Search results for: polymer matrix composites

Authors: Jyoti Sahu, Vinay A. Juvekar

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Electrolytes are often used to bring about salting-in and salting-out of organic molecules and polymers (e.g. polyethylene glycols/proteins) from the aqueous solutions. For quantification of these phenomena, a thermodynamic model which can accurately predict activity coefficient of electrolyte as a function of temperature is needed. The thermodynamics models available in the literature contain a large number of empirical parameters. These parameters are estimated using lower/upper critical solution temperature of the solution in the electrolyte/organic molecule at different temperatures. Since the number of parameters is large, inaccuracy can bethe creep in during their estimation, which can affect the reliability of prediction beyond the range in which these parameters are estimated. Cloud point of solution is related to its free energy through temperature and composition derivative. Hence, the Cloud point measurement can be used for accurate estimation of the temperature and composition dependence of parameters in the model for free energy. Hence, if we use a two pronged procedure in which we first use cloud point of solution to estimate some of the parameters of the thermodynamic model and determine the rest using osmotic coefficient data, we gain on two counts. First, since the parameters, estimated in each of the two steps, are fewer, we achieve higher accuracy of estimation. The second and more important gain is that the resulting model parameters are more sensitive to temperature. This is crucial when we wish to use the model outside temperatures window within which the parameter estimation is sought. The focus of the present work is to prove this proposition. We have used electrolyte (NaCl/Na2CO3)-water-organic molecule (Iso-propanol/ethanol) as the model system. The model of Robinson-Stokes-Glukauf is modified by incorporating the temperature dependent Flory-Huggins interaction parameters. The Helmholtz free energy expression contains, in addition to electrostatic and translational entropic contributions, three Flory-Huggins pairwise interaction contributions viz., and (w-water, p-polymer, s-salt). These parameters depend both on temperature and concentrations. The concentration dependence is expressed in the form of a quadratic expression involving the volume fractions of the interacting species. The temperature dependence is expressed in the form .To obtain the temperature-dependent interaction parameters for organic molecule-water and electrolyte-water systems, Critical solution temperature of electrolyte -water-organic molecules is measured using cloud point measuring apparatus The temperature and composition dependent interaction parameters for electrolyte-water-organic molecule are estimated through measurement of cloud point of solution. The model is used to estimate critical solution temperature (CST) of electrolyte water-organic molecules solution. We have experimentally determined the critical solution temperature of different compositions of electrolyte-water-organic molecule solution and compared the results with the estimates based on our model. The two sets of values show good agreement. On the other hand when only osmotic coefficients are used for estimation of the free energy model, CST predicted using the resulting model show poor agreement with the experiments. Thus, the importance of the CST data in the estimation of parameters of the thermodynamic model is confirmed through this work.

Keywords: concentrated electrolytes, Debye-Hückel theory, interaction parameters, Robinson-Stokes-Glueckauf model, Flory-Huggins model, critical solution temperature

Procedia PDF Downloads 359

Authors: A. Mulry, C. Kealey, D. B. Brady

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Planktonic bacteria can form biofilms which are microbial aggregates embedded within a matrix of extracellular polymeric substances (EPS). They can be found attached to abiotic or biotic surfaces. Biofilms are responsible for oral diseases such as dental caries, gingivitis and the progression of periodontal disease. Biofilms can resist 500 to 1000 times the concentration of biocides and antibiotics used to kill planktonic bacteria. Biofilm development on oral surfaces involves four stages, initial attachment, early development, maturation and dispersal of planktonic cells. The Minimum Inhibitory Concentration (MIC) was determined using a range of saturated and unsaturated fatty acids using the resazurin assay, followed by serial dilution and spot plating on BHI agar plates to establish the Minimum Bactericidal Concentration (MBC). Log reduction of bacteria was also evaluated for each fatty acid. The Minimum Biofilm Inhibition Concentration (MBIC) was determined using crystal violet assay in 96 well plates on forming and pre-formed S. mutans biofilms using BHI supplemented with 1% sucrose. Saturated medium-chain fatty acids Octanoic (C8.0), Decanoic (C10.0) and Undecanoic acid (C11.0) do not display strong antibiofilm properties; however, Lauric (C12.0) and Myristic (C14.0) display moderate antibiofilm properties with 97.83% and 97.5% biofilm inhibition with 1000 µM respectively. Monounsaturated, Oleic acid (C18.1) and polyunsaturated large chain fatty acids, Linoleic acid (C18.2) display potent antibiofilm properties with biofilm inhibition of 99.73% at 125 µM and 100% at 65.5 µM, respectively. Long-chain polyunsaturated Omega-3 fatty acids α-Linoleic (C18.3), Eicosapentaenoic Acid (EPA) (C20.5), Docosahexaenoic Acid (DHA) (C22.6) have displayed strong antibiofilm efficacy from concentrations ranging from 31.25-250µg/ml. DHA is the most promising antibiofilm agent with an MBIC of 99.73% with 15.625µg/ml. This may be due to the presence of six double bonds and the structural orientation of the fatty acid. To conclude, fatty acids displaying the most antimicrobial activity appear to be medium or long-chain unsaturated fatty acids containing one or more double bonds. Most promising agents include Omega-3-fatty acids Linoleic, α-Linoleic, EPA and DHA, as well as Omega-9 fatty acid Oleic acid. These results indicate that fatty acids have the potential to be used as antimicrobials and antibiofilm agents against S. mutans. Future work involves further screening of the most potent fatty acids against a range of bacteria, including Gram-positive and Gram-negative oral pathogens. Future work will involve incorporating the most effective fatty acids onto dental implant devices to prevent biofilm formation.

Keywords: antibiofilm, biofilm, fatty acids, S. mutans

Procedia PDF Downloads 122

Authors: Veronique Jubera, Ka-Young Kim, U-Chan Chung, Amelie Veillere, Jean-Marc Heintz

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Emitting materials and all solid state lasers are widely used in the field of optical applications and materials science as a source of excitement, instrumental measurements, medical applications, metal shaping etc. Recently promising optical efficiencies were recorded on ceramics which result from a cheaper and faster ways to obtain crystallized materials. The choice and optimization of the sintering process is the key point to fabricate transparent ceramics. It includes a high control on the preparation of the powder with the choice of an adequate synthesis, a pre-heat-treatment, the reproducibility of the sintering cycle, the polishing and post-annealing of the ceramic. The densification is the main factor needed to reach a satisfying transparency, and many technologies are now available. The symmetry of the unit cell plays a crucial role in the diffusion rate of the material. Therefore, the cubic symmetry compounds having an isotropic refractive index is preferred. The cubic Y3NbO7 matrix is an interesting host which can accept a high concentration of rare earth doping element and it has been demonstrated that SPS is an efficient way to sinter this material. The optimization of diffusion losses requires a microstructure of fine ceramics, generally less than one hundred nanometers. In this case, grain growth is not an obstacle to transparency. The ceramics properties are then isotropic thereby to free-shaping step by orienting the ceramics as this is the case for the compounds of lower symmetry. After optimization of the synthesis route, several SPS parameters as heating rate, holding, dwell time and pressure were adjusted in order to increase the densification of the Eu3+ doped Y3NbO7 pellets. The luminescence data coupled with X-Ray diffraction analysis and electronic diffraction microscopy highlight the existence of several distorted environments of the doping element in the studied defective fluorite-type host lattice. Indeed, the fast and high crystallization rate obtained to put in evidence a lack of miscibility in the phase diagram, being the final composition of the pellet driven by the ratio between niobium and yttrium elements. By following the luminescence properties, we demonstrate a direct impact on the SPS process on this material.

Keywords: emission, niobate of rare earth, Spark plasma sintering, lack of miscibility

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Authors: E. G. Karvelas, C. Liosis, A. Theodorakakos, T. E. Karakasidis

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Magnetic navigation of the drug inside the human vessels is a very important concept since the drug is delivered to the desired area. Consequently, the quantity of the drug required to reach therapeutic levels is being reduced while the drug concentration at targeted sites is increased. Magnetic navigation of drug agents can be achieved with the use of magnetic nanoparticles where anti-tumor agents are loaded on the surface of the nanoparticles. The magnetic field that is required to navigate the particles inside the human arteries is produced by a magnetic resonance imaging (MRI) device. The main factors which influence the efficiency of the usage of magnetic nanoparticles for biomedical applications in magnetic driving are the size and the magnetization of the biocompatible nanoparticles. In this study, a computational platform for the simulation of the optimal gradient magnetic fields for the navigation of magnetic nanoparticles inside a carotid artery is presented. For the propulsion model of the particles, seven major forces are considered, i.e., the magnetic force from MRIs main magnet static field as well as the magnetic field gradient force from the special propulsion gradient coils. The static field is responsible for the aggregation of nanoparticles, while the magnetic gradient contributes to the navigation of the agglomerates that are formed. Moreover, the contact forces among the aggregated nanoparticles and the wall and the Stokes drag force for each particle are considered, while only spherical particles are used in this study. In addition, gravitational forces due to gravity and the force due to buoyancy are included. Finally, Van der Walls force and Brownian motion are taken into account in the simulation. The OpenFoam platform is used for the calculation of the flow field and the uncoupled equations of particles' motion. To verify the optimal gradient magnetic fields, a covariance matrix adaptation evolution strategy (CMAES) is used in order to navigate the particles into the desired area. A desired trajectory is inserted into the computational geometry, which the particles are going to be navigated in. Initially, the CMAES optimization strategy provides the OpenFOAM program with random values of the gradient magnetic field. At the end of each simulation, the computational platform evaluates the distance between the particles and the desired trajectory. The present model can simulate the motion of particles when they are navigated by the magnetic field that is produced by the MRI device. Under the influence of fluid flow, the model investigates the effect of different gradient magnetic fields in order to minimize the distance of particles from the desired trajectory. In addition, the platform can navigate the particles into the desired trajectory with an efficiency between 80-90%. On the other hand, a small number of particles are stuck to the walls and remains there for the rest of the simulation.

