Various physical processes are known to cause acceleration, loss, and transport of energetic electrons in the Earth's radiation belts, but their quantitative roles in different time and space need ...further investigation. During the largest storm over the past decade (17 March 2015), relativistic electrons experienced fairly rapid acceleration up to ~7 MeV within 2 days after an initial substantial dropout, as observed by Van Allen Probes. In the present paper, we evaluate the relative roles of various physical processes during the recovery phase of this large storm using a 3‐D diffusion simulation. By quantitatively comparing the observed and simulated electron evolution, we found that chorus plays a critical role in accelerating electrons up to several MeV near the developing peak location and produces characteristic flat‐top pitch angle distributions. By only including radial diffusion, the simulation underestimates the observed electron acceleration, while radial diffusion plays an important role in redistributing electrons and potentially accelerates them to even higher energies. Moreover, plasmaspheric hiss is found to provide efficient pitch angle scattering losses for hundreds of keV electrons, while its scattering effect on > 1 MeV electrons is relatively slow. Although an additional loss process is required to fully explain the overestimated electron fluxes at multi‐MeV, the combined physical processes of radial diffusion and pitch angle and energy diffusion by chorus and hiss reproduce the observed electron dynamics remarkably well, suggesting that quasi‐linear diffusion theory is reasonable to evaluate radiation belt electron dynamics during this big storm.
Key Points
Radiation belt electrons experienced rapid acceleration up to multi‐MeV during 17 March 2015 storm
Chorus plays an important role in accelerating electrons to multi‐MeV near PSD peak location
Radial diffusion is critical in redistributing electrons and could provide further acceleration
We performed a statistical study of the proton pancake pitch angle distributions (PADs) at the energy from 10 to 300 eV with the Helium Oxygen Proton Electron instrument on board the Van Allen ...Probes. The occurrence rate of low energy proton pancake PADs and their dependence on the energy, L shell, magnetic local time (MLT) and AL* index are analyzed. The results indicate that: (a) the occurrence rate of pancake PADs decreases as the proton energy increases; (b) under active geomagnetic activities (AL* < −300 nT), pancake PADs preferentially occur in the dayside; (c) under weak geomagnetic activities (AL* > −100 nT), the occurrence rate of pancake PADs has little dependence on MLT. We further discuss the contribution of magnetosonic (MS) waves on the formation of proton pancake PADs at low energy. The strong correlation between the occurrence of pancake PADs and the appearance of MS waves indicates that MS waves contribute to the formation of low energy proton pancake PADs. Moreover, the proton diffusion coefficients caused by MS waves suggest that MS waves can cause the proton heating at low energies in high density regions.
Plain Language Summary
Studying the characteristics of the pitch angle distributions (PAD) of different particles is crucial to understand particle dynamics in the Earth's magnetosphere. However, previous studies mostly focused on high‐energy electrons and paid little attention to low‐energy protons. The twin Van Allen Probes with advanced instrument provide us a great opportunity to investigate low‐energy proton in detail. In our research, we adopt an automatic method to find out the pancake PAD of low energy protons. We then analyze the occurrence rate of low‐energy proton pancake PAD under different conditions. The results show that low‐energy proton pancake PAD is more likely to appear in the dayside region under strong geomagnetic activities. Moreover, we study the relationship between proton pancake PADs and magnetosonic (MS) waves. It is found that MS wave can cause the proton heating at low energies in high density regions, which may affect the occurrence rate of proton pancake PADs.
Key Points
The occurrence rate of proton pancake pitch angle distribution (PAD) at the energy below 300 eV increases with the decrease of energy
The occurrence rate of proton pancake distribution is higher when magnetosonic (MS) waves occur than when MS waves do not appear
MS waves can heat the low energies (<300 eV) protons in high‐density regions, contributing to the proton pancake PADs
Electromagnetic ion cyclotron (EMIC) waves and magnetosonic waves are commonly observed in the Earth's magnetosphere associated with enhanced ring current activity. Using wave and ion measurements ...from the Van Allen Probes, we identify clear correlations between the hydrogen‐ and helium‐band EMIC waves with the enhancement of trapped helium and oxygen ion fluxes, respectively. We calculate the diffusion coefficients of different ion species using quasi‐linear theory to understand the effects of resonant scattering by EMIC waves. Our calculations indicate that EMIC waves can cause pitch angle scattering loss of several keV to hundreds of keV ions, and heating of tens of eV to several keV helium and oxygen ions by hydrogen‐ and helium‐band EMIC waves, respectively. Moreover, we found that magnetosonic waves can cause the resonant heating of thermal protons. Our study indicates the importance of energy transfer from the EMIC and magnetosonic waves to ions with different species at thermal energies.
