Characterization of surface wetting uniformity in hydrophobic tubes using ferrofluid droplets

Hydrophobic surfaces, or water repellent surfaces, have interesting properties for applications on selfcleaning, anti-icing, antifogging and fluid drag reduction. To develop more efficient surfaces, proper characterization methods need to be developed as the current methods available are not sufficient. In this thesis, the theoretical background behind wetting phenomena on hydrophobic surfaces and various techniques for characterizing wetting properties are presented. Furthermore, a new characterization technique applied to hollow, non planar surfaces and more specifically to transparent tubes is proposed. This technique measures wetting inhomogeneities using magnetically controlled water-like droplets over the entire length of the samples. This technique can measure the retentive force, a dissipative force related to the contact angle hysteresis at the three-phase contact line. This technique is used to see differences in wetting properties using reference tubes and their annealed counterparts using two different ferrofluids. As a non-destructive and quantitative characterization method, this technique could readily be used for quality control in academia and industries

Heterogeneity in tribologically transformed structure (TTS) of Ti-6Al-4V under fretting

Fretting wear is a surface degradation process caused by oscillatory motion and contact slipping. During gross slip, high local stresses and plastic deformation in the surface and subsurface can lead to the creation of a nanosized grained structure called Tribologically Transformed Structure (TTS). The current paper studies the formation of TTS in an alpha-beta Ti-6Al-4V alloy under fretting loading while changing the contact pressure and the number of fretting cycles.Cross-sections of wear scars are observed after polishing and chemical etching. Above a threshold pressure of 300 MPa, TTS appears early in the contact (before 1000 cycles) along with two other structures: a Third Body Layer (TBL) made of compacted debris and a General Deformed Layer (GDL) which is the plastic zone under the TTS. TTS first appears as islands and merges in the middle of the contact after enough cycles. Below 200 MPa, only TBL and GDL are formed. At 200 MPa, only small, localized TTS is found. All structures have the same chemical compositions as the initial bulk material except for the nitrided TBL. TTS has a very high hardness compared to the bulk. TTS was carefully extracted using a Focused Ion Beam (FIB) and its microstructure was observed with a Transmission Electron Microscope (TEM). It shows extreme grain refinement and is composed of two alternated zones. The first zone I is composed of $\alpha$ grains with a size of 20 to 50 nm with crystallographic texture. Zone II comprises nanosized equiaxed grains whose sizes range from 5 to 20 nm without texture. The results made it possible to establish a scenario of the appearance of the TTS according to the conditions of contact pressure and number of fretting cycles

IMGT/GeneInfo: T cell receptor gamma TRG and delta TRD genes in database give access to all TR potential V(D)J recombinations

BACKGROUND: Adaptative immune repertoire diversity in vertebrate species is generated by recombination of variable (V), diversity (D) and joining (J) genes in the immunoglobulin (IG) loci of B lymphocytes and in the T cell receptor (TR) loci of T lymphocytes. These V-J and V-D-J gene rearrangements at the DNA level involve recombination signal sequences (RSS). Whereas many data exist, they are scattered in non specialized resources with different nomenclatures (eg. flat files) and are difficult to extract. DESCRIPTION: IMGT/GeneInfo is an online information system that provides, through a user-friendly interface, exhaustive information resulting from the complex mechanisms of T cell receptor V-J and V-D-J recombinations. T cells comprise two populations which express the αβ and γδ TR, respectively. The first version of the system dealt with the Homo sapiens and Mus musculus TRA and TRB loci whose gene rearrangements allow the synthesis of the αβ TR chains. In this paper, we present the second version of IMGT/GeneInfo where we complete the database for the Homo sapiens and Mus musculus TRG and TRD loci along with the introduction of a quality control procedure for existing and new data. We also include new functionalities to the four loci analysis, giving, to date, a very informative tool which allows to work on V(D)J genes of all TR loci in both human and mouse species. IMGT/GeneInfo provides more than 59,000 rearrangement combinations with a full gene description which is freely available at . CONCLUSION: IMGT/GeneInfo allows all TR information sequences to be in the same spot, and are now available within two computer-mouse clicks. This is useful for biologists and bioinformaticians for the study of T lymphocyte V(D)J gene rearrangements and their applications in immune response analysis

