bluuebunny/crossref_metadata_2025_split huggingface dataset:
Emission Quenching of a Poly(Phenylene Ethynylene) (PPE) in the Solid State
Authors: George Wayne N. , Steinke Joachim H. G. , de Mello John C. , Giles Mark , McCulloch Iain 
Published: April 2011

ABSTRACTThe ability of a poly(phenylene ethynylene) conjugated polyelectrolyte to detect a small molecule quencher in the solid state was assessed by coating the polymer onto a plastic-backed, non-fluorescent, silica-gel TLC plate. The efficiency of the emission quenching process was quantified by noting the resulting loss of emission with increasing quencher concentration, in accordance with the Stern-Volmer relation. The emission quenching induced by the addition of the analyte occurred with Stern-Volmer constants in the range of 103 M−1.
State-of-the-Art Developments in the Field of Electroactive Polymers
Authors: Vinogradov Aleksandra , Su Ji , Jenkins Christopher , Bar-Cohen Yoseph 
Published: April 2011

ABSTRACTThe paper presents a review in the field of electroactive polymers. It outlines the main classes of electroactive polymers, their properties and applications. Current efforts to synthesize electroactive polymers with novel or improved characteristics along with the challenges, opportunities and future research directions are discussed.
The Effect of Temperature Exposure on Polypyrrole Actuation
Authors: Cole Matthew , Madden John D. 
Published: April 2011

ABSTRACTPolypyrrole actuators offer attractive possibilities due to their large electrochemical stress (>5MPa), moderate to large strain (>2 %) and low voltage operation (<2 V). However, little is known about their temperature dependence response, with nearly all previous tests performed at room temperature. To test the effects of increasing temperature, polypyrrole films in water and propylene carbonate were thermally cycled twice from 22°C to 80°C. Length and actuation were measured before, after and between cycling. Results show that polypyrrole in TBAPF6(propylene carbonate) underwent a 4.8% irrecoverable contraction during the first cycle and lost half it’s actuation each cycle. Polypyrrole in NaPF6(aq) showed a 2.1% initial expansion in length on the first cycle followed by a 2.1% contraction on the next cycle, while active strain amplitude dropped from 7.7% to 5.9% to 4.9%. Polypyrrole in NaCl(aq) has a net contraction of 6% over two cycles with no significant change in it’s original 3.5% actuation amplitude. This suggests that although films in NaPF6(aq) have the best initial strain, films in NaCl(aq) maintain the most consistent strain amplitude in response to temperature on the timescales observed. Strain to charge ratio was found to decrease slightly, but the majority of the loss in actuation for films is correlated with a reduction in charge transfer each cycle. This reduction may result from a reduction in the active volume of film.
Introduction to First-Principles Electronic Structure Methods: Application to Actinide Materials
Authors: Klepeis John E 
Published: April 2011

AbstractThe purpose of this paper is to provide an introduction for non-experts to first-principles electronic structure methods that are widely used in the field of condensed-matter physics, including applications to actinide materials. The methods I describe are based on density functional theory (DFT) within the local density approximation (LDA) and the generalized gradient approximation (GGA). In addition to explaining the meaning of this terminology I also describe the underlying theory itself in some detail in order to enable a better understanding of the relative strengths and weaknesses of the methods. I briefly mention some particular numerical implementations of DFT, including the linear muffin-tin orbital (LMTO), linear augmented plane wave (LAPW), and pseudopotential methods, as well as general methodologies that go beyond DFT and specifically address some of the weaknesses of the theory. The last third of the paper is devoted to a few selected applications that illustrate the ideas discussed in the first two-thirds. In particular, I conclude by addressing the current controversy regarding magnetic DFT calculations for actinide materials. Throughout this paper particular emphasis is placed on providing the appropriate background to enable the non-expert to gain a better appreciation of the application of first-principles electronic structure methods to the study of actinide and other materials.
5f Delocalization of Bulk FCC Americium and the (111) Surface: A FP-LAPW Electronic Structure Study
Authors: Gao Da , Ray Asok K 
Published: April 2011

