Radiation measurements of shockwaves in synthetic air and pure nitrogen

Absolute radiance measurements in synthetic air and pure nitrogen have been performed in the Oxford T6 Stalker Tunnel while operating in Aluminium Shock Tube mode. Spatially and spectrally resolved data have been attained for shock speeds from 5.7 to 8 km/s and post-shock pressures from ∼10 to ∼100 kPa. Two independent telecentric optical set ups acquire data from the UV/Vis (200 to 520 nm) and Vis/NIR (585 to 850 nm) regions. The data are presented in multiple formats. An example 2D spectral-spatial map of absolute radiance is provided. Equilibrium spectral radiance comparisons against CEA-NEQAIR demonstrate improved agreement since prior campaigns in both T6 and the Electric Arc Shock Tube at NASA Ames. Spatial radiance profiles demonstrate lower pressure conditions can improve the resolution of non-equilibrium relaxation. Finally, spectral profiles progressing through the relaxation region for a low pressure synthetic air test case are shown. The motivation of this paper is to provide reliable calibrated data that, in future work, can be used to extract thermochemical rates and upon which numerical codes and facility results can be benchmarked against

Quantification of magma ascent rate through rockfall monitoring at the growing/collapsing lava dome of Volcán de Colima, Mexico

International audienceThe most recent eruptive phase of Volc'an de Colima, Mexico, started in 1998 and was characterized by dome growth with a variable effusion rate, interrupted intermittently by explosive eruptions. Between November 2009 and June 2011, activity at the dome was mostly limited to a lobe on the western side where it had previously started overflowing the crater rim, leading to the generation of rockfall events. As a consequence of this, no significant increase in dome volume was perceivable and the rate of magma ascent, a crucial parameter for volcano monitoring and hazard assessment could no longer be quantified via measurements of the dome's dimensions. Here, we present alternative approaches to quantify the magma ascent rate. We estimate the volume of individual rockfalls through the detailed analysis of sets of photographs (before and after individual rockfall events). The relationship between volume and infrared images of the freshly exposed dome surface and the seismic signals related to the rockfall events were then investigated. Larger rockfall events exhibited a correlation between its previously estimated volume and the surface temperature of the freshly exposed dome surface, as well as the mean temperature of rockfall mass distributed over the slope. We showed that for larger events, the volume of the rockfall correlates with the maximum temperature of the newly exposed lava dome as well as a proxy for seismic energy. It was therefore possible to calibrate the seismic signals using the volumes estimated from photographs and the count of rockfalls over a certain period was used to estimate the magma extrusion flux for the period investigated. Over the course of the measurement period, significant changes were observed in number of rockfalls, rockfall volume and hence averaged extrusion rate. The extrusion rate was not constant: it increased from 0.008±0.003 to 0.02±0.007m3 s−1 during 2010 and dropped down to 0.008±0.003m3 s−1 again in March 2011. In June 2011, magma extrusion had come to a halt. The methodology presented represents a reliable tool to constrain the growth rate of domes that are repeatedly affected by partial collapses. There is a good correlation between thermal and seismic energies and rockfall volume. Thus it is possible to calibrate the seismic records associated with the rockfalls (a continuous monitoring tool) to improve volcano monitoring at volcanoes with active dome growth

Numerical simulations of carbon contaminants in T6 shock tube tests

The influence of carbon contamination on a range of synthetic air and pure nitrogen shock tube experiments conducted in Oxford’s T6 Stalker Tunnel is investigated using a numerical model designed for thermochemically reacting flows. Experimental conditions range from 6 to 7 km/s with fill pressures between 18 and 100 Pa. The addition of carbon was found to significantly improve agreement between the numerical model and experimental data, especially after the non-equilibrium peak and during relaxation towards equilibrium. For the chosen thermochemistry set and test conditions, minimal affect on the chemical kinetics of the original test gas was found especially for the neutral species, with minor changes for ion and electron number densities. The performance of the chosen thermochemistry model in radiance regions corresponding to NO and non-equilibrium atomic oxygen was poor, with improvements also required for the parameters governing translational-vibrational relaxation

Effect of Immobilisation on Neuromuscular Function In Vivo in Humans: A Systematic Review

This is the final version. Available on open access from Springer Verlag via the DOI in this recordData Availability Statement: Data and materials are available on request from the corresponding author.Background: Muscle strength loss following immobilisation has been predominantly attributed to rapid muscle atrophy. However, this cannot fully explain the magnitude of muscle strength loss, so changes in neuromuscular function (NMF) may be involved. Objectives: We systematically reviewed literature that quantified changes in muscle strength, size and NMF following periods of limb immobilisation in vivo in humans. Methods: Studies were identified following systematic searches, assessed for inclusion, data extracted and quality appraised by two reviewers. Data were tabulated and reported narratively. Results: Forty eligible studies were included, 22 immobilised lower and 18 immobilised upper limbs. Limb immobilisation ranged from 12 h to 56 days. Isometric muscle strength and muscle size declined following immobilisation; however, change magnitude was greater for strength than size. Evoked resting twitch force decreased for lower but increased for upper limbs. Rate of force development either remained unchanged or slowed for lower and typically slowed for upper limbs. Twitch relaxation rate slowed for both lower and upper limbs. Central motor drive typically decreased for both locations, while electromyography amplitude during maximum voluntary contractions decreased for the lower and presented mixed findings for the upper limbs. Trends imply faster rates of NMF loss relative to size earlier in immobilisation periods for all outcomes. Conclusions: Limb immobilisation results in non-uniform loss of isometric muscle strength, size and NMF over time. Different outcomes between upper and lower limbs could be attributed to higher degrees of central neural control of upper limb musculature. Future research should focus on muscle function losses and mechanisms following acute immobilisation. Registration: PROSPERO reference: CRD42016033692

Crystal plasticity as an indicator of the viscous-brittle transition in magmas

Understanding the flow of multi-phase (melt, crystals and bubbles) magmas is of great importance for interpreting eruption dynamics. Here we report the first observation of crystal plasticity, identified using electron backscatter diffraction, in plagioclase in andesite dome lavas from Volcán de Colima, Mexico. The same lavas, deformed experimentally at volcanic conduit temperature and load conditions, exhibit a further, systematic plastic response in the crystalline fraction, observable as a lattice misorientation. At higher stress, and higher crystal fraction, the amount of strain accommodated by crystal plasticity is larger. Crystal plastic distortion is highest in the intact segments of broken crystals, which have exceeded their plastic limit. We infer that crystal plasticity precludes failure and can punctuate the viscous-brittle transition in crystal-bearing magmas at certain shallow magmatic conditions. Since crystal plasticity varies systematically with imposed conditions, this raises the possibility that it may be used as a strain marker in well-constrained systems