Susceptibility to periodic breathing with assisted ventilation during sleep in normal subjects

Assisted ventilation with pressure support (PSV) or proportional assist (PAV) ventilation has the potential to produce periodic breathing (PB) during sleep. We hypothesized that PB will develop when PSV level exceeds the product of spontaneous tidal volume (VT) and elastance (VTsp . E) but that the actual level at which PB will develop [PSV(PB)] will be influenced by the DeltaPCO2 (difference between eupneic PCO2 and CO2 apneic threshold) and by DeltaRR [response of respiratory rate (RR) to PSV]. We also wished to determine the PAV level at which PB develops to assess inherent ventilatory stability in normal subjects. Twelve normal subjects underwent polysomnography while connected to a PSV/PAV ventilator prototype. Level of assist with either mode was increased in small steps (2-5 min each) until PB developed or the subject awakened. End-tidal PCO2, VT, RR, and airway pressure (Paw) were continuously monitored, and the pressure generated by respiratory muscle (Pmus) was calculated. The pressure amplification factor (PAF) at the highest PAV level was calculated from [(DeltaPaw + Pmus)/Pmus], where DeltaPaw is peak Paw - continuous positive airway pressure. PB with central apneas developed in 11 of 12 subjects on PSV. DeltaPCO2 ranged from 1.5 to 5.8 Torr. Changes in RR with PSV were small and bidirectional (+1.1 to -3.5 min-1). With use of stepwise regression, PSV(PB) was significantly correlated with VTsp (P = 0.001), E (P = 0.00009), DeltaPCO2 (P = 0.007), and DeltaRR (P = 0.006). The final regression model was as follows: PSV(PB) = 11.1 VTsp + 0.3E - 0.4 DeltaPCO2 - 0.34 DeltaRR - 3.4 (r = 0.98). PB developed in five subjects on PAV at amplification factors of 1.5-3.4. It failed to occur in seven subjects, despite PAF of up to 7.6. We conclude that 1) a PCO2 apneic threshold exists during sleep at 1.5-5.8 Torr below eupneic PCO2, 2) the development of PB during PSV is entirely predictable during sleep, and 3) the inherent susceptibility to PB varies considerably among normal subjects.     

The relation between cancer of the colon and rectum and nutrition, in Rio de Janeiro

A retrospective study was carried out on the type of habitual diet consumed in the Niterói (Rio de Janeiro) city. Two groups of subjects were integrated: the Experimental Group, formed by patients with neoplasms of the large intestine and rectum, and the Control Group, formed by individuals with no gastrointestinal disorders. The information obtained through direct inquiry, strongly suggests that cancer of the colon and rectum may be related to the high proportion of fat and low proportion of dietary fiber found in the diets of the patients studied.     

Un processeur de détection de contours en temps réel dans une image de télévision

Objects identification and localization and more generally scene analysis, need a preliminary step of edge detection. Because of the very important amount of data to be processed, implementing any edge detection algorithm on a conventional computer leads to a high computational cost, too high for many applications: in robotics for instance. The authors present here an on-line real time processor which works upon the digitized signal of a TV camera. This processor computes the two components of the gradient associated with each pixel, using a Sobel operator. Then it selects edge pixels on the basis of informations about the gradient in the neighbourhood of each pixel. The processed image appears synchronously with the video signal, delayed by a 2 TV lines duration compared to the original image.     

Surface treatment of a 316L type stainless steel by explosive: microstructural characterization and monotonic tensile behaviour

A new surface-treatment process using a thin layer of primary explosive was applied to a 316L type stainless steel. The induced microstructural modifications and the residual mechanical properties of the treated material have been evaluated. The surface roughness quality and the microhardness increase are higher than after usual shot-peening treatments. The near-surface microstructure, observed by transmission electron microscopy, is composed of numerous mechanical twins the density of which decreases with increasing depth. The yield strength (0.2% offset) of the treated layer has been evaluated and related to the mean value of the microhardness in this layer.     

Effect of very high temperature short exposures on the dissolution of the γ′ phase in single crystal MC2 superalloy

Time-temperature dependence of the γ′ phase volume fraction was investigated for a second generation single crystal nickel-based superalloy exposed to very short high temperature regimes (1,100–1,200 °C). In this temperature range, the dissolution of the strengthening γ′ phase occurs. Evolution of the γ′ volume fraction in transient regimes has been established for each temperature and activation energy of the dissolution phenomenon were determined. They directly attest from the activity of the diffusing species involved during this phenomenon. From these analyses, the volume fraction at equilibrium was established for the entire temperature range where dissolution occurs. A model, based on a time/temperature equivalence, is proposed to quantify the γ′ volume fraction dissolved during short high temperature exposure.     

PCQoS: power controlled QoS tuning for wireless ad hoc networks

Mobile ad hoc networks typically use a common transmission power approach for the discovery of routes and the transmission of data packets. In this paper we present PCQoS; a power-controlled Quality of Service (QoS) scheme for wireless ad hoc networks which builds QoS mechanisms for specific applications that wish to tradeoff better QoS performance for sub-optimal paths. PCQoS allows selected flows to modify their transmit power as a way to add and remove relay nodes from their paths in order to coarsely modify their observed application QoS performance. We present simulation results and show that PCQoS can be used to provide coarse control over traditional QoS metrics (e.g., delay, throughput). To the best of our knowledge the PCQoS protocol represents the first attempt to use variable-range transmission control as a means to provide QoS differentiation to applications in wireless ad hoc networks.