Chemical-looping oxidative dehydrogenation(CL-ODH)is a process designed for the conversion of alkanes into olefins through cyclic redox reactions,eliminating the need for gaseous O_(2).In this work,we investigated the...Chemical-looping oxidative dehydrogenation(CL-ODH)is a process designed for the conversion of alkanes into olefins through cyclic redox reactions,eliminating the need for gaseous O_(2).In this work,we investigated the use of Ca_(2)MnO_(4)-layered perovskites modified with NaNO_(3) dopants,serving as redox catalysts(also known as oxygen carriers),for the CL-ODH of ethane within a temperature range of 700-780℃.Our findings revealed that the incorporation of NaNO_(3) as a modifier significantly-nhanced the selectivity for-thylene generation from Ca_(2)MnO_(4).At 750℃and a gas hourly space velocity of 1300 h^(-1),we achieved an-thane conversion up to 68.17%,accompanied by a corresponding-thylene yield of 57.39%.X-ray photoelectron spectroscopy analysis unveiled that the doping NaNO_(3) onto Ca_(2)MnO_(4) not only played a role in reducing the oxidation state of Mn ions but also increased the lattice oxygen content of the redox catalyst.Furthermore,formation of NaNO_(3) shell on the surface of Ca_(2)MnO_(4) led to a reduction in the concentration of manganese sites and modulated the oxygen-releasing behavior in a step-wise manner.This modulation contributed significantly to the enhanced selectivity for ethylene of the NaNO_(3)-doped Ca_(2)MnO_(4) catalyst.These findings provide compelling evidence for the potential of Ca_(2)MnO_(4)-layered perovskites as promising redox catalysts in the context of CL-ODH reactions.展开更多
By employing metal oxides as oxygen carriers,chemical looping demonstrates its effectiveness in transferring oxygen between reduction and oxidation environments to partially oxidize fuels into syngas and convert CO_(2...By employing metal oxides as oxygen carriers,chemical looping demonstrates its effectiveness in transferring oxygen between reduction and oxidation environments to partially oxidize fuels into syngas and convert CO_(2) into CO.Generally,NiFe_(2_)O_(4) oxygen carriers have demonstrated remarkable efficiency in chemical looping CO_(2) conversion.Nevertheless,the intricate process of atomic migration and evolution within the internal structure of bimetallic oxygen carriers during continuous high‐temperature redox cycling remains unclear.Consequently,the lack of a fundamental understanding of the complex ionic migration and oxygen transfer associated with energy conversion processes hampers the design of high‐performance oxygen carriers.Thus,in this study,we employed in situ characterization techniques and theoretical calculations to investigate the ion migration behavior and structural evolution in the bulk of NiFe_(2_)O_(4) oxygen carriers during H_(2) reduction and CO_(2)/lab air oxidation cycles.We discovered that during the H_(2) reduction step,lattice oxygen rapidly migrates to vacancy layers to replenish consumed active oxygen species,while Ni leaches from the material and migrates to the surface.During the CO_(2) splitting step,Ni migrates toward the core of the bimetallic oxygen carrier,forming Fe–Ni alloys.During the air oxidation step,Fe–Ni migrates outward,creating a hollow structure owing to the Kirkendall effect triggered by the swift transfer of lattice oxygen.The metal atom migration paths depend on the oxygen transfer rates.These discoveries highlight the significance of regulating the release–recovery rate of lattice oxygen to uphold the structures and reactivity of oxygen carriers.This work offers a comprehensive understanding of the oxidation/reduction‐driven atomic interdiffusion behavior of bimetallic oxygen carriers.展开更多
BACKGROUND Schwannomas are uncommon tumors originating from Schwann cells,forming the neural sheath.They account for approximately 2%-6%of all mesenchymal tumors and are most commonly identified in peripheral nerve tr...BACKGROUND Schwannomas are uncommon tumors originating from Schwann cells,forming the neural sheath.They account for approximately 2%-6%of all mesenchymal tumors and are most commonly identified in peripheral nerve trunks,with rarity in the gastrointestinal tract.Among gastrointestinal locations,the stomach harbors the majority of nerve sheath tumors,while such occurrences in the sigmoid colon are exceptionally infrequent.CASE SUMMARY This study presented a clinical case involving a 60-year-old female patient who,during colonoscopy,was diagnosed with a submucosal lesion that was later identified as a nerve sheath tumor.The patient underwent surgical resection,and the diagnosis was confirmed through immunohistochemistry.This study highlighted an exceptionally uncommon occurrence of a nerve sheath tumor in the sigmoid colon,which was effectively managed within our department.Additionally,a comprehensive review of relevant studies was conducted.CONCLUSION The preoperative diagnosis of nerve sheath tumors poses challenges,as the definitive diagnosis still relies on pathology and immunohistochemistry.Although categorized as benign,these tumors have the potential to demonstrate malignant behavior.Consequently,the optimal treatment approach entails the complete surgical excision of the tumor,ensuring the absence of residual lesions at the margins.展开更多
BACKGROUND Previous research has highlighted correlations between blood cell counts and chronic liver disease.Nonetheless,the causal relationships remain unknown.AIM To evaluate the causal effect of blood cell traits ...BACKGROUND Previous research has highlighted correlations between blood cell counts and chronic liver disease.Nonetheless,the causal relationships remain unknown.AIM To evaluate the causal effect of blood cell traits on liver enzymes and nonalcoholic fatty liver disease(NAFLD)risk.METHODS Independent genetic variants strongly associated with blood cell traits were extracted from a genome-wide association study(GWAS)conducted by the Blood Cell Consortium.Summary-level data for liver enzymes were obtained from the United Kingdom Biobank.NAFLD data were obtained from a GWAS meta-analysis(8434 cases and 770180 controls,discovery dataset)and the Fingen GWAS(2275 cases and 372727 controls,replication dataset).This analysis was conducted using the inverse-variance weighted method,followed by various sensitivity analyses.RESULTS One SD increase in the genetically predicted haemoglobin concentration(HGB)was associated with aβof 0.0078(95%CI:0.0059-0.0096),0.0108(95%CI:0.0080-0.0136),0.0361(95%CI:0.0156-0.0567),and 0.0083(95%CI:00046-0.0121)for alkaline phosphatase(ALP),alanine aminotransferase(ALT),aspartate aminotransferase,and gammaglutamyl transferase,respectively.Genetically predicted haematocrit was associated with ALP(β=0.0078,95%CI:0.0052-0.0104)and ALT(β=0.0057,95%CI:0.0039-0.0075).Genetically determined HGB and the reticulocyte fraction of red blood cells increased the risk of NAFLD[odds ratio(OR)=1.199,95%CI:1.087-1.322]and(OR=1.157,95%CI:1.071-1.250).The results of the sensitivity analyses remained significant.CONCLUSION Novel causal blood cell traits related to liver enzymes and NAFLD development were revealed through Mendelian randomization analysis,which may facilitate the diagnosis and prevention of NAFLD.展开更多
