A study of the viscometric and volumetric properties of some multi-component liquid regular solutions at different temperatures.

The densities and kinematic viscosities of the quinary liquid regular system octane(1)-hexane(2)-ethylbenzene(3)-cyclohexane(4)-toluene(5) and two of its quaternary subsystems were measured at 293.15 K and 298.15 K. In addition, the densities and kinematic viscosities of the quinary liquid regular system octane(1)-heptane(2)-ethylbenzene(3)-cyclohexane(4)-toluene(5) and all of its quaternary and ternary subsystems were measured at the same two temperatures. The data collected in the present study were employed in testing the predictive capabilities of some of the most widely used viscosity models for liquid mixtures. Comparison of the predictive capabilities of the various literature models showed indicated that the generalized McAllister three-body collision model gave the lowest deviation from the experimental results.Dept. of Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .E443. Source: Masters Abstracts International, Volume: 43-01, page: 0257. Adviser: Abdul-Fattah A. Asfour. Thesis (M.A.Sc.)--University of Windsor (Canada), 2004

Triethylphosphite as a network forming agent enhances in-vitro biocompatibility and corrosion protection of hybrid organic-inorganic sol-gel coatings for Ti6Al4V alloys

The biocompatibility and life of metallic implants can be enhanced through improving the biocompatibility and corrosion protection characteristics of the coatings used with these materials. In this study, triethylphosphite (TEP) was used to introduce phosphorus into organic-inorganic hybrid silica based sol gel coatings prepared using γ-methacryloxypropyltrimethoxysilane and tetramethylorthosilicate. Addition of TEP dramatically increased the rate of intermolecular condensation and resulted in materials showing greater cross linking. Protein (fibrinogen) uptake, osteoblast in vitro biocompatibility and corrosion resistance was enhanced in coatings containing TEP. Although higher concentrations of phosphorus supported the greatest improvement in biocompatibility, a compromise in the phosphorus concentration used would be required if corrosion resistance was most desirable parameter for optimisation. Films prepared by dip coating on Ti6Al4V alloys from these sols offer a promising alternative to wholly metallic prostheses

Solar-wind ventilation to enhance the cabinet dryer performance for medicinal herbs and horticultural products

This paper presents the design, construction and performance evaluation of a mixed-mode solar cabinet dryer (SCD) for medicinal herbs and horticultural products.  Solar- wind ventilation system is used to enhance the cabinet dryer performance.  The solar cabinet is equipped with a vertical blackened solar chimney and a flat plate solar collector to enhance buoyancy force.  The chimney is provided with suction axial fan that can rotate smoothly by wind power.  The performance of SCD was evaluated without load (empty) and with load (potato chips and peppermint).  After performing various standardized pretreatments, products were dried separately under open sun, SCD and electric oven.  Results of parametric studies indicated that, highest drying air temperature was achieved at 60° collector tilt angle followed by 30°, when the dehydration system tracked the sun.  The developed SCD exhibited sufficient ability to dry the chips and peppermint reasonably to a safe moisture level within 9-10 and 5-6 hrs (≈1 clear sunny day), respectively.  The best chips colour was achieved at 15 s frying time.  All the fried chips and dried peppermint were well accepted by the panelists.  The SCD ensures a superior quality of the dried products.  In terms of electricity requirement, frying time, health conscious and utilization of solar energy, the enhanced SCD is considered a suitable method for drying potato chips as well as peppermint. Keywords: solar cabinet, solar collector, windmill, drying, chips, peppermint

