Height Fluctuations and Surface Gradients in Topographic Measurements.

Topographic maps are composed of pixels associated with coordinates (x, y, z) on a surface. Each pixel location (x, y) is linked with fluctuations in a measured height sample (z). Fluctuations here are uncertainties in heights estimated from multiple topographic measurements at the same position. Height samples (z) are measured at individual locations (x, y) in topographic measurements and compared with gradients on topographies. Here, gradients are slopes on a surface calculated at the scale of the sampling interval from inclination angles of vectors that are normal to triangular facets formed by adjacent height samples (z = z(x, y)). Similarities between maps of gradients logs and height fluctuations are apparent. This shows that the fluctuations are exponentially dependent on local surface gradients. The highest fluctuations correspond to tool/material interactions for turned surfaces and to regions of maximum plastic deformation for sandblasted surfaces. Finally, for abraded, heterogeneous, multilayer surfaces, fluctuations are dependent on both abrasion and light/sub-layer interactions. It appears that the natures of irregular surface topographies govern fluctuation regimes, and that regions which are indicative of surface functionality, or integrity, can have the highest fluctuations.

[Affirming one's gender: supporting and accompanying trans young people and their families]. / Affirmer son genre : soutenir et accompagner les jeunes trans et leur famille.

Support for trans teenagers and young adults is based on a comprehensive approach to care, taking into account the needs and desires of the individual and his or her environment. It involves welcoming their requests and listening to their questions, in order to help them assert themselves. The aim is to be particularly attentive to these young people, sometimes in vulnerable psychological, social and educational situations, as well as to their families, by welcoming them, listening to them and taking charge of them through multidisciplinary networks.

Top-down Determination of Fluctuations in Topographic Measurements.

A top-down method is presented and studied for quantifying topographic map height (z) fluctuations directly from measurements on surfaces of interest. Contrary to bottom-up methods used in dimensional metrology, this method does not require knowledge of transfer functions and fluctuations of an instrument. Fluctuations are considered here to be indicative of some kinds of uncertainties. Multiple (n), successive topographic measurements (z = z(x,y)) are made at one location without moving the measurand relative to the measurement instrument. The measured heights (z) at each position (x,y) are analyzed statistically. Fluctuation maps are generated from the calculated variances. Three surfaces were measured with two interferometric measuring microscopes (Bruker ContourGT™ and Zygo NewView™ 7300). These surfaces included an anisotropic, turned surface; an isotropic, sandblasted surface; and an abraded, heterogeneous, multilayer surface having different, complex, multiscale morphologies. In demonstrating the method, it was found that few non-measured points persisted for all 100 measurements at any location. The distributions of uncertainties are similar to those of certain features on topographic maps at the same locations, suggesting that topographic features can augment measurement fluctuations. This was especially observed on the abraded ophthalmic lens; a scratch divides the topographic map into two zones with different uncertainty values. The distributions of fluctuations can be non-Gaussian. Additionally, they can vary between regions within some measurements.

[Ethical implications of supporting trans or questioning children and adolescents: Articulation with reproductive health]. / Enjeux éthiques de l'accompagnement des enfants et des adolescents et adolescentes trans ou en questionnement : articulation à la santé reproductive.

Supporting children and adolescents who are trans or who are questioning cannot be done without an ethical reflection on one's own practice as a health professional. It is important to consider the young person as a whole, including reproductive health issues. This article proposes, through the principles of Beauchamps and Childress, an ethical reflection on the issues of beneficence - not maleficence, and of autonomy and justice for adolescents, young adults, and future trans or questioning parents. For adolescents, concerning the possibilities of medical treatment of gender affirmation, we need to propose information in terms of impact on fertility and, if necessary, proposals for the possibilities of preserving their reproductive capacities. These issues require to question the state of scientific knowledge in terms of parenthood of trans people and questioning. We propose here a state of knowledge of these realities, put in perspectives of the axes of ethical reflections inherent to guidance. In fine, it appears that the major ethical stake concerns the child to be born. Finally, it is necessary to consider the quality of life of the future parents and the impact of their medical follow-up.

Title: Enjeux éthiques de l'accompagnement des enfants et des adolescents et adolescentes trans ou en questionnement : articulation à la santé reproductive. Abstract: L'accompagnement des enfants et des adolescents et adolescentes trans ou en questionnement ne peut faire l'économie d'une pensée éthique réflexive de sa propre pratique en tant que professionnel de santé. Il est important de considérer le jeune dans sa globalité, et cela également en ce qui concerne les enjeux en santé reproductive. Cet article propose, au travers des principes de Tom Beauchamps et James Childress1, une réflexion éthique des enjeux de bienfaisance/non nuisance, d'autonomie et de justice, pour les adolescents, jeunes adultes, et futurs parents trans ou en questionnement. Pour les adolescents et les adolescentes, autour des possibilités de traitement médical d'affirmation de genre, il est nécessaire de proposer des informations, en termes d'impact sur la fertilité et, le cas échéant, des propositions de possibilités de conservation de ses capacités reproductives. Ces enjeux nécessitent d'interroger l'état des connaissances scientifiques en termes de parentalité des personnes trans et en questionnement. Nous proposons ici un état des lieux des connaissances de ces réalités, mises en perspective des axes de réflexions éthiques inhérentes aux accompagnements. In fine, il apparaît que l'enjeu éthique majeur porte sur l'enfant à naître. À cela, il est nécessaire de considérer la qualité de vie des futurs parents et l'impact des accompagnements médicaux des personnes.

