Mask breathing system for the Apollo command module

Breathing mask for Apollo command module spacecre

Improved calibration of the radii of cool stars based on 3D simulations of convection: implications for the solar model

Main sequence, solar-like stars (M < 1.5 Msun) have outer convective envelopes that are sufficiently thick to affect significantly their overall structure. The radii of these stars, in particular, are sensitive to the details of inefficient, super-adiabatic convection occurring in their outermost layers. The standard treatment of convection in stellar evolution models, based on the Mixing-Length Theory (MLT), provides only a very approximate description of convection in the super-adiabatic regime. Moreover, it contains a free parameter, alpha_MLT, whose standard calibration is based on the Sun, and is routinely applied to other stars ignoring the differences in their global parameters (e.g., effective temperature, gravity, chemical composition) and previous evolutionary history. In this paper, we present a calibration of alpha_MLT based on three-dimensional radiation-hydrodynamics (3D RHD) simulations of convection. The value of alpha_MLT is adjusted to match the specific entropy in the deep, adiabatic layers of the convective envelope to the corresponding value obtained from the 3D RHD simulations, as a function of the position of the star in the (log g, log T_eff) plane and its chemical composition. We have constructed a model of the present-day Sun using such entropy-based calibration. We find that its past luminosity evolution is not affected by the entropy calibration. The predicted solar radius, however, exceeds that of the standard model during the past several billion years, resulting in a lower surface temperature. This illustrative calculation also demonstrates the viability of the entropy approach for calibrating the radii of other late-type stars.Comment: 16 pages, 14 figures, accepted for publication in the Astrophysical Journa

Stimulating Canonical WNT Signaling in Pituitary Progenitors Inhibits Differentiation of Hormone Cell Types

The mouse pituitary gland secretes hormones that regulate many physiological processes including growth, stress response, and reproduction. The canonical WNT signaling pathway, activation of which results in nuclear accumulation of β-CATENIN and transcription of target genes including LEF1, is crucial for proper development of the pituitary gland. Pituitary progenitors that lack β-CATENIN at embryonic day of development 8.5 (E8.5) cannot form three of the six cell types of the anterior pituitary that produce growth hormone (GH), thyroid stimulating hormone (TSH), and prolactin (PRL). Additionally, stimulating canonical WNT signaling through creation of degradation-resistant β-CATENIN at E9.5 causes pituitary tumors and results in a reduction in the number of GH and TSH secreting cells. However, if canonical WNT signaling is stimulated in differentiating pituitary cells at E14.5, there is no loss of hormone cell types or tumor formation, demonstrating that the timing of the signaling is critical. Based on these results we chose to activate canonical WNT signaling at E11.5 in pituitary progenitors by creating a degradation-resistant β-CATENIN using a Cre/loxP strategy to excise a portion of β-CATENIN exon 3 necessary for normal degradation. We found that activation of canonical WNT signaling at E11.5 resulted in hyperplastic pituitaries, increased epithelial-like tissue, and complete loss of all hormone-producing cell lineages. Our results demonstrate that proper regulation and timing of canonical WNT signaling during pituitary development is critical for proper differentiation of pituitary progenitors into hormone cell types

Relationship Between the Built Environment, Physical Activity, and Chronic Disease Among Individuals with Disabilities in Rural Communities

