Nonlinear analysis of a simple model of temperature evolution in a satellite

We analyse a simple model of the heat transfer to and from a small satellite orbiting round a solar system planet. Our approach considers the satellite isothermal, with external heat input from the environment and from internal energy dissipation, and output to the environment as black-body radiation. The resulting nonlinear ordinary differential equation for the satellite's temperature is analysed by qualitative, perturbation and numerical methods, which show that the temperature approaches a periodic pattern (attracting limit cycle). This approach can occur in two ways, according to the values of the parameters: (i) a slow decay towards the limit cycle over a time longer than the period, or (ii) a fast decay towards the limit cycle over a time shorter than the period. In the first case, an exactly soluble average equation is valid. We discuss the consequences of our model for the thermal stability of satellites.Comment: 13 pages, 4 figures (5 EPS files

Magnetic transition in nanocrystalline soft magnetic alloys analyzed via ac inductive techniques

The magnetic transition in a FeSiBCuNb nanocrystalline alloy, associated with the decoupling of ferromagnetic crystallites around the Curie point of the residual amorphous matrix, is analyzed in this work through the temperature dependence of the ac axial magnetic permeability and impedance of the samples. The temperature dependence of both complex magnitudes presents a maximum in the irreversible contribution at a certain transition temperature. While for low values of the exciting ac magnetic field the transition temperature lies below the Curie temperature of the amorphous phase, a shift above this Curie point is observed increasing the amplitude of the applied ac magnetic field. The detected field dependence is interpreted taking into account the ac nature of the inductive characterization techniques and the actual temperature dependence of the coercivity of the samples

Disseny d'activitats d'auto-aprenentatge motivacionals per a l'increment del rendiment acadèmic i la convergència amb l'espai europeu d'educació superior

Aquest projecte sorgeix arrel de la necessitat d'incrementar el rendiment acadèmic dels estudiants i d'implementar les noves directrius de l'Espai Europeu d'Educació Superior (EEES) en una assignatura troncal de 1r. cicle de la Llicenciatura de Psicologia, Psicologia de la Personalitat. El projecte s'ha dividit en dues grans fases: la primera fase del projecte s'ha dut a terme durant el curs 2005-06 i presenta una proposta de reestructuració tant del mètode i materials docents com del procés d'ensenyament-aprenentatge, en funció de les directrius de l'European Credit Transfer System (ECTS). La segona fase està prevista per al curs 2006-07 i consistirà en aplicar i comprovar l'efectivitat dels nous recursos docents proposats. Tot el procés de disseny d'innovació docent està orientat a incrementar tant la motivació com el rendiment acadèmic dels estudiants i ha estat consensuat entre els diferents professors de l'assignatura, en base a la Declaració de Bolonya (1999) i al projecte Tuning (2000) de formació per competències. El resultat final de la suma dels diferents materials dissenyats ha estat el disseny del PORTAFOLIO de l'estudiant i la creació d'un BANC DIGITAL D'ÍTEMS d'autoavaluació disponible per internet a través del programa d'e.learning MOODLE, que s'integraran a partir de la segona fase del projecte al curs 2006-07. Tanmateix, les noves eines docents han implicat l'adaptació i diversificació de l'avaluació dels aprenentatges amb estratègies alternatives al tradicional examen final per tal de poder valorar adequadament les competències relacionades, no només amb el saber, sinó també amb el saber fer i el saber estar.Les conclusions derivades d'aquest projecte accentuen la necessitat d'obtenir recursos extra, tant econòmics com de personal, per poder aplicar les noves directrius dels ECTS, alhora que demanen al professorat universitari un esforç inicial d'adaptació a les reestructuracions docents de l'EEES i als canvis socials i laborals del s. XXI

Linear approach to the orbiting spacecraft thermal problem

We develop a linear method for solving the nonlinear differential equations of a lumped-parameter thermal model of a spacecraft moving in a closed orbit. Our method, based on perturbation theory, is compared with heuristic linearizations of the same equations. The essential feature of the linear approach is that it provides a decomposition in thermal modes, like the decomposition of mechanical vibrations in normal modes. The stationary periodic solution of the linear equations can be alternately expressed as an explicit integral or as a Fourier series. We apply our method to a minimal thermal model of a satellite with ten isothermal parts (nodes) and we compare the method with direct numerical integration of the nonlinear equations. We briefly study the computational complexity of our method for general thermal models of orbiting spacecraft and conclude that it is certainly useful for reduced models and conceptual design but it can also be more efficient than the direct integration of the equations for large models. The results of the Fourier series computations for the ten-node satellite model show that the periodic solution at the second perturbative order is sufficiently accurate.Comment: 20 pages, 11 figures, accepted in Journal of Thermophysics and Heat Transfe

Nonlinear analysis of spacecraft thermal models

We study the differential equations of lumped-parameter models of spacecraft thermal control. Firstly, we consider a satellite model consisting of two isothermal parts (nodes): an outer part that absorbs heat from the environment as radiation of various types and radiates heat as a black-body, and an inner part that just dissipates heat at a constant rate. The resulting system of two nonlinear ordinary differential equations for the satellite's temperatures is analyzed with various methods, which prove that the temperatures approach a steady state if the heat input is constant, whereas they approach a limit cycle if it varies periodically. Secondly, we generalize those methods to study a many-node thermal model of a spacecraft: this model also has a stable steady state under constant heat inputs that becomes a limit cycle if the inputs vary periodically. Finally, we propose new numerical analyses of spacecraft thermal models based on our results, to complement the analyses normally carried out with commercial software packages.Comment: 29 pages, 4 figure

