bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Method for the growth of Low Temperature Silicon Structures for 3-D Flash Memory Devices
Authors: Mih Thomas A , Cross Richard BM , Paul Shashi
Published: February 2009

Low temperature (≤400°C) growth of polycrystalline silicon (poly-Si) is carried out using plasma-enhanced chemical vapour deposition. After an initial preparation step poly-Si was grown on the substrates. Optical band gap studies of the poly-Si films have been correlated to hydrogen content of the films as well as to their photoconductivity. Furthermore, the suitability of these films for use as information storage materials for future generation 3-D flash memory devices is investigated using capacitance-voltage (C-V) measurements via metal-insulator-semiconductor device structures. C-V analysis indicates strong charge storage behavior for the poly-Si films.
Utilizing Quantum Dots to Enhance Solar Spectrum Conversion Efficiencies for Photovoltaics
Authors: Savage Richard N , Mayer Hans , Lewis Matthew , Marrujo Dan M
Published: February 2009

Silicon-based photovoltaics typically convert less than 30% of the solar spectrum into usable electric power. This study explores the utilization of CdSe based quantum dots as spectral converters that absorb the under utilized UV portion of the solar spectrum and fluoresce at wavelengths near the band-gap of silicon-based solar cells. A flexible 1 mm thick thin-film structure that contains an array of microfluidic channels is designed and fabricated in polydimethylsiloxane (PDMS) using soft-lithographic techniques. The channels are approximately 85 microns wide by 37 microns tall and are filled with a solution containing the quantum dots. The thin-film structure can easily be attached to the surface of a single-junction solar cell. As a result, solar energy striking the coated solar cell with wavelengths less than 450 nm, which would normally experience low conversion efficiency, are absorbed by the quantum dots which fluoresce at 620nm. The high energy photons are converted to photons near the band-gap which increase the overall conversion efficiency of the solar cell. The quantum dots employed in this study are fabricated with a CdSe core (5.2 nm) and a ZnS outer shell and they exhibit a 25 nm hydrodynamic diameter. The UV-VIS spectral transmission properties of PDMS, along with its refractive index, are determined in order to characterize the spectral conversion efficiency of the thin-film structure. A model is developed to predict the optimum path length and concentration of quantum dots required to improve the power output of an amorphous silicon solar cell by 10%.
Integration of Postclosure Safety Analysis with Repository Design for the Yucca Mountain Repository through the Selection of Design Control Parameters
Authors: Nieder-Westermann Gerald Hans , Spencer Robert H. , Andrews Robert W , Brown Neil
Published: February 2009

The Yucca Mountain repository combines multiple barriers, both natural and engineered, which work both individually and collectively to limit the movement of water and the potential release and movement of radionuclides to the accessible environment. Engineered structures, systems and components (SSCs) are designed to function in the natural environment utilizing materials chosen to perform their intended functions in order to meet the postclosure performance objectives. Similarly, the features of the natural environment are expected to respond to the presence of the repository through geomechanical, hydrogeologic and geochemical changes.
At Yucca Mountain, specific features, both engineered and natural have been identified as requiring design control during repository construction and operations. The integration between design and postclosure safety analysis is facilitated using design control parameters. The term “design control parameters” includes functions and performance requirements allocated to SSCs through the design process, as well as the attributes of SSCs that are developed during design (e.g., dimensions; weights; materials; fabrication and quality-control processes; and operating conditions). These control parameters provide an interface between the design and the analyzed postclosure safety bases, which needs to be maintained through the licensing process. Maintenance of the design is controlled through configuration management and procedural safety controls.
The design control parameters serve three key purposes. First, they identify key aspects of the design that serve as the design bases for the designers of the SSCs of the facility. Second, they provide a useful input to the analyses of relevant postclosure features, events and processes (FEPs) and are used to either exclude FEPs from the postclosure safety analysis or as an input to models of included FEPs in the safety analysis. Finally, they provide important controlled interface constraints between the design and safety analyses organizations that are amenable to configuration management.
Several examples of such design controls will be presented in this briefing. The first type of design controls relates to the location of the underground facility, including standoffs from faults and the ground surface. The second type of design controls relates to the configuration of the engineered features including the spacing of emplacement driftsand drip shield dimensions and characteristics. A third type of design controls relates to constraints on handling, loading and emplacing waste forms in canisters and waste packages in the emplacement drifts.
Iron Redox Reactions in Model Nuclear Waste Glasses and Melts
Authors: Cochain Benjamin , Neuville Daniel R. , Roux Jacques , Ligny Dominique De , Testemale Denis , Pinet Olivier , Richet Pascal
Published: February 2009

The influence of boron on the kinetics of oxidation of iron in silicate melts relevant to nuclear waste storage has been investigated by XANES experiments. The measurements have been performed isothermally as a function of time at the iron K-edge. The redox kinetics become slower with increasing B2O3 content either close to the glass transition range, where the redox kinetics are controlled by diffusion of network-modifying cations, or at superliquidus temperatures where oxygen diffusion is the rate-limiting factor. In both ranges the kinetics can be interpreted in terms of boron speciation and interaction with alkali cations. Below the liquidus, however, the long times needed to reach redox equilibrium allow sintering of the powders investigated to take place so that the resulting changes in sample geometry prevent determinations of oxidation kinetic parameters from being made.
Oxygen Lattice Distortions and U Oxidation State in UO2+x Fluorite Structures
Authors: Desgranges Lionel , Baldinozzi Gianguido
Published: February 2009

