In the thesis CuPc thin films were investigated by (in situ) SE and RAS, which are employed to determine the out-of-plane and in-plane optical anisotropy and molecular orientation, respectively. CuPc is a promising candidate of organic semiconductors used in organic field effect transistors, organic light emitting diodes and organic solar cells. Vicinal Si(111) substrates are interesting due to the in-plane anisotropy caused by the steps and terraces on the surface. The strength of in-plane anisotropy of vicinal Si(111) is dependent on the offcut angle. The influence of offcut angle on out-of-plane and in-plane molecular orientation in CuPc thin films is explored. The in situ investigation of CuPc films suggests that structural changes occur during film growth. In addition, two different surface modification layers were utilized to examine the effect on CuPc molecular orientation: OTS monolayer with upright standing molecules and PTCDA layers with flat lying molecules. Metal-organic interface plays an important role in organic electronic devices. In-CuPc is chosen to be an example system investigated employing in situ SE and RAS. When In was thermally evaporated onto CuPc film, In atoms firstly diffuse into the CuPc film underneath and then aggregate to form clusters on top. Hafnium dioxide (HfO2) is currently a hot topic to replace the conventionally used SiO2 as gate dielectrics in order to minimize leakage current when further scaling down microelectronic devices. Since HfO2 films are often crystalline, in order to obtain amorphous films which are beneficial to minimize leakage current, aluminum oxide (Al2O3) (k value: 9) which stays amorphous at much higher temperatures are combined to overcome this difficulty. Two series of ultra-thin samples were deposited by atomic layer deposition: mixed layers HfxAl1-xOz and bilayers HfO2 on Al2O3. Optical constants and bandgap are determined using SE in the energy range of 0.7-10 eV. It is found that the (effective) optical bandgap of both mixed layer and bilayer structures can be tuned by the film composition. Aging effect of high-k films was observed after storage of samples in air for two months, which is attributed to further oxidation of the dielectric films caused by the oxygen diffusion from ambient air to high-k films. / In dieser Arbeit werden dünne Schichten aus Kupferphthalozyanin (CuPc) mittels spektroskopischer (in-situ) Ellipsometrie (SE) und (in-situ) Reflektions-Anisotropie-Spektroskopie (RAS) untersucht, um die optische Anisotropie in einer Ebene parallel und senkrecht zur Schichtoberfläche und die molekulare Orientierung zu bestimmen. CuPc ist ein aussichtsreicher Kandidat als organischer Halbleiter in organischen Feldeffekt-Transistoren, organischen Leuchtdioden und organischen Solarzellen. Vizinale Si(111)-Substrate sind wegen der Anisotropie in der Substratebene interessant, die durch die Treppen und Terrassen auf der Oberfläche verursacht wird. Die Stärke der Anisotropie der vizinalen Si(111)-Oberfläche ist vom Schnittwinkel (Offcut) abhängig. Es wird der Einfluss des Offcut-Winkels auf die molekulare Orientierung in dünnen CuPc-Schichten parallel und senkrecht zur Substratoberfläche untersucht. Die in-situ Untersuchungen von CuPc-Schichten weisen darauf hin, dass strukturelle Veränderungen beim Wachstum auftreten. Darüber hinaus wurden zwei unterschiedliche Oberflächenmodifizierungsschichten, um deren Wirkung auf die molekulare Orientierung von CuPc zu untersuchen, verwendet: eine OTS-Monoschicht mit aufrecht stehenden Molekülen und PTCDA-Schichten mit flach liegenden Molekülen. Metall-organische Grenzflächen spielen eine wichtige Rolle in organischen elektronischen Bauelementen. In-CuPc wird als Beispiel für ein Metall-organisches System durch in-situ SE und RAS untersucht. Wenn In thermisch auf eine CuPc-Schicht aufgedampft wird, diffundieren In-Atome zunächst in die darunterliegende CuPc-Schicht und bilden dann Cluster auf der Schicht. Hafniumdioxid (HfO2) ist ein heißer Kandidat für das Ersetzen des herkömmlich als Gate-Dielektrikum verwendeten SiO2 mit dem Ziel, die Leckströme bei der weiteren Verkleinerung mikroelektronischer Bauelemente zu minimieren. Um amorphe Schichten, die vorteilhaft zur Minimierung der Leckströme sind, zu erhalten, werden die HfO2-Schichten, die oft kristallin sind, mit Aluminiumoxid (Al2O3) (k-Wert: 9) kombiniert, das bei wesentlich höheren Temperaturen amorph bleibt. Zwei Serien von ultra-dünnen Proben wurden durch Atomlagenabscheidung hergestellt: Mischschichten HfxAl1-xOz und Doppelschichten HfO2 auf Al2O3. Die optischen Konstanten und Bandlücken wurden mittels SE im Energiebereich von 0,7 bis 10 eV bestimmt. Es hat sich gezeigt, dass die (effektive) Bandlücke der Misch- und Doppelschichten durch die Komposition abgestimmt werden kann. Nach Lagerung der High-k-Schichten für zwei Monate an Luft konnte ein Alterungseffekt beobachtet werden. Dieser wird auf die weitere Oxidation der dielektrischen Schichten, die durch Sauerstoffdiffusion aus der Umgebungsluft in die High-k-Schichten ermöglicht wird, zurückgeführt.

