Showing papers on "Water environment published in 1989"

The development and influence of gas bubbles in phreatic aquifers under natural flow conditions

Abstract: In a phreatic aquifer, bubbles may result from the entrapment of air during groundwater recharge and/or bacterial metabolism. The calculated critical depth of about 1 m at which bubbles are most likely to be found in a granular aquifer, coincides with the depth of 0.60 m of an almost stagnant water layer (specific discharge 1 × 10-6 cm sec-1) found at the water table region under natural flow conditions. Bubbles clog pores and therefore reduce the hydraulic conductivity without significantly reducing the volumetric water content. Stagnation at the water table region results since prevailing pressures (in the order of 10-1 atmospheres) are not sufficiently large to move bubbles through porous media in a water environment.

The Activity of Rifampin and Analogs against Staphylococcus epidermidis Biofilms in a CAPD Environment Model

Abstract: Rifampin has been noted to exhibit exceptional antimicrobial activity against Staphylococcus epidermidis biofilms as compared to commonly used antibiotics. To further explore this unique effect of rifampin, we evaluated the antimicrobial activity of three commercially available preparations of rifampin, two rifampin analogs (CGP29861 and rifapentine) and the parent compound rifamycin SV. These were tested against standardized S. epidermidis biofilms in various milieus. All six members of the rifamycin group tested demonstrated marked antimicrobial activity but with minor foci of resisters when tested in a peptone water environment. The microscopy of the exposed biofilms showed profound lysis and morphological distortion of the remaining cells. The synergistic elimination of the foci of resistance was achieved in an environment of fresh peritoneal dialysis (PD) solution or by the addition of vancomycin. Neither vancomycin nor fresh PD solution demonstrated significant antimicrobial activity when tested alone with biofilm preparations. Spent PD fluid markedly antagonized the activity of the rifamycins with the exception of the rifampin analogs, an effect primarily of pH. The synergistic effect of vancomycin with the rifamycins was not affected either by protein content or pH, leaving the antagonistic properties of spent PD fluid unexplained. The variable activity of the different members of the rifamycin group underlines the importance of structural differences in determining their interaction with bacterial biofilms. Further precision of the nature of these structural interactions is seen to have considerable potential for therapeutic advancement of catheter-associated sepsis.

Influence of crop water environment and dry matter accumulation on grain yield of no-till winter wheat

Abstract: The influence of crop water environment on the productivity of no-till winter wheat (Triticum aestivum L. ’Norstar’) was observed for 17 site-years of trials in Saskatchewan between 1984 and 1986. Growing season precipitation (P) averaged 212 mm (approximately 120% of average) and pan evaporation (E) averaged 749 mm for these trials. Precipitation was approximately evenly distributed across the growing season while E increased from a low of 6.5 mm d−1 in early May to a high of 8.3 mm d−1 immediately after anthesis. Consequently, water stress was highest after anthesis. Total evapotranspiration (ET) (soil water use to 130 cm plus growing season P) ranged from 171 to 364 mm and approximately 20% of the ET was derived from soil water reserves. The average ratio of ET before and after anthesis was 1:7:1 and in many instances water utilized after anthesis was almost exclusively derived from intermittent rainfall events. Several yield-water models were fit to the data in order to establish a relationship betwee...

Extractive Bioconversions in Aqueous Phase Systems

Abstract: The use of biocatalysts to perform conversions in processes is very appealing in many aspects. The reaction conditions — atmospheric pressure, ambient temperature, water environment and steroselectivity, all favour for biocatalysis. The drawbacks have, however, not been listed frequently, but should, of course, be considered as important. Bioconversions are often slow in relation to chemical processes, they yield a dilute product stream in water, and are often product inhibited. When designing biocatalytic processes, it is thus important to find conditions that fully exploit the advantages offered by the biocatalyst without neglecting the challenges raised by the mentioned limitations.

