La estructura sísmica de la corteza de la Zona de Ossa Morena y su interpretación geológica

El experimento de sísmica de reflexión profunda IBERSEIS ha proporcionado una imagen de la corteza del Orógeno Varisco en el sudoeste de Iberia. Este artículo se centra en la descripción de la corteza de la Zona de Ossa Morena (OMZ), que está claramente dividida en una corteza superior, con reflectividad de buzamiento al NE, y una corteza inferior de pobre reflectividad. Las estructuras geológicas cartografiadas en superficie se correlacionan bien con la reflectividad de la corteza superior, y en la imagen sísmica se ven enraizar en la corteza media. Ésta está constituida por un cuerpo muy reflectivo, interpretado como una gran intrusión de rocas básicas. La imagen de las suturas que limitan la OMZ muestra el carácter fuertemente transpresivo de la colisión orogénica varisca registrada en el sudoeste de Iberia. La Moho actual es plana y, en consecuencia, no se observa la raíz del orógeno

Spectroscopic and Mechanistic Studies of Heterodimetallic Forms of Metallo-β-lactamase NDM-1

In an effort to characterize the roles of each metal ion in metallo-β-lactamase NDM-1, heterodimetallic analogues (CoCo-, ZnCo-, and CoCd-) of the enzyme were generated and characterized. UV–vis, 1H NMR, EPR, and EXAFS spectroscopies were used to confirm the fidelity of the metal substitutions, including the presence of a homogeneous, heterodimetallic cluster, with a single-atom bridge. This marks the first preparation of a metallo-β-lactamase selectively substituted with a paramagnetic metal ion, Co(II), either in the Zn1 (CoCd-NDM-1) or in the Zn2 site (ZnCo-NDM-1), as well as both (CoCo-NDM-1). We then used these metal-substituted forms of the enzyme to probe the reaction mechanism, using steady-state and stopped-flow kinetics, stopped-flow fluorescence, and rapid-freeze-quench EPR. Both metal sites show significant effects on the kinetic constants, and both paramagnetic variants (CoCd- and ZnCo-NDM-1) showed significant structural changes on reaction with substrate. These changes are discussed in terms of a minimal kinetic mechanism that incorporates all of the data

On the exploitation of differential aerodynamic lift and drag as a means to control satellite formation flight

For a satellite formation to maintain its intended design despite present perturbations (formation keeping), to change the formation design (reconfiguration) or to perform a rendezvous maneuver, control forces need to be generated. To do so, chemical and/or electric thrusters are currently the methods of choice. However, their utilization has detrimental effects on small satellites’ limited mass, volume and power budgets. Since the mid-80s, the potential of using differential drag as a means of propellant-less source of control for satellite formation flight is actively researched. This method consists of varying the aerodynamic drag experienced by different spacecraft, thus generating differential accelerations between them. Its main disadvantage, that its controllability is mainly limited to the in-plain relative motion, can be overcome using differential lift as a means to control the out-of-plane motion. Due to its promising benefits, a variety of studies from researchers around the world have enhanced the state-of-the-art over the past decades which results in a multitude of available literature. In this paper, an extensive literature review of the efforts which led to the current state-of-the-art of different lift and drag-based satellite formation control is presented. Based on the insights gained during the review process, key knowledge gaps that need to be addressed in the field of differential lift to enhance the current state-of-the-art are revealed and discussed. In closer detail, the interdependence between the feasibility domain/the maneuver time and increased differential lift forces achieved using advanced satellite surface materials promoting quasi-specular or specular reflection, as currently being developed in the course of the DISCOVERER project, is discussed

Concepts and Applications of Aerodynamic Attitude and Orbital Control for Spacecraft in Very Low Earth Orbit

