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1,416 results on '"Takiguchi, M."'

4. Photon correlation measurements of stochastic limit cycles emerging from high-$Q$ nonlinear silicon photonic crystal microcavities

Author

Takemura, N., Takiguchi, M., Sumikura, H., Kuramochi, E., Shinya, A., and Notomi, M.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Nonlinear Sciences - Adaptation and Self-Organizing Systems, Physics - Optics
Abstract

We performed measurements of photon correlation [$g^{(2)}(\tau)$] in driven nonlinear high-$Q$ silicon (Si) photonic crystal (PhC) microcavities. The measured $g^{(2)}(\tau)$ exhibits a damped oscillatory behavior when input pump power exceeds a critical value. From comparison between experiments and simulations, we attribute the measured oscillation of $g^{(2)}(\tau)$ to self-pulsing (a limit cycle) emerging from an interplay between photon, carrier, and thermal dynamics. Namely, the oscillation frequency of $g^{(2)}(\tau)$ corresponds to the oscillation period of the limit cycle, while its finite coherence (damping) time originates from the stochastic nature of the limit cycle. From the standpoint of phase reduction theory, we interpret the measured coherence time of $g^{(2)}(\tau)$ as the coherence (diffusion) time of a generalized phase of the limit cycle. Furthermore, we show that an increase in laser input power enhances the coherence time of $g^{(2)}(\tau)$ up to the order of microseconds, which could be a demonstration of the stabilization of a stochastic limit cycle through pumping.

Published
2020
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8. Spontaneous emission inhibition of telecom-band quantum disks inside single nanowire on different substrates

Author

Birowosuto, M. D., Zhang, G., Yokoo, A., Takiguchi, M., and Notomi, M.

Subjects
Physics - Optics, Condensed Matter - Materials Science, Quantum Physics
Abstract

We investigate the inhibited spontaneous emission of telecom-band InAs quantum disks (Qdisks) in InP nanowires (NWs). We have evaluated how the inhibition is affected by different disk diameter and thickness. We also compared the inhibition in standing InP NWs and those NWs laying on silica (SiO2), and silicon (Si) substrates. We found that the inhibition is altered when we put the NW on the high-refractive index materials of Si. Experimentally, the inhibition factor $\zeta$ of the Qdisk emission at 1,500 nm decreases from 4.6 to 2.5 for NW on SiO2 and Si substrates, respectively. Those inhibitions are even much smaller than that of 6.4 of the standing NW. The inhibition factors well agree with those calculated from the coupling of the Qdisk to the fundamental guided mode and the continuum of radiative modes. Our observation can be useful for the integration of the NW as light sources in the photonic nanodevices., Comment: 19 pages, 6 figures (Appendix is not included)

Published
2014
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9. Movable high Q nanoresonators realized by semiconductor nanowires on a Si photonic crystal platform

Author

Birowosuto, M. D., Yokoo, A., Zhang, G., Tateno, K., Kuramochi, E., Taniyama, H., Takiguchi, M., and Notomi, M.

Subjects
Physics - Optics, Quantum Physics
Abstract

Subwavelength semiconductor nanowires have recently attracted interest for photonic applications because they possess various unique optical properties and offer great potential for miniaturizing devices. However, realizing tight light confinement or efficient coupling with photonic circuits is not straightforward and remains a challenge. Here we show that a high Q nanocavity can be created by placing a single III/V semiconductor nanowire with a diameter of under 100 nm in a grooved waveguide in a Si photonic crystal, by means of nanoprobe manipulation. We observe very fast spontaneous emission (91 ps) from nanowires accelerated by the strong Purcell enhancement in nanocavities, which proves that very strong light confinement can be achieved. Furthermore, this system enables us to move the nanocavity anywhere along the waveguide. This configuration provides a significant degree of flexibility in integrated photonics and permits the addition and displacement of various functionalities of III/V nanocavity devices in Si photonic circuits., Comment: 19 pages, 4 figures, first version to Nature Materials 2014

Published
2014
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13. Design for ultrahigh-Q position-controlled nanocavities of single semiconductor nanowires in 2D photonic crystals

Author

Birowosuto, M. D., Yokoo, A., Taniyama, H., Kuramochi, E., Takiguchi, M., and Notomi, M.

Subjects
Physics - Optics
Abstract

Using Finite-Difference Time-Domain (FDTD) simulation, we show that ultrahigh- Q nanocavities can be obtained through the manipulation of a single semiconductor nanowire (NW) inside a slot in a line defect of a two-dimensional (2D) photonic crystal. By controlling the design and its lattice parameters of the photonic crystal, we have achieved a quality factor Q larger than 106 and a mode volume Vc smaller than 0.11 {\mu}m3 (1.25 of a cubic wavelength in the NW) for a cavity peak in the telecommunication band. This design is useful for realizing a position-controlled cavity in a photonic crystal. Here we also discuss the small dependence of the Qfactor, the Vc, and the cavity peak in relation to the position of the NWinside the slot and the potential application to the cavity quantum electrodynamics (QED) using the embedded-emitter NW., Comment: 22 pages, 8 figures, to appear, Journal of Applied Physics 112 (2012)

Published
2012
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17. Adrenocortical hypoperfusion detected by contrast‐enhanced ultrasound in a dog with trilostane‐induced hypoadrenocorticism.

