A review of research literature provides a starting point for determining salient approaches for intervention and evaluation, issues related to program implementation and sustainability, and strengths and limitations of existing approaches.
Determining Ethyl Esters in Fish Oil with Solid Phase Microextraction and GC–MS
Authors: Sullivan Jenna C. , Budge Suzanne M. , St‐Onge M.
Published: June 2009

The long‐chain polyunsaturated fatty acids (PUFA) found in fish oil, specifically eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) play an important part in human health. As a result, fish oil supplements are commonly consumed by people around the world. Supplements in the form of triacylglycerols (TAG) can be sold at a premium price, compared to those in the ethyl ester (EE) forms. Producers of TAG supplements require a simple, rapid method to determine the authenticity of their raw material. Here, we describe a method to quantify EE in fish oil using solid phase microextraction headspace analysis and GCMS. Despite the variation in linear ranges of the calibration curves with volatility of the EE, 30 individual FA were quantified including common saturated FA such as palmitic and stearic acid, as well as longer chain PUFA, such as EPA and DHA. The method was then applied to three commercial fish oils in the TAG form and two of the products were found to contain EE, with one containing EE above 1.5% w/w, indicating that contamination had occurred. With growing consumer interest in fish oil products, the method proposed here will help resolve future issues of authenticity in fish oils.
Moral Bias in Large Elections: Theory and Experimental Evidence
Authors: FEDDERSEN TIMOTHY , GAILMARD SEAN , SANDRONI ALVARO
Published: June 2009

We argue that large elections may exhibit amoral bias(i.e., conditional on the distribution of preferences within the electorate, alternatives understood by voters to be morally superior are more likely to win in large elections than in small ones). This bias can result fromethical expressivepreferences, which include a payoff voters obtain from taking an action they believe to be ethical. In large elections, pivot probability is small, so expressive preferences become more important relative to material self-interest. Ethical expressive preferences can have a disproportionate impact on results in large elections for two reasons. As pivot probability declines, ethical expressive motivations make agents more likely to vote on the basis of ethical considerations than on the basis of narrow self-interest, and the set of agents who choose to vote increasingly consist of agents with large ethical expressive payoffs. We provide experimental evidence that is consistent with the hypothesis of moral bias.
Numerical simulations of non-spherical bubble collapse
Authors: JOHNSEN ERIC , COLONIUS TIM
Published: June 2009

A high-order accurate shock- and interface-capturing scheme is used to simulate the collapse of a gas bubble in water. In order to better understand the damage caused by collapsing bubbles, the dynamics of the shock-induced and Rayleigh collapse of a bubble near a planar rigid surface and in a free field are analysed. Collapse times, bubble displacements, interfacial velocities and surface pressures are quantified as a function of the pressure ratio driving the collapse and of the initial bubble stand-off distance from the wall; these quantities are compared to the available theory and experiments and show good agreement with the data for both the bubble dynamics and the propagation of the shock emitted upon the collapse. Non-spherical collapse involves the formation of a re-entrant jet directed towards the wall or in the direction of propagation of the incoming shock. In shock-induced collapse, very high jet velocities can be achieved, and the finite time for shock propagation through the bubble may be non-negligible compared to the collapse time for the pressure ratios of interest. Several types of shock waves are generated during the collapse, including precursor and water-hammer shocks that arise from the re-entrant jet formation and its impact upon the distal side of the bubble, respectively. The water-hammer shock can generate very high pressures on the wall, far exceeding those from the incident shock. The potential damage to the neighbouring surface is quantified by measuring the wall pressure. The range of stand-off distances and the surface area for which amplification of the incident shock due to bubble collapse occurs is determined.
Local improvements to reduced-order models using sensitivity analysis of the proper orthogonal decomposition
Authors: HAY ALEXANDER , BORGGAARD JEFFREY T. , PELLETIER DOMINIQUE
Published: June 2009

