Analysis of Wide-gap Semiconductors with Superconducting XAFS Apparatus

Shiki, S.,Zen, N.,Matsubayashi, N.,Koike, M.,Ukibe, M.,Kitajima, Y.,Nagamachi, S.,Ohkubo, M. The Korean Superconductivity Society 2012 Progress in superconductivity Vol.14 No.2

Fluorescent yield X-ray absorption fine structure (XAFS) spectroscopy is useful for analyzing local structure of specific elements in matrices. We developed an XAFS apparatus with a 100-pixel superconducting tunnel junction (STJ) detector array with a high sensitivity and a high resolution for light-element dopants in wide-gap semiconductors. An STJ detector has a pixel size of $100{\mu}m$ square, and an asymmetric layer structure of Nb(300 nm)-Al(70 nm)/AlOx/Al(70 nm)-Nb(50 nm). The 100-pixel STJ array has an effective area of $1mm^2$. The XAFS apparatus with the STJ array detector was installed in BL-11A of High Energy Accelerator Research Organization, Photon Factory (KEK PF). Fluorescent X-ray spectrum for boron nitride showed that the average energy resolution of the 100-pixels is 12 eV in full width half maximum for the N-K line, and The C-K and N-K lines are separated without peak tail overlap. We analyzed the N dopant atoms implanted into 4H-SiC substrates at a dose of 300 ppm in a 200 nm-thick surface layer. From a comparison between measured X-ray Absorption Near Edge Structure (XANES) spectra and ab initio FEFF calculations, it has been revealed that the N atoms substitute for the C site of the SiC lattice.

Investigation of the Hyperne Coupling Constant of Locally Noncentrosymmetric Heavy-fermion Superconductor CeRh₂As₂

Shiki Ogata,Shunsaku Kitagawa,Mayu Kibune,Kenji Ishida,Katsuki Kinjo,Manuel Brando,Christoph Geibel,Seunghyun Khim,Elena Hassinger 한국물리학회 2023 새물리 Vol.73 No.12

We performed <SUP>75</SUP>As-NMR measurements in H k ab to investigate the normal-state magnetic properties of CeRh₂As₂, a recently-discovered heavy-fermion superconductor. We compared the NMR Knight shift K with the magnetic susceptibility χ<SUP>ab</SUP>, and estimated the hyperfine coupling constant Ahf from the slope of the K - χ plot. We observed that the magnitude of A<SUB>hf;ab</SUB> at the As(1) site changes at around 20 K owing to emerging the heavy-fermion state, which was also observed in Ahf at the As(2) site and in H || c. The sign of A<SUB>hf;ab</SUB> at the As(1) site is negative in low temperature. These are important for the analysis of the NMR results of CeRh₂As₂ in the superconducting state.

Analysis of Wide-gap Semiconductors with Superconducting XAFS Apparatus

S. Shiki,N. Zen,M. Koike,M. Ukibe,Y. Kitajima,S. Nagamachi,M. Ohkubo,N. Matsubayashi 한국초전도학회 2012 Progress in superconductivity Vol.14 No.2

Fluorescent yield X-ray absorption fine structure (XAFS) spectroscopy is useful for analyzing local structure of specific elements in matrices. We developed an XAFS apparatus with a 100-pixel superconducting tunnel junction (STJ) detector array with a high sensitivity and a high resolution for light-element dopants in wide-gap semiconductors. An STJ detector has a pixel size of 100 μm square, and an asymmetric layer structure of Nb(300 nm)-Al(70 nm)/AlOx/Al(70 nm)-Nb(50 nm). The 100-pixel STJ array has an effective area of 1 mm2. The XAFS apparatus with the STJ array detector was installed in BL-11A of High Energy Accelerator Research Organization, Photon Factory (KEK PF). Fluorescent X-ray spectrum for boron nitride showed that the average energy resolution of the 100-pixels is 12 eV in full width half maximum for the N-K line, and The C-K and N-K lines are separated without peak tail overlap. We analyzed the N dopant atoms implanted into 4H-SiC substrates at a dose of 300 ppm in a 200 nm-thick surface layer. From a comparison between measured X-ray Absorption Near Edge Structure (XANES) spectra and ab initio FEFF calculations, it has been revealed that the N atoms substitute for the C site of the SiC lattice.

