Naoji Moriya

Nanoparticle size analysis with relaxation of induced grating by dielectrophoresis

We propose an alternative approach to the use of dynamic light scattering (DLS) for the analysis of particle sizes ranging from 5 nm to 100 nm. This approach employs a combination of 1) diffusion, 2) density grating, and 3) dielectrophoresis (DEP), and measures the diffusion coefficient from the decay rate of the diffracted light intensity in the relaxation process of particle density modulation generated by DEP. Both the experiments and the theoretical analysis confirm the reliable determination of particle size independently of the refractive index. The new method records a decay signal directly without an autocorrelator and is expected to have a less extreme sensitivity dependence on particle size than DLS.

New evaluation beamline for soft x-ray optical elements

An evaluation system capable of measuring the wavelength and angular characteristics of the absolute reflectivity (or diffraction efficiency) of soft x-ray optical elements has been designed and constructed. The system was installed on a beamline (BL-11) of the AURORA, a superconducting compact storage ring, at the Synchrotron Radiation Center, Ritsumeikan University. To cover a wavelength range of 0.5 nm<λ<25 nm, this system incorporates two types of Monk–Gillieson monochromators. One is a conventional type equipped with three varied-line-spacing gratings, allowing a choice of two included angles. The other is a new type that employs a scanning mechanism based on surface normal rotation. The outline of the system and some preliminary experimental data obtained in the course of test runs are described.

New type of Monk-Gillieson monochromator capable of covering a 0.7- to 25-nm range

A new type of monochromators that incorporates two kinds of Monk-Gillieson monochromators has been designed and constructed for the purpose of realizing an evaluation beamline for characterizing soft X-ray optical elements in a wide wavelength range of 0.7-25 nm. One of the monochromators is a conventional type equipped with three varied-line-spacing plane gratings, allowing a choice of two inclusion angles. The other is a new type that employs a scanning mechanism based on Surface Normal Rotation (SNR). The SNR scheme provides high throughput at short wavelengths and simple scanning mechanism by means of a grating rotation about its normal. The monochromators is operated in the SNR and conventional modes over the ranges of 0.7-2.0 nm and 2.0-25 nm, respectively. The system was installed on a beamline of the AURORA, a superconducting compact storage ring, at the Synchrotron Radiation Center, Ritsumeikan University. In this paper we describe the optical and mechanical designs of the monochromators, and a practical method of wavelength calibration. Also experimental data are shown which demonstrate the performance and versatility of the new type of Monk-Gillieson monochromators.

Consecutive incorporation of fluorophore-labeled nucleotides by mammalian DNA polymerase β

In the present study, we investigated mammalian polymerases that consecutively incorporate various fluorophore-labeled nucleotides. We found that rat DNA polymerase beta (pol beta) consecutively incorporated fluorophore-labeled nucleotides to a greater extent than four bacterial polymerases, Sequenase Version 2.0, Vent(R) (exo-), DNA polymerase IIIalpha and the Klenow fragment, and the mammalian polymerases DNA polymerase alpha and human DNA polymerase delta, under mesophilic conditions. Furthermore, we investigated the kinetics of correct or mismatched incorporation with labeled nucleotides during synthesis by rat pol beta. The kinetic parameters K(m) and k(cat) were measured and used for evaluating: (i) the discrimination against correct pair incorporation of labeled nucleotides relative to unlabeled nucleotides; and (ii) the fidelity for all nucleotide combinations of mismatched pairs in the presence of labeled or unlabeled nucleotides. We also investigated the effect of fluorophore-labeled nucleotides on terminal deoxynucleotidyl transferase activity of rat pol beta. We have demonstrated for the first time that mammalian pol beta can consecutively incorporate various fluorophore-labeled dNTPs. These findings suggest that pol beta is useful for high-density labeling of DNA probes and single-molecule sequencing for high-speed genome analysis.

A beam intensity monitor for the evaluation beamline for soft x-ray optical elements

Evaluation Beamline for Soft X-Ray Optical Elements (BL-11) at the SR Center of Ritsumeikan University has been operated to measure the wavelength and angular characteristics of soft x-ray optical components in a wavelength range of 0.65-25 nm using a reflecto-diffractometer (RD). The beam intensity monitor that has been equipped in BL-11 has observed the signal of the zero-th order light. For the purpose of more accurate evaluation of the performance of optical components, a new beam intensity monitor to measure the intensity of the first order light from the monochromator in BL-11 has been developed and installed in just front of RD. The strong positive correlation between the signal of the beam monitor and a detector equipped in the RD is shown. It is successful that the beam intensity of the first order light can be monitored in real time.

Soft x-ray reflectivity and structure evaluation of Ni/Ti and Ni-N/Ti-N multilayers

We fabricated Ni/Ti and Ni-N/Ti-N multilayers structures containing N mirrors use as a grazing-incident angle reflector to focus x-ray micro-beams. The multilayer structures were fabricated by magnetron sputtering. The layer structures were evaluated by using an x-ray diffractometer and the soft x-ray reflectivities were measured at Beamline 6.3.2 at the Advanced Light Source (ALS). Although the Ni/Ti multilayer has a high interface roughness of about 1.36 nm, the soft-x-ray peak reflectivity of this mirror showed fairly high reflectivity of 39%, at just above the Ti-absorption edge with a 9-degree incident angle. The peak reflectivity of Ni-N/Ti-N multilayer mirrors was 36% in almost the same conditions as the reflectivity measurement of the Ni/Ti multilayer.