In the past few years,many groups have focused on the research and development of GaN-based ultraviolet laser diodes(UV LDs).Great progresses have been achieved even though many challenges exist.In this article,we ana...In the past few years,many groups have focused on the research and development of GaN-based ultraviolet laser diodes(UV LDs).Great progresses have been achieved even though many challenges exist.In this article,we analyze the challenges of developing GaN-based ultraviolet laser diodes,and the approaches to improve the performance of ultraviolet laser diode are reviewed.With these techniques,room temperature(RT)pulsed oscillation of AlGaN UVA(ultraviolet A)LD has been realized,with a lasing wavelength of 357.9 nm.Combining with the suppression of thermal effect,the high output power of 3.8 W UV LD with a lasing wavelength of 386.5 nm was also fabricated.展开更多
The accurate prediction of the strength of rocks after high-temperature treatment is important for the safety maintenance of rock in deep underground engineering.Five machine learning(ML)techniques were adopted in thi...The accurate prediction of the strength of rocks after high-temperature treatment is important for the safety maintenance of rock in deep underground engineering.Five machine learning(ML)techniques were adopted in this study,i.e.back propagation neural network(BPNN),AdaBoost-based classification and regression tree(AdaBoost-CART),support vector machine(SVM),K-nearest neighbor(KNN),and radial basis function neural network(RBFNN).A total of 351 data points with seven input parameters(i.e.diameter and height of specimen,density,temperature,confining pressure,crack damage stress and elastic modulus)and one output parameter(triaxial compressive strength)were utilized.The root mean square error(RMSE),mean absolute error(MAE)and correlation coefficient(R)were used to evaluate the prediction performance of the five ML models.The results demonstrated that the BPNN shows a better prediction performance than the other models with RMSE,MAE and R values on the testing dataset of 15.4 MPa,11.03 MPa and 0.9921,respectively.The results indicated that the ML techniques are effective for accurately predicting the triaxial compressive strength of rocks after different high-temperature treatments.展开更多
Theasinensin A(TSA),a dimer of epigallocatechin gallate,has been preliminarily demonstrated to have hypoglycemia and anti-inflammatory effects.However,little information is available on its potential mechanisms of ant...Theasinensin A(TSA),a dimer of epigallocatechin gallate,has been preliminarily demonstrated to have hypoglycemia and anti-inflammatory effects.However,little information is available on its potential mechanisms of anti-diabetes.Therefore,the present study aimed to investigate the influence of TSA on glucose and lipid metabolism and gut microbiota in high-fat-diet/streptozotocin-induced diabetic mice.As result,TSA improved polydipsia,polyphagia and impaired glucose tolerance of diabetic mice,declined the fasting blood glucose and hepatic triglyceride level,and enhanced the expression at mRNA level of insulin receptor substrate,phosphoinositide 3-kinase,protein kinase B and glucagon-like peptide 1 receptor(GLP-1R)in the diabetic liver.Moreover,TSA could restore the disorder of gut microbiota of diabetic mice.High-dose(100 mg/kg)TSA showed better benefi cial effects from the blood biochemical parameters,hepatic function and gut microbiota.In general,high-dose TSA significantly modulated gut microbiota by increasing the relative abundance of Akkermansia and decreasing the relative abundances of Acetatifactor,Anaerotruncus,Pseudofl avonifactor,Oscillibacter and Clostridium clusters.The results indicated that TSA could exert an anti-diabetes effect in diabetic mice through restoring glucose homeostasis,declining hepatic steatosis,activating insulin and GLP-1 signaling pathways,and ameliorating gut microbiota dysbiosis.展开更多
Heteroatomic substitution and vacancy engineering of spinel oxides can theoretically optimize the oxygen evolution reaction(OER)through charge redistribution and d-band center modification but still remain a great cha...Heteroatomic substitution and vacancy engineering of spinel oxides can theoretically optimize the oxygen evolution reaction(OER)through charge redistribution and d-band center modification but still remain a great challenge in both the preparation and catalytic mechanism.Herein,we proposed a novel and efficient Ar-plasma(P)-assisted strategy to construct heteroatom Mo-substituted and oxygen vacancies enriched hierarchical spinel Co_(3)O_(4)porous nanoneedle arrays in situ grown on carbon cloth(denoted P-Mo-Co_(3)O_(4)@CC)to improve the OER performance.Ar-plasma technology can efficiently generate vacancy sites at the surface of hydroxide,which induces the anchoring of Mo anion salts through electrostatic interaction,finally facilitating the substitution of Mo atoms and the formation of oxygen vacancies on the Co_(3)O_(4)surface.The P-Mo-Co_(3)O_(4)@CC affords a low overpotential of only 276 mV at 10 mA cm^(−2)for the OER,which is 58 mV superior to that of Mo-free Co_(3)O_(4)@CC and surpasses commercial RuO_(2)catalyst.The robust stability and satisfactory selectivity(nearly 100%Faradic efficiency)of P-Mo-Co_(3)O_(4)@CC for the OER are also demonstrated.Theoreti-cal studies demonstrate that Mo with variable valance states can efficiently regulates the atomic ratio of Co^(3+)/Co^(2+)and increases the number of oxygen vacancies,thereby inducing charge redistribution and tuning the d-band center of Co_(3)O_(4),which improve the adsorption energy of oxygen intermediates(e.g.,*OOH)on P-Mo-Co_(3)O_(4)@CC during OER.Furthermore,the two-electrode OER//HER electrolyzer equipped with P-Mo-Co_(3)O_(4)@CC as anode displays a low operation potential of 1.54 V to deliver a current density of 10 mA cm^(−2),and also exhibits good reversibility and anticurrent fluctuation ability under simulated real energy supply conditions,demonstrating the great potential of P-Mo-Co_(3)O_(4)@CC in water electrolysis.展开更多
