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排序方式: 共有78条查询结果,搜索用时 171 毫秒
71.
B.M. Dinelli D. Alpaslan L. Magnani 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(2):141-157
In this paper we describe a retrieval approach for the simultaneous determination of the altitude distributions of p, T and VMR of atmospheric constituents from limb-scanning measurements of the atmosphere. This analysis method, named multi-target retrieval (MTR), has been designed and implemented in a computer code aimed at the analysis of MIPAS-ENVISAT observations; however, the concepts implemented in MTR have a general validity and can be extended to the analysis of all type of limb-scanning observations. In order to assess performance and advantages of the proposed approach, MTR has been compared with the sequential analysis system implemented by ESA as the level-2 processor for MIPAS measurements. The comparison has been performed on a common set of target species and spectral intervals. The performed tests have shown that MTR produces results of better quality than a sequential retrieval. However, the simultaneous retrieval of p, T and water VMR has not lead to satisfactory results below the tropopause, because of the high correlation occurring between p and water VMR in the troposphere. We have shown that this problem can be fixed extending the MTR analysis to at least one further target whose spectral features decouple the retrieval of pressure and water VMR. Ozone was found to be a suitable target for this purpose. The advantages of the MTR analysis system in terms of systematic errors have also been discussed. 相似文献
72.
73.
N Belotto V Reiner F Verga G Canobbio F Lietti P Magnani C Lucarelli 《Journal of chromatography. A》1991,572(1-2):327-332
A new assay is described for 2'-deoxy-5-iodouridine, a drug employed as an antiviral agent by topical application. The parent drug, its systemic metabolite 5-iodouracil and an internal standard (5-iodouridine) were extracted from salted serum by an ethyl acetate partition at pH 6.7, back-extracted in alkalinized water and injected into a reversed-phase column. Potassium phosphate buffer-acetonitrile (95:5, v/v) eluted the analytes at a flow-rate of 1.5 ml/min. Detection was at 290 nm. The method proved to be linear in the 100-2000 ng/ml range. 相似文献
74.
K. Popa R.J.M. Konings F. Wastin E. Colineau N. Magnani P.E. Raison 《Journal of Physics and Chemistry of Solids》2008,69(1):70-75
The heat capacity of cerium zirconate pyrochlore, Ce2Zr2O7, was measured from 0.4 to 305 K by hybrid adiabatic relaxation method for various magnetic field strengths. Magnetisation measurements were performed on the sample also. The results revealed a low-temperature anomaly that showed Schottky-type characteristics with increasing magnetic field strength. The estimated entropy due to the magnetic ordering of the two Ce3+ moments is 1.37R, close to the theoretical value for a doublet ground state (1.39R). The enthalpy increments relative to 298.15 K were measured by drop calorimetry from 531 to 1556 K. The obtained results significantly differ from those reported in the literature; the origin of the discrepancy is due to the probable oxidation of the pyrochlore structure into fluorite. 相似文献
75.
C.D. Pinheiro E. Longo E.R. Leite F.M. Pontes R. Magnani J.A. Varela P.S. Pizanni T.M. Boschi F. Lanciotti 《Applied Physics A: Materials Science & Processing》2003,77(1):81-85
We discuss the nature of visible photoluminescence at room temperature in amorphous strontium titanate in the light of the
results of a recent experimental and quantum mechanical theoretical study. Our calculation of the electronic structure involves
the use of first-principles molecular calculations to simulate the variation of the electronic structure in the strontium
titanate crystalline phase, which is known to have a direct band gap, and we also make an in-depth examination of amorphous
strontium titanate. The results of our simulations of amorphous strontium titanate indicate that the formation of five-fold
coordination in the amorphous system may introduce delocalized electronic levels in the highest occupied molecular orbital
and the lowest unoccupied molecular orbital. These delocalized electronic levels are ascribed to the formation of a tail in
the absorbance-spectrum curve. Optical absorption measurements experimentally showed the presence of a tail. The results are
interpreted by the nature of these exponential optical edges and tails associated with defects promoted by the disordered
structure of the amorphous material. We associate them with localized states in the band gap.
Received: 15 January 2002 / Accepted: 7 August 2002 / Published online: 4 December 2002
RID="*"
ID="*"Corresponding author. Fax: +55-16/2615-215, E-mail: derl@power.ufscar.br 相似文献
76.
77.
N. Magnani S. Carretta R. Caciuffo 《Journal of Physics and Chemistry of Solids》2007,68(11):2020-2023
We present a perturbative model for crystal-field calculations in f-electron compounds, which keeps into account the mixing between states labelled by different total angular momentum J. We use this model to analyze the results of inelastic neutron scattering experiments on actinide dioxides accumulated over a number of years. By comparing our calculations with the published results of other experiments, we point out that a unified crystal-field picture for this series of compounds clearly emerges. 相似文献
78.
Tintori C Corradi V Magnani M Manetti F Botta M 《Journal of chemical information and modeling》2008,48(11):2166-2179
Pharmacophoresthree-dimensional (3D) arrangements of essential features enabling a molecule to exert a particular biological effectconstitute a very useful tool in drug design both in hit discovery and hit-to-lead optimization process. Two basic approaches for pharmacophoric model generation can be used by chemists, depending on the availability or not of the target 3D structure. In view of the rapidly growing number of protein structures that are now available, receptor-based pharmacophore generation methods are becoming more and more used. Since most of them require the knowledge of the 3D structure of the ligand-target complex, they cannot be applied when no compounds targeting the binding site of interest are known. Here, a GRID-based procedure for the generation of receptor-based pharmacophores starting from the knowledge of the sole protein structure is described and successfully applied to address three different tasks in the field of medicinal chemistry. 相似文献