The aim of this study was to examine and quantify the growth of extension twins and the associated texture change in an extruded AM30 magnesium alloy during compression along the extrusion direction. Three stages of t...The aim of this study was to examine and quantify the growth of extension twins and the associated texture change in an extruded AM30 magnesium alloy during compression along the extrusion direction. Three stages of twin growth with increasing strain were observed due to twin-dislocation interactions, together with increasing texture volume fraction of {1210}〈0001〉 and {01- 10}〈0001〉 components. Stage I was characterized by a relatively slow and gradually accelerating growth. A steady-state twin growth was reached in stage II, where the twin width increased linearly with increasing strain. Stage III twin growth became decelerated, exhibiting a plateau-like character.展开更多
One in three monochorionic twins may develop complications during pregnancy. Monochorionic twins, especially monochorionic diamniotic (MCDA), present specific problems caused by the presence of interfetal placental an...One in three monochorionic twins may develop complications during pregnancy. Monochorionic twins, especially monochorionic diamniotic (MCDA), present specific problems caused by the presence of interfetal placental anastomoses. The first critical step in the management of MCDA twins is identification in the first trimester. Secondly, close follow-up every 2 weeks is mandatory to allow early diagnosis and timely treatment of twin-twin transfusion syndrome. Other potentially severe complications include selective fetal growth restriction, twin anemia polycythemia syndrome or single fetal death. Thirdly, a correct differential diagnosis is critical to establish the best therapy. This may represent a clinical challenge since MCDA twin complications often overlap. A simple diagnostic algorithm may be of great help to establish the right diagnosis and management option. In this review we summarize the main steps for the clinical follow-up, differential diagnosis, and targeted management of MCDA twins complications.展开更多
Previously, synthetic hexagonal bismuth sulfide iodide (polar space group P63, a = 15.629(3) ?, c = 4.018(1) ?, Z = 2) has been described by the rather unsatisfactory fractional formula Bi19/3IS9 [1] 08D0C9EA79F9BACE1...Previously, synthetic hexagonal bismuth sulfide iodide (polar space group P63, a = 15.629(3) ?, c = 4.018(1) ?, Z = 2) has been described by the rather unsatisfactory fractional formula Bi19/3IS9 [1] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310037003600350038003400370039000000 -[3] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310037003600350038003400370036000000 . A redetermination of the structure using old but reliable photographic intensity data indicated the presence of additional split positions and reduced atomic occupancies. From the observed pattern of this “averaged” structure a consistent model of a superstructure with lattice parameters of a' = √13·a = 56.35(1) ?, c' = c, and a formula Bi5-x(Bi2S3)39I12S emerged, with 2 formula units in a cell of likewise P63 space group. Structural modulation may be provoked by the space the lone electron pair of Bi requires. When Bi on the 0, 0, z position of the “averaged” cell is transferred to two general six-fold sites and one unoccupied twofold one of the super-cell, more structural stability is guaranteed due to compensation of its basal plane dipole momentum. Owing to the limited intensity data available, more details of the superstructure are not accessible yet. Some physical properties and solar cell application are discussed together with suggestions of ambient temperature synthesis routes of c-axis oriented nano-rod sheets.展开更多
Upon non-equilibrium solidifications, dendrite growth, generally as precursor of as-solidified structures,has severe effects on subsequent phase transformations. Considering synergy of thermodynamics and kinetics cont...Upon non-equilibrium solidifications, dendrite growth, generally as precursor of as-solidified structures,has severe effects on subsequent phase transformations. Considering synergy of thermodynamics and kinetics controlling interface migration and following conservation of heat flux in solid temperature field, a more flexible modeling for the dendrite growth is herein developed for multi-component alloys,where, two inherent problems, i.e. correlation between thermodynamics and kinetics(i.e. the thermokinetic correlation), and theoretical connection between dendrite growth model and practical processing,have been successfully solved. Accordingly, both the thermodynamic driving force G and the effective kinetic energy barrier Qeffhave been found to control quantitatively the dendrite growth(i.e. especially the growth velocity, V), as reflected by the thermo-kinetic trade-off. Compared with previous models, it is the thermo-kinetic correlation that guarantees quantitative connection between the practical processing parameters and the current theoretical framework, as well as more reasonable description for kinetic behaviors involved. Applied to the vertical twin-roll casting(VTC), the present model, realizes a good prediction for kissing points, which influences significantly alloy design and processing optimization.This work deduces quantitatively the thermo-kinetic correlation controlling the dendrite growth, and by proposing the parameter-triplets(i.e. G-Qeff-V), further opens a new beginning for connecting solidification theories with industrial applications, such as the VTC.展开更多
