The parameters of fluorescence induction kinetics and the maximal light-saturated net CO2 assimilation rate (P-sat) of the flag leaves of four cultivars of winter wheat (Triticum aestivum L.) were compared at three di...The parameters of fluorescence induction kinetics and the maximal light-saturated net CO2 assimilation rate (P-sat) of the flag leaves of four cultivars of winter wheat (Triticum aestivum L.) were compared at three different developing stages for the first time. From the blooming stage to the milky stage, the quantum efficiency of PS II photochemistry (F-v/F-m) declined slightly only at the milk stage. The photochemical quenching co-efficient (qP), actual quantum yield of photosystem II (PS II)electron transport (Phi (PSII)) and P-sat decreased substantially (> 15%), while the non-photochemical quenching co-efficient (qN) increased significantly (> 100%). There existed a linear correlation between the Phi (PSII) and the P-sat (r = 0.918). The results indicate that with the senescence of the flag leaves of winter wheat the photosynthetic efficiency including that of the energy transport and the CO2 assimilation significantly decreased.展开更多
AIM: To investigate the effect of various concentrations of tetrandrine on activation of quiescent rat hepatic stellate cells (HSCs) and transforming growth factor-β (TGF-β) signaling in vitro.METHODS: HSCs were iso...AIM: To investigate the effect of various concentrations of tetrandrine on activation of quiescent rat hepatic stellate cells (HSCs) and transforming growth factor-β (TGF-β) signaling in vitro.METHODS: HSCs were isolated from rats by in situperfusion of liver and 18% Nycodenz gradient centrifugation, and primarily cultured on uncoated plastic plates for 24 hwith DMEM containing 20% fetal bovine serum (FBS/DMEM) before the culture medium was substituted with 2% FBS/DMEM for another 24 h. Then, the HSCs were cultured in 2% FBS/DMEM with tetrandrine (0.25, 0.5, 1,2 mg/L, respectively). Cell morphological features were observed under an inverted microscope, smooth muscleα-actin (α-SMA) was detected by immunocytochemistry and image analysis system, laminin (LN) and type Ⅲprocollagen (PCⅢ) in supernatants were determined byradioimmunoassay. TGF-β1 mRNA, Smad 7 mRNA and Smad 7 protein were analyzed with RT-PCR and Western blotting, respectively.RESULTS: Tetrandrine at the concentrations of 0.25-2 mg/L prevented morphological transformation of HSC from the quiescent state to the activated one, while α-SMA, LN and PCⅢ expressions were inhibited. As estimated by gray values, the expression of α-SMA in tetrandrine groups (0.25, 0.5, 1, 2 mg/L) was reduced from 21.3% to 42.2%(control: 0.67, tetrandrine groups: 0.82, 0.85, 0.96, or 0.96, respectively, which were statistically different from the control, P<0.01), and the difference was more significant in tetrandrine at 1 and 2 mg/L. The content of LN in supernatants was significantly decreased in tetrandrine groups to 58.5%, 69.1%, 65.8% or 60.0% that of the control respectively, and that of PCⅢ to 84.6%, 81.5%,75.7% or 80.7% respectively (P<0.05 vs control), with no significant difference among tetrandrine groups. RTPCR showed that TGF-β1 mRNA expression was reduced by tetrandrine treatments from 56.56% to 87.90% in comparison with the control, while Smad 7 mRNA was increased 1.4-4.8 times. The TGF-β1 mRNA and Smad 7 mRNA expression was in a significant negative correlation (r= -0.755, P<0.01), and both were significantly correlated with α-SMA protein expression (r = -0.938, P<0.01;r = 0.938, P<0.01, respectively). The up-regulation of Smad 7 protein by tetrandrine (1 mg/L)was confirmed by Western blotting as well.CONCLUSION: Tetrandrine has a direct inhibiting effect on the activation of rat HSCs in culture. It up-regulates the expression of Smad 7 which in turn blocks TGF-β1 expression and signaling.展开更多
A number of mechanisms are known to influence coexistence in small mammal communities. However, the role ofbehavioral interactions in promoting species coexistence is under-represented in the literature. We studied th...A number of mechanisms are known to influence coexistence in small mammal communities. However, the role ofbehavioral interactions in promoting species coexistence is under-represented in the literature. We studied the behavioral interactionsof two coexisting small mammals, the Namaqua rock mouse Micaelamys namaquensis (Rodentia) and the Rock sengi Elephantulusmyurus (Macroscelidae), which have high dietary and microhabitat overlap. Using wild-caught individuals, intra- andinterspecific dyadic encounters were staged in tanks on a neutral rocky outcrop. Interspecific dyads displayed significantly moreactive avoidance behavior. There was no support for the prediction that the larger, more specialist species, E. myurus, is behaviorallydominant over M. namaquensis. Intraspecific encounters of E. myurus showed significantly more passive avoidance andamicable behavior, whereas the behavior of M. namaquensis did not differ between intra- and inter-specific encounters, both ofwhich were characterized by low levels of aggression and amicability. Thus, due to the lack of aggression, direct competition appearsweak and instead mutual avoidance may reduce or minimize interspecific interactions, potentially promoting coexistence.展开更多
