Showing papers on "Water environment published in 1991"

Effect of environmental conditions on the infectivity of Flexibacter columnaris to fish

Abstract: . Columnaris disease, Flexibacter columnaris infection, was first described in North America. Recent publications indicate that its distribution is worldwide. Both warmwater and coldwater fish are infected with F. columnaris. All freshwater fish are probably susceptible to the disease under environmental conditions favourable to the bacterium and stressful to the fish. Flexibacter columnaris cannot tolerate sea water. Generally, outbreaks occur when the average water temperatures reach 15°C. The bacterium apparently enters the fish through the skin and gills. The swarms of bacteria involved give the lesions a characteristic yellow pigmentation. The external lesions destroy the skin, muscle and gill tissues. It is relatively easy to isolate the bacteria from the internal organs of the diseased fish, but there is no evidence of internal tissue damage. In this short review, emphasis is placed on several factors relative to water environment which play a role in the development of outbreaks of columnaris disease: 1 The optimum temperature for an outbreak of F. columnaris infection is thought to be between 20 and 30°C. Mortalities seldom occur at temperatures below 15°C, although highly virulent strains can kill fish at lower temperatures. 2 Flexibacter columnaris can survive longer in water of normal to high hardness, as well as in water containing small amounts of sodium, potassium, calcium or magnesium salts, but it cannot live in sea water. 3 Flexibacter columnaris grows well on paniculate fish feeds so that such deposits in the water may act as reservoirs of infection. 4 An important source of infection is feral fish. In the Columbia River or the Fraser River, resident coarse fish such as suckers, Catostomus spp., are thought to transmit the infection to returning adult salmon. 5 Flexibacter columnaris fails to invade fish in the presence of competitive bacteria like Citrobacter freundii when its initial numbers are approximately one in a 100 less than those of the competitors. 6 Crowding seems to be not only a stressor for fish, but also a factor that increases the chance of adhesion of F. columnaris to the external tissues of fish.

Savanna ecology and management : Australian perspectives and intercontinental comparisons

Abstract: 1. Australasian Savannas: Overviews Australia's Unique Biota: Implications For Ecological Processes Northern Australian Savannas: Management For Pastorial Production Stability And Stress In The Savanna Forests Of Mainland South-East Asia Savannas Of North-East India Tropical Grasslands Of Sri Lanka And India 2. Ecological Determinants Of Savannas: Abiotic And Biotic: Savannas Of Northern South America: A Steady State Regulated By Water-Fire Interactions On A Background Of Low Nutrient Availability The Influence Of Soil Fertility On The Ecology Of Southern African Dry Savannas Nitrogen-Use Efficiency For Growth In A Cultivated African Grass And A Native South American Pasture Grass Nutrient Cycling In Australian Savannas Herbivory By Insects In Australian Tropical Savannas: A Review Large Herbivorous Mammals: Exotic Species In Northern Australia 3. Biological Mosaics And Tree/Grass Ratios: Development And Stability Of Grass/Woody Mosiacs In A Subtropical Savanna Parkland, Texas, USA The Origin And Extent Of Nutrient-Enriched Patches Within A Nutrient-Poor Savanna In South Africa Tree Community Dynamics In A Humid Savanna Of The Cote-d'Ivoire: Modelling The Effects Of Fire And Competition With Grass And Neighbours Tree/Grass Ratios In East African Savannas: A Comparison Of Existing Models Stress And Disturbance: Vegetation Dynamics In The Dry Chaco Region Of Argentina 4. Savanna Management For Pastoral Industries: Management Of Savannas For Livestock Production In North-East Australia: Contrasts Across The Tree-Grass Continuum The Water Environment And Implications For Productivity Philippine Grasslands: Liveweight Gains In Cattle And Buffaloes, With And Without Introduced Legumes Australia's Northern Savannas: A Time For Change In Management Philosophy RSPM: A Resource Systems Planning Model For Integrated Resource Management RANGEPACK: The Philosophy Underlying The Development Of A Microcomputer-Based Decision Support System For Pastoral Land Management SHRUBKILL: A Decision Support System For Management Burns In Australian Savannas

