| 1. |
- Abramowski, A., et al.
(författare)
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HESS observations of the Carina nebula and its enigmatic colliding wind binary Eta Carinae
- 2012
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 424:1, s. 128-135
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Tidskriftsartikel (refereegranskat)abstract
- The massive binary system Eta Carinae and the surrounding H ii complex, the Carina nebula, are potential particle acceleration sites from which very high energy (VHE; E= 100 GeV) ?-ray emission could be expected. This paper presents data collected during VHE ?-ray observations with the HESS telescope array from 2004 to 2010, which cover a full orbit of Eta Carinae. In the 33.1-h data set no hint of significant ?-ray emission from Eta Carinae has been found and an upper limit on the ?-ray flux of (99 per cent confidence level) is derived above the energy threshold of 470 GeV. Together with the detection of high energy (HE; 0.1 =E= 100 GeV) ?-ray emission by the Fermi Large Area Telescope up to 100 GeV, and assuming a continuation of the average HE spectral index into the VHE domain, these results imply a cut-off in the ?-ray spectrum between the HE and VHE ?-ray range. This could be caused either by a cut-off in the accelerated particle distribution or by severe ?? absorption losses in the wind collision region. Furthermore, the search for extended ?-ray emission from the Carina nebula resulted in an upper limit on the ?-ray flux of (99 per cent confidence level). The derived upper limit of 23 on the cosmic ray enhancement factor is compared with results found for the old-age mixed-morphology supernova remnant W28.
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| 2. |
- André, Ph., et al.
(författare)
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Probing the cold magnetised Universe with SPICA-POL (B-BOP)
- 2019
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Ingår i: Publications Astronomical Society of Australia. - : Cambridge University Press (CUP). - 1323-3580 .- 1448-6083. ; 36
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Forskningsöversikt (refereegranskat)abstract
- Space Infrared Telescope for Cosmology and Astrophysics (SPICA), the cryogenic infrared space telescope recently pre-selected for a 'Phase A' concept study as one of the three remaining candidates for European Space Agency (ESA's) fifth medium class (M5) mission, is foreseen to include a far-infrared polarimetric imager [SPICA-POL, now called B-fields with BOlometers and Polarizers (B-BOP)], which would offer a unique opportunity to resolve major issues in our understanding of the nearby, cold magnetised Universe. This paper presents an overview of the main science drivers for B-BOP, including high dynamic range polarimetric imaging of the cold interstellar medium (ISM) in both our Milky Way and nearby galaxies. Thanks to a cooled telescope, B-BOP will deliver wide-field 100-350 mu m images of linearly polarised dust emission in Stokes Q and U with a resolution, signal-to-noise ratio, and both intensity and spatial dynamic ranges comparable to those achieved by Herschel images of the cold ISM in total intensity (Stokes I). The B-BOP 200 mu m images will also have a factor similar to 30 higher resolution than Planck polarisation data. This will make B-BOP a unique tool for characterising the statistical properties of the magnetised ISM and probing the role of magnetic fields in the formation and evolution of the interstellar web of dusty molecular filaments giving birth to most stars in our Galaxy. B-BOP will also be a powerful instrument for studying the magnetism of nearby galaxies and testing Galactic dynamo models, constraining the physics of dust grain alignment, informing the problem of the interaction of cosmic rays with molecular clouds, tracing magnetic fields in the inner layers of protoplanetary disks, and monitoring accretion bursts in embedded protostars.
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| 3. |
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| 4. |
- Petersson, J, et al.
