Two Methods for Converting a Heavy-Water Research Reactor to Use Low-Enriched-Uranium Fuel to Improve Proliferation Resistance After Startup

This article demonstrates the feasibility of converting a heavy-water research reactor from natural to low-enriched uranium in order to slow the production of weapon-usable plutonium, even if the core cannot be physically reconfigured. The analysis was performed for Iran’s IR-40 reactor at Arak in support of negotiations with Iran, but the methods have application to future reactors that present similar nonproliferation challenges. Two methods are considered, and both retain identical power, thermal-hydraulic, and safety profiles as the original reactor design. The conversion options can be implemented at any time during the reactor’s life. The two methods have competing effects on achievable burnup, and they can be combined to produce an optimized core that matches both the fresh-core reactivity and maximum burnup of the original reactor. For the IR-40 example, the optimized design produces weapon-grade plutonium at only about 19% of the rate of the unmodified reactor for the same power level. Additionally, a reactor so converted could not be readily converted back to natural-uranium fuel without replacement heavy water, and it would retain the ability to produce medical isotopes at rates that exceed the original design through the use of LEU targets

Vascular endothelial growth factor's angiogenic role in tumor growth and metastasis

Thesis (M.S.) University of Alaska Fairbanks, 2005Angiogenesis and vasculogenesis are two very important processes in the development and maintenance of mammalian health. All structures of the body (human or animal) need certain essential elements in order to live thrive and maintain. The angiogenic role is to supply and support tissue with ample vasculature, thus providing a route of access for the transportation of essential nutrients and the removal of waste in a sustained fashion. Just like normal tissue, tumorogenic tissue is no exception; neoplastic tissue has the same nutritional requirements which must be supported via vascularization. Vascular endothelial growth factor (VEGF) has been shown to be a key mediating factor in the underlying cascade of chemical events leading to angiogenesis, which makes it a very important precursor molecule for early neoplasia detection. The overall purpose of this study was to establish circulatory baseline VEGF levels in healthy dog models. Baseline levels of VEGF in plasma will aid as a model in detection, comparison and evaluating of disease progression in sled dogs. There were significant differences between male and female dogs and exercising males and exercising females. A significant factor affecting baseline levels was gender. In addition there is some data which suggest that breed may playa role in baseline VEGF levels

Development of a Low Profile, Endoscopic Implant for Long Term Brain Imaging

The increased public awareness of concussion and traumatic brain injury has motivated continued research into the brain, its functions, and especially its response to injury, with a focus on improving the brain’s repair capabilities. However, due to the critical nature of the tissue, it is currently difficult for researchers to acquire high resolution images below the cortex without sacrificing a lab animal. Sacrificing an animal greatly reduces the amount of data that can be obtained from it, making longitudinal studies unappealing or unfeasible because a large number of animals is needed to obtain useful data over multiple time points. Additionally, inter-animal variance can further obfuscate results. The gradient index (GRIN) lens is a form of micro-endoscope that can penetrate the cortex to obtain high resolution, in vivo images when used with a multiphoton microscope system. The lens is implanted through the skull and into the brain, providing a column of material that refracts and refocuses the laser beam, unlike the natural tissue, which scatters light. This dissertation describes the development of a low profile GRIN lens implant system suitable for longitudinal imaging, as well as the co-development of a restraint system to accommodate the new implant on a microscope stage. The imaging protocol is detailed, and images acquired over three months are shown. The developed device drastically reduced the size of implant both above the skull and within the brain tissue compared to previously reported GRIN lenses, while still obtaining the expected high resolution images. This research also found that labelled axons in transgenic mice appear in unique, recognizable patterns which remain consistent over months of imaging, meaning future studies may use the axons themselves as landmarks. An experimental design for analyzing traumatic brain injury is also developed, which could incorporate a future implant

Endothelial phenotype differs by both sex and vessel function

Endothelial cells (the cells that line our blood vessels) were once thought to be an inert cellophane-like wrapper separating flowing blood from tissue. However, as our understanding of the human body has progressed, we have come to know that the endothelium is actually an incredibly important, metabolic ally active organ. Endothelial dysfunction appears to be an early hallmark of multiple disease states, including, but not limited to, cardiovascular disease, type II diabetes, and atherosclerosis. While it is often presumed that all non-specialized endothelial cells are the same, and thus will have the same response to various pharmacological agents, disease states, and stimuli, this may not be true. Our goal is to understand if endothelial cell phenotypes (characteristics expressed by the cell) vary based on their origin (the blood vessel they come from), or by sex, and if so, to what degree. Specifically, our research focused on primary cultures of aortic (a conduit vessel) endothelial cells and of skeletal muscle microvasculature (exchange vessels) endothelial cells from both male and female rats, then compared them to one another, after being grown under identical conditions. Our results strongly suggest that endothelial cells vary in size, growth rates, and protein expression, based on their origin and their sex. The implication is that medicines could affect different parts of our bodies indifferent ways, as well as affecting males and females differently. When studying functions mediated by vascular endothelium, it is important to use cells from an anatomical/functional location that best describes the question under investigation (or multiple locations if looking systemically), AND both sexes, as both characteristics determine the phenotype

Valuated matroid polytopes and linking system composition.

