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Maryam Shams
Lahijani
author
Mina
Ramezani
author
text
article
2003
per
Iranian International Journal of Science(Not Publish)
دانشگاه تهران
4
v.
0
no.
2003
https://iijs.ut.ac.ir/article_30791_30c6815d2fe3d4d8c812d63778f1bd18.pdf
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M.T.
Taghizadeh
author
Sh.
Ghaffari
author
text
article
2003
per
Polyvinyl chloride was first dehydrochlorinated by LiCl in DMF at 353 K and then grafted with methylmethacrylate using benzoylperoxide as free radical initiator in an inert atmosphere. Studies were carried out to determine the optimum graft condition such as initiator, monomer and polymer concentration.
It was found that the percentage of grafting and rate of grafting were all dependent to some extent, on the concentration of the initiator, monomer and polymer, reaction time and temperature. The kinetics of the graft polymerization of MMA onto PVC was studied by gravimetry.
The following rate expression observed:
Rg = K[MMA]0.977[DHPVC]0.545[BPO]0.545
Suitable mechanism is suggested. The dehydrochlorination and the graft copolymer were characterized by FT-IR spectroscopy.
The overall activation energy is found to be 37.44 KJ/mol, within the temperature range 40-70 ?C.
Iranian International Journal of Science(Not Publish)
دانشگاه تهران
4
v.
0
no.
2003
https://iijs.ut.ac.ir/article_30792_9949c14c707109b8e8f4dfdc0fb08f77.pdf
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Mohammad Hossein
Adabi
author
Prasada
Rao
author
text
article
2003
per
Major and minor elements in bulk rocks are due to occurrence of mostly quartz, ankerite, illite and minor pyrite. Silicification forms megaquartz by dissolution and replacement of carbonates. Illite is unaffected during ankerite formation. Gold mineralization is unrelated to quartz, illite and pyrite contents. Gold mineralization is related to ankerite formation because gold content increases with increasing ankerite values.
Gold mineralization occurred in a reducing burial environment. Fe in solution was high due to alteration of ultramafics and leaching of clay minerals during silicification. During silicification fluids were acidic and as these solutions progressively dissolved and replaced carbonate, the alkalinity of fluids increased and formed ankerite. In alkaline conditions, gold precipitated along with ankerite.
Iranian International Journal of Science(Not Publish)
دانشگاه تهران
4
v.
0
no.
2003
https://iijs.ut.ac.ir/article_30793_79fc3ce0d67d0245af8e29a451d774d1.pdf
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Morteza
Fattahi
author
text
article
2003
per
Dating is critical for the development of theories relating to many aspects of geology over Quaternary timescales (0-2 millions). Among different dating methods luminescence has the potential for covering a significant range of Quaternary time. In the last 3 decays, from 1967 to 2003, the use of luminescence signals from naturally occurring minerals has gone through a major transformation, from thermoluminescence (TL) dating of pottery to optically stimulated luminescence (OSL) dating of sediments. The present work reports aspects of recent advances of luminescence technique from naturally occurring minerals for dating applications. It has provided information about basic principles of luminescence dating and shows very briefly its progress from blue TL to OSL and red luminescence.
Iranian International Journal of Science(Not Publish)
دانشگاه تهران
4
v.
0
no.
