4,495 research outputs found
Repeated supra-maximal sprint cycling with and without sodium bicarbonate supplementation induces endothelial microparticle release
Under normal homeostatic conditions, the endothelium releases microparticles (MP), which are known to increase under stressful conditions and in disease states. CD105 (endoglin) and CD106 (vascular cell adhesion molecule-1) are expressed on the surface of endothelial cells and increased expression in response to stress may be observed. A randomised-controlled double-blinded study aimed to examine the use of endothelial microparticles as a marker for the state of one’s endothelium, as well as whether maintaining acid-base homeostasis affects the release of these MP. This study tested seven healthy male volunteers, who completed a strenuous cycling protocol, with venous blood analysed for CD105+ and CD106+ MP by flow cytometry at regular intervals. Prior to each trial participants consumed either 0.3 g·kg-1 body mass of sodium bicarbonate (NaHCO3), or 0.045 g·kg-1 body mass of sodium chloride (NaCl). A significant rise in endothelial CD105+MP and CD106+MP (p < 0.05) was observed at 90 minutes post exercise. A significant trend was shown for these MP to return to resting levels 180 minutes post exercise in both groups. No significance was found between experimental groups, suggesting that maintaining acid-base variables closer to basal levels has little effect upon the endothelial stress response for this particular exercise mode. In conclusion, strenuous exercise is accompanied by MP release and the endothelium is able to rapidly recover in healthy individuals, whilst maintaining acid-base homeostasis does not attenuate the MP release from the endothelium after exercise
Implications of a pre-exercise alkalosis-mediated attenuation of HSP72 on its response to a subsequent bout of exercise
The aim of this study was to investigate if a pre-exercise alkalosis-mediated attenuation of HSP72 had any effect on the response of the same stress protein after a subsequent exercise. Seven physically active males [25.0 ± 6.5 years, 182.1 ± 6.0 cm, 74.0 ± 8.3 kg, peak aerobic power (PPO) 316 ± 46 W] performed a repeated sprint exercise (EXB1) following a dose of 0.3 g kg⁻¹ body mass of sodium bicarbonate (BICARB), or a placebo of 0.045 g kg⁻¹ body mass of sodium chloride (PLAC). Participants then completed a 90-min intermittent cycling protocol (EXB2). Monocyte expressed HSP72 was significantly attenuated after EXB1 in BICARB compared to PLAC, however, there was no difference in the HSP72 response to the subsequent EXB2 between conditions. Furthermore there was no difference between conditions for measures of oxidative stress (protein carbonyl and HSP32). These findings confirm the sensitivity of the HSP72 response to exercise-induced changes in acid–base status in vivo, but suggest that the attenuated response has little effect upon subsequent stress in the same day
Mid-infrared observations of the ultraluminous galaxies IRAS14348-1447, IRAS19254-7245, and IRAS23128-5919
We present a study of the three ultraluminous infrared galaxies
IRAS14348-1447, IRAS19254-7245, and IRAS23128-5919, based on mid-infrared (MIR)
spectro-imaging (5-18microns) observations performed with ISOCAM. We find that
the MIR emission from each system, which consists of a pair of interacting late
type galaxies, is principally confined to the nuclear regions with diameters of
1-2kpc and can account for more than 95% of their IRAS 12micron flux. In each
interacting system, the galaxy hosting an active galactic nucleus (AGN)
dominates the total spectrum and shows stronger dust continuum (12-16microns)
relative to the Unidentified Infrared Band (UIB) emission (6-9microns),
suggestive of its enhanced radiation field. The MIR dominant galaxy also
exhibits elevated 15micron/Halpha and 15micron/K ratios which trace the high
extinction due to the large quantities of molecular gas and dust present in its
central regions. Using only diagnostics based on our mid-infrared spectra, we
can establish that the Seyfert galaxy IRAS19254-7245 exhibits MIR spectral
features of an AGN while the MIR spectrum of the Seyfert (or LINER) member of
IRAS23128-5919 is characteristic of dust emission principally heated by star
forming regions.Comment: Accepted for publication in Astronomy & Astrophysics, 13 pages, 9
figure
Can rainfall be a useful predictor of epidemic risk across temporal and spatial scales?
