Development of high Tc (greater than 100 K) Bi, Tl and Y-based materials as superconducting circuit elements

Results on this project over the past three years have shown that the Bi and Tl-based superconducting materials in bulk form are noticeably different from the Y-based 123 material in that superconductivity is considerably harder to achieve, maintain and reproduce. This is due primarily to the difficulty in obtaining the higher Tc phase in pure form since it commonly co-exists with other undesirable, lower Tc phases. In particular, it has been found that long processing times for calcining and firing (20 - 200 hrs.) and close control of temperatures which are very near the melting point are required in order to obtain higher proportions of the desirable, high Tc (2223) phase

Development of high Tc (greater than 110K) Bi, Tl and Y-based materials as superconducting circuit elements

Experimental work was continued on the development and characterization of bulk and hot pressed powders and tapecast materials in the Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O systems. A process for producing warp-free, sintered, superconducting tapes of Bi composition Bi1Sr2Ca2 Cu3O(x) was established. The procedure requires a triple calcination at 830 C for 24 hours and sintering at 845 C from 20 to 200 hours. Hot pressing the triple calcined powder at 845 C for 6 hours at 5000 psi yielded a dense material, which on further heat treatment at 845 C for 24 hours, exhibited a Tc of 108.2K. The Bi compositions were found to be much less oxygen sensitive than the Y compositions. This was especially noted in the case of the hot pressed materials which were superconducting as hot pressed, a condition that could not be achieved in the Y compositions. Safire-type grounding links are in the process of being fabricated from these materials

Development of high T(sub c) (greater than 110 K) Bi, Tl, and Y-based materials as superconducting circuit elements

Experimental work has continued on the development and characterization of bulk and hot pressed powders and tapecast materials in the Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O systems. A process for producing warp-free, sintered, superconducting tapes of Bi composition Bi2Sr2Ca2Cu3O(x) with a mixed oxide process was established. This procedure required a triple calcination at 830 C for 24 hours and sintering at 845 C from 20 to 200 hours. Hot pressing the triple calcined powder at 845 C for 6 hours at 5000 psi yielded a dense material which on further heat treatment at 845 C for 24 hours exhibited a Tc of 108.2 K. A further improvement in the processing of the bismuth materials was achieved via a chemical coprecipitation process wherein the starting nitrate materials were coprecipitated with oxalic acid, thus yielding a more chemically homogeneous, more reactive powder. With the coprecipitated powders, only one calcine at 830 C for 12 hours and a final sinter at 845 C for 30 hours was sufficient to produce a bulk superconducting material with a Tc of 108.4 K. SAFIRE-type grounding links were successfully fabricated from sintered, tapecast, coprecipitated BSCCO 2223 powders. Compositional and processing investigations were continued on the Tl-based superconductors. Manganese and lithium additions and sintering temperature and time were examined to determine their influence on superconducting properties. It was found that lithium substitutions for copper enhance the transition temperatures while manganese additions produced deleterious effects on the superconducting properties. A suitable procedure for producing reproducible bulk and tapecast material of Tl composition Tl2Ba2Ca2Cu3O(x) was developed and used in fabricating uniform superconducting tapes. The highest transition temperature for Tl-based tapes was measured at 110.2 K. Thallium superconducting SAFIRE-type grounding links were fabricated from the tapes

Chemical Synthesis of Bacterial Siderophores and Applications in Pathogen Detection

Bacterial siderophores are a class of small organic compounds that are produced endogenously by bacteria to chelate essential ferric iron from their surroundings. Because the bioavailability of ferric iron is extremely low is physiological pH, the host of a parasitic infection can be a poor source of soluble Fe3+. Consequently, bacteria rely upon siderophore transport systems to efficiently scavenge the nutrient. Nearly every bacteria

Development of high Tc (greater than 110K) Bi, Tl and Y-based materials as superconducting circuit elements

