Spatial Mixing and Non-local Markov chains

We consider spin systems with nearest-neighbor interactions on an $n$-vertex $d$-dimensional cube of the integer lattice graph $\mathbb{Z}^d$. We study the effects that exponential decay with distance of spin correlations, specifically the strong spatial mixing condition (SSM), has on the rate of convergence to equilibrium distribution of non-local Markov chains. We prove that SSM implies $O(\log n)$ mixing of a block dynamics whose steps can be implemented efficiently. We then develop a methodology, consisting of several new comparison inequalities concerning various block dynamics, that allow us to extend this result to other non-local dynamics. As a first application of our method we prove that, if SSM holds, then the relaxation time (i.e., the inverse spectral gap) of general block dynamics is $O(r)$, where $r$ is the number of blocks. A second application of our technology concerns the Swendsen-Wang dynamics for the ferromagnetic Ising and Potts models. We show that SSM implies an $O(1)$ bound for the relaxation time. As a by-product of this implication we observe that the relaxation time of the Swendsen-Wang dynamics in square boxes of $\mathbb{Z}^2$ is $O(1)$ throughout the subcritical regime of the $q$-state Potts model, for all $q \ge 2$. We also prove that for monotone spin systems SSM implies that the mixing time of systematic scan dynamics is $O(\log n (\log \log n)^2)$. Systematic scan dynamics are widely employed in practice but have proved hard to analyze. Our proofs use a variety of techniques for the analysis of Markov chains including coupling, functional analysis and linear algebra

Downy mildew of sweet basil (Ocimum basilicum) caused by Peronospora sp. in Argentina

In the green belt surrounding Buenos Aires and La Plata cities, Argentina, sweet basil (Ocimum basilicum) is grown commercially under greenhouse mainly for fresh consumption. In February 2008, plants showing typical symptoms of downy mildew were found in greenhouses in La Plata. The disease was widespread in the cropped area with 100% prevalence. Infection resulted in chlorotic leaves with a greyish to dark brown fungal-like growth on the lower surfaces. A sample was deposited in the local herbarium (KUS-F23241). Conidiophores were subhyaline, 230­ 460 X 7-11 pm, straight, monopodially branched, in 4-6 orders, and emergent from stomata. Ultimate branchlets were mostly in pairs, slightly curved, 10-25 (-30) pm long and had subtruncate tips. Conidia were broadly ellipsoidal to subglobose, greyish brown, and measured 24*3- 32-5 X 22-5-26-5 pm (length/width ratio = 1-06-1-23). This pathogen is unequivocally in the genus Peronospora, and well concordant with characters ofthe unnamedPeronospora speciesreported in basil (Belbahri et al., 2005).Facultad de Ciencias Agrarias y Forestale

Current Trends of Teaching Computer Programming in Undergraduate CS Programs: A Survey from Ecuadorian Universities

Abstract. Computer programming has become a relevant element of the modern era. Practically it is involved in all sectors of modern society. Currently, many universities around the globe offer bachelor’s degree programs that contain computer programming related courses. In order to gain insight into how computer programming is taught in Ecuadorian Higher Education Institutions (HEIs), we have conducted the first national survey on teaching computer programming in undergraduate CS programs. In this survey participated 53 respondents from 13 Ecuadorian HEIs. We report on programming paradigms, programming languages, integrated development environments and teaching strategies used in the programming learning process. We found that the object-oriented paradigm along with the Java programming language are the most often used. The NetBeans integrated development environment is the most commonly used among the respondents. Concerning teaching strategies, e-learning platforms are commonly used as part of computer programming courses. More than half of the respondents use collaborative strategies such as pair programming in their courses. Finally, a half of the respondents use traditional computer labs for teaching programming; however, other approaches such as mobile devices, games and simulations, Arduino kits and robots start to be used as a teaching strategy. Our findings can serve as a starting point for addressing reforms in computer programming courses taught in Ecuadorian CS undergraduate programs

