The consideration of time dependence is essential for the study of deformation and fracturing processes of rock materials, especially for those subjected to strong compressive and tensile stresses. In this paper, the ...The consideration of time dependence is essential for the study of deformation and fracturing processes of rock materials, especially for those subjected to strong compressive and tensile stresses. In this paper, the self-developed direct tension device and creep testing machine RLW-2000M are used to conduct the creep tests on red sandstone under uniaxial compressive and tensile stresses. The short-term and long-term creep behaviors of rocks under compressive and tensile stresses are investigated, as well as the long-term strength of rocks. It is shown that, under low-stress levels, the creep curve of sandstone consists of decay and steady creep stages; while under high-stress levels, it presents the accelerated creep stage and creep fracture presents characteristics of brittle materials. The relationship between tensile stress and time under uniaxial tension is also put forward. Finally, a nonlinear viscoelastoplastic creep model is used to describe the creep behaviors of rocks under uniaxial compressive and tensile stresses.展开更多
The Subei Shoal is the largest sandy ridge in the southern Yellow Sea and is important source for nutrient loading to the sea.Here,the nutrient fluxes in the Subei Shoal associated with eddy diffusion and submarine gr...The Subei Shoal is the largest sandy ridge in the southern Yellow Sea and is important source for nutrient loading to the sea.Here,the nutrient fluxes in the Subei Shoal associated with eddy diffusion and submarine groundwater discharge(SGD)were assessed to understand their impacts on the nutrient budget in the Yellow Sea.Based on the analysis of 223 Ra and 224 Ra in the field observation,the offshore eddy diffusivity mixing coefficient and SGD were estimated to be 2.3×10^(8)cm^(2)/s and 2.6×10^(9)m^(3)/d(16 cm/d),respectively,in the Subei Shoal.Combined the significant offshore decreasing gradients of nutrient in seawater of the Subei Shoal,the spatially integrated nutrient outwelling fluxes to the Yellow Sea were 262-1465μmol/(m^(2)·d)for DIN,5.2-21μmol/(m^(2)·d)for DIP and711-913μmol/(m^(2)·d)for DSi.Compared to the riverine input,atmospheric deposition and mariculture,nutrient outwelling from the Subei Shoal might play an important role in nutrient budget of the Yellow Sea.These nutrient fluxes could provide 4.1%-23%N and 1.3%-5.3%P requirements for the primary productivity,and the deviated DIN/DIP ratios have the potential to affect the growth of phytoplankton in the marine ecosystem of the Yellow Sea.展开更多
To the Editor:Malignant brain tumors represent a substantial morbidity and mortality burden globally,with 308,102 new cases and 251,329 cancer-related deaths in 20201.Brain tumors encompass primary tumors originating ...To the Editor:Malignant brain tumors represent a substantial morbidity and mortality burden globally,with 308,102 new cases and 251,329 cancer-related deaths in 20201.Brain tumors encompass primary tumors originating in the brain and brain metastases(BM)that have been spread from cancer lesions of other organs.Besides,BM are the most prevalent intracranial malignant tumor affecting approximately 20%-40%of cancer patients2.展开更多
Background: Exercise, as the cornerstone of pulmonary rehabilitation, is recommended to chronic obstructive pulmonary disease (COPD) patients. The underlying molecular basis and metabolic process were not fully elucid...Background: Exercise, as the cornerstone of pulmonary rehabilitation, is recommended to chronic obstructive pulmonary disease (COPD) patients. The underlying molecular basis and metabolic process were not fully elucidated. Methods: Sprague-Dawley rats were classified into five groups: non-COPD/rest ( n = 8), non-COPD/exercise ( n = 7), COPD/rest ( n = 7), COPD/medium exercise ( n = 10), and COPD/intensive exercise ( n = 10). COPD animals were exposed to cigarette smoke and lipopolysaccharide instillation for 90 days, while the non-COPD control animals were exposed to room air. Non-COPD/exercise and COPD/medium exercise animals were trained on a treadmill at a decline of 5° and a speed of 15 m/min while animals in the COPD/intensive exercise group were trained at a decline of 5° and a