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Takayoshi Kobayashi

Publications and source records attributed to Takayoshi Kobayashi.

18 recordsLinked to original sources
PubMed2006

Confined breather-type excitation in a quinoidal thiophene after sub-5 fs pulse excitation.

A quinoidal thiophene molecule which is a prototype of the repeated unit of s-trans-cis-polyacetylene was studied by sub-5 fs spectroscopy. A breatherlike mode modulation of both the amplitude and frequency of the C[Double Bond]C stretching was observed for the first time. It generates two sidebands of 2238 and 700 cm(-1) with a separation of 769 cm(-1) corresponding to the modulation frequency. The latter mode is very close to the C-S-C ring deformation, which indicate that this mode mediates coupling between the breather mode and the C(beta)-C(beta) stretching mode. It was also found that the breather-type excitation has a longer lifetime (2-3 ps) than in all-trans-polyacetylene (50 fs) due to its confinement.

Journal Article↗
PubMed2006

Predominant motor symptoms in a 74-year-old man with a small elongation in the spinocerebellar atrophy type 1 gene.

The patient was a 74-year-old man who developed gait and bulbar disturbances, which progressed for several years. His mother and a sister complained of a similar disturbance. On admission, generalized muscle atrophy and weakness were prominent, especially in the distal portions of the legs, with bulbar involvement. The patellar tendon reflexes were retained and the Achilles tendon reflexes were decreased with a positive right Babinski's sign. The ocular movements were restricted in vertical directions and, to a lesser extent, in horizontal directions. Sensory disturbance, ataxia, and extrapyramidal signs were not apparent on admission. A needle electromyogram demonstrated neurogenic changes. The laboratory examination was normal except for elevated blood glucose (320 mg/dL) and creatine kinase (1760 U/L). His general condition deteriorated so rapidly that intractable respiratory distress due to pneumonia led to a fatal outcome. The clinical diagnosis was motor neuron disease, although a familial background and a disturbance in ocular movements might have suggested other possibilities.

Aged↗
PubMed2006

Genotoxicity studies OF p-dimethylaminoazobenzene (DAB).

The potential genotoxicity of the rodent liver carcinogen p-dimethylaminoazobenzene (DAB) was evaluated in compliance with the guidelines for genotoxicity studies of drugs (Notification No. 1604, Nov. 1, 1999, Ministry of Health and Welfare, Japan) and the OECD guidelines for testing chemicals. DAB was clearly positive in both the bacterial reverse mutation test (Ames test) and in vitro chromosomal aberration test in the presence of metabolic activation, whereas it was weakly positive at toxic doses in the rat bone marrow micronucleus test. It has been reported that DAB was clearly positive in in vivo genotoxicity tests, i.e., a mouse alkaline single cell gel electrophoresis (comet) assay and a young rat liver micronucleus test. These results suggest that the test system using the liver is effective for in vivo genotoxicity assessment of chemicals that show mutagenicity in in vitro genotoxicity tests in the presence of metabolic activation.

Animals↗
PubMed2005

New high-efficiency source of a three-photon w state and its full characterization using quantum state tomography.

We propose and demonstrate a new scheme of high-efficiency generation of the three-photon polarization-entangled W state, which is a typical three-qubit entangled state. The high efficiency has enabled the first full characterization of the state by quantum state tomography. We have analyzed the obtained state and observed its nature of tripartite entanglement and robustness of entanglement.

Journal Article↗
PubMed2005

Carrier-envelope phase-controlled quantum interference in optical poling.

We demonstrate the efficiency of the optical poling process that depends on the CE phase-controlled quantum interference. For the experiment we employed our noncollinear optical parametric amplifier system for the self-stabilization of the CE phase, with the f-to-2f spectral interferometry system to control the CE phase.

Journal Article↗
PubMed2005

Real-time charge oscillation between monomers in a dimeric system associated with intermolecular vibration induced by an ultrashort pulse.

Ultrafast charge resonant (CR) dynamics between two molecules in a dimer system has been studied theoretically and experimentally using 6-fs laser pulses and a thin film of amorphous-phase phthalocyanine tin(IV) dichloride (SnPc). The modulation of the absorbance change in the bleaching spectral range of the CR absorption band was analyzed to obtain the amount of charge resonantly transferred back and forth by a dimeric vibration induced by photoexcitation. The modulation can be explained in terms of a periodic change in the cross section and a periodic energy shift, where both are induced by the change in the overlap integral caused by the accordion-type intermolecular vibration. The associated change in distance between two molecules with the intermolecular vibration was estimated to be 0.09 A, which corresponds to 2.5% of the mean distance between the two SnPc molecules in the dimeric system.

