Chest wall motion in preterm infants using respiratory inductive plethysmography.

Preterm infant tidal breathing may be different from that of healthy full-term infants because of various features of the premature thorax. The purpose of this project was to describe chest wall motion in the preterm infant (gestational age <37 weeks) and compare it with chest wall motion data in a group of healthy, full-term infants. We wanted to use an objective bedside method for assessment with minimal disruption to the infant. The study population consisted of 61 preterm human infants whose mean(+/-sD) postconceptional age at time of study was 35.3+/-2.1 weeks. During the study, the infants were quietly awake in a prone position. Preterm infants had initially been admitted to a level III neonatal intensive care unit for acute management and had been transferred to a step-down area, where they were in stable condition for study. Data were collected with a semiquantitatively calibrated, noninvasive respiratory inductive plethysmograph. Mean(+/-SD) phase angle was significantly greater in preterm infants than in full-term infants (60.6+/-39.8 degrees versus 12.5+/-5.0 degrees, respectively, p < or = 0.0001). The laboured breathing index was significantly greater in preterm infants than in full-term infants (1.35+/-0.35 versus 1.01+/-0.01, respectively, p = 0.001). The ribcage contribution to breathing did not differ significantly between preterm and full-term infants (25.5+/-17.7% versus 36.3+/-14.4%, respectively, p = 0.11). These results indicate a significant increase in the degree of ribcage and abdomen asynchrony in the preterm subjects compared to the full-term infants. Plethysmography provided a time-efficient and objective method of assessing chest wall motion in this fragile population.

Cyclic liquefaction and its evaluation based on the SPT and CPT

Soil liquefaction is a major concern for structures constructed with or on sandy soils. This paper describes the phenomena of soil liquefaction, provides suitable definitions, and provides an update on methods to evaluate cyclic liquefaction using primarily the Standard Penetration. Test and the Cone Penetration Test (CPT). A new method is described to estimate grain characteristics directly from the CPT and to incorporate this into one of the methods for evaluating resistance to cyclic example is also described ffor correcting the results of the CPT in thin layers. A worked example is also provided. This paper is the final submission from the authors to the proceedings of the 1996 NCEER workshop on soil liquefaction; a similar version has been submitted for review to the Canadian Geotechnical Journal. (AU)

CANLEX (Canadian Liquefaction Experiment) : A one year update

The Canadian Geotechnical engineering community has embarked on a major study regarding the liquefaction of sand entitled The Canadian Liquefaction Experiment (CANLEX) through a collaborative effort of industry, engineering consultants and university participants, with the support of the Natural Sciences and Engineering Research Council of Canada (NSERC). The study is examining the characterization of sand for dynamic and static liquefaction. The project was started in 1993 and is expected to last at least 3 years with equal funding by both industry and NSERC for a total of about C$1.8M. This paper provides a brief progress report on the Project. Three test sites have been selected and characterized using in-situ testing, conventional sampling as well as in-situ freeezing to obtain undisturbed samples. Laboratory testing is underway on both reconstituted samples and undisturbed samples. A full scale liquefaction event is planned for year three of the Project and a feasibility study regarding the event has been completed. As part of the planning for the liquefaction event some preliminary centrifuge testing has been carried out. A static liquefaction flow failure has been successfully produced in the centrifuge. As part of the Project, a set of definitions for liquefaction have been defined and a flow chart developed to aid in the liquefaction analyses.(AU)