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Ultrafine bainitic steels, which are derived from nanostructured carbide-free bainitic steels, exhibit a remarkable combination of ultra-high strength and toughness together with excellent wear resistance. Their excellent integrated mechanical properties has made ultrafine bainitic steels a popular choice for application as wear-resistant parts. In this study, a 0.7-C low alloy ultrafine bainitic steel was designed, and the effects of different austempering temperatures on the bainitic transformation kinetics, microstructure, and dry sliding wear resistance of ultrafine bainitic steels were studied. Dilatometry, two-body abrasion testing, optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction, laser-scanning confocal microscopy, and energy-dispersive spectrometry were used to study the abovementioned effects. Meanwhile, the wear performance and wear mechanism under two-body abrasion of ultrafine baintic steels with different austempering temperatures were also studied. The results demonstrate that the microstructures of ultrafine bainitic steel produced at different austempering temperatures comprise both lamellar bainitic ferrite and film-like and blocky retained austenite. With increasing austempering temperature, the transformation rate of bainite increases, and the incubation period and phase transformation completion time of bainite significantly reduce; in addition, the bainitic ferrite plates are more coarsened, the volume fraction of retained austenite increases, and the hardness decreases. Moreover, when the ultrafine bainitic steel is subjected to the twobody abrasion test, the wear surface is mainly featured by furrows and grooves, and the predominant wear mechanism is micro-cutting. Furthermore, the wear resistance of ultrafine bainite post austempering at different temperatures is better than that of tempered martensite; this wear resistance increases with decreasing isothermal temperatures. Ultrafine baintic steel post austempering at 250℃ possesses the best wear resistance, and the relative wear resistance is 1.28 times higher than that of tempered martensitic steel; this is attributed to the refined microstructure and the transformation induced plasticity (TRIP) effect of ultrafine bainitic steel.

During tensile and temperature tests, the latent heat of hot-rolled TRIP steel was dynamically investigated by observing the stress-strain and thermal curves. The results indicated that during the tensile test, the hot-rolled TRIP steel increased the thermal energy, which originated from the partial transformation of plastic work and martensitic transformation. Therefore, the actual heat of the measured sample was higher than that converted by plastic work. During the low speed tensile test, the thermal energy of the TRIP steel was supplemented by the average integrated heat loss coefficient. Through calculation and deduction, it was confirmed that a certain amount of the unstable residual austenite first became martensite, when the plastic deformation had just begun. As the strain increased further, the amount of the remaining, stable, retained austenite that would become martensite, decreased gradually according to its stability. Most of the retained austenite had almost become martensite before the end of the uniform elongation. During the deformation process of the hot rolled TRIP steel, the martensitic transformation could be dynamically described by the change of latent heat.

In view of slow phase transformation rate in high-carbon,silicon-rich and low-alloy bainite steel(nanostructured bainite steel),the effects of alloy elements on the overall kinetics of low temperature bainite phase transformation were analyzed by using the thermodynamic theory of bainite phase transformation,and a composition of 0.83C-2.44Si-0.43Mn-0.73Al(mass fraction,%) was designed to develop a novel nanostructured bainitic steel. The overall phase transformation kinetics of this new designed nanobainitic steel at different temperatures were investigated by dilatometry. The effects of heat treatment parameters on the microstructure and mechanical properties were analyzed by scanning electron microscopy,X-ray diffraction and electron backscatter diffraction. It is found that the nanobainitic steel,which exhibited excellent mechanical properties with an ultimate tensile strength of 1401 MPa,a total elongation rate of 42.21% and a strength and ductility product of 59136 MPa·%,can be obtained by austempering at 350℃. In addition,transformation-induced plasticity(TRIP) effect appears during tensile testing at room temperature. When austempered at 230℃,the nanobainitic steel has a finer microstructure with the thickness of bainite ferrite laths less than 100 nm,and its tensile strength can reach up to 2169 MPa.

