1,664 research outputs found
An Extinction Map and Color Magnitude Diagram for the Globular Cluster NGC 3201
Differential variations of up to mag on a scale of
arcminutes across NGC 3201 are presented in the form of an extinction map. This
map, created by calculating average values for stars in small
subregions of the field with respect to a fiducial region, greatly improves the
appearance of the CMD of the cluster. We describe how we implemented this
technique in detail with our data for NGC 3201. A comparison between our map
and that of the same region extracted from the COBE/DIRBE reddening maps
published by Schlegel, Finkbeiner, & Davis (1998) (SFD) displays larger-scale
similarities between the two maps as well as smaller-scale features which show
up in our map but not in the SFD map. Several methods of determining an
zeropoint to add to our differential extinction map are presented.
Isochrone fitting proved to be the most successful one, but it produces an
average for the cluster which is smaller than previously published
values by . Finally, our results seem to support the statement
by Arce & Goodman (1999) that the SFD maps overestimate the reddening in
regions of high extinction.Comment: 19 pages, 12 figures, 1 table, accepted for publication in AJ (March
2001). Full resolution version may be obtained at
http://www.astro.lsa.umich.edu/users/kaspar/html/ngc3201.pdf (PDF) and at
http://www.astro.lsa.umich.edu/users/kaspar/html/ngc3201.ps.gz (PS
Mapping Differential Reddening in the Inner Galactic Globular Cluster System
A serious limitation in the study of many globular clusters—especially those located near the Galactic center—has been the existence of large and differential extinction by foreground dust. In a series of papers, we intend to map the differential extinction and remove its effects, using a new dereddening technique, in a sample of clusters in the direction of the inner Galaxy, observed using the Magellan 6.5 m telescope and the Hubble Space Telescope. These observations and their analysis will let us produce high-quality color-magnitude diagrams of these poorly studied clusters that will allow us to determine these clusters' relative ages, distances, and chemistry and to address important questions about the formation and the evolution of the inner Galaxy. We also intend to use the maps of the differential extinction to sample and characterize the interstellar medium along the numerous low-latitude lines of sight where the clusters in our sample lie. In this first paper, we describe in detail our dereddening method along with the powerful statistics tools that allow us to apply it, and we show the kind of results that we can expect, applying the method to M62, one of the clusters in our sample. The width of the main sequence and lower red giant branch narrows by a factor of two after applying our dereddening technique, which will significantly help to constrain the age, distance, and metallicity of the cluster
Uncloaking globular clusters in the inner Galaxy
Extensive photometric studies of the globular clusters located towards the
center of the Milky Way have been historically neglected. The presence of
patchy differential reddening in front of these clusters has proven to be a
significant obstacle to their detailed study. We present here a well-defined
and reasonably homogeneous photometric database for 25 of the brightest
Galactic globular clusters located in the direction of the inner Galaxy. These
data were obtained in the B, V, and I bands using the Magellan 6.5m telescope
and the Hubble Space Telescope. A new technique is extensively used in this
paper to map the differential reddening in the individual cluster fields, and
to produce cleaner, dereddened color-magnitude diagrams for all the clusters in
the database. Subsequent papers will detail the astrophysical analysis of the
cluster populations, and the properties of the obscuring material along the
clusters' lines of sight.Comment: Accepted for publication in A
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Prmt5 is a regulator of muscle stem cell expansion in adult mice.
Skeletal muscle stem cells (MuSC), also called satellite cells, are indispensable for maintenance and regeneration of adult skeletal muscles. Yet, a comprehensive picture of the regulatory events controlling the fate of MuSC is missing. Here, we determine the proteome of MuSC to design a loss-of-function screen, and identify 120 genes important for MuSC function including the arginine methyltransferase Prmt5. MuSC-specific inactivation of Prmt5 in adult mice prevents expansion of MuSC, abolishes long-term MuSC maintenance and abrogates skeletal muscle regeneration. Interestingly, Prmt5 is dispensable for proliferation and differentiation of Pax7(+) myogenic progenitor cells during mouse embryonic development, indicating significant differences between embryonic and adult myogenesis. Mechanistic studies reveal that Prmt5 controls proliferation of adult MuSC by direct epigenetic silencing of the cell cycle inhibitor p21. We reason that Prmt5 generates a poised state that keeps MuSC in a standby mode, thus allowing rapid MuSC amplification under disease conditions
Zaboravljene tajne zanata
Prikaz knjige: Tajne o bojama. Priručnik za pripravu boja iz 15. stoljeća, prev. i prir. J. Matijević i J. Zelić; ur. K. Škarić, 2016
Discrete soliton ratchets driven by biharmonic fields
Directed motion of topological solitons (kinks or antikinks) in the damped
and AC-driven discrete sine-Gordon system is investigated. We show that if the
driving field breaks certain time-space symmetries, the soliton can perform
unidirectional motion. The phenomenon resembles the well known effects of
ratchet transport and nonlinear harmonic mixing. Direction of the motion and
its velocity depends on the shape of the AC drive. Necessary conditions for the
occurrence of the effect are formulated. In comparison with the previously
studied continuum case, the discrete case shows a number of new features:
non-zero depinning threshold for the driving amplitude, locking to the rational
fractions of the driving frequency, and diffusive ratchet motion in the case of
weak intersite coupling.Comment: 13 pages, 13 figure
Kulturna baština i konzerviranje – između tradicije i novih znanosti
Prikaz seminara: Nuklearne tehnike u zaštiti kulturne baštine u mediteranskoj regiji - međunarodni seminar i radionica, Institute for Conservation & Management of Cultural Heritage, Kalkara, Malta, 19.-23.9.2005
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