Repeated muscle damage blunts the increase in heat strain during subsequent exercise heat stress

Purpose Exercise-induced muscle damage (EIMD) has recently been shown to increase heat strain during exercise heat stress (HS), and represents a risk factor for exertional heat illness (EHI). We hypothesised that a repeated bout of EIMD blunts the increase in rectal temperature (T re) during subsequent endurance exercise in the heat. Methods Sixteen non-heat-acclimated males were randomly allocated to EIMD (n = 9) or control (CON, n = 7). EIMD performed a downhill running treatment at -10 % gradient for 60 min at 65 % V. O2max in 20 °C, 40 % RH. CON participants performed the same treatment but at +1 % gradient. Following treatment, participants rested for 30 min, then performed HS (+1 % gradient running for 40 min at 65 % V. O2max in 33 °C, 50 % RH) during which thermoregulatory measures were assessed. Both groups repeated the treatment and subsequent HS 14 days later. Isometric quadriceps strength was assessed at baseline, and 48 h post-treatment. Results The decrease in leg strength 48 h post-EIMD trial 1 (-7.5 %) was absent 48 h post-EIMD trial 2 (+2.9 %) demonstrating a repeated bout effect. Final T re during HS was lower following EIMD trial 2 (39.25 ± 0.47 °C) compared with EIMD trial 1 (39.59 ± 0.49 °C, P < 0.01), with CON showing no difference. Thermal sensation and the T re threshold for sweating onset were also lower during HS on EIMD trial 2. Conclusion The repeated bout effect blunted the increase in heat strain during HS conducted after EIMD. Incorporating a muscle-damaging bout into training could be a strategy to reduce the risk of EHI and improve endurance performance in individuals undertaking heavy exercise with an eccentric component in the heat

Defects and Their Origin in Thin Films of (001) Alkaline Earth Oxides

MgO is used as an optical isolation layer for waveguides epitaxially grown on Si. Crystalline perfection of MgO is critical because it serves as a substrate for the single crytal, perovskite guiding layer. Imperfections in the MgO will result in imperfections in the guiding layer and lead to large optical losses for the planar waveguide structure. It is shown that the most common defect to form in thin MgO films are twin boundaries between {l_brace}111{r_brace}-type planes. Highest density of twins is observed when (001) MgO is grown directly on silicon/MgO interlayers containing Ba. Twinning is shown to accommodate the large size of Ba impurities incorporated in the MgO films through formation of internal grain boundaries and oper surface other than the growing (001) of MgO

Loading a vapor cell magneto-optic trap using light-induced atom desorption

Low intensity white light was used to increase the loading rate of $^{87}$Rb atoms into a vapor cell magneto-optic trap by inducing non-thermal desorption of Rb atoms from the stainless steel walls of the vapor cell. An increased Rb partial pressure reached a new equilibrium value in less than 10 seconds after switching on the broadband light source. After the source was turned off, the partial pressure returned to its previous value in $1/e$ times as short as 10 seconds.Comment: 7 pages, 6 figure

Wide Angle Polarization Analysis with Neutron Spin Filters

AbstractWe report substantial improvements in a compact wide angle neutron spin filter system that was recently employed on the Multi- Axis Crystal Spectrometer at the Center for Neutron Research at the U.S. National Institute of Standards and Technology. The apparatus consists of a cylindrical 3He polarizer cell and wide-angle 3He analyzer cells, a vertical solenoid to provide a uniform magnetic field, and a shielded radio-frequency solenoid for the polarizer cell. Nuclear magnetic resonance is employed to reverse the polarization in the polarizer cell and monitor the 3He polarization in all cells. The first experiment using this apparatus was carried out with cylindrical analyzer cells with limited angular coverage due to low polarizations in fused quartz cells. We present results for aluminosilicate glass analyzer cells that cover 110 ∘ and have long relaxation times (100h to 400h). Using two 100W diode bars spectrally narrowed with chirped volume Bragg gratings, we have obtained 65% - 80% 3He polarization in these cells. The 3He polarization has been measured by neutron transmission and electron paramagnetic resonance. Additional progress includes an improved holding field solenoid and decreased spin-flip losses

Vertical structure of stratospheric water vapour trends derived from merged satellite data

