Influence of multi-phase phenomena on semibatch crystallization processes of aqueous solutions

Crystal properties, product quality and particle size are determined by the operating conditions in the crystallization process. Thus, in order to obtain desired end-products, the crystallization process should be effectively controlled based on reliable kinetic information, which can be provided by powerful analytical tools such as Raman spectrometry and thermal analysis. The present research work studied various crystallization processes such as reactive crystallization, precipitation with anti-solvent and evaporation crystallization. The goal of the work was to understand more comprehensively the fundamentals, phenomena and utilizations of crystallization, and establish proper methods to control particle size distribution, especially for three phase gas-liquid-solid crystallization systems. As a part of the solid-liquid equilibrium studies in this work, prediction of KCl solubility in a MgCl2-KCl-H2O system was studied theoretically. Additionally, a solubility prediction model by Pitzer thermodynamic model was investigated based on solubility measurements of potassium dihydrogen phosphate with the presence of non-electronic organic substances in aqueous solutions. The prediction model helps to extend literature data and offers an easy and economical way to choose solvent for anti-solvent precipitation. Using experimental and modern analytical methods, precipitation kinetics and mass transfer in reactive crystallization of magnesium carbonate hydrates with magnesium hydroxide slurry and CO2 gas were systematically investigated. The obtained results gave deeper insight into gas-liquid-solid interactions and the mechanisms of this heterogeneous crystallization process. The research approach developed can provide theoretical guidance and act as a useful reference to promote development of gas-liquid reactive crystallization. Gas-liquid mass transfer of absorption in the presence of solid particles in a stirred tank was investigated in order to gain understanding of how different-sized particles interact with gas bubbles. Based on obtained volumetric mass transfer coefficient values, it was found that the influence of the presence of small particles on gas-liquid mass transfer cannot be ignored since there are interactions between bubbles and particles. Raman spectrometry was successfully applied for liquid and solids analysis in semi-batch anti-solvent precipitation and evaporation crystallization. Real-time information such as supersaturation, formation of precipitates and identification of crystal polymorphs could be obtained by Raman spectrometry. The solubility prediction models, monitoring methods for precipitation and empirical model for absorption developed in this study together with the methodologies used gives valuable information for aspects of industrial crystallization. Furthermore, Raman analysis was seen to be a potential controlling method for various crystallization processes.

Phase transitions in biodegradable films based on blends of gelatin and poly (vinyl alcohol)

The aim of this work was to study the effect of the hydrolysis degree (HD) and the concentration (C PVA) of two types of poly (vinyl alcohol) (PVA) and the effect of the type and the concentration of plasticizers on the phase properties of biodegradable films based on blends of gelatin and PVA, using a response-surface methodology. The films were made by casting and the studied properties were their glass (Tg) and melting (Tm) transition temperatures, which were determined by diferential scanning calorimetry (DSC). For the data obtained on the first scan, the fitting of the linear model was statistically significant and predictive only for the second melting temperature. In this case, the most important effect on the second Tm of the first scan was due to the HD of the PVA. In relation to the second scan, the linear model could be fit to Tg data with only two statistically significant parameters. Both the PVA and plasticizer concentrations had an important effect on Tg. Concerning the second Tm of the second scan, the linear model was fit to data with two statistically significant parameters, namely the HD and the plasticizer concentration. But, the most important effect was provoked by the HD of the PVA.

Phonon spectra and thermodynamic properties of rare gas solids based on empirical and semi-empirical (ab initio) two-body potentials : a comparative study /