This report is presented in two parts. Part 1 deals primarily with Bi-based materials and a small amount of work on a Y-based composition while Part 2 covers work on Tl-based materials. In Part 1, a reliable and reproducible process for producing bulk bismuth-based superconductors has been developed. It is noted however, that a percentage of the tapecast material experiences curling and fracturing after a 30 hour sintering period and is thus in need of further examination. The Bi-Sr-Ca-Cu-O (BSCCO) material has been characterized by critical temperature data, X-ray diffraction data, and surface morphology. In the case of T sub c, it is not critical to anneal the material. It appears that the BSCCO material has the possibility of producing a better grounding strap than that of the 123 material. Attempts to reproduce near room temperature superconductors in the Y-Ba-Cu-O system were unsuccessful. In Part 2, several methods of processing the high temperature superconductor Tl2Ba2Ca2Cu3O10 were investigated; i.e., different precursor compositions were sintered at various sintering times and temperatures. The highest superconductig temperature was found to be 117.8K when fired at 900 C for three hours. Higher sintering temperatures produced a melted sample which was nonsuperconducting at liquid nitrogen temperature. Also, a preliminary study found Li2O substitutions for copper appeared to increase the transition temperature and create fluxing action upon sintering. It was suggested that lower sintering temperatures might be obtained with lithium additions to produce reliable Tl2Ba2Ca2Cu3O10 processing methods

The Impact on Informal Supporters of Domestic Violence Survivors:A Systematic Literature Review

Domestic violence (DV) is experienced by 1 in 4 women in the United Kingdom during their lifetime, and most survivors will seek informal support from the people around them, even if they choose not to access help from professionals. Support from these relatives, friends, neighbors, and colleagues can provide a buffer against effects on the survivor’s physical health, mental health, and quality of life, and has been shown to be protective against future abuse. There has been an absence of research studying members of survivors’ networks and, in particular, investigating how the impact of DV might diffuse to affect them. A systematic literature review of reported research (either in peer-reviewed journals or in gray literature) was undertaken to explore the impacts of DV on survivor networks. Of the articles found, 24 had data relating to the topic area, though no study addressed the question directly. Framework analysis and meta-ethnography generated the following themes: physical health impacts, negative impacts on psychological well-being, direct impacts from the perpetrator, and beneficial impacts on psychological well-being. The studies in this review indicated that informal supporters may be experiencing substantial impact, including vicarious trauma and the risk of physical harm. Currently, there is little support available which is directly aimed at informal supporters of DV survivors, thus these findings have practical and policy implications, in order to acknowledge and meet their needs. </jats:p

Qualitative study to explore the health and well-being impacts on adults providing informal support to female domestic violence survivors

Objectives Domestic violence (DV) is hazardous to survivors\u27 health, from injuries sustained and from resultant chronic physical and mental health problems. Support from friends and relatives is significant in the lives of DV survivors; research shows associations between positive support and the health, well-being and safety of survivors. Little is known about how people close to survivors are impacted. The aim of this study was exploratory, with the following research question: what are the health and well-being impacts on adults who provide informal support to female DV survivors?Design A qualitative study using semistructured interviews conducted face to face, by telephone or using Skype. A thematic analysis of the narratives was carried out.Setting Community-based, across the UK.Participants People were eligible to take part if they had had a close relationship (either as friend, colleague or family member) with a woman who had experienced DV, and were aged 16 or over during the time they knew the survivor. Participants were recruited via posters in community venues, social media and radio advertisement. 23 participants were recruited and interviewed; the majority were women, most were white and ages ranged from mid-20s to 80.Results Generated themes included: negative impacts on psychological and emotional well-being of informal supporters, and related physical health impacts. Some psychological impacts were over a limited period; others were chronic and had the potential to be severe and enduring. The impacts described suggested that those providing informal support to survivors may be experiencing secondary traumatic stress as they journey alongside the survivor.Conclusions Friends and relatives of DV survivors experience substantial impact on their own health and well-being. There are no direct services to support this group. These findings have practical and policy implications, so that the needs of informal supporters are legitimised and met

Development of high Tc (greater than 100 K) Bi, Tl and Y-based materials as superconducting circuit elements

