bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of the Temperature-Dependent Surface Morphology of p-Sexiphenyl Thin Films on KCl(001)
Authors: Kintzel E.J. , Gillman E.S. , Skofronick J.G. , Safron S.A. , Smilgies D.-M. 
Published: April 2011

ABSTRACTInvestigation into the temperature dependence of the surface morphology of a thin film of p-sexiphenyl (p-6P) on KCl(001) was carried out by atomic force microscopy (AFM). An individual p-6P film was prepared by vapor deposition at a base pressure of ∼1x10-8 mbar onto a KCl(001) surface which was maintained at 323 K during deposition. The AFM was carried out in a separate vacuum chamber, in situ, at a base pressure of ∼1x10-6 mbar. The p-6P film was cooled and maintained at discrete temperatures in the range from 294 K to 128 K as AFM measurements were performed. Similar surface morphologies are observed for film temperatures maintained at 294, 264, and 227 K, and 188 and 128 K during the AFM measurements. AFM images for the first set of film temperatures (294 - 227 K) indicate the presence of block-like islands of p-6P, with well-defined crystallite boundaries. AFM images of the films in the second set (188 and 128 K) indicate the presence of triangular wedge-shaped structures of p-6P preferentially aligned nearly in the direction of the [110]KCl. Comparison of these wedge-shaped structures at the indicated film temperatures reveals they are rotated by approximately 180° with respect to each other. Subsequent images of the surface of the p-6P film captured again at 294 K, after the final 128 K temperature study was completed, revealed the same surface features found for the initial 294 K film temperature.
Rigid Optical Chromophore: The Photophysical Properties of p-Phenylene Benzobisthiazole Derivative
Authors: Lee Seung-Hwan , Otomo Akira , Nakahama Tatsuo , Yamada Toshiki , Yokoyama Shiyoshi , Mashiko Shinro 
Published: April 2011

ABSTRACTA novel rigid and planar chromophore, p-phenylene benzobisthiazole unit with donor and acceptor groups, has been synthesized for second-order nonlinear optical applications. The first hyperpolarizability, β, of the nonlinear optical (NLO) chromophore has been measured by a Hyper-Rayleigh Scattering technique at 1064 nm in 1,1,1,3,3,3-hexafluoro-2-propanol solution. The β value of the NLO chromophore is 405E-30 esu, which is about seventeen times that of the p-NA (nitroaniline) value. The chromophore showed good thermal stability up to 330 °C in nitrogen atmosphere.
Theoretical Study of The Luminescence Effects in Trinuclear Silver Organometallic Compounds
Authors: Salcedo Roberto , Sansores L. Enrique , Martínez Ana 
Published: April 2011

ABSTRACTThe luminescence and related phenomena of a trinuclear silver organometallic complex has been studied from a theoretical viewpoint (B3LYP/6-31G* level). The study takes into account the relation between this compound and the [Au(CH3N=COCH3)3] that has been characterised and studied on the base of its solvoluminescence behaviour.
Line Shape Analysis of Photoluminescence Spectra on Solutions of MD-PPV
Authors: Santos L. F. , Marconi F.M. , Bianchi R.F. , Marletta A. , Nunes L. A. O. , Faria R. M. , Balogh D.T. 
Published: April 2011

ABSTRACTIn this work, we study the influence of organic solvents on the absorption and emission spectra of solutions and films of a soluble poly-(p-phenylenevinylene)- PPV derivative, the poly(3-methoxy-5-dodecoxy-p-phenylene-vinylene)- MD-PPV. We carried out absorption in the UV-Vis range, photoluminescence (PL) and photoluminescence excitation (PLE) measurements of MD-PPV solutions and cast films from five different solvents at room temperature. UV-Vis measurements show a solvatochromic effect, presenting a blue shift of the lowest-energy edge of the φ-φ* transition band for different solvents. PL spectra, on the other hand, show a multi-peak behavior, which is fitted considering an excitonic transition model followed by vibronic structure replica. It is observed that the first vibronic peak intensity tends to increase in comparison to the excitonic peak as δH increases, indicating that the solubility parameter of the solvent has a direct influence on the electron-phonon coupling. In addition, deviations from the intrachain model were observed for aromatic solvents, suggesting that aggregate formation can take place in the emission spectrum. Excitation spectra show that a new excitation peak comes out around 550 nm for poorer solvent solutions at higher PLE detection wavelengths, which is consistent with aggregate states emission.
Resonant Tunneling and the Substituent Effect on Negative Differential Resistance in a Molecular Junction
Authors: Matsunaga Nikita , Sohlberg Karl 
Published: April 2011

