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Raptor functional diversity in scrubland-agricultural landscapes of northern-central-Mexican dryland environments
Get PDF"Raptor birds have widespread distributions in different environments throughout the planet. Yet, they are highly sensitive to landscape disturbances. We studied raptors in northern-central Mexico at the Highland plateau of San Luis Potosí and Zacatecas, in three landscape types that differed in proportion of agriculture. Our main goal was to determine whether small proportion of agriculture at the landscape level influences species richness, ecological diversity, and functional diversity. We conducted raptor road surveys during 1 year, from April 2015 to February 2016. We registered a total of 332 birds belonging to 14 diurnal raptor species. The most abundant species were Cathartes aura (turkey vulture), Falco sparverius (American kestrel), Caracara cheriway (crested caracara), and Buteo jamaicensis (red-tailed hawk). Three species: Aquila chrysaetos (golden eagle), Pandion haliaetus (osprey), and Falco columbarius (merlin) were exclusively recorded in the less-degraded, scrubland landscapes. However, no significant differences on average diversity were found between landscape types. Contrastingly, scrubland landscapes had the highest average functional diversity, followed by mixed landscapes, and then by agricultural landscapes, with significant differences in functional diversity between scrubland and agricultural landscapes. Overall, observed species richness in the study area formed four functional groups. These groups change and loose species as proportion of agriculture in the landscape progressively increases. The results suggested that the contribution of species richness to functional diversity, both for scrubland landscapes, which have the greatest functional diversity, and agricultural landscapes, which hold the smallest functional diversity, is important because there is substantial functional redundancy among landscape types.
Propiedades magnéticas y distribución de tamaños de nanopartículas de magnetita recubiertas con ácido oleico
Get PDF"The particle size and particle size distribution are very important to biomedical applications because the uptake of nanoparticles is strongly dependent on particle size. Oleic acid coated magnetite nanoparticles were synthesized by using chemical co-precipitation. The average particle size and particle size distribution measured by different techniques are compared. The crystallite sizes estimated by X-Ray Diffraction (9.32 nm) and the average particle size calculated by Transmission Electron Microscopy (9.46 nm) are very similar. Atomic Force Microscopy revealed an average diameter of 1030 nm, which is bigger than estimated by other techniques due to the oleic acid layer covering the nanoparticles. The distribution of magnetic sizes of nanoparticles was also estimated through the magnetic response of the system, using the Langevin model (9.11 nm). Anisotropy constant (Ka = 4.74 *105 erg/cm3) and blocking temperature (TB = 118 K) were obtained.
Determinación de las distribuciones del campo de interacción y campo de rotación en redes de nanoalambres magnéticos a partir de ciclos menores de magnetización
Get PDFTesis (Maestría en Nanociencias y Materiales)"En este trabajo se han propuesto y validado dos métodos para determinar el campo de interacción y la coercividad intrínseca en ensambles de partículas entre las cuales hay una interacción dipolar magnética empleando ciclos menores de magnetización. Experimentalmente se utilizaron redes de nanoalambres magnéticos de NiFe y CoFe con diámetros de 29, 35 y 50 nm de diámetro, alturas promedio de 18 micrómetros y con fracciones de volumen de 4.5, 5 y 11.4\% a fin de variar la intensidad del campo de interacción. Las mediciones de magnetometría se hicieron utilizando un magnetómetro de gradiente alternante con el campo aplicado paralelo al eje de los alambres y todas las mediciones se realizaron a temperatura ambiente.
El primer método permite medir el campo de interacción y la coercividad intrínseca para el punto de retorno de un ciclo menor, a partir de las diferencias entre las remanencias de la parte descendente y ascendente del ciclo menor. De manera que midiendo un número mayor de ciclos menores permite obtener el campo de interacción y de coercividad intrínseca para el mismo número de puntos sobre el ciclo de histéresis
El segundo método permite determinar el campo de interacción y la coercividad intrínseca en cada punto de un ciclo menor. Este se basa en la translación vertical de cada ciclo menor lo cual permite encontrar directamente los campos de rotación positivo y negativo asociados a cada cambio en la magnetización. Esto es análogo a los campos de rotación en un histerión asimétrico, a partir de los cuales se calculan los correspondientes campos de interacción y de coercividad intrínseca. Este método parece más robusto ya que para cada ciclo menor se obtienen curvas para el campo de interacción y la curva intrínseca de campos coercitivos.
