Retention and Distribution of 1-Naphthol and Naphthol Polymerization Products on Surface Soils

Sorption and extractability of naphthol and naphthol polymerization products (NPP) were evaluated in two surface soils. NPP were generated by the addition of horseradish peroxidase and H2O2 to naphthol solutions in contact with the surface soils. While NPP retention on the forest soil was lower compared to the parent naphthol, no difference in sorption of naphthol and NPP was observed in the agricultural soil. The agricultural soil retained more naphthol and NPP than the forest soil. The NPP sorption behavior noted in this study was in contrast to that of phenol polymerization products observed by other researchers. The presence of phenol and 2,4-dichlorophenol as cosolutes had no significant impact on naphthol or NPP retention on the two soils, and naphthol was more easily extracted from both soils whenever phenol was present as a cosolute. Characterization of the naphthol polymerization products using reverse-phase high-pressure liquid chromatography and octanol-water partitioning indicated that significant fractions of the water-soluble and insoluble NPP were comprised of oligomers that were more polar than the parent 1-naphthol. This decrease in polarity upon polymerization is believed to have been responsible for the NPP retention and binding behavior observed in this study.     

Reactive ion etching of trenches in 6H-SiC

In this paper, we report the reactive ion etching (RIE) of trenches in 6H-silicon carbide using SF₆/O₂. The plasma parameters: etchant composition, gas flow rate, chamber pressure, and radio frequency power were optimized to obtain a maximum etch rate of 360Å/min. The etch rate of SiC was found to exhibit a direct correlation with the dc self bias except when the O₂ percentage was varied. Trenches were fabricated using the optimized conditions. It was found that the trench surface was extremely rough due to the aluminum micromasking effect. To overcome this effect, a Teflon^TM sheet was used to cover the cathode during the experiment. The trenches fabricated using this modification were found to have smooth etched surfaces and sidewalls. The angle of anisotropy of these trenches was approximately 80° which is suitable for device applications.     

De-agglomeration of thorium oxalate - a method for the synthesis of sinteractive thoria

Thorium oxalate was obtained by precipitation in water and in non-aqueous solvents and de-agglomerated by ultrasonication in both aqueous as well as non-aqueous media. Sinteractive thoria (crystallite size 6-20 nm) obtained from the de-agglomerated thorium oxalate was characterised for residual carbon, crystallite size, specific surface area, particle size distribution and bulk density. Microstructure of the precursor and the product was studied using TEM and HRTEM. The morphology of the sintered pellets was studied using SEM. The reactivity of the calcined powders was determined by measuring the density of the sintered compacts. The solvent used for de-agglomeration was found to have significant influence on the microstructure of the powders. Thoria derived through aqueous precipitation route could be sintered to a density of 9.7 Mg m⁻³ at 1673 K. It was demonstrated that ultrasonic de-agglomeration could be a useful method for obtaining sinteractive thoria.     

Reduced computation blind super-exponential equaliser

Super-exponential blind equalisation methods offer a significant improvement over conventional techniques. The authors propose a new technique, the novel modified eigenvector approach (mEVA), and compare it with the eigenvector approach (EVA). It appears that the mEVA has the same performance as the EVA, but with with significantly reduced computation     

Deflection characteristics of some special configurations of snake-type robots

The redundant robots analyzed here have large numbers of degrees of freedom. Such robots are analogous to snake or tentacles and are useful for operation in highly constrained environments and novel forms of locomotion — here it has been defined as critical manipulation. In this paper the end-point deflection of hyper-redundant robots have been studied by parameterization of the flexible links of the robot manipulator. A number of planar configurations of the redundant manipulator were taken into consideration for the present study and the configuration which gives minimum end-point deflection has been recommended for the critical manipulation. This work is significant for some of the research activities recently going on in NASA's Kennedy Space Center towards the application of hyper-redundant robots for manipulation inside the space Shuttle Cargo Bay.     

