bluuebunny/crossref_metadata_2025_split huggingface dataset:
Possible Formation of H-type Aggregates in H2TPyP/PMMA Guest Host Films
Authors: Mota Wesley da Silva , Melo Wanessa Canedo , Nunes Luiz Antônio de Oliveira , Machado Antônio Eduardo da Hora , Batista Alzir Azevedo , Guedes Ilde , Barbosa Newton Martins 
Published: August 2010

AbstractIn this work we have employed UV-Vis absorbance and excitation techniques in addition to quantum chemical calculations to investigate the probable formation of H-type aggregates of zero charged aryl substituted porphyrin in a guest- host solid state structure. The films were factored via casting technique mixing free-base tetrapyridyl porphyrins (H2TPyP) and polymethilmethacrilate polymer (PMMA) chlorophorm solutions. A pathway for the possible formation of H-type aggregate is suggested.
Neutron Diffraction Study of the Structural Changes Occurring During the Low Temperature Oxidation of UO2
Authors: Baldinozzi Gianguido , Desgranges Lionel , Rousseau Gurvan 
Published: August 2010

AbstractThe oxidation of uranium dioxide has been studied for more than 50 years. It was first studied for fuel fabrication purposes and then later on for safety reasons to design a dry storage facility for spent nuclear fuel that could last several hundred years. Therefore, understanding the changes occurring during the oxidation process is essential, and a sound prediction of the behavior of uranium oxides requires the accurate description of the elementary mechanisms on an atomic scale. Only the models based on elementary mechanisms should provide a reliable extrapolation of laboratory results over timeframes spanning several centuries. The oxidation mechanism of uranium oxides requires understanding the structural parameters of all the phases observed during the process. Uranium dioxide crystal structure undergoes several modifications during the low temperature oxidation that transforms UO2 into U3O8. The symmetries and the structural parameters of UO2, β-U4O9, β-U3O7 and U3O8 were determined by refining neutron diffraction patterns on pure single-phase samples. Neutron diffraction patterns, collected during the in situ oxidation of powder samples at 483 K were also analyzed performing Rietveld refinements. The lattice parameters and relative ratios of the four pure phases were measured during the progression of the isothermal oxidation. The transformation of UO2 into U3O8 involves a complex modification of the oxygen sublattice and the onset of complex superstructures for U4O9 and U3O7, associated with regular stacks of complex defects known as cuboctahedra which consist of 13 oxygen interstitial atoms. The structural modifications during the oxidation process are discussed.
Radiation Tolerance and Disorder – Can They Be Linked?
Authors: Whittle Karl , Blackford Mark , Smith Katherine L. , Lumpkin Gregory , Zaluzec Nestor J. 
Published: August 2010

AbstractThe future expansion of nuclear power provides materials challenges that are not easily overcome, for example the safe immobilisation of nuclear waste is an important component in any future expansion of nuclear power. The use of ceramic-based materials, as opposed to borosilicate glasses, is now being investigated widely. The ability of ceramics to be tailored to a specific waste stream is now understood and obtainable quickly and with minimal cost. A second component that limits the expansion of fission-based technologies is the development of materials that are not only tolerant of radiation damage, but are also capable of retaining mechanical strength at high temperatures. One concern for any material however, is the effect of radiation damage, primarily from alpha-decay damage, which in many systems can transform the material from crystalline to amorphous. The effects of such radiation damage on both the structural and chemical properties can range from trivial to critical, for example volume expansion and are the primary focus of much research. As part of a long-term research programme the effects on radiation tolerance of a range of ordered and disordered materials are discused.
Quantification of Trace and Ultra-trace Elements in Nuclear Grade Manufactured Graphites by Fast-Flow Glow Discharge Mass Spectrometry and by Inductively Coupled Plasma – Mass Spectrometry after Microwave – Induced Combustion Digestions
Authors: Wang Xinwei , Bhagat Gaurav , O'Brien Kevin Michael , Putyera Karol 
Published: August 2010

