The transition metal trichalcogenides(TMTs)with quasi-one-dimensional(quasi-1D)layered crystal structure represent a unique platform to explore intriguing physical properties.Herein,we report the successful growth of ...The transition metal trichalcogenides(TMTs)with quasi-one-dimensional(quasi-1D)layered crystal structure represent a unique platform to explore intriguing physical properties.Herein,we report the successful growth of a new TMT TiSe_(3)single crystal by using a high-pressure and high-temperature technique.The crystal structure of TiSe_(3)was determined by measuring the single-crystal x-ray diffraction and selected area electron diffraction.The 1D chain-like structure along the b-axis is formed by the TiSe_(6)prisms which share their tops and bottoms with each other.TiSe_(3)is a narrow band gap semiconductor with electron-type carriers under ambient conditions identified by the electrical and Hall effect measurements.It exhibits a pressure-induced semiconductor-to-metal transition around 4 GPa.As the pressure further increases to~6 GPa,a pressure-induced Lifshitz transition occurs,as indicated by the electrical transport measurements,high-pressure crystal structure characterizations,and electronic band structure calculations.展开更多
In today’s higher education system,the physical education program is not only for teaching sports skills and exercising physical fitness but also an important position for cultivating students’character,emotions,and...In today’s higher education system,the physical education program is not only for teaching sports skills and exercising physical fitness but also an important position for cultivating students’character,emotions,and values.With the in-depth development of the concept of ideological education,the ideology of college physical education courses has become an important direction of educational reform.In this paper,we will discuss the connotation of the concept of ideology and politics in college physical education courses,analyze the methods to effectively integrate the ideology and politics elements while guaranteeing the quality of teaching,and put forward the corresponding strategies to improve the quality,with a view to providing new ideas and methods for the construction of ideology and politics in college physical education courses.展开更多
To evaluate the thermal behavior of tunnels,an equivalent thermal conductivity(ETC)model for the fractured rock masses surrounding tunnels was proposed,based on the series-parallel theory,which incorporates the heat t...To evaluate the thermal behavior of tunnels,an equivalent thermal conductivity(ETC)model for the fractured rock masses surrounding tunnels was proposed,based on the series-parallel theory,which incorporates the heat transfer characteristics of the surrounding rock.A thermal probe test(TPT)was subsequently conducted at the Dajian Mountain Tunnel(China),and the heat transfer model of the thermal probe was developed and calibrated based on the TPT results.The ETCs of different test areas in the borehole were calculated based on the fracture parameters(dip direction,dip angle,opening,trace length),obtained via a digital borehole photography test.Finally,the new ETC model,the volumeaveraged model,and the non-fracture model were compared for accuracy in heat transfer calculation.The results demonstrate that(1)the error of heat transfer calculation error was reduced by 17.2%e69.2%using the new ETC model.(2)For the ETCs of different thermal response test areas,the minimum and maximum values were 2.15 W/(m K)and 3.7 W/(m K),respectively,with the fracture effect causing up to a 41.2%reduction in thermal conductivity.(3)For the ETC of the borehole,the ETC value was 2.53 W/(m K),with the fracture effect leading to a 31.6%reduction in thermal conductivity.The effect of fractures on the thermal conductivity of rock mass could not be ignored.This ETC model addresses the challenge of determining the ETC for the heterogeneous surrounding rock of tunnels and provides a more accurate representation of the in situ thermal behavior of tunnels.展开更多
Partial substitution of synthetic nitrogen(N)with organic fertilizers(PSOF)is of great significance in improving soil ecosystem functions in systems that have deteriorated due to the excessive application of chemical ...Partial substitution of synthetic nitrogen(N)with organic fertilizers(PSOF)is of great significance in improving soil ecosystem functions in systems that have deteriorated due to the excessive application of chemical N fertilizer.However,existing studies typically focus on individual soil functions,neglecting the fact that multiple functions occur simultaneously.It remains unclear how PSOF influences multiple soil functions and whether these impacts are related to soil microbial communities.Here,we examined the impacts of partial substitutions(25%–50%)of chemical N fertilizer with organic form(pig manure or municipal sludge)in a vegetable field on soil multifunctionality,by measuring a range of soil functions involving primary production(vegetable yield and quality),nutrient cycling(soil enzyme activities,ammonia volatilization,N leaching,and N runoff),and climate regulation(soil organic carbon sequestration and nitrous oxide emission).We observed that PSOF improved soil multifunctionality,with a 50%substitution of chemical N fertilizer with pig manure being the best management practice;the result was strongly related to the diversities and network complexities of bacteria and fungi.Random forest analysis further revealed that soil multifunctionality was best explained by the bacterial-fungal network complexity,followed by available phosphorus level and bacterial diversity.The PSOF also shifted the composition of bacterial and fungal communities,with increased relative abundances of dominant bacteria phyla,such as Bacteroidetes,Gemmatimonadetes,and Myxococcota,and fungal phyla,such as Basidiomycota and Olpidiomycota.The observed increases in soil multifunctionality were consistent with significant increases in the relative abundances of keystone taxa such as Blastocladiomycota,Chaetomiaceae,and Nocardiopsaceae.Together,these findings indicate that PSOF can enhance interactions within and among microbial communities and that such practices have the potential to improve soil ecosystem multifunctionality and contribute to the development of sustainable agriculture.展开更多
