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Positron Annihilation in Cotton Cellulose

100%

Golonka P., Mayer J., Dryzek E.

Acta Physica Polonica A

2001

vol. 99

issue 3-4

363-367

The changes of the cotton fibre microstructure as a result of annealing at temperatures from 20ºC to 300ºC were investigated by positron lifetime spectroscopy and differential scanning calorimetry. The aim of the paper was to examine the cotton cellulose thermal degradation process.

Fast Stochastic Reorientations in Nematic PAA and PAP

88%

Podsiadły R., Mayer J., Janik J. A., Krawczyk J., Stanek T.

Acta Physica Polonica A

1997

vol. 91

issue 3

513-518

Incoherent quasielastic neutron scattering spectra were measured for nematic para-azoxyanisole (PAA) and para-azoxyphenetole (PAP) with the energy resolution of ca. 30 μ eV, at Dubna IBR-2 reactor. Data processing contained a careful background subtraction and the multiple scattering correction. The corrected spectra were subjected to a reorientational model fitting procedure. For PAA, a model of two convoluted reorientations - that of benzene rings coupled with the terminals and that of the whole molecule around the long molecular axis - gave a fairly good description of the quasielastic neutron scattering spectrum. For PAP, introducing a third motion - interconformational jumps in the ethoxy terminals - in addition to motions suggested for PAA, gave a good agreement with the measured quasielastic neutron scattering spectrum.

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2 Acta Physica Polonica A

1 2001

1 1997

2 Mayer J.

1 Dryzek E.

1 Golonka P.

1 Janik J. A.

1 Krawczyk J.

1 Podsiadły R.

1 Stanek T.

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Positron Annihilation in Cotton Cellulose

Fast Stochastic Reorientations in Nematic PAA and PAP