Steady potential responses from the rat cortex during conditioning

Zusammenfassung Während Versuchsreihen an Ratten über Gewöhnung, Paarung und Auslöschung wurden jeweils signifikante Veränderungen des kortikalen Bestandespotentials (Gleichspannung) als Antwort auf Schallreiz gemessen.

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Supported by a grant from the Medical Research Foundation of Texas.     

Theoretical prediction of carcinogenicity: quasi-quantification by quasi-valence.

We have shown the recently proposed method for prediction of carcinogenicity by "average quasi-valence number" to be neither a good predictor of carcinogenicity, nor of non-carcinogenicity.     

The biometry of the cirripede,Chthamalus stellatus (Poli)

Résumé Les données deTenerelli sur les dimensions (hauteur et diamètre basal) deChthamalus stellatus stellatus (Poli) etC. stellatus depressus (Poli) sont analysées ici par des méthodes statistiques. On peut constater une ligne de régression commune à tous les échantillons de chaque sous-espèce, pris à plusieurs niveaux. Les lignes de régression pour les deux sous-espèces en question offrent des différences significatives. Leur croissance diffère également.     

Albedo of the south pole on Mars determined by topographic forcing of atmosphere dynamics

The nature of the martian south polar cap has remained enigmatic since the first spacecraft observations. In particular, the presence of a perennial carbon dioxide ice cap, the formation of a vast area of black 'slab ice' known as the Cryptic region and the asymmetric springtime retreat of the cap have eluded explanation. Here we present observations and climate modelling that indicate the south pole of Mars is characterized by two distinct regional climates that are the result of dynamical forcing by the largest southern impact basins, Argyre and Hellas. The style of surface frost deposition is controlled by these regional climates. In the cold and stormy conditions that exist poleward of 60 degrees S and extend 180 degrees in longitude west from the Mountains of Mitchel (approximately 30 degrees W), surface frost accumulation is dominated by precipitation. In the opposite hemisphere, the polar atmosphere is relatively warm and clear and frost accumulation is dominated by direct vapour deposition. It is the differences in these deposition styles that determine the cap albedo.     

Coral record of increased sediment flux to the inner Great Barrier Reef since European settlement

The effect of European settlement on water quality in the Great Barrier Reef of Australia is a long-standing and controversial issue. Erosion and sediment transport in river catchments in this region have increased substantially since European settlement, but the magnitude of these changes remains uncertain. Here we report analyses of Ba/Ca ratios in long-lived Porites coral from Havannah Reef--a site on the inner Great Barrier Reef that is influenced by flood plumes from the Burdekin river--to establish a record of sediment fluxes from about 1750 to 1998. We find that, in the early part of the record, suspended sediment from river floods reached the inner reef area only occasionally, whereas after about 1870--following the beginning of European settlement--a five- to tenfold increase in the delivery of sediments is recorded with the highest fluxes occurring during the drought-breaking floods. We conclude that, since European settlement, land-use practices such as clearing and overstocking have led to major degradation of the semi-arid river catchments, resulting in substantially increased sediment loads entering the inner Great Barrier Reef.