Problems in the rehabilitation of seventy-two World War II tuberculous veterans at Cushing Veterans' Administration Hospital, Framingham, Massachusetts.

Thesis (M.S.)--Boston Universit

Inverted vertical AlGaN deep ultraviolet LEDs grown on p-SiC substrates by molecular beam epitaxy

Deep ultraviolet light emitting diodes (UV LEDs) are an important emerging technology for a number of applications such as water/air/surface disinfection, communications, and epoxy curing. However, as of yet, deep UV LEDs grown on sapphire substrates are neither efficient enough nor powerful enough to fully serve these and other potential applications. The majority of UV LEDs reported so far in the literature are grown on sapphire substrates and their design consists of AlGaN quantum wells (QWs) embedded in an AlGaN p-i-n junction with the n-type layer on the sapphire. These devices suffer from a high concentration of threading defects originating from the large lattice mismatch between the sapphire substrate and AlGaN alloys. Other issues include the poor doping efficiency of the n- and particularly the p-AlGaN alloys, the extraction of light through the sapphire substrate, and the heat dissipation through the thermally insulating sapphire substrate. These problems have historically limited the internal quantum efficiency (IQE), injection efficiency (IE), and light extraction efficiency (EE) of devices. As a means of addressing these efficiency and power challenges, I have contributed to the development of a novel inverted vertical deep UV LED design based on AlGaN grown on p-SiC substrates. Starting with a p-SiC substrate that serves as the p-type side of the p-i-n junction largely eliminates the necessity for the notoriously difficult p-type doping of AlGaN alloys, and allows for efficient heat dissipation through the highly thermally conductive SiC substrate. UV light absorption in the SiC substrate can be addressed by first growing p-type doped distributed Bragg reflectors (DBRs) on top of the substrate prior to the deposition of the active region of the device. A number of n-AlGaN films, AlGaN/AlGaN multiple quantum wells, and p-type doped AlGaN DBRs were grown by molecular beam epitaxy (MBE). These were characterized in situ by reflected high energy electron diffraction (RHEED) and ex situ by x-ray diffraction, scanning electron microscopy, atomic force microscopy, photoluminescence, and reflectivity. Using the primary elements of the proposed design, this research culminated in the MBE growth, fabrication, and characterization of prototype deep UV LED devices emitting below 300 nm

Dynamique adaptative de diversification des cultures et recomposition des paysages ruraux à Santchou (Ouest-Cameroun)

Au Cameroun, la libéralisation intervenue dans la filière café-cacao au début des années 1990 s’est accompagnée d’une paupérisation croissante des producteurs. Ces derniers ont adopté des stratégies d’adaptation diverses. Dans un contexte de crise caféière au Cameroun, le présent article vise à évaluer les stratégies paysannes de diversification des cultures de rente et leurs impacts dans la recomposition des paysages ruraux. Des enquêtes ont été menées auprès de 400 producteursrépartis dans les trois bassins de production de Santchou. Les résultats montrent que depuis la libéralisation des filières agricoles et la crise caféière qui a suivi, les producteurs dans leurs stratégies de survie ont diversifié les cultures de rente dans leurs exploitations familiales. Même si la caféiculture reste dominante, il faut relever que les cultures du cacao et du palmier à huile jadis rare connaissent une croissance fulgurante. Avec la saturation foncière, les cacaoyers et les palmiers sont non seulement insérés entre les lignes mais aussi, remplacent les plants de caféiers morts. Il en résulte une recomposition, voire une restructuration des paysages ruraux avec le développement des systèmes agroforestiers de multicultures caféierscacaoyers-palmiers. Pour la durabilité de ces nouveaux systèmes un accompagnement adapté de ces changements endogènes est nécessaire. In Cameroon, the liberalization that occurred in the coffee-cocoa sector in the early 1990s came alone with an increasing impoverishment of producers who had to develop adaptation strategies to survive. In the context of the coffee crisis in Cameroon, this article aims at assessing farmers' cash crops diversification strategies and their impacts on the recomposition of rural landscapes. Surveys were conducted with 400 farmers in the three Santchou production basins. The results show that since the agricultural commodity chains liberalization and the coffee crisis that followed, farmers have diversified their cash crops strategies on their family farms. Although coffee culture still dominates, cocoa and oil palm farming, which were once rare, are experiencing an explosive growth. With land saturation, not only are cocoa and palm trees planted between the rows, they are also, replacing dead coffee trees. As a result, we observe a recomposition, or even a restructuring of rural landscapes with the development of agroforestry systems of multiple cropping (that is coffee, cocoa and palms trees). In order to assure the sustainability of these new systems, an appropriate support of these endogenous changes is essential

Dissecting the Non-human Primate Brain in Stereotaxic Space

The use of non-human primates provides an excellent translational model for our understanding of developmental and aging processes in humans1-6. In addition, the use of non-human primates has recently afforded the opportunity to naturally model complex psychiatric disorders such as alcohol abuse7. Here we describe a technique for blocking the brain in the coronal plane of the vervet monkey (Chlorocebus aethiops sabeus) in the intact skull in stereotaxic space. The method described here provides a standard plane of section between blocks and subjects and minimizes partial sections between blocks. Sectioning a block of tissue in the coronal plane also facilitates the delineation of an area of interest. This method provides manageable sized blocks since a single hemisphere of the vervet monkey yields more than 1200 sections when slicing at 50μm. Furthermore by blocking the brain into 1cm blocks, it facilitates penetration of sucrose for cyroprotection and allows the block to be sliced on a standard cryostat