AbstractFF-GDMS and MIC-ICP-MS methods were developed for the determination of mg/kg- and μg/kg-level B, Mg, Al, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Sb, W and Pb in nuclear-grade graphite. Consistent results have been achieved in determining trace elements like B, Ti, Cr, Mn, Zr, Sb and Pb by both methods, which vary mostly less than ±30%, and are in line with the manufacturer reference values. On Mg, Al, Fe, Co, Zn, Mo and W, FF-GDMS analyses also show good agreement with the manufacturer's data. Continuing efforts in identifying source of interference, which has limited the MIC-ICP-MS analysis of these elements, is currently underway.
In situ Characterization of UO2 Microstructure Changes During an Annealing Test in an Environmental Scanning Electron Microscope
Authors: Marcet Mathieu , Pontillon Yves , Desgranges Lionel , Simeone David , Aubrun Isabelle , Felines Isabelle , Brunaud Laurent 
Published: August 2010

AbstractA 1 μg High Burn Up Structure (HBS) fragment was extracted from a UO2 fuel pellet irradiated for 7 cycles in a EDF Pressurised Water Reactor (PWR). In situ examinations were performed with an Environmental Scanning Electron Microscope (ESEM) in order to characterize UO2 microstructure evolution during a temperature ramp up to 1,600K. The results are compared to previously published data on HBS annealing tests performed in a Knudsen cell where observed burst releases are explained as sample cracking during the experimental sequence.
Effect of Oversized Alloying Elements on Damage Rates and Recovery in Zirconium
Authors: Borysenko Valeriy , Petrusenko Yuri , Barankov Dmitro 
Published: August 2010

AbstractStudies were made into the influence of oversized rare-earth atoms on the processes of radiation defect accumulation and annealing in two-component zirconium alloys. Zr and Zr-X alloys (where X = Sc, Dy, Y, Gd and La) have been irradiated with 2 MeV electrons at 82 K. The radiation-induced resistivity has been measured in situ as a function of dose. As compared to unalloyed zirconium, the alloys have exhibited a decrease in the resistivity gain, this decrease being proportional to both the concentration and the size of dopant atoms. A possible explanation for the effect is offered. The difference between the recovery processes in zirconium and in its alloys has been studied. To this end, the irradiated specimens were subjected to isochronal annealing at temperatures between 82 and 350 K. It is shown that Dy, Y, Gd and La atoms trap interstitial atoms at stage I of the recovery. The dissociation of interstitial-impurity complexes takes place at stage II. In zirconium alloys with Dy, Y and Gd, splitting of recovery stage III into two substages has been revealed. The Zr-La alloy has not shown this splitting. Isothermal annealing data were used to determine the activation energies of recovery stages, and also to calculate the activation energy spectra for zirconium and its alloys. The oversized atoms of rare-earth metals are shown to interact effectively with both the interstitials and the vacancies in the zirconium matrix. This effect must be taken into account when developing new radiation-resistant Zr-base alloys or modifying the ones already existing.
Enhanced Hydrogen Storage Properties of Magnesium Nanotrees with Nanoleaves
Authors: Cansizoglu Mehmet , Karabacak Tansel 
Published: August 2010

