Harmonic G-structures

For closed and connected subgroups G of SO(n), we study the energy functional on the space of G-structures of a (compact) Riemannian manifold M, where G-structures are considered as sections of the quotient bundle O(M)/G. Then, we deduce the corresponding first and second variation formulae and the characterising conditions for critical points by means of tools closely related with the study of G-structures. In this direction, we show the role in the energy functional played by the intrinsic torsion of the G-structure. Moreover, we analyse the particular case G=U(n) for even-dimensional manifolds. This leads to the study of harmonic almost Hermitian manifolds and harmonic maps from M into O(M)/U(n).Comment: 27 pages, minor correction

Toxicity of several d-endotoxins of Bacillus thuringiensis against Helicoverpa armigera (Lepidoptera: Noctuidae) from Spain

Toxicity and larval growth inhibition of eleven insecticidal proteins of Bacillus thuringiensis were evaluated against neonate larvae of Helicoverpa armigera, a major pest of important crops in Spain and other countries, by a whole-diet contamination method. The most active toxins were Cry1Ac4 and Cry2Aa1, with LC50 values of 3.5 and 6.3 μg/ml, respectively. At the concentrations tested, Cry1Ac4, Cry2Aa1, Cry9Ca, Cry1Fa1, Cry1Ab3, Cry2Ab2, Cry1Da, and Cry1Ja1, produced a significant growth inhibition, whereas Cry1Aa3, Cry1Ca2, and Cry1Ea had no effect

Controladores difusos adaptativos como módulos de propiedad intelectual para FPGAs

La continua demanda por parte del mercado microelectrónico de aplicaciones novedosas, con elevados niveles de complejidad y tiempos de desarrollo cortos ha motivado el impulso de las técnicas de diseño basadas en el concepto de “reusabilidad” y el desarrollo de elementos de sistemas como módulos de propiedad intelectual o módulos IP. En esta comunicación se describe la implementación de controladores difusos como módulos IP para FPGAs. Los controladores operan como periféricos conectables al bus OPB para los procesadores disponibles en las FPGAs de Xilinx. El empleo de las memorias internas de las FPGAs para almacenar las bases de conocimiento permite definir o ajustar la funcionalidad en tiempo de operación.Ministerio de Educaión y Ciencia TEC2005-04359/MI

High-fidelity, broadband stimulated-Brillouin-scattering-based slow light using fast noise modulation

We demonstrate a 5-GHz-broadband tunable slow-light device based on stimulated Brillouin scattering in a standard highly-nonlinear optical fiber pumped by a noise-current-modulated laser beam. The noise modulation waveform uses an optimized pseudo-random distribution of the laser drive voltage to obtain an optimal flat-topped gain profile, which minimizes the pulse distortion and maximizes pulse delay for a given pump power. Eye-diagram and signal-to-noise ratio (SNR) analysis show that this new broadband slow-light technique significantly increases the fidelity of a delayed data sequence, while maintaining the delay performance. A fractional delay of 0.81 with a SNR of 5.2 is achieved at the pump power of 350 mW using a 2-km-long highly nonlinear fiber with the fast noise-modulation method, demonstrating a 50% increase in eye-opening and a 36% increase in SNR compared to a previous slow-modulation method

Influence of ships emissions in the ultrafine particles pollution in an urban coastal air

Comunicación presentada en: V Reunión Española de Ciencia y Tecnología de Aerosoles – RECTA 2011 celebrada del 27 al 29 de junio de 2011 en CIEMAT, Madrid.Experimental data (2008-2009) of particle number (N≥2.5 nm diameter) and black carbon (BC) concen-trations and of gaseous pollutants recorded in the city of Santa Cruz de Tenerife was analyzed in order to asses the impact of ship emissions on the ultrafine particle (UFP) concentrations in coastal urban areas. The observed relationship between N and the other air pollutants, allowed segregating the contribu-tion of vehicle exhaust and of ship emissions to the UFP con-centrations in the urban ambient air. The influence of fresh vehicle exhaus

Effects of Jatropha lubricant thermo-oxidation on the tribological behaviour of engine cylinder liners as measured by a reciprocating friction test

Bio-lubricants have emerged as a potential and viable way to replace, totally or partially, mineral oils due to their effectiveness in the boundary lubrication regime for different applications, including, automotive engine operation. However, the effect of thermo-oxidation caused by the long-term use of the bio-lubricants on their tribological properties has been scarcely analysed. In this work, the effect of thermo-oxidation of Jatropha oil (JO), an engine mineral oil (EMO) and a blend made up of 80%vol. EMO and 20%vol. JO (B20) on the tribological behaviour of a simulated piston ring/engine cylinder liner interface was studied in reciprocating friction tests at 26 and 100 °C. The oils were thermally oxidized and characterized in terms of carbonyl compounds, depletion of ZDDP additives, changes in kinematic viscosity and viscosity index. Friction coefficients, wear rates and scar morphologies were assessed. Thermo-oxidation resulted in significant viscosity increases in JO compared to EMO and B20. Also, it generated increased friction coefficients for JO and B20. However, they were lower than those for fresh and aged EMO. EMO increased the wear rate after thermo-oxidation in contrast to JO. Smearing was generated using most oil samples while severe scuffing was only produced by using fresh JO at 100 °C