Search

Based on multi‐model large‐ensemble experiments provided by Polar Amplification Model Intercomparison Project (PAMIP), we investigate the influence of the projected sea ice loss in Barents‐Kara Seas (BKS) and Sea of Okhotsk (SOK) on the Arctic stratospheric polar vortex (SPV). Results show that future BKS sea ice reduction leads to a weakened SPV during November‐February by enhancing the upward‐propagating planetary wave 1, which is more pronounced during Quasi‐Biennial Oscillation (QBO) easterly than westerly phase. Through weakening the upward‐propagating planetary wave 2, future SOK sea ice reduction is favorable for a strengthened SPV during January‐April. Inter‐model spread in the magnitudes of SPV responses to BKS sea ice reduction can be largely explained by the divergent planetary wave responses, but less so for SOK sea ice reduction. Results from a linearized baroclinic model further validate the importance of the planetary‐scale wave responses in explaining the differing SPV responses to sea‐ice loss over the two regions. Plain Language Summary: Arctic sea ice reduction influences the Northern Hemispheric weather and climate through modulating Arctic stratospheric polar vortex, which is a band of strong westerly encircling the pole during winter at ∼15–40 km above the Earth's surface. However, sea ice reduction over different regions could lead to different effects on the polar vortex. Here, we compare the effects of future sea ice reduction over the Barents‐Kara Seas, in the far‐north Atlantic Ocean, and the Sea of Okhotsk, in the northwest Pacific Ocean. We use carefully designed numerical simulations to estimate the effects of sea ice reduction, separately in the above‐mentioned two regions, on the polar vortex. Sea ice reduction over the Barents‐Kara Seas weakens the polar vortex, whereas sea ice reduction over Sea of Okhotsk strengthens the polar vortex. These contrasting effects are explained by opposing changes in wave activity entering the stratosphere from below. Barents‐Kara sea ice reduction leads to the strengthened upward propagating planetary waves, which break in the stratosphere and slow the polar vortex. Conversely, Okhotsk sea ice loss reduces upward waves and strengthens the polar vortex. Key Points: Barents‐Kara and Sea of Okhotsk sea ice loss weakens and strengthens polar vortex, respectively, with attendant changes in SSW frequencyPlanetary wave responses to Barents‐Kara and Okhotsk sea ice loss interfere constructively and destructively with mean flow, respectivelyPolar vortex weakening induced by Barents‐Kara sea ice loss is greater during easterly than westerly Quasi‐Biennial Oscillation phase [ABSTRACT FROM AUTHOR]

Snowpacks are natural water reservoirs providing a considerable amount of water for humans and ecosystems. However, current global snow products (e.g., ESA GlobSnow v3.0), lack high spatial resolution and regional calibrations necessary to capture the high heterogeneity of snow water equivalents (SWEs) in complex Asian mountainous terrains. Therefore, our understanding of snow drought characteristics in China remains limited. Herein, we used an improved SWE product calibrated specifically for China to explore the characteristics of snow droughts, delineated by a standardized SWE index (SWEI) between 1993 and 2019. Our analysis was focused over three main snow‐covered regions of China: Qinghai–Tibet Plateau (QTP), northern Xinjiang, Northeast China. Especially during the period from 1993 to 2010, we found that the SWEI increased significantly at rates of 0.022/yr (Northeast China), 0.017/yr (northern Xinjiang), and 0.011/yr (QTP) (p < 0.01, Mann‐Kendall trend test). Increased SWEI contributed to decreasing snow drought events across China, with an obvious short‐term characteristic, whilst area proportion of the identified 1‐month snow droughts was above 46.5% across three regions. Furthermore, we found that the occurrence of snow droughts was likely mediated by large‐scale atmospheric circulation, since increased water vapor transport caused a significant vapor flux convergence in cold seasons over three regions, especially in northern Xinjiang and Northeast China. Plain Language Summary: Snow droughts are caused by snow water equivalent (SWE) deficits and pose a significant climatic risk to humans and natural systems, particularly in snow‐dependent watersheds. Hence, understanding their main characteristics and driving forces is crucial for diagnosing and predicting potential climate risks. However, current research is not clear in terms of the occurrence and characteristics of snow drought in China. Therefore, we aim to investigate snow droughts based on specially calibrated SWE data in China. Alongside the increase of SWE in the three main snow‐covered areas across China, we found that the intensity of snow drought in China showed a clear downward trend, whilst both the extent and number of snow droughts decreased rapidly. Overall, these changes were likely regulated by atmospheric circulation, with the southward water vapor flux clearly increasing, providing a reliable source of water vapor and promoting the increase of snowfall. Our findings provide an important basis for the management and regulation of spring water resources to snow droughts in snow‐dependent watersheds. Key Points: A reliable snow water equivalent product calibrated specifically for China was used to assess snow droughtsBetween 1993 and 2019, the occurrence of snow droughts decreased rapidly, alongside their intensity and extentThe occurrence of snow droughts was regulated by large‐scale water vapor transport [ABSTRACT FROM AUTHOR]

