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S Tajima

Publications and source records attributed to S Tajima.

At least 37 records · Page 2Linked to original sources
PubMed2003

Measurements of GnE/GnM from the 2H(e-->,en-->)1H Reaction to Q2=1.45 (GeV/c)2.

We report new measurements of the ratio of the electric form factor to the magnetic form factor of the neutron, G(n)(E)/G(n)(M), obtained via recoil polarimetry from the quasielastic 2H(e-->,e(')n-->)1H reaction at Q2 values of 0.45, 1.13, and 1.45 (GeV/c)(2) with relative statistical uncertainties of 7.6% and 8.4% at the two higher Q2 points, which points have never been achieved in polarization measurements.

Journal Article↗
PubMed2003

Determination of the Fermi surface of MgB2 by the de Haas-van Alphen effect.

We report measurements of the de Haas-van Alphen (dHvA) effect for single crystals of MgB2, in magnetic fields up to 32 T. In contrast to our earlier work, dHvA orbits from all four sheets of the Fermi surface were detected. Our results are in good overall agreement with calculations of the electronic structure and the electron-phonon mass enhancements of the various orbits, but there are some small quantitative discrepancies. In particular, systematic differences in the relative volumes of the Fermi-surface sheets and the magnitudes of the electron-phonon coupling constants could be large enough to affect detailed calculations of T(c) and other superconducting properties.

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PubMed2003

c-Axis Raman scattering spectra of MgB2: observation of a dirty-limit gap in the pi bands.

Raman scattering spectra from the ac face of thick MgB2 single crystals were measured in zz, xz, and xx polarizations. In zz and xz polarizations a threshold at around 29 cm(-1) forms in the below T(c) continuum but no pair-breaking peak is seen, in contrast to the sharp pair-breaking peak at around 100 cm(-1) in xx polarization. The zz and xz spectra are consistent with Raman scattering from a dirty superconductor while the sharp peak in the xx spectra argues for a clean system. Analysis of the spectra resolves this contradiction, placing the larger and smaller gap magnitudes in the sigma and pi bands and indicating that relatively strong impurity scattering is restricted to the pi bands.

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PubMed2003

Search for E(2g) phonon modes in MgB2 single crystals by point-contact spectroscopy.

The electron-phonon interaction in magnesium diboride MgB2 single crystals is investigated by point-contact (PC) spectroscopy. For the first time the electron coupling with E(2g) phonon modes is resolved in the PC spectra. The correlation between intensity of the extremely broad E(2g) modes in the PC spectra and value of the superconducting gap is established. Our observations favor current theoretical models for electron-phonon mediated superconductivity in MgB2, and they better match the harmonic phonon model.

Journal Article↗
PubMed2003

Facial lichen striatus: successful treatment with tacrolimus ointment.

We report a 22-year-old Japanese woman with facial lichen striatus (LS). The distribution of the lesions corresponded to that of Blaschko's lines. Histology of the lesional skin showed an inflammatory cell infiltrate around hair follicles and eccrine glands. Treatment of the linear lesions with tacrolimus ointment once or twice daily resulted in a dramatical improvement in a short time. LS is a T-cell-mediated inflammatory disease and tacrolimus ointment may be an effective alternative treatment for this disease especially when the lesions are located on the face.

Adult↗
PubMed2002

Specific heat of single crystal MgB2: a two-band superconductor with two different anisotropies.

Heat-capacity measurements of a 39 microg MgB2 single crystal in fields up to 14 T and below 3 K allow the determination of the low-temperature linear term of the specific heat, its field dependence, and its anisotropy. Our results are compatible with two-band superconductivity, the band carrying the smaller gap being isotropic, that carrying the larger gap having an anisotropy of approximately 5. Three different upper critical fields are thus needed to describe the superconducting state of MgB2.

Journal Article↗
PubMed2002

New Josephson plasma modes in underdoped YBa2Cu3O6.6 induced by a parallel magnetic field.

The c-axis reflectivity spectrum of underdoped YBa2Cu3O6.6 (YBCO) is measured below T(c)=59 K in parallel magnetic fields H parallel CuO2 up to 7 T. Upon application of a parallel field, a new peak appears at finite frequency in the optical conductivity at the expense of suppression of c-axis condensate weight. We conclude that the dramatic change originates from different Josephson coupling strengths between bilayers with and without Josephson vortices. We find that the 400 cm(-1) broad conductivity peak in YBCO gains the spectral weight under parallel magnetic field; this indicates that the condensate weight at omega=0 is distributed to this peak as well as to the new optical Josephson mode.

