The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the s...The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the surrounding rock, a mechanical model was developed for the stability of the roadway support and surrounding rock. Analysis of the bearing capacity of the roof back-wall guard-board and modelling of the equations for the maximum deflection and the maximum compressive stress of the top and side beams of the I-shaped steel support were undertaken. Simultaneously, the model was used to calculate and analyse the stability of the top and side beams of the I-shaped steel support structure and analyse the criteria for their stability. The results provide a reliable theoretical basis for the judgment of the stability of the surrounding rock and support structure. The theoretical evaluation results are consistent with field data. Finally, the key support parameters of the top and side beams of the I-shaped steel support structure and the variation of the maximum deflection and the maximum compressive stress as affected by the influence of the guard-board length were investigated. It is concluded that, as the back-board length increases, the maximum compressive stress in the top beam of the I-shaped steel support increases while the compressive stress in the side beam decreases. The results show that the accuracy of judgment of the stability of a supported retreating roadway is improved, providing guidance for the design of such typical I-shaped steel support and back-board structures.展开更多
The Arab Spring in the spring of 2011 soon brought the Middle East into an abyss of chaos, instability, terrorism and civil war. Over the past six years, the Syria conflict in some areas tended to cool down. President...The Arab Spring in the spring of 2011 soon brought the Middle East into an abyss of chaos, instability, terrorism and civil war. Over the past six years, the Syria conflict in some areas tended to cool down. President Trump reached an agreement with Russian President Putin on building a new ＂conflict relegation zone＂ on July 7, 2017. After three years of hard fighting, Iraq liberated Mosul on July 9, 2017. Full restoration of territorial integrity is just around the comer. ISIS lost Mosul, and was trapped in Racca. Further loss of land and territory is just a matter of time.展开更多
The North China Craton(NCC) witnessed Mesozoic vigorous tectono-thermal activities and transition in the nature of deep lithosphere. These processes took place in three periods:(1) Late Paleozoic to Early Jurassic(~17...The North China Craton(NCC) witnessed Mesozoic vigorous tectono-thermal activities and transition in the nature of deep lithosphere. These processes took place in three periods:(1) Late Paleozoic to Early Jurassic(~170 Ma);(2) Middle Jurassic to Early Cretaceous(160-140 Ma);(3) Early Cretaceous to Cenozoic(140 Ma to present). The last two stages saw the lithospheric mantle replacement and coupled basin-mountain response within the North China Craton due to subduction and retreating of the Paleo-Pacific plate, and is the emphasis in this paper. In the first period,the subduction and closure of the PaleoAsian Ocean triggered the back-arc extension, syn-collisional compression and then post-collisional extension accompanied by ubiquitous magmatism along the northern margin of the NCC. Similar processes happened in the southern margin of the craton as the subduction of the Paleo-Tethys ocean and collision with the South China Block. These processes had caused the chemical modification and mechanical destruction of the cratonic margins. The margins could serve as conduits for the asthenosphere upwelling and had the priority for magmatism and deformation. The second period saw the closure of the Mongol-Okhotsk ocean and the shear deformation and magmatism induced by the drifting of the Paleo-Pacific slab. The former led to two pulse of N-S trending compression(Episodes A and B of the Yanshan Movement) and thus the pre-existing continental marginal basins were disintegrated into sporadically basin and range pro vince by the Mesozoic magmatic plutons and NE-SW trending faults.With the anticlockwise rotation of the Paleo-Pacific moving direction, the subduction-related magmatism migrated into the inner part of the craton and the Tanlu fault became normal fault from a sinistral one. The NCC thus turned into a back-arc extension setting at the end of this period. In the third period, the refractory subcontinental lithospheric mantle(SCLM) was firstly remarkably eroded and thinned by the subduction-induced asthenospheric upwelling, especially those beneath the weakzones(i.e.,cratonic margins and the lithospheric Tanlu fault zone). Then a slightly lithospheric thickening occurred when the upwelled asthenosphere got cool and transformed to be lithospheric mantle accreted(~125 Ma) beneath the thinned SCLM. Besides, the magmatism continuously moved southeastward and the extensional deformations preferentially developed in weak zones, which include the Early Cenozoic normal fault transformed from the Jurassic thrust in the Trans-North Orogenic Belt, the crustal detachment and the subsidence of Bohai basin caused by the continuous normal strike slip of the Tanlu fault, the Cenozoic graben basins originated from the fault depression in the Trans-North Orogenic Belt, the Bohai Basin and the Sulu Orogenic belt. With small block size, inner lithospheric weak zones and the surrounding subductions/collisions, the Mesozoic NCC was characterized by(1) lithospheric thinning and crustal detachment triggered by the subduction-induced asthenospheric upwelling.Local crustal contraction and orogenesis appeared in the Trans-North Orogenic Belt coupled with the crustal detachment;(2)then upwelled asthenosphere got cool to be newly-accreted lithospheric mantle and crustal grabens and basin subsidence happened, as a result of the subduction zone retreating. Therefore, the subduction and retreating of the western Pacific plate is the outside dynamics which resulted in mantle replacement and coupled basin-mountain respond within the North China Craton. We consider that the Mesozoic decratonization of the North China Craton,or the Yanshan Movement, is a comprehensive consequence of complex geological processes proceeding surrounding and within craton, involving both the deep lithospheric mantle and shallow continental crust.展开更多
During Carboniferous time,tremendous juvenile arc crust was formed in the southern Central Asian Orogenic Belt(CAOB),although its origin remains unclear.Herein,we presented zircon U-Pb-Hf and whole-rock geochemical an...During Carboniferous time,tremendous juvenile arc crust was formed in the southern Central Asian Orogenic Belt(CAOB),although its origin remains unclear.Herein,we presented zircon U-Pb-Hf and whole-rock geochemical and Sr-Nd isotopic data for a suite of volcanic and pyroclastic rocks from the Khan-Bogd area in southern Mongolia.These Carboniferous pyroclastic rocks generally have some early Paleozoic zircons,probably derived from the granitic and sedimentary rocks of the Lake Zone and the Gobi-Altai Zone to the north,indicative of a continental arc nature.In addition,they have a main zircon U-Pb age of ca.370–330 Ma,positive Hf and Nd isotopes,and mafic-intermediate arc affinity,similar to the coeval arc magmatism.Moreover,the pyroclastic rocks of the northern area have more mafic and older volcanic components with depositional time(ca.350–370 Ma;Visean and Bashkirian stages)earlier than that in the southern area(mainly ca.350–315 Ma;Serpukhovian and Bashkirian stages).Combining a preexisting northward subduction supported by the available magnetotelluric data with a slab rollback model of the main oceanic basin of the Paleo-Asian Ocean(PAO)during Carboniferous and Triassic times,we infer that the Carboniferous arc magmatism was probably derived from a backarc ocean triggered by slab rollback.Thus,the juvenile arc volcanism of Mongolia,together with other areas(e.g.,Junggar)in the southern CAOB,represented a significant lateral accretion that terminated after the Carboniferous due to a significant contraction of the PAO.展开更多
At dawn in Wufu Village,in Dinghu District of Zhaoqing City,Guangdong Province,the newly restored Chaoyangli Cultural Retreat is already welcoming its first visitors.A visitor surnamed Chen,who has travelled from Guan...At dawn in Wufu Village,in Dinghu District of Zhaoqing City,Guangdong Province,the newly restored Chaoyangli Cultural Retreat is already welcoming its first visitors.A visitor surnamed Chen,who has travelled from Guangzhou with his child,stops in front of the Chaxi Academy to admire local intangible cultural heritage crafts.展开更多
