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101.
102.
José Antonio Murillo Pulgarín Aurelia Alañón Molina Guadalupe Pérez-Olivares Nieto 《Mikrochimica acta》2007,159(3-4):349-356
Hydroflumethiazide was determined from the chemiluminescence produced in its reaction with Ce(IV) in acidic medium containing
rhodamine 6G as a sensitizer using flow injection techniques (stopped flow mode). A straightforward automatic method based
on measuring the peak height and peak area, which are directly proportional to the hydroflumethiazide concentration, was thus
developed. The calibration graphs were linear over the concentration range of 1.0–30 μg mL−1. The limit of detection as determined according to Clayton was 0.97 and 0.91 μg mL−1 for peak height and peak area measurements, respectively. The relative standard deviation for ten samples was less than 3.0%
with both types of measurements. The procedure was applied to the determination of hydroflumethiazide in pharmaceutical formulations,
yielding excellent recoveries, since the determination is free of interference from common excipients and other drugs which
are present in the formulation. 相似文献
103.
Jiuping Xu Zhigao Liao Juan J. Nieto 《Journal of Mathematical Analysis and Applications》2010,368(1):54-68
This paper investigates the first order linear fuzzy differential dynamical systems with fuzzy matrices. We use a complex number representation of the α-level sets of the fuzzy system, and obtain the solution by employing such representation. It is applicable to practical computations and has also some implications for the theory of fuzzy differential equations. We then present some properties of the 2-dimensional dynamical systems and their phase portraits. Some examples are considered to show the richness of the theory and we can clearly see that new behaviors appear. We finally present some conclusions and new directions for further research in the area of fuzzy dynamical systems. 相似文献
104.
Alfonso G. Rubia Mateo M. Salgado Carlos T. Nieto Alejandro Manchado David Díez Francisca Sanz Narciso M. Garrido 《Tetrahedron: Asymmetry》2017,28(10):1394-1400
The asymmetric synthesis of methyl (E)-4-((1R,2S,3R)-3-amino-2-((E)-2-methoxycarbonyl-eten-1-yl)cyclohexyl)but-2-enoate 14 has been achieved from dimethyl (2E,7E)-nona-2,7-dienedioate 2. A key step is the asymmetric synthesis of 1-hydroxyoctahydro-1H-isochromene derivative 5 whose X-ray analysis corroborated the stereochemistry of the new stereocenters. The asymmetric synthesis of the isochromenyl acetate derivative 11 shows the potential of this methodology for fused cyclohexanic system heterocyclic synthesis. 相似文献
105.
Yong-Kui Chang Zhi-Han Zhao Juan J. Nieto 《Numerical Functional Analysis & Optimization》2013,34(12):1219-1238
This article is mainly concerned with the existence and uniqueness of almost periodic and pseudo almost periodic mild solutions to a class of partial differential equations in Banach spaces. Under some reasonable assumptions, the main results are proved in α-norm. Our results cover the cases that the functions F 1; F 2 take values in different spaces such as X, X α, and X ß, where α ≤ β ∈ (0; 1). 相似文献
106.
Two-dimensional (2D) inhomogeneous electron assemblies are becoming increasingly important in Condensed Matter and associated
technologies. Here, therefore, we contribute to the Density Functional Theory of such 2D electronic systems by calculating,
analytically, (i) the idempotent Dirac density matrix γ(r, r′) generated by two closed shells for the bare Coulomb potential −Ze
2/r and (ii) the exchange energy density ex(r){\varepsilon_x({\bf r})} . Some progress is also possible concerning the exchange potential V
x
(r), one non-local approximation being the Slater potential 2ex(r)/n(r){2\varepsilon_x(r)/n(r)} , with n(r) the ground state electron density. However, to complete the theory of V
x
(r), the functional derivative of the single-particle kinetic energy per unit area δt(s)/δn(r) is still required. 相似文献
107.
