As a widely-applied engineering material in cold regions, the frozen subgrade soils are usually subjected to seismic loading, which are also dramatically influenced by the freeze-thaw(F-T)cycles due to the varying tem...As a widely-applied engineering material in cold regions, the frozen subgrade soils are usually subjected to seismic loading, which are also dramatically influenced by the freeze-thaw(F-T)cycles due to the varying temperature. A series of dynamic cyclic triaxial experiments were conducted through a cryogenic triaxial apparatus for exploring the influences of F-T cycles on the dynamic mechanical properties of frozen subgrade clay.According to the experimental results of frozen clay at the temperature of-10℃, the dynamic responses and microstructure variation at different times of F-T cycles(0, 1, 5, and 20 cycles) were explored in detail.It is experimentally demonstrated that the dynamic stress-strain curves and dynamic volumetric strain curves of frozen clay are significantly sparse after 20F-T cycles. Meanwhile, the cyclic number at failure(Nf) of the frozen specimen reduces by 89% after 20freeze-thaw cycles at a low ratio of the dynamic stress amplitude. In addition, with the increasing F-T cycles,the axial accumulative strain, residual deformation,and the value of damage variable of frozen clay increase, while the dynamic resilient modulus and dynamic strength decrease. Finally, the influence of the F-T cycles on the failure mechanisms of frozen clay was discussed in terms of the microstructure variation. These studies contribute to a better understanding of the fundamental changes in the dynamic mechanical of frozen soils exposed to F-T cycles in cold and seismic regions.展开更多
Using a new low-temperature dynamic triaxial apparatus, the influence law of freezing-thawing cycles on clay shear strength is studied. In this research, the concept of correction coefficients of freezing-thawing cycl...Using a new low-temperature dynamic triaxial apparatus, the influence law of freezing-thawing cycles on clay shear strength is studied. In this research, the concept of correction coefficients of freezing-thawing cycles on clay static strength, cohesion and internal friction angles is proposed, and the change patterns, correction curves and regressive formulae of clay static strength, cohesion and internal friction angles under freezing-thawing cycles are given. The test results indicate that with increasing numbers of freezing-thawing cycles, the clay static strength and cohesion decrease exponentially but the internal friction angle increases exponentially. The performance of static strength, cohesion and internal friction angles are different with increasing numbers of freezing-thawing cycles, i.e., the static strength decreases constantly until about 30% of the initial static strength prior to the freezing-thawing cycling and then stays basically stable. After 5-7 freezing-thawing cycles, the cohesion decreases gradually to about 70% of the initial cohesion. The internal friction angle increases about 20% after the first freezing-thawing cycle, then increases gradually close to a stable value which is an increase of about 40% of the internal friction angle. The freezing-thawing process can increase the variation of the density of the soil samples; therefore, strict density discreteness standards of frozen soil sample preparation should be established to ensure the reliability of the test results.展开更多
This study aimed to assess pregnancy outcomes after high-quality D5- and D6-blastocyst transfer in frozen cycles of in vitro fertilization and embryo transfer and to further evaluate whether there was a difference in ...This study aimed to assess pregnancy outcomes after high-quality D5- and D6-blastocyst transfer in frozen cycles of in vitro fertilization and embryo transfer and to further evaluate whether there was a difference in blastocyst development potentials with different developmental speeds and in pregnancy outcomes. A retrospective analysis was conducted to analyze 247 frozen cycles in our center from September 2015 to July 2017, which were divided into two groups: a D5-FET group with 193 cycles of D5-blastocyst transfer, and a D6-FET group with 54 cycles of D6-blastocyst transfer. Hormone replacement method was utilized to prepare frozen-cycle endometria. Pregnancy outcomes were analyzed and compared between these two groups. The mean ages of the two groups were 31.45 ± 4.43 years and 31.98 ± 4.84 years, respectively, with no statistically significant differences (P > 0.05). The difference in the endometrial thickness during transfer was also not statistically significant. The implantation rate in the D5-FET group was 60.13%, significantly higher than that in the D6-FET group (31.58%, P P < 0.05). No statistically significant differences were found in the abortion rate and ectopic pregnancy rate between the two groups. The implantation, biochemical pregnancy, and clinical pregnancy rates of the blastocyst D5 were all superior to those of the blastocyst D6. In clinics, therefore, D5-blastocyst transfer could be prioritized for embryo transfer.展开更多
