Search results for: Mohamed Bouafia

Authors: Aïssa Manallah, Mohamed Bouafia

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Ellipsometry is an optical method based on the study of the behavior of polarized light. The light reflected on a surface induces a change in the polarization state which depends on the characteristics of the material (complex refractive index and thickness of the different layers constituting the device). The purpose of this work is to determine the optical properties of semiconductor thin films by ellipsometry. This paper describes the experimental aspects concerning the semiconductor samples, the SE400 ellipsometer principle, and the results obtained by direct measurements of ellipsometric parameters and modelling using appropriate software.

Keywords: ellipsometry, optical constants, semiconductors, thin films

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Authors: Asma Ammar, Nabiha Bouafia , Asma BenCheikh, Mohamed Mahjoub, Olfa Ezzi, Wadiaa Bannour, Radhia Helali, Mansour Njah

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Background: The objective of the present study was to identify factors associated with vaccination against Hepatitis B virus (HBV) among healthcare workers (HWs) in the University Hospital Center (UHC) Farhat Hached Sousse, Tunisia. Methods: We conducted a descriptive cross-sectional study all licensed physicians (n= 206) and a representative sample of paramedical staff (n= 372) exercising at UHC Hached Sousse (Tunisia) during two months (January and February 2014). Data were collected using a self-administered and pre-tested questionnaire, which composed by 21 questions. In order to determinate factors associated with vaccination against hepatitis B among HWs, this questionnaire was based on the Health Belief Model, one of the most classical behavior theories. Logistic regression with the stepwise method of Hosmer and Lemeshow was used to identify the determinants of the use of vaccination against HBV. Results: The response rates were 79.8%. Fifty two percent believe that HBV is frequent in our healthcare units and 60.6% consider it a severe infection. The prevalence of HWs vaccination was 39%, 95% CI [34.49%; 43.5%]. In multivariate analysis, determinants of the use of vaccination against HBV among HWs were young age (p=10-4), male gender (p = 0. 006), high or very high importance accorded to health (p = 0.035), perception membership in a risk group for HBV infection (p = 0.038) and very favorable or favorable opinion about vaccination against HVB (p=10-4). Conclusion: The results of our study should be considered in any strategy for preventing VHB infection in HWs. In the mean time, coverage with standard vaccines should be improved also by supplying complete information on the risks of VHB infection and on the safety and efficacy of vaccination.

Keywords: Hepatitis B virus, healthcare workers, prevalence, vaccination

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Authors: S. Bouafia Chergui, Nihal Oturan, Hussein Khalaf, Mehmet A. Oturan

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The aim of this work was to compare the degradation of a mixture of three cationic dyes by advanced oxidation processes (electro-Fenton, photo-Fenton) in aqueous solution. These processes are based on the in situ production of hydroxyl radical, a highly strong oxidant, which allows the degradation of organic pollutants until their mineralization into CO2 and H2O. Under optimal operating conditions, the evolution of total organic carbon (TOC) and electrical energy efficiency have been investigated for the two processes.

Keywords: photo-fenton, electro-fenton, energy efficiency, water treatment

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Authors: Mohamed Abdalla Elamein Boshara, Peter Charles Woods, Nour Eldin Mohamed Elshaiekh

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Knowledge Management has become very important for Disaster Management response and planning. This paper proposes the implementation of a Knowledge Management System with a sustainable data collection mechanism for reliable and timely information management to support decision makers in making the right decisions in the timely manner.

Keywords: knowledge management, disaster management, incident tracking, web application

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Authors: Ammar Asma, Bouafia Nabiha, Ghammam Rim, Ezzi Olfa, Ben Cheikh Asma, Mahjoub Mohamed, Helali Radhia, Sma Nesrine, Chouchène Imed, Boussarsar Hamadi, Njah Mansour

