33 research outputs found
Moving shadow detection with support vector domain description in the color ratios space
No full textInternational audienc
Bulimic behaviors in the tunisian general population: prevalence and associated factors
No full textIntroduction
Bulimic behaviors (BB) are a major public health problem, due to their prognosis and serious psychological, somatic, and social consequences. The exact etiopathogenesis of BB is still poorly understood, and the literature suggests the interaction of multiple factors.
Objectives
The aim of our study was to estimate the prevalence of BB in the Tunisian general population and to identify the associated risk factors.
Methods
We conducted a cross-sectional, descriptive, and analytical study of Facebook group members, using an online questionnaire, from February 17, 2023, to May 26, 2023. All respondents over the age of 18 were included in the study. All participants filled out a socio-demographic questionnaire. Body mass index (BMI) was calculated from weight and height. The Bulimic Investigatory Test, Edinburgh (BITE) was used to screen and assess the intensity of bulimic behaviors.
Results
A total of 528 responses were included in the study. The mean age of the sample was 33.3±11.95 years, and the M/F sex ratio was 0.41. Subjects were unmarried in 63.4% of cases, of low socio-economic status in 19.5%, with a university education in 75.2%, and with a psychiatric history in 25.6% of cases. The mean BMI was 25.15±4.98. The mean BITE score was 10.76±6.85, and 6.6% of our population were at high risk of developing BB.
In the bivariate study, female gender (p<0.001), unmarried marital status (p=0.001), university education (p<0.001), and the presence of a psychiatric history (p<0.001) were significantly associated with a high risk of developing BB. Moreover, the BITE score was negatively correlated with age (r=-0.231; p<0.001) and positively correlated with BMI (r=0.307; p<0.001).
Conclusions
This study highlighted the magnitude of the risk of bulimic behaviors in the Tunisian general population and the need to set up programs to prevent and control these disorders.
Disclosure of Interest
None Declare
Oxydation humide des polluants organiques par l'oxygène moléculaire activée par le couple H²O²/Fe²+: Optimisation des paramètres opératoires
No full textOxydation humide des polluants organiques par l'oxygène moléculaire activée par le couple H²O²/Fe²+: Optimisation des paramètres opératoires
No full textL'oxydation humide par l'oxygène moléculaire (procédé WAO) activée par le couple (H202/Fe2+) a été mise en oeuvre pour l'oxydation de la pollution organique aqueuse à travers deux composés modèles: l'acide succinique, normalement oxydable, et l'acide acétique, réputé réfractaire. L'influence des différents facteurs a été étudiée par la planification d'expériences. Après leur recensement, une étape préliminaire de criblage a été menée à bien en utilisant une matrice de Plackett et Burman. Seuls les paramètres les plus influents ont été gardés pour l'étape ultérieure d'établissement de modèles prévisionnels à partir d'une matrice composite centrée orthogonale. Les modèles établis ont été validés et ont permis de déterminer les conditions optimales de fonctionnement. L'effet de la température fait apparaître un optimum, à environ 200 °C, au-delà duquel la décomposition du peroxyde devient trop rapide. L'effet de la quantité de peroxyde d'hydrogène introduit est déterminant et l'ajout de moins de 20 % de la quantité stoechiomé- trique permet d'obtenir à 200 °C, avec environ 10 ppm de sels de fer, une efficacité de traitement d'environ 70% pour un composé normalement oxydable. Dans des conditions analogues, le procédé conventionnel sans promoteur conduit à une efficacité inférieure à 5 %.Wet air oxidation (WAO) is a liquid phase oxidation process using molecular oxygen at high temperature (250-300°C) and high pressure (50-150 bar). It can help treating toxic organic aqueous wastes from chemical industries with efficiencies up to 98% after 1 hour. The process can also help treating sludges from domestic sewage treatment facilities. It is usually very cost effective because of the very high operating pressure.This paper deals with the promoted wet air oxidation of acetic acid, rnodel compound for refractory wastes, and succinic acid, model for readily oxidized wastes. The study was conducted