Soil slope stability in seasonally frozen regions is a challenging problem for geotechnical engineers.The freezethaw process of soil slope caused by the temperature fluctuation increases the difficulty in predicting t...Soil slope stability in seasonally frozen regions is a challenging problem for geotechnical engineers.The freezethaw process of soil slope caused by the temperature fluctuation increases the difficulty in predicting the slope stability because the soil property is influenced by the freeze-thaw cycle.In addition,the frozen soil,which has ice crystal,ice lens and experienced freeze-thaw process,could present stronger heterogeneity.Previous research has not investigated the combined effect of soil heterogeneity and freeze-thaw cycle.This paper studies the influence of soil heterogeneity on the stability of frozen soil slope under freeze-thaw cycles.The local average subdivision(LAS)is utilized to model the soil heterogeneity.A typical slope geometry has been chosen and analysed as an illustrative example and the strength reduction method is used to calculate the factor of safety(FOS)of slope.It has been found that when the temperature is steady,the FOS of the frozen soil slope is influenced by the spatial variability of the thermal conductivity,but the influence is not significant.When the standard deviation and the SOF of the thermal conductivity increase,the mean of the FOS is equal to the FOS of the homogeneous case and the standard deviation of the FOS also increases.After the frozen soil goes through freeze-thaw process,the FOS of the frozen soil slope decreases due to the reduction in the cohesion and the internal friction angle caused by the freeze-thaw cycles.Furthermore,the decreasing ratio of the FOS becomes more scattered after the 5th freeze-thaw cycle compared to that of the FOS after the 1st freeze-thaw cycle.The larger variability of the FOS could induce inaccuracy in the prediction of the frozen soil slope stability.展开更多
Objectives:To assess the clinical outcomes of frozen-thawed blastocysts transfer in natural and hormonally controlled cycles.Methods:A retrospective analysis of natural and hormonally controlled cycle for 246 frozen-t...Objectives:To assess the clinical outcomes of frozen-thawed blastocysts transfer in natural and hormonally controlled cycles.Methods:A retrospective analysis of natural and hormonally controlled cycle for 246 frozen-thawed blastocyst transfer cycles,the clinical pregnancy rate,implantation rate,early abortion rate were compared.Results:Of the 192 hormonally controlled cycles,the cancel rate,clinical pregnancy rate per ET,implantation rate and abortion rate were 7.3%(14/192),53.9%(96/178),38.8%(131/338)and 11.5%(11/96)respectively,whereas in 54 natural cycles,these rates were 16.7%(9/54),68.9%(31/45),52.9%(45/85)and 16.1%(5/31)respectively.There was no significant difference between the two groups with regard to the clinical pregnancy and abortion rate per ET,but the cancel rate and implantation rate were higher in natural cycles.However,the pregnancy and implantation rates of patients without PCOS in hormonal control cycles(57.2%,40.9%)were similar with those in natural cycles(P>0.05).Conclusion:These findings suggested that both hormonally controlled and natural cycles had similar pregnancy outcomes in frozen-thawed blastocysts transfer.展开更多
Highway frost heave and thawing settlement caused by water migration towards the freezing front and ice lens development is widespread in the alpine meadow area of the southeast QinghaiTibet Plateau(QTP). A laboratory...Highway frost heave and thawing settlement caused by water migration towards the freezing front and ice lens development is widespread in the alpine meadow area of the southeast QinghaiTibet Plateau(QTP). A laboratory experiment on a highway reconstruction and expansion project in the QTP was carried out in this work to analyze the effects of fine particle content, initial water content, and the number of freeze-thaw cycles(FTCs) on frost depth, temperature gradient(Grad T), total water intake, and water intake flux. Based on the results of the laboratory experiment, a modified model of migration potential related to fine particle content, freeze-thaw history, and freezing time was established. The results show that, with the increase of fine particle content, the frost depth of soil decreases, the curve of total water intake over time is transformed from an Sshape to an arch, and the curve of water intake flux over time is transformed from a peak shape to descending shape. The variation trend of migration potential with freezing time and the freeze-thaw history is the same as that of water intake flux with freezing time and freeze-thaw history. The variation trend of soil intake flux can be used as a reference to determine the variation trend of soil migration potential. This study provides a reference for the design and construction of highway subgrade in the alpine meadow area of the QTP.展开更多
BACKGROUND: The first successful pregnancy from a frozen-thawed embryo transfer (FTET) was reported in 1983 and after more than three decades, significant changes have been introduced into clinical practice. OBJECTIVE...BACKGROUND: The first successful pregnancy from a frozen-thawed embryo transfer (FTET) was reported in 1983 and after more than three decades, significant changes have been introduced into clinical practice. OBJECTIVE: To compare endometrial preparation for frozen thawed embryo transfer (FTET) in supplemented natural cycle (NC) by hCG (human chorionic gonadotropin) versus HRT (hormonal replacement therapy) by estrogen and progesterone in regularly cycling women. METHODS: A prospective trial was conducted on 40 patients that were divided into two treatment groups. The first group underwent endometrial preparation by supplemented natural cycle by HCG, and the second group underwent endometrial preparation by HRT (estrogen and progesterone). RESULTS: No significant difference was revealed between the two groups regarding ongoing clinical pregnancy rate. CONCLUSION: This study concluded that there is no significant difference in clinical pregnancy rate between the two methods of endometrial preparation for frozen thawed embryo transfer;supplemented natural cycle by hCG or HRT by estrogen and progesterone, in regularly cycling women.展开更多
