On the use of the FluoroProbe®, a phytoplankton quantification method based on fluorescence excitation spectra for large-scale surveys of lakes and reservoirs

Although microscope analysis is very useful for studying phytoplankton community composition, it does not allow for high frequency (spatial and/or temporal) data acquisition. In an attempt to overcome this issue, fluorescence-based approaches that use selective excitation of pigment antennae have spread rapidly. However, the ability of spectral fluorescence to provide accurate estimates of phytoplankton biomass and composition is still debated, and only a few datasets have been tested to date.In this study, we sampled of a wide range of water bodies (n = 50) in the Ile-de-France region (North Central France). We used the resulting extensive dataset to assess the ability of the bbe-Moldaenke FluoroProbe II (FP) to estimate phytoplankton community composition in lakes and reservoirs.We demonstrated that FP data yields better estimates of total phytoplankton biovolume than do spectrophotometric chlorophyll a measures and that FP data can be further corrected using the average chlorophyll a to biovolume ratio among phytoplankton groups. Overall, group-specific relationships between FP and biovolume data were consistent. However, we identified a number of cases where caution is required. We found that Euglenophytes are expected to depart from the global FP vs. biovolume relationship of the ‘green’ group due to varying Fv/Fm and pigment content in response to environmental conditions (photoautotrophic vs. photoheterotrophic growth). Then, it appears necessary to consider the composition of the Chromophytes community in order to obtain a good agreement between both biomass estimation methods. Finally, we confirmed the misattribution toward the ‘red’ group of phycoerythrin-containing cyanobacteria and the occurrence of a strong scattering in the relationship between the FP vs. biovolume of the ‘blue’ group that can be partly attributed to the occurrence of large colony-forming cyanobacteria (e.g., Microcystis spp, Aphanizomenon flos-aquae).We propose correcting procedures to improve the quality of data obtained from spectral fluorescence tools in the context of large-scale sampling of lakes and reservoirs.     

A thermomechanical model for the analysis of disc brake using the finite element method in frictional contact

Abstract

In this work, a numerical simulation of the transient thermal analysis and the static structural one was performed here sequentially, with the coupled thermo-structural method using the ANSYS software. Numerical procedure of calculation relies on important steps such that the CFD thermal analysis has been well illustrated in 3D, showing the effects of heat distribution over the brake disc. This CFD analysis helped in the calculation of the values of the thermal coefficients (h) that have been exploited in the 3D transient evolution of the brake disc temperatures. Three different brake disc materials were selected in this simulation and comparative analysis of the results was conducted in order, to derive the one with the best thermal behavior. Finally, the resolution of the coupled thermomechanical model allows to visualize other important results of this research such as; the deformations, and the equivalent stresses of Von Mises of the disc, as well as the contact pressure of the brake pads. Following our analysis and results we draw from it, we derive several conclusions. The choice makes it possible to deliver the best brake rotor so as to ensure and guarantee the good braking performance of the vehicles.     

Desalting of phenylalanine solutions by electrodialysis with ion-exchange membranes

This paper describes the optimization of the recovery of phenylalanine from an industrial waste stream by electrodialysis. An electrodialysis apparatus, consisting of three compartments equipped with ADP and CDS ion exchange membranes, was tested. These membranes without pretreatment appeared to be less efficient than the first pretreatment membranes which were immersed in a salt waste stream for 18h. The electrodialysis process with pretreated membranes yielded 87% of recovered phenylalanine. Furthermore, this process has also been successful in removing 98% of salts (Na₂SO₄ and (NH₄)₂SO₄), from the initial solution with an average current efficiency in the range of 96%. In the second pretreatment, the membranes were soaked in a bovine serum albumin solution for 2h before the commencement of the experiment. The results obtained show that the phenylalanine loss is significantly reduced. This loss did not exceed 5% and had an average current efficiency of 98%.     

