目的观察外源性硫化氢的供体硫氢化钠(Na HS)对糖尿病大鼠心肌硫氧还蛋白(Trx)系统的影响。方法雄性SD大鼠随机分为正常组、糖尿病组、(14、28、56)μmol/kg Na HS处理组,每组6只。采用一次性腹腔注射链脲佐菌素的方法制备1型糖尿病大...目的观察外源性硫化氢的供体硫氢化钠(Na HS)对糖尿病大鼠心肌硫氧还蛋白(Trx)系统的影响。方法雄性SD大鼠随机分为正常组、糖尿病组、(14、28、56)μmol/kg Na HS处理组,每组6只。采用一次性腹腔注射链脲佐菌素的方法制备1型糖尿病大鼠模型。造模成功4周后,Na HS处理组大鼠每天分别腹腔注射Na HS溶液(14、28、56)μmol/kg。处理4周后,测空腹血糖值(FBG)和左心室动力学指标;HE染色观察心肌病变情况、透射电镜观察心肌超微结构变化;利用试剂盒检测血清乳酸脱氢酶(LDH)、肌酸激酶(CK)和肌酸激酶MB同工酶(CK-MB),ELISA检测血清白细胞介素1β(IL-1β)、IL-6和肿瘤坏死因子α(TNF-α)水平;利用试剂盒检测心肌组织总抗氧化能力(T-AOC)、脂质过氧化物(LPO)和丙二醛(MDA)含量;反转录PCR检测心肌组织血红素加氧酶1(HO-1)mRNA水平,Western blot法检测心肌组织Trx、Trx相互作用蛋白(TXNIP)和烟酰胺腺嘌呤二核苷酸磷酸氧化酶2(NOX2)的蛋白水平。结果与正常组比较,糖尿病组左心室收缩和舒张功能均降低,心肌组织形态和心肌细胞超微结构损伤明显;FBG、LDH、CK、CK-MB、IL-1β、IL-6、TNF-α、LPO和MDA均明显增高,T-AOC明显下降;心肌Trx蛋白表达明显降低,HO-1 mRNA、TXNIP和NOX2蛋白表达明显增加。与糖尿病组比较,各剂量Na HS处理组中左心室收缩和舒张功能、心肌组织形态和心肌细胞超微结构均得到改善;LDH、CK、CK-MB、IL-1β、IL-6、TNF-α、LPO和MDA均下降,T-AOC增高;心肌组织HO-1 mRNA和Trx蛋白表达增强,TXNIP和NOX2蛋白表达降低。结论 Na HS处理可以减轻糖尿病大鼠心肌损伤,其机制可能与激活Trx系统,增强抗氧化能力及抑制炎症因子释放相关。展开更多
This paper presents a preliminary experimental investigation on magnetohydrodynamic （MHD） power generation using seeded supersonic argon flow as working fluid. Helium and argon are used as driver and driven gas resp...This paper presents a preliminary experimental investigation on magnetohydrodynamic （MHD） power generation using seeded supersonic argon flow as working fluid. Helium and argon are used as driver and driven gas respectively in a shock tunnel. Equilibrium contact surface operating mode is used to obtain high temperature gas, and the conductivity is obtained by adding seed K2CO3 powder into the driven section. Under the conditions of nozzle inlet total pressure being 0.32 MPa, total temperature 6 504 K, magnetic field density about 0.5 T and nozzle outlet velocity 1 959 m/s, induction voltage and short-circuit current of the segmentation MHD power generation channel are measured, and the experimental results agree with theoretical calculations; the average conductivity is about 20 S/m calculated from characteristics of voltage and current. When load factor is 0.5, the maximum power density of the MHD power generation channel reaches 4.797 1 MW/m3, and the maximum enthalpy extraction rate is 0.34%. Finally, the principle and method of indirect testing for gas state parameters are derived and analyzed.展开更多
Influences of Hall effects on the flow characteristics and performance of the magnetohydrodyanmic (MHD) converging channel as an MHD generator are studied numerically in the present study. The numerical algorithm used...Influences of Hall effects on the flow characteristics and performance of the magnetohydrodyanmic (MHD) converging channel as an MHD generator are studied numerically in the present study. The numerical algorithm used is composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations, in conjunction with an SOR method for solving the elliptic equation governing the electrical potential of the electric field. It is found that Hall effects may lead to distortions in both the flow field and electric field in the MHD converging channel. The electric current lines are distorted and induce eddy currents, which will be mitigated by Hall effects. Comparisons of parameters characterizing the performance of the MHD generator for different geometry also reveal that the Hall effects may deteriorate the performance of MHD generator, especially for converging channel.展开更多
