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Akiyama R, Sumida K, Ichinokura S, Nakanishi R, Kimura A, Kokh KA, Tereshchenko OE, Hasegawa S. Shubnikov-de Haas oscillations in p and n-type topological insulator (Bi x Sb 1-x ) 2Te 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:265001. [PMID: 29770777 DOI: 10.1088/1361-648x/aac59b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We show Shubnikov-de Haas (SdH) oscillations in topological insulator (Bi x Sb1-x )2Te3 flakes whose carrier types are p-type (x = 0.29, 0.34) and n-type (x = 0.42). The physical properties such as the Berry phase, carrier mobility, and scattering time significantly changed by tuning the Fermi-level position with the concentration x. The analyses of SdH oscillations by Landau-level fan diagram, Lifshitz-Kosevich theory, and Dingle-plot in the p-type samples with x = 0.29 and 0.34 showed the Berry phase of zero and a relatively low mobility (2000-6000 cm2 V-1 s-1). This is due to the dominant bulk component in transport. On the other hand, the mobility in the n-type sample with x = 0.42 reached a very large value ~17 000 cm2 V-1 s-1 and the Berry phase of near π, whereas the SdH oscillations were neither purely two- nor three-dimensional. These suggest that the transport channel has a surface-bulk coupling state which makes the carrier scattering lesser and enhances the mobility and has a character between two- and three-dimension.
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Murata K, Akiyama R, Noro I, Nishio A, Nakagawa S, Yoshioka Y, Deguchi T, Matsuda H, Ishida Y. Search for effective plant materials for Alzheimer's disease. Am J Transl Res 2017. [DOI: 10.1055/s-0037-1608412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Hirahara T, Eremeev SV, Shirasawa T, Okuyama Y, Kubo T, Nakanishi R, Akiyama R, Takayama A, Hajiri T, Ideta SI, Matsunami M, Sumida K, Miyamoto K, Takagi Y, Tanaka K, Okuda T, Yokoyama T, Kimura SI, Hasegawa S, Chulkov EV. Large-Gap Magnetic Topological Heterostructure Formed by Subsurface Incorporation of a Ferromagnetic Layer. NANO LETTERS 2017; 17:3493-3500. [PMID: 28545300 DOI: 10.1021/acs.nanolett.7b00560] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Inducing magnetism into topological insulators is intriguing for utilizing exotic phenomena such as the quantum anomalous Hall effect (QAHE) for technological applications. While most studies have focused on doping magnetic impurities to open a gap at the surface-state Dirac point, many undesirable effects have been reported to appear in some cases that makes it difficult to determine whether the gap opening is due to the time-reversal symmetry breaking or not. Furthermore, the realization of the QAHE has been limited to low temperatures. Here we have succeeded in generating a massive Dirac cone in a MnBi2Se4/Bi2Se3 heterostructure, which was fabricated by self-assembling a MnBi2Se4 layer on top of the Bi2Se3 surface as a result of the codeposition of Mn and Se. Our experimental results, supported by relativistic ab initio calculations, demonstrate that the fabricated MnBi2Se4/Bi2Se3 heterostructure shows ferromagnetism up to room temperature and a clear Dirac cone gap opening of ∼100 meV without any other significant changes in the rest of the band structure. It can be considered as a result of the direct interaction of the surface Dirac cone and the magnetic layer rather than a magnetic proximity effect. This spontaneously formed self-assembled heterostructure with a massive Dirac spectrum, characterized by a nontrivial Chern number C = -1, has a potential to realize the QAHE at significantly higher temperatures than reported up to now and can serve as a platform for developing future "topotronics" devices.
