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1.
Kevin R. Stuart Arnold G. Eversole David E. Brune 《Journal of the World Aquaculture Society》2001,32(1):105-111
Abstract.— The freshwater mussel Elliptio complanata was provided water containing green algae and cyanobacteria delivered from the Partitioned Aquaculture System (PAS) at eight flow rates to determine algal filtration rates as mg of particulate organic carbon (POC)/kg wet tissue weight per h. The dominant taxon in cyanobacterial waters was Microcystis while the dominant taxa in green algal waters were Scenedesmus and Ankistrodesmus . The cell counts of Scenedesmus and Ankistrodesmus were the only algal taxa that were significantly different between the incoming water and water filtered by mussels. Filtration rates of POC obtained from green algal water were significantly greater than from cyanobacteria-dominated waters at all flow rates. A significant increase in mean filtration rate was observed as flow rates increased. The filtration rate of green algae increased as POC concentration increased, peaking at 28 mg C/L. A maximum filtration rate was not observed with cyanobacterial waters. 相似文献
2.
Christopher R. Mueller Arnold G. Eversole Hakan Turker David E. Brune 《Journal of the World Aquaculture Society》2004,35(3):372-382
Growers produce over 2.8 million kg of catfish (over $350 million wholesale revenue) annually in the United States. The microbiology of the phytoplankton community in culture water affects the growth and flavor of the catfish and is a consideration for growers. Filter feeders, like silver carp and freshwater mussels, in controlled growth systems are used to adjust the phytoplankton species. Our goal was to successfully control the algal populations with filter feeders in catfish production. We used silver carp Hypophthalmichthys molitrix as a filter feeder in Partitioned Aquaculture System (PAS) water. Silver carp completely eliminated the cyanobacteria Microcystis by size and biovolume reduction. This created the desired effect of small green algae dominating the algal community. A significant but opposite change was observed when freshwater mussels Elliptio complanata filtered PAS water resulting in Microcystis biovolume and size dominance in the PAS; a less desirable algal community. This study also showed an immediate shift in the phytoplankton community when silver carp and mussels were interchanged between PAS waters. The size-selective filtration by the two filter-feeding taxa was important in determining the composition of the PAS phytoplankton community, and it was apparent that filtration with silver carp successfully depleted undesirable algae. 相似文献
3.
Seismic waves generated by earthquakes or explosions show a delay in travel times as they propagate across the Sierra Nevada from all directions except that of the Nevada test site. Early arriving waves from the test site can be explained if they emerge through a rock layer with high seismic velocity from the sharp eastern edge of the Sierran root. Such a layer could be formed by the subducted ophiolite slab that crops out in the western Sierra Nevada foothills. A synthesis of all seismic data indicates that the Sierran root projects downward into the mantle to a depth of about 55 kilometers beneath the high Sierra. 相似文献
4.
A new design in a high rate nitrification system has been tested at the laboratory scale. Ammonia removal rates per unit of filter volume at influent ammonia levels of 0.02 mg NH3-N were observed to be 5 to 10 times more rapid than rates observed in conventional field-scale nitrification filters. At these levels 95 to 99% ammonia removal has been achieved with filter detention times as short as 3 minutes. The data are compared to data for various field units and the reasons for the observed high removal rates are discussed. The possibility of retaining these high efficiencies in scaled-up filters is also discussed. 相似文献
5.
Barley seedlings were grown in hydroponic culture in the presence of toxic concentrations of cadmium (Cd), molybdenum (Mo), nickel (Ni), and zinc (Zn) and analyzed for element composition [boron (B), calcium (Ca), Cd, iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), phosphorus (P), and Zn]. In a first survey, heavy metal concentrations were selected which resulted in a similar inhibition of root growth. Toxic concentrations of Cd, Mo, Ni, and Zn revealed both similar and distinct effects on specific leaf and root element contents. Examples for such responses were decreasing contents in root Mn and Mg at elevated levels of all heavy metals, including Mo, in the medium. In contrast, changes in root contents of B were specific for the applied type of heavy metal stress. The heavy metal dependent changes in B, Ca, Mg, and Mn contents were studied in more detail. In some cases, severe heavy metal toxicity caused excessive accumulation or depletion of nutrient elements that may be deleterious to the plants in addition to other primary damages caused by the heavy metal ions. 相似文献
6.