Plain Language Summary
Electromagnetic ion cyclotron (EMIC) waves and magnetosonic waves are plasma waves commonly observed in the Earth's magnetosphere. The EMIC waves and magnetosonic waves are associated with the ions drifting around the Earth. We use satellite observations of the plasma waves and ions to study the relation between EMIC or magnetosonic waves with ions at thermal energies. The measurement clearly indicates the correlation between the enhancement of proton, helium, and oxygen fluxes with magnetosonic waves, hydrogen‐band EMIC waves, and helium‐band EMIC waves, respectively. We use the physics‐based model to quantify the possible heating of ions with different species by different wave modes. Our calculation suggests that the protons, helium, and oxygen ions at thermal energies could be effectively heated by magnetosonic waves, hydrogen‐band EMIC waves, and helium‐band EMIC waves, respectively. The model results explain the measured correlation between the ions and waves. Our study suggests that the EMIC and magnetosonic waves which are generated by the ions in ring current could transfer energy to the lower energy ions.
Key Points
EMIC waves in different frequency bands and magnetosonic waves are correlated with the enhancement of ion fluxes of different species
EMIC and magnetosonic waves could heat different ion species at thermal energies through resonant interaction
Field‐aligned thermal ions are accelerated to larger pitch angles and trapped ion fluxes increase due to the EMIC and magnetosonic waves
Abstract The objective of this study was to investigate the clinical features of Kimura's disease in the head and neck region and to compare the local recurrence rate between three therapies used for ...the treatment of this disease. The clinicopathological information of 46 hospitalized patients suffering from Kimura's disease in the head and neck region over a 10-year period was reviewed retrospectively. All lesions were clinically observed in the head and neck region. These 46 patients underwent a total of 58 treatments; nine patients underwent multiple treatments due to local recurrence. Of the 58 treatments, 32 involved surgical excision alone, 24 involved surgical excision and postoperative low-dose radiotherapy (20–40 Gy), one was a combination of ultrasound-guided core needle biopsy and radiotherapy, and one was a combination of incisional biopsy and subsequent radiotherapy. During the follow-up period, nine patients suffered 16 local recurrences. The recurrence rate of surgical excision combined with low-dose radiotherapy was much lower than that of surgical excision alone or radiotherapy alone (both P < 0.05). It is concluded that Kimura's disease is a benign condition with a good prognosis, and surgical excision combined with postoperative low-dose radiotherapy is associated with the lowest local recurrence rate in the treatment of this disease.
Soil contamination in urban environment by trace metals is of public concerns. For better risk assessment, it is important to determine their background concentrations in urban soils. For this study, ...we determined the background concentrations of 9 trace metals including As, Ba, Cd, Co, Cu, Ni, Pb, Se, and Zn in 214 urban soils in Florida from two large cities (Orlando and Tampa) and 4 small cities (Clay County, Ocala, Pensacola and West Palm Beach). The objectives were to determine: 1) total concentrations of trace metals in urban soils in cities of different size; 2) compare background concentrations to Florida Soil Cleanup Target Levels (FSCTLs); and 3) determine their distribution and variability in urban soils via multivariate statistical analysis. Elemental concentrations in urban soils were variable, with Pb being the highest in 5 cities (165–552 mg kg−1) and Zn being the highest concentration in Tampa (1,000 mg kg−1). Besides, the As and Pb concentrations in some soils exceeded the FSCTL for residential sites at 2.1 mg kg−1 As and 400 mg kg−1 Pb. Among the cities, Clay County and Orlando had the lowest concentrations for most elements, with Cd, Co, and As being the lowest while Ba, Pb and Zn being the highest. Among all values, geometric means were the lowest while 95th percentile was the highest for all metals. Most 95th percentile values were 2–3 folds higher than the GM data, with Pb presenting the greatest difference, being 4 times greater than GM value (58.9 vs. 13.6 mg kg−1). Still they were lower than FSCTL, with As exceeding FSCTL for residential sites at 2.1 mg kg−1. In addition, the linear discriminate analysis showed distinct separation among the cities: Ocala (Ba & Ni) and Pensacola (As & Pb) were distinctly different from each other and from other cities with higher metal concentrations. The large variations among elemental concentrations showed the importance to establish proper background concentrations of trace metals in urban soils.
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•Background concentrations of 9 trace elements in 214 urban soils were determined.•Arithmetic and geometric mean, 95th percentile and upper confidence level were calculated.•Regardless city size, human activities had similar impacts on elemental concentrations.•As, Ba, Cr and Pb levels exceeded Florida Soil Cleanup Target Levels for residential sites.•Among all values, GM was the lowest while 95th percentile was the highest.
Large concentration variations showed the importance to establish proper background concentrations of trace metals in urban soils.
