Bathymetric gradients of biodiversity in the deep-sea benthos constitute a major class of large-scale biogeographic phenomena. They are typically portrayed and interpreted as variation in alpha diversity (the number of species recovered in individual samples) along depth transects. Here, we examine the depth ranges of deep-sea gastropods and bivalves in the eastern and western North Atlantic. This approach shows that the abyssal molluscan fauna largely represents deeper range extensions for a subset of bathyal species. Most abyssal species have larval dispersal, and adults live at densities that appear to be too low for successful reproduction. These patterns suggest a new explanation for abyssal biodiversity. For many species, bathyal and abyssal populations may form a source-sink system in which abyssal populations are regulated by a balance between chronic extinction arising from vulnerabilities to Allee effects and immigration from bathyal sources. An increased significance of source-sink dynamics with depth may be driven by the exponential decrease in organic carbon flux to the benthos with increasing depth and distance from productive coastal systems. The abyss, which is the largest marine benthic environment, may afford more limited ecological and evolutionary opportunity than the bathyal zone.
Summary. Bone marrow (BM) samples from 24 patients with acute leukaemia (AML 17, ALL seven) in first complete remission were compared to samples from 10 normal donors with regard to their content in long-term culture-initiating cells (LTC-IC) as assessed by a limiting dilution assay and the clonogeneic capacity of these cells, in order to determine whether remission marrow cells displayed any specific defect at the primitive stem cell level. The frequency of LTC-IC in the whole patient group was 1 in 3487 Ϯ 3125 mononuclear cells (MNC) as compared to 1 in 794 Ϯ 492 MNC in normal controls (P ¼ 0·0009), with no difference between AML and ALL. Moreover, the clonogeneic capacities were 2·66 Ϯ 0·7 (range 1·8-1·6) and 4·0 Ϯ 1·6 (range 2·2-7·9) CFC per LTC-IC in patients and controls respectively (P ¼ 0·0015). These quantitative and qualitative defects were aggravated by treatment with mafosfamide at a dose of 50 mg/10 7 MNC/ ml, where the mean recovery of LTC-IC after in vitro purging was 42%. In nine patients autografted with purged marrow following high-dose radiochemotherapy, no correlation could be detected between the dose of LTC-IC (mean 6742 Ϯ 7877/kg) and the kinetics of recovery of haemopoiesis. We concluded that, in acute leukaemia patients in complete remission, the presumably normal residual stem cell pool was not only quantitatively diminished but also qualitatively altered in its capacity to give rise to clonogeneic progenitor cells.
The main em phasis of this study is the investigation of the gate degradation or rupture, aiming to determine the nature of the so-called SEGR phenomena. This article presents experimental data showing heavy ions induced gate degradation in power MOSFETs. In the experiments, backside and front-side irradiations are performed. The heavy ions ranges are tuned in such way to control whether they hit the gate or not, during backside irradiation. Gate-to-source current Igss (4)) is measured versus Heavy Ions (H.I.) fluence 4>. Post-irradiation-Gate-StressTest (PGST) allows to measure breakdown voltage VBD(4)) as being decreasing with (H.I.) fluence. Based on these experimental results, an hypothesis of substrate-generated "hot carriers" impact overlap may explain gate degradation until SEGR triggering. This last hypothesis is supported by statistical approach model of heavy ions multiple impact.
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