H. Brune 《Plant foods for human nutrition (Dordrecht, Netherlands)》1969,18(1-3):134-151
Zusammenfassung Die Stickstoff-Düngung kann in der Regel neben einer Ertragssteigerung im Pflanzenaufwuchs auch zu einer quantitativen Variation der N-haltigen Substanz in der erntereifen Nahrungspflanze führen. Diese Qualitätsveränderung des Nahrungsmittels im Komplex Rohprotein (N × 6,25) oder anderer N-haltiger Pflanzen-Inhaltsstoffe (z.B. NO3) ist ernährungsphysiologisch bedeutsam.Das Studium des N-Stoffwechsels der Pflanze unter verschiedenen Umweltbedingungen, insbesondere der Stickstoff-Düngung, hat bis heute einen umfassenden Einblick in die chemisch-analytisch erfaßbaren Fraktionen der N-haltigen Substanz in der Pflanze gebracht. Die ernährungsphysiologische Bedeutung des Komplexes der N-Fraktionen und ihrer Variabilität kann in der Regel nur grob eingeschätzt werden. Die Ursachen hierfür liegen nicht zuletzt im erforderlichen Aufwand für ernährungsphysiologische Untersuchungen.Es wird ein Einblick in den Verwertungsgang von N-Verbindungen aus Pflanzen im tierischen Organismus gegeben und die Reaktionen hervorgehoben, die ernährungsphysiologisch primär relevant erscheinen. Methoden zur Erfassung ernährungsphysiologischer Wirkungen und die Wahl geeigneter Versuchstiere für die Übertragbarkeit der Versuchsergebnisse auf den Menschen, werden diskutiert.Die Gesamtproblematik wird an Hand von Beispielen über die Änderung des biologischen Eiweißwertes durch N-Düngung (Getreide, Kartoffeln, Grünkohl) und der Wirksamkeit spezifischer ernährungsphysiologischer Noxen (NO3 im Spinat) aufgezeigt.Es wird aus den Beispielen die Schlußfolgerung gezogen, daß auf dem Gebiet der Ernährungsforschung eine Zusammenarbeit mehrerer Folgedisciplinen — Pflanzenproduktion-Ernährungsphysiologie — notwendig ist.
Vortrag gehalten auf der gemeinsamen Tagung der Internationalen Vereinigung zur Erforschung der Qualität von Nahrungspflanzen (CIQ) und der Deutschen Gesellschaft für Qualitätsforschung (Pflanzliche Nahrungsmittel) (DGQ) in Mainz (25.–27. März 1969) am 26.3.1969. 相似文献
Besides its growth stimulating and yield increasing effect on plants, fertilization with nitrogen may also lead to quantitative variation in the quality of food plants, ripe for harvesting.This variation in the quality of plant foods estimated by their crude protein (N × 6.25) content or other N-containing compounds (e.g. NO3) is of nutritional importance.Research in the nitrogen-metabolism of plants grown on variable conditions, e. g. fertilizing with different amounts of nitrogen, resulted in an extensive knowledge on N-constituents of plants as can be measured by chemical analytical methods.The nutritional significance of all the N-containing fractions and their variability in plant material can so far be estimated only marginally. Reasons for this are mainly due to the high expense of nutritional experiments. The metabolic course of N-constituents from plants feed to the animal is described, stressing those reactions being most important to nutrition. Methods of estimating the nutritive effects of plant material are discussed. The reliability of applying results obtained by animal experiments to the human are considered. The overall problems are demonstrated on figures showing the variation in the biological value (B V) of plant foods having given different amounts of N (cereals, potatoes, kale) and the effect of specific nutritionally peculiar reacting compounds (e.g. NO3 in spinach).It is concluded that research in nutrition demands cooperation of several disciplines such as plant production and nutritional physiology.
