2,291 research outputs found
Vesignieite BaCu3V2O8(OH)2 as a Candidate Spin-1/2 Kagome Antiferromagnet
A polycrystalline sample of vesignieite BaCu3V2O8(OH)2 comprising a nearly
ideal kagome lattice composed of Cu2+ ions carrying spin 1/2 has been
synthesized and studied by magnetization and heat capacity measurements.
Magnetic susceptibility shows a neither long range order, a spin glass
transition nor a spin gap down to 2 K, in spite of a moderately strong
antiferromagnetic interaction of J/kB = 53 K between nearest-neighbor spins. A
broad peak observed at a temperature corresponding to 0.4J in intrinsic
magnetic susceptibility indicates a marked development of the short-range
order. The ground state of vesignieite is probably a gapless spin liquid or is
accompanied by a very small gap less than J/30.Comment: 4 pages, 5 figure
Cardiac-specific Conditional Knockout of the 18-kDa Mitochondrial Translocator Protein Protects from Pressure Overload Induced Heart Failure.
Heart failure (HF) is characterized by abnormal mitochondrial calcium (Ca2+) handling, energy failure and impaired mitophagy resulting in contractile dysfunction and myocyte death. We have previously shown that the 18-kDa mitochondrial translocator protein of the outer mitochondrial membrane (TSPO) can modulate mitochondrial Ca2+ uptake. Experiments were designed to test the role of the TSPO in a murine pressure-overload model of HF induced by transverse aortic constriction (TAC). Conditional, cardiac-specific TSPO knockout (KO) mice were generated using the Cre-loxP system. TSPO-KO and wild-type (WT) mice underwent TAC for 8 weeks. TAC-induced HF significantly increased TSPO expression in WT mice, associated with a marked reduction in systolic function, mitochondrial Ca2+ uptake, complex I activity and energetics. In contrast, TSPO-KO mice undergoing TAC had preserved ejection fraction, and exhibited fewer clinical signs of HF and fibrosis. Mitochondrial Ca2+ uptake and energetics were restored in TSPO KO mice, associated with decreased ROS, improved complex I activity and preserved mitophagy. Thus, HF increases TSPO expression, while preventing this increase limits the progression of HF, preserves ATP production and decreases oxidative stress, thereby preventing metabolic failure. These findings suggest that pharmacological interventions directed at TSPO may provide novel therapeutics to prevent or treat HF
On the formulation of the dynamic mixed subgridâscale model
The dynamic mixed subgridâscale model of Zang et al. [Phys. Fluids A 5, 3186 (1993)] (DMM1) is modified with respect to the incorporation of the similarity model in order to remove a mathematical inconsistency. Compared to DMM1, the magnitude of the dynamic model coefficient of the modified model (DMM2) is increased considerably, while it is still significantly smaller than as occurs in the dynamic subgridâscale eddyâviscosity model of Germano [J. Fluid Mech. 238, 325 (1992)] (DSM). Large eddy simulations(LES) for the weakly compressible mixing layer are conducted using these three models and results are compared with direct numerical simulation (DNS) data. LES based on DMM1 gives a significant improvement over LES using DSM, while even better agreement is achieved with DMM2
Magnetic ground state and spin fluctuations in MnGe chiral magnet as studied by Muon Spin Rotation
We have studied by muon spin resonance ({\mu}SR) the helical ground state and
fluctuating chiral phase recently observed in the MnGe chiral magnet. At low
temperature, the muon polarization shows double period oscillations at short
time scales. Their analysis, akin to that recently developed for MnSi [A. Amato
et al., Phys. Rev. B 89, 184425 (2014)], provides an estimation of the field
distribution induced by the Mn helical order at the muon site. The refined muon
position agrees nicely with ab initio calculations. With increasing
temperature, an inhomogeneous fluctuating chiral phase sets in, characterized
by two well separated frequency ranges which coexist in the sample. Rapid and
slow fluctuations, respectively associated with short range and long range
ordered helices, coexist in a large temperature range below T = 170 K. We
discuss the results with respect to MnSi, taking the short helical period,
metastable quenched state and peculiar band structure of MnGe into account.Comment: 13 pages, 11 figure
Coral diversity matches marine park zonation but not economic value of coral reef sites at St. Eustatius, eastern Caribbean
Stony corals play a key role in the marine biodiversity of many tropical coastal areas as suppliers of substrate, food and shelter for other reef organisms. Therefore, it is remarkable that coral diversity usually does not play a role in the planning of protected areas in coral reef areas. In the present study we examine how stony coral diversity patterns relate to marine park zonation and the economic value of reefs around St. Eustatius, a small island in the eastern Caribbean, with fisheries and tourism as important sources of income. The marine park contains two no-take reserves. A biodiversity survey was performed at 39 sites, 24 inside the reserves and 15 outside; 22 had a maximum depth >18 m and 17 were shallower. Data on economic value per site were obtained from the literature. Corals were photographed for the verification of identifications made in the field. Coral species richness (n = 49) was highest in the no-take reserves and species composition was mainly affected by maximum depth. No distinct relation is observed between coral diversity and fishery value or total economic value. Based on the outcome of this study we suggest that in future designs of marine park zonation in reef areas, coral diversity should be taken into consideration. This is best served by including reef areas with a continuous depth gradient from shallow flats to deep slopes
Students' Perspective on the Impact of English Teacher Development Programs on Teaching Quality in Indonesia
- âŠ