Experimental work on this project over the last four years has resulted in establishing processing and characterization techniques for producing both the Bi-based and Tl-based superconductors in their high temperature (2223) forms. In the bulk, dry pressed form, maximum critical temperatures (Tc) of 108.2 K and 117.8 K, respectively, were measured. Results have further shown that the Bi and Tl-based superconducting materials in bulk form are noticeably different from the Y-based 123 material in that superconductivity is considerably harder to achieve, maintain, and reproduce. This is due primarily to the difficulty in obtaining the higher Tc phase in pure form since it commonly co-exists with other undesirable, lower Tc phases. In particular, it has been found that long processing times for calcining and firing (20 - 200 hrs.) and close control of temperatures which are very near the melting point are required in order to obtain higher proportions of the desirable, high Tc (2223) phase. Thus far, the BSCCO bulk materials has been prepared in uniaxially pressed, hot pressed, and tapecast form. The uniaxially pressed material has been synthesized by the mixed oxide, coprecipitation, and melt quenching processes. The tapecast and hot pressed materials have been prepared via the mixed oxide process. In addition, thick films of BSCCO (2223 phase) have been prepared by screen printing on to yttria and magnesia stabilized zirconia with only moderate success; i.e., superconductivity was achieved in these thick films, but the highest Tc obtained in these films was 89.0 K. The Tc's of the bulk hot pressed, tapecast, and screen printed thick film materials were found to be 108.2, 102.4, and 89.0 K, respectively

Bioanalytical techniques for the analysis of mitochondrial heterogeneity

University of Minnesota Ph.D. dissertation. October 2013. Major: Chemistry. Advisor: Edgar A. Arriaga. 1 computer file (PDF); xii, 212 pages, appendices A-C.In this thesis, techniques are described for the measurement of individual mitochondrial isoelectric point (pI) using capillary isoelectric focusing (cIEF) with laser-induced fluorescence detection, simulation of the contribution of mitochondrial surface compositions to pI, and determination of individual mitochondrial membrane potential and electrophoretic mobility using capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). These techniques provide insight into mitochondrial heterogeneity, which could increase fundamental understanding of the role played by mitochondria in aging.A method was developed to determine the pIs of individual mitochondria by cIEF. This method provides reproducible distributions and accurate determination of individual mitochondrial pI by the use of internal standards, and was able to detect changes in mitochondrial pI distributions caused by changes to the mitochondrial surface by treatment with trypsin. Application of this method demonstrated the heterogeneity of mitochondrial pI, which reflects the heterogeneity of mitochondrial surface compositions.To model the effect of surface composition on mitochondrial pI heterogeneity, a method was developed to predict mitochondrial pI values using simulated surface compositions consisting of different percentages of amino acids and phospholipids found in the mitochondrial outer membrane. This method was validated by predicting the pI values of known mitochondrial outer membrane proteins then extended to isolated mitochondria and used to model a pI distribution determined experimentally by cIEF. Significant changes in the percentages of some amino acids and phospholipids were predicted for observed pI differences between individual mitochondria. This model provides insight into the heterogeneity of mitochondrial pI and contribution of surface compositions. Distributions of individual mitochondrial membrane potential and electrophoretic mobility were measured using CE-LIF. Mitochondria from cultured cells and mouse muscle and liver tissue were labeled with JC-1, a ratiometric dye which indicates membrane potential. Analysis of specific regions of interest defined by performing CE-LIF of depolarized samples makes this method capable of analyzing mitochondrial membrane potential even in preparations where depolarized mitochondria may be present due to biological variation or experimental factors that result in damage to mitochondria or may be insufficient to keep all mitochondria polarized. This analysis revealed additional differences between samples and an effect of membrane potential on electrophoretic mobility. This method allows for the characterization of mitochondrial heterogeneity in membrane potential and surface properties.In the future, these methods can be applied to biological models of aging to elucidate the role that mitochondrial heterogeneity plays in age-related dysfunction and disease