Journal Article↗
PubMed2002

Peak effect in single crystal MgB(2) superconductor for H axially c-axis.

We have studied the phase diagram of the MgB(2) superconductor using a single crystal for the H parallel c-axis. For the first time we report the existence of peak effect in the screening current in the MgB(2) for the H parallel c-axis. In the magnetic field regime 10<H<13.5 kOe the local fundamental diamagnetic moment displays a very narrow diamagnetic step. For higher fields this step is transformed to a peak (peak effect) and, finally, for H<10 kOe the diamagnetic step is transformed to a gradual transition.

Journal Article↗
PubMed2002

Observation of structures of chain vortices inside anisotropic high- Tc superconductors.

In order to elucidate the formation mechanism of unconventional arrangements of vortices in high- Tc superconducting thin films at an inclined magnetic field to the layer plane, we investigated the structures of vortex lines inside the films by Lorentz microscopy using our 1-MV field-emission electron microscope. Our observation results concluded that vortex lines are tilted to form linear chains in YBaCu3O(7,8). Vortex lines in the chain-lattice state in Bi2Sr2CaCu2O(8+delta), on the other hand, are all perpendicular to the layer plane, and therefore only vortices lined up along Josephson vortices form chains.

Journal Article↗
PubMed2002

de Haas-van Alphen effect in single crystal MgB2.

We report observations of quantum oscillations in single crystals of the high temperature superconductor MgB2. Three de Haas-van Alphen frequencies are clearly resolved. Comparison with band structure calculations strongly suggests that two of these come from a single warped Fermi surface tube along the c direction, and that the third arises from cylindrical sections of an in-plane honeycomb network. The measured values of the effective mass range from (0.44-0.68)m(e). By comparing these to calculated band masses, we find that the electron-phonon coupling strength lambda is a factor of approximately 3 larger for the c-axis tube orbits than for the in-plane network orbit, in accord with recent microscopic calculations.

Journal Article↗
PubMed2002

Electronic structure of MgB2 from angle-resolved photoemission spectroscopy.

The first angle-resolved photoemission spectroscopy results from MgB2 single crystals are reported. Along the GammaK and GammaM directions, we observed three distinct dispersive features approaching the Fermi energy. These can be assigned to the theoretically predicted sigma (B 2p(x,y)) and pi (B 2p(z)) bands. In addition, a small parabolic-like band is detected around the Gamma point, which can be attributed to a surface-derived state. The overall agreement between our results and the band calculations suggests that the electronic structure of MgB2 is of a conventional nature, thus implying that electron correlations are weak and may be of little importance to superconductivity in this system.

Journal Article↗
PubMed2002

Superconducting gap in MgB(2): electronic Raman scattering measurements of single crystals.

Polarization-resolved Raman scattering measurements were performed on MgB(2) single crystals to determine the magnitude, symmetry, and temperature dependence of the superconducting gap. A single sharp peak due to Cooper pair breaking appears in the electronic continuum below T(c), reaching a maximum Raman shift of 105 +/- 1 cm(-1) [2 Delta(0)/k(B)T(c) = 3.96 +/- 0.09] and showing up to 5 cm(-1) anisotropy between polarized and depolarized spectra. The temperature dependence of 2 Delta follows that predicted from BCS theory, while the anisotropy decreases with decreasing temperature. It is concluded that the Raman results are consistent with a slightly anisotropic s-wave gap in a conventional BCS superconductor.

Journal Article↗
PubMed2002

Exponential temperature dependence of the penetration depth in single crystal MgB2.

The temperature dependence of the London penetration depth, lambda(T), was measured in both single crystal and polycrystalline MgB2 samples by a high-resolution, radio frequency technique. A clear exponential temperature dependence of lambda(T) was observed at low temperature, indicating s-wave pairing. A BCS fit to the lowest temperature data gives an in-plane energy gap Delta of 30+/-2 K (2Delta/T(c) = 1.5+/-0.1), which is significantly smaller than the standard BCS weak coupling value of 3.5. We find that the data are best described by a two-gap model.

Journal Article↗
PubMed2002

Expression of the 67-kDa elastin receptor in perforating skin disorders.

