An endoribonuclease-prepared siRNA screen in human cells identifies genes essential for cell division

RNA interference (RNAi) is an evolutionarily conserved defence mechanism whereby genes are specifically silenced through degradation of messenger RNAs; this process is mediated by homologous double-stranded (ds)RNA molecules. In invertebrates, long dsRNAs have been used for genome-wide screens and have provided insights into gene functions. Because long dsRNA triggers a nonspecific interferon response in many vertebrates, short interfering (si)RNA or short hairpin (sh)RNAs must be used for these organisms to ensure specific gene silencing. Here we report the generation of a genome-scale library of endoribonuclease-prepared short interfering (esi)RNAs from a sequence-verified complementary DNA collection representing 15,497 human genes. We used 5,305 esiRNAs from this library to screen for genes required for cell division in HeLa cells. Using a primary high-throughput cell viability screen followed by a secondary high content videomicroscopy assay, we identified 37 genes required for cell division. These include several splicing factors for which knockdown generates mitotic spindle defects. In addition, a putative nuclear-export terminator was found to speed up cell proliferation and mitotic progression after knockdown. Thus, our study uncovers new aspects of cell division and establishes esiRNA as a versatile approach for genomic RNAi screens in mammalian cells.     

燃烧室偶合系统不稳定传热的数值分析

本文在轴对称不稳定热传导有限元分析模型的基础上,提出了一个内燃机燃烧室的活塞与缸套偶合系统的不稳定传热数值分析模型。该模型考虑了在燃气与边界的对流和热幅射非线性热交换条件下运动着的活塞、活塞环、缸套和润滑油膜之间在传热过程中的相互作用和影响,可以预测上述系统各部分的温度波动分布、瞬态温度场以及瞬态热流分布。     

苏联无綫电电子学的发展——为紀念A.C.波波夫100周年誕辰而作

在环顾无綫电电子学科学技术方面多种多样的成就的时候,現在完全可以有根据地說,1859年伟大的俄罗斯科学家兼发明家A.C.波波夫关于可以不用导线(即用无綫电波)能够传输訊号的发明是科学技术发展中新紀元的开端。在此以前,电磁波被认为只不过是一个物理学的概念。那时还沒有发現它可貴的性貭,而現在这些性貭的利用已經在无綫电通訊、广播、电视、无綫电导航、射电頻譜学、射电天文学等部門中获得了許多輝煌的成就。只是由于电真空器件的广泛应用才有可能掌握无     

大地構造物理学—地質学中一个有前途的新方向

苏联科学家認为大地構造物理学是一个新的科学方向,它的任务是同时利用地質学和物理学的方法来研究地壳中产生的構造形变的机制作用。地壳中岩层揉挤成折皺,形成大片断裂以及地壳內各个部分沿着这些断裂又发生位移的現象,无論从理論的观点还是从实际的观点出发都是极有兴趣的問題。各个时期內折皺形成过程的发展和断裂的产生,是地壳生存史上极重要的一个方面,而引起構造形变的原因和产生形变的条件,应該是从理論上闡述地壳和整个地球发展一般問題的重要組成部分。以后,地壳上有用矿产的形成和聚集都与折皺和断裂的形成作用和分布有着密切的联系。因此,为了对矿产的分布規律有一个较完整的概念,必須了解产生这些構造形变的条件。此外,既然地質学家們在研     

Hsp70 chaperones: Cellular functions and molecular mechanism

Hsp70 proteins are central components of the cellular network of molecular chaperones and folding catalysts. They assist a large variety of protein folding processes in the cell by transient association of their substrate binding domain with short hydrophobic peptide segments within their substrate proteins. The substrate binding and release cycle is driven by the switching of Hsp70 between the low-affinity ATP bound state and the high-affinity ADP bound state. Thus, ATP binding and hydrolysis are essential in vitro and in vivo for the chaperone activity of Hsp70 proteins. This ATPase cycle is controlled by co-chaperones of the family of J-domain proteins, which target Hsp70s to their substrates, and by nucleotide exchange factors, which determine the lifetime of the Hsp70-substrate complex. Additional co-chaperones fine-tune this chaperone cycle. For specific tasks the Hsp70 cycle is coupled to the action of other chaperones, such as Hsp90 and Hsp100.Received 21 October 2004; received after revision 24 November 2004; accepted 6 December 2004     

