Two distinct red giant branch populations in the globular cluster NGC 2419 as tracers of a merger event in the Milky Way

Recent spectroscopic observations of the outer halo globular cluster (GC) NGC 2419 show that it is unique among GCs, in terms of chemical abundance patterns, and some suggest that it was originated in the nucleus of a dwarf galaxy. Here we show, from the Subaru narrow-band photometry employing a calcium filter, that the red giant-branch (RGB) of this GC is split into two distinct subpopulations. Comparison with spectroscopy has confirmed that the redder RGB stars in the $hk$[=(Ca$-b)-(b-y)$] index are enhanced in [Ca/H] by $\sim$0.2 dex compared to the bluer RGB stars. Our population model further indicates that the calcium-rich second generation stars are also enhanced in helium abundance by a large amount ($\Delta$Y = 0.19). Our photometry, together with the results for other massive GCs (e.g., $\omega$ Cen, M22, and NGC 1851), suggests that the discrete distribution of RGB stars in the $hk$ index might be a universal characteristic of this growing group of peculiar GCs. The planned narrow-band calcium photometry for the Local Group dwarf galaxies would help to establish an empirical connection between these GCs and the primordial building blocks in the hierarchical merging paradigm of galaxy formation.Comment: 4 pages, 4 figures, 1 table, accepted for the publication in ApJ

Shifting Focus in Development Studies : Papers in Development and Society , 1998-2013

How has development studies – especially the one on and in East Asia in general, and South Korea in particular – changed over the last decade and a half? We trace the recent trends through a review of articles published in Development and Society (D&S). Bibliographic metadata on a total of 201 authors and 199 papers for the period of 1998-2013 are collected and analyzed. For context, we find that, both in terms of authorship and regional coverage, the range of locales has expanded steadily. For content, research appears to have moved away from topics largely associated with quantity of development toward quality of development during the period. We conclude by discussing the implications for the future direction of development studies and suggesting strategies for D&S to follow in order to enhance its role in the field of development studies

Enzymatic analysis of the effect of naturally occurring Leu138Pro mutation identified in SHV β-lactamase on hydrolysis of penicillin and ampicillin

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to analyze the significance of leucine to proline substitution at position 138(Leu138Pro) on the hydrolysis of penicillin and ampicillin that we identified in the <it>bla</it>_SHVgene of clinical <it>Escherichia coli </it>swine isolate.</p> <p>Results</p> <p>Kinetic analysis of the mutant proteins showed that <it>K</it>_{<it>m </it>}value of the purified L138P mutant was comparatively higher than SHV-1, SHV-33 and SHV-33(L138P) enzyme for penicillin and ampicillin. Docking simulation of the SHV-1 and SHV-(L138P) enzymes also confirmed that β-lactamases preferred penicillin to ampicillin and the SHV-1 had a higher binding affinity for antibiotics compared to the SHV-(L138P) and other mutants.</p> <p>Conclusions</p> <p>Our result demonstrated that L138P has a reduced role in penicillin and ampicillin hydrolyzing properties of SHV β-lactamases. These naturally occurring mutations rendering reduced function of the existing protein could trigger the emergence or acquisition of more effective alternative mechanisms for β-lactam hydrolysis.</p

Permanent Pacemaker for Syncope after Heart Transplantation with Bicaval Technique

Sinus node dysfunction occurs occasionally after heart transplantation and may be caused by surgical trauma, ischemia to the sinus node, rejection, drug therapy, and increasing donor age. However, the timing and indication of permanent pacemaker insertion due to sinus node dysfunction following heart transplantation is contentious. Here, we report a case of a permanent pacemaker insertion for syncope due to sinus arrest after heart transplantation, even with a bicaval technique, which has been known to associate with few incidences of sinus node dysfunction

The Presence of Two Distinct Red Giant Branches in the Globular Cluster NGC 1851

There is a growing body of evidence for the presence of multiple stellar populations in some globular clusters, including NGC 1851. For most of these peculiar globular clusters, however, the evidence for the multiple red giant-branches (RGBs) having different heavy elemental abundances as observed in Omega Centauri is hitherto lacking, although spreads in some lighter elements are reported. It is therefore not clear whether they also share the suggested dwarf galaxy origin of Omega Cen or not. Here we show from the CTIO 4m UVI photometry of the globular cluster NGC 1851 that its RGB is clearly split into two in the U - I color. The two distinct RGB populations are also clearly separated in the abundance of heavy elements as traced by Calcium, suggesting that the type II supernovae enrichment is also responsible, in addition to the pollutions of lighter elements by intermediate mass asymptotic giant branch stars or fast-rotating massive stars. The RGB split, however, is not shown in the V - I color, as indicated by previous observations. Our stellar population models show that this and the presence of bimodal horizontal-branch distribution in NGC 1851 can be naturally reproduced if the metal-rich second generation stars are also enhanced in helium.Comment: 13 pages, 4 figures, accepted for publication in the Astrophysical Journal Letter

Adsorptive removal of CO2 from CO2-CH4 mixture using cation-exchanged zeolites

Raw natural gas and landfill gas contains methane as its major component, but it also contains considerable amounts of contaminants such as CO2 and H2S (i.e. acid gases) that can cause corrosion and fouling of the pipeline and equipment during transportation and liquefaction. Amine-based CO2 gas removal processes have been employed in the gas industry, but these processes have disadvantages including high regeneration energy requirements and inefficiencies; these issues have not been adequately solved to date. Currently, adsorptive acid gas removal technologies have received significant interest because of the simplicity of adsorbent regeneration by thermal or pressure variation1). Numerous micro- and mesoporous adsorbents including zeolites [2-3], titanosilicates[4], activated carbons[5-6], metal-organic-framework (MOF) [7], and silica-alumina materials[8-9] were studied for this type of application. However, the CO2/CH4 selectivity of the aforementioned adsorbents was not high enough for commercial applications.In this study, different cation-exchanged zeolites were synthesized, physicochemically characterized, and evaluated for adsorptive removal of CO2 from CO2-CH4 mixtures. The adsorption isotherms of CO2 and CH4 in the pressure and temperature ranges 0 − 3MPa and 10 – 40 oC, respectively, for different cation-exchanged zeolites were measured and compared. The ideal-adsorbed solution theory (IAST) was employed for the estimation of CO2/CH4 selectivity for the different cation-exchanged zeolites. References 1) D. Aaron, C. Tsouris, Separ. Sci. Technol. 2005, 40, 321–348 2) J. Collins, US Patent No. 3,751,878. 1973. 3) M. W. Seery, US Patent No. 5,938,819. 1999 4) W. B. Dolan, M.J. Mitariten, US Patent No. 6,610,124 B1. 2003 5) A. Kapoor, R.T. Yang, Chem. Eng. Sci. 1989, 44, 1723–1733 6) A. Jayaraman, Chiao, A. S.; Padin, J.; Yang, R. T.; Munson, C. L., Separ. Sci. Technol. 2002 37, 2505–2528 7) L. Hamon, E. Jolimaitre, G. Pringruber , Ind. Eng. Chem. Res. 2010, 49, 7497-7503 8) W.B. Dolan, M.J. Mitariten, US patent No. 2003/0047071, 2003 9) G. Bellussi, P. Broccia, A. Carati, R. Millini, P. Pollesel, C. Rizzo, M. Tagliabue, Micropor. Mesopor. Mat., 2011, 146, 134–14