The rate of multiple pregnancy is increasing, mainly because of the widespread use of assisted reproduction techniques and families’ desire for twins. Twin pregnancy accounts for a higher risk of chromosomal abnormal...The rate of multiple pregnancy is increasing, mainly because of the widespread use of assisted reproduction techniques and families’ desire for twins. Twin pregnancy accounts for a higher risk of chromosomal abnormalities, structural malformations, and neonatal adverse events than singleton pregnancy. The presence of artery-vein anastomoses, unbalanced placenta sharing, and abnormal cord insertion in monochorionic twins is associated with twin complications such as twin-to-twin transfusion syndrome, selective intrauterine growth restriction, and twin anemia polycythemia sequence. Although many guidelines and studies have established and improved the processes about the antenatal surveillance and management of twin pregnancy, they also raise more controversies and challenges. This review aims to highlight the international consensus on the antenatal care of twin pregnancies and analyze the controversies and predicaments based on the published International Federation of Gynecology and Obstetrics guidelines and research.展开更多
High-quality single crystals of Bi_(2)WO_(6) are grown using a flux method.With different flux growth recipes,we aim to control the crystallization temperature to be lower and higher than the ferroelectric transition ...High-quality single crystals of Bi_(2)WO_(6) are grown using a flux method.With different flux growth recipes,we aim to control the crystallization temperature to be lower and higher than the ferroelectric transition temperature,resulting in mono-domain and multi-domain Bi_(2)WO_(6) crystals,respectively.Abundant ferroelastic orthorhombic twin domains are observed in the multi-domain crystals under an optical microscope.PFM studies unveil the 90°polarization change across those ferroelastic domain walls,as well as the absence of 180°ferroelectric domains in the as-grown multi-domain crystals,indicating a high energy cost of 180°ferroelectric domains.Moreover,a 45°tilt of the 90°ferroelectric domain walls is discovered,and this tilt creates a new type of charged 90°ferroelectric walls,which have not been observed in other bulk ferroelectrics.展开更多
In this work,we carried out three-dimensional(3D)atomic-scale study on the growth characteristics of{10-12}twin in magnesium(Mg).The study was performed by MD simulations on Mg single crystals with an initial twin nuc...In this work,we carried out three-dimensional(3D)atomic-scale study on the growth characteristics of{10-12}twin in magnesium(Mg).The study was performed by MD simulations on Mg single crystals with an initial twin nucleus structures.A detailed atomistic analysis reveals that a stabilized 3D{10-12}twin nucleus is bounded by basal/prismatic(BP)interfaces,prismatic/basal(PB)interfaces,and{10-11}interfaces.Later,a{10-12}twin boundary(TB)occurs at the junction of the BP and PB interface with the growth of the twin nucleus.In this process,two twinning mechanisms are involved:a pure-shuffle mechanism in which{10-11}interface migration along the[11-20]direction is mediated by atomic shuffle,and a glide-shuffle mechanism in which BP/PB and{10-12}TB movements are realized by the migration of disconnections along the relevant interfaces.In addition,we systematically investigate the stress state associated with the activation of twinning,aiming to discover the intrinsic relationship of the elastic stress field to twin growth on an atomic scale.The results suggest that the elastic stress in the matrix is an important driving force for twin growth,much similar to what stress does for a crack.In addition,it is rather remarkable that the{10-11}interface has a greater ability to migrate than other interfaces,and this is thought to be a main factor for the rapid growth of a{10-12}twin.展开更多
