Release of noble gases and nitrogen from grain-surface sites in lunar ilmenite by closed-system oxidation

Noble gases and nitrogen were extracted from a 100 to 150 microns ilmenite separate from lunar soil 71501 by closed system stepped heating in approx. 10 torr O2 at 300 C, 400 C, 500 C, 600 C and 630 C, followed by stepped pyrolysis at ten temperatures between 680 C and approx. 1500 C. The five oxidation steps together liberated approx. 65% of the total He-4, 45% of the Ne-20, 23% of the N-14 and Ar-36, 12% of the Kr-84 and 8% of the Xe-132 in the sample; Ne-20/Ar-36 and Ne-20/Ne-22 ratios agree with the solar wind composition experiment, and Kr-84/Ar-36 and Xe-132/Ar-36 are within approx. 10% of Cameron's estimates for the sun and solar wind. The remaining gases, released above 630 C by pyrolysis, are strongly fractionated with respect to the SWC-Cameron solar wind elemental composition. Large concentrations of fractionated noble gases in grain interiors, their virtual absence in the relatively unfractionated surface gas reservoir, and the high N/noble gas ratio all imply that most of the solar wind noble gases initially implanted in grain surfaces are eventually lost by diffusion. Loss limits can be estimated by considering two given scenarios. It is concluded tat approx. 70 to 97% or more of the Ar implanted in 71501 ilmenite grains has diffusively escaped

E-textbooks and connectivity: proposing an analytical framework

This paper is concerned with the development of e-textbooks. We claim that analysis (and design) of e-textbooks requires the development of a specific frame. Digital affordances provide particular opportunities (e.g. in terms of interactions between users) that require specific considerations for their analysis, as teachers and students use them for their individual and collective purposes. In this study, we develop a framework for mathematics e-textbook analysis, based on the notion of “connectivity.” We introduce criteria to assess the different aspects of connectivity and build an analysis grid for e-textbooks. We illustrate the framework proposed by analyzing 2 commonly used French grade 10 mathematics e-textbooks. The results of the analyses show that there are major differences between the 2 e-textbooks in terms of connectivity, which can be related to differences in their design. Beyond these 2 examples, we claim that focusing on connectivity is a useful and relevant way of analyzing e-textbooks, as it can provide a window into issues of interactivity, both practically and cognitively

The persistence of multiple strains of avian influenza in live bird markets.

Multiple subtypes of avian influenza (AI) and novel reassortants are frequently isolated from live bird markets (LBMs). However, our understanding of the drivers of persistence of multiple AI subtypes is limited. We propose a stochastic model of AI transmission within an LBM that incorporates market size, turnover rate and the balance of direct versus environmental transmissibility. We investigate the relationship between these factors and the critical community size (CCS) for the persistence of single and multiple AI strains within an LBM. We fit different models of seeding from farms to two-strain surveillance data collected from Shantou, China. For a single strain and plausible estimates for continuous turnover rates and transmissibility, the CCS was approximately 11 800 birds, only a 4.2% increase in this estimate was needed to ensure persistence of the co-infecting strains (two strains in a single host). Precise values of CCS estimates were sensitive to changes in market turnover rate and duration of the latent period. Assuming a gradual daily sell rate of birds the estimated CCS was higher than when an instantaneous selling rate was assumed. We were able to reproduce prevalence dynamics similar to observations from a single market in China with infection seeded every 5-15 days, and a maximum non-seeding duration of 80 days. Our findings suggest that persistence of co-infections is more likely to be owing to sequential infection of single strains rather than ongoing transmission of both strains concurrently. In any given system for a fixed set of ecological and epidemiological conditions, there is an LBM size below which the risk of sustained co-circulation is low and which may suggest a clear policy opportunity to reduce the frequency of influenza co-infection in poultry

In situ measurement of atmospheric krypton and xenon on Mars with Mars Science Laboratory

Mars Science Laboratory's Sample Analysis at Mars (SAM) investigation has measured all of the stable isotopes of the heavy noble gases krypton and xenon in the martian atmosphere, in situ, from the Curiosity Rover at Gale Crater, Mars. Previous knowledge of martian atmospheric krypton and xenon isotope ratios has been based upon a combination of the Viking mission's krypton and xenon detections and measurements of noble gas isotope ratios in martian meteorites. However, the meteorite measurements reveal an impure mixture of atmospheric, mantle, and spallation contributions. The xenon and krypton isotopic measurements reported here include the complete set of stable isotopes, unmeasured by Viking. The new results generally agree with Mars meteorite measurements but also provide a unique opportunity to identify various non-atmospheric heavy noble gas components in the meteorites. Kr isotopic measurements define a solar-like atmospheric composition, but deviating from the solar wind pattern at 80Kr and 82Kr in a manner consistent with contributions originating from neutron capture in Br. The Xe measurements suggest an intriguing possibility that isotopes lighter than 132Xe have been enriched to varying degrees by spallation and neutron capture products degassed to the atmosphere from the regolith, and a model is constructed to explore this possibility. Such a spallation component, however, is not apparent in atmospheric Xe trapped in the glassy phases of martian meteorites

Development and Characterisation of a Gas System and its Associated Slow-Control System for an ATLAS Small-Strip Thin Gap Chamber Testing Facility