A numerical treatment of non-linear higher-order geometric evolution equations with the level set and the finite element method is presented. The isotropic, weak anisotropic and strong anisotropic situation is discussed. Most of the equations considered in this work arise from the field of thin film growth. A short introduction to the subject is given. Four different models are discussed: mean curvature flow, surface diffusion, a kinetic model, which combines the effects of mean curvature flow and surface diffusion and includes a further kinetic component, and an adatom model, which incorporates in addition free adatoms. As an introduction to the numerical schemes, first the isotropic and weak anisotropic situation is considered. Then strong anisotropies (non-convex anisotropies) are used to simulate the phenomena of faceting and coarsening. The experimentally observed effect of corner and edge roundings is reached in the simulation through the regularization of the strong anisotropy with a higher-order curvature term. The curvature regularization leads to an increase by two in the order of the equations, which results in highly non-linear equations of up to 6th order. For the numerical solution, the equations are transformed into systems of second order equations, which are solved with a Schur complement approach. The adatom model constitutes a diffusion equation on a moving surface. An operator splitting approach is used for the numerical solution. In difference to other works, which restrict to the isotropic situation, also the anisotropic situation is discussed and solved numerically. Furthermore, a treatment of geometric evolution equations on implicitly given curved surfaces with the level set method is given. In particular, the numerical solution of surface diffusion on curved surfaces is presented. The equations are discretized in space by standard linear finite elements. For the time discretization a semi-implicit discretization scheme is employed. The derivation of the numerical schemes is presented in detail, and numerous computational results are given for the 2D and 3D situation. To keep computational costs low, the finite element grid is adaptively refined near the moving curves and surfaces resp. A redistancing algorithm based on a local Hopf-Lax formula is used. The algorithm has been extended by the authors to the 3D case. A detailed description of the algorithm in 3D is presented in this work. / In der Arbeit geht es um die numerische Behandlung nicht-linearer geometrischer Evolutionsgleichungen höherer Ordnung mit Levelset- und Finite-Elemente-Verfahren. Der isotrope, schwach anisotrope und stark anisotrope Fall wird diskutiert. Die meisten in dieser Arbeit betrachteten Gleichungen entstammen dem Gebiet des Dünnschicht-Wachstums. Eine kurze Einführung in dieses Gebiet wird gegeben. Es werden vier verschiedene Modelle diskutiert: mittlerer Krümmungsfluss, Oberflächendiffusion, ein kinetisches Modell, welches die Effekte des mittleren Krümmungsflusses und der Oberflächendiffusion kombiniert und zusätzlich eine kinetische Komponente beinhaltet, und ein Adatom-Modell, welches außerdem freie Adatome berücksichtigt. Als Einführung in die numerischen Schemata, wird zuerst der isotrope und schwach anisotrope Fall betrachtet. Anschließend werden starke Anisotropien (nicht-konvexe Anisotropien) benutzt, um Facettierungs- und Vergröberungsphänomene zu simulieren. Der in Experimenten beobachtete Effekt der Ecken- und Kanten-Abrundung wird in der Simulation durch die Regularisierung der starken Anisotropie durch einen Krümmungsterm höherer Ordnung erreicht. Die Krümmungsregularisierung führt zu einer Erhöhung der Ordnung der Gleichung um zwei, was hochgradig nicht-lineare Gleichungen von bis zu sechster Ordnung ergibt. Für die numerische Lösung werden die Gleichungen auf Systeme zweiter Ordnungsgleichungen transformiert, welche mit einem Schurkomplement-Ansatz gelöst werden. Das Adatom-Modell bildet eine Diffusionsgleichung auf einer bewegten Fläche. Zur numerischen Lösung wird ein Operatorsplitting-Ansatz verwendet. Im Unterschied zu anderen Arbeiten, die sich auf den isotropen Fall beschränken, wird auch der anisotrope Fall diskutiert und numerisch gelöst. Außerdem werden geometrische Evolutionsgleichungen auf implizit gegebenen gekrümmten Flächen mit Levelset-Verfahren behandelt. Insbesondere wird die numerische Lösung von Oberflächendiffusion auf gekrümmten Flächen dargestellt. Die