All iodinated contrast media (CM) are known to cause both immediate (≤1 h) and nonimmediate (>1 h) hypersensitivity reactions. Although for most immediate reactions an allergic hypersensitivity ...cannot be demonstrated, recent studies indicate that the severe immediate reactions may be IgE‐mediated, while most of the nonimmediate exanthematous skin reactions, appear to be T‐cell mediated. Patients who experience such hypersensitivity reactions are therefore advised to undergo an allergologic evaluation. Several investigators have found skin testing to be useful in confirming a CM allergy, especially in patients with nonimmediate skin eruptions. If a patient with confirmed allergy to a CM needs a new CM exposure, a skin test negative CM should be chosen and premedication may be tried. However, none of these precautional measures is a guarantee against a repeat reaction. More research focusing on pathomechanisms, diagnostic testing and premedication is therefore clearly needed in order to prevent CM‐induced hypersensitivity reactions in the future.
Frost is one of the principal limiting factors for agricultural production in the high Andean region. One of the most important grain crops in that region, quinoa (
Chenopodium quinoa Willd.), is ...generally less affected by frost than most other crop species, but little is known about its specific mechanisms for frost resistance. This study was undertaken to help understand quinoa’s response to various intensities and durations of frost under different levels of relative humidity (RH). The effect of frost on seed yield and plant death rate was studied, and content of soluble sugars, proteins, and free proline, was analyzed, in order to develop criteria for the selection of cultivars with improved resistance to frost. On the basis of greenhouse and phytotron experiments, it was concluded that at the two-leaf stage, cultivars from the altiplano of Peru, 3800
m above sea level, tolerated −8
°C for 4
h, whereas a cultivar from the Andean valleys tolerated the same temperature for only 2
h. At −4
°C, plant death rate increased from 25% at high relative humidity to 56% at low RH After a frost treatment of −4
°C applied at the two-leaf stage, final seed yield was reduced by 9% compared to control plants not exposed to frost. For the same treatment applied at the 12-leaf and flowering stages, yield reductions were 51 and 66%, respectively, indicating that frost for 2
h or more during anthesis caused significant damage to the plants. In general, an increased level of soluble sugars implied a greater tolerance to frost, resulting in higher yields.
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.
We present the asteroseismic analysis of 1948 F-, G- and K-type main-sequence and subgiant stars observed by the National Aeronautics and Space Administration Kepler mission. We detect and ...characterize solar-like oscillations in 642 of these stars. This represents the largest cohort of main-sequence and subgiant solar-like oscillators observed to date. The photometric observations are analysed using the methods developed by nine independent research teams. The results are combined to validate the determined global asteroseismic parameters and calculate the relative precision by which the parameters can be obtained. We correlate the relative number of detected solar-like oscillators with stellar parameters from the Kepler Input Catalogue and find a deficiency for stars with effective temperatures in the range 5300 ≲T
eff≲ 5700 K and a drop-off in detected oscillations in stars approaching the red edge of the classical instability strip. We compare the power-law relationships between the frequency of peak power, νmax, the mean large frequency separation, Δν, and the maximum mode amplitude, A
max, and show that there are significant method-dependent differences in the results obtained. This illustrates the need for multiple complementary analysis methods to be used to assess the robustness and reproducibility of results derived from global asteroseismic parameters.
Context.
The response of imaging atmospheric Cherenkov telescopes to incident
γ
-ray-initiated showers in the atmosphere changes as the telescopes age due to exposure to light and weather. These ...aging processes affect the reconstructed energies of the events and
γ
-ray fluxes.
Aims.
This work discusses the implementation of signal calibration methods for the Very Energetic Radiation Imaging Telescope Array System (VERITAS) to account for changes in the optical throughput and detector performance over time.
Methods.
The total throughput of a Cherenkov telescope is the product of camera-dependent factors, such as the photomultiplier tube gains and their quantum efficiencies, and the mirror reflectivity and Winston cone response to incoming radiation. This document summarizes different methods to determine how the camera gains and mirror reflectivity have evolved over time and how we can calibrate this changing throughput in reconstruction pipelines for imaging atmospheric Cherenkov telescopes. The implementation is validated against seven years of observations with the VERITAS telescopes of the Crab Nebula, which is a reference object in very-high-energy astronomy.
Results.
Regular optical throughput monitoring and the corresponding signal calibrations are found to be critical for the reconstruction of extensive air shower images. The proposed implementation is applied as a correction to the signals of the photomultiplier tubes in the telescope simulation to produce fine-tuned instrument response functions. This method is shown to be effective for calibrating the acquired
γ
-ray data and for recovering the correct energy of the events and photon fluxes. At the same time, it keeps the computational effort of generating Monte Carlo simulations for instrument response functions affordably low.
