1,396 research outputs found
Multipole ordering in f-electron systems
In order to investigate multipole ordering in f-electron systems from a
microscopic viewpoint, we study the so-called \Gamma_8 models on three kinds of
lattices, simple cubic (sc), bcc, and fcc, based on a j-j coupling scheme with
f-electron hopping integrals through (ff\sigma) bonding. From the \Gamma_8
model, we derive an effective model for each lattice structure by using the
second-order perturbation theory with respect to (ff\sigma). By further
applying mean-field theory to the effective model, we find a \Gamma_{3g}
antiferro-quadrupole transition for the sc lattice, a \Gamma_{2u}
antiferro-octupole transition for the bcc lattice, and a longitudinal triple-q
\Gamma_{5u} octupole transition for the fcc lattice.Comment: 2 pages, 3 figure
Phase structure of the large-N reduced gauge theory and generalized Weingarten model
We study a generalization of Weingarten model reduced to a point, which
becomes the large-N reduced U(N) gauge theory in a special limit. We find that
the U(1)^d symmetry is broken one by one, and restored simultaneously as U(1)^d
-> U(1)^{d-1} -> ... -> U(1) -> 1 -> U(1)^d as we change the coupling
constants. In this model we can develop an efficient algorithm and we can see
the phase structure of large-N reduced model clearly, and therefore this model
would be useful for the study of the unitary model.Comment: LaTeX-2e, 11 pages with 11 figures; typos correcte
Analysis of f-p model for octupole ordering in NpO2
In order to examine the origin of octupole ordering in NpO2, we propose a
microscopic model constituted of neptunium 5f and oxygen 2p orbitals. To study
multipole ordering, we derive effective multipole interactions from the f-p
model by using the fourth-order perturbation theory in terms of p-f hopping
integrals. Analyzing the effective model numerically, we find a tendency toward
\Gamma_{5u} antiferro-octupole ordering.Comment: 4 pages, 3 figure
Microscopic theory of multipole ordering in NpO2
In order to examine the mysterious ordered phase of NpO2 from a microscopic
viewpoint, we investigate an f-electron model on an fcc lattice constructed
based on a j-j coupling scheme. First, an effective model with multipole
interactions is derived in the strong-coupling limit. Numerical analysis of the
model clearly indicates that the interactions for \Gamma_{4u} and \Gamma_{5u}
moments are relevant to the ground state. Then, by applying mean-field theory
to the simplified model including only such interactions, we conclude that
longitudinal triple-q \Gamma_{5u} octupole order is realized in NpO2 through
the combined effects of multipole interactions and anisotropy of the
\Gamma_{5u} moment.Comment: 5 pages, 2 figure
Multipole Fluctuations in Filled Skutterudites
In order to clarify exotic multipole properties of filled skutterudites, we
evaluate multipole susceptibility for =15, where is the local
-electron number, on the basis of a multiorbital Anderson model constructed
using the - coupling scheme. For =1, magnetic fluctuations dominate
over low-temperature electronic properties, while for =2 and 4, electronic
states are dominated by both magnetic and quadrupole fluctuations. For =3
and 5, octupole fluctuations are found to be significant, depending on the
crystalline electric field potential. We discuss possible relevance of the
results to actual materials.Comment: 4 pages, 3 figures, JPSJ2.cls. To be published in J. Phys. Soc. Jp
Glucan dendrimer for carbohydrate drugs
Dendrimers are highly branched and star-shaped polymers with nanometer-scale dimensions. The nanostructured macromolecules are known for their defined structures, versatility in drug delivery, and high functional properties similar to biomoleclules.
We developed a new way to synthesize glucan dendrimer like glycogen by using branching enzyme (EC 2.4.1.18) and glucan phosphorylase (EC 2.4.1.1) by using glucose-1-phosphate as a substrate. This way enables us to produce glucan dendrimers with strictly controlled molecular size and branching structure. In this context, we developed specific glycosylation technology to substitute glucose residues at non-reducing ends with galactose, mannose, glucosamine, glucuronic acid, or N-acetylglucosamine residues. Glucose dendrimers having glucosamine and/or glucuronic acid residues are successfully used for conjugation of other functional molecules. The nano-particle conjugated glucan dendrimers with peptide antigen and nucleotide adjuvant is a potential platform for vaccine.
We investigated the glucan dendrimers function as a drug carrier. The uptake of several glucose dendrimers into antigen-presenting cells (APCs), such as dendritic cell and macrophage, were examined. Glucose dendrimers were incorporated into APCs, and introducing various sugar moieties into glucan dendrimers enhance the uptake them by APCs. When glucan dendrimer-peptide conjugates were added to the cultured APCs, the peptides were effectively presented on the surface of APCs. FITC-labeled glucan dendrimers injected subcutaneously in mice accumulated into inguinal lymph nodes, which play important role to introduce acquired immune respons
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