Spacecraft operations below 450km, namely Very Low Earth Orbit (VLEO), can offer significant advantages over traditional low Earth orbits, for example enhanced ground resolution for Earth observation, improved communications latency and link budget, or improved signal-to-noise ratio. Recently, these lower orbits have begun to be exploited as a result of technology development, particularly component miniaturisation and cost-reduction, and concerns over the increasing debris population in commercially exploited orbits. However, the high cost of orbital launch and challenges associated with atmospheric drag, causing orbital decay and eventually re-entry are still a key barrier to their wider use for large commercial and civil spacecraft. Efforts to address the impact of aerodynamic drag are being sought through the development of novel drag-compensation propulsion systems and identification of materials which can reduce aerodynamic drag by specularly reflecting the incident gas. However, the presence of aerodynamic forces can also be utilised to augment or improve spacecraft operations at these very low altitudes by providing the capability to perform coarse pointing control and trim or internal momentum management for example. This paper presents concepts for the advantageous use of spacecraft aerodynamics developed as part of DISCOVERER, a Horizon 2020 funded project with the aim to revolutionise Earth observation satellite operations in VLEO. The combination of novel spacecraft geometries and use of aerodynamic control methods are explored, demonstrating the potential for a new generation of Earth observation satellites operating at lower altitudes

Discoverer - Making commercial satellite operations in very low earth orbit a reality

DISCOVERER is a €5.7M European Commission funded Horizon 2020 project developing technologies to enable commercially-viable sustained-operation of satellites in very low Earth orbits. Why operate closer to the Earth? For communications applications latency is significantly reduced and link budgets improved, and for remote sensing improved link budgets allow higher resolution or smaller instruments, all providing cost benefits. In addition, all applications benefit from increased launch mass to lower altitudes, whilst end-of-life removal is ensured due to the increased atmospheric drag. However, this drag must also be minimised and compensated for. One of the key technologies being developed by DISCOVERER are materials that encourage specular reflection of the residual atmosphere at these altitudes. Combined with appropriate geometric designs these can significantly reduce drag, provide usable lift for aerodynamic attitude and orbit control, and improve the collection efficiency of aerodynamic intakes for atmosphere breathing electric propulsion systems, all of which are being developed as part of DISCOVERER. The paper provides highlights from the developments to date, and the potential for a new class of aerodynamic commercial satellites operating at altitudes below the International Space Station

Inductive Plasma Thruster (IPT) design for an Atmosphere-Breathing Electric Propulsion System (ABEP)

Challenging space missions include those at very low altitudes, where the atmosphere is source of aerodynamic drag on the spacecraft, therefore an efficient propulsion system is required to extend the mission lifetime. One solution is Atmosphere-Breathing Electric Propulsion (ABEP). It collects atmospheric particles to use as propellant for an electric thruster. This would minimize the requirement of limited propellant availability. The system could be applied to any planet with atmosphere, enabling new mission at these altitude ranges for continuous orbiting. Challenging is also the presence of reactive chemical species, such as atomic oxygen in Earth orbit. Such components are erosion source of (not only) propulsion system components, i.e. acceleration grids, electrodes, and discharge channels of conventional EP systems (RIT and HET). IRS is developing within the DISCOVERER project an intake and a thruster for an ABEP system. This paper deals with the design and first operation of the inductive plasma thruster (IPT) developed at IRS. The paper describes its design aided by numerical tools such as HELIC and ADAMANT. Such a device is based on RF electrodeless discharge aided by externally applied static magnetic field. The IPT is composed by a movable injector, to variate the discharge channel length, and a movable electromagnet to variate position and intensity of the magnetic field. By changing these parameters along with a novel antenna design for electric propulsion, the aim is to achieve the highest efficiency for the ionization stage by enabling the formation of helicon-based discharge. Finally, the designed IPT is presented and the feature of the birdcage antenna highlighted

