Abstract
The shell-type supernova remnant HESS J1731 − 347 emits TeV gamma-rays, and is a key object for the study of the cosmic ray acceleration potential of supernova remnants. We use 0.5–1 arcmin ...Mopra CO/CS(1–0) data in conjunction with H i data to calculate column densities towards the HESS J1731 − 347 region. We trace gas within at least four Galactic arms, typically tracing total (atomic+molecular) line-of-sight H column densities of 2–3× 1022 cm−2. Assuming standard X-factor values and that most of the H i/CO emission seen towards HESS J1731 − 347 is on the near-side of the Galaxy, X-ray absorption column densities are consistent with H i+CO-derived column densities foreground to, but not beyond, the Scutum–Crux Galactic arm, suggesting a kinematic distance of ∼3.2 kpc for HESS J1731 − 347. At this kinematic distance, we also find dense, infrared-dark gas traced by CS(1–0) emission coincident with the north of HESS J1731 − 347, the nearby H ii region G353.43−0.37 and the nearby unidentified gamma-ray source HESS J1729 − 345. This dense gas lends weight to the idea that HESS J1729 − 345 and HESS J1731 − 347 are connected, perhaps via escaping cosmic-rays.
Abstract
The Galactic Center (GC) region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of nonthermal radiation. The inner 375 pc × 600 pc ...region, called the Central Molecular Zone, is home to the supermassive black hole Sagittarius A*, massive cloud complexes, and particle accelerators such as supernova remnants (SNRs). We present the results of our improved analysis of the very-high-energy gamma-ray emission above 2 TeV from the GC using 125 hr of data taken with the Very Energetic Radiation Imaging Telescope Array System imaging-atmospheric Cerenkov telescope between 2010 and 2018. The central source VER J1745–290, consistent with the position of Sagittarius A*, is detected at a significance of 38 standard deviations above the background level (38
σ
), and we report its spectrum and light curve. Its differential spectrum is consistent with a power law with exponential cutoff, with a spectral index of
, a flux normalization at 5.3 TeV of
TeV
−1
cm
−2
s
−1
, and cutoff energy of
TeV. We also present results on the diffuse emission near the GC, obtained by combining data from multiple regions along the GC ridge, which yield a cumulative significance of 9.5
σ
. The diffuse GC ridge spectrum is best fit by a power law with a hard index of 2.19 ± 0.20, showing no evidence of a cutoff up to 40 TeV. This strengthens the evidence for a potential accelerator of PeV cosmic rays being present in the GC. We also provide spectra of the other sources in our field of view with significant detections, composite SNR G0.9+0.1, and HESS J1746–285.
This study analyses persistence in growth rates for a data set of manufacturing firms of all sizes. Previous quantile autoregressions of firm growth rates show that extreme growth events are likely ...to be negatively correlated over time, thus questioning the existence of persistent outperformers. By supplementing the quantile regression analyses with transition probability matrices, our study shows that "bouncing" firms coexist with persistent outperformers. This result is shown to be robust for all size classes as well as for the exclusion of firms who experienced acquisitions or spin-offs.
Programmed cell death is necessary for homeostasis in multicellular organisms and it is also widely recognized to occur in unicellular organisms. However, the mechanisms through which it occurs in ...unicells, and the enzymes involved within the final response is still the subject of heated debate. It is shown here that exposure of the unicellular microalga Dunaliella viridis to several environmental stresses, induced different cell death morphotypes, depending on the stimulus received. Senescent cells demonstrated classical and unambiguous apoptotic-like characteristics such as chromatin condensation, DNA fragmentation, intact organelles, and blebbing of the cell membrane. Acute heat shock caused general swelling and altered plasma membrane, but the presence of chromatin clusters and DNA strand breaks suggested a necrotic-like event. UV irradiated cells presented changes typical for necrosis, together with apoptotic characteristics resembling an intermediate cell-death phenotype termed aponecrosis-like. Cells subjected to hyperosmotic shock revealed chromatin spotting without DNA fragmentation, and extensive cytoplasmic swelling and vacuolization, comparable to a paraptotic-like cell death phenotype. Nitrogen-starved cells showed pyknosis, blebbing, and cytoplasmic consumption, indicating a similarity to autophagic/vacuolar-like cell death. The caspase-like activity DEVDase was measured by using the fluorescent substrate Ac-DEVD-AMC and antibodies against the human caspase-3 active enzyme cross-reacted with bands, the intensity of which paralleled the activity. All the environmental stresses tested produced a substantial increase in both DEVDase activity and protein levels. The irreversible caspase-3 inhibitor Z-DEVD-FMK completely inhibited the enzymatic activity whereas serine and aspartyl proteases inhibitors did not. These results show that cell death in D. viridis does not conform to a single pattern and that environmental stimuli may produce different types of cell death depending on the type and intensity of the stimulus, all of which help to understand the cell death-dependent and cell death-independent functions of caspase-like proteins. Hence, these data support the theory that alternative, non-apoptotic programmed cell death (PCDs), exist either in parallel or in an independent manner with apoptosis and were already present in single-celled organisms that evolved some 1.2-1.6 billion years ago.
