The dual quark condensate in local and nonlocal NJL models: an order parameter for deconfinement?

We study the beahviour of the dual quark condensate $\Sigma_1$ in the Nambu-Jona-Lasinio (NJL) model and its nonlocal variant. In quantum chromodynamics $\Sigma_1$ can be realted to the breaking of the center symmetry and is therefore an (approximate) order parameter of confinement. The deconfinement transition is then signaled by a strong rise of $\Sigma_1$ as a function of temperature. However, a similar behaviour is also seen in the NJL model, which is known to have no confinement. Indeed, it was shown that in this model the rise of $\Sigma_1$ is triggered by the chiral phase transition. In order to shed more light on this issue, we calculate $\Sigma_1$ for several variants of the NJL model, some of which have been suggested to be confining. Switching between "confining" and "non-confining" models and parametrizations we find no qualitative difference in the behaviour of $\Sigma_1$, namely, it always rises in the region of the chiral phase transition. We conclude that without having established a relation to the center symmetry in a given model, $\Sigma_1$ should not blindly be regarded as an order parameter of confinement

Presencia y abundancia de aves acuáticas en la Meseta Strobel, Patagonia, Argentina

La meseta Strobel, ubicada en la estepa patagónica, alberga más de 1500 lagunas que son utilizadas regularmente por aves acuáticas, incluyendo una de las principales poblaciones reproductivas del Macá Tobiano (Podiceps gallardoi), una especie endémica de la Patagonia austral. Se registró la presencia y abundancia de aves acuáticas en 41 lagunas, cubriendo el amplio espectro de la variabilidad ambiental de la región. Se llevaron a cabo seis campañas de campo desde fines de primavera a principios de otoño en el período 2004–2006. Se registraron un total de 18 especies de aves acuáticas correspondientes a cinco familias. La familia Anatidae fue la más representada con 12 especies, constituyendo el 85% de las aves acuáticas observadas. La distribución de las aves entre las lagunas fue variable, desde un 2.4% de lagunas ocupadas por el Falaropo Común (Steganopus tricolor) y el Pato Zambullidor Grande (Oxyura jamaicensis) hasta un 80% ocupadas por el Cisne Cuello Negro (Cygnus melanocorypha), y la abundancia varió mucho entre especies y estaciones. El Macá Tobiano, en particular, fue observado en 14 lagunas (1–81 individuos). Seis especies fueron detectadas reproduciéndose en la meseta: el Macá Tobiano, el Macá Plateado (Podiceps occipitalis), el Quetro Volador (Tachyeres patachonicus), el Pato Crestón (Anas specularioides), el Cauquén Común (Chloephaga picta) y la Gallareta Chica (Fulica leucoptera). El Macá Tobiano nidificó en cuatro lagunas, tres de las cuales no habían sido reportadas previamente como sitio de reproducción. Los resultados evidencian la necesidad de generar estudios futuros basados en la dinámica de uso de las lagunas para determinar adecuadamente la importancia de la meseta Strobel como hábitat para la avifauna acuática.The Strobel Plateau is a conspicuous and representative basaltic plateau (“meseta”) in the Patagonian steppe, Argentina. This plateau is dotted with more than 1500 shallow lakes, which are regularly used by waterbirds and support one of the main breeding populations of the near threatened Hooded Grebe (Podiceps gallardoi). We collected data on bird presence and abundance in 41 shallow lakes, covering a wide spectrum of the wetland environmental variability found in the area. We conducted six surveys from spring to fall between 2004 and 2006. We recorded a total of 18 waterbird species, which represent 5 different families. Anatidae was the family most represented with 12 species, accounting for 85% of the observed waterbirds. Waterbird distribution among lakes was variable, from 2.4% occupied lakes for Wilson’s Phalarope (Steganopus tricolor) and Andean Ruddy-Duck (Oxyura jamaicensis) to 80% for Black-necked Swan (Cygnus melanocorypha), and abundance varied greatly both between species and seasons. The Hooded Grebe, in particular, was recorded in 14 lakes (1–81 individuals). Six species were detected breeding in the area: Hooded Grebe, Silvery Grebe (Podiceps occipitalis), Flying Steamer-Duck (Tachyeres patachonicus), Crested Duck (Anas specularioides), Upland Goose (Chloephaga picta), and White-winged Coot (Fulica leucoptera). The Hooded Grebe nested at four lakes, three of them not previously known to hold breeding birds. Results point to the need of further studies on the dynamic nature of waterbird lake use to adequately assess the importance of the Strobel Plateau as waterbird habitat.Fil: Lancelotti, Julio Lucio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Pozzi, Luciana Melina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Marquez, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Yorio, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Wildlife Conservation Society; Estados UnidosFil: Pascual, Miguel Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentin

