Seeding hESCs to achieve optimal colony clonality

Human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) have promising clinical applications which often rely on clonally-homogeneous cell populations. To achieve this, it is important to ensure that each colony originates from a single founding cell and to avoid subsequent merging of colonies during their growth. Clonal homogeneity can be obtained with low seeding densities; however, this leads to low yield and viability. It is therefore important to quantitatively assess how seeding density affects clonality loss so that experimental protocols can be optimised to meet the required standards. Here we develop a quantitative framework for modelling the growth of hESC colonies from a given seeding density based on stochastic exponential growth. This allows us to identify the timescales for colony merges and over which colony size no longer predicts the number of founding cells. We demonstrate the success of our model by applying it to our own experiments of hESC colony growth; while this is based on a particular experimental set-up, the model can be applied more generally to other cell lines and experimental conditions to predict these important timescales

Comparing Open-Ended Choice Experiments and Experimental Auctions: An Application to Golden Rice

We use two different experimental valuation methods to estimate consumer demand for genetically-modified golden rice. The first is an open-ended choice experiment (OECE) where participants name the quantities of golden rice and conventional rice demanded at each of several price combinations, one of which will be randomly chosen as binding. This allows us to estimate market demand by aggregating demand across participants. This estimate of market demand also allows us to estimate own-price elasticity and consumer surplus for golden rice. Comparing willingness-to-pay (WTP) estimates from the OECE with those from a uniform-price auction, we find that OECE WTP estimates exhibit less affiliation across rounds, and the effects of positive and negative information under the OECE are more consistent with prior expectations and existing studies. We also find that while auction WTP estimates more than double across five rounds, OECE WTP estimates are stable across rounds and are always roughly equal to those from the final auction round.choice experiments, experimental auctions, golden rice, valuation

Correlated random walks of human embryonic stem cells in vitro

We perform a detailed analysis of the migratory motion of human embryonic stem cells in two-dimensions, both when isolated and in close proximity to another cell, recorded with time-lapse microscopic imaging. We show that isolated cells tend to perform an unusual locally anisotropic walk, moving backwards and forwards along a preferred local direction correlated over a timescale of around 50 min and aligned with the axis of the cell elongation. Increasing elongation of the cell shape is associated with increased instantaneous migration speed. We also show that two cells in close proximity tend to move in the same direction, with the average separation of m or less and the correlation length of around 25 μm, a typical cell diameter. These results can be used as a basis for the mathematical modelling of the formation of clonal hESC colonies

Etude comparative de la résorption alvéolaire mandibulaire après radiothérapie et/ou chimiothérapie chez l’homme

A prospective study of mandibular alveolar bone resorption has been achieved on 49 patients with upper aerodigestive tract tumor and treated by radiation therapy and/or a chemotherapy, on 30 patients who were not treated. All these patients were subjected to dental extractions followed by X rays in coronal and sagittal view, during at least one year, at the rate of one X ray every three months. The comparative study enabled to show a quite similar resorption for the two population, a slightly more important resorption on incisor and canin regions, and a stopping of the resorption about five months later according to dental extractions.Radiation therapy and chemotherapy (therapeutic doses) may not have significant influence on alveolar bone resorption after dental extractions.Une étude prospective de la résorption osseuse alvéolaire mandibulaire a été réalisée sur 49 patients atteints d’un cancer des voies aéro-digestives supérieures et traités par radiothérapie et/ou chimiothérapie sur 30 patients ne recevant pas ce type de traitement.Tous ces patients ont subi des avulsions dentaires suivies de radiographies en incidence frontale et sagittale, pendant une période minimale de un an, à raison d’une radiographie tous les trois mois environ.L’étude comparative a permis de montrer des phénomènes de résorption sensiblement identique pour les deux populations, une résorption légèrement plus prononcée au niveau de la région incisivo-canine, et une stabilisation de la résorption vers le 5ème mois suivant les avulsions dentaires.La radiothérapie et la chimiothérapie (à doses thérapeutiques) ne semblent pas influer de façon significative sur l’involution osseuse alvéolaire post extractionnelle

Experimental observations of topologically guided water waves within non-hexagonal structures

We investigate symmetry-protected topological water waves within a strategically engineered square lattice system. Thus far, symmetry-protected topological modes in hexagonal systems have primarily been studied in electromagnetism and acoustics, i.e. dispersionless media. Herein, we show experimentally how crucial geometrical properties of square structures allow for topological transport that is ordinarily forbidden within conventional hexagonal structures. We perform numerical simulations that take into account the inherent dispersion within water waves and devise a topological insulator that supports symmetry-protected transport along the domain walls. Our measurements, viewed with a high-speed camera under stroboscopic illumination, unambiguously demonstrate the valley-locked transport of water waves within a non-hexagonal structure. Due to the tunability of the energy's directionality by geometry, our results could be used for developing highly-efficient energy harvesters, filters and beam-splitters within dispersive media

