Estimating means and variances: The comparative efficiency of composite and grab samples

This paper compares the efficiencies of two sampling techniques for estimating a population mean and variance. One procedure, called grab sampling, consists of collecting and analyzing one sample per period. The second procedure, called composite sampling, collectsn samples per period which are then pooled and analyzed as a single sample. We review the well known fact that composite sampling provides a superior estimate of the mean. However, it is somewhat surprising that composite sampling does not always generate a more efficient estimate of the variance. For populations with platykurtic distributions, grab sampling gives a more efficient estimate of the variance, whereas composite sampling is better for leptokurtic distributions. These conditions on kurtosis can be related to peakedness and skewness. For example, a necessary condition for composite sampling to provide a more efficient estimate of the variance is that the population density function evaluated at the mean (i.e.f()) be greater than . If , then a grab sample is more efficient. In spite of this result, however, composite sampling does provide a smaller estimate of standard error than does grab sampling in the context of estimating population means.     

Immunity in children with exposure to environmental lead: II. Effects on humoral immunity

Lead has been found to depress the immune system in animal studies at levels far below those responsible for overt toxicity. Literature studies in animal systems most clearly showed an effect of lead on response to a specific immunogenic stimulus. Data are sparse concerning the effects of lead on the immune system in the human population at greatest risk for exposure-children up to six years of age. This portion of the Phase I study reports concentrations of IgG, IgM, IgA, and IgE, as well as antibody titers to the specific antigenic stimuli provided by the vaccines against diphtheria, tetanus, and Rubella. The study population consisted of a group of 193 children, ages 9 months to 6 years, who participate in the WIC (Women, Infants and Children) and Lead Poisoning Prevention Programs in the urban area of Springfield-Greene County Missouri. Blood lead levels ranged from 1 to 50 g dL^–1. Total Ig levels were determined and the data were analysed. No consistent significant differences were observed among the risk categories in the five age groups examined. A single Ig class in each of three age groups showed apparent significant differences among the various risk categories, but these differences were not correlated with blood lead. An analysis of specific antibody titers to diphtheria, tetanus, and Rubella was performed. Regression analyses of current data in Phase I of this study suggest a detrimental effect of lead on the antibody titres to diphtheria and Rubella.     

Structural and functional responses of a freshwater plankton community to acute copper stress

An in-situ experiment was performed to quantify the impacts of copper sulfate on plankton structure and carbon dynamics. Plankton were exposed to 140 microg litre(-1) copper in quadruplicate mesocosms. Community structure was monitored for 14 days by microscopical counts and compared with untreated controls. Carbon dynamics were assessed by tracer studies using (14)C bicarbonate and (14)C glucose, to follow the fate of carbon in the algal- and bacterial-based pathways, respectively. Copper reduced the dry-weight biomass of zooplankton, ciliates, flagellates, and autotrophic phytoplankton. Bacterial biomass was increased by an order of magnitude relative to the controls. The bacterial response was most likely due to reduced grazing pressure and/or nutrient release from dying plankton. Copper reduced the effectiveness of the food web in transporting carbon to the surviving zooplankton. Bacterial-based pathways were more greatly affected than algal-based pathways, because zooplankton in the copper treatment were macro-grazers (cyclopoids), which cannot utilize bacteria.     

Interactions between copper and cadmium modify metal organ distribution in mature tilapia, Oreochromis mossambicus

Sexually mature female tilapia were exposed to sublethal concentrations of waterborne Cu and/or Cd over 6 days, and subsequent body concentrations of these metals were determined in several organs. The results show that the distribution of Cu and Cd was metal and organ specific. This is demonstrated, for example, by the observation that in tilapia, Cu exposure did not result in Cu accumulation in the liver, whereas in the intestinal wall, notably high concentrations of Cu and Cd were measured in metal exposed fish. In addition to single metal exposed fish, we also determined Cu and Cd body distribution in Cu?Cd co-exposed fish. The observed interactions in metal accumulation were most pronounced in the organs of fish exposed to low, environmentally realistic, metal concentrations.     