Ensuring the accurate detection of pineapple fruits under the high planting density and serious homogenization represents a current and significant challenge.In this study,an enhanced lightweight detection framework,d...Ensuring the accurate detection of pineapple fruits under the high planting density and serious homogenization represents a current and significant challenge.In this study,an enhanced lightweight detection framework,derived from the improved You Only Look Once version 5s(YOLOv5sp),is investigated in terms of the rapid and precise recognition of pineapple fruit for the agricultural robot.Three Convolutional Block Attention Module(CBAM)attention modules are considered the backbone network responsible for feature extraction,and the SIoU loss function is introduced to replace the CIoU loss function to handle the orientation angle and the penalization index.Eventually,the designed YOLOv5sp detection result of the mAP@0.5 value is 94.5%,which is 6.30%higher than YOLOv4,1.83%higher than Faster R-CNN,and 6.90%higher than classical YOLOv5s.At the same time,compared with the models SHFP-YOLO and RGDP-YOLOv7-tiny in other pineapple detection literature,the mAP@0.5 of the designed model is 4.54%and 3.5%higher,respectively.Furthermore,when it comes to the agricultural robot operating in diverse natural situations,the YOLOv5sp algorithm can maintain a successful picking rate of 90%with an average time of 15 s,exhibiting the effectiveness of the visual component in engineering scenarios.These research results can accelerate the transition of pineapple harvesting from manual to automated operations.展开更多
Organophosphate esters(OPEs)are emerging flame retardants widely used in products such as furniture,electronic equipment,construction,and plastics.It has been demonstrated that OPEs are harmful to humans and aquatic o...Organophosphate esters(OPEs)are emerging flame retardants widely used in products such as furniture,electronic equipment,construction,and plastics.It has been demonstrated that OPEs are harmful to humans and aquatic organisms,thus posing a threat to ecosystems.Considering that reservoirs are critical sources of drinking water for residents in Southern China,this study quantified nine OPEs in water samples collected from 29 reservoirs and their tributaries.The temporal and spatial distributions of OPEs were analyzed and their ecological risks were assessed.The results showed an extensive presence of OPEs in reservoirs,and the median concentration of S9OPEs was much higher in the dry season(65.3 ng/L)than in the wet season(21.3 ng/L).Triisobutyl phosphate(TiBP)(median:5.24 ng/L)and tris(2-ethylhexyl)phosphate(TEHP)(median:10.8 ng/L)dominated in the wet and dry seasons,respectively.Other OPEs varied considerably in concentrations over time,related to their physical and chemical properties,environmental factors(e.g.,precipitation and temperature),and varied applications.Furthermore,the significant correlations of individual OPEs suggest their shared utilization,emission sources,and environmental behaviors.Spatially,there was no significant difference(P>0.05)among the S9OPEs concentrations in water samples from different sites(inlet,reservoir,outlet,and tributary)of the reservoirs.Additionally,the concentrations of OPEs in reservoir water samples could be linked to industrial development,economic conditions,and population density.OPEs in the reservoir pose low ecological risks(RQ<0.1),except for EDHPP and TEHP,which present median ecological risks(RQ?0.54 and 0.38,respectively).Future studies could investigate more OPEs and their joint effects with other organic pollutants,as well as survey the chemical reactions and degradation pathways of OPEs in different environmental matrices to assess their potential ecotoxicity more comprehensively.展开更多
Humic substances(HS),which are defined as a series of highly acidic,relatively high-molecular-weight,and yellow to black colored substances formed during the decay and transformation of plant and microbial remains,ubi...Humic substances(HS),which are defined as a series of highly acidic,relatively high-molecular-weight,and yellow to black colored substances formed during the decay and transformation of plant and microbial remains,ubiquitously occur in nature.Humic substances represent the largest stable organic carbon pool in terrestrial environments and are the central characteristic of the soil.However,the validity of the HS concept and the justification of their extraction procedure have been recently debated.Here,we argue that the traditional humic paradigm is still relevant.Humic substances are distinctive and complex because the extracted HS formed during the humification are chemically distinct from their precursors and are heterogeneous among soils.By reviewing the concept,formation pathways,and stabilization of HS,we propose that the key question facing soil scientists is whether HS are soil microbial residues or unique synthesized compounds.Without revealing the distinctiveness of HS,it is impossible to address this question,as the structure,composition,and reactivity of HS are still poorly known owing to the heterogeneity and geographical variability of HS and the limits of the currently available analytical techniques.In our view,the distinctiveness of HS is fundamental to the soil,and thus further studies should be focused on revealing the distinctiveness of HS and explaining why HS hold this distinctiveness.展开更多
The synchronized development of mineralized bone and blood vessels is a fundamental requirement for successful bone tissue regeneration.Adequate energy production forms the cornerstone supporting new bone formation.ET...The synchronized development of mineralized bone and blood vessels is a fundamental requirement for successful bone tissue regeneration.Adequate energy production forms the cornerstone supporting new bone formation.ETS variant 2(ETV2)has been identified as a transcription factor that promotes energy metabolism reprogramming and facilitates the coordination between osteogenesis and angiogenesis.In vitro molecular experiments have demonstrated that ETV2 enhances osteogenic differentiation of dental pulp stem cells(DPSCs)by regulating the ETV2-prolyl hydroxylase 2(PHD2)-hypoxia-inducible factor-1α(HIF-1α)-vascular endothelial growth factor A(VEGFA)axis.Notably,ETV2 achieves the rapid reprogramming of energy metabolism by simultaneously accelerating mitochondrial aerobic respiration and glycolysis,thus fulfilling the energy requirements essential to expedite osteogenic differentiation.Furthermore,decreasedα-ketoglutarate release from ETV2-modified DPSCs contributes to microcirculation reconstruction.Additionally,we engineered hydroxyapatite/chitosan microspheres(HA/CS MS)with biomimetic nanostructures to facilitate multiple ETV2-DPSC functions and further enhanced the osteogenic differentiation.Animal experiments have validated the synergistic effect of ETV2-modified DPSCs and HA/CS MS in promoting the critical-size bone defect regeneration.In summary,this study offers a novel treatment approach for vascularized bone tissue regeneration that relies on energy metabolism activation and the maintenance of a stable local hypoxia signaling state.展开更多
