In this work,a morphology transition mode is revealed in ultra-high molecular weight polyethylene(UHMWPE)when stretching at 120℃:moving from the slightly deformed region to the necked region,the morphology transfers ...In this work,a morphology transition mode is revealed in ultra-high molecular weight polyethylene(UHMWPE)when stretching at 120℃:moving from the slightly deformed region to the necked region,the morphology transfers from small spherulites to a mixture of transcrystalline and enlarged spherulites,and finally to pure transcrystalline;meanwhile,the lamellae making up the transcrystalline or spherulite were fragmented into smaller ones;spatial scan by wide-angle X-ray scattering(WAXS)and small angle X-ray scattering(SAXS)revealed that the crystallinity is increased from 25.3%to 30.1%and the crystal orientation was enhanced greatly,but the lamellae orientation was quite weak.The rise of enlarged spherulites or a mixture of transcrystalline and spherulites can also be found in UHMWPE stretched at 140 and 148℃,whereas absent in UHMWPE stretched at 30℃.In situ WAXS/SAXS measurements suggest that during stretching at 30℃,the crystallinity is reduced drastically,and a few voids are formed as the size increases from 50 nm to 210 nm;during stretching at 120℃,the crystallinity is reduced only slightly,and the kinking of lamellae occurs at large Hencky strain;during stretching at 140 and 148℃,an increase in crystallinity with stretching strain can be found,and the lamellae are also kinked.Taking the microstructure and morphology transition into consideration,a mesoscale morphology transition mode is proposed,in the stretching-induced crystallization the fragmented lamellae can be rearranged into new supra-structures such as spherulite or transcrystalline during hot stretching.展开更多
Lead-free dielectric ceramics can be used to make quick charge-discharge capacitor devices due to their high power density.Their use in advanced electronic systems,however,has been hampered by their poor energy storag...Lead-free dielectric ceramics can be used to make quick charge-discharge capacitor devices due to their high power density.Their use in advanced electronic systems,however,has been hampered by their poor energy storage performance(ESP),which includes low energy storage efficiency and recoverable energy storage density(Wrec).In this work,we adopted a combinatorial optimization strategy to improve the ESP in(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)-based relaxor ferroelectric ceramics.To begin,the Bi-containing complex ions Bi(Mg_(2/3)Nb_(1/3))O_(3)(BMN)were introduced into a BNT-based matrix in order to improve the diffuse phase transition,increase Bi-O bond coupling,avoid macro domain development,and limit polarization response hysteresis.Second,the viscous polymer process was employed to reduce sample thickness and porosity,resulting in an apparent increase in breakdown strength in(1-x)[0.7(Bi_(1/2)Na_(1/2))TiO_(3)]-0.3SrTiO_(3)-xBi(Mg_(2/3)Nb_(1/3))O_(3)(BS-xBMN)ceramics.Finally,in x=0.20 composition,an amazing Wrecof 5.62 J·cm^(-3)and an ultra-high efficiency of 91.4%were simultaneously achieved at a relatively low field of 330 kV·cm^(-1),together with remarkable temperature stability in the temperature range of 30-140℃(3.5 J·cm^(-3)±5%variation).This research presents a new lead-free dielectric material with superior ESP for use in pulsed power capacitors.展开更多
Strontium titanate（STO）is an n-type oxide thermoelectric material,which has shown great prospects in recent years.The doping of La and Nb into STO can improve its power factor,whereas its thermal conductivity is sti...Strontium titanate（STO）is an n-type oxide thermoelectric material,which has shown great prospects in recent years.The doping of La and Nb into STO can improve its power factor,whereas its thermal conductivity is still very high.Thus,in order to obtain a high thermoelectric figure-of-merit z T,it is very important to reduce its thermal conductivity.In this paper,using a combination of a hydrothermal method and a high-efficiency sintering method,we succeed in preparing a composite of pure STO and La Nb-doped STO,which simultaneously realizes lower thermal conductivity and higherSeebeck coefficient,therefore,the thermoelectric properties of STO are significantly improved.In the SrTiO3/La Nb–SrTiO3 bulk samples,the lowest thermal conductivity is 2.57 W·m^-1·K^-1 and the highest z T is 0.35 at 1000 K for the STO/La（10）Nb（20）–STO sample.展开更多
