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Blakeslee, John P.,Cho, Hyejeon,Peng, Eric W.,Ferrarese, Laura,Jordá,n, André,s,Martel, André,R. IOP Publishing 2012 The Astrophysical journal Vol.746 No.1
<P>We combine new Wide Field Camera 3 IR Channel (WFC3/IR) F160W (H-160) imaging data for NGC 1399, the central galaxy in the Fornax cluster, with archival F475W (g(475)), F606W (V-606), F814W (I-814), and F850LP (z.(850)) optical data from the Advanced Camera for Surveys (ACS). The purely optical g(475)-I-814, V-606-I-814, and g(475)-z(850) colors of NGC 1399's rich globular cluster (GC) system exhibit clear bimodality, at least for magnitudes I-814 > 21.5. The optical-IR I-814-H-160 color distribution appears unimodal, and this impression is confirmed by mixture modeling analysis. The V-606-H-160 colors show marginal evidence for bimodality, consistent with bimodality in V-606-I-814 and unimodality in I-814-H-160. If bimodality is imposed for I-814-H-160 with a double Gaussian model, the preferred blue/red split differs from that for optical colors; these 'differing bimodalities' mean that the optical and optical-IR colors cannot both be linearly proportional to metallicity. Consistent with the differing color distributions, the dependence of I-814-H-160 on g(475)-I-814 for the matched GC sample is significantly nonlinear, with an inflection point near the trough in the g(475)-I-814 color distribution; the result is similar for the I-814-H-160 dependence on g(475)-z(850) colors taken from the ACS Fornax Cluster Survey. These g(475)-z(850) colors have been calibrated empirically against metallicity; applying this calibration yields a continuous, skewed, but single-peaked metallicity distribution. Taken together, these results indicate that nonlinear color-metallicity relations play an important role in shaping the observed bimodal distributions of optical colors in extragalactic GC systems.</P>
Cho, Hyejeon,Blakeslee, John P.,Chies-Santos, Ana L.,Jee, M. James,Jensen, Joseph B.,Peng, Eric W.,Lee, Young-Wook American Astronomical Society 2016 The Astrophysical journal Vol.822 No.2
<P>We present new Hubble Space Telescope (HST) optical and near-infrared (NIR) photometry of the rich globular cluster (GC) system NGC 4874, the cD galaxy in the core of the Coma cluster (Abell 1656). NGC 4874 was observed with the HST Advanced Camera for Surveys in the F475W (g(475)) and F814W (I-814) passbands and with the Wide Field Camera. 3 IR Channel in F160W (H-160). The GCs in this field exhibit a bimodal optical color distribution with more than half of the GCs falling on the red side at g(475)-I-814 > 1. Bimodality is also present, though less conspicuously, in the optical-NIR I-814-H-160 color. Consistent with past work, we find evidence for nonlinearity in the g(475)-I-814 versus I-814-H-160 color-color relation. Our results thus underscore the need for understanding the detailed form of the color-metallicity relations in interpreting observational data on GC bimodality. We also find a very strong color-magnitude trend, or 'blue tilt,' for the blue component of the optical color distribution of the NGC 4874 GC system. A similarly strong trend is present for the overall mean I-814-H-160 color as a function of magnitude; for M-814 < -10 mag, these trends imply a steep mass-metallicity scaling with Z proportional to M-GC(1.4 +/- 0.4), but the scaling is not a simple power law and becomes much weaker at lower masses. As in other similar systems, the spatial distribution of the blue GCs is more extended than that of the red GCs, partly because of blue GCs associated with surrounding cluster galaxies. In addition, the center of the GC system is displaced by 4 +/- 1 kpc toward the southwest from the luminosity center of NGC 4874, in the direction of NGC 4872. Finally, we remark on a dwarf elliptical galaxy with a noticeably asymmetrical GC distribution. Interestingly, this dwarf has a velocity of nearly -3000 km s(-1) with respect to NGC 4874; we suggest it is on its first infall into the cluster core and is undergoing stripping of its GC system by the cluster potential.</P>
Self-Sealing of Nanoporous Low Dielectric Constant Patterns Fabricated by Nanoimprint Lithography
Ro, Hyun Wook,Peng, Huagen,Niihara, Ken-ichi,Lee, Hae-Jeong,Lin, Eric K.,Karim, Alamgir,Gidley, David W.,Jinnai, Hiroshi,Yoon, Do Y.,Soles, Christopher L. WILEY-VCH Verlag 2008 ADVANCED MATERIALS Vol.20 No.10
