Search results for "Concentration."

Mass action model for solute distribution between water and micelles. Partial molar volumes of butanol and pentanol in dodecyl surfactant solutions

1986

The densities of 1-butanol and 1-pentanol were measured in aqueous solutions of dodecyltrimethylammonium bromide and dodecyldimethylamine oxide and the partial molar volumes at infinite dilution of the alcohols in aqueous surfactants solutions were obtained. The observed trends of this quantity as a function of the surfactant concentration were rationalized using a mass-action model for the alcohol distribution between the aqueous and the micellar phase. At the same time, the model was revised to account for the alcohol effect on the surfactant micellization equilibrium. The partial molar volume of alcohols in the aqueous and in the micellar phases and the ratios between the binding constan…

Effect of Stiffness on the Micellization Behavior of Model H4T4 Surfactant Chains

2006

The micellization behavior of a series of model surfactants, all with four head and tail groups (H4T4) but with different degrees of chain stiffness, was studied using grand canonical Monte Carlo simulations on a cubic lattice. The critical micelle concentration, micellar size, and thermodynamics of micellization were examined. In all cases investigated, the critical micelle concentration was found to increase with increasing temperature as observed for nonionic surfactants in apolar or slightly polar solvents. At a fixed reduced temperature and increasing chain stiffness, in agreement with previous observations, it was found that the critical micelle concentration decreased and the average…

Thermodynamic properties of alcohols in a micellar phase. Binding constants and partial molar volumes of pentanol in sodium dodecylsulfate micelles a…

1984

Densities of the ternary system water-sodium dodecylsulfate (NaDS)-pentanol and of the binary systems butanol-octane and pentanol-octane were measured at 15, 25, and 35 °C. The apparent molar volume of pentanol in the ternary system was analyzed using a mass-action model for the alcohol distribution in micellar solutions. The partial molar volume of alcohol bound to the micelles and the ratio between the binding constant and the aggregation number of the surfactant are calculated. The partial molar volume binding constant, is discussed in terms of solubilization sites of the alcohol in the micelles whereas the binding constant is compared with that derived from the Nernstian partition const…

Effect of 3,4-dichloroaniline on the early life stages of the zebrafish (Brachydanio rerio): results of a comparative laboratory study.

1991

An early life-stage (ELS) test was conducted with the zebrafish and 3,4-dichloroaniline (3,4-DCA) in eight laboratories. Based on the results from all eight laboratories, an LOEC of 200 micrograms 3,4-dichloroaniline/liter applies for the early life stages of the zebrafish. Effects observed were reduction of the survival rate and malformations. If the 100 micrograms/liter concentration additionally tested by one laboratory is included in the assessment, an LOEC of 100 micrograms 3,4-DCA/liter is obtained for the survival rate and increase in length. The NOEC is 20 micrograms/liter. The present results of a comparative laboratory study with the zebrafish show that a 42-day ELS test can be co…

Biological responses of Rhynchophorus ferrugineus (Coleoptera: Curculionidae) to Steinernema carpocapsae (Nematoda: Steinernematidae).

2013

Rhynchophorus ferrugineus (Olivier 1790) (Coleoptera: Curculionidae) is becoming a serious problem in Mediterranean areas where it is well-adapted, and now is present even in the United States (California). The infestations are primarily in urban areas where chemical control is not advisable and million of Euros are spent to control it. The effects of the entomopathogenic nematode Steinernema carpocapsae (Nematoda: Steinernematidae) on mortality, growth, as well as the immune activity of R. ferrugineus larvae, were investigated. R. ferrugineus mortality exhibited a positive trend with the dosage and duration of exposure to S. carpocapsae. The median lethal dose and median lethal time, impor…

Les dynamiques du périurbain dijonnais entre 1990 et 1999

2009

Un étalement urbain accompagne désormais la croissance des villes, notamment les plus grandes. Principalement expliqué par un desserrement résidentiel, il est aussi la résultante des dynamiques de centralisation de l’emploi et de spécialisation des zones d’activité à l’intérieur des aires urbaines. L’exemple dijonnais met bien en lumière ce double mouvement qui affecte les communes de sa périphérie et contribue à accroître les mobilités. Urban sprawl arises from the growth of cities, especially of the biggest cities. This urban sprawl is accounted for mainly by residential clearing. It results also from the dynamics of centralization of employment and from specialization of activity zones i…

Relationships between oxygen concentration and patterns of energy metabolism in the rotifer Brachionus plicatilis

1992

Abstract 1. 1. Activities of 10 enzymes and accumulation of two metabolites under experimental hypoxia were investigated in the rotifer Brachionus plicatilis . 2. 2. Pyruvate kinase (PK), lactate dehydrogenase (LDH), malic enzyme (ME), phosphoenolpyruvate carboxykinase (PEPCK), malate dehydrogenase (MDH) and fumarase (FUM) activities showed great increase at low oxygen levels. Alcohol dehydrogenase (ADH) activity was not detected. 3. 3. Alanine concentration showed an increase with low oxygen concentrations, while alanine aminotransferase (GTP) showed a slight activity increase with oxygen levels. The high alanine concentration was interpreted as enhanced proteolysis. 4. 4. Our results show…

Phase selection of calcium carbonate through the chirality of adsorbed amino acids.

2007

New Insight to the Chemistry of Polyaza[n]paracyclophanes. A 15N NMR Study

2001

Preferential localization of Lactococcus lactis cells entrapped in a caseinate/alginate phase separated system.

2013

International audience; This study aimed to entrap bioprotective lactic acid bacteria in a sodium caseinate/sodium alginate aqueous two-phase system. Phase diagram at pH = 7 showed that sodium alginate and sodium caseinate were not miscible when their concentrations exceeded 1% (w/w) and 6% (w/w), respectively. The stability of the caseinate/alginate two-phase system was also checked at pH values of 6.0 and 5.5. Lactococcus lactis subsp. lactis LAB3 cells were added in a 4% (w/w) caseinate/1.5% (w/w) alginate two-phase system at pH = 7. Fluorescence microscopy allowed to observe that the caseinate-rich phase formed droplets dispersed in a continuous alginate-rich phase. The distribution of …