11,479 research outputs found
The intermediate age open cluster NGC 2660
We present CCD UBVI photometry of the intermediate old open cluster NGC2660,
covering from the red giants region to about seven magnitudes below the main
sequence turn-off. Using the synthetic Colour - Magnitude Diagram method, we
estimate in a self-consistent way values for distance modulus ((m-M)0 ~= 12.2),
reddening (E(B-V) ~= 0.40), metallicity ([Fe/H] about solar), and age (age ~ 1
Gyr). A 30% population of binary stars turns out to be probably present.Comment: 12 pages, 8 (encapsulated) figures, to be published on MNRA
Detection of t(7;12)(q36;p13) in paediatric leukaemia using dual colour fluorescence in situ hybridisation
The identification of chromosomal rearrangements is of utmost importance for the diagnosis and classification of specific leukaemia subtypes and therefore has an impact on therapy choices in individual cases. The t(7;12)(q36;p13) is a cryptic rearrangement that is difficult to recognise using conventional cytogenetic methods and is often undetected by reverse transcription polymerase chain reaction due to the absence of a fusion transcript in many cases. Here we present a reliable and easy to use dual colour fluorescence in situ hybridisation assay for the detection of the t(7;12)(q36;p13) rearrangement. A comparison with previous similar work is given and advantages and limitations of this novel approach are discussed
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HLXB9 gene expression, and nuclear location during in vitro neuronal differentiation in the SK-N-BE neuroblastoma cell line
Copyright @ 2014 Leotta et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Different parts of the genome occupy specific compartments of the cell nucleus based on the gene content and the transcriptional activity. An example of this is the altered nuclear positioning of the HLXB9 gene in leukaemia cells observed in association with its over-expression. This phenomenon was attributed to the presence of a chromosomal translocation with breakpoint proximal to the HLXB9 gene. Before becoming an interesting gene in cancer biology, HLXB9 was studied as a developmental gene. This homeobox gene is also known as MNX1 (motor neuron and pancreas homeobox 1) and it is relevant for both motor neuronal and pancreatic beta cells development. A spectrum of mutations in this gene are causative of sacral agenesis and more broadly, of what is known as the Currarino Syndrome, a constitutional autosomal dominant disorder. Experimental work on animal models has shown that HLXB9 has an essential role in motor neuronal differentiation. Here we present data to show that, upon treatment with retinoic acid, the HLXB9 gene becomes over-expressed during the early stages of neuronal differentiation and that this corresponds to a reposition of the gene in the nucleus. More precisely, we used the SK-N-BE human neuroblastoma cell line as an in vitro model and we demonstrated a transient transcription of HLXB9 at the 4th and 5th days of differentiation that corresponded to the presence, predominantly in the cell nuclei, of the encoded protein HB9. The nuclear positioning of the HLXB9 gene was monitored at different stages: a peripheral location was noted in the proliferating cells whereas a more internal position was noted during differentiation, that is while HLXB9 was transcriptionally active. Our findings suggest that HLXB9 can be considered a marker of early neuronal differentiation, possibly involving chromatin remodeling pathways
Galactic Evolution Of D And 3He Including Stellar Production Of 3He
New stellar models which track the production and destruction of He (and
D) have been evolved for a range of stellar masses , metallicities and initial (main
sequence) He mass fractions . Armed
with the He yields from these stellar models we have followed the evolution
of D and He using a variety of chemical evolution models with and without
infall of primordial or processed material. Production of new He by the
lower mass stars overwhelms any reasonable primordial contributions and leads
to predicted abundances in the presolar nebula and/or the present interstellar
medium in excess of the observationally inferred values. This result, which
obtains even for zero primordial D and He, and was anticipated by Rood,
Steigman \& Tinsley (1976), is insensitive to the choice of chemical evolution
model; it is driven by the large He yields from low mass stars. In an
attempt to ameliorate this problem we have considered a number of non-standard
models in which the yields from low mass stars have been modified. Although
several of these non-standard models may be consistent with the He data,
they may be inconsistent with observations of C/C, O and,
most seriously, the super-He rich planetary nebulae (Rood, Bania \& Wilson
1992). Even using the most extreme of these non-standard models (Hogan 1995),
we obtain a generous upper bound to pre-galactic He: X which, nonetheless, leads to a stringent lower bound to the
universal density of nucleons.Comment: 21 pages, plus 10 figures, accepted by Ap
Temperature-dependent density profiles of trapped boson-fermion mixtures
We present a semiclassical three-fluid model for a Bose-condensed mixture of
interacting Bose and Fermi gases confined in harmonic traps at finite
temperature. The model is used to characterize the experimentally relevant
behaviour of the equilibrium density profile of the fermions with varying
composition and temperature across the onset of degeneracy, for coupling
strengths relevant to a mixture of
K and K atoms.Comment: 9 pages, 2 postscript figures, accepted for publication in Eur. Phys.
Jour.
Kinetic energy of a trapped Fermi gas interacting with a Bose-Einstein condensate
We study a confined mixture of bosons and fermions in the regime of quantal
degeneracy, with particular attention to the effects of the interactions on the
kinetic energy of the fermionic component. We are able to explore a wide region
of system parameters by identifying two scaling variables which completely
determine its state at low temperature. These are the ratio of the
boson-fermion and boson-boson interaction strengths and the ratio of the radii
of the two clouds. We find that the effect of the interactions can be sizeable
for reasonable choices of the parameters and that its experimental study can be
used to infer the sign of the boson-fermion scattering length. The interplay
between interactions and thermal effects in the fermionic kinetic energy is
also discussed.Comment: REVTEX, 8 pages, 6 figures included. Small corrections to text and
figures, accepted for publication in EPJ
Transition to hydrodynamics in colliding fermion clouds
We study the transition from the collisionless to the hydrodynamic regime in
a two-component spin-polarized mixture of 40K atoms by exciting its dipolar
oscillation modes inside harmonic traps. The time evolution of the mixture is
described by the Vlasov-Landau equations and numerically solved with a fully
three-dimensional concurrent code. We observe a master/slave behaviour of the
oscillation frequencies depending on the dipolar mode that is excited.
Regardless of the initial conditions, the transition to hydrodynamics is found
to shift to lower values of the collision rate as temperature decreases.Comment: 11 pages, iop style. submitted to the proceedings of the Levico 2003
worksho
Excised acoustic black holes: the scattering problem in the time domain
The scattering process of a dynamic perturbation impinging on a draining-tub
model of an acoustic black hole is numerically solved in the time domain.
Analogies with real black holes of General Relativity are explored by using
recently developed mathematical tools involving finite elements methods,
excision techniques, and constrained evolution schemes for strongly hyperbolic
systems. In particular it is shown that superradiant scattering of a
quasi-monochromatic wavepacket can produce strong amplification of the signal,
offering the possibility of a significant extraction of rotational energy at
suitable values of the angular frequency of the vortex and of the central
frequency of the wavepacket. The results show that theoretical tools recently
developed for gravitational waves can be brought to fruition in the study of
other problems in which strong anisotropies are present.Comment: 8 pages, 9 figure
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