《自然》（20190411出版）一周论文导读

翻译 | 宗华

Nature, 11 April 2019, Volume 568 Issue 7751

《自然》2019年4月11日，第7751期568卷

物理学Physics

 

Electric field correlation measurements on the electromagnetic vacuum state

电磁真空状态下的电场相关测量

▲ 作者：Ileana-Cristina Benea-Chelmus, Francesca Fabiana Settembrini, Giacomo Scalari & Jérôme Faist

▲ 链接：

https://www.nature.com/articles/s41586-019-1083-9

▲ 摘要：

量子力学归因于电磁辐射零点电场波动的基态。这种波动贯穿于所有频率的真空空间。

这里，我们利用放置在低温环境下非线性晶体中的电光检测，对太赫兹频率范围内这些波动的场相关性进行了直接测量。

我们研究了它们的时空相干性。这种相干性在零时间延迟和空间距离下，峰值为6.2×10⁻²伏特平方每平方米，对应于0.25伏特每米的波动真空场。通过这种测量，我们确定了电光探测带宽内电磁辐射基态的光谱组成。

▲ Abstract

Quantum mechanics ascribes to the ground state of the electromagnetic radiation zero-point electric field fluctuations that permeate empty space at all frequencies. Here we perform a direct measurement of the field correlation on these fluctuations in the terahertz frequency range by using electro-optic detection in a nonlinear crystal placed in a cryogenic environment. We investigate their temporal and spatial coherence, which, at zero time delay and spatial distance, has a peak value of 6.2 × 10⁻² volts squared per square metre, corresponding to a fluctuating vacuum field of 0.25 volts per metre. With this measurement, we determine the spectral components of the ground state of electromagnetic radiation within the bandwidth of our electro-optic detection.

Ultrafast spin-lasers

超速自旋激光器

▲ 作者：Markus Lindemann, Gaofeng Xu, Tobias Pusch, Rainer Michalzik, et al

▲ 链接：

https://www.nature.com/articles/s41586-019-1073-y

▲ 摘要：

自旋电子学利用电子的自旋和电荷，发展了电荷载子自旋和光子自旋的自旋激光器。

这里，我们通过实验证明，普通半导体激光器中载子自旋和光偏振之间的耦合可使室温调制频率超过200千兆赫，比最好的传统半导体激光器高出近一个数量级。

令人惊讶的是，这种自旋激光器的超快运行依赖于较短的载子自旋弛豫时间和较大的折射率各向异性。这两种特性在自旋电子学和传统激光器中都被普遍认为是有害的。

▲ Abstract

Spintronics, in which both the spin and the charge of the electron are used, has led to the development of spin-lasers, in which charge-carrier spin and photon spin are exploited. Here we show experimentally that the coupling between carrier spin and light polarization in common semiconductor lasers can enable room-temperature modulation frequencies above 200 gigahertz, exceeding by nearly an order of magnitude the best conventional semiconductor lasers. Surprisingly, this ultrafast operation of the resultant spin-laser relies on a short carrier spin relaxation time and a large anisotropy of the refractive index, both of which are commonly viewed as detrimental in spintronics and conventional lasers.

生物学Biology

CD22 blockade restores homeostatic microglial phagocytosis in ageing brains

CD22阻滞剂可恢复衰老大脑内稳态的小胶质细胞吞噬作用

▲ 作者：John V. Pluvinage, Michael S. Haney, Benjamin A. H. Smith

▲ 链接：

https://www.nature.com/articles/s41586-019-1088-4

▲ 摘要：

小胶质细胞通过吞噬蛋白质聚集物和细胞碎片维持中枢神经系统的稳态。这种功能在衰老和神经退行性疾病期间恶化，并伴随认知能力下降。

我们将CRISPR-Cas9敲除筛选与RNA测序分析结合，以发现与年龄相关的小胶质细胞吞噬的基因修饰物。这些筛选结果表明，CD22是一种典型的B细胞受体，是一种吞噬的负调控因子，在衰老的小胶质细胞上上调。

CD22介导同α2,6连接的唾液酸的抗吞噬作用，同时抑制CD22可促进体内髓鞘碎片、β淀粉样蛋白寡聚物和α-突触核蛋白的清除。

阻断CD22功能的抗体在中枢神经系统的长期传递，使小胶质细胞重新编程，进入稳态转录状态，并改善老年小鼠的认知功能。

▲ Abstract

Microglia maintain homeostasis in the central nervous system through phagocytic clearance of protein aggregates and cellular debris. This function deteriorates during ageing and neurodegenerative disease, concomitant with cognitive decline. We combined CRISPR–Cas9 knockout screens with RNA sequencing analysis to discover age-related genetic modifiers of microglial phagocytosis. These screens identified CD22, a canonical B cell receptor, as a negative regulator of phagocytosis that is upregulated on aged microglia. CD22 mediates the anti-phagocytic effect of α2,6-linked sialic acid, and inhibition of CD22 promotes the clearance of myelin debris, amyloid-β oligomers and α-synuclein fibrils in vivo. Long-term central nervous system delivery of an antibody that blocks CD22 function reprograms microglia towards a homeostatic transcriptional state and improves cognitive function in aged mice.

