1,200 research outputs found
Magnetization curve of the kagome-strip-lattice antiferromagnet
We study the magnetization curve of the Heisenberg model on the
quasi-one-dimensional kagome-strip lattice that shares the same lattice
structure in the inner part with the two-dimensional kagome lattice. Our
numerical calculations based on the density matrix renormalization group method
reveal that the system shows several magnetization plateaus between zero
magnetization and the saturated one; we find the presence of the magnetic
plateaus with the n=7 height of the saturation for n =1,2,3,4,5 and 6 in the S
=1/2 case, whereas we detect only the magnetic plateaus of n =1,3,5 and 6 in
the S =1 case. In the cases of n =2,4 and 6 for the S=1/2 system, the
Oshikawa-Yamanaka-Affleck condition suggests the occurrence of the
translational symmetry breaking (TSB). We numerically confirm this non-trivial
TSB in our results of local magnetizations. We have also found that the
macroscopic jump appears near the saturation field irrespective of the spin
amplitude as well as the two-dimensional kagome model.Comment: 6pages, 3figures, accepted for publication in Journal of Low
Temperature Physic
Ferrimagnetism of the Heisenberg Models on the Quasi-One-Dimensional Kagome Strip Lattices
We study the ground-state properties of the S=1/2 Heisenberg models on the
quasi-onedimensional kagome strip lattices by the exact diagonalization and
density matrix renormalization group methods. The models with two different
strip widths share the same lattice structure in their inner part with the
spatially anisotropic two-dimensional kagome lattice. When there is no magnetic
frustration, the well-known Lieb-Mattis ferrimagnetic state is realized in both
models. When the strength of magnetic frustration is increased, on the other
hand, the Lieb-Mattis-type ferrimagnetism is collapsed. We find that there
exists a non-Lieb-Mattis ferrimagnetic state between the Lieb-Mattis
ferrimagnetic state and the nonmagnetic ground state. The local magnetization
clearly shows an incommensurate modulation with long-distance periodicity in
the non-Lieb-Mattis ferrimagnetic state. The intermediate non-Lieb-Mattis
ferrimagnetic state occurs irrespective of strip width, which suggests that the
intermediate phase of the two-dimensional kagome lattice is also the
non-Lieb-Mattis-type ferrimagnetism.Comment: 9pages, 11figures, accepted for publication in J. Phys. Soc. Jp
Endothelium-derived relaxing factor and coronary vasospasm.
The endothelium releases the powerful vasodilator and antiaggregatory substance, EDRF, both under basal conditions and upon stimulation by a wide variety of agents. Endothelial injury or dysfunction may play an important role in the spasmogenicity of the coronary artery, although other possible alterations related to atherosclerosis should also be considered. Among the possible stimuli, aggregating platelets are important as a source of vasoconstrictor substances. The endothelium may also produce the vasoactive substances EDHF and EDCF(s). Their pathophysiologic significance remains to be determined.link_to_subscribed_fulltex
Characterization of Knots and Links Arising From Site-specific Recombination on Twist Knots
We develop a model characterizing all possible knots and links arising from
recombination starting with a twist knot substrate, extending previous work of
Buck and Flapan. We show that all knot or link products fall into three
well-understood families of knots and links, and prove that given a positive
integer , the number of product knots and links with minimal crossing number
equal to grows proportionally to . In the (common) case of twist knot
substrates whose products have minimal crossing number one more than the
substrate, we prove that the types of products are tightly prescribed. Finally,
we give two simple examples to illustrate how this model can help determine
previously uncharacterized experimental data.Comment: 32 pages, 7 tables, 27 figures, revised: figures re-arranged, and
minor corrections. To appear in Journal of Physics
Frustration-Induced Ferrimagnetism in Heisenberg Spin Chains
We study ground-state properties of the Heisenberg frustrated spin chain with
interactions up to fourth nearest neighbors by the exact-diagonalization method
and the density matrix renormalization group method. We find that
ferrimagnetism is realized not only in the case of S=1/2 but also S=1 despite
that there is only a single spin site in each unit cell determined from the
