Showing papers by "Tohoku University published in 2003"

First results from KamLAND: evidence for reactor antineutrino disappearance.

Abstract: KamLAND has measured the flux of ν _e’s from distant nuclear reactors. We find fewer ν _e events than expected from standard assumptions about ν _e propagation at the 99.95% C.L. In a 162 ton·yr exposure the ratio of the observed inverse β-decay events to the expected number without ν _e disappearance is 0.611±0.085(stat)±0.041(syst) for ν _e energies >3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the “large mixing angle” region are excluded.

Ferromagnetism above room temperature in bulk and transparent thin films of Mn-doped ZnO

Abstract: The search for ferromagnetism above room temperature in dilute magnetic semiconductors has been intense in recent years. We report the first observations of ferromagnetism above room temperature for dilute ( 700 °C) methods were used, samples were found to exhibit clustering and were not ferromagnetic at room temperature. This capability to fabricate ferromagnetic Mn-doped ZnO semiconductors promises new spintronic devices as well as magneto-optic components.

Observation of a Narrow Charmoniumlike State in Exclusive B±→K±π+π-J/ψ Decays

Abstract: We report the observation of a narrow charmoniumlike state produced in the exclusive decay process B+/--->K+/-pi(+)pi(-)J/psi. This state, which decays into pi(+)pi(-)J/psi, has a mass of 3872.0+/-0.6(stat)+/-0.5(syst) MeV, a value that is very near the M(D0)+M(D(*0)) mass threshold. The results are based on an analysis of 152M B-Bmacr; events collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider. The signal has a statistical significance that is in excess of 10sigma.

Itinerant-electron metamagnetic transition and large magnetocaloric effects in La(FexSi1-x)13 compounds and their hydrides

Abstract: The itinerant-electron metamagnetic (IEM) transition and magnetocaloric effects (MCE's) in the $\mathrm{La}({\mathrm{Fe}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}{)}_{13}$ and $\mathrm{La}({\mathrm{Fe}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}{)}_{13}{\mathrm{H}}_{y}$ compounds have been investigated. The $\mathrm{La}({\mathrm{Fe}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}{)}_{13}$ compounds exhibit large values of both the isothermal entropy change $\ensuremath{\Delta}{S}_{\mathrm{m}}$ and the adiabatic temperature change $\ensuremath{\Delta}{T}_{\mathrm{ad}}$ around the Curie temperature ${T}_{\mathrm{C}}$ in relatively low magnetic fields. Such large MCE's are explained by a large magnetization change at ${T}_{\mathrm{C}}$ and a strong temperature dependence of the critical field ${B}_{\mathrm{C}}$ for the IEM transition. By hydrogen absorption into the compounds, ${T}_{\mathrm{C}}$ is increased up to about 330 K, keeping the metamagnetic transition properties. Accordingly, the extension of the working temperature range having the large MCE's in relatively low magnetic fields is demonstrated by controlling y in the $\mathrm{La}({\mathrm{Fe}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}{)}_{13}{\mathrm{H}}_{y}$ compounds. The correlation between the increase of ${T}_{\mathrm{C}}$ and the large MCE's in the $\mathrm{La}({\mathrm{Fe}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}{)}_{13}{\mathrm{H}}_{y}$ compounds is discussed by taking the magnetovolume effects into consideration.

Characterizing carbon nanotube samples with resonance Raman scattering

Abstract: The basic concepts and characteristics of Raman spectra from carbon nanotubes (both isolated and bundled) are presented. The general characteristics of the radial breathing mode, tangential mode (G band), disorder-induced mode (D-band) and other Raman features are presented, with the focus directed toward their use for carbon nanotube characterization. Polarization analysis, surface enhanced Raman spectroscopy and complementary optical techniques are also discussed in terms of their advantages and limitations.

The first data release of the sloan digital sky survey

Abstract: The Sloan Digital Sky Survey (SDSS) has validated and made publicly available its First Data Release. This consists of 2099 deg2 of five-band (u, g, r, i, z) imaging data, 186,240 spectra of galaxies, quasars, stars and calibrating blank sky patches selected over 1360 deg2 of this area, and tables of measured parameters from these data. The imaging data go to a depth of r ≈ 22.6 and are photometrically and astrometrically calibrated to 2% rms and 100 mas rms per coordinate, respectively. The spectra cover the range 3800–9200 A, with a resolution of 1800–2100. This paper describes the characteristics of the data with emphasis on improvements since the release of commissioning data (the SDSS Early Data Release) and serves as a pointer to extensive published and on-line documentation of the survey.