(författare)
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Physiological evaluation of a new quantitative SPECT method measuring regional ventilation and perfusion
- 2004
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Ingår i: Journal of applied physiology (Bethesda, Md. : 1985). - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 96:3, s. 1127-1136
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a new quantitative single-photon-emission computed tomography (SPECT) method that uses 113mIn-labeled albumin macroaggregates and Technegas (99mTc) to estimate the distributions of regional ventilation and perfusion for the whole lung. The multiple inert-gas elimination technique (MIGET) and whole lung respiratory gas exchange were used as physiological evaluations of the SPECT method. Regional ventilation and perfusion were estimated by SPECT in nine healthy volunteers during awake, spontaneous breathing. Radiotracers were administered with subjects sitting upright, and SPECT images were acquired with subjects supine. Whole lung gas exchange of MIGET gases and arterial Po2 and Pco2 gases was predicted from estimates of regional ventilation and perfusion. We found a good agreement between measured and SPECT-predicted exchange of MIGET and respiratory gases. Correlations ( r2) between SPECT-predicted and measured inert-gas excretions and retentions were 0.99. The method offers a new tool for measuring regional ventilation and perfusion in humans.
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| 5. |
- Borges, Joao Batista, et al.
(författare)
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First-time imaging of effects of inspired oxygen concentration on regional lung volumes and breathing pattern during hypergravity
- 2015
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 115:2, s. 353-363
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Tidskriftsartikel (refereegranskat)abstract
- Aeroatelectasis can develop in aircrew flying the latest generation high-performance aircraft. Causes alleged are relative hyperoxia, increased gravity in the head-to-foot direction (+G(z)), and compression of legs and stomach by anti-G trousers (AGT). We aimed to assess, in real time, the effects of hyperoxia, +G(z) accelerations and AGT inflation on changes in regional lung volumes and breathing pattern evaluated in an axial plane by electrical impedance tomography (EIT). The protocol mimicked a routine peacetime flight in combat aircraft. Eight subjects wearing AGT were studied in a human centrifuge during 1 h 15 min exposure of +1 to +3.5G(z). They performed this sequence three times, breathing AIR, 44.5 % O-2 or 100 % O-2. Continuous recording of functional EIT enabled uninterrupted assessment of regional lung volumes at the 5th intercostal level. Breathing pattern was also monitored. EIT data showed that +3.5G(z), compared with any moment without hypergravity, caused an abrupt decrease in regional tidal volume (V-T) and regional end-expiratory lung volume (EELV) measured in the EIT slice, independently of inspired oxygen concentration. Breathing AIR or 44.5 % O-2, sub-regional EELV measured in the EIT slice decreased similarly in dorsal and ventral regions, but sub-regional V-T measured in the EIT slice decreased significantly more dorsally than ventrally. Breathing 100 % O-2, EELV and V-T decreased similarly in both regions. Inspired tidal volume increased in hyperoxia, whereas breathing frequency increased in hypergravity and hyperoxia. Our findings suggest that hypergravity and AGT inflation cause airway closure and air trapping in gravity-dependent lung regions, facilitating absorption atelectasis formation, in particular during hyperoxia.
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| 6. |
- Dussault, C., et al.
(författare)
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Hyperoxia and hypergravity are independent risk factors of atelectasis in healthy sitting humans : a pulmonary ultrasound and SPECT/CT study
- 2016
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 121:1, s. 66-77
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Tidskriftsartikel (refereegranskat)abstract
- Aeroatelectasis has developed in aircrew flying routine peacetime flights on the latest generation high-performance aircraft, when undergoing excessive oxygen supply. To single out the effects of hyperoxia and hypergravity on lung tissue compression, and on ventilation and perfusion, eight subjects were studied before and after 1 h 15 min exposure to +1 to +3.5 G(z) in a human centrifuge. They performed the protocol three times, breathing air, 44.5% O-2, or 100% O-2 and underwent functional and topographical imaging of the whole lung by ultrasound and single-photon emission computed tomography combined with computed tomography (SPECT/CT). Ultrasound lung comets (ULC) and atelectasis both increased after exposure. The number of ULC was <1 pre protocol (i.e., normal lung) and larger post 100% O-2 (22 +/- 3, mean +/- SD) than in all other conditions (P < 0.001). Post 44.5% O-2 differed from air (P < 0.05). Seven subjects showed low-to medium-grade atelectasis post 100% O-2. There was an effect on grade of gas mixture and hypergravity, with interaction (P < 0.001, respectively); 100% O-2, 44.5% O-2, and air differed from each other (P < 0.05). SPECT ventilation and perfusion were always normal. Ultrasound concurred with CT in showing normal lung in the upper third and ULC/atelectasis in posterior and inferior areas, not for other localizations. In conclusion, hyperoxia and hypergravity are independent risk factors of reversible atelectasis formation. Ultrasound is a useful screening tool. Together with electrical impedance tomography measurements (reported separately), these findings show that zones with decreased ventilation prone to transient airway closure are present above atelectatic areas.