Effective breast cancer combination therapy targeting BACH1 and mitochondrial metabolism

针对BACH1和线粒体代谢的有效乳腺癌联合疗法

▲ 作者：Jiyoung Lee, Ali E. Yesilkanal, Joseph P. Wynne, et al

▲ 链接：

https://www.nature.com/articles/s41586-019-1005-x

▲ 摘要：

线粒体代谢是癌症治疗的一个有吸引力的目标。重编程代谢通路可改善代谢抑制剂的能力，从而抑制治疗方案有限的癌症，如三阴性乳腺癌（TNBC）。

这里，我们证实，在TNBC患者肿瘤中表达增加的血液结合转录因子——BTB和CNC同源性1 （BACH1），以线粒体代谢为目标。BACH1在三羧酸循环中降低葡萄糖利用率，并且负调控电子传递链（ETC）基因的转录。

shRNA引发的BACH1损耗或者氯高铁血红素导致的降解，使细胞对二甲双胍等抑制剂敏感，从而抑制细胞系和来自患者的肿瘤异种移植物的生长。

▲ Abstract

Mitochondrial metabolism is an attractive target for cancer therapy. Reprogramming metabolic pathways could improve the ability of metabolic inhibitors to suppress cancers with limited treatment options, such as triple-negative breast cancer (TNBC). Here we show that BTB and CNC homology1 (BACH1), a haem-binding transcription factor that is increased in expression in tumours from patients with TNBC, targets mitochondrial metabolism. BACH1 decreases glucose utilization in the tricarboxylic acid cycle and negatively regulates transcription of electron transport chain (ETC) genes. BACH1 depletion by shRNA or degradation by hemin sensitizes cells to ETC inhibitors such as metformin, suppressing growth of both cell line and patient-derived tumour xenografts.

古人类学Paleoanthropology

 

A new species of Homo from the Late Pleistocene of the Philippines

来自晚更新世菲律宾的一个新人种

▲ 作者：Florent Détroit, Armand Salvador Mijares, Julien Corny, et al

▲ 链接：

https://www.nature.com/articles/s41586-019-1067-9

▲ 摘要：

2007年，科学家在卡劳洞穴（位于菲律宾吕宋岛北部）发现了古人类的第三块跖骨。其年代可追溯到6.7万年前，这是菲律宾发现人类存在的最早的直接证据。

对这块跖骨的分析表明，它属于人属，但不清楚属于哪个物种。这里，我们发现了另外12种古人类元素。

它们代表了至少3个个体，并且在卡劳洞穴中被发现的地层与先前发现跖骨的地层相同。这些标本显示了原始和派生形态特征的组合，而这不同于在人属的其他物种（包括弗洛瑞斯人和智人）中发现的特征组合。我们证明，其属于一个新物种，并称之为吕宋人。

▲ Abstract

A hominin third metatarsal discovered in 2007 in Callao Cave (Northern Luzon, the Philippines) and dated to 67 thousand years ago provided the earliest direct evidence of a human presence in the Philippines. Analysis of this foot bone suggested that it belonged to the genus Homo, but to which species was unclear. Here we report the discovery of twelve additional hominin elements that represent at least three individuals that were found in the same stratigraphic layer of Callao Cave as the previously discovered metatarsal. These specimens display a combination of primitive and derived morphological features that is different from the combination of features found in other species in the genus Homo (including Homo floresiensis and Homo sapiens) and warrants their attribution to a new species, which we name Homo luzonensis.

 

生态学Ecology

Five decades of northern land carbon uptake revealed by the interhemispheric CO₂ gradient

两半球间二氧化碳梯度揭示了北半球陆地50年的碳吸收情况

▲ 作者：P. Ciais, J. Tan, X. Wang, C. Roedenbeck, et al

▲ 链接：

https://www.nature.com/articles/s41586-019-1078-6

▲ 摘要：

过去几十年里，全球陆地和海洋碳汇随着二氧化碳排放量的增加而成比例地增加。人们认为，北半球的陆地对全球陆地碳汇的贡献占主导地位。

这里，利用1958~2016年间大气二氧化碳两半球间梯度的测量结果，我们发现，北半球陆地碳汇在上世纪60年代到80年代后期保持稳定，然后在上世纪90年代每年增加0.5±0.4 petagram（1个petagram=1015亿克）碳，并且在本世纪初每年增加0.6 ± 0.5 petagram碳。

上世纪90年代北半球陆地碳汇的增加占同期全球陆地碳通量增加的65%。21世纪头十年的后续增长大于全球陆地碳通量的增长，这表明南半球的碳吸收同步下降。

▲ Abstract

The global land and ocean carbon sinks have increased proportionally with increasing carbon dioxide emissions during the past decades. It is thought that Northern Hemisphere lands make a dominant contribution to the global land carbon sink. Here, using measurements of the interhemispheric gradient of atmospheric carbon dioxide from 1958 to 2016, we show that the northern land sink remained stable between the 1960s and the late 1980s, then increased by 0.5 ± 0.4 petagrams of carbon per year during the 1990s and by 0.6 ± 0.5 petagrams of carbon per year during the 2000s. The increase of the northern land sink in the 1990s accounts for 65% of the increase in the global land carbon flux during that period. The subsequent increase in the 2000s is larger than the increase in the global land carbon flux, suggesting a coincident decrease of carbon uptake in the Southern Hemisphere.

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