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  • 1
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    Emerging Roles of Mammalian Sirtuin SIRT7 in Cancer (2014)
    The American Association for Cancer Research (AACR)
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    Publication Date: 2014-04-02
    Description: SIRT7 belongs to the Sirtuin family of NAD-dependent enzymes, the members of which play diverse roles in aging, metabolism, and disease biology. Increased SIRT7 expression is observed in human cancers and growing evidence suggests important SIRT7 functions in fundamental cellular programs with an impact on oncogenic transformation and tumor biology. SIRT7 associates with chromatin, where it catalyzes selective deacetylation of lysine 18 on histone H3 (H3K18), an emerging epigenetic biomarker of aggressive tumors and poor clinical outcome in patients with cancer. Through H3K18 deacetylation at specific promoters, SIRT7 controls a tumor-suppressive gene expression program that stabilizes the transformed state of cancer cells. SIRT7 also orchestrates several molecular processes, including rRNA and tRNA synthesis, which ultimately promote the increased ribosome biogenesis necessary for tumor cell growth and proliferation. Remarkably, inactivation of SIRT7 can reverse the transformed phenotype of cancer cells and reduce their tumorigenicity in vivo. These findings place SIRT7 at the crossroads of chromatin signaling, metabolic, and tumor-regulatory pathways. Thus, SIRT7 is a promising pharmacologic target for epigenetic cancer therapy. The development of SIRT7 modulators may allow new therapeutic strategies that control tumor progression by reprogramming the chromatin landscape and biosynthetic machinery of cancer cells. Clin Cancer Res; 20(7); 1741–6. ©2014 AACR .
    Print ISSN: 1078-0432
    Electronic ISSN: 1557-3265
    Topics: Medicine
    Published by The American Association for Cancer Research (AACR)
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  • 2
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    An eclipsing-binary distance to the Large Magellanic Cloud accurate to two per cent (2013)
    Nature Publishing Group (NPG)
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    Publication Date: 2013-03-08
    Description: In the era of precision cosmology, it is essential to determine the Hubble constant to an accuracy of three per cent or better. At present, its uncertainty is dominated by the uncertainty in the distance to the Large Magellanic Cloud (LMC), which, being our second-closest galaxy, serves as the best anchor point for the cosmic distance scale. Observations of eclipsing binaries offer a unique opportunity to measure stellar parameters and distances precisely and accurately. The eclipsing-binary method was previously applied to the LMC, but the accuracy of the distance results was lessened by the need to model the bright, early-type systems used in those studies. Here we report determinations of the distances to eight long-period, late-type eclipsing systems in the LMC, composed of cool, giant stars. For these systems, we can accurately measure both the linear and the angular sizes of their components and avoid the most important problems related to the hot, early-type systems. The LMC distance that we derive from these systems (49.97 +/- 0.19 (statistical) +/- 1.11 (systematic) kiloparsecs) is accurate to 2.2 per cent and provides a firm base for a 3-per-cent determination of the Hubble constant, with prospects for improvement to 2 per cent in the future.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pietrzynski, G -- Graczyk, D -- Gieren, W -- Thompson, I B -- Pilecki, B -- Udalski, A -- Soszynski, I -- Kozlowski, S -- Konorski, P -- Suchomska, K -- Bono, G -- Moroni, P G Prada -- Villanova, S -- Nardetto, N -- Bresolin, F -- Kudritzki, R P -- Storm, J -- Gallenne, A -- Smolec, R -- Minniti, D -- Kubiak, M -- Szymanski, M K -- Poleski, R -- Wyrzykowski, L -- Ulaczyk, K -- Pietrukowicz, P -- Gorski, M -- Karczmarek, P -- England -- Nature. 2013 Mar 7;495(7439):76-9. doi: 10.1038/nature11878.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Universidad de Concepcion, Departamento de Astronomia, Casilla 160-C, Concepcion, Chile. pietrzyn@astrouw.edu.pl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23467166" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - VIII. The totally eclipsing double-giant system HD 187669 (2015)