speed of 18 m/min. After eight weeks of exercise/rest, we used ultrasonography, immunohistochemistry, transmission electron microscopy, oxidative capacity of mitochondria, airflow-assisted desorption electrospray ionization-mass spectrometry imaging (AFADESI-MSI), and transcriptomics analyses to assess rectal femoris (RF). Results: At the end of 90 days, COPD rats’ weight gain was smaller than control by 59.48 ± 15.33 g ( P = 0.0005). The oxidative muscle fibers proportion was lower ( P < 0.0001). At the end of additional eight weeks of exercise/rest, compared to COPD/rest, COPD/medium exercise group showed advantages in weight gain, femoral artery peak flow velocity (Δ58.22 mm/s, 95% CI: 13.85-102.60 mm/s, P = 0.0104), RF diameters (Δ0.16 mm, 95% CI: 0.04-0.28 mm, P = 0.0093), myofibrils diameter (Δ0.06 μm, 95% CI: 0.02-0.10 μm, P = 0.006), oxidative muscle fiber percentage (Δ4.84%, 95% CI: 0.15-9.53%, P = 0.0434), mitochondria oxidative phosphorylate capacity ( P < 0.0001). Biomolecules spatial distribution in situ and bioinformatic analyses of transcriptomics suggested COPD-related alteration in metabolites and gene expression, which can be impacted by exercise. Conclusion: COPD rat model had multi-level structure and function impairment, which can be mitigated by exercise.展开更多
The anisotropic two-dimensional （2D） layered material rhenium disulfide （ReSe2） has attracted considerable attention because of its unusual properties and promising applications in electronic and optoelectronic de...The anisotropic two-dimensional （2D） layered material rhenium disulfide （ReSe2） has attracted considerable attention because of its unusual properties and promising applications in electronic and optoelectronic devices. However, because of its low lattice symmetry and interlayer decoupling, anisotropic growth and out-of-plane growth occur easily, yielding thick flakes, dendritic structure, or flower-like structure. In this stud34 we demonstrated a bottom-up method for the controlled and scalable synthesis of ReSe2 by van der Waals epitaxy. To achieve controllable growth, a micro-reactor with a confined reaction space was constructed by stacking two mica substrates in the chemical vapor deposition system. Within the confined reaction space, the nucleation density and growth rate of ReSe2 were significantly reduced, favoring the large-area synthesis of ReSe2 with a uniform monolayer thickness. The morphological evolution of ReSe2 with growth temperature indicated that the anisotropic growth was suppressed at a low growth temperature （〈600 ℃）. Field-effect transistors employing the grown ReSe2 exhibited p-type conduction with a current ON/OFF ratio up to 10s and a hole carrier mobility of 0.98 cm^2/（V·s）. Furthermore, the ReSe2 device exhibited an outstanding photoresponse to near-infrared light, with responsivity up to 8.4 and 5.1 A/W for 850- and 940-nm light, respectively. This work not only promotes the large-scale application of ReSe2 in high-performance electronic devices but also clarifies the growth mechanism of low-lattice symmetry 2D materials.展开更多
Anisotropic two-dimensional (2D) materials exhibit lattice-orientation dependent optical and electrical properties. Carriers doping of such materials has been used to modulate their energy band structures for opto-ele...Anisotropic two-dimensional (2D) materials exhibit lattice-orientation dependent optical and electrical properties. Carriers doping of such materials has been used to modulate their energy band structures for opto-electronic applications. Herein, we show that by stacking monolayer rhenium disulfide (ReS2) on a flat gold film, the electrons doping in ReS2 can affect the in-plane anisotropic Raman enhancement of molecules adsorbed on ReS2. The change of enhancement factor and the degree of anisotropy in enhancement with layer number are sensitively dependent on the doping level of ReS2 by gold, which is further confirmed by Kelvin probe force microscopy (KPFM) measurements. These findings could open an avenue for probing anisotropic electronic interactions between molecules and 2D materials with low symmetry using Raman enhancement effect.展开更多
