University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 10 2 1999 06 01 A SEGMENTED REGRESSION MODEL FOR DESCRIPTION OF MICROBIAL GROWTH - 31486 EN Journal Article A segmented regression model for the description of microbial growth has been suggested. The model is able to predict the exponential growth, logistic growth, logistic growth with a phase of decline, diauxic growth, microbial growth in synchronous cultures and the oscillatory growth https://jsciences.ut.ac.ir/article_31486_8d9fd5db21fef20298b0a1b76ca29334.pdf

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 10 2 1999 06 01 CLONING AND EXPRESSION OF A HUMAN INTERFERON a2 GENE IN E. COLI - 31487 EN Journal Article The plasmid pALCA1SIFN containing cDNA that encodes the human interferon a-2b was obtained from the ATCC(no. 531667). In this system the expression of the gene is under the control of an alcA promoter. alcA p is a specific promoter for expression of different genes in Aspergillusfilamentous. In this plasmid the coding region of IFN?-2b is preceded by the coding region of a synthetic signal peptide. For direct expression of the IFNa-2b gene under the control of a T7/lac promotor of pET24d(+) expression vector, three subcloning steps were carried out which resulted in the construction of 3 new plamids. pHA1, pHA2 and pHA4 in which the IFNa-2 gene is under the control of lacp, lacuv5p and T7 promoter, respectively. Another plasrnid, pHA3, was also constiucted and is a modified version of pET24d(+). Provided there is a synthetic signal peptide preceding the coding region of IFNa2 gene, the protein can be seen in either system, as shown by western blotting, albeit with a different level of expression. The best product can be seen in the pHA4plasmid with a T7 pas judged by dot and western blotting https://jsciences.ut.ac.ir/article_31487_20906d510c44acb485fbf89daca562ac.pdf

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 10 2 1999 06 01 FLOW INJECTIOW DETERMINATION OF FLUORIDE BY MURTN-ALUMINUM REAGEM WITH SPECTROEUORIMIETRIC DETECTION - 31488 EN Journal Article A flow injection system is reported for the determination of fluoride based on its effects on the fluorescence intensity of Al-morin complex at pH 3.0 in ethanol-warn mixture. The effect of important parameters such as excitation and emission wavelengths, pH, reagents concenkations, flow rate of the carrier stream, sample injection volume, time of measurepent and interferences are reported. Cation and anion exchange resins were used to remove interferences and to preconcenttate fluoride ions prior to measurement. Calibration curve was linear over the range of 5- 20000 ng ml of fluoride. The deteetion limit was 3 ng ml and the relative standard deviation for the determination of 100 ng ml of fluoride was ±38.7'he proposed method was used to determine ffuofide in natural water samples. R&overy was 97.5- 105% for the fluoride added to the water samples. The relative standard deviation for the andysis of these samples was less than 5%. https://jsciences.ut.ac.ir/article_31488_007491783420080b25639249163d109d.pdf

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 10 2 1999 06 01 THE ROLE OF AMINES AS TEMPLATES IN DIRECTING THE STRUCTURE OF ZEOLITES - 31489 EN Journal Article In this article, we have investigated the role of dimethylamine (DMA), tributylamine (TBA), Triethanoleamine (TEA), Trishydroxymethylamine (TRIZMA), and Hexamethyleneterraamine (HMTA), in the formation of zeolitic compounds. The experiments were carried out in acidic and basic media using Si/Al< 10 and Si/A1>10. The structure of the resulting synthetic zeolites were similar to Natro Davyne, ammonium sodalite, analcime, and mordenite. We also recognized that HMTA in basic media resulted in a new crystalline Compound https://jsciences.ut.ac.ir/article_31489_bf2c43a821883512a0e6558da13d7328.pdf