ABSTRACTRecently there has been an explosion of interest in the potential use of individual molecules as electronic device elements. The electrical characteristics of molecular junctions, individual molecules spanning the gap between two metal electrodes, have been reported and certain molecular species have been found to exhibit highly nonlinear current versus applied-voltage (I/V) properties. Intriguingly, these nonlinearities (pronounced peaks) in the I/V behavior are extremely sensitive to the functionalization of the molecule forming the junction. The substitution of a single functional group can completely eliminate the nonlinear behavior. Many have suggested that resonant tunneling could lead to the observed nonlinearities. Resonant tunneling requires a double potential barrier along the electron transfer coordinate. We propose a possible physical origin for such a double potential barrier and support the model with first principles electronic structure calculations. Next we discuss a quantum mechanical tunneling model for electron transport through the double potential barrier. The model gives insight into the origin of nonlinear I/V behavior in molecular junctions and the effect of substituent functional groups on the junction molecule.
The Precursor Polymer Approach to Electrodeposition and Patterning of Conjugated Polymer Ultrathin Films
Authors: Advincula Rigoberto , Xia Chuanjun , Taranekar Prasad , Deng Suxiang , Onishi Ken 
Published: April 2011

ABSTRACTIn this paper, we report strategies for electrodepositing and patterning ultrathin films of conjugated polymers on flat electrode surfaces using the precursor polymer approach. This involves a rational synthesis design of the precursor polymer followed by careful electrodeposition and characterization of ultrathin films on conducting substrates. This has resulted in the preparation of smooth, high optical quality films, which should be important for applications involving flat electrode surfaces in devices. Characterization was made using surface sensitive spectroscopic and microscopic techniques. Copolymerization with monomers, polymer backbone design, and grafting on modified surfaces are key points in this strategy. Novel methods of in-situ characterization techniques have also been developed combing electrochemistry and surface plasmon resonance techniques.
Thermo-optical switches using coated microsphere resonators
Authors: Tapalian C. , Laine J.-P. , Lane P. A. 
Published: April 2011

ABSTRACTWe report optical switching by a silica microsphere optical resonator coated by a conjugated polymer. Microspheres were fabricated by melting the tip of an optical fiber and coated by dipping in a 1 mg/ml toluene solution of poly(2,5-dioctyloxy-1,4-phenylenevinylene) (DOOPPV). The resonator properties were characterized by evanescently coupling 1.55 μm light propagating along a stripline-pedestal anti-resonant reflecting optical waveguide into optical whispering gallery modes (WGMs). WGM linewidths less than 2 MHz were measured, corresponding to cavity Q > 108. WGM resonant frequency shifts as large as 3.2 GHz were observed when 405 nm pump light with a power density of ∼100 mW/cm2 was incident on the microsphere. The time constant of the observed frequency shifts is approximately 0.165 seconds, leading us to attribute the frequency shift to thermo-optic effects. Such a system should be capable of thermo-optically switching at speeds on the order of 10 kHz.
Radionuclide Uptake and Transport on Microbes in Potential Repository Drifts at Yucca Mountain, Nevada
Authors: Jolley Darren M. 
Published: April 2011

