Reaction Phenomena Research Articles

Bio-ionic liquid pretreatment and ultrasound-promoted enzymatic hydrolysis of black soybean okara

The effective processing method to produce fermentable sugars and modify the microstructure of black soybean okara using bio-ionic liquid (bio-IL) pretreatment and ultrasound-promoted enzymatic hydrolysis was investigated. The morphology and structural characteristics of okara before and after bio-IL pretreatment and enzymatic hydrolysis under different ultrasonic frequencies were analyzed by field emission scanning electron microscope (FE-SEM), X-ray energy dispersive spectrometer (EDS), and Fourier transform infrared spectroscopy (FTIR). Without pretreatment, the production of total reducing sugar (TRS) under ultrasound (40kHz/300W) was 3.4 times of that without ultrasound. Using the bio-IL choline acetate ([Ch][OAc]) in water for the pretreatment of black soybean okara, the TRS production of enzymatic hydrolysis was further increased to 5.2 times of that without ultrasound in 4h of reaction. The analysis by FTIR and EDS showed that the highly structured matrix of okara was unfolded and broken by the action of combining ultrasound and choline acetate pretreatment, due to which the surface structures with large pores were presented to facilitate the reduction of unfavorable hindrance for enzymatic hydrolysis. The simplified kinetic model was proposed to describe the transport and reaction phenomena of enzymes in a solid-liquid system by using two kinetic parameters to show the impeded behavior of enzyme within the matrix of okara. The combination of bio-IL pretreatment and ultrasound-promoted enzymatic hydrolysis was able to make the efficient structural changes of black soybean okara to enhance the digestion of enzymes, and the okara could be valorized for use in foods.

Morphology Transformation of Chalcogenide Nanoparticles Triggered by Cation Exchange Reactions

Plenty of chalcogenide families with tremendous potential for functional applications remain unexplored due to the limitations of conventional synthesis methods. However, cation exchange reactions in colloidal synthesis offer an alternative way to overcome these limitations and provide a route to synthesize pure phases and morphologies that otherwise are challenging to achieve. In this work, we demonstrate the possibility of Sb3+ to undergo cation exchange reactions with Cu+ in Cu2–xSe nanoparticles and study an uncommon morphology transformation from Cu2–xSe nanoparticles to Cu3SbSe3 nanoplates. The morphology transformation is dictated by a growth process of assembly and merging of primary nanoparticles triggered by the incorporation of Sb cations into the Cu2–xSe lattice and the rearrangement of the anion framework. By studying this unprecedented phenomenon in cation exchange reactions and adding Sb to the list of available elements for exchange, this work provides insight into the unexplored potential...

Conservation laws, symmetries, and exact solutions of the classical Burgers–Fisher equation in two dimensions

This work investigates a spatially two-dimensional advection–diffusion–reaction equation that generalizes the Burgers’ and the Fisher’s equations, having the properties of convective phenomenon from Burgers equation as well as diffusion transport and reaction phenomena from Fisher’s equation. The two-dimensional equation is analysed from the point of view of the theory of symmetry reductions in partial differential equations. Conservation laws and exact solutions from double reductions are derived. Finally, an explicit shock wave solution is obtained.

CFD design and simulation of ethylene dichloride (EDC) thermal cracking reactor

ABSTRACTAt high temperature, ethylene dichloride decomposes into vinyl chloride monomer and HCl by a complex reaction mechanism. Due to chemical reaction type and heat transfer mechanism, design and simulation of cracking reactors are complicated. This process is very important from either chemical reaction or transport phenomena’s point of view. In this study, 2D simulation of cracking reactor is performed with FLUENT software. Simulation results were compared with the experimental data. Then, we investigate the simulation results and effect of various parameters on the process. Results show that with process progress and temperature increase during reactor length, conversion and coke formation amount are increased. At the end of the process, conversion is 52.69 that has good agreement with industrial data. Addition of promoter to the process fluid and fluid behavior in different coil outlet temperatures was studied; finally, the effects of these factors are described in detail.