Plant disease epidemics are largely driven by within-season weather variables when inoculum is not limiting. Commonly, predictors in risk assessment models are based on the interaction of temperature and wetness-related variables, relationships which are determined experimentally. There is an increasing interest in providing within-season or inter-seasonal risk information at the region or continent scale, which commonly use models developed for a smaller scale. Hence, the scale matching dilemma that challenges epidemiologists and meteorologists: upscale models or downscale weather data? Successful applications may be found in both cases, which should be supported by validation datasets whenever possible, to prove the usefulness of the approach. For some diseases, rainfall is key for inoculum dispersal and, in warmer regions (e.g., tropics) where temperature is less limiting for epidemics, rainfall extends wetness periods. The drawbacks of using rainfall at small scales relate to its discrete nature and high spatial variability. However, for pre- or early-season predictions at large spatial scales sources of reasonably accurate rainfall summaries are available and may prove useful. The availability of disease datasets at various scales allows the development and evaluation of new models to be applied at the correct scale. We will showcase examples and discuss the usefulness of rainfall as key variable to predict soybean rust and wheat scab from field to region
High-pressure behaviour of GeO2: a simulation study
In this work we study the high pressure behaviour of liquid and glassy GeO2
by means of molecular dynamics simulations. The interaction potential, which
includes dipole polarization effects, was parameterized from first-principles
calculations. Our simulations reproduce the most recent experimental data to a
high degree of precision. The proportion of the various GeOn polyhedra is
determined as a function of the pressure: a smooth transition from tetrahedral
to octahedral network is observed. Finally, the study of high-pressure, liquid
germania confirms that this material presents an anomalous behaviour of the
diffusivity as observed in analog systems such as silica and water. The
importance of penta-coordinated germanium ions for such behaviour is stressed.Comment: 16 pages, 4 figures, accepted as a Fast Track Communication on
Journal of Physics: Condensed Matte
A milestone toward understanding PDR properties in the extreme environment of LMC-30Dor
More complete knowledge of galaxy evolution requires understanding the
process of star formation and interaction between the interstellar radiation
field and the interstellar medium in galactic environments traversing a wide
range of physical parameter space. Here we focus on the impact of massive star
formation on the surrounding low metallicity ISM in 30 Doradus in the Large
Magellanic Cloud. A low metal abundance, as is the case of some galaxies of the
early universe, results in less ultra-violet shielding for the formation of the
molecular gas necessary for star formation to proceed. The half-solar
metallicity gas in this region is strongly irradiated by the super star cluster
R136, making it an ideal laboratory to study the structure of the ISM in an
extreme environment. Our spatially resolved study investigates the gas heating
and cooling mechanisms, particularly in the photo-dissociation regions where
the chemistry and thermal balance are regulated by far-ultraviolet photons (6
eV< h\nu <13.6 eV).
We present Herschel observations of far-infrared fine-structure lines
obtained with PACS and SPIRE/FTS. We have combined atomic fine-structure lines
from Herschel and Spitzer observations with ground-based CO data to provide
diagnostics on the properties and the structure of the gas by modeling it with
the Meudon PDR code. We derive the spatial distribution of the radiation field,
the pressure, the size, and the filling factor of the photodissociated gas and
molecular clouds. We find a range of pressure of ~ 10^5 - 1.7x10^6 cm^{-3} K
and a range of incident radiation field G_UV ~ 10^2 - 2.5x10^4 through PDR
modeling. Assuming a plane-parallel geometry and a uniform medium, we find a
total extinction of 1-3 mag , which correspond to a PDR cloud size of 0.2 to
3pc, with small CO depth scale of 0.06 to 0.5pc. We also determine the three
dimensional structure of the gas. (Abridged)Comment: 20 pages, 23 figures, accepted in A&
Birkhoff's Theorem for Three-Dimensional AdS Gravity
All three-dimensional matter-free spacetimes with negative cosmological
constant, compatible with cyclic symmetry are identified. The only cyclic
solutions are the 2+1 (BTZ) black hole with SO(2) x R isometry, and the
self-dual Coussaert-Henneaux spacetimes, with isometry groups SO(2) x SO(2,1)
or SO(2) x SO(2).Comment: 11 pages, RevTeX4; minor typos corrected, Ref. added, accepted for
publication in Phys. Rev.
