The improved energy confinement has been observed in many tokamaks with center pellet injection since 1980＇s. The pellet enhanced performance （ PEP ） was achieved with high power additional heating in JET and other...The improved energy confinement has been observed in many tokamaks with center pellet injection since 1980＇s. The pellet enhanced performance （ PEP ） was achieved with high power additional heating in JET and other large tokamaks. The mechanism of the PEP mode has been analyzed theoretically . The analysis shows that a few mechanisms are involved in the reduction of anomalous transport and the relative weight of these mechanisms depends on the experimental conditions. In this paper we report the pellet injection experiment results without auxiliary heating on HL-2A tokamak. Our works focus on the investigation of the electron heat transport in ohmic discharges with center pellet fuelling.展开更多
Perturbative experiments on electron heat transport have been successfully con- ducted on the HL-2A tokamak. The pulse propagation of the electron temperature is induced by the supersonic molecular beam injection （S...Perturbative experiments on electron heat transport have been successfully con- ducted on the HL-2A tokamak. The pulse propagation of the electron temperature is induced by the supersonic molecular beam injection （SMBI）, which has characteristics of good localization and deep deposition. A model based on the electron heat transport in cylindrical geometry has been applied to reconstruct the measured amplitude and phase profiles of the electron temperature perturbation. The results show that the heat transport is significantly reduced near the pedestal region of the H-mode plasma. In the ＂profile stiffness/resilience＂ region, similar heat diffusivities have been observed in L-mode and H-mode plasmas, which verifies the gradient-driven transport physics in tokamaks.展开更多
Heat as a stressor of poultry has been studied extensively for many decades; it affects poultry production on a worldwide basis and has significant impact on well-being and production. More recently, the involvement o...Heat as a stressor of poultry has been studied extensively for many decades; it affects poultry production on a worldwide basis and has significant impact on well-being and production. More recently, the involvement of heat stress in inducing oxidative stress has received much interest. Oxidative stress is defined as the presence of reactive species in excess of the available antioxidant capacity of animal cells. Reactive species can modify several biologically cellular macromolecules and can interfere with cell signaling pathways. Furthermore, during the last decade, there has been an ever-increasing interest in the use of a wide array of natural feed-delivered phytochemicals that have potential antioxidant properties for poultry. In light of this, the current review aims to（1） summarize the mechanisms through which heat stress triggers excessive superoxide radical production in the mitochondrion and progresses into oxidative stress,（2） illustrate that this pathophysiology is dependent on the intensity and duration of heat stress,（3） present different nutritional strategies for mitigation of mitochondrial dysfunction, with particular focus on antioxidant phytochemicals.Oxidative stress that occurs with heat exposure can be manifest in all parts of the body; however, mitochondrial dysfunction underlies oxidative stress. In the initial phase of acute heat stress, mitochondrial substrate oxidation and electron transport chain activity are increased resulting in excessive superoxide production. During the later stage of acute heat stress, down-regulation of avian uncoupling protein worsens the oxidative stress situation causing mitochondrial dysfunction and tissue damage. Typically, antioxidant enzyme activities are upregulated. Chronic heat stress, however, leads to downsizing of mitochondrial metabolic oxidative capacity, up-regulation of avian uncoupling protein, a clear alteration in the pattern of antioxidant enzyme activities, and depletion of antioxidant reserves.Some phytochemicals, such as various types of flavonoids and related compounds, were shown to be beneficial in chronic heat-stressed poultry, but were less or not effective in non-heat-stressed counterparts. This supports the contention that antioxidant phytochemicals have potential under challenging conditions. Though substantial progress has been made in our understanding of the association between heat stress and oxidative stress, the means by which phytochemicals can alleviate oxidative stress have been sparsely explored.展开更多
