Evaluation of the efficiency of measures for sulphidic mine waste mitigation

To control the environmentally detrimental impact of acid rock drainage, two different countermeasures, layers of acid-buffering materials and sodium dodecyl sulphate addition, were tested for their efficiency in laboratory percolation experiments. In the experiment with a layer of calcium bentonite, only the iron output was reduced. The experiments with layers of concrete grains demonstrated a decrease of the microbial activity as well as a precipitation of heavy-metal ions, whereas the cell numbers did not decrease. Furthermore, finely grained concrete (1–5 mm) formed a water-tight hardpan (self-sealing layer). In the experiment with 1 mM sodium dodecyl sulphate, all the microorganisms were killed and hence metal sulphide dissolution was stopped. With 0.1 mM sodium dodecyl sulphate only a short, transient inhibition of leaching was achieved. The bacteria remained alive. Received: 16 February 1998 / Accepted: 23 February 1998     

Kinetic properties of liver pyruvate kinase from the flounder (Platichthys flesus L.)

Pyruvate kinase, purified from flounder liver, in two forms, i.e. PK I and PK II, is characterized by sigmoid kinetics with phosphoenolpyruvate as substrate at pH 6.3, 6.7 and 7.7. K0.5 for PEP increases with increasing pH. PK I and PK II show hyperbolic kinetics with ADP, but are inhibited by ADP concentrations above 1-2 mM. K0.5 for ADP decreases with increasing pH. PK I and PK II differ in their K0.5 values for PEP with a factor of at least 2, showing the highest figures for the latter. K0.5 for ADP is about the same for the two enzyme forms. Other nucleotide diphosphates can replace ADP as the substrate. When the nucleoside diphosphates are arranged in a rank order showing decreasing effectiveness as substrate, different rank orders are obtained for PK I and PK II.     

Importance of Hydrogen Sulfide, Thiosulfate, and Methylmercaptan for Growth of Thiobacilli during Simulation of Concrete Corrosion

Biogenic sulfuric acid corrosion of concrete surfaces caused by thiobacilli was reproduced in simulation experiments. At 9 months after inoculation with thiobacilli, concrete blocks were severely corroded. The sulfur compounds hydrogen sulfide, thiosulfate, and methylmercaptan were tested for their corrosive action. With hydrogen sulfide, severe corrosion was noted. The flora was dominated by Thiobacillus thiooxidans. Thiosulfate led to medium corrosion and a dominance of Thiobacillus neapolitanus and Thiobacillus intermedius. Methylmercaptan resulted in negligible corrosion. A flora of heterotrophs and fungi grew on the blocks. This result implies that methylmercaptan cannot be degraded by thiobacilli.     

QALYs, age and fairness

... We can therefore conclude that either we should go for equality; and in that case QALYs are unfair because they haven't got enough of an ageist bias. Or we should accept consequentialism; and in that case QALYs have just the right sort of ageist bias. No plausible case can, however, be made for the claim that QALYs have an unfair bias against old people. Other things being equal we ought when distributing resources essential for survival favour the young. This ethical claim can be supported both by reference to equality (the life-time-view) and by reference to consequentialism (and the premises that resources generally will be more useful when given to young people).     

Geographical and latitudinal variation in growth patterns and adult body size of Swedish moose (Alces alces)

We examined the geographical pattern in growth and adult body size among 14 populations of Swedish moose (Alces alces) using data from 4,294 moose (1.5 years old) killed during the hunting season in 1989–1992. In both sexes, adult body mass was significantly positively correlated with latitude. Moose in northern populations had a 15–20% larger adult body mass than moose in the south. Juvenile body mass was correlated with neither latitude nor adult body mass. Thus, variation in time (years) and rate of body growth after the juvenile stage were responsible for most of the variation in adult body mass among populations. Moose in northern populations grew for approximately 2 more years of life than southern moose. In contrast to adult body mass, skeletal size (measured as jawbone length) was not correlated with latitude, suggesting that variation in adult body mass was primarily due to differences in fat reserves. Discrimination between population characteristics, such as moose density, climate, and the amount of browse available to moose, showed climatic harshness to be the most important variable explaining geographical variation in body mass among populations. The results support the notion that in mammals body size increases with latitude in accordance with Bergmann's rule. We conclude that (1) variation in patterns of growth after the juvenile stage is the main cause of the latitudinal trend in adult body size in moose, and (2) climatic conditions are a more important factor than population density and availability of food in explaining geographical variation in growth patterns and adult body mass between populations of Swedish moose.     

Sulfur chemistry,biofilm, and the (in)direct attack mechanism — a critical evaluation of bacterial leaching

It has been shown (a) that bacterial leaching of metal sulfides apparently requires the attachment of leach bacteria to metal sulfides, (b) that exopolymerbound iron compounds are responsible for or at least considerably increase the rate of the biological attack over the chemical rate, (c) that the primary attacking agent in leaching environments is the ferric iron hexahydrate ion, (c) that thiosulfate is the first intermediate sulfur compound, giving rise to a variety of other compounds including polythionate-containing periplasmic granula, and (d) that we have no idea about the actual concentrations of protons, ferrous/ferric and/or other cations, and sulfur compounds in the reaction space between the bacterium and the sulfide surface.     

Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans

Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and D. simulans for two common allozyme forms, as well as for several other less common variants. Parallel latitudinal clines in the frequencies of the common EST6-F and EST6-S allozymes in these species have previously been interpreted in terms of a shared amino acid polymorphism that distinguishes the two variants and is subject to selection. Here we compare the sequences of four D. simulans Est-6 isolates and show that overall estimates of nucleotide heterozygosity in both coding and 5' flanking regions are more than threefold higher than those obtained previously for this gene in D. melanogaster. Nevertheless, the ratio of replacement to exon silent-site polymorphism in D. simulans is less than the ratio of replacement to silent divergence between D. simulans and D. melanogaster, which could be the result of increased efficiency of selection against replacement polymorphisms in D. simulans or to divergent selection between the two species. We also find that the amino acid polymorphisms separating EST6- F and EST6-S in D. simulans are not the same as those that separate these allozymes in D. melanogaster, implying that the shared clines do not reflect shared molecular targets for selection. All comparisons within and between the two species reveal a remarkable paucity of variation in a stretch of nearly 400 bp immediately 5' of the gene, indicative of strong selective constraint to retain essential aspects of Est-6 promoter function.      

Oxidation of fatty alcohols to acids in the caecum of a gourami (Trichogaster cosby).

Oxidation of fatty alcohols to acids in gourami caeca was investigated by measuring the reduction of NAD+ and the formation of labeled hexadecanoic acid from [1(-14)C]hexadecanol. Virtually all dehydrogenase activity is in the microsomal fraction. Maximal activity is obtained with NAD+ as cofactor whereas with NADP+ 60% of that activity is obtained. The enzyme is rather specific for long chain alcohols and 2 NADH are formed for each molecule of hexadecanol oxidized to acid. It is stabilized by mercaptoethanol, and completely inhibited by p-chloromercuribenzoate. The activity is optimal at pH 9.5. At higher pH, small amounts of aldehyde are found. The first reaction in the sequence, fatty alcohol leads to aldehyde leads to acid seems to occur under the more physiological condition at a much slower rate than the second reaction so that free aldehyde is not detected. Addition of palmitic acid indicated an uncompetitive product inhibition. The oxidation of alcohol to acid is reversible only to a very minor extent even in the presence of NADPH, CoA, ATP and Mg2+. Location, activity and properties of the enzyme are in agreement with the earlier observation from dietary experiments that in the gourami fatty alcohols of wax esters are oxidized to acids in the course of absorption.