Keywords: artery, drug, nanoparticles, navigation

Procedia PDF Downloads 88

Authors: S. B. Q. Tran

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Drop condensation is the phenomenon that the tiny drops form when the oversaturated vapour present in the environment condenses on a substrate and makes the droplet growth. Recently, this subject has received much attention due to its applications in many fields such as thin film growth, heat transfer, recovery of atmospheric water and polymer templating. In literature, many papers investigated theoretically and experimentally in macro droplet growth with the size of millimeter scale of radius. However few papers about nanodroplet condensation are found in the literature especially theoretical work. In order to understand the droplet growth in nanoscale, we perform the numerical simulation work to study nanodroplet growth. We investigate and discuss the role of the droplet shape and monomer diffusion on drop growth and their effect on growth law. The effect of droplet shape is studied by doing parametric studies of contact angle and disjoining pressure magnitude. Besides, the effect of pinning and de-pinning behaviours is also studied. We investigate the axisymmetric homogeneous growth of 10–100 nm single water nanodroplet on a substrate surface. The main mechanism of droplet growth is attributed to the accumulation of laterally diffusing water monomers, formed by the absorption of water vapour in the environment onto the substrate. Under assumptions of quasi-steady thermodynamic equilibrium, the nanodroplet evolves according to the augmented Young–Laplace equation. Using continuum theory, we model the dynamics of nanodroplet growth including the coupled effects of disjoining pressure, contact angle and monomer diffusion with the assumption of constant flux of water monomers at the far field. The simulation result is validated by comparing with the published experimental result. For the case of nanodroplet growth with constant contact angle, our numerical results show that the initial droplet growth is transient by monomer diffusion. When the flux at the far field is small, at the beginning, the droplet grows by the diffusion of initially available water monomers on the substrate and after that by the flux at the far field. In the steady late growth rate of droplet radius and droplet height follow a power law of 1/3, which is unaffected by the substrate disjoining pressure and contact angle. However, it is found that the droplet grows faster in radial direction than high direction when disjoining pressure and contact angle increase. The simulation also shows the information of computational domain effect in the transient growth period. When the computational domain size is larger, the mass coming in the free substrate domain is higher. So the mass coming in the droplet is also higher. The droplet grows and reaches the steady state faster. For the case of pinning and de-pinning droplet growth, the simulation shows that the disjoining pressure does not affect the droplet radius growth law 1/3 in steady state. However the disjoining pressure modifies the growth rate of the droplet height, which then follows a power law of 1/4. We demonstrate how spatial depletion of monomers could lead to a growth arrest of the nanodroplet, as observed experimentally.

Keywords: augmented young-laplace equation, contact angle, disjoining pressure, nanodroplet growth

Procedia PDF Downloads 245

Authors: Mohamed Alimoussa, Alice Porebski, Nicolas Vandenbroucke, Rachid Oulad Haj Thami, Sana El Fkihi

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Color and texture are highly discriminant visual cues that provide an essential information in many types of images. Color texture representation and classification is therefore one of the most challenging problems in computer vision and image processing applications. Color textures can be represented in different color spaces by using multiple image descriptors which generate a high dimensional set of texture features. In order to reduce the dimensionality of the feature set, feature selection techniques can be used. The goal of feature selection is to find a relevant subset from an original feature space that can improve the accuracy and efficiency of a classification algorithm. Traditionally, feature selection is focused on removing irrelevant features, neglecting the possible redundancy between relevant ones. This is why some feature selection approaches prefer to use feature clustering analysis to aid and guide the search. These techniques can be divided into two categories. i) Feature clustering-based ranking algorithm uses feature clustering as an analysis that comes before feature ranking. Indeed, after dividing the feature set into groups, these approaches perform a feature ranking in order to select the most discriminant feature of each group. ii) Feature clustering-based subset search algorithms can use feature clustering following one of three strategies; as an initial step that comes before the search, binded and combined with the search or as the search alternative and replacement. In this paper, we propose a new feature clustering-based sequential selection approach for the purpose of color texture representation and classification. Our approach is a three step algorithm. First, irrelevant features are removed from the feature set thanks to a class-correlation measure. Then, introducing a new automatic feature clustering algorithm, the feature set is divided into several feature clusters. Finally, a sequential search algorithm, based on a filter model and a separability measure, builds a relevant and non redundant feature subset: at each step, a feature is selected and features of the same cluster are removed and thus not considered thereafter. This allows to significantly speed up the selection process since large number of redundant features are eliminated at each step. The proposed algorithm uses the clustering algorithm binded and combined with the search. Experiments using a combination of two well known texture descriptors, namely Haralick features extracted from Reduced Size Chromatic Co-occurence Matrices (RSCCMs) and features extracted from Local Binary patterns (LBP) image histograms, on five color texture data sets, Outex, NewBarktex, Parquet, Stex and USPtex demonstrate the efficiency of our method compared to seven of the state of the art methods in terms of accuracy and computation time.

Keywords: feature selection, color texture classification, feature clustering, color LBP, chromatic cooccurrence matrix

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Authors: Dimitrios Bakavos, Dimitrios Tsivoulas, Chaowalit Limmaneevichitr

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Aluminium cast alloys, of the Al-Si system, are widely used for shape castings. Their microstructures can be further improved on one hand, by alloying modification and on the other, by optimised artificial ageing. In this project four hypoeutectic Al-alloys, the A356, A356+ Ag, A356+Sc, and A356+Ag+Sc have been studied. The interactions of Ag and Sc during solidification and artificial ageing at 170°C to a T6 temper have been investigated in details. The evolution of the eutectic microstructure is studied by thermal analysis and interrupted solidification. The ageing kinetics of the alloys has been identified by hardness measurements. The precipitate phases, number density, and chemical composition has been analysed by means of transmission electron microscopy (TEM) and EDS analysis. Furthermore, the SHT effect onto the Si eutectic particles for the four alloys has been investigated by means of optical microscopy, image analysis, and the UTS strength has been compared with the UTS of the alloys after casting. The results suggest that the Ag additions, significantly enhance the ageing kinetics of the A356 alloy. The formation of β” precipitates were kinetically accelerated and an increase of 8% and 5% in peak hardness strength has been observed compared to the base A356 and A356-Sc alloy. The EDS analysis demonstrates that Ag is present on the β” precipitate composition. After prolonged ageing 100 hours at 170°C, the A356-Ag exhibits 17% higher hardness strength compared to the other three alloys. During solidification, Sc additions change the macroscopic eutectic growth mode to the propagation of a defined eutectic front from the mold walls opposite to the heat flux direction. In contrast, Ag has no significance effect on the solidification mode revealing a macroscopic eutectic growth similar to A356 base alloy. However, the mechanical strength of the as cast A356-Ag, A356-Sc, and A356+Ag+Sc additions has increased by 5, 30, and 35 MPa, respectively. The outcome is a tribute to the refining of the eutectic Si that takes place which it is strong in the A356-Sc alloy and more profound when silver and scandium has been combined. Moreover after SHT the Al alloy with the highest mechanical strength, is the one with Ag additions, in contrast to the as-cast condition where the Sc and Sc+Ag alloy was the strongest. The increase of strength is mainly attributed to the dissolution of grain boundary precipitates the increase of the solute content into the matrix, the spherodisation, and coarsening of the eutectic Si. Therefore, we could safely conclude for an A356 hypoeutectic alloy additions of: Ag exhibits a refining effect on the Si eutectic which is improved when is combined with Sc. In addition Ag enhance, the ageing kinetics increases the hardness and retains its strength at prolonged artificial ageing in a Al-7Si 0.3Mg hypoeutectic alloy. Finally the addition of Sc is beneficial due to the refinement of the α-Al grain and modification-refinement of the eutectic Si increasing the strength of the as-cast product.