The anomalous Hall effect and magnetic monopoles in momentum space.

Abstract: Efforts to find the magnetic monopole in real space have been made in cosmic rays and in particle accelerators, but there has not yet been any firm evidence for its existence because of its very heavy mass, ∼10 16 giga–electron volts We show that the magnetic monopole can appear in the crystal momentum space of solids in the accessible low-energy region (∼01 to 1 electron volts) in the context of the anomalous Hall effect We report experimental results together with first-principles calculations on the ferromagnetic crystal SrRuO 3 that provide evidence for the magnetic monopole in the crystal momentum space

Activation of peroxisome proliferator-activated receptor δ induces fatty acid β-oxidation in skeletal muscle and attenuates metabolic syndrome

Abstract: In this study, we defined the role of peroxisome proliferator-activated receptor beta/delta (PPARdelta) in metabolic homeostasis by using subtype selective agonists. Analysis of rat L6 myotubes treated with the PPARdelta subtype-selective agonist, GW501516, by the Affymetrix oligonucleotide microarrays revealed that PPARdelta controls fatty acid oxidation by regulating genes involved in fatty acid transport, beta-oxidation, and mitochondrial respiration. Similar PPARdelta-mediated gene activation was observed in the skeletal muscle of GW501516-treated mice. Accordingly, GW501516 treatment induced fatty acid beta-oxidation in L6 myotubes as well as in mouse skeletal muscles. Administration of GW501516 to mice fed a high-fat diet ameliorated diet-induced obesity and insulin resistance, an effect accompanied by enhanced metabolic rate and fatty acid beta-oxidation, proliferation of mitochondria, and a marked reduction of lipid droplets in skeletal muscles. Despite a modest body weight change relative to vehicle-treated mice, GW501516 treatment also markedly improved diabetes as revealed by the decrease in plasma glucose and blood insulin levels in genetically obese ob/ob mice. These data suggest that PPARdelta is pivotal to control the program for fatty acid oxidation in the skeletal muscle, thereby ameliorating obesity and insulin resistance through its activation in obese animals.

Understanding the function–structure and function–mutation relationships of p53 tumor suppressor protein by high-resolution missense mutation analysis

Abstract: Inactivation of the tumor suppressor p53 by missense mutations is the most frequent genetic alteration in human cancers. The common missense mutations in the TP53 gene disrupt the ability of p53 to bind to DNA and consequently to transactivate downstream genes. However, it is still not fully understood how a large number of the remaining mutations affect p53 structure and function. Here, we used a comprehensive site-directed mutagenesis technique and a yeast-based functional assay to construct, express, and evaluate 2,314 p53 mutants representing all possible amino acid substitutions caused by a point mutation throughout the protein (5.9 substitutions per residue), and correlated p53 function with structure- and tumor-derived mutations. This high-resolution mutation analysis allows evaluation of previous predictions and hypotheses through interrelation of function, structure and mutation.

The Super-Kamiokande detector

Abstract: Super-Kamiokande is the world's largest water Cherenkov detector, with net mass 50,000 tons. During the period April, 1996 to July, 2001, Super-Kamiokande I collected 1678 live-days of data, observing neutrinos from the Sun, Earth's atmosphere, and the K2K long-baseline neutrino beam with high efficiency. These data provided crucial information for our current understanding of neutrino oscillations, as well as setting stringent limits on nucleon decay. In this paper, we describe the detector in detail, including its site, configuration, data acquisition equipment, online and offline software, and calibration systems which were used during Super-Kamiokande I.

Indications of neutrino oscillation in a 250 km long-baseline experiment.

