The South Atlantic Anomaly (SAA) refers to a region where the strength of the magnetic field is notably weaker compared to a dipole field. While previous studies have primarily focused on its effects ...on the inner radiation belt, this study investigates its impact on the aurora system. By analyzing 2 years' worth of data obtained by the Fengyun‐3E/ACMag instrument, we discover that magnetic fluctuations within the auroral oval are significantly weaker in the longitude sector corresponding to the SAA, as compared to those outside this area. This characteristic remains permanent and independent of seasons and geomagnetic activities. Additional investigation using Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager (DMSP/SSUSI) observations reveals a similar phenomenon in the auroral intensity. Therefore, our results demonstrate that the SAA substantially weakens the aurora system, shedding new light on the effects of magnetic anomalies on planetary auroras and magnetosphere‐ionosphere‐thermosphere coupling.
Plain Language Summary
The South Atlantic Anomaly (SAA) is a unique location on Earth where the magnetic field is weaker than normal. This region has drawn a lot of attention because its weakened magnetic field brings the inner Van Allen radiation belt unusually close to the Earth's surface, which poses a threat to satellites passing through it. Here, we uncovered another interesting aspect of the SAA: its impact on the aurora system. To investigate this, we first examined 2 years' worth of data from the ACMag instruments on the Fengyun‐3E satellite, which orbits the Earth at an altitude of 836 km in a dawn‐dusk, Sun‐synchronous orbit. Our findings reveal that the magnetic fluctuations within the southern auroral oval are significantly weaker in the region that aligns with the SAA. This weakening effect is consistently present, regardless of the season or the level of geomagnetic activity. To reinforce our results, we also analyzed auroral intensity from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instrument on the Defense Meteorological Satellite Program (DMSP) satellite, and it corroborated the same weakening trend in this data set. In conclusion, our observations demonstrate that the SAA has a substantial impact on weakening the aurora system. This discovery deepens our understanding of how magnetic anomalies can influence planetary auroras.
Key Points
The effects of the South Atlantic Anomaly (SAA) on the terrestrial aurora system are examined using multiple instruments
Observations reveal a substantial weakening of auroral magnetic fluctuations and auroral intensity in the SAA longitude sector
The results indicate considering magnetic anomalies like the SAA is essential for comprehensively understanding planetary aurora systems
By designing a structured gas density profile between the dual-stage gas jets to manipulate electron seeding and energy chirp reversal for compressing the energy spread, we have experimentally ...produced high-brightness high-energy electron beams from a cascaded laser wakefield accelerator with peak energies in the range of 200-600 MeV, 0.4%-1.2% rms energy spread, 10-80 pC charge, and ∼0.2 mrad rms divergence. The maximum six-dimensional brightness B_{6D,n} is estimated as ∼6.5×10^{15} A/m^{2}/0.1%, which is very close to the typical brightness of e beams from state-of-the-art linac drivers. These high-brightness high-energy e beams may lead to the realization of compact monoenergetic gamma-ray and intense coherent x-ray radiation sources.
With the aim of gathering temporal trends on bacterial epidemiology and resistance from multiple laboratories in China, the CHINET surveillance system was organized in 2005. Antimicrobial ...susceptibility testing was carried out according to a unified protocol using the Kirby-Bauer method or automated systems. Results were analyzed according to Clinical and Laboratory Standards Institute (CLSI) 2014 definitions. Between 2005 and 2014, the number of bacterial isolates ranged between 22 774 and 84 572 annually. Rates of extended-spectrum β-lactamase production among Escherichia coli isolates were stable, between 51.7 and 55.8%. Resistance of E. coli and Klebsiella pneumoniae to amikacin, ciprofloxacin, piperacillin/tazobactam and cefoperazone/sulbactam decreased with time. Carbapenem resistance among K. pneumoniae isolates increased from 2.4 to 13.4%. Resistance of Pseudomonas aeruginosa strains against all of antimicrobial agents tested including imipenem and meropenem decreased with time. On the contrary, resistance of Acinetobacter baumannii strains to carbapenems increased from 31 to 66.7%. A marked decrease of methicillin resistance from 69% in 2005 to 44.6% in 2014 was observed for Staphylococcus aureus. Carbapenem resistance rates in K. pneumoniae and A. baumannii in China are high. Our results indicate the importance of bacterial surveillance studies.
A simple, efficient scheme was developed to obtain near-gigaelectronvolt electron beams with energy spreads of few per-mille level in a single-stage laser wakefield accelerator. Longitudinal plasma ...density was tailored to control relativistic laser-beam evolution, resulting in injection, dechirping, and a quasi-phase-stable acceleration. With this scheme, electron beams with peak energies of 780–840 MeV, rms energy spreads of 2.4‰–4.1‰, charges of 8.5–23.6 pC, and rms divergences of 0.1–0.4 mrad were experimentally obtained. Quasi-three-dimensional particle-in-cell simulations agreed well with the experimental results. The dechirping strength was estimated to reach up to 11 TeV/mm/m, which is higher than previously obtained results. Such high-quality electron beams will boost the development of compact intense coherent radiation sources and x-ray free-electron lasers.
