Abstract: The Quadratic Assignment Problem (QAP) consists of finding an optimal allocation of n facilities to n locations in such a way as to minimize the cost of interaction between facilities. The QAP is considered as a NP-hard. This article presents an application of QAP that consists of modeling a traffic system by introducing a probability transition matrix to transform the QAP into the Stochastic Quadratic Assignment Problem (SQAP). The objective of this article is to find solutions for SQAP through the implementation of the metaheuristic Greedy Randomized Adaptive Search Procedure (GRASP), in the JAVA programming language. The program is executed for a set of test instances and the results obtained by the application of two search strategies that make four combinations in the construction phases and the post processing phases of the metaheuristics. The program was also executed for a problem that presents instances of size n = 12 to 30, whose optimal solution is given. Given the need to offer solutions to logistics problems of the NP-hard class, a tool for approximating the optimal solutions is presented.

RESUMEN No es clara la carga de morbimortalidad de la lesión cardíaca clínicamente evidente secundaria a la enfermedad por coronavirus de 2019 (COVID-19) en los niños en edad escolar. A lo largo de 12 meses, en un importante hospital pediátrico académico en la región del medio oeste de Estados Unidos, hubo 1481 casos de COVID-19 sin hospitalización en niños en edad escolar por lo demás sanos, en quienes se hicieron 195 pruebas cardíacas. Si bien aparecieron hallazgos fortuitos, no se descubrió ninguna patología cardíaca relacionada con la COVID-19. Además, ~3 % de los niños solamente tuvieron síntomas cardíacos agudos que requirieron una evaluación por el área de cardiología pediátrica. Los niños que no fueron hospitalizados por COVID-19 tienen un riesgo muy bajo de desarrollar daño cardíaco clínicamente significativo y son más propensos a presentar hallazgos fortuitos.

The present study reports five metazoan parasites recorded from silver kob (Argyrosomus inodorus). Five fish were collected monthly (n=55) for 11 months in 2017-2018 (excluding July 2017) using conventional angling gear in Toscanini, Mile 108 and Henties Bay, northern Namibia. Fish were examined individually for ecto- and endo-parasites. Photomicrographs, drawings and measurements of parasites were made using a camera lucida and calibrated eyepiece of an Olympus (BX50) compound microscope and/or a Zeiss (Discovery V8) camera calibrated on a Leica dissecting microscope. Amongst species found, monogeneans including Diplectanum sciaenae van Beneden & Hesse, 1863, two species of Calceostoma van Beneden, 1858, one species of Sciaenacotyle Mamaev, 1989 and one acanthocephalan Corynosoma australe Johnston, 1937 were found and are reported here. This is the first study of parasites found from silver kob of the Atlantic Ocean. Silver kob has potential to be used as a mariculture species. In addition to mariculture, information obtained from this study may also be used as a baseline for stock structure and biological tagging. SIGNIFICANCE: • Silver kob has potential to be used as a mariculture species. Information obtained from this study will therefore form awareness to future mariculture silver kob farmers in terms of parasites that can infest and infect silver kob, hence making it possible to apply specific prevention and control measures. In addition to mariculture, results obtained from this study may be used as a baseline for biological tagging for stock structure assessment using parasites.

ABSTRACT The freshwater prawn Macrobrachium acanthurus represents a valuable resource for fishermen's communities in Mexico, although the information of its culture conditions and nutrition is still scarce. Prebiotics are defined as non-digestible components that are metabolized by specific health-promoting bacteria in the host's digestive system, improving the health status and growth performance of cultured aquatic organisms. Fructooligosaccharides (FOS) and mannan oligosaccharides (MOS) are among the most used prebiotics in aquaculture. The present work aimed to determine the effects of dietary FOS and MOS in the growth performance, immune responses, and sexual maturity of juvenile freshwater prawn Macrobrachium acanthurus. Juveniles (0.06 ± 0.001 g) were fed with diets supplemented with a 3 g kg−1 diet of commercial FOS and MOS for 80 days. At the end of the feeding trial, the following indices were calculated: weight gain, specific growth rate, and feed conversion efficiency, as well as superoxide dismutase and lysozyme activities in hepatopancreas tissue. The growth performance, survival, juveniles’ protein contents did no show significant differences among the groups. No differences were detected in superoxide dismutase and lysozyme activities among experimental groups. Around day 60 of the feeding trial, the females fed with the prebiotics maturated, and by the end of the trial, several of them were carrying eggs. It seems that prebiotics might have a role in sexual maturation, but further research is necessary to establish if prebiotics influences the early maturation of M. acanthurus.

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) have recently been recognized as important techniques for R&D of products and processes, as is attested by several successful applications in different areas of chemical engineering in recent years. In this article we present new experimental methods based on MRI to study flow and microstructure of concentrated emulsions. The objective is to present the unique features of this noninvasive technique to accurately measure different properties of flowing particulate opaque systems. Experimental results of velocity profiles, spatial distribution of droplet sizes and spatial homogeneity of an oil-in-water dispersion in a horizontal, concentric cylinder geometry using different pulse sequences are presented. The application of these techniques allowed probing important information on flow and microstructure of multiphase systems of interest in chemical engineering and food science.