Functional Liftings of Vectorial Variational Problems with Laplacian Regularization

We propose a functional lifting-based convex relaxation of variational problems with Laplacian-based second-order regularization. The approach rests on ideas from the calibration method as well as from sublabel-accurate continuous multilabeling approaches, and makes these approaches amenable for variational problems with vectorial data and higher-order regularization, as is common in image processing applications. We motivate the approach in the function space setting and prove that, in the special case of absolute Laplacian regularization, it encompasses the discretization-first sublabel-accurate continuous multilabeling approach as a special case. We present a mathematical connection between the lifted and original functional and discuss possible interpretations of minimizers in the lifted function space. Finally, we exemplarily apply the proposed approach to 2D image registration problems.Comment: 12 pages, 3 figures; accepted at the conference "Scale Space and Variational Methods" in Hofgeismar, Germany 201

Evolution de la morphologie mandibulaire au cours de la sénescence chez l’homme

The mandible is situated in a complex matritial context. It takes part in a great number of functions: manducation, deglutition, respiration and has an important part in gesticulations.On the other hand, it is deeply involved in the cervico-cephalic static of human being.The involution or simply changes of these different functions due to age can bring about variations of the mandibular morphology.The comparison between two subgroups of population, one made of 25 to 45 year-old subjects, the other made of 75 to 95 year-old subjects has led us to the following conclusions.The posterior mandibular regions (condyle, coronoid apophyses, gonion angle) remain relatively stable during life.The anterior mandibular regions are much more malleable even in toothed old men.We noticed :— a discrete but real apposition process in the region of the geni-apophyses;— an important appositional process in the anterior part of the basilar edge and in the region of the symphysis.La mandibule est située dans un contexte matriciel complexe; elle participe à un grand nombre de fonctions, mastication, déglutition, respiration et participe activement à la mimique. D’autre part, elle est profondément impliquée dans la statique cervico-céphalique de l’individu.L’involution, ou plus simplement les modifications avec l’âge de ces différentes fonctions sont susceptibles d’entraîner des variations de la morphologie mandibulaire.La comparaison de deux sous-populations, l’une constituée de sujets âgés de 25 à 45 ans, l’autre de sujets âgés de 75 à 95 ans nous a mené aux conclusions suivantes:— les régions mandibulaires postérieures (condyle, coroné, angle goniaque) restent relativement stables au cours de la vie.— les régions mandibulaires antérieures sont beaucoup plus malléables même chez le vieillard denté. On note:= un processus d’apposition discret mais réel dans la région des apophyses geni.= un processus appositionnel important dans la partie antérieure du rebord basilaire et dans la région de la symphyse

Improving surface acousto-optical interaction by high aspect ratio electrodes

International audienceThe acousto-optical interaction of an optical wave confined inside a waveguide and a surface acoustic wave launched by an interdigital transducer (IDT) at the surface of a piezoelectric material is considered. The IDT with high aspect ratio electrodes supports several acoustic modes that are strongly confined to the surface, causing a significant increase in the strain underneath the surface. A finite element method is employed to model the surface acoustic waves generated by a finite length IDT with 12 electrode pairs and subsequently to study their interaction with an optical wave propagating in a waveguide buried in the lithium niobate substrate supporting the electrodes. The interaction can be increased up to 600 times using these new types of surface acoustic waves as compared to using a conventional IDT with thin electrodes. This result could find applications in improved acousto-optical integrated modulators

Contribution à l’étude du vieillissement facial. Evolution des tissus mous

Ageing of the face is one of the most apparent. Face varies in shape and aspect. The reasons of these modifications are various: skin ageing, lost of teeth, changes in facial skeleton and modifications of the whole facial soft tissues.Soft tissues evolution in mentalis and anterior nasal spin regions was studied on a 206, 21 to 101 years old subjects population.It was shown that in both men and women samples the soft tissues thickness increase in the mentalis region and decrease in that of anterior nasal spin.Le vieillissement facial est l’un des plus visibles. Le visage change d’aspect et de forme. Les causes de ces transformations sont multiples: sénescence du revêtement cutané lui-même, apparition des édentements, modifications du squelette facial, modifications des tissus mous faciaux dans leur ensemble. Les tissus mous des régions mentonnière et naso-labiale ont été étudiés sur une population de 206 sujets âgés de 21 à 101 ans. Il apparait que l’épaisseur des tissus mous dans la région du menton augmente avec l’âge chez l’homme et chez la femme, que cette augmentation est plus nette chez cette dernière et qu’elle se manifeste dans les deux sexes vers cinquante ans. Au contraire, l’épaisseur des tissus mous dans la région naso-labiale évolue dans le sens de la diminution dans les deux sexes et d’une façon plus progressive au cours de la vie.Il est vraisemblable que l’on puisse rapprocher ces modifications morphologiques de l’existence d’une activité fonctionnelle différente des tissus mous des étages moyen et inférieur de la face