Development and testing of hermetic, laser-ignited pyrotechnic and explosive components

During the last decade there has been increasing interest in the use of lasers in place of electrical systems to ignite various pyrotechnic and explosive materials. The principal driving force for this work was the requirement for safer energetic components which would be insensitive to electrostatic and electromagnetic radiation. In the last few years this research has accelerated since the basic concepts have proven viable. At the present time it is appropriate to shift the research emphasis in laser initiation from the scientific arena--whether it can be done--to the engineering realm--how it can be put into actual practice in the field. Laser initiation research and development at EG&G Mound was in three principal areas: (1) laser/energetic material interactions; (2) development of novel processing techniques for fabricating hermetic (helium leak rate of less than 1 x 10(exp -8) cu cm/s) laser components; and (3) evaluation and testing of laser-ignited components. Research in these three areas has resulted in the development of high quality, hermetic, laser initiated components. Examples are presented which demonstrate the practicality of fabricating hermetic, laser initiated explosive or pyrotechnic components that can be used in the next generation of ignitors, actuators, and detonators

Understanding How Students from Rural Culture Make Meaning of Campus Recreation Engagement

Research indicates that students are more likely to persist when they are involved in extracurricular programs such as campus recreation. Because institutional funding is predicated upon graduation rates, ascertaining persistence impact of these programs is crucial. The purpose of this qualitative study was to gain an understanding of the persistence needs of students from rural backgrounds relative to their engagement in campus recreation within the framework of Astin’s Input-Environment-Outcomes model. Data were collected from nine students at a residential, agricultural State College in the southeastern United States. Results indicated 1) participants (7/9) became involved immediately in campus recreation; 2) all participants were aware of wellness benefits derived; 3) participants (8/9) perceived that campus recreation involvement positively influenced persistence by complementing their academic responsibilities; and 4) participants (8/9) believed their rural background provided extra motivation to persist. Results can be used to assist administrators making intentional extracurricular investment decisions.Chapter I: INTRODUCTION 1 -- National Focus on Student Persistence in Higher Education 2 -- Campus Recreation and Holistic Wellness 4 -- Impact on College Persistence 5 -- Students from Rural Cultures 5 -- Statement of the Problem 6 -- Purpose of the Study 7 -- Research Questions 7 -- Significance of the Study 9 -- Organization of the Study 11 -- Chapter II: LITERATURE REVIEW 12 -- Conceptual Framework 13 -- Student Development 16 -- Persistence 19 -- Persistence and Rural High School Students 20 -- Momentum Year 21 -- Mindset 22 -- Grit 23 -- Students from Rural Background 24 -- Framing Rural Culture 25 -- Socioeconomic Challenges of Rurality 27 -- Rural Culture in Higher Education 30 -- Rurality and First-Generation College Students 32 -- Extracurricular Programming and Persistence 35 -- Physical Activity 37 -- Structured 38 -- Unstructured 40 -- Campus Recreation 41 -- Campus Recreation and Persistence 43 -- Campus Recreation and Wellness 44 -- National Intramural and Recreational Sports Association 48 -- Summary 48 -- Chapter III: METHODOLOGY 51 -- Research Design 51 -- Research Questions 52 -- Setting 52 -- Data Collection 53 -- Approval to Conduct the Study 53 -- Consent to Participate in Study 53 -- Sampling Procedure 54 -- Participant Selection 55 -- Student Interviews 55 -- Data Processing and Analysis 56 -- Validity 58 -- Researcher-Interviewer 58 -- Beliefs and Biases 60 -- Reactivity 62 -- Trustworthiness 63 -- Summary 64 -- Chapter IV: RESULTS (FINDING) 66 -- Brief Profiles of the Participants 69 -- How Campus Recreation is Experienced 77 -- Immediate Involvement 78 -- Wellness Appreciation 80 -- Perceptions of Campus Recreation Impact on Persistence 83 -- Miscellaneous Gem 86 -- Rural Background Input and Extra Motivation to Persist 86 -- Summary 88 -- Chapter V: JOURNAL READY ARTICLE 89 -- Abstract 89 -- Literature Review 90 -- Physical Activity and Wellness 92 -- Persistence 95 -- Momentum Year 95 -- Mindset 96 -- Grit 98 -- Research Design and Methods 99 -- Research Questions 100 -- Participants 101 -- Data Collection 101 -- Data Processing and Analysis 103 -- Validity and Trustworthiness 104 -- Findings 105 -- Immediate Involvement 105 -- Wellness Appreciation 106 -- Academic Complement 107 -- Discussion and Conclusions 108 -- Practical Implications 112 -- Limitations 113 -- Future Research 115 -- REFERENCES 116 -- APPENDIX A: Institutional Review Board Protocol Exemption Report 149 -- APPENDIX B: Letter of Cooperation 151 -- APPENDIX C: Consent Statement 153 -- APPENDIX D: Invitation to Participate 156 -- APPENDIX E: Interview Guide 158 -- APPENDIX F: Researcher Identity Memo 162 -- APPENDIX G: Questions and Methods Matrix 169.Hull, Karla M.Archibald, JamesWorkman, JamieCruz, Becky K. daEd.D.Education in Leadershi

