Carbon nanotubes (CNTs) have gathered a lot of interest because of their extraordinary mechanical, electrical and thermal properties and have potential applications in a wide variety of areas such as material-reinforcement and nano-electronics. The properties of nanotubes are dependent on their diameter and methods for determining this using atomic force microscopy (AFM) in tapping mode assume that the measured height of the tubes represent the real diameter. Based on early, faulty calculations, the forces in tapping mode were assumed to be much lower than in contact mode, however it was later shown that forces in tapping mode can at point of impact rival the forces present in contact mode. This means that there is a potential risk of tube deformation during tapping mode measurements, resulting in incorrectly determined diameters. This work studies CNTs deposited on a silicon-substrate to analyze the effect of three common AFM settings (tapping frequency, free oscillation amplitude and setpoint) to determine their effect on measured CNT diameters and recommendations for choosing settings are given. / Kolnanorör har skapat mycket intresse på grund av sina extraordinära mekaniska, elektriska och termiska egenskaper och har lovande tillämpningar inom en mängd olika områden så som materialförstärkning och nanoelektronik. Kolnanorörens egenskaper påverkas kraftigt av deras diameter och de metoder som använder sig av atomkraftsmikroskopi(AFM) för att mäta diametern hos rören antar att den höjd-data man får fram är ett bra mått på den verkliga diametern hos rören. Baserat på tidiga, felaktiga beräkningar, antog man att kraften i ’tapping mode’ skulle vara mycket lägre än i ’contact mode’ vilket skulle leda till att man inte deformerar ytan man undersöker. Senare forskning visade att kraften mellan spets och prov kan vara lika stor eller rentutav större i tapping mode än i contact mode under det ögonblick då spetsen slår ner i provytan. Det medför att det finns en potentiell risk för att man deformerar kolnanorören när man mäter på dom vilket skulle resultera i att man får felaktiga värden på deras diametrar. Under det här projektet har kolnanorör som placerats på ett kisel-substrat undersökts för att analysera hur tre vanliga inställningar hos AFMet påverkar de erhållna värdena för diametern hos kolnanorören. De tre inställningarna som testats är svängnings-frekvensen, svängnings-amplituden i luft och börvärdet hos svängnings-amplituden.

<p>In this study the formation of supported membranes onto planar solid supports has been investigated. The stability and activity of reconstituted membrane receptors has been studied. The potential use of such preparations in biosensor applications is discussed.</p><p>The lipid films were made by the Langmuir Blodgett and by the liposome fusion techniques. These supported films were characterised by ellipsometry, atomic force microscopy, surface plasmon resonance (SPR) and resonant mirror techniques. The thickness of the films was in agreement with that of a cell membrane. The kinetics of formation of the lipid films was studied and discussed.</p><p>The proteins, bacteriorhodopsin, cytochrome oxidase, acetylcholinesterase and the nicotinic acetylcholine receptor were reconstituted into the supported membrane. The subsequent analysis showed that the proteins were individually distributed and that the activity was retained, in some cases for several weeks after immobilisation.</p><p>The glycolipids, GM1, GM2, GD1b, asialo-GM1, globotriaosylceramide, lactosylceramide and galactosylceramide, were also reconstituted into the supported membranes. Their specific interaction with the toxin ricin or with its B-chain was examined using SPR. The affinity of intact toxin and of its B-chain differed markedly and was pH dependent. The carbohydrate chain length and charge density of the glycolipids also influenced the affinity.</p>

In this study the formation of supported membranes onto planar solid supports has been investigated. The stability and activity of reconstituted membrane receptors has been studied. The potential use of such preparations in biosensor applications is discussed. The lipid films were made by the Langmuir Blodgett and by the liposome fusion techniques. These supported films were characterised by ellipsometry, atomic force microscopy, surface plasmon resonance (SPR) and resonant mirror techniques. The thickness of the films was in agreement with that of a cell membrane. The kinetics of formation of the lipid films was studied and discussed. The proteins, bacteriorhodopsin, cytochrome oxidase, acetylcholinesterase and the nicotinic acetylcholine receptor were reconstituted into the supported membrane. The subsequent analysis showed that the proteins were individually distributed and that the activity was retained, in some cases for several weeks after immobilisation. The glycolipids, GM1, GM2, GD1b, asialo-GM1, globotriaosylceramide, lactosylceramide and galactosylceramide, were also reconstituted into the supported membranes. Their specific interaction with the toxin ricin or with its B-chain was examined using SPR. The affinity of intact toxin and of its B-chain differed markedly and was pH dependent. The carbohydrate chain length and charge density of the glycolipids also influenced the affinity.

