Electron paramagnetic resonance imaging using magnetic-field-gradient spinning

A novel X-band CW EPR imaging has been developed using magnetic-field-gradient (MFG) spinning to obtain spatial distributions of electron paramagnetic species. Spinning MFG EPR imaging for 65 projection spectra required just 55 s while conventional imaging took 11 min 40 s, that is, the acquisition time for the new system is one order of magnitude shorter than that for conventional EPR imaging. Spinning MFG EPR imaging allows one to measure reconstructed images in an interactive manner where resolution and condition can be changed quickly.     

ESR study of amorphous Ge-S and Ge-S-Ag in bulk and film forms

The assignment of ESR signals in Ge-S glasses to certain types of defect has been proposed. The origin of the signal is two types of Ge dangling bond for GeS_x bulks with x < 2, and is two types of S dangling bond for those with x > 2. In the film sample with x > 2, the ESR center density is largely enhanced, and Ge dangling bonds exist in addition to S dangling bonds. The decrease of the ESR center density by Ag doping is explained by the reduction of randomness in the glass structure.     

In situ observation of photoinduced refractive-index changes in filaments formed in glasses by femtosecond laser pulses

We investigated the relationship between the formation of filaments and local refractive-index changes induced by femtosecond laser pulses in silica glass. In situ observation revealed that the location of a filament coincided with that of the refractive-index change. Observation also showed that the region of refractive-index change was elongated toward the upstream direction of the laser pulses with increasing exposure time. The region of refractive-index change was several hundred micrometers long, and its diameter was smaller than 2 mum. The refractive-index change was confirmed by two of three different methods to be as large as 0.8 x 10(-2).     

Pushing exercise program to correct glottal incompetence

A voice therapy program using pushing exercises to correct glottal incompetence is described. The program utilizes various types of instrumentation to determine whether or not a given patient is likely to benefit from the treatment. The program also provides feedback of target voices. Three cases with incomplete glottal closure and subsequent vocal dysphonia characterized by an asthenic breathy quality are used to illustrate the program. Details of the program, termination criteria, and problems and precautions learned from treating 29 patients over a 3-year period are presented.     

Estimation of the Refractive Index Change in Glass Induced by Femtosecond Laser Pulses

It is known that local refractive index change occurs when femtosecond laser pulses with extremely high peak power are launched into glass. We focused 130-femtosecond laser pulses of 800 nm into the bulk of glass and examined the shape of the induced refractive index change. We found that the length of the spot of the refractive index change along the optical axis reached about 30 μm despite the diameter being about 2 μm. To estimate the distribution of induced refractive index change, we fabricated Bragg grating by scanning the focused spot and calculated the amount of the change by applying Kogelnik’s coupled mode theory to the measured diffraction efficiencies of the higher order diffracted beams.     

Dielectric constants of adsorbed CO on Cu and Ag

Adsorption of CO on evaporated Ag and Cu films was studied by ellipsometry and resistivity measurements. Changes in ellipsometric angles δΔ and δψ due to adsorption of CO were analyzed by an improved linear approximation of the stratified layer model of adsorption. Adsorption of CO on Cu induced a 23% increase in the relative resistivity change (δR/R) which was proportional to δψ, while adsorption of CO on Ag induced a 1% increase without the proportionality. The dielectric constant of CO adsorbed on Ag is $\text{?}{}_1\text{= 2.2?0.7i}$ at λ = 1152 nm in comparison to ?₁ = 2.1 for gas phase CO; that of CO on Cu is $\text{?}{}_1\text{= ?4.8 ? 8.5i}$, which is consistent with the prediction by the Bennett and Penn theory. The large difference in $\text{}\text{?}$ge₁, of adsorbed CO on Ag and Cu is understood in terms of the energy level of the 2 π molecular orbital of adsorbed CO relative to the Fermi level. A possibility of adlayer plasmon excitation is discussed.     

High-quality InAlN/GaN heterostructures grown by metal–organic vapor phase epitaxy

We fabricated high-quality InAlN/GaN heterostructures by metal–organic vapor phase epitaxy (MOVPE). X-ray diffraction measurements revealed that InAlN/GaN heterostructures grown under optimal conditions have flat surfaces and abrupt heterointerfaces. Electron mobility from 1200 to 2000 cm²/V s was obtained at room temperature. To our knowledge, this mobility is the highest ever reported for InAlN/GaN heterostructures. We also investigated the relationship between the Al composition and sheet electron density (N_s) for the first time. N_s increased from 1.0×10¹² to 2.7×10¹³ cm⁻² when the Al composition increased from 0.78 to 0.89.     

High-spin isomers in Rn in the region of triple neutron core-excitations

The level scheme of ²¹²Rn has been extended to spins of ∼38?$\sim 38?$ and excitation energies of about 13 MeV using the ²⁰⁴Hg(¹³C, 5n)²¹²Rn reaction and γ-ray spectroscopy. Time correlated techniques have been used to obtain sensitivity to weak transitions and channel selectivity. The excitation energy of the 22⁺ core-excited isomer has been established at 6174 keV. Two isomers with τ=25(2) ns$\tau =25(2)\text{ns}$ and τ=12(2) ns$\tau =12(2)\text{ns}$ are identified at 12211 and 12548 keV, respectively. These are the highest-spin nuclear isomers now known, and are attributed to configurations involving triple neutron core-excitations coupled to the aligned valence protons. Semi-empirical shell-model calculations can account for most states observed, but with significant energy discrepancies for some configurations.     

Biosynthesis of Indole Diterpene Lolitrems: Radical-Induced Cyclization of an Epoxyalcohol Affording a Characteristic Lolitremane Skeleton

Lolitrems are tremorgenic indole diterpenes that exhibit a unique 5/6 bicyclic system of the indole moiety. Although genetic analysis has indicated that the prenyltransferase LtmE and the cytochrome P450 LtmJ are involved in the construction of this unique structure, the detailed mechanism remains to be elucidated. Herein, we report the reconstitution of the biosynthetic pathway for lolitrems employing a recently established genome-editing technique for the expression host Aspergillus oryzae. Heterologous expression and bioconversion of the various intermediates revealed that LtmJ catalyzes multistep oxidation to furnish the lolitrem core. We also isolated the key reaction intermediate with an epoxyalcohol moiety. This observation allowed us to establish the mechanism of radical-induced cyclization, which was firmly supported by density functional theory calculations and a model experiment with a synthetic analogue.     

The control of very low oxygen partial pressures with stabilized zirconia cell

Control of very low oxygen partial pressures was performed in the range of 10⁻²¹-10⁻²⁴ Pa at 750°C by pumping oxygen into the purified hydrogen stream with a stabilized zirconia cell. The oxygen partial pressures were monitored by a stabilized zirconia sensor. The stabilized zirconia oxygen sensor was calibrated by H₂-CO₂ gas buffer mixture in the range of oxygen pressure from 10⁻¹⁷ to 10⁻²¹ Pa, and oxygen partial pressures below 10⁻²¹ Pa were measured by extrapolating the calibration line to very low oxygen partial pressures. The lowest oxygen partial pressure controlled was 10⁻²⁴ Pa at 750°C, which was limited by gas leaks in the system and also by the reduction of the ionic transference number in solid electrolyte used as the oxygen pump.