Exercise-induced whole-body dehydration does not affect airway responsiveness in athletes but may impair small airway function

Exercise-induced bronchoconstriction (EIB) is the transient narrowing of the airways that occurs during or shortly after strenuous exercise. Loss of water from the airway surface, due to the conditioning of large volumes of air during exercise, is the main physiological stimulus for EIB. We proposed that exercise-induced whole-body dehydration would interfere with hydration of the airways and, consequently, increase the risk and/or severity of EIB. We also investigated the effects of whole-body dehydration on resting lung function

Overview of the Main Propulsion System for a Nuclear Thermal Propulsion Flight Demonstrator

A demonstration of a Nuclear Thermal Propulsion (NTP) engine has not been conducted in over 50 years. Several tests were conducted during the NERVA program but no NTP engine was ever flown in space. In the last several years there has been a considerable amount of conceptual design work on NTP engines conducted. With the prospect of human Mars missions in the 2030s there has been a renewed interest in NTP engines. A concept design study was conducted with the intent to design 2 flight demonstrator vehicles that would buy down programmatic and technical risks associated with launching and operating nuclear reactors in space. The intent of the first demonstrator mission would be to employ a simplified NTP engine and buy down programmatic risks whereas the second demonstrator would buy down technical risks with a NTP engine designed to be similar to an operational NTP model. The results of the study showed that a simplified NTP engine demonstrator could be feasibly built and flown in the near term with mostly high TRL, commercial off-the-shelf components

Near-infrared and X-ray obscuration to the nucleus of the Seyfert 2 galaxy NGC 3281

We present the results of a near-infrared and X-ray study of the Seyfert 2 galaxy NGC 3281. Emission from the Seyfert nucleus is detected in both regions of the electromagnetic spectrum, allowing us to infer both the equivalent line of sight hydrogen column density, N_H = 71.0(+11.3,-12.3)e26/m^2 and the extinction due to dust, A_V = 22+/-11 magnitudes (90% confidence intervals). We infer a ratio of N_H/A_V which is an order of magnitude larger than that determined along lines of sight in the Milky Way and discuss possible interpretations. We consider the most plausible explanation to be a dense cloud in the foreground of both the X-ray and infrared emitting regions which obscures the entire X-ray source but only a fraction of the much larger infrared source.Comment: 23 pages including 9 figure

Cryogenic propellant venting under low pressure conditions Final report

Wall temperatures and heat transfer coefficients for solid-vapor mixtures of para hydrogen and nitrogen venting under low pressur

Students' preferences in undergraduate mathematics assessment

Existing research into students' preferences for assessment methods has been developed from a restricted sample: in particular, the voice of students in the ‘hard-pure sciences’ has rarely been heard. We conducted a mixed method study to explore mathematics students' preferences of assessment methods. In contrast to the message from the general assessment literature, we found that mathematics students differentially prefer traditional assessment methods such as closed book examination; they perceive them to be fairer than innovative methods and they perceive traditional methods to be the best discriminators of mathematical ability. We also found that although students prefer to be assessed by traditional methods they are also concerned by the mix of methods they encounter during their degree, suggesting that more account needs to be taken about the students' views of this mix. We discuss the impact of the results on the way general findings about assessment preference should be interpreted

The summative assessment diet: how we assess in mathematics degrees

Much research and many papers on mathematics pedagogy have discussed assessment and, in particular, the need to provide a varied diet of methods by which students are assessed for the award of their degree. In this article, we explore the mix of assessment methods provided across a range of UK university mathematics departments. We examine the relationship between the mix of assessment methods and type of institution and between the type of assessment and the mathematical topic. We found that closed book exam is still the most common assessment method in undergraduate mathematics, with some new assessment methods, such as projects and presentations, now used in most UK institutions

Students’ views of oral performance assessment in mathematics: straddling the ‘assessment of’ and ‘assessment for’ learning divide

