a b s t r a c tThe 'Chicken Creek' artificial catchment area, Welzow-South, E Germany, created to study processes and structures of initial ecosystem development, discharges into a small experimental lake (A =3805 m 2 , V= 3992 m 3 , z max = 2.4 m). This lake was man-made in 2005 and filled by natural surface runoff until January 2006. In summer 2006 and 2008, the actual development of sediments and the evolution of the phosphorus (P) cycle were studied. 19.7% of the original lake volume was filled by sediment within the first 3 years. A fine-grained sediment representing silt (6.3-63 mm) accumulated at high accretion rates at the deepest point (200 mm a À 1 , 0-24 mm week À 1 ) due to massive erosion in the catchment. The sediment is low in organic matter (2.5-5.2%) and total P (TP, 0.31-0.97 mg g À 1 ). Low amounts of P associated with degradable organic matter and surplus of metal hydroxides (Fe:P $ 40, Al:P $ 20) favor an efficient P binding and low dissolved P concentrations in pore water (1-107 mg l À 1 ).Hence, the mineral sediment quality and the low rates of P release (0.06 mg m À 2 d À 1 ) revealed that a lake at an initial stage of development has essentially no sedimentary P cycle compared to eutrophic shallow lakes. However, the increasing emersed and submersed macrophyte growth will control further lake succession by intensifying the internal nutrient cycling. The macrophytes drive the evolution of a sedimentary P cycle by mobilizing and translocating P, by accumulating carbon and thus by stimulating microbial and redox processes.
Dissolved gases produce a gas pressure. This gas pressure is the appropriate physical quantity for judging the possibility of bubble formation and hence it is central for understanding exchange of climate-relevant gases between (limnic) water and the atmosphere. The contribution of ebullition has widely been neglected in numerical simulations. We present measurements from six lacustrine waterbodies in Central Germany: including a natural lake, a drinking water reservoir, a mine pit lake, a sand excavation lake, a flooded quarry, and a small flooded lignite opencast, which has been heavily polluted. Seasonal changes of oxygen and temperature are complemented by numerical simulations of nitrogen and calculations of vapor pressure to quantify the contributions and their dynamics in lacustrine waters. In addition, accumulation of gases in monimolimnetic waters is demonstrated. We sum the partial pressures of the gases to yield a quantitative value for total gas pressure to reason which processes can force ebullition at which locations. In conclusion, only a small number of gases contribute decisively to gas pressure and hence can be crucial for bubble formation.
The hemophilias are inherited disorders of the coagulation system with no apparent effects on primary hemostasis. However, bleeding times and platelet aggregation have been reported as abnormal. These observations have been ascribed to undiagnosed Von Willebrand’s Disease (VWD), effects of factor replacement, or drugs. We evaluated three patients with hemophilia including one patient with factor VIII deficiency, one with factor VIII and inhibitor, and one factor IX who had persistent bleeding despite their standard treatment. Initial evaluation of primary hemostasis demonstrated abnormal bleeding time and or platelet function analysis (PFA-100). VWD antigen and ristocetin cofactor were normal. Electron microscopy demonstrated alpha and or delta granule storage pool deficiency. Careful review of all drugs the patients were on did not explain this finding. Repeat evaluation of one patient over time demonstrated persistence of abnormal function. Treatment with DDAVP(Desmopressin) normalized in vitro function in 2 patients. After documentation of these abnormalities, two patients were treated with DDAVP with or without platelets as well as factor replacement or in face of inhibitors FEIBA or FVIIa. Clinical improvement was seen in the 2 patients after this intervention. A prospective study of our hemophilia population has been initiated with the goal of documenting the frequency of storage pool deficiency, the importance of the disorder to bleeding episodes and treatment response, and to determine whether this is inherited or acquired.
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