Micellization and morphological characterization of Ag-micelles prepared by poly(vinyl acetate)-silver nitrate in solvent/nonsolvent system

The inducing method for preparing Ag-micelle solution with the use of mixed solvent/nonsolvent, and the morphological characterization of the generated metal-micelles were investigated and reported in this paper. In this method, an Ag containing metal chelate polymer (MCP) raw solution was preprepared by dissolving poly(vinyl acetate) (PVAc)-silver nitrate (AgNO3) MCP in cone. formic acid, and a mixed solvent of HCOOH/H2O with specific water composition was then added to induce the micellization of the MCP chain. The critical water concentration (CWC) that was needed for inducing the formation of the Ag-micelles, and the water concentration at which the flocculation of the Ag-micelles occurred in micellar solution, were studied by measuring the transmittance of the dilute MCP solution; the results showed that a long-lasting MCP solution with stable micelles might be prepared by using a H2O/ HCOOH solvent of specific weight ratio 1:1.2. The effect of the AgNO3 concentration on the morphology of the Ag-micelles was also investigated by transmission electron microscopy (TEM). At AgNO3 concentration below 0.5 wt%, the Ag-micelles displayed a variety of core-shell structure; but as the AgNO3 concentration was increased to 1.0-2.0 wt%, micelles that had Ag-solid embedded in the micellar core were observed

Ni Interdiffusion Coefficient and Activation Energy in Cu6Sn5

Ni diffusion in Cu6Sn5 intermetallic compound was investigated. First, we successfully fabricated preferred-orientation Cu6Sn5 crystal by liquid-phase electroepitaxy (LPEE). Then, Ni/Cu6Sn5 diffusion couples were produced by sputtering from a Ni thin film onto the Cu6Sn5 crystal. Ni/Cu6Sn5 diffusion couples were annealed at different temperatures of 120A degrees C, 160A degrees C, 200A degrees C, 255A degrees C, 290A degrees C, and 320A degrees C for 2 h in a vacuum. The Ni atomic profile across the Ni/Cu6Sn5 interface was obtained by electron spectroscopy for chemical analysis (ESCA). From the Ni atomic profiles, the Matano method was used to evaluate the Ni interdiffusion coefficients ((D) over tilde (Ni)) in the Cu6Sn5 crystal obtained with different annealing temperatures, which then yields the activation energy for Ni diffusion in the Cu6Sn5 crystal at a particular Ni content. We found that, as Ni diffuses in the ternary Cu6-x Ni (x) Sn-5 compound phase, the activation energy of Ni interdiffusion decreases with the Ni content

Optical properties of large area WS2 grown by chemical vapor deposition

Transition metal dichalcogenides (TMDs) have attracted great attention for fundamental physics and possible application as optoelectronic devices [1-5]. Monolayers of TMDs are direct gap semiconductors with optical transition in inequivalent at K and K´ valleys and distinct optical selection rules due to the combination of spin-orbit interaction and broken inversion symmetry. As a consequence, optical excitation with circularly polarized light results in circularly polarized emission. Actually, recent studies for TMDs have evidenced important valley polarization degree and large excitonics effects as well particularly at lower temperatures [1-5]. In this work, we have investigated optical properties from large are a monolayers of WS2 on 295nm SiO2/Si grown by Van der Waals Epitaxy Chemical Vapor Deposition. Particularly , we have investigated polarization resolved photoluminescence (PL ) spectra for different light excitation intensities and temperatures using a 532 nm solid state laser. The s + and s - light excitation and detection were obtained using appropriate quarter wave plates and linear polarizers. At lower temperatures, we have observed different PL peaks for the WS2 monolayer. The temperature and laser power dependence of PL spectra evidences that the observed peaks are associated to neutral (X), charged excitons (X- ) and biexcitons (XX). Therefore, our results reveal important many -body interactions in atomically thin WS2 semiconductor

Dewetting Retardation on Ag/Cu Coated Light Emitting Diode Lead Frames During the Solder Immersion Process

The process of SnPb immersion in Ag/Cu coated light emitting diode lead frames (LED LFs) (alloy 42) was investigated. SnPb solder was found to cause dewetting of the LF substrate after 6 s of immersion. We believed that the dewetting of the SnPb solder could be attributed to spalling of the interfacial compound grains. The addition of a small amount of Ni to the molten SnPb solder (0.1 wt.%) retarded that spalling and helped to prevent dewetting. The mechanisms for spalling retardation by the addition of Ni additives are as follows: (1) the Ni additives slow down the reaction rate between the molten SnPb solder and the Ag/Cu plating layer; (2) the Ni additives participate in interfacial reactions to form (Cu,Ni)(6)Sn(5) ternary compounds, which are more stable than binary compounds and have a slower ripening process

