Characterization of zeolite NaA membrane by FTIR-ATR and its application to the rapid evaluation of dehydration performance.

A zeolite NaA (LTA) membrane supported by an alumina porous support tube was characterized by Fourier Transform Infrared Attenuated Total Reflectance method (FTIR-ATR) with a diamond prism as the waveguide. A method using the FTIR-ATR was developed to estimate rapidly the EtOH/H2O pervaporation (PV) performance of the membrane. The Si-O asymmetric stretching vibration region of LTA membrane spectra synthesized hydrothermally on seeded alumina substrates showed a bimodal peak (830 - 1200 cm(-1)). The two peaks were assigned to a surface LTA directly derived from the seed crystal (1012 cm(-1)), and to LTA and/or amorphous substances embedded in the alumina porous support (930 cm(-1)). The spectrum from LTA membrane synthesized on nonseeded alumina substrate, however, showed a single broad peak similar to the powder-formed one. These results indicate that the Si-O spectral shape of the LTA membrane is influenced strongly by the synthesis method. Also, the FTIR-ATR of the LTA membrane can detect the Si-O peaks as part of the depth information. It was first shown that the relative ratio (930 cm(-1)/1012 cm(-1)) of the two Si-O peaks from the LTA membranes on seeded alumina substrates closely relates to the water selectivity (alpha) in the PV of EtOH/H2O mixture; the alpha increases exponentially with the peak ratio. This result suggests that the differences in the vertical distribution of LTA crystal and amorphous material strongly affect the dehydration performance in the EtOH/H2O PV, that is, the amorphous-like material embedded in the alumina porous support plays an important role. The relative peak ratio measurement can be used for the rapid evaluation of the dehydration performance of the membrane.     

Optimization of double plasma jet torches in a scramjet combustor

Ignition tests by double plasma jet (PJ) torches in a supersonic flow were conducted. Two PJ torches with different feedstocks were arranged in a straight line in the direction of flow. The Mach number of the airflow was 2.3, and the total temperature and total pressure of the main flow were those of room conditions. A C₂H₄ fuel perpendicularly injected with its sonic speed into the main flow was tested. A combination of O₂–O₂ feedstocks for the two torches was more effective than other combinations such as H₂/N₂–O₂. Moreover, the effectiveness of the double PJs was found to be almost the same as that of a single PJ. These results indicate that combustion reactions of the main fuel injected upstream of the PJ were mostly completed in the vicinity of the upstream PJ. The upstream PJ was considered to be dominant for ignition and the combustion process, indicating that the influence of the downstream PJ was small. On the other hand, the advantage of the double PJs over the single PJ in reducing damage to the torch nozzle was confirmed.     

Disorder in GeSe2 small crystals and medium-range structure in amorphous GeSe2

The Raman scattering spectra of various forms of GeSe₂, such as amorphous films, single crystals, and small crystals prepared by a gas-evaporation deposition technique, are investigated with an excitation photon energy ranging from 2.1 to 2.8 eV. In the spectra of the crystals, there are two Raman bands, originating from two types of breathing vibrations of the GeSe_4/2 tetrahedra: one is spread over the corner-sharing tetrahedra and the other is quasi-localized on the edge-sharing tetrahedra. In addition to the resonant Raman scattering related to the edge-sharing tetrahedra through the exciton transition observed with 2.71 eV excitation in the single crystals, a new resonant spectrum is found only in the small crystals with 2.54 eV excitation. With increasing disorder in the crystals, the intensity ratio between the two breathing vibration bands increases in the off-resonant excitation region. The Raman spectra in the amorphous states are ascribed to the breathing vibrations of GeSe_4/2 tetrahedra which form a medium-range structure topologically similar to that of crystalline fragments.     

Solvent‐Slaved Protein Motions Accompany Proton but Not Hydride Tunneling in Light‐Activated Protochlorophyllide Oxidoreductase

H ⁺ but not H ^? : The reduction reaction of protochlorophyllide catalyzed by protochlorophyllide oxidoreductase features solvent‐slaved motions that control the proton‐ but not the hydride‐tunneling mechanism. These motions imply a long‐range dynamic network from the solvent to the enzyme active site that facilitate proton transfer (see picture, left). Motions for hydride transfer are more localized and are not slaved by the solvent (see picture, right).

     

Polarized ethylenes. IV. Synthesis of polarized ethylenes using thioamides and methyl dithiocarboxylates and their application to syntheses of pyrazoles,pyrimidines, pyrazolo[3,4-d]pyrimidines,and 5-aza[2.2.3]cyclazines

Polarized ethylenes having both electron-donating (an amino or a methylthio group) and electron-accepting (cyano, carbamoyl, methyl ester) groups on the adjacent two olefinic carbon atoms were prepared by the condensation of S-alkylthioamidinium salts or methyl dithiocarboxylates with the corresponding active methylene compounds in good yields. These polarized ethylenes were alternatively synthesized by the reaction of thioamides or methyl dithiocarboxylates with tetracyanoethylene oxide in good yields. Reactions of these polarized ethylenes with hydrazine or guanidine derivatives occurred smoothly to give the corresponding pyrazole and pyrimidine derivatives in good yields. The synthesis of 5-aza[2.2.3]cyclazine derivatives using polarized ethylenes is also described.     

Bacopasides III-V: three new triterpenoid glycosides from Bacopa monniera

Three new saponins, designated as bacopasides III, IV and V have been isolated from Bacopa monniera WETTST. and their structures have been elucidated as 3-O-alpha-L-arabinofuranosyl (1-->2)-beta-D-glucopyranosyl jujubogenin (1), 3-O-beta-D-glucopyranosyl (1-->3)-alpha-L-arabinopyranosyl jujubogenin (2) and 3-O-beta-D-glucopyranosyl (1-->3)-alpha-L-arabinopyranosyl pseudojujubogenin (3) mainly on the basis of two dimensional (2D) NMR and other spectral analyses.     

Color Appearance of a Patch Explained by RVSI for the Conditions of Various Colors of Room Illumination and of Various Luminance Levels of the Patch

Whenever we enter a space illuminated differently from a previous space whether in color or in illuminance, we can quickly adapt to the new atmosphere and can again perceive white for the originally white object; this is known as color constancy. This phenomenon is explained by rotation of the recognition axis of the recognized visual space of illumination (RVSI) toward the illumination color. The explanation then predicts that the color appearance of a test patch changes radically toward the opposite direction from the color of illumination when the physical property of the test patch is kept unchanged at a neutral white. This prediction was confirmed by Experiment 1, where eight different colors of illumination were employed. The test patch appeared very vivid in color and shifted toward the opposite direction from the color of the illumination. In RVSI theory the light source color mode is explained by the release of the test patch from the restriction of RVSI. The release can be achieved by increasing the luminance of the test patch and the color appearance of the patch should then return to its own color as it is no longer controlled by RVSI. In Experiment 2 these predictions were investigated by increasing the luminance of the test patch to a much higher level than that of the objects in the lit room fixed at an illuminance of about 1001x. The color appearance of the test patch indeed became the light source color and returned to the original neutral white. Emphasis was given in the course of the experiments that the subjects were observing the test patch presented in a real 3D space where the subjects also stayed inside so that they could properly construct RVSI for the space.