444 research outputs found
Trends in high energy particle accelerators
Particle accelerators of higher and higher energy and intensity are required, as the investigation of subatomic matter needs to be pursued with higher and higher resolving power. To keep pace with this need while keeping physical dimensions and the cost of accelerator installations affordable, ever new ideas and technologies must be devised. After a brief general introduction and a summary of accelerator physics basics, we review the main lines of development of state of the art installations recently built, in construction or on the drafting board. New physics and technology challenges they pose and main topics still open to further research and development are also outlined
Modelowanie Rozkladu Pól Magnetycznych Sluzacych Do Prowadzenia Wiazki Plazmy Powstajacej W Wyladowaniach Lukowych
High-resolution observations of molecular emission lines toward the CI Tau proto-planetary disc: Planet-carved gaps or shadowing?
Recent observations have revealed that most proto-planetary discs show a
pattern of bright rings and dark gaps. However, most of the high-resolution
observations have focused only on the continuum emission. In this Paper we
present high-resolution ALMA band 7 (0.89mm) observations of the disc around
the star CI Tau in the CO & CO -2 and CS -6 emission
lines. Our recent work demonstrated that the disc around CI Tau contains three
gaps and rings in continuum emission, and we look for their counterparts in the
gas emission. While we find no counterpart of the third gap and ring in
CO, the disc has a gap in emission at the location of the second
continuum ring (rather than gap). We demonstrate that this is mostly an
artefact of the continuum subtraction, although a residual gap still remains
after accounting for this effect. Through radiative transfer modelling we
propose this is due to the inner disc shadowing the outer parts of the disc and
making them colder. This raises a note of caution in mapping high-resolution
gas emission lines observations to the gas surface density - while possible,
this needs to be done carefully. In contrast to CO, CS emission shows
instead a ring morphology, most likely due to chemical effects. Finally, we
note that CO is heavily absorbed by the foreground preventing any
morphological study using this line
Detecting the halo heating from AGN feedback with ALMA
The Sunyaev-Zel'dovich (SZ) effect can potentially be used to investigate the
heating of the circumgalactic medium and subsequent suppression of cold gas
accretion onto the host galaxy caused by quasar feedback. We use a deep ALMA
observation of HE0515-4414 in band 4, the most luminous quasar known at the
peak of cosmic star formation (z=1.7), to search for the SZ signal tracing the
heating of the galaxy's halo. ALMA's sensitivity to a broad range of spatial
scales enables us to disentangle emitting compact sources from the negative,
extended SZ signal. We obtain a marginal S-Z detection (~3.3) on scales
of about 300 kpc (30-40 arcsec), at the 0.2 mJy level, 0.5 mJy after applying a
correction factor for primary beam attenuation and flux that is resolved out by
the array. We show that our result is consistent with a simulated ALMA
observation of a similar quasar in the FABLE cosmological simulations. We
emphasise that detecting an SZ signal is more easily achieved in the visibility
plane than in the (inferred) images. We also confirm a marginal detection
(3.2) of a potential SZ dip on smaller scales (<100 kpc) already
claimed by other authors, possibly highlighting the complex structure of the
halo heating. Finally, we use SZ maps from the FABLE cosmological simulations,
convolved with ALMA simulations, to illustrate that band 3 observations are
much more effective in detecting the SZ signal with higher significance, and
discuss the optimal observing strategy.RM and SC acknowledge ERC Advanced Grant 695671 "QUENCH". SB, RM and SC acknowledge support by the Science and Technology Facilities Council (STFC). M.T. has been supported by the DISCSIM project, grant agreement 341137 funded by the European Research Council under ERC-2013-ADG and by the UK Science and Technology research Council (STFC)
Intranucleolar localization of DNA topoisomerase IIalpha is a distinctive feature of necrotic, but not of apoptotic, Jurkat T-cells.
Gas Density Perturbations Induced by One or More Forming Planets in the AS 209 Protoplanetary Disk as Seen with ALMA
The formation of planets occurs within protoplanetary disks surrounding young
stars, resulting in perturbation of the gas and dust surface densities. Here,
we report the first evidence of spatially resolved gas surface density
() perturbation towards the AS~209 protoplanetary disk from the
optically thin CO () emission. The observations were carried out
at 1.3~mm with ALMA at a spatial resolution of about 0.3\arcsec
0.2\arcsec (corresponding to 38 25 au). The CO
emission shows a compact (60~au), centrally peaked emission and an outer
ring peaking at 140~au, consistent with that observed in the continuum emission
and, its azimuthally averaged radial intensity profile presents a deficit that
is spatially coincident with the previously reported dust map. This deficit can
only be reproduced with our physico-thermochemical disk model by lowering
by nearly an order of magnitude in the dust gaps. Another
salient result is that contrary to CO, the DCO () emission
peaks between the two dust gaps. We infer that the best scenario to explain our
observations (CO deficit and DCO enhancement) is a gas
perturbation due to forming-planet(s), that is commensurate with previous
continuum observations of the source along with hydrodynamical simulations. Our
findings confirm that the previously observed dust gaps are very likely due to
perturbation of the gas surface density that is induced by a planet of at least
0.2~M in formation. Finally, our observations also show the
potential of using CO isotopologues to probe the presence of saturn mass
planet(s)
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