PhD Theses.Valuated matroids are a generalisation of matroids; matroids themselves being an abstraction of the notion of independence. Valuated matroids have many equivalent de nitions including via independent sets and circuits, and in this thesis we show that a valuated matroid has an equivalent de nition in terms of a rank function which we construct by analogy with the matroid rank function by looking at matroid and valuated matroid polytopes. We separately construct a hyperoperation which is an extension of a previously studied operation of composing valuated matroids, this being the composition of valuated linking systems. The composition of valuated linking systems can be seen as a generalisation of matrix multiplication to tropical linear spaces. In particular, the hyperoperation we introduce has been in uenced by viewing matrices as representing linear spaces, which we can do by looking at their row space, and consequently by how these relate to Pl ucker coordinates. Working tropically, since tropical linear spaces are equivalent to valuated matroids, which are also known as tropical Pl ucker vectors, we create the hyperoperation by using the parallels with matrices representing linear spaces over a eld. We describe the hyperproduct completely for small rank, where this operation forms a hypergroup. In higher rank we investigate what known matroid subdivisions it contains, as well as also showing that it does not form a fan, and nor is it convex in general. We also conjecture this hyperoperation forms a hypergroup for higher rank, and present some investigation towards this

Physical cryptographic verification of nuclear warheads

How does one prove a claim about a highly sensitive object such as a nuclear weapon without revealing information about the object? This paradox has challenged nuclear arms control for more than five decades. We present a mechanism in the form of an interactive proof system that can validate the structure and composition of an object, such as a nuclear warhead, to arbitrary precision without revealing either its structure or composition. We introduce a tomographic method that simultaneously resolves both the geometric and isotopic makeup of an object. We also introduce a method of protecting information using a provably secure cryptographic hash that does not rely on electronics or software. These techniques, when combined with a suitable protocol, constitute an interactive proof system that could reject hoax items and clear authentic warheads with excellent sensitivity in reasonably short measurement times. Keywords: isotopic tomography; nuclear weapons; disarmament; verificationUnited States. Department of Energy (Award DE-NA0002534

Overexpression of a family of RPEL proteins modifies cell shape

AbstractProteins containing RPEL motifs (e.g., MAL) are important in the regulation of gene expression by the actin cytoskeleton. Screening the ENSEMBL database for RPEL proteins identified four additional proteins that contain RPEL motifs and nuclear localisation sequences, three of which (RPEL-A, RPEL-B and RPEL-C) are expressed in adult mouse tissues with different expression profiles. The mRNAs encoding RPEL-B and RPEL-C were subject to alternative splicing. Expression of these genes in cells indicated that they had a marked effect on cell shape. Furthermore, when expressed with a nuclear localised actin all of the different forms became restricted to the nucleus

Ca 2+/calmodulin-dependent protein kinase kinase beta is regulated by multisite phosphorylation

Ca2+/calmodulin-dependent protein kinase kinase β (CaMKKβ) is a serine/threonine-directed kinase that is activated following increases in intracellular Ca2+. CaMKKβ activates Ca2+/calmodulin-dependent protein kinase I, Ca2+/calmodulin-dependent protein kinase IV, and the AMP-dependent protein kinase in a number of physiological pathways, including learning and memory formation, neuronal differentiation, and regulation of energy balance. Here, we report the novel regulation of CaMKKβ activity by multisite phosphorylation. We identify three phosphorylation sites in the N terminus of CaMKKβ, which regulate its Ca2+/calmodulin-independent autonomous activity. We then identify the kinases responsible for these phosphorylations as cyclin-dependent kinase 5 (CDK5) and glycogen synthase kinase 3 (GSK3). In addition to regulation of autonomous activity, we find that phosphorylation of CaMKKβ regulates its half-life. We find that cellular levels of CaMKKβ correlate with CDK5 activity and are regulated developmentally in neurons. Finally, we demonstrate that appropriate phosphorylation of CaMKKβ is critical for its role in neurite development. These results reveal a novel regulatory mechanism for CaMKKβ-dependent signaling cascades

A Guide for Policy, Practice and Patients on Wellbeing and Sickle Cell Disorder (SCD)

This guide is based on research examining the shielding experiences of people with sickle cell disorders (SCD) and parents of children with the condition during the COVID-19 pandemic. The aim was to improve NHS services for this population group. Services have duties under the Equality Act 2010 to ensure equity and tackle health inequalities. Since SCD disproportionately affects Black, Asian and Minority Ethnic (BAME) communities, there are also duties not to engage in direct or indirect racist discrimination, nor in harassment or victimization. It is important that anti-racist and anti-bias training is offered in all NHS services and cultural competency encouraged amongst all staff. Additionally, that conditions affecting the BAME population, like SCD, become a mandatory part of all nursing and medical educational and NHS training programmes