Los resultados arrojados por ambos métodos son consistentes entre sí, así como también concuerdan razonablemente con el valor promedio del campo de interacción obtenido a partir de las curvas de remanencia IRM y DCD y con el valor que arroja el modelo de campo medio para redes de nanoalambres, por lo que ambos métodos se consideran correctos.""In this work two methods have been proposed and validated to determine the field
of interaction and intrinsic coercivity in particle assemblies between which there is a
magnetic dipole interaction using minor loops of magnetization. Experimental magnetic networks of NiFe and CoFe were used with diameters of 29, 35 and 50 nm in diameter, average heights of 18 microns and with volume fractions of 4.5, 5 and 11.4% in order to vary the eld strength of interaction. The magnetometry measurements were made using a gradient magnetometer alternating with the applied field parallel to the axis of the wires and all measurements were performed at room temperature. The first method allows to measure the interaction field and the intrinsic coercivity for the return point of a minor loop, from the differences between the remanences of the descending and ascending part of the minor loop. Thus, by measuring a larger number of minor loops it is possible to obtain the field of interaction and intrinsic coercivity for the same number of points on the hysteresis cycle The second method allows to determine the interaction field and the intrinsic coercivity at each point (M;H) of a minor loop. This is based on the vertical translation of each minor loop which allows to find directly
the fields of positive and negative rotation associated with each change in magnetization. This is analogous to the fields of rotation in an asymmetric hysterion, from which the corresponding elds of interaction and intrinsic coercivity are calculated. This method seems more robust since for each minor loop are obtained for the interaction field and the intrinsic curve of coercive fields.
The results from both methods are consistent with each other, as well as reasonably agree with the average value of the interaction field obtained from the IRM and DCD remanence curves and with the value given by the mean field model for nano-wire networks , So both methods are considered correct.
Output-feedback global continuous finite-time and exponential stabilization of bounded-input mechanical systems
Get PDF"This work proposes an output-feedback global continuous controller for the finite-time or (local) exponential stabilization of bounded-input mechanical systems. The control design is carried out within the analytical framework of local homogeneity. The proposed approach avoids velocity measurements on the feedback through the use of a dynamic dissipator expressed in a generalized non-linear form. The analytical results are supported through simulation tests. In particular, such implementations show the performance differences obtained through diverse particular dynamic dissipator structures, as well as the contrast among the finite-time and exponential convergence achievable through the proposed scheme.
