The bridge deck on the Yuzhong side of Zengjiayan Jialing River Bridge is close to subway lines and light rail stations.It is necessary to set up transfer stairways on both sides of the bridge.The construction technol...The bridge deck on the Yuzhong side of Zengjiayan Jialing River Bridge is close to subway lines and light rail stations.It is necessary to set up transfer stairways on both sides of the bridge.The construction technology of installing and replacing with tunnel under special conditions is discussed to provide reference for bridge construction.展开更多
The middle-scale Heima zinnwaldite deposit is situated in the southeastern Tibetan Plateau,SW China.The NNW-to NS-trending orebodies are hosted in the Gaoligongshan metamorphic zone.To clarify the zinnwaldite genesis ...The middle-scale Heima zinnwaldite deposit is situated in the southeastern Tibetan Plateau,SW China.The NNW-to NS-trending orebodies are hosted in the Gaoligongshan metamorphic zone.To clarify the zinnwaldite genesis at Heima,this study presents an integrated investigation of the Heima pegmatites,combining precise geochronology,isotopic tracing,and detailed mineral chemistry to constrain its formation age,petrogenetic origin,and mineralization processes.Our robust geochronological framework,employing magmatic zircon(56.93±0.53 Ma)and cassiterite(57.0±4.2 Ma),establishes the pegmatite emplacement during the Late Paleocene to Early Eocene,representing the maximum age of lithium mineralization.Hf isotopic compositions(εHf_((t))=−14.3 to−12.4)demonstrate that the Heima pegmatite originated from remelting of ancient sediments,distinguishing it from contemporaneous Eocene Gangdese-Tengchong granites(εHf_((t))=−12.7 to+11.0)that show mantle contributions.This crustal signature aligns with the evolutionary trend of Hf isotopes in regional gneissic granites(600−420 Ma),supporting an anatectic origin from ancient continental crust rather than being derivatives of nearby Eocene granitic plutons.Detailed geochemical analysis of Li-micas reveals two distinct generations with contrasting formation mechanisms.The primary mica-Ia(53.45±0.86 Ma,Rb-Sr age)exhibits extreme incompatible element enrichment(Li,Be,Rb,Cs)and remarkably low K/Rb ratios(3.98-4.37),characteristic of crystallization from highly fractionated granitic melts.In contrast,secondary mica-Ib and mica-Ⅱ(17.9-16.0 Ma,Rb-Sr age)show significant Nb-Ta-W enrichment,reflecting precipitation from F-P-rich hydrothermal fluids during Miocene metamorphic-hydrothermal events.Principal component analysis(PCA)confirms the compositional disparity between these mica generations,with the later phases attributed to fluid-induced alteration and reworking.Regional correlation identifies two distinct lithium mineralization episodes in the Gongshan area,southeast Tibetan Plateau.The Eocene phase(~55 Ma)is zinnwaldite-dominant(e.g.,Heima,Puladi),associated with crustal melting following Neo-Tethyan closure.The Miocene phase(~17 Ma)is spodumene-dominant(e.g.,Danzhu,Peili),linked to Himalayan leucogranites formed as the rapid exhumation,denudation,and decompression partial melting of Himalayan Crystalline Complex.展开更多
In this paper,a self-developed master-slave follow-up disc cutter is used to conduct rock-breaking tests on hard sandstone samples.Different working parameters were employed in the tests(e.g.cutting depth,cutting spee...In this paper,a self-developed master-slave follow-up disc cutter is used to conduct rock-breaking tests on hard sandstone samples.Different working parameters were employed in the tests(e.g.cutting depth,cutting speed,cutting angle,and rotational speed)in order to explore their influences on cutting performance.The results indicate that the thrust,torque,vibration velocity,and roughness all increased continuously with increase of the propulsion speed and cutting depth.At the same time,the specific energy consumption was found to decrease continuously.As the rotational speed was increased,the thrust increased at first and then decreased.In contrast,the torque and roughness continuously decreased,and the specific energy consumption and vibration speed continuously increased.When the cutting angle was increased,the thrust remained unchanged.However,the torque,specific energy consumption,and vibration speed all decreased continuously,and the roughness increased continuously.The temperature of the surface of the cutting tool was found to be relatively uniformly distributed during the rock-breaking process;the highest temperatures generated were in the range of 200-300℃.As the propulsion speed,cutting depth,and cutting angle were increased,the proportion of tensile fractures produced appeared to increase and the proportion of shear fractures decreased.As the rotational speed was increased,the proportion of tensile fractures decreased and the proportion of shear fractures increased.The results could provide useful information on the rock-breaking behavior involved and can be used to offer technical support for engineers using master-slave follow-up disc cutters in the field.展开更多
This study introduces a test system for microwave-induced fracturing of hard rocks under true triaxial stress.The test system comprises a true triaxial stress loading system,an open-ended microwaveinduced fracturing s...This study introduces a test system for microwave-induced fracturing of hard rocks under true triaxial stress.The test system comprises a true triaxial stress loading system,an open-ended microwaveinduced fracturing system,a data acquisition system,an acoustic emission(AE)monitoring system,and an auxiliary specimen loading system.Microwave-induced surface and borehole fracturing tests under true triaxial stress were fulfilled for the first time,which overcomes the problem of microwave leakage in the coupling loading of true triaxial stress and microwave.By developing the dynamic monitoring system,the thermal response and fracture evolution were obtained during microwave irradiation.The monitoring system includes the infrared thermometry technique for monitoring rock surface temperature,the distributed optic fiber sensing technique for monitoring temperature in borehole in rock,the AE technique and two-dimensional digital speckle correlation technique for monitoring the evolution of thermal damage and the rock fracturing process.To validate the advantages of the test system and investigate the characteristics of microwave-induced fracturing of hard rocks,the study demonstrates the experimental methods and results for microwave-induced surface and borehole fracturing under true triaxial stress.The results show that thermal cracking presented intermittent characteristics(calm eactiveecalm)during microwave-induced surface and borehole fracturing of basalt.In addition,true triaxial stress can inhibit the development and distribution of thermal cracks during microwave-induced surface fracturing.When microwave-induced borehole fracturing occurs,it promotes the distribution of thermal cracks in rock,but inhibits the width of cracks.The results also prove the reliability of the test system.展开更多
Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-powe...Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-power microwave subsystem (100 kW), a true triaxial testing machine, a dynamic monitoring subsystem, and an electromagnetic shielding subsystem. It can realize rapid microwave-induced fracturing, intelligent tuning of impedance, dynamic feedback under strong microwave fields, and active control of microwave parameters by addressing the following issues: the instability and insecurity of the system, the discharge breakdown between coaxial lines during high-power microwave output, and a lack of feedback of rock-microwave response. In this study, microwave-induced surface and borehole fracturing tests under true triaxial stress were carried out. Experimental comparisons imply that high-power microwave irradiation can reduce the fracturing time of hard rock and that the fracture range (160 mm) of a 915-MHz microwave source is about three times that of 2.45 GHz. After microwave-induced borehole fracturing, many tensile cracks occur on the rock surface and in the borehole: the maximum reduction of the P-wave velocity is 12.8%. The test results show that a high-power microwave source of 915 MHz is more conducive to assisting mechanical rock breaking and destressing. The system can promote the development of microwave-assisted rock breaking equipment.展开更多
In order to understand the influence of different factors on the microwave response characteristics of ores,the effects of electrical conductivity,metal mineral content,compactness,metal mineral distribution,microwave...In order to understand the influence of different factors on the microwave response characteristics of ores,the effects of electrical conductivity,metal mineral content,compactness,metal mineral distribution,microwave frequency and temperature on the dielectric properties of synthetic ores(metal mineral and quartz)were studied.Microwave heating tests were carried out on three types of natural ores(Hongtoushan copper ore,Sishanling iron ore and Dandong gold ore)with significant differences in metal mineral contents.The test results showed that under microwave irradiation,the stronger the electrical conductivity of the metal minerals,the smaller the penetration depth in synthetic ore.For those metal minerals with lower electrical conductivity,the microwave absorption coefficient of the synthetic samples increases with increasing metal mineral content.For those metal minerals with higher electrical conductivity,the microwave absorption coefficient of the samples first increases and then decreases as the metal mineral content increases.When the metal minerals are distributed in layers,the penetration depth is much less than that given a uniform distribution.The penetration depth in the sample at microwave frequency of 915 MHz is greater than that at 2.45 GHz.The higher the electrical conductivity of metal minerals used in synthetic ores,the higher the high-temperature sensitivity of electromagnetic shielding coefficient(0.C-500.C).The Hongtoushan copper ore with high metal mineral content exhibits obvious size effect.The effects of ore structure and crystal particle size on the distribution characteristics of microcracks were discussed.Based on the test results,a quantitative prediction model of microwave sensitivity of ore was proposed,which provides guidance for the prediction of ore heating effect and the selection of microwave heating sequence of ore.展开更多
Microwave-assisted mechanical excavation has great application prospects in mines and tunnels,but there are few field experiments on microwave-assisted rock breaking.This paper takes the Sishanling iron mine as the re...Microwave-assisted mechanical excavation has great application prospects in mines and tunnels,but there are few field experiments on microwave-assisted rock breaking.This paper takes the Sishanling iron mine as the research object and adopts the self-developed high-power microwave-induced fracturing test system for hard rock to conduct field experiments of microwave-induced fracturing of iron ore.The heating and reflection evolution characteristics of ore under different microwave parameters(antenna type,power,and working distance)were studied,and the optimal microwave parameters were obtained.Subsequently,the ore was irradiated with the optimal microwave parameters,and the cracking effect of the ore under the action of the high-power open microwave was analyzed.The results show that the reflection coefficient(standing wave ratio)can be rapidly(<5 s)and automatically adjusted below the preset threshold value(1.6)as microwave irradiation is performed.When using a right-angle horn antenna with a working distance of 5 cm,the effect of automatic reflection adjustment reaches the best among other antenna types and working distances.When the working distance is the same,the average temperature of the irradiation surface and the area of the high-temperature area under the action of the two antennas(right-angled and equal-angled horn antenna)are basically the same and decrease with the increase of working distance.The optimal microwave parameters are:a right-angle horn antenna with a working distance of 5 cm.Subsequently,in further experiments,the optimal parameters were used to irradiate for 20 s and 40 s at a microwave power of 60 kW,respectively.The surface damage extended 38 cm×30 cm and 53 cm×30 cm,respectively,and the damage extended to a depth of about 50 cm.The drilling speed was increased by 56.2%and 66.5%,respectively,compared to the case when microwaves were not used.展开更多