Gleichungen werden im Ort mit linearen Standard-Finiten-Elementen diskretisiert. Als Zeitdiskretisierung wird ein semi-implizites Diskretisierungsschema verwendet. Die Herleitung der numerischen Schemata wird detailliert dargestellt, und zahlreiche numerische Ergebnisse für den 2D und 3D Fall sind gegeben. Um den Rechenaufwand gering zu halten, wird das Finite-Elemente-Gitter adaptiv an den bewegten Kurven bzw. den bewegten Flächen verfeinert. Es wird ein Redistancing-Algorithmus basierend auf einer lokalen Hopf-Lax Formel benutzt. Der Algorithmus wurde von den Autoren auf den 3D Fall erweitert. In dieser Arbeit wird der Algorithmus für den 3D Fall detailliert beschrieben.

The work presented in this thesis was broadly focussed on the investigation of the magnetic behaviour of different superconducting materials in the form of bulk (singe crystals and pellets) and thin films (nanomagnetic devices like superconducting spin valves etc). Neutrons and muons were extensively used to probe the structural and magnetic behaviour of these systems at the nanoscale along with bulk characterisation techniques like high-sensitive magnetic property measurements, scanning probe microscopy and magneto-transport measurements etc. The nanoscale interplay of Superconductivity and Ferromagnetism was studied in the thin film structures using a combination of Polarised Neutron Reflectivity (PNR) and Low Energy Muon Spin Rotation (LE-µSR) techniques while bulk Muon Spin Rotation (µSR) technique was used for microscopic magnetic investigation in the bulk materials. In the Fe/Pb heterostructure, evidence of the Proximity Effect was observed in the form of an enhancement of the superconducting penetration depth (λs) with an increase in the ferromagnetic layer thickness (dF) in both the bilayered and the trilayered structures. The existence of an Inverted Magnetic Region was also detected at the Ferromagnet-Superconductor (F/S) interface in the normal state possibly originating from the induced spin polarisation within the Pb layer in the presence of the neighbouring Fe layer(s). The spatial size (height and width) of the Inverted Magnetic Region did not change much while cooling the sample below the superconducting transition temperature(Tc)and it also stayed unaffected by an increase in the Fe layer thickness and by a change of the applied magnetic field. In the superconducting spin valve structure containing Permalloy (Py) as ferromagnetic layer and Nb as the superconducting layer, LE-µSR measurements revealed the evidence of the decay of magnetic flux density (as a function of thickness) within the Nb layer symmetrically from the Py/Nb interfaces towards the centre of the Nb layer in the normal state. The thickness dependent magnetisation decay occurred over two characteristic length scales in the normal state that stayed of similar values in the superconducting state also. In the superconducting state, an additional contribution towards the magnetisation was found in the vicinity of the Py/Nb interfaces possibly originating from the spin polarisation of the singlet Cooper pairs in these areas. The nanoscale magnetic investigation on a highly engineered F/S/F structure (where each of the F blocks made of multiple Co/Pd layers with magnetic moments aligned perpendicular to the plane of these layers and neighbouring magnetic blocks separated by Ru layers giving rise to antiferromagnetic alignment) using LE-µSR showed an antisymmetric thickness dependent magnetic flux density profile with two characteristic length scales. In the superconducting state, the magnetic flux density profile got modified within the superconducting Nb₆₇Ti₃₃ layer near the F/S interfaces in a way similar to that of observed in the case of Py/Nb system, most likely because of the spin polarisation of the superconducting electron pairs. The vortex magnetic phase diagram of Bi₂Sr₂Ca₂Cu₃O10-δ was studied using the Muon Spin Rotation (µSR) technique to explore the effects of vortex lattice melting and rearrangements for vortex transitions and crossover as a function of magnetic field and temperatures. At low magnetic fields, the flux vortices undergo a first order melting transition from a vortex lattice to a vortex liquid state with increasing temperature while another transition also occurred with increasing field at fixed temperature to a vortex glass phase at the lowest temperatures. Evidence of a frozen liquid phase was found in