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1.
OA al-Swayeh MS al-Humayyd AA Mustafa AS al-Tuwaijri RS al-Rashed AT Ali 《Canadian Metallurgical Quarterly》1997,12(7):481-489
Recent evidence suggests that oxygen-derived free radicals are involved in mediating gastric microvascular and parenchymal cell injuries induced by ischaemia and reperfusion. Therefore, the effect of the locally acting anti-ulcer drug, sucralfate, was studied on ischaemia and reperfusion (e.g. induced gastric lesions, intraluminal bleeding, changes in vascular permeability and non-protein sulfhydryl levels in the rat stomach). Allopurinol was used as a known standard antioxidant drug. Rats were subjected to 30 min of gastric ischaemia in the presence of 100 mmol/L hydrochloric acid and reperfusion periods of 15, 30 or 60 min duration. The gastric lesions were assessed microscopically under an inverted microscope. The vascular permeability was quantified by measuring the extravasated Evans blue in the stomach. There were significantly greater numbers of gastric lesions, intraluminal bleeding and leakage of Evans blue during all reperfusion periods as compared with those of ischaemia, with maximum effects occurring at 60 min following reperfusion. Pretreatment with sucralfate (31.25-250 mg/kg, p.o.) or allopurinol (12.5-50 mg/kg, i.p.) 30 min before the procedure, dose-dependently reduced the gastric lesions, intraluminal bleeding, and decreased the vascular permeability induced by ischaemia and reperfusion. Furthermore, sucralfate dose-dependently reverses the ischaemia and reperfusion-induced depletion of mucosal non-protein sulfhydryl levels and inhibited the superoxide radical production in both cell-free xanthine-xanthine oxidase and in the stimulated polymorphonuclear cellular systems. These results suggest that the protection produced by sucralfate against gastric injury may be due to its antioxidant effects. 相似文献
2.
The aim of this paper is to give a general quantitative requirement which the loop gain must satisfy in order to stabilize a given unstable (possibly nonlinear and time-varying) plant, namely that the gain must exceed one. 相似文献
3.
A monitoring of tool wear in different cutting operations has been studied for many years. Special techniques have been used to detect a wear status basing upon cutting forces, acoustic emission, temperature, torque and power, vibration, noise and acceleration sensors. The adapting of a proper prediction method allows to solve problems of an automatic supervision in Computer Integrated Manufacturing systems. A task of the abrasive edge wear index prediction can be formulated as follows: disposing by the data collection of the edge wear status in a time period preceding the concerning the wear status in the successive time period embraced by the prediction method. 相似文献
4.
Larissa Canilha Walter Carvalho Marco Giulietti Maria Das Graças Almeida Felipe João Batista Almeida E Silva 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(5):715-721
BACKGROUND: Xylitol bioproduction from lignocellulosic residues comprises hydrolysis of the hemicellulose, detoxification of the hydrolysate, bioconversion of the xylose, and recovery of xylitol from the fermented hydrolysate. There are relatively few reports on xylitol recovery from fermented media. In the present study, ion‐exchange resins were used to clarify a fermented wheat straw hemicellulosic hydrolysate, which was then vacuum‐concentrated and submitted to cooling in the presence of ethanol for xylitol crystallization. RESULTS: Sequential adsorption into two anion‐exchange resins (A‐860S and A‐500PS) promoted considerable reductions in the content of soluble by‐products (up to 97.5%) and in medium coloration (99.5%). Vacuum concentration led to a dark‐colored viscous solution that inhibited xylitol crystallization. This inhibition could be overcome by mixing the concentrated medium with a commercial xylitol solution. Such a strategy led to xylitol crystals with up to 95.9% purity. The crystallization yield (43.5%) was close to that observed when using commercial xylitol solution (51.4%). CONCLUSION: The experimental data demonstrate the feasibility of using ion‐exchange resins followed by cooling in the presence of ethanol as a strategy to promote the fast recovery and purification of xylitol from hemicellulose‐derived fermentation media. Copyright © 2008 Society of Chemical Industry 相似文献
5.
Effect of flexure induced transverse crack and self-healing on chloride diffusivity of reinforced mortar 总被引:2,自引:0,他引:2
Mustafa Şahmaran 《Journal of Materials Science》2007,42(22):9131-9136
Cracks in reinforced concrete are unavoidable. Durability is of increasing concern in the concrete industry, and it is significantly
affected by the presence of cracks. The corrosion of reinforcing steel due to chloride ions in deicing salts or sea-water
is a major cause of premature deterioration of reinforced concrete structures. Although, it is generally recognized that cracks
accelerate the ingress of chlorides in concrete, a lack of consensus on this subject does not yet allow reliable quantification
of their effects. The present work studies the relationship between crack widths and chloride diffusivity. Flexural load was
introduced to generate cracks of width ranging between 29 and 390 μm. As crack width was increased, the effective diffusion
coefficient was also increased, thus reducing the initiation period of corrosion process. For cracks with widths less than
135 μm, the effect of crack widths on the effective diffusion coefficient of mortar was found to be marginal, whereas for
crack widths higher than 135 μm the effective diffusion coefficient increased rapidly. Therefore, the effect of crack width
on chloride penetration was more pronounced when the crack width is higher than 135 μm. Results also indicate that the relation
between the effective diffusion coefficient and crack width was found to be power function. In addition, a significant amount
of self-healing was observed within the cracks with width below 50 μm subjected to NaCl solution exposure. The present research
may provide insight into developing design criteria for a durable concrete and in predicting service life of a concrete structures. 相似文献
6.