An extremely heavy rainfall event occurred in Zhengzhou,China,on 20 July 2021 and produced an hourly rainfall rate of 201.9 mm,which broke the station record for China's Mainland.Based on radar observations and a ...An extremely heavy rainfall event occurred in Zhengzhou,China,on 20 July 2021 and produced an hourly rainfall rate of 201.9 mm,which broke the station record for China's Mainland.Based on radar observations and a convection-permitting simulation using the WRF-ARW model,this paper investigates the multiscale processes,especially those at the mesoscale,that support the extreme observed hourly rainfall.Results show that the extreme rainfall occurred in an environment characteristic of warm-sector heavy rainfall,with abundant warm moist air transported from the ocean by an abnormally northward-displaced western Pacific subtropical high and Typhoon In-Fa(2021).However,rather than through back building and echo training of convective cells often found in warm-sector heavy rainfall events,this extreme hourly rainfall event was caused by a single,quasi-stationary storm in Zhengzhou.Scale separation analysis reveals that the extreme-rainproducing storm was supported and maintained by the dynamic lifting of low-level converging flows from the north,south,and east of the storm.The low-level northerly flow originated from a mesoscale barrier jet on the eastern slope of the Taihang Mountain due to terrain blocking of large-scale easterly flows,which reached an overall balance with the southerly winds in association with a low-level meso-β-scale vortex located to the west of Zhengzhou.The large-scale easterly inflows that fed the deep convection via transport of thermodynamically unstable air into the storm prevented the eastward propagation of the weak,shallow cold pool.As a result,the convective storm was nearly stationary over Zhengzhou,resulting in record-breaking hourly precipitation.展开更多
During the pre-summer rainy season,heavy rainfall occurs frequently in South China.Based on polarimetric radar observations,the microphysical characteristics and processes of convective features associated with extrem...During the pre-summer rainy season,heavy rainfall occurs frequently in South China.Based on polarimetric radar observations,the microphysical characteristics and processes of convective features associated with extreme rainfall rates(ERCFs)are examined.In the regions with high ERCF occurrence frequency,sub-regional differences are found in the lightning flash rate(LFR)distributions.In the region with higher LFRs,the ERCFs have larger volumes of high reflectivity factor above the freezing level,corresponding to more active riming processes.In addition,these ERCFs are more organized and display larger spatial coverage,which may be related to the stronger low-level wind shear and higher terrain in the region.In the region with lower LFRs,the ERCFs have lower echo tops and lower-echo centroids.However,no clear differences of the most unstable convective available potential energy(MUCAPE)exist in the ERCFs in the regions with different LFR characteristics.Regardless of the LFRs,raindrop collisional coalescence is the main process for the growth of raindrops in the ERCFs.In the ERCFs within the region with lower LFRs,the main mechanism for the rapid increase of liquid water content with decreasing altitude below 4 km is through the warm-rain processes converting cloud drops to raindrops.However,in those with higher LFRs,the liquid water content generally decreases with decreasing altitude.展开更多
The first long-term rainfall monitoring experiment using the commercial microwave links(CMLs)network in East China is introduced.The network,located in Jiangyin,Jiangsu Province,consists of 49 links with frequencies r...The first long-term rainfall monitoring experiment using the commercial microwave links(CMLs)network in East China is introduced.The network,located in Jiangyin,Jiangsu Province,consists of 49 links with frequencies ranging from 15 GHz to 26 GHz and lengths from 1.14 km to 4.78 km.An OTT PARSIVEL disdrometer is deployed to refine the local rain-induced attenuation relationship,and the CML observations are compared simultaneously with five rain gauges.The inversion parameters of the CML are optimized by minimizing the error of the accumulated rainfall of historical rainfall events.The inversion results show that the daily accumulated rainfall retrieved by the CMLs agrees well with the rain gauge measurements.As an opportunistic approach to monitor near-surface rainfall with high spatiotemporal representativeness and accuracy,the CML network can be used to monitor and forecast urban flood disasters,especially in regions where the widepread deployment of conventional meteorological instruments is impractical.展开更多
A mesoscale convective system(MCS)is an organized cluster of thunderstorms known to be the most important convective mode in causing disastrous high-impact weather,such as heavy rainfall,hail,damaging winds,and tornad...A mesoscale convective system(MCS)is an organized cluster of thunderstorms known to be the most important convective mode in causing disastrous high-impact weather,such as heavy rainfall,hail,damaging winds,and tornadoes.The small spatial scale and fast temporal evolution of MCSs make their observation and prediction very challenging.East Asia is home to the world’s most prominent monsoon,setting the stage for various severe convective weather events.MCSs and their associated high-impact weather have long been critical issues of concern;as such,their research efforts are valued by governments in East Asia.展开更多
Park 7 gene encodes a conserved protein called DJ-1 protein, which involves autophagy stress, but the mechanism is unclear. Therefore, it is necessary to explore the mechanism of DJ-1 regulation PC-12 autophagical str...Park 7 gene encodes a conserved protein called DJ-1 protein, which involves autophagy stress, but the mechanism is unclear. Therefore, it is necessary to explore the mechanism of DJ-1 regulation PC-12 autophagical stress. Using CRISPR/Cas9 technique to construct DJ-1 knockout PC-12 cell lines, we culture wild-type and DJ-1 knockout PC-12 cell lines, establish oxidative stress cell model by MPP+, and divide them into wild-type control group (WT), wild-type intervention group (WT + MPP+), DJ-1 knockout control group (KO) and DJ-1 knockout intervention group (KO + MPP+), and explore the role of DJ-1 in regulating neuronal autophagy stress by cell viability assay, immunofluorescence, confocal, western blotting and electron microscopy. The results show that the growth ability of DJ-1 knockout cells is inferior to that of normal cells, and DJ-1 knockout cells are more sensitive to oxidative stress and more vulnerable to damage than wild-type cells. Exposing to MPP+, DJ-1 proteins undergo oxidative responses at Cys-106 sites, while DJ-1 knockout PC-12 cells do not show similar responses. The wild-type PC-12 cells have the confocal in both anti-oxidant DJ-1 antibody and anti-C-Raf phosphorylation antibody. The activated DJ-1 induces the