Finsler geometry on higher order tensor fields and applications to high angular resolution diffusion imaging.

We study 3D-multidirectional images, using Finsler geometry. The application considered here is in medical image analysis, specifically in High Angular Resolution Diffusion Imaging (HARDI) (Tuch et al. in Magn. Reson. Med. 48(6):1358–1372, 2004) of the brain. The goal is to reveal the architecture of the neural fibers in brain white matter. To the variety of existing techniques, we wish to add novel approaches that exploit differential geometry and tensor calculus. In Diffusion Tensor Imaging (DTI), the diffusion of water is modeled by a symmetric positive definite second order tensor, leading naturally to a Riemannian geometric framework. A limitation is that it is based on the assumption that there exists a single dominant direction of fibers restricting the thermal motion of water molecules. Using HARDI data and higher order tensor models, we can extract multiple relevant directions, and Finsler geometry provides the natural geometric generalization appropriate for multi-fiber analysis. In this paper we provide an exact criterion to determine whether a spherical function satisfies the strong convexity criterion essential for a Finsler norm. We also show a novel fiber tracking method in Finsler setting. Our model incorporates a scale parameter, which can be beneficial in view of the noisy nature of the data. We demonstrate our methods on analytic as well as simulated and real HARDI data

Definitive endoderm derived from human embryonic stem cells highly express the integrin receptors αV and β5

Human embryonic stem cells (hESCs) can be directed to differentiate into a number of endoderm cell types, however mature functional cells have yet to be produced in vitro. This suggests that there may be important factors that have yet to be described, which may be essential for the proper derivation of these cells. One such factor is the integrin mediated interactions between a cell and the extracellular matrix (ECM). On this basis, the present study investigated the role of the ECM in the directed differentiation of hESCs to definitive endoderm via analysis of integrin gene expression. The results showed that definitive endoderm can be efficiently and effectively derived from hESCs in a feeder free, single defined ECM of laminin. Analysis of integrin expression also showed that definitive endoderm highly express the integrins αV and β5, which have the ability to bind to vitronectin, whilst expression of the pluripotency related laminin binding integrins α3, α6 and β4 were downregulated. This suggested a potential role of vitronectin binding integrins in the development of definitive endoderm. © 2010 Landes Bioscience

Insulin trafficking in a glucose responsive engineered human liver cell line is regulated by the interaction of ATP-sensitive potassium channels and voltage- gated calcium channels

Type I diabetes is caused by the autoimmune destruction of pancreatic beta (â) cells [1]. Current treatment requires multiple daily injections of insulin to control blood glucose levels. Tight glucose control lowers, but does not eliminate, the onset of diabetic complications, which greatly reduce the quality and longevity of life for patients. Transplantation of pancreatic tissue as a treatment is restricted by the scarcity of donors and the requirement for lifelong immunosuppression to preserve the graft, which carries adverse side-effects. This is of particular concern as Type 1 diabetes predominantly affects children. Lack of glucose control could be overcome by genetically engineering "an artificial â-cell" that is capable of synthesising, storing and secreting insulin in response to metabolic signals. The donor cell type must be readily accessible and capable of being engineered to synthesise, process, store and secrete insulin under physiological conditions

An case of extreme particulate matter concentrations over Central Europe caused by dust emitted over the southern Ukraine

On 24 March 2007, an extraordinary dust plume was observed in the Central European troposphere. Satellite observations revealed its origins in a dust storm in Southern Ukraine, where large amounts of soil were resuspended from dried-out farmlands at wind gusts up to 30 m s?1. Along the pathway of the plume, maximum particulate matter (PM10) mass concentrations between 200 and 1400 ?g m?3 occurred in Slovakia, the Czech Republic, Poland, and Germany. Over Germany, the dust plume was characterised by a volume extinction coefficient up to 400 Mm?1 and a particle optical depth of 0.71 at wavelength 0.532 ?m. In-situ size distribution measurements as well as the wavelength dependence of light extinction from lidar and Sun photometer measurements confirmed the presence of a coarse particle mode with diameters around 2?3 ?m. Chemical particle analyses suggested a fraction of 75% crustal material in daily average PM10 and up to 85% in the coarser fraction PM10?2.5. Based on the particle characteristics as well as a lack of increased CO and CO2 levels, a significant impact of biomass burning was ruled out. The reasons for the high particle concentrations in the dust plume were twofold: First, dust was transported very rapidly into Central Europe in a boundary layer jet under dry conditions. Second, the dust plume was confined to a relatively stable boundary layer of 1.4?1.8 km height, and could therefore neither expand nor dilute efficiently. Our findings illustrate the capacity of combined in situ and remote sensing measurements to characterise large-scale dust plumes with a variety of aerosol parameters. Although such plumes from Southern Eurasia seem to occur rather infrequently in Central Europe, its unexpected features highlights the need to improve the description of dust emission, transport and transformation processes needs, particularly when facing the possible effects of further anthropogenic desertification and climate change

