The α5 subunit-containing gamma-amino butyric acid type A receptors(α5 GABAARs) are a distinct subpopulation that are specifically distributed in the mammalian hippocampus and also mediate tonic inhibitory currents ...The α5 subunit-containing gamma-amino butyric acid type A receptors(α5 GABAARs) are a distinct subpopulation that are specifically distributed in the mammalian hippocampus and also mediate tonic inhibitory currents in hippocampal neurons. These tonic currents can be enhanced by low-dose isoflurane, which is associated with learning and memory impairment. Inverse agonists of α5 GABAARs, such as L-655,708, are able to reverse the short-term memory deficit caused by low-dose isoflurane in young animals. However, whether these negative allosteric modulators have the same effects on aged rats remains unclear. In the present study, we mainly investigated the effects of L-655,708 on low-dose(1.3%) isoflurane-induced learning and memory impairment in elderly rats. Young(3-month-old) and aged(24-month-old) Wistar rats were randomly assigned to receive L-655,708 0.5 hour before or 23.5 hours after 1.3% isoflurane anesthesia.The Morris Water Maze tests demonstrated that L-655,708 injected before or after anesthesia could reverse the memory deficit in young rats. But in aged rats, application of L-655,708 only before anesthesia showed similar effects. Reverse transcription-polymerase chain reaction showed that low-dose isoflurane decreased the mRNA expression of α5 GABAARs in aging hippocampal neurons but increased that in young animals. These findings indicate that L-655,708 prevented but could not reverse 1.3% isoflurane-induced spatial learning and memory impairment in aged Wistar rats. All experimental procedures and protocols were approved by the Experimental Animal Ethics Committee of Academy of Military Medical Science of China(approval No. NBCDSER-IACUC-2015128) in December 2015.展开更多
Soil sulfur fractions, including monocalcium phosphate-extractable S, slowly soluble inorganic S, C- O-S ,C-bonded S and unidentified organic S, were analyzed for 48 soils, as representatives of 6 major groups ofupl...Soil sulfur fractions, including monocalcium phosphate-extractable S, slowly soluble inorganic S, C- O-S ,C-bonded S and unidentified organic S, were analyzed for 48 soils, as representatives of 6 major groups ofupland soils, fiuvisol, cinnamon soil, loessial soil, chestnut soil, black soil and brown soil, in North China.The contemns of total S and monocalcium phosphate-extractable S in the above 48 soils ranged from 234 to860 and 5.1 to 220.3 mg kg--1 , respectively, and each of 6 soil groups contained the samples with a low level ofphosph ate-extractable S. Great differences in the average contents of each fraction of S were observed amongthe above 6 soil groups. Expressed as average percentage of the total S in soils, fiuvisols, cinnamon soils,loessial soils, chestnut soils, black soils and brown soils contained 6.1%, 9.5%, 5.7%, 13.2%, 3.5% and 6.8%monocalcium phosphate-extractable S, 5. 7%, 3. 0%, 9. 3%, 1 0. 4%, 3. 2% and 3. 1 % slowly soluble inorganic S ,51.6%, 26.7%, 17.4%, 31.2%, 28.9% and 22.7% C-O-S, 11.0%, 9.1%, 6.6%, 6.8%, 9.7% and 9.4% in C-bondedS, and 25.6%, 51.7%, 60.8%, 38.4%, 54.7% and 53.0% unidentified organic S, respectively. For the above 6groups of soils, the mean C/N ratios were remarkably similar, ranging from 9.7 to 10.7, while the mean N/Sratios ranged from 1.16 to 3.12. The highest ratios of C/N, C/C-O-S and C/C-bonded S were found in blacksoils, averaging 30.4, 104.9 and 314.7, respectively, while the lowest ratios arose in chestnut soil, averaging12.4, 39.7 and 183.3, respectively.展开更多
Sharp bending as one of the mechanical properties of double-stranded DNA(dsDNA) on the nanoscale is essential for biological functions and processes. Force sensors with optical readout have been designed to measure th...Sharp bending as one of the mechanical properties of double-stranded DNA(dsDNA) on the nanoscale is essential for biological functions and processes. Force sensors with optical readout have been designed to measure the forces inside short, strained loops composed of both dsDNA and single-stranded DNA(ssDNA). Recent FRET singlemolecule experiments were carried out based on the same force sensor design, but provided totally contrary results. In the