\u3ci\u3eThe Magic Mirror\u3c/i\u3e

Mary Alice was a pretty little girl. She knew that, too. She knew that because her parents told her so everyday

Una introducción a la metalogenia de Cuba bajo la perspectiva de la tectónica de placas

Six main metallogenic epochs can be distinguished in the geological constitution of the island of Cuba. A first stage from Jurassic to Early Cretaceous times, included a rift episode involving materials from the Bahama and Yucatán continental paleomargin. Base metals sedex deposits (Pb-Zn-Cu) and Mn, associated with gold and silve r, are to be found in the detrital and carbonated series associated to this process. An arc (or arcs) of volcanic islands developed during the Aptian (Neocomian?)-Campanian stage. Three metallotects are to be found associated to the formation and development of this arc: a) the uppermost part of the suprasubduction zone mantle section, where bodies of ophiolitic chromitites occur, b) the back-arc volcanosedimentary submarine series, with volcanogenic deposits of massive sulfides (Kuroko and Cyprus type), Mn oxide exhalative mineralizations and zeolite deposits, and, c) the intrusive series and rocks in the axial zone of the arc, with iron and polymetallic skarn deposits, porphyry copper deposits and Au-Ag epithermal deposits. The first collisional process, between the Yucatán paleomargin and the Cretaceous volcanic arc, as well as the beginning of the collision between the Caribbean plate and the North-American plate, took place during the late Campanian-Danian stage. Orogenic gold mineralizations and, probably, tumgsten deposits date from this period. A volcanic arc, trending E-W, developed in eastern Cuba from Late Danian to Middle Eocene times. Major volcanogenic Mn deposits in Cuba are located within the Paleogene volcanic island arc in eastern Cuba. This volcanic activity also originated some major volcanogenic sulfide deposits, skarn and porphyry copper deposits, as well as zeolite deposits. Known metallotects in this geodynamic environment include: a) the volcanic and volcanosedimentary series located along the axial arc-back arc boundary, with volcanogenic sulfide deposits (Kuroko type) and Mn oxide volcanogenic deposits, and b) granitic intrusives related to the axial arc volcanic, with skarn and porphyry copper deposits. In western and central Cuba, in turn, piggy-back sedimentary basins associated to the collisional process between the Caribbean plate and the North-American plate developed during Danian-Middle Eocene times. Major orogenic gold mineralizations are associated with this process. A series of post-volcanic basins developed during the Middle Eocene-Late Eocene stages in eastern Cuba, some of which are associated to Mn resedimented mineralizations. Meanwhile, the development of sedimentary basins with olistostromes, associated to the collisional process, continued in central and western Cuba. Cuba finally joined the North-American plate at the end of this episode. Orogenic gold mineralizations may also occur in association with these processes. A shelf environment was established in Cuba from Late Eocene to Quatern a ry times. At that point, extensive Fe-Ni-Co laterite crusts (one of the largest examples of this type of deposit worldwide), bauxite crusts, gossan deposits (Fe, Au, Ag), resedimented Mn deposits, and marine and fluvial placer deposits, rich in noble metals, originated

Distinct Populations of HCN Pacemaker Channels Produce Voltage-dependent and Voltage-independent Currents

Hyperpolarization-activated HCN pacemaker channels are critical for the generation of spontaneous activity and the regulation of excitability in the heart and in many types of neurons. These channels produce both a voltage-dependent current (Ih) and a voltage-independent current (Iinst or VIC). In this study, we explored the molecular basis of the voltage-independent current. We found that for the spHCN isoform, VIC averaged ∼4% of the maximum HCN conductance that could be activated by hyperpolarization. Cyclic AMP increased the voltage-independent current in spHCN to ∼8% of maximum. In HCN2, VIC was ∼2% of the maximal current, and was little affected by cAMP. VIC in both spHCN and HCN2 was blocked rapidly both by ZD7288 (an HCN channel blocker that is thought to bind in the conduction pore) and by application of Cd2+ to channels containing an introduced cysteine in the pore (spHCN-464C or HCN2-436C). These results suggest that VIC flows through the main conduction pathway, down the central axis of the protein. We suspected that VIC simply represented a nonzero limiting open probability for HCN channels at positive voltages. Surprisingly, we found instead that the spHCN channels carrying VIC were not in rapid equilibrium with the channels carrying the voltage-dependent current, because they could be blocked independently; a single application of blocker at a depolarized potential essentially eliminated VIC with little change in Ih. Thus, VIC appears to be produced by a distinct population of HCN channels. This voltage-independent current could contribute significantly to the role of HCN channels in neurons and myocytes; VIC flowing through the channels at physiological potentials would tend to promote excitability by accelerating both depolarization and repolarization

