Active X-ray optics for the next generation of X-ray space telescopes

Described within is the design, manufacture, metrology and X-ray testing of an active X-ray prototype intended for the next generation of X-ray telescopes. One of the challenges faced by the X-ray telescope community is how to combine high resolution and high sensitivity into one system, as weight limitations place constraints on the optics that can be launched. Therefore the mandate of the active X-ray prototype is to provide high sensitivity through the ability of the optics to be nested and to deliver high angular resolution through the active control of the optic’s form. Piezoelectric unimorph actuators provide the active component: it is intended that they will correct for figure errors within the optic and therefore increase the angular resolution capability. The prototype’s design is based upon an ellipsoidal segment which provides point-to-point focussing of an X-ray source. The prototype itself is composed of an electroformed nickel optic where the non-reflective surface is populated with 30 piezoelectric actuators and it is the production of the prototype that is the core of the presented research. Metrology of the actuators’ influence functions is presented and highlight the prototype’s ability to deform its optic surface by microns. In addition, the measured influence functions are compared against finite element models and a distinct similarity between the functions is observed. The prototype was tested at an X-ray beamline facility in November 2008 and the results showed the prototype’s ability to correct the optic to achieve an improved angular resolution: from 0.786 arc-minutes to 0.686 arc-minutes in terms of full width half maximum. Finally, difficulties in the manufacture of the prototype and X-ray testing shall be presented alongside future work in conclusion to this thesis

The epidemiology of chronic kidney disease

The epidemiology of chronic kidney disease. The world's disease profile is changing, and chronic diseases now account for the majority of global morbidity and mortality, rather than infectious diseases. The causes of chronic kidney diseases reflect this change and diabetes, together with hypertension, is now the major cause of end-stage renal failure worldwide, not only within the developed world, but also increasingly within the emerging world.Diabetes is of epidemic proportions, and its prevalence will double in the next 25 years, particularly in the developing countries. This will place an enormous financial burden on countries, including the cost of the management of end-stage renal failure. Thus, it is medically and economically imperative for awareness, detection, and prevention programs to be introduced across the world, particularly in the developing countries. This will require concerted action from global institutions, governments, health service providers, and medical practitioners

Playing in the Doll\u27s House of Revolution : White Students and Activists Involved in the Black Power Movement

When Stokey Charmichael first uttered the words “black power” to a crowd of civil rights supporters during the “March Against Fear” on June 16th, 1966, it marked an important – and disillusioning – moment for white students and activists involved in the movement, a shift from a civil rights struggle fought not only through nonviolent methods but also through coalitions between whites and blacks. In the years that followed, many of these white activists struggled to find a place in the burgeoning black power movement that often shunned them and the more pacifist approach to rights struggles associated with them. Many dropped out of the movement following this shift, or transferred their energies to other causes; others, however, found themselves involved in Black Power organizations such as the Black Panthers, or supporting their activities despite qualms about their policies and often-violent actions. The question thus must be asked: why did many whites join and support a movement that often excluded or devalued them as a matter of policy? This paper explores the complex social and psychological reasons behind many of these activists’ support for Black Power – as well as the implications of their involvement for race relations to this day

Cell Cycle Control by Cyclin-CDKS in Chlamydomonas ReinhardtII

The cell cycle consists of a series of events, including replication and segregation of the genome, that occurs in order to ensure successful reproduction of cells. In fungi and animals, this process is carefully regulated by a set of protein complexes with alternating, oscillating activity. A well established model has been developed for animals and fungi in which the activities of various cyclin-dependent kinases (CDKs) and the anaphase promoting complex (APC) drive the events of the cell cycle at the appropriate time and in the appropriate order. While this model has been extremely useful for understanding cell division in these lineages, it is not necessarily applicable to other groups of eukaryotes. Animals and fungi belong to a relatively recently diverged group called the Opisthokonts, so their shared features do not necessarily extend to their eukaryotic cousins, including plants, a very important lineage of particular concern to humanity. Chlamydomonas reinhardtii is a unicellular member of the plant kingdom. Its simple genome (compared to land plants) and easily observed cell division cycle have facilitated the collection of a large number of conditional mutations that block the cell cycle at high temperature. Mutations in two CDKs, CDKA1 and CDKB1, and two subunits of the APC are included in this set. The phenotypes of these mutants at restrictive-temperature revealed that CDKA1, unlike its ortholog in the Opisthokonts, is not required for mitosis, and instead plays a role in cell cycle initiation. CDKB1, on the other hand, is a plant-specific CDK and is required for promoting the events of mitosis. The APC plays a similar role to its counterpart in Opisthokonts in driving the metaphase-to-anaphase transition. In this thesis, we present the results of our efforts to better understand the function and regulation of the kinases CDKA1 and CDKB1 and two Chlamydomonas cyclins, CYCA1 and CYCB1. We characterize the role of these molecules in cell division timing, DNA replication, spindle formation, and cytokinesis and explore the nature of their regulatory interactions and their control by the APC. We also describe a genetic screen to identify parallel pathways that promote cell cycle initiation alongside CDKA1 and speculate on a possible common thread among the identified mutations. A genetic screen for genes involved in cell cycle initiation uncovers many null mutations in CDKA1, showing definitively that CDKA1 is inessential for cell division in Chlamydomonas, and likely all plants. Disruption of both CDKA1 and CYCA1 results in a delay in cell division, and CYCA1 is specifically required for biochemical activity of CDKA1, suggesting they may act as a complex to promote the initiation of cell division. CYCB1 is required for timely DNA replication and mitotic spindle formation in a similar manner to CDKB1, and, consistently, is also required for biochemical activation of CDKB1. We propose that CYCB1 and CDKB1 form a complex and together constitute the primary mitotic inducer in Chlamydomonas. Both CDKA1 and CDKB1 are downregulated by the APC, and CDKA1 kinase activity is inhibited by CYCB1- CDKB1. A model is presented incorporating these and prior findings concerning the function and regulatory interaction among these cell cycle regulators. Several possible positive and negative feedback loops become apparent which may ensure switch-like activation or appropriate ordering of the activity of various complexes