Contact lens | EPFL Graph Search

Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmetic or therapeutic reasons. In 2010, the worldwide market for contact lenses was estimated at

6.1 billion, while the US soft lens market was estimated at

2.1 billion. Multiple analysts estimated that the global market for contact lenses would reach $11.7 billion by 2015. , the average age of contact lens wearers globally was 31 years old, and two-thirds of wearers were female. People choose to wear contact lenses for many reasons. Aesthetics and cosmetics are main motivating factors for people who want to avoid wearing glasses or to change the appearance or color of their eyes. Others wear contact lenses for functional or optical reasons. When compared with spectacles, contact lenses typically provide better peripheral vision,

Contact Mechanics for Hyperelastic Materials

Youssef Eddebbarh

Understanding the mechanical behavior of soft materials is of great importance for many applica-tions, especially for bioengineering and clinical applications. Hertzian theory is frequently used to characterize the mechanical properties of such materials. However, these materials undergo large deformations resulting in non-linear stress-strain response, which cannot be accurately captured by Hertzian contact. These materials are also rate sensitive, where at high velocities, external e˙ects such as air can influence the mechanical response. In this study, we experimentally in-vestigated the contact response of a soft spherical impactor on a rigid substrate and by using the principle of Total Internal reflection, we directly measured the contact radius. The e˙ects of specimen size, loading rate and boundary conditions were also examined and we found that, for the studied velocities, only the boundary conditions a˙ects both the radius-displacement and load-displacement relationships, leading to deviations from the theory at di˙erent indentation depths. We finished by setting up an experiment consisting of a pendulum for studying the e˙ects of high velocities and the influence air.

2021

Analysis of long-range gene regulation at the HoxD locus

Ana Rita De Carvalho Amândio Lhopitallier

Hoxd genes are essential for the development of the various body axes in vertebrates and hence the underlying regulatory mechanisms are of paramount importance. Among these various mechanisms are long-range acting enhancers, which are located in the two adjacent regulatory landscapes. Analyses of chromatin architecture at this gene cluster has revealed the existence of two topologically associating domains (TADs) flanking the cluster and encompassing these regulatory landscapes. However, the dynamics of such regulatory regions as well as the stability and functional contribution of specific enhancer-promoter interactions during development remains to be established. In this work, we analysed the 3D chromatin organization and transcription profile at the HoxD locus, at different time points during genital tubercle (GT) development, and observe that the 3D conformation of this regulatory region predates the embryonic emergence of the GT. Along with this tissue development, we observe a reduction in transcript levels correlating with a decrease in enhancer-promoter chromatin loops within the adjacent gene desert. This decrease occurs while maintaining a subset of CTCF/Cohesin associated contacts, which are preserved independently from the transcriptional status of the gene cluster. To further explore the functional contribution of this regulatory landscape, we used CRISPR-Cas9 technology to generate mice carrying partial deletions of this region, as well as targeted deletions of both transient (enhancer associated) and constitutive (CTCF/Cohesin associated) contacts. We observe that single deletions of both transient and constitutive contacts displayed little if any effect on Hoxd genes expression in the GT. On the contrary, the single deletion of a previous characterized Hoxd enhancer, the Prox element, or deletions comprising several enhancers, result in the reduction of Hoxd genes expression levels. Overall our results suggest that not all enhancer elements within a complex regulatory landscape have the same functional strength, and highlight the existence of a dynamic yet robust system to tightly regulate Hoxd genes expression.

EPFL2019

Analysis of long-range gene regulation at the HoxD locus

Ana Rita De Carvalho Amândio Lhopitallier

EPFL2019