19,402 research outputs found
Transcriptional adaptation of Mycobacterium tuberculosis within macrophages: Insights into the phagosomal environment
Little is known about the biochemical environment in phagosomes harboring an infectious agent. To assess the state of this organelle we captured the transcriptional responses of Mycobacterium tuberculosis (MTB) in macrophages from wild-type and nitric oxide (NO) synthase 2–deficient mice before and after immunologic activation. The intraphagosomal transcriptome was compared with the transcriptome of MTB in standard broth culture and during growth in diverse conditions designed to simulate features of the phagosomal environment. Genes expressed differentially as a consequence of intraphagosomal residence included an interferon � – and NO-induced response that intensifies an iron-scavenging program, converts the microbe from aerobic to anaerobic respiration, and induces a dormancy regulon. Induction of genes involved in the activation and �-oxidation of fatty acids indicated that fatty acids furnish carbon and energy. Induction of �E-dependent, sodium dodecyl sulfate–regulated genes and genes involved in mycolic acid modification pointed to damage and repair of the cell envelope. Sentinel genes within the intraphagosomal transcriptome were induced similarly by MTB in the lungs of mice. The microbial transcriptome thus served as a bioprobe of the MTB phagosomal environment
Courant-like brackets and loop spaces
We study the algebra of local functionals equipped with a Poisson bracket. We
discuss the underlying algebraic structures related to a version of the
Courant-Dorfman algebra. As a main illustration, we consider the functionals
over the cotangent bundle of the superloop space over a smooth manifold. We
present a number of examples of the Courant-like brackets arising from this
analysis.Comment: 20 pages, the version published in JHE
A luminous blue kilonova and an off-axis jet from a compact binary merger at z=0.1341
The recent discovery of a faint gamma-ray burst (GRB) coincident with the
gravitational wave (GW) event GW 170817 revealed the existence of a population
of low-luminosity short duration gamma-ray transients produced by neutron star
mergers in the nearby Universe. These events could be routinely detected by
existing gamma-ray monitors, yet previous observations failed to identify them
without the aid of GW triggers. Here we show that GRB150101B was an analogue of
GRB170817A located at a cosmological distance. GRB 150101B was a faint short
duration GRB characterized by a bright optical counterpart and a long-lived
X-ray afterglow. These properties are unusual for standard short GRBs and are
instead consistent with an explosion viewed off-axis: the optical light is
produced by a luminous kilonova component, while the observed X-rays trace the
GRB afterglow viewed at an angle of ~13 degrees. Our findings suggest that
these properties could be common among future electromagnetic counterparts of
GW sources.Comment: 28 pages, 8 figures, 2 tables. Accepted for publicatio
The Angstrom Project Alert System: real-time detection of extragalactic microlensing
The Angstrom Project is undertaking an optical survey of stellar microlensing
events across the bulge region of the Andromeda Galaxy (M31) using a
distributed network of two-meter class telescopes. The Angstrom Project Alert
System (APAS) has been developed to identify in real time candidate
microlensing and transient events using data from the Liverpool and Faulkes
North robotic telescopes. This is the first time that real-time microlensing
discovery has been attempted outside of the Milky Way and its satellite
galaxies. The APAS is designed to enable follow-up studies of M31 microlensing
systems, including searches for gas giant planets in M31. Here we describe the
APAS and we present a few example light curves obtained during its
commissioning phase which clearly demonstrate its real-time capability to
identify microlensing candidates as well as other transient sources.Comment: 4 pages, submitted to ApJ Letter
The Origin of the Intrinsic Scatter in the Relation Between Black Hole Mass and Bulge Luminosity for Nearby Active Galaxies
We investigate the origin of the intrinsic scatter in the correlation between
black hole mass (MBH) and bulge luminosity [L(bulge)] in a sample of 45
massive, local (z < 0.35) type~1 active galactic nuclei (AGNs). We derive MBH
from published optical spectra assuming a spherical broad-line region, and
L(bulge) from detailed two-dimensional decomposition of archival optical Hubble
Space Telescope images. AGNs follow the MBH-L(bulge) relation of inactive
galaxies, but the zero point is shifted by an average of \Delta log MBH ~ -0.3
dex. We show that the magnitude of the zero point offset, which is responsible
for the intrinsic scatter in the MBH-L(bulge) relation, is correlated with
several AGN and host galaxy properties, all of which are ultimately related to,
or directly impact, the BH mass accretion rate. At a given bulge luminosity,
sources with higher Eddington ratios have lower MBH. The zero point offset can
be explained by a change in the normalization of the virial product used to
estimate MBH, in conjunction with modest BH growth (~ 10%--40%) during the AGN
phase. Galaxy mergers and tidal interactions appear to play an important role
in regulating AGN fueling in low-redshift AGNs.Comment: To appear in ApJ; 67 pages, 56 figures, 4 tables, version with full
resolution figures at http://users.ociw.edu/mjkim/papers/scatter.pd
Critical Properties of Ternary Deep Eutectic Solvents Using Group Contribution with Extended Lee-Kesler Mixing Rules.
