Quantitative diffraction imaging using attosecond pulses

We have proposed and developed a method to utilize attosecond pulses in diffraction imaging techniques applied to complex samples. In this study, the effects of the broadband properties of the wavefield owing to attosecond pulses are considered in the reconstruction of images through the decomposition of the broad spectrum into multi-spectral components. This method successfully reconstructs the multi-spectral information of complex samples, probes, and spectral bandwidths using broadband diffraction intensities generated from computational scanning experiments. The results obtained in this research open the opportunities to perform quantitative ultrafast imaging using the attosecond pulses.Comment: 17 page

Raman scattering gain in DOO-PPV films

Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United StatesMaxim N. Shkunov, Werner Gellermann, Akihiko Fujii, Katsumi Yoshino, and Z. Valy Vardeny "Raman scattering gain in DOO-PPV films", Proc. SPIE 3145, Optical Probes of Conjugated Polymers, (1 December 1997). DOI: https://doi.org/10.1117/12.29552

Laser action in conducting polymers

We discuss both cooperative radiation and stimulated emission and consider their role in spectral narrowing of luminescent conducting polymers. We argue that cooperative radiation is favored in films with poor optical confinement. On the other hand, directional stimulated emission can be observed in dilute solution and thin films with superior optical confinement. Spectral narrowing in this case can be achieved by increasing either the excitation length or excitation intensity. The optical gain and loss coefficients are measured. Narrow line (approximately 1.5 cm-1) laser emission is observed in cylindrical microcavities formed by thin polymer films coated around glass fibers in the red and green spectral ranges. The cavity quality factors of these plastic lasers are mainly determined by selfabsorption and estimated to be about 5000.Optical Scnce, Engineering and Instrumentation '97, 1997, San Diego, CA, United StatesSergey V. Frolov, Maxim N. Shkunov, Z. Valy Vardeny, Masanori Ozaki, and Katsumi Yoshino "Laser action in conducting polymers", Proc. SPIE 3145, Optical Probes of Conjugated Polymers, (1 December 1997). DOI: https://doi.org/10.1117/12.29552

Studies of Raman scattering in novel disubstituted acetylene polymers

We have studied resonant and non-resonant Raman scattering spectra in thin films of novel disubstituted acetylene polymers such as poly(1-ethyl-2-phenylacetylene) (PEtPA), poly(1-n-hexyl-2-phenylacetylene) (PHxPA) and poly(1-phenyl- 2-p-n-butylphenylacetylene) (PDPA-nBu), which possess high photoluminescence (PL) quantum efficiency. We found that the Raman scattering frequency dispersion is smaller in disubstituted acetylene polymers than in other acetylene polymers, in agreement with many other strongly luminescent polymers. Assuming the model of short polyene conjugation length in these acetylene polymers, we can obtain the conjugation length (N) for each polymer from the respective phonon frequency of the carbon-carbon double bond; we obtained N equals 7 for PDPA-nBu, and N equals 5 or 6 for PHxPA and PEtPA. The related energies of 11Bu and 21Ag can be estimated from these N and are in good agreement with the respective absorption and PL spectra of the various disubstituted polymers.Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United StatesAkihiko Fujii, Maxim N. Shkunov, Z. Valy Vardeny, Kazuya Tada, Katsumi Yoshino, Masahiro Teraguchi, and Toshio Masuda "Studies of Raman scattering in novel disubstituted acetylene polymers", Proc. SPIE 3145, Optical Probes of Conjugated Polymers, (1 December 1997). DOI: https://doi.org/10.1117/12.29554

Crystalline ground state in chiral Gross-Neveu and Cooper pair models at finite densities

We study the possibility of spatially non-uniform ground state in (1+1)-dimensional models with quartic fermi interactions at finite fermion densities by introducing chemical potential \mu. We examine the chiral Gross-Neveu model and the Cooper pair model as toy models of the chiral symmetry breaking and the difermion pair condensates which are presumed to exist in QCD. We confirm in the chiral Gross-Neveu model that the ground state has a crystalline structure in which the chiral condensate oscillates in space with wave number 2\mu. Whereas in the Cooper pair model we find that the vacuum structure is spatially uniform. Some discussions are given to explain this difference.Comment: 18 pages, REVTeX, 3 eps figure

Guidelines for the proper use of etanercept in Japan

Application of biological agents targeting inflammatory cytokines such as tumor necrosis factor-α (TNF-α) dramatically caused a paradigm shift in the treatment of rheumatoid arthritis (RA). Infliximab, a chimeric anti-TNF-α monoclonal antibody, has initially been introduced to Japan in 2003 and shown to be dramatically effective in alleviating arthritis refractory to conventional treatment. However, serious adverse events such as bacterial pneumonia, tuberculosis, and Pneumocystis jiroveci pneumonia were reported to be in relatively high incidence; i.e., 2%, 0.3%, and 0.4%, respectively, in a strict postmarketing surveillance of an initial 4000 cases in Japan. Etancercept, a recombinant chimeric protein consisting of p75 TNF-α receptor and human IgG, was subsequently introduced to Japan in March of 2005. We therefore drew up treatment guidelines for the use of etanercept to avoid potential serous adverse events, since only approximately 150 cases have been included in the clinical study of etanercept in Japan. The guidelines were initially designed by the principal investigators (N.M, T.T., K.E.) of rheumatoid arthritis study groups of the Ministry of Health, Labor and Welfare (MHLW), Japan, and finally approved by the board of directors of the Japan College of Rheumatology. The MHLW assigned a duty to the pharmaceutical companies to perform a complete postmarketing surveillance of an initial 3000 cases to explore any adverse events, and this was performed according to the treatment guidelines shown in this article

Revealing novel aspects of light-matter coupling in terahertz two-dimensional coherent spectroscopy: the case of the amplitude mode in superconductors

Recently developed terahertz (THz) two-dimensional coherent spectroscopy (2DCS) is a powerful technique to obtain materials information in a fashion qualitatively different from other spectroscopies. Here, we utilized THz 2DCS to investigate the THz nonlinear response of conventional superconductor NbN. Using broad-band THz pulses as light sources, we observed a third-order nonlinear signal whose spectral components are peaked at twice the superconducting gap energy $2\Delta$. With narrow-band THz pulses, a THz nonlinear signal was identified at the driving frequency $\Omega$ and exhibited a resonant enhancement at temperature when $\Omega = 2\Delta$. General theoretical considerations show that such a resonance can only arise from a disorder-activated paramagnetic coupling between the light and the electronic current. This proves that the nonlinear THz response can access processes distinct from the diamagnetic Raman-like density fluctuations, which are believed to dominate the nonlinear response at optical frequencies in metals. Our numerical simulations reveal that even for a small amount of disorder, the $\Omega=2\Delta$ resonance is dominated by the superconducting amplitude mode over the entire investigated disorder range. This is in contrast to other resonances, whose amplitude-mode contribution depends on disorder. Our findings demonstrate the unique ability of THz 2DCS to explore collective excitations inaccessible in other spectroscopies