Objective: To investigate the effects of Lycium barbarum polysaccharide (LBP) on experimental gastric ulcers in rats.Methods: The ulcers were induced by water-immersion restraint stress, acetic acid and pylorus-ligati...Objective: To investigate the effects of Lycium barbarum polysaccharide (LBP) on experimental gastric ulcers in rats.Methods: The ulcers were induced by water-immersion restraint stress, acetic acid and pylorus-ligation in rats. In each model, animals were divided randomly into 4 groups and administrated with LBP of 100 mg/kg and 300 mg/kg, ranitidine 100 mg/kg (as a reference standard) and saline respectively. Mucosal lesions were scored as ulcer index. In the pylorus-ligation model, we also compared the gastric juice volume, total acidity, acid output and pepsin activity among groups.Results: Oral administration of LBP inhibited the formation of the acute gastric lesions induced by physical stress such as water-immersion restraint (P<0.05), and accelerated the healing of chronic gastric ulcer model induced by acetic acid (P<0.05 to P<0.01). In the pylorus-ligated rats, significant decrease was also seen in ulcer index (P<0.05 to P<0.01), total acidity (P<0.05), acid output (P<0.05 to P<0.01). LBP 300 mg/kg even showed marked reduction of the volume (P<0.05) and pepsin activity (P<0.05) in the gastric juice. These effects were in a dose-dependent manner. Conclusion: LBP has protective effects on treating gastric ulcer and this action may relate to the reduction of acid output and pepsin activity in the gastric juice.展开更多
In a two-dimensional (219) dusty plasma system, the size of particles is considered under two different interparticle potentials (Yukawa potential and Dressed potential). The structural and dynamical characters a...In a two-dimensional (219) dusty plasma system, the size of particles is considered under two different interparticle potentials (Yukawa potential and Dressed potential). The structural and dynamical characters are investigated by molecular dynamics simulation respectively. The results show that the 2D systems via Yukawa and Dressed potentials have a different critical coupling constant F corresponding to the systems beginning to coagulate and exhibit different crystal configurations. Also we find that the size of particles has little influence on the 2D system's structure characters.展开更多
In order to optimize the transitional time during the successive exposure scans for a step-and-scan lithography and improve the productivity in a wafer production process, an investigation of the motion trajectory pla...In order to optimize the transitional time during the successive exposure scans for a step-and-scan lithography and improve the productivity in a wafer production process, an investigation of the motion trajectory planning along the scanning direction for wafer stage was carried out. The motions of wafer stage were divided into two respective logical moves (i. e. step-move and scan-move) and the multi-motionoverlap algorithms (MMOA) were presented for optimizing the transitional time between the successive exposure scans. The conventional motion planning method, the Hazelton method and the MMOA were analyzed theoretically and simulated using MATLAB under four different exposure field sizes. The results show that the total time between two successive scans consumed by MMOA is reduced by 4.82%, 2.62%, 3.06% and 3.96%, compared with those of the conventional motion planning method; and reduced by 2.58%, 0.76%, 1.63% and 2.92%, compared with those of the Hazehon method respectively. The theoretical analyses and simulation results illuminate that the MMOA can effectively minimize the transitional step time between successive exposure scans and therefore increase the wafer fabricating productivity.展开更多
