7,199 research outputs found

    Short communication: First report of thresher sharks (Alopiidae) in the Gulf of Antalya

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    Generally, Alopiidae family members are active, strong-swimming, pelagic, coastal and deep-water sharks. They are characterized by a very long upper caudal lobe. They have two dorsal fins; the second dorsal and anal fins are very small. They can be found in all warm oceans and mainly feed on small to moderately large schooling fishes and squids. Up to now, only three species have been described in family Alopiidae with two of them Alopias vulpinus (Bonnaterre, 1788) and Alopias superciliosus (Lowe, 1839) reported from the Mediterranean Sea. The third species (A. pelagicus) is reported from the Pacific Ocean. ... This study aimed to improve the lack of data on these species in the Mediterranean Sea

    A novel non-Fermi-liquid state in the iron-pnictide FeCrAs

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    We report transport and thermodynamic properties of stoichiometric single crystals of the hexagonal iron-pnictide FeCrAs. The in-plane resistivity shows an unusual "non-metallic" dependence on temperature T, rising continuously with decreasing T from ~ 800 K to below 100 mK. The c-axis resistivity is similar, except for a sharp drop upon entry into an antiferromagnetic state at T_N 125 K. Below 10 K the resistivity follows a non-Fermi-liquid power law, rho(T) = rho_0 - AT^x with x<1, while the specific heat shows Fermi liquid behaviour with a large Sommerfeld coefficient, gamma ~ 30 mJ/mol K^2. The high temperature properties are reminiscent of those of the parent compounds of the new layered iron-pnictide superconductors, however the T -> 0 properties suggest a new class of non-Fermi liquid.Comment: 6 pages, 4 figure

    Production of Dimethyl Ether (DME) for Transportation Fuel

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    Dimethyl Ether (DME) is a proposed alternative to diesel fuel that is being looked into by car and truck manufacturers worldwide. The current market, based almost completely in China, is primed for growth and a U.S. based DME total plant that is economical and environmentally feasible stands to pave the way for America’s DME market, especially since states such as California have approved DME for use as vehicle fuel (Fuel Smarts). Conventionally, the DME is produced by feeding Methanol into a xed-bed gas-phase reactor over a ɣ-alumina catalyst (Dimian et al). Using this process and normal operating conditions (250-400°C and up to 20 bar) operations can reach 70-80% Methanol conversion. The proposed process utilizes the innovative reactive distillation technology and Amberlyst 35 catalyst to achieve a 99.8% Methanol conversion and produce 35,418 kilograms of DME fuel per hour. The reactive distillation is executed at ~130°C (in the reactive stages) and 700 kPa (condenser pressure), and produces water as a byproduct, which exits as the bottoms stream. In order to create a process that is environmentally sustainable, the small amounts of Methanol and DME in the bottoms stream are removed using biotreatment and the water is then released into a nearby river. The product DME is mixed with mineral oil to meet ISO standards and is then stored in an on-site spherical tank farm. Diesel prices will be undercut by the DME product at 1.716agalloninordertoincentivisecompaniestomaketheswitchtoDMEfuel.TheDMEtotalplant,locatedinBeaumont,Texas,servestoprovidethelocallong−haultruckingindustrywithacleanerburningfuelforaplantlifeof20years.TheDMEtotalplanthasanInternalRateofReturn(IRR)of12.61.716 a gallon in order to incentivise companies to make the switch to DME fuel. The DME total plant, located in Beaumont, Texas, serves to provide the local long-haul trucking industry with a cleaner burning fuel for a plant life of 20 years. The DME total plant has an Internal Rate of Return (IRR) of 12.6%, a Net Present Value (NPV) in 2020 of approximately 12 million, and will turn its rst pro t in 2033. The report addresses nancial, economic, and process concerns to deliver recommendations for the construction that is safest for the environment, the investor, and the plant operator