Deformation behavior as well as microstructural evolutions of a rolled AZ31 magnesium alloy with and without pre-existing extension twins were studied using compression tests which performed along different orientatio...Deformation behavior as well as microstructural evolutions of a rolled AZ31 magnesium alloy with and without pre-existing extension twins were studied using compression tests which performed along different orientations at a temperature range of 25–350 ℃. The results implied that the initial texture not only influence the evolution of flow stress, but also change the size and fraction of recrystallized grains.In contrast to samples parallel to rolling and transverse directions, compression along normal direction resulted in a respectful softening at 150 ℃. The largest size and fraction of new grains at 250 ℃ were recorded after deformation along rolling direction, while the maximum flow softening was observed during deformation along normal direction. The anisotropy in microstructural evolutions was still retained at 350 ℃. Pre-existing twins could reduce the anisotropy of material in respect of flow stress as well as DRX progression, where TD sample showed the lowest DRX fraction at 250 ℃. Quaternion misorientation data obtained from EBSD analysis of pretwinned material implied that initial texture could not significantly influence final texture. A different misorientation distribution was realized after deformation of pretwinned material along ND and RD directions.展开更多
Hexagonal and triangular monodisperse Fe3O4 nanosheets have been synthesized via a two-step microemulsion solvothermal approach in which uniform Fe3O4 nanoparticles are first prepared and then these hydrophobic nanocr...Hexagonal and triangular monodisperse Fe3O4 nanosheets have been synthesized via a two-step microemulsion solvothermal approach in which uniform Fe3O4 nanoparticles are first prepared and then these hydrophobic nanocrystals are dispersed in a uniform microemulsion environment as ＂seeds＂ for further re-growth through a secondary solvothermal process. The growth of anisotropic morphologies has been explained by the presence and orientation of twin planes in the face-centered cubic Fe3O4 which direct the shape of the growing particles. In particular, reentrant grooves resulting from twin planes are favorable sites for the addition of adatoms, leading to anisotropic growth. Triangular nanosheets are believed to contain one twin face which directs the growth of the primary particles in two dimensions. Hexagonal nanosheets are believed to contain two parallel planes that allow the growth edges to regenerate one another. The growth mechanism is evidenced by the analysis of high-resolution transmission electron microscopy （HRTEM） results and the as-prepared Fe3O4 nanoparticles have been shown to be an effective catalyst in the synthesis of quinoxaline.展开更多
Martensites distributed along the austenite grain boundaries and twin boundaries have been examined in Fe-C,Fe-Ni-C and Fe-Cr-Mn-Mo-C alloys.The martensites may nucleate preferentially and grow easily along these boun...Martensites distributed along the austenite grain boundaries and twin boundaries have been examined in Fe-C,Fe-Ni-C and Fe-Cr-Mn-Mo-C alloys.The martensites may nucleate preferentially and grow easily along these boundaries.In the mixed martensites,the preferentially formed one is plate or butterfly martensite展开更多
BACKGROUND A twin pregnancy can carry greater risks than singleton pregnancies.About 60 in 100 twin pregnancies result in spontaneous birth before 37 wk,which is associated with several complications in the premature ...BACKGROUND A twin pregnancy can carry greater risks than singleton pregnancies.About 60 in 100 twin pregnancies result in spontaneous birth before 37 wk,which is associated with several complications in the premature babies.Clinical detection of biomarkers may help to predict the possibility of premature birth so that corresponding interventions can be given to the pregnant women in a timely manner,in order to reduce the risk of preterm birth and improve the outcomes of the newborn infants.AIM To explore the clinical value of transvaginal ultrasound measurement of cervical length combined with insulin-like growth factor binding protein-1(IGFBP-1)hyperphosphorylation in cervical secretions as predictors of preterm delivery in twin pregnancies.METHODS A total of 254 pregnant women with twin pregnancies,who were admitted to Hainan General Hospital and underwent maternity examination,were selected as the study subjects from January 2015 to December 2018.All participants received transvaginal ultrasound measurement of cervical length and phosphorylated IGFBP-1(phIGFBP-1)test between 24 and 34 wk gestation.The pregnancy outcomes were analyzed.RESULTS Of the women with a positive phIGFBP-1 test result,preterm birth rate was higher in those with a cervical length≤25 mm than those with a cervical length>25 mm(all P<0.05).Similarly,in women with a negative phIGFBP-1 test result,preterm birth rate was higher in those with a cervical length≤25 mm than those with a cervical length>25 mm(all P<0.05).The sensitivity,specificity,and positive and negative predictive values of the phIGFBP-1 test combined with the cervical length test were 95.71%,91.21%,95.12%and 92.22%,respectively,for the prediction of preterm birth.CONCLUSION Cervical length combined with phIGFBP-1 tests is of value for the prediction of outcomes of preterm delivery in twin pregnancies.展开更多
