Using 448.0×106 ψ(3686) events collected with the BESIII detector, an amplitude analysis is performed for ψ(3686)→γχc1, χc1→ηπ+π− decays. The most dominant two-body structure observed is a0(980)±π∓; ...a0(980)±→ηπ±. The a0(980) line shape is modeled using a dispersion relation, and a significant nonzero a0(980) coupling to the η′π channel is measured. We observe χc1→a2(1700)π production for the first time, with a significance larger than 17σ. The production of mesons with exotic quantum numbers, JPC=1−+, is investigated, and upper limits for the branching fractions χc1→π1(1400)±π∓, χc1→π1(1600)±π∓, and χc1→π1(2015)±π∓, with subsequent π1(X)±→ηπ± decay, are determined.
Recent years have seen increasing interest in the characterization of sub-Neptune-sized planets because of their prevalence in the Galaxy, contrasted with their absence in our solar system. HD 97658 ...is one of the brightest stars hosting a planet of this kind, and we present the transmission spectrum of this planet by combining four Hubble Space Telescope transits, 12 Spitzer/IRAC transits, and eight MOST transits of this system. Our transmission spectrum has a higher signal-to-noise ratio than those from previous works, and the result suggests that the slight increase in transit depth from wavelength 1.1-1.7 m reported in previous works on the transmission spectrum of this planet is likely systematic. Nonetheless, our atmospheric modeling results are inconclusive, as no model provides an excellent match to our data. Nonetheless, we find that atmospheres with high C/O ratios (C/O 0.8) and metallicities of 100× solar metallicity are favored. We combine the mid-transit times from all of the new Spitzer and MOST observations and obtain an updated orbital period of P = 9.489295 0.000005, with a best-fit transit time center at T0 = 2456361.80690 0.00038 (BJD). No transit timing variations are found in this system. We also present new measurements of the stellar rotation period (34 2 days) and stellar activity cycle (9.6 yr) of the host star HD 97658. Finally, we calculate and rank the Transmission Spectroscopy Metric of all confirmed planets cooler than 1000 K and with sizes between 1 R⊕ and 4 R⊕. We find that at least a third of small planets cooler than 1000 K can be well characterized using James Webb Space Telescope, and of those, HD 97658b is ranked fifth, meaning that it remains a high-priority target for atmospheric characterization.
The major risk of microplastics in marine environments is the bioaccumulation in marine organisms. Plastic ingestion by marine organisms has been investigated and recently more attention has been ...given to microplastics in seafood. However, it is seldom reported the occurrence of microplastics in marine commercial dried fish products available for human consumption. Here, we report the occurrence of microplastics in 14different marine dried fish products from seven Asian countries. Microplastics were observed in most dried fish, with fibers representing ~80% of the total-microplastics. The major plastic polymers, identified using Micro-Raman spectroscopy, included polyethylene (35%), polyethylene terephthalate (26%), polystyrene (18%), polyvinyl chloride (12%), and polypropylene (9%). The highest count, in either per individual (1.92 ± 0.12) or per gram of dried fish (0.56 ± 0.03), were found in Etrumeus micropus from Japan. Marine dried fish, which are typically eaten whole, may contribute to the ingestion of microplastics by humans, posing potential health risks especially in Asian countries. Further studies are needed to identify the occurrence of smaller sized microplastics and nanoplastics and their potential health impacts.
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•Microplastics were observed in most dried fish from Asian countries.•The highest microplastic level was found in a dried fish product from Japan.•Polyethylene was the most detected polymer in dried fish products.•The health effects of consuming these dried fish in Asia need to be evaluated.
Abstract
Al
0.85
Ga
0.15
As
0.56
Sb
0.44
has recently attracted significant research interest as a material for 1550 nm low-noise short-wave infrared (SWIR) avalanche photodiodes (APDs) due to the ...very wide ratio between its electron and hole ionization coefficients. This work reports new experimental excess noise data for thick Al
0.85
Ga
0.15
As
0.56
Sb
0.44
PIN and NIP structures, measuring low noise at significantly higher multiplication values than previously reported (
F
= 2.2 at
M
= 38). These results disagree with the classical McIntyre excess noise theory, which overestimates the expected noise based on the ionization coefficients reported for this alloy. Even the addition of ‘dead space’ effects cannot account for these discrepancies. The only way to explain the low excess noise observed is to conclude that the spatial probability distributions for impact ionization of electrons and holes in this material follows a Weibull–Fréchet distribution function even at relatively low electric-fields. Knowledge of the ionization coefficients alone is no longer sufficient to predict the excess noise properties of this material system and consequently the electric-field dependent electron and hole ionization probability distributions are extracted for this alloy.
Jupiter's X‐Ray and UV Dark Polar Region Dunn, W. R.; Weigt, D. M.; Grodent, D. ...
Geophysical research letters,
16 June 2022, Letnik:
49, Številka:
11
Journal Article, Web Resource
Recenzirano
Odprti dostop
We present 14 simultaneous Chandra X‐ray Observatory (CXO)‐Hubble Space Telescope (HST) observations of Jupiter's Northern X‐ray and ultraviolet (UV) aurorae from 2016 to 2019. Despite the variety of ...dynamic UV and X‐ray auroral structures, one region is conspicuous by its persistent absence of emission: the dark polar region (DPR). Previous HST observations have shown that very little UV emission is produced by the DPR. We find that the DPR also produces very few X‐ray photons. For all 14 observations, the low level of X‐ray emission from the DPR is consistent (within 2‐standard deviations) with scattered solar emission and/or photons spread by Chandra's Point Spread Function from known X‐ray‐bright regions. We therefore conclude that for these 14 observations the DPR produced no statistically significant detectable X‐ray signature.
