The NASA-Lewis program on fusion energy for space power and propulsion, 1958-1978

An historical synopsis is provided of the NASA-Lewis research program on fusion energy for space power and propulsion systems. It was initiated to explore the potential applications of fusion energy to space power and propulsion systems. Some fusion related accomplishments and program areas covered include: basic research on the Electric Field Bumpy Torus (EFBT) magnetoelectric fusion containment concept, including identification of its radial transport mechanism and confinement time scaling; operation of the Pilot Rig mirror machine, the first superconducting magnet facility to be used in plasma physics or fusion research; operation of the Superconducting Bumpy Torus magnet facility, first used to generate a toroidal magnetic field; steady state production of neutrons from DD reactions; studies of the direct conversion of plasma enthalpy to thrust by a direct fusion rocket via propellant addition and magnetic nozzles; power and propulsion system studies, including D(3)He power balance, neutron shielding, and refrigeration requirements; and development of large volume, high field superconducting and cryogenic magnet technology

Compensation for nonlinear effects due to high heat flux in thin-film thermometry

Compensation for nonlinear effects due to high heat flux in thin-film thermometr

A Multi-Dimensional Trust Model for Heterogeneous Contract Observations

In this paper we develop a novel probabilistic model of computational trust that allows agents to exchange and combine reputation reports over heterogeneous, correlated multi-dimensional contracts. We consider the specific case of an agent attempting to procure a bundle of services that are subject to correlated quality of service failures (e.g. due to use of shared resources or infrastructure), and where the direct experience of other agents within the system consists of contracts over different combinations of these services. To this end, we present a formalism based on the Kalman filter that represents trust as a vector estimate of the probability that each service will be successfully delivered, and a covariance matrix that describes the uncertainty and correlations between these probabilities. We describe how the agents’ direct experiences of contract outcomes can be represented and combined within this formalism, and we empirically demonstrate that our formalism provides significantly better trustworthiness estimates than the alternative of using separate single-dimensional trust models for each separate service (where information regarding the correlations between each estimate is lost)

A Method for Determining Optimum Re-entry Trajectories

Determining optimum atmospheric reentry trajectories using Pontryagin maximum principl

Understanding the Student Perspective of Teacher-Student Engagement in First-Year Studies Courses

Higher education institutions continue to seek high impact retention methods to address student attrition, particularly during the first year of college. First-year studies courses represent a major institutional intervention and retention resource designed to help higher education institutions meet the unique academic and social needs of students transitioning from high school to college. Teacher-student engagement is considered to be an essential part of student retention efforts. However, most of the research on teacher-student engagement has focused on pedagogical strategies and the teachers’ perspectives of engagement. What is lacking in the literature are studies of students’ perspectives of classroom engagement. This study sought to discover what students find most meaningful during teacher-student engagement in the first-year studies course. I employed one-on-one semi-structured interviews as the primary source of data. Interviews were held with eight students enrolled in first year studies courses taught by five instructors ranked in the top 10% of all first year studies courses offered by a Research One university. (Rankings were determined by overall course scores on a university-wide faculty evaluation instrument.) Results revealed three themes in what students reported as meaningful in their first year studies experiences: (1) teacher-student rapport, (2) course facilitation, and (3) student-to-student interaction inside and outside of the classroom. Implications include the need for multi-site studies and replications of this single-site study on other campuses. Recommendations for practice focused on institutional policy making, teaching strategies, and decision making by higher education administrators concerned to improve student retention at their respective higher education institutions

Plasticity in transmission strategies of the malaria parasite, Plasmodium chabaudi : environmental and genetic effects

Parasites may alter their behaviour to cope with changes in the within-host environment. In particular, investment in transmission may alter in response to the availability of parasite resources or host immune responses. However, experimental and theoretical studies have drawn conflicting conclusions regarding parasites' optimal (adaptive) responses to deterioration in habitat quality. We analyse data from acute infections with six genotypes of the rodent malaria species to quantify how investment in transmission (gametocytes) is influenced by the within-host environment. Using a minimum of modelling assumptions, we find that proportional investment in gametocytogenesis increases sharply with host anaemia and also increases at low parasite densities. Further, stronger dependence of investment on parasite density is associated with greater virulence of the parasite genotype. Our study provides a robust quantitative framework for studying parasites' responses to the host environment and whether these responses are adaptive, which is crucial for predicting the short-term and evolutionary impact of transmission-blocking treatments for parasitic diseases

Top and Bottom: a Brane of Their Own

We consider extra dimensional descriptions of models where there are two separate strongly interacting sectors contributing to electroweak symmetry breaking (``topcolor'' type models). In the extra dimensional picture there would be two separate (anti-de Sitter) bulks meeting on the Planck brane, with each bulk having its own corresponding IR (TeV) brane. Sources for electroweak symmetry breaking can then be localized on both of these IR branes, while the different generations of fermions may be separated from each other. We describe the modes propagating in such a setup, and consider the cases where the electroweak symmetry breaking on either of the two IR branes come either from a higgsless scenario (via boundary conditions) or a (top-)Higgs. We show that the tension that exists between obtaining a large top quark mass and the correct value of the Zb\bar{b} couplings in ordinary higgsless models can be largely relieved in the higgsless--top-Higgs versions of the two IR brane models. This may also be true in the purely higgsless--higgsless case, however since that model is necessarily in the strongly coupled regime the tree-level results for the properties of the third generation may get large corrections. A necessary consequence of such models is the appearance of additional pseudo-Goldstone bosons (``top-pions''), which would be strongly coupled to the third generation.Comment: 34 pages, LaTeX, 6 figures. v2: figure 2 fixed, footnote, comments and references adde

Development of reverse-transcription PCR techniques to analyse the density and sex ratio of gametocytes in genetically diverse Plasmodium chabaudi infections

We have developed cross-genotype and genotype-specific quantitative reverse-transcription PCR (qRT-PCR) assays to detect and quantify the number of parasites, transmission stages (gametocytes) and male gametocytes in blood stage Plasmodium chabaudi infections. Our cross-genotype assays are reliable, repeatable and generate counts that correlate strongly (R(2)s > 90%) with counts expected from blood smears. Our genotype-specific assays can distinguish and quantify different stages of genetically distinct parasite clones (genotypes) in mixed infections and are as sensitive as our cross-genotype assays. Using these assays we show that gametocyte density and gametocyte sex ratios vary during infections for two genetically distinct parasite lines (genotypes) and present the first data to reveal how sex ratio is affected when each genotype experiences competition in mixed-genotype infections. Successful infection of mosquito vectors depends on both gametocyte density and their sex ratio and we discuss the implications of competition in genetically diverse infections for transmission success

Consolidated bibliography of military and civilian studies in personnel retention and job turnover

Working Paper Serieshttp://archive.org/details/consolidatedbibl35reecNAN

In-Situ Measurements of Pore Pressures

As engineering moves into deeper waters, measurements of soil properties in the laboratory may be highly suspect if the soils are gassy. Strength and pore-pressure data are presented and discussed. A suggestion is made for development of pore-pressure gauges to detect the presence of clathrates