The microstructure and mechanical properties of as-cast Al−Cu−Li−Mg−Zn alloys fabricated by conventional gravity casting and centrifugal casting techniques combined with rapid solidification were investigated.Experime...The microstructure and mechanical properties of as-cast Al−Cu−Li−Mg−Zn alloys fabricated by conventional gravity casting and centrifugal casting techniques combined with rapid solidification were investigated.Experimental results demonstrated that compared with the gravity casting technique,the water-cooling centrifugal casting technique significantly reduces porosity,refinesα(Al)grains and secondary phases,modifies the morphology of secondary phases,and mitigates both macro-and micro-segregation.These improvements arise from the synergistic effects of the vigorous backflow,centrifugal field,vibration and rapid solidification.Porosity and coarse plate-like Al13Fe4/Al7Cu2Fe phase result in the fracture before the gravity-cast alloy reaches the yield point.The centrifugal-cast alloy,however,exhibits an ultra-high yield strength of 292.0 MPa and a moderate elongation of 6.1%.This high yield strength is attributed to solid solution strengthening(SSS)of 225.3 MPa,and grain boundary strengthening(GBS)of 35.7 MPa.Li contributes the most to SSS with a scaling factor of 7.9 MPa·wt.%^(-1).The elongation of the centrifugal-cast alloy can be effectively enhanced by reducing the porosity and segregation behavior,refining the microstructure and changing the morphology of secondary phases.展开更多
Dear Editor,Solute carrier family 26 member 8(SLC26A8)gene belongs to the solute carrier 26(SLC26)family.It demonstrates distinct expression in male spermatozoa.This gene potentially plays a role in the formation of t...Dear Editor,Solute carrier family 26 member 8(SLC26A8)gene belongs to the solute carrier 26(SLC26)family.It demonstrates distinct expression in male spermatozoa.This gene potentially plays a role in the formation of the sperm annulus,a circular structure linking the midpiece and principal piece of mature sperm flagella.1 Studies in mice have shown that the deficiency of Slc26A8 leads to compromised sperm motility,capacitation,and structural anomalies.These include disarray in the mitochondrial sheath,abnormalities in the annulus,and bending of the flagella.2,3 Nevertheless,our comprehension of SLC26A8 mutations in male infertility is still restricted,with only a limited number of studies addressing this aspect.4-6 Therefore,further research is crucial to elucidate the functional significance of mutations in SLC26A8.展开更多
Background:Several studies have clearly demonstrated a significantly higher incidence of persistent pulmonary hypertension of the newborn (PPHN) in neonates delivered by caesarean section (CS) compared to those delive...Background:Several studies have clearly demonstrated a significantly higher incidence of persistent pulmonary hypertension of the newborn (PPHN) in neonates delivered by caesarean section (CS) compared to those delivered vaginally.The pathophysiological factors underlying the link between CS and PPHN are still poorly understood.In this review,we describe the mechanisms that could explain the association between CS delivery and subsequent PPHN,as well as potential preventive measures.Data sources:A literature search was conducted by electronic scanning of databases such as PubMed and Web of Science using the key words 'persistent pulmonary hypertension of the newborn','caesarean section','iatrogenic prematarity','oxidative stress','late preterm','labor' and 'vasoaetive agents'.Results:Iatrogenic prematurity,higher rates of late preterm delivery and lack of physiological changes of labor play an important role in the association between CS and PPHN.CS delivery also results in limited endogenous pulmonary vasodilator synthesis and lower levels of protective anti-oxidants in the neonates.In addition,CS delivery exposes infants to a higher risk of respiratory distress syndrome and its concomitant increase in endothelin-1 levels,which might indirectly lead to a higher risk of developing PPHN.We believe that neonates delivered by CS are exposed to a combination of these pathophysiological events,culminating in an endpoint of respiratory distress,hypoxia,acidosis,and delayed transition and thereby increased risks of PPHN.The use of antenatal corticosteroids prior to elective CS in late preterm deliveries,promoting accurate informed-consent process,delaying elective CS to 39 weeks of gestation or beyond and antenatal maternal anti-oxidant supplementation could potentially mitigate the effects of CS delivery and minimize CS-related PPHN.Conclusions:The link between CS delivery and PPHN is complex.In view of the rising rates of CS worldwide,there is an urgent need to further explore the mechanisms linking CS to PPHN and experimentally test therapeutic options in order to allow effective targeted interventions.展开更多