Subduction Zones of the Caribbean : the sedimentary, magmatic, metamorphic and ore-deposit records UNESCO/iugs igcp Project 546 Subduction Zones of the Caribbean

The International Union of Geosciences (IUGS) and UNESCO IGCP project 546 Subduction Zones of the Caribbean (http://www.ugr.es/~agcasco/igcp546/) was launched in 2007 and scheduled to be completed by the end of the current year 2011. It was set up with the aim of gathering researchers interested in the geological evolution of the Caribbean realm. The development of this region is largely controlled by a number of subduction zones that formed along its margins from the break-up of Pangea during the Jurassic until Present. The current setting is characterized by a very complex plate-tectonic configuration dominated by subduction zones, large-scale strike-slip faults, volcanic arcs and collision belts (Figure 1). The project was built upon previous developments of IGCP project 433 Caribbean Plate Tectonics (2000-2005), of which the Special Volume 4 (Issue 1-2) of Geologica Acta Caribbean Plate Tectonics. Stratigraphic, Magmatic, Metamorphic and Tectonic Events (Iturralde Vinent and Lidiak, 2006) deserves mentioning

New data on the ophiolitic VMS deposits of Moeche (Cabo Ortegal Complex, NW Spain)

As a result of the variscan collision, several allochtonous complexes were emplaced on the Iberian margin in Devonian times, among them the Cabo Ortegal Complex comprising the Moeche ophiolitic sequence. Copper has been won from several mines (Piquitos I & II, Barqueira, Maruxa) from disseminated ores and thin massive sulphide layers in the Moeche Unit, a strongly deformed meta-volcanic sequence comprising mainly quartz-chlorite schists and mylonites, which defines the top of the ophiolite. The ores were metamorphosed and strongly deformed under brittle conditions (for pyrite), but their textures are often apparently post-deformational, due to very common solution-transfer processes; they are composed mostly of pyrite and chalcopyrite, with minor sphalerite, pyrrhotite, etc., and with traces of native gold and PGE. The geology, mineralogy, and geochemistry of the orebodies relate closely to VMS of the Cu-Zn (Cyprus) type. Fluid inclusion studies allowed an estimation of metamorphic conditions at pressures of 2/2’5 kb and T 325/350ºC. New determinations using the chlorite geothermometer yield temperatures around 320 ºC, corresponding to pressures near 2 kb according to the isochores deduced from the fluid inclusion study, although in the Barqueira mine higher temperatures, up to 350 ºC, are found, corresponding to presssures up to 2’5 kb. Pb isotopic compositions of pyrite point to a double source of Pb, i.e. a main mantle and a subordinate crustal source. The values for 87SR/86Sr in pyrite support this interpretation, but some results suggest later mobilization in an open system, corresponding to solution-transfer. Age determinations of pyrite deduced from the Pb isotope uranogenic graph, ≈ 480 Ma, do not fit with the metamorphic ages published for the Moeche Unit, and might point to the age of Pb extraction from the mantle

El Principio de orientación perceptivo-auditivo-musical en la actividad rítmica deportiva

The subject raises essential elements of the Principle of perceptual-auditory-musical orientation as precepts based on a methodological orientation towards decision-making in perceptual-auditory-musical processes, manifested in the teaching position of the teacher, for the determination of the aids that are require in the interpretation of the information contained in the musical work. For the development of this research, investigation methods and techniques from the different levels were used. The solution presented, contains resources necessary for proper musical appreciation, manifested in the expressive and sound media from the rhythmic sporting activity.La temática aborda elementos esenciales del Principio de orientación perceptivo-auditivo-musical como preceptos basados en una orientación metodológica hacia la toma de decisiones en los procesos perceptivos-auditivos-musicales, manifestada en la postura didáctica del docente, para la determinación de las ayudas que se requieren en la interpretación de la información contenida en la obra musical. Para el desarrollo de esta investigación se emplearon métodos y técnicas de investigación de los diferentes niveles. La solución que se presenta, contiene recursos necesarios para una correcta apreciación musical, manifestados en los medios expresivos y sonoros desde la actividad rítmica deportiva