Petrological and chronological considerations on the hercynian granitic rocks from Galicia (NW Spain)

[Resumen] Se realiza un estudio sobre más de 600 análisis químicos correspondientes a los diversos grupos de granitoides hercínicos de Galicia, y se establecen valores medios representativos para la composición química mayoritaria de estos grupos. La comparación con las medias previamente establecidas para el N. O. de Galicia, permite observar un desplazamiento hacia términos composicionales más ácidospara el conjunto de los granitoides sincinemáticos más profundos, que resulta notablemente más acentuado en el grupo de los granitoides sincinemáticos predominantemente biotíticos. Para los granitoides postcinemáticos, las desviaciones observadas son en cambio poco significativas. El examen de los datos normativos medios, pone en evidencia un carácter peralumínico generalizado para todo el conjunto, apreciándose no obstante un drástico descenso en el contenido en corindón para los granitoides postcinemáticos, que marca una distribución bimodal para este componente normativo. La clasificación petrológica con base en la mineralogía normativa pone de manifiesto un espectro composicional que fluctúa esencialmente entre granitos y monzogranitos, con muy escasa representación de los términos granodior1ticos. La variabilidad observada para los elementos mayores más signiflcativos presenta pautas poco dispersivas. Los espectros de tierras raras tienen una configuración muy similar para los granitoides precoces predominantemente biotíticos, los granitos de dos micas sincinemáticos y los granitoides inhomogéneos, con anomalías negativas de Eu poco acentuadas. Por el contrario, los granitoides tardicinemáticos someros y los granitoides post-cinemáticos, presentan también espectros bastante similares entre sí, con anomalís negativas de Eu que pueden ser considerables. Las dataciones cronológicas efectuadas por el método de Rb-Sr en roca total en algunos de los plutones post-cinemáticos se encuentran en un intervalo aproximado de 275-287 m. a., mientras que la mayoría de las dataciones sobre unidades sincinemáticas de dos micas y predominantemente biotíticas fluctúan entre 295 y 323 m. a., aunque se encuentran algunos datos fuera de este entorno, que precisan futuras verificaciones..[Abstract] A survey over more than 600 chemical analysis of Hercynian granitic rocks from Galicia is presented, and a new set of representative mean compositional values of the main groups is calculated. In general, these new mean values are richer in Si02 than the previously available ones. This difference is more conspicous in the biotite rich synkinematic group, and is minium in the postkynematic granitoids. The average normative compostion, shows a systematic peraluminous character for aH the granitoids. However, the group of postkynematic granitoids, are poorer in normative corundum than the other groups, which results in a bimodal distribution of this normative component. The normative petrological c1assification shows a compositional spectrúm ranging mainly from granites to monzogranites. The Granodioritic rocks are very scarce. The variation trends for the main mayor elements display patterns with little dispersion. The REE spectra for the biotite rich synkinematic granites, two mica synkinematic granites and inhomogenous granites are very similar, and show negligible Eu anomalies. By contrast, the shaHow level intrusion late-kynematic and postkynematic granites, display conspicous Eu anomalies and have similar spectra patterns, but different from the previously referred ones. Whole-rock-Rb-Sr ages for the postkynematic plutons range from 287 to 275 M. y. The majority of the data the synkinematic units range from 323 to 295 M. y. However, sorne chronological data faH out of these intervals, showing the need of further studies

Avian Foraging Patterns in Crop Field Edges Adjacent to Woody Habitat

As natural predators of pest insects, woodland birds provide biological pest suppression in crop fields adjacent to woody edges. Although many birds using these habitats forage widely, earlier studies have found that most foraging activity occurs within 50 m of the woody edge. The goals of this study were to determine the primary area of use, or functional edge, for birds foraging in crop fields adjacent to woody edges, and to evaluate their foraging distance patterns. During the summers of 2005 and 2006, avian foraging behavior was observed at 12 research sites in east central Nebraska that contained either a shelterbelt or woody riparian edge. At each site, perches were provided at 10 m intervals out from the edge and insect larvae were placed in feeders at random locations to simulate a pest insect food resource. Birds were recorded foraging in five distance categories out from the edge (0–10, 10–20, 20–30, 30–40, and 40–50 m). Seven species foraged primarily within 20 m of the edge (72% all observations; 79% without perch or feeder observations). Ten species foraged throughout the plots but six of these generally foraged more often (45% and 49%) and four less often (30% and 30%) within 20 m of the edge. The 13 species that tended to forage more often within 20 m of the edge, with 56% of their foraging overall in this area, also tended to forage farther when perch and feeder observations were included, indicating willingness to forage farther when food resources were available. Based on a repeated measures analysis of variance, foraging distances appeared to be greater at sites with soybean as the planted crop, although this apparent trend was significant for only some species. There was no clear difference in foraging distances outward from shelterbelt versus riparian sites. These results indicate that conservation efforts within the 20 m functional edge offer potential to enhance the sustainability of both birds and crops in agricultural

