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S Tajima

Publications and source records attributed to S Tajima.

At least 19 recordsLinked to original sources
PubMed2006

Anisotropic drude response and the effect of anisotropic C substitution in.

The in-plane and the out-of-plane optical spectra of small single crystals of Mg(B1-xCx)2 were directly determined by a microscope spectroscopy technique. Contrary to previous reports, the estimated plasma frequencies for both directions are quite consistent with the band calculation. A multi-Drude picture corresponding to a multiband system is necessary to explain the whole spectral profile. The spectral changes with the carbon substitution indicate a decrease of carrier concentration as well as an increase of scattering rate, particularly, in the sigma bands.

Journal Article↗
PubMed2005

Negative quantum interference between the electronic Raman scattering processes of CuO chains and CuO2 planes of heavily overdoped (Y, Ca)Ba2Cu3O(7-delta).

We found a strong X-Y anisotropy of the pair-breaking peak in the Raman scattering of heavily overdoped (Y, Ca)Ba2Cu3O(7-delta) (T(c) = 65 K). The pair-breaking peak is radically suppressed in the YY-polarized spectrum. We ascribe this anomaly to the effect of quantum interference between the Raman processes of the CuO-chain and the CuO2-plane electronic excitations that might take place as a result of the increase in the transfer matrix due to overdoping.

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↗
PubMed2005

Surface modification of low-density polyethylene by inductively coupled argon plasma.

The surface chemistry and nanotopography of low-density polyethylene (LDPE) were modified by downstream, inductively coupled, radio frequency (rf) Ar plasma without inducing surface damage. The extent of surface modification was controlled by the applied ion energy fluence, determined from the plasma ion density measured with a Langmuir probe. The treated LDPE surfaces were characterized by atomic force microscope (AFM) imaging, contact angle measurements, and X-ray photoelectron spectroscopy (XPS). Analysis of AFM surface images confirmed that topography changes occurred at the nanoscale and that surface damage was insignificant. Contact angle measurements demonstrated an enhancement of the surface hydrophilicity with the increase of the plasma power. XPS results showed surface chemistry changes involving the development of different carbon-oxygen functionalities that increased the surface hydrophilicity. Physical and chemical surface modification was achieved under conditions conducive to high-density inductively coupled rf plasma.

Algorithms↗
PubMed2005

Mott gap excitations in twin-free YBa2Cu3O7-delta (Tc=93 K) studied by resonant inelastic x-ray scattering.

Mott gap excitations in the optimally doped high-T(c) superconductor YBa(2)Cu(3)O(7-delta) (T(c)=93 K) have been studied by the resonant inelastic x-ray scattering method. Anisotropic spectra in the ab plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the b* direction, while the excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculations based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra when different values of the on-site Coulomb energy are assumed. The Mott gap of the CuO chain site is found to be much smaller than that of the CuO2 plane site.

Journal Article↗
PubMed2004

Angular distributions for (3,4)(Lambda)H bound states in the (3,4)He(e,e(')K+) reaction.

The (3,4)(Lambda)H and (4)(Lambda)H hypernuclear bound states have been observed for the first time in kaon electroproduction on (3,4)He targets. The production cross sections have been determined at Q(2)=0.35 GeV2 and W=1.91 GeV. For either hypernucleus the nuclear form factor is determined by comparing the angular distribution of the (3,4)He(e,e(')K+)(3,4)(Lambda)H processes to the elementary cross section 1H(e,e K+)Lambda on the free proton, measured during the same experiment.

Journal Article↗
PubMed2004

Dispersion of magnetic excitations in optimally doped superconducting YBa2Cu3O6.95.

Detailed neutron scattering measurements of YBa2Cu3O6.95 found that the resonance peak and incommensurate magnetic scattering induced by superconductivity represent the same physical phenomenon: two dispersive branches that converge near 41 meV and the in-plane wave vector q(AF)=(pi/a,pi/a) to form the resonance peak. One branch has a circular symmetry around q(AF) and quadratic downward dispersion from approximately 41 meV to the spin gap of 33+/-1 meV. The other, of lower intensity, disperses from approximately 41 meV to at least 55 meV. Our results exclude a quartet of vertical incommensurate rods in q-omega space expected from spin waves produced by dynamical charge stripes as an origin of the observed incommensurate scattering in optimally doped YBCO.

