Journal of Sciences, Islamic Republic of Iran
Year:2002 | Volume:13 | Issue:1|Papers Count:17

A phenetic analysis of the 12 taxa or operational taxonomic units (OTUs) belonging to the three sections; Genea, Neobromus, and Nevskiella of the genus Bromus was performed. Unweighted pair-group method using arithmetic averages (UPGMA) and weighted pair-group method using arithmetic averages (WPGMA) clustering and factoriel method analyses were used to set the taxa apart. Forty-four characters including 4 vegetative and 38 reproductive characters, the chromosome number and the geographical distribution were considered in this study. The outcomes of multivariate analyses were compared with different conventional classifications. The results show that four major phenetically well-defined groups existed which confirmed the Sale"s concept. This finding, however, is in odd with that expressed in Flora of U.S.S.R. The relations between the taxa were discussed, and a key to identify them was presented.

Inducible nitric oxide synthase (iNOS) gene expresses a calcium calmudolinindependent enzyme which can catalyse NO production from L-arginine. The induction of iNOS activity has been demonstrated in a wide variety of cell types under stimulation with cytokines and lipopoly saccharide (LPS). Previous studies indicated that all nitric oxide synthases (NOS) activated in human umbilical vein endothelial cells (HUVEC) were calcium dependent. In this work we indicate that endothelial cells can express iNOS mRNA under stimulation by cytokines, LPS and H2O2. We also found that iNOS mRNA expression has increased by augmentation of H2O2 concentration and its expression depends on increasing in time. Therefore we conclude that two isoforms of NOS are expressed in the HUVEC and induction of iNOS enzyme by H2O2 and NO production in endothelial cells may represent a novel cellular defence mechanism against oxidative stress and infections.

A multivariate statistical analysis was performed on morphological characters of sixty-one populations of Avena eriantha Dur. A. clauda Dur., A. barbata Pott ex Link., A. wiestii Steud., A. fatua L., A. sterilis ssp. ludoviciana L. and A. sativa L. Factor analysis revealed that intraspecific morphological variations are due to quantitative characters. Interspecific as well as intersectional relationships were investigated using cluster, discriminant analysis and ordination method based on principal components supporting the Baum’s classification.

About 35 samples were collected from lower and upper parts of the proposed Frasnian-Famennian boundary in three sections of Upper Devonian marine sediments of the Kerman province. The biostratigraphical and geochemical studies indicate that about 45% extinction of brachiopods probably caused by the Frasnian-Famennian bioevents, which is slightly higher than thr rate of Devonian- Carboniferous extinction elsewhere. The results of isotopic carbon and oxygen isotope analysis (δ 13C%0 VPDB and δ 10O %VPDB) show a sudden decrease at the proposed Frasnian-Famennian extinction boundary which is followed by positive values above this horizon. The negative excursion may indicate a biomass extinction due to either a meteorite impact or decay of organic matter. The isotopic variations are correlated with those of faunal changes and their extinctions in the area.

Sheikh-Ali copper deposit is located 300-km southeast of Kerman in an “ophiolitic coloured melange” complex at the southeastern part of the Zagros Crushed Zone. The rock units mainly consist of pillow basalt lavas, diabase, pelagic limestone, radiolarian chert, calcareous sandstone and graywacke of Upper Cretaceous age. These units locally have an east-west trend and are emplaced as a slice between serpentinite and other ultrabasic rocks such as dunite and harzburgite, through thrust fault contacts. The country rock which hosts directly the ore horizon is a brown to red goethitic silica horizon. The silicic ore horizon was deposited stratiformly between the pelagic limestones and embedded by the pillow basaltic lavas. Chloritic and propylitic alterations can be seen in the surrounding rocks. The geometry of ore is lenticular and the lenses are conformable with the pelagic limestones, as well as pillow basalt lavas. The mineral paragenesis mainly includes pyrite, chalcopyrite, sphalerite, specularite, silica, quartz and calcite. The ore textures are massive, laminar, colloform, disseminated and rarely veinlets are present. The silicic ore horizon is about 550 meters long and 0.7 to 8.5 meters thickness. Mean and maximum content of Cu in massive ore is about 2.5 and 4.8 percent, respectively. Maximum content of Au and Ag in massive ore is about 0.64 and 75 g/t, respectively. Geochemical studies show excellent correlation between Cu and Zn in different parts of the ore body. Furthermore, the REE patterns are similar in both the pillow basalts and the ore bodies. Geological, lithological, geochemical and ore paragenesis studies suggest that the deposit can be introduced as a Cyprus-type (Ophiolite-hosted) VMS deposit, resulting from submarine volcanic exhalites and fumaroles, synchronous with the formation of country rocks.

We consider a mixed boundary value problem for a quarter-plane with a Robin condition on one edge. We have developed two procedures, one based on the advanced theory of dual integral equations and the other, in our opinion simpler technique, relying on conformal mapping. Both of the procedures are of interest, because the former may be easier to adapt to other boundary value problems.

This paper deals with a theoretical mathematical analysis of one-dimensional solidification problem, in which kinetic undercooling is incorporated into the This temperature condition at the interface. A model problem with nonlinear kinetic law is considered. We prove a local result intimate for the uniqueness of solution of the corresponding free boundary problem.

Utilization of Photodisintegration reaction of Deuterium, 2H(γ,n)1H, is a precise technique for determining the percentage of 2H in tritiated and natural water. The 23Na(n,γ)24Na reaction is a suitable γ-source for producing the 2H(γ,n)1H reaction. Tehran Research Reactor was used as a neutron source for producing 24Na isotopes. The BF3 detectors were used to detect the neutron emission of H2 content of water. We obtained a linear calibration plot by repeating the experiment with many samples of different concentrations of tritiated water. With this simple portable apparatus which have been used for this purpose for the first time, and corresponding linear plot, we can monitor and determine easily and accurately the 2H concentration of an unknown sample.