Internet traffic exhibits multifaceted burstiness and correlation structure over a wide span of time scales. Previous work analyzed this structure in terms of heavy-tailed session characteristics, as well as TCP timeouts and congestion avoidance, in relatively long time scales. We focus on shorter scales, typically less than 100-1000 milliseconds. Our objective is to identify the actual mechanisms that are responsible for creating bursty traffic in those scales. We show that TCP self-clocking, joint with queueing in the network, can shape the packet interarrivals of a TCP connection in a two-level ON-OFF pattern. This structure creates strong correlations and burstiness in time scales that extend up to the Round-Trip Time (RTT) of the connection. This effect is more important for bulk transfers that have a large bandwidth-delay product relative to their window size. Also, the aggregation of many flows, without rescaling their packet interarrivals, does not converge to a Poisson stream, as one might expect from classical superposition results. Instead, the burstiness in those scales can be significantly reduced by TCP pacing. In particular, we focus on the importance of the minimum pacing timer, and show that a 10-millisecond timer would be too coarse for removing short-scale traffic burstiness, while a 1-millisecond timer would be sufficient to make the traffic almost as smooth as a Poisson stream in sub-RTT scales.
The algorithm recommendation is attracting increasing attention in solving real-world capacitated vehicle routing problems (CVRPs), due to the fact that existing meta-heuristic algorithms often show different performances on different CVRPs. To effectively perform algorithm recommendation for CVRPs, it becomes vital to extract suitable features to characterize the CVRPs accurately. To this end, in this article three groups of penetrating features are proposed to capture the characteristics of CVRPs. The first group consists of some basic features of CVRPs, where several features are suggested to capture the distribution of customer demand, the relationship between customer demand and vehicle capacity, besides some common attributes widely used in CVRPs. The second group is composed of the features extracted from some CVRP solutions generated by local search, where in addition to the feasible and better solutions, the worse solutions and the distribution of travel cost are also used to measure the sensitivity of CVRPs to local search operations. The third group is made up of image features obtained by depicting CVRP instances through images, which is first introduced by us to enhance the generalization of algorithm recommendation. Furthermore, based on the three groups of features, an algorithm recommendation method called ARM-I is built on the basis of a KNN classifier to recommend suitable algorithm for CVRPs. Experimental results on several selected benchmarks demonstrate the effectiveness of the designed features. More interestingly, the proposed ARM-I shows high generalization on real-world instances.
Background: HVTN 505, a phase 2b trial assessing if a DNA/ rAd5 HIV vaccine prime/boost regimen reduces HIV acquisition or viremia post infection, halted vaccinations in 2013 due to efficacy futility, though it induced substantial CD8 + Tcell responses. We examined whether vaccine-induced T cells in HVTN 505 were unable to inhibit virus replication, as a potential reason for their inability to control viremia post infection. Methods: CD8 + T cells from 48 participants (38 vaccine, 10 placebo) were tested pre-immunization and at peak immunogenicity (4 weeks post rAd5 boost) for their ability to inhibit HIV-1 replication in autologous CD4 + T cells infected with a NanoLuc Ò -secreting JR-CSF infectious molecular clone. Relative light units (RLU) were measured at day 7, Dlog inhibition of virus (difference of log RLU in the presence vs. absence of CD8 + T cells) is reported for an effector:target ratio of 5:1. Responses were considered positive if above the mean + 3SD of baseline and placebo samples (1.05 log). Seven subjects with chronic HIV infection on antiretroviral treatment (ART) served as controls. Results: Viral inhibition by CD8 + T cells was significantly greater in vaccinees at peak immunogenicity than pre-immunization (p < 0.0001); no changes over time were observed in placebo recipients (p = 0.7). The response rate was 61%, with median Dlog inhibition of 1.9 logs (range 1.2-2.6) in responders. This level of inhibition is similar to that in HIV-infected subjects requiring ART to control viremia (median 2.1 logs, range 1.7-2.8; p = 0.06). Conclusions: The DNA/rAd5 vaccine in HVTN 505 led to significant induction of CD8 + T-cell responses able to inhibit HIV-1 replication in vitro, but the magnitude in responders was comparable to that observed in treated HIV infected subjects requiring ART to control viremia. It is thus likely that vaccination must elicit responses of higher magnitude (such as those observed in elite HIV controllers in similar assays) to drive an overall reduction in viral load post infection.
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