Pinus yunnanensis Franch. is an particular conifer tree species in Yunnan–Guizhou plateau in southwest China. The morphological and anatomical traits of needles are important to evaluate geographic variation and popu...Pinus yunnanensis Franch. is an particular conifer tree species in Yunnan–Guizhou plateau in southwest China. The morphological and anatomical traits of needles are important to evaluate geographic variation and population dynamics of conifer species. Seedlings from seven populations of P. yunnanensis were analyzed, looking at 22 morphological and anatomical needle traits. The results showed that variations among and within populations were significantly different for all traits and the variance components within populations were generally higher than that among populations in the most tested needle traits. The proportions of three-needle fascicle were significantly different among populations. The traits related to needle size in both morphology and anatomy were positive with latitude and negative with annual temperature and precipitation. Ratio indices, including mesophyllarea/vascular bundle area, mesophyll area/resin canals area, vascular bundle area/resin canals area and mesophyll area/(resin canals area and vascular bundle area), were negatively correlated with elevation and positively correlated with the annual mean temperature, showing some fitness feature for the populations. Needle traits were more significantly correlated with longitude than with other four environmental factors. Needle length was significantly correlated with almost all environmental factors. First four principal components accounted for 81.596 % of the variation with eigenvalues [1; the differences among populations were mainly dependent on needle width,stomatal density, section areas of vascular bundle, total resin canals, and mesophyll, as well as area ratio traits.Seven populations were divided into three categories by Euclidean distance. Variations in needle traits among the populations have shown systematic microevolution in terms of geographic impact on P. yunnanensis. This study would provide empirical data to characterize adaptation and genetic variation of P. yunnanensis, which would be helpful for management of genetic resources and reasonable utilization of them in future.展开更多
Variations in the phenotypic characteristics of conifer needles is a consequence of genetic evolution that has been widely used in geographic variation and ecological studies.Although many studies are based on an in s...Variations in the phenotypic characteristics of conifer needles is a consequence of genetic evolution that has been widely used in geographic variation and ecological studies.Although many studies are based on an in situ sampling strategy and generally realize the contribution of environmental effects to variation in needle traits,it is still uncertain which needle traits are most influenced by genetic effects and which are most influenced by the environment.Using both a common garden experiment to eliminate environmental heterogeneity and an in situ sampling strategy,we compared 18 Pinus tabuliformis needle traits among 10 geographical populations.Using both sampling strategies,we found significant differences in needle traits among populations and among individuals within populations.Differences in the‘‘among-population’’variance component between the two sampling strategies revealed the environmental contribution among natural populations for each trait.The among-population variance in the following traits exceeded 8%:needle length,number of stomata within 2 mm(NS2),number of stomatal lines on the planar side,number of resin canals(RCN)and the resin canal area(RCA).For the stability of needle traits,NS2,RCN,RCA,ratio of the vascular bundle area to the RCA(VBA/RCA),and MA/RCA differed significantly in more than five provenance changes between the common garden populations and natural populations,which may be susceptible to environmental effects.Conversely,the crosssectional area,mesophyll area(MA),MA/(VBA+RCA),and MA/VBA were phenotypically stable.Geographic variation patterns and systematic relation of needle traits differed between the two sampling strategies,suggesting that in situ sampling results may reflect environmental effects and deviate statistical parameters for genetic study.Future studies of genetic evolution in the context of geographic variation should be based on appropriate sampling strategies and stable phenotypic traits.展开更多
