The Selectivity of Milking of Dunaliella salina

The process of the simultaneous production and extraction of carotenoids, milking, of Dunaliella salina was studied. We would like to know the selectivity of this process. Could all the carotenoids produced be extracted? And would it be possible to vary the profile of the produced carotenoids and, consequently, influence the type of carotenoids extracted? By using three different D. salina strains and three different stress conditions, we varied the profiles of the carotenoids produced. Between Dunaliella bardawil and D. salina 19/18, no remarkable differences were seen in the extraction profiles, although D. salina 19/18 seemed to be better extractable. D. salina 19/25 was not “milkable” at all. The milking process could only be called selective for secondary carotenoids in case gentle mixing was used. In aerated flat-panel photobioreactors, extraction was much better, but selectiveness decreased and also chlorophyll and primary carotenoids were extracted. This was possibly related to cell damage due to shear stress

Where less may be more: how the rare biosphere pulls ecosystems strings

Rare species are increasingly recognized as crucial, yet vulnerable components of Earth’s ecosystems. This is also true for microbial communities, which are typically composed of a high number of relatively rare species. Recent studies have demonstrated that rare species can have an over-proportional role in biogeochemical cycles and may be a hidden driver of microbiome function. In this review, we provide an ecological overview of the rare microbial biosphere, including causes of rarity and the impacts of rare species on ecosystem functioning. We discuss how rare species can have a preponderant role for local biodiversity and species turnover with rarity potentially bound to phylogenetically conserved features. Rare microbes may therefore be overlooked keystone species regulating the functioning of host-associated, terrestrial and aquatic environments. We conclude this review with recommendations to guide scientists interested in investigating this rapidly emerging research area

On the benefit of fast-neutron reactor fuel depletion for transportation

International audienceIn recent years, some efforts have been devoted in France to research projects for handling Phenix Fast-neutron Reactor (FR): wet storage, reprocessing process and transportation. This paper assesses the benefit of taking account of the depletion of FR fuel elements for transportation. After a brief presentation of the calculation tools and models for depletion and criticality calculations, the depletion and criticality options are discussed. Then, interesting results show that the use of a low burnup level may allow an optimised loading of FR fissile fuel assemblies in the TN ® 17/2 transport cask. Furthermore, the results for FR fissile assemblies also encompass criticality calculations for FR fertile assemblies. Indeed, due to TN ® 17/2 transport cask design, substantial margins are available for FR fertile assemblies, even for strongly conservative hypotheses on fuel inventory. Consequently, considering their irradiation is not of interest for this case, but could be for other transportation configurations. Finally, the paper focuses on depletion codes validation, a key element for a straightforward and effective implementation of this approach

Criticality codes biases and associated uncertainties determination for fissile nuclear material transportation using different approaches

International audienceCriticality safety analysis regarding fissile nuclear material transportation or operations requires, among many aspects, the experimental validation of the criticality codes with the associated cross-section libraries. The requirements for the experimental validation of the criticality code is to analyze the similarity between a selected set of critical experiments and the industrial configuration studied to determine the calculational biases and the associated uncertainties using different methods.The method currently used in France for addressing the bias and its associated uncertainty is mainly based on expert judgment and the knowledge of available experiments. This approach uses descriptive parameters (geometry, composition…) and some macroscopic calculated parameters to infer experiments potentially representative of an industrial case and the corresponding biases. The biases of the reference experiments are then transposed to the industrial case depending of the representativity of the experiments. This step can be facilitated by doing a linear regression of keff versus the parameter that best describes the configuration. An alternative method is to study the similarity between the selected experiments and the industrial case using the statistical approach based on the Generalized Linear Least Square Method (GLLSM). This method allows the propagation of uncertainties in nuclear data and discrepancies between calculations and reference benchmarks for a selection of experiments to linearly adjust the calculated keff values to reference values and therefore exhibit a bias and uncertainty due to nuclear data for an industrial case. The aim of the paper is to compare these two methodologies on an Orano TN transport and storage cask for BWR used fuel at around 15 GWD/MTU. A first selection of experiments was drawn using expert judgment. This selection was then restricted to experiments that were shown to be the closest to the industrial case regarding the Ck “similarity” parameter calculated with the SCALE 6.2.1 package. Applying both methodologies to the industrial case highlights that they both give comparable biases with regards to the uncertainties

(Table 2) Geochemistry in magnesiochromite at DSDP Hole 78-543A

(Table 2) Geochemistry in magnesiochromite at DSDP Hole 78-543