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 10 2 1999 06 01 TRIPHENYLPHOSPHINE CATALYZED AROMATIC ELECTROPHILIC SUBSTITUTION OF 2-HYDROXYACETOPHENONE MEDIATED BY VINYLTRIPHENYLPHOSPHONIUM CATION - 31490 EN Journal Article Protonation of the highly reactive 1:l intermediate produced in the reaction between triphenylphosphine and dimethyl acetylenedicarboxylate by 2- hydroxyacetophenone leads to vinyltriphenylphosphonium salt, which undergoes aromatic electrophilic substitution reaction with the conjugate base to produce compounds 4,5, and 6 in 1 : 1.2:0.5 ratios https://jsciences.ut.ac.ir/article_31490_1894ea678da89602948e674a85fbfe09.pdf

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 10 2 1999 06 01 THE ALMOST SURE CONVERGENCE OF WEIGHTED SUMS OF NEGATIVELY DEPENDENT RANDOM VARIABLES - 31491 EN Journal Article In this paper we study the almost universal convergence of weighted sums for sequence {x ,n } of negatively dependent (ND) uniformly bounded random variables, where a, k21 is an may of nonnegative real numbers such that 0(k ) for every ?> 0 and E|x | F | =0 , F = ?(X ,…, X ) for every n>l. https://jsciences.ut.ac.ir/article_31491_25d80b451b5c76cf01048f4b1d367e35.pdf

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 10 2 1999 06 01 PERIODIC SOLUTIONS OF CERTAIN THREE DIMENSIONAL AUTONOMOUS SYSTEMS - 31492 EN Journal Article There has been extensive work on the existence of periodic solutions for nonlinear second order autonomous differantial equations, but little work regarding the third order problems. The popular Poincare-Bendixon theorem applies well to the former but not the latter (see [2] and [3]). We give a necessary condition for the existence of periodic solutions for the third order autonomous systems, This may become useful in further investigations. Our claims are proved and supported by certain examples. https://jsciences.ut.ac.ir/article_31492_29093d10b0c57f776c78f839d0203739.pdf

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 10 2 1999 06 01 THE STEFAN PROBLEM WITH KINETIC FUNCTIONS AT THE FREE BOUNDARY - 31493 EN Journal Article This paper considers a class of one-dimensional solidification problem in which kinetic undercooling is incorporated into the temperature condition at the interface. A model problem with nonlinear kinetic law is considered. The main result is an existence theorem. The mathematical effects of the kinetic term are discussed https://jsciences.ut.ac.ir/article_31493_1f79c37c38ef31e2174277b34e5aa64b.pdf

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 10 2 1999 06 01 A NUMERICAL RENORMALIZATION GROUP APPROACH FOR AN ELECTRON-PHONON INTERACTION - 31494 EN Journal Article A finite chain calculation in terms of Hubbard X-operators is explored by setting up a vibronic Harniltonian. The model conveniently transformed into a form so that in the case of strong coupling a numerical renormalization group approach is applicable. To test the technique, a one particle Green function is calculated for the model Harniltonian https://jsciences.ut.ac.ir/article_31494_db07748a120b8752dcac49ddfe281b71.pdf

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 10 2 1999 06 01 OPTICAL PROPERTIES OF CO-EVAPORATED THIN FILMS OF BINARY Bi 0-Te 0 AND Bi 0 -V 0 SYSTEMS - 31495 EN Journal Article Thin films of binary Bi 0 -TeO and Bi 0 -V 0 systems were prepared by the thermal co-evaporation technique in a vacuum at room temperature. The optical absorption edge of these systems are studied in the wavelength of 200-800 nm using a PERKIN-ELMER uv/Vis spectrophotometer. It is found that the value of n=3/2 in the Davis-Mott equation is best fitted for the fundamental absorption edge for these materials. It is also found that the optical energy gap (E ) for the Bi o - v o system lies between 0.65 and 3.5 eV. and for the Bi 0 -TeO system between 0.95 and 3.25 eV. depending on the film composition. The exponential behaviour of the absorption coefficient with photon energy for the systems under invesgiation are verified as suggested by Urbach https://jsciences.ut.ac.ir/article_31495_348a43bb0eadc84915bcd8d95f373b0f.pdf