Self-organized swimming with odd elasticity.

We theoretically investigate self-oscillating waves of an active material, which were recently introduced as a nonsymmetric part of the elastic moduli, termed odd elasticity. Using Purcell's three-link swimmer model, we reveal that an odd-elastic filament at low Reynolds number can swim in a self-organized manner and that the time-periodic dynamics are characterized by a stable limit cycle generated by elastohydrodynamic interactions. Also, we consider a noisy shape gait and derive a swimming formula for a general elastic material in the Stokes regime with its elasticity modulus being represented by a nonsymmetric matrix, demonstrating that the odd elasticity produces biased net locomotion from random noise.

Driving a Microswimmer with Wall-Induced Flow.

Active walls such as cilia and bacteria carpets generate background flows that can influence the trajectories of microswimmers moving nearby. Recent advances in artificial magnetic cilia carpets offer the potentiality to use a similar wall-generated background flow to steer bio-hybrid microrobots. In this paper, we provide some ground theoretical and numerical work assessing the viability of this novel means of swimmer guidance by setting up a simple model of a spherical swimmer in an oscillatory flow and analysing it from the control theory viewpoint. We show a property of local controllability around the reference free trajectories and investigate the bang-bang structure of the control for time-optimal trajectories, with an estimation of the minimal time for suitable objectives. By direct simulation, we have demonstrated that the wall actuation can improve the wall-following transport by nearly 50%, which can be interpreted by synchronous flow structure. Although an open-loop control with a periodic bang-bang actuation loses some robustness and effectiveness, a feedback control is found to improve its robustness and effective transport, even with hydrodynamic wall-swimmer interactions. The results shed light on the potentialities of flow control and open the way to future experiments on swimmer guidance.

Control and controllability of microswimmers by a shearing flow.

With the continuing rapid development of artificial microrobots and active particles, questions of microswimmer guidance and control are becoming ever more relevant and prevalent. In both the applications and theoretical study of such microscale swimmers, control is often mediated by an engineered property of the swimmer, such as in the case of magnetically propelled microrobots. In this work, we will consider a modality of control that is applicable in more generality, effecting guidance via modulation of a background fluid flow. Here, considering a model swimmer in a commonplace flow and simple geometry, we analyse and subsequently establish the efficacy of flow-mediated microswimmer positional control, later touching upon a question of optimal control. Moving beyond idealized notions of controllability and towards considerations of practical utility, we then evaluate the robustness of this control modality to sources of variation that may be present in applications, examining in particular the effects of measurement inaccuracy and rotational noise. This exploration gives rise to a number of cautionary observations, which, overall, demonstrate the need for the careful assessment of both policy and behavioural robustness when designing control schemes for use in practice.

The asymptotic coarse-graining formulation of slender-rods, bio-filaments and flagella.

The inertialess fluid-structure interactions of active and passive inextensible filaments and slender-rods are ubiquitous in nature, from the dynamics of semi-flexible polymers and cytoskeletal filaments to cellular mechanics and flagella. The coupling between the geometry of deformation and the physical interaction governing the dynamics of bio-filaments is complex. Governing equations negotiate elastohydrodynamical interactions with non-holonomic constraints arising from the filament inextensibility. Such elastohydrodynamic systems are structurally convoluted, prone to numerical errors, thus requiring penalization methods and high-order spatio-temporal propagators. The asymptotic coarse-graining formulation presented here exploits the momentum balance in the asymptotic limit of small rod-like elements which are integrated semi-analytically. This greatly simplifies the elastohydrodynamic interactions and overcomes previous numerical instability. The resulting matricial system is straightforward and intuitive to implement, and allows for a fast and efficient computation, more than a hundred times faster than previous schemes. Only basic knowledge of systems of linear equations is required, and implementation achieved with any solver of choice. Generalizations for complex interaction of multiple rods, Brownian polymer dynamics, active filaments and non-local hydrodynamics are also straightforward. We demonstrate these in four examples commonly found in biological systems, including the dynamics of filaments and flagella. Three of these systems are novel in the literature. We additionally provide a Matlab code that can be used as a basis for further generalizations.