Background To determine the trend and causes of neonatal mortality in a large level Ⅲ neonatal intensive care unit in Shanghai during a 15-year period. Methods This is a retrospective, single-centered study. All neon...Background To determine the trend and causes of neonatal mortality in a large level Ⅲ neonatal intensive care unit in Shanghai during a 15-year period. Methods This is a retrospective, single-centered study. All neonates who died during the period from January 1, 1999 to December 31, 2013 at Children's Hospital of Fudan University were included. We extracted relevant clinical information from their medical records, analyzed neonatal mortality rate and the characteristics of these patients, and compared neonatal deaths between different periods and populations. Results Among a total of 50,957 admissions during the study period, there were 929 neonatal deaths. The neonatal mortality rate was 1.82%. Trends in neonatal mortality rate showed an increase in the period from 1.0% in 2003 to 2.2% in 2013. The main causes of neonatal mortality were complications of preterm birth (33.6%), congenital anomalies (21.3%), infections (12.6%), and birth asphyxia (9.1%). The proportions of complications of preterm birth (P < 0.001) and congenital anomalies (P = 0.018) increased yearly, while the proportions of birth asphyxia (P < 0.001) and infections (P < 0.001) decreased. Proportions of deaths caused by birth asphyxia (P = 0.005) and infections (P < 0.001) were both higher in the migrating population than in the permanent residents. Conclusions Neonatal mortality rate increased from 2003 to 2013 in our study. The proportion of preterm infants in neonatal deaths also increased within the same period. Complications of preterm birth were the main cause of neonatal mortality and the percentage increased year by year. Neonates in the migrating population appeared to be at a higher risk of death during the neonatal period compared to those in the permanent residents, and efforts should be made towards improving perinatal care to prevent infections and birth asphyxia in this vulnerable population.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52003249,12072325 and 52273027)the Natural Science Foundation of Henan(No.242300421236).
文摘In this work,a morphology transition mode is revealed in ultra-high molecular weight polyethylene(UHMWPE)when stretching at 120℃:moving from the slightly deformed region to the necked region,the morphology transfers from small spherulites to a mixture of transcrystalline and enlarged spherulites,and finally to pure transcrystalline;meanwhile,the lamellae making up the transcrystalline or spherulite were fragmented into smaller ones;spatial scan by wide-angle X-ray scattering(WAXS)and small angle X-ray scattering(SAXS)revealed that the crystallinity is increased from 25.3%to 30.1%and the crystal orientation was enhanced greatly,but the lamellae orientation was quite weak.The rise of enlarged spherulites or a mixture of transcrystalline and spherulites can also be found in UHMWPE stretched at 140 and 148℃,whereas absent in UHMWPE stretched at 30℃.In situ WAXS/SAXS measurements suggest that during stretching at 30℃,the crystallinity is reduced drastically,and a few voids are formed as the size increases from 50 nm to 210 nm;during stretching at 120℃,the crystallinity is reduced only slightly,and the kinking of lamellae occurs at large Hencky strain;during stretching at 140 and 148℃,an increase in crystallinity with stretching strain can be found,and the lamellae are also kinked.Taking the microstructure and morphology transition into consideration,a mesoscale morphology transition mode is proposed,in the stretching-induced crystallization the fragmented lamellae can be rearranged into new supra-structures such as spherulite or transcrystalline during hot stretching.
