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To meet the requirements of shorter synchronization time and higher life for the synchronizer in transmission, mathematical models aiming at synchronization time and synchronizer life were established separately based on Newton’s second law and adhesive wear theory, M-B fractal contact model. The evaluation function was constructed by ideal point method to establish a multi-objective parameter optimization model with the two objectives. Using the AHP to determine weight value of the target in the multi-objective optimization model, and using the improved particle swarm algorithm to optimize the multi-objective parameter optimization model. The results show that the synchronization time is reduced by 8% and the synchronizer life is increased by 9% compared with that before optimization, the two objectives are improved better. The using of the improved particle swarm algorithm improves the performance of the synchronizer, and the application of the ideal point method effectively avoids the problem that the high order of magnitude dominates the multi-objective optimization.

In order to investigate the friction and wear properties of polymer materials used for mechanical seals of ship stern shafts in actual working environments, five materials, namely, cast polyurethane elastomer (CPU), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), glass fiber modified polyhexamethylene butylamine (CF/PA46) composite, and glass fiber modified polytetrafluoroethylene (CF/PTFE) composite, were selected, and their friction and wear performance tests were conducted under the load of 0. 5 MPa and the linear velocity of 7 m/s. The results show that CPU, PET, PBT, CF/PA46 materials exhibit varying degrees of peeling and furrowing under high load and high rotational speed conditions, resulting in large friction coefficients and wear losses, while CF/PTFE composites only exhibit some relatively slight tears and wear marks, exhibiting optimal friction and wear performance. Compared to CPU, PET, PBT, and CF/PA46, the average friction coefficient of CF/PTFE is decreased by 66. 6%,80. 4%,86. 1%,and 87. 8%,respectively, and the wear amount per unit time is decreased by 91. 7%,92. 7%,88. 6%,and 97. 0%, respectively. The friction and wear performance is optimal. [ABSTRACT FROM AUTHOR]

In order to improve the bearing capacity of water-lubricated bearings, the tribological properties of thermoplastic polyurethane (TPU) bearing materials were improved by the hydration of hydrogels under water lubrication conditions. Hydrogel particles were prepared by using polyvinyl alcohol, sodium alginate, chitosan and other materials, and hydro-gel/TPU composites were prepared by melt blending. The friction and wear properties of the composites were tested under loads of 0. 3 MPa and 0. 5 MPa. The wear surface morphology was observed by laser interference surface profiler and scanning electron microscope, and the wear mechanism was analyzed. The results show that the hydrogel particles can improve the lubrication condition of the friction pair through hydration lubrication, thereby reducing the friction coefficient and wear amount, and improving the friction performance of the composite. When the mass fraction of hydrogel is 4%,the composite has the best friction and wear properties, and compared with the TPU sample, the average friction coefficient reduction rate under the working conditions of 0. 3 MPa and 0. 5 MPa is 52. 31% and 43. 94%, respectively. This research provides a method for developing high performance materials for water lubricated bearings. [ABSTRACT FROM AUTHOR]

An analysis of the Class Background Registers of Yanshan county, Hebei, shows that households of landlord and rich peasant status accounted for less than 10 percent of the local population and possessed less than 15 percent of the land, while households of poor and lower-middle peasant standing owned about half of the land. Overall, land distribution was relatively balanced, as seen in the Gini coefficient of 0.3–0.4 in the distribution of land rights and the fact that about half of the households owned 2–5 mu of land per capita. But the economic condition of the rural population was not determined by the factor of land distribution alone; in places where the natural endowment was poor, off-farm income-making activities mattered a great deal to local residents. Such activities took various forms, which could improve as well as worsen people's livelihood. An analysis of social mobility in this area further shows the perpetuation of the existing class structure. Those whose grandparents had lived in poverty found it difficult to move up socially. On the whole, the rural area under study shows a prolonged trend of deterioration, which is meaningful for understanding the land reform. 摘要: 通过对盐山县《阶级成分登记表》的分析，地主和富农人口占比低于10%，土地占比不足15%，贫下中农的土地占比接近半数。地权分配的基尼系数是0.3–0.4，有一半左右的家庭人均土地集中在2–5亩，土地分配相对合理。不能从单纯的土地分配来观察农民的经济状况，在自然条件较差的地区，农业外的兼业占有重要地位。农民的兼业活动十分丰富，也因其而维生、致富、致贫。从社会流动情况来看，农村的阶层固化现象较严重。如果祖父辈生活水平低，子辈向上流动的难度很大。从整体上看，农村出现了缓慢下沉的趋势，这与土地改革之间存在历史关联。 [ABSTRACT FROM AUTHOR]