Heat treatment for heat-transfer pipe

Abstract: PURPOSE:To improve the corrosion resistance, particularly uniform corrosion resistance, of a pipe without the addition of new stages, by carrying out a part of the grain boundary-strengthening heat treatment process of a heat- transfer pipe made of Ni-base alloy under specific conditions and then forming an oxide film composed principally of chromium oxide on the surface of the above heat-transfer pipe. CONSTITUTION:As a part of the above heat treatment process in which the above pipe containing, by weight, 20-35% Cr and 40-70% Ni is heated and held under a vacuum as high as >=about 10 Torr, heat treatment is carried out by lowering the degree of vacuum to 10 -10 Torr under the conditions within the area enclosed with straight lines connecting the points A, B, C, D, E, F and A in figure, by which an oxide film composed principally of chromium oxide is formed on the surface of the above pipe. By this method, the corrosion resistance, particularly uniform corrosion resistance, of the above pipe used under a high-temp. and high-pressure water environment can be improved to a greater extent.

Dispensing fish lure

Abstract: A scent-dispensing fishing lure includes a liquid-dispensing cavity which receives a fish-attracting liquid The lure includes a mixing mechanism for mixing the fish-attracting liquid and environmental water in the cavity An inlet port is located at the front end of the cavity and allows entry of environmental water into the cavity while an outlet port is located at the rear end of the cavity and allows exit of a mixture of environmental water and the fish-attracting liquid into the water environment

Hydration of B-DNA: comparison between the water network around poly(dG).poly(dC) and poly(dG-dC).poly(dG-dC) on the basis of Monte Carlo computations.

Abstract: A computational method is elaborated for studying the water environment around regular polynucleotide duplexes; it allows rigorous structural information on the hydration shell of DNA to be obtained. The crucial aspect of this Monte Carlo simulation is the use of periodical boundary conditions. The output data consists of local maxima of water density in the space near the DNA molecule and the properties of one- and two-membered water bridges as function of pairs of polar groups of DNA. In the present paper the results for poly(dG) · poly(dC) and poly(dG-dC) · poly(dG-dC) are presented. The differences in their hydration shells are of a purely structural nature and are caused by the symmetry of the polar groups of the polymers under study, the symmetry being reflected by the hydration shell. The homopolymer duplex hydration shell mirrors the mononucleotide repeat. The water molecules contacting the polynucleotide in the minor groove are located nearly in the plane midway between the planes of successive base pairs. One water molecule per base pair forms a water bridge facing two polar groups of bases from adjacent base pairs and on different strands making a “spine”-like structure. In contrast, the major groove hydration is stabilized exclusively by two-membered water bridges; the water molecules deepest in the groove are concentrated near the plane of the corresponding base pair. The alternating polymer is characterized by a marked dyad symmetry of the hydration shell corresponding to the axis between two successive base pairs. The minor groove hydration of the dCpdG step resembles the characteristic features of the homopolymer, but the bridge between the O2 oxygens of the other base-stacking type is formed by two water molecules. The major groove hydration is characterized by high probability of one-membered water bridges and by localization of a water molecule on the dyad axis of the dGpdC step. The found structural elements are discussed as reasonable invariants of a dynamic hydration shell.

Fatigue crack growth behavior of pressure vessel steels and submerged arc weldments in a high-temperature pressurized water environment

Abstract: The fatigue crack growth rate (FCGR) properties of SA508 C1 2a and SA533 Gr A C1 2 pressure vessel steels and the corresponding automatic submerged are weldments were developed in a high-temperature pressurized water (HPW) environment at 288 °C (550°F) and 7.2 MPa (1044 psi) at load ratios of 0.02 and 0.50. The HPW enviromment FCGR properties of these pressure vessel steels and submerged arc weldments were generally conservative, compared with the approrpriate American Society of Mechanical Engineers (ASME) Section XI water environmental reference curve. The growth rate of fatigue cracks in the base materials, however, was considerably faster in the HPW environment than in a corresponding 288°C (550°F) base line air environment. The growth rate of fatigue cracks in the two submerged are weldments was also accelerated in the HPW environment but to a significantly lesser degree than that demonstrated by the corresponding base materials. In the air environment, fatigue striations were observed, independent of material and load ratio, while in the HPW environment, some intergranular facets were present. The greater environmental effect on crack growth rates displayed by the base materials, as compared with the weldments, was attributed to a different sulfide composition and morphology.

