The characteristics of hot deformation of an α＋β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si with acicular microstructure were studied using isothermal hot compressive tests in a strain rate range of 0.01-10 s^-1 at ...The characteristics of hot deformation of an α＋β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si with acicular microstructure were studied using isothermal hot compressive tests in a strain rate range of 0.01-10 s^-1 at 860-1 100 ℃. The true stress-tree strain curves of alloy hot-compressed in the α＋β region exhibit a peak stress followed by continuous flow softening; whereas in the β region, the flow stress attains a steady-state regime. At a strain rate of 10 s^-1 and in a wide temperature range, the alloy exhibits plastic flow instability. According to the kinetic rate equation, the apparent activation energies are estimated to be about 633 kJ/mol in the α＋β region and 281 kJ/mol in the β region, respectively. The processing maps show a domain of the globularization process of a colony structure and α dynamic recrystallization in the temperature range of 860-960 ℃ with a peak efficiency of about 60%, and a domain of β dynamic recrystallization in the β region with a peak efficiency of 80%.展开更多
On March 6,2010,an earthquake of M L4. 5 took place in Luanxian,Hebei Province,with plenty of foreshocks and aftershocks. From December 2009 to March 2010,a series of M L≥ 2. 5 earthquakes were recorded by the digita...On March 6,2010,an earthquake of M L4. 5 took place in Luanxian,Hebei Province,with plenty of foreshocks and aftershocks. From December 2009 to March 2010,a series of M L≥ 2. 5 earthquakes were recorded by the digital seismic network of the capital region,which were selected to calculate the apparent stress in this region. The results show that,firstly,a high value anomaly of apparent stress appeared before the M L4. 5 and peak value appeared on the main shock, which then decreased after the ML4. 5 earthquake. The apparent stress of the main shock is much greater than that of most aftershocks,the sequence type is considered as a main shock-aftershock. Secondly,the size of apparent stress perfectly reflects the state of the stress field in the hypocenter region,and we can discuss seismic sequence properties through the changing process of apparent stress,in combination with the traditional methods to identify a sequence more accurately. Finally,in the case of magnitude less than or equal to M L3. 3,correlation between magnitude and apparent stress is positive.展开更多
The sea-land breeze circulation(SLBC) occurs regularly at coastal locations and influences the local weather and climate significantly. In this study, based on the observed surface wind in 9 conventional meteorologica...The sea-land breeze circulation(SLBC) occurs regularly at coastal locations and influences the local weather and climate significantly. In this study, based on the observed surface wind in 9 conventional meteorological stations of Hainan Island, the frequency of sea-land breeze(SLB) is studied to depict the diurnal and seasonal variations. The statistics indicated that there is a monthly average of 12.2 SLB days and an occurrence frequency of about 40%, with the maximum frequency(49%) in summer and the minimum frequency(29%) in autumn. SLB frequencies(41%) are comparable in winter and spring. A higher frequency of SLB is present in the southern and central mountains due to the enhancement effect of the mountain-valley breeze. Due to the synoptic wind the number of SLB days in the northern hilly area is less than in other areas. Moreover, the WRF model, adopted to simulate the SLBC over the island for all seasons, performs reasonably well reproducing the phenomenon, evolution and mechanism of SLBC. Chiefly affected by the difference of temperature between sea and land, the SLBC varies in coverage and intensity with the seasons and reaches the greatest intensity in summer. The typical depth is about 2.5 km for sea breeze circulation and about 1.5 km for land breeze circulation. A strong convergence zone with severe ascending motion appears on the line parallel to the major axis of the island, penetrating 60 to 100 km inland. This type of weak sea breeze convergence zone in winter is north-south oriented. The features of SLBC in spring are similar both to that in summer with southerly wind and to that in winter with easterly wind. The coverage and intensity of SLBC in autumn is the weakest and confined to the southwest edge of the central mountainous area. The land breeze is inherently very weak and easily affected by the topography and weather. The coverage and intensity of the land breeze convergence line is significantly less than those of the sea breeze. The orographic forcing of the central mountain exhibits significant impacts on low-level airflow. A windward land breeze front usually occurs along the coastline between the wee hours and the morning in summer, with an arc-shaped convergence zone about 10 to 30 km off shore. In winter the arc-shaped convergence zone is weak and appears only in the southeast coastal area. Landing on the flat regions of northern to western parts of the island and going inland from there, the sea breeze front at the leeward side meets with that at the windward side in the centre of the island when sea breeze fully develops, causing an intense convergence zone throughout the whole island. Consistent with prevailing winds in direction, the windward sea breeze and leeward land breeze develop quickly but are not distinguishable from background winds.展开更多