Keywords: ageing, casting, mechanical strength, precipitates

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Authors: Rahul Jain, Jagdish Chander, Anish Gupta

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Introduction: Laparoscopic common bile duct exploration (LCBDE) allows cholecystectomy and the removal of common bile duct (CBD) stones to be performed during the same sitting, thereby decreasing hospital stay. CBD exploration through choledochotomy can be closed primarily with an absorbable suture material, but can lead to biliary leakage postoperatively. In this study we tried to find a solution to further lower the incidence of bile leakage by using fibrin glue to reinforce the sutures put on choledochotomy suture line. It has haemostatic and sealing action, through strengthening the last step of the physiological coagulation and biostimulation, which favours the formation of new tissue matrix. Methodology: This study was conducted at a tertiary care teaching hospital in New Delhi, India, from 2011 to 2013. 20 patients with CBD stones documented on MRCP with CBD diameter of 9 mm or more were included in this study. Patients were randomized into two groups namely Group A in which choledochotomy was closed with polyglactin 4-0 suture and suture line reinforced with fibrin glue, and Group ‘B’ in which choledochotomy was closed with polyglactin 4-0 suture alone. Both the groups were evaluated and compared on clinical parameters such as operative time, drain content, drain output, no. of days drain was required, blood loss & transfusion requirements, length of postoperative hospital stay and conversion to open surgery. Results: The operative time for Group A ranged from 60 to 210 min (mean 131.50 min) and Group B 65 to 300 min (mean 140 minutes). The blood loss in group A ranged from 10 to 120 ml (mean 51.50 ml), in group B it ranged from 10 to 200 ml (mean 53.50 ml). In Group A, there was no case of bile leak but there was bile leak in 2 cases in Group B, minimum 0 and maximum 900 ml with a mean of 97 ml and p value of 0.147 with no statistically significant difference in bile leak in test and control groups. The minimum and maximum serous drainage in Group A was nil & 80 ml (mean 11 ml) and in Group B was nil & 270 ml (mean 72.50 ml). The p value came as 0.028 which is statistically significant. Thus serous leakage in Group A was significantly less than in Group B. The drains in Group A were removed from 2 to 4 days (mean: 3 days) while in Group B from 2 to 9 days (mean: 3.9 days). The patients in Group A stayed in hospital post operatively from 3 to 8 days (mean: 5.30) while in Group B it ranged from 3 to 10 days with a mean of 5 days. Conclusion: Fibrin glue application on CBD decreases bile leakage but in statistically insignificant manner. Fibrin glue application on CBD can significantly decrease post operative serous drainage after LCBDE. Fibrin glue application on CBD is safe and easy technique without any significant adverse effects and can help less experienced surgeons performing LCBDE.

Keywords: bile leak, fibrin glue, LCBDE, serous leak

Procedia PDF Downloads 190

Authors: Luminiţa Duţică, Gheorghe Duţică

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Many of the interrogations or dilemmas of the contemporary world found the answer in what was generically called the appeal to matrix. This genuine spiritual exercise of re-connection of the present to origins, to the primary source, revealed the ontological condition of timelessness, ahistorical, immutable (epi)phenomena, of those pure essences concentrated in the archetypal-referential layer of the human existence. The musical creation was no exception to this trend, the impasse generated by the deterministic excesses of the whole serialism or, conversely, by some questionable results of the extreme indeterminism proper to the avant-garde movements, stimulating the orientation of many composers to rediscover a universal grammar, as an emanation of a new ‘collective’ order (reverse of the utopian individualism). In this context, the music of oral tradition and therefore the world of the ancient modes represented a true revelation for the composers of the twentieth century, who were suddenly in front of some unsuspected (re)sources, with a major impact on all levels of edification of the musical work: morphology, syntax, timbrality, semantics etc. For the contemporary Romanian creators, the music of rituals, existing in the local archaic culture, opened unsuspected perspectives for which it meant to be a synthetic, inclusive and recoverer vision, where the primary (archetypal) genuine elements merge with the latest achievements of language of the European composers. Thus, anchored in a strong and genuine modal source, the compositions analysed in this paper evoke, in a manner as modern as possible, the atmosphere of some ancestral rituals such as: the invocation of rain during the drought (Paparudele, Scaloianul), funeral ceremony (Bocetul), traditions specific to the winter holidays and new year (Colinda, Cântecul de stea, Sorcova, Folklore traditional dances) etc. The reactivity of those rituals in the sound context of the twentieth century meant potentiating or resizing the archaic spirit of the primordial symbolic entities, in terms of some complexity levels generated by the technique of harmonies of chordal layers, of complex aggregates (gravitational or non-gravitational, geometric), of the mixture polyphonies and with global effect (group, mass), by the technique of heterophony, of texture and cluster, leading to the implementation of some processes of collective improvisation and instrumental theatre.

Keywords: archetype, improvisation, polyphony, ritual, instrumental theatre

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Authors: Aitor Bilbao, Dragos Axinte, John Billingham

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The inverse problem in Energy Beam (EB) Processes consists of defining the control parameters, in particular the 2D beam path (position and orientation of the beam as a function of time), to arrive at a prescribed solution (freeform surface). This inverse problem is well understood for conventional machining, because the cutting tool geometry is well defined and the material removal is a time independent process. In contrast, EB machining is achieved through the local interaction of a beam of particular characteristics (e.g. energy distribution), which leads to a surface-dependent removal rate. Furthermore, EB machining is a time-dependent process in which not only the beam varies with the dwell time, but any acceleration/deceleration of the machine/beam delivery system, when performing raster paths will influence the actual geometry of the surface to be generated. Two different EB processes, Abrasive Water Machining (AWJM) and Pulsed Laser Ablation (PLA), are studied. Even though they are considered as independent different technologies, both can be described as time-dependent processes. AWJM can be considered as a continuous process and the etched material depends on the feed speed of the jet at each instant during the process. On the other hand, PLA processes are usually defined as discrete systems and the total removed material is calculated by the summation of the different pulses shot during the process. The overlapping of these shots depends on the feed speed and the frequency between two consecutive shots. However, if the feed speed is sufficiently slow compared with the frequency, then consecutive shots are close enough and the behaviour can be similar to a continuous process. Using this approximation a generic continuous model can be described for both processes. The inverse problem is usually solved for this kind of process by simply controlling dwell time in proportion to the required depth of milling at each single pixel on the surface using a linear model of the process. However, this approach does not always lead to the good solution since linear models are only valid when shallow surfaces are etched. The solution of the inverse problem is improved by using a discrete adjoint optimization algorithm. Moreover, the calculation of the Jacobian matrix consumes less computation time than finite difference approaches. The influence of the dynamics of the machine on the actual movement of the jet is also important and should be taken into account. When the parameters of the controller are not known or cannot be changed, a simple approximation is used for the choice of the slope of a step profile. Several experimental tests are performed for both technologies to show the usefulness of this approach.

Keywords: abrasive waterjet machining, energy beam processes, inverse problem, pulsed laser ablation

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Authors: Bhupendra G. Prajapati, Alpesh R. Patel

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The aim of this research work is to develop sustained release multi-particulates dosage form of Dexketoprofen trometamol, which is the pharmacologically active isomer of ketoprofen. The objective is to utilization of active enantiomer with minimal dose and administration frequency, extended release multi-particulates dosage form development for better patience compliance was explored. Drug loaded and sustained release coated pellets were prepared by fluidized bed coating principle by wurster coater. Microcrystalline cellulose as core pellets, povidone as binder and talc as anti-tacking agents were selected during drug loading while Kollicoat SR 30D as sustained release polymer, triethyl citrate as plasticizer and micronized talc as an anti-adherent were used in sustained release coating. Binder optimization trial in drug loading showed that there was increase in process efficiency with increase in the binder concentration. 5 and 7.5%w/w concentration of Povidone K30 with respect to drug amount gave more than 90% process efficiency while higher amount of rejects (agglomerates) were observed for drug layering trial batch taken with 7.5% binder. So for drug loading, optimum Povidone concentration was selected as 5% of drug substance quantity since this trial had good process feasibility and good adhesion of the drug onto the MCC pellets. 2% w/w concentration of talc with respect to total drug layering solid mass shows better anti-tacking property to remove unnecessary static charge as well as agglomeration generation during spraying process. Optimized drug loaded pellets were coated for sustained release coating from 16 to 28% w/w coating to get desired drug release profile and results suggested that 22% w/w coating weight gain is necessary to get the required drug release profile. Three critical process parameters of Wurster coating for sustained release were further statistically optimized for desired quality target product profile attributes like agglomerates formation, process efficiency, and drug release profile using central composite design (CCD) by Minitab software. Results show that derived design space consisting 1.0 to 1.2 bar atomization air pressure, 7.8 to 10.0 gm/min spray rate and 29-34°C product bed temperature gave pre-defined drug product quality attributes. Scanning Image microscopy study results were also dictate that optimized batch pellets had very narrow particle size distribution and smooth surface which were ideal properties for reproducible drug release profile. The study also focused on optimized dexketoprofen trometamol pellets formulation retain its quality attributes while administering with common vehicle, a liquid (water) or semisolid food (apple sauce). Conclusion: Sustained release multi-particulates were successfully developed for dexketoprofen trometamol which may be useful to improve acceptability and palatability of a dosage form for better patient compliance.

