2,036 research outputs found
Chaotic scattering with direct processes: A generalization of Poisson's kernel for non-unitary scattering matrices
The problem of chaotic scattering in presence of direct processes or prompt
responses is mapped via a transformation to the case of scattering in absence
of such processes for non-unitary scattering matrices, \tilde S. In the absence
of prompt responses, \tilde S is uniformly distributed according to its
invariant measure in the space of \tilde S matrices with zero average, < \tilde
S > =0. In the presence of direct processes, the distribution of \tilde S is
non-uniform and it is characterized by the average (\neq 0). In
contrast to the case of unitary matrices S, where the invariant measures of S
for chaotic scattering with and without direct processes are related through
the well known Poisson kernel, here we show that for non-unitary scattering
matrices the invariant measures are related by the Poisson kernel squared. Our
results are relevant to situations where flux conservation is not satisfied.
For example, transport experiments in chaotic systems, where gains or losses
are present, like microwave chaotic cavities or graphs, and acoustic or elastic
resonators.Comment: Added two appendices and references. Corrected typo
Lipomatosis epidural lumbosacra idiopática: revisión de la bibliografía y caso clínico
La lipomatosis epidural es una afección que aparece generalmente en relación
con hipercortisolismos endógenos o exógenos, siendo más raras las formas idiopáticas,
de las que se han descrito únicamente 17 casos. Se presenta un nuevo caso con sintomatología
compatible con estenosis de canal, y que tras estudios de imagen se demostró
que correspondía con una lipomatosis epidural lumbosacra. Se le encomendó al paciente
una reducción de peso, con lo que se alivió parcialmente la sintomatología, permaneciendo
estable en la actualidad. Se revisa la bibliografía de este raro proceso, exponiendo
los distintos hallazgos encontrados. Algunos autores proponen una reducción de
peso, lo cual puede aliviar la sintomatología. Para casos rebeldes está indicada la laminectomía
asociada al despegamiento de la grasa sin realizar exploración intradural.Epidural lipomatosis is an affection that is usually related to endogenic or exogenous hipercortisolism. Less frequently, it can be idiopathic. To date only 17 cases have been documented. A new case is presented in a patient suffering from symptoms resembling lumbar spinal stenosis. The radiological studies revealed a compression of the dural sac at lumbosacral levéis, caused by tissue similar in density to fat. Weight reduction, was recommended to the patients and a partial relief of symptoms was achieved. The authors reviewed the pathogeny of epidural lipomatosis and its various different treatments. In the idiopathic form, weight reduction is recomended first, reserving surgery for those cases that do not respond to this initial treatment. Surgical treatment should consist of laminectomy and fat debulking, and should not include intradural exploration
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Ectomycorrhizal fungal communities and their functional traits mediate plant–soil interactions in trace element contaminated soils
There is an increasing consensus that microbial communities have an important role in mediating ecosystem processes. Trait-based ecology predicts that the impact of the microbial communities on ecosystem functions will be mediated by the expression of their traits at community level. The link between the response of microbial community traits to environmental conditions and its effect on plant functioning is a gap in most current microbial ecology studies. In this study, we analyzed functional traits of ectomycorrhizal fungal species in order to understand the importance of their community assembly for the soil–plant relationships in holm oak trees (Quercus ilex subsp. ballota) growing in a gradient of exposure to anthropogenic trace element (TE) contamination after a metalliferous tailings spill. Particularly, we addressed how the ectomycorrhizal composition and morphological traits at community level mediate plant response to TE contamination and its capacity for phytoremediation. Ectomycorrhizal fungal taxonomy and functional diversity explained a high proportion of variance of tree functional traits, both in roots and leaves. Trees where ectomycorrhizal fungal communities were dominated by the abundant taxa Hebeloma cavipes and Thelephora terrestris showed a conservative root economics spectrum, while trees colonized by rare taxa presented a resource acquisition strategy. Conservative roots presented ectomycorrhizal functional traits characterized by high rhizomorphs formation and low melanization which may be driven by resource limitation. Soil-to-root transfer of TEs was explained substantially by the ectomycorrhizal fungal species composition, with the highest transfer found in trees whose roots were colonized by Hebeloma cavipes. Leaf phosphorus was related to ectomycorrhizal species composition, specifically higher leaf phosphorus was related to the root colonization by Thelephora terrestris. These findings support that ectomycorrhizal fungal community composition and their functional traits mediate plant performance in metal-contaminated soils, and have a high influence on plant capacity for phytoremediation of contaminants. The study also corroborates the overall effects of ectomycorrhizal fungi on ecosystem functioning through their mediation over the plant economics spectrum
Functional diversity of ectomycorrhizal fungal communities is reduced by trace element contamination
10 páginas.-- 2 figuras.-- 3 tablas.-- 105 referencias.-- Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.soilbio.2018.03.021Trait-based approaches are useful tools to explain ecological assembly rules and ecosystem functioning. However, their use for soil microbiota has not been explored in depth yet. We explored trait-based functional changes of ectomycorrhizal (ECM) fungal communities associated with holm oak (Quercus ilex subsp. ballota) in a trace element contaminated area.