The high-temperature mechanical properties of Al-TRIP steel with 0.16% C,1.49% Mn and 1.35% Al,which is applied to automobiles,were investigated by using a Gleeble 3500 machine. The phase transition temperature interval was measured by differential scanning calorimetry(DSC). The fractographs and microstructures near the tensile fracture of the steel at different tensile temperatures were analyzed by means of a scanning electron microscope and an optical microscope. The zero ductility temperature(ZDT) and the zero strength temperature(ZST) of the steel were measured to be 1425℃ and 1430℃,respectively. The brittleness temperature interval Ⅰ is from 1400℃ to the melting point,and the brittleness temperature interval Ⅲ is from 800℃ to 925℃.Ferrite precipitation from austenite grain boundaries is the main cause of the presence of the brittleness temperature interval Ⅲ. With specimens cooling from 975℃ to 700℃,the proportion of ferrite increases continuously,while the reduction of area(ψ) decreases firstly and then increases. When the proportion of ferrite reaches to 8.1%(at 850℃),the value of ψ decreases to 28.9%; but when being stretched at 800℃,the proportion of ferrite is greater than 16.7%,and the value of ψ is more than 38.5%. A small number of Al N particles precipitate in the steel at 1275.6℃. These Al N particles are coarse,but they have no influence on the ductility of the steel.

The effect of Nb on the microstructure and mechanical properties of low-alloy wear-resistant steel was analyzed by optical microscopy,scanning electron microscopy,transmission electron microscopy and mechanical property test. By adding 0.034% Nb in low-alloy wear-resistant steel,the hardness increases by HB 9,the Charpy impact energy soars to 37.6J from 29.4J at -20℃ and the anti-wear performance improves by 3.5%. Microstructure refinement and precipitation strengthening are main reasons for the improvement of hardness and impact toughness. Nano-sized particles of Nb C in the Nb-bearing steel precipitate in the process of austenization,pin the austenite grain boundaries and inhibit the growth of austenite grains. This pining type is in accordance with the Zener model,but different from precedent research.

The microstructures of hot rolled Ti-Mo-bearing low-carbon steel and its precipitation characterization of nano-sized carbides were studied by scanning electron microscopy and transmission electron microscopy. It is shown that precipitation strengthening due to nano-sized carbides is estimated to be approximately 291 MPa. The row spacing of interphase precipitation decreases with the drop of isothermal holding temperature. Though the row spacing of interphase precipitation in ferrite shows a relatively small scatter,it tends to be almost constant against distance from the center of ferrite transformed at different holding temperatures. The observed α/γ interfacial microstructure and interphase precipitation simulation by different theories indicate that this interphase precipitation has a close relationship with the formation of mobile ledges,and the row spacing of interphase precipitation is determined by factors such as ledge height,boundary diffusion coefficient,holding temperature,and ledge velocity.

Recurrent spontaneous abortion (RSA) is one of the most common pregnancy complications in gynecology and obstetrics. The etiology of RSA is complex and diverse. In addition to the known causes such as autoimmune abnormalities, thrombophilia, endocrine factors, anatomical abnormalities of female genital tract, chromosome abnormalities of husband and wife, and fetal chromosome or gene abnormalities, there are still 40%-50% of patients cannot find the exact cause, which is called unexplained recurrent spontaneous abortion (URSA). Due to the unknown etiology, it also brings great trouble to develop effective therapy. In recent years, with the development of reproductive immunology, more and more evidences suggest that the occurrence of URSA is related to the imbalance of maternal-fetal immune mechanisms, which also brings hope for the development of therapeutic strategies for URSA. This article reviews the concept of maternal-fetal interface and maternal-fetal immune tolerance, the mechanism of formation and imbalance of maternal-fetal immune tolerance, and the research progress of immune pathogenesis of URSA. [ABSTRACT FROM AUTHOR]