Bacterial quorum sensing (QS) has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data...Bacterial quorum sensing (QS) has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data showed that smafl RNAs played important role in the QS of Vibrio harveyi and it can permit the fine-tuning of gene regulation and mmntenance of homeostasis. According to Michaelis-Menten kinetics and mass action law in this paper, we construct a mathematical model to investigate the mechanism induced QS by coexist of small RNA and signal molecular (AI) and show that there are periodic oscillation when the time delay and Hill coefficient exceed a critical value and the periodic oscillation produces the change of concentration and induces QS. These results are fit to the experimental results. In the meanwhile, we also get some theoretical value of Hopf Bifurcation on time deday. In addition, we also find this network is robust against noise.展开更多
Jack London was one of the outstanding American writers in the late nineteenth and early twentieth century. The Call of the Wild which was based on the Klondike Gold Rush, was the most famous and popular one in China....Jack London was one of the outstanding American writers in the late nineteenth and early twentieth century. The Call of the Wild which was based on the Klondike Gold Rush, was the most famous and popular one in China. These years, lots of scholars have discussed it from various aspects, such as the contents, the themes, the writing styles and its characters. In this short novel, the protagonist Buck is humanized by the author. He is endowed with lots of human qualities, such as loyalty, brave, self-esteem, intelligence and so on. What are the reasons of humanization of the dog protagonist.? Finding out the reasons could help us understand this novel better and it may offer some references for the research on Jack London' s animal novels.展开更多
This paper presents a study that explored the effects of cooperative learning on Chinese students' interactional strategy use in the EFL classroom. A quasi-experimental research design was adopted. The experimental c...This paper presents a study that explored the effects of cooperative learning on Chinese students' interactional strategy use in the EFL classroom. A quasi-experimental research design was adopted. The experimental class (EC) participated in cooperative learning for 30 minutes in each 90-minute session in an integrated skills course while the control class (CC) had the same course following a teacher-fronted format. Interactional data of EC and CC were collected for comparison from the pre- and post-tasks conducted at the beginning and the end of the experiment respectively. The results show that EC appeared to have made more gains in interactional strategy use than CC after the experiment. Although CC made more progress in elaboration than EC, EC produced more uptakes, used much less Chinese and made fewer message abandonments, suggesting better oral fluency in their interaction as a result of cooperative learning.展开更多
To explore the condensation characteristics of vapor flow inside vertical small-diameter tubes, the classical Nusselt theory is revised and an analytical model with variable tube wall temperature is established by con...To explore the condensation characteristics of vapor flow inside vertical small-diameter tubes, the classical Nusselt theory is revised and an analytical model with variable tube wall temperature is established by considering the effect of surface tension exerted by condensate film bending as well as the effect of shear stress on vapor-liquid interface. The effects of various factors including tube wall temperature and gravityon flow condensation in small-diameter tubes are analyzed theoretically to show the heat transfer characteristics. Comparison with the experimental data indicates that the proposed analytical model is fit to reveal the fundamental characteristics of flow condensation heat transfer in vertical small-diameter tube.展开更多
Objective: To investigate the effects of sodium ferulate (SF), an intravenous drug made from traditional Chinese herbs, on activation of postsynaptic density-95 (PSD-95) and neuroprotection after transient cerebr...Objective: To investigate the effects of sodium ferulate (SF), an intravenous drug made from traditional Chinese herbs, on activation of postsynaptic density-95 (PSD-95) and neuroprotection after transient cerebral artery occlusion in rats. Methods: Forty-six male Sprague-Dawley rats were randomized into 2 groups ( n = 23 in each group) : the control group and the SF group. After anesthesia, the middle cerebral artery occlusion (MCAO) was conducted with the intraluminal filament technique. The neurological deficit was assessed with the method devised by Bederson et al.