phosphorylation of C-Raf at Ser338 sites to activate directly C-Raf, and subsequently activates ERK1/2 signaling pathways to antagonize MPP+-induced neurotoxicity. Lack of DJ-1, oxidative stress can not promote C-Raf activation. Although the phosphorylation level of cell ERK is also increased, the increase of intranucleus pERK is not obvious. Wild type and DJ-1 knockout PC-12 cells can produce autophagical stress in the face of oxidative stress, but the proportion of autophagolysosomes produced in wild type PC-12 cells is larger than that in DJ-1 knockout cells. PD98059 can reduce autophagy stress in the state of oxidative stress in wild-type PC-12 cells, and the number of autophagolysosomes is similarly reduced, while sorafenib decreased slightly DJ-1 the autophagical stress, and the proportion of autophagolysosomes decreased more. Therefore, we can infer that activated DJ-1 directly phosphorylates C-Raf at Ser-338 sites, then activating C-Raf, subsequent activation of the MEK/ERK pathway. DJ-1 promotes autophagy maturation through the C-Raf/ERK pathway, thereby improving cell survival.展开更多
Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have be...Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have been successfully utilized to investigate precipitation microphysics and improve radar quantitative precipitation estimation(QPE).The recent progress in dual-pol radar research and applications in China is summarized in four aspects.Firstly,the characteristics of several representative dual-pol radars are reviewed.Various approaches have been developed for radar data quality control,including calibration,attenuation correction,calculation of specific differential phase shift,and identification and removal of non-meteorological echoes.Using dual-pol radar measurements,the microphysical characteristics derived from raindrop size distribution retrieval,hydrometeor classification,and QPE is better understood in China.The limited number of studies in China that have sought to use dual-pol radar data to validate the microphysical parameterization and initialization of numerical models and assimilate dual-pol data into numerical models are summarized.The challenges of applying dual-pol data in numerical models and emerging technologies that may make significant impacts on the field of radar meteorology are discussed.展开更多
Seasonal variations of rainfall microphysics in East China are investigated using data from the observations of a twodimensional video disdrometer and a vertically pointing micro rain radar. The precipitation and rain...Seasonal variations of rainfall microphysics in East China are investigated using data from the observations of a twodimensional video disdrometer and a vertically pointing micro rain radar. The precipitation and rain drop size distribution(DSD) characteristics are revealed for different rain types and seasons. Summer rainfall is dominated by convective rain,while during the other seasons the contribution of stratiform rain to rainfall amount is equal to or even larger than that of convective rain. The mean mass-weighted diameter versus the generalized intercept parameter pairs of convective rain are plotted roughly around the "maritime" cluster, indicating a maritime nature of convective precipitation throughout the year in East China. The localized rainfall estimators, i.e., rainfall kinetic energy–rain rate, shape–slope, and radar reflectivity–rain rate relations are further derived. DSD variability is believed to be a major source of diversity of the aforementioned derived estimators. These newly derived relations would certainly improve the accuracy of rainfall kinetic energy estimation, DSD retrieval, and quantitative precipitation estimation in this specific region.展开更多
As a newly discovered type of RNA, circular RNAs(circRNAs) are widespread throughout the eukaryotic genome. The expression of circRNAs is regulated by both cis-elements and trans-factors, and the expression pattern of...As a newly discovered type of RNA, circular RNAs(circRNAs) are widespread throughout the eukaryotic genome. The expression of circRNAs is regulated by both cis-elements and trans-factors, and the expression pattern of circRNAs is cell type-and diseasespecific. Similar to other types of non-coding RNAs, functions of circRNAs are also versatile. CircRNAs have been reported previously to function as microRNA(miRNA) sponges, protein sponges, coding RNAs or scaffolds for protein complexes.Recently, several circRNAs have been reported to play important roles in human malignancies, including glioma. Here, we reviewed several reports related to circRNAs and glioma, as well as the potential diagnostic and therapeutic applications of circRNAs in brain cancer. In general, some circRNAs, such as circSMARCA5 and circCFH, are found to be expressed in a gliomaspecific pattern, these circRNAs may be used as tumor biomarkers. In addition, some circRNAs have been found to play oncogenic roles in glioma(e.g., circNFIX and circNT5E), whereas others have been reported to function as tumor suppressors(e.g.,circFBXW7 and circSHPRH). Furthermore, circRNA is a good tool for protein expression because of its higher stability compared to linear RNAs. Thus, circRNAs may also be an ideal choice for gene/protein delivery in future brain cancer therapies. There are some challenges in circRNA research in glioma and other diseases. Research related to circRNAs in glioma is comparatively new and many mysteries remain to be solved.展开更多
Objective Acute aortic dissection （AAD） is a catastrophic event with high early mortality rate, but to date, no data on the incidence of AAD in China's Mainland is available. This study aimed to estimate the inc...Objective Acute aortic dissection （AAD） is a catastrophic event with high early mortality rate, but to date, no data on the incidence of AAD in China's Mainland is available. This study aimed to estimate the incidence of AAD in China and characterize the clinical profile, management and in-hospital outcomes of this vascular event. Methods We used the China Health Insurance Research Data （the CHIRA Data） 2011 which comprises all inpatient hospital records （300,886） during the period of Jan. 1st 2011 to Dec. 31 2011 of 3,335,000 randomly sampled beneficiaries （1,718,500 men and 1,616,500 women） from 25 cities and counties in different economic-geographic regions of China's Mainland. Patients with acute aortic dissection were identified according to International Classification of Disease 10m Revision （ICD-10） of I71.0, The estimated incidence of AAD was calculated using the equation： estimated incidence = 2.0 × （40% × hospital admission rate） ＋ 60% × hospital admission rate. Results The hospital admission rate was 2.0/100,000 （65/3,325,000, 95% CI： 1.2-2.8）. The estimated annual incidence of AAD was 2.8/100,000 （95% CI： 1.9-3.6） and was higher in male than in female （3.7 vs. 1.5, P 〈 0.001）. The mean age was 58.9 ± 13.4 years. During the mean hospital stay of 23 ±6 days, the overall in-hospital mortality was 13.9% （9/65）. Conclusions Our study showed relatively lower but not negligible incidence and in-hospital mortality of AAD in the mainland of China. The mean age of patients with AAD in Chinese was younger than that reported by researches from west countries, while the male to female incidence ratio is similar to those reported by other studies.展开更多
