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790 results on '"Kasama, T"'

154. Transverse domain walls in nanoconstrictions

Author

Backes, D., primary, Schieback, C., additional, Kläui, M., additional, Junginger, F., additional, Ehrke, H., additional, Nielaba, P., additional, Rüdiger, U., additional, Heyderman, L. J., additional, Chen, C. S., additional, Kasama, T., additional, Dunin-Borkowski, R. E., additional, Vaz, C. A. F., additional, and Bland, J. A. C., additional

Published
2007
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159. Quantitative determination of domain wall coupling energetics

Author

Laufenberg, M., primary, Bedau, D., additional, Ehrke, H., additional, Kläui, M., additional, Rüdiger, U., additional, Backes, D., additional, Heyderman, L. J., additional, Nolting, F., additional, Vaz, C. A. F., additional, Bland, J. A. C., additional, Kasama, T., additional, Dunin-Borkowski, R. E., additional, Cherifi, S., additional, Locatelli, A., additional, and Heun, S., additional

Published
2006
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164. Direct observation of domain-wall pinning at nanoscale constrictions

Author

Kläui, M., primary, Ehrke, H., additional, Rüdiger, U., additional, Kasama, T., additional, Dunin-Borkowski, R. E., additional, Backes, D., additional, Heyderman, L. J., additional, Vaz, C. A. F., additional, Bland, J. A. C., additional, Faini, G., additional, Cambril, E., additional, and Wernsdorfer, W., additional

Published
2005
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167. Aberration correction: Some Advantages and Alternatives

Author

Dunin-Borkowski, R. E., primary, Kasama, T., additional, Cervera, L., additional, Twitchett, A. C., additional, Midgley, P. A., additional, Robins, A. C., additional, Smith, D. W., additional, Gronsky, J. J., additional, Thomas, C. M., additional, Fischione, P. E., additional, Hetherington, C. J. D., additional, and Kirkland, A. I., additional

Published
2004
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168. Domain Wall Spin Structures in 3d Metal Ferromagnetic Nanostructures.

Author

Haug, Rolf, Laufenberg, M., Kläui, M., Backes, D., Bührer, W., Ehrke, H., Bedau, D., Rüdiger, U., Nolting, F., Heyderman, L. J., Cherifi, S., Locatelli, A., Belkhou, R., Heun, S., Vaz, C. A. F., Bland, J. A. C., Kasama, T., Dunin-Borkowski, R. E., Pavlovska, A., and Bauer, E.

Abstract

In this article, a comprehensive study of head-to-head domain wall spin structures in Ni80Fe20 and Co nanostructures is presented. Quantitative domain wall type phase diagrams for NiFe and Co are obtained and compared with available theoretical predictions and micromagnetic simulations. Differences to the experiment are explained taking into account thermal excitations. Thermally induced domain wall type transformations are observed from which a vortex core nucleation barrier height is obtained. The stray field of a domain wall is mapped directly with sub-10nm resolution using off-axis electron holography, and the field intensity is found to decrease as 1/r with distance. The magnetic dipolar coupling of domain walls in NiFe and Co elements is studied using X-ray magnetic circular dicroism photoemission electron microscopy. We observe that the spin structures of interacting domain walls change from vortex to transverse walls, when the distance between the walls is reduced. Using the measured stray field values, the energy barrier height distribution for the nucleation of a vortex core is obtained. [ABSTRACT FROM AUTHOR]

Published
2007
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171. Electron holography of doped semiconductors: when does it work and is it quantitative?

Author

Cullis, A. G., Hutchison, J. L., Dunin-Borkowski, R. E., Twitchett, A. C., Midgley, P. A., McCartney, M. R., Kasama, T., Cooper, D., and Somodi, P. K.

Abstract

The application of off-axis electron holography to the measurement and interpretation of variations in electrostatic potential in doped semiconductors is described and reviewed. Both experimental measurements and computer simulations of electrostatic potentials in thin specimens are presented, and the degree to which parameters such as the built-in voltage and the depletion width across a p-n junction can be measured reliably is discussed. [ABSTRACT FROM AUTHOR]

Published
2005
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188. Effect of post-growth annealing on secondary phase formation in low-temperature-grown Mn-doped GaAs.

Author

Kovkcs, A., Sadowski, J., Kasama, T., Duchamp, M., and Dunin-Borkowski, R. E.

Subjects
GALLIUM arsenide, TRANSMISSION electron microscopes, MOLECULAR beam epitaxy, X-ray spectroscopy, SCANNING transmission electron microscopy, CRYSTALLOGRAPHY
Abstract

The microstructures of annealed GaAs layers containing 0.1%, 0.5% and 2% Mn are studied using aberration-corrected transmission electron microscopy (TEM). The layers were grown by molecular beam epitaxy at 270 ?C. After heat treatment at 400, 560 and 630 ?C, they are found to contain precipitate complexes of cubic or hexagonal (Mn, Ga) As, orthorhombic or rhombohedral As and voids. Information about the crystallographic structures and compositions of the phases is obtained using high-resolution TEM, scanning TEM and energy-dispersive x-ray spectroscopy. A phase diagram for secondary phase formation in annealed GaMnAs layers doped with low Mn concentrations is proposed. [ABSTRACT FROM AUTHOR]

Published
2013
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196. Dose-specific biphasic effects of simvastatin on the expression of CXCL10 and CX3CL1 by human osteoblasts.