An approach to design new coatings for biomedical applications

Ti6Al4V alloy is widely used as implants for orthopedic and dental applications because of its superior mechanical properties, excellent corrosion resistance and good biocompatibility. However, it takes long period of several months for Ti6Al4V implants to integrate with the bone tissue due to their bio-inert feature in nature. An innovating and incipient method to solve the above mentioned drawbacks consist of the development of new coatings which could improve both the biological and corrosion protection performance of the Ti6Al4V alloy. Thus, a variety of strategies have been implemented to modify the surface of Ti6Al4V-based implants and enhance bone growth and their initial stability. A common approach is the deposition of bioactive hybrid coatings including inorganic and organic units on the surface of the Ti6Al4V alloy via sol-gel method. The sol–gel route is of great interest as it offers the possibility of tailoring the material properties by variation of the relative composition of the precursors used. The aim of this thesis is focused on the development of new coatings, starting with inorganic hydroxyapatite (HAp) deposited onto Ti6Al4V substrate prepared through solgel route. The effect of thermal treatment temperature on both in-vitro bioactivity and corrosion performance has been studied in simulated body fluid solution (SBF). A complete physical-chemical characterization was done in all the thermally treated coatings obtained. In-vitro tests in SBF were carried out in order to investigate the biological performance of the films. Due to the high temperature required for synthesizing HAp in crystalline form, porous and cracked coatings have been obtained, as a result of the thermal treatments applied to the prepared coatings. Although of these cracks, on the film was produced the precipitation of bone-like apatite after immersion in SBF. These precipitation products lead also to an improvement of the corrosion performance through blocking effect. The corrosion protection of the coating depends on its ability to act as a physical barrier preventing the penetration of corrosive species to reach the metal surface. This fact stimulated us to reach other goals through the preparation of sets of various new organic-inorganic hybrids. These new coatings have been also prepared through sol-gel route. To obtain workable films and their optimum preparation conditions, a new study has been carried out. The aim of this new study has been to optimize the organic– inorganic hybrid preparation method through studying the structural changes which take place during the hydrolysis and condensation processes of a mixture of γ- methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethylorthosilicate (TMOS) in solution after the addition of water and ethanol. FTIR, liquid-state ²⁹Si and ¹³C nuclear magnetic resonance (NMR) have been applied for this purpose. The results indicated that, the hydrolysis process of the two silane precursors is a time-dependent process and four hours of reaction are required for obtaining workable films. Then, after the results obtained in the first two stages of this PhD thesis, three different organic-inorganic hybrid coatings have been prepared. These coatings have been based on the MAPTMS/TMOS matrix modified with different phosphorous precursors; HAp as solid phosphorus precursor and triethylphosphite (TEP) and dimethylsilylphosphite (DMTSP) as liquid phosphorus precursors. These precursors have been added in different amounts with the aim to obtain new materials of physicalchemical and biological interest. At this level, during investigation, the following four aspects have been taken into account: 1. Evaluation of the effect of the addition of the different phosphorous precursors on the densification of the siloxane network. 2. Physical-chemical characterization of the resulting coatings. 3. Evaluation of the in-vitro osteointegration of the coatings through assays of normal human osteoblast cytotoxicity and adhesion. 4. Evaluation of the corrosion performance of the coatings. The results obtained along this study have shown that, all the prepared coatings are relatively hydrophobic with respect to the un-coated alloy. All the modified films are denser than the control one based on the MAPTMS/TMOS matrix. This fact allows these coatings to act as effective physical barriers against corrosion. The presence of phosphorus precursors results in further cross-linking and at the same time act as binding sites for protein adsorption. The importance of phosphorus in cell division and proliferation make also these coatings bioactive. The coating based on MAPTMS/TMOS/DMTSP showed the best biological performance in terms of cell proliferation and adhesion. Concerning the barrier properties provided by the designed hybrid films, the sol-gel films obtained by the chemical modification of the MAPTMS/TMOS matrix with TEP, showed the best barrier properties when immersed in SBF for 30 days. -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Las aleaciones de Ti6Al4V son ampliamente utilizadas como biomaterial metálico para prótesis e implantes dentales debido a sus buenas propiedades mecánicas, excelente resistencia a la corrosión y buena biocompatibilidad. Sin embargo, son necesarios varios meses para una buena osteointegración debido a la naturaleza inerte de la aleación. Un método innovador para solucionar esta desventaja consiste en el desarrollo de nuevos recubrimientos que confieran bioactividad a la superficie de la aleación Ti6Al4V a la vez que mejoran su resistencia a la corrosión. Por esta razón, distintos tipos de estrategias se han desarrollado estos últimos años para modificar la superficie de los implantes fabricados a partir de la aleación Ti6Al4V. Todas ellas tienen como objetivo principal mejorar la interfase implante-hueso activando la formación de tejido óseo y mejorando su estabilidad en la fase inicial se osteointegración. Uno de los mejores métodos para conseguir estas interfases se basa en la aplicación de recubrimientos bioactivos sobre la