230 research outputs found
Glass-like Thermal-Transport in Symmetry-Broken Clathrates
We present the quantitative interpretation for the glass-like behavior of
thermal conductivities for type-I clathrate compounds involving
off-centered guest ions. It is shown that the dipole-dipole interaction
generated in cage/guest-ion systems is crucial to reproduce the characteristics
of thermal conductivities for these symmetry-broken clathrates. The above
scenario also explains well the difference of between the -type
and the -type -BGS found recently by K. Suekuni et al. [Phys. Rev. B,
77 (2008) 235119.
Phonon-glass electron-crystal thermoelectric clathrates: Experiments and theory
Type-I clathrate compounds have attracted a great deal of interest in
connection with the search for efficient thermoelectric materials. These
compounds constitute networked cages consisting of nano-scale
tetrakaidecahedrons (14 hedrons) and dodecahedrons (12 hedrons), in which the
group 1 or 2 elements in the periodic table are encaged as the so-called
rattling guest atom. It is remarkable that, though these compounds have
crystalline cubic-structure, they exhibit glass-like phonon thermal
conductivity over the whole temperature range depending on the states of
rattling guest atoms in the tetrakaidecahedron. In addition, these compounds
show unusual glass-like specific heats and THz-frequency phonon dynamics,
providing a remarkable broad peak almost identical to those observed in
topologically disordered amorphous materials or structural glasses, the
so-called Boson peak. An efficient thermoelectric effect is realized in
compounds showing these glass-like characteristics. This decade, a number of
experimental works dealing with type-I clathrate compounds have been published.
These are diffraction experiments, thermal and spectroscopic experiments in
addition to those based on heat and electronic transport. These form the raw
materials for this article based on advances this decade. The subject of this
article involves interesting phenomena from the viewpoint of not only physics
but also from the view point of the practical problem of elaborating efficient
thermoelectric materials. This review presents a survey of a wide range of
experimental investigations of type-I clathrate compounds, together with a
review of theoretical interpretations of the peculiar thermal and dynamic
properties observed in these materials.Comment: 51pages, 43 figure
Theory of spin Hall magnetoresistance
We present a theory of the spin Hall magnetoresistance (SMR) in multilayers
made from an insulating ferromagnet F, such as yttrium iron garnet (YIG), and a
normal metal N with spin-orbit interactions, such as platinum (Pt). The SMR is
induced by the simultaneous action of spin Hall and inverse spin Hall effects
and therefore a non-equilibrium proximity phenomenon. We compute the SMR in
FN and FNF layered systems, treating N by spin-diffusion theory with
quantum mechanical boundary conditions at the interfaces in terms of the
spin-mixing conductance. Our results explain the experimentally observed spin
Hall magnetoresistance in NF bilayers. For FNF spin valves we predict
an enhanced SMR amplitude when magnetizations are collinear. The SMR and the
spin-transfer torques in these trilayers can be controlled by the magnetic
configuration
A Method for Producing Transgenic Cells Using a Multi-Integrase System on a Human Artificial Chromosome Vector
The production of cells capable of expressing gene(s) of interest is important for a variety of applications in biomedicine and biotechnology, including gene therapy and animal transgenesis. The ability to insert transgenes at a precise location in the genome, using site-specific recombinases such as Cre, FLP, and ΦC31, has major benefits for the efficiency of transgenesis. Recent work on integrases from ΦC31, R4, TP901-1 and Bxb1 phages demonstrated that these recombinases catalyze site-specific recombination in mammalian cells. In the present study, we examined the activities of integrases on site-specific recombination and gene expression in mammalian cells. We designed a human artificial chromosome (HAC) vector containing five recombination sites (ΦC31 attP, R4 attP, TP901-1 attP, Bxb1 attP and FRT; multi-integrase HAC vector) and de novo mammalian codon-optimized integrases. The multi-integrase HAC vector has several functions, including gene integration in a precise locus and avoiding genomic position effects; therefore, it was used as a platform to investigate integrase activities. Integrases carried out site-specific recombination at frequencies ranging from 39.3–96.8%. Additionally, we observed homogenous gene expression in 77.3–87.5% of colonies obtained using the multi-integrase HAC vector. This vector is also transferable to another cell line, and is capable of accepting genes of interest in this environment. These data suggest that integrases have high DNA recombination efficiencies in mammalian cells. The multi-integrase HAC vector enables us to produce transgene-expressing cells efficiently and create platform cell lines for gene expression
唾液腺内視鏡下唾石摘出システムの開発
The procedures of sialendoscopic sialolithectomy have been progressively developing for more than the last ten years. However, any procedures reported previously in the world, needed an incision of the papilla or duct wall of the salivary gland to insert the sialendoscope. Therefore, I developed three types of fine sialendoscope, which could be inserted into the duct without incision of the papilla or duct wall of the salivary gland. One is a sialendoscope of 1.1-mm outer-diameter(POLYDIAGNOST GmbH, Germany) with 6000-pixels optic fibers, and it has a working channel to insert an ultra fine basket forceps of 0.38-mm outer-diameter and an irrigation channel. Two is a sialendoscope of 1.2-mm outerdiameter(FiberTech Co., Ltd., Japan) with 1600-pixels optic fibers and a working channel. Three is a sialendoscope of 1.40-mm outer妖iameter (POLYDIAGNOST GmbH, Germany) with 3000-pixels optic fibers, and it has a working channel to insert a 1.9 Fr basket forceps (Boston Scientific Corporation, USA) or a 1.9 Fr probe of an electrohydraulic lithotripter AUTOLITH^[○!R] (Northgate Technologies Inc., Elgin, U.S.A.). Using these newly developed sialendoscope, I established a non-surgical endoscopic sialolithectomy system, and succeeded to remove the sialoliths of the submandibular gland safely and surely under the sialendoscopic observations with a minimal invasion
Protective effects of calmodulin antagonists (trifluoperazine and W-7) on hypothermic ischemic rat hearts.
