On what Terms and why the Thermodynamic Properties of Polymer Solutions Depend on Chain Length up to the Melt

Theoretical considerations based on chain connectivity and conformational variability of polymers have lead to an uncomplicated relation for the dependence of the Flory-Huggins interaction parameter, chi, on the volume fraction of the polymer, phi, and on its number of segments, N. The validity of this expression is being tested extensively by means of vapor pressure measurements and inverse gas chromatography (complemented by osmotic and light scattering data from literature) for solutions of poly(dimethylsiloxane) in the thermodynamically vastly different solvents n-octane (n-C8), toluene (TL), and methylethylketone (MEK) over the entire range of composition for at least six different molecular masses of the polymer. The new approach is capable to model the measured chi (phi, N) very well, irrespective of the thermodynamic quality of the solvent, in contrast to traditional expressions, which are often restricted to good solvents but fail for bad ones and vice versa. At constant polymer concentration the chi values result lowest for n-C8 (best solvent) and highest for MEK (theta solvent); the data for TL fall between. The influences of N depend strongly on the thermodynamic quality of the solvent and are not restricted to dilute solutions. For good solvents chi increases with rising N. The effect is most pronounced for n-C8, where the different curves for chi (phi) fan out considerably. The influences of N become less distinct for TL, and for MEK they vanish at the (endothermal) theta temperature. For worse than theta conditions, the chi values of the long chains become less than that of short ones. This change in the sign of N-influences is in agreement with the present concept of conformational relaxation

Iowa\u27s Changing Forest Resources

After a period of decline in area extending from the 1850s to 1974, Iowa\u27s forest area increased between 1974 and 1990. Although the area increase is encouraging, it may be fleeting. In addition, changes in forest stand structure and forest ownership patterns along with other pressures may make it difficult to maintain healthy forest ecosystems in the future. Notes from the original land survey in Iowa coupled with information from U.S. Forest Service forest inventories make it possible to look at changes in forest area and forest tree types. Unfortunately, similar long-term data do not exist to make possible a comparison of changes in other species associated with the forest. For that reason, this paper looks primarily at those commercial and non-commercial tree species that have been assessed during U.S. Forest Service inventories conducted in Iowa

Structure and dynamics of colloidal depletion gels: coincidence of transitions and heterogeneity

Transitions in structural heterogeneity of colloidal depletion gels formed through short-range attractive interactions are correlated with their dynamical arrest. The system is a density and refractive index matched suspension of 0.20 volume fraction poly(methyl methacyrlate) colloids with the non-adsorbing depletant polystyrene added at a size ratio of depletant to colloid of 0.043. As the strength of the short-range attractive interaction is increased, clusters become increasingly structurally heterogeneous, as characterized by number-density fluctuations, and dynamically immobilized, as characterized by the single-particle mean-squared displacement. The number of free colloids in the suspension also progressively declines. As an immobile cluster to gel transition is traversed, structural heterogeneity abruptly decreases. Simultaneously, the mean single-particle dynamics saturates at a localization length on the order of the short-range attractive potential range. Both immobile cluster and gel regimes show dynamical heterogeneity. Non-Gaussian distributions of single particle displacements reveal enhanced populations of dynamical trajectories localized on two different length scales. Similar dependencies of number density fluctuations, free particle number and dynamical length scales on the order of the range of short-range attraction suggests a collective structural origin of dynamic heterogeneity in colloidal gels.Comment: 14 pages, 10 figure

Loss of solutions in shear banding fluids in shear banding fluids driven by second normal stress differences

Edge fracture occurs frequently in non-Newtonian fluids. A similar instability has often been reported at the free surface of fluids undergoing shear banding, and leads to expulsion of the sample. In this paper the distortion of the free surface of such a shear banding fluid is calculated by balancing the surface tension against the second normal stresses induced in the two shear bands, and simultaneously requiring a continuous and smooth meniscus. We show that wormlike micelles typically retain meniscus integrity when shear banding, but in some cases can lose integrity for a range of average applied shear rates during which one expects shear banding. This meniscus fracture would lead to ejection of the sample as the shear banding region is swept through. We further show that entangled polymer solutions are expected to display a propensity for fracture, because of their much larger second normal stresses. These calculations are consistent with available data in the literature. We also estimate the meniscus distortion of a three band configuration, as has been observed in some wormlike micellar solutions in a cone and plate geometry.Comment: 23 pages, to be published in Journal of Rheolog

KULTUREL DYNAMIK I OPLEVELSESBYRUMMET – EN ANALYSE AF BRANDTS KLÆDEFABRIK

CULTURAL DYNAMIC IN THE URBAN EXPERIENCE SCAPE – AN ANALYSIS OF BRANDTS KLÆDEFABRIKBrandts Klædefabrik (Brandt’s Textile Mill) is a cultural cluster in the city of Odense, Denmark. The cultural experiences available at Brandts Klædefabrik cover a wide field and are relevant for people of all levels of education and all ages, embracing as they do not only fine culture but also triviality and excitement. Brandts Klædefabrik is therefore a culturally inclusive place, although its symbolic power is dominated by a cultural and economic elitetrying to maintain an exclusively controlled social and physical order in the urban space. However, Brandts Klædefabrik is part of a city which contains a wide range of cultural groups: a Danish cultural elite, immigrants, homeless people and drug addicts. In this cultural multiplicity Brandts Klædefabrik is a cultural cluster and an urban entertainment district which does not include marginalised groups. Paradoxically, the attempt to maintainan exclusive order to satisfy an audience with buying power runs against the creative profile of the area, in which cultural and social multiplicity are important values. The area around Brandts Klædefabrik is a public space; but if it is going to be a public domain and the scene of cultural exchanges between different groups in the city, it needs to become more culturally inclusive. Brandts Klædefabrik may turn into a public domain if a cultural dynamic and multiplicity are given the chance to unfold there

