bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leaching Behaviour of Low -Activity Alpha-Doped UO2.
Authors: Rondinella Vincenzo V. , Cobos Joaquin , Wiss Thierry 
Published: April 2011

AbstractSo-called alpha-doped UO2(i.e. UO2containing short-lived alpha-emitters) can reproduce the activity levels of spent fuel at different ages. Previous experiments showed significant effects of alpha-radiolysis at relatively high alpha-activity levels (e.g., in the range 108– 1010Bq/g). This study shows the results of leaching tests done on low alpha-activity material (106– 107Bq/g). UO2containing ∼10 and ∼1 wt. %233U was leached at room temperature in deionized and carbonated water under deaerated conditions. Higher release in carbonated water was observed. A clear radiolytic enhancement of the concentration of uranium in solution was observed for the material containing 10 wt. %233U. The dissolved U concentration was very close to the values previously observed for higher activity alpha-doped UO2and confirmed the finding that under relatively high surface/volume condition the measured amount of U in solution is essentially independent of the alpha-activity level. No significant radiolysis effect was detected for the material doped with 1%233U compared to undoped UO2after ∼4 months of leaching. The post- leaching SEM examination revealed no pronounced etching of the surfaces.
Spin Effects of Low-dimensional Electron Gases Studied by Far-infrared Photoconductivity Experiments
Authors: Hu C. -M. 
Published: April 2011

AbstractWe review our recent work on spin effects in low-dimensional electron gases studied using far-infrared photoconductivity technique. We measure the spin-orbit coupling parameter α via spectroscopy by detecting the combined resonance. Detailed filling-factor dependent study shows the collective nature of this excitation, in accordance to theoretical predictions that both Kohn and Larmor theorem are broken for long-wavelength excitations that changes both the Landau and spin quantum numbers. We find that the long spin-relaxation time of a two-dimensional electron gas results in a novel bolometric spin effect, which gives rise to a substantial photo resistance change by reversing the spin polarization of electrons at the Fermi-level.
Theory of Electrically Controlled Resonant Tunneling Spin Devices
Authors: Ting David Z.-Y. , Cartoixà Xavier 
Published: April 2011

AbstractWe report device concepts that exploit spin-orbit coupling for creating spin polarized current sources using nonmagnetic semiconductor resonant tunneling heterostructures, without external magnetic fields. The resonant interband tunneling spin filter exploits large valence band spin-orbit interaction to provide strong spin selectivity. The bi-directional spin pump induces the simultaneous flow of oppositely spin-polarized current components in opposite directions through spin-dependent resonant tunneling. The efficiency of resonant tunneling spin devices can be improved when the effects of structural inversion asymmetry (SIA) and bulk inversion asymmetry (BIA) are combined properly, and incorporated into device design. The current spin polarizations of the proposed devices are electrically controllable, and potentially amenable to high-speed modulation. In principle, the electrically modulated spin-polarized current source could be integrated in optoelectronic devices for added functionality.
Rashba spin-orbit coupling in InGaAs/InP quantum wires
Authors: Knobbe Jens , Guzenko Vitaliy A. , Schäpers Thomas 
Published: April 2011

AbstractThe effect of Rashba spin-orbit coupling on the transport properties of InGaAs/InP quantum wire structures is investigated. The geometry of the wire structures was defined by selective wet chemical etching. For wires without a gate a clear beating pattern, due to the presence of the Rashba spin-orbit coupling, is observed for wires with a width down to 600 nm. For narrower wires no beating pattern is found. The experimental observations are explained by contribution of the Rashba spin-orbit coupling to the one-dimensional magnetosubbands. By depleting the one-dimensional conductor by means of a gate electrode the Rashba coupling strength could be controlled.
Biomimetic Surfaces via Dextran Immobilization: Grafting Density and Surface Properties
Authors: Miksa Davide , Irish Elizabeth R. , Chen Dwayne , Composto Russell J. , Eckmann David M. 
Published: April 2011