Dissociation cross sections of ground-state and excited charmonia with light mesons in the quark model

We present numerical results for the dissociation cross sections of ground-state, orbitally- and radially-excited charmonia in collisions with light mesons. Our results are derived using the nonrelativistic quark model, so all parameters are determined by fits to the experimental meson spectrum. Examples of dissociation into both exclusive and inclusive final states are considered. The dissociation cross sections of several C=(+) charmonia may be of considerable importance for the study of heavy ion collisions, since these states are expected to be produced more copiously than the J/psi. The relative importance of the productions of ground-state and orbitally-excited charmed mesons in a pion-charmonium collision is demonstrated through the $\sqrt {s}$-dependent charmonium dissociation cross sections.Comment: 9 pages, 8 figure

Projected SO(5) Hamiltonian for Cuprates and Its Applications

The projected SO(5) (pSO(5)) Hamiltonian incorporates the quantum spin and superconducting fluctuations of underdoped cuprates in terms of four bosons moving on a coarse grained lattice. A simple mean field approximation can explain some key feautures of the experimental phase diagram: (i) The Mott transition between antiferromagnet and superconductor, (ii) The increase of T_c and superfluid stiffness with hole concentration x and (iii) The increase of antiferromagnetic resonance energy as sqrt{x-x_c} in the superconducting phase. We apply this theory to explain the ``two gaps'' problem found in underdoped cuprate Superconductor-Normal- Superconductor junctions. In particular we explain the sharp subgap Andreev peaks of the differential resistance, as signatures of the antiferromagnetic resonance (the magnon mass gap). A critical test of this theory is proposed. The tunneling charge, as measured by shot noise, should change by increments of Delta Q= 2e at the Andreev peaks, rather than by Delta Q=e as in conventional superconductors.Comment: 3 EPS figure

Study of Interfacial Reactions Between Sn(Cu) Solders and Ni-Co Alloy Layers

The interfacial reactions between electroplated Ni-yCo alloy layers and Sn(Cu) solders at 250 degrees C are studied. For pure Co layers, CoSn(3) is the only interfacial compound phase formed at the Sn(Cu)/Co interfaces regardless of the Cu concentration. Also, the addition of Cu to Sn(Cu) solders has no obvious influence on the CoSn(3) compound growth at the Sn(Cu)/Co interfaces. For Ni-63Co layers, (Co,Ni,Cu)Sn(3) is the only interfacial compound phase formed at the Sn(Cu)/Ni-63Co interfaces. Unlike in the pure Co layer cases, the Cu additives in the Sn(Cu) solders clearly suppress the growth rate of the interfacial (Co,Ni,Cu)Sn(3) compound layer. For Ni-20Co layers, the interfacial compound formation at the Sn(Cu)/Ni-20Co interfaces depends on the Cu content in the Sn(Cu) solders and the reflow time. In the case of high Cu content in the Sn(Cu) solders (Sn-0.7Cu and Sn-1.2Cu), an additional needle-like interfacial (Ni(x),Co(y),Cu(1-x-y))(3)Sn(4) phase forms above the continuous (Ni(x),Cu(y),Co(1-x-y))Sn(2) compound layer. The Ni content in the Ni-yCo layer can indeed reduce the interfacial compound formation at the Sn(Cu)/Ni-yCo interfaces. With pure Sn solders, the thickness of the compound layer monotonically decreases with the Ni content in the Ni-yCo layer. As for reactions with the Sn(Cu) solders, as the compound thickness decreases, the Ni content in the Ni-yCo layers increases

