Photoionization in solid solutions at 77°K. Ionization potentials

The ionization potential of two aromatic solutes in ethylene glycol/water- and ethanol-glass at 77°K has been measured. It is found that the ionization potential decreases with increasing polarity of the matrix. No correspondence was found between the trap depth of e^?_t and the decrease in ionization potential from gaseous phase to solid phase.     

Effects of UV radiation of cells

UV radiation interacts with mammalian cells in a very complex manner, although DNA appears to be the main chromophore. Recent literature within this field is reviewed. The review is concentrated on the following main topics: Chromophores for UV action, photoproducts in DNA, repair of UV-induced DNA damage, wavelength interactions, inactivation, mutagenesis, transformation and protection mechanisms against UV damage.     

Rheological and thermal study of delayed crystallization in poly(butylene terephthalate)/ethylene‐co‐ethyl acrylate blends

The effects of the composition and resulting morphology on the crystallization and rheology of blends containing poly(butylene terephthalate) (PBT) and an ethylene‐co‐ethyl acrylate (EEA) copolymer, two immiscible polymers, were studied over the entire range of volume fractions. Differential scanning calorimetry (DSC) thermograms recorded during cooling showed important differences, mainly in terms of the PBT crystallization temperatures, depending on the blend composition. In addition to the classical crystallization peaks of PBT and EEA, a third crystallization peak appeared for blends containing less than 60% PBT. This peak was attributed to a delayed crystallization of PBT. This phenomenon was examined in terms of homogeneous crystallization. Linear viscoelastic measurements allowed the delayed crystallization behavior in these polymer blends to be displayed. Indeed, the variation of the storage modulus with the temperature showed increasing steps during cooling. These sudden increases appeared at temperatures very close to those at which the crystallization peaks were observed in the DSC experiments. This behavior was verified for different blend compositions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 714–721, 2004     

Trapped hydrogen atoms in irradiated frozen solutions. Isotope effects

Isotope effects in the yields of H- and D-atoms in acid, neutral and alkaline matrices have been studied by EPR methods. In acid matrices the isotope effect is the same in UV- and X-irradiated matrices, but in neutral and alkaline matrices the effect is larger in UV-irradiated matrices. Furthermore, when the H- and D-atoms are formed by photobleaching of trapped electrons the isotope effect is strongly dependent on the wavelength of the bleaching light, increasing with increasing wavelenghts. The isotope effect in sulphuric acid matrices is dependent on the concentration of the acid. The observation are briefly discussed.     

On the decay of H and D atoms in aqueous sulphuric acid glasses. Isotope effects

Glassy samples of a mixture of 9.16 M H₂SO₄ in H₂O and 9.16 M D₂SO₄ in D₂O were X-irradiated at 77 K. ESR-measurements showed that the decay of D atoms was considerably faster than the decay of atoms at 118 K. This isotope effect was even more pronounced when the decay of H atoms in 9.16 M H₂SO₄ and D atoms in 9.16 M D₂SO₄ were measured separately. At 77 K no isotope effects were found, neither with, nor without 1 M 2-propanol as an H-atom scavenger.