An examination by nitrogen adsorption of the thermal decomposition of pure and silica-doped goethite

Goethite, pure and doped with silica by co-precipitation, was calcined at temperatures up to 900°c. The textures of the goethites and derived iron oxides were examined by nitrogen adsorption and electron, microscopy. With the latter the progressive elimination at higher temperatures of the porosity created by dehydroxylation at 300°c was followed. A sample of iron oxide produced by calcination of pure goethite at 900°c was found to possess the simplest texture. The dimensionless adsorption isotherm for this sample, which is similar to that reported in the literature for alumina, provided the reference data used in the interpretation of the isotherms for the other samples. A number of features of the pore size data derived could be satisfactorily correlated with observations made in the electron microscope. Doping with silica caused the goethite needles to grow in spherulite-like aggregates. This texture inhibited interparticle sintering at high temperatures but did not influence the behaviour of the pore system produced in the needles by dehydroxylation.     

The nature of pseudoboehmite and its role in the crystallisation of amorphous aluminium hydroxide

Pseudoboehmite samples were prepared by ageing the amorphous hydroxide obtained by the hydrolysis of aluminium s-butoxide using water or aqueous ethanol. Further ageing resulted in the formation of a mixture of crystalline trihydroxides. The two re-crystallisation stages are accompanied by similar but opposite changes in the volume of the aqueous suspension but pseudoboehmite can only be identified by X-ray diffraction in a separated xerogel. Crystallinity of the latter was shown to be enhanced by preparation in 80% ethanol but at concentrations providing only a little more than the water needed for hydrolysis of the alkoxide a new modification of pseudoboehmite was observed. X-ray line broadening and displacement indicated that it possessed an even greater degree of lattice strain than exists in the common form. The composition and specific surface of a number of pseudoboehmite xerogels suggest that the major part of the water, in excess of that in the basic structures AlOOH, is present in a surface monolayer with a minor amount responsible for lattice strain.     

Predicting garment pattern dimensions from photographic and anthropometric data

Traditional linear measurements (lengths and circumferences taken over the body surface with a tape measure) were compared with measurements of frontal and lateral view photographs for usefulness in determining pattern dimensions for the upper torso of the female body form. The statistical regression models developed indicated that, while linear measurements provided slightly more accuracy in predicting a few of the pattern dimensions, the photographic measurements were more accurate in predicting others, particularly pattern angles. Photographic measurements hold promise as an alternative to the more intrusive linear measurements for predicting pattern dimensions.     

Generation of selenium hydride from alkaline solutions: a new concept of the hydride generation-atomic absorption technique

The use of hydride generation is often useful in environmental analysis. The normal acid sodium tetrahydroborate reaction provides exceptional sensitivity with continuous flow hydride generators. In some situations there are interferences which will mask the sensitivity. An alternative chemistry system is described here and is shown to offer similar sensitivity to that normally used. A commercial continuous flow analyser is used in this work.     

Safety of conjugated linoleic acid (CLA) in overweight or obese human volunteers

The main objective of the study was to investigate the safety of conjugated linoleic acid (CLA) in healthy volunteers. The effect of CLA on body composition was also investigated. The trial design was a randomized, double‐blind placebo controlled study including 60 overweight or obese volunteers (body mass index (BMI) 27.5—39.0 kg/m²). The subjects were divided into two groups receiving 3.4 g CLA or placebo (4.5 g olive oil) daily for 12 weeks. The safety was evaluated by analysis of blood parameters and by clinical examinations at baseline and week 12. Vital signs and adverse events were registered at baseline, week 6, and week 12. Bio Impedance Assessment was applied for body composition measurements. 55 subjects completed the study. Adverse events occurred in 10% of the subjects. No difference in adverse events or other safety parameters was found between the treatment groups. Small changes in the laboratory safety data were not regarded as clinically significant. Moreover, no clinically significant changes in vital signs were observed in any of the groups. In the CLA group, mean weight was reduced by 1.1 kg (paired t‐test p = 0.005), while mean BMI was reduced by 0.4 kg/m²(p = 0.007). However, the overall treatment effect of CLA on body weight and BMI was not significant. There were no differences found between the groups with regard to efficacy parameters. The results indicate that CLA in the given dose is a safe substance in healthy populations with regard to the safety parameters investigated.     

Fate of dissolved organic nitrogen in two stage trickling filter process

Dissolved organic nitrogen (DON) represents a significant portion of nitrogen in the final effluent of wastewater treatment plants (WWTPs). Biodegradable portion of DON (BDON) can support algal growth and/or consume dissolved oxygen in the receiving waters. The fate of DON and BDON has not been studied for trickling filter WWTPs. DON and BDON data were collected along the treatment train of a WWTP with a two-stage trickling filter process. DON concentrations in the influent and effluent were 27% and 14% of total dissolved nitrogen (TDN). The plant removed about 62% and 72% of the influent DON and BDON mainly by the trickling filters. The final effluent BDON values averaged 1.8 mg/L. BDON was found to be between 51% and 69% of the DON in raw wastewater and after various treatment units. The fate of DON and BDON through the two-stage trickling filter treatment plant was modeled. The BioWin v3.1 model was successfully applied to simulate ammonia, nitrite, nitrate, TDN, DON and BDON concentrations along the treatment train. The maximum growth rates for ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria, and AOB half saturation constant influenced ammonia and nitrate output results. Hydrolysis and ammonification rates influenced all of the nitrogen species in the model output, including BDON.     

HIV in children

Because children acquire HIV infection differently than adults, this article begins with a discussion of the epidemiology of AIDS in children. This is followed by a discussion of factors related to progression of the disease and survival in pediatric AIDS. A discussion of the pulmonary manifestations in children is followed by a suggested approach to the HIV-infected child with respiratory symptoms.     

Extending the life of water-cooled copper cooling fingers for furnace refractories

To extend the service life of refractory linings in high-temperature furnaces, it is becoming common to embed copper cooling devices in the lining. These devices extract enough heat from the hearth of the furnace to freeze a protective thin layer of slag onto the surface of the lining. However, the cooling devices may lose their efficiency over time. It is believed that high-temperature oxidation of copper is responsible for the loss in heat-extraction capacity. To test coolers under severe conditions, immersion tests were carried out in molten matte and slag of laboratory-scale cooling elements protected by various means. A composite cooler was developed that consists of a copper core shielded by a Cu-4 wt.% Al alloy sheet. Although the rate of heat extraction is not as high as that of the un-alloyed copper, this cooler still extracts heat at a very high rate. For more information, contact Gabriel Plascencia, CIITEC-IPN, Cerrada Cecati s/n, C.P. 02250, Mexico, D.F.; e-mail g.plascencia@utoronto.ca.