3,611 research outputs found
Velocity map imaging of the dynamics of reactions of Cl atoms with neopentane and tetramethyl silane
Channel diffusion of sodium in a silicate glass
We use classical molecular dynamics simulations to study the dynamics of
sodium atoms in amorphous NaO-4SiO. We find that the sodium
trajectories form a well connected network of pockets and channels. Inside
these channels the motion of the atoms is not cooperative but rather given by
independent thermally activated hops of individual atoms between the pockets.
By determining the probability that an atom returns to a given starting site,
we show that such events are not important for the dynamics of this system.Comment: 10 pages of Latex, 5 figures, one figure added, text expande
Sub-arcsecond high sensitivity measurements of the DG~Tau jet with e-MERLIN
We present very high spatial resolution deep radio continuum observations at
5 GHz (6 cm) made with e-MERLIN of the young stars DG Tau A and B. Assuming it
is launched very close (~=1 au) from the star, our results suggest that the DG
Tau A outflow initially starts as a poorly focused wind and undergoes
significant collimation further along the jet (~=50 au). We derive jet
parameters for DG Tau A and find an initial jet opening angle of 86 degrees
within 2 au of the source, a mass-loss rate of 1.5x10^-8 solar masses/yr for
the ionised component of the jet, and the total ejection/accretion ratio to
range from 0.06-0.3. These results are in line with predictions from MHD
jet-launching theories.Comment: Accepted MNRAS Letter
Linkage mapping of the gpdA gene of Aspergillus nidulans
In the last few years many genes of several Aspergillus species have been cloned and sequenced. For many of these genes mutant alleles and genetic linkage data are also available. However, for those genes for which no mutant alleles have been isolated, genetic mapping was not possible. Here we report linkage mapping of the glyceraldehyde-3- phosphate dehydrogenase gene (gpdA) of A. nidulans for which no mutant alleles have been isolated. The method used is applicable to all other cloned genes
First Observations of the Magnetic Field Geometry in Pre-stellar Cores
We present the first published maps of magnetic fields in pre-stellar cores,
to test theoretical ideas about the way in which the magnetic field geometry
affects the star formation process. The observations are JCMT-SCUBA maps of 850
micron thermal emission from dust. Linear polarizations at typically ten or
more independent positions in each of three objects, L1544, L183 and L43 were
measured, and the geometries of the magnetic fields in the plane of the sky
were mapped from the polarization directions. The observed polarizations in all
three objects appear smooth and fairly uniform. In L1544 and L183 the mean
magnetic fields are at an angle of around 30 degrees to the minor axes of the
cores. The L43 B-field appears to have been influenced in its southern half,
such that it is parallel to the wall of a cavity produced by a CO outflow from
a nearby T Tauri star, whilst in the northern half the field appears less
disturbed and has an angle of 44 degrees to the core minor axis. We briefly
compare our results with published models of magnetized cloud cores and
conclude that no current model can explain these observations simultaneously
with previous ISOCAM data.Comment: 13 pages, 3 figs, to appear in ApJ Letter
Discovery of the Fomalhaut C debris disc
Fomalhaut is one of the most interesting and well studied nearby stars,
hosting at least one planet, a spectacular debris ring, and two distant
low-mass stellar companions (TW PsA and LP 876-10, a.k.a. Fomalhaut B & C). We
observed both companions with Herschel, and while no disc was detected around
the secondary, TW PsA, we have discovered the second debris disc in the
Fomalhaut system, around LP 876-10. This detection is only the second case of
two debris discs seen in a multiple system, both of which are relatively wide
(3000 AU for HD 223352/40 and 158 kAU [0.77 pc] for Fomalhaut/LP
876-10). The disc is cool (24K) and relatively bright, with a fractional
luminosity , and represents the rare
observation of a debris disc around an M dwarf. Further work should attempt to
find if the presence of two discs in the Fomalhaut system is coincidental,
perhaps simply due to the relatively young system age of 440 Myr, or if the
stellar components have dynamically interacted and the system is even more
complex than it currently appears.Comment: Published in MNRAS Letters. Merry Xma
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