AbstractThe electronic properties of bulk fcc americium and the (111) surface have been investigated with the full-potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2K suite of programs The study is carried out for the anti-ferromagnetic ground state of Am at different levels of theory: (1) scalar-relativity vs. full-relativity; (2) local-density approximation (LDA) vs. generalized-gradient approximation (GGA). Our results indicate that spin orbit coupling plays an important role in determining the electronic properties of both bulk fcc americium and the (111) surface. In general, LDA is found to give a higher total energy compared to GGA results. The spin orbit coupling shows a similar effect on the surface calculations regardless of the model, GGA versus LDA. The 5f localized-delocalized transition of americium is employed to explain our results. In addition, the quantum size effects in the surface energies and the work functions of fcc (111) americium ultra thin films (UTF) are also examined.
Using Nano-focussed Bremstrahlung Isochromat Spectroscopy (nBIS) to Determine the Unoccupied Electronic Structure of Pu
Authors: Butterfield Martin , Tobin James , Teslich Nick , Bliss Annie , Wall Mark , McMahan Andy , Chung Brandon , Schwartz Adam , Kutepov A.L 
Published: April 2011

AbstractThe investigation of the actinides is of great interest because of their unique electronic structure. At the pivotal point of the behavior of the electronic structure of the actinide series is plutonium. Pu has the most complex phase diagram of all metals, both with regard to the intricacy of the crystal structures and the number of different phases. While there are a number of ongoing experimental efforts directed at determining the occupied electronic structure of Pu, there is essentially no experimental data on the unoccupied electronic structure of Pu. We aim to determine the conduction band (unoccupied) electronic structure of Pu and other actinides in a phase specific fashion and emphasizing bulk contributions by using Nano-focussed Bremstrahlung Isochromat Spectroscopy (nBIS). BIS is the high-energy variant of inverse photoelectron spectroscopy (IPES: electron in, photon out), which is essentially the time reversal of photoelectron spectroscopy (photon in, electron out). IPES can be used to follow the dispersion of electronic states in ordered samples. Owing to its low energies, IPES is usually very surface sensitive. However, by working at higher energies, we will sample preferentially for bulk properties, downgrading the impact of surface effects. Thus, from BIS, we would have a direct measure of the conduction band or unoccupied electronic structure of the bulk Pu. By using a nano-focused electron source associated with a SEM, we hope to gather phase specific information from crystallites within polycrystalline Pu samples. We will discuss the experimental arrangement required to carry out such an experiment and our progress in building such a system.
Spinodal ordering and precipitation in U-6wt%Nb
Authors: Hsiung Luke Lieh-Ming , Zhou Jikou 
Published: April 2011

AbstractA combinative approach of microhardness testing, tensile testing, and TEM microstructural analysis was employed to study the microstructure and mechanical instability of a water-quenched U-6wt.% Nb (WQ-U6Nb) alloy subjected to different aging schedules including artificial aging at 200°C, 15-year natural aging at ambient temperatures, and 15-year natural aging followed by accelerative aging at 200°C. The changes in mechanical property during and after the aging processes were examined using microhardness and tensile-testing methods. During the early stages of artificial aging at 200°C, the microhardness of WQ-U6Nb alloy increased, i.e., age hardening, as a result of the development of nanoscale modulation caused by spinodal decomposition. Coarsening of the modulated structure occurred after a prolonged aging at 200°C for 16 hours, and it led to a decrease of microhardness, i.e., age softening. Phase instability was also found to occur in WQ-U6Nb alloy that was subjected to a 15-year natural aging at ambient temperatures. The formation of partially ordered domains resulting from a spinodal modulation with an atomic-scale wavelength rendered the appearance of swirl-shape antiphase domain boundaries (APBs) observed in TEM images. Although it did not cause a significant change in microhardness, 15-year natural aging has dramatically affected the aging mechanisms of the alloy isothermally aged at 200°C. Microhardness values of the NA alloy continuously increased after isothermal aging at 200°C for 96 hours as a result of the phase decomposition of partially ordered domains into Nb-depleted α phase and Nb-enriched U3Nb ordered phase in the alloy. It is concluded that the long-term natural aging changes the transformation pathway of WQ-U6Nb, and it leads to order-disorder transformation and precipitation hardening of WQ-U6Nb alloy.
Thorium-Based Thin Films as Highly Reflective Mirrors in the EUV
Authors: Johnson Jed E. , Allred David D. , Turley R. Steven , Evans William R. , Sandberg Richard L. 
Published: April 2011