Filtration of zinc ions utilising pretreated Streptomyces rimosus biomass

The performance of biofiltration of zinc utilising pretreated Streptomyces rimosus was studied. Streptomyces rimosus biomass is able to bind zinc ions in batch mode. The biomass granules may be regenerated easily by using a biomass pretreatment which confers rigidity to biosolids, without decreasing the zinc uptake capacity, thus allowing collection of the biomass by filtration. Accordingly, biomass was pretreated with an anionic enzymatic tension active product (Extran AP41) and regeneration with a cleaning product (HCl) was successfully realised. It was shown that the optimum concentration of biomass and pressure range are found to be between 50 and 120 g dm^?3 and 0.5 and 1 × 10⁵ Pa, respectively. Complete regeneration was reached after three cycles under optimal experimental conditions when the biosorbent was saturated with synthetic ZnCl₂ solution. The filterability of biosolids was demonstrated. A combination of a batch reactor and a filtration process made it possible to increase the performance of the complete treatment process. The biosorption capacity of the biomass to bind Zn ions was slightly increased (from X = 14 mg g^?1 in batch mode to X = 16.1 mg g^?1 in a process combining batch reactor and pressure filtration) and the experimental contact time was considerably reduced. Integration of the filtration process produced a dewatering cake which considerably facilitated the regeneration operation. Copyright © 2003 Society of Chemical Industry     

Mechanism of phenol adsorption onto electro-activated carbon granules

The main purpose of this paper is to determine the mechanisms which govern the adsorption of the phenol onto electro-activated carbon granules. This new activation technique allowed an increase of the performance of the adsorbent. Two models were utilised to understand the improvement in the performance of electroactivated carbon granules. The first, a simple external resistance model based on film resistance, gave acceptable predictions, with an error of less than 15%, between the theoretical results and experimental data independent of the activation potential and phenol initial concentration. The second linear model, based on diffusion phenomena, was more representative in describing the experiment than the first model. It was observed that the electro-activation method did not change the mechanism which governs phenol adsorption onto granular carbon. Indeed, the same mathematical model based on diffusion phenomena made it possible to predict with a very low error (less than 5%) the experimental data obtained for the favourable activation potential, without activation potential and with an unfavourable activation potential. The electro-activation technique makes it possible to increase the number of active sites that improve the performance of the electro-activated granular carbon compared with conventional granular activated carbon.     

An analytical method for solving exact solutions of the convective heat transfer in fully developed laminar flow through a circular tube

This paper proposes an exact solution to the classical Graetz problem in terms of an infinite series represented by a nonlinear partial differential equation considering two space variables, two boundary conditions, and one initial condition. The mathematical derivation utilized the separation of variables method where several stages were completed to reach the solution to the Graetz problem.     

Thermal behavior of full and ventilated disc brakes of vehicles

Braking is a process which converts a vehicle’s kinetic energy into mechanical energy which must be dissipated in the form of heat. During the braking phase, the frictional heat generated at the interface of the disc and pads can lead to high temperatures. This phenomenon is even more important than the tangential stress. The relative sliding speeds during contact are also important. The prediction of surface temperature for a brake rotor is regarded as an important step in studying brake system performance. The frictional heat generated on the rotor surface can influence excessive temperature rise which, in turn, leads to undesirable effects such as thermal elastic instability (TEI), premature wear, brake fluid vaporization (BFV) and thermally excited vibrations (TEV). The objective of this study is to analyze the thermal behavior of the full and ventilated brake discs of the vehicles using computing code ANSYS. The modeling of the temperature distribution in the disc brake is used to identify all the factors and the entering parameters concerned at the time of the braking operation, such as the type of braking, the geometric design of the disc and the material used. The results obtained by the simulation are satisfactory compared to those of the specialized literature.     

Preparation of activated carbon from olive mill solid residue

A process was developed for producing high quality activated carbon from Algerian mill waste. The solid olive mill residue was carbonized at 800 °C and physically activated with CO₂, air or steam. An optimum activation temperature of about 850 °C was determined for all the activation agents used. Steam appeared to be the most efficient activator as compared with air and CO₂. An optimal activation time of about 2 h was then determined with steam as the optimum activation agent. The porous structure of the activated carbon was characterized by nitrogen adsorption at −196 °C, and in all cases the surface areas, calculated by DR and BET methods, confirmed the production of a material with good microstructural characteristics and specific surfaces exceeding 1500 m² g⁻¹ for the carbon prepared by steam activation. Phenol adsorption isotherms gave the adsorption properties and the adsorption capacity of about 11.24 mg of phenol per gram of the activated carbon produced. The kinetics of the phenol adsorption onto the porous material was evaluated by means of two models: the external resistance model and the linear model. The second model appeared to constitute a more appropriate fit for the experimental data. © 2000 Society of Chemical Industry