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Background: Central venous catheter associated infections (CVC-AI) are among the serious hospital-acquired infections. The aims of this study are to determine the incidence of CVC-AI, and their risk factors among patients followed in a Tunisian medical intensive care unit (ICU). Materials / Methods: A prospective cohort study conducted between September 15th, 2015 and November 15th, 2016 in an 8-bed medical ICU including all patients admitted for more than 48h. CVC-AI were defined according to CDC of ATLANTA criteria. The enrollment was based on clinical and laboratory diagnosis of CVC-AI. For all subjects, age, sex, underlying diseases, SAPS II score, ICU length of stay, exposure to CVC (number of CVC placed, site of insertion and duration catheterization) were recorded. Risk factors were analyzed by conditional stepwise logistic regression. The p-value of < 0.05 was considered significant. Results: Among 192 eligible patients, 144 patients (75%) had a central venous catheter. Twenty-eight patients (19.4%) had developed CVC-AI with density rate incidence 20.02/1000 CVC-days. Among these infections, 60.7% (n=17) were systemic CVC-AI (with negative blood culture), and 35.7% (n=10) were bloodstream CVC-AI. The mean SAPS II of patients with CVC-AI was 32.76 14.48; their mean Charlson index was 1.77 1.55, their mean duration of catheterization was 15.46 10.81 days and the mean duration of one central line was 5.8+/-3.72 days. Gram-negative bacteria was determined in 53.5 % of CVC-AI (n= 15) dominated by multi-drug resistant Acinetobacter baumani (n=7). Staphylococci were isolated in 3 CVC-AI. Fourteen (50%) patients with CVC-AI died. Univariate analysis identified men (p=0.034), the referral from another hospital department (p=0.03), tobacco (p=0.006), duration of sedation (p=0.003) and the duration of catheterization (p=0), as possible risk factors of CVC-AI. Multivariate analysis showed that independent factors of CVC-AI were, male sex; OR= 5.73, IC 95% [2; 16.46], p=0.001, Ramsay score; OR= 1.57, IC 95% [1.036; 2.38], p=0.033, and duration of catheterization; OR=1.093, IC 95% [1.035; 1.15], p=0.001. Conclusion: In a monocenter cohort, CVC-AI had a high density and is associated with poor outcome. Identifying the risk factors is necessary to find solutions for this major health problem.

Keywords: central venous catheter associated infection, intensive care unit, prospective cohort studies, risk factors

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Authors: Amr A. EL Hanafy, Yasir Anwar, Saleh A. Mohamed, Saleh Mohamed Saleh Al-Garni, Jamal S. M. Sabir , Osama A. H. Abu Zinadah, Mohamed Morsi Ahmed

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In the vicinity of the red sea about 15 fungi species were isolated from oil contaminated sites. On the basis of aptitude to degrade the crude oil and DCPIP assay, two fungal isolates were selected amongst 15 oil degrading strains. Analysis of ITS-1, ITS-2 and amplicon pyrosequencing studies of fungal diversity revealed that these strains belong to Penicillium and Aspergillus species. Two strains that proved to be the most efficient in degrading crude oil was Aspergillus niger (54 %) and Penicillium commune (48 %) Subsequent to two weeks of cultivation in BHS medium the degradation rate were recorded by using spectrophotometer and GC-MS. Hence, it is cleared that these fungal strains has the capability of degradation and can be utilized for cleaning the Saudi Arabian environment.

Keywords: fungal strains, hydrocarbon contaminants, molecular identification, biodegradation, GC-MS

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Authors: Mohamed Saïd Kahaleras, François Lanzetta, Mohamed Khan, Guillaume Layes, Philippe Nika

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This paper presents an experimental work to characterize the dynamic operation of a metal regenerator crossed by dry compressible air alternating flow. Unsteady dynamic measurements concern the pressure, velocity and temperature of the gas at the ends and inside the channels of the regenerator. The regenerators are tested under isothermal conditions and thermal axial temperature gradient.

Keywords: friction factor, oscillating flow, regenerator, stirling machine

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Authors: Abdallah Mohamed Kamel Mohamed Ali, Samah Saad Zahran, Mohamed Hamed Rashad

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Background: Flexible flatfoot (FFF) has been considered as a risk factor for several lower limb injuries and mechanical low back pain. This was attributed to the dysfunction of the lumbopelvic-hip complex musculature. Objective: To investigate the influence of FFF on electromyographic activities of erector spinae and multifidus. Methods: A cross-section study was held between an FFF group (20 subjects) and a normal foot group (20 subjects). A surface electromyography was used to assess the electromyographic activity of erector spinae and multifidus. Group differences were assessed by the T-test. Results: There was a significant increase in EMG activities of erector spinae and multifidus in the FFF group compared with the normal group. Conclusion: There is an increase in EMG activities in erector spinae and multifidus in FFF subjects compared with normal subjects.

