60 research outputs found
Angle-resolved photoemission study of MX-chain compound [Ni(chxn)Br]Br
We report on the results of angle-resolved photoemission experiments on a
quasi-one-dimensional -chain compound [Ni(chxn)Br]Br (chxn =
1,2-cyclohexanediamine), a one-dimensional Heisenberg system with
and K, which shows a gigantic non-linear optical effect. A "band"
having about 500 meV energy dispersion is found in the first half of the
Brillouin zone , but disappears at . Two
dispersive features, expected from the spin-charge separation, as have been
observed in other quasi-one-dimensional systems like SrCuO, are not
detected. These characteristic features are well reproduced by the -
chain model calculations with a small charge-transfer energy compared
with that of one-dimensional Cu-O based compounds. We propose that this smaller
is the origin of the absence of clear spin- and charge-separation in
the photoemission spectra and strong non-linear optical effect in
[Ni(chxn)Br]Br.Comment: 4 pages, 3 figure
Anisotropic Optical Conductivity Accompanied by a Small Energy Gap in One-Dimensional Thermoelectric Telluride Ta4SiTe4
We investigated the optical properties of single crystals of one-dimensional
telluride Ta4SiTe4, which shows high thermoelectric performance below room
temperature. Optical conductivity estimated from reflectivity spectra indicates
the presence of a small energy gap of 0.1-0.15 eV at the Fermi energy. At the
lowest energy, optical conductivity along the Ta4SiTe4 chain is an order of
magnitude higher than that perpendicular to this direction, reflecting the
anisotropic electron conduction in Ta4SiTe4. These results indicate that
coexistence of a very small band gap and anisotropic electron conduction is a
promising strategy to develop a high-performance thermoelectric material for
low temperature applications.Comment: 6 pages, 4 figure
A novel approach for the endothelialization of xenogeneic decellularized vascular tissues by human cells utilizing surface modification and dynamic culture
Decellularized xenogeneic vascular grafts can be used in revascularization surgeries. We have developed decellularization methods using high hydrostatic pressure (HHP), which preserves the extracellular structure. Here, we attempted ex vivo endothelialization of HHP-decellularized xenogeneic tissues using human endothelial cells (ECs) to prevent clot formation against human blood. Slices of porcine aortic endothelium were decellularized using HHP and coated with gelatin. Human umbilical vein ECs were directly seeded and cultured under dynamic flow or static conditions for 14 days. Dynamic flow cultures tend to demonstrate higher cell coverage. We then coated the tissues with the E8 fragment of human laminin-411 (hL411), which has high affinity for ECs, and found that Dynamic/hL411showed high area coverage, almost reaching 100% (Dynamic/Gelatin vs Dynamic/hL411; 58.7 ± 11.4 vs 97.5 ± 1.9%, P = 0.0017). Immunostaining revealed sufficient endothelial cell coverage as a single cell layer in Dynamic/hL411. A clot formation assay using human whole blood showed low clot formation in Dynamic/hL411, almost similar to that in the negative control, polytetrafluoroethylene. Surface modification of HHP-decellularized xenogeneic endothelial tissues combined with dynamic culture achieved sufficient ex vivo endothelialization along with prevention of clot formation, indicating their potential for clinical use as vascular grafts in the future
Spin frustration in antiperovskite systems: (TTF˙+or TSF˙+)3[(Mo6X14)2−Y−]
Two novel antiperovskite charge-transfer (CT) solids composed of a tetraselenafulvalene radical cation (TSF˙+), a dianionic molybdenum cluster unit [Mo6X14]2−, and a halogen anion (Y−) (X, Y = Cl, Br) were prepared by electrocrystallization. Their crystal structures and magnetic properties with regard to spin frustration are discussed together with those of isostructural tetrathiafulvalene (TTF) CT solids previously reported. Both TSF and TTF salts have an apex sharing distorted octahedral spin lattice with a rhombohedral R[3 with combining macron] space group. The calculated overlap integrals based on the crystal structures and insulating nature of the TSF salts indicate that they are Mott insulators. Their spin susceptibilities obeyed the Curie–Weiss law and exhibited an antiferromagnetic ordering at lower temperatures for the TSF salts (Néel temperature, TN = 3.0 K for X = Y = Cl and 5.5 K for X = Y = Br) than the TTF salts. The Curie–Weiss temperatures (|ΘCW| ∼ 1.6–6.3 K) for the TSF salts are lower than those of the TTF salts. For the TSF salts, spin-flop behavior was detected at 3.2 T for X = Y = Cl and 1.5 T for X = Y = Br at 1.9 K. Due to both the distortion of the octahedral geometry of the spin lattice and the anisotropic molecular orientation, the geometrical spin frustrations in TSF and TTF systems are weakened
Regular-Triangle Trimer and Charge Order Preserving the Anderson Condition in the Pyrochlore Structure of CsWO
Since the discovery of the Verwey transition in magnetite, transition metal
compounds with pyrochlore structures have been intensively studied as a
platform for realizing remarkable electronic phase transitions. We report the
discovery of a unique phase transition that preserves the cubic symmetry of the
beta-pyrochlore oxide CsWO, where each of W 5d electrons are confined
in regular-triangle W3 trimers. This trimer formation is an unprecedented
self-organization of d electrons, which can be resolved into a charge order
satisfying the Anderson condition in a nontrivial way, orbital order caused by
the distortion of WO6 octahedra, and the formation of a spin-singlet pair in a
regular-triangle trimer. Electronic instability due to the unusual
three-dimensional nesting of Fermi surfaces and the localized nature of the 5d
electrons characteristic of the pyrochlore oxides were found to play important
roles in this unique charge-orbital-spin coupled phenomenon.Comment: 7 pages, 3 figure
Influence of Extraction of 'Bound Wax D' of BCG with Trichloroacetic Acid on Its Adjuvant Activity on Development of a Delayed Type of Hypersensitivity
Changes in Susceptibility of Staphylococcus aureus and Corynebacterium diphtheriae Cell Walls to Egg White Lysozyme, the L₃-and L₁₁-Enzymes Caused by Trichloroacetic Acid Treatment
Adjuvant Activity in Development of a Delayed Type of Hypersensitivity of a Lipid Fraction Isolated from Enzymically Digested Cell Walls of Corynebacterium diphtheriae
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