The lonely runner with seven runners

Suppose $k+1$ runners having nonzero constant speeds run laps on a unit-length circular track starting at the same time and place. A runner is said to be lonely if she is at distance at least $1/(k+1)$ along the track to every other runner. The lonely runner conjecture states that every runner gets lonely. The conjecture has been proved up to six runners ($k\le 5$). A formulation of the problem is related to the regular chromatic number of distance graphs. We use a new tool developed in this context to solve the first open case of the conjecture with seven runners

Evaluation of 1,4-Dioxane Biodegradation Under Aerobic and Anaerobic Conditions

Used mainly as a solvent stabilizer, 1,4-dioxane is present at many sites contaminated along with chlorinated solvents and other chemical compounds. Considered a probable human carcinogen by the U.S. Environmental Protection Agency, this contaminant has raised considerable concerns because of its potential adverse effects on health. Therefore, remediation of 1,4-dioxane has gained importance, and although there are several approaches for its treatment, such as ex situ physicochemical processes, bioremediation is a key alternative because it is a low energy demanding process. Anaerobic conditions are present at most contaminated sites, however, there is insufficient scientific evidence for anaerobic biodegradation of 1,4-dioxane. On the other hand, aerobic biodegradation of 1,4-dioxane has been widely studied under metabolic and cometabolic conditions. Nevertheless, limited information is known about the rate of 1,4-dioxane cometabolism with substrates, such as propane, that can be used for in situ bioremediation. Bacteria that grow on 1,4-dioxane have a low affinity for the contaminant since their half saturation coefficient (Ks) values are often high, but the contaminant half saturation coefficients (Kc) associated with cometabolism are usually lower. However, kinetic parameters for cometabolic biodegradation of 1,4-dioxane with a non-toxic and convenient substrate such as propane have not been evaluated. Based on the gaps in the scientific literature, and in order to expand the understanding of 1,4-dioxane biodegradation and its potential in situ bioremediation applications, the objectives of this study included: 1) Estimate the kinetic parameters for 1,4-dioxane metabolism and for cometabolism by propane-oxidizing bacteria that are relevant to field applications in bioremediation; and 2) Evaluate the potential for in situ bioremediation of a 1,4-dioxane plume using metabolic and cometabolic biosparging and bioaugmentation, based on simulations using a subsurface transport model; and 3) Evaluate the potential for anaerobic biodegradation of 1,4-dioxane. To achieve the first objective, kinetic parameters for aerobic cometabolic biodegradation of 1,4-dioxane by propane-oxidizing bacteria were evaluated for a pure culture, Rhodococcus ruber ENV425, and a mixed culture, ENV487. The 1,4-dioxane metabolizer Pseudonocardia dioxanivorans CB1190 was also tested for its kinetic parameters. Kinetics for metabolic and cometabolic biodegradation of 1,4-dioxane were successfully modeled using modified Monod equations. Results indicate that the propanotrophic bacteria have lower half saturation constants (KC = 6.05 ± 0.26 and 3.25 ± 0.05 mg COD L-1) for 1,4-dioxane than CB1190 (KS = 11.5 ± 0.4 mg COD L-1). Other parameters measured included the biomass yield (Y) for propane and 1,4-dioxane, transformation capacity (TC), half saturation coefficients for oxygen (KSO and KCO), biomass decay coefficient (b), and substrate utilization rates (kS and kC). Coinhibition parameters (KiS and KiC) between propane and 1,4-dioxane were also estimated. Batch simulations showed that cometabolism is more advantageous than metabolism when the initial concentration of 1,4-dioxane is low (~1 mg L-1) and that both processes are heavily impacted by dissolved oxygen concentrations less than 2 mg L-1. The second objective was achieved by simulating the effect of biodegradation reactions on a 1,4-dioxane subsurface plume treated with biosparging and bioaugmentation. The effect of the injection rates of propane, biomass and oxygen as well as the initial 1,4-dioxane concentrations were evaluated in terms of the time to reach an average 1,4-dioxane level of 1 µg L-1, as well as the percentage of 1,4-dioxane that underwent biodegradation. Data from a biosparging pilot study at Vandenburg Air Force base was used to calibrate the model as it applied to propanotrophic cometabolism. The simulation results indicated that propanotrophic cometabolism achieves remediation at a faster rate when the initial 1,4-dioxane concentration is less than 7.5 mg L-1; lower concentrations do not support enough growth of microbes that grow of 1,4-dioxane to adequately offset the effect of cell decay. A continuous supply of propane to support cometabolism negates the effect of cell decay. The model provides a framework for comparing metabolic and cometabolic approaches to in situ bioremediation at other sites. To achieve the third objective, microcosms were prepared with groundwater and sediment from two contaminated sites at which the field data suggest that 1,4-dioxane is undergoing anaerobic biodegradation. The groundwater contains high levels of acetone and isopropanol, which ensure anaerobic conditions. High levels of halogenated solvents are also present. The microcosms were amended with uniformly labeled [14C]-1,4-dioxane to characterize degradation products. Amendments included Fe(III) oxide, Fe(III)-ethylene-diaminetetraacetic acid (Fe(III)-EDTA), anthraquinone disulfonate (AQDS), sulfate and oxygen. Following four years of incubation, biodegradation of many of the halogenated solvents was observed, as was iron reduction, sulfate reduction, and methanogenesis. However, there was no significant evidence to support biodegradation of 1,4-dioxane under anaerobic conditions, although partial mineralization in aerobic microcosms was observed. Further laboratory studies are needed to determine the feasibility of anaerobic biodegradation of 1,4-dioxane. Until then, aerobic treatment remains the only viable bioremediation alternative