Keywords: dexketoprofen trometamol, pellets, fluid bed technology, central composite design

Procedia PDF Downloads 112

Authors: Ameni Mejri, Moufida Hajjaj, Salem Hasnaoui, Ridha Bouallegue

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The technology advances have most lately made the millimeter wave (mmWave) communication possible. Due to the huge amount of spectrum that is available in MmWave frequency bands, this promising candidate is considered as a key technology for the deployment of 5G cellular networks. In order to enhance system capacity and achieve spectral efficiency, very large antenna arrays are employed at mmWave systems by exploiting array gain. However, it has been shown that conventional beamforming strategies are not suitable for mmWave hardware implementation. Therefore, new features are required for mmWave cellular applications. Unlike traditional multiple-input-multiple-output (MIMO) systems for which only digital precoders are essential to accomplish precoding, MIMO technology seems to be different at mmWave because of digital precoding limitations. Moreover, precoding implements a greater number of radio frequency (RF) chains supporting more signal mixers and analog-to-digital converters. As RF chain cost and power consumption is increasing, we need to resort to another alternative. Although the hybrid precoding architecture has been regarded as the best solution based on a combination between a baseband precoder and an RF precoder, we still do not get the optimal design of hybrid precoders. According to the mapping strategies from RF chains to the different antenna elements, there are two main categories of hybrid precoding architecture. Given as a hybrid precoding sub-array architecture, the partially-connected structure reduces hardware complexity by using a less number of phase shifters, whereas it sacrifices some beamforming gain. In this paper, we treat the hybrid precoder design in mmWave MIMO systems as a problem of matrix factorization. Thus, we adopt the alternating minimization principle in order to solve the design problem. Further, we present our proposed algorithm for the partially-connected structure, which is based on the iterative hard thresholding method. Through simulation results, we show that our hybrid precoding algorithm provides significant performance gains over existing algorithms. We also show that the proposed approach reduces significantly the computational complexity. Furthermore, valuable design insights are provided when we use the proposed algorithm to make simulation comparisons between the hybrid precoding partially-connected structure and the fully-connected structure.

Keywords: alternating minimization, hybrid precoding, iterative hard thresholding, low-complexity, millimeter wave communication, partially-connected structure

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Authors: Jin Yue

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Fresh produces especially fruits, vegetables, meats and aquatic products have limited shelf life and are highly susceptible to deterioration. Essential oils (EOs) extracted from plants have excellent antioxidant and broad-spectrum antibacterial activities, and they can play as natural food preservatives. But EOs are volatile, water insoluble, pungent, and easily decomposing under light and heat. Many approaches have been developed to improve the solubility and stability of EOs such as polymeric film, coating, nanoparticles, nano-emulsions and nanofibers. Construction of active packaging film which can incorporate EOs with high loading efficiency and controlled release of EOs has received great attention. It is still difficult to achieve accurate release of antibacterial compounds at specific target locations in active packaging. In this research, a relative humidity-responsive packaging material was designed, employing the electrospinning technique to fabricate a nanofibrous film loaded with a 4-terpineol/β-cyclodextrin inclusion complexes (4-TA/β-CD ICs). Functioning as an innovative food packaging material, the film demonstrated commendable attributes including pleasing appearance, thermal stability, mechanical properties, and effective barrier properties. The incorporation of inclusion complexes greatly enhanced the antioxidant and antibacterial activity of the film, particularly against Shewanella putrefaciens, with an inhibitory efficiency of up to 65%. Crucially, the film realized controlled release of 4-TA under 98% high relative humidity conditions by inducing the plasticization of polymers caused by water molecules, swelling of polymer chains, and destruction of hydrogen bonds within the cyclodextrin inclusion complex. This film with a long-term antimicrobial effect successfully extended the shelf life of Litopenaeus vannamei shrimp to 7 days at 4 °C. To further improve the loading efficiency and long-acting release of EOs, we synthesized the γ-cyclodextrin-metal organic frameworks (γ-CD-MOFs), and then efficiently anchored γ-CD-MOFs on chitosan-cellulose (CS-CEL) composite film by in situ growth method for controlled releasing of carvacrol (CAR). We found that the growth efficiency of γ-CD-MOFs was the highest when the concentration of CEL dispersion was 5%. The anchoring of γ-CD-MOFs on CS-CEL film significantly improved the surface area of CS-CEL film from 1.0294 m2/g to 43.3458 m2/g. The molecular docking and 1H NMR spectra indicated that γ-CD-MOF has better complexing and stabilizing ability for CAR molecules than γ-CD. In addition, the release of CAR reached 99.71±0.22% on the 10th day, while under 22% RH, the release pattern of CAR was a plateau with 14.71 ± 4.46%. The inhibition rate of this film against E. coli, S. aureus and B. cinerea was more than 99%, and extended the shelf life of strawberries to 7 days. By incorporating the merits of natural biopolymers and MOFs, this active packaging offers great potential as a substitute for traditional packaging materials.

Keywords: active packaging, antibacterial activity, controlled release, essential oils, food quality control

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Authors: Aušra Černauskienė

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The heritage of modern architecture is closely related to the materiality and technology used to implement the buildings. Concrete is one of the most ubiquitous post-war building materials with enormous aesthetic and structural potential that architects have creatively used for everyday buildings and exceptional architectural objects that have survived. Concrete's material, structural, and architectural development over the post-war years has produced a remarkably rich and diverse typology of buildings, for implementation of which unique handicraft skills and industrialized novelties were used. Nonetheless, in the opinion of the public, concrete architecture is often treated as ugly and obsolete, and in Lithuania, it also has negative associations with the scarcity of the Soviet era. Moreover, aesthetic non-appreciation is not the only challenge that concrete architecture meets. It also no longer meets the needs of contemporary requirements: buildings are of poor energy class, have little potential for transformation, and have an obsolete surrounding environment. Thus, as a young heritage, concrete architecture is not yet sufficiently appreciated by society and heritage specialists, as it takes a short time to rethink what they mean from a historical perspective. However, concrete architecture is considered ambiguous but has its character and specificity that needs to be carefully studied in terms of cultural heritage to avoid the risk of poor renovation or even demolition, which has increasingly risen in recent decades in Lithuania. For example, several valuable pieces of post-war concrete architecture, such as the Banga restaurant and the Summer Stage in Palanga, were demolished without understanding their cultural value. Many unique concrete structures and raw concrete surfaces were painted or plastered, paying little attention to the appearance of authentic material. Furthermore, it raises a discussion on how to preserve buildings of different typologies: for example, innovative public buildings in their aesthetic, spatial solutions, and mass housing areas built using precast concrete panels. It is evident that the most traditional preservation strategy, conservation, is not the only option for preserving post-war concrete architecture, and more options should be considered. The first step in choosing the right strategy in each case is an appropriate assessment of the cultural significance. For this reason, an evaluation matrix for post-war concrete architecture is proposed. In one direction, an analysis of different typological groups of buildings is suggested, with the designation of ownership rights; in the other direction – the analysis of traditional value aspects such as aesthetic, technological, and relevant for modern architecture such as social, economic, and sustainability factors. By examining these parameters together, three relevant scenarios for preserving post-war concrete architecture were distinguished: conservation, renovation, and reuse, and they are revealed using examples of concrete architecture in Lithuania.

Keywords: modern heritage, value aspects, typology, conservation, upgrade, reuse

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Authors: Shilpa Sahoo, Michel Louge, Anthony Reeves, Olivier Desjardins, Susan Daniel, Sadik Omowunmi

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The microgravity on the International Space Station (ISS) was exploited to study the imbibition of water into a network of hydrophilic cylindrical capillaries on time and length scales long enough to observe details hitherto inaccessible under Earth gravity. When a drop touches a porous medium, it spreads as if laid on a composite surface. The surface first behaves as a hydrophobic material, as liquid must penetrate pores filled with air. When contact is established, some of the liquid is drawn into pores by a capillarity that is resisted by viscous forces growing with length of the imbibed region. This process always begins with an inertial regime that is complicated by possible contact pinning. To study imbibition on Earth, time and distance must be shrunk to mitigate gravity-induced distortion. These small scales make it impossible to observe the inertial and pinning processes in detail. Instead, in the International Space Station (ISS), astronaut Luca Parmitano slowly extruded water spheres until they touched any of nine capillary plates. The 12mm diameter droplets were large enough for high-speed GX1050C video cameras on top and side to visualize details near individual capillaries, and long enough to observe dynamics of the entire imbibition process. To investigate the role of contact pinning, a text matrix was produced which consisted nine kinds of porous capillary plates made of gold-coated brass treated with Self-Assembled Monolayers (SAM) that fixed advancing and receding contact angles to known values. In the ISS, long-term microgravity allowed unambiguous observations of the role of contact line pinning during the inertial phase of imbibition. The high-speed videos of spreading and imbibition on the porous plates were analyzed using computer vision software to calculate the radius of the droplet contact patch with the plate and height of the droplet vs time. These observations are compared with numerical simulations and with data that we obtained at the ESA ZARM free-fall tower in Bremen with a unique mechanism producing relatively large water spheres and similarity in the results were observed. The data obtained from the ISS can be used as a benchmark for further numerical simulations in the field.

