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Measurement of Source Star Colors with the <i>K</i>2C9-CFHT Multi-color Microlensing Survey
Zang, Weicheng,Penny, Matthew T.,Zhu, Wei,Mao, Shude,Fouqué,, Pascal,Udalski, Andrzej,Hwang, Kyu-Ha,Wang, Tianshu,Huang, Chelsea,Boyajian, Tabetha. S.,Barentsen, Geert Astronomical Society of the Pacific 2018 Publications of the Astronomical Society of the Pa Vol.130 No.992
Zhao, Linlin,Pence, Matthew G.,Christov, Plamen P.,Wawrzak, Zdzislaw,Choi, Jeong-Yun,Rizzo, Carmelo J.,Egli, Martin,Guengerich, F. Peter American Society for Biochemistry and Molecular Bi 2012 The Journal of biological chemistry Vol.287 No.42
<P><I>N</I><SUP>2</SUP>,3-Ethenoguanine (<I>N</I><SUP>2</SUP>,3-ϵG) is one of the exocyclic DNA adducts produced by endogenous processes (<I>e.g.</I> lipid peroxidation) and exposure to bioactivated vinyl monomers such as vinyl chloride, which is a known human carcinogen. Existing studies exploring the miscoding potential of this lesion are quite indirect because of the lability of the glycosidic bond. We utilized a 2′-fluoro isostere approach to stabilize this lesion and synthesized oligonucleotides containing 2′-fluoro-<I>N</I><SUP>2</SUP>,3-ϵ-2′-deoxyarabinoguanosine to investigate the miscoding potential of <I>N</I><SUP>2</SUP>,3-ϵG by Y-family human DNA polymerases (pols). In primer extension assays, pol η and pol κ replicated through <I>N</I><SUP>2</SUP>,3-ϵG, whereas pol ι and REV1 yielded only 1-base incorporation. Steady-state kinetics revealed that dCTP incorporation is preferred opposite <I>N</I><SUP>2</SUP>,3-ϵG with relative efficiencies in the order of pol κ > REV1 > pol η ≈ pol ι, and dTTP misincorporation is the major miscoding event by all four Y-family human DNA pols. Pol ι had the highest dTTP misincorporation frequency (0.71) followed by pol η (0.63). REV1 misincorporated dTTP and dGTP with much lower frequencies. Crystal structures of pol ι with <I>N</I><SUP>2</SUP>,3-ϵG paired to dCTP and dTTP revealed Hoogsteen-like base pairing mechanisms. Two hydrogen bonds were observed in the <I>N</I><SUP>2</SUP>,3-ϵG:dCTP base pair, whereas only one appears to be present in the case of the <I>N</I><SUP>2</SUP>,3-ϵG:dTTP pair. Base pairing mechanisms derived from the crystal structures explain the slightly favored dCTP insertion for pol ι in steady-state kinetic analysis. Taken together, these results provide a basis for the mutagenic potential of <I>N</I><SUP>2</SUP>,3-ϵG.</P>
WFIRST ULTRA-PRECISE ASTROMETRY II: ASTEROSEISMOLOGY
Andrew Gould,Daniel Huber,Matthew Penny,Dennis Stello 한국천문학회 2015 Journal of The Korean Astronomical Society Vol.48 No.2
WFIRST microlensing observations will return high-precision parallaxes, σ(π) . 0.3 μas, for the roughly 1 million stars with H < 14 in its 2.8 deg2 field toward the Galactic bulge. Combined with its 40,000 epochs of high precision photometry (∼ 0.7 mmag at Hvega = 14 and ∼ 0.1 mmag at H = 8), this will yield a wealth of asteroseismic data of giant stars, primarily in the Galactic bulge but including a substantial fraction of disk stars at all Galactocentric radii interior to the Sun. For brighter stars, the astrometric data will yield an external check on the radii derived from the two asteroseismic parameters, the large-frequency separation hνnli and the frequency of maximum oscillation power νmax, while for the fainter ones, it will enable a mass measurement from the single measurable asteroseismic parameter νmax. Simulations based on Kepler data indicate that WFIRST will be capable of detecting oscillations in stars from slightly less luminous than the red clump to the tip of the red giant branch, yielding roughly 1 million detections.
Henderson, Calen B.,Poleski, Radosław,Penny, Matthew,Street, Rachel A.,Bennett, David P.,Hogg, David W.,Gaudi, B. Scott,Zhu, W.,Barclay, T.,Barentsen, G.,Howell, S. B.,Mullally, F.,Udalski, A.,Szyma Astronomical Society of the Pacific 2016 Publications of the Astronomical Society of the Pa Vol.128 No.970
<P>K2's Campaign 9 (K2C9) will conduct a similar to 3.7 deg(2) survey toward the Galactic bulge from 2016 April 22 through July 2 that will leverage the spatial separation between K2 and the Earth to facilitate measurement of the microlens parallax pi(E) for greater than or similar to 170 microlensing events. These will include several that are planetary in nature as well as many short-timescale microlensing events, which are potentially indicative of free-floating planets (FFPs). These satellite parallax measurements will in turn allow for the direct measurement of the masses of and distances to the lensing systems. In this article we provide an overview of the K2C9 space-and ground-based microlensing survey. Specifically, we detail the demographic questions that can be addressed by this program, including the frequency of FFPs and the Galactic distribution of exoplanets, the observational parameters of K2C9, and the array of resources dedicated to concurrent observations. Finally, we outline the avenues through which the larger community can become involved, and generally encourage participation in K2C9, which constitutes an important pathfinding mission and community exercise in anticipation of WFIRST.</P>
OPTIMAL SURVEY STRATEGIES AND PREDICTED PLANET YIELDS FOR THE KOREAN MICROLENSING TELESCOPE NETWORK
Henderson, Calen B.,Gaudi, B. Scott,Han, Cheongho,Skowron, Jan,Penny, Matthew T.,Nataf, David,Gould, Andrew P. IOP Publishing 2014 The Astrophysical journal Vol.794 No.1
<P>The Korean Microlensing Telescope Network (KMTNet) will consist of three 1.6 m telescopes each with a 4 deg(2) field of view (FoV) and will be dedicated to monitoring the Galactic Bulge to detect exoplanets via gravitational microlensing. KMTNet's combination of aperture size, FoV, cadence, and longitudinal coverage will provide a unique opportunity to probe exoplanet demographics in an unbiased way. Here we present simulations that optimize the observing strategy for and predict the planetary yields of KMTNet. We find preferences for four target fields located in the central Bulge and an exposure time of t(exp) = 120 s, leading to the detection of similar to 2200 microlensing events per year. We estimate the planet detection rates for planets with mass and separation across the ranges 0.1 <= M-p/M-circle plus <= 1000 and 0.4 <= a/AU <= 16, respectively. Normalizing these rates to the cool-planet mass function of Cassan et al., we predict KMTNet will be approximately uniformly sensitive to planets with mass 5 <= M-p/M-circle plus <= 1000 and will detect similar to 20 planets per year per dex in mass across that range. For lower-mass planets with mass 0.1 <= M-p/M-circle plus < 5, we predict KMTNet will detect similar to 10 planets per year. We also compute the yields KMTNet will obtain for free-floating planets (FFPs) and predict KMTNet will detect similar to 1 Earth-mass FFP per year, assuming an underlying population of one such planet per star in the Galaxy. Lastly, we investigate the dependence of these detection rates on the number of observatories, the photometric precision limit, and optimistic assumptions regarding seeing, throughput, and flux measurement uncertainties.</P>