current work, Monte Carlo simulations were performed under three conditions to clarify the discrepancy between the two experiments. The criterion that the work done by the force exerted on dsDNA by ssDNA should be larger than the nearest-neighbor(NN) stacking interaction energy is used to identify the generation of the fork at the junction of dsDNA and ssDNA. When the contour length of dsDNA in the sensor is larger than its critical length, the fork begins to generate at the junction of dsDNA and ssDNA, even with a kink in dsDNA. The forces inferred from simulations under three conditions are consistent with the ones inferred from experiments, including extra large force and can be grouped into two different states, namely, fork states and kink states. The phase diagrams constructed in the phase space of the NN stacking interaction energy and excited energy indicate that the transition between the fork state and kink state is difficult to identify in the phase space with an ultra small or large number of forks, but it can be detected in the phase space with a medium number of forks and kinks.展开更多
Internal polyhedral structures of a granular system can be investigated using the Voronoi tessellations.This technique has gained increasing recognition in research of kinetic properties of granular flows.For systems ...Internal polyhedral structures of a granular system can be investigated using the Voronoi tessellations.This technique has gained increasing recognition in research of kinetic properties of granular flows.For systems with mono-sized spherical particles,Voronoi tessellations can be utilized,while radial Voronoi tessellations are necessary for analyzing systems with multi-sized spherical particles.However,research about polyhedral structures of non-spherical particle systems is limited.We utilize the discrete element method to simulate a system of ellipsoidal particles,defined by the equation(x/a)^(2)+(y/1)^(2)+(z/1/a)^(2)=1,where a ranges from 1.1 to 2.0.The system is then dissected by using tangent planes at the contact points,and the geometric quantities of the resulting polyhedra in different shaped systems,such as surface area,volume,number of vertices,number of edges,and number of faces,are calculated.Meanwhile,the longitudinal and transverse wave velocities within the system are calculated with the time-of-flight method.The results demonstrate a strong correlation between the sound velocity of the system and the geometry of the dissected polyhedra.The sound velocity of the system increases with the increase in a,peaking at a=1.3,and then decreases as a continues to increase.The average volume,surface area,number of vertices,number of edges,and number of faces of the polyhedra decrease with the increase in sound velocity.That is,these quantities initially decrease with the increase in a,reaching minima at a=1.3,and then increase with further increase of a.The relationship between sound velocity and the geometric quantities of the dissected polyhedra can serve as a reference for acoustic material design.展开更多
The anisotropy in the particle systems of different packing structures affects the sound velocity. The acoustic propagation process in four kinds of packing structures（denoted as S45, H60, S90, and D） of two-dimensi...The anisotropy in the particle systems of different packing structures affects the sound velocity. The acoustic propagation process in four kinds of packing structures（denoted as S45, H60, S90, and D） of two-dimensional granular system is simulated by the discrete element method. The velocity vtof obtained by the time of flight method and the velocity vc obtained from the stiffness tensor of the system are compared. Different sound velocities reflect various packing structures and force distributions within the system. The compression wave velocities of H60 and S90 are nearly the same, and transmit faster than that of D packing structure, while the sound velocity of S45 is the smallest. The shear wave velocities of S45 and H60 are nearly the same, and transmit faster than that of D packing structure. The compression wave velocity is sensitive to the volume fraction of the structure, however, the shear wave velocity is more sensitive to the geometrical structure itself. As the normal stress p is larger than 1 MPa, vtof and vc are almost equal, and the stiffness tensors of various structures explain the difference of sound velocities. When the normal stress is less than 1 MPa, with the coordination number unchanged, the law vtof ∝ p^1/4 still exists. This demonstrates that apart from different power laws between force and deformation as well as the change of the coordination number under different stresses, there are other complicated causes of vtof∝ p^1/4, and an explanation of the deviation from vtof ∝ p^1/6 is given from the perspective of dissipation.展开更多