AbstractHydrogen storage in advanced solid state materials has been an intense area of research due to many drawbacks in conventional high pressure or cryogenic liquid hydrogen storage methods. A practical hydrogen storing material is required to have high storage capacity and fast dehydrogenation kinetics. Among many solid state materials for hydrogen storage, magnesium hydride (MgH2) combines a hydrogen capacity of 7.6 wt % with the benefit of the low cost of production and abundance. The main difficulties for implementing MgH2 are slow absorption/desorption kinetics and high reactivity towards air and oxygen, which are also common issues in most lightweight metal hydrides. Previously, improvements in hydrogen storage and release properties have been reported by using nanostructured magnesium that can be obtained through various fabrication methods including ball-milling, mechanical alloying, and vapor transport. In this study, we investigate the hydrogen absorption and desorption properties of magnesium “nanotrees” fabricated by glancing angle deposition (GLAD) technique, and also conventional Mg thin films deposited at normal incidence. Mg nanotrees are about 15 μm long, 10 μm wide, and incorporate “nanoleaves” of about 20 nm in thickness and 1,2 μm in lateral width. A quartz crystal microbalance (QCM) gas absorption/desorption measurement system has been used for our hydrogen storage studies. Nanostructured and thin film Mg have been deposited directly on the surface of the gold coated unpolished quartz crystal samples. QCM hydrogen storage experiments have been performed at temperatures ranging between 100-300 °C, and at H2 pressures of 10 and 30 bars. Our QCM measurements revealed that Mg nanotrees can absorb hydrogen at lower temperatures and also at a faster rate compared to Mg thin film. In addition, Mg nanotrees can reach hydrogen storage values of about 4.80 wt% at 100 °C, and up to about 6.71 wt% (which is close to the theoretical maximum storage value of Mg) at temperatures lower than 150 °C. The significant enhancement in hydrogen absorption properties of our Mg nanotrees is believed to originate from novel physical properties of their nanoleaves. These nanoleaves are very thin (∼20 nm) and both surfaces are exposed to hydrogen enhancing the diffusion rate of hydrogen together with a decreased diffusion length. Based on X-ray diffraction measurements, individual nanoleaves have non-close-packed crystal planes that can further enhance the hydrogen absorption kinetics. In addition, our nanostructured Mg have been observed to quite resistant to surface oxidation, which is believed to due to the single crystal property of the Mg nanoleaves, which further improves the absorption kinetics of hydrogen.
Synthesis of Pt-TM(transition metals) Catalysts and Their Hydrogenation Ability of Methyl Acrylate
Authors: Amari Miki , Okada Satoshi , Demura Masahiko , Nishio Keishi , Shibata Hirobumi , Kineri Tohru , Gunji Takahiro , Tamura Ryuji 
Published: August 2010

AbstractWe have prepared a number of Pt-TM(transition metals) alloys with various TM elements and evaluated their catalytic abilities by means of hydrogenation of methyl acrylate. High catalytic activities are obtained when the crystalline structures are similar, i.e., fcc structure, indicating that the crystal structure of a catalyst plays an important role in hydrogenation of methyl acrylate. Furthermore, for a certain TM element, i.e., Mo, the catalytic activity is found to surpass that of Pt metal.
Could Porosity Induce Gaps in the Vibrational Density of States of Nanoporous Silicon?
Authors: Noyola Juan Carlos , Valladares Alexander , Valladares R. M. , Valladares Ariel A. 
Published: August 2010

AbstractAs in our previous work [1] nanoporous silicon periodic supercells with 1000 atoms but now with 80 % porosity were constructed using the Tersoff potential and our novel approach [2]. The approach consists first in constructing a crystalline diamond-like supercell with a density (volume) close to the real value, and then lowering the density by increasing the volume, subjecting the resulting periodic supercell to Tersoff-based molecular dynamics processes at a temperature of 300 K, followed by geometry relaxation [1]. As in the ab initio approach [2] the resulting samples are also essentially amorphous and display pores along some of the crystallographic directions. We report the radial (pair) distribution function (RDF), g(r), the bond angle distribution, the pore structure where prominent and a computational prediction for the vibrational density of states for this structure. We then compare it to the 50 % porous sample presented in Ref [1]. The soft acoustic phonons are displaced towards lower energy in the 80 % porosity sample whereas the optical modes are displaced towards higher energies. The pseudo gap, existing in the 50 % porous sample, is depleted even more in the 80 % sample indicating a tendency towards the creation of a phonon gap for higher porosity materials. Some conjectures that point to the possible engineering of porous materials to produce predetermined phonon properties are discussed.
Stress-controlled phonon-impurity resonances in terahertz silicon lasers
Authors: Pavlov Sergey G. 
Published: August 2010

AbstractOptically pumped terahertz silicon lasers utilize transitions between shallow donor states at low lattice temperatures. Population inversion in these lasers is built-up due to selective relaxation routes of optically excited electrons into impurity ground state. Each relaxation step of the electron occurs under assistance of intervalley and intravalley phonons with energies approaching the particular energy gaps between interacting excited donor states. These impurity phonon interactions determine, at the end, the lifetimes of the laser levels, and, therefore, efficiency of intracenter silicon lasers. Deformation of silicon crystal is a classical example of controllable influence on energy spectrum of shallow donor levels due to specific splitting and shifts of conduction band valleys. Using moderate (up to 400 MPa) external uniaxial deformation of a crystal, one can radically modify the impurity spectra while the phononic spectra remain almost unchanged. We have demonstrated significant improvement of efficiency for intracenter silicon lasers followed by changes of lifetime for the upper and the lower laser levels due to moving the impurity levels either into or out of resonance with corresponding intervalley phonon frequencies.
Effect of Alloying Elements on the Elastic Properties of γ-Ni and γ'-Ni3Al from First-principles Calculations
Authors: Wang Yunjiang , Wang Chongyu 
Published: August 2010

