Proof-of-Principle Experiment for Testing Strong-Field Quantum Electrodynamics with Exotic Atoms: High Precision X-Ray Spectroscopy of Muonic Neon.

To test bound-state quantum electrodynamics (BSQED) in the strong-field regime, we have performed high precision x-ray spectroscopy of the 5g-4f and 5f- 4d transitions (BSQED contribution of 2.4 and 5.2 eV, respectively) of muonic neon atoms in the low-pressure gas phase without bound electrons. Muonic atoms have been recently proposed as an alternative to few-electron high-Z ions for BSQED tests by focusing on circular Rydberg states where nuclear contributions are negligibly small. We determined the 5g_{9/2}- 4f_{7/2} transition energy to be 6297.08±0.04(stat)±0.13(syst) eV using superconducting transition-edge sensor microcalorimeters (5.2-5.5 eV FWHM resolution), which agrees well with the most advanced BSQED theoretical prediction of 6297.26 eV.

Measurements of Strong-Interaction Effects in Kaonic-Helium Isotopes at Sub-eV Precision with X-Ray Microcalorimeters.

We have measured the 3d→2p transition x rays of kaonic ^{3}He and ^{4}He atoms using superconducting transition-edge-sensor microcalorimeters with an energy resolution better than 6 eV (FWHM). We determined the energies to be 6224.5±0.4(stat)±0.2(syst) eV and 6463.7±0.3(stat)±0.1(syst) eV, and widths to be 2.5±1.0(stat)±0.4(syst) eV and 1.0±0.6(stat)±0.3(stat) eV, for kaonic ^{3}He and ^{4}He, respectively. These values are nearly 10 times more precise than in previous measurements. Our results exclude the large strong-interaction shifts and widths that are suggested by a coupled-channel approach and agree with calculations based on optical-potential models.

Deexcitation Dynamics of Muonic Atoms Revealed by High-Precision Spectroscopy of Electronic K X Rays.

We observed electronic K x rays emitted from muonic iron atoms using superconducting transition-edge sensor microcalorimeters. The energy resolution of 5.2 eV in FWHM allowed us to observe the asymmetric broad profile of the electronic characteristic Kα and Kß x rays together with the hypersatellite K^{h}α x rays around 6 keV. This signature reflects the time-dependent screening of the nuclear charge by the negative muon and the L-shell electrons, accompanied by electron side feeding. Assisted by a simulation, these data clearly reveal the electronic K- and L-shell hole production and their temporal evolution on the 10-20 fs scale during the muon cascade process.

Shot Noise of 1,4-Benzenedithiol Single-Molecule Junctions.

We report measurements of the shot noise on single-molecule Au-1,4-benzenedithiol-Au junctions, fabricated with the mechanically controllable break junction (MCBJ) technique at 4.2 K in a wide range of conductance values from 10(-2) to 0.24 conductance quanta. We introduce a simple measurement scheme using a current amplifier and a spectrum analyzer and that does not imply special requirements regarding the electrical leads. The experimental findings provide evidence that the current is carried by a single conduction channel throughout the whole conductance range. This observation suggests that the number of channels is limited by the Au-thiol bonds and that contributions due to direct tunneling from the Au to the π-system of the aromatic ring are negligible also for high conductance. The results are supported by quantum transport calculations using density functional theory.

Energy-level alignments and photo-induced carrier processes at the heteromolecular interface of quaterrylene and N,N'-dioctyl-3,4,9,10-perylenedicarboximide.

Photo-induced carrier processes at the heteromolecular interface of N,N'-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C(8)) and quaterrylene (QT) on a molecular scale were examined by optical and photoelectron spectroscopy. The energy level alignments of the molecules were determined by X-ray photoelectron spectroscopy and the optical absorption spectra for detailed investigation of the photo-induced carrier process were analysed. A reduction in photoluminescence from PTCDI-C(8) on QT was observed, clearly demonstrating that the excitons generated in the PTCDI-C(8) layer are effectively dissociated at the heteromolecular interface. One important factor inducing this effective charge dissociation is the highly ordered molecular packing, which acts to increase the exciton diffusion length. Moreover, a specific increase in the photoluminescence excitation spectrum was observed around 3 eV, indicating that simultaneous exciton generation in both the QT and PTCDI-C(8) layers effectively suppresses such charge dissociation of the excitons. In other words, the existence of excitons in each molecule at the heteromolecular interface and HOMO-LUMO level alignment at the interface play an essential role in charge dissociation. Our results provide a striking insight into intermolecular interactions in the carrier process at the heteromolecular interface such as exciton generation, the recombination and dissociation processes, and the photovoltaic effect in organic semiconductors.

New method for simultaneous measurement of frequency spectra of complex dielectric constants of polyelectrolyte solutions.

A high-speed and high-accuracy measurement of relaxational frequency spectra of complex dielectric constants of polyelectrolyte solutions with a high conductivity was realized by a new digital signal processing technique. In this method, a sum of sinusoidal waves of geometrical series of frequencies is utilized as a multifrequency excitation signal and demodulation of the resulting response is carried out simply by addition and subtraction of digital signals in a minicomputer. This new technique is superior to the conventional cross correlation method using the fast Fourier transform in that it greatly reduces the processing time and avoids effectively the influence of a quantization error. The result for a DNA solution obtained by this method is presented to demonstrate the utility of this method.

Low frequency dielectric relaxation and light scattering under AC electric field of DNA solutions.