One of the most commonly used molecular inputs for ionic liquids and deep eutectic solvents (DESs) in the literature are the critical properties and acentric factors, which can be easily determined using the modified Lydersen-Joback-Reid (LJR) method with Lee-Kesler mixing rules. However, the method used in the literature is generally applicable only to binary mixtures of DESs. Nevertheless, ternary DESs are considered to be more interesting and may provide further tailorability for developing task-specific DESs for particular applications. Therefore, in this work, a new framework for estimating the critical properties and the acentric factor of ternary DESs based on their molecular structures is presented by adjusting the framework reported in the literature with an extended version of the Lee-Kesler mixing rules. The presented framework was applied to a data set consisting of 87 ternary DESs with 334 distinct compositions. For validation, the estimated critical properties and acentric factors were used to predict the densities of the ternary DESs. The results showed excellent agreement between the experimental and calculated data, with an average absolute relative deviation (AARD) of 5.203% for ternary DESs and 5.712% for 260 binary DESs (573 compositions). The developed methodology was incorporated into a user-friendly Excel worksheet for computing the critical properties and acentric factors of any ternary or binary DES, which is provided in the Supporting Information. This work promotes the creation of robust, accessible, and user-friendly models capable of predicting the properties of new ternary DESs based on critical properties, thus saving time and resources
Multi-Attribute SCADA-Specific Intrusion Detection System for Power Networks
The increased interconnectivity and complexity of supervisory control and data acquisition (SCADA) systems in power system networks has exposed the systems to a multitude of potential vulnerabilities. In this paper, we present a novel approach for a next-generation SCADA-specific intrusion detection system (IDS). The proposed system analyzes multiple attributes in order to provide a comprehensive solution that is able to mitigate varied cyber-attack threats. The multiattribute IDS comprises a heterogeneous white list and behavior-based concept in order to make SCADA cybersystems more secure. This paper also proposes a multilayer cyber-security framework based on IDS for protecting SCADA cybersecurity in smart grids without compromising the availability of normal data. In addition, this paper presents a SCADA-specific cybersecurity testbed to investigate simulated attacks, which has been used in this paper to validate the proposed approach
Focusing and Compression of Ultrashort Pulses through Scattering Media
Light scattering in inhomogeneous media induces wavefront distortions which
pose an inherent limitation in many optical applications. Examples range from
microscopy and nanosurgery to astronomy. In recent years, ongoing efforts have
made the correction of spatial distortions possible by wavefront shaping
techniques. However, when ultrashort pulses are employed scattering induces
temporal distortions which hinder their use in nonlinear processes such as in
multiphoton microscopy and quantum control experiments. Here we show that
correction of both spatial and temporal distortions can be attained by
manipulating only the spatial degrees of freedom of the incident wavefront.
Moreover, by optimizing a nonlinear signal the refocused pulse can be shorter
than the input pulse. We demonstrate focusing of 100fs pulses through a 1mm
thick brain tissue, and 1000-fold enhancement of a localized two-photon
fluorescence signal. Our results open up new possibilities for optical
manipulation and nonlinear imaging in scattering media
Essential self-adjointness for combinatorial Schr\"odinger operators II- Metrically non complete graphs
We consider weighted graphs, we equip them with a metric structure given by a
weighted distance, and we discuss essential self-adjointness for weighted graph
Laplacians and Schr\"odinger operators in the metrically non complete case.Comment: Revisited version: Ognjen Milatovic wrote to us that he had
discovered a gap in the proof of theorem 4.2 of our paper. As a consequence
we propose to make an additional assumption (regularity property of the
graph) to this theorem. A new subsection (4.1) is devoted to the study of
this property and some details have been changed in the proof of theorem 4.
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