Avian Foraging Patterns in Crop Field Edges Adjacent to Woody Habitat

As natural predators of pest insects, woodland birds provide biological pest suppression in crop fields adjacent to woody edges. Although many birds using these habitats forage widely, earlier studies have found that most foraging activity occurs within 50 m of the woody edge. The goals of this study were to determine the primary area of use, or functional edge, for birds foraging in crop fields adjacent to woody edges, and to evaluate their foraging distance patterns. During the summers of 2005 and 2006, avian foraging behavior was observed at 12 research sites in east central Nebraska that contained either a shelterbelt or woody riparian edge. At each site, perches were provided at 10 m intervals out from the edge and insect larvae were placed in feeders at random locations to simulate a pest insect food resource. Birds were recorded foraging in five distance categories out from the edge (0–10, 10–20, 20–30, 30–40, and 40–50 m). Seven species foraged primarily within 20 m of the edge (72% all observations; 79% without perch or feeder observations). Ten species foraged throughout the plots but six of these generally foraged more often (45% and 49%) and four less often (30% and 30%) within 20 m of the edge. The 13 species that tended to forage more often within 20 m of the edge, with 56% of their foraging overall in this area, also tended to forage farther when perch and feeder observations were included, indicating willingness to forage farther when food resources were available. Based on a repeated measures analysis of variance, foraging distances appeared to be greater at sites with soybean as the planted crop, although this apparent trend was significant for only some species. There was no clear difference in foraging distances outward from shelterbelt versus riparian sites. These results indicate that conservation efforts within the 20 m functional edge offer potential to enhance the sustainability of both birds and crops in agricultural

Petrological and geochronological study of the postkinematic pluton of Neira (Lugo, Spain)

[Resumen] El plutón granítico de Neira intruye discordantemente en metasedimentos precámbricos y cámbricos y en granitoides sincinemáticos de dos micas, con posterioridad al desarrollo de las fases deformativas hercínicas principales. En este macizo plutónico se distinguen dos unidades intrusivas principales y el espectro litológico fundamental fluctua entre granodioritas biotíticas y leucogranitos moscovíticos-biotíticos, con predominio de las variedades graníticas (adamellíticas). Estos términos petrol6gicos están relacionados entre sí a través de un proceso evolutivo controlado fundamentalmente por cristalización fraccionada, desempeñando un importante papel los minerales accesorios. La datación de esta unidad plutónica por el procedimiento Rb-Sr en roca total, proporciona una edad de 287 ± 5 Ma, con una relaci6n inicial 87 Sr /86 Sr de 0.7074 ± 0.0004, que corresponde a un episodio intrusivo Estefaniense[Abstract] Neira granitic pluton intrudes in cambrian and precambrian metasediments and in synkinematic two mica granites after the development of the two main hercynian tectonic phases. Two intrusive units are distinguished in this pluton and its petrological composition ranges from biotitic granodiorites to two mica leucogranites, predominating biotitic adamellites. This suite of rocks is related by an evolution process mainly ruled by crystal fractionation. The accesory minerals play an important role in this process. Rb-Sr dating of this plutonic unit gives and age of 287 ± 5 M y and an initial 87 Sr/86 Sr = 0.7074 ± 0.0004

Moving Five-Branes in Low-Energy Heterotic M-Theory

We construct cosmological solutions of four-dimensional effective heterotic M-theory with a moving five-brane and evolving dilaton and T modulus. It is shown that the five-brane generates a transition between two asymptotic rolling-radii solutions. Moreover, the five-brane motion always drives the solutions towards strong coupling asymptotically. We present an explicit example of a negative-time branch solution which ends in a brane collision accompanied by a small-instanton transition. The five-dimensional origin of some of our solutions is also discussed.Comment: 16 pages, Latex, 3 eps figure

Beauty is Attractive: Moduli Trapping at Enhanced Symmetry Points

We study quantum effects on moduli dynamics arising from the production of particles which are light at special points in moduli space. The resulting forces trap the moduli at these points, which often exhibit enhanced symmetry. Moduli trapping occurs in time-dependent quantum field theory, as well as in systems of moving D-branes, where it leads the branes to combine into stacks. Trapping also occurs in an expanding universe, though the range over which the moduli can roll is limited by Hubble friction. We observe that a scalar field trapped on a steep potential can induce a stage of acceleration of the universe, which we call trapped inflation. Moduli trapping ameliorates the cosmological moduli problem and may affect vacuum selection. In particular, rolling moduli are most powerfully attracted to the points with the largest number of light particles, which are often the points of greatest symmetry. Given suitable assumptions about the dynamics of the very early universe, this effect might help to explain why among the plethora of possible vacuum states of string theory, we appear to live in one with a large number of light particles and (spontaneously broken) symmetries. In other words, some of the surprising properties of our world might arise not through pure chance or miraculous cancellations, but through a natural selection mechanism during dynamical evolution.Comment: 50 pages, 4 figures; v2: added references and an appendix describing a related classical proces

