bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Density Hexagonal Nickel Nanowire Arrays with 65 and 100 nm-PERIOD
Authors: Nielsch Kornelius , Wehrspohn Ralf B. , Fischer Saskia F. , Kronmüller Helmut , Barthel Jochen , Kirschner Jürgen , Schweinböck Thomas , Weiss Dieter , Gösele Ulrich 
Published: April 2011

AbstractHighly ordered alumina pore channel arrays are used as templates for the fabrication of magnetic nanowire arrays. These well-defined templates are based on the approach by Masuda and Fukuda and have an interpore distance of 65 and 100 nm and a monodisperse pore diameter of ≍30 nm. The pore channels are hexagonally arranged in 2D-domains, which extend over more than ten interpore distances. Nearly 100% metal filling of the alumina pore structures is obtained by a novel pulsed electrodeposition technique. Due to the high ordering degree of the nanowires arrays, we detect a squareness of ≍100% and coercive fields of 1200 Oe in the direction of the nanowires. The MFM measurements have been carried out by applying magnetic fields on magnetized and demagnetized samples to study the switching behavior of individual nanowires inside the arrays. Magnetic wires have been locally switched by a strong MFM tip and a variable external magnetic field. The MFM results show a good agreement with the bulk magnetic hysteresis loops.
Chiral Polyalkylthiophenes for Organic Light Emitting Diodes
Authors: Lebon F. , Longhi G. , Abbate S. , Catellani M. , Luzzati S. , Bolognesi A. 
Published: April 2011

ABSTRACTChiral polyalkylthiophenes are noncentrosymmetric organic materials which can be used both in second harmonic-generation devices and in polarized light emitting diodes. In this work we present the synthesis and the characterization of a polyalkylthiophene with a chiral center very close to the conjugated backbone: poly(3-[(S)-2-methylbutyl]thiophene) (PMBT). Circular dichroism (CD) measurements have been carried out to ascertain the chirality of these materials. The CD spectra show intense signals both in mixed solvents and in the solid state. The strong Cotton effect can be associated to a highly ordered aggregated phase whose nature is still under investigation. We also present the photo and electroluminescence characterization of single layer light emitting diode (LED) with the following configuration: ITO (Tin Indium Oxide)/PMBT/Al.
Highly Sensitive Optical Sensors Using Electrospun Polymeric Nanofibrous Membranes
Authors: Wang Xianyan , Lee Soo-Hyoung. , Drew Christopher , Senecal Kris J. , Kumar Jayant , Samuelson Lynne A. 
Published: April 2011

ABSTRACTIn recent years, polymer films have found an increasing role in sensors due to their unique characteristics. It is widely accepted that the sensitivity of a film is proportional to the surface area per unit mass. Thin films with very large surface areas can be easily fabricated by electrospinning, wherein a polymer solution is exposed to a high static voltage, creating sub-micron or nanometer scale fibers collected as a non-woven membrane. Electrospun nanofibrous membranes have surface areas approximately one to two orders of the magnitude higher than those found in continuous thin films. It is expected that their sensitivities are potentially as large. In this paper, the first use of an electrospun membrane as a highly responsive fluorescence quenching-based optical sensor is reported. A new fluorescent polymer, polyacrylic acid - poly (pyrene methanol) (PAA-PM), was synthesized via covalent attachment of the fluorescent indicator, pyrene methanol (PM), onto polyacrylic acid (PAA). Optical chemical sensors were then fabricated by electrospinning PAA-PM and thermal crosslinkable polyurethane latex mixture solutions. The synthesis, characterization, electrospinning fabrication, and comparison of the sensitivities to analytes such as ferric ions, mercury, and 2,4-dinitrotoluene between the electrospun membranes and electrostatically layer-by-layer (ELBL) assembled films are presented.
Growth and Morphology of Pentacene Films on Oxide Surfaces
Authors: Ruiz Ricardo , Feldman Leonard C. , Haglund Richard F. , McKee Rodney A. , Koch Norbert , Nickel Bert A. , Pflaum Jens , Scoles Giacinto , Kahn Antoine 
Published: April 2011