The diurnal variation of precipitation over the Dabie Mountains(DBM) in eastern China during the 2013 mei-yu season is investigated with forecasts of a regional convection-permitting model. Simulated precipitation is ...The diurnal variation of precipitation over the Dabie Mountains(DBM) in eastern China during the 2013 mei-yu season is investigated with forecasts of a regional convection-permitting model. Simulated precipitation is verified against surface rain-gauge observations. The observed morning precipitation peak on the windward(relative to the prevailing synoptic-scale wind) side of the DBM is reproduced with good spatial and temporal accuracy. The interaction between the DBM and a nocturnal boundary layer low-level jet(BLJ) due to the inertial oscillation mechanism is shown to be responsible for this precipitation peak. The BLJ is aligned with the lower-level southwesterly synoptic-scale flow that carries abundant moisture.The BLJ core is established at around 0200 LST upwind of the mountains. It moves towards the DBM and reaches maximum intensity at about 70 km ahead of the mountains. When the BLJ impinges upon the windward side of the DBM in the early morning, mechanical lifting of moist air leads to condensation and subsequent precipitation.展开更多
This paper examines how assimilating surface observations can improve the analysis and forecast ability of a four- dimensional Variational Doppler Radar Analysis System （VDRAS）. Observed surface temperature and wind...This paper examines how assimilating surface observations can improve the analysis and forecast ability of a four- dimensional Variational Doppler Radar Analysis System （VDRAS）. Observed surface temperature and winds are assimilated together with radar radial velocity and reflectivity into a convection-permitting model using the VDRAS four-dimensional variational （4DVAR） data assimilation system. A squall-line case observed during a field campaign is selected to investigate the performance of the technique. A single observation experiment shows that assimilating surface observations can influence the analyzed fields in both the horizontal and vertical directions. The surface-based cold pool, divergence and gust front of the squall line are all strengthened through the assimilation of the single surface observation. Three experiments--assimilating radar data only, assimilating radar data with surface data blended in a mesoscale background, and assimilating both radar and surface observations with a 4DVAR cost function--are conducted to examine the impact of the surface data assimilation. Independent surface and wind profiler observations are used for verification. The result shows that the analysis and forecast are improved when surface observations are assimilated in addition to radar observations. It is also shown that the additional surface data can help improve the analysis and forecast at low levels. Surface and low-level features of the squall line-- including the surface warm inflow, cold pool, gust front, and low-level wind--are much closer to the observations after assimilating the surface data in VDRAS.展开更多
Isothermal oxidation behaviors of Ti-45Al-2Fe-2Mo-1Cr intermetallics with different oxygen contents were studied under the condition of 950 °C, 100 h in air, and the oxidation kinetic parameters were also evaluat...Isothermal oxidation behaviors of Ti-45Al-2Fe-2Mo-1Cr intermetallics with different oxygen contents were studied under the condition of 950 °C, 100 h in air, and the oxidation kinetic parameters were also evaluated. The results show that the oxidation resistance of the TiAl intermetallics is negatively related to the oxygen content, and both the mass gain and thickness of oxide scale increase with the oxygen content. The sub-surface microstructure of the oxide scales varies with the oxygen content. Z phase is observed in the sub-surface area of the low-oxygen-content alloy, while the τ2(Al2FeTi) phase is found in the medium-oxygen-content and the high-oxygen-content alloys. The deterioration of oxidation resistance is due to the enhanced internal oxidation with the increase of oxygen content. It is possible to improve the oxidation resistance by controlling the oxygen content.展开更多
1.Introduction Compared with the United States,whose annual number of tornadoes can exceed 1000,the average number of tornadoes per year in China over the past half a century is estimated to be fewer than 100（Fan and...1.Introduction Compared with the United States,whose annual number of tornadoes can exceed 1000,the average number of tornadoes per year in China over the past half a century is estimated to be fewer than 100（Fan and Yu,2015）,even though both countries are located in a similar latitudinal zone of the Northern Hemisphere.展开更多
With the development of urbanization,whether precipitation characteristics in Guangdong Province,China,from 1981 to 2015 have changed are investigated using rain gauge data from 76 stations.These characteristics inclu...With the development of urbanization,whether precipitation characteristics in Guangdong Province,China,from 1981 to 2015 have changed are investigated using rain gauge data from 76 stations.These characteristics include annual precipitation,rainfall frequency,intense rainfall(defined as hourly precipitation≥20 mm),light precipitation(defined as hourly precipitation≤2.5 mm),and extreme rainfall(defined as hourly rainfall exceeding the 99.9 th percentile of the hourly rainfall distribution).During these 35 years,the annual precipitation shows an increasing trend in the urban areas.While rainfall frequency and light precipitation have a decreasing trend,intense rainfall frequency shows an increasing trend.The heavy and extreme rainfall frequency both exhibit an increasing trend in the Pearl River Delta region,where urbanization is the most significant.These trends in both the warm seasons(May-October)and during the pre-flood season(April-June)appear to be more significant.On the contrary,the annual precipitation amount in rural areas has a decreasing trend.Although the heavy and extreme precipitation also show an increasing trend,it is not as strong and significant as that in the urban areas.During periods in which a tropical cyclone makes landfall along the South China Coast,the rainfall in urban areas has been consistently more than that in surrounding areas.The precipitation in the urban areas and to their west is higher after 1995,when the urbanization accelerated.These results suggest that urbanization has a significant impact on the precipitation characteristics of Guangdong Province.展开更多
基金support of National Natural Science Foundation of China(22179027)gratefully acknowledged.This work was also supported by the Natural Science Foundation of Guangxi Province(2021GXNSFAA075063,2018GXNSFDA281005)+1 种基金the National Key Research and Development Program of China(2017YFE0105500)Science&Technology Research Project of Guangdong Province(2017A020216009).
