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Biomedical subjects

N Kaneko

Publications and source records attributed to N Kaneko.

At least 19 recordsLinked to original sources
PubMed2006

Gap-inhomogeneity-induced electronic states in superconducting Bi2Sr2CaCu2O(8+delta).

In this Letter, we analyze, using scanning tunneling spectroscopy, the density of electronic states in nearly optimally doped Bi2Sr2CaCu2O(8+delta) in zero magnetic field. Focusing on the superconducting gap, we find patches of what appear to be two different phases in a background of some average gap, one with a relatively small gap and sharp large coherence peaks and one characterized by a large gap with broad weak coherence peaks. We compare these spectra with calculations of the local density of states for a simple phenomenological model in which a 2xi0 x 2xi0 patch with an enhanced or suppressed d-wave gap amplitude is embedded in a region with a uniform average d-wave gap.

Journal Article↗
PubMed2005

Charge-transfer excitations in the model superconductor HgBa(2)CuO(4+delta).

We report a Cu -edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa(2)CuO(4+delta) at optimal doping (T(c)=96.5 K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly dispersive (<0.5 eV) electron-hole excitations, including a mode at 2 eV. The observation of this 2 eV excitation suggests the existence of a remnant charge-transfer gap deep in the superconducting phase. Quite generally, our results, which include additional data for the Mott insulator La(2)CuO(4), demonstrate the importance of exploring the incident photon-energy dependence of the RIXS cross section.

Journal Article↗
PubMed2005

Muon spin relaxation studies of magnetic-field-induced effects in high-Tc superconductors.

Muon spin relaxation measurements in high transverse magnetic fields [FORMULA: SEE TEXT] revealed strong field-induced quasistatic magnetism in the underdoped and Eu-doped (La,Sr)2CuO4 and La1.875Ba0.125CuO4, existing well above Tc and TN. The susceptibility counterpart of Cu spin polarization, derived from the muon spin relaxation rate, exhibits a divergent behavior towards T approximately 25 K. No field-induced magnetism was detected in overdoped La1.81Sr0.19CuO4, optimally doped Bi2212, and Zn-doped YBa2Cu3O7.

Journal Article↗
PubMed2004

Coupling of the B1g phonon to the antinodal electronic states of Bi2Sr2Ca0.92Y0.08Cu2O8+delta.

Angle-resolved photoemission spectroscopy on optimally doped Bi(2)Sr(2)Ca(0.92)Y(0.08)Cu(2)O(8+delta) uncovers a coupling of the electronic bands to a 40 meV mode in an extended k-space region away from the nodal direction, leading to a new interpretation of the strong renormalization of the electronic structure seen in Bi2212. Phenomenological agreements with neutron and Raman experiments suggest that this mode is the B(1g) oxygen bond-buckling phonon. A theoretical calculation based on this assignment reproduces the electronic renormalization seen in the data.

Journal Article↗
PubMed2004

A universal scaling relation in high-temperature superconductors.

Since the discovery of superconductivity at elevated temperatures in the copper oxide materials there has been a considerable effort to find universal trends and correlations amongst physical quantities, as a clue to the origin of the superconductivity. One of the earliest patterns that emerged was the linear scaling of the superfluid density (rho(s)) with the superconducting transition temperature (T(c)), which marks the onset of phase coherence. This is referred to as the Uemura relation, and it works reasonably well for the underdoped materials. It does not, however, describe optimally doped (where T(c) is a maximum) or overdoped materials. Similarly, an attempt to scale the superfluid density with the d.c. conductivity (sigma(dc)) was only partially successful. Here we report a simple scaling relation (rho(s) proportional, variant sigma(dc)T(c), with sigma(dc) measured at approximately T(c)) that holds for all tested high-T(c) materials. It holds regardless of doping level, nature of dopant (electrons versus holes), crystal structure and type of disorder, and direction (parallel or perpendicular to the copper-oxygen planes).

Journal Article↗
PubMed2003

Coexistence of periodic modulation of quasiparticle states and superconductivity in Bi2Sr2CaCu2O8+delta.

