Heavy metal toxicity and the aetiology of glaucoma

Despite recent advances, our understanding of the aetiological mechanisms underlying glaucoma remains incomplete. Heavy metals toxicity has been linked to the development of neurodegenerative diseases and various ocular pathologies. Given the similarities in pathophysiology between glaucoma and some neurodegenerative disorders, it is plausible that heavy metal toxicity may play a role in the development of glaucoma. Heavy metal exposure may be occupational, or through water or dietary contamination. In this report, we review mechanisms for systemic and neurotoxicity for arsenic, cadmium, chromium, cobalt, lead, mercury, and manganese, and weigh the evidence for an association between glaucoma and the accumulation of heavy metals either in ocular tissues or in the central nervous system

Penetration characteristics of a liquid droplet impacting on a narrow gap:Experimental and numerical analysis

Experimentalists are limited in the amount of information they can derive from drop impact experiments on porous surfaces because of the short timescales involved and the normally opaque nature of porous materials. Numerical simulations can supplement experiments and provide researchers with previously unattainable information such as velocity and pressure profiles, and quantification of fluid volume flow rates into the pores. Ethanol drops, 2.0 mm in diameter, are impacted on a narrow gap at Weber numbers that match the impact of water drops, also 2.0 mm in diameter, on the same gap size in a previous study. The experiments show the ethanol drops cleaving at all Weber numbers tested, while the water drops completely enter the gap at low Weber numbers and only cleave at higher Weber numbers. A volume of fluid numerical model of the experiments is constructed in OpenFOAM and used to probe the interior of the drops during impact. For the water drop, a high-pressure region fills the drop during impact which continuously drives liquid into the gap. For the ethanol drops, the high-pressure region is smaller and quickly attenuates, which results in a near-zero vertical velocity at the entrance of the gap. Compared to water, the lower surface tension of ethanol causes these drops to spread further upon impact, recoil less, and overall have less liquid over the gap, which promotes cleaving. Against a superficial thought, when the penetration of liquids into porous materials is to be maximized, a higher surface tension liquid is therefore desirable

Smoothed particle hydrodynamics for modelling cold-water coral habitats in changing oceans

The importance of the growth, proliferation and longevity of reef-forming cold-water corals is paramount as they support various complex bio-diverse habitats and provide many essential ecosystem services. These cold-water coral reefs consist of layers of living coral tissue that grow on top of large masses of coral skeleton. Here, the Goldilocks Principle is used to simulate growth in optimal conditions and model how cold-water corals engineer their habitat to survive and prosper. A computational fluid dynamics model is created based on the Smoothed Particle Hydrodynamics method, a mesh-free Lagrangian numerical method. The SPH solver is written in the C++ programming language and parallelised with OpenMP to improve its efficiency and reduce the execution times. The solver is validated against analytical and numerical solutions and the growth model is then validated against in situ data of real cold-water coral colonies. The numerical results suggest that the longevity of cold-water corals depends on how well they can manage their energetic reserves when exposed to sub-optimal prey-catching conditions

Smoothed particle hydrodynamics for modelling cold-water coral habitats in changing oceans

The importance of the growth, proliferation and longevity of reef-forming cold-water corals is paramount as they support various complex bio-diverse habitats and provide many essential ecosystem services. These cold-water coral reefs consist of layers of living coral tissue that grow on top of large masses of coral skeleton. Here, the Goldilocks Principle is used to simulate growth in optimal conditions and model how cold-water corals engineer their habitat to survive and prosper. A computational fluid dynamics model is created based on the Smoothed Particle Hydrodynamics method, a mesh-free Lagrangian numerical method. The SPH solver is written in the C++ programming language and parallelised with OpenMP to improve its efficiency and reduce the execution times. The solver is validated against analytical and numerical solutions and the growth model is then validated against in situ data of real cold-water coral colonies. The numerical results suggest that the longevity of cold-water corals depends on how well they can manage their energetic reserves when exposed to sub-optimal prey-catching conditions

Optimization for time-driven link sleeping reconfigurations in ISP backbone networks

Backbone network energy efficiency has recently become a primary concern for Internet Service Providers and regulators. The common solutions for energy conservation in such an environment include sleep mode reconfigurations and rate adaptation at network devices when the traffic volume is low. It has been observed that many ISP networks exhibit regular traffic dynamicity patterns which can be exploited for practical time-driven link sleeping configurations. In this work, we propose a joint optimization algorithm to compute the reduced network topology and its actual configuration duration during daily operations. The main idea is first to intelligently remove network links using a greedy heuristic, without causing network congestion during off-peak time. Following that, a robust algorithm is applied to determine the window size of the configuration duration of the reduced topology, making sure that a unified configuration with optimized energy efficiency performance can be enforced exactly at the same time period on a daily basis. Our algorithm was evaluated using on a Point-of-Presence representation of the GÉANT network and its real traffic matrices. According to our simulation results, the reduced network topology obtained is able to achieve 18.6% energy reduction during that period without causing significant network performance deterioration. The contribution from this work is a practical but efficient approach for energy savings in ISP networks, which can be directly deployed on legacy routing platforms without requiring any protocol extension. © 2012 IEEE

An integrated bandwidth allocation and admission control framework for the support of heterogeneous real-time traffic in class-based IP networks

The support of real-time traffic in class-based IP networks requires the reservation of resources in all the links along the end-to-end paths through appropriate queuing and forwarding mechanisms. This resource allocation should be accompanied by appropriate admission control procedures in order to guarantee that newly admitted real-time traffic flows do not cause any violation to the Quality of Service (QoS) experienced by the already established real-time traffic flows. In this paper we initially aim to highlight certain issues with respect to the areas of bandwidth allocation and admission control for the support of real-time traffic in class-based IP networks. We investigate the implications of topological placement of both the bandwidth allocation and admission control schemes. We show that the performance of bandwidth allocation and admission control schemes depends highly on the location of the employed procedures with respect to the end-users requesting the services and the various network boundaries (access, metro, core, etc.). Based on our results we conclude that the strategies for applying these schemes should be location-aware, because the performance of bandwidth allocation and admission control at different points in a class-based IP network, and for the same traffic load, can be quite different and can deviate greatly from the expected performance. Through simulations we also try to provide a quantitative view of the aforementioned deviations. Taking the implications of this “location-awareness” into account, we subsequently present a new Measurement-based Admission Control (MBAC) scheme for real-time traffic that uses measurements of aggregate bandwidth only, without keeping the state of any per-flow information. In this scheme there is no assumption made on the nature of the traffic characteristics of the real-time traffic flows, which can be of heterogeneous nature. Through simulations we show that the admission control scheme is robust with respect to traffic heterogeneity and measurement errors. We also show that our scheme compares favorably against other admission control schemes in the literature