in order to determine the promoting effect when adding small dosages of hydrogen peroxide (with iron salts) during oxidation by molecular oxygen. It was previously shown that the initiating step is very temperature dependent (Reaction I) and limits the overall oxidation process The addition of small amounts of H2O2/Fe2+ (Fenton's reagent) can promote the forrnation of very reactive OH• radicals able to develop R• radicals (Reaction IV), even at a low temperature. Then, the oxidation (Reactions VI and VII) continues using molecular oxygen, but the peroxide should be added continuously during a batch test in order to maintain the initiating step.An optimal design methodology was used in order to assess the dependency of the oxidation effrciency on the various parameters and mainly on the promotors. At frrst, a Plackett and Burman design of experiments (PE1) was used to screen the most important variables among those likely to have an effect. The design of experiments, the conditions of the runs and the results (tables 1 to 3) allowed the determination of a new experimental domain and the selection of the four most important variables for the further design of experiments. At the same time, the effect of an addition of phenol (able to reduce iron to the ferrous species, more efficient) was considered. For succinic acid oxidation, a central composite optimal design (PE2) was used (tables 4 and 5). The results allowed us to establish a predictive model (Relationship lX, table 6 and figure 2) and typical results are presented in figures 3 and 4. Approximately 50% oxidation efficiencies could be obtained at 200°C; without peroxide addition, only 5% efficiency is obtained under similar conditions. Moreover, it was observed that the optimum temperature is around 205°C and that phenol is not compatible with peroxide as a promotor. A third optimal design (PE3) was used to predict the efficiency of the method for the treatrnent of acetic acid, a model for a refractory waste. It is composed only of a fractional factorial design (table 7 and 8) and the bias corresponds to the main quadratic effect of temperature (Relationship XIII and table 10). The optimum temperâture is also 205°C and greater than 20% oxidation efficiencies are obtained; at such a temperature, acetic acid cannot be oxidized with the conventional process.The results obtained for the two model compounds validate this oxidation technique. The addition of about 10 ppm of ferrous iron and of less than 20% of the stoichiometric amount in hydrogen peroxide can turn a high pressure WAO process into a medium pressure one
A multi-view interest point based approach to photometric realism within augmented reality systems.
No full textIntegrating virtual objects into real environments presents a number of technical and aesthetic challenges which limit the impressiveness of current augmented reality applications. Although some of these challenges have recently been addressed, others are still active areas of research. The quality of the models and textures used, accurate geometric world alignment and the quality of illumination correspondence all need to be considered. Literature shows the latter to be the least mature field and is the focus of this paper. This paper introduces a new photometric registration technique that makes use of image interest points. The technique attains illumination correspondence without the need for pre-calibration or unnatural calibration objects, instead natural image features such as shadow and object interest points are use. The operational complexity of the technique is low and real-time processing of live data is achieved. Current progress and future work are discussed in the paper
Illuminant Condition Matching in Augmented Reality: A Multi-Vision, Interest Point Based Approach
No full textFor the output of an augmented reality application to
appear realistic a number of issues need to be taken into
consideration. The illumination correspondence between
the real and virtual components should be taken into account
as well as the scene level of detail and the accuracy
of alignment between the two worlds. This paper focuses
on matching world illumination and photometric registration
methods. It introduces a new technique that aims to
utilize shadow/object interest point correspondences in order
to locate and virtually reproduce real-life illuminants.