Keywords: droplet imbibition, hydrophilic surface, inertial phase, porous medium

Procedia PDF Downloads 112

Authors: Alan Ruiz-Padilla, Brando Villalobos-Villalobos, Yeniley Ruiz-Noa, Claudia Mendoza-Macías, Claudia Palafox-Sánchez, Miguel Marín-Rosales, Álvaro Cruz, Rubén Rangel-Salazar

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Introduction: In patients with rheumatoid arthritis, resistance or poor response to disease modifying antirheumatic drugs (DMARD) may be a reflection of the increase in g-P. The expression of g-P may be important in mediating the effluence of DMARD from the cell. In addition, P-glycoprotein is involved in the transport of cytokines, IL-1, IL-2 and IL-4, from normal lymphocytes activated to the surrounding extracellular matrix, thus influencing the activity of RA. The involvement of P-glycoprotein in the transmembrane transport of cytokines can serve as a modulator of the efficacy of DMARD. It was shown that a number of lymphocytes with glycoprotein P activity is increased in patients with RA; therefore, P-glycoprotein expression could be related to the activity of RA and could be a predictor of poor response to therapy. Objective: To evaluate in RA patients, if the G2677T/A MDR1 polymorphisms is associated with differences in the rate of therapeutic response to disease-modifying antirheumatic agents in patients with rheumatoid arthritis. Material and Methods: A prospective cohort study was conducted. Fifty seven patients with RA were included. They had an active disease according to DAS-28 (score >3.2). We excluded patients receiving biological agents. All the patients were followed during 6 months in order to identify the rate of therapeutic response according to the American College of Rheumatology (ACR) criteria. At the baseline peripheral blood samples were taken in order to identify the G2677T/A MDR1 polymorphisms using PCR- Specific allele. The fragment was identified by electrophoresis in polyacrylamide gels stained with ethidium bromide. For statistical analysis, the genotypic and allelic frequencies of MDR1 gene polymorphism between responders and non-responders were determined. Chi-square tests as well as, relative risks with 95% confidence intervals (95%CI) were computed to identify differences in the risk for achieving therapeutic response. Results: RA patients had a mean age of 47.33 ± 12.52 years, 87.7% were women with a mean for DAS-28 score of 6.45 ± 1.12. At the 6 months, the rate of therapeutic response was 68.7 %. The observed genotype frequencies were: for G/G 40%, T/T 32%, A/A 19%, G/T 7% and for A/A genotype 2%. Patients with G allele developed at 6 months of treatment, higher rate for therapeutic response assessed by ACR20 compared to patients with others alleles (p=0.039). Conclusions: Patients with G allele of the - G2677T/A MDR1 polymorphisms had a higher rate of therapeutic response at 6 months with DMARD. These preliminary data support the requirement for a deep evaluation of these and other genotypes as factors that may influence the therapeutic response in RA.

Keywords: pharmacogenetics, MDR1, P-glycoprotein, therapeutic response, rheumatoid arthritis

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Authors: Suchhanda Ghosh, A. K. Paul

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Nickel, an industrially important metal is not mined in India, due to the lack of its primary mining resources. But, the chromite deposits occurring in the Sukinda and Baula-Nuasahi region of Odhisa, India, is reported to contain around 0.99% of nickel entrapped in the goethite matrix of the lateritic iron rich ore. Weathering of the dumped chromite mining overburden often leads to the contamination of the ground as well as the surface water with toxic nickel. Microbes inherent to this metal contaminated environment are reported to be capable of removal as well as detoxification of various metals including nickel. Nickel resistant fungal isolates obtained in pure form from the metal rich overburden were evaluated for their potential to biosorb nickel by using their dried biomass. Penicillium simplicissimum SAU203 was the best nickel biosorbant among the 20 fungi tested and was capable to sorbing 16.85 mg Ni/g biomass from a solution containing 50 mg/l of Ni. The identity of the isolate was confirmed using 18S rRNA gene analysis. The sorption capacity of the isolate was further standardized following Langmuir and Freundlich adsorption isotherm models and the results reflected energy efficient sorption. Fourier-transform infrared spectroscopy studies of the nickel loaded and control biomass in a comparative basis revealed the involvement of hydroxyl, amine and carboxylic groups in Ni binding. The sorption process was also optimized for several standard parameters like initial metal ion concentration, initial sorbet concentration, incubation temperature and pH, presence of additional cations and pre-treatment of the biomass by different chemicals. Optimisation leads to significant improvements in the process of nickel biosorption on to the fungal biomass. P. simplicissimum SAU203 could sorb 54.73 mg Ni/g biomass with an initial Ni concentration of 200 mg/l in solution and 21.8 mg Ni/g biomass with an initial biomass concentration of 1g/l solution. Optimum temperature and pH for biosorption was recorded to be 30°C and pH 6.5 respectively. Presence of Zn and Fe ions improved the sorption of Ni(II), whereas, cobalt had a negative impact. Pre-treatment of biomass with various chemical and physical agents has affected the proficiency of Ni sorption by P. simplicissimum SAU203 biomass, autoclaving as well as treatment of biomass with 0.5 M sulfuric acid and acetic acid reduced the sorption as compared to the untreated biomass, whereas, NaOH and Na₂CO₃ and Twin 80 (0.5 M) treated biomass resulted in augmented metal sorption. Hence, on the basis of the present study, it can be concluded that P. simplicissimum SAU203 has the potential for the removal as well as detoxification of nickel from contaminated environments in general and particularly from the chromite mining areas of Odhisa, India.

Keywords: nickel, fungal biosorption, Penicillium simplicissimum SAU203, Indian chromite mines, mining overburden

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Authors: Gunawan Muhammad, Takashi Atsumi, Akira Komaru

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Pinctada fucata has been the most important pearl culture species in Japan and known as Japanese Akoya Pearl Oyster. However, during summer 1994, mass mortality devastated pearl culture in most parts of Japan. Therefore, pearl farmers started to import Chinese Pearl Oysters from Hainan Island that came from the same species because they are believed to be more resistant towards high water temperature, despite their lack of ability in producing high-quality pearls. The local farmers were then hybridized Japanese and Chinese pearl oysters and currently known as Hybrid pearl oysters, as an attempt to produce a new oyster's strain which is more resistant towards high temperature but also able to produce higher quality pearls. However, despite both strains were implanted by mantle tissues from the same group of donors, the thickness of pearl nacre produced by both strains was different, even though tablet thickness shows a rather similar pattern. Hence, this leads to a question of whether mother oysters play a major role in both nacre deposition rate and tablet thickness of pearls or not. This study first describes the nacre deposition rate of the shells of Japanese and Hybrid mother oysters towards the water temperature condition in Ago Bay, Mie Prefecture, Japan. Later, a comparative study was conducted among 4 shell positions that had been chosen according to the mantle tissue location and shell growth directions. A correlative study was then taken between shells and pearls nacre deposition rate to know whether mother oyster ability in depositing nacre on their shells is related to that of pearls. All the four shell positions were significantly different in shell nacre growth rate (Kruskal-Wallis, p-value < 0.05), and the third position have faster nacre growth among the other three both in Japanese and Hybrid strains, especially in warm temperature. The ability to deposit nacre between Japanese and Hybrid during warm water conditions (August and September) is also significantly different in almost all positions (Mann Whitney U, p-value < 0.01), Japanese oyster growth faster than Hybrid in all four positions. This leads to a different total growth among the two strains and a higher possibility of thicker nacre thickness in Japanese shell nacre. Tablet thickness is significantly different among all positions of shells (Kruskal-Wallis, p-value < 0.01), the 2nd position deposited rather thinner tablet thickness than the other three, including on the 6th month of culture which is more desirable in producing pearls with good luster. This result gives us new information that pearl growth rate is highly affected by the mother oysters; however, nacre tablet thickness might be the result of the shell matrix expressed by different mantle position from donor oysters.

Keywords: nacre, deposition, biomineralization, pearl aquaculture, pearl oyster, Akoya pearl, pearl

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Authors: Parisa Shirzadeh

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Drug delivery systems in which drugs are traditionally used, multi-stage and at specified intervals by patients, do not meet the needs of the world's up-to-date drug delivery. In today's world, we are dealing with a huge number of recombinant peptide and protean drugs and analogues of hormones in the body, most of which are made with genetic engineering techniques. Most of these drugs are used to treat critical diseases such as cancer. Due to the limitations of the traditional method, researchers sought to find ways to solve the problems of the traditional method to a large extent. Following these efforts, controlled drug release systems were introduced, which have many advantages. Using controlled release of the drug in the body, the concentration of the drug is kept at a certain level, and in a short time, it is done at a higher rate. Graphene is a natural material that is biodegradable, non-toxic, and natural compared to carbon nanotubes; its price is lower than carbon nanotubes and is cost-effective for industrialization. On the other hand, the presence of highly effective surfaces and wide surfaces of graphene plates makes it more effective to modify graphene than carbon nanotubes. Graphene oxide is often synthesized using concentrated oxidizers such as sulfuric acid, nitric acid, and potassium permanganate based on Hummer 1 method. In comparison with the initial graphene, the resulting graphene oxide is heavier and has carboxyl, hydroxyl, and epoxy groups. Therefore, graphene oxide is very hydrophilic and easily dissolves in water and creates a stable solution. On the other hand, because the hydroxyl, carboxyl, and epoxy groups created on the surface are highly reactive, they have the ability to work with other functional groups such as amines, esters, polymers, etc. Connect and bring new features to the surface of graphene. In fact, it can be concluded that the creation of hydroxyl groups, Carboxyl, and epoxy and in fact graphene oxidation is the first step and step in creating other functional groups on the surface of graphene. Chitosan is a natural polymer and does not cause toxicity in the body. Due to its chemical structure and having OH and NH groups, it is suitable for binding to graphene oxide and increasing its solubility in aqueous solutions. Graphene oxide (GO) has been modified by chitosan (CS) covalently, developed for control release of doxorubicin (DOX). In this study, GO is produced by the hummer method under acidic conditions. Then, it is chlorinated by oxalyl chloride to increase its reactivity against amine. After that, in the presence of chitosan, the amino reaction was performed to form amide transplantation, and the doxorubicin was connected to the carrier surface by π-π interaction in buffer phosphate. GO, GO-CS, and GO-CS-DOX characterized by FT-IR, RAMAN, TGA, and SEM. The ability to load and release is determined by UV-Visible spectroscopy. The loading result showed a high capacity of DOX absorption (99%) and pH dependence identified as a result of DOX release from GO-CS nanosheet at pH 5.3 and 7.4, which show a fast release rate in acidic conditions.