ABSTRACTPentacene thin films were grown in ultra high vacuum on amorphous SiO2 and on a high dielectric constant material, crystalline BaTiO3. During pentacene deposition, substrates were held at three different temperatures (-650, 250 and 750 C). In general, three different morphologies were identified: a first closed interfacial layer, a thin film mode composed of faceted grains with single molecule step height, and a volume mode with features substantially higher than those of the thin film mode. Analysis was carried out by atomic force microscopy and in some cases by synchrotron X-ray diffraction.
Photo-Electron Spectroscopy Study of Energy Levels in Conjugated Oligomers
Authors: Veenstra S.C. , Heeres A. , Stalmach U. , Wildeman J. , Hadziioannou G. , Sawatzky G.A. , Jonkman H.T. 
Published: April 2011

ABSTRACTWe report on the valence orbital structure of poly(para-phenylenevinylene) (PPV)-like oligomers. We studied these molecules as isolated oligomers in the gas phase, as well as in thin films deposited on metal substrates. We use a simple model based on a previously reported Hamiltonian that accurately describes the development of the low lying electronic excitations as a function of the number of repeating units. In the study on the thin organic films we report on the energy level alignment at metal / organic and organic / organic interfaces, where the organic layer is either a PPV-like oligomer or C60. The results are important for understanding organic photovoltaic devices.
Fabrication of refractive index and relief gratings in polymer films for DFB lasers
Authors: Kavc T. , Langer G. , Kern W. , Kranzelbinder G. , Toussaere E. , Turnbull G.A. , Samuel I.D.W. , Iskra K.F. , Neger T. 
Published: April 2011

ABSTRACTA styrene copolymer of 4-vinylbenzyl thiocyanate (PST-co-VBT) was employed as recording material for optical interference patterns with periods ∧ < 1 μm. Using lower intensity laser irradiation (4 mJ cm-2, λ = 266 nm), refractive index gratings were produced in PST-co-VBT by an UV induced photoisomerization SCN - NCS. Subsequent modification of the patterns with gaseous amines yielded surface relief gratings via the formation of derivatives of thiourea. Laser irradiation with higher pulse energies (7 mJ cm-2, λ = 266 nm) directly produced surface relief gratings (modulation depth 30 nm). These gratings were also reactive towards amine reagents and allowed a selective functionalization of the grooves of the relief (“reactive gratings”). Optically inscribed gratings in PST-co-VBT were employed as optical resonators for distributed feedback (DFB) lasing. With a laser dye (DCM) dissolved in PST-co-VBT, optically pumped DFB laser action was observed after inscribing index and relief gratings. The pumping threshold for lasing Ith was 250 nJ cm-2 at λ = 532 nm.
Influence of Thermal Aging on the Mechanical and Corrosion Properties of GTAW Welds of Alloy N06022
Authors: Summers Tammy S. Edgecumbe , Rebak Raúl B. , Palmer Todd A. , Crook Paul 
Published: April 2011

ABSTRACTThe phase stability of C-22 alloy (UNS N06022) gas tungsten arc welds was studied by aging samples at 593, 649, 704, and 760°C for times up to 6,000 hours. The tensile properties and the Charpy impact toughness of these samples were measured in the as-welded condition as well as after aging. The corrosion resistance was measured using standard immersion tests in acidic ferric sulfate (ASTM G 28 A) and 2.5% hydrochloric acid solutions at the boiling point. The microstructures of weld samples were examined using scanning electron microscopy (SEM). Precipitate volume fraction measurements were made using optical microscopy.Degradation of the mechanical and corrosion properties of C-22 welds due to aging at all temperatures investigated was seen to occur sooner than was seen in C-22 base metal. An evaluation of the kinetics of nucleation and growth of the precipitates forming at these temperatures, however, indicated that no significant changes in TCP phase morphology would occur at temperatures below approximately 300°C.a
Building the Safety Case for a Disposal Facility for Spent Fuel, HLW and Long-lived ILW in Switzerland
Authors: Smith Paul A. , Zuidema Piet , Johnson Lawrence H. , Schneider Jürg W. , Gribi Peter 
Published: April 2011