The epilepsies are a heterogenous group of symptom complexes, whose common features is the recurrence of seizures. There is no certain therapy for epilepsy. In order to promote new advances for the prevention of epilepsy the molecular mechanism of epileptic activities should be clarified. In the present study the goal is to obtain information for molecular mechanism of epilepsy. To achieve this, molecular alterations from pentylenetetrazol (PTZ)-induced epileptic activities on rat brain tissue and cell membranes were investigated by Fourier Transform Infrared (FTIR) spectroscopy, Fourier Transform Infrared Microscopy and Atomic Force Microscopy (AFM). Moreover, the therapeutic role of an antiepileptic agent vigabatrin (VGB) on epileptic rat brain membranes were examined at molecular level. For better understanding of the action mechanism of PTZ and an antiepileptic drug VGB in cell membranes we firstly studied at model level using multilamellar liposomes (MLVs). We investigated PTZ-DPPC MLVs interactions in terms of lipid phase behavior, order and dynamics and nature of hydrogen bonding around its polar part, using Fourier Transform Infrared (FTIR) spectroscopy, Differential Scanning Calorimetry (DSC), Electronspin Resonans Spectroscopy (ESR) and Steady State Fluorescence Spectroscopy. According to our data, PTZ has no ability to interact with membrane lipids. On the other hand, the results of VGB-DPPC interactions showed that VGB strongly interact with the head group and/or the region near the head of membrane phospholipids. The molecular investigation of PTZ-induced epileptic activities revealed that PTZ-induced seizures cause a decrease in the lipid and protein content, membrane fluidity and glycogen level. They stimulate alterations in membrane packing and the secondary structure of proteins as well as lipid peroxidation. In addition, our results show the transcription of early genes following high dose PTZ administration. All these molecular alterations variatins are only resulted from the consequences of epileptic activities not from convulsant agent PTZ itself. The important finding is that, VGB restored some of the alterations by PTZ-induced epileptic activities on brain cell membrane. For instance, it restored membrane fluidity, lipid peroxidation, phospholipid degradation and changes in membrane organization. However, it was found that VGB has no significant effects on the changes in protein secondary structure.

Surface modification techniques have played important roles in various aspects of modern technology. They have been employed to improve substrates by altering surface physicochemical properties. An ideal surface modifying technique would be a method that is applicable to any kind of materials prepared from a wide range of polymers and that can occur under mild reaction conditions. The work in this thesis has utilized four main concepts: I) the development of a ‘grafting-from’ technique by covalently growing polymer grafts from particle surfaces, II) the presence of steric and electrosteric forces due to long-range repulsive interactions between particles, III) a combined surface grafting and layer-by-layer approach to create polyelectrolyte multilayers (PEMs) on particle surfaces to fabricate strong and functional materials, and IV) the roles of hydrophilic polymer grafts and substrate geometry on surface degradation. A non-destructive surface grafting technique was developed and applied to polylactide (PLA) particle surfaces. Their successful modification was verified by observed changes to the surface chemistry, morphology and topography of the particles. To quantify the aggregation behavior of grafted and non-grafted particles, force interaction measurements were performed using colloidal probe atomic force microscopy (AFM). Long-range repulsive interactions were observed when symmetric systems, i.e., hydrophilic polymer grafts on two interacting surfaces, and asymmetric system were applied. Electrosteric forces were observed when the symmetric substrates interacted at pH 7.4. When PEMs were alternately assembled on the surface of poly(L-lactide) (PLLA) particles, the grafted surfaces played a dominated role in altering the surface chemistry and morphology of the particles. Three-dimensional scaffolds of surface grafted particle coated with PEMs demonstrated high mechanical performance that agreed well with the mechanical performance of cancellous bone. Nanomaterials were used to functionalize the scaffolds and further influence their physicochemical properties. For example, when magnetic nanoparticles were used to functionalize the scaffolds, a high electrical conductivity was imparted, which is important for bone tissue regeneration. Furthermore, the stability of the surface grafted particles was evaluated in phosphate buffered saline (PBS) solution. The nature of the hydrophilic polymer grafts and the geometry of the PLLA substrates played central roles in altering the surface properties of films and particles. After 10 days of PBS immersion, larger alterations in the surface morphology were observed on the film compared with microparticles grafted with poly(acrylic acid) (PAA). In contrast to the PAA-grafted substrates, the morphology of poly(acrylamide) (PAAm)-grafted substrates was not affected by PBS immersion. Additionally, PAAm-grafted microparticulate substrates encountered surface degradation more rapidly than PAAm-grafted film substrates. / <p>QC 20151002</p>

