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11.
To improve the understanding of the electrochemical effects observed on an original potentiometric gas sensor, interactions of oxygen with the device were investigated. This gas sensor is made of a solid electrolyte (treated Na-β-alumina) associated with two metallic electrodes (gold and platinum) located in the same gas mixture. Adsorption of charged oxygen species, considered responsible for the electrical response developed by the sensor, was investigated by work function measurements. Results showed that charged oxygen species only form on partially gold or platinum covered solid electrolyte. Comparison of these results with those obtained in a previous calorimetric study of interactions between oxygen and the same materials suggests the existence of at least two different oxygen species adsorbed on the surface of the sensitive element. The first one, located on the solid electrolyte surface, is neutral and characterized by an endothermal reaction of formation. The second one is charged and probably produced at the gas/solid electrolyte/metallic electrode interface. A mechanism based on the concept of “three phase boundary” and similar to the “reverse spillover” phenomenon is proposed to account for the adsorption of these oxygen species. 相似文献
12.
Ana M. Piloto 《Tetrahedron》2006,62(39):9258-9267
Four carboxylic fused furans are presented as new fluorescent labels for the amino and hydroxyl functions of organic molecules. Various representative l-amino acids were chosen as models, labelled at their N-terminus and also at their side-chain. Fluorescent derivatives were obtained in high yields, and their absorption and emission properties were studied. 相似文献
13.
M. A. Macrì C. Del Gratta L. Di Donato S. Di Luzio G. L. Romani S. Della Penna A. Pasquarelli 《Il Nuovo Cimento D》1994,16(5):425-432
Summary A preliminary study is here reported on a new potential marker for biomagnetic measurements. The marker consists of superparamagnetic
polymer microspheres which were detected in the presence of external steady magnetic fields by means of an r.f.-SQUID magnetometer.
The particles were prepared in samples differing in the concentration value and immersed in a homogeneous magnetic field of
variable intensity. A simple model was taken into account for the distribution of the microspheres in the samples, so that
the theoretical values were compared to the marker field values measured by the biomagnetic sensor. The overall sensitivity
of the experimental apparatus and the minimum concentration value of the marker were then estimated. 相似文献
14.
Polyphysa peniculus was grown in artificial seawater in the presence of arsenate, arsenite, monomethylarsonate and dimethylarsinic acid. The separation and identification of some of the arsenic species produced in the cells as well as in the growth medium were achieved by using hydride generation–gas chromatography–atomic absorption spectrometry methodology. Arsenite and dimethylarsinate were detected following incubation with arsenate. When the alga was treated with arsenite, dimethylarsinate was the major metabolite in the cells and in the growth medium; trace amounts of monomethylarsonate were also detected in the cells. With monomethylarsonate as a substrate, the metabolite is dimethylarsinate. Polyphysa peniculus did not metabolize dimethylarsinic acid when it was used as a substrate. Significant amounts of more complex arsenic species, such as arsenosungars, were not observed in the cells or medium on the evidence of flow injection–microwave digestion–hydride generation–atomic absorption spectrometry methodology. Transfer of the exposed cells to fresh medium caused release of most cell–associated arsenicals to the surrounding environment. 相似文献
15.
中国西南武陵山区跳蛛新种记述(蜘蛛目:跳蛛科) 总被引:2,自引:0,他引:2
本文记述跳蛛科13个新种,采自西南武陵山地区。暗跳蛛Asemonea、列锡蛛Lycidas和法老蛛Pharacocerus 3属为我国新记录属。 相似文献
16.
