New results on metric-locating-dominating sets of graphs

A dominating set S of a graph is a metric-locating-dominating set if each vertex of the graph is uniquely distinguished by its distanc es from the elements of S , and the minimum cardinality of such a set is called the metri c-location- domination number. In this paper, we undertake a study that, in general graphs and specific families, relates metric-locating-dominatin g sets to other special sets: resolving sets, dominating sets, locating-dominating set s and doubly resolving sets. We first characterize classes of trees according to cer tain relationships between their metric-location-domination number and thei r metric dimension and domination number. Then, we show different methods to tran sform metric- locating-dominating sets into locating-dominating sets a nd doubly resolving sets. Our methods produce new bounds on the minimum cardinalities of all those sets, some of them involving parameters that have not been related so farPostprint (published version

Determinantes del tipo impositivo efectivo en el sector turístico: un modelo dinámico con datos de panel

This paper presents a dynamic model of the Effective Tax Rate (ETR) in the tourism sector. A dynamic model where the lagged endogenous variable ETR has been included as a regressor to identify the dynamic structure of the variable due to the existence of temporal adjustments between the short and long run in ETR payments has been estimated. The empirical analysis based on a panel data set over the 2008-2013 period explores the determinants of the ETR variable by using a Generalised Method of Moments (GMM) estimator controlling for heterogeneity in the tourism sector. The Arellano-Bond system GMM estimator has been used to estimate the model. The study seeks to shed light on the determinants of tax burden in the tourism sector covering the lack of studies on this topic. The findings obtained suggest that the ETR borne is determined by size, financing structure and type of entity. We deem the finding of the existence of non-linear relationships between ETR and size and financing structure relevant.Este artículo presenta un modelo dinámico para el Tipo Impositivo Efectivo (TIE) en el sector turístico. Este modelo dinámico ha sido estimado usando la variable endógena retardada TIE como regresor para identificar la estructura dinámica de dicha variable, debido a la existencia de ajustes entre el corto y largo plazo en los pagos del TIE. El análisis empírico basado en datos de panel en el periodo 2008-2013 explora los determinantes de la variable TIE utilizándose el estimador del Método Generalizado de Momentos (GMM) controlando la heterogeneidad en el sector turístico. El estimador de Arellano-Bond ha sido utilizado para estimar el modelo. Este estudio busca arrojar luz sobre los determinantes de las cargas impositivas en el sector turístico debido a la escasez de estudios en esta materia. Los resultados obtenidos sugieren que el TIE se encuentra determinado por el tamaño, la estructura financiera y el tipo de empresa. Igualmente consideramos relevante el hallazgo de relaciones no lineales entre el TIE y el tamaño y la estructura de financiación

Metal Accumulation by Jatropha curcas L. Adult Plants Grown on Heavy Metal-Contaminated Soil

Jatropha curcas has the ability to phytoextract high amounts of heavy metals during its first months just after seeding. Notwithstanding, there is scarce information about metal uptake by adult J. curcas plants. To shed light on this issue, 4-year-old J. curcas L. plants were planted in a soil mixture of peat moss and mining soil (high metals content), and the biomass growth and metal absorption during 90 days were compared with those of plants growing in peat moss. The main metal found in the mining soil was Fe (31985 mg kg-1) along with high amounts of As (23717 mg kg-1). After the 90-day phytoremediation, the plant removed 29% of Fe and 44% of As from the soil mixture. Results revealed that J. curcas L. translocated high amounts of metals to its aerial parts, so that translocation factors were much higher than 1. Because of the high translocation and bioaccumulation factors obtained, J. curcas L. can be regarded as a hyperaccumulator plant. Despite the great capacity of J. curcas L. to phytoremediate heavy-metal-contaminated soils, the main drawback is the subsequent handling of the metal-contaminated biomass, although some potential applications have been recently highlighted for this biomass.University of Seville (VIPPIT-2019-I.5

El riesgo en el contrato de obra

Este artículo pretende dar respuesta al interrogante planteado a partir de una metodología empírica y práctica, de análisis de la legislación, la jurisprudencia y la doctrina, para arribar a unas conclusiones útiles para entidades públicas y contratistas del Estado

El impacto de los programas de crédito para la reactivación del tejido productivo y el empleo tras la pandemia: el caso de Argentina

