Journal of Sciences, Islamic Republic of Iran
Year:2007 | Volume:18 | Issue:2|Papers Count:12

Effects of toxic concentrations (up to 100µM) of copper (Cu) and manganese (Mn) on growth and oxidative defense system of rice (Oryza sativa L.) and sunflower (Helianthus annuus L.) were studied under three light intensities in hydroponic medium. Rice expressed higher susceptibility to both Cu and Mn toxicity than sunflower. Higher light intensity strengthened the effect of toxicity of Cu while ameliorated that of Mn. Activity of ascorbate peroxidase and glutathione reductase responded to Cu and Mn differently in rice. Cu toxicity increased their activity but Mn did not change or rather decreased it. Activity of catalase was induced in response to both Cu and Mn particularly under higher light intensities. Activity of peroxidase, in contrast to other tested enzymes, was correlated with growth response of plants. Copper was not effective in induction of malondialdehyde accumulation. Mn, in concentrations causing no growth inhibition (100µM), resulted in a significant increase of malondialdehyde. Changes in the tissue content of proline, similar with peroxidase activity, was mainly associated with stress conditions as judged by growth data. On the other word, activity of peroxidase and accumulation of proline monitored the stress conditions without any protecting role and any effect on adaptation of plants. Our results suggested that the antioxidant capacity of plants is not independently correlated with the growth response of plants without regarding the other physiological responses to metal exposure.

A Sigma factor gene which is important in the global regulation of heat shock responses in prokaryotes, rpoH, was isolated from Flexibacter chinesis by PCR, sequenced and compared to the rpoH genes of a variety of other organisms. The rpoH gene was 98% similar to other previously characterized genes. A mutant of rpoH was produced (JR102) which had a reduced growth rate at both low and high temperature. JR102 also produced filaments when grown at temperatures greater than the organism’s optimum growth temperature. During the stationary phase when the wild-type cell size was reducing, the cell size of JR102 did not change, suggesting that cells division was inhibited in the mutant. The results presented in this paper suggest that F. chinensis subjected to starvation and other stresses reduces its cell size by miniaturization or cell division to conserve energy. Anything which prevents the formation of these miniaturized cells reduces the chances of the bacterium surviving under stress conditions.

In the present research the growth and metabolism of cyanobacterium Fischerella sp. FS18, isolated from rice fields of Gillan Province (Iran), were evaluated in different nitrogen sources. This strain is a good candidate as biological fertilizer due to high efficiency to N2 fixation. In this way, cells in logarithmic phase of stock were treated with different nitrogen sources (N-free, 1 & 2 mM NH4+ and 5 and 10mM NO3-). Results indicated that maximum growth rate belonged to NO3- treatment. Dry weights of Fischerella sp. FS18 in N-free medium and ammonium were in decreasing order of preference; and NH4+ 2mM was drastically toxic for this strain. The highest chlorophyll concentration was detected in N-free medium. NO3- 5mM and NH4+ 2mM had the lower contents of this pigment. Photosynthesis rate varied the same as chlorophyll. phycocyanin and phycoerythrin had the highest rate in nitrate. The highest light-saturated photosynthetic rate and also steepest initial slope clearly belonged to nitrogen free-medium. All types of combined nitrogen sources had inhibitory effect on nitrogenase activity, regardless of the concentrations used. Our results indicated that Fischerella sp. FS18 is a potent diazotrophic species with increasing growth in the presence of nitrate; and ammonium 2mM seems to be toxic for it.

A fermentation process for production of super coiled plasmid DNA in E. coli for use as a DNA vaccine was developed. In the process a feed-back control nutrient feeding strategy based on pH and DO was used to regulate the cell growth rate by controlling the interactivity of the nutrient feed rate, pH and DO. The process increased the total yield of plasmid DNA by approximately 4 fold as compared to batch fermentation. The final cell yields of the process reached 56 gl-1 dry cell weights (OD550 nm 112) within 23 h. A plasmid DNA of 5.6 gl-1 was obtained by using an alkaline lyses method.

Alkylation of benzene with 1-dodecene catalyzed by metal-pillared montmorillonite (M-PILC, M=Al, Cr, Fe, Al-Fe, Fe-Cr) was successfully carried out. The formation of linear monoalkylbenzenes in 98% yield in the presence of Fe-PILC during two hours is remarkable. The 2-phenydodecane obtained with 30% concentration within the other 3-, 4-, 5-, and 6-monosubstituted products is similar to that obtained in Universal Oil Products Detal catalysis process.