The mechanism involved in deep-seated landslide-debris flow disaster chains has been studied for many years,however,it is still not completely understood.This study aims to analyze the key factors that were involved a...The mechanism involved in deep-seated landslide-debris flow disaster chains has been studied for many years,however,it is still not completely understood.This study aims to analyze the key factors that were involved and led to the geological disaster of Shaziba 62.0 m deep landslide-debris flow.Two extensive field investigations were conducted before and after the slope failure event.The study further used drilled cores,high-density resistivity method,and aerial photographs to obtain valuable insights into the disaster chain.It was found that opencast coal mining operations broke the locked segment of the front edge and heavy rainfall softened the slip zones along the faults.Mechanical calculations demonstrated that the coupling condition of the opencast coal mining and heavy rainfall triggered the landslide.A new evolution model was put forth to describe the complex mechanism of combining progressive retreat and tractive failure of hydraulic drive landslide,which was governed by the bedding-plane rock layer.Surface runoff caused the mass of the landslide to liquefy throughout the sliding process,resulting in overlapping deposits,debris-flow-barrier-lake,and erosion.These new insights led to the indication of a different triggering mechanism of landslides-debris flows,as well as laid the foundation for the proposed physical and mechanical mechanism model based on progressive retreat soil-rock mixed landslides with an upper locked segment and lower weak interlayer under heavy rainfall.展开更多
The Barents Sea is a marginal sea of the Arctic Ocean and contains substantial hydrocarbon resources.In recent years,the Barents Sea has emerged as one of the Arctic regions with the most pronounced sea ice variabilit...The Barents Sea is a marginal sea of the Arctic Ocean and contains substantial hydrocarbon resources.In recent years,the Barents Sea has emerged as one of the Arctic regions with the most pronounced sea ice variability.To analyze sea ice changes in the Barents Sea,sea ice data from the National Snow and Ice Data Center were utilized.A remarkable decline in sea ice has been witnessed in the northern and eastern regions.This phenomenon has expanded the ice-free operational area for marine structures,highlighting the significance of wave factors.A site within this area was chosen to estimate the wave parameters.The wave data from ERA5 were categorized according to wave energy in each season.Four mixture joint distribution models for the wave height and period were constructed based on the mixture distribution method and copula theory,and environmental contours were developed and compared with the conditional probability method.Despite differences in the design parameter results,the mixture models demonstrate good performance in sample fitting,particularly in the distribution tails.Among these models,the Gaussian copula offers the best fit.展开更多
As a highly sensitive indicator of climate change in the arid northwest region of China,glacier dynamics in the Kaidu-Konqi River Basin directly influence regional runoff patterns,thereby playing a crucial role in sha...As a highly sensitive indicator of climate change in the arid northwest region of China,glacier dynamics in the Kaidu-Konqi River Basin directly influence regional runoff patterns,thereby playing a crucial role in shapingregional hydrology and maintaining ecological stability.This study systematically assessed glacier distribution in2020 and analyzed glacier changes from 1972 to 2020 using the Chinese Glacier Inventory of Xinjiang in 2020(CGI-XJ2020),historical satellite imagery from 1972,and data from the Second Chinese Glacier Inventory.In2020,the basin contained 713 glaciers covering 313.99 km^(2),with an estimated glacier volume of 11.81 km^(3)(0.41%glacier coverage).Glaciers were predominantly clustered in the northern and southwestern mountains.Small glaciers(<0.5 km^(2))comprised 78%of the glacier count but only 3%of the total area,whereas glaciers≥0.5 km^(2)accounted for 97%of the total area and 83.6%of the glacier volume.From 1972 to 2020,the totalglacier area decreased by 42.28%(229.99 km^(2))and glacier volume by 49.51%(11.58 km^(3)),equating to meanannual rates of−0.88%and−1.03%,respectively.Glacier retreat drives temporary increases in meltwatersupply but threatens long-term regional runoff stability and ecological water security.The retreat rate variedover different periods,with a more pronounced decline observed between 1972 and 2007.These findingshighlight an accelerating glacier loss in the basin,underscoring the need for continued monitoring and assess-ment of its hydrological and ecological impacts.展开更多
BACKGROUND Chronic hepatitis B(CHB)patients rarely achieve functional cure with initial pegylated interferon alpha-2b(Peg-IFNα-2b)therapy.Validated tools to guide retreatment candidates are lacking.We hypothesized th...BACKGROUND Chronic hepatitis B(CHB)patients rarely achieve functional cure with initial pegylated interferon alpha-2b(Peg-IFNα-2b)therapy.Validated tools to guide retreatment candidates are lacking.We hypothesized that clinical indicators predict hepatitis B surface antigen(HBsAg)clearance during retreatment.AIM To develop a prediction model for HBsAg clearance in Peg-IFNα-2b retreatment.METHODS In this retrospective cohort study,we enrolled 135 CHB/compensated cirrhosis patients receiving Peg-IFNα-2b retreatment after initial non-clearance at Tianjin University Central Hospital(2017-2025).Predictors were identified through univariate Cox,least absolute shrinkage and selection operator,and multivariate Cox regression.Model performance was assessed via receiver operating characteristic analysis and Harrell’s C-index,with risk stratification by X-tile optimization.RESULTS HBsAg clearance rate was 20.74%(28/135).Independent predictors included:Combination nucleos(t)ide analogue(NA)therapy during initial treatment[hazard ratio(HR)=0.276,95%confidence interval(CI):0.092-0.833],baseline HBsAg at retreatment(HR=0.571,95%CI:0.410-0.795),HBsAg decline after initial treatment(HR=2.050,95%CI:1.108-3.793),and treatment interval(HR=1.013/week,95%CI:1.008-1.018).The retreatment HBsAg clearance prediction score(RHCP-S)demonstrated area under the curve of 0.920(95%CI:0.863-0.946),sensitivity of 92.3%,specificity of 79.3%.Clearance rates differed significantly:RHCP-S challenge group(≤74 points):3.45%,RHCP-S probable group(74-110 points):29.63%,RHCP-S dominant group(≥110 points):80.95%(P<0.001).CONCLUSION The overall HBsAg clearance rate with Peg-IFNα-2b retreatment was 20.74%(28/135).The RHCP-S model identifies optimal retreatment candidates(≥110 points)with 80.95%clearance probability,associated with the absence of combination NA therapy during initial treatment,greater initial HBsAg decline,longer intervals,and lower retreatment HBsAg.展开更多
Increasing population density and development of mountainous terrain have brought human settlements within reach of landslide hazards.In recent years,due to the shortening of return period for severe natural events su...Increasing population density and development of mountainous terrain have brought human settlements within reach of landslide hazards.In recent years,due to the shortening of return period for severe natural events such as heavy rainfall,snowline retreating,great earthquake together with human activities,catastrophic landslides happened more frequently than before,resulting in large-scale casualties due to the increasing occurrences of rapid long-runout rock avalanches,especially in China.This paper presents some typical case histories related to the catastrophic landslides,including the Guanling rock avalanche,the Yigong rockslide-debris avalanche,the Wenchuan earthquake-induced landslides and the Danba landslide.They occurred in the last decade.Moreover,taking the Jiweishan catastrophic rockslide-fragment flow and the Yuhuangge landslide located in the new Wushan Town for examples,early-warning system and risk management on landslides are discussed in detail.展开更多