The technique is attractive as it makes use of natural calibration
objects in the form of natural scene geometry and
associated shadows. Computational complexity is kept relatively
low by using an interest point based approach. Further
work to be undertaken is discussed
Structural, Optical, Electric and Dielectric Characterization of LiMnO2 Compound
No full textLithium-ion batteries, which are the predominant energy source in electric cars, laptops, mobile phones, and digital cameras, are made up of LiMnO2 [1-5]. It was created using an enhanced solid state and one of the suggested solid electrolytes due to its extra ordinary ionic conductivity. The XRD characteristic of LiMnO2 has undergone a Rietveld refinement, which has identified a monoclinic crystal structure with C2/m space groups. Raman and IR spectroscopies show the presence of MnO6 and LiO6 octahedral groups in this material. Mapping of the elemental microstructure using scanning electronmicroscopy (SEM) and energy dispersive spectroscopy revealed the homogeneity and permeability morphology of LiMnO2 particles. Their dielectric characteristics were measured between 0.1 and 106 Hz and between 303 and 423 K, respectively. The band gap energy has been established and appears to be equal to 1.85 eV, which confirms the semiconductor nature of this compound. The analysis of the electrical data of the impedance spectra and the imaginary part of the complex modulus shows the presence of two types of relaxations corresponding to the grain and grain boundary effects in the two compounds. The thermal evolution of relaxation time and DC conductivity follows Arrhenius' law with a change in activation energy around 353 K. In addition, the frequency behavior of the AC conductivity of this sample was analyzed using Joncher's universal law. Therefore, the variation of s1 and s2, due to temperature, showed the presence of a change in the conduction mechanism around 353 K. Conduction in this material is provided by the low-temperature NSPT model and the high-temperature CBH model
Nouveaux procédés d'oxydation chimique pour l'élimination des rejets aqueux phénolés
No full textPour faire face au problème posé par les rejets aqueux chargés en phénol, deux procédés d'épuration par voie chimique sont proposés. Les deux méthodes font appel au peroxyde d'hydrogène. Celui-ci joue le rôle de promoteur de radicaux lors de l'oxydation de la charge organique par l'oxygène moléculaire dans le premier procédé qui s'inspire de la technique « Wet Air Oxidation » et constitue l'agent oxydant dans le second procédé intitulé « Wet Peroxide Oxidation ».L'introduction en continu de peroxyde d'hydrogène permet d'initier la réaction d'oxydation du phénol par l'oxygène moléculaire et de réduire considérable-ment les conditions de température et de pression de fonctionnement de la technique WAO classique. La réduction de la Demande Chimique en Oxygène de l'effluent dépasse 95 % à 160 °C en introduisant du peroxyde d'hydrogène à raison de 10 % de la quantité stoechiométrique nécessaire pour l'oxydation complète du phénol. Le second procédé consiste à utiliser l'oxydation par le peroxyde d'hydrogène en présence de fer ferreux (réactif de Fenton) dans des conditions de température (environ 120 °C) conduisant à un abattement important de la charge organique de l'effluent. A température élevée, la compétition entre la réaction de décomposition du peroxyde en oxygène moléculaire inactif et celle de décomposition en radicaux qui développent le processus d'oxydation engendre des conditions opératoires optimales pour lesquelles l'efficacité du procédé est maximale.Ces deux procédés apportent une solution technique satisfaisante pour traiter, avec un abattement important de la demande chimique en oxygène et du carbone organique, les effluents aqueux assez fortement chargés en composés phénolés.Despite of a growing concern about the problems of wastes elimination during the previous years, there is still a lack of processes in order to treat industrial aqueous wastes. Organic aqueous wastes and specially phenolic wastes, that can be either nonbiodegradable or toxic, give rise to one of the main problems. Landfilling disposal and related methods are a priori rejected as they appear to leaving the legacy of a problem we have net been able to solve rather than to considering our environment as being borrowed from the future mankind. Various oxidation techniques are suited for the elimination of this class of wastes. But, because of the environmental and economical drawbacks of incineration, it seems that liquid phase oxidation techniques should be preferred.The paper reviews : two liquid phase purification techniques using the chemical oxidation route; phenol being used as a test compound. The first technique is adapted from the wet air oxidation (WAO) process and uses molecular oxygen as the oxidizing agent. In the meantime, hydrogen peroxide is added at a low dosage and promotes the radicle reactions. Thus, the reaction temperature and pressure can be set at lower values (typically 160 °C, 25 bar) than