ABSTRACTThis paper describes a generic methodology for building the safety case for a geological repository, which is currently being applied to a possible facility for spent fuel, vitrified highlevel waste and long-lived intermediate-level waste in the Opalinus Clay of Northern Switzerland. The methodology involves:1. the identification of certain basic disposal principles,2. the choice of a disposal system, via a flexible repository development strategy,3. the derivation of the system concept, based on current understanding of the phenomena that characterise, and may influence, the disposal system and its evolution,4. the derivation of a safety concept, based on reliable, well understood and effective pillars of safety,5. the illustration of the radiological consequences of the disposal system through the definition and analysis of a wide range of assessment cases, and6. the compilation of the arguments and analyses that constitute the safety case, as well as guidance for future stages of the repository programme. A range of measures, including audits, are used to promote completeness of the phenomena considered in the safety case, and to avoid inadvertent bias.
Diffusion and Sorption of Radioactive Cesium and Cobalt in Regolith Materials of Central Australia
Authors: Itakura Takashi , Leo Chin Jian , McOrist Gordon D. , Payne Timothy E. 
Published: April 2011

ABSTRACTDiffusion and sorption are potentially the most important factors governing the transport of radionuclides in clays and under stationary subsurface environmental conditions. Preliminary studies have been performed to measure the transport of 137Cs and 60Co with no advection, using reconstituted samples of three regolith materials collected from a region in South Australia. The samples were saturated with CaSO4 solution to imitate the pore water chemistry of the in situ environment. A double diffusion cell testing apparatus made of polycarbonate resin was used to measure the transport of the selected radionuclides through the samples. A curve fitting procedure employing one-dimensional contaminant equations with a “stop-start” technique was used to estimate the diffusion (D) and sorption coefficients (Kd) from the measured concentration-time profiles. Results from these experiments are compared with those obtained from batch sorption tests.
The Redox Environment of Deep Groundwaters Associated with the Tono Uranium Deposit, Japan
Authors: Arthur Randy , Iwatsuki Teruki , Hama Katsuhiro , Amano Kenji , Metcalfe Richard , Ota Kunio 
Published: April 2011

ABSTRACTAn unconformity underlying the Tono uranium deposit in central Japan represents the approximate location of a redox front separating relatively oxidizing groundwaters (Eh ≈0 mV) in the weathered, fractured Toki granite (TG) from strongly reducing pore fluids (Eh ≈-360 mV) in sedimentary rocks of the overlying Lower Toki Lignite-bearing Formation (TL). Uranium has been effectively immobilized in the TL during the past 10 million years. Stable and reversible redox potentials measured in-situ in boreholes penetrating the sedimentary rocks and granite appear to be controlled by the Fe(III)-oxyhydroxide – Fe2+ redox couple. A simplified analytical model of front migration suggests that chemical buffering by pyrite alone would limit the propagation velocity of the front into the TL to less than 8x10−6 m yr−1. The model is constrained by Darcy fluxes derived from groundwater flow models and relative 14C groundwater ages, average modal abundances of pyrite in the TL, and the analytical detection limit for dissolved oxygen in TG groundwaters (2 ppm). Model results also suggest that the redox buffering capacity of the TL would be exhausted within 10 million years if an upper bound O2(aq) concentration in TG groundwaters fixed by equilibrium with atmospheric O2(g) (8.5 ppm) is assumed. Immobilization of uranium in the TL is thus attributable to oxidation-reduction reactions that minimize O2(aq) concentrations primarily in the TG, and secondarily in the TL.
Application of the Systems Analysis Approach to a Natural Analogue Project
Authors: Stenhouse M.J. , Arthur R. , Ota K. , Iwatsuki T. , Metcalfe R. , Takase H. 
Published: April 2011

ABSTRACTThe Tono uranium deposit (Gifu Prefecture, central Japan) was formed about 10 million years ago and available evidence suggests that this deposit has remained stable, i.e. uranium has not migrated significantly since then. Substantial field and modeling work is being carried out to better understand the hydrogeological and geochemical processes affecting or governing uranium transport and immobilization in and around the Tono uranium deposit. A systems analysis approach has been applied to the Tono deposit natural analogue project. Application of a systems analysis approach to a generic research project is novel and is different from prevailing applications. Previous applications of a systems analysis approach have been principally concerned with performance and safety assessments for radioactive waste disposal. The systems analysis approach provides a convenient framework for this project, having been used in the Tono Natural Analogue Project (TAP) to:• define the system to be studied;• identify features, events and processes (FEPs) associated with this system;• identify external factors (EFEPs) which are likely to have influenced the Tono area or study site or uranium deposit;• define interactions between pairs of FEPs; and• develop credible scenarios for evolution of the area or uranium deposit.The results from the systems analysis approach allow us to:• develop possible scenarios for how the Tono area or study site evolved,• evaluate uncertainty and how it propagates backwards in time,• link field characterization data with predictive modeling, and• identify gaps in data and, hence, identify additional characterization needs.
A Solid Solution Model for Sorption of Radionuclides in Cement
Authors: Emrén Allan T. 
Published: April 2011