Mamiko Hori Cécile Pagnoux Jean-François Baumard Masayuki Nogami 《Journal of Materials Science》2007,42(1):80-86
A new method is proposed to produce gold nanoparticles (GNP) by in situ reduction of a gold salt dissolved in water. The reducing
agent used is Tiron instead of the citrate anion most often mentioned in literature. The influence of various parameters has
been investigated, such as the content of Tiron with respect to that of the precursor of gold HAuCl4, or the initial pH of the solution after mixing of reactants. It is shown that Tiron also exerts a positive influence as
a dispersant, which impedes agglomeration of gold nanoparticles. The typical average size of GNP synthesized in the present
work is close to 7 nm. 相似文献
7.
Physically based simulation of human hair is a well studied and well known problem. But the “pure” physically based representation of hair (and other animation elements) is not the only concern of the animators, who want to “control” the creation and animation phases of the content. This paper describes a sketch-based tool, with which a user can both create hair models with different styling parameters and produce animations of these created hair models using physically and key frame-based techniques. The model creation and animation production tasks are all performed with direct manipulation techniques in real-time. 相似文献
8.
Ezequiel R. Soulé Guillermo E. Eliçabe Roberto J. J. Williams 《Polymer Bulletin》2008,60(2-3):417-423
An unexpected experimental finding is reported where the primary morphology developed during polymerization-induced
phase separation in a rubber-modified thermoplastic practically disappears at high conversions. This process
was evidenced by light scattering (LS) and scanning electron microscopy (SEM) for a particular composition
of solutions of polyisobutylene oligomers (PIB) in isobornylmethacrylate (IBoMA), during the free-radical
polymerization of the monomer. The primary phase separation produced a dispersion of domains rich in PIB
containing significant amounts of the monomer (IBoMA). Polymerization of the monomer in these domains occurred
at high overall conversions producing the filling of dispersed domains with a PIBoMA-PIB blend that could
not be distinguished from the matrix. Under these conditions the final material had the appearance of a
homogeneous blend. 相似文献
9.
Conceptual damage-sensitive features for structural health monitoring: Laboratory and field demonstrations 总被引:2,自引:0,他引:2
F. Necati Catbas Mustafa Gul Jason L. Burkett 《Mechanical Systems and Signal Processing》2008,22(7):1650-1669
The use of damage-sensitive features to evaluate structural condition or health is a very critical aspect of structural health monitoring. The purpose of this paper is to investigate the potential of two different damage-sensitive features for detecting damage. Different damage scenarios are simulated on a large-scale laboratory structure and a three-span highway bridge for demonstration. The features presented in this paper are the modal flexibility-based deflection and curvature both of which are obtained directly from dynamic properties. In the literature, flexibility associated with mode shapes and mode shapes curvatures have been mostly explored. In this study, multi-input–multi-output dynamic data are used to obtain modal flexibility, which is a close approximation to the actual flexibility. A main novelty is that the curvature is calculated from the deflected shapes using the modal flexibility as opposed to using modal vectors. In this paper, the theory of the methodology is explained and then experimental studies and results are presented. For the experimental studies, the laboratory specimen and the three-span bridge were gradually damaged. It is shown that both deflection and curvature are conceptual and physically meaningful features for damage detection and localization. The issues and the requirements for these features to perform successfully are also presented. 相似文献
10.
Jürgen Schönbeçk 《NTM》2004,12(2):80-99
Thomas Fincke (January 6th, 1561–April 24th, 1656), born in Flensburg (Germany), was one of the very most important and significant scientists in Denmark during the
seventeenth century, a mathematician and astrologer and physician in the beginning of modern science, a representative of
humanism and an influentual academic organizer. He studied in Strasbourg (since 1577) and Padua (since 1583) and received
his M.D. in Basel (1587), he practised as a physician throughout his life (since 1587 or 1590) and became a professor at Copenhagen
(1591). But he was best known because of his Geometriae rotundi libri XIIII (1583), a famous book on plane and spherical trigonometry, based not on Euclid but on Petrus Ramus. In this influentual work,
in which Fincke introduced the terms tangent and secant and probable first noticed the Law of Tangents and the so-called Newton-Oppel-Mauduit-Simpson-Mollweide-Gauss-formula,
he showed himself to be „abreast of the mathematics of his time“.
相似文献