文摘Chemical-looping oxidative dehydrogenation(CL-ODH)is a process designed for the conversion of alkanes into olefins through cyclic redox reactions,eliminating the need for gaseous O_(2).In this work,we investigated the use of Ca_(2)MnO_(4)-layered perovskites modified with NaNO_(3) dopants,serving as redox catalysts(also known as oxygen carriers),for the CL-ODH of ethane within a temperature range of 700-780℃.Our findings revealed that the incorporation of NaNO_(3) as a modifier significantly-nhanced the selectivity for-thylene generation from Ca_(2)MnO_(4).At 750℃and a gas hourly space velocity of 1300 h^(-1),we achieved an-thane conversion up to 68.17%,accompanied by a corresponding-thylene yield of 57.39%.X-ray photoelectron spectroscopy analysis unveiled that the doping NaNO_(3) onto Ca_(2)MnO_(4) not only played a role in reducing the oxidation state of Mn ions but also increased the lattice oxygen content of the redox catalyst.Furthermore,formation of NaNO_(3) shell on the surface of Ca_(2)MnO_(4) led to a reduction in the concentration of manganese sites and modulated the oxygen-releasing behavior in a step-wise manner.This modulation contributed significantly to the enhanced selectivity for ethylene of the NaNO_(3)-doped Ca_(2)MnO_(4) catalyst.These findings provide compelling evidence for the potential of Ca_(2)MnO_(4)-layered perovskites as promising redox catalysts in the context of CL-ODH reactions.
基金National Natural Science Foundation of China,Grant/Award Numbers:52076209,52006224,52106285,22179027Foundation and Applied Foundation Research of Guangdong Province,Grant/Award Number:2022B1515020045+1 种基金Natural Science Foundation of Guangxi Province,Grant/Award Number:2021GXNSFAA075036Young Talent Support Project of Guangzhou Association for Science and Technology,Grant/Award Number:QT‐2023‐042。
文摘By employing metal oxides as oxygen carriers,chemical looping demonstrates its effectiveness in transferring oxygen between reduction and oxidation environments to partially oxidize fuels into syngas and convert CO_(2) into CO.Generally,NiFe_(2_)O_(4) oxygen carriers have demonstrated remarkable efficiency in chemical looping CO_(2) conversion.Nevertheless,the intricate process of atomic migration and evolution within the internal structure of bimetallic oxygen carriers during continuous high‐temperature redox cycling remains unclear.Consequently,the lack of a fundamental understanding of the complex ionic migration and oxygen transfer associated with energy conversion processes hampers the design of high‐performance oxygen carriers.Thus,in this study,we employed in situ characterization techniques and theoretical calculations to investigate the ion migration behavior and structural evolution in the bulk of NiFe_(2_)O_(4) oxygen carriers during H_(2) reduction and CO_(2)/lab air oxidation cycles.We discovered that during the H_(2) reduction step,lattice oxygen rapidly migrates to vacancy layers to replenish consumed active oxygen species,while Ni leaches from the material and migrates to the surface.During the CO_(2) splitting step,Ni migrates toward the core of the bimetallic oxygen carrier,forming Fe–Ni alloys.During the air oxidation step,Fe–Ni migrates outward,creating a hollow structure owing to the Kirkendall effect triggered by the swift transfer of lattice oxygen.The metal atom migration paths depend on the oxygen transfer rates.These discoveries highlight the significance of regulating the release–recovery rate of lattice oxygen to uphold the structures and reactivity of oxygen carriers.This work offers a comprehensive understanding of the oxidation/reduction‐driven atomic interdiffusion behavior of bimetallic oxygen carriers.
文摘BACKGROUND Schwannomas are uncommon tumors originating from Schwann cells,forming the neural sheath.They account for approximately 2%-6%of all mesenchymal tumors and are most commonly identified in peripheral nerve trunks,with rarity in the gastrointestinal tract.Among gastrointestinal locations,the stomach harbors the majority of nerve sheath tumors,while such occurrences in the sigmoid colon are exceptionally infrequent.CASE SUMMARY This study presented a clinical case involving a 60-year-old female patient who,during colonoscopy,was diagnosed with a submucosal lesion that was later identified as a nerve sheath tumor.The patient underwent surgical resection,and the diagnosis was confirmed through immunohistochemistry.This study highlighted an exceptionally uncommon occurrence of a nerve sheath tumor in the sigmoid colon,which was effectively managed within our department.Additionally,a comprehensive review of relevant studies was conducted.CONCLUSION The preoperative diagnosis of nerve sheath tumors poses challenges,as the definitive diagnosis still relies on pathology and immunohistochemistry.Although categorized as benign,these tumors have the potential to demonstrate malignant behavior.Consequently,the optimal treatment approach entails the complete surgical excision of the tumor,ensuring the absence of residual lesions at the margins.
基金the Shanghai Natural Science Foundation of China,No.23ZR1447800and the Fengxian District Science and Technology Commission Project,China,No.20211838.
文摘BACKGROUND Previous research has highlighted correlations between blood cell counts and chronic liver disease.Nonetheless,the causal relationships remain unknown.AIM To evaluate the causal effect of blood cell traits on liver enzymes and nonalcoholic fatty liver disease(NAFLD)risk.METHODS Independent genetic variants strongly associated with blood cell traits were extracted from a genome-wide association study(GWAS)conducted by the Blood Cell Consortium.Summary-level data for liver enzymes were obtained from the United Kingdom Biobank.NAFLD data were obtained from a GWAS meta-analysis(8434 cases and 770180 controls,discovery dataset)and the Fingen GWAS(2275 cases and 372727 controls,replication dataset).This analysis was conducted using the inverse-variance weighted method,followed by various sensitivity analyses.RESULTS One SD increase in the genetically predicted haemoglobin concentration(HGB)was associated with aβof 0.0078(95%CI:0.0059-0.0096),0.0108(95%CI:0.0080-0.0136),0.0361(95%CI:0.0156-0.0567),and 0.0083(95%CI:00046-0.0121)for alkaline phosphatase(ALP),alanine aminotransferase(ALT),aspartate aminotransferase,and gammaglutamyl transferase,respectively.Genetically predicted haematocrit was associated with ALP(β=0.0078,95%CI:0.0052-0.0104)and ALT(β=0.0057,95%CI:0.0039-0.0075).Genetically determined HGB and the reticulocyte fraction of red blood cells increased the risk of NAFLD[odds ratio(OR)=1.199,95%CI:1.087-1.322]and(OR=1.157,95%CI:1.071-1.250).The results of the sensitivity analyses remained significant.CONCLUSION Novel causal blood cell traits related to liver enzymes and NAFLD development were revealed through Mendelian randomization analysis,which may facilitate the diagnosis and prevention of NAFLD.
