Journal of Sciences, Islamic Republic of Iran
Volume:12 Issue: 1, Winter 2001

Biotransformation of benzo[a]pyrene (BaP) in the presence of microsomal fractions derived from liver and epiderm of adult and weanling rats was examined. The aim of this study was to evaluate the effect of age on the capacity of two organs in transformation of BaP. Subcellular fractions were prepared from skin and liver by ultracentrifugation and were used as the source of BaP metabolizing enzymes in a reconstitution assay system. Microsomal fractions are sources of cytochrome P-450 and cytosols are the source of glutathione S-transferase (GST). In a metabolic activation assay system, cytochrome P-450 catalyses the formation of reactive epoxide of BaP which can then interact with exogenous DNA. Adult rat liver microsomes with the highest cytochrome P-450 and maximum capacity for BaP-DNA adducts formation (~204 pmol BaP bound/mg DNA) are considered as positive control in this assay system. The adduct formation in the presence of adult and young rats was approximately 204 and 27 pmol/mg DNA, respectively. Microsomes prepared from skin samples of adult and young rats mediated approximately 49 and 16 pmol BaP binding to DNA respectively. With the addition of cytosol to the microsome-mediated system an in vitro detoxification model has been established. The results obtained by the addition of different cytosolic samples showed that liver cytosol which contains highest GST activity caused about 28% inhibition in BaP binding to DNA. The inhibitory effects of cytosolic fraction from weanling liver, adult skin and weanling skin were 17, 19 and ~9% respectively. These data show that isolated subcellular fractions from young rats are less efficient in the biotansformation of BaP. However, the results obtained in vitro do not reflect the changes in vivo. Further, in vivo experiments should be carried out after BaP administration to animals to confirm the differences in the BaP-DNA adduct formation and BaP-glutathione conjunction in tissues of young and adult animals.

Thiophosgene and 1-chloroethyl chlorothionoformate react readily with tertiary amines, and give the dialkylamine hydrochloride after hydrolysis of the initial product with water. Benzyl and allyl groups are cleaved in preference to methyl and other alkyl groups. The rection with the isoquinoline alkaloid narcotine occurs particularly easily.

Hexamethylenetetramine-bromine on wet alumina rapidly regenerates carbonyl compounds from their corresponding semicarbazone using microwave under solventless system.

The alluvial plain of Sarvestan bears the sole source of potable water in Sarvestan county, Fars Province, Iran. In recent years, due to extended heavy pumping, the groundwater storage has been reduced continuously. The UNGWM (United Nation Ground Water Model) is used to evaluate the hydraulic characteristics of the Sarvestan aquifer and its future response to various regimes of recharge and discharge. The model is a finite difference solution of differential equations for the two-dimensional, isotropic, nonhomogeneous transient flow of water in a porous medium. The aquifer parameters are determined through a combination of visual and rational comparison of simulated and observed groundwater contour maps while adjusting the aquifer boundary inflow-outflow rates at the aquifer recovery period. To validate the parameter values several simulated isopotential maps are compared with observed ones by optimizing the infiltrated rainfall rate into the aquifer. Using the established parameters values, boundary inflow-outflow rates and infiltrated rainfall rate, the annual well hydrographs were simulated. A very good match was found between simulated and observed hydrographs in terms of trend, fluctuations and values. The response of the aquifer to some dictated regimes of discharge and recharge was predicted. The critical zones where pumpage must be prevented are specified and the location of production wells to be drilled in the future is also defined. The UNGWM is validated as a valuable tool for groundwater resource assessment.

Here we consider some non-autonomous ordinary differential equations of order n and present some results and theorems on the existence of periodic solutions for them, which are sufficient conditions, section 1. Also we include generalizations of these results to vector differential equations and examinations of some practical examples by numerical simulation, section 2. For some special cases that extendibility of the solutions can be verified and under other suitable conditions, we show that the frequency of the periodic solutions can be arbitrary small†.

We prove the existence of steady 2-dimensional flows, containing a bounded vortex, and approaching a uniform flow at infinity. The data prescribed is the rearrangement class of the vorticity field. The corresponding stream function satisfies a semilinear elliptic partial differential equation. The result is proved by maximizing the kinetic energy over all flows whose vorticity fields are rearrangements of a prescribed function.

In the transformation semigroup (X, S) we introduce the height of a closed nonempty invariant subset of X, define the transformed dimension of nonempty subset S of X and obtain some results and relations.

In an axisymmetric CO2-N2-H2O gas dynamic laser, let Γ denote the intersection of the vertical plane of symmetry with the upper part of the (supersonic) nozzle. To obtain a maximal small signal gain, some authors have tested several families of curves for Γ. To find the most general solution for Γ, an application of Pontryagin’s principle led to the conjuncture that the optimal Γ must consist of two straight lines of slopes m and 0 smoothly joined by a parabolic arc. (The parabolic section will vanish if nonsmooth Γ is allowed.) The conjecture was settled in the affirmative for special cases. The present work extends these results in the following directions. (i) For the nonsmooth case, Pontryagin’s principle produces no singularity and Γ consists of k straight lines of certain slopes m and 0. (ii) A “semi-uncoupled” approximation is used to show, in (i), that k = 2. (“coupled” stands for the dynamic coupling between vibrational temperatures and translational temperature.) (iii) An uncoupled approximation is used in the smooth case to show that the general Γ consists of a line segment of slope m, a parabolic arc and a horizontal line. (iv) The small signal gain increases whenever the slope m and/or the curvature of the parabolic section increase. However, the latter two quantities must be bounded to reduce gas detachment from the walls or oblique shock waves in the active media. (v) Finally, the optimal shapes and gains are numerically calculated for several values of the stagnation pressure and molar fractions of the gas mixture.

Based on the crystal and magnetic structural properties of some Gd intermetallic compounds, it is shown that with increasing conduction electron concentration, Gd experiences electronic and magnetic instability, and that these behaviors point to the appearance of Kondo Lattice. We suggest that the conduction electrons have gained local character. It is shown that Kondo effect should be observed at around x=0.4. Resistivity studies confirm the calculations, and a Kondo temperature of around 70 K found for Gd2Au0.4Al0.6.