Increased risk for chronic disease is closely associated with individual nutrition, tobacco use, and physical inactivity. This thesis focuses on physical activity as a means of preventing select chronic diseases. A major barrier preventing engagement in physical activity is the built environment. Populations residing in rural environment are not afforded the abundance of opportunities for physical activity prevalent in most urban networks. Of the demographic living in rural environments, individuals with disability face additional barriers to physical activity than those without disability. This leads to a higher prevalence of chronic diseases associated with sedentary lifestyles among populations with disability. Few studies address the correlation between physical activity, chronic disease, and the built environment as they relate to individuals with disability. This thesis utilized independent samples t tests to evaluate variation among physical activity levels and the prevalence of chronic disease. In the first paper, four research objectives defined the parameters for comparison: (1) physical activity for individuals with disability in rural versus urban environments; (2) physical activity in rural environments for individuals with and without disability; (3) prevalence of chronic disease for individuals with disability in rural versus urban areas; and (4) prevalence of chronic disease in rural environments for individuals with and without disability. The four research objectives of the second paper are: (1) rural and urban physical activity comparison for the highest disability classification; (2) rural and urban physical activity comparison for individuals with disability using equipment; (3) rural and urban physical activity comparison for individuals with disability resulting from physical, mental, or emotional impairments; and (4) rural and urban physical activity comparison for individuals not reporting disability. The 2011 Behavioral Risk Factor Surveillance System (BRFSS) provided the data used to evaluate the correlation between these variables. The results of both studies indicate important statistical significance relating the rural built environment to lower levels of physical activity for individuals with disability. The varied statistical significance and small effect sizes, however, were contrary to the hypothesis and warrants further exploration of the complex relationship regarding the built environment, physical activity, and chronic disease

Classical dynamics near the triple collision in a three-body Coulomb problem

We investigate the classical motion of three charged particles with both attractive and repulsive interaction.The triple collision is a main source of chaos in such three body Coulomb problems.By employing the McGehee scaling technique, we analyse here for the first time in detail the three-body dynamics near the triple collision in 3 degrees of freedom.We reveal surprisingly simple dynamical patterns in large parts of the chaotic phase space. The underlying degree of order in the form of approximate Markov partitions may help in understanding the global structures observed in quantum spectra of two-electron atoms.Comment: 4 pages, 3 figure

Effect of plyometric training on swimming block start performance in adolescents

This study aimed to identify the effect of plyometric training (PT), when added to habitual training (HT) regimes, on swim start performance. After the completion of a baseline competitive swim start, 22 adolescent swimmers were randomly assigned to either a PT (n = 11, age: 13.1 ± 1.4 yr, mass: 50.6 ± 12.3 kg, stature: 162.9 ± 11.9 cm) or an HT group (n = 11, age: 12.6 ± 1.9 yr, mass: 43.3 ± 11.6 kg, stature: 157.6 ± 11.9 cm). Over an 8-week preseason period, the HT group continued with their normal training program, whereas the PT group added 2 additional 1-hour plyometric-specific sessions, incorporating prescribed exercises relating to the swimming block start (SBS). After completion of the training intervention, post-training swim start performance was reassessed. For both baseline and post-trials, swim performance was recorded using videography (50Hz Canon MVX460) in the sagital plane of motion. Through the use of Silicon Coach Pro analysis package, data revealed significantly greater change between baseline and post-trials for PT when compared with the HT group for swim performance time to 5.5 m (−0.59 s vs. −0.21 s; p < 0.01) and velocity of take-off to contact (0.19 ms−1 vs. −0.07 ms−1; p < 0.01). Considering the practical importance of a successful swim start to overall performance outcome, the current study has found that inclusion of suitable and safely implemented PT to adolescent performers, in addition to HT routines, can have a positive impact on swim start performance

Relationship between the entomologic inoculation rate and the force of infection for Plasmodium falciparum malaria.

We propose a stochastic model for the relationship between the entomologic inoculation rate (EIR) for Plasmodium falciparum malaria and the force of infection in endemic areas. The model incorporates effects of increased exposure to mosquito bites as a result of the growth in body surface area with the age of the host, naturally acquired pre-erythrocytic immunity, and the reduction in the proportion of entomologically assessed inoculations leading to infection, as the EIR increases. It is fitted to multiple datasets from field studies of the relationship between malaria infection and the EIR. We propose that this model can account for non-monotonic relationships between the age of the host and the parasite prevalence and incidence of disease. It provides a parsimonious explanation for the faster acquisition of natural immunity in adults than in children exposed to high EIRs. This forms one component of a new stochastic model for the entire transmission cycle of P. falciparum that we have derived to estimate the potential epidemiologic impact of malaria vaccines and other malaria control interventions