The micropolar fluid model for blood flow through a tapered artery with a stenosis

A micropolar model for axisymmetric blood flow through an axially nonsymmetreic but radially symmetric mild stenosis tapered artery is presented. To estimate the effect of the stenosis shape, a suitable geometry has been considered such that the axial shape of the stenosis can be changed easily just by varying a parameter （referred to as the shape parameter）. The model is also used to study the effect of the taper angle Ф. Flow parameters such as the velocity, the resistance to flow （the resistance impedance）, the wall shear stress distribution in the stenotic region and its magnitude at the maximum height of the stenosis （stenosis throat） have been computed for different values of the shape parameter n, the taper angle Ф, the coupling number N and the micropolar parameter m. It is shown that the resistance to flow decreases with increasing the shape parameter n and the micropolar parameter m while it increases with increasing the coupling number N. So, the magnitude of the resistance impedance is higher for a micropolar fluid than that for a Newtonian fluid model. Finally, the velocity profile, the wall shear stress distribution in the stenotic region and its magnitude at the maximum height of the stenosis are discussed for different values of the parameters involved on the problem.     

Hemocompatibile Thin Films Assessed under Blood Flow Shear Forces

The aim of this study was to minimize the risk of life-threatening thromboembolism in the ventricle through the use of a new biomimetic heart valve based on metal–polymer composites. Finite volume element simulations of blood adhesion to the material were carried out, encompassing radial flow and the cone and plane test together with determination of the effect of boundary conditions. Both tilt-disc and bicuspid valves do not have optimized blood flow due to their design based on rigid valve materials (leaflet made of pyrolytic carbon). The main objective was the development of materials with specific properties dedicated to contact with blood. Materials were evaluated by dynamic tests using blood, concentrates, and whole human blood. Hemostability tests under hydrodynamic conditions were related to the mechanical properties of thin-film materials obtained from tribological tests. The quality of the coatings was high enough to avoid damage to the coating even as they were exposed up to maximum loading. Analysis towards blood concentrates of the hydrogenated carbon sample and the nitrogen-doped hydrogenated carbon sample revealed that the interaction of the coating with erythrocytes was the strongest. Hemocompatibility evaluation under hydrodynamic conditions confirmed very good properties of the developed coatings.     

сОДЕРжАНИь РАБОт, ОпУБлИкОВАННых тОлькО В ЧЕшскОМ ИжДАНИИ НАстОьЩЕгО жУРНАлА

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Abstracts of Papers which have appeared only in the Czech Edition of this Journal

     

On some properties of almost-analytic tensors in an *O-space

Summary We consider an *O-space which is a kind of almost-Hermitian space. There is stated a theorem, that is, in a compact *O-space a skew-symmetric covariant almost-analytic tensor is closed. From this theorem, we get many important properties of almost-analytic tensors in an almost-K?hlerian space or a K-space and an interesting result related to the Lie derivative.     

Simultaneous Production of Lipids and Carotenoids by the Red Yeast Rhodotorula from Waste Glycerol Fraction and Potato Wastewater

Applied Biochemistry and Biotechnology - Abstract The objective of this study was to determine the possibility of simultaneous biosynthesis of lipids and carotenoids by the Rhodotorula yeast...     

Immobilization of soil mercury by colloidal sulphur in the laboratory experiment

The results of the laboratory pot experiments on soil mercury (Hg) immobilisation with a non-toxic and price-reasonable agent — colloidal sulphur (S) water suspension, are presented. It was shown that fertilisation with small agrochemical doses of colloidal S reduces excess Hg effectively as follows: in interstitial waters by a factor 2 – 12 times for total Hg, and 22– 680 times for “reactive” Hg; in stems and leaves of oats – 7 – 22 times; and in moss bags, reflecting soil Hg degassing, 7 – 15 times, for the most heavily Hg-spiked soils. The results obtained allowed to conclude that the immobilization of Hg occurs through Hg binding to the newly formed S-bearing functional groups in humic acids and/or sulphides.      

The Multifaceted Role of Curcumin in Advanced Nanocurcumin Form in the Treatment and Management of Chronic Disorders

Curcumin is the primary polyphenol in turmeric’s curcuminoid class. It has a wide range of therapeutic applications, such as anti-inflammatory, antioxidant, antidiabetic, hepatoprotective, antibacterial, and anticancer effects against various cancers, but has poor solubility and low bioavailability. Objective: To improve curcumin’s bioavailability, plasma concentration, and cellular permeability processes. The nanocurcumin approach over curcumin has been proven appropriate for encapsulating or loading curcumin (nanocurcumin) to increase its therapeutic potential. Conclusion: Though incorporating curcumin into nanocurcumin form may be a viable method for overcoming its intrinsic limitations, and there are reasonable concerns regarding its toxicological safety once it enters biological pathways. This review article mainly highlights the therapeutic benefits of nanocurcumin over curcumin.     

Enthalpimetric and Colorimetric Determinations of the Inhibition Constant for the Inhibition of Urease by Boric Acid

Continuous enthalpimetric and fixed-time-point colorimetric analytical studies of jack bean urease-catalyzed hydrolysis of urea uninhibited and inhibited by boric acid were performed. The effect of boric acid on urease activity was studied in 100 mM phosphate buffer of pH 7 (H₃PO₄+NaOH, 2 mM EDTA) at 25°C. The inhibition constant of boric acid was obtained with use of differential and integration methods. It was found that boric acid is a simple competitive inhibitor of urease. The methods produced comparable values of the inhibition constant K_i: the former 0.19 mM and the latter 0.18 mM. This revised version was published online in July 2006 with corrections to the Cover Date.