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Often people write these metrics as \(ds^2 = \sum_{i,j} g_{ij}\,dx^i\,dx^j\), where each \(dx^i\) is a covector (1-form), i.e. an element of the dual space \(T_p^*M\). For finite dimensional vectorspaces there is a canonical isomorphism between them and their dual: given the coordinate basis \(\bigl\{\frac{\partial}{\partial x^1},\dots,\frac{\partial}{\partial x^n}\bigr\}\) of \(T_pM\), there is a unique dual basis \(\{dx^1,\dots,dx^n\}\) of \(T_p^*M\) defined by \[dx^i\!\left(\frac{\partial}{\partial x^j}\right) = \delta^i{}_j.\] This extends to isomorphisms \(T_pM \to T_p^*M\). Under this identification, the bilinear form \(g_p\) on \(T_pM \times T_pM\) is represented by the symmetric tensor \(\sum_{i,j} g_{ij}\,dx^i \otimes dx^j\) acting on pairs of tangent vectors via \[\left(\sum_{i,j} g_{ij}\,dx^i\otimes dx^j\right)\!\!\left(\frac{\partial}{\partial x^k},\frac{\partial}{\partial x^l}\right) = g_{kl},\] which recovers exactly the inner products \(g_p\!\left(\frac{\partial}{\partial x^k},\frac{\partial}{\partial x^l}\right)\) from before. So both descriptions carry identical information;
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Артем Соколов (Редактор отдела «Силовые структуры»)
针对器官移植与自身免疫病治疗，行业当前主要采用类固醇、钙调磷酸酶阻滞剂、抗代谢药物等广谱免疫抑制，相关药物会非选择性地抑制所有免疫细胞，过度抑制人体免疫功能，导致全身免疫反应缺陷，使患者易患机会性感染、侵袭性癌症等，并伴随多种严重与长期的副作用与并发症，从而严重影响患者的生存率和生活质量。，这一点在快连下载安装中也有详细论述
При этом первая и вторая «шапки» фейкового документа конфликтуют с собой по смыслу, не имея ничего общего друг с другом.
В России спрогнозировали стабильное изменение цен на топливо14:55。业内人士推荐电影作为进阶阅读