The effect of alkaline treatment of shrimp chitin on the molecular weight, the degree of deacetylation and degree of crystallinity of the resulting chitosan is studied. The viscosity of chitosan solutions from repeatedly deacetylated chitin is studied. It is shown that repeated treatment of chitin/chitosan with alkali causes the destruction of polysaccharide macromolecules. After four-time deacetylation and one-time deacetylation of chitin/chitosan for four hours, the molecular weight of the polysaccharide decreases by ten times. The maximum degree of chitosan deacetylation under experimental conditions was 92.0 -92.5%. The diffractograms of chitin and chitosan from the Northern shrimp are of the form typical for samples containing an amorphous phase in addition to a crystalline phase. The degree of crystallinity of chitin from Northern shrimp was 40.8%, of chitosan samples after one-, two-, and three-time deacetylation was 62-65%. For a sample of chitosan obtained after four-time deacetylation, recrystallization, and drying in a freeze dryer, the degree of crystallinity is close to the degree of crystallinity of shrimp chitin. The investigated acetic acid chitosan solutions with a concentration of 5% (wt.) and the chitosan molecular weight of 250, 160 and 130 kDa in their rheological properties are liquid-like non-Newtonian systems, their viscosity decreasing with increasing shear stress. After four-time deacetylation of chitin, the viscosity of chitosan solutions practically does not change with increasing shear stress, which apparently can be due to a significant decrease in the molecular weight of chitosan under these conditions.
This article presents a computational approach to examining immigrant incorporation through shifts in the social “mainstream.” Analyzing a historical corpus of American etiquette books, texts from 1922–2017 describing social norms, we identify mainstream shifts related to long-standing groups which once were and may currently still be seen as immigrant outsiders in the United States: Catholic, Chinese, Irish, Italian, Jewish, Mexican, and Muslim groups. The analysis takes a computational grounded theory approach, combining qualitative readings and computational text analyses. Using word embeddings, we operationalize the chosen groups as focal group concepts. We extract sections of text that are salient to the focal group concepts to create group-specific text corpora. Two computational approaches make it possible to examine mainstream shifts in these corpora. First, we use sentiment analysis to observe the positive sentiment in each corpus and its change over time. Second, we observe changes in each corpus's position on a semantic dimension represented by the poles of “strange” and “normal.” The results indicate mainstream shifts through increases in positive sentiment and movement from strange to normal over time for most of the group-specific corpora. These research techniques can be adapted to other studies of social sentiment and symbolic inclusion.
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