superficie de la aleación. Concretamente, mediante el método sol-gel se pueden obtener recubrimientos bioactivos híbridos órgano-inorgánicos sobre la superficie de la aleación. El método sol-gel es de gran interés para la obtención de este tipo de recubrimientos porque ofrece la posibilidad de diseñar a medida las propiedades del material y/o recubrimiento deseado mediante la variación de la composición relativa de los precursores utilizados. El objetivo principal de esta tesis se centra en el desarrollo de nuevos recubrimientos multifuncionales con buenas propiedades bioactivas y anticorrosivas. El procedimiento seguido para la consecución del objetivo principal ha consistido en varias etapas. La primera ha sido partir de la síntesis de un material de bioactividad conocida, Hidroxiapatita (HAp), y optimizar los parámetros del proceso sol-gel para conseguir las mejores propiedades bioactivas tanto en forma de nanopartículas como aplicado como recubrimiento inorgánico sobre la superficie de la aleación Ti6Al4V. Para ello, se ha estudiado el efecto de la temperatura de tratamiento tanto en la respuesta bioactiva de las nanoparticulas de HAp, como en la bioactividad y la resistencia a la corrosión del recubrimiento inorgánico de HAp sobre la aleación. La respuesta bioactiva in-vitro y la resistencia a la corrosión se han estudiado en presencia de fluido fisiológico simulado (SBF). Se han obtenido nanopartículas de HAp con una excelente bioactividad. En el caso de los recubrimientos inorgánicos de HAp, debido a las altas temperaturas para conseguir la forma cristalina de la HAp, se generaron algunas grietas en los recubrimientos. A pesar de ello, en la evaluación de bioactividad mostraron precipitación de apatita con estructura similar a la ósea. Dicha precipitación también contribuyó a mejorar el efecto barrera del recubrimiento, mediante el bloqueo de poros y grietas, evitando así la incorporación de iones tóxicos provenientes de la superficie de la aleación al fluido fisiológico. La protección frente a la corrosión de un recubrimiento depende, en parte, de su habilidad para actuar como barrera evitando el acceso de especies corrosivas a la superficie metálica. Este hecho pone de manifiesto la necesidad de desarrollar otro tipo de recubrimientos, actuando como estimulo para la consecución de los siguientes objetivos de esta tesis. De esta forma, partiendo de los resultados obtenidos en la primera etapa con los recubrimientos inorgánicos de HAp, posteriormente, se ha ido aumentando la complejidad de los nuevos recubrimientos desarrollados hasta alcanzar los objetivos propuestos, bioactividad y resistencia a la corrosión. Con el fin de obtener nuevos recubrimientos viables, así como sus optimas condiciones de preparación, primeramente se desarrollo un nuevo estudio cuyo objetivo concreto ha sido la optimización del método de preparación de un nuevo recubrimiento hibrido órgano-inorgánico mediante el estudio de los cambios estructurales que tienen lugar durante los procesos de hidrólisis y condensación de una mezcla de γ- metacriloxipropiltrimetoxisilano (MAPTMS) y tetrametilortosilicato (TMOS) en solución después de la adición de agua y etanol. Este estudio se realizo mediante Espectroscopia Infraroja (IR) y Resonancia Magnetico-Nuclear (RMN) del ²⁹Si y ¹³C en estado líquido. Los resultados indicaron que la hidrólisis de estos dos precursores es un proceso dependiente del tiempo y cuatro horas de reacción es el tiempo optimo para obtener recubrimientos viables de ser aplicados y posteriormente poder actuar como matriz hibrida de recubrimientos más complejos. Tras los resultados obtenidos en estas dos primeras etapas descritas, se han diseñado y obtenido tres nuevos recubrimientos híbridos órgano-inorgánico con las propiedades requeridas. Dichos recubrimientos se basan en una matriz de MAPTMS/TMOS que ha sido modificada con distintos precursores de fósforo para dotarles de la deseada bioactividad. Los precursores de fósforo utilizados han sido nanoparticulas de HAp, como precursor sólido de fósforo y trietilfosfito (TEP) y dimetilsililfosfito (DMTSP) como precursores líquidos de fósforo. Estos precursores se han añadido en distintas cantidades con el objetivo de obtener nuevos recubrimientos de interés físico, químico y biológico. En esta etapa, durante la investigación, se han tenido en cuenta los siguientes aspectos: 1. Evaluación del efecto de la adición de los diferentes precursores de fósforo en la densificación de la matriz siloxánica. 2. Caracterización físico-química de los recubrimientos obtenidos. 3. Evaluación in-vitro de la osteointegración a partir de ensayos de citotoxicidad y adhesión de osteoblastos humanos. 4. Evaluación del comportamiento frente a la corrosión de los recubrimientos. Los principales resultados obtenidos a lo largo de este estudio han demostrado que todos los recubrimientos preparados tienen un comportamiento ligeramente más hidrofóbico que la superficie de la aleación Ti6Al4V. Todos los recubrimientos modificados con los distintos precursores de fósforo tienen mayor densidad que la matriz MAPTMS/TMOS de partida. Este hecho les confiere a estos recubrimientos unas buenas propiedades para actuar como una barrera física efectiva entre la superficie de la aleación y el medio fisiológico, mejorando así su comportamiento frente a la corrosión. La presencia de los precursores de fosforo en estado liquido, ha resultado en un aumento del grado de entrecruzamiento creando al mismo tiempo el fósforo sitios activos preferentes para la adsorción de proteínas. La importancia del fósforo en la división y proliferación celular confiere a su vez a estos recubrimientos bioactividad. De todos los recubrimientos obtenidos y estudiados, el recubrimiento basado en MAPTMS/TMOS/DMTSP mostró la mejor respuesta biológica en términos de proliferación y adhesión de osteoblastos. En relación con las propiedades barrera ofrecidas por los recubrimientos diseñados, el recubrimiento obtenido mediante modificación química con TEP de la matriz MAPTMS/TMOS de partida ha sido el que mejores propiedades barrera ha mostrado durante 30 días de inmersión en SBF