This technical paper seeks to narrow the knowledge gap concerning the impacts of financing and provision of credit to accelerate recovery and adjustments in the wake of a crisis. Due to the lack of data in developing countries, the literature surrounding evaluation of this type of program in Latin American and Caribbean countries is relatively recent and scarcer still is the measurement of the impact of such programs in the context of the crisis caused by the COVID-19 pandemic. This work analyzes the impact of credit programs on the recovery productive structure and employment throughout the entire territory of Argentina, using key economic variables, and distinguishing between the different instruments utilized. The results suggest that the programs did indeed help to increase the number of workers employed and their real wages in beneficiary firms during the first three quarters of 2021; moreover, they impacted the sustainability of these Argentinian firms, increasing their chances of survival.Esta nota contribuye a reducir la brecha de conocimiento sobre los impactos del financiamiento para acelerar la recuperación y el ajuste después de una crisis, a través de la provisión de crédito. La falta de datos en los países en desarrollo hace que la literatura de evaluación de este tipo de programas en países latinoamericanos sea relativamente reciente, y es aún más escasa la medición del impacto de programas en el contexto de la crisis generada por la pandemia de COVID-19. Este trabajo cubre una brecha de conocimiento significativa al proveer un análisis del impacto del programa de crédito para la recuperación del tejido productivo y el empleo en Argentina, para todo el territorio nacional, sobre variables económicas clave, y distinguiendo entre los diferentes instrumentos utilizados. Los resultados sugieren que el programa habría contribuido a incrementar la cantidad de trabajadores empleados y su salario real en las empresas beneficiarias durante los primeros tres trimestres de 2021. Además, influyó en la sostenibilidad de estas empresas argentinas, dado que incrementó su probabilidad de supervivencia

Dominating 2-broadcast in graphs: complexity, bounds and extremal graphs

Limited dominating broadcasts were proposed as a variant of dominating broadcasts, where the broadcast function is upper bounded. As a natural extension of domination, we consider dominating 2-broadcasts along with the associated parameter, the dominating 2-broadcast number. We prove that computing the dominating 2-broadcast number is a NP-complete problem, but can be achieved in linear time for trees. We also give an upper bound for this parameter, that is tight for graphs as large as desired.Peer ReviewedPostprint (author's final draft

El sentido de la dispersión y su desarrollo en el currículo

La dispersión es un concepto básico en estadística, pues cuantifica la variabilidad en las distribuciones de datos y las distribuciones de probabilidad, estando ligada tanto al análisis exploratorio de datos, como a la probabilidad. Es también esencial en inferencia, pues permite valorar la precisión de las estimaciones o del riesgo asumido en los procesos de decisión. La finalidad de este trabajo es analizar la forma en que este concepto se contempla en las directrices curriculares españolas y establecer comparaciones con las de otros países. Todo ello para colaborar en una mejor adquisición del sentido de la dispersión en los estudiantes

Influence of the welan gum biopolymer concentration on the rheological properties, droplet size distribution and physical stability of thyme oil/W emulsions

The objective of this work is to obtain a stable and natural antimicrobial delivery system. Thus, the effect of the addition of a natural polysaccharide such as welan gum on the linear viscoelastic properties, flow behaviour, droplet size distribution and physical stability of thyme oil/W emulsions formulated with a wheat-derived surfactant was studied. All emulsions obtained show submicron diameters regardless of the concentration of welan. Emulsion without gum shows Newtonian behaviour under steady shear. Meanwhile, emulsions containing welan gum show a weak gel-like behaviour with higher G′ and G″ values on increasing the content of gum in the emulsion. Their flow curves illustrate a shear thinning behaviour with much greater viscosity than that exhibited by emulsions without gum. This behaviour fits well to the Cross model. The main destabilization process of thyme oil/W emulsion without gum is creaming versus flocculation and coalescence in emulsions containing welan. Rheology, diffraction laser and multiple light scattering techniques have proved that welan gum is an important rheological modifier for thyme oil/W ecological emulsions, it being possible to control the rheological properties of these emulsions by adjusting the concentration of gum. However, welan gum does not improve the physical stability of these emulsions.Ministerio de Economía y Competitividad CTQ2015-70700-

Characterization of novel nanoemulsions, with improved properties, based on rosemary essential oil and biopolymers

ACKGROUND: Nowadays, it is of great interest to develop stable and sustainable formulations that act as nanocarriers of active ingredients. In this work, the droplet size distribution, rheology and physical stability of nanoemulsions with improved properties containing rosemary essential oil and biopolymers as a function of the concentration of these polysaccharides were investigated. RESULTS: Mean diameters below 150 nm were achieved, indicating nanostructures were obtained. Regardless of gum type, a gel-like structure and a shear thinning behaviour was achieved. In addition, an increase of G′, G″ and viscosity and a decrease of J0, J1, J2, λ1 and λ2 with increasing gum concentration were observed, due to the formation of a three-dimensional network in the aqueous phase. Slight differences between nanoemulsions containing welan or xanthan were found. Creaming, depletion flocculation and gel aggregation were the main destabilization processes at low, intermediate and high gum concentration, respectively. A 0.4 wt% gum nanoemulsion exhibited the best physical stability. CONCLUSION: These stable and sustainable nanoemulsions with improved rheological properties contribute to the development of biodegradable and non-toxic food or agrochemical products. © 2020 Society of Chemical Industry.Ministerio de Economía y Competitividad CTQ2015-70700-