AbstractAs applications for extreme ultraviolet (EUV) radiation have been identified, the demand for better optics has also increased. Thorium and thorium oxide thin films (19 to 61 nm thick) were RF-sputtered and characterized using atomic force microscopy (AFM), spectroscopic ellipsometry, low-angle x-ray diffraction (LAXRD), x-ray photoelectron spectroscopy (XPS), and x-ray absorption near edge structure (XANES) in order to assess their capability as EUV reflectors. Their reflectance and absorption at different energies were also measured and analyzed at the Advanced Light Source in Berkeley. The reflectance of oxidized thorium is reported between 2 and 32 nm at 5, 10, and 15 degrees from grazing. The imaginary component of the complex index of refraction, β, is also reported between 12.5 and 18 nm. Thin films of thorium were found to reflect better between 6.5 and 9.4 nm at 5 degrees from grazing than all other known materials, including iridium, gold, nickel, uranium dioxide, and uranium nitride. The measured reflectance does not coincide with reflectance curves calculated from the Center for X-Ray Optics (CXRO) atomic scattering factor data. We observe large energy shifts of up to 20 eV, suggesting the need for better film characterization and possibly an update of the tabulated optical constants.
Phase Composition and Leach Resistance of Actinide-Bearing Murataite Ceramics
Authors: Stefanovsky Sergey , Yudintsev S.V. , Nikonov B.S. , Mokhov A.V. , Perevalov S.A. , Stefanovsky O.I. , Ptashkin A.G. 
Published: April 2011

AbstractPhase composition of the murataite-based ceramics containing 10 wt.% ThO2, UO2, NpO2 or PuO2 and leaching of actinides using a MCC-1 procedure were studied. The ceramics were prepared by melting of oxide mixtures in Pt ampoules in air at ∼1500 °C. They are composed of predominant murataite-type phases and contain traces of extra phases (rutile, crichtonite, perovskite). At least two murataite-related phases with five- and eight-fold elementary fluorite unit cell (5C and 8C) were simultaneously observed. Minor phase 3C (murataite) in the ceramics doped with ThO2 and UO2 was also found. In the Th-bearing sample the 5C phase prevails over the 8C phase. In the U-bearing ceramic they co-exist in comparable amounts. The sample produced at 1500 °C contains crichtonite whereas the ceramic produced at lower temperature (1400 °C) contained rutile. Higher temperature favors further rutile reactions with formation of crichtonite. The Np- and Pu-doped ceramics are also composed of major the 5C and the 8C phases and minor rutile and crichtonite (in Pu-loaded sample only). Unlike the sample prepared under slightly re-ducing conditions (in glassy carbon crucible) the Pu-doped ceramic produced under neutral conditions (in Pt ampoule) doesn’t contain perovskite-type phase. Occurrence of perovskite in the first sample was sup-posed to be due to reduction of some Pu(IV) to Pu(III) during experiment. Leach rates (7-day MCC-1 test, 90 °C) of the actinide elements from all the ceramics studied are at the level of 10-6-10-7 g/(m2·day).
Pressure induced phase transitions in AmCm alloy
Authors: Li Sa , Ahuja Rajeev , Johansson Borje 
Published: April 2011

AbstractWe have studied the crystal structure of the AmCm binary alloy under high pressure by means of first-principles self-consistent total-energy calculations using the generalized gradient approximation (GGA) for the density functional theory (DFT). The virtual crystal approximation (VCA) is used for the description of the alloy system. In the present study, we investigated the double hexagonal (P63/mmc) structure, the face centered cubic (Fm3m) structure, the face-centered orthorhombic (Fddd) structure and the primitive orthorhombic (Pnma) structure for the AmCm alloy. Antiferromagnetic calculations have been compared with ferromagnetic calculations for all these phases. Our results are in general good agreement with recent experiment performed by Lindbaum et al. [J. Phys.: Condens. Matter. 15, S2297 (2003)].
High Pressure Structural transitions in Cm metal
Authors: Ahuja Rajeev , Li Sa , Johansson Börje 
Published: April 2011

AbstractThe high pressure behaviour of Cm metal is investigated theoretically using ab initio electronic structure methods. Our calculations reproduce the structural phase transitions which are obsereved in recent experiment performed by Heatman et al. [Science 309, 110 (2005)]. Calculated transition pressures are in reasonable agreement with the experiment. Calculations performed in antiferromagnetic state is essential to reproduce the stability of Cm-III phase. Thus stability of Cm-III phase is related to the spin polarization of 5f electrons.
Theoretical study of protactinium at high pressure
Authors: Johansson Börje , Li Sa , Eyvaz Eyvaz , Ahuja Rajeev 
Published: April 2011