AbstractBiomimetic surfaces were prepared by chemisorption of oxidized dextran (Mw = 110 kDa) onto SiO2 substrates that were previously modified with aminopropyl-tri-ethoxy silane (APTES). The kinetics of dextran oxidation by sodium metaperiodate (NaIO4) were quantified by 1H NMR and pH measurements. The extent of oxidation was then used to control the morphology of the biomimetic surface. Oxidation times of 0.5, 1, 2, 4, and 24 hours resulted in <20, ∼30, ∼40, ∼50 and 100% oxidation, respectively. The surfaces were characterized by contact angle analysis and atomic force microscopy (AFM). Surfaces prepared with low oxidation times revealed a more densely packed “brushy” layer when imaged by AFM than those prepared at low oxidation times. Finally, the contact angle data revealed, quite unexpectedly, that the surface with the greatest entropic freedom (0.5 h) wetted the fastest and to the greatest extent (θAPTES>θ1h>θ2,4h>θ0.5h).
Fluorophore Conformation in Green Fluorescent Protein: A Quantum Mechanics/Molecular Mechanics Study
Authors: Trohalaki Steven , Patnaik Soumya S. , Pachter Ruth 
Published: April 2011

AbstractGreen Fluorescent Protein (GFP) is a widely used fluorescent marker exhibiting two excitation peaks – a strong peak at 398 nm and a second at 475 nm, with the fluorescence at ca. 510 nm. Its molecular structure consists of a β-barrel composed of 11 β-strands and a central helix containing the fluorophore. Two different forms of the fluorophore – a protonated/neutral fluorophore and a de-protonated/anionic fluorophore – are thought to be responsible for the two distinct spectroscopic states. Notably, the isolated fluorophore in solution is efficiently quenched. Conformational flexibility within the protein cavity is an implicitly important factor that governs the photochemistry of GFP. However, the literature contains accounts of studies that reach conflicting conclusions, claiming that either the fluorophore's barrier to internal rotation is negligibly small or that the protein cavity is not complementary to a planar fluorophore. In this work, we calculate the torsional potential of one of the two exocyclic bonds that connect the two rings in the fluorophore, taking into account its immediate environment by applying a quantum mechanics/molecular mechanics method, with the ultimate aim of evaluating the protein-environment effects on the fluorescence.
Teaching Undergraduates Nanotechnology
Authors: Shapter J.G. , Hale P. , Maddox L.M. , Ford M. J. , Waclawik E. R. 
Published: April 2011

AbstractOne of the first nanotechnology undergraduate degrees in the world was established at Flinders University in 2000. In this paper we present our experience of developing and delivering this degree in a climate where “traditional” physical sciences are under considerable strain. We will discuss the motivation for this initiative, structure of the established course and educational issues relating to its development.
Teaching Computational Materials Science for Nanoscale Science and Engineering
Authors: Glotzer S.C. , Horsch M.A. , Lamm M.H. , Iacovella C.R. , Zhang Z.L. 
Published: April 2011

AbstractWe describe the development of a graduate level course designed to teach computational materials science and its application to nanoscale science and engineering. We discuss the use of MatDL, a web-based digital library and materials science resource, as a collaborative learning tool within the context of the course.
AtomLab: A tool for teaching materials science and simulation on the atomic scale
Authors: Falk Michael L. 
Published: April 2011

AbstractAtomLab is a publicly available software package created to help students and faculty design and execute simulations for instructional purposes. AtomLab has been utilized as a learning environment within which to teach simulation techniques to graduate students. It has also been used to provide conceptual tools for undergraduate education. This paper presents a brief description of the AtomLab environment and of an undergraduate educational module designed to teach the atomic mechanisms of transport. Data is presented regarding the educational outcomes that were met using this module and the student response to the exercise.
Goniometry of Direct Lattice Vectors Supporting Students' Comprehension of Crystallographic Core Concepts and Demonstrating Image-Based Nanocrystallography
Authors: Moeck P. , Padmanabhan K. , Qin W. , Fraundorf P. 
Published: April 2011

AbstractWe are of the opinion that students of an introductory materials science and engineering course should gain a thorough understanding of crystallographic core concepts by applying them quasi-experimentally in computer simulation sessions that run parallel to the lectures. Software simulations of goniometry of direct lattice vectors in a transmission electron microscope (TEM) will serve two purposes at once: to introduce students to practical aspects of electron microscopy and support their comprehension of crystallographic core concepts. We use the programming software Matlab and Java (Jmol applets) on a PC platform for the creation of software simulations that demonstrate this methodology and complement already existing software simulations. The newly created software is used in classroom demonstrations of an introductory materials science and engineering course at Portland State University and will become freely accessible over the internet. This software will also support and promote image-based nanocrystallography in TEM.
Development of a Hybrid Enzyme-Based Porous Silicon Platform for Chemical Warfare Agent Detection
Authors: Létant Sonia E. , Hart Bradley R. , Kane Staci R. , Hadi Masood Z. , Shields Sharon J. , Cheng Tu-Chen , Rastogi Vipin K. , Del Eckels J. , Reynolds John G. 
Published: April 2011

