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151.
F. López Arbeloa T. López Arbeloa I. López Arbeloa A. Costela I. García-Moreno J.M. Figuera F. Amat-Guerri R. Sastre 《Applied physics. B, Lasers and optics》1997,64(6):651-657
2 laser) pulses. In these solid media the rhodamine chromophore shows a photophysical behaviour similar to that in a liquid
solution, and its photostability clearly increases when the chromophore is bound to the polymeric chain. These new solid materials
show laser efficiencies that depend on the HEMA/MMA ratio, in some cases with values close to 20%.
Received: 15 May 1996/Revised version: 26 November 1996 相似文献
152.
C. Taboada-Pan I. Brandariz J. L. Barriada T. Vilario M. E. Sastre de Vicente 《Fluid Phase Equilibria》2001,180(1-2):313-325
The renewed theoretical interest in the proton transfer associated to the amino group together with the scarcity of acid-base studies of amines in moderate to concentrated saline media focussed our attention on the study of the basicities of some alkylamines, namely monomethyl, dimethyl and trimethylamine, in aqueous saline solutions of KCl at various temperatures.
A non-conventional analysis of stoichiometric equilibrium constants versus ionic strength data is carried out. On one hand, Pitzer’s model is easily applied to calculate the salting coefficient and the thermodynamic equilibrium constant of the alkylamines. On the other hand, the mean spherical approximation has the advantage over the Debye–Hückel based theories that it can account for effects produced by species of different sizes. Here, it is applied to predict the dependence of the salting behavior on the size of the alkylamines. 相似文献
153.
Costela A. García-Moreno I. Gómez C. Amat-Guerri F. Liras M. Sastre R. 《Applied physics. B, Lasers and optics》2003,76(4):365-369
We report on the laser action of modified dipyrromethene.BF2 complexes both dissolved in poly(methyl methacrylate) and copolymerized with methyl methacrylate. All recently synthesized
dyes have the chromophore core of laser dye pyrromethene 567, differing in the substituent in position 8. The new dyes showed
important and most significant increases in both lasing efficiency and photostability. When the laser samples were pumped
transversely at 534 nm, laser emission was obtained with efficiencies of over 30% in most cases, to be compared with a lasing
efficiency of 12% exhibited by reference dye pyrromethene 567 under the same experimental conditions. Some of the materials
exhibited highly photostable laser action, with no sign of degradation in the laser output after 60000 pump pulses at the
same position of the sample at a repetition rate of 10 Hz, whereas the laser emission of reference dye pyrromethene 567 dropped
to zero after less than 40000 pump pulses.
Received: 19 November 2002 /
Revised version: 20 February 2003 / Published online: 9 April 2003
RID="*"
ID="*"Corresponding author. Fax: +34-91/564-2431, E-mail: acostela@iqfr.csic.es 相似文献
154.
G. Berger M. Maziere C. Prenant J. Sastre A. Syrota D. Comar 《Journal of Radioanalytical and Nuclear Chemistry》1982,74(1-2):301-306
A method is described by which 60 mCi11C propranolol may be obtained from about 1 Ci11CO2 in 30 min without irradiation risk for personnel. The product is chromatographically pure, sterile and apyrogenic with a
specific activity between 500 mCi and 2 Ci/μmole at the time of use. The synthesis involves the preparation of11C acetone followed by fixation of the isopropyl group on the precursor [1-amino-3-(1-naphtyloxy)-2-propanol] by formation
of an imine, then reduction of the latter by sodium cyanoboro hydride. The influence of certain parameters (reagents, precursor,
impurities) on the final product is discussed. 相似文献
155.
Gouloumis A Liu SG Sastre A Vazquez P Echegoyen L Torres T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(19):3600-3607
Phthalocyanines linked to C60 have been synthesized by two general strategies. One of them involves the addition of an azomethine ylide prepared in situ from a formyl phthalocyanine to C60, and the other one involves a statistical condensation of two substituted phthalonitriles, one of them bearing the C60 moiety covalently attached. These new phthalocyanine-fullerene dyads have been studied by cyclic voltammetry and Osteryoung square wave voltammetry, and inter- and intramolecular electronic interactions between the two electroactive subunits have been demonstrated. 相似文献
156.
157.