Early Paleozoic accretionary orogens dominated the Western Gondwana margin and were characterized by nearly continuous subduction associated with crustal extension and back-arc basin development.The southwestern margi...Early Paleozoic accretionary orogens dominated the Western Gondwana margin and were characterized by nearly continuous subduction associated with crustal extension and back-arc basin development.The southwestern margin is represented by Famatinian and Pampean basement realms exposed in South America,both related to the protracted Paleozoic evolution of the Terra Australis Orogen,whereas the northwestern margin is mainly recorded in Cadomian domains of Europe and adjacent regions.However,no clear relationships between these regions were so far established.Based on a compilation and reevaluation of geological,paleomagnetic,petrological,geochronological and isotopic evidence,this contribution focuses on crustal-scale tectonic and geodynamic processes occurring in Western Gondwana accretionary orogens,aiming at disentangling their common Early Paleozoic evolution.Data show that accretionary orogens were dominated by high-temperature/lowpressure metamorphism and relatively high geothermal gradients,resulting from the development of extended/hyperextended margins and bulk transtensional deformation.In this sense,retreating-mode accretionary orogens characterized the Early Paleozoic Gondwana margin,though short-lived pulses of compression/transpression also occurred.The existence of retreating subduction zones favoured mantle-derived magmatism and mixing with relatively young(meta)sedimentary sources in a thin continental crust.Crustal reworking of previous forearc sequences due to trenchward arc migration thus took place through assimilation and anatexis in the arc/back-arc regions.Therefore,retreating-mode accretionary orogens were the locus of Early Paleozoic crustal growth in Western Gondwana,intimately associated with major flare-up events,such as those related to the Cadomian and Famatian arcs.Slab roll back,probably resulting from decreasing convergence rates and plate velocities after Gondwana assembly,was a key factor for orogen-scale geodynamic processes.Coupled with synchronous oblique subduction and crustal-scale dextral deformation,slab roll back might trigger toroidal mantle flow,thus accounting for bulk dextral transtension,back-arc extension/transtension and a large-scale anticlockwise rotation of Gondwana mainland.展开更多
Along the recently evacuated shores of the retreating Dead Sea black mud deposits have been exposed and hence subjected to head ward erosion resulting in landslides and land collapses threatening herewith the infrastr...Along the recently evacuated shores of the retreating Dead Sea black mud deposits have been exposed and hence subjected to head ward erosion resulting in landslides and land collapses threatening herewith the infrastructure in the area. The geotechnical and mineralogical characterization of the black mud show the presence of a variety of clays including smectite, kaolinite, illite, montmorollinite and muscovite with a natural water content near the liquid limit. These geotechnical and mineralogical properties indicate that the mud is prone to rapid erosion and sliding, which actually hit the area and have until now caused damages and degrading topography and geology in the area. The study also refers the origin of the black mud and its organic content to the erosion and deposition of Upper Cretaceous-Tertiary oil shale deposits formerly covering the whole surrounding areas of the Dead Sea. The study suggests engineering solutions to the geologic degradation processes in the area, before further damage to the infrastructure takes place.展开更多
In this study, we analyzed glacier changes in the Aksu River Basin during the period 1975–2016, based on Landsat MSS/TM/ETM+/OLI imagery analysis and the Chinese Glacier Inventory(CGI). The results showed that the to...In this study, we analyzed glacier changes in the Aksu River Basin during the period 1975–2016, based on Landsat MSS/TM/ETM+/OLI imagery analysis and the Chinese Glacier Inventory(CGI). The results showed that the total number, area, and volume of the studied glaciers in the Aksu River Basin decreased by 202(7.65%), 965.7 km^2(25.88%), and 74.85–78.52 km^3(23.72%–24.3%), respectively. The rate of glacier retreat in the basin was slower in the north, northwest and west, but reached the highest in the east(measuring 0.86% yr^(-1)). Furthermore, there were significant regional differences in the distribution and change of glaciers, the Kumalak River Basin had the largest glacier number and area, about 63.15% and 76.47% of the studied basin, and the rate of glacier retreat in the Kumalak River Basin was 0.65% yr^(-1), it was higher than the Toxkan River Basin which reached 0.57% yr^(-1). We found the shrinkage rate of glacier for different periods in the past 41 years, during 1975–1990 the glaciers showed the greatest retreat, while the rate of glacier area retreat slowed down significantly from 1990 to 2000. In recent 16 years since 2000, the rate of glacier retreat in the Toxkan River Basin was higher compared with 1990–2000. The RGI50^(-1)3.04920 glacier of Kumalak River Basin had been in a state of retreat since 1990. Over the past 41 years, the temperature and precipitation in the Aksu River Basin increased obviously, and the warming temperatures were clearly the main reason for glacier retreat in the region, while the increased precipitation in the mountain area may have a direct relation with the retreating rate of glaciers.展开更多
AIM： To evaluate the effectiveness of ultrasonographic screening for early detection of hepatocellular carcinoma （HCC）. METHODS： The data of 14 968 patients who had ultrasonography （US） for chronic liver disease...AIM： To evaluate the effectiveness of ultrasonographic screening for early detection of hepatocellular carcinoma （HCC）. METHODS： The data of 14 968 patients who had ultrasonography （US） for chronic liver diseases were collected into a database program from June 1995 to June 2005. The risk factors for HCC were also studied. A total of 6089 patients who had repeated US were enrolled, 264 patients were diagnosed with HCC during follow-up （mean, 39 mo）. RESULTS： The detection rate of small HCC （≤ 3 cm in diameter） was 67.7%. The tumor size detected by screening at the intervals of 6 mo was significantly smaller than that at longer intervals. Only 29.3% of HCC patients had an elevated serum alpha fetoprotein （AFP） level above 400 ng/mL. The risk of HCC development during follow-up was higher in patients with liver cirrhosis （10.9%） and hepatitis C （9.0%） than in patients with chronic hepatitis （4.2%）, hepatitis B （4.9%） and non-B, non-C hepatitis （NBNC, 3.9%）. CONCLUSION： US screening at a interval of 6 mo is beneficial to high-risk patients over 40 years old and the early detection of HCC prolongs survival.展开更多
Soil erosion on the Loess Plateau of China is effectively controlled due to the implementation of several ecological restoration projects that improve soil properties and reduce soil erodibility. However, few studies ...Soil erosion on the Loess Plateau of China is effectively controlled due to the implementation of several ecological restoration projects that improve soil properties and reduce soil erodibility. However, few studies have examined the effects of vegetation restoration on soil properties and erodibility of gully head in the gully regions of the Loess Plateau. The objectives of this study were to quantify the effects of vegetation restoration on soil properties and erodibility in this region. Specifically, a control site in a slope cropland and 9 sites in 3 restored land-use types （5 sites in grassland, 3 in woodland and 1 in shrubland） in the Nanxiaohegou watershed of a typical gully region on the Loess Plateau were selected, and soil and root samples were collected to assess soil properties and root characteristics. Soil erodibility factor was calculated by the Erosion Productivity Impact Calculator method. Our results revealed that vegetation restoration increased soil sand content, soil saturated hydraulic conductivity, organic matter content and mean weight diameter of water-stable aggregate but decreased soil silt and clay contents and soil disintegration rate. A significant difference in soil erodibility was observed among different vegetation restoration patterns or land-use types. Compared with cropland, soil erodibility decreased in the restored lands by 3.99% to 21.43%. The restoration patterns of Cleistogenes caespitosa K. and Artemisia sacrorum L. in the grassland showed the lowest soil erodibility and can be considered as the optimal vegetation restoration pattern for improving soil anti-erodibility of the gully heads. Additionally, the negative linear change in soil erodibility for grassland with restoration time was faster than those of woodland and shrubland. Soil erodibility was significantly correlated with soil particle size distribution, soil disintegration rate, soil saturated hydraulic conductivity, water-stable aggregate stability, organic matter content and root characteristics （including root average diameter, root length density, root surface density and root biomass density）, but it showed no association with soil bulk density and soil total porosity. These findings indicate that although vegetation destruction is a short-term process, returning the soil erodibility of cropland to the level of grassland, woodland and shrubland is a long-term process （8-50 years）.展开更多
