ABSTRACT
Objective To develop a novel stress fracture animal model system based on dynamic cyclic mechanical loading.Methods Ulnae and tibiae of rats were respectively fixed using differently shaped fixtures (including a fixed holder and a movable holder).The axial mechanical loading was applied via a linear actuator based on LabVIEW control program.During the loading process,a load cell and a laser displacement transducer were used to detect the force and displacement changes in the limbs,respectively.The two signals were sampled at real time by PC-based LabVIEW data acquisition program.A compressive loading test (peak force of 50 N) was conducted to examine the consistency and reliability of cyclic loads after completing the loading system.The loading system and an ElectroForce 3220 mechanical testing machine were respectively used to measure and compare the Young's modulus of a standard ultra-high molecular weight polyethylene (UHMWPE)cylinder to calibrate the loading system.Results The compressive loading test (peak force of 50 N) demonstrated that the mechanical loading system was able to apply consistent loads with controllable intensity and time.The calibration experiment indicated the accuracy of the loading system.Conclusion The novel mechanical loading device has characteristics of precision,scientificity and reliability,and it is approaching the real development situation of stress fracture,which may provide a reliable experimental base for exploring the precautionary measures of stress fracture.
ABSTRACT
Objective To develop a ribbed,oxygen-enriched and inflatable tent to fulfill the requirements for mobile enriched oxygen supply under plateau conditions.Methods The tent was developed with ribbed skeleton,PVC material,nested structure,buffer door,channel for fresh air dispersion,exhaust recovery pipeline and etc,and the self-developed plateau oxygen enrichers were involved in to establish a mobile oxygen-enriched room.The enrichers were divided into four grades of 20,50,70 and 100 m3/h,which were used to execute 8-h oxygen-enriched fresh air dispersion in the tent.The change curves of the fractions for oxygen and carbon dioxide were compared and analyzed at 5 disperse points in the tent.Results Optimal effect was acquired with 20 m3/h oxygen enricher,the oxygen concentration reached 27％ in the tent after 8-h dispersion,while the carbon dioxide fraction was 1 800 ppm (1 ppm=l×l0-6) and it took 3-h to raise oxygen concentration to 25％.Conclusion The tent combined with 20 m3/h oxygen enricher decreases the equivalent altitude from 5 000 m to less than 3 000 m,and is hopeful to be spreaded in the plateau troops after improvement.