Manganese （Mn） is becoming an important factor limiting crop growth and yields especially on acid soils. The present study was designed to explore the hypothesis that brassinosteroid application can enhance the tole...Manganese （Mn） is becoming an important factor limiting crop growth and yields especially on acid soils. The present study was designed to explore the hypothesis that brassinosteroid application can enhance the tolerance of maize （Zea mays L.） to Mn stress and if so, whether or not the mechanism underlying involves regulation of antioxidative metabolism in leaves. The effects of 24-epibrassinosteroid （EBR） on the growth, photosynthesis, water status, lipid peroxidation, accumulation of reactive oxygen species, and activities or contents of antioxidant defense system in maize plants under Mn stress were investigated by a pot experiment. At supplemented Mn concentrations of 150-750 mg kg^-1 soil, the growth of plants was inhibited in a concentration-dependent manner. The semi-lethal concentration was 550 mg Mn kgq soil. Foliage application with 0.1 mg L^-1 EBR significantly reduced the decrease in dry mass, chlorophyll content, photosynthetic rate, leaf water content, and water potential of plants grown in the soil spiked with 550 mg kg^-1 Mn. The oxidative stress caused by excess Mn, as reflected by the increase in malondialdehyde （MDA） content and lipoxygenase （LOX, EC 1.13.11.12） activity, accumulation of superoxide radical and H2O2, was greatly decreased by EBR treatment. Further investigations revealed that EBR application enhanced the activities of superoxide dismutase （SOD, EC 1.15.1.1）, peroxidase （POD, EC 1.11.1.7）, catalase （EC 1.11.1.6）, ascorbate peroxidase （APX, EC 1.11. 1.11）, dehydroascorbate reductase （DHAR, EC 1.8.5.1）, and glutathione reductase （GR, EC 1.6.4.2）, and the contents of reduced ascorbate and glutathione, compared with the plants without EBR treatment. It is concluded that the ameliorative effects of EBR on Mn toxicity are due to the upregulation of antioxidative capacity in maize under Mn stress.展开更多
Although,dietary proteins play a crucial role in poultry profit maximization,through the sustenance of birds`welfare,growth and development,yet metabolic excesses from crude protein(CP)degradation is detrimental to br...Although,dietary proteins play a crucial role in poultry profit maximization,through the sustenance of birds`welfare,growth and development,yet metabolic excesses from crude protein(CP)degradation is detrimental to broiler chickens(BC)affected by heat stress.This study evaluated the effect of dietary protein levels on blood profile of heat-stressed BC at starter phase(SP)and finisher phase(FP).Arbor Acre BC(n=288)were randomly allotted to four dietary treatments(T1-23%CP;T2-21%CP;T3-19%CP;and T4-17%CP)with six replicate groups in a completely randomized design.Data were subjected to descriptive analysis,analysis of variance(p=0.05)and correlation statistics.Protein intake(PI)was not significantly affected by varying CP in diets at SP,but not at FP,where PI significantly increased with increasing dietary CP.PER had a negative correlation with PCV(r=-0.89,p<0.01),Hb(r=-0.88,p<0.01),RBC(r=-0.93,p<0.01)and PI(r=-0.78,p<0.01).Metabolic excesses including heat dissipation from dietary proteins influenced PCV,Hb,platelets and glucose of heat-stressed broilers.展开更多
Unloading induces negative excess porewater pressure in soil mass around a foundation pit during excavation. In this work, the dissipation rule of negative excess porewater pressure after excavation was studied. Analy...Unloading induces negative excess porewater pressure in soil mass around a foundation pit during excavation. In this work, the dissipation rule of negative excess porewater pressure after excavation was studied. Analytical formulas for calculating the negative excess porewater pressures and the effective stresses were derived based on one-dimensional consolidation theory and Terzaghi’s effective stress principle. The influence of the dissipation of negative excess porewater pressure on earth pressure inside and outside a foundation pit and the stability of the retaining structure were analyzed through a numerical example. It was indicated that the dissipation of negative excess porewater pressure is harmful to the stability of the retaining structure and that rapid construction can make full use of the negative porewater pressure.展开更多
The paper describes the investigation of mechanisms of cast structure formation in Hadfield steel depending on the changes in the cooling rate of a casting in the following two temperature ranges： crystallization tem...The paper describes the investigation of mechanisms of cast structure formation in Hadfield steel depending on the changes in the cooling rate of a casting in the following two temperature ranges： crystallization temperature（1,200-1,390 ℃） and the temperature of excessive phase separation（560-790 ℃）. Changes in the cooling rate of the crystallization temperature range from 1.1 to 25.0 ℃s^-1 result in the reduction of the average size of austenite grains from 266 to 131 μm. At the same time, the magnitude of developing shrinkage stresses changes from ＋195 to 0 MPa. When the cooling rate is higher than 16 ℃^-1, no shrinkage stresses are formed in the casting. Changes in the cooling rate of the casting in the temperature range of the excessive phase separation influence the number of phases, their morphology and chemical