Shigella spp. and entero-invasive Escherichia coli:diagnostics, clinical implications and impact on public health

The bacteria Shigella spp. and entero-invasive Escherichia coli (EIEC) cause a watery or bloody diarrhea in humans. This disease is known as dysentery or shigellosis. Shigella spp. and EIEC are related to that extent that distinction with culture or molecular methods at laboratories is challenging. As in many other countries, the Netherlands regulates only the control of infections with Shigella spp. through laws and guidelines. However, the problematic distinction of Shigella spp. and EIEC hampers the compliance to these regulations. The RIVM, UMCG and Certe collaborated to investigate the diagnostics, the clinical implications of Shigella spp. and EIEC and their impact on public health in the Netherlands. These studies are described in this thesis. First, different opportunities for the improvement of current diagnostics were examined. Unfortunately, it appeared that distinction of Shigella spp. and EIEC remained difficult, even with modern methods. Second, a study was conducted in cooperation with multiple health care institutions in which the consequences of infections with Shigella spp. and EIEC were assessed. The results indicated that there were no differences in severity of disease caused by these bacteria. Third, it was demonstrated that the detailed assessment of the genomes of the bacteria improved the determination of both the similarity of bacteria isolated from different patients and the source of the infections. Finally, suggestions for improvement of the shigellosis guidelines were made, which are now part of a reconsideration of these guidelines

Uniqueness of maximal spacetime boundaries

Given an extendible spacetime one may ask how much, if any, uniqueness can in general be expected of the extension. Locally, this question was considered and comprehensively answered in a recent paper of Sbierski, where he obtains local uniqueness results for anchored spacetime extensions of similar character to earlier work for conformal boundaries by Chru\'sciel. Globally, it is known that non-uniqueness can arise from timelike geodesics behaving pathologically in the sense that there exist points along two distinct timelike geodesics which become arbitrarily close to each other interspersed with points which do not approach each other. We show that this is in some sense the only obstruction to uniqueness of maximal future boundaries: Working with extensions that are manifolds with boundary we prove that, under suitable assumptions on the regularity of the considered extensions and excluding the existence of such ''intertwined timelike geodesics'', extendible spacetimes admit a unique maximal future boundary extension. This is analogous to results of Chru\'sciel for the conformal boundary

Hormonal determinants of successful aging in men

The average length of human life is currently 75 to 78 years and may increase to 85 years during the coming two decades, but it is not clear whether these additional years will be satisfying to live. Most data indicate modest gain in the number of healthy years lived but a far greater increase in years of compromised physicaL mental and social function. The number of days of restricted activity and the number of admissions to hospitals and nursing homes sharply increases after age 70. One U.S. health interview survey indicates that. at present, more than 25 million aging people suffer from physical impairment. whereas the number of people requiring assistance in activities of daily living increases from 14% at age 65 to 75 to 45% in those over 85 years old

Oxidation of thin film binary entropy alloys

In recent years, material science has put significant effort into understanding the behavior of multiple principle element alloys (MPEAs), notably the category high entropy alloys (HEAs). Most of these studies have been conducted on the micro to macro scales, yet the nanoscale remains relatively unexplored. Additionally, investigating the structural changes caused by amorphous oxidation for thin film MPEAs is particularly new, with no fundamental theory having been found. By studying ambient oxidation of thin film binary entropy alloys, we show how the Hume-Rothery rules affect the oxide formation and in particular the requirement of an increased temperature prior to the formation of polycrystalline oxides for these systems, compared to their single metal counterparts