On cellulose dissolution and gelation

Cellulose is the World’s most abundant biopolymer and an important renewable raw material for many materials. For applications like textile fibers it is necessary to first dissolve the cellulose pulp. However, dissolving cellulose turns out to be a challenge. This crystalline polymer is insoluble in most classical polar and non-polar solvents, but soluble in certain ionic liquids and also (partly) in concentrated NaOH. Replacing sodium with the larger and more hydrophobic/amphiphilic tetrabutyl ammonium cation, increases the solubility. Cellulose solutions can turn into gels. The reason for this appears to involve the issue of crystal polymorphism. While natural (wood) cellulose, so called Cellulose I dissolves, solutions may become supersaturated with respect to the more stable Cellulose II. Recrystallizing polymers from semi-dilute solutions may lead to gelation as chains can participate in more than one nucleus

Ossification of ungular cartilages in front feet of cold-blooded trotters - a clinical radiographic evaluation of development over time

BACKGROUND: It has not yet been shown that ossification of ungular cartilages (OUC) is a pathological condition. Beside heredity, factors such as sex, age, repeated concussion, local trauma, hoof and body size have been suggested as contributing factors for OUC development. By comparing radiographs of front hooves from cold-blooded trotters with different age we wanted to evaluate when development of OUC in cold-blooded trotters occurs and if and when it stabilizes in relation to age and workload. Diagnosis and grading of OUC were based on radiological field examinations of 649 Swedish and Norwegian cold-blooded trotters’ front hooves. A hundred and forty-seven of the horses were re-examined 3-13 years (mean age 9, median 8 years) after the first occasion. All radiographs were evaluated blind, using two different grading systems for OUC. Work load, in form of number of races completed, and body size score were collected from official data. Four statistical ordinal regression models were used, compared and evaluated. RESULTS: We identified a breakpoint at 2.8 ± 0.38 years of age when ossification ends and proposed a simpler grading system with more consistent results. There was no significant correlation between body size and grade of OUC. Comparison of different statistical methods for evaluation of ordinal data revealed a piecewise linear regression model as most suitable. CONCLUSIONS: Individuals with OUC developed this condition during the stage of life when their hooves develop in size. Results from this study can assist equine practitioners when examining and for understanding this condition in their clinical work and is also beneficial for the Scandinavian equine industry when devising breeding programs

The Nordic countries and Europe in the twentieth century : an introduction

Aineisto on Opiskelijakirjaston digitoimaa ja Opiskelijakirjasto vastaa aineiston käyttöluvist