The potential geographic distribution and favorable climatic conditions of Machilus thunbergii under current and future predicted climates in China are predicted based on MaxEnt model and ArcGIS software. The results ...The potential geographic distribution and favorable climatic conditions of Machilus thunbergii under current and future predicted climates in China are predicted based on MaxEnt model and ArcGIS software. The results show that the AUC values in different time periods and emission seniors are more than 0.9, which indicates the prediction is excellent. Precipitation of the coldest quarter, precipitation of the driest month, annual precipitation, mean diurnal range, and temperature annual range are the most important environmental factors affecting the distribution of Machilus thunbergii. At present, the suitable areas of Machilus thunbergii are mainly concentrated in the eastern subtropics of China, with a total area of 118.47 × 104 km2. The medium-suitability area and the high-suitability area are concentrated in Wuyi Mountains, Luoxiao Mountains, Xuefeng Mountains, Nanling and east of Taiwan Mountains. With the change of climate, the suitable area increases, and the medium-suitability area and high-suitability area migrate and expand to the east, and the low-suitability area expands slightly to the west and north. So, the simulated distribution of Machilus thunbergii should be one of priorities, when instigating in-situ conservation. The research results can provide a theoretical reference for the popularization and planting of Machilus thunbergii.展开更多
To describe the dynamic cracking process of the CLT vertical layer,the correlation between a load-displacement curve,specimen cracking,and planar shear failure mechanism of the CLT were explored.A three-point bending ...To describe the dynamic cracking process of the CLT vertical layer,the correlation between a load-displacement curve,specimen cracking,and planar shear failure mechanism of the CLT were explored.A three-point bending test and an improved planar shear test are used to evaluate the shear performance of the CLT.In this study,the load-displacement curve is recorded,the experimental part is synchronized with the video,the dynamic process of cracking of the vertical layer is observed and analyzed throughout the test.From the load-displacement curve,the image characteristics of the initial cracking and the sudden increase of the cracking of the specimen are summar-ized.The description results of the whole dynamic process of the CLT vertical layer cracking are analyzed by pla-nar shear strength value,cracking phenomenon,and azimuth angle of cracking surface.The main conclusions show that the three-point bending test and the improved plain shear test can be used to test the plain shear strength of the CLT,with a difference of only 5.7%.The original crack and the new crack expansion account for 18.9%and 81.1%of the main cracking surface,respectively.And the vertical layer of the CLT specimen under three-point bending has three cracking morphologies,such as radial shake,ring shake,neither along with the radial shake nor along with the ring shake.The azimuth angle of the cracking surface of the CLT vertical layer under planar shear is quite consistent with the first main plane azimuth of the vertical layer of the CLT specimens under the three-point bending test and the shearing test.The shape in the cracking direction of the left half-span or the right half-span of the vertical layer of the specimen is similar to the Chinese character eight.展开更多
To improve the impact sound insulation performance of building floors and meet the objective requirements for living comfort of residents,in this article,three kinds of elastic cushion materials,Portuguese cork board,...To improve the impact sound insulation performance of building floors and meet the objective requirements for living comfort of residents,in this article,three kinds of elastic cushion materials,Portuguese cork board,BGL insulation sound insulation foam board,and EPP polypropylene plastic foam board,are applied to the sound insulation of a light frame wood floor structure of the same bedroom and compared to the ordinary floor.This study uses the transfer function method and transient excitation method to measure the sound insulation,damping ratio,and elastic modulus of materials,as well as the sound insulation of the floor under the jumping excitation method of daily behavior.Through comparative analysis,the results and factors of improving the sound insulation performance of the floor are obtained,according to which three types of elastic cushion materials and the floor covering composed of them have higher vibration and noise reduction performance.Among them,the overall sound insulation performance of BGL board floor is the highest,followed by EPP board and cork board floor,and ordinary OSB floor is the lowest.Under the jumping excitation method,three floating floors can improve the impact sound insulation performance of the middle and low-frequency bands.展开更多
Weeds cause tremendous economic and ecological damage worldwide.The number of genomes established for weed species has sharply increased during the recent decade,with some 26 weed species having been sequenced and de ...Weeds cause tremendous economic and ecological damage worldwide.The number of genomes established for weed species has sharply increased during the recent decade,with some 26 weed species having been sequenced and de novo genomes assembled.These genomes range from 270 Mb(Barbarea vulgaris)to almost 4.4 Gb(Aegilops tauschii).Importantly,chromosome-level assemblies are now available for 17 of these 26 species,and genomic investigations on weed populations have been conducted in at least 12 species.The resulting genomic data have greatly facilitated studies of weed management and biology,especially origin and evolution.Available weed genomes have indeed revealed valuable weed-derived genetic materials for crop improvement.In this review,we summarize the recent progress made in weed genomics and provide a perspective for further exploitation in this emerging field.展开更多