Das chemisch-mechanische Planarisieren (CMP) in der Halbleiterindustrie ist ein Prozess mit sehr vielen Einflussgrößen, wobei das Polierergebnis unter anderem von den Eigenschaften der Wechselwirkungskomponenten Wafer, Poliersuspension und Polierpad abhängig ist. Bei der Entwicklung neuer Schaltkreisentwürfe werden die strukturellen Abhängigkeiten der Topografie nach dem CMP häufig im Verlauf von zeit- und kostenintensiven Lernzyklen aufgedeckt und angepasst. Um Dauer und Kosten für die Entwicklung neuer Schaltkreise zu reduzieren, sollte im Rahmen eines BMBF-Projektes ein umfassendes Gesamtmodell, welches den Polierprozess ausführlich beschreibt, entwickelt werden. Für die Umsetzung dieses Vorhabens ist ein umfassendes qualitatives und quantitatives Verständnis der mechanisch-hydrodynamischen und physikalisch-chemischen Mechanismen zu erarbeiten, welche den Materialabtrag und die Planarisierung beim CMP bestimmen. Ziel der vorliegenden Arbeit war es zum einen, mittels direkter Kraftmessung am AFM die Wechselwirkungskräfte zwischen den Festkörperoberflächen von Schleifpartikel und Wafer sowie zwischen den Schleifpartikeln untereinander in CMP-relevanten Flüssigkeiten und ihre Bedeutung für das CMP zu untersuchen. Um die Wechselwirkungskräfte am AFM bestimmen zu können, war zuvor die Entwicklung einer geeigneten Versuchsanordnung nötig. Zur Absicherung der Ergebnisse aus den Kraftmessungen wurde eine Methode erarbeitet, um die zwischenpartikulären Wechselwirkungen mittels rheologischer Untersuchungen indirekt bestimmen zu können. Des Weiteren fanden rheologische Messungen zur Untersuchung der Fließeigenschaften der Poliersuspensionen statt, wobei außerdem der Einfluss anwendungsrelevanter hydrodynamischer Kräfte auf die Stabilität der Poliersuspension zu überprüfen war. Als Poliersuspensionen kamen kommerziell verfügbare Slurries sowie eine Modellslurry zum Einsatz. Neben Systemen mit dispergierten Silica-Partikeln wurde auch eine Slurry mit Ceria-Partikeln als disperse Phase betrachtet. Die kontinuierliche Phase einer Poliersuspension ist ein Mehrkomponentensystem und enthält unterschiedlichste Additive. Untersucht wurde der Einfluss von pH-Wert und Elektrolytkonzentration auf die Wechselwirkungskräfte, das Fließverhalten sowie den Materialabtrag.

Les membranes cellulaires sont impliquées dans de nombreux processus cellulaires : la diffusion des médicaments et des ions, la transduction des signaux, la génération d'énergie, le développement cellulaire (fusion et fission). Les bicouches phospholipides sont les principaux composants des membranes cellulaires, elles constituent une barrière dynamique protégeant les réactions biochimiques cellulaires. La détermination des propriétés biochimiques et mécaniques des bicouches lipidiques et leur évolution avec les conditions environnementales est nécessaire pour étudier la nature des processus cellulaires et l'influence des agents externes (résistance mécanique, perméabilité et réponse biologique). Pour mener de telles caractérisations, des modèles simplifiés de membrane biomimétique, tels que des bicouches lipidiques supportées (SLB), ont été développés. Parmi les techniques de caractérisation disponibles, la microscopie à force atomique (AFM) a été largement utilisée pour étudier l'organisation nanométrique des SLB dans des conditions physiologiques. AFM peut produire des images à la haute résolution et peut également être utilisé pour quantifier la résistance mécanique des SLB au moyen d'expériences de perforation. Pendant 30 ans, AFM a traversé de nombreux développements. Très récemment, le Mode circulaire AFM (CM-AFM) a été développé à l'Université de Technologie de Compiègne. CM-AFM est capable de générer un mouvement de glissement de la pointe AFM sur l'échantillon à une vitesse élevée, constante et continue et de mesurer les forces de frottement latéral rapidement et exactement simultanément avec les forces verticales. Pour la première fois, le CM-AFM sert à caractériser les échantillons biologiques dans des conditions physiologiques, ce qui permet de mesurer simultanément les forces de poinçonnage et de frottement en fonction de la vitesse de glissement. Il offre pour la première fois la capacité de décrire le comportement de friction des SLB en complément de la force de perforation. En raison du besoin important de mesure quantitative, l'optimisation du protocole CM-AFM a été effectuée en premier. Le protocole d'étalonnage du scanner a été établi avec succès pour assurer la précision de la vitesse de glissement. En outre, le protocole d'étalonnage des pointes, basé