Design of the Artificial Antenna System in Photosynthesis

Tamiaki, Hitoshi,Yagai, Shiki Korean Society of Photoscience 2002 Journal of Photosciences Vol.9 No.2

Zinc chlorin 1 possessing tertiary 3$^1$_hydroxy and 13$^1$-oxo groups was synthesized as a model for the antenna chlorophylls of photosynthetic green bacteria. Self-aggregation of 1 in nonpolar organic solvents was examined and compared to 2 and 3 possessing a secondary and primary 3$^1$_hydroxy group, respectively. Zinc chlorin 1 self-aggregated in I%(v/v) CH$_2$Cl$_2$-hexane to form oligomers and showed a red-shifted Qy maximum at 704 nm compared to the monomer (648 nm in CH$_2$CI2$_2$). This red-shift is larger than that of 3$^1$S-2 (648 to 697 nm) and comparable to that of3$^1$R-2 (648 to 705 nm), but smaller than that of 1 (648 to 740 nm), indicating that while a single 3$^1$-methyl group (primary to secondary OH) suppressed tight and/or extended aggregation, the additional 3$^1$-methyl group (secondary to tertiary OH) did not further suppress aggregation. The relative stability of the aggregates was in the order 3> 3$^1$R-2∼ 1 > 3$^1$S-2 as determined by visible spectral analyses. Molecular modeling calculations on oligomers of zinc chlorins 1, 3$^1$ R-2 and 3 gave similar well-ordered energy-minimized structures, while 3 stacked more tightly than 3$^1$ R- 2 and 1. In contrast, 3$^1$S-2 gave a relatively disordered (twisted) structure. The calculated oligomeric structures could explain the visible spectral data of 1-3 in nonpolar organic solvents. Moreover, self- aggregation of synthetic zinc 13$^1$_oxo-hlorins 4-6 possessing a 2-hydroxyethyl, 3-hydroxypropyl and 3- hydroxy-I-propenyl group at the 3-position in nonpolar organic solvents was discussed.

Superconducting Strip Ion Detectors for Time-of-flight Mass Spectrometer

Zen, N.,Suzuki, K.,Shiki, S.,Ukibe, M.,Koike, M.,Casaburi, A.,Ejrnaes, M.,Cristiano, R.,Ohkubo, M. The Korean Superconductivity Society 2012 Progress in superconductivity Vol.14 No.2

Superconducting detectors are promising as ion detectors for time-of-flight mass spectrometers (TOF MS). They can achieve mass-independent detection efficiency even for macromolecular bombardments, because output signals are produced through the deposited kinetic energy at ion impact instead of secondary electron emission that is the ion detection mechanism of conventional microchannel plate (MCP) detectors or secondary electron multipliers (SEM). Among the superconducting detectors, the superconducting strip ion detectors (SSIDs), which consist of several hundreds of superconducting lines with a width of a few hundreds nm and a thickness of a few tens of nm, have a fast response time of less than 1 ns. Inherently, the response time of SSIDs is determined by kinetic inductance, so that it was difficult to realize a fast SSID with a large detection area. However, we succeeded in realizing the detector size up to $5{\times}5mm^2$ without response time degradation by using a parallel configuration.

Superconducting Strip Ion Detectors for Time-of-flight Mass Spectrometer

N. Zen,K. Suzuki,S. Shiki,M. Ukibe,M. Koike,A. Casaburi,M. Ejrnaes,R. Cristiano,M. Ohkubo 한국초전도학회 2012 Progress in superconductivity Vol.14 No.2

Superconducting detectors are promising as ion detectors for time-of-flight mass spectrometers (TOF MS). They can achieve mass-independent detection efficiency even for macromolecular bombardments, because output signals are produced through the deposited kinetic energy at ion impact instead of secondary electron emission that is the ion detection mechanism of conventional microchannel plate (MCP) detectors or secondary electron multipliers (SEM). Among the superconducting detectors, the superconducting strip ion detectors (SSIDs), which consist of several hundreds of superconducting lines with a width of a few hundreds nm and a thickness of a few tens of nm, have a fast response time of less than 1 ns. Inherently, the response time of SSIDs is determined by kinetic inductance, so that it was difficult to realize a fast SSID with a large detection area. However, we succeeded in realizing the detector size up to 5×5 mm2 without response time degradation by using a parallel configuration.