ABSTRACTRadionuclide adsorption onto microbes, microbial retention in the engineered barrier system (EBS), and their potential release from the EBS as microbial colloids have been investigated. The microbial source term for these calculations was derived using MING V 1.0 software code [1]. Multiple model calculations from MING representing variations in possible microbial communities in the EBS were abstracted into two equations representing one meter segments of potential repository drift containing either commercial spent nuclear fuel (CSNF) or defense high level waste (HLW) packages. These two equations (Equations 1 and 2) represent the average cumulative microbial biomass generated in the EBS at any given time. A distribution for uranium uptake onto microbes (162.88 ± 133.05 mg U/gm dry cell) was applied to the microbial source term. The distribution was derived from the data set in Suzuki and Banfield [2] representing 45 different species of bacteria and fungus, covering uranium uptake at optimum pH values of 1 to 7. The mass of uranium sorbed onto the biomass was either sequestered in the EBS or transported as a microbial colloid based on a regression of data from Jewett et al. [3] representing microbial sorption onto air-water interfaces in unsaturated column experiments. Over one million years, it is estimated that EBS microbes may adsorb from 77 to 2302 kg of uranium [2302 kg U > 100% of the uranium available in a one meter segment of a CSNF waste package] per meter of waste package depending on the saturation of the invert and type of waste package. Over the same time, microbial colloids may transport from 8 to 1250 kg of adsorbed uranium per meter of waste package from the EBS.
Characterization and Dissolution of ZrTh3UO10 and Th3UO8 Ceramics
Authors: Curran Gini , Sevestre Yoann , Rattray Wendy , Allen Patrick G. , Czerwinski Ken R. 
Published: April 2011

ABSTRACTThoria-urania-zirconia ceramics were studied in order to investigate the long-term behavior of potential thorium fuels in a repository environment. The ceramics were prepared by coprecipitation of the metal salts. Zirconia was added to determine if further stabilization against dissolution of the thoria-urania system could be achieved. In addition, 0.5 wt% MgO was added to some samples to increase stability and density. The inclusion of Zr in the ceramics did not dramatically decrease the leaching of thorium from the matrix.Material properties of the ceramic were analyzed using electron microscopy techniques such as Energy Dispersive X-ray (EDX) analysis and Electron Energy Loss Spectroscopy (EELS). X-ray diffraction and synchrotron-based x-ray absorption studies including extended xray fine structure (EXAFS) and x-ray absorption near edge spectroscopy (XANES) were also used to reveal elements of the phase structure and chemistry of the ceramics. X-ray diffraction (XRD) and EDX show that these ceramics separate into a zirconium-based phase and an actinide-based phase with low mutual affinity of thorium and zirconium, as well as partial solubilization of uranium in zirconium. The comparison of EELS spectra collected for the ceramics with spectra collected for UO2 and U3O8 reference materials also allow the assessment of uranium oxidation state independently in the two separate phases. Assessment of the bulk oxidation state using XANES correlated well with the EELS analysis. Interatomic distances and the bulk crystal structure were determined using EXAFS.
Depleted Uranium Dioxide Waste Package for Spent Nuclear Fuel
Authors: Forsberg Charles W. , Dole Leslie R. 
Published: April 2011

ABSTRACTDepleted uranium dioxide (DUO2) waste packages (WPs) for disposal of spent nuclear fuel (SNF) are being investigated to (1) reduce radionuclide releases from WPs, (2) decrease the potential for repository nuclear criticality events, (3) provide radiation shielding, and (4) provide a means to beneficially use excess depleted uranium (DU). The DUO2 is incorporated into the WP as (1) a particulate fill for void spaces within the package and (2) a component of a DUO2-steel cermet (DUO2 embedded in steel) that replaces the steel components of the WP. Depending upon the design, there is 3 to 8 times as much DUO2 as SNF UO2 in the WP. Most radionuclides in the SNF cannot be released until the UO2 crystal structure is destroyed. The DUO2 surrounding the SNF slows the degradation of the SNF UO2 in the interior. This behavior is similar to the mechanisms that slow the degradation of natural uranium ore bodies containing UO2. The results of initial investigations and the expected thermodynamic WP behavior are described.
Neptunium Incorporation into Uranium(Vi) Compounds formed During Aqueous Corrosion of Neptunium-Bearing Uranium Oxides
Authors: Finch Robert J. , Fortner Jeffery A. , Buck Edgar C. , Wol Stephen F. 
Published: April 2011