The structural changes induced by the changes of the uranium oxidation state in the ideal fluorite lattice of pure UO2 are discussed. Experimental results evidence strong distortions of the oxygen sub-lattice due to dynamic (at high temperature) or static (at low temperature) fluctuations of the local charges in the cationic sublattice. These changes in the oxidation state are often described using the Vegard’s law because a linear dependence of lattice parameter is observed over a wide range of compositions. Nevertheless, an ideal solid solution model cannot explain this behavior where the elastic effects are directly related to the ionic radii of the cations. Strong evidence is provided that enthalpy effects are relevant in these systems and that they are directly associated with the local structural changes observed during neutron scattering experiments.
Estimation of Ra Concentration in High-level Radioactive Waste Disposal System
Authors: Yoshida Yasushi , Yoshikawa Hideki
Published: February 2009

Concentrations of Ra in groundwater was thought to be affected by substitution reactions with alkaline earth elements contained in a mineral, because the concentration of Ra is less than the solubility of known Ra containing phases. The substitution reaction was simulated using a partition coefficient. Calcite is a dominant mineral to react with Ra in a geological disposal system. However, previous identification of reactive layers of calcite or reversibility of the substitution reaction has not been confirmed. A re-distribution experiment was therefore undertaken and it was found that an estimated 21±13 layers near the surface were reactive and within them substitution equilibrium was achieved. Using these results, a model to estimate Ra concentration was established and adopted to analyze Ra migration. The effects of substitution of Ra and Ca were reasonably simulated.
Synthesis and Activity of Co-doped Barium Cerium Zirconate for Hydrogen Reforming and Purification
Authors: Suresh Aravind , Basu Joysurya , Sammes Nigel M , Carter Barry C , Wilhite Benjamin A
Published: February 2009

BaCe0.25Zr0.60Co0.15O3-x (BCZC) was synthesized via oxalate co-precipitation route. Material was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Catalytic activity of BCZC with respect to hydrogen generation via methanol partial oxidation was determined. Conductivity of the material at different temperatures and under different environments was determined by AC impedance spectroscopy. XRD and TEM results indicated that BCZC was synthesized as a homogeneous cubic phase material. Catalyst tests indicated that BCZC was catalytically active towards hydrogen generation and AC impedance results were positive enough to warrant further electrochemical studies.
Structure and Microstructure Study of Oxides of the La2/3-xLi3xTiO3-family
Authors: Amador Ulises , García-Martín Susana , Morata-Orrantia Ainhoa , Rodríguez-Carvajal Juan , Alario-Franco Miguel Ángel
Published: February 2009

Materials of the La2/3-xLi3xTiO3–family have been studied by selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), powder synchrotron X-ray diffraction and powder neutron diffraction. HRTEM showed that the materials have a complex domain-microstructure. The size and shape of the domains have been obtained from synchrotron X-ray diffraction data; besides, other extended defects such as strains and compositional fluctuations have been detected. The complementary use of local (SAED and HRTEM) and average (SXRD and NPD) techniques have allowed us to propose a model to refine the crystal structure of these oxides also accounting for their microstructure. All these materials have a perovskite-related structure with a diagonal unit cell (≈√2ap x √2ap x 2ap) as a consequence of the tilting of the TiO6 octahedra. Ordering of lanthanum and lithium ions and vacancies along the 2ap-axis, as well as displacements of titanium ions from the centre of the octahedra, have been determined. The Li+ ions present a distorted square planar coordination and are located in interstitial positions of the structure, which could explain the very high ionic conductivity of this type of materials. The lithium conductivity depends on the oxide composition and its crystal microstructure, which varies with the thermal treatment of the sample.
Unidirectional Solidification and Single Crystal Growth of Al-rich Ti-Al Alloys
Authors: Drevermann Anne , Schmitz Georg J. , Behr Günther , Schaberger-Zimmermann Elke , Guguschev Christo
Published: February 2009

To investigate the basic mechanical and thermomechanical properties of TiAl alloys with high Aluminium content sufficiently large single crystalline domains are required. To fabricate these samples undirectional solidification in Bridgman Stockbarger furnaces and optical floating zone devices were used. Focus of investigation were grain selection and impurity contamination. Both processes allow for growth of single crystal domains of some millimetres diameter and a few centimetres length. However in a Bridgman Stockbarger furnace the long contact times with the crucible proved detrimental to oxidation issues whereas in the optical floating zone device oxidation is negligible due to containerless processing.
Development of G4 TiAl Alloys by Spark Plasma Sintering
Authors: Jabbar Houria , Monchoux Jean-Philippe , Thomas Marc , Couret Alain
Published: February 2009

G4 alloys (Ti51Al47Re1W1Si0.2) are developed by Spark Plasma Sintering (SPS) with the aim to improve the creep resistance of SPS materials. The microstructure is analyzed by Scanning and Transmission Electron Microscopies (SEM and TEM). The mechanical properties at low and high temperatures are measured. The addition of heavy elements does not lead to an improvement of the mechanical strength.
Observation of <2c+a> Dislocation Glide in Duplex Ti-48at.% Al after Room Temperature Tensile Deformation
Authors: Wiezorek Jörg M. K. , Kulovits Andreas K.
Published: February 2009