Molecular gas in super spiral galaxies

We thank the referee for the careful revision of the manuscript and constructive comments. UL acknowledges support by the research projects AYA2017-84897-P and PID2020-114414GB-I00 from the Spanish Ministerio de Economía y Competitividad, from the European Regional Development Funds (FEDER) and the Junta de Andalucía (Spain) grants FQM108. This work is based on observations carried out under project numbers 205-19 and 068-20 with the IRAM 30m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). This research made use of the “K-corrections calculator” service available at http://kcor.sai.msu.ru/ . This research made use of Astropy, a community- developed core Python ( http://www.python.org ) package for Astronomy (Astropy Collaboration 2013, 2018); ipython (Pérez & Granger 2007); matplotlib (Hunter 2007); SciPy, a collection of open source software for scientific computing in Python (Virtanen et al. 2020); and NumPy, a structure for efficient numerical computation (van der Walt et al. 2011). This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This work was made possible by the NASA/IPAC Extragalactic Database and the NASA/ IPAC Infrared Science Archive, which are both operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We acknowledge the usage of the HyperLeda database ( http://leda.univ-lyon1.fr ).At the highest stellar masses (log(M*) ≳ 11.5 M⊙), only a small fraction of galaxies are disk-like and actively star-forming objects. These so-called ‘super spirals’ are ideal objects to better understand how galaxy evolution proceeds and to extend our knowledge about the relation between stars and gas to a higher stellar mass regime. We present new CO(1–0) data for a sample of 46 super spirals and for 18 slightly lower-mass (log(M*) > 11.0 M⊙) galaxies with broad HI lines – HI fast-rotators (HI-FRs). We analyze their molecular gas mass, derived from CO(1–0), in relation to their star formation rate (SFR) and stellar mass, and compare the results to values and scaling relations derived from lower-mass galaxies. We confirm that super spirals follow the same star-forming main sequence (SFMS) as lower-mass galaxies. We find that they possess abundant molecular gas (mean redshift-corrected molecular gas mass fraction (log(fmol, zcorr) = −1.36 ± 0.02), which lies above the extrapolation of the scaling relation with stellar mass derived from lower-mass galaxies, but within the relation between fmol and the distance to the SFMS. The molecular gas depletion time, τdep = Mmol/SFR, is higher than for lower-mass galaxies on the SFMS (τdep = 9.30 ± 0.03, compared to τdep = 9.00 ± 0.02 for the comparison sample) and seems to continue an increasing trend with stellar mass. HI-FR galaxies have an atomic-to-molecular gas mass ratio that is in agreement with that of lower-mass galaxies, indicating that the conversion from the atomic to molecular gas proceeds in a similar way. We conclude that the availability of molecular gas is a crucial factor to enable star formation to continue and that, if gas is present, quenching is not a necessary destiny for high-mass galaxies. The difference in gas depletion time suggests that the properties of the molecular gas at high stellar masses are less favorable for star formation.Spanish Ministerio de Economía y Competitividad AYA2017-84897-P, PID2020-114414GB-I00European Regional Development Funds (FEDER) AYA2017-84897-P, PID2020-114414GB-I00Junta de Andalucía (Spain) FQM108INSU/CNRS (France) 205-19, 068-20MPG (Germany) 205-19, 068-20IGN (Spain) 205-19, 068-20IPACNational Aeronautics and Space Administration NASACentre National de la Recherche Scientifique CNR

Revisión del proceso de osmosis inversa aplicado a la descontaminación de un líquido residual de curtido

En este trabajo se estudiaron aspectos relevantes del proceso de ósmosis inversa cuando es utilizado para reducir el contenido de sustancias nocivas disueltas en un líquido residual de curtido. La muestra provino de una curtiembre que trabaja con sulfato de cromo(III) 33% básico y el enmascarante ácido fórmico. Inicialmente se separaron materiales proteínicos y grasas por medio de tamizado seguido de ultrafiltración. La composición química después de reducirse la mencionada carga orgánica fue: 0,99 g L"1 de cromo(III); 12,51 g L"1 de sodio; 11,53 g L"1 de sulfato; 11,20 g L"1 de cloruro; 0,26 g L"1 de materiales proteínicos; 0,18 g L"1 de grasas y pH 3,63. Volúmenes de 24 L del efluente pre"tratado fueron descontaminados mediante ósmosis inversa, finalizándose cada ciclo luego de producir 18 L de permeado. La capacidad del equipo empleado fue determinada en términos de los porcentajes factor de conversión y paso aparente de sales. Se comprobó que bajo nuestras condiciones experimentales el ensuciamiento de la membrana semipermeable ocurría muy rápido y que la remoción del cromo(III) fue cuasi cuantitativa. Los otros componentes inorgánicos mayoritarios también fueron separados, pero con menor eficiencia: sulfato > sodio > cloruro. Finalmente, se estableció que el tiempo es una variable operativa capaz de potenciar el transporte por difusión de aquellas especies cuyo gradiente de concentración más ha aumentado, principalmente cromo(III) y en menor proporción sulfato.Publicado en Terceras Jornadas de Investigación, Transferencia y Extensión. La Plata : Universidad Nacional de La Plata, 2015.Facultad de Ingenierí

Revisión del proceso de osmosis inversa aplicado a la descontaminación de un líquido residual de curtido

