University of the East Venezuela
Cumana, Venezuela
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Esteve R.,University of Malaga | Marquina-Aponte V.,University of the East Venezuela | Ramirez-Maestre C.,University of Malaga
Journal of Pain | Year: 2014

This study investigated the association between anxiety sensitivity and pain catastrophizing in children, caregivers' anxiety sensitivity and catastrophizing about children's pain and responses to children's pain, pain intensity reported by children, and pain intensity estimated by caregivers. The participants were 102 children scheduled for outpatient surgery and their female caregivers. Before the operation, caregivers' catastrophizing about children's pain, children's pain catastrophizing, and their anxiety sensitivity were assessed, as well as caregivers' responses to children's pain. Pain intensity reported by children and estimated by caregivers was evaluated after the operation and 24 hours afterward. Analyses were performed via path analysis. The results indicated that children and caregivers characterized by higher levels of anxiety sensitivity reported higher levels of pain catastrophizing and catastrophic thinking about children's pain, respectively. Caregivers with higher levels of catastrophic thinking about the children's pain reported higher levels of solicitousness and higher estimations of the children's pain intensity after the operation. Higher levels of children's pain catastrophizing were associated with more frequent responses of discouragement and higher pain intensity reported after the operation. These findings highlight the relevance of catastrophizing about children's pain and children's pain catastrophizing in the experience of postoperative pain in children. Perspective Path analysis was used to test a hypothetical model of the associations between anxiety sensitivity, catastrophizing, parental responses, and postoperative pain in children. The results highlight the association between children's and parents' pain catastrophizing and discouragement and solicitous responses and the role of anxiety sensitivity as a traitlike factor associated with catastrophizing. © 2014 by the American Pain Society.

Esteve R.,University of Malaga | Marquina-Aponte V.,University of the East Venezuela
Child: Care, Health and Development | Year: 2012

Background Previous studies on children's pain perspectives remain limited to English-speaking populations. Methods An exploratory cross-sectional descriptive design was used to investigate the developmental progression of children's pain perspectives, including their pain experience, its definition and attributes, causality and coping. The Children's Pain Perspectives Inventory was applied to 180 healthy Spanish children. A coding system was developed following the content analysis method. Three age groups were compared: 4-6 years, corresponding to the Piagetian pre-operational stage of cognitive development; 7-11 years, corresponding to stage of concrete operations; and 12-14 years, corresponding to the period of early formal operations. Results In children between 4 and 6, the predominant narratives related to physical injuries, the notion of causality and the definition of pain. In children between 7 and 11, the predominant narratives were those in which pain was described as a sensation in one part of the body. The view of pain as having an emotional basis significantly increased with age and was more frequent in adolescents. In contrast, children between 4-6 and 7-11 indicated that pain occurs spontaneously. The denial of any positive aspects of pain significantly decreased with age; some children between 7 and 11 referred to the 'possibility of relief', while the view that pain is a 'learning experience' was significantly more frequent among adolescents aged between 12 and 14 years. The use of cognitive strategies to control pain significantly increased with age. Between 12 and 14 years of age, adolescents communicate pain by non-verbal behaviour and reported that they do not express demands for relief. Conclusions There was a progression from concrete to more complex notions of pain as age increased. These results may be of use to health professionals and parents to understand how children at various developmental stages express and cope with pain and to develop tools that effectively assess and manage pain in children. © 2011 Blackwell Publishing Ltd.

