363 research outputs found
Dynamics of short pressure probes
Report presents practical information for incorporating particle impact protection features and average total pressure measurement into probe design while optimizing probe transient response. Computer program calculates probe response, based on Bergh-Tijdeman equation
Welcome to the Twilight Zone: The Mid-Infrared Properties of Poststarburst Galaxies
We investigate the optical and Wide-field Survey Explorer (WISE) colors of
"E+A" identified post-starburst galaxies, including a deep analysis on 190
post-starbursts detected in the 2{\mu}m All Sky Survey Extended Source Catalog.
The post-starburst galaxies appear in both the optical green valley and the
WISE Infrared Transition Zone (IRTZ). Furthermore, we find that post-starbursts
occupy a distinct region [3.4]-[4.6] vs. [4.6]-[12] WISE colors, enabling the
identification of this class of transitioning galaxies through the use of
broad-band photometric criteria alone. We have investigated possible causes for
the WISE colors of post-starbursts by constructing a composite spectral energy
distribution (SED), finding that mid-infrared (4-12{\mu}m) properties of
post-starbursts are consistent with either 11.3{\mu}m polycyclic aromatic
hydrocarbon emission, or Thermally Pulsating Asymptotic Giant Branch (TP-AGB)
and post-AGB stars. The composite SED of extended post- starburst galaxies with
22{\mu}m emission detected with signal to noise >3 requires a hot dust
component to produce their observed rising mid-infrared SED between 12 and
22{\mu}m. The composite SED of WISE 22{\mu}m non-detections (S/N<3), created by
stacking 22{\mu}m images, is also flat, requiring a hot dust component. The
most likely source of this mid-infrared emission of these E+A galaxies is a
buried active galactic nucleus. The inferred upper limit to the Eddington
ratios of post-starbursts are 1e-2 to 1e-4, with an average of 1e-3. This
suggests that AGNs are not radiatively dominant in these systems. This could
mean that including selections able to identify active galactic nuclei as part
of a search for transitioning and post-starburst galaxies would create a more
complete census of the transition pathways taken as a galaxy quenches its star
formation.Comment: 13 pages, 11 figures, accepted for publication in the Astrophysical
Journa
Casimir forces in binary liquid mixtures
If two ore more bodies are immersed in a critical fluid critical fluctuations
of the order parameter generate long ranged forces between these bodies. Due to
the underlying mechanism these forces are close analogues of the well known
Casimir forces in electromagnetism. For the special case of a binary liquid
mixture near its critical demixing transition confined to a simple parallel
plate geometry it is shown that the corresponding critical Casimir forces can
be of the same order of magnitude as the dispersion (van der Waals) forces
between the plates. In wetting experiments or by direct measurements with an
atomic force microscope the resulting modification of the usual dispersion
forces in the critical regime should therefore be easily detectable. Analytical
estimates for the Casimir amplitudes Delta in d=4-epsilon are compared with
corresponding Monte-Carlo results in d=3 and their quantitative effect on the
thickness of critical wetting layers and on force measurements is discussed.Comment: 34 pages LaTeX with revtex and epsf style, to appear in Phys. Rev.
A fully parallel, high precision, N-body code running on hybrid computing platforms
We present a new implementation of the numerical integration of the
classical, gravitational, N-body problem based on a high order Hermite's
integration scheme with block time steps, with a direct evaluation of the
particle-particle forces. The main innovation of this code (called HiGPUs) is
its full parallelization, exploiting both OpenMP and MPI in the use of the
multicore Central Processing Units as well as either Compute Unified Device
Architecture (CUDA) or OpenCL for the hosted Graphic Processing Units. We
tested both performance and accuracy of the code using up to 256 GPUs in the
supercomputer IBM iDataPlex DX360M3 Linux Infiniband Cluster provided by the
italian supercomputing consortium CINECA, for values of N up to 8 millions. We
were able to follow the evolution of a system of 8 million bodies for few
crossing times, task previously unreached by direct summation codes. The code
is freely available to the scientific community.Comment: Paper submitted to Journal of Computational Physics consisting in 28
pages, 9 figures.The previous submitted version was lacking of the
bibliography, for a Tex proble
AGN Feedback Driven Molecular Outflow in NGC 1266
NGC 1266 is a nearby field galaxy observed as part of the ATLAS3D survey
(Cappellari et al. 2011). NGC 1266 has been shown to host a compact (< 200 pc)
molecular disk and a mass-loaded molecular outflow driven by the AGN (Alatalo
et al. 2011). Very Long Basline Array (VLBA) observations at 1.65 GHz revealed