Glaciers are one of the most important land covers in alpine regions and especially sensitive to global climate change. Remote sensing has proved to be the best method of investigating the extent of glacial variations...Glaciers are one of the most important land covers in alpine regions and especially sensitive to global climate change. Remote sensing has proved to be the best method of investigating the extent of glacial variations in remote mountainous areas. Using Landsat thematic mapping （TM） and multi-spectral-scanner （MSS） images from Mt. Qomolangma （Everest） National Nature Preserve （QNNP）, central high Himalayas for 1976, 1988 and 2006 we derived glacial extent for these three periods. A combination of object-oriented image interpretation methods, expert knowledge rules and field surveys were employed. Results showed that （1） the glacial area in 2006 was 2710.17 ＋ 0.011 km2 （about 7.41% of the whole study area）, and located mainly to the south and between 4700 m to 6800 m above sea level; （2） from 1976 to 2006, glaciers reduced by 501.91± 0.035 km2 and glacial lakes expanded by 36.88 ＋ 0.035 kin2; the rate of glacier retreat was higher in sub-basins on the southern slopes （16.79%） of the Himalayas than on the northern slopes （14.40%）; most glaciers retreated, and mainly occurred at an elevation of 4700-6400 m, and the estimated upper limit of the retreat zone is between 6600 m and 6700 m; （3） increase in temperature and decrease in precipitation over the study period are the key factors driving retreat.展开更多
Understanding the dominant force responsible for supercontinent breakup is crucial for establishing Earth＇s geodynamic evolution that includes supercontinent cycles and plate tectonics. Conventionally,two forces have...Understanding the dominant force responsible for supercontinent breakup is crucial for establishing Earth＇s geodynamic evolution that includes supercontinent cycles and plate tectonics. Conventionally,two forces have been considered： the push by mantle plumes from the sub-continental mantle which is called the active force for breakup, and the dragging force from oceanic subduction retreat which is called the passive force for breakup. However, the relative importance of these two forces is unclear. Here we model the supercontinent breakup coupled with global mantle convection in order to address this question. Our global model features a spherical harmonic degree-2 structure, which includes a major subduction girdle and two large upwelling（superplume） systems. Based on this global mantle structure,we examine the distribution of extensional stress applied to the supercontinent by both subsupercontinent mantle upwellings and subduction retreat at the supercontinent peripheral. Our results show that：（1） at the center half of the supercontinent, plume push stress is ～3 times larger than the stress induced by subduction retreat;（2） an average hot anomaly of no higher than 50 K beneath the supercontinent can produce a push force strong enough to cause the initialization of supercontinent breakup;（3） the extensional stress induced by subduction retreat concentrates on a ～600 km wide zone on the boundary of the supercontinent, but has far less impact to the interior of the supercontinent. We therefore conclude that although circum-supercontinent subduction retreat assists supercontinent breakup, sub-supercontinent mantle upwelling is the essential force.展开更多
AIM: To establish the efficacy and safety of a 7-d therapeutic regimen using omeprazole,bismuth subcitrate,furazolidone and amoxicillin in patients with peptic ulcer disease who had been previously treated with other ...AIM: To establish the efficacy and safety of a 7-d therapeutic regimen using omeprazole,bismuth subcitrate,furazolidone and amoxicillin in patients with peptic ulcer disease who had been previously treated with other therapeutic regimens without success.METHODS: Open cohort study which included patients with peptic ulcer who had previously been treated unsuccessfully with one or more eradication regimens.The therapeutic regimen consisted of 20 mg omeprazole,240 mg colloidal bismuth subcitrate,1000 mg amoxicillin,and 200 mg furazolidone,taken twice a day for 7 d.Patients were considered as eradicated when samples taken from the gastric antrum and corpus 12 wk after the end of treatment were negative for Helicobacter pylori (H pylori) (rapid urease test and histology).Safety was determined by the presence of adverse effects.RESULTS: Fifty-one patients were enrolled.The eradication rate was 68.8% (31/45).Adverse effects were reported by 31.4% of the patients,and these were usually considered to be slight or moderate in the majority of the cases.Three patients had to withdraw from the treatment due to the presence of severe adverse effects.CONCLUSION: The association of bismuth,furazolidone,amoxicillin and a proton-pump inhibitor is a valuable alternative for patients who failed to respond to other eradication regimens.It is an effective,cheap and safe option for salvage therapy of positive patients.展开更多
Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic dec...Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic decline to about 4.28×10^6 km^2, which was 50% lower than conditions in the 1950 s to the 1970 s(Serreze et al., 2008). That was a record low over the course of the modern satellite record, since 1979(note that the year 2012 became the new record low). This astonishing event drew wide-ranging attention in 2007-2009 during the 4 th International Polar Year. The dramatic decline of sea ice attracts many scientists’ interest and has become the focus of intense research since then. Currently, sea ice retreat is not only appearing around the marginal ice zone, but also in the pack ice inside the central Arctic(Zhao et al., 2018). In fact, premonitory signs had already been seen through other evidence. Before the disintegration of the Soviet Union, US naval submarines had been conducting an extensive survey under the sea ice and taking measurements of sea ice thickness. Their measurements revealed a gradual decrease of ice thickness to 1.8 m during winter by the end of the 20 th century, in contrast to the climatological mean of 3.1 m(Rothrock et al., 1999). However, this alarming result did not draw much attention since the Arctic was still severely cold at that time.展开更多
基金Project(2014QNA50) supported by Fundamental Research Funds for the Central Universities,ChinaProject(51404248) supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development(PAPD) of Jiangsu Higher Education Institutions,China
文摘The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the surrounding rock, a mechanical model was developed for the stability of the roadway support and surrounding rock. Analysis of the bearing capacity of the roof back-wall guard-board and modelling of the equations for the maximum deflection and the maximum compressive stress of the top and side beams of the I-shaped steel support were undertaken. Simultaneously, the model was used to calculate and analyse the stability of the top and side beams of the I-shaped steel support structure and analyse the criteria for their stability. The results provide a reliable theoretical basis for the judgment of the stability of the surrounding rock and support structure. The theoretical evaluation results are consistent with field data. Finally, the key support parameters of the top and side beams of the I-shaped steel support structure and the variation of the maximum deflection and the maximum compressive stress as affected by the influence of the guard-board length were investigated. It is concluded that, as the back-board length increases, the maximum compressive stress in the top beam of the I-shaped steel support increases while the compressive stress in the side beam decreases. The results show that the accuracy of judgment of the stability of a supported retreating roadway is improved, providing guidance for the design of such typical I-shaped steel support and back-board structures.