Using the scattering matrix method, we investigate the thermal transport m a nanostructure at low temperarures. It is found that phonon transport exhibits some novel and interesting features： resonant transmission, r...Using the scattering matrix method, we investigate the thermal transport m a nanostructure at low temperarures. It is found that phonon transport exhibits some novel and interesting features： resonant transmission, resonant reflection, and small thermal conductance. A comparison between thermal conductances is performed when stress-free and hard-wall boundary conditions are applied for acoustic modes, respectively. The result indicates that the characteristics of the thermal conductance versus temperature for different types of boundary conditions are qualitatively different.展开更多
The electron-transport machinery in photosynthetic membranes is known to be very sensitive to heat. In this study, the rate of electron transport (ETR) driven by photosystem I (PSI) and photosystem II (PSII) during he...The electron-transport machinery in photosynthetic membranes is known to be very sensitive to heat. In this study, the rate of electron transport (ETR) driven by photosystem I (PSI) and photosystem II (PSII) during heat stress in the wild-type Synechocystis sp. strain PCC 6803 (WT) and its ndh gene inactiva-tion mutants △ndhB (M55) and △ndhD1/ndhD2 (D1/D2) was simultaneously assessed by using the novel Dual-PAM-100 measuring system. The rate of electron transport driven by the photosystems (ETRPSs) in the WT, M55, and D1/D2 cells incubated at 30℃ and at 55℃ for 10 min was compared. Incubation at 55 ℃ for 10 min significantly inhibited PSII-driven ETR (ETRPSII) in the WT, M55 and D1/D2 cells, and the ex-tent of inhibition in both the M55 and D1/D2 cells was greater than that in the WT cells. Further, PSI-driven ETR (ETRPSI) was stimulated in both the WT and D1/D2 cells, and this rate was increased to a greater extent in the D1/D2 than in the WT cells. However, ETRPSI was considerably inhibited in the M55 cells. Analysis of the effect of heat stress on ETRPSs with regard to the alterations in the 2 active NDH-1 complexes in the WT, M55, and D1/D2 cells indicated that the active NDH-1 supercomplex and medi-umcomplex are essential for alleviating the heat-induced inhibition of ETRPSII and for accelerating the heat-induced stimulation of ETRPSI, respectively. Further, it is believed that these effects are most likely brought about by the electron transport mediated by each of these 2 active NDH-1 complexes.展开更多
在共振磁场扰动(resonant magnetic perturbation,RMP)控制边界局域模(edge localized modes,ELMs)的试验中,在ELMs被缓解的条件下,研究了RMP对电子热输运的影响。结果表明,RMP对等离子体的输运增强集中在边界位置。从电子回旋辐射诊断...在共振磁场扰动(resonant magnetic perturbation,RMP)控制边界局域模(edge localized modes,ELMs)的试验中,在ELMs被缓解的条件下,研究了RMP对电子热输运的影响。结果表明,RMP对等离子体的输运增强集中在边界位置。从电子回旋辐射诊断给出的电子温度中观察到,ELMs的每次爆发均会引起边界电子温度的崩塌且崩塌沿等离子体径向向内传播,传播速度不受RMP影响。通过指数函数拟合方法,对电子温度崩塌后的恢复过程进行分析,得到了恢复特征时间,并用该恢复特征时间近似表征输运特征时间。在RMP投入期间,边界位置处的恢复特征时间变短,电子热输运增强。输运的增强因子沿径向向外增大,在边界处达到3.5。展开更多
The structure,specific heat,magnetic and electrical properties of MnTe1-xSbx（x=0,0.1,0.15,0.2 and 0.25） alloys have been investigated.The MnTe1-xSbx alloys crystallize in a hexagonal NiAs-type structure,and the impu...The structure,specific heat,magnetic and electrical properties of MnTe1-xSbx（x=0,0.1,0.15,0.2 and 0.25） alloys have been investigated.The MnTe1-xSbx alloys crystallize in a hexagonal NiAs-type structure,and the impurity of MnSb phase appears when x≥0.15.The MnTe0.9Sb0.1 compound exhibits ferrimagnetic behavior with hysteresis loops even at 350 K,showing that the magnetic properties of MnTe compound are very sensitive to little compositional change.The ferromagnetism in the MnTe1-xSbx alloys with higher Sb contents may be attributed to the impurity of MnSb phase.Energy dispersive X-ray spectroscopy analysis on the MnTe0.9Sb0.1 compound indicates that Sb is very difficult to dope into the lattice of MnTe.So the anomaly of resistivity at 300 K of MnTe0.9Sb0.1 and the peak of specific heat around 304 K of all the alloys are thought to be related with the antiferromagnetic interactions of MnTe-based lattice.展开更多
基金The author thank the HL-2A team for carrying out the experiments and Profs. D0NG Jiaqi,GA0 Qingdi,LI Jiquan and WANG Aike for benefit discussion and suggestion.Supported by the National Natural Science Foundation of China （ 10335060 and 10235010 ）
文摘The improved energy confinement has been observed in many tokamaks with center pellet injection since 1980＇s. The pellet enhanced performance （ PEP ） was achieved with high power additional heating in JET and other large tokamaks. The mechanism of the PEP mode has been analyzed theoretically . The analysis shows that a few mechanisms are involved in the reduction of anomalous transport and the relative weight of these mechanisms depends on the experimental conditions. In this paper we report the pellet injection experiment results without auxiliary heating on HL-2A tokamak. Our works focus on the investigation of the electron heat transport in ohmic discharges with center pellet fuelling.