In order to optimize the laser ablation performance of a micro-thruster with 1U dimensions,which employs a micro semiconductor laser,the impacts of pulse width and glycidyl azide polymer(GAP)thickness on thrust perfor...In order to optimize the laser ablation performance of a micro-thruster with 1U dimensions,which employs a micro semiconductor laser,the impacts of pulse width and glycidyl azide polymer(GAP)thickness on thrust performance were researched.The results showed that with a GAP thickness of 200μm,the single-pulse impulse(I)increased gradually with the increase in the laser pulse width from 50 to 800μs,while the specific impulse(I_(sp)),impulse coupling coefficient(Cm)and ablation efficiency(η)all reached optimal values with a 200μs pulse width.It is worth noting that the optimal pulse width is identical to the ignition delay time.Both Cmandηpeaked with a pulse width of 200μs,reaching 242.22μN W^(-1)and 35.4%,respectively.With the increase in GAP thickness,I and Cmincreased gradually.GAP of different thicknesses corresponded to different optimal laser pulse widths.Under a certain laser pulse width,the optimal GAP thickness should be the most vertical thickness of the ablation pit,and the various propulsion performance parameters at this time were also optimal.With the current laser parameters,the optimal GAP thickness was approximately 150μm,I_(sp)was approximately 322.22 s,andηwas approximately 34.94%.展开更多
In situ monitoring of bone regeneration enables timely diagnosis and intervention by acquiring vital biological parameters.However,an existing gap exists in the availability of effective methodologies for continuous a...In situ monitoring of bone regeneration enables timely diagnosis and intervention by acquiring vital biological parameters.However,an existing gap exists in the availability of effective methodologies for continuous and dynamic monitoring of the bone tissue regeneration process,encompassing the concurrent visualization of bone formation and implant degradation.Here,we present an integrated scaffold designed to facilitate real-time monitoring of both bone formation and implant degradation during the repair of bone defects.Laponite(Lap),CyP-loaded mesoporous silica(CyP@MSNs)and ultrasmall superparamagnetic iron oxide nanoparticles(USPIO@SiO2)were incorporated into a bioink containing bone marrow mesenchymal stem cells(BMSCs)to fabricate functional scaffolds denoted as C@M/GLU using 3D bioprinting technology.In both in vivo and in vitro experiments,the composite scaffold has demonstrated a significant enhancement of bone regeneration through the controlled release of silicon(Si)and magnesium(Mg)ions.Employing near-infrared fluorescence(NIR-FL)imaging,the composite scaffold facilitates the monitoring of alkaline phosphate(ALP)expression,providing an accurate reflection of the scaffold’s initial osteogenic activity.Meanwhile,the degradation of scaffolds was monitored by tracking the changes in the magnetic resonance(MR)signals at various time points.These findings indicate that the designed scaffold holds potential as an in situ bone implant for combined visualization of osteogenesis and implant degradation throughout the bone repair process.展开更多
Many ongoing tunnel projects provide a favorable opportunity for the investigation and application of tunnel lining ground heat exchangers(GHEs).Tunnel lining GHEs can be connected to a heat pump to extract geothermal...Many ongoing tunnel projects provide a favorable opportunity for the investigation and application of tunnel lining ground heat exchangers(GHEs).Tunnel lining GHEs can be connected to a heat pump to extract geothermal energy for heating and cooling buildings.Numerous studies have focused on the thermal performance of tunnel lining GHEs;however,the studies on the interaction between heat pumps and tunnel lining GHEs are relatively rare.In this study,a coupled heat transfer model of heat pumps and tunnel lining GHEs was proposed and then calibrated based on in situ test results.The model was used to evaluate the energy efficiency of a heat pump with tunnel lining GHEs under different conditions.The results show that the energy efficiency ratio(EER)increases exponentially with the absorber pipe length and thermal conductivity of the surrounding rock.The EER is governed by the convection heat transfer coefficient,which varies exponentially;meanwhile,the EER decreases approximately linearly with the annual average air temperature in the tunnel.Different types of heat pumps affect the EER significantly,and the EER of a Type-3 heat pump is higher than that of a Type-1 heat pump by 27.1%.Based on the aforementioned results,an empirical formula for the EER and absorber pipe length was established.Moreover,a preliminary design method for the absorber pipe length based on this empirical formula was developed.The method was employed to determine the appropriate absorber pipe length for the tunnel lining GHEs in the Shapu tunnel in Shenzhen,China.Finally,groups of absorber pipe layouts with a pipe spacing of 0.5 m,area of 135 m2,and length of 293.5 m were preliminarily determined.展开更多
This paper is concerned with a diffusive Holling-Tanner prey-predator model in a bounded domain with Dirichlet boundary condition and a free boundary. The global existence of the unique solution is proved. Moreover, t...This paper is concerned with a diffusive Holling-Tanner prey-predator model in a bounded domain with Dirichlet boundary condition and a free boundary. The global existence of the unique solution is proved. Moreover, the criteria governing spreading- vanishing are derived by mainly using the comparison principle. The results show that if the length of the occupying line is bigger than a threshold value （spreading barrier）, then the spreading of predators will make an achievement, and, if the length of the occupying line is smaller than this spreading barrier and the spreading coefficient is relatively small depending on initial size of predators, then the predators will fail in establishing themselves and eventually die out.展开更多
Cartilage defects are one of the most common symptoms of osteoarthritis(OA),a degenerative disease that affects millions of people world-wide and places a significant socio-economic burden on society.Hydrogels,which a...Cartilage defects are one of the most common symptoms of osteoarthritis(OA),a degenerative disease that affects millions of people world-wide and places a significant socio-economic burden on society.Hydrogels,which are a class of biomaterials that are elastic,and display smooth surfaces while exhibiting high water content,are promising candidates for cartilage regeneration.In recent years,various kinds of hydrogels have been developed and applied for the repair of cartilage defects in vitro or in vivo,some of which are hopeful to enter clinical trials.In this review,recent research findings and developments of hydrogels for cartilage defects repair are summarized.We discuss the principle of cartilage regeneration,and outline the requirements that have to be fulfilled for the deployment of hydrogels for medical applications.We also highlight the development of advanced hydrogels with tailored properties for different kinds of cartilage defects to meet the requirements of cartilage tissue engineering and precision medicine.展开更多