The Kabirkuh section in the Ilam Province of southwestern Iran contains one of the most complete Late Maastrichtian to early Danian sequences similar to those known from the eastern Tethys realm. The Cretaceous-Tertiary boundary is marked by a 1-2 cm thick kidney-red shale in the uppermost Gurpi Formation. All Late Maastrichtian planktonic foraminiferal biozones CF1 to CF4 (equivalent to the Abathomphalus mayaroensis zone) and Danian zones P0 (Parvularugo globigerina extensa), Pla (Parvularugoglobigerina eugubina) and Parasubbotina pseudobulloides are present. Faunal studies show that all but six of the Cretaceous species identified (22 of 29 species) disappeared at or below the K-T boundary in zone CF1 (P. hantkeninoides). Another 6 species (Heterohelix globulosa, H. navarroensis, H. dentata, Hedbergella monmouthensis, H. holmdelensis, Guembelitria cretacea) appear to have survived into the early Danian. Early disappearances appear to be environmentally controlled. Coarse ornamented species with small populations disappeared first, whereas small species with little or no ornamentation and generally large populations tended to survive after the environment changing. This indicates a pattern of gradual and selective faunal turnover in planktonic foraminifera during the latest Maastrichtian and into the earliest Danian that is similar to that observed at the El Kef stratotype of Tunisia, as well as K-T sequences in Egypt, Italy, Spain and Mexico.

The relation between MS and logM0 is examined using Harvard CMT M0, with Mpragues both and the improved surface wave magnitude scale Mts [1] applied to ISC data. Although Mts shows less scatter than Mpragues, neither dataset supports a slope of MS against logM0 which tends to 1.0 towards smaller magnitudes. Instead, a good linear fit of slope 0.76 using Mts is found throughout the fitted range of M0=(2.0×1024 to 1.26×1027 dyne-cm), and this linearity extends down to M0=2.5×1023 dyne-cm. This suggests that previous proposals that MS data support a theoretical slope of 1.0 in the low range of magnitude which may be expected from established relationships, is not justified.

Consider the semidirect product group H ×t K, where H and K are two arbitrary locally compact groups and K is also abelian. We introduce the continuous wavelet transform associated to some square integrable representations H ×t K. Moreover, we try to obtain a concrete form for admissible vectors of these integrable representations.

In this paper we give some characterizations of topological extreme amenability. Also we answer a question raised by Ling [5]. In particular we prove that if T is a Borel subset of a locally compact semigroup S such that M(S)* has a multiplicative topological left invariant mean then T is topological left lumpy if and only if there is a multiplicative topological left invariant mean M on M(S)* such that M(XT)=1, where XT is the characteristic functional of T. Consequently if T is a topological left lumpy locally compact Borel subsemigroup of a locally compact semigroup S, then T is extremely topological left amenable if and only if S is.

In this paper we start with Meyer-Ter-Vehn isobaric fusion model and try to reconstruct all equations by introducing a dimensionless variable Yi=ri/Rm . Then we investigate the proper sets of spark confinement parameter and temperature {Hs,Ts} which satisfy ignition conditions of spark ignition in deuterium-tritium (DT) equimolar mixture in terms of isentrope parameter, a, implosion velocity, Uim. Finally, limiting fuel energy gain curve (Gf*) as function of ignition energy (Eign) for different implosion velocities is calculated. By this simple modification of our original formulation, we obtain fuel energy scaling as Efµa3 Uim-10 for desirable range of ignition parameters. Since in our formulation HsTs product has appeared, it enabled us to insert a scaling relation for ignition condition in fuel energy, Ef which this in turn decreases implosion velocity exponent in our scaling relation to 7.0.

Neutron dose-equivalent buildup factors were calculated for point isotropic neutron sources irradiating infinite slablike shields of lead, iron and water using the MCNP code. The factors are presented for some source neutron energies in the range from 0.025 eV to 14 MeV, and for shield thicknesses from 0.5 to 10 mfp. Since the MCNP code considers all kinds of neutron interactions with matter, and the variance reduction techniques available in this code allows one to reach correct answers, one can say that the buildup factors presented here are accurate enough to be used in neutron shielding and dosimetry calculations. Comparison of the results obtained here with some previously calculated buildup factors, shows good agreements.