The complex narrow line region in NGC 4151

We present new narrow band images of NGC 4151, taken in excellent seeing conditions with the 4.2-m William Herschel Telescope on La Palma. These reveal a wealth of detail that can be used to test models for the anisotropy of the narrow-line region.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Data acquisition interfaces for GHRIL ITV-IPD detectors

So as to meet the requirements of high spatial resolution techniques, two data acquisition interfaces for ITV and IPD detectors have been developed. These permit a synchronized and simultaneous observation between both of them. The synchronized temporal resolution is 20ms, as well as the data of the ITV, while the reading interface from the IPD permits a temporal resolution of 50s. The ITV signal is stored on the video-recorder while the IPD interface is developed through transputers which store the data, with the time tags, on computer disc.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain     

Climatic constraints for the maize-soybean system in the humid subtropical region of Argentina

The implementation of two summer crops in the same growing season is a possible alternative for land intensification in areas with a long frost-free period. The aim of this study was to analyse the strategy of land intensification through the implementation of the maize-soybean succession at two locations (Reconquista, 29°09′S 59°40′W and Las Breñas, 27°05′S 61°5′W) of the humid subtropical region of Argentina. CERES-Maize and CROPGRO-Soybean models were used to evaluate the impact of inter-annual variability of climate (36 years) of both locations on rain-fed grain yields of the following productive alternatives: (i) monoculture of maize, (ii) monoculture of soybean and (iii) the succession of a short-cycle maize followed by soybean as the second summer crop (maize-soybean system). The maize-soybean system was evaluated by the method of land equivalent ratio (LER), based on the sum of the relative grain yields of its components. The impact of the inter-annual variability of climate and of “El Niño” or “La Niña” episodes (El Niño Southern Oscillation phenomenon (ENSO)) on LER values was analysed. Simulated yields of maize monoculture (5687 kg ha^?1; CV = 49.7% and 5637 kg ha^?1; CV = 57.6% at Reconquista and Las Breñas, respectively) were higher than those of the short-cycle maize, especially at Las Breñas (5448 kg ha^?1; CV = 49.3% and 2322 kg ha^?1; CV = 33.9% at Reconquista and Las Breñas, respectively). Simulated yields of the soybean monoculture were higher (3588 kg ha^?1; CV = 26.1% and 2883 kg ha^?1; CV = 20.7% at Reconquista and Las Breñas, respectively) that those of the soybean as the second crop (2634 kg ha^?1; CV = 38.1% and 2456 kg ha^?1; CV = 32.9% at Reconquista and Las Breñas, respectively) at both locations. Average LERs were 1.69 (CV = 11.4%) at Reconquista and 1.41 (CV = 26.1%) at Las Breñas, and the inter-annual variability of LER was mainly determined by grain yields of (i) soybean as the second crop at Reconquista and (ii) maize monoculture at Las Breñas. Soil water content after maize harvest and rainfalls during reproductive period of soybean as the second crop conditioned LER values, but they were generally greater than 1. At Reconquista, LER values were not affected by the different episodes of ENSO phenomenon. By contrast, at Las Breñas, LER values were higher during La Niña episodes (1.48; CV = 26.6%) than during El Niño episodes (1.32; CV = 23.7%) mainly by their effects on grain yields of maize monoculture. Therefore, crop simulation models demonstrate the possibility to intensify land use (40–70%) at two locations of the humid subtropical region of Argentina, by the implementation of the maize-soybean system.     

Veso: virtual earth-sun observatory

We present the Virtual Earth-Sun Observatory (VESO) at the web site http://www.veso.unam.mx. This site shows a real time integrated database obtained from four instruments of the Instituto de Geofisica-UNAM studying Sun-Earth connection phenomena. (1) The Solar Radio Interferometer (RIS, Radio Interferómetro Solar) measures the lower solar atmosphere radiation at 7.5 GHz, revealing microwave bursts associated with solar activity. (2) The Mexican Array Radio Telescope (MEXART, Observatorio de Centelleo Interplanetario de Coeneo) will detect solar wind large-scale disturbances between Sun and Earth (e.g., Interplanetary counterparts of Coronal Mass Ejections (ICMES) and Stream Interaction Regions (SIR)) employing the interplanetary scintillation technique (IPS) operating at 140 MHz. (3) The Cosmic Ray Observatory (RC) detects high energy galactic particles, whose flow is affected by magnetic disturbances in the solar wind, and (4) the Teoloyucan Geomagnetic Observatory (TEO) measures the variations in the Earths magnetic field. The VESO instruments provide data from four different points of the complex chain of the solar terrestrial relations and will allow the study of intense solar events causing geomagnetic activity. The VESO project is part of the celebration of the International Heliophysical Year (IHY) and the Electronic Geophysical Year (EGY) in Mexico.     

