The Gravity Collective: A Search for the Electromagnetic Counterpart to the Neutron Star-Black Hole Merger GW190814

We present optical follow-up imaging obtained with the Katzman Automatic Imaging Telescope, Las Cumbres Observatory Global Telescope Network, Nickel Telescope, Swope Telescope, and Thacher Telescope of the LIGO/Virgo gravitational wave (GW) signal from the neutron star-black hole (NSBH) merger GW190814. We searched the GW190814 localization region (19 deg$^{2}$ for the 90th percentile best localization), covering a total of 51 deg$^{2}$ and 94.6% of the two-dimensional localization region. Analyzing the properties of 189 transients that we consider as candidate counterparts to the NSBH merger, including their localizations, discovery times from merger, optical spectra, likely host-galaxy redshifts, and photometric evolution, we conclude that none of these objects are likely to be associated with GW190814. Based on this finding, we consider the likely optical properties of an electromagnetic counterpart to GW190814, including possible kilonovae and short gamma-ray burst afterglows. Using the joint limits from our follow-up imaging, we conclude that a counterpart with an $r$-band decline rate of 0.68 mag day$^{-1}$, similar to the kilonova AT 2017gfo, could peak at an absolute magnitude of at most $-17.8$ mag (50% confidence). Our data are not constraining for ''red'' kilonovae and rule out ''blue'' kilonovae with $M>0.5 M_{\odot}$ (30% confidence). We strongly rule out all known types of short gamma-ray burst afterglows with viewing angles $<$17$^{\circ}$ assuming an initial jet opening angle of $\sim$$5.2^{\circ}$ and explosion energies and circumburst densities similar to afterglows explored in the literature. Finally, we explore the possibility that GW190814 merged in the disk of an active galactic nucleus, of which we find four in the localization region, but we do not find any candidate counterparts among these sources.Comment: 86 pages, 9 figure

International Urban Design Studio 2018, Kyojima-Sumida District, Tokyo

The Tokyo Smart City Studio is a practical capstone project housed within the Eco Urban Lab at Georgia Tech’s School of City and Regional Planning and School of Architecture. Throughout the four-month semester, students collaborate on innovative urban design solutions for some of Tokyo’s most important problems. In conjunction with the Global Carbon Project (GCP), the National Institute for Environmental Studies of Japan, the Department of Urban Engineering of the University of Tokyo, and the University of Tsukuba, Georgia Tech Students tackled issues ranging from energy consumption and disaster preparedness to heat stress and a vulnerable elderly population. The group completed five comprehensive reviews, a week-long site visit to Tokyo, multiple workshopping sessions, an Architecture Exposition, and two final reports. The focus area of this year’s studio was Kyojima, a one-half kilometer neighborhood in Sumida-Ku. In the late 19th century, this neighborhood was characterized by paddy fields, marshes, and a few small factories. It’s known for its traditional Japanese crafts, tight alleyways, and wooden tenement housing. The area is dense and in need of revitalization. Kirakira Street, the neighborhood’s once bustling shopping destination, is in substantial economic decline. This document is a detailed report of all student proposals aimed at assisting community members and other Kyojima stakeholders with technological, design, and policy solutions

An Amish founder mutation disrupts a PI(3)P-WHAMM-Arp2/3 complex-driven autophagosomal remodeling pathway.

Actin nucleation factors function to organize, shape, and move membrane-bound organelles, yet they remain poorly defined in relation to disease. Galloway-Mowat syndrome (GMS) is an inherited disorder characterized by microcephaly and nephrosis resulting from mutations in the WDR73 gene. This core clinical phenotype appears frequently in the Amish, where virtually all affected individuals harbor homozygous founder mutations in WDR73 as well as the closely linked WHAMM gene, which encodes a nucleation factor. Here we show that patient cells with both mutations exhibit cytoskeletal irregularities and severe defects in autophagy. Reintroduction of wild-type WHAMM restored autophagosomal biogenesis to patient cells, while inactivation of WHAMM in healthy cell lines inhibited lipidation of the autophagosomal protein LC3 and clearance of ubiquitinated protein aggregates. Normal WHAMM function involved binding to the phospholipid PI(3)P and promoting actin nucleation at nascent autophagosomes. These results reveal a cytoskeletal pathway controlling autophagosomal remodeling and illustrate several molecular processes that are perturbed in Amish GMS patients