基金the National Natural Science Foundation of China (NSFC)(Grant Nos.U22A20596 and 41771066)the Science and Technology Project of Qinghai-Tibet Railway Company (QZ2021-G03)。
文摘As a widely-applied engineering material in cold regions, the frozen subgrade soils are usually subjected to seismic loading, which are also dramatically influenced by the freeze-thaw(F-T)cycles due to the varying temperature. A series of dynamic cyclic triaxial experiments were conducted through a cryogenic triaxial apparatus for exploring the influences of F-T cycles on the dynamic mechanical properties of frozen subgrade clay.According to the experimental results of frozen clay at the temperature of-10℃, the dynamic responses and microstructure variation at different times of F-T cycles(0, 1, 5, and 20 cycles) were explored in detail.It is experimentally demonstrated that the dynamic stress-strain curves and dynamic volumetric strain curves of frozen clay are significantly sparse after 20F-T cycles. Meanwhile, the cyclic number at failure(Nf) of the frozen specimen reduces by 89% after 20freeze-thaw cycles at a low ratio of the dynamic stress amplitude. In addition, with the increasing F-T cycles,the axial accumulative strain, residual deformation,and the value of damage variable of frozen clay increase, while the dynamic resilient modulus and dynamic strength decrease. Finally, the influence of the F-T cycles on the failure mechanisms of frozen clay was discussed in terms of the microstructure variation. These studies contribute to a better understanding of the fundamental changes in the dynamic mechanical of frozen soils exposed to F-T cycles in cold and seismic regions.
基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant No.2018D12National Natural Science Foundation of Heilongjiang Province under Grant No.E 2016045+1 种基金National Natural Science Foundation of China under Grant No.5137816451508140
文摘Using a new low-temperature dynamic triaxial apparatus, the influence law of freezing-thawing cycles on clay shear strength is studied. In this research, the concept of correction coefficients of freezing-thawing cycles on clay static strength, cohesion and internal friction angles is proposed, and the change patterns, correction curves and regressive formulae of clay static strength, cohesion and internal friction angles under freezing-thawing cycles are given. The test results indicate that with increasing numbers of freezing-thawing cycles, the clay static strength and cohesion decrease exponentially but the internal friction angle increases exponentially. The performance of static strength, cohesion and internal friction angles are different with increasing numbers of freezing-thawing cycles, i.e., the static strength decreases constantly until about 30% of the initial static strength prior to the freezing-thawing cycling and then stays basically stable. After 5-7 freezing-thawing cycles, the cohesion decreases gradually to about 70% of the initial cohesion. The internal friction angle increases about 20% after the first freezing-thawing cycle, then increases gradually close to a stable value which is an increase of about 40% of the internal friction angle. The freezing-thawing process can increase the variation of the density of the soil samples; therefore, strict density discreteness standards of frozen soil sample preparation should be established to ensure the reliability of the test results.
文摘This study aimed to assess pregnancy outcomes after high-quality D5- and D6-blastocyst transfer in frozen cycles of in vitro fertilization and embryo transfer and to further evaluate whether there was a difference in blastocyst development potentials with different developmental speeds and in pregnancy outcomes. A retrospective analysis was conducted to analyze 247 frozen cycles in our center from September 2015 to July 2017, which were divided into two groups: a D5-FET group with 193 cycles of D5-blastocyst transfer, and a D6-FET group with 54 cycles of D6-blastocyst transfer. Hormone replacement method was utilized to prepare frozen-cycle endometria. Pregnancy outcomes were analyzed and compared between these two groups. The mean ages of the two groups were 31.45 ± 4.43 years and 31.98 ± 4.84 years, respectively, with no statistically significant differences (P > 0.05). The difference in the endometrial thickness during transfer was also not statistically significant. The implantation rate in the D5-FET group was 60.13%, significantly higher than that in the D6-FET group (31.58%, P P < 0.05). No statistically significant differences were found in the abortion rate and ectopic pregnancy rate between the two groups. The implantation, biochemical pregnancy, and clinical pregnancy rates of the blastocyst D5 were all superior to those of the blastocyst D6. In clinics, therefore, D5-blastocyst transfer could be prioritized for embryo transfer.
基金The research is supported by the Natural Science Foundation of Anhui Province(Grant No.1908085QE242)the Fundamental Research Funds for the Central Universities(Grant No.JZ2021HGTB0097)the Natural Science Foundation of China(NSFC)(Grant No.51908175).The financial support is gratefully acknowledged.
