Vitamin D Deficiency and Exogenous Vitamin D Excess Similarly Increase Diffuse Atherosclerotic Calcification in Apolipoprotein E Knockout Mice

Background: Observational data associate lower levels of serum vitamin D with coronary artery calcification, cardiovascular events and mortality. However, there is little interventional evidence demonstrating that moderate vitamin D deficiency plays a causative role in cardiovascular disease. This study examined the cardiovascular effects of dietary vitamin D deficiency and of vitamin D receptor agonist (paricalcitol) administration in apolipoprotein E knockout mice. Methods: Mice were fed atherogenic diets with normal vitamin D content (1.5IU/kg) or without vitamin D. Paricalcitol, or matched vehicle, was administered 3× weekly by intraperitoneal injection. Following 20 weeks of these interventions cardiovascular phenotype was characterized by histological assessment of aortic sinus atheroma, soluble markers, blood pressure and echocardiography. To place the cardiovascular assessments in the context of intervention effects on bone, structural changes at the tibia were assessed by microtomography. Results: Vitamin D deficient diet induced significant reductions in plasma vitamin D (p<0.001), trabecular bone volume (p<0.01) and bone mineral density (p<0.005). These changes were accompanied by an increase in calcification density (number of calcifications per mm2) of von Kossa-stained aortic sinus atheroma (461 versus 200, p<0.01). Paricalcitol administration suppressed parathyroid hormone (p<0.001), elevated plasma calcium phosphate product (p<0.005) and induced an increase in calcification density (472 versus 200, p<0.005) similar to that seen with vitamin D deficiency. Atheroma burden, blood pressure, metabolic profile and measures of left ventricular hypertrophy were unaffected by the interventions. Conclusion: Vitamin D deficiency, as well as excess, increases atherosclerotic calcification. This phenotype is induced before other measures of cardiovascular pathology associated clinically with vitamin D deficiency. Thus, maintenance of an optimal range of vitamin D signalling may be important for prevention of atherosclerotic calcification

Pre- and post-boiling nucleation thermal and fluid flow transients during the startup of capillary pumped loops (CPLs)

During the fully flooded startup of a Capillary Pumped Loop (CPL), accelerated vapor growth caused by the boiling incipient superheat results in rapid pressure and fluid flow transients within the loop. A number of factors influence the vapor growth rate and the induced variations in the differential pressure across the evaporator wick, which is important for determining whether or not the startup will be successful. The primary objectives of the current study are to evaluate the effects of procedural and design variations on the startup performance of CPLs and to develop predictive tools that will result in an improved fundamental understanding of the startup. An analytical solution for the temperature profile in a cylindrical evaporator subject to a uniform heat flux prior to the initiation of boiling is derived using the Green\u27s Function method. Also, an approximate solution is derived for the case in which the evaporator is heated by means of a constant conductance to a heat dissipating device. Results of this model for the preheating stage of startup suggest potential design and procedural modifications that can improve startup success for the CPL. A three-dimensional transient conduction model of the evaporator following vapor formation is developed to determine the effect that design parameters have upon the vapor phase growth. A system level fluid flow model of the CPL is coupled to the vapor growth model, which allows the differential pressure spike across the evaporator wick to be calculated. Key design parameters are identified from the model results that have the potential to significantly reduce the bubble growth rate and the corresponding differential pressure spike. All of the model results indicate that design modifications are available that can significantly improve the chances for successful startup of CPLs under flooded startup conditions

Modeling and Analysis of a Thermophotovoltaic Integrated Self-Powered Furnace

This work investigates the energy efficiency and carbon reduction potential of self-powered residential building heating equipment using a thermodynamic modeling approach. An integrated thermophotovoltaic power module and residential scale furnace system (40,000 Btu/h) were modeled and studied in detail to assess the influence of different design configurations on primary energy efficiency. Operational characteristics such as total power generation, electrical efficiency, and heat recovery were examined in a self-powered system configuration. A sensitivity analysis was conducted to determine the influence of the electric grid’s carbon dioxide footprint (carbon intensity) and the cost of electricity on the environmental, as well as the economic, benefit associated with the self-powered configuration. Compared with a traditional furnace powered by an electric grid at a carbon intensity of 0.5 kg CO2eq/kWhEL, the self-powered furnace was shown to decrease the annual carbon dioxide emissions by approximately 550 kg (~75% reduction), while also saving more than USD 200 in utility expenses, annually. Additionally, the carbon emission reduction potential of blending different concentrations of hydrogen in natural gas fuel was also studied