50,730 research outputs found
Replacement of fluid-filter elements without interruption of flow
Gatling-type filter assembly, preloaded with several filter elements enables filter replacement without breaking into the operative fluid system. When the filter element becomes contaminated, a unit inner subassembly is rotated 60 degrees to position a clean filter in the line
Highly Ionised Gas as a Diagnostic of the Inner NLR
The spectra of AGN from the ultraviolet to the near infrared, exhibit
emission lines covering a wide range of ionisation states, from neutral species
such as [O I] 6300A, up to [Fe XIV] 5303A. Here we report on some recent
studies of the properties of highly ionised lines (HILs), plus two case studies
of individual objects. Future IFU observations at high spatial and good
spectral resolution, will probe the excitation and kinematics of the gas in the
zone between the extended NLR and unresolved BLR. Multi-component SED fitting
can be used to link the source of photoionisation with the strengths and ratios
of the HILs.Comment: Proceedings of the IAU Symposium: Co-evolution of Central Black Holes
and Galaxie
SCUBA polarisation observations of the magnetic fields in the prestellar cores L1498 and L1517B
We have mapped linearly polarized dust emission from the prestellar cores
L1498 and L1517B with the James Clerk Maxwell Telescope (JCMT) using the
Submillimetre Common User Bolometer Array (SCUBA) and its polarimeter SCUBAPOL
at a wavelength of 850um. We use these measurements to determine the
plane-of-sky magnetic field orientation in the cores. In L1498 we see a
magnetic field across the peak of the core that lies at an offset of 19 degrees
to the short axis of the core. This is similar to the offsets seen in previous
observations of prestellar cores. To the southeast of the peak, in the
filamentary tail of the core, we see that the magnetic field has rotated to lie
almost parallel to the long axis of the filament. We hypothesise that the field
in the core may have decoupled from the field in the filament that connects the
core to the rest of the cloud. We use the Chandrasekhar-Fermi (CF) method to
measure the plane-of-sky field strength in the core of L1498 to be 10 +/- 7 uG.
In L1517B we see a more gradual turn in the field direction from the northern
part of the core to the south. This appears to follow a twist in the filament
in which the core is buried, with the field staying at a roughly constant 25
degree offset to the short axis of the filament, also consistent with previous
observations of prestellar cores. We again use the CF method and calculate the
magnetic field strength in L1517B also to be 30 +/- 10 uG. Both cores appear to
be roughly virialised. Comparison with our previous work on somewhat denser
cores shows that, for the denser cores, thermal and non-thermal (including
magnetic) support are approximately equal, while for the lower density cores
studied here, thermal support dominates.Comment: 6 pages, 2 figures; accepted for publication by MNRA
From 2D Integrable Systems to Self-Dual Gravity
We explain how to construct solutions to the self-dual Einstein vacuum
equations from solutions of various two-dimensional integrable systems by
exploiting the fact that the Lax formulations of both systems can be embedded
in that of the self-dual Yang--Mills equations. We illustrate this by
constructing explicit self-dual vacuum metrics on , where
is a homogeneous space for a real subgroup of SL(2, \C) associated
with the two-dimensional system.Comment: 9 pages, LaTex, no figure
Hydrodynamics of photoionized columns in the Eagle Nebula, M 16
We present hydrodynamical simulations of the formation, structure and
evolution of photoionized columns, with parameters based on those observed in
the Eagle Nebula. On the basis of these simulations we argue that there is no
unequivocal evidence that the dense neutral clumps at heads of the columns were
cores in the pre-existing molecular cloud. In our simulations, a variety of
initial conditions leads to the formation and maintenance of near-equilibrium
columns. Therefore, it is likely that narrow columns will often occur in
regions with large-scale inhomogeneities, but that observations of such columns
can tell us little about the processes by which they formed. The manner in
which the columns in our simulations develop suggests that their evolution may
result in extended sequences of radiation-induced star formation.Comment: 12 pages, 9 figures, Latex, MN macros, in press with MNRA
Dual-spin attitude control for outer planet missions
The applicability of dual-spin technology to a Jupiter orbiter with probe mission was investigated. Basic mission and system level attitude control requirements were established and preliminary mechanization and control concepts developed. A comprehensive 18-degree-of-freedom digital simulation was utilized extensively to establish control laws, study dynamic interactions, and determined key sensitivities. Fundamental system/subsystem constraints were identified, and the applicability of dual-spin technology to a Jupiter orbiter with probe mission was validated
-SDYM fields and heavenly spaces: II. Reductions of the -SDYM system
Reductions of self-dual Yang-Mills (SDYM) system for -bracket Lie
algebra to the Husain-Park (HP) heavenly equation and to
sl(N,{\boldmath{C}) SDYM equation are given. An example of a sequence of
chiral fields () tending for to a curved heavenly
space is found.Comment: 18 page
- …