In order to realize superconductivity in cuprates with the T′-type structure, not only chemical substitution (Ce doping) but also postgrowth reduction annealing is necessary. In the case of thin ...films, however, well-designed reduction annealing alone without Ce doping can induce superconductivity in the T′-type cuprates. In order to unveil the origin of superconductivity in the Ce-undoped T′-type cuprates, we have performed bulk-sensitive hard x-ray photoemission and soft x-ray absorption spectroscopy on superconducting and nonsuperconducting Nd2−xCexCuO4 (x=0, 0.15, and 0.19) thin films. By postgrowth annealing, core-level spectra exhibited dramatic changes, which we attributed to the enhancement of core-hole screening in the CuO2 plane and the shift of chemical potential along with changes in the band filling. The result suggests that the superconducting Nd2CuO4 film is doped with electrons despite the absence of the Ce substitution.
A persistent photoinduced metal-to-insulator transition has been confirmed in a manganite thin film, Pr_(0.55)(Ca_(0.75)Sr_(0.25))_(0.45)MnO3, near a multicritical point by monitoring with transport ...measurements and x-ray photoemission spectroscopy. Together with the previously reported reverse effect, the photoinduced insulator-to-metal transition, it is found that the relative stability of the metallic and insulating phases interchanges around 80 K in the middle of a very wide hysteresis loop, which is a manifestation of the large potential barrier due to the long-range elastic energy. It is shown that photons are much more effective in overcoming the barrier via the electronically excited intermediate states than via the heat mode.
We report on a photoemission study of Ta2NiSe5 that has a quasi-one-dimensional structure and an insulating ground state. Ni 2p core-level spectra show that the Ni 3d subshell is partially occupied ...and the Ni 3d states are heavily hybridized with the Se 4p states. In angle-resolved photoemission spectra, the valence-band top is found to be extremely flat, indicating that the ground state can be viewed as an excitonic insulator state between the Ni 3d-Se 4p hole and the Ta 5d electron. We argue that the high atomic polarizability of Se plays an important role to stabilize the excitonic state.
Naive CD4(+) T cells are activated by antigen-presenting cells (APCs) and differentiate into distinct types of helper T (T(h)) cells in the lymph node or spleen. Oxygen (O(2)) tension is generally ...low in these secondary lymphoid tissues compared with the bloodstream or atmosphere. However, the effect of changes in O(2) concentration on the differentiation of T(h) cells remains unclear. Here, we established a novel model of T(h)-cell differentiation, which mimics physiological O(2) conditions. We primed naive CD4(+) T cells under 5% O(2), which has been observed in the lymph node or spleen and reoxygenated under normoxia that mimicked the O(2) concentration in blood. In this model, the differentiation of T(h)17 cells, but not T(h)1 or iTreg cells, was enhanced. Under the condition of 5% O(2), mammalian target of rapamycin complex 1 (mTORC1) was activated and led to the stabilization of hypoxia-inducible factor 1α (HIF-1α) in T(h)17 cells. The activation of mTORC1 and the acceleration of T(h)17-cell differentiation, which occurred when cells were primed under 5% O(2), were not observed in the absence of HIF-1α but were accelerated in the absence of von Hippel-Lindau tumor suppressor protein (vHL), a factor critical for HIF-1α degradation. Thus, a positive feedback loop between HIF-1α and mTORC1 induced by hypoxia followed by reoxygenation accelerates T(h)17-cell differentiation.
In Japan, more than 90% of oesophageal malignancies are squamous cell carcinomas, and superficial and early carcinomas now account for about 40% and 20%, respectively, of all oesophageal carcinomas. ...Definition of early carcinoma has changed on the basis of new data. As of 2007, early carcinoma is defined as intramucosal carcinoma with or without metastasis. In the subclassification based on depth of cancer invasion, m1 and m2 carcinomas have no metastasis and are considered curable by endoscopic mucosal resection alone, whereas < 10% of m3 carcinomas and about 20% of sm1 carcinomas have lymph node metastasis. The relationship between various pathological findings and the incidence of lymph node metastasis has been reviewed. High‐grade squamous dysplasia (squamous cell carcinoma in situ in Japan) requires surgical or endoscopic removal. Very minute carcinomas have recently been detected by magnifying endoscopy and/or narrowband imaging. Endocytoscopy could replace biopsy histopathological examination for diagnosis of oesophageal squamous cell carcinoma, and endocytoscopic diagnosis and endoscopic therapy may be performed simultaneously. As a result of advances in the development of endoscopes, pathologists are now expected to diagnose very minute lesions, < 1 mm in size, in the oesophagus.
Photoemission Spectroscopy of Ta2NiSe5 Wakisaka, Y.; Sudayama, T.; Takubo, K. ...
Journal of superconductivity and novel magnetism,
07/2012, Letnik:
25, Številka:
5
Journal Article, Conference Proceeding
Recenzirano
We report temperature-dependent angle-resolved photoemission spectroscopy measurement of Ta
2
NiSe
5
which shows a semiconductor-semiconductor structural phase transition at around 330 K. ...Characteristically, flat band at the top of the valence band is observed, which is ascribed to the excitonic insulator effect. The top valence band shifts to higher binding energy and its bandwidth increases as the temperature decreases.
As the system exceeds the transition temperature, the flat feature of the valence band weakens though the exciton fluctuations remain finite.
We studied the photoinduced dynamics of spinel MnV sub(1.8) Al sub(0.2) O sub(4) and pyrochlore Yb sub(2) V sub(2) O sub(7) as prototypical Mott-Hubbard insulators with magnetic ordering. We found ...that the Mott excitation spectrum is suppressed much sooner than 1 ps after photoirradiation, and subsequently it shows an energy shift over several or several tens of picoseconds, which is caused by the melting of magnetic ordering. This indicates that the Mott excitation spectrum is dominated not only by the Coulomb repulsion energy but also by magnetic interactions, and their different energy scales lead to the different time scales in the photoinduced dynamics.
•The resonant magneto-optical Kerr effect was investigated at the soft X-ray region for a magnetic nanofilm of transition metal.•The s- and p-polarized incident lights were generated from a novel ...segmented cross-undulator.•The large Kerr rotation angles at Fe L absorption edges show the sign inversion, which was consistent to the theoretical model.
The resonant magneto-optical Kerr effect of an Fe nanofilm at the L-edge was investigated by theoretically and experimentally using the polarization controlled undulator. Large values of the Kerr rotation angle (θK) were measured at the L2 and L3 absorption edges for both of s- and p-polarized incident lights. Furthermore, the sign changes of θK depending on the photon energy and the polarization of incident light were also observed.
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