Representing anisotropic subduction zones with isotropic velocity models: A characterization of the problem and some steps on a possible path forward

Despite the widely known fact that mantle flow in and around subduction zones produces the development of considerable seismic anisotropy, most P-wave tomography efforts still rely on the assumption of isotropy. In this study, we explore the potential effects of erroneous assumption on tomographic images and explore an alternative approach. We conduct a series of synthetic tomography tests based on a geodynamic simulation of subduction and rollback. The simulation results provide a self-consistent distribution of isotropic (thermal) anomalies and seismic anisotropy which we use to calculate synthetic delay times for a number of realistic and hypothetical event distributions. We find that anisotropy-induced artifacts are abundant and significant for teleseismic, local and mixed event distributions. The occurrence of artifacts is not reduced, and indeed can be exacerbated, by increasing richness in ray-path azimuths and incidence angles. The artifacts that we observe are, in all cases, important enough to significantly impact the interpretation of the images. We test an approach based on prescribing the anisotropy field as an a priori constraint and find that even coarse approximations to the true anisotropy field produce useful results. Using approximate anisotropy, fields can result in reduced RMS misfit to the travel time delays and reduced abundance and severity of imaging artifacts. We propose that the use of anisotropy fields derived from geodynamic modeling and constrained by seismic observables may constitute a viable alternative to isotropic tomography that does not require the inversion for anisotropy parameters in each node of the model

Kinematics and Convergent Tectonics of the Northwestern South American Plate During the Cenozoic

The interaction of the northern Nazca and southwestern Caribbean oceanic plates with northwestern South America (NWSA) and the collision of the Panama-Choco arc (PCA) have significant implications on the evolution of the northern Andes. Based on a quantitative kinematic reconstruction of the Caribbean and Farallon/Farallon-derived plates, we reconstructed the subducting geometries beneath NWSA and the PCA accretion to the continent. The persistent northeastward migration of the Caribbean plate relative to NWSA in Cenozoic time caused the continuous northward advance of the Farallon-Caribbean plate boundary, which in turn resulted in its progressive concave trench bending against NWSA. The increasing complexity during the Paleogene included the onset of Caribbean shallow subduction, the PCA approaching the continent, and the forced shallow Farallon subduction that ended in the fragmentation of the Farallon Plate into the Nazca and Cocos plates and the Coiba and Malpelo microplates by the late Oligocene. The convergence tectonics after late Oligocene comprised the accretional process of the PCA to NWSA, which evolved from subduction erosion of the forearc to collisional tectonics by the middle Miocene, as well as changes of convergence angle and slab dip of the Farallon-derived plates, and the attachment of the Coiba and Malpelo microplates to the Nazca plate around 9 Ma, resulting in a change of convergence directions. During the Pliocene, the Nazca slab broke at 5.5°N, shaping the modern configuration. Overall, the proposed reconstruction is supported by geophysical data and is well correlated with the magmatic and deformation history of the northern Andes

Subduction-driven recycling of continental margin lithosphere

Whereas subduction recycling of oceanic lithosphere is one of the central themes of plate tectonics, the recycling of continental lithosphere appears to be far more complicated and less well understood(1). Delamination and convective downwelling are two widely recognized processes invoked to explain the removal of lithospheric mantle under or adjacent to orogenic belts(2-5). Here we relate oceanic plate subduction to removal of adjacent continental lithosphere in certain plate tectonic settings. We have developed teleseismic body wave images from dense broadband seismic experiments that show higher than expected volumes of anomalously fast mantle associated with the subducted Atlantic slab under northeastern South America and the Alboran slab beneath the Gibraltar arc region(6,7); the anomalies are under, and are aligned with, the continental margins at depths greater than 200 kilometres. Rayleigh wave analysis(8,9) finds that the lithospheric mantle under the continental margins is significantly thinner than expected, and that thin lithosphere extends from the orogens adjacent to the subduction zones inland to the edges of nearby cratonic cores. Taking these data together, here we describe a process that can lead to the loss of continental lithosphere adjacent to a subduction zone. Subducting oceanic plates can viscously entrain and remove the bottom of the continental thermal boundary layer lithosphere from adjacent continental margins. This drives surface tectonics and pre-conditions the margins for further deformation by creating topography along the lithosphere-asthenosphere boundary. This can lead to development of secondary downwellings under the continental interior, probably under both South America and the Gibraltar arc(8,10), and to delamination of the entire lithospheric mantle, as around the Gibraltar arc(11). This process reconciles numerous, sometimes mutually exclusive, geodynamic models proposed to explain the complex oceanic-continental tectonics of these subduction zones(12-17)This research was supported by US National Science Foundation grants EAR 0003572, 0607801 and 0808939 (A.L.), EAR 0808931 (E.D.H.), EAR 0809023 and 1054638 (M.S.M.), the Venezuelan National Fund for Science, Technology and Innovation grant G-2002000478 and PDVSA-INTEVEP-FUNVISIS cooperative agreement 2004-141 (M.S.), the Spanish Ministry of Science and Innovation grants CSD2006-00041, CGL2009-09727 and CGL2010-15146 (J.G. and R.C.), and by an A. v. Humboldt Foundation Research Prize (A.L.).Peer Reviewe

