Pre-Congestion Notification marking

Pre-Congestion Notification (PCN) builds on the concepts of RFC 3168, "The addition of Explicit Congestion Notification to IP". However, Pre-Congestion Notification aims at providing notification before any congestion actually occurs. Pre-Congestion Notification is applied to real-time flows (such as voice, video and multimedia streaming) in DiffServ networks. As described in [CL-DEPLOY], it enables "pre" congestion control through two procedures, flow admission control and flow pre-emption. The draft proposes algorithms that determine when a PCN-enabled router writes Admission Marking and Pre-emption Marking in a packet header, depending on the traffic level. The draft also proposes how to encode these markings. We present simulation results with PCN working in an edge-to-edge scenario using the marking algorithms described. Other marking algorithms will be investigated in the future

Variability and short-term determinants of walking capacity in patients with intermittent claudication

OBJECTIVE: Global positioning system (GPS) recordings can provide valid information on walking capacity in patients with peripheral arterial disease (PAD) and intermittent claudication (IC) during community-based outdoor walking. This study used GPS to determine the variability of the free-living walking distance between two stops (WDBS), induced by lower-limb pain, which may exist within a single stroll in PAD patients with IC and the potential associated parameters obtained from GPS analysis.METHODS: This cross-sectional study of 57 PAD patients with IC was conducted in a university hospital. The intervention was a 1-hour free-living walking in a flat public park with GPS recording at 0.5 Hz. GPS-computed parameters for each patient were WDBS, previous stop duration (PSD), cumulated time from the beginning of the stroll, and average walking speed for each walking bout. The coefficient of variation of each parameter was calculated for patients with the number of walking bouts (N(WB)) >or=5 during their stroll. A multivariate analysis was performed to correlate WDBS with the other parameters. RESULTS: Mean (SD) maximal individual WDBS was 1905 (1189) vs 550 (621) meters for patients with N(WB) <5 vs N(WB) >or= 5, respectively (P < .001). In the 36 patients with N(WB) >or= 5, the coefficient of variation for individual WDBS was 43%. Only PSD and cumulated time were statistically associated with WDBS in 16 and 5 patients, respectively. CONCLUSIONS: A wide short-term variability of WDBS exists and likely contributes to the difficulties experienced by patients with IC to estimate their maximal walking distance at leisurely pace. Incomplete recovery from a preceding walk, as estimated through PSD, seems to dominantly account for the WDBS in patients with IC

Pre-Congestion Notification marking

Pre-Congestion Notification (PCN) builds on the concepts of RFC 3168, "The addition of Explicit Congestion Notification to IP". However, Pre-Congestion Notification aims at providing notification before any congestion actually occurs. Pre-Congestion Notification is applied to \ud real-time flows (such as voice, video and multimedia streaming) in DiffServ networks. As described in [CL-DEPLOY], it enables "pre" congestion control through two procedures, flow admission control and flow pre-emption. The draft proposes algorithms that determine when a \ud PCN-enabled router writes Admission Marking and Pre-emption Marking in a packet header, depending on the traffic level. The draft also proposes how to encode these markings. We present simulation results with PCN working in an edge-to-edge scenario using the marking algorithms described. Other marking algorithms will be investigated in the future. \u

An edge-to-edge Deployment Model for Pre-Congestion Notification: Admission Control over a DiffServ Region

This document describes a deployment model for pre-congestion notification (PCN) operating in a large DiffServ-based region of the Internet. PCN-based admission control protects the quality of service of existing flows in normal circumstances, whilst if necessary (eg after a large failure) pre-emption of some flows preserves the quality of service of the remaining flows. Each link has a configured-admission-rate and a configured-pre-emption-rate, and a router marks packets that exceed these rates. Hence routers give an early warning of their own potential congestion, before packets need to be dropped. Gateways around the edges of the PCN-region convert measurements of packet rates and their markings into decisions about whether to admit new flows, and (if necessary) into the rate of excess traffic that should be pre-empted. Per-flow admission states are kept at the gateways only, while the PCN markers that are required for all routers operate on the aggregate traffic - hence there is no scalability impact on interior routers

Development and Feasibility of a Smartphone, ECG and GPS Based System for Remotely Monitoring Exercise in Cardiac Rehabilitation