Thermal instability and kinetics analysis on triacetone triperoxide (TATP)

Differential Scanning Calorimetry (DSC), Thermogravimetry(TG) and vent sizing package 2 (VSP2) were performed to understand thermal behavior and decomposition kinetics of triacetone triperoxide (TATP) under non-isothermal and adiabatic conditions, respectively. Then the maximum self-heating rate [(dT/dt)max], maximum pressure rise rate[(dP/dt)max] were acquired. DSC studies revealed a coupling phenomenon of decomposition reaction and phase transition. Based on the DSC data, the thermal decomposition kinetic parameters were worked out and compared through the Friedman and ASTM E698 methods. The results indicated that Heat of decomposition (ΔHd) was extraordinary large even up to 2700 Jg−1 for which recrystallized with methanol merely. The activation energy of which used methanol to recrystallize was 155.5kJ/mol by (ASTM) E-698 methods. By Friedman method Linear regression was able to reach a high enough level when the reaction progress (α) was between 0.1–0.9. The results can be used to calculate the optimal parameters for processing a safer design and establish the database of TATP for loss prevention protocol.

Modeling Reactive Mixtures: Case Study for Spills of Formaldehyde Solutions

When a liquid mixture, such as an aqueous formaldehyde solution, is released into the environment, the rate of evaporation into the atmosphere depends strongly on chemical reactions that regulate the evolution of formaldehyde vapors. Most of the consequence modeling methods and models currently used in the industry usually ignore any reaction phenomena. This article describes a dynamic model developed using the Aspen® Custom Modeling (ACM) tool kit. In the case of formaldehyde solutions, the thermodynamics and reaction kinetics of a mixture of formaldehyde (HCHO), water and methanol (CH3OH) are computed from models available in the open literature. The liquid‐phase, reversible, chemical reactions between water and formaldehyde, as well as methanol and formaldehyde, form oligomers—most of which are nonvolatile. The mass transfer and heat transfer coefficients between the surface of the spill and the atmosphere are computed by established correlations for flow over a semi‐infinite flat surface.For a release scenario, the model computes the time‐varying liquid and vapor phase compositions and conditions. It also computes the required vaporization rates for HCHO and CH3OH resulting from, for example, a 54 wt% formaldehyde solution spill onto a relatively dry surface of a fixed area under specific meteorological conditions. The article presents details regarding the formaldehyde spill modeling methodology, with examples. © 2018 American Institute of Chemical Engineers Process Process Saf Prog 38: 61–70, 2019

Microwave-assisted synthesis of imprinted polymer for selective removal of arsenic from drinking water by applying Taguchi statistical method

In the present study, As3+ imprinted polymer as an active detoxification material has been synthesized through microwave assisted preparation method. By inducing the microwave radiation during the polymerization process decreases the reaction time to about 10 folds than conventional method. The imprinted polymer is one of the best possible techniques for the removal of arsenic, and various other contaminants from drinking water. The SEM and FTIR analyses have been conducted to clarify microstructure, surface morphology and size distribution of the synthesized imprinted polymer. The main parameters affecting the pzc, pH, agitation time, shaking speed, concentration, the temperature of adsorbent and percent of sorption, have been examined and optimized by Taguchi design. Taguchi L9 orthogonal array was employed to optimize the important factors versus % sorption values with nine experimental runs at 3 levels. Moreover, to understand the reaction phenomenon Langmuir and Freundlich isotherms, kinetic models and thermodynamics of adsorption process were calculated. The relative selectivity coefficient of imprinted polymer for As3+/Cd2, As3+/Zn2+, As3+/Ni2+were respectively 45.93, 131.01, 262.63 times greater than for non-imprinted polymer. The limit of detections (LOD) and limit of quantification (LOQ) of the proposed procedure for As3+ ion was found to be 1.0 µg/L and 3.3 µg/L for the As3+ ion respectively, with the relative standard deviation (RSD) of 4%. The excellent adsorption performance along with their low cost and convenient synthesis makes this range of adsorbent highly promising for commercial applications in drinking water purification and water treatment.