Numerical Modelling Of The V-J Combinations Of The T Cell Receptor TRA/TRD Locus

T-Cell antigen Receptor (TR) repertoire is generated through rearrangements of V and J genes encoding α and β chains. The quantification and frequency for every V-J combination during ontogeny and development of the immune system remain to be precisely established. We have addressed this issue by building a model able to account for Vα-Jα gene rearrangements during thymus development of mice. So we developed a numerical model on the whole TRA/TRD locus, based on experimental data, to estimate how Vα and Jα genes become accessible to rearrangements. The progressive opening of the locus to V-J gene recombinations is modeled through windows of accessibility of different sizes and with different speeds of progression. Furthermore, the possibility of successive secondary V-J rearrangements was included in the modelling. The model points out some unbalanced V-J associations resulting from a preferential access to gene rearrangements and from a non-uniform partition of the accessibility of the J genes, depending on their location in the locus. The model shows that 3 to 4 successive rearrangements are sufficient to explain the use of all the V and J genes of the locus. Finally, the model provides information on both the kinetics of rearrangements and frequencies of each V-J associations. The model accounts for the essential features of the observed rearrangements on the TRA/TRD locus and may provide a reference for the repertoire of the V-J combinatorial diversity

Worry and ruminative brooding: associations with cognitive and physical health in older adults

IntroductionMental health conditions are associated with cognition and physical function in older adults. We examined whether worry and ruminative brooding, key symptoms of certain mental health conditions, are related to subjective and/or objective measures of cognitive and physical (cardiovascular) health.MethodsWe used baseline data from 282 participants from the SCD-Well and Age-Well trials (178 female; agemean = 71.1 years). We measured worry and ruminative brooding using the Penn State Worry Questionnaire and the Ruminative Response Scale-brooding subscale. We assessed subjective physical health using the WHOQOL-Bref physical subscale, and objective physical health via blood pressure and modified versions of the Framingham Risk Score and Charlson Comorbidity Index. With subjective and objective cognition, we utilized the Cognitive Difficulties Scale and a global composite (modified Preclinical Alzheimer’s Cognitive Composite, PACC5, with the Wechsler Adult Intelligence Scale-IV, category fluency, Mattis Dementia Rating Scale-2, and either the California Verbal Learning Test or the Rey Auditory Verbal Learning Test). We conducted linear regressions, adjusted for education, age, sex and cohort.ResultsWorry and ruminative brooding were negatively associated with subjective physical health (worry: β = −0.245, 95%CI −0.357 to −0.133, p < 0.001; ruminative brooding: β = −0.224, 95%CI −0.334 to −0.113, p < 0.001) and subjective cognitive difficulties (worry: β = 0.196, 95%CI 0.091 to 0.302, p < 0.001; ruminative brooding: β = 0.239, 95%CI 0.133 to 0.346, p < 0.001). We did not observe associations between worry or ruminative brooding and any measure of objective health.DiscussionWorry and ruminative brooding may be common mechanisms associated with subjective but not objective health. Alternatively, cognitively unimpaired older adults may become aware of subtle changes not captured by objective measures used in this study. Interventions reducing worry and ruminative brooding may promote subjective physical and cognitive health; however, more research is needed to determine causality of the relationships

Study of Tribologically Transformed Structures of Ti-6Al-4V formed by fretting : formation mecanisms, micromecanical properties and wear modelling