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Imura Y, Koizumi S, Akiyama R, Morita-Imura C, Kawai T. Highly Stable Silica-Coated Gold Nanoflowers Supported on Alumina. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4313-4318. [PMID: 28402668 DOI: 10.1021/acs.langmuir.7b00974] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Shape-controlled nanocrystals, such as nanowires and nanoflowers, are attractive because of their potential novel optical and catalytic properties. However, the dispersion and morphological stabilities of shape-controlled nanocrystals are easily destroyed by changing the dispersion solvent and temperature. Methods of support and the silica coating are known to improve the dispersion and morphological stabilities of metal nanocrystals. The silica-coating method often causes morphological changes in shape-controlled nanocrystals because the silica coating is formed in mixed solutions of water and organic solvents such as ethanol, and this results in aggregation due to changes in the dispersion solvent. Furthermore, ligand exchange, designed to improve the dispersion stability in the solvent, often causes morphological changes. This article introduces a method for the preparation of highly stable silica-coated Au nanoflowers (AuNFs) supported on Al2O3. The method of support prevents the aggregation and precipitation of AuNFs when the solvent is changed from water to water/ethanol. Through stability improvement, silica coating of AuNFs/Al2O3 was conducted in water/ethanol without ligand exchange that causes morphological changes. Furthermore, silica-coated AuNFs/Al2O3 exhibit high morphological stability under high-temperature conditions compared to uncoated AuNFs/Al2O3. These results are very useful when preparing highly morphologically stable, silica-coated, shape-controlled nanocrystals without ligand exchange.
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Akiyama R, Fujisawa K, Sakurai R, Kuroda S. Weak antilocalization in (111) thin films of a topological crystalline insulator SnTe. ACTA ACUST UNITED AC 2014. [DOI: 10.1088/1742-6596/568/5/052001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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31
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Nakamura Y, Yoshimori A, Akiyama R. Effects of the solvation structure on diffusion of a large particle in a binary mixture studied by perturbation theory. J Mol Liq 2014. [DOI: 10.1016/j.molliq.2014.06.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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32
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Akiyama R, Ågren J. Conflicting selection on the timing of germination in a natural population of Arabidopsis thaliana. J Evol Biol 2013; 27:193-9. [DOI: 10.1111/jeb.12293] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 10/07/2013] [Accepted: 10/29/2013] [Indexed: 01/22/2023]
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Tsuru T, Akiyama R, Kohashi K, Okumura K. [Case of a 13-year-old boy with hyponatremia due to lamotrigine-induced syndrome of inappropriate secretion of antidiuretic hormone]. NO TO HATTATSU = BRAIN AND DEVELOPMENT 2012; 44:73-74. [PMID: 22352036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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34
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Moriya K, Chiba Y, Yoneta H, Akiyama R, Tazawa H. Simultaneous measurements of instantaneous heart rate and breathing activity in newly hatched chicks. Br Poult Sci 2010; 44:761-6. [PMID: 14965099 DOI: 10.1080/00071660310001643732] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
1. Among three types of fluctuations of instantaneous heart rate (IHR) found previously in newly hatched chicks, a high frequency oscillation with a mean frequency of about 0.7 Hz (Type I) appeared to be concurrent with breathing (Moriya et al., Comparative Biochemistry and Physiology, 124A: 461-468, 1999). 2. In order to confirm that Type I HR fluctuation is respiratory sinus arrhythmia (RSA), breathing activity was measured by a condenser microphone, simultaneously with IHR. 3. The microphone detected pressure changes caused by breathing (acoustorespirogram, ARG) and also unexpectedly movement, probably twitch, of hatchlings. 4. Simultaneous measurements of IHR and ARG demonstrated that oscillatory frequency of Type I HR fluctuation coincided with breathing frequency and IHR increased with inspiration, confirming that Type I HR oscillation is RSA. 5. In addition, large transient HR accelerations (Type III HR fluctuation) simultaneously occurred with movement or twitch of the hatchlings, suggesting that Type III HR fluctuation and movement of hatchlings have the same origin, probably sympathetic nerve function.