The contact form of rock-concrete has a crucial influence on the failure characteristics of the stability of rock-concrete engineering.To study the influence of contact surface on the mechanical properties of rock-con...The contact form of rock-concrete has a crucial influence on the failure characteristics of the stability of rock-concrete engineering.To study the influence of contact surface on the mechanical properties of rock-concrete composite specimens under compressive loads,the two different contact forms of rock-concrete composite specimens are designed,the mechanical properties of these two different specimens are analyzed under triaxial compressive condition,and analysis comparison on the stress-strain curves and failure forms of the two specimens is carried out.The influence of contact surface constraint on the mechanical properties of rock-concrete composite specimens is obtained.Results show that the stress and strain of rock-concrete composite specimens with contact surface constraint are obviously higher than those without.Averagely,compared with composite specimens without the contact surface,the existence of contact surface constraint can increase the axial peak stress of composite specimens by 24%and the axial peak strain by 16%.According to the characteristics of the fracture surface,the theory of microcrack development is used to explain the contact surface constraint of rock-concrete composite specimens,which explains the difference of mechanical properties between the two rock-concrete composite specimens in the experiment.Research results cannot only enrich the research content of the mechanics of rock contact,but also can serve as a valuable reference for the understanding of the corresponding mechanics mechanism of other similar composite specimens.展开更多
基金Supported by the West Region Communication Construction Technology Project of the Ministry of Communications (2009318000001)the National Natural Science Foundation of China (50808187)
文摘The consideration of time dependence is essential for the study of deformation and fracturing processes of rock materials, especially for those subjected to strong compressive and tensile stresses. In this paper, the self-developed direct tension device and creep testing machine RLW-2000M are used to conduct the creep tests on red sandstone under uniaxial compressive and tensile stresses. The short-term and long-term creep behaviors of rocks under compressive and tensile stresses are investigated, as well as the long-term strength of rocks. It is shown that, under low-stress levels, the creep curve of sandstone consists of decay and steady creep stages; while under high-stress levels, it presents the accelerated creep stage and creep fracture presents characteristics of brittle materials. The relationship between tensile stress and time under uniaxial tension is also put forward. Finally, a nonlinear viscoelastoplastic creep model is used to describe the creep behaviors of rocks under uniaxial compressive and tensile stresses.
基金The National Science and Technology Major Project of the Ministry of Science and Technology of China under contract No.2016YFC1402106the National Natural Science Foundation of China under contract Nos 41376089,41576083,41976040,41876127 and 42030402the China Postdoctoral Science Foundation under contract No.2020M671048。
文摘The Subei Shoal is the largest sandy ridge in the southern Yellow Sea and is important source for nutrient loading to the sea.Here,the nutrient fluxes in the Subei Shoal associated with eddy diffusion and submarine groundwater discharge(SGD)were assessed to understand their impacts on the nutrient budget in the Yellow Sea.Based on the analysis of 223 Ra and 224 Ra in the field observation,the offshore eddy diffusivity mixing coefficient and SGD were estimated to be 2.3×10^(8)cm^(2)/s and 2.6×10^(9)m^(3)/d(16 cm/d),respectively,in the Subei Shoal.Combined the significant offshore decreasing gradients of nutrient in seawater of the Subei Shoal,the spatially integrated nutrient outwelling fluxes to the Yellow Sea were 262-1465μmol/(m^(2)·d)for DIN,5.2-21μmol/(m^(2)·d)for DIP and711-913μmol/(m^(2)·d)for DSi.Compared to the riverine input,atmospheric deposition and mariculture,nutrient outwelling from the Subei Shoal might play an important role in nutrient budget of the Yellow Sea.These nutrient fluxes could provide 4.1%-23%N and 1.3%-5.3%P requirements for the primary productivity,and the deviated DIN/DIP ratios have the potential to affect the growth of phytoplankton in the marine ecosystem of the Yellow Sea.
