Journal of Sciences, Islamic Republic of Iran
Volume:14 Issue: 3, Summer 2003

Antifungal and antibacterial activity of some heterocystous cyanobacteria from paddy-fields in the north of Iran was studied. Soil samples were collected from paddy-fields of Gillan, Mazandaran and Golestan Provinces and cyanobacteria were isolated. Supernatants, methanolic and hexane extracts from biomass of 150 strains of cyanobacteria were isolated and screened against six strains of bacteria and eight strains of fungi. Methanolic extracts and culture supernatants of 21 strains of cyanobacteria exhibited significant antibacterial effect and 13 strains showed antifungal effect. No antimicrobial activity was detected in the hexane extracts and no extract inhibited the growth of E. coli. According to these results, it is concluded that strains of Stigonemataceae including Fischerella and Stigonema species, seem to be more potential for producing antimicrobial substances than other strains.

The denaturation behavior of free and calcium saturated MRP8/MRP14 (calprotectin) in sodium dodecyl sulphate (SDS) and urea was studied by fluorescence spectroscopy. The sigmoidal denaturation curve was plotted in order to estimate the thermodynamic parameters, assuming a two-state mechanism in terms of the Pace model. SDS, anionic surfactant, affects free and calcium saturated MRP8/MRP14 at a millimolar level as a result of direct interaction between free and calcium saturated protein and surfactant as an amphipatic molecule. Urea also affects free and calcium saturated MRP8/MRP14 but at a molar level and as a result of indirect interaction with the surrounding of free and calcium saturated protein (a change in the water structure). The thermodynamic data indicate that ΔG°H2O of saturated human MRP8/MRP14 is larger than that of free form. Therefore, calcium bound protein is more stable and resistant to the denaturant agent.

The effects of different concentrations of CdCl2 and AlCl3 on NH4+ and NO2− oxidation in an aqueous system were investigated. AlCl3 had no effect on NH4+ removal and its oxidation to NO2−, whereas NO2− disappearance was greatly enhanced by AlCl3. In contrast, CdCl2 delayed removal of NH4+ and its subsequent oxidation to NO2− and also decreased the rate of NO2− disappearance. When compared to the controls, NO3− production from NH4+ oxidation decreased severely by CdCl2 whereas slight increase in NO3− production was observed in the presence of AlCl3. The results presented provide evidence for differential sensitivity of NH4+ and NO2− oxidation to AlCl3 and CdCl2 in an aquatic environment.

The effect of Annona squamosa, Lawsonia inermis and their combination with other herbal molluscicides were studied on different enzyme activity in the nervous tissue of Lymnaea acuminata. Twenty-Four hour in vivo exposure to 40% and 80% of 24 h LC50 of plant derived molluscicides and their combination with other molluscicides such as Cedrus deodara, Azadirachta indica oil, Allium sativum, Polianthes tuberosa bulb and oleoresin of Zingiber officinale and acetogenins caused a significant reduction in the activity of acetylcholinesterase, cytochrome oxidase and Na+/K+ ATPase in the nervous tissue of L. acuminata. Combination of C. deodara with A. squamosa or L. inermis inhibited the acetylcholinesterase activity in the nervous tissue up to 60% and 58.70% of control, respectively. Acetogenin was more effective against Na+/K+ ATPase and cytochrome oxidase. Inhibition of these enzymes even at lower concentrations of plant derived molluscicides present in binary mixture with respect to their single treatment inhibit the enzyme activity nearly up to same level.

In this study a special type of silicoaluminophosphate with opal structure (Opal-SAPO) was prepared under microwave condition using tetraethylorthosili-cate (TEOS), triethanolamine (TEA), aluminiumisopropoxid and phosphoric acid 85%. The product was characterized by X-ray diffraction (XRD), thermogravi-metric (TGA) and Fourier Infrared Spectroscopy (FTIR).The crystalline product showed a good activity and selectivity for regeneration of methylethylketone, benzaldehyde, and cyclohexanone from their semicarbazones derivatives.

Experiments were conducted to study the ability of surfactant-modified clinoptilolite for molybdate adsorption from aqueous solutions. Clinoptilolite was treated with some cationic surfactants. Adsorption of surfactants on zeolite surface was confirmed by chemical analysis, IR (Infra-Red Spectroscopy), DTG (Derivative Thermogravimetry) and SEM (Scanning Electron Microscopy) techniques. The modified zeolites were reacted with molybdate solutions having a known activity of radionuclide 99Mo. The results indicated that surfactant modification enhances the ability of zeolite for molybdate adsorption, particularly at pHs lower than 5.5. Adsorption capacity of modified zeolite depends on the surfactant type. The presence of studied anions always reduced the adsorption of molybdate whereas Cs+ increased it. Desorption studies showed that surfactant-modified clinoptilolite is a good candidate for removal and immobilization of 99Mo.

The formation of atoll garnet in the Ardara aureole, NW Ireland, is discussed using the textural, chemical and Electron Backscatter Diffraction (EBSD) data. Textural evidence suggests the possibility of incipient of garnet replacement from the core. In addition, the presence of staurolite and andalusite in the core of small atoll garnets as well as the occurrence of sillimanite in the core of large atoll garnet reveal the prograde nature of atoll formation. The microprobe analyses and EBSD data also indicate that atoll garnets in the Ardara aureole developed by pre-existing idioblastic garnets being replaced by mainly biotite to produce atoll forms.

The origin of the Proterozoic Choghart iron oxide deposit in the Bafq mining district of Central Iran has been the subject of a long-standing dispute. Some authors believe that it was formed from magma, while others suggest metasomatic replacement of preexisting rocks. The present study on the basis of new oxygen isotope, REE and geochemical data concludes that neither of these two hypotheses can alone explain the formation of Choghart deposit. Instead, it is suggested that the separation of an iron oxide melt and the ensuing hydrothermal processes dominated by alkali metasomatism were both involved to different degrees in the formation of Choghart and other similar deposits in Central Iran.

In this paper, we extend and generalize some recent results on the strong laws of large numbers (SLLN) for pairwise independent random variables [3]. No assumption is made concerning the existence of independence among the random variables (henceforth r.v.’s). Also Chandra’s result on Cesàro uniformly integrable r.v.’s is extended.

Complicated potential structure formed at a constriction of positive column of a DC discharge with heated cathode in He at low discharge currents is investigated. According to the potential structure, electrons and ions are accelerated by the electric field and their energy distribution functions acquire multi humped shapes. Additional maximums on distribution functions quickly disappear due to collisions and radial losses. The nature of current passing through the Potential Structure (PS) is cleared up on the base of measured distributions. Attempt was made to calculate potential drop in DL taking into account electron energy distribution variations.