Coaxial tube array space transmission line characterization

The coaxial tube array tether/transmission line used to connect an SP-100 nuclear power system to the space station was characterized over the range of reactor-to-platform separation distances of 1 to 10 km. Characterization was done with respect to array performance, physical dimensions and masses. Using a fixed design procedure, a family of designs was generated for the same power level (300 kWe), power loss (1.5 percent), and meteoroid survival probability (99.5 percent over 10 yr). To differentiate between vacuum insulated and gas insulated lines, two different maximum values of the E field were considered: 20 kV/cm (appropriate to vacuum insulation) and 50 kV/cm (compressed SF6). Core conductor, tube, bumper, standoff, spacer and bumper support dimensions, and masses were also calculated. The results of the characterization show mainly how transmission line size and mass scale with reactor-to-platform separation distance

Nearest neighbor - A new non-parametric test used for classifying spectral data

Nonparametric statistical interference program for spectral data classificatio

Primordial helium recombination III: Thomson scattering, isotope shifts, and cumulative results

Upcoming precision measurements of the temperature anisotropy of the cosmic microwave background (CMB) at high multipoles will need to be complemented by a more complete understanding of recombination, which determines the damping of anisotropies on these scales. This is the third in a series of papers describing an accurate theory of HeI and HeII recombination. Here we describe the effect of Thomson scattering, the $^3$He isotope shift, the contribution of rare decays, collisional processes, and peculiar motion. These effects are found to be negligible: Thomson and $^3$He scattering modify the free electron fraction $x_e$ at the level of several $\times 10^{-4}$. The uncertainty in the $2^3P^o-1^1S$ rate is significant, and for conservative estimates gives uncertainties in $x_e$ of order $10^{-3}$. We describe several convergence tests for the atomic level code and its inputs, derive an overall $C_\ell$ error budget, and relate shifts in $x_e(z)$ to the changes in $C_\ell$, which are at the level of 0.5% at $\ell =3000$. Finally, we summarize the main corrections developed thus far. The remaining uncertainty from known effects is $\sim 0.3$ in $x_e$.Comment: 19 pages, 15 figures, to be submitted to PR

Identifying Catalysts for Sustained Innovation of Inclusion Teachers

The researcher examined nine areas of support that can be of assistance to sustaining innovative methodology in four school systems in Upper East Tennessee. Five types of innovation were examined. This study looked at nine supports as well as years of involvement by the practicing educator. The research design was a comparative study with forty hypotheses used to test differences in perceived degree of assistance to commitment. Teachers were surveyed and asked to rate supports for sustained innovation. Teachers also rated actual and ideal involvement. The research questions were tested and statistically analyzed using t-test and analysis of variance. Significant differences were found between demographic groups. Teachers sustaining child-centered instruction rated seven of the nine areas of support significantly higher than peer teachers. The methodology of student assessment had five areas of support rated significantly higher, alternative scheduling had two areas of support rated significantly higher, and the thematic approach had one area. Training/conference/workshops was the only area of support that had a significant difference common to all four of these methodologies. Recommendations for further research were made to augment the study

Bordism Groups of Immersions and Classes Represented by Self-Intersections

We prove a geometrical version of Herbert's theorem by considering the self-intersection immersions of a self-transverse immersion up to bordism. This generalises Herbert's theorem to additional cohomology theories and gives a commutative diagram in the homotopy of Thom complexes. The proof uses Koschorke and Sanderson's operations and the fact that bordism of immersions gives a functor on the category of smooth manifolds and immersions.Comment: 16 page

Giving Back: A mixed methods study of the contributions of US-Based Nigerian physicians to home country health systems

Background: There is increased interest in the capacity of US immigrants to contribute to their homelands via entrepreneurship and philanthropy. However, there has been little research examining how immigrant physicians may support health systems and what factors facilitate or raise barriers to increased support. Methods: This study used an observational design with paper questionnaire and interview components. Our sample was drawn from attendees of a 2011 conference for US Based Nigerian physicians respondents who were not US residents, physicians, and of Nigerian birth or parentage were excluded from further analysis. Respondents were randomly selected to complete a follow-up interview with separate scripts for those having made past financial contributions or medical service trips to support Nigerian healthcare (Group A) and those who had done neither (Group B). Survey results were analyzed using Fischer exact tests and interviews were coded in pairs using thematic content analysis. Results: Seventy-five of 156 (48%) individuals who attended the conference met inclusion criteria and completed the survey, and 13 follow-up interviews were completed. In surveys, 65% percent of respondents indicated a donation to an agency providing healthcare in Nigeria the previous year, 57% indicated having gone on medical service trips in the prior 10years and 45% indicated it was "very likely" or "likely" that they would return to Nigeria to practice medicine. In interviews, respondents tended to favor gifts in kind and financial gifts as modes of contribution, with medical education facilities as the most popular target. Personal connections, often forged in medical school, tended to facilitate contributions. Individuals desiring to return permanently focused on their potential impact and worried about health system under-preparedness those not desiring permanent return centered on how safety, financial security and health systems issues presented barriers. Conclusions: This study demonstrates several mechanisms by which health systems may benefit from expatriate engagement. Greater identification of reliable local partners for diaspora, deeper collaboration with those partners and a focus on sustainable interventions might improve the quantity and impact of contributions. Ethnic medical associations have a unique role in organizing and facilitating diaspora response. Public-private partnerships may help diaspora negotiate the challenges of repatriation

Time-Dependent Corrections to the Ly-alpha Escape Probability During Cosmological Hydrogen Recombination

We consider the effects connected with the detailed radiative transfer during the epoch of cosmological recombination on the ionization history of our Universe. We focus on the escape of photons from the hydrogen Lyman-alpha resonance at redshifts 600<~ z <~ 2000, one of two key mechanisms defining the rate of cosmological recombination. We approach this problem within the standard formulation, and corrections due to two-photon interactions are deferred to another paper. As a main result we show here that within a non-stationary approach to the escape problem, the resulting correction in the free electron fraction, N_e, is about ~1.6-1.8% in the redshift range 800<~z<~1200. Therefore the discussed process results in one of the largest modifications to the ionization history close to the maximum of Thomson-visibility function at z~1100 considered so far. We prove our results both numerically and analytically, deriving the escape probability, and considering both Lyman-alpha line emission and line absorption in a way different from the Sobolev approximation. In particular, we give a detailed derivation of the Sobolev escape probability during hydrogen recombination, and explain the underlying assumptions. We then discuss the escape of photons for the case of coherent scattering in the lab frame, solving this problem analytically in the quasi-stationary approximation and also in the time-dependent case. We show here that during hydrogen recombination the Sobolev approximation for the escape probability is not valid at the level of DP/P~5-10%. This is because during recombination the ionization degree changes significantly over a characteristic time Dz/z~10%, so that at percent level accuracy the photon distribution is not evolving (abridged)Comment: 18 pages, 12 figures, accepted versio

Variable-delay Polarization Modulators for Cryogenic Millimeter-wave Applications

We describe the design, construction, and initial validation of the variable-delay polarization modulator (VPM) designed for the PIPER cosmic microwave background polarimeter. The VPM modulates between linear and circular polarization by introducing a variable phase delay between orthogonal linear polarizations. Each VPM has a diameter of 39 cm and is engineered to operate in a cryogenic environment (1.5 K). We describe the mechanical design and performance of the kinematic double-blade flexure and drive mechanism along with the construction of the high precision wire grid polarizers.Comment: 8 pages, 10 Figures, Submitted to Review of Scientific Instrument