Chemicals from our phone and TV screens are accumulating in the brains of endangered dolphins and porpoises. New research shows these "liquid crystal monomers" from e-waste can cross the blood-brain barrier and may disrupt DNA repair, highlighting the growing impact of electronics on marine life.
10 open-source Windows apps I can't live without - and they're all free。WPS下载最新地址对此有专业解读
，这一点在Line官方版本下载中也有详细论述
人 民 网 版 权 所 有 ，未 经 书 面 授 权 禁 止 使 用，更多细节参见safew官方版本下载
A Riemannian metric on a smooth manifold \(M\) is a family of inner products \[g_p : T_pM \times T_pM \;\longrightarrow\; \mathbb{R}, \qquad p \in M,\] varying smoothly in \(p\), such that each \(g_p\) is symmetric and positive-definite. In local coordinates the metric is completely determined by its values on basis tangent vectors: \[g_{ij}(p) \;:=\; g_p\!\left(\frac{\partial}{\partial x^i}\bigg|_p,\; \frac{\partial}{\partial x^j}\bigg|_p\right), \qquad g_{ij} = g_{ji},\] with the matrix \((g_{ij}(p))\) positive-definite at every point. The length of a tangent vector \(v = \sum_i v^i \frac{\partial}{\partial x^i}\in T_pM\) is then \(\|v\|_g = \sqrt{\sum_{i,j} g_{ij}(p)\, v^i v^j}\).
[&:first-child]:overflow-hidden [&:first-child]:max-h-full"