Background The intrauterine environment has a profound and long-lasting influence on the health of the offspring.However,its impact on the postnatal catch-up growth of twin children remains unclarified.Therefore,this ...Background The intrauterine environment has a profound and long-lasting influence on the health of the offspring.However,its impact on the postnatal catch-up growth of twin children remains unclarified.Therefore,this study aimed to explore the maternal factors in pregnancy associated with twin offspring growth.Methods This study included 3142 live twin children born to 1571 mothers from the Beijing Birth Cohort Study conducted from 2016 to 2021 in Beijing,China.Original and corrected weight-for-age standard deviation scores of the twin offspring from birth to 36 months of age were calculated according to the World Health Organization Child Growth Standards.The corresponding weight trajectories were identified by the latent trajectory model.Maternal factors in pregnancy associated with the weight trajectories of the twin offspring were examined after adjustment for potential confounders.Results Five weight trajectories of the twin children were identified,with 4.9%(154/3142)exhibiting insufficient catch-up growth,30.6%(961/3142),and 46.8%(1469/3142)showing adequate catch-up growth from different birth weights,and 15.0%(472/3142)and 2.7%(86/3142)showing various degrees of excessive catch-up growth.Maternal short stature[adjusted odds ratio(OR)=0.691,95%confidence interval(CI)=0.563–0.848,P=0.0004]and lower total gestational weight gain(GWG)(adjusted OR=0.774,95%CI=0.616–0.972,P=0.03)were associated with insufficient catch-up growth of the offspring.Maternal stature(adjusted OR=1.331,95%CI=1.168–1.518,P<0.001),higher pre-pregnancy body mass index(BMI)(adjusted OR=1.230,95%CI=1.090–1.387,P<0.001),total GWG(adjusted OR=1.207,95%CI=1.068–1.364,P=0.002),GWG rate(adjusted OR=1.165,95%CI=1.027–1.321,P=0.02),total cholesterol(TC)(adjusted OR=1.150,95%CI=1.018–1.300,P=0.03)and low-density lipoprotein-cholesterol(LDL-C)(adjusted OR=1.177,95%CI=1.041–1.330)in early pregnancy were associated with excessive growth of the offspring.The pattern of weight trajectories was similar between monochorionic and dichorion展开更多
Objective: To investigate whether the fetal gender affects the incidence of pre-eclampsia (PE) and fetal growth restriction (FGR) in singleton and twin pregnancies.Methods: This was a 10-year single-center, retrospect...Objective: To investigate whether the fetal gender affects the incidence of pre-eclampsia (PE) and fetal growth restriction (FGR) in singleton and twin pregnancies.Methods: This was a 10-year single-center, retrospective, cohort study from January 2009 to January 2019. A total of 57,129 singleton and 3699 twin pregnancies aged between 18-55 years old were recruited at the Third Affiliated Hospital of Guangzhou Medical University, China. We used multivariable logistic regression to analyze the effect of fetal gender on the incidence of PE and FGR.Results: In singleton pregnancies, the incidence rates of PE and FGR with a female fetus were higher than those with a male fetus (6.4% (1713/26,793)vs. 5.9% (1803/30,336),P < 0.05 and 3.5% (932/26,793)vs. 2.4% (745/30,336),P < 0.05, respectively). A female fetus was an independent risk factor for either PE or FGR (adjusted odds ratio: 1.169 or 1.563;95% confidence interval: 1.036-1.319 or 1.349-1.810, respectively). In twin pregnancies, the incidence of early-onset PE was greater in pregnancies with two females compared with two males or one male plus one female (4.6% (46/1003)vs. 4.1% (54/1305)vs. 2.4% (33/1391),P < 0.05). Female-female twins was an independent risk factor for PE (adjusted odds ratio: 1.367, 95% confidence interval: 1.011-1.849), especially early-onset PE.Conclusion: The female fetus was associated with PE in both singleton and twin pregnancies and was also a risk factor of FGR in singleton pregnancies.展开更多
基金the Natural Sciences and Engineering Research Council of Canada(NSERC)AUTO21 Networks of Centres of Excellence of Canada for providing financial support
文摘The aim of this study was to examine and quantify the growth of extension twins and the associated texture change in an extruded AM30 magnesium alloy during compression along the extrusion direction. Three stages of twin growth with increasing strain were observed due to twin-dislocation interactions, together with increasing texture volume fraction of {1210}〈0001〉 and {01- 10}〈0001〉 components. Stage I was characterized by a relatively slow and gradually accelerating growth. A steady-state twin growth was reached in stage II, where the twin width increased linearly with increasing strain. Stage III twin growth became decelerated, exhibiting a plateau-like character.