Keywords: electromyography, flatfoot, low back pain, paraspinal muscles

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Authors: S. Benbia, W. Bouafia, D. Khellaf, A. Chennaf, M. Yahia

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Our study was designed to highlight changes in certain biochemical parameters (CH, TG, HDL, GOT, GPT, LDL, and CRP), obese women infertile fertile witnesses and research potential pathophysiological link between obesity and infertility in this population of women. This practical work was focused on a population of 24 obese women infertile, compared to controls, subjects without any pathology causing disruption of parameters to be studied to determine the contribution of obesity in the etiology of infertility. The assay results revealed a highly significant difference between the two groups in serum CH, TG, HDL, TGO and TGP (P < 0.0001) and in the rate of LDL (p = 0.0017) and CRP (p = 0.02). The hormonal balance also shows a significant difference between the two groups (P < 0.0001).The present study indicates that obesity is associated with infertility, but there is no direct pathophysiological link between obesity and infertility has not been determined. Further in-depth studies are needed to determine the exact mechanism by which overweight leads to female infertility.

Keywords: obesity, fertility, infertility, biochemical, women

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Authors: Mohammed Y. Abdellah, Mohamed K. Hassan, A. F. Mohamed, Shadi M. Munshi, A. M. Hashem

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Pips made from glass fiber reinforced polymer has competitive role in petroleum industry. The need of evaluating the mechanical behavior of (GRP) pipes is essential objects. Stress relaxation illustrates how polymers relieve stress under constant strain. Static relaxation test is carried out at room temperature. The material gives poor static relaxation strength, two loading cycles have been observed for the tested specimen.

Keywords: GRP, sandwich composite material, static relaxation, stress relief

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Authors: Djamal Atlaoui, Youcef Bouafia

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This work deals with the experimental study of the mechanical behavior, by shear tests (fracture shear), elements of concrete beams reinforced with fibers in chips. These fibers come from the machining waste of the steel parts. The shear tests are carried out on prismatic specimens of dimensions 10 x 20 x 120 cm³. The fibers are characterized by mechanical resistance and tearing. The optimal composition of the concrete was determined by the workability test. Two fiber contents are selected for this study (W = 0.6% and W = 0.8%) and a BT control concrete (W = 0%) of the same composition as the matrix is developed to serve as a reference with a sand-to-gravel ratio (S/G) of concrete matrix equal to 1. The comparison of the different results obtained shows that the chips fibers confer a significant ductility to the material after cracking of the concrete. Also, the fibers used limit diagonal cracks in shear and improve strength and rigidity.

Keywords: characterization, chips fibers, cracking mode, ductility, undulation, shear

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Authors: I. Toumi, Y. Abed, A. Bouafia

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This paper presents a methodology for identifying the cohesive soil parameters that takes into account different constitutive equations. The procedure, applied to identify the parameters of generalized Prager model associated to the Drucker & Prager failure criterion from a pressuremeter expansion curve, is based on an inverse analysis approach, which consists of minimizing the function representing the difference between the experimental curve and the simulated curve using a simplex algorithm. The model response on pressuremeter path and its identification from experimental data lead to the determination of the friction angle, the cohesion and the Young modulus. Some parameters effects on the simulated curves and stresses path around pressuremeter probe are presented. Comparisons between the parameters determined with the proposed method and those obtained by other means are also presented.

Keywords: cohesive soils, cavity expansion, pressuremeter test, finite element method, optimization procedure, simplex algorithm

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Authors: Mohamed Driouich, Kamal Gueraoui, Mohamed Sammouda

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The main objective of this work is to establish a numerical code for studying the flow of molten polymers in deformable pipes. Using an iterative numerical method based on finite differences, we determine the profiles of the fluid velocity, the temperature and the apparent viscosity of the fluid. The numerical code presented can also be applied to other industrial applications.

