18,800 research outputs found

    The significance of sedimentation and sediments to phytoplankton growth in drinking-water reservoirs

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    In the mesotrophic-eutrophic Saidenbach Reservoir in Saxony, the nanoplankton and cyanobacteria have increased at the expense of diatom dominance, due to a doubling of the external phosphorus load in the last 15 years. However, the phosphorus sedimentation flux is still very high (up to 80% of the input), corresponding to more than 2 g m2 d-1 in terms of dry weight. There is a strong correlation between the abundance of diatoms in the euphotic zone and their sedimentation flux (with a delay of about 2 weeks). Only about 25% of the deposited material could be clearly attributed to plankton biomass; the remainder resulted from flocculation and precipitation processes or directly from the inflow of clay minerals. The ash content of the deposited material was high (73%). Thus the sedimentation flux can be considered to operate as an internal water-treatment/oligotrophication process within the lake. The neighbouring Neunzehnhain Reservoir still has a very clear water with a transparency up to 18 m depth. Though the sediment was not much lower than Saidenbach sediment in total phosphorus and total numbers of bacteria, sulphide was always absent and the ratio of Fe 2+ to Fe 3+ was very low in the upper (0- 5 cm) layer. Thus the external and internal phosphorus loads do not attain the critical level necessary to induce a ÔÇŁphosphorus - phytoplanktonÔÇŁ feedback loop

    LOOPUS Mob-D: System concept for a public mobile satellite system providing integrated digital services for the Northern Hemisphere from an elliptical orbit

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    A new concept for a satellite based public mobile communications system, LOOPUS Mob-D, is introduced, whereby most of the classical problems in mobile satellite systems are approached in a different way. The LOOPUS system will offer a total capacity of 6000 high rate channels in three service areas (Europe, Asia, and North America), covering the entire Northern Hemisphere with a set of group special mobile (GSM) compatible mobile services, eventually providing the 'office in the car'. Special characteristics of the LOOPUS orbit and the communications network architecture are highlighted

    Ecology of fishes in Upper Newport Bay, California: seasonal dynamics and community structure

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    A total of 366 bimonthly (January 1978-January 1979) samples taken with six types of gear (otter trawl, gill net, bag seine, small seine, drop net, square enclosure - all with replication except the gill net) at four stations in upper Newport Bay, California yielded 51,816 fishes belonging to 46 species and weighing over 353 kg. Atherinops affinis (topsmelt) was the most abundant species accounting for 76% of total individuals. Seven species, all of low trophic levels, made up over 97% of the total catch. Mugil cephalus (striped mullet) ranked first in biomass (= 36% of the total) with six species accounting for more than 80% of the total biomass. The largest number of individuals (71%) was collected with the bag seine, the greatest number of species (35) was captured with the otter trawl and the largest percentage of the biomass (56%)was obtained with the gill net. Species richness, number of individuals and biomass were lowest in January (1978 or 1979) or March and highest in July (numbers, biomass) or September (species). Bimonthly diversity (H') values ranged from 0.48 to 2.17 (overall value 1.05) and tended to be inversely related to abundance levels. Species richness was greatest at Station 4 (the lowermost station) and least at Station 1 (the uppermost station). Numbers of individuals and biomass peaked at Station 2 and reached lowest levels at Station 1. Length-frequency analysis of six of the most abundant species indicated utilization of the upper bay by two or more stages in the life history of these species. More than 92,000 eggs belonging to seven taxa and an unknown category and 426 larvae from 20 taxa were collected with a 0.5 m net mounted on an epibenthic sled during the same bimonthly periods and at the same stations as the juvenile/adult samples. Most of the eggs were collected at Station 2 in May with the numbers overwhelmingly dominated by those of Anchoa compressa (deepbody anchovy) (99.7% of total numbers). The most abundant larva was that of Clevelandia ios (arrow goby). Nearly 60% of the total larval catch was made up of members of the family Gobiidae. Larval taxa and individuals were fewest in January (1978). The number of taxa was highest in March, September and January (1979) whereas larval numbers peaked in May. The number of taxa and of individual larvae varied only slightly among the four stations. Asymptotic species accumulation curves indicated adequate sampling of juvenile/adult fishes. Cluster analysis produced eight species groups of resident and periodic species that variously utilize the three main habitats (channel, inshore, pannes) in the upper bay. Species richness and abundance were positively correlated with both temperature and salinity. Temperature, salinity and depth of capture were frequently correlated with individual species abundances and were used in combination to partially explain the spatial utilization of species and species groups. The upper bay fish community is important and worthy of preservation for at least three reasons: 1) it contains species assemblages not duplicated in any other coastal environment; 2) it contains life history stages of a variety of coastal fish species; and 3) it contains large populations of small, low-trophic level species and juveniles of other species which serve as forage for larger, predatory species that are frequently of economic importance. Members of the fish community respond noticeably to altered environmental conditions such as the heavy rainfall (and accompanying low salinity and high turbidity) that occurred during the early months of 1978. The short and long term, as yet often unpredictable, fluctuations in the populations emphasize the need for periodic monitoring and for the development of a mathematical model of the fish community if it is to be thoroughly understood and properly managed. (102pp.