文摘One in three monochorionic twins may develop complications during pregnancy. Monochorionic twins, especially monochorionic diamniotic (MCDA), present specific problems caused by the presence of interfetal placental anastomoses. The first critical step in the management of MCDA twins is identification in the first trimester. Secondly, close follow-up every 2 weeks is mandatory to allow early diagnosis and timely treatment of twin-twin transfusion syndrome. Other potentially severe complications include selective fetal growth restriction, twin anemia polycythemia syndrome or single fetal death. Thirdly, a correct differential diagnosis is critical to establish the best therapy. This may represent a clinical challenge since MCDA twin complications often overlap. A simple diagnostic algorithm may be of great help to establish the right diagnosis and management option. In this review we summarize the main steps for the clinical follow-up, differential diagnosis, and targeted management of MCDA twins complications.
文摘Previously, synthetic hexagonal bismuth sulfide iodide (polar space group P63, a = 15.629(3) ?, c = 4.018(1) ?, Z = 2) has been described by the rather unsatisfactory fractional formula Bi19/3IS9 [1] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310037003600350038003400370039000000 -[3] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310037003600350038003400370036000000 . A redetermination of the structure using old but reliable photographic intensity data indicated the presence of additional split positions and reduced atomic occupancies. From the observed pattern of this “averaged” structure a consistent model of a superstructure with lattice parameters of a' = √13·a = 56.35(1) ?, c' = c, and a formula Bi5-x(Bi2S3)39I12S emerged, with 2 formula units in a cell of likewise P63 space group. Structural modulation may be provoked by the space the lone electron pair of Bi requires. When Bi on the 0, 0, z position of the “averaged” cell is transferred to two general six-fold sites and one unoccupied twofold one of the super-cell, more structural stability is guaranteed due to compensation of its basal plane dipole momentum. Owing to the limited intensity data available, more details of the superstructure are not accessible yet. Some physical properties and solar cell application are discussed together with suggestions of ambient temperature synthesis routes of c-axis oriented nano-rod sheets.
基金supported financially by the National Key R&D Program of China (Nos. 2017YFB0703001 and 2017YFB0305100)the Natural Science Foundation of China (Nos. 51790483,51790481,51134011,51431008 and 51671075)+3 种基金the Fundamental Research Funds for the Central Universities (No. 3102017jc01002)the Research Fund of the State Key Laboratory of Solidification Processing (Nos. 2019-TZ-01 and 2019-BJ-02)the China Postdoctoral Science Foundation (No. 2018M643729and 2019T120942)the Natural Science Basic Research Plan in Shaanxi Province of China(No. 2019JQ-091)
文摘Upon non-equilibrium solidifications, dendrite growth, generally as precursor of as-solidified structures,has severe effects on subsequent phase transformations. Considering synergy of thermodynamics and kinetics controlling interface migration and following conservation of heat flux in solid temperature field, a more flexible modeling for the dendrite growth is herein developed for multi-component alloys,where, two inherent problems, i.e. correlation between thermodynamics and kinetics(i.e. the thermokinetic correlation), and theoretical connection between dendrite growth model and practical processing,have been successfully solved. Accordingly, both the thermodynamic driving force G and the effective kinetic energy barrier Qeffhave been found to control quantitatively the dendrite growth(i.e. especially the growth velocity, V), as reflected by the thermo-kinetic trade-off. Compared with previous models, it is the thermo-kinetic correlation that guarantees quantitative connection between the practical processing parameters and the current theoretical framework, as well as more reasonable description for kinetic behaviors involved. Applied to the vertical twin-roll casting(VTC), the present model, realizes a good prediction for kissing points, which influences significantly alloy design and processing optimization.This work deduces quantitatively the thermo-kinetic correlation controlling the dendrite growth, and by proposing the parameter-triplets(i.e. G-Qeff-V), further opens a new beginning for connecting solidification theories with industrial applications, such as the VTC.