Economic impact of sport: Topic of growing interest for the scientific literature

El estudio del impacto económico en el deporte como disciplina científica surge para la identificación del beneficio económico de grandes eventos deportivos. Su evolución se ha dirigido a enfoques más amplios, estudiando no sólo el aspecto económico sino también los efectos intangibles, en grandes y pequeños eventos, instalaciones, y franquicias. En el presente estudio se analiza la evolución del tratamiento del impacto económico del deporte en la ciencia mediante un estudio bibliométrico del periodo 1984-2013. Los resultados obtenidos se han empleado como base para conocer la percepción de los expertos en la temática sobre los aspectos clave de la investigación en este campo. Se concluye que el estudio del impacto económico del deporte tiene capacidad de evolución tanto en el área de la economía del deporte como en otras áreas de estudio. Además estos estudios tienen una clara aplicación práctica en la mejora de la gestión de eventos e instalaciones deportivasThe study of the economic impact on the sport as a scientific discipline was born for the identification of the economic benefits of major sports events. Its evolution has led to broader approaches. It has been applied to the study not only of the economic aspect but also the intangible effects in both large and small events, in facilities and franchises. In the present work, the evolution of the study the economic impact of sport science is analyzed using bibliometric during the period 1984-2013. The results from these analyses have been used to prepare a questionnaire in order to get the perception of experts in the field on key aspects of research in the scientific issues. From the work, it can be concluded that the economic impact of sport science is capable of evolution in the area of economics of sport and in a complementary manner in other areas. In addition, this kind of studies has a clear practical application for improving the management of sports events and sporting facilitie

Colegialidad docente: Un estudio comparativo (España/México) de validación de constructo para el diseño de un instrumento de evaluación

En Bakieva (2011) y Bakieva, Jornet y Carmona (2012) se aportan las bases teóricas y una primera validación de constructo realizada en España para el desarrollo de un instrumento de evaluación de colegialidad docente en Educación Primaria y Secundaria. Aquí presentamos un segundo análisis comparativo de los juicios de dos grupos de profesorado de España y México, que han valorado las dimensiones que componen la Colegialidad Docente. Finalmente, identificamos tres dimensiones de Colegialidad Docente: Satisfacción Laboral, como percepción de lo que ¿recibe¿ el sujeto en esa institución, Clima Institucional, como percepción exterior de lo que se vive en la institucional, y Compromiso Institucional, como percepción de lo que el sujeto está ¿dispuesto a dar¿ a la institución. El trabajo aporta evidencias de validación de la parte teórica por jueces, comparando las valoraciones de profesorado de dos países. El estudio se basa en el juicio de expertos y analiza la concordancia y nivel de las valoraciones de todos los elementos de la escala de Colegialidad en dos criterios: relevancia para el constructo teórico, y susceptibilidad de cambio de los elementos. En términos generales, puede señalarse que existe el consenso entre los jueces de España y México, y eso constituye una evidencia positiva en cuanto a la selección de elementos de evaluación establecidos para la Colegialidad Docente. En el criterio de susceptibilidad de cambio se aprecian diferencias importantes en la valoración