文摘The Arab Spring in the spring of 2011 soon brought the Middle East into an abyss of chaos, instability, terrorism and civil war. Over the past six years, the Syria conflict in some areas tended to cool down. President Trump reached an agreement with Russian President Putin on building a new ＂conflict relegation zone＂ on July 7, 2017. After three years of hard fighting, Iraq liberated Mosul on July 9, 2017. Full restoration of territorial integrity is just around the comer. ISIS lost Mosul, and was trapped in Racca. Further loss of land and territory is just a matter of time.
基金supported by the National Key R&D Program of China(Grant No.2016YFC0600403)the National Natural Science Foundation of China(Grant No.91214204)
文摘The North China Craton(NCC) witnessed Mesozoic vigorous tectono-thermal activities and transition in the nature of deep lithosphere. These processes took place in three periods:(1) Late Paleozoic to Early Jurassic(~170 Ma);(2) Middle Jurassic to Early Cretaceous(160-140 Ma);(3) Early Cretaceous to Cenozoic(140 Ma to present). The last two stages saw the lithospheric mantle replacement and coupled basin-mountain response within the North China Craton due to subduction and retreating of the Paleo-Pacific plate, and is the emphasis in this paper. In the first period,the subduction and closure of the PaleoAsian Ocean triggered the back-arc extension, syn-collisional compression and then post-collisional extension accompanied by ubiquitous magmatism along the northern margin of the NCC. Similar processes happened in the southern margin of the craton as the subduction of the Paleo-Tethys ocean and collision with the South China Block. These processes had caused the chemical modification and mechanical destruction of the cratonic margins. The margins could serve as conduits for the asthenosphere upwelling and had the priority for magmatism and deformation. The second period saw the closure of the Mongol-Okhotsk ocean and the shear deformation and magmatism induced by the drifting of the Paleo-Pacific slab. The former led to two pulse of N-S trending compression(Episodes A and B of the Yanshan Movement) and thus the pre-existing continental marginal basins were disintegrated into sporadically basin and range pro vince by the Mesozoic magmatic plutons and NE-SW trending faults.With the anticlockwise rotation of the Paleo-Pacific moving direction, the subduction-related magmatism migrated into the inner part of the craton and the Tanlu fault became normal fault from a sinistral one. The NCC thus turned into a back-arc extension setting at the end of this period. In the third period, the refractory subcontinental lithospheric mantle(SCLM) was firstly remarkably eroded and thinned by the subduction-induced asthenospheric upwelling, especially those beneath the weakzones(i.e.,cratonic margins and the lithospheric Tanlu fault zone). Then a slightly lithospheric thickening occurred when the upwelled asthenosphere got cool and transformed to be lithospheric mantle accreted(~125 Ma) beneath the thinned SCLM. Besides, the magmatism continuously moved southeastward and the extensional deformations preferentially developed in weak zones, which include the Early Cenozoic normal fault transformed from the Jurassic thrust in the Trans-North Orogenic Belt, the crustal detachment and the subsidence of Bohai basin caused by the continuous normal strike slip of the Tanlu fault, the Cenozoic graben basins originated from the fault depression in the Trans-North Orogenic Belt, the Bohai Basin and the Sulu Orogenic belt. With small block size, inner lithospheric weak zones and the surrounding subductions/collisions, the Mesozoic NCC was characterized by(1) lithospheric thinning and crustal detachment triggered by the subduction-induced asthenospheric upwelling.Local crustal contraction and orogenesis appeared in the Trans-North Orogenic Belt coupled with the crustal detachment;(2)then upwelled asthenosphere got cool to be newly-accreted lithospheric mantle and crustal grabens and basin subsidence happened, as a result of the subduction zone retreating. Therefore, the subduction and retreating of the western Pacific plate is the outside dynamics which resulted in mantle replacement and coupled basin-mountain respond within the North China Craton. We consider that the Mesozoic decratonization of the North China Craton,or the Yanshan Movement, is a comprehensive consequence of complex geological processes proceeding surrounding and within craton, involving both the deep lithospheric mantle and shallow continental crust.
基金financially supported by the National Natural Science Foundation of China(42102260,42172236,42072264,41902229,and 42072267)Hong Kong Research Grants Council General Research Fund(17307918)+1 种基金the Fundamental Research Funds for the Central Universities,Chang’an University,China(300102272204)Opening Foundation of State Key Laboratory of Continental Dynamics,Northwest University,China(21LCD09)。
文摘During Carboniferous time,tremendous juvenile arc crust was formed in the southern Central Asian Orogenic Belt(CAOB),although its origin remains unclear.Herein,we presented zircon U-Pb-Hf and whole-rock geochemical and Sr-Nd isotopic data for a suite of volcanic and pyroclastic rocks from the Khan-Bogd area in southern Mongolia.These Carboniferous pyroclastic rocks generally have some early Paleozoic zircons,probably derived from the granitic and sedimentary rocks of the Lake Zone and the Gobi-Altai Zone to the north,indicative of a continental arc nature.In addition,they have a main zircon U-Pb age of ca.370–330 Ma,positive Hf and Nd isotopes,and mafic-intermediate arc affinity,similar to the coeval arc magmatism.Moreover,the pyroclastic rocks of the northern area have more mafic and older volcanic components with depositional time(ca.350–370 Ma;Visean and Bashkirian stages)earlier than that in the southern area(mainly ca.350–315 Ma;Serpukhovian and Bashkirian stages).Combining a preexisting northward subduction supported by the available magnetotelluric data with a slab rollback model of the main oceanic basin of the Paleo-Asian Ocean(PAO)during Carboniferous and Triassic times,we infer that the Carboniferous arc magmatism was probably derived from a backarc ocean triggered by slab rollback.Thus,the juvenile arc volcanism of Mongolia,together with other areas(e.g.,Junggar)in the southern CAOB,represented a significant lateral accretion that terminated after the Carboniferous due to a significant contraction of the PAO.