In this study we investigated the deformation behavior of the hexagonal ordered phase α2- Ti3Al in Duplex TiAl under tensile loading. Transmission electron microscopy (TEM) revealed that the orientation relation ships (OR) between α2-Ti3Al and the L10 ordered γ- TiAl phase are very different as compared to the OR common in fully lamellar PST TiAl. We observed deformation related <2c+a> dislocation activity on pyramidal slip systems in the α2-phase during post situ TEM analyses. We rationalize this observation by the possible build up of pile up stresses in γ-TiAl due to the different OR with the α2-Ti3Al phase that can possibly lead to the activation of <2c+a> dislocation activity on pyramidal slip systems with similarly resolved stresses in the α2-Ti3Al phase.
Intermetallic Bond Coats: Systems Compatibility and Platinum-Group Metal Additions
Authors: Pollock Tresa , Widrevitz Dan , Pong Russell , Cao Fang , Tryon Bryan
Published: February 2009

Intermetallic interlayers are key to the performance of thermal barrier coating systems. The role of platinum group metal (PGM) additions to B2 bond coat interlayers has been investigated with emphasis on diffusional aspects of coating structure evolution and properties. Additions of Ru and Ir to NiAl reduce interdiffusion and the resultant thickness of the coating and interdiffusion zone. Relative to Pt and Pd, Ru and Ir slow diffusion. Ru additions to NiAl increase creep resistance but degrade oxidation kinetics.
Structure and Disorder of the Laves Phases in the Co-Nb System
Authors: Kreiner Guido Michael , Grüner Daniel , Grin Yuri , Stein Frank , Palm Martin , Ormeci Alim
Published: February 2009

A special feature of the Co-Nb system is the occurrence of the three different types of Laves phase with the ideal composition NbCo2. The C36 and the C14 phases are stable only at high temperatures and exhibit small homogeneity ranges, whereas the C15 phase forms with a broad homogeneity range enclosing the ideal composition. In case of C36 and Co-rich C15 the additional Co atoms substitute Nb atoms (Nb1-xCox)Co2.In the C36 phase the Co atoms preferentially occupy one of the two crystallographic Nb sites and are locally displaced by approx. 20 pm from the original Nb positions allowing the formation of favorable short Nb-Co bonds. In Nb-rich C14 only one of two crystallographic sites is occupied by Nb. The Kagomé layers of the Co atoms are distorted in the crystal structures of the hexagonal Laves phases. The deviation from the idealized crystal structure is mainly governed by the valence electron concentration. Quantum mechanical calculations show that the distortion is already an inherent feature of the point defect-free structures.
Comparing Ion Distributions around RNA and DNA Helical and Loop-loop Motifs
Authors: Semichaevsky Andrey V , Marlowe Ashley E , Yingling Yaroslava G
Published: February 2009

Nucleic acid nanoparticles can self-assembly through the formation of complementary loop-loop interactions or stem-stem interactions. Presence and concentration of ions can significantly affect the self-assembly process and the stability of the nanostructure. In this paper we use explicit molecular dynamics simulations to examine the variations in cationic distributions around DNA and RNA helices and loop-loop interactions with identical sequence except for Thymine to Uracil substitution. Our simulations show that the ionic distributions are different around RNA and DNA motifs which could be related to the discrepancy in stability of loop-loop complexes.
Multiscale Computer Simulation of Tensile Failure in Polymer-Coated Silica Aerogels
Authors: Good Brian
Published: February 2009

The low thermal conductivities of silica aerogels have made them of interest to the aerospace community for applications such as cryotank insulation. Recent advances in the application of conformal polymer coatings to these gels have made them significantly stronger, and potentially useful as lightweight materials for impact absorption as well. In this work, we perform multiscale computer simulations to investigate the tensile strength and failure behavior of silica and polymer-coated silica aerogels. The gels' nanostructure is simulated via a Diffusion Limited Cluster Aggregation (DLCA) procedure. The procedure produces fractal aggregates that exhibit fractal dimensions similar to those observed in real aerogels. The largest distinct feature of the clusters is the so-called secondary particle, typically tens of nm in diameter, which is composed of primary particles of amorphous silica an order of magnitude smaller. The secondary particles are connected by amorphous silica bridges that are typically smaller in diameter than the particles they connect. We investigate tensile failure via the application of a uniaxial tensile strain to the DLCA clusters. In computing the energetics of tensile strain, the detailed structure of the secondary particles is ignored, and the interaction among secondary particles is described by Morse pair potentials, representing the strain energetics of the silica gel and the polymer coating, parameterized such that the potential ranges are much smaller than the secondary particle size. The Morse parameters are obtained by separate atomistic simulation of models of the interparticle bridges and polymer coatings, with the tensile behavior of these bridges modeled via molecular statics. We consider the energetics of tensile strain and tensile failure, and compare qualitative features of low-and high-density gel failure.
Lateral migration and segregation of vesicles with viscosity contrast in simple shear and Poiseuille flows
Authors: Coupier Gwennou , Callens Natacha , Kaoui Badr , Minetti Christophe , Dubois Frank , Misbah Chaouqi , Podgorski Thomas
Published: February 2009

