The Equivalence Principle and the Constants of Nature

We briefly review the various contexts within which one might address the issue of ``why'' the dimensionless constants of Nature have the particular values that they are observed to have. Both the general historical trend, in physics, of replacing a-priori-given, absolute structures by dynamical entities, and anthropic considerations, suggest that coupling ``constants'' have a dynamical nature. This hints at the existence of observable violations of the Equivalence Principle at some level, and motivates the need for improved tests of the Equivalence Principle.Comment: 12 pages; invited talk at the ISSI Workshop on the Nature of Gravity: Confronting Theory and Experiment in Space, Bern, Switzerland, 6-10 October 2008; to appear in Space Science Review

Simulating rewetting events in intermittent rivers and ephemeral streams: A global analysis of leached nutrients and organic matter

Climate change and human pressures are changing the global distribution and the ex‐ tent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (precon‐ ditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experi‐ mentally simulated, under standard laboratory conditions, rewetting of leaves, river‐ bed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative character‐ istics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dis‐ solved substances during rewetting events (56%–98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contrib‐ uted most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental vari‐ ables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached sub‐ stances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying event

In search of the miraculous

Track 1 Paulina Sundin: The ringing stone of Haga (7'32") Track 2 Sten-Olof Hellstrom: In my own words (8'36") Track 3 Rose Dodd: Playing the bones (10'52") Track 4 Barbara Elison: In search of the miraculous (7'05") Track 5 Nicolas Bernier: bourrasques electriques (6'00") Track 6 Jamie Fawcus: Stoop (11'22") Track 7 Dominic Thibault: Enfant robot au coeur fondant (or the incredible secret of the caramilk injected in a generation) (14'38") Track 8 Mark Bokowiec: Amera (8'13"

Oxidative cross-linking of chemically and enzymatically modified sugar-beet pectin

36 ref.International audienc

Aliment et santé. Les fibres alimentaires : intérêts fonctionnels et nutritionnels

National audienc

Etude structurale des chaines laterales des pectines de betterave

National audienc

Etude structurale des chaines laterales des pectines de betterave

26 ref.National audienc

Etude structurale des chaines laterales des pectines de betterave

National audienc

Chemical and physico-chemical properties of fibres from algal extraction by-products

International audienc