Fifteen upland soils collected from the major arable areas in North China were used to assess the availability of soil sulfur (S) to plants in a pot experiment. Soils were extracted with various reagents and the extra...Fifteen upland soils collected from the major arable areas in North China were used to assess the availability of soil sulfur (S) to plants in a pot experiment. Soils were extracted with various reagents and the extractable S was determined using turbidimetric method or inductively coupled plasma atomic emission spectrometry (ICP-AES), respectively. In addition, mineralizable organic S, organic S, N/S ratio, sulfur availability index (SAI) and available sulfur correction value (ASC) in soils were also determined. The S amount extracted by 1.5 g L-1 CaCl2 was nearly equivalent to that by 0.25 mol L-1 KCl (40 ℃), and both of them were slightly smaller than that by 0.01 mol L-1 Ca(H2PO4)2 solution, as measured by turbidimetric method or ICP-AES. The extractable S measured by turbidimetric method was consistently smaller than that by ICP-AES. All methods tested except that for organic S and N/S ratio produced satisfactory results in the regression analyses of the relationships between the amounts of S extracted and plant dry matter weight and S uptake in the pot experiment. In general, 0.01 mol L-1 Ca (H2PO4) 2-extracted S determined by ICP-AES or turbidimetric method and 0.25 mol L-1 KCl(40℃)-extracted S determined by ICP-AES appeared to be the best indicators for evaluation of soil available S.展开更多
Liukeng is an old village situated on a green hills-surrounded basin land in the southwest of Le'an County, Jiangxi Province. The Wujiang River meanders through it and stretches all the way to join the Ganjiang Ri...Liukeng is an old village situated on a green hills-surrounded basin land in the southwest of Le'an County, Jiangxi Province. The Wujiang River meanders through it and stretches all the way to join the Ganjiang River, the province's mother river. With an area of about 3.6 square kilometers, the village is where some 4,000 people surnamed Dong currently live and Drosper.展开更多
文摘The α5 subunit-containing gamma-amino butyric acid type A receptors(α5 GABAARs) are a distinct subpopulation that are specifically distributed in the mammalian hippocampus and also mediate tonic inhibitory currents in hippocampal neurons. These tonic currents can be enhanced by low-dose isoflurane, which is associated with learning and memory impairment. Inverse agonists of α5 GABAARs, such as L-655,708, are able to reverse the short-term memory deficit caused by low-dose isoflurane in young animals. However, whether these negative allosteric modulators have the same effects on aged rats remains unclear. In the present study, we mainly investigated the effects of L-655,708 on low-dose(1.3%) isoflurane-induced learning and memory impairment in elderly rats. Young(3-month-old) and aged(24-month-old) Wistar rats were randomly assigned to receive L-655,708 0.5 hour before or 23.5 hours after 1.3% isoflurane anesthesia.The Morris Water Maze tests demonstrated that L-655,708 injected before or after anesthesia could reverse the memory deficit in young rats. But in aged rats, application of L-655,708 only before anesthesia showed similar effects. Reverse transcription-polymerase chain reaction showed that low-dose isoflurane decreased the mRNA expression of α5 GABAARs in aging hippocampal neurons but increased that in young animals. These findings indicate that L-655,708 prevented but could not reverse 1.3% isoflurane-induced spatial learning and memory impairment in aged Wistar rats. All experimental procedures and protocols were approved by the Experimental Animal Ethics Committee of Academy of Military Medical Science of China(approval No. NBCDSER-IACUC-2015128) in December 2015.
