The role of increasing temperature variability in European summer heatwaves

Instrumental observations and reconstructions of global and hemispheric temperature evolution reveal a pronounced warming during the past approximately 150 years. One expression of this warming is the observed increase in the occurrence of heatwaves. Conceptually this increase is understood as a shift of the statistical distribution towards warmer temperatures, while changes in the width of the distribution are often considered small. Here we show that this framework fails to explain the record-breaking central European summer temperatures in 2003, although it is consistent with observations from previous years. We find that an event like that of summer 2003 is statistically extremely unlikely, even when the observed warming is taken into account. We propose that a regime with an increased variability of temperatures (in addition to increases in mean temperature) may be able to account for summer 2003. To test this proposal, we simulate possible future European climate with a regional climate model in a scenario with increased atmospheric greenhouse-gas concentrations, and find that temperature variability increases by up to 100%, with maximum changes in central and eastern Europe.     

Re-Os isotopic evidence for long-lived heterogeneity and equilibration processes in the Earth's upper mantle

The geochemical composition of the Earth's upper mantle is thought to reflect 4.5 billion years of melt extraction, as well as the recycling of crustal materials. The fractionation of rhenium and osmium during partial melting in the upper mantle makes the Re-Os isotopic system well suited for tracing the extraction of melt and recycling of the resulting mid-ocean-ridge basalt. Here we report osmium isotope compositions of more than 700 osmium-rich platinum-group element alloys derived from the upper mantle. The osmium isotopic data form a wide, essentially gaussian distribution, demonstrating that, with respect to Re-Os isotope systematics, the upper mantle is extremely heterogeneous. As depleted and enriched domains can apparently remain unequilibrated on a timescale of billions of years, effective equilibration seems to require high degrees of partial melting, such as occur under mid-ocean ridges or in back-arc settings, where percolating melts enhance the mobility of both osmium and rhenium. We infer that the gaussian shape of the osmium isotope distribution is the signature of a random mixing process between depleted and enriched domains, resulting from a 'plum pudding' distribution in the upper mantle, rather than from individual melt depletion events.     

Relations entre oxydation phosphorylante et structure des mitochondries hépatiques de rats carencés en vitamines B1 et B2

Summary In the experimental B₁-avitaminosis a decrease of oxidative ATP-resynthesis in liver homogenates, and a significant diminution of the optical density of mitochondrial suspension were simultaneously observed: in other words a probable parallelism in the alteration of function and structure. In ariboflavinosis neither oxidative phosphorylation nor optical density seems to be notably impaired, but the nitrogen content of mitochondrial suspensions decreases significantly. Therefore this second type of avitaminosis would appear to affect the mitochondrial population rather than energetic metabolism or structural integrity of the protoplasmic granules.

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Communication présentée au 3^e Congrès International de Biochimie, Bruxelles 1955.     

Influence of ventilatory and circulatory changes on the pharmacokinetics of halothane and isoflurane

In two groups of dogs, uptake and elimination of halothane and isoflurane were studied using a closed-loop anesthesia system which automatically controlled end-tidal halothane or isoflurane partial pressure at minimal alveolar concentration (MAC) equivalent levels. Hemodynamic and respiratory variables were recorded and the anesthetic partial pressure was measured in the inspired and expired air, as well as in the arterial, cerebrovenous and mixed venous blood. Data were recorded during wash-in, hyperventilation, hypercirculation, hypotension and wash-out. For halothane, the controller delivered a higher inspired partial pressure than for isoflurane to compensate for the higher blood/gas partition coefficient. This was especially pronounced during the wash-in and the hypercirculation periods. Smaller differences between halothane and isoflurane partial pressures occurred during hyperventilation, hypotension and the wash-out period and could be explained by the lower solubility of isoflurane. These results show that even under unstable ventilatory and hemodynamic conditions, the inspired concentration of isoflurane has to be adjusted less often and to a smaller degree than that of halothane if end-tidal concentrations are to be maintained constant.     

Mesure de l'oxydation phosphorylante à l'aide de phosphore radioactif dans la cellule hépatique

Summary We have briefly described an apparatus which permits us to register quantitatively different substances labelled with radioactive isotopes, formerly separated by paper chromatography. We were able to show by the Krebs' method, thus simplified, that the oxidative resynthesis of ATP is diminished in the hepatic homogenates of rats during a beri-beri crisis.     

Structure of an ABC transporter in complex with its binding protein

ATP-binding cassette (ABC) transporter proteins carry diverse substrates across cell membranes. Whereas clinically relevant ABC exporters are implicated in various diseases or cause multidrug resistance of cancer cells, bacterial ABC importers are essential for the uptake of nutrients, including rare elements such as molybdenum. A detailed understanding of their mechanisms requires direct visualization at high resolution and in distinct conformations. Our recent structure of the multidrug ABC exporter Sav1866 has revealed an outward-facing conformation of the transmembrane domains coupled to a closed conformation of the nucleotide-binding domains, reflecting the ATP-bound state. Here we present the 3.1 A crystal structure of a putative molybdate transporter (ModB2C2) from Archaeoglobus fulgidus in complex with its binding protein (ModA). Twelve transmembrane helices of the ModB subunits provide an inward-facing conformation, with a closed gate near the external membrane boundary. The ATP-hydrolysing ModC subunits reveal a nucleotide-free, open conformation, whereas the attached binding protein aligns the substrate-binding cleft with the entrance to the presumed translocation pathway. Structural comparison of ModB2C2A with Sav1866 suggests a common alternating access and release mechanism, with binding of ATP promoting an outward-facing conformation and dissociation of the hydrolysis products promoting an inward-facing conformation.     

The influence of iodine-labelling on the non-specific fixation of immunoglobulins to tissues

Résumé On recherche si le marquage au radio-iode peut dénaturer les immunoglobulines au point d'en modifier la fixation non spécifique aux tissus (affinité non spécifique). Des 4 techniques de marquage essayées, 2 ne modifient pas cette propriété, tandis que les 2 autres augmentent nettement la proportion d'immunoglobulines fixées.

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Supported by the Swiss National Funds for Scientific Research.     

Reaction patterns of dark- and light-adaptedHydra to light stimuli

Zusammenfassung Die Kontraktionsintensität bleibt auch dann unverändert, wenn die Polypen vonHydra attenuata dem Dunkel-Hell-Wechsel (je 2 min) während 3 h ausgesetzt werden. Dunkeladaptierte Hydren reagieren auf Lichtreize auffallend empfindlicher als bei 3000 Lux helladaptierte Tiere.

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These investigations were generously supported by a grant (No. 3991) from the Schweizerische Nationalfonds zur Förderung der wissenschaftlichen Forschung.