The discovery of the Borobia world-class stratiform magnesite deposit (Soria,Spain): a preliminary report

A new world-class stratiform magnesite deposit has been recently discovered near the village of Borobia in Soria, Spain. The mineralization consists of a 25-45 m massive to banded magnesite layer sandwiched in between a Lower Cambrian carbonate formation and an upper shale horizon. It forms an arcuate belt striking NW-SE to W-E, which outcrops for 7.3 km in two elevations separated by a central valley that is covered by a thin layer of Pleistocene sediments. The orebody is confined by two regionally important faults and is probably associated with the dolomitization and silicification of the Cambrian limestones. Geological ore resources are estimated to exceed 175 Mt with MgO contents varying from 36 to 47% by weight. At present, the owners, Magnesitas y Dolomías de Borobia, S.L., are at an advanced stage of planning for extraction. This report presents some results of an ongoing geological exploration programme and shows the general features of the geology and mineralogy of the Borobia deposit.     

Development and Application of 2D and 3D GRASS Modules for Simulation of Thermally Driven Slope Winds

The ability to manage and process fully three‐dimensional information has only recently been made available for a few Geographical Information Systems (GIS). An example of integrated and complementary use of 2D and 3D GRASS modules for the evaluation and representation of thermally induced slope winds over complex terrain is presented. The analytic solution provided by Prandtl (1942) to evaluate wind velocity and (potential) temperature anomaly induced by either diurnal heating or nocturnal cooling on a constant angle slope is adopted to evaluate wind and temperature profiles at any point over both idealised and real complex terrain. As these quantities depend on the slope angle of the ground and on the distance from the slope surface suitable procedures are introduced to determine the coordinate n of a point in the 3D volume measured along the direction locally normal to the terrain surface. A new GRASS module has been developed to evaluate this quantity and to generate a 3D raster file where each cell is assigned the value of the cell on the surface belonging to the normal vector. The application of the algorithm implemented in GRASS to an ideal valley and to a real valley close to the city of Trento in the Alps provides results in accordance with data reported in the literature. An extension of Prandtl's (1942) model to take into account humidity and evaporation processes on the soil is also proposed and implemented.     

The thin and medium filters of the EPIC camera on-board XMM-Newton: measured performance after more than 15 years of operation

After more than 15 years of operation of the EPIC camera on board the XMM-Newton X-ray observatory, we have reviewed the status of its Thin and Medium filters. We have selected a set of Thin and Medium back-up filters among those still available in the EPIC consortium and have started a program to investigate their status by different laboratory measurements including: UV/VIS transmission, Raman scattering, X-Ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Furthermore, we have investigated the status of the EPIC flight filters by performing an analysis of the optical loading in the PN offset maps to gauge variations in the optical and UV transmission. We both investigated repeated observations of single optically bright targets and performed a statistical analysis of the extent of loading versus visual magnitude at different epochs. We report the results of the measurements conducted up to now. Most notably, we find no evidence for change in the UV/VIS transmission of the back-up filters in ground tests spanning a 2 year period and we find no evidence for change in the optical transmission of the thin filter of the EPIC-pn camera from 2002 to 2012. We point out some lessons learned for the development and calibration programs of filters for X-ray detectors in future Astronomy missions.     

Complexity as a streamflow metric of hydrologic alteration

We explore the potential of using a complexity measure from statistical physics as a streamflow metric of basin-scale hydrologic alteration. The complexity measure that we employ is a non-trivial function of entropy. To determine entropy, we use the so-called permutation entropy (PE) approach. The PE approach is desirable in this case since it accounts for temporal streamflow information and it only requires a weak form of stationarity to be satisfied. To compute the complexity measure and assess hydrologic alteration, we employ daily streamflow records from 22 urban basins, located in the metropolitan areas of the cities of Baltimore, Philadelphia, and Washington DC, in the United States. We use urbanization to represent hydrologic alteration since urban basins are characterized by varied and often pronounced human impacts. Based on our application of the complexity measure to urban basins, we find that complexity tends to decline with increasing hydrologic alteration while entropy rises. According to this evidence, heavily urbanized basins tend to be temporally less complex (less ordered or structured) and more random than basins with low urbanization. This complexity loss may have important implications for stream ecosystems whose ability to provide ecosystem services depend on the flow regime. We also find that the complexity measure performs better in detecting alteration to the streamflow than more conventional metrics (e.g., variance and median of streamflow). We conclude that complexity is a useful streamflow metric for assessing basin-scale hydrologic alteration.     

