Ghana

A strategic task for building research in the Ghanaian context should be to give new life to well-tried methods and to develop the local resources of labour and materials, writes the director of the Building and Road Research Institute at Kumasi. The reasons are not only economic - saving scarce foreign exchange - but social, by creating viable local industries. This article concentrates on the housing-related studies and reports a few projects which have tried to apply the concepts in a practical way.     

New chemical structural features of coal. The structure of coal products

The object of this paper is to demonstrate the usefulness of the transalkylation reaction for determining chemical structural features of products derived from coal. For example, the method is applied to derivatized coals, coals modified by thermolysis, and materials physically or chemically separated from coals. Data are presented for the pyridine soluble and insoluble parts of two coals, an O-methylated coal, a Birch reduced coal, a solvent refined coal, and a coke. Similarities and differences in chemical make-up of these materials are discussed.     

Survival of rotavirus SA-11 on vegetables

Survival of rotavirus on lettuce, radishes, and carrots was studied to evaluate the potential of rotavirus transmission by vegetables irrigated with wastewater. The vegetables were contaminated with rotavirus SA-11 and stored at 4°C and room temperature in covered and uncovered containers to simulate post harvest conditions. Virus decay rates were greater on radishes and carrots than lettuce. Decay rates of rotavirus on lettuce, radish, and carrot ranged from ?0·057 to ?0·479 (log₁₀ pfu/day). Rotavirus SA-11 survived on lettuce, radish, and carrot for 25 to 30 days at 4°C but at room temperature survival was very different for the various vegetables varying from 5 to 25 days. Greatest survival was always observed on the lettuce. These data suggest that rotaviruses can survive long enough on contaminated vegetables as to be transmitted by this vehicle.     

The impact of multiple failure modes on estimating product field reliability

A difficulty in reliability modeling is how to capture the impact of all of the various reliability defect types. The general approach to optimizing burn-in that we describe in this article addresses a multiple-defect environment. The approach has four main parts: (i) modeling the product's failure rate distribution, (ii) establishing the Pareto distribution of reliability defects, (iii) assessing the kinetic information of each reliability defect, and (iv) estimating the DPPM under product use conditions. This article compares and contrasts the acceleration effects of various extrinsic defects found in 130- and 90-nm CMOS technology products.     

Analytical approaches to characterising fish tainting potential of oil sands process waters.

A three-stage study has been carried out with rainbow trout (Oncorhyncus mykiss) to develop analytical approaches which can provide a fingerprint for tainting by oil sands chemicals from process-affected waters and natural sources. The objective was to find a simpler alternative to sensory evaluation. In the first stage, a set of seven test compounds was added to fish tissue which was analysed by headspace and solvent (dichloromethane, DCM) extraction followed by gas chromatography-mass spectrometry (GC-MS). In the second stage, fingerlings (5-20 g) were exposed for 96 hours to the test compound mixture at 1.0 and 0.5 times the estimated tainting threshold concentrations. In the final stage, fingerlings were exposed for 96 hours to an oil sands process water at 5, 10, 20 and 50% concentrations in clean water. None of the test compounds was identified in DCM extracts of tissue from exposed fish. Two long-chain aldehydes, hexadecanal and 9-octadecenal, were tentatively identified in these extracts by matching of mass spectra with library spectra.     

The possibility of evolving a theory for predicting the service life of reinforced concrete structures

The development in recent years with increasing air pollution, increasing need of energy saving and last not least the growing number of damage in old structures leads to a raising demand to calculate the durability of structures, too. The paper has been prepared by request of the RILEM Technical Committee 45-LTO to show that, in principle, it is possible to evolve a theory for predicting the service life of r.c. structures and to sketch a way how that could be achieved. A lot of necessary basic data can be found scattered in the literature. To collect these data will be the first step to take.     

Ultrasound as a pre-oxidation for biological landfill leachate treatment.

In this study, the effects of low energy ultrasound irradiation on landfill leachate treatment by means of sequencing bath reactor were investigated. The aim of this work was to estimate the influence of leachate irradiation time on aerobic treatment efficiency. The sonification of the leachate was carried out in static conditions using the disintegrator UD-20. The field frequency of 22 kHz (the power output equals to 180 W) and amplitude of 12 microm was applied. The sonification time was changed in the range of 30-140 s. It was found that ultrasonic pretreatment enhances the subsequent aerobic digestion resulting in a better degradation of landfill leachate. The sonification of raw leachate leads to enhancement of COD and ammonia removal as compare to experiment without ultrasound.     

Multichip Differential Phase-Shift-Keyed Transmission Over (Non)Linear Optical Channels

The recently introduced multichip differential phase-shift keying (MC-DPSK) optical transmission format, entailing the modulation of relative phases over a moving transmission window of successive chip intervals, is analytically and numerically analyzed. The maximum-likelihood optimal MC-DPSK receiver is derived and synthesized using integrated-optic Mach-Zehnder delay interferometers, whose electrical outputs are interpreted as generalized Stokes' parameters. The MC-DPSK performance over a nonlinear fiber channel, limited by the combination of amplified spontaneous emission noise and self-phase modulation, is further derived and simulated, demonstrating that the lowest complexity three-chip binary-phase MC-DPSK receiver provides an ~1-dB Q-factor advantage over conventional DPSK.