Superconducting Tunnel Junction Detectors for Mass Spectrometry

M. Ohkubo,N. Zen,T. Kitazume,S. Shiki,M. Ukibe,M. Koike 한국초전도학회 2012 Progress in superconductivity Vol.14 No.2

With conventional mass spectrometry (MS), ions are separated according to mass/charge (m/z) ratios. We must speculate the z values to obtain the m values. Superconducting tunnel junction (STJ) detectors can solve this problem, and true mass spectrometry becomes possible instead of m/z spectrometry. The STJ detectors were installed in MS instruments with a variety of ion sources. As an example, we report fragmentation analysis of a non-covalent protein complex of hemoglobin.

Superconducting Tunnel Junction Detectors for Mass Spectrometry

Ohkubo, M.,Zen, N.,Kitazume, T.,Ukibe, M.,Shiki, S.,Koike, M. The Korean Superconductivity Society 2012 Progress in superconductivity Vol.14 No.2

With conventional mass spectrometry (MS), ions are separated according to mass/charge (m/z) ratios. We must speculate the z values to obtain the m values. Superconducting tunnel junction (STJ) detectors can solve this problem, and true mass spectrometry becomes possible instead of m/z spectrometry. The STJ detectors were installed in MS instruments with a variety of ion sources. As an example, we report fragmentation analysis of a non-covalent protein complex of hemoglobin.

Late-onset Systemic Lupus Erythematosus with Protein-losing Enteropathy, Vitiligo, and Diffuse Alveolar Hemorrhage

Masashi Ohe,Risshi Kudoh,Masahide Seki,Motohiro Endo,Mirei Shiki 이화여자대학교 의과학연구소 2015 EMJ (Ewha medical journal) Vol.38 No.3

A 60-year-old man who had been diagnosed with protein-losing enteropathy (PLE) and vitiligo at age 51 years was admitted with dyspnea, hemoptysis, and lower-limb edema. On the basis of computed tomography findings, the cause of respiratory symptoms was thought to be diffuse alveolar hemorrhage (DAH). The final diagnosis of lateonset systemic lupus erythematosus (SLE) was established on the basis of renal biopsy examinations that revealed evidence of active SLE with lupus nephritis (World Health Organization, class V) and positive results for antinuclear antibody. DAH, as well as PLE and vitiligo were attributed to SLE. The patient was successfully treated with methylprednisolone and then prednisolone in combination with cyclosporin A. Because lateonset SLE is rare and patients tend to show atypical symptoms, close attention should be paid to the preceding symptoms.

Histopathological subtyping of high- grade serous ovarian cancer using whole slide imaging

Chiho Miyagawa,Hidekatsu Nakai,Tomoyuki Otani,Ryusuke Murakami,Shiki Takamura,Hisamitsu Takaya,Kosuke Murakami,Masaki Mandai,Noriomi Matsumura 대한부인종양학회 2023 Journal of Gynecologic Oncology Vol.34 No.4

Objective: We have established 4 histopathologic subtyping of high-grade serous ovarian cancer (HGSOC) and reported that the mesenchymal transition (MT) type has a worse prognosis than the other subtypes. In this study, we modified the histopathologic subtyping algorithm to achieve high interobserver agreement in whole slide imaging (WSI) and to characterize the tumor biology of MT type for treatment individualization. Methods: Four observers performed histopathological subtyping using WSI of HGSOC in The Cancer Genome Atlas data. As a validation set, cases from Kindai and Kyoto Universities were independently evaluated by the 4 observers to determine concordance rates. In addition, genes highly expressed in MT type were examined by gene ontology term analysis. Immunohistochemistry was also performed to validate the pathway analysis. Results: After algorithm modification, the kappa coefficient, which indicates interobserver agreement, was greater than 0.5 (moderate agreement) for the 4 classifications and greater than 0.7 (substantial agreement) for the 2 classifications (MT vs. non-MT). Gene expression analysis showed that gene ontology terms related to angiogenesis and immune response were enriched in the genes highly expressed in the MT type. CD31 positive microvessel density was higher in the MT type compared to the non-MT type, and tumor groups with high infiltration of CD8/CD103 positive immune cells were observed in the MT type. Conclusion: We developed an algorithm for reproducible histopathologic subtyping classification of HGSOC using WSI. The results of this study may be useful for treatment individualization of HGSOC, including angiogenesis inhibitors and immunotherapy.