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The influence of strain rate on the mechanical response of two different nanostructured pure coppers was investigated under uniaxial compression. The first nanostructured copper was elaborated by powder metallurgy using the Spark Plasma Sintering (SPS) process. The second nanostructured copper was elaborated by Severe Plastic Deformation (SPD). Conventional characterizations were conducted with quasi-static compression and tensile tests, hardness tests and, with microstructure analysis. The effect of strain rate was evaluated under uniaxial compression at strain rates varying from 10-4 to 10+4 s-1. The high strain rate data were generated with a direct Hopkinson impact technique. The increase of strength with strain rates was analysed and discussed from the Scanning Electron Microscope observations and grain size distribution. The mechanical properties are consequently dependent on the metallurgical history of these samples prepared according to two different routes.

Our laboratory previously reported that active glottal closure was present in 90% of spontaneous central apneas in premature lambs while maintaining a high-apneic lung volume (Renolleau S, Letourneau P, Niyonsenga T, and Praud JP. Am J Respir Crit Care Med 159: 1396-1404, 1999.) The present study aimed at testing whether this mechanism limits postapnea oxygen desaturation. Four premature lambs were instrumented for recording states of alertness, thyroarytenoid muscle and diaphragm electromyographic (EMG) activity, nasal airflow, lung volume changes, and pulse oximetry. One thousand four hundred fifty-two spontaneous central apneas (isolated or during periodic breathing) were analyzed in nonsedated lambs. Apneas, with high lung volume maintained by active glottal closure, were compared with apneas, with a tracheostomy opened at apnea onset. Oxygen desaturation slopes were lower when high-apneic lung volume was actively maintained during both wakefulness and quiet sleep. Furthermore, oxygen desaturation slopes were lower after isolated apneas with continuous thyroarytenoid EMG during wakefulness, compared with apneas with noncontinuous thyroarytenoid EMG (= glottis opened shortly after apnea onset). These results highlight the importance of maintaining high-alveolar oxygen stores during central apneas by active glottal closure to limit desaturation in newborns.

The postnatal development of ventilatory reflexes originating from bronchopulmonary receptors was assessed in preterm vs. full-term lambs. Ventilation and arterial pressure were repeatedly measured in 10 preterm (gestational age, 132 days) and 7 full-term lambs without sedation from day 1 to day 42. The Hering-Breuer inhibitory reflex (slowly adapting stretch receptors) was assessed by the increase in expiratory time during end-inspiratory occlusion. The pulmonary chemoreflex (C-fiber endings) was assessed by the initial apnea + bradycardia + systemic hypotension and the secondary tachypnea after capsaicin intravenous injection. Results show the following. 1) Premature birth did not modify the maturation of the Hering-Breuer reflex. 2) Whereas a classic pulmonary chemoreflex was observed in the very first hours of life in preterm lambs, the tachypneic component of this reflex was weaker than in full-term lambs on day 1. 3) Premature birth led to a reversed postnatal maturation of this tachypneic response (tendency to increase with postnatal age). Our findings suggest that premature birth in lambs modifies postnatal maturation of the pulmonary chemoreflex.

Fifteen nondemented subjects with memory complaints underwent serial single photon emission computed tomography (SPECT) studies with technetium-99m-d, l-hexamethyl-propylene amine oxime (HMPAO) as tracer. Scans were carried out under a baseline conditions and during the learning phase of the Memory Efficiency Profile (MEP), a combined visual perception and memory task developed by Rey. Results indicate a positive correlation between activation, as indexed by HMPAO uptake, and neuropsychological assessment. Right temporal activation was correlated with MEP immediate recall. The right cerebellum was correlated with both MEP immediate and delayed recall. This study suggests that SPECT can show cortical activation during cognitive performance in subjects with mild memory impairment.

We studied c-erb-B2 gene amplification of DNA of primary breast tumours without distant metastasis from 236 women admitted to our institute during 1992. For 125 of them, we had a serum sample at diagnosis, before any treatment. C-erb-B2 gene amplification (> or = 2 copies) was observed in 26% (62/236) of the cases. There was a correlation with higher histological grades (p < 0.03) and with absence of hormone receptors: ER-(p < 0.0001). PgR-(p < 0.0001), association ER- and PgR-(p < 0.0000). Large tumours T3 and T4 taken together tended to present more c-erb B2 gene amplifications (p < 0.08). There was no correlation with age, histological type or nodal status. At diagnosis, mean concentration of serum c-erb-B2 oncoprotein was 8.5 +/- 18 U/ml with a median of 4 U/ml (4-150). Choosing a cut-off value of 8 U/ml gave a sensitivity of 21% (26/125). Serum levels of c-erb-B2 oncoprotein were correlated with tumour spread: large tumours T3-T4 (p < 0.001), nodal involvement (N+) (p < 0.01), association T3-T4 and N+(p < 0.0005), high levels of CA 15:3 (normal value < 25 IU/ml) (p < 0.05). There was no other correlation, particularly with age, histological type, hormone receptors or c-erb-B2 gene amplification. c-erb-B2 oncoprotein serum levels could be helpful to detect recurrences. Assessment of c-erb-B2 oncoprotein serum concentration, before treatment, as an independent prognostic factor is necessary.