Canaloplasty: current value in the management of glaucoma

Canaloplasty is a nonpenetrating blebless surgical technique for open-angle glaucoma, in which a flexible microcatheter is inserted within Schlemm's canal for the entire 360 degrees. When the microcatheter exits the opposite end, a 10-0 prolene suture is tied and it is then withdrawn, by pulling microcatheter back through the canal in the opposite direction. Ligation of prolene suture provides tension on the canal and facilitates aqueous outflow. The main advantage of canaloplasty is that this technique avoids the major complications of fistulating surgery related to blebs and hypotony. Currently, canaloplasty is performed in glaucoma patients with early to moderate disease and combination with cataract surgery is a suitable option in patients with clinically significant lens opacities

Dynamics of anchored oscillating nanomenisci

We present a self-contained study of the dynamics of oscillating nanomenisci anchored on nanometric topographical defects around a cylindrical nanofiber with a radius below 100 nm. Using frequency-modulation atomic force microscopy (FM-AFM), we show that the friction coefficient surges as the contact angle is decreased. We propose a theoretical model within the lubrification approximation that reproduces the experimental data and provides a comprehensive description of the dynamics of the nanomeniscus. The dissipation pattern in the vicinity of the contact line and the anchoring properties are discussed as a function of liquid and surface properties in addition to the forcing conditions

Application of physical clogging models to Managed Aquifer Recharge: a review of modelling approaches from engineering fields

Managed Aquifer Recharge (MAR) sites suffer from the long-lasting problem of clogging. The causes of clogging are physical, biological, chemical and mechanical processes and their complex interaction, with physical clogging being recognised as the predominant process. The intrusion and deposition of particles during water recharge affect the hydraulic properties of the infiltration surface, resulting in a decline in the infiltration capacity of the site over the operating years. Cleaning operations are necessary to restore the original infiltration rates. For this purpose, assessing the risk of clogging can determine the site’s vulnerability and improve the scheme’s design. Numerical models are essential to replicate physical clogging processes and predict the decline in infiltration rates. So far, predictive tools for physical clogging assessment have been missing in MAR literature. Hence, the purpose of this study is to analyse and reorganise physical clogging models from applied engineering fields dealing with water infiltration in natural heterogeneous systems. The modelling approaches are illustrated, starting from the main assumptions and conceptualisation of the soil volume and intruding particles. The individual processes are untangled from the multiple studies and reorganised in a systematic comparison of mathematical equations relevant to MAR applications. The numerical models’ predictive power is evaluated for transferability, following limitations and recommendations for a process-based model applicable to surface spreading schemes. Finally, perspectives are given for clogging risk assessment at MAR sites from modelling and site characterisation. The predictive tool could assist decision-makers in planning the MAR site by implementing cost-effective strategies to lower the risk of physical clogging

Patient Safety in Ophthalmology

AbstractModern ophthalmic surgery has reached very high safety standards. Yet, given the large number of ophthalmic procedures, medical errors are common in eye care. This chapter presents general safety issues in ophthalmic surgery and focuses on the most common procedures: cataract surgery and intravitreal injection therapy. The literature on the translation of safety strategies to ophthalmology is summarized alongside with guidance elaborated by professional and regulatory bodies that are of greatest importance in eye care. The perspective adopted in this chapter is largely that of ophthalmology trainees, who are asked to guide the progression of ophthalmology toward safer care

Lacunar Infarction in Type 2 Diabetes Is Associated with an Elevated Intracranial Arterial Pulsatility Index

Purpose: The arterial pulsatility index (PI) is measured by transcranial Doppler ultrasonography (TCD) and is postulated to reflect the vascular resistance distal to the artery being examined. An increased PI of the intracranial artery is often reported with diabetes mellitus (DM), old age, hypertension, intracranial hypertension, vascular dementia, and small artery disease. Microvascular complication of DM, which may contribute to cerebral infarction, involves the small perforating artery and may influence the PI of the proximal artery. Materials and Methods: We performed a TCD examination in patients with type 2 DM with acute lacunar infarction (DML, n = 35), type 2 DM without cerebral infarction (DMO, n = 69), and in control cases with no DM or cerebral infarction (control group, n = 41). We then compared the TCD findings among these groups. Results: The PI was significantly higher in the DML and DMO groups than in the control group (1.05, 0.93, 0.73. respectively, for the right middle cerebral artery; 1.04, 0.90, 0.73, respectively, for the left middle cerebral artery; 0.97, 0.89, 0.70, respectively, for the basilar artery). The PI was also significantly higher in the DML group than in the DMO group for both middle cerebral arteries. The flow velocity was comparable among the three groups. Conclusion: The elevated PI of the intracranial arteries may reflect diabetic cerebral microvascular complications. The PI measurement using TCD may be a useful predictor of lacunar infarction in type 2 DM patients

Self-propelled active droplets : a short story of their interactions.