基金supported by National Natural Science Foundation of China (Nos. 10975048,10975049 and 11005037)the National Magnetic Confinement Fusion Science Program of China (Nos. 2010GB102003,2010GB101003 and 2010GB101004)
文摘Perturbative experiments on electron heat transport have been successfully con- ducted on the HL-2A tokamak. The pulse propagation of the electron temperature is induced by the supersonic molecular beam injection （SMBI）, which has characteristics of good localization and deep deposition. A model based on the electron heat transport in cylindrical geometry has been applied to reconstruct the measured amplitude and phase profiles of the electron temperature perturbation. The results show that the heat transport is significantly reduced near the pedestal region of the H-mode plasma. In the ＂profile stiffness/resilience＂ region, similar heat diffusivities have been observed in L-mode and H-mode plasmas, which verifies the gradient-driven transport physics in tokamaks.
基金the Special Research Fund(BOF)of Ghent University(Belgium)for the financial support of Abdol ah Akbarian(grant number 01SF2711)
文摘Heat as a stressor of poultry has been studied extensively for many decades; it affects poultry production on a worldwide basis and has significant impact on well-being and production. More recently, the involvement of heat stress in inducing oxidative stress has received much interest. Oxidative stress is defined as the presence of reactive species in excess of the available antioxidant capacity of animal cells. Reactive species can modify several biologically cellular macromolecules and can interfere with cell signaling pathways. Furthermore, during the last decade, there has been an ever-increasing interest in the use of a wide array of natural feed-delivered phytochemicals that have potential antioxidant properties for poultry. In light of this, the current review aims to（1） summarize the mechanisms through which heat stress triggers excessive superoxide radical production in the mitochondrion and progresses into oxidative stress,（2） illustrate that this pathophysiology is dependent on the intensity and duration of heat stress,（3） present different nutritional strategies for mitigation of mitochondrial dysfunction, with particular focus on antioxidant phytochemicals.Oxidative stress that occurs with heat exposure can be manifest in all parts of the body; however, mitochondrial dysfunction underlies oxidative stress. In the initial phase of acute heat stress, mitochondrial substrate oxidation and electron transport chain activity are increased resulting in excessive superoxide production. During the later stage of acute heat stress, down-regulation of avian uncoupling protein worsens the oxidative stress situation causing mitochondrial dysfunction and tissue damage. Typically, antioxidant enzyme activities are upregulated. Chronic heat stress, however, leads to downsizing of mitochondrial metabolic oxidative capacity, up-regulation of avian uncoupling protein, a clear alteration in the pattern of antioxidant enzyme activities, and depletion of antioxidant reserves.Some phytochemicals, such as various types of flavonoids and related compounds, were shown to be beneficial in chronic heat-stressed poultry, but were less or not effective in non-heat-stressed counterparts. This supports the contention that antioxidant phytochemicals have potential under challenging conditions. Though substantial progress has been made in our understanding of the association between heat stress and oxidative stress, the means by which phytochemicals can alleviate oxidative stress have been sparsely explored.
基金Supported by the National Natural Science Foundation of China under Grant No 10547132, and the Young Teacher Foundation of Tianjin University under Grant No 5110117.