Background Despite its efficacy and cost-effectiveness, exercise-based cardiac rehabilitation is undertaken by less than one-third of clinically eligible cardiac patients in every country for which data is available. Reasons for non-participation include the unavailability of hospital-based rehabilitation programs, or excessive travel time and distance. For this reason, there have been calls for the development of more flexible alternatives. Methodology and Principal Findings We developed a system to enable walking-based cardiac rehabilitation in which the patient's single-lead ECG, heart rate, GPS-based speed and location are transmitted by a programmed smartphone to a secure server for real-time monitoring by a qualified exercise scientist. The feasibility of this approach was evaluated in 134 remotely-monitored exercise assessment and exercise sessions in cardiac patients unable to undertake hospital-based rehabilitation. Completion rates, rates of technical problems, detection of ECG changes, pre- and post-intervention six minute walk test (6 MWT), cardiac depression and Quality of Life (QOL) were key measures. The system was rated as easy and quick to use. It allowed participants to complete six weeks of exercise-based rehabilitation near their homes, worksites, or when travelling. The majority of sessions were completed without any technical problems, although periodic signal loss in areas of poor coverage was an occasional limitation. Several exercise and post-exercise ECG changes were detected. Participants showed improvements comparable to those reported for hospital-based programs, walking significantly further on the post-intervention 6 MWT, 637 m (95% CI: 565–726), than on the pre-test, 524 m (95% CI: 420–655), and reporting significantly reduced levels of cardiac depression and significantly improved physical health-related QOL. Conclusions and Significance The system provided a feasible and very flexible alternative form of supervised cardiac rehabilitation for those unable to access hospital-based programs, with the potential to address a well-recognised deficiency in health care provision in many countries. Future research should assess its longer-term efficacy, cost-effectiveness and safety in larger samples representing the spectrum of cardiac morbidity and severity

Functional claudication distance: a reliable and valid measurement to assess functional limitation in patients with intermittent claudication

BACKGROUND: Disease severity and functional impairment in patients with intermittent claudication is usually quantified by the measurement of pain-free walking distance (intermittent claudication distance, ICD) and maximal walking distance (absolute claudication distance, ACD). However, the distance at which a patient would prefer to stop because of claudication pain seems a definition that is more correspondent with the actual daily life walking distance. We conducted a study in which the distance a patient prefers to stop was defined as the functional claudication distance (FCD), and estimated the reliability and validity of this measurement. METHODS: In this clinical validity study we included patients with intermittent claudication, following a supervised exercise therapy program. The first study part consisted of two standardised treadmill tests. During each test ICD, FCD and ACD were determined. Primary endpoint was the reliability as represented by the calculated intra-class correlation coefficients. In the second study part patients performed a standardised treadmill test and filled out the Rand-36 questionnaire. Spearman's rho was calculated to assess validity. RESULTS: The intra-class correlation coefficients of ICD, FCD and ACD were 0.940, 0.959, and 0.975 respectively. FCD correlated significantly with five out of nine domains, namely physical function (rho = 0.571), physical role (rho = 0.532), vitality (rho = 0.416), pain (rho = 0.416) and health change (rho = 0.414). CONCLUSION: FCD is a reliable and valid measurement for determining functional capacity in trained patients with intermittent claudication. Furthermore it seems that FCD better reflects the actual functional impairment. In future studies, FCD could be used alongside ICD and ACD

High methylmercury in Arctic and subarctic ponds is related to nutrient levels in the warming eastern Canadian Arctic

Permafrost thaw ponds are ubiquitous in the eastern Canadian Arctic, yet little information exists on their potential as sources of methylmercury (MeHg) to freshwaters. They are microbially active and conducive to methylation of inorganic mercury, and are also affected by Arctic warming. This multiyear study investigated thaw ponds in a discontinuous permafrost region in the Subarctic taiga (Kuujjuarapik-Whapmagoostui, QC) and a continuous permafrost region in the Arctic tundra (Bylot Island, NU). MeHg concentrations in thaw ponds were well above levels measured in most freshwater ecosystems in the Canadian Arctic (>0.1 ng L−1). On Bylot, ice-wedge trough ponds showed significantly higher MeHg (0.3−2.2 ng L−1) than polygonal ponds (0.1−0.3 ng L−1) or lakes (<0.1 ng L−1). High MeHg was measured in the bottom waters of Subarctic thaw ponds near Kuujjuarapik (0.1−3.1 ng L−1). High water MeHg concentrations in thaw ponds were strongly correlated with variables associated with high inputs of organic matter (DOC, a320, Fe), nutrients (TP, TN), and microbial activity (dissolved CO2 and CH4). Thawing permafrost due to Arctic warming will continue to release nutrients and organic carbon into these systems and increase ponding in some regions, likely stimulating higher water concentrations of MeHg. Greater hydrological connectivity from permafrost thawing may potentially increase transport of MeHg from thaw ponds to neighboring aquatic ecosystems