A novel three-phase mixture approach for the numerical modeling of self-aerated flows

This work presents a novel theoretical/numerical model for the simulation of self-aerated flows under a Reynolds-Averaged Navier-Stokes (RANS) framework. The new formulation is based on a three-phase mixture approach composed of a continuous air phase, a bubble phase, and a continuous water phase. A mass transfer mechanism that does not depend on an entrainment function and does not require calibration accounts for the incorporation of air into the flow. A modification in the formulation of the Volume-of-Fluid algorithm (used to track the free surface) allows one to capture the increase in water depth due to the presence of bubbles. The proposed formulation recovers the traditional Volume-of-Fluid formulation for free surface flows in the absence of bubbles, allowing the model to represent simultaneously the aerated and not aerated regions of a flow. Governing equations for the mixture are derived from mass and momentum conservation equations for each phase, and a numerical algorithm that ensures the boundedness of the numerical solution is proposed. The model is tested and validated using four experimental cases: a degassing tank, a bubble plume, a plunging jet, and a stepped spillway, showing very satisfactory results. The new methodology provides a significant advance in the current capabilities for simulating self-aerated flows.Fil: Zabaleta, Federico. University of California at Davis; Estados UnidosFil: Marquez Damian, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; ArgentinaFil: Bombardelli, Fabián A.. University of California at Davis; Estados Unido

Plasticidad fenotípica en una microescala geográfica: el mejillín, Perumytilus purpuratus, que habita en las marismas rocosas de la Patagonia

Understanding phenotypic plasticity of species at different spatial scales is vital in the current context of an increasing pace of environmental changes. Through this knowledge, it is possible to predict their potential to adapt and/or evolve in face of new environmental conditions such as climate change, and/or to understand their ecological range expansion. In Patagonian rocky salt-marshes, one of the most abundant invertebrate species is the scorched mussel Perumytilus purpuratus. In this system, this mussel can be found inhabiting both vegetated and non-vegetated patches, which differ in critical environmental conditions. We performed a field study evaluating whether mussels growing in vegetated patches differ in shell shape from those growing in adjacent non-vegetated patches. We sampled individuals from both patch types and assessed their shell shape and size using geometric morphometrics. The results showed that mussels from vegetated patches had shells that were more dorsoventrally expanded, anterodorsally restricted and globose in shape than those from non-vegetated patches, which showed the opposite traits resulting in a more elongated shell. The differences found could be driven by the different conditions of temperature, desiccation rate, wave action and population density to which mussels are exposed in each patch type. These results revealed the striking phenotypic plasticity of shell form of this native species at a fine-grained scale, which could be one of the explanations for its success in its ecological range expansion.Poder comprender la plasticidad fenotípica de las especies, a diferentes escalas espaciales, es fundamental en un contexto de crecientes cambios ambientales. A través de este conocimiento, es posible predecir su potencial para adaptarse y/o evolucionar frente a nuevas condiciones ambientales tales como el cambio climático, y/o entender el modo en el que se expanden o expandieron sus rangos ecológicos. En las marismas rocosas patagónicas, una de las especies de invertebrados marinos más abundantes es el mejillín Perumytilus purpuratus. En este sistema, se lo encuentra en parches vegetados y sin vegetación que difieren en condiciones ambientales críticas. Mediante un estudio a campo, evaluamos si los mejillines que crecen en parches vegetados difieren en la forma de la concha de aquéllos que crecen en parches adyacentes sin vegetación. Para ello, se colectaron individuos de ambos tipos de parches y se evaluó la forma y el tamaño de las valvas utilizando morfometría geométrica. Los resultados mostraron que los mejillines de parches con vegetación presentan conchas más expandidas dorsoventralmente, con restricción anterodorsal, generando una forma globosa en comparación con la de los individuos de parches sin vegetación. Las distintas formas encontradas podrían deberse a las diferentes condiciones de temperatura, desecación, acción de las olas y densidad poblacional a las que están expuestos los mejillines en cada tipo de parche. Estos resultados muestran la presencia de plasticidad fenotípica en la forma de las valvas de esta especie nativa a una microescala espacial, lo que explicaría el éxito de esta especie en su expansión hacia nuevos ambientes.Fil: González Giorigis, Yamila. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Sueiro, Maria Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Marquez, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentin

Mass Mortality of Foundation Species on Rocky Shores: Testing a Methodology for a Continental Monitoring Program

