Localization transition on complex networks via spectral statistics

The spectral statistics of complex networks are numerically studied. The features of the Anderson metal-insulator transition are found to be similar for a wide range of different networks. A metal-insulator transition as a function of the disorder can be observed for different classes of complex networks for which the average connectivity is small. The critical index of the transition corresponds to the mean field expectation. When the connectivity is higher, the amount of disorder needed to reach a certain degree of localization is proportional to the average connectivity, though a precise transition cannot be identified. The absence of a clear transition at high connectivity is probably due to the very compact structure of the highly connected networks, resulting in a small diameter even for a large number of sites.Comment: 6 pages, expanded introduction and referencess (to appear in PRE

Betanodavirus infection in marine fish aquaculture in Malaysia

Betanodavirus is known to cause mass mortality in many marine aquaculture fish species. In this study, we detected the virus in four different marine aquaculture fish species in Malaysia. These included humpback grouper (Cromileptisaltivelis), brown marbled grouper (Epinephelusfuscoguttatus), Asian seabass (Latescalcarifer) and golden pompano (Trachinoltusblochii). Out of 246 fish specimens analyzed using RT-PCR, 60.98% detected infected by the virus. Histological pathological analysis showed extensive cell vacuolationin the brain and retina tissues of severely infected specimens. However, some of the fish specimens detected positive using RT-PCR did not exhibit cell vacoulation which indicate the carrier state of those specimens. The RT-PCR amplification method developed in this study was shown useful as biosecurity tool in monitoringBetanodavirus infection in aquaculture. Although the origin of Betanodavirus in Malaysia is difficult to ascertained, evidence showed that some infections may have been contributed by the importation of fish fingerlings form neighboring countries. Currently, effective treatment of the viral disease is still impossible hence strict biosecurity measures need to be carried out in order to control the spread of the virus in fish stocks. These can include enforcement of biosecurity check and quarantine of every batch of imported fish, the use of virus-free broodstocks in hatchery, and proper disposal of infected fish stocks. In addition, good aquaculture practices must be carried in aquaculture farms or fish nursery all the time

EVIDENCE OF HIGH CONSUMPTION OF WASTE BY THE ANDEAN CONDOR (VULTUR GRYPHUS) IN AN ANTHROPIZED ENVIRONMENT OF CHILE

Abstract · Anthropogenic food subsidies and waste disposals have become a new food resource for wildlife, including the Andean Condor (Vultur gryphus), a situation that implies benefits and health risks. To increase understanding of Andean Condor feeding habits in the most anthropized area in Chile, we analyzed 280 pellets collected during 2016 from one roost in the Metropolitan Region, central Chile. We identified the main diagnostic elements microscopically and expressed them as percentage of occurrence (percentage of each item in relation to all pellets). We found 12 prey categories (including mammals, birds, and plant material) and 9 waste categories. Condors fed mainly on mammals (99%); livestock was their main feeding source (52%), followed by native (22%) and exotic wild species (19%). Birds were detected less frequently (8%). We found a high occurrence of waste (31%), of which plastic remains were the main item (27%). According to our results, landfills serve as a complementary food source for condors, probably a low-quality but easily accessible, and which exposes them to a variety of health and mortality risks. Despite the fact that Andean Condors can reach distant places in foraging flights to find food resources, a high proportion of the population is attracted to rubbish dumps and landfills. Despite the spatio-temporal limitations of our results, this is the first record that describes and quantifies a high presence of waste as a component of the Andean Condor diet. We recommend a more comprehensive study to assess their feeding habits and habitat preferences in a broader spatio-temporal context, and to determine the possible impact of the use of waste disposals on Andean Condor populations.Resumen · Evidencia de alto consumo de basura por el Cóndor Andino (Vultur gryphus) en un ambiente antropizado de Chile Los subsidios antropogénicos y sitios de disposición de basura se han convertido en una nueva fuente de alimentación para la fauna, incluido el Cóndor Andino (Vultur gryphus), lo que implica beneficios y riesgos. Con el fin de estudiar los hábitos alimenticios del cóndor andino en un área altamente antropizada, analizamos 280 egagrópilas colectadas durante 2016 en un dormidero de la Región Metropolitana, en Chile central. Identificamos microscópicamente los principales elementos diagnósticos y los expresamos como porcentaje de ocurrencia (porcentaje de cada ítem respecto del total de pellet). Encontramos 12 ítems dietarios (incluyendo mamíferos, aves y materia vegetal) y 9 ítems de basura. Los cóndores se alimentaron principalmente de mamíferos (99%); el ganado fue la principal fuente de alimento (52%), seguido por especies silvestres nativas (22%) y exóticas (19%), mientras que las aves estuvieron escasamente representadas (8%). Encontramos una alta ocurrencia de basura (31%), de la cual los restos de plástico fueron el principal ítem (27%). De acuerdo a nuestros resultados, los basurales sirven como una fuente complementaria de alimentación para los cóndores, probablemente de baja calidad, pero de fácil acceso, y que los expone a una variedad de riesgos de mortalidad y para su salud. Aunque el Cóndor Andino puede alcanzar lugares distantes en sus vuelos de forrajeo, una alta proporción de su población es atraída a vertederos y rellenos sanitarios. A pesar de las limitaciones espaciotemporales de nuestros resultados, este es el primer registro que describe y cuantifica la alta presencia de basura como componente de la dieta del Cóndor Andino. Recomendamos ampliar el estudio para evaluar sus hábitos alimentarios y preferencias de hábitat en un contexto espacial y temporal amplio y poder determinar el posible impacto del uso de basurales en poblaciones de Cóndor Andino

Strategies to increase austenite FCC relative phase stability in high-Mn steels

Several strategies to increase the FCC austenite stability compared to BCC and HCP martensites have been tested and are discussed. The relative stability of the different phases was analyzed by studying the effects of: a) grain size, b) antiferromagnetic ordering of the austenite, c) thermal cycling through the FCC-HCP transition, d) plastic deformation of the austenite and e) combined effects. As a first step, the effect of decreasing the grain size was analyzed in Fe-Mn alloys for Mn contents smaller than 18 wt.%, where BCC and HCP martensites compete in stability. Formation of the BCC phase is inhibited for 15 wt.% and 17 wt.% of Mn for grain sizes smaller than 2 μm. This enabled, for the first time at these compositions, the measurement of the Neel temperature of the austenite using specific heat and magnetic measurements. A comparison of the obtained transition temperatures with accepted models is discussed. The effect of modifying the grain size on the FCC-HCP transition temperatures was also analyzed for 15 wt.% and 17 wt.% Mn contents showing a complete HCP inhibition for grain sizes smaller than 200 nm. A nucleation model for the HCP martensite is considered which includes an additional resistance to the transformation term depending on the austenitic grain size. Additional combined effects on the FCC stabilization are discussed like the interaction between the antiferromagnetic ordering and the introduction of defects by thermal cycling through the martensitic transformation. The analysis can be easily applied to systems with a larger number of components. Results obtained in the Fe-Mn-Cr system are also presented.The authors acknowledge the financial support from ANPCyT (PICT-2017-2198), CONICET (PIP 2015-112-201501-00521), CONICET (PIP 2017e2019 GI 0634), ANPCyT (PICT-2017-4518), and Universidad Nacional de Cuyo (06/C516 and 06/C588)