the intermediate field region at low temperature in the form of a lagoon in the superconducting vortex state which is in agreement with earlier observations made in BiSCCO-2212. The magnetic behaviour of the unconventional superconductor Sr₂RuO₄ was investigated using µSR to find the evidence of normal state magnetism and the nature of the vortex state. In the normal state, a weak hysteretic magnetic signal was detected over a wide temperature and field range believed to be supporting the evidence of a chiral order parameter. The nature of the vortex lattice structure was obtained in different parts of the magnetic phase diagram and the evidence of magnetic field driven transition in the lattice structure was detected from a Triangular→Square structure while the vortex lattice stayed Triangular over the entire temperature region below Tc at low fields with a disappearance of pinning at higher temperatures.

<p>We have studied fundamental aspects of time-resolved two-photon excited fluorescence depolarisation. The thesis presents experimental as well as theoretical progress. We show that a multi-photon induced instrumental response function obtained from a suspension of gold nanoparticles is appropriate for the analysis of two-photon excited fluorescence decays obtained using time-correlated single photon counting detection. Theoretical expressions have been derived for the fluorescence anisotropy decay obtained upon two-photon excitation of various molecular systems in liquid solutions: a) an anisotropic rigid rotor that undergoes rotational diffusion in the presence of ultrafast unresolved restricted reorientations, e.g. librations. b) a molecular group covalently attached to a stationary macromolecule, and undergoing local reorientation in a uniaxial ordering potential. A new approach to the analysis of two-photon excited fluorescence depolarisation experiments was developed, which combines data obtained by using linearly and circularly polarised excitation light, in a global manner. In the analysis, knowledge about unresolved reorientations was obtained from one-photon excitation studies of the corresponding systems. By means of this procedure it has been possible to obtain quantitative information about the molecular two-photon absorption tensor for perylene and two of its derivatives. Thereby the symmetry of the final excited and intermediate vibronic states could be assigned. The analysis reveals that the two-photon transition studied with the 800 nm laser exhibits mixed character. An important finding from the experiments was that the two-photon absorption tensor appears to be solvent dependent. Furthermore, the thesis presents the first theoretical treatment of two-photon excited donor-donor energy migration in the presence of molecular reorientation and which applies the extended Förster theory. Explicit expressions for molecules that belong to the point groups D_2h, D₂ and C_2v are given. Preliminary experiments are finally also reported on a two-photon excited donor-donor energy migration system consisting of a bisanthryl-bisteroid. </p>

The mechanical and acoustic anisotropy of media is a governing factor in the behaviour of multilayered systems including such media. The understanding of the mechanisms conditioning the dynamic behaviour of multilayered systems is of paramount importance. In particular, the intrinsic anisotropy of poroelastic media presents a potential for the optimal design of systems for multifunctional performances. Indeed, these multilayered systems are bound by stiffness, thermal and acoustic performance constraints in simultaneously. A plane wave method is presented to study the influence of material orientation in the dynamic behaviour of multilayered systems composed of anisotropic poroelastic media. The method is applied to a system composed of an anisotropic open-celled melamine foam core in between two metal sheets. This particular multilayered configuration allows to shed light on phenomena intrinsic to layers composed of anisotropic poroelastic materials, such as the frequency shift of the fundamental resonance of the panel, or the compression-shear coupling effects taking place in the poroelastic core layers. The latter phenomena is of particular importance, as it is evidenced on the unconventional polarisation of waves in anisotropic poroelastic media. Finally, the method is adapted to the optimisation of multilayered systems for acoustic performance. the design variables are consequently the core material orientations with respect to the global coordinate system. The solutions to the optimisation problem are analysed in terms of dynamic behaviour, thus allowing to correlate acoustic performance of the overall structure, and the response of each individual layer. / <p>QC 20161110</p>