usually. In this way, the conventional WAO process, which is very capital intensive because of temperature and pressure constraints is turned into a more affordable process. The second technique uses hydrogen peroxide as the oxidizer. it is associated to a ferrous salt as in the Fenton's reagent but it is run out under temperature (about 120 °C) so that a very important total organic carbon (TOC) removal efficiency con be obtained. This technique was named wet peroxide oxidation (WPO) process. As opposed to WAO, WPO needs only limited capital but generates higher running colts. Yet, both techniques can be regarded as efficient and economically satisfying in order to treat organic aqueous wastes containing fair amounts of phenol or phenolic compounds.The test compound was selected considering the frequent occurrence of phenol within the wastewaters of refineries, steel works and chemical industries. Their biological treatment is still very difficult for high concentrations despite of an important research activity. Treatment times and efficiencies of physicochemical methods are not but seldom satisfactory. Then, liquid phase oxidation methods have their whole interest. As it was reported that phenolic compounds (methylphenols, chloro-phenols) oxidation proceeds in a similar way than for phenol, the last molecule was considered for assessing the efficiency of both oxidation methods.The first method (WAO) was tested using a completely mixed batch reactor (stirred autoclave): The cold reactor was loaded with a phenol (2100 mg. 1-1) and ferrous sulfate (10 mg. l-11) solution al the convenient pH value (3.5). After heating at the rated temperature, the run was started by injecting instantaneously a large amount of oxygen (10 times the amount necessary). At the same time, a dosing pump was started and fed continuously hydrogen peroxide within the reactor all along the run (90 minutes). The total amount injected was usually 10 % of the amount necessary for a stoechiometric oxidation. The promoting effect of hydrogen peroxide on molecular oxygen is evidenced on figure 2 where the initiating period is shortened and on figure 3 where the oxidation efficiency actually obtained (curve 3) is greater than expected by adding the efficiencies of molecular oxygen and hydrogen peroxide oxidations if separated (curve 2). WAO promoted with hydrogen peroxide gave after 90 minutes better oxidation efficiencies at 160 °C than conventional WAO at 220 °C, then turning into a medium pressure process a high pressure one. The promoting effect of the peroxide is more marked at 160 °C than above 200 °C where a rapid decomposition occurs; dosages greater 15 % do not significantly increase the efficiency and dosages as small as 0,2 % have already a significant affect (see figure 5). Various compounds have been identified and the oxidation sequence is as follows : phenol -> dihydroxy-benzenes -> maleic acid -> oxalic, formic, acetic acids. Most of the remaining chemical oxygen demand (COD) of the oxidized solutions is acetic acid. Only more drastic experimental conditions allow its total removal.The WPO runs (second oxidation method) were conducted into a similar reactor. It was batch loaded with the phenol (2300 mg. 1-1) and ferrous sulfate (30 mg. l-1) solution at pH 3.5. After heating at 120 °C, the run was started and hydrogen peroxide was continuously fed using a dosing pump. The total amount injected all along the run (60 minutes) was the amount necessary for a stoechiometric oxidation. A similar oxidation sequence than reported hereon was observed; pyrocatechol, bydroquinone and oxalic acid were evidenced (figure 9) but, in this case, only very limited amounts of formic and acetic acids were detected. For the two processes, tables 2 and 3 summarize the material balances of the various products as a function of the oxidation time. A 90 % COD removal efficiency and a 70 % total organic carbon (TOC) removal efficiency is reported on figure 10. This result has to be compared with the TOC removal efficiencies (< 25 %) reported for the usual Fenton’s reagent at room temperature. The changes of the pH value and of the COD/TOC ratio (figure 11) during the run are easily explained by considering that oxalic acid is quite the sole product remaining after oxidation contrarily to promoted WAO where acetic acid is the major remaining product. Besides the production of radicles that bring on the oxidation process, a side-reaction decomposes hydrogen peroxide into molecular oxygen which is net active at such a low temperature. The competition between the two reactions makes optimum operating conditions to exist and to lead to a maximum efficiency of the process.Both processes bring on new methods in order to treat fairly concentrated phenolic solutions with a typical 90 % COD removal efficiency. The products remaining after oxidation (mainly acetic acid or oxalic acid) should not be regarded as a drawback of these processes. In actual fact, such compounds can be easily treated by adding a biological post-treatment unit to the chemical oxidation