The molecular mechanism underlying gastric cancer (GC) invasion and metastasis is still poorly understood. In this study, we tried to investigate the roles of CXCR4 and CXCR2 signalings in gastric ...cancer metastasis. A highly invasive gastric cancer cell model was established. Chemokines receptors were profiled to search for the accountable ones. Then the underlying molecular mechanism was investigated using both in vitro and in vivo techniques, and the clinical relevance of CXCR4 and CXCR2 expression was studied in gastric cancer samples. CXCR4 and CXCR2 were highly expressed in a high invasive gastric cancer cell model and in gastric cancer tissues. Overexpression of CXCR4 and CXCR2 was associated with more advanced tumor stage and poorer survival for GC patients. CXCR4 and CXCR2 expression strongly correlated with each other in the way that CXCR2 expression changed accordingly with the activity of CXCR4 signaling and CXCR4 expression also changed in agreement with CXCR2 activity. Further studies demonstrated CXCR4 and CXCR2 can both activated NF-κB and STAT3 signaling, while NF-κBp65 can then transcriptionally activate CXCR4 and STAT3 can activate CXCR2 expression. This crosstalk between CXCR4 and CXCR2 contributed to EMT, migration and invasion of gastric cancer. Finally, Co-inhibition of CXCR4 and CXCR2 is more effective in reducing gastric cancer metastasis. Our results demonstrated that CXCR4 and CXCR2 cross-activate each other to promote the metastasis of gastric cancer.
Abstract
The electronic instabilities in CsV
3
Sb
5
are believed to originate from the V 3
d
-electrons on the kagome plane, however the role of Sb 5
p
-electrons for 3-dimensional orders is largely ...unexplored. Here, using resonant tender X-ray scattering and high-pressure X-ray scattering, we report a rare realization of conjoined charge density waves (CDWs) in CsV
3
Sb
5
, where a 2 × 2 × 1 CDW in the kagome sublattice and a Sb 5
p
-electron assisted 2 × 2 × 2 CDW coexist. At ambient pressure, we discover a resonant enhancement on Sb
L
1
-edge (2
s
→5
p
) at the 2 × 2 × 2 CDW wavevectors. The resonance, however, is absent at the 2 × 2 × 1 CDW wavevectors. Applying hydrostatic pressure, CDW transition temperatures are separated, where the 2 × 2 × 2 CDW emerges 4 K above the 2 × 2 × 1 CDW at 1 GPa. These observations demonstrate that symmetry-breaking phases in CsV
3
Sb
5
go beyond the minimal framework of kagome electronic bands near van Hove filling.
Nitro-aromatic compounds (NACs), as important contributors to the light absorption by brown carbon, have been widely observed in various ambient atmospheres; however, their formation in the urban ...atmosphere was little studied. In this work, we report an intensive field study of NACs in summer 2016 at an urban Beijing site, characterized by both high-NOx and anthropogenic VOC dominated conditions. We investigated the factors that influence NAC formation (e.g., NO2, VOC precursors, RH and photolysis) through quantification of eight NACs, along with major components in fine particulate matter, selected volatile organic compounds, and gases. The average total concentration of the quantified NACs was 6.63 ng m-3, higher than those reported in other summertime studies (0.14–6.44 ng m-3). 4-Nitrophenol (4NP, 32.4 %) and 4-nitrocatechol (4NC, 28.5 %) were the top two most abundant NACs, followed by methyl-nitrocatechol (MNC), methyl-nitrophenol (MNP), and dimethyl-nitrophenol (DMNP). The oxidation of toluene and benzene in the presence of NOx was found to be a more dominant source of NACs than primary biomass burning emissions. The NO2 concentration level was found to be an important factor influencing the secondary formation of NACs. A transition from low- to high-NOx regimes coincided with a shift from organic- to inorganic-dominated oxidation products. The transition thresholds were NO2∼20 ppb for daytime andNO2∼25 ppb for nighttime conditions. Under low-NOx conditions, NACs increased with NO2, while the NO3- concentrations and (NO3-)/NACs ratios were lower, implying organic-dominated products. Under high-NOx conditions, NAC concentrations did not further increase with NO2, while theNO3- concentrations and (NO3-)/NACs ratios showed increasing trends, signaling a shift from organic- to inorganic-dominated products. Nighttime enhancements were observed for 3M4NC and 4M5NC, while daytime enhancements were noted for 4NP, 2M4NP, and DMNP, indicating different formation pathways for these two groups of NACs. Our analysis suggested that the aqueous-phase oxidation was likely the major formation pathway of 4M5NC and 3M5NC, while photo-oxidation of toluene and benzene in the presence of NO2 could be more important for the formation of nitrophenol and its derivatives. Using the (3M4NC+4M5NC) / 4NP ratios as an indicator of the relative contribution of aqueous-phase and gas-phase oxidation pathways to NAC formation, we observed that the relative contribution of aqueous-phase pathways increased at elevated ambient RH and remained constant at RH > 30 %. We also found that the concentrations of VOC precursors (e.g., toluene and benzene) and aerosol surface area acted as important factors in promoting NAC formation, and photolysis as an important loss pathway for nitrophenols.
