Images in Christmas Balls

We describe light-reflection properties of spherically curved mirrors, like balls in the Christmas tree. In particular, we study the position of the image which is formed somewhere beyond the surface of a spherical mirror, when an eye observes the image of a pointlike light source. The considered problem, originally posed by Abu Ali Hasan Ibn al-Haitham -- alias Alhazen -- more than a millennium ago, turned out to have the now well known analytic solution of a biquadratic equation, being still of great relevance, e.g. for the aberration-free construction of telescopes. We do not attempt to perform an exhaustive survey of the rich historical and engineering literature on the subject, but develop a simple pedagogical approach to the issue, which we believe to be of continuing interest in view of its maltreating in many high-school textbooks.Comment: 13 pages, 7 figures plain LaTeX; Also see http://cft.fis.uc.pt/eef/mirrors.htm, revised version has simplified formulas, more transparent for a wider audience, one reference adde

Optical fiber feasibility study in Accelerated Pavement Testing facility

The presented research has been carried out within the European project Intelligent Roads (INTRO). The major objective followed was to assess the potential of optical fiber for pavement monitoring in comparison with classical strain gauges. Thus, both measurement devices have been tested under the same conditions in a full scale Accelerated Pavement Testing (APT) at LAVOC. This facility allows the user to control different parameters such as loading configuration and temperature and, as a matter of facts, limit the disturbances. A total number of 10 strain gauges and 8 optical fibers have been installed and tested for various conditions. This study showed rather consistent and comparable results for both optical fiber and strain gauges measurements. The comparison with calculated deformation also highlighted the consistency of the measurements results. The sensitivity of the measurement system has also been highlighted and permitted to conclude with some recommendations for further developments

Pavement underlayers with a high percentage of re-used materials

Development of high performance underlayers with low cost materials and high percentage of re-us

Elaboration d'un plan des classes de trafic pondéral du réseau routier de la ville de Lausanne

La présente étude vise à fournir une analyse du trafic lourd présent sur le réseau routier de la ville de Lausanne et établir la classe de trafic pondéral de chacune des routes du réseau principal. Le rapport établi donne les explications nécessaires à la compréhension de la démarche et à l’utilisation du fichier Excel « Détails de la détermination des CT » qui constitue l’élément principal de l’étude. Ce fichier contient toutes les étapes depuis le recensement des différents bus par tronçon de route jusqu’à la détermination de la classe de trafic, il reprend l’ensemble des données et donne les résultats obtenus

Dissemination of antibiotic resistance genes associated with the sporobiota in sediments impacted by wastewater.

Aquatic ecosystems serve as a dissemination pathway and a reservoir of both antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARG). In this study, we investigate the role of the bacterial sporobiota to act as a vector for ARG dispersal in aquatic ecosystems. The sporobiota was operationally defined as the resilient fraction of the bacterial community withstanding a harsh extraction treatment eliminating the easily lysed fraction of the total bacterial community. The sporobiota has been identified as a critical component of the human microbiome, and therefore potentially a key element in the dissemination of ARG in human-impacted environments. A region of Lake Geneva in which the accumulation of ARG in the sediments has been previously linked to the deposition of treated wastewater was selected to investigate the dissemination of <i>tet</i> (W) and <i>sul</i> 1, two genes conferring resistance to tetracycline and sulfonamide, respectively. Analysis of the abundance of these ARG within the sporobiome (collection of genes of the sporobiota) and correlation with community composition and environmental parameters demonstrated that ARG can spread across the environment with the sporobiota being the dispersal vector. A highly abundant OTU affiliated with the genus <i>Clostridium</i> was identified as a potential specific vector for the dissemination of <i>tet</i> (W), due to a strong correlation with <i>tet</i> (W) frequency (ARG copy numbers/ng DNA). The high dispersal rate, long-term survival, and potential reactivation of the sporobiota constitute a serious concern in terms of dissemination and persistence of ARG in the environment