Keywords: graphene oxide, chitosan, nanosheet, controlled drug release, doxorubicin

Procedia PDF Downloads 95

Authors: Shadan Dwairi

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Defining proper requirements is one of the key factors for a successful construction projects. Although there have been many attempts put forward in assist in identifying requirements, but still this area is under developed. In Buildings Information Modelling (BIM) projects. The Employer Information Requirements (EIR) is the fundamental requirements document and a necessary ingredient in achieving a successful BIM project. The provision on full and clear EIR is essential to achieving BIM Level-2. As Defined by PAS 1192-2, EIR is a “pre-tender document that sets out the information to be delivered and the standards and processes to be adopted by the supplier as part of the project delivery process”. It also notes that “EIR should be incorporated into tender documentation to enable suppliers to produce an initial BIM Execution Plan (BEP)”. The importance of effective definition of EIR lies in its contribution to a better productivity during the construction process in terms of cost and time, in addition to improving the quality of the built asset. Proper and clear information is a key aspect of the EIR, in terms of the information it contains and more importantly the information the client receives at the end of the project that will enable the effective management and operation of the asset, where typically about 60%-80% of the cost is spent. This paper reports on the research done in developing the Ontology-based tool for Employer Information Requirements (OntEIR). OntEIR has proven the ability to produce a full and complete set of EIRs, which ensures that the clients’ information needs for the final model delivered by BIM is clearly defined from the beginning of the process. It also reports on the work being done into transforming OntEIR into a smart tool for Defining Employer Information Requirements (smartEIR). smartEIR transforms the OntEIR tool into enabling it to develop custom EIR- tailored for the: Project Type, Project Requirements, and the Client Capabilities. The initial idea behind smartEIR is moving away from the notion “One EIR fits All”. smartEIR utilizes the links made in OntEIR and creating a 3D matrix that transforms it into a smart tool. The OntEIR tool is based on the OntEIR framework that utilizes both Ontology and the Decomposition of Goals to elicit and extract the complete set of requirements needed for a full and comprehensive EIR. A new ctaegorisation system for requirements is also introduced in the framework and tool, which facilitates the understanding and enhances the clarification of the requirements especially for novice clients. Findings of the evaluation of the tool that was done with experts in the industry, showed that the OntEIR tool contributes towards effective and efficient development of EIRs that provide a better understanding of the information requirements as requested by BIM, and support the production of a complete BIM Execution Plan (BEP) and a Master Information Delivery Plan (MIDP).

Keywords: building information modelling, employer information requirements, ontology, web-based, tool

Procedia PDF Downloads 106

Authors: Hemin Yuan, Yun Wang, Xiangchun Wang

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Gas hydrate is drawing attention due to the fact that it has an enormous amount all over the world, which is almost twice the conventional hydrocarbon reserves, making it a potential alternative source of energy. It is widely distributed in permafrost and continental ocean shelves, and many countries have launched national programs for investigating the gas hydrate. Gas hydrate is mainly explored through seismic methods, which include bottom simulating reflectors (BSR), amplitude blanking, and polarity reverse. These seismic methods are effective at finding the gas hydrate formations but usually contain large uncertainties when applying to invert the micro-scale petrophysical properties of the formations due to lack of constraints. Rock physics modeling links the micro-scale structures of the rocks to the macro-scale elastic properties and can work as effective constraints for the seismic methods. A number of rock physics models have been proposed for gas hydrate modeling, which addresses different mechanisms and applications. However, these models are generally not well classified, and it is confusing to determine the appropriate model for a specific study. Moreover, since the modeling usually involves multiple models and steps, it is difficult to determine the source of uncertainties. To solve these problems, we summarize the developed models/methods and make four classifications of the models according to the hydrate micro-scale morphology in sediments, the purpose of reservoir characterization, the stage of gas hydrate generation, and the lithology type of hosting sediments. Some sub-categories may overlap each other, but they have different priorities. Besides, we also analyze the priorities of different models, bring up the shortcomings, and explain the appropriate application scenarios. Moreover, by comparing the models, we summarize a general workflow of the modeling procedure, which includes rock matrix forming, dry rock frame generating, pore fluids mixing, and final fluid substitution in the rock frame. These procedures have been widely used in various gas hydrate modeling and have been confirmed to be effective. We also analyze the potential sources of uncertainties in each modeling step, which enables us to clearly recognize the potential uncertainties in the modeling. In the end, we explicate the general problems of the current models, including the influences of pressure and temperature, pore geometry, hydrate morphology, and rock structure change during gas hydrate dissociation and re-generation. We also point out that attenuation is also severely affected by gas hydrate in sediments and may work as an indicator to map gas hydrate concentration. Our work classifies rock physics models of gas hydrate into different categories, generalizes the modeling workflow, analyzes the modeling uncertainties and potential problems, which can facilitate the rock physics characterization of gas hydrate bearding sediments and provide hints for future studies.

Keywords: gas hydrate, rock physics model, modeling classification, hydrate morphology

Procedia PDF Downloads 116

Authors: Laura Canagueral-Pellice, Antonio Munar-Frau, Adaia Valls-Ontanon, Joao Carames, Federico Hernandez-Alfaro, Jordi Caballe-Serrano

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Objective: Guided bone regeneration (GBR) aims to replace the missing bone with a new structure to achieve long-term stability of rehabilitations. The aim of the present systematic review and meta-analysis is to determine the effect of barrier membranes on histological outcomes after GBR procedures. Moreover, the effect of the grafting material and tissue gain were analyzed. Materials & methods: Two independent reviewers performed an electronic search in Pubmed and Scopus, identifying all eligible publications up to March 2020. Only randomized controlled trials (RCTs) assessing a histological analysis of augmented areas were included. Results: A total of 6 publications were included for the present systematic review. A total of 110 biopsied sites were analysed; 10 corresponded to vertical bone augmentation procedures, whereas 100 analysed horizontal regeneration procedures. A mean tissue gain of 3 ± 1.48mm was obtained for horizontal defects. Histological assessment of new bone formation, residual particle and sub-epithelial connective tissue (SCT) was reported. The four main barrier membranes used were natural collagen membranes, e-PTFE, polylactic resorbable membranes and acellular dermal matrix membranes (AMDG). The analysis demonstrated that resorbable membranes result in higher values of new bone formation and lower values of residual particles and SCT. Xenograft resulted in lower new bone formation compared to allograft; however, no statistically significant differences were observed regarding residual particle and SCT. Overall, regeneration procedures adding autogenous bone, plasma derivate or growth factors achieved in general greater new bone formation and tissue gain. Conclusions: There is limited evidence favoring the effect of a certain type of barrier membrane in GBR. Data needs to be evaluated carefully; however, resorbable membranes are correlated with greater new bone formation values, especially when combined with allograft materials and/or the addition of autogenous bone, platelet reach plasma (PRP) or growth factors in the regeneration area. More studies assessing the histological outcomes of different GBR protocols and procedures testing different biomaterials are needed to maximize the clinical and histological outcomes in bone regeneration science.