    The performance of object decomposition techniques for spatial query processing

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    International arms trade: Revealed political preferences or cartel behaviour?

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    On the basis of a world matrix of international trade in majorconventional weapons for 1985, a comparison is made between the regional structure of arms trade and the regional structure of trade in civilian goods from a comparable technological background. It turns out that there are striking divergencies between both kinds of trade structures, even within military alliances. These divergencies are then captured by an indicator which is named revealed political preference (RPP). It is argued that introducing a free-trade regime within NATO and other industrialised western countries would make arms trade increase, and, in particular, make the shares of Japan and West Germany in arms exports rise manifold, thereby raising world economic welfare. It is suggested that different hypotheses for explaining world arms-trade structures are relevant according to the region analysed, like the trading-with-the-enemy hypothesis with respect to the arms trade between advanced and less-developed countries, or the military-industrial-complex hypothesis for arms trade within alliances.

    Comparative invention performance of major industrial countries: Patterns and explanations

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    The paper firsjt presents an analysis of invention performance; as measured by patenting activities, of six countries (France, Italy, Japan, United Kingdom, USSR, West Germany) relative to the United States for 41 SIC industries over the past twenty years. It turns out that Non U.S. countries as a whole have increased their (relative) invention performance in all fields of technology, including high technology fields. In the second section hypotheses which can be supposed to explain the relative decline of the United States' patenting activities are discussed and tested. There is strong evidence that catching up processes as well as integration effects contributed most to the relative decrease of the United States; there also is evidence, that government interventions regarding technology production have had counter-productive effects in the United States.

    Towards a funded system of social security: Design and implications ; the case of Germany

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    What would a feasible system of social security in Germany have looked like in the year of 1995 and beyond? In order to find an answer we describe three base systems: ( l ) a purely funded system of social security, (2) a fully mandatory funded system of social security, and (3) a partially mandatory funded system. It is argued that - neglecting problems of transition - a purely funded system would be the best in economic terms; a fully mandatory funded system would need almost as many controls as the currently prevailing system (often labelled pay-asyou- go system). A partially mandatory funded system, assuring some kind of basic income, would need less controls and less governmental authority than the fully mandatory system but more than a funded system. After quantification of two scenarios which represent components of the three base systems, a system of taxation with respect to contributions and/or benefits is discussed which is at the same time simple in terms of costs of bureaucracy and does not tax economic growth more than necessary.

    Growth, growth fluctuations, and the stages of technological advance

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    It is a well-established tradition to define the subject before embarking on an investigation. In our case, definition is to be concerned with economic development and scientific-technical progress. The former poses no problem in the economist's profession. According to Mirabeau, every moral or physical advance can be grasped by one indicator, which he called the net product. Today, Mirabeau would probably encounter objections as far as the measurement of moral progress by the net product is concerned, although some would argue that also today morals, as well as gods, are always with the winners. Anyhow, real changes in the availability of goods and services is, according to national and international standards, measured by changes in real net social product; conceptual problems - e.g., of how to treat the non-pecuniary costs (environmental pollution) and benefits (value added of housewives) - are, of course, part of every measurement. What matters here is that the approach as such is hardly controversial.

    Institutional change in search of the market: The case of Slovenia

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    Six main characteristics of an economic order are discussed and empirically evaluated for the case of Slovenia. All of them pertain to the institutional setting ab urbe condita; they comprise the legal and jurisdictional situation, the role of private property, the institutionalised strive at competition among firms and individuals, the liberty of markets, the solution of the big assignment problem, and the approach to foreign-trade relations. All six aspects impinge upon the conditions which confront investors in material and in human capital in Slovenia. The analysis shows that Slovenia has had, for three years now, by and large the same problems that other countries in transition had. For example, it still has, among others, tight regulations regarding foreign exchange transactions, and a highly socialist property system burdened with too complicated procedures of privatisation. The authors conclude that in Slovenia, as in the other formerly socialist economies, transformation should first and foremost aim at being coherent. Secondly, first things should come first; the first thing would be to privatise. With a proper approach of institutional reforms there should be no barrier to achieving two-digit rates of real growth, just like Germany had after transition into a market economy in 1949.
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