^ 8 The 2, 3, 4-triphenyltetrazolium chloride staining was used to assess the infarct volume. We adopted a modified six-point scale to conduct neurobehavioral evaluation. Immediately the activation of postsynaptic density-95 ( PSD- 95 ) was studied with Western blot analysis system in the cortex and striatum of rat brain. Results : The neurologic deficit score of the SF group decreased substantially compared with that of the control group ( P 〈0.05). The infarct volume of the control group (168.1 mm^3 ± 42.2 mm^3) was significantly larger than that of the SF group (61.5 mm^3 ± 28.7 mm^3 ) at 24 hours after reperfusion (P 〈 0.01 ). And the rats showed some neurological deficit. The activity of PSD-95 in the SF group at most timepoints was less than that in the control group. No upregulation of PSD-95 protein could be detected in the contralateral cortex. Conclusions : Sodium ferulate can induce a neuroproteetive effect against the transient focal cerebral isehemie injury and weaken the activation of PSD-95 in isehemie area after MCAO.展开更多
In hand reared birds and mammals, it is generally considered that the development of hoarding behavior is the result of an interaction between the development and maturation of the nervous system and learning from ind...In hand reared birds and mammals, it is generally considered that the development of hoarding behavior is the result of an interaction between the development and maturation of the nervous system and learning from individual experience. How- ever, few studies have been done on wild animals. We tested differences in hoarding behavior between captive reared and wild individuals of two sympatric small rodents, Korean field mice Apodemus peninsulae and Chinese white-bellied rats Niviventer confucianus. Our aim was to identify if lack of experience from the wild would result in poorly developed hoarding behavior. The Korean field mice perform scatter- and larder-hoarding behaviors whereas Chinese white-bellied rats hoard food in larders only. Within outdoor enclosures we compared seed-hoarding behavior in reared juveniles (RJ, 40-50 d old, pregnant mothers were captured in the wild), wild juveniles (WJ, as young as the RJ) and wild adults (WA, over-winter animals). We found that a lack of experience from the wild had significant effects on seed-hoarding behavior for both species. The RJ-group removed and hoarded fewer seeds than the WJ- and WA-groups. The two latter groups hoarded seeds in a similar way. In the Korean filed mouse the ILl-group placed more seeds on the ground surface than other groups. These findings suggest that wild experience is important for the acquisition of an appropriate food-hoarding behavior (especially for scatter-hoarding) in these species展开更多
To reduce the fuel consumption of internal combustion engines, more attention has been paid to the tribological performance of the piston ring pack during the cold start and idle operations. In this research, a numeri...To reduce the fuel consumption of internal combustion engines, more attention has been paid to the tribological performance of the piston ring pack during the cold start and idle operations. In this research, a numerical model considering the cylinder liner deformation and the piston ring conformability is developed to predict the blow-by, lubrication, friction and wear of the piston ring pack under different operating conditions. The gas flow rate, inter-ring gas pressures, minimum oil film thickness, frictional force and wear load during cold start are calculated and compared with those during warm idle operating conditions. The results show that cylinder liner deformation and piston ring conformability together obviously affect blow-by and other tribological performance. Meanwhile, it is found that friction loss is larger during cold start than during warm idle operating conditions. However, the wear process is more severe during warm idle operation than during cold start. From this research, the blow-by and tribological performance of the piston ring pack during cold start and warm idle operations are understood more deeply.展开更多
文摘The parameters of fluorescence induction kinetics and the maximal light-saturated net CO2 assimilation rate (P-sat) of the flag leaves of four cultivars of winter wheat (Triticum aestivum L.) were compared at three different developing stages for the first time. From the blooming stage to the milky stage, the quantum efficiency of PS II photochemistry (F-v/F-m) declined slightly only at the milk stage. The photochemical quenching co-efficient (qP), actual quantum yield of photosystem II (PS II)electron transport (Phi (PSII)) and P-sat decreased substantially (> 15%), while the non-photochemical quenching co-efficient (qN) increased significantly (> 100%). There existed a linear correlation between the Phi (PSII) and the P-sat (r = 0.918). The results indicate that with the senescence of the flag leaves of winter wheat the photosynthetic efficiency including that of the energy transport and the CO2 assimilation significantly decreased.