Introduction The safety outcomes of endovascular therapy for intracranial artery stenosis in a real-world stetting are largely unknown.The Clinical Registration Trial of Intracranial Stenting for Patients with Symptom...Introduction The safety outcomes of endovascular therapy for intracranial artery stenosis in a real-world stetting are largely unknown.The Clinical Registration Trial of Intracranial Stenting for Patients with Symptomatic Intracranial Artery Stenosis(CRTICAS)was a prospective,multicentre,real-world registry designed to assess these outcomes and the impact of centre experience.Methods 1140 severe,symptomatic intracranial arterial stenosis(ICAS)patients treated with endovascular therapy were included from 26 centres,further divided into three groups according to the annual centre volume of intracranial angioplasty and stent placement procedures over 2 years:(1)high volume for≥25 cases/year;(2)moderate volume for 10–25 cases/year and(3)low volume for<10 cases/year.Results The rate of 30-day stroke,transient ischaemic attack or death was 9.7%(111),with 5.4%,21.1%and 9.7%in high-volume,moderate-volume and low-volume centres,respectively(p<0.05).Multivariable logistic regression confirmed high-volume centres had a significantly lower primary endpoint compared with moderate-volume centres(OR=0.187,95%CI:0.056 to 0.627;p≤0.0001),while moderate-volume and low-volume centres showed no significant difference(p=0.8456).Conclusion Compared with the preceding randomised controlled trials,this real-world,prospective,multicentre registry shows a lower complication rate of endovascular treatment for symptomatic ICAS.Non-uniform utilisation in endovascular technology,institutional experience and patient selection in different volumes of centres may have an impact on overall safety of this treatment.展开更多
In order to meet the objective requirements of the safety and comfort of the modern lightweight timber floors,and strengthen the research on the coupling performance of the lightweight timber floors vibration characte...In order to meet the objective requirements of the safety and comfort of the modern lightweight timber floors,and strengthen the research on the coupling performance of the lightweight timber floors vibration characteristics and the building comfort,this article discusses the floor of a two-story prefabricated lightweight timber building demonstration house.In this paper,the floor structure of a two-story light-weight wooden house has been carried out on structural calculation modal and experimental modal,static uniform load and concentrated load deflection value testing.The evaluation of the deflection value of the floor structure,the mode shape,the coupling of the fundamental frequency mode parameters,and the vibration comfort were also studied.The results show that the fundamental frequency simulation value,one-way modal test value and two-way modal test value of the floor structure all meet the requirements of BS-6472(BS6472-1:2008).That is,the floor structure is not lower than 8 Hz design requirements,and meets the frequency of BS-6472(BS6472-1:2008).The weighted root mean square acceleration is lower than the requirement of 0.45 m/s^(2);the first three natural frequencies of the floor structure calculated by the finite element simulation are 16.413,31.847 and 48.921 Hz,and the fundamental frequency mode is the bending vibration in the length and width directions.The second order is the bending mode in the length direction,and the third order is the bending mode in the width direction.The fundamental frequency of the two-way modal test of the floor structure is the first-order bending mode in the X direction;and the second-order natural frequency is the second-order bending vibration shape in the X direction.when the uniform load is mainly the weight of floor own,the simulated maximum deflection value is 1.0658 mm;the simulation is performed according to the standard value of 0.566 kN/m for the uniform load of the floor design,and the simulation is the largest.The maximum deflection value of the simulated floor is 1.47383 mm at its midpoint,which meets the requirements of National Building Code of Canada-2015(NBCC).The maximum deflection limit of the light wood structure floor system is lower than 3 m and the maximum deflection limit is 2 mm;the six deflection value test lines simulated under a concentrated load of 1 kN all present a parabolic distribution and are symmetrical.The above results has engineering application value for promoting the research on the vibration characteristics of the fabricated lightweight timber floors structure and its optimization design.展开更多
基金This work was supported by the National Key R&D Program of China(2022YFB3605104)National Natural Science Foundation of China(62250038,61904172,61974162,62034008,62074142,and 62074140)+1 种基金Strategic Priority Research Program of Chinese Academy of Sciences(XDB43030101)Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(2022SX-TD016).
