Processing Stability and Biodegradation of Polylactic Acid (PLA) Composites Reinforced with Cotton Linters or Maple Hardwood Fibres

Polylactic acid (PLA) composites comprising up to 25 wt% cotton linter (CL) or up to 50 % maple wood fibre (WF) were prepared by compounding and injection moulding. A reduction of crystallinity in the PLA matrix was observed as a result of the thermal processing method. These PLACL and PLAWF composites provided excellent improvements in both stiffness (with increases in tensile and flexural modulus) and toughness (increases in notched impact strength) properties over the neat PLA resin, while the tensile and flexural strengths of the composites were generally unchanged, while the strain at break values were reduced in comparison to the neat PLA. DMA results indicated incorporating these fibres caused the mechanical loss factor (tan δ) to decrease, suggesting better damping capabilities were achieved with the composites. SEM analysis of the impact fractured surfaces of the PLACL composites showed debonding-cavitation at the matrix-fibre interface while the PLAWF composites showed good wetting along its matrix-fibre interface. The composting of these composites up to 90 days showed that the degradation onset time was increased when increasing the fibre loadings, but the maximum degree of degradation and the maximum daily rates of degradation were decreased compared to neat PLA. On a weight basis of fibre loading, the PLACL composites had a quicker onset of biodegradation, a higher maximum daily rate of biodegradation and, overall, a higher degree of biodegradation at 90 days than the PLAWF composites, possibly due to the quicker thermal hydrolysis observed in the PLA matrix of the PLACL composites during processing and composting.     

Incidence of thyroid disease following exposure to polybrominated biphenyls and polychlorinated biphenyls, Michigan, 1974-2006

Thyroid hormones, which influence body metabolism and development, could be affected by persistent organic pollutants. We sought to examine the relationship between polybrominated biphenyls (PBBs) and polychlorinated biphenyls (PCBs) and thyroid disease. We employed incidence density sampling to perform a nested case control analysis of the Michigan Long-Term PBB Cohort. Cohort members (n = 3333) were exposed to PBBs through contaminated cattle feed in 1973-1974 and to PCBs through daily life. Those with detectable serum PBB and PCB concentrations at enrollment were categorized into tertiles of PBB and PCB exposure. Case-patients were cohort members answering “Yes” to “Has a healthcare provider ever told you that you had a thyroid problem?” during follow-up interviews; control-patients were cohort members answering “No”. We used odds ratios (OR) with 95% confidence intervals (CI) to compare odds of thyroid disease by PBB and PCB exposure and by various risk factors. Total cumulative thyroid disease incidence after 33 years was 13.9% among women and 2.6% among men. After adjusting for body mass index, we found no statistically significant differences in odds of any type of thyroid disease among women or men with elevated PBB or PCB exposure. Compared to control-patients, women with thyroid disease had increased odds of being overweight/obese (OR = 2.82, 95% CI: 1.94-4.11) and developing infertility (OR = 1.71, 95% CI: 1.08-2.69), diabetes (OR = 1.61, 95% CI: 1.04-2.51), or arthritis (OR = 1.71, 95% CI: 1.18-2.50) during follow-up. Additional research should explore potential associations between PBBs/PCBs and thyroid disease among children exposed in utero.     

A field assessment of floor slipperiness in a fish market in Taiwan

A field assessment of floor slipperiness in 10 fish stands in a fish market in Taiwan was conducted using both friction measurements and subjective ratings. The friction measurements were conducted using the Portable Skid Resistance Tester (PSRT). The subjective ratings of floor slipperiness of both the workers and the customers were collected. The friction measurement results showed that the sink areas had both the lowest friction values and subjective ratings. The overall friction measurement results and the subjective ratings were in fair agreement (r = 0.46 and ρ = 0.49). The customers perceived the walkways as somewhere between “very slippery” to “somewhat slippery” and the picking-up areas as “very slippery.” These were different from the perceptions of the workers where they perceived both areas as “somewhat slippery.”     

The unequal distribution of occupational health and safety risks among immigrants to Canada compared to Canadian-born labour market participants: 1993–2005

ObjectivesTo examine the prevalence of occupational health and safety risk factors among immigrants to Canada compared to Canadian-born labour force participants.MethodsUsing data from Statistic Canada’s Survey of Labour and Income Dynamics, we examined the differential probabilities of six different occupational health and safety risks: non-membership in a union or collective bargaining agreement; employment in physically demanding occupations; employment in a workplace with less than 20 employees; regular shift work; irregular shift work; and having non-permanent employment. Our main independent variables were length of time in Canada, visible minority status, mother tongue, and location where highest level of education was attained. Models were adjusted for age, gender, education, marital status, province of residence, living in an urban or rural location, and industry group.ResultsOf the six occupational health and safety risks examined we found that our main independent variables describing aspects of immigration status were associated with five; the exception being irregular shift work. Adjustment for industry did not attenuate these relationships to a large extent.ConclusionsImmigrants to Canada are faced with many occupational health and safety risks compared to Canadian-born respondents. These risks may be heightened among immigrants as they may not have knowledge of workplace rights and protections or have problems communicating health and safety risks or concerns. The timely provision information on occupational health and safety to immigrants before they start working should be a priority as they integrate into the Canadian labour market.     

