Vol. 5 Issue 2
Darwish Amin
A new simple, accurate, and sensitive titrimetric method has been developed for the determination of antipyrine, 4-aminoantipyrine and dipyrone. The method is based on the oxidation of the entitled compounds with an excess of a chloroform solution of iodine, removal of its excess and determination of the resulting iodide by the "so-called" Leipert procedure after 6-fold amplification. Antipyrine and 4-aminoantipyrine undergo quantitative oxidation in a media ranging from 0.1 M hydrochloric acid to 0.1 M sodium acetate solution with a consumption of 2 and 3 moles of iodine per mole of antipyrine and 4-aminoantipyrine, respectively. However, dipyrone consumes 3 moles of iodine in 0.1 M hydrochloric acid solution. The present method enables analysis of amounts as low as 30.10 and 20 micrograms of antipyrine, 4-aminoantipyrine and dipyrone, respectively. The recoveries ranging from 98.1-102.2%, and standard deviation from 0.1-1.6%, depending on the concentration level.
Hamad A. Al-Lohedan
Cationic micelles of myristyltrimethylammonium bromide (MTABr) and cetyltrimethylammonium bromide (CTABr) inhibit the reactions of hydroxide ion with N-alkyl-2-chloropyridinium salts (alkyl = Me, Et, propyl, i.e., A1-3) because the substrates are largely in the aqueous pseudophase which is depleted in OH- by cationic micelles. Added Br- displaces OH- from the micelles and decreases micellar inhibition. The corresponding reaction of decyl (A4) and tetradecyl (A5) derivatives is catalyzed by both MTABr and CTABr which bind both reactants. These divers rate effects can be accounted for quantitatively in terms of the pseudophase ion-exchange model, which considers reactions in both the aqueous and micellar pseudophases and the distribution of both reactants between these pseudophases
Ghalib M.A. El-Asa'ad
Seven trace fossils from three Mesozoic formations in Central Saudi Arabia and their associated palaeoenvironments are described. These trace fossils are: Rhizocorallium, recognized from burrowed micrite and shelly biomicrite of the Upper Marrat Formation (Upper Toarcian) at Khashm Qaradan. The micrite and shelly biomicrite were deposited in an intertidal to subtidal environment. Thalassinoides sp. 1, recognized from supratidal, heavily dolomitized micrites of the Lower Marrat Formation (Lower Toarcian) at Khashm Al-Dhibi and from an intertidal, heavily burrowed algal biomicrite of the lowermost part of the Aruma Formation (Coniacian) at Khashm AI-Khanasir and Khashm Al-Buwaibiyat. Chondrites, Thalassinoides ornatus Kennedy, Thalassinoides saxonicus Geintz and Thalassinoides sp. 2 were recognized from arenaceous limestone lithofacies (biopelsparite, biorudmicrite, biosparimicrite) of the Middle part of the Hanifa Formation (Oxfordian) in the Ma'ashbah area. The arenaceous limestone lithofacies were deposited on the inner shelf of a shallow, high energy, marine basin above wave base. The trace fossil Laevicyclus was recognized from fossiliferous, dolomitic biomicrite of the Middle Aruma Formation (Maestrichtian) at Khashm Hajajah. These fossiliferous, dolomitic biomicrites were deposited in a shallow, littoral, warm marine environment.
Abdulaziz S. Al-Ruwais and Adel A. Ali
An analysis of the fading problem encountered on a microwave link along the Red Sea coast of Saudi Arabia is presented. The analysis is based on field measurements of two received signals at 4 and 6 GHz. Obstruction and multipath fading are identified to be the main types of fading which cause the outage of this link. Analyses of possible diversity improvement are presented for both frequency and space diversity . It is shown that modified antenna system design or practical increase in tower heights are unlikely to bring a satisfactory solution to the problem. Moving some of the tower sites away from the coast will lead, possibly, to more reliable system performance.
M.Hamed, N. Farrag and H. Yasin
The mathematical analysis for determining the optimum and economic compensation of the reactive power of loads in distribution networks is presented for both single and multi-feeder systems. This entails study of the optimum distribution of 1lkV-rating capacitors in the network and is repeated for the case when the total installed capacity of capacitors is unknown. The economic criteria for the use of 0.4 kV capacitors is also considered and their need checked by a deduced formula. An algorithm for obtaining the economic distribution of capacitors is determined in order to compensate the reactive powers in transmission systems. It is based on both a hierarchy principle and partition technique with the equivalent circuit at different hierarchy levels. The parameters of the equivalent circuit depend on the economic characteristics of reactive power compensation. For simplicity, these characteristics may be approximated in the form of a second-order polynomial.
N.A. Razik and M. Abdul Momen
The effects of austenitizing time and temperature, water, air, oil, and molten lead quenching media on the mechanical and structural properties of the hot-rolled steel have been investigated using Vickers hardness testing. tensile testing and the scanning electron microscopy.
The microstructure of the as-received or the air-quenched steel consisted of proeutectoid ferrite and pearlite areas. Water quenching has produced high strength lenticular martensite but quench cracks were observed. Bainitic structures were obtained in the palm-oil quenched specimens. When Petromin oil was used as a quenching medium, a lamellar martensitic structure was produced.
From the strengthening point of view it was suggested that the rods produced after hot rolling could be cooled directly into palm oil or Petromin-type oil as this would improve the strength of the steel by about 20-60%.
Mohamed A. Gaffar and Abd El Aziz A.F. Abd El Aziz
Large single crystals of pure and doped Triglycine sulphate are obtained in the temperature range 44 to 28°C using the falling temperature technique. The divalent ions Ni2+, C02+ and Cu2+ as well as the trivalent Cr3+ and Fe3+ are used as the dopant ions. The effect of these ions upon the speed of growth, crystal parameters, density, crystal morphology, surface relief, color and crystal purity is presented. The variation in the measured physical properties is strongly dependent on the complexes formed by the dopants.
H.J.W. Muller-Kirsten
The relationship between the splitting of asymptotically degenerate energy levels and the large order behavior of the Rayleigh-Schrodinger perturbation expansion is investigated in the case of a periodic potential
I.I. Bashter and P.N. Cooper
The neutron fluxes from an Am/Be source and from a graphite slab bombarded with 14.1 MeV neutrons have been measured by an NE-213 organic scintillator using a zero cross-over technique and compared with that measured by a charge comparison method. The accuracy of the measured Am/Be spectrum was examined using the standard spectrum and other measurements. Measured spectra from the graphite assembly were tested using the calculated results of the one dimensional discrete ordinate code ANISN using the ZZFEWG 1/31-1F neutron library. The experimental technique, in this work, is shown to be useful in measuring the neutrons in the range 14.1 MeV to 1.8 MeV for D-T fusion reactor neutronics
K.S. Bhatia and M. Marafi
WE have measured radiative lifetimes of 4p^2 3P(2,1,0) states of calcium using time resolved laser spectroscopy. The States were populated by stepwise excitation using a combination of pulse modulated tunable dye laser and a weak d.c. discharge. Measured lifetimes tau for these states are tau1 (3p2) = 6.6 (4)ns, tau2 (3P1)= 5.4(4)ns and tau3 (3P2) = 7.3 (7)ns