304 research outputs found
GBM Observations of V404 Cyg During its 2015 Outburst
V404 Cygni was discovered in 1989 by the X-ray satellite during its
only previously observed X-ray outburst and soon after confirmed as a black
hole binary. On June 15, 2015, the Gamma Ray Burst Monitor (GBM) triggered on a
new outburst of V404 Cygni. We present 13 days of GBM observations of this
outburst including Earth occultation flux measurements, spectral and temporal
analysis. The Earth occultation fluxes reached 30 Crab with detected emission
to 100 keV and determined, via hardness ratios, that the source was in a hard
state. At high luminosity, spectral analysis between 8 and 300 keV showed that
the electron temperature decreased with increasing luminosity. This is expected
if the protons and electrons are in thermal equilibrium during an outburst with
the electrons cooled by the Compton scattering of softer seed photons from the
disk. However, the implied seed photon temperatures are unusually high,
suggesting a contribution from another source, such as the jet. No evidence of
state transitions is seen during this time period. The temporal analysis
reveals power spectra that can be modeled with two or three strong, broad
Lorentzians, similar to the power spectra of black hole binaries in their hard
state
qBounce: Systematic shifts of transition frequencies of gravitational states of ultra-cold neutrons using Ramsey gravity resonance spectroscopy
qBounce is using quantum states of ultra-cold neutrons in the gravitational
field of the Earth to investigate gravitation in the micrometre range. We
present current measurements taken in 2021 at the Institut Laue-Langevin (ILL)
to determine energy differences of these states by mechanically induced
transitions. This allows a determination of the local acceleration using a
quantum measurement. The data presented here results in .
The classical local value at the experiment is . We present
an analysis of systematic effects that induces shifts of the transition
frequency of order 100 mHz. The inferred value for at the experiment shows
a systematic shift of
Cryptic Polyketide Synthase Genes in Non-Pathogenic Clostridium SPP
Modular type I polyketide synthases (PKS) produce a vast array of bacterial metabolites with highly diverse biological functions. Notably, all known polyketides were isolated from aerobic bacteria, and yet no example has been reported for strict anaerobes. In this study we explored the diversity and distribution of PKS genes in the genus Clostridium. In addition to comparative genomic analyses combined with predictions of modular type I polyketide synthase (PKS) gene clusters in sequenced genomes of Clostridium spp., a representative selection of other species inhabiting a variety of ecological niches was investigated by PCR screening for PKS genes. Our data reveal that all studied pathogenic Clostridium spp. are devoid of putative PKS genes. In stark contrast, cryptic PKS genes are widespread in genomes of non-pathogenic Clostridium species. According to phylogenetic analyses, the Clostridium PKS genes have unusual and diverse origins. However, reverse transcription quantitative PCR demonstrates that these genes are silent under standard cultivation conditions, explaining why the related metabolites have been overlooked until now. This study presents clostridia as a putative source for novel bioactive polyketides
The Natural Product Domain Seeker NaPDoS: A Phylogeny Based Bioinformatic Tool to Classify Secondary Metabolite Gene Diversity
New bioinformatic tools are needed to analyze the growing volume of DNA sequence data. This is especially true in the case of secondary metabolite biosynthesis, where the highly repetitive nature of the associated genes creates major challenges for accurate sequence assembly and analysis. Here we introduce the web tool Natural Product Domain Seeker (NaPDoS), which provides an automated method to assess the secondary metabolite biosynthetic gene diversity and novelty of strains or environments. NaPDoS analyses are based on the phylogenetic relationships of sequence tags derived from polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) genes, respectively. The sequence tags correspond to PKS-derived ketosynthase domains and NRPS-derived condensation domains and are compared to an internal database of experimentally characterized biosynthetic genes. NaPDoS provides a rapid mechanism to extract and classify ketosynthase and condensation domains from PCR products, genomes, and metagenomic datasets. Close database matches provide a mechanism to infer the generalized structures of secondary metabolites while new phylogenetic lineages provide targets for the discovery of new enzyme architectures or mechanisms of secondary metabolite assembly. Here we outline the main features of NaPDoS and test it on four draft genome sequences and two metagenomic datasets. The results provide a rapid method to assess secondary metabolite biosynthetic gene diversity and richness in organisms or environments and a mechanism to identify genes that may be associated with uncharacterized biochemistry
The 3rd Fermi GBM Gamma-Ray Burst Catalog: The First Six Years
Since its launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has
triggered and located on average approximately two gamma-ray bursts (GRB) every
three days. Here we present the third of a series of catalogs of GRBs detected
by GBM, extending the second catalog by two more years, through the middle of
July 2014. The resulting list includes 1405 triggers identified as GRBs. The
intention of the GBM GRB catalog is to provide information to the community on
the most important observables of the GBM detected GRBs. For each GRB the
location and main characteristics of the prompt emission, the duration, peak
flux and fluence are derived. The latter two quantities are calculated for the
50-300~keV energy band, where the maximum energy release of GRBs in the
instrument reference system is observed, and also for a broader energy band
from 10-1000 keV, exploiting the full energy range of GBM's low-energy NaI(Tl)
detectors. Using statistical methods to assess clustering, we find that the
hardness and duration of GRBs are better fitted by a two-component model with
short-hard and long-soft bursts, than by a model with three components.
Furthermore, information is provided on the settings and modifications of the
triggering criteria and exceptional operational conditions during years five
and six in the mission. This third catalog is an official product of the Fermi
GBM science team, and the data files containing the complete results are
available from the High-Energy Astrophysics Science Archive Research Center
(HEASARC).Comment: 225 pages, 13 figures and 8 tables. Accepted for publication in
Astrophysical Journal Supplement 201
First Results from Fermi GBM Earth Occultation Monitoring: Observations of Soft Gamma-Ray Sources Above 100 keV
The NaI and BGO detectors on the Gamma-ray Burst Monitor (GBM) on Fermi are
now being used for long-term monitoring of the hard X-ray/low energy gamma-ray
sky. Using the Earth occultation technique as demonstrated previously by the
BATSE instrument on the Compton Gamma-Ray Observatory, GBM can be used to
produce multiband light curves and spectra for known sources and transient
outbursts in the 8 keV to 1 MeV energy range with its NaI detectors and up to
40 MeV with its BGO detectors. Over 85% of the sky is viewed every orbit, and
the precession of the Fermi orbit allows the entire sky to be viewed every ~26
days with sensitivity exceeding that of BATSE at energies below ~25 keV and
above ~1.5 MeV. We briefly describe the technique and present preliminary
results using the NaI detectors after the first two years of observations at
energies above 100 keV. Eight sources are detected with a significance greater
than 7 sigma: the Crab, Cyg X-1, SWIFT J1753.5-0127, 1E 1740-29, Cen A, GRS
1915+105, and the transient sources XTE J1752-223 and GX 339-4. Two of the
sources, the Crab and Cyg X-1, have also been detected above 300 keV.Comment: 13 pages, 9 figures, submitted to Ap
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