Systems with two symmetric absorbing states: relating the microscopic dynamics with the macroscopic behavior

We propose a general approach to study spin models with two symmetric absorbing states. Starting from the microscopic dynamics on a square lattice, we derive a Langevin equation for the time evolution of the magnetization field, that successfully explains coarsening properties of a wide range of nonlinear voter models and systems with intermediate states. We find that the macroscopic behavior only depends on the first derivatives of the spin-flip probabilities. Moreover, an analysis of the mean-field term reveals the three types of transitions commonly observed in these systems -generalized voter, Ising and directed percolation-. Monte Carlo simulations of the spin dynamics qualitatively agree with theoretical predictions.Comment: 5 pages, 2 figure

Dynamical phase coexistence: A simple solution to the "savanna problem"

We introduce the concept of 'dynamical phase coexistence' to provide a simple solution for a long-standing problem in theoretical ecology, the so-called "savanna problem". The challenge is to understand why in savanna ecosystems trees and grasses coexist in a robust way with large spatio-temporal variability. We propose a simple model, a variant of the Contact Process (CP), which includes two key extra features: varying external (environmental/rainfall) conditions and tree age. The system fluctuates locally between a woodland and a grassland phase, corresponding to the active and absorbing phases of the underlying pure contact process. This leads to a highly variable stable phase characterized by patches of the woodland and grassland phases coexisting dynamically. We show that the mean time to tree extinction under this model increases as a power-law of system size and can be of the order of 10,000,000 years in even moderately sized savannas. Finally, we demonstrate that while local interactions among trees may influence tree spatial distribution and the order of the transition between woodland and grassland phases, they do not affect dynamical coexistence. We expect dynamical coexistence to be relevant in other contexts in physics, biology or the social sciences.Comment: 8 pages, 7 figures. Accepted for publication in Journal of Theoretical Biolog

Fertility and survival of Swedish Red and White × Holstein crossbred cows and purebred Holstein cows

Swedish Red and White × Holstein (S×H) cows were compared with pure Holstein (HOL) cows for fertility and survival traits in 2 commercial dairy farms in central-southern Córdoba province, Argentina, over 6 years (2008–2013). The following traits were evaluated: first service conception rate (FSCR), overall conception rate (CR), number of services per conception (SC), days open (DO), mortality rate, culling rate, survival to subsequent calvings, and length of productive life (LPL). The data set consisted of 506 lactations from 240 S×H crossbred cows and 1,331 lactations from 576 HOL cows. The FSCR and CR were analyzed using logistic regression, DO and LPL were analyzed using a Cox's proportional hazards regression model, and differences of proportions were calculated for mortality rate, culling rate, and survival to subsequent calvings. The S×H cows were superior to HOL cows in overall lactations for all the fertility traits (+10.5% FSCR, +7.7% CR, −0.5 SC, and 35 fewer DO). During the first lactation, S×H cows were superior to HOL cows for all fertility traits (+12.8% FSCR, +8.0% CR, −0.4 SC, and 34 fewer DO). In the second lactation, S×H cows exhibited lower SC (−0.5) and 21 fewer DO than HOL cows. In the third or greater lactations, S×H cows showed higher FSCR (+11.0%) and CR (+12.2%), lower SC (−0.8), and 44 fewer DO than pure HOL cows. In addition, S×H cows had a lower mortality rate (−4.7%) and a lower culling rate (−13.7%) than HOL cows. Due to the higher fertility and lower mortality and culling rates, the S×H cows had higher survival to the second (+9.2%), third (+16.9%), and fourth (+18.7%) calvings than HOL cows. Because of these results, S×H cows had longer LPL (+10.3 mo) than HOL cows. These results indicate that S×H cows had higher fertility and survival than HOL cows on commercial dairy farms in Argentina.Fil: Pipino, D. F.. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Producción Animal; ArgentinaFil: Piccardi, Mónica Belén. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Unidad de Fitopatología y Modelización Agrícola - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Unidad de Fitopatología y Modelización Agrícola; ArgentinaFil: Lopez Villalobos, Nicolas. Massey University; Nueva ZelandaFil: Hickson, R. E.. Massey University; Nueva ZelandaFil: Vazquez, Maria Isabel. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Producción Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentin

Análisis de diversidad genética en poblaciones de Bauhinia forficata subsp. pruinosa (Pezuña de vaca, o buey, Pata de vaca) mediante el uso de marcadores moleculares