Global concern around substantial losses of biodiversity has led to the development of a number of monitoring programs. Networks were established to obtain appropriate data on the spatial and temporal variation of marine species on rocky shores. Recently, the Marine Biodiversity Observation Network Pole to Pole of the Americas (MBONP2P) program was established and is coordinating biodiversity surveys along coastal areas throughout the continent. The goal of this paper was to test the usefulness and adequacy of a methodology proposed for the MBON P2P program. Changes in benthic assemblage cover were studied on monitored sites in northern Patagonia before and after the 2019 austral summer. Long-term dynamics of mussel bed is described based on existing data. Results showed that assemblages before the 2019 austral summer were different from assemblages after it. Thus, a mussel mass mortality event could be detected with this methodology. It took less than a year for mussel cover to drop from 90 to almost 0%; even where substantial changes in mussel bed cover were not registered in the previous ∼20 years at the study area. This simple methodology is an adequate tool for monitoring rocky intertidal habitats. Yearly monitoring is needed, as a minimum, to perceive this kind of process timely. Real-time detection offers the opportunity of properly understanding the causes that lead to the loss of key community components, such as these foundation species. Furthermore, it would provide early warning to decision-makers enhancing the chances of conservation of natural environments and their ecosystem services.Fil: Mendez, María Martha. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Livore, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; ArgentinaFil: Marquez, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Bigatti, Gregorio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Universidad Espíritu Santo; Ecuado

Use of Shell-shape to discrimate between Brachidontes rodriguezii and Brachidontes purpuratus species (Mytilidae) in the transition zone of their distributions (South-western Atlantic)

Mussels are important components of rocky shore assemblages throughout the world. Several Mytilid species are found as multilayered beds in the intertidal along the coasts of the South-western Atlantic. However, in contrast to the North communities in the Pacific and Atlantic, those of the Southwestern Atlantic are dominated by species of small size, locally named mejillines. These mid-intertidal beds attached to consolidated substrates are dominated by virtual monocultures of two small-sized species of Brachidontes: B. rodriguezii (d?Orbigny, 1842) and B. (= Perumytilus) purpuratus Lamarck, 1819, respectively distributed in the warm and cold temperate sectors of the South-western Atlantic; both coexisting in the transition zone between 40º and 44º S latitude. Nevertheless, there has been some confusion about the separation of Brachidontes rodriguezii and B. purpuratus, as well as about the boundaries of their distribution ranges in the Southwestern Atlantic. Here, on the basis of a morphogeometric analysis of shell morphology, we describe a feasible way for the identification of both species.Fil: Van Der Molen, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Marquez, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Universidad Nacional de Córdoba; ArgentinaFil: Idaszkin, Yanina Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Universidad Nacional de Córdoba; ArgentinaFil: Adami, Mariana Laura. Museo de La Plata; Argentin

Screening of tolerance of Atriplex vulgatissima under zinc or lead experimental conditions. An integrative perspective by using the integrated biological response index (IBRv2)

The search for plants with a high capacity to tolerate and accumulate metals is an important issue in phytoremediation. In this sense, this study was conducted in the halophyte Atriplex vulgatissima to evaluate the effects of different concentrations of lead (Pb, 50 and 100 μM) or zinc (Zn, 100 and 200 μM) on morphological, physiological, and biochemical parameters as well as the accumulation patterns of this species. The results indicated that while essential metal Zn showed high translocation from roots to shoots (TF > 1), non-essential Pb was mainly accumulated in the roots (BCF>1). Regarding shape, both metals induced slenderness of the blade, but only Zn treatment reduced leaf size. No difference in biomass production and photosynthetic parameters was found between Pb and Zn treatments. Pb treatments did not show significant differences between treatments regarding water content (WC), pigment concentration, and the activity of superoxide dismutase (SOD) and guaiacol peroxidase (GPx), but did result in a decrease in catalase activity at 100 μM Pb. On the other hand, 200 μM Zn leads to a clear reduction in WC and pigment concentrations, along with an increase in SOD and GPx activities. In addition, ascorbate peroxidase (APx) activity showed a hormesis effect at 50 μM Pb and 100 μM Zn. Malondialdehyde increased with both Pb and Zn treatments. The integrated biological index (IBRv2) indicated that 200 μM Zn was the most affected treatment (IBRv2 = 19.02) and that under the same concentrations of metals (100 μM Pb or Zn), Pb treatments presented major stress (IBRv2 = 11.55). A. vulgatissima is a metallophyte with the potential for Pb phytostabilization and Zn phytoextraction, as well as a bioindicator of these metals. Its high biomass and deep roots, combined with its halophytic traits, make it suitable for bioremediation and monitoring programs.Fil: Pollicelli, Maria de la Paz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; ArgentinaFil: Marquez, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina. Universidad Nacional de la Patagonia. Facultad de Ciencias Naturales. Sede Puerto Madryn; ArgentinaFil: Pollicelli, Maria Debora. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Idaszkin, Yanina Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Universidad Nacional de la Patagonia. Facultad de Ingeniería. Sede Puerto Madryn; Argentin

