The Lotka-Volterra models with non-local reaction terms

In this paper we consider a diffusive Lotka-Volterra system including nonlocal terms in the reaction functions. We analyze the main types of interactions between species: competition, predator-prey and cooperation. We provide existence and non-existence of positive solutions results. For that, we employ mainly bifurcation method and a priori bounds

Caracterización demográfica de las edades jóvenes en Cuba

This paper presents a characterization of the Cuban population under 30 years old, and its particularities in the composition and structure by age and other demographic differentials. It analyzes the evolution of the group 0-29 years old, and the subgroups 0-14, 15-19 and 15-29 during some selected years, as well as the fundamental characteristics related to mortality, fertility and migration. Emphasis is placed on the need to attend to young ages, to know their characteristics and demographic trends, which is vital for the development of a country. Young people represent an important human resource within society; they act as agents of social change, transformation, economic development and progress. / RESUMEN El artículo presenta una caracterización de la población cubana menor de 30 años de edad y sus particularidades en la composición y estructura por edad, junto a otros diferenciales demográficos. Analiza la evolución del grupo 0-29 años, y los subgrupos 0-14, 15- 19 y 15-29, durante algunos años seleccionados, así como las características fundamentales relacionadas con la mortalidad, la fecundidad y las migraciones. Conocer las características y tendencias demográficas de estas edades es vital para el desarrollo de un país. Los jóvenes representan un recurso humano importante dentro de la sociedad; actúan como agentes de cambio social, transformación, desarrollo económico y progreso

Tendencias de la fecundidad adolescente en Cuba hasta el 2020. / Trends in teenage fertility in Cuba until 2020.

The study of adolescent fertility and its trends continues to be a priority for the social sciences. The political will to decrease this indicator is notable on international agendas, and for Cuba it is a priority. The article analyzes adolescent fertility, its evolutionary trend in the years up to 2020, and the behavior of its determinants. An approach to adolescent pregnancy in the context of COVID-19 in Cuba is presented. Demographic analysis is used as a method. Descriptive statistics (absolute and relative frequency), and comparison between years for an approximation of the possible impact of COVID-19 on adolescent fertility. The result is the disarticulation of Cuban fertility expressed in its low global fertility rate (TFR) and the specific adolescent fertility rate above what is expected and desired. Resistance to the notable decline in adolescent fertility continues, mainly in the eastern part of the country. Discontinuation rates exceed the fertility rate in this age group, accounting for the high rate of adolescent pregnancy. Contraception and marriage as proximate determinants still express gaps in the exercise of sexual and reproductive rights. The weight of adolescent fertility increased from 16.7% in 2019 to 17% in 2020, which means that adolescent girls contributed more to total fertility in 2020, the year of the pandemic, than in 2019. Among its conclusions, it stands out that in the context of COVID-19, adolescent fertility and its determinants have been impacted by all the conditions that this generates and are mediated by the social and economic scenario of the country, realizing that for an in-depth analysis in this regard, other data. / RESUMEN El estudio de la fecundidad adolescente y sus tendencias continúa siendo una prioridad para las ciencias sociales. La voluntad política del descenso de este indicador es notable en las agendas internacionales, y para Cuba es una prioridad. El artículo analiza la fecundidad adolescente, su tendencia en la evolución en los años hasta el 2020, y el comportamiento de sus determinantes. Se presenta una aproximación al embarazo adolescente en el contexto de la COVID-19 en Cuba. Se utiliza el análisis demográfico como método. La estadística descriptiva (frecuencia absoluta y relativa), y la comparación entre años para una aproximación al posible impacto de la COVID-19 sobre la fecundidad adolescente. Se muestra como resultado la desarticulación de la fecundidad cubana expresada en su baja tasa global de fecundidad (TGF) y la tasa específica de fecundidad adolescente por encima de lo esperado y deseado. Se mantiene la resistencia al descenso notable de la fecundidad adolescente, fundamentalmente en la zona oriental del país. Las tasas de interrupción supera la tasa de fecundidad en este grupo de edad, dando cuenta de la alta tasa de embarazo adolescente. La anticoncepción y la nupcialidad como determinantes próximos aún expresan brechas en el ejercicio de los derechos sexuales y reproductivos. El peso de la fecundidad adolescente aumentó de 16,7% en 2019 a 17% en el 2020, significa que las adolescentes contribuyeron a la fecundidad total más en el 2020, año de la pandemia, que en el 2019. Entre sus conclusiones se destaca que en el contexto de la COVID-19 la fecundidad adolescente y sus determinantes han sido impactadas por todas las condiciones que ello engendra y son mediatizadas por el escenario social y económico del país, dando cuenta de que para un análisis profundo al respecto se necesitan otros datos

