The germination of pollen grain in vitro and the growth of pollen tube in the pistil of rice were observed with a microscope. The stigma was removed at different time points after pollination to study its effect on se...The germination of pollen grain in vitro and the growth of pollen tube in the pistil of rice were observed with a microscope. The stigma was removed at different time points after pollination to study its effect on seed setting rate. The rice pollen grain started to germinate at 2 min after pollination and the pollen tube penetrated stigma into style in 5-10 min, 30 min later the end of pollen tube reached the bottom of ovary, and only some pollen tubes arrived at embryo sac at 40 min after pollination. Meanwhile, a small amount of callose began to deposit in the pollen tubes, a great deal of callose was observed at 50 min after pollination, whereas the pollen grain began to shrink. The growing rates of pollen tube in the rice stigma, style and ovary were 1500, 5000, and 5400 μm/h, respectively. The seed setting rate was quite low when the stigma was removed at about 10-15 min after pollination, gradually increased when it removed at 20 min to 50 min after pollination, and over 60% when it removed at 50 min after pollination and finally tended to be stable.展开更多
Catastrophe theory was used to investigate the fracture behavior of thin-wall cylindrical tubes subjected to internal explosive pressure. Based on the energy theory and catastrophe theory, a cusp catastrophe model for...Catastrophe theory was used to investigate the fracture behavior of thin-wall cylindrical tubes subjected to internal explosive pressure. Based on the energy theory and catastrophe theory, a cusp catastrophe model for the fracture vas established, and a critical condition associated with the model is given.展开更多
The almond （Prunus dulcis） is a self-incompatible species that requires various orchard management techniques to encourage pollination and achieve a good fruit set. Fungicides are commonly applied to almond flowers ...The almond （Prunus dulcis） is a self-incompatible species that requires various orchard management techniques to encourage pollination and achieve a good fruit set. Fungicides are commonly applied to almond flowers to control fungaI infections, such as ＂blossom blight＂ and ＇brown rot＂ that damage the flowers and developing fruits. However there is evidence that the application of some of these products may adversely affect pollination and fruit set. The effects of the fungicides captan, chlorothalonyl, propiconazole, mancozeb and dichloran on fruit set were studied in an orchard using ＂Nonpareil＂ and ＂Carmel＂ almond trees. The effects on in vitro pollen germination and pollen tube elongation were studied using ＂Carmel＂ pollen. With respect to Non Pareil fruit set, all fungicidal treatments were statistically similar to the control （11.5%） but being propiconazole （13.1%） and chlorotalonil （5.6%） different between them. Fruit set for ＂Carmel＂ was significantly lower than the control （26.1%） with all fungicidal treatments. After 24 hours, in vitro ＂Carmel＂ pollen germination was significantly higher in the control （90.5%） compared with the fungicidal treatments, with the exception of chlorothalonyl （70.2%）. Pollen tube growth in the control was four times greater than in the fungicide treatments at 24 hours, none of which were significantly different from the other treatments. It can be concluded that the application of certain fungicides has a clearly detrimental effect on fruit set in ＂Nonpareil＂ and ＂Carmel＂ almond trees and on ＂Carmel＂ pollen activity.展开更多
The rapid development of aviation and aerospace technologies has led to increased interest in the application of numerically controlled(NC) technology for bending light-weight titanium alloy tubes.In order to study an...The rapid development of aviation and aerospace technologies has led to increased interest in the application of numerically controlled(NC) technology for bending light-weight titanium alloy tubes.In order to study and develop advanced NC bending technology,it is necessary to understand the bending performance of medium strength TA18(Ti-3Al-2.5V,ASTM Gr.9) titanium alloy tubes during NC bending under different die sets.This paper focuses on the bending performance of medium strength TA18 tubes under different NC bending die sets,including the variations in the stress,strain,wall thickness,cross sectional deformation,and defects.The results show that adding a wiper die to the base die set decreases the radial,hoop,and tangential compressive stress and the tangential compressive strain,and adding a mandrel to the base die set also decreases these stresses,but increases the radial and hoop tensile stress and decreases the hoop compressive strain obviously,and brings about a three-dimensional tensile stress concentration where the mandrel provides support.For the NC bending of medium strength TA18 tubes,the flattening of cross section is more sensitive index than the thinning of wall thickness.Introducing a mandrel can improve the flattening of cross section obviously but it has a little worse effect on the thinning of wall thickness,and adding a wiper die to the base die set can inhibit the occurrence of the inside bulge but worsen the flattening of the cross section remarkably.Considering the above effects of the mandrel and wiper die on bending performance,it is reasonable to apply the die set comprising a bending die,clamp die,and pressure die for tubes with a small diameter and the die set including an appropriate mandrel additionally for tubes with a larger diameter,in order to bend the medium strength TA18 tubes with high quality and at low cost.展开更多
基金the National Natural Science Foundation of China (Grants Nos. 30070454 and 30471045)
文摘The germination of pollen grain in vitro and the growth of pollen tube in the pistil of rice were observed with a microscope. The stigma was removed at different time points after pollination to study its effect on seed setting rate. The rice pollen grain started to germinate at 2 min after pollination and the pollen tube penetrated stigma into style in 5-10 min, 30 min later the end of pollen tube reached the bottom of ovary, and only some pollen tubes arrived at embryo sac at 40 min after pollination. Meanwhile, a small amount of callose began to deposit in the pollen tubes, a great deal of callose was observed at 50 min after pollination, whereas the pollen grain began to shrink. The growing rates of pollen tube in the rice stigma, style and ovary were 1500, 5000, and 5400 μm/h, respectively. The seed setting rate was quite low when the stigma was removed at about 10-15 min after pollination, gradually increased when it removed at 20 min to 50 min after pollination, and over 60% when it removed at 50 min after pollination and finally tended to be stable.