Association with an ammonium-excreting bacterium allows diazotrophic culture of oil-rich eukaryotic microalgae

Concerns regarding the depletion of the world's reserves of oil and global climate change have promoted an intensification of research and development toward the production of biofuels and other alternative sources of energy during the last years. There is currently much interest in developing the technology for third-generation biofuels from microalgal biomass mainly because of its potential for high yields and reduced land use changes in comparison with biofuels derived from plant feedstocks. Regardless of the nature of the feedstock, the use of fertilizers, especially nitrogen, entails a potential economic and environmental drawback for the sustainability of biofuel production. In this work, we have studied the possibility of nitrogen biofertilization by diazotrophic bacteria applied to cultured microalgae as a promising feedstock for next-generation biofuels. We have obtained an Azotobacter vinelandii mutant strain that accumulates several times more ammonium in culture medium than wild-type cells. The ammonium excreted by the mutant cells is bioavailable to promote the growth of nondiazotrophic microalgae. Moreover, this synthetic symbiosis was able to produce an oil-rich microalgal biomass using both carbon and nitrogen from the air. This work provides a proof of concept that artificial symbiosis may be considered an alternative strategy for the low-N-intensive cultivation of microalgae for the sustainable production of next-generation biofuels and other bioproducts.Fil: Ortiz Marquez, Juan César Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología; ArgentinaFil: Do Nascimento, Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología; ArgentinaFil: Dublan, María de Los Ángeles. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología; ArgentinaFil: Curatti, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología; Argentin

Plant-adapted Escherichia coli show increased lettuce colonizing ability, resistance to oxidative stress and chemotactic response

Background: Escherichia coli is a widespread gut commensal and often a versatile pathogen of public health concern. E. coli are also frequently found in different environments and/or alternative secondary hosts, such as plant tissues. The lifestyle of E. coli in plants is poorly understood and has potential implications for food safety. Methods/Principal Findings: This work shows that a human commensal strain of E. coli K12 readily colonizes lettuce seedlings and produces large microcolony-like cell aggregates in leaves, especially in young leaves, in proximity to the vascular tissue. Our observations strongly suggest that those cell aggregates arise from multiplication of single bacterial cells that reach those spots. We showed that E. coli isolated from colonized leaves progressively colonize lettuce seedlings to higher titers, suggesting a fast adaptation process. E. coli cells isolated from leaves presented a dramatic rise in tolerance to oxidative stress and became more chemotactic responsive towards lettuce leaf extracts. Mutant strains impaired in their chemotactic response were less efficient lettuce colonizers than the chemotactic isogenic strain. However, acclimation to oxidative stress and/or minimal medium alone failed to prime E. coli cells for enhanced lettuce colonization efficiency. Conclusion/Significance: These findings help to understand the physiological adaptation during the alternative lifestyle of E. coli in/on plant tissues.Fil: Dublan, María de Los Ángeles. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones En Biodiversidad y Biotecnología; ArgentinaFil: Ortiz Marquez, Juan César Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones En Biodiversidad y Biotecnología; Argentina. Fundación para Investigaciones Biológicas Aplicadas; ArgentinaFil: Lett, Lina Analía Carola. Universidad Nacional del Centro de la Provincia de Buenos Aires; ArgentinaFil: Curatti, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones En Biodiversidad y Biotecnología; Argentina. Fundación para Investigaciones Biológicas Aplicadas; Argentin

The dual quark condensate in local and nonlocal NJL models: An order parameter for deconfinement?

We study the behavior of the dual quark condensate ∑1 in the Nambu–Jona-Lasinio (NJL) model and its nonlocal variant. In quantum chromodynamics ∑1 can be related to the breaking of the center symmetry and is therefore an (approximate) order parameter of confinement. The deconfinement transition is then signaled by a strong rise of ∑1 as a function of temperature. However, a similar behavior is also seen in the NJL model, which is known to have no confinement. Indeed, it was shown that in this model the rise of ∑1 is triggered by the chiral phase transition. In order to shed more light on this issue, we calculate ∑1 for several variants of the NJL model, some of which have been suggested to be confining. Switching between “confining” and “non-confining” models and parametrizations we find no qualitative difference in the behavior of ∑1, namely, it always rises in the region of the chiral phase transition. We conclude that without having established a relation to the center symmetry in a given model, ∑1 should not blindly be regarded as an order parameter of confinement