We study the phonon dispersion, cohesive and thermal properties of raxe gas solids Ne, Ar, Kr, and Xe, using a variety of potentials obtained from different approaches; such as, fitting to crystal properties, purely ab initio calculations for molecules and dimers or ab initio calculations for solid crystalline phase, a combination of ab initio calculations and fitting to either gas phase data or sohd state properties. We explore whether potentials derived with a certain approaxih have any obvious benefit over the others in reproducing the solid state properties. In particular, we study phonon dispersion, isothermal ajid adiabatic bulk moduli, thermal expansion, and elastic (shear) constants as a function of temperatiue. Anharmonic effects on thermal expansion, specific heat, and bulk moduli have been studied using A^ perturbation theory in the high temperature limit using the neaxest-neighbor central force (nncf) model as developed by Shukla and MacDonald [4]. In our study, we find that potentials based on fitting to the crystal properties have some advantage, particularly for Kr and Xe, in terms of reproducing the thermodynamic properties over an extended range of temperatiures, but agreement with the phonon frequencies with the measured values is not guaranteed. For the lighter element Ne, the LJ potential which is based on fitting to the gas phase data produces best results for the thermodynamic properties; however, the Eggenberger potential for Ne, where the potential is based on combining ab initio quantum chemical calculations and molecular dynamics simulations, produces results that have better agreement with the measured dispersion, and elastic (shear) values. For At, the Morse-type potential, which is based on M0ller-Plesset perturbation theory to fourth order (MP4) ab initio calculations, yields the best results for the thermodynamic properties, elastic (shear) constants, and the phonon dispersion curves.

Implication de la voie ERK3/4-MK5 dans la phase G2/M du cycle cellulaire

La division cellulaire est influencée par les différents stimuli provenant de l’extérieur ou de l’intérieur de la cellule. Plusieurs réseaux enzymatiques élaborés au cours de l’évolution relayent l’information générée par ces signaux. Les modules MAP kinases sont extrêmement importants au sein de la cellule. Chez l’humain, 14 MAP kinases sont regroupées en sept voies distinctes intervenant dans le contrôle d’une myriade de processus cellulaires. ERK3/4 sont des homologues de ERK1/2 pour lesquelles on ne connaît que très peu de choses concernant leurs fonctions et régulation. Ces MAP kinases sont dites atypiques puisqu’elles ont des particularités structurales et des modes de régulation qui diffèrent des autres MAP kinases classiques. Ainsi, notre laboratoire a démontré que l’activité de ERK3 est régulée par le système ubiquitine-protéasome et qu’elle pourrait avoir un rôle à jouer dans le contrôle de la différenciation et la prolifération cellulaire. La première étude présentée décrit la régulation de ERK3 au cours du cycle cellulaire. Nous avons observé que ERK3 est hyperphosphorylée et s’accumule spécifiquement au cours de la mitose. Des analyses de spectrométrie de masse ont mené à l’identification de quatre sites de phosphorylation situés à l’extrémité du domaine C-terminal. Nous avons pu démontrer que la kinase mitotique CDK1/cycline B phosphoryle ces sites et que les phosphatases CDC14A et CDC14B les déphosphorylent. Finalement, nous démontrons que la phosphorylation mitotique de ERK3 a pour effet de la stabiliser. Au début de mes études doctorales, la kinase MK5 fut identifiée comme premier partenaire et substrat de ERK3. MK5 a très peu de fonctions connues. Des données dans la littérature suggèrent qu’elle peut moduler le cycle cellulaire dans certaines conditions. Par exemple, MK5 a récemment été identifié comme inducteur de la sénescence induite par l’oncogène Ras. Dans la deuxième étude, nous décrivons une nouvelle fonction de MK5 dans le contrôle du cycle cellulaire. Nous démontrons par des expériences de gain et perte de fonction que MK5 ralentit l’entrée en mitose suite à un arrêt de la réplication. Cette fonction est dépendante de l’activité enzymatique de MK5 qui régule indirectement l’activité de CDK1/cycline B. Finalement, nous avons identifié Cdc25A comme un nouveau substrat in vitro de MK5 dont la surexpression supprime l’effet de MK5 sur l’entrée en mitose. En conclusion, nos résultats décrivent un nouveau mécanisme de régulation de ERK3 au cours de la mitose, ainsi qu’une nouvelle fonction pour MK5 dans le contrôle de l’entrée en mitose en réponse à des stress de la réplication. Ces résultats démontrent pour la première fois l’implication de ces protéines au cours de la transition G2/M. Nos travaux établissent de nouvelles pistes d’études pour mieux comprendre les rôles encore peu définis des kinases ERK3/4-MK5.