Two sampling sites representing the urban and suburban area of Chengdu, China were sampled and analyzed for selected chemicals to characterize the evolution of the chemical composition of fogwater. A trend of total or...Two sampling sites representing the urban and suburban area of Chengdu, China were sampled and analyzed for selected chemicals to characterize the evolution of the chemical composition of fogwater. A trend of total organic carbon （TOC） 〉 total nitrogen （TN） 〉 total inorganic carbon （TIC） was observed for both sites. Variation of inorganic ions indicated that inorganic pollutants were not accumulated in the fog. Concentrations of n-alkanes （C11-C37） at the urban site ranged from 7.58 to 27.75 ng/mL while at the suburban site concentrations were 2.57-21.55 ng/mL. The highest concentration of n-alkanes was observed in the mature period of fog （393.12 ng/mL） which was more than ten times that in the fog formation period （27.83 ng/mL） and the fog dissipation period （14.87 ng/mL）. Concentrations of Σ15PAHs were in the range of 7.27-38.52 ng/mL at the urban site and 2.59-22.69 ng/mL at the suburban site. Contents of PAHs in the mature period of fog （27.15 ng/mL） 〉 fog dissipation period （11.59 ng/mL） 〉 fog formation period （6.42 ng/mL）. Concentrations of dicarboxylic acids （C5-C9） ranged from 10.92 to 40.78 ng/mL, with glutaric acid （C5） as the dominant dicarboxylic acid. These data provide strong indications of the accumulation of certain organic chemicals of environmental concern in fog and fog water, and provide additional insights about processes in urban and suburban air acting on organic chemicals with similar physical chemical properties.展开更多
Background Although vascular dementia(VaD)is not uncommon in the hospital,most studies on VaD are community based.This study on VaD is the first to use a national hospital information system(HIS)in China.Methods This ...Background Although vascular dementia(VaD)is not uncommon in the hospital,most studies on VaD are community based.This study on VaD is the first to use a national hospital information system(HIS)in China.Methods This study was a hospital population-based cohort study,and data were acquired from the Hospital Quality Monitoring System,a Chinese national database that covers 1531 tertiary hospitals in China.The medical records in the HIS included demographic information,diagnoses,procedures,expenses,etc.VaD was diagnosed by hospital attending physicians and identified by the International Classification of Diseases(ICD)10 code(F01.0-F01.9).Results 1259(82.23%)tertiary hospitals were included in this study,and 274230 hospitalisation records of 123700 VaD patients from 2016 to 2018 were identified for analysis.VaD(51.27%)was the most common type of dementia in hospitalised patients.The age-adjusted and sex-adjusted hospital incidence of VaD was estimated to be 2.97 per 100000 person-years(95%CI 2.92 to 3.02).The mean age of VaD patients admitted to hospitals was 74.13±10.88,with more male(61.0%)patients.The main comorbidities were hypertension(67.2%),heart disease(63.6%)and cerebral infarction(55.5%).The mortality rate of VaD in hospital was 28.91‰(95%CI 28.0 to 29.9)between 2016 and 2018.The top 1 cause of death due to VaD was pneumonia and other respiratory disorders.Conclusions VaD is the most common form of dementia in hospitalised patients.It casts huge burdens on affected patients and their caregivers.Vascular risk factors are prevalent in VaD patients.Reducing these factors is essential to improve patient care.The leading causes of death by VaD are pneumonia and other respiratory disorders.Hospital care and the management of respiratory illness are critical for VaD care in the hospital.展开更多
Background and Aims: Chronic hepatitis B virus(HBV)in-fection remains a major public health problem globally.Here,we describe the baseline characteristics and treatment pro-files of HBV-infected patients recruited to ...Background and Aims: Chronic hepatitis B virus(HBV)in-fection remains a major public health problem globally.Here,we describe the baseline characteristics and treatment pro-files of HBV-infected patients recruited to the China Registry of Hepatitis B.Methods: Inclusion criteria were patients with different stages of chronic HBV infection and complete key data.Exclusion criteria were patients with hepatocellular car-cinoma.The baseline clinical,laboratory and treatment pro-files were analyzed.Results: Finally,40,431 patients were included.The median age was 43 years,with 65.2%being men and 51.3%being positive for hepatitis B e antigen(HBeAg).The most common initial diagnosis was chronic hep-atitis B(81.0%),followed by cirrhosis(9.3%),inactive carrier of hepatitis B surface antigen(HBsAg)(6.7%),and immune tolerant phase of hepatitis B infection(3.0%).Among the 21,228 patients who were on treatment,88.0%,10.0%and 2.0%received nucleos(t)ide analogues(NAs),interferon or combination of NAs and interferon,respectively.The propor-tion of patients who received preferred NAs(entecavir or te-nofovir disoproxil fumarate)had increased from 13.5%in 2003 to 79.7%in 2016.Conclusions: We concluded that middle-aged men accounted for most of the patients with chronic hepatitis B in this cross-sectional study.About half of the patients were HBeAg-positive.NAs were the most com-monly used therapy,and use of the preferred NAs had steadily increased in the past decade.展开更多