Résumé En régle générale, la fumure azotée peut également entrainer à coté d'un accroissement du rendement des cultures une modification quantitative des substances contenant de l'azot dans les plantes alimentaires à maturité. Cette modification de la qualité des produits alimentaires en ce qui concerne les matières azotées totales (N × 6,25) ou d'autres substances végétales azotées est d'une grande importance sur le plan de la physiologie de la nutrition.L'étude du métabolisme de l'azot chez les végétaux dans des conditions ambiantes diverses, en particulier lors de la fumure azotée, a donné jusqu'à présent un vaste aperçu des composants chimiquement analysables de la matière azotée végétale.L'importance nutritionelle de l'ensemble des composants azotés et de leur variabilité ne peut en général être estimée qu'approximativement. Cela provient particulièrement de l'importance des moyens nécessaires pour les recherches de physiologie nutritionelle.Nous donnons un aperçu sur le cours de la transformation des composés azotés végétaux dans l'organisme animal et soulignons les réactions qui semblent importantes au point de vue de la physiologie de la nutrition.Nous discutons les méthodes d'appréciation de la valeur nutritionelle et le choix des animaux d'expérience permettant l'application des résultats à l'homme. La position du problème est mise en évidence au moyen d'exemples qui montrent la modification de la valeur biologique de la protéine par la fumure azotée (céréales, pommes de terre, chou vert) et qui montrent l'action des nuisanies spécifiques nutritionelles (NO3 dans les épinards).On peut conclure à l'aide de ces exemples qu'une collaboration de plusieurs disciplines complémentaires-production des plantes - physiologie de la nutrition — est indispensable dans le domaine des recherches sur la nutrition.
Vortrag gehalten auf der gemeinsamen Tagung der Internationalen Vereinigung zur Erforschung der Qualität von Nahrungspflanzen (CIQ) und der Deutschen Gesellschaft für Qualitätsforschung (Pflanzliche Nahrungsmittel) (DGQ) in Mainz (25.–27. März 1969) am 26.3.1969. 相似文献
7.
Brune H 《Science (New York, N.Y.)》2006,312(5776):1005-1006
8.
A dynamic model of dissolved oxygen behavior in a stillwater aquaculture pond is presented. Using theories and principles that have been established for aerobic waste-water treatment ponds and shallow lakes and reservoirs, equations were developed to describe the short-term dissolved oxygen fluctuations of an aquaculture pond. Components considered in this model include the consumption and production of oxygen by phytoplankton, fish, detritus, and the process of reaeration. Factors affecting these components can be specified by the user; these include meteorologic and geographic data, and phytoplankton, fish, and detrital characteristics. After comparing the model to field data and analyzing the sensitivity of its components, areas of research which may have an impact on pond management are identified. 相似文献
9.
A laboratory experiment shows that ridge-ridge transform faults, inactive fracture zones, and other features characteristic of spreading oceanic ridges can be produced in a variety of paraffins. Although the resultant pattern depends upon the temperature of the wax and the ratio of spreading rate to surface cooling, the characteristic orthogonal ridge transform fault system is a preferred mode of separation. Symmetric spreading occurs under conditions of no tensile strength across the ridge, and the stability of transform faults is a consequence of their lack of shear strength. The experiment also shows that properties characteristic of oceanic ridges occur under conditions of passive convection where upwelling of material at the ridge crest is a result only of hydrostatic forces in the fluid; that is, the plate separation is caused not by large convective forces beneath the ridge but rather by tensile forces in the plate. 相似文献
10.
How strong is the case linking global release of chlorofluorocarbons to episodic disappearance of ozone from the Antarctic stratosphere each austral spring? Three lines of evidence defining a link are (i) observed containment in the vortex of ClO concentrations two orders of magnitude greater than normal levels; (ii) in situ observations obtained during ten high-altitude aircraft flights into the vortex as the ozone hole was forming that show a decrease in ozone concentrations as ClO concentrations increased; and (iii) a comparison between observed ozone loss rates and those predicted with the use of absolute concentrations of ClO and BrO, the rate-limiting radicals in an array of proposed catalytic cycles. Recent advances in our understanding of the kinetics, photochemistry, and structural details of key intermediates in these catalytic cycles as well as an improved absolute calibration for ClO and BrO concentrations at the temperatures and pressures encountered in the lower antarctic stratosphere have been essential for defining the link. 相似文献