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5月15日Science中文摘要

 

摘要 : 本期封面是上个月在古巴哈瓦那的一个年轻女正在检查她的智能手机。古巴和美国的关系缓和预计能更好地让古巴科学家融入全球社会,同时促进联合研究古巴惊人的珊瑚礁和蚊子传播基孔肯雅病等研究。

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 古巴重新与世界建立连接

本期封面是上个月在古巴哈瓦那的一个年轻女正在检查她的智能手机。古巴和美国的关系缓和预计能更好地让古巴科学家融入全球社会,同时促进联合研究古巴惊人的珊瑚礁和蚊子传播基孔肯雅病等研究。

原文链接:

In from the cold

原文摘要:

Ernesto Altshuler has a principle for doing science in one of the world's more challenging settings, Cuba. Faced with scant resources and a persistent brain drain, the University of Havana physicist says he became a “guerrilla scientist.”

That didn't mean toting a Kalashnikov. “My strategy to survive as an experimental physicist was to violate the boundaries of safe science,” Altshuler says, “invading zones wher I was not a specialist, looking around for new phenomena with wider eyes, seeing scientific instruments in daily life objects, attacking and retreating from serendipitous findings like a guerrilla.” He has used ants to model how panicked people behave, for example, and has studied how bits of tea leaves seem to defy gravity by climbing a stream of tea into a pot's spout. In his studies of granular materials, Altshuler spent about $100 “to obtain the same quality of data” as other researchers who spend millions of dollars on microgravity experiments, says Thorsten Pöschel, a physicist at the Friedrich-Alexander University Erlangen-Nürnberg in Germany. “This should have embarrassed some of our colleagues.”

给世界上最穷困的人带来持续改善的项目

一项新的分析显示,一个结合直接援助与培训的计划可帮助世界上最贫困的家庭从极端贫穷“毕业”进入可持续性的生活标准。这项计划在埃塞俄比亚、加纳、洪都拉斯、印度、巴基斯坦和秘鲁的1万1000个家庭中进行了测试。该计划在结束1年后,其对超贫困家庭的正面影响(特别是资产的积累和食品消费方面)仍然持续存在。

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A Multifaceted program causes lasting progress for the very poor: Evidence from six countries

原文摘要:

Working in six countries with an international consortium, we investigate whether a multifaceted Graduation program can help the extreme poor establish sustainable self-employment activities and generate lasting improvements in their well-being. The program targets the poorest members in a village and provides a productive asset grant, training and support, life skills coaching, temporary cash consumption support, and typically access to savings accounts and health information or services. In each country, the program was adjusted to suit different contexts and cultures, while staying true to the same overall principles. This multipronged approach is relatively expensive, but the theory of change is that the combination of these activities is necessary and sufficient to obtain a persistent impact. We do not test whether each of the program dimensions is individually necessary. Instead, we examine the “sufficiency” claim: A year after the conclusion of the program, and 3 years after the asset transfer, are program participants earning more income and achieving stable improvements in their well-being?

如何保持一个斑马鱼大脑神经再生能力

即使在斑马鱼的大脑,这个似乎可以比人类的大脑产生更好的产生新的神经元大脑里,再生能力可能不是无限的。巴博萨等人描绘出单个斑马鱼神经细胞与时间变化。即使在斑马鱼的大脑,这个似乎可以比人类的大脑产生更好的产生新的神经元大脑里,再生能力可能不是无限的。巴博萨等人描绘出单个斑马鱼神经细胞与时间变化。研究发现,神经干细胞维持神经元的数量,但不是完全替代,当脑部发生损伤时候,更多的干细胞被拉进神经通路,剩下更少的部分满足未来的替代的需要。

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Live imaging of adult neural stem cell behavior in the intact and injured zebrafish brain

原文摘要:

Adult neural stem cells are the source for restoring injured brain tissue. We used repetitive imaging to follow single stem cells in the intact and injured adult zebrafish telencephalon in vivo and found that neurons are generated by both direct conversions of stem cells into postmitotic neurons and via intermediate progenitors amplifying the neuronal output. We observed an imbalance of direct conversion consuming the stem cells and asymmetric and symmetric self-renewing divisions, leading to depletion of stem cells over time. After brain injury, neuronal progenitors are recruited to the injury site. These progenitors are generated by symmetric divisions that deplete the pool of stem cells, a mode of neurogenesis absent in the intact telencephalon. Our analysis revealed changes in the behavior of stem cells underlying generation of additional neurons during regeneration.

传播小分子RNA保护基因组

在动物身上,PIWI-interacting rna(piRNAs)是小非编码RNA,保护我们的生殖细胞系不受转座子的破坏。为了做到这个,piRNAs 以转座子RNAs作为目标并黏住它。一个切断了的长单链RNA前体是piRNA合成的启动子,piRNAs还可以进行自我延续放大周期,现在研究发现piRNA产生可以从piRNA形成的时间点开始严格地持续一个阶段时间。传播piRNA合成大大增加他们的序列多样性,可能帮助他们更有效地目标内生和小转座子。

原文链接:

piRNA-guided slicing specifies transcripts for Zucchini-dependent, phased piRNA biogenesis

原文摘要:

In animal gonads, PIWI-clade Argonaute proteins repress transposons sequence-specifically via bound Piwi-interacting RNAs (piRNAs). These are processed from single-stranded precursor RNAs by largely unknown mechanisms. Here we show that primary piRNA biogenesis is a 3′-directed and phased process that, in theDrosophila germ line, is initiated by secondary piRNA-guided transcript cleavage. Phasing results from consecutive endonucleolytic cleavages catalyzed by Zucchini, implying coupled formation of 3′ and 5′ ends of flanking piRNAs. Unexpectedly, Zucchini also participates in 3′ end formation of secondary piRNAs. Its function can, however, be bypassed by downstream piRNA-guided precursor cleavages coupled to exonucleolytic trimming. Our data uncover an evolutionarily conserved piRNA biogenesis mechanism in which Zucchini plays a central role in defining piRNA 5′ and 3′ ends.

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