Background and purpose Cardiovascular diseases and dementia are two major diseases in the elderly.Atherosclerosis is associated with future vascular events and cognitive impairment.The PolyvasculaR Evaluation for Cogn...Background and purpose Cardiovascular diseases and dementia are two major diseases in the elderly.Atherosclerosis is associated with future vascular events and cognitive impairment.The PolyvasculaR Evaluation for Cognitive Impairment and vaScular Events(PRECISE)study is a population-based prospective cohort study with comprehensive evaluation of multiterritorial artery stenosis and plaque using advanced vascular imaging techniques and prospective collection of vascular events and cognitive assessments.Methods Between May 2017 and September 2019,the PRECISE study enrolled 3067 community-dwelling adults with ages between 50 and 75 years cluster sampled from six villages and four communities of Lishui city in China.Data are collected in face-to face interviews at baseline,2-year and 4-year follow-up visits.Brain MRI including high-resolution sequences for intracranial and carotidal arteries and CT angiography for thoracoabdominal arteries were performed at baseline and will be rescanned after 4 years.Cardiovascular/cerebrovascular events and cognitive assessment will be prospectively collected after the enrollment.Blood and urine samples were collected and biomarkers were tested at baseline.Results A total of 3067 subjects were enrolled,among which 53.5%were female with an average age of 61.2±6.7 years.Among them,2.8%,8.1%,43.1%and 21.6%had a history of stroke,coronary heart diseases,hypertension and diabetes mellitus,respectively.Conclusions The PRECISE study is a population-based prospective cohort study with comprehensive evaluation of atherosclerotic stenosis and plaque using advanced vascular imaging techniques.Data from this cohort provide us an opportunity to precisely evaluate polyvascular atherosclerosis and its association with future vascular events and cognitive impairment.展开更多
In this paper,silver(Ag)nanoparticle-modified zinc oxide(ZnO)nanowall photoconductive ultraviolet photodetector was prepared by using magnetron sputtering technology,electron beam evaporation method and hydrothermal m...In this paper,silver(Ag)nanoparticle-modified zinc oxide(ZnO)nanowall photoconductive ultraviolet photodetector was prepared by using magnetron sputtering technology,electron beam evaporation method and hydrothermal method.The results showed that ZnO nanowalls exhibited a hexagonal wurtzite structure.ZnO nanowalls grew uniformly perpendicular to the substrate,and metallic Ag nanoparticles were uniformly attached to the surface of ZnO nanowalls,effectively improving the ZnO nanowall absorption capability in the ultraviolet light region.The dark current of the Ag-modified ZnO nanowall UV detector deposited by sputtering for 40 s was 0.042 mA,revealing a decrease of 44%.Under the irradiation of ultraviolet light with a wavelength of 325 nm,the photocurrent reached 3.088 mA,which increased by four times.The responsivity increased from 27.29 to 101.07mA/W,and the sensitivity increased from 8.07 to 73.52.In addition to the good repeatability and stability,the response time was reduced by 64%,and the recovery time was decreased by 50%.展开更多
Background Small subcortical infarcts account for up to 25%of ischaemic strokes.Thalamus is one of the subcortical structures that commonly manifest with lacunar infarcts on MRI of the brain.Studies have shown that th...Background Small subcortical infarcts account for up to 25%of ischaemic strokes.Thalamus is one of the subcortical structures that commonly manifest with lacunar infarcts on MRI of the brain.Studies have shown that thalamus infarction is associated with cognitive decline.However,due to the lack of proper animal models,little is known about the mechanism.We aimed to establish a focal thalamus infarction model,characterise the infarct lesion and assess functional effects.Methods Male C57BL/6J mice were anaesthetised,and Rose Bengal dye was injected through the tail vein.The right thalamus was illuminated with green laser light by stereotactic implantation of optic fibre.Characteristics of the infarct and lesion evolution were evaluated by histological analysis and 7T MRI at various times.The cognitive and neurological functions were assessed by behavioural tests.Retrograde tracing was performed to analyse neural connections.Results An ischaemic lesion with small vessel occlusion was observed in the thalamus.It became a small circumscribed infarct with reactive astrocytes accumulated in the infarct periphery on day 21.The mice with thalamic infarction demonstrated impaired learning and memory without significant neurological deficits.Retrogradely labelled neurons in the retrosplenial granular cortex were reduced.Conclusion This study established a mouse model of thalamic lacunar infarction that exhibits cognitive impairment.Neural connection dysfunctions may play a potential role in post-stroke cognitive impairment.This model helps to clarify the pathophysiology of post-stroke cognitive impairment and to develop potential therapies.展开更多
To the Editor:Atopic dermatitis(AD)is the most common chronic allergic skin disease worldwide.House dust mite(HDM)is the most prevalent aeroallergen and pathogenic cause,which triggers skin barrier disruption and poly...To the Editor:Atopic dermatitis(AD)is the most common chronic allergic skin disease worldwide.House dust mite(HDM)is the most prevalent aeroallergen and pathogenic cause,which triggers skin barrier disruption and polysensitization.Allergen immunotherapy(AIT)may be the only etiologic treatment to improve the natural history of AD by applying a dose of specific allergens to stimulate adaptive immunity in the body.[1,2]However,the effects of HDM AIT showed controversial results recently.This study aimed to investigate the effectiveness and safety of AIT for HDM.展开更多
文摘The bridge deck on the Yuzhong side of Zengjiayan Jialing River Bridge is close to subway lines and light rail stations.It is necessary to set up transfer stairways on both sides of the bridge.The construction technology of installing and replacing with tunnel under special conditions is discussed to provide reference for bridge construction.
基金supported by the Ministry of Natural Resources-Provincial Joint Cooperation Project in 2024(No.2024ZRBSHZ126)The Second Comprehensive Scientific Research Project on the Qinghai-Tibetan Plateau“Assessment of Current Status and Future Prospects for Rare Metal Resources”(No.2019QZKK0802)+4 种基金Yunnan Foundation Project(No.202201AU070162)Career Development Fund for Early-Career Geologists at YIGS(No.YDKYR[2024]3)YDIG Expert Innovation Studio(No.YDIG[2024]24)New round of Yunnan Province prospecting Action and Project of Geological Exploration Fund(No.K202408)KUST-NSRF Talent Development Project(No.KKZ3202421133).