文摘Soil sulfur fractions, including monocalcium phosphate-extractable S, slowly soluble inorganic S, C- O-S ,C-bonded S and unidentified organic S, were analyzed for 48 soils, as representatives of 6 major groups ofupland soils, fiuvisol, cinnamon soil, loessial soil, chestnut soil, black soil and brown soil, in North China.The contemns of total S and monocalcium phosphate-extractable S in the above 48 soils ranged from 234 to860 and 5.1 to 220.3 mg kg--1 , respectively, and each of 6 soil groups contained the samples with a low level ofphosph ate-extractable S. Great differences in the average contents of each fraction of S were observed amongthe above 6 soil groups. Expressed as average percentage of the total S in soils, fiuvisols, cinnamon soils,loessial soils, chestnut soils, black soils and brown soils contained 6.1%, 9.5%, 5.7%, 13.2%, 3.5% and 6.8%monocalcium phosphate-extractable S, 5. 7%, 3. 0%, 9. 3%, 1 0. 4%, 3. 2% and 3. 1 % slowly soluble inorganic S ,51.6%, 26.7%, 17.4%, 31.2%, 28.9% and 22.7% C-O-S, 11.0%, 9.1%, 6.6%, 6.8%, 9.7% and 9.4% in C-bondedS, and 25.6%, 51.7%, 60.8%, 38.4%, 54.7% and 53.0% unidentified organic S, respectively. For the above 6groups of soils, the mean C/N ratios were remarkably similar, ranging from 9.7 to 10.7, while the mean N/Sratios ranged from 1.16 to 3.12. The highest ratios of C/N, C/C-O-S and C/C-bonded S were found in blacksoils, averaging 30.4, 104.9 and 314.7, respectively, while the lowest ratios arose in chestnut soil, averaging12.4, 39.7 and 183.3, respectively.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11204045,11464004,and 11864006the State Scholarship Fund(20173015)Guizhou Scientific and Technological Program(20185781)
文摘Sharp bending as one of the mechanical properties of double-stranded DNA(dsDNA) on the nanoscale is essential for biological functions and processes. Force sensors with optical readout have been designed to measure the forces inside short, strained loops composed of both dsDNA and single-stranded DNA(ssDNA). Recent FRET singlemolecule experiments were carried out based on the same force sensor design, but provided totally contrary results. In the current work, Monte Carlo simulations were performed under three conditions to clarify the discrepancy between the two experiments. The criterion that the work done by the force exerted on dsDNA by ssDNA should be larger than the nearest-neighbor(NN) stacking interaction energy is used to identify the generation of the fork at the junction of dsDNA and ssDNA. When the contour length of dsDNA in the sensor is larger than its critical length, the fork begins to generate at the junction of dsDNA and ssDNA, even with a kink in dsDNA. The forces inferred from simulations under three conditions are consistent with the ones inferred from experiments, including extra large force and can be grouped into two different states, namely, fork states and kink states. The phase diagrams constructed in the phase space of the NN stacking interaction energy and excited energy indicate that the transition between the fork state and kink state is difficult to identify in the phase space with an ultra small or large number of forks, but it can be detected in the phase space with a medium number of forks and kinks.
基金Supported by the National Natural Science Foundation of China(Grant Nos.12262005,11962003,and 11602062)the Postgraduate Education Reform and Quality Improvement Project of Henan Province(Grant No.YJS2024AL138)the Graduate Education Reform Project of Henan Province(Grant No.2023SJGLX096Y).
