本文讨论了曲面的切球丛的黎曼几何性质。证明了如下定理1 设(V,g)是2-维黎曼流形,(T(?)V,(?))是 V 上的切球丛,(?)为 Sasaki 度量,那么1)如果(T(?)V,(?))有正的截面曲率则 V 的 Gauss 曲率 k 必满足:0<k<4/(3c^2).2)(T(?)V,(?))...本文讨论了曲面的切球丛的黎曼几何性质。证明了如下定理1 设(V,g)是2-维黎曼流形,(T(?)V,(?))是 V 上的切球丛,(?)为 Sasaki 度量,那么1)如果(T(?)V,(?))有正的截面曲率则 V 的 Gauss 曲率 k 必满足:0<k<4/(3c^2).2)(T(?)V,(?))为共形平坦空间的充要条件是曲面 V 有常 Gauss 曲率。展开更多
Thirty-six medicinal plant species belonging to 25 families were surveyed to study Arbuscular mycorrhizal （AM） fungal diversity from different localities of North and South Goa of Western Ghats, Goa region, India. A...Thirty-six medicinal plant species belonging to 25 families were surveyed to study Arbuscular mycorrhizal （AM） fungal diversity from different localities of North and South Goa of Western Ghats, Goa region, India. A total of 30 medicinal plant species were found to be mycorrhizal and six plant species showed absence of AM fungal colonization. Forty two AM fungal species belonging to five genera viz., Glomus, Acaulospora, Scutellospora, Gigaspora and Ambispora were recovered from the rhizosphere soil. Glomus was found to be the most dominant genera in the study sites, and Glomus fasciculatum the most dominant AM fungal species. Negative significant correlation was observed between percent colonization and spore density. Simpson＇s and Shannon Weiner diversity index studies carried out in North and South Goa exhibited less variation in both the sites, indicating a stable and a diverse plant community.展开更多
A differentiable manifold is said to be contact if it admits a linear functional f on the tangent bundle satisfying f ∧(df)^(M-1)≠0.This remark obtain the following the classification:Let M be a complete connected c...A differentiable manifold is said to be contact if it admits a linear functional f on the tangent bundle satisfying f ∧(df)^(M-1)≠0.This remark obtain the following the classification:Let M be a complete connected contact hyper-surface of CH^2(-4),then M is congruent to one of the following: (i)A tube of radius r>0 around a totally geodesic,totally real hyperbolic space form H^2(-1); (ii)A tube of radius r>0 around a totally geodesic complex hyperbolic space form CH^1(-4); (iii)A geodesic hypersphere of radius r>0,or (iv)A horosphere.展开更多
We give the classification of globally generated vector bundles of rank 2 on a smooth quadric surface with c1(2,2)in terms of the indices of the bundles,and extend the result to arbitrary higher rank case.We also inve...We give the classification of globally generated vector bundles of rank 2 on a smooth quadric surface with c1(2,2)in terms of the indices of the bundles,and extend the result to arbitrary higher rank case.We also investigate their indecomposability and give the sufficient and necessary condition on numeric data of vector bundles for indecomposability.展开更多
文摘本文讨论了曲面的切球丛的黎曼几何性质。证明了如下定理1 设(V,g)是2-维黎曼流形,(T(?)V,(?))是 V 上的切球丛,(?)为 Sasaki 度量,那么1)如果(T(?)V,(?))有正的截面曲率则 V 的 Gauss 曲率 k 必满足:0<k<4/(3c^2).2)(T(?)V,(?))为共形平坦空间的充要条件是曲面 V 有常 Gauss 曲率。
文摘世界最大的影音电子展会(2006 Interna tional CES)于日前,在美国拉斯维加斯大会中心(Las Vegas Convention Center)举行,同时进行的高级音响展THE Show,有 2500家的电子类参展商展出他们的新产品, 吸引到十多万名的科技业者及零售商与会。此次的展会规模比2005年有所扩大,会场包括Las Vegas Convention Center、Las Ve gas Hilton旅馆、Renaissance Las Vegas、 Sandz Expo and Convention Center、Alexi Park 会场。
基金support provided by the Planning Commission,Government of India,New Delhi for carrying out this study
文摘Thirty-six medicinal plant species belonging to 25 families were surveyed to study Arbuscular mycorrhizal （AM） fungal diversity from different localities of North and South Goa of Western Ghats, Goa region, India. A total of 30 medicinal plant species were found to be mycorrhizal and six plant species showed absence of AM fungal colonization. Forty two AM fungal species belonging to five genera viz., Glomus, Acaulospora, Scutellospora, Gigaspora and Ambispora were recovered from the rhizosphere soil. Glomus was found to be the most dominant genera in the study sites, and Glomus fasciculatum the most dominant AM fungal species. Negative significant correlation was observed between percent colonization and spore density. Simpson＇s and Shannon Weiner diversity index studies carried out in North and South Goa exhibited less variation in both the sites, indicating a stable and a diverse plant community.
文摘A differentiable manifold is said to be contact if it admits a linear functional f on the tangent bundle satisfying f ∧(df)^(M-1)≠0.This remark obtain the following the classification:Let M be a complete connected contact hyper-surface of CH^2(-4),then M is congruent to one of the following: (i)A tube of radius r>0 around a totally geodesic,totally real hyperbolic space form H^2(-1); (ii)A tube of radius r>0 around a totally geodesic complex hyperbolic space form CH^1(-4); (iii)A geodesic hypersphere of radius r>0,or (iv)A horosphere.
基金supported by Ministero dell’Istruzione,dell’Universit`ae della Ricerca(Italy)and Gruppo Nazionale per le Strutture Algebrice,Geometriche e le loro Applicazioni of Istituto di Alta Matematica"F.Severi"(Italy),Basic Science Research Program through National Research Foundation of Korea funded by Ministry of Education and Science Technology(Grant No.2010-0009195)the framework of PRIN2010/11‘Geometria delle variet`a algebriche’,cofinanced by Ministero dell’Istruzione,dell’Universit`ae della Ricerca(Italy)
文摘We give the classification of globally generated vector bundles of rank 2 on a smooth quadric surface with c1(2,2)in terms of the indices of the bundles,and extend the result to arbitrary higher rank case.We also investigate their indecomposability and give the sufficient and necessary condition on numeric data of vector bundles for indecomposability.