In this article we show, using scanning tunneling spectroscopy, the existence of static striped density of electronic states in nearly optimally doped Bi2Sr2CaCu2O8+delta in zero field. This modulation is aligned with the Cu-O bonds, with a periodicity of four lattice constants, and exhibits features characteristic of a two-dimensional system of line objects. We further show that the density of states modulation manifests itself as a shift of states from above to below the superconducting gap. The fact that a single energy scale (i.e., the gap) appears for both superconductivity and stripes suggests that these two effects have the same origin.

Journal Article↗
PubMed2003

Postnatal and postprandial changes in plasma concentrations of glicentin in term and preterm infants.

AIM: To examined the changes in basal plasma concentrations of glicentin in developing children and the postnatal and postprandial changes in plasma glicentin levels in infants. METHODS: Glicentin, an active component of enteroglucagon, is considered to have a significant trophic action on the intestinal mucosa. Fasting plasma concentrations of glicentin in healthy children and in term and preterm infants were measured before and 30 min after feeding during the first 14 d of life. RESULTS: Plasma basal concentrations of glicentin in children under 1 y of age were significantly higher than those in children aged 1 to 15 y. Plasma basal concentrations of glicentin at 5 or 6 d (2496 and 2190 pg/ml) and at 14 d (2987 and 2817 pg/ml) after birth were significantly higher than those at 1 or 2 d (1098 and 1240 pg/ml) after birth in normal birthweight (NBW) and low-birthweight (LBW) infants. There was no significant difference in the glicentin level between infants at 1 or 2 d (1864 pg/ml) and at 5 or 6 d (1910 pg/ml) after birth in very-low birthweight (VLBW) infants, but the levels at 14 d (3310 pg/ml) after birth were significantly higher than either of those levels. Plasma glicentin concentrations after feeding were significantly higher than those before feeding at 1 or 2 d and at 5 or 6 d after birth in NBW and LBW infants, but a significant increase in the plasma glicentin level after feeding was first observed at 14 d after birth in VLBW infants. There were no significant differences in the basal plasma (2401 and 2718 pg/ml) and postprandial (3007 and 3912 pg/ml) glicentin levels between breastfed and formula-fed infants. CONCLUSION: The results of the study suggest that glicentin may play an important role in intestinal mucosal growth in the early period of life, although its role in VLBW infants should be further investigated.

Breast Feeding↗
PubMed2003

Effects of SRT and DO on N2O reductase activity in an anoxic-oxic activated sludge system.

Nitrous oxide (N2O) is emitted from wastewater treatment processes, and is known to be a green house gas contributing to global warming. It is thus important to develop technology that can suppress N2O emission. The effects of sludge retention time (SRT) and dissolved oxygen (DO) on N2O emission in an anoxic-oxic activated sludge system were estimated. Moreover, the microbial community structure in the sludge, which plays an important role in N2O suppression, was clarified based on nitrous oxide reductase (nosZ) gene analysis by molecular biological techniques. The results showed that under low SRT conditions, nitrification efficiency was reduced and the N2O emission rate in the oxic reactors was increased. It was also observed that N2O emission was enhanced under low DO conditions, where the available oxygen is insufficient for nitrification. Moreover, molecular analysis revealed that the clones identified in this study were closely related to Ralstonia eutropha and Paracoccus denitrificans. The fact that the identified sequences are not closely related to known culturable denitrifier nosZ sequences indicates a substantial in situ diversity of denitrifiers contributing to N2O suppression, which are not reflected in the cultivatable fraction of the population. The further application of these new molecular techniques should serve to enhance our knowledge of the microbial community of denitrifying bacteria contributing to N2O suppression in wastewater treatment systems.

Air Pollution↗
PubMed2002

Doping dependence of an n-type cuprate superconductor investigated by angle-resolved photoemission spectroscopy.

We present an angle-resolved photoemission doping dependence study of the n-type cuprate superconductor Nd(2-x)Ce(x)CuO(4+/-delta), from the half-filled Mott insulator to the T(c) = 24 K superconductor. In Nd2CuO4, we reveal the charge-transfer band for the first time. As electrons are doped into the system, this feature's intensity decreases with the concomitant formation of near- E(F) spectral weight. At low doping, the Fermi surface is an electron-pocket (with volume approximately x) centered at (pi,0). Further doping leads to the creation of a new holelike Fermi surface (volume approximately 1+x) centered at (pi,pi). These findings shed light on the Mott gap, its doping evolution, as well as the anomalous transport properties of the n-type cuprates.

