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Herrera-Martinez A.D.,University Centro Occidental Lisandro Alvarado | Rodriguez-Morales A.J.,University of Los Andes, Venezuela | Rodriguez-Morales A.J.,Central University of Venezuela
Tropical Biomedicine | Year: 2010

Climate change and variability is affecting human health and disease direct or indirectly through many mechanisms. Dengue is one those diseases that is strongly influenced by climate variability. In this study we assess potential associations between macroclimatic variation and dengue cases in a western pediatric hospital of Venezuela in an eight-year period. Between 2001 and 2008, 7,523 cases of dengue were reported in the Hospital Agustin Zubillaga, Barquisimeto, Venezuela. Climatic periods marked a difference of 23.15% in the mean incidence of cases, from El Niño weeks (-14.16% of cases below the mean incidence) to La Niña months (+8.99% of cases above it) (p=0.0001). Linear regression showed significantly higher dengue incidence with lower values of Oceanic Niño Index (ONI) (El Niño periods) and lower dengue incidence with higher values of ONI (La Niña periods) (p=0.0002). As has been shown herein, climate variability is an important element influencing the dengue epidemiology in Venezuela. However, it is necessary to extend these studies in this and other countries in the region, because these models can be applied for surveillance as well for prediction of dengue. Source

Escalona A.,University Centro Occidental Lisandro Alvarado | Salas-Sanjuan M.C.,University of Almeria | Dos Santos C.,Ministerio de Medio Ambiente | Guzman M.,University of Almeria
ITEA Informacion Tecnica Economica Agraria | Year: 2014

Zinnia and tagete flowers present vivid and uniform colors, ideal characteristics for its use in urban landscapes, including applications in vertical gardens coverage and green roofs. In these systems, it is necessary to optimize the use of water and irrigation management in order to ensure the survival of vegetation cover. With the aim of selecting plants suitable for use in vertical gardens and green roofs, we evaluated the effects of irrigation water salinity using a recirculating hydroponic nutrient solution. The ion content in the tissues of plants and their effects on the ornamental characteristics were characterized. 6, 30 and 50 mM NaCl was added to nutrient solutions to obtain final electrical conductivities of 2.0, 4.5 and 6.5 dS m−1, respectively. The increases in salinity affected plant growth, causing a decrease in biomass, height and major and minor diameters. However, salinity did not affect zinnia flower production and did not produce toxicity symptoms in tagete leaves despite the significant accumulation of Na+ and Cl− in these tissues. These results highlight the salinity tolerance of tagete and zinnia, and their possible use in urban landscape irrigated with poor quality water. © 2014 Asociacion Interprofesional para el Desarrollo Agrario. All rights reserved. Source

Torrealba R.S.,University Centro Occidental Lisandro Alvarado
General Relativity and Gravitation | Year: 2010

In this work there are proposed several new 6D brane worlds based on exact topological solutions to the vortex equations for the Abelian Higgs model, with suitable boundary conditions and symmetry breaking potentials similar to the mexican hat. Just as happens for RS domain wall brane worlds, it is shown that the massless mode of linearized gravity is localized in the neighborhood of the string-vortex solution while there are not massive bounded states. The correction to the newtonian limit of the effective 4D gravity is calculated. © 2010 Springer Science+Business Media, LLC. Source

Aquatic hyphomycetes are important components of water courses from the ecological and biotechnological points of view, due to their enzymatic battery and thus are considered as indicators of water quality. They are a group of microscopic anamorphic fungi that, in the aquatic ecosystem, degrade and alter the plant material that falls into the water, thereby enabling it to be used as a food resource by other organisms. In Venezuela, studies have been made that increase the records of these fungi species in different streams. The aim of this study was to elaborate an inventory of hyphomycetes species in 'La Estación' stream, located at the Ecological Station 'La Guáquira', Yaracuy State, and relate it to local physicochemical and microbio-logical factors. Weekly samples were collected during a year, under sterile conditions, from stream water and foam, in order to analyze the water quality and identify the fungi species. A total of 40 species were identified, of which Dicranidion gracile and Isthmotricladia laeensis are new reports for the country. Significant relationships were only found between the richness/abundance of conidia and the precipitation regime: Campylospora parvula, Clavastospora tentacula and Diplocladiella sp. were present only during the dry season, while Campylospora filicladia and Campylospora chaetocladia were present only during the rainy season. Source

Phosphorus deficiency in tropical soils is a common constrain. Acidulated phosphate rock with sulfuric acid (RFA) is a natural source of P, but a cheaper alternative is the acidification of phosphate rock by replacing 30% of sulfuric acid with ammonium thiosulfate (R30T). To test the efficiency of those fertilizers and superphosphate two experiments were conducted using an acidic soil and a neutral one. The doses of P applied were 0, 70, 140 and 210 mg·kg-1. A completely randomized design was used with four replications, and cowpea plants were grown. Plants were harvested at 35 days old and dry matter (DM), P uptake, residual P and Ca in soil, and root length (RL) were determined. When RFA was applied, DM and P uptake were similar to those in R30T and SFT. DM was highly related to soil P and Ca contents as well as to P concentration in the plant. RL increased as available P was higher in the acidic soil, but not in neutral soil. It is concluded that partial acidulation of phosphate rock with ammonium thiosulfate and sulfuric acid produces a fertilizer as efficient as the RFA for growth of the root system in both acid and neutral soil, and confirmed its efficiency in the production of dry matter and phosphorus uptake by the plant. Source

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