1,309 research outputs found
NMR relaxation rate and dynamical structure factors in nematic and multipolar liquids of frustrated spin chains under magnetic fields
Recently, it has been shown that spin nematic (quadrupolar) or higher
multipolar correlation functions exhibit a quasi long-range order in the wide
region of the field-induced Tomonaga-Luttinger-liquid (TLL) phase in spin-1/2
zigzag chains. In this paper, we point out that the temperature dependence of
the NMR relaxation rate 1/T_1 in these multipolar TLLs is qualitatively
different from that in more conventional TLLs of one-dimensional quantum
magnets (e.g., the spin-1/2 Heisenberg chain); 1/T_1 decreases with lowering
temperature in multipolar TLL. We also discuss low-energy features in spin
dynamical structure factors which are characteristic of the multipolar TLL
phases.Comment: 4+epsilon pages, 2 figures, published versio
New species of Boletellus section Boletellus (Boletaceae, Boletales) from Japan, B. aurocontextus sp. nov. and B. areolatus sp. nov.
We describe and illustrate two new species of Boletellus section Boletellus, B. aurocontextus sp. nov. and B. areolatus sp. nov., which are generally assumed to be B. emodensis. In this study, we reconstructed separate molecular phylogenetic trees of section Boletellus using the nucleotide sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA, the largest subunit (RPB1) and the second-largest subunit (RPB2) of nuclear RNA polymerase II gene and mitochondrial cytochrome oxidase subunit 3 (cox3) gene. We also examined the morphologies of B. emodensis sensu lato (s.l.) and other related species for comparison. The molecular phylogenetic tree inferred from the sequences of nuclear DNA (ITS, and combined dataset of RPB1 and RPB2) indicated that three genetically and phylogenetically well-separated lineages were present within B. emodensis s.l. These three lineages were also distinguished on the basis of the molecular phylogenetic tree constructed using the sequences of mitochondrial DNA (cox3), suggesting distinct cytonuclear disequilibria (i.e., evidence of reproductive isolation) among these lineages. Therefore, these three lineages can be treated as independent species: B. aurocontextus, B. areolatus, and B. emodensis. Boletellus aurocontextus and B. areolatus are also distinct from B. emodensis by the macro- and microscopic morphologies. Boletellus aurocontextus is characterized by a pileus with bright yellow to lemon yellow context, which can be observed through a gap in the scales, and basidiospores with relatively large length (mean spore length, 21.4 μm; quotient of spore length and width, 2.51). In contrast, B. areolatus is characterized by a pileus with floccose to appressed thin scaly patches, a stipe with pallid or pale cream color at the upper half, and basidiospores with relatively small length (mean spore length, 16.5 μm; quotient of spore length and width, 1.80)
Spin-Nematic and Spin-Density-Wave Orders in Spatially Anisotropic Frustrated Magnets in a Magnetic Field
We develop a microscopic theory of finite-temperature spin-nematic orderings
in three-dimensional spatially anisotropic magnets consisting of weakly-coupled
frustrated spin-1/2 chains with nearest-neighbor and next-nearest-neighbor
couplings in a magnetic field. Combining a field theoretical technique with
density-matrix renormalization group results, we complete finite-temperature
phase diagrams in a wide magnetic-field range that possess spin-bond-nematic
and incommensurate spin-density-wave ordered phases. The effects of a four-spin
interaction are also studied. The relevance of our results to
quasi-one-dimensional edge-shared cuprate magnets such as LiCuVO4 is discussed.Comment: 5 pages (2 column version), 4 figures, Revtex, published versio
Interpretation of some Yb-based valence-fluctuating crystals as approximants to a dodecagonal quasicrystal
The hexagonal ZrNiAl-type (space group: P-62m) and the tetragonal
Mo2FeB2-type (space group: P4/mbm) structures, which are frequently formed in
the same Yb-based alloys and exhibit physical properties related to
valence-fluctuation, can be regarded as approximants of a hypothetical
dodecagonal quasicrystal. Using Pd-Sn-Yb system as an example, a model of
quasicrystal structure has been constructed, of which 5-dimensional crystal
(space group: P12/mmm, aDD=5.66 {\AA} and c=3.72 {\AA}) consists of four types
of acceptance regions located at the following crystallographic sites; Yb
[00000], Pd[1/3 0 1/3 0 1/2], Pd[1/3 1/3 1/3 1/3 0] and Sn[1/2 00 1/2 1/2]. In
the 3-dimensional space, the quasicrystal is composed of three types of
columns, of which c-projections correspond to a square, an equilateral triangle
and a 3-fold hexagon. They are fragments of two known crystals, the hexagonal
{\alpha}-YbPdSn and the tetragonal Yb2Pd2Sn structures. The model of the
hypothetical quasicrystal may be applicable as a platform to treat in a unified
manner the heavy fermion properties in the two types of Yb-based crystals.Comment: 19 pages, 6 figure
Worm-like carbon shell chains produced from wood
Large-scale utilization of wood which command absolute majority in biomass for functional carbon precursors contributes to reduce greenhouse effect. Wood char generally has a limit on material usage because of its non-graphitic structure^1^, so we developed a new functional wood char by iron-, or nickel-catalyzed carbonization, which has a graphite-like structure with mesopores good for electroconductivity and liquid phase adsorption capacity for macro molecules^2-5^. However the fine structure of the wood char is still not clear. Here we report more than 70 wt % of iron-catalyzed wood char is filled with chained carbon shells formed by 3~20 defective stacking layers of carbon hexagonal planes, which look like nanometer-sized worms swarm. We name them "carbon shell chains". The discussion of the formation mechanism reveals that the wood cell wall plays an important role for their efficient production. They are stable at 1800 ºC under vacuum, but in air, burn under 600 ºC, and are perfectly conversed into hydrogen and carbon monoxide in a short time by steam at 900 ºC. The control of their decomposition will bring out a new talent in the wood char as a big source of supply for nano-graphite or nano-graphene, for which nanometer size and edge effects have recently attracted considerable attention^6^. In addition, a simple and easy preparation of carbon shell chains implies that they may be naturally produced on or in the earth rich in iron, and might be misinterpreted as nano-worms, though most of them may decompose into organic gases
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