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Tsudzuki M, Onitsuka S, Akiyama R, Iwamizu M, Goto N, Nishibori M, Takahashi H, Ishikawa A. Identification of quantitative trait loci affecting shank length, body weight and carcass weight from the Japanese cockfighting chicken breed, Oh-Shamo (Japanese Large Game). Cytogenet Genome Res 2007; 117:288-95. [PMID: 17675870 DOI: 10.1159/000103190] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Accepted: 09/11/2006] [Indexed: 11/19/2022] Open
Abstract
We performed a quantitative trait locus (QTL) analysis to map QTLs controlling shank length, body weight, and carcass weight in a resource family of 245 F(2) birds developed from a cross of the large-sized, native, Japanese cockfighting breed, Oh-Shamo (Japanese Large Game), and the White Leghorn breed of chickens. Interval mapping revealed three significant QTLs for shank length on chromosomes 1, 4 and 24 at the experiment-wise 5% level, and a suggestive shank length QTL on chromosome 27 at the experiment-wise 10% level. For body weight two QTLs, one significant and the other suggestive, were identified on chromosomes 4 and 24, respectively. As expected, QTLs for carcass weight, which was highly correlated with body weight (r = 0.95), were detected at the same chromosomal locations as the detected body weight QTLs. Interestingly, the chromosomal locations containing these body weight and carcass weight QTLs coincided with those of two of the four shank length QTLs detected. No QTL with an epistatic interaction effect was discovered for any trait. The total contribution of all detected QTLs to genetic variance was 98.4%, 27.0% and 25.9% for shank length, body weight and carcass weight, respectively, indicating that most shank length QTLs have been identified but many body weight and carcass weight QTLs have been overlooked by the present analysis because of a low coverage rate of the 88 microsatellite markers used here (approximately 46% of the whole genome).
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Chiba Y, Yoneta H, Fukuoka S, Akiyama R, Tazawa H. Ontogeny of Respiratory Sinus Arrhythmia in the Domestic Fowl. ACTA ACUST UNITED AC 2004. [DOI: 10.3184/147020604783637895] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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37
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Moriya K, Akiyama R, Dzialowski E, Burggren W, Tazawa H. Development of Heart Rate Circadian Rhythm in Chickens. ACTA ACUST UNITED AC 2004. [DOI: 10.3184/147020604783638128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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38
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Chiba Y, Fukuoka S, Niiya A, Akiyama R, Tazawa H. Development of cholinergic chronotropic control in chick (Gallus gallus domesticus) embryos. Comp Biochem Physiol A Mol Integr Physiol 2004; 137:65-73. [PMID: 14720592 DOI: 10.1016/s1095-6433(03)00271-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In chick (Gallus gallus domesticus) embryos, instantaneous heart rate begins to fluctuate with the appearance of rapid, transient decelerations at around the end of the second week of incubation. Previously, it was shown that instantaneous heart rate decelerations were eliminated by administration of atropine and concurrently heart rate baseline was elevated in late embryos. Because the previous study lacked statistical treatment and there has been recent controversy over the development of tonic vagal control of the heart, we reexamine the hypothesis that transient decelerations of instantaneous heart rate are mediated by vagus nerve and the vagal tone begins to appear at around the end of the second week of incubation. Atropine administration tests were conducted for sixty-seven 11- to 14-day-old and 18-day-old embryos in total. Heart rate decelerations appeared sporadically in three out of ten 12-day-old embryos, but the difference of mode heart rate before and after administration of atropine was not significant. Seven out of nine 13-day-old embryos and all nine 14-day-old embryos showed heart rate decelerations and the difference of mode heart rate before and after atropine administration was significant. In late (18-day-old) embryos, magnitude and frequency of instantaneous heart rate decelerations further increased with additional appearance of transient, irregular accelerations. Administration of varying doses of atropine completely eliminated the heart rate decelerations and elevated the heart rate baseline more markedly than in young embryos, indicating the maturation of vagal tone late in incubation.
