The interest for biofilm-based systems for microalgae and related compounds production has been increasing lately. Although extensive literature has been reported on productivity, the physiological characterization (photosynthetic activity and composition) of attached cells at early stages of biofilm development has seldom been investigated. In this work, the effect of light intensity and inoculum cell density on 3-days Chlorella vulgaris biofilms developed on membranes was studied. Biomass production was clearly impacted by mechanism of photo-limitation occurring in biofilms acclimated to low light intensity (50 µmol m -2 s -1 ). A higher electron transport capacity and lower chlorophyll content in biofilms at high light intensity (500 µmol m -2 s -1 ) were also measured which are in line with patterns observed for suspended microalgae cultures. In addition, optimal conditions in terms of light (250 µmol m -2 s -1 ) combined with low (4.8 ×10 6 cells cm -2 ) or high inoculum density (28.8 ×10 6 cells cm -2 ) were identified to optimize biomass and lipids production, respectively. On the whole, measuring physiological profiles of immobilized cells at the initial stages of biofilm development provides information to efficiently operate and optimize biofilm-based systems.

A kind of adaptive subcarrier, bit and power allocation method utilizing Hopfield neural network (HNN) to minimize the overall transmit power of multiuser OFDM is studied in this paper. In order to find the power optimal subcarrier, bit and power allocation under the constraints that one subcarrier can only be allocated to one user and all users are allocated the same numbers of subcarrier, the number of bits of each subcarrier is finite, bit data can be allocated to each subcarrier, two kinds of new energy constrained functions are constructed for the HNN. It is shown through numerical simulations that the proposed methods can find the optimal allocation with less complexity compared with the exhaustive method.

The interest in microalgae bio lm-based systems has been increasing lately due to their high potential for biomass production. However, more studies focusing on the rst stages of this bioprocess, such as support selection and inoculum properties, which may nally affect biomass productivity, are required.The aim of this study was therefore to assess the impact of support nature and inoculum properties on microalgae bio lms productivity and physiology. Results suggest that physico-chemical properties of the support (micro-texture, hydrophobicity and chemical functional groups) affect the attachment of Chlorella vulgaris. Signi cant differences in cell-distribution pattern and bio lm structure on polyamidebased (Terrazzo) and Cotton-based fabrics were observed. Compared to Cotton, cells grown on Terrazzo showed higher biomass productivity (3.20-fold), photosynthetic capacity (1.32-fold) and carbohydrate pool (1.36-fold), which may be explained by differences in light availability due to support micro-texture.A high inoculum density, resulted in a lower bio lm growth likely due to a lower light/nutrient availability for the cells. Furthermore, when immobilized on fabrics, cells pre-acclimated to 350 µmol photons m -2 s -1 grew faster than those pre-acclimated to low light (50 µmol photons m -2 s -1 ), demonstrating the in uence of light-history of the inoculum cells on bio lm productivity. Therefore, this work con rmed the importance of support and inoculum properties for bio lm-based systems.