CLORURO DE BENZALCONIO EN EL TRATAMIENTO DE LA DERMATOMICOSIS CAUSADA POR Trichophyton sp. EN EL CUY (Cavia cobayo)

Se evaluó la eficacia del cloruro de benzalconio en el tratamiento de la dermatomicosis causada por Trichophyton sp. en el cuy (Cavia cobayo). Se utilizó 200 cuyes de 2 meses de edad que presentaban signos clínicos de dermatomicosis. Los cuyes fueron divididos al azar en dos grupos (A y B) similares. Al grupo A se le aplicó una solución acuosa de cloruro de benzalconio al 0.1% como único tratamiento y en el grupo B se empleó agua como placebo. Previo al tratamiento, se tomaron muestras de pelos y escamas de piel para examen directo y cultivo en los medios Dermatophytes Test Medium (DTM) y Mycobiotic, así como biopsias de piel para estudio histológico. Todas las muestras resultaron positivas a hongos entre el 3º y 7º día, tipificándose la especie Trichophyton mentagrophytes con la ayuda de microcultivos y lectura en agar urea. El 60% de las muestras fueron positivas al examen directo. El estudio histológico mostró hiperqueratosis ligera. El 100% de los cuyes del grupo A mostró curación clínica con crecimiento de pelo al finalizar la 4a semana post-tratamiento. Se concluye que una sola aplicación de cloruro de benzalconio al 0.1% en solución es eficaz para el tratamiento topical de la dermatomicosis causada por Trichophyton mentagrophytes; lográndose una eficacia del 70% en la tercera semana post-tratamiento, sin que cause daño a la piel y sin ser afectada por la presencia de materia orgánica.The efficacy of benzalkonium chloride for the treatment of dermatomicosis caused by Trichophyton sp. in guinea pig (Cavia cobayo) was evaluated in 200 guinea pigs of two months old, that showed typical clinical signs of dermatomicosis. Hair samples and skin grudges were taken for direct exam and for in vitro culture in Dermatophytes Test Medium and Mycobiotic. Skin biopsies for pathobiology were prepared. The guinea pig were divided in groups A and B of 100 animals each. Group A was treated with 0.1% aqueous benzalkonium chloride solution, whereas group B was treated with water as placebo. All samples were positive to media culture by 3rd to 7th day and Trichophyton mentagrophytes was isolated. Sixty percent of the samples were positive to direct exam. Histological study showed mild hyperkeratosis. Healing of lesions and hair growth were observed in all treated guinea pigs by the end of 4th week. The study showed that a single application of 0.1% aqueous benzalkonium chloride solution was effective for topical treatment on guinea pig dermatomycosis

Subduction-driven recycling of continental margin lithosphere.

[EN]Whereas subduction recycling of oceanic lithosphere is one of the central themes of plate tectonics, the recycling of continental lithosphere appears to be far more complicated and less well understood1. Delamination and convective downwelling are two widely recognized processes invoked to explain the removal of lithospheric mantle under or adjacent to orogenic belts2,3,4,5. Here we relate oceanic plate subduction to removal of adjacent continental lithosphere in certain plate tectonic settings. We have developed teleseismic body wave images from dense broadband seismic experiments that show higher than expected volumes of anomalously fast mantle associated with the subducted Atlantic slab under northeastern South America and the Alboran slab beneath the Gibraltar arc region6,7; the anomalies are under, and are aligned with, the continental margins at depths greater than 200 kilometres. Rayleigh wave analysis8,9 finds that the lithospheric mantle under the continental margins is significantly thinner than expected, and that thin lithosphere extends from the orogens adjacent to the subduction zones inland to the edges of nearby cratonic cores. Taking these data together, here we describe a process that can lead to the loss of continental lithosphere adjacent to a subduction zone. Subducting oceanic plates can viscously entrain and remove the bottom of the continental thermal boundary layer lithosphere from adjacent continental margins. This drives surface tectonics and pre-conditions the margins for further deformation by creating topography along the lithosphere–asthenosphere boundary. This can lead to development of secondary downwellings under the continental interior, probably under both South America and the Gibraltar arc8,10, and to delamination of the entire lithospheric mantle, as around the Gibraltar arc11. This process reconciles numerous, sometimes mutually exclusive, geodynamic models proposed to explain the complex oceanic-continental tectonics of these subduction zones12,13,14,15,16,17