On the effect of decreasing CO2 concentration in the atmosphere

In the present paper the effect of an abrupt change of the atmospheric radiative forcing is investigated by means of a global climate model that includes a mixed layer ocean. In assessing if, under such a change, the model response has a bifurcation point, the steady solution is studied for a sudden decrease of CO₂ concentration from its actual value. It is found that there is a critical threshold for CO₂ content below which the model ends up to a snowball Earth. It occurs for a few percentage changes of CO₂ concentration around the threshold because the model strongly depends on the relationship among atmospheric temperature, water vapor content and the sudden ice-albedo feedback activation, even in the subtropical regions. Moreover, results suggest that the transition to ice-covered Earth is clearly favoured when Q-flux corrections (i.e. the parameterization of ocean heat transports) are removed.     

Control of the earthquake and wind dynamic response of steel‐framed buildings by using additional braces and/or viscoelastic dampers

The insertion of steel braces equipped with viscoelastic dampers (VEDs) (‘dissipative braces’) is a very effective technique to improve the seismic or wind behaviour of framed buildings. The main purpose of this work is to compare the earthquake and wind dynamic response of steel‐framed buildings with VEDs and achieve optimal properties of dampers and supporting braces. To this end, a numerical investigation is carried out with reference to the steel K‐braced framed structure of a 15‐storey office building, which is designed according to the provisions of Eurocodes 1 and 3, and to four structures derived from the first one by the insertion of additional diagonal braces and/or VEDs. With regard to the VEDs, the following cases are examined: absence of dampers; insertion of dampers supported by the existing K‐braces in each of the structures with or without additional diagonal braces; insertion of dampers supported by additional diagonal braces. Dynamic analyses are carried out in the time domain using a step‐by‐step initial stress‐like iterative procedure. For this purpose, the frame members and the VEDs are idealized, respectively, by a bilinear model, which allows the simulation of the nonlinear behaviour under seismic loads, and a six‐element generalized model, which can be considered as an in‐parallel‐combination of two Maxwell models and one Kelvin model. Artificially generated accelerograms, whose response spectra match those adopted by Eurocode 8 for a medium subsoil class and for different levels of peak ground acceleration, are considered to simulate seismic loads. Along‐wind loads are considered assuming, at each storey, time histories of the wind velocity for a return period T_r=5 years, according to an equivalent spectrum technique. Copyright © 2010 John Wiley & Sons, Ltd.     

Distribution of the genus Hypoplectrus (Teleostei: Serranidae) in the Greater Caribbean Region: support for a color‐based speciation

The reef‐associated fish genus Hypoplectrus (Serranidae), endemic to the western Atlantic Ocean, represents an ideal model to study speciation within a potentially highly dispersive (marine) ecosystem, because it consists of a complex of at least 10 morphs differentiated primarily by coloration. Although several recent studies on genetics, diet, and fertilization reveal little to no difference between the Hypoplectrus color morphs, there is still not a full understanding of what keeps these morphs distinct or drives their variation. Ecological information is needed alongside the genetic information to better understand this variation. Based on presence/absence records from scientific literature and direct observations in coral reefs, this work examined the distribution of the genus Hypoplectrus in the Greater Caribbean region. Some color morphs occurred simultaneously at given locations, but others showed geographic restrictions. Using cluster and nMDS analyses, we found three major groupings according to distribution: (i) widespread (Hypoplectrus puella, Hypoplectrus unicolor, and Hypoplectrus nigricans), (ii) less widespread (Hypoplectrus indigo, Hypoplectrus gummigutta, Hypoplectrus chlorurus, Hypoplectrus aberrans, and Hypoplectrus guttavarius), and (iii) geographically confined or segregated (Hypoplectrus gemma, Hypoplectrus providencianus). Geographic sections selected for the Greater Caribbean (eastern, western and northern) were dominated by at least three widely distributed Hypoplectrus morphs. New geographic records of some color morphs were documented and compared to previous established distribution ranges in the Greater Caribbean.