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When a Pb/PbO, electrode immersed in 117504 solution is subjected to polarization in the lead dioxide potential region (p > 1.0 V vs. Hg/Hg,504 reference electrode), 11,0 is decomposed releasing oxygen. The aim of this investigation is to elucidate the mechanism of the reactions taking place on oxygen evolution. Linear-sweep-voltametric cycling according to various cycling programs has been performed, and the structure of the anodic layer has been examined through scanning electron micrscopy and x-ray diffraction. It has been established that at potentials in the region 1.0 < p> 1.3 V the electrode has passive behavior (i.e., only a weak current passes through it), and in the range 1.3

1.0 V and leads to the formation of OH radicals, the second takes place at p> 1.3 V It is assumed that these reactions proceed in the hydrated PbO(OH), layer of the lead dioxide. Both reactions are localized in a certain number of active centers in the hydrated PbO(OH), layer. At p < 1.3 V, the products of the first electrochemical reaction block these active centers and hence the current decreases significantly. At p> 1.3 \7 the second electrochemical reaction proceeds, as a result of which oxygen is evolved due to oxidation of the OH radicals and consequent unblocking of the active centers. The electrode is activated, and the reaction resistance is the dominant rate-limiting factor. The present contribution proposes a mechanism of the elementary processes that occur on oxygen evolution in light of the gel-crystal structure of the PbO, layer. This mechanism involves the hydrated polymer chains in the gel layer.

DS, Allendorf FW. Population structure and partial anadromy in Oncorhynchus mykiss from Kamchatka: relevance for conservation strategies around the Pacific Rim.Abstract -Conservation of life-history diversity found in Oncorhynchus mykiss requires knowledge of the underlying population structure and genetic basis of this variability. We analysed variation at 10 microsatellite loci from seven rivers across Kamchatka to identify population structure and to test for divergence between life-history forms. We found lower heterozygosity in Kamchatkan populations compared with North American populations, but population structure was substantial (region-wide F ST ¼ 0.11) and followed an isolation-by-distance pattern similar to that reported for older North American populations. We found no evidence for genetic divergence between resident and anadromous individuals in the Sopochnaya River or between typically anadromous individuals and 'half-pounders' in the Utkholok River. A review of other studies of reproductive isolation, in combination with our results, suggests: (1) that pristine populations of steelhead should be expected to exhibit partial anadromy; and (2) that managing anadromous and resident individuals separately without demonstrating reproductive isolation is biologically unsound.

Up to now, the positive lead dioxide active mass (PAM) has been treated as a crystal system. Its behavior, however, could not be fully explained by its crystal nature. In the present paper, a new approach is suggested which views PAM as a gel-crystal system. Crystal zones are built of PbO~. and exhibit electron conductivity. Gel zones are composed of hydrated lead dioxide, PbO(OH)~, that forms linear polymer chains. These allow electrons to move in the gel hopping from one Pb 4 § ion to the other along the polymer chain and from one polymer chain to the other between the crystal zones. This determines the electron conductivity of the gel. Besides, PAM seems to meet all requirements of a good proton (ion) conductor. This gel-crystal structure of PAM explains more deeply its electrochemical behavior during charge, discharge, and overcharge as well as the relation between PAM crystallinity and polarization and plate capacity.

Potentiostatic oxidations of lead in 1N H2SO4 were performed in the potential range between −900 and +1400 mv (with respect to the mercury/mercury sulfate electrode). The anodic layer was subjected to x‐ray diffraction and chemical analysis. According to the phases present three potential ranges are discerned. From −956 to about −300 mv only PbSO4 is present. From −300 to +900 mv large amounts of PbSO4 and normalPbO‐normaltet are formed as well as small amounts of normalPbO·PbSO4 , 3normalPbO·PbSO4·H2O , 5normalPbO·2H2O or normalPbO orthorhombic and α‐PbO2 . Above +900 mv the divalent lead compound content decreases, while that of α‐PbO2 . rapidly increases. Above +1200 mv β‐PbO2 . is formed.