<B>Graphic Abstract</B> <P>The cross-sectional TEM image shows that line-space patterns can be directly imprinted, with high fidelity, into highly porous spin-on organosilicate materials. This publication quantifies how the porosity and distribution of pores within the patterns are affected by the nanoimprint lithography processes, including evidence for a densified pattern surface. <img src='wiley_img/09359648-2008-20-10-ADMA200701994-content.gif' alt='wiley_img/09359648-2008-20-10-ADMA200701994-content'> </P>
Park, Jung-Nam,Zhang, Peng,Hu, Yong-Sheng,McFarland, Eric W IOP Pub 2010 Nanotechnology Vol.21 No.22
<P>A nanocomposite catalyst composed of ferromagnetic magnetite cores (15.5 ± 2.0 nm) and silica shells with a thickness of 4.5 ± 1.0 nm (Fe<SUB>3</SUB>O<SUB>4</SUB><I>@</I>SiO<SUB>2</SUB>) was prepared by a two-step microemulsion-based synthesis. X-ray photoelectron spectroscopy and Raman spectroscopy after oxidation support the presence of a stable Fe<SUB>3</SUB>O<SUB>4</SUB> core and a surface phase of γ-Fe<SUB>2</SUB>O<SUB>3</SUB>. The nanocomposite structure exhibited 100% conversion of CO in oxygen at a residence time of 0.1 s at 310 °C. When pre-oxidized, the Fe<SUB>3</SUB>O<SUB>4</SUB>@SiO<SUB>2</SUB> catalyst is shown to be a suitable solid oxygen carrier for chemical looping combustion of methane at 700 °C. The nanocomposites retain their magnetism following the reaction which provides the potential for use of magnetic separation and capture in moving bed reactor applications. The core magnetite within the silica shell is resistant to sintering and a bulk phase transition to temperatures as high as 700 °C. These catalysts can be of use in applications of high temperature applications where catalyst recovery by magnetic separation may be required. </P>
Yoon, Suk-Jin,Lee, Sang-Yoon,Blakeslee, John P.,Peng, Eric W.,Sohn, Sangmo T.,Cho, Jaeil,Kim, Hak-Sub,Chung, Chul,Kim, Sooyoung,Lee, Young-Wook IOP Publishing 2011 The Astrophysical journal Vol.743 No.2
<P>One of the conundrums in extragalactic astronomy is the discrepancy in observed metallicity distribution functions (MDFs) between the two prime stellar components of early-type galaxies-globular clusters (GCs) and halo field stars. This is generally taken as evidence of highly decoupled evolutionary histories between GC systems and their parent galaxies. Here we show, however, that new developments in linking the observed GC colors to their intrinsic metallicities suggest nonlinear color-to-metallicity conversions, which translate observed color distributions into strongly peaked, unimodal MDFs with broad metal-poor tails. Remarkably, the inferred GC MDFs are similar to the MDFs of resolved field stars in nearby elliptical galaxies and those produced by chemical evolution models of galaxies. The GC MDF shape, characterized by a sharp peak with a metal-poor tail, indicates a virtually continuous chemical enrichment with a relatively short timescale. The characteristic shape emerges across three orders of magnitude in the host galaxy mass, suggesting a universal process of chemical enrichment among various GC systems. Given that GCs are bluer than field stars within the same galaxy, it is plausible that the chemical enrichment processes of GCs ceased somewhat earlier than that of the field stellar population, and if so, GCs preferentially trace the major, vigorous mode of star formation events in galactic formation. We further suggest a possible systematic age difference among GC systems, in that the GC systems in more luminous galaxies are older. This is consistent with the downsizing paradigm whereby stars of brighter galaxies, on average, formed earlier than those of dimmer galaxies; this additionally supports the similar nature shared by GCs and field stars. Although the sample used in this study (the Hubble Space Telescope Advanced Camera for Surveys/Wide Field Channel, WFPC2, and WFC3 photometry for the GC systems in the Virgo galaxy cluster) confines our discussion to R less than or similar to R-e for giant ellipticals and less than or similar to 10 R-e for normal ellipticals, our findings suggest that GC systems and their parent galaxies have shared a more common origin than previously thought, and hence greatly simplify theories of galaxy formation.</P>