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40 resultados encontrados para: TEMA: Composición química
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1.
Libro

2.
Libro
Aquatic chemistry: chemical equilibria and rates in natural waters / Werner Stumm, James J. Morgan
Stumm, Werner (1924-) ; Morgan, James J. (coaut.) (1932-) ;
New York : John Wiley and Sons , c1996
Clasificación: 553.7 / S8
Bibliotecas: Chetumal
Cerrar
SIBE Chetumal
ECO030000821 (Disponible)
Disponibles para prestamo: 1

3.
Artículo
Aquatic ecosystems of the Yucatán Peninsula (Mexico), Belize, and Guatemala
Pérez, Liseth ; Bugja, Rita (coaut.) ; Lorenschat, Julia (coaut.) ; Brenner, Mark (coaut.) ; Curtis, Jason H. (coaut.) ; Hoelzmann, Philipp (coaut.) ; Islebe, Gerald A. (coaut.) ; Scharf, Burkhard (coaut.) ; Schwalb, Antje (coaut.) ;
Contenido en: Hydrobiologia Vol. 661, no. 1 (February 2011), p. 407-433 ISSN: 0018-8158
Resumen en: Inglés |
Resumen en inglés

This study presents limnological and morphological characteristics, physical and chemical properties of waters, and geochemistry of surface sediments for 63 aquatic ecosystems located on the karst Yucatán Peninsula and surrounding areas of Belize and the Guatemalan highlands and eastern lowlands. Our principal goal was to classify the aquatic systems based on their water variables. A principal component analysis (PCA) of the surface water chemistry data showed that a large fraction of the variance (29%) in water chemistry is explained by conductivity and major ion concentrations. The broad conductivity range, from 168 to 55,300 μS cm−1 reflects saline water intrusion affecting coastal aquatic environments, and the steep NW–S precipitation gradient, from ~450 to >3,200 mm year−1. Coastal waterbodies Celestún and Laguna Rosada displayed the highest conductivities. Minimum surface water temperatures of 21.6°C were measured in highland lakes, and warmest temperatures, up to 31.7°C, were recorded in the lowland waterbodies. Most lakes showed thermal stratification during the sampling period, with the exception of some shallow (<10 m) systems. Lakes Chichancanab, Milagros, and Bacalar displayed sulfate-rich waters. Waters of sinkholes had relatively high conductivities (<3,670 μS cm−1) and a broad range of δ18O values (−4.1 to +3.8‰).

Ca, HCO3, and SO4 dominated the waters of the lowland lakes, whereas Na was the dominant cation in highland lakes. Coastal aquatic ecosystems were dominated by Na and Cl. Cluster analysis based on surface water variables classified aquatic environments of the lowlands and highlands into three groups: (1) lowland lakes, ponds, wetlands, and coastal waterbodies (2) highland lakes, and (3) sinkholes and rivers. A broad trophic state gradient was recorded, ranging from the eutrophic Lake Amatitlán and the Timul sinkhole to oligotrophic Laguna Ayarza, with the highest water transparency (11.4 m). We used major and trace elements in surface sediments to assess pollution of waterbodies. Lakes Amatitlán, Atescatempa, El Rosario, Cayucón, Chacan-Lara, La Misteriosa, rivers Subín and Río Dulce, the wetland Jamolún, and the sinkhole Petén de Monos showed evidence of pollution and urban development. Their surface sediments displayed high concentrations of As, Cu, Fe, Ni, Pb, Se, Zn, and Zr, which suggest moderate to strong pollution.


4.
Libro
Índice | Resumen en: Inglés |
Resumen en inglés

Archaean Geochemistry 1972 - 1984 The realisation that the continental crust contains well-preserved relics which date as far back as 4/5 of the Earth's age has given a great impetus to the study of early Precambrian terrains. As late as the mid-sixties the Archaean still constituted the 'terra-in­ cognita' of earth science. High metamorphic grades, poor out­ crop, and not least a widely assumed obliteration of early crustal records by convective recycling and thermal reworking had com­ bined to discourage research in this field. Many excellent local studies existed, notably around gold mining centres, but remained unrelated to a broader regional and theoretical understanding. This situation has changed as the consequence of two inter-related factors: (1) advances in isotopic methods and their application to Precambrian rocks, and (2) the recognition that some of the oldest terrains have retained a wealth of primary igneous and sedi­ mentary textures and even geochemical characteristics.

