6,440 research outputs found
The phase transitions in 2D Z(N) vector models for N>4
We investigate both analytically and numerically the renormalization group
equations in 2D Z(N) vector models. The position of the critical points of the
two phase transitions for N>4 is established and the critical index \nu\ is
computed. For N=7, 17 the critical points are located by Monte Carlo
simulations and some of the corresponding critical indices are determined. The
behavior of the helicity modulus is studied for N=5, 7, 17. Using these and
other available Monte Carlo data we discuss the scaling of the critical points
with N and some other open theoretical problems.Comment: 19 pages, 8 figures, 10 tables; version to appear on Phys. Rev.
Constraining the ages of the fireballs in the wake of the dIrr galaxy VCC1217 / IC3418
A complex of Halpha emitting blobs with strong FUV excess is associated to
the dIrr galaxy VCC1217 / IC3418 (Hester et al. 2010), and extends up to 17 Kpc
in the South-East direction. These outstanding features can be morphologically
divided into diffuse filaments and compact knots, where most of the star
formation activity traced by Halpha takes place. We investigate the properties
of the galaxy and the blobs using a multiwavelength approach in order to
constrain their origin. We collect publicly available data in UV and Halpha and
observe the scene in the optical U,g,r,i bands with LBT. The photometric data
allows to evaluate the star formation rate and to perform a SED fitting
separately of the galaxy and the blobs in order to constrain their stellar
population age. Moreover we analyze the color and luminosity profile of the
galaxy and its spectrum to investigate its recent interaction with the Virgo
cluster. Our analysis confirms that the most plausible mechanism for the
formation of the blobs is ram pressure stripping by the Virgo cluster IGM. The
galaxy colors, luminosity profile and SED are consistent with a sudden gas
depletion in the last few hundred Myr. The SED fitting of the blobs constrains
their ages in < 400 Myr.Comment: 10 pages, 11 figures, accepted for publication in Astronomy and
Astrophysic
Murine models of sleep apnea: functional implications of altered macrophage polarity and epigenetic modifications in adipose and vascular tissues
Obstructive sleep apnea (OSA) is a highly prevalent disease across the lifespan, is characterized by chronic intermittent hypoxia and sleep fragmentation, and has been independently associated with substantial cardiometabolic morbidity. However, the reversibility of end-organ morbidity with treatment is not always apparent, suggesting that both tissue remodeling and epigenetic mechanisms may be operationally involved. Here, we review the cumulative evidence focused around murine models of OSA to illustrate the temporal dependencies of cardiometabolic dysfunction and its reversibility, and more particularly to discuss the critical contributions of tissue macrophages to adipose tissue insulin resistance and vascular atherogenesis. In addition, we describe initial findings potentially implicating epigenetic alterations in both the emergence of the cardiometabolic morbidity of OSA, and in its reversibility with treatment. We anticipate that improved understanding of macrophage biology and epigenetics in the context of intermittent hypoxia and sleep fragmentation will lead to discovery of novel therapeutic targets and improved cardiovascular and metabolic outcomes in OSA
Hydrogen Arrangements on Defective Quasi-Molecular BN Fragments
Considering the ever-increasing interest in metal-free materials, some potential chemical applications of quasi-molecular boron nitride (BN) derivatives were tested. Specifically, the behavior of BN fragments was analyzed when given defects, producing local electron density changes, were introduced by using topological engineering approaches. The inserted structural faults were Schottky-like divacancy (BN-d) defects, assembled in the fragment frame by the subtraction of one pair of B and N atoms or Stone-Wales (SW) defects. This study is aimed at highlighting the role of these important classes of defects in BN materials hypothesizing their future use in H-2-based processes, related to either (i) H-2 activation or (ii) H-2 production, from preadsorbed hydrogenated molecular species on BN sites. Here, it has been observed that BN species, embodying SW defects, are characterized by endothermic H-2 adsorption and fragmentation phenomena in order to guess their potential use in processes based on the transformation or production of hydrogen. On the contrary, in the presence of BN-d defects, and for reasons strictly related to local structural changes occurring along with the hydrogen rearrangements on the defective BN fragments, a possible use can be inferred. Precautions must be however taken to decrease the material rigidity that could actually decrease the ability of the BN fragment to flatten. This conversely seems to be a necessary requirement to have strong exothermic effects, following the rearrangements of the H-2 molecules
Advances on Testing C-Planarity of Embedded Flat Clustered Graphs
We show a polynomial-time algorithm for testing c-planarity of embedded flat
clustered graphs with at most two vertices per cluster on each face.Comment: Accepted at GD '1
The Arecibo Galaxy Environment Survey: II. A HI view of the Abell cluster 1367 and its outskirts
We present 21 cm HI line observations of 5x1 square degrees centered on the
local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment
Survey. One hundred sources are detected (79 new HI measurements and 50 new
redshifts), more than half belonging to the cluster core and its infalling
region. Combining the HI data with SDSS optical imaging we show that our HI
selected sample follows scaling relations similar to the ones usually observed
in optically selected samples. Interestingly all galaxies in our sample appear
to have nearly the same baryon fraction independently of their size, surface
brightness and luminosity. The most striking difference between HI and
optically selected samples resides in their large scale distribution: whereas
optical and X-ray observations trace the cluster core very well, in HI there is
almost no evidence of the presence of the cluster. Some implications on the
determination of the cluster luminosity function and HI distribution for
samples selected at different wavelength are also discussed.Comment: 22 pages, 15 figures, 4 tables. Accepted for publication on MNRAS
Main Journal. High resolution version of this paper can be downloaded at
http://www.astro.cf.ac.uk/pub/Luca.Cortese/papers/ages_a1367.pdf . Datacubes
and catalogs can be downloaded at http://www.naic.edu/~ages/public_data.htm
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