Formation of a magnetite/hematite epitaxial bilayer generated with low energy ion bombardment

We have used a low-energy ion bombardment to fabricate an epitaxial single-crystalline magnetite/hematite bilayer grown on Au(111). This non-conventional fabrication method involves the transformation of the upper layers of a single-crystalline hematite thin film to single-crystalline magnetite, a process driven by the preferential sputtering of oxygen atoms and favoured by the good structural matching of both phases. We show the reversibility of the transformation between hematite and magnetite, always keeping the epitaxial and single- crystalline character of the films. The magnetic characterization of the bilayer grown using this method shows that the magnetic response is mainly determined by the magnetite thin film, exhibiting a high coercivity. Published by AIP Publishing

The Sunrise Mission

The first science flight of the balloon-borne \Sunrise telescope took place in June 2009 from ESRANGE (near Kiruna/Sweden) to Somerset Island in northern Canada. We describe the scientific aims and mission concept of the project and give an overview and a description of the various hardware components: the 1-m main telescope with its postfocus science instruments (the UV filter imager SuFI and the imaging vector magnetograph IMaX) and support instruments (image stabilizing and light distribution system ISLiD and correlating wavefront sensor CWS), the optomechanical support structure and the instrument mounting concept, the gondola structure and the power, pointing, and telemetry systems, and the general electronics architecture. We also explain the optimization of the structural and thermal design of the complete payload. The preparations for the science flight are described, including AIV and ground calibration of the instruments. The course of events during the science flight is outlined, up to the recovery activities. Finally, the in-flight performance of the instrumentation is briefly summarized.Comment: 35 pages, 17 figure

Upward convergence in working conditions

Social convergence has gained an equal footing alongside economic convergence as an EU goal in the wake of the economic crisis. This report presents the results of a study into convergence in working conditions, a major component of social policymaking. It examines whether working conditions have improved over the past two decades in the EU as a whole and whether dissimilarities between Member States in this area have narrowed

SEOM clinical guideline for treatment of kidney cancer (2017)

The goal of this article is to provide recommendations about the management of kidney cancer. Based on pathologic and molecular features, several kidney cancer variants were described. Nephron-sparing techniques are the gold standard of localized disease. After a randomized trial, sunitinib could be considered in adjuvant treatment in high-risk patients. Patients with advanced disease constitute a heterogeneous population. Prognostic classification should be considered. Both sunitinib and pazopanib are the standard options for first-line systemic therapy in advanced renal cell carcinoma. Based on the results of two randomized trials, both nivolumab and cabozantinib should be considered the standard for second and further lines of therapy. Response evaluation for present therapies is a challenge

Guanosine inhibits hepatitis C virus replication and increases indel frequencies, associated with altered intracellular nucleotide pools

In the course of experiments aimed at deciphering the inhibition mechanism of mycophenolic acid and ribavirin in hepatitis C virus (HCV) infection, we observed an inhibitory effect of the nucleoside guanosine (Gua). Here, we report that Gua, and not the other standard nucleosides, inhibits HCV replication in human hepatoma cells. Gua did not directly inhibit the in vitro polymerase activity of NS5B, but it modified the intracellular levels of nucleoside di- and tri-phosphates (NDPs and NTPs), leading to deficient HCV RNA replication and reduction of infectious progeny virus production. Changes in the concentrations of NTPs or NDPs modified NS5B RNA polymerase activity in vitro, in particular de novo RNA synthesis and template switching. Furthermore, the Gua-mediated changes were associated with a significant increase in the number of indels in viral RNA, which may account for the reduction of the specific infectivity of the viral progeny, suggesting the presence of defective genomes. Thus, a proper NTP:NDP balance appears to be critical to ensure HCV polymerase fidelity and minimal production of defective genomes.CP is supported by the Miguel Servet program (grants CP14/00121 and CP19/00001) of the Instituto de Salud Carlos III cofinanced by FEDER. CP has received funding from Ministerio de Ciencia, Innovacio´n y Universidades (grant BFU2017-91384-EXP), from Instituto de Salud Carlos III (grants PI18/00210 and PI21/00139), from Fundación La Marato´ (grant 525/C/2021), and from CSIC (grant CSIC-COV19-014). ED has received funding from CIBERehd (Centro de Investigación en Red de Enfermedades Hepáticas y Digestivas, Instituto de Salud Carlos III), from Ministerio de Economía y Competitividad (grants SAF2014-52400-R, SAF2017-87846-R, and PID2020-113888RB-I00), and from Comunidad de Madrid/FEDER (grants S2013/ABI-2906 PLATESA, and S2018/BAA-4370 PLATESA2). AM has received funding from Ministerio de Economía y Competitividad (grants SAF2016-80451-P, PID2019-106068GB-I00, EQC2018-004420-P, and EQC2018-004631-P), and Plan Propio of Universidad de Castilla-La Mancha. A.G-P and L.DM have received funding from Consejería de Transformación Económica, Industria, Conocimiento y Universidades, Junta de Andalucía, cofinanced by FEDER and FSE (grants BIO-264, and P10-CVI-6561) and Plan Propio of Universidad de Málaga.Peer reviewe