ABSTRACTof these two main phases in cement, portlandite is rather compact while the gel phase has a very irregular morphology, probably fractal. This work essentially deals with sorption that takes place as absorption in the gel phase, but the same theory is applicable for any of the phases present in cement. It is also able to handle sorption in any combination of phases in the cement. A model for multi component solid mixtures has been developed, essentially following the Guggenheim excess free enthalpy approach. Measurement of Kd for one gel composition makes it possible to calculate Kd values during the entire process of cement degradation. The main limitation is that the concentration of the radionuclide has to be low enough for all higher terms in the series expansion to be negligible. The model is mostly valid for elements forming cations and it also requires the sorbed element to form a compound of reasonably low solubility with one of the anions in cement (hydroxide or silicate). Kd values for Ni in cement has been taken from the literature and used to illustrate the model.
Mechanical Testing of Electrotextile Cables and Connectors
Authors: Slade Jeremiah , Wilson Patricia , Farrell Brian , Teverovsky Justyna , Thomson Douglas , Bowman Jeremy , Agpaoa-Kraus Marty , Horowitz Wendy , Tierney Edward , Offray C. M. , Winterhalter Carole 
Published: April 2011

ABSTRACTToday's complex geo-political climate has forced the U.S. armed services into new operational strategies. The prevalence of international terrorism, the threat from chemical and biological weapons, and the pressure to “do more with less” has placed increasing demands on the military. This new operational environment requires highly mobile troops having enhanced decision-making capability provided through the rapid transfer and dissemination of information to each member of the squad. What is missing is the ability to process and use this information via an Intranet at the level of the individual soldier. The purpose of our work has been to develop, evaluate and implement such a wearable conductive network for the dismounted soldier.
Ionic Liquid Based Gel Electrolyte Compositions for Dye Sensitized Solar Cells
Authors: Chittibabu K. G. , Hadjikyriacou S. , Li L. 
Published: April 2011

ABSTRACTKonarka Technologies has developed efficient electrolyte compositions based on nonvolatile ionic liquids. The electrolyte compositions were subsequently gelled using a metal ion complexation technique, without compromising the photovoltaic performance of the dye sensitized solar cells (DSSCs). The photovoltaic performance of the gel electrolyte incorporated DSSCs is quite stable for extended period of time even in the absence of sealing. Detailed results on performance and stability of the gel electrolyte incorporated DSSCs are presented.
Polymer-on-Polymer Stamping on Micro- and Nano-Scales
Authors: Gourdin Shoshana , Crites Travis , Coe Seth , Bulovic Vladimir , Hammond Paula 
Published: April 2011

ABSTRACTThe goal of the project was to determine whether PDAC (poly (diallyldimethylammonium chloride), also abbreviated PDADMAC) could be printed reproducibly to create patterns with a sub-micron resolution. PDAC was stamped onto bare silicon using PDMS stamps having features only about 150 nm wide. A variety of aqueous PDAC inks were tried, to study the effect of concentration and ionic strength on the pattern produced. In order to get good prints, new stamping techniques were also required. A rigid stamping apparatus was built to ensure steady placement, and the stamps were spin coated with a different ink solution to produce thin, even coats of ink. [1] Using these methods, the pattern transferred.
Effect of Process Variables and Dopants on Characteristics of Electrochemically-Deposited Pedot Films
Authors: Oka Mihir A. , Hardaker Stephen S. , Nazir Farzad , Gregory Richard V. , Brenneman Keith R. , Lessner Philip M. 
Published: April 2011

ABSTRACTPoly(3,4-ethlyenedioxythiophene), PEDOT, has found wide use in applications such as electrostatic coatings, antistatic layers and electrode materials in electronic devices. Electrochemical deposition of PEDOT is a prominent means of obtaining thin, uniform films. However, the relationship of these films' properties to their morphological structure is still poorly understood. We have prepared PEDOT films by electrochemical oxidation of monomer (3,4-ethylenedioxythiophene), EDOT, under constant current conditions, employing a variety of electrolytes, and processing conditions. We report the effect of using different dopants, deposition time, deposition temperature and current density on the observed conductivity of PEDOT films. Atomic force microscopy studies were carried out to determine the possible effect of the process variables on the resulting film morphology. Also, the effect of residual solvent on the conductivity of the films was studied by thermogravimetric analysis (TGA).
Giant exciton-light coupling in large size semiconductor quantum dots
Authors: Gil Bernard , Kavokin Alexey V. 
Published: April 2011