文摘At dawn in Wufu Village,in Dinghu District of Zhaoqing City,Guangdong Province,the newly restored Chaoyangli Cultural Retreat is already welcoming its first visitors.A visitor surnamed Chen,who has travelled from Guangzhou with his child,stops in front of the Chaxi Academy to admire local intangible cultural heritage crafts.
基金the Key Research and Development Project of Hubei Province(No.2021BCA219)。
文摘The mechanism involved in deep-seated landslide-debris flow disaster chains has been studied for many years,however,it is still not completely understood.This study aims to analyze the key factors that were involved and led to the geological disaster of Shaziba 62.0 m deep landslide-debris flow.Two extensive field investigations were conducted before and after the slope failure event.The study further used drilled cores,high-density resistivity method,and aerial photographs to obtain valuable insights into the disaster chain.It was found that opencast coal mining operations broke the locked segment of the front edge and heavy rainfall softened the slip zones along the faults.Mechanical calculations demonstrated that the coupling condition of the opencast coal mining and heavy rainfall triggered the landslide.A new evolution model was put forth to describe the complex mechanism of combining progressive retreat and tractive failure of hydraulic drive landslide,which was governed by the bedding-plane rock layer.Surface runoff caused the mass of the landslide to liquefy throughout the sliding process,resulting in overlapping deposits,debris-flow-barrier-lake,and erosion.These new insights led to the indication of a different triggering mechanism of landslides-debris flows,as well as laid the foundation for the proposed physical and mechanical mechanism model based on progressive retreat soil-rock mixed landslides with an upper locked segment and lower weak interlayer under heavy rainfall.
基金the National Natural Science Foundation of China(No.52171284)the Natural Science Foundation of Shandong Province(No.ZR2023QE016).
文摘The Barents Sea is a marginal sea of the Arctic Ocean and contains substantial hydrocarbon resources.In recent years,the Barents Sea has emerged as one of the Arctic regions with the most pronounced sea ice variability.To analyze sea ice changes in the Barents Sea,sea ice data from the National Snow and Ice Data Center were utilized.A remarkable decline in sea ice has been witnessed in the northern and eastern regions.This phenomenon has expanded the ice-free operational area for marine structures,highlighting the significance of wave factors.A site within this area was chosen to estimate the wave parameters.The wave data from ERA5 were categorized according to wave energy in each season.Four mixture joint distribution models for the wave height and period were constructed based on the mixture distribution method and copula theory,and environmental contours were developed and compared with the conditional probability method.Despite differences in the design parameter results,the mixture models demonstrate good performance in sample fitting,particularly in the distribution tails.Among these models,the Gaussian copula offers the best fit.
基金supported by the Third Xinjiang Scientific Expedition Program(Grant Nos.2022xjkk0101,2022xjkk0802)the Second Qinghai-Tibet Scientific Expedition Program(Grant No.2019QZKK0201)+2 种基金the National Natural Science Foundation of China(Grant No.42301166)the China-Tajikistan intergovernmental Joint R&D Project(Grant No.2025YFE0102800)the Science and Technology Program of Gansu Province(Grant Nos.23ZDFA017,22ZD6FA005)
文摘As a highly sensitive indicator of climate change in the arid northwest region of China,glacier dynamics in the Kaidu-Konqi River Basin directly influence regional runoff patterns,thereby playing a crucial role in shapingregional hydrology and maintaining ecological stability.This study systematically assessed glacier distribution in2020 and analyzed glacier changes from 1972 to 2020 using the Chinese Glacier Inventory of Xinjiang in 2020(CGI-XJ2020),historical satellite imagery from 1972,and data from the Second Chinese Glacier Inventory.In2020,the basin contained 713 glaciers covering 313.99 km^(2),with an estimated glacier volume of 11.81 km^(3)(0.41%glacier coverage).Glaciers were predominantly clustered in the northern and southwestern mountains.Small glaciers(<0.5 km^(2))comprised 78%of the glacier count but only 3%of the total area,whereas glaciers≥0.5 km^(2)accounted for 97%of the total area and 83.6%of the glacier volume.From 1972 to 2020,the totalglacier area decreased by 42.28%(229.99 km^(2))and glacier volume by 49.51%(11.58 km^(3)),equating to meanannual rates of−0.88%and−1.03%,respectively.Glacier retreat drives temporary increases in meltwatersupply but threatens long-term regional runoff stability and ecological water security.The retreat rate variedover different periods,with a more pronounced decline observed between 1972 and 2007.These findingshighlight an accelerating glacier loss in the basin,underscoring the need for continued monitoring and assess-ment of its hydrological and ecological impacts.
基金Supported by the Tianjin Health Research Project(Key Project),No.TJWJ2024ZD004Tianjin Key Medical Discipline(Specialty)Construction Project,No.TJYXZDXK-034A.
文摘BACKGROUND Chronic hepatitis B(CHB)patients rarely achieve functional cure with initial pegylated interferon alpha-2b(Peg-IFNα-2b)therapy.Validated tools to guide retreatment candidates are lacking.We hypothesized that clinical indicators predict hepatitis B surface antigen(HBsAg)clearance during retreatment.AIM To develop a prediction model for HBsAg clearance in Peg-IFNα-2b retreatment.METHODS In this retrospective cohort study,we enrolled 135 CHB/compensated cirrhosis patients receiving Peg-IFNα-2b retreatment after initial non-clearance at Tianjin University Central Hospital(2017-2025).Predictors were identified through univariate Cox,least absolute shrinkage and selection operator,and multivariate Cox regression.Model performance was assessed via receiver operating characteristic analysis and Harrell’s C-index,with risk stratification by X-tile optimization.RESULTS HBsAg clearance rate was 20.74%(28/135).Independent predictors included:Combination nucleos(t)ide analogue(NA)therapy during initial treatment[hazard ratio(HR)=0.276,95%confidence interval(CI):0.092-0.833],baseline HBsAg at retreatment(HR=0.571,95%CI:0.410-0.795),HBsAg decline after initial treatment(HR=2.050,95%CI:1.108-3.793),and treatment interval(HR=1.013/week,95%CI:1.008-1.018).The retreatment HBsAg clearance prediction score(RHCP-S)demonstrated area under the curve of 0.920(95%CI:0.863-0.946),sensitivity of 92.3%,specificity of 79.3%.Clearance rates differed significantly:RHCP-S challenge group(≤74 points):3.45%,RHCP-S probable group(74-110 points):29.63%,RHCP-S dominant group(≥110 points):80.95%(P<0.001).CONCLUSION The overall HBsAg clearance rate with Peg-IFNα-2b retreatment was 20.74%(28/135).The RHCP-S model identifies optimal retreatment candidates(≥110 points)with 80.95%clearance probability,associated with the absence of combination NA therapy during initial treatment,greater initial HBsAg decline,longer intervals,and lower retreatment HBsAg.