This paper explores the views of a group of students who took an oral performance assessment in a first-year mathematics module. Such assessments are unusual for most subjects in the UK, but particularly within the generally homogenous assessment diet of undergraduate mathematics. The evidence presented here resonates with some, but not all, of the existing literature on oral assessment and suggests that, despite concerns about anxiety and fairness, students see oral assessments as encouraging a focus on understanding, being relatively authentic and reactive to their needs. We argue that, suitably implemented, oral assessment may be a viable assessment method for straddling the ‘assessment for’ and ‘assessment of’ learning divide in higher education

Two quantum Simpson's paradoxes

The so-called Simpson's "paradox", or Yule-Simpson (YS) effect, occurs in classical statistics when the correlations that are present among different sets of samples are reversed if the sets are combined together, thus ignoring one or more lurking variables. Here we illustrate the occurrence of two analogue effects in quantum measurements. The first, which we term quantum-classical YS effect, may occur with quantum limited measurements and with lurking variables coming from the mixing of states, whereas the second, here referred to as quantum-quantum YS effect, may take place when coherent superpositions of quantum states are allowed. By analyzing quantum measurements on low dimensional systems (qubits and qutrits), we show that the two effects may occur independently, and that the quantum-quantum YS effect is more likely to occur than the corresponding quantum-classical one. We also found that there exist classes of superposition states for which the quantum-classical YS effect cannot occur for any measurement and, at the same time, the quantum-quantum YS effect takes place in a consistent fraction of the possible measurement settings. The occurrence of the effect in the presence of partial coherence is discussed as well as its possible implications for quantum hypothesis testing.Comment: published versio

Microscopic two-nucleon overlaps and knockout reactions from 12^{12}C

The nuclear structure dependence of direct reactions that remove a pair of like or unlike nucleons from a fast $^{12}$C projectile beam are considered. Specifically, we study the differences in the two-nucleon correlations present and the predicted removal cross sections when using $p$-shell shell-model and multi-$\hbar\omega$ no-core shell-model (NCSM) descriptions of the two-nucleon overlaps for the transitions to the mass $A$=10 projectile residues. The NCSM calculations use modern chiral two-nucleon and three-nucleon (NN+3N) interactions. The $np$-removal cross sections to low-lying $T$=0, $^{10}$B final states are enhanced when using the NCSM two-nucleon amplitudes. The calculated absolute and relative partial cross sections to the low energy $^{10}$B final states show a significant sensitivity to the interactions used, suggesting that assessments of the overlap functions for these transitions and confirmations of their structure could be made using final-state-exclusive measurements of the $np$-removal cross sections and the associated momentum distributions of the forward travelling projectile-like residues.Comment: 9 pages, 7 figure

Estimating the masses of extra-solar planets

All extra-solar planet masses that have been derived spectroscopically are lower limits since the inclination of the orbit to our line-of-sight is unknown except for transiting systems. It is, however, possible to determine the inclination angle, i, between the rotation axis of a star and an observer's line-of-sight from measurements of the projected equatorial velocity (v sin i), the stellar rotation period (P_rot) and the stellar radius (R_star). This allows the removal of the sin i dependency of spectroscopically derived extra-solar planet masses under the assumption that the planetary orbits lie perpendicular to the stellar rotation axis. We have carried out an extensive literature search and present a catalogue of v sin i, P_rot, and R_star estimates for exoplanet host stars. In addition, we have used Hipparcos parallaxes and the Barnes-Evans relationship to further supplement the R_star estimates obtained from the literature. Using this catalogue, we have obtained sin i estimates using a Markov-chain Monte Carlo analysis. This allows proper 1-sigma two-tailed confidence limits to be placed on the derived sin i's along with the transit probability for each planet to be determined. While a small proportion of systems yield sin i's significantly greater than 1, most likely due to poor P_rot estimations, the large majority are acceptable. We are further encouraged by the cases where we have data on transiting systems, as the technique indicates inclinations of ~90 degrees and high transit probabilities. In total, we estimate the true masses of 133 extra-solar planets. Of these, only 6 have revised masses that place them above the 13 Jupiter mass deuterium burning limit. Our work reveals a population of high-mass planets with low eccentricities and we speculate that these may represent the signature of different planetary formation mechanisms at work.Comment: 40 pages, 6 tables, 2 figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Society after editing of Tables 1 & 6 for electronic publication. Html abstract shortened for astro-ph submissio