An episode of extremely high PM concentrations over Central Europe caused by dust emitted over the southern Ukraine

International audienceOn 24 March 2007, the atmosphere over Central Europe was affected by an episode of exceptionally high mass concentrations of aerosol particles, most likely caused by a dust storm in the Southern Ukraine on the preceding day. At ground-based measurement stations in Slovakia, the Czech Republic, Poland and Germany PM10 mass concentrations rose to values between 200 and 1400 ?g m?3. An evaluation of PM10 measurements from 360 monitoring stations showed that the dust cloud advanced along a narrow corridor at speeds of up to 70 km h?1. According to lidar observations over Leipzig, Germany, the high aerosol concentrations were confined to a homogeneous boundary layer of 1800 m height. The wavelength dependence of light extinction using both lidar and sun photometer measurements suggested the dominance of coarse particles during the main event. At a wavelength of 532 nm, relatively high volume extinction coefficients (300?400 Mm?1) and a particle optical depth of 0.65 was observed. In-situ measurements with an aerodynamic particle sizer at Melpitz, Germany, confirmed the presence of a coarse particle mode with a mode diameter >2 ?m, whose maximum concentration coincided with that of PM10. A chemical particle analysis confirmed the dominance of non-volatile and insoluble matter in the coarse mode as well as high enrichments of Ti and Fe, which are characteristic of soil dust. A combination of back trajectory calculations and satellite images allowed to identify the dust source with confidence: On 23 March 2007, large amounts of dust were emitted from dried-out farmlands in the southern Ukraine, facilitated by wind gusts up to 100 km h?1. The unusual vertical stability and confined height of this dust layer as well as the rapid transport under dry conditions led to the conservation of high aerosol mass concentrations along the transect and thus to the extraordinary high aerosol concentrations over Central Europe. Our observations demonstrate the capacity of a combined apparatus of in situ and remote sensing measurements to characterise such a dust with a variety of aerosol parameters. As a conclusion, the description of dust emission, transport and transformation processes needs to be improved, especially when facing the possible effects of further anthropogenic desertification and climate change

Atmospheric aerosols at the Pierre Auger Observatory and environmental implications

The Pierre Auger Observatory detects the highest energy cosmic rays. Calorimetric measurements of extensive air showers induced by cosmic rays are performed with a fluorescence detector. Thus, one of the main challenges is the atmospheric monitoring, especially for aerosols in suspension in the atmosphere. Several methods are described which have been developed to measure the aerosol optical depth profile and aerosol phase function, using lasers and other light sources as recorded by the fluorescence detector. The origin of atmospheric aerosols traveling through the Auger site is also presented, highlighting the effect of surrounding areas to atmospheric properties. In the aim to extend the Pierre Auger Observatory to an atmospheric research platform, a discussion about a collaborative project is presented.Comment: Regular Article, 16 pages, 12 figure

Design and Development of a Web Extension to Help Facilitate the Learning of a Foreign Language

Learning a foreign language is a time consuming task that requires perseverance, commitment and hard work. The time required to learn a foreign language can range from hundreds to thousands of hours, depending on the language being learnt and the native language of the learner. Two major barriers to learning a language are lack of motivation and time. Spending increasing amounts of time online also has a detrimental effect on learning a language. The global digital language learning industry is growing and the market has more than doubled in size in the last decade due to the world becoming increasingly interconnected. There is a need to provide users with a web browser extension that is both interactive and continuous for learning a language. This paper presents the design and development of a web browser extension that will help facilitate the learning of foreign languages. The web extension overrides the default content when either a new tab or window is opened with interactive language learning material. The web extension is compatible with the desktop version of the Chrome web browser. Each time a new tab or window is opened, a range of language learning material are presented at random, which can be read, understood and completed in 30 seconds or less with immediate feedback. Overriding the web browser’s functionality ensures the user is exposed to language learning material