In der vorliegenden Arbeit wird ein gemischtes Element gegen Locking-Effekte untersucht. Dazu wird ein Fünf-Feld-Hu-Washizu-Funktional (CoFEM-Element) für lineare und quadratische Hexaeder-Elemente unter einer hyperelastischen, isotropen, polykonvexen sowie einer transversal-isotropen Materialformulierung implementiert. Die resultierenden nichtlinearen Gleichungen werden mithilfe eines Mehrebenen-NEWTON-RAPHSON-Verfahren unter Beachtung einer konsistenten Linearisierung gelöst. Als repräsentatives Beispiel der numerischen Untersuchungen dient der einseitig eingespannte Cook-Balken mit einer quadratischen Druckverteilung am Rand. Zur Beurteilung des CoFEM-Elements wird das räumliche Konvergenzverhalten für unterschiedliche Polynomgrade und für verschiedene Netze unter Beachtung der algorithmischen Effizienz untersucht. / This paper presents a mixed finite element formulation of Hu-Washizu type (CoFEM) designed to reduce locking effects with respect to a linear and quadratic approximation in space. We consider a hyperelastic, isotropic, polyconvex material formulation as well as transverse isotropy. The resulting nonlinear algebraic equations are solved with a multilevel NEWTON-RAPHSON method. As a numerical example serves a cook-like cantilever beam with a quadratic distribution of in-plane load on the Neumann boundary. We analyze the spatial convergence with respect to the polynomial degree of the underlying Lagrange polynomials and with respect to the level of mesh refinement in terms of algorithmic efficiency.

Nanomagnetic logic, incorporating logic bits in the magnetization orientations of single-domain nanomagnets, has garnered attention as an alternative to transistor-based logic due to its non-volatility and unprecedented energy-efficiency. The energy efficiency of this scheme is determined by the method used to flip the magnetization orientations of the nanomagnets in response to one or more inputs and produce the desired output. Unfortunately, the large dissipative losses that occur when nanomagnets are switched with a magnetic field or spin-transfer-torque inhibit the promised energy-efficiency. Another technique offering superior energy efficiency, “straintronics”, involves the application of a voltage to a piezoelectric layer to generate a strain which is transferred to an elastically coupled magnetrostrictive layer, causing magnetization rotation. The functionality of this scheme can be enhanced further by introducing magnetocrystalline anisotropy in the magnetostrictive layer, thereby generating four stable magnetization states (instead of the two stable directions produced by shape anisotropy in ellipsoidal nanomagnets). Numerical simulations were performed to implement a low-power universal logic gate (NOR) using such 4-state magnetostrictive/piezoelectric nanomagnets (Ni/PZT) by clocking the piezoelectric layer with a small electrostatic potential (~0.2 V) to switch the magnetization of the magnetic layer. Unidirectional and reliable logic propagation in this system was also demonstrated theoretically. Besides doubling the logic density (4-state versus 2-state) for logic applications, these four-state nanomagnets can be exploited for higher order applications such as image reconstruction and recognition in the presence of noise, associative memory and neuromorphic computing. Experimental work in strain-based switching has been limited to magnets that are multi-domain or magnets where strain moves domain walls. In this work, we also demonstrate strain-based switching in 2-state single-domain ellipsoidal magnetostrictive nanomagnets of lateral dimensions ~200 nm fabricated on a piezoelectric substrate (PMN-PT) and studied using Magnetic Force Microscopy (MFM). A nanomagnetic Boolean NOT gate and unidirectional bit information propagation through a finite chain of dipole-coupled nanomagnets are also shown through strain-based "clocking". This is the first experimental demonstration of strain-based switching in nanomagnets and clocking of nanomagnetic logic (Boolean NOT gate), as well as logic propagation in an array of nanomagnets.