Using 15N tracer technique,we investigated the potential rates of denitrification,anaerobic ammonium oxidation,dis-similatory nitrate reduction to ammonium(DNRA),and their partitioning among nitrate reduction,as well ...Using 15N tracer technique,we investigated the potential rates of denitrification,anaerobic ammonium oxidation,dis-similatory nitrate reduction to ammonium(DNRA),and their partitioning among nitrate reduction,as well as the N_(2)O emission rates in a paddy soil receiving various biochar(0%,0.03%,0.1%,0.5%,and 1.0%;w/w)and straw(0.1%)over six consecutive years.Results showed that except for the 1.0%amendment treatment,biochar significantly(P<0.05)increased denitrification rates by 10.19‒75.96%compared with non-biochar amended treatment,and that biochar significantly(P<0.05)increased DNRA rates by 1.63‒6.84 folds relative to non-biochar amended treatment.Conse-quently,biochar shifted more NO3-partitioning toward DNRA process,as suggested by the increased DNRA/(denitri-fication+DNRA)ratios from 1.60 to 13.18%.On the other hand,biochar significantly(P<0.05)reduced N_(2)O emission rates by 61.86-97.65%accompanied by a significant decrease in N_(2)O/(N_(2)O+N_(2))ratios(65.29-98.39%),indicating bio-char amendment facilitated the reduction of N_(2)O to N_(2).The promoting effects of biochar on DNRA rates and DNRA/(denitrification+DNRA)ratios were attributed to the increased carbon availability and the altered nitrate reducer communities.Collectively,our study suggests that biochar amendment in the paddy soil is helpful for N conservation by favoring nitrate partitioning toward DNRA process,which deepens our understanding of how biochar mediates N cycling in the paddy field.展开更多
Corneal injuries will cause corneal surface diseases that may lead to blindness in millions of people worldwide.There is a tremendous need for biomaterials that can promote corneal regeneration with practical feasibil...Corneal injuries will cause corneal surface diseases that may lead to blindness in millions of people worldwide.There is a tremendous need for biomaterials that can promote corneal regeneration with practical feasibility.Here we demonstrate a strategy of a protein coating for corneal injury regeneration.We synthesize an o-nitrosobenzaldehyde group(NB)-modified gelatin(GelNB),which could adhere directly to the corneal surface with covalent bonding to form a thin molecular coating.The molecular coating could avoid rapid clearance and provide a favorable environment for cell migration,thereby effectively accelerating corneal repair and regeneration.The histological structure of the regenerated cornea is more similar to the native cornea.This molecular coating can be used conveniently as an eye drop solution,which makes it a promising strategy for corneal regeneration.展开更多
The advancement of Internet of Things has stimulated huge demands on low-voltage flexible electronics.Carbon-nanotube(CNT)-based electronics are of great promise to this end for their intrinsic flexibility,high carrie...The advancement of Internet of Things has stimulated huge demands on low-voltage flexible electronics.Carbon-nanotube(CNT)-based electronics are of great promise to this end for their intrinsic flexibility,high carrier mobility,and capability to synthesize as semiconducting or metallic to serve as the channels,electrodes,and interconnects of circuits.However,the gate dielectric often has to adopt brittle oxides,which can seriously limit the device flexibility.Herein,we show that a hybrid polyimide-Al2O3 material can serve as a good gate dielectric to realize truly intrinsic flexibility of transistors and circuits based on CNTs.With this hybrid dielectric,high-performance all-CNT transistors and integrated circuits of inverters,ring oscillators,and logic gates are demonstrated.Particularly,the inverters exhibit a remarkably high gain of 342.5 and can be used as an analog amplifier for millivolt small signals.Ultralow voltage(50 mV)operation is also feasible,which highlights the great promise for low-power applications.展开更多
With the rapid development of electronic equipment and communication technology,the demand for polymer composites with high thermal conductivity and mechanical properties has increased significantly.However,its nondeg...With the rapid development of electronic equipment and communication technology,the demand for polymer composites with high thermal conductivity and mechanical properties has increased significantly.However,its nondegradable polymer matrix will inevitably bring more and more serious environmental pollution.Therefore,it is urgent to develop biodegradable thermally conductive polymer composites.In this work,biodegradable poly(butylene adipate-coterephthalate)(PBAT)is used as the matrix material,and vacuum-assisted filtration technology is employed to prepare carbon nanotube(CNT)and cellulose nanocrystal(CNC)networks with high thermal conductivity.Then CNT-CNC/PBAT composites with high thermal conductivity and excellent mechanical properties are prepared by the ultrasonic-assisted forced infiltration method.Both experiment and simulation methods are used to systematically investigate the thermally conductive and dissipation performances of the CNT-CNC/PBAT composites.Above all,a simple alcoholysis reaction is applied to realize the separation of the PBAT matrix and functional fillers without destroying the conductive network skeleton,which makes it possible for the recycling of thermally conductive polymer composites.展开更多
基金the National Key R&D Program of China(Grant Nos.2023YFA1406100 and 2024YFA1400066)the Open Research Fund of Beijing National Laboratory for Condensed Matter Physics(Grant No.2023BNLCMPKF002)+6 种基金supported by the National Natural Science Foundation of China(Grant Nos.52288102 and 52090020)the S&T Program of Hebei(Grant No.225A1102D)the Open Projects from the State Key Laboratory of Metastable Materials Science and Technology,Yanshan University(Grant No.202301)carried out at the Synergetic Extreme Condition User Facility(SE-CUF)of the Chinese Academy of Sciencessupport from the Analytical Instrumentation Center(Grant No.SPST-AIC10112914)School of Physical Science and Technology(SPST),ShanghaiTech Universitysupported by the Double First-Class Initiative Fund of ShanghaiTech University.
