30 research outputs found
Thin electron-scale layers at the magnetopause
We use data from the four Cluster satellites to examine the microphysics of a thin electron-scale layer discovered on the magnetospheric side of the magnetopause. Here the ion and electron motions are decoupled in a layer about 20 km (a few electron scales) wide, including currents and strong electric fields. In this layer the electrons are E x B drifting with the ions as a background, and the region can be described by Hall MHD physics. A unique identification of the source of the thin layer is not possible, but our observations are consistent with recent simulations showing thin layers associated with the separatrix extending far away from a reconnection diffusion region
Energy input from the exterior cusp into the ionosphere: Correlated ground-based and satellite observations
The energy transport from the exterior cusp into the ionosphere is investigated using coordinated ground-based (EISCAT and MIRACLE) and satellite ( Cluster) observations. EISCAT and MIRACLE data are used to estimate the plasma heating in the F-region and the Joule heating in the E-region. Cluster measurements are used to derive the electromagnetic and particle energy fluxes at the high altitudes. These fluxes are then compared with the energy deposition into the ionospheric cusp during a 30 minutes long time interval in which Cluster and EISCAT are nearly conjugated. It is shown that the particles seen at about 9 Re in the exterior cusp carry an earthward energy flux that corresponds to the observed heating of the F-region. The estimated earthward Poynting flux is more than enough to account for the Joule heating in the E-region
Cluster observations of ULF waves with pulsating electron beams above the high latitude dusk-side auroral region
We report observations by the four Cluster satellites of particle acceleration associated with ULF (Alfven) waves at an altitude of 6R(E) above the dusk-side auroral region. All satellites observed upward accelerated ions and upgoing electron beams, which coincided with the upward field-aligned current around the plasmasheet boundary region. Here we study in detail one region of Alfvenic ULF waves observed together with upward electron beams, both having a quasi-periodicity of about 2 minutes. The ULF waves have a downward Poynting flux. Comparing data from different spacecraft, the observed electron beams are likely caused by the ULF waves in localized (0.5degrees latitude extension) flux tubes in the plasmasheet boundary region. The high-energy keV plasmasheet dispersive ion signatures showed similar periodicity, which suggests that the generation region of the ULF Alfven waves is near the magnetospheric flank, and in turn induce time-varying particle energization
Biology and biotechnology of Trichoderma
Fungi of the genus Trichoderma are soilborne, green-spored ascomycetes that can be found all over the world. They have been studied with respect to various characteristics and applications and are known as successful colonizers of their habitats, efficiently fighting their competitors. Once established, they launch their potent degradative machinery for decomposition of the often heterogeneous substrate at hand. Therefore, distribution and phylogeny, defense mechanisms, beneficial as well as deleterious interaction with hosts, enzyme production and secretion, sexual development, and response to environmental conditions such as nutrients and light have been studied in great detail with many species of this genus, thus rendering Trichoderma one of the best studied fungi with the genome of three species currently available. Efficient biocontrol strains of the genus are being developed as promising biological fungicides, and their weaponry for this function also includes secondary metabolites with potential applications as novel antibiotics. The cellulases produced by Trichoderma reesei, the biotechnological workhorse of the genus, are important industrial products, especially with respect to production of second generation biofuels from cellulosic waste. Genetic engineering not only led to significant improvements in industrial processes but also to intriguing insights into the biology of these fungi and is now complemented by the availability of a sexual cycle in T. reesei/Hypocrea jecorina, which significantly facilitates both industrial and basic research. This review aims to give a broad overview on the qualities and versatility of the best studied Trichoderma species and to highlight intriguing findings as well as promising applications
Método hÃbrido para categorización de texto basado en aprendizaje y reglas
En este artÃculo se presenta un nuevo método hÃbrido de categorización automática de texto, que combina un algoritmo de aprendizaje computacional, que permite construir un modelo base de clasificación sin mucho esfuerzo a partir de un corpus etiquetado, con un sistema basado en reglas en cascada que se emplea para filtrar y reordenar los resultados de dicho modelo base. El modelo puede afinarse añadiendo reglas especÃficas para aquellas categorÃas difÃciles que no se han entrenado de forma satisfactoria. Se describe una implementación realizada mediante el algoritmo kNN y un lenguaje básico de reglas basado en listas de términos que aparecen en el texto a clasificar. El sistema se ha evaluado en diferentes escenarios incluyendo el corpus de noticias Reuters-21578 para comparación con otros enfoques, y los modelos IPTC y EUROVOC. Los resultados demuestran que el sistema obtiene una precisión y cobertura comparables con las de los mejores métodos del estado del arte
Reduced-dynamic and kinematic baseline determination for the Swarm mission
The Swarm mission of the European Space
Agency was launched in November 2013 with the objective
of performing measurements of the earth’s magnetic
field with unprecedented accuracy. At the beginning of data
collection, two satellites started to fly in orbits with a
separation in ascending nodes of 1�–1.5� at an altitude of
about 480 km, and a third satellite has been placed in a
higher orbit with an altitude of 530 km. The three spacecraft
are equipped with dual-frequency eight-channel GPS
receivers for the generation of precise orbits. Although
such orbits support the fulfillment of the primary objectives
of the mission, precise space baselines may be helpful for
studying the earth’s gravity field, a spin-off application of
the Swarm mission. Hitherto, a particular challenge for the
computation of precise baselines from Swarm has been the
presence of half-cycle ambiguities in GPS carrier phase
observations, which complicate the implementation of
integer ambiguity resolution methods. The present study
shows the feasibility of generating carrier phase observations
with full-cycle ambiguities, which in turn has been
used to improve the performance of reduced-dynamic and
kinematic precise baseline determination schemes. The
implemented strategies have been tested in a period of
90 days in 2016. The obtained reduced-dynamic and
kinematic baseline products were evaluated by inter-product
and inter-agency comparisons using two independent
software tools