基金supported by the National Science Foundation of China(Grant No.42122036)the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(2019QZKK0105)+2 种基金the National Key R&D Programs of China(2018YFC1507300)the National Science Foundation of China(Grant No.91837207)the Beijing Climate Center(QHMS2021008).
文摘An extremely heavy rainfall event occurred in Zhengzhou,China,on 20 July 2021 and produced an hourly rainfall rate of 201.9 mm,which broke the station record for China's Mainland.Based on radar observations and a convection-permitting simulation using the WRF-ARW model,this paper investigates the multiscale processes,especially those at the mesoscale,that support the extreme observed hourly rainfall.Results show that the extreme rainfall occurred in an environment characteristic of warm-sector heavy rainfall,with abundant warm moist air transported from the ocean by an abnormally northward-displaced western Pacific subtropical high and Typhoon In-Fa(2021).However,rather than through back building and echo training of convective cells often found in warm-sector heavy rainfall events,this extreme hourly rainfall event was caused by a single,quasi-stationary storm in Zhengzhou.Scale separation analysis reveals that the extreme-rainproducing storm was supported and maintained by the dynamic lifting of low-level converging flows from the north,south,and east of the storm.The low-level northerly flow originated from a mesoscale barrier jet on the eastern slope of the Taihang Mountain due to terrain blocking of large-scale easterly flows,which reached an overall balance with the southerly winds in association with a low-level meso-β-scale vortex located to the west of Zhengzhou.The large-scale easterly inflows that fed the deep convection via transport of thermodynamically unstable air into the storm prevented the eastward propagation of the weak,shallow cold pool.As a result,the convective storm was nearly stationary over Zhengzhou,resulting in record-breaking hourly precipitation.
基金primarily supported by the National Natural Science Foundation of China(Grant Nos.42025501,41905019,and 61827901)the National Key Research and Development Program of China(Grant 2018YFC1506404 and Grant 2017YFC1501703)。
文摘During the pre-summer rainy season,heavy rainfall occurs frequently in South China.Based on polarimetric radar observations,the microphysical characteristics and processes of convective features associated with extreme rainfall rates(ERCFs)are examined.In the regions with high ERCF occurrence frequency,sub-regional differences are found in the lightning flash rate(LFR)distributions.In the region with higher LFRs,the ERCFs have larger volumes of high reflectivity factor above the freezing level,corresponding to more active riming processes.In addition,these ERCFs are more organized and display larger spatial coverage,which may be related to the stronger low-level wind shear and higher terrain in the region.In the region with lower LFRs,the ERCFs have lower echo tops and lower-echo centroids.However,no clear differences of the most unstable convective available potential energy(MUCAPE)exist in the ERCFs in the regions with different LFR characteristics.Regardless of the LFRs,raindrop collisional coalescence is the main process for the growth of raindrops in the ERCFs.In the ERCFs within the region with lower LFRs,the main mechanism for the rapid increase of liquid water content with decreasing altitude below 4 km is through the warm-rain processes converting cloud drops to raindrops.However,in those with higher LFRs,the liquid water content generally decreases with decreasing altitude.
基金This research was funded by the China Postdoctoral Science Foundation(2021M701650)the Excellent Youth Scholars of the Natural Science Foundation of Hunan Province of China(2021JJ20046)+1 种基金the Open Grants of the State Key Laboratory of Severe Weather(Grant 2021LASW-A01)the National Natural Science Foundation of China(Grant No.42222505).
文摘The first long-term rainfall monitoring experiment using the commercial microwave links(CMLs)network in East China is introduced.The network,located in Jiangyin,Jiangsu Province,consists of 49 links with frequencies ranging from 15 GHz to 26 GHz and lengths from 1.14 km to 4.78 km.An OTT PARSIVEL disdrometer is deployed to refine the local rain-induced attenuation relationship,and the CML observations are compared simultaneously with five rain gauges.The inversion parameters of the CML are optimized by minimizing the error of the accumulated rainfall of historical rainfall events.The inversion results show that the daily accumulated rainfall retrieved by the CMLs agrees well with the rain gauge measurements.As an opportunistic approach to monitor near-surface rainfall with high spatiotemporal representativeness and accuracy,the CML network can be used to monitor and forecast urban flood disasters,especially in regions where the widepread deployment of conventional meteorological instruments is impractical.
文摘A mesoscale convective system(MCS)is an organized cluster of thunderstorms known to be the most important convective mode in causing disastrous high-impact weather,such as heavy rainfall,hail,damaging winds,and tornadoes.The small spatial scale and fast temporal evolution of MCSs make their observation and prediction very challenging.East Asia is home to the world’s most prominent monsoon,setting the stage for various severe convective weather events.MCSs and their associated high-impact weather have long been critical issues of concern;as such,their research efforts are valued by governments in East Asia.