文摘The middle-scale Heima zinnwaldite deposit is situated in the southeastern Tibetan Plateau,SW China.The NNW-to NS-trending orebodies are hosted in the Gaoligongshan metamorphic zone.To clarify the zinnwaldite genesis at Heima,this study presents an integrated investigation of the Heima pegmatites,combining precise geochronology,isotopic tracing,and detailed mineral chemistry to constrain its formation age,petrogenetic origin,and mineralization processes.Our robust geochronological framework,employing magmatic zircon(56.93±0.53 Ma)and cassiterite(57.0±4.2 Ma),establishes the pegmatite emplacement during the Late Paleocene to Early Eocene,representing the maximum age of lithium mineralization.Hf isotopic compositions(εHf_((t))=−14.3 to−12.4)demonstrate that the Heima pegmatite originated from remelting of ancient sediments,distinguishing it from contemporaneous Eocene Gangdese-Tengchong granites(εHf_((t))=−12.7 to+11.0)that show mantle contributions.This crustal signature aligns with the evolutionary trend of Hf isotopes in regional gneissic granites(600−420 Ma),supporting an anatectic origin from ancient continental crust rather than being derivatives of nearby Eocene granitic plutons.Detailed geochemical analysis of Li-micas reveals two distinct generations with contrasting formation mechanisms.The primary mica-Ia(53.45±0.86 Ma,Rb-Sr age)exhibits extreme incompatible element enrichment(Li,Be,Rb,Cs)and remarkably low K/Rb ratios(3.98-4.37),characteristic of crystallization from highly fractionated granitic melts.In contrast,secondary mica-Ib and mica-Ⅱ(17.9-16.0 Ma,Rb-Sr age)show significant Nb-Ta-W enrichment,reflecting precipitation from F-P-rich hydrothermal fluids during Miocene metamorphic-hydrothermal events.Principal component analysis(PCA)confirms the compositional disparity between these mica generations,with the later phases attributed to fluid-induced alteration and reworking.Regional correlation identifies two distinct lithium mineralization episodes in the Gongshan area,southeast Tibetan Plateau.The Eocene phase(~55 Ma)is zinnwaldite-dominant(e.g.,Heima,Puladi),associated with crustal melting following Neo-Tethyan closure.The Miocene phase(~17 Ma)is spodumene-dominant(e.g.,Danzhu,Peili),linked to Himalayan leucogranites formed as the rapid exhumation,denudation,and decompression partial melting of Himalayan Crystalline Complex.
基金study was supported by the National Key Research and Development Program of China(Grant No.2023YFC2907202)the National Natural Science Foundation of China(Grant No.52404116)the Postdoctoral Fellowship Program of CPSF(Grant No.GZB20240129).
文摘In this paper,a self-developed master-slave follow-up disc cutter is used to conduct rock-breaking tests on hard sandstone samples.Different working parameters were employed in the tests(e.g.cutting depth,cutting speed,cutting angle,and rotational speed)in order to explore their influences on cutting performance.The results indicate that the thrust,torque,vibration velocity,and roughness all increased continuously with increase of the propulsion speed and cutting depth.At the same time,the specific energy consumption was found to decrease continuously.As the rotational speed was increased,the thrust increased at first and then decreased.In contrast,the torque and roughness continuously decreased,and the specific energy consumption and vibration speed continuously increased.When the cutting angle was increased,the thrust remained unchanged.However,the torque,specific energy consumption,and vibration speed all decreased continuously,and the roughness increased continuously.The temperature of the surface of the cutting tool was found to be relatively uniformly distributed during the rock-breaking process;the highest temperatures generated were in the range of 200-300℃.As the propulsion speed,cutting depth,and cutting angle were increased,the proportion of tensile fractures produced appeared to increase and the proportion of shear fractures decreased.As the rotational speed was increased,the proportion of tensile fractures decreased and the proportion of shear fractures increased.The results could provide useful information on the rock-breaking behavior involved and can be used to offer technical support for engineers using master-slave follow-up disc cutters in the field.
基金the National Natural Science Foundation of China(Grant No.41827806)and the Liaoning Revitalization Talent Program(Grant No.XLYC1801002).
文摘This study introduces a test system for microwave-induced fracturing of hard rocks under true triaxial stress.The test system comprises a true triaxial stress loading system,an open-ended microwaveinduced fracturing system,a data acquisition system,an acoustic emission(AE)monitoring system,and an auxiliary specimen loading system.Microwave-induced surface and borehole fracturing tests under true triaxial stress were fulfilled for the first time,which overcomes the problem of microwave leakage in the coupling loading of true triaxial stress and microwave.By developing the dynamic monitoring system,the thermal response and fracture evolution were obtained during microwave irradiation.The monitoring system includes the infrared thermometry technique for monitoring rock surface temperature,the distributed optic fiber sensing technique for monitoring temperature in borehole in rock,the AE technique and two-dimensional digital speckle correlation technique for monitoring the evolution of thermal damage and the rock fracturing process.To validate the advantages of the test system and investigate the characteristics of microwave-induced fracturing of hard rocks,the study demonstrates the experimental methods and results for microwave-induced surface and borehole fracturing under true triaxial stress.The results show that thermal cracking presented intermittent characteristics(calm eactiveecalm)during microwave-induced surface and borehole fracturing of basalt.In addition,true triaxial stress can inhibit the development and distribution of thermal cracks during microwave-induced surface fracturing.When microwave-induced borehole fracturing occurs,it promotes the distribution of thermal cracks in rock,but inhibits the width of cracks.The results also prove the reliability of the test system.