基金Supported by the College Science and Technology Developing Foundation of Shanghai, No. 02BK14
文摘AIM: To investigate the effect of various concentrations of tetrandrine on activation of quiescent rat hepatic stellate cells (HSCs) and transforming growth factor-β (TGF-β) signaling in vitro.METHODS: HSCs were isolated from rats by in situperfusion of liver and 18% Nycodenz gradient centrifugation, and primarily cultured on uncoated plastic plates for 24 hwith DMEM containing 20% fetal bovine serum (FBS/DMEM) before the culture medium was substituted with 2% FBS/DMEM for another 24 h. Then, the HSCs were cultured in 2% FBS/DMEM with tetrandrine (0.25, 0.5, 1,2 mg/L, respectively). Cell morphological features were observed under an inverted microscope, smooth muscleα-actin (α-SMA) was detected by immunocytochemistry and image analysis system, laminin (LN) and type Ⅲprocollagen (PCⅢ) in supernatants were determined byradioimmunoassay. TGF-β1 mRNA, Smad 7 mRNA and Smad 7 protein were analyzed with RT-PCR and Western blotting, respectively.RESULTS: Tetrandrine at the concentrations of 0.25-2 mg/L prevented morphological transformation of HSC from the quiescent state to the activated one, while α-SMA, LN and PCⅢ expressions were inhibited. As estimated by gray values, the expression of α-SMA in tetrandrine groups (0.25, 0.5, 1, 2 mg/L) was reduced from 21.3% to 42.2%(control: 0.67, tetrandrine groups: 0.82, 0.85, 0.96, or 0.96, respectively, which were statistically different from the control, P<0.01), and the difference was more significant in tetrandrine at 1 and 2 mg/L. The content of LN in supernatants was significantly decreased in tetrandrine groups to 58.5%, 69.1%, 65.8% or 60.0% that of the control respectively, and that of PCⅢ to 84.6%, 81.5%,75.7% or 80.7% respectively (P<0.05 vs control), with no significant difference among tetrandrine groups. RTPCR showed that TGF-β1 mRNA expression was reduced by tetrandrine treatments from 56.56% to 87.90% in comparison with the control, while Smad 7 mRNA was increased 1.4-4.8 times. The TGF-β1 mRNA and Smad 7 mRNA expression was in a significant negative correlation (r= -0.755, P<0.01), and both were significantly correlated with α-SMA protein expression (r = -0.938, P<0.01;r = 0.938, P<0.01, respectively). The up-regulation of Smad 7 protein by tetrandrine (1 mg/L)was confirmed by Western blotting as well.CONCLUSION: Tetrandrine has a direct inhibiting effect on the activation of rat HSCs in culture. It up-regulates the expression of Smad 7 which in turn blocks TGF-β1 expression and signaling.
基金provided by the National Research Foundation (Grant number:2069110)the University of the Witwatersrand
文摘A number of mechanisms are known to influence coexistence in small mammal communities. However, the role ofbehavioral interactions in promoting species coexistence is under-represented in the literature. We studied the behavioral interactionsof two coexisting small mammals, the Namaqua rock mouse Micaelamys namaquensis (Rodentia) and the Rock sengi Elephantulusmyurus (Macroscelidae), which have high dietary and microhabitat overlap. Using wild-caught individuals, intra- andinterspecific dyadic encounters were staged in tanks on a neutral rocky outcrop. Interspecific dyads displayed significantly moreactive avoidance behavior. There was no support for the prediction that the larger, more specialist species, E. myurus, is behaviorallydominant over M. namaquensis. Intraspecific encounters of E. myurus showed significantly more passive avoidance andamicable behavior, whereas the behavior of M. namaquensis did not differ between intra- and inter-specific encounters, both ofwhich were characterized by low levels of aggression and amicability. Thus, due to the lack of aggression, direct competition appearsweak and instead mutual avoidance may reduce or minimize interspecific interactions, potentially promoting coexistence.
文摘Objective: To investigate the effects of Lycium barbarum polysaccharide (LBP) on experimental gastric ulcers in rats.Methods: The ulcers were induced by water-immersion restraint stress, acetic acid and pylorus-ligation in rats. In each model, animals were divided randomly into 4 groups and administrated with LBP of 100 mg/kg and 300 mg/kg, ranitidine 100 mg/kg (as a reference standard) and saline respectively. Mucosal lesions were scored as ulcer index. In the pylorus-ligation model, we also compared the gastric juice volume, total acidity, acid output and pepsin activity among groups.Results: Oral administration of LBP inhibited the formation of the acute gastric lesions induced by physical stress such as water-immersion restraint (P<0.05), and accelerated the healing of chronic gastric ulcer model induced by acetic acid (P<0.05 to P<0.01). In the pylorus-ligated rats, significant decrease was also seen in ulcer index (P<0.05 to P<0.01), total acidity (P<0.05), acid output (P<0.05 to P<0.01). LBP 300 mg/kg even showed marked reduction of the volume (P<0.05) and pepsin activity (P<0.05) in the gastric juice. These effects were in a dose-dependent manner. Conclusion: LBP has protective effects on treating gastric ulcer and this action may relate to the reduction of acid output and pepsin activity in the gastric juice.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10547121 and 10175036
文摘In a two-dimensional (219) dusty plasma system, the size of particles is considered under two different interparticle potentials (Yukawa potential and Dressed potential). The structural and dynamical characters are investigated by molecular dynamics simulation respectively. The results show that the 2D systems via Yukawa and Dressed potentials have a different critical coupling constant F corresponding to the systems beginning to coagulate and exhibit different crystal configurations. Also we find that the size of particles has little influence on the 2D system's structure characters.