    Oxford University Press
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    Publication Date: 2015-02-26
    Description: We present the first full orbital and physical analysis of HD 187669, recognized by the All-Sky Automated Survey (ASAS) as the eclipsing binary ASAS J195222-3233.7. We combined multi-band photometry from the ASAS and SuperWASP public archives and 0.41-m PROMPT robotic telescopes with our high-precision radial velocities from the HARPS spectrograph. Two different approaches were used for the analysis: (1) fitting to all data simultaneously with the WD code and (2) analysing each light curve (with jktebop ) and radial velocities separately and combining the partial results at the end. This system also shows a total primary (deeper) eclipse, lasting for about 6 d. A spectrum obtained during this eclipse was used to perform atmospheric analysis with the moog and sme codes to constrain the physical parameters of the secondary. We found that ASAS J195222-3233.7 is a double-lined spectroscopic binary composed of two evolved, late-type giants, with masses of M 1  = 1.504 ± 0.004 and M 2  = 1.505 ± 0.004 M , and radii of R 1  = 11.33 ± 0.28 and R 2  = 22.62 ± 0.50 R . It is slightly less metal abundant than the Sun, and has a P  = 88.39 d orbit. Its properties are well reproduced by a 2.38-Gyr isochrone, and thanks to the metallicity estimation from the totality spectrum and high precision of the masses, it was possible to constrain the age down to 0.1 Gyr. It is the first so evolved Galactic eclipsing binary measured with such good accuracy, and as such it is a unique benchmark for studying the late stages of stellar evolution.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 4
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    The cosmological lithium problem outside the Galaxy: the Sagittarius globular cluster M54 (2014)
    Oxford University Press
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    Publication Date: 2014-09-11
    Description: The cosmological Li problem is the observed discrepancy between Li abundance ( A (Li)) measured in Galactic dwarf, old and metal-poor stars (traditionally assumed to be equal to the initial value A(Li) 0 ), and that predicted by standard big bang nucleosynthesis (BBN) calculations (A(Li) BBN ). Here, we attack the Li problem by considering an alternative diagnostic, namely the surface Li abundance of red giant branch stars that in a colour–magnitude diagram populate the region between the completion of the first dredge-up and the red giant branch bump. We obtained high-resolution spectra with the FLAMES facility at the Very Large Telescope for a sample of red giants in the globular cluster M54, belonging to the Sagittarius dwarf galaxy. We obtain A(Li) = 0.93 ± 0.11 dex, translating – after taking into account the dilution due to the dredge-up – to initial abundances (A(Li) 0 ) in the range 2.35–2.29 dex, depending on whether or not atomic diffusion is considered. This is the first measurement of Li in the Sagittarius galaxy and the more distant estimate of A(Li) 0 in old stars obtained so far. The A(Li) 0 estimated in M54 is lower by ~0.35 dex than A(Li) BBN , hence incompatible at a level of ~3. Our result shows that this discrepancy is a universal problem concerning both the Milky Way and extragalactic systems. Either modifications of BBN calculations, or a combination of atomic diffusion plus a suitably tuned additional mixing during the main sequence, need to be invoked to solve the discrepancy.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    The Araucaria Project: accurate stellar parameters and distance to evolved eclipsing binary ASAS J180057-2333.8 in Sagittarius Arm (2015)
    Oxford University Press
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    Publication Date: 2015-06-12
