696 research outputs found
Giant nonlinear conduction and thyristor-like negative derivative resistance in BaIrO3 single crystals
We synthesized single-crystalline samples of monoclinic BaIrO3 using a molten
flux method, and measured their magnetization, resistivity, Seebeck coefficient
and nonlinear voltage-current characteristics. The magnetization rapidly
increases below a ferromagnetic transition temperature TC of 180 K, where the
resistivity concomitantly shows a hump-type anomaly, followed by a sharp
increase below 30 K. The Seebeck coefficient suddenly increases below TC, and
shows linear temperature dependence below 50 K. A most striking feature of this
compound is that the anomalously giant nonlinear conduction is observed below
30 K, where a small current density of 20 A/cm2 dramatically suppresses the
sharp increase in resistivity to induce a metallic conduction down to 4 K.Comment: 10 pages, 4 figures Submitted to Physical Review Letter
Effects of Phytohormone on Lateral Bud Elongation and Acidinvertase Activity During the Regrowth of Sorghum Bicolor M.
The relationships of phytohormone and sucrose metabolism in the stem ofoesorghum after cutting were studied using the stem disks treated with various plantoegrowth regulators The release of buds after incubating was accelerated by 6-benzyladenoprine riboside (6- BAR) treatment. But, on abcisic acid (ABA) andoeindole acetic acid (IAA ) treatment the release of buds was retarded. The length ofoeelongated buds on all hormonal treatments was shorter than the non-treated at the end of incubated period tested. Invertase activities were stimulated on all hormonal treatments. On 6-BAR treatment, invertase activities were the highest. But there were no relationships between invertase activities and the bud growth. Therefore, we considered that the release of buds was regulated directly by hormone balance and then the elongation during 3 days after incubation was not affected by invertase activities
Parity-broken ground state for the spin-1 pyrochlore antiferromagnet
The ground-state properties of the spin-1 pyrochlore antiferromagnet are
studied by applying the VBS-like tetrahedron-unit decomposition to the original
spin system. The symmetrization required on every vertex is taken into account
by introducing a ferromagnetic coupling. The pairwise effective Hamiltonian
between the adjacent tetrahedrons is obtained by considering the next nearest
neighbor and the third neighbor exchange interactions. We find that the
transverse component of the spin chirality exhibits a long-range order,
breaking the parity symmetry of the tetrahedral group, while the chirality
itself is not broken.Comment: 4 pages, 3 figures, REVTeX(ver.3.1
Geometrical frustration induced (semi-)metal to insulator transition
We study the low-energy properties of the geometrically frustrated Hubbard
model on a three-dimensional pyrochlore lattice and a two-dimensional
checkerboard lattice on the basis of the renormalization group method and mean
field analysis. It is found that in the half-filling case, a (semi-)metal to
insulator transition (MIT) occurs. Also, in the insulating phase, which has a
spin gap, the spin rotational symmetry is not broken, while charge ordering
exists. The results are applied to the description of the MIT observed in the
pyrochlore system .Comment: 4 pages, 5 figure
ICME international survey on teachers working and learning through collaboration
This article presents preliminary results from a survey commissioned for ICME 13 (2016) focusing on "Teachers Working and Learning Through Collaboration". It takes as a starting point a previous survey, commissioned for ICME 10 in 2004 that focused on Mathematics Teacher Education. The current survey focuses centrally on teachers involved in collaborations, sometimes in formal settings of professional development, but also in a more diverse range of collaborative settings including research initiatives. The roles of teachers involved in the collaboration, survey methods, decisions and limitations are described. While some of the findings to date resonate with those of the earlier survey, other findings highlight characteristics and issues relating to the differing ways in which teachers collaborate, either with other teachers or the various 'others', most notably mathematics teacher educator researchers. The roles and relationships that contribute to learning in such collaborations, as well as theories and methodologies found in survey sources, are a
focus of the findings presented here. Studies rarely theorised collaboration, and few of those that did so reported explicitly on how their theoretical frame shaped the design of research methodologies/approaches guiding activities with teachers. One significant outcome has been the difficulty of relating teachers' learning to collaboration within a project, although many initiatives report developments in teaching, teacher learning and students' learning
Classical generalized constant coupling model for geometrically frustrated antiferromagnets
A generalized constant coupling approximation for classical geometrically
frustrated antiferromagnets is presented. Starting from a frustrated unit we
introduce the interactions with the surrounding units in terms of an internal
effective field which is fixed by a self consistency condition. Results for the
magnetic susceptibility and specific heat are compared with Monte Carlo data
for the classical Heisenberg model for the pyrochlore and kagome lattices. The
predictions for the susceptibility are found to be essentially exact, and the
corresponding predictions for the specific heat are found to be in very good
agreement with the Monte Carlo results.Comment: 4 pages, 3 figures, 2 columns. Discussion about the zero T value of
the pyrochlore specific heat correcte
Hole-doping effects on a frustrated spin ladder
Hole-doping effects are investigated on the {\it t-J} ladder model with the
linked-tetrahedra structure. We discuss how a metal-insulator transition occurs
upon hole doping with particular emphasis on the effects of geometrical
frustration. By computing the electron density and the spin correlation
function by the density matrix renormalization group, we show that strong
frustration triggers a first-order transition to a metallic phase, when holes
are doped into the plaquette-singlet phase. By examining spin excitations in a
metallic case in detail, we discuss whether the spin-gap phase persists upon
hole doping according to the strength of frustration. It is further shown that
the lowest excited state in a spin-gap metallic phase can be described in two
independent quasiparticles.Comment: 7 pages, 9 figure
- …