composition, the values of phase stresses, and the possibility of martensitic transformation. Changing in the cooling rate from 0.24 to 5.46 ℃^-1 results in the decrease of the amount of the excessive phase from 14.8% to 2.1%, which is composed of eutectic and carbides depending on the cooling rate, their quantitative ratio and morphology change. Such changes in the microstructure are reflected on the changes of value of developing phase stresses. When the cooling rate is 0.24 ℃^-1, it is ＋100 MPa, while the increase of the cooling rate to 1.4 ℃^-1 results in the decrease of tensile stresses to 0 MPa and their qualitative stresses change to compressive ones. Further increase of the cooling rate results in the increase of the value of compressive stresses. When the cooling rate is 5.5 ℃^-1, their value reaches-92 MPa. Martensite forming in the structure of Hadfield steel is possible if the cooling rate of the casting in the range of excessive phase separation is less than 0.25 ℃^-1.展开更多
Wave induced excess flow of momentum （WIEFM） is the averaged flow of momentum over a wave period due to wave presence, which may also be called 3-D radiation stress. In this paper, the 3-D current equations with WIE...Wave induced excess flow of momentum （WIEFM） is the averaged flow of momentum over a wave period due to wave presence, which may also be called 3-D radiation stress. In this paper, the 3-D current equations with WIEFM are derived from the averaged Navier-Stokes equations over a wave period, in which the velocity is separated into the largescale backgrotmd velocity, the wave particle velocity and the turbulent fluctuation velocity. A concept of wave fluctuating layer （WFL） is put forward, which is the vertical column from the wave trough to wave ridge. The mathematical expressions of WIEFM in WFL and below WFL are given separately. The parameterized expressions of WIEFM are set up according to the linear wave theory. The integration of WIEFM in the vertical direction equals the traditional radiation stress （namely 2-D radiation stress） given by Longuet-Higgins and Stewart.展开更多
Comprehensive tests on Hangzhou intact soft clay were performed, which were used to obtain the soils' critical response to undrained dynamic stress paths under different combinations of principal stress orientatio...Comprehensive tests on Hangzhou intact soft clay were performed, which were used to obtain the soils' critical response to undrained dynamic stress paths under different combinations of principal stress orientation. The different combinations included cyclic principal stress rotation (CPSR for short), cyclic shear with abrupt change of principal stress orientation (CAPSO for short) and cyclic shear with fixed principal stress orientation (CFPSO for short). On one side, under all these stress paths, samples have obvious strain inflection points and shear bands, and the excess pore water pressure is far from the level of initial effective confining pressure at failure. Stress paths of major principal stress orientation (α) alternating from negative and positive have quite different influence on soil's properties with those in which α is kept negative or positive. On the other side, due to the soil's strongly initial anisotropy, samples under double-amplitudes CPSR and CAPSO (or single-amplitude CPSR and CFPSO) have similar properties on dynamic shear strength and pore water pressure development tendency when α is kept within ±45°, while have quite different properties when α oversteps ±45°.展开更多
基金supported by the National High Technology Research and Development Program of China (2005AA219040)
文摘Manganese （Mn） is becoming an important factor limiting crop growth and yields especially on acid soils. The present study was designed to explore the hypothesis that brassinosteroid application can enhance the tolerance of maize （Zea mays L.） to Mn stress and if so, whether or not the mechanism underlying involves regulation of antioxidative metabolism in leaves. The effects of 24-epibrassinosteroid （EBR） on the growth, photosynthesis, water status, lipid peroxidation, accumulation of reactive oxygen species, and activities or contents of antioxidant defense system in maize plants under Mn stress were investigated by a pot experiment. At supplemented Mn concentrations of 150-750 mg kg^-1 soil, the growth of plants was inhibited in a concentration-dependent manner. The semi-lethal concentration was 550 mg Mn kgq soil. Foliage application with 0.1 mg L^-1 EBR significantly reduced the decrease in dry mass, chlorophyll content, photosynthetic rate, leaf water content, and water potential of plants grown in the soil spiked with 550 mg kg^-1 Mn. The oxidative stress caused by excess Mn, as reflected by the increase in malondialdehyde （MDA） content and lipoxygenase （LOX, EC 1.13.11.12） activity, accumulation of superoxide radical and H2O2, was greatly decreased by EBR treatment. Further investigations revealed that EBR application enhanced the activities of superoxide dismutase （SOD, EC 1.15.1.1）, peroxidase （POD, EC 1.11.1.7）, catalase （EC 1.11.1.6）, ascorbate peroxidase （APX, EC 1.11. 1.11）, dehydroascorbate reductase （DHAR, EC 1.8.5.1）, and glutathione reductase （GR, EC 1.6.4.2）, and the contents of reduced ascorbate and glutathione, compared with the plants without EBR treatment. It is concluded that the ameliorative effects of EBR on Mn toxicity are due to the upregulation of antioxidative capacity in maize under Mn stress.
