From an analysis of the long cadence light curves of M and K dwarfs obtained by the K2 observations, 3589 flares on 548 M dwarfs and 1647 flares on 343 K dwarfs have been identified. We compared the ...M and K dwarfs' flares with the G dwarfs' flares reported by Shibayama et al. The later type stars' flare occurrence frequencies are higher than those of the earlier type stars, but the earlier type stars produce more powerful flares than those of the later type stars. For the stars of all spectral types, the flare activities, including the flare energy, peak amplitude, and percentage of magnetic activity, increase with faster rotation of stars. The longer the flare duration is, the more energy the flare releases, but an upper limit exists. The saturation energy of M, K, and G dwarfs are derived to be about 1 × 1035 erg, 4 × 1035 erg and 1 × 1036 erg, respectively, in the present study. We estimated the power-law indices of the flare frequency distributions of three spectral type stars. They are 1.82 0.02 (M dwarfs) and 1.86 0.02 (K dwarfs) in comparison to the 2.01 0.03 for the G dwarfs found by Shibayama et al. For stars with Prot ≤ 10 days, they are 1.78 0.02 (M dwarfs), 1.82 0.03 (K dwarfs), and 2.09 0.04 (G dwarfs). The power-law indices of flare frequency distributions of the fast-rotating M- and K-type stars are nearly the same. This indicates that the flare or magnetic mechanisms of different types of low-mass stars may be similar in some sense.
Hyperflares of M Dwarfs Chang, H.-Y.; Lin, C.-L.; Ip, W.-H. ...
The Astrophysical journal,
11/2018, Letnik:
867, Številka:
1
Journal Article
Recenzirano
From a study of the light curves of the M dwarfs observed by the Kepler space telescope in its primary mission, a number of flare events with the peak flux increases reaching more than the nominal ...stellar luminosity have been found. One of them, KIC 9201463, produced an extreme flare with the peak flux increase jumping to five times the quiet-time value. In relative terms, this class of hyperflares is much stronger than the superflares of the solar-type stars and could have a very important influence on the atmospheric evolution and the potential development of biospheres of habitable super-Earths orbiting around M dwarf stars. A cross-correlation of the flare activities of some of these M dwarf stars and their H equivalent width (EW) values derived from the LAMOST project indicates that the H EW values can be used to monitor the occurrence of hyperflares as well as the level of flare activity of different classes of M dwarfs with fast to slow rotations, and hence the long-term environmental effects of star-planet interaction of exoplanets.
Summary
Background
The risk factors for gastrointestinal bleeding (GIB) in clopidogrel users have not been identified.
Aim
To clarify whether clopidogrel use is a risk factor for upper GIB (UGIB) and ...lower GIB (LGIB) and identify the risk factors in clopidogrel users.
Methods
Using the National Health Insurance Research Database of Taiwan, 3238 clopidogrel users and 12 952 age‐, sex‐, and enrolment time‐matched controls in a 1:4 ratio were extracted for comparison from a cohort dataset of 1 000 000 randomly sampled subjects. Cox proportional hazard regression models were used to identify the independent risk factors for UGIB and LGIB in all enrollees and clopidogrel users after adjustments for age, gender, comorbidity i.e., coronary artery disease, hypertension, diabetes, chronic obstructive pulmonary disease, chronic kidney disease (CKD), cirrhosis, uncomplicated peptic ulcer disease, and peptic ulcer bleeding (PUB), and medications e.g., nonsteroidal anti‐inflammatory drugs (NSAIDs), cyclooxygenase‐2 inhibitors, aspirin, steroids, selective serotonin reuptake inhibitors (SSRIs), warfarin and alendronate.
Results
Cox proportional hazard regression analysis showed that use of clopidogrel increased the risk of UGIB hazard ratio (HR): 3.66; 95% confidence interval (CI): 2.96–4.51 and LGIB HR: 3.52, 95% CI: 2.74–4.52. Age, CKD, PUB history, use of aspirin and NSAIDs were independent risk factors for UGIB in the clopidogrel users. Age, CKD, PUB history, use of aspirin and SSRIs were independent risk factors for LGIB.
Conclusions
In clopidogrel users, age, CKD, PUB history, use of aspirin and NSAIDs are independent risk factors for UGIB; age, CKD, PUB history, use of aspirin and SSRIs are independent risk factors for LGIB.
