Magnetic support of the optical emission line filaments in NGC 1275

The giant elliptical galaxy NGC 1275, at the centre of the Perseus cluster, is surrounded by a well-known giant nebulosity of emission-line filaments, which are plausibly in excess of 10(8) years old. The filaments are dragged out from the centre of the galaxy by radio-emitting 'bubbles' rising buoyantly in the hot intracluster gas, before later falling back. They act as markers of the feedback process by which energy is transferred from the central massive black hole to the surrounding gas. The mechanism by which the filaments are stabilized against tidal shear and dissipation into the surrounding extremely hot (4 x 10(7) K) gas has been unclear. Here we report observations that resolve thread-like structures in the filaments. Some threads extend over 6 kpc, yet are only 70 pc wide. We conclude that magnetic fields in the threads, in pressure balance with the surrounding gas, stabilize the filaments, so allowing a large mass of cold gas to accumulate and delay star formation.     

An evolutionarily conserved mechanism for presynaptic trapping

Presynaptic differentiation takes place over three interrelated acts involving the biogenesis and trafficking of molecular complexes of active zone material, the “trapping” or stabilization of active zone sites, and the subsequent development of mature synapses. Although the identities of proteins involved with establishing presynaptic specializations have been increasingly delineated, the exact functional mechanisms by which the active zone is assembled remain poorly understood. Here, we discuss a theoretical model for how the trapping stage of presynaptic differentiation might occur in developing neurons. We suggest that subsets of active zone proteins containing polyglutamine domains undergo concentration-dependent prion-like conversions as they accumulate at the plasma membrane. This conversion might serve to aggregate the proteins into a singular structure, which is then able to recruit scaffolding agents necessary for regulated synaptic transmission. A brief informatics analysis in support of this ‘Q’ assembly hypothesis—across commonly used models of synaptogenesis—is presented.     

Quality Evaluation of Image Recording Strategies for Limited Angle Tomography

In this paper we propose a new method for evaluating image recording strategies for limited angle tomography.In limited angle tomography exact three-dimensional(3-D) reconstruction is not achievable.With this method a metric for the reachable reconstruction quality by defined X-ray source trajectories is calculated.The result of our method is independent of reconstruction algorithms.Our approach is based on the gradients of the scanned volume and their grade of determinability.Compared to simulated reconstr...     

The magnetic nature of disk accretion onto black holes

Although disk accretion onto compact objects-white dwarfs, neutron stars and black holes-is central to much of high-energy astrophysics, the mechanisms that enable this process have remained observationally difficult to determine. Accretion disks must transfer angular momentum in order for matter to travel radially inward onto the compact object. Internal viscosity from magnetic processes and disk winds can both in principle transfer angular momentum, but hitherto we lacked evidence that either occurs. Here we report that an X-ray-absorbing wind discovered in an observation of the stellar-mass black hole binary GRO J1655 - 40 (ref. 6) must be powered by a magnetic process that can also drive accretion through the disk. Detailed spectral analysis and modelling of the wind shows that it can only be powered by pressure generated by magnetic viscosity internal to the disk or magnetocentrifugal forces. This result demonstrates that disk accretion onto black holes is a fundamentally magnetic process.     

City living and urban upbringing affect neural social stress processing in humans

More than half of the world's population now lives in cities, making the creation of a healthy urban environment a major policy priority. Cities have both health risks and benefits, but mental health is negatively affected: mood and anxiety disorders are more prevalent in city dwellers and the incidence of schizophrenia is strongly increased in people born and raised in cities. Although these findings have been widely attributed to the urban social environment, the neural processes that could mediate such associations are unknown. Here we show, using functional magnetic resonance imaging in three independent experiments, that urban upbringing and city living have dissociable impacts on social evaluative stress processing in humans. Current city living was associated with increased amygdala activity, whereas urban upbringing affected the perigenual anterior cingulate cortex, a key region for regulation of amygdala activity, negative affect and stress. These findings were regionally and behaviourally specific, as no other brain structures were affected and no urbanicity effect was seen during control experiments invoking cognitive processing without stress. Our results identify distinct neural mechanisms for an established environmental risk factor, link the urban environment for the first time to social stress processing, suggest that brain regions differ in vulnerability to this risk factor across the lifespan, and indicate that experimental interrogation of epidemiological associations is a promising strategy in social neuroscience.     