a compact (diameter < 1.2 pc), high bright- ness temperature continuum source
most consistent with a low-level AGN origin. The VLBA continuum source is
positioned at the center of the molecular disk and may be responsible for the
expulsion of molecular gas in NGC 1266. Thus, the candidate AGN-driven
molecular outflow in NGC 1266 supports the picture in which AGNs do play a
significant role in the quenching of star formation and ultimately the
evolution of the red sequence of galaxies.Comment: 2 pages, Proceedings from IAU Symposium 290: Feeding compact objects,
Accretion on all scale
Identification and characterisation of tomato torrado virus, a new plant picorna-like virus from tomato
A new virus was isolated from tomato plants from the Murcia region in Spain which showed symptoms of ‘torrado disease’ very distinct necrotic, almost burn-like symptoms on leaves of infected plants. The virus particles are isometric with a diameter of approximately 28 nm. The viral genome consists of two (+)ssRNA molecules of 7793 (RNA1) and 5389 nts (RNA2). RNA1 contains one open reading frame (ORF) encoding a predicted polyprotein of 241 kDa that shows conserved regions with motifs typical for a protease-cofactor, a helicase, a protease and an RNA-dependent RNA polymerase. RNA2 contains two, partially overlapping ORFs potentially encoding proteins of 20 and 134 kDa. These viral RNAs are encapsidated by three proteins with estimated sizes of 35, 26 and 23 kDa. Direct protein sequencing mapped these coat proteins to ORF2 on RNA2. Phylogenetic analyses of nucleotide and derived amino acid sequences showed that the virus is related to but distinct from viruses belonging to the genera Sequivirus, Sadwavirus and Cheravirus. This new virus, for which the name tomato torrado virus is proposed, most likely represents a member of a new plant virus genus
Quenching of Star Formation in Molecular Outflow Host NGC 1266
We detail the rich molecular story of NGC 1266, its serendipitous discovery
within the ATLAS3D survey (Cappellari et al. 2011) and how it plays host to an
AGN-driven molecular outflow, potentially quenching all of its star formation
(SF) within the next 100 Myr. While major mergers appear to play a role in
instigating outflows in other systems, deep imaging of NGC 1266 as well as
stellar kinematic observations from SAURON, have failed to provide evidence
that NGC 1266 has recently been involved in a major interaction. The molecular
gas and the instantaneous SF tracers indicate that the current sites of star
formation are located in a hypercompact disk within 200 pc of the nucleus (Fig.
1; SF rate ~ 2 Msuns/yr). On the other hand, tracers of recent star formation,
such as the H{\beta} absorption map from SAURON and stellar population analysis
show that the young stars are distributed throughout a larger area of the
galaxy than current star formation. As the AGN at the center of NGC 1266
continues to drive cold gas out of the galaxy, we expect star formation rates
to decline as the star formation is ultimately quenched. Thus, NGC 1266 is in
the midst of a key portion of its evolution and continued studies of this
unique galaxy may help improve our understanding of how galaxies transition
from the blue to the red sequence (Alatalo et al. 2011).Comment: 1 page, Proceedings IAU symposium No. 292: Molecular gas, dust and
star formation in galaxies, ed. by Tony Wong and Juergen Ot
Male age is associated with extra-pair paternity, but not with extra-pair mating behaviour
Extra-pair paternity is the result of copulation between a female and a male other than her social partner. In socially monogamous birds, old males are most likely to sire extra-pair offspring. The male manipulation and female choice hypotheses predict that age-specific male mating behaviour could explain this old-over-young male advantage. These hypotheses have been difficult to test because copulations and the individuals involved are hard to observe. Here, we studied the mating behaviour and pairing contexts of captive house sparrows, Passer domesticus. Our set-up mimicked the complex social environment experienced by wild house sparrows. We found that middle-aged males, which would be considered old in natural populations, gained most extra-pair paternity. However, both, female solicitation behaviour and subsequent extra-pair matings were not associated with male age. Further, copulations were more likely when solicited by females than when initiated by males (i.e. unsolicited copulations). Male initiated within-pair copulations were more common than male initiated extra-pair copulations. To conclude, our results did not support either hypothesis regarding age-specific male mating behaviour. Instead, female choice, independent of male age, governed copulation success, especially in an extra-pair context. Post-copulatory mechanisms might determine why older males sire more extra-pair offspring
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