The behavior of zirconium atoms at the W(100) surface associated with oxygen adsorption at different sample temperatures has been studied by Auger electron spectroscopy (AES), ion scattering spectroscopy (ISS), and the relative change of the work function (Δф) measured by the onset of the secondary electron energy distribution. The results have revealed: (i) adsorption of zirconium onto the W(100) surface followed by the elevation of the sample temperature up to 1710 K in an oxygen partial pressure of 2.7 × 10−4 induces complete diffusion of zirconium atoms into the W(100) substrate; (ii) further exposure of oxygen induces co-existence of oxygen and tungsten on the surface at 1710 K, resulting in a work function of 4.37 eV; (iii) keeping the sample temperature at 1710 K, simple evacuation of the system has resulted in surface segregation of zirconium atoms to the surface to form a zirconium atomic layer on the top-most surface, reducing the work function to 2.7 eV. The results have revealed that this specific behavior of zirconium atoms at high temperature assures, with very good reproducibility, the highly stable performance and long service life of Zr---O/W(100)-emitters in practical use, even in a low vacuum of 10−6 Pa. 相似文献
17.
In proportion to the environmental pollution problems caused by organotin compounds, the genotoxicities of tin compounds in the environments have become of interest so as to estimate their safety in recent years. In this work, isolated λ-DNA (double-strand DNA) was incubated with inorganic tin(II) and tin(IV) and five organotin compounds [n-butyltin trichloride, di(n-butyltin) dichloride, methyltin trichloride, dimethyltin dichloride and trimethyltin chloride] in reaction systems both with and without hydrogen peroxide (H2O2) content. The tin compounds tested in this study did not induce DNA breakage in the absence of hydrogen peroxide. Divalent inorganic tin (SnCl2) and tetravalent inorganic tin (SnCl4) caused DNA breakage in the presence of hydrogen peroxide (10 mM), and the DNA damage activity of inorganic tin was much more potent in divalent inorganic tin (SnCl2) than in tetravalent inorganic tin (SnCl4). Divalent inorganic tin (SnCl2) induced DNA breakage in a concentration-dependent fashion at concentrations greater than 0.1 mM of SnCl2 in the presence of hydrogen peroxide (10 mM). DNA breakage was not caused by n-butyltin compounds and methyltin compounds either in the presence or in the absence of hydrogen peroxide. 相似文献
18.
中国六种管巢蛛记述(蜘蛛目:管巢蛛科) 总被引:2,自引:0,他引:2
本文记述我国管巢蛛6种,即白马管巢蛛Clubiona baimaensis sp. nov.、朝鲜管巢蛛C. corena Paik 金氏管巢蛛C. kimyongkii Paik、琴形管巢蛛C. lyriformis sp. nov.、臼齿管巢蛛C. moralis sp. nov.和江原管巢蛛C. wolchongsensis Paik。其中3种为新种,3种为我国新纪录。文中并提出,乌苏里管巢蛛C. ussurica Michailov(♀)可能与金氏管巢蛛(♂)为同种,因而乌苏里管巢蛛的拉丁字名应为后一种的同物异名。 相似文献
19.
The effect of gamma irradiation in air is investigated on four thermoplastic polyesters (PET, PBT, PEN, PCT-co-ET) in films containing aromatic rings, in order to evaluate the influence of aromatic density and the role of oxygen on radiation resistance. Physical-chemical-nuclear analyses were used to this purpose. EPR measurements were carried out to detect radical stability against oxygen permeation. Viscometric investigations reported a very similar trend for all the investigated polyesters: a chain break effect that decreases at the highest doses. FT-IR analyses focused on the formation of oxidized species. Positron annihilation spectra pointed out a decrease of the intensity of ortho-positronium formation, while its lifetime remains unchanged with radiation dose. 相似文献
20.
Jing Yang 《Applied Surface Science》2006,253(4):1988-1994
To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Nitrogen and carbon doping TiO2−x−yNxCy films were obtained by heating the TiO2 gel in an ionized N2 gas and then were calcined at 500 °C. The TiO2−x−yNxCy films have revealed an improvement over the TiO2 films under visible light (wavelength, 500 nm) in optical absorption and photocatalytic activity such as photodegradation of methyl orange. X-ray photoemission spectroscopy, infrared spectrum and UV-visible (UV-vis) spectroscopy were used to find the difference of two kinds of films. Nitrogen and carbon doped into substitutional sites of TiO2 has been proven to be indispensable for band-gap narrowing and photocatalytic activity. 相似文献