Ecology of microalgae in a high rate pond for piggery effluent purification in Singapore

Summary An integrated system for the collection, treatment and utilisation of piggery wastewater has been developed in Singapore which uses the cultivation of microalgae in high rate ponds to achieve reduction of BOD₅ and COD₅ of the effluent as well as producing single cell protein. A wide range of algal flora occurs in the ponds;Oocystis, Micratinium, Scenedesmus, Ankistrodesmus, Chlorella andOscillatoria spp were identified. Total algal counts, recorded from 1979 to 1981, ranged up to 10⁷ per ml of pond water. There were considerable variations in the algal population and in the predominating species. No discernible pattern was evident. Consequently pond operations were frequently disturbed by these fluctuations in population which in turn was attributed to the heterogeneous composition of the piggery waste, to variable weather conditions and to predation by larger organisms particularlyMoina. After passing through the ponds, the total suspended solids were removed by a novel dissolved air flotation method which gave a clear effluent showing an 87% reduction in BOD₅ value.

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Resumen En Singapur se ha desrrollado un sistema integrado para le recogida, tratamiento y utilización de aguas residuales de pocilgas. Este sistema usa el cultivo de microalgas en estanques, de caudal rápido afin de reducir las DBO₅ y DCO₅ del efluencte produciendo asimismo proteínas celulares. La flora de algas producida en estos estanques es amplia y variada, habiendose identificado:Oocystis, Micratinium, Scenesdemus, Ankistrodesmus, Chlorella y Oscillatoria. Los recuentos totales de algas tomados desde 1979 a 1981 llegaron a alcanzar 10;⁷ por ml de agua del estanque. Se observaron variaciones considerables tanto en la población total de algas como en las especies predominantes sin que se pudiese, determinar un patrón de variación característico. Estas fluctuaciones en la población, causantes de frecuentes alteraciones en el funcionamiento del estanque, se atribuyeron a la composición heterogenea de los resuduos, a las variaciones climáticas y la predación por otros organismos particularmenteMoina Después de su paso por los estanque los solidos suspendidos totales se eliminaron mediante un nuevo método de flotación con aire disuelto, obteniendose un efluente limpio con una reducción de la DBO₅ del 87%.

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Résumé Un système intégré pour la collecte, le traitement et l'utilisation d'eaux résiduaires de porcherie a été développé à Singapoure. Il utilise la culture de micro-algues tant pour la réduction accélérée en lagune de la DBO₅ et de la DCO de l'effluent que pour la production de protéines uni-cellulaires. On trouve une large gamme de flore algale dans les lagunes; des espèces d'-Oocystis, deMicratinium, deScenedesmus, Ankistrodesmus, deChlorella etd'Oscillatoria out été identifiées. Les comptages totaux d'algues, enregistrées de 1979 à 1981, ont donné jusqu' à 10⁷ cellules par ml d'eau de la lagune. On a observé des variations considérables de population algale tant quantitatives que qualitatives. On ne discernait pas de spectres évidents. En conséquence, les opérations lagunaires ont été fréquemment perturbées par ces fermentations en population, qui, à leur tour, ont été attribuées à la composition hétérogène de l'effluent de porcherie, aux conditions atmosphériques et climatiques variables et à la prédation par des organismes plus conséquents, plus particulièrement desMoina. Après passage par les lagunes, les solides totaux en suspension ont été enlevés par une méthode nouvelle de flottation à l'air dissous, qui a donné un effluent limpide, présentant une réduction de DBO₅ de 87%.

     

Modulation of postinhibitory increase in plasma prolactin by domperidone in patients with prolactin secreting adenoma

To evaluate the PRL secretory mechanism in patients with PRL-secreting adenoma (PRL-oma), plasma PRL responses to dopamine (DA) were studied in these cases and in normal subjects. Plasma PRL values showed clear decreases during the infusion of DA (5 micrograms/kg/min for 90 min) in both 6 normal and 7 PRL-oma subjects (%decrease: 43.8 +/- 3.9% vs. 53.9 +/- 5.6%; NS) and postinhibitory increases after the termination. However, the postinhibitory increase occurred more promptly and markedly in PRL-oma patients than in normal subjects, i.e. the postinhibitory increase exceeded the basal level 45 min after the termination of DA infusion in PRL-oma patients, whereas the increase in normal subjects did not exceed the basal level even 90 min after the infusion. When domperidone was injected at the termination of DA infusion, the postinhibitory increases were significantly enhanced in either PRL-oma or normal subjects. The maximal increments in plasma PRL in the combination test of DA plus domperidone were significantly larger in PRL-oma patients, but were almost the same in normal controls, compared to the single domperidone test. In contrast, TRH did not modify the postinhibitory rises in 9 PRL-oma patients. These results indicate that the secretory properties and the sensitivities of lactotrophs to decreasing action of DA might be different between PRL-oma patients and normal controls. Further, the postinhibitory rebound phenomenon in PRL-oma patients is possibly determined by an overshoot of PRL storage concomitantly with a decreasing DA action.(ABSTRACT TRUNCATED AT 250 WORDS)     

Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes

Statistical methods for computing the standard errors of the branching points of an evolutionary tree are developed. These methods are for the unweighted pair-group method-determined (UPGMA) trees reconstructed from molecular data such as amino acid sequences, nucleotide sequences, restriction-sites data, and electrophoretic distances. They were applied to data for the human, chimpanzee, gorilla, orangutan, and gibbon species. Among the four different sets of data used, DNA sequences for an 895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979) gave the least reliable one. The DNA sequence data suggested that the chimpanzee is the closest and that the gorilla is the next closest to the human species. The orangutan and gibbon are more distantly related to man than is the gorilla. This topology of the tree is in agreement with that for the tree obtained from chromosomal studies and DNA-hybridization experiments. However, the difference between the branching point for the human and the chimpanzee species and that for the gorilla species and the human-chimpanzee group is not statistically significant. In addition to this analysis, various factors that affect the accuracy of an estimated tree are discussed.      

Species preservations in an optimal harvest model with random prices

In this paper, we consider an optimal harvest model in which the objective is to maximize the expected return. The unit price of biomass is assumed constant until a random time when the price increases by a given amount. Furthermore, due to obvious environmental protection requirements, it is assumed that the fishery population is bounded from below for all time so as to reduce the danger of species extinction. Clearly, this problem is an optimal control problem in which a random parameter is involved. However, due to its special structure, it is shown that the problem is convertible into a deterministic optimal control problem and hence is solvable by an existing optimal control software package, MISER. The practical implication of several computed results obtained by this approach is discussed. They are also compared with other related results in the literature.