Weight Change and Mechanical Properties of GRP Panel in Hot Water

Abstract: This study deals with the effects of water environment on the mechanical properties of glass-fibre reinforced plastics (GRP) panels. After GRP panels are immersed in hot water (80°C) for 3000 h, they are weighed, and tensile, bending and acoustic emission (AE) tests are performed. Ultimate strength and elastic moduli decrease in proportion to increases of weight due to water absorption; however, elastic moduli eventually reach a constant value. It is clear that these phenomena are caused by debonding at the fibre/matrix interface, which is observed by AE amplitude distribution histograms and scanning electron micrographs of the fracture surface.

A Study on the Mechanism of the Bacterial Competitive Effects on Flexibacter columnaris Infection : Effects of the Time-lag between the Exposures of Fish to F.columnaris and Its Competitor

Abstract: Effects of the time-lag between the exposures of fish (loach) to Flexibacter columnaris and a competitive bacterium, Citrobacter freundii on the invasion by F.columnaris were investigated.It was found that the competitor could prevent invasion of the fish by F.columnaris if it was added within 1/2h after exposure to F.columnaris. In this case, F.columnaris failed to increase in number on the body surface of fish and water environment. The invasion of fish by F.columnaris did not occur when C.freundii was added prior to F.columnaris. On the other hand, F.columnbris was able to establish itself on the body of fish and successfully invaded fish when the competitor was added 1h or later after exposure of the fish to F.columnaris. In that case, the number of F.columnaris on the body surface as well as in the water environment gradually increased. The number of C.freundii on the body surface increased initially but decreased after 48h of exposure. In the water environment, C.freundii did not significantly vary in number.

Propagation of Delamination Fatigue Cracks in CFRP in Water

Abstract: The effect of a water environment on the near-threshold growth of delamination fatigue cracks was investigated with unidirectional laminates made from Ciba Geigy prepregs 914C (T300/914) and from Toray prepregs P305 (T300/#2500). Tests were carried out under mode I opening loading using double cantilever beam specimens. The crack growth rate was correlated to the equivalent stress intensity range without respect to the stress ratio. For 914C laminate, the crack growth rate in water was about one tenth of that in air in the power-law region. For P305 laminate, the effect of a water environment was small in the power-law region. Near the threshold, the crack grew slower in water than in air for both laminates. When the 914C laminate specimen was moisture-conditioned, the rate in water was about 300 times faster than that for the specimen in water without conditioning. These environmental effects were explained on the bases of fractography and fracture mechanisms.

Japanese contributions to fields of predicting and combating Environmentally Assisted Cracking(EAC) of steels in LWR water.

Abstract: Two major currents of the EAC relevant activities in Japan are reviewed in some chronological manner. One is the studies on the acceleration of fatigue crack growth in LWR. The work was first pioneered early in Japan, and extensive collaborative works have followed interacting with the international activities, which have yielded a clear views on the potential issues of the RPV structural steels used in the domestic NPPs. Another is the development of materials and techniques to combat the stress corrosion cracking of the structural materials in LWR water environment. Extensive collaboration among the government agencies, utilities, industries and academic societies lead the issues to a dramatic solution in rather short period. Both of those two aspects are stressed to have generic significance in the present and future nuclear technology.

Sampling device for water environment under ice layer

Abstract: The utility model provides a sampling device for water environmental monitor under ice layer, comprising a sampling rod, a rod joint, a limiting buckle, a rubber pipe, a rower pump, a sampler, a plankton sieve cloth or a sediment sampler. When needing sampling, the sampling rod and the rubber pipe are made to delimit the certain depth by the limiting buckle, and the rower pump is operated to get the water sample or the plankton of the required depth fault on the sampler or the plankton sieve cloth.