As an important part of electronic packaging materials, low‐dielectric materials can ensure effective signal transmission between electronic components and have an impact on the performance of microprocessor chips. Herein, a porous poly(ether sulfone) membrane with low dielectric constant is fabricated via a breath figure method to meet requirements for high performance of new packaging materials. Perfluorononyl oxide side groups are introduced into the molecular structure of a block poly(ether sulfone) polymer by post‐grafting, and the pore‐making process and the dielectric properties of the materials are studied. The resulting multi‐block copolymers are found to have different electric and thermal properties depending on the molar ratio of perfluorononyl oxide side groups. Regular honeycomb pores can be formed with a polymer segment length of 8/16. Besides, the porous membranes with ordered pore structure on the surface possess low dielectric constant values ranging from 1.57 to 2.19 at 10 kHz. © 2021 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

The hormone melatonin is synthesized from serotonin by two enzymatic reactions (AANAT and ASMT/HIOMT) in the pineal gland following a circadian rhythm with low levels during the day and high levels at night. The robust nightly peak of melatonin secretion is an output signal of the circadian clock to the whole organism. However, so far the regulatory roles of endogenous melatonin in mammalian biological rhythms and physiology processes are poorly understood. Here, we establish congenic mouse lines (>N10 generations) that are proficient or deficient in melatonin synthesis (AH+/+ or AH−/− mice, respectively) on the C57BL/6J genetic background by crossing melatonin‐proficient MSM/Ms with C57BL/6J. AH+/+ mice displayed robust nightly peak of melatonin secretion and had significantly higher levels of pineal and plasma melatonin vs AH−/− mice. Using this mice model, we investigated the role of endogenous melatonin in regulating multiple biological rhythms, physiological processes, and rhythmic behaviors. In the melatonin‐proficient (AH+/+) mice, the rate of re‐entrainment of wheel‐running activity was accelerated following a 6‐hour phase advance of dark onset when comparted with AH−/− mice, suggesting a role of endogenous melatonin in facilitating clock adjustment. Further in the AH+/+ mice, there was a significant decrease in body weight, gonadal weight and reproductive performance, and a significant increase in daily torpor (a hypothermic and hypometabolic state lasting only hours during adverse conditions). Endogenous melatonin, however, had no effect in the modulation of the diurnal rhythm of 2‐[125I]‐iodomelatonin receptor expression in the SCN, free‐running wheel behavior in constant darkness, life span, spontaneous homecage behaviors, and various types of social‐emotional behaviors. The findings also shed light on the role of endogenous melatonin in mice domestication and provide new insights into melatonin's action in reducing energy expenditure during a food shortage. In summary, the congenic mice model generated in this study offers a significant advantage toward understanding of the role of endogenous melatonin in regulating melatonin receptor‐mediated rhythm behaviors and physiological functions. [ABSTRACT FROM AUTHOR]

The task of pedestrian detection is to identify the location and size of pedestrians in images or videos. However, occlusions are very common in real‐life scenarios, which make pedestrian detection more difficult. In order to solve the occlusion problem in pedestrian detection, a semantic feature enhancement module to acquire more informative and richer semantic features is proposed. The detector enhances semantic features by fusing feature maps of different layers, and detects pedestrians based on their locations and scales. The Experiments performed on Caltech and CityPersons datasets show that the algorithm achieves superior performance for detecting occluded pedestrians, especially heavily occluded ones. 30.6% and 47.9% log‐average missing rates are achieved in the heavily occluded subsets of Caltech and Cityperons, respectively. Moreover, this method is robust to the detection of heavily occluded pedestrians, and the module can be easily used by other detection frameworks. [ABSTRACT FROM AUTHOR]

Aims: The Schistosoma japonicum (S japonicum)‐infected ApoE gene deficiency (ApoE−/−) mice were used to determine effect of ApoE on hepatic immunopathology. Methods: Murine activities and appetite, body weight, and ratio of liver weight to its body weight (Hepatic mass index, HMI) were observed. Worm load and liver egg burden were evaluated as the infection intensity. Number and size of liver egg granulomas and serum levels of alanine aminotransferase (ALT) were investigated. We analysed hepatic fibrosis by markers of fibrosis in tissue, detected hepatic Th17 and Treg frequency by flow cytometry, and measured hepatic expressions of RORγt, Foxp3, IL‐17A and TGF‐β1 via qPCR. Lipid metabolism was determined by serum levels of cholesterol (TC) and triglyceride (TG) as well as hepatic Oil red O staining. Results: In the infected ApoE−/− mice, the increased infection intensity aggravated the hepatic immunopathology (evidenced by increased HMI, elevated egg granulomas and increased ALT levels) and fibrosis (increased hepatic collagen deposition). ApoE deficiency resulted in significantly elevated ratio of hepatic Th17/Treg and higher serum levels of TC and TG, along with higher level of hepatic Oil red O staining. Conclusions: ApoE deficiency promotes hepatic pathology and fibrosis by exacerbating Th17/Treg imbalance and altering lipid metabolism in murine schistosomiasis japonica. [ABSTRACT FROM AUTHOR]