    Description: We have analyzed the double-lined eclipsing binary system ASAS J180057-2333.8 from the All Sky Automated Survey (ASAS) catalogue. We measure absolute physical and orbital parameters for this system based on archival V -band and I -band ASAS photometry, as well as on high-resolution spectroscopic data obtained with ESO 3.6 m/HARPS and CORALIE spectrographs. The physical and orbital parameters of the system were derived with an accuracy of about 0.5–3 per cent. The system is a very rare configuration of two bright well-detached giants of spectral types K1 and K4 and luminosity class II. The radii of the stars are R 1 = 52.12 ± 1.38 and R 2 = 67.63 ± 1.40 R and their masses are M 1 = 4.914 ± 0.021 and M 2 = 4.875 ± 0.021 M . The exquisite accuracy of 0.5 per cent obtained for the masses of the components is one of the best mass determinations for giants. We derived a precise distance to the system of 2.14 ± 0.06 kpc (stat.) ± 0.05 (syst.) which places the star in the Sagittarius–Carina arm. The Galactic rotational velocity of the star is s = 258 ± 26 km s –1 assuming 0 = 238 km s –1 . A comparison with parsec isochrones places the system at the early phase of core helium burning with an age of slightly larger than 100 million years. The effect of overshooting on stellar evolutionary tracks was explored using the mesa star code.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 6
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    The origin and chemical evolution of the exotic globular cluster NGC 3201 (2013)
    Oxford University Press
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    Publication Date: 2013-07-14
    Description: NGC 3201 is a globular cluster (GC) which shows very peculiar kinematic characteristics including an extreme radial velocity and a highly retrograde orbit, strongly suggesting an extragalactic origin. Our aims are to study NGC 3201 in the context of multiple populations (MPs), hoping to constrain possible candidates for the self-enrichment by studying the chemical abundance pattern, as well as adding insight into the origin of this intriguing cluster. We present a detailed chemical abundance analysis of eight red giant branch stars using high-resolution spectroscopy. We measured 29 elements and found [Fe/H] = –1.53±0.01; we cannot rule out a metallicity spread of ~0.12 dex, and an α-enhancement typical of halo GCs. However, significant spreads are observed in the abundances of all light elements except for Mg. We confirm the presence of an extended Na–O anticorrelation. n-capture elements generally are dominated by the r-process, in good agreement with the bulk of Galactic GCs. The total (C+N+O) abundance is slightly supersolar and requires a small downward correction to the isochrone age, yielding 11.4 Gyr. Kinematically, NGC 3201 appears likely to have had an extragalactic origin but its chemical evolution is similar to most other, presumably native, Galactic GCs.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 7
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    Two groups of red giants with distinct chemical abundances in the bulge globular cluster NGC 6553 through the eyes of APOGEE (2016)
    Oxford University Press
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    Publication Date: 2016-11-29
    Description: Multiple populations revealed in globular clusters (GCs) are important windows to the formation and evolution of these stellar systems. The metal-rich GCs in the Galactic bulge are an indispensable part of this picture, but the high optical extinction in this region has prevented extensive research. In this work, we use the high-resolution near-infrared (NIR) spectroscopic data from Apache Point Observatory Galactic Evolution Experiment (APOGEE) to study the chemical abundances of NGC 6553, which is one of the most metal-rich bulge GCs. We identify 10 red giants as cluster members using their positions, radial velocities, iron abundances, and NIR photometry. Our sample stars show a mean radial velocity of –0.14 ± 5.47 km s –1 , and a mean [Fe/H] of –0.15 ± 0.05. We clearly separate two populations of stars in C and N in this GC for the first time. NGC 6553 is the most metal-rich GC where the multiple stellar population phenomenon is found until now. Substantial chemical variations are also found in Na, O, and Al. However, the two populations show similar Si, Ca, and iron-peak element abundances. Therefore, we infer that the CNO, NeNa, and MgAl cycles have been activated, but the MgAl cycle is too weak to show its effect on Mg. Type Ia and Type II supernovae do not seem to have significantly polluted the second generation stars. Comparing with other GC studies, NGC 6553 shows similar chemical variations as other relatively metal-rich GCs. We also confront current GC formation theories with our results, and suggest possible avenues for improvement in the models.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 8
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    The Araucaria Project: accurate stellar parameters and distance to evolved eclipsing binary ASAS J180057-2333.8 in Sagittarius Arm (2015)
