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排序方式: 共有141条查询结果,搜索用时 546 毫秒
1.
Annalisa Baldi Bruno Franchi 《Calculus of Variations and Partial Differential Equations》2003,16(3):283-298
Abstract. In this paper we study the notion of perimeter associated with doubling metric measures or strongly weights. We prove that the metric perimeter in the sense of L. Ambrosio and M. Miranda jr. coincides with the metric Minkowski
content and can be obtained also as a -limit of Modica-Mortola type degenerate integral functionals.
Received: 27 August 2001 / Accepted: 29 November 2001 / Published online: 10 June 2002
Investigation supported by University of Bologna, funds for selected research topics and by GNAMPA of INdAM, Italy. The authors
are very grateful to Luigi Ambrosio and Francesco Serra Cassano for making their preprints available to them, for listening
with patience and for many unvaluable suggestions. 相似文献
2.
Lucarini M Franchi P Pedulli GF Gentilini C Polizzi S Pengo P Scrimin P Pasquato L 《Journal of the American Chemical Society》2005,127(47):16384-16385
ESR spectroscopy has been used to study the interaction of para-pentylbenzyl hydroxyalkyl nitroxide with the monolayer of water-soluble protected gold clusters having a core diameter ranging from 1.6 to 5.3 nm. The solubilization of the nitroxide probe in the more hydrophobic environment of the monolayer strongly depends on the size of the gold core. In particular, the partition equilibrium constant increases as the nanoparticle diameter decreases. These results have been attributed to the different packing of the chains in the monolayer resulting from the different radius of curvature of the investigated nanoparticles. This represents, to the best of our knowledge, the first report demonstrating that the core size of metallic nanoparticles affects the solvating properties of the protective organic monolayer. 相似文献
3.
This review is focused on the different chromatographic strategies for blood alcohol determination which can be adopted for clinical and/or forensic purposes. Particular attention is paid to gas chromatography and to high-performance liquid chromatography. However, other analytical techniques in common use, such as chemical and enzymic methods, are also briefly presented, together with some, at present unusual or experimental, approaches, such as enzymic reactors and catalytic electrodes, which are suitable for application in column liquid chromatography. Finally, mention is made of the methods for the determination of acetaldehyde, the major ethanol metabolite, and of some proposed markers of chronic alcohol abuse, such as acetaldehyde-protein adducts and carbohydrate-deficient transferrin. In order to give the background of knowledge for the rational choice of an analytical strategy, an updated outline of ethanol metabolism and toxicology is presented, together with basic information for the interpretation of the results. Problems concerning blood sampling and storage are also discussed. 相似文献
4.
Giovanni Brigati Paola Franchi Marco Lucarini Gian Franco Pedulli Luca Valgimigli 《Research on Chemical Intermediates》2002,28(2-3):131-141
An EPR investigation of the kinetics of the exit, k -, and entrance, k +, processes in micelles of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide and polyoxyethylene(6)decanol of a family of para-substituted benzyl tert -butyl nitroxides and para-substituted benzyl hydroxyalkyl nitroxides is reported. The inclusion of nitroxide probes in the hydrophobic environment of the micelle gives rise to a reduction of the value of both nitrogen and β-proton splittings, with the result that the resonance fields for the MI(2H β ) = ±1lines of the free and included species are significantly different. The rate constants were obtained by analyzing the EPR line shape variations as function of surfactant concentration and temperature. The experimental value of k + obtained from the study of benzyl tert-butyl nitroxide indicates that the association reaction is very close to being controlled by diffusion. The value of the exit rate, k -, instead, depends on the probe hydrocarbon chain length. A comparison of our results with those obtained by luminescence quenching techniques is also reported. 相似文献
5.
6.
Pinheiro PF Segatelli TM Francia CC Martinez M Padovani CR Franchi MR Martinez FE 《Micron (Oxford, England : 1993)》2007,38(7):734-746
The extreme use of ethanol causes metabolic and pathologic changes in testes and urogenital system in different animal species. The enzyme alcohol dehydrogenase (ADH) catalyses the conversion of ethanol into carcinogenic metabolite acetaldehyde which is partly excreted into the urine. However, papers relating the chronic ethanol consumption to the urethral morphology are unknown. This work evaluates the toxic effect of the chronic ethanol ingestion on the urethral epithelium of UChA and UChB rats. Conventional techniques of histology, histochemistry, immunohistochemistry and ultrastructural analysis were used. The analysis showed the presence of lipid drops and intercellular spaces in the epithelial cells in the urethra of UChA and UChB rats compared to control rats. Urethral neuroendocrine cell were observed and characterized for presenting vesicles containing electron-dense granules associated with nervous fibers. We conclude that the chronic consumption of ethanol induces the presence lipid drops in the epithelial cells of the urethra of UChA and UChB rats. The NE cells of the urethra of UChA and UChB rats did not show alterations under chronic effect of the ethanol. 相似文献
7.
Dr. Elmar Kataev Daniel Wechsler Prof. Federico J. Williams Julia Köbl Dr. Natalia Tsud Dr. Stefano Franchi Prof. Hans-Peter Steinrück Dr. Ole Lytken 《Chemphyschem》2020,21(20):2293-2300
Thin-film growth of molecular systems is of interest for many applications, such as for instance organic electronics. In this study, we demonstrate how X-ray photoelectron spectroscopy (XPS) can be used to study the growth behavior of such molecular systems. In XPS, coverages are often calculated assuming a uniform thickness across a surface. This results in an error for rough films, and the magnitude of this error depends on the kinetic energy of the photoelectrons analyzed. We have used this kinetic-energy dependency to estimate the roughnesses of thin porphyrin films grown on rutile TiO2(110). We used two different molecules: cobalt (II) monocarboxyphenyl-10,15,20-triphenylporphyrin (CoMCTPP), with carboxylic-acid anchor groups, and cobalt (II) tetraphenylporphyrin (CoTPP), without anchor groups. We find CoMCTPP to grow as rough films at room temperature across the studied coverage range, whereas for CoTPP the first two layers remain smooth and even; depositing additional CoTPP results in rough films. Although, XPS is not a common technique for measuring roughness, it is fast and provides information of both roughness and thickness in one measurement. 相似文献
8.
Franchi P Lucarini M Pedulli GF Sciotto D 《Angewandte Chemie (International ed. in English)》2000,39(1):263-265
Distinct EPR signals are observed for the free and included species for the inclusion of the neutral benzyl tert-butyl nitroxide probe into a calix[4]arene host in water (shown schematically). Computer simulation of the EPR spectra recorded at various temperature enabled direct determination of the activation and kinetic parameters for this inclusion process. 相似文献
9.
10.
Giovanna Bruni Vittorio Berbenni Franco Sartor Chiara Milanese Alessandro Girella Dionigio Franchi Amedeo Marini 《Journal of Thermal Analysis and Calorimetry》2012,108(1):235-241
In this work, thermoanalytical, diffractometry, and microscopy measurements have been performed in order to characterize the
effect of high energy milling on a drug active in the migraine prophylaxis and smoke cessation. We can assert that the mechanical
treatment induces only a partial amorphisation of the solid phase, in particular it reduces the crystal order by producing
lattice defects which propagate from the surface to the bulk crystal. For this reason, the DSC is able to detect the presence
of ordered solid, while the powder X-ray diffractometry, because of its low penetration depth, does not reach the crystalline
core of the particles. 相似文献