Reaction of zirconium fluoride glass with water: kinetics of dissolution

When liquid water contacts a zirconium-barium-lanthanum fluoride glass, at least three different processes occur. Barium and zirconium fluoride dissolve into the water, water penetrates into the glass, and zirconium fluoride crystals grow on the glass surface, in static solution. The rate of dissolution, as measured by solution analysis, is possibly controlled by diffusion in the solid surface; surface blockage and surface reactions are other possible kinetic steps involved. Diffusion in solution is not the controlling mechanism. Hydrogen profiles in the glass surface suggest that the penetration rate of water into the glass is controlled by diffusion and a surface reaction.     

Non-darcy natural convection from a heated vertical plate in saturated porous media with mass transfer

The nonsimilar and self-similar flows for the steady natural convection over a vertical heated surface in a saturated porous medium with mass transfer using non-Darcy model have been studied under boundary layer approximations. The differential equations governing both the nonsimilar and self-similar flows have been solved numerically using an implicit finite-difference scheme developed by Keller. The results indicate that both heat transfer and velocity field are appreciably affected by the modified Grashof number and mass transfer except that the effect of the modified Grashof number on the heat transfer for large suction is very small. It is found that the maximum velocity occurs at the wall and it increases as the modified Grashof number or injection increases.     

Pad effects on material-removal rate in chemical-mechanical planarization

The role of a porous pad in controlling material-removal rate (MRR) during the chemical-mechanical planarization (CMP) process has been studied numerically. The numerical results are used to develop a phenomenological model that correlates the forces on each individual abrasive particle to the applied nominal pressure. The model provides a physical explanation for the experimentally observed domains of pressure-dependent MRR, where the pad deformation controls the load sharing between active-abrasive particles and direct pad-wafer contact. The predicted correlations between MRR and slurry characteristics, i.e., particle size and concentration, are in agreement with experimentally measured trends reported by Ouma¹ and Izumitani.²     

Photostability of polyetherurethaneureas

Polyetherurethaneureas (PEUUs) were synthesised from polyethylene-glycols (PEGs) of molecular weight 400, 600 and 1000, 4,4′-diphenylmethanediisocyanate (MDI) and aliphatic diamine chain extenders, 1,3-propanediamine (PDA) and 1,6-hexanediamine (HDA). Polymer films were irradiated with 365 nm light at 293 K and the effects of polyether soft segment length and urea hard segment on photo-oxidative stability were studied by following the variation in weight-average molecular weight (M _w), gel formation and stress-strain properties. Changes in ultraviolet and infrared spectroscopy were monitored on photo-oxidation and hydroperoxide content determined. The soft segment length was increased by increasing the molecular weight of PEG from 400 to 1000 and hard segment structure was changed by variation of diamine. It was noted that the structure of urea and polyether soft segment length plays an important role in photostability of PEUUs. PDA chain extended PEUUs were more stable than HDA chain extended PEUUs.     

Effect of Calcium Lactate, 4-Hexyl Resorcinol and Vacuum Packing on Physico-chemical, Sensory and Microbiological Qualities of Minimally Processed Litchi (Litchi chinensis Sonn.)

Litchi (Litchi chinensis Sonn.) fruits are very susceptible to pericarp browning which adversely affects consumer acceptability even though the aril portion remains in excellent condition. Litchi arils (litchis) were treated with a solution containing 0–2% (w/v) calcium lactate (CL), 0–0.02% (w/v) 4‐hexyl resorcinol (4‐HR) and 1% potassium sorbate. The pH of solution was adjusted to 4.0 with citric acid. Treated litchis were packed in polystyrene trays, over‐wrapped with polypropylene film, vacuum‐packed (0, 47409.3, 94831.9 Pa) and stored at 4 ± 2 °C. Drip losses, pH, total soluble solids (TSS), sensory attributes and microbiological quality of stored samples were estimated. A four‐factor, three‐level experimental design (D₆ Hokes design) with 19 experiments was chosen. Mathematical models were developed to analyse and predict the effect of CL, 4‐HR, in‐package vacuum and storage time on the responses. TSS, pH and sensory scores decreased significantly (P 0.01), whereas drip losses and microbial count increased significantly (P 0.01) with time. Drip loss was significantly (P 0.1) reduced by addition of CL. 4‐HR prevented browning and changes in colour score during storage were significantly less. Vacuum in packages exerted significant (P 0.01) effect over pH, TSS, sensory and microbiological qualities of minimally processed litchis.     

Miniaturization and bandwidth enhancement of a cavity backed circular microstrip patch antenna

The resonant frequency of a circular patch antenna with and without circular cavity is measured. The patch miniaturization in the presence of the cavity is proved. Different methods of reducing resonant frequencies and broadening bandwidth without significantly reducing antenna gain are presented. Capacitively loaded patch and slits on the patch stimulate the patch at lower frequencies and multiple resonances, thus help miniaturization. Finally ferrite loading on the feed probe further increases the bandwidth without significantly reducing the antenna gain. The method is much more improved than that for a resistive loaded patch and a deformed patch. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Fluorescence in situ hybridization (FISH): DNA probe production and hybridization criteria

We describe methods for the production of fluorescence in situ hybridization (FISH) probes and the utilization of these probes for the detection of complementary DNA sequences with accuracy and sensitivity for application in both basic research and clinical diagnosis. Due to the frequent use of FISH in many laboratories, it is important to apply the most convenient and reproducible approach. This review describes some of the most recent techniques, and includes versatile, effective and simple methods of probe production and fluorescence in situ hybridization. We also describe methods for the production of region-specific and chromosome-specific DNA probes and hybridization techniques for the visualization of these probes.