Nitrogen transformations and fluxes in fish ponds: a modelling approach

Nitrogen is a key element in aquatic environments, and in Aquaculture it is an important pond management variable. In current aquaculture research two important goals are to maintain the water quality within the system, and to improve the retention of nutrients applied to the system in order to minimize the discharge. The principal objectives of this study were to integrate the information available of nitrogen processes in fish ponds into a predictive model, and to investigate further the nitrogen dynamics between the water, the sediments and the biota present in this systems. First, a nitrogen balance in fish ponds was followed along a growing cycle; by combining estimates of the deposition rates of uneaten feed, faeces and dead phytoplankton with measurements of nitrogen accumulation in the sediment, the rate of decomposition of organic matter in the sediment was evaluated. The cumulative recovery at the end of the experiment was almost 100%, meaning that the nitrogen budget in the system studied can be fully explained without any consideration of nitrogen volatilisation, due to either denitrification or ammonia volatilisation. The interactions between various N-species are complex and difficult to integrate. A model that calculates the amounts of various N-compounds in the water column and in the sediment was constructed, and used to gain insight into the relative importance of transformation processes between the various N-compounds. The model was divided into three modules: fish, phytoplankton and sediment-water.All concentrations of the various N-species present were simulated well except the N retained in organic matter in the sediment. To improve our understanding of the bottom organic matter dynamics, and make the model a more comprehensive predictive tool, an estimation of the principal sources of organic matter that accumulate in fish pond bottoms was assessed. Organic matter accumulation in fish ponds was quantified, and the data was used to construct, to calibrate and to validate a dynamic simulation model of organic matter deposition/decomposition in fish ponds. Besides, the rates of sedimentation and resuspension were measured along a growing cycle, following the influence of nutrient input, water parameters, fish biomass and fish size on these processes. Using a dilution analysis method to differentiate between sedimented and resuspended particles, sedimentation and resuspension rates were calculated. The rate of material collected in sediment traps increased from 88.5 to 330 g/m 2 per day along the growing cycle, but the relative resuspension did not change significantly, being always in the range of 42 to 47% of the total collected material. The processes of sedimentation of organic matter and resuspension were included in the original model. The proportion of three principal sources of organic matter that accumulate in the pond bottom were also included as parameters of the sedimentation process. A logistic equation relating the rate of resuspension and the fish biomass was calculated; and seepage, as a potential loss of nitrogen from the system, was also considered. The additions to the model represented a substantial improvement to model simulations.</p

Center of pressure displacements in individual swith Down syndrome during a bipedal position

Objetivo:Valorar el equilibrio de adultos con síndrome de Down a través del estudio del desplazamiento del centro depresiones. Método: Estudio transversal de casos y controles. Doce sujetos con síndrome de Down y 12 sin síndrome de Down formaron parte del estudio. Todos los participantes realizaron 2 pruebas sobre plataforma dinamométrica: i)estática con ojos abiertos y ii) estática con ojos cerrados. Las señales del centro de presiones fueron analizadas en el dominio temporal. Se utilizaron contrastes no paramétricos para el análisis estadístico de los datos Resultados:Los resultados mostraron diferencias significativas entre- grupos en las variables rango ante-roposterior, fuerza anteroposterior y fuerzamedio-lateral(p<0.05). Las comparaciones intragrupos mostraron peores resultados en las pruebas con ojos cerrados en ambos grupos. Conclusión:En el presente trabajo las personas con síndrome de Down presentaron un control del equilibrio mermado al compararlo con sujetos sin síndrome de Down. Los datos obtenidos no son concluyentes para determinar cuál de los sistemas involucrados en el control del equilibrio es el responsable de estos resultados.Objective: To evaluate body balance of adults with Down syndrome based on the analysis of their centre of pressure behaviour. Method: Cross-sectional case control-study. Twelve individuals with Down syndrome and twelve without Down syndrome took part in the study. All the participants were tested under two conditions on a force plate: i) static with eyes open and ii) static with eyes closed. Centre of pressure signals were analyzed in time domain. Non-parametric contrasts were used for statistical analysis. Results: Statistical differences between groups were found in anteroposterior range, anterior-posterior force and medio-lateral force (p < 0.05). Within-groups comparisons showed poorer results in eyes closed conditions for both groups. Conclusion: Individuals with Down syndrome involved in the present study showed deficits in balance control when compared with people without Down syndrome. The obtained data are not conclusive. The participation of the different systems which control balance in people with Down syndrome remains unknownObjetivo: Avaliar o equilíbrio de adultos com síndrome de Down através do estudo do desprendimento do centro de pressão. Método: Estudo transversal de caso e controlos. Doze sujeitos com SD e 12 sem Síndrome de Down fizeram parte do estudo. Todos os participantes realizaram 2 provas sobre plataforma dinamométrica: i) estática com olhos abertos e ii) estática com olhos fechados. Os sinais dos centros de pressões foram analisados em domínio temporal. Foram utilizados testes não paramétricos para a análise estatística dos dados. Resultados: Os resultados mostraram diferenc¸ as significativas entre grupos nas variáveis de intervalo ântero-posterior, forc¸ a ântero-posterior e forc¸ a médio-lateral (p < 0.05). As comparac¸ ões intragrupos mostram piores resultados nas provas de equilíbrio com olhos fechados para ambos os grupos. Conclusão: No presente estudo, as pessoas com Síndrome de Down apresentaram um controlo de equilíbrio diminuído em comparac¸ ão a sujeitos sem Síndrome de Down. Os dados obtidos não são conclusivos paradeterminar qualdos sistemas envolvidosno controlodo equilíbrio é responsávelpor estes resultado