文摘Internal polyhedral structures of a granular system can be investigated using the Voronoi tessellations.This technique has gained increasing recognition in research of kinetic properties of granular flows.For systems with mono-sized spherical particles,Voronoi tessellations can be utilized,while radial Voronoi tessellations are necessary for analyzing systems with multi-sized spherical particles.However,research about polyhedral structures of non-spherical particle systems is limited.We utilize the discrete element method to simulate a system of ellipsoidal particles,defined by the equation(x/a)^(2)+(y/1)^(2)+(z/1/a)^(2)=1,where a ranges from 1.1 to 2.0.The system is then dissected by using tangent planes at the contact points,and the geometric quantities of the resulting polyhedra in different shaped systems,such as surface area,volume,number of vertices,number of edges,and number of faces,are calculated.Meanwhile,the longitudinal and transverse wave velocities within the system are calculated with the time-of-flight method.The results demonstrate a strong correlation between the sound velocity of the system and the geometry of the dissected polyhedra.The sound velocity of the system increases with the increase in a,peaking at a=1.3,and then decreases as a continues to increase.The average volume,surface area,number of vertices,number of edges,and number of faces of the polyhedra decrease with the increase in sound velocity.That is,these quantities initially decrease with the increase in a,reaching minima at a=1.3,and then increase with further increase of a.The relationship between sound velocity and the geometric quantities of the dissected polyhedra can serve as a reference for acoustic material design.
基金Project supported by the National Natural Science Foundation of China(Grant No.11547009)the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11602062)+1 种基金the Natural Science Foundation of Guizhou Province,China(Grant No.2012/2166)the Research Foundation of Guizhou University for Talent Introduction,China(Grant No.2011/02)
文摘The anisotropy in the particle systems of different packing structures affects the sound velocity. The acoustic propagation process in four kinds of packing structures（denoted as S45, H60, S90, and D） of two-dimensional granular system is simulated by the discrete element method. The velocity vtof obtained by the time of flight method and the velocity vc obtained from the stiffness tensor of the system are compared. Different sound velocities reflect various packing structures and force distributions within the system. The compression wave velocities of H60 and S90 are nearly the same, and transmit faster than that of D packing structure, while the sound velocity of S45 is the smallest. The shear wave velocities of S45 and H60 are nearly the same, and transmit faster than that of D packing structure. The compression wave velocity is sensitive to the volume fraction of the structure, however, the shear wave velocity is more sensitive to the geometrical structure itself. As the normal stress p is larger than 1 MPa, vtof and vc are almost equal, and the stiffness tensors of various structures explain the difference of sound velocities. When the normal stress is less than 1 MPa, with the coordination number unchanged, the law vtof ∝ p^1/4 still exists. This demonstrates that apart from different power laws between force and deformation as well as the change of the coordination number under different stresses, there are other complicated causes of vtof∝ p^1/4, and an explanation of the deviation from vtof ∝ p^1/6 is given from the perspective of dissipation.
文摘Fifteen upland soils collected from the major arable areas in North China were used to assess the availability of soil sulfur (S) to plants in a pot experiment. Soils were extracted with various reagents and the extractable S was determined using turbidimetric method or inductively coupled plasma atomic emission spectrometry (ICP-AES), respectively. In addition, mineralizable organic S, organic S, N/S ratio, sulfur availability index (SAI) and available sulfur correction value (ASC) in soils were also determined. The S amount extracted by 1.5 g L-1 CaCl2 was nearly equivalent to that by 0.25 mol L-1 KCl (40 ℃), and both of them were slightly smaller than that by 0.01 mol L-1 Ca(H2PO4)2 solution, as measured by turbidimetric method or ICP-AES. The extractable S measured by turbidimetric method was consistently smaller than that by ICP-AES. All methods tested except that for organic S and N/S ratio produced satisfactory results in the regression analyses of the relationships between the amounts of S extracted and plant dry matter weight and S uptake in the pot experiment. In general, 0.01 mol L-1 Ca (H2PO4) 2-extracted S determined by ICP-AES or turbidimetric method and 0.25 mol L-1 KCl(40℃)-extracted S determined by ICP-AES appeared to be the best indicators for evaluation of soil available S.
文摘Liukeng is an old village situated on a green hills-surrounded basin land in the southwest of Le'an County, Jiangxi Province. The Wujiang River meanders through it and stretches all the way to join the Ganjiang River, the province's mother river. With an area of about 3.6 square kilometers, the village is where some 4,000 people surnamed Dong currently live and Drosper.