Lateral migration of vesicles (closed lipidic membranes) in a flow is characterized as a function of the relevant flow parameters and mechanical properties of the vesicles. We consider low Reynolds number flows, and migration is only due to viscous effects. Through experiments and simulations, we exhibit two different origins for such cross streamline migration: the presence of a wall, and a non1constant shear rate, as for instance in a Poiseuille flow. Such migration modifies the distribution of vesicles in a sheared polydisperse suspension; we present preliminary results proving that the hydrodynamic interactions between vesicles greatly modify the distribution of vesicles according to their sizes and deflation.
MEH-PPV Based Blue-light Dosimeter for Hyperbilirubinemia Treatment
Authors: da Silva Autreto Pedro Alves , Vasconcelos Claudia K , Flores Marcelo Z S , Galvao Douglas S , Bianchi Rodrigo R
Published: February 2009

In this work, we have theoretically investigated a model for the poly(2-methoxy-5(2'- ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV) photodegradation based on structural models for MEH-PPV oligomers in vacuum and in solvent (chloroform). We investigated how the incorporation of oxygen and breaking of vinyl double bonds affect the absorption spectra. The theoretical results are in excellent agreement with the experimental data if we assume that the incorporation of carbonyl group is the main mechanism associated with the photodegradation processes.
DC and AC Measurements of Magnetite Nanoparticulates and Implications for Nonlinear Response
Authors: Liong Silvia , Moore Ricky Lamar
Published: February 2009

This paper discusses preparation, characterization and measurement of linear DC and AC magnetic properties of magnetite (Fe3O4) nanoparticles (size ranges of 7-50 nm and 5 microns) and polymer composites of those particulates. Selected data and analysis are taken from the PhD thesis of Liong [1]. The goal of this research is to obtain magnetic data, specifically magnetization, anisotropy and coercivity as functions of particle size. These will be used as inputs to non linear magnetic simulations and in planning for future nonlinear magnetic measurements. Magnetite nanoparticles were synthesized by chemical coprecipitation, a method that allowed for the production of samples in gram quantities. Vibrating sample magnetometry was used to measure the room-temperature DC magnetization and coercivity of the particulates. Coaxial line impedance measurements were used to measure low frequency and dispersive AC permeability of Fe3O4–polymer composites from 1 Megahertz to 10 Gigahertz. AC data are applied to infer particulate magnetic susceptibility and anisotropy field change with particle size. Particle size was calculated from XTD data and supported by TEM images.

Measured DC saturation magnetization and coercivity decreased with particle dimension while anisotropy was calculated to increase. Magnetization data are consistent with models that calculate nanoparticle magnetization as a volumetric average of a spherical bulk material core and a passive outer shell. The shell thickness was calculated at 0.84 nm, very near one lattice constant of bulk Fe3O4, 0.8394 nm. Composites containing particulate volume fractions less than 20% were fabricated. Effective media theory was applied to measured AC composite permeability to extract particle magnetic properties and thereby anisotropy field, which increased by an order of magnitude from the bulk. Permeability decreased with particulate size.
Nanoscale “Curtain Rods”: High-Throughput Tools for Studying DNA-Protein Interactions
Authors: Fazio Teresa , Visnapuu Mari-Liis , Wind Shalom J. , Greene Eric
Published: February 2009

In this work, we combine nanoscale engineering with single-molecule biology to probe the biochemical interactions between individual proteins and DNA. This approach, a vast improvement over previous methods, constructs a platform to observe thousands of protein-DNA interactions in real time with unprecedented detail. A key challenge in these experiments involves collecting enough statistically relevant data in order to analyze reactions which are designed to be probed individually. “DNA curtains” are formed by flowing the DNA tethered to a lipid bilayer across nanopatterned barriers, facilitating massively parallel data acquisition.
Modeling of Toluene Diffusion and Swelling Behavior in EEA-CNP Conductive Polymer NanoComposite (CPC)
Authors: Thevenot Sylvain , Salagnac P. , Glouannec P. , Feller Jean-François
Published: February 2009

Electrically Conductive Polymer nanocomposites have attracted lots of attention in the last years, especially for their sensitivities to external solicitations, like temperature or pressure variation. This work concerns the modelling of toluene diffusion behaviour in poly(ethylene-co-ethyl acrylate) (EEA)-carbon nanoparticles (CNP) CPC. One of the main objective of our work was to control and model the physical mechanisms involved in this type of material during sorption and desorption phases in the presence of solvent vapour. Two approaches was explore, thin layer to study quick electrical response and thick layer to look after swelling effect induces by toluene. The thick layer mass measurement was compare with our diffusion model.
Conducting Polymer nanoComposites (CPC): Nanocharacterisation of layer by layer sprayed PMMA-CNT vapour sensors by Atomic force Microscopy in current Sensing Mode (CS-AFM)
Authors: Kumar Bijandra , Castro Mickaël , Lu Jianbo , Feller Jean-François
Published: February 2009

Organic vapour sensors based on poly (methylmethacrylate)-multi-wall carbon nanotubes (PMMA-CNT) conductive polymer nanocomposite (CPC) were developed via layer by layer technique by spray deposition. CPC Sensors were exposed to three different classes of solvents (chloroform, methanol and water) and their chemo-electrical properties were followed as a function of CNTcontent in dynamic mode. Detection time was found to be shorter than that necessary for full recovery of initial state. CNT real three dimensional network has been visualized by Atomic force microscopy in a field assisted intermittent contact mode. More interestingly real conductive network system and electrical ability of CPC have been explored by current-sensing atomic force microscopy (CS-AFM). Realistic effect of voltage on electrical conductivity has been found linear.
Electrospinning and Characterization of the Stable and “Metastable” Self-Assembled Poly(ethylene oxide)-Urea Complexes
Authors: Liu Yang , Antaya Hélène , Pellerin Christian
Published: February 2009