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Tamura A, Akiyama R, Chiba Y, Moriya K, Dzialowski EM, Burggren WW, Tazawa H. Heart rate responses to cooling in emu hatchlings. Comp Biochem Physiol A Mol Integr Physiol 2003; 134:829-38. [PMID: 12814791 DOI: 10.1016/s1095-6433(03)00017-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Among fluctuations of instantaneous heart rate (IHR) in newly hatched chicks, heart rate (HR) oscillation with a mean frequency of 0.7 Hz has been designated as Type II HR variability characterized by low frequency (LF) oscillation [Comp. Biochem. Physiol. Part A 124 (1999) 461]. In response to exposure to lowered ambient temperature (Ta), chick hatchlings raised their HR baseline accompanied with the production or augmentation of Type II HR oscillation, indicating that LF oscillation is a phenomenon relating to thermoregulation [J. Therm. Biol. 26 (2001) 281]. In emu hatchlings that are precocial like chickens, Type II HR oscillation also occurred, but less frequently in comparison with chick hatchlings [Comp. Biochem. Physiol. Part A 131 (2002) 787]. This present experiment was conducted to elucidate how IHR of emu hatchlings responds to changes in Ta. Six hatchlings were measured for IHR and skin temperature (Ts) during a 3-h period when they were exposed to controlled Ta (ca. 35 degrees C), lowered Ta (ca. 15-30 degrees C) and again the controlled Ta for individual 1-h periods. In response to all the cooling and re-warming procedures, HR baseline changed depending upon the intensity of the Ta differences; i.e. large differences of Ta produced large changes in HR. HR fluctuations tended to augment during cooling with a few exceptions, but LF oscillation was not produced. Thus, LF oscillation, which was scarce even at the controlled Ta, could not be used as a thermoregulatory indicator in emus.
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Chiba Y, Khandoker AH, Nobuta M, Moriya K, Akiyama R, Tazawa H. Development of respiratory rhythms in perinatal chick embryos. Comp Biochem Physiol A Mol Integr Physiol 2002; 131:817-24. [PMID: 11897192 DOI: 10.1016/s1095-6433(02)00019-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In chick embryos, gas exchange takes place via the chorioallantoic membrane (CAM) and the lungs at approximately 1 day prior to hatching. The present study was designed to elucidate the development of respiratory rhythms in the chick embryo during the whole pipping (perinatal) period with a condenser-microphone measuring system. The microphone was hermetically attached on the eggshell over the air cell on day 18 of incubation. It first detected a cardiogenic signal (i.e. acoustocardiogram), and then beak clapping and breathing signals (acoustorespirogram, ARG). The first signals of lung ventilation appeared intermittently and irregularly approximately once per 5 s among the clapping signals after the embryo penetrated its beak into the air cell (internal pipping, IP). The respiratory rhythm then developed irregularly, with a subsequent more regular rate. The envelope pattern of breathing from the onset of IP through external pipping (EP) to hatching was constructed by a specially devised procedure, which eliminated external and internal noises. The envelope patterns indicated that the IP, EP and whole perinatal periods of 10 embryos were 14.1+/-6.4 (S.D.), 13.6+/-4.0 and 27.6+/-5.4 h, respectively. In addition, they also indicated the period of embryonic hatching activity (i.e. climax) which was 48+/-19 min. The development of respiratory rhythm was also shown by the instantaneous respiratory rate (IRR) which was designated as an inverse value of two adjacent ARG waves.
