674 research outputs found
Nonlinear saturation of resistive tearing modes in a cylindrical tokamak with and without solving the dynamics
We show that the saturation of resistive tearing modes in a cylindrical
tokamak, as well as the corresponding island width, can be directly calculated
with an MHD equilibrium code without solving the dynamics and without
considering resistivity. The results are compared to initial value resistive
MHD simulations and to an analytical nonlinear theory. For small enough
islands, the agreement is remarkable. For sufficiently large islands, the
equilibrium calculations, which assume a flat current profile inside the
island, overestimate the saturation amplitude. On the other hand, excellent
agreement between nonlinear resistive MHD simulations and nonlinear theory is
observed for all the considered tearing unstable equilibria
Detailed Analysis of Skype Traffic
Skype is beyond any doubt the VoIP application in the current Internet application spectrum. Its amazing success has drawn the attention of telecom operators and the research commu- nity, both interested in knowing its internal mechanisms, charac- terizing its traffic, understanding its users' behavior. In this paper, we investigate the characteristics of traffic streams generated by voice and video communications, and the signaling traffic generated by Skype. Our approach is twofold, as we make use of both active and passive measurement techniques to gather a deep understanding on the traffic Skype generates. From extensive testbed experiments, we devise a source model which takes into ac- count: i) the service type, i.e., SkypeOut calls or calls between two Skype clients, ii) the selected source Codec, iii) the adopted trans- port layer protocol, and iv) network conditions. Leveraging on the use of an accurate Skype classification engine that we recently pro- posed, we study and characterize Skype traffic based on extensive passive measurements collected from our campus LA
Lagrangian Coherent Structures as a new frame to investigate the particle transport in highly chaotic magnetic systems
Experimental Assessment of BitTorrent Completion Time in Heterogeneous TCP/uTP swarms
BitTorrent, one of the most widespread used P2P application for file-sharing,
recently got rid of TCP by introducing an application-level congestion control
protocol named uTP. The aim of this new protocol is to efficiently use the
available link capacity, while minimizing its interference with the rest of
user traffic (e.g., Web, VoIP and gaming) sharing the same access bottleneck.
In this paper we perform an experimental study of the impact of uTP on the
torrent completion time, the metric that better captures the user experience.
We run BitTorrent applications in a flash crowd scenario over a dedicated
cluster platform, under both homogeneous and heterogeneous swarm population.
Experiments show that an all-uTP swarms have shorter torrent download time with
respect to all-TCP swarms. Interestingly, at the same time, we observe that
even shorter completion times can be achieved under careful mixtures of TCP and
uTP traffic.Comment: 14 pages, under submissio
Immunotherapy and cardiovascular diseases: novel avenues for immunotherapeutic approaches
As current therapies for cardiovascular disease (CVD), predominantly based on lipid lowering, still face an unacceptable residual risk, novel treatment strategies are being explored. Besides lipids, inflammatory processes play a major role in the pathogenesis of atherosclerosis, the underlying cause of the majority of CVD. The first clinical trials targeting the interleukin-1 beta-inflammasome axis have shown that targeting this pathway is successful in reducing cardiovascular events but did not decrease overall CVD mortality. Hence, novel and improved immunotherapeutics to treat CVD are being awaited
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