Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

This work assessed the age distribution of Cadomian/Pan-African orogenic events (550-590 and 605-790Ma, respectively) in several zones of Iberian Massif by means of detrital and inherited zircon analysis compilation. Detrital zircon age spectra show that throughout the late Neoproterozoic-to-Early Ordovician era (~120Ma sedimentary record), the main systematic peak occurs at ~610Ma, followed by peaks at typical Cadomian ages (~590-550Ma). Inherited zircons incorporated in Cambrian-to-Lower Ordovician igneous rocks show typical Cadomian ages (~590-550Ma) but, once again, a remarkably consistent Pan-African ~610Ma peak occurs. In accordance with compiled zircon data and taking into account the evidence of North African peri-cratonic inliers, Ediacaran (~610Ma) zircons incorporated in Paleozoic magmas provide indirect evidence of Pan-African magmatism, suggesting that these magmas and synorogenic sediments are likely to constitute the cryptic stratigraphic infrastructure of most of the Iberian Massif. The main source of ~610Ma inherited zircons may be the lateral chrono-equivalents of the Saghro and Bou Salda-M`Gouna Groups (Anti-Atlas, Morocco) and/or coeval igneous rocks from West African Craton or Trans-Sahara Belt, emplaced at a stratigraphic level below the late-Ediacaran sediments of the Ossa Morena Zone and the Central Iberian Zone. Assuming that the Iberian crust is a fragment of the Pan-African orogen, a relative paleoposition situated between the West African Craton and the Trans-Saharan Belt during the Late Neoproterozoic is proposed. The closed-system behaviour of Stenian-Tonian detrital zircon ages in the Trans-Sahara Belt suggests that this mega-cordillera acted as a barrier, in paleogeographic terms, separating the Sahara Metacraton from Iberia. In Iberia, the opening of the system to Stenian-Tonian detrital zircons during the Ordovician indicates that, at that time, the Trans-Saharan Belt had already become a vast peneplain, which favoured a large drainage system with a long-distance transport mechanism that fed the passive continental margins.

Detrital zircon grains from Cambrian–Lower Ordovician sandstones and quartzites sampled in the Pyrenees were dated by LA-ICPMS in order to assess their provenance sources. Resulting age distributions are compared to other available datasets from neighbouring margins, such as Morocco, the Iberian Peninsula, southern France and Sardinia. Kolmogorov-Smirnov (K-S) test and Crystallization Age-Depositional Age (CA-DA) diagrams were used to compare zircon populations estimating their possible correlation with the arc/rift/drift geodynamic evolution of the northwestern Gondwana margin. During Terreneuvian times, zircon populations allowed the distinction of i) a southwesternmost edge (Atlas-Ossa-Morena Rift) mostly influenced by Panafrican and Anti-Atlasian sources (ca. 0.63–0.54), ii) a northeasternmost edge (Sardinia) recording the influence of the Saharan Metacraton and the Arabian Nubian Shield, with an distinct Stenian–Tonian shift (ca. 1.25–0.85Ga) and iii) an intermediate palaeogeographic transect, where lies the Central Iberian, West Asturian-Leonese and Cantabrian Zones, the Montagne Noire and the Pyrenees sharing similar populations and a chronologically progressive influence from Anti-Atlasian/Panafrican to Saharan Metacraton/Arabian Nubian Shield sources. This gradual modification in zircon percentage populations supports similar trends based on climatically sensitive indicators, biogeographic patterns of Cambrian Epoch 2 archaeocyathan and microfossil assemblages, and laterally correlatable episodes of carbonate production, all of them pointing to a Cambrian setting for the Pyrenean Basin between the Montagne Noire (Occitan Domain) and the Sardinian margins of NW Gondwana. The Terreneuvian zircon patterns recorded in the Pyrenees gradually evolved from Cambrian Epoch 2 to Early Ordovician times, reflecting the geodynamic evolution from Panafrican and Cadomian arc-related to rift-dominant conditions. During Furongian and Ordovician times, the relative percentage of zircon populations led to a more spread age curve, characteristic of extensional settings and pointing to rift (passive margin) conditions.