Marginal bleaching of thalli of Rhizocarpon as evidence for acid rain in the Norra Storfjället, Sweden

Recent lichen surveys in the foreland of The Syterb?cken glacier reveal that the crustose lichens, principally species of Rhizocarpon section Rhizocarpon, exhibit marginal bleaching, readily distinguishable from normal pigmented forms. The largest elliptical thallus of Rhizocarpon measured 290 mm maximum diameter on a bedrock outcrop beyond the margin of Little Ice Age moraines in the upper Syterb?cken Valley. Many small and large thalli of Rhizocarpon suffered damage to the periphery of individual thalli. We examine here some of the possible hypotheses explaining these occurrences. Among others, these are bedrock lithology, ice crystal blasting, long-term snowbank cover, ultraviolet exposure and acid rain. While at this time none of the possibilities can be ruled out entirely, acid rain would appear to be at least one of the factors involved. Acid rain, which is known to produce a soil pH as low as 3.3 in the field area, appears to provide a high input of H(+) ions that the lichen algal component cannot withstand. However, the lack of similar effects on associated foliose or fruticose forms raises the possibility that perhaps two or more factors specific to the environment of Rhizocarpon are operating.     

Labelling ecofriendly products in india — an emerging option for environmental production

Summary The labelling of ecofriendly products has been introduced in a number of developed countries to assist in the protection of the environment. Recently, developing countries like India, have introduced the scheme. This paper examines the steps involved in establishing the Indian Ecomark. For the successful implementation of the scheme the effective coordination of a number of agencies is necessary. Consumers, as well as manufacturers, have to be educated in the longterm benefits of the scheme. Initiatives necessary for the successful implementation of Ecomark have been highlighted.Mr S. S. Arvind is a member of faculty at the Centre for Energy, Environment and Technology, at the Administrative Staff College of India. He is currently on secondment to the Centre for Technology Development, Clark University, 950, Main Street, Worcester MA 01610-1477, USA. Mr E.V. Muley is a scientist working for the Ministry of Environment and Forests, Government of India, Paryavaran Bhavan, CGO Complex, Lodi Road, New Delhi 110003, India.     

Linear least squares method for time series analysis with an application to a methane time series

A simple method of time series analysis, based upon linear least squares curve fitting, is developed. The method's advantages and disadvantages are discussed, and an example is presented using the Vostok Core methane record.     

Uranium enrichment by the separation-nozzle process

The Science of Nature - The development of reliable manufacturing methods for commercial separation elements, the successful operation of separative stages, and extensive tests performed on plant...     

Ecoprofit-Styria-prepare Thirteen pollution prevention case studies in the Styrian industry

The paper focuses upon the organization of a federal state-funded pollution prevention project in the Styrian industry. The project includes 13 companies from the textile, pulp and paper, machine building, wood working and printed circuit board manufacturing industries, covering most of the sectors and sizes in the Styrian industry. It started in January 1994 and will last for one year. It will demonstrate the possibilities of pollution prevention and the need for further research work. This project will make use of the methods and tools that were refined in the Austrian Prepare project. As a first step, a systematic balance of all the inputs and outputs of a company is made, after which the weak points and inefficiencies of material and energy use are identified and the options for improvements, both economical and ecological, are defined. Consequently, modifications in products and production lead to a situation with less waste and emissions. The preliminary lessons from these projects are presented: as a rule, the utilities (consumption of process materials and water, cleaning, energy, preparatory and finishing steps) are treated as black boxes and usually represent a considerable optimization potential. In these areas especially there is usually a lack of information and coordination as well as a need for a systematic and comprehensive approach. Leadership in the company and creative consultants are needed for starting lasting successful pollution prevention projects.     

Der deutsch-britisch-französische Höchstflußreaktor in Grenoble und sein Forschungsprogramm

The 57-MW high-flux reactor of the Institute Max von Laue-Paul Langevin at Grenoble serves as a central neutron-beam facility for laboratories and research institutes in the three member countries, the United Kingdom, France, and the Federal Republic of Germany. The heavy-water-moderated and -cooled reactor is equipped with hot, thermal, and cold moderators, providing neutrons with high intensity over an unusual wide range of energies (wavelengths) extending from some 0.1 meV (30 Å) up to some 500 meV (0.4 Å). An extensive system of neutron guides with different curvatures permits the transport of neutrons over distances ranging up to 140 m with minimal intensity losses for neutrons in the useful wavelength band. The transmitted beams, in addition, exhibit very low background contamination by fast and epithermal neutrons, and γ-radiation. A large variety of high-resolution neutron spectrometers provide unique opportunities in fields such as nuclear physics, crystallography, solid-state physics, chemistry, metallurgy, and biology.