38 research outputs found
Internal velocity factors
Computer program analyzes the entries and planetary trajectories of space vehicles. It obtains the equivalence of altitude and flight path angle, respectively, to acceleration load factor with respect to velocity for a given inertial velocity
High--Resolution 3D Simulations of Relativistic Jets
We have performed high-resolution 3D simulations of relativistic jets with
beam flow Lorentz factors up to 7, a spatial resolution of 8 cells per beam
radius, and for up to 75 normalized time units to study the morphology and
dynamics of 3D relativistic jets. Our simulations show that the coherent fast
backflows found in axisymmetric models are not present in 3D models. We further
find that when the jet is exposed to non-axisymmetric perturbations, (i) it
does not display the strong perturbations found for 3D classical hydrodynamic
and MHD jets (at least during the period of time covered by our simulations),
and (ii) it does propagate according to the 1D estimate. Small 3D effects in
the relativistic beam give rise to a lumpy distribution of apparent speeds like
that observed in M87. The beam is surrounded by a boundary layer of high
specific internal energy. The properties of this layer are briefly discussed.Comment: 15 pages, 4 figures. Accepted to be publish in the ApJ Letters.
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Relativistic MHD Simulations of Jets with Toroidal Magnetic Fields
This paper presents an application of the recent relativistic HLLC
approximate Riemann solver by Mignone & Bodo to magnetized flows with vanishing
normal component of the magnetic field.
The numerical scheme is validated in two dimensions by investigating the
propagation of axisymmetric jets with toroidal magnetic fields.
The selected jet models show that the HLLC solver yields sharper resolution
of contact and shear waves and better convergence properties over the
traditional HLL approach.Comment: 12 pages, 5 figure
X-ray-emitting Atmospheres of B2 Radio Galaxies
We report ROSAT PSPC spatial and spectral analysis of the eight B2 radio
galaxies NGC 315, NGC 326, 4C 35.03, B2 0326+39, NGC 2484, B2 1040+31, B2
1855+37, and 3C 449, expected to be representative of the class of low-power
radio galaxies. Multiple X-ray components are present in each, and the gas
components have a wide range of linear sizes and follow an extrapolation of the
cluster X-ray luminosity/temperature correlation, implying that there is no
relationship between the presence of a radio galaxy and the gas fraction of the
environment. No large-scale cooling flows are found. There is no correlation of
radio-galaxy size with the scale or density of the X-ray atmosphere. This
suggests that it is processes on scales less than those of the overall gaseous
environments which are the major influence on radio-source dynamics. The
intergalactic medium is usually sufficient to confine the outer parts of the
radio structures, in some cases even to within 5 kpc of the core. In the case
of NGC 315, an extrapolation suggests that the pressure of the atmosphere may
match the minimum pressure in the radio source over a factor of about 40 in
linear size (a factor of about 1600 in pressure).Comment: 34 pages, including 10 figures, using aasms4.sty To appear in the Ap
EVN Observations of GRS1915+105
We obtained EVN observations of the X-ray transient source GRS1915+105 in its
radio-loud state. In 2 images obtained before a major flare, the source is
resolved, showing two opposite asymmetric jets. This indicates that steady jets
exist also before a major flare, with an estimated velocity of 0.2-0.6c.Comment: Proceedings of the 5th EVN Symposium, Eds. J. Conway, A. Polatidis,
R. Booth, Onsala Observatory, Sweden (June 2000
defining the role of nanonetting in the electrical behaviour of composite nanofiber nets
The electrical behaviour of MWCNT-based composite nanofiber/nets can be tuned by controlling the morphology of the secondary nanoweb
Bradykinin B2 receptor expression in the bronchial mucosa of allergic asthmatics: the role of NF-kB
Bradykinin (BK) mediates acute allergic asthma and airway remodelling. Nuclear factor-kappa B (NF-kB) is potentially involved in BK B2 receptor (B2R) regulation. In this observational cross-sectional study, B2R and NF-kB expression was evaluated in bronchial biopsies from mild asthmatics (after diluent/allergen challenge) and healthy controls, examining the role of NF-kB in B2R expression in primary human fibroblasts from normal and asthmatic subjects (HNBFb and HABFb). B2R and NF-kB (total and nuclear) expression was analysed by immunohistochemistry in biopsies from 10 mild intermittent asthmatics (48 h after diluent/allergen challenge) and 10 controls undergoing bronchoscopy. B2R co-localization in 5B5(+) and αSMA(+) mesenchymal cells was studied by immunofluorescence/confocal microscopy, and B2R expression in HABFb/HNBFb incubated with interleukin (IL)-4/IL-13 with/without BK, and after NF-kB inhibitor, by Western blotting. Bronchial mucosa B2R and nuclear NF-kB expression was higher in asthmatics after diluent (B2R only) and allergen challenge than in controls (P < 0.05), while B2R and NF-kB (total and nuclear) increased after allergen compared with after diluent (P < 0.05). Allergen exposure increased B2R expression in 5B5(+) and αSMA(+) cells. Constitutive B2R protein expression was higher in HABFb than in HNBFb (P < 0.05) and increased in both cell types after IL-13 or IL-4/IL-13 and BK treatment. This increase was suppressed by a NF-kB inhibitor (P < 0.05). Bronchial B2R expression is constitutively elevated in allergic asthma and is further increased after allergen exposure together with NF-kB expression. NF-kB inhibitor blocked IL-4/IL-13-induced increase in B2R expression in cultured fibroblasts, suggesting a role as potential anti-asthma dru