Continuous chemoselective methylation of functionalized amines and diols with supercritical methanol over solid acid and acid-base bifunctional catalysts

The selective N-methylation of bifunctionalized amines with supercritical methanol (scCH(3)OH) promoted by the conventional solid acids (H-mordenite, beta-zeolite, amorphous silica-alumina) and acid-base bifunctional catalysts (Cs-P-Si mixed oxide and gamma-alumina) was investigated in a continuous-flow, fixed-bed reactor. The use of scCH(3)OH in the reaction of 2-aminoethanol with methanol (amine/CH(3)OH = 1/10.8) over the solid catalysts led to a significant improvement in the chemoselectivity of the N-methylation. Among the catalysts examined, the Cs-P-Si mixed oxide provided the most efficient catalyst performance in terms of selectivity and reactivity at 300 degrees C and 8.2 MPa; the N-methylation selectivity in the products reaching up to 94% at 86% conversion. The present selective methylation was successfully applied to the synthesis of N-methylated amino alcohols and diamines as well as O-methylated ethylene glycol. Noticeably, ethoxyethylamine was less reactive, suggesting that the hydroxy group of the amino alcohols is a crucial structural factor in determining high reactivity and selectivity, possibly because of the tethering effect of another terminus, a hydroxo group, to the catalyst surface. The magic-angle-spinning NMR spectroscopy and X-ray diffraction analysis of the Cs-P-Si mixed oxide catalyst revealed that the acidic and basic sites originate from P(2)O(5)/SiO(2) and Cs/SiO(2), respectively, and the weak acid-base paired sites are attributed to three kinds of cesium phosphates on SiO(2). The weak acid-base sites on the catalyst surface might be responsible for the selective dehydrative methylation.     

Observation of electrostatically released DNA from gold electrodes with controlled threshold voltages

DNA oligo-nucleotides, localized at Au metal electrodes in aqueous solution, are found to be released when applying a negative bias voltage to the electrode. The release was confirmed by monitoring the intensity of the fluorescence of cyanine dyes (Cy3) linked to the 5' end of the DNA. The threshold voltage of the release changes depending on the kind of linker added to the DNA 3'-terminal. The amount of released DNA depends on the duration of the voltage pulse. Using this technique, we can retain DNA at Au electrodes or Au needles, and release the desired amount of DNA at a precise location in a target. The results suggest that DNA injection into living cells is possible with this method.     

Dual-axes confocal microscopy with post-objective scanning and low-coherence heterodyne detection

We present a dual-axes confocal microscope that employs postobjective scanning and low-coherence heterodyne detection to collect vertical cross-sectional images from biological tissue with high axial resolution, reduced noise from scattered light, deep tissue penetration, and a large dynamic range. This architecture can be scaled down to millimeter dimensions with microelectromechanical systems technology for performance of in vivo optical biopsy.     

Beam-polarization asymmetries for the p(gamma-->, K+)Lambda and p(gamma-->, K+)Sigma(0) reactions for E(gamma)=1.5-2.4 GeV

Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6相似文献   

Diastereoselective photochromism of a bisbenzothienylethene governed by steric as well as electronic interactions

Introduction of an asymmetric center to C-2 of one of the benzothiophene rings of bisbenzothienylperfluorocyclopentene results in a highly diastereoselective photochromic system. The stereogenic center bears a hydrogen atom, a methyl group, and a methoxymethoxy group. The steric as well as the electronic repulsions gave an 87-88% diastereomer excess in various solvents at room temperature with 80-85% conversion to the colored form. The enantioselective synthesis was also carried out. Upon photoirradiation in hexane, a change in optical rotation at 820 nm, where neither the open form nor the colored form absorbs light, was observed repeatedly.     

Focusing in microlenses close to a wavelength in diameter

Light focused from air into a spherical microlens is affected by diffraction at the lens surface as its diameter approaches the wavelength of light. Through an extension of Mie theory, we show that a converging wave that is incident upon a Si microlens with a diameter less than approximately 4lambda creates a spot as much as 25% smaller than predicted with vector diffraction theory. Si microlenses only a wavelength in diameter are shown to be virtually insensitive to variations in the maximum illumination angle, and changes in index of refraction are not found to cause the proportional changes in spot size that would be expected from vector diffraction theory.     

Time-Dependent Coupled-Channel Calculations of Muon-Transfer Cross Sections in Muonic Deuterium and Triton Collisions

A time-dependent coupled channel (TDCC) method has been developed to study rearrangement reactions in few-body Coulomb systems. We apply the TDCC method to muon transfer in muonic deuterium and triton collisions. The muon-transfer cross section (S-wave) is calculated for triton energies of 100 eV–3 keV. The present result is in good agreement with the previous calculation with the coupled rearrangement channel method [Hyp. Interact. 82 (1993), 45]. We also illustrate time evolution of wave functions to understand qualitatively the muon-transfer reaction.     

Validity of retinal oxygen saturation analysis: Hyperspectral imaging in visible wavelength with fundus camera and liquid crystal wavelength tunable filter

The purpose of this paper was to investigate the feasibility of a newly developed hyperspectral fundus imaging camera with a liquid crystal tunable filter. The intensities of different wavelengths of light transmitted through an artery, vein, and the area surrounding these vessels and reflected out were measured, and the differential spectral absorptions were analyzed. Measurements were made from 16 normal eyes and from two artificial capillaries. The ratios of absorption (ROA) of arteries to veins from 500 to 580 nm (range 1) and from 600 to 720 nm (range 2) were calculated. For all eyes, the ROA_range1 was larger than ROA_range2. The ROA obtained from the artificial capillary filled with blood saturated with oxygen or nitrogen was similar to that of simulated data of oxy- and deoxyhemoglobin extinction rate. Most ROAs of human eyes were lower than those of the simulated data and the artificial capillaries. Oxygen saturation analysis by hyperspectral fundus imaging of retinal vessels were qualitatively in agreement with thein vitro analysis or simulated values. However, further improvements are necessary to evaluate the oxygen saturation quantitatively in the retinal blood vessels.     

Intramolecular conjugate addition of γ- and δ-trichloroacetimidoyloxy-α,β-unsaturated esters in an acyclic system

An intramolecular conjugate addition of γ- and δ-trichloroacetimidoyloxy-α,β-unsaturated esters, a new way to construct 1,2-amino or 1,3-amino alcohol moieties in an acyclic system, is described. Very concise synthesis of d-vancosamine and 3-epi-d-vancosamine derivatives was also achieved utilizing this methodology.     

On generalized poly-Bernoulli numbers and related L-functions

Different two generalizations of the Dirichlet L-functions which are based on the construction of Arakawa–Kaneko?s zeta function are treated. Further special values at non-positive integers of such functions are evaluated and generalized poly-Bernoulli numbers are introduced via those values.