Neutron-irradiation effects on track etching and optical characteristics of CR-39 (DOP) nuclear track detector

The effects of thermal neutron-irradiation in the neutron fluence range of (1.77–7.08) 10¹¹ n/cm², on the etching and optical characteristics of diethylene glycol bis allyl carbonate (dioctyl phthalate doped), CR-39 (DOP) nuclear track detector have been studied using etching and UV–visible spectroscopic techniques. The bulk etch rates determined at different fluences were found to increase with an increase in neutron fluence up to 3.54 × 10¹¹ n/cm², and then decrease at higher neutron fluence. The optical absorption spectra in the wavelength range of 200–800 nm were also recorded for the unirradiated and neutron irradiated samples in the above fluence range. The optical energy gaps (E _g) were determined by the shift in optical absorption edges as observed by UV–visible spectra of the neutron irradiated sample, using Tauc’s expression. The UV–visible spectra results were further supported by determining the activation energies for bulk etching.     

Freezing-induced splashing during impact of molten metal droplets with high Weber numbers

The impact of molten tin droplets (0.6 mm diameter) on solid surfaces was observed for a range of impact velocities (10–30 m/s), substrate temperatures (25–200 °C) and substrate materials (stainless steel, aluminum and glass). The substrate was mounted on the rim of a rotating flywheel and the collision of single droplets with the moving substrate was photographed. Droplet impact Reynolds number ranged from 2.2 × 10⁴ to 6.5 × 10⁴ and Weber number from 8.0 × 10² to 7.2 × 10³. On a hot surface there was no splashing and droplets spread to form disk-like splats with smooth edges. Solidification around the edges of droplets spreading on cold surfaces created a solid rim that obstructed flow and triggered splashing. An analytical model was developed to predict the transition temperature at which splashing disappeared by assuming that the thickness of the solid layer had to equal that of the splat in the time the droplet spread to its maximum extent in order to obstruct liquid flow. The model predicted the transition temperature for aluminum and stainless steel surfaces, assuming that thermal contact resistance between the droplet and substrate varied between 10⁻⁶ and 10⁻⁷ m² K/W. The model also predicted that tin droplets would not splash on glass surfaces maintained at or above room temperature, and this was confirmed by experiments.     

Influence of corn processing and frequency of feeding on cow performance

Twenty cows, including five fitted with rumen cannulae, were used to study the influence of corn processing and frequency of feeding on milk yield and ruminal fermentation characteristics. Cows were assigned to five treatments in a 5 x 5 Latin square experiment. Each period was 3 wk. Cows were fed 45% forage and 55% grain in a total mixed ration. Diets contained 35% corn either coarsely ground and fed once a day (1x), finely ground (FGC) fed 1x, steam-flaked (SFC) fed lx, FGC fed four times a day (4x), or SFC fed 4x. Processing of corn and frequency of feeding had no influence on dry matter intake. Digestibility of starch was increased 6 and 3 percentage units by feeding SFC corn compared with coarsely and finely ground corn, respectively. Cows fed SFC or FGC produced 4% more milk with lower fat content compared with coarsely ground corn. Increasing the feeding frequency did not improve milk fat content. The fat-corrected milk yield was not different among treatments. Feeding SFC resulted in a low acetate-to-propionate ratio in the rumen fluid than FGC. Cows fed SFC produced 45 and 115 g more milk protein per cow/d than cows fed FGC or coarse, respectively. With the value of increased milk protein observed in this study, it would be more economical to feed SFC or finely ground corn to dairy cows compared with coarse ground. The breakeven price of flaking corn in this study was $32 and $12/metric tonne compared with coarse and FGC, respectively. Based on a survey conducted by the authors, the price of flaking corn in the United States ranged between $7 to $22/metric tonne during year 2000.     

Conjugated linoleic acid content of milk and cheese from cows fed extruded oilseeds

Extruded oilseeds were fed to 24 dairy cows to study the influence on the conjugated linoleic acid content of milk and cheese. Cows were fed one of three diets that contained forage and grain in a ratio of 47:53. A control diet containing 13.5% soybean meal was compared with diets containing 12% full fat extruded soybeans or 12% full fat extruded cottonseed. The control, extruded soybean, and extruded cottonseed diets contained 2.73, 4.89, and 4.56% fatty acids, respectively. Measurements were made during the last 5 wk of the 8-wk experiment. The DM intakes and 3.5% fat-corrected milk yields were higher for cows fed the extruded soybean and extruded cottonseed diets than for cows fed the control diet. A tendency for lower fat and protein contents in the milk of cows fed the extruded soybean and extruded cottonseed diets was detected. Most of the C18 fatty acids were increased in the milk and cheese when extruded soybeans and cottonseeds were fed. The conjugated linoleic acid content in milk and cheese increased a mean of 109% when full fat extruded soybeans were fed and increased 77% when cottonseeds were fed compared with the conjugated linoleic acid content when the control diet was fed. Processing the milk into cheese did not alter the conjugated linoleic acid content. The conjugated linoleic acid content of milk and cheese can be increased by the inclusion of full fat extruded soybeans and full fat extruded cottonseeds in the diets of dairy cows.     

