點(diǎn)擊科學(xué)

封面圖展示了通過(guò)多通道電子顯微鏡揭示出的反滲透膜三維納米結(jié)構(gòu) （圖中金色部分），以及為了提高性能而控制其聚合物質(zhì)量分布的需求。納米分辨率級(jí)別的容積重建被用作顯示流線的水流模擬輸入（灰色部分;如圖所示，水流自上而下流動(dòng)）。為了實(shí)現(xiàn)最大化水產(chǎn)量，關(guān)鍵就是最大限度地減少“死區(qū)”，從而在整個(gè)薄膜上獲取更均勻的密度。

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.

封面圖上展示的是一個(gè)缺乏糖基化的小鼠精子在繞圈游動(dòng)。糖基化是微管蛋白的一種翻譯后修飾，主要存在于纖毛和鞭毛中，它有助于協(xié)調(diào)纖毛軸動(dòng)力蛋白馬達(dá)，為鞭毛拍擊提供動(dòng)力。缺乏糖基化會(huì)導(dǎo)致異常的鞭毛拍擊，從而導(dǎo)致精子繞圈游動(dòng)而不是直線行進(jìn)。這種情況的發(fā)生會(huì)進(jìn)一步嚴(yán)重影響雄性的生育能力。

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.

封面圖展示的是位于波多黎各阿雷西博天文臺(tái)的射電望遠(yuǎn)鏡，其寬度達(dá)到305米，這張俯拍圖片拍攝于上世紀(jì)80年代末。近60年來(lái)，該望遠(yuǎn)鏡一直處于天文學(xué)、行星科學(xué)及大氣科學(xué)的領(lǐng)先地位。2020年12月1日，其重型儀器平臺(tái)由于懸索失效而倒塌損壞。研究人員在倡議重建的同時(shí)，也在調(diào)查事故發(fā)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條莫桑比克射毒眼鏡蛇，某些眼鏡蛇會(huì)將噴吐毒液作為一種有效的遠(yuǎn)程防御機(jī)制。毒蛇所噴射毒液的3種來(lái)源與毒液成分的聚合型變化一致，這使得毒液能夠通過(guò)增強(qiáng)受體的疼痛發(fā)揮防御功能。這些發(fā)現(xiàn)強(qiáng)調(diào)了進(jìn)化過(guò)程可以將復(fù)雜的適應(yīng)性引導(dǎo)到可重復(fù)的路徑上。

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.

（陶陶編譯）