ABSTRACTWe report results of experimental studies on the behavior of Np during aqueous corrosion of unirradiated Np-bearing U oxides. Np-doped U oxides were reacted in humid air at 90°C and 150°C for several weeks within sealed stainless-steel vessels. Reacted solids were examined by scanning and transmission electron microscopies (SEM and TEM), electron energy-loss spectroscopy (EELS), and X-ray powder diffraction (XRD). Dehydrated schoepite, (UO2)O0.25-z(OH)1.5+2z (0 ≤z ≤0.15), is the predominant U(VI) compound formed in these experiments. Preliminary EELS analysis on crushed grains verify that dehydrated schoepite formed at 150°C contains up to approximately 2 wt.% Np, corresponding to a maximum Np:U molar ratio of approximately 1:40. These are maximum values because the degree to which surface-sorbed Np is present on the grains analyzed is not yet known. Crystalline NpO2 also precipitated during these experiments, and the concentration of Np in dehydrated schoepite may represent the maximum amount of Np that can be incorporated into dehydrated schoepite under the experimental conditions.
Ionic Size Limits for A Ions in Brannerite (ATi2O6) and Pyrochlore (CaATi2O7) Titanate Structures ( A = tetravalent rare earths and actinides)
Authors: Vance E. R. , Carter M. L. , Stewart M. W. A. , Day R. A. , Begg B. D. , Ball C. J. 
Published: April 2011

ABSTRACTThe lower limit of the size of the octahedral A4+ ion in the ATi2O6 brannerite structure is just smaller than that of Ce/Pu. Attempts to expand the A ion size beyond that of Th by (a) substituting a Ba ion plus two U5+ ions for three A ions or (b) substituting one Ba plus one hexavalent ion for two A ions did not succeed. Ge, Sn and Zr substitutions in the Ti site of ThTi2O6 do not exceed 0.2 formula unit in ceramic preparations. These and other coupled substitutions in the B site of ThTi2O6 showed that the average B site size could tolerate deviations of < 1%. Ce4+ is unusually stabilised in air atmospheres at temperatures close to the melting point of 1400°C in the A site of brannerite. Lattice parameter data on different endmember ATi2O6 brannerites are given. The lower and upper size limits for the eightfold A ions in the pyrochlore structure are around 0.100 and 0.117 nm respectively. A BaUTi2O7 stoichiometry did not produce a pyrochlore structure, and when fired in either argon or air yielded a mixture of BaUTiO6, whose structure is still uncertain, plus brannerite and rutile.
Microanalysis of Radiation Damage Across a Zoned Zircon Crystal
Authors: Palenik Chris S. , Ewing Rodney C. 
Published: April 2011

ABSTRACTAn oscillatory-zoned single crystal of zircon (ZrSiO4) from Sri Lanka (560 Ma) provides a unique opportunity to study radiation effects over the dose range of 2.1 - 10.6·1015 á-decay events/mg (0.1 - 0.5 dpa). Each zone has a different radiation dose due to variations in the U (0.09 - 0.53 wt %) and Th (0 - 0.11 wt %) content, but all zones share the same thermal history. The zones span a nearly complete range of microstructures from crystalline to aperiodic. Measurements of birefringence show an inverse-linear correlation with dose over the range of doses observed. Micro-Raman spectroscopy results show that a decrease in peak frequency relative to an undamaged zircon, peak broadening and decreases in peak intensity occur with the accumulation of radiation damage.
Protein/Polymer Hybrid Biomimetic Valves
Authors: Ho Dean , Schmidt Jacob J. , Montemagno Carlo D. 
Published: April 2011

ABSTRACTMembrane channel and pore proteins represent a versatile class of molecules that offer opportunities to serve as engineered nano-valves. We are inserting OmpF, a voltage-gatable pore protein, into planar membranes for applications in microfluidics and sensing. To emulate and improve upon natural membranes, we have selected triblock copolymers containing UV cross-linkable end groups. We are developing a microfabricated version of a conventional black lipid membrane/copolymer characterization apparatus which will enable us to rapidly analyze composite membrane properties as a function of area and applied electrical bias. We show that only slight deviations of conventional planar lipid membrane formation procedures with triblock copolymers are sufficient for polymer monolayer membrane formation. We report the results of the preliminary tests on polymer membrane formation and stability as well as the construction of the microfabricated device.
Biomimetic Poly(L-Lactic Acid) Scaffolds with Interconnected Macropores, Collagen-Like Nano-Scale Fibers, and Bone-Like Apatite
Authors: Chen Victor J. , Ma Peter X. 
Published: April 2011