Organic-rich transitional facies in silled basins: Response to sea-level change

Abstract: High-resolution profiles of organic carbon, {delta}{sup 13}C{sub org}, sulfur, {delta}{sup 38}S, and some trace elements in cores from two silled basins, Kau Bay (Indonesia) and the Black Sea, allow division of the sedimentary record into three distinct units, representing a Pleistocene fresh-water-brackish water facies (unit 3), a Holocene transitional facies (unit 2), and a modern fully marine facies (unit 1). The geochemical characteristics of these units are strikingly similar for both basins. The sediments form unit 3 are characterized by the predominance of terrestrial organic matter, Mo and U concentrations at crustal abundance, and positive {delta}{sup 34}S values. The transitional sediments (unit 2) are strongly enriched in marine organic matter and Mo, V, and U and have intermediate {delta} {sup 34}S values. Sediments from the modern marine facies (unit 1) are moderately organic-carbon rich and slightly enriched in Mo and U and have negative {delta}{sup 34}S values. The organic-carbon-rich sediments from unit 2 were formed by increased production during the transition from the Pleistocene isolated fresh-water-brackish water environment to the modern open-marine facies. This temporarily higher productivity was caused by displacement of nutrients from the deep water into the euphotic zone, owing to the gradual infilling by marine waters.

Separable missile nosecap

Abstract: This invention provides provides a separable nosecap for the forward end of a homing torpedo, the nosecap and torpedo comprising a missile that is launched into the atmosphere for a ballistic trajectory to a distant underwater target. The nosecap comprises a nosecap shell having a volume of rigid cushioning foam material within its interior space defining a cavity into which is mounted a pneumatic apparatus including a flexible inflatable sleeve for forcefully disengaging the nosecap from the torpedo after the missile has entered the water environment. The inflatable sleeve engages the forward end of the torpedo and, upon inflation and axial extension, the sleeve disengages the nosecap from its mounting to the torpedo such that a homing mechanism of the torpedo may guide it to the intended target.

Three-dimensional optical microscopy of water trees in polyethylene

Abstract: Polyethylene is used as high-voltage electrical insulation in cable, and fails when subjected to the combination of water environment and electrical field. The three-dimensional microstructure of water trees, which are precursors to dielectric breakdown, has been revealed with laser scanning confocal optical microscopy. Two-dimensional images which represented optical serial sections were recorded in digital form, and reconstructed in a computer to produce three-dimensional views of the microstructure. Both stereo pairs and computed tomographic reconstructions were made. The material was stained with a fluorescent dye and the fluorescent image was compared to the standard unstained image. The dye was found to increase the signal-to-noise ratio and improve the quality of the image significantly.

Parametric Effects on Glass Reaction in the Unsaturated Test Method

Abstract: The Unsaturated Test Method has been applied to study glass reaction under conditions that may be present at the potential Yucca Mountain site, currently under evaluation for storage of reprocessed high-level nuclear waste. The results from five separate sets of parametric experiments are presented wherein test parameters ranging from water contact volume to sensitization of metal in contact with the glass were examined. The most significant effect was observed when the volume of water, as controlled by the water inject volume and interval period, was such to allow exfoliation of reacted glass to occur. The extent of reaction was also influenced to a lesser extent by the degree of sensitization of the 304L stainless steel. For each experiment, the release of cations from the glass and alteration of the glass were examined. The major alteration product is a smectite clay that forms both from precipitation from solution and from in-situ alteration of the glass itself. It is this clay that undergoes exfoliation as water drips from the glass. A comparison is made between the results of the parametric experiments with those of static leach tests. In the static tests the rates of release become progressively reduced through 39 weeks while, in contrast, they remain relatively constant in the parametric experiments for at least 300 weeks. This differing behavior may be attributable to the dripping water environment where fresh water is periodically added and where evaporation can occur.

