Questioning the structure of Sr

The stable structures of argon clusters doped with a strontium cation were computationally determined using a many-body polarizable potential fitted to reproduce highly accurate electronic structure calculations at the coupled cluster level of theory. The basin-hopping global optimization method was employed to locate putative lowest energy structures of Sr+Arn clusters with n < 160, and the effects of zero-point energy corrections and of possible entropy-driven structural transitions were accounted for in the (quantum) harmonic approximation. The results suggest an overall icosahedral growth pattern over the investigated size range, with the strontium cation being generally twelvefold coordinated by argon atoms also arranged into an icosahedron. However, the strain between the first coordination shell and the remaining cluster is significant, with the cation not always residing at the center of the cluster despite being much more strongly bound. As a result, non-icosahedral coordination shells are also occasionally found with local decahedral or cubic arrangements. This structural diversity could explain the relative discrepancies with existing mass spectrometry abundances

Enhancement of fermentative hydrogen production by Thermotoga maritima through hyperthermophilic anaerobic co-digestion of fruit-vegetable and fish wastes

International audienceIn this work, different proportions of model fruit and vegetable wastes (MFVW) and acid hydrolyzed fish wastes (AHFW) were used for hydrogen production in a minimum culture medium based on seawater. Experiments were performed in pH-controlled Stirred Tank Reactor (STR) with or without the addition of nitrogen and sulfur sources. The total H2 production and the maximum hydrogen productivity of T. maritima in the culture medium, containing MFVW and AHFW (45 mmol L−1 carbohydrates) at a C/N ratio of 12, were 132 mmol L−1 and 15 mmol h−1 L−1, respectively. However, tripling the concentration of carbohydrates to reach a C/N ratio of 22, has increased two times the maximum H2 productivity (28 mmol h−1 L−1) due to the improvement in nutrient balance. The cumulative H2 production was 285 mmol L−1, yielding a potential energy generation of 0.12103 MJ ton−1 wastes, which could be an interesting alternative for energy recovery

Theoretical investigation of the electronic properties of alkali atoms interacting with helium rare gas using a pseudopotential approach

International audienc

Spectroscopic and structural investigation for the ground and excited states of CaNa+ molecular ion

International audienc

A simple gas pressure manometer for measuring hydrogen production by hydrogenogenic cultures in serum bottles

International audienceThis study investigated the determination of hydrogen production by three H2-producing microorganisms (Thermotoga maritima, Thermococcus kodakarensis KOD1 and Enterobacter cloacae) cultured in 116-mL serum bottles. A gas pressure manometer was used to measure total pressure in the serum-bottle headspace. It was demonstrated that total pressure is the sum of the saturation pressure of water, the pressure expansion of gases, and the partial pressures of H2 () and CO2 (). A linear relationship was established between the partial pressure of H2 measured by gas chromatography and the sum of the partial pressures of H2 and CO2 measured by the manometer. When pH of culture medium was not controlled (pH decreased from 7 to 5), the ratio was close to stoichiometric H2/CO2 yield ratio of the most plausible metabolic pathways of each strain. values were 1.7, 1.9 and 0.9 for T. maritima, T. kodakarensis and E. cloacae, respectively. In these experimental conditions, can be deduced from total pressure measured by manometer