Une fois immergées dans un liquide saturé en surfactants, une microgoutte composée d’eau ou d’huile peut s’auto-propulser à une vitesse de l’ordre de quelques rayons par seconde. Bien que l’origine physico-chimique exacte de ce phénomène reste encore débattue, de récents travaux ont permis de comprendre qu’il est lié à la solubilisation de ces gouttes dans leur milieu. Une goutte active apparaît alors comme émettant un ensemble d’espèces chimiques, appelé soluté, qui a pour effet d’augmenter la tension de surface. Par conséquent, une distribution inhomogène de soluté à l’interface de la goutte génère un écoulement dit de Marangoni qui propulse la goutte. L’autopropulsion s’explique alors par une instabilité issue du couplage entre la dynamique de transport du soluté et l’écoulement Marangoni qui en résulte.Cette thèse a pour but d'étudier les interactions entre plusieurs de ces gouttes ou en présence d’un confinement. Le premier chapitre introduit des notions générales de mécanique des fluides à bas Reynolds ainsi qu’une description de systèmes de gouttes actives étudiés expérimentalement. Le deuxième chapitre présente le cadre mathématique modélisant l’autopropulsion d’une goutte seule, puis fournit une discussion traitant des interactions hydro-chimiques attendues en présence de plusieurs gouttes ou d’un mur. Le troisième chapitre présente une dérivation exacte des interactions hydro-chimiques entre une goutte active et un mur dans le cas axisymétrique. Cette approche a permis de quantifier l’influence de l’advection du soluté sur la dynamique de collision et de soulever des effets de retard survenant à haut nombre de Péclet. Dans le quatrième chapitre, on étudie alors les conséquences sur la dynamique de collision d’une différence de taille entre deux gouttes actives. On montre alors que même une faible différence de rayon peut conduire à des régimes très différents et appelés rebond, poursuite et pause. Le cinquième chapitre introduit un modèle simplifié de la dynamique d’une goutte active, utilisé dans l’étude des collisions obliques. Si une collision symétrique tend à aligner les gouttes, des conditions initiales asymétriques peuvent à l’inverse les disperser. Enfin, le sixième chapitre apporte la conclusion de ce manuscrit et suggère diverses perspectives pour la suite de l'étude des interactions de gouttes actives.When immersed in a surfactant-saturated fluid, droplets made out of oil or water can self-propel at velocities attaining several radii per second. While the exact physicochemical mechanisms underlying this behaviour are still under debate, recent studies have shown that they are related to the solubilisation of the droplet. Indeed, these active droplets release a mixture of chemical species, i.e. solute, locally modifying their surface tension. When a non-uniform solute distribution is attained at the droplet surface, the imbalance in surface tension induces Marangoni flows, producing a net fluid flow and the droplet's swimming motion. Thus, a droplet's self-propulsion results from the coupling of solute transport dynamics to the resulting Marangoni flows. In this thesis, we aim to study the behaviour of several active droplets interacting with each other, as well as with fixed boundaries. In the first chapter, we introduce some key aspects of low Reynolds number fluid mechanics and describe the physical system of interest, namely active droplets like those used in recent experiments. The mathematical framework employed to model the self-propulsion of active droplets is presented in chapter two, together with a preliminary discussion of the hydro-chemical interactions involved in the presence of multiple droplets and generic boundaries. In chapter three we provide the exact derivation of the hydro-chemical interactions involved for a droplet colliding against a rigid wall, or with another active droplet. In the fourth chapter, we study the influence of the size-ratio on head-on collisions of two droplets. Here we show that collision dynamics are highly dependent on the droplet's size ratio, leading to three different regimes, i.e. rebound, chasing and pausing. In chapter five we introduce a simplified framework for modelling the behaviour of active droplets' dynamics, which is then employed to study the general case of oblique collisions. While we notice a significant alignment of the droplets when initial conditions are symmetric, we show that the system can become highly asymmetric with the introduction of a misalignment in the drops' initial conditions. In the sixth and final chapter, we provide several perspectives regarding the study of active droplet interactions

Norman L. Brown (éd.). Les énergies renouvelables : techniques d'utilisation dans le Tiers Monde rural

Lippera Daniel. Norman L. Brown (éd.). Les énergies renouvelables : techniques d'utilisation dans le Tiers Monde rural. In: Politique étrangère, n°2 - 1981 - 46ᵉannée. pp. 488-489

Norman L. Brown (éd.). Les énergies renouvelables : techniques d'utilisation dans le Tiers Monde rural

Lippera Daniel. Norman L. Brown (éd.). Les énergies renouvelables : techniques d'utilisation dans le Tiers Monde rural. In: Politique étrangère, n°2 - 1981 - 46ᵉannée. pp. 488-489

Gouttes actives auto-propulsées : une histoire d'interaction.

