Multiple scale theory of topology driven pattern on directed networks

Dynamical processes on networks are currently being considered in different domains of cross-disciplinary interest. Reaction-diffusion systems hosted on directed graphs are in particular relevant for their widespread applications, from neuroscience, to computer networks and traffic systems. Due to the peculiar spectrum of the discrete Laplacian operator, homogeneous fixed points can turn unstable, on a directed support, because of the topology of the network, a phenomenon which cannot be induced on undirected graphs. A linear analysis can be performed to single out the conditions that underly the instability. The complete characterization of the patterns, which are eventually attained beyond the linear regime of exponential growth, calls instead for a full non linear treatment. By performing a multiple time scale perturbative calculation, we here derive an effective equation for the non linear evolution of the amplitude of the most unstable mode, close to the threshold of criticality. This is a Stuart-Landau equation whose complex coefficients appear to depend on the topological features of the embedding directed graph. The theory proves adequate versus simulations, as confirmed by operating with a paradigmatic reaction-diffusion model

El tóxico nuestro de cada día

Muchas ocupaciones, profesiones y diversas disciplinas científicas implican la manipulación de sustancias químicas peligrosas. También las utilizamos diariamente en el ámbito hogareño. ¡Sí, en casa también las manipulamos! De esta manera, en nuestras actividades cotidianas nos exponemos a una gran variedad de sustancias, así como liberamos al medioambiente otra cantidad, convirtiéndose en el reservorio final de sus residuos o derivados.Fil: Bartel, Laura. Universidad Nacional de La Pampa; ArgentinaFil: Fanelli, Silvia Laura. Universidad Nacional de La Pampa; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Instituto de Limnología "dr. Raul A. Ringuelet". Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Instituto de Limnología; ArgentinaFil: Poggio Herrero, Ingrid Violeta. Universidad Nacional de La Pampa; Argentin

Benznidazole levels in blood vary with age in rats

Benznidazole (Bz) exhibits toxic side effects in animal studies and clinical use. Reductive metabolism of Bz in liver microsomes modulates the duration of its chemotherapeutic effect and its toxicity. The rate of this metabolism depends on age and is less intense in newborns and youngsters than in adults. In the present study, we determined Bz blood levels in rats of different ages that received Bz intragastrically (100 mg/kg). We developed and validated a high-pressure liquid chromatography with UV detector method for determination of Bz levels in whole blood. Bz levels were significantly higher and persisted for longer periods of time in the blood of young rats when compared to that of adult animals.Instituto de Limnología "Dr. Raúl A. Ringuelet

Benznidazole levels in blood vary with age in rats

Benznidazole (Bz) exhibits toxic side effects in animal studies and clinical use. Reductive metabolism of Bz in liver microsomes modulates the duration of its chemotherapeutic effect and its toxicity. The rate of this metabolism depends on age and is less intense in newborns and youngsters than in adults. In the present study, we determined Bz blood levels in rats of different ages that received Bz intragastrically (100 mg/kg). We developed and validated a high-pressure liquid chromatography with UV detector method for determination of Bz levels in whole blood. Bz levels were significantly higher and persisted for longer periods of time in the blood of young rats when compared to that of adult animals.Instituto de Limnología "Dr. Raúl A. Ringuelet

Lung ultrasound in systemic sclerosis: correlation with high-resolution computed tomography, pulmonary function tests and clinical variables of disease

Interstitial lung disease (ILD) is a hallmark of systemic sclerosis (SSc). Although high-resolution computed tomography (HRCT) is the gold standard to diagnose ILD, recently lung ultrasound (LUS) has emerged in SSc patients as a new promising technique for the ILD evaluation, noninvasive and radiation-free. The aim of this study was to evaluate if there is a correlation between LUS, chest HRCT, pulmonary function tests findings and clinical variables of the disease. Thirty-nine patients (33 women and 6 men; mean age 51 ± 15.2 years) underwent clinical examination, HRCT, pulmonary function tests and LUS for detection of B-lines. A positive correlation exists between the number of B-lines and the HRCT score (r = 0.81, p < 0.0001), conversely a negative correlation exists between the number of B-lines and diffusing capacity of the lung for carbon monoxide (DLCO) (r = −0.63, p < 0.0001). The number of B-lines increases along with the progression of the capillaroscopic damage. A statistically significant difference in the number of B-lines was found between patients with and without digital ulcers [42 (3–84) vs 16 (4–55)]. We found that the number of B-lines increased with the progression of both HRCT score and digital vascular damage. LUS may therefore, be a useful tool to determine the best timing for HRCT execution, thus, preventing for many patients a continuous and useless exposure to ionizing radiatio

Effect of agrochemicals on macroinvertebrate assemblages in Pampasic streams, Buenos Aires, Argentina

Agricultural practices have been intensified in recent decades in Argentina. The Pampa plain is the main agricultural region of the country. The effect of increased application of agrochemicals on the invertebrate fauna of the Pampasic streams remains unreported. In the present study, we compared the abundance and composition of invertebrate assemblages in seven Pampasic streams with contrasting soil use in their basins. Two streams run through intensively cropped plots, two drain basins with livestock fields, while the other three are located within a biosphere Reserve. Higher nutrient and insecticide concentrations were measured in the streams draining cropped basins, related with pesticide applications and crop fertilization. The invertebrate assemblage composition of the cropped streams differed significantly from the others and between the two. Present evidence suggests that the impact of agrochemicals results in a change in composition with decreased abundance or absence of sensitive species such as Hyalellidae, Caenidae, Baetidae and Curculionidae and increased abundance of more tolerant taxa: Ostracoda, Glossiphoniidae (Hirudinea), Ancylidae (Gundlanchia), Ampullariidae (Pomacea canaliculata), Sphaeriidae and Dugesiidae. Available information suggests that macrophyte cover and composition also influence the invertebrate assemblages of the Pampasic streams.Facultad de Ciencias Naturales y MuseoInstituto de Limnología "Dr. Raúl A. Ringuelet

Evaluación del posible riesgo ambiental asociado a la presencia de contaminantes en efluentes generados por establecimientos lecheros y la industria láctea

El estudio de los riesgos derivados de la exposición a sustancias químicas presentes en el ambiente es un área de vacancia relativa en la provincia de La Pampa. La industria láctea, es un sector productivo que genera grandes volúmenes de residuos sólidos y líquidos. Los efluentes líquidos vertidos, sin un adecuado tratamiento, pueden generar un gran impacto ambiental. El objetivo de este trabajo fue utilizar bioensayos para determinar la toxicidad de efluentes de establecimientos lecheros primarios e industrias lácteas, estimando la efectividad del tratamiento previo a la disposición final. El diagnóstico ecotoxicológico permite avanzar en la evaluación del riesgo y toma de decisiones respecto a la eficiencia del tratamiento, la disposición final de los mismos, y/o sus usos potenciales. Dentro del marco de interés estatal y privado, es esencial la evaluación previa de dichos efluentes, para mejorar su gestión y reutilización.Instituto de Limnología "Dr. Raúl A. Ringuelet

El tóxico nuestro de cada día

Muchas ocupaciones, profesiones y diversas disciplinas científicas implican la manipulación de sustancias químicas peligrosas. También las utilizamos diariamente en el ámbito hogareño. ¡Sí, en casa también las manipulamos! De esta manera, en nuestras actividades cotidianas nos exponemos a una gran variedad de sustancias, así como liberamos al medioambiente otra cantidad, convirtiéndose en el reservorio final de sus residuos o derivados.Instituto de Limnología "Dr. Raúl A. Ringuelet