Development of a ninety string solar array simulator

A power source was developed to support testing for the Space Station Freedom Power Management and Distribution (PMAD) DC Testbed. The intent was to simulate as closely as possible the steady-state and transient responses of a solar array. Several breadboards and one thermal prototype were built and tested. Responses were successfully verified and improved upon during successive breadboards. The completed 90-string simulator consists of four power MOSFETs, four 25 watt source resistors, and four 250 watt drain source bypass resistors per string, in addition to the control circuitry

Teachers\u27 Perspectives on the Impact of Physical Activity on Classroom Behavior

Research shows that there are numerous benefits to allowing students to be physically active throughout the school day, such as increasing motivation, decreasing behavioral issues, and improving on-task behavior (Centers for Disease Control and Prevention, 2018) The purpose of this research was to assess, from the perspective of teachers and teacher aids, the relationship between physical activity and elementary school aged students’ academic and behavioral performance in the classroom. Previous research conducted supports that the inclusion of physical activity during the school day helps improve students’ academic and behavioral performance in the classroom. Teachers and teacher aides were chosen as participants because they observe and interact with students on a daily basis. The survey asked participants to indicate if they include physical activity during class-time, the duration and types of such activities, and what benefits they believe come from these activities. The overall findings of this study show most participants include exercise breaks for their students and favor the idea that class-time physical activity is beneficial for students

Mechanisms Underlying Memory Deficits Following West Nile Virus Neuroinvasive Disease

Neurocognitive sequelae are observed in \u3e50% of patients who survive neuroinvasive infections with encephalitic arboviruses, such as the mosquito-borne West Nile virus (WNV). Early diagnosis and high survival rates from WNV neuroinvasive disease (WNND) (\u3e90%) have thus led cumulatively to approximately ten thousand patients living with neurocognitive impairments, with 1-3000 cases accruing yearly, yet underlying mechanisms responsible for these deficits have not been investigated. Within the last 15 years, studies have begun uncover many pathways which are utilized both by the developing CNS as well as the immune system, including the use of cytokines in the regulation of progenitor cell proliferation and synaptic refinement via the classical complement cascade. Under healthy conditions, an intact blood-brain-barrier limits potential crosstalk between these domains. But amidst settings of CNS infection or damage, invocation of CNS developmental programs could be initiated by proinflammatory factors. With this in mind, the chapters of this thesis are centered around a theme of studying pathways utilized by both the immune system and the developing CNS and determining what the consequences are for cognition and memory during CNS West Nile virus infection. First we have established a novel murine model of recovery from WNND in which intracranial inoculation of the attenuated mutant WNV-NS5-E218A leads to similar CNS viral loads and inflammation as peripheral inoculation of its parent strain, WNV-NY99, with rates of survival and cognitive dysfunction that mirror human WNND. WNV-NS5-E218A-recovered mice exhibit impaired spatial learning without significant alterations in cortical and hippocampal volume or total neuron numbers, but exhibit persistently activated microglia. Whole transcriptome analysis of hippocampi from WNV-NS5-E218A-recovered mice with poor spatial learning revealed increased expression of genes known to drive microglial effects on synaptic pruning, including the classical complement pathway and phagocytosis. Indeed, the classical complement cascade initiation factor, C1qA, was found to be produced primarily by microglia and localized to infected neurons and synapses during WNND. Electron and confocal microscopy revealed a loss of hippocampal mossy fiber synapses while synaptophysin-positive puncta and phagosomes containing synaptic vesicles were observed within microglia. This loss of mossy fiber synapses was also observed in human WNND post-mortem samples. Importantly, mice with fewer microglia (IL34 -/-) or mice deficient in complement (C3 -/-) were protected from WNV-induced synapse loss. This study provides a novel murine model of WNV-induced spatial memory impairment, provides evidence that viral infection of adult neurons may induce complement-mediated elimination of synapses, and identifies a potential mechanism underlying neurocognitive impairments experienced by patients recovering from WNND. Next we report that during WNND recovery, significantly fewer new granule cell neurons are born within the hippocampal dentate gyrus, as revealed by BrdU-labeling. And although neuronal progenitor cells (NPCs) are not direct targets of WNV infection, their homeostatic levels of proliferation, differentiation, and migration were significantly altered. Using immunohistochemistry and flow cytometry coupled with in vivo BrdU labeling during acute WNV infection, we found NPCs within the subventricular (SVZ) and subgranular (SGZ) neurogenic zones generated fewer new neuroblasts, but greater numbers of astrocytes, an effect which slowly recovers over about 45 days. This effect was dependent upon Interleukin-1 receptor (IL-1R) signaling, which we have previously shown to be necessary for promotion of viral clearance by T lymphocytes. Lastly, mice deficient in IL-1R were resistant to the WNV-mediated impairment in spatial learning and memory via the Barnes maze task at 45 days post infection, suggesting that alterations to neuronal progenitor cell homeostasis could also underlie long term cognitive consequences of WNND

Analyzing the Bitcoin Ponzi Scheme Ecosystem

This paper analyzes the supply and demand for Bitcoinbased Ponzi schemes. There are a variety of these types of scams: from long cons such as Bitcoin Savings & Trust to overnight doubling schemes that do not take off. We investigate what makes some Ponzi schemes successful and others less so. By scouring 11 424 threads on bitcointalk.org, we identify 1 780 distinct scams. Of these, half lasted a week or less. Using survival analysis, we identify factors that affect scam persistence. One approach that appears to elongate the life of the scam is when the scammer interacts a lot with their victims, such as by posting more than a quarter of the comments in the related thread. By contrast, we also find that scams are shorter-lived when the scammers register their account on the same day that they post about their scam. Surprisingly, more daily posts by victims is associated with the scam ending sooner