ESTIMATING GENOME-WIDE COPY NUMBER USING ALLELE SPECIFIC MIXTURE MODELS

Genomic changes such as copy number alterations are thought to be one of the major underlying causes of human phenotypic variation among normal and disease subjects [23,11,25,26,5,4,7,18]. These include chromosomal regions with so-called copy number alterations: instead of the expected two copies, a section of the chromosome for a particular individual may have zero copies (homozygous deletion), one copy (hemizygous deletions), or more than two copies (amplifications). The canonical example is Down syndrome which is caused by an extra copy of chromosome 21. Identification of such abnormalities in smaller regions has been of great interest, because it is believed to be an underlying cause of cancer. More than one decade ago comparative genomic hybridization (CGH)technology was developed to detect copy number changes in a high-throughput fashion. However, this technology only provides a 10 MB resolution which limits the ability to detect copy number alterations spanning small regions. It is widely believed that a copy number alteration as small as one base can have significant downstream effects, thus microarray manufacturers have developed technologies that provide much higher resolution. Unfortunately, strong probe effects and variation introduced by sample preparation procedures have made single-point copy number estimates too imprecise to be useful. CGH arrays use a two-color hybridization, usually comparing a sample of interest to a reference sample, which to some degree removes the probe effect. However, the resolution is not nearly high enough to provide single-point copy number estimates. Various groups have proposed statistical procedures that pool data from neighboring locations to successfully improve precision. However, these procedure need to average across relatively large regions to work effectively thus greatly reducing the resolution. Recently, regression-type models that account for probe-effect have been proposed and appear to improve accuracy as well as precision. In this paper, we propose a mixture model solution specifically designed for single-point estimation, that provides various advantages over the existing methodology. We use a 314 sample database, constructed with public datasets, to motivate and fit models for the conditional distribution of the observed intensities given allele specific copy numbers. With the estimated models in place we can compute posterior probabilities that provide a useful prediction rule as well as a confidence measure for each call. Software to implement this procedure will be available in the Bioconductor oligo packagehttp://www.bioconductor.org)

Flow-FISH analysis and isolation of clostridial strains in an anaerobic semi-solid bio-hydrogen producing system by hydrogenase gene target

By using hydrogenase gene-targeted polymerase chain reaction (PCR) and reverse transcriptase PCR (RT-PCR), the predominant clostridial hydrogenase that may have contributed to biohydrogen production in an anaerobic semi-solid fermentation system has been monitored. The results revealed that a Clostridium pasteurianum-like hydrogenase gene sequence can be detected by both PCR and RT-PCR and suggested that the bacterial strain possessing this specific hydrogenase gene was dominant in hydrogenase activity and population. Whereas another Clostridium saccharobutylicum-like hydrogenase gene can be detected only by RT-PCR and suggest that the bacterial strain possessing this specific hydrogenase gene may be less dominant in population. In this study, hydrogenase gene-targeted fluorescence in situ hybridization (FISH) and flow cytometry analysis confirmed that only 6.6% of the total eubacterial cells in a hydrogen-producing culture were detected to express the C. saccharobutylicum-like hydrogenase, whereas the eubacteria that expressed the C. pasteurianum-like hydrogenase was 25.6%. A clostridial strain M1 possessing the identical nucleotide sequences of the C. saccharobutylicum-like hydrogenase gene was then isolated and identified as Clostridium butyricum based on 16S rRNA sequence. Comparing to the original inoculum with mixed microflora, either using C. butyricum M1 as the only inoculum or co-culturing with a Bacillus thermoamylovorans isolate will guarantee an effective and even better production of hydrogen from brewery yeast waste

Hamiltonian Study of Improved U(1U(1 Lattice Gauge Theory in Three Dimensions

A comprehensive analysis of the Symanzik improved anisotropic three-dimensional U(1) lattice gauge theory in the Hamiltonian limit is made. Monte Carlo techniques are used to obtain numerical results for the static potential, ratio of the renormalized and bare anisotropies, the string tension, lowest glueball masses and the mass ratio. Evidence that rotational symmetry is established more accurately for the Symanzik improved anisotropic action is presented. The discretization errors in the static potential and the renormalization of the bare anisotropy are found to be only a few percent compared to errors of about 20-25% for the unimproved gauge action. Evidence of scaling in the string tension, antisymmetric mass gap and the mass ratio is observed in the weak coupling region and the behaviour is tested against analytic and numerical results obtained in various other Hamiltonian studies of the theory. We find that more accurate determination of the scaling coefficients of the string tension and the antisymmetric mass gap has been achieved, and the agreement with various other Hamiltonian studies of the theory is excellent. The improved action is found to give faster convergence to the continuum limit. Very clear evidence is obtained that in the continuum limit the glueball ratio $M_{S}/M_{A}$ approaches exactly 2, as expected in a theory of free, massive bosons.Comment: 13 pages, 15 figures, submitted to Phys. Rev.