文摘In the past few years,many groups have focused on the research and development of GaN-based ultraviolet laser diodes(UV LDs).Great progresses have been achieved even though many challenges exist.In this article,we analyze the challenges of developing GaN-based ultraviolet laser diodes,and the approaches to improve the performance of ultraviolet laser diode are reviewed.With these techniques,room temperature(RT)pulsed oscillation of AlGaN UVA(ultraviolet A)LD has been realized,with a lasing wavelength of 357.9 nm.Combining with the suppression of thermal effect,the high output power of 3.8 W UV LD with a lasing wavelength of 386.5 nm was also fabricated.
基金We acknowledge the funding support from the National Natural Science Foundation of China(Grant No.51778575)Postdoctoral Science Foundation of China(Grant No.2021M692481)Fundamental Research Funds for the Central Universities of China(Grant No.2042021kf0055).The authors would like to thank the anonymous reviewers and editors for their constructive suggestions which greatly improve the quality of this paper.The authors are also grateful for the permission from Elsevier.
文摘The accurate prediction of the strength of rocks after high-temperature treatment is important for the safety maintenance of rock in deep underground engineering.Five machine learning(ML)techniques were adopted in this study,i.e.back propagation neural network(BPNN),AdaBoost-based classification and regression tree(AdaBoost-CART),support vector machine(SVM),K-nearest neighbor(KNN),and radial basis function neural network(RBFNN).A total of 351 data points with seven input parameters(i.e.diameter and height of specimen,density,temperature,confining pressure,crack damage stress and elastic modulus)and one output parameter(triaxial compressive strength)were utilized.The root mean square error(RMSE),mean absolute error(MAE)and correlation coefficient(R)were used to evaluate the prediction performance of the five ML models.The results demonstrated that the BPNN shows a better prediction performance than the other models with RMSE,MAE and R values on the testing dataset of 15.4 MPa,11.03 MPa and 0.9921,respectively.The results indicated that the ML techniques are effective for accurately predicting the triaxial compressive strength of rocks after different high-temperature treatments.
基金supported by the Key Technology R&D Program of Jiangsu Province(BE2020341)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Theasinensin A(TSA),a dimer of epigallocatechin gallate,has been preliminarily demonstrated to have hypoglycemia and anti-inflammatory effects.However,little information is available on its potential mechanisms of anti-diabetes.Therefore,the present study aimed to investigate the influence of TSA on glucose and lipid metabolism and gut microbiota in high-fat-diet/streptozotocin-induced diabetic mice.As result,TSA improved polydipsia,polyphagia and impaired glucose tolerance of diabetic mice,declined the fasting blood glucose and hepatic triglyceride level,and enhanced the expression at mRNA level of insulin receptor substrate,phosphoinositide 3-kinase,protein kinase B and glucagon-like peptide 1 receptor(GLP-1R)in the diabetic liver.Moreover,TSA could restore the disorder of gut microbiota of diabetic mice.High-dose(100 mg/kg)TSA showed better benefi cial effects from the blood biochemical parameters,hepatic function and gut microbiota.In general,high-dose TSA significantly modulated gut microbiota by increasing the relative abundance of Akkermansia and decreasing the relative abundances of Acetatifactor,Anaerotruncus,Pseudofl avonifactor,Oscillibacter and Clostridium clusters.The results indicated that TSA could exert an anti-diabetes effect in diabetic mice through restoring glucose homeostasis,declining hepatic steatosis,activating insulin and GLP-1 signaling pathways,and ameliorating gut microbiota dysbiosis.