Author

Kasama T, Isozaki T, Sato M, Takahashi R, Wakabayashi K, and Tezuka M

Abstract

Objective: To better understand the effects of simvastatin (SS) on the expression and secretion of two chemokines, CXCL10 and CX3CL1, by osteoblasts, and to test whether inhibition of isoprenoid intermediates of cholesterol biosynthesis were involved in the effects of SS. Methods: Human osteoblasts were incubated in the presence or absence of the inflammatory cytokines tumor necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ), with and without SS (0.1-100 μM). Culture supernatants were then collected, and expression of CXCL10 and CX3CL1 mRNA in osteoblasts was examined using quantitative TaqMan real-time polymerase chain reaction. The levels of CXCL10 and CX3CL1 were measured using enzyme-linked immunosorbent assays. Results: At a high concentration (100 μM), SS inhibited expression and secretion of the chemokines and showed cytotoxity, whereas at lower concentrations (0.1-1 μM) SS stimulated the expression and secretion of the chemokines. Expression and secretion of CXCL10 or CX3CL1 from osteoblasts were induced by stimulation with TNF-α and IFN-γ. In addition, SS exerted a biphasic effect on the evoked induction of CXCL10 and CX3CL1. Chemokine expression and secretion was also assayed in the presence of mevalonate (MEV), geranylgeranyl pyrophosphate (GGPP) or farnesyl pyrophosphate (FPP). MEV abolished both the inhibitory effect of high-dose SS and the stimulatory effect of low-dose SS. On the other hand, GGPP abolished only the inhibitory effects of high-dose SS, and FPP had no effect at all. Conclusions: These findings suggest that osteoblasts are an important cellular source of CXCL10 and CX3CL1, and that statins such as SS may modulate the inflammatory process in bone tissues to inhibit bone resorption and stimulate bone formation through biphasic modulation chemokine synthesis. [ABSTRACT FROM AUTHOR]

Published
2009

199. Three-dimensional tomographic imaging and characterization of iron compounds within Alzheimer's plaque core material.

Author

Collingwood JF, Chong RK, Kasama T, Cervera-Gontard L, Dunin-Borkowski RE, Perry G, Pósfai M, Siedlak SL, Simpson ET, Smith MA, Dobson J, Collingwood, Joanna F, Chong, Ryan K K, Kasama, Takeshi, Cervera-Gontard, Lionel, Dunin-Borkowski, Rafal E, Perry, George, Pósfai, Mihály, Siedlak, Sandra L, and Simpson, Edward T

Abstract

Although it has been known for over 50 years that abnormal concentrations of iron are associated with virtually all neurodegenerative diseases, including Alzheimer's disease, its origin, nature and role have remained a mystery. Here, we use high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray (EDX) spectroscopy and electron energy-loss spectroscopy (EELS), electron tomography, and electron diffraction to image and characterize iron-rich plaque core material - a hallmark of Alzheimer's disease pathology - in three dimensions. In these cores, we unequivocally identify biogenic magnetite and/or maghemite as the dominant iron compound. Our results provide an indication that abnormal iron biomineralization processes are likely occurring within the plaque or the surrounding diseased tissue and may play a role in aberrant peptide aggregation. The size distribution of the magnetite cores implies formation from a ferritin precursor, implicating a malfunction of the primary iron storage protein in the brain. [ABSTRACT FROM AUTHOR]

Published
2008
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200. Increased serum levels of soluble fractalkine (CX3CL1) correlate with disease activity in rheumatoid vasculitis.

Author

Matsunawa M, Isozaki T, Odai T, Yajima N, Takeuchi HT, Negishi M, Ide H, Adachi M, and Kasama T

Abstract

OBJECTIVE: To determine levels of soluble fractalkine (sFkn) in rheumatoid arthritis (RA) patients with and without rheumatoid vasculitis (RV), and to assess the relationship of sFkn levels to disease activity. METHODS: Serum was obtained from 98 RA patients (54 without vasculitis, 36 with extraarticular manifestations but without histologically proven vasculitis, and 8 with histologically proven vasculitis) and from 38 healthy individuals. Levels of sFkn were measured by enzyme-linked immunosorbent assay. Expression of Fkn and CX(3)CR1 was quantified by real-time polymerase chain reaction. Vasculitis disease activity was assessed using the Birmingham Vasculitis Activity Score and the Vasculitis Activity Index. RESULTS: Serum sFkn levels were significantly higher in patients with RA than in controls and were significantly higher in RA patients with RV than in those without vasculitic complications. Statistically significant correlations were observed between serum sFkn levels in RA patients and levels of C-reactive protein, rheumatoid factor, immune complex, and complement. In the RV group, sFkn levels also correlated with disease activity. Immunohistochemical analysis indicated that Fkn levels were associated mainly with endothelial cells in vasculitic arteries. In addition, expression of CX(3)CR1 messenger RNA was significantly greater in peripheral blood mononuclear cells from patients with active RV than in those from other RA patients or controls. Notably, serum sFkn levels were significantly diminished following successful treatment and clinical improvement. CONCLUSION: These findings suggest that Fkn and CX(3)CR1 play crucial roles in the pathogenesis of RV and that sFkn may serve as a serologic inflammatory marker of disease activity in RA patients with vasculitis. [ABSTRACT FROM AUTHOR]

Published
2006
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