The Mid-infrared Instrument for JWST and Its In-flight Performance

The Mid-Infrared Instrument (MIRI) extends the reach of the James Webb Space Telescope (JWST) to 28.5 μm. It provides subarcsecond-resolution imaging, high sensitivity coronagraphy, and spectroscopy at resolutions of λ/Δλ ∼ 100-3500, with the high-resolution mode employing an integral field unit to provide spatial data cubes. The resulting broad suite of capabilities will enable huge advances in studies over this wavelength range. This overview describes the history of acquiring this capability for JWST. It discusses the basic attributes of the instrument optics, the detector arrays, and the cryocooler that keeps everything at approximately 7 K. It gives a short description of the data pipeline and of the instrument performance demonstrated during JWST commissioning. The bottom line is that the telescope and MIRI are both operating to the standards set by pre-launch predictions, and all of the MIRI capabilities are operating at, or even a bit better than, the level that had been expected. The paper is also designed to act as a roadmap to more detailed papers on different aspects of MIRI

Promotionalism, motivationalism and reasons to perform physically impossible actions

In this paper I grant the Humean premise that some reasons for action are grounded in the desires of the agents whose reasons they are. I then consider the question of the relation between the reasons and the desires that ground them. According to promotionalism, a desire that p grounds a reason to φ insofar as A’s φing helps promote p. According to motivationalism a desire that p grounds a reason to φ insofar as it explains why, in certain circumstances, A would be motivated to φ. I then give an argument favouring motivationalism, namely that promotionalism entails that agents have reasons to perform physically impossible actions, whereas motivationalism entails that there are no such reasons. Although this is a version of the ‘Too Many Reasons’ objection to promotionalism, I show that existing responses to that problem do not transfer to the case of reasons to perform physically impossible actions. In the penultimate section I consider and reject some objections to motivationalism made by promotionalists. The conclusion is that Humeans about reasons for action should prefer motivationalism

Interiorización de ideales estéticos, insatisfacción corporal y motivación por la musculatura en usuarios de gimnasio

Existen pocas investigaciones acerca de la imagen corporal masculina, en especial de la motivación por la musculatura. El objetivo fue comparar la interiorización del modelo estético, la insatisfacción corporal y la motivación por la musculatura en 81 varones usuarios de gimnasio y 98 sedentarios. Los participantes contestaron la Escala de Motivación por la Musculatura, el Cuestionario de Imagen Corporal y el Cuestionario de Influencias del Modelo Estético Corporal. Los resultados indicaron mayor puntuación en las medidas de los usuarios de gimnasios, en comparación con los varones sedentarios, excepto en las subescalas de influencia de los modelos musculosos e insatisfacción corporal. En los usuarios de gimnasio se observaron correlaciones de mayor magnitud, entre las escalas y subescalas, en comparación con los varones sedentarios. Este estudio aporta evidencias sobre algunos aspectos relacionados con las preocupaciones por la imagen corporal en los varones, especialmente en usuarios de gimnasios

Femtosecond optical parametric oscillators based on periodically poled lithium niobate

We describe two configurations of collinearly pumped femtosecond optical parametric oscillator based on periodically poled lithium niobate and tunable in the infrared from 975 nm to 4.98 mu m. Maximum output powers of 240 mW for the signal and 106 mW for the idler were recorded with 25 mW of average power measured at 4.88 mu m. An overall conversion efficiency of 35% and slope efficiencies for the signal of 46% at a wavelength of 1.04 mu m and 70% at 1.11 mu m were measured. Interferometric autocorrelations of the signal and idler pulses at various wavelengths within the tuning range have been obtained and imply nearly transform-limited pulse durations of about 140 fs for the signal and about 190 fs for the idler.</p