Adsorption of an aqueous mixture of surfactants on silica

in Langmuir (2000), 16(24), 9192-9198

The behavior of mixtures of a nonionic surfactant, pentaethylene glycol monodecyl ether (C10E5), and an anionic surfactant, sodium dodecyl sulfate (SDS), was studied at the water−silica interface. In ... [more ▼]

The behavior of mixtures of a nonionic surfactant, pentaethylene glycol monodecyl ether (C10E5), and an anionic surfactant, sodium dodecyl sulfate (SDS), was studied at the water−silica interface. In contrast to the C10E5 surfactant, which is adsorbed at the silica−water interface at pH 6, the adsorption of the anionic surfactant is not observed. In the presence of SDS, the adsorption of C10E5 is severely restricted as result of the formation of mixed micelles in solution. This behavior is consistent with the adsorption free energy, ΔGads, of C10E5 and the free energy of mixed micellization, ΔGmix.mic, of SDS and C10E5. Flow microcalorimetry (FMC) results showed that the addition of C10E5/SDS mixtures to silica precoated with C10E5 resulted in the release of the preadsorbed nonionic surfactant; the whole phenomenon is exothermic. Combination of calorimetric data (FMC and isothermal titration calorimetry), self-diffusion coefficients, and the regular solution theory led to the conclusion that the main driving force for the C10E5 desorption was the formation of mixed micelles by unimeric SDS and the released nonionic surfactant. [less ▲]

Prevention of neonatal group B streptococcal disease in Belgium: hospital policy, obstetricians' practice and laboratory processing

Poster (2000, November 25)

Le vieillissement cognitif: Au-delà des facteurs généraux

in Cognitiques = Cognitics (2000, November 25), 4

Exploration de l'effet de simple exposition dans le vieillissement

in Cognitiques = Cognitics (2000, November 24), 4

La simple exposition répétée à un stimulus conduit les sujets à préférer ce stimulus par rapport à des stimuli non présentés. Nous avons exploré cet effet chez 22 sujets âgés (de 60 à 70 ans) et 22 sujets ... [more ▼]

La simple exposition répétée à un stimulus conduit les sujets à préférer ce stimulus par rapport à des stimuli non présentés. Nous avons exploré cet effet chez 22 sujets âgés (de 60 à 70 ans) et 22 sujets jeunes (de 20 à 30 ans) appariés quant au niveau d’éducation. Dans une première phase, on demande aux sujets d'estimer l'âge de 15 visages-cibles, non familiers. Ces 15 visages sont présentés durant 15 msec., cinq fois dans un ordre aléatoire. Ensuite, on présente aux sujets 15 paires de visages (un visage-cible et un visage non présenté) et on leur demande de choisir le visage qu'ils préfèrent. Enfin, un test de reconnaissance leur est administré. En ce qui concerne le jugement de préférence, les sujets âgés et les sujets jeunes choisissent préférentiellement le visage exposé antérieurement, avec une performance supérieure au hasard. De plus, la performance des deux groupes ne diffère pas significativement. Par contre, la performance des sujets âgés en reconnaissance est significativement inférieure à celle des sujets jeunes. En conclusion, ces résultats indiquent que les processus sous-tendant l'effet de simple exposition sont préservés par le vieillissement en dépit d'une reconnaissance explicite déficitaire. [less ▲]

Comment évaluer des compétences en classe d'histoire ?

in PAQUAY, Léopold (Ed.) L'évalution des compétences chez l'apprenant. Pratiques, méthodes et fondements (2000, November 22)

Resistance of Isolated Pulmonary Mitochondria During in Vitro Anoxia/Reoxygenation

in Biochimica et Biophysica Acta (2000), 1460(2-3), 346-52

The aim of the study was to investigate the effect of in vitro anoxia/reoxygenation on the oxidative phosphorylation of isolated lung mitochondria. Mitochondria were isolated after harvesting from fresh ... [more ▼]

The aim of the study was to investigate the effect of in vitro anoxia/reoxygenation on the oxidative phosphorylation of isolated lung mitochondria. Mitochondria were isolated after harvesting from fresh pig lungs flushed with Euro-Collins solution. Mitochondrial respiratory parameters were determined in isolated mitochondria before anoxia (control), after 5-45 min anoxia followed by 5 min reoxygenation, and after 25 or 40 min of in vitro incubation in order to follow the in vitro aging of mitochondria during respiratory assays. Respiratory parameters measured after anoxia/reoxygenation did not show any oxidative phosphorylation dysfunction, indicating a high resistance of pulmonary mitochondria to in vitro anoxia/reoxygenation (up to 45 min anoxia). These results indicate that mitochondria are not directly responsible of their oxidative phosphorylation damage observed after in vivo ischemia (K. Willet et al., Transplantation 69 (2000) 582) but are a target of others cellular injuries leading to mitochondrial dysfunction in vivo. [less ▲]

Pharmacological evaluation of 4,6-disubstituted 2,2-dimethylchromans structurally related to the KATP channel opener cromakalim

Poster (2000, November 18)

Urinary excretion of high Mr PEG (>4000 Da) in rats

Poster (2000, November 18)

Mechanisms of Persistent Nf-Kappa B Activity in the Bronchi of an Animal Model of Asthma

in Journal of Immunology (2000), 165(10), 5822-5830

In most cells trans-activating NF-kappaB induces many inflammatory proteins as well as its own inhibitor, IkappaB-alpha, thus assuring a transient response upon stimulation. However, NF-kappaB-dependent ... [more ▼]

In most cells trans-activating NF-kappaB induces many inflammatory proteins as well as its own inhibitor, IkappaB-alpha, thus assuring a transient response upon stimulation. However, NF-kappaB-dependent inflammatory gene expression is persistent in asthmatic bronchi, even after allergen eviction. In the present report we used bronchial brushing samples (BBSs) from heaves-affected horses (a spontaneous model of asthma) to elucidate the mechanisms by which NF-kappaB activity is maintained in asthmatic airways. NF-kappaB activity was high in granulocytic and nongranulocytic BBS cells. However, NF-kappaB activity highly correlated to granulocyte percentage and was only abrogated after granulocytic death in cultured BBSs. Before granulocytic death, NF-kappaB activity was suppressed by simultaneous addition of neutralizing anti-IL-1beta and anti-TNF-alpha Abs to the medium of cultured BBSs. Surprisingly, IkappaB-beta, whose expression is not regulated by NF-kappaB, unlike IkappaB-alpha, was the most prominent NF-kappaB inhibitor found in BBSs. The amounts of IkappaB-beta were low in BBSs obtained from diseased horses, but drastically increased after addition of the neutralizing anti-IL-1beta and anti-TNF-alpha Abs. These results indicate that sustained NF-kappaB activation in asthmatic bronchi is driven by granulocytes and is mediated by IL-1beta and TNF-alpha. Moreover, an imbalance between high levels of IL-1beta- and TNF-alpha-mediated IkappaB-beta degradation and low levels of IkappaB-beta synthesis is likely to be the mechanism preventing NF-kappaB deactivation in asthmatic airways before granulocytic death. [less ▲]

A homologous radioimmunoassay for quantification of insulin-like growth factor-binding protein-3 in blood from cattle.

in Proceedings of the 2nd Belgian Workshop on Animal Endocrinology. (2000, November 15)