基金support from the Na-tional Natural Science Foundation of China(Grant No.41827806)the liaoning Revitalization Talent Program of China(Grant No.XLYCYSZX1902).
文摘Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-power microwave subsystem (100 kW), a true triaxial testing machine, a dynamic monitoring subsystem, and an electromagnetic shielding subsystem. It can realize rapid microwave-induced fracturing, intelligent tuning of impedance, dynamic feedback under strong microwave fields, and active control of microwave parameters by addressing the following issues: the instability and insecurity of the system, the discharge breakdown between coaxial lines during high-power microwave output, and a lack of feedback of rock-microwave response. In this study, microwave-induced surface and borehole fracturing tests under true triaxial stress were carried out. Experimental comparisons imply that high-power microwave irradiation can reduce the fracturing time of hard rock and that the fracture range (160 mm) of a 915-MHz microwave source is about three times that of 2.45 GHz. After microwave-induced borehole fracturing, many tensile cracks occur on the rock surface and in the borehole: the maximum reduction of the P-wave velocity is 12.8%. The test results show that a high-power microwave source of 915 MHz is more conducive to assisting mechanical rock breaking and destressing. The system can promote the development of microwave-assisted rock breaking equipment.
基金financial support from the National Natural Science Foundation of China(Grant No.41827806)supported by Liaoning Revitalization Talents Program(Grant No.XLYC1801002)。
文摘In order to understand the influence of different factors on the microwave response characteristics of ores,the effects of electrical conductivity,metal mineral content,compactness,metal mineral distribution,microwave frequency and temperature on the dielectric properties of synthetic ores(metal mineral and quartz)were studied.Microwave heating tests were carried out on three types of natural ores(Hongtoushan copper ore,Sishanling iron ore and Dandong gold ore)with significant differences in metal mineral contents.The test results showed that under microwave irradiation,the stronger the electrical conductivity of the metal minerals,the smaller the penetration depth in synthetic ore.For those metal minerals with lower electrical conductivity,the microwave absorption coefficient of the synthetic samples increases with increasing metal mineral content.For those metal minerals with higher electrical conductivity,the microwave absorption coefficient of the samples first increases and then decreases as the metal mineral content increases.When the metal minerals are distributed in layers,the penetration depth is much less than that given a uniform distribution.The penetration depth in the sample at microwave frequency of 915 MHz is greater than that at 2.45 GHz.The higher the electrical conductivity of metal minerals used in synthetic ores,the higher the high-temperature sensitivity of electromagnetic shielding coefficient(0.C-500.C).The Hongtoushan copper ore with high metal mineral content exhibits obvious size effect.The effects of ore structure and crystal particle size on the distribution characteristics of microcracks were discussed.Based on the test results,a quantitative prediction model of microwave sensitivity of ore was proposed,which provides guidance for the prediction of ore heating effect and the selection of microwave heating sequence of ore.
基金financial support from the National Natural Science Foundation of China(Grant No.41827806)the Liaoning Provincial Science and Technology Program of China(Grant No.2022JH2/101300109).
文摘Microwave-assisted mechanical excavation has great application prospects in mines and tunnels,but there are few field experiments on microwave-assisted rock breaking.This paper takes the Sishanling iron mine as the research object and adopts the self-developed high-power microwave-induced fracturing test system for hard rock to conduct field experiments of microwave-induced fracturing of iron ore.The heating and reflection evolution characteristics of ore under different microwave parameters(antenna type,power,and working distance)were studied,and the optimal microwave parameters were obtained.Subsequently,the ore was irradiated with the optimal microwave parameters,and the cracking effect of the ore under the action of the high-power open microwave was analyzed.The results show that the reflection coefficient(standing wave ratio)can be rapidly(<5 s)and automatically adjusted below the preset threshold value(1.6)as microwave irradiation is performed.When using a right-angle horn antenna with a working distance of 5 cm,the effect of automatic reflection adjustment reaches the best among other antenna types and working distances.When the working distance is the same,the average temperature of the irradiation surface and the area of the high-temperature area under the action of the two antennas(right-angled and equal-angled horn antenna)are basically the same and decrease with the increase of working distance.The optimal microwave parameters are:a right-angle horn antenna with a working distance of 5 cm.Subsequently,in further experiments,the optimal parameters were used to irradiate for 20 s and 40 s at a microwave power of 60 kW,respectively.The surface damage extended 38 cm×30 cm and 53 cm×30 cm,respectively,and the damage extended to a depth of about 50 cm.The drilling speed was increased by 56.2%and 66.5%,respectively,compared to the case when microwaves were not used.