We found a variation in ECM fungal species composition determined by soil C, Ca and trace elements; however, taxonomic diversity was not dependant on contamination level. Mean trait values of ECM fungal communities showed less rhizomorph and emanating hyphae production when increasing contamination, and the community converged towards species developing rhizomorphs less frequently. We suggest that trace elements in soils acted as the main environmental filter of trait diversity of ECM fungal communities. The effect of soil nutrients, i.e. soil C, affected the community mean trait values of emanating hyphae but did not cause a convergence in its distribution.
In summary, we found a reduction in the functional diversity of ECM fungal communities due to trace element contamination with potential to affect ecosystem functioning. This finding supports the potential of trait-based approaches to assess changes in the functional diversity of soil microbial communities.This work was supported by European Union Seventh Framework Programme (FP7/2007–2013) [grant number 603498 - RECARE]; Spanish Ministry of Economy and Competitiveness [grant number CGL2014-52858-R - RESTECO]; Spanish National Research Programme - European Union (Feder) [grant number CGL2015-69118-C2-2-P - COEXMED-II]. During manuscript preparation, ALG was supported by European Union's Horizon 2020 Marie Curie Individual Fellowship [grant number 708530 - DISPMIC]. MTD is thankful the University of Sevilla for a postdoctoral fellowship (V Plan Propio de Investigación).Peer reviewe
Earliest Porotic Hyperostosis on a 1.5-Million-year-old Hominin, olduvai gorge, Tanzania.
Meat-eating was an important factor affecting early hominin brain expansion, social organization and geographic movement. Stone tool butchery marks on ungulate fossils in several African archaeological assemblages demonstrate a significant level of carnivory by Pleistocene hominins, but the discovery at Olduvai Gorge of a child's pathological cranial fragments indicates that some hominins probably experienced scarcity of animal foods during various stages of their life histories. The child's parietal fragments, excavated from 1.5-million-year-old sediments, show porotic hyperostosis, a pathology associated with anemia. Nutritional deficiencies, including anemia, are most common at weaning, when children lose passive immunity received through their mothers' milk. Our results suggest, alternatively, that (1) the developmentally disruptive potential of weaning reached far beyond sedentary Holocene food-producing societies and into the early Pleistocene, or that (2) a hominin mother's meat-deficient diet negatively altered the nutritional content of her breast milk to the extent that her nursing child ultimately died from malnourishment. Either way, this discovery highlights that by at least 1.5 million years ago early human physiology was already adapted to a diet that included the regular consumption of meat
Scaling behavior in a stochastic self-gravitating system
A system of stochastic differential equations for the velocity and density of
a classical self-gravitating matter is investigated by means of the field
theoretic renormalization group. The existence of two types of large-scale
scaling behavior, associated to physically admissible fixed points of the
renormalization-group equations, is established. Their regions of stability are
identified and the corresponding scaling dimensions are calculated in the
one-loop approximation (first order of the epsilon expansion). The velocity and
density fields have independent scaling dimensions. Our analysis supports the
importance of the rotational (nonpotential) components of the velocity field in
the formation of those scaling laws.Comment: 6 pages, REVTEX3 source, 1 PS figur
Horizontal flow fields observed in Hinode G-band images II. Flow fields in the final stages of sunspot decay
We present a subset of multi-wavelengths observations obtained with the
Japanese Hinode mission, the Solar Dynamics Observatory (SDO), and the Vacuum
Tower Telescope (VTT) at Observatorio del Teide, Tenerife, Spain during the
time period from 2010 November 18-23. Horizontal proper motions were derived
from G-band and Ca II H images, whereas line-of-sight velocities were extracted
from VTT Echelle H-alpha 656.28 nm spectra and Fe I 630.25 nm spectral data of
the Hinode/Spectro-Polarimeter, which also provided three-dimensional magnetic
field information. The Helioseismic and Magnetic Imager on board SDO provided
continuum images and line-of-sight magnetograms as context for the
high-resolution observations for the entire disk passage of the active region.
We have performed a quantitative study of photospheric and chromospheric flow
fields in and around decaying sunspots. In one of the trailing sunspots of
active region NOAA 11126, we observed moat flow and moving magnetic features
(MMFs), even after its penumbra had decayed. We also noticed a superpenumbral
structure around this pore. MMFs follow well-defined, radial paths from the
spot all the way to the border of a supergranular cell surrounding the spot. In
contrast, flux emergence near the other sunspot prevented it from establishing
such well ordered flow patterns, which could even be observed around a tiny
pore of just 2 Mm diameter. After the disappearance of the sunspots/pores a
coherent patch of abnormal granulation remained at their location, which was
characterized by more uniform horizontal proper motions, low divergence values,
and diminished photospheric Doppler velocities. This region, thus, differs
significantly from granulation and other areas covered by G-band bright points.