基金the National Basic Research Program of China(No.2003CB716206)the National Natural Science Foundation of China(No.50605025)
文摘In order to optimize the transitional time during the successive exposure scans for a step-and-scan lithography and improve the productivity in a wafer production process, an investigation of the motion trajectory planning along the scanning direction for wafer stage was carried out. The motions of wafer stage were divided into two respective logical moves (i. e. step-move and scan-move) and the multi-motionoverlap algorithms (MMOA) were presented for optimizing the transitional time between the successive exposure scans. The conventional motion planning method, the Hazelton method and the MMOA were analyzed theoretically and simulated using MATLAB under four different exposure field sizes. The results show that the total time between two successive scans consumed by MMOA is reduced by 4.82%, 2.62%, 3.06% and 3.96%, compared with those of the conventional motion planning method; and reduced by 2.58%, 0.76%, 1.63% and 2.92%, compared with those of the Hazehon method respectively. The theoretical analyses and simulation results illuminate that the MMOA can effectively minimize the transitional step time between successive exposure scans and therefore increase the wafer fabricating productivity.
基金Supported by National Natural Science Foundation of China under Grant Nos. 10802043 and 10832006, Program for Science & Technology Innovation Talents in Universities of Henan under Grant No. 2009HASTIT033 and Key Disciplines of Shanghai municipality ($30104)
文摘Bacterial quorum sensing (QS) has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data showed that smafl RNAs played important role in the QS of Vibrio harveyi and it can permit the fine-tuning of gene regulation and mmntenance of homeostasis. According to Michaelis-Menten kinetics and mass action law in this paper, we construct a mathematical model to investigate the mechanism induced QS by coexist of small RNA and signal molecular (AI) and show that there are periodic oscillation when the time delay and Hill coefficient exceed a critical value and the periodic oscillation produces the change of concentration and induces QS. These results are fit to the experimental results. In the meanwhile, we also get some theoretical value of Hopf Bifurcation on time deday. In addition, we also find this network is robust against noise.
文摘Jack London was one of the outstanding American writers in the late nineteenth and early twentieth century. The Call of the Wild which was based on the Klondike Gold Rush, was the most famous and popular one in China. These years, lots of scholars have discussed it from various aspects, such as the contents, the themes, the writing styles and its characters. In this short novel, the protagonist Buck is humanized by the author. He is endowed with lots of human qualities, such as loyalty, brave, self-esteem, intelligence and so on. What are the reasons of humanization of the dog protagonist.? Finding out the reasons could help us understand this novel better and it may offer some references for the research on Jack London' s animal novels.
文摘This paper presents a study that explored the effects of cooperative learning on Chinese students' interactional strategy use in the EFL classroom. A quasi-experimental research design was adopted. The experimental class (EC) participated in cooperative learning for 30 minutes in each 90-minute session in an integrated skills course while the control class (CC) had the same course following a teacher-fronted format. Interactional data of EC and CC were collected for comparison from the pre- and post-tasks conducted at the beginning and the end of the experiment respectively. The results show that EC appeared to have made more gains in interactional strategy use than CC after the experiment. Although CC made more progress in elaboration than EC, EC produced more uptakes, used much less Chinese and made fewer message abandonments, suggesting better oral fluency in their interaction as a result of cooperative learning.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 59995550-3) .
