Left-handed properties of a composite structure with metallic wires in a homogeneous Lorentz medium

The electromagnetic properties of a composite structure with metallic wires in a Lorentz medium were studied. The results show that the electromagnetic properties of the medium host influence the plasma resonance of metallic wires and the left-handed character of the composite. The plasma frequency of metallic wires reduces with the rise of permittivity or permeability of the medium host. Also, the negative permeability of the medium can destroy the wires' plasma resonance and prevent the realization of left-handed properties. The high loss of medium permittivity or permeability also inhibits the metallic plasma resonance. The negative influence of the media host on the left-handed properties of the composite structure can be effectively reduced by proper structure design, such as introducing a nonmagnetic medium in the host or using an anisotropic medium.     

Processing of refractory materials using various magnesium sources derived from Zinelbulak talc-magnesite

Magnesia (MgO) is widely used in the production of refractory materials due to its high melting point, high thermal shock, and excellent slag resistance. The properties of refractory materials depend upon magnesia sources and processing parameters. In this work, three different magnesium sources, namely, magnesium hydroxide concentrate, magnesium carbonate concentrate, and intermediate flotation concentrate, were obtained from the Zinelbulak talc-magnesite, Uzbekistan, by causticization-hydration and flotation processes, respectively. A series of refractory materials were prepared on the basis of these magnesium sources, and their effects on physico-mechanical properties and microstructures were investigated as a function of sintering temperature, molding pressure, and the particle size of magnesium sources. The experimental results showed that a refractory material obtained from the magnesium hydroxide concentrate at 1600℃ for 4 h demonstrated favorable parameters due mainly to a higher degree of contact among fine particles. The results obtained from X-ray diffraction and optical microscopy confirmed the presence of periclase and forsterite as the predominant phases in refractory specimens. The prepared refractory materials meet the requirements of the State Standards (Nos.4689-94 and 14832-96) for magnesia and forsterite refractories, respectively. It is, therefore, suggested herein that the use of different magnesium sources derived from the Zinelbulak talc-magnesite will offer the potential to provide economic benefits in the refractory industry.     

Microstructure and properties of hydrophobic films derived from Fe-W amorphous alloy

Amorphous metals are totally different from crystalline metals in regard to atom arrangement. Amorphous metals do not have grain boundaries and weak spots that crystalline materials contain, making them more resistant to wear and corrosion. In this study, amorphous Fe-W alloy films were first prepared by an electroplating method and were then made hydrophobic by modification with a water repellent (heptadecafluoro-1,1,2,2-tetradecyl) trimethoxysilane. Hierarchical micro-nano structures can be obtained by slightly oxidizing the as-deposited alloy, accompanied by phase transformation from amorphous to crystalline during heat treatment. The micro-nano structures can trap air to form an extremely thin cushion of air between the water and the film, which is critical to producing hydrophobicity in the film. Results show that the average values of capacitance, roughness factor, and impedance for specific surface areas of a 600℃ heat-treated sample are greater than those of a sample treated at 500℃. Importantly, the coating can be fabricated on various metal substrates to act as a corrosion retardant.     

As-cast structure of DC casting 7075 aluminum alloy obtained under dual-frequency electromagnetic field

We have experimentally determined the as-cast structures of semi-continuous casting 7075 aluminum alloy obtained in the presence of dual-frequency electromagnetic field. Results suggest that the use of dual-frequency electromagnetic field during the semi-continuous casting process of 7075 aluminum alloy ingots reduces the thickness of the surface segregation layer, increases the height of the melt meniscus, enhances the surface quality of the ingot, and changes the surface morphology of the melt pool. Moreover, low-frequency electromagnetic field was found to show the most obvious influence on improving the as-cast structure because of its high permeability in conductors.     

Structural refinement of 00Cr13Ni5Mo2 supermartensitic stainless steel during single-stage intercritical tempering

The 00Cr13Ni5Mo2 supermartensitic stainless steel was first tempered at 570–730℃ for 2 h to observe the microstructure and hardness changes. The tempering temperature was set to 600, 650, and 700℃, which is below, equal to, and above the austenite transformation start temperature, respectively, for each holding period to investigate the effects of tempering time on the structure and properties of the steel. The microstructure of the specimens was examined by optical microscopy and transmission electronic microscopy, and the phase composition was detected by X-ray diffraction. As expected, lath refinement was observed in the steel tempered at 700℃, and the refinement degree significantly depended on the tempering time. Contrary to normal steel softening by tempering, the hardness performance of the steel was significantly enhanced primarily because of the refinement of martensite laths after single-stage intercritical tempering. It is believed that the reverse transformation of martensite (α′) to austenite (γ) is responsible for the refinement.     

Formation mechanism of the protective layer in a blast furnace hearth

A variety of techniques, such as chemical analysis, scanning electron microscopy-energy dispersive spectroscopy, and X-ray diffraction, were applied to characterize the adhesion protective layer formed below the blast furnace taphole level when a certain amount of titanium- bearing burden was used. Samples of the protective layer were extracted to identify the chemical composition, phase assemblage, and distribution. Furthermore, the formation mechanism of the protective layer was determined after clarifying the source of each component. Finally, a technical strategy was proposed for achieving a stable protective layer in the hearth. The results show that the protective layer mainly exists in a bilayer form in the sidewall, namely, a titanium-bearing layer and a graphite layer. Both the layers contain the slag phase whose major crystalline phase is magnesium melilite (Ca₂MgSi₂O₇) and the main source of the slag phase is coke ash. It is clearly determined that solid particles such as graphite, Ti(C,N) and MgAl₂O₄ play an important role in the formation of the protective layer, and the key factor for promoting the formation of a stable protective layer is reasonable control of the evolution behavior of coke.     