Le fretting est un phénomène de dégradation des surfaces sous faibles amplitudes de glissements alternés. Durant les sollicitations de fretting, des couches superficielles subissent une transformation de leur microstructure, apparaissant blanche après attaque chimique, et deviennent fragiles. Ces couches sont appelées Transformations Tribologiques Superficielles (TTS) et elles participent à la formation de débris. Ces travaux de recherche visent à comprendre la genèse des TTS dans un contact plan-plan de TA6V soumis à des sollicitations de fretting, ainsi qu'à caractériser leur comportement mécanique.Les conditions d'apparition des TTS sont tout d'abord évaluées expérimentalement en faisant varier les paramètres de la sollicitation de fretting, notamment la pression de contact. La cinétique de formation est étudiée en analysant la présence et la morphologie de la TTS pour différents nombres de cycles de fretting. Des analyses chimiques EDX, observation optiques et MEB des coupes transverses des traces de fretting après attaque chimique sont réalisées. Les résultats montrent que les TTS apparaissent d'abord localement, par îlots, avant de former une zone unique et élargie au centre du contact avec une épaisseur limitée à moins de 100 microns. Cependant, des pressions inférieures ou égales à 200 MPa ne permettent pas l'observation des TTS, suggérant l'établissement d'une valeur seuil de pression pour leur formation dans le contact.La deuxième partie de l'étude se consacre à la caractérisation de la microstructure et de la texture cristallographique des TTS. Les TTS étant des matériaux à nanograins, des analyses MET ont permis de décrire précisément leur structure. Les phases en présences sont identifiées grâce aux clichés de diffraction électronique. Des analyses chimiques EDS et EELS sont réalisées. La méthode Astar est utilisée afin d'établir la texture locale des TTS à une résolution nanoscopique. Il en ressort que les TTS sont constituées de deux couches de nanograins alternées. L'une est constituée de grains de phase alpha de 20 à 50 nm ayant une texture cristallographique marquée, l'autre de grains (aussi de phase alpha) faisant quelques nanomètres de diamètre et sans texture évidente. La présence d'azote est également détectée dans cette dernière couche. Un mécanisme de formation des TTS par recristallisation dynamique continue, couplée à une localisation de la déformation plastique en bandes, est avancé afin d'expliquer la microstructure hétérogène observée.La destruction des TTS est un enjeu lui aussi capital. Cependant, l'épaisseur très faible des TTS (< 100 microns) rend la détermination de leurs caractéristiques mécaniques difficile. Des essais de flexion de micro-poutre entaillées, usinées et sollicitées sous MEB-FIB, ont permis d'identifier la ténacité des TTS et de révéler leur fragilité importante. Leur microstructure hétérogène a également un impact vis-à-vis du chemin de fissuration.Dans une dernière partie, une nouvelle approche numérique a été mise en place afin d'estimer les niveaux de déformations plastiques cumulées dans nos contacts. Cette simulation est faite en deux étapes. D'abord l'usure est simulée par un modèle multiphysique prenant en compte des phénomènes d'oxydation des surfaces. Ensuite, un calcul élasto-plastique est réalisé sur la surface usée numériquement afin d'estimer la déformation plastique cumulée lors du fretting. Ces simulations ont permis de confirmer l'apparition des TTS sous forme d'îlots par un processus plastique et démontrent l'intérêt des simulations pour expliquer la formation des TTS.Fretting is a surface degradation phenomenon occurring under low-amplitude alternating sliding. During fretting loading, superficial layers undergo microstructural transformations, appearing white after chemical etching, and become brittle. These layers are named Tribologically Transformed Structures (TTS) and contribute to debris formation. This research aims to understand the genesis of TTS in a plane-plane contact of Ti-Al-4V alloy subjected to fretting loading and to characterize their mechanical behavior.First, TTS formation was evaluated under various contact conditions, particularly by modifying the contact pressure. The kinetics of TTS formation are studied by analyzing the localization and morphology of TTS for different fretting cycle numbers. EDX chemical analyses, optical observations, and SEM of cross-sectional cuts of fretting scars after chemical etching are conducted. The results show that TTS initially appear locally as islands before forming a single, enlarged zone at the center of the contact with a thickness smaller than 100 microns. However, pressures inferior or equal to 200 MPa do not allow TTS to form, suggesting the establishment of a pressure threshold for their appearance in the contact.The second part of the study focuses on the characterization of the microstructure and crystallographic texture of TTS. Since TTS are nanograin materials, TEM analyses are needed to describe their structure. The phases are identified through electron diffraction patterns, while EDS and EELS chemical analyses are executed. The Astar method is employed to establish the local texture of TTS zones at a nanoscopic resolution. It emerges that TTS consist of two alternating layers of nanograins. One layer comprises larger alpha phase grains (20 to 50 nm) with a distinct crystallographic texture, while the other consists of smaller grains (also of the alpha phase) with a few nanometers in diameter and lacking an untextured. The presence of nitrogen is also detected in this layer. A mechanism of TTS formation by continuous dynamic recrystallization coupled with localization of plastic deformation into bands is introduced to explain the observed heterogeneous microstructure.The destruction of TTS is also a critical issue. However, the very low thickness of TTS (<100 microns) renders the determination of their mechanical characteristics challenging. Flexural tests of notched micro-cantilevers, machined and loaded in a SEM-FIB, were used to identify the fracture toughness of TTS and revealed their significant brittleness. Their heterogeneous microstructure also impacts the crack propagation path.Finally, a novel numerical approach has been implemented to estimate cumulative levels of plastic deformation within the contacts. This simulation is conducted in two stages. First, wear is simulated using a multiphysical model that takes into account surface oxidation phenomena. Then, an elasto-plastic calculation is performed on the worn surface to estimate the cumulative plastic deformation during fretting. These simulations confirm the appearance of TTS in the form of islands via a plastic process, highlighting the utility of simulations in explaining TTS formation