Aims Recent studies have revealed heritable phenotypic plasticity through vegetative generations.In this sense,changes in gene regulation induced by the environment,such as DNA methylation(i.e.epigenetic changes),can ...Aims Recent studies have revealed heritable phenotypic plasticity through vegetative generations.In this sense,changes in gene regulation induced by the environment,such as DNA methylation(i.e.epigenetic changes),can result in reversible plastic responses being transferred to the offspring generations.This trans-generational plasticity is expected to be especially relevant in clonal plants,since reduction of sexual reproduction can decrease the potential for adaptation through genetic variation.Many of the most aggressive plant invaders are clonal,and clonality has been suggested as key to explain plant invasiveness.Here we aim to determine whether trans-generational effects occur in the clonal invader Alternanthera philoxeroides,and whether such effects differ between populations from native and non-native ranges.Methods In a common garden experiment,parent plants of A.philoxeroides from populations collected in Brazil(native range)and Iberian Peninsula(non-native range)were grown in high and low soil nutrient conditions,and offspring plants were transplanted to control conditions with high nutrients.To test the potential role of DNA methylation on trans-generational plasticity,half of the parent plants were treated with the demethylating agent,5-azacytidine.Important Findings Trans-generational effects were observed both in populations from the native and the non-native ranges.Interestingly,trans-generational effects occurred on growth variables(number of ramets,stem mass,root mass and total mass)in the population from the native range,but on biomass partitioning in the population from the non-native range.Trans-generational effects of the population from the native range may be explained by a‘silver-spoon’effect,whereas those of the population from the non-native range could be explained by epigenetic transmission due to DNA methylation.Our study highlights the importance of trans-generational effects on the growth of a clonal plant,which could help to understand the mechanisms underlying expansion success of many clonal plants.展开更多
It is well established that the decline in female reproductive outcomes is related to postovulatory aging of oocytes and advanced maternal age.Poor oocyte quality is correlated with compromised genetic integrity and e...It is well established that the decline in female reproductive outcomes is related to postovulatory aging of oocytes and advanced maternal age.Poor oocyte quality is correlated with compromised genetic integrity and epigenetic changes during the oocyte aging process.Here,we review the epigenetic alterations,mainly focused on DNA methylation,histone acetylation and methylation associated with postovulatory oocyte aging as well as advanced maternal age.Furthermore,we address the underlying epigenetic mechanisms that contribute to the decline in oocyte quality during oocyte aging.展开更多
基金Project(50901063) supported by the National Natural Science Foundation of ChinaProject(2007DS0414, 2007BS05006) supported by the Science and Technology Program of Shangdong Province, ChinaProject supported by the Open Research Fund from State Key Laboratory of Rolling and Automation, Northeastern University, China
文摘The characteristics of hot deformation of an α＋β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si with acicular microstructure were studied using isothermal hot compressive tests in a strain rate range of 0.01-10 s^-1 at 860-1 100 ℃. The true stress-tree strain curves of alloy hot-compressed in the α＋β region exhibit a peak stress followed by continuous flow softening; whereas in the β region, the flow stress attains a steady-state regime. At a strain rate of 10 s^-1 and in a wide temperature range, the alloy exhibits plastic flow instability. According to the kinetic rate equation, the apparent activation energies are estimated to be about 633 kJ/mol in the α＋β region and 281 kJ/mol in the β region, respectively. The processing maps show a domain of the globularization process of a colony structure and α dynamic recrystallization in the temperature range of 860-960 ℃ with a peak efficiency of about 60%, and a domain of β dynamic recrystallization in the β region with a peak efficiency of 80%.
基金funded by the Spark Program of the Earthquake Sciences(XH14005Y)Seismic Situation Tracing Youth Task in 2015(2015010307)Subjects of "Earthquake Monitoring,Prediction and Scieatific Research of 2015",Earthquake Administration of Tianjin Municipality,China(150201)
文摘On March 6,2010,an earthquake of M L4. 5 took place in Luanxian,Hebei Province,with plenty of foreshocks and aftershocks. From December 2009 to March 2010,a series of M L≥ 2. 5 earthquakes were recorded by the digital seismic network of the capital region,which were selected to calculate the apparent stress in this region. The results show that,firstly,a high value anomaly of apparent stress appeared before the M L4. 5 and peak value appeared on the main shock, which then decreased after the ML4. 5 earthquake. The apparent stress of the main shock is much greater than that of most aftershocks,the sequence type is considered as a main shock-aftershock. Secondly,the size of apparent stress perfectly reflects the state of the stress field in the hypocenter region,and we can discuss seismic sequence properties through the changing process of apparent stress,in combination with the traditional methods to identify a sequence more accurately. Finally,in the case of magnitude less than or equal to M L3. 3,correlation between magnitude and apparent stress is positive.
