698 research outputs found

    The effect of high Intensity interval training (HIIT) upon resting and ambulatory blood pressure in physically inactive males and females

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    Purpose: Physical inactivity is associated with and increased risk of hypertension and cardiovascular disease. High intensity interval training (HIIT) has been shown to reduce resting blood pressure. However, the response of HIIT upon ambulatory blood pressure has been limited, despite evidence highlighting that the use of ambulatory blood pressure monitoring can be of clinical significance. Therefore, the aim of the present study was to investigate the effects of HIIT upon resting and ambulatory blood pressure. Methods: In a randomised controlled trial 41 physically inactive males and females (aged 23 ± 2.7 years) completed 4 weeks of HIIT. The HIIT protocol consisted of 3 x 30s maximal cycle ergometer sprints with a resistance of 7.5% body weight, with 2 minutes active recovery in between intervals. In total, 12 sessions were performed. Ambulatory blood pressure was measured using a Welch Allyn 6100 ambulatory blood pressure monitor. Results: Following the 4-week HIIT intervention, it was reported that there were statistically significant reductions in resting systolic blood pressure (-6.86 ± 8.76 mmHg, P < 0.041) when compared against the control group. It was also reported that there was a statistically significant reduction in 24-hour systolic blood pressure (-4.06 ± 8.08 mmHg, P < 0.008), 24-hour diastolic blood pressure (-3.43 ± 8.18 mmHg, P < 0.012) and 24-hour mean blood pressure (-2.17 ± 4.04 mmHg, P < 0.002) when compared against the control group. Conclusion: A 4-week HIIT programme was associated with a significant decrease in resting systolic blood pressure in addition to significant reductions in 24 hour systolic, diastolic and mean ambulatory blood pressure

    High-Resolution spectroscopy of the low-mass X-ray binary EXO 0748-67

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    We present initial results from observations of the low-mass X-ray binary EXO 0748-67 with the Reflection Grating Spectrometer on board the XMM-Newton Observatory. The spectra exhibit discrete structure due to absorption and emission from ionized neon, oxygen, and nitrogen. We use the quantitative constraints imposed by the spectral features to develop an empirical model of the circumsource material. This consists of a thickened accretion disk with emission and absorption in the plasma orbiting high above the binary plane. This model presents challenges to current theories of accretion in X-ray binary systems.Comment: 5 pages, 4 figures, accepted by A&A letters, XMM special issu

    Intrinsic Energy Localization through Discrete Gap Breathers in One-Dimensional Diatomic Granular Crystals

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    We present a systematic study of the existence and stability of discrete breathers that are spatially localized in the bulk of a one-dimensional chain of compressed elastic beads that interact via Hertzian contact. The chain is diatomic, consisting of a periodic arrangement of heavy and light spherical particles. We examine two families of discrete gap breathers: (1) an unstable discrete gap breather that is centered on a heavy particle and characterized by a symmetric spatial energy profile and (2) a potentially stable discrete gap breather that is centered on a light particle and is characterized by an asymmetric spatial energy profile. We investigate their existence, structure, and stability throughout the band gap of the linear spectrum and classify them into four regimes: a regime near the lower optical band edge of the linear spectrum, a moderately discrete regime, a strongly discrete regime that lies deep within the band gap of the linearized version of the system, and a regime near the upper acoustic band edge. We contrast discrete breathers in anharmonic FPU-type diatomic chains with those in diatomic granular crystals, which have a tensionless interaction potential between adjacent particles, and highlight in that the asymmetric nature of the latter interaction potential may lead to a form of hybrid bulk-surface localized solutions

    Implications of X-Ray Line Variations for 4U1822-371

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    4U 1822-371 is one of the proto-type accretion disk coronal sources with an orbital period of about 5.6 hours. The binary is viewed almost edge-on at a high inclination angle of 83 degrees, which makes it a unique candidate to study binary orbital and accretion disk dynamics in high powered X-ray sources. We observed the X-ray source in 4U 1822-371 with the Chandra High Energy Transmission Grating Spectrometer (HETGS) for almost nine binary orbits. X-ray eclipse times provide an update of the orbital ephemeris. We find that our result follows the quadratic function implied by previous observations; however, it suggests a flatter trend. Detailed line dynamics also confirm a previous suggestion that the observed photo-ionized line emission originates from a confined region in the outer edge of the accretion disk near the hot spot. Line properties allow us to impose limits on the size of accretion disk, the central corona, and the emission region. The photo-ionized plasma is consistent with ionization parameters of log(xi) > 2, and when combined with disk size and reasonable assumptions for the plasma density, this suggests illuminating disk luminosities which are over an order of magnitude higher than what is actually observed. That is, we do not directly observe the central emitting X-ray source. The spectral continua are best fit by a flat power law with a high energy cut-off and partial covering absorption (N_H ranging from 5.4-6.3x10^{22} cm^{-2}) with a covering fraction of about 50%. We discuss some implications of our findings with respect to the photo-ionized line emission for the basic properties of the X-ray source.Comment: Submitted to the Astrophysical Journa

    High Resolution Spectroscopy of the X-ray Photoionized Wind in Cygnus X-3 with the Chandra High Energy Transmission Grating Spectrometer

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    We present a preliminary analysis of the 1--10 keV spectrum of the massive X-ray binary Cyg X-3, obtained with the High Energy Transmission Grating Spectrometer on the Chandra X-ray Observatory. The source reveals a richly detailed discrete emission spectrum, with clear signatures of photoionization-driven excitation. Among the spectroscopic novelties in the data are the first astrophysical detections of a number of He-like 'triplets' (Si, S, Ar) with emission line ratios characteristic of photoionization equilibrium, fully resolved narrow radiative recombination continua of Mg, Si, and S, the presence of the H-like Fe Balmer series, and a clear detection of a ~ 800 km/s large scale velocity field, as well as a ~1500 km/s FWHM Doppler broadening in the source. We briefly touch on the implications of these findings for the structure of the Wolf-Rayet wind.Comment: 11 pages, 3 figures; Accepted for publication in ApJ Letter
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