基金supported by the Urban Meteorology Scientific Research Fund (No. UMRF200903)the Scientific Research Foundation of Chengdu University of Information Technology (No. CSRF201004)the Imported Talent Research Project of Chengdu University of Information Technology (No. KYTZ200919)
文摘Two sampling sites representing the urban and suburban area of Chengdu, China were sampled and analyzed for selected chemicals to characterize the evolution of the chemical composition of fogwater. A trend of total organic carbon （TOC） 〉 total nitrogen （TN） 〉 total inorganic carbon （TIC） was observed for both sites. Variation of inorganic ions indicated that inorganic pollutants were not accumulated in the fog. Concentrations of n-alkanes （C11-C37） at the urban site ranged from 7.58 to 27.75 ng/mL while at the suburban site concentrations were 2.57-21.55 ng/mL. The highest concentration of n-alkanes was observed in the mature period of fog （393.12 ng/mL） which was more than ten times that in the fog formation period （27.83 ng/mL） and the fog dissipation period （14.87 ng/mL）. Concentrations of Σ15PAHs were in the range of 7.27-38.52 ng/mL at the urban site and 2.59-22.69 ng/mL at the suburban site. Contents of PAHs in the mature period of fog （27.15 ng/mL） 〉 fog dissipation period （11.59 ng/mL） 〉 fog formation period （6.42 ng/mL）. Concentrations of dicarboxylic acids （C5-C9） ranged from 10.92 to 40.78 ng/mL, with glutaric acid （C5） as the dominant dicarboxylic acid. These data provide strong indications of the accumulation of certain organic chemicals of environmental concern in fog and fog water, and provide additional insights about processes in urban and suburban air acting on organic chemicals with similar physical chemical properties.
基金the Beijing Municipal Science&Technology Commission(Grant No.Z181100001518005)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB39000000).
文摘Background Although vascular dementia(VaD)is not uncommon in the hospital,most studies on VaD are community based.This study on VaD is the first to use a national hospital information system(HIS)in China.Methods This study was a hospital population-based cohort study,and data were acquired from the Hospital Quality Monitoring System,a Chinese national database that covers 1531 tertiary hospitals in China.The medical records in the HIS included demographic information,diagnoses,procedures,expenses,etc.VaD was diagnosed by hospital attending physicians and identified by the International Classification of Diseases(ICD)10 code(F01.0-F01.9).Results 1259(82.23%)tertiary hospitals were included in this study,and 274230 hospitalisation records of 123700 VaD patients from 2016 to 2018 were identified for analysis.VaD(51.27%)was the most common type of dementia in hospitalised patients.The age-adjusted and sex-adjusted hospital incidence of VaD was estimated to be 2.97 per 100000 person-years(95%CI 2.92 to 3.02).The mean age of VaD patients admitted to hospitals was 74.13±10.88,with more male(61.0%)patients.The main comorbidities were hypertension(67.2%),heart disease(63.6%)and cerebral infarction(55.5%).The mortality rate of VaD in hospital was 28.91‰(95%CI 28.0 to 29.9)between 2016 and 2018.The top 1 cause of death due to VaD was pneumonia and other respiratory disorders.Conclusions VaD is the most common form of dementia in hospitalised patients.It casts huge burdens on affected patients and their caregivers.Vascular risk factors are prevalent in VaD patients.Reducing these factors is essential to improve patient care.The leading causes of death by VaD are pneumonia and other respiratory disorders.Hospital care and the management of respiratory illness are critical for VaD care in the hospital.
文摘Background and Aims: Chronic hepatitis B virus(HBV)in-fection remains a major public health problem globally.Here,we describe the baseline characteristics and treatment pro-files of HBV-infected patients recruited to the China Registry of Hepatitis B.Methods: Inclusion criteria were patients with different stages of chronic HBV infection and complete key data.Exclusion criteria were patients with hepatocellular car-cinoma.The baseline clinical,laboratory and treatment pro-files were analyzed.Results: Finally,40,431 patients were included.The median age was 43 years,with 65.2%being men and 51.3%being positive for hepatitis B e antigen(HBeAg).The most common initial diagnosis was chronic hep-atitis B(81.0%),followed by cirrhosis(9.3%),inactive carrier of hepatitis B surface antigen(HBsAg)(6.7%),and immune tolerant phase of hepatitis B infection(3.0%).Among the 21,228 patients who were on treatment,88.0%,10.0%and 2.0%received nucleos(t)ide analogues(NAs),interferon or combination of NAs and interferon,respectively.The propor-tion of patients who received preferred NAs(entecavir or te-nofovir disoproxil fumarate)had increased from 13.5%in 2003 to 79.7%in 2016.Conclusions: We concluded that middle-aged men accounted for most of the patients with chronic hepatitis B in this cross-sectional study.About half of the patients were HBeAg-positive.NAs were the most com-monly used therapy,and use of the preferred NAs had steadily increased in the past decade.
基金supported by grants from Ministry of Science and Technology of the People’s Republic of China(2017YFC1310902,2018YFC1311706,2016YFC0901002,2017YFC1310901,2017YFC1307905 and 2018YFC1312801)Beijing Hospitals Authority Youth Programme(QML20190501)+4 种基金National Natural Science Foundation of China(81971091)Beijing Science and Technology Plan/Brain Science and Research North Science Center Project(Z181100001518005)The Strategic Priority Research Program of the Chinese Academy of Sciences(XDB39000000)Lishui Science&Technology Bureau(2019ZDYF18)grants from AstraZeneca Investment(China)Co.,Ltd(CSA2017KY007).
