Cell nuclei detection using globally optimal active contours with shape prior

Cell nuclei detection in fluorescent microscopic images is an important and time consuming task for a wide range of biological applications. Blur, clutter, bleed through and partial occlusion of nuclei make this a challenging task for automated detection of individual nuclei using image analysis. This paper proposes a novel and robust detection method based on the active contour framework. The method exploits prior knowledge of the nucleus shape in order to better detect individual nuclei. The method is formulated as the optimization of a convex energy function. The proposed method shows accurate detection results even for clusters of nuclei where state of the art methods fail

Three-dimensional flow structure behind an Ahmed vehicle model

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.The lasting high fuel cost has recently inspired resurgence in drag reduction research for vehicles, which calls for a thorough understanding of the vehicle wake. The simplified Ahmed vehicle model is characterized by controllable flow separation, thus especially suitable for this purpose. In spite of a considerable number of previous investigations, our knowledge of flow around this model remains incomplete. This work aims to revisit turbulent flow structure behind this model. Two rear slant angles, i.e., α = 25º and 35º, of the model were examined, representing two distinct flow regimes. The Reynolds number was 5.26×104 based on the model height (H) and incident flow velocity. Using particle image velocimetry (PIV), flow was measured with and without a gap (g/H = 0.174) between the vehicle underside and ground in three orthogonal planes, viz. the x-z, x-y and y-z planes, where x, y and z are the coordinates along longitudinal, transverse and spanwise directions, respectively. The flow at g/H = 0 serves as an important reference for the understanding of the highly complicated vehicle wake (g/H ≠ 0). While reconfirming the well documented major characteristics of the mean flow structure, both instantaneous and time-averaged PIV data unveil a number of important features of the flow structure, which have not been previously reported. As such, considerably modified flow structure models are proposed for both regimes. The time-averaged velocities, second moments of fluctuating velocities and vorticity components are presented and discussed, along with their dependence on g/H in the two distinct flow regimes.dc201

Foundations of Dissipative Particle Dynamics

We derive a mesoscopic modeling and simulation technique that is very close to the technique known as dissipative particle dynamics. The model is derived from molecular dynamics by means of a systematic coarse-graining procedure. Thus the rules governing our new form of dissipative particle dynamics reflect the underlying molecular dynamics; in particular all the underlying conservation laws carry over from the microscopic to the mesoscopic descriptions. Whereas previously the dissipative particles were spheres of fixed size and mass, now they are defined as cells on a Voronoi lattice with variable masses and sizes. This Voronoi lattice arises naturally from the coarse-graining procedure which may be applied iteratively and thus represents a form of renormalisation-group mapping. It enables us to select any desired local scale for the mesoscopic description of a given problem. Indeed, the method may be used to deal with situations in which several different length scales are simultaneously present. Simulations carried out with the present scheme show good agreement with theoretical predictions for the equilibrium behavior.Comment: 18 pages, 7 figure

China Engages Global Health Governance: Processes and Dilemmas

Using HIV/AIDS, Severe Acute Respiratory Syndrome (SARS), and avian influenza as case studies, this paper discusses the processes and dilemmas of China's participation in health governance, both at the domestic level and the global level. Globalization has eroded the boundary between public and private health and between domestic and global health governance. In addition, the SARS outbreak of 2002-2003 focused global attention on China's public health. As a rising power with the largest population on earth, China is expected by the international community to play a better and more active role in health management. Since the turn of this century, China has increasingly embraced multilateralism in health governance. This paper argues that China's multilateral cooperation is driven by both necessity and conscious design. International concerns about good governance and its aspiration to become a 'responsible' state have exerted a normative effect on China to change tack. Its interactions with United Nations agencies have triggered a learning process for China to securitize the spread of infectious diseases as a security threat. Conversely, China has utilized multilateralism to gain access to international resources and technical assistance. It is still a matter of debate whether China's cooperative engagement with global health governance can endure, because of the persistent problems of withholding information on disease outbreaks and because of its insistence on the Westphalian notion of sovereignty