Characterizing the genomic landscape of cancers is a routine part of clinical care that began with the discovery of the Philadelphia chromosome and has since coevolved with genomic technologies. ...Genomic analysis of tumors at the nucleotide level using DNA sequencing has revolutionized the understanding of cancer biology and identified new molecular drivers of disease that have led to therapeutic advances and improved patient outcomes. However, the application of next‐generation sequencing in the clinical laboratory has generally been limited until very recently to targeted analysis of selected genes. Recent technological innovations and reductions in sequencing costs are now able to deliver the long‐promised goal of tumor whole‐genome sequencing as a practical clinical assay.
The effect of procalcitonin-guided use of antibiotics on treatment for suspected lower respiratory tract infection is unclear.
In 14 U.S. hospitals with high adherence to quality measures for the ...treatment of pneumonia, we provided guidance for clinicians about national clinical practice recommendations for the treatment of lower respiratory tract infections and the interpretation of procalcitonin assays. We then randomly assigned patients who presented to the emergency department with a suspected lower respiratory tract infection and for whom the treating physician was uncertain whether antibiotic therapy was indicated to one of two groups: the procalcitonin group, in which the treating clinicians were provided with real-time initial (and serial, if the patient was hospitalized) procalcitonin assay results and an antibiotic use guideline with graded recommendations based on four tiers of procalcitonin levels, or the usual-care group. We hypothesized that within 30 days after enrollment the total antibiotic-days would be lower - and the percentage of patients with adverse outcomes would not be more than 4.5 percentage points higher - in the procalcitonin group than in the usual-care group.
A total of 1656 patients were included in the final analysis cohort (826 randomly assigned to the procalcitonin group and 830 to the usual-care group), of whom 782 (47.2%) were hospitalized and 984 (59.4%) received antibiotics within 30 days. The treating clinician received procalcitonin assay results for 792 of 826 patients (95.9%) in the procalcitonin group (median time from sample collection to assay result, 77 minutes) and for 18 of 830 patients (2.2%) in the usual-care group. In both groups, the procalcitonin-level tier was associated with the decision to prescribe antibiotics in the emergency department. There was no significant difference between the procalcitonin group and the usual-care group in antibiotic-days (mean, 4.2 and 4.3 days, respectively; difference, -0.05 day; 95% confidence interval CI, -0.6 to 0.5; P=0.87) or the proportion of patients with adverse outcomes (11.7% 96 patients and 13.1% 109 patients; difference, -1.5 percentage points; 95% CI, -4.6 to 1.7; P<0.001 for noninferiority) within 30 days.
The provision of procalcitonin assay results, along with instructions on their interpretation, to emergency department and hospital-based clinicians did not result in less use of antibiotics than did usual care among patients with suspected lower respiratory tract infection. (Funded by the National Institute of General Medical Sciences; ProACT ClinicalTrials.gov number, NCT02130986 .).
Context.
Dust is formed out of stellar material and it is constantly affected by different mechanisms occurring in the interstellar medium. Depending on their size, the behaviour of dust grains vary ...under these mechanisms and, therefore, the dust grain size distribution evolves as part of the dust evolution itself. Following how the grain size distribution evolves is a difficult computing task that has only recently become the subject of consideration. Smoothed particle hydrodynamic (SPH) simulations of a single galaxy, together with cosmological simulations, are producing the first predictions of the evolution of dust grain size distribution.
Aims.
We compare, for the first time, the evolution of the dust grain size distribution as predicted by SPH simulations and results from observations. We are able to validate not only the predictions of the evolution of the small-to-large grain mass ratio (
D
S
/
D
L
) within a galaxy, but we also provide observational constraints for recent cosmological simulations that include the grain size distribution in the dust evolution framework.
Methods.
We selected a sample of three spiral galaxies with different masses: M 101, NGC 628, and M 33. We fitted the dust spectral energy distribution across the disc of each object and derived the abundance of the different grain types included in the dust model. We analysed how the radial distribution of the relative abundance of the different grain size populations changes over the whole disc within each galaxy. The
D
S
/
D
L
ratio as a function of the galactocentric distance and metallicity is directly compared to what has been predicted by the SPH simulations.
Results.
We find a good agreement between the observed radial distribution of
D
S
/
D
L
and what was obtained from the SPH simulations of a single galaxy. The comparison agrees with the expected evolutionary stage of each galaxy. We show that the central parts of NGC 628 at a high metallicity and with a high molecular gas fraction are mainly affected not only by accretion, but also by the coagulation of dust grains. The centre of M 33, having a lower metallicity and lower molecular gas fraction, presents an increase in the
D
S
/
D
L
ratio, demonstrating that shattering is very effective for creating a large fraction of small grains. Finally, the observational results provided by our galaxies confirm the general relations predicted by the cosmological simulations based on the two-grain size approximation. However, we also present evidence that the simulations could be overestimating the amount of large grains in high massive galaxies.
