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We investigate the properties of a trace-gas sensing scheme based on Rydberg excitations at the example of an idealized model system. Rydberg states in thermal rubidium (Rb) are created using a 2-photon cw excitation. These Rydberg-excited atoms ionize via collisions with a background gas of nitrogen (N2). The emerging charges are then measured as an electric current, which is on the order of several picoampere. Due to the 2-photon excitation, this sensing method has a large intrinsic selectivity combined with a promising sensitivity of 10 ppb at an absolute concentration of 1 ppm. The determination of the detection limit is limited by the optical reference measurement but is at least 500 ppb. [ABSTRACT FROM AUTHOR]

Highlights • Implementation of a 4-marker foot model to evaluate dynamic navicular drop (dND). • Magnitudes of static dND are not reflected in dynamic dND measures. • The gait style, running or walking, has a large effect on the dND. • Increasing dND in running and decreasing dND in walking for increasing gait speed. Abstract Introduction Variations of gait speed influence kinematic variables that may have an effect on dynamic foot deformation. The influence of gait speed on the navicular drop has not yet been investigated. Methods The navicular drop was evaluated in static and dynamic conditions using a 3D-motion capture system. The dynamic navicular drop was evaluated on a treadmill while walking and running at three different speeds. A repeated measures ANOVA and post-hoc tests were conducted to evaluate the differences in dynamic navicular drop, corresponding unloaded navicular height at foot strike and loaded navicular height during stance. Results Higher walking speed led to a significant decrease in navicular height at foot strike and a subsequent decrease of dynamic navicular drop (p = 0.006). Across increasing running speeds, minimum navicular height was significantly decreased which in consequence led to an increased dynamic navicular drop (p = 0.015). For walking and running at the same speed, there was a large effect of gait style with an increase of dynamic navicular drop by 3.5 mm (p < 0.001) during running. Discussion The change of gait from walking to running at the same speed had a large effect on dynamic navicular drop. The values of navicular height at foot strike and minimum navicular height during stance should be taken into account for the interpretation of dynamic navicular drop measures. Static and dynamic navicular drop measures differ substantially. [ABSTRACT FROM AUTHOR]

We demonstrate the applicability of 2-photon Rydberg excitations of nitric oxide (NO) at room temperature in a gas mixture with helium (He) as an optogalvanic gas sensor. The charges created initially from preceding collisions of excited NO Rydberg molecules with free electrons are measured as a current on metallic electrodes inside a glass cell and amplified using a custom-designed high-bandwidth transimpedance amplifier attached to the cell. We find that this gas sensing method is capable of detecting NO concentrations lower than 10 ppm even at atmospheric pressures, currently only limited by the way we prepare gas dilutions. [ABSTRACT FROM AUTHOR]