文摘The transition metal trichalcogenides(TMTs)with quasi-one-dimensional(quasi-1D)layered crystal structure represent a unique platform to explore intriguing physical properties.Herein,we report the successful growth of a new TMT TiSe_(3)single crystal by using a high-pressure and high-temperature technique.The crystal structure of TiSe_(3)was determined by measuring the single-crystal x-ray diffraction and selected area electron diffraction.The 1D chain-like structure along the b-axis is formed by the TiSe_(6)prisms which share their tops and bottoms with each other.TiSe_(3)is a narrow band gap semiconductor with electron-type carriers under ambient conditions identified by the electrical and Hall effect measurements.It exhibits a pressure-induced semiconductor-to-metal transition around 4 GPa.As the pressure further increases to~6 GPa,a pressure-induced Lifshitz transition occurs,as indicated by the electrical transport measurements,high-pressure crystal structure characterizations,and electronic band structure calculations.
文摘In today’s higher education system,the physical education program is not only for teaching sports skills and exercising physical fitness but also an important position for cultivating students’character,emotions,and values.With the in-depth development of the concept of ideological education,the ideology of college physical education courses has become an important direction of educational reform.In this paper,we will discuss the connotation of the concept of ideology and politics in college physical education courses,analyze the methods to effectively integrate the ideology and politics elements while guaranteeing the quality of teaching,and put forward the corresponding strategies to improve the quality,with a view to providing new ideas and methods for the construction of ideology and politics in college physical education courses.
基金funded by the National Natural Science Foundation of China(Grant Nos.52278398 and U23A0664).
文摘To evaluate the thermal behavior of tunnels,an equivalent thermal conductivity(ETC)model for the fractured rock masses surrounding tunnels was proposed,based on the series-parallel theory,which incorporates the heat transfer characteristics of the surrounding rock.A thermal probe test(TPT)was subsequently conducted at the Dajian Mountain Tunnel(China),and the heat transfer model of the thermal probe was developed and calibrated based on the TPT results.The ETCs of different test areas in the borehole were calculated based on the fracture parameters(dip direction,dip angle,opening,trace length),obtained via a digital borehole photography test.Finally,the new ETC model,the volumeaveraged model,and the non-fracture model were compared for accuracy in heat transfer calculation.The results demonstrate that(1)the error of heat transfer calculation error was reduced by 17.2%e69.2%using the new ETC model.(2)For the ETCs of different thermal response test areas,the minimum and maximum values were 2.15 W/(m K)and 3.7 W/(m K),respectively,with the fracture effect causing up to a 41.2%reduction in thermal conductivity.(3)For the ETC of the borehole,the ETC value was 2.53 W/(m K),with the fracture effect leading to a 31.6%reduction in thermal conductivity.The effect of fractures on the thermal conductivity of rock mass could not be ignored.This ETC model addresses the challenge of determining the ETC for the heterogeneous surrounding rock of tunnels and provides a more accurate representation of the in situ thermal behavior of tunnels.
基金supported by the National Natural Science Foundation of China(Nos.41961124004,42207361,and42061124001)。
文摘Partial substitution of synthetic nitrogen(N)with organic fertilizers(PSOF)is of great significance in improving soil ecosystem functions in systems that have deteriorated due to the excessive application of chemical N fertilizer.However,existing studies typically focus on individual soil functions,neglecting the fact that multiple functions occur simultaneously.It remains unclear how PSOF influences multiple soil functions and whether these impacts are related to soil microbial communities.Here,we examined the impacts of partial substitutions(25%–50%)of chemical N fertilizer with organic form(pig manure or municipal sludge)in a vegetable field on soil multifunctionality,by measuring a range of soil functions involving primary production(vegetable yield and quality),nutrient cycling(soil enzyme activities,ammonia volatilization,N leaching,and N runoff),and climate regulation(soil organic carbon sequestration and nitrous oxide emission).We observed that PSOF improved soil multifunctionality,with a 50%substitution of chemical N fertilizer with pig manure being the best management practice;the result was strongly related to the diversities and network complexities of bacteria and fungi.Random forest analysis further revealed that soil multifunctionality was best explained by the bacterial-fungal network complexity,followed by available phosphorus level and bacterial diversity.The PSOF also shifted the composition of bacterial and fungal communities,with increased relative abundances of dominant bacteria phyla,such as Bacteroidetes,Gemmatimonadetes,and Myxococcota,and fungal phyla,such as Basidiomycota and Olpidiomycota.The observed increases in soil multifunctionality were consistent with significant increases in the relative abundances of keystone taxa such as Blastocladiomycota,Chaetomiaceae,and Nocardiopsaceae.Together,these findings indicate that PSOF can enhance interactions within and among microbial communities and that such practices have the potential to improve soil ecosystem multifunctionality and contribute to the development of sustainable agriculture.
基金supported by the 2024 Basic and Applied Research Project of Guangzhou Science and Technology Plan(Grant No.2024A04J4140)the National Key Laboratory of Agricultural Equipment Technology Project(Grant No.NSKLAET-202408)+1 种基金the Key Laboratory of Spectroscopy Sensing Ministry of Agriculture and Rural Affairs(Grant No.2024ZJUGP004)the Young Talent Support Project of Guangzhou Association for Science and Technology(Grant No.QT2024-006).