基金National Natural Science Foundation of China,Grant/Award Numbers:21875112,22109073Natural Science Foundation of Jiangsu Province,Grant/Award Number:BK20221321。
文摘Heteroatomic substitution and vacancy engineering of spinel oxides can theoretically optimize the oxygen evolution reaction(OER)through charge redistribution and d-band center modification but still remain a great challenge in both the preparation and catalytic mechanism.Herein,we proposed a novel and efficient Ar-plasma(P)-assisted strategy to construct heteroatom Mo-substituted and oxygen vacancies enriched hierarchical spinel Co_(3)O_(4)porous nanoneedle arrays in situ grown on carbon cloth(denoted P-Mo-Co_(3)O_(4)@CC)to improve the OER performance.Ar-plasma technology can efficiently generate vacancy sites at the surface of hydroxide,which induces the anchoring of Mo anion salts through electrostatic interaction,finally facilitating the substitution of Mo atoms and the formation of oxygen vacancies on the Co_(3)O_(4)surface.The P-Mo-Co_(3)O_(4)@CC affords a low overpotential of only 276 mV at 10 mA cm^(−2)for the OER,which is 58 mV superior to that of Mo-free Co_(3)O_(4)@CC and surpasses commercial RuO_(2)catalyst.The robust stability and satisfactory selectivity(nearly 100%Faradic efficiency)of P-Mo-Co_(3)O_(4)@CC for the OER are also demonstrated.Theoreti-cal studies demonstrate that Mo with variable valance states can efficiently regulates the atomic ratio of Co^(3+)/Co^(2+)and increases the number of oxygen vacancies,thereby inducing charge redistribution and tuning the d-band center of Co_(3)O_(4),which improve the adsorption energy of oxygen intermediates(e.g.,*OOH)on P-Mo-Co_(3)O_(4)@CC during OER.Furthermore,the two-electrode OER//HER electrolyzer equipped with P-Mo-Co_(3)O_(4)@CC as anode displays a low operation potential of 1.54 V to deliver a current density of 10 mA cm^(−2),and also exhibits good reversibility and anticurrent fluctuation ability under simulated real energy supply conditions,demonstrating the great potential of P-Mo-Co_(3)O_(4)@CC in water electrolysis.
基金finically supported by the Natural Science Foundation of China(31070591)Special National Forestry Public Welfare Industry Research(201104022)the support of Southwest Forestry University
文摘Pinus yunnanensis Franch. is an particular conifer tree species in Yunnan–Guizhou plateau in southwest China. The morphological and anatomical traits of needles are important to evaluate geographic variation and population dynamics of conifer species. Seedlings from seven populations of P. yunnanensis were analyzed, looking at 22 morphological and anatomical needle traits. The results showed that variations among and within populations were significantly different for all traits and the variance components within populations were generally higher than that among populations in the most tested needle traits. The proportions of three-needle fascicle were significantly different among populations. The traits related to needle size in both morphology and anatomy were positive with latitude and negative with annual temperature and precipitation. Ratio indices, including mesophyllarea/vascular bundle area, mesophyll area/resin canals area, vascular bundle area/resin canals area and mesophyll area/(resin canals area and vascular bundle area), were negatively correlated with elevation and positively correlated with the annual mean temperature, showing some fitness feature for the populations. Needle traits were more significantly correlated with longitude than with other four environmental factors. Needle length was significantly correlated with almost all environmental factors. First four principal components accounted for 81.596 % of the variation with eigenvalues [1; the differences among populations were mainly dependent on needle width,stomatal density, section areas of vascular bundle, total resin canals, and mesophyll, as well as area ratio traits.Seven populations were divided into three categories by Euclidean distance. Variations in needle traits among the populations have shown systematic microevolution in terms of geographic impact on P. yunnanensis. This study would provide empirical data to characterize adaptation and genetic variation of P. yunnanensis, which would be helpful for management of genetic resources and reasonable utilization of them in future.
基金funded by the Fundamental Research Funds for the Central Universities(2015ZCQ-SW-02)
文摘Variations in the phenotypic characteristics of conifer needles is a consequence of genetic evolution that has been widely used in geographic variation and ecological studies.Although many studies are based on an in situ sampling strategy and generally realize the contribution of environmental effects to variation in needle traits,it is still uncertain which needle traits are most influenced by genetic effects and which are most influenced by the environment.Using both a common garden experiment to eliminate environmental heterogeneity and an in situ sampling strategy,we compared 18 Pinus tabuliformis needle traits among 10 geographical populations.Using both sampling strategies,we found significant differences in needle traits among populations and among individuals within populations.Differences in the‘‘among-population’’variance component between the two sampling strategies revealed the environmental contribution among natural populations for each trait.The among-population variance in the following traits exceeded 8%:needle length,number of stomata within 2 mm(NS2),number of stomatal lines on the planar side,number of resin canals(RCN)and the resin canal area(RCA).For the stability of needle traits,NS2,RCN,RCA,ratio of the vascular bundle area to the RCA(VBA/RCA),and MA/RCA differed significantly in more than five provenance changes between the common garden populations and natural populations,which may be susceptible to environmental effects.Conversely,the crosssectional area,mesophyll area(MA),MA/(VBA+RCA),and MA/VBA were phenotypically stable.Geographic variation patterns and systematic relation of needle traits differed between the two sampling strategies,suggesting that in situ sampling results may reflect environmental effects and deviate statistical parameters for genetic study.Future studies of genetic evolution in the context of geographic variation should be based on appropriate sampling strategies and stable phenotypic traits.