Wild-type microglia arrest pathology in a mouse model of Rett syndrome

Rett syndrome is an X-linked autism spectrum disorder. The disease is characterized in most cases by mutation of the MECP2 gene, which encodes a methyl-CpG-binding protein. Although MECP2 is expressed in many tissues, the disease is generally attributed to a primary neuronal dysfunction. However, as shown recently, glia, specifically astrocytes, also contribute to Rett pathophysiology. Here we examine the role of another form of glia, microglia, in a murine model of Rett syndrome. Transplantation of wild-type bone marrow into irradiation-conditioned Mecp2-null hosts resulted in engraftment of brain parenchyma by bone-marrow-derived myeloid cells of microglial phenotype, and arrest of disease development. However, when cranial irradiation was blocked by lead shield, and microglial engraftment was prevented, disease was not arrested. Similarly, targeted expression of MECP2 in myeloid cells, driven by Lysm(cre) on an Mecp2-null background, markedly attenuated disease symptoms. Thus, through multiple approaches, wild-type Mecp2-expressing microglia within the context of an Mecp2-null male mouse arrested numerous facets of disease pathology: lifespan was increased, breathing patterns were normalized, apnoeas were reduced, body weight was increased to near that of wild type, and locomotor activity was improved. Mecp2(+/-) females also showed significant improvements as a result of wild-type microglial engraftment. These benefits mediated by wild-type microglia, however, were diminished when phagocytic activity was inhibited pharmacologically by using annexin V to block phosphatydilserine residues on apoptotic targets, thus preventing recognition and engulfment by tissue-resident phagocytes. These results suggest the importance of microglial phagocytic activity in Rett syndrome. Our data implicate microglia as major players in the pathophysiology of this devastating disorder, and suggest that bone marrow transplantation might offer a feasible therapeutic approach for it.     

Quantum teleportation and entanglement distribution over 100-kilometre free-space channels

Transferring an unknown quantum state over arbitrary distances is essential for large-scale quantum communication and distributed quantum networks. It can be achieved with the help of long-distance quantum teleportation and entanglement distribution. The latter is also important for fundamental tests of the laws of quantum mechanics. Although quantum teleportation and entanglement distribution over moderate distances have been realized using optical fibre links, the huge photon loss and decoherence in fibres necessitate the use of quantum repeaters for larger distances. However, the practical realization of quantum repeaters remains experimentally challenging. Free-space channels, first used for quantum key distribution, offer a more promising approach because photon loss and decoherence are almost negligible in the atmosphere. Furthermore, by using satellites, ultra-long-distance quantum communication and tests of quantum foundations could be achieved on a global scale. Previous experiments have achieved free-space distribution of entangled photon pairs over distances of 600?metres (ref. 14) and 13?kilometres (ref. 15), and transfer of triggered single photons over a 144-kilometre one-link free-space channel. Most recently, following a modified scheme, free-space quantum teleportation over 16?kilometres was demonstrated with a single pair of entangled photons. Here we report quantum teleportation of independent qubits over a 97-kilometre one-link free-space channel with multi-photon entanglement. An average fidelity of 80.4?±?0.9 per cent is achieved for six distinct states. Furthermore, we demonstrate entanglement distribution over a two-link channel, in which the entangled photons are separated by 101.8?kilometres. Violation of the Clauser-Horne-Shimony-Holt inequality is observed without the locality loophole. Besides being of fundamental interest, our results represent an important step towards a global quantum network. Moreover, the high-frequency and high-accuracy acquiring, pointing and tracking technique developed in our experiment can be directly used for future satellite-based quantum communication and large-scale tests of quantum foundations.     

A gigantic feathered dinosaur from the lower cretaceous of China

Numerous feathered dinosaur specimens have recently been recovered from the Middle-Upper Jurassic and Lower Cretaceous deposits of northeastern China, but most of them represent small animals. Here we report the discovery of a gigantic new basal tyrannosauroid, Yutyrannus huali gen. et sp. nov., based on three nearly complete skeletons representing two distinct ontogenetic stages from the Lower Cretaceous Yixian Formation of Liaoning Province, China. Y. huali shares some features, particularly of the cranium, with derived tyrannosauroids, but is similar to other basal tyrannosauroids in possessing a three-fingered manus and a typical theropod pes. Morphometric analysis suggests that Y. huali differed from tyrannosaurids in its growth strategy. Most significantly, Y. huali bears long filamentous feathers, thus providing direct evidence for the presence of extensively feathered gigantic dinosaurs and offering new insights into early feather evolution.     

The effect of water on the electrical conductivity of olivine

It is well known that water (as a source of hydrogen) affects the physical and chemical properties of minerals--for example, plastic deformation and melting temperature--and accordingly plays an important role in the dynamics and geochemical evolution of the Earth. Estimating the water content of the Earth's mantle by direct sampling provides only a limited data set from shallow regions (<200 km depth). Geophysical observations such as electrical conductivity are considered to be sensitive to water content, but there has been no experimental study to determine the effect of water on the electrical conductivity of olivine, the most abundant mineral in the Earth's mantle. Here we report a laboratory study of the dependence of the electrical conductivity of olivine aggregates on water content at high temperature and pressure. The electrical conductivity of synthetic polycrystalline olivine was determined from a.c. impedance measurements at a pressure of 4 GPa for a temperature range of 873-1,273 K for water contents of 0.01-0.08 wt%. The results show that the electrical conductivity is strongly dependent on water content but depends only modestly on temperature. The water content dependence of conductivity is best explained by a model in which electrical conduction is due to the motion of free protons. A comparison of the laboratory data with geophysical observations suggests that the typical oceanic asthenosphere contains approximately 10(-2) wt% water, whereas the water content in the continental upper mantle is less than approximately 10(-3) wt%.