文摘Background and purpose Cardiovascular diseases and dementia are two major diseases in the elderly.Atherosclerosis is associated with future vascular events and cognitive impairment.The PolyvasculaR Evaluation for Cognitive Impairment and vaScular Events(PRECISE)study is a population-based prospective cohort study with comprehensive evaluation of multiterritorial artery stenosis and plaque using advanced vascular imaging techniques and prospective collection of vascular events and cognitive assessments.Methods Between May 2017 and September 2019,the PRECISE study enrolled 3067 community-dwelling adults with ages between 50 and 75 years cluster sampled from six villages and four communities of Lishui city in China.Data are collected in face-to face interviews at baseline,2-year and 4-year follow-up visits.Brain MRI including high-resolution sequences for intracranial and carotidal arteries and CT angiography for thoracoabdominal arteries were performed at baseline and will be rescanned after 4 years.Cardiovascular/cerebrovascular events and cognitive assessment will be prospectively collected after the enrollment.Blood and urine samples were collected and biomarkers were tested at baseline.Results A total of 3067 subjects were enrolled,among which 53.5%were female with an average age of 61.2±6.7 years.Among them,2.8%,8.1%,43.1%and 21.6%had a history of stroke,coronary heart diseases,hypertension and diabetes mellitus,respectively.Conclusions The PRECISE study is a population-based prospective cohort study with comprehensive evaluation of atherosclerotic stenosis and plaque using advanced vascular imaging techniques.Data from this cohort provide us an opportunity to precisely evaluate polyvascular atherosclerosis and its association with future vascular events and cognitive impairment.
基金Support from the Yan’an University 2023 research project(2023CGZH-014)2023 university students innovation and entrepreneurship project(D2023206)are gratefully acknowlegedfunded by the National Natural Science Foundation of China(No.62264015).
文摘In this paper,silver(Ag)nanoparticle-modified zinc oxide(ZnO)nanowall photoconductive ultraviolet photodetector was prepared by using magnetron sputtering technology,electron beam evaporation method and hydrothermal method.The results showed that ZnO nanowalls exhibited a hexagonal wurtzite structure.ZnO nanowalls grew uniformly perpendicular to the substrate,and metallic Ag nanoparticles were uniformly attached to the surface of ZnO nanowalls,effectively improving the ZnO nanowall absorption capability in the ultraviolet light region.The dark current of the Ag-modified ZnO nanowall UV detector deposited by sputtering for 40 s was 0.042 mA,revealing a decrease of 44%.Under the irradiation of ultraviolet light with a wavelength of 325 nm,the photocurrent reached 3.088 mA,which increased by four times.The responsivity increased from 27.29 to 101.07mA/W,and the sensitivity increased from 8.07 to 73.52.In addition to the good repeatability and stability,the response time was reduced by 64%,and the recovery time was decreased by 50%.
基金supported by the National Key Plan for Scientific Research and Development of China(2020YFA0509304 and 2021YFA0805300)the Chinese Academy of Sciences(XDB39000000)+3 种基金the National Natural Science Foundation of China(82030034,32121002,and 81971123)CAMS Innovation Fund for Medical Sciences(2021-I2M-C&T-B-012)the Fundamental Research Funds for the Central Universities(YD9110002027)the Guangzhou Key Research Program on Brain Science(202007030008)。
基金the Beijing Municipal Science&Technology Commission(Grant No.D171100003017002)National Key R&D Program of China(Grant No.2018YFC1312903)+1 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(XDB39000000)National Science and Technology Major Project(Grant No.2017ZX09304018).
文摘Background Small subcortical infarcts account for up to 25%of ischaemic strokes.Thalamus is one of the subcortical structures that commonly manifest with lacunar infarcts on MRI of the brain.Studies have shown that thalamus infarction is associated with cognitive decline.However,due to the lack of proper animal models,little is known about the mechanism.We aimed to establish a focal thalamus infarction model,characterise the infarct lesion and assess functional effects.Methods Male C57BL/6J mice were anaesthetised,and Rose Bengal dye was injected through the tail vein.The right thalamus was illuminated with green laser light by stereotactic implantation of optic fibre.Characteristics of the infarct and lesion evolution were evaluated by histological analysis and 7T MRI at various times.The cognitive and neurological functions were assessed by behavioural tests.Retrograde tracing was performed to analyse neural connections.Results An ischaemic lesion with small vessel occlusion was observed in the thalamus.It became a small circumscribed infarct with reactive astrocytes accumulated in the infarct periphery on day 21.The mice with thalamic infarction demonstrated impaired learning and memory without significant neurological deficits.Retrogradely labelled neurons in the retrosplenial granular cortex were reduced.Conclusion This study established a mouse model of thalamic lacunar infarction that exhibits cognitive impairment.Neural connection dysfunctions may play a potential role in post-stroke cognitive impairment.This model helps to clarify the pathophysiology of post-stroke cognitive impairment and to develop potential therapies.
基金supported by grants from the National Key Research&Development Program of China(Nos.2021YFC2701704 and 2021YFC2701700)the National Natural Science Foundation of China(Nos.81971433,82271749,and 82201905)+1 种基金Project of the Science and Technology Bureau of Sichuan Province(No.2023NSFSC0544)the Fundamental Research Funds for the Central University(No.SCU2023D006)
文摘To the Editor:Atopic dermatitis(AD)is the most common chronic allergic skin disease worldwide.House dust mite(HDM)is the most prevalent aeroallergen and pathogenic cause,which triggers skin barrier disruption and polysensitization.Allergen immunotherapy(AIT)may be the only etiologic treatment to improve the natural history of AD by applying a dose of specific allergens to stimulate adaptive immunity in the body.[1,2]However,the effects of HDM AIT showed controversial results recently.This study aimed to investigate the effectiveness and safety of AIT for HDM.