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41
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Tanaka K, Yonetake K, Masuko T, Akiyama R. Shearing microscopy using polarized optical microscope with shear stage and spectral analyser to study liquid crystalline polymers. J Microsc 2002; 205:15-20. [PMID: 11856377 DOI: 10.1046/j.0022-2720.2001.00972.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In-situ polarized optical microscopy using a shear stage and a spectral analyser as well as a CCD camera were applied to study the phase transition under shear flow for a thermotropic and side-chain-type liquid crystalline polysiloxane. The onset of the appearance of anisotropic texture of the polysiloxane was observed under shear flow using the CCD camera at temperatures much higher than the isotropic-liquid crystalline phase transition temperature if the polysiloxane was cooled from the isotropic phase in the quiescent state. Both the onset temperature and the temperature for full development of the anisotropic texture across the field of view became higher as the shear rate increased. The transmitted light intensity was also measured using a spectral analyser with crossed polarisers at wavelengths from 300 nm to 800 nm, and the integrated intensity of the spectrum was calculated. Changes in the spectrum and the integrated intensity against temperature in the cooling process were compared with observation using the CCD camera. Temperature dependence of the integrated intensity showed that the onset of the appearance of the anisotropic texture under high shear rates was detected at temperatures slightly higher than that observed using the CCD camera.
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Tazawa H, Moriya K, Tamura A, Komoro T, Akiyama R. Ontogenetic study of thermoregulation in birds. J Therm Biol 2001. [DOI: 10.1016/s0306-4565(01)00031-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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43
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Kobayashi S, Ishida T, Akiyama R. Catalytic asymmetric dihydroxylation using phenoxyethoxymethyl-polystyrene (PEM)-based novel microencapsulated osmium tetroxide (PEM-MC OsO4). Org Lett 2001; 3:2649-52. [PMID: 11506600 DOI: 10.1021/ol0161965] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text]. A phenoxyethoxymethyl-polystyrene (PEM)-based novel polymer-supported osmium catalyst has been developed. The catalyst was readily prepared from PEM polymer based on a microencapsulation technique, and asymmetric dihydroxylation of olefins has been successfully performed using (DHQD)2PHAL as a chiral ligand and K3Fe(CN)6 as a cooxidant in H2O/acetone. The catalyst was recovered quantitatively by simple filtration and reused without loss of activity several times.
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Kobayashi S, Akiyama R, Kitagawa H. Polymer-supported glyoxylate and alpha-imino acetates. Versatile reagents for the synthesis of alpha-hydroxycarboxylic acid and alpha-amino acid libraries. JOURNAL OF COMBINATORIAL CHEMISTRY 2001; 3:196-204. [PMID: 11300861 DOI: 10.1021/cc0000850] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Polymer-supported glyoxylate.monohydrate (3) and alpha-imino acetates (7) have been readily prepared from chloromethylated resin via two or three steps. The ene reactions of 3 with alkenes were successfully performed in the presence of Yb(OTf)3 (50 mol %) to afford, after cleavage from the polymer support, the corresponding alpha-hydroxycarboxylic acid esters in good yields. The reactions of 7 with silyl enolates, Danishefsky's diene, and alkenes also proceeded smoothly in the presence of Sc(OTf)3 (20 mol %) to give the corresponding alpha-amino acid, pyridone, and tetrahydroquinoline derivatives, respectively, in good yields.
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Tanaka K, Oiwa Y, Kiguchi T, Akiyama R. Simultaneous optical observation of anisotropic texture for a concentrated solution of poly(γ-benzyl- l -glutamate) under transient stress response in shear flow. Colloid Polym Sci 2000. [DOI: 10.1007/s003960000388] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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46
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Tanaka K, Nakamura K, Akiyama R. Time scales for structural formation in an electrorheological suspension probed by optical and electrical responses. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 62:5378-5382. [PMID: 11089099 DOI: 10.1103/physreve.62.5378] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2000] [Indexed: 05/23/2023]
Abstract
Responses of the diffuse transmitted light intensity and the current passing through an electrorheological suspension to the stepwise electric field were measured in the quiescent state, and the time scales for the structural formation of the polarized particles were reported. It was found experimentally that both of the responses consist of plural modes, the faster and slower modes even in the quiescent state. The optical response was also expressed as an exponential function with two modes, which take place in succession.