A quality assurance and performance qualification laboratory was built at McGill University for the Canadian-made small-strip Thin Gap Chamber (sTGC) muon detectors produced for the 2019-2020 ATLAS experiment muon spectrometer upgrade. The facility uses cosmic rays as a muon source to ionise the quenching gas mixture of pentane and carbon dioxide flowing through the sTGC detector. A gas system was developed and characterised for this purpose, with a simple and efficient gas condenser design utilizing a Peltier thermoelectric cooler (TEC). The gas system was tested to provide the desired 45 vol% pentane concentration. For continuous operations, a state-machine system was implemented with alerting and remote monitoring features to run all cosmic-ray data-acquisition associated slow-control systems, such as high/low voltage, gas system and environmental monitoring, in a safe and continuous mode, even in the absence of an operator.Comment: 23 pages, LaTeX, 14 figures, 4 tables, proof corrections for Journal of Instrumentation (JINST), including corrected Fig. 8b

Reconstruction of environmental histories to investigate patterns of larval radiated shanny (Ulvaria subbifurcata) growth and selective survival in a large bay of Newfoundland

We used otolith microstructure analysis to reconstruct the growth histories of larval radiated shanny ( Ulvaria subbifurcata ) collected over a 2-week period in Trinity Bay, Newfoundland. A dynamic 3-dimensional, eddy-resolving circulation model of the region provided larval drift patterns, which were combined with measurements of temperature and zooplankton abundance to assess the environmental history of the larvae. The abundance of juvenile and adult capelin ( Mallotus villosus ), the dominant planktivorous fish in this area, was monitored using five hydroacoustic surveys. The goal was to determine whether environmental histories are helpful in explaining spatial and temporal differences in larval shanny growth, measured as cumulative distribution functions (CDF) of growth rates. We found evidence for a selective loss of slower growing individuals and recognized considerable spatial differences in the CDF of larval growth rates. Consistent patterns in capelin abundance suggested that faster growing survivors, sampled at the end of the 2-week period, developed in areas of low predator densities. A dome-shaped relationship between temperature and larval growth was observed, explaining a significant but small amount of the overall variability (14%). Effects of experienced prey concentrations on larval growth rates could not be demonstrated

On a three-body confinement force in hadron spectroscopy

Recently it has been argued that a three-body colour confinement interaction can affect the stability condition of a three-quark system and the spectrum of a tetraquark described by any constituent quark model. Here we discuss the role of a three-body colour confinement interaction in a simple quark model and present some of its implications for the spectra of baryons, tetraquarks and six-quark systems.Comment: 19 pages (RevTeX), addition of new material regarding the NN interaction, more accurate discussion of the baryonic case, accepted for publication in Phys. Rev.

Quantal phases, disorder effects and superconductivity in spin-Peierls systems

In view of recent developments in the investigation on cuprate high-T${}_{\rm c}$ superconductors and the spin-Peierls compound CuGeO${}_{3}$, we study the effect of dilute impurity doping on the spin-Peierls state in quasi-one dimensional systems. We identify a common origin for the emergence of antiferromagnetic order upon the introduction of static vacancies, and superconductivity for mobile holes.Comment: 4 pages revtex; revised versio

B016 Impact of a 14-night intermittent hypoxia (IH) exposure on metabolic and cardiopulmonary adaptations to exercise in healthy subjects

IntroductionModifications in exercise tolerance have been reported in obstructive sleep apnea (OSA) patients. Also specific mechanisms have been speculated related to intermittent hypoxia (IH), hypertension, obesity or metabolic disturbance associated to OSA may play a significant role in exercise limitation. In order to eliminate these confounding factors we aimed to evaluate the effects of IH exposure during 14 nights in healthy subjects on exercise capacity, cardio-respiratory response and substrate oxidation during exercise.Methods12 healthy subjects (BMI: 21.8 0.5kg.m-2) were exposed to repetitive sequences of hypoxia — re-oxygenation during sleep in a hypoxic tent with appropriate cyclic re-oxygenation (rate: 30 desaturations.h-1). Maximal and sub-maximal exercise tests were performed before and after exposure in order to investigate cardiorespiratory variables and substrate oxidation parameters.ResultsIH did not modify maximal exercise parameters (VO2, heart rate, power output) nor ventilatory threshold (VTh). But this was achieved with a significant PETCO2 reduction and a VE/VCO2 increase during both maximal (Pre IH vs Post IH at VTh and Max, p<0.05) and sub-maximal (Pre vs Post at 30 % and 60 % Pmax, p<0.05) exercise tests, indicating hyperventilation. At the 1st min recovery after submaximal exercise test, diastolic arterial blood pressure (DBP) was higher after IH exposure (Pre: 60±3 vs Post: 78±2mmHg) in favour of a delayed DBP recovery following acute exercise. During sub-maximal exercise, subjects reached maximal lipid oxidation at higher power output and presented a decreased blood lactate at the same percentage of relative power after IH exposure.ConclusionExposure to 14 days of nocturnal IH is associated with an increased ventilatory response to subsequent exercise at sea level. Furthermore, delayed DBP recovery after exercise is in favor of early IH-induced cardiovascular modifications. This observation related to muscular exercise adaptations confirms the efficacy of the model in reproducing early cardiovascular alterations occurring in OSAS. Moreover, this model induces metabolic adaptations as soon as 14 nights of exposure