Starling resister and stability of sleep ventilation

The upper airway can be described as a collapsible segment (the pharynx) interposed between two rigid bony (the cavum) or cartilaginous (the trachea) segments. Due to this structure, the pharynx behaves as a collapsible tube, in which airflow does not depend on the downstream pressure, but is limited to a maximum value which depends only on the upstream pressure and on the pressure surrounding the collapsible segment; this behavior, known as a Starling resistor can be modeled by the waterfall effect. Thus, the upper airways can be in three different conditions: an occluded condition, in which no flow is possible, a patent condition, in which flow depends on the difference between upstream and downstream pressures (according to Poiseuille's law), and a situation in which flow is limited. The behavior of the upper airway is largely dependent on its anatomic structure, but functional factors play a critical role. Among these sleep state is both a determinant of the collapsibility of the pharynx, and determined by the simulation of upper airway mechanoreceptors whose activity depends on the activity of respiratory muscles. Thus the interplay of three factors: ventilatory drive, upper airway collapsibility, and arousal threshold can predict most of the situations of stable and unstable ventilatory behavior during sleep. The level of the arousal threshold governs the stability of the ventilatory pattern, as it determines whether a combination of slow, respiratory effort, and blood gases can be maintained or is interrupted by an arousal.     

Experimental data base for containment thermalhydraulic analysis

This paper describes the joint research project DABASCO which is supported by the European Community under a cost-shared contract and participated by nine European institutions. The main objective of the project is to provide a generic experimental data base for the development of physical models and correlations for containment thermalhydraulic analysis. The project consists of seven separate-effects experimental programs which deal with new innovative conceptual features, e.g. passive decay heat removal and spray systems. The results of the various stages of the test programs will be assessed by industrial partners in relation to their applicability to reactor conditions.     

Use of fibrous polyamide material in road construction

Conclusions The possibility of using fibrous materials based on waste from the manufacture of polyamide fibre in road construction has been examined.The effect of the acidity of the medium on the lifetime of fibrous polyamide material has been established.Translated from Khimicheskie Volokna, No. 1, pp. 34–35, January–February, 1984.     

Computer control of an algal bioreactor with simulated diurnal illumination

Design details are presented for the construction of a microcomputer based system to measure and control the growth of an algal population in a continuous-flow bioreactor. Diurnal variation in the light intensity was simulated by computer control of a Venetian blind placed in front of the solar lamps. An indirect method of biomass estimation was based on balancing the amount of nitrogen (NH₃) in and out of the system. The computer-control system held the algal biomass at a constant concentration while fluctuations in CO₂ partial pressure, turbulence and light intensity occurred. Under diurnal illumination, CO₂ assimilation began without lag when illumination started, although there was a lag before ammonia utilisation began.     

Investigation of PWR accident situations at BETHSY facility

For several years an extensive programme of separate effect tests related to PWR safety has been conducted in France and in particular at the Nuclear Center of Grenoble. Recently the BETHSY integral test facility - three identical loops, full height and pressure - has been constructed with the main objectives of contributing to the verification of the CATHARE calculation code of accidents and to the validation of the physical bases of Emergency Operating Procedures.So far several tests have been (November 1988) carried out, among which natural circulation under various conditions (single phase, two-phase, symmetric or asymmetric conditions, different core power, variable steam generator liquid level), 2 inches cold leg break, steam bubble formation and collapse in the upper head. Summarized results of some of these tests are introduced and compared to a first CATHARE calculation as far as the 2″ cold leg break is concerned.