7,247 research outputs found
Short communication: First report of thresher sharks (Alopiidae) in the Gulf of Antalya
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
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
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 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 CaFeAs family of materials
We report a combination of Fe K x-ray emission spectroscopy and
-intio calculations to investigate the correlation between structural and
magnetic degrees of freedom in CaFe(AsP). The
puzzling temperature behavior of the local moment found in rare earth-doped
CaFeAs [\textit{H. Gretarsson, et al., Phys. Rev. Lett. {\bf 110},
047003 (2013)}] is also observed in CaFe(AsP). 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 CaFe(AsP) () and CaLaFeAs at all
temperatures. The anomalous growth of the local moments with increasing
temperature can be understood from the observed large thermal expansion of the
-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 CaFeAs 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
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 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 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
Bod1, a novel kinetochore protein required for chromosome biorientation
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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