Electron paramagnetic resonance and electron spin echo modulation analysis of the silver atom environment in γ-irradiated silver-exchanged sodium montmorillonite and its Al13 pillared derivative

Abstract: Silver atoms are formed by radiolytic reduction at 77 K of Ag+-exchanged montmorillonite and Al13 pillared montmorillonite clays. EPR shows that the Ag-atom hyperfine constant is about the same as for Ag0 generated in glassy aqueous solutions and distinctly different from Ag0 generated in polycrystalline aqueous solutions. This indicates that the water environment in the clay interlayer region is rather disordered as in a glassy matrix. Electron spin echo modulation analysis shows that Ag0 in the fully hydrated clay is coordinated by four water molecules in its first solvation shell as in bulk solution and that this number decreases as the montmorillonite is dehydrated. For solvation of Ag0 by methanol and ethanol, however, the Ag0 is solvated by fewer alcohol molecules in the clay interlayer than in bulk solution. No 27Al modulation is observed for Ag0 in montmorillonite even when partially dehydrated, indicating that Ag0 does not interact with 27Al in the octahedral sheet of a clay layer. However, 27Al modulation is detected in Al13 pillared montmorillonite, showing Ag0 interaction with 27Al in the pillar. No paramagnetic Ag clusters are observed in the clays in contrast to their ready formation in zeolites and in frozen solutions.

Shear Waves in Marine Sediments — Bridging the Gap from Theory to Field Applications

Abstract: The relationship between primitive variables such as porosity and mean grain size and the velocity and attenuation of shear waves propagating in a marine sediment can be established on the basis of correlations with many field measurements or, more basically, may be derived from the physics governing the response of particulate material in a water environment. In this paper we discuss some of the progress that has been made along the latter path wherein porosity, permeability and other variables that may be measured in the lab or estimated from geological descriptions may be used to estimate seismo-acoustic properties via a mathematical model that reflects all the significant physics of the problem. This model, which may be termed “poro-viscoelastic”, is a complex research tool that may be used to derive much simpler “fleet-oriented” models for making estimates of properties in selected environments. We first briefly discuss the fundamental model and then compare the results of predictions made using the model with field measurements at several well-documented sites.

In Situ Differential Reflectance Study of the Etching of SiO2 Films

Abstract: : A differential reflectance technique has been applied to study the etching of Silicon dioxide films on Silicon substrates in-situ in the liquid Hydrogen Fluoride/Water environment as well as ex-situ. Essentially, the technique scans an incident optical beam in the spectral range of 200-800 nm across two adjacent samples at near normal incidence and the reflected beams are detected using lock-in amplification so as to measure only the difference in the reflectance spectra. This study demonstrates the great sensitivity of the technique to follow the etching experiment in-situ, and in conjunction with simulated spectra and ex-situ results, a new spectral feature is seen which may be evidence for an electric double layer at the Si surface in the etch solution. In microelectronics processing, the cleaning of silicon substrates prior to processing and the etching of SiO2 films on Si for various lithographic procedures often involves the use of aqueous HF solutions. Previous studies have shown that the use of HF alters the Si surface and the oxidation kinetics. More recent studies have confirmed these results and indicate that the major effect is at the Si surface.

Release and behaviour of Cr, Mn, Ni and Pb in a fly‐ash/soil/water environment: column experiment

Abstract: A column experiment study has been carried out in order to understand the phenomenon of leaching of selected trace elements like Cr, Mn, Ni and Pb by the action of acidic rain water on a fly‐ash/soil bed in a water environment, fly‐ash/soil such as in a landfill area of fly‐ash disposal sites. Metals measured at depth of 8?, 16? and 24? of soils in columns showed variation in concentrations. However, a lower pH with lower total metals and higher available metals concentrations in a top layer soil than in subsequent lower layers of alluvial soils have been observed. pH has been found as one of the most important parameters in regulating the change in available and total metal content in layers of soils. Metals retention in soil and their release into leachate water were also found to be dependent on organic matter, cation exchange capacity, adsorption/precipitation and subsequent mobility of heavy metals in soil, in order of importance. The metals content in the leachate's water were not formed proportiona...