sur la méthode de Wedge et un échantillon rayé, est également conçu pour déterminer la constante d'étalonnage de la force latérale. Nous avons utilisé CM-AFM pour mesurer les propriétés tribologiques des échantillons solides pour améliorer l'équipement sous milieu liquide. Ensuite, les propriétés mécaniques (forces de poinçonnage et de frottement) des SLB ont été mesurées en fonction de la vitesse de glissement. Les SLB purs et mixtes ont été préparés par la méthode de fusion des vésicules. Différents médias ont également été utilisés pour étudier l'effet des cations monovalents sur les propriétés mécaniques des SLB. Dans tous les cas, la force de frottement augmente linéairement avec la vitesse de glissement, ce qui nous permet de déduire le coefficient visqueux de frottement. Comme prévu, la force de poinçonnage et le coefficient visqueux de frottement sont influencés par la composition des mélanges de lipides, par la nature des cations en milieu liquide et par la longueur des chaînes hydrocarbonées mais pas de manière similaire. L'interprétation de l'évolution du coefficient de force de frottement visqueux avec le système étudié est particulièrement délicate car la force de frottement pourrait être influencée par les propriétés d'interface ou de volume. Cette problématique sera le défi pour les prochaines études. Néanmoins, nos résultats illustrent la puissance de la technique CM-AFM et ouvre de nombreuses possibilités pour caractériser d'autres échantillons biologiques (cellules et tissus) afin de mieux comprendre les mécanismes élémentaires de friction. / Cell membranes are involved in many cellular processes: drugs and ions diffusion, signal transduction, energy generation, cell development (fusion and fission). Phospholipid bilayers are the main components of cell membranes, they act as a dynamic barrier protecting cellular biochemical reactions. The determination of biochemical and mechanical properties of lipid bilayers and their evolution with environmental conditions is necessary to study the nature of cellular processes and the influence of external agents (mechanical resistance, permeability, and biological response). To conduct such characterizations, simplified biomimetic membrane models, such as supported lipid bilayers (SLBs), were developed. Among the available characterization techniques, atomic force microscopy (AFM) has been widely used to study the nanoscale organization of SLBs under physiological conditions. AFM can yield high resolution images and it can also be used to quantify the mechanical resistance of SLBs by means of punch through experiments. For 30 years, AFM has been through many developments. Very recently, the Circular Mode AFM (CM-AFM) has been developed at the Université de Technologie de Compiègne. CM-AFM is able to generate a sliding movement of the AFM tip on the sample at high, constant and continuous velocity and to measure the lateral friction forces fast and accurately simultaneously with the vertical forces. For the first time CM-AFM is used to characterize biological samples under physiological conditions, allowing the simultaneous measurement of both the punch-through and the friction forces as a function of the sliding velocity. It offers for the first time the ability to describe the friction behavior of SLBs in complement of the punch-through force. Due to the important need for quantitative measurement, optimization of the CM-AFM protocol has been done first. Protocol of scanner calibration has been successfully established to ensure the accuracy of sliding velocity. Besides, the protocol for tip calibration, based on wedge method and a scratched sample, is also made to determine the lateral force calibration constant. We have employed CM-AFM to measure the tribological properties of solid samples to improve the equipment under liquid medium. Then, the mechanical properties (punchthrough and friction forces) of SLBs were measured as function of the sliding velocity. Pure and mixed SLBs were prepared by the vesicle fusion method. Various media were also used to study the effect of monovalent cations to the mechanical properties of SLBs. In all cases, the friction force increases linearly with the sliding velocity allowing us to deduce the friction viscous coefficient. As expected both the punchthrough force and the friction viscous coefficient are influenced by the composition of lipid mixtures, by the nature of cations in liquid medium, and by the length of hydrocarbon chains but not in a similar fashion. The interpretation of the evolution of the viscous friction force coefficient with the studied system is particularly tricky as the friction force could be influenced by interface or volume properties. This problematic will be the challenge for the next studies. Nevertheless, our results illustrate how powerful the CM-AFM technique is and it opens wide opportunities to characterize other biological samples (cells and tissues) to gain a better understanding of the elementary mechanisms of friction.