文摘Although,dietary proteins play a crucial role in poultry profit maximization,through the sustenance of birds`welfare,growth and development,yet metabolic excesses from crude protein(CP)degradation is detrimental to broiler chickens(BC)affected by heat stress.This study evaluated the effect of dietary protein levels on blood profile of heat-stressed BC at starter phase(SP)and finisher phase(FP).Arbor Acre BC(n=288)were randomly allotted to four dietary treatments(T1-23%CP;T2-21%CP;T3-19%CP;and T4-17%CP)with six replicate groups in a completely randomized design.Data were subjected to descriptive analysis,analysis of variance(p=0.05)and correlation statistics.Protein intake(PI)was not significantly affected by varying CP in diets at SP,but not at FP,where PI significantly increased with increasing dietary CP.PER had a negative correlation with PCV(r=-0.89,p<0.01),Hb(r=-0.88,p<0.01),RBC(r=-0.93,p<0.01)and PI(r=-0.78,p<0.01).Metabolic excesses including heat dissipation from dietary proteins influenced PCV,Hb,platelets and glucose of heat-stressed broilers.
基金Project (No. 20030335027) supported by the National ResearchFoundation for the Doctoral Program of Higher Education of China
文摘Unloading induces negative excess porewater pressure in soil mass around a foundation pit during excavation. In this work, the dissipation rule of negative excess porewater pressure after excavation was studied. Analytical formulas for calculating the negative excess porewater pressures and the effective stresses were derived based on one-dimensional consolidation theory and Terzaghi’s effective stress principle. The influence of the dissipation of negative excess porewater pressure on earth pressure inside and outside a foundation pit and the stability of the retaining structure were analyzed through a numerical example. It was indicated that the dissipation of negative excess porewater pressure is harmful to the stability of the retaining structure and that rapid construction can make full use of the negative porewater pressure.
基金financially supported by the grant of the Russian Science Foundation(project no.15-19-10020)
文摘The paper describes the investigation of mechanisms of cast structure formation in Hadfield steel depending on the changes in the cooling rate of a casting in the following two temperature ranges： crystallization temperature（1,200-1,390 ℃） and the temperature of excessive phase separation（560-790 ℃）. Changes in the cooling rate of the crystallization temperature range from 1.1 to 25.0 ℃s^-1 result in the reduction of the average size of austenite grains from 266 to 131 μm. At the same time, the magnitude of developing shrinkage stresses changes from ＋195 to 0 MPa. When the cooling rate is higher than 16 ℃^-1, no shrinkage stresses are formed in the casting. Changes in the cooling rate of the casting in the temperature range of the excessive phase separation influence the number of phases, their morphology and chemical composition, the values of phase stresses, and the possibility of martensitic transformation. Changing in the cooling rate from 0.24 to 5.46 ℃^-1 results in the decrease of the amount of the excessive phase from 14.8% to 2.1%, which is composed of eutectic and carbides depending on the cooling rate, their quantitative ratio and morphology change. Such changes in the microstructure are reflected on the changes of value of developing phase stresses. When the cooling rate is 0.24 ℃^-1, it is ＋100 MPa, while the increase of the cooling rate to 1.4 ℃^-1 results in the decrease of tensile stresses to 0 MPa and their qualitative stresses change to compressive ones. Further increase of the cooling rate results in the increase of the value of compressive stresses. When the cooling rate is 5.5 ℃^-1, their value reaches-92 MPa. Martensite forming in the structure of Hadfield steel is possible if the cooling rate of the casting in the range of excessive phase separation is less than 0.25 ℃^-1.
基金This project was supported bythe Major State Basic Research Program(Grant No.2002412403)the NationalNatural Science Foundation of China(Grant No.40306014)
文摘Wave induced excess flow of momentum （WIEFM） is the averaged flow of momentum over a wave period due to wave presence, which may also be called 3-D radiation stress. In this paper, the 3-D current equations with WIEFM are derived from the averaged Navier-Stokes equations over a wave period, in which the velocity is separated into the largescale backgrotmd velocity, the wave particle velocity and the turbulent fluctuation velocity. A concept of wave fluctuating layer （WFL） is put forward, which is the vertical column from the wave trough to wave ridge. The mathematical expressions of WIEFM in WFL and below WFL are given separately. The parameterized expressions of WIEFM are set up according to the linear wave theory. The integration of WIEFM in the vertical direction equals the traditional radiation stress （namely 2-D radiation stress） given by Longuet-Higgins and Stewart.
基金Projects(50308025 50639010) supported by the National Natural Science Foundation of China
文摘Comprehensive tests on Hangzhou intact soft clay were performed, which were used to obtain the soils' critical response to undrained dynamic stress paths under different combinations of principal stress orientation. The different combinations included cyclic principal stress rotation (CPSR for short), cyclic shear with abrupt change of principal stress orientation (CAPSO for short) and cyclic shear with fixed principal stress orientation (CFPSO for short). On one side, under all these stress paths, samples have obvious strain inflection points and shear bands, and the excess pore water pressure is far from the level of initial effective confining pressure at failure. Stress paths of major principal stress orientation (α) alternating from negative and positive have quite different influence on soil's properties with those in which α is kept negative or positive. On the other side, due to the soil's strongly initial anisotropy, samples under double-amplitudes CPSR and CAPSO (or single-amplitude CPSR and CFPSO) have similar properties on dynamic shear strength and pore water pressure development tendency when α is kept within ±45°, while have quite different properties when α oversteps ±45°.
