Space telescope phase B definition study. Volume 2A: Science instruments, f24 field camera

The analysis and design of the F/24 field camera for the space telescope are discussed. The camera was designed for application to the radial bay of the optical telescope assembly and has an on axis field of view of 3 arc-minutes by 3 arc-minutes

CORRELATION BETWEEN ELECTROMYOGRAPHIC ACTIVITY AND STRENGTH OF THE FLEXOR MUSCLES OF THE WRIST

INTRODUCTION: In analysing the electromyographic (EMG) signal, researchers are often led to interpret variations of the signal as variation in strength of muscle contraction. However, the relationship between the force exerted and the electrical activity of a muscle are not well established. This is due to the considerable variation of data acquisition and processing techniques, the detection site of the muscles analysed, as well as the alterations in their length and the type of contraction. The object of this paper was to evaluate the correlation between electrical activity and muscular strength. METHODS AND PROCEDURES: The flexor muscles of the wrist of the non dominant member of 21 female volunteers (mean age = 21 years, sd = ± 1.5) with no history of skeletal muscle dysfuntion, were analysed. The EMG signal was captured by active surface electrode (DELSYS), over the belly of the muscle in the longitudinal sense of the fibres, having a gain of 10 Hz. The electrode was coupled to a 16 channel 12/36 electromyograph (AqDados - LYNX TECNOLOGIA ELETRÔNICA LTDA), which permitted a gain of 50 Hz. The system bandwidth was 10 to 500 Hz, with an overall gain of 1,000. The data acquisition rate was 1,000 Hz. In order to eliminate possible interferences, a ground electrode was coupled to the distal segment of the forearm. Muscular strength was measured by means of a load cell (model MM/50 kg, KRATOS), placed perpendicularly in the center of the palm surface of the hand. The electrode and the load cell were connected to a 16 channel signal acquisition system (AQDADOS 4.0, LYNIX). The temperature of the room was kept at 23ºC, ± 1. The EMG registers and the strength were collected simultaneously. Result were obtained from the average of three repetitions, shown in RMS and Kgf respectively. The data was collected with the hand fixed to a device which limited the wrist to 45º of flexion and 45º of extension, providing an isometric contraction. RESULTS AND DISCUSSION: The results demonstrated a positive correlation between electromyographic activity and strength of contraction (r = 0.76) in the 45º flexion position, whereas, for the 45º extension position, the correlation was not significant (r = 0.23), considering the sample analysed. The data suggest that there is a positive correlation between EMG and strength, depending on the position of the muscle analysed

The Chemical Origin of SEY at Technical Surfaces

The secondary emission yield (SEY) properties of colaminated Cu samples for LHC beam screens are correlated to the surface chemical composition determined by X-ray photoelectron spectroscopy. The surface of the "as received" samples is characterized by the presence of significant quantities of contaminating adsorbates and by the maximum of the SEY curve (dmax) being as high as 2.2. After extended electron scrubbing at kinetic energy of 10 and 500 eV, the dmax value drops to the ultimate values of 1.35 and 1.1, respectively. In both cases the surface oxidized phases are significantly reduced, whereas only in the sample scrubbed at 500 eV the formation of a graphitic-like C layer is observed. We find that the electron scrubbing of technical Cu surfaces can be described as occurring in two steps, where the first step consists in the electron induced desorption of weakly bound contaminants that occurs indifferently at 10 and at 500 eV and corresponds to a partial decrease of dmax, and the second step, activated by more energetic electrons and becoming evident at high doses, which increases the number of graphitic-like C-C bonds via the dissociation of adsorbates already contaminating the "as received" surface or accumulating on this surface during irradiation. Our results demonstrate how the kinetic energy of impinging electrons is a crucial parameter when conditioning technical surfaces of Cu and other metals by means of electron induced chemical processing.Comment: 6 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Italy; CERN Yellow Report CERN-2013-002, pp.99-10