Índice

1. Mantle chemistry and accretion history of the earth
2. Geochemical characteristics of archaean ultramafic and mafic volcanic rocks: implications for mantle composition and evolution
3. Archaean sedimentary rocks and their relation to the composition of the archaean continental crust
4. Spatial and temporal variations of archaean metallogenic associations in terms of evolution of granitoid-greenstone terrains with particular emphasis on the western australian shield
5. Magma mixing in komatiitic lavas from munro township, Ontario
6. Oxygen isotope compositions of minerals and rocks and chemical alteration patterns in pillow lavas from the barberton greenstone belt, south Africa
7. Petrology and geochemistry of layered ultramafic to mafic complexes from the archaean craton of karnataka, southern India
8. Pressures, temperatures and metamorphic fluids across an unbroken amphibolite facies to granulite facies transition in southern Karnataka, India
9. Origin of archaean charnockites from southern India
10. Radiometric ages (rb-sr, sm-nd, u-pb) and ree geochemistry of archaean granulite gneisses from eastern hebei province, China
11. The most ancient rocks in the ussr territory by u-pb data on accessory zircons
12. Age and evolution of the early precambrian continental crust of the Ukrainian shield
13. Significance of early archaean mafic-ultramafic xenolith patterns
Subject Index


5.
Libro
BAC: Centros de Actividades Biológica del Pacífico mexicano / D. Llunch-Belda, J. Elorduy-Garay, S. E. Lluch-Cota y G. Ponce-Díaz, editoras
Lluch Belda, Daniel (editor) ; Elorduy Garay, J. (editor) ; Lluch Cota, S. E. (editor) ; Ponce Díaz, Germán (editor) ;
Distrito Federal, México : Centro de Investigaciones Biológicas del Noroeste , c2000
Clasificación: 574.52636 / B33
Bibliotecas: San Cristóbal
Cerrar
SIBE San Cristóbal
ECO010009613 (Disponible)
Disponibles para prestamo: 1

6.
- Artículo con arbitraje
*En hemeroteca, SIBE-Chetumal, SIBE-San Cristóbal
Bioindicators of climate and trophic state in lowland and highland aquatic ecosystems of the Northern Neotropics
Pérez, Liseth ; Lorenschat, Julia (coaut.) ; Massaferro, Julieta (coaut.) ; Pailles, Christine (coaut.) ; Sylvestre, Florence (coaut.) ; Hollwedel, Werner (coaut.) ; Brandorff, Gerd Oltmann (coaut.) ; Brenner, Mark (coaut.) ; Islebe, Gerald A. (coaut.) ; Lozano, María del Socorro (coaut.) ; Scharf, Burkhard (coaut.) ; Schwalb, Antje (coaut.) ;
Contenido en: Revista de Biología Tropical Vol. 61, no. 2 (June 2013), p. 603-644 ISSN: 0034-7744
Bibliotecas: Chetumal , San Cristóbal
Cerrar
SIBE Chetumal
35622-30 (Disponible)
Disponibles para prestamo: 1
Cerrar
SIBE San Cristóbal
35622-20 (Disponible)
Disponibles para prestamo: 1
Nota: En hemeroteca, SIBE-Chetumal, SIBE-San Cristóbal
PDF
Resumen en: Español | Inglés |
Resumen en español

Los quironómidos, diatomeas y microcrustaceos que habitan ecosistemas acuáticos en el norte de los Neotrópicos son abundantes y diversos. Algunas especies son altamente sensibles a cambios en la composición química del agua y en el estado trófico. Este estudio se realizó como el primer paso para desarrollar funciones de transferencia para inferir condiciones ambientales en el norte de las tierras bajas de los Neotrópicos. Es por esto que las abundancias de especies bioindicadoras se relacionaron con múltiples variables ambientales con el fin de explotar al máximo su uso como indicadores ambientales y paleoambientales. Recolectamos y analizamos muestras de agua y de sedimento superficial de 63 cuerpos de agua, ubicados a lo largo de un gradiente trófico y de gradientes marcados de altitud (~0-1 560m.s.n.m.) y de precipitación (~400-3 200mm/año), desde el NO de la Península de Yucatán (México) hasta el sur de Guatemala. Relacionamos 14 variables limnológicas con las abundancias relativas de 282 especies de diatomeas, 66 morfoespecies de quironómidos, 51 especies de cladóceros, 29 especies de ostrácodos no-marinos y seis especies de agua dulce de cladóceros calanoides. La estadística multivariada indicó que el bicarbonato es el principal determinante de la distribución de quironómidos y copépodos.

El estado trófico es el segundo factor más importante en determinar la distribución de quironómidos. La conductividad, que está relacionada con el gradiente de precipitación e influencia marina en la Península de Yucatán, es la principal variable en influir las comunidades de diatomeas, ostrácodos y cladóceros. Las diatomeas, quironómidos y cladóceros (H=2.4-2.6) presentaron diversidades más altas que los ostrácodos y copépodos (H=0.7-1.8). La riqueza de especies y la diversidad fueron más altas en las elevaciones bajas (<450m.s.n.m) que en elevaciones altas en Guatemala. La distribución y diversidad de bioindicadores es afectada por múltiples factores incluyendo la altitud, precipitación, composición química del agua, estado trófico y el impacto humano.