文摘Ensuring the accurate detection of pineapple fruits under the high planting density and serious homogenization represents a current and significant challenge.In this study,an enhanced lightweight detection framework,derived from the improved You Only Look Once version 5s(YOLOv5sp),is investigated in terms of the rapid and precise recognition of pineapple fruit for the agricultural robot.Three Convolutional Block Attention Module(CBAM)attention modules are considered the backbone network responsible for feature extraction,and the SIoU loss function is introduced to replace the CIoU loss function to handle the orientation angle and the penalization index.Eventually,the designed YOLOv5sp detection result of the mAP@0.5 value is 94.5%,which is 6.30%higher than YOLOv4,1.83%higher than Faster R-CNN,and 6.90%higher than classical YOLOv5s.At the same time,compared with the models SHFP-YOLO and RGDP-YOLOv7-tiny in other pineapple detection literature,the mAP@0.5 of the designed model is 4.54%and 3.5%higher,respectively.Furthermore,when it comes to the agricultural robot operating in diverse natural situations,the YOLOv5sp algorithm can maintain a successful picking rate of 90%with an average time of 15 s,exhibiting the effectiveness of the visual component in engineering scenarios.These research results can accelerate the transition of pineapple harvesting from manual to automated operations.
基金supported by the National Natural Science Foundation of China(No.42277424 and No.42077385)the Shenzhen Science and Technology Program(JCYJ20230807110903008 and JCYJ20210324122400002).
文摘Organophosphate esters(OPEs)are emerging flame retardants widely used in products such as furniture,electronic equipment,construction,and plastics.It has been demonstrated that OPEs are harmful to humans and aquatic organisms,thus posing a threat to ecosystems.Considering that reservoirs are critical sources of drinking water for residents in Southern China,this study quantified nine OPEs in water samples collected from 29 reservoirs and their tributaries.The temporal and spatial distributions of OPEs were analyzed and their ecological risks were assessed.The results showed an extensive presence of OPEs in reservoirs,and the median concentration of S9OPEs was much higher in the dry season(65.3 ng/L)than in the wet season(21.3 ng/L).Triisobutyl phosphate(TiBP)(median:5.24 ng/L)and tris(2-ethylhexyl)phosphate(TEHP)(median:10.8 ng/L)dominated in the wet and dry seasons,respectively.Other OPEs varied considerably in concentrations over time,related to their physical and chemical properties,environmental factors(e.g.,precipitation and temperature),and varied applications.Furthermore,the significant correlations of individual OPEs suggest their shared utilization,emission sources,and environmental behaviors.Spatially,there was no significant difference(P>0.05)among the S9OPEs concentrations in water samples from different sites(inlet,reservoir,outlet,and tributary)of the reservoirs.Additionally,the concentrations of OPEs in reservoir water samples could be linked to industrial development,economic conditions,and population density.OPEs in the reservoir pose low ecological risks(RQ<0.1),except for EDHPP and TEHP,which present median ecological risks(RQ?0.54 and 0.38,respectively).Future studies could investigate more OPEs and their joint effects with other organic pollutants,as well as survey the chemical reactions and degradation pathways of OPEs in different environmental matrices to assess their potential ecotoxicity more comprehensively.
基金supported by the National Natural Science Foundation of China(Nos.41571231 and 41201221)the National Key Research and Development Program of China(No.2016YFD0200304)+3 种基金the Scientific Instrument and Equipment Development Project of Chinese Academy Sciences(CAS)(No.YJKYYQ20170058)the Natural Science Foundation of Jiangsu Province,China(No.BK2012496)the Youth Innovation Promotion Association,CAS(No.2017362)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.19KJB180010)。
文摘Humic substances(HS),which are defined as a series of highly acidic,relatively high-molecular-weight,and yellow to black colored substances formed during the decay and transformation of plant and microbial remains,ubiquitously occur in nature.Humic substances represent the largest stable organic carbon pool in terrestrial environments and are the central characteristic of the soil.However,the validity of the HS concept and the justification of their extraction procedure have been recently debated.Here,we argue that the traditional humic paradigm is still relevant.Humic substances are distinctive and complex because the extracted HS formed during the humification are chemically distinct from their precursors and are heterogeneous among soils.By reviewing the concept,formation pathways,and stabilization of HS,we propose that the key question facing soil scientists is whether HS are soil microbial residues or unique synthesized compounds.Without revealing the distinctiveness of HS,it is impossible to address this question,as the structure,composition,and reactivity of HS are still poorly known owing to the heterogeneity and geographical variability of HS and the limits of the currently available analytical techniques.In our view,the distinctiveness of HS is fundamental to the soil,and thus further studies should be focused on revealing the distinctiveness of HS and explaining why HS hold this distinctiveness.
基金supported by the National Natural Science Foundation of China (grants 82301039)the Natural Science Foundation of the Anhui Higher Education Institutions of China (grant 2022AH050758)+2 种基金Anhui Institute of Translational Medicine,Natural Sciences (grant 2022zhyx-C87)National Natural Science Foundation of China (82170951)Beijing Municipal Natural Science Foundation (7222079).
文摘The synchronized development of mineralized bone and blood vessels is a fundamental requirement for successful bone tissue regeneration.Adequate energy production forms the cornerstone supporting new bone formation.ETS variant 2(ETV2)has been identified as a transcription factor that promotes energy metabolism reprogramming and facilitates the coordination between osteogenesis and angiogenesis.In vitro molecular experiments have demonstrated that ETV2 enhances osteogenic differentiation of dental pulp stem cells(DPSCs)by regulating the ETV2-prolyl hydroxylase 2(PHD2)-hypoxia-inducible factor-1α(HIF-1α)-vascular endothelial growth factor A(VEGFA)axis.Notably,ETV2 achieves the rapid reprogramming of energy metabolism by simultaneously accelerating mitochondrial aerobic respiration and glycolysis,thus fulfilling the energy requirements essential to expedite osteogenic differentiation.Furthermore,decreasedα-ketoglutarate release from ETV2-modified DPSCs contributes to microcirculation reconstruction.Additionally,we engineered hydroxyapatite/chitosan microspheres(HA/CS MS)with biomimetic nanostructures to facilitate multiple ETV2-DPSC functions and further enhanced the osteogenic differentiation.Animal experiments have validated the synergistic effect of ETV2-modified DPSCs and HA/CS MS in promoting the critical-size bone defect regeneration.In summary,this study offers a novel treatment approach for vascularized bone tissue regeneration that relies on energy metabolism activation and the maintenance of a stable local hypoxia signaling state.
