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Schrifttumsberichte

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Schrifttumsberichte

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High Tg hole transport polymers for the fabrication ofbright and efficient organic light-emitting devices with an air-stablecathode

An organic electroluminescent device with a luminous efficiency of 20 Im/W, at 14 cd/m², and an external quantum efficiency of 4.6% has been fabricated using a high T_g hole transport polymer, a small molecule emission layer, and a LiF/Al cathode. The device quantum efficiency can be increased by tuning the ionization potential of the hole-transport moieties. When tested under pulsed voltage mode, in air at room temperature, and without any encapsulation, the device showed a high peak brightness of 4.4×10⁶ cd/m² at 100 A/cm² and an efficiency of 4.4 cd/A     

Schrifttumsberichte

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Glucose-dependent insulin response and milk production in heifers within a segregating resource family population

An experiment was initiated to evaluate the glucose-dependent insulin response in relation to milk production in F₂ crossbred cattle with respect to secretion type (Holstein) and accretion type (Charolais). For this purpose, F₂ offspring were generated by mating Charolais bulls with German Holstein cows and a following intercross of the F₁ individuals. In 52 dairy heifers of 5 F₂ half-sib families, glucose-dependent insulin responses were investigated during first lactation to test the hypothesis that the different genetic disposition for milk production within the F₂ population would affect the insulin response to glucose. Heifers received intravenous glucose infusions (1 g/kg of BW^0.75) 10 d before, and 30 and 100 d after parturition. Blood samples were taken before and at 7, 14, 21, and 28 min after glucose challenge. Glucose and insulin concentrations were measured in blood, and glucose half-life as well as areas under the curve for glucose (AUC_gluc) and insulin (AUC_ins) were calculated. Milk yield was low but differed among F₂ families. Before parturition, insulin concentrations after glucose challenge showed no between-family differences for AUC_ins. In contrast, on d 30 and 100 of lactation, glucose half-life and AUC_ins differed among families. Calculated correlations revealed a significant negative relationship between AUC_ins and milk yield as well as glucose half-life on d 30 and 100 of lactation. In conclusion, milk production as well as the glucose-dependent insulin response of F₂ Charolais × German Holstein crossbred dairy heifers differed between half-sib families, with both parameters displaying an inverse relation to each other.     

Effect of Carbon‐Based Materials on the Early Hydration of Tricalcium Silicate

Two types of carbon‐based materials, i.e., mesoporous carbon and HNO₃‐oxidized carbon nanotubes, with nearly the same specific surface area and abundant in surface oxygen‐containing functional groups were selected in order to examine their effect on the hydration of tricalcium silicate (C₃S), the main portland cement component, in early stages. Different methods, including XPS and TG‐MS analyses, electrokinetic potential measurements, as well as determination of adsorption capacity for calcium ions from aqueous solutions, were used to investigate the physicochemical surface properties of the selected carbon‐based materials. It was found that the carbon‐based materials with high specific surface area and rich in oxygen‐containing functional groups on their surfaces have a catalytic effect on early C₃S hydration. It was observed that the modification of C₃S paste with the selected materials added in high concentrations (1 wt% and higher) led to an increase in the rate and degree of C₃S hydration in the early stages. The mechanism of early C₃S hydration accelerated by carbon‐based materials rich in surface functional groups was clarified by the example of the mesoporous carbon. It was found that the oxygen‐containing functional groups present on the carbon surface have both an influence on the content of calcium ions in the aqueous phase of the C₃S paste and an indirect positive effect in relation to the specific surface of C₃S.