2019-06-21

封面图展示的是南非林波波省马蓬古布韦国家公园里的一只雌性小岩羚。小岩羚是一种反刍动物，也是世界上分布最广的食草哺乳动物谱系之一。本期刊中的3篇论文分别探讨了反刍动物的基因组，用以确定与它们的多样性和茁壮成长进化能力息息相关的具体特征。

A female steenbok (Raphicerus campestris) in Mapungubwe National Park, Limpopo Province, South Africa. Steenboks are ruminants, one of the most widespread lineages of herbivorous mammals across the globe. Three papers in this issue explore ruminant genomes to identify specific traits that underlie their ability to diversify and thrive evolutionarily.

2019-06-28

封面图展示的是一对延时涡旋激光脉冲（图中红色部分）的图示，它们互相耦合地向上转换为具有自转矩的极紫外（EUV）涡旋脉冲（图中青色部分）。这一特性表现为轨道角动量（OAM）在平稳的时间上的增加（由EUV光束的空间扭转频率表示），从低OAM（右上）到高OAM（左下）逐步提升。

Illustration of a pair of time-delayed vortex laser pulses (red) being coherently up-converted into extreme ultraviolet (EUV) vortex pulses (cyan) that possess self-torque. This property manifests as a smooth, temporal increase in orbital angular momentum (OAM) (represented by the frequency of spatial twists in the EUV beam), progressing from low OAM (top right) to high OAM (bottom left).

2019-07-05

封面图展示的是细菌基因编辑技术（CRISPR）系统，这是一种适应性免疫防御机制。如今，一种新的CRISPR亚型已经表明被转座子增选，从而实现它们插入基因组的目标区域。这种功能强大的CRISPR-Cas12k系统可通过编程实现精确而高效的靶向基因插入，在基因组编辑应用中具有巨大的潜力。

The bacterial CRISPR system is an adaptive immune defense mechanism. A new subtype of CRISPR is now shown to be co-opted by transposons to achieve their insertion into the targeted regions of the genome. This powerful CRISPR-Cas12k system can be programmed to achieve precise and efficient targeted gene insertion, which holds great potential in genome editing applications.

2019-07-12

封面图展示的是一种可编程张力、以纤维为基础的人造肌肉，它由热塑性塑料和弹性纤维层构成，在加热后，它可以驱动一个微型打印手臂，举起重量是自身650倍的哑铃。这些以纤维为基础的肌肉，长达数百米，在力量和横向维度方面高度可调，因此可能为机器人和假肢制造方面提供更多机会。

Upon heating, a strain-programmable fiber-based artificial muscle composed of thermoplastic and elastomer layers actuates a miniature printed arm and lifts a dumbbell 650 times its own weight. These fiber-based muscles, fabricated at lengths of hundreds of meters, are highly tunable in terms of power and lateral dimensions and thus may offer opportunities in robotics and prosthetics.