Effects of Fluoride Release on Enamel Color Alteration

The aim of this study is to evaluate teeth discoloration after the usage of adhesive fluoride release. Material and Method: 80 extracted healthy premolars divided into two groups were used in the study, with metal brackets being bonded in both groups,. The first group universal adhesive was applied (transbond light cure adhesive paste-Transbond XT), whereas in the second group fluoride releasing bonding material was used (opal bond MV composite and opal seal). The measurement of color parameters was performed using the spectrophotometer vita easyshade 4.0 to calculate ΔL, Δa, Δb, and ΔE. Statistical Analysis: 3-way mixed analysis of variances (ANOVA) was used to compare ΔE before using adhesive material and after the procedure. On the other hand, it was used to compare Δa, Δb, and ΔL before and after using adhesive material. The statistical significance level was established at P< 0.05. Boferroni correction was used to create mean differences between the results. Results: The result of this study showed that ΔE* values were increased in all groups. The mean difference of ΔE* value in the first group (3M adhesive material) was 2.54± 1.57. At the same time, the ΔE value in opal adhesive group was 4.43±5.4. These results showed that fluoride seal had direct effect on enamel color after a period of three months teeth storage. Results showed above the normal limit and produced visible color change on the surface of the teeth after finishing procedure. On the other hand, ΔL values were increased in both groups, with a significant difference in the first group (p value 0.04) and with no significant difference in the second group (p value 0.239). Conclusion: The highest color changes were observed after the finishing procedure in opal bond MV composites and the opal seal groups. This was done by increasing ΔE value due to the presence of fluoride release adhesive structure. Transbond light cure adhesive past-Transbond XT had acceptable clinical change after the debonding and finishing procedure by increasing ΔE value

Gouvernance de la chaîne globale de valeur et coordination des acteurs locaux : la filière d'exportation des tomates fraîches au Maroc et en Turquie

