Blue photo‐ and electroluminescence based on poly(2‐benzoyl‐1,4‐phenylene) and poly(2,5‐dibenzoyl‐1,4‐phenylene)

Poly(2‐benzoyl‐1,4‐phenylene) (PBP) and poly(2,5‐dibenzoyl‐1,4‐phenylene) (PDBP) were synthesized by coupling polymerization using a Ni catalyst of 2,5‐dichlorobenzophenone and 2,5‐dichloro‐1,4‐dibenzophenone, respectively. These polymers are soluble in common organic solvents, have high thermal stability and show bright blue photoluminescence. Light‐emitting diodes fabricated with these polymers as the active layer emit blue electroluminescence with wavelength at 433 nm for PBP and 475 nm for PDBP. Copyright © 1999 John Wiley & Sons, Ltd.     

Heat-induced effective exchange coupling in magnetic multilayers with semiconductors

Two ferromagnetic films separated by an amorphous semiconducting spacer layer are exchange coupled across the spacer. The coupling is reversibly temperature dependent with a positive temperature coefficient making such layered systems a 2-D realization of the concept of heat-induced magnetism. By studying ferromagentic Fe layers separated by amorphous Si, Ge, or ZnSe layers we explore the possibilities to generate such an effective exchange coupling and address the question of the mechanism responsible for it.     

Nucleophilic displacement of aromatic fluorine,Part II Indazoles,indazolo[2,3-c]quinazolines,indazolo[2,3-d] [1,4]benzodiazepines and indazolo[2,3-c]benzo-1,2,3-triazenes

3-(2-Arninophenyl)indazoles 2 were prepared by the reaction of the o-fluorobenzophenones 1 with hydrazines. These indazoles were converted to the tetracyclic title compounds by conventional methods.     

Quinazolines and 1,4-benzodiazepines LVII. 1H-1,4-benzodiazepines

The preparation of the title compounds 3 and 4 using two different methods of synthesis is described. These compounds are readily reduced to 2,3-dihydro-1H-derivatives 5 . Oxidation of 2-alkylthio-1H-1,4-benzodiazepines leads to the corresponding sulfoxides and sulfones. The oxidative rearrangement of sulfones 9 to a 2H-1,4-benzodiazepin-2-one derivative 10 is also given. The “normal” addition of azodicarboxylate together with an unusual addition of two moles of acetylenedicarboxylate to the enamine double bond of 1H compounds is discussed.     

Quinazolines and 1,4-benzodiazepines. XCIII. Synthesis of imidazo[1,5-a][1,4]benzodiazepines from nitrooximes

The displacement of the nitro group in nitrooximes by other nucleophiles was used to prepare various 2-(hydroxyimino)methyl- and 2-(methoxyimino)methyl-1,4-benzodiazepines. These compounds were converted to imidazo[1,5-a][1,4]benzodiazepines bearing a tertiary amine, methoxy or thiomethyl group in the 3-position.     

Conformational reorientation of immunoglobulin G during nonspecific interaction with surfaces.

To achieve a better understanding of the nonspecific adsorption process of proteins on solid surfaces, the mechanism of this interaction was investigated by a model system comprising the structurally flexible ("soft") protein goat anti-rabbit immunoglobulin G and a set of chemically defined surfaces. The thermodynamic properties of both protein and surfaces were derived from contact angle measurements by applying the Lifshitz-van der Waals acid-base approach, and the Gibbs free enthalpy of interaction was calculated. The protein shows two conformational states, one hydrophobic and the other hydrophilic. The interaction energy indicates that the hydrophobic conformation favorably adsorbs onto the surfaces. With real-time binding kinetics, measured by a supercritical angle fluorescence biosensor, we show that during the nonspecific adsorption the protein performs a reorientation in its three-dimensional amino acid structure from a hydrophilic to a hydrophobic molecular structure. Unlike the rates of adsorption and desorption, the transition rate is independent of the type of surface and only influenced by the structural reorganization of the protein.     

A freely falling magneto-optical trap drop tower experiment

We experimentally demonstrate the possibility of preparing ultracold atoms in the environment of weightlessness at the earth-bound short-term microgravity laboratory Drop Tower Bremen, a facility of ZARM – University of Bremen. Our approach is based on a freely falling magneto-optical trap (MOT) drop tower experiment performed within the ATKAT collaboration (“Atom-Catapult”) as a preliminary part of the QUANTUS pilot project (“Quantum Systems in Weightlessness”) pursuing a Bose–Einstein condensate (BEC) in microgravity at the drop tower [1, 2]. Furthermore we give a complete account of the specific drop tower requirements to realize a compact and robust setup for trapping and cooling neutral rubidium ⁸⁷Rb atoms in microgravity conditions. We also present the results of the first realized freely falling MOT and further accomplished experiments during several drops. The goal of the preliminary ATKAT pilot project is to initiate a basis for extended atom-optical experiments which aim at realizing, observing and investigating ultracold quantum matter in microgravity. PACS 67.85.-d