shape of the Hamiltonian. Our numerical results suggest that a
"multi-sublattice structure" is not required for the occurrence of
ferrimagnetism in quantum spin systems with isotropic interactions.Comment: 6 pages, 3 figures, accepted for publication in Journal of the
Physical Society of Japa
Grain-size dependence of the relationship between intergranular and intragranular deformation of nanocrystalline Al by molecular dynamics simulations
金沢大学大学院自然科学研究科機能開発システム金沢大学工学部The strength of nanocrystalline aluminum has been studied using molecular dynamics simulation. Nanocrystalline models consisting of hexagonal grains with grain size d between 5 nm and 80 nm are deformed by the application of tension. A transition from grain-size hardening to grain-size softening can be observed in the region where d≈30nm, which is the optimum grain size for strength. In the grain-size hardening region, nanocrystalline models primarily deform by intragranular deformation. Consequently, a pile-up of dislocations can be observed. When the grain size becomes less than 30 nm, where the thickness of the grain boundaries cannot be neglected in comparison to the grain sizes, the dominant deformation mechanism of nanocrystalline metals is intergranular deformation by grain boundary sliding. Further, geometrical misfits by grain boundary sliding are accommodated by the grain rotation mechanism. Moreover, cooperative grain boundary sliding occurs in the 5 nm model. The optimum grain size is controlled by the relationship between resistance to intergranular deformation by grain boundary processes and intragranular deformation resisted by the grain boundary. Therefore, the primary role of the grain boundary changes in the region where the optimum grain size is observed. © 2005 The American Physical Society
Li+D Reaction in Pd and Au for 30<E_d<75 keV(I. Nuclear Physics)
Thick target yields of α particles emitted in the ^Li (d, α) ^He reactions in PdLi_x and AuLi_x were measured as a function of the bombarding energy between 30 and 75 keV. It was found that the reaction rate in Pd at lower energies is enhanced strongly over the one predicted by the cross section for the reaction with bare nuclei, but no enhancement is observed in Au. A screening energy is introduced to reproduce the excitation function of the thick target yield for each metal. The deduced value for Pd amounts to 1500±310 eV, whereas it is only 60±150 eV for Au. The enhancement in the Pd case cannot be explained by electron screening alone but suggests the existence of an additional and important mechanism of screening in metal
Ethyl pyruvate improves pulmonary function in mice with bleomycin-induced lung injury as monitored with hyperpolarized 129Xe MR imaging
Purpose: High Mobility Group Box1 (HMGB1), which is one of the damage-associated molecular pattern molecules relating to various inflammatory diseases, has gained interest as a therapeutic target because of its involvement in wound healing processes. In the present study, we investigated HMGB1 as a potential therapeutic target in a model of lung fibrosis using a preclinical hyperpolarized 129Xe (HPXe) MRI system.
Methods: Lung injury was induced by intra-peritoneal injection of bleomycin (BLM) in 19 mice. Three weeks post-injection (when fibrosis was confirmed histologically), administration of ethyl pyruvate (EP) and alogliptin (ALG), which are down- and up-regulators of HMGB1, respectively, was commenced in six and seven of the 19 mice, respectively, and continued for a further 3 weeks. A separate sham-instilled group was formed of five mice, which were administered with saline for 6 weeks. Over the second 3-week period, the effects of disease progression and pharmacological therapy in the four groups of mice were monitored by HPXe MRI metrics of fractional ventilation and gas-exchange function.
Results: Gas-exchange function in BLM mice was significantly reduced after 3 weeks of BLM challenge compared to sham-instilled mice (P < 0.05). Ethyl pyruvate was found to improve HPXe MRI metrics of both ventilation and gas exchange, and repair tissue damage (assessed histologically), to a similar level as sham-instilled mice (P < 0.05), whilst ALG treatment caused no significant improvement of pulmonary function.
Conclusion: This study demonstrates the down-regulator of HMGB1, EP, as a potential therapeutic agent for pulmonary fibrosis, as assessed by a non-invasive HPXe MRI protocol
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