基金supported by the grant National Natural Science Foundation of China(82272951,82272953)Beijing Municipal Health Commission(Beijing Demonstration Research Ward BCRW20200303)Chinese Academy of Medical Sciences(2022-I2M-C&T-B-070).
文摘To the Editor:Malignant brain tumors represent a substantial morbidity and mortality burden globally,with 308,102 new cases and 251,329 cancer-related deaths in 20201.Brain tumors encompass primary tumors originating in the brain and brain metastases(BM)that have been spread from cancer lesions of other organs.Besides,BM are the most prevalent intracranial malignant tumor affecting approximately 20%-40%of cancer patients2.
基金supported by grants from Chinese Academy of Medical Sciences,Innovation Fund for Medical Sciences(CIFMS)(No.2021-I2M-1-049)and(2)China-Japan Friendship Hospital Foundation for Young Scholars(No.2018-1-QN-11).
文摘Background: Exercise, as the cornerstone of pulmonary rehabilitation, is recommended to chronic obstructive pulmonary disease (COPD) patients. The underlying molecular basis and metabolic process were not fully elucidated. Methods: Sprague-Dawley rats were classified into five groups: non-COPD/rest ( n = 8), non-COPD/exercise ( n = 7), COPD/rest ( n = 7), COPD/medium exercise ( n = 10), and COPD/intensive exercise ( n = 10). COPD animals were exposed to cigarette smoke and lipopolysaccharide instillation for 90 days, while the non-COPD control animals were exposed to room air. Non-COPD/exercise and COPD/medium exercise animals were trained on a treadmill at a decline of 5° and a speed of 15 m/min while animals in the COPD/intensive exercise group were trained at a decline of 5° and a speed of 18 m/min. After eight weeks of exercise/rest, we used ultrasonography, immunohistochemistry, transmission electron microscopy, oxidative capacity of mitochondria, airflow-assisted desorption electrospray ionization-mass spectrometry imaging (AFADESI-MSI), and transcriptomics analyses to assess rectal femoris (RF). Results: At the end of 90 days, COPD rats’ weight gain was smaller than control by 59.48 ± 15.33 g ( P = 0.0005). The oxidative muscle fibers proportion was lower ( P < 0.0001). At the end of additional eight weeks of exercise/rest, compared to COPD/rest, COPD/medium exercise group showed advantages in weight gain, femoral artery peak flow velocity (Δ58.22 mm/s, 95% CI: 13.85-102.60 mm/s, P = 0.0104), RF diameters (Δ0.16 mm, 95% CI: 0.04-0.28 mm, P = 0.0093), myofibrils diameter (Δ0.06 μm, 95% CI: 0.02-0.10 μm, P = 0.006), oxidative muscle fiber percentage (Δ4.84%, 95% CI: 0.15-9.53%, P = 0.0434), mitochondria oxidative phosphorylate capacity ( P < 0.0001). Biomolecules spatial distribution in situ and bioinformatic analyses of transcriptomics suggested COPD-related alteration in metabolites and gene expression, which can be impacted by exercise. Conclusion: COPD rat model had multi-level structure and function impairment, which can be mitigated by exercise.
基金The authors acknowledge the insightful suggestions and comments from Dr. S. C. Zhang and N. N. Mao at Peking University. This work was supported by the National Natural Science Foundation of China （Nos. 51502167 and 21473110）, and the fundamental Research Funds for the Central Universities （No. GK201502003）, L. Z. and J. K. acknowledge the funding by the Center for Integrated Quantum Materials under NSF （No. DMR-1231319）.