Mapping copy number variation by population-scale genome sequencing

Genomic structural variants (SVs) are abundant in humans, differing from other forms of variation in extent, origin and functional impact. Despite progress in SV characterization, the nucleotide resolution architecture of most SVs remains unknown. We constructed a map of unbalanced SVs (that is, copy number variants) based on whole genome DNA sequencing data from 185 human genomes, integrating evidence from complementary SV discovery approaches with extensive experimental validations. Our map encompassed 22,025 deletions and 6,000 additional SVs, including insertions and tandem duplications. Most SVs (53%) were mapped to nucleotide resolution, which facilitated analysing their origin and functional impact. We examined numerous whole and partial gene deletions with a genotyping approach and observed a depletion of gene disruptions amongst high frequency deletions. Furthermore, we observed differences in the size spectra of SVs originating from distinct formation mechanisms, and constructed a map of SV hotspots formed by common mechanisms. Our analytical framework and SV map serves as a resource for sequencing-based association studies.     

集成电路电磁适应性的时钟信号调制

电磁干扰(EMI)是瞬时功能故障的主要来源之一,原因是电源供电线上的噪声注入引起了VDD和GND的额定值的波动.介绍了一种新的方法来增强片上系统(SoC)关于电源和接地电压瞬变时的信号完整性,并且这种方法完全符合IEC 61000-4-29 标准.其基本思想是设计和IEC 61000-4-29兼容的集成电路,通过局部和动态地将时钟占空比去适应传播延迟的变化和扰动的逻辑路径.当无法满足时,该方法导致暂时把集成电路的工作频率减小到满足该标准的最小值.根据异常电网活动,时钟占空比调制(CDCM)是通过使用正和/或负边沿时钟展宽逻辑(CSL)块来实现的.基于这个概念,在尽可能保持时钟高速频率的同时,数字电路对于电源供电线上波动的耐受性将会更强.该方法可被视作一种在线提供动态自适应同步的监视技术.通过SPICE模拟,实验结果表明此方法的有效性.     

Complex zeolite structure solved by combining powder diffraction and electron microscopy

Many industrially important materials, ranging from ceramics to catalysts to pharmaceuticals, are polycrystalline and cannot be grown as single crystals. This means that non-conventional methods of structure analysis must be applied to obtain the structural information that is fundamental to the understanding of the properties of these materials. Electron microscopy might appear to be a natural approach, but only relatively simple structures have been solved by this route. Powder diffraction is another obvious option, but the overlap of reflections with similar diffraction angles causes an ambiguity in the relative intensities of those reflections. Various ways of overcoming or circumventing this problem have been developed, and several of these involve incorporating chemical information into the structure determination process. For complex zeolite structures, the FOCUS algorithm has proved to be effective. Because it operates in both real and reciprocal space, phase information obtained from high-resolution transmission electron microscopy images can be incorporated directly into this algorithm in a simple way. Here we show that by doing so, the complexity limit can be extended much further. The power of this approach has been demonstrated with the solution of the structure of the zeolite TNU-9 (|H9.3|[Al9.3Si182.7O384]; ref. 10) with 24 topologically distinct (Si,Al) atoms and 52 such O atoms. For comparison, ITQ-22 (ref. 11), the most complex zeolite known to date, has 16 topologically distinct (Si,Ge) atoms.     

Modifications de la glicémie et des groupements-SH du sang des Lapins durant le reflexe de l'orientation

Summary The orientation reflex, to a new milieu, causes increase of the glycemia and the non-protein -SH groups, and a diminution of the protein and total -SH groups of rabbit's blood.     

Action of plastid phospholipase D on free and lipoprotein-bound phospholipids

Résumé Les phospholipides en état de lipoprotéine sont hydrolysés à un rythme plus accéléré par la phospholipase D des chloroplastes que ne le sont les phospholipides purifiécs. La remarquable affinité de l'enzyme pour les soustrats en forme lipoprotéique se manifeste en l'absence de l'éthère éthylique qui est l'activateur indispensable à l'hydrolyse des phospholipides purifiées.

---

---

This work was supported by a research grant (AI-03171) from the U.S. National Institutes of Health.