Keywords: barrier membrane, graft material, guided bone regeneration, implant surgery, histology

Procedia PDF Downloads 124

Authors: Mikaela Kutrolli, Noah S. Pereira, Vanessa Scanlon, Mohamadmahdi Samandari, Ali Tamayol

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Bone tissue engineering has drawn significant attention and various biomaterials have been tested. Polymers such as polycaprolactone (PCL) offer excellent biocompatibility, reasonable mechanical properties, and biodegradability. However, PCL scaffolds suffer a critical drawback: a lack of micro/mesoporosity, affecting cell attachment, tissue integration, and mineralization. It also results in a slow degradation rate. While 3D-printing has addressed the issue of macroporosity through CAD-guided fabrication, PCL scaffolds still exhibit poor smaller-scale porosity. To overcome this, we generated composites of PCL, hydroxyapatite (HA), and powdered sucrose (PS). The latter serves as a sacrificial material to generate porous particles after sucrose dissolution. Additionally, we have incorporated dexamethasone (DEX) to boost the PCL osteogenic properties. The resulting scaffolds maintain controlled macroporosity from the lattice print structure but also develop micro/mesoporosity within PCL fibers when exposed to aqueous environments. The study involved mixing PS into solvent-dissolved PCL in different weight ratios of PS to PCL (70:30, 50:50, and 30:70 wt%). The resulting composite was used for 3D printing of scaffolds at room temperature. Printability was optimized by adjusting pressure, speed, and layer height through filament collapse and fusion test. Enzymatic degradation, porogen leaching, and DEX release profiles were characterized. Physical properties were assessed using wettability, SEM, and micro-CT to quantify the porosity (percentage, pore size, and interconnectivity). Raman spectroscopy was used to verify the absence of sugar after leaching. Mechanical characteristics were evaluated via compression testing before and after porogen leaching. Bone marrow stromal cells (BMSCs) behavior in the printed scaffolds was studied by assessing viability, metabolic activity, osteo-differentiation, and mineralization. The scaffolds with a 70% sugar concentration exhibited superior printability and reached the highest porosity of 80%, but performed poorly during mechanical testing. A 50% PS concentration demonstrated a 70% porosity, with an average pore size of 25 µm, favoring cell attachment. No trace of sucrose was found in Raman after leaching the sugar for 8 hours. Water contact angle results show improved hydrophilicity as the sugar concentration increased, making the scaffolds more conductive to cell adhesion. The behavior of bone marrow stromal cells (BMSCs) showed positive viability and proliferation results with an increasing trend of mineralization and osteo-differentiation as the sucrose concentration increased. The addition of HA and DEX also promoted mineralization and osteo-differentiation in the cultures. The integration of PS as porogen at a concentration of 50%wt within PCL scaffolds presents a promising approach to address the poor cell attachment and tissue integration issues of PCL in bone tissue engineering. The method allows for the fabrication of scaffolds with tunable porosity and mechanical properties, suitable for various applications. The addition of HA and DEX further enhanced the scaffolds. Future studies will apply the scaffolds in an in-vivo model to thoroughly investigate their performance.

Keywords: bone, PCL, 3D printing, tissue engineering

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Authors: Raj Kumar, Prem Felix Siril

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The poor aqueous solubility of many pharmaceutical drugs and potential drug candidates is a big challenge in drug development. Nanoformulation of such candidates is one of the major solutions for the delivery of such drugs. We initially developed the evaporation assisted solvent-antisolvent interaction (EASAI) method. EASAI method is use full to prepared nanoparticles of poor water soluble drugs with spherical morphology and particles size below 100 nm. However, to further improve the effect formulation to reduce number of dose and side effect it is important to control the delivery of drugs. However, many drug delivery systems are available. Among the many nano-drug carrier systems, solid lipid nanoparticles (SLNs) have many advantages over the others such as high biocompatibility, stability, non-toxicity and ability to achieve controlled release of drugs and drug targeting. SLNs can be administered through all existing routes due to high biocompatibility of lipids. SLNs are usually composed of lipid, surfactant and drug were encapsulated in lipid matrix. A number of non-steroidal anti-inflammatory drugs (NSAIDs) have poor bioavailability resulting from their poor aqueous solubility. In the present work, SLNs loaded with NSAIDs such as Nabumetone (NBT), Ketoprofen (KP) and Ibuprofen (IBP) were successfully prepared using different lipids and surfactants. We studied and optimized experimental parameters using a number of lipids, surfactants and NSAIDs. The effect of different experimental parameters such as lipid to surfactant ratio, volume of water, temperature, drug concentration and sonication time on the particles size of SLNs during the preparation using hot-melt sonication was studied. It was found that particles size was directly proportional to drug concentration and inversely proportional to surfactant concentration, volume of water added and temperature of water. SLNs prepared at optimized condition were characterized thoroughly by using different techniques such as dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). We successfully prepared the SLN of below 220 nm using different lipids and surfactants combination. The drugs KP, NBT and IBP showed 74%, 69% and 53% percentage of entrapment efficiency with drug loading of 2%, 7% and 6% respectively in SLNs of Campul GMS 50K and Gelucire 50/13. In-vitro drug release profile of drug loaded SLNs is shown that nearly 100% of drug was release in 6 h.

Keywords: nanoparticles, delivery, solid lipid nanoparticles, hot-melt sonication, poor water soluble drugs, solubility, bioavailability

Procedia PDF Downloads 289

Authors: Luay Jum'a

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Many challenges are facing third-party logistics (3PL) providers in the domestic and global markets which create a volatile decision making environment. All these challenges such as managing changes in consumer behaviour, demanding expectations from customers and time compressions have turned into complex problems for 3PL providers. Since the movement towards increased outsourcing outpaces movement towards insourcing, the need to achieve a competitive advantage over competitors in 3PL market increases. This trend continues to grow over the years and as a result, areas of strengths and improvements are highlighted through the analysis of the LSQ factors that lead to B2B customers’ satisfaction which become a priority for 3PL companies. Consequently, 3PL companies are increasingly focusing on the most important issues from the perspective of their customers and relying more on this value of information in making their managerial decisions. Therefore, this study is concerned with providing guidance for improving logistics service quality (LSQ) levels in the context of 3PL industry in Jordan. The study focused on the most important factors in LSQ and used a managerial tool that guides 3PL companies in making LSQ improvements based on a quadrant analysis of two main dimensions: LSQ declared importance and LSQ inferred importance. Although, a considerable amount of research has been conducted to investigate the relationship between logistics service quality (LSQ) and customer satisfaction, there remains a lack of developing managerial tools to aid in the process of LSQ improvement decision-making. Moreover, the main advantage for the companies to use 3PL service providers as a trend is due to the realised percentage of cost reduction on the total cost of logistics operations and the incremental improvement in customer service. In this regard, having a managerial tool that help 3PL service providers in managing the LSQ factors portfolio effectively and efficiently would be a great investment for service providers. One way of suggesting LSQ improvement actions for 3PL service providers is via the adoption of analysis tools that perform attribute categorisation such as Importance–Performance matrix. In mind of the above, it can be stated that the use of quadrant analysis will provide a valuable opportunity for 3PL service providers to identify improvement opportunities as customer service attributes or factors importance are identified in two different techniques that complete each other. Moreover, the data were collected through conducting a survey and 293 questionnaires were returned from business-to-business (B2B) customers of 3PL companies in Jordan. The results showed that the LSQ factors vary in their importance and 3PL companies should focus on some LSQ factors more than other factors. Moreover, ordering procedures, timeliness/responsiveness LSQ factors considered being crucial in 3PL businesses and therefore they need to have more focus and development by 3PL service providers in the Jordanian market.

Keywords: logistics service quality, managerial decisions, quadrant analysis, third party logistics service provider

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Authors: Henrry Vicente Rojas Asuero, Holger Manuel Benavides Muñoz

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Approximately 80% of the energy consumed worldwide is generated from fossil sources, which are responsible for the emission of a large volume of greenhouse gases. For this reason, the global trend, at present, is the widespread use of energy produced from renewable sources. This seeks safety and diversification of energy supply, based on social cohesion, economic feasibility and environmental protection. In this scenario, small hydropower systems (P ≤ 10MW) stand out due to their high efficiency, economic competitiveness and low environmental impact. Small hydropower systems, along with wind and solar energy, are expected to represent a significant percentage of the world's energy matrix in the near term. Among the various technologies present in the state of the art, relating to small hydropower systems, is the Gravitational Water Vortex Power Plant, a recent technology that excels because of its versatility of operation, since it can operate with jumps in the range of 0.70 m-2.00 m and flow rates from 1 m3/s to 20 m3/s. Its operating system is based on the utilization of the energy of rotation contained within a large water vortex artificially induced. This paper presents the study and experimental design of an optimal hydraulic structure with the capacity to induce the artificial formation of a gravitational water vortex trough a system of easy application and high efficiency, able to operate in conditions of very low head and minimum flow. The proposed structure consists of a channel, with variable base, vortex inductor, tangential flow generator, coupled to a circular tank with a conical transition bottom hole. In the laboratory test, the angular velocity of the water vortex was related to the geometric characteristics of the inductor channel, as well as the influence of the conical transition bottom hole on the physical characteristics of the water vortex. The results show angular velocity values of greater magnitude as a function of depth, in addition the presence of the conical transition in the bottom hole of the circular tank improves the water vortex formation conditions while increasing the angular velocity values. Thus, the proposed system is a sustainable solution for the energy supply of rural areas near to watercourses.

