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Search Results: 1 - 10 of 495184 matches for " Miguel Angel Hernández-García "
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Hydrolysis of Trivalent Holmium in Aqueous Solutions of 2 M Ionic Strength by Spectrophotometric and Potentiometric Methods  [PDF]
Miguel Angel Hernández-García, Hilario López-González, Alberto Rojas-Hernández
Advances in Materials Physics and Chemistry (AMPC) , 2015, DOI: 10.4236/ampc.2015.55017
Abstract: The first hydrolysis constants of trivalent holmium in 2 M NaClO4 and 2 M NaCl at 303 K and in CO2 free conditions were determined. The pCH borderlines of precipitation and first hydrolysis were determined by means of a spectrophotometric method and last one with the program SQUAD. Independently, the stability constant for the first hydrolytic species was determined, by means of potentiometric pH titrations whose data were treated with the program SUPERQUAD. The hydrolysis constants obtained were: \"\"?and \"\". These values attained by both methods are the same. The log10β1,Cl constants for the species HoCl2+ was also calculated for 2 M ionic strength and 303 K from the hydrolysis constant obtained in both perchlorate and chloride media. This value was logβ1,Cl = -0.56.
Relaciones sociambientales entre comunidades y áreas naturales protegidas. Reserva de la Biosfera Calakmul: entre el conflicto y la conservación
Sosa-Montes, Mauricio;Durán-Ferman, Pedro;Hernández-García, Miguel ángel;
Revista Chapingo. Serie ciencias forestales y del ambiente , 2012, DOI: 10.5154/r.rchscfa.2010.10.097
Abstract: in the calakmul biosphere reserve (cbr), a conflictive relationship has developed between communities and reserve management because their relationship is governed by a principle by which the logic of environmental management subordinates the logic of those who have profited from the region's resources and is manifested in restrictions on land use and productive activities. thus, the objective of this research was to determine the root causes of the conflict. for the analysis of the conflictive relationships, qualitative indicators that emerged directly from the information obtained through the use of structured questionnaires, in-depth interviews and direct observation were used. to check the validity of the qualitative analysis, two statistical methods were used: correlation coefficient and principal components. it was found that the conflict is due to the producers or rural communities not participating in the planning processes and in the making, implementation and evaluation of decisions related to actions carried out in the cbr by reserve management.
Necesidades de información de los usuarios de Atención Primaria desde la perspectiva de los profesionales sanitarios: un estudio Delphi
Maderuelo-Fernández,José ángel; Hernández-García,Ignacio; González-Hierro,Miguel; Velázquez-San Francisco,Isabel;
Gaceta Sanitaria , 2009, DOI: 10.1590/S0213-91112009000500003
Abstract: objective: to determine the information needed by patients in relation to the supply of primary care services from the perspective of health professionals. methods: the delphi technique was used as a consensus method. seventy experts were asked to participate: 35 primary care physicians, 32 nurse practitioners, and three pediatricians in rural and non-rural health centers in the health area of salamanca between may and december 2006. the questionnaires used were structured into six sections: patients' knowledge of their health, services in their health centers, administrative topics, the media, information expectations, and communication barriers. in the third questionnaire, prioritized answers were scored between 5 points and 1 point according to their importance. results: all three questionnaires were completed by 44 experts (62.8%). the information needs with the highest scores were information on patients' diseases (4.0 points), subjects related to patients' responsibility for their health (3.8) and preventive advice (3.6), followed by subjects relating to access (4.2), emergencies (3.4), physicians' and nurse practitioners' services (3.6), and places to go to get information (4.0). the lack of coordination between primary and hospital care (4.1) and excessive bureaucracy (3.5) were considered to limit communication and information. conclusions: the factors identified focus on contents that allow patients to get involved in their own process and to take active part in the decision-making that concerns them. other important factors were information about services and the access to them.