Parámetros Productivos de Cuyes Criados con Dietas Suplementadas con Aceite de Pescado y Semillas de Sacha Inchi

The aim of the study was to determine the productive parameters of guinea pigs raised with diets supplemented with fish oil and sacha inchi seeds. Forty eight male guinea pigs of 42 days old were used, with an initial body weight of 615 g. The guinea pigs were randomly assigned to 4 treatments with 3 repetitions (rearing pools) of 4 animals each. Dietary treatments were: T0: Control, T1: diet supplemented with 1.0% fish oil; T2: diet supplemented with 4.0% sacha inchi seed; and T3: diet supplemented with 1.0% fish oil + 4.0% sacha inchi seed. The experimental phase lasted 28 days. Body weight gain, feed intake, feed conversion and carcass yield were evaluated. The average of individual body weight gain ranged between 315 and 353 g per treatment, consumption ranged between 1172 and 1224 g dry matter, feed conversion ranged between 3.53 and 3.73 and carcass yield varied between 69.4 and 71.7% without statistical differences between treatments.El objetivo del estudio fue determinar los parámetros productivos de cuyes con el uso de dietas suplementadas con aceite de pescado y semilla de sacha inchi. Se utilizaron 48 cuyes machos de 42 días de edad, con un peso inicial de 615 g. Los cuyes fueron asignados al azar a 4 tratamientos con 3 repeticiones (pozas) de 4 cuyes cada una. Los tratamientos dietéticos fueron: T0: Control, T1: Dieta suplementada con 1.0% de aceite de pescado; T2: Dieta suplementada con 4.0% de semilla de sacha inchi; y T3: Dieta suplementada con 1.0% de aceite de pescado + 4.0% de semilla de sacha inchi. La fase experimental tuvo una duración de 28 días. Se evaluó la ganancia de peso, consumo de alimento, conversión alimenticia y rendimiento de carcasa. El promedio de ganancia de peso individual en las 4 semanas varió entre 315 y 353 g por tratamiento, el consumo varió entre 1172 y 1224 g de materia seca, la conversión alimenticia varió entre 3.53 y 3.73 y el rendimiento de carcasa varió entre 69.4 y 71.7%, sin diferencia estadística entre tratamientos

Comportamiento productivo de cuyes (Cavia porcellus) de engorde suplementados con tres niveles de butirato de sodio en la dieta

The aim of this study was to evaluate the effect of dietary supplementation with sodium butyrate (BS) on productive performance in fattening guinea pigs. Fifty 14-21 days old weaned male guinea pigs were randomly distributed in five treatments (0, 100, 200, 300 ppm of BS, 200 ppm of Zn-Bacitracin). Body weight gain, feed consumption and feed conversion were evaluated 70 days after supplementation. No response patterns were detected due to BS or Zn-Bacitracin treatments. It is concluded that, under the experimental conditions, supplementation with BS did not improve the productive parameters evaluated.El objetivo del presente estudio fue evaluar el efecto de la suplementación de butirato de sodio (BS) en la dieta sobre el comportamiento productivo de cuyes de engorde. Cincuenta cuyes machos destetados, de 14 a 21 días de edad, fueron distribuidos al azar en cinco tratamientos (0, 100, 200, 300 ppm de BS, 200 ppm de Zn-Bacitracina). Se determinó la ganancia de peso, el consumo de alimento y la conversión alimenticia a los 70 días de la suplementación. No se detectaron patrones de respuesta por efecto del BS ni de Zn-Bacitracina. Se concluye que, bajo las condiciones experimentales, la suplementación con BS no mejoró los parámetros productivos evaluados

Aplicación de la espectroscopía del infrarrojo cercano – NIRS – para determinar el valor nutritivo de variedades de alfalfa (Medicago sativa L) y trébol rojo (Trifolium pratense L)

