What are the Best Hierarchical Descriptors for Complex Networks?

This work reviews several hierarchical measurements of the topology of complex networks and then applies feature selection concepts and methods in order to quantify the relative importance of each measurement with respect to the discrimination between four representative theoretical network models, namely Erd\"{o}s-R\'enyi, Barab\'asi-Albert, Watts-Strogatz as well as a geographical type of network. The obtained results confirmed that the four models can be well-separated by using a combination of measurements. In addition, the relative contribution of each considered feature for the overall discrimination of the models was quantified in terms of the respective weights in the canonical projection into two dimensions, with the traditional clustering coefficient, hierarchical clustering coefficient and neighborhood clustering coefficient resulting particularly effective. Interestingly, the average shortest path length and hierarchical node degrees contributed little for the separation of the four network models.Comment: 9 pages, 4 figure

V_H replacement in rearranged immunoglobulin genes

Examples suggesting that all or part of the V<sub>H</sub> segment of a rearranged V<sub>H</sub>DJ<sub>H</sub> may be replaced by all or part of another V<sub>H</sub> have been appearing since the 1980s. Evidence has been presented of two rather different types of replacement. One of these has gained acceptance and has now been clearly demonstrated to occur. The other, proposed more recently, has not yet gained general acceptance because the same effect can be produced by polymerase chain reaction artefact. We review both types of replacement including a critical examination of evidence for the latter. The first type involves RAG proteins and recombination signal sequences (RSS) and occurs in immature B cells. The second was also thought to be brought about by RAG proteins and RSS. However, it has been reported in hypermutating cells which are not thought to express RAG proteins but in which activation-induced cytidine deaminase (AID) has recently been shown to initiate homologous recombination. Re-examination of the published sequences reveals AID target sites in V<sub>H</sub>-V<sub>H</sub> junction regions and examples that resemble gene conversion

Long-term Tracking in the Wild: A Benchmark

We introduce the OxUvA dataset and benchmark for evaluating single-object tracking algorithms. Benchmarks have enabled great strides in the field of object tracking by defining standardized evaluations on large sets of diverse videos. However, these works have focused exclusively on sequences that are just tens of seconds in length and in which the target is always visible. Consequently, most researchers have designed methods tailored to this "short-term" scenario, which is poorly representative of practitioners' needs. Aiming to address this disparity, we compile a long-term, large-scale tracking dataset of sequences with average length greater than two minutes and with frequent target object disappearance. The OxUvA dataset is much larger than the object tracking datasets of recent years: it comprises 366 sequences spanning 14 hours of video. We assess the performance of several algorithms, considering both the ability to locate the target and to determine whether it is present or absent. Our goal is to offer the community a large and diverse benchmark to enable the design and evaluation of tracking methods ready to be used "in the wild". The project website is http://oxuva.netComment: To appear at ECCV 201

Node-node distance distribution for growing networks

We present the simulation of the time evolution of the distance matrix. The result is the node-node distance distribution for various kinds of networks. For the exponential trees, analytical formulas are derived for the moments of the distance distribution.Comment: presented during the 37-th Polish Physicists' Meeting, Gdansk, Poland, 15-19 Sep. 2003, 6 pages, 3 figure

Reservoir implantation for flood dampening in the Macaé River basin using the Mohid Land model

The use of computational models of varied complexity helps to understand the hydrological dynamics studying different scenarios of urban flood. In this perspective, a hydrological model of the Macaé river basin (RH-VIII) was built using the MOHID Land platform to simulate the implementation of a hypothetical attenuation reservoir for flood mitigation in the Macaé urban region. The results indicate that the maximum flows obtained with the simulation from project rainfalls were compatible with values observed in the literature, in the region of interest. The analysis of the flood hydrograms (m3/s) indicates a high efficiency in flood mitigation near the reservoir region, higher than 50%, while at the lower part of the basin, more urbanized region, the attenuation was of the order of 10%.The use of computational models of varied complexity helps to understand the hydrological dynamics studying different scenarios of urban flood. In this perspective, a hydrological model of the Macaé river basin (RH-VIII) was built using the MOHID Land platform to simulate the implementation of a hypothetical attenuation reservoir for flood mitigation in the Macaé urban region. The results indicate that the maximum flows obtained with the simulation from project rainfalls were compatible with values observed in the literature, in the region of interest. The analysis of the flood hydrograms (m3/s) indicates a high efficiency in flood mitigation near the reservoir region, higher than 50%, while at the lower part of the basin, more urbanized region, the attenuation was of the order of 10%

Structural constraints in complex networks

We present a link rewiring mechanism to produce surrogates of a network where both the degree distribution and the rich--club connectivity are preserved. We consider three real networks, the AS--Internet, the protein interaction and the scientific collaboration. We show that for a given degree distribution, the rich--club connectivity is sensitive to the degree--degree correlation, and on the other hand the degree--degree correlation is constrained by the rich--club connectivity. In particular, in the case of the Internet, the assortative coefficient is always negative and a minor change in its value can reverse the network's rich--club structure completely; while fixing the degree distribution and the rich--club connectivity restricts the assortative coefficient to such a narrow range, that a reasonable model of the Internet can be produced by considering mainly the degree distribution and the rich--club connectivity. We also comment on the suitability of using the maximal random network as a null model to assess the rich--club connectivity in real networks.Comment: To appear in New Journal of Physics (www.njp.org

Bad news travels fast! | Notícia ruim corre depressa!

Many proverbs are created through everyday experience. Although many of them are readily understood by ordinary people, the more detailed view generates many questions and doubts related to their credibility. Motivated by one of these proverbs, in the present paper, we analyse propagation of news in the network of electronic contacts (e-mails). More specifically, we propose transmission protocols intended to reproduce properties of real systems. These protocols are simulated in a real e-mail network and in the random network proposed by p. Erdos and a. Rényi prize. The results suggest that news spreads faster in the random network. The hubs in the real network tend to attract the news, in prejudice to the less connected nodes

Enhanced mitochondrial superoxide scavenging does not Improve muscle insulin action in the high fat-fed mouse

Improving mitochondrial oxidant scavenging may be a viable strategy for the treatment of insulin resistance and diabetes. Mice overexpressing the mitochondrial matrix isoform of superoxide dismutase (sod2(tg) mice) and/or transgenically expressing catalase within the mitochondrial matrix (mcat(tg) mice) have increased scavenging of O2(˙-) and H2O2, respectively. Furthermore, muscle insulin action is partially preserved in high fat (HF)-fed mcat(tg) mice. The goal of the current study was to test the hypothesis that increased O2(˙-) scavenging alone or in combination with increased H2O2 scavenging (mtAO mice) enhances in vivo muscle insulin action in the HF-fed mouse. Insulin action was examined in conscious, unrestrained and unstressed wild type (WT), sod2(tg), mcat(tg) and mtAO mice using hyperinsulinemic-euglycemic clamps (insulin clamps) combined with radioactive glucose tracers following sixteen weeks of normal chow or HF (60% calories from fat) feeding. Glucose infusion rates, whole body glucose disappearance, and muscle glucose uptake during the insulin clamp were similar in chow- and HF-fed WT and sod2(tg) mice. Consistent with our previous work, HF-fed mcat(tg) mice had improved muscle insulin action, however, an additive effect was not seen in mtAO mice. Insulin-stimulated Akt phosphorylation in muscle from clamped mice was consistent with glucose flux measurements. These results demonstrate that increased O2(˙-) scavenging does not improve muscle insulin action in the HF-fed mouse alone or when coupled to increased H2O2 scavenging