Purification, Immobilization and Characterization of Lipase Isoenzyme from Aspergillus niger with C8 Magnetic Particles  [PDF]
Samanta Hernández-García, María Inmaculada García-García, Francisco García-Carmona
Advances in Bioscience and Biotechnology (ABB) , 2014, DOI: 10.4236/abb.2014.57075
Abstract:

The purification of a lipase isoenzyme from an Aspergillus niger lipase A is reported in this manuscript. Purification was carried out in a simple adsorption step, in which the lipase was offered at low ionic strength to the commercially available C8 modified magnetic particles, MaKProt C8. When the isoenzyme was desorbed with a 0.2% solution of Triton X-100, the SDS-PAGE gel showed a single pure band with a molecular weight of 35 KDa. The purified fraction showed 66.75-fold purification compared with the crude extract. The pure fraction was characterized along with the crude extract and the lipase adsorbed on the MaKProt C8. The purified and the adsorbed lipase showed better activity for the tested substrates (p-nitrophenyl acetate, decanoate, myristate and palmitate) than the crude extract, the preferred substrates being myristate (26.7 μmol·min-1·mg-1) and decanoate (17.4 μmol·min-1·mg-1), respectively. The temperature and pH profiles showed no change for the three enzymes, the optimum temperature being 37°C and the best pH 7.0.

A multi-wavelength view of the central kiloparsec region in the Luminous Infrared Galaxy NGC1614
Rubén Herrero-Illana,Miguel á. Pérez-Torres,Almudena Alonso-Herrero,Antxon Alberdi,Luis Colina,Andreas Efstathiou,Lorena Hernández-García,Daniel Miralles-Caballero,Petri V?is?nen,Christopher C. Packham,Vinesh Rajpaul,Albert A. Zijlstra
Physics , 2014, DOI: 10.1088/0004-637X/786/2/156
Abstract: The Luminous Infrared Galaxy NGC1614 hosts a prominent circumnuclear ring of star formation. However, the nature of the dominant emitting mechanism in its central ~100 pc is still under debate. We present sub-arcsecond angular resolution radio, mid-infrared, Pa-alpha, optical, and X-ray observations of NGC1614, aimed at studying in detail both the circumnuclear ring and the nuclear region. The 8.4 GHz continuum emission traced by the Very Large Array (VLA) and the Gemini/T-ReCS 8.7 micron emission, as well as the Pa-alpha line emission, show remarkable morphological similarities within the star-forming ring, suggesting that the underlying emission mechanisms are tightly related. We used an HST/NICMOS Pa-alpha map of similar resolution to our radio maps to disentangle the thermal free-free and non-thermal synchrotron radio emission, from which we obtained the intrinsic synchrotron power-law for each individual region within the central kpc of NGC1614. The radio ring surrounds a relatively faint, steep-spectrum source at the very center of the galaxy, suggesting that the central source is not powered by an AGN, but rather by a compact (r < 90 pc) starburst. Chandra X-ray data also show that the central kpc region is dominated by starburst activity, without requiring the existence of an AGN. We also used publicly available infrared data to model-fit the spectral energy distribution of both the starburst ring and a putative AGN in NGC1614. In summary, we conclude that there is no need to invoke an AGN to explain the observed bolometric properties of the galaxy.
Seasonal and regional characterization of horizontal stirring in the global ocean
I. Hernández-Carrasco,C. López,E. Hernández-García,A. Turiel
Physics , 2011, DOI: 10.1029/2012JC008222
Abstract: Recent work on Lagrangian descriptors has shown that Lyapunov Exponents can be applied to observed or simulated data to characterize the horizontal stirring and transport properties of the oceanic flow. However, a more detailed analysis of regional dependence and seasonal variability was still lacking. In this paper, we analyze the near-surface velocity field obtained from the Ocean general circulation model For the Earth Simulator (OFES) using Finite-Size Lyapunov Exponents (FSLE). We have characterized regional and seasonal variability. Our results show that horizontal stirring, as measured by FSLEs, is seasonally-varying, with maximum values in Summer time. FSLEs also strongly vary depending on the region: we have first characterized the stirring properties of Northern and Southern Hemispheres, then the main oceanic basins and currents. We have finally studied the relation between averages of FSLE and some Eulerian descriptors such as Eddy Kinetic Energy (EKE) and vorticity (w) over the different regions.
