Private Standards and Employment Insecurity: GlobalGAP in the Senegalese Horticulture Export Sector

Crop Production/Industries, International Relations/Trade, Labor and Human Capital,

Clinical Studies in Scanning Laser Polarimetry

Glaucoma is the second leading cause of irreversible blindness worldwide. When left untreated, glaucoma results in visual field loss and eventually in blindness. In considering the diagnosis of glaucoma, the physician will evaluate the intraocular pressure, the optic nerve head and the visual field. This seems to be a straightforward diagnostic process, but, surprisingly, there is still no consensus on the criteria for the signs on which the diagnosis is based. Glaucoma is a progressive optic neuropathy characterized by death of retinal ganglion cells. The course of events that eventually leads to death of these cells is not exactly known, but the retinal nerve fiber layer, which is made up of the axons of the retinal ganglion cells, thins. Scanning laser polarimetry is an imaging technique that can detect glaucoma by assessing the thickness of the retinal nerve fiber layer. Scanning laser polarimetry came onto the market in 1993. The working principle is based on the fact that in the nerve fiber layer a phase shift occurs in polarized laser light that is sent through the nerve fiber layer. This so called retardation is thought to be linearly correlated with nerve fiber layer thickness. In the past, scanning laser polarimetry has shown to discriminate well between normal and glaucomatous eyes. The goal of this thesis was to investigate the clinical performance of the GDx (a revised version of the first scanning laser polarimeter, the Nerve Fiber Analyzer). In summary, the GDx provides fast, objective and quantitative data on nerve fiber layer thickness. The applicability and reproducibility of measurements are high and the image acquisition is user and patient friendly. The GDx yields useful sensitivity and specificity values for the detection of glaucoma, whereas its role in follow-up remains to be investigated. As it stands, the GDx holds insufficient validity to serve as a single test for glaucoma. It does, however, provide a very useful addition to the existing tests we run in patients to make the correct diagnosis

Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate-to-ammonium reducers

The estuarine nitrogen cycle can be substantially altered due to anthropogenic activities resulting in increased amounts of inorganic nitrogen (mainly nitrate). In the past, denitrification was considered to be the main ecosystem process removing reactive nitrogen from the estuarine ecosystem. However, recent reports on the contribution of dissimilatory nitrate reduction to ammonium (DNRA) to nitrogen removal in these systems indicated a similar or higher importance, although the ratio between both processes remains ambiguous. Compared to denitrification, DNRA has been underexplored for the last decades and the key organisms carrying out the process in marine environments are largely unknown. Hence, as a first step to better understand the interplay between denitrification, DNRA and reduction of nitrate to nitrite in estuarine sediments, nitrogen reduction potentials were determined in sediments of the Paulina polder mudflat (Westerschelde estuary). We observed high variability in dominant nitrogen removing processes over a short distance (1.6m) with nitrous oxide, ammonium and nitrite production rates differing significantly between all sampling sites. Denitrification occurred at all sites, DNRA was either the dominant process (two out of five sites) or absent, while nitrate reduction to nitrite was observed in most sites but never dominant. In addition, novel nitrate-to-ammonium reducers assigned to Thalassospira, Celenbacter, and Halomonas, for which DNRA was thus far unreported, were isolated, with DNRA phenotype reconfirmed through nrfA gene amplification. This study demonstrates high small scale heterogeneity among dissimilatory nitrate reduction processes in estuarine sediments and provides novel marine DNRA organisms that represent valuable alternatives to the current model organisms

Beer Drinking Nations. The Determinants of Global Beer Consumption.

In this paper we analyze the evolution of beer consumption between countries and over time. Historically, there have been major changes in beer consumption in the world. In recent times, per capita consumption has decreased in traditional " beer drinking nations" while it increased strongly in emerging economies. Recently, China has overtaken the US as the largest beer economy. A quantitative empirical analysis shows the relationship between income and beer consumption has an inverse U-shape. Beer consumption initially increases with rising incomes, but at higher levels of income beer consumption falls. Increased openness to trade and globalization has contributed to a convergence in alcohol consumption patterns across countries. In countries that were originally "beer drinking nations", the share of beer in total alcohol consumption reduced while this is not the case in countries which traditionally drank mostly wine or spirits. Climatic conditions, religion, and relative prices also influence beer consumption.

The early life history of the clam Macoma balthica in a high CO₂ world

This study investigated the effects of experimentally manipulated seawater carbonate chemistry on several early life history processes of the Baltic tellin (Macoma balthica), a widely distributed bivalve that plays a critical role in the functioning of many coastal habitats. We demonstrate that ocean acidification significantly depresses fertilization, embryogenesis, larval development and survival during the pelagic phase. Fertilization and the formation of a D-shaped shell during embryogenesis were severely diminished: successful fertilization was reduced by 11% at a 0.6 pH unit decrease from present (pH 8.1) conditions, while hatching success was depressed by 34 and 87%, respectively at a 0.3 and 0.6 pH unit decrease. Under acidified conditions, larvae were still able to develop a shell during the post-embryonic phase, but higher larval mortality rates indicate that fewer larvae may metamorphose and settle in an acidified ocean. The cumulative impact of decreasing seawater pH on fertilization, embryogenesis and survival to the benthic stage is estimated to reduce the number of competent settlers by 38% for a 0.3 pH unit decrease, and by 89% for a 0.6 pH unit decrease from present conditions. Additionally, slower growth rates and a delayed metamorphosis at a smaller size were indicative for larvae developed under acidified conditions. This may further decline the recruit population size due to a longer subjection to perturbations, such as predation, during the pelagic phase. In general, early life history processes were most severely compromised at similar to pH 7.5, which corresponds to seawater undersaturated with respect to aragonite. Since recent models predict a comparable decrease in pH in coastal waters in the near future, this study indicates that future populations of Macoma balthica are likely to decline as a consequence of ongoing ocean acidification