    Structural origin of the anomalous temperature dependence of the local magnetic moments in the CaFe2_{2}As2_{2} family of materials

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    We report a combination of Fe Kβ\beta x-ray emission spectroscopy and abab-intio calculations to investigate the correlation between structural and magnetic degrees of freedom in CaFe2_{2}(As1−x_{1-x}Px_{x} )2_{2}. The puzzling temperature behavior of the local moment found in rare earth-doped CaFe2_{2}As2_{2} [\textit{H. Gretarsson, et al., Phys. Rev. Lett. {\bf 110}, 047003 (2013)}] is also observed in CaFe2_{2}(As1−x_{1-x}Px_{x})2_{2}. We explain this phenomenon based on first-principles calculations with scaled magnetic interaction. One scaling parameter is sufficient to describe quantitatively the magnetic moments in both CaFe2_{2}(As1−x_{1-x}Px_{x} )2_{2} (x=0.055x=0.055) and Ca0.78_{0.78}% La0.22_{0.22}Fe2_{2}As2_{2} at all temperatures. The anomalous growth of the local moments with increasing temperature can be understood from the observed large thermal expansion of the cc-axis lattice parameter combined with strong magnetoelastic coupling. These effects originate from the strong tendency to form As-As dimers across the Ca layer in the CaFe2_{2}As2_{2} family of materials. Our results emphasize the dual local-itinerant character of magnetism in Fe pnictides

    Quadratic Dirac fermions and the competition of ordered states in twisted bilayer graphene

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    Magic-angle twisted bilayer graphene (TBG) exhibits a captivating phase diagram as a function of doping, featuring superconductivity and a variety of insulating and magnetic states. The bands host Dirac fermions with a reduced Fermi velocity; experiments have shown that the Dirac dispersion reappears near integer fillings of the moir\'e unit cell -- referred to as the Dirac revival\textit{Dirac revival} phenomenon. The reduced velocity of these Dirac states leads us to propose a scenario in which the Dirac fermions possess an approximately quadratic dispersion. The quadratic momentum dependence and particle-hole degeneracy at the Dirac point results in a logarithmic enhancement of interaction effects, which does not appear for a linear dispersion. The resulting non-trivial renormalisation group (RG) flow naturally produces the qualitative phase diagram as a function of doping -- with nematic and insulating states near integer fillings, which give way to superconducting states past a critical relative doping. The RG method further produces different results to strong-coupling Hartree-Fock treatments: producing T-IVC insulating states for repulsive interactions, explaining the results of very recent STM experiments, alongside nodal A2A_2 superconductivity near half-filling, whose properties explain puzzles in tunnelling studies of the superconducting state. The model explains a diverse range of additional experimental observations, unifying many aspects of the phase diagram of TBG

    Multiple Solutions of Singular Perturbation Problems

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    Bod1, a novel kinetochore protein required for chromosome biorientation

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    We have combined the proteomic analysis of Xenopus laevis in vitro–assembled chromosomes with RNA interference and live cell imaging in HeLa cells to identify novel factors required for proper chromosome segregation. The first of these is Bod1, a protein conserved throughout metazoans that associates with a large macromolecular complex and localizes with kinetochores and spindle poles during mitosis. Small interfering RNA depletion of Bod1 in HeLa cells produces elongated mitotic spindles with severe biorientation defects. Bod1-depleted cells form syntelic attachments that can oscillate and generate enough force to separate sister kinetochores, suggesting that microtubule–kinetochore interactions were intact. Releasing Bod1-depleted cells from a monastrol block increases the frequency of syntelic attachments and the number of cells displaying biorientation defects. Bod1 depletion does not affect the activity or localization of Aurora B but does cause mislocalization of the microtubule depolymerase mitotic centromere- associated kinesin and prevents its efficient phosphorylation by Aurora B. Therefore, Bod1 is a novel kinetochore protein that is required for the detection or resolution of syntelic attachments in mitotic spindles
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