Vertical thermal-buoyant jets

Abstract: A study of plane thermal-buoyant jets is presented. Experiments were conducted in water, and the results are compared with two integral models, namely a buoyant jet model and a thermal jet model. In the buoyant jet model the equation of state is linear, while in the thermal jet model the equation of state is nonlinear. It is concluded that the buoyant jet model does not adequately predict the behaviour of thermal buoyant jets in a cold water environment. For such flows it is necessary to use the actual equation of state for water.

2000 AD: Water Environment Problems of China

Abstract: The problems of water supply of China in 2000 are revealed by statistical data. It is shown that 450 cities will be short of fresh water; a great quantity is utilised in agriculture much of which can be saved; groundwater is over‐extracted; the level of water is falling by an average of 1‐2mu each year which has caused the subsiding of regional earth; the quality of drinking water and of water utilised in industry becomes poorer; water resources are polluted because of the increase in organic pollutants, the number and size of cities, the pollution of nutrient and colon bacillus, the decrease in the area of lakes, the shortage of money for administration, the amount of polluted water drained without efficient treatment, the low re‐utilisation ratio of water, and the low rate of sewerage system development.

Austenitic iron-base alloy

Abstract: PURPOSE:To refine a structure, to prevent the formation of Cr carbide in grain boundaries, and to improve corrosion resistance by reducing C content in an austenitic stainless steel and adding specific small amounts of Zr to the above steel. CONSTITUTION:At the time of producing a member used in a high-temp. pure water environment in a nuclear reactor, a stock prepared by adding 0.02-1.0% Zr to an austenitic stainless steel having a composition consisting of, by weight, 9.0-11.0% Ni, 18.0-20.0% Cr, <0.03% C, <2.0% Mn, <0.005% P, <0.004% S, <0.03% Si, and the balance Fe is used. Since the grain size of the austenitic stainless steel is refined by the addition of Zr, and further, Zr carbide is formed in the grain boundaries and the formation of Cr carbide is prevented, the grain boundaries are free from the occurrence of Cr-deficient phase due to the formation of Zr carbide, and, as a result, the austenitic stainless steel member free from deterioration in corrosion resistance and having superior corrosion resistance can be obtained.

Heat treating method for improving corrosion resistance of solid-solution strengthened ni base alloy

Abstract: PURPOSE:To provide the heat treating method for improving the corrosion resistance of a solid-soln. strengthened Ni base alloy for a nuclear reactor for solving the serious problem of the corrosive damage of 'Inconel(R)' 600 used for a structure in a BWR(boiling water reactor) caused by the sensitization of material in a reactor water environment of BWR. CONSTITUTION:This method is characterized in that in heat treatment in the final stage, for obtaining high corrosion resistance and good mechanical properties of a solid solution strengthened Ni base alloy, setting its heating temp. to 1000 to 1100 deg.C, allowing >=60% of the C content therein to enter into solid solution, regulating the grain size to fine one of >=4 grain size number and thereafter executing rapid cooling from the heating temp. to 300 deg.C at >=200 deg.C/sec cooling rate.

A Probabilistic Assessment for the Stress Corrosion Cracking Lifetime of Sensitized 304 Stainless Steel in Sodium Chloride Solutions

Abstract: Since stress corrosion crack initiation/propagation process is essentially a stochastic one, a series of uniaxial constant load tests have been conducted on sensitized 304 stainless steel specimens in neutral chloride solutions to examine the effects of stress, temperature, crevice and chloride ion concentration on probability distribution of intergranular stress corrosion cracking lifetime. By examining the effects of various acceleration factors, the lifetime distribution can be satisfactorily presented by the exponential probability distribution model as that of sensitized stainless steels in high-temperature and high-purity water environment systems. The tendency of both the location parameter, i.e., lower limit of lifetime distribution, and the scale parameter, i.e., standard deviation of lifetime distribution, to increase with decreasing stress, temperature and chloride ion concentration, also the ratio of those two parameters is constant.