Keywords: experimental model, gravitational water vortex power plant, renewable energy, small hydropower

Procedia PDF Downloads 268

Authors: Kaushik Vaideeswaran, Jean Gobet, Patrick Margraf, Olha Sereda

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Nitrocarburisation is a surface hardening technique often applied to improve the wear resistance of steel surfaces. It is considered to be a promising solution in comparison with other processes such as flame spraying, owing to the formation of a diffusion layer which provides mechanical integrity, as well as its cost-effectiveness. To improve other tribological properties of the surface such as the coefficient of friction (COF), dry lubricants are utilized. Currently, the lifetime of steel components in many applications using either of these techniques individually are faced with the limitations of the two: high COF for nitrocarburized surfaces and low wear resistance of dry lubricant coatings. To this end, the current study involves the creation of a hybrid surface using the impregnation of a dry lubricant on to a nitrocarburized surface. The mechanical strength and hardness of Gerster SA’s nitrocarburized surfaces accompanied by the impregnation of the porous outermost layer with a solid lubricant will create a hybrid surface possessing both outstanding wear resistance and a low friction coefficient and with high adherence to the substrate. Gerster SA has the state-of-the-art technology for the surface hardening of various steels. Through their expertise in the field, the nitrocarburizing process parameters (atmosphere, temperature, dwelling time) were optimized to obtain samples that have a distinct porous structure (in terms of size, shape, and density) as observed by metallographic and microscopic analyses. The porosity thus obtained is suitable for the impregnation of a dry lubricant. A commercially available dry lubricant with a thermoplastic matrix was employed for the impregnation process, which was optimized to obtain a void-free interface with the surface of the nitrocarburized layer (henceforth called hybrid surface). In parallel, metallic samples without nitrocarburisation were also impregnated with the same dry lubricant as a reference (henceforth called reference surface). The reference and the nitrocarburized surfaces, with and without the dry lubricant were tested for their tribological behavior by sliding against a quenched steel ball using a nanotribometer. Without any lubricant, the nitrocarburized surface showed a wear rate 5x lower than the reference metal. In the presence of a thin film of dry lubricant ( < 2 micrometers) and under the application of high loads (500 mN or ~800 MPa), while the COF for the reference surface increased from ~0.1 to > 0.3 within 120 m, the hybrid surface retained a COF < 0.2 for over 400m of sliding. In addition, while the steel ball sliding against the reference surface showed heavy wear, the corresponding ball sliding against the hybrid surface showed very limited wear. Observations of the sliding tracks in the hybrid surface using Electron Microscopy show the presence of the nitrocarburized nodules as well as the lubricant, whereas no traces of the lubricant were found in the sliding track on the reference surface. In this manner, the clear advantage of combining nitrocarburisation with the impregnation of a dry lubricant towards forming a hybrid surface has been demonstrated.

Keywords: dry lubrication, hybrid surfaces, improved wear resistance, nitrocarburisation, steels

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Authors: Sunitha Sampathi, Pankaj Kumar Tiriya, Sonia Gera, Sravanthi Reddy Pailla, V. Likhitha, A. J. Maruthi

Abstract:

Surgical site infections (SSIs) are the most common nosocomial infections localized at the incision site. With an estimated 27 million surgical procedures each year in USA, approximately 2-5% rate of SSIs are predicted to occur annually. SSIs are treated with antibiotic medication. Current trend suggest that the direct drug delivery from the suture to the scared tissue can improve patient comfort and wound recovery. For that reason coating the surface of the medical device such as suture and catguts with broad spectrum antibiotics can prevent the formation of bactierial colonies with out comprimising the mechanical properties of the sutures.Hence, the present study was aimed to develop and evaluate a surgical suture coated with an antibiotic Ciprofloxacin hydrochloride loaded on gold nanoparticles. Gold nanoparticles were synthesized by chemical reduction method and conjugated with ciprofloxacin using Polyvinylpyrolidone as stabilizer and gold as carrier. Ciprofloxacin conjugated gold nanoparticles were coated over an absorbable surgical suture made of Polyglactan using sodium alginate as an immobilising agent by slurry dipping technique. The average particle size and Polydispersity Index of drug conjugated gold NPs were found to be 129±2.35 nm and 0.243±0.36 respectively. Gold nanoparticles are characterized by UV-Vis absorption spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), Scanning electron microscopy and Transmission electron microscopy. FT-IR revealed that there is no chemical interaction between drug and polymer. Antimicrobial activity for coated sutures was evaluated by disc diffusion method on culture plates of both gram negative (E-coli) and gram positive bacteria (Staphylococcus aureus) and results found to be satisfactory. In vivo studies for coated sutures was performed on Swiss albino mice and histological evaluation of intestinal wound healing parameters such as wound edges in mucosa, muscularis, presence of necrosis, exudates, granulation tissue, granulocytes, macrophages, restoration, and repair of mucosal epithelium and muscularis propria on day 7 after surgery were studied. The control animal group, sutured with plain suture (uncoated suture) showed signs of restoration and repair, but presence of necrosis, heamorraghic infiltration and granulation tissue was still noticed. Whereas the animal group treated with ciprofloxacin and ciprofloxacin gold nanoparticle coated sutures has shown promising decrease in terms of haemorraghic infiltration, granulation tissue, necrosis and better repaired muscularis layers on comparision with plain coated sutures indicating faster rate of repair and less chance of sepsis. Hence coating of sutures with broad spectrum antibiotics can be an alternate technique to reduce SSIs.

Keywords: ciprofloxacin hydrochloride, gold nanoparticles, surgical site infections, sutures

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Authors: Osman Adiguzel

Abstract:

Shape memory effect is a peculiar property exhibited by certain alloy systems and based on martensitic transformation, and shape memory properties are closely related to the microstructures of the material. Shape memory effect is linked with martensitic transformation, which is a solid state phase transformation and occurs with the cooperative movement of atoms by means of lattice invariant shears on cooling from high-temperature parent phase. Lattice twinning and detwinning can be considered as elementary processes activated during the transformation. Thermally induced martensite occurs as martensite variants, in self-accommodating manner and consists of lattice twins. Also, this martensite is called the twinned martensite or multivariant martensite. Deformation of shape memory alloys in martensitic state proceeds through a martensite variant reorientation. The martensite variants turn into the reoriented single variants with deformation, and the reorientation process has great importance for the shape memory behavior. Copper based alloys exhibit this property in metastable β- phase region, which has DO3 –type ordered lattice in ternary case at high temperature, and these structures martensiticaly turn into the layered complex structures with lattice twinning mechanism, on cooling from high temperature parent phase region. The twinning occurs as martensite variants with lattice invariant shears in two opposite directions, <110 > -type directions on the {110}- type plane of austenite matrix. Lattice invariant shear is not uniform in copper based ternary alloys and gives rise to the formation of unusual layered structures, like 3R, 9R, or 18R depending on the stacking sequences on the close-packed planes of the ordered lattice. The unit cell and periodicity are completed through 18 atomic layers in case of 18R-structure. On the other hand, the deformed material recovers the original shape on heating above the austenite finish temperature. Meanwhile, the material returns to the twinned martensite structures (thermally induced martensite structure) in one way (irreversible) shape memory effect on cooling below the martensite finish temperature, whereas the material returns to the detwinned martensite structure (deformed martensite) in two-way (reversible) shape memory effect. Shortly one can say that the microstructural mechanisms, responsible for the shape memory effect are the twinning and detwinning processes as well as martensitic transformation. In the present contribution, x-ray diffraction, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) studies were carried out on two copper-based ternary alloys, CuZnAl, and CuAlMn.

Keywords: shape memory effect, martensitic transformation, twinning and detwinning, layered structures

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Authors: Antonieta Heyden Megale

Abstract:

With the advent of globalization, the social, cultural and linguistic situation of the whole world has changed. In this scenario, the teaching of English, in Brazil, has become a booming business and the belief that this language is essential to a successful life is played by the media that sees it as a commodity and spares no effort to sell it. In this context, it has become evident the growth of bilingual and international schools that have English and Portuguese as languages of instruction. According to federal legislation, all schools in the country must follow the Curriculum guidelines proposed by the Ministry of Education of Brazil. It is then mandatory that, in addition to the specific foreign curriculum an international school subscribes to, it must also teach all subjects of the official minimum curriculum and these subjects have to be taught in Portuguese. It is important to emphasize that, in these schools, English is the most prestigious language. Therefore, firstly, Brazilian teachers who teach Portuguese in such contexts find themselves in a situation in which they teach in a low-status language. Secondly, because such teachers’ actions are guided by a different cultural matrix, which differs considerably from Anglo-Saxon values and beliefs, they often experience intercultural conflict in their workplace. Taking it consideration, this research, focusing on the trajectories of a specific group of Brazilian teachers of Portuguese in international and bilingual schools located in the city of São Paulo, intends to analyze how they discursively represent their own professional identities and practices. More specifically the objectives of this research are to understand, from the perspective of the investigated teachers, how they (i) rebuilt narratively their professional careers and explain the factors that led them to an international or to an immersion bilingual school; (ii) position themselves with respect to their linguistic repertoire; (iii) interpret the intercultural practices they are involved with in school and (v) position themselves by foregrounding categories to determine their membership in the group of Portuguese teachers. We have worked with these teachers’ autobiographical narratives. The autobiographical approach assumes that the stories told by teachers are systems of meaning involved in the production of identities and subjectivities in the context of power relations. The teachers' narratives were elicited by the following trigger: "I would like you to tell me how you became a teacher in a bilingual/international school and what your impressions are about your work and about the context in which it is inserted". These narratives were produced orally, recorded, and transcribed for analysis. The teachers were also invited to draw their "linguistic portraits". The theoretical concepts of positioning and the indexical cues were taken into consideration in data analysis. The narratives produced by the teachers point to intercultural conflicts related to their expectations and representations of others, which are never neutral or objective truths but discursive constructions.

Keywords: bilingual schools, identity, interculturality, narrative

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