A fully automatic gridding method for cDNA microarray images

<p>Abstract</p> <p>Background</p> <p>Processing cDNA microarray images is a crucial step in gene expression analysis, since any errors in early stages affect subsequent steps, leading to possibly erroneous biological conclusions. When processing the underlying images, accurately separating the sub-grids and spots is extremely important for subsequent steps that include segmentation, quantification, normalization and clustering.</p> <p>Results</p> <p>We propose a parameterless and fully automatic approach that first detects the sub-grids given the entire microarray image, and then detects the locations of the spots in each sub-grid. The approach, first, detects and corrects rotations in the images by applying an affine transformation, followed by a polynomial-time optimal multi-level thresholding algorithm used to find the positions of the sub-grids in the image and the positions of the spots in each sub-grid. Additionally, a new validity index is proposed in order to find the correct number of sub-grids in the image, and the correct number of spots in each sub-grid. Moreover, a refinement procedure is used to correct possible misalignments and increase the accuracy of the method.</p> <p>Conclusions</p> <p>Extensive experiments on real-life microarray images and a comparison to other methods show that the proposed method performs these tasks fully automatically and with a very high degree of accuracy. Moreover, unlike previous methods, the proposed approach can be used in various type of microarray images with different resolutions and spot sizes and does not need any parameter to be adjusted.</p

Windbreaks in North American Agricultural Systems

Windbreaks are a major component of successful agricultural systems throughout the world. The focus of this chapter is on temperate-zone, commercial, agricultural systems in North America, where windbreaks contribute to both producer profitability and environmental quality by increasing crop production while simultaneously reducing the level of off-farm inputs. They help control erosion and blowing snow, improve animal health and survival under winter conditions, reduce energy consumption of the farmstead unit, and enhance habitat diversity, providing refuges for predatory birds and insects. On a larger landscape scale windbreaks provide habitat for various types of wildlife and have the potential to contribute significant benefits to the carbon balance equation, easing the economic burdens associated with climate change. For a windbreak to function properly, it must be designed with the needs of the landowner in mind. The ability of a windbreak to meet a specific need is determined by its structure: both external structure, width, height, shape, and orientation as well as the internal structure; the amount and arrangement of the branches, leaves, and stems of the trees or shrubs in the windbreak. In response to windbreak structure, wind flow in the vicinity of a windbreak is altered and the microclimate in sheltered areas is changed; temperatures tend to be slightly higher and evaporation is reduced. These types of changes in microclimate can be utilized to enhance agricultural sustainability and profitability. While specific mechanisms of the shelter response remain unclear and are topics for further research, the two biggest challenges we face are: developing a better understanding of why producers are reluctant to adopt windbreak technology and defining the role of woody plants in the agricultural landscape

Cosmological Evolution of Brane World Moduli

We study cosmological consequences of non-constant brane world moduli in five dimensional brane world models with bulk scalars and two boundary branes. We focus on the case where the brane tension is an exponential function of the bulk scalar field, $U_b \propto \exp{(\alpha \phi)}$. In the limit $\alpha \to 0$, the model reduces to the two-brane model of Randall-Sundrum, whereas larger values of $\alpha$ allow for a less warped bulk geometry. Using the moduli space approximation, we derive the four-dimensional low-energy effective action from a supergravity-inspired five-dimensional theory. For arbitrary values of $\alpha$, the resulting theory has the form of a bi-scalar-tensor theory. We show that, in order to be consistent with local gravitational observations, $\alpha$ has to be small (less than $10^{-2}$) and the separation of the branes must be large. We study the cosmological evolution of the interbrane distance and the bulk scalar field for different matter contents on each branes. Our findings indicate that attractor solutions exist which drive the moduli fields towards values consistent with observations. The efficiency of the attractor mechanism crucially depends on the matter content on each branes. In the five-dimensional description, the attractors correspond to the motion of the negative tension brane towards a bulk singularity, which signals the eventual breakdown of the four-dimensional description and the necessity of a better understanding of the bulk singularity.Comment: 18 pages, 10 figures, typos and factor of 2 corrected, version to appear in Physical Review

Phenomenology of heterotic M-theory with five-branes

We analyze some phenomenological implications of heterotic M-theory with five-branes. Recent results for the effective 4-dimensional action are used to perform a systematic analysis of the parameter space, finding the restrictions that result from requiring the volume of the Calabi-Yau to remain positive. Then the different scales of the theory, namely, the 11-dimensional Planck mass, the compactification scale and the orbifold scale, are evaluated. The expressions for the soft supersymmetry-breaking terms are computed and discussed in detail for the whole parameter space. With this information we study the theoretical predictions for the supersymmetric contribution to the muon anomalous magnetic moment, using the recent experimental result as a constraint on the parameter space. We finally analyze the neutralino as a dark matter candidate in this construction. In particular, the neutralino-nucleon cross-section is computed and compared with the sensitivities explored by present dark matter detectors.Comment: Final version to appear in Phys. Rev. D. Some comments and references added. 37 pages, 19 figure