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Explanatory AI, Indexical Reference, and Perception
Reseaichen in AI often say that certain types of reference are baaed on perception. Their models, however, do not reflect perceptual functioning, but instead represent denotation, an intellectuaUy modeled relation, by using exact feature matching in a serial device as the basic mechanism for reference. I point out four problems in this use of denotation: substitution of an intellectual model for a perceptual one; unclarity about the nature of referential identification; relative neglect of the role of contrast in reference; and inexact matches. I then suggest an alternative theoretical account for perceptually based indexical reference, the figure-ground model, and I e:q>lain how this model handles the four problems
Low mass binary neutron star mergers : gravitational waves and neutrino emission
Neutron star mergers are among the most promising sources of gravitational
waves for advanced ground-based detectors. These mergers are also expected to
power bright electromagnetic signals, in the form of short gamma-ray bursts,
infrared/optical transients, and radio emission. Simulations of these mergers
with fully general relativistic codes are critical to understand the merger and
post-merger gravitational wave signals and their neutrinos and electromagnetic
counterparts. In this paper, we employ the SpEC code to simulate the merger of
low-mass neutron star binaries (two neutron stars) for a set of
three nuclear-theory based, finite temperature equations of state. We show that
the frequency peaks of the post-merger gravitational wave signal are in good
agreement with predictions obtained from simulations using a simpler treatment
of gravity. We find, however, that only the fundamental mode of the remnant is
excited for long periods of time: emission at the secondary peaks is damped on
a millisecond timescale in the simulated binaries. For such low-mass systems,
the remnant is a massive neutron star which, depending on the equation of
state, is either permanently stable or long-lived. We observe strong
excitations of l=2, m=2 modes, both in the massive neutron star and in the form
of hot, shocked tidal arms in the surrounding accretion torus. We estimate the
neutrino emission of the remnant using a neutrino leakage scheme and, in one
case, compare these results with a gray two-moment neutrino transport scheme.
We confirm the complex geometry of the neutrino emission, also observed in
previous simulations with neutrino leakage, and show explicitly the presence of
important differences in the neutrino luminosity, disk composition, and outflow
properties between the neutrino leakage and transport schemes.Comment: Accepted by PRD; 23 pages; 24 figures; 4 table
Post-merger evolution of a neutron star-black hole binary with neutrino transport
We present a first simulation of the post-merger evolution of a black
hole-neutron star binary in full general relativity using an energy-integrated
general relativistic truncated moment formalism for neutrino transport. We
describe our implementation of the moment formalism and important tests of our
code, before studying the formation phase of a disk after a black hole-neutron
star merger. We use as initial data an existing general relativistic simulation
of the merger of a neutron star of 1.4 solar mass with a black hole of 7 solar
mass and dimensionless spin a/M=0.8. Comparing with a simpler leakage scheme
for the treatment of the neutrinos, we find noticeable differences in the
neutron to proton ratio in and around the disk, and in the neutrino luminosity.
We find that the electron neutrino luminosity is much lower in the transport
simulations, and that the remnant is less neutron-rich. The spatial
distribution of the neutrinos is significantly affected by relativistic
effects. Over the short timescale evolved, we do not observe purely
neutrino-driven outflows. However, a small amount of material (3e-4Msun) is
ejected in the polar region during the circularization of the disk. Most of
that material is ejected early in the formation of the disk, and is fairly
neutron rich. Through r-process nucleosynthesis, that material should produce
high-opacity lanthanides in the polar region, and could thus affect the
lightcurve of radioactively powered electromagnetic transients. We also show
that by the end of the simulation, while the bulk of the disk is neutron-rich,
its outer layers have a higher electron fraction. As that material would be the
first to be unbound by disk outflows on longer timescales, the changes in Ye
experienced during the formation of the disk could have an impact on the
nucleosynthesis outputs from neutrino-driven and viscously-driven outflows.