Keywords: numerical code, molten polymers, deformable pipes, finite differences

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Authors: Yousif Mohamed Y. Abdallah, Eltayeb Wagi Allah Eltayeb, Mohamed E. Gar-elnabi, Mohamed Ahmed Ali

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To characterize coronary artery obstruction and related findings in ischemic heart patients using cardiac scintigraphy for the identification of myocardial ischemia, 146 patients were studied at basal conditions and also asked for fasting after night till the intravenous injection of the radiopharmaceutical. After the injection time about 15 to 20 minutes, the patient should eat a fatty meal and chocolate for the good excretion of the gall bladder, to evaluate the performance and regional wall motion of the left ventricle (LV). The results showed that the body mass index percentage in this sample was in range of 43.05 to 61.05. The number of patients who were catheter candidates were 56 with 43% and the patients that were not candidate to cathode were 74 patients with 57% of all patients. For the group of patients where type of ischemia was assessed, 29.5% of patients had reversible posterior and inferior wall, 15.1% of patients had fixed large from apex to base, 9.6% of patients had mild basal inferior wall, 4.8 % of patients had mild anterior wall, 6.2% of patients had antro-septal and 34.9% of patients had moderate ischemia.

Keywords: myocardial ischemia, myocardial scintigraphy, contrast ventriculography, coronary artery obstruction

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Authors: Noura Shehab-Eldeen, Mohamed Elsherbeeny, Hossam Elmetwally, Mohamed Salama, Ahmed Lotfy, Mohamed Elgamal, Hussein Sheashaa, Mohamed Sobh

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Mitochondrial toxins including papaverine may be implicated in the etiology and pathogenesis of Parkinson's disease. The aim was to detect the effect of papaverine on the proliferation and viability of neural stem cells. Rat neural progenitor cells were isolated from embryos (E14) brains. The dispersed tissues were allowed to settle, then, The supernatant was centrifuged at 1,000 g for 5 min. The pellet was placed in Hank’s solution cultured as free-floating neurospheres Dulbecco’s modified Eagle medium (DMEM) and Hams F12 (3:1) supplemented with B27 (Invitrogen GmBH, Karlsruhe, Germany), 20 ng/mL epidermal growth factor (EGF; Biosource, Karlsruhe, Germany), 20 ng/mL recombinant human fibroblast growth factor (rhFGF; R&D Systems, Wiesbaden-Nordenstadt, Germany), and penicillin and streptomycin (1:100; Invitrogen) at 37°C with 7.5% CO2 . Differentiation was initiated by growth factor withdrawal and plating onto a poly-d-lysine/ laminin matrix. The neurospheres were fed every 2-3 days by replacing 50% of the culture media with fresh media. The culture suspension was transferred to a dish containing 16 wells. The wells were divided as follows: 4 wells received no papaverine (control), 4 wells 1 u, 4 wells 5 u and 4 wells 10 u of papaverine solution. In the next 2 weeks, photography (0,4,5,11days) and viability test were done. The photographs were analysed. Results : papaverine didn't affect proliferation of neurospheres, while it affected viability compared to control , this was dose related. Conclusion: This indicates the harmful effect of papaverine suggesting it to be a candidate neurotoxin causing Parkinsonism.

Keywords: neurospheres, neural stem cells, papaverine, Parkinsonism

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Authors: Medjram Sofiane, Babahenini Mohamed Chaouki, Mohamed Benali Yamina

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Skin detection is an important task for computer vision systems. A good method for skin detection means a good and successful result of the system. The colour is a good descriptor that allows us to detect skin colour in the images, but because of lightings effects and objects that have a similar colour skin, skin detection becomes difficult. In this paper, we proposed a method using the YCbCr colour space for skin detection and lighting effects elimination, then we use the information of texture to eliminate the false regions detected by the YCbCr colour skin model.

Keywords: skin detection, YCbCr, GLCM, texture, human skin

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Authors: Chebaani Mohamed, Gplea Amar, Benchouia Mohamed Toufik

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Direct torque control is characterized by the merits of fast response, simple structure and strong robustness to the motor parameters variations. This paper proposes the implementation of DTC-SVM of an induction motor drive using Predictive controller. The principle of the method is explained and the system mathematical description is provided. The derived control algorithm is implemented both in the simulation software MatLab/Simulink and on the real induction motor drive with dSPACE control system. Simulated and measured results in steady states and transients are presented.