Objective. To investigate the difference of prolactin (PRL) expression in peripheral blood and decidual stromal cells (DSCs) between unexplained recurrent pregnancy loss (URPL) and normal early pregnancy. Methods. Eighty cases of URPL patients in our hospital from March 2018 to March 2019 were recruited. Seventy women with induced abortion and 190 normal pregnancy women were selected as controls. Fasting peripheral blood and decidua tissues were collected. The level of PRL in peripheral blood was detected by enzyme-linked immunosorbent assay. Quantitative real time PCR (RT-qPCR), Western bloting (WB) and immunohistochemistry (IHC) were used to detect the PRL expression of DSCs. Independent sample t test was used to compare the data of the two different groups, and one-way analysis of variance test was used to compare the data of the groups. Results. In the URPL group, 21 cases were excluded for chromosomal abnormality, and 59 cases were finally included. There were 70 cases in the induced abortion group. One hundred and seventy-seven cases in the normal pregnancy group completed follow-up, of which 157 cases were classified as final live birth in the normal pregnancy group, and the rest 20 cases subsequently had pregnancy loss, of which 19 miscarriages occurred in the first 10 weeks of gestation, classified as pregnancy loss in the normal pregnancy group. The PRL levels of peripheral blood in the final live birth in the normal pregnancy group and induced abortion group were similar, with no significant difference between the two groups in the same gestation, and they all increased significantly with advancing gestation (normal pregnancy with final live birth group: 5-5+6 week vs 6-7+6 week, P = 0.002; 6-7+6 week vs 8-9+6 week,P = 0.012;Induced abortion group: 5-5+6 week vs 6-7+6 week, P = 0.015; 6-7+6 week vs 8-9+6 week, P = 0.023). The levels of PRL in the peripheral blood of patients with URPL had no significant change with advancing gestation, and they were significantly lower than those of women with final live birth in the normal pregnancy group and induced abortion women in the same gestation from the 6th week (6-7+6week: P = 0.012, 0.024; 8-9+6 week: P = 0.015, 0.003). In addition, the levels of PRL in the peripheral blood of the women in the normal pregnancy group who later suffered miscarriage were similar to those in the URPL group of the same gestation. The PRL expression of DSCs in the induced abortion group increased significantly in both RNA and protein level with advancing gestation (5-5+6 week vs 6-7+6 week: RT-qPCR, P = 0.020; WB, P = 0.010; IHC,P = 0.030. 6-7+6 week vs 8-9+6 week: RT-qPCR, P = 0.011; WB, P = 0.034; IHC, P = 0.012). However, the increase of PRL expression of DSCs in the URPL group was delayed: the PRL expression of DSCs in women with 6-7+6week and 8-9+6 week of gestation was significantly lower than that in women accepting induced abortion of the same gestation (6-7+6 week: RT-qPCR, P = 0.012; WB, P = 0.014; IHC,P = 0.028. 8-9+6 week: RT-qPCR, P = 0.011; WB, P = 0.030;IHC, P = 0.026). Conclusion. PRL expression of the decidua is defective. The PRL expression of DSCs in URPL patients is deficient, and the lack of decidualization of DSCs may be related to the occurrence of URPL. The low level of PRL in peripheral blood after 6 weeks of gestation may indicate embryonic dysplasia. [ABSTRACT FROM AUTHOR]

PURPOSE: To investigate the clinical method to remove a gutta-percha and root canal sealers. METHODS: 168 root canals which had been filled with gutta-percha were selected, all root canals needed endodontic retreatment. The root canal fillings were removed and the root canal was re-prepared with the method of desocclusol and manual mechanical method. Then the root canal was filled again with lateral condensation technique. RESULTS: With manual mechanical method and desocclusol, all original root canal fillings were removed completely. The combined method could effectively prevent the formation of step, root canal-side wear, broken equipment or other complications during the course of retreatment. The success rate of retreatment was 89.3%. CONCLUSIONS: Combined manual mechanical method with desocclusol could improve the success rate of recanalization of the root canal and saved time and effort. It is a method which could reduce the intensity and improve the efficiency of dentists, and worthy of wide clinical application. Supported by Research Fund of Department of Health of Jiangxi Province(20063127)and Jiangxi Provincial Department of Science and Technology (2008BB2860). [ABSTRACT FROM AUTHOR]

Purpose: To investigate the clinical method to remove a gutta-percha and root canal sealers., Methods: 168 root canals which had been filled with gutta-percha were selected,all root canals needed endodontic retreatment.The root canal fillings were removed and the root canal was re-prepared with the method of desocclusol and manual mechanical method. Then the root canal was filled again with lateral condensation technique., Results: With manual mechanical method and desocclusol,all original root canal fillings were removed completely. The combined method could effectively prevent the formation of step,root canal-side wear,broken equipment or other complications during the course of retreatment.The success rate of retreatment was 89.3%., Conclusions: Combined manual mechanical method with desocclusol could improve the success rate of recanalization of the root canal and saved time and effort. It is a method which could reduce the intensity and improve the efficiency of dentists, and worthy of wide clinical application.