Weak cathodal transcranial direct current stimulation (tDCS) of the human hand area modulates corticospinal excitability with a suppression of motor-evoked potentials (MEPs) evoked by transcranial ...magnetic stimulation (TMS). The changes in excitability persist beyond the time of stimulation if tDCS is given for several minutes and can remain stable for an hour or more. The aim of present study was to evaluate whether a long-lasting suppression of cortical excitability could be induced by prolonged cathodal tDCS (20 min of stimulation). We also explored the impact of brain-derived neurotrophic factor (BDNF) gene polymorphisms, on tDCS after-effects. Cortical excitability to single and paired-pulse TMS was evaluated both for the stimulated and contralateral hemisphere, before and up to 24 h after 20 min of cathodal tDCS. We evaluated threshold and amplitude of MEPs, short interval intracortical inhibition (SICI), and intracortical facilitation (ICF). tDCS produced a pronounced suppression of MEP amplitude that was still significant at 3 h after the end of stimulation. The BDNF genotype had not influence on tDCS after-effects. Thresholds for MEPs, SICI and ICF were not affected. No significant effect was observed in the contralateral hemisphere. Twenty minutes of cathodal tDCS is capable of inducing a long-lasting suppression of the excitability of the human motor cortex.
Abstract Introduction Increased mortality in people with schizophrenia, compared to the general population, has been consistently reported worldwide. This mortality has been attributed predominantly ...to “unnatural” deaths-suicide, accidents, and homicide. Recent studies have shown an increase in natural causes of death. Our objective is to compare the mortality of schizophrenic and schizoaffective subjects to the general US population. Methods 319 Olmsted County residents meeting DSM-IV-TR criteria for schizophrenia or schizoaffective disorder seen at the Mayo Clinic between 1950 and 1980 were followed until February 2005 for a median of 23.5 years. Results At the end of follow-up, 44% of patients were deceased. Mortality was significantly ( p < 0.001) increased compared to the Caucasian population in the US for persons of like age, gender, and calendar year of birth. The median survival following diagnosis was 36.2 years. Death certificate cited cause of death was cardiac (29%), cancer — including lung (19%), and pulmonary disease (17%). Concerningly, there was no association with the year of diagnosis to survival. Conclusions Tsuang and colleagues showed in 1975 that mortality in schizophrenics and later, those with schizoaffective disorder was significantly increased compared to the US general population. Thirty years later, with a demographically similar population, we have found the same pattern of increased mortality. In light of continued improvements in the general population's lifespan, the survival gap in schizophrenia/schizoaffective disorder appears to be increasing.
Abstract
Flat-spectrum radio quasars (FSRQs) are the most luminous blazars at GeV energies but only rarely emit detectable fluxes of TeV gamma rays, typically during bright GeV flares. We explore the ...gamma-ray variability and spectral characteristics of three FSRQs that have been observed at GeV and TeV energies by Fermi-LAT and VERITAS, making use of almost 100 hr of VERITAS observations spread over 10 yr: 3C 279, PKS 1222+216, and Ton 599. We explain the GeV flux distributions of the sources in terms of a model derived from a stochastic differential equation describing fluctuations in the magnetic field in the accretion disk and estimate the timescales of magnetic flux accumulation and stochastic instabilities in their accretion disks. We identify distinct flares using a procedure based on Bayesian blocks and analyze their daily and subdaily variability and gamma-ray energy spectra. Using observations from VERITAS, as well as Fermi, Swift, and the Steward Observatory, we model the broadband spectral energy distributions of PKS 1222+216 and Ton 599 during very high energy (VHE)–detected flares in 2014 and 2017, respectively, strongly constraining the jet Doppler factors and gamma-ray emission region locations during these events. Finally, we place theoretical constraints on the potential production of PeV-scale neutrinos during these VHE flares.
Abstract
HESS J0632+057 belongs to a rare subclass of binary systems that emit gamma rays above 100 GeV. It stands out for its distinctive high-energy light curve, which features a sharp “primary” ...peak and broader “secondary” peak. We present the results of contemporaneous observations by NuSTAR and VERITAS during the secondary peak between 2019 December and 2020 February, when the orbital phase (
ϕ
) is between 0.55 and 0.75. NuSTAR detected X-ray spectral evolution, while VERITAS detected TeV emission. We fit a leptonic wind-collision model to the multiwavelength spectra data obtained over the four NuSTAR and VERITAS observations, constraining the pulsar spin-down luminosity and the magnetization parameter at the shock. Despite long-term monitoring of the source from 2019 October to 2020 March, the MDM observatory did not detect significant variation in H
α
and H
β
line equivalent widths, an expected signature of Be-disk interaction with the pulsar. Furthermore, fitting folded Swift-XRT light-curve data with an intrabinary shock model constrained the orbital parameters, suggesting two orbital phases (at
ϕ
D
= 0.13 and 0.37), where the pulsar crosses the Be-disk, as well as phases for the periastron (
ϕ
0
= 0.30) and inferior conjunction (
ϕ
IFC
= 0.75). The broadband X-ray spectra with Swift-XRT and NuSTAR allowed us to measure a higher neutral hydrogen column density at one of the predicted disk-passing phases.
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