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| 7. |
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| 8. |
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| 9. |
- Montmerle, S, et al.
(författare)
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Effects of gravity and blood volume shifts on cardiogenic oscillations in respired gas
- 2005
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Ingår i: Journal of applied physiology (Bethesda, Md. : 1985). - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 99:3, s. 931-936
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Tidskriftsartikel (refereegranskat)abstract
- During the cardiac cycle, cardiogenic oscillations of expired gas ( x) concentrations (COS[ x]) are generated. At the same time, there are heart-synchronous cardiogenic oscillations of airway flow (COSflow), where inflow occurs during systole. We hypothesized that both phenomena, although primarily generated by the heartbeat, would react differently to the cephalad blood shift caused by inflation of an anti-gravity (anti-G) suit and to changes in gravity. Twelve seated subjects performed a rebreathing-breath-holding-expiration maneuver with a gas mixture containing O2 and He at normal (1 G) and moderately increased gravity (2 G); an anti-G suit was inflated to 85 mmHg in each condition. When the anti-G suit was inflated, COSflow amplitude increased ( P = 0.0028) at 1 G to 186% of the control value without inflation (1-G control) and at 2 G to 203% of the control value without inflation (2-G control). In contrast, the amplitude of COS of the concentration of the blood-soluble gas O2 (COS[O2/He]), an index of the differences in pulmonary perfusion between lung units, declined to 75% of the 1-G control value and to 74% of the 2-G control value ( P = 0.0030). There were no significant changes in COSflow or COS[O2/He] amplitudes with gravity. We conclude that the heart-synchronous mechanical agitation of the lungs, as expressed by COSflow, is highly dependent on peripheral-to-central blood shifts. In contrast, COS[blood-soluble gas] appears relatively independent of this mechanical agitation and seems to be determined mainly by differences in intrapulmonary perfusion.
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| 10. |
- Montmerle, S, et al.
(författare)
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Lung function during and after prolonged head-down bed rest
- 2002
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Ingår i: Journal of applied physiology (Bethesda, Md. : 1985). - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 92:1, s. 75-83
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Tidskriftsartikel (refereegranskat)abstract
- We determined the effects of prolonged head-down tilt bed rest (HDT) on lung mechanics and gas exchange. Six subjects were studied in supine and upright postures before (control), during [ day 113(D113)], and after (R + number of days of recovery) 120 days of HDT. Peak expiratory flow (PF) never differed between positions at any time and never differed from controls. Maximal midexpiratory flow (FEF25–75%) was lower in the supine than in the upright posture before HDT and was reduced in the supine posture by about 20% between baseline and D113, R + 0, and R + 3. The diffusing capacity for carbon monoxide corrected to a standardized alveolar volume (volume-corrected Dl CO) was lower in the upright than in the supine posture and decreased in both postures by 20% between baseline and R + 0 and by 15% between baseline and R + 15. Pulmonary blood flow (Q˙C) increased from R + 0 to R + 3 by 20 (supine) and 35% (upright). As PF is mostly effort dependent, our data speak against major respiratory muscle deconditioning after 120 days of HDT. The decrease in FEF25–75% suggests a reduction in elastic recoil. Time courses of volume-corrected Dl CO andQ˙C could be explained by a decrease in central blood volume during and immediately after HDT.
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