Darriwilian Conodont Biostratigraphy of the Las Chacritas Formation, Central Precordillera (San Juan Province, Argentina)

The Las Chacritas Fm in the type section in the Sierra de La Trampa, Central Precordillera (San Juan Province) was deposited in an outer carbonate ramp setting that evolved from relatively deep to shallow water. Samples from this well-exposed Middle Ordovician section yielded collections of low-diversity conodont faunas stratigraphically significant. The top of the underlying San Juan Fm and the lower and middle parts of the Las Chacritas Fm contain conodonts representative of the Lenodus variabilis Zone, and the upper part of the Las Chacritas Fm yields conodonts that correlate with the Paroistodus horridus subzone of the upper part of the Lenodus variabilis Zone. The occurrence of Dzikodus tablepointensis and Eoplacognathus pseudoplanus in the upper part of the Paroistodus horridus subzone is especially significant. The occurrence of Histiodella kristinae in the highest levels indicates that the top of the Las Chacritas Fm correlates with the Eoplacognathus suecicus Zone. Conodont biofacies are analyzed trough the entire section, supporting an outer platform or open sea conditions. Baltic and Sino-Pacific affinities are stated

Comparative Analysis for Web Applications Based on REST Services: MEAN Stack and Java EE Stack

The use of REST (Representational State Transfer Protocol) web services has increased and has become the most widely used implementation today. The most crucial part of a web development project based on REST services is the choice of the right tools for the front-end, back-end, and database environment. The main objective of this work is to test the MEAN stack as an effective solution for a web application based on REST services. JavaScript has been the client-side programming language running in the browser. The MEAN stack consists of MongoDB (database), Node.js. (web server), Express (back-end), and Angular (front-end) to build web applications. We compare the MEAN stack with a very popular stack such as Java EE that groups MongoDB (database), Apache/Tomcat (web server), Spring boot (back-end) and JSP/HTML/CSS (front-end), with respect to its components, features, and environment configuration. Two similar applications were built with the MEAN and Java EE stacks. We compared and analyzed several features and test criteria such as response time, performance, and data loading.     Keywords: software architecture, Javascript, REST, web service, Java E

Ordovician conodonts of the Devendeus Formation at the Angosto de La Quesera (Cordillera Oriental of Salta, Argentina) : Taxonomic considerations and biostratigraphic significance

Conodonts recovered from the Devendeus Formation at the Angosto de La Quesera locality (Cordillera Oriental of Salta) in northwestern Argentina include Nogamiconus sp., Problematoconites perforatus, Drepanoistodus sp., Oneotodus sp., Scolopodus filosus, Teridontus nakamurai and Variabiloconus sp., as a part of an association that defines a pre-Paltodus deltifer Zone. The material most likely represents the Cordylodus angulatus and/or the lower part of the Rossodus manitouensis Zone. These microfossils support the dating of the Devendeus Formation as Tremadocian (Early Ordovician)

Low molecular weight ϵ-caprolactone-pcoumaric acid copolymers as potential biomaterials for skin regeneration applications

ϵ-caprolactone-p-coumaric acid copolymers at different mole ratios (ϵ-caprolactone:p-coumaric acid 1:0, 10:1, 8:1, 6:1, 4:1, and 2:1) were synthesized by melt-polycondensation and using 4-dodecylbenzene sulfonic acid as catalyst. Chemical analysis by NMR and GPC showed that copolyesters were formed with decreasing molecular weight as p-coumaric acid content was increased. Physical characteristics, such as thermal and mechanical properties, as well as water uptake and water permeability, depended on the mole fraction of pcoumaric acid. The p-coumarate repetitive units increased the antioxidant capacity of the copolymers, showing antibacterial activity against the common pathogen Escherichia coli. In addition, all the synthesized copolyesters, except the one with the highest concentration of the phenolic acid, were cytocompatible and hemocompatible, thus becoming potentially useful for skin regeneration applications

When is it Beneficial to Reject Improvements?

We investigate two popular trajectory-based algorithms from biology and physics to answer a question of general significance: when is it beneficial to reject improvements? A distinguishing factor of SSWM (Strong Selection Weak Mutation), a popular model from population genetics, compared to the Metropolis algorithm (MA), is that the former can reject improvements, while the latter always accepts them. We investigate when one strategy outperforms the other. Since we prove that both algorithms converge to the same stationary distribution, we concentrate on identifying a class of functions inducing large mixing times, where the algorithms will outperform each other over a long period of time. The outcome of the analysis is the definition of a function where SSWM is efficient, while Metropolis requires at least exponential time

Experiencias sorprendentes de química con indicadores de pH caseros

En este trabajo se describen varias experiencias sencillas relacionadas con las reacciones ácido-base. Todas ellas pueden realizarse con utensilios de cocina y usando sustancias baratas que pueden encontrarse fácilmente en un supermercado, una farmacia o en casa. En concreto, se describe la forma de obtener algunos indicadores de pH a partir de extractos vegetales o de medicamentos. Además, se proponen varias experiencias en las que se hace uso de estos indicadores con el fin de estudiar las reacciones ácido-base. Todas estas experiencias están enfocadas a alumnos de enseñanza secundaria.Palabras clave: demostraciones de química, experiencias de química, indicadores de pH, materiales y reactivos caseros.Amazing chemistry experiences with home pH indicatorsIn this work, several experiments related with acid-base chemical reactions are described. All the experiments can be done with kitchen utensils and using cheap substances that can be easily found in supermarkets, pharmacies and even at home. Specifically, it is described how to obtain pH indicators from vegetal extracts and medicines. In addition, several experiments using these pH indicators are proposed in order to study the acid-base chemical reactions. All these experiments are addressed to secondary school students.Keywords: Chemistry experiments; pH indicators; home materials and reagents; chemical demonstrations

Secadero solar forzado para productos agricolas

Se propone un secadero solar forzado, formado por un colector solar y una cámara de secado donde se coloca el producto. El colector construido tiene una cobertura de policarbonato de 7.5 m2 . Las paredes de la cámara construida con placas de cemento autoclavadas, tiene una cubierta de policarbonato y una puerta de ingreso en la parte posterior. En el interior se colocan bandejas apiladas donde se coloca el producto. El aire de secado fluye a través del producto por circulación forzada impulsado por medio de dos ventiladores de 0,45 kW, colocados debajo de las bandejas. Para el primer ensayo se eligió papa cortada en bastones. El contenido de humedad de las papas se redujo al 20 % durante 2 días de secado. Se analizan los resultados experimentales durante el tiempo de secadoFil: García, V.. Universidad Nacional de Catamarca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Iriarte, Adolfo Antonio. Universidad Nacional de Catamarca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Justinovich, S.. Universidad Nacional de Catamarca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Angel, L.. Universidad Nacional de Catamarca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Heredia, T.. Universidad Nacional de Catamarca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía no Convencional; Argentin