Stratospheric water vapour is a powerful greenhouse gas. The longest available record from balloon observations over Boulder, Colorado, USA shows increases in stratospheric water vapour concentrations that cannot be fully explained by observed changes in the main drivers, tropical tropopause temperatures and methane. Satellite observations could help resolve the issue, but constructing a reliable long-term data record from individual short satellite records is challenging. Here we present an approach to merge satellite data sets with the help of a chemistry–climate model nudged to observed meteorology. We use the models’ water vapour as a transfer function between data sets that overcomes issues arising from instrument drift and short overlap periods. In the lower stratosphere, our water vapour record extends back to 1988 and water vapour concentrations largely follow tropical tropopause temperatures. Lower and mid-stratospheric long-term trends are negative, and the trends from Boulder are shown not to be globally representative. In the upper stratosphere, our record extends back to 1986 and shows positive long-term trends. The altitudinal differences in the trends are explained by methane oxidation together with a strengthened lower-stratospheric and a weakened upper stratospheric circulation inferred by this analysis. Our results call into question previous estimates of surface radiative forcing based on presumed global long-term increases in water vapour concentrations in the lower stratosphere

Confined granular packings: structure, stress, and forces

The structure and stresses of static granular packs in cylindrical containers are studied using large-scale discrete element molecular dynamics simulations in three dimensions. We generate packings by both pouring and sedimentation and examine how the final state depends on the method of construction. The vertical stress becomes depth-independent for deep piles and we compare these stress depth-profiles to the classical Janssen theory. The majority of the tangential forces for particle-wall contacts are found to be close to the Coulomb failure criterion, in agreement with the theory of Janssen, while particle-particle contacts in the bulk are far from the Coulomb criterion. In addition, we show that a linear hydrostatic-like region at the top of the packings unexplained by the Janssen theory arises because most of the particle-wall tangential forces in this region are far from the Coulomb yield criterion. The distributions of particle-particle and particle-wall contact forces $P(f)$ exhibit exponential-like decay at large forces in agreement with previous studies.Comment: 11 pages, 11 figures, submitted to PRE (v2) added new references, fixed typo

Compact jets as probes for sub-parsec scale regions in AGN

Compact relativistic jets in active galactic nuclei offer an effective tool for investigating the physics of nuclear regions in galaxies. The emission properties, dynamics, and evolution of jets in AGN are closely connected to the characteristics of the central supermassive black hole, accretion disk and broad-line region in active galaxies. Recent results from studies of the nuclear regions in several active galaxies with prominent outflows are reviewed in this contribution.Comment: AASLaTeX, 5 pages, 4 figures. Accepted in Astrophysics and Space Scienc

The Fueling and Evolution of AGN: Internal and External Triggers

In this chapter, I review the fueling and evolution of active galactic nuclei (AGN) under the influence of internal and external triggers, namely intrinsic properties of host galaxies (morphological or Hubble type, color, presence of bars and other non-axisymmetric features, etc) and external factors such as environment and interactions. The most daunting challenge in fueling AGN is arguably the angular momentum problem as even matter located at a radius of a few hundred pc must lose more than 99.99 % of its specific angular momentum before it is fit for consumption by a BH. I review mass accretion rates, angular momentum requirements, the effectiveness of different fueling mechanisms, and the growth and mass density of black BHs at different epochs. I discuss connections between the nuclear and larger-scale properties of AGN, both locally and at intermediate redshifts, outlining some recent results from the GEMS and GOODS HST surveys.Comment: Invited Review Chapter to appear in LNP Volume on "AGN Physics on All Scales", Chapter 6, in press. 40 pages, 12 figures. Typo in Eq 5 correcte

Creativity and commerce: Michael Klinger and new film history

The crisis in film studies and history concerning their legitimacy and objectives has provoked a reinvigoration of scholarly energy in historical enquiry. 'New film history' attempts to address the concerns of historians and film scholars by working self-reflexively with an expanded range of sources and a wider conception of 'film' as a dynamic set of processes rather than a series of texts. The practice of new film history is here exemplified through a detailed case study of the independent British producer Michael Klinger (active 1961-87) with a specific focus on his unsuccessful attempt to produce a war film, Green Beach, based on a memoir of the Dieppe raid (August 1942). This case study demonstrates the importance of analysing the producer's role in understanding the complexities of film-making, the continual struggle to balance the competing demands of creativity and commerce. In addition, its subject matter - an undercover raid and a Jewish hero - disturbed the dominant myths concerning the Second World War, creating what turned out to be intractable ideological as well as financial problems. The paper concludes that the concerns of film historians need to engage with broader cultural and social histories. © 2010 Taylor & Francis