基金supported by the National Key Research and Development Plan(2018YFC1002900)the Research and Development Projects in Key Areas of Guangdong Province(2019B020227001)。
文摘The rate of multiple pregnancy is increasing, mainly because of the widespread use of assisted reproduction techniques and families’ desire for twins. Twin pregnancy accounts for a higher risk of chromosomal abnormalities, structural malformations, and neonatal adverse events than singleton pregnancy. The presence of artery-vein anastomoses, unbalanced placenta sharing, and abnormal cord insertion in monochorionic twins is associated with twin complications such as twin-to-twin transfusion syndrome, selective intrauterine growth restriction, and twin anemia polycythemia sequence. Although many guidelines and studies have established and improved the processes about the antenatal surveillance and management of twin pregnancy, they also raise more controversies and challenges. This review aims to highlight the international consensus on the antenatal care of twin pregnancies and analyze the controversies and predicaments based on the published International Federation of Gynecology and Obstetrics guidelines and research.
基金supported by the Center for Quantum Materials Synthesis(cQMS)funded by the Gordon and Betty Moore Foundation’s EPiQS initiative through grant GBMF10104by Rutgers University.
文摘High-quality single crystals of Bi_(2)WO_(6) are grown using a flux method.With different flux growth recipes,we aim to control the crystallization temperature to be lower and higher than the ferroelectric transition temperature,resulting in mono-domain and multi-domain Bi_(2)WO_(6) crystals,respectively.Abundant ferroelastic orthorhombic twin domains are observed in the multi-domain crystals under an optical microscope.PFM studies unveil the 90°polarization change across those ferroelastic domain walls,as well as the absence of 180°ferroelectric domains in the as-grown multi-domain crystals,indicating a high energy cost of 180°ferroelectric domains.Moreover,a 45°tilt of the 90°ferroelectric domain walls is discovered,and this tilt creates a new type of charged 90°ferroelectric walls,which have not been observed in other bulk ferroelectrics.
基金The authors are grateful for the support from the National Natural Science Foundation of China(No.51471038)the Fundamental Research Funds for the Central Universities(No.2018CDPTCG0001/42)the National special support program for high-level personnel recruitment.
文摘In this work,we carried out three-dimensional(3D)atomic-scale study on the growth characteristics of{10-12}twin in magnesium(Mg).The study was performed by MD simulations on Mg single crystals with an initial twin nucleus structures.A detailed atomistic analysis reveals that a stabilized 3D{10-12}twin nucleus is bounded by basal/prismatic(BP)interfaces,prismatic/basal(PB)interfaces,and{10-11}interfaces.Later,a{10-12}twin boundary(TB)occurs at the junction of the BP and PB interface with the growth of the twin nucleus.In this process,two twinning mechanisms are involved:a pure-shuffle mechanism in which{10-11}interface migration along the[11-20]direction is mediated by atomic shuffle,and a glide-shuffle mechanism in which BP/PB and{10-12}TB movements are realized by the migration of disconnections along the relevant interfaces.In addition,we systematically investigate the stress state associated with the activation of twinning,aiming to discover the intrinsic relationship of the elastic stress field to twin growth on an atomic scale.The results suggest that the elastic stress in the matrix is an important driving force for twin growth,much similar to what stress does for a crack.In addition,it is rather remarkable that the{10-11}interface has a greater ability to migrate than other interfaces,and this is thought to be a main factor for the rapid growth of a{10-12}twin.
