Alternative approach to community detection in networks

The problem of community detection is relevant in many disciplines of science and modularity optimization is the widely accepted method for this purpose. It has recently been shown that this approach presents a resolution limit by which it is not possible to detect communities with sizes smaller than a threshold which depends on the network size. Moreover, it might happen that the communities resulting from such an approach do not satisfy the usual qualitative definition of commune, i.e., nodes in a commune are more connected among themselves than to nodes outside the commune. In this article we introduce a new method for community detection in complex networks. We define new merit factors based on the weak and strong community definitions formulated by Radicchi et al (Proc. Nat. Acad. Sci. USA 101, 2658-2663 (2004)) and we show that this local definitions avoid the resolution limit problem found in the modularity optimization approach.Comment: 17 pages, 6 figure

Memory effects induce structure in social networks with activity-driven agents

Activity-driven modeling has been recently proposed as an alternative growth mechanism for time varying networks, displaying power-law degree distribution in time-aggregated representation. This approach assumes memoryless agents developing random connections, thus leading to random networks that fail to reproduce two-nodes degree correlations and the high clustering coefficient widely observed in real social networks. In this work we introduce these missing topological features by accounting for memory effects on the dynamic evolution of time-aggregated networks. To this end, we propose an activity-driven network growth model including a triadic-closure step as main connectivity mechanism. We show that this mechanism provides some of the fundamental topological features expected for social networks. We derive analytical results and perform extensive numerical simulations in regimes with and without population growth. Finally, we present two cases of study, one comprising face-to-face encounters in a closed gathering, while the other one from an online social friendship network.Comment: 19 pages, 12 figures, Major changes. Re-written wor

Epidemiologic investigation of immune-mediated polyradiculoneuropathy among abattoir workers exposed to porcine brain

Background In October 2007, a cluster of patients experiencing a novel polyradiculoneuropathy was identified at a pork abattoir (Plant A). Patients worked in the primary carcass processing area (warm room); the majority processed severed heads (head-table). An investigation was initiated to determine risk factors for illness. Methods and Results Symptoms of the reported patients were unlike previously described occupational associated illnesses. A case-control study was conducted at Plant A. A case was defined as evidence of symptoms of peripheral neuropathy and compatible electrodiagnostic testing in a pork abattoir worker. Two control groups were used - randomly selected non-ill warm-room workers (n = 49), and all non-ill head-table workers (n = 56). Consenting cases and controls were interviewed and blood and throat swabs were collected. The 26 largest U.S. pork abattoirs were surveyed to identify additional cases. Fifteen cases were identified at Plant A; illness onsets occurred during May 2004–November 2007. Median age was 32 years (range, 21–55 years). Cases were more likely than warm-room controls to have ever worked at the head-table (adjusted odds ratio [AOR], 6.6; 95% confidence interval [CI], 1.6–26.7), removed brains or removed muscle from the backs of heads (AOR, 10.3; 95% CI, 1.5–68.5), and worked within 0–10 feet of the brain removal operation (AOR, 9.9; 95% CI, 1.2–80.0). Associations remained when comparing head-table cases and head-table controls. Workers removed brains by using compressed air that liquefied brain and generated aerosolized droplets, exposing themselves and nearby workers. Eight additional cases were identified in the only two other abattoirs using this technique. The three abattoirs that used this technique have stopped brain removal, and no new cases have been reported after 24 months of follow up. Cases compared to controls had higher median interferon-gamma (IFNγ) levels (21.7 pg/ml; vs 14.8 pg/ml, P<0.001). Discussion This novel polyradiculoneuropathy was associated with removing porcine brains with compressed air. An autoimmune mechanism is supported by higher levels of IFNγ in cases than in controls consistent with other immune mediated illnesses occurring in association with neural tissue exposure. Abattoirs should not use compressed air to remove brains and should avoid procedures that aerosolize CNS tissue. This outbreak highlights the potential for respiratory or mucosal exposure to cause an immune-mediated illness in an occupational setting

Epidemiologic investigation of immune-mediated polyradiculoneuropathy among abattoir workers exposed to porcine brain