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Kobayashi S, Akiyama R, Kitagawa H. Polymer-supported alpha-imino acetates. Versatile reagents for the synthesis of alpha-amino acid libraries. JOURNAL OF COMBINATORIAL CHEMISTRY 2000; 2:438-40. [PMID: 11029165 DOI: 10.1021/cc000015t] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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48
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Akiyama R, Nagashima T, Tazawa H. Dynamical systems analysis of arterial blood pressure signals in relation to heart rate fluctuations in chick embryos. Comp Biochem Physiol A Mol Integr Physiol 1999; 124:469-74. [PMID: 10682245 DOI: 10.1016/s1095-6433(99)00139-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We attempted a new approach based on a modern dynamical system theory to reconstruct the arterial blood pressure signals in relation to heart rate fluctuations of developing chick embryos. The dynamical systems approach in general is to model a phenomenon that is presented by a single time series record and approximate the dynamical property (e.g. heart rate fluctuations) of a system based only on information contained in a single-variable (arterial blood pressure) of the system. The time-series data of the arterial blood pressure was reconstructed in 3-dimensional space to draw characteristic orbits. Since the reconstructed orbits of the blood pressure should retain information contained in the pressure signals, we attempted to derive instantaneous heart rate (IHR) from the reconstructed orbits. The derived IHR presenting HR fluctuations coincided well with the IHR obtained conventionally from the peak-to-peak time intervals of the maximum blood pressure. Movements of the reconstructed orbits of the arterial blood pressure in 3-dimensional space reflected HR fluctuations (i.e. transient decelerations and accelerations).
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Akiyama R, Matsuhisa A, Pearson JT, Tazawa H. Long-term measurement of heart rate in chicken eggs. Comp Biochem Physiol A Mol Integr Physiol 1999; 124:483-90. [PMID: 10682247 DOI: 10.1016/s1095-6433(99)00141-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Taking advantage of acoustocardiogram (ACG), we measured the heart rate (HR) of chick embryos continuously from day 12 until hatching and then investigated the development of HR irregularities (HRI), HR variability (HRV), and the existence of a circadian rhythm in mean HR (MHR). HRI comprised transient bradycardia and tachycardia, which first developed on day 14 and 16 in most embryos, respectively. Transient bradycardia increased in frequency and magnitude with embryonic development and occurred over periods of up to 30 min in some embryos. MHR was maximal on around days 14-15 and thereafter decreased to about 250-260 bpm on days 16-18. Baseline HRV, which is an oscillation of the MHR baseline, occurred as HR decreased from days 15-16 and became predominant on days 17-18. The magnitude of the baseline oscillations reached up to 50 bpm in some embryos and the period ranged between about 40-90 min (ultradian rhythm). A circadian rhythm of MHR was not found in late chick embryos. On days 18-19, embryonic activities were augmented and then breathing movements began to occur, disturbing ACG signals and thus making it difficult to measure the HR. Instead, the development of breathing activities was recorded. Breathing frequency was irregular at first and then increased to a maximum of about 1.5 Hz prior to hatching.
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Arai N, Akiyama R, Niimi N, Nakatsubo H, Inoue T. Meiotic contraction of CAG repeats in Saccharomyces cerevisiae. Genes Genet Syst 1999; 74:159-67. [PMID: 10650843 DOI: 10.1266/ggs.74.159] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Several human neurodegenerative disorders are caused by expansion of CAG repeats that occurs during meiosis or gametogenesis. We anticipated that the CAG repeats cloned in a plasmid of Saccharomyces cerevisiae might undergo a change in the number of repeats during meiosis and sporulation. To test this possibility, we devised a new method to change in vitro the number of CAG repeats and constructed plasmids carrying (CAG)39, (CAG)65 or (CAG)123 from a plasmid carrying (CAG)18. We monitored the number of colonies showing an altered length of the repeat tracts during mitosis and meiotic growth. Contraction of long CAG repeat was found to occur frequently, whereas a few cases of expansion were observed. The contraction was equally enhanced in both orientations when the host cells grew through meiosis. Thus, our results suggest that long CAG repeats are destabilized during meiosis or gametogenesis in S. cerevisiae.
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