基金Project for Developing and Planning Key National Fundamental Science Research(2010CB428501)Project for Developing and Planning National High-Technology Research(2008AA06A415,2009AA06A41802)Science and Technology Planning Project for Guangdong Province(2012A061400012)
文摘The sea-land breeze circulation(SLBC) occurs regularly at coastal locations and influences the local weather and climate significantly. In this study, based on the observed surface wind in 9 conventional meteorological stations of Hainan Island, the frequency of sea-land breeze(SLB) is studied to depict the diurnal and seasonal variations. The statistics indicated that there is a monthly average of 12.2 SLB days and an occurrence frequency of about 40%, with the maximum frequency(49%) in summer and the minimum frequency(29%) in autumn. SLB frequencies(41%) are comparable in winter and spring. A higher frequency of SLB is present in the southern and central mountains due to the enhancement effect of the mountain-valley breeze. Due to the synoptic wind the number of SLB days in the northern hilly area is less than in other areas. Moreover, the WRF model, adopted to simulate the SLBC over the island for all seasons, performs reasonably well reproducing the phenomenon, evolution and mechanism of SLBC. Chiefly affected by the difference of temperature between sea and land, the SLBC varies in coverage and intensity with the seasons and reaches the greatest intensity in summer. The typical depth is about 2.5 km for sea breeze circulation and about 1.5 km for land breeze circulation. A strong convergence zone with severe ascending motion appears on the line parallel to the major axis of the island, penetrating 60 to 100 km inland. This type of weak sea breeze convergence zone in winter is north-south oriented. The features of SLBC in spring are similar both to that in summer with southerly wind and to that in winter with easterly wind. The coverage and intensity of SLBC in autumn is the weakest and confined to the southwest edge of the central mountainous area. The land breeze is inherently very weak and easily affected by the topography and weather. The coverage and intensity of the land breeze convergence line is significantly less than those of the sea breeze. The orographic forcing of the central mountain exhibits significant impacts on low-level airflow. A windward land breeze front usually occurs along the coastline between the wee hours and the morning in summer, with an arc-shaped convergence zone about 10 to 30 km off shore. In winter the arc-shaped convergence zone is weak and appears only in the southeast coastal area. Landing on the flat regions of northern to western parts of the island and going inland from there, the sea breeze front at the leeward side meets with that at the windward side in the centre of the island when sea breeze fully develops, causing an intense convergence zone throughout the whole island. Consistent with prevailing winds in direction, the windward sea breeze and leeward land breeze develop quickly but are not distinguishable from background winds.
基金supported by a mobility grant from the University of A Coruña(Inditex-UDC 2017 program)This is a contribution from the Alien Species Network(Ref.ED431D 2017/20-Xunta de Galicia,Autonomous Government of Galicia).D.M.S.M.thanks the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico/CNPq(307839/2014-1)for her Research Fellowship.
文摘Aims Recent studies have revealed heritable phenotypic plasticity through vegetative generations.In this sense,changes in gene regulation induced by the environment,such as DNA methylation(i.e.epigenetic changes),can result in reversible plastic responses being transferred to the offspring generations.This trans-generational plasticity is expected to be especially relevant in clonal plants,since reduction of sexual reproduction can decrease the potential for adaptation through genetic variation.Many of the most aggressive plant invaders are clonal,and clonality has been suggested as key to explain plant invasiveness.Here we aim to determine whether trans-generational effects occur in the clonal invader Alternanthera philoxeroides,and whether such effects differ between populations from native and non-native ranges.Methods In a common garden experiment,parent plants of A.philoxeroides from populations collected in Brazil(native range)and Iberian Peninsula(non-native range)were grown in high and low soil nutrient conditions,and offspring plants were transplanted to control conditions with high nutrients.To test the potential role of DNA methylation on trans-generational plasticity,half of the parent plants were treated with the demethylating agent,5-azacytidine.Important Findings Trans-generational effects were observed both in populations from the native and the non-native ranges.Interestingly,trans-generational effects occurred on growth variables(number of ramets,stem mass,root mass and total mass)in the population from the native range,but on biomass partitioning in the population from the non-native range.Trans-generational effects of the population from the native range may be explained by a‘silver-spoon’effect,whereas those of the population from the non-native range could be explained by epigenetic transmission due to DNA methylation.Our study highlights the importance of trans-generational effects on the growth of a clonal plant,which could help to understand the mechanisms underlying expansion success of many clonal plants.
基金supported in part by the National Natural Science Foundation of China (Grant No. 81100422)National Basic Research Program of China (Grant Nos. 2012CB944404 and 2011CB944501)
文摘It is well established that the decline in female reproductive outcomes is related to postovulatory aging of oocytes and advanced maternal age.Poor oocyte quality is correlated with compromised genetic integrity and epigenetic changes during the oocyte aging process.Here,we review the epigenetic alterations,mainly focused on DNA methylation,histone acetylation and methylation associated with postovulatory oocyte aging as well as advanced maternal age.Furthermore,we address the underlying epigenetic mechanisms that contribute to the decline in oocyte quality during oocyte aging.