The aim of this study was to determine the applicability of near infrared spectroscopy (NIRS) for the nutritional assessment of two important forage species in the country: alfalfa (Medicago sativa L) and red clover (Trifolium pratense L). For this, 75 samples of alfalfa varieties (SW 8210, WL 625HQ) and 75 of red clover varieties (Quiñequeli, Kendland) obtained from the paddocks of the IVITA El Mantaro Experimental Station, Junín region, Peru were used. Proximal analysis was performed determining the content of crude protein (CP), ether extract (EE), crude fibre (CF), total ash (TA) and neutral detergent fibre (NDF), and the spectrum was captured using NIRS equipment. The calibration and validation models were developed to estimate the predictive capacity using Partial Least Squares (PLS), and the accuracy and precision statistics used were the Correlation Coefficient (R), Determination Coefficient (R2), Root Mean Square Error of Calibration (RMSEC), Root Mean Square of Prediction Error (RMSEP), Ratio of Range to Error (RER) and Residual Predictive Deviation (RPD). The mathematical models obtained showed that the NIRS technique has a good predictive capacity for the nutritional components of CP, TA and NDF (R2: 0.97, 0.99, 0.94; RPD: 2.00, 2.17 and 2.00, respectively) for varieties of alfalfa and red clover.El objetivo del presente estudio fue determinar la aplicabilidad de la espectroscopía del infrarrojo cercano (NIRS) para la valoración nutritiva de dos especies forrajeras de importancia en el país: alfalfa (Medicago sativa L) y trébol rojo (Trifolium pratense L). Se utilizaron 75 muestras de variedades de alfalfa (SW 8210, WL 625HQ) y 75 de variedades de trébol rojo (Quiñequeli, Kendland) obtenidas de los campos de la Estación Experimental IVITA El Mantaro, región Junín, Perú. Se realizó el análisis proximal determinando el contenido de proteína cruda (PC), extracto etéreo (EE), fibra cruda (FC), cenizas totales (CZ) y fibra detergente neutra (FDN) y se hizo la captura del espectro mediante un equipo NIRS. Se elaboraron los modelos de calibración y validación para estimar la capacidad predictiva mediante Cuadrados Mínimos Parciales (PLS), siendo los estadísticos de exactitud y precisión usados el Coeficiente de Correlación (R), Coeficiente de Determinación (R2), Raíz Cuadrada Media del Error de Calibración (RMSEC), Raíz Cuadrada Media del Error de Predicción (RMSEP), Proporción del Rango con el Error (RER) y Desviación Residual Predictiva (RPD). Los modelos matemáticos obtenidos muestran que la técnica NIRS posee una capacidad de predicción buena de los componentes nutricionales de PC, CZ y FDN (R2:0.97, 0.99, 0.94; RPD: 2.00, 2.17 y 2.00, respectivamente) para variedades de alfalfa y trébol rojo

Efecto de la inclusión de probiótico, prebiótico y simbiótico en la dieta sobre los parámetros productivos del cuy (Cavia porcellus)

The present study evaluated the effect of the inclusion of probiotic, prebiotic and the combination of both (symbiotic) in the diet on the productive parameters of guinea pigs (Cavia porcellus). Fifty 3-day-old male guinea pigs were selected from a Prolific-Dairy maternal line developed in the IVITA-El Mantaro Research Station (Peru) and randomly distributed in five treatments consisting of a basal diet of forages (rye-grass and red clover). supplemented with wheat bran (T5), plus probiotic (T1), prebiotic (T2), symbiotic (T3) and antibiotic growth-promoter (AGP) (T4). The probiotic was a mixture of six bacterial species isolated from the intestine and guinea pig faeces; the prebiotic was a commercial mannanoligosaccharide and the APC was Zn-bacitracin. The response to treatments was evaluated for 56 days in terms of body weight gain, feed intake and feed conversion ratio. No significant or consistent responses were observed as effect of the treatments. The lack of response to AGP and the good body weight gains obtained suggested that, under the conditions of the study, the intestinal microbial balance of the animals was appropriate.El presente estudio evaluó el efecto de la inclusión de probiótico, prebiótico y la combinación de ambos (simbiótico) en la dieta sobre los parámetros productivos del cuy (Cavia porcellus). Se seleccionaron 50 cuyes machos de 3 días de edad de una línea materna Prolífica-Lechera desarrollada en la Estación IVITA-El Mantaro (Perú) y fueron distribuidos aleatoriamente en cinco tratamientos consistentes en una dieta basal de forrajes (rye-grass y trébol rojo) complementada con afrechillo de trigo (T5), más probiótico (T1), prebiótico (T2), simbiótico (T3) y antibiótico promotor del crecimiento (APC) (T4). El probiótico fue un consorcio de seis especies bacterianas aisladas del intestino y heces de cuy; el prebiótico fue un mananoligosacárido comercial y el APC fue Zn-bacitracina. La respuesta a los tratamientos fue evaluada por 56 días en términos de ganancia de peso, consumo de alimento y conversión alimenticia. No se observaron respuestas significativas ni consistentes por efecto de los tratamientos. La falta de respuesta al APC y las buenas ganancias de peso obtenidas sugieren que, bajo las condiciones del estudio, el balance microbiano intestinal de los animales era apropiado