基金supported in part by the National Science Center (Poland) under grant No. 2018/31/B/ST8/00942。
文摘Deformation behavior as well as microstructural evolutions of a rolled AZ31 magnesium alloy with and without pre-existing extension twins were studied using compression tests which performed along different orientations at a temperature range of 25–350 ℃. The results implied that the initial texture not only influence the evolution of flow stress, but also change the size and fraction of recrystallized grains.In contrast to samples parallel to rolling and transverse directions, compression along normal direction resulted in a respectful softening at 150 ℃. The largest size and fraction of new grains at 250 ℃ were recorded after deformation along rolling direction, while the maximum flow softening was observed during deformation along normal direction. The anisotropy in microstructural evolutions was still retained at 350 ℃. Pre-existing twins could reduce the anisotropy of material in respect of flow stress as well as DRX progression, where TD sample showed the lowest DRX fraction at 250 ℃. Quaternion misorientation data obtained from EBSD analysis of pretwinned material implied that initial texture could not significantly influence final texture. A different misorientation distribution was realized after deformation of pretwinned material along ND and RD directions.
基金This work was supported by the National Natural Science Foundation ol： China （Nos. 20901069, 50873093, and 21271156） and the Henan Province Scientific and Technological Research Program （No. 092102210054）.
文摘Hexagonal and triangular monodisperse Fe3O4 nanosheets have been synthesized via a two-step microemulsion solvothermal approach in which uniform Fe3O4 nanoparticles are first prepared and then these hydrophobic nanocrystals are dispersed in a uniform microemulsion environment as ＂seeds＂ for further re-growth through a secondary solvothermal process. The growth of anisotropic morphologies has been explained by the presence and orientation of twin planes in the face-centered cubic Fe3O4 which direct the shape of the growing particles. In particular, reentrant grooves resulting from twin planes are favorable sites for the addition of adatoms, leading to anisotropic growth. Triangular nanosheets are believed to contain one twin face which directs the growth of the primary particles in two dimensions. Hexagonal nanosheets are believed to contain two parallel planes that allow the growth edges to regenerate one another. The growth mechanism is evidenced by the analysis of high-resolution transmission electron microscopy （HRTEM） results and the as-prepared Fe3O4 nanoparticles have been shown to be an effective catalyst in the synthesis of quinoxaline.
文摘Martensites distributed along the austenite grain boundaries and twin boundaries have been examined in Fe-C,Fe-Ni-C and Fe-Cr-Mn-Mo-C alloys.The martensites may nucleate preferentially and grow easily along these boundaries.In the mixed martensites,the preferentially formed one is plate or butterfly martensite
文摘BACKGROUND A twin pregnancy can carry greater risks than singleton pregnancies.About 60 in 100 twin pregnancies result in spontaneous birth before 37 wk,which is associated with several complications in the premature babies.Clinical detection of biomarkers may help to predict the possibility of premature birth so that corresponding interventions can be given to the pregnant women in a timely manner,in order to reduce the risk of preterm birth and improve the outcomes of the newborn infants.AIM To explore the clinical value of transvaginal ultrasound measurement of cervical length combined with insulin-like growth factor binding protein-1(IGFBP-1)hyperphosphorylation in cervical secretions as predictors of preterm delivery in twin pregnancies.METHODS A total of 254 pregnant women with twin pregnancies,who were admitted to Hainan General Hospital and underwent maternity examination,were selected as the study subjects from January 2015 to December 2018.All participants received transvaginal ultrasound measurement of cervical length and phosphorylated IGFBP-1(phIGFBP-1)test between 24 and 34 wk gestation.The pregnancy outcomes were analyzed.RESULTS Of the women with a positive phIGFBP-1 test result,preterm birth rate was higher in those with a cervical length≤25 mm than those with a cervical length>25 mm(all P<0.05).Similarly,in women with a negative phIGFBP-1 test result,preterm birth rate was higher in those with a cervical length≤25 mm than those with a cervical length>25 mm(all P<0.05).The sensitivity,specificity,and positive and negative predictive values of the phIGFBP-1 test combined with the cervical length test were 95.71%,91.21%,95.12%and 92.22%,respectively,for the prediction of preterm birth.CONCLUSION Cervical length combined with phIGFBP-1 tests is of value for the prediction of outcomes of preterm delivery in twin pregnancies.
