Droplet actuation induced by coalescence: experimental evidences and phenomenological modeling

This paper considers the interaction between two droplets placed on a substrate in immediate vicinity. We show here that when the two droplets are of different fluids and especially when one of the droplet is highly volatile, a wealth of fascinating phenomena can be observed. In particular, the interaction may result in the actuation of the droplet system, i.e. its displacement over a finite length. In order to control this displacement, we consider droplets confined on a hydrophilic stripe created by plasma-treating a PDMS substrate. This controlled actuation opens up unexplored opportunities in the field of microfluidics. In order to explain the observed actuation phenomenon, we propose a simple phenomenological model based on Newton's second law and a simple balance between the driving force arising from surface energy gradients and the viscous resistive force. This simple model is able to reproduce qualitatively and quantitatively the observed droplet dynamics

Distribution épidémiologique de l’infection à VIH chez les femmes enceintes dans les dix régions du Cameroun et implications stratégiques pour les programmes de prévention

Introduction: le Cameroun se situe dans un contexte d'épidémie  généralisée du VIH. La sous-population des femmes enceintes, facilementaccessible au sein de la population générale, représente une cible  robante pour mener la surveillance du VIH et estimer l'évolution épidémiologique. L'objectif de notre étude était d'évaluer la distribution épidémiologique du VIH chez les femmes enceintes.Méthodes: étude transversale menée en 2012 chez 6521 femmes  enceintes (49,3% âgées de 15-24 ans) en première consultation prénatale (CPN1) dans 60 sites des 10 régions Camerounaises. L'algorithme en série a été utilisé pour le sérodiagnostic du VIH.Résultats: la prévalence du VIH était de 7,8% (508/6521), avec une  différence non significative (p=0,297) entre milieu rural (7,4%) et milieu urbain (8,1%). En zone rurale, cette prévalence variait de 0,7% à  l'Extrême-Nord à 11,8% au Sud. Cependant, en zone urbaine elle variait de 4% à l'Ouest à 11,1% au Sud-Ouest. Suivant l'âge, la prévalence était plus élevée (11,3%) chez les femmes de 35-39 ans. Suivant le niveau de scolarisation, la prévalence du VIH était plus faible (4,4%) chez celles non-scolarisées, et plus élevée (9,3%) chez celles ayant un niveau  primaire. Selon la profession, l'infection était plus élevée chez les  coiffeuses (15,5%), secrétaires (14,8%), commerçantes (12,9%) et  institutrices/enseignantes (10,8%). Conclusion: la prévalence du VIH reste élevée chez les femmes enceintes au Cameroun, sans distinction entre milieux rural et urbain. Les stratégies de prévention devraient s'orienter préférentiellement chez les femmes enceintes âgées, celles du niveau d'instruction primaire, et celles du  secteur des petites et moyennes entreprises

Second Generation Steroidal 4-Aminoquinolines Are Potent, Dual-Target Inhibitors of the Botulinum Neurotoxin Serotype A Metalloprotease and P. falciparum Malaria

Significantly more potent second generation 4-amino-7-chloroquinoline (4,7-ACQ) based inhibitors of the botulinum neurotoxin serotype A (BoNT/A) light chain were synthesized. Introducing an amino group at the C(3) position of the cholate component markedly increased potency (IC50 values for such derivatives ranged from 0.81 to 2.27 mu M). Two additional subclasses were prepared: bis(steroidal)-4,7-ACQ derivatives and bis(4,7-ACQ)cholate derivatives; both classes provided inhibitors with nanomolar-range potencies (e.g., the K-i of compound 67 is 0.10 mu M). During BoNT/A challenge using primary neurons, select derivatives protected SNAP-25 by up to 89%. Docking simulations were performed to rationalize the compounds' in vitro potencies. In addition to specific residue contacts, coordination of the enzyme's catalytic zinc and expulsion of the enzyme's catalytic water were a consistent theme. With respect to antimalarial activity, the compounds provided better IC90 activities against chloroquine resistant (CQR) malaria than CQ, and seven compounds were more active than mefloquine against CQR strain W2

Influence of aspect ratio on vortex formation in X-junctions: Direct numerical simulations and eigenmode decomposition

We study numerically the appearance and number of axial vortices in the outlets of X-shaped junctions of two perpendicular channels of rectangular sections with facing inlets. We explore the effect of the aspect ratio of the cross section, AR, on the number of vortices created at the center of the junction. Direct numerical simulations (DNSs) performed for different values of the Reynolds number Re and AR demonstrate that vortices with their axis parallel to the outlets, referred to as axial vortices, appear above critical Reynolds numbers Rec. As AR increases from 1 to 11, the number of vortices observed increases from 1 to 4, independently of Re. For AR = 1, the single axial vortex induces an interpenetration of the inlet fluids in the whole section; instead, for larger AR’s for which more vortices appear, the two inlet fluids remain largely segregated in bands, except close to the vortices. The linear stability analysis demonstrates that only one leading eigenmode is unstable for a given set of values of AR and Re. This mode provides a simplified model of the flow field, reproducing its key features such as the number of vortices and their distance. Its determination with this method requires a much smaller computational load than the DNS. This approach is shown to allow one to determine quickly and precisely the critical Reynolds number Rec and the sensitivity function S, which characterizes the influence of variations of the base flow on the unstable one.Peer reviewe

A high content imaging assay for identification of Botulinum neurotoxin inhibitors.

Synaptosomal-associated protein-25 (SNAP-25) is a component of the soluble NSF attachment protein receptor (SNARE) complex that is essential for synaptic neurotransmitter release. Botulinum neurotoxin serotype A (BoNT/A) is a zinc metalloprotease that blocks exocytosis of neurotransmitter by cleaving the SNAP-25 component of the SNARE complex. Currently there are no licensed medicines to treat BoNT/A poisoning after internalization of the toxin by motor neurons. The development of effective therapeutic measures to counter BoNT/A intoxication has been limited, due in part to the lack of robust high-throughput assays for screening small molecule libraries. Here we describe a high content imaging (HCI) assay with utility for identification of BoNT/A inhibitors. Initial optimization efforts focused on improving the reproducibility of inter-plate results across multiple, independent experiments. Automation of immunostaining, image acquisition, and image analysis were found to increase assay c