Effect of temporal relationship between respiration and body motion on motion sickness

Background - This study investigated the effect controlling the phase of respiration on the development of nausea provoked by periodic motion at 0.2 Hz which is maximal for provocation of motion sickness. Methods - Subjects were exposed to 60° peak–peak, pitch backwards from upright motion while viewing a video of the environment with 180° phase delay. Motion duration was a maximum of 30 min and frequency was set to match individuals' spontaneous respiration. Conditions were: A, spontaneous breathing; B, inspiration cued to begin when head-down; C, inspiration cued to begin when upright; D, inspiration cued with a ±18° desynchronizing phase drift with respect to the tilt cycle. Nausea was rated and ventilation was recorded. Results - Magnitudes of nausea ratings were ordered D < C < B < A (p = 0.008) and speed at which nausea developed were ordered A < B < C < D (p = 0.001). Discussion - The lower sickness ratings and prolonged times to develop nausea in B, C, D confirm that controlled breathing gives some protection against motion sickness. The differences between B, C and D in the development of nausea support the hypothesis of Von Gierke and Parker [von Gierke HE, Parker DE. Differences in otolith and abdominal viscera graviceptor dynamics: implications for motion sickness and perceived body position. Aviat Space Environ Med. 65:747–51, 1994.] that motion sickness can be provoked by a conflicting mismatch between visceral and otolithic signals of orientation to the vertical. The mismatch is greatest in the more provocative condition B because the viscera are mechanically unloaded due to exhalation when the body attains uprightness whereas mismatch is lessened by the mechanical reinforcement afforded by inspiration in (C) and by inconstant relationships between visceral and otolithic signals in (D), both of which afford better protection against sickness

Industrial activities

Causes of increased propension to sleepiness in industrial employees can be roughly divided into two classes. The first group of causes is common to all production activities, and includes: shift and night work, work-related stress, physical and mental fatigue, and the use of illegal or legal drugs and alcohol. All these causes have been discussed in previous chapters. Some industrial activities may also expose workers to specific factors that may increase the drowsiness. An effective prevention of the potential damage of drowsiness in industries must carefully consider these intrinsic causes of sleepiness. This chapter will examine briefly the causes of increased daytime sleepiness in industrial activities, considering separately the organizational and physical factors and the properly neurotoxic agents that can be that may be present in the production cycle

Goal-oriented error estimation and mesh adaptation for shallow water modelling

This study presents a novel goal-oriented error estimate for the nonlinear shallow water equations solved using a mixed discontinuous/continuous Galerkin approach. This error estimator takes account of the discontinuities in the discrete solu-tion and is used to drive two metric-based mesh adaptation algorithms: one which yields isotropic meshes and another which yields anisotropic meshes. An implementation of these goal-oriented mesh adaptation algorithms is described, including a method for approximating the adjoint error term which arises in the error estimate. Results are presented for simulations of two model tidal farm configurations computed using the Thetis coastal ocean model (Kärnä et al. in Geosci Model Dev 11(11):4359–4382, 2018). Convergence analysis indicates that meshes resulting from the goal-oriented adaptation strategies permit accurate QoI estimation using fewer computational resources than uniform refinement