基金supported by the Scientific Research Common Program of Beijing Municipal Commission of Education(KM202110025007)the National Natural Science Foundation of China(82171671)+1 种基金the National Key Research and Development(2016YFC1000304)Beijing Hospitals Authority’Ascent Plan(DFL20191402).
文摘Background The intrauterine environment has a profound and long-lasting influence on the health of the offspring.However,its impact on the postnatal catch-up growth of twin children remains unclarified.Therefore,this study aimed to explore the maternal factors in pregnancy associated with twin offspring growth.Methods This study included 3142 live twin children born to 1571 mothers from the Beijing Birth Cohort Study conducted from 2016 to 2021 in Beijing,China.Original and corrected weight-for-age standard deviation scores of the twin offspring from birth to 36 months of age were calculated according to the World Health Organization Child Growth Standards.The corresponding weight trajectories were identified by the latent trajectory model.Maternal factors in pregnancy associated with the weight trajectories of the twin offspring were examined after adjustment for potential confounders.Results Five weight trajectories of the twin children were identified,with 4.9%(154/3142)exhibiting insufficient catch-up growth,30.6%(961/3142),and 46.8%(1469/3142)showing adequate catch-up growth from different birth weights,and 15.0%(472/3142)and 2.7%(86/3142)showing various degrees of excessive catch-up growth.Maternal short stature[adjusted odds ratio(OR)=0.691,95%confidence interval(CI)=0.563–0.848,P=0.0004]and lower total gestational weight gain(GWG)(adjusted OR=0.774,95%CI=0.616–0.972,P=0.03)were associated with insufficient catch-up growth of the offspring.Maternal stature(adjusted OR=1.331,95%CI=1.168–1.518,P<0.001),higher pre-pregnancy body mass index(BMI)(adjusted OR=1.230,95%CI=1.090–1.387,P<0.001),total GWG(adjusted OR=1.207,95%CI=1.068–1.364,P=0.002),GWG rate(adjusted OR=1.165,95%CI=1.027–1.321,P=0.02),total cholesterol(TC)(adjusted OR=1.150,95%CI=1.018–1.300,P=0.03)and low-density lipoprotein-cholesterol(LDL-C)(adjusted OR=1.177,95%CI=1.041–1.330)in early pregnancy were associated with excessive growth of the offspring.The pattern of weight trajectories was similar between monochorionic and dichorion
基金National Key R&D Program of China(No. 2016YFC1000405, 2017YFC1001402, 2018YFC1004104, and 2018YFC10029002)National Natural Science Foundation(No. 81830045, 81671533, 81571518, and 81971415)General program of Guangdong province Natural Science Foundation(No. 2020A1515010273)。
文摘Objective: To investigate whether the fetal gender affects the incidence of pre-eclampsia (PE) and fetal growth restriction (FGR) in singleton and twin pregnancies.Methods: This was a 10-year single-center, retrospective, cohort study from January 2009 to January 2019. A total of 57,129 singleton and 3699 twin pregnancies aged between 18-55 years old were recruited at the Third Affiliated Hospital of Guangzhou Medical University, China. We used multivariable logistic regression to analyze the effect of fetal gender on the incidence of PE and FGR.Results: In singleton pregnancies, the incidence rates of PE and FGR with a female fetus were higher than those with a male fetus (6.4% (1713/26,793)vs. 5.9% (1803/30,336),P < 0.05 and 3.5% (932/26,793)vs. 2.4% (745/30,336),P < 0.05, respectively). A female fetus was an independent risk factor for either PE or FGR (adjusted odds ratio: 1.169 or 1.563;95% confidence interval: 1.036-1.319 or 1.349-1.810, respectively). In twin pregnancies, the incidence of early-onset PE was greater in pregnancies with two females compared with two males or one male plus one female (4.6% (46/1003)vs. 4.1% (54/1305)vs. 2.4% (33/1391),P < 0.05). Female-female twins was an independent risk factor for PE (adjusted odds ratio: 1.367, 95% confidence interval: 1.011-1.849), especially early-onset PE.Conclusion: The female fetus was associated with PE in both singleton and twin pregnancies and was also a risk factor of FGR in singleton pregnancies.
