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CO and CI maps of the starburst galaxy M82
The first map of an external galaxy in the 3P₁ - 3P0 fine-structure line of atomic carbon (CI) is presented towards the nucleus of the starbuster M82, and compared with the distinction of the CO J = 4 - 3 molecular emission. The CI traces features that are seen in lower transition CO maps, and shows that CI and the CO are well mixed and have similar spatial distributions. There are small differences between the CO J = 4 - 3 line and lower transition CO data towards the NE part of the molecular ring, where the emission is less prominent. The abundance ratio [CI]/[CO] across M82 is very high, with an average value ~ 0.5 across most of the nucleus, a factor at least 5 times that which is typical of dense molecular cloud cores seen in our own Galaxy. This means that on average, CI is overabundant towards M82. This result can be explained using models which provide enhancements to the CI abundance above normal Interstellar Medium values, a result of a greater cosmic ray flux in M82, or where there is substantial mixing of the gas
The Deepest Radio Study of the Pulsar Wind Nebula G21.5-0.9: Still No Evidence for the Supernova Shell
We report on sensitive new 1.4-GHz VLA radio observations of the pulsar wind
nebula G21.5-0.9, powered by PSR J1833-1034, and its environs. Our observations
were targeted at searching for the radio counterpart of the shell-like
structure seen surrounding the pulsar wind nebula in X-rays. Some such radio
emission might be expected as the ejecta from the <~ 1000 yr old supernova
expand and interact with the surrounding medium. We find, however, no radio
emission from the shell, and can place a conservative 3-sigma upper limit on
its 1-GHz surface brightness of 7 x 10^-22 W/m^2/Hz/sr, comparable to the
lowest limits obtained for radio emission from shells around other pulsar-wind
nebulae. Our widefield radio image also shows the presence of two extended
objects of low-surface brightness. We re-examine previous 327-MHz images, on
which both the new objects are visible. We identify the first, G21.64-0.84, as
a new shell-type supernova remnant, with a diameter of ~13' and an unusual
double-shell structure. The second, G21.45-0.59, ~1' in diameter, is likely an
HII region.Comment: 8 Pages, submitted to MNRA
Cyclic motion control for programmable bevel-tip needles 3D steering: a simulation study
Flexible, steerable, soft needles are desirable in Minimally Invasive Surgery to achieve complex trajectories while maintaining the benefits of percutaneous intervention compared to open surgery. One such needle is the multi-segment Programmable Bevel-tip Needle (PBN), which is inspired by the mechanical design of the ovipositor of certain wasps. PBNs can steer in 3D whilst minimizing the force applied to the surrounding substrate, due to the cyclic motion of the segments. Taking inspiration also from the control strategy of the wasp to perform insertions and lay their eggs, this paper presents the design of a cyclic controller that can steer a PBN to produce a desired trajectory in 3D. The performance of the controller is demonstrated in simulation in comparison to that of a direct controller without cyclic motion. It is shown that, while the same steering curvatures can be attained by both controllers, the time taken to achieve the configuration is longer for the cyclic controller, leading to issues of potential under-steering and longer insertion times
Cyclotron effective mass of 2D electron layer at GaAs/AlGaAs heterojunction subject to in-plane magnetic fields
We have found that Fermi contours of a two-dimensional electron gas at
\rmGaAs/Al_xGa_{1-x}As interface deviate from a standard circular shape under
the combined influence of an approximately triangular confining potential and
the strong in-plane magnetic field. The distortion of a Fermi contour manifests
itself through an increase of the electron effective cyclotron mass which has
been measured by the cyclotron resonance in the far-infrared transmission
spectra and by the thermal damping of Shubnikov-de Haas oscillations in tilted
magnetic fields with an in-plane component up to 5 T. The observed increase of
the cyclotron effective mass reaches almost 5 \% of its zero field value which
is in good agreement with results of a self-consistent calculation.Comment: 4 pages, Revtex, figures can be obtained on request from
[email protected]; to appear in Phys. Rev. B (in press). No changes, the
corrupted submission replace
Calibration of centre-of-mass energies at LEP 2 for a precise measurement of the W boson mass
The determination of the centre-of-mass energies for all LEP 2 running is
presented. Accurate knowledge of these energies is of primary importance to set
the absolute energy scale for the measurement of the W boson mass. The beam
energy between 80 and 104 GeV is derived from continuous measurements of the
magnetic bending field by 16 NMR probes situated in a number of the LEP
dipoles. The relationship between the fields measured by the probes and the
beam energy is defined in the NMR model, which is calibrated against precise
measurements of the average beam energy between 41 and 61 GeV made using the
resonant depolarisation technique. The validity of the NMR model is verified by
three independent methods: the flux-loop, which is sensitive to the bending
field of all the dipoles of LEP; the spectrometer, which determines the energy
through measurements of the deflection of the beam in a magnet of known
integrated field; and an analysis of the variation of the synchrotron tune with
the total RF voltage. To obtain the centre-of-mass energies, corrections are
then applied to account for sources of bending field external to the dipoles,
and variations in the local beam energy at each interaction point. The relative
error on the centre-of-mass energy determination for the majority of LEP 2
running is 1.2 x 10^{-4}, which is sufficiently precise so as not to introduce
a dominant uncertainty on the W mass measurement.Comment: 79 pages, 45 figures, submitted to EPJ
Fishes of the Charlotte Harbor Estuarine System, Florida
To date, 255 fish species in 95 families have been reliably reported from the Charlotte Harbor estuarine system in southwest Florida. The species list was compiled from recent fishery-independent collections, a review of reports and peer-reviewed literature, and examination of cataloged specimens at the Florida Museum of Natural History. Thirty-nine species are new records for this estuarine system. Many of the newly documented species are common on the west Florida continental shelf and associated inshore habitats. Twenty-two previously reported species were not included in the species list presented herein on the basis of more recent research, doubtful original identifications, or questionable locality data
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