Search results for "Low oxygen"
showing 4 items of 14 documents
L’élongation des loges chez les foraminifères planctoniques du Crétacé inférieur: une adaptation à la sous-oxygénation des eaux?
1998
Abstract Planktic foraminifera with radially elongated chambers appeared on four occasions in the early Cretaceous of the Vocontian Basin (SE France). These appearances coincided with or followed the deposition of organic rich levels which are evidence of hypoxic to anoxic conditions at the sea-floor. In addition, oxygen deficient surface waters are inferred from the occasional presence of Hedbergellas with deformed (insufficiently calcified) walls. It is suggested that the elongation of the chambers of these foraminifera was an adaptive response to the low oxygen content of surface waters, the increased surface area of the test allowing better gas exchange with sea water and the intake of …
HETEROGENEOUS OXYGEN TRANSPORT WITHIN MALIGNANT TUMORS
1981
Publisher Summary This chapter discusses the heterogeneous oxygen transport within malignant tumors. Many solid tumors disturbances in the vascularization and in the microcirculation generally lead to distinct restrictions in the convective and diffusive transport. Beyond that, a heterogeneous distribution of the transport conditions develops causing an insufficient and heterogeneous substrate supply as well as an inadequate drainage of wastes. As one of the compulsory manifestations, a poor and heterogeneous oxygen supply becomes more extensively evident with increasing tumor size or age. The polarographic measurements of the local tissue pO 2 values in animal tumors show that very low oxy…
Synthesis and characterization of NdNiO3 prepared by low temperature methods
1992
Abstract NdNiO3 has been prepared with an orthorhombic perovskite structure by a low temperature and low oxygen pressure method starting from a nickel(III) oxide precursor, β-NiO(OH). The compound LaNiO3 has also been obtained by this method. This chemical-precursor-based synthesis overcomes problems related to the use of high oxygen pressures in the synthesis.
Brachionus plicatilis tolerance to low oxygen concentrations
1989
Tolerance to low oxygen concentrations is expected in Brachionus plicatilis, a rotifer adapted to live in saline warm waters. The population dynamics of a clone of this species, isolated from an endorreic saline lake, was studied under controlled laboratory conditions. Although their growth and metabolism is extremely reduced, B. plicatilis populations are able to maintain relatively high-density populations (a mean of 35 ind ml−1) in oxygen concentrations below 1 mgl−1, for more than one month. Major features of population growth related to oxygen are discussed.