AbstractThe effect of alloying elements Ta, Mo, W, Cr, Re, Ru, Co, and Ir on the elastic properties of both γ-Ni and γ′-Ni3Al is studied by first-principles method. Results for lattice properties, elastic moduli and the ductile/brittle behaviors are all presented. Our calculated values agree well with the existing experimental observations. Results show all the additions decrease the lattice misfit between and γ′ phases. Different alloying elements are found to have different effect on the elastic moduli of γ-Ni. Whereas all the alloying elements slightly increase the moduli of γ′-Ni3Al expect Co. Both of the two phases are becoming more brittle with alloying elements, but Co is excepted. The electronic structures of γ′ phase alloyed with different elements are provided as example to elucidate the different strengthening mechanisms.
On Effective Indenters Used in Nanoindentation Data Analysis
Authors: Fu Guanghui , Cao Ling , Cao Tiesheng 
Published: August 2010

AbstractEffective indenter concept was introduced by Pharr and Bolshakov to explain nanoindentation unloading curves. This paper shows that the contact stiffness under a uniform pressure distribution is 57% higher than what is given by the fundamental relation. This is due to the fact that there is no physical indenter that gives a uniform pressure distribution during elastic contact, and the fundamental relation used in nanoindentation data analysis does not apply.
The Micromechanisms of Deformation in Nanoporous Gold
Authors: Dou Rui , Derby Brian 
Published: August 2010

AbstractWe have carried out a TEM investigation of the micromechanisms of deformation in these nanoporous gold specimens after compression testing. We find that the nanoporous specimens show deformation localised to the nodes between the ligaments of the foamed structure, with very high densities of microtwins and Shockley partial dislocations in these regions. These deformation structures are very different from those seen after solid nanowires are tested in compression, which show very low dislocation densities and a few sparsely distributed twins. However, similar dislocation structures to those found in the nanoporous specimens are observed in the larger nanowires when they are deformed in bending. The currently accepted model for the deformation of nanoporous gold, implicitly assumes that the deformation of these structures is by bending near the nodes where ligaments intersect. We hypothesis that the much higher dislocation densities seen in both the nanoporous gold and the nanowires deformed in bending are evidence for the presence of geometrically necessary dislocations in these deformed structures.
Electrospun Polymer/MWCNTs Nanofiber Reinforced Composites “Improvement of Interfacial Bonding by Surface Modified Nanofibers”
Authors: Ozden Elif , Menceloglu Yusuf Ziya , Papila Melih 
Published: August 2010

AbstractIn-house synthesized copolymers Polystyrene-co-glycidyl methacrylate (PSt-co-GMA) are electrospun as mat of surface modified nanofibers with and without multi walled carbon nanotubes (MWCNTs). Composites are then formed by embedding layers of the nanofiber mats into epoxy resin. Interfacial bonding between polymer matrix and the nanofibers, and surface modification driven enhancement in mechanical response is assessed under flexural loads. Results indicate that at elevated temperture storage modulus of epoxy reinforced by PSt-co-GMA nanofibers and PSt-co-GMA/ MWCNTs composite nanofibers is about 10 and 20 times higher than the neat epoxy, respectively, despite weight fraction of the nanofibers being as low as 2%. Interfacial interaction is revealed by the storage modulus comparison of unmodified Polystyrene (PSt) and modified PSt-co-GMA nanofiber reinforced composite. To enhance further the resulting “crosslinked” structure, crosslinking agent ethylenediamine is also sprayed on the nanofibrous mats. Increased crosslinking density improves mechanical response of sprayed-over PSt-co-GMA nanofibers reinforced composites which is about 4 times higher than plain PSt-co-GMA nanofibers.
Silicide Film Formation in the Ta/Ti/Si System by RF Induction Heating
Authors: Pelleg Joshua , Rosenberg Shmuel , Sinder Misha 
Published: August 2010