Two experiments were conducted to determine the effects of Lactobacillus plantarum B1 on broiler performance, cecal bacteria, and ileal and cecal short chain fatty acids (SCFA). The study also ...determined whether it was necessary to feed Lactobacillus throughout the entire growth period or if the beneficial effects could be obtained by supplementation during the starter or finisher period only. Experiment 1 was conducted with 72 broilers assigned to 2 treatments (N = 6). One treatment was the basal diet (Con), and the other was the basal diet supplemented with 2 × 109 cfu/kg L. plantarum B1 (Wh). In experiment 2, 144 one-day-old broilers were assigned to 4 treatments (N = 6) including a basal diet (Con), the basal diet supplemented with 2 × 109 cfu/kg L. plantarum B1 during d one to 21 only (St), the basal diet supplemented with L. plantarum B1 during d 22 to 42 only (Fn), and, finally, the basal diet supplemented with L. plantarum B1 from d one to 42 (Wh). Experiment 1 showed that L. plantarum B1 enhanced broiler average daily gain (ADG) and feed conversion ratio (FCR). In experiment 2, during the starter period, broilers in the Wh and St treatments had higher ADG (P < 0.05) than broilers in the Con and Fn, while during the finisher period, broilers in the Wh and Fn had higher ADG (P < 0.01) and improved FCR (P < 0.01) compared with broilers in the Con and St. On d 42, broilers in the Wh and Fn had decreased E. coli (P < 0.05) and increased lactic acid bacteria (P < 0.05) in their cecal digesta. L. plantarum B1 also increased (P < 0.05) ileal mucosal sIgA as well as ileal and cecal SCFA. However, L. plantarum B1 had no effect on intestinal morphology. In conclusion, L. plantarum B1 plays a positive role in broilers. Supplementation during the finisher period or the entire growth period is superior to supplementation during the starter period only.
This assessment, by the United Nations Environment Programme (UNEP) Environmental Effects Assessment Panel (EEAP), one of three Panels informing the Parties to the Montreal Protocol, provides an ...update, since our previous extensive assessment (Photochem. Photobiol. Sci., 2019, 18, 595-828), of recent findings of current and projected interactive environmental effects of ultraviolet (UV) radiation, stratospheric ozone, and climate change. These effects include those on human health, air quality, terrestrial and aquatic ecosystems, biogeochemical cycles, and materials used in construction and other services. The present update evaluates further evidence of the consequences of human activity on climate change that are altering the exposure of organisms and ecosystems to UV radiation. This in turn reveals the interactive effects of many climate change factors with UV radiation that have implications for the atmosphere, feedbacks, contaminant fate and transport, organismal responses, and many outdoor materials including plastics, wood, and fabrics. The universal ratification of the Montreal Protocol, signed by 197 countries, has led to the regulation and phase-out of chemicals that deplete the stratospheric ozone layer. Although this treaty has had unprecedented success in protecting the ozone layer, and hence all life on Earth from damaging UV radiation, it is also making a substantial contribution to reducing climate warming because many of the chemicals under this treaty are greenhouse gases.
In this paper, we present a minimum spanning tree (MST)-based algorithm, called local minimum spanning tree (LMST), for topology control in wireless multihop networks. In this algorithm, each node ...builds its LMST independently and only keeps on-tree nodes that are one-hop away as its neighbors in the final topology. We analytically prove several important properties of LMST: 1) the topology derived under LMST preserves the network connectivity; 2) the node degree of any node in the resulting topology is bounded by 6; and 3) the topology can be transformed into one with bidirectional links (without impairing the network connectivity) after removal of all unidirectional links. Simulation results show that LMST can increase the network capacity as well as reduce the energy consumption.
This assessment by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) provides the latest scientific update since our most recent comprehensive ...assessment (Photochemical and Photobiological Sciences, 2019, 18, 595–828). The interactive effects between the stratospheric ozone layer, solar ultraviolet (UV) radiation, and climate change are presented within the framework of the Montreal Protocol and the United Nations Sustainable Development Goals. We address how these global environmental changes affect the atmosphere and air quality; human health; terrestrial and aquatic ecosystems; biogeochemical cycles; and materials used in outdoor construction, solar energy technologies, and fabrics. In many cases, there is a growing influence from changes in seasonality and extreme events due to climate change. Additionally, we assess the transmission and environmental effects of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for the COVID-19 pandemic, in the context of linkages with solar UV radiation and the Montreal Protocol.
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