Fractional order chaotic systems and their electronic design
Get PDF"Con el desarrollo del cálculo fraccionario y la teoría del caos, los sistemas caóticos de orden fraccionario se han convertido en una forma útil de evaluar las características de los sistemas dinámicos. En esta dirección, esta tesis es principalmente relacionada, es decir, en el estudio de sistemas caóticos de orden fraccionario, basado en sistemas disipativos de inestables, un sistema disipativo de inestable de orden fraccionario es propuesto. Algunas propiedades dinámicas como puntos de equilibrio, exponentes de Lyapunov, diagramas de bifurcación y comportamientos dinámicos caóticos del sistema caótico de orden fraccionario son estudiados. Los resultados obtenidos muestran claramente que el sistema discutido presenta un comportamiento caótico. Por medio de considerar la teoría del cálculo fraccionario y simulaciones numéricas, se muestra que el comportamiento caótico existe
en el sistema de tres ecuaciones diferenciales de orden fraccionario acopladas,
con un orden menor a tres. Estos resultados son validados por la existencia de un exponente positivo de Lyapunov, además de algunos diagramas de fase. Por otra parte, la presencia de caos es también verificada obteniendo la herradura topológica. Dicha prueba topológica garantiza la generaci´n de caos en el sistema de orden fraccionario propuesto. En orden de verificar la efectividad del sistema propuesto, un circuito electrónico es diseñado con el fin de sintetizar el sistema caótico de orden fraccionario.""With the development of fractional order calculus and chaos theory, the fractional order chaotic systems have become a useful way to evaluate characteristics of dynamical systems and forecast the trend of complex systems. In this direction, this thesis is primarily concerned with the study of fractional order chaotic systems, based on an unstable dissipative system (UDS), a fractional order unstable dissipative system (FOUDS) is proposed. Dynamical properties, such as equilibrium points, Lyapunov exponents, bifurcation diagrams and phase diagrams of the fractional order chaotic system are studied. The obtained results shown that the fractional order unstable dissipative system has a chaotic behavior. By utilizing the fractional calculus theory and computer simulations, it is found that chaos exists in the fractional order three dimensional system with order less than three. The lowest order to yield chaos in this system is 2.4. The results are validated by the existence of one positive Lyapunov exponent, phase diagrams; Besides, the presence of chaos is also verified obtaining the topological horseshoe. That topological proof guarantees the chaos generation in the proposed fractional order unstable dissipative system. In order to verify the effectiveness of the proposed system, an electronic circuit is designed with the purpose of synthesize the fractional order chaotic system, the fractional order integral is realized with electronic circuit utilizing the synthesis of a fractance circuit. The realization has been done via synthesis as passive RC circuits connected to an operational amplifier. The continuos fractional expansion have been utilized on fractional integration transfer function which has been approximated to integer order rational transfer function considering the Charef Method. The analogue electronics circuits have been
simulated using HSPICE.
Diversification of the kinetic properties of yeast NADP‐glutamate‐dehydrogenase isozymes proceeds independently of their evolutionary origin
Get PDF"In the yeast Saccharomyces cerevisiae, the ScGDH1 and ScGDH3 encoded glutamate dehydrogenases (NADP‐GDHs) catalyze the synthesis of glutamate from ammonium and α‐ketoglutarate (α‐KG). Previous kinetic characterization showed that these enzymes displayed different allosteric properties and respectively high or low rate of α‐KG utilization. Accordingly, the coordinated action of ScGdh1 and ScGdh3, regulated balanced α‐KG utilization for glutamate biosynthesis under either fermentative or respiratory conditions, safeguarding energy provision. Here, we have addressed the question of whether there is a correlation between the regulation and kinetic properties of the NADP‐GDH isozymes present in S. cerevisiae (ScGdh1 and ScGdh3), Kluyveromyces lactis (KlGdh1), and Lachancea kluyveri (LkGdh1) and their evolutionary history. Our results show that the kinetic properties of K. lactis and L. kluyveri single NADP‐GDHs are respectively similar to either ScGDH3 or ScGDH1, which arose from the whole genome duplication event of the S. cerevisiae lineage, although, KlGDH1 and LkGDH1 originated from a GDH clade, through an ancient interspecies hybridization event that preceded the divergence between the Saccharomyces clade and the one containing the genera Kluyveromyces, Lachancea, and Eremothecium. Thus, the kinetic properties which determine the NADP‐GDHs capacity to utilize α‐KG and synthesize glutamate do not correlate with their evolutionary origin.
Generation of multi-scroll attractors without equilibria via piecewise linear systems
Get PDF"In this paper, we present a new class of dynamical system without equilibria which possesses a multiscroll attractor. It is a piecewise-linear system which is simple, stable, displays chaotic behavior and serves as a model for analogous non-linear systems. We test for chaos using the 0-1 Test for Chaos from Gottwald and Melbourne [SIAM J. Appl. Dyn. Syst. 8(1), 129-145 (2009)]. Piecewise-linear (PWL) systems are switching systems composed of linear affine subsystems along with a rule which determines the acting subsystem. These systems are known to be capable of producing chaotic attractors, as in the well studied Chua's circuit. This paper discusses the generation of multiscroll attractors without equilibria based on PWL systems.