The proper orthogonal decomposition (POD) is the prevailing method for basis generation in the model reduction of fluids. A serious limitation of this method, however, is that it is empirical. In other words, this basis accurately represents the flow data used to generate it, but may not be accurate when applied ‘off-design’. Thus, the reduced-order model may lose accuracy for flow parameters (e.g. Reynolds number, initial or boundary conditions and forcing parameters) different from those used to generate the POD basis and generally does. This paper investigates the use of sensitivity analysis in the basis selection step to partially address this limitation. We examine two strategies that use the sensitivity of the POD modes with respect to the problem parameters. Numerical experiments performed on the flow past a square cylinder over a range of Reynolds numbers demonstrate the effectiveness of these strategies. The newly derived bases allow for a more accurate representation of the flows when exploring the parameter space. Expanding the POD basis built at one state with its sensitivity leads to low-dimensional dynamical systems having attractors that approximate fairly well the attractor of the full-order Navier–Stokes equations for large parameter changes.
Grain sorting effects on the formation of tidal sand waves
Authors: VAN OYEN TOMAS , BLONDEAUX PAOLO
Published: June 2009

A model is developed to investigate the process which leads to the formation of sand waves in shallow tidal seas characterized by a heterogeneous sea bed composition. The main goal of the analysis is the evaluation of the effects that a graded sediment has on the formation of the bottom forms and the investigation of the sorting process induced by the growth of the bottom forms. The analysis is based on the study of the stability of the flat bed configuration, i.e. small amplitude perturbations are added to the flat bottom and a linear analysis of their time development is made. For an oscillatory tidal current dominated by one tidal constituent, the results show that the graded sediment can stabilize or destabilize the flat bottom configuration with respect to the uniform sediment case, depending on the standard deviation σ* of the grain size distribution and on the ratio between the horizontal tidal excursion and the water depth. For moderate values of , i.e. values just larger than the critical value for which the sediment is moved and sand waves appear, the presence of a sand mixture stabilizes the flat bed. On the other hand, for large values of , the mixture has a destabilizing effect. In both cases the effect that a sand mixture has on the stability of the flat bed configuration is relatively small. Moreover, for moderate values of , the fine fraction of the mixture tends to pile up at the crests of the bottom forms while the coarse fraction moves towards the troughs. For large values of , the grain size distribution depends on the value of σ*. The results are physically interpreted and provide a possible explanation of the apparently conflicting field observations of the grain size distribution along the sand wave profile, carried out in the North Sea.
Global linear stability of the non-parallel Batchelor vortex
Authors: HEATON C. J. , NICHOLS J. W. , SCHMID P. J.
Published: June 2009

Linear stability of the non-parallel Batchelor vortex is studied using global modes. This family of swirling wakes and jets has been extensively studied under the parallel-flow approximation, and in this paper we extend to more realistic non-parallel base flows. Our base flow is obtained as an exact steady solution of the Navier–Stokes equations by direct numerical simulation (with imposed axisymmetry to damp all instabilities). Global stability modes are computed by numerical simulation of the linearized equations, using the implicitly restarted Arnoldi method, and we discuss fully the numerical and convergence issues encountered. Emphasis is placed on exploring the general structure of the global spectrum, and in particular the correspondence between global modes and local absolute modes which is anticipated by weakly non-parallel asymptotic theory. We believe that our computed global modes for a weakly non-parallel vortex are the first to display this correspondence with local absolute modes. Superpositions of global modes are also studied, allowing an investigation of the amplifier dynamics of this unstable flow. For an illustrative case we find global non-modal transient growth via a convective mechanism. Generally amplifier dynamics, via convective growth, are prevalent over short time intervals, and resonator dynamics, via global mode growth, become prevalent at later times.
A simple model for low-frequency unsteadiness in shock-induced separation
Authors: PIPONNIAU S. , DUSSAUGE J. P. , DEBIÈVE J. F. , DUPONT P.
Published: June 2009

A model to explain the low-frequency unsteadiness found in shock-induced separation is proposed for cases in which the flow is reattaching downstream. It is based on the properties of fluid entrainment in the mixing layer generated downstream of the separation shock whose low-frequency motions are related to successive contractions and dilatations of the separated bubble. The main aerodynamic parameters on which the process depends are presented. This model is consistent with experimental observations obtained by particle image velocimetry (PIV) in a Mach 2.3 oblique shock wave/turbulent boundary layer interaction, as well as with several different configurations reported in the literature for Mach numbers ranging from 0 to 5.