AbstractWe have studied the crystal structure of Pa metal under high pressure by means of first-principles calculations based on the density functional theory (DFT) using the generalized gradient approximation (GGA). The body centered tetragonal (bct) to orthorhombic (α-U) phase transition was calculated to take place at 29 GPa and with a volume change of 1.3%. The calculated c/a for the bct phase reaches the ideal c/a value (0.816) at around 50 GPa. A bulk modulus of 113 GPa was derived from a Murnaghan equation of state (EOS) fitting procedure. Our results are in general good agreement with recent experiment performed by Haire et al. [Phys. Rev. B 67, 134101 (2003)]. We have also calculated the phonon spectrum for fcc, bct and bcc Pa. The latter gives imaginary frequencies showing the low temperature instability of this crystallographic phase for Pa.
Behavior of Uranium(VI) during HEDPA Leaching for Aluminum Dissolution in Tank Waste Sludges
Authors: Powell Brian Anthony , Rao Linfeng , Nash Kenneth L. , Martin Leigh 
Published: April 2011

AbstractBatch adsorption/dissolution experiments were conducted to examine the interactions between 233U(VI) and a synthetic aluminum oxyhydroxide (boehmite, γ-AlOOH) in 1.0M NaCl suspensions containing 1-hydroxyethane-1,1-diphosphonic acid (HEDPA). In the pH range 4 to 9, complexation of Al(III) by HEDPA significantly enhanced dissolution of boehmite. This phenomenon was especially pronounced in the neutral pH region where the solubility of aluminum, in the absence of complexants, is limited by the formation of sparsely soluble aluminum hydroxides. At high pH levels, dissolution of synthetic boehmite was inhibited by HEDPA, likely due to sorption of Al(III)/HEDPA complexes. Addition of HEDPA to equilibrated U(VI)-synthetic boehmite suspensions yielded an increase in the aqueous phase uranium concentration. The concentration of uranium continually increased over 59 days. Partitioning of uranium between the solid and aqueous phase was found to correlate well with HEDPA partitioning.
On-line Data Management for High-throughput Experimentation
Authors: Lippmaa Mikk , Meguro Shinya , Ohnishi Tsuyoshi , Koinuma Hideomi , Takeuchi Ichiro 
Published: April 2011

AbstractWe discuss visualization and data dependency issues related to managing sample characterization data from high-throughput experiments. We are developing software for on-line storage, sharing, and visualization of data from combinatorial or high-throughput experiments. The system is based on a centralized database and a Web interface that can be accessed from any networked computer. The greatest challenge facing us is the variety of data types and formats that such a system has to support so that data from many different sources, i.e. from synthesis and characterization instruments, could be combined. In order to minimize the software development effort, we have developed generalized extensible markup language (XML) schema for storing and processing experimental data. The use of a standard data format like XML, together with the relevant schema definitions can be used to implement storage, processing, visualization and other tools that are generic and thus greatly simplify the task of managing high-throughput experiments.
An SEM Study Of The Effect of Altering the Reaction pH on Fluoride Catalysed Silica Sol-Gel Templating Of Self-Assembling Peptide Fibrils
Authors: Meegan Jonathan , Aggeli Amalia , Ansell Richard J , Brown Andy P , Brydson Rik 
Published: April 2011

AbstractThe templating of hydrolysed silane species by self-assembling peptide fibrils has been extensively studied at the Centre for Self Organising Molecular Systems based in the University of Leeds . In this paper we present an SEM based study of the pH effects on the peptide fibril templates and the fluoride catalysed templating chemistry and the resulting silica nanotubes.
Adhesion Properties between Swollen Hydrogels in Air
Authors: Sakasegawa Daisuke , Sato Takaya , Goto Motoaki , Suzuki Atsushi 
Published: April 2011

AbstractAdhesion between swollen hydrogels was studied using a simple tack-evaluation technique by a point contact in air at room temperature. The hydrogel used here was poly(sodium acrylate) (PSA) gel physically cross-linked by aluminum ions. The adhesion force and the separation energy showed a power-law increase with separation velocity, normal force, and waiting period　prior to separate. Effects of the degrees of protonation in PSA as well as of dehydration on the adhesive properties are also presented. The results are discussed in terms of the surface molecular interaction and the bulk elastic and viscous properties.
Nano-Thermometry: Transmission Electron Microscopy of Femtosecond Laser Irradiated Co/Si Multilayer Thin Foils
Authors: Picard Yoosuf , Yalisove Steven M. 
Published: April 2011

