Minimally-invasive nasal sampling in children offers accurate pneumococcal colonization detection

Nasopharyngeal colonization of potential respiratory pathogens such as Streptococcus pneumoniae is the major source of transmission and precursor of invasive disease. Swabbing deeply the nasopharynx, which is currently recommended by WHO, provides accurate pneumococcal detection but is unpleasant. We showed that nasal lining fluid filter strips offer equal detection sensitivity.

Research of Influences on Second Interface Cementation Performance in Well Cementation of Adding Metakaolin into Drilling Fluid

It is difficult for conventional drilling fluid filter cake to form integration cementation with cement sheath, which causing weak cementation of the second interface. Therefore the following researches on improving the second interface cementation strength were carried out based on alkali activation mechanism of metakaolin. Cementation strength between metakaolin drilling fluid filter cake and cement sheath has been observed; the mechanism has been analyzed through SEM, XRD and FT-IR; engineering application performance of metakaolin drilling fluid has been studied; and circulation time of the technology has been researched. The results of the experiments showed that: 1) adding metakaolin into drilling fluid was helpful to improve the second interface cementing performance; 2) calcium hydroxide produced by cement hydration inspired metakaolin to generate C-S-H gel and realized overall cementation of filter cake and cement sheath; 3) through select particle size of metakaolin matched with other solids in drilling fluid, drilling fluid performance index could meet requirements of engineering application; 4) and for best results, the circulation time of metakaolin drilling fluid should be more than 40 minutes. The results prove that metakaolin drilling fluid can improve the second interface cementation performance, showing feasibility on flied using and practical values on improving wellbore integrity.

Attenuating characteristics of a multi-element buffer bottle in an aircraft piston pump

Pressure pulsation of an aircraft piston pump and accompanying vibrations are often sources of unreliability and fatigue of an aircraft hydraulic energy system. To reduce discharge pressure pulsation, a buffer bottle is usually installed inside the pump for space consideration that generally restricts its chamber volume resulting in a high working frequency range usually well exceeding the pressure pulsation frequencies corresponding to the normal operating speed range of the pump and hard to be adjusted once installed. To meet this challenge, this paper presents a method for designing a multi-element buffer bottle as an integrated fluid filter network formed by sub-elemental circuits (consisting of orifice, pipe and T-off) that can be assembled in an aircraft piston-pump. This design method of a compact fluid filter network is illustrated with a practical example based on a multi-element buffer bottle. Based on impedance models, results of an in-depth numerical investigation analyzing the effects of different buffer-bottle designs, geometrical parameters and adjustable orifice dimensions on pressure pulsation attenuation are discussed. The method for tuning the operating resonant frequency of a multi-element buffer bottle for pressure attenuation using a changeable orifice diameter is demonstrated experimentally confirming the buffer bottle as an attractive alternative to the conventional methods based on large-volume chambers.