文摘Increasing population density and development of mountainous terrain have brought human settlements within reach of landslide hazards.In recent years,due to the shortening of return period for severe natural events such as heavy rainfall,snowline retreating,great earthquake together with human activities,catastrophic landslides happened more frequently than before,resulting in large-scale casualties due to the increasing occurrences of rapid long-runout rock avalanches,especially in China.This paper presents some typical case histories related to the catastrophic landslides,including the Guanling rock avalanche,the Yigong rockslide-debris avalanche,the Wenchuan earthquake-induced landslides and the Danba landslide.They occurred in the last decade.Moreover,taking the Jiweishan catastrophic rockslide-fragment flow and the Yuhuangge landslide located in the new Wushan Town for examples,early-warning system and risk management on landslides are discussed in detail.
基金financial support of the National Geographic Society(grant CP-123R17)Agencia Nacional de Promocion Científica y Tecnologica(PICT-2017-1092)financial support by the Deutsche Forschungsgemeinschaft during numerous projects in Brittanny,the Eastern Alps and Saxo-Thuringia。
文摘Early Paleozoic accretionary orogens dominated the Western Gondwana margin and were characterized by nearly continuous subduction associated with crustal extension and back-arc basin development.The southwestern margin is represented by Famatinian and Pampean basement realms exposed in South America,both related to the protracted Paleozoic evolution of the Terra Australis Orogen,whereas the northwestern margin is mainly recorded in Cadomian domains of Europe and adjacent regions.However,no clear relationships between these regions were so far established.Based on a compilation and reevaluation of geological,paleomagnetic,petrological,geochronological and isotopic evidence,this contribution focuses on crustal-scale tectonic and geodynamic processes occurring in Western Gondwana accretionary orogens,aiming at disentangling their common Early Paleozoic evolution.Data show that accretionary orogens were dominated by high-temperature/lowpressure metamorphism and relatively high geothermal gradients,resulting from the development of extended/hyperextended margins and bulk transtensional deformation.In this sense,retreating-mode accretionary orogens characterized the Early Paleozoic Gondwana margin,though short-lived pulses of compression/transpression also occurred.The existence of retreating subduction zones favoured mantle-derived magmatism and mixing with relatively young(meta)sedimentary sources in a thin continental crust.Crustal reworking of previous forearc sequences due to trenchward arc migration thus took place through assimilation and anatexis in the arc/back-arc regions.Therefore,retreating-mode accretionary orogens were the locus of Early Paleozoic crustal growth in Western Gondwana,intimately associated with major flare-up events,such as those related to the Cadomian and Famatian arcs.Slab roll back,probably resulting from decreasing convergence rates and plate velocities after Gondwana assembly,was a key factor for orogen-scale geodynamic processes.Coupled with synchronous oblique subduction and crustal-scale dextral deformation,slab roll back might trigger toroidal mantle flow,thus accounting for bulk dextral transtension,back-arc extension/transtension and a large-scale anticlockwise rotation of Gondwana mainland.
文摘Along the recently evacuated shores of the retreating Dead Sea black mud deposits have been exposed and hence subjected to head ward erosion resulting in landslides and land collapses threatening herewith the infrastructure in the area. The geotechnical and mineralogical characterization of the black mud show the presence of a variety of clays including smectite, kaolinite, illite, montmorollinite and muscovite with a natural water content near the liquid limit. These geotechnical and mineralogical properties indicate that the mud is prone to rapid erosion and sliding, which actually hit the area and have until now caused damages and degrading topography and geology in the area. The study also refers the origin of the black mud and its organic content to the erosion and deposition of Upper Cretaceous-Tertiary oil shale deposits formerly covering the whole surrounding areas of the Dead Sea. The study suggests engineering solutions to the geologic degradation processes in the area, before further damage to the infrastructure takes place.
基金National Natural Science Foundation of China,No.41630859,No.41471030
文摘In this study, we analyzed glacier changes in the Aksu River Basin during the period 1975–2016, based on Landsat MSS/TM/ETM+/OLI imagery analysis and the Chinese Glacier Inventory(CGI). The results showed that the total number, area, and volume of the studied glaciers in the Aksu River Basin decreased by 202(7.65%), 965.7 km^2(25.88%), and 74.85–78.52 km^3(23.72%–24.3%), respectively. The rate of glacier retreat in the basin was slower in the north, northwest and west, but reached the highest in the east(measuring 0.86% yr^(-1)). Furthermore, there were significant regional differences in the distribution and change of glaciers, the Kumalak River Basin had the largest glacier number and area, about 63.15% and 76.47% of the studied basin, and the rate of glacier retreat in the Kumalak River Basin was 0.65% yr^(-1), it was higher than the Toxkan River Basin which reached 0.57% yr^(-1). We found the shrinkage rate of glacier for different periods in the past 41 years, during 1975–1990 the glaciers showed the greatest retreat, while the rate of glacier area retreat slowed down significantly from 1990 to 2000. In recent 16 years since 2000, the rate of glacier retreat in the Toxkan River Basin was higher compared with 1990–2000. The RGI50^(-1)3.04920 glacier of Kumalak River Basin had been in a state of retreat since 1990. Over the past 41 years, the temperature and precipitation in the Aksu River Basin increased obviously, and the warming temperatures were clearly the main reason for glacier retreat in the region, while the increased precipitation in the mountain area may have a direct relation with the retreating rate of glaciers.
文摘AIM： To evaluate the effectiveness of ultrasonographic screening for early detection of hepatocellular carcinoma （HCC）. METHODS： The data of 14 968 patients who had ultrasonography （US） for chronic liver diseases were collected into a database program from June 1995 to June 2005. The risk factors for HCC were also studied. A total of 6089 patients who had repeated US were enrolled, 264 patients were diagnosed with HCC during follow-up （mean, 39 mo）. RESULTS： The detection rate of small HCC （≤ 3 cm in diameter） was 67.7%. The tumor size detected by screening at the intervals of 6 mo was significantly smaller than that at longer intervals. Only 29.3% of HCC patients had an elevated serum alpha fetoprotein （AFP） level above 400 ng/mL. The risk of HCC development during follow-up was higher in patients with liver cirrhosis （10.9%） and hepatitis C （9.0%） than in patients with chronic hepatitis （4.2%）, hepatitis B （4.9%） and non-B, non-C hepatitis （NBNC, 3.9%）. CONCLUSION： US screening at a interval of 6 mo is beneficial to high-risk patients over 40 years old and the early detection of HCC prolongs survival.