Epithelial-Mesenchymal-Transition : a proposed mechanism in the development of Bronchiolitis Obliterans

La transplantation pulmonaire pour les patients avec une maladie pulmonaire en phase terminale est leur seul espoir de survie. Malheureusement, certains greffés du poumon rencontrent des difficultés après la transplantation du poumon, dont l'un est le rejet chronique du greffon pulmonaire également connu histologiquement comme la bronchiolite oblitérante et cliniquement comme syndrome de bronchiolite oblitérante. L'étiologie exacte de la BO reste mal comprise. Certaines hypothèses suggèrent l'implication des cellules épithéliales dans le processus de remodelage des voies respiratoires, conduisant à l'obstruction des voies aériennes. Un des mécanismes proposés est un processus de transition, connue sous le nom de transition épithéliale-mésenchymateuse (TEM). Lors de ce processus, les cellules perdent leurs propriétés épithéliales, acquièrent un phénotype mésenchymateux et deviennent plus mobiles et envahissantes. Cette transformation leur permet de participer activement au processus de remodelage bronchique dans la bronchiolite oblitérante. L’induction de la TEM peut être due à certains facteurs tels que l'inflammation et l'apoptose. Le principal objectif de ce travail de maîtrise est de détecter in vivo la présence de la TEM dans des biopsies transbronchiques obtenues chez des greffés et de l’associer à leurs conditions cliniques. Le deuxième objectif est d'induire la TEM in vitro dans les cellules épithéliales des petites voies aériennes à l'aide de milieux conditionnés apoptotiques et non apoptotiques produits par les cellules endothéliales microvasculaires humaines du poumon. D’autre part, nous avons évalué si des médiateurs connus pour participer au processus de TEM tels que le facteur de croissance du tissu conjonctif (CTGF)et le facteur de croissance transformant bêta (TGF-beta) ainsi que le perlecan sont présents dans les milieux conditionnés utilisés.

Étude de la phase isolant topologique chez le composé demi-Heusler GdBiPt.

Il sera question dans ce mémoire de maîtrise de l’étude d’une nouvelle classification des états solides de la matière appelée isolant topologique. Plus précisément, nous étudierons cette classification chez le composé demi-Heusler GdBiPt. Nous avons principalement cherché à savoir si ce composé ternaire est un isolant topologique antiferromagnétique. Une analyse de la susceptibilité magnétique ainsi que de la chaleur spécifique du maté- riau montre la présence d’une transition antiferromagnétique à 8.85(3) K. Une mesure d’anisotropie de cette susceptibilité montre que les plans de spins sont ordonnés sui- vant la direction (1,1,1) et finalement des mesures de résistivité électronique ainsi que de l’effet Hall nous indiquent que nous avons un matériau semimétallique lorsque nous sommes en présence d’antiferromagnétisme. Présentement, les expériences menées ne nous permettent pas d’associer cet état métallique aux états surfaciques issus de l’état d’isolant topologique.

Nature, culture et progrès : histoire comparative du concept de transition entre paléolithiques moyen et supérieur en archéologie préhistorique

Doctorat effectué en cotutelle Pour le département d'histoire de l'Université de Montréal, M.M. Jacques G. Ruelland et Othmar Keel, Pour le laboratoire P.A.C.E.A.– U.M.R. 5199. C.N.R.S., de l'École doctorale des sciences Terre-Mer, directeurs successifs, M. P.-Y. Demars, puis M. Michel Lenoir. Thèse soutenue à Bordeaux le 6 juin 2012.

Use of photoacoustic effect for the detection of phase transitions in liquid crystal mixtures

We report on a laser induced photoacoustic study of the nematic-to-isotropic transition in certain commercial nematic liquid crystal mixtures, namely BL001, BL002, BL032 and BL035. A simple analysis of the experimental data using the Rosencwaig–Gersho theory shows that the heat capacities of all these compounds exhibit a sharp peak as the temperature of the sample is varied across the transition region. Also, substantial differences in the photoacoustic signal amplitudes in nematic and isotropic phases have been noticed for all the mixtures. The increased light scattering property of the nematic phase may be the reason for the enhanced photoacoustic signal amplitude in this phase.