CFD Steady Model Applied to a Biomass Boiler Operating in Air Enrichment Conditions

A numerical model is proposed to perform CFD simulations of biomass boilers working in different operating conditions and analyse the results with low computational effort. The model is based on steady fluxes that represent the biomass thermal conversion stages through the conservation of mass, energy, and chemical species in the packed bed region. The conversion reactions are combined with heat and mass transfer submodels that release the combustion products to the gas flow. The gas flow is calculated through classical finite volume techniques to model the transport and reaction phenomena. The overall process is calculated in a steady state with a fast, efficient, and reasonably accurate method, which allows the results to converge without long computation times. The modelling is applied to the simulation of a 30 kW domestic boiler, and the results are compared with experimental tests with reasonably good results for such a simple model. The model is also applied to study the effect of air enrichment in boiler performance and gas emissions. The boiler operation is simulated using different oxygen concentrations that range from 21% to 90% in the feeding air, and parameters such as the heat transferred, fume temperatures, and emissions of CO, CO2, and NOx are analysed. The results show that with a moderated air enrichment of 40% oxygen, the energy performance can be increased by 8%, CO emissions are noticeably reduced, and NOx remains practically stable.

Reusing the generated sludge as Fe source in Fenton process for treating crepe rubber wastewater

Sludge recycling in Fenton oxidation was performed following the simplest procedure for studying the reaction phenomena and the role of Fe using methanol as the model compound and crepe rubber wastewater (CRWW) as the industrial application. CRWW is odorous and high in organics, nitrogen and phosphorus. Despite the capability of degrading hardly decomposable substances, large Fe3+ sludge production confines the useful application of Fenton oxidation. This sludge is hazardous due to residual organics adsorption from treated wastewater. Batch-mode experiments were performed at 25 °C and pH 2–3 for 24 h. After neutralization (adjusting pH > 9) and centrifugation, concentrated sludge was applied in the subsequent Fenton run as the Fe source. TOC reductions of 100% and 97% in conventional Fenton and 100% and 77% in sludge reuse systems were achieved for methanol and CRWW solutions, respectively, for initial COD:H2O2:Fe2+ mass ratio of 1:8:2 with effective reuse cycles. Fe in the sludge system behaved primarily as a heterogeneous catalyst, while dissolved Fe contributed to homogeneous catalytic reactions. Dissolved Fe2+ and total Fe were accumulated in sludge runs for enhancing the homogeneous process. Outcomes indicate that the simplest sludge reuse method experimented in this work can be effectively applied as an environmentally and economically promising method.

Development of Unstructured Mesh-Based Numerical Method for Sodium-Water Reaction Phenomenon

When pressurized water or vapor leaks from a failed heat transfer tube in a steam generator (SG) of sodium-cooled fast reactors, a high-velocity, high-temperature jet with sodium-water chemical reaction may cause wastage on the adjacent tubes. For safety assessment of the SG, a computational fluid dynamics code SERAPHIM, in which a compressible multicomponent multiphase flow with sodium-water chemical reaction is computed, has been developed. The original SERAPHIM code is based on the finite difference method. In this study, an unstructured mesh-based numerical method was developed and introduced into the SERAPHIM code to advance a numerical accuracy for a complex-shaped domain including multiple heat transfer tubes. The multiphase flow under the tube failure accident is calculated by the multifluid model considering compressibility. The governing equations are solved by the Highly Simplified Marker And Cell (HSMAC) method. The original HSMAC method was modified for compressible multiphase flows in the unstructured mesh. Validity of the unstructured mesh-based SERAPHIM code was investigated through the analysis of an underexpanded jet experiment, which is a key phenomenon in the tube failure accident. The calculated pressure profile showed good agreement with the experimental data. Numerical analysis of water vapor discharging into liquid sodium was also performed. The calculated behavior of the reacting jet agreed with the previous experimental knowledge. It was demonstrated that the proposed numerical method could be applicable to evaluation of the sodium-water reaction phenomenon.

Transport and reaction phenomena in multilayer membranes functioning as bioartificial kidney devices

Classic hemodialysis only provides a limited removal of protein bound uremic toxins (PBUT) in patients with chronic kidney disease. A bioartificial kidney device, BAK, composed of a living cell monolayer of conditionally immortalized proximal tubule epithelial kidney cells (ciPTEC) cultured of hollow fiber polymeric membrane can remove protein bound uremic toxins from the blood in combination with classic hemodialysis. The development and clinical implementation of the BAK requires lots of optimization. This investigation is expensive and time consuming therefore modeling studies could help to optimize experiments and improve its design.In this work, a 3D mathematical model of the BAK is developed. The transport and reaction mechanisms associated with the removal of PBUT indoxyl sulfate are considered and various conditions are simulated. The model describes a single hollow fiber membrane and considers different domains for the blood flow, the membrane, the cell monolayer, and the dialysate region. A mathematical description of the relevant transport and/or reaction mechanisms is provided in each domain, and the corresponding differential equations are solved numerically. Since not all the modeling constants are experimentally available, a parametric study is performed for their quantification, including the active transport kinetics of the toxins through the cell monolayer, in comparison to the passive transport rates by diffusion. The parametric study also provides a background for the extraction of usually unknown quantities, including notably the Organic Anion Transporter (OAT) concentrations, with the support of experimental data. Satisfactory reproduction of experimental findings is achieved, and the role of systemic variables that affect significantly the uremic toxin removal is identified.