文摘Park 7 gene encodes a conserved protein called DJ-1 protein, which involves autophagy stress, but the mechanism is unclear. Therefore, it is necessary to explore the mechanism of DJ-1 regulation PC-12 autophagical stress. Using CRISPR/Cas9 technique to construct DJ-1 knockout PC-12 cell lines, we culture wild-type and DJ-1 knockout PC-12 cell lines, establish oxidative stress cell model by MPP+, and divide them into wild-type control group (WT), wild-type intervention group (WT + MPP+), DJ-1 knockout control group (KO) and DJ-1 knockout intervention group (KO + MPP+), and explore the role of DJ-1 in regulating neuronal autophagy stress by cell viability assay, immunofluorescence, confocal, western blotting and electron microscopy. The results show that the growth ability of DJ-1 knockout cells is inferior to that of normal cells, and DJ-1 knockout cells are more sensitive to oxidative stress and more vulnerable to damage than wild-type cells. Exposing to MPP+, DJ-1 proteins undergo oxidative responses at Cys-106 sites, while DJ-1 knockout PC-12 cells do not show similar responses. The wild-type PC-12 cells have the confocal in both anti-oxidant DJ-1 antibody and anti-C-Raf phosphorylation antibody. The activated DJ-1 induces the phosphorylation of C-Raf at Ser338 sites to activate directly C-Raf, and subsequently activates ERK1/2 signaling pathways to antagonize MPP+-induced neurotoxicity. Lack of DJ-1, oxidative stress can not promote C-Raf activation. Although the phosphorylation level of cell ERK is also increased, the increase of intranucleus pERK is not obvious. Wild type and DJ-1 knockout PC-12 cells can produce autophagical stress in the face of oxidative stress, but the proportion of autophagolysosomes produced in wild type PC-12 cells is larger than that in DJ-1 knockout cells. PD98059 can reduce autophagy stress in the state of oxidative stress in wild-type PC-12 cells, and the number of autophagolysosomes is similarly reduced, while sorafenib decreased slightly DJ-1 the autophagical stress, and the proportion of autophagolysosomes decreased more. Therefore, we can infer that activated DJ-1 directly phosphorylates C-Raf at Ser-338 sites, then activating C-Raf, subsequent activation of the MEK/ERK pathway. DJ-1 promotes autophagy maturation through the C-Raf/ERK pathway, thereby improving cell survival.
基金primarily supported by the National Key Research and Development Program of China(Grant Nos.2017YFC1501703 and 2018YFC1506404)the National Natural Science Foundation of China(Grant Nos.41875053,41475015 and 41322032)+2 种基金the National Fundamental Research 973 Program of China(Grant Nos.2013CB430101 and2015CB452800)the Open Research Program of the State Key Laboratory of Severe Weatherthe Key Research Development Program of Jiangsu Science and Technology Department(Social Development Program,No.BE2016732)
文摘Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have been successfully utilized to investigate precipitation microphysics and improve radar quantitative precipitation estimation(QPE).The recent progress in dual-pol radar research and applications in China is summarized in four aspects.Firstly,the characteristics of several representative dual-pol radars are reviewed.Various approaches have been developed for radar data quality control,including calibration,attenuation correction,calculation of specific differential phase shift,and identification and removal of non-meteorological echoes.Using dual-pol radar measurements,the microphysical characteristics derived from raindrop size distribution retrieval,hydrometeor classification,and QPE is better understood in China.The limited number of studies in China that have sought to use dual-pol radar data to validate the microphysical parameterization and initialization of numerical models and assimilate dual-pol data into numerical models are summarized.The challenges of applying dual-pol data in numerical models and emerging technologies that may make significant impacts on the field of radar meteorology are discussed.
基金primarily supported by the National Key Research and Development Program of China(Grant No.2017YFC1501703)the National Natural Science Foundation of China(Grant Nos.41875053,41475015 and 41322032)+1 种基金the National Fundamental Research 973 Program of China(Grant Nos.2013CB430101 and 2015CB452800)collected by a National 973 Project(Grant No.2013CB430101)
文摘Seasonal variations of rainfall microphysics in East China are investigated using data from the observations of a twodimensional video disdrometer and a vertically pointing micro rain radar. The precipitation and rain drop size distribution(DSD) characteristics are revealed for different rain types and seasons. Summer rainfall is dominated by convective rain,while during the other seasons the contribution of stratiform rain to rainfall amount is equal to or even larger than that of convective rain. The mean mass-weighted diameter versus the generalized intercept parameter pairs of convective rain are plotted roughly around the "maritime" cluster, indicating a maritime nature of convective precipitation throughout the year in East China. The localized rainfall estimators, i.e., rainfall kinetic energy–rain rate, shape–slope, and radar reflectivity–rain rate relations are further derived. DSD variability is believed to be a major source of diversity of the aforementioned derived estimators. These newly derived relations would certainly improve the accuracy of rainfall kinetic energy estimation, DSD retrieval, and quantitative precipitation estimation in this specific region.
文摘As a newly discovered type of RNA, circular RNAs(circRNAs) are widespread throughout the eukaryotic genome. The expression of circRNAs is regulated by both cis-elements and trans-factors, and the expression pattern of circRNAs is cell type-and diseasespecific. Similar to other types of non-coding RNAs, functions of circRNAs are also versatile. CircRNAs have been reported previously to function as microRNA(miRNA) sponges, protein sponges, coding RNAs or scaffolds for protein complexes.Recently, several circRNAs have been reported to play important roles in human malignancies, including glioma. Here, we reviewed several reports related to circRNAs and glioma, as well as the potential diagnostic and therapeutic applications of circRNAs in brain cancer. In general, some circRNAs, such as circSMARCA5 and circCFH, are found to be expressed in a gliomaspecific pattern, these circRNAs may be used as tumor biomarkers. In addition, some circRNAs have been found to play oncogenic roles in glioma(e.g., circNFIX and circNT5E), whereas others have been reported to function as tumor suppressors(e.g.,circFBXW7 and circSHPRH). Furthermore, circRNA is a good tool for protein expression because of its higher stability compared to linear RNAs. Thus, circRNAs may also be an ideal choice for gene/protein delivery in future brain cancer therapies. There are some challenges in circRNA research in glioma and other diseases. Research related to circRNAs in glioma is comparatively new and many mysteries remain to be solved.
文摘Objective Acute aortic dissection （AAD） is a catastrophic event with high early mortality rate, but to date, no data on the incidence of AAD in China's Mainland is available. This study aimed to estimate the incidence of AAD in China and characterize the clinical profile, management and in-hospital outcomes of this vascular event. Methods We used the China Health Insurance Research Data （the CHIRA Data） 2011 which comprises all inpatient hospital records （300,886） during the period of Jan. 1st 2011 to Dec. 31 2011 of 3,335,000 randomly sampled beneficiaries （1,718,500 men and 1,616,500 women） from 25 cities and counties in different economic-geographic regions of China's Mainland. Patients with acute aortic dissection were identified according to International Classification of Disease 10m Revision （ICD-10） of I71.0, The estimated incidence of AAD was calculated using the equation： estimated incidence = 2.0 × （40% × hospital admission rate） ＋ 60% × hospital admission rate. Results The hospital admission rate was 2.0/100,000 （65/3,325,000, 95% CI： 1.2-2.8）. The estimated annual incidence of AAD was 2.8/100,000 （95% CI： 1.9-3.6） and was higher in male than in female （3.7 vs. 1.5, P 〈 0.001）. The mean age was 58.9 ± 13.4 years. During the mean hospital stay of 23 ±6 days, the overall in-hospital mortality was 13.9% （9/65）. Conclusions Our study showed relatively lower but not negligible incidence and in-hospital mortality of AAD in the mainland of China. The mean age of patients with AAD in Chinese was younger than that reported by researches from west countries, while the male to female incidence ratio is similar to those reported by other studies.