2003
https://iijs.ut.ac.ir/article_30794_e1f2ed21aef8daea304c429ea85299ac.pdf
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Nasser
Arzani
author
text
article
2003
per
The scarcity of water in arid lands highlights the importance of qanats, whereas in the populated areas of the Kavir borders, groundwater utilization by deep tube wells stresses and gradually dries out the ancient qanats. This case study is from the history and fate of ancient qanats in Abarkoh Plain, where is located in the western part of the Gavkhoni-Abarkoh-Sirjan depression in central Iran. The studied area is a large Quaternary alluvial fan (more than 35 km long and 20 km wide) in the western border of Abarkoh depression, which terminates into a playa lake in the center of this depression. The reason for the drying up of ancient qanats has been studies based on the rock-facies analysis of the exposed geology and 1400 recently drilled samples from 94 shallow and deepwater wells. The Abarkoh qanats are constructed in the proximal to mid-fan deposits of the alluvial fans. The tube wells are also scattered in this area and in the distal part of the alluvial fans, where they grade into the playa lake sediments. The complex distribution of the basin-fill deposits (alluvial fan to playa sediments) mainly controlled the position, water discharge and quality of the aquifers. The recoverable groundwater is also within the karstified, coral-algal limestones of the Qom Formation, which occurs as shallow to deep, confined and unconfined aquifers under the mid-fan sediments. The relation between the depth of qanats (mother wells and galleries) and adjacent, recently drilled, deep tube wells, controlled their competition in water discharge. Drop in water tables, not only dried most of the qanats, but also changed the quality of water, due to the penetration of the salty water of the playa lake to the upper-hand aquifers.
This study highlights the contrast between the use of deepwater tube wells and the life of ancient qanats. The greatest effort and achievement in ground-water utilization by ancient people in arid lands and Kavir borders is under threat. This needs to be considered carefully because the level of underground water table in Kavir borders (salt-flat apron) and its effect on desertification is a well-known fact.
Iranian International Journal of Science(Not Publish)
دانشگاه تهران
4
v.
0
no.
2003
https://iijs.ut.ac.ir/article_30795_213cac2bc853b6ebce08ab14278a2888.pdf
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D.
Sridharan
author
P.
Sakthivel
author
S.K.Srivatsa
author
text
article
2003
per
The World Wide Web contains huge amount of dynamic, heterogeneous, and hyperlinked distributed documents. Many modern information retrieval systems are developed based on matching process, which is automated, but classification and query formulations are manual process. The approach taken in this paper is to add intelligence to Information Retrieval by way of Document Classification based on Vector Space Model using Inter-connected neurons with relevance feed back from the retrieved documents to the intelligent classifier as well as to the user query. The basic idea is to integrate three existing techniques: classification, query expansion and relevance feedback both to classified documents and user query to achieve a concept-based information search for the Web.
Iranian International Journal of Science(Not Publish)
دانشگاه تهران
4
v.
0
no.
2003
https://iijs.ut.ac.ir/article_30796_8864bb28690de8347d36b8d712de71d1.pdf
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M.
Shiahmorteza
author
R.
Yazdanparast
author
M.
Zolnorian
author
text
article
2003
per
Variation in the composition of the production media were investigated to optimize the excretion of the cellulolytic enzymes by Trichoderma reesei (CBS383.73) and a Botrytis sp. isolated from the microflora of Iran. The culture filtrate of Trichoderma reesei showed a cellulolytic activity of 300 mFPU/ml after 13 days of growth in a medium containing walseth cellulose (0.5%, w/v)at pH 5. Under similar production conditions, except for the initial pH of 7, the culture filtrate of Botrytis sp. showed an activity of 360 mFPU/ml. Replacement of walseth cellulose with H2O2 – treated bagasse, Barely husks, wheat husks, or sawdust (0.5% w/v) in the presence of the inducer (0.5% w/v, walseth cellulase) enhanced the extent of enzyme production by Trichoderma reesei to 780 mFPU/mL. The Botrytis sp. did not excreate cellulolytic enzyme using (as the main sources of carbon), the H2O2-treated bagasse or sawdust plus 0.5% walseth cellulose. However, the culture filtrate of the Botrutis sp. showed a cellulolytic activity of 679 or 463 mFPU/ml using the H2O2-treated wheat or barely husks(1% w/v) plus 0.5% walseth cellulose, respectively. In addition, the Calcium hydroxide treatment of the agricultural wastes depressed totally the enzyme secretion by the Botrytis sp. except for the treated sawdust which enhanced the enzyme production almost by a factor of seven in the absence of the inducer
Iranian International Journal of Science(Not Publish)
دانشگاه تهران
4
v.
0
no.
2003
https://iijs.ut.ac.ir/article_30797_54f084d8f9520bfbb4739e345df5888a.pdf