Photometry of KIC 10483436 was obtained continuously with 1-min exposures over a 27-d period from the Kepler satellite. The light curve shows rotational variations from surface spots with a period of ...4.303 ± 0.002 d, an amplitude of about 6 mmag and eight pulsation frequencies typical of roAp stars. The high-frequency pattern consists of a quintuplet of equally spaced peaks where the frequency of the dominant central peak (68 μmag amplitude) is 1353.00 μHz (P= 12.32 min). A second set of three peaks of lower amplitude are also visible. These appear to form part of a quintuplet centred on 1511.6 μHz with the central peak and one side peak missing. The equidistant frequency spacing is 2.69 μHz, which corresponds to the 4.303 d rotation period. However, the amplitudes (12 μmag) of these peaks are too close to the detection level to allow definite identification of the multiplets. Although no spectrum is available, the character of the pulsations shows that this is a roAp star with two high-frequency modes modulated in amplitude in accordance with the oblique pulsator model. The 4.303-d variation in the light curve, which is interpreted as rotational modulation, shows harmonics as high as the 26th. These harmonics are probably a result of many patches of varying surface brightness associated with surface abundance variations characteristic of Ap stars.
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.
Quinoa (
Chenopodium quinoa Willd.) is traditionally grown in the mountain regions of the Andes where frost is common. However, the physiological mechanisms responsible for the frost resistance ...observed in quinoa are largely unknown. For this reason, a study on cultivars of quinoa originating from the Andean highlands and from the inter-Andean valleys was performed. Frost tolerance was determined by measuring the average lethal temperature of 50% of the leaf tissues (LT
50) by ion leakage, and supercooling activity was assessed by thermal analysis using thermocouples. Quinoa demonstrated supercooling capacity (a mechanism that prevents immediate damage by freezing temperatures) of 5
°C. Ice nucleation temperature was always lower than the LT
50. This indicates that the main survival mechanism of quinoa to frost is avoidance of ice formation by moderate supercooling. The study revealed that quinoa has a high soluble sugar content, which may cause a lowering of the freezing point and therefore contributing to lower the LT
50. It is suggested that the content of proline and soluble sugars, such as sucrose, may serve as indicators of frost tolerance in quinoa breeding material.
Context.
Thanks to the relative ease of finding and characterizing small planets around M-dwarf stars, these objects have become cornerstones in the field of exoplanet studies. The current paucity of ...planets in long-period orbits around M dwarfs makes such objects particularly compelling as they provide clues about the formation and evolution of these systems.
Aims.
In this study we present the discovery of TOI-2257 b (TIC 198485881), a long-period (35 d) sub-Neptune orbiting an M3 star at 57.8 pc. Its transit depth is about 0.4%, large enough to be detected with medium-size, ground-based telescopes. The long transit duration suggests the planet is in a highly eccentric orbit (
e
~ 0.5), which would make it the most eccentric planet known to be transiting an M-dwarf star.
Methods.
We combined TESS and ground-based data obtained with the 1.0-meter SAINT-EX, 0.60-meter TRAPPIST-North, and 1.2-meter FLWO telescopes to find a planetary size of 2.2
R
⊕
and an orbital period of 35.19 days. In addition, we make use of archival data, high-resolution imaging, and vetting packages to support our planetary interpretation.
Results.
With its long period and high eccentricity, TOI-2257 b falls into a novel slice of parameter space. Despite the planet’s low equilibrium temperature (~256 K), its host star’s small size (
R
*
= 0.311 ± 0.015) and relative infrared brightness (
K
mag
= 10.7) make it a suitable candidate for atmospheric exploration via transmission spectroscopy.
Context. Small planets transiting bright nearby stars are essential to our understanding of the formation and evolution of exoplanetary systems. However, few constitute prime targets for atmospheric ...characterization, and even fewer are part of multiple star systems. Aims. This work aims to validate TOI-4336 A b, a sub-Neptune-sized exoplanet candidate identified by the TESS space-based transit survey around a nearby M dwarf. Methods. We validated the planetary nature of TOI-4336 A b through the global analysis of TESS and follow-up multi-band high-precision photometric data from ground-based telescopes, medium- and high-resolution spectroscopy of the host star, high-resolution speckle imaging, and archival images. Results. The newly discovered exoplanet TOI-4336 A b has a radius of 2.1 ± 0.1 R ⊕ . Its host star is an M3.5-dwarf star with a mass of 0.33 ± 0.01 M ⊙ and a radius of 0.33 ± 0.02 R ⊙ , and is a member of a hierarchical triple M-dwarf system 22 pc away from the Sun. The planet’s orbital period of 16.3 days places it at the inner edge of the habitable zone of its host star, which is the brightest of the inner binary pair. The parameters of the system make TOI-4336 A b an extremely promising target for the detailed atmospheric characterization of a temperate sub-Neptune by transit transmission spectroscopy with JWST.
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