Journal Article↗
PubMed2002

Electronic structure of the trilayer cuprate superconductor Bi(2)Sr(2)Ca(2)Cu(3)O(10+delta).

The low-energy electronic structure of the nearly optimally doped trilayer cuprate superconductor Bi(2)Sr(2)Ca(2)Cu(3)O(10+delta) is investigated by angle-resolved photoemission spectroscopy. The normal state quasiparticle dispersion and Fermi surface and the superconducting d-wave gap and coherence peak are observed and compared with those of single- and bilayer systems. We find that both the superconducting gap magnitude and the relative coherence-peak intensity scale linearly with T(c) for various optimally doped materials.

Journal Article↗
PubMed2001

Anomalous electronic structure and pseudogap effects in Nd1.85Ce0.15CuO4.

We report a high-resolution angle-resolved photoemission spectroscopic study of the electron-doped ( n-type) cuprate superconductor Nd1.85Ce0.15CuO4. We observe regions along the Fermi surface where the near- E(F) intensity is suppressed and the spectral features are broad in a manner reminiscent of the high-energy "pseudogap" in the underdoped p-type (hole doped) cuprates. However, instead of occurring near the (pi,0) region, as in the p-type materials, this pseudogap falls near the intersection of the underlying Fermi surface with the antiferromagnetic Brillouin zone boundary.

Journal Article↗
PubMed2001

Nature of e(g) electron order in La(1-x)Sr(1+x)MnO(4).

X-ray scattering measurements of the low-temperature structure of La(1-x)Sr(1+x)MnO(4) ( 0.33< or =x< or =0.67) indicate the existence of three distinct regions: a disordered phase (x<0.4), a charge-ordered phase (x> or =0.5), and a mixed phase (0.4< or =x<0.5). For x>0.5, the modulation vector associated with the charge order is incommensurate with the lattice and depends linearly on the concentration of e(g) electrons. The primary superlattice reflections are strongly suppressed along the modulation direction and the higher harmonics are weak, implying the existence of a largely transverse and nearly sinusoidal structural distortion, consistent with a charge-density wave of the e(g) electrons.

Journal Article↗
PubMed2001

Localization of annexin V in rat normal kidney and experimental glomerulonephritis.

The localization of annexin V, a calcium binding protein, was immunochemically and immunohistologically studied in experimental rat glomerulonephritis using annexin V polyclonal antibody. Plasma and urinary annexin V levels were measured by a sandwich enzyme-linked immunosorbent assay (ELISA). Urinary annexin V level, which was correlated with urinary L-lactate dehydrogenase activity, N-acetyl-beta-D-glucosaminidase activity and protein level, increased time-dependently after the injection of nephritogenic antigen (bovine glomerular basement membrane), progressively increasing to attain a peak level at 4 weeks of 51.5 +/- 11.3 ng/h. However, plasma annexin V level showed no increase during the study period. Normal kidneys showed strong staining for annexin V in distal tubules, being particularly strong in tubules of the inner stripe of the outer medulla, but could not be detected in proximal tubules. Annexin V was seen in visceral epithelial cells. Bowman's capsule of the glomerulus, the vascular endothelium of arterioles and interlobular arteries, and vascular smooth muscle. In nephritis, the lumen of distal tubules and the luminal cell membrane were deeply stained, with leakage of annexin V being observed from tubular cells. In the present study, renal annexin V was markedly excreted into urine, and its urinary level reflected the severity of damage of renal tissue and the progression of nephritis. These changes of annexin V in the distal tubule and visceral epithelial cells may be of significance in cell injury of the kidney.

Animals↗
PubMed2001

Hyperthermia: is it an ominous sign after cardiac arrest?

