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Search Results: 1 - 10 of 219414 matches for " Paco Cárdenas "
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Molecular Phylogeny of the Astrophorida (Porifera, Demospongiaep) Reveals an Unexpected High Level of Spicule Homoplasy
Paco Cárdenas,Joana R. Xavier,Julie Reveillaud,Christoffer Schander,Hans Tore Rapp
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018318
Abstract: The Astrophorida (Porifera, Demospongiaep) is geographically and bathymetrically widely distributed. Systema Porifera currently includes five families in this order: Ancorinidae, Calthropellidae, Geodiidae, Pachastrellidae and Thrombidae. To date, molecular phylogenetic studies including Astrophorida species are scarce and offer limited sampling. Phylogenetic relationships within this order are therefore for the most part unknown and hypotheses based on morphology largely untested. Astrophorida taxa have very diverse spicule sets that make them a model of choice to investigate spicule evolution.
Relationships between Host Phylogeny, Host Type and Bacterial Community Diversity in Cold-Water Coral Reef Sponges
Sandra Sch?ttner, Friederike Hoffmann, Paco Cárdenas, Hans Tore Rapp, Antje Boetius, Alban Ramette
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0055505
Abstract: Cold-water coral reefs are known to locally enhance the diversity of deep-sea fauna as well as of microbes. Sponges are among the most diverse faunal groups in these ecosystems, and many of them host large abundances of microbes in their tissues. In this study, twelve sponge species from three cold-water coral reefs off Norway were investigated for the relationship between sponge phylogenetic classification (species and family level), as well as sponge type (high versus low microbial abundance), and the diversity of sponge-associated bacterial communities, taking also geographic location and water depth into account. Community analysis by Automated Ribosomal Intergenic Spacer Analysis (ARISA) showed that as many as 345 (79%) of the 437 different bacterial operational taxonomic units (OTUs) detected in the dataset were shared between sponges and sediments, while only 70 (16%) appeared purely sponge-associated. Furthermore, changes in bacterial community structure were significantly related to sponge species (63% of explained community variation), sponge family (52%) or sponge type (30%), whereas mesoscale geographic distances and water depth showed comparatively small effects (<5% each). In addition, a highly significant, positive relationship between bacterial community dissimilarity and sponge phylogenetic distance was observed within the ancient family of the Geodiidae. Overall, the high diversity of sponges in cold-water coral reefs, combined with the observed sponge-related variation in bacterial community structure, support the idea that sponges represent heterogeneous, yet structured microbial habitats that contribute significantly to enhancing bacterial diversity in deep-sea ecosystems.
Estimation of solar illumination time on the earth by an analytical model: a fertile scenery for to teach physics
Paco Talero,Fernanda Santana,César Mora
Physics , 2012,
Abstract: We proposed an analytical model for the calculus of illumination time of the Earth for any time of year and any latitude, this model assumes the obliquity of the ecliptic as constant, the light beams as parallels, the Earth as spherical, the movement of translation of Earth as uniform circular, also this model showed a context of the astronomy whereby the teachers can teach the basic physics.It was built through a relationship between the movement of translation and of rotation of the wave front light, then we found the of illumination zone on the Earth and the illumination time is estimated in a particular latitude with the uniform circular movement of Earth. Present model was confronted with the numerical results of the Geoscience Australia Agency and it is found a maxim perceptual error of 1,6%, this value was assigned primarily to the difference between the circular trajectory, in this model, and the elliptical trajectory that is the real. Without the use of spherical trigonometry was obtained an analytical model that estimates very close the solar illumination time at any time of year and any latitude on earth, the model provides an authentic context for studying basic aspects of physics.
An Iterative Method for Solving Two Special Cases of Lane-Emden Type Equation  [PDF]
Pedro Pablo Cárdenas Alzate
American Journal of Computational Mathematics (AJCM) , 2014, DOI: 10.4236/ajcm.2014.43021
Abstract:

In this work we apply the differential transformation method or DTM for solving some classes of Lane-Emden type equations as a model for the dimensionless density distribution in an isothermal gas sphere \"\" and as a study of the gravitational potential of (white-dwarf) stars ,\"\" which are nonlinear ordinary differential equations on the semi-infinite domain [1] [2]. The efficiency of the DTM is illustrated by investigating the convergence results for this type of the Lane-Emden equations. The numerical results show the reliability and accuracy of this method.