ABSTRACTHighly porous nano-fibrous poly(L-lactic acid) (PLLA) scaffolds were prepared and incubated in a simulated body fluid which resulted in thein situformation of partially carbonated bone-like apatite. The macroporous interconnected architecture was created with a three-dimensional mold of thermally-bonded paraffin microspheres. PLLA solution was cast over the paraffin mold and was thermally induced to phase separate to form nano-scale fibers that mimic the fibrous structures of type I collagen. To potentially improve the osteoconductivity of these scaffolds, they were incubated in a buffered simulated body fluid at 37°C for certain periods of time to allow for apatite formation. It was seen that over time, the apatite particles increased in size. In addition, the growth of apatite particles on the nano-fibrous scaffolds was compared with the growth of particles on similar porous PLLA scaffolds with a solid-walled (not nano-fibrous) morphology. It was seen that the initial number of particles per unit area and the overall increase in mass of the scaffolds were significantly higher in the nano-fibrous scaffolds than in the solid-walled scaffolds. These novel scaffolds have well-defined architectures at three different size scales: (i) interconnected spherical pores ∼250–400 m in diameter; (ii) fibrous collagen-like matrix with fibers 50–500 nm in diameter; and (iii) carbonated bone-like apatite particles at the nanometer to micrometer scales; the scaffolds may serve as superior support for bone tissue regeneration.
Deformable interconnects for conformal integrated circuits
Authors: Périchon Lacour Stéphanie , Huang Zhenyu , Suo Zhigang , Wagner Sigurd 
Published: April 2011

ABSTRACTThe electro-mechanical response of thin gold layers evaporated onto silicone substrates is reported. Gold layers are prepared either thin and flat or thin and wavy on the compliant substrate. The electrical resistance of gold/silicone stripes is measured and analyzed during tensile deformation. For a 100-nm thick gold layer evaporated on a 1-mm thick silicone membrane, we have observed electrical continuity up to ∼ 22 % strain. This maximum strain decreases when the gold layer thickness is raised.
Sub-wetting layer continuum states in the self-organized quantum dot samples
Authors: K. Král , P. Zdeněk , Khás Z. , Čerňanský M. 
Published: April 2011

ABSTRACTIn polar semiconductor samples of the self-organized quantum dots, grown by the Stranski-Krastanow growth method, the lowest-energy extended states of the motion of the electronic excitations, are assumed to be the wetting-layer states. The coupling between these extended states and the electronic states localized in the individual quantum dots, may influence the optical spectra of such samples in the sub-wetting layer region of energy. This effect is studied assuming the Fröhlich's coupling between the electrons and the polar optical phonons. The contribution of this interaction to the appearance of the sub-wetting layer continuum in the optical spectra, and to the level broadening of the localized states, pointed out in some experiments, is estimated.
Investigation of the Shape of InGaAs/GaAs Quantum Dots
Authors: Lehman Susan Y. , Roshko Alexana , Mirin Richard P. , Bonevich John E. 
Published: April 2011

ABSTRACTThree samples of self-assembled In0.44Ga0.56As quantum dots (QDs) grown on (001) GaAs by molecular beam epitaxy (MBE) were studied using atomic force microscopy (AFM) and high-resolution transmission electron microscopy (TEM) in order to characterize the height, faceting, and densities of the QDs. The cross-sectional TEM images show both pyramidal dots and dots with multiple side facets. Multiple faceting has been observed only in dots more than 8.5 nm in height and allows increased dot volume without a substantial increase in base area. Addition of a GaAs capping layer is found to increase the diameter of the QDs from roughly 40 nm to as much as 200 nm. The areal QD density is found to vary up to 50 % over the central 2 cm x 2 cm section of wafer and by as much as 23 % on a length scale of micrometers.
Dislocation-induced spatial alignment of self-assembled InAs/GaAs quantum dots
Authors: Lee H. S. , Lee J. Y. , Kim T. W. , Park Y. J. 
Published: April 2011

ABSTRACTWe have studied the alignment of self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy using misfit dislocations generated due to the strained InxGa1-xAs/GaAs superlattice system. Structural characteristics of aligned SAQDs have been investigated by using atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. AFM and TEM images showed that vertical stacked InAs QD arrays were aligned along <110> direction on the controlled strained layer. The anisotropic alignments along the [110] and [110] directions are closely related with the anisotropy of strain-relief for both directions, which affect the anisotropic diffusivity of indium adatoms on the strained superlattice layer. The strong alignment appears on the highly strained layer. These results indicate that aligned InAs quantum dots formed by changing the periods of strained superlattice hold promise for potential applications in nanoelectronic devices, such as single electron tunneling devices.