Proximity effect in Ag-Pb alloys

The superconducting properties and the microstructure of the Ag_100-xPb_x alloys, 1 ≤ x ≤ 5, prepared by rapid quenching from the liquid state with and without subsequent heat treatments, have been studied. The x-ray diffraction measurements show that supersaturated solid solutions of Pb in Ag can be obtained up to 3.2 at.% Pb as compared to less than 0.1 at.% Pb at equilibrium. It was found that by suitable heat treatment it is possible to vary the size and distribution of the Pb precipitates in the Ag matrix and reproducible superconducting properties in the alloy can be observed. The superconducting transition temperature of these samples can be qualitatively explained by the Silvert and Singh's theoretical calculation. The theory developed for the case of layer structure can be extended to three dimensions to explain the critical current versus temperature behavior. The critical current versus field behavior of these alloys can be explained by the modification of the Josephson effect. Combining these results together with the critical magnetic field measurements and the microstructure studies of the alloys, it can be concluded that the three-dimensional proximity effect is the main mechanism for the superconductivity in the Ag-Pb alloys. Based on the Hilsch empirical formula which was based on experimental results obtained on layer structures, the experimental data in this investigation show that the electron-phonon-electron interaction in silver is attractive. The interaction parameter NV obtained is approximately 0.06, which would lead to a value of 10^-5 °K for the superconducting transition temperature of Ag. These values are in agreement with other determinations which were done on vapor-deposited metallic film sandwiches. Hence, the Hilsch empirical relation valid for layer structures is also valid in the three-dimensional case. Because the transition temperature and the critical current can be varied in a wide range by controlling the heat treatments, the Ag-Pb superconductors might have some useful applications.

Metalotioneinen mailak eta metalen banaketa Ag eta Cu pean mantendutako ostretan

Laburpena: Ikerlan hau itsasoaren kutsaduran zentratzen da, itsasoak arriskutsuak eta kaltegarriak diren substantziak jasotzen dituelako, bai ibaietako ekarpenarengatik, baita zuzeneko karguetatik. Organismo behale gisa ostrak erabiliko dira, izaki iragazleak izanik elikagaien irenstearen ondorioz medio urtsutik kutsatzaileak metatzen dituztelako eta gainera, ingurugiroan dauden mailen gainetik kontzentratzen dituztelako. Ostretan zilarra (Ag) eta kobrea (Cu) bezalako metalen eragina aztertuko da, horretarako, metalen aurreko esposizio biomarkatzaileak erabiliko dira. Besteak beste, autometalografia erabiliko da metalen mailak eta banaketa ostren ehunetan neurtzeko eta metalotioneinen mailak ere neurtuko dira. Ostrek metalekiko izan duten esposizio denborak 0, 6, 7, 13 eta 14 egunetakoak izan dira, bai itsasoko eta bai estuarioko uretan mantenduz. Emaitzak ikusita behatu da estuarioko laginek, normalean, metal kontzentrazio baxuagoak aurkezten dituztela, eta zenbait kasutan kontrolek metalen pean jarritako laginak baino metal kontzentrazio handiagoak erakutsi dituzte aste bat igaro eta gero. Bigarren astean, metal mailen jaitsiera bat behatu da. Beste alde batetik, metalotioneinetan neurtutako indukzio mailak oso baxuak izan dira. Metalen distribuzioa ehun desberdinetan aldez aurretik beste molusku batzuetan deskribatutakoen oso antzekoa izan da ostretan.

Preparation and optical properties of Ag/PPy composite colloids

Ag/PPy (polypyrrole) composite colloids were prepared through the reaction of silver nitrate with pyrrole solution in DNIF either in the dark, or under the irradiation of femtosecond laser (fs) pulse or UV lamp. The UV-vis spectra of the nanocomposite colloid display an intense absorption band around 620 nm, accompanied by a weak one around 470 nm. The colors and optical absorption spectra of as-synthesized colloids can be reversibly tuned between blue and red, corresponding to absorption band of 620 urn and 526 urn, within few seconds by adding base and acid solutions or gases in turn into the composite colloid suspension. In addition, excess of H+ solution enhanced the absorption band around 470 nm and, at the same time, depressed that around 620 nm. The possible mechanism for the formation and optical absorption properties of the Ag/PPy composite colloid was proposed. (C) 2006 Elsevier B.V. All rights reserved.

Ag~+-Li~+离子交换制作Er~(3+)/Yb~(3+)共掺磷酸盐玻璃平面光波导(英文)

制备了化学稳定的Er^3＋／Yb^3＋共掺的磷酸盐玻璃，并在其中制作了用于光放大器和激光器的平面光波导．这种磷酸盐玻璃的失重速率为4．7×10^-5g·cm^-2·hr^-1，小于Kigre公司商业化的磷酸盐玻璃QX／Er的失重速率．采用Ag^＋-Li^＋交换技术制作了平面光波导并用m-线光谱在632．8nm测量了平面光波导的有效折射率．根据反WKB法得到折射率形貌，计算了离子交换参数如：离子交换深度、表面折射率，折射率改变和扩散系数等．

Space-selective co-precipitation of silver and gold nanoparticles in femtosecond laser pulses irradiated Ag+, Au3+ co-doped silicate glass

We report on space-selective co-precipitation of silver and gold nanoparticles in Ag+, Au3+ co-doped silicate glasses by irradiation of femtosecond laser pulses and subsequent annealing at high temperatures. The color of the irradiated area in the glass sample changed from yellow to red with the increase of the annealing temperature. The effects of average laser power and annealing temperature on precipitation of the nanoparticles were investigated. A reasonable mechanism was proposed to explain the observed phenomena. (c) 2006 Elsevier Ltd. All rights reserved.

Nanosecond nonlinear absorption in Au and Ag nanoparticles precipitated glasses induced by a femtosecond laser

We obtain Au and Ag nanoparticles precipitated in glasses by irradiation of focused femtosecond pulses, and investigate the nonlinear absorptions of the glasses by using Z-scan technique with ns pulses at 532 nm. We observe the saturable absorption behavior for An nanoparticles precipitated glasses and the reverse saturable ones for Ag ones. We also obtain, by fitting to the experimental results in the light of the local field effect near and away from the surface plasmon resonance, chi(m)((3)) = 4.5 x 10(-7) and 5.9 x 10(-8) esu for m the imaginary parts of the third-order susceptibilities for Au and Ag nanoparticles, respectively. The nonlinear response of Au nanoparticles in the glass samples arises mainly from the hot-electron contribution and the saturation of the interband transitions near the surface plasmon resonance, whereas that of Ag nanoparticles in the glass samples from the interband transitions. These show that the obtained glasses can be used as optoelectronic devices suiting for different demands. (c) 2005 Elsevier B.V. All rights reserved.