Silicon carbide resonant tuning fork for microsensing applications in high temperature and high G shock environments

We present the fabrication and testing of a silicon carbide(SiC)balanced mass double-ended tuning fork that survives harsh environments without compromising the device strain sensitivity and resolution bandwidth.The device features a material stack that survives corrosive environments and enables high-temperature operation.To perform high-temperature testing,a specialized setup was constructed that allows the tuning fork to be characterized using traditional silicon electronics.The tuning fork has been operated at 600 ℃ in the presence of dry steam for short durations.This tuning fork has also been tested to 64 000 G using a hard-launch,soft-catch shock implemented with a light gas gun.However,the device still has a strain sensitivity of 66 Hz/με and strain resolution of 0.045 με in a 10 kHz bandwidth.As such,this balanced-mass double-ended tuning fork can be used to create a variety of different sensors including strain gauges,accelerometers,gyroscopes,and pressure transducers.Given the adaptable fabrication process flow,this device could be useful to micro-electro-mechanical systems(MEMS) designers creating sensors for a variety of different applications.     

Magnetic and flotation studies of banded hematite quartzite (BHQ) ore for the production of pellet grade concentrate

To identify and establish beneficiation techniques for banded hematite quartzite (BHQ) iron ore, a comprehensive research on BHQ ore treatment was carried out. The BHQ ore was assayed as 38.9wt% Fe, 42.5wt% SiO₂, and 1.0wt% Al₂O₃. In this ore, hematite and quartz are present as the major mineral phases where goethite, martite, and magnetite are present in small amounts. The liberation of hematite particles can be enhanced to about 82% by reducing the particle size to below 63 μm. The rejection of silica particles can be obtained by magnetic and flotation separation techniques. Overall, the BHQ ore can be enriched to 65.3wt% Fe at 61.9% iron recovery. A flowsheet has been suggested for the commercial exploitation of the BHQ ore.     

地球气候变化的另类视角——罗伯特·劳克林认为:看待气候问题应与整个地质时间概念相关联

对地质时间概念以及一些基本的科学概念更多一些了解,也许我们就能以一种新的视角来看待地球气候变化以及地球能源的未来     

搞笑车尾贴

在提升生活品质的期待中,越来越多的人成为有车族。可机动车的猛增却引发越来越严重、越来越频繁的道路拥堵。开车上路当然得盯着前面的车屁股,不过别担心枯燥,有你乐的!     

Spectroscopic confirmation of a galaxy at redshift z = 8.6

Galaxies had their most significant impact on the Universe when they assembled their first generations of stars. Energetic photons emitted by young, massive stars in primeval galaxies ionized the intergalactic medium surrounding their host galaxies, cleared sightlines along which the light of the young galaxies could escape, and fundamentally altered the physical state of the intergalactic gas in the Universe continuously until the present day. Observations of the cosmic microwave background, and of galaxies and quasars at the highest redshifts, suggest that the Universe was reionized through a complex process that was completed about a billion years after the Big Bang, by redshift z?≈?6. Detecting ionizing Lyman-α photons from increasingly distant galaxies places important constraints on the timing, location and nature of the sources responsible for reionization. Here we report the detection of Lyα photons emitted less than 600?million years after the Big Bang. UDFy-38135539 (ref. 5) is at a redshift of z = 8.5549?±?0.0002, which is greater than those of the previously known most distant objects, at z = 8.2 (refs 6 and 7) and z = 6.96 (ref. 8). We find that this single source is unlikely to provide enough photons to ionize the volume necessary for the emission line to escape, requiring a significant contribution from other, probably fainter galaxies nearby.