90 research outputs found
Effect of the nifedipine-atenolol association on arterial myocyte migration and proliferation
No full textThe in vitro effect of nifedipine and atenolol, either alone or in combination, on the proliferation and migration of rat aortic smooth muscle cells was investigated. Nifedipine inhibited the replication of arterial myocytes in concentrations ranging between 10 and 100 microM. The inhibition, evaluated as cell number, was dose- and time-dependent with an IC50 of 39 and 34 microM after 48 and 72 h, respectively; the cell doubling time increased with drug concentrations up to 118 h versus 28 h for controls. Atenolol alone failed to reduce arterial myocyte proliferation, and did not influence the effect of nifedipine on cell proliferation. Nifedipine and atenolol alone inhibited in a dose-dependent manner rat aortic myocytes migration induced by fibrinogen as chemotactic agent. When the combination nifedipine-atenolol was investigated, an additive inhibitory effect on cell migration was observed. These results provide in vitro support for a potential effect of this drug association on early steps of atherogenesis
Jovian stratospheric temperature during the two months following the impacts of comet Shoemaker-Levy 9
No full textWe present millimeter heterodyne observations of Jupiter performed at the IRAM 30-m telescope during and immediately after the infall of comet Shoemaker-Levy 9 on the planet. Rotational lines of CO and CS were first observed in emission during the impacts. They faded rapidly and turned into absorption features after July 28, 1994. The shapes of the lines imply that persistent layers of newly created molecular compounds remained in the upper stratosphere. Modeling of these lines was performed by taking into account the specific geometry of the impact sites. The main results concern: (i) the CO mass at the impact site G 10.5 h after impact, which is found in the range 0.5-2 x 10(14) g, iii the CS mass derived on the Q1+R+S complex, which is between 0.9 and 2.5 x 10(12) g one week after the impacts, (iii) the temporal evolution of the stratospheric temperature through July and September 1994. Assuming an exponential decrease of the perturbed temperature in the upper stratosphere, a cooling time constant of 29 h is found for the 10-mu bar region. Moreover, the temperature near 10-mu bar became colder than in pre-impact conditions between 2 and 3 weeks after the impacts, before returning to unperturbed values. Comparison is presented with published temperature evolution models of the SL9 sites. (C) 2001 Elsevier Science Ltd. All rights reserved
The awakening of BL Lacertae: observations by Fermi, Swift and the GASP-WEBT
No full textSince the launch of the Fermi satellite, BL Lacertae has been moderately active at ?-rays and optical frequencies until 2011 May, when the source started a series of strong flares. The exceptional optical sampling achieved by the GLAST–AGILE Support Program of the Whole Earth Blazar Telescope in collaboration with the Steward Observatory allows us to perform a detailed comparison with the daily γ-ray observations by Fermi. Discrete correlation analysis between the optical and γ-ray emission reveals correlation with a time lag of 0 ± 1 d, which suggests cospatiality of the corresponding jet emitting regions. A better definition of the time lag is hindered by the daily gaps in the sampling of the extremely fast flux variations. In general, optical flares present more structure and develop on longer time-scales than corresponding γ-ray flares. Observations at X-rays and at millimetre wavelengths reveal a common trend, which suggests that the region producing the mm and X-ray radiation is located downstream from the optical and γ-ray-emitting zone in the jet. The mean optical degree of polarization slightly decreases over the considered period and in general it is higher when the flux is lower. The optical electric vector polarization angle (EVPA) shows a preferred orientation of about 15°, nearly aligned with the radio core EVPA and mean jet direction. Oscillations around it increase during the 2011–2012 outburst. We investigate the effects of a geometrical interpretation of the long-term flux variability on the polarization. A helical magnetic field model predicts an evolution of the mean polarization that is in reasonable agreement with the observations. These can be fully explained by introducing slight variations in the compression factor in a transverse shock waves model
Jovian stratospheric temperature during the two months following the impacts of comet Shoemaker-Levy 9
No full textWe present millimeter heterodyne observations of Jupiter performed at the IRAM 30-m telescope during and immediately after the infall of comet Shoemaker-Levy 9 on the planet. Rotational lines of CO and CS were first observed in emission during the impacts. They faded rapidly and turned into absorption features after July 28, 1994. The shapes of the lines imply that persistent layers of newly created molecular compounds remained in the upper stratosphere. Modeling of these lines was performed by taking into account the specific geometry of the impact sites. The main results concern: (i) the CO mass at the impact site G 10.5 h after impact, which is found in the range 0.5-2 x 10(14) g, iii the CS mass derived on the Q1+R+S complex, which is between 0.9 and 2.5 x 10(12) g one week after the impacts, (iii) the temporal evolution of the stratospheric temperature through July and September 1994. Assuming an exponential decrease of the perturbed temperature in the upper stratosphere, a cooling time constant of 29 h is found for the 10-mu bar region. Moreover, the temperature near 10-mu bar became colder than in pre-impact conditions between 2 and 3 weeks after the impacts, before returning to unperturbed values. Comparison is presented with published temperature evolution models of the SL9 sites. (C) 2001 Elsevier Science Ltd. All rights reserved.</p
A dual origin for Neptune's carbon monoxide?