This study presents a new geochemical, petrological, and geochronological U-Pb dataset from Ediacaran metabasites and associated rocks of the Canigó and Cap de Creus massifs, Eastern Pyrenees. Metabasites are composed of calcic amphibole + plagioclase + chlorite + epidote ± quartz plus titanite + apatite + ilmenite ± biotite ± rutile as accessory phases and show relict igneous textures. Peak pressure-temperature determinations share common conditions, ranging 452-482ºC and 5.2-7.7kbar, which suggest Barrovian-type metamorphism, most likely related to a collisional setting. The metabasites correspond to evolved basaltic rocks (Mg#<0.55) with moderate TiO2 content (up to 2.08wt.%) and relatively low Cr (43-416ppm). The rocks are moderately enriched in Light Rare Earth Elements (LREE) relative to Heavy Rare Earth Elements (HREE) (average (La/Lu)n of 2.7) and the N-MORB normalized multi-element patterns show negative slopes, with prominent negative Nb anomalies ((Nb/La)NMORB=0.33–0.78). These variations are akin to island arc tholeiites generated in back-arc basins and to other metabasites described in the Eastern Pyrenees with a putative Ediacaran age, and they differ from the Ordovician tholeiitic metabasites from the Canigó massif, which derived from a contaminated E-MORB source. The positive ƐNd(T) values (0.82-3.05) of the studied metabasites preclude a notable contribution from an older continental crust. Detrital zircon U-Pb dating Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) of one chlorite-rich schist sample in contact with the metabasites from the Canigó massif yielded a main peak at ca. 632Ma and apparent maximum age of deposition at ca. 550Ma. We argue that the Cadomian metabasites from the Pyrenees formed during back-arc extension in the continental margin of Gondwana and were later affected by (probably early Variscan) medium-P metamorphism before the Low-Pressure High-Temperature (LP-HT) metamorphism classically described in the Pyrenees.

Despite the so-called exotic nature of the South Portuguese Zone relatively to the other major domains of the Iberian Massif of peri-Gondwanan affinity, Devonian detrital rocks of the oldest strata in the Iberian Pyrite Belt have a remarkable resemblance with the Ossa-Morena Zone’s Neoproterozoic-Cambrian rocks and the West Meguma’s Cambrian-Ordovician rocks, presenting the so-called “West African signature”. Using published U-Pb detrital zircon data, we discuss the similarities and dissimilarities between the Iberian Pyrite Belt, Ossa-Morena Zone and West Meguma Terrane through multidimensional scaling, comparing them with other zones of the Iberian Massif, Saxo-Thuringian Zone, Avalonia-Ganderia, and the North African cratonic regions. Our findings show that multidimensional scaling is not entirely effective in displaying the dissimilarities between the peri-Gondwanan terranes due to the background noise caused by the overwhelming number of Cadomian-Panafrican ages. However, it becomes a powerful tool if these ages are filtered. A dominant Meguma-type provenance (Cambro-Ordovician) for the Middle-Upper Devonian rocks of the Iberian Pyrite Belt is demonstrated, mainly attending to their similar Birimian-Eburnean pattern. The possibility of minor contributions from the lower Cambrian rocks of the Ossa-Morena Zone into the Iberian Pyrite Belt quartzites is unlikely, as the latter lack the 1.9Ga peak that characterises the Ossa-Morena Zone sediments. Additionally, the remarkable similarities between Ossa-Morena Zone’s and West Meguma’s detrital rocks strongly suggest a similar paleogeographic setting (but diachronic) for both terrains from the Ediacaran to Lower Ordovician times relative to the North African blocks.