AbstractSilicidation of Ta-Ti-Si film on Si (111) and Si (100) substrates was investigated by a new radio frequency (RF) heating in order to evaluate the progress of reaction and establish whether the substrate orientation influence on the rate of reaction prevails. Substrate orientation was observed notwithstanding the high temperatures applied and the very short duration of RF. It was observed that while the reaction on Si (111) goes to completion, on Si (100) substrates under the same conditions intermediate phases remained.
A qualitative analysis of the RF treatment of a conductor film on the silicon substrate is presented. It is done for the first time using the mathematical approach of the heat explosion theory. According to the analysis the specimens might experience either heating at constant temperature or by a sudden temperature increase. The relation between the parameters for the heat explosion regime is presented in simple analytical form. Measurable quantities such as sheet resistance and the magnetic field applied determine the stage of the process. The value of the resulting sheet resistance indicates whether the progress of the RF occurred by heating in the slow growth temperature regime or in the heat explosion stage where reactions of a conductor film occur within a fraction of a second.
Controlling Neuronal Growth on Au Surfaces by Directed Assembly of Proteins
Authors: Staii Cristian , Viesselman Chris , Ballweg Jason , Hart Steven , Williams Justin C , Dent Erik W , Coppersmith Susan N , Eriksson Mark 
Published: August 2010

AbstractStudying how individual neuronal cells grow and interact with each other is of fundamental importance for understanding the functions of the nervous system. However, the mechanism of axonal navigation to their target region and their specific interactions with guidance factors such as membrane-bound proteins, chemical and temperature gradients, mechanical guidance cues, etc. are not well understood. Here we describe a new approach for controlling the adhesion, growth and interconnectivity of cortical neurons on Au surfaces. Specifically, we use Atomic Force Microscopy (AFM) nanolithography to immobilize growth-factor proteins at well-defined locations on Au surfaces. These surface-immobilized proteins act as a) adhesion proteins for neuronal cells (i.e. well-defined locations where the cells “stick” to the surface), and b) promoters/inhibitors for the growth of neurites. Our results show that protein patterns can be used to confine neuronal cells and to control their growth and interconnectivity on Au surfaces. We also show that AFM nanolithography presents unique advantages for this type of work, such as high degree of control over location and shape of the protein patterns, and application of proteins in aqueous solutions (protein buffers), such that the proteins are very likely to retain their folding conformation/bioactivity.
Oligonuleotide Delivery with Dendritic Poly(L-lysine) for Treatments of the Liver Disorders
Authors: Watanabe Kazuto , Harada-Shiba Mriko , Suzuki Akira , Higuchi Yuriko , Kawakami Shigeru , Hashida Mitsuru , Gokuden Risa , Kurihara Ryohsuke , Sugao Yusuke , Mori Takeshi , Katayama Yoshiki , Niidome Takuro 
Published: August 2010

AbstractA cationic peptide dendrier, dendritic poly(L-lysine), forms complexes with oligonucleotides and can deliver them to liver after intravenous injection. Here, we tried to deliver apolipoprotein B-specific siRNA for the treatment of hypercholesterolemia and NFκB decoy for the hepatitis treatment. Significant therapeutic effects in those disease model mice were observed after intravenous injection of the oligonucleotides complexes with dendritic poly(L-lysine).
Nano- and Micro-Scale Adhesion in Drug-eluting Stents
Authors: Tan Ting , Meng Juan , Rahbar Nima , Li Hannah , Papandreou George , Maryanoff Cynthia , Soboyejo Winston oluwole 
Published: August 2010

AbstractThis paper presents a combined experimental and theoretical/computational study of adhesion and interfacial fracture between multilayers in a CYPHER®model drug eluting stents (DES). Atomic Force Microscopy (AFM) is used to obtain pull-off forces between coated AFM tips and substrates that simulate the bimaterial surfaces in the DES. Adhesion theories and fracture mechanics concepts are then applied to obtain estimates of the fracture toughness over a range of mode mixities between pure mode I and pure mode II. The trends in the estimates are shown to be in good agreement with experimental measurements of interfacial fracture toughness obtained from Brazil disk specimens over the same range of mode mixities.