World market or regional integration and food security in West Africa

The problem of food security in West Africa was put on the international agenda in 1974 at the international food conference in Rome following the Great Sahelian Drought of 1968-1973. In those years preoccupation with food security was limited mainly to the Sahel countries and concentrated on estimating the availability and use of resources for grain production. Nowadays, studies in the field of food security focus not only on production, but also on the functioning of the food market, and on consumption and nutrition. This paper concentrates on the debate whether sustainable food security in West Africa will be achieved by protection measures for national food production, by a liberalization of the food trade that facih'tates cheap imports of food from the world market, or by stimulating regional food trade through regional co-operation

Progressive leukoencephalopathy impairs neurobehavioral development in sialin-deficient mice

Slc17a5−/− mice represent an animal model for the infantile form of sialic acid storage disease (SASD). We analyzed genetic and histological time-course expression of myelin and oligodendrocyte (OL) lineage markers in different parts of the CNS, and related this to postnatal neurobehavioral development in these mice. Sialin-deficient mice display a distinct spatiotemporal pattern of sialic acid storage, CNS hypomyelination and leukoencephalopathy. Whereas few genes are differentially expressed in the perinatal stage (p0), microarray analysis revealed increased differential gene expression in later postnatal stages (p10–p18). This included progressive upregulation of neuroinflammatory genes, as well as continuous down-regulation of genes that encode myelin constituents and typical OL lineage markers. Age-related histopathological analysis indicates that initial myelination occurs normally in hindbrain regions, but progression to more frontal areas is affected in Slc17a5−/− mice. This course of progressive leukoencephalopathy and CNS hypomyelination delays neurobehavioral development in sialin-deficient mice. Slc17a5−/− mice successfully achieve early neurobehavioral milestones, but exhibit progressive delay of later-stage sensory and motor milestones. The present findings may contribute to further understanding of the processes of CNS myelination as well as help to develop therapeutic strategies for SASD and other myelination disorders

Nonlinear effects in resonant layers in solar and space plasmas

The present paper reviews recent advances in the theory of nonlinear driven magnetohydrodynamic (MHD) waves in slow and Alfven resonant layers. Simple estimations show that in the vicinity of resonant positions the amplitude of variables can grow over the threshold where linear descriptions are valid. Using the method of matched asymptotic expansions, governing equations of dynamics inside the dissipative layer and jump conditions across the dissipative layers are derived. These relations are essential when studying the efficiency of resonant absorption. Nonlinearity in dissipative layers can generate new effects, such as mean flows, which can have serious implications on the stability and efficiency of the resonance

History and highlights of the teratological collection in the Museum Anatomicum of Leiden University, The Netherlands

The anatomical collection of the Anatomical Museum of Leiden University Medical Center (historically referred to as Museum Anatomicum Academiae Lugduno-Batavae) houses and maintains more than 13,000 unique anatomical, pathological and zoological specimens, and include the oldest teratological specimens of The Netherlands. Throughout four centuries hundreds of teratological specimens were acquired by more than a dozen collectors. Due to the rich history of this vast collection, teratological specimens can be investigated in a unique retrospective sight going back almost four centuries. The entire 19th century collection was described in full detail by Eduard Sandifort (1742-1814) and his son Gerard Sandifort (1779-1848). Efforts were made to re-describe, re-diagnose and re-categorize all present human teratological specimens, and to match them with historical descriptions. In the extant collection a total of 642 human teratological specimens were identified, including exceptional conditions such as faciocranioschisis and conjoined twins discordant for cyclopia, and sirenomelia. Both father and son Sandifort differed in their opinion regarding the causative explanation of congenital anomalies. Whereas, their contemporaries Wouter Van Doeveren (1730-1783) and Andreas Bonn (1738-1817) both presented an interesting view on how congenital anomalies were perceived and explained during the 18th and 19th centuries; the golden age of descriptive teratology. Although this enormous collection is almost 400 years old, it still impresses scientists, (bio)medical students, and laymen visiting and exploring the collections of the Museum Anatomicum in Leiden, The Netherland

Luminescence Line Broadening of CdSe Nanoplatelets and Quantum Dots for Application in w-LEDs

Nanoplatelets (NPLs) of CdSe are an emerging class of luminescent materials, combining tunable and narrow emission bands with high quantum yields. This is promising for application in white light LEDs (w-LEDs) and displays. The origin of the narrow spectral width of exciton emission in core NPL compared to core-shell NPL and quantum dot (QD) emission is not fully understood. Here we investigate and compare temperature-dependent emission spectra of core and core-shell CdSe NPLs and QDs. A wide temperature range, 4-423 K, is chosen to gain insight into contributions from homogeneous and inhomogeneous broadening and also to extend measurements into a temperature regime that is relevant for operating conditions in w-LEDs (T ≈ 423 K). The results show that temperature-induced homogeneous broadening does not strongly vary between the various CdSe nanostructures (ΔEhom ≈ 60-80 meV at 423 K) indicating that electron-phonon coupling strengths are similar. Only for the smallest QDs is stronger coupling observed. The origin of the narrow bandwidth reported at 300 K for core CdSe NPLs is attributed to a very narrow inhomogeneous line width. At 423 K, the spectral width of NPL exciton emission is still narrower than that of QDs. A comparison with traditional w-LED phosphors is made to outline advantages (tunability, narrow bandwidth, high efficiency) and disadvantages (color shift, stability issues) of NPLs for application in w-LEDs