South-polar features on Venus similar to those near the north pole

Venus has no seasons, slow rotation and a very massive atmosphere, which is mainly carbon dioxide with clouds primarily of sulphuric acid droplets. Infrared observations by previous missions to Venus revealed a bright 'dipole' feature surrounded by a cold 'collar' at its north pole. The polar dipole is a 'double-eye' feature at the centre of a vast vortex that rotates around the pole, and is possibly associated with rapid downwelling. The polar cold collar is a wide, shallow river of cold air that circulates around the polar vortex. One outstanding question has been whether the global circulation was symmetric, such that a dipole feature existed at the south pole. Here we report observations of Venus' south-polar region, where we have seen clouds with morphology much like those around the north pole, but rotating somewhat faster than the northern dipole. The vortex may extend down to the lower cloud layers that lie at about 50 km height and perhaps deeper. The spectroscopic properties of the clouds around the south pole are compatible with a sulphuric acid composition.     

Observation of ferrotoroidic domains

Domains are of unparalleled technological importance as they are used for information storage and for electronic, magnetic and optical switches. They are an essential property of any ferroic material. Three forms of ferroic order are widely known: ferromagnetism, a spontaneous magnetization; ferroelectricity, a spontaneous polarization; and ferroelasticity, a spontaneous strain. It is currently debated whether to include an ordered arrangement of magnetic vortices as a fourth form of ferroic order, termed ferrotoroidicity. Although there are reasons to expect this form of order from the point of view of thermodynamics, a crucial hallmark of the ferroic state--that is, ferrotoroidic domains--has not hitherto been observed. Here ferrotoroidic domains are spatially resolved by optical second harmonic generation in LiCoPO4, where they coexist with independent antiferromagnetic domains. Their space- and time-asymmetric nature relates ferrotoroidics to multiferroics with magnetoelectric phase control and to other systems in which space and time asymmetry leads to possibilities for future applications.     

Scanning-tunnelling spectra of cuprates

The study of bosonic modes that couple to the charge carriers is a key element in understanding superconductivity. Using atomic-resolution scanning-tunnelling microscopy (STM) to extract the spectrum of these modes in the high-temperature superconductor Bi2Sr2CaCu2O(8+delta), Lee et al. find a mode whose frequency does not depend on doping but that changes on isotopic substitution of 16O with 18O. From this, they infer a role for lattice modes (phonons). However, examination of their data reveals a weaker, but distinct, feature that has all the characteristics of the magnetic excitation identified as the bosonic mode in other competing experiments. We therefore suggest that the lattice mode seen by Lee et al. is not relevant to superconductivity and is due to inelastic tunnelling through the insulating oxide layer.     

HDAC6 rescues neurodegeneration and provides an essential link between autophagy and the UPS

A prominent feature of late-onset neurodegenerative diseases is accumulation of misfolded protein in vulnerable neurons. When levels of misfolded protein overwhelm degradative pathways, the result is cellular toxicity and neurodegeneration. Cellular mechanisms for degrading misfolded protein include the ubiquitin-proteasome system (UPS), the main non-lysosomal degradative pathway for ubiquitinated proteins, and autophagy, a lysosome-mediated degradative pathway. The UPS and autophagy have long been viewed as complementary degradation systems with no point of intersection. This view has been challenged by two observations suggesting an apparent interaction: impairment of the UPS induces autophagy in vitro, and conditional knockout of autophagy in the mouse brain leads to neurodegeneration with ubiquitin-positive pathology. It is not known whether autophagy is strictly a parallel degradation system, or whether it is a compensatory degradation system when the UPS is impaired; furthermore, if there is a compensatory interaction between these systems, the molecular link is not known. Here we show that autophagy acts as a compensatory degradation system when the UPS is impaired in Drosophila melanogaster, and that histone deacetylase 6 (HDAC6), a microtubule-associated deacetylase that interacts with polyubiquitinated proteins, is an essential mechanistic link in this compensatory interaction. We found that compensatory autophagy was induced in response to mutations affecting the proteasome and in response to UPS impairment in a fly model of the neurodegenerative disease spinobulbar muscular atrophy. Autophagy compensated for impaired UPS function in an HDAC6-dependent manner. Furthermore, expression of HDAC6 was sufficient to rescue degeneration associated with UPS dysfunction in vivo in an autophagy-dependent manner. This study suggests that impairment of autophagy (for example, associated with ageing or genetic variation) might predispose to neurodegeneration. Morover, these findings suggest that it may be possible to intervene in neurodegeneration by augmenting HDAC6 to enhance autophagy.     

