La dispersion moléculaire d’un principe actif (PA) dans un polymère est généralement utilisée pour accroitre à la fois la solubilité et la stabilité physique de sa forme amorphe. Cependant, ce type de formulation demande une parfaite connaissance de la solubilité du PA dans le polymère. Cependant, les méthodes actuelles pour déterminer les courbes de solubilité sont longues et fastidieuses à mettre en oeuvre. Dans cette thèse, nous présentons une méthode originale pour déterminer efficacement la solubilité des PA dans les polymères. L’originalité de cette méthode réside dans le fait que les états d’équilibre saturés sont ici atteints par démixtion d’une solution solide amorphe sursaturée en PA et non par la méthode classique de dissolution du PA cristallin au sein du polymère amorphe. Les états d’équilibre saturés sont donc beaucoup plus rapides à atteindre en raison de la mobilité moléculaire accrue résultant de la forte plastification du polymère imposée par les conditions de sursaturation. Nous avons aussi testé la possibilité de prédire les courbes de solubilité par des méthodes numériques ab-initio (par dynamique moléculaire et méthodes quantiques). Les méthodes expérimentales et numériques ont été validées en étudiant des systèmes polymère/PA dont les courbes de solubilité ont déjà été déterminées par des méthodes classiques. Les systèmes étudiés sont : PVPK12/indométacine, PVPK30/griséofulvine et β-cyclodextrine méthylée/griséofulvine. Les techniques d’investigations utilisées sont esentiellement l’analyse enthalpique différentielle à balayage (DSC) et la diffraction des rayons X sur poudre (DRX). / The molecular dispersion of a drug into a polymer is generally used to increase both its solubility and the physical stability of its amorphous form. However, this formulation route requires a perfect knowledge of the solubility of the drug in the polymer. This property is in particular important for selecting appropriate polymers for formulations since it defines the maximal drug loading which prevents recrystallization. However, up to now, the determination of the solubility curve of drug/polymer systems is a long and tedious task. In this thesis we present an original method to determine faster the solubility of drugs into polymers. The originality of the method lies in the fact that the equilibrium saturated state is here reached by demixing of a supersaturated amorphous solid solution and not by the usual dissolution of a crystalline drug into an amorphous polymer. The equilibrium saturated states are thus much faster to reach due to the extra molecular mobility resulting from the strong plasticizing effect associated with the supersaturation conditions. We also test the ability of ab-initio numerical techniques (using molecular dynamics and quantum methods) to predict solubility curves. Both experimental and numerical techniques are validated using drug/polymer systems whose solubility curves have already been determined by conventional methods. The investigated systems are: PVPK12/indomethacin, PVPK30/griseofulvin and methylated β-cyclodextrine/griseofulvin. The investigation techniques are mainly Differential Scanning Calorimetry (DSC) and Powder X-Ray Diffraction (PXRD).

M.Ing. / In this dissertation the emphasis falls on the use of the 1550 run WDM systems that make use of standard single-mode fibre. The reason for this is that more than 50 million kilometres of standard telecommunication fibre is already installed in the worldwide telephone network. Therefore, from an economical point of view, the fourth generation of lightwave systems has to make use of this existing base. Using single-mode fibre at high bit-rate (- 10 Gb/s) dispersion becomes a problem. Furthermore, if amplifiers are used, as in the case of long-haul WDM systems, non-linear effects also become important although the input power levels are low (-1 mW). Thus, the system performance is influenced by both the dispersion problem and fibre non-linearities. In this dissertation the influence of these effects was investigated and the use of different dispersion management schemes was considered in order to minimise the dispersion and the effects of these non-linearities on the optical signals. It was seen that by using pre-compensation, the optical pulses would become narrower whereas by using post-compensation, the pulses would be broader than the original input pulses. Thus, the combined effect of fibre non-linearity and fibre dispersion led to the fact that the order in which dispersion compensation is realised is important. By using symmetrical dispersion compensation that is defined as a dispersion compensation scheme that makes use of an equal amount of pre- and post-compensation sections, the tendency of pulse narrowing and pulse broadening can be balanced. It was found from simulations, that pre-compensation led to a smaller SPM penalty than postcompensation, whereas in the case of cross-phase ,modulation, the opposite is true. Using lumped dispersion compensation at the,en(f:o£ the system, it was found that both SPM and XPM penalties could be minimised. It was found that negative and positive lumped dispersion compensation could be used to improve the system perfortriance of pre- and post compensation schemes respectively. The performance of symmetrical compensation also improved by using a positive lumped dispersion compensation regarding SPM penalty, but in the case of XPM penalty, it was found that lumped dispersion compensation could not be used to improve this penalty. Furthermore, the effect of not using 100% dispersion compensation per span on the system performance was determined. From simulations, it followed that under-compensation will lead to an improvement in the system performances of the post- and symmetrical dispersion compensation, whereas an over-compensation will lead to an improvement in the precompensation case. It was also shown that XPM index penalty decreases in all of these dispersion compensation schemes if 100% compensation per span is not used. The reason for this is the inter -span walk-off that reduces the XPM distortion by reducing the localised buildup of phase distortions. Finally, it was shown that by independently controlling the input power levels in the SMF and DCF the best system performance is possible. Furthermore, by making use of lumped dispersion compensation or by not using 100% dispersion compensation per span, the system performance of the pre-, post- and symmetrical dispersion conipensation schemes can be improved quite a lot. Comparing the results of the pre-, post- and symmetrical dispersion compensation schemes that made use of independent control of power levels with the pre-, post- and symmetrical dispersion compensation schemes that did not use independent control ofpower levels, the Q factors were improved from 6.2 to 8, from 5.4 to 9 and from 7.5 to 11 in each case respectively.