Journal Article↗
PubMed2005

The synthesis of 7-substituted-3-dinitrostyryl cephalosporins and their ability for detecting extended spectrum beta-lactamases (ESBLs).

We synthesized 7-substituted-3-(2,4-dinitrostyryl)cephalosporin derivatives which were Nitrocefin analogs, for detecting extended spectrum beta-lactamase (ESBL) specifically. HMRZ-86 which has carboxypropyloxyimino group on 7-aminothiazolacetamide substituent were not hydrolyzed by class A, C and D beta-lactamases, but it was hydrolyzed by ESBL and metallo beta-lactamase (class B), then its color changed from yellow to red. The hydrolysis of metallo beta-lactamase was inhibited by adding sodium mercapto acetic acid (SMA). Therefore HMRZ-86 is a useful chromogenic agent to detect ESBL specifically.

Cephalosporins↗
PubMed2004

Sellmeier dispersion for phase-matched terahertz generation in ZnGeP2.

A Sellmeier dispersion of zinc germanium diphosphide (ZnGeP2) crystal has been formulated to determine the phase-matching characteristics of the crystal for the generation of coherent tunable terahertz radiation by difference-frequency mixing techniques. The results computed with the formulated Sellmeier dispersion provide an excellent fit to the experimental data.

Journal Article↗
PubMed2004

Self-stabilization of the carrier-envelope phase of an optical parametric amplifier verified with a photonic crystal fiber.

Experimental verification is given for self-stabilization of the carrier-envelope phase (CEP) of idler pulses from a noncollinear optical parametric amplifier. The verification is performed by spectral interference (SI) between an octave-broadened supercontinuum (SC) and its second harmonic. This SC is generated by nonlinear propagation of the second harmonic of the idler through a photonic crystal fiber (PCF). Although the modulational instability causes the intensity and CEP fluctuation and the amplified spontaneous emission noise in PCF degrades the visibility of SI, the CEP is verified to be stabilized.

Journal Article↗
PubMed2004

Quasi-monocyclic near-infrared pulses with a stabilized carrier-envelope phase characterized by noncollinear cross-correlation frequency-resolved optical gating.

Precise characterization of noncollinear optical parametric amplifier idler pulses that have bandwidths of more than an octave with a center wavelength at 990 nm was demonstrated. The method employed was cross-correlation frequency-resolved optical gating with broadband sum-frequency mixing to take advantage of the idler's angular dispersion. Compression to near the transform limit was achieved to produce quasi-monocyclic near-infrared pulses by use of a deformable membrane mirror.

Journal Article↗
PubMed2004

[Alterations of antiproliferative effects of serum obtained from patients with acute cerebral infarction treated with a radical scavenger, edaravone, with or without amlodipine using an in vitro cultured basilar artery smooth muscle cells].

The guinea-pig basilar artery smooth muscle cell (GBa-SM3) culture system in the Dulbecco's modified Eagle's medium for 3 days serves as a useful in vitro model for assessing antiproliferative effects of various therapeutic agents on vessels. With use of this system we studied whether human serum obtained from patients with acute cerebral infarction (n = 16) would have a proliferative effect on vessels and whether an administration of a free radical scavenger, edaravone, with or without amlodipine would elicit antiproliferative effects. The control serum was obtained from 3 healthy human subjects. Time courses of the cell growth and survival were measured colorimetrically by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrzolium bromide (MTT) test. The stimulatory effect on the proliferation of GBa-SM3 cells of patients' serum obtained immediately after infarction was significantly (p < 0.05) greater than those obtained from the same patients after the treatment of edaravone for 2 weeks. In addition, the serum obtained from the patients treated by edaravone and amlodipine (n = 7) showed a significantly (p < 0.05) greater antiproliferative effect than that obtained from those treated by edaravone (n = 9). In conclusion, edaravone may have a clinically beneficial antiproliferative effect on vascular smooth muscle cells. Co-administration of amlodipine, possessing an antioxidative calcium channel blocker, with edaravone may be a promising combination to patients with acute cerebral infarction. Further controlled clinical trials with a large number of patients should be warranted.

Acute Disease↗
PubMed2004

[Channelopathy update].

Electrophysiological techniques, molecular technology and molecular genetics have been quickly developed in the late 20th century. Now many genetical abnormalities of channel proteins including voltage gated ion channels, ligand gated ion channels and Ca induced Ca channel have been discovered. In this article, I briefly review these genetical abnormality of ion channels ("channelopathies") and the pathophysiological background of these channelopathies.