An investigation of fatigue strength correction factor for oxygenated high temperature water environment

Abstract: Strain cycled fatigue tests of carbon and low alloy steels were carried out in high temperature oxygenated pure water to observe the effects of strain rate, test temperature and dissolved oxygen content on fatigue life. From the analysis of the results, a proposal was made for a new environmental fatigue strength correction factor. It is available for simple modifications of the design fatigue curve specified in the ASME Boiler and Pressure Vessel Code, Section III for the purpose of taking into account the deleterious effects of slow strain rate in high temperature and oxygenated water environment.

Stress Corrosion Cracking Behavior of Granite under Pressurized High Temperature Water Environments and Crack Propagation Resistance

Abstract: In the development of design and control methodolgy for hot, dry rock (HDR) geothermal reservoir cracks, a full understanding of the environmentally assisted cracking behaviors of rock under the reservoir conditions is a prerequisite. In this stdy, the significance of time-dependent material degradation is demonstrated, which is induced by the water-rock interactions. In a 350°C, 18 MPa water environment, pre-immersion of 2 inch CT specimens of granite is given for different periods using an autoclave, after which the ultrasonic wave velocity measurements and fracture toughness tests are performed. The results show that the hydrothermal environment causes the time-dependent material degradation throughout the specimens tested, and that the crack propagation resistance of the granite is also time-dependent and decreases with increasing immersion time. Based on the experimental results, an immersion time-dependent crack growth model is proposed and applied to simulate the stress corrosion cracking test which has been conducted in the 350°C, 18 MPa water. It is shown that the proposed model allows us to predict the stress corrosion cracking behaviors under the pressurized high-temperature water environments.

The Impact of Flue‐gas Desulphurization on the Water Environment

Abstract: Electricity generation in the UK is dominated by fossil fuels, principally coal. In order to reduce emissions of sulphur dioxide to the atmosphere new fossil fuel-fired power stations will be equipped with flue-gas desulphurization (FGD) facilities, and in the short term the Central Electricity Generating Board proposes to retrofit FGD systems to 6000 MW of its coal-fired generation capacity, including the 4000-MW station at Drax. The first generation of these plants will be based on the limestone-gypsum process. In addition to the product gypsum the process generates a liquid effluent as a result of the need to remove chloride from the process inter alia to protect gypsum quality. This effluent also contains other contaminants such as metals, fluoride and nitrate, and a mathematical model has been developed to predict effluent volumes and composition as a function of different coal, limestone and process water combinations. The model also calculates the effect of the discharge of this effluent on a receiving watercourse, both untreated and following treatment based on neutralization and precipitation/sedimentation. The paper discusses the development of the mathematical model and the impact of treated FGD effluent on power station cooling-water discharges, via which the effluent would normally be discharged, for both once-through and recirculating cooling systems used at coastal and inland stations respectively.

CORMIX1: Expert System for Mixing Zone Analysis of Pollutant Discharges Into the Water Environment

Abstract: The Cornell Mixing Zone Expert System (CORMIX) is an integrated software package for the analysis, prediction, and design of aqueous toxic or conventional pollutant discharges into watercourses. Subsystem CORMIX1 is for the analysis of single port discharges. Emphasis is placed on the geometry and dilution characteristics of the initial mixing zone as well as far field mixing processes. The problem domain of CORMIX is discharges into flowing environments such as rivers, estuaries, lakes and coastal waters. CORMIX1 includes positively and negatively buoyant discharges into stratified crossflow. It contains the limiting cases of neutrally buoyant discharges and unstratified stagnant environments.

A rearing tank for aquatic organisms

Abstract: A unit for the cultivation of aquatic organisms where the zonal structure and operation make it possible to establish the required physical/chemical water environment for optimal growth and comfort. The unit is specifically designed for the cultivation of aquatic organisms ashore or in water and consists of a rearing tank which is devided into zones with associated support systems for the supply of water, the reuse of water, water treatment for reuse, water outlet, flow initiation, the division of zones and the sorting of fish. The unit is designed for the cultivation of all aquatic organisms that can be reared.