This diploma thesis is oriented to analysis of physiological effect of synthetic estrogen ethinylestradiol (EE), which represents the main component of steroid-based substance used in hormonal contraception. From wide range of physiologically important protein molecules, which might be effected by this steroid, thesis focuses to the study of the sodium plus potassium activated, magnesium dependent adenosinetriphosphatase (Na+, K+ - ATPase), which is selectively inhibited by cardiac glycosides such as ouabain (g strophantine). Na+, K+ - ATPase represents an important plasma membrane bound enzyme, which catalyzes the active transport of sodium and potassium across plasma membrane. In the first part of this work, Na+, K+ - ATPase was determined by binding of radioactively labeled selective inhibitor of this enzyme [3H]ouabain, used for this purpose. In the second part of this work, plasma membrane fluidity was analyzed by steady-state fluorescence anisotropy of DPH. The effect of EE on [3H]ouabain binding was studied first under in vitro conditions by using human embryonic kidney cells (HEK293) which were cultivated for 24 hours in the presence of EE in tissue culture medium. Second, the effect of EE was also studied under in vivo conditions, by subcutaneous application of EE to the female rats of Wistar...

Le site d’action des bactériocines de la sous-classe IIa est la membrane cytoplasmique des bactéries à Gram positif. Le mécanisme d’action se décompose en trois étapes : (i) adsorption de la bactériocine sur la membrane ; (ii) structuration du peptide et insertion dans la bicouche lipidique ; (iii) formation de pores. La présence de pores provoque des fuites de composés vitaux aboutissant soit à un arrêt de la croissance soit à la mort de la bactérie. Le degré de pénétration de la mésentérocine 52A dans la membrane a été mesuré grâce à l’anisotropie de fluorescence de deux sondes, le TMA-DPH et le DPH, respectivement localisées à la surface et en profondeur de la bicouche lipidique. Des résultats différents ont été obtenus avec deux espèces bactériennes appartenant au genre Listeria. Dans un cas, le peptide s’insère partiellement dans la membrane et dans l’autre en profondeur. Ces résultats suggèrent que la mésentérocine 52A peut suivre deux mécanismes distincts aboutissant à une bactériostase. Pour mieux comprendre les interactions entre la bactériocine et la cellule cible, le degré de pénétration de la mésentérocine 52A dans la membrane de trois souches de Leuconostoc, la première sensible, la seconde naturellement insensible et la dernière rendue résistante, a été caractérisé. Il semblerait que le phénotype de résistance soit corrélé avec les propriétés physico-chimiques de l’enveloppe cellulaire. Afin de pouvoir généraliser les résultats observés avec la mésentérocine 52A, d’autres bactériocines de la sous-classe IIa, les carnobactériocines Cbn BM1 et Cbn B2, produites par la souche Carnobacterium maltaromaticum CP5, ont été étudiées. Dans un premier temps, ces bactériocines ont été produites et purifiées à partir d’une souche d’Escherichia coli recombinante. L’étape de production en fermenteur a été optimisée, des quantités de l’ordre de 300 mg de peptides ont été produites. Le mode d’action des carnobactériocines, seules ou en combinaison, a été déterminé vis-à-vis de cellules procaryotes ou eucaryotes. Les carnobactériocines Cbn BM1 et Cbn B2 ont un mode d’action synergique contre les bactéries sensibles et ne présentent pas de cytotoxicité vis-à-vis des cellules de la lignée Caco-2 / The action site of sub-class IIa bacteriocins is the cytoplasmic membrane of Gram-positive bacteria. The current view of the mechanism of action is divided into three steps: (i) adsorption of bacteriocins on the membrane; (ii) apparition of the structures of peptide and integration into the lipid double layer (iii) formation of pores. The presence of pores leads to efflux of vital cell compounds. They cause growth stop or bacterial death. The degree of penetration of mesenterocin 52A into the membrane was measured by fluorescence anisotropy of two probes, TMA-DPH and the DPH, which target the surface or the depth of the membrane, respectively. Different results were obtained with two bacterial species of the genus Listeria. In the