Jesús Angulo Dr. Pedro M. Enríquez‐Navas Pedro M. Nieto Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(26):7803-7812
The direct evaluation of dissociation constants (KD) from the variation of saturation transfer difference (STD) NMR spectroscopy values with the receptor–ligand ratio is not feasible due to the complex dependence of STD intensities on the spectral properties of the observed signals. Indirect evaluation, by competition experiments, allows the determination of KD, as long as a ligand of known affinity is available for the protein under study. Herein, we present a novel protocol based on STD NMR spectroscopy for the direct measurements of receptor–ligand dissociation constants (KD) from single‐ligand titration experiments. The influence of several experimental factors on STD values has been studied in detail, confirming the marked impact on standard determinations of protein–ligand affinities by STD NMR spectroscopy. These factors, namely, STD saturation time, ligand residence time in the complex, and the intensity of the signal, affect the accumulation of saturation in the free ligand by processes closely related to fast protein–ligand rebinding and longitudinal relaxation of the ligand signals. The proposed method avoids the dependence of the magnitudes of ligand STD signals at a given saturation time on spurious factors by constructing the binding isotherms using the initial growth rates of the STD amplification factors, in a similar way to the use of NOE growing rates to estimate cross relaxation rates for distance evaluations. Herein, it is demonstrated that the effects of these factors are cancelled out by analyzing the protein–ligand association curve using STD values at the limit of zero saturation time, when virtually no ligand rebinding or relaxation takes place. The approach is validated for two well‐studied protein–ligand systems: the binding of the saccharides GlcNAc and GlcNAcβ1,4GlcNAc (chitobiose) to the wheat germ agglutinin (WGA) lectin, and the interaction of the amino acid L ‐tryptophan to bovine serum albumin (BSA). In all cases, the experimental KD measured under different experimental conditions converged to the thermodynamic values. The proposed protocol allows accurate determinations of protein–ligand dissociation constants, extending the applicability of the STD NMR spectroscopy for affinity measurements, which is of particular relevance for those proteins for which a ligand of known affinity is not available. 相似文献
108.
The sterol composition of macromycete fungus Laetiporus sulphureus was analyzed by GC-MS. The fungus contained mainly C16 to C20 fatty acids, C16 to C24 fatty acid ethyl esters, and C28, C29,
and C30, Δ5, Δ7, and Δ5,7 conventional sterols, and in minor amounts Δ0 analogues with saturated and unsaturated side chains. Moreover, ergosterol peroxide and cerevisterol were identified. This
sterol pattern was compared with those of other members of the family Polyporaceae reported in the literature.
Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 170–172, March–April, 2009. 相似文献
109.
This paper discusses the periodic boundary value problem for first-order nonlinear impulsive integro-differential equations. We prove some new comparison principles, and then establish new existence results for extremal solutions by using these principles and the monotone iterative technique. These results improve and extend all known relevant conclusions from the literature. Some examples are also given to illustrate the advantage of our results. 相似文献
110.
C. Betegón Biempica J.J. del Coz Díaz P.J. García Nieto I. Peñuelas Sánchez 《Applied Mathematical Modelling》2009
The aim of this paper is to study the residual stresses in an UIC-60 rail and their reduction by means of roller straightening. Both experimental and numerical investigations have been carried out in the past to reveal the formation of dominant longitudinal residual stresses. However, the agreement between both investigations was not particularly good. The finite element method (FEM) has also been used to simulate one, two and three-dimensional analyses of a rail during roller straightening processes. The present model considers the longitudinal movement of a rail through the straightening machine, contact conditions between rail and rollers and kinematic hardening so as to take into account the plastic behaviour of the rail material (steel). These results were compared with the experimental investigations and good agreement was observed. In this respect, this paper presents a novel, more realistic numerical simulation by FEM for the roller straightening process. Finally, an improvement of the straightening process in order to obtain smaller residual stress in the rail section is proposed. 相似文献