Abstract: A helmet comprising: an inner shell; an outer shell; a sliding interface between the inner shell and the outer shell; and a switch configured to be selectively switchable between first and second discrete modes, the first mode allowing relative sliding between the inner shell and the outer shell at the sliding interface in response to an impact to the helmet, the second mode preventing relative sliding between the inner shell and the outer shell at the sliding interface.

Abstract: A method and a server for determining a service level in a network for a user. The network includes information on the at least one user and at least one application associated with the at least one user. In the method at least one application is classified into a group among multiple groups according to an importance set for each of the at least one application, utilization of network resources by each of the application is determined by monitoring a characteristic within the network, at least one network parameter is determined for each of the groups based on the utilization of the network resources, a group in which exists at least one most important application associated with the user is determined, and the service level is provided for the user, which corresponds to the determined group.

Abstract: The invention concerns a system for achieving an optical image of an object (136), and/or for achieving optical collimation (137) of light from a light source (130), comprising a concave mirror (131: 134), the surface normal of which forms an angle with the incident light in a beam. A negative lens (132, 133) that co-operates with the concave mirror is arranged in the incident and/or exit beam paths such that an image with eliminated or reduced imaging aberrations is achieved in a focal plane (135), and/or that the exit light from a light sources (130) is collimated (137).

Abstract: The invention concerns a system for achieving an optical image of an object (136), and/or for achieving optical collimation (137) of light from a light source (130), comprising a concave mirror (131, 134), the surface normal of which forms an angle with the incident light in a beam. A negative lens (132, 133) that co-operates with the concave mirror is arranged in the incident and/or exit beam paths such that an image with eliminated or reduced imaging aberrations is achieved in a focal plane (135), and/or that the exit light from a light source (130) is collimated (137).

Abstract: An apparatus for carrying out spectral analysis of optical radiation emitted from a light source (11) comprises a spectral detector (1) having an entrance aperture (10) for the radiation from thelight source (11), a first imaging optical component (11), a first imaging optical component (12), a diffraction grating (14) for wavelength dispersion of the radiation, order sorting means (131, 132) for separation of the spectral orders of the diffraction grating (14), a second imaging optical component (15), and a detecting unit (16) for registration of the light source spectrum divided into order spectra through the order sorting means (131, 132). The order sorting means (131, 132) comprise at least two refractive optical components manufactured from different material. The two refractive optical components (131 and 132) together with the diffraction grating (14) and the imaging optical components (12 and 15) produce a substantially uniform distribution of the order spectra on the detector unit (16).

Abstract: To eliminate astigmatism and coma in a spectrograph the distance between the entrance slot and a first concave mirror, as well as the relative angular positions of the entrance slot, the plane grating, the two concave mirrors and the focal plane are selected so as to satisfy the following conditions.