文摘Using the scattering matrix method, we investigate the thermal transport m a nanostructure at low temperarures. It is found that phonon transport exhibits some novel and interesting features： resonant transmission, resonant reflection, and small thermal conductance. A comparison between thermal conductances is performed when stress-free and hard-wall boundary conditions are applied for acoustic modes, respectively. The result indicates that the characteristics of the thermal conductance versus temperature for different types of boundary conditions are qualitatively different.
基金Supported by the National Natural Science Foundation of China (Grant No. 30770175)the Natural Science Foundation of Shanghai Muncipality (Grant No. 07ZR14086)+2 种基金the Innovation Program of Shanghai Municipal Education Commission (Grant No. 08ZZ67)the Key Foundation Project of Shanghai (Grant No. 06JC14091)the Leading Academic Discipline Project of Shanghai Municipal Education Commission (Grant No. J50401)
文摘The electron-transport machinery in photosynthetic membranes is known to be very sensitive to heat. In this study, the rate of electron transport (ETR) driven by photosystem I (PSI) and photosystem II (PSII) during heat stress in the wild-type Synechocystis sp. strain PCC 6803 (WT) and its ndh gene inactiva-tion mutants △ndhB (M55) and △ndhD1/ndhD2 (D1/D2) was simultaneously assessed by using the novel Dual-PAM-100 measuring system. The rate of electron transport driven by the photosystems (ETRPSs) in the WT, M55, and D1/D2 cells incubated at 30℃ and at 55℃ for 10 min was compared. Incubation at 55 ℃ for 10 min significantly inhibited PSII-driven ETR (ETRPSII) in the WT, M55 and D1/D2 cells, and the ex-tent of inhibition in both the M55 and D1/D2 cells was greater than that in the WT cells. Further, PSI-driven ETR (ETRPSI) was stimulated in both the WT and D1/D2 cells, and this rate was increased to a greater extent in the D1/D2 than in the WT cells. However, ETRPSI was considerably inhibited in the M55 cells. Analysis of the effect of heat stress on ETRPSs with regard to the alterations in the 2 active NDH-1 complexes in the WT, M55, and D1/D2 cells indicated that the active NDH-1 supercomplex and medi-umcomplex are essential for alleviating the heat-induced inhibition of ETRPSII and for accelerating the heat-induced stimulation of ETRPSI, respectively. Further, it is believed that these effects are most likely brought about by the electron transport mediated by each of these 2 active NDH-1 complexes.
文摘在共振磁场扰动(resonant magnetic perturbation,RMP)控制边界局域模(edge localized modes,ELMs)的试验中,在ELMs被缓解的条件下,研究了RMP对电子热输运的影响。结果表明,RMP对等离子体的输运增强集中在边界位置。从电子回旋辐射诊断给出的电子温度中观察到,ELMs的每次爆发均会引起边界电子温度的崩塌且崩塌沿等离子体径向向内传播,传播速度不受RMP影响。通过指数函数拟合方法,对电子温度崩塌后的恢复过程进行分析,得到了恢复特征时间,并用该恢复特征时间近似表征输运特征时间。在RMP投入期间,边界位置处的恢复特征时间变短,电子热输运增强。输运的增强因子沿径向向外增大,在边界处达到3.5。
基金supported by the National Basic Research Program of China (No.2010CB934603)the National Natural Science Foundation of China (No.50831006)
文摘The structure,specific heat,magnetic and electrical properties of MnTe1-xSbx（x=0,0.1,0.15,0.2 and 0.25） alloys have been investigated.The MnTe1-xSbx alloys crystallize in a hexagonal NiAs-type structure,and the impurity of MnSb phase appears when x≥0.15.The MnTe0.9Sb0.1 compound exhibits ferrimagnetic behavior with hysteresis loops even at 350 K,showing that the magnetic properties of MnTe compound are very sensitive to little compositional change.The ferromagnetism in the MnTe1-xSbx alloys with higher Sb contents may be attributed to the impurity of MnSb phase.Energy dispersive X-ray spectroscopy analysis on the MnTe0.9Sb0.1 compound indicates that Sb is very difficult to dope into the lattice of MnTe.So the anomaly of resistivity at 300 K of MnTe0.9Sb0.1 and the peak of specific heat around 304 K of all the alloys are thought to be related with the antiferromagnetic interactions of MnTe-based lattice.