Abstract: The K2K experiment observed indications of neutrino oscillation after 250 km flight of υμ. The observed number of events in the data corresponding to 4.8 x 1019 protons on target is 56, while 80.1 5.4 +6.2 is expected. Both the decrease of the events and observed spectrum shape distortion are consistent with neutrino oscillation. The probability that the observations are statistical fluctuation of non oscillation is less than 1%. The allowed region of oscillation parameters is consistent with the one obtained from the atmospheric neutrino observation. After the accident of Super-Kamiokande (SK) detector, the reconstruction of SK has finished in 2002 and the K2K experiment resumed in December 2002.

Evidence for a narrow S = +1 baryon resonance in photoproduction from the neutron.

Abstract: The $\ensuremath{\gamma}n\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}n$ reaction on $^{12}\mathrm{C}$ has been studied by measuring both ${K}^{+}$ and ${K}^{\ensuremath{-}}$ at forward angles. A sharp baryon resonance peak was observed at $1.54\ifmmode\pm\else\textpm\fi{}0.01\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}/{c}^{2}$ with a width smaller than $25\text{ }\text{ }\mathrm{M}\mathrm{e}\mathrm{V}/{c}^{2}$ and a Gaussian significance of $4.6\ensuremath{\sigma}$. The strangeness quantum number ($S$) of the baryon resonance is $+1$. It can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic five-quark state ($uudd\overline{s}$) that decays into a ${K}^{+}$ and a neutron. The resonance is consistent with the lowest member of an antidecuplet of baryons predicted by the chiral soliton model.

Novel splice variants of the receptor for advanced glycation end-products expressed in human vascular endothelial cells and pericytes, and their putative roles in diabetes-induced vascular injury.

Abstract: The binding of advanced glycation end-products (AGE) to the receptor for AGE (RAGE) is known to deteriorate various cell functions and is implicated in the pathogenesis of diabetic vascular complications. In the present study, we show that the cellular constituents of small vessels, endothelial cells (EC) and pericytes express novel splice variants of RAGE mRNA coding for the isoforms that lack the N-terminal V-type immunoglobulin-like domain (N-truncated) or the C-terminal transmembrane domain (C-truncated), as well as the known full-length mRNA. The ratio of the expression of the three variants was different between EC and pericytes; the content of the C-truncated form was highest in EC, whereas the full-length form was the most abundant in pericytes. Transfection experiments with COS-7 cells demonstrated that those variant mRNAs were translated into proteins as deduced; C-truncated RAGE was efficiently secreted into the culture media, and N-truncated RAGE was located mainly on the plasma membrane. The three isoforms were also detected in primary cultured human EC and pericytes. Further, full-length and C-truncated forms of RAGE bound to an AGE-conjugated column, whereas N-truncated RAGE did not. The AGE induction of extracellular-signal-related kinase phosphorylation and vascular endothelial growth factor in EC and of the growth and cord-like structure formation of EC was abolished completely by C-truncated RAGE, indicating that this endogenous secretory receptor (endogenous secretory RAGE) is cytoprotective against AGE. The results may contribute to our understanding of the molecular basis for the diversity of cellular responses to AGE and for individual variations in the susceptibility to diabetic vascular complications.

Loss of teratogenic response to 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) in mice lacking the Ah (dioxin) receptor

Abstract: Background: The aryl hydrocarbon receptor (AhR or dioxin receptor) is a ligand-activated transcription factor that is considered to mediate pleiotropic biological responses such as teratogenesis, tumour promotion, epithelial hyperplasia and the induction of drug-metabolizing enzymes to environmental contaminants usually represented by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In contrast to the role of AhR in the regulatory mechanism of xenobiotic-metabolizing enzymes, there is no direct proof that the AhR is involved in the teratogenic effects of TCDD. Results: To gain insight into the physiological and teratogenic role of the AhR, we have used gene targeting in mice to disrupt the murine Ahr gene by homologous recombination. Ahr-null mice were viable and fertile and were apparently normal at birth, but displayed a slightly slower growth rate than wild-type mice for the first few weeks of life. When pregnant dams were administered with TCDD by gavage, at a dose of 40 μg/kg body weight at gestation day 12.5, none of the Ahr-null mutant foetuses were sensitive to the teratogenic effects of TCDD, although almost all wild-type foetuses suffered from cleft palate and hydronephrosis. In heterozygous Ahr+/− genotypes, nearly all foetuses suffered from hydronephrosis in response to TCDD treatment, while haplo-insufficiency was observed in the incidence of cleft palate. Conclusion: These results clearly show that the AhR is involved in the malformation of the palate and kidney in mouse embryos caused by TCDD and suggests that the mechanism of its involvement differs between the cleft palate and hydronephrosis.

