University of Catania

About: University of Catania is a education organization based out in Catania, Italy. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 14599 authors who have published 41195 publications receiving 1032705 citations. The organization is also known as: Università degli Studi di Catania & Universita degli Studi di Catania.

Elementary processes governing the evolution of road networks

Abstract: Urbanisation is a fundamental phenomenon whose quantitative characterisation is still inadequate. We report here the empirical analysis of a unique data set regarding almost 200 years of evolution of the road network in a large area located north of Milan (Italy). We find that urbanisation is characterised by the homogenisation of cell shapes, and by the stability throughout time of high–centrality roads which constitute the backbone of the urban structure, confirming the importance of historical paths. We show quantitatively that the growth of the network is governed by two elementary processes: (i) ‘densification’, corresponding to an increase in the local density of roads around existing urban centres and (ii) ‘exploration’, whereby new roads trigger the spatial evolution of the urbanisation front. The empirical identification of such simple elementary mechanisms suggests the existence of general, simple properties of urbanisation and opens new directions for its modelling and quantitative description.

TCP-Peach: a new congestion control scheme for satellite IP networks

Abstract: Current TCP protocols have lower throughput performance in satellite networks mainly due to the effects of long propagation delays and high link error rates. In this paper, a new congestion control scheme called TCP-Peach is introduced for satellite networks. TCP-Peach is composed of two new algorithms, namely Sudden Start and Rapid Recovery, as well as the two traditional TCP algorithms, Congestion Avoidance and Fast Retransmit. The new algorithms are based on the novel concept of using dummy segments to probe the availability of network resources without carrying any new information to the sender. Dummy segments are treated as low-priority segments and accordingly they do not effect the delivery of actual data traffic. Simulation experiments show that TCP-Peach outperforms other TCP schemes for satellite networks in terms of goodput. It also provides a fair share of network resources.

Neuroprotection by Glial Metabotropic Glutamate Receptors Is Mediated by Transforming Growth Factor-β

Abstract: The medium collected from cultured astrocytes transiently exposed to the group-II metabotropic glutamate (mGlu) receptor agonists (2S,1′R,2′R,3′R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV) or (S)-4-carboxy-3-hydroxyphenylglycine (4C3HPG) is neuroprotective when transferred to mixed cortical cultures challenged with NMDA ([Bruno et al., 1997][1]). The following data indicate that this particular form of neuroprotection is mediated by transforming growth factor-β (TGFβ). (1) TGFβ1 and -β2 were highly neuroprotective against NMDA toxicity, and their action was less than additive with that produced by the medium collected from astrocytes treated with DCG-IV or 4C3HPG (GM/DCG-IV or GM/4C3HPG); (2) antibodies that specifically neutralized the actions of TGFβ1 or -β2 prevented the neuroprotective activity of DCG-IV or 4C3HPG, as well as the activity of GM/DCG-IV or GM/4C3HPG; and (3) a transient exposure of cultured astrocytes to either DCG-IV or 4C3HPG led to a delayed increase in both intracellular and extracellular levels of TGFβ. We therefore conclude that a transient activation of group-II mGlu receptors (presumably mGlu3 receptors) in astrocytes leads to an increased formation and release of TGFβ, which in turn protects neighbor neurons against excitotoxic death. These results offer a new strategy for increasing the local production of neuroprotective factors in the CNS. [1]: #ref-2

In-hospital outcomes of percutaneous coronary intervention in patients with chronic total occlusion: insights from the ERCTO (European Registry of Chronic Total Occlusion) registry.

Abstract: AIMS: In comparison with non-occlusive lesions, percutaneous coronary intervention (PCI) of chronic total occlusions (CTO) represents a greater challenge for the interventionalist, due to lower procedural success rates, relatively higher incidence of procedural complications and the increased rate of restenosis. The European Registry of Chronic Total Occlusion (ERCTO) was created with the goal of evaluating the real impact of CTO PCI in the European context, trying to analyse the rates of procedural success, technical information from the CTO procedures and patient outcome. METHODS AND RESULTS: Data collection was carried out in 16 centres across Europe, starting from the beginning of January 2008. In two years of activity, a total of 1,914 patients with 1,983 CTO lesions were consecutively enrolled in the registry. Overall procedural success was achieved in 1,607 lesions (82.9%); anterograde procedures obtained higher procedural success of retrograde ones (83.2% versus 64.5%, p<0.001). Coronary perforation occurred more frequently in patients who underwent retrograde approach (4.7% versus 2.1%, p=0.04). Although no differences were observed in terms of 30-day major adverse cardiac events between anterograde and retrograde treated patients, a trend toward higher periprocedural non-Q-wave myocardial infarction was found in patients in which the retrograde approach was attempted (2.1% versus 1% p=0.08). Moreover, retrograde approach was related with longer procedural and fluoroscopy times (156.9±62.5 min vs. 98.2±52.8 min and 73.3±59.9 min vs. 38.2±43.9 min respectively, p<0.001) and higher contrast load administration (402±161 cc vs. 302±184 cc, p<0.001). CONCLUSIONS: The first report of the ERCTO registry by the EuroCTO club shows a high procedural success rate obtained by expert European operators in a "real-world" consecutive series of patients, comparable with those reported by Japanese registries. The rate of observed procedural adverse events was low and similar to the non-CTO PCI series. In this registry, retrograde procedures were associated with extended fluoroscopy exposure and procedural time, increased contrast load administration as well as a higher incidence of coronary perforations. Such outcomes should become the standard of care that all centres undertaking CTO PCI should aspire to.

Method to find community structures based on information centrality.

Abstract: Community structures are an important feature of many social, biological, and technological networks. Here we study a variation on the method for detecting such communities proposed by Girvan and Newman and based on the idea of using centrality measures to define the community boundaries [M. Girvan and M. E. J. Newman, Proc. Natl. Acad. Sci. U.S.A. 99, 7821 (2002)]. We develop an algorithm of hierarchical clustering that consists in finding and removing iteratively the edge with the highest information centrality. We test the algorithm on computer generated and real-world networks whose community structure is already known or has been studied by means of other methods. We show that our algorithm, although it runs to completion in a time O(n4) , is very effective especially when the communities are very mixed and hardly detectable by the other methods.