A systematic, house-based serological survey for Trypanosoma cruzi seroreactivity was conducted in three contiguous communities in Olopa municipality, Chiquimula Department, Guatemala. Blood samples from a total of 292 individuals in 63 households were examined by enzyme-linked immunosorbent assay. The seropositive rate ranged from 0% to 20.8% for the three communities, with a mean of 15.1%. Log-linear models showed that seroprevalence was significantly related to age (P < 0.005) but not to sex. However, when the age group with the lowest prevalence (1-9 years) was excluded from the analysis, age was not a significant factor (P = 0.55). Data from a stratified sample collected at the same time were combined with those of the systematic sample to analyze the relationship between seropositivity and possible explanatory variables. Log-linear models, based on 586 individuals in 129 households from the two surveys, revealed a significant positive association between seropositivity and thatched roofs (P = 0.01).

Una encuesta serológica sistemática y domiciliaria para detectar serorreactividad a Trypanosoma cruzi se llevó a cabo en tres comunidades contiguas de la municipalidad de Olapa, en el departamento de Chiquimula, Guatemala. Se examinaron mediante inmunoadsorción enzimática muestras de sangre obtenidas de un total de 292 habitantes que residían en 63 viviendas. La tasa de seropositividad varió de 0 a 20,8% en las tres comunidades y tuvo una media de 15,1%. Los modelos logarítmico-lineales mostraron una asociación significativa entre la seroprevalencia y la edad (P < 0,05), pero no entre aquella y el sexo. No obstante, cuando el grupo de edad que tuvo la seroprevalencia más baja (el de 1 a 9 años) se excluyó del análisis, la edad dejó de ser un factor significativo (P = 0,55). Datos obtenidos de una muestra estratificada recogida simultáneamente se combinaron con los de la muestra sistemática con el fin de analizar la relación entre la seropositividad y algunas variables que podrían ser explicativas. Los modelos logarítmico-lineales, aplicados en 586 habitantes de 129 viviendas incluidas en ambas encuestas, revelaron una asociación positiva significativa entre la seropositividad y la presencia de techo de paja (P = 0,01).

Fósseis de madeira, ossos e dentes achados no Estado do Amazonas, ao longo do rio Purus e do rio Acre, foram estudados, usando-se microscópia convencional e micro-varredura. A espectrometria de massa foi utilizada para investigar os níveis tos menores e traços em algumas amostras de osso fossilizado. Os estudos microscópicos mostram que há pouca alteração das texturas originais. As amostras de madeira fossilizada foram identificadas em lâmina delgada como madeira de lei. Nestas amostras a substituição da matéria original por siderita sugere que a fossilização ocorreu em sedimentos rasos, nos quais as águas intersticiais foram saturadas pelo carbonato de ferro. A precipitação de fases secundarias de ferro foi observada freqüentemente nas rachaduras e vãos, nas amostras tanto de ossos fossilizado como de madeira fossilizada. Outras fases secundárias incluem a sílica, óxidos de ferro e carbonato de manganês. A associação ín tima dessas fases secundárias com as estruturas biológicas originais pode ser evidência para um papel microbiológico na formação dessas fases. Os padrões de concentração semelhante de terras raras em dois ossos em localidades modernas diferentes indicam histórias diagenéticas semelhantes. A preservação virtualmente completa das texturas originais sugere que estudos microscópicos podem ser úteis na classificação dos fósseis e até na identificação de materiais originais. Padrões de concentração de terras raras em ossos fossilizados podem refletir as composições de água subterrânea na época de fossilização.

Fossils of wood, bone and teeth found along the Upper Purus River οf Amazonia. were studied using conventional microscopy and scanning electron microscopy. Mass spectometry was also used to investigate minor and trace element signatures of bone samples.The microsopy studies showed that there was little alteration of original textures. In the fossil wood samples, identified In thin section as tropical hardwood trees, the replacement of the original material with siderite suggests that fossilization occured in shallow sediments in which interstitial waters were saturated with respect to iron carbenate. In samples of both fossilized bone and wood, precipitation of secondary iron phases was commonly observed in cracks and voids. Other secondary phases Included silica, iron oxides, manganese carbonate. The intimate assοciation οf these secondary phases with the original biological structures could be evidence for a microbiological role in the formation of these phases. The similarity in rare earth element (REE) signatures for 2 fossil bone samples from different modern locations indicates their having shared similar diagenetic histories.The virtually complete preservation of original textures suggests that microscοpic studies could be useful in classifying fossil and even in identifying original materials. Rare carth signatures in fossilized bone may reflect ground water compositions at the time of fossilization.