A Survey of the Implementation of Numerical Schemes for Linear Advection Equation  [PDF]
Pedro Pablo Cárdenas Alzate
Advances in Pure Mathematics (APM) , 2014, DOI: 10.4236/apm.2014.48052
Abstract:

The interpolation method in a semi-Lagrangian scheme is decisive to its performance. Given the number of grid points one is considering to use for the interpolation, it does not necessarily follow that maximum formal accuracy should give the best results. For the advection equation, the driving force of this method is the method of the characteristics, which accounts for the flow of information in the model equation. This leads naturally to an interpolation problem since the foot point is not in general located on a grid point. We use another interpolation scheme that will allow achieving the high order for the box initial condition.

A Survey of the Implementation of Numerical Schemes for the Heat Equation Using Forward Euler in Time  [PDF]
Pedro Pablo Cárdenas Alzate
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.213135
Abstract: We establish the conditions for the compute of the Global Truncation Error (GTE), stability restriction on the time step and we prove the consistency using forward Euler in time and a fourth order discretization in space for Heat Equation with smooth initial conditions and Dirichlet boundary conditions.
A Special Case of Variational Formulation for Two-Point Boundary Value Problem in L2(Ω)  [PDF]
Pedro Pablo Cárdenas Alzate
Applied Mathematics (AM) , 2015, DOI: 10.4236/am.2015.64065
Abstract: We consider the nonlinear boundary value problems for elliptic partial differential equations and using a maximum principle for this problem we show uniqueness and continuous dependence on data. We use the strong version of the maximum principle to prove that all solutions of two-point BVP are positives and we also show a numerical example by applying finite difference method for a two-point BVP in one dimension based on discrete version of the maximum principle.
Assessment and Monitoring Damage by Coraebus florentinus (Coleoptera: Buprestidae) in Mediterranean Oak Forests  [PDF]
Ana M. Cárdenas, Patricia Gallardo
Open Journal of Ecology (OJE) , 2018, DOI: 10.4236/oje.2018.85020
Abstract: Coraebus florentinus (Herbst) is a wood borer beetle that damages the most abundant Quercus species making up the Mediterranean forests. Damage is due to the feeding activity of the larvae which cuts the sap flow into the branch where it develops, drying it. In the last decades, the geographical range and the damage records of this species have expanded northwardly as a result of the climate global change since warmer conditions favor higher reproduction and quicker development of this species. On this paper, historical series of data after ten years evaluating damages by C. florentinus in Hornachuelos Natural Park (Southern Spain) are analyzed under the perspective of the environmental temperature increase linked to the global climate change. The assessment was done between 2007 and 2017, in two sampling plots of Mediterranean mixed-oak forests where holm and cork oaks are the predominant tree species. Results show that the infestation levels of this species at the beginning of the assessment period were higher than those described previously in the nineties and that they increased progressively during the monitoring time. The results also agree with the expansion of its distribution areas noticed in other areas of Europe. The foreseeable rising of damages of C. florentinus is discussed, at greater scale, under the perspective of future scenery of environmental warming and oaks decaying by losing fitness due to higher soil aridity.
Estimation of solar zenith passage on the Earth's surface by a simple harmonic motion
Paco Talero,Fernanda Santana y César Mora
Physics , 2013,
Abstract: The kinematics of the Solar zenith passage on the Earth was shown as a simple harmonic motion. This analytical model used the uniform circular motion to describe the Earth's rotation relative to its axis and relative to the Sun, also this model considered the sunlight beams parallel and constant the obliquity of the ecliptic. We made a contrast between some data taken from of the software Stellarium 0.12.1 and the model, we obtained an uncertainty $\Delta t=1d$; this result allow to project the model as an astronomical context conducive to develop the kinematics of simple harmonic motion.
Semi-quantitative diagram about temporal evolution in basic physics learning: a study with engineering students
Paco Talero,César Mora,Orlando Organista,Luis Barbosa
Physics , 2012,
Abstract: We show a new semi-quantitative technique of analysis about of temporal evolution of learning of basic physics concepts. In this technique we arrange a geometric diagram with the score and the homogeneity (H-S), in this diagram we have a quantitative and qualitative information about the learning of students and the effectiveness instruction. We applied this technique to study the temporal evolution of the graphical interpretation of motion in one dimension through tutorials in a introductory course physics with 20 students of engineering at the Universidad Central de Bogot\'a Colombia for a period of 6 weeks. We found in the general diagram that (Smax,Hmax)=(0.75,0.75).
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