基金supported by National Natural Science Foundation of China (Nos. 11502301, 11602304 and 62175260)
文摘In order to optimize the laser ablation performance of a micro-thruster with 1U dimensions,which employs a micro semiconductor laser,the impacts of pulse width and glycidyl azide polymer(GAP)thickness on thrust performance were researched.The results showed that with a GAP thickness of 200μm,the single-pulse impulse(I)increased gradually with the increase in the laser pulse width from 50 to 800μs,while the specific impulse(I_(sp)),impulse coupling coefficient(Cm)and ablation efficiency(η)all reached optimal values with a 200μs pulse width.It is worth noting that the optimal pulse width is identical to the ignition delay time.Both Cmandηpeaked with a pulse width of 200μs,reaching 242.22μN W^(-1)and 35.4%,respectively.With the increase in GAP thickness,I and Cmincreased gradually.GAP of different thicknesses corresponded to different optimal laser pulse widths.Under a certain laser pulse width,the optimal GAP thickness should be the most vertical thickness of the ablation pit,and the various propulsion performance parameters at this time were also optimal.With the current laser parameters,the optimal GAP thickness was approximately 150μm,I_(sp)was approximately 322.22 s,andηwas approximately 34.94%.
基金support from various resources,including the National Natural Science Foundation of China (grant numbers 32071350,32271412,32171404)the Shanghai Rising-Star Program (grant numbers 22QA1400100)+1 种基金the Fundamental Research Funds for the Central Universities (grant numbers 2232019A3-06,2232021D-10)the Science and Technology Commission of Shanghai Municipality (grant numbers 21ZR1403100,19440741600,20DZ2254900).
文摘In situ monitoring of bone regeneration enables timely diagnosis and intervention by acquiring vital biological parameters.However,an existing gap exists in the availability of effective methodologies for continuous and dynamic monitoring of the bone tissue regeneration process,encompassing the concurrent visualization of bone formation and implant degradation.Here,we present an integrated scaffold designed to facilitate real-time monitoring of both bone formation and implant degradation during the repair of bone defects.Laponite(Lap),CyP-loaded mesoporous silica(CyP@MSNs)and ultrasmall superparamagnetic iron oxide nanoparticles(USPIO@SiO2)were incorporated into a bioink containing bone marrow mesenchymal stem cells(BMSCs)to fabricate functional scaffolds denoted as C@M/GLU using 3D bioprinting technology.In both in vivo and in vitro experiments,the composite scaffold has demonstrated a significant enhancement of bone regeneration through the controlled release of silicon(Si)and magnesium(Mg)ions.Employing near-infrared fluorescence(NIR-FL)imaging,the composite scaffold facilitates the monitoring of alkaline phosphate(ALP)expression,providing an accurate reflection of the scaffold’s initial osteogenic activity.Meanwhile,the degradation of scaffolds was monitored by tracking the changes in the magnetic resonance(MR)signals at various time points.These findings indicate that the designed scaffold holds potential as an in situ bone implant for combined visualization of osteogenesis and implant degradation throughout the bone repair process.
基金funded by the National Natural Science Foundation of China(Grant numbers:51778138,and 51978162).
文摘Many ongoing tunnel projects provide a favorable opportunity for the investigation and application of tunnel lining ground heat exchangers(GHEs).Tunnel lining GHEs can be connected to a heat pump to extract geothermal energy for heating and cooling buildings.Numerous studies have focused on the thermal performance of tunnel lining GHEs;however,the studies on the interaction between heat pumps and tunnel lining GHEs are relatively rare.In this study,a coupled heat transfer model of heat pumps and tunnel lining GHEs was proposed and then calibrated based on in situ test results.The model was used to evaluate the energy efficiency of a heat pump with tunnel lining GHEs under different conditions.The results show that the energy efficiency ratio(EER)increases exponentially with the absorber pipe length and thermal conductivity of the surrounding rock.The EER is governed by the convection heat transfer coefficient,which varies exponentially;meanwhile,the EER decreases approximately linearly with the annual average air temperature in the tunnel.Different types of heat pumps affect the EER significantly,and the EER of a Type-3 heat pump is higher than that of a Type-1 heat pump by 27.1%.Based on the aforementioned results,an empirical formula for the EER and absorber pipe length was established.Moreover,a preliminary design method for the absorber pipe length based on this empirical formula was developed.The method was employed to determine the appropriate absorber pipe length for the tunnel lining GHEs in the Shapu tunnel in Shenzhen,China.Finally,groups of absorber pipe layouts with a pipe spacing of 0.5 m,area of 135 m2,and length of 293.5 m were preliminarily determined.
文摘This paper is concerned with a diffusive Holling-Tanner prey-predator model in a bounded domain with Dirichlet boundary condition and a free boundary. The global existence of the unique solution is proved. Moreover, the criteria governing spreading- vanishing are derived by mainly using the comparison principle. The results show that if the length of the occupying line is bigger than a threshold value （spreading barrier）, then the spreading of predators will make an achievement, and, if the length of the occupying line is smaller than this spreading barrier and the spreading coefficient is relatively small depending on initial size of predators, then the predators will fail in establishing themselves and eventually die out.
基金National key R&D program of China(2017YFA0104900)NSFC grants(31830029,81630065,81902187)+1 种基金the Zhejiang Provincial Natural Science Foundation of China(No.LQ19E030019,LY19C070003)China Postdoctoral Science Foundation(2019M652112,2018M642442,2019M662084).