We introduce in this paper a method to calculate the Hessenberg matrix of a sum of measures from the Hessenberg matrices of the component measures. Our method extends the spectral techniques used by G. Mantica to calculate the Jacobi matrix associated with a sum of measures from the Jacobi matrices of each of the measures.We apply this method to approximate the Hessenberg matrix associated with a self-similar measure and compare it with the result obtained by a former method for self-similar measures which uses a fixed point theorem for moment matrices. Results are given for a series of classical examples of self-similar measures.Finally, we also apply the method introduced in this paper to some examples of sums of (not self-similar) measures obtaining the exact value of the sections of the Hessenberg matrix. 相似文献
158.
M. Pons S. Nonell I. García-Moreno Á. Costela R. Sastre 《Applied physics. B, Lasers and optics》2002,75(6-7):687-694
A dual-beam pulsed-laser time-resolved thermal lens (TRTL) has been used to study the heat dissipation effects in solid polymers
employed as laser dyes. The laser-dye samples studied are polymer solutions of rhodamine 6G (Rh6G), namely homopolymers of
methyl methacrylate (MMA) and copolymers of methyl methacrylate and 2-hydroxyethyl methacrylate (HEMA) with MMA:HEMA compositions
1:1 and 7:3 vol./vol., where the dye is either dissolved or modified and copolymerized with methacrylate monomers. The long-term
stability of the laser material is independent of the thermal diffusivity of the samples, as determined by the TRTL technique.
This suggests that the rate of heat dissipation does not play a major role in the photostability of the samples. In contrast,
the TRTL experiments have revealed permanent changes in the optical properties of the polymers when subjected to a large number
of laser pulses. This is explained in terms of permanent plastic deformation of the matrices.
Received: 19 June 2002 / Revised version: 1 August 2002 / Published online: 15 November 2002
RID="*"
ID="*"Dedicated to Prof. S.E. Braslavsky on the occasion of her 60th birthday. This work was presented at the V Congreso de
Fotoquímica, Torremolinos, Spain, 2001
RID="**"
ID="**"Corresponding author. Fax: +34-93/205-6266, E-mail: s.nonell@iqs.es 相似文献
159.
van Kan HJ Spieksma M Groeneveld GJ Toraño JS van den Berg LH Guchelaar HJ 《Biomedical chromatography : BMC》2004,18(9):723-726
A specific, accurate and precise high-performance liquid chromatographic assay was developed for the determination of riluzole, a drug used to treat patients with amyotrophic lateral sclerosis. Samples were treated by extraction with dichloromethane followed by reversed-phase chromatography with ultraviolet detection at 260 nm. Preset validation criteria were met from 20 to 2000 ng/mL with a linear response curve. Extraction recovery of riluzole was 65-76%. The accuracy of the method was 102-103%. Intra- and inter-day coefficients of variation were in the ranges 2.8-4.9% and 1.8-9.7%. A detection limit of 5 ng/mL was found. Determination of concentrations in serum and plasma resulted in similar results below 500 ng/mL. At higher values a matrix effect cannot be excluded. This presented method can be used to monitor plasma or serum levels in ALS patients treated with riluzole. 相似文献
160.
The potential of capillaries noncovalently coated with a bilayer of oppositely charged polymers for the analysis of peptides by CE-MS was investigated. Bilayer coatings were produced by subsequently rinsing fused-silica capillaries with a solution of Polybrene (PB) and poly(vinyl sulfonate) (PVS). The PB-PVS coating showed to be fully compatible with MS detection causing no ionization suppression or background signals. The bilayer coating provided a considerable EOF at low pH, thereby facilitating the fast separation of peptides using a BGE of formic acid (pH 2.5). Under optimized CE-MS conditions, for enkephalin peptides high separation efficiencies were obtained with plate numbers in the range of 300,000-500,000. It is demonstrated that both the cancellation of the hydrodynamic capillary flow induced by the nebulizer gas and a sufficiently high-data acquisition rate are crucial for achieving these efficiencies. The overall performance of the CE-MS system using PB-PVS-coated capillaries was evaluated by the analysis of a tryptic digest of cytochrome c. The system provided an efficient separation of the peptide mixture, which could be effectively monitored by MS/MS detection allowing identification of at least 13 peptides within a time interval of 1.5 min. In addition, the PB-PVS coating proved to be very consistent yielding stable CE-MS patterns with highly favorable migration time reproducibilities (RSDs < 1% over a 3-day period). 相似文献