abstract: Alzheimer's disease (AD) is the most common form of dementia leading to cognitive dysfunction and memory loss as well as emotional and behavioral disorders. It is the 6th leading cause of death in United States, and the only one among top 10 death causes that cannot be prevented, cured or slowed. An estimated 5.4 million Americans live with AD, and this number is expected to triple by year 2050 as the baby boomers age. The cost of care for AD in the US is about $200 billion each year. Unfortunately, in addition to the lack of an effective treatment or AD, there is also a lack of an effective diagnosis, particularly an early diagnosis which would enable treatment to begin before significant neuronal damage has occurred. Increasing evidence implicates soluble oligomeric forms of beta-amyloid and tau in the onset and progression of AD. While many studies have focused on beta-amyloid, soluble oligomeric tau species may also play an important role in AD pathogenesis. Antibodies that selectively identify and target specific oligomeric tau variants would be valuable tools for both diagnostic and therapeutic applications and also to study the etiology of AD and other neurodegenerative diseases. Recombinant human tau (rhTau) in monomeric, dimeric, trimeric and fibrillar forms were synthesized and purified to perform LDH assay on human neuroblastoma cells, so that trimeric but not monomeric or dimeric rhTau was identified as extracellularly neurotoxic to neuronal cells. A novel biopanning protocol was designed based on phage display technique and atomic force microscopy (AFM), and used to isolate single chain antibody variable domain fragments (scFvs) that selectively recognize the toxic tau oligomers. These scFvs selectively bind tau variants in brain tissue of human AD patients and AD-related tau transgenic rodent models and have potential value as early diagnostic biomarkers for AD and as potential therapeutics to selectively target toxic tau aggregates. / Dissertation/Thesis / Doctoral Dissertation Chemical Engineering 2014

A oxidação anódica local utilizando o Microscópio de Força Atômica (AFM - Atomic Force Microscopy) foi investigada aplicando-se uma tensão negativa entre sonda de nitreto de silício e superfícies de Si. Todas as amostras foram limpas em uma solução de 1 NH4OH (30%): 1H2O2 (38%): 4H2O(DI) a 80ºC conhecida na literatura como SC1 (Standard Cleaning 1) ou, alternativamente, uma imersão em solução diluída de ácido hidrofluorídrico seguido de SC1 ou fervura em álcool isopropílico. As nano-oxidações consistiram de padrões quadrados localizados de óxido com área de 0,25 µm² e foram obtidos através do crescimento de linhas paralelas com espaço e comprimento interlinear constante (<2 nm) e várias varreduras dos quadrados em uma mesma área. Das análises de AFM, foram obtidos perfis transversais e 3D, os quais foram empregados na obtenção da espessura do óxido como função da tensão aplicada, número de varreduras e intervalo de tempo após a limpeza SC1. Foi observado que a espessura aumenta com a tensão negativa aplicada e com o número de varreduras. Também foram realizadas simulações para levantar as distribuições de tensão e de campo elétrico no sistema sonda-ar-silício ou sonda-ar-óxido-silício(substrato). Observou-se uma oxidação local assistida por um alto campo elétrico capaz de induzir difusão iônica local finita na extremidade da sonda. Foi simulado também o efeito das diferentes terminações de sonda do AFM, circular ou pontiaguda, no campo elétrico e na queda de tensão. Foram também realizadas oxidações com sondas recobertas com ouro em superfícies de Si precedidas de imersão simples em solução de ácido hidrofluorídrico seguido ou não do procedimento de limpeza SC1. Por fim, análises de absorção por infravermelho (FTIR) foram realizadas em superfícies de Si oxidadas por AFM para analisar a estrutura dos óxidos anódicos obtidos. A oxidação anódica utilizando sondas de nitreto de silício ocorre apenas após pré-limpeza terminada com SC1, sendo catalisada pelos altos campos elétricos (_ 106 V/cm), tendo como elementos reagentes, as espécies H2O adsorvidas e o óxido nativo hidrolisado na superfície após a etapa de limpeza SC1. / Local anodic oxidation of silicon using Atomic Force Microscopy (AFM) was investigated by applying a negative voltage between silicon nitride tip and Si surfaces. All samples were cleaned with an ammonium-based solution known in literature as standard cleaning 1 (SC1) or a dip in a diluted hydrofluoric acid solution followed by SC1 or, also, boiling in isopropyl alcohol. Localized squares patterns of oxide, 0.25 