The use of photon activation analysis for the determination of Sm,Eu, Gd and Dy in boron carbide

An installation for photon activation analysis recently completed at CBNM, Geel, is described. Synthetic standards prepared from pure graphite are used for the non-destructive determination of lanthanides in boron carbide. The induced activities of¹⁵³Sm,^152mEu,¹⁵⁹Gd and¹⁵⁷Dy were measured using a single open-ended coaxial Ge(Li) detector and the photopeak areas were calculated using the GAFIT program. For the irradiation parameters used, the limits of detection are communicated. This paper has been presented at the 5th Symposium on the Recent Developments in Activation Analysis. 17th–21st July, 1978, St. Catherine's College, Oxford.     

Synthesis of novel pyrrolidin-2-ones: γ-aminobutyric acid cyclic analogues

Some new N-substituted pyrrolidin-2-ones, cyclic analogues of baclofen and of 3-(5-methoxybenzo-[b]furan-2-yl)-γ-aminobutyric acid, have been prepared and characterized, starting from 4-(4-chlorophenyl)-pyrrolidin-2-one and 4-(5-methoxybenzo[b]furan-2-yl)pyrrolidin-2-one.     

Affinity chromatography study of magnesium and calcium binding to human serum albumin: pH and temperature variations

The magnesium and calcium binding on human serum albumin (HSA) was studied using an affinity chromatography approach. The effects of the mobile phase pH, its ionic strength and column temperature on the transfer equilibrium constants were studied. The thermodynamic data corresponding to the electrostatic interactions occurring during the HSA-ion binding were determined. Enthalpy-entropy compensation revealed that the ion binding mechanism at HSA was independent of the ionic strength, the same at four pH values (6.5, 8, 8.5 and 9), but presented a weak change at physiological pH around 7-7.5 due to a HSA phase transition. A theoretical model based on the Gouy-Chapman theory allows to determine the relative charge density of the HSA surface implied in the binding process and the variation of the number of ions bound to one albumin molecule with the pH.     

Control of transient chaos in tent maps near crisis. II. Periodic orbit targeting

Recent work on a symbolic approach to the calculation of probability distributions arising in the application of the Ott-Grebogi-Yorke strategy to transiently chaotic tent maps is extended to the case of control to a nontrivial periodic orbit. Closed forms are derived for the probability of control being achieved and the average number of iterations to control when it occurs. Both single-component and multiple-component targeting are considered, and illustrative examples of the results obtained are presented.     

C1‐Linked Spirobifluorene Dimers: Pure Hydrocarbon Hosts for High‐Performance Blue Phosphorescent OLEDs

Reported here are C1‐linked spiro‐bifluorene dimers. A comprehensive study is carried out to analyze the electronic properties of these highly twisted structures. This work shows that the C1‐position enables the design of pure hydrocarbon materials, with a high triplet energy, for hosting blue phosphors in efficient phosphorescent OLEDs (PhOLEDs). To date, this work describes the highest performance of blue PhOLEDs ever reported for pure hydrocarbons (external quantum efficiency of ca. 23 %), thus highlighting the potential of the C1‐spirobifluorene scaffold in organic electronics.     

Donor/Acceptor Dihydroindeno[1,2‐a]fluorene and Dihydroindeno[2,1‐b]fluorene: Towards New Families of Organic Semiconductors

New families of donor/acceptor semiconductors based on dihydroindeno[1,2‐a]fluorene and dihydroindeno[2,1‐b]fluorene are reported. Due to the spiro bridges, this new generation of dihydroindenofluorenes allows a spatial separation of HOMO and LUMO, which retains the high E_T value of the dihydroindenofluorene backbone and excellent physical properties. This control of the electronic and physical properties has allowed a second generation of dihydroindeno[1,2‐a]fluorene to be obtained with strongly enhanced performance in green and sky‐blue phosphorescent organic light‐emitting diodes (PhOLEDs) relative to the first generation of materials. To date, this is the highest performance ever reported for a blue PhOLED by using a dihydroindenofluorene derivative. Through this structure–property relationship study, a remarkable difference of performance between syn and anti isomers has also been highlighted. This surprising behaviour has been attributed to the different symmetry of the two molecules, and highlights the importance of the geometry profiles in the design of host materials for PhOLEDs.     

9H‐Quinolino[3,2,1‐k]phenothiazine: A New Electron‐Rich Fragment for Organic Electronics

A new electron‐rich fragment, namely the quinolinophenothiazine (QPTZ) is reported. The QPTZ fragment incorporated in spiroconfigured materials leads to higher performance in blue Phosphorescent OLEDs than structurally related phenylacridine and indoloacridine based materials (increasing the HOMO energy level, modulating the spin‐orbit coupling, etc.) and leads to highly efficient blue phosphorescent organic light emitting diodes, indicating the strong potential of this new molecular fragment in organic electronics.     

The investigation of the mannich reaction of 4,5-dimethyl-1,2-dithiole-3-thione

4,5-Dimethyl-1,2-dithiole-3-thione 1 reacts with primary amines and formaldehyde to give the mono-, retro-, bis-Mannich bases in moderate yield.     

Ueber die Verbindungen der Kohlenwasserstoffe mit der Pikrins?ure und ihre Anwendung in der Analyse

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