Solution electrospinning was used to prepare fibers of both the stable – trigonal α and “metastable” – orthorhombic β complexes between poly(ethylene oxide) (PEO) and urea. The 300-800 nm fibers were highly crystalline and both types presented a relatively large level of molecular orientation. Characterization of the poorly-studied β complex was performed using wide-angle X-ray diffraction, infrared spectroscopy, optical microscopy and differential scanning calorimetry. It was shown that β complex possesses a 3:2 PEO:urea stoichiometry, in contrast with a previously suggested 1:1 molar ratio, and that the α inclusion complex keeps the 4:9 molar ratio as when prepared by the conventional co-crystallization method. A new structural model was suggested for the β complex, in which the unit cell would contain 12 PEO repeat units (4 chains in the ab plane with 3 repeat units along the c axis) and 8 urea molecules arranged in a ribbon-like structure and intercalated between the two PEO layers. This layer-structured β complex is quite different from the usual channel-like α inclusion complex and results in different phase transitional properties.
Growth of ultra thin ZnSe nanowires
Authors: Wong Tai Lun , Cai Yuan , Chan Siu Keung , Sou Iam Keong , Wang Ning
Published: February 2009

We report here the growth of ultra thin ZnSe nanowires at low temperatures by Au-catalyzed molecule beam epitaxy and structural characterization of the nanowires. ZnSe nanowires may contain a high density of stacking faults and twins from low temperature growth and show a phase change from cubic to hexagonal structures. Ultra thin ZnSe nanowires can grow at a temperature below the eutectic point, and the relationship between the growth rates and nanowire diameters is V = 1/dn + C0 (C0 is a constant and n is a fitting parameter). The growth rate of the ultra thin nanowires at low temperatures can be elucidated based on the model involving interface incorporation and diffusion, in which the catalyst is solidified, and the nanowire growth is controlled through the diffusion of atoms into the interface between catalyst and the nanowire. The growth rate of ZnSe ultra-thin nanowires has been simulated.
Epitaxial growth of Si nanowires by a modified VLS method using molten Ga as growth assistant
Authors: Gewalt Annika , Kalkofen Bodo , Lisker Marco , Burte Edmund P.
Published: February 2009

In this paper the deposition and morphological characterization of gallium island structures on silicon and first results of silicon wire growth assisted by the created gallium droplets is presented. The islands and wires were grown on (111)-oriented single crystalline p-doped silicon substrates by microwave plasma enhanced chemical vapor deposition (MW PECVD) using trimethylgallium (TMGa) and silane (SiH4) as precursors for island and wire growth, respectively. The samples were investigated by SEM, EDS, XPS, and AFM.
Langmuir-Blodgett films of One-dimensional Nanowires composed of Amphiphilic Tetrathiafulvalenes and Electron Acceptor
Authors: Tatewaki Yoko , Takizawa Junko , Hatanaka Tatsuya , Kimura Mutsumi , Shirai Hirofusa
Published: February 2009

We found that novel amphiphilic tetrathiafulvalene (TTF; 1) organized into supramolecular assemblies by the addition of electron acceptor 2,3,5,6-tetrafluoro-7,7'f,8,8'f-tetracyano-p-quinodimethane (F4TCNQ) at the air-water interface. The assemblies on the air-water interface can be transferred onto the surface of mica and the morphologies of transferred films were investigated by AFM. The morphology of Langmuir-Blodgett films strongly depended on the ratio between 1 and F4TCNQ. Film of 1:1 mixture of 1 and F4TCNQ formed nanoscopic wires having an average dimension of 5.0 (height) × 70 (width) × 3000 (length) nm. On the other hand, the film of 2:1 mixture of 1 and F4TCNQ showed the mixed domains of wires and flat monolayers. Thus, the completely charge-transferred complex (1+)(F4TCNQ-) formed one-dimensional nanowires having a micrometer length. Room temperature electrical conductivities of cast film for 1:1 and 2:1 mixed layers of 1 and F4TCNQ were 2.4 × 10−4 and 8.0 × 10−5 S cm−1, respectively.
Structural and Electronic Properties of Rare-Earth Nanowires
Authors: Pratt Andrew , Woffinden Charles , Bonet Christopher , Tear Steve P.
Published: February 2009

Sub-monolayer coverages of the rare-earth metal Ho were deposited onto Si(001) substrates at elevated temperatures resulting in the formation of rare-earth silicide nanowires. Between the nanowires the substrate area reconstructs into either a 2×4 or 2×7 reconstruction depending on the specific preparation conditions. We have studied the structural and electronic properties of both the nanowires and the reconstructed areas with the complementary techniques of scanning tunneling microscopy (STM) and metastable de-excitation spectroscopy (MDS) revealing the electronic similarities between the 2×4 and 2×7 phases. Evidence for the presence of hybridized Si 3s3p-Ho 6s5d bonds suggests that these reconstructions form as a precursor to nanowire growth.
Hydrothermal Synthesis and Photocatalytic Activity of Titanium Dioxide Nanotubes, Nanowires and Nanospheres
Authors: Wang Jin , Li Ming , Zhi Mingjia , Manivannan Ayyakkannu , Wu Nianqiang
Published: February 2009