This paper studies the effective polytropic index in the central plasma sheet(CPS) by using the method of Kartalev et al.(2006), which adopts the denoising technique of Haar wavelet to identify the homogeneous MHD Ber...This paper studies the effective polytropic index in the central plasma sheet(CPS) by using the method of Kartalev et al.(2006), which adopts the denoising technique of Haar wavelet to identify the homogeneous MHD Bernoulli integral(MBI) and has been frequently used to study the polytropic relation in the solar wind. We chose the quiet CPS crossing by Cluster C1 during the interval 08:51:00–09:19:00 UT on 03 August 2001. In the central plasma sheet, thermal pressure energy per unit mass is the most important part in MBI, and kinetic energy of fluid motion and electromagnetic energy per unit mass are less important. In the MBI, there are many peaks, which correspond to isothermal or near isothermal processes. The interval lengths of homogenous MBI regions are generally less than 1 min. The polytropic indexes are calculated by linearly fitting the data of lnp and lnn within a 16 s window, which is shifted forward by 8 s step length. Those polytropic indexes with |R|≥0.8(R is the correlation coefficient between lnp and lnn) and p-value≤0.1 in the homogeneous regions are almost all in the range of [0, 1]. The mean and median effective polytropic indexes with high R and low p-value in homogeneous regions are 0.34 and 0.32 respectively, which are much different from the polytropic index obtained by traditional method(?trad=?0.15). This result indicates that the CPS is not uniform even during quiet time and the blanket applications of polytropic law to plasma sheet may return misleading value of polytropic index. The polytropic indexes in homogeneous regions with a high correlation coefficient basically have good regression significance and are thus credible. These results are very important to understand the energy transport in magnetotail in the MHD frame.展开更多
It has been confirmed that dipolarization fronts(DFs)are the result of the interchange instability in the Earth's magnetotail.In this paper,we use a Hall MHD model to simulate the evolution of the interchange inst...It has been confirmed that dipolarization fronts(DFs)are the result of the interchange instability in the Earth's magnetotail.In this paper,we use a Hall MHD model to simulate the evolution of the interchange instability that produces DFs along the leading edge.A test particle simulation is performed to study the physical phenomenon of ion acceleration at the DF.The numerical simulation indicates that almost all particles move earthward and dawnward and then drift to the tail.The DF-reflected ion population at the duskside appears earlier as a consequence of the asymmetric Hall electric field.Ions that are distributed in a dawn-dusk asymmetric semicircle behind the DF tend to be accelerated to higher energies(>13.5 keV).These high-energy particles eventually concentrate in the dawnside.Ions experience effective acceleration by the dawnward electric field,while they drift through the dawn flank at the front,toward the tail.展开更多
基金National Natural Science Foundation of China （10972236） The Scientific and Technical Innovation for Postgraduates of Air Force Engineering University （DX2010102）
文摘This paper presents a preliminary experimental investigation on magnetohydrodynamic （MHD） power generation using seeded supersonic argon flow as working fluid. Helium and argon are used as driver and driven gas respectively in a shock tunnel. Equilibrium contact surface operating mode is used to obtain high temperature gas, and the conductivity is obtained by adding seed K2CO3 powder into the driven section. Under the conditions of nozzle inlet total pressure being 0.32 MPa, total temperature 6 504 K, magnetic field density about 0.5 T and nozzle outlet velocity 1 959 m/s, induction voltage and short-circuit current of the segmentation MHD power generation channel are measured, and the experimental results agree with theoretical calculations; the average conductivity is about 20 S/m calculated from characteristics of voltage and current. When load factor is 0.5, the maximum power density of the MHD power generation channel reaches 4.797 1 MW/m3, and the maximum enthalpy extraction rate is 0.34%. Finally, the principle and method of indirect testing for gas state parameters are derived and analyzed.
