点击科学

封面图展示了通过多通道电子显微镜揭示出的反渗透膜三维纳米结构 （图中金色部分），以及为了提高性能而控制其聚合物质量分布的需求。纳米分辨率级别的容积重建被用作显示流线的水流模拟输入（灰色部分;如图所示，水流自上而下流动）。为了实现最大化水产量，关键就是最大限度地减少“死区”，从而在整个薄膜上获取更均匀的密度。

Multimodal electronmicroscopy reveals the threedimensional nanostructure （gold）of reverseosmosis membranes.as well as the need to controltheir polymer mass distributionfor improved performance.Volume reconstructions withnanometer resolution are used asinputs for water flow simulationsthat reveal streamLines （gray：here. water flows from topto bottom）. Minimizing lideadzonesll， thereby achieving amore uniform density throughoutthe membranes. is key tomaxmizing water production.

封面图上展示的是一个缺乏糖基化的小鼠精子在绕圈游动。糖基化是微管蛋白的一种翻译后修饰，主要存在于纤毛和鞭毛中，它有助于协调纤毛轴动力蛋白马达，为鞭毛拍击提供动力。缺乏糖基化会导致异常的鞭毛拍击，从而导致精子绕圈游动而不是直线行进。这种情况的发生会进一步严重影响雄性的生育能力。

A mouse sperm lackingglycylation swlms in circles.Glycylation is a posttranslationalmodification of tubulin that ispredominately found in cilia andflagella， where it contributes tOcoordinating axonemal dyneinmotors that power the flagellarbeating. Lack of glycylationcauses an abnormal flageLlar beatand results iIl circular instead ofstraight sperm swlmming. This inturn severelv affects male fertility.

封面图展示的是位于波多黎各阿雷西博天文台的射电望远镜，其宽度达到305米，这张俯拍图片拍摄于上世纪80年代末。近60年来，该望远镜一直处于天文学、行星科学及大气科学的领先地位。2020年12月1日，其重型仪器平台由于悬索失效而倒塌损坏。研究人员在倡议重建的同时，也在调查事故发生的原因。

The 30s-meterwide radiodish of Puerto Rico S AreciboObservatory. as seen from abovein the late 1980s. For nearly 60years. the telescope stood at thevanguard of astronomy， planetaryscience. and atmospheric science.On l December 2020， itS heavyinstrument platform collapsedafter the failure of its suspensioncables. Researchers are examiningthe causes of the disaster even asthey advocate for rebuilding.

封面圖上展示的是一条莫桑比克射毒眼镜蛇，某些眼镜蛇会将喷吐毒液作为一种有效的远程防御机制。毒蛇所喷射毒液的3种来源与毒液成分的聚合型变化一致，这使得毒液能够通过增强受体的疼痛发挥防御功能。这些发现强调了进化过程可以将复杂的适应性引导到可重复的路径上。

Some cobras. such asthis Mozambique spitting cobra （Najamossambica）. use venom spitting as an effective long-range defense mechanism. The three origins of venom spitting in snakes coincide with convergent changes to venom composition，

aLlowing venomto serve a defensive function by producing enhanced pain inthe recipient. These findings emphasize that evolution canfunnel complex adaptations down repeatable pathways.

（陶陶编译）