Effect of the recycling process and binder type on bituminous mixtures with 100% reclaimed asphalt pavement

There is a great interest in increasing the amount of recycled material used in asphalt mixes because of the beneficial impact on the environment. This is leading to the development of different recycling procedures, from cold in-situ to hot in-plant recycling. The objective of the study presented in this paper is to evaluate cracking resistance of recycled mixes manufactured by three types of processes, i.e., cold with emulsion, hot with high penetration bitumens and hot with emulsion (half-warm mixture), using 100% of reclaimed asphalt pavement (RAP) at different temperatures. Differences in their workability and ease of use are also analysed by gyratory compaction.Peer ReviewedPostprint (author's final draft

Sensitivity of the g-mode frequencies to pulsation codes and their parameters

From the recent work of the Evolution and Seismic Tools Activity (ESTA, Lebreton et al. 2006; Monteiro et al. 2008), whose Task 2 is devoted to compare pulsational frequencies computed using most of the pulsational codes available in the asteroseismic community, the dependence of the theoretical frequencies with non-physical choices is now quite well fixed. To ensure that the accuracy of the computed frequencies is of the same order of magnitude or better than the observational errors, some requirements in the equilibrium models and the numerical resolutions of the pulsational equations must be followed. In particular, we have verified the numerical accuracy obtained with the Saclay seismic model, which is used to study the solar g-mode region (60 to 140$\mu$Hz). We have compared the results coming from the Aarhus adiabatic pulsation code (ADIPLS), with the frequencies computed with the Granada Code (GraCo) taking into account several possible choices. We have concluded that the present equilibrium models and the use of the Richardson extrapolation ensure an accuracy of the order of $0.01 \mu Hz$ in the determination of the frequencies, which is quite enough for our purposes.Comment: 10 pages, 5 figures, accepted in Solar Physic

Influence of Low-Degree High-Order p-Mode Splittings on the Solar Rotation Profile

The solar rotation profile is well constrained down to about 0.25 R thanks to the study of acoustic modes. Since the radius of the inner turning point of a resonant acoustic mode is inversely proportional to the ratio of its frequency to its degree, only the low-degree p modes reach the core. The higher the order of these modes, the deeper they penetrate into the Sun and thus they carry more diagnostic information on the inner regions. Unfortunately, the estimates of frequency splittings at high frequency from Sun-as-a-star measurements have higher observational errors due to mode blending, resulting in weaker constraints on the rotation profile in the inner core. Therefore inversions for the solar internal rotation use only modes below 2.4 mHz for l < 4. In the work presented here, we used an 11.5 year-long time series to compute the rotational frequency splittings for modes l < 4 using velocities measured with the GOLF instrument. We carried out a theoretical study of the influence of the low-degree modes in the region 2 to 3.5 mHz on the inferred rotation profile as a function of their error bars.Comment: Accepted for publication in Solar Physics. 17 Pages, 9 figure

Vortex tubes in velocity fields of laboratory isotropic turbulence: dependence on the Reynolds number

The streamwise and transverse velocities are measured simultaneously in isotropic grid turbulence at relatively high Reynolds numbers, Re(lambda) = 110-330. Using a conditional averaging technique, we extract typical intermittency patterns, which are consistent with velocity profiles of a model for a vortex tube, i.e., Burgers vortex. The radii of the vortex tubes are several of the Kolmogorov length regardless of the Reynolds number. Using the distribution of an interval between successive enhancements of a small-scale velocity increment, we study the spatial distribution of vortex tubes. The vortex tubes tend to cluster together. This tendency is increasingly significant with the Reynolds number. Using statistics of velocity increments, we also study the energetical importance of vortex tubes as a function of the scale. The vortex tubes are important over the background flow at small scales especially below the Taylor microscale. At a fixed scale, the importance is increasingly significant with the Reynolds number.Comment: 8 pages, 3 PS files for 8 figures, to appear in Physical Review