基金financially supported by the National Natural Science Foundation of China(No.52172127)the International Cooperation Project of Shaanxi Province+4 种基金China(No.2022KWZ-22)the National Key Research and Development Program of China(Nos.2021YFE0115000,2021YFB3800602)the Fundamental Research Funds for the Central Universities(No.XJTU)the Natural Science Basis Research Plan in Shaanxi Province of China(No.2020JM-635)the Youth Innovation Team of Shaanxi Universities and Scientific Research Program Funded by Shaanxi Provincial Education Department(No.21JK0869)。
文摘Lead-free dielectric ceramics can be used to make quick charge-discharge capacitor devices due to their high power density.Their use in advanced electronic systems,however,has been hampered by their poor energy storage performance(ESP),which includes low energy storage efficiency and recoverable energy storage density(Wrec).In this work,we adopted a combinatorial optimization strategy to improve the ESP in(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)-based relaxor ferroelectric ceramics.To begin,the Bi-containing complex ions Bi(Mg_(2/3)Nb_(1/3))O_(3)(BMN)were introduced into a BNT-based matrix in order to improve the diffuse phase transition,increase Bi-O bond coupling,avoid macro domain development,and limit polarization response hysteresis.Second,the viscous polymer process was employed to reduce sample thickness and porosity,resulting in an apparent increase in breakdown strength in(1-x)[0.7(Bi_(1/2)Na_(1/2))TiO_(3)]-0.3SrTiO_(3)-xBi(Mg_(2/3)Nb_(1/3))O_(3)(BS-xBMN)ceramics.Finally,in x=0.20 composition,an amazing Wrecof 5.62 J·cm^(-3)and an ultra-high efficiency of 91.4%were simultaneously achieved at a relatively low field of 330 kV·cm^(-1),together with remarkable temperature stability in the temperature range of 30-140℃(3.5 J·cm^(-3)±5%variation).This research presents a new lead-free dielectric material with superior ESP for use in pulsed power capacitors.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61751404,51702168,and 51665042)the Fund from the State Key Laboratory of New Ceramic and Fine Processing(Tsinghua University),China(Grant No.KF201608)+1 种基金the Fund from the Guangxi Key Laboratory of Information Materials,Guilin University of Electronic Technology,China(Grant No.151004-K)the Natural Science Foundation of Inner Mongolia Autonomous Region,China(Grant Nos.2016BS0507 and 2015MS0509)
文摘Strontium titanate（STO）is an n-type oxide thermoelectric material,which has shown great prospects in recent years.The doping of La and Nb into STO can improve its power factor,whereas its thermal conductivity is still very high.Thus,in order to obtain a high thermoelectric figure-of-merit z T,it is very important to reduce its thermal conductivity.In this paper,using a combination of a hydrothermal method and a high-efficiency sintering method,we succeed in preparing a composite of pure STO and La Nb-doped STO,which simultaneously realizes lower thermal conductivity and higherSeebeck coefficient,therefore,the thermoelectric properties of STO are significantly improved.In the SrTiO3/La Nb–SrTiO3 bulk samples,the lowest thermal conductivity is 2.57 W·m^-1·K^-1 and the highest z T is 0.35 at 1000 K for the STO/La（10）Nb（20）–STO sample.
基金financially supported by the Natural Science Foundation of Ningbo,China (No.2023J053)。
文摘The microstructure and mechanical properties of as-cast Al−Cu−Li−Mg−Zn alloys fabricated by conventional gravity casting and centrifugal casting techniques combined with rapid solidification were investigated.Experimental results demonstrated that compared with the gravity casting technique,the water-cooling centrifugal casting technique significantly reduces porosity,refinesα(Al)grains and secondary phases,modifies the morphology of secondary phases,and mitigates both macro-and micro-segregation.These improvements arise from the synergistic effects of the vigorous backflow,centrifugal field,vibration and rapid solidification.Porosity and coarse plate-like Al13Fe4/Al7Cu2Fe phase result in the fracture before the gravity-cast alloy reaches the yield point.The centrifugal-cast alloy,however,exhibits an ultra-high yield strength of 292.0 MPa and a moderate elongation of 6.1%.This high yield strength is attributed to solid solution strengthening(SSS)of 225.3 MPa,and grain boundary strengthening(GBS)of 35.7 MPa.Li contributes the most to SSS with a scaling factor of 7.9 MPa·wt.%^(-1).The elongation of the centrifugal-cast alloy can be effectively enhanced by reducing the porosity and segregation behavior,refining the microstructure and changing the morphology of secondary phases.
基金support from grants provided by the Gansu Provincial Natural Science Foundation of China(23JRRA1046)the Gansu Association for Science and Technology(GSHZTS 2022-04)the National College Student Innovation and Entrepreneurship Training Program(202310730222).