Author

Nagata, N., Aoshima, K., Nakamura, K., and Takiguchi, M.

Subjects
CONTRAST-enhanced ultrasound, CHIHUAHUA (Dog breed), ADRENOCORTICOTROPIC hormone, AUTOPSY, ADRENAL glands, ADRENAL tumors, ADRENAL insufficiency
Abstract

A 12‐year‐old neutered male Chihuahua dog was diagnosed with pituitary‐dependent hypercortisolism and treated with trilostane. Eighty‐nine days later, the dog showed lethargy accompanied by hyponatraemia and hyperkalaemia. Hypoadrenocorticism due to trilostane was suspected, but the result of the adrenocorticotropic hormone stimulation test was not conclusive. Contrast‐enhanced ultrasound showed loss of adrenocortical blood flow in both adrenal glands, indicating adrenocortical hypoperfusion and isolated hypoadrenocorticism. Treatment with fludrocortisone acetate improved the condition and electrolyte abnormalities. Thirteen months later, the dog showed alopecia, and an adrenocorticotropic hormone stimulation test revealed increased cortisol concentration, indicating hypercortisolism recurrence. The dog died due to progressive deterioration 22 months after the initial presentation. Post‐mortem examination revealed focally extensive necrosis with marked calcification in the parenchyma of the adrenal glands and regeneration of the cells in the zona fasciculata with severe fibrosis. Adrenocortical hypoperfusion detected by contrast‐enhanced ultrasound can support the diagnosis of adrenal necrosis and hypoadrenocorticism. [ABSTRACT FROM AUTHOR]

Published
2023
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19. Impact of micropolymorphism outside the 1 peptide binding groove in the clinically-relevant allele HLA-C*14 on T cell responses in HIV-1 infection

Author

Chikata, T, Paes, W, Kuse, N, Partridge, T, Ternette, N, Borrow, P, and Takiguchi, M

Abstract

There is increasing evidence for the importance of HLA-C-restricted CD8+ 28 T-cells in HIV-1 control, but these responses are relatively poorly investigated. Numbers of HLA-C-restricted HIV-1 epitopes identified are much smaller than those of HLA-A-restricted or HLA-B-restricted ones. Here, we utilized a mass spectrometry-based approach to identify HIV-1 peptides presented by HLA-C*14:03 protective and HLA-C*14:02 non-protective alleles. We identified twenty-five 8-11mer HLA-I-bound HIV-1 peptides from HIV-1-infected HLA-C*14:02+ /14:03+ 34 cells. Analysis of T-cell responses to these peptides identified novel 6 T-cell epitopes targeted in HIV-1-infected HLA-C*14:02+ /14:03+ subjects. Analyses using HLA-stabilization assays demonstrated that all 6 epitope peptides exhibited higher binding to and greater cell-surface stabilization of HLA-C*14:02 than HLA-C*14:03. T-cell response magnitudes were typically higher in HLA-C*14:02+ than HLA-C*14:03+ individuals,with responses to the Pol KM9 and Nef epitopes being significantly higher. The results show that HLA-C*14:02 can elicit stronger T cell responses to HIV-1 than HLA-C*14:03 and suggest that the single amino acid difference between these HLA-C14 subtypes at position 21, outside the peptide-binding groove, indirectly influences the stability of peptide-HLA-C*14 complexes and induction/expansion of HIV-specific T-cells. Taken together with a previous finding that KIR2DL2+ NK cells recognized HLA-C*14:03+ HIV-1-infected cells more than HLA-C*14:02+ one, the present study indicates that these HLA-C*14 subtypes differentially impact on HIV-1 control by T-cells and NK cells.

Published
2022

21. Twig cutting by the black rat, Rattus rattus (rodentia: muridae), on the Ogasawara (Bonin) Islands

Author

Yabe, T., Hashimoto, T., Takiguchi, M., Aoki, M., and Fujita, M.

Subjects
Rattus rattus -- Food and nutrition -- Research, Food habits -- Research
Abstract

Introduced black rats (Rattus rattus) have been reported to damage endemic plants of the Ogasawara Islands by gnawing. This study used seasonal field observations of plants together with analysis of rat stomach contents and age structure to help understand the cause or mechanism of black rat twig-cutting activities. Twigs of Ochrosia nakaiana and Hibiscus glaber were found to be cut by black rats on the islands of Nishijima, Anijima, and Mukojima in March and April 2006 and 2007. Fragments of twig tissues in rat feces proved that the rats ate twigs, rather than only gnawing or cutting them. Age compositions of trapped black rats showed that the season of plant damage corresponded with that of low breeding activities of the rats and scarcity of preferred foods (January-March). We assume a link between low breeding activities of the black rats and food shortage, which motivated the rats to consume twig tissues. doi: 10.2984/64.1.093, The black rat, Rattus rattus, is one of several invasive rodents including the Norway rat, R. norvegicus, and the house mouse, Mus musculus, on the Ogasawara (Bonin) Islands (Kawakami 2002), [...]