Spectroscopy takes electrochemistry beyond the interface: A compact analytical solution for the reversible first-order catalytic mechanism

The monitoring of the non-interfacial phenomena of mass transport and homogeneous chemical reactions by combining spectroscopic and electrochemical methods is examined. The spectroelectrochemical study of a charge transfer process is addressed, considering the possibilities that the electro-consumed species is regenerated in solution by means of a first-order chemical reaction or that the diffusivity of the oxidized and reduced species differ from each other significantly.Novel closed-form explicit analytical expressions for the concentration profiles and the absorbance response of all the species for any voltammetric technique are deduced, taking into account the two main working arrangements: the normal-beam and parallel-beam modes. The analytical solutions are particularized to double potential step chronoamperometry and to cyclic voltammetry. The corresponding chronoabsorptometric and voltabsorptometric responses in parallel-mode are proven to provide additional information with respect to electrochemical-only measurements, as well as insights into the solution regions next to the interface where the concentration changes and equilibrium disruption take place. With this theory the absorptometric response can be related to the physicochemical dynamics of the redox system and optimum configuration and conditions for the study of diffusion and reaction layers, the species diffusion coefficients and the chemical kinetic and equilibrium constants can be established.

Evaluation of Effect of Particle Size Distribution on Lithium-Ion Battery Performance By Multi-Element Network Model

For the improvement of Lithium-ion Batteries (LiBs) performance, the optimum structure design of porous electrode is needed. In particular, the relationship between porous structure and the internal phenomena has to be understood well from the viewpoint of improvement of capacity, output power density and durability [1]. In LiBs electrode layer, the ratio of the electrode thickness and the diameter of active material is approximately 20, and this value is less than usual porous media electrode and devices, such as polymer electrolyte fuel cell [2,3], separation membrane and some packed bed system. So, it is difficult to treat LiBs electrode as homogeneous porous media. It is needed to evaluate the mass transport performance and the formation of electrochemical reaction field with the information of local structure that are the particle size and the position of each particle. Numerical simulation approach is effective to understand the internal phenomena and to design the optimum electrode structure. However, the microscopic structure, which is affected by particle size distribution, agglomeration and migration, cannot be targeted by usual homogeneous structure simulation [4]. Recently, though some microscopic simulation have already been tried to evaluate the effect of heterogeneous structure on cell performance, the calculation time and the calculation size are remarkable subjects. In our group, we have already developed Multi-Element Network Model for LiBs simulation [5]. In porous electrode layer, imaginary pore spheres with greatest diameter were located between active material particles. These imaginary pore spheres represent electrolyte over the space by defining electrolyte information such as ion electric potential and Li ion concentration. After constructing electrode structures, the active material particle network and pore network were built. By building the Multi-Element Network, the electronic conduction can be calculated in particle network, as the ionic conduction and diffusion were calculated with pore network, while the electrode reaction occurring at interface between active material particles and electrolyte can be calculated. Based on the porous electrode theory, the reaction and mass transport phenomena at discharge condition was simulated. As a result, in the case of small particle for enlargement of reaction interface, the continuity and the tortuosity of electrolyte phase was changed even if the volume ratio is constant. Especially, the bimodal particle size distribution strongly affect output density more than the monomodal distribution. By this simulation, the relationship between microscopic structure and the cell performance can be discussed. In addition, in our presentation, we will discuss the effect of the micro-scale structure on cell performance with actual porous electrode layer.