When immersed in a surfactant-saturated fluid, droplets made out of oil or water can self-propel at velocities attaining several radii per second. While the exact physicochemical mechanisms underlying this behaviour are still under debate, recent studies have shown that they are related to the solubilisation of the droplet. Indeed, these active droplets release a mixture of chemical species, i.e. solute, locally modifying their surface tension. When a non-uniform solute distribution is attained at the droplet surface, the imbalance in surface tension induces Marangoni flows, producing a net fluid flow and the droplet's swimming motion. Thus, a droplet's self-propulsion results from the coupling of solute transport dynamics to the resulting Marangoni flows. In this thesis, we aim to study the behaviour of several active droplets interacting with each other, as well as with fixed boundaries. In the first chapter, we introduce some key aspects of low Reynolds number fluid mechanics and describe the physical system of interest, namely active droplets like those used in recent experiments. The mathematical framework employed to model the self-propulsion of active droplets is presented in chapter two, together with a preliminary discussion of the hydro-chemical interactions involved in the presence of multiple droplets and generic boundaries. In chapter three we provide the exact derivation of the hydro-chemical interactions involved for a droplet colliding against a rigid wall, or with another active droplet. In the fourth chapter, we study the influence of the size-ratio on head-on collisions of two droplets. Here we show that collision dynamics are highly dependent on the droplet's size ratio, leading to three different regimes, i.e. rebound, chasing and pausing. In chapter five we introduce a simplified framework for modelling the behaviour of active droplets' dynamics, which is then employed to study the general case of oblique collisions. While we notice a significant alignment of the droplets when initial conditions are symmetric, we show that the system can become highly asymmetric with the introduction of a misalignment in the drops' initial conditions. In the sixth and final chapter, we provide several perspectives regarding the study of active droplet interactions.Une fois immergées dans un liquide saturé en surfactants, une microgoutte composée d’eau ou d’huile peut s’auto-propulser à une vitesse de l’ordre de quelques rayons par seconde. Bien que l’origine physico-chimique exacte de ce phénomène reste encore débattue, de récents travaux ont permis de comprendre qu’il est lié à la solubilisation de ces gouttes dans leur milieu. Une goutte active apparaît alors comme émettant un ensemble d’espèces chimiques, appelé soluté, qui a pour effet d’augmenter la tension de surface. Par conséquent, une distribution inhomogène de soluté à l’interface de la goutte génère un écoulement dit de Marangoni qui propulse la goutte. L’autopropulsion s’explique alors par une instabilité issue du couplage entre la dynamique de transport du soluté et l’écoulement Marangoni qui en résulte.Cette thèse a pour but d'étudier les interactions entre plusieurs de ces gouttes ou en présence d’un confinement. Le premier chapitre introduit des notions générales de mécanique des fluides à bas Reynolds ainsi qu’une description de systèmes de gouttes actives étudiés expérimentalement. Le deuxième chapitre présente le cadre mathématique modélisant l’autopropulsion d’une goutte seule, puis fournit une discussion traitant des interactions hydro-chimiques attendues en présence de plusieurs gouttes ou d’un mur. Le troisième chapitre présente une dérivation exacte des interactions hydro-chimiques entre une goutte active et un mur dans le cas axisymétrique. Cette approche a permis de quantifier l’influence de l’advection du soluté sur la dynamique de collision et de soulever des effets de retard survenant à haut nombre de Péclet. Dans le quatrième chapitre, on étudie alors les conséquences sur la dynamique de collision d’une différence de taille entre deux gouttes actives. On montre alors que même une faible différence de rayon peut conduire à des régimes très différents et appelés rebond, poursuite et pause. Le cinquième chapitre introduit un modèle simplifié de la dynamique d’une goutte active, utilisé dans l’étude des collisions obliques. Si une collision symétrique tend à aligner les gouttes, des conditions initiales asymétriques peuvent à l’inverse les disperser. Enfin, le sixième chapitre apporte la conclusion de ce manuscrit et suggère diverses perspectives pour la suite de l'étude des interactions de gouttes actives