SUPERPOSED MESOSCOPIC FOLDS IN THE BUENAVISTA ANTICLINE, COLOMBIAN LLANOS FOOTHILLS.

    The structural evolution of the Llanos foothills, Eastern Cordillera of Colombia, involves the reactivation of deep-seated faults, the origin of which has to be sought for in Late Paleozoic and Early Cretaceous rift events. These faults are blind and refer to major, E-vergent anticlines which make up the eastern deformation front of this mountain chain. Their ge-ometry can be simulated using the "tri-shear" model. For our study area we perform a structural analysis at map scale by the contouring of the basement-cover interface and compare observations at outcrop scale. Both scales display N-S and E-W trending folds. E-W trending folds have not been reported so far from the Eastern Cordillera and, discussing their origin, we evoke three hypotheses: 1) a regional N-S contraction; 2) their formation in a relay zone during a sinistral fault reactivation; and 3), local down-slope mass movements on the fanks of a major E-W trending structural high.   Key Words: Blind faults, fault reactivation, superposed folds, oblique contraction, Llanos foothills of Colombia.  La evolución del frente de deformación del piedemonte llanero se caracteriza por la reactivación de fallas corticales cuyo origen se debe a eventos distensivos del Paleozoico Superior y del Cretáceo Inferior. Estas fallas son típicamente ciegas y se asocian a pliegues con una vergencia pronunciada hacia el E. Una posible simulación cinemática para su formación se apoya en el mecanismo de una zona de cizalla triangular ("tri-shear"). Para el área de estudio presentamos un análisis estructural a nivel de mapa por medio de un contorneo de la interfase basamento-cobertera y observaciones relacionadas a los aforamientos. En ambas escalas se evidencian pliegues de dirección N-S y de dirección E-W. Para explicar los plie­gues de dirección E-W discutimos tres hipótesis, una primera evocando un acortamiento N-S regional, otra atribuyendo el acortamiento N-S a una reactivación sinestral de fallas mayores y una ultima basada en movimientos de masa de las unidades lodosas del Cretáceo Inferior.   Palabras clave: Fallas ciegas, reactivación de fallas, pliegues sobrepuestos, contracción oblicua, piedemonte llanero.     &nbsp

SUPERPOSED MESOSCOPIC FOLDS IN THE BUENAVISTA ANTICLINE, COLOMBIAN LLANOS FOOTHILLS.

    The structural evolution of the Llanos foothills, Eastern Cordillera of Colombia, involves the reactivation of deep-seated faults, the origin of which has to be sought for in Late Paleozoic and Early Cretaceous rift events. These faults are blind and refer to major, E-vergent anticlines which make up the eastern deformation front of this mountain chain. Their ge-ometry can be simulated using the "tri-shear" model. For our study area we perform a structural analysis at map scale by the contouring of the basement-cover interface and compare observations at outcrop scale. Both scales display N-S and E-W trending folds. E-W trending folds have not been reported so far from the Eastern Cordillera and, discussing their origin, we evoke three hypotheses: 1) a regional N-S contraction; 2) their formation in a relay zone during a sinistral fault reactivation; and 3), local down-slope mass movements on the fanks of a major E-W trending structural high.   Key Words: Blind faults, fault reactivation, superposed folds, oblique contraction, Llanos foothills of Colombia.  La evolución del frente de deformación del piedemonte llanero se caracteriza por la reactivación de fallas corticales cuyo origen se debe a eventos distensivos del Paleozoico Superior y del Cretáceo Inferior. Estas fallas son típicamente ciegas y se asocian a pliegues con una vergencia pronunciada hacia el E. Una posible simulación cinemática para su formación se apoya en el mecanismo de una zona de cizalla triangular ("tri-shear"). Para el área de estudio presentamos un análisis estructural a nivel de mapa por medio de un contorneo de la interfase basamento-cobertera y observaciones relacionadas a los aforamientos. En ambas escalas se evidencian pliegues de dirección N-S y de dirección E-W. Para explicar los plie­gues de dirección E-W discutimos tres hipótesis, una primera evocando un acortamiento N-S regional, otra atribuyendo el acortamiento N-S a una reactivación sinestral de fallas mayores y una ultima basada en movimientos de masa de las unidades lodosas del Cretáceo Inferior.   Palabras clave: Fallas ciegas, reactivación de fallas, pliegues sobrepuestos, contracción oblicua, piedemonte llanero.     &nbsp