TiO2 nanostructures with various morphologies and crystal structures were obtained by calcination of alkaline hydrothermal synthesized hydrogen titanate at different temperatures. The photocatalytic activities of the as-prepared samples were investigated by degradation of methyl orange aqueous solution under ultraviolet irradiation. The effects of the phase composition, crystallinity, surface area and shape of the nanostructures were evaluated. The results showed that high crystallinity, pure anatase phase and nanowire structure are favorable for the photocatalysis. The dependence of the photocatalytic activity on the surface area is not significant as usually expected.
Fabrication of ZnO Bridging Nanowire Device by a Single-Step Chemical Vapor Deposition Method
Authors: Li Yanbo , Nagatomo Ippei , Uchino Ryohei , Yamada Ichiro , Delaunay Jean-Jacques
Published: February 2009

ZnO nanowires are directly integrated into a working device by a single-step chemical vapor deposition (CVD) method. Gold catalyst is patterned on a quartz glass substrate using a comb-shaped shadow mask and then ZnO is grown on the patterned substrate by CVD. Thick ZnO layers formed on the gold-patterned areas serve as native electrodes. Ultra-long (˜100 μm) ZnO nanowires grown across the gap between the ZnO electrodes and the nanowires serve as the sensing elements of the device. The device exhibits high sensitivity and fast response to UV illumination in air. Our method can be used to fabricate other metal oxide semiconductor bridging nanowire devices, which have promising applications in photodetection and gas sensing.
Modelling of the oxidation of Suspended Silicon Nanowires
Authors: Fazzini Pier-Francesco , Bonafos Caroline , Hubert Alexandre , Colonna Jean-Pierre , Ernst Thomas , Respaud Marc , Gloux Florence
Published: February 2009

The oxidation of suspended Si nanowires is studied under wet and dry conditions. The nanowire characteristics are extracted from Electron Microscopy images. In parallel, the Deal and Grove model is extended to cylindrical geometry. The used model also assumes that stress effects reduce the oxidation rate and predicts the retardation of oxide growth on curved surface, leading to a self-limited process. The model predictions show a good agreement with experiments.
Novel Inorganic DC Lateral Thin Film Electroluminescent Devices Composed of ZnO Nanorods and ZnS Phosphor
Authors: Satoh Tomomasa , Matsuzawa Yuki , Koishikawa Hiroaki , Hirate Takashi
Published: February 2009

A novel inorganic thin-film electroluminescence (TFEL) device exhibiting bright EL emission when driven by a low DC voltage is demonstrated. The DC-TFEL device is based on a composite layer in which aluminum-doped ZnO nanorods are vertically embedded in ZnS:Mn as an EL phosphor. The DC driving voltage is then applied laterally to the composite layer via two side electrodes set 3.5 mm apart. The aluminum-doped ZnO nanorods were synthesized on a glass substrate by low-pressure thermal chemical vapor deposition combined with laser ablation, and the composite layer was formed by electron-beam deposition of ZnS:Mn onto the ZnO nanorods. The thickness of the composite layer was about 160 nm. After electrical modification to breakdown a basal conduction ZnO path, the lateral DC-TFEL device exhibited bright EL emission without avalanche breakdown, achieving a luminance of 747 cd/m2 at 4200 V with a luminous efficiency of 9.2×10−3 lm/W.
Development of conducting buffer architectures using cube textured IBAD-TiN layers
Authors: Hühne Ruben , Güth Konrad , Kidszun Martin , Kaltofen Rainer , Matias Vladimir , Rowley John , Schultz Ludwig , Holzapfel Bernhard
Published: February 2009

Ion-beam assisted deposition (IBAD) offers the possibility to prepare thin textured films on amorphous or non-textured substrates. In particular, the textured nucleation of TiN is promising for the development of a conducting buffer layer architecture for YBCO coated conductors based on the IBAD approach. Accordingly, cube textured IBAD-TiN layers have been deposited reactively using pulsed laser deposition on Si/Si3N4 substrates as well as on polished Hastelloy tapes using different amorphous seed layers. Metallic buffer layers such as Au, Pt or Ir were grown epitaxially on top of the TiN layer showing texture values similar to the IBAD layer. Smooth layers were obtained using a double layer of Au/Pt or Au/Ir. Biaxially textured YBCO layers were achieved using SrRuO3 or Nb-doped SrTiO3 as a conductive oxide cap layer. Finally, different amorphous conducting seed layers were applied for the IBAD-TiN process. Highly textured TiN films were achieved on amorphous Ta0.75Ni0.25 layers showing a similar in-plane orientation of about 8° as on standard seed layers.
Structural, thermal and rheological studies on newly developed polyesters randomly copolymerized with poly (tetramethylene glycol) (PTMG)
Authors: Osamu Matsumoto , Atsushi Hotta
Published: February 2009

Poly (cyclohexanedimethanol cyclohexanedicarboxlic acid) (PCC), a fairly newly synthesized polyester, has been studied. Having a good experience of increasing both thermal stability and service temperature when applied to typical polymers, poly (tetramethylene glycol) (PTMG) was selected as a softening agent that was randomly copolymerized into the PCC chains. Another widely-used polyester, poly (ethylene terephthalate) (PET) was also produced in order to investigate the effect of PTMG, which was compared with the properties of the newly developed random PCC-PTMG copolymers (PCCP). In this study, the crystalline structures, the thermal and the mechanical properties of both PCC and PET containing different ratios of the random segment of PTMG were investigated by differential scanning calorimetery (DSC) and tensile tester.