En este trabajo se estudiaron aspectos relevantes del proceso de ósmosis inversa cuando es utilizado para reducir el contenido de sustancias nocivas disueltas en un líquido residual de curtido. La muestra provino de una curtiembre que trabaja con sulfato de cromo(III) 33% básico y el enmascarante ácido fórmico. Inicialmente se separaron materiales proteínicos y grasas por medio de tamizado seguido de ultrafiltración. La composición química después de reducirse la mencionada carga orgánica fue: 0,99 g L"1 de cromo(III); 12,51 g L"1 de sodio; 11,53 g L"1 de sulfato; 11,20 g L"1 de cloruro; 0,26 g L"1 de materiales proteínicos; 0,18 g L"1 de grasas y pH 3,63. Volúmenes de 24 L del efluente pre"tratado fueron descontaminados mediante ósmosis inversa, finalizándose cada ciclo luego de producir 18 L de permeado. La capacidad del equipo empleado fue determinada en términos de los porcentajes factor de conversión y paso aparente de sales. Se comprobó que bajo nuestras condiciones experimentales el ensuciamiento de la membrana semipermeable ocurría muy rápido y que la remoción del cromo(III) fue cuasi cuantitativa. Los otros componentes inorgánicos mayoritarios también fueron separados, pero con menor eficiencia: sulfato > sodio > cloruro. Finalmente, se estableció que el tiempo es una variable operativa capaz de potenciar el transporte por difusión de aquellas especies cuyo gradiente de concentración más ha aumentado, principalmente cromo(III) y en menor proporción sulfato.Publicado en Terceras Jornadas de Investigación, Transferencia y Extensión. La Plata : Universidad Nacional de La Plata, 2015.Facultad de Ingenierí

Revisión del proceso de osmosis inversa aplicado a la descontaminación de un líquido residual de curtido

En este trabajo se estudiaron aspectos relevantes del proceso de ósmosis inversa cuando es utilizado para reducir el contenido de sustancias nocivas disueltas en un líquido residual de curtido. La muestra provino de una curtiembre que trabaja con sulfato de cromo(III) 33% básico y el enmascarante ácido fórmico. Inicialmente se separaron materiales proteínicos y grasas por medio de tamizado seguido de ultrafiltración. La composición química después de reducirse la mencionada carga orgánica fue: 0,99 g L"1 de cromo(III); 12,51 g L"1 de sodio; 11,53 g L"1 de sulfato; 11,20 g L"1 de cloruro; 0,26 g L"1 de materiales proteínicos; 0,18 g L"1 de grasas y pH 3,63. Volúmenes de 24 L del efluente pre"tratado fueron descontaminados mediante ósmosis inversa, finalizándose cada ciclo luego de producir 18 L de permeado. La capacidad del equipo empleado fue determinada en términos de los porcentajes factor de conversión y paso aparente de sales. Se comprobó que bajo nuestras condiciones experimentales el ensuciamiento de la membrana semipermeable ocurría muy rápido y que la remoción del cromo(III) fue cuasi cuantitativa. Los otros componentes inorgánicos mayoritarios también fueron separados, pero con menor eficiencia: sulfato > sodio > cloruro. Finalmente, se estableció que el tiempo es una variable operativa capaz de potenciar el transporte por difusión de aquellas especies cuyo gradiente de concentración más ha aumentado, principalmente cromo(III) y en menor proporción sulfato.Publicado en Terceras Jornadas de Investigación, Transferencia y Extensión. La Plata : Universidad Nacional de La Plata, 2015.Facultad de Ingenierí

A systematic quality evaluation and review of nanomaterial genotoxicity studies: a regulatory perspective

The number of publications in the field of nanogenotoxicology and the amount of genotoxicity data on nanomaterials (NMs) in several databases generated by European Union (EU) funded projects have increased during the last decade. In parallel, large research efforts have contributed to both our understanding of key physico-chemical (PC) parameters regarding NM characterization as well as the limitations of toxicological assays originally designed for soluble chemicals. Hence, it is becoming increasingly clear that not all of these data are reliable or relevant from the regulatory perspective. The aim of this systematic review is to investigate the extent of studies on genotoxicity of NMs that can be considered reliable and relevant by current standards and bring focus to what is needed for a study to be useful from the regulatory point of view. Due to the vast number of studies available, we chose to limit our search to two large groups, which have raised substantial interest in recent years: nanofibers (including nanotubes) and metal-containing nanoparticles. Focusing on peer-reviewed publications, we evaluated the completeness of PC characterization of the tested NMs, documentation of the model system, study design, and results according to the quality assessment approach developed in the EU FP-7 GUIDEnano project. Further, building on recently published recommendations for best practices in nanogenotoxicology research, we created a set of criteria that address assay-specific reliability and relevance for risk assessment purposes. Articles were then reviewed, the qualifying publications discussed, and the most common shortcomings in NM genotoxicity studies highlighted. Moreover, several EU projects under the FP7 and H2020 framework set the aim to collectively feed the information they produced into the eNanoMapper database. As a result, and over the years, the eNanoMapper database has been extended with data of various quality depending on the existing knowledge at the time of entry. These activities are highly relevant since negative results are often not published. Here, we have reviewed the NanoInformaTIX instance under the eNanoMapper database, which hosts data from nine EU initiatives. We evaluated the data quality and the feasibility of use of the data from a regulatory perspective for each experimental entry