Fluidized-bed reactor modeling for production of silicon by silane pyrolysis

An ideal backmixed reactor model (CSTR) and a fluidized bed bubbling reactor model (FBBR) were developed for silane pyrolysis. Silane decomposition is assumed to occur via two pathways: homogeneous decomposition and heterogeneous chemical vapor deposition (CVD). Both models account for homogeneous and heterogeneous silane decomposition, homogeneous nucleation, coagulation and growth by diffusion of fines, scavenging of fines by large particles, elutriation of fines and CVD growth of large seed particles. At present the models do not account for attrition. The preliminary comparison of the model predictions with experimental results shows reasonable agreement. The CSTR model with no adjustable parameter yields a lower bound on fines formed and upper estimate on production rates. The FBBR model overpredicts the formation of fines but could be matched to experimental data by adjusting the unkown jet emulsion exchange efficients. The models clearly indicate that in order to suppress the formation of fines (smoke) good gas-solid contacting in the grid region must be achieved and the formation of the bubbles suppressed

Radiative capture of polarized neutrons by polarized protons

A model-independent irreducible tensor approach to p(n,gamma)d is presented and an explicit form for the spin-structure of the matrix for the reaction is obtained in terms of the Pauli spin-matrices for the neutron and the proton. Expressing the multipole amplitudes in terms of the triplet --> triplet and singlet --> triplet transitions, we point out how the initial singlet and triplet contributions to the differential cross section can be determined empirically.Comment: Revised version; typeset using RevTeX4; 6 pages, no figure

Deuteron photodisintegration with polarized photons at astrophysical energies

Following precise experimental studies at the Duke Free-Electron Laser Laboratory, we discuss photodisintegration of deuterons with 100% linearly polarized photons using a model independent theoretical approach taking together $M1$ and $E1$ amplitudes simultaneously. The isoscalar $M1_s$ contribution is also taken exactly into account. From the existing experimental measurement on doubly polarized thermal neutron capture, it is seen that the isoscalar $M1_s$ contribution could be of the same order of magnitude as the experimentally measured cross sections at energies relevant to Big Bang Nucleosynthesis (BBN). Therefore appropriate measurements on deuteron photodisintegration are suggested to empirically determine the $M1_s$ contribution at astrophysical energies.Comment: 5 Pages, Latex-2

Standards relevant to transformers – Part III

CIGRÉ counts more than 3,500 experts from all around the world working together to optimise the existing equipment and power systems, including transformers

Curcumin, garcinol and dietary N-​3 fatty acids, lower the release of lysosomal enzymes in rat peritoneal macrophages

Male Wistar rats (12rats​/group) were fed a diet contg. 8 wt % coconut oil or groundnut oil or cod-​liver oil for a total period of 8 wk. The diets were also supplemented with 2 wt % groundnut oil for providing essential fatty acids. During the last 2 wk, 6 rats form each group were addnl. given curcumin (30 mg​/kg body wt​/day) or garcinol (5 mg​/kg body wt​/day) in 1 mL groundnut oil. The peritoneal macrophages from rats fed cod-​liver oil diet secreted lower levels of lysosomal enzymes collagenase, elastase and hyaluronidase as compared to those from rats fed coconut oil or groundnut oil diets. Curcumin and garcinol significantly lowered the secretion of these lysosomal enzymes from macrophages in animals given coconut oil or groundnut oil diet. These studies indicated that dietary cod-​liver oil (rich in n-​3 fatty acids)​, and spice principles curcumin and garcinol can lower the secretory functions of macrophages in a beneficial manner. (Mol Cell Biochem 203:153-​161, 2000)​

Standards relevant to transformers – Part IV

Last three parts of this series covered the evolution of Standards / Technical Brochures related to Power Transformers under IEC, IEEE and CIGRE and listed current standards issued by them. Now we see the evolution of transformer standards in Britain and the current position of European Standards (EN) on Transformers