Ibvs and the long-term monitoring of behaviour of variable stars

Roles of the Information Bulletin on Variable Stars (IBVS) in servicing some of the information needs of observers of variable stars are briefly summarized.     

On the nature of high luminosity ULIRGs

We present the preliminary results for a sample of 21 high luminosity ULIRGs (L_IR > 10^12.3 L⊙), selected from the 1Jy sample. Based on R band imaging we have performed an analysis of their morphologies. The main result obtained is that about half of the host galaxies are represented by spheroids and in the other half an exponential disk has been detected or they show still trace of a merging process going on. Regarding the relation between morphology and nuclear activity it seems that more advanced mergers appear in the most active galaxies. Hence the data support the evolutionary scheme proposed by Sanders 15 years ago that ULIRGs can be the earliest precursors of optical QSOs. This revised version was published online in August 2006 with corrections to the Cover Date.     

Long-Term Evolution of FU Ori-Type Stars at Infrared Wavelengths

We investigated the brightness evolution of 5 FU Ori systems in the 1–200 μm wavelength range using observations from the Infrared Space Observatory, 2MASS and MSX data. The SEDs were compared with earlier ones derived from the IRAS photometry and ground-based observations around the epoch 1983. In three cases no difference was seen, in one object the near- and mid-infrared part of the spectrum became fainter by a factor of 2, and in the fifth case a marginal fading was observed. We study in detail the case of V1057 Cyg.     

THERMAP: a mid-infrared spectro-imager for space missions to small bodies in the inner solar system

We present THERMAP, a mid-infrared spectro-imager for space missions to small bodies in the inner solar system, developed in the framework of the MarcoPolo-R asteroid sample return mission. THERMAP is very well suited to characterize the surface thermal environment of a NEO and to map its surface composition. The instrument has two channels, one for imaging and one for spectroscopy: it is both a thermal camera with full 2D imaging capabilities and a slit spectrometer. THERMAP takes advantage of the recent technological developments of uncooled microbolometer arrays, sensitive in the mid-infrared spectral range. THERMAP can acquire thermal images (8–18 μm) of the surface and perform absolute temperature measurements with a precision better than 3.5 K above 200 K. THERMAP can acquire mid-infrared spectra (8–16 μm) of the surface with a spectral resolution Δλ of 0.3 μm. For surface temperatures above 350 K, spectra have a signal-to-noise ratio >60 in the spectral range 9–13 μm where most emission features occur.     

Dynamic fuzzy neural network for simulating the fixed-bed adsorption of cadmium,nickel, and zinc on bone char

This study introduces the application of a dynamic fuzzy neural network for fitting and simulating the adsorption of nickel, cadmium, and zinc ions in mono- and bi-metallic solutions (nickel–cadmium, nickel–zinc, and cadmium–zinc) using packed-bed columns with bone char. This neural network model has shown a flexible and self-adaptive architecture with a faster learning speed than that of traditional artificial neural approaches. Results showed that this neural network model was reliable for representing the high asymmetry behavior of concentration profiles in both mono- and bi-metallic breakthrough curves where its accuracy was quite reasonable. Breakthrough parameters for mono-component and binary systems of tested heavy metals were calculated and compared. This analysis showed that the removal of these heavy metal ions in binary systems was a strong competitive adsorption process where the presence of co-ions reduced the removal performance of bone char at fixed-bed adsorbers. Results of surface characterization of adsorbent samples with X-ray photoelectron and infrared spectroscopy supported a removal mechanism based on an ion exchange between calcium from hydroxyapatite of bone char and heavy metal ions in the solution forming new metal–phosphate interactions in the adsorbent surface.     

The impact of aquifer stratification on saltwater intrusion characteristics. Comprehensive laboratory and numerical study

Laboratory experiments and numerical simulations were utilized in this study to assess the impact of aquifer stratification on saltwater intrusion. Three homogeneous and six layered aquifers were investigated. Image processing algorithms facilitated the precise calculation of saltwater wedge toe length, width of the mixing zone, and angle of intrusion. It was concluded that the length of intrusion in stratified aquifers is predominantly a function of permeability contrast, total aquifer transmissivity and the number of heterogeneous layers, being positively correlated to all three. When a lower permeability layer overlays or underlays more permeable zones its mixing zone widens, while it becomes thinner for the higher permeability strata. The change in the width of the mixing zone (WMZ) is positively correlated to permeability contrast, while it applies to all strata irrespectively of their relative vertical position in the aquifer. Variations in the applied hydraulic head causes the transient widening of WMZ. These peak WMZ values are larger during saltwater retreat and are negatively correlated to the layer's permeability and distance from the aquifer's bottom. Moreover, steeper angles of intrusion are observed in cases where low permeability layers overlay more permeable strata, and milder ones in the inverse aquifer setups. The presence of a low permeability upper layer results in the confinement of the saltwater wedge in the lower part of the stratified aquifer. This occurs until a critical hydraulic head difference is applied to the system. This hydraulic gradient value was found to be a function of layer width and permeability contrast alike.     