文摘Dear Editor,Solute carrier family 26 member 8(SLC26A8)gene belongs to the solute carrier 26(SLC26)family.It demonstrates distinct expression in male spermatozoa.This gene potentially plays a role in the formation of the sperm annulus,a circular structure linking the midpiece and principal piece of mature sperm flagella.1 Studies in mice have shown that the deficiency of Slc26A8 leads to compromised sperm motility,capacitation,and structural anomalies.These include disarray in the mitochondrial sheath,abnormalities in the annulus,and bending of the flagella.2,3 Nevertheless,our comprehension of SLC26A8 mutations in male infertility is still restricted,with only a limited number of studies addressing this aspect.4-6 Therefore,further research is crucial to elucidate the functional significance of mutations in SLC26A8.
文摘Background:Several studies have clearly demonstrated a significantly higher incidence of persistent pulmonary hypertension of the newborn (PPHN) in neonates delivered by caesarean section (CS) compared to those delivered vaginally.The pathophysiological factors underlying the link between CS and PPHN are still poorly understood.In this review,we describe the mechanisms that could explain the association between CS delivery and subsequent PPHN,as well as potential preventive measures.Data sources:A literature search was conducted by electronic scanning of databases such as PubMed and Web of Science using the key words 'persistent pulmonary hypertension of the newborn','caesarean section','iatrogenic prematarity','oxidative stress','late preterm','labor' and 'vasoaetive agents'.Results:Iatrogenic prematurity,higher rates of late preterm delivery and lack of physiological changes of labor play an important role in the association between CS and PPHN.CS delivery also results in limited endogenous pulmonary vasodilator synthesis and lower levels of protective anti-oxidants in the neonates.In addition,CS delivery exposes infants to a higher risk of respiratory distress syndrome and its concomitant increase in endothelin-1 levels,which might indirectly lead to a higher risk of developing PPHN.We believe that neonates delivered by CS are exposed to a combination of these pathophysiological events,culminating in an endpoint of respiratory distress,hypoxia,acidosis,and delayed transition and thereby increased risks of PPHN.The use of antenatal corticosteroids prior to elective CS in late preterm deliveries,promoting accurate informed-consent process,delaying elective CS to 39 weeks of gestation or beyond and antenatal maternal anti-oxidant supplementation could potentially mitigate the effects of CS delivery and minimize CS-related PPHN.Conclusions:The link between CS delivery and PPHN is complex.In view of the rising rates of CS worldwide,there is an urgent need to further explore the mechanisms linking CS to PPHN and experimentally test therapeutic options in order to allow effective targeted interventions.
文摘Background To determine the trend and causes of neonatal mortality in a large level Ⅲ neonatal intensive care unit in Shanghai during a 15-year period. Methods This is a retrospective, single-centered study. All neonates who died during the period from January 1, 1999 to December 31, 2013 at Children's Hospital of Fudan University were included. We extracted relevant clinical information from their medical records, analyzed neonatal mortality rate and the characteristics of these patients, and compared neonatal deaths between different periods and populations. Results Among a total of 50,957 admissions during the study period, there were 929 neonatal deaths. The neonatal mortality rate was 1.82%. Trends in neonatal mortality rate showed an increase in the period from 1.0% in 2003 to 2.2% in 2013. The main causes of neonatal mortality were complications of preterm birth (33.6%), congenital anomalies (21.3%), infections (12.6%), and birth asphyxia (9.1%). The proportions of complications of preterm birth (P < 0.001) and congenital anomalies (P = 0.018) increased yearly, while the proportions of birth asphyxia (P < 0.001) and infections (P < 0.001) decreased. Proportions of deaths caused by birth asphyxia (P = 0.005) and infections (P < 0.001) were both higher in the migrating population than in the permanent residents. Conclusions Neonatal mortality rate increased from 2003 to 2013 in our study. The proportion of preterm infants in neonatal deaths also increased within the same period. Complications of preterm birth were the main cause of neonatal mortality and the percentage increased year by year. Neonates in the migrating population appeared to be at a higher risk of death during the neonatal period compared to those in the permanent residents, and efforts should be made towards improving perinatal care to prevent infections and birth asphyxia in this vulnerable population.