Non-Steady wall-bounded flows of viscoelastic fluids under periodic forcing
Anier Hernández-García,Antonio Fernández-Barbero,Oscar Sotolongo-Costa
Physics , 2013, DOI: 10.1007/s13538-014-0211-0
Abstract: The problem of oscillating flows inside pipes under periodic forcing of viscoelastic fluids is addressed here. Starting from the linear Oldroyd-B model, a generalized Darcy's law is obtained in frequency domain and an explicit expression for the dependence of the dynamic permeability on fluid parameters and forcing frequency is derived. Previous results in both viscoelastic and Newtonian fluids are here shown to be particular cases of our results. On the basis of our calculations, a possible explanation for the observed damping of local dynamic response as the forcing frequency increases is given. Good fitting with recent experimental studies of wave propagation in viscoelastic media is here exhibited. Sound wave propagation in viscoelastic media flowing inside straight pipes is investigated. In particular, we obtain the local dynamic response for weakly compressible flows.
Extracting directed information flow networks: an application to genetics and semantics
A. P. Masucci,A. Kalampokis,V. M. Eguíluz,E. Hernández-García
Physics , 2010, DOI: 10.1103/PhysRevE.83.026103
Abstract: We introduce a general method to infer the directional information flow between populations whose elements are described by n-dimensional vectors of symbolic attributes. The method is based on the Jensen-Shannon divergence and on the Shannon entropy and has a wide range of application. We show here the results of two applications: first extracting the network of genetic flow between the meadows of the seagrass Poseidonia Oceanica, where the meadow elements are specified by sets of microsatellite markers, then we extract the semantic flow network from a set of Wikipedia pages, showing the semantic channels between different areas of knowledge.
Diversity and Noise Effects in a Model of Homeostatic Regulation of the Sleep-Wake Cycle
Marco Patriarca ,Svetlana Postnova,Hans A. Braun,Emilio Hernández-García,Raúl Toral
PLOS Computational Biology , 2012, DOI: 10.1371/journal.pcbi.1002650
Abstract: Recent advances in sleep neurobiology have allowed development of physiologically based mathematical models of sleep regulation that account for the neuronal dynamics responsible for the regulation of sleep-wake cycles and allow detailed examination of the underlying mechanisms. Neuronal systems in general, and those involved in sleep regulation in particular, are noisy and heterogeneous by their nature. It has been shown in various systems that certain levels of noise and diversity can significantly improve signal encoding. However, these phenomena, especially the effects of diversity, are rarely considered in the models of sleep regulation. The present paper is focused on a neuron-based physiologically motivated model of sleep-wake cycles that proposes a novel mechanism of the homeostatic regulation of sleep based on the dynamics of a wake-promoting neuropeptide orexin. Here this model is generalized by the introduction of intrinsic diversity and noise in the orexin-producing neurons, in order to study the effect of their presence on the sleep-wake cycle. A simple quantitative measure of the quality of a sleep-wake cycle is introduced and used to systematically study the generalized model for different levels of noise and diversity. The model is shown to exhibit a clear diversity-induced resonance: that is, the best wake-sleep cycle turns out to correspond to an intermediate level of diversity at the synapses of the orexin-producing neurons. On the other hand, only a mild evidence of stochastic resonance is found, when the level of noise is varied. These results show that disorder, especially in the form of quenched diversity, can be a key-element for an efficient or optimal functioning of the homeostatic regulation of the sleep-wake cycle. Furthermore, this study provides an example of a constructive role of diversity in a neuronal system that can be extended beyond the system studied here.
Radiación solar y supervivencia en una plantación de vara de perlilla (Symphoricarpos microphyllus H.B.K.)
Hernández-García, J. D.;Rodríguez-Trejo, D. A.;
Revista Chapingo. Serie ciencias forestales y del ambiente , 2008,
Abstract: a "vara de perlilla" (symphoricarpos microphyllus h.b.k.) plantation was established in the forest nursery of the división de ciencias forestales, universidad autónoma chapingo. the objective was to study survival and growth under different solar radiation condi-tions. the shrubs were planted under a pine forest plantation in different light conditions. with a digital camera with hemispheric lens and the hemiview program?, were measured direct and diffuse solar radiation, and visible sky. from the shrubs was recorded survival, number and length of branches, shoot and root biomass and total biomass. the probability of mortality was obtained with a logistic model, using as explanatory variable direct solar radiation. also was employed linear regression. the logistic model was significant (p= 0.0970), with higher mortality at higher light levels. the lineal regressions were not significant or had a verly low r2.
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