A SEGMENTED REGRESSION MODEL FOR
DESCRIPTION OF MICROBIAL GROWTH
text
article
1999
eng
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
Journal of Sciences, Islamic Republic of Iran
University of Tehran
1016-1104
10
v.
2
no.
1999
https://jsciences.ut.ac.ir/article_31486_a6a94e0cb2211074359c5c7c1dee8e1a.pdf
CLONING AND EXPRESSION OF A HUMAN
INTERFERON a2 GENE IN E. COLI
text
article
1999
eng
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
Journal of Sciences, Islamic Republic of Iran
University of Tehran
1016-1104
10
v.
2
no.
1999
https://jsciences.ut.ac.ir/article_31487_fe2b5abdb5995f963ecedef9efe18921.pdf
FLOW INJECTIOW DETERMINATION OF
FLUORIDE BY MURTN-ALUMINUM REAGEM
WITH SPECTROEUORIMIETRIC DETECTION
text
article
1999
eng
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%.
Journal of Sciences, Islamic Republic of Iran
University of Tehran
1016-1104
10
v.
2
no.
1999
https://jsciences.ut.ac.ir/article_31488_c92a6924551206c857cb20d274b13dbf.pdf
THE ROLE OF AMINES AS TEMPLATES IN
DIRECTING THE STRUCTURE OF ZEOLITES
text
article
1999
eng
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
Journal of Sciences, Islamic Republic of Iran
University of Tehran
1016-1104
10
v.
2
no.
1999
https://jsciences.ut.ac.ir/article_31489_f33b1c572a8c130a0ff08036750782ad.pdf
TRIPHENYLPHOSPHINE CATALYZED
AROMATIC ELECTROPHILIC SUBSTITUTION
OF 2-HYDROXYACETOPHENONE MEDIATED
BY VINYLTRIPHENYLPHOSPHONIUM CATION
text
article
1999
eng
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
Journal of Sciences, Islamic Republic of Iran
University of Tehran
1016-1104
10
v.
2
no.
1999
https://jsciences.ut.ac.ir/article_31490_060817ab8db73ca0677704776142eb51.pdf
THE ALMOST SURE CONVERGENCE OF
WEIGHTED SUMS OF NEGATIVELY
DEPENDENT RANDOM VARIABLES
text
article
1999
eng
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.
Journal of Sciences, Islamic Republic of Iran
University of Tehran
1016-1104
10
v.
2
no.
1999
https://jsciences.ut.ac.ir/article_31491_325f50702cb644e39015ba4051cb68b0.pdf
PERIODIC SOLUTIONS OF CERTAIN THREE
DIMENSIONAL AUTONOMOUS SYSTEMS
text
article
1999
eng
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.
Journal of Sciences, Islamic Republic of Iran
University of Tehran
1016-1104
10
v.
2
no.
1999
https://jsciences.ut.ac.ir/article_31492_4c876434368592fefa4f89f39e5bc3b9.pdf
THE STEFAN PROBLEM WITH KINETIC
FUNCTIONS AT THE FREE BOUNDARY
text
article
1999
eng
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
Journal of Sciences, Islamic Republic of Iran
University of Tehran
1016-1104
10
v.
2
no.
1999
https://jsciences.ut.ac.ir/article_31493_28ff0070e5ca590e7b279f1b5eff4f94.pdf
A NUMERICAL RENORMALIZATION GROUP
APPROACH FOR AN ELECTRON-PHONON
INTERACTION
text
article
1999
eng
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
Journal of Sciences, Islamic Republic of Iran
University of Tehran
1016-1104
10
v.
2
no.
1999
https://jsciences.ut.ac.ir/article_31494_8d28269f0740fee42b52a14e263e5f01.pdf
OPTICAL PROPERTIES OF CO-EVAPORATED
THIN FILMS OF BINARY Bi 0-Te 0 AND
Bi 0 -V 0 SYSTEMS
text
article
1999
eng
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
Journal of Sciences, Islamic Republic of Iran
University of Tehran
1016-1104
10
v.
2
no.
1999
https://jsciences.ut.ac.ir/article_31495_5e0a4e032d34988c55c2978529fdc754.pdf