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Wie viele Landwirte zaehlt das Jahr 2000?
1988
Anker P. | Schmitz P.M.
Estudo comparativo da rentabilidade de géneros alimentares a frescos e congelados : análise de custos de equivalentes
1988
Caldeira, Ana Paula Bettencourt | Kent-Smith, Luiza
Revisão bibliográfica sobre técnicas epidemiológicas, fibras alimentares e sua relação com o cancro colo-rectal
1988
Amaral, Teresa Maria de Serpa Pinto Freitas do | Maia, Joaquim de Oliveira Costa
Faktory, limitiruyushchie chislennost' blagorodnykh olenej v Moldavii.
1988
Chegorka P.T.
The complexation of protons, aluminium and calcium by aquatic humic substances: A model incorporating binding-site heterogeneity and macroionic effects
1988
Tipping, E. | Backes, C.A. | Hurley, Margaret Anne
A model is presented that describes the competitive binding of protons and metal ions (Al3+, AlOH2+, Ca2+) by humic substances (HS) in the pH range 3–6 and at different ionic strengths, and allows the net humic charge to be calculated. The HS are treated in terms of two types of carboxyl group, together with other more weakly-acidic groups, and the influence of humic (macroionic) charge is taken into account. Eight parameters are involved: total humic acidity, which can be measured directly, content of COOH groups, 4 intrinsic equilibrium constants (2 for H+ binding, 2 for metal binding), and 2 parameters accounting for charge effects at different ionic strengths. The model was applied to 4 aquatic humic samples, parameters being estimated from acid-base titration data. The equilibrium contents did not vary greatly among the humic samples, which is consistent with the idea that the functional groups in each sample are chemically the same. The effect of humic charge on complexation varies considerably among the samples. The model was reasonably successful at predicting humic-bound Al in laboratory-prepared solutions and field samples. Calculations based on the model suggest that, (1) Ca2+ does not compete significantly with Al for binding to HS under natural acid conditions, and (2) that there is a direct relationship between humic solubility and net humic charge.
Mostrar más [+] Menos [-]A model of solid-solution interactions in acid organic soils, based on the complexation properties of humic substances
1988
Tipping, E. | Hurley, Margaret Anne
CHAOS (Complexation by Humic Acids in Organic Soils) is a quantitative chemical model of organic soils that incorporates complexation by the functional groups of humic substances and non-specific ion-exchange reactions. The two types of interaction are linked by the net humic charge, Z, which depends on the extents of proton and metal complexation, and which in turn determines ionic concentrations in the diffuse part of the electrical double layer, by a Donnan equilibrium. CHAOS was found to account satisfactorily for the results of acid-base titration experiments (pH range 3–5) with soil samples, giving reasonable simultaneous predictions of solution pH and concentration of A13+. Predictive calculations with CHAOS suggest that organic soils acidified by acid rain would respond on a time-scale of years-to-decades to reductions in rain acidity. An associated effect might be an increase in the concentration of dissolved organic matter in the soil solution.
Mostrar más [+] Menos [-]EIA and the Planning Process
1988
Clark, Michael | Herrington, John
Geneticka analiza broja plodova po biljci paprike.
1988
Gvozdenovic Dj.
The genetic base, number of fruits, i.e. the mode of inheritance and the components of the genetic variance of peppers were studied. Six pepper varieties, diallel crosses without reciprocal crossing, were used in this study. The following has been determined: for the analyzed property, the number of fruits per plant of the 6 varieties in the F1 and F2 generations, significant differences were observed. The effects of the additive and non-additive genes played a significant role in the inheritance of the number of fruits, while the role of the additive genes prevailed. The calculated value of the degree of domination of H1D was lower than the unit indicating partial dominance. Recessive genes were predominant in the F1 generation, while the dominant genes were predominant in the F2 generation for the studied property. The greatest part of the total genetic variability of the number of fruits per plant in peppers is of an additive character.
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