Rapid Targeted Gene Disruption in Bacillus Anthracis

Anthrax is a zoonotic disease recognized to affect herbivores since Biblical times and has the widest range of susceptible host species of any known pathogen. The ease with which the bacterium can be weaponized and its recent deliberate use as an agent of terror, have highlighted the importance of gaining a deeper understanding and effective countermeasures for this important pathogen. High quality sequence data has opened the possibility of systematic dissection of how genes distributed on both the bacterial chromosome and associated plasmids have made it such a successful pathogen. However, low transformation efficiency and relatively few genetic tools for chromosomal manipulation have hampered full interrogation of its genome. Results: Group II introns have been developed into an efficient tool for site-specific gene inactivation in several organisms. We have adapted group II intron targeting technology for application in Bacillus anthracis and generated vectors that permit gene inactivation through group II intron insertion. The vectors developed permit screening for the desired insertion through PCR or direct selection of intron insertions using a selection scheme that activates a kanamycin resistance marker upon successful intron insertion. Conclusions: The design and vector construction described here provides a useful tool for high throughput experimental interrogation of the Bacillus anthracis genome and will benefit efforts to develop improved vaccines and therapeutics.Chem-Bio Diagnostics program from the Department of Defense Chemical and Biological Defense program through the Defense Threat Reduction Agency (DTRA) B102387MNIH GM037949Welch Foundation F-1607Cellular and Molecular Biolog

Unstable decay and state selection II

The decay of unstable states when several metastable states are available for occupation is investigated using path-integral techniques. Specifically, a method is described which allows the probabilities with which the metastable states are occupied to be calculated by finding optimal paths, and fluctuations about them, in the weak noise limit. The method is illustrated on a system described by two coupled Langevin equations, which are found in the study of instabilities in fluid dynamics and superconductivity. The problem involves a subtle interplay between non-linearities and noise, and a naive approximation scheme which does not take this into account is shown to be unsatisfactory. The use of optimal paths is briefly reviewed and then applied to finding the conditional probability of ending up in one of the metastable states, having begun in the unstable state. There are several aspects of the calculation which distinguish it from most others involving optimal paths: (i) the paths do not begin and end on an attractor, and moreover, the final point is to a large extent arbitrary, (ii) the interplay between the fluctuations and the leading order contribution are at the heart of the method, and (iii) the final result involves quantities which are not exponentially small in the noise strength. This final result, which gives the probability of a particular state being selected in terms of the parameters of the dynamics, is remarkably simple and agrees well with the results of numerical simulations. The method should be applicable to similar problems in a number of other areas such as state selection in lasers, activationless chemical reactions and population dynamics in fluctuating environments.Comment: 28 pages, 6 figures. Accepted for publication in Phys. Rev.

Superheating fields of superconductors: Asymptotic analysis and numerical results

The superheated Meissner state in type-I superconductors is studied both analytically and numerically within the framework of Ginzburg-Landau theory. Using the method of matched asymptotic expansions we have developed a systematic expansion for the solutions of the Ginzburg-Landau equations in the limit of small $\kappa$, and have determined the maximum superheating field $H_{\rm sh}$ for the existence of the metastable, superheated Meissner state as an expansion in powers of $\kappa^{1/2}$. Our numerical solutions of these equations agree quite well with the asymptotic solutions for $\kappa<0.5$. The same asymptotic methods are also used to study the stability of the solutions, as well as a modified version of the Ginzburg-Landau equations which incorporates nonlocal electrodynamics. Finally, we compare our numerical results for the superheating field for large-$\kappa$ against recent asymptotic results for large-$\kappa$, and again find a close agreement. Our results demonstrate the efficacy of the method of matched asymptotic expansions for dealing with problems in inhomogeneous superconductivity involving boundary layers.Comment: 14 pages, 8 uuencoded figures, Revtex 3.