Journal Article↗
PubMed2004

Kinetic study of racemization of aspartyl residues in synthetic elastin peptides.

We previously reported that biologically uncommon D-aspartyl residues are present in sun-damaged skin from elderly people, possibly in elastin. Here, we report the kinetics of Asp racemization in model peptides corresponding to elastin sequences from exons 6 and 26. We estimated the activation energy (E) of racemization of Asp residues, the racemization rates (RR) at 37 degrees C and the time (t) required for the D/L ratio of Asp to approximate to 1.0 (D/L ratio of Asp=0.99) at 37 degrees C. For an exon 6 peptide, E=29.0 kcal/mol, RR=2.59 x 10(-2)/yr and t=101.0 yr. For an exon 26A peptide E=26.2 kcal/mol, RR=4.27 x 10(-2)/yr and t=61.3 yr; and for a second exon 26A peptide E=25.7 kcal/mol, RR=5.55 x 10(-2)/yr and t=47.0 yr. These results suggest that racemization of Asp residues in elastin could occur within a human life span. We propose that D-Asp could be a useful molecular indicators of aging.

Aging↗
PubMed2004

Kohn anomaly in MgB2 by inelastic X-ray scattering.

We study phonons in MgB2 using inelastic x-ray scattering (1.6 and 6 meV resolution). We clearly observe the softening and broadening of the crucial E(2g) mode through the Kohn anomaly along GammaM, in excellent agreement with ab initio calculations. Low temperature measurements (just above and below T(c)) show negligible changes for the momentum transfers investigated and no change in the E(2g) mode at A between room temperature and 16 K. We report the presence of a longitudinal mode along GammaA near in energy to the E(2g) mode that is not predicted by theory.

Journal Article↗
PubMed2004

Softening of Cu-O bond stretching phonons in tetragonal HgBa2CuO4+delta.

Phonons in nearly optimally doped HgBa(2)CuO(4+delta) were studied by inelastic x-ray scattering. The dispersion of the low-energy modes is well described by a shell model, while the Cu-O bond stretching mode at high energy shows strong softening towards the zone boundary, which deviates strongly from the model. This seems to be common in the hole-doped high-T(c) superconducting cuprates, and, based on this work, not related to a lattice distortion specific to each material.

Journal Article↗
PubMed2004

Measurement of the electric form factor of the neutron at Q2=0.5 and 1.0 GeV2/c2.

The electric form factor of the neutron was determined from measurements of the d-->(e-->,e'n)p reaction for quasielastic kinematics. Polarized electrons were scattered off a polarized deuterated ammonia (15ND3) target in which the deuteron polarization was perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle detector. We find G(n)(E)=0.0526+/-0.0033(stat)+/-0.0026(sys) and 0.0454+/-0.0054+/-0.0037 at Q(2)=0.5 and 1.0 (GeV/c)(2), respectively.

Journal Article↗
PubMed2004

Advanced glycation end product (AGE)-immunoreactive materials in chronic prurigo patients receiving a long-standing haemodialysis.

We report two patients with chronic prurigo who suffered from chronic renal failure and were treated by haemodialysis. Histological examination of pruritic nodules revealed that the papillary dermis of the lesional skin was eosinophilic and amorphous, and free from dermal cell infiltration. Immunohistochemical study demonstrated that advanced glycation end product (AGE)-immunoreactive materials accumulated in the papillary dermis of the lesional skin. This immunohistochemical finding was never observed in the nonlesional skin adjacent to prurigo nodules of the present cases, and renal disease-free prurigo skin (n = 6) and nonprurigo skin of haemodialysis patients (n = 3). AGE-modified materials in the papillary dermis may be related to the pathogenesis of prurigo nodules in the haemodialysis patients.

Aged↗
PubMed2004

HSP47 is a useful marker for skin fibroblasts in formalin-fixed, paraffin-embedded tissue specimens.