Porosity and size gradation of saturated gravel with percolated fines

Fine particles may infiltrate through coarse alluvial beds and eventually saturate the subsurface pore space. It is essential to understand the conditions that lead to bed saturation, and to forecast the packing characteristics of saturated beds to assess the effect of excess fine sediment supply on a number of processes that occur in the stream–sediment boundary. To address this problem, in this study, a new method is introduced to predict the grain‐size distribution for the saturated condition, and the resulting porosity decrease, given the characteristics of the bed and the supplied sediments. The new method consists of the numerical aggregation of infilling fines in a finite bed volume, during which the bed properties change to affect further infilling. An existing semi‐empirical, particle packing model is implemented to identify these properties. It is shown that these types of models are adequate to describe regimes of natural sediment fabric quantitatively, and are thus useful tools in the analysis of sediment infiltration processes. Unlike previous developments to quantify saturated bed conditions, which assume that the supplied material is uniform and finer than the bed pore openings, the method developed herein considers poorly sorted fines, and can identify size fractions that are able to ingress into the bed due to being smaller than the particles that form the bed structure. Application of the new method to published experimental data showed that the final content of infiltrated fines is strongly sensitive to the initial bed packing density, highlighting the need to measure and understand open‐work gravel deposits. In addition, the new method was shown to be suitable for assessing the degree of bed saturation, when it was applied to a published data set of field samples.     

Evidence of episodic long-lived eruptions in the Yuma,Ginsburg, Jesús Baraza and Tasyo mud volcanoes,Gulf of Cádiz

High-resolution single channel and multichannel seismic reflection profiles and multibeam bathymetric and backscatter data collected during several cruises over the period 1999 to 2007 have enabled characterising not only the seabed morphology but also the subsurface structural elements of the Yuma, Ginsburg, Jesús Baraza and Tasyo mud volcanoes (MVs) in the Gulf of Cádiz at 1,050–1,250 m water depth. These MVs vary strongly in morphology and size. The data reveal elongated cone-shaped edifices, rimmed depressions, and scarps interpreted as flank failures developed by collapse, faulting, compaction and gravitational processes. MV architecture is characterised by both extrusive and intrusive complexes, comprising stacked edifices (including seabed cones and up to four buried bicones) underlain by chaotic vertical zones and downward-tapering cones suggesting feeder systems. These intrusive structures represent the upper layer of the feeder system linking the fluid mud sources with the constructional edifices. The overall architecture is interpreted to be the result of successive events of mud extrusion and outbuilding alternating with periods of dormancy. Each mud extrusion phase is connected with the development of an edifice, represented by a seabed cone or a buried bicone. In all four MVs, the stacked edifices and the intrusive complexes penetrate Late Miocene–Quaternary units and are rooted in the Gulf of Cádiz wedge emplaced during the late Tortonian. Major phases of mud extrusion and outbuilding took place since the Late Pliocene, even though in the Yuma and Jesús Baraza MVs mud volcanism started in the Late Miocene shortly after the emplacement of the Gulf of Cádiz wedge. This study shows that fluid venting in the eastern sector of the Gulf of Cádiz promoted the outbuilding of large long-lived mud volcanoes active since the Late Miocene, and which have been reactivated repeatedly until recent times.     

Submerged vegetation complexity modifies benthic infauna communities: the hidden role of the belowground system

Marine plants provide a variety of functions with high economic and ecological values in ecosystems. The above‐ (AG) and below‐ground (BG) systems increase the structural complexity of plants, which also enhance faunal abundance and diversity. The ecological role of the AG compartment in structuring inter‐tidal macrobenthic communities has been widely studied; however, this is not the case for the BG compartment. This study addressed the effects of variation in vegetation complexity (in both AG and BG systems) on associated macrobenthic infauna with respect to abundance, species richness, composition, weight and body type. To achieve this aim, a field experiment using artificial vegetation mimics was carried out using replicated treatments with different AG‐BG complexity ratios. We found a significant increase in the density and the number of taxa of macrobenthic infaunal species in plots with vegetation mimics compared with unvegetated areas, regardless of either AG or BG complexity. This effect was found even when AG parts were not present (i.e. when only BG parts were used). Furthermore, a positive relationship between structural complexity and diversity was recorded. Variation in one or both plant compartments was strongly related to diversity changes in the associated macrobenthic infauna. In conclusion, our experimental set‐up provides the first evidence that the BG compartment is at least as important as the AG compartment in controlling diversity in inter‐tidal vegetated areas because it was able to strongly affect community structure even when the AG system was totally absent.     

Object-oriented and pixel-based classification approaches to classify tropical successional stages using airborne high–spatial resolution images

Airborne high–spatial resolution images were evaluated for mapping purposes in a complex Atlantic rainforest environment in southern Brazil. Two study sites, covered predominantly by secondary evergreen rainforest, were surveyed by airborne multispectral high-resolution imagery. These aerophotogrammetric images were acquired at four spectral bands (visible to near-infrared) with spatial resolution of 0.39 m. We evaluated different data input scenarios to suit the object-oriented classification approach. In addition to the four spectral bands, auxiliary products such as band ratios and digital elevation models were considered. Comparisons with traditional pixel-based classifiers were also performed. The results showed that the object-based classification approach yielded a better overall accuracy, ranging from 89% to 91%, than the pixel-based classifications, which ranged from 62% to 63%. The individual classification accuracy of forest-related classes, such as young successional forest stages, benefits the object-based approach. These classes have been reported in the literature as the most difficult to map in tropical environments. The results confirm the potential of object-based classification for mapping procedures and discrimination of successional forest stages and other related land use and land cover classes in complex Atlantic rainforest environments. The methodology is suggested for further SAAPI acquisitions in order to monitor such endangered environment as well as to support National Land and Environmental Management Protocols.