Silicon Refining by Solidification from Liquid Si–Zn Alloy and Floating Zone Method

This study evaluated the refining ability of a proposed production process for solar-grade silicon utilizing the electrolytic reduction of SiO₂ on a liquid zinc electrode in molten salt. The distribution behaviors of impurity elements during the precipitation of solid silicon from a liquid Si–Zn alloy were studied by thermodynamic calculations at 923 K. In the precipitation experiment, silicon granules were recovered from a liquid Si–Zn alloy, which was prepared from metallurgical-grade silicon. The impurity removal ratios exceeded 99% for C, Al, and Ca, and 90% for Fe. High removal ratios were attained for B and O as well. As the post-processing, a silicon ingot was produced from the precipitated silicon granules by the floating zone method. The Zn residue in the precipitated silicon was completely evaporated during the floating zone refining. The total content of metallic elements (Al, Ca, Fe, Ti, and Zn) was lower than 0.2 ppmw, even though metallurgical-grade silicon was used as the starting material

The development of recombinant Adenoviral vaccines to target pneumovirus infection

Respiratory Syncytial Virus (RSV) is a member of the pneumovirus genus (family Paramyxoviridae, subfamily Pneumovirinae). RSV is an important respiratory virus of both infants and the elderly, representing an underappreciated burden on health care systems. In addition, re-infections can occur despite the presence of pre-existing immunity, suggesting that immunological memory to RSV is incomplete. To date, treatment of RSV infection is limited to the provision of supportive care and no effective vaccine is available. Although several are currently under investigation, these candidates focus upon the delivery of the F and G antigens of RSV to stimulate the immune system, rather than the internal antigens, which may provide cross protection between different subtypes of RSV. Vaccine development has been greatly hindered by the lack of an appropriate animal model in which to study vaccine efficacy and pneumovirus pathogenesis. Pneumonia virus of mice (PVM) is also a member of the Pneumovirus genus and, like RSV infection of humans, causes a bronchiolitis and fatal pneumonia in its natural host, the mouse. PVM has been proposed as an appropriate model system in which to both study pneumovirus pathogenesis and vaccine efficacy. The PVM model system was adapted to investigate a potential vaccination strategy to address the lack of an available RSV vaccine. Replication deficient recombinant adenovirus serotype 5 (rAd5) vectors were constructed which expressed the F, M and N genes of PVM J3666, in addition to a control construct, which expressed the LacZ gene of E. coli. The constructs were administered via the intranasal route to BALB/c mice and were able to elicit complete protection against a lethal dose of pathogenic PVM J3666, in both short-term experiments and in a long-term experiment, up to 20 weeks post immunisation. The protection effect elicited by the constructs was observed when administered in a single dose, and in alternative mouse strains, C3H/He-mg and C57BL/6, which had differing immunity haplotypes. The rAd5 vectors generated a PVM specific IgG humoral response to PVM and Ad5 antigen which did not correlate as the primary mediator of protection. The rAd5 candidate expressing the N gene of PVM was shown to induce IFNγ secreting T-cells. The use of a peptide library of PVM N protein determined that a specific response could be identified towards the amino acids N41-90, N81-130, N161-210 and N281-330. Thus, the PVM infection model of BALB/c mice provides an immunological platform to facilitate the study of RSV and PVM pathogenesis, immunology and vaccine development.EThOS - Electronic Theses Online ServiceMedical Research Council (Great Britain) (MRC)GBUnited Kingdo

Electrolytic Production of Silicon Using Liquid Zn Alloy Cathode in Molten CaCl₂

2019 Liquid Metal Processing & Casting Conference (LMPC2019), Birmingham, UK, 8-11 September, 2019.A new electrolytic production process for solar-grade Si has been proposed utilizing a liquid Si–Zn alloy cathode in molten CaCl₂. The process consists of three major processes: electrolysis, precipitation, and refining. One of the advantages of the process is the attainability of high purity by application of a solidification refining from the liquid Si–Zn alloy. The residual zinc is easily removed afterwards due to its high volatility. To establish this process, the behavior of liquid Zn metal in molten CaCl₂ at 1123 K was investigated. Evaporation of Zn metal was largely suppressed by immersion into the molten salt, which enabled the use of a Zn electrode despite its high vapor pressure. Based on the results of cyclic voltammetry, the reduction of SiO₂ on a liquid Zn cathode was conducted by potentiostatic electrolysis at 0.9 V vs. Ca²⁺/Ca. Precipitated Si particles were recovered in the solidified Zn matrix

Properdin in immunity : in vitro and in vivo investigations

The complement system is one of the defence systems used by the host to protect itself against pathogens. It is divided into three complement pathways: the antibodydependent classical pathway, the lectin pathway and the alternative pathway. This latter antibody-independent pathway is auto-activated and leads to the generation and the deposition of C3b molecules on the pathogen’s surface. Properdin, the only positive regulator of this pathway, plays a major role by stabilising the alternative C3 convertase that leads to the creation of the amplification loop. Only little was known about the biology of properdin at the beginning of this project, despite the fact that properdin was discovered more than 50 years ago and despite the important role played by this molecule in immunity, as illustrated by the higher susceptibility to severe meningococcal disease encountered by properdin-deficient people. My thesis dealt with three experimental outlines to determine the role of properdin in immunity Properdin was examined from its global expression by various organs to its specific expression by different cell types. I have first shown using molecular biology and bioinformatics tools that properdin was expressed at a relatively high level in different lymphoid organs. I have then examined in more detail the expression of properdin by one of these organs, namely the spleen, using immunofluorescence. Properdin was thus shown to be present only in the white pulp compartment of this organ, where it was organised in clusters of properdin-positive cells possessing long cytoplasmic extensions. Next, I studied the expression of properdin by auxiliary cells. I have first given evidence that properdin was deposited on the surface of platelets and that this level of deposition was related to the activation state of the platelets. I have then shown for the first time that properdin was expressed by two mast cell lines. Microscopic analyses then demonstrated that properdin was present on the mast cell membrane and was present mainly as clusters on membrane extensions similar to vesicles in the process of being released. Further analyses on vesicles released by mast cells confirmed that properdin was enriched in a fraction of vesicles similar in size and in shape to microvesicles. Finally, the role played by properdin during bacterial infection was investigated using a pneumococcal pneumonia model. This study showed that properdin-deficient mice presented a worse level of infection than their wild-type littermates 2 days postinfection. This was associated with an unexpected higher survival rate for properdindeficient animals one week following the challenge. Therefore, in this model, while properdin was seen to be beneficial during the first 48 hours post-infection, by controlling the infection, the absence of properdin led to increased survival following infection. This study thus showed for the first time that properdin could play a bivalent role during infection, the higher inflammatory response engendered by properdin turning from being beneficial to being detrimental to the host over time.EThOS - Electronic Theses Online ServiceGBUnited Kingdo