Alternate splicing and glycosylation produce multiple CD45 isoforms which are selectively expressed on the surface of cells of the haemopoietic system. The expression of CD45RA, CD45RB and CD45RO on CD34+ and CD34- haemopoietic cells from umbilical cord blood, bone marrow and fetal liver were studied by flow cytometry. CD34+ subpopulations defined by CD45 isoform expression were sorted from bone marrow and tested in long-term culture assays. By combining results of functional studies with phenotypic data and previously published information, the following pattern of CD45 isoform expression on early haemopoietic cells was established. The most primitive CD34+ cells are CD45RO+ CD45RB+ and express low or undetectable levels of CD45RA. Upon erythroid differentiation, CD34+ cells remain CD45RO+ CD45RB+, whereas commitment into the myeloid and lymphoid lineages coincides with down-regulation of CD45RO and up-regulation of CD45RA. As a result, the majority of CD34+ cells can be divided into two mutually exclusive populations of cells which express either CD45RO or CD45RA. This notion was confirmed in this study by three-colour immunofluorescence. The alternative expression of various CD45 isoforms on functionally distinct haemopoietic cells suggests an important role for these molecules in the proliferation and differentiation of haemopoietic cells.

Polyvinyl alcohol (PVA) was blended with starch (S) in presence of glacial acetic acid as crosslinking agent. The effect of blend ratio and molecular weight of PVA on the physical, thermal and mechanical properties of PVA/S blends were investigated using various techniques such as DSC, TGA, SEM, tensile strength, and solubility tests. Furthermore, biodegradability of the blend films was also studied. In addition, FTIR spectroscopy was used to check the hydrogen bonding interaction between PVA and S in the blends. The obtained results showed that the physico-mechanical properties are strongly dependent on the molecular weight and PVA content in PVA/S blends. DSC and SEM analyses of PVA/S blend showed a single glass transition temperature indicating the formation of completely miscible blends with a single phase due to the formation of hydrogen bonds between the hydroxyl groups of PVA and starch. In addition, PVA/S blend films exhibited good mechanical properties, thermal stability as compared with the pure PVA. More interestingly, the results showed enhancement in biodegradability of PVA/S blend films and particularly in moist soil, which can be exploited for manufacturing of biodegradable and environmentally friendly packaging materials at low cost.

A critical review is presented which draws together results from model tests and computations on the mechanisms by which the spud-can foundation of an independent leg offshore jack-up structure can penetrate deeply into the seabed through both uniform and stratified deposits. Particular consideration is given to the so-called punch-through mode in layered soil profiles, where a strong stratum overlies a weaker one. Little evidence has been found to support the mechanical basis of two methods of analysis commonly used in the offshore industry where foundations often have dimensions in excess of 10 m while conventional laboratory models have rarely exceeded 100 mm. New model tests performed in a centrifuge with stresses appropriate to offshore foundations are reported and these show different mechanisms from many unit gravity models. The need for a reappraisal of the basis of analysis is established. Where large volumes of soil are displaced by spud-can preloading, offshore analysis should explicitly address the pattern of soil flow around the foundation and the reality of post-installation geometry. L'article présente une revue critique qui rassemble les résultats obtenus à partir d'essais sur modèle et de calculs des mécanismes par lesquels la fondation type ‘spud-can’ (semelles enlargies) d'une construction à pied indépendant élevée par des vérins au large peut pénétrer profondément dans le fond de la mer dans des dépôts uniformes ou stratifiés. On étudie particulièrement la pénétration par poin¸connement de sols stratifiés dans lesquels une couche resistance repose sur une couche molle. II n'y a que très peu de données qui confirment la base mécanique de deux méthodes d‘analyse généralement employées dans l'industrie au large, où les fondations ont souvent des dimensions supérieures à 10 m, tandis que les modèles normaux dans le laboratoire n'excédent que rarement 100 mm. L'article décrit de nouveaux essais sur modèles eflectués dans une centrifugeuse avec des contraintes propres aux fondations au large; ceux ci révelènt des mecanismes différents obtenus à partir de beaucoup de modèles de gravité unitaire. Le besoin de ré-examiner la base de l'analyse est démontré clairement. Dans le cas où de grands volumes de sol sont déplacés par préchargement par une fondation type ‘spud-can’ l'analyse au large devrait se concentrer de façon explicite sur les chemins d'écoulement du sol autour de la fondation et aussi surles réalités de la géometrie apres la mise en place.

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