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排序方式: 共有151条查询结果,搜索用时 15 毫秒
51.
Salvatore Sortino Giancarlo Marconi Salvatore Giuffrida Guido De Guidi Sandra Monti 《Photochemistry and photobiology》1999,70(5):731-736
The photophysical properties of rufloxacin, 9-fluoro-2r3-dihydro-10-(4-methyl-l-pyrazinyl)-7-oxo-7-H-pyri-do[l,2,3-de]-l,4-benzothiazin-6-carboxylic acid, a fluoroquinolone antibacterial drug exhibiting photosensitizing action toward biological substrates, were studied in aqueous solutions at neutral pH. The lowest excited electronic states of the zwitterion were characterized by both experimental techniques and theoretical methods. Steady-state and time-resolved emission, triplet-state absorption and singlet oxygen production were investigated. The results indicate that the lowest excited singlet is a fluorescent, relatively long-lived state (φr= 0.075, Tr? 4.5 ns) with an efficient intersystem crossing to the triplet manifold (φisc? 0-7)- The lowest triplet is a long-lived state (TT? 10 μs at 295 K in 0.01 M phosphate buffer), with properties that make it a good candidate for being the precursor of the photodecarboxylation of the drug. It is quenched by oxygen at a rate of 1.7 times 109M-1 s-1 and singlet oxygen is formed with a quantum yield of 0.32 in air-saturated solutions. 相似文献
52.
P. W. Wachulak M. G. Capeluto C. S. Menoni J. J. Rocca M. C. Marconi 《Opto-Electronics Review》2008,16(4):444-450
The recent development of table top extreme ultraviolet (EUV) lasers have enabled new applications that so far were restricted
to the use of large facilities. These compact sources bring now to the laboratory environment the capabilities that will allow
a broader application of techniques related to nanotechnology and nanofabrication. In this paper we review the advances in
the utilization of EUV lasers in nanopatterning. In particular we show results of the nanopatterning using a table-top capillary
discharge laser producing 0.12-mJ laser pulses with 1.2-ns time duration at a wavelength λ = 46.9 nm. The nanopatterning was
realized by interferometric lithography using a Lloyd’s mirror interferometer. Two standard photoresists were used in this
work, polymethyl methacrylate (PMMA) and hydrogen silsesquioxane (HSQ). Pillars with a full width half maximum (FWHM) diameter
of 60 nm and holes with FWHM diameter of 130 nm were obtained over areas in excess of 500×500 μm2. 相似文献
53.
Luther BM Wang Y Marconi MC Chilla JL Larotonda MA Rocca JJ 《Physical review letters》2004,92(23):235002
We have demonstrated the guiding of laser pulses with peak intensities up to 2.2 x 10(17) W/cm(2) in a 5.5 cm long plasma column containing highly charged Ar ions generated by a fast capillary discharge. A rapid discharge-driven hydrodynamic compression guides progressively lower order modes through a plasma with increasing density and degree of ionization, until the guide collapses on axis. The lowest order mode (FWHM approximately 50 microm) is guided with 75% transmission efficiency shortly before the plasma reaches the conditions for lasing in Ne-like Ar. The subsequent rapid plasma expansion forms a significantly leakier and more absorbent guide. 相似文献
54.
Fernández M Padrón C Marconi L Ghini S Colombo R Sabatini AG Girotti S 《Journal of chromatography. A》2001,907(1-2):257-265
The solvation parameter model has been applied to the characterization of micellar electrokinetic chromatographic (MEKC) systems with mixtures of lithium dodecyl sulfate and lithium perfluorooctanesulfonate as surfactant. The variation in MEKC surfactant composition results in changes in the coefficients of the correlation equation, which in turns leads to information on solute-solvent and solute-micelle interactions. Lithium perfluorooctanesulfonate is more dipolar and hydrogen bond acidic but less polarizable and hydrogen bond basic than lithium dodecyl sulfate. Therefore mixtures of lithium dodecyl sulfate and lithium perfluorooctanesulfonate cover a very wide range of polarity and hydrogen bond properties, which in turn results in important selectivity changes for analytes with different solute properties. 相似文献
55.
56.