文摘Catastrophe theory was used to investigate the fracture behavior of thin-wall cylindrical tubes subjected to internal explosive pressure. Based on the energy theory and catastrophe theory, a cusp catastrophe model for the fracture vas established, and a critical condition associated with the model is given.
文摘The almond （Prunus dulcis） is a self-incompatible species that requires various orchard management techniques to encourage pollination and achieve a good fruit set. Fungicides are commonly applied to almond flowers to control fungaI infections, such as ＂blossom blight＂ and ＇brown rot＂ that damage the flowers and developing fruits. However there is evidence that the application of some of these products may adversely affect pollination and fruit set. The effects of the fungicides captan, chlorothalonyl, propiconazole, mancozeb and dichloran on fruit set were studied in an orchard using ＂Nonpareil＂ and ＂Carmel＂ almond trees. The effects on in vitro pollen germination and pollen tube elongation were studied using ＂Carmel＂ pollen. With respect to Non Pareil fruit set, all fungicidal treatments were statistically similar to the control （11.5%） but being propiconazole （13.1%） and chlorotalonil （5.6%） different between them. Fruit set for ＂Carmel＂ was significantly lower than the control （26.1%） with all fungicidal treatments. After 24 hours, in vitro ＂Carmel＂ pollen germination was significantly higher in the control （90.5%） compared with the fungicidal treatments, with the exception of chlorothalonyl （70.2%）. Pollen tube growth in the control was four times greater than in the fungicide treatments at 24 hours, none of which were significantly different from the other treatments. It can be concluded that the application of certain fungicides has a clearly detrimental effect on fruit set in ＂Nonpareil＂ and ＂Carmel＂ almond trees and on ＂Carmel＂ pollen activity.
基金supported by the Program for New Century Excellent Talents in University of China (NCET-08-0462)the Fund of the State Key Laboratory of Solidification Processing in NWPU (Grant No. KP200919)the 111 Project of China (B08040)
文摘The rapid development of aviation and aerospace technologies has led to increased interest in the application of numerically controlled(NC) technology for bending light-weight titanium alloy tubes.In order to study and develop advanced NC bending technology,it is necessary to understand the bending performance of medium strength TA18(Ti-3Al-2.5V,ASTM Gr.9) titanium alloy tubes during NC bending under different die sets.This paper focuses on the bending performance of medium strength TA18 tubes under different NC bending die sets,including the variations in the stress,strain,wall thickness,cross sectional deformation,and defects.The results show that adding a wiper die to the base die set decreases the radial,hoop,and tangential compressive stress and the tangential compressive strain,and adding a mandrel to the base die set also decreases these stresses,but increases the radial and hoop tensile stress and decreases the hoop compressive strain obviously,and brings about a three-dimensional tensile stress concentration where the mandrel provides support.For the NC bending of medium strength TA18 tubes,the flattening of cross section is more sensitive index than the thinning of wall thickness.Introducing a mandrel can improve the flattening of cross section obviously but it has a little worse effect on the thinning of wall thickness,and adding a wiper die to the base die set can inhibit the occurrence of the inside bulge but worsen the flattening of the cross section remarkably.Considering the above effects of the mandrel and wiper die on bending performance,it is reasonable to apply the die set comprising a bending die,clamp die,and pressure die for tubes with a small diameter and the die set including an appropriate mandrel additionally for tubes with a larger diameter,in order to bend the medium strength TA18 tubes with high quality and at low cost.