文摘Cartilage defects are one of the most common symptoms of osteoarthritis(OA),a degenerative disease that affects millions of people world-wide and places a significant socio-economic burden on society.Hydrogels,which are a class of biomaterials that are elastic,and display smooth surfaces while exhibiting high water content,are promising candidates for cartilage regeneration.In recent years,various kinds of hydrogels have been developed and applied for the repair of cartilage defects in vitro or in vivo,some of which are hopeful to enter clinical trials.In this review,recent research findings and developments of hydrogels for cartilage defects repair are summarized.We discuss the principle of cartilage regeneration,and outline the requirements that have to be fulfilled for the deployment of hydrogels for medical applications.We also highlight the development of advanced hydrogels with tailored properties for different kinds of cartilage defects to meet the requirements of cartilage tissue engineering and precision medicine.
基金the National Natural Science Foundation of China(No.U20A20113 and 42177303)the National Key Research and Development Program of China(No.2021YFD1700802).
文摘Using 15N tracer technique,we investigated the potential rates of denitrification,anaerobic ammonium oxidation,dis-similatory nitrate reduction to ammonium(DNRA),and their partitioning among nitrate reduction,as well as the N_(2)O emission rates in a paddy soil receiving various biochar(0%,0.03%,0.1%,0.5%,and 1.0%;w/w)and straw(0.1%)over six consecutive years.Results showed that except for the 1.0%amendment treatment,biochar significantly(P<0.05)increased denitrification rates by 10.19‒75.96%compared with non-biochar amended treatment,and that biochar significantly(P<0.05)increased DNRA rates by 1.63‒6.84 folds relative to non-biochar amended treatment.Conse-quently,biochar shifted more NO3-partitioning toward DNRA process,as suggested by the increased DNRA/(denitri-fication+DNRA)ratios from 1.60 to 13.18%.On the other hand,biochar significantly(P<0.05)reduced N_(2)O emission rates by 61.86-97.65%accompanied by a significant decrease in N_(2)O/(N_(2)O+N_(2))ratios(65.29-98.39%),indicating bio-char amendment facilitated the reduction of N_(2)O to N_(2).The promoting effects of biochar on DNRA rates and DNRA/(denitrification+DNRA)ratios were attributed to the increased carbon availability and the altered nitrate reducer communities.Collectively,our study suggests that biochar amendment in the paddy soil is helpful for N conservation by favoring nitrate partitioning toward DNRA process,which deepens our understanding of how biochar mediates N cycling in the paddy field.
基金This work was supported by the National Key R&D Program of China(2017YFA0104900)National Natural Science Foundation of China(31830029,32000957,81972053).
文摘Corneal injuries will cause corneal surface diseases that may lead to blindness in millions of people worldwide.There is a tremendous need for biomaterials that can promote corneal regeneration with practical feasibility.Here we demonstrate a strategy of a protein coating for corneal injury regeneration.We synthesize an o-nitrosobenzaldehyde group(NB)-modified gelatin(GelNB),which could adhere directly to the corneal surface with covalent bonding to form a thin molecular coating.The molecular coating could avoid rapid clearance and provide a favorable environment for cell migration,thereby effectively accelerating corneal repair and regeneration.The histological structure of the regenerated cornea is more similar to the native cornea.This molecular coating can be used conveniently as an eye drop solution,which makes it a promising strategy for corneal regeneration.
基金supported by National Natural Science Foundation of China (62074008,22175005 and 51961165105)Guangdong Basic and Applied Basic Research Foundation (2020B1515120039)+1 种基金Shenzhen Fundamental Research Program (GXWD20201231165807007-20200827122756001,JCYJ20180507181702150,JCYJ20200109110628172,and GXWD20201231165807007-20200802205241003)supported by State Key Laboratory of Nuclear Physics and Technology,Peking University under contract no.NPT2020KFJ20.
文摘The advancement of Internet of Things has stimulated huge demands on low-voltage flexible electronics.Carbon-nanotube(CNT)-based electronics are of great promise to this end for their intrinsic flexibility,high carrier mobility,and capability to synthesize as semiconducting or metallic to serve as the channels,electrodes,and interconnects of circuits.However,the gate dielectric often has to adopt brittle oxides,which can seriously limit the device flexibility.Herein,we show that a hybrid polyimide-Al2O3 material can serve as a good gate dielectric to realize truly intrinsic flexibility of transistors and circuits based on CNTs.With this hybrid dielectric,high-performance all-CNT transistors and integrated circuits of inverters,ring oscillators,and logic gates are demonstrated.Particularly,the inverters exhibit a remarkably high gain of 342.5 and can be used as an analog amplifier for millivolt small signals.Ultralow voltage(50 mV)operation is also feasible,which highlights the great promise for low-power applications.
基金Basic Science Center Program,Grant/Award Number:51988102National Natural Science Foundation of China,Grant/Award Numbers:52003019,52073011+1 种基金National Natural Science Foundation of China,Sinopec Key Projects,Grant/Award Number:420043-6Talents Introduction Project in Beijing University of Chemical Technology,Grant/Award Number:buctrc201909。
文摘With the rapid development of electronic equipment and communication technology,the demand for polymer composites with high thermal conductivity and mechanical properties has increased significantly.However,its nondegradable polymer matrix will inevitably bring more and more serious environmental pollution.Therefore,it is urgent to develop biodegradable thermally conductive polymer composites.In this work,biodegradable poly(butylene adipate-coterephthalate)(PBAT)is used as the matrix material,and vacuum-assisted filtration technology is employed to prepare carbon nanotube(CNT)and cellulose nanocrystal(CNC)networks with high thermal conductivity.Then CNT-CNC/PBAT composites with high thermal conductivity and excellent mechanical properties are prepared by the ultrasonic-assisted forced infiltration method.Both experiment and simulation methods are used to systematically investigate the thermally conductive and dissipation performances of the CNT-CNC/PBAT composites.Above all,a simple alcoholysis reaction is applied to realize the separation of the PBAT matrix and functional fillers without destroying the conductive network skeleton,which makes it possible for the recycling of thermally conductive polymer composites.