Spitzer Secondary Eclipse Observations of Five Cool Gas Giant Planets and Empirical Trends in Cool Planet Emission Spectra

In this work we present Spitzer 3.6 and 4.5 micron secondary eclipse observations of five new cool (<1200 K) transiting gas giant planets: HAT-P-19b, WASP-6b, WASP-10b, WASP-39b, and WASP-67b. We compare our measured eclipse depths to the predictions of a suite of atmosphere models and to eclipse depths for planets with previously published observations in order to constrain the temperature- and mass-dependent properties of gas giant planet atmospheres. We find that the dayside emission spectra of planets less massive than Jupiter require models with efficient circulation of energy to the night side and/or increased albedos, while those with masses greater than that of Jupiter are consistently best-matched by models with inefficient circulation and low albedos. At these relatively low temperatures we expect the atmospheric methane to CO ratio to vary as a function of metallicity, and we therefore use our observations of these planets to constrain their atmospheric metallicities. We find that the most massive planets have dayside emission spectra that are best-matched by solar metallicity atmosphere models, but we are not able to place strong constraints on metallicities of the smaller planets in our sample. Interestingly, we find that the ratio of the 3.6 and 4.5 micron brightness temperatures for these cool transiting planets is independent of planet temperature, and instead exhibits a tentative correlation with planet mass. If this trend can be confirmed, it would suggest that the shape of these planets' emission spectra depends primarily on their masses, consistent with the hypothesis that lower-mass planets are more likely to have metal-rich atmospheres.Comment: 16 pages, 14 figures, accepted for publication in Ap

Characteristics of Welding Fume Aerosol Investigated in Three Swedish Workshops

Potentially high human exposures to nanometer sized airborne particles occur due to welding and other thermal processes in industrial environments. Detailed field measurements of physical and chemical particle characteristics were performed in three work-shops in Sweden. Measurements were performed both in the plume 5-20 cm above the welding point and in the background air (more than 5 m away from the nearest known particle source). Particle number and mass concentrations were measured on-line. A low pressure impactor was used for size-resolved chemical particle composition. The in-plume measurements generated the chemical signatures for different welding processes. These signatures were then used to identify contributions from various processes to the particle concentrations in different size classes. The background number and mass concentrations increased by more than an order of magnitude during intense activities in the work-shops compared to low activities during breaks

2-Cyano-1-methyl­pyridinium nitrate

In the title compound, C7H7N2 +·NO3 −, all atoms except the methyl H atoms lie on a crystallographic mirror plane. The inter­layer distance, including that between aligned N atoms from alternating cations and anions in adjacent layers, is exceptionally short at 3.055 (1) Å. Two-dimensional C—H⋯O hydrogen-bonded networks link cations to anions, while C—H⋯N inter­actions link cations within each layer. Anion–π inter­actions with the cations assist in binding the layers together

A chronometric exploration of high-resolution ‘sensitive TMS masking’ effects on subjective and objective measures of vision

Transcranial magnetic stimulation (TMS) can induce masking by interfering with ongoing neural activity in early visual cortex. Previous work has explored the chronometry of occipital involvement in vision by using single pulses of TMS with high temporal resolution. However, conventionally TMS intensities have been high and the only measure used to evaluate masking was objective in nature. Recent studies have begun to incorporate subjective measures of vision, alongside objective ones. The current study goes beyond previous work in two regards. First, we explored both objective vision (an orientation discrimination task) and subjective vision (a stimulus visibility rating on a four-point scale), across a wide range of time windows with high temporal resolution. Second, we used a very sensitive TMS-masking paradigm: stimulation was at relatively low TMS intensities, with a figure-8 coil, and the small stimulus was difficult to discriminate already at baseline level. We hypothesized that this should increase the effective temporal resolution of our paradigm. Perhaps for this reason, we are able to report a rather interesting masking curve. Within the classical-masking time window, previously reported to encompass broad SOAs anywhere between 60 and 120 ms, we report not one, but at least two dips in objective performance, with no masking in-between. The subjective measure of vision did not mirror this pattern. These preliminary data from our exploratory design suggest that, with sensitive TMS masking, we might be able to reveal visual processes in early visual cortex previously unreported