1,722,220 research outputs found
Oxidative degradation of non-recycled and recycled paper
No full textThe degradation of paper-based materials involves several and complex mechanisms, such as hydrolysis and oxidation. The behaviour of different types of pulps can be very variable. In this study, the difference upon oxidation of contemporary non-recycled and recycled papers, which now constitute a considerable fibre source, is investigated. A 0.015 M potassium periodate solution is used to oxidise five types of paper, two non-recycled and three recycled, for 0.5, 1, 2 and 4 h. The effects of such oxidation treatments are evaluated in terms of carbonyl content and degree of polymerisation (DP). A modified procedure of the Szabolcs’s method and viscometry are used to measure the carbonyl content and DP, respectively. The carbonyl groups are found to increase more rapidly in the recycled papers than in the non-recycled ones. On the contrary, oxidation causes a larger decrease of the DP values in the non-recycled papers, the paper made of pure cellulose being the most sensitive in terms of depolymerisation. The DP values measured for pure cellulose paper are in line with previously reported data. Moreover, in accordance with the Ekenstam equation, the plots of the reciprocal of DP as a function of oxidation time show good linear correlations for all types of paper investigated. Pseudo rate constants are thus calculated from the slopes of these plots, those of the non-recycled papers being found to be higher than those of the recycled papers. Graphic abstract: [Figure not available: see fulltext.]
Dissociative electron attachment to di-tert-butylperoxide, artemisinin, and beta-artemether
No full textA theoretical and experimental study on the molecular and electronic structures of artemisinin and related drug molecules
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“La giustizia costituzionale in Italia ed in Spagna: modelli a confronto e prospettive future”
No full text“La giustizia costituzionale in Italia ed in Spagna: modelli a confronto e prospettive future
A study of the molecular structure and spectroscopic properties of tetrahydro[4]beltene and related compounds
No full textVertical electron affinities in substituted trimethylsilanes
No full textThe gas-phase negative electron affinities obtained by means of electron transmission spectroscopy (ETS) in the series (CH3)3Si-X (with X = I, Br, Cl, Si(CH3)3, SCH3, OCH3, N(CH3)2, CH3) are compared. The electron-acceptor properies of these compounds are enhanced when the substituent contains third-row (or heavier) elements. Geometries and charge distributions in the neutral molecules are calculated at the 3-21G* and 6-31G** ab initio levels (except for X = I, Br). The LUMO energies predicted by 3-21G*, 6-31G**, *SCF and semiempirical MNDO calculations are compared with the resonance energy trend observed in the ET spectra
Probing the molecular and electronic structure of capsaicin: A spectroscopic and quantum mechanical study
No full textSpectroscopic and theoretical determination of the electronic structure of anisole, thioanisole, and methoxy- and methylthiobenzonitriles: A contribution to the study of organic conducting polymers
No full textGas-phase ionization and attachment energy (IE and AE) values of some para- and ortho-cyano derivatives of anisole and thioanisole (p-NCPhXCH3, X = O, S and o-NCPhXR, X = O, R = CH3; X = S, R = H, CH3, and C(CH3)3) have been determined experimentally. The assignments of the spectra, based on those of the parent compounds PhXMe, NCPh, and XMe2 (Me = CH3), agree with the results of theoretical HF/6-31G** calculations. The calculations correctly reproduce the prevalence of the planar rotamer of the oxy-derivatives with respect to the gauche one, while overestimating the relative stability of the gauche conformer of the thio-derivatives.
The two rotamers of the thio-derivatives have similar energy and their valence energy levels do not sizeably differ. In addition, PhSMe and p-NCPhSMe have HOMO-LUMO energy gaps (9.5 eV) in the oxy-derivatives and there are indications that the methylthio group has larger polarizability than the methoxy group. These data suggest that poly(p-phenylene sulfide) is more suitable than poly(p-phenylene oxide) to carry electricity under mild doping
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