Susanna Insogna Serena Frison Elisabetta Marconi Alessandro Bacaloni 《International journal of environmental analytical chemistry》2013,93(14-15):1343-1359
In order to understand behaviour and environmental fate of manmade chemicals in remote and cold areas, during the XXVII Italian Expedition carried out in Antarctica throughout the austral summer 2011/2012, superficial snow and lake water were sampled along the Ross Sea's South coast and their content of some low-molecular weight volatile halogenated hydrocarbons was evaluated. In consideration of their important role in stratospheric ozone chemistry, some volatile chlorinated hydrocarbons (VCHCs) and trihalomethanes (THMs) were investigated. The analyses were realised with a dedicated system composed by a purge-and-trap injector coupled to a gas chromatograph with a mass spectrometer (PTI-GC-MS) operating in SIM mode. The investigated VCHCs (chloroform; 1,1,1-trichloroethane; tetrachloromethane; trichloroethylene and tetrachloroethylene) were present in all analysed samples, and concentration levels ranged from units to hundreds of ng L?1 according to considered matrix. For the first time, THMs (bromoform; dibromochloromethane; bromodichloromethane), were measured in Antarctic lake waters and freshly deposited snow; their concentration levels ranged from units to tens of ng L?1. In order to assess eventual temporal variations, VCHC content in aqueous Antarctic matrices was compared with levels occurring in the past Italian Antarctic expeditions: for some banned substances, a decrease in concentration was observed, probably due to worldwide use restrictions. Finally, current Antarctic and Italian VCHC and THM levels in snow and lake water samples were compared and were found to be quite similar, differing at most by one order of magnitude, corroborating the hypothesis of an accumulation of halogenated compounds in Antarctic aqueous matrices. 相似文献
57.
Giancarlo Marconi 《Chemical physics》1981,57(3):311-318
The relative enhancement of the Raman intensities in the pre-resonance region has been computed for naphthalene, using the vibronic coupling expansion proposed by Albrecht. The relevant vibronic and transition moments have been computed in the CNDO/S approximation, while the normal coordinates of naphthalene have been evaluated using a MINDO/3 program. The experimental pattern of intensities is reproduced in a satisfactory way both for b3g and ag vibrations. The most important states and the main vibronic terms in the expansion are individuated and discussed with respect to the vibronic borrowing present in the Fluorescence spectrum of naphthalene. 相似文献
58.
Circular dichroism (CD) spectra of non-covalent ligand : biomolecule couples contain information on the equilibrium geometries of the associated structures that can be retrieved upon comparison of the sign and intensity of the experimental CD bands with the quantum mechanically calculated rotational strengths of low energy supramolecular complexes, obtained from molecular modelling methods. For both chiral and achiral ligands this approach proved useful to reach a structure based rationale of ground and excited state properties of the non-covalent ligand : protein associates. In this Perspective we illustrate the potential of this method focusing on the main achievements of our recent spectroscopic, conformational and photochemical studies on drug-albumin complexes and collocate it in the frame of current methodologies of molecular modelling and spectroscopic investigation of ligand : biomolecule binding. 相似文献
59.
P. W. Wachulak M. C. Marconi A. Isoyan L. Urbanski A. Bartnik H. Fiedorowicz R. A. Bartels 《Opto-Electronics Review》2012,20(1):1-14
Imaging systems with nanometer resolution are instrumental to the development of the fast evolving field of nanoscience and
nanotechnology. Decreasing the wavelength of illumination is a direct way to improve the spatial resolution in photon-based
imaging systems and motivated a strong interest in short wavelength imaging techniques in the extreme ultraviolet (EUV) region.
In this review paper, various EUV imaging techniques, such as 2D and 3D holography, EUV microscopy using Fresnel zone plates,
EUV reconstruction of computer generated hologram (CGH) and generalized Talbot self-imaging will be presented utilizing both
coherent and incoherent compact laboratory EUV sources. Some of the results lead to the imaging with spatial resolution reaching
50 nm in a very short exposure time. These techniques can be used in a variety of applications from actinic mask inspection
in the EUV lithography, biological imaging to mask-less lithographic processes in nanofabrication. 相似文献
60.