AIM: This study was undertaken to assess whether heat-shock protein (HSP)47 is a useful cell marker for skin fibroblasts in formalin-fixed, paraffin-embedded skin specimens. BACKGROUND: HSP47, a 47-kDa HSP, is a collagen-specific molecular chaperone localized in the endoplasmic reticulum. HSP47 plays an essential role in collagen biosynthesis in skin fibroblasts. METHODS: Immunohistochemistry was performed to detect HSP47 in skin fibroblast cultures and skin tissue sections. RESULTS: Immunostaining for HSP47 clearly detected skin fibroblasts in paraffin tissue sections as well as in fibroblast cultures and frozen tissue sections. HSP47 staining on paraffin sections from diseased skin specimens revealed that skin ulcer, keloid, nodular fascitis, spindle cell lipoma, and dermatofibroma had strong signals for HSP47 compared with the signals obtained from normal skin. Dermatofibrosarcoma protuberans had many HSP47 positive cells, but signals on individual cells were not as strong as those seen from the above benign proliferative disease samples. In neurofibroma, a small number of faintly positive cells were detected. Our double-immunostaining studies also demonstrated that HSP47 staining distinguished skin fibroblasts from CD68-positive histiocytes/macrophages, factor VIII-related antigen-positive endothelial cells, or factor XIIIa-positive dermal dendritic cells. CD34-positive interstitial cells coexpressed HSP47 in spindle cell lipoma. CONCLUSIONS: These findings indicate that HSP47 staining can detect skin fibroblasts in routine, paraffin-embedded specimens. A panel approach using HSP47 and other cell markers on paraffin sections may help the identification of the cell type involved with mesenchymal proliferative disorders.

Biomarkers↗
PubMed2004

Leukocytapheresis treatment for pyoderma gangrenosum.

A 42-year-old man presented with painful erythema with pustules and multiple small ulcers on the shins. He had suffered from ulcerative colitis (UC) and received oral glucocorticosteroid and salicylazosulfapyridine therapies for 7 years. Biopsy of the lesion demonstrated mixed cellular infiltrates with dominant neutrophils. The patient was diagnosed with pyoderma gangrenosum (PG) and underwent leukocytapheresis (LCAP), an extracorporeal leucocyte removal therapy, once a week for 5 weeks without changing the doses of the oral medications. The skin lesions as well as clinical signs of UC rapidly improved after LCAP, and no recurrence was seen during a follow-up period. There were no major complications during LCAP. LCAP will provide an effective and safe tool for the treatment of PG.

Adult↗
PubMed2003

Magnetic-field-induced finite-size effect in the nigh-temperature superconductor YBa2Cu3O(7-delta): a comparison with rotating superfluid 4He.

The effect of strong magnetic fields (11 T) on superconductivity in YBa2Cu3O(7-delta) is investigated using high-resolution thermal expansion. We show that the field-induced broadening of the superconducting transition is due to a finite-size effect resulting from the field-induced vortex-vortex length scale. The physics of this broadening has recently been elucidated for the closely related case of rotating superfluid 4He [Phys. Rev. B 60, 12 373 (1999)]]. Our results imply that the primary effect of magnetic fields of the order of 10 T is to destroy the phase coherence; the pairing, on the other hand, appears to be quite insensitive to these fields.

Journal Article↗
PubMed2003

Features of the electron density in magnesium diboride: reconstruction from X-ray diffraction data and comparison with TB-LMTO and FPLO calculations.

Features of the electron density in MgB(2) reconstructed from room-temperature single-crystal X-ray diffraction intensities using a multipole model are considered. Topological analysis of the total electron density has been applied to characterize the atomic interactions in magnesium diboride. The shared-type B-B interaction in the B-atom layer reveals that both sigma and pi components of the bonding are strong. A closed-shell-type weak B-B pi interaction along the c axis of the unit cell has also been found. The Mg-B closed-shell interaction exhibits a bond path that is significantly curved towards the vertical Mg-atom chain ([110] direction). The latter two facts reflect two sorts of bonding interactions along the [001] direction. Integration of the electron density over the zero-flux atomic basins reveals a charge transfer of approximately 1.4 (1) electrons from the Mg atoms to the B-atom network. The calculated electric-field gradients at nuclear positions are in good agreement with experimental NMR values. The anharmonic displacement of the B atoms is also discussed. Calculations of the electron density by tight-binding linear muffin-tin orbital (TB-LMTO) and full-potential non-orthogonal local orbital (FPLO) methods confirm the results of the reconstruction from X-ray diffraction; for example, a charge transfer of 1.5 and 1.6 electrons, respectively, was found.

Journal Article↗