文摘Influences of Hall effects on the flow characteristics and performance of the magnetohydrodyanmic (MHD) converging channel as an MHD generator are studied numerically in the present study. The numerical algorithm used is composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations, in conjunction with an SOR method for solving the elliptic equation governing the electrical potential of the electric field. It is found that Hall effects may lead to distortions in both the flow field and electric field in the MHD converging channel. The electric current lines are distorted and induce eddy currents, which will be mitigated by Hall effects. Comparisons of parameters characterizing the performance of the MHD generator for different geometry also reveal that the Hall effects may deteriorate the performance of MHD generator, especially for converging channel.
基金supported by the National Natural Science Foundation of China(Grant Nos.41431071,41174141,41474124)the National Basic Research Program of China(Grant No.2011CB811404)
文摘This paper studies the effective polytropic index in the central plasma sheet(CPS) by using the method of Kartalev et al.(2006), which adopts the denoising technique of Haar wavelet to identify the homogeneous MHD Bernoulli integral(MBI) and has been frequently used to study the polytropic relation in the solar wind. We chose the quiet CPS crossing by Cluster C1 during the interval 08:51:00–09:19:00 UT on 03 August 2001. In the central plasma sheet, thermal pressure energy per unit mass is the most important part in MBI, and kinetic energy of fluid motion and electromagnetic energy per unit mass are less important. In the MBI, there are many peaks, which correspond to isothermal or near isothermal processes. The interval lengths of homogenous MBI regions are generally less than 1 min. The polytropic indexes are calculated by linearly fitting the data of lnp and lnn within a 16 s window, which is shifted forward by 8 s step length. Those polytropic indexes with |R|≥0.8(R is the correlation coefficient between lnp and lnn) and p-value≤0.1 in the homogeneous regions are almost all in the range of [0, 1]. The mean and median effective polytropic indexes with high R and low p-value in homogeneous regions are 0.34 and 0.32 respectively, which are much different from the polytropic index obtained by traditional method(?trad=?0.15). This result indicates that the CPS is not uniform even during quiet time and the blanket applications of polytropic law to plasma sheet may return misleading value of polytropic index. The polytropic indexes in homogeneous regions with a high correlation coefficient basically have good regression significance and are thus credible. These results are very important to understand the energy transport in magnetotail in the MHD frame.
基金This work was supported by the pre-research projects on Civil Aerospace Technologies funded by China’s National Space Administration(CNSA)(Grant No.D020103)and the National Natural Science Foundation of China(Grant Nos.41474144,41674176).
文摘It has been confirmed that dipolarization fronts(DFs)are the result of the interchange instability in the Earth's magnetotail.In this paper,we use a Hall MHD model to simulate the evolution of the interchange instability that produces DFs along the leading edge.A test particle simulation is performed to study the physical phenomenon of ion acceleration at the DF.The numerical simulation indicates that almost all particles move earthward and dawnward and then drift to the tail.The DF-reflected ion population at the duskside appears earlier as a consequence of the asymmetric Hall electric field.Ions that are distributed in a dawn-dusk asymmetric semicircle behind the DF tend to be accelerated to higher energies(>13.5 keV).These high-energy particles eventually concentrate in the dawnside.Ions experience effective acceleration by the dawnward electric field,while they drift through the dawn flank at the front,toward the tail.