It was found that the crystallization rate of pure PCC was significantly slow, whereas for PCCP, PTMG effectively accelerated the crystallization rate with increasing PTMG, and the sample with 25 wt% of PTMG had the fastest crystallization rate in all PCCP samples. Here, the PTMG acted as an accelerator, simultaneously depressing the movement of PCC molecular chains. The elastic recovery test indicated that the ability of PTMG as a softening agent was highly demonstrated at 20 wt% of PTMG. The results of PCCP were compared with those of PET-PTMG copolymers (PETP) and it was found that there were optimum values of PTMG for the crystallization rate on both samples. Additionally, the results of the elastic recovery test indicated that the softening effects observed in PCCP were more pronounced than those observed in PETP.
Classic and molecular study of Giardia duodenalis in children from a daycare center in the region of Presidente Prudente, São Paulo, Brazil
Authors: Tashima Nair Toshiko , Simões Maria Jacira Silva , Leite Clarice Queico Fujimura , Fluminhan Antonio , Nogueira Marco Antonio , Malaspina Ana Carolina
Published: February 2009

Epidemiological studies on giardiasis by using molecular techniques such as RAPD (Randomly Amplified Polymorphic DNA) may give information on factors related to the transmission of Giardia duodenalis. The aim of this work was to assess the epidemiology of G. duodenalis in 101 children attended at a daycare center in Presidente Bernardes, SP, Brazil. After parasitological examinations in feces samples, 15 children presented cysts of G. duodenalis. Their respective parents, brothers and pets, besides the daycare center workers, also had their feces submitted to parasitological analysis. Seven mothers and nine brothers also presented G. duodenalis cysts, while fathers, daycare workers and pets (dogs) did not presented the parasite. Besides the 15 cases with G. duodenalis, other 23 children presented other enteroparasites (Entamoeba coli, Endolimax nana, Enterobius vermicularis, Ascaris lumbricoides and Trichuris trichiura). Samples of G. duodenalis cysts from children and their relatives were submitted to molecular typing by RAPD after genomic DNA extraction and amplification of a fragment of the 18S rDNA region by PCR. After examining 31 isolates of G. duodenalis (children and their respective mothers and brothers), it was concluded that the parasite transmission occurred in children, probably during daily cohabitation at the daycare center, but not at home among their relatives or pets.
Enteroparasitosis and their ethnographic relationship to food handlers in a tourist and economic center in Paraná, Southern Brazil
Authors: Takizawa Maria das Graças Marciano Hirata , Falavigna Dina Lúcia Morais , Gomes Mônica Lúcia
Published: February 2009

This study reports on the occurrence of enteroparasites based on data from an ethnographic study of food handlers in the city of Cascavel, Paraná, Brazil. Fecal material from 343 food handlers of both sexes, between 14 and 75 years of age, was analyzed using Lutz, modified Ritchie and Ziehl-Neelsen techniques. Ethnographic relationships were investigated by means of specific questionnaires. Positive fecal samples were found for 131 (38.2%) handlers. Endolimax nana (67.9%) was the predominant species, followed by Entamoeba coli (35.9%), Blastocystis hominis (28.2%), Entamoeba histolytica/dispar (10.1%) and Giardia duodenalis (8.4%). Protozoan infections were more common than helminth infections (p = 0.00). The positive results for some parasites were associated with the male sex, professional category, and the performance of other activities (p < 0.05). The high overall occurrence of enteroparasites found indicates improper hygiene and sanitation conditions. Effective educational measures should be implemented to prevent the transfer of pathogenic organisms to food via handling.
Identification of Paracoccidioides brasiliensis in adrenal glands biopsies of two patients with paracoccidioidomycosis and adrenal insufficiency
Authors: Agudelo Carlos Andrés , Muñoz Carolina , Ramírez Alex , Gutierrez Jonhairo , Velez Santiago , Perez Juan Camilo , Velez Alejandro , Tobon Angela María , Restrepo Angela
Published: February 2009

The authors report two cases of adrenal insufficiency secondary to infiltration of the adrenal glands by Paracoccidioides brasiliensis. The first patient had been treated for a chronic multifocal form of paracoccidiodomycosis 11 years ago. The diagnosis of the mycosis was done simultaneous with that of the adrenal insufficiency in the second patient. In both patients the diagnosis was done by direct visualization of fungus in adrenal biopsies. They were treated with hormonal supplements and itraconazol by 12 and six months, without relapses during the follow-up period.
Primary aspergilloma and subacute invasive aspergillosis in two AIDS patients
Authors: Martinez Roberto , Castro Gleusa de , Machado Alcyone A. , Moya Maria Janete
Published: February 2009

Although uncommon, invasive aspergillosis in the setting of AIDS is important because of its peculiar clinical presentation and high lethality. This report examines two AIDS patients with a history of severe cellular immunosuppression and previous neutropenia, who developed subacute invasive aspergillosis. One female patient developed primary lung aspergilloma, with dissemination to the mediastinum, vertebrae, and spine, which was fatal despite antifungal treatment. The second patient, who had multiple cavitary brain lesions, and eye and lung involvement, recovered following voriconazole and itraconazole, and drugs for increasing neutrophil and CD4+ lymphocyte levels. These cases demonstrate the importance of Aspergillus infections following neutropenia in AIDS patients, and emphasize the need for early and effective antifungal therapy.
Invasive Aspergillus flavus sinusitis: case report in a patient with biphenotypic acute leukemia
Authors: Xavier Melissa Orzechowski , Oliveira Flávio de Mattos , Almeida Valdir de , Prolla Gabriel , Severo Luiz Carlos
Published: February 2009