浅谈无线远传水表的测试

智能远传水表是普通发讯水表加上电子采集模块而组成,具有不入户抄表的优点,解决了抄表扰民的困扰.且计量精确、灵敏度高,有利于资源的合理分配和利用,因此适应了智能化住宅小区建设的需求,文章介绍了无线智能水表的技术参数要求及参数测量方法.     

基于M-Bus传输协议的便携式水表运行监测系统的开发

文章介绍了M-Bus传输协议的便携式水表运行监测系统的开发背景,开发过程中采用的技术路线以及关键技术,该套系统是对全自动抄表系统的一种补充,给用户提供多一种抄表方案的选择.     

基于M-Bus传输协议的便携式水表运行监测系统的开发

文章介绍了M-Bus传输协议的便携式水表运行监测系统的开发背景,开发过程中采用的技术路线以及关键技术,该套系统是对全自动抄表系统的一种补充,给用户提供多一种抄表方案的选择。     

A hydrothermal origin for isotopically anomalous cap dolostone cements from south China

The release of methane into the atmosphere through destabilization of clathrates is a positive feedback mechanism capable of amplifying global warming trends that may have operated several times in the geological past. Such methane release is a hypothesized cause or amplifier for one of the most drastic global warming events in Earth history, the end of the Marinoan 'snowball Earth' ice age, ～635?Myr ago. A key piece of evidence supporting this hypothesis is the occurrence of exceptionally depleted carbon isotope signatures (δ(13)C(PDB) down to -48‰; ref. 8) in post-glacial cap dolostones (that is, dolostone overlying glacial deposits) from south China; these signatures have been interpreted as products of methane oxidation at the time of deposition. Here we show, on the basis of carbonate clumped isotope thermometry, (87)Sr/(86)Sr isotope ratios, trace element content and clay mineral evidence, that carbonates bearing the (13)C-depleted signatures crystallized more than 1.6?Myr after deposition of the cap dolostone. Our results indicate that highly (13)C-depleted carbonate cements grew from hydrothermal fluids and suggest that their carbon isotope signatures are a consequence of thermogenic methane oxidation at depth. This finding not only negates carbon isotope evidence for methane release during Marinoan deglaciation in south China, but also eliminates the only known occurrence of a Precambrian sedimentary carbonate with highly (13)C-depleted signatures related to methane oxidation in a seep environment. We propose that the capacity to form highly (13)C-depleted seep carbonates, through biogenic anaeorobic oxidation of methane using sulphate, was limited in the Precambrian period by low sulphate concentrations in sea water. As a consequence, although clathrate destabilization may or may not have had a role in the exit from the 'snowball' state, it would not have left extreme carbon isotope signals in cap dolostones.     

Oxysterols direct immune cell migration via EBI2

Epstein-Barr virus-induced gene 2 (EBI2, also known as GPR183) is a G-protein-coupled receptor that is required for humoral immune responses; polymorphisms in the receptor have been associated with inflammatory autoimmune diseases. The natural ligand for EBI2 has been unknown. Here we describe the identification of 7α,25-dihydroxycholesterol (also called 7α,25-OHC or 5-cholesten-3β,7α,25-triol) as a potent and selective agonist of EBI2. Functional activation of human EBI2 by 7α,25-OHC and closely related oxysterols was verified by monitoring second messenger readouts and saturable, high-affinity radioligand binding. Furthermore, we find that 7α,25-OHC and closely related oxysterols act as chemoattractants for immune cells expressing EBI2 by directing cell migration in vitro and in vivo. A critical enzyme required for the generation of 7α,25-OHC is cholesterol 25-hydroxylase (CH25H). Similar to EBI2 receptor knockout mice, mice deficient in CH25H fail to position activated B cells within the spleen to the outer follicle and mount a reduced plasma cell response after an immune challenge. This demonstrates that CH25H generates EBI2 biological activity in vivo and indicates that the EBI2-oxysterol signalling pathway has an important role in the adaptive immune response.