Use of photoacoustic effect for the detection of phase transitions in liquid crystal mixtures

We report on a laser induced photoacoustic study of the nematic-to-isotropic transition in certain commercial nematic liquid crystal mixtures, namely BL001, BL002, BL032 and BL035. A simple analysis of the experimental data using the Rosencwaig–Gersho theory shows that the heat capacities of all these compounds exhibit a sharp peak as the temperature of the sample is varied across the transition region. Also, substantial differences in the photoacoustic signal amplitudes in nematic and isotropic phases have been noticed for all the mixtures. The increased light scattering property of the nematic phase may be the reason for the enhanced photoacoustic signal amplitude in this phase

Use of photoacoustic effect for the detection of phase transitions in liquid crystal mixtures

We report on a laser induced photoacoustic study of the nematic-to-isotropic transition in certain commercial nematic liquid crystal mixtures, namely BL001, BL002, BL032 and BL035. A simple analysis of the experimental data using the Rosencwaig–Gersho theory shows that the heat capacities of all these compounds exhibit a sharp peak as the temperature of the sample is varied across the transition region. Also, substantial differences in the photoacoustic signal amplitudes in nematic and isotropic phases have been noticed for all the mixtures. The increased light scattering property of the nematic phase may be the reason for the enhanced photoacoustic signal amplitude in this phase.

Preparation and characterization of nanocrystalline transition metal-loaded sulfated titania through sol-gel method

Transition metal-loaded (3%) nanocrystalline sulfated titania (ST) powders are prepared using the sol–gel technique. Anatase is found as the active phase in all the samples. Sulfate ion impregnation decreases the crystallite size and stabilizes the anatase phase of TiO2. Acidity of the samples is found to increase by the incorporation of sulfate ion and also by the modification by transition metal ions. All the prepared catalysts are found stable up to 700 °C.

Studies on catalysis by transition metal promoted sulphated zirconia

The present project was a systematic investigation of the physico-chemical properties and catalytic activity of some transition metal promoted sulphated zirconia systems. The characterisation and catalytic activity results were compared with that of pure Zr02 and simple sulphated zirconia systems. Sulphated zirconia samples were prepared by a controlled impregnation technique. In the case of metal incorporated systems, a single step impregnation was carried out using required amounts of sulphuric acid and metal salt solutions. As a preliminary step, optimisation of calcination temperature and sulphate content was achieved. For further studies, the optimised sulphate loading of 10 ml per gram of hydrous zirconium oxide and a calcination temperature of 700°C was employed. Metal incorporation had a positive influence on the physico-chemical properties. Vapour phase cumene conversion served as a test reaction for acidity. Some industrially important reactions like Friedel-Crafts reaction, phenol hydroxylation, nitration, etc. were selected to test the catalytic activity of the prepared systems.

Catalytic activity of some of the perovskite-type mixed oxides (ABO3) consisting of rare earth and 3d transition metals

The catalytic activity of some of the ABO3 (A = La, Pr and Sm, B= Cr, Mn, Fe, Co and Ni) perovskite-type oxides for the liquid phase reduction of ketone and oxidation of alcohol in 2-propanol medium has been studied. The data have been correlated with the surface electron donor properties of these oxides. The surface electron donor properties have been determined from the adsorption of electron acceptors of varying electron affinities on the oxide surface.

Use of mirage effect for the detection of phase transitions in liquid crystals

he phenomenon of single beam mirage effect, otherwise known as photothermal deflection (PTD) effect using a He–Ne laser beam has been employed to detect phase transitions in some liquid crystals. It has been observed that anomalous changes in amplitude occur in the PTD signal level near the transition temperature. The experimental details and the results of measurements made in liquid crystals E8, M21 and M24 are given in this paper.

Laser Induced Photoacoustic Technique for the Detection of Phase Transitions in Liquid Crystals

In this paper we report the use of a laser induced phoroacoustic technique for the detection of multiple phase transitions in heptyl-oxy-cyanobiphenyl (70CB) and octyl-oxy-cyanobiphenyl (80CB) liquid crystals. The observed photoacoustic signal amplitude profile carries clear signatures of two tirst order transitions in 70CB and two tirst order and a second order transitions in 80CB. Analysis of the experimental data using Rosencwaig-Gersho theory shows that the sudden decrease in the photoacoustic (PA) signal amplitude during phase transitions is due to a sharp increase in the heat capacity of the samples near the transition temperatures.