文摘Soil slope stability in seasonally frozen regions is a challenging problem for geotechnical engineers.The freezethaw process of soil slope caused by the temperature fluctuation increases the difficulty in predicting the slope stability because the soil property is influenced by the freeze-thaw cycle.In addition,the frozen soil,which has ice crystal,ice lens and experienced freeze-thaw process,could present stronger heterogeneity.Previous research has not investigated the combined effect of soil heterogeneity and freeze-thaw cycle.This paper studies the influence of soil heterogeneity on the stability of frozen soil slope under freeze-thaw cycles.The local average subdivision(LAS)is utilized to model the soil heterogeneity.A typical slope geometry has been chosen and analysed as an illustrative example and the strength reduction method is used to calculate the factor of safety(FOS)of slope.It has been found that when the temperature is steady,the FOS of the frozen soil slope is influenced by the spatial variability of the thermal conductivity,but the influence is not significant.When the standard deviation and the SOF of the thermal conductivity increase,the mean of the FOS is equal to the FOS of the homogeneous case and the standard deviation of the FOS also increases.After the frozen soil goes through freeze-thaw process,the FOS of the frozen soil slope decreases due to the reduction in the cohesion and the internal friction angle caused by the freeze-thaw cycles.Furthermore,the decreasing ratio of the FOS becomes more scattered after the 5th freeze-thaw cycle compared to that of the FOS after the 1st freeze-thaw cycle.The larger variability of the FOS could induce inaccuracy in the prediction of the frozen soil slope stability.
文摘Objectives:To assess the clinical outcomes of frozen-thawed blastocysts transfer in natural and hormonally controlled cycles.Methods:A retrospective analysis of natural and hormonally controlled cycle for 246 frozen-thawed blastocyst transfer cycles,the clinical pregnancy rate,implantation rate,early abortion rate were compared.Results:Of the 192 hormonally controlled cycles,the cancel rate,clinical pregnancy rate per ET,implantation rate and abortion rate were 7.3%(14/192),53.9%(96/178),38.8%(131/338)and 11.5%(11/96)respectively,whereas in 54 natural cycles,these rates were 16.7%(9/54),68.9%(31/45),52.9%(45/85)and 16.1%(5/31)respectively.There was no significant difference between the two groups with regard to the clinical pregnancy and abortion rate per ET,but the cancel rate and implantation rate were higher in natural cycles.However,the pregnancy and implantation rates of patients without PCOS in hormonal control cycles(57.2%,40.9%)were similar with those in natural cycles(P>0.05).Conclusion:These findings suggested that both hormonally controlled and natural cycles had similar pregnancy outcomes in frozen-thawed blastocysts transfer.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.310821173701)Natural Science Basic Research Program of Shaanxi(Grant No.2020JQ-379)。
文摘Highway frost heave and thawing settlement caused by water migration towards the freezing front and ice lens development is widespread in the alpine meadow area of the southeast QinghaiTibet Plateau(QTP). A laboratory experiment on a highway reconstruction and expansion project in the QTP was carried out in this work to analyze the effects of fine particle content, initial water content, and the number of freeze-thaw cycles(FTCs) on frost depth, temperature gradient(Grad T), total water intake, and water intake flux. Based on the results of the laboratory experiment, a modified model of migration potential related to fine particle content, freeze-thaw history, and freezing time was established. The results show that, with the increase of fine particle content, the frost depth of soil decreases, the curve of total water intake over time is transformed from an Sshape to an arch, and the curve of water intake flux over time is transformed from a peak shape to descending shape. The variation trend of migration potential with freezing time and the freeze-thaw history is the same as that of water intake flux with freezing time and freeze-thaw history. The variation trend of soil intake flux can be used as a reference to determine the variation trend of soil migration potential. This study provides a reference for the design and construction of highway subgrade in the alpine meadow area of the QTP.
文摘BACKGROUND: The first successful pregnancy from a frozen-thawed embryo transfer (FTET) was reported in 1983 and after more than three decades, significant changes have been introduced into clinical practice. OBJECTIVE: To compare endometrial preparation for frozen thawed embryo transfer (FTET) in supplemented natural cycle (NC) by hCG (human chorionic gonadotropin) versus HRT (hormonal replacement therapy) by estrogen and progesterone in regularly cycling women. METHODS: A prospective trial was conducted on 40 patients that were divided into two treatment groups. The first group underwent endometrial preparation by supplemented natural cycle by HCG, and the second group underwent endometrial preparation by HRT (estrogen and progesterone). RESULTS: No significant difference was revealed between the two groups regarding ongoing clinical pregnancy rate. CONCLUSION: This study concluded that there is no significant difference in clinical pregnancy rate between the two methods of endometrial preparation for frozen thawed embryo transfer;supplemented natural cycle by hCG or HRT by estrogen and progesterone, in regularly cycling women.