    Oxford University Press
    Details
    Publication Date: 2015-05-31
    Description: We have analyzed the double-lined eclipsing binary system ASAS J180057-2333.8 from the All Sky Automated Survey (ASAS) catalogue. We measure absolute physical and orbital parameters for this system based on archival V -band and I -band ASAS photometry, as well as on high-resolution spectroscopic data obtained with ESO 3.6 m/HARPS and CORALIE spectrographs. The physical and orbital parameters of the system were derived with an accuracy of about 0.5–3 per cent. The system is a very rare configuration of two bright well-detached giants of spectral types K1 and K4 and luminosity class II. The radii of the stars are R 1 = 52.12 ± 1.38 and R 2 = 67.63 ± 1.40 R and their masses are M 1 = 4.914 ± 0.021 and M 2 = 4.875 ± 0.021 M . The exquisite accuracy of 0.5 per cent obtained for the masses of the components is one of the best mass determinations for giants. We derived a precise distance to the system of 2.14 ± 0.06 kpc (stat.) ± 0.05 (syst.) which places the star in the Sagittarius–Carina arm. The Galactic rotational velocity of the star is s = 258 ± 26 km s –1 assuming 0 = 238 km s –1 . A comparison with PARSEC isochrones places the system at the early phase of core helium burning with an age of slightly larger than 100 million years. The effect of overshooting on stellar evolutionary tracks was explored using the mesa star code.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    On the eclipsing binary ELHC 10 with occulting dark disc in the Large Magellanic Cloud (2016)
    Oxford University Press
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    Publication Date: 2016-02-06
    Description: We investigate the luminous star ELHC 10 located in the bar of the Large Magellanic Cloud (LMC), concluding that it is a SB1 long-period eclipsing binary where the main eclipse is produced by an opaque structure hiding the secondary star. For the more luminous component we determine an effective temperature of 6500 ± 250 K, log g = 1.0 ± 0.5 and luminosity 5970 L . From the radial velocities of their photospheric lines, we calculate a mass function of 7.37 ± 0.55 M . Besides Balmer and forbidden N ii emission, we find splitting of metallic lines, characterized by strong discrete absorption components, alternatively seen at the blue and red side of the photospheric spectrum. These observations hardly can be interpreted in terms of an structured atmosphere but might reflect mass streams in an interacting binary. The primary shows signatures of s-process nucleosynthesis and might be a low-mass post-asymptotic giant branch star with a rare evolutionary past if the binary is semidetached. The peak separation and constancy of radial velocity in H α suggest that most of the Balmer emission comes from a circumbinary disc.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    A spectroscopic study of the globular Cluster NGC 4147 (2016)
    Oxford University Press
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    Publication Date: 2016-06-11
    Description: We present the abundance analysis for a sample of 18 red giant branch stars in the metal-poor globular cluster NGC 4147 based on medium- and high-resolution spectra. This is the first extensive spectroscopic study of this cluster. We derive abundances of C, N, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Y, Ba, and Eu. We find a metallicity of [Fe/H] = –1.84 ± 0.02 and an α-enhancement of +0.38 ± 0.05 (errors on the mean), typical of halo globular clusters in this metallicity regime. A significant spread is observed in the abundances of light elements C, N, O, Na, and Al. In particular, we found an Na–O anticorrelation and Na–Al correlation. The cluster contains only ~15 per cent of stars that belong to the first generation (Na-poor and O-rich). This implies that it suffered a severe mass-loss during its lifetime. Its [Ca/Fe] and [Ti/Fe] mean values agree better with the Galactic halo trend than with the trend of extragalactic environments at the cluster metallicity. This possibly suggests that NGC 4147 is a genuine Galactic object at odd with what claimed by some author that proposed the cluster to be member of the Sagittarius dwarf galaxy. An antirelation between the light s- process element Y and Na may also be present.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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