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At least 1,351 records · Page 75Linked to original sources
PubMed2006

Insight into the molecular arrangement of high-density polyethylene polymer chains in blends of polystyrene/highdensity polyethylene from differential scanning calorimetry and Raman techniques.

Polystyrene/high-density polyethylene (PS/HDPE) blends were synthesized by melt blending in a single screw extruder. Co-continuity measurements using solvent extraction and scanning electron (SEM) micrographs showed that co-continuity was obtained around 35% PS. Thermal analyses measurements revealed a reduction in crystallinity of the HDPE phase around the co-continuous composition. Raman analyses across the entire composition range of these blends showed an increase in the normalized integral intensities of the 1128 cm(-1) and 1061 cm(-1) stretching vibrations of the HDPE molecules. The presence of all-trans HDPE chains that are not packed into an orthorhombic structure is used to explain the simultaneous occurrence of reduced crystallinity and increased intensity of all-trans HDPE stretch vibrations.

Journal Article↗
PubMedDate not supplied

Profiling cryopreservation protocols for Ribes ciliatum using differential scanning calorimetry.

DSC analysis was performed at three points in the cryopreservation process on encapsulated-dehydrated meristems of Ribes ciliatum. Meristems were excised from shoots pre-treated with either sucrose or glucose, encapsulated in alginate beads, dehydrated in sucrose solutions, air dried, and plunged in liquid nitrogen. Thermal analysis revealed glass transitions during cooling of air-desiccated meristems, however, on rewarming a small endothermic event was detected suggesting glass destabilization can occur. Interestingly, this did not occur in alginate beads or meristems when these components were cooled and rewarmed separately. The possibility exists that thermal and moisture gradients may arise within the alginate bead/tissue complex and we propose that the heterogeneous composition of the meristems and the surrounding alginate may promote ice nucleation on rewarming. The significance of this regarding the stabilization of glasses formed in alginate beads and their encapsulated meristems is discussed. This study also reports an approach to Ribes cryopreservation in which the pregrowth of shoots in 0.75M sucrose for 1 week can be used as a substitute for cold acclimation.

Journal Article↗
PubMedDate not supplied

Glucose disposal in obese non-diabetic and diabetic type II patients. A study by indirect calorimetry and euglycemic insulin clamp.

Insulin resistance is a characteristic finding in obesity and in non insulin dependent (Type II) diabetes mellitus. However, the interaction between diabetes and obesity has been poorly characterized and the metabolic disturbances contributing to the defect in insulin-mediated glucose uptake have not been defined. To examine these questions euglycemic and hyperinsulinemic clamp studies (40 mU/m2/min) were performed in 10 control non-obese subjects, 10 non diabetic obese subjects, 8 normal weight Type II diabetics, and 12 obese Type II diabetics. During the insulin clamp study total body glucose uptake in the obese non diabetics (157 +/- 18 mg/m2.min, p less than 0.01), the normal weight diabetics (159 +/- 21, p less than 0.01) and the obese diabetics (125 +/- 11, p less than 0.001) was significantly reduced compared to the non-obese non diabetic control group (249 +/- 22 mg/m2.min). The impairment in total body glucose uptake was the result mainly of a defect in non-oxidative glucose disposal. Indeed non-oxidative glucose disposal was blunted by 50% in the obese groups (p less than 0.01), somewhat less significantly in the non-obese diabetic group (p less than 0.05) but more when obesity and diabetes mellitus were combined (p less than 0.001). Total glucose oxidation was significantly diminished (p less than 0.01) in both diabetic groups but not in the obese non diabetic group when compared to lean control. A significant inverse correlation between the fasting free fatty acids levels and total glucose uptake (r = -0.453, p less than 0.001) and total glucose oxidation (r = -0.446, p less than 0.001) during the clamp was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

[Distribution and constitutional changes of edema fluid in cytotoxic brain edema analyzed by electron microscopy and differential scanning calorimetry].

To understand the pathogenesis of brain edema, we studied distribution and constitutional changes of brain-tissue water by morphological and thermoanalytical methods in cytotoxic brain edema induced by 6-aminonicotinamide (6-ANA). Ninety-two Wistar rats were divided into three groups; Group I rats receiving physiological salt solution intraperitoneally served as controls. Group II and III animals were intraperitoneally given 120 mg/kg and 36 mg/kg of 6-ANA respectively. All animals were starved after injection of drugs to exclude differences in water intake. Then they were decapitated at 3, 6, 12, 24, 36 or 48 hours to measure specific gravity (SG) of large brain tissue (1.1-1.5 g), and to evaluate water content (WC) and free water ratio (FWR) of small brain-tissue samples (15-35 mg) taken from the frontal cortex; WC was measured by a drying-weighing method, and FWR was analyzed with a differential scanning calorimeter. Moreover morphological changes of the frontal cortex of the brain were studied in Group II (n = 12) at 3, 6, 12, 24 and 48 hours with an electron microscope. Neurological status of animals administered 6-ANA (Group II and III) deteriorated with time. Morphological studies showed that perivascular astrocytes and astrocytic processes in the cerebral cortex were swollen most remarkably at 48 hours. However neuronal and endothelial cells were almost intact. The FWR of Group I decreased significantly about four per cent (p less than 0.001) after being starved for 48 hours. But the SG and WC of the group showed little change.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Aminonicotinamide↗
PubMed1981

[Variations in carbohydrate, lipid and protein oxidation evaluated by indirect calorimetry in obese subjects on a "single-meal" low-calorie diet].

Four obese patients were given a single-meal diet (Kcal, 684) for two periods of three days each. CO2 production and 02 consumption were measured every four hours for 30'. At the same times urine samples were collected for nitrogen evaluations. By Consolatio's formulas the amount of carbohydrates, lipids and proteins oxidated in the three days of both periods was calculated. No changes in carbohydrate and lipid oxidation rates were found during the three days with meal at h.10, while a progressive increase in lipid oxidation and a progressive decrease in carbohydrates oxidation could be observed with meal at h. 18. No change with both regimes could be observed in protein oxidation. Furthermore a circadian rhythm of lipid and carbohydrate oxidation with both regimens was observed, while protein oxidation showed a circadian rhythm only with meal at h.10.

Adult↗