Arsenic (As) in soils is of major environmental concern due to its ubiquity and carcinogenicity. Pteris vittata (Chinese brake fern) is the first known As-hyperaccumulator, which is highly efficient ...in extracting As from soils and translocating it to the fronds, making it possible to be used for phytoremediation of As-contaminated soils. In addition, P. vittata has served as a model plant to study As metabolisms in plants. Based on the recent advances, we reviewed the mechanisms of efficient As solubilization and transformation in rhizosphere soils of P. vittata and effective As uptake, translocation and detoxification in P. vittata. We also provided future research perspectives to further improve As phytoremediation by P. vittata.
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•P. vittata solubilizes Fe minerals via root exudates phytate and bacterial siderophores.•Rhizosphere bacterial oxidation of AsIII to AsV enhances As uptake by P. vittata.•Phosphate transporters mediate efficient AsV uptake in P. vittata.•ACR3s mediate AsIII translocation to the fronds and AsIII efflux outside the roots.•Arsenite efflux transporters ACR3s are critical for As metabolisms in P. vittata.
Review the mechanisms of efficient As solubilization in soils and effective As accumulation by As-hyperaccumulator Pteris vittata.
This is the first paper to present a hybrid method coupling an Improved Meshless Local Petrov Galerkin method with Rankine source solution (IMLPG_R) based on the Navier–Stokes (NS) equations, with a ...finite element method (FEM) based on the fully nonlinear potential flow theory (FNPT) in order to efficiently simulate the violent waves and their interaction with marine structures. The two models are strongly coupled in space and time domains using a moving overlapping zone, wherein the information from both the solvers is exchanged. In the time domain, the Runge–Kutta 2nd order method is nested with a predictor–corrector scheme. In the space domain, numerical techniques including ‘Feeding Particles’ and two-layer particle interpolation with relaxation coefficients are introduced to achieve the robust coupling of the two models. The properties and behaviours of the new hybrid model are tested by modelling a regular wave, solitary wave and Cnoidal wave including breaking and overtopping. It is validated by comparing the results of the method with analytical solutions, results from other methods and experimental data. The paper demonstrates that the method can produce satisfactory results but uses much less computational time compared with a method based on the full NS model.
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•Two new arsenic reductases PvHAC1 and PvHAC2 were isolated in Pteris vittata (PV)•AsV reduction in As-hyperaccumulator PV was mainly in the rhizomes not the roots•AsV reduction by ...PvHAC1 in rhizomes was critical for As hyperaccumulation by PV•AsV reduction by arsenic reductase PvHAC2 occurred in P. vittata fronds•Expressing PvHAC2 enhanced As tolerance and reduced As accumulation in A. thaliana.
Arsenic-hyperaccumulator Pteris vittata is efficient in As absorption, reduction, and translocation. But the molecular mechanisms and locations of arsenate (AsV) reduction in P. vittata are still unclear. Here, we identified two new arsenate reductase genes from P. vittata, PvHAC1 and PvHAC2. Two PvHAC genes encoded a rhodanase-like protein, which were localized in the cytoplasm and nucleus. Both recombinant Escherichia coli strains and transgenic Arabidopsis thaliana lines showed arsenate reductase ability after expressing PvHAC genes. Further, expressing PvHAC2 enhanced As tolerance and reduced As accumulation in A. thaliana shoots under AsV exposure. Based on expression pattern analysis, PvHAC1 and PvHAC2 were predominantly expressed in the rhizomes and fronds of P. vittata. Different from those of HAC homologous genes in non-hyperaccumulators, little PvHAC was expressed in the roots. Besides, PvHAC1 expression was strongly upregulated under AsV exposure but not AsIII. The data suggest that arsenate reductase PvHAC1 in the rhizomes coupled with arsenate reductase PvHAC2 in the fronds of P. vittata played a critical role in As-hyperaccumulation by P. vittata, which helps to further improve its utility in phytoremediation of As-contaminated soils.
This study aimed to systematically clarify attitudes and influencing factors of the public toward COVID-19 vaccination for children or adolescents.
This was a scoping review.
This scoping review ...screened, included, sorted, and analyzed relevant studies on COVID-19 vaccination for children or adolescents before December 31, 2021, in databases, including PubMed, Elsevier, Web of Science, Cochrane Library, and Wiley.
A total of 34 studies were included. The results showed that the public’s acceptance rate toward COVID-19 vaccination for children or adolescents ranged from 4.9% (southeast Nigerian mothers) to 91% (Brazilian parents). Parents’ or adolescents’ age, gender, education level, and cognition and behavior characteristics for the vaccines were the central factors affecting vaccination. The vaccine’s safety, effectiveness, and potential side-effects were the main reasons affecting vaccination.
Realizing current public attitudes of COVID-19 vaccination for adolescents or children can effectively develop intervention measures and control the pandemic as soon as possible through herd immunity.
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