A server blade chassis having at least one mechanically actuated variable air flow damper is presented. The pen comprises a hollow case, an ink cartridge, a mechanical spring and a mobile magnetic element. With this fixing apparatus, switching of the intensity of magnetic coupling between the center core and heat-producing roller can be performed simply by rotating the center core. The non-aqueous electrolyte contains a non-aqueous solvent, 1,3-dioxane and a dinitrile compound additives, and an electrolyte salt.