Bibliothek

Notizen: Studies have been done on the absorption and metabolism of the hair colourant 2-nitro-p-phenylenediamine (2-NPPD) in rats with particular reference to skin penetration.When [14C]2-NPPD was given orally or injected intraperitoneally into male and female rats, excretion was rapid and mainly in the faeces (60%) and urine (35%). No radioactivity was measurable in the expired air. At 3 days after dosing, approximately 2% of the dose was retained in the body.Application of [14C]2-NPPD in ethanol to the clipped skin of rats gave a high skin penetration. Male rats absorbed less (11.7 μg cm-2) through the skin than did female rats (24.6 μg cm-2).Application of [14C]2-NPPD in a solution of a hair colourant product base to the clipped skin of rats gave a high penetration if the skin was occluded or not rinsed. Penetration was much reduced after rinsing and protection by non-occlusive patches. With these latter conditions, skin penetration in clipped rats treated with a 0.5% (w/v) solution of [14C]2-NPPD doubled to 6.1 μg cm-2 when the contact time was increased from 5 to 30 minutes, increased two to three times after two and three repeated applications, increased in proportion to the applied concentration and was reduced by half when applied to unclipped skin.The metabolic pattern in urine from rats after different routes of administration showed only a trace of the parent [14C]2-NPPD but six other radioactive components. The identity of these components has not yet been fully resolved. Blood levels of radio-activity during 2 days after topical administration were low.Under realistic conditions of use by the consumer the calculated dose through the skin based on the experimental rat data is up to 10 μg/kg body weight per application of a semi-permanent hair colourant product containing 1% of 2-NPPD. L'adsorption transcutanée de la 2-nitro-p-phenylenediamine On a étudié l'adsorption transcutanée et le métabolisme du colorant capillaire 2-nitro-p-phenylènediamine (2-NPPD) sur le rat.Lorsque la [14C]2-NPPD est administrée par voie orale ou injectée par voie intra-péritonéale sur des rats mâles et femelles, l'excrétion est rapide et principalement dans les fèces (60%) et dans les urines (35%). Il n'y a pas de radioactivité mesurable dans l'air expiré. Trois jours après l'administration, environ 2% de la dose est retenue dans l'organisme.

Notizen: The effect of aqueous solutions of 2-hydroxyacids of chain length C3 to C10 on the extensibility of undamaged and solvent-damaged guinea-pig footpad stratum corneum has been studied. The increase in extensibility of solvent-damaged corneum, caused by treatment with hydroxyacid, reached a maximum with 2-hydroxycaprylic acid (C8); on undamaged corneum, 2-hydroxycaprylic acid was the only hydroxyacid studied to give a significant effect. The increase in corneum extensibility produced by 2-hydroxyacids decreases when the pH is raised from 3 to 4. This loss of effect correlates with the ionization of the hydroxyacid (pK˜ 3.85).The binding of radiolabelled 2-hydroxycaproic (C6) and 2-hydroxycaprylic acids to stratum corneum has been studied. 2-Hydroxycaprylic acid binds much more strongly than 2-hydroxycaproic acid, the difference in the binding being consistent with the hydrophobic binding energy of two methylene groups. Raising the pH above 3.5 results in a large decrease in the binding of 2-hydroxycaprylic acid in line with the corresponding reduction in extensibility.Treatment with 2-hydroxyacids results in a small increase in the water-binding capacity of solvent-damaged stratum corneum, but in a decrease in the water-binding capacity of undamaged stratum corneum. These data are discussed in terms of a possible mechanism for the plasticizing of stratum corneum. Effet des 2-hydroxyacides sur la couche cornée du coussin des pattes de cobaye

Notizen: A compact, high-peak-power, user-friendly, single-longitudinal-mode (SLM) tunable dye laser has been developed. The device yields (approximately-greater-than)12 mJ pulses of 6 ns duration and ∼2.7×transform-limited linewidths of 〈200 MHz. Seamless single-mode tunability of (approximately-greater-than)20 cm−1 is possible without resetting. The dye laser makes efficient use of the pump laser, with ∼10% conversion of the 532 nm pump energy to tunable dye power and occupies 〈4 m2 (including pump laser and all diagnostics). The linewidth of the device can be switched from 〈200 MHz SLM operation to 〈0.5 cm−1 broadband modeless operation by moving one mirror. This allows rapid interchange between high-resolution scanning and a "fast survey scan'' mode of operation to isolate the spectral region of interest at low resolution.

Notizen: We present a systematic study of the infrared multiphoton excitation and dissociation of several polyatomic molecules. The molecules range in size from SO2, with three vibrational modes, to C3F7I, with 27. A gradual transition occurs from intensity dependent excitation, characteristic of a sparse density of vibrational states in small molecules, to a fluence dominated absorption characteristic of a quasicontinuum of vibrational states in large, heavy molecules. Molecules with ten or more atoms showed no intensity dependence under pulsed CO2 laser excitation at a fixed energy fluence. For a molecule to have a high probability of dissociation under realizable conditions of laser intensity and fluence, quasicontinuum region excitation must dominate. All molecules appeared to have statistically coupled vibrational modes at high levels of vibrational energy.

Notizen: We discuss the lattice dynamics of argon, krypton, and xenon overlayers on the Ag(111) surface. We consider monolayer, bilayer, trilayer and 25 layer films of each of these adsorbates. Data are also presented on the dispersion relations of selected branches of the phonon spectra of these overlayers. The data have been obtained by the method of angle-resolved inelastic He scattering. Several models of the lattice dynamics are compared with the data. It is concluded that the gas phase potentials proposed by Barker and co-workers prove suitable for a description of lateral interactions between the adsorbates, within the accuracy of the available data, provided that the phonon spectra are calculated for a lattice with the experimentally determined lattice constants.