Nutrient Loading by Precipitation in the Maracaibo Lake Basin, Venezuela

Nutrient content and pH of rain samples collected at nine sites during 1988-1996 were studied to determine the amounts of N, P and S added by precipitation over Maracaibo Lake basin. The basin is a wide depression occupied by Lake Maracaibo and extensive alluvial plains and delimited by a mountainous zone of variable physiolgraphic characteristics with different cattle ranching and industrial activities. Rain pHs averaged ≈ 4 to 6, individual samples occasionally reached as low as pH 3 in the south basin. NH₄ ⁺ levels were significantly higher (up to 2.6 mg/l NH₄-N) than NO₃ ^? plus NO₂ ^?. Phosphorus levels were low, ranging from undetectable to 1.5 mg/l. The amounts of inorganic N/ha/yr added ranged from ≈ 5.4 Kg in the north to ≈ 8 Kg in the south basin; around the lakeshore, it was estimated that ≈ 9.8–16.8 Kg TN/ha (≈ 55 % as organic-N) are annually deposited. The annual amounts of SO₄-S/ha added range from ≈ 10 to 13 Kg. The contribution of precipitation to P in the ecosystem is very small; ≈ 0.02 – 0.8 Kg of PO₄-P/ha/yr was added in basin. The results of this study show that precipitation represents a significant factor for the total nitrogen and sulfur loading to Maracaibo Lake Basin.     

A comparison of methods for soil microbial population and biomass studies

A comparison was made of 15 different techniques which are used in assessing soil microbial populations and/or biomasses. These include direct observations (fungal standing crop, fluorescein diacetate active mycelia, acridine orange stained bacteria), cultural methods (bacterial plate counts), physiological methods (total microbial, bacterial and fungal biomasses, O₂-uptake), soil enzyme analyses (dehydrogenase, catalase, alkaline and acid phosphatase, protease, amylase), and ATP-analyses. The various techniques were applied to six soils known to have different microbial characteristics. The results are discussed with respect to the convertability of counts and measurements into microbial biomasses, the variability of the techniques, the correlations within comparable groups of methods, and the practical limitations in application of individual methods to different soils.     

Der Einfluß von Klärschlamm auf die mikrobielle Tätigkeit im Boden

The influence of sewage sludge on microbial activity in soil The effect of untreated, pasteurized and irradiated sewage sludge on soil biology was studied in model and field experiments. Sewage sludge from the sewage plant Geiselbullach in the west of Munich city was used for these experiments. The investigations were performed with 4 soil types according to the different locations. All the results demonstrate that there is an increase in biomass after application of sewage sludge while there were definite influences from the location. No significant relation could be observed according to sewage sludge treatment. Under favourable lab conditions the mineralization of the organic matter applied to the soil with higher amounts of sewage sludge induces in short time a definite decrease in pH. In accordance with these changes in pH there is a corresponding decrease in microbial biomass. Early results on the influence of microbial N-cycle demonstrated that amounts of sewage sludge applied under practical conditions brought an increase in denitrification capacity of the soil. In the experiment with soils nitrification rate was doubled after sewage sludge application.     

Connection between Archaeopteris and Callixylon

Characters of two Upper Devonian genera, Archaeopteris, often considered to be a fern, and Callixylon, classified with the gymnosperms, have been recognized in a single specimen.     

Multilineage potential of adult human mesenchymal stem cells

Human mesenchymal stem cells are thought to be multipotent cells, which are present in adult marrow, that can replicate as undifferentiated cells and that have the potential to differentiate to lineages of mesenchymal tissues, including bone, cartilage, fat, tendon, muscle, and marrow stroma. Cells that have the characteristics of human mesenchymal stem cells were isolated from marrow aspirates of volunteer donors. These cells displayed a stable phenotype and remained as a monolayer in vitro. These adult stem cells could be induced to differentiate exclusively into the adipocytic, chondrocytic, or osteocytic lineages. Individual stem cells were identified that, when expanded to colonies, retained their multilineage potential.     

Ginkgophyton (Psygmophyllum) with a Stem of Gymnospermic Structure

A specimen identified as Ginkgophyton (Psygmophyllum) with a structurally preserved stem of gymnospermic organization has been collected from a late Devonian stratum in New York.     

Creutzfeldt-Jakob disease (spongiform encephalopathy): transmission to the chimpanzee

Biopsy material taken from the brain of a patient with CreutzfeldtJakob disease with status spongiosus induced a similar fatal encephalopathy in a chimpanzee 13 months after inoculation.     

Chalcocite Oxidation and Coupled Carbon Dioxide Fixation by Thiobacillus ferrooxidans

The reaction of cell suspensions of Thiobacillus ferrooxidans with pulverized chalcocite (Cu(2)S) in a Warburg manometric apparatus resulted in oxygen uptake accompanied by increased solubilization of copper and fixation of carbon dioxide. Since the only detectable oxidized products were cupric ions and the more oxidized form of the sulfide mineral, that is, digenite or covellite, the apparent source of energy for the carbon dioxide fixation was provided by the oxidation of the cuprous copper of the chalcocite.