Some questions about subspace-hypercyclic operators

A bounded linear operator T on a Banach space X is called subspace-hypercyclic for a subspace M if Orb. (T, x) ∩ M is dense in M for a vector x∈ M. We show examples that answer some questions posed by H. Rezaei (2013) [7]. In particular, we provide an example of an operator T such that Orb. (T, x) ∩ M is somewhere dense in M, but it is not everywhere dense in M. © 2013 Elsevier Ltd.This work is supported in part by MEC and FEDER, Project MTM2010-14909. The first author was also supported by a grant from CONACYT.Jiménez-Munguía, RR.; Martínez-Avendaño, RA.; Peris Manguillot, A. (2013). Some questions about subspace-hypercyclic operators. Journal of Mathematical Analysis and Applications. 408:209-212. https://doi.org/10.1016/j.jmaa.2013.05.068S20921240

Theory of Stellar Oscillations

In recent years, astronomers have witnessed major progresses in the field of stellar physics. This was made possible thanks to the combination of a solid theoretical understanding of the phenomena of stellar pulsations and the availability of a tremendous amount of exquisite space-based asteroseismic data. In this context, this chapter reviews the basic theory of stellar pulsations, considering small, adiabatic perturbations to a static, spherically symmetric equilibrium. It starts with a brief discussion of the solar oscillation spectrum, followed by the setting of the theoretical problem, including the presentation of the equations of hydrodynamics, their perturbation, and a discussion of the functional form of the solutions. Emphasis is put on the physical properties of the different types of modes, in particular acoustic (p-) and gravity (g-) modes and their propagation cavities. The surface (f-) mode solutions are also discussed. While not attempting to be comprehensive, it is hoped that the summary presented in this chapter addresses the most important theoretical aspects that are required for a solid start in stellar pulsations research.Comment: Lecture presented at the IVth Azores International Advanced School in Space Sciences on "Asteroseismology and Exoplanets: Listening to the Stars and Searching for New Worlds" (arXiv:1709.00645), which took place in Horta, Azores Islands, Portugal in July 201

Osmotic stress tolerance in forage oat varieties (Avena Sativa L.) based on osmotic potential trials

Received: April 1st, 2022 ; Accepted: December 12th, 2022 ; Published: February 7th, 2023 ; Correspondence: [email protected]; [email protected] oats (Avena sativa L.) are globally important for milk and meat production, and, to a lesser extent, for the human diet. In Mexico, oats are a strategic crop, occupying the fourth place in cultivated area, only after maize for grain, bean, and sorghum for grain. Droughts are the main problem for oat production in Mexico. This study evaluated the germination and seedling growth of several oat varieties in response to drought stress simulated by PEG-6000 treatments of different osmotic pressure in order to identify drought-resistant genotypes. The Teporaca genotype was the most outstanding in the three levels of OP compared to its control with 0.0 of Osmotic Potential (OP). The Teporaca genotype showed the largest root length and the lowest diminishment of root length under osmotic stress conditions. This genotype also had the largest shoot length in the three osmotic stress levels. Regarding root fresh weight, Babicora stands out with 98.5% and Teporaca with 43% in the most severe level. Teporaca, Menonita, and Babicora showed the outstanding root dry weights of 346.5%, 327.2%, and 251.2%, respectively. These varieties had higher root dry weight than their own controls in water in the most severe level of OP. In conclusion, the Teporaca, Menonita, and Karma genotypes showed the highest osmotic stress tolerance and could be used as sources of favorable alleles to improve oat drought tolerance

Simulación de un concentrador solar de disco parabólico para producción de potencia y enfriamiento

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMEN: En este trabajo se presenta la modelación y simulación de un concentrador solar de disco parabólico para alimentar térmicamente a un sistema de refrigeración por absorción y a un motor Stirling, con diferente eficiencia, acoplado con un sistema de refrigeración por compresión. El enfriamiento producido por este sistema se utiliza para aire acondicionado de una vivienda. El estudio fue realizado mediante balances de energía y de masa, en cada componente de los sistemas de refrigeración y del sistema solar. La transferencia de calor por convección y por radiación también fueron considerados. Los resultados muestran que el colector solar alcanza eficiencia térmica de hasta 0.82 para relación de concentración de 100. El concentrador solar produce hasta 1.3 kW. En tanto que el sistema completo puede producir enfriamiento de 2.3 kW y 0.47 kW por el sistema de compresión y el de absorción respectivamente. La potencia de la bomba de la disolución es hasta 20 veces menor que la potencia requerida por el compresor del sistema de compresión.ABSTRACT: This paper presents the dish solar collector modeling and simulation for thermally driving an absorption refrigeration system and a Stirling engine, with different efficiency, coupled with a compression refrigeration system. The cooling produced by the system is used for home air conditioning. The study by means energy and mass balances, in each component of the cooling systems and the solar system was carried out. The Convection and radiation heat transfer also has been considered. The results show that the solar collector reaches thermal efficiency of up to 0.82 for a concentration ratio of 100. The solar concentrator produces up to 1.3 kW. While the complete system 2.3 kW and 0.47 kW of cooling by the compression and absorption system respectively can produce. The power of the solution pump is up to 20 times less than the power required by the compressor of the compression system.info:eu-repo/semantics/publishedVersio