The use of calcium sulfoaluminate cement to mitigate the alkali silica reaction in mortars

The mitigation of the alkali silica reaction in concrete has been the interest of many studies by using low-alkali cement or supplementary cementitious materials. In this paper, calcium sulfoaluminate cement, characterized by its low alkali content and low pH, is used as a mean to reach this goal.Therefore, the main objective is to verify if the composition of a sulfoaluminate cement paste can mitigate the alkali silica reaction compared to that of a Portland cement. The reactive flint aggregate from north of France was used to initiate the alkali silica reaction phenomena with two types of cements: Portland cement CEMI 52.5 N from Holcim, and calcium sulfoaluminate cement Alpenat from Vicat. Alkalis were added by introducing NaOH or NaCl in the mortar mixing solution; six mortars were made. Two references – with Portland or sulfoaluminate cement – without addition of extra amount of alkali, and the four other mortars with either NaOH or NaCl. The results show that, for the reference mortars non expansion/alteration has been detected during the test duration of 140 days. For Portland cement mortar, with same alkali content but coming from two different sources (NaOH or NaCl), the expansion is almost the same. The expansion measurements show that the using of calcium sulfoaluminate cement can mitigate the alkali silica reaction in mortars by reducing its expansion 7 times compared to that of Portland cement mortars. This result was confirmed by the microstructural observations, where the frequency of the alterations – due to the alkali silica reaction – is much less in sulfoaluminate based mortars than the one of the alterations in Portland based mortars.

Solid-State Spalling of Ag3Sn in an Eutectic SnPb Solder Joint with an Ag Thin Film/Ge Cell

Spalling of intermetallic compounds is a common and detrimental phenomenon in the wetting reaction between Sn-based solders and under-bump metallizations; however, it is still not clear whether spalling will appear in solid-state aging. Here, the solid-state spalling of Ag-Sn intermetallic compounds at the interface between an eutectic Sn-Pb solder and an Ag/Ge substrate are examined during aging. Scanning electron microscopy (SEM) observations showed that Ag-Sn intermetallic compounds departed from the Ge substrate after the silver thin film was completely depleted during solid-state aging. This solid-state detachment of Ag-Sn intermetallic compounds was substantiated using deep etching. Despite this significant change in interfacial architecture caused by spalling, there is no considerable decline in the shear strength, implying that the interfacial joining was still effective. Thermodynamic analysis suggests that the spalling may be attributed to the open rapid diffusion paths among scalloped Ag3Sn in solid-state aging, limited thickness of the Ag layer and poor adhesion between Ag3Sn and the Ge substrate.

Multi-scale modeling of thermo-oxidation effects on the flexural behavior of cross-ply bismaleimide composites

Mechanical properties of high-temperature polymer matrix composites deteriorate during their service. Oxidation plays a significant role in determining the residual elastic and strength properties of the composite. The present work investigates the oxidative aging damage of cross-ply bismaleimide composites, both experimentally and numerically. Also, this work introduces a better understanding of the significant damage mechanisms, and their respective time ranges. Micro/macro-scale thermo-oxidation behavior and flexural failure were simulated for 1,700 hours of aging. Thermo-oxidation behavior of the cross-ply laminates was simulated using a multi-fiber multi-layer representative volume element. Thermo-oxidation is a diffusion–reaction phenomenon that depends on temperature and oxidation state in time and space domains. In this work, the proportionality between oxidation state evolution and reaction rate was modeled using a new form of time-dependent parameter. Owing to aging damage, the required properties for the flexural test simulation were reduced in the meso-scale. The current study presents a damage state assuming proportionality between the average crack length and oxidized layer thickness based on a continuum damage mechanics approach. Scanning electron micrographs showed that the onset of the “blunt” transverse (through-thickness) micro-cracking/debonding in the superficial layers was at 500 hours under $176.7~{}^{\circ}\mbox{C}$ ( $350~^{\circ}\mbox{F}$ ), where oxidative cracking dominates aging mechanisms. The “blunt” micro-cracks propagated in the transverse direction near 1000 hours rendering the crack faces in contact with the oxidative air. After about 1,700 hours of aging, the weight loss ratio was 0.5%, and the flexural modulus and strength reduced by 19% and 10%, respectively. Prior to 500 hours, where cracking was not noticeable in the “crack-free region”, the strengths reduction was not significant based on the numerical simulations. In the crack-free and oxidative damage dominated regions, the elastic property numerical reduction was significant.

Mechanical and Reaction Properties of Al/TiH2/PTFE under Quasi‐Static Compression

TiH2 is introduced into Al/PTFE reaction system for the first time. In order to study the mechanical and reaction properties of Al/TiH2/PTFE composites, five kinds of mixtures with different TiH2 contents and the contrasting TiH2/PTFE mixture are prepared. The true stress–strain curves and reaction phenomena are recorded during the quasi‐static compression experiments; The reaction residues are analyzed with XRD to understand the reaction mechanism. The results show that the introduction of TiH2 can significantly influence the strength of the composites; With the increasing of TiH2 content, the mechanical strength is firstly increase and then decrease; When the content is the same, the reinforcing effect of TiH2 particles on PTFE matrix is greater than that of Al. Violent reaction are observed in the four Al/TiH2/PTFE composites with the content of TiH2 below 20%, but not in TiH2/PTFE. Furthermore, compared with Al/PTFE material, special flames are found during the reaction of composites with TiH2, which become even more obvious with the increasing of TiH2 content. The material reaction mechanism denotes that the high temperature of the crack tip result in the reaction of Al and PTFE, which activates TiH2 to release hydrogen and generate TiC, resulting TiH2 to fully release its energy.

Evaluation of the Toxin-to-Protein Binding Rates during Hemodialysis Using Sorbent-Loaded Mixed-Matrix Membranes

The transport and reaction phenomena that take place in multi-layered mixed-matrix membranes with activated carbon (AC) sorbents that are expected to improve extra-corporeal blood purification, are studied at the macroscopic scale. A model was developed that aims at the description of the removal efficiency of harmful uremic toxins from the blood in the presence of carbon-adsorptive particles and produces results that are aligned with the experimental data. The importance of the generally unknown kinetic rate constants of the association of toxins to albumin is investigated through sensitivity analysis. Matching with further experimental data allowed the extraction of vital kinetic rate constants for key uremic toxins such as indoxyl sulfate (IS) and p-cresyl sulfate (PCS). Moreover, the effects of the plasma composition, as well as of the membrane loading with activated carbon, on the total removal of the protein-bound toxins are quantified and discussed.

Development of a multicomponent reaction rate model coupling thermodynamics and kinetics for reaction between high Mn-high Al steel and CaO-SiO2-type molten mold flux

A new multi-component reaction model was developed in order to describe complex reaction phenomena between a high Mn-high Al steel and a CaO-SiO2-type molten mold flux. This model is an extension of Robertson's multicomponent mixed-transport-control theory (Robertson et al., 1984) [7], where rate controlling step is assumed to be a mass transport of diffusing species in a boundary layer, while chemical equilibrium is assumed at the reaction interface. This model also employs a CALPHAD type multicomponent-multiphase thermodynamic calculations for chemical equilibria at the interface. By explicitly taking into account 1) local equilibrium at the liquid steel-liquid flux interface, 2) flux density equations for each diffusing species in the steel and the flux phases, and 3) instantaneous change of mass transfer coefficients of all diffusing species in the flux phase by varying viscosity of the flux, previous laboratory scale experimental data could be well explained under various [pct Al]0, [pct Si]0 in the liquid steel, (pct CaO)/(pct SiO2), (pct Al2O3)0, (pct MgO)0 in the liquid flux, and reaction temperature. From the model calculations under the various [pct Al]0, it was concluded that the present reaction model can be successfully applicable from low [pct Al] to high [pct Al] conditions in liquid steel. The present model was further extended in simulating composition change in a mold flux in a continuous casting mold, where the steel and the flux continuously enter and leave. The model calculations show good agreement with pilot plant scale data available in literature. From the calculation results under different casting variables such as [pct Al]0, mold flux pool depth, and mold flux consumption rate, the Al2O3 accumulation in the CaO-SiO2-type mold flux during the continuous casting was discussed.

<p>LES DISCOURS HAINEUX SUR <em>FACEBOOK </em>: LE CAS DES RÉACTIONS DES TUNISIENS AUX ATTENTATS TERRORISTES DE 2016</p>

Terrorist attacks generate many reactions on the Internet, most often filled with emotions. Our study focuses on the hate-speech in Arabic and French of Tunisian facebookers in response to the attacks in Tunisia and Belgium in March 2016. Our corpus consists of comments on the Shems FM radio Facebook page.Two axes will be developed. The first deal the social phenomenon of public reaction to tragic events. The second characterize the impact of information on Tunisian representations of the attacks. The third is an answer to the initial hypothesis.