µm² in area, were formed by growing parallel lines with constant interlinear spacing and length and several scans in the same area. From AFM analysis with non-biased tip, it was obtained 3D and section profiles, which were used to obtain the oxide thickness as a function of the applied voltage, number of scans and interval of time after SC1 cleaning. It was noteworthy that thickness increases with the applied negative voltage and with the number of scans. Simulations were performed in order to model voltage and electric field distributions of the system tip-air-silicon or tip-air-oxide-silicon(substrate) indicating a local oxidation assisted by high electrical field and local ionic diffusion of species. It was simulated the effect of tip termination, circular or sharpen, on the electric field and voltage distributions. In addition, oxidations were performed using Au coated tips onto Si surfaces previously dipped in diluted hydrofluoric acid solution followed or not by SC1 cleaning process. Finally, infrared absorption analysis (FTIR) were performed in order to analise the structure of the obtained anodic oxides. The anodic oxidation using silicon nitride tips has occurred only after SC1 precleaning step, being catalized by high electric field (_ 106 V/cm), having as reagents, the adsorbed water species and hydrolized native oxide on the surface after the SC1 cleaning step.

Le composé intermétallique ordonné Ni3Al, de structure L12, présente une augmentation de contrainte d'écoulement avec la température, jusqu'à une température dite de "pic" au-delà de laquelle celle-ci décroit. Ce comportement, usuellement appelé anomalie de contrainte d'écoulement, est mis à profit dans les superalliages base nickel pour les applications hautes températures. Il a été étudiée de façon extensive ces trente dernières années et a donné lieu à de nombreuses modélisations. La plupart des modèles proposés considère qu'un processus thermiquement activé de glissement dévié des dislocations, à partir de leur plan de glissement primaire {111} sur le plan cubique de déviation {010}, joue un rôle clé dans la compréhension de l'anomalie. La distance de glissement dévié peut cependant fortement différer. Les traces de glissement laissées par l'émergence des dislocations mobiles à la surface d'échantillons déformés plastiquement permettent de visualiser les événements de déviations et de caractériser les mécanismes élémentaires de déformation plastique. Nous avons mesuré des paramètres essentiels pour modéliser la plasticité globale de l'intermétallique Ni3Al, comme : le nombre, la hauteur, la longueur des traces de glissement correspondant aux plans {111} et {010}. Ces paramètres qui caractérisent à la fois l'activité des sources et le libre parcours moyen des dislocations, suggèrent que l'anomalie s'accompagne d'un fort taux d'épuisement de la densité de dislocations mobiles. De nombreuses longues déviations dans les plans {010} ainsi que des doubles glissement dévié entre plans {111} adjacents, ont été mis en évidence. Ceci suggère deux processus de glissement dévié. / Ni3Al intermetallic compounds, that correspond to the strengthening phase of nickel-based superalloys, are well known to exhibit within a given range of temperature, an anomalous behaviour of flow strength. This positive temperature dependence of flow strength, called yield stress anomaly (YSA), has been the subject of extensive experimental studies concerning mechanical properties and dislocation microstructures, which have yielded several plausible models. Most of these models considers that a thermally activated cross-slip process, from the primary {111} onto the cube cross-slip {010} planes, plays a key role in the understanding of the YSA. However, the height of the cross-slipped segment in the {010} plane can be drastically different. The slip traces resulting from the emergence of moving dislocations at the surface in plastically deformed samples, allow us to visualize cross-slip events and to characterize the elementary mechanisms controlling plastic deformation. The number, height and length of slip traces corresponding to {111} and {010} planes, that are key parameters for modelling the plastic behaviour of Ni3Al intermetallic, are examined. These parameters reflect both the source activity and dislocation mean free path of dislocations; their values suggest that the YSA takes place with a strong exhaustion of mobile dislocations. Several larger deviations on the {010} planes, as well as double cross-slip between {111} neighbouring planes, are highlighted. These results suggest two different cross-slip process.