Mercury's capture into the 3/2 spin-orbit resonance as a result of its chaotic dynamics

Mercury is locked into a 3/2 spin-orbit resonance where it rotates three times on its axis for every two orbits around the sun. The stability of this equilibrium state is well established, but our understanding of how this state initially arose remains unsatisfactory. Unless one uses an unrealistic tidal model with constant torques (which cannot account for the observed damping of the libration of the planet) the computed probability of capture into 3/2 resonance is very low (about 7 per cent). This led to the proposal that core-mantle friction may have increased the capture probability, but such a process requires very specific values of the core viscosity. Here we show that the chaotic evolution of Mercury's orbit can drive its eccentricity beyond 0.325 during the planet's history, which very efficiently leads to its capture into the 3/2 resonance. In our numerical integrations of 1,000 orbits of Mercury over 4 Gyr, capture into the 3/2 spin-orbit resonant state was the most probable final outcome of the planet's evolution, occurring 55.4 per cent of the time.     

The influence of ridge migration on the magmatic segmentation of mid-ocean ridges

The Earth's mid-ocean ridges display systematic changes in depth and shape, which subdivide the ridges into discrete spreading segments bounded by transform faults and smaller non-transform offsets of the axis. These morphological changes have been attributed to spatial variations in the supply of magma from the mantle, although the origin of the variations is poorly understood. Here we show that magmatic segmentation of ridges with fast and intermediate spreading rates is directly related to the migration velocity of the spreading axis over the mantle. For over 9,500 km of mid-ocean ridge examined, leading ridge segments in the 'hotspot' reference frame coincide with the shallow magmatically robust segments across 86 per cent of all transform faults and 73 per cent of all second-order discontinuities. We attribute this relationship to asymmetric mantle upwelling and melt production due to ridge migration, with focusing of melt towards ridge segments across discontinuities. The model is consistent with variations in crustal structure across discontinuities of the East Pacific Rise, and may explain variations in depth of melting and the distribution of enriched lavas.     

Early association of electrocardiogram alteration with infarct size and cardiac function after myocardial infarction

OBJECTIVE: Myocardial infarction (MI) is the main cause of heart failure, but the relationship between the extent of MI and cardiac function has not been clearly determined. The present study was undertaken to investigate early changes in the electrocardiogram associated with infarct size and cardiac function after MI. METHODS: MI was induced by ligating the left anterior descending coronary artery in rats. Electrocardiograms, echocardiographs and hemodynamic parameters were assessed and myocardial infarct size was measured from mid-transverse sections stained with Masson's trichrome. RESULTS: The sum of pathological Q wave amplitudes was strongly correlated with myocardial infarct size (r = 0.920, P < 0.0001), left ventricular ejection fraction (r = -0.868, P < 0.0001) and left ventricular end diastolic pressure (r = 0.835, P < 0.0004). Furthermore, there was close relationship between MI size and cardiac function as assessed by left ventricular ejection fraction (r = -0.913, P < 0.0001) and left ventricular end diastolic pressure (r = 0.893, P < 0.0001). CONCLUSION: The sum of pathological Q wave amplitudes after MI can be used to estimate the extent of MI as well as cardiac function.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower ()rdovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as “oil families“, although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any “oil family“. Despite their close stratigraphic proximity, it is evident that the oils of the/rower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new “oil family“ within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

Variation of the fine structure in granulocytes of great apes

Zusammenfassung Elektronenmikroskopische Untersuchungen der Granulocyten anthropoider Affen ergaben Unterschiede in der Struktur der eosinophilen Granula und eine bisher unbekannte fibrilläre Granulationsform in Orangutan Neutrophilen.

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These studies were supported by U.S. Public Health Service Grant No. FR 00165 from the National Institutes of Health and Atomic Energy Commission grant No. AT (30-1) 3808.     

Étude biochimique des poissons: 1. Variations semestrielles de la teneur en eau et en protéines du tissu musculaire de la truite Arc-en-ciel (Salmo gairdnerii Rich)

Summary The authors have noted, during the reproductive cycle of the Rainbow trout (Salmo gairdnerii Rich), important variations concerning water and total proteins content. This study shows a great correlation between the biological process and biochemical variations.     

Sulfur exchange between thiotaurine and hypotaurine

Résumé Les auteurs ont préparé avec une enzyme de la thiotaurine et de l'hypotaurine marquées par le et S³⁵ ont démontré que ces deux composés peuvent échanger spontanément un atome de soufre en se transformant l'un dans l'autre.