EXSHOF: An artificial intelligence approach to high-order filter synthesis

A two-tier expert-system-based synthesis of high-order filters is developed. Expert-system techniques have been used for choosing a particular biquad structure and for selection of the high-order filter structure as well. The data inputs will be either filter specifications or transfer functions and the output will be a detailed filter circuit with all its element values. EXSHOF ( pert System based ynthesis of igh rder ilter) is totally menu-driven and highly interactive. It assumes little knowledge of computers or filters from the user. The complete package is implemented in Turbo PASCAL and Turbo PROLOG languages.     

Biomass and energy production in Casuarina equisetifolia plantation stands in the degraded dry tropics of the Vindhyan plateau, India

Two age groups of Casuarina equisetifolia (Forst.) plantation stands in the Renukoot forest division of the Vindhyan plateau were investigated over the span of three years for total and component biomass, annual net primary production, energy storage and annual net energy fixation. A high range of biomass (44–81 t ha⁻¹) was recorded in a densely populated stand at ages 5–7 years in comparison to a sparsely populated stand at ages 8–10 years. The contribution of the hole component gradually increased with increasing diameter class while foliage and branch components had a large proportion of biomass in the lower diameter classes. Maximum litterfall occurred in May and foliage litter contributed 87–95% of total litterfall. The energy content and storage in component parts were higher than some other promising tree species for energy plantation in the dry tropics. Production estimates of 19–29 t ha⁻¹ yr⁻¹ showed that the performance of Casuarina is good for dry tropical conditions. The biomass accumulation ratio and production efficiency showed a significant positive and negative (logarithmic) relationship, respectively with plantation age. The energy conserving efficiency of the 5-year old stand was more than twice that of the 8-year old stand.     

Chemical structure of coal macerals in Balmer 10 coal and fusinite from Illinois coal as indicated by reductive alkylation

A Canadian Cretaceous coking coal from the Balmer 10 seam, Fernie, British Columbia, was separated by sink-and-float methods into vitrinite and a semifusinite-rich fraction. A portion of the vitrinite fraction was oxidized in air at 100 °C for 72 h to destroy the coking properties. The fresh vitrinite, oxidized vitrinite, and semifusinite of the Balmer coal, and the fusinite from Illinois coal, were each subjected to the reductive alkylation procedure of Sternberg, to cleave the ether linkages and octylate the products. The oxygen functional groups before and after ether cleavage were determined, as were the extractabilities by benzene of the octylated products. Thus the molecular weights of the benzenesoluble fractions of the octylated cleavage products were: fresh vitrinite 1930, oxidized vitrinite 1830, and fusinite 1490. The molecular-weight distribution of the octylated cleavage products was estimated by volatility analysis, which demonstrated the presence of much lower-molecular-weight material. Dilatation analysis of fresh and oxidized vitrinite showed that after cleavage of the ether linkages with potassium in tetrahydrofuran, the two could be brought to the same state. The dilatation behaviour of semifusinite after cleavage of the ether links and octylation showed only contraction, whereas the oxidized vitrinite treated in a similar manner exhibited a large dilatation.     

Use of waste materials--Bottom Ash and De-Oiled Soya, as potential adsorbents for the removal of Amaranth from aqueous solutions

Bottom Ash, a power plan t waste material and De-Oiled Soya, an agriculture waste product were successfully utilized in removing trisodium 2-hydroxy-1-(4-sulphonato-1-naphthylazo)naphthalene-3,6-disulphonate--a water-soluble hazardous azo dye (Amaranth). The paper incorporates thermodynamic and kinetic studies for the adsorption of the dye on these two waste materials as adsorbents. Characterization of each adsorbent was carried out by I.R. and D.T.A. curves. Batch adsorption studies were made by measuring effects of pH, adsorbate concentration, sieve size, adsorbent dosage, contact time, temperature etc. Specific rate constants for the processes were calculated by kinetic measurements and a first order adsorption kinetics was observed in each case. Langmuir and Freundlich adsorption isotherms were applied to calculate thermodynamic parameters. The adsorption on Bottom Ash takes place via film diffusion process at lower concentrations and via particle diffusion process at higher concentrations, while in the case of De-Oiled Soya process only particle diffusion takes place in the entire concentration range.