文摘The anisotropic two-dimensional （2D） layered material rhenium disulfide （ReSe2） has attracted considerable attention because of its unusual properties and promising applications in electronic and optoelectronic devices. However, because of its low lattice symmetry and interlayer decoupling, anisotropic growth and out-of-plane growth occur easily, yielding thick flakes, dendritic structure, or flower-like structure. In this stud34 we demonstrated a bottom-up method for the controlled and scalable synthesis of ReSe2 by van der Waals epitaxy. To achieve controllable growth, a micro-reactor with a confined reaction space was constructed by stacking two mica substrates in the chemical vapor deposition system. Within the confined reaction space, the nucleation density and growth rate of ReSe2 were significantly reduced, favoring the large-area synthesis of ReSe2 with a uniform monolayer thickness. The morphological evolution of ReSe2 with growth temperature indicated that the anisotropic growth was suppressed at a low growth temperature （〈600 ℃）. Field-effect transistors employing the grown ReSe2 exhibited p-type conduction with a current ON/OFF ratio up to 10s and a hole carrier mobility of 0.98 cm^2/（V·s）. Furthermore, the ReSe2 device exhibited an outstanding photoresponse to near-infrared light, with responsivity up to 8.4 and 5.1 A/W for 850- and 940-nm light, respectively. This work not only promotes the large-scale application of ReSe2 in high-performance electronic devices but also clarifies the growth mechanism of low-lattice symmetry 2D materials.
基金National Natural Science Foundation of China (Nos. 51432002, 51720105003, 21790052, 11374355 and 21573004)the Ministry of Science and Technology of China (Nos. 2016YFA0200100 and 2015CB932400)the Beijing Municipal Science and Technology Project (No. Z161100002116026).
文摘Anisotropic two-dimensional (2D) materials exhibit lattice-orientation dependent optical and electrical properties. Carriers doping of such materials has been used to modulate their energy band structures for opto-electronic applications. Herein, we show that by stacking monolayer rhenium disulfide (ReS2) on a flat gold film, the electrons doping in ReS2 can affect the in-plane anisotropic Raman enhancement of molecules adsorbed on ReS2. The change of enhancement factor and the degree of anisotropy in enhancement with layer number are sensitively dependent on the doping level of ReS2 by gold, which is further confirmed by Kelvin probe force microscopy (KPFM) measurements. These findings could open an avenue for probing anisotropic electronic interactions between molecules and 2D materials with low symmetry using Raman enhancement effect.
基金This study was partially supported by the National Natural Science Foundation of China(Grant Nos.41302223,51908097)Science and Technology Plan Projects of Municipal Administration of State Land,Resources and Housing,Chongqing Municipal Government(No.KJ-2015047)+3 种基金Chongqing No.3 Colleges and Universities Youth Backbone Teachers Funding Plans and Chongqing Research Program of Basic Research and Frontier Technology(Nos.cstc2016jcyjA0074,cstc2016jcyjA0933,cstc2015jcyjA90012,cstc2019jcyj-msxmX0258)Scientific and Technological Research Program of Chongqing Municipal Education Commission(Nos.KJ1713327,KJ1600532)The Key Laboratory of Well Stability and Fluid&Rock Mechanics in Oil and Gas Reservoir of Shaanxi Province,Xi'an Shiyou University(No.FRM 20190201002)Chongqing University of Science and Technology Graduate Student Science and Technology Innovation Program(No.YKJCX1720601).
文摘The contact form of rock-concrete has a crucial influence on the failure characteristics of the stability of rock-concrete engineering.To study the influence of contact surface on the mechanical properties of rock-concrete composite specimens under compressive loads,the two different contact forms of rock-concrete composite specimens are designed,the mechanical properties of these two different specimens are analyzed under triaxial compressive condition,and analysis comparison on the stress-strain curves and failure forms of the two specimens is carried out.The influence of contact surface constraint on the mechanical properties of rock-concrete composite specimens is obtained.Results show that the stress and strain of rock-concrete composite specimens with contact surface constraint are obviously higher than those without.Averagely,compared with composite specimens without the contact surface,the existence of contact surface constraint can increase the axial peak stress of composite specimens by 24%and the axial peak strain by 16%.According to the characteristics of the fracture surface,the theory of microcrack development is used to explain the contact surface constraint of rock-concrete composite specimens,which explains the difference of mechanical properties between the two rock-concrete composite specimens in the experiment.Research results cannot only enrich the research content of the mechanics of rock contact,but also can serve as a valuable reference for the understanding of the corresponding mechanics mechanism of other similar composite specimens.
