A study on the preparation and characteristics of zeolite membrane PLOT column by in-situ synthesis

Summary The preparation of a zeolite membrane PLOT column by in-situ synthesis is described. The advantages of this new column are discussed. Some analytical applications to alkanes, arenes, esters, alkyl halides and ethers on the zeolite membrane PLOT column compared with those on a coated zeolite PLOT column are reported.     

Palladium-catalyzed stereospecific 1,4-hydrogen migration of cis-cyclohex-2-en-1,4-diol systems

It has been revealed that the generation of 2-cyclohexenones from cis-1,4-dihydroxycyclohexene derivatives under PdCl₂(PPh₃)₂-HCO₂NH₄ system takes place in an intramolecular pathway involving unprecedented mode of suprafacial 1,4-hydrogen migration across the 1,4-allylic centers.     

An unusual structure of the hydrated sodium chloride complex of cryptand [2.2.2]

The solid state structure of the Na[2.2.2]C1 · 3H₂O complex has the sodium ion displaced towards one of the cryptand nitrogens and the chloride and water molecules associated by hydrogen bonds to form a pseudo cube with two chloride ions at opposite corners of the cube and water oxygens at the other six corners.     

Study of kinetics and mechanism of the acid dissociation of copper(II) complex of novel C-functionalized macrocyclic dioxotetraamines

The kinetics of the acid dissociation of copper(II) complexes of novel C-functionalized macrocyclic dioxotetraamines has been studied by means of a stopped-flow spectrophotometer. The acid dissociation rate follows the law V_d = C_comkK₁K₂H ²/(1+K₁H+K₁K₂H ²). From the experimental facts we have obtained, the dissociation kinetics are interpreted by a mechanism involving the negatively charged carbonyl oxygen of the complex being rapidly protonated in a pre-equilibrium step, the rate-determining step being intramolecular hydrogen (enolic tautomer) migration (to imine nitrogen). The dissociation rate reached a plateau in the strongly acidic solution. By means of temperature coefficient method, ΔH ^φ, ΔS ^φ of the pre-equilibrium step and ΔH ^≠, ΔS^≠ of the rate-determining step were obtained. The results of 13-membered macrocyclic dioxotetraamines have been discussed. The influence of the substituents to the acid dissociation rates has also been discussed. The Bronsted type linear free energy relationships do also exist in these C-functionalized dioxotetraamine copper(II) complexes.     

A SMOOTH C1 INTERPOLATION FOR TWO-DIMENSIONAL CONTACT PROBLEMS USING PARAMETRIC CURVE TECHNIQUE

A smooth C1 interpolation for two-dimensional contact problems using paxametric curve technique was developed and implemented. The parametric curve can ensure C1 continuity of the contact surfaces and provide a unique surface normal vector. Some numerical examples were used to illustrate the advantages of the newly developed representation of contact surface. The results reveal a significant improvement in the prediction of contact stresses and contactarea. The predicted contact stresses are less sensitive to the mismatch in meshes of the different contacting bodies.     

Separation and determination of 10-hydroxy-2-decenoic acid in royal jelly by capillary electrophoresis

Summary The application of capillary electrophoresis (CE) to the separation and determination of the active ingredient, 10-hydroxy-2-decenoic acid, in royal jelly with direct on-column UV detection at 214 nm is described. Using a cathodic injection and anodic detection scheme, 10-hydroxy-2-decenoic acid (10-HDA) was separated and detected in less than 10 min in a fused silica capillary column with a phosphate buffer at pH 7.3 with an applied voltage of 20 KV followed by direct UV detection. The use of cetyltrimethylammonium bromide (CTAB) as electroosmotic flow modifier allows the rapid separation of 10-HDA from other constituents in royal jelly by reversing the direction of electroosmotic flow. The influence of organic solvents in the electrolyte on separation selectivity is also discussed.     

High-power harmonic gyro-TWT's. II. Nonlinear theory and design

For pt.I, see ibid., vol.20, no.3, p.155-162 (1992). Based on an analytical study of the stability problems of gyrotron traveling wave amplifiers (gyro-TWTs), an extremely high power second-harmonic gyro-TWT has been designed, evaluated and optimized with a self-consistent nonlinear numerical simulation code. The design, which is based on the magnetron-injection-gun (MIG)-type beam, is presented. Using a 100 kV, 25 A MIG beam with α=1 and an axial velocity spread of 5%, nonlinear self-consistent analysis of a three-stage second-harmonic gyro-TWT amplifier predicts a peak output power of 533 kW, peak efficiency of 21.3% and a 7.4% saturated bandwidth, which verifies the theoretical predictions that a stable harmonic gyro-TWT can generate power levels an order of magnitude higher than those possible from a fundamental gyro-TWT. It is shown that the positioning of the electron beam is very important. A multistage structure is used to recover the loss in gain resulting from shortening the interaction sections to ensure stability     

Facile formation of water-insoluble cyclodextrin/Nafion composite films on solid surfaces

The water-insoluble poly-beta-cyclodextrin (poly-CD)/Nafion composite film was easily prepared by casting a mixed solution of poly-CD and Nafion onto substrate plates. FT-IR measurements showed that the 50/50 wt% poly-CD/Nafion composite film remained stable on the glass and quartz substrates after immersion in water for more than 3 h, while a pure poly-CD film was almost completely dissolved by immersion within 1 h. The film stability was also evaluated from the amount of p-nitrophenol (p-NP) inclusion in the film, which was determined from the decrease in UV-vis absorbance of the p-NP solution into which the film was immersed. The composition dependence of the inclusion amount showed that the film was stable up to 50 wt% CD, but became less stable with further increase in the CD concentration in the film. From the isotherms for the inclusion of p-NP and 1-naphthoate (1-Naph) into the film, the inclusion (stability) constants were determined to be 3.7x10(3) M(-1) and 1.9x10(2) M(-1), respectively. These results show that the selective inclusion of CD is retained after preparation of the composite film.