AbstractPre-thinned foils composed of amorphous silicon and polycrystalline cobalt were irradiated using femtosecond pulse-length lasers at fluences sufficient for ablation (material removal). The resultant ablated hole and surrounding vicinity was studied using transmission electron microscopy to determine modifications to the structure. Evidence of cobalt silicide formation was observed within a 3 micron radius of the laser hole edge by use of selected area electron diffraction (SAED). In addition, elongated grains of crystalline silicon was observed within 500 nm of the laser hole edge, indicating melting of the amorphous silicon and heat dissipation slow enough to allow recyrstallization. This initial work demonstrates the use of pre-designed nanostructured multilayer systems as a method for nanoscale profiling of heat dissipation following pulsed laser irradiation.
Poly(methyl phenyl siloxane) in Random Nanoporous Glasses: Comparison of coated and uncoated confining surfaces
Authors: Schöenhals Andreas , Goering Harald , Schick Christoph 
Published: April 2011

AbstractThe effect of a nanometer confinement on the molecular dynamics of poly(methyl phenyl siloxane) (PMPS) was studied by dielectric spectroscopy (DS) and temperature modulated DSC (TMDSC). As confining hosts random nanoporous glasses with nominal pore sizes of 2.5 nm – 20 nm have been used. Epically it is focused on the influence of a surface treatment on the dynamical behavior. DS and TMDSC experiments show that for PMPS in 7.5 nm pores the molecular dynamics is faster than in the bulk which originates from an inherent length scale of the underlying molecular motions. There is no influence of the surface treatment on the glassy dynamics for this pore size.At a pore size of 5 nm the temperature dependence of the relaxation times changes from a Vogel / Fulcher / Tammann like behavior to an Arrhenius one where the apparent activation energy depends on pore size. For silanized pores a higher value (102 kJ / mol) is found than for natives pores (73 kJ / mol). For a pore size of 2.5 nm the activation energy is independent of the surface treatment. The value of ca. 40 kJ / mol points to a real localized process.The increment of the specific heat capacity at the glass transition depends strongly on pore size and vanishes at a finite length scale which can be regarded as minimal length scale for glass transition to appear. The actual value depends on surface treatment. From this difference the thickness of an immobilized boundary layer of about 1 nm is estimated for uncoated pores.
Spontaneous Imbibition of Liquids into Nanopores
Authors: Huber Patrick , Knorr Klaus , Kityk Andriy V. 
Published: April 2011

AbstractWe present measurements on the spontaneous imbibition of water, a linear hydrocarbon (n-C16H34) and a liquid crystal (8OCB) into the pore space of monolithic, nanoporous Vycor glass (mean pore radius 5nm). Measurements of the mass uptake as a function of time, m(t), are in good agreement with the Lucas-Washburn - prediction typical of imbibition of liquids into porous hosts. The relative capillary rise velocities scale as expected from the bulk fluid parameters.
In situ SAXS/WAXS of Zeolite Microwave Hydrothermal Synthesis
Authors: Tompsett Geoff A. , Panzarella Bernard , Conner W. Curt , Jones Keith W 
Published: April 2011

ABSTRACTThe microwave hydrothermal synthesis of silicalite zeolite was monitored in situ using small and wide angle X-ray scattering (SAXS and WAXS). A custom-built waveguide reactor provided the microwave heating at 2.45 GHz frequency. Microwave power up to 300 W was supplied by a SAIREM generator via a coax connection. A sample port in the waveguide section allowed a thin-walled glass sample vessel to be held in the microwave field. The sample vial was sealed with a fiber optic temperature probe used for monitoring the temperature. Silicalite zeolite precursor solutions were heated temperatures between 100 and 130°C for up to 120 minutes. The SAXS or WAXS patterns were simultaneously scanned during the reaction under microwaves via X-ray beam through slots in the side of the waveguide. The progress of silicalite zeolite formation was followed and the analysis of SAXS patterns showed the primary particles of 2 nm shifted to aggregates of 5.8 nm in diameter, in 120 minutes at 130°C.