Irwin A.J.,Mount Allison University | Finkel Z.V.,Mount Allison University | Muller-Karger F.E.,University of South Florida | Ghinaglia L.T.,University of the East Venezuela
Proceedings of the National Academy of Sciences of the United States of America | Year: 2015

Model projections indicate that climate change may dramatically restructure phytoplankton communities, with cascading consequences for marine food webs. It is currently not known whether evolutionary change is likely to be able to keep pace with the rate of climate change. For simplicity, and in the absence of evidence to the contrary, most model projections assume species have fixed environmental preferences and will not adapt to changing environmental conditions on the century scale. Using 15 y of observations from Station CARIACO (Carbon Retention in a Colored Ocean), we show that most of the dominant species from a marine phytoplankton community were able to adapt their realized niches to track average increases in water temperature and irradiance, but the majority of species exhibited a fixed niche for nitrate. We do not know the extent of this adaptive capacity, so we cannot conclude that phytoplankton will be able to adapt to the changes anticipated over the next century, but community ecosystem models can no longer assume that phytoplankton cannot adapt. © 2015, National Academy of Sciences. All rights reserved.

Valderrama G.,University of the East Venezuela | Kiennemann A.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health | Goldwasser M.R.,Central University of Venezuela
Journal of Power Sources | Year: 2010

La1-xSrxNi0.4Co0.6O 3 and La0.8Sr0.2Ni1-yCoyO 3 solid solutions with perovskite-type structure were synthesized by the sol-gel resin method and used as catalytic precursors in the dry reforming of methane with CO2 to syngas, between 873 and 1073 K at atmospheric pressure under continuous flow of reactant gases with CH4CO2 = 1 ratio. These quaternary oxides were characterized by X-ray diffraction (XRD), BET specific surface area and temperature-programmed reduction (TPR) techniques. XRD analyses of the more intense diffraction peaks and cell parameter measurements showed formation of La-Sr-Ni-Co-O solid solutions with La0.9Sr0.1CoO3 and or La0.9Sr0.1NiO3 as the main crystallographic phases present on the solids depending on the degree of substitution. TPR analyses showed that Sr doping decreases the temperature of reduction via formation of intermediary species producing Ni0, Co0 with particle sizes in the range of nanometers over the SrO and La2O3 phases. These metallic nano particles highly dispersed in the solid matrix are responsible for the high activity shown during the reaction and avoid carbon formation. The presence of Sr in doping quantities also promotes the secondary reactions of carbon formation and water-gas shift in a very small extension during the dry reforming reaction. © 2009 Elsevier B.V. All rights reserved.

Valderrama G.,University of the East Venezuela | Urbina De Navarro C.,Central University of Venezuela | Goldwasser M.R.,Central University of Venezuela
Journal of Power Sources | Year: 2013

A series of perovskite-type oxides based on La-Sr-Co (La 1-xSrxCoO3) were synthesized by the auto combustion method and used as precursors for the catalytic methane dry reforming (MDR) at 1073 K, atmospheric pressure under continuous flow of reactant gases with a CH4:CO2 = 1:1 ratio. Catalysts were characterized by techniques such as X-ray diffraction (XRD), BET specific surface area, temperature-programmed reduction-oxidation (TPR-TPO) and scanning-transmission electron microscopy (SEM-TEM). Formation of La-Sr-Co-O solid solutions was confirmed by the more intense diffraction peaks and cell parameter measurements. It was observed that the activation/reduction process occurs through intermediary species producing Co0 nano-size particles over the SrO and La2O3 phases, which are highly dispersed in the La2O2CO3-SrO solid matrix responsible for the high activity and low carbon formation despite the severe reaction conditions used. The presence of Sr in doping quantities slightly promotes secondary reactions such as carbon formation and water-gas shift retarding partially the dry reforming reaction. © 2013 Elsevier B.V. All rights reserved.

Anacona J.,University of the East Venezuela | Santaella J.,University of the East Venezuela
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

M(II) coordination compounds of Mn, Fe, Co and Ni with a Schiff base (HL) derived from the condensation of cephaclor antibiotic with 1,2-diaminobenzene were synthesized and characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and 1H NMR spectral studies. The analytical and molar conductance values indicated that the chloride ions coordinate to the metal ions. Based on these studies, the general formulae [M(L)Cl(H2O)] (M(II) = Mn, Fe, Co, Ni) are proposed for the complexes. The ligand HL behaves as a monoanionic tetradentate NNNO chelating agent. © 2013 Elsevier B.V. All rights reserved.

The infrared spectroscopy study of zeolite samples, obtained by steam treatment at 560-960 °C of the ZSM-5 catalyst (framework Si/Al ratio of 13), suggests an association between adsorbed molecular water and extra-framework aluminum hydroxyls generated after treatment. Moreover, infrared spectroscopy of adsorbed pyridine shows the reduction of the densities of Bronsted and Lewis sites, when treatment temperature rises, with contradicts the frequently accepted mechanism of the transformation of two bridged Si-OH-Al groups for each Lewis site generated. The gradual conversion of the octahedral extra-framework aluminum (Lewis-associated) in polymeric species with low acidity is the most probable cause of this behavior. On the other hand, the apparent decline of the acid Bronsted strength, with the increase in the temperature of the hydrothermal treatment, has two possible causes: a) the decreasing accessibility, of the pyridine molecular probe to bridged Si-OH-Al groups with the strongest Bronsted acidity, inside the channels, and b) the gradual transformation of these groups into extra framework species of weak acidity.

Luiggi Agreda N.J.,University of the East Venezuela
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2015

When studying the phase changes process in a rolled AA8011 alloy using DSC, we find that the peaks associated with phase precipitation under this microstructural condition are different from those obtained in homogenized microstructures. The differences observed are attributable, first, to the recovery process occurring at temperatures below 423 K (150 °C), which interacts with the precipitation of Si-rich precipitates or with Guinier–Preston zones both coexistent in that temperature range; and second, to the recrystallization above 473 K (200 °C), which coexists with precipitation of the α-AlFeSi phase. In this work, the precipitation and recovery–recrystallization kinetics are experimentally obtained and deconvoluted in peaks characteristic for each of the mechanisms involved; i.e., precipitation of GP zones, recovery, precipitation of α phase, and recrystallization. The deconvolution is achieved using functions of Gauss, Weibull, and Fraser–Suzuki; and the characterization of each reaction deconvoluted is realized through both Jhonson–Melh–Avrami–Erofeev–Kolmorokov kinetic models and Sesták–Berggren combined kinetic model. The kinetic study evinces that in addition to the expected reactions, other reactions, necessary for good experimental adjustment, appear. An isoconversional study is undertaken to numerically evaluate the kinetic triplet of every process. © 2015, The Minerals, Metals & Materials Society and ASM International.

Oliveira J.J.,University of the East Venezuela
Nonlinear Analysis: Real World Applications | Year: 2011

In this paper, a generalized neural network of CohenGrossberg type with both discrete time-varying and distributed unbounded delays is considered. Based on M-matrix theory, sufficient conditions are established to ensure the existence and global attractivity of an equilibrium point. The global exponential stability of the equilibrium is also addressed, but for the model with bounded discrete time-varying delays. A comparison of results shows that these results generalize and improve those in some earlier publications. © 2011 Elsevier Ltd. All rights reserved.

Luiggi A. N.J.,University of the East Venezuela
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2010

The precipitation of phases in the Al-Fe-Si system has been studied using differential scanning calorimetry (DSC) and thermoelectric power (ΔS) in homogenized and deformed by rolling samples. Two predominant associated effects being observed on homogenized samples: the first one, after precipitation of Fe and Si at temperatures lower than 673 K (400 °C) and the second, the Al 3Fe phase, at a temperature close to 773 K (500 °C). In DSC, the effect of severe deformation by rolling is manifest in two ways: (1) displacing the peaks reported in homogenized samples and (2) introducing two new exothermic transformations associated with the processes of recovery and recrystallization. In ΔS, the two transformations are maintained, although displaced and magnified by the effect of a faster and more abundant Fe precipitation. The isoconversional method is used to calculate the activation of precipitated phases. © 2010 The Minerals, Metals & Materials Society and ASM International.

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