[Abridged]Comment: 29 pages, 25 figure
Isolation of Novel Trypanosomatid, Zelonia australiensis sp. nov. (Kinetoplastida: Trypanosomatidae) Provides Support for a Gondwanan Origin of Dixenous Parasitism in the Leishmaniinae
© 2017 Barratt et al. The genus Leishmania includes approximately 53 species, 20 of which cause human leishmaniais; a significant albeit neglected tropical disease. Leishmaniasis has afflicted humans for millennia, but how ancient is Leishmania and where did it arise? These questions have been hotly debated for decades and several theories have been proposed. One theory suggests Leishmania originated in the Palearctic, and dispersed to the New World via the Bering land bridge. Others propose that Leishmania evolved in the Neotropics. The Multiple Origins theory suggests that separation of certain Old World and New World species occurred due to the opening of the Atlantic Ocean. Some suggest that the ancestor of the dixenous genera Leishmania, Endotrypanum and Porcisia evolved on Gondwana between 90 and 140 million years ago. In the present study a detailed molecular and morphological characterisation was performed on a novel Australian trypanosomatid following its isolation in Australia’s tropics from the native black fly, Simulium (Morops) dycei Colbo, 1976. Phylogenetic analyses were conducted and confirmed this parasite as a sibling to Zelonia costaricensis, a close relative of Leishmania previously isolated from a reduviid bug in Costa Rica. Consequently, this parasite was assigned the name Zelonia australiensis sp. nov. Assuming Z. costaricensis and Z. australiensis diverged when Australia and South America became completely separated, their divergence occurred between 36 and 41 million years ago at least. Using this vicariance event as a calibration point for a phylogenetic time tree, the common ancestor of the dixenous genera Leishmania, Endotrypanum and Porcisia appeared in Gondwana approximately 91 million years ago. Ultimately, this study contributes to our understanding of trypanosomatid diversity, and of Leishmania origins by providing support for a Gondwanan origin of dixenous parasitism in the Leishmaniinae
Genetic Evidence for Selective Transport of Opsin and Arrestin by Kinesin-II in Mammalian Photoreceptors
AbstractTo test whether kinesin-II is important for transport in the mammalian photoreceptor cilium, and to identify its potential cargoes, we used Cre-loxP mutagenesis to remove the kinesin-II subunit, KIF3A, specifically from photoreceptors. Complete loss of KIF3A caused large accumulations of opsin, arrestin, and membranes within the photoreceptor inner segment, while the localization of α-transducin was unaffected. Other membrane, organelle, and transport markers, as well as opsin processing appeared normal. Loss of KIF3A ultimately caused apoptotic photoreceptor cell death similar to a known opsin transport mutant. The data suggest that kinesin-II is required to transport opsin and arrestin from the inner to the outer segment and that blocks in this transport pathway lead to photoreceptor cell death as found in retinitis pigmentosa
The Central Laser Facility at the Pierre Auger Observatory
The Central Laser Facility is located near the middle of the Pierre Auger
Observatory in Argentina. It features a UV laser and optics that direct a beam
of calibrated pulsed light into the sky. Light scattered from this beam
produces tracks in the Auger optical detectors which normally record nitrogen
fluorescence tracks from cosmic ray air showers. The Central Laser Facility
provides a "test beam" to investigate properties of the atmosphere and the
fluorescence detectors. The laser can send light via optical fiber
simultaneously to the nearest surface detector tank for hybrid timing analyses.
We describe the facility and show some examples of its many uses.Comment: 4 pages, 5 figures, submitted to 29th ICRC Pune Indi
Spirocyclic chromanes exhibit antiplasmodial activities and inhibit all intraerythrocytic life cycle stages
AbstractWe screened a collection of synthetic compounds consisting of natural-product-like substructural motifs to identify a spirocyclic chromane as a novel antiplasmodial pharmacophore using an unbiased cell-based assay. The most active spirocyclic compound UCF 201 exhibits a 50% effective concentration (EC50) of 350Â nM against the chloroquine-resistant Dd2 strain and a selectivity over 50 using human liver HepG2 cells. Our analyses of physicochemical properties of UCF 201 showed that it is in compliance with Lipinski's parameters and has an acceptable physicochemical profile. We have performed a limited structure-activity-relationship study with commercially available chromanes preserving the spirocyclic motif. Our evaluation of stage specificities of UCF 201 indicated that the compound is early-acting in blocking parasite development at ring, trophozoite and schizont stages of development as well as merozoite invasion. SPC is an attractive lead candidate scaffold because of its ability to act on all stages of parasite's aexual life cycle unlike current antimalarials
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