Keywords: induction motor, DTC-SVM, predictive controller, implementation, dSPACE, Matlab, Simulink

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Authors: Halimi Mohamed Taher, Kordoghli Bassem, Ben Hassen Mohamed, Sakli Faouzi

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Textile and clothing manufacturing industry is based largely on subcontracting system. Choosing the right subcontractor became a strategic decision that can affect the financial position of the company and even his market position. Subcontracting firms in Tunisia are lead to define an appropriate selection process which takes into account several quantitative and qualitative criteria. In this study, a methodology is proposed that includes a Fuzzy Analytic Hierarchy Process (AHP) in order to incorporate the ambiguities and uncertainties in qualitative decision. Best subcontractors for two Tunisian firms are determined based on model results.

Keywords: AHP, subcontractor, multicriteria, selection

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Authors: Zaidour Mohamed, Ghalem Ali Jr., Achit Henni Mohamed

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This project is destined to study pole junctions of reinforced concrete beams subjected to seismic loads. A literature review was made to clarify the work done by researchers in the last three decades and especially the results of the last two years that were studied for the determination of the method of calculating the transverse reinforcement in the different nodes of a structure. For implementation efforts in the columns and beams of a building R + 4 in zone 3 were calculated using the finite element method through software. These results are the basis of our work which led to the calculation of the transverse reinforcement of the nodes of the structure in question.

Keywords: beam–column joints, cyclic loading, shearing force, damaged joint

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Authors: Mohamed Amarouayache, Badia Amrouche, Gharbi Akila, Boukadoume Mohamed

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This work is devoted to the modeling of DC-DC converter (boost) used for MPPT applications to set conditions of stability. For this, we establish a linear mathematical model of the DC-DC converter with an average small signal model. This model has allowed us to apply conventional linear methods of automation. A mathematical relationship between the duty cycle and the voltage of the panel has been set up. With this relationship we specify the conditions of the stability in closed-loop depending on the system parameters (the elements of storage capacity and inductance, PWM control).

Keywords: MPPT, PWM, stability, criterion of Routh, average small signal model

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Authors: Hind O. Osman, Tilal Elsaman, Bashir A. Yousef, Esraa Elhadi, Aimun A. E. Ahmed, Eyman Mohamed Eltayib, Malik Suliman Mohamed, Magdi Awadalla Mohamed

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Epilepsy is the most common neurological condition and cause of substantial morbidity and mortality. In the present study, the molecular hybridization tool was adopted to obtain six Schiff bases of isatin and adamantane-1-carbohydrazide (18–23). Then, their anticonvulsant activity was evaluated using a pentylenetetrazole- (PTZ-) induced seizure model using phenobarbitone as a positive control. Our findings showed that compounds 18–23 provided significant protection against PTZ-induced seizure, and maximum activities were associated with compound 23. Moreover, all investigated compounds increased the latency of induced convulsion and reduced the duration of epilepsy, with compound 23 being the best. Interestingly, most of the synthesized molecules showed a reduction in neurological symptoms and severity of the seizure. Molecular docking studies suggest GABA-A receptor as a potential target, and in silico ADME screening revealed that the pharmaceutical properties of compound 23 are within the specified limit. Thus, compound 23 was identified as a promising candidate that warrants further drug discovery processes.

Keywords: isatin and adamantane, anticonvulsant activity, PTZ-induced seizure, molecular docking

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Authors: Mohamed Adel Sennouni, Jamal Zbitou, Benaissa Abboud, Abdelwahed Tribak, Hamid Bennis, Mohamed Latrach

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A compact UWB planar antenna fed with a microstrip-line is proposed. The new design is composed of a rectangular patch with symmetric L-shaped slots and fed by 50 Ω microstrip transmission line and a reduced ground-plane which have a periodic slots with an overall size of 47 mm x 20 mm. It is intended to be used in wireless applications that cover the ultra-wideband (UWB) frequency band. A wider impedance bandwidth of around 116.5% (1.875

Keywords: UWB planar antenna, L-shaped slots, wireless applications, impedance band-width, radiation pattern, CST