Background In October 2007, a cluster of patients experiencing a novel polyradiculoneuropathy was identified at a pork abattoir (Plant A). Patients worked in the primary carcass processing area (warm room); the majority processed severed heads (head-table). An investigation was initiated to determine risk factors for illness. Methods and Results Symptoms of the reported patients were unlike previously described occupational associated illnesses. A case-control study was conducted at Plant A. A case was defined as evidence of symptoms of peripheral neuropathy and compatible electrodiagnostic testing in a pork abattoir worker. Two control groups were used - randomly selected non-ill warm-room workers (n = 49), and all non-ill head-table workers (n = 56). Consenting cases and controls were interviewed and blood and throat swabs were collected. The 26 largest U.S. pork abattoirs were surveyed to identify additional cases. Fifteen cases were identified at Plant A; illness onsets occurred during May 2004–November 2007. Median age was 32 years (range, 21–55 years). Cases were more likely than warm-room controls to have ever worked at the head-table (adjusted odds ratio [AOR], 6.6; 95% confidence interval [CI], 1.6–26.7), removed brains or removed muscle from the backs of heads (AOR, 10.3; 95% CI, 1.5–68.5), and worked within 0–10 feet of the brain removal operation (AOR, 9.9; 95% CI, 1.2–80.0). Associations remained when comparing head-table cases and head-table controls. Workers removed brains by using compressed air that liquefied brain and generated aerosolized droplets, exposing themselves and nearby workers. Eight additional cases were identified in the only two other abattoirs using this technique. The three abattoirs that used this technique have stopped brain removal, and no new cases have been reported after 24 months of follow up. Cases compared to controls had higher median interferon-gamma (IFNγ) levels (21.7 pg/ml; vs 14.8 pg/ml, P<0.001). Discussion This novel polyradiculoneuropathy was associated with removing porcine brains with compressed air. An autoimmune mechanism is supported by higher levels of IFNγ in cases than in controls consistent with other immune mediated illnesses occurring in association with neural tissue exposure. Abattoirs should not use compressed air to remove brains and should avoid procedures that aerosolize CNS tissue. This outbreak highlights the potential for respiratory or mucosal exposure to cause an immune-mediated illness in an occupational setting

El Uso de Insecticidas para el Control de Haematobia Irritans (L.) (Diptera: Muscidae) en la Argentina

Se efectuaron 806 encuestas en 11 provincias para conocer los insecticidas ylas técnicas de aplicación que se utilizan para el control de la Haematobia irritansen los sistemas productivos de bovinos para leche, carne, cría o ciclo completo enla Argentina. Se observó un uso generalizado de piretroides aplicados en formatópica aunque con ciertas particularidades manifestadas en tres agrupamientos:el primero para Corrientes (ganadería de cría mayoritariamente en la zona infestadacon la garrapata común del vacuno) con propensión a la ausencia de tratamientos;un segundo agrupamiento que caracteriza al resto de la ganadería de cría también en el área infestada con garrapatas, donde es más común el uso depiretroides asociado con avermectinas pero también el uso de avermectinas comoúnico insecticida, con tendencia hacia la aplicación tópica combinada con inyeccióny el empleo de baños de inmersión. El tercer agrupamiento abarca a la regiónlibre de garrapatas con sistemas productivos para leche, invernada y ciclocompleto en la llanura pampeana y Entre Ríos; donde es relativamente común eluso de piretroides asociado con organo-fosforados y el uso de organo-fosforadoscomo único insecticida; la aplicación tópica de biocidas combinado con aspersióno caravanas junto con el uso único de caravanas o aspersión es más notorio eneste agrupamiento.Fil: Suarez, Víctor Humberto. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Castellino, Marta Elena. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Aguirre, Héctor David. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Alcaraz, Eliana Sabrina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Cafrune, Maria Mercedes. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Cetrá, B.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Fader, O. W.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Luciani, C. A.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Mangold, Atilio Jose. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Medus, P. D.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Guglielmone, Alberto Alejandro. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; Argentin

Community detection in networks

The problem of community detection is relevant in many disciplines of science. A community is usually defined, in a qualitative way, as a subset of nodes of a network which are more connected among themselves than to the rest of the network. In this article, we introduce a new method for community detection in complex networks. We define new merit factors based on the weak and strong community definitions formulated by Radicchi et al. [2004] and we show that this local definition properly describes the communities observed experimentally in two typical social networks. © 2010 World Scientific Publishing Company.Fil: Dorso, Claudio Oscar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Medus, A. D.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentin