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Domingo L.,University of California at Santa Cruz | Prado J.L.,Valle Private University | Alberdi M.T.,CSIC - National Museum of Natural Sciences
Quaternary Science Reviews | Year: 2012

The modern South American mammalian assemblage was determined by the closure of the Panama isthmus (∼2.7-3.1 Ma) and later on, by profound climatic and environmental fluctuations occurred during the Quaternary as well as by the appearance of humans in the continent. In the present study, stable isotope analyses (δ 13C, δ18OCO3 and δ18OPO4) have been carried out on Pleistocene-Holocene northern inmigrant and endemic taxa from a broad latitudinal and altitudinal distribution in South America with the purpose of characterizing their paleoecology and the effects of the paleobiogeographic distribution on stable isotope results. Equids and gomphotheres show a wide range of δ 13C values going from woodlands to pure C 4 grasslands. In the case of equids, Hippidion shows lower δ 13C values than Equus in the Late Pleistocene, whereas, in the case of gomphotheres, Cuvieronius and Stegomastodon differ in their δ 18O values on account on differences in their paleobiogeography with the former found in the Andean corridor and the latter dispersing through an eastern route. Isotope data of the rest of taxa (immigrant and endemic) are in general in good agreement with other previous isotopic and non-isotopic studies. The latitude threshold between mixed C 3-C 4 and pure C 3 conditions have been pinpointed at ∼33°S in the Middle and the Late Pleistocene. Mammalian δ 18O values are intimately related to latitudinal and altitudinal distribution, with the latter exerting an overriding influence independently of latitude. Calculated altitudinal gradients (between -0.23‰/100 m and -0.40‰/100 m) are within the range of modern gradients. © 2012 Elsevier Ltd.


Sedo J.,Research Center en Nanociencia y | Saiz-Poseu J.,Valle Private University | Busque F.,Autonomous University of Barcelona | Ruiz-Molina D.,Research Center en Nanociencia y
Advanced Materials | Year: 2013

Catechols are found in nature taking part in a remarkably broad scope of biochemical processes and functions. Though not exclusively, such versatility may be traced back to several properties uniquely found together in the o-dihydroxyaryl chemical function; namely, its ability to establish reversible equilibria at moderate redox potentials and pHs and to irreversibly cross-link through complex oxidation mechanisms; its excellent chelating properties, greatly exemplified by, but by no means exclusive, to the binding of Fe 3+; and the diverse modes of interaction of the vicinal hydroxyl groups with all kinds of surfaces of remarkably different chemical and physical nature. Thanks to this diversity, catechols can be found either as simple molecular systems, forming part of supramolacular structures, coordinated to different metal ions or as macromolecules mostly arising from polymerization mechanisms through covalent bonds. Such versatility has allowed catechols to participate in several natural processes and functions that range from the adhesive properties of marine organisms to the storage of some transition metal ions. As a result of such an astonishing range of functionalities, catechol-based systems have in recent years been subject to intense research, aimed at mimicking these natural systems in order to develop new functional materials and coatings. A comprehensive review of these studies is discussed in this paper. Catechols participate in several natural processes and functions that range from the adhesive properties of marine organisms to the storage of certain metals ions. Accordingly, many scientists worldwide have been studying and mimicking these natural systems to develop new active materials and coatings. A detailed revision of a wide variety of relevant studies in this field is discussed in this Review. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Osorio L.,Valle Private University
Biomédica : revista del Instituto Nacional de Salud | Year: 2015

An increasing number of countries are adopting good clinical practices guidelines as part of the regulation of clinical studies to register pharmaceutical products and other health-related products. Consequently, all parties involved in the research and development of these products should know them, implement them and ensure their compliance. However, good clinical practices guidelines are just one of the initiatives seeking to achieve the highest ethical and scientific standards in health research and in other areas where humans are research subjects. This review defines such practices and their objectives presenting in a practical manner their legal framework in Colombia, and clarifying their application in studies where interventions use no medications or those that are not clinical trials. Finally, the work discusses the challenges to ensure that good clinical practices contribute to the protection of research participants, the education of trustworthy health professionals, and a culture of respect for human beings.


Prado J.L.,Valle Private University | Alberdi M.T.,CSIC - National Museum of Natural Sciences
Quaternary International | Year: 2010

Knowledge of the fossil mammals from the Pampean Region of Argentina has greatly increased in recent years. To analyze the patterns of change in regional climates and environments through the Quaternary, the fossil record of land-mammals was used. Two principal factors affected mammalian diversity in the Pampean Region during the Pleistocene: glaciations and the climatic, environmental, and sea-level changes associated with them; and the large numbers of North American taxa that immigrated to South America. From the Pliocene, the regional climatic conditions changed from being warm and wet to being colder, drier, and more seasonal. During the Pleistocene, as a consequence of glacial cycles, cold and dry conditions were interrupted by relatively short warmer and wetter periods. Several pulses of expansion and contraction of steppes and subtropical forests are recorded. This change in habitat produced the provincialism that has characterized the mammal faunas from the Pampean Region. Finally, the most notable characteristic of the Quaternary mammal fauna of South America is the almost complete extinction of large mammals during the latest Pleistocene-earliest Holocene. The evidence presented here is most consistent with a model that explains megafaunal extinction through climatic fluctuations, as it appears that only a few species of large mammals survived until the Holocene. Nevertheless, a human presence could have accelerated the process of extinction. © 2009 Elsevier Ltd and INQUA.


We studied the abundance, richness and composition of hunting ants and their variation in production systems in department of Caquetá-Colombia, 27 farms were selected in three productive systems (agroforestry, silvopastoral and traditional), in this nine kinds of soil uses were identified. The proportions of clean pasture, agroforestry and old stubble contributed most to differentiating the systems. Five points were sampled per farm using four different methods for sampling ants (TSBF, formalin soil washing, screening of litter and direct search). A total of 280 organisms was collected, corresponding to Nine genera and 35 species, belonging to the subfamilies Ectatomminae, Paraponerinae and Ponerinae. Pachycondyla was the most diverse genus (13 species). The abundance of ants was directly correlated with species richness and the number of exclusive species. The highest richness was observed in the agroforestry (24 species), followed by silvopastoral (19) and the lowest in traditional (8). Five species were common in the three systems and seven species marked the most differences in composition between systems (this was: Ectatomma ruidum, Hypoponera sp.1 and sp.4, Odontomachus haematodus, O. brunneus and Pachycondyla constricta). The species Odontomachus brunneus was indicator for the traditional system and Paraponera clavata was in silvopastoral system. Direct search was the most efficient method to sample ants in the Colombian Amazon foothills.


Lavat A.E.,Valle Private University | Grasselli M.C.,Valle Private University | Lovecchio E.G.,Valle Private University
Ceramics International | Year: 2010

The use of aluminous refractory materials containing MgAl2O4-spinel has led to a major breakthrough in the service life of refractory coatings applied in the industries and in the quality of the products. Many researches have been conducted to improve the synthetic procedures in order to reduce the production cost of these materials. In this way, refractory cements involving in situ generated spinel phase have been obtained from mixtures of active alumina and dolomites. Other investigations have demonstrated that γ alumina is advantageous in comparison with the α polymorph in the synthesis and sintering properties of pure MgAl2O4-spinel. In this article, the performance of both polymorphs of alumina, used as raw materials in the preparation of the refractory cements, along with dolomite proceeding from Olavarría, in the centre of Buenos Aires Province (Argentine), is compared. The thermal and structural changes which take place during the firing of the batches up to 1450 °C were studied by the combination of diffractometric and infrared spectroscopy data, at the most remarkable reaction steps. According to these results, the study of phase changes within the investigated thermal range allowed to establish the main differences in the composition of both mixtures in each firing step. Independently of the type of alumina used, a mixed phase product consisting of spinel, as a major phase, accompanied by CaAl2O4 (CA) and CaAl4O7 (CA2), as secondary phases, was obtained. In addition, it was found that the formation of these phases at lower temperature is favoured by γ-Al2O3. © 2009 Elsevier Ltd and Techna Group S.r.l.


Diaz F.,Valle Private University | Endersby N.M.,University of Melbourne | Hoffmann A.A.,University of Melbourne
Insect Science | Year: 2015

The whitefly Bemisia tabaci (Gennadius) is one of the most important pests causing economic losses in a variety of cropping systems around the world. This species was recently found in a coastal region of Colombia and has now spread inland. To investigate this invasive process, the genetic structure of B. tabaci was examined in 8 sampling locations from 2 infested regions (coastal, inland) using 9 microsatellite markers and the mitochondrial COI gene. The mitochondrial analysis indicated that only the invasive species of the B. tabaci complex Middle East-Asia Minor 1 (MEAM 1 known previously as biotype B) was present. The microsatellite data pointed to genetic differences among the regions and no isolation by distance within regions. The coastal region in the Caribbean appears to have been the initial point of invasion, while the inland region in the Southwest showed genetic variation among populations most likely reflecting founder events and ongoing changes associated with climatic and topographical heterogeneity. These findings have implications for tracking and managing B. tabaci. © 2015 Institute of Zoology, Chinese Academy of Sciences.


Gasmi T.,Valle Private University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

High stability and energy-efficient TE-CO2 laser pulse clipper using gas breakdown techniques for high spatial resolution chemical plume detection is presented. The most dominant time constant, attributed to TE-CO2 unclipped laser pulses, is its nitrogen tail which extends for several microseconds beyond the gain-switched spike. Near-field scattered signal, produced by unclipped laser pulses, interferes with the weak signal backscattered from the long range and far field atmospheric aerosols which ultimately degrades the range resolution of LIDARS to some hundreds of meters. Short laser pulses can be obtained by various techniques such as mode locking, free induction decay, pulse slicing with electro-optic switched. However, output pulses from these require further amplification for any useful application due to their very low energy content. This problem is circumvented in this work by the use of a plasma clipper that achieves high range-resolved remote sensing in the atmosphere. Complete extinction of the nitrogen tail is obtained at pressures extending from 375 up to 1500 Torr for nitrogen and argon gases and approximately 105, for helium. Optimum pressures for helium, argon, and nitrogen, that provide the best stability of the transmitted energy and complete extinction of the nitrogen tail, are identified. Excellent range resolutions can be achieved with TE-CO2 laser-based LIDAR systems. Clipped laser pulses are also field tested. © 2014 SPIE.


Encina R.L.,Valle Private University | Alberdi M.T.,CSIC - National Museum of Natural Sciences
Neues Jahrbuch fur Geologie und Palaontologie - Abhandlungen | Year: 2011

There is an abundant fossil record of the family Gomphotheriidae in Chile, which is entirely ascribed to the late Pleistocene. Despite this, the lack of taxonomically diagnostic material has lead to an extended discussion, which has not reached a consensus regarding the number of forms of gomphotheres effectively present. This paper discusses the taxonomy of Chilean gomphotheres, based on tooth morphology and biometry, paleoecological and biogeographical data. The morphology of the tusks indicates the presence of the Stegomastodon genus in Chile, while bivariate and multivariate analyses of the teeth show an important amount of variability within the studied sample, although with a tendency towards larger sizes for the genus Stegomastodon and the Chilean samples than for Cuvieronius, especially among the M3s and m3s. In spite of this, in this paper only the specimens from localities that yielded molars associated with tusks are assigned to the genus Stegomastodon. Biogeographic information is consistent with the presence of a lowland-adapted taxon such as Stegomastodon, which could have reached the Chilean territory either through an Andean corridor from Argentina, or through a low-altitude route from Peru, then by the northern region of Chile. Bibliographic isotopic data also indicates an adaptative change to C3 feeding along a latitudinal gradient, around 35-41°S, which makes the Chilean and south Argentinean results quite similar at these latitudes. Due to the metric variability observed, the Chilean samples could not be assigned to individual species. © 2011 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.


Prado J.L.,Valle Private University | Sanchez B.,CSIC - National Museum of Natural Sciences | Alberdi M.T.,CSIC - National Museum of Natural Sciences
BMC Ecology | Year: 2011

Background: Stable isotope ratios (13C/12C and 18O/16O) in fossil teeth and bone provide key archives for understanding the ecology of extinct horses during the Plio-Pleistocene in South America; however, what happened in areas of sympatry between Equus (Amerhippus) and Hippidion is less understood.Results: Here, we use stable carbon and oxygen isotopes preserved in 67 fossil tooth and bone samples for seven species of horses from 25 different localities to document the magnitude of the dietary shifts of horses and ancient floral change during the Plio-Pleistocene. Dietary reconstructions inferred from stable isotopes of both genera of horses present in South America document dietary separation and environmental changes in ancient ecosystems, including C3/C4transitions. Stable isotope data demonstrate changes in C4grass consumption, inter-species dietary partitioning and variation in isotopic niche breadth of mixed feeders with latitudinal gradient.Conclusions: The data for Hippidion indicate a preference varying from C3plants to mixed C3-C4plants in their diet. Equus (Amerhippus) shows three different patterns of dietary partitioning Equus (A.) neogeus from the province of Buenos Aires indicate a preference for C3plants in the diet. Equus (A.) andium from Ecuador and Equus (A.) insulatus from Bolivia show a preference for to a diet of mixed C3-C4plants, while Equus (A.) santaeelenae from La Carolina (sea level of Ecuador) and Brazil are mostly C4feeders. These results confirm that ancient feeding ecology cannot always be inferred from dental morphology. While the carbon isotope composition of horses skeletal material decreased as latitude increased, we found evidence of boundary between a mixed C3/C4diet signal and a pure C4signal around 32° S and a change from a mixed diet signal to an exclusively C3signal around 35°S.We found that the horses living at high altitudes and at low to middle latitude still have a C4component in their diet, except the specimens from 4000 m, which have a pure C3diet. The change in altitudinal vegetation gradients during the Pleistocene is one of several possibilities to explain the C4dietary component in horses living at high altitudes. Other alternative explanations imply that the horses fed partially at lower altitudes. © 2011 Prado et al; licensee BioMed Central Ltd.

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