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Authors: S. Cherif, A. Medjahed, M. Bouafia, A. Manallah

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A light wave is characterized by 4 characteristics: its amplitude, its frequency, its phase and the direction of polarization of its luminous vector (the electric field). It is in this last characteristic that we will be interested. The polarization of the light was introduced in order to describe the vectorial behavior of the light; it describes the way in which the electric field evolves in a point of space. Our work consists in studying diffusing mediums. Different types of biological fluids were selected to study the evolution of each with increasing scattering power of the medium, and in the same time to make a comparison between them. When crossing these mediums, the light undergoes modifications and/or deterioration of its initial state of polarization. This phenomenon is related to the properties of the medium, the idea is to compare the characteristics of the entering and outgoing light from the studied medium by a white light. The advantage of this model is that it is experimentally accessible workable intensity measurements with CCD sensors and allows operation in 2D. The latter information is used to discriminate some physical properties of the studied areas. We chose four types of milk to study the evolution of each with increasing scattering power of the medium.

Keywords: light polarization, Mueller matrix, Mueller images, diffusing medium, milk

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Authors: Sidi Mohamed Mesli, Mohamed Habchi, Mohamed Kotbi, Rafik Benallal, Abdelali Derouiche

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Fluoride glasses with a nominal composition of BaMnMF7 (M = FeV assuming isomorphous replacement) have been structurally modelled through the simultaneous simulation of their neutron diffraction patterns by a reverse Monte Carlo (RMC) model and by a Rietveld for disordered materials (RDM) method. Model is consistent with an expected network of interconnected [MF6] polyhedra. The RMC results are accompanied by artificial satellite peaks. To remedy this problem, we use an extension of the RMC algorithm, which introduces an energy penalty term in acceptance criteria. This method is called the Hybrid Reverse Monte Carlo (HRMC) method. The idea of this paper is to apply the (HRMC) method to the title glasses, in order to make a study of the phenomenon nature of order and disorder by displaying and discussing the partial pair distribution functions (PDFs) g(r). We suggest that this method can be used to describe average correlations between components of fluoride glass or similar system.

Keywords: fluoride glasses, RMC simulation, neutron scattering, hybrid RMC simulation, Lennard-Jones potential, partial pair distribution functions

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Authors: Kamel Zemour, Kada Mohamed Amine Chouhim, Mohamed Mairif, Tadj Eddine Adda Ardjan

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Many recent studies show the positive effect of phenolic compounds in olive oil on health. They are known for their biological properties, where they have shown potential activity as an antioxidant, anti-inflammatory, and antimicrobial agents. However, this characteristic is rarely studied in olive oil from different regions of Algeria. Different samples collected from the western region of Algeria were evaluated for their polyphenol content, antioxidant activity, and antimicrobial effect. The obtained results demonstrated that this oil is rich in polyphenols and revealed high antimicrobial activity against Staphylococcus aureus and Escherichia coli. Finally, this study has highlighted the nutritional and pharmaceutical importance of olive oil grown in Algeria.

Keywords: olive oil, polyphenols, antioxidant activity, antimicrobial activity

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Authors: Bouafia-Chergui Souâd, Chabani Malika, Bensmaili Aicha

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Water treatment and especially, medicament pollutants are nowadays important problems. Degradation of oxytetracycline was carried out using combined process of low-frequency ultrasound (US), ultraviolet irradiation and a catalyst. The effectiveness of the coupled processes has been evaluated by studying the effects of various operating parameters including initial OTC concentration, solution pH and catalyst mass. For the photolysis process, the monochromatic ultraviolet light wavelength utilized was 365 nm. The sonolysis experiments were performed with ultrasound at a frequency of 40 kHz. The heterogeneous photocatalysis was studied in the presence of TiO2. The processes were employed individually, and simultaneously to examine the details of the processes and to investigate the contribution of each process. Low UV intensity (12W), low pH and high mass of TiO2 conditions enhanced the sono-photocatalytic degradation of OTC. The results showed that the individual contribution sonochemical and photochemical reactions are very low, however, their coupling increases the degradation rate of 8 times compared to photolysis and 2 times compared to sonolysis. There is a synergistic effect between the two modes of radiation, UV and U.S. leading to 82.04% degradation yield. An application of these combined processes on the treatment of a real pharmaceutical wastewater was examined.