BACKGROUND: Perforating skin dermatoses include elastosis perforans serpiginosa (EPS), reactive perforating collagenosis, Kyrle's disease and perforating folliculitis. In addition to these four diseases, an acquired form of perforating dermatosis associated with diabetes mellitus and/or chronic renal failure has been reported for which the term acquired perforating dermatosis (APD) was proposed. The molecular mechanism of transepidermal elimination of dermal components in perforating skin dermatoses remains unclear. We recently demonstrated that the 67-kDa elastin receptor can be detected in the epidermis eliminating altered elastic fibres in EPS, suggesting that the elastin-keratinocyte interaction may play a role in transepidermal elimination in EPS. OBJECTIVES: To determine whether the 67-kDa elastin receptor is involved in other perforating diseases. METHODS: Paraffin-embedded skin specimens from new cases of EPS (n = 2), APD (n = 15) and perforating granuloma annulare (PGA; n = 2) were studied immunohistochemically using a specific antibody to the 67-kDa elastin receptor. In one case of EPS, two different sites from a single lesion, a central atrophic area and a peripheral keratotic area, were studied. RESULTS: Expression of the elastin receptor was detected in the epidermis surrounding the elastic materials in both cases of EPS. The elastin receptor was not detected in the central inactive area, whereas it was expressed strongly in the peripheral keratotic active area. The elastin receptor was also detected in three of 15 cases of APD in which a few elastic fibres were found in the eliminated dermal materials. In one case of APD, the elastin receptor was not detected in spite of the presence of a few elastic fibres in the eliminated materials. The elastin receptor was not detected in either case of PGA. CONCLUSIONS: Expression of the elastin receptor in EPS was seen in both cases studied and was dependent on the stage of the lesion. Expression of the elastin receptor in APD appeared to be related to the amount of elastic fibres in the eliminated materials. Thus, expression of the elastin receptor in perforating skin disorders may depend on the stage of the lesion and/or the content of elastic fibres in the dermal materials being eliminated.

Adult↗
PubMed2002

Coexistence of beta2 microglobulin and lambda light chain in amyloid fibrils of dialysis-unrelated plasma cell dyscrasia-associated systemic amyloidosis.

BACKGROUND: Systemic amyloidosis occurs as a result of amyloid deposition in various tissues. The amyloid fibrils in systemic amyloidosis have been reported to originate from immunoglobulin light chains. OBJECTIVE: We studied the composition of amyloid fibrils from two patients with plasma cell-associated systemic amyloidosis (PASA). METHODS: A double immunofluorescence study of the lesional skin of PASA was undertaken. Amyloid proteins were extracted with distilled water from one case of PASA. RESULTS: The double immunofluorescence study showed that anti-lambda light chain and anti-beta2 microglobulin antibodies mostly reacted with the same area of amyloid deposit. Amyloid deposits from two patients with PASA who had never undergone haemodialysis showed a positive reaction with the antibodies for beta2 microglobulin as well as immunoglobulin lambda light chain. By the use of immunoblot assay of amyloid fibril proteins, polypeptides immunoreactive with antigamma light chain antibody (29 kDa) and with anti-beta2 microglobulin antibody (12 kDa) were detected. CONCLUSIONS: These results indicate that beta2 microglobulin is a component of amyloid fibrils in PASA.

Aged↗
PubMed2002

Twenty-year changes in the prevalence of overweight in Japanese adults: the National Nutrition Survey 1976-95.

The aim of this study was to describe the 20-year changes in body mass index (BMI; kgm(-2)) and the prevalence of overweight in Japanese adults. Cross-sectional annual nationwide surveys (National Nutrition Survey, Japan) were carried out with a large probability sample of the Japanese population. Data sets of the 1976-95 surveys, comprising 91983 men and 120822 women (> or =20 years of age), were used. The analyses were carried out in age and gender groups, and by residential area according to the size of the municipality (metropolitan areas, cities and small towns). The mean BMI increaseed in men with an increment of +0.44 kg m(-2) 10 years(-1) and slightly decreased in women, by -0.09 kg m(-2) 10 years(-1), after adjustment for age. A decreasing trend of mean BMI was most significant in the female 20-29 years age-group (-0.38 kg m(-2) 10 years(-1)), in contrast to an increasing trend observed in elderly women (60-69 and 70+ years age-groups). The prevalence of preobese (BMI: 25-29.9kg m(-2)) and obese (BMI > or = 30 kg m(-2)) men increased from 14.5% and 0.8%, respectively, in the time-period 1976-80 to 20.5% and 2.01% during 1991-95. The increasing trend was most evident in the youngest age-group (20-29 years) and in those from small towns. The overall prevalence of preobese and obese women did not change during the 20-year study period. The prevalence in younger women decreased, this trend being more prominent in metropolitan areas. Although the prevalence of overweight (BMI > or =25 kg m(-2)) in Japanese men and elderly women has increased in the last 20 years, the mean BMI in younger women, especially those in metropolitan areas, has decreased. A population approach to control obesity and prevent obesity-associated diseases should be mainly focused on men and women older than 40 years of age.

Adult↗