Human inhibitory receptors Ig-like transcript 2 (ILT2) and ILT4 compete with CD8 for MHC class I binding and bind preferentially to HLA-G

Abstract: Ig-like transcript 4 (ILT4) (also known as leukocyte Ig-like receptor 2, CD85d, and LILRB2) is a cell surface receptor expressed mainly on myelomonocytic cells, whereas ILT2 (also known as leukocyte Ig-like receptor 1, CD85j, and LILRB1) is expressed on a wider range of immune cells including subsets of natural killer and T cells. Both ILTs contain immunoreceptor tyrosine-based inhibitory receptor motifs in their cytoplasmic tails that inhibit cellular responses by recruiting phosphatases such as SHP-1 (Src homology 2 domain containing tyrosine phosphatase 1). Although these ILTs have been shown to recognize a broad range of classical and nonclassical human MHC class I molecules (MHCIs), their precise binding properties remain controversial. We have used surface plasmon resonance to analyze the interaction of soluble forms of ILT4 and ILT2 with several MHCIs. Although the range of affinities measured was quite broad (Kd = 2-45 microM), some interesting differences were observed. ILT2 generally bound with a 2- to 3-fold higher affinity than ILT4 to the same MHCI. Furthermore, ILT2 and ILT4 bound to HLA-G with a 3- to 4-fold higher affinity than to classical MHCIs, suggesting that ILT/HLA-G recognition may play a dominant role in the regulation of natural killer, T, and myelomonocytic cell activation. Finally, we show that ILT2 and ILT4 effectively compete with CD8 for MHCI binding, raising the possibility that ILT2 modulates CD8+ T cell activation by blocking the CD8 binding as well as by recruiting inhibitory molecules through its immunoreceptor tyrosine-based inhibitory receptor motif.

Cobalt-based bulk glassy alloy with ultrahigh strength and soft magnetic properties

Abstract: Bulk metallic glasses—formed by supercooling the liquid state of certain metallic alloys—have potentially superior mechanical properties to crystalline materials. Here, we report a Co43Fe20Ta5.5B31.5 glassy alloy exhibiting ultrahigh fracture strength of 5,185 MPa, high Young's modulus of 268 GPa, high specific strength of 6.0 × 105 Nm kg−1 and high specific Young's modulus of 31 × 106 Nm kg−1. The strength, specific strength and specific Young's modulus are higher than previous values reported for any bulk crystalline or glassy alloys1,2,3. Excellent formability is manifested by large tensile elongation of 1,400% and large reduction ratio in thickness above 90% in the supercooled liquid region. The ultrahigh-strength alloy also exhibited soft magnetic properties with extremely high permeability of 550,000. This alloy is promising as a new ultrahigh-strength material with good deformability and soft magnetic properties.

Stable and controlled amphoteric doping by encapsulation of organic molecules inside carbon nanotubes.

Abstract: Single-walled carbon nanotubes (SWNTs) have strong potential for molecular electronics, owing to their unique structural and electronic properties. However, various outstanding issues still need to be resolved before SWNT-based devices can be made. In particular, large-scale, air-stable and controlled doping is highly desirable. Here we present a method for integrating organic molecules into SWNTs that promises to push the performance limit of these materials for molecular electronics. Reaction of SWNTs with molecules having large electron affinity and small ionization energy achieved p- and n-type doping, respectively. Optical characterization revealed that charge transfer between SWNTs and molecules starts at certain critical energies. X-ray diffraction experiments revealed that molecules are predominantly encapsulated inside SWNTs, resulting in an improved stability in air. The simplicity of the synthetic process offers a viable route for the large-scale production of SWNTs with controlled doping states.