文摘The potential geographic distribution and favorable climatic conditions of Machilus thunbergii under current and future predicted climates in China are predicted based on MaxEnt model and ArcGIS software. The results show that the AUC values in different time periods and emission seniors are more than 0.9, which indicates the prediction is excellent. Precipitation of the coldest quarter, precipitation of the driest month, annual precipitation, mean diurnal range, and temperature annual range are the most important environmental factors affecting the distribution of Machilus thunbergii. At present, the suitable areas of Machilus thunbergii are mainly concentrated in the eastern subtropics of China, with a total area of 118.47 × 104 km2. The medium-suitability area and the high-suitability area are concentrated in Wuyi Mountains, Luoxiao Mountains, Xuefeng Mountains, Nanling and east of Taiwan Mountains. With the change of climate, the suitable area increases, and the medium-suitability area and high-suitability area migrate and expand to the east, and the low-suitability area expands slightly to the west and north. So, the simulated distribution of Machilus thunbergii should be one of priorities, when instigating in-situ conservation. The research results can provide a theoretical reference for the popularization and planting of Machilus thunbergii.
文摘To describe the dynamic cracking process of the CLT vertical layer,the correlation between a load-displacement curve,specimen cracking,and planar shear failure mechanism of the CLT were explored.A three-point bending test and an improved planar shear test are used to evaluate the shear performance of the CLT.In this study,the load-displacement curve is recorded,the experimental part is synchronized with the video,the dynamic process of cracking of the vertical layer is observed and analyzed throughout the test.From the load-displacement curve,the image characteristics of the initial cracking and the sudden increase of the cracking of the specimen are summar-ized.The description results of the whole dynamic process of the CLT vertical layer cracking are analyzed by pla-nar shear strength value,cracking phenomenon,and azimuth angle of cracking surface.The main conclusions show that the three-point bending test and the improved plain shear test can be used to test the plain shear strength of the CLT,with a difference of only 5.7%.The original crack and the new crack expansion account for 18.9%and 81.1%of the main cracking surface,respectively.And the vertical layer of the CLT specimen under three-point bending has three cracking morphologies,such as radial shake,ring shake,neither along with the radial shake nor along with the ring shake.The azimuth angle of the cracking surface of the CLT vertical layer under planar shear is quite consistent with the first main plane azimuth of the vertical layer of the CLT specimens under the three-point bending test and the shearing test.The shape in the cracking direction of the left half-span or the right half-span of the vertical layer of the specimen is similar to the Chinese character eight.
基金This study was funded by Co-Innovation Center of Efficient Processing and Utilization of Forest Resources(Nanjing Forestry University,Nanjing,210037,China).
文摘To improve the impact sound insulation performance of building floors and meet the objective requirements for living comfort of residents,in this article,three kinds of elastic cushion materials,Portuguese cork board,BGL insulation sound insulation foam board,and EPP polypropylene plastic foam board,are applied to the sound insulation of a light frame wood floor structure of the same bedroom and compared to the ordinary floor.This study uses the transfer function method and transient excitation method to measure the sound insulation,damping ratio,and elastic modulus of materials,as well as the sound insulation of the floor under the jumping excitation method of daily behavior.Through comparative analysis,the results and factors of improving the sound insulation performance of the floor are obtained,according to which three types of elastic cushion materials and the floor covering composed of them have higher vibration and noise reduction performance.Among them,the overall sound insulation performance of BGL board floor is the highest,followed by EPP board and cork board floor,and ordinary OSB floor is the lowest.Under the jumping excitation method,three floating floors can improve the impact sound insulation performance of the middle and low-frequency bands.
基金supported by National Natural Science Foundation of China(31971865)to LF.