OBJECTIVE: To clarify the clinical characteristics of hyperthermia at an early stage after resuscitation from cardiac arrest (CA). MATERIALS AND METHODS: We reviewed the medical records of 43 adult patients with non-traumatic out-of-hospital CA, who survived for longer than 24 h after admission to our intensive care unit (ICU) between January, 1995, and December, 1998. The patients were divided into two groups: a clinical brain death (CBD) group (n=23) and a non-CBD group (n=20), and various factors relating to hyperthermia were compared between the two groups. RESULTS: The mean value of peak axillary temperatures within 72 h of admission was 39.8+/-0.9 degrees C for the CBD group, which was significantly greater than 38.3+/-0.6 degrees C for the non-CBD group (P<0.0001). The time of occurrence of the peak axillary temperature was at 19+/-16 h of admission in the CBD group and 20+/-18 h in the non-CBD group (not significantly different). There were no significant differences in risk factors relating to the occurrence of hyperthermia between the two groups, except for the number of patients who received epinephrine at ICU. In 23 patients with a peak axillary temperature of > or =39 degrees C during the first 72 h of hospitalization, brain death was diagnosed in 20 patients, whereas only 3 of 20 patients having a peak axillary temperature of <39 degrees C developed brain death (odds ratio, 37.8; 95% confidence interval, 6.72-212.2). CONCLUSION: Hyperthermia at an early stage after resuscitation from CA may be associated with the outcome of brain death.

Aged↗
PubMed2001

Effects of addition of hydrophobic sucrose fatty acid oligoesters on crystallization rates of n-hexadecane in oil-in-water emulsions.

Ultrasonic velocity measurements were made on crystallization rates of n-hexadecane dispersed in an oil-in-water (O/W) emulsion (20 wt.% oil and 80 wt.% water) in which Tween 20 was employed for emulsification. Highly hydrophobic emulsifiers, sucrose fatty acid oligoesters involving stearic acid (S-170), lauric acid (L-195) and oleic acid (O-170) moieties, were added to n-hexadecane in an attempt to modify the crystallization rate of n-hexadecane. The crystallization process of n-hexadecane was monitored by variations in the ultrasonic velocity values, which increase with increasing amount of crystal fractions in the oil phase of the emulsion. In comparison with the results of the O/W emulsion systems with the additive P-170 (a sucrose palmitate) (N.Kaneko et al., J. Crystal Growth 197 (1999) 263), the following results were obtained: (a) the addition of S-170 accelerated the nucleation in the emulsion system in the same manner as P-170, no acceleration was revealed with the additive O-170, and L-195 showed moderate effects; (b) the rate of crystal growth was retarded by S-170 and L-195, but not by O-170; (c) the effects of acceleration of nucleation occurred singly in the emulsion system, but not in the bulk system; and (d) the acceleration of nucleation was exhibited through two stages with increasing concentrations of the additives. These results showed the remarkable influence of the fatty acid chain structures of sucrose oligoesters on the acceleration of heterogeneous nucleation of n-hexadecane in the O/W emulsions. The heterogeneous nucleation effected by the addition of S-170 and P-170 was discussed taking into account the adsorption at the oil-water interface and the formation of reversed micelles of the sucrose oligoesters added in the oil phase.

Journal Article↗
PubMed2001

Reversal of cisplatin resistance by the 1,4-benzothiazepine derivative, JTV-519.

The 1,4-benzothiazepine derivative JTV-519 is a new type of calcium ion channel modulator. We examined the modulatory effect of JTV-519 on the antitumor activity of several platinum compounds (cisplatin, carboplatin, and nedaplatin) in a human cancer cell line resistant to cisplatin (PC-14 / CDDP) in vitro. PC-14 / CDDP cells showed 8-fold resistance to cisplatin compared with the parental PC-14 cells as determined by dye formation [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, MTT] assay. In PC-14 / CDDP, but not PC-14 cells, augmentation of cytotoxicity was observed when a nontoxic concentration (10 mM) of JTV-519 was combined with the platinum compounds. Increased intracellular cisplatin accumulation was observed in PC-14 / CDDP cells in the presence of JTV-519 as measured by atomic absorption assay. Therefore, increased cisplatin accumulation was considered to be a possible mechanism underlying the reversing effect of JTV-519 on cisplatin resistance. These results suggest that JTV-519 is a potent agent reversing cisplatin resistance.

Antineoplastic Agents↗