Keywords: sonolysis, photocatalysis, combined process, antibiotic

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Authors: Nabiha Bouafia, Asma Ben Cheikh, Asma Ammar, Olfa Ezzi, Mohamed Mahjoub, Khaoula Meddeb, Imed Chouchene, Hamadi Boussarsar, Mansour Njah

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Background: Hospital acquired infections (HAI) cause significant morbidity, mortality, length of stay and hospital costs, especially in the intensive care unit (ICU), because of the debilitated immune systems of their patients and exposure to invasive devices. The aims of this study were to determine the rate and the risk factors of HAI in an ICU of a university hospital in Tunisia. Materials/Methods: A prospective study was conducted in the 8-bed adult medical ICU of a University Hospital (Sousse Tunisia) during 14 months from September 15th, 2015 to November 15th, 2016. Patients admitted for more than 48h were included. Their surveillance was stopped after the discharge from ICU or death. HAIs were defined according to standard Centers for Disease Control and Prevention criteria. Risk factors were analyzed by conditional stepwise logistic regression. The p-value of < 0.05 was considered significant. Results: During the study, 192 patients had admitted for more than 48 hours. Their mean age was 59.3± 18.20 years and 57.1% were male. Acute respiratory failure was the main reason of admission (72%). The mean SAPS II score calculated at admission was 32.5 ± 14 (range: 6 - 78). The exposure to the mechanical ventilation (MV) and the central venous catheter were observed in 169 (88 %) and 144 (75 %) patients, respectively. Seventy-three patients (38.02%) developed 94 HAIs. The incidence density of HAIs was 41.53 per 1000 patient day. Mortality rate in patients with HAIs was 65.8 %( n= 48). Regarding the type of infection, Ventilator Associated Pneumoniae (VAP) and central venous catheter Associated Infections (CVC AI) were the most frequent with Incidence density: 14.88/1000 days of MV for VAP and 20.02/1000 CVC days for CVC AI. There were 5 Peripheral Venous Catheter Associated Infections, 2 urinary tract infections, and 21 other HAIs. Gram-negative bacteria were the most common germs identified in HAIs: Multidrug resistant Acinetobacter Baumanii (45%) and Klebsiella pneumoniae (10.96%) were the most frequently isolated. Univariate analysis showed that transfer from another hospital department (p= 0.001), intubation (p < 10-4), tracheostomy (p < 10-4), age (p=0.028), grade of acute respiratory failure (p=0.01), duration of sedation (p < 10-4), number of CVC (p < 10-4), length of mechanical ventilation (p < 10-4) and length of stay (p < 10-4), were associated to high risk of HAIS in ICU. Multivariate analysis reveals that independent risk factors for HAIs are: transfer from another hospital department: OR=13.44, IC 95% [3.9, 44.2], p < 10-4, duration of sedation: OR= 1.18, IC 95% [1.049, 1.325], p=0.006, high number of CVC: OR=2.78, IC 95% [1.73, 4.487], p < 10-4, and length of stay in ICU: OR= 1.14, IC 95% [1.066,1.22], p < 10-4. Conclusion: Prevention of nosocomial infections in ICUs is a priority of health care systems all around the world. Yet, their control requires an understanding of epidemiological data collected in these units.

Keywords: healthcare associated infections, incidence, intensive care unit, risk factors

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Authors: Ali Akrmi, Mohamed Beji, Ahmed Baklouti, Fatma Djouani, Philippe Lang, Mohamed M. Chehimi

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Poly(vinyl chloride) (PVC) is a highly versatile polymer with excellent balance of properties and numerous applications such as water pipes, packaging and polymer materials of importance in the biomedical sector. However, depending on the applications, it is necessary to modify PVC by mixing with a plasticizer; surface modification using plasma, surface grafting or flame treatment; or bulk chemical modification which affects the entire PVC chains at an extent that can be tuned by the polymer chemist. The targeted applications are improvement of chemical resistance, avoiding or limitation of migration of toxic plasticizers, improvement of antibacterial properties, or control of blood compatibility.