文摘To explore the condensation characteristics of vapor flow inside vertical small-diameter tubes, the classical Nusselt theory is revised and an analytical model with variable tube wall temperature is established by considering the effect of surface tension exerted by condensate film bending as well as the effect of shear stress on vapor-liquid interface. The effects of various factors including tube wall temperature and gravityon flow condensation in small-diameter tubes are analyzed theoretically to show the heat transfer characteristics. Comparison with the experimental data indicates that the proposed analytical model is fit to reveal the fundamental characteristics of flow condensation heat transfer in vertical small-diameter tube.
文摘Objective: To investigate the effects of sodium ferulate (SF), an intravenous drug made from traditional Chinese herbs, on activation of postsynaptic density-95 (PSD-95) and neuroprotection after transient cerebral artery occlusion in rats. Methods: Forty-six male Sprague-Dawley rats were randomized into 2 groups ( n = 23 in each group) : the control group and the SF group. After anesthesia, the middle cerebral artery occlusion (MCAO) was conducted with the intraluminal filament technique. The neurological deficit was assessed with the method devised by Bederson et al.^ 8 The 2, 3, 4-triphenyltetrazolium chloride staining was used to assess the infarct volume. We adopted a modified six-point scale to conduct neurobehavioral evaluation. Immediately the activation of postsynaptic density-95 ( PSD- 95 ) was studied with Western blot analysis system in the cortex and striatum of rat brain. Results : The neurologic deficit score of the SF group decreased substantially compared with that of the control group ( P 〈0.05). The infarct volume of the control group (168.1 mm^3 ± 42.2 mm^3) was significantly larger than that of the SF group (61.5 mm^3 ± 28.7 mm^3 ) at 24 hours after reperfusion (P 〈 0.01 ). And the rats showed some neurological deficit. The activity of PSD-95 in the SF group at most timepoints was less than that in the control group. No upregulation of PSD-95 protein could be detected in the contralateral cortex. Conclusions : Sodium ferulate can induce a neuroproteetive effect against the transient focal cerebral isehemie injury and weaken the activation of PSD-95 in isehemie area after MCAO.
文摘In hand reared birds and mammals, it is generally considered that the development of hoarding behavior is the result of an interaction between the development and maturation of the nervous system and learning from individual experience. How- ever, few studies have been done on wild animals. We tested differences in hoarding behavior between captive reared and wild individuals of two sympatric small rodents, Korean field mice Apodemus peninsulae and Chinese white-bellied rats Niviventer confucianus. Our aim was to identify if lack of experience from the wild would result in poorly developed hoarding behavior. The Korean field mice perform scatter- and larder-hoarding behaviors whereas Chinese white-bellied rats hoard food in larders only. Within outdoor enclosures we compared seed-hoarding behavior in reared juveniles (RJ, 40-50 d old, pregnant mothers were captured in the wild), wild juveniles (WJ, as young as the RJ) and wild adults (WA, over-winter animals). We found that a lack of experience from the wild had significant effects on seed-hoarding behavior for both species. The RJ-group removed and hoarded fewer seeds than the WJ- and WA-groups. The two latter groups hoarded seeds in a similar way. In the Korean filed mouse the ILl-group placed more seeds on the ground surface than other groups. These findings suggest that wild experience is important for the acquisition of an appropriate food-hoarding behavior (especially for scatter-hoarding) in these species
基金supported by the National Natural Science Foundation of China(Grant No.51375300)the Research Project of State Key Laboratory of Mechanical System and Vibration(Grant No.MSVZD201401)
文摘To reduce the fuel consumption of internal combustion engines, more attention has been paid to the tribological performance of the piston ring pack during the cold start and idle operations. In this research, a numerical model considering the cylinder liner deformation and the piston ring conformability is developed to predict the blow-by, lubrication, friction and wear of the piston ring pack under different operating conditions. The gas flow rate, inter-ring gas pressures, minimum oil film thickness, frictional force and wear load during cold start are calculated and compared with those during warm idle operating conditions. The results show that cylinder liner deformation and piston ring conformability together obviously affect blow-by and other tribological performance. Meanwhile, it is found that friction loss is larger during cold start than during warm idle operating conditions. However, the wear process is more severe during warm idle operation than during cold start. From this research, the blow-by and tribological performance of the piston ring pack during cold start and warm idle operations are understood more deeply.