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Approved for public release; distribution is unlimited / Theory and simulations of the railgun and free electron laser are presented, as well as a suggestion for extending the railgun lifecycle. The theory, design, and analysis of an electromagnetic railgun using a numerical model are discussed. The effects of varying electrical pulse formations, rail materials and geometries are explored. The application of a metallurgical process to mitigate hypervelocity gouging in railgun rails is proposed. This concept, to delay the onset velocity of gouging by laser-peening rails surfaces, may significantly increase the velocity at which projectiles acceptably traverse the barrel and extend the useful life of rails. If successful, this process would apply to any pair of materials in sliding contact at high relative velocity, including rocket sled tracks and light gas guns barrels. The status of proof-of-concept tests at LLNL, UC Davis, and UT is covered. FEL simulations investigating the effect that electron beam focal point variations have on the optical mode within the undulator are presented. / Lieutenant, United States Navy

Thesis (Ed.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / The purpose of this study is to determine some of the effects of self-directed learning in elementary science on the growth of fifth grade pupils. It was attempted to measure pupil growth in four areas: A. Fact absorption B. General Science Knowledge C. Liking for science D. Learning to generalize Printed materials instructed pupils in the use of simple apparatus to collect data and solve elementary science problems. The approach was inductive and required making generalizations on observed phenomena. A need exists for facilitating the use of activity science in classes where the teacher is unfamiliar with the content and process of science. Teachers who are unfamiliar with science do not deal adequately with the tactics and strategy of science investigation. Materials directed to the student which lead him through the experience of actual investigation might help to overaome some of the reluctance to engage in science activities evidenced by teachers untrained in science. If it can be shown that students are able to learn as much factual material by self-instruction as through the average textbook oriented study, then schools might be able to carry on a science activity program using the processes of science investigation without extensive teacher retraining programs and without loss of subject matter learning. Four self-directed science studies were tried on 128 students of six classes selected at random from schools of a mixed factory-suburban town. One hundred thirty-two students in seven classes were used as a control group. The study was conducted over a period of six months. Experimental and control groups were equated as to I.Q. ratings and scores on a standardized reading test. Teachers were equated on the basis of a town wide supervisors' survey. It was decided to investigate the comparative performance of the experimental and control groups using four different measuring instruments. 1. Growth in specific subject matter knowledge as measured on a prepared fact test. 2. Growth in general science knowledge as measured on a standardized science test. 3. Changes in possible liking for science as measured on a standardized attitude survey. 4. Growth in ability to generalize as measured on an organizational ability test. The four different tests were administered before and after the study and the change in performance was compared across groups for statistical differences. experimental and control groups were also compared in upper and lower I.Q. halves and by sex. The results of the experiment were as follows: 1. Fact absorption There was no significant difference between the experimental and control groups in gain of factual knowledge, nor was there difference when groups were compared according to sex and I.Q. 2. General Science Knowledge The upper I.Q. pupils of the control group enlarged their general science knowledge significantly more than did the experimental group. Between the two main groups there was no significant difference in gain of general science knowledge. 3. Liking for Science. After self-study activities the upper I.Q. groups expressed a liking for science significantly greater than the corresponding control group. The girls of the experimental groups gained in choices for science more than did the girls of the control group. There was no significant difference in the scores of the total groups. 4. Learning to Generalize. There were no significant differences in gains in organizational abilities between the experimental and control groups and none between the sex groups and I.Q. groups. SUMMARY: Although the present study showed no advantage for self-study activity science over traditional science studies,there is indication that the students learn the factual content as well when learning by themselves as when taught by a teacher. If longer exposure to science self-study activities is needed to show results in behavior of the students, there is much to gain and little to lose by allowing the student to pursue his science studies on his own. / 2031-01-01

