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101.
Silvestro L Gheorghe M Iordachescu A Ciuca V Tudoroniu A Rizea Savu S Tarcomnicu I 《Analytical and bioanalytical chemistry》2011,401(3):1023-1034
A new sensitive and fast quantitative analytical method for the simultaneous determination of clopidogrel, its main metabolite
clopidogrel carboxylic acid, and the newly described acyl glucuronide metabolite, in human plasma samples, is presented. The
analytical procedures (plasma storage, handling, and extract storage in the autosampler) were optimized in order to avoid
back-conversion; a known drawback in measurements of clopidogrel. Clopidogrel acyl glucuronide was confirmed as a major source
of back-conversion to the parent drug in the presence of methanol, and thorough stability experiments were carried out to
find the most appropriate conditions for an accurate analysis of clopidogrel and the two metabolites. The method was validated
by assessing selectivity, sensitivity, linearity, accuracy, and precision for all three analytes, in accordance to Food and
Drug Administration guidelines. Spiked quality controls in plasma as well as incurred samples were used to verify back-conversion
in the selected conditions, with results meeting European Medicines Agency acceptance criteria (concentrations within 80–120%
of the first reading). The method was then applied to a pharmacokinetic study, and for the first time, a pharmacokinetic curve
of clopidogrel acyl glucuronide in human plasma is presented. The concentrations ranged up to 1,048.684 ng/mL, with a mean
of 470.268 ng/mL, while clopidogrel had a mean C
max of 1.348 ng/mL; these orders of magnitude show how much the back-conversion of this metabolite may influence clopidogrel
quantification if it is not properly controlled. 相似文献
102.
Let Xn denote the state of a device after n repairs. We assume that the time between two repairs is the time τ taken by a Wiener process {W(t), t ? 0}, starting from w0 and with drift μ < 0, to reach c ∈ [0, w0). After the nth repair, the process takes on either the value Xn?1 + 1 or Xn?1 + 2. The probability that Xn = Xn?1 + j, for j = 1, 2, depends on whether τ ? t0 (a fixed constant) or τ > t0. The device is considered to be worn out when Xn ? k, where k ∈ {1, 2, …}. This model is based on the ones proposed by Rishel (1991) [1] and Tseng and Peng (2007) [2]. We obtain an explicit expression for the mean lifetime of the device. Numerical methods are used to illustrate the analytical findings. 相似文献
103.
Nonlinear Dynamics - The aeroelastic behavior of a planar prismatic visco-elastic structure, subject to a turbulent wind, flowing orthogonally to its plane, is studied in the nonlinear field. The... 相似文献
104.
In this first part a straight general wave-guide with a perfectly conducting outer wall and several dielectrics, excited by an electrically generally polarized matter is considered and the electromagnetic field is determined. 相似文献
105.
Simona Bronco Giambattista Consiglio Silvia Di Benedetto Matthias Fehr Felix Spindler Antonio Togni 《Helvetica chimica acta》1995,78(4):883-886
Cationic Pd-complexes modified by dicyclohexyl{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}phosphine ( 1a ) give very active catalytic systems for the regioregular isotactic specific copolymerization of propene with CO. Other alk-1-enes also give stereoregular and regioregular copolymers, even if with lower productivity. The copolymers are isolated as poly(4-alkyl-tetrahydrofuran-2,2,5,5-tetrayl-2-oxy-2-methylenes) B in the solid state and give the isomeric poly(2-alkyl-1-oxopropane-1,3-diyls) A by dissolution in (CF3)2CHOH. Solid polymer A (R = Et) is formed back at least partially when the dissolved material is reprecipitated from MeOH. The use of the related (ferrocenyl)diphosphine ligands 1b ? e and 2 as the catalyst modifier shows that the presence of both elements of chirality and of large substituents on the P-atoms of the ligand is necessary to achieve good stereocontrol, and that the large difference in basicity between the two P-atoms is probably the reason for the good catalytic activity. 相似文献
106.
Simona Percec Ross Getty Will Marshall Gabriel Skidd Roger French 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):541-550
Oligomers consisting of aromatic building blocks separated by alkynyl units were synthesized by Sonogashira cross-coupling of aryl halides with terminal acetylenes. Strong electron acceptors such as F and CF3 and weak electron donors like CH3 were placed as substituents on one of the benzene rings. Acetyl-protected sulfhydryl groups were attached to one end of these molecules to promote their self-organization on gold surfaces. The electron-transport properties of such self-assembled monolayers (SAMs) are highly sensitive to the local order of the molecules in the solid state. Single crystals were analyzed by X-ray diffraction experiments that revealed structural details that could lead to a better understanding of the electron-transport properties. The unsymmetrical substitution of the aromatic rings by electron-active groups in the ortho-, meta-, or para positions resulted in changes of such molecular parameters as bonding and torsion angles and planarity. These parameters, in turn, can affect the angle of the molecular attachment to a gold substrate and the density of the resulting SAMs. Patterned SAMs of some of these molecules and comparison alkane thiols were obtained on gold by microcontact printing or flooding. The SAM thickness was determined by spectroscopic ellipsometry. Surface potential differences between adjacent SAMs or between SAMs and the gold substrate were measured by scanning surface potential microscopy under ambient conditions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 541–550, 2004 相似文献
107.
Simona Lai Emanuela Locci Giuseppe Saba Ivan Husu Giancarlo Masci Vittorio Crescenzi Adolfo Lai 《Journal of polymer science. Part A, Polymer chemistry》2003,41(20):3123-3131
Dry and hydrated poly(vinyl alcohol) (PVA) gels with 55% (a‐PVA) and 61% (s‐PVA) syndiotacticity and related PVA/lactyl chitosan (LC) blends have been investigated with 129Xe and cross‐polarization/magic‐angle‐spinning 13C NMR techniques. Although the dry gels exhibit two broad 129Xe resonances in the slow‐to‐intermediate exchange limit, both hydrated gels show three resonances. The corresponding dry blends exhibit two signals, the chemical shifts and line widths of which change with respect to those of pure PVA, whereas one (a‐PVA/LC) or two (s‐PVA/LC) signals appear in the spectra of the hydrated blends. A comparative analysis of the data demonstrates that LC rearranges the domains of the polymeric matrix in both the dry and hydrated blends according to the syndiotacticity of the PVA chains. Information on the molecular motions of the amorphous and swollen polymeric domains in the kilohertz range has been obtained from an analysis of the spin‐lattice relaxation times. These data indicate that the dynamics and arrangement of the PVA chains in the gels are strongly affected by their tacticity and the addition of the copolymer LC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3123–3131, 2003 相似文献
108.
A procedure is proposed for generating Serber-type spin eigenfunctions withM
s = 0. The procedure uses the time-reversal invariance of these functions to increase the efficiency and to reduce the storage requirements. Simplifications in calculating the matrix elements of an observable operator which follow from the use of the time-reversal symmetry are briefly discussed. 相似文献
109.
The direct and the coincidence spectra of gamma-rays from the131Sb decay have been measured by means of different Ge(Li) detectors. The Sb sources have been prepared from mixture of235U thermal neutron fission products. The proposed level scheme of the131Te nuclei is based on the coincidence measurements, the analysis of the energy sums and the reaction data. The 49 of the total number of 64 gamma-rays observed have been placed in the present decay scheme. Properties of the some levels in131Te are compared with those observed in other oddmass Te isotopes. A probable structure of some of the excited states in131Te is discussed. 相似文献
110.
A high yield 2,4,5,8-tetrahydro-1,3-diox-5-azocine synthesis, which employs a sequence of cycloaddition and photoinduced rearrangement has been developed. 相似文献