Here we report a case of invasive pansinusitis with proptosis of the right eye caused by Aspergillus flavus in an immunocompromised patient with acute biphenotypic leukemia without aggressive therapy response.
Funções de pedotransferência para a curva de resistência do solo à penetração
Authors: Almeida Cinara Xavier de , Centurion  , Freddi Onã da Silva , Jorge Ricardo Falqueto , Barbosa José Carlos
Published: February 2009

A estimativa da curva de resistência do solo à penetração (CRP) a partir de variáveis de fácil obtenção, como o conteúdo de água, representa uma medida útil não só para a quantificação do estado de compactação, mas também para facilitar a interpretação da resistência do solo à penetração obtida em diferentes condições de campo. O objetivo deste trabalho foi estimar a CRP em solos de diferentes granulometrias e densidades, a partir de dados obtidos com o penetrômetro de impacto. O experimento foi realizado no laboratório de Pedologia da Faculdade de Ciências Agrárias e Veterinárias (UNESP), Jaboticabal, SP. Foram utilizadas quatro classes de solos: Neossolo Quartzarênico, Argissolo Vermelho-Amarelo, Latossolo Vermelho distrófico e Latossolo Vermelho acriférrico, os quais foram coletados na camada de 0-0,20 m. Colunas de PVC, com dimensões de 0,25 m de diâmetro e 0,6 m de altura, foram preenchidas de forma a obter duas condições de compactação: menor densidade e maior densidade do solo. O conteúdo de água nos solos, inicialmente elevado até o ponto de saturação, foi monitorado diariamente por meio de um medidor eletrônico tipo TDR (Profile Probe PR2 acoplado ao Moisture Meter HH2). A resistência do solo à penetração foi mensurada por meio de um penetrômetro de impacto adaptado para vaso. Os pares de dados entre a resistência do solo à penetração e o conteúdo de água foram ajustados, e as CRP foram submetidas ao teste de significância. A relação entre a resistência do solo à penetração e o conteúdo de água foi descrita pelo modelo exponencial decrescente: , em que RP representa a resistência do solo à penetração (MPa); Ug é o conteúdo de água (kg kg-1); e A, B e C são os coeficientes da equação. Foram obtidos coeficientes de determinação que variaram de 0,79 a 0,96.
Lixiviação de cátions favorecida pela presença de ânions inorgânicos e ácidos orgânicos de baixa massa molecular em solos adubados com camas de aviário
Authors: Gebrim Fabrício de Oliveira , Silva Ivo Ribeiro , Novais Roberto Ferreira , Vergütz Leonardus , Procópio Lorena Costa , Nunes Tiago Novais , Jesus Guilherme Luiz de
Published: February 2009

Com o incremento exponencial da avicultura no Brasil, a disponibilidade de dejetos de aves e de cama de aviário tem aumentado de maneira semelhante. A proibição de uso desses produtos na ração animal tem feito com que eles sejam direcionados para a produção agrícola como fertilizantes. Ainda há na literatura carência de informação sobre lixiviação de bases no perfil do solo em conseqüência do efeito de ânions inorgânicos acompanhantes, como cloreto, nitrato e sulfato, e do efeito complexante de ácidos orgânicos de baixa massa molecular. O objetivo deste trabalho foi estudar o efeito da aplicação de cama de aviário na lixiviação de Ca, Mg, K e Na em solos e sua associação com ânions inorgânicos e ácidos orgânicos de baixa molecular. Amostras de dois Latossolos Vermelho-Amarelos, um de textura média e outro de textura argilosa, foram colocadas em colunas de PVC constituídas de cinco anéis, cada um com 10 cm de altura e 5 cm de diâmetro, ligados entre si com fita adesiva. O solo colocado no anel superior recebeu, homogeneamente, cinco tipos de camas de aviário: casca de café, casca de arroz, sabugo de milho, capim-napier e maravalha, totalizando 160 t ha-1 de material seco, comparado à testemunha (sem a cama de aviário). O experimento constituiu um fatorial 5 x 2, com cinco camas e dois solos, dispostos em blocos casualizados com três repetições. As colunas foram submetidas a 10 percolações com água deionizada, duas vezes por semana, até atingirem o volume de 1.200 mm de chuvas. Nos 10 percolados, foram analisadas as concentrações de Ca, Mg, K e Na, dos ânions Cl-, NO3-e SO4(2-) e de ácidos orgânicos de baixa massa molecular. Houve grande lixiviação de bases nas colunas, principalmente até a terceira percolação. Esse fato foi causado pela adição dessas bases, em doses elevadas, pelas camas de aviário e, aparentemente, também pelo efeito dos ânions acompanhantes Cl-, NO3-e SO4(2-)no solo de textura média, Cl-e NO3-no solo de textura argilosa e, de maneira menos expressiva, pelo efeito acompanhante/complexante dos ácidos orgânicos de baixa massa molecular. No solo argiloso, a percolação de Ca esteve positivamente correlacionada com a concentração dos ácidos málico e oxálico. A concomitante elevada concentração de ácido acético nos percolados de solos tratados com todas as camas sugere que este pode estar favorecendo a lixiviação de bases no solo, provavelmente como ânion acompanhante.