Cerebrospinal fluid (CSF) dynamics play an important role in maintaining a stable central nervous system environment and are influenced by different physiological processes. Multiple studies have investigated these processes but the impact of each of them on CSF flow is not well understood. A deeper insight into the CSF dynamics and the processes impacting them is crucial to better understand neurological disorders such as hydrocephalus, Chiari malformation, and intracranial hypertension. This study presents a 3D computational fluid dynamics (CFD) model which incorporates physiological processes as boundary conditions. CSF production and pulsatile arterial and venous volume changes are implemented as inlet boundary conditions. At the outlets, 2-element windkessel models are imposed to simulate CSF compliance and absorption. The total compliance is first tuned using a 0D model to obtain physiological pressure pulsations. Then, simulation results are compared with in vivo flow measurements in the spinal subarachnoid space (SAS) and cerebral aqueduct, and intracranial pressure values reported in the literature. Finally, the impact of the distribution of and total compliance on CSF pressures and velocities is evaluated. Without respiration effects, compliance of 0.17 ml/mmHg yielded pressure pulsations with an amplitude of 5 mmHg and an average value within the physiological range of 7–15 mmHg. Also, model flow rates were found to be in good agreement with reported values. However, when adding respiration effects, similar pressure amplitudes required an increase of compliance value to 0.51 ml/mmHg, which is within the range of 0.4–1.2 ml/mmHg measured in vivo. Moreover, altering the distribution of compliance over the four different outlets impacted the local flow, including the flow through the foramen magnum. The contribution of compliance to each outlet was directly proportional to the outflow at that outlet. Meanwhile, the value of total compliance impacted intracranial pressure. In conclusion, a computational model of the CSF has been developed that can simulate CSF pressures and velocities by incorporating boundary conditions based on physiological processes. By tuning these boundary conditions, we were able to obtain CSF pressures and flows within the physiological range.
Abstract-As the number of wireless sensor network applications continues to grow, the need for specialized task scheduling mechanisms, aware of the sensor devices' capabilities and realtime resource availability, is becoming more and more apparent. In this paper, we therefore propose a generic model for task scheduling in heterogeneous networks, which we subsequently use to schedule distributed reasoning tasks, originating from a real-world WSN monitoring and management application. By means of simulation, we evaluate several developed scheduling heuristics and compare the results to an optimal solution of the same WSN task scheduling problem, obtained using ILP. Experiments show that our heuristics produce acceptable task schedules while maintaining a low resource footprint.
Abstract-We propose a software platform which pairs context awareness with over-the-top (OTT) service deployment. By augmenting OTT services with local context information, we allow them to react upon various types of changes in the environment in which they are being deployed. This lets service providers offer more personalized and fine-grained applications, while making use of a third-party infrastructure, via the OTT paradigm.Through UML diagrams, we describe the architecture of the proposed service platform. By means of a detailed illustrative scenario, the components involved are further clarified. In addition, in order to prove the feasibility of the architecture, a prototype implementation was developed and deployed on a large wireless sensor network test bed. Using a set of benchmarks, we identified the strengths and weaknesses of both test bed and prototype.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.