Lewis Acid Mediated Addition of Tri-n-Butylstannylmethylisoxazole with Aldehydes

Lewis acid mediated addition of 5-(tri-n-butylstannyl)methyl-3-methylisoxazole and its analogues with aldehydes have been carried out. Corresponding 5-(β-hydroxy)ethylisoxazoles were obtained in moderate yields, without ring opening of the isoxazole.     

On the Curvature of the Free Boundary for the Obstacle Problem in Two Dimensions

We give a new proof of the fact that the free boundary for the obstacle problem in two dimensions satisfies a natural and sharp inner ball condition.     

M-Mode Color Doppler Ultrasonic Imaging of Vertical Tongue Movement During Articulatory Movement

To observe and estimate the movement of the tongue, ultrasonic investigation is the most harmless real-time monitoring procedure for analyzing articulatory movements. Color Doppler ultrasonic imaging is special in that it can only sample a moving target, and it can indicate the velocity and direction of the target by color and brightness in real time. This study assessed and demonstrated the validity of M-mode color Doppler ultrasonic imaging to observe the movements of the tongue during syllable repetition tasks performed by normal subjects and dysarthric patients, those affected by amyotrophic lateral sclerosis, cerebellar ataxia, Parkinsonism, and polymyopathy. When the transducer was set below the jaw, upward movement was indicated by a blue signal and downward movement was indicated by a red one on the screen of the ultrasound machine. We also measured the velocity of the tongue by contrast scale classified by 15 degrees. Thus, we could observe vertical tongue movement by a color-coded pattern after quantitative analysis. The Doppler signal patterns of normal subjects were verified by simultaneous video x-ray fluorography recordings. The findings for dysarthric patients corresponded well with previously reported features analyzed by other methods. Therefore, color Doppler ultrasonic imaging of the tongue is a useful procedure to researchers for clinical speech and voice studies.     

Once-holed tori embedded in Riemann surfaces

Once-holed tori are the most primitive noncompact Riemann surfaces of positive genus, and consitute a partially ordered set, the order being defined in terms of conforaml embeddings. We consider some families of once-holed tori that are conformally embedded in target Riemann surfaces of conformal mappings of a given noncompact Riemann surface of genus one, and establish an analogue of the one-quarter theorem of Koebe. We also investigate families of once-holed tori conformally embedded in a Riemann surface of positive genus.      

Acute toxicity and metabolism of arsenocholine in mice

The acute toxicity of arsenocholine was examined in mice by oral administration and intravenous injection. The LD₅₀ values of arsenocholine were 6.5 g kg^?1 for oral administration and 187 mg kg^?1 for oral administration and 187 mg kg^?1 for intravenous injection. Decreases of respiration and spontaneous motility were observed in the mice dosed orally at 12 g kg^?1. The animals exhibited ataxia and finally showed paralysis of the hind legs within 20 min of administration. When arsenocholine was administered orally to mice at 5 or 50 mg As kg^?1, the greater part of the arsenic administered was recovered in urine within 96 h. The metabolite of arsenocholine in urine was identified as arsenobetaine by high-performance liquid chromatography-inductively coupled plasma emission spectrometry (HPLC ICP) and fast atom bombardment mass spectrometry (FAB MS). These results suggested that the major part of orally administered arsenocholine was absorbed from the gastrointestinal tract in mice and then rapidly excreted in urine with biotransformation.     

Far-infrared spectroscopy by synchrotron radiation at the UVSOR Facility

At the UVSOR Facility, Institute for Molecular Science, the practical use of the synchrotron radiation as a far-infrared light source has started. A spectroscopic system has been constructed at the beam line BL6A1 of UVSOR storage ring, which covers the wavenumber region from 5 to 250 cm^–1. The cross sectional diameter of the light beam at the sample position is as small as 3 mm with the angular divergence of about 100 mrad. The system has been made mainly for the transmission and reflection measurements of small samples with small angular divergence by the use of the high brightness of the synchrotron radiation. Examples of observed transmission and reflectivity spectra are shown.     

Photodissociation of multilayered trimethylaluminum adsorbed on a cryogenic substrate: A time-of-flight mass-spectrometric study

Photodissociation of trimethylaluminum [Al(CH₃)₃] adsorbed on a silica (SiO₂) substrate at 110 K has been studied by multiphoton ionization time-of-flight mass spectrometry. Translational energy distributions of aluminum and AlCH₃ fragments can be fitted with a composition of two Maxwell–Boltzmann distributions. The two components are attributed to different environments of photodissociating parent molecules in the multilayer.     

Preparation and characterization of Co–Pt bimetallic magnetic nanoparticles

CoPt₃ nanoparticles are synthesized by a two-stage route using NaBH₄ as a reductant. The nanoparticles are characterized by thermogravimetry (TG) and differential thermal analysis (DTA), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Structural and spectroscopic studies show that the nanoparticles adopt a face-centered-cubic (FCC) crystalline structure with an average particle size of 2.6 nm. SQUID studies reveal that as-synthesized nanoparticles are superparamagnetic at room temperature and ferromagnetic at 1.85 K with coercivity of 980 Oe. Annealing of the samples at 500 °C causes an increase of particle size and a decrease of coercivity.     

Photodissociation and geminate dynamics in solution phase: Picosecond transient absorption studies of tetraphenylhydrazines and diphenyl disulfides

Photodissociation of aromatic molecules and the following geminate dynamics of the photochemically produced fragment radical pair in liquid phase are discussed in relation to the results of ultrafast transient absorption measurements. Photodissociation of tetraphenylhydrazine occurs from the unequilibrated excited singlet state competing with the relaxation to the fluorescence state. In addition to the rapid fragmentation, the N?N bond rupture is clearly demonstrated to take place in the fluorescence state of tetraphenyl-and tetratolyl-hydrazine in tens of picoseconds time scale. In the case of di-p-aminophenyl disulfide in nonpolar solvents, geminate recombination of the p-aminophenylthiyl radical and the formation of the radical dimer were observed in tens of picoseconds. The observed slow geminate recombination can be explained by the repulsion between the large dipole of the fragment radical preventing the reformation of the S?S bond and by the restricted conformation required for the dimer formation at the encounter of radicals.