No full textHeterodyne observations of Neptune have provided a measurement
of the CO(2–1) line profile with a total bandpass of almost
8 GHz and a resolution of 4 MHz. The lineshape indicates that the CO mole
fraction in Neptune's atmosphere is not uniform, but increases by a factor of
~2 from the troposphere/lower stratosphere (0.5 ppm at mbar)
to the upper stratosphere (1 ppm at mbar). This indicates the existence
of both external and internal sources of CO. The equivalent flux associated
with the external source is ~ cm-2 s-1. We
propose that the stratospheric CO results from a large (2 km) cometary
impact that occurred ~200 years ago, although there remains problems
with this hypothesis
AN EXTERNAL ORIGIN FOR CARBON MONOXIDE ON URANUS FROM HERSCHEL/SPIRE?
No full textPrevious studies have demonstrated an external source of CO on Jupiter, Saturn, and Neptune. However, it has not been possible to demonstrate this on Uranus because of its low CO abundance, low upper-tropospheric temperatures, and low stratospheric thermal gradient, which make detection very challenging. Here we use 17 Herschel/SPIRE observation sequences spanning 3 yr (2009-2012), which cover 14.6-51.8 cm(-1) with a combined integration time of 5 hr. These spectra were originally taken for routine calibration purposes, so were corrected for continuum offsets prior to analysis. The final stacked spectra had an extremely low noise level of 10-50 pW cm(-2) sr(-1)/cm(-1). Despite this, CO was not observed, but we were able to obtain stringent 3 sigma upper limits at the 0.1-0.2 bar level of 2.1 ppb for a uniform profile, and 9.4 ppb for a stratosphere-only profile-an order of magnitude improvement over previous studies. Comparison with observed CO fluorescence by Encrenaz et al. suggests the majority of Uranus' stratospheric CO has an external origin. It thus appears that external supply of oxygen species-via comets, micrometeorites, or dust-is an important process on all giant planets in our solar system.</p
Spectral-Line On-The-Fly at the IRAM 30 m Telescope
No full textWe implemented spectral-line On-The-Fly (SLOTF) observing at the IRAM 30-m about three years ago. This observing mode is now producing fully sampled images of superb quality and with sizes not previously feasible with the 30-m. Representative results will be shown in this talk and elsewhere at this conference. With the current system we move the telescope beam across the source at a constant velocity, while data are taken (``dumped'') every 1 or 2 seconds. We can scan along the principal directions of any spherical coordinate system on the sky. Individual scan lines can have any length; they can be preceded and followed by off-source reference measurements. The receivers, backends, and atmosphere are sufficiently stable for SLOTF with rather long time periods between off-source reference measurements. We can use simultaneously up to 4 receivers and 12 spectrometer bands of the filterbanks and autocorrelators. A new version of the class software contains special extensions and features for SLOTF. You can get detailed and up-to-date information about SLOTF at the 30-m from the IRAM-Granada WWW site: IRAM-Granada. Faster and even more flexible OTF observing, for continuum as well as for spectral lines, will be a major feature of the future telescope control and data handling system for the 30-m, which we are planning now
Spectral-Line On-The-Fly at the IRAM 30 m Telescope
No full textWe implemented spectral-line On-The-Fly (SLOTF) observing at the IRAM 30-m about three years ago. This observing mode is now producing fully sampled images of superb quality and with sizes not previously feasible with the 30-m. Representative results will be shown in this talk and elsewhere at this conference. With the current system we move the telescope beam across the source at a constant velocity, while data are taken (``dumped'') every 1 or 2 seconds. We can scan along the principal directions of any spherical coordinate system on the sky. Individual scan lines can have any length; they can be preceded and followed by off-source reference measurements. The receivers, backends, and atmosphere are sufficiently stable for SLOTF with rather long time periods between off-source reference measurements. We can use simultaneously up to 4 receivers and 12 spectrometer bands of the filterbanks and autocorrelators. A new version of the class software contains special extensions and features for SLOTF. You can get detailed and up-to-date information about SLOTF at the 30-m from the IRAM-Granada WWW site: IRAM-Granada. Faster and even more flexible OTF observing, for continuum as well as for spectral lines, will be a major feature of the future telescope control and data handling system for the 30-m, which we are planning now
Long-term Evolution of CO and CS in the Jupiter Stratosphere after the Comet Shoemaker-Levy 9 Collision: Millimeter Observations with the IRAM-30m Telescope
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Ground-based measurements of middle atmospheric water vapor at 183 GHz during very dry tropospheric conditions
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