Polymeric photosensitizer-embedded self-expanding metal stent for repeatable endoscopic photodynamic therapy of cholangiocarcinoma

Photodynamic therapy (PDT) is a new therapeutic approach for the palliative treatment of malignant bile duct obstruction. In this study, we designed photosensitizer-embedded self-expanding nonvascular metal stent (PDT-stent) which allows repeatable photodynamic treatment of cholangiocarcinoma without systemic injection of photosensitizer. Polymeric photosensitizer (pullulan acetate-conjugated pheophorbide A; PPA) was incorporated in self-expanding nonvascular metal stent. Residence of PPA in the stent was estimated in buffer solution and subcutaneous implantation on mouse. Photodynamic activity of PDT-stent was evaluated through laserexposure on stent-layered tumor cell lines, HCT-116 tumor-xenograft mouse models and endoscopic intervention of PDT-stent on bile duct of mini pigs. Photo-fluorescence imaging of the PDT-stent demonstrated homogeneous embedding of polymeric Pheo-A (PPA) on stent membrane. PDT-stent sustained its photodynamic activities at least for 2 month. And which implies repeatable endoscopic PDT is possible after stent emplacement. The PDT-stent after light exposure successfully generated cytotoxic singlet oxygen in the surrounding tissues, inducing apoptotic degradation of tumor cells and regression of xenograft tumors on mouse models. Endoscopic biliary in-stent photodynamic treatments on minipigs also suggested the potential efficacy of PDT-stent on cholangiocarcinoma. In vivo and in vitro studies revealed our PDT-stent, allows repeatable endoscopic biliary PDT, has the potential for the combination therapy (stent plus PDT) of cholangiocarcinoma. © 2014 Elsevier Ltd.

Exploring the benefits of using multi-touch devices in performing information search tasks: An analysis in terms of performance, cognitive load and task engagement

Over the last decade, multi-touch devices (MTD) have spread in a range of contexts. In the learning context, MTD accessibility leads more and more teachers to use them in their classroom, assuming that it will improve the learning activities. Despite a growing interest, only few studies have focused on the impacts of MTD use in terms of performance and suitability in a learning context.However, even if the use of touch-sensitive screens rather than a mouse and keyboard seems to be the easiest and fastest way to realize common learning tasks (as for instance web surfing), we notice that the use of MTD may lead to a less favorable outcome. More precisely, tasks that require users to generate complex and/or less common gestures may increase extrinsic cognitive load and impair performance, especially for intrinsically complex tasks. It is hypothesized that task and gesture complexity will affect users’ cognitive resources and decrease task efficacy and efficiency. Because MTD are supposed to be more appealing, it is assumed that it will also impact cognitive absorption. The present study also takes into account user’s prior knowledge concerning MTD use and gestures by using experience with MTD as a moderator. Sixty university students were asked to perform information search tasks on an online encyclopedia. Tasks were set up so that users had to generate the most commonly used mouse actions (e.g. left/right click, scrolling, zooming, text encoding…). Two conditions were created: MTD use and laptop use (with mouse and keyboard) in order to make a comparison between the two devices. An eye tracking device was used to measure user’s attention and cognitive load. Our study sheds light on some important aspects towards the use of MTD and the added value compared to a laptop in a student learning context.

Quel dispositif utiliser pour la consultation d’une encyclopédie en ligne ?Impact des modalités d’interaction sur la performance et les processus cognitifs

info:eu-repo/semantics/nonPublished

We want to touch IT. Are hybrid laptops just new fancy gadgets or a new revolution?

While the number of traditional laptops and computers sold has dipped slightly year over year, manufacturers have developed new hybrid laptops with touch screens to build on the tactile trend. This market is moving quickly to make touch the rule rather than the exception and the sales of these devices have tripled since the launch of Windows 8 in 2012, to reach more than sixty million units sold in 2015. Unlike tablets, that benefit from easy-to-use applications specially designed for tactile interactions, hybrid laptops are intended to be used with regular user-interfaces. Hence, one could ask whether tactile interactions are suited for every task and activity performed with such interfaces. Since hybrid laptops are increasingly used in educational situations, this study focuses on information search tasks which are commonly performed for learning purposes. It is hypothesized that tasks that require complex and/or less common gestures will increase user's cognitive load and impair task performance in terms of efficacy and efficiency. A study was carried out in a usability laboratory with 30 participants for whom prior experience with tactile devices has been controlled. They were asked to perform information search tasks on an online encyclopaedia by using only the touch screen of and hybrid laptop. Tasks were selected with respect to their level of cognitive demand (amount of information that had to be maintained in working memory) and the complexity of gestures needed (left and/or right clicks, zoom, text selection and/or input.), and grouped into 4 sets accordingly. Task performance was measured by the number of tasks succeeded (efficacy) and time spent on each task (efficiency). Perceived cognitive load was assessed thanks to a questionnaire given after each set of tasks. An eye tracking device was used to monitor users' attention allocation and to provide objective cognitive load measures based on pupil dilation and the Index of Cognitive Activity. Each experimental run took approximately one hour. The results of this within-subjects design indicate that tasks involving complex gestures led to a lower efficacy, especially when the tasks were cognitively demanding. Regarding efficacy, there is no significant differences between sets of tasks excepted for tasks with low cognitive demand and complex gestures that required more time to be achieved. Surprisingly, users that declared the biggest experience with tactile devices spent more time than less frequent users. Cognitive load measures indicate that participants reported having devoted more mental effort in the interaction when they had to use complex gestures.

Extraction of polydispersity information from photon correlation data

Photon correlation spectroscopy (PCS) is a light-scattering technique for particle size diagnosis. It has been used mainly in the investigation of hydrosol particles since it is based on the measurement of the correlation function of the light scattered from the Brownian motion of suspended particles. Recently this technique also proved useful for studying soot particles in flames and similar aerosol systems. In the case of a polydispersed system the problem of recovering the particle size distribution can be reduced to the problem of inverting the Laplace transform. In this paper we review several methods introduced by the authors for the solution of this problem. We present some numerical results and we discuss the resolution limits characterizing the reconstruction of the size distributions. © 1989.

Catalyse et pot catalytique

Dans la lignée des précédents fascicules de chimie, ce dossier est consacré à la catalyse :qu'est-ce que la catalyse ?Exemples de réactions catalysées, le pot catalytique, quel carburant choisir ?Finie la pollution automobile ?La pile à combustible.