Effect of cathode structure on neutron yield performance of a miniature plasma focus device

In this Letter we report the effect of two different cathode structures - tubular and squirrel cage, on neutron output from a miniature plasma focus device. The squirrel cage cathode is typical of most DPF sources, with an outer, tubular envelope that serves as a vacuum housing, but does not carry current. The tubular cathode carries the return current and also serves as the vacuum envelope, thereby minimizing the size of the DPF head. The maximum average neutron yield of (1.82±0.52)×¹⁰⁵ n/shot for the tubular cathode at 4 mbar was enhanced to (1.15±0.2)×¹⁰⁶ n/shot with squirrel cage cathode at 6 mbar operation. These results are explained on the basis of a current sheath loading/mass choking effect. The penalty for using a non-transparent cathode negates the advantage of the smaller size of the DPF head.     

Acoustic wave propagation in barium monochalcogenides in the B1 phase

Temperature dependence of ultrasonic attenuation due to phonon-phonon interaction and thermoelastic loss have been studied in (NaCl-type) barium monochalcogenides [BaX, X = S, Se, Te], in the temperature range 50–500 K; for longitudinal and shear modes of propagation along 〈100〉, 〈110〉, 〈111〉 directions. Second and third order elastic constants have been evaluated using electrostatic and Born repulsive potentials and taking interactions up to next nearest neighbours. Gruneisen parameters, nonlinearity constants, nonlinearity constants ratios and viscous drag due to screw and edge dislocations have also been evaluated for longitudinal and shear waves at 300 K. In the present investigation, it has been found that phonon-phonon interaction is the dominant cause for ultrasonic attenuation. The possible implications of results have been discussed. The text was submitted by the authors in English.     

Cosmic (Super)String Constraints from 21 cm Radiation

We calculate the contribution of cosmic strings arising from a phase transition in the early Universe, or cosmic superstrings arising from brane inflation, to the cosmic 21 cm power spectrum at redshifts z > or =30. Future experiments can exploit this effect to constrain the cosmic string tension G mu and probe virtually the entire brane inflation model space allowed by current observations. Although current experiments with a collecting area of approximately 1 km2 will not provide any useful constraints, future experiments with a collecting area of 10(4)-10(6) km2 covering the cleanest 10% of the sky can, in principle, constrain cosmic strings with tension G mu > or = 10(-10)-10(-12) (superstring/phase transition mass scale >10(13) GeV).     

Ferulic Acid: A Natural Phenol That Inhibits Neoplastic Events through Modulation of Oncogenic Signaling

Despite the immense therapeutic advances in the field of health sciences, cancer is still to be found among the global leading causes of morbidity and mortality. Ethnomedicinally, natural bioactive compounds isolated from various plant sources have been used for the treatment of several cancer types and have gained notable attention. Ferulic acid, a natural compound derived from various seeds, nuts, leaves, and fruits, exhibits a variety of pharmacological effects in cancer, including its proapoptotic, cell-cycle-arresting, anti-metastatic, and anti-inflammatory activities. This review study presents a thorough overview of the molecular targets and cellular signaling pathways modulated by ferulic acid in diverse malignancies, showing high potential for this phenolic acid to be developed as a candidate agent for novel anticancer therapeutics. In addition, current investigations to develop promising synergistic formulations are also discussed.     

A microhardness test to analyse thermal change in guargum, polyacrylonitrile and their blends

The Vickers microhardness test is found to be a suitable analytical method for studying thermal change in thin films of polymers. It is utilised to analyse the effect of thermal pretreatment (annealing and quenching) on the surface microhardness of guargum (GG); a natural polymer), polyacrylonitrile (PAN; a synthetic polymer) and their cast blends, guargum-grafted-polyacrylonitrile (GG-g-PAN) and polyacrylonitrile-guargum (PAN-GG). Annealing at various temperatures reveals the change in configuration and crystallinity of thin films of polymers. Peak values of hardness are found to occur in GG, PAN and PAN-GG but not in GG-g-PAN. The quenched hardness for GG is found to be nonlinear with temperature. However, for other polymers quenched hardness decreases, initially, up to a certain temperature and then starts increasing; such temperatures for PAN, PAN-GG and GG-g-PAN are 86, 66 and 86°C, respectively. The behaviour of polymer blends on quenching can be represented by a calculated value of the exponent which is 0·62 and 0·75 for GG-g-PAN and PAN-GG, respectively.     

Paraconductivity of Ge-covered tin films,II

The temperature dependence if the excess electrical conductivity of thin superconducting tin films (a) covered by a protective germanium layer and (b) sandwiched between two germanium layers above the transition temperature has been measured. These thin films have been deposited on glass substrates held at room temperature. It was found that the pair- breaking parameter δ for germanium covered tin filns varies exponentially with normal state sheet resistance R^□_N and could be represented by δ = 3.77×10^-4 exp (1.76R^□_N) in the range 0.28?R^□_N<1.6ohm/?. Higher R^?_N samples show close agreement with Aslamazov-Larkin expression. Information obtained from type (b) samples showed that although protective germanium layer increases the δ values, sandwich type structure lowers it significantly. Results show that such a strong dependence of δ could be related to changes in the Cooper pair relaxation time and the proximity effect.     

Synthesis and properties of some chromium(III) β-diketonate complexes

Summary Equimolar quantities of CrCl₃ · 3THF and-diketones, -dkH, react to yield CrCl₂(-dk) · 2THF and CrCl₂(-dk) · THF complexes in coordinating and noncoordinating solvents respectively. For 1 : 2 and 1 : 3 molar ratios of reactants, derivatives of general formulae CrCl(-dk)₂ and Cr(-dk)₃ (where-dkH = acerylacetrrnc, benzoylacetonc and dibenzoylmethane) have been isolated. All complexes have been characterized by elemental analysis, molecular weights and by i.r. spectra.     

On neutron charge structure

The aim of the present work is to investigate the charge structure of neutron by calculating its root mean square charge radius r _n ^{2 1/2} and the corresponding charge form factor,G _n(q), within the general framework of quark-parton model. The neutron (the nucleon in general) is considered to be disc-like in conformity with the idea of Lorentz invariance. Using the proton charge radius, r _p ² =0·707 fm² as input, our calculations not only reproduce the observed negative sign correctly but also give reasonable value for the magnitude of r _n ² when compared with the experimental limits. –0·16r _n ² –0·11 (fm²). Predictiona are also made for the proton and the neutron charge form factors and the results compared with the data.One of us (D. P.) would like to express his gratitude to Professor A. N. Mitra for his interest and advice in the work, and to Dr. S. M. Mustafa for the warm hospitality at the University of Mosul.     

Synthesis of Silicon Carbide Whiskers from Substituted Silicon Alkoxides and Rayon Fibres

Silicon carbide whiskers (SiC_W) were synthesized through sol-gel process by impregnating the rayon fibres with sols of methyltriethoxysilane (MTEOS), phenyltriethoxysilane (PTEOS) and dimethyldiethoxysilane (DMDEOS) and pyrolyzing the impregnated rayon fibres at 1400°C in argon atmosphere. The SiC_W synthesized through this method were needle like, straight and their aspect ratio was found to be greater than 100 except in the case where DMDEOS was used as silica source.