Heterogeneity in tribologically transformed structure (TTS) of Ti–6Al–4V under fretting

International audienceFretting wear is a surface degradation process caused by oscillatory motion and contact slipping. During gross slip, high local stresses and plastic deformation in the surface and subsurface can lead to the creation of a nanosized grained structure called Tribologically Transformed Structure (TTS). The current paper studies the formation of TTS in an alpha-beta Ti-6Al-4V alloy under fretting loading while changing the contact pressure and the number of fretting cycles.Cross-sections of wear scars are observed after polishing and chemical etching. Above a threshold pressure of 300 MPa, TTS appears early in the contact (before 1000 cycles) along with two other structures: a Third Body Layer (TBL) made of compacted debris and a General Deformed Layer (GDL) which is the plastic zone under the TTS. TTS first appears as islands and merges in the middle of the contact after enough cycles. Below 200 MPa, only TBL and GDL are formed. At 200 MPa, only small, localized TTS is found. All structures have the same chemical compositions as the initial bulk material except for the nitrided TBL. TTS has a very high hardness compared to the bulk. TTS was carefully extracted using a Focused Ion Beam (FIB) and its microstructure was observed with a Transmission Electron Microscope (TEM). It shows extreme grain refinement and is composed of two alternated zones. The first zone I is composed of α grains with a size of 20 to 50 nm with crystallographic texture. Zone II comprises nanosized equiaxed grains whose sizes range from 5 to 20 nm without texture. The results made it possible to establish a scenario of the appearance of the TTS according to the conditions of contact pressure and number of fretting cycles

IMGT/GeneInfo: enhancing V(D)J recombination database accessibility

IMGT/GeneInfo is a user-friendly online information system that provides information on data resulting from the complex mechanisms of immunoglobulin (IG) and T cell receptor (TR) V(D)J recombinations. For the first time, it is possible to visualize all the rearrangement parameters on a single page. IMGT/GeneInfo is part of the international ImMunoGeneTics information system® (IMGT), a high-quality integrated knowledge resource specializing in IG, TR, major histocompatibility complex (MHC), and related proteins of the immune system of human and other vertebrate species. The IMGT/GeneInfo system was developed by the TIMC and ICH laboratories (with the collaboration of LIGM), and is the first example of an external system being incorporated into IMGT. In this paper, we report the first part of this work. IMGT/GeneInfo_TR deals with the human and mouse TRA/TRD and TRB loci of the TR. Data handling and visualization are complementary to the current data and tools in IMGT, and will subsequently allow the modelling of V(D)J gene use, and thus, to predict non-standard recombination profiles which may eventually be found in conditions such as leukaemias or lymphomas. Access to IMGT/GeneInfo is free and can be found at http://imgt.cines.fr/GeneInfo