Contaminated Land: Implications for Water Pollution

Abstract: The water environment is often neglected in the assessment of the impact of contaminated land and its redevelopment. The lack of effective legislative controls over derelict contaminated land areas and the poor appreciation of water pollution by developers and planning authorities in the undertaking and controlling of site redevelopment has severely hindered effective clean-up and protection of groundwater and surface waters. The formation of the National Rivers Authority, the publication of the House of Commons Environment Committee's report and the implementation of the Environmental Protection Act 1990 have given the subject a new impetus. The preparation of registers by local authorities, which identify contaminated land areas, could be enhanced by the National River Authority's assessment of key sites. It is hoped to initiate clean-up by cooperation, but the testing of legislative powers has been encouraged by the Government, if only to reveal their inadequacies.

Austenitic stainless steel excellent in neutron irradiation embrittlement resistance and its use

Abstract: PURPOSE:To provide the steel used for nuclear reactor, unclear fusion reactor, etc, by regulating respective contents of Mn, Cr, and Ni so thai Cr concentration in grain boundaries does not practically fall below Cr concentration in a matrix owing to neutron irradiation CONSTITUTION:This austenitic stainless steel is composed of a steel having a composition containing, by weight, <=003% C, <=1% Si, 5-25% Mn, 15-26% Cr, and 10-20% Ni, and the ratio of the atomic volume of Cr to the average atomic volume of the base phase of this steel is regulated to 0900-1030 This steel is prepared in consideration for a phenomenon of the occurrence of Cr- deficient layer in the grain boundaries due to the ejection and diffusion of Cr caused by neutron irradiation and has superior corrosion resistance under a high temp water environment subjected to corpuscular beam irradiation

Sticking suppressing method for radioactive material of piping or equipment for nuclear power plant

Abstract: PURPOSE: To suppress the sticking of a radioactive material by forming an oxide film on the surface of the piping, equipment, etc., of the plant which contacts reactor water by autoclave processing before the piping, equipment, etc., is installed in the plant. CONSTITUTION: The oxide film is formed on the surface of the piping or equipment which contacts the reactor water outside a nuclear power plant system by bringing the surface into contact with high-temperature, high-pressure pure water which is degassed and contains a fine amount of dissolved oxygen and making the pure water flow before the surface contacts the nuclear reactor water. Structure materials of a pressure vessel, piping, a pump, valves, etc., provided around a plant reactor use stainless steel by 97% of the water contacting area. An increase in the film amount of the stainless steel in reactor water environment is represented by a logarithmic rule of time. Namely, its growing speed decreases as the film is grown. Therefore, the proper nonradioactive oxide film is formed previously to suppress new film forma tion after dipping in liquid wherein a radioactive material is dissolved, and the sticking of the radioactive material which is caused frequently in film formation can, therefore, be suppressed. COPYRIGHT: (C)1991,JPO&Japio

Ceramic coating for valve seats and stems by plasma chemical vapor deposition

Abstract: To extend the lifetime of the valve seats and stems used in nuclear power plants, we have developed a unique ceramic coating technique using plasma chemical vapor deposition (CVD). Multilayer coatings of Al 2 O 3 /TiN/TiC, Al 2 O 3 /TiC and TiN/TiC were deposited onto Stellite and stainless steel substrates. The mechanical and physical properties of the coatings were evaluated by various methods. The coated specimens showed good wear resistance in a high-temperature water environment. Corrosion resistance was evaluated in an autoclave at a temperature of 548 K for 200 h. The coated specimens showed excellent performance in reducing the cobalt level dissolved in the testing solution. The weight loss of the multilayer-coated AISI403 specimen, as evaluated by a cavitation erosion test, was less than 1% of that of the uncoated AISI403. However, for the coated Stellite-padded AISI316L substrate, the weight loss was almost the same as that of the uncoated specimen.

Water-activated sonobuoy system

Abstract: A water-activated sonobuoy system is provided to release a plurality of sle, water-activated sound sources into a water environment. In the preferred embodiment, a plurality of water-impenetrable tubes are attached and sealed at one end to a float and are open on their other end. A plurality of water-activated sound sources are stored within each tube. Water-degradable barriers are used to isolate each of the sound sources within the tubes. Water-degradable endcaps are used to seal the open end of each tube. Upon being placed in the water, the endcaps dissolve to release the first sound source in each tube. This in turn exposes the first barrier in the tube to water. Each exposed barrier subsequently dissolves in the water to release the next water-activated sound source in each tube. This process continues until all sound sources have been released into the water. Appropriate venting is provided in both the barriers and the float to permit controlled water entry from the bottom of the tubes.