Objective: To study the effect on endocrine system of SD rats exposed to low-dose arsenic., Methods: A subchronic test on rats which were divided into five groups randomly( the control group, 0. 05, 0. 1, 0. 2, 0. 4 μg / m L), 20 rats each group, half male and female. A total of 200 rats were allowed to acclimate for 1 week and their hormones level were measured by RIA method after 110 and 194 days., Results: The hormones level of rats was disordered in different groups. The T level of male rats exposedto arsenic for 110 days were( 4. 80 ± 4. 26), ( 4. 54 ± 3. 31), ( 1. 27 ± 1. 51), ( 1. 93 ±2. 23) and( 4. 83 ± 2. 31) ng / m L( P = 0. 05), respectively. The T4 level of each female group were( 40. 20 ± 7. 10), ( 40. 85 ± 8. 66), ( 46. 49 ± 8. 52), ( 44. 66 ± 11. 83) and( 26. 80 ± 8. 12) ng /m L, compared with control group, 0. 4 μg /m L group decreased obviously( P < 0. 05). Meanwhile, their Cort level of each group were( 312. 10 ±10. 61), ( 333. 15 ± 15. 73), ( 341. 13 ± 19. 25), ( 342. 59 ± 25. 96) and( 314. 84 ±16. 76) ng / m L, and the 0. 05, 0. 1 and 0. 2 μg / m L groups were significantly increased( P < 0. 05). Furthermore, the T4 level of male groups exposed to arsenic for 194 days were( 23. 06 ± 5. 54), ( 33. 18 ± 5. 29), ( 34. 23 ± 4. 15), ( 37. 19 ± 4. 13) and( 39. 92± 6. 27) ng / m L, respectively. Compared with control group, all experimental group significantly increased( all P < 0. 05). Additionally, the T3 level of female group were( 0. 84 ± 0. 12), ( 0. 89 ± 0. 14), ( 0. 83 ± 0. 15), ( 0. 96 ± 0. 16) and( 0. 75 ± 0. 11)ng / m L, and 0. 2 μg / m L group obviously increased( P < 0. 05). Obvious change of hormone had not been found in other group exposed to subchronic low-dose arsenic( all P> 0. 05)., Conclusion: Subchronic low-dose arsenic exposure have slight endocrine effects on SD rats.

Objective: To detect ERbeta mRNA expression of subjects exposed to different arsenic drinking water, and to analyze the potential relationship between their abnormal expression and heart injury caused by arsenic in order to study the endocrine disturbing effect of arsenic., Methods: Molecular epidemiological method was used. The study subjects included a total of 273 residents exposed to arsenic via drinking water,and they were divided into four groups according to arsenic concentration, and their blood ERbeta mRNA expression was detected by real-time RT-PCR., Results: The level of ERbeta mRNA expression rose with increasing of water As and urine As (r = 0.159, 0.21, P < 0.05). The prevalence of Q-Tc interval prolongation aggravated with increasing of water As(chi2 = 4.35, P = 0.037), while according with the variation of ERbeta mRNA expression. Tp-Te interval prolonged with increasing of water As (r = 0.199, P = 0.023), as well prolonged with increasing of ERbeta mRNA expression (r = 0.205, P = 0.019). The prevalence of arrhythmia was almost according with the variation of ERbeta mRNA expression., Conclusion: chronic arsenic exposure can potentially disturb ERbeta mRNA expression, as well as there are possible relationship between ERbeta mRNA abnormal expression and Q-Tc interval prolongation and Tp-Te interval prolonged caused by arsenic.

This study was aimed to identify pET21b-HPV16E2/BL21(DE3) strain and to optimize the expression of human papillomavirus type 16 (HPV16) E2 protein by orthogonal analysis. Four influence factors on two levels were selected to increase the target protein quantity. The four factors were induction time, induction temperature, inductor concentration and cell density. The quantity of HPV16 E2 protein was used as the evaluation parameter. Induced by IPTG, HPV16 E2 protein was analyzed by SDS-PAGE and Western Blot. Target protein was analyzed by GIS imaging system to quantify the protein level. SPSS13. 0 software was applied to analyze the result. Data showed that the expression strain pET211rHPV16 E2/BL21(DE3) was identified correctly. HPV16 E2 protein expressed mainly at insoluble form. The 42KD protein band was identified by SDS-PAGE and Western blot. Orthogonal test was applied on influence factor analysis and expression optimization successfully. Main influence factors were inductor concentration and induction temperature. The optimimum condition of maximum expression quantity was 37 degrees C, 7h, 1.0 mmol/L IPTG and OD600 1.0. In this experiment, orthogonal test could not only be used to analyze the influential factors and promote the target protein expression, but also be used to provide a better experiment method for molecular biological study.