ABSTRACTWe investigate the strength of the coupling of the electronic states with the electromagnetic field in semiconductor nanospheres, taking into account the retardation effect. We show that the coupling strength is particularly strong: the bulk properties are so enhanced that the radiative decay time can reach some 30 picoseconds for quantum dots sizes of some 30 nm.
Observation of Quantum Confinement Effects in Nanocrystalline Silicon Dot Floating Gate Single Electron Memory Devices
Authors: Huang Shaoyun , Banerjee Souri , Oda Shunri 
Published: April 2011

ABSTRACTElectron charging and discharging processes in floating gate MOS memory based on nanocrystalline silicon (nc-Si) dots were investigated at room temperature using capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. Sequential electron discharging processes from nc-Si dots manifest themselves clearly in G-V spectroscopy after charging of the dots. According to the conductance peak structure resulting from the Coulomb blockade as well as quantum confinement effects of nc-Si dots, electron-addition energy is estimated to be 50 meV. Taking the electron-charging energy between the silicon substrate and the floating dot (30 meV) into account, the quantum confinement energy is found to be comparable to the electron charging energy for an nc-Si dot of 8 nm in diameter embedded in the silicon oxide.
Self-assembled Si/Ge quantum dot structures for novel device applications
Authors: Brunner K. , Bougeard D. , Janotta A. , Herbst M. , Tan P. H. , Riedl H. , Stutzmann M. , Abstreiter G. 
Published: April 2011

ABSTRACTThe band structure of self-assembled Si/Ge quantum dot structures deposited by molecular beam epitaxy in the Stranski Krastanov growth mode is characterized by optical and electrical spectroscopy. Interband and intraband absorption, photocurrent, photoluminescence, Raman and admittance spectroscopy of structures with quantum dots of about 20 nm lateral size offer insight into the discrete level scheme within the valence band, the optical transitions and the lifetime of localized hole states. The results are discussed with respect to their possible applications in infrared light detection, storage and quantum-logic devices.
Diffusional Coating of Nanoparticles
Authors: Lavine James P. 
Published: April 2011

ABSTRACTThe time-dependent diffusion of particles to an absorbing sphere is investigated with three random walk models. The first uses consecutive independent particles and finds the capture time distributions are exponential for a range of values of the surface absorption probability. The next two models are of the ensemble variety and assume that only a finite number of particles may be absorbed by the sphere. These models investigate depletion effects and concentration dependence. The latter is probed by varying the initial number of diffusing particles. It is found
Two-dimensional Epitaxial Growth of Strained InGaAs on GaAs (001)
Authors: Wen Hong , Wang Zhiming , Salamo G.J. 
Published: April 2011

ABSTRACTMolecular beam epitaxy growth of lattice mismatched In0.53Ga0.47As / GaAs(100) system is studied by in situ scanning tunneling microscope (STM) and reflection high energy electron diffraction. InGaAs layers with a thickness ranging up to 250 nm do not exhibit a smooth surface when grown under In-rich conditions. RHEED and STM confirm the well-ordered (4×2) reconstruction and mono-layer steps associated with this unique planar growth mode. Large STM scans reveal a characteristic morphology of rectangular shaped islands distributed on large flat terraces which are typically more than 300 nm width but only mono-layer steps.
Fabrication of Si-Ge Compound Nanowires by the FZ Melting Vapor Method
Authors: Hu Quanli , Araki Hiroshi , Suzuki Hiroshi , Ishikawa Nobuhiro , Yang Wen , Noda Tetsuji 
Published: April 2011

ABSTRACTA simple method, floating zone melting vapor, was used for fabricating nanowires of Si-Ge material. Single-crystalline nanowires were successfully synthesized. TEM images of these nanowires indicated that each nanowire consists of an inner single-crystalline core and an outer layer. An observation using high-resolution transmission electron microscopy (HRTEM) showed that almost all nanowires have a similar growth orientation to the crystalline core: [210]. The coexistence of germanium-self-catalyzed and oxide-assisted mechanisms has also been suggested.