by Chan Wah Lun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 252-260). / Acknowledgments --- p.i / Abstract --- p.ii / Contents --- p.vi / Naming of TCS mutants and modified TCS protein --- p.x / Abbreviations --- p.xi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Physical and chemical properties of Trichosanthin --- p.1 / Chapter 1.2 --- Biological activities of Trichosanthin --- p.3 / Chapter 1.3 --- Renal tubular reabsorption and nephrotoxicity of Trichosanthin --- p.10 / Chapter 1.4 --- Objective and strategies of study --- p.11 / Chapter Chapter 2 --- Materials and methods --- p.19 / Chapter 2.1 --- General Techniques --- p.19 / Chapter 2.2 --- Site directed mutagenesis of Trichosanthin --- p.21 / Chapter 2.3 --- DNA sequencing --- p.37 / Chapter 2.4 --- Overexpression of modified Trichosanthin in E. coli --- p.42 / Chapter 2.5 --- Purification of modified Trichosanthin --- p.43 / Chapter 2.6 --- Breaking of Disulphide bridge between modified TCS --- p.44 / Chapter 2.7 --- Coupling of DX T40 to modified Trichosanthin --- p.44 / Chapter 2.8 --- Biological activities of modified Trichosanthin and Dextran-modified trichosantin conjugates --- p.46 / Chapter 2.9 --- Immunogenicity of modified Trichosanthin and Dextran-trichosanthin conjugates --- p.50 / Chapter 2.10 --- Nephrotoxicity of Trichosanthin and Dextran-trichosanthin conjugates --- p.53 / Chapter Chapter 3 --- Construction of TCS mutants --- p.61 / Chapter 3.1 --- Introduction --- p.61 / Chapter 3.2 --- Method --- p.61 / Chapter 3.3 --- Results --- p.62 / Chapter 3.3.1 --- Construction of K173C mutant --- p.62 / Chapter 3.3.2 --- Construction of R29C mutant --- p.64 / Chapter 3.3.3 --- Construction of K173C R29C double mutant --- p.65 / Chapter 3.4 --- Discussion --- p.66 / Chapter Chapter 4 --- "Expression,Purification and Ribosome- inactivating activities of Modified Trichosanthin proteins" --- p.87 / Chapter 4.1 --- Introduction --- p.87 / Chapter 4.2 --- Method --- p.87 / Chapter 4.3 --- Results --- p.88 / Chapter 4.3.1 --- "Expression, purification and ribosome-inactivating activity of K173C" --- p.88 / Chapter 4.3.2 --- "Expression ,purification and ribosome-inactivating activity of R29C" --- p.89 / Chapter 4.3.3 --- "Expression, purification and ribosome-inactivating activity of K173C R29C" --- p.90 / Chapter 4.4 --- Discussion --- p.91 / Chapter Chapter 5 --- Coupling of Dextran T40 to modified Trichosanthin --- p.108 / Chapter 5.1 --- Introduction --- p.108 / Chapter 5.2 --- Method --- p.109 / Chapter 5.3 --- Results --- p.109 / Chapter 5.3.1 --- Coupling of R29C --- p.109 / Chapter 5.3.2 --- Coupling of K173C --- p.111 / Chapter 5.3.3 --- Coupling of R29CK173C --- p.111 / Chapter 5.4 --- Discussion --- p.111 / Chapter Chapter 6 --- Biological Activities of modified Trichosanthin and Dextran-modified trichosanthin conjugates --- p.128 / Chapter 6.1 --- Introduction --- p.128 / Chapter 6.2 --- Method --- p.128 / Chapter 6.3 --- Results --- p.130 / Chapter 6.3.1 --- In vivo Biological activity- Mid-term abortifacient activity --- p.130 / Chapter 6.3.2 --- In vitro biological activities / Chapter 6.3.2a --- Ribosome-inactivating activity --- p.131 / Chapter 6.3.2b --- Anti-tumour activity --- p.132 / Chapter 6.4 --- Discussion --- p.133 / Chapter Chapter 7 --- Immunogenicity of Dextran-modified trichosanthin conjugates --- p.156 / Chapter 7.1 --- Introduction --- p.156 / Chapter 7.2 --- Method --- p.157 / Chapter 7.3 --- Results / Chapter 7.3.1 --- Immunogenicity without denaturation of protein --- p.158 / Chapter 7.3.2 --- Immunogenicity with denaturation of protein --- p.161 / Chapter 7.4 --- Discussion --- p.162 / Chapter Chapter 8 --- Nephrotoxicity of Trichosanthin and Dextran-Trichosanthin conjugates --- p.199 / Chapter 8.1 --- Introduction --- p.200 / Chapter 8.2 --- Method --- p.202 / Chapter 8.3 --- Results --- p.202 / Chapter 8.3.1 --- Functional study on nephrotoxicity of Trichosanthin --- p.202 / Chapter 8.3.2 --- Morphological study on the nephrotoxicity of Trichosanthin --- p.203 / Chapter 8.3.3 --- The effect of coupling of Dextran T40 on the nephrotoxicity of Trichosanthin --- p.206 / Chapter 8.4 --- Discussion --- p.207 / Chapter Chapter 9 --- General Discussion --- p.244 / References --- p.252

Transcriptional regulation is a determinant of stability of recombinant protein production in CHO cells. Fundamental studies of recombinant gene transcription in relation to chromatin environment and promoter regulation are important for CHO cell line development and selection. This study has developed a methodology based on a cell/vector system to study recombinant transcription and expression stability of different promoters and/or proteins in the similar genomic environment. The CHO-FRT mini-pools developed in this project were mini-pools of CHO-S cell lines containing Flp Recombination Target (FRT) sites with ß-galactosidase gene, under the influence of a SV40 promoter. Continuous culture of these mini-pools for 8 weeks using a robotic system demonstrated that 20% of the mini-pools studied revealed an unstable profile (with 30% loss of protein expression). Two of these mini-pools with different characteristics, CHO-FRT 1 (low producer/unstable) and CHO-FRT 108 (high producer/stable), were selected to be used on the study of influence of SV40 and CMV promoters in long-term recombinant expression. Genes encoding fluorescent proteins were integrated in a site-directed manner under the influence of SV40 or CMV promoters. A sub-clonal population of the top 10% yellow fluorescent protein (YFP) expressing cells of each mini-pool/promoter combination was selected by cell sorting and cultured for 4 weeks. During this period protein expression was monitored by flow cytometry and compared between both promoters. The results revealed that both SV40 and CMV promoters had an unstable expression with different degrees of instability and long-term expressing behaviours. For CMV, instability was considerably high displaying a long-term logarithmic loss of 50-80% of productivity while for SV40 the loss of productivity observed was only 40-45% with a linear behaviour during long-term culture. The vector system generated contained an MS2-RNA tag sequence cloned 3'- of the recombinant gene to track the recombinant mRNA by using the MS2/MCP-GFP system. This study showed the development of a protocol to measure the transcriptional output of recombinant promoters in CHO cells. The results showed background signal in CHO cells that requires further optimisation studies to allow the direct live cell image quantification of the transcriptional activity of recombinant promoters. Although not yet optimised, the successful combination of site-directed integration with recombinant mRNA tagging method has the potential to become a valuable tool to study the mechanisms of transcriptional activity and stability of transcription driven by different promoters in CHO cells.