Objective: To study the effect on endocrine system of female rats exposed to chronic arsenic., Methods: 50 female Wistar rats were randomly divided into five groups: control group, 0.05, 0.1, 0.2 and 0.4 microg/ml arsenic groups. The hormone levels were determined by RIA exposing arsenic for 32 weeks., Results: The hormone levels of female rats were disorder in different arsenic groups. E2, P level increased and LH level decreased in arsenic groups compared to controls, but there were no significant differences( P > 0.05). FSH and PRL level increased in low arsenic group and decreased in high arsenic groups (P > 0.05). GnRH and Cort level increased in arsenic groups, and GnRH level obviously increased in 0.4 microg/ml group and Cort level obviously increased in 0.1 and 0.4 microg/ml groups (P < 0.05)., Conclusions: The hormone levels were disordered in rats exposed to chronic arsenic.

Objective: By measure the changes of serumal estadiol and progesterone levels of kunming female mice, which are chronically exposed to different concentrations of arsenic trioxide, discuss the estrogen-like effects of arsenic., Methods: Select the Kunming female mice exposed to different drinking water of arsenic trioxide (0, 0.05, 0.10, 0.20, 0.40 microg/ml) for 20 weeks as the research subjects in this study. Use the method of radioimmunology to measure concentrations of serumal estadiol and progesterone of female adult mice., Results: Compared with the control group, there exists the changes of the concentrations of the serumal estadiol and progesterone of Km female adult mice, which are chronically exposed to the arsenic. Compared to the control group, the differences of the concentrations of the serumal estadiol in the 0.05 microg/ml group and 0.10 microg/ml group have no statistical significance (P > 0.05), the concentrations of estadiol in the 0.20 microg/ml group (P < 0.01) and 0.40 microg/ ml group (P < 0.05) decrease. Compared to the control group, the differences of the concentrations of the serumal progesterone in the 0.05 microg/ml group, 0.20 microg/ml group and 0.40 microg/ml group have no statistical significance (P > 0.05), the concentration of serumal progesterone in the 0.10 microg/ml group (P < 0.01) decrease., Conclusion: Chronically arsenic exposure can interfere the levels of serumal hormones. Arsenic has the estrogen-like effects.

Pancreas is an important mixed gland having both endocrine and exocrine functions, and has been proven regeneration after injury. To explore the cell lineage tracing methods in pancreas in vivo and the regenerate cells source, we used pseudo-type retrovirus to transfect adult mouse pancreas which had been partially pancreatectomized by rubbing the kerf using a cotton stick saturated with retrovirus suspension then injecting 100 microL retrovirus suspension into pancreas, injecting 100 microL retrovirus by caudal vein, or interperitoneally injecting retrovirus respectively. The results showed that the method of rubbing the kerf then injection of retrovirus suspension into pancreas could more effectively mark the pancreatic cells than the caudal vein injection and the intraperitoneal injection did in vivo. Furthermore, this study also found that some acinus cells could accept injury stimulus signals to regenerate through resuming mitosis after pancreatic injury. This study establishes a cell lineage tracing method in pancreas in vivo using retrovirus and offers a clue for gene therapy of pancreatic diseases using retrovirus vectors.

Actinobacillus pleuropneumoniae is a very important respiratory pathogen for swine and causes great economic losses in pig industry worldwide. Signature-tagged mutagenesis (STM) is an effective method to identify virulence genes in bacteria. In this study, we selected nalidixic acid-resistant strains of APP serotypes 1 and 3 by in vitro cultivation, and used as receipt strains for constructing transposon mutants by mating with E. coli CC 118 lambdapir or S17-1 lambdapir containing mini-Tn10 tag plasmids pLOF/TAG1-48, with or without the help of E. coli DH5alpha (pRK2073). We screened mutant strains by antibiotics selection, PCR and Southern blot identification. Our data revealed that nalidixic acid-resistance of APP strains could easily be induced in vitro and the resistance was due to the mutation in the DNA gyrase A subunit gene gyrA. In the mating experiments, the bi-parental mating was more effective and easier than tri-parental mating. Different APP strains showed a different mating and transposon efficiency in the bi-parental mating, with the strains of serotype 1 much higher than serotype 3 and the reference strain of serotype 3 higher than the field strains. These data were helpful for the construction of STM mutants and pickup of virulence genes of APP.