ORIGINAL_ARTICLE

https://jsciences.ut.ac.ir/article_31021_5a1dd684f3e7c7a3b08b9b77b7a0cca9.pdf
20070601
ORIGINAL_ARTICLE

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 wildtype 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.
https://jsciences.ut.ac.ir/article_31022_a22b8b2bf04bdaffaa34c14320fcad43.pdf
20070601
ORIGINAL_ARTICLE

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 (Nfree, 1 & 2 mM NH4+ and 5 and 10 mM NO3?). Results indicated that maximum growth rate belonged to NO3? treatment. Dry weights of Fischerella sp. FS18 in Nfree medium and ammonium were in decreasing order of preference; and NH4+ 2 mM was drastically toxic for this strain. The highest chlorophyll concentration was detected in Nfree medium. NO3? 5 mM and NH4+ 2 mM 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 lightsaturated photosynthetic rate and also steepest initial slope clearly belonged to nitrogen freemedium. 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.
https://jsciences.ut.ac.ir/article_31023_0516b03f6ed5741b01ee700b6da68e31.pdf
20070601
ORIGINAL_ARTICLE

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 feedback 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 g l?1 was obtained by using an alkaline lyses method.
https://jsciences.ut.ac.ir/article_31024_d00da6d464ed6a5f3a95e46853ff3f90.pdf
20070601
ORIGINAL_ARTICLE

Alkylation of benzene with 1dodecene catalyzed by metalpillared montmorillonite (MPILC, M = Al, Cr, Fe, AlFe, FeCr) was successfully carried out. The formation of linear monoalkylbenzenes in 98% yield in the presence of FePILC during two hours is remarkable. The 2phenydodecane obtained with 30% concentration within the other 3, 4, 5, and 6monosubstituted products is similar to that obtained in Universal Oil Products Detal catalysis process.
https://jsciences.ut.ac.ir/article_31025_a155baee22b25177ebde65efa23812cc.pdf
20070601
ORIGINAL_ARTICLE

https://jsciences.ut.ac.ir/article_31026_23f4a56b0f389e92063946deca532833.pdf
20070601
ORIGINAL_ARTICLE

The relation between MS and logM0 is examined using Harvard CMT M0, with both and the improved surface wave magnitude scale [1] applied to ISC data. Although shows less scatter than , 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 is found throughout the fitted range of M0 (2.0×1024 to 1.26×1027 dynecm), and this linearity extends down to M0=2.5×1023 dynecm. 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.
https://jsciences.ut.ac.ir/article_31027_027c9c4275f58f1b2b4781aa4c08f01c.pdf
20070601
ORIGINAL_ARTICLE

Consider the semidirect product group H ×? 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 ×? K.
Moreover, we try to obtain a concrete form for admissible vectors of these
integrable representations.
https://jsciences.ut.ac.ir/article_31028_4c8a6408e8874f64dda9ec267a9a3483.pdf
20070601
ORIGINAL_ARTICLE

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(?T)=1, where ?T 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.
https://jsciences.ut.ac.ir/article_31029_95f5c4d654b611ba0ab45032a80c47e4.pdf
20070601
ORIGINAL_ARTICLE

Neutron doseequivalent 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.
https://jsciences.ut.ac.ir/article_31030_7eb0ac51a1f3d7a9e2f24e173d271354.pdf
20070601
ORIGINAL_ARTICLE

In this paper we start with MeyerTerVehn isobaric fusion model and try to reconstruct all equations by introducing a dimensionless variable ?i=ri/Rm. Then we investigate the proper sets of spark confinement parameter and temperature {Hs,Ts} which satisfy ignition conditions of spark ignition in deuteriumtritium (DT) equimolar mixture in terms of isentrope parameter, ?, 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 Ef??3 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.
https://jsciences.ut.ac.ir/article_31031_e9007856ef498d0a98b6dc2ca5ed300f.pdf
20070601