3 resultados para granular

em Memorial University Research Repository


Relevância:

20.00% 20.00%

Publicador:

Resumo:

A large series of laboratory ice crushing experiments was performed to investigate the effects of external boundary condition and indenter contact geometry on ice load magnitude under crushing conditions. Four boundary conditions were considered: dry cases, submerged cases, and cases with the presence of snow and granular ice material on the indenter surface. Indenter geometries were a flat plate, wedge shaped indenter, (reverse) conical indenter, and spherical indenter. These were impacted with artificially produced ice specimens of conical shape with 20° and 30° cone angles. All indenter – ice combinations were tested in dry and submerged environments at 1 mm/s and 100 mm/s indentation rates. Additional tests with the flat indentation plate were conducted at 10 mm/s impact velocity and a subset of scenarios with snow and granular ice material was evaluated. The tests were performed using a material testing system (MTS) machine located inside a cold room at an ambient temperature of - 7°C. Data acquisition comprised time, vertical force, and displacement. In several tests with the flat plate and wedge shaped indenter, supplementary information on local pressure patterns and contact area were obtained using tactile pressure sensors. All tests were recorded with a high speed video camera and still photos were taken before and after each test. Thin sections were taken of some specimens as well. Ice loads were found to strongly depend on contact condition, interrelated with pre-existing confinement and indentation rate. Submergence yielded higher forces, especially at the high indentation rate. This was very evident for the flat indentation plate and spherical indenter, and with restrictions for the wedge shaped indenter. No indication was found for the conical indenter. For the conical indenter it was concluded that the structural restriction due to the indenter geometry was dominating. The working surface for the water to act was not sufficient to influence the failure processes and associated ice loads. The presence of snow and granular ice significantly increased the forces at the low indentation rate (with the flat indentation plate) that were higher compared to submerged cases and far above the dry contact condition. Contact area measurements revealed a correlation of higher forces with a concurrent increase in actual contact area that depended on the respective boundary condition. In submergence, ice debris constitution was changed; ice extrusion, as well as crack development and propagation were impeded. Snow and granular ice seemed to provide additional material sources for establishing larger contact areas. The dry contact condition generally had the smallest real contact area, as well as the lowest forces. The comparison of nominal and measured contact areas revealed distinct deviations. The incorporation of those differences in contact process pressures-area relationships indicated that the overall process pressure was not substantially affected by the increased loads.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Heat shock factor 1 (Hsf1) is a protein known to be involved in both stress and developmental processes through the regulation of heat shock proteins. However, to date, no studies have been performed on examining its expression in the myometrium during pregnancy. During pregnancy, the uterus undergoes many structural and functional changes, and it also endures both mechanical and hormonal stresses. Therefore, the purpose of this thesis was to characterize the expression of Hsf1, and its associated factors in the uterus during pregnancy. Immunoblot analysis determined that Hsf1 protein expression was high early in gestation (day (d) 6) and then decreased significantly from mid gestation onwards (specifically when compared to d15, d17 and d22, p<0.05, n=5). Immunofluorescence analysis, demonstrated that Hsf1 was readily detectable in the myometrium but did not markedly change over gestation. Hsf1 was also localized mainly in the cytoplasm of myometrial cells, with some granular staining in the nucleus. Many related proteins of Hsf1 were also detectable in the myometrium, during pregnancy, such as PARP-1 and Hsf2. These results indicate that Hsf1 could play an important role early in gestation either to aid in myometrial cell proliferation or to upregulate expression of key genes necessary for subsequent myometrial differentiation.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Hemocytes of the insects Lambdina fiscellaria fiscellaria and Choristoneura fumiferana did not adhere to the protoplasts of ~he fungus EntomoEhthora egressa. Hemocyte reaction for both insect species to test-particles was not suppressed by the protoplasts. The spherule cells of _-L. fiscellaria fiscellaria adhered to the spherical hyphal bodies and hyphae of ~· ~gressa. The granular cells of -c. fumiferana adhered to the hyphae of ~· egress~. Protoplasts exposed to papain were attacked by the granular ·cells of -c. fumiferana. Spent growth medium of both protoplast isolates produced paralysis when injected into -c. fumiferana larvae. Evidence suggests that heat-stable proteins may be involved. Protoplast isolates showed differences in the growth rates and regeneration sequences using coagulated egg yolk medium, a highly modified version of Grace's insect tissue . culture medium (MGM) and modifications of MGM and in the presence of C0₂. The isolates also differed in the changes that they induced in MGM composition during protoplast growth and in the rates of glucose utilization and protein secretion. The serum of c. fumiferana larvae contained protein(s) which we believe adhere to the cell membranes of the protoplasts of E. egressa. Evidence is presented for hemocyteplasn~ interaction in the presence of protoplasts. Components in the larval serum were found to influence protoplast growth patterns. The possibility of antiprotoplast serum activity is presented. Melanin, toxic levels of ninhydrinpositive compounds and antiprotoplast proteins may have been involved in this activity. The granular cells of -L. fiscellaria fiscellaria and Q• fumiferana adhered to the hyphae of ,Rhizopus ~i$rican~. Spores of Absidia repens and the bacteria Escherichia coli and Bacillus cereus adhered to the granular cells of both species of· insects. The granular cells and plasmatocytes of -c. fumiferana were capable of phagocytosing -B. cereus. Adhesion of .A... . repens spores to c. fumiferana granular cells ~ . - was stimulated by N-acetylglucosamine and glucosamine, moderately reduced by D-fucose, D-arabinose, D-mannose, D-galatose and sucrose and mildly reduced by D-glucose, D-fructose and trehalose. There was no evidence of humoral opsonins in larval hemolymph favoring test-particle-hemocyte interaction. Granular cells of c. fumiferana exposed to papain had reduced affinities for A. repens spores.