International audienceDans le processus de la globalisation, les filières locales sont de plus en plus insérées dans des chaînes d'approvisionnement de grandes entreprises qui reconfigurent continuellement leurs périmètres d'activités. Ces grandes entreprises, en érigeant et en appliquant leurs propres normes, élargissent leur zone d'influence au-delà de leurs pays d'origine et ainsi apparaissent en tant qu'agents clés incontestables gouvernant les chaînes de valeur qui s'étendent au niveau mondial. Cet article en mobilisant le référentiel théorique de la chaîne globale de valeur, démontre cette évolution dans les pays du Bassin méditerranéen. L'exemple des filières d'exportation des tomates fraîches du Maroc et de la Turquie illustre ce changement dans la coordination des filières locales par des entreprises agrotertiaires européennes. Les auteurs concluent que les acteurs locaux devaient opter pour des stratégies collectives pour garder le pouvoir de négociation face aux agents clés de la chaîne globale. Pour cela, il est préconisé de faire une mise à niveau continuelle des compétences locales par des investissements dans les domaines de la qualité sanitaire des produits horticoles

Controlled Rate Thermal Analysis (CRTA) as New Method to Control the Specific Surface in Hydroxyapatite Thin Coatings

The control of the texture in synthetic hydroxyapatite ceramics had limited their application in the field of the materials for bone implantation, even more when it is used as a filling in cements and other formulations in orthopedic surgery. The present article shows preliminary results demonstrating the effectiveness of a modification of the controlled rate thermal analysis (CRTA), developed by J. Rouquerol, used for the preparation of ceramic materials with controlled textural characteristics, during the formation of ceramic powders of synthetic hydroxyapatite at low temperatures. The thermal treatments of the hydroxyapatite were carried out in a device connected to a computer, to control temperature and pressure system, keeping the decomposition speed constant. Results, reported when preparing ceramic powders of hydroxyapatite at 300 and 850°C under controlled pressure, using synthetic hydroxyapatite with a Ca/P molar ratio equal to 1.64, were checked using IR spectroscopy and X‐ray diffraction, showed that the formed phase corresponds to that of crystalline hydroxyapatite, even at 300°C of maximum temperature. Values of specific surface (BET) between 17 and 66 m2/g, with pore size in the range of 50–300 Å in both cases are obtained by N2 absorption isotherms, when analyzing the isotherms of nitrogen absorption

Multifunctional sol-gel derived thin film based on nanocrystaline hydroxyapatite powders

The aim of this work was to prepare bioactive hydroxyapatite coatings by sol-gel method and to study the effect of thermal treatment temperature upon the bioactivity and corrosion protection of these coatings on Ti6Al4V alloy. The application of (DTA/TGA) and (XRD) has provided valuable information about the phase transformation, mass loss, identification of the phases developed, crystallite size and degree of crystallinity. (SEM/EDX) has been applied to study the surface morphology of coated samples before and after immersion in simulated body fluid (SBF) to detect the biomimetic precipitation of the bonelike apatite. The obtained results show that all the prepared samples are ceramic nanocrystalline with crystal structure and composition like hydroxyapatite, with little deviations from that present in the human bone. The bioactivity of the studied samples is found to be closely related to the thermal treatments applied. That is, the bioactivity decreases as the temperature of the thermal treatment increase. Coatings from such prepared hydroxyapatite sol have been accomplished by dip-coating technique on non-toxic Ti6Al4V alloy for biomedical applications. The corrosion behaviour of the resulting hydroxyapatite coatings in a (SBF) has been studied by electrochemical impedance spectroscopy (EIS). The hydroxyapatite coated Ti6Al4V alloy displayed excellent bioactivity when soaked in the (SBF) and acceptable corrosion protection behaviour.This work has been supported by the National Program for Materials, Spanish Ministry of Science and Innovation (Project MAT2006-04486). A.A. El hadad acknowledges a pre-doctoral contract JAE financed by CSIC; V. Barranco acknowledges a Ramon y Cajal researcher contract financed by CSIC-MICIN