The effects of realistic surface properties on low temperature space observatories

I investigate the effects of modelling radiative heat transfer correctly on equilibrium temperatures of passively cooled telescopes. I compare the traditional diffuse approximation with a surface exhibiting the directional properties of gold, both with an emissivity of 0.03. I also modeled surfaces with much lower, more realistic emissivities. Directional surface properties are derived from values of optical constants at room temperature since there exists a dearth of reliable data at cryogenic temperatures. The effect of using optical constants at different wavelengths is also investigated. My simulations show the diffuse assumption produces higher temperatures than the directional surface. Both surfaces produce higher temperatures than the low emissivity cases when conductivity is low, whilst the reverse is true for high conductivity. The directional surface always outperformed the diffuse surface For radiative exchange, the diffuse approximation simply produces pessimistic results. However, incorrect modelling of radiative exchange can have knock-on effects. The higher emissivity, diffuse approximation predicts much greater improvements due to tilted sunshields than would realistically occur. This may recommend unnecessary changes to telescope designs in the attempt to improve cooling performance. The lack of reliable directional radiative data for candidate passive cooling materials will require a major measurement program before a mission is launched. In this thesis I describe apparatus to help in such measurements. The bi-directional reflectometer quickly and accurately builds up a picture of directional surface properties, performing very well when combined with a reliable laser and measuring device, the few component parts being relatively cheap. Thus, the many directional measurements required for accurate modelling could be made cheaply and quickly. The multiple reflection cell was designed to make high accuracy measurements at one angle only. This was not as effective as hoped due to laser problems, but should be able to make very good measurements. Further work is recommended

Changes in carbohydrates of Navy beans during hydration and subsequent thermal processing

Navy beans were subjected to six different hydration protocols that varied in time, temperature, and methodology after which they were thermally processed in both a brine solution and a typical baked bean sauce. Beans, isolated starch, and hydration fluid were analyzed immediately after the completion of hydration protocols. Significant differences were noted between those protocols utilizing low heat (1 and 2) and those utilizing high heat methods (3-6). Bean from low heat protocols were firmer overall. Starch granules from low heat beans were smaller in overall size, experienced less surface damage retained birefringence, and could absorb more water (higher swell factor). Analysis of the hydration fluid showed no noticeable differences. Analysis of the canned products showed that intense thermal processing effectively caused gelatinization in all protocols as confirmed by DSC and light microscopy. Isolated starch had little to no abilities to retain water. Granules from all protocols in both mediums showed extensive damage, cracking, and possible leaching which is believed to be the cause of substantially lower amylose findings in starch isolated from canned as compared to hydrated beans. Analysis of brine solution revealed increased leaching of carbohydrates, amylose, and proteins. The Kramer compression shear cell detected significant texture differences in beans canned in brine that were hydrated by novel protocols 5 and 6 but not in novel protocol 4, the current protocol (3), and the traditional protocols (1 and 2). Likewise, a probe texture analyzer, determined beans hydrated by protocols 5 and 6 to have firmer skin and flesh overall as compared to the other protocols. The Kramer sheer press was not able to detect differences in beans canned in sauce while the probe texture analyzer was able to detect differences in beans from traditional protocol 1 compared to protocols 3-6. Overall, it was discovered that novel hydration protocols 5 and 6 produce firmer beans when canned in brine solution compared to the current (3) and traditional protocol (1). Beans hydrated by current (3) and novel protocols (4 – 6) show no significant differences in texture when canned in typical baked bean sauce

Insights into the Development of Chemotherapeutics Targeting PFKFB Enzymes

The PFKFB enzymes control the primary checkpoint in the glycolytic pathway and are implicated in a multitude of diseases: from cancer, to schizophrenia, to diabetes, and heart disease. The inducible isoform, PFKFB3, is known to be associated with the upregulation of glycolysis in many cancers. The first study within this work investigates the potential for using tier-based approaches of virtual screening to target small molecule kinases, with PFKFB3 serving as a case study. For this investigation, bioactive compounds for PFKFB3 were identified from a compound library of 1364 compounds via high-throughput screening, with bioactive compounds being further characterized as either competitive or non-competitive for F6P. Using the F6P-competitive compounds, several structure based docking programs were assessed individually and in conjunction with a pharmacophore screening. The results showed that the tiered virtual screening approach, using pharmacophore screening in addition to structure-based docking, improved enrichments rates in 80% of cases, reduced CPU costs up to 7-fold, and lessened variability among different structure-based docking methods. The second study investigates the structural and kinetic characteristics of citrate inhibition on the heart PFKFB isoenzyme, PFKFB2. High levels of citrate, an intermediate of the TCA cycle, signify an abundance of biosynthetic precursors and that additional glucose need not be degraded for this purpose. Previous studies have noted that citrate acts as an important negative feed-back mechanism to limit glycolytic activity by inhibiting PFKFB enzymes, yet the structural and mechanistic details of citrate’s inhibition had not been determined. To study the molecular basis for citrate inhibition, the three-dimensional structures of the human and bovine PFKFB2 orthologues were solved, each in complex with citrate. For both cases, citrate primarily occupied the binding site of Fructose-6-phosphate (F6P), competitively blocking F6P from binding. Additionally, a carboxy arm of citrate extended into the γ-phosphate binding site of ATP, sterically and electrostatically blocking the catalytic binding mode for ATP. In the human orthologue, which utilized AMPPNP as an ATP analogue, conformational changes were observed in the 2-kinase domain as well as the binding mode for AMPPNP. This study gives new insights as to how the citrate-mediate negative feedback loop influences glycolytic flux through PFKFB enzymes

A Bayesian Approach to Aerial Localization of Radioactive Sources

Securing nuclear material has become an important area for the safety of the U.S. and other countries. Within nuclear security, there is a potential to use orphaned or stolen radioactive sources to cause harm. As the amount of radioisotopes used by government and commercial businesses increases, the need to secure these sources becomes exponentially more difficult. It is well known that there have been several cases of lost, orphaned or stolen nuclear sources across the globe. There is a need for state-of-the-art radiation search methods to search for these potentially dangerous radioactive sources that could be misplaced. While there are several well established methods for ground-based source search, the options for using air-based detection systems are not as effective. This thesis describes the development and implementation of the Broad-Area Search Bayesian Processor (BASBP) algorithm. This program was created to effectively search for lost sources from an unmanned aerial detection system. This approach utilizes Bayes\u27 theory coupled to a MCNP weighting method to quickly estimate the location of possible radioactive sources. This Bayesian algorithm shows improvements in source localization for low-level source isotopes. BASBP has been shown to locate radioactive sources that are weaker than standard minimum detectable activities. It also shows promise for using other data to more effectively locate lost radioactive sources