Spin injection and detection in magnetic nanostructures

Abstract: We study theoretically the spin transport in a nonmagnetic metal connected to ferromagnetic injector and detector electrodes. We derive a general expression for the spin accumulation signal which covers from the metallic to the tunneling regime. This enables us to discuss recent controversy on spin injection and detection experiments. Extending the result to a superconducting device, we find that the spin accumulation signal is strongly enhanced by opening of the superconducting gap since a gapped superconductor is a low carrier system for spin transport but not for charge. The enhancement is also expected in semiconductor devices.

Distorted perovskite with e g 1 configuration as a frustrated spin system

Abstract: The evolution of spin- and orbital-ordered states has been investigated for a series of insulating perovskites $R{\mathrm{MnO}}_{3}$ $(R=\mathrm{L}\mathrm{a},\mathrm{P}\mathrm{r},\mathrm{N}\mathrm{d},\dots{}).$ $R{\mathrm{MnO}}_{3}$ with a large ${\mathrm{GdFeO}}_{3}$-type distortion is regarded as a frustrated spin system having ferromagnetic nearest-neighbor and antiferromagnetic (AF) next-nearest-neighbor (NNN) interactions within a ${\mathrm{MnO}}_{2}$ plane. The staggered orbital order associated with the ${\mathrm{GdFeO}}_{3}$-type distortion induces the anisotropic NNN interaction, and yields unique sinusoidal and up-up-down-down AF ordered states in the distorted perovskites with ${e}_{g}^{1}$ configuration.

Role of the prolyl isomerase Pin1 in protecting against age-dependent neurodegeneration

Abstract: The neuropathological hallmarks of Alzheimer's disease and other tauopathies include senile plaques and/or neurofibrillary tangles. Although mouse models have been created by overexpressing specific proteins including beta-amyloid precursor protein, presenilin and tau, no model has been generated by gene knockout. Phosphorylation of tau and other proteins on serine or threonine residues preceding proline seems to precede tangle formation and neurodegeneration in Alzheimer's disease. Notably, these phospho(Ser/Thr)-Pro motifs exist in two distinct conformations, whose conversion in some proteins is catalysed by the Pin1 prolyl isomerase. Pin1 activity can directly restore the conformation and function of phosphorylated tau or it can do so indirectly by promoting its dephosphorylation, which suggests that Pin1 is involved in neurodegeneration; however, genetic evidence is lacking. Here we show that Pin1 expression is inversely correlated with predicted neuronal vulnerability and actual neurofibrillary degeneration in Alzheimer's disease. Pin1 knockout in mice causes progressive age-dependent neuropathy characterized by motor and behavioural deficits, tau hyperphosphorylation, tau filament formation and neuronal degeneration. Thus, Pin1 is pivotal in protecting against age-dependent neurodegeneration, providing insight into the pathogenesis and treatment of Alzheimer's disease and other tauopathies.

Low-density lipoprotein receptor-related protein 5 (LRP5) is essential for normal cholesterol metabolism and glucose-induced insulin secretion

Abstract: A Wnt coreceptor low-density lipoprotein receptor-related protein 5 (LRP5) plays an essential role in bone accrual and eye development. Here, we show that LRP5 is also required for normal cholesterol and glucose metabolism. The production of mice lacking LRP5 revealed that LRP5 deficiency led to increased plasma cholesterol levels in mice fed a high-fat diet, because of the decreased hepatic clearance of chylomicron remnants. In addition, when fed a normal diet, LRP5-deficient mice showed a markedly impaired glucose tolerance. The LRP5-deficient islets had a marked reduction in the levels of intracellular ATP and Ca2+ in response to glucose, and thereby glucose-induced insulin secretion was decreased. The intracellular inositol 1,4,5-trisphosphate (IP3) production in response to glucose was also reduced in LRP5−/− islets. Real-time PCR analysis revealed a marked reduction of various transcripts for genes involved in glucose sensing in LRP5−/− islets. Furthermore, exposure of LRP5+/+ islets to Wnt-3a and Wnt-5a stimulates glucose-induced insulin secretion and this stimulation was blocked by the addition of a soluble form of Wnt receptor, secreted Frizzled-related protein-1. In contrast, LRP5-deficient islets lacked the Wnt-3a-stimulated insulin secretion. These data suggest that Wnt/LRP5 signaling contributes to the glucose-induced insulin secretion in the islets.