Objective: To investigate whether A/G polymorphism at position 49 in exon 1 of cytotoxic T lymphocyte antigen-4 (CTLA-4) gene confers the susceptibility to unexplained recurrent spontaneous abortion in Chinese population., Methods: One hundred and sixty-eight restrictive Chinese women with unexplained recurrent spontaneous abortion (URSA) and 117 women with normal pregnancy as control were included in this study. Polymerase chain reaction restrictive fragment length polymorphism (PCR-RFLP) was used to detect the polymorphism at position 49 in exon 1 of CTLA-4 gene. The frequency of alleles G/A, genotypes AA/AG/GG and phenotypes A+ (AA + AG)/G+ (GG + AG) of CTLA-4 were compared between URSA patients and controls., Results: The different distributions of alleles G/A, genotype AA/AG/GG and phenotypes A+/G+ of CTLA-4 were observed between URSA patients and controls. The frequencies of both G allele [68.4% (230/336) vs 59.4% (139/234), P < 0.05] and GG genotype [48.8% (82/168) vs 33.3% (39/117), P < 0.05] were significantly higher in URSA group than that in control group, while the frequencies of AG genotype [39.3% (66/168) vs 52.1% (61/117), P < 0.05] and A+ (AA + AG) phenotype [51.2% (86/168) vs 66.7% (78/117), P < 0.05] were significantly lower in URSA group than that in control group., Conclusions: The results suggest that A/G polymorphism in exon-1 of CTLA-4 might confer the susceptibility to RSA in Chinese women.

The environmental DNA was directly extracted from the sediment in Parece Vela Basin, Pacific Ocean, at a depth of 5010 m. Bacterial 16S rRNA gene library of 32 clones was generated using bacterial universal primers and 16S rDNA sequences were analyzed phylogenetically. 17 phylotypes were obtained. The library was dominated by gamma-Proteobacteria, alpha-Proteobacteria and marine uncultured bacteria. Sixty-two percent of the cloned sequences was highly related to the known bacteria in the genus Halomonas, Alcanivorax, Pseudomonas, Acinetobacter, Pseudoalteromonas (> 96% sequence similarity), while some of the cloned sequences showed less affiliation with known taxa (< 94% sequence similarity) and may represent novel taxa.

Objective: To investigate the association between the C677T and A1298C mutation of 5,10-methylenetetrahydrofolate reductase (MTHFR) gene and unexplained recurrent spontaneous abortion (URSA) in Chinese population., Methods: Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to detect the mutation of C677T and A1298C of MTHFR in 148 cases with URSA and 82 normal controls., Results: (1) The distribution frequencies of C667T associated 3 genotypes between the URSA and control group showed statistically significant difference (P = 0.012). The frequencies of C677T genotypes were: CC (33.3%), CT (53.1%), TT (13.6%) in URSA group and CC (52.4%), CT (51.5%), TT (6.1%) in control group, respectively. And the frequency of CC genotype in URSA group was decreased significantly (P = 0.005), while the frequency of T allele in URSA was increased (P < 0.005). (2) The prevalence of the MTHFR A1298C associated 3 genotypes and A/C alleles in URSA group did not differ significantly from the control. (3) According to the linkage analysis of C677T and A1298C, 8 linkage genotypes were found, and the frequency of 677CC/1298AA in URSA was significantly lower compared with the control, the linkage of 677 (CT + TT)/1298CC was only observed in URSA group., Conclusions: The mutations of MTHFR C677T and A1298C play a role in the mechanism of unexplained recurrent spontaneous abortion.