Water Pollution Control with Two-Phase Dense-Bubble Plumes

Abstract: Miscible dense liquids discharged in a water environment form dense plumes. These plumes do not mix well with ambient water, and spread along the bottom. It is possible, however, to transform a dense plume into a quasi-buoyant plume by introducing a gas (e.g. air or oxygen) into the flow. This two-phase plume is named dense-bubble plume. An integral model is formulated to study dense-bubble plumes and assist in designing dense-bubble outfalls. The study shows that air flow has a significant effect on the development of a dense plume when it approaches a critical value. The plume reaches the free surface, and dilution is maximized, when air flow is greater than the critical value. When air flow is less than the critical value, only a fraction of the plume fluid is carried to the free surface. In this case, part of the plume separates, falls back, and spreads on the bottom. The critical supply of air is found to vary with water depth and discharge densimetric Froude number.

Glycation of lysozyme in a restricted water environment.

Abstract: Fast atom bombardment mass spectrometry (FAB) was used to determine the glycation sites of lysozyme in a restricted water environment. A 30-day incubation at 25 degrees C, and 65% relative humidity (R.H.) resulted in glycation at lysine-1 while a much shorter (3-day) incubation at 50 degrees C and 65% R.H. resulted in diglycation at lysine-1 as well as glycation at lysine-13 and lysine-33.

Abstract: Sedimentology and Biostratigraphy of Cores in Miocene Deposits, Offshore Louisiana, Gulf of Mexico

Abstract: As oil exploration in the Gulf of Mexico advances further basinwards, key late Tertiary and Quaternary reservoir targets are increasingly sought in deepwater systems tracts dominated by turbidite and other gravity flow deposits. Depositional and stratigraphic models in deepwater settings are diverse and commonly complex. This is especially so in the Gulf of Mexico, where the interaction of sediment and shallow buried salt adds to an already complex picture. Acquisition of conventional cores increases our understanding of deepwater deposition, particularly in paleo-slope settings. Nearly 120m (400) of near continuous core recovered from Miocene slope deposits, offshore Louisiana has been described and analyzed for sedimentological and biostratigraphic information. Provisional results show that in this case study sandy slope deposition comprises a wide variety of gravity flow processes in broadly a middle bathyal setting. However, two distinct slope associations are clearly recognized from biostratigraphic and sedimentological signatures. Association A is characterized by relatively organized and undisturbed sandy turbidites that display vertical thickening and thinning trends, but which yield little or no flora and fauna. Individual sand beds range from less than one mm to a few metres in thickness, are very fine to fine grained and typically exhibit cross- and planar lamination structures. Association B is irregularly bedded, has coarser sands and yields a rich assemblage of reworked and indigenous flora and fauna that identify local and regional source areas for the slope sediments. The sand beds in this association are up to 6m in thickness, contain numerous mudstone clasts and shell fragments and are interbedded with disturbed claystone and siltstone lithofacies. Interpretation of these two contrasting slope associations is assisted by local seismic mapping. These analyses provide a structural and stratigraphic context that is similar for both associations. Therefore the principal control on major changes in slope deposition in this case study appears to be external variations in the nature of sediment supply. Association A may reflect a period of relatively well structured turbidite deposition, comprising numerous individual sandy and barren flows, during which background hemipelagic deposition was either diluted of excluded at the site of deposition. Association B, in contrast, may reflect rather catastrophic slope processes, during which the initiation of large and sandy turbidites, together with rafted and slumped mudstones resulted in a diverse array of shallow water facies being redeposited in a much deeper water environment. End_Page 556------------------------ Figure 1. The sedimentological and stratigraphic significance of these major changes in slope processes is difficult to address from a single case study. However, it is possible to make some links with the overall seismic stratigraphy of the Mio-Pliocene shelf margin updip from the core location. These analyses suggest periodic break-up of shelf margin deltas and/or the initiation of canyon features may well be linked to the slope associations identified in the core. End_of_Record - Last_Page 557-------