The cardioprotective effect of calmodulin antagonists, trifluoperazine (TFP) and N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7) was examined on the isolated rat heart exposed to hypothermic and ischemic conditions by measuring distribution of lysosomal enzymes in myocardial cells, and leakage of creatine kinase (CK) during reperfusion and postischemic recovery in myocardial systolic function. Experimental hearts were infused with 20 degrees C Krebs-Henseleit bicarbonate buffer (KHB) or KHB containing TFP or W-7 for 2min every 30min during hypothermic ischemia. After ischemia for 120min at 20 degrees C, rat hearts were reperfused at 37 degrees C for 30min. TFP and W-7 improved functional recovery and prevented CK release. In TFP treated hearts, leakage of lysosomal enzymes was reduced significantly, whereas stabilization of lysosomes by W-7 did not occur. These results suggest that calcium-calmodulin dependent enzymes may play an important role in the development of cellular damage of the myocardium during hypothermic ischemia, although levels of leakage of lysosomal enzymes may be unreliable predictors of functional recovery after hypothermic ischemia.</P></p
Periductal Induction of High Endothelial Venule-Like Vessels in Type 1 Autoimmune Pancreatitis
信州大学博士(医学)・学位論文・平成24年3月31日授与(甲第946号)・丸山 雅史This is a non-final version of an article published in final form in PANCREAS. 42(1):53-59 (2013).Objectives: Type 1 autoimmune pancreatitis (AIP) is histologically characterized by dense lymphoplasmacytic infiltration and marked storiform fibrosis, manifestations associated with pancreatic ducts. Such periductal lymphocyte recruitment is thought to be elicited by dysregulation of mechanisms governing physiological lymphocyte homing. The present study was undertaken to determine whether vascular addressins including peripheral lymph node addressin and mucosal addressin cell adhesion molecule 1 (MAdCAM-1) play a role in type 1 AIP histogenesis. Methods: Tissue sections of type 1 AIP and tumor-associated non-AIP chronic pancreatitis, as well as normal pancreas, were subjected to immunohistochemical analysis using vascular addressin-related antibodies. Results: The number of periductal mouse endothelial cell antigen 79-positive high endothelial venule (HEV)-like vessels was increased in type 1 AIP relative to that seen in non-AIP chronic pancreatitis, whereas the number of MAdCAM-1-positive HEV-like vessels did not differ between the 2 conditions. Mouse endothelial cell antigen 79 antigens are expressed on duct-forming epithelial cells not only in pancreas but also in salivary glands, which often harbor extrapancreatic lesions in type 1 AIP. Conclusions: Type 1 AIP can be characterized by periductal induction of MECA-79-positive HEV-like vessels. MECA-79-positive 6-sulfo sialyl Lewis X-related carbohydrate antigens expressed on duct-forming epithelial cells could be associated with type 1 AIP pathogenesis.ArticlePANCREAS. 42(1):53-59 (2013)journal articl
Melt-Mixing by Novel Pitched-Tip Kneading Disks in a Co-Rotating Twin-Screw Extruder
Melt-mixing in twin-screw extruders is a key process in the development of
polymer composites. Quantifying the mixing performance of kneading elements
based on their internal physical processes is a challenging problem. We discuss
melt-mixing by novel kneading elements called "pitched-tip kneading disk
(ptKD)". The disk-stagger angle and tip angle are the main geometric parameters
of the ptKDs. We investigated four typical arrangements of the ptKDs, which are
forward and backward disk-staggers combined with forward and backward tips.
Numerical simulations under a certain feed rate and screw revolution speed were
performed, and the mixing process was investigated using Lagrangian statistics.
It was found that the four types had different mixing characteristics, and
their mixing processes were explained by the coupling effect of drag flow with
the disk staggering and pitched-tip and pressure flows, which are controlled by
operational conditions. The use of a pitched-tip effectively to controls the
balance of the pressurization and mixing ability
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