基金supported by the Special Foundation of the China Meteorological Administration (Grant No.GYHY201506006)supported by the National Science Foundation of China (Grant Nos.41405100,41322032 and 41275031)
文摘The diurnal variation of precipitation over the Dabie Mountains(DBM) in eastern China during the 2013 mei-yu season is investigated with forecasts of a regional convection-permitting model. Simulated precipitation is verified against surface rain-gauge observations. The observed morning precipitation peak on the windward(relative to the prevailing synoptic-scale wind) side of the DBM is reproduced with good spatial and temporal accuracy. The interaction between the DBM and a nocturnal boundary layer low-level jet(BLJ) due to the inertial oscillation mechanism is shown to be responsible for this precipitation peak. The BLJ is aligned with the lower-level southwesterly synoptic-scale flow that carries abundant moisture.The BLJ core is established at around 0200 LST upwind of the mountains. It moves towards the DBM and reaches maximum intensity at about 70 km ahead of the mountains. When the BLJ impinges upon the windward side of the DBM in the early morning, mechanical lifting of moist air leads to condensation and subsequent precipitation.
基金primarily supported by the National Fundamental Research 973 Program of China(Grant No.2013CB430101)the National Natural Science Foundation of China(Grant Nos.41275031,41322032 and 41475015)+1 种基金the Social Commonwealth Research Program(Grant Nos.GYHY201506004 and GYHY201006007)the Program for New Century Excellent Talents in Universities of China
文摘This paper examines how assimilating surface observations can improve the analysis and forecast ability of a four- dimensional Variational Doppler Radar Analysis System （VDRAS）. Observed surface temperature and winds are assimilated together with radar radial velocity and reflectivity into a convection-permitting model using the VDRAS four-dimensional variational （4DVAR） data assimilation system. A squall-line case observed during a field campaign is selected to investigate the performance of the technique. A single observation experiment shows that assimilating surface observations can influence the analyzed fields in both the horizontal and vertical directions. The surface-based cold pool, divergence and gust front of the squall line are all strengthened through the assimilation of the single surface observation. Three experiments--assimilating radar data only, assimilating radar data with surface data blended in a mesoscale background, and assimilating both radar and surface observations with a 4DVAR cost function--are conducted to examine the impact of the surface data assimilation. Independent surface and wind profiler observations are used for verification. The result shows that the analysis and forecast are improved when surface observations are assimilated in addition to radar observations. It is also shown that the additional surface data can help improve the analysis and forecast at low levels. Surface and low-level features of the squall line-- including the surface warm inflow, cold pool, gust front, and low-level wind--are much closer to the observations after assimilating the surface data in VDRAS.
基金Project(2014CB644002) supported by the National Key Fundamental Research and Development of ChinaProject(2017JJ2311) supported by the Natural Science Foundation of Hunan Province,ChinaProject(KFJJ11-7M) supported by the State Key Laboratory of Explosion Science and Technology,China
文摘Isothermal oxidation behaviors of Ti-45Al-2Fe-2Mo-1Cr intermetallics with different oxygen contents were studied under the condition of 950 °C, 100 h in air, and the oxidation kinetic parameters were also evaluated. The results show that the oxidation resistance of the TiAl intermetallics is negatively related to the oxygen content, and both the mass gain and thickness of oxide scale increase with the oxygen content. The sub-surface microstructure of the oxide scales varies with the oxygen content. Z phase is observed in the sub-surface area of the low-oxygen-content alloy, while the τ2(Al2FeTi) phase is found in the medium-oxygen-content and the high-oxygen-content alloys. The deterioration of oxidation resistance is due to the enhanced internal oxidation with the increase of oxygen content. It is possible to improve the oxidation resistance by controlling the oxygen content.
基金supported by the Ministry of Science and Technology of China National "973" Fundamental Research Program (Grant No.2013CB430103)
文摘1.Introduction Compared with the United States,whose annual number of tornadoes can exceed 1000,the average number of tornadoes per year in China over the past half a century is estimated to be fewer than 100（Fan and Yu,2015）,even though both countries are located in a similar latitudinal zone of the Northern Hemisphere.
基金primarily supported by the National Key Research and Development Program of China(Grant Nos.2017YFC1501703 and 2018YFC 1506404)the National Natural Science Foundation of China(Grant Nos.41875053,41805025,41475015 and 41322032)+2 种基金the Open Research Program of the State Key Laboratory of Severe Weatherthe 5th“333 High-level Personnel Training Project”of Jiangsu Province(BRA2019037)supported by the Research Grants Council of the Hong Kong Special Administrative Region of China(Grant No.CityU 11301417)。
文摘With the development of urbanization,whether precipitation characteristics in Guangdong Province,China,from 1981 to 2015 have changed are investigated using rain gauge data from 76 stations.These characteristics include annual precipitation,rainfall frequency,intense rainfall(defined as hourly precipitation≥20 mm),light precipitation(defined as hourly precipitation≤2.5 mm),and extreme rainfall(defined as hourly rainfall exceeding the 99.9 th percentile of the hourly rainfall distribution).During these 35 years,the annual precipitation shows an increasing trend in the urban areas.While rainfall frequency and light precipitation have a decreasing trend,intense rainfall frequency shows an increasing trend.The heavy and extreme rainfall frequency both exhibit an increasing trend in the Pearl River Delta region,where urbanization is the most significant.These trends in both the warm seasons(May-October)and during the pre-flood season(April-June)appear to be more significant.On the contrary,the annual precipitation amount in rural areas has a decreasing trend.Although the heavy and extreme precipitation also show an increasing trend,it is not as strong and significant as that in the urban areas.During periods in which a tropical cyclone makes landfall along the South China Coast,the rainfall in urban areas has been consistently more than that in surrounding areas.The precipitation in the urban areas and to their west is higher after 1995,when the urbanization accelerated.These results suggest that urbanization has a significant impact on the precipitation characteristics of Guangdong Province.