Plain Language Summary
Jupiter produces the most powerful ultraviolet (UV) and X‐ray aurorae in the solar system. While the UV and X‐ray aurora of the planet have each been explored independently, previous work exploring the spatial connection between Jupiter's X‐ray and UV aurorae was limited to a single simultaneous Chandra X‐ray Observatory (CXO) and Hubble Space Telescope (HST) observation from 2003. Since 2016, the arrival of the Juno spacecraft at Jupiter has led to extensive observing campaigns with CXO and HST, resulting in many new simultaneous X‐ray‐UV observations. Here, we present the analysis of 14 simultaneous CXO and HST observations of Jupiter's Northern aurorae from 2016 to 2019. While much of the emission from these bright aurorae is dynamic, there is one region that is dim for all 14 observations: Jupiter's dark polar region. Previous observations of this region have shown that it produces very little UV light. However, the extent to which X‐ray light is produced by the region remained unexplored and could provide the key to identifying why the region is so dark and what this tells us about the Jovian system. Across these 14 observations, we find that the region produces no significant X‐ray emission.
Key Points
We compare 14 simultaneous Chandra X‐ray Observatory and Hubble Space Telescope UV observations of Jupiter's Northern Aurorae
We detect no statistically significant X‐ray emission from the UV dark polar region (DPR)
The DPR expands and the X‐ray and UV emission on the swirl region boundary shifts when the aurora show solar wind compression morphology
Grassland biomass monitoring is essential for assessing grassland health and carbon cycling. However, monitoring grassland biomass in drylands based on satellite remote sensing is ...challenging.Statistical regression models and machine learning have been used for the construction of grassland biomass models, but the predictive power for different grassland types is unclear. Additionally, the selection of the most appropriate variables to construct a biomass inversion model for different grassland types must be explored. Therefore,1201 ground-truthed data points collected from 2014-2021,including 15 Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation indices,geographic location and topographic data,and meteorological factors and vegetation biophysical indicators were screened for key variables using principal component analysis (PCA). The accuracy of multiple linear regression models, exponential regression models, power function models, support vector machine (SVM) models, random forest (RF) models, and neural network models was evaluated for the inversion of three types of grassland biomass. The results were as follows: (1) The biomass inversion accuracy of single vegetation indices was low, and the optimal vegetation indices were the soil-adjusted vegetation index (SAVI) (R2 = 0.255), normalized difference vegetation index (NDVI) (R2 = 0.372) and optimized soil-adjusted vegetation index (OSAVI) (R2 = 0.285). (2)Grassland above-ground biomass (AGB) was affected by various factors such as geographic location,topography, and meteorological factors, and the inverse models using a single environmental variable had large errors. (3) The main variables used to model biomass in the three types of grasslands were different. SAVI, aspect, slope, and precipitation (Prec.) were selected for desert grasslands; NDVI,shortwave infrared 2 (SWI2), longitude, mean temperature, and annual precipitation were selected for steppe;and OSAVI, phytochrome ratio (PPR), longitude, precipitation, and temperature were selected for meadows. (4) The non-parametric meadow biomass model was superior to the statistical regression model. (5) The RF model was the best model for the inversion of grassland biomass in Xinjiang, and this model had the highest accuracy for grassland biomass inversion (R2 = 0.656, root mean square error (RMSE) = 815.6 kg/ha),followed by meadow (R2 = 0.610, RMSE = 547.9 kg/ha) and desert grassland (R2 = 0.441, RMSE = 353.6 kg/ha).
Using 1310.6×106 J/ψ and 447.9×106 ψ(3686) events collected with the BESIII detector at the BEPCII e+e− collider, the branching fractions and the angular distributions of J/ψ and ψ(3686) decays to ...ΛΛ¯ and Σ0Σ¯0 final states are measured. The branching fractions are determined, with much improved precision, to be 19.43±0.03±0.33, 11.64±0.04±0.23, 3.97±0.02±0.12 and 2.44±0.03±0.11 for J/ψ→ΛΛ¯, J/ψ→Σ0Σ¯0, ψ(3686)→ΛΛ¯ and ψ(3686)→Σ0Σ¯0, respectively. The polar angular distributions of ψ(3686) decays are measured for the first time, while those of J/ψ decays are measured with much improved precision. In addition, the ratios of branching fractions B(ψ(3686)→ΛΛ¯)B(J/ψ→ΛΛ¯) and B(ψ(3686)→Σ0Σ¯0)B(J/ψ→Σ0Σ¯0) are determined to test the “12% rule.”
We study the singly Cabibbo suppressed decays Λc+→pη and Λc+→pπ0 using Λc+Λ¯c− pairs produced by e+e− collisions at a center-of-mass energy of s=4.6 GeV. The data sample was collected by the BESIII ...detector at the BEPCII collider and corresponds to an integrated luminosity of 567 pb−1. We find the first evidence for the decay Λc+→pη with a statistical significance of 4.2σ and measure its branching fraction to be B(Λc+→pη)=(1.24±0.28(stat)±0.10(syst))×10−3. No significant Λc+→pπ0 signal is observed. We set an upper limit on its branching fraction B(Λc+→pπ0)<2.7×10−4 at the 90% confidence level.
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