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The authors made a comparative study of the resistance of three strains of virus, Sabin poliovirus I, Mahoney poliovirus I and réovirus I, in sea-water and in river water, “in vitro” and “in situ” in dialysis bags. The results show the preponderant role of the incubation temperature and the exchanges existing between bags on the resistance of the viral strains. The role of these different factors is discussed. 相似文献
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The Science of Nature - 相似文献
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In this work, the impact of moisture on the volatility of heavy metals present in municipal solid wastes (MSW) in a laboratory scale simulated incinerator was studied, using synthetic waste consisting of 5.4 g of wood powder, 2.6 g lava, 1.9 polythene, 0.19 g polyvinyl chloride, and a given quantity of water and heavy metals represented by lead, zinc and copper in forms of metallic, chlorides and oxides. It is found that the presence of high moisture in MSW will greatly reduce the volatilization of heavy metals in MSW in the incineration process. The volatilization behavior of chlorides, oxides and the metallic species with respect to the effect of moistures is quite different. For copper, the presence of moisture in MSW depresses the volatilization of oxides, and increases that of chloride and the metallic species, while in contrast, the volatilization of both lead and zinc is always depressed by the presence of moisture in MSW, regardless of the chemical forms used. The chemical mechanisms, which govern the volatilization behaviors of different chemical forms in the incineration process, are proposed. Hydrolysis, dewatering of hydrolyzed species, sublimation, chemical transformation of less volatiles to more volatiles or reverse, may participate in and affect the volatilization of heavy metals in MSW. 相似文献
199.
The impact of nitrogen fertilizers on gaseous emissions duringwinter and spring-thaw is not well understood and was the objective of this research. Using a micrometeorological method,N2O, NO and NOx fluxes from ryegrass were measured from November 1997 to March 1998. Three different mineralfertilizers were applied in November: urea (U), slow-release urea(SRU) and ammonium nitrate (AN). N2O emissions during the winter were small, increasing significantly in March. Total losses of N2O-N were significantly higher from SRU and U plots, with winter N2O emissions accounting for 50% of annual losses. Nitric oxide fluxes from all plots weresmall during the measurement period (<0.9 ng N m-2 s-1). The NO fluxes from U and AN fertilized plots were significantly higher than from SRU and control plots. NO2 fluxes were always negative (–6 ng N m-2 s-1)indicating deposition, but decreased to –2 ng N m-2s-1 when snow was present on the soil surface. Our resultsindicate that the form of inorganic N applied has an effect on NO+ N2O emissions but not on NO2 fluxes.Sponsored by CAPES – Brasília, Brazil 相似文献
200.
Cooperation among non-kin has been attributed sometimes to reciprocal altruism: Two or more individuals exchange behaviour
that benefits the respective partner. According to direct reciprocity, cooperation is based on past behaviour of a known partner.
In contrast, in generalised reciprocity, cooperation is based on anonymous social experience where the identity of the partner
is irrelevant. In a previous study, female Norway rats (Rattus norvegicus) were found to cooperate according to a generalised reciprocity mechanism. In this study, we tested whether Norway rats would
also cooperate as predicted by a direct reciprocity mechanism and whether direct reciprocity would cause a higher propensity
to cooperate than generalised reciprocity. Focal animals were experimentally manipulated to receive social experience from
known or unknown, helpful or defecting partners in an instrumental cooperative task. Our first experiment shows that rats
are more helpful towards a partner from which they had received help before than towards a partner that had not helped (i.e.
direct reciprocity). Our second experiment revealed that after receiving help by others, rats were more helpful towards a
partner from which they had received help before than towards a new partner (i.e. direct reciprocity generated a higher cooperation
propensity than generalised reciprocity). We conclude that in female Norway rats, the tendency to cooperate is influenced
by partner-specific information. To our knowledge, this is the first study to demonstrate direct reciprocity in rodents, and
it is the first study testing direct vs generalised reciprocity in animals. 相似文献