Kulturformidling i de regionale kulturaftaler: Demokratiets og deltagelsens kompleksitet

Formålet med artiklen er på baggrund af Cultural Policy Studies (Bennett 2013) at diskutere forholdet mellem demokrati (Biesta 2014; Habermas 1989; Rancière 2003) og deltagelse (Rancière 2004; Rogoff 2005; Sternfeld 2013) i to regionale kulturformidlingsprojekter i Danmark. De regionale kulturaftaler, KulturMetropolØresund og Kulturregion Fyn, er en del af kulturpolitiske visioner om at demokratisere formidling af kunst og kultur både geografisk og socialt (Kulturministeriet 2007). ”Steder i Ishøj. Steder i mig” og ”Lyden af Fyn” er to eksempler på nye kulturformidlingsprojekter under de regionale kulturaftaler. Fælles for projekterne er, at de er knyttet til borgernes deltagelse. I artiklen argumenterer jeg for, at kulturformidlingsprojekterne på den ene side er udtryk for governmentality (Foucault 1982; 1991) ved at forsøge at styre deltagernes adfærd. På den anden side opstår der sprækker af ”dissens” og ”subjektivering” i projekterne (Rancière 2003). Der skal ganske lidt til, før deltagerne agerer anderledes end forventet og fortolker projekternes kulturelle værdier på deres egne præmisser. De to eksempler illustrerer betydningen af refleksioner over begreberne, og hvordan de operationaliseres. Sådanne refleksioner kan både bidrage til at udvikle teorier om kulturel deltagelse og skabe et bedre udgangspunkt for udviklingen af demokratisk kulturformidling.This article is based on Cultural Policy Studies (Bennett 2013) and discusses the relation between democracy (Biesta 2014; Habermas 1989; Rancière 2003) and participation (Rancière 2004, Rogoff 2005, Sternfeld 2013) in two contemporary regional cultural communication projects in Denmark. The regional cultural agreements, CultureMetropolisOresund and Cultural Region Funen, are part of cultural political visions of making the communication of art and culture more democratic both geographically and socially (The Ministry of Culture 2007). “They are two examples of contemporary cultural communication projects within the regional cultural agreements, and they are both concerned with the value of participation of the citizens. In the article I argue that the cultural communication projects on one hand show evidence of governmentality (Foucault 1982; 1991) and try to control the conduct of the participants. On the other hand cracks of “dissensus” and subjectification emerge in the projects (Rancière 2003), when participants act differently than expected and interpret the cultural value of the projects on their own terms. The two cases illustrate the importance of reflections on the basic concepts and how they are operationalized. Such reflections can help develop theories on cultural participation and create a stronger basis for the development of democratic cultural communication

Kulturformidling i de regionale kulturaftaler: Demokratiets og deltagelsens kompleksitet

Formålet med artiklen er på baggrund af Cultural Policy Studies (Bennett 2013) at diskutere forholdet mellem demokrati (Biesta 2014; Habermas 1989; Rancière 2003) og deltagelse (Rancière 2004; Rogoff 2005; Sternfeld 2013) i to regionale kulturformidlingsprojekter i Danmark. De regionale kulturaftaler, KulturMetropolØresund og Kulturregion Fyn, er en del af kulturpolitiske visioner om at demokratisere formidling af kunst og kultur både geografisk og socialt (Kulturministeriet 2007). ”Steder i Ishøj. Steder i mig” og ”Lyden af Fyn” er to eksempler på nye kulturformidlingsprojekter under de regionale kulturaftaler. Fælles for projekterne er, at de er knyttet til borgernes deltagelse. I artiklen argumenterer jeg for, at kulturformidlingsprojekterne på den ene side er udtryk for governmentality (Foucault 1982; 1991) ved at forsøge at styre deltagernes adfærd. På den anden side opstår der sprækker af ”dissens” og ”subjektivering” i projekterne (Rancière 2003). Der skal ganske lidt til, før deltagerne agerer anderledes end forventet og fortolker projekternes kulturelle værdier på deres egne præmisser. De to eksempler illustrerer betydningen af refleksioner over begreberne, og hvordan de operationaliseres. Sådanne refleksioner kan både bidrage til at udvikle teorier om kulturel deltagelse og skabe et bedre udgangspunkt for udviklingen af demokratisk kulturformidling.This article is based on Cultural Policy Studies (Bennett 2013) and discusses the relation between democracy (Biesta 2014; Habermas 1989; Rancière 2003) and participation (Rancière 2004, Rogoff 2005, Sternfeld 2013) in two contemporary regional cultural communication projects in Denmark. The regional cultural agreements, CultureMetropolisOresund and Cultural Region Funen, are part of cultural political visions of making the communication of art and culture more democratic both geographically and socially (The Ministry of Culture 2007). “They are two examples of contemporary cultural communication projects within the regional cultural agreements, and they are both concerned with the value of participation of the citizens. In the article I argue that the cultural communication projects on one hand show evidence of governmentality (Foucault 1982; 1991) and try to control the conduct of the participants. On the other hand cracks of “dissensus” and subjectification emerge in the projects (Rancière 2003), when participants act differently than expected and interpret the cultural value of the projects on their own terms. The two cases illustrate the importance of reflections on the basic concepts and how they are operationalized. Such reflections can help develop theories on cultural participation and create a stronger basis for the development of democratic cultural communication