Hydrogen adsorption on silicalite in the presence of water and benzene

¹H NMR techniques in the temperature range 200–280 K under isobaric conditions are used to investigate concurrent adsorption of hydrogen and water in the pores of silicalite, a microporous silica. The possibility for a small (up to a few weight percent) quantity of water to exist in the pores is demonstrated. Water is found to exist in the form of two types of cluster structures differing in the degree of water association. A conclusion about the stabilization of the weakly associated form by weakly polar organic molecules is made. Water is shown to promote the hydrogen adsorption process; when its concentration is c _H2O = 2 wt %, adsorption increases more than twofold. A suggestion that this effect is caused by the formation of water-hydrogen cluster structures in the pores is made.     

Lifting up an infinite chain of prime ideals to a valuation ring

We prove that for an arbitrary chain of prime ideals in an integral domain, there exists a valuation domain which has a chain of prime ideals lying over .

     

[2 + 3]-Cycloadditions to C60 fullerene. Synthesis of pyrrolidinofullerenes

Pyrrolidinofullerenes were synthesized by reaction of C₆₀ fullerene with N-methylglycine and substituted aromatic aldehydes.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1695–1697.Original Russian Text Copyright © 2004 by Loginova, Gunkin.This revised version was published online in April 2005 with a corrected cover date.     

Adsorption of cinnamic and caffeic acids on the surface of highly dispersed silica from different solvents

The adsorption of cinnamic and caffeic acids on initial and partially silylated highly dispersed silica A-300 from polar (water-ethanol solution), low polar (chloroform and dichloroethane), and apolar (hexane and carbon tetrachloride) solvents is investigated. The dependence of adsorption on solvent polarity is established. It is disclosed that the dependences of the adsorption of cinnamic and caffeic acids on the degree of surface hydrophobization have different characters.     

Curing reaction of o-cresol novolac epoxy resin according to hardener change

The investigations of cure kinetics and glass transition temperature (T_g) versus reaction conversion (α) of o-cresol novolac epoxy resin with the change of hardener were performed. All kinetic parameters of the curing reaction such as the reaction rate order, activation energy, and frequency factor were calculated. The curing mechanisms were classified into two types. One was an autocatalytic mechanism and the other was a nth order kinetic mechanism. The constants related to the chain mobility of polymer segments were obtained by using the DiBenedetto equation. We have tried to correlate the relationships between curing mechanism and molecular structures of hardeners from these results. © 1993 John Wiley & Sons, Inc.     

Odd-even behavior of ferroelectricity and antiferroelectricity in two homologous series of bent-core mesogens

Two chiral bent-core mesogens Pn-O-PIMB(n - 2)* (n = 9 and 10) and their oxygen analogues Pn-O-PIMB(n - 2)*-(n - 4)O (n = 8, 9, and 10) with omega-[(S)-amyloxy]alkoxy terminal groups were prepared, and their phase structures were investigated by means of electro-optic, polarization reversal current and second harmonic generation measurements in order to clarify the effect of the interlayer steric interaction on the emergence of polar orderings. The odd-even behavior for the alternative appearance of ferroelectricity and antiferroelectricity was observed in two homologous series; the bent-core mesogens P10-O-PIMB8*, P8-O-PIMB6*-4O, and P10-O-PIMB8*-6O in addition to the previously reported P6-O-PIMB4* and P8-O-PIMB6*, where the length of chains n is even, exhibited ferroelectric phases. On the contrary, the mesogens P7-O-PIMB5*, P9-O-PIMB7*, and P9-O-PIMB7*-5O, where n is odd, showed antiferroelectric phases. It is obvious that the interlayer steric interaction plays a major role for the emergence of a variety of phase structures.     

Complex polarizability as used to analyze dielectric relaxation measurements

The effect of representing dielectric properties in terms of the complex polarizability ^c = – i is examined. Loss curves ( and tan ) are shifted towards higher frequencies, revealing the existence of new relaxations and allowing the clarifications of ones already known. We have calculated the shift ratios (at maximum or tan )/ (at maximum or tan ) from the more conventional empirical equations representing the dielectric behavior. Some examples are given.     

Multiple melting endotherms in isothermally melt-crystallized poly(butylene terephthalate)

The melting behavior of poly(butylene terephthalate) crystallized isothermally for various times was examined using differential scanning calorimetry. After short crystallization times, the DSC analysis gave two melting peaks, but after longer times, the analysis gave three peaks. The latter triplet of DSC peaks can be denoted as low, middle, and high, starting with the lowest temperature endotherm. The DSC peaks were simulated using a measured recrystallization rate and behavior for PBT and an assumed initial melting point distribution. The low and middle peaks represent the original melting peaks arising from isothermal crystallization. The high melting peak arises from recrystallization during the DSC heating scan. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1757–1767, 1998     

Aggregation of fullerence C60 in o-dichlorobenzene

Aggregation of C₆₀ fullerene in o-phenyl dichloride was studies by the spectrophotometry method.