Bauhinia. forficata Link. subsp. pruinosa (Vogel) Fortunato & Wunderlin, crece naturalmente desde Paraguay, Sur de Brasil hasta Argentina, y tiene antecedente de uso ornamental y terapéutico (diurético, antidiarreico, hipoglucemiante). Este proyecto tiene como objetivo la caracterización de poblaciones de bauhinia forficata subsp pruinosa utilizando marcadores moleculares. Existen SSRs diseñados en taxones afines: Cercis canadensis L. y C. chinensis, de los que hay antecedentes de transferibilidad entre especies. Por ello se evaluó su transferencia en las poblaciones de Bauhinia. Estos resultados asociados a los que se obtengan de las evaluaciones químicas permitirán conocer su relación con los biotipos que se identifiquen.  Para esto, se extrajo ADN mediante el método de Dellaporta (1983) de 10 individuos del Jardín botánico Arturo E. Ragonese, se cuantificó y se realizó PCR de los SSRs seleccionados. El producto se sembró, junto con un marcador de peso molecular, en geles desnaturalizantes de poliacrilamida en cubas de secuenciación teñidos con nitrato de plata y revelados con hidróxido de sodio. Hasta el momento, se evaluaron 15 SSRs (6 provinieron de C. chinensis   y 9 de C. canandensis). De estos 15 SSRs, 11 mostraron productos de amplificación. De ellos 9 fueron polimórficos indicando diferencias interpoblacionales, que podrían indicar variabilidad química y por lo tanto resta correlacionar la actividad biológica de los distintos biotipos. Además, algunos SSRs mostraron más de un locus, información que respalda lo señalado por Poggio et al. que en la subfamilia Cercidoideae, Bauhinia (2n=28) se generó por hibridación y poliploídia a partir del ancestro Cercis (2n= 14). Además, se realizó el muestreo de 20 puntos de colecta distribuidas en las provincias de Misiones, Córdoba y Buenos Aires de por lo menos tres individuos por punto. Estos individuos serán evaluados mediante técnicas de SSR para determinar mediante distintos parámetros la variabilidad intra e interpoblacional

Role of bulge epidermal stem cells and TSLP signaling in psoriasis

Psoriasis is a common inflammatory skin disease involving a cross-talk between epidermal and immune cells. The role of specific epidermal stem cell populations, including hair follicle stem cells (HF-SCs) in psoriasis is not well defined. Here, we show reduced expression of c-JUN and JUNB in bulge HF-SCs in patients with scalp psoriasis. Using lineage tracing in mouse models of skin inflammation with inducible deletion of c-Jun and JunB, we found that mutant bulge HF-SCs initiate epidermal hyperplasia and skin inflammation. Mechanistically, thymic stromal lymphopoietin (TSLP) was identified in mutant cells as a paracrine factor stimulating proliferation of neighboring non-mutant epidermal cells, while mutant inter-follicular epidermal (IFE) cells are lost over time. Blocking TSLP in psoriasis-like mice reduced skin inflammation and decreased epidermal proliferation, VEGFα expression, and STAT5 activation. These findings unravel distinct roles of HF-SCs and IFE cells in inflammatory skin disease and provide novel mechanistic insights into epidermal cell interactions in inflammation.We thank Drs. M. Serrano and M. Perez-Moreno for the Gt(ROSA)26Sortrn4(ACTB-tdTomato,-EGFP)Luo/J and K15-Cre-PGR mouse lines. We are very grateful to Drs. M. Perez-Moreno, F. Real, O. Uluckan, L. Bakiri and the laboratory members of the Sibilia and Wagner groups for critical reading of the manuscript and valuable suggestions. We thank V. Bermeo, G. Medrano, S. Leceta, O. Grana, and M. Perez for their technical help and IT support. We acknowledge R. Paus laboratory members for the shipment of hair follicle samples. N.G.L. received funding from the People programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement no 608765. A.I is funded by the Institute of Health Carlos III (PI16/01430). The Wagner laboratory was funded by a grant from the Spanish Ministry of Economy and competitiveness (SAF2015-70857RE, cofounded by the European Regional Development Fund) and is supported by the ERC (ERC-AdG 2016 CSI-Fun).S

Prevalence and correlates of food insecurity among students attending a midsize rural university in Oregon

Objective: To examine the prevalence and identify correlates of food insecurity among students attending a rural university in Oregon. Methods: Cross-sectional non-probability survey of 354 students attending a midsize rural university in Oregon during May 2011. Main outcome was food insecurity measured using the USDA Household Food Security Survey Module: Six-Item Short Form. Socioeconomic and demographic variables were included in multivariate logistic regression models. Results: Over half of students (59%) were food insecure at some point during the previous year. Having fair/poor health (OR: 2.08, 95%CI: 1.07 – 4.63), being employed (OR: 1.73, 95%CI: 1.04 – 2.88) and with incomes below $15,000 per year (OR: 2.23, 95% CI: 1.07 – 4.63) was associated with food insecurity. In turn, good academic performance (GPA 3.1 or higher) was inversely associated with food insecurity. Conclusions: Food insecurity seems to be a significant issue for college students. It is necessary to expand research on different campus settings, and further strengthen support systems to increase access to nutritious foods for this population.This is the author's peer-reviewed accepted manuscript. The version of record is copyrighted by Elsevier and can be found at: http://www.jneb.org/home.Keywords: Food insecurity, Oregon, Rural, College student