ABSTRACTThe goal of our research is to combine porous silicon and enzymes in order to build hybrid platforms for extremely selective chemical sensing applications. For this, a new synthetic route to covalently anchor bio-molecules on photo-luminescent porous silicon (PL PSi) while preserving the optical properties of the matrix was developed. The hydride terminated porous silicon surface was covalently functionalized with t-butyloxycarbonyl protected amine by light-assisted hydrosysilation. Protein cross-linker chemistry was then used to extend the linker and immobilize various enzymes. The glu-coronidase enzyme/p-nitro-phenyl-beta-glucoronide substrate test system provided a proof of concept for an enzyme-based porous silicon detector. The enzymatic activity and the luminescence of the porous silicon platform were both retained after the functionali-zation procedure and, charge transfer between the products of the enzymatic breakdown and the silicon quantum dots was demonstrated. The organophosphorous hydrolase enzyme OPAA was then immobilized and tested on p-nitrophenyl-soman, a surrogate substrate for soman. The production of the hydrolysis product, p-nitrophenol, correlated with the reversible luminescence quenching of the porous silicon matrix demonstrating the relevance of the enzyme-based platform for detection applications. This detection scheme, although indirect, takes advantage of the extreme specificity of enzymes. The approach is general and can be implemented for a series of target molecules.
Sol-gel derived porous silica as a constituent material for designing optical fiber chemical sensors
Authors: Tao Shiquan , Fanguy Joseph C. , Xu Lina 
Published: April 2011

AbstractSol-gel processes were developed to prepare nano porous silica materials. The obtained porous sol-gel silica (PSGS) materials have been used as constituent materials in designing optical fiber chemical sensors. A PSGS membrane coated on the surface of an optical fiber was used as a transducer for sensing humidity level in air. A PSGS membrane doped with an ammonia indicator dye has been coated on an optical fiber to sense ammonia in air. Both of the coating based sensors are reversible and fast response. In the tested range, relative humidity (RH) in air down to 3% can be detected with the PSGS coated fiber optic sensor. The fiber optic ammonia sensor with ammonia indicator doped PSGS coating can be used to sense ammonia in air down to sub-ppm level. PSGS has also been used as a constituent material in preparing porous silica optical fibers. The obtained porous optical fibers have been used to design optical fiber chemical sensors for sensing humidity, ammonia and volatile organic compounds. A CuCl2 doped PSGS fiber has been tested for sensing ammonia in a high temperature gas sample. Ammonia in the high temperature air gas diffuses into the PSGS fiber, reversibly reacts with CuCl2 doped in the PSGS fiber to form a complex. The formed complex was detected with fiber optic spectrometric method. This sensor can detect ammonia in a high temperature (450 °C) air gas stream down 0.3 ppm. Techniques of preparing PSGS, coating PSGS on an optical fiber, making a porous optical fiber with PSGS as a constituent material will be presented. Examples of optical fiber sensors using PSGS coatings and a PSGS fiber as transducers for gas sensing are presented.
A Titania Nanotube-Array Room-Temperature Sensor for Selective Detection of Low Hydrogen Concentrations
Authors: Varghese Oomman K. , Mor Gopal K. , Paulose Maggie , Grimes Craig A. 
Published: April 2011

ABSTRACTA tremendous variation in electrical resistance, from the semiconductor to metallic range, has been observed in titania nanotube arrays at room temperature, ≈ 25°C, in the presence of low ppm hydrogen gas concentrations (≤ 1000 ppm). The nanotube arrays are fabricated by anodizing titanium foil in an aqueous fluoride containing electrolyte solution. Subsequently, the arrays are annealed in an oxygen ambient, then coated with a 10 nm layer of palladium by evaporation. Electrical contacts are made by sputtering a small (e.g. 1 mm diameter) platinum disk atop the Pd coated nanotube-array. These sensors exhibit a resistance variation of the order of over 107 (1,000,000,000%) in the presence of 1000 ppm hydrogen at 23°C. To the best of our knowledge this dynamic change in electrical resistance the largest known response of any material, to any gas, at any temperature. The sensors demonstrate complete reversibility, repeatability, high selectivity, no drift and wide dynamic range. The nanoscale geometry of the nanotubes, in particular the points of tube-to-tube contact, is believed to be responsible for the outstanding hydrogen gas sensitivities.
A Novel Theoretical Model for Semiconductor Oxide Gas Sensor
Authors: Shukla Satyajit , Seal Sudipta 
Published: April 2011

ABSTRACTA new constitutive equation for the gas sensitivity of n-type semiconductor oxide thin film gas sensor has been proposed here based on a single-crystal model. The derived constitutive equation shows the dependence of the gas sensitivity on various critical parameters such as nanocrystallite size, space-charge-layer thickness, reducing gas concentration, bulk charge-carrier-concentration, surface-density of states, oxygen-ion-vacancy concentration, operating temperature, and film thickness. The present theoretical model is applicable to all n-type semiconductor oxides gas sensors.
Gas sensors based on semiconductor oxides: basic aspects onto materials and working principles
Authors: Cristina M. , Giberti Alessio , Guidi Vincenzo , Malagù Cesare , Vendemiati Beatrice , Martinelli Giuliano 
Published: April 2011

ABSTRACTThe properties of the most important semiconductor oxides for gas sensing, such as SnO2, TiO2, WO3 and their modifications due to ion-addition or to catalyzers, have been reviewed. The oxide powders, synthesized via wet chemical routes, have been characterized both as dispersed powders and as sintered films. Deposition of thick film gas sensors was carried out through screen-printing technology. They have been studied comparing the electrical behavior under identical environmental conditions. Potential barrier heights have been measured via stimulated temperature measurements and density of ionized donors obtained via Hall Effect. A theoretical model has been developed to justify the size dependent behavior of nanocrystalline oxides.
Chemical Vapor Depositions of Single Walled Carbon Nanotube thin films and their applications for sensors in aqueous solutions
Authors: Fu Qiang , An Lei , Lu Chenguang , Liu Jie 
Published: April 2011

AbstractHigh-density and high-quality single walled carbon nanotubes are directly grown on surface by Chemical Vapor Depositions. We found that those SWNT thin films could be used to fabricate thin film field-effect transistors. Those transistors are very sensitive to surface charges changes in aqueous solutions and could be used tobuild chemical sensors.
Gas Selectivity of Polycrystalline Thick Films of SrPb1−xBixO3−δ
Authors: Michel Carlos R. , Santillán Gloria , Quino Abraham , Chávez Arturo 
Published: April 2011

ABSTRACTPolycrystalline samples of the perovskites: SrPb1−xBixO3−δ (x = 0, 0.1) were prepared from the dissolution of stoichiometric amounts of Sr(NO3), Pb(NO3)2 and Bi(NO3)3 in aqueous media. The solutions were heat-dried at 75°C obtaining powder precursors. To determine the temperature of formation of these phases, thermal analyses were made on them. Calcination at 650°C for 6 h produced pure samples, which were characterized by X-ray powder diffraction. The surface microstructure of powders was analyzed by scanning electron microscopy, and showed that this preparation procedure yield micron-sized particles, which formed agglomerations. To evaluate their gas sensing behavior, the resulting powders were finely ground and mixed with acetone to form thick-films. The electrical conductivity vs. temperature of films was measured in dry air, O2 and CO2, and resulted that SrPb0.9Bi0.1O3−δ has a better sensitivity to O2 compared to SrPbO3−δ, caused by the partial substitution of lead by bismuth.
Nanomatertials as Low Density Lipoprotein (LDL) Sensors
Authors: Tang Tao , Liu Xiaolei , Li Chao , Lei Bo , Zhang Daihua , Rouhanizadeh Mahsa , Hsiai Tzung , Zhou Chongwu 
Published: April 2011

ABSTRACTIn2O3nanowire and carbon nanotube transistors were used to study the chemical gating effects in response to LDL particles. Low density lipoprotein (LDL) cholesterol in blood constitutes a risk factor for coronary artery disease (heart attack). The interactions of LDL particles with these two different surfaces were investigated. The degree of LDL particles binding to carbon nanotubes was ten-fold higher than to In2O3nanowires possibly owing to the hydrophobic/hydrophilic interactions. The conductance of field effect transistors (FET) based on nanowires and nanotubes showed complementary responses after exposure to LDL particles. While In2O3nanowire transistors exhibited higher conductance accompanied by a negative shift of the threshold voltage, nanotube transistors displayed a lower conductance. This phenomenon was attributed to the complementary doping between the n-type In2O3nanowires and p-type carbon nanotubes.
Printable Electronics: Patterning of Conductive Materials for Novel Applications
Authors: Karwa Anupama , Xia Yu , Clark Daniel M. , Smith Thomas W. , Kahn Bruce E. 
Published: April 2011

ABSTRACTThe convergence of materials science, printing, and electronics promises to offer low cost and high volume production of devices such as transistors, RFID tags, wearable electronics and other novel applications. Although a number of “soft lithographic” techniques have been used to make these devices, they are slow and have a limited production volume [5], [14-15].Here high volume printing processes like rotary letterpress, flexography and offset lithography have been investigated for patterning conductive materials [1]. The synthesis and development of conducting inks using electrically functional polymers has been studied. The feasibility of using such inks in high volume printing processes has been studied. An attempt has been made to print conductive interdigitated electrodes using these inks to obtain uniform coating properties and appropriate electrical characteristics. Various process parameters like type of substrate, inking time and speed, printing pressure, printing force and ink formulation have been investigated.
Mechanism of the Oxygen Interaction with a Surface of Thin Nanosized Metal Oxide Film
Authors: Brinzari Vladimir I. , Dmitriev Serghei V. , Korotcenkov Ghenadii S. 
Published: April 2011

ABSTRACTThis paper presents result of investigation of the oxygen interaction with a surface of semiconductor metal oxide film. The idea to carry out such research is connected with the key role, which oxygen plays in the processes of impurity gas molecules detection in atmosphere and semiconductor surface sensibilization. Numerical modeling of the interaction was carried out for different temperatures and oxygen partial pressures. Results of modeling are compared with the results of experimental study of oxygen-semiconductor film system.
Low Cost Integrated Sensors Utilizing Patterned Nano-Structured Titania Arrays Fabricated Using a Simple Process
Authors: Samah Zuruzi Abu , Kolmakov Andrei , Moskovits Martin , MacDonald Noel C. 
Published: April 2011

ABSTRACTUsing a novel low-temperature process, we demonstrate the facile integration of crack-free nanostructured titania (NST) as sensing elements in microsystems. Unlike conventional sol-gel methods, NST layers of interconnected nano-walls and nano-wires were formed by reacting Ti surfaces with aqueous hydrogen peroxide solution. Cracks were observed in NST layers formed on blanket Ti films but absent on arrays of patterned Ti pads below a threshold dimension. Analyses using TEM, high resolution SEM, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) reveal that NST consists of anatase TiO2 nano-crystals. NST pads were found able to detect oxygen gas of a few ppm. NST pad arrays were integrated on rigid and flexible substrates with potential applications in low cost and wearable sensing systems.
Future Directions of Non-volatile Memory Technologies
Authors: Fazio Albert 
Published: April 2011

ABSTRACTIt expected that for many years to come, the majority of the nonvolatile memories shipped will be based on current mainstream flash technologies, which utilize transistor based charge storage memory cells and multi-level-cell concepts, for storing more than one logic bit in a single physical cell. Moore's law will continue to drive transistor based memory technology scaling but technology complexity will be increasing. In order to meet technology scaling, the mainstream transistor based flash technologies will start evolving to incorporate material and structural innovations. This paper will review the current status and discuss the approaches being explored to provide scaling solutions for future transistor based non-volatile memory products. Based on the introduction of material innovations, it is expected that the planar transistor based flash memory cell can scale into the 32nm node. Further, more complex, structural innovations will be required to maintain further scaling. New memory concepts, not relying on transistors as a basis of the memory cell, provide new opportunities for future low cost memories. Several of these new concepts will be summarized and contrasted with the mainstream transistor based flash memory technologies.