基金supported by the National Natural Science Foundation of China(41571275)the Western Action Plan Project of the Chinese Academy of Sciences(KZCX-XB3-13)the Major Program of the National Natural Science Foundation of China(41790444/D0214)
文摘Soil erosion on the Loess Plateau of China is effectively controlled due to the implementation of several ecological restoration projects that improve soil properties and reduce soil erodibility. However, few studies have examined the effects of vegetation restoration on soil properties and erodibility of gully head in the gully regions of the Loess Plateau. The objectives of this study were to quantify the effects of vegetation restoration on soil properties and erodibility in this region. Specifically, a control site in a slope cropland and 9 sites in 3 restored land-use types （5 sites in grassland, 3 in woodland and 1 in shrubland） in the Nanxiaohegou watershed of a typical gully region on the Loess Plateau were selected, and soil and root samples were collected to assess soil properties and root characteristics. Soil erodibility factor was calculated by the Erosion Productivity Impact Calculator method. Our results revealed that vegetation restoration increased soil sand content, soil saturated hydraulic conductivity, organic matter content and mean weight diameter of water-stable aggregate but decreased soil silt and clay contents and soil disintegration rate. A significant difference in soil erodibility was observed among different vegetation restoration patterns or land-use types. Compared with cropland, soil erodibility decreased in the restored lands by 3.99% to 21.43%. The restoration patterns of Cleistogenes caespitosa K. and Artemisia sacrorum L. in the grassland showed the lowest soil erodibility and can be considered as the optimal vegetation restoration pattern for improving soil anti-erodibility of the gully heads. Additionally, the negative linear change in soil erodibility for grassland with restoration time was faster than those of woodland and shrubland. Soil erodibility was significantly correlated with soil particle size distribution, soil disintegration rate, soil saturated hydraulic conductivity, water-stable aggregate stability, organic matter content and root characteristics （including root average diameter, root length density, root surface density and root biomass density）, but it showed no association with soil bulk density and soil total porosity. These findings indicate that although vegetation destruction is a short-term process, returning the soil erodibility of cropland to the level of grassland, woodland and shrubland is a long-term process （8-50 years）.
基金The External Cooperation Program of the Chinese Academy of Sciences,No.GJHZ0954National Basic Research Program of China,No.2005CB422006Institutional Consolidation for the Coordinated and Integrated Monitoring of Natural Resources towards Sustainable Development and Environmental Conservation in the Hindu Kush-Karakoram-Himalaya Mountain Complex
文摘Glaciers are one of the most important land covers in alpine regions and especially sensitive to global climate change. Remote sensing has proved to be the best method of investigating the extent of glacial variations in remote mountainous areas. Using Landsat thematic mapping （TM） and multi-spectral-scanner （MSS） images from Mt. Qomolangma （Everest） National Nature Preserve （QNNP）, central high Himalayas for 1976, 1988 and 2006 we derived glacial extent for these three periods. A combination of object-oriented image interpretation methods, expert knowledge rules and field surveys were employed. Results showed that （1） the glacial area in 2006 was 2710.17 ＋ 0.011 km2 （about 7.41% of the whole study area）, and located mainly to the south and between 4700 m to 6800 m above sea level; （2） from 1976 to 2006, glaciers reduced by 501.91± 0.035 km2 and glacial lakes expanded by 36.88 ＋ 0.035 kin2; the rate of glacier retreat was higher in sub-basins on the southern slopes （16.79%） of the Himalayas than on the northern slopes （14.40%）; most glaciers retreated, and mainly occurred at an elevation of 4700-6400 m, and the estimated upper limit of the retreat zone is between 6600 m and 6700 m; （3） increase in temperature and decrease in precipitation over the study period are the key factors driving retreat.
基金supported by Australian Research Council Australian Laureate Fellowship grant to ZXL (FL150100133)by China’s Thousand Talents Plan (2015)+2 种基金NSFC41674098 to NZsupported by resources provided by the High-performance Computing Platform of Peking Universitythe Pawsey Supercomputing Centre with funding from the Australian Government and the Government of Western Australia
文摘Understanding the dominant force responsible for supercontinent breakup is crucial for establishing Earth＇s geodynamic evolution that includes supercontinent cycles and plate tectonics. Conventionally,two forces have been considered： the push by mantle plumes from the sub-continental mantle which is called the active force for breakup, and the dragging force from oceanic subduction retreat which is called the passive force for breakup. However, the relative importance of these two forces is unclear. Here we model the supercontinent breakup coupled with global mantle convection in order to address this question. Our global model features a spherical harmonic degree-2 structure, which includes a major subduction girdle and two large upwelling（superplume） systems. Based on this global mantle structure,we examine the distribution of extensional stress applied to the supercontinent by both subsupercontinent mantle upwellings and subduction retreat at the supercontinent peripheral. Our results show that：（1） at the center half of the supercontinent, plume push stress is ～3 times larger than the stress induced by subduction retreat;（2） an average hot anomaly of no higher than 50 K beneath the supercontinent can produce a push force strong enough to cause the initialization of supercontinent breakup;（3） the extensional stress induced by subduction retreat concentrates on a ～600 km wide zone on the boundary of the supercontinent, but has far less impact to the interior of the supercontinent. We therefore conclude that although circum-supercontinent subduction retreat assists supercontinent breakup, sub-supercontinent mantle upwelling is the essential force.
文摘AIM: To establish the efficacy and safety of a 7-d therapeutic regimen using omeprazole,bismuth subcitrate,furazolidone and amoxicillin in patients with peptic ulcer disease who had been previously treated with other therapeutic regimens without success.METHODS: Open cohort study which included patients with peptic ulcer who had previously been treated unsuccessfully with one or more eradication regimens.The therapeutic regimen consisted of 20 mg omeprazole,240 mg colloidal bismuth subcitrate,1000 mg amoxicillin,and 200 mg furazolidone,taken twice a day for 7 d.Patients were considered as eradicated when samples taken from the gastric antrum and corpus 12 wk after the end of treatment were negative for Helicobacter pylori (H pylori) (rapid urease test and histology).Safety was determined by the presence of adverse effects.RESULTS: Fifty-one patients were enrolled.The eradication rate was 68.8% (31/45).Adverse effects were reported by 31.4% of the patients,and these were usually considered to be slight or moderate in the majority of the cases.Three patients had to withdraw from the treatment due to the presence of severe adverse effects.CONCLUSION: The association of bismuth,furazolidone,amoxicillin and a proton-pump inhibitor is a valuable alternative for patients who failed to respond to other eradication regimens.It is an effective,cheap and safe option for salvage therapy of positive patients.
基金Funding was provided by Global Change Research Program of China (No. 2015CB953900)the Key Project of the National Natural Science Foundation of China (No. 41330960)
文摘Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic decline to about 4.28×10^6 km^2, which was 50% lower than conditions in the 1950 s to the 1970 s(Serreze et al., 2008). That was a record low over the course of the modern satellite record, since 1979(note that the year 2012 became the new record low). This astonishing event drew wide-ranging attention in 2007-2009 during the 4 th International Polar Year. The dramatic decline of sea ice attracts many scientists’ interest and has become the focus of intense research since then. Currently, sea ice retreat is not only appearing around the marginal ice zone, but also in the pack ice inside the central Arctic(Zhao et al., 2018). In fact, premonitory signs had already been seen through other evidence. Before the disintegration of the Soviet Union, US naval submarines had been conducting an extensive survey under the sea ice and taking measurements of sea ice thickness. Their measurements revealed a gradual decrease of ice thickness to 1.8 m during winter by the end of the 20 th century, in contrast to the climatological mean of 3.1 m(Rothrock et al., 1999). However, this alarming result did not draw much attention since the Arctic was still severely cold at that time.