Humans↗
PubMed2003

Down-regulation of an ankyrin repeat-containing protein, V-1, during skeletal muscle differentiation and its re-expression in the regenerative process of muscular dystrophy.

Using Western blot analysis and immunohistochemical methods, we examined the expression of V-1, a member of the ankyrin repeat-containing protein family, during differentiation and regeneration of skeletal muscle. The expression of V-1 was high in cultured myoblasts and decreased during their differentiation into myotubes, while high expression was maintained when muscle differentiation was inhibited by treatment with basic fibroblast growth factor. Down-regulation of V-1 also occurred during in vivo muscle differentiation from embryonic to postnatal stages, reaching an undetectable level in mature skeletal muscle. In contrast, strong V-1 immunoreactivity was detected again in myoblasts and regenerating muscle fibers with a small diameter, which were observed in Duchenne muscular dystrophy and its animal model, mdx mouse. Thus, it seems that V-1 is a good marker for early stage of muscle regeneration and changes of its expression suggest that V-1 plays a role in prenatal muscle differentiation and postnatal muscle regeneration.

Adult↗
PubMed2002

Excitation of a breather mode of bound soliton pairs in trans-polyacetylene by sub-five-femtosecond optical pulses.

Trans-polyacetylene with a degenerate ground state has a nonlinear excitation of soliton after photoexcitation, due to the electron-phonon coupling. The excess energy of an excited electron-hole pair over a soliton pair creation induces a breather oscillation characterized by collective stretching vibration of the carbon-carbon bonds. A time-frequency analysis of pump probe signal shows that instantaneous frequencies of stretching modes are modulated for approximately 50 fs after excitation and the modulation period is 44+/-3 fs consistent with the theoretical expectation, clearly verifying the breather.

Journal Article↗
PubMed2002

Controlling the carrier-envelope phase of ultrashort light pulses with optical parametric amplifiers.

The phase link between signal, idler, and pump waves in a parametric interaction allows generation of an idler pulse with a phase independent of that of the input pulse. We suggest the use of a white-light seeded optical parametric amplifier as a self-stabilized source of few-cycle pulses, in which the phase of the electric field is exactly reproduced in each laser shot.

Journal Article↗
PubMed2002

Structural analysis of an extracellular polysaccharide bioflocculant of Klebsiella pneumoniae.

The glycoside composition and sequence of an extracellular polysaccharide flocculant of Klebsiella pneumoniae H12 was analyzed. GC and HPLC analysis of the acid-hydrolysate identified its constituent monosaccharides as D-Glc, D-Man, D-Gal, and D-GlcA in an approximate molar ratio of 3.9:1.0:2.3:3.6. To analyze the glycoside sequence, the polysaccharide was partially hydrolyzed by acid and enzyme treatment. GC, HPLC, TLC, MALDI-TOF/MS, and 1H- and 13C- NMR spectroscopy characterized the obtained oligosaccharides. The results clarified the partial structure of H12 polysaccharide as a linear polymer of a unit of pentasaccharide with a side chain of one D-GlcA to D-Glc moiety (see below). Although the existence of other sequences or other constituent glycosides could not be fully excluded, H12 polysaccharide must be a novel types as such a complicated unit for a polymer has not so far been reported. The partial structure of a H12 polysaccharide flocculant is also discussed in this report. [structure: see text]

Carbohydrate Sequence↗
PubMedDate not supplied

Sub-5-fs real-time spectroscopy of transition states in bacteriorhodopsin during retinal isomerization.

By using a sub-5-fs visible laser pulse, we have made the first observation of the vibrational spectra of the transition state during trans-cis isomerization in the retinal chromophore of bacteriorhodopsin (bR(S68). No instant isomerization of the retinal occurs in spite of electron promotion from the bonding pi-orbital to the anti-bonding pi*-orbital. The difference between the in-plane and out-of-plane vibrational frequencies (about 1150-1250 and 900-1000 cm(-1), respectively) is reduced during the first time period. The vibrational spectra after this period became very broad and weak and are ascribed to a "silent state." The silent state lasts for 700-900 fs until the chromophore isomerizes to the cis-C13 = C14 conformation. The frequency of the C = C stretching mode was modulated by the torsion mode of the C13 = C14 double bond with a period of 200 fs. The modulation was clearly observed for four to five periods. Using the empirical equation for the relation between bond length and stretching frequency, we determined the transitional C = C bond length with about 0.01 angstroms accuracy during the torsion motion around the double bond with 1-fs time resolution.

Bacteriorhodopsins↗