Synthesis,characterization and use of polymer‐supported phase transfer catalyst in organic reactions

A polymer‐supported (PS) phase transfer catalyst, polyethylene‐g‐quaternary ammonium salt (PE‐g‐Q_N⁺), is prepared through a three‐step graft copolymerization of maleic anhydride (MAn) onto polyethylene (PE) by photochemical method using 1% benzophenone (Bz) as photosensitizer. Post grafted acid hydrolysis of polyethylene‐g‐maleic anhydride (PE‐g‐MAn) results in the preparation of PE‐g‐succinic acid which on further treatment with tetrabutylammonium bromide (TBAB) under basic conditions in tetrahydrofuran (THF) gives PE‐g‐Q_N⁺. Optimum conditions pertaining to maximum percentage of grafting have been evaluated as a function of concentration of maleic anhydride, amount of photosensitizer, and time of reaction. Maximum percentage of grafting (25%) was obtained using 3.57 mol of MAn and 0.5 mL of 1% Bz in 120 min. The PE and graft copolymers, PE‐g‐MAn, and PE‐g‐Q_N⁺ were characterized by FTIR Spectroscopy and thermogravimetric analysis (TGA). The ionic nature of quaternary ammonium salt, PE‐g‐Q_N⁺ has also been confirmed by conductance measurements. PE‐g‐Q_N⁺ reagent have been used successfully for polymerization, amidation, and esterification reactions. The products obtained were characterized by FTIR and H¹NMR spectral methods. The reagent was reused for the further reactions and it was observed that the polymeric reagent polymerize, amidate, and esterificate the compounds successfully but with little lower product yield. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Magnetic, magnetocaloric and neutron diffraction studies on TbNi5−xMx (M = Co and Fe) compounds

The effect of substitution of Co and Fe for Ni in TbNi₅ on the structural, magnetic and magneto-thermal properties has been investigated. Considerable enhancement of Curie temperature is observed with Fe substitution, whereas the increase is nominal in the case of Co. Neutron diffraction measurements reveal the redistribution of moments and site preference of substitutional ions in Ni 2c and 3g sites. In TbNi₄Fe, both Ni and Fe as well as Tb are found to carry moment while in the case of TbNi₄Co, mainly Tb carries the moment. Magnetocaloric behavior has been investigated from the magnetization and the heat capacity measurements. The magnetic and magnetocaloric properties are found to be strongly correlated in these compounds.     

Buoyancy-aided momentum and heat transfer in a vertical channel with a built-in square cylinder

This study focuses on the confined upward flow and heat transfer around a square cylinder under the effect of aiding buoyancy (Richardson number, Ri=0–1) in the vertical channel for Reynolds number (Re)=1–40 and blockage ratio (BR)=25–50% for the air as working fluid. Flow is found to be steady and symmetric for the range of settings. For Re≤2, no separation zone occurs for BR=25% and 30%. However, for BR=50%, no wakes are observed for Re≤3. The onset of flow separation takes place between Re=2 and 3 for BR=25% and 30%; whereas, for BR=50%, it exists between Re=3 and 4, irrespective of the value of Ri. Heat transfer correlations have also been obtained at different values of Re, BR and Ri.     

Steady mixed convection across a confined square cylinder

The effects of cross-buoyancy and of Prandtl number on the flow and heat transfer characteristics of an isothermal square cylinder confined in a channel has been investigated here. The numerical results have been presented for the range of conditions as: 1 ≤ Re ≤ 30, 0.7 ≤ Pr ≤ 100 (the maximum value of Peclet number being 3000) and 0 ≤ Ri ≤ 1for a fixed blockage ratio of 0.125. The overall drag and lift coefficients, local and average Nusselt numbers and the representative streamline and isotherm plots are presented to elucidate the role of Reynolds number, Prandtl number and Richardson number. The drag coefficient is found to be less sensitive to the Richardson number than the lift coefficient.