Seasonal breeding aggregations in low-density populations of the bathyal echinoid Stylocidaris lineata

Reproduction of bathyal cidaroid sea urchins was studied between 1985 and 1991 with the aid of a manned submersible in the northern Bahamas. During May 1988 and February 1990, discrete, single-species aggregations of Stylocidaris lineata containing 2 to 6 individuals were observed between 510 and 640 m depths. Reproductive conditions of isolated and aggregated individuals were determined histologically. In February, all individuals, regardless of their spatial distribution, contained developing gametes. During the May spawning season, most isolated individuals contained spent gonads with only relict gametes, whereas individuals in discrete aggregations mostly contained ripe gonads with mature or nearly-mature gametes. Aggregations were not observed during the autumn months, when gonads were spent or immature. These data suggest that bathyal cidaroids aggregate for reproduction. An in situ survey during May indicated that pairs of S. lineata are more common than larger clumps, but no more so than predicted by chance. Homosexual and heterosexual pairs occur at the relative frequencies predicted on the basis of sex ratio. We evaluated the need for reproductive aggregation by applying Denny's (1988) model that predicts downstream sperm concentration in a turbulent boundary layer. Flow parameters were measured with dye injected from the submersible, sperm-release rate was estimated in the laboratory, and the relationship between fertilization success and sperm concentration was determined in a laboratory dilution-experiment. The model predicted that, on smooth sandy bottoms at bathyal depths, sperm concentration should remain high enough to fertilize at least some eggs several meters directly downstream from a spawning male. Aggregation may facilitate spawning synchrony, increase gamete encounter probabilities, or cause gametes to be retained at high concentrations near the adults long enough for fertilization to occur.     

Chemical signals in bumble bee foraging

Summary Foraging bumblebees (Bombus vosnesenskii) deposit a substance on rewarding flowers which assists in discrimination between rewarding and nonrewarding flowers in a controlled laboratory environment. Discrimination occurs while the bee is on a flower; workers probe rewarding flowers as well as empty ones that have rewarded in the recent past, but they do not probe flowers that have had no reward. Recognition is not the result of honey contamination left on the flower by the bee during feeding. The deposit is only slightly soluble in water or ethyl alcohol but is very soluble in pentane.     

Manganese nodules and marine technology

This article examines the problems and prospects of manganese nodule mining. The technological requirements for the exploitation of nodule deposits are considered, superimposed on an interdisciplinary policy-oriented approach. The technological dimension is emphasized because its crucial importance is often underrated when deep ocean mining is assessed. This dimension cannot be divorced from the interactions between economics, international law and oceanography. The technological problems and opportunities of nodule mining are diverse. Provided delays at the UN and economic uncertainties do not channel some of the interest into land-based alternatives, this could be an important area of future technical development.     

Book reviews

Land and Leisure — Concepts and Methods in Outdoor Recreation

Second Edition — edited by C. S. Von Doren, G. B. Priddle and J. E. Lewis.

Methuen & Co., £5.95. 1979.

Countryside Planning — The First Three Decades, 1945–76

Andrew W. Gilg.

Methuen & Co. £3.50. 1979.

Social Problems and the City

D. T. Herbert and D. M. Smith

Oxford University Press. £8.50. 271 pp.

Slum Housing and Residential Renewal — The Case of Urban Britain

D. A. Kirby

Topics in Applied Geography Series. Longmans. £2.95. 1979.

From Blacksmiths to White Elephants: Benwell's Changing Shops

Benwell Community Project Final Report, Series No. 7, Newcastle upon Tyne 1979. 72 pp. 80p.

The Debate on Urban Policy — Decentralisation versus Improvement

Robert Coursey

Retailing and Planning Associates 1977. 93 pp.

Urban Deprivation and Government Initiatives

Paul Lawless

Faber. £8.95 (hard‐back), 251 pp.

A Guide to Historic Buildings Law Fourth Edition

Peace, D., and Purdy, I. M.

Cambridgeshire County Council, County Planning Department, 1979.

98 pp. (paperback), £5.35 post paid.

Research and Intelligence

Papers delivered at the Annual Conference 1978, Inlogov University of Birmingham Edited by E. M. Davies

£4.30. 257 pp.

Geography and the Urban Environment : Progress in Research and Applications

Vol. II. Edited by D. T. Herbert, R. J. Johnston.

Wiley, London. 308 pp.

Facts about the New Towns : A Socio‐Economic Digest

A. G. Champion, K. Clegg and R. L. Davies

R.P.A., Corbridge, 1978.

Physical Planning in the Member States of the E.E.C.

C. Wood and N. Lee, Occasional Paper No. 2.

Department of Town and Country Planning, University of Manchester, 1978. 59pp.     

Book reviews

ENFORCEMENT AND STOP NOTICES

Felix Bourne

Sweet and Maxwell, London 1986

SMALL FACTORIES AND ECONOMIC DEVELOPMENT

By Martin Perry

(Aldershot; Gower, 1986, pp.xvi + 229) £22.50

WHATEVER HAPPENED TO PLANNING?

Peter Ambrose, 1986

Methuen, London and New York, 288pp, £8.95.