An experimental investigation of the velocity of sound in liquid helium at temperatures near 1° K was abandoned (at an early stage)^when the results of Whitney and Chase(16) became available. The original investigation, which had been motivated by the idea that the peak in the attenuation-temperature curve near 1° K is related to a corresponding feature in the velocity-temperature curve, evolved into a search for mathematical relations connecting the temperature variations of velocity and attenuation. Classical dispersion theory is reviewed, with emphasis on its physical and mathematical foundations. Applications of the theory in the fields of electrical network design, dielectric dispersion and ultrasonics are described in order to illustrate the use and the limitations of the Kramers-Kronig relations. The possibility of extending the scope of the Kramers-Kronig relations, by using variables other than frequency, is discussed. A brief sketch of the quantum mechanical basis of linear response theory is given in support of a proposal to use reciprocal temperature as a variable in dispersion-type relations. An attempt was made to apply dispersion relations in reciprocal temperature to the problem of ultrasonic propagation in liquid helium and a comparison of the predicted and the experimentally observed attenuations at the λ point was found to give encouraging results. The interferometer, to have been used in the proposed experiment is described. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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Most of the remaining oil reserves are stored in carbonate reservoirs. Improving recovery from these reserves is paramount to uninterrupted energy supply and any future energy transition, should it happen. One of the aspects of recovery improvement is crude oil-brine-carbonate rock interface chemistry. The study of these interactions must be supported by: 1) a correct reactive transport model that describes the advective-dispersive forces in porous media; and 2) convincing experimental evidence consonant with the reactive transport model. As a part of such a larger study, this work addresses some modeling and experimental aspects of dispersive tracer transport through porous media. At both field and laboratory scales, tracer data allows estimation of brine-accessible pore volume and hydrodynamic dispersion. In addition to tracer transport during laboratory-scale coreflood experiments, one typically observes adsorption, dissolution/precipitation, ion-exchange, or all. Without proper tracer data interpretation, these phenomena cannot be distinguished. Therefore, tracer experiments are vital for a meaningful interpretation of any coreflood experiment. The modeling part of the work first discusses choice of boundary conditions that capture the peculiarities of laboratory-scale experiments. We find that Robin or third-kind boundary condition in both inlet and outlet is appropriate for description of the experimental results. Next, the modeling part presents a validated numerical approach to simulate dispersive tracer transport through the experimental system with high hydrodynamic dispersion. Tracer coreflood experiments are performed on $1.5''$ by $3''$ Indiana limestone core plugs with high hydrodynamic dispersion due to extreme rock heterogeneity. Chloride ion is used as the tracer in these experiments. Effluent from the cores is collected each 0.1 pore volume, and the concentration history data are recorded for at least 3 pore volumes. Finally, in the last part of this work, we present how the recorded concentration history data were scaled to the dimensionless model output and assess fit quality. The scaling parameters yield porosity and Péclet number that allow estimation of fluid accessible pore volume and hydrodynamic dispersion. The porosity of the core samples estimated from tracer data is close to those measured using helium pycnometer and/or brine imbibition. Very high hydrodynamic dispersion coefficients obtained from the tracer points correlate well with the scarcely published data on Indiana limestone.

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No / Pure anhydrous polymorphs of carbamazepine were prepared by solution-enhanced dispersion with supercritical fluids (SEDSTM). Crystallization of the polymorphs was studied. Mechanisms are proposed that consider the thermodynamics of carbamazepine, supersaturation in the SEDSTM process, and the binary phase equilibria of organic solvents and the carbon dioxide antisolvent. -Carbamazepine was crystallized at high supersaturations and low temperatures, -carbamazepine crystallized from a methanol-carbon dioxide phase split, and -carbamazepine crystallized via nucleation at high temperatures and low supersaturation.