Summary: Bowman–Birk trypsin inhibitors (BBIs) play important roles in animal and plant immunity, but how these protease inhibitors are involved in the immune system remains unclear. Here, we show that the rice (Oryza sativa) BBI protein APIP4 is a common target of a fungal effector and an NLR receptor for innate immunity. APIP4 exhibited trypsin inhibitor activity in vitro and in vivo. Knockout of APIP4 in rice enhanced susceptibility, and overexpression of APIP4 increased resistance to the fungal pathogen Magnaporthe oryzae. The M. oryzae effector AvrPiz‐t interacted with APIP4 and suppressed APIP4 trypsin inhibitor activity. By contrast, the rice NLR protein Piz‐t interacted with APIP4, enhancing APIP4 transcript and protein levels, and protease inhibitor activity. Our findings reveal a novel host defence mechanism in which a host protease inhibitor targeted by a fungal pathogen is protected by an NLR receptor. [ABSTRACT FROM AUTHOR]

Using potential vorticity to define Northern Hemisphere (NH) stratospheric polar vortex strength and position, the influence of the QBO on the polar vortex in winter is analyzed. The results show that the weakened/enhanced NH polar vortex in the lower stratosphere during easterly/westerly QBO (E/WQBO) phases is more noticeable in January and February than in November and December. Furthermore, the NH polar vortex shows a shift toward the Eurasian continent and away from North America in winter during EQBO phases compared with that during WQBO phases, with a greater shift in January and February than in November and December. The weaker QBO impact on the zonal mean zonal wind and temperature in February found in previous studies may be related to the cancelling effects of opposite‐signed anomalies over Eurasia and North America induced by the polar vortex shift associated with the QBO. During EQBO phases the upper stratospheric easterly anomalies in early winter increase the frequency of negative refractive index in the middle and high latitudes in late winter. Less planetary wave 1 propagates upward into the upper stratosphere and more wave 1 accumulates in the lower stratosphere, leading to the weakening and shift of the polar vortex in late winter. In addition, the poleward displacement of the subtropical jet during EQBO phases causes more poleward propagation of synoptic‐scale waves in the lower stratosphere, and thus more Rossby wave breaking events over Eurasia in late winter than during WQBO phases, further weakening and shifting the polar vortex in EQBO phases. Key Points: Arctic stratospheric polar vortex shows a shift toward Eurasian and away from North America in winter during EQBO phasesA stronger weakening and shift of Arctic stratospheric polar vortex during EQBO phases is found in late winter than in early winterWeaker QBO impact on the zonal mean of zonal wind in February is related to the cancelling effects induced by the polar vortex shift [ABSTRACT FROM AUTHOR]

A new hyperbranched poly(phenylene sulfide) (HPPS) is successfully synthesized by modified polycondensation of an AB2 monomer with a core molecule. [ABSTRACT FROM AUTHOR]

Background cGMP-hydrolyzing phosphodiesterase type 5 (PDE5) regulates vascular smooth muscle cell (SMC) contraction by antagonizing cGMP-dependent protein kinase I (PKGI)-dependent SMC relaxation. SMC contractile dysfunction is implicated in the pathogenesis of aortic aneurysm. PDE5 inhibitors have been used for treating erectile dysfunction, such as drug Viagra (sildenafil). However, a few clinical cases have reported the association of Viagra usage with aortic dissection, and reduced PDE5A expression was found in human aortic aneurysm tissues. Therefore, we aimed to investigate the effect of sildenafil on experimental abdominal aortic aneurysm (AAA), the most common form of aortic aneurysm in elderly men. Methods and Results AAA was induced in C57BL/6J male mice by periaortic elastase in combination with blocking elastin/collagen formation via 3-aminopropionitrile fumarate salt for 35 days. PDE5A protein levels detected by immunostaining were significantly reduced in mouse AAA. Sildenafil application in drinking water significantly aggravated aortic wall dilation and elastin degradation with pre-existing moderate AAA. The phosphorylation level of myosin light chain 2 at Ser19, a biochemical marker of SMC contraction, was significantly reduced by sildenafil in AAA. Proximity ligation assay further revealed that the interaction between cGMP and PKGI was significantly increased by sildenafil in AAA, suggesting an elevation of PKGI activation in AAA. Conclusions Sildenafil treatment aggravated the degradation of elastin fibers and progression of experimental AAA by dysregulating cGMP and contractile signaling in SMCs. Our findings may raise the caution of clinical usage of Viagra in aneurysmal patients.