The effects of star formation on the low-metallicity ISM: NGC4214 mapped with Herschel/PACS spectroscopy
We present Herschel/PACS spectroscopic maps of the dwarf galaxy NC4214
observed in 6 far infrared fine-structure lines: [C II] 158mu, [O III] 88mu, [O
I] 63mu, [O I] 146mu, [N II] 122mu, and [N II] 205mu. The maps are sampled to
the full telescope spatial resolution and reveal unprecedented detail on ~ 150
pc size scales. We detect [C II] emission over the whole mapped area, [O III]
being the most luminous FIR line. The ratio of [O III]/[C II] peaks at about 2
toward the sites of massive star formation, higher than ratios seen in dusty
starburst galaxies. The [C II]/CO ratios are 20 000 to 70 000 toward the 2
massive clusters, which are at least an order of magnitude larger than spiral
or dusty starbursts, and cannot be reconciled with single-slab PDR models.
Toward the 2 massive star-forming regions, we find that L[CII] is 0.5 to 0.8%
of the LTIR . All of the lines together contribute up to 2% of LTIR . These
extreme findings are a consequence of the lower metallicity and young,
massive-star formation commonly found in dwarf galaxies. These conditions
promote large-scale photodissociation into the molecular reservoir, which is
evident in the FIR line ratios. This illustrates the necessity to move to
multiphase models applicable to star-forming clusters or galaxies as a whole.Comment: Accepted for publication in the A&A Herschel Special Issu
Circulating endothelial microparticles reduce in concentration following an exercise programme in women with polycystic ovary syndrome
Purpose: Endothelial dysfunction is a known comorbidity in women with polycystic ovary syndrome (PCOS). The aim was to assess if supervised, moderate intensity exercise could potentially impact markers of endothelial disruption; endothelial cell derived microparticles (EMP). Methods: The current study investigated the effects of a supervised 8-week moderate intensity exercise programme on EMP in women with PCOS (n=11) and control women free from any known disease (n=10). EMP were enumerated via specific antibody (CD105, CD106) labelling and flow cytometry.Results: CD105+MP significantly reduced in women with PCOS from pre to post exercise programme, with CD105+ MP reducing from 2114 CD105+ MP per µl platelet free plasma (PFP) to 424 CD105+ MP per µl PFP (p = 0.025). Control women showed no significant change in CD105+ MP (p = 0.25) after completing the same exercise programme. CD106+ MP showed no change in either PCOS (p = 0.95) or control groups (p = 0.99). No significant correlations existed with the changes in endothelial microparticles (EMP) compared to body composition changes as a result of exercise. Conclusion: Supervised, moderate intensity exercise independent of substantial weight loss reduced circulating CD105+MP, likely reflecting an improvement in endothelial function in women with PCOS compared to healthy control women. Additionally, EMP may be a useful marker for physical improvement in exercise programmes for clinical populations
Non-standard grain properties, dark gas reservoir, and extended submillimeter excess, probed by Herschel in the Large Magellanic Cloud
Context. Herschel provides crucial constraints on the IR SEDs of galaxies, allowing unprecedented accuracy on the dust mass estimates. However, these estimates rely on non-linear models and poorly-known optical properties.
Aims. In this paper, we perform detailed modelling of the Spitzer and Herschel observations of the LMC, in order to: (i) systematically study the uncertainties and biases affecting dust mass estimates; and to (ii) explore the peculiar ISM properties of the LMC.
Methods. To achieve these goals, we have modelled the spatially resolved SEDs with two alternate grain compositions, to study the impact of different submillimetre opacities on the dust mass. We have rigorously propagated the observational errors (noise and calibration) through the entire fitting process, in order to derive consistent parameter uncertainties.
Results. First, we show that using the integrated SED leads to underestimating the dust mass by ≃50% compared to the value obtained with sufficient spatial resolution, for the region we studied. This might be the case, in general, for unresolved galaxies. Second, we show that Milky Way type grains produce higher gas-to-dust mass ratios than what seems possible according to the element abundances in the LMC. A spatial analysis shows that this dilemma is the result of an exceptional property: the grains of the LMC have on average a larger intrinsic submm opacity (emissivity index β ≃ 1.7 and opacity κ_(abs)(160 μm) = 1.6 m^2 kg^(-1)) than those of the Galaxy. By studying the spatial distribution of the gas-to-dust mass ratio, we are able to constrain the fraction of unseen gas mass between ≃10, and ≃100% and show that it is not sufficient to explain the gas-to-dust mass ratio obtained with Milky Way type grains. Finally, we confirm the detection of a 500 μm extended emission excess with an average relative amplitude of ≃15%, varying up to 40%. This excess anticorrelates well with the dust mass surface density. Although we do not know the origin of this excess, we show that it is unlikely the result of very cold dust, or CMB fluctuations
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