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  1. Abstract

    The great comet C/1995 O1 (Hale–Bopp) presented a remarkable opportunity to study its long-term brightness over four years. We used 2240 observations published in theInternational Comet Quarterlyfrom 17 observers during 1995 July to 1999 September to create a secular lightcurve. In order to account for observer differences, we present a novel algorithm to reduce scatter and increase precision in a lightcurve compiled from many sources. It is implemented in a publicly available code, ICQSPLITTER, which uses a self-consistent statistical approach. To first order, the comet’s lightcurve approximates anr−4response for both pre- and postperihelion distances. The preperihelion data are better fit with a fifth-order polynomial with inflection points at 4.0, 2.6, 2.1, and 1.1 au, some of which are associated with physical changes in the coma. Outbursts may have occurred a few days before perihelion and at ∼2.2 and 7.4 au postperihelion. TheAfρvalues derived from the final magnitudes are consistent with anr−1.5dependence on heliocentric distance and are within a factor of 2–4 of those derived from spectroscopy and narrowband photometry. We present correlation equations for visual magnitudes and CO and H2O production rates that are consistent with the preperihelion brightness increasing due to CO outgassing until about 2.6–3.0 au frommore »the Sun and then are strongly correlated with H2O production rates. We also present two generalized correlation equations that may be useful for observation planning and data analysis with theJames Webb Space Telescopeand other observatories.

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  2. The dentate gyrus (DG) is a region of the adult rodent brain that undergoes continuous neurogenesis. Seizures and loss or dysfunction of GABAergic synapses onto adult-born dentate granule cells (GCs) alter their dendritic growth and migration, resulting in dysmorphic and hyperexcitable GCs. Additionally, transplants of fetal GABAergic interneurons in the DG of mice with temporal lobe epilepsy (TLE) result in seizure suppression, but it is unknown whether increasing interneurons with these transplants restores GABAergic innervation to adult-born GCs. Here we address this question by retroviral birth-dating GCs at different times up to 12 weeks after pilocarpine-induced TLE in adult mice. ChR2-EYFP-expressing MGE-derived GABAergic interneurons from E13.5 mouse embryos were transplanted into the DG of the TLE mice and GCs with transplant-derived inhibitory post-synaptic currents were identified by patch-clamp electrophysiology and optogenetic interrogation. Putative synaptic sites between GCs and GABAergic transplants were also confirmed by intracellular biocytin staining, immunohistochemistry, and confocal imaging. 3D reconstructions of dendritic arbors and quantitative morphometric analyses were carried out in >150 adult-born GCs. GABAergic inputs from transplanted interneurons correlated with markedly shorter GC dendrites, compared to GCs that were not innervated by the transplants. Moreover, these effects were confined to distal dendritic branches and a shortmore »time window of 6-8 weeks. The effects were independent of seizures as they were also observed in naïve mice with MGE transplants. These findings are consistent with the hypothesis that increased inhibitory currents over a smaller dendritic arbor in adult-born GCs may reduce their excitability and lead to seizure suppression.« less