Resumen en inglés

Chironomids, diatoms and microcrustaceans that inhabit aquatic ecosystems of the Northern Neotropics are abundant and diverse. Some species are highly sensitive to changes in water chemical composition and trophic state. This study was undertaken as a first step in developing transfer functions to infer past environmental conditions in the Northern lowland Neotropics. Bioindicator species abundances were related to multiple environmental variables to exploit their use as environmental and paleoenvironmental indicators. We collected and analyzed water and surface sediment samples from 63 waterbodies located along a broad trophic state gradient and steep gradients of altitude (~0-1 560m.a.s.l.) and precipitation (~400-3 200mm/y), from NW Yucatán Peninsula (Mexico) to southern Guatemala. We related 14 limnological variables to relative abundances of 282 diatom species, 66 chironomid morphospecies, 51 species of cladocerans, 29 non-marine ostracode species and six freshwater calanoid copepods. Multivariate statistics indicated that bicarbonate is the strongest driver of chironomid and copepod distribution. Trophic state is the second most important factor that determines chironomid distribution. Conductivity, which is related to the precipitation gradient and marine influence on the Yucatán Peninsula, is the main variable that shapes diatom, ostracode and cladoceran communities. Diatoms, chironomids and cladocerans displayed higher diversities (H=2.4-2.6) than ostracodes and copepods (H=0.7- 1.8). Species richness and diversity were greater at lower elevations (<450m.a.s.l.) than at higher elevations in Guatemala. Distribution and diversity of bioindicators are influenced by multiple factors including altitude, precipitation, water chemistry, trophic state and human impact.


7.
Libro
Bioquímica de los microorganismos / Ramón Parés i Farràs, Antonio Juárez Giménez
Parés i Farràs, Ramón ; Juárez Giménez, Antonio (coaut.) ;
Barcelona, España : Editorial Reverté , 1997
Clasificación: 579 / P3
Bibliotecas: Villahermosa
Cerrar
SIBE Villahermosa
ECO050005100 (Disponible)
Disponibles para prestamo: 1

8.
Artículo
Características agronómicas y químicas del género Buddleia en los Altos de Chiapas
Camacho Morfín, Deneb ; Nahed Toral, José (coaut.) ; Ochoa Gaona, Susana (coaut.) ; Morfín Loyden, L. (coaut.) ; Soto Pinto, Lorena (coaut.) (1958-) ; Jiménez Ferrer, Guillermo (coaut.) ;
Clasificación: AR/635.93396 / C3
Contenido en: Investigación Multidisciplinaria (1996), p. 16-19
Bibliotecas: San Cristóbal
Cerrar
SIBE San Cristóbal
ECO010012870 (Disponible)
Disponibles para prestamo: 1

9.
- Capítulo de libro con arbitraje
*Solicítelo con su bibliotecario/a
Characterization of Scaptotrigona mexicana Pot-Pollen from Veracruz, Mexico
Contreras Oliva, Adriana (autora) ; Pérez Sato, Juan Antonio (autor) ; Gómez Merino, Fernando Carlos (autor) ; López Garay, Luz Anel (autora) ; Villanueva Gutiérrez, Rogel (autor) ; Crosby Galván, María Magdalena (autora) ; Trejo Téllez, Libia Iris (autora) ;
Disponible en línea
Contenido en: Pot-pollen in stingless bee melittology / Patricia Vit, Silvia R.M. Pedro, David W. Roubik, editors Cham, Switzerland, German : Springer International Publishing AG, 2018 p. 325-337 ISBN:978-3-319-61838-8 :: 978-3-319-61839-5 (eBook)
Nota: Solicítelo con su bibliotecario/a

10.
Artículo
PDF
Resumen en: Inglés |
Resumen en inglés

This study was aimed at evaluating thein vitroeffect of the edible mushroom (EM) Pleurotus eryngiiagainst the eggs and larvae (L3) of Haemonchus contortus. The evaluation included acetone (AE) and hydroalcoholic (HA) extracts of the following strains: ECS-1138, ECS-1156, ECS-1255, ECS-1258, ECS-1261, ECS-1282, and ECS-1292. The HA extract of the ECS-1255 strain showed thehighest effect on mortality rates of L3 (18.83%) at 20 μg/mL. After subjecting this HA extract to a normal phase chromatography column, five fractions were obtained; fraction F5 (100% MeOH) was the most effective against eggs, with hatching inhibition percentages of 88.77 and 91.87% at 20 and 40 mg/mL, respectively. Gas chromatography-mass spectrometry (GC-MS) subjected this fraction to an acetylation reaction to determine the content of the secondary metabolites. The GC-MSanalysis showed that the F5 fraction was composed of trehalose CAS: 6138-23-4, polyols (L-iditol CAS: 488-45-9, galactitol CAS:608-66-2, D-mannitol CAS: 69-65-8, D-glucitol CAS: 50-70-4, and myoinositol CAS: 87-89-8), adipic acid CAS: 124-04-9, stearic acid CAS: 57-11-4, squalene CAS: 111-02-4, and β-sitosterol CAS: 83-46-5.