New water-soluble polymers and copolymers by interaction of polyelectrolytes with formamide

Viscometric measurements on aqueous solutions of the strongly acidic polyelectrolyte, poly(2-acrylamido, 2-methyl propane sulphonic acid) (PAS), have shown the necessity to include salt at a very high concentration in order to screen the charges. PAS was found to dissolve in formamide, but the properties of the isolated polymer demonstrated the occurrence of chemical changes during the dissolution process. Several procedures proved the conversion of sulphonic acid moieties to sulphonamide groups to an extent depending on the time and temperature of dissolution. At elevated temperature and extended times dissolution afforded complete conversion, i.e., a solution in formamide of a new neutral polymer, poly(2-acrylamido, 2-methyl propane sulphonamide) (PASAM), which does not require the inclusion of salts. By light scattering, the degree of polymerization of this PASAM was shown to be the same as that of the original PAS. The viscometric behavior of the PASAM in salt-free water was that of a neutral polymer. Similar tests on the dissolution of the weakly acidic polyelectrolyte, poly(acrylic acid) (PAA) in formamide also showed the occurrence of amidation, but even after extended times PAA is not converted completely to polyacrylamide. © 1992 John Wiley & Sons, Inc.     

Time-Resolved Electron Paramagnetic Resonance Study of Photoionization of Tyrosine Anion in Aqueous Solution

Abstract— Photoionization of the amino acid tyrosine in basic water was studied by time-resolved electron paramagnetic resonance (TREPR) at X-band (9.5 GHz). Photoionization of deprotonated tyrosine leads to a spin-polarized emissive/absorptive chemically induced dynamic electron polarization (CIDEP) spectrum produced by the radical pair mechanism, with the tyrosyl radical in emission and the solvated electron in absorption, which implies a triplet precursor. The exchange interaction, J, is found to be negative for this radical pair. The triplet photoionization channel is determined to be monophotonic. The singlet channel of photoionization of deprotonated tyrosine is seen only upon addition of the electron acceptor 2-bro-mo-2-methylpropionic acid (BMPA) to the sample. The singlet channel is isolated by performing TREPR on a sample containing tyrosine, BMPA and a triplet quencher (2,4-hexadienoic acid). This channel is also found to be monophotonic.     

Preparation of MCM-41 in Industrial Scale and Its Application in Heavy Oil Processing

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The reaction of carbon monoxide with platinum ylids

The platinum(II) ylids [X₂Pt{CH(py)CH₂CH₃}(py)] (X = Cl, Br; PY = pyridine) react with carbon monoxide to give the platinum carbonyls [CO(X₂)Pt{CH(py)CH₂CH₂CH₃}] which lose CO on heating or in solution. The platinum(IV) ylids [Cl₄Pt{CH(py)CH₂CH₃}(py)] and[Cl₂I(CH₃)Pt{CH(py)CH₂CH₃}(py)] also react with CO to give Pt(CO)-ylid compounds.     

Administering Rule Development in Rule-Based Expert Systems

One recommended approach to the building of expert systems is to start with a very simple system and to expand the level of detail as the system evolves. With this approach there is the practical problem of organizing the rules as the system develops. This paper describes the use of a folding editor for easing this administrative overhead.     

Theα- andβ-decay of187Pb

Sources of¹⁸⁷Pb were produced by the¹⁴²Nd(⁴⁸Ti, 3n)¹⁸⁷Pb reaction followed by online mass separation of the products. Measurements ofγ-γ andα-γ coincidences and half-lives were performed. Twoα-emitting states in¹⁸⁷Pb were found with half-lives of 15.2±0.3 s and 18.3±0.3 s, respectively. Theα-γ coincidences yielded excitation energy and possible spin values for a few levels in¹⁸³Hg. Gamma-transitions in¹⁸⁷Tl were identified and a level scheme for¹⁸⁷Tl is proposed on the basis of the coincidence relationships and the level systematics of the heavier odd-thallium isotopes.     

Generalized van der Waals theory VIII. An improved analysis of the liquid/gas interface

We extend a preceding application of the GvdW theory to the prediction of interface profiles and surface tension in simple fluids by incorporating a variational determination of the effective hard-sphere diameter. This has previously been found to improve the predicted equation of state. Here we find that it also improves the prediction of interface profiles and surface tension in LJ(12-6) fluids. The agreement with experiment and simulation when these quantities are considered as functions ofT/T _c is to within about 5%. As in our earlier calculations the nonlocal entropie effects are found to reduce the surface tension by 5%–10%. In the present conceptually more accurate theory this significantly improves the agreement with experiment and simulation.     

Unusual temperature effects on the non-equivalence of geminal methyl groups

The geminal anisochronism (Δδ) of the isopropyl methyl groups in the ¹H n.m.r. spectrum of N-[2-methyl-1-(1-naphthyl)propylidene]benzylamine showed unusually pronounced temperature and solvent effects. It is noteworthy that both accidental and dynamic equivalences were encountered. Slow rotation around the naphthyl–imino bond is responsible for the diastereotopic nature of the geminal methyl groups, and possible reasons for the temperature and solvent effects are considered. Surprisingly, the temperature effect was not reflected in the ¹³C anisochronism of the methyl carbon nuclei. These observations underline the need for caution in drawing firm conclusions from variable temperature studies on geminal non-equivalence.