Published
2010
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31. Analysis of oil film thickness on a piston ring of diesel engine: effect of oil film temperature

Author

Harigaya, Y., Suzuki, M., and Takiguchi, M.

Subjects
Lubricating oils -- Testing, Diesel motor -- Equipment and supplies, Diesel motor -- Testing, Viscosity -- Testing, Engineering and manufacturing industries, Science and technology
Abstract

This paper describes an analysis of oil film thickness on a piston ring of a diesel engine. The analysis of the oil film thickness has been performed by using Reynolds equation and unsteady, two-dimensional energy equation with heat generated from viscous dissipation. The mean oil film temperature was determined from the calculation of the temperature distribution in the oil field which was calculated using the energy equation. The oil film viscosity was then estimated using the mean oil film temperature. The effect of oil film temperature on the oil film thickness of a piston ring was examined. This model has been verified with published experimental results. Moreover, the heat flow at ring and liner surfaces was examined. Results show that the oil film thickness could be calculated using the viscosity estimated from the mean oil film temperature. The calculated values generally agree with the measured values. For higher engine speed conditions, the maximum values of the calculated oil film thickness are larger than the measured values. [DOI: 10.1115/1.1501078]

Published
2003

37. Transport performance of Bi-2212 current leads prepared by a diffusion process

Author

Yamada, Y., Takiguchi, M., Suzuki, O., Tachikawa, K., Iwamoto, A., Tamura, H., and Mito, T.

Subjects
Superconductors -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Bi-2212 current leads were prepared by a diffusion process and their transport performance was monitored.

Published
2001

40. Bi-2212 current leads prepared by the diffusion process

Author

Yamada, Y., Takiguchi, M., Tachikawa, K., Iwamoto, A., and Mito, T.

Subjects
Superconductivity -- Research, Business, Electronics, Electronics and electrical industries
Abstract

The diffusion process was used to prepare Bi-2212 current leads which were synthesized via diffusion reaction betweenSR-Ca-Cu oxide substrates and Bi-Cu oxide coating with the addition of AG.

Published
2000

47. Identification of immunodominant HIV-1 epitopes presented by 2 HLA-C*12:02, a protective allele, using an immunopeptidomics 3 approach

Author

Chikata, T, Paes, W, Akahoshi, T, Partridge, T, Murakoshi, H, Gatanaga, H, Ternette, N, Oka, S, Borrow, P, and Takiguchi, M

Abstract

Despite the fact that cell-surface expression of HLA-C on both uninfected and HIV-infected cells is lower than that of HLA-A and -B, increasing evidence suggests an important role for HLA-C and HLA-C-restricted CD8+ T cell responses in determining the efficiency of viral control in HIV-1-infected individuals. Nonetheless, HLA-C-restricted T cell responses are much less well-studied than HLA-A/B-restricted ones, and relatively few optimal HIV-1 CD8+ T cell epitopes restricted by HLA-C alleles have been defined. Recent improvements in the sensitivity of mass spectrometry (MS)-based approaches for profiling the immunopeptidome present an opportunity for epitope discovery on a large scale. Here, we employed a mass spectrometry (MS)-based immunopeptidomic strategy to characterize HIV-1 peptides presented by a protective allele, HLA-C*12:02. We identified a total of 10,799 unique 8-12-mer peptides, including 15 HIV-1 peptides. The latter included 2 previously-reported immunodominant HIV-1 epitopes; and analysis of T cell responses to the other HIV-1 peptides detected revealed an additional immunodominant epitope. These findings illustrate the utility of MS-based approaches for epitope definition, and emphasize the capacity of HLA-C to present immunodominant T cell epitopes in HIV-infected individuals, indicating the importance of further evaluation of HLA-C-restricted responses to identify novel targets for HIV-1 prophylactic and therapeutic strategies. IMPORTANCE Mass spectrometry (MS)-based approaches are increasingly being employed for large-scale identification of HLA-bound peptides derived from pathogens, but only very limited profiling of the HIV-1 immunopeptidome has been conducted to date. Notably, a growing body of evidence has recently begun to indicate a protective role for HLA-C in HIV-1 infection, which may suggest that despite the fact that levels of HLA-C expression on both uninfected and HIV-1-infected cells are lower than those of HLA-A/B, HLA-C still presents epitopes to CD8+ T cells effectively. To explore this, we analyzed HLA-C*12:02-restricted HIV-1 peptides presented on HIV-1-infected cells expressing only HLA-C*12:02 (a protective allele) using LC-MS/MS. We identified a number of novel HLA-C*12:02-bound HIV-1 peptides, and showed that although the majority of them did not elicit T cell responses during natural infection in a Japanese cohort, they included three immunodominant epitopes, emphasizing the contribution of HLA-C to epitope presentation on HIV-infected cells.

Published
2019

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