Progress and opportunities for monitoring greenhouse gases fluxes in Mexican ecosystems: the MexFlux network

Understanding ecosystem processes from a functional point of view is essential to study relationships among climate variability, biogeochemical cycles, and surface-atmosphere interactions. Increasingly during the last decades, the eddy covariance (EC) method has been applied in terrestrial, marine and urban ecosystems to quantify fluxes of greenhouse gases (e.g., CO₂, H₂O) and energy (e.g., sensible and latent heat). Networks of EC systems have been established in different regions and have provided scientific information that has been used for designing environmental and adaptation policies. In this context, this article outlines the conceptual and technical framework for the establishment of an EC regional network (i.e., MexFlux) to measure the surface-atmosphere exchange of heat and greenhouse gases in Mexico. The goal of the network is to improve our understanding of how climate variability and environmental change influence the dynamics of Mexican ecosystems. First, we discuss the relevance of CO₂ and water vapor exchange between terrestrial ecosystems and the atmosphere. Second, we briefly describe the EC basis and present examples of measurements in terrestrial and urban ecosystems of Mexico. Finally, we describe the conceptual and operational goals at short-, medium-, and long-term scales for continuity of the MexFlux network.     

Source characterization and spatio–temporal evolution of the metal pollution in the sediments of the Basque estuaries (Bay of Biscay)

According to Water Framework Directive requirements, Member States must identify and analyze effects derived from human pressures in aquatic systems. As different kind of pressures can impact water bodies at different scales, analyses of spatio-temporal evolution of water bodies becomes essential in order to understand ecosystem responses. In this investigation, an analysis of spatio-temporal evolution of sedimentary metal pollution (Cd, Cr, Cu, Hg, Ni, Pb, Zn) in 12 Basque estuaries (Bay of Biscay) is presented. Data collected in extensive sampling surveys is the basis for the GIS-based statistical approach used. The implementation of pollution abatement measures is reflected in a long-term decontamination process, mostly evident in estuaries with highest historical sediment pollution levels. Spatial evolution is determined by either naturally occurring or human driven processes. Such spatial processes are more obviously being reflected in estuaries with lower historical sediment pollution levels.     

Archeointensity investigation on pottery vestiges from Puertas de Rolón, Capacha culture: In search for affinity with other Mesoamerican pre-Hispanic cultures

We report the results of a rock magnetic and archeointensity study on pottery fragments recovered at the archaeological site of Puertas de Rolón, Capacha culture (Colima), that is considered one of the most important pre-Classic cultural developments of western Mesoamerica, Mexico. Standard rock magnetic experiments were carried out in order to investigate the reliability of the ancient field strength recovered from studied materials. Six out of the seven analyzed fragments gave reliable intensity determinations. The mean archeointensity value obtained in this study is 35.3 ± 3.4 μT. It is in good agreement with another contemporaneous Mesoamerican mean archeointensity of 34.3 ± 1.1 μT obtained for El Opeño. Statistically similar rock-magnetic parameters between ceramics from El Opeño and Puertas de Rolón potsherds appear to be related to clay-sources with similar geological settings and weathering processes. Alternatively, ancient trade or interexchange between western (Capacha Culture) and eastern Mesoamerica locations, as it has been proposed earlier, seem to be supported by results obtained in this study.     

DInSAR analysis of ALOS PALSAR images for the assessment of very slow landslides: the Tena Valley case study

In this work we analyse the performance of advanced land observing satellite (ALOS) phased array type L-band syntetic aperture radar (PALSAR) images for mapping and monitoring of very slow landslides using conventional differential interferometry in the Tena Valley (Central Pyrenees, Spain). These results are compared with those retrieved in previous works where multi-band advanced differential interferometric synthetic aperture radar (DInSAR) analysis was performed for the same area using PSI techniques. The study area is largely underlain by slates (ca. 80 %) where large deep-seated very slow earth flows are dominant. The results reveal that DInSAR analysis is able to measure displacements of landslides with a greater spatial coverage than PSI analysis, but for a lower amount of them (nine against 51). Overall, the combination of the DInSAR and multi-band PSI analysis permitted to map and monitor 68 % of the landslides in Tena Valley. From this amount, 63 landslides are considered as active. The main advantage of DInSAR with respect to PSI analysis is the capability to detect faster movements (up to 145 cm?year^?1) derived from the 46 days interferograms. That is the case of Sextas and La Selva landslides where an acceleration of the moving mass was measured after intense rainfall periods producing major damages to linear infrastructures. The combination of measured displacement from ALOS interferograms, with the observed damages on the A-136 road, was useful to assess the potential damage that could cause these slow movements. In general, it is demonstrated that even though PSI analysis provides a better performance in terms of landslide mapping, L-band DInSAR analysis provides an added value for landslide hazard assessment through radar remote sensing. For this reason it is necessary to encourage the launch of new satellite missions similar to ALOS PALSAR that could operate with shorter revisiting time periods.