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91.
M. Fátima Barroso M. João Ramalhosa Cristina Delerue-Matos M. Carmo V.F. Vaz 《International journal of environmental analytical chemistry》2013,93(14):1049-1062
A biochemical gas-sensor (bio-sniffer) was constructed for convenient measurement of odourless hydrogen peroxide (H2O2) vapour, which is harmful to skin and mucous membranes. An enzyme-immobilized membrane was fabricated by spreading the mixture of catalase and photo-crosslinkable polymer on a dialysis membrane. An H2O2 biosensor was constructed by attaching this catalase-immobilized membrane to the sensitive top of a Clark-type oxygen electrode, and the oxygen generation from the decomposition of H2O2 catalysed by catalase was measured amperometrically. This biosensor was first applied to the measurement of H2O2 solution and was able to quantify the concentrations of H2O2 solution from 0.02 to 10.0?mmol?L?1. Then, this biosensor was applied to gaseous phase as a bio-sniffer and was able to detect the odourless H2O2 vapour with the calibration range from 0.5 to 30?ppm, where the threshold limit value assigned by the American Conference of Governmental Industrial Hygienists (1?ppm) is covered. 相似文献
92.
R. Arvinte J. BorgesR.E. Sousa D. MunteanuN.P. Barradas E. AlvesF. Vaz L. Marques 《Applied Surface Science》2011,257(21):9120-9124
Metallic oxynitrides have attracted the attention of several researchers in the last decade due to their versatile properties. Through the addition of a small amount of oxygen into a transition metal nitride film, the material's bonding states between ionic and covalent types can be tailored, thus opening a wide range of electrical, optical, mechanical and tribological responses. Among the oxynitrides, chromium oxynitride (CrNxOy) has many interesting applications in different technological fields. In the present work the electrical behavior of CrNxOy thin films, deposited by DC reactive magnetron sputtering, were investigated and correlated with their compositional and structural properties. The reactive gas flow, gas pressure, and target potential were monitored during the deposition in order to control the chemical composition, which depend strongly on reactive sputtering process. Depending on the particular deposition parameters that were selected, it was possible to identify three types of films with different growth conditions and physical properties. The electrical resistivity of the films, measured at room temperature, was found to depend strongly on the chemical composition of the samples. 相似文献
93.
A Cobalt Pyrenylnitronylnitroxide Single‐Chain Magnet with High Coercivity and Record Blocking Temperature 下载免费PDF全文
Dr. Maria G. F. Vaz Dr. Rafael A. Allão Cassaro Dr. Handan Akpinar Dr. John A. Schlueter Prof. Paul M. Lahti Prof. Miguel A. Novak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(18):5460-5467
Coordination of a [Co(hfac)2] moiety (hfac=hexafluoroacetylacetonate) with a nitronylnitroxide radical linked to bulky, rigid pyrene (PyrNN) gives a helical 1:1 chain complex, in which both oxygen atoms of the radical NO. groups are bonded to CoII ions with strong antiferromagnetic exchange. The complex shows single‐chain magnet (SCM) behavior with frequency‐dependent magnetic susceptibility, field‐cooled and zero‐field‐cooled susceptibility divergence with a high blocking temperature of around 14 K (a record among SCMs), and hysteresis with a very large coercivity of 32 kOe at 8 K. The magnetic behavior is partly related to good chain isolation induced by the large pyrene units. Two magnetic relaxation processes have been observed, a slower one attributable to longer, and a faster one attributable to short chains. No evidence of magnetic ordering has been found. 相似文献
94.
L. C. Vaz J. M. Alexander N. Carjan 《Zeitschrift für Physik A Hadrons and Nuclei》1986,324(3):331-345
There is quite a variety of statistical-model equations in the literature that have been derived with different assumptions and for various classes of nuclear reactions. Some have been obtained by consideration of the quantum mechanics and some by semiclassical approximations thereto. Often it is not clear whether or not the results of certain analyses are clouded by these semiclassical approximations. We consider three statistical models that have been heavily employed in recent years: (1) fission decay from a rigid rotor (2) particle evaporation from a spherical system and (3) fission decay from two uncoupled spheres. Comparisons are made of numerical results from semiclassical and from quantum mechanical equations for certain specific reactions. In addition, some general features are displayed and discussed for the differences between these formalisms. For average spins that are often encountered in heavy ion reactions, the results are very similar. We conclude that major differences in current analyses are not due to the methodology; instead they must center on assumptions concerning the physical nature of the transition-state (or decision-point) configurations and their associated level densities. 相似文献
95.
Canonical forms are obtained for the metrics of space-times admitting a surface generating Killing pair, one member of which is hypersurface orthogonal. 相似文献
96.
N. N. Ajitanand John M. Alexander H. Delagrange E. Duek D. Ø. Eriksen D. Guerreau Morton Kaplan M. Kildir L. Kowalski R. Lacey D. Logan D. J. Moses G. F. Peaslee Louis C. Vaz M. S. Zisman 《Zeitschrift für Physik A Hadrons and Nuclei》1984,316(2):169-176
Multiplicities are compared for4He evaporation in reactions of40Ar and56Fe projectiles (8.5 MeV/u) with withnatAg and238U targets. Coincidence requirements involving fusion-fission and projectile-like fragments have been used to select separate entrance-channel spin zones. Evaporation-like4He emission from the composite nuclei is shown to be large for mean spins ≦100?, and to decrease dramatically with increasing spin. Coincidence measurements between two4He particles have also been studied for40Ar+natAg. This requirement is shown to select reactions that lead to evaporation residues and therefore to a zone of relatively low spin. The shapes of the4He spectra provide an interesting probe of the mechanism and also of the thermodynamic properties of hot nuclei. 相似文献
97.
C. D. Collinson Estelita da Graça Lopes Rodrigues Vaz 《General Relativity and Gravitation》1982,14(1):5-15
It is shown that if in some local coordinate system the componentsR
i
jkl of the curvature tensor of an empty space-time are known, then, provided the space-time is not of Petrov typeN with hypersurface orthogonal geodesic rays, the components of the metric tensor are uniquely determined up to a trivial constant scaling factor. The Petrov type-N empty space-times with hypersurface orthogonal geodesic rays are investigated. The most general mappings leaving the curvature tensorR
i
jkl invariant are found for each class of these space-times. 相似文献
98.
Starting from the electron Lagrangian density and expanding it with a more general idempotent than the one used by Hestenes, we achieve to show how the algebraic structure of the ideals draws a distinction between electrons and positrons without any need of the charge conjugation. A remarkable fact, consequence of the formalism used, is evidenced by the magnetization density discriminating the sign of the charge of the particles involved. 相似文献
99.
M. Klui L. Lopez-Diaz J. Rothman C. A. F. Vaz J. A. C. Bland Z. Cui 《Journal of magnetism and magnetic materials》2002,240(1-3):7-10
We present the results of a study of the magnetic switching properties of arrays of narrow Co(1 0 0) epitaxial ring magnets, with outer diameters between 1 and 2 μm, varying inner diameters and varying film thickness. We discuss measurements and the results of numerical computations of the switching fields for the transition from the vortex state to the ‘onion’ state. A large dependence on the ring width and the film thickness is found. 相似文献
100.
The metric of type-N Robinson-Trautman space-times is generated by a real functionP satisfying certain field equations. Canonical forms forP are obtained under the assumption that at least one curvature collineation exists. In order to give an example of the improper subgroup structure of a group of curvature collineations all the curvature collineations are determined for the space-times corresponding to one of the two canonical forms. 相似文献