first hand, the peptide is partially inserted into the membrane and in the second hand in depth. These results suggest that mesenterocin 52A can exhibit two different mechanisms leading to the same antibacterial effect. To better understand the interactions between bacteriocins and the target cell, the degree of penetration of mesenterocin 52A into the membrane of three Leuconostoc strains, the first sensitive, the second naturally resistant and last induced resistant, was characterized. It seems that the resistance phenotype is correlated with physical and chemical properties of the cell envelope. To generalize the results observed with mesenterocin 52A, other bacteriocins of sub-class IIa, the carnobacteriocins Cbn BM1 and Cbn B2, produced by Carnobacterium maltaromaticum CP5 strain, were studied. These bacteriocins were produced in E. coli and subsequently purified. The optimization of the production process in a reactor led to purify up to 300 mg of peptides for 1.5 liter of culture. The mode of action of carnobacteriocins, alone or in combination, was determined with prokaryotic or eukaryotic cells as targets. The carnobacteriocins Cbn BM1 and Cbn B2 have a synergistic mode of action against sensitive bacteria and are not cytotoxic against Caco-2 cell line

Le travail présenté dans ce mémoire a pour objectif d'aboutir à une meilleure caractérisation expérimentale du comportement non drainé du sable d'Hostun à l'échelle locale, en relation avec les différentes méthodes de reconstitution utilisées. On vise en particulier à mettre en évidence la façon dont la microstructure influence les propriétés des sols granulaires, notamment vis-à-vis de l'instabilité de liquéfaction. Le point clé de ce travail consiste en l'utilisation de capteurs piézoélectriques pour mesurer les vitesses d'onde de cisaillement au sein d'éprouvettes triaxiales reconstituées par trois techniques différentes à savoir le damage humide, la pluviation à sec et la pluviation sous eau. Les résultats obtenus mettent en évidence l'influence considérable du mode de fabrication sur le comportement mécanique du sable. Ils montrent que pour une même densité initiale, et à même pression de confinement, le comportement mécanique observé est très différent selon les trois modes de préparation. Les valeurs de vitesses d'onde de cisaillement enregistrées sont différentes d'un mode de déposition à un autre. Concernant l'anisotropie, le matériau préparé par damage humide présente un certain degré d'anisotropie inhérente, qui est toutefois minimal. En revanche, la pluviation à sec et la pluviation sous eau induisent des structures initiales plus isotropes. / This work aims to achieve a better experimental characterization of the undrained behavior of the Hostun HN31 sand at the local scale, depending on the different procedures used for sample reconstitution. We particularly highlight the influence of the microstructure on the mechanical behavior of sand especially in relation to liquefaction instability. The key point of this work consists of the use of piezoelectric transducers to measure shear wave velocities within triaxial sand specimens. These specimens have been prepared by different methods, namely: moist tamping, dry pluviation and water pluviation. The obtained results highlight the considerable influence of the deposition mode on the mechanical behavior of sand. They show that for the same initial density, and at the same confining pressure, the mechanical behavior is very different from the three preparation methods. Furthermore, the values of shear wave velocity are different from one deposition mode to another. Concerning the anisotropy, the material prepared by moist tamping presents an inherent degree of anisotropy, which it is however minimal. On the other hand, dry pluviation and water pluviation induce more isotropic initial structures. Moreover, the initial anisotropy is less important than the anisotropy induced by loading. These experimental results indicate that the initial state of a granular medium can not be described by only couple of scalar variables of initial density and confining pressure: a variable that can reflect the initial microstructure and an evolution law of this variable are necessary to model the experimental observations.