Keywords: poly(vinyl chloride), nucleophilic substitution, sulfonylcarbamates, XPS

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Authors: Sifeddine Abderrahmani, Sonia Bouafia

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The finite element method is the most practical tool for the analysis of structures, whatever the geometrical shape and behavior. It is extensively used in many high-tech industries, such as civil or military engineering, for the modeling of bridges, motor bodies, fuselages, and airplane wings. Additionally, experience demonstrates that engineers like modeling their structures using the most basic finite elements. Numerous models of finite elements may be utilized in the numerical analysis depending on the interpolation field that is selected, and it is generally known that convergence to the proper value will occur considerably more quickly with a good displacement pattern than with a poor pattern, saving computation time. The method for creating finite elements using the strain approach (S.B.A.) is presented in this presentation. When the results are compared with those provided by equivalent displacement-based elements, having the same total number of degrees of freedom, an excellent convergence can be obtained through some application and validation tests using recently developed membrane elements, plate bending elements, and flat shell elements. The effectiveness and performance of the strain-based finite elements in modeling structures are proven by the findings for deflections and stresses.

Keywords: finite elements, plate bending, strain approach, displacement formulation, shell element

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Authors: Ammar Asma, Bouafia Nabiha, Ben Cheikh Asma, Ezzi Olfa, Mahjoub Mohamed, Sma Nesrine, Chouchène Imed, Boussarsar Hamadi, Njah Mansour

Abstract:

Background: Ventilator-associated pneumonia (VAP) is currently recognized as one of the most relevant causes of morbidity and mortality among intensive care unit (ICU) patients worldwide. Identifying modifiable risk factors for VAP could be helpful for future controlled interventional studies aiming at improving prevention of VAP. The purposes of this study were to determine the incidence and risk factors for VAP in in a Tunisian medical ICU. Materials / Methods: A retrospective case-control study design based on the prospective database collected over a 14-month period from September 15th, 2015 through November 15th, 2016 in an 8-bed medical ICU. Patients under ventilation for over 48 h were included. The number of cases was estimated by Epi-info Software with the power of statistical test equal to 90 %. Each case patient was successfully matched to two controls according to the length of mechanical ventilation (MV) before VAP for cases and the total length of MV in controls. VAP in the ICU was defined according to American Thoracic Society; Infectious Diseases Society of America guidelines. Early onset or late-onset VAP were defined whether the infectious process occurred within or after 96 h of ICU admission. Patients’ risk factors, causes of admission, comorbidities and respiratory specimens collected were reviewed. Univariate and multivariate analyses were performed to determine variables associated with VAP with a p-value < 0.05. Results: During the period study, a total of 169 patients under mechanical ventilation were considered, 34 patients (20.11%) developed at least one episode of VAP in the ICU. The incidence rate for VAP was 14.88/1000 ventilation days. Among these cases, 9 (26.5 %) were early-onset VAP and 25 (73.5 %) were late-onset VAP. It was a certain diagnosis in 66.7% of cases. Tracheal aspiration was positive in 80% of cases. Multi-drug resistant Acinerobacter baumanii was the most common species detected in cases; 67.64% (n=23). The rate of mortality out of cases was 88.23% (n= 30). In univariate analysis, the patients with VAP were statistically more likely to suffer from cardiovascular diseases (p=0.035) and prolonged duration of sedation (p=0.009) and tracheostomy (p=0.001), they also had a higher number of re-intubation (p=0.017) and a longer total time of intubation (p=0.012). Multivariate analysis showed that cardiovascular diseases (OR= 4.44; 95% IC= [1.3 - 14]; p=0.016), tracheostomy (OR= 4.2; 95% IC= [1.16 -15.12]; p= 0.028) and prolonged duration of sedation (OR=1.21; 95% IC= [1.07, 1.36]; p=0.002) were independent risk factors for the development of VAP. Conclusion: VAP constitutes a therapeutic challenge in an ICU setting, therefore; strategies that effectively prevent VAP are needed. An infection control-training program intended to all professional heath care in this unit insisting on bundles and elaboration of procedures are planned to reduce effectively incidence rate of VAP.

Keywords: case control study, intensive care unit, risk factors, ventilator associated pneumonia

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