Joel D. Hartman

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Polymerization of actin filaments directed by the actin-related protein (Arp)2/3 complex supports many types of cellular movements. However, questions remain regarding the relative contributions of Arp2/3 complex versus other mechanisms of actin filament nucleation to processes such as path finding by neuronal growth cones; this is because of the lack of(More)
Nitric oxide (NO) is an important messenger both systemically and in the CNS. In digital Ca2+ imaging and patch-clamp experiments, clinically available nitroso compounds that generate NO are shown to inhibit responses mediated by the NMDA subtype of the glutamate receptor on rat cortical neurons in vitro. A mechanism of action for this effect was(More)
We provide evidence that the obliquities of stars with close-in giant planets were initially nearly random, and that the low obliquities that are often observed are a consequence of star-planet tidal interactions. The evidence is based on 14 new measurements of the Rossiter-McLaughlin effect (for the systems HAT-P-6, HAT-P-7, HATP-16, HAT-P-24, HAT-P-32,(More)
The Kepler spacecraft is monitoring more than 150,000 stars for evidence of planets transiting those stars. We report the detection of two Saturn-size planets that transit the same Sun-like star, based on 7 months of Kepler observations. Their 19.2- and 38.9-day periods are presently increasing and decreasing at respective average rates of 4 and 39 minutes(More)
We present the first secondary eclipse and phase curve observations for the highly eccentric hot Jupiter HAT-P-2b in the 3.6, 4.5, 5.8, and 8.0 μm bands of the Spitzer Space Telescope. The 3.6 and 4.5 μm data sets span an entire orbital period of HAT-P-2b (P = 5.6334729 d), making them the longest continuous phase curve observations obtained to date and the(More)
The Kepler mission is monitoring the brightness of ~150,000 stars, searching for evidence of planetary transits. As part of the Hunt for Exomoons with Kepler (HEK) project, we report a planetary system with two confirmed planets and one candidate planet discovered with the publicly available data for KOI-872. Planet b transits the host star with a period(More)
Stellar-mass black holes are found in X-ray-emitting binary systems, where their mass can be determined from the dynamics of their companion stars. Models of stellar evolution have difficulty producing black holes in close binaries with masses more than ten times that of the Sun (>10; ref. 4), which is consistent with the fact that the most massive stellar(More)
We have conducted a deep (15 . r . 23), 20 night survey for transiting planets in the intermediate age open cluster M37 (NGC 2099) using the Megacam wide-field mosaic CCD camera on the 6.5m Multiple Mirror Telescope (MMT). In this paper we describe the observations and data reduction procedures for the survey and analyze the stellar content and dynamical(More)
We present deep optical photometry of the afterglow of gamma-ray burst (GRB) 041006 and its associated hypernova obtained over 65 days after detection (55 R-band epochs on 10 different nights). Our early data (t < 4 days) joined with published GCN data indicates a steepening decay, approaching Fν ∝ t −0.6 at early times (t ≪ 1 day) and Fν ∝ t −1.3 at late(More)