Replication in bandwidth-symmetric BitTorrent networks

The popular and well-known BitTorrent peer-to-peer protocol offers fast file distribution in a highly scalable way. Several studies have investigated the properties of this protocol, mostly focusing on heterogeneous end-user environments such as the Internet, with asymmetric connections. In this paper however, we focus on the usage of the BitTorrent protocol in homogeneous local environments with symmetric bandwidth properties. Compared with a traditional client-server setup, the use of BitTorrent in such settings can offer huge benefits in performance and scalability, allowing bandwidth sharing and high speed file distribution. We aim to improve the performance of such networks with a novel mechanism for replication using so-called replicators, which replicate a subset of the files in the system. A mathematical model of the resulting Replicated BitTorrent is presented and validated by emulation. Furthermore, we present simulation results that provide insight in the performance of Replicated BitTorrent networks with dynamic peer arrivals and departures. The results show that Replicated BitTorrent significantly improves download times in local bandwidth-symmetric BitTorrent networks

On the extrapolation to ITER of discharges in present tokamaks

An expression for the extrapolated fusion gain G = Pfusion /5 Pheat (Pfusion being the total fusion power and Pheat the total heating power) of ITER in terms of the confinement improvement factor (H) and the normalised beta (betaN) is derived in this paper. It is shown that an increase in normalised beta can be expected to have a negative or neutral influence on G depending on the chosen confinement scaling law. Figures of merit like H betaN / q95^2 should be used with care, since large values of this quantity do not guarantee high values of G, and might not be attainable with the heating power installed on ITER.Comment: 6 Pages, 3 figures, Submitted to Nuclear Fusion on the 29th of November 200

Altered distribution of mucosal NK cells during HIV infection.

The human gut mucosa is a major site of human immunodeficiency virus (HIV) infection and infection-associated pathogenesis. Increasing evidence shows that natural killer (NK) cells have an important role in control of HIV infection, but the mechanism(s) by which they mediate antiviral activity in the gut is unclear. Here, we show that two distinct subsets of NK cells exist in the gut, one localized to intraepithelial spaces (intraepithelial lymphocytes, IELs) and the other to the lamina propria (LP). The frequency of both subsets of NK cells was reduced in chronic infection, whereas IEL NK cells remained stable in spontaneous controllers with protective killer immunoglobulin-like receptor/human leukocyte antigen genotypes. Both IEL and LP NK cells were significantly expanded in immunological non-responsive patients, who incompletely recovered CD4+ T cells on highly active antiretroviral therapy (HAART). These data suggest that both IEL and LP NK cells may expand in the gut in an effort to compensate for compromised CD4+ T-cell recovery, but that only IEL NK cells may be involved in providing durable control of HIV in the gut

Whole body and hepatic insulin action in normal, starved, and diabetic rats

In normal (N), 3-days starved (S), and streptozotocin-treated (65 mg/kg) 3-days diabetic (D) rats we examined the in vivo dose-response relationship between plasma insulin levels vs. whole body glucose uptake (BGU) and inhibition of hepatic glucose production (HGP) in conscious rats, as determined with the four-step sequential hyperinsulinemic euglycemic clamp technique, combined with [3-3H]glucose infusion. Twelve-hour fasting (basal) HGP was 3.0 +/- 0.2, 2.1 +/- 0.2, and 5.4 +/- 0.5 mg/min in N, S, and D rats, respectively. Next, all rats were clamped at matched glycemia (6 mM). Lowering plasma glucose in D rats from +/- 20 to 6.0 mM did not increase plasma norepinephrine, epinephrine, glucagon, and corticosterone levels. For BGU, insulin sensitivity was increased (70 +/- 11 microU/ml) in S and unchanged (113 +/- 21 microU/ml) in D compared with N rats (105 +/- 10 microU/ml). Insulin responsiveness was unchanged (12.4 +/- 0.8 mg/min) in S and decreased (8.5 +/- 0.8 mg/min) in D compared with N rats (12.3 +/- 0.7 mg/min). For HGP, insulin sensitivity was unchanged (68 +/- 10 microU/ml) in S and decreased (157 +/- 21 microU/ml) in D compared with N rats (71 +/- 5 microU/ml). Insulin responsiveness was identical among N, S, and D rats (complete suppression of HGP). In summary, 1) insulin resistance in D rats is caused by hepatic insensitivity and by a reduction in BGU responsiveness. 2) S rats show normal hepatic insulin action, but insulin sensitivity for BGU is increased. Therefore, S and D rats both suffering from a comparable catabolic state (10-15% body wt loss in 3 days) show opposite effects on in vivo insulin action. This indicates that in vivo insulin resistance in D rats is not caused by the catabolic state per se

Local participation in complex technological projects as bridging between different communities in Belgium

Local community participation in complex technological projects, where technological innovations and risks need to be managed, is notoriously challenging. Relations with local inhabitants easily take the form of exclusion, protest, controversy or litigation. While such projects represent opportunities for creating knowledge, business or societal benefits from the perspective of the community of driving actors, they often represent a potential threat to health, safety or prosperity from the perspective of the community of people who happen to live near the facilities. What are the challenges in dealing with this difference and which practices are helpful in bridging this gap? In this paper we analyse the functioning of an organised group of local inhabitants in the development of an Enhanced Landfill Mining project in Belgium where previously landfilled waste is going to be used for recycling and energy production. We find that setting up a multi-actor platform, organising a group of involved locals, combining formal and informal communication channels, maintaining a mutually credible dialogue and involving knowledgeable local people as bridging figures are important ingredients to bridge the gap in this case. We also discuss the emerging challenges of local community participation for all actors involved and especially for the organised group of ‘Locals’ who risk to become a victim of its own success by being incorporated too much in the project consortium and leaving a new gap to be bridged with the rest of the local community. Keywords: local community; community participation; stakeholders; waste disposal; Belgiu

The effect of helium on plasma performance at ASDEX Upgrade and JET

EUROfusion Consortium 63305

Neoclassical tearing modes on AUG: improved scaling laws, high confinement at high β_N and new stabilization experiments

The accuracy of the scaling laws derived so far for the normalised beta values at the onset of neoclassical tearing modes is limited as the results depend on the presence and magnitude of seed islands. Therefore power ramp down experiments have been performed on ASDEX Upgrade, allowing to find a scaling law for the critical β value at which the NTMs disappear. For (m,n)=(3,2) NTMs these critical beta values have been found to scale nearly proportional to ρ*. As it has been recently found on ASDEX Upgrade, at high βN values there is a regime in which (3,2) NTMs cause a much smaller confinement degradation as one would expect from the β dependence of the saturated island size. The transition to this regime allows high confinement (H = 1) at high beta values ( βN > 2.3) on ASDEX Upgrade in spite of the presence of (3,2) NTMs. The plasma conditions for the transition into such a high confinement regime are discussed in detail. Furthermore, new results on NTM stabilization by localized ECCD will be presented, showing that NTMs remain stabilized even with increased heating power and thus normalized beta values well above the NTM threshold