Recalcitrant deep and shallow nodes in Aristolochia (Aristolochiaceae) illuminated using anchored hybrid enrichment
Get PDF"Recalcitrant relationships are characterized by very short internodes that can be found among shallow and deep phylogenetic scales all over the tree of life. Adding large amounts of presumably informative sequences, while decreasing systematic error, has been suggested as a possible approach to increase phylogenetic resolution. The development of enrichment strategies, coupled with next generation sequencing, resulted in a cost-effective way to facilitate the reconstruction of recalcitrant relationships. By applying the anchored hybrid enrichment (AHE) genome partitioning strategy to Aristolochia using an universal angiosperm probe set, we obtained 231–233 out of 517 single or low copy nuclear loci originally contained in the enrichment kit, resulting in a total alignment length of 154,756 bp to 160,150 bp. Since Aristolochia (Piperales; magnoliids) is distantly related to any angiosperm species whose genome has been used for the plant AHE probe design (Amborella trichopoda being the closest), it serves as a proof of universality for this probe set. Aristolochia comprises approximately 500 species grouped in several clades (OTUs), whose relationships to each other are partially unknown. Previous phylogenetic studies have shown that these lineages branched deep in time and in quick succession, seen as short-deep internodes. Short-shallow internodes are also characteristic of some Aristolochia lineages such as Aristolochia subsection Pentandrae, a clade of presumably recent diversification. This subsection is here included to test the performance of AHE at species level. Filtering and subsampling loci using the phylogenetic informativeness method resolves several recalcitrant phylogenetic relationships within Aristolochia. By assuming different ploidy levels during bioinformatics processing of raw data, first hints are obtained that polyploidization contributed to the evolution of Aristolochia. Phylogenetic results are discussed in the light of current systematics and morphology.
Cholinergic signaling plasticity maintains viscerosensory responses during Aspiculuris tetraptera infection in mice small intestine
Get PDF"Intestinal parasites alter gastrointestinal (GI) functions like the cholinergic function. Aspiculuris tetraptera is a pinworm frequently observed in laboratory facilities, which infests the mice cecum and proximal colon. However, little is known about the impact of this infection on the GI sensitivity. Here, we investigated possible changes in spontaneous mesenteric nerve activity and on the mechanosensitivity function of worm-free regions of naturally infected mice with A. tetraptera. Infection increased the basal firing of mesenteric afferent nerves in jejunum. Our findings indicate that nicotinic but not muscarinic receptors, similarly affect spontaneous nerve firing in control and infected animals; these axons are mainly vagal. No difference between groups was observed on spontaneous activity after nicotinic receptor inhibition. However, and contrary to the control group, during infection, the muscarinic signaling was shown to be elevated during mechanosensory experiments. In conclusion, we showed for the first time that alterations induced by infection of the basal afferent activity were independent of the cholinergic function but changes in mechanosensitivity were mediated by muscarinic, but not nicotinic, receptors and specifically by high threshold nerve fibers (activated above 20 mm Hg), known to play a role in nociception. These plastic changes within the muscarinic signaling would function as a compensatory mechanism to maintain a full mechanosensory response and the excitability of nociceptors during infection. These changes indicate that pinworm colonic infection can target other tissues away from the colon.
Viscosity and normal stress forces of Lennard-Jones chains using reverse non-equilibrium molecular dynamics
Get PDF"Reverse non-equilibrium molecular dynamics was applied for the calculation of the viscosity for different chain lengths. Each chain consisted of m tangent spherical sites, where m was 1, 2, 4, 8 or 16, respectively. From these results, shear thinning was observed at high shear rates. The normal stress forces were also estimated via the calculation of the total stress tensor, and they were related to the shear thinning effect depending on the length of the chain. Furthermore, a power law equation was used to fit the rheological curves of each chain, making possible the calculation of the viscoelasticity as a function of the sites involved in the chains.