Multistep scattering in the 160 MeV208Pb(α, α′) reaction

New experimental data has been obtained for the²⁰⁸Pb(α, α′) reaction induced by 160 MeV alpha particles, for inelastic scattering to forward angles. We use these data to investigate the applicability of the multistep scattering theory of Feshbach, Kerman, and Koonin for describing this reaction. The mechanism we study, following the work of Gadioli et al. [1], is of the incident alpha particle remaining intact throughout the scattering process, exciting nucleon particle-hole pairs through multistep process. We conclude that this mechanism, combined with compound nucleus decay at low emission energies, can account for much of the observed data. However, there are indications that other processes also contribute at energies above the compound nucleus emission regime, and we outline future theoretical analyses that are needed.     

Network design using the characteristic polynomial

The characteristic polynomial is shown here to be an effective tool in network design. A versatile computer program is constructed to tackle different kinds of network with different specifications. The method has been applied to lumped, distributed and lumped-distributed filters taking examples of induced losses or mismatches.     

The effect of oxygen plasma generated by different microwave modes on NdBa2Cu3O6+δ superconductor: structure and IR studies

The effect of longitudinal and transverse modes of oxygen plasma generated by microwave source with frequency 2.45 GHz has been used to characterize polycrystalline samples of NdBa₂Cu₃O_6+δ (Nd-123) high T_c-superconductor. For this purpose we have developed a simple oxidation technique, used by us earlier, to investigate the effect of different modes on the appearance of superconductivity in Nd-123. Our main results show that the mode of microwave plasma and time of exposure can control the local arrangement of oxygen vacancies in CuO_δ basal plane. Samples exposed to the transverse mode reveals a well ordered orthorhombic phase transition while the longitudinal modes caused the samples to have a non-superconducting tetragonal structure for all of the exposure time. The T_c vs. δ curve does not show the typical 60 K plateau corresponding to the ortho-II phase. The IR spectrum show bands at shorter wavelengths which corresponding to the metal oxides.     

Internal Bremsstrahlung accompanying non-unique second-forbiddenβ-decay of36CL

The inner Bremsstrahlung spectrum (I.B.) associated wih the non-unique second forbidden-transition of³⁶Cl was measured using a single channel NaI (Tl) scintillation spectrometer. After making all the necessary corrections, the experimental results were compared with the corresponding theoretical distributions due to the KUB, Lewis and Ford, Nilsson, Ford and Martin and Chang and Falkoff. Also a comparison with those calculated according to Nilsson theory after applying the shape correction factor (M. KUB) was done. The measured spectrum is found to show fairly good agreement with M. KUB theory and its found to deviate therafter from all five theories.The authors would like to thank Prof. Dr. M. El-Nadi and Prof. Dr. O.E. Badawy for their suggestions, interest and encouragement.     

Photon-electron energy deposition in CANDU reactor channels: Simulation and modelling

Simulation of photon-electron transport in a CANDU reactor fuel channel using the Monte Carlo method for calculating the energy deposition in the coolant is studied. The geometry of the CANDU fuel channel is very complex so methods that make such simulations more practicable, without adversely affecting the results, are introduced. In this regard, the use of simplifying assumptions and simplified geometrical models on the performance of two different Monte Carlo codes has been compared. An ETRAN-based code (SANDYL), and the code EGS4 produced comparable results, although the former performs faster in accounting for low energy electrons. A simplified computational model is also introduced. This model is based on decoupling photon-electron transport simulations by the use of electron-energy-transfer functions. The results obtained using the model are successfully validated using the EGS4 and SANDYL codes. A significant computational speedup (about a factor of seven compared to Monte Carlo simulations) is achieved with this model.     

Simultaneous determination of Sudan dyes and carotenoids in red pepper and tomato products by HPLC

To simultaneously detect Sudan dyes and carotenoids in red pepper and tomato products, high-performance liquid chromatography (HPLC) methods with photodiode-array detection are developed and validated. The methods include the use of end-capped and nonend-capped adsorbents with a gradient elution system starting with water containing methanol. Water content of 9% in the starting mobile phase is found to be necessary to ensure sufficient separation of Sudan dyes and to avoid overlapping or interference with the carotenoids of considerable content. The data of the validation reveal the accuracy and precision of the developed methods. A limit of Sudan dyes detection of 1-5 microg/g in red pepper or tomato sauce could be approached. The methods provide excellent separation of the carotenoids from the unsaponified extracts of red pepper and the tomato products.     

Conductance of acidified stannic acid solutions

Summary The conductance of sodium stannate solutions containing varying quantities of SnO₂, was measured after admixing to hydrochloric acid. The conductance drops as the SnO₂ content increases and then passes through a maximum, the position of which depends on the concentration of stannic oxide in the solution. The drop in conductance is due to adsorption of H⁺ ions from solution. The presence of the maxima may be due to a change in the size of the micelles. Similar experiments were carried out with perchloric or tartaric acid as acidifying agents. Electrophoretic mobility experiments indicated that the micelles are positively charged in HCl solutions and that the Zeta potentials vary in the same direction as that of the conductance. Desorption of ions could be affected by dilution.

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Zusammenfassung Die Leitf?higkeit von Natriumstannatl?sungen, die verschiedene Mengen an SnO₂ enthalten, wurde nach Zumischung von Salzs?ure gemessen. Die Leitf?higkeit f?llt, wenn der Zinnoxydgehalt steigt, sie durchl?uft dann ein Maximum, dessen Lage von der Konzentration des Zinnoxyds in der L?sung abh?ngt. Der Abfall der Leitf?higkeit ist der Adsorption von H-Ionen aus der L?sung zuzuschreiben. Das Auftreten des Maximums k?nnte mit einem Wechsel in der Gr?\e der Mizellen zusammenh?ngen. ?hnliche Experimente wurden mit perchloriger oder Weins?ure als azidifizierenden Medien durchgeführt. Aus Messungen der elektrophoretischen Beweglichkeit folgt, da\ die Mizellen in HCl-L?sungen positiv geladen sind und da\ die Zetapotentiale in gleicher Art diese Leitf?higkeiten variieren. Eine Desorption von Ionen konnte durch Verdünnung erreicht werden.

     

Triazoles and fused triazoles,III: Facile and efficient synthesis of 2,5-disubstituted-s-triazolo[3,4-b]-1,3,4-thiadiazoles

Summary The development of a facile and efficient method for the synthesis of 2,5-diaryl-s-triazolo[3,4-b]-1,3,4-thiadiazoles4 a–e from the corresponding 3-aryl-4-amino-5-mercapto-s-triazole (2), is described. 3-Aryl-4-arylideneamino-5-mercapto-s-triazoles (3 a–e) were cyclized to compounds4 a–e by heating in nitrobenzene for a few minutes.Part II: See Ref. [11]