Low frequency dielectric relaxation of aqueous DNA was measured in a frequency range from 0.1 Hz to 30 kHz. Agreement was found between dielectric relaxation time and rotational one estimated from reduced viscosity for dilute solutions of DNA. The low frequency relaxation is thus ascribed to rotation of the major axis of DNA chains elongated by electrostatic repulsion between charges on the chain. A quasi-permanent dipole moment of DNA estimated from the dielectric increment is well explained by the fluctuation of dissociation of DNA. The above conclusion was confirmed for DNA samples of various molecular weights and for solutions in water ethanol mixtures. Effects of binding of salts and dyes are also interpreted in terms of the same mechanism. Light scattering of aqueous DNA under a.c. electric field supports the above conclusion.

Immunosuppression by ultraviolet B rays via eyes in mice.

Irradiation by ultraviolet B (UV-B; 280-320 nm) initiates suppression of contact hypersensitivity. Immunosuppression was induced in C57BL/6N Crj mice by exposure of the dorsal skin or the eyes to a 10 kJ/m2 dose of UV-B radiation from 20SE sunlamps, followed by sensitization with 0.5% fluorescein isothiocyanate (FITC). The degree of immunosuppression induced by UV-B eye irradiation was equal to that induced by UV-B skin irradiation. When mice were irradiated with UV-B into the eyes after the optic nerve had been cut, systemic immunosuppression was not induced.

Critical behavior of nonlinear permittivity in the smectic-A phase of chiral liquid crystals.

We study the nonlinear permittivity of chiral liquid crystals in the smectic-A (Sm-A) phase near the ferroelectric smectic-C* (Sm-C*) phase and the smectic-C(*)(alpha) (Sm-C(*)(alpha)) phase theoretically and experimentally. The third-order nonlinear permittivity epsilon(3) shows the critical behavior with the exponent of four near the Sm-C* phase and its sign depends on the order of the phase transition. In the case of the Sm-A-Sm-C(*)(alpha) phase transition, the sign inversion of epsilon(3), presumably due to the large fluctuation of order parameter, is observed near the transition temperature.

Electro-optic response of a ferroelectric liquid crystal in thick free-standing films.

We study the electro-optic response of a ferroelectric liquid crystal in free-standing films as thick as the helical pitch. In the films thicker than about one pitch, two relaxation modes are observed in the frequency spectra. The relaxation frequency of the slower mode decreases when increasing the film thickness, while that of the faster mode, which appears at approximately 1 kHz, is almost independent of the film thickness. In thinner films, a single relaxation mode is observed at several hundred Hz. The obtained relaxation spectra are discussed in comparison to the theoretical spectra of the phase mode in a system of finite length along the helical axis calculated by Urbanc and Zeks [Phys. Rev. E 52, 3892 (1995)].

Pigmented contact dermatitis due to musk moskene.

Musk moskene is a soft, sweet fragrance resembling musk ambrette which introduces a very desirable creamy powder note for cosmetic fragrance. Because of its advantages, which include low cost, oil solubility, and less sensitive to sunlight, musk moskene has recently increased its share of the market. In this paper, we reported a case with pigmented contact dermatitis from musk moskene in cheek rouges. Patch test positive reactions to cheek rouges resulted in hyperpigmentation. Both the perfume used in the cheek rouges and musk moskene, which was a component of that perfume, showed strongly positive reactions. Residual hyperpigmentation was seen on the regions of the perfume and musk moskene patch testings. Hyperpigmentation on cheeks of the patient gradually diminished after discontinuing use of the causative cheek rouge.

Establishment of an in vitro cell derived from human angiosarcoma.

We have succeeded in the establishment of a human endothelial cell line derived from a human angiosarcoma. These cells grew as monolayers with a "cobble stone" morphology. The cells produced endothelin and showed Weibel-Palade bodies in their cytoplasm. These findings show that the cells have specific differenciated functions, and might be useful for both fundamental endothelial cell biology and biological investigation of angiosarcoma.

A genomic study on the cultivable and nerve invading Mycobacterium HI-75 after the recovery 3 months of the inoculation to nude mice.

The sequence of the polymerase chain reaction (PCR) product of 16S ribosomal RNA (16S rRNA) of the leproma-derived and cultivable Mycobacterium HI-75 (M. HI-75) which was obtained from the infected regions of inoculated mice, was examined and compared with that of the cultured bacteria by the direct sequencing techniques. The sequence was completely consistent with the cultured bacilli in the comparable 837 bases of 16S rRNA. The mycobacterium examined in this study was originally isolated as M. leprae (ML) by Skinsnes, et al. in 1975 from leproma of a lepromatous type Hansen's disease patient and therefore named as Mycobacterium leprae HI-75 by them, and was maintained from 1984 using either Ogawa's or Sauton's media in the beginning and Ogawa's medium enriched with glucronic acid and N-acetyl-D-glucosamine recently. Sasaki and Hamit reported the nerve invasion and the growth of the inoculated bacilli either to the nude mice or the I131 treated immunocompromised Swiss mice. We previously reported that cultured HI-75 was most similar to M. scrofulaceum by the direct sequencing of the gene of 16S rRNA. The 16S rRNA obtained from the mouse tissue in the present study indicated that M. HI-75 would be a variant of M. scrofulaceum possessing an ability to invade into peripheral nerve. The results suggest that the HI-75 strain claims a nature as a pathogen to develop a leproma-like lesion.