To enhance skin permeability to medicine, the argon-fluoride excimer laser (ArF laser) was used to partially ablate the stratum corneum. Skin permeability to dextran (20 kDa) was studied in the Yucatan micro-pig skin in vitro. The cumulative amount of dextran permeating across the full-thickness skin was not detected for 30 h in the unirradiated skin; we obtained up to 90.5 microg/cm2 in laser-irradiated skin. In the case where the total laser energy was kept constant at 7.1 J/cm2, permeability was mainly influenced by laser fluence rather than laser pulses. Many granular structures of about 2 microm were found on the stratum corneum surface of ablated skin. Size and density of these structures were changed according to irradiation conditions. Skin permeability may be estimated by these structural changes. Our partial stratum corneum ablation by ArF laser could be suitable for transdermal drug delivery.

Tetravalent plutonium / Malonic acid / Succinic acid / Formation constant / SolubilitySummary. The complex formation constants of tetravalent plutonium ion with malonic and succinic acids in aqueous solution were determined by the solvent-extraction method. Also, by taking the known values of the solubility products, the hydrolysis constants and the formation constants, the experimental solubility data of plutonium in the presence of carboxylates were analyzed.

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It has been shown that the main uranium ore mineral, pitchblende (uranium dioxide), is a natural analog of synthetic uraninite (also uranium dioxide), which constitutes 96% of spent nuclear fuel (SNF). Geochronological studies of the U-Pb isotope systems in unaltered pitchblende from the orebodies reveal that these systems remained completely closed over the entire period (approximately 135 Ma) since the formation of the deposits. The bulk of the primary uranium ores within the Streltsovskoye ore field was influenced to various degrees by post-ore hydrothermal solutions that led to pitchblende spherulites being replaced by pseudomorphs of an amorphous phase with a U-Si composition; this phase also re-precipitated in veinlets proximal to the pitchblende pseudomorphs. A technique specially developed by the authors was used to carry out quantitative counts of the abundance of uranium minerals by calculating the uranium mass balance in one of the orebodies subjected to hydrothermal alteration. The calculations reveal minimal uranium loss from the orebody. Uranium liberated in the process of the pseudomorphic replacement of pitchblende was immediately fixed, in situ, in the newly formed coffinite-like amorphous U-Si phase as a result of the development of an efficient geochemical barrier that prevented the long-distance migration of uranium. In assessing the long-term safety of underground SNF repositories, the results of the present study give us confidence that SNF uraninite, in terms of the preservation of its integrity as a mineral phase, provides for the reliable long-term isolation of uranium, transuranium elements, and fission products that are "sealed" in the uraninite matrix. In the case of the mineral transformation of the uraninite matrix by hydrothermal solutions, the liberated uranium would be efficiently immobilized by the newly formed amorphous U-Si phase.