Agronomic classification between vineyards ('Verdejo') using NDVI and Sentinel-2 and evaluation of their wines

A classification between three vineyards belonging to the Appellation of Origin Rueda (Castilla y León, Spain) has been established in veraison to determine the productive capacities of each vineyard and to study their impact on the grape quality. Several open-access multispectral images obtained from the SENTINEL-2A satellite in the year 2016 were used to calculate the NDVI (Normalized Difference Vegetation Index), which provides information about the vigour of the vineyards. Eleven cloud-free images were assessed and based on the NDVI, three vigour levels were established: high vigour (0.356-0.458), medium vigour (0.285-0.355) and low vigour (0.166-0.284). A level of vigour was assigned to each vineyard according to the NDVI mean values of its pixels. Significant differences were found in the pruning wood weight and yield: high, medium and low vigour values were 2438, 1895 and 1487 kg·ha-1 and 15984, 12990 and 10576 kg·ha-1, respectively. The highest values of total acidity (6.04 g·L-1) and tartaric acid (9.05 g·L-1) have been obtained in low vigour, as well as the lowest values of pH (3.26), malic acid (0.42 g·L-1) and potassium (1640 ppm). Finally, one wine per vigour was produced and a tasting was carried out to check if the differences between the vineyards were perceptible. According to the obtained results, the NDVI is a good indicator to classify vineyards, finding notable differences between the experimental treatments studied

Design of an electroflotation system for the concentration and harvesting of freshwater microalgae

Microalgae are considered as one of the most promising alternatives for the integrated use of agro-industrial water residues and the production of metabolites of high industrial interest. This is due to algae can grow on wastewater which in turn can reduce the emission of nutrients to rivers and lakes. However, the greatest scientific-technological barrier is the concentration and separation of the biomass produced. There are several processes used at different levels (from laboratory to industrial scale) such as flocculation, centrifugation, flotation, etc. These can be very expensive or can (possibly) contaminate the biomass. Unlike the previous ones, electroflotation has been proposed as a cost-efficient method, nevertheless its final efficiency will depend heavily on the type of alga and culture medium. Taking into account the above, the present project aims to design an electroflotation system for the concentration and harvest of microalgae biomass. The effect of several factors (pH, time, voltage and distance between the electrodes) and for types of materials (Copper, Aluminium, Iron and Steel) on biomass recovery efficiency from a culture of Chlorella vulgaris UTEX 1803 was evaluated by the implementation of a Design of experiments (43 non-factorial design) using STATISTICA 7.0. Results show that, the materials with higher concentration efficiency were cooper and aluminium with 40 and 80% respectively, and the most relevant factors were distance between electrodes (1-2 cm), time (>20 min) and Voltage (>15V). In order to increase the efficiency of the overall process a new 43 experimental factorial design was proposed using as factors distance between electrodes, time, voltage and agitation. Results show that agitation positively affects the total efficiency until reaching a total concentration of the biomass (100%). It was found that a voltage close to 50V and a time greater than 25 min positively affect the final efficiency of the copper and aluminium electrodes, however aluminium has the highest efficiency (> 95%) compared to copper (<85%)

The circular economy approach to improving CNP ratio in inland fishery wastewater for increasing algal biomass production

In this work, the capacity of wastewater from an inland fishery system in Colombia (Norte de Santander) was tested as culture medium for Chlorella sp. and Scenedesmus sp. Due to insufficient N and P concentrations for successful algae growth, the effect of wastewater replenishment with NO3, PO4, and Na2CO3 or NaHCO3 as a carbon source was analyzed using a three-factor nonfactorial response surface design. The results showed that the addition of NaNO3 (0.125 g/L), K2HPO4 (0.075 g/L), KH2PO4 (0.75 g/L), and NaHCO3 (0.5 and 2 g/L for Chlorella sp. and Scenedesmus sp. respectively) significantly increased the biomass of Chlorella sp. (0.87 g/L) and Scenedesmus sp. (0.83 g/L). Although these results show that the addition of other nutrients is not necessary (Na, Mg, SO4, Ca, etc.), it is still essential to determine the quality of the biomass produced in terms of its application as a feed supplement for fish production