From the deglacial period to the mid-Holocene, North Africa was characterized by much wetter conditions than today. The broad timing of this period, termed the African Humid Period, is well known. However, the rapidity of the onset and termination of the African Humid Period are contested, with strong evidence for both abrupt and gradual change. We use optically stimulated luminescence dating o...

Polysaccharides and related glycopolymers offer a unique challenge to analytical ultracentrifugafion for two clear reasons. Firstly, there is a growing demand for basic solution biophysical information on these substances: molecular weights, molecular weight distributions, conformation, conformation distributions; information which analytical ultracentrifuge can, in principle, supply. This info...

It is generally believed that the erythrocyte sedimentation (E.S.R.) is retarded and tends to fall to normal when decompensation occurs in rheumatic fever and other heart diseases known to be associated with elevated values.2' 4, 5, 7. 9 Observations by McGinnis and co-workers,6 who excluded patients who presented evidence of other conditions known to lead to elevation of the E.S.R., however, d...

The sedimentation velocity profiles of the entities in mouse bone marrow responsible for erythropoietic burst formation (BFU-E) and for erythrocytic colony formation (CFU-E) have been studied under conditions designed to determine whether the values observed are real or result from cell interactions occurring during culture of the fractions. Bone marrow cells of adult C3Hf/Bi mice were subjecte...

Located in the middle of Sahel, study area is an integral part Bahr-El-Ghazal region. It crossed by a fossil valley, which has geological history similar to that rivers disappeared under influence climate change where evaporation phenomena were intense. From hydrogeological point view, free water table this region housed sedimentary formations different natures. passes from sand tablecloth fluv...

We consider the sedimentation of high aspect ratio fibers in a Newtonian fluid under Stokes’ flow conditions. Measurements of the mean sedimentation velocity, variance of the sedimentation velocity, and the orientation distribution are presented using a modification of the novel experimental technique described by Nicolai et al. [Phys. Fluids 7, 12 (1995)]. We find a steady state where the fibe...