Diferenciales sociodemográficos de la COVID-19 en la juventud cubana. / Sociodemographic differentials of COVID-19 in cuban youth.

The demography's objects of study are the composition and dynamics of the population, as well as the social, environmental, and economic factors that determine it. This creates a specific context, which affects the configuration of the characteristics of the COVID-19 pandemic. The composition of the population is an important component for the analysis of the pandemic. Three of its elements are fundamental: the size of the population, density and urbanization; the distribution by sex and age; and, the patterns of co-residence and relationships between generations. This article addresses the distribution by sex and age and the behavior in the evolution of COVID-19 in Cuba, of the young population, particularly those between 15 and 29 years of age; in the period between March 11, 2020 (date of the first confirmed cases in the country) until June 2021. / RESUMEN La demografía tiene como objeto de estudio la composición y la dinámica de la población, así como los factores sociales, ambientales, económicos, que la determinan. Ello crea un contexto específico, que incide en la configuración de las características de la pandemia. La composición de la población es un componente importante para el análisis de la pandemia. Tres de sus elementos son fundamentales: el tamaño de la población, densidad y urbanización; la distribución por sexo y edad; y, los patrones de co-residencia y relaciones entre generaciones. Este artículo aborda la distribución por sexo y la edad y el comportamiento en la evolución de la COVID-19 en Cuba en la población joven, en particular en las edades comprendidas entre los 15 y 29 años de edad; en el periodo entre el 11 de marzo de 2020 (fecha de los primeros casos confirmados en el país) hasta el mes de junio de 2021

Profesionales de la psicología: ¿Inmunes ante la COVID-19? Supervisión psicológica para una mayor calidad en la atención a la población. / Psychology professionals: Immune to COVID-19? Psychological supervision for a higher quality of care for the population.

The article addresses the experience of a group of psychology professionals in Cuba, in the course of the development of a distance psychological counseling service, and the need for psychological supervision as part of the operation of this work modality. The context of the COVID-19 pandemic in which the service worked and the results of some of these groups are exposed. The need for the updating of psychological supervision is founded given the psychological risk to which these psychology professionals may be exposed. / RESUMEN El artículo aborda la experiencia de un grupo de profesionales de la psicología en Cuba, en el transcurso del desarrollo de un servicio de orientación psicológica a distancia, y la necesidad de la supervisión psicológica como parte del funcionamiento de esta modalidad de trabajo. Se expone el contexto de la pandemia COVID-19 en el que funcionó el servicio y los resultados de algunos de estos grupos. Se fundamenta la necesidad de la reactualización de la supervisión psicológica dado el riesgo psicológico al que pueden exponerse estos profesionales de la psicología

Halogenated Indole Alkaloids from Marine Invertebrates

This review discusses the isolation, structural elucidation, and biological activities of halogenated indole alkaloids obtained from marine invertebrates. Meridianins and related compounds (variolins, psammopemmins, and aplicyanins), as well as aplysinopsins and leptoclinidamines, are focused on. A compilation of the 13C-NMR spectral data of these selected natural indole alkaloids is also provided

Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates

Aim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types

Geography and ecology shape the phylogenetic composition of Amazonian tree communities

AimAmazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types.LocationAmazonia.TaxonAngiosperms (Magnoliids; Monocots; Eudicots).MethodsData for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny.ResultsIn the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types.Main ConclusionNumerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions