Electron transfer characteristics of amino acid adsorption on epitaxial graphene FETs on SiC substrates

Clarifying the adsorption characteristics of biomolecules on graphene surfaces is critical for the development of field-effect transistor (FET)-based biosensors for detecting pH, DNA, proteins, and other biomarkers. Although there are many reports on biomolecule detection using graphene FETs, the detection mechanism has not yet been clarified. In this study, the adsorption behavior and electron transfer characteristics of 20 proteinogenic amino acids on graphene field-effect transistors are investigated. Large single-crystal graphene films were epitaxially grown on SiC substrates by a resist-free metal stencil mask lithography process then patterned by air plasma etching to form FET devices. Amino acids with different charge conditions (positive or negative charge) were introduced onto the epitaxial graphene surface in solution. The charge neutral points of the drain current vs gate voltage curves shifted in the negative gate voltage direction after the introduction of all amino acids, regardless of the type of amino acid and its charge condition. These amino acid adsorption characteristics agree well with previously reported protein adsorption characteristics on epitaxial graphene surfaces, indicating that the adsorption of proteins in the liquid phase occurs by electron doping to the graphene surface. These results indicate that non-specific protein binding always leads to electron doping of epitaxial graphene FETs

Ambegaokar-Baratoff relations of Josephson critical current in heterojunctions with multi-gap superconductors

An extension of the Ambegaokar-Baratoff relation to a superconductor-insulator-superconductor (SIS) Josephson junction with multiple tunneling channels is derived. Appling the resultant relation to a SIS Josephson junction formed by an iron-based (five-band) and a single-band Bardeen-Cooper-Schrieffer (BCS) type superconductors, a theoretical bound of the Josephson critical current ($I_{\rm c}$) multiplied by the resistance of the junction ($R_{\rm n}$) is given. We reveal that such a bound is useful for identifying the pairing symmetry of iron-pnictide superconductors. One finds that if a measured value of $I_{\rm c}R_{\rm n}$ is smaller than the bound then the symmetry is $\pm s$-wave, and otherwise $s$-wave without any sign changes. In addition, we stress that temperature dependence of $I_{\rm c}R_{\rm n}$ is sensitive to the difference of the gap functions from the BCS type gap formula in the above heterojunction.Comment: 7 pages, 6 figure

Melina II: a web tool for comparisons among several predictive algorithms to find potential motifs from promoter regions

We present the second version of Melina, a web-based tool for promoter analysis. Melina II shows potential DNA motifs in promoter regions with a combination of several available programs, Consensus, MEME, Gibbs sampler, MDscan and Weeder, as well as several parameter settings. It allows running a maximum of four programs simultaneously, and comparing their results with graphical representations. In addition, users can build a weight matrix from a predicted motif and apply it to upstream sequences of several typical genomes (human, mouse, S. cerevisiae, E. coli, B. subtilis or A. thaliana) or to public motif databases (JASPAR or DBTBS) in order to find similar motifs. Melina II is a client/server system developed by using Adobe (Macromedia) Flash and is accessible over the web at http://melina.hgc.jp

Thermal desorption of structured water layer on epitaxial graphene

Thermal desorption of the structured water layer on graphene was observed in this study via electrical conductivity measurements. Specifically, a structured water layer was formed on the graphene surface via deionized water treatment, following which we examined the thermal desorption process of the layer using sheet resistance measurements. The water molecules acting as a p-type dopant were strongly adsorbed on graphene, forming a solid layer. Consequently, the layer was completely removed from the graphene surface at 300⁡°C. The thermal desorption spectrum of the structured water layer on graphene was quantitatively obtained by converting the measured sheet resistance to carrier density change

Anode properties of thick-film electrodes prepared by gas deposition of Ni-coated Si particles

Thick-film electrodes of Si particles coated with Ni, Ni-Sn, and Ni-P were fabricated by electroless deposition followed by gas deposition to form the anode of a Li-ion battery. The electrode of Ni-coated Si showed remarkably improved cycling performance with a discharge capacity of 580 mA h g-1 at the 1000th cycle, which is possibly caused by its higher elastic modulus than that of the uncoated Si electrode. The electrode of Si coated with Ni-P, which consisted of Ni3P, with the lower coating amount exhibited a higher initial capacity and excellent cycling performance with a capacity of 790 mA h g-1 at the 1000th cycle, whereas poor performance was obtained for the electrode of Si coated with Ni-Sn. The excellent performance in the case of Ni-P coating is attributed to the smaller amount of coating, the high elastic modulus, and the lower reactivity of Ni3P with Li ions in comparison with Ni3Sn in Ni-Sn

Anode Properties of Composite Thick-Film Electrodes Consisted of Si and Various Metal Silicides

Thick-film electrodes of composite active materials consisted of Si and various metal silicides, FeSi2/Si, VSi2/Si, or MmSi2/Si, were prepared by mechanical alloying followed by gas deposition for anodes of Li-ion batteries. We investigated a relationship between the performance of these electrodes and properties of the silicide, the electrical resistivity, the referential breaking strength, and the thermodynamic stability. The MmSi2/Si composite electrode exhibited superb cycling performance, where the discharge capacity of 380 mA h g-1 was maintained even at the 1000th cycle. It is suggested that thermodynamically stable MmSi2 in the composite electrode can improve the electrical conductivity of the electrode and can release the stress induced by a volumetric change of Si for a long period

Dual Microcatheter Retrograde Transvenous Obliteration of Gastric Varices: Coil Embolization as a Substitute for Balloon Occlusion

Dual microcatheter retrograde transvenous obliteration (DMRTO) of gastric varices enables dual microcatheters to be advanced to the gastric varices themselves or to a site adjacent to the varices. The sclerosing agent is infused through the first microcatheter following coil embolization of the outflow vessels through the second microcatheter, which is placed several centimeters back from the varices. We present two cases of gastric varices in whom balloon-occluded retrograde transvenous obliteration failed, because of angulated gastrosubphrenic shunt in case 1 and a tortuous and elongated gastrorenal shunt in case 2. DMRTO successfully achieved eradication of the gastric varices in both cases