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Thank you reviewers

One of the current limitations to the progress of the digital television program in Cuba is the purchasing capacity and liquidity that the country has to acquire the receiving equipment. The above statement, coupled with the need to implement the analog switch-off in the national territory, has led to seek autonomous solutions. Consequently, at the Central University "Marta Abreu" of Las Villas (UCLV), a prototype of a set-top box (STB) is proposed. This highly integrated device, for digital terrestrial television signals, includes a tuning and demodulation module (NIM, Network Interface Module), a general purpose single board computer (SBC, Single Board Computer) with an operating system based on free software components that allows technological independence and provides facilities for the implementation of new services with high added value. This solution is based on the design and development of a Printed Circuit Board (PCB) that serves as an interface between the SBC and the NIM, for its future manufacture and commercialization in the country. To validate the feasibility of the proposal, the structure of the data frames must be experimentally corroborated, to then design the software procedure dedicated to the real-time processing of the signal. It is also necessary to comply with the timing requirements of the control, configuration and monitoring signals present in the different working modes of the Digital Terrestrial Multimedia Broadcasting (DTMB) standard, which are included in GB 20600-2006.

In this research, the identification of the post-combustion sub-process of a lateritic ore reduction furnace was addressed, in the “Comandante Ernesto Che Guevara" Nickel and Cobalt Production Company, due to the fact that complex multivariable processes are generated in the furnaces of multiple hearths and its modeling contains a high rate of uncertainty. A multi-layer recurrent artificial neural model with NARX structure and time delay was proposed, which more accurately reflects the dynamic characteristics of the post-combustion thread than the mathematical models reported in the state of the art, thus proving the potential offered by this tool of artificial intelligence. To estimate and validate the model, process data from a 3 months operating time period was used, measured through the supervision, control and data acquisition system, in order to relate the temperature of hearths four and six versus the air flow to these hearths. Based on rigorous process testing and analysis, including random cross-validation methods and Akaike's information criterion, the model is able to predict the temperature of hearth four and six with a mean square fit (RMSE) of less than 5°C. Therefore, the operator may have an idea of ​​the behavior of the post-combustion thermal profile, and make decisions in order to reduce environmental pollution and contribute to the energy efficiency of the process.

The vertiginous technological development and increasing evolutionary rhythm of current networks make management vital. However, the existence of heterogeneous management derived from the heterogeneity of telecommunications networks causes inefficiencies and increased cost of network operation, among others. Some of the problems caused by heterogeneous management are: the need to know and have personnel to operate each of the proprietary management systems corresponding to technologies and equipment from different manufacturers, work with different management protocols and deal with the diversity and incompatibility of data management that lead to inconsistency and even possible duplication of management information. This article presents the design and implementation of an Integrated Management System for local area network (LAN) switches using the SNMP protocol. Features of the SNMP protocol, Remote Monitoring MIB (RMON), and LAN switch management are briefly reviewed. For the design of the system, requirements were taken into account that considered the current needs of integrated management in the operating companies of telecommunications services. The programming was done using the Python language and was divided into several modules: user access and administration; LAN switch inventory and management; statistics, events and alarms; and diagnostic functions. Its validation was carried out by implementing the system in a small test scenario in the network of a public operator of telecommunications services, obtaining satisfactory results.

This research presents an extension of the SPICE loudspeaker work done by Leach for a measured and simulated overhung-type moving-coil dynamic loudspeaker. In the present work, LTspice software was used, which implements SPICE. The complete equivalent electrical, mechanical, and acoustic models from the electroacoustic analogies were developed, which allowed verifying the original equivalent model. Sub-circuits were then developed, allowing direct measurement of the velocity and volume velocity emitted by the diaphragm in the complete equivalent mechanical circuit. In addition, three models of electrical inductance and three models of radiation acoustic impedance were implemented. Furthermore, the thermal linear model of the loudspeaker and the resistance model with temperature variation of the voice coil were implemented. The results of the models showed consistency in the measured and simulated responses of the loudspeaker used. The different electrical inductance and radiation acoustic impedance models showed their use and implementation advantages and disadvantages. The thermal linear model showed a reasonable estimation of the measured temperature in the loudspeaker, except for the cooling of the voice coil. Finally, the results of the implementation of the thermal model on the electrical resistance of the loudspeaker were as expected according to the literature, i.e., increasing the temperature increases the magnitude of the input electrical impedance, decreases the displacement and velocity of the diaphragm, and decreases the sound pressure level.