Poleward transport of equatorial fish larvae in the Atlantic Eastern Boundary Current system

Fish larval distributions support the hypothesis that East: Atlantic "upwelling" undercurrents are interconnected, and can entrain plankton from the Equatorial Undercurrents towards temperate latitudes. This conclusion is based on historic and recently collected data on the distribution of adults and larvae of mainly two equatorial, mesopelagic fish species Bathylagus argyrogaster and Hygophum macrochir and consistent with hydrographic data. Along the continental slope these larvae occur 440 to 920 km polewards of the reproductive ranges of their adults. Larval B. argyrogaster occurs mainly below the thermocline and reaches farther polewards than larval H. macrochir, which dwells mainly at thermocline depths. At tropical latitudes the larvae of both species occur frequently, and within a generally poleward flow. Immediately polewards of the Cape Verde Frontal Zone, and Angola-Benguela Frontal Zone, respectively, the larvae become rare and more deeply distributed. At these fronts the poleward flows are thought to submerge below the equatorward flows of the Canary Current and Benguela Current, and to form theslope-undercurrents of the Northwest and Southwest African upwelling systems. Larvae in these undercurrents reach minimum latitudes of 22 degrees N and 23 degrees 30'S. At the poleward flanks of East Atlantic cyclonic gyres,such as the Guinea Dome, Central Mauritanian Gyre, and Angola Dome, retroflections of the poleward current systems occur, also entraining and transporting larvae offshore

Effects of dentifrices differing in fluoride compounds on artificial enamel caries lesions in vitro

The aim of this study was to compare the caries-preventive effect of a stabilized stannous fluoride/sodium fluoride dentifrice containing sodium hexametaphosphate with those of a regular, solely sodium fluoride-containing and amine fluoride-containing dentifrice on pre-demineralized bovine enamel specimens using a pH-cycling model. Bovine enamel specimens with two artificial lesions each were prepared. Baseline mineral loss of both lesions was analyzed using transversal microradiography (TMR). Eighty-five specimens with a mean (SD) baseline mineral loss of 3393 (683) vol% × µm were selected and randomly allocated to five groups (n = 13/15). Treatments during pH-cycling (28 days and 2 × 20 min demineralization/day) were: brushing twice daily with slurries of AmF (1400 ppm F-), NaF (1450 ppm F-), SnF2/NaF (1100 ppm F-/350 ppm F-), and fluoride-free (FF) dentifrices or they were immersed in distilled water and remained unbrushed (NB). Subsequently, from each specimen one lesion was covered with acid-resistant varnish, while the remaining lesion was demineralized for another 14 days. Differences in integrated mineral loss (∆∆Z) were calculated between values before and after pH-cycling (∆∆Z E1) as well as before pH-cycling and after second demineralization (∆∆Z E2) using TMR. Treatments AmF and NaF induced a significantly higher mineral gain (∆∆Z E1/∆∆Z E2) compared to treatments FF and NB (p < 0.05; ANOVA test). Except for treatments AmF and NaF no significant differences in mineral loss between before and after pH-cycling could be observed (p < 0.05; t test) [∆∆Z E1: AmF:1563 (767); NaF:1222 (1246); SnF2/NaF:258 (1259); FF:-52 (1223); NB:-151 (834)]. Both dentifrices with either AmF or NaF promoted remineralization, whereas SnF2/NaF dentifrice did not promote remineralization in a biofilm-free pH-cycling model