Abstract Our aim was to differentiate IgG4-related sialadenitis, primary Sjögren syndrome, and chronic obstructive submandibular sialadenitis by analysing clinical, radiographic, and pathological ...features. Fifty-five patients, 50, and 50 were enrolled, respectively and their baseline characteristics and serological, sialographic, and pathological findings compared. The male:female ratio for IgG4-related sialadenitis was 1:1.2 for primary Sjögren syndrome 1:15.7, and for chronic obstructive submandibular sialadenitis1:0.92. Numbers with enlarged salivary glands were 55, 16, and 50; with xerostomia 26, 48, and 0; with a history of allergy 26, 4, and 6, and with coexisting systemic disease 12, 19, and 0 (p = 0.14). Mean (SD) serum IgG4 concentrations were 109.1 (97.9), 4.9. (1.9) g/L, and 5.3 (1.6) g/L, p < 0.001 in all cases. Sialography showed enlargement of the gland, dilatation of the duct, and slightly decreased secretory function in IgG4-related disease; obvious sialectasia and decreased secretory function in Sjögren syndrome; and dilatation of Wharton’s duct and filling defects in obstructive sialadenitis. Histopathological examination showed lymphoplasmacytic infiltration with storiform fibrosis, lymphoplasmacytic inflammation and lymphoepithelial lesions, and dilatation of the duct with epithelial metaplasia in the three groups, respectively. The number of IgG4-positive plasma cells was 123 (45)/HPF, 8 (3)/HPF, and 5 (4)/HPF, while the IgG4-/IgG-positive cell ratio was 71.7 (13.9)%, 4.6 (2.5)%, 18.9 (19.7)%, respectively (p < 0.001). The three conditions have different clinical, radiographic, and pathological features that provide important clues to the differential diagnosis. Serological and histological tests are important, and comprehensive consideration is necessary.
In December 2019, novel coronavirus pneumonia epidemic occurred in Wuhan, Hubei Province, and spread rapidly across the country. In the early stages of the epidemic, China adopted the containment ...strategy and implemented a series of core measures around this strategic point, including social mobilization, strengthening case isolation and close contacts tracking management, blocking epidemic areas and traffic control to reduce personnel movements and increase social distance, environmental measures and personal protection, with a view to controlling the epidemic as soon as possible in limited areas such as Wuhan. This article summarizes the background, key points and core measures in the country and provinces. It sent prospects for future prevention and control strategies.
Previous studies of geometric and morphologic parameters of intracranial aneurysms have been conducted to determine rupture risk, which remains incompletely defined due to patient-specific risk ...factors, such as sex, hypertension, and age. To this end, we compared characteristics of ruptured and unruptured aneurysms in the same patients with symmetric bilateral intracranial aneurysms.
Between January 2008 and March 2014, 2361 patients with 2674 aneurysms were diagnosed by CT angiography or surgical findings at 4 medical centers. Geometric and morphologic parameters examined for symmetric bilateral intracranial aneurysms comprised aneurysm wall regularity, size, neck width, aspect ratio, size ratio, neck-to-parent artery ratio, and area ratio. Univariate and multivariate statistical analyses were performed to determine independent risk factors for rupture.
Sixty-three patients (48 women, 15 men; mean age, 62.5 ± 9.8 years) with symmetric bilateral aneurysms were eligible for the study and were included. The most frequent aneurysm location was the posterior communicating artery. Univariate analysis disclosed that aneurysm size, aspect ratio, size ratio, area ratio, and irregular wall differed between patients with ruptured and unruptured aneurysms. Multivariate analysis indicated that aspect ratio of ≥1.6 (adjusted OR, 9.521; 95% CI, 2.182-41.535), area ratio of ≥1.5 (adjusted OR, 4.089; 95% CI, 1.247-13.406), and irregular shape (adjusted OR, 10.443; 95% CI 3.394-32.135) were significant predictive factors for aneurysm rupture after adjustment for aneurysm size.
An aspect ratio of ≥1.6, area ratio of ≥1.5, and irregular wall are associated with aneurysm rupture independent of aneurysm size and patient characteristics. These characteristics alone can help in distinguishing ruptured bilateral intracranial aneurysms from unruptured ones.
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