We conclude that this peculiar flow pattern is a signature of sunspot decay and
the dispersal of magnetic flux.Comment: 13 pages, 11 figures, accepted for publication in Astronomy and
Astrophysic
Hierarchical and hybrid polymer nanocomposites based on carbon nanotubes and inorganic fullerene type nanoparticles
The influence of singlewalled carbon nanotubes (SWCNT) and inorganic fullerenelike tungsten disulfide nanoparticles (IFWS2) on the morphology and thermal, mechanical and electrical performance of multifunctional fibrereinforced polymer composites has been investigated. Significant improvements were observed in stiffness, strength and toughness in poly (ether ether ketone) (PEEK) / (SWCNT) / glass fibre (GF) laminates when a compatibilizer was used for wrapping the CNTs. Hybrid poly(phenylene sulphide) (PPS)/IFWS2/ carbon fibre (CF) reinforced polymer composites showed improved mechanical and tribological properties attributed to a synergetic effect between the IF nanoparticles and CF
Interacciones en el manejo forestal y las prácticas agrícolas en comunidades originarias del Estado de México, México: el modelo de paisajes bioculturales a escala local: Interactions in forest management and agricultural practices in communities originating from the State of Mexico, Mexico: the biocultural landscape model at a local scale
La implementación del modelo de paisajes bioculturales a escala local en los pueblos originarios de México podría conducir a la resignificación de dichos paisajes bioculturales, ya que permite la integración de prácticas y saberes para su gestión sostenible. El objetivo de este estudio fue identificar las dimensiones que caracterizan a los aspectos de los paisajes bioculturales, así como las interacciones en el manejo forestal y las prácticas agrícolas en comunidades originarias del Estado de México, México, para relacionarlas con los objetivos a escala local del modelo de paisajes bioculturales. Con un enfoque cualitativo, se realizó un taller participativo dirigido a miembros de Organizaciones No Gubernamentales (ONG) y académicos especialistas en el tema, que constó de dos etapas. En la primera etapa, por equipos de trabajo, se identificó las dimensiones que caracterizan a los aspectos de los paisajes bioculturales de comunidades originarias, así como las tres dimensiones más importantes de cada aspecto; en la segunda etapa, de manera grupal, se identificaron las interacciones bosque-agricultura, bosque y agricultura, así como su relación con los objetivos locales de la implementación del modelo de paisajes bioculturales. Concluyendo que la identificación de las interacciones en el manejo forestal y las prácticas agrícolas en comunidades originarias podría facilitar el diseño e implementación de los diferentes objetivos a escala local de dicho modelo.
The implementation of the biocultural landscapes model at a local scale in the indigenous peoples of Mexico could lead to the resignification of said biocultural landscapes, since it allows the integration of practices and knowledge for their sustainable management. The objective of this study was to identify the dimensions that characterize the aspects of biocultural landscapes, as well as the interactions in forest management and agricultural practices in communities originating from the State of Mexico, Mexico, to relate them to the local-scale objectives of the biocultural landscape model. With a qualitative approach, a participatory workshop was held aimed at members of Non-Governmental Organizations (NGOs) and academics specializing in the topic, which consisted of two stages. In the first stage, by work teams, the dimensions that characterize the aspects of the biocultural landscapes of native communities were identified, as well as the three most important dimensions of each aspect; In the second stage, in a group manner, the forest-agriculture, forest and agriculture interactions were identified, as well as their relationship with the local objectives of the implementation of the biocultural landscape model. Concluding that the identification of interactions in forest management and agricultural practices in native communities could facilitate the design and implementation of the different objectives at the local scale of said model
The Imaging Magnetograph eXperiment (IMaX) for the Sunrise balloon-borne solar observatory
The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter built by
four institutions in Spain that flew on board the Sunrise balloon-borne
telesocope in June 2009 for almost six days over the Arctic Circle. As a
polarimeter IMaX uses fast polarization modulation (based on the use of two
liquid crystal retarders), real-time image accumulation, and dual beam
polarimetry to reach polarization sensitivities of 0.1%. As a spectrograph, the
instrument uses a LiNbO3 etalon in double pass and a narrow band pre-filter to
achieve a spectral resolution of 85 mAA. IMaX uses the high Zeeman sensitive
line of Fe I at 5250.2 AA and observes all four Stokes parameters at various
points inside the spectral line. This allows vector magnetograms, Dopplergrams,
and intensity frames to be produced that, after reconstruction, reach spatial
resolutions in the 0.15-0.18 arcsec range over a 50x50 arcsec FOV. Time
cadences vary between ten and 33 seconds, although the shortest one only
includes longitudinal polarimetry. The spectral line is sampled in various ways
depending on the applied observing mode, from just two points inside the line
to 11 of them. All observing modes include one extra wavelength point in the
nearby continuum. Gauss equivalent sensitivities are four Gauss for
longitudinal fields and 80 Gauss for transverse fields per wavelength sample.
The LOS velocities are estimated with statistical errors of the order of 5-40
m/s. The design, calibration and integration phases of the instrument, together
with the implemented data reduction scheme are described in some detail.Comment: 17 figure
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