ABSTRACT
The aim of this study was to characterize the process of atomization and drying of layer-by-layer emulsions containing lecithin (single layer emulsion) and lecithin/chitosan (bilayer emulsion) and the oxidative stability of the microcapsules during storage. For this purpose, the analysis of the emulsion spray droplet size during two-fluid nozzle and rotary atomization was carried out to identify suitable process parameters. The drying behaviour of single and bilayer emulsions was investigated by calculation of the volume flow density during single-droplet drying during acoustic levitation. In spray-dried solid particles, the oxidative stability in the single layer microcapsules was higher than in the bilayer microcapsules. This was partly attributed to lower microencapsulation efficiency in the bilayer microcapsules compared to the single layer microcapsules. Furthermore, it could be shown, that excess chitosan in the bulk carrier matrix affects the free volume elements and thus oxygen diffusion.
Subject(s)
Chitosan/chemistry , Fish Oils/chemistry , Lecithins/chemistry , Lipid Bilayers/chemistry , Capsules/chemistry , Emulsions/chemistryABSTRACT
Positron annihilation lifetime spectroscopy (PALS) is employed to characterize the temperature dependence of the free volume in two van der Waals liquids: 1, 1'-bis(p-methoxyphenyl)cyclohexane (BMPC) and 1, 1'-di(4-methoxy-5-methylphenyl)cyclohexane (BMMPC). From the PALS spectra analysed with the routine LifeTime9.0, the size (volume) distribution of local free volumes (subnanometer size holes), its mean, [v(h)], and mean dispersion, σ(h), were calculated. A comparison with the macroscopic volume from pressure-volume-temperature (PV T) experiments delivered the hole density and the specific hole free volume and a complete characterization of the free volume microstructure in that sense. These data are used in correlation with structural (α) relaxation data from broad-band dielectric spectroscopy (BDS) in terms of the Cohen-Grest and Cohen-Turnbull free volume models. An extension of the latter model allows us to quantify deviations between experiments and theory and an attempt to systematize these in terms of T(g) or of the fragility. The experimental data for several fragile and less fragile glass formers are involved in the final discussion. It was concluded that, for large differences in the fragility of different glass formers, the positron lifetime mirrors clearly the different character of these materials. For small differences in the fragility, additional properties like the character of bonds and chemical structure of the material may affect size, distribution and thermal behaviour of the free volume.
Subject(s)
Chemistry/methods , Cyclohexanes/chemistry , Physics/methods , Glass/chemistry , Hot Temperature , Materials Testing , Polymers/chemistry , Spectrophotometry/methods , TemperatureABSTRACT
The free volume in thin films of poly(N-isopropylacrylamid) end-capped with n-butyltriocarbonate (nbc-PNIPAM) is probed with positron annihilation lifetime spectroscopy (PALS). The PALS measurements are performed as function of energy to obtain depth profiles of the free volume of nbc-PNIPAM films. The range of nbc-PNIPAM films with thicknesses from 40 to 200 nm is focused. With decreasing film thickness the free volume increases in good agreement with an increase in the maximum swelling capability of the nbc-PNIPAM films. Thus in thin hydrogel films the sorption and swelling behavior is governed by free volume.
ABSTRACT
Using a radiotracer technique, we have measured the isotope effect E = dln(D)/dln(m(1/2)) of Co diffusion in CoxZr1-x glasses for 0. 31
ABSTRACT
Starting with the hypothesis that children's aggressive and potentially violent behavior is the climax of escalating conflicts that cannot be expressed or showed in any other way, we analyse, in the following article, the conditions from which these behavior pattern arise. We have focused on the following areas; the individual, the family, the school and society, and we have tried to show how the development of children's aggressive behavior is determined by the problem constellations in these different contexts. Insecure and disorganised early bonding experiences and/or dysfunctional family relationship patterns combined with parental upbringing methods that support or condone aggressive behavior, can lead to children having fewer resources or social skills available than their peers in kindergarten and school. This may result in conflict and lack of social integration in these institutions.
Subject(s)
Aggression/psychology , Personality Development , Socialization , Violence/psychology , Adolescent , Adult , Child , Child, Preschool , Humans , Infant , Parenting/psychology , Risk Factors , Social EnvironmentABSTRACT
FAUSTLOS is a curriculum that has been developed for the prevention of aggression and potentially violent behavior in children in nursery and primary school. A lack of social skills is regarded as one of the fundamental causes that deteriorates problem and conflict solving. FAUSTLOS is the German version of an American program called Second Step that has been developed by the Committee for Children in Seattle and has been successfully put into practice in several American states over the last eight years. The project "Kinder und Gewalt" has adapted it for the German speaking countries. FAUSTLOS is at present in its pilot phase. The following is a general survey of the inception, contents and methods of the curriculum and the planning and execution of the pilot phase.