A shadow detector for photosynthesis efficiency

Plants tolerate large variations in the intensity of the light environment by controlling the efficiency of solar to chemical energy conversion. To do this, plants have a mechanism to detect the intensity, duration, and change in light as they experience moving shadows, flickering light, and cloud cover. Sugars are the primary products of CO2 fixation, a metabolic pathway that is rate limited by this solar energy conversion. We propose that sugar is a signal encoding information about the intensity, duration and change in the light environment. We previously showed that the Arabidopsis heterotrimeric G protein complex including its receptor-like Regulator of G signaling protein, AtRGS1, detects both the concentration and the exposure time of sugars [Fu, et al 2014 Cell 156: 1084–1095]. This unique property, designated dose-duration reciprocity, is a behavior that emerges from the system architecture / system motif. Here, we show that another property of the signaling system is to detect large changes in light while at the same time, filtering types of fluctuation in light that do not affect photosynthesis efficiency. When AtRGS1 is genetically ablated, photosynthesis efficiency is reduced in a changing-but not a constant-light environment. Mathematical modeling revealed that information about changes in the light environment is encoded in the amount of free AtRGS1 that becomes compartmentalized following stimulation. We propose that this property determines when to adjust photosynthetic efficiency in an environment where light intensity changes abruptly caused by moving shadows on top of a background of light changing gradually from sun rise to sun set and fluctuating light such as that caused by fluttering leaves

Crystalline surface structures induced by ion sputtering of Al-rich icosahedral quasicrystals

Low-energy electron diffraction patterns, produced from quasicrystal surfaces by ion sputtering and annealing to temperatures below ∼700 K, can be assigned to various terminations of the cubic CsCl structure. The assignments are based upon ratios of spot spacings, estimates of surface lattice constants, bulk phase diagrams vs surface compositions, and comparisons with previous work. The CsCl overlayers are deeper than about five atomic layers, because they obscure the diffraction spots from the underlying quasicrystalline substrate. These patterns transform irreversibly to quasicrystalline(like) patterns upon annealing to higher temperatures, indicating that the cubic overlayers are metastable. Based upon the data for three chemically identical, but symmetrically inequivalent surfaces, a model is developed for the relation between the cubic overlayers and the quasicrystalline substrate. The model is based upon the related symmetries of cubic close-packed and icosahedral-packed materials. The model explains not only the symmetries of the cubic surface terminations, but also the number and orientation of domains

The Ursinus Weekly, November 13, 1975

Volleyball team is Division A champ • Myrin hrs. changed? • Pre-legal Soc. is revived • SFARC update • U.S.A. as seen by Kahata • Temple University lists Irish Studies • Pollution expert talks • Editorial: Pride and perseverance • Editor\u27s comment: My reply to your opinions • Saturday Lunch • Forum review: Ambassador discusses U.N. • Bearpit opens • A new light on Lantern • Newmans organize • A conversation in the board room • Devils demonize Bears! • Diving into action • Intramurals • Mr. Karas • NBA West • A season of kickshttps://digitalcommons.ursinus.edu/weekly/1046/thumbnail.jp

Host tropism determination by convergent evolution of immunological evasion in the Lyme disease system [preprint]

Microparasites selectively adapt in some hosts, known as host tropism. Transmitted through ticks and carried mainly by mammals and birds, the Lyme disease (LD) bacterium is a well-suited model to study such tropism. LD bacteria species vary in host ranges through mechanisms eluding characterization. By feeding ticks infected with different LD bacteria species, utilizing feeding chambers and live mice and quail, we found species-level differences of bacterial transmission. These differences localize on the tick blood meal, and complement, a defense in vertebrate blood, and a bacterial polymorphic protein, CspA, which inactivates complement by binding to a host complement inhibitor, FH. CspA selectively confers bacterial transmission to vertebrates that produce FH capable of allele-specific recognition. Phylogenetic analyses revealed convergent evolution as the driver of such findings, which likely emerged during the last glacial maximum. Our results identify LD bacterial determinants of host tropism, defining an evolutionary mechanism that shapes host-microparasite associations

Host tropism determination by convergent evolution of immunological evasion in the Lyme disease system

Pathogens possess the ability to adapt and survive in some host species but not in others-an ecological trait known as host tropism. Transmitted through ticks and carried mainly by mammals and birds, the Lyme disease (LD) bacterium is a well-suited model to study such tropism. Three main causative agents of LD, Borrelia burgdorferi, B. afzelii, and B. garinii, vary in host ranges through mechanisms eluding characterization. By feeding ticks infected with different Borrelia species, utilizing feeding chambers and live mice and quail, we found species-level differences in bacterial transmission. These differences localize on the tick blood meal, and specifically complement, a defense in vertebrate blood, and a polymorphic bacterial protein, CspA, which inactivates complement by binding to a host complement inhibitor, Factor H (FH). CspA selectively confers bacterial transmission to vertebrates that produce FH capable of allele-specific recognition. CspA is the only member of the Pfam54 gene family to exhibit host-specific FH-binding. Phylogenetic analyses revealed convergent evolution as the driver of such uniqueness, and that FH-binding likely emerged during the last glacial maximum. Our results identify a determinant of host tropism in Lyme disease infection, thus defining an evolutionary mechanism that shapes host-pathogen associations