Picroside-I attenuated isoproterenol-induced heart damage via modification of cardio-morphology, infarct size and inflammatory cascade

Purpose: To study the effect of picroside-I (PIC-I) on isoproterenol (ISO)-induced heart damage in rats through determination of infarct size, antioxidant enzymes, cardiac/inflammatory and apoptotic markers, as well as cardio-morphology.Methods: A total of 32 rats were divided equally into 4 groups. Rats in normal control group were treated with saline only, while myocardial infarction (MI) rat model was prepared by intraperitoneal (i.p.) injection of ISO at a concentration of 100 mg/kg. Rats pretreated with PIC-Iat dose 10 mg/kg (i.p) for 28 days and administered with isoproterenol. Another group of rats was administered only with PIC-I (10 mg/kg) for 28 days.Results: After 28 days of pretreatment with PIC-I, there were significant increases in arterial blood pressure and cardiac antioxidants, as well as marked decreases in infarct size, cardiac markers, inflammatory markers and apoptotic markers in rats with ISO-induced heart damage, when compared with rats given ISO alone. Rats administered PIC-I showed better histology, with reduced necrosis and prominent cardiac fibers.Conclusion: PIC-1 pre-treatment for 28 days significantly reversed elevations in infarct size, cardiac/inflammatory and apoptotic markers, and also improved antioxidant status and cardiacmorphology in rats with ISO-induced heart damage. Keywords: Picroside-I, Isoproterenol, Infarct size, Inflammation, Apoptosi

Fracture Analysis of Brittle Materials Based on Nonlinear FEM and Application in Arch Dam with Fractures

Current fracture analysis models based on fracture mechanics or continuum damage mechanics are still limited in the application to three-dimensional structure. Based on deformation reinforcement theory coming from elastoperfect plastic theory, unbalanced force is proposed to predict initiation and propagation of cracks. Unbalanced force is the driving force of time-dependent deformation according to Perzyna’s viscoplasticity theory. It is also related to the damage driving force in viscoplastic damage model. The distribution of unbalanced force indicates cracks initiation area, while its direction predicts possible cracks propagation path. Uniaxial compression test of precrack specimen is performed as verification to this method. The trend and distribution of cracks are in good agreement with numerical results, proving that unbalanced force is feasible and effective for fracture analysis. The method is applied in fracture analysis of Xiaowan high arch dam, which is subjected to some cracks in dam due to the temperature control program. The results show that the deformation and stress of cracks and the stress characteristics of dam are insensitive to grouting of cracks. The existing cracks are stable and dam heel is still the most possible cracking position

Finite element analysis of temperature field of traction motor

Due to the fact of immeasurable inner temperature of inverter-fed traction motor, three-dimension finite element model of part of rotor iron core and half a rotor bearing were established. The convective heat transfer coefficient between the air gap of motor and rotor surface were calculated by the heat transfer and fluid mechanics theory. The influence of temperature rise on the stator and rotor resistance was considered for thermal loss calculation. The influence of the end of stator and rotor on axial temperature distribution was also taken into account. Then three-dimensional transient temperature field of the motor was simulated at the rated load. Temperature field with different loads was also computed. The aim has been to optimize the design with respect to the transient stresses. According to contrastive analysis compared with other method, it demonstrated the accuracy of simulation model and thermal field calculation results

Compaction and sealing properties of bentonite/claystone mixture: Impacts of bentonite fraction, water content and dry density

International audienc

Long-term effect of water chemistry on the swelling pressure and hydraulic conductivity of compacted claystone/bentonite mixture with technological gaps

International audienc

Investigation of the hydraulic conductivity of an unsaturated compacted bentonite/claystone mixture

International audienceA pre-compacted MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture has been proposed as a candidate sealing material in a French deep geological repository for high-level radioactive waste. An in-depth understanding of the hydraulic property of this material is essential for accessing the over-pack corrosion and nuclide migration along the gallery. In this study, water flow in the compacted bentonite/claystone mixture was investigated by carrying out infiltration and water retention tests under constant-volume conditions alongside detailed microstructure observation. The evolution of total water hydraulic conductivity with suction was experimentally determined based on the instantaneous profile method. It was observed that the measured total hydraulic conductivity increased slowly at high suctions, then quickly at low suctions and finally approached the saturated value. A new method was developed based on the evolving pore structure, accounting for both vapour and liquid-water hydraulic conductivities. The total hydraulic conductivity predicted by the proposed method agreed well with the measured value, indicating the reliability of the predictive method. The vapour hydraulic conductivity was larger than the liquid-water one at a suction larger than 15·2 MPa, while liquid-water hydraulic conductivity became dominant at a suction lower than 15·2 MPa. In addition, based on the predicted vapour and liquid-water hydraulic conductivities, a numerical model was set up to simulate the water infiltration process. Comparison between the simulation and the measurement showed close agreement, validating the two-phase water flow mechanism in the bentonite/claystone mixture

Investigating the swelling pressure of highly compacted bentonite/sand mixtures under constant-volume conditions

International audienc

Effect of water chemistry on the hydro-mechanical behaviour of compacted mixtures of claystone and Na + /Ca 2+ bentonites for deep geological repositories for deep geological repositories

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Evaluation of swelling pressure of bentonite/claystone mixtures from pore size distribution

International audienceThe swelling behaviour of expansive clays is strongly related to the interaction between clay particles. In this paper, a series of constant-volume swelling pressure and mercury intrusion porosimetry (MIP) tests were carried out on MX80 bentonite/Callovo-Oxfordian (COx) claystone mixtures with different bentonite fractions and dry densities. Results show that the swelling pressure increased linearly with the increase of dry density. Additionally, at a given dry density, the larger the bentonite fraction, the larger the swelling pressure. From the MIP results, the inter-particle pore volume decreased with the increases of bentonite fraction and dry density. To link the macroscopic swelling behaviour with the microstructure features, a new method was proposed, allowing the determination of the average inter-particle distance from the pore size distribution. Moreover, a linear relationship was identified between the swelling pressure and the average inter-particle distance in a semi-logarithmic plane, regardless of the bentonite fraction and montmorillonite content

An insight into grain interaction in bentonite/claystone mixtures

International audienceThis paper investigates the swelling mechanism of Callovo-Oxfordian (COx) claystone grain in its mixtures with bentonite which are potential candidate for engineered barriers in the French high-level radioactive waste disposal. The swelling pressures of MX80 bentonite/COx claystone mixtures with various bentonite fractions and dry densities were first experimentally determined by carrying out infiltration tests under constant-volume conditions. According to the experimental results, the claystone void ratio after hydration in the mixtures was estimated by taking into account the bentonite-claystone grain interaction. Then, the volume change of claystone grain under different pressures applied by swollen bentonite was determined. The volumetric strain of claystone grain was found to decrease linearly with the increase of pressure. This allowed the indirect determination of the swelling pressure of claystone grain. The determined value was found to be comparable to that estimated from the relationship between the void ratio and the swelling pressure in the direction perpendicular to the stratification of intact COx claystone, confirming the identified swelling mechanism of bentonite/claystone mixtures