文摘Weeds cause tremendous economic and ecological damage worldwide.The number of genomes established for weed species has sharply increased during the recent decade,with some 26 weed species having been sequenced and de novo genomes assembled.These genomes range from 270 Mb(Barbarea vulgaris)to almost 4.4 Gb(Aegilops tauschii).Importantly,chromosome-level assemblies are now available for 17 of these 26 species,and genomic investigations on weed populations have been conducted in at least 12 species.The resulting genomic data have greatly facilitated studies of weed management and biology,especially origin and evolution.Available weed genomes have indeed revealed valuable weed-derived genetic materials for crop improvement.In this review,we summarize the recent progress made in weed genomics and provide a perspective for further exploitation in this emerging field.
基金supported by the National Key Research and Development Project(2016YFC1301703)the Beijing Scientific and Technologic Project(D161100003816002).
文摘Introduction The safety outcomes of endovascular therapy for intracranial artery stenosis in a real-world stetting are largely unknown.The Clinical Registration Trial of Intracranial Stenting for Patients with Symptomatic Intracranial Artery Stenosis(CRTICAS)was a prospective,multicentre,real-world registry designed to assess these outcomes and the impact of centre experience.Methods 1140 severe,symptomatic intracranial arterial stenosis(ICAS)patients treated with endovascular therapy were included from 26 centres,further divided into three groups according to the annual centre volume of intracranial angioplasty and stent placement procedures over 2 years:(1)high volume for≥25 cases/year;(2)moderate volume for 10–25 cases/year and(3)low volume for<10 cases/year.Results The rate of 30-day stroke,transient ischaemic attack or death was 9.7%(111),with 5.4%,21.1%and 9.7%in high-volume,moderate-volume and low-volume centres,respectively(p<0.05).Multivariable logistic regression confirmed high-volume centres had a significantly lower primary endpoint compared with moderate-volume centres(OR=0.187,95%CI:0.056 to 0.627;p≤0.0001),while moderate-volume and low-volume centres showed no significant difference(p=0.8456).Conclusion Compared with the preceding randomised controlled trials,this real-world,prospective,multicentre registry shows a lower complication rate of endovascular treatment for symptomatic ICAS.Non-uniform utilisation in endovascular technology,institutional experience and patient selection in different volumes of centres may have an impact on overall safety of this treatment.
基金funded by Co-Innovation Center of Efficient Processing and Utilization of Forest Resources,Nanjing Forestry University,Nanjing 210037,China.
文摘In order to meet the objective requirements of the safety and comfort of the modern lightweight timber floors,and strengthen the research on the coupling performance of the lightweight timber floors vibration characteristics and the building comfort,this article discusses the floor of a two-story prefabricated lightweight timber building demonstration house.In this paper,the floor structure of a two-story light-weight wooden house has been carried out on structural calculation modal and experimental modal,static uniform load and concentrated load deflection value testing.The evaluation of the deflection value of the floor structure,the mode shape,the coupling of the fundamental frequency mode parameters,and the vibration comfort were also studied.The results show that the fundamental frequency simulation value,one-way modal test value and two-way modal test value of the floor structure all meet the requirements of BS-6472(BS6472-1:2008).That is,the floor structure is not lower than 8 Hz design requirements,and meets the frequency of BS-6472(BS6472-1:2008).The weighted root mean square acceleration is lower than the requirement of 0.45 m/s^(2);the first three natural frequencies of the floor structure calculated by the finite element simulation are 16.413,31.847 and 48.921 Hz,and the fundamental frequency mode is the bending vibration in the length and width directions.The second order is the bending mode in the length direction,and the third order is the bending mode in the width direction.The fundamental frequency of the two-way modal test of the floor structure is the first-order bending mode in the X direction;and the second-order natural frequency is the second-order bending vibration shape in the X direction.when the uniform load is mainly the weight of floor own,the simulated maximum deflection value is 1.0658 mm;the simulation is performed according to the standard value of 0.566 kN/m for the uniform load of the floor design,and the simulation is the largest.The maximum deflection value of the simulated floor is 1.47383 mm at its midpoint,which meets the requirements of National Building Code of Canada-2015(NBCC).The maximum deflection limit of the light wood structure floor system is lower than 3 m and the maximum deflection limit is 2 mm;the six deflection value test lines simulated under a concentrated load of 1 kN all present a parabolic distribution and are symmetrical.The above results has engineering application value for promoting the research on the vibration characteristics of the fabricated lightweight timber floors structure and its optimization design.