Earth Observation Technologies: Low-End-Market Disruptive Innovation

After decades of traditional space businesses, the space paradigm is changing. New approaches to more efficient missions in terms of costs, design, and manufacturing processes are fostered. For instance, placing big constellations of micro- and nano-satellites in Low Earth Orbit and Very Low Earth Orbit (LEO and VLEO) enables the space community to obtain a huge amount of data in near real-time with an unprecedented temporal resolution. Beyond technology innovations, other drivers promote innovation in the space sector like the increasing demand for Earth Observation (EO) data by the commercial sector. Perez et al. stated that the EO industry is the second market in terms of operative satellites (661 units), micro- and nano-satellites being the higher share of them (61%). Technological and market drivers encourage the emergence of new start-ups in the space environment like Skybox, OneWeb, Telesat, Planet, and OpenCosmos, among others, with novel business models that change the accessibility, affordability, ownership, and commercialization of space products and services. This chapter shows some results of the H2020 DISCOVERER (DISruptive teChnOlogies for VERy low Earth oRbit platforms) Project and focuses on understanding how micro- and nano-satellites have been disrupting the EO market in front of traditional platforms

Anales de Edafología y Agrobiología Tomo 34 Número 3-4

Estudio de la materia orgánica del ranker atlántico. I. Caracterización general, por P. Rodríguez Seoane, T. Carballas y F. Guitián Ojea.-- Movimiento y distribución de sales solubles en suelos calizos, por F. G. Fernández, M. Caro y A. Cerda.-- The availability of added and native phosphorus to barley grown in sorne Egyptian soils .containing different levels of calciurn carbonate, by M. H. Nafady.-- The measurernent of soil pH in calciurn chloride solutions, by M. H. Nafady.- Nuevas aportaciones al conocimiento del género Mnema (nernatoda) y su distribución en los suelos españoles, por María Arias.-- Estudios bioquímicos y fisiológicos en aceituna. III. Variaciones en el crecimiento de hojas y frutos, por J. P. Donaire, A. J. Sánchez-Raya, J. López Corge y L. Recalde.-- Importancia de la rnicorrización espontánea en ensayos de nutrición vegetal en suelos deficientes en fósforo, por R. Azcón y J. M. Barea.-- Andosoles canarios. J. Características generales de estos suelos, por E. Fernández Caldas y M. L. Tejedor Salguero.-- Andosoles canarios. II. Intergrados andosol-tierra parda oligotrófica. Características morfológicas y quírnkas, por M. L. Tejedor Salguero y E. Fernández Caldas.-- Andosoles canarios. lll. Jntergrados andosol-tierra parda otigotrófica. Catacterísticas físicas, por E. Fernández Caldas y M. L. Tejedor Salguero.-- Andosoles canario;. IV. In ter grados andosol-tierra parda ohgotrófica. Características mineralógicas. Interpretación y clasificación, por C. Rodríguez Pascual, P. Quantin, M. L. Tejedor Salguero y E. Fernández Caldas.-- Estudios recapitualtivos.-- La vid una revisión de las condiciones del cultivo, por C. González O. y M. Lachica.—Notas científicas.-- Nota sobre la determinación del carbono orgánico en suelos, por J. F. Gallardo.—Notas.-- Ampliación de la Comisión Permanente de la Junta de Gobierno del Patronato Alonso de Herrera.-- Nombramiento de Secretario del Centro de Edafología y Biología Aplicada de Tenerife.-- Nombramientos en el Instituto de Alimentación v Productividad Animal.-- Cambio de representantes del Patronato Alonso de Herrera en la Comisión Asesora de la Investigación Científica y Técnica.-- Convenio con ASPA.-- Dimisión del Director del Centro de Edafología y Biología Aplicada del Segura de Murcia.-- Nombramientos de representantes en los C. R. l. D. A. S.-- Designación de Jurados para Premios del C. S. l. C.-- Informes del Secretario Adjunto del C. S. I. C. sobre reuniones en Europa.-- Convenio entre la Estación Experimental del Zaidín y la Universidad de Nápoles.-- Donación de terrenos a la Diputación de Badajoz.-- Seminario Oleícola Internacional.-- Congreso de la Unión Fitopatológica Mediterránea.-- Situaciones de personal.-- Reunión de la Comisión de Protección Vegetal.-- Día Forestal Mundial.-- Congresos y reuniones internacionales y viajes.-- Premio Agrícola Aedos.-- BibliografíaPeer reviewed2019-08.- CopyBook.- Libnova.- Biblioteca ICA