A Query Language for Software Architecture Information (Extended version)

Software maintenance is an important part of a software system's life cycle. Maintenance tasks of existing software systems suffer from architecture information that is diverging over time (architectural drift). The Digital Architecture Twin (DArT) can support software maintenance by providing up-to-date architecture information. For this, the DArT gathers such information and co-evolves with a software system, enabling continuous reverse engineering. But the crucial link for stakeholders to retrieve this information is missing. To fill this gap, we contribute the Architecture Information Query Language (AIQL), which enables stakeholders to access up-to-date and tailored architecture information. We derived four application scenarios in the context of continuous reverse engineering. We showed that the AIQL provides the required functionality to formulate queries for the application scenarios and that the language scales for use with real-world software systems. In a user study, stakeholders agreed that the language is easy to understand and assessed its value to the specific stakeholder for the application scenarios

rac-(2R,3S)-2-Phenyl-3-(3-phenyl-1,2,3,4-tetra­hydro­quinoxalin-2-yl)quinoxaline

The title compound, C28H22N4, is the unexpected by-product of the reaction of 2-hydroxy­acetophenone and 1,2-diamino­benzene under iodine catalysis, during which a carbon–carbon σ-bond between two quinoxaline units was formed. Although a fully oxidized title compound should sterically be possible, only one quinoxaline ring is fully oxidized while the second ring remains in the reduced form. As expected, the tetra­hydro­quinoxaline unit is not planar; it adopts a sofa conformation, whereby the atom joining the two heterocyclic systems lies out of the plane of the other atoms. The quinoxaline ring system makes a dihedral angle of 53.61 (4)° with its phenyl ring substituent. The crystal packing is determined by pairs of N—H⋯N, N—H⋯π and weak C—H⋯N hydrogen bonds, forming a chain parallel to the a axis

Managing spatial sustainability trade-offs: The case of wind power

The deployment of onshore wind power involves spatial sustainability trade-offs, e.g., between the minimization of energy system costs, the mitigation of impacts on humans and biodiversity, and equity concerns. We analyze challenges arising for decision-making if wind power generation capacity has to be allocated spatially in the presence of such trade-offs. The analysis is based on a game developed for and played by stakeholders in Germany. The results of the game illustrate that there is no unanimously agreed ranking of sustainability criteria among the participating stakeholders. They disagreed not only on the weights of different criteria but also their definition and measurement. Group discussions further revealed that equity concerns mattered for spatial allocation. Yet, stakeholders used quite different concepts of equity. The results support the importance of transparent, multi-level and participatory approaches to take decisions on the spatial allocation of wind power generation capacity

Iridium complexes on the basis of 2-methyl-3-phenylquinoxalines: Highly efficient and stable triplet emitters for organic light-emitting diodes

Organische Leuchtdioden (OLEDs) haben sich seit den achtziger Jahren zu einem interessanten Forschungsgebiet sowohl für Beleuchtungs- als auch Bildschirmanwendungen entwickelt. Die Emission bei OLEDs beruht auf dem Prinzip der Elektrolumineszenz, die im Gegensatz zu den anorganischen LEDs durch organische bzw. metallorganische Materialien entsteht. Diese Materialien werden als wenige Nanometer dicke Schichten zwischen zwei Elektroden eingebettet und emittieren durch Anlegen eines Potentials Licht. Ziel der vorliegenden Arbeit war die Darstellung von neuen stabilen Farbstoffen auf Basis von Triplett-Emittern mit Iridium als Zentralatom, die im roten Spektralbereich emittieren und zukünftig zur Darstellung weiß emittierender OLEDs eingesetzt werden können. Als geeignete Liganden für derartige Komplexe wurden die in Veröffentlichungen bisher nicht verwendeten 2 Methyl-3-phenylchinoxaline ausgewählt. Diese besitzen eine hohe Ähnlichkeit zu dem in der Literatur dominierenden und als effizient bewiesenen Ligandenkonzept von 2 Phenylpyridin und bilden mit dem Metallzentrum in der Cyclometallierung einen Fünfring aus. Aufgrund des größeren aromatischen Systems und dem zusätzlich eingeführten elektronegativeren Stickstoffatom emittieren Iridiumkomplexe mit Chinoxalin-Liganden jedoch bathochromer. Insgesamt konnten im Rahmen dieser Arbeit 17 neue, bisher nicht beschriebene heteroleptische Chinoxalin-Komplexe mit Ausbeuten von bis zu 96 % hergestellt werden. Diese wurden aus sechs ebenfalls in der Literatur nicht beschriebenen cyclometallierten Vorstufen hergestellt, die aus den synthetisierten Chinoxalinen in Ausbeuten von bis zu 80 % erhalten wurden. Homoleptische Komplexe mit den Chinoxalin-Liganden konnten, vermutlich aus sterischen Gründen, nicht erhalten werden. Die Umsetzung führte zur effizienten Bildung von Pyrrolo[1,2-a]chinoxalinen. Die Entstehung dieses und auch anderer Nebenprodukte wurde eingehender untersucht. Die neuen heteroleptischen Komplexe wurden vollständig charakterisiert und untereinander verglichen. Die Strukturbestimmungen wiesen eine meridionale Geometrie meist mit einer bevorzugten stereochemischen Konfiguration auf. Ebenso zeigten die NMR-Spektren bei den Chinoxalin-Komplexen deutlich das Vorliegen der meridionalen Konfiguration in Lösung. In den ESI-Massenspektren der cyclometallierten Vorstufen konnte das Vorliegen von Radikalkationen, die einem Iridiumzentrum mit zwei umgebenden cyclometallierten Liganden entsprachen, beobachtet werden. Die Emissionsmaxima der Chinoxalin-Komplexe konnten durch Substitution der Liganden in einem Bereich von 605 bis 664 nm eingestellt werden. Eine Reihe ausgewählter Metallkomplexe wurde äußerst erfolgreich in OLEDs eingesetzt und zeigte hohe Effizienzen und eine beachtliche Stabilität.Organic light-emitting diodes (OLEDs) have emerged to an interesting area of research for lighting and display applications since the 1980s. The emission of OLEDs is based on the principle of electroluminescence and contrary to inorganic LEDs originates from organic or organometallic compounds. These compounds are embedded in a few nanometer thick layer between two electrodes and emit light on application of a potential. The aim of the present work was to design new stable dyes on the basis of triplet emitters with an iridium core emitting light in the red spectrum and the capability to be used in white OLEDs in the future. As suitable ligands for these complexes the literature unseen 2-methyl-3-phenylquinoxalines were chosen. They possess a high similarity to the well-known and proven to be efficient ligands based on 2-phenylpyridines and also form a five-membered ring during cyclometalation. Due to the enlarged aromatic system and the additionally introduced electronegative nitrogen atom these iridium complexes comparably emit bathochromic. Within the scope of this work 17 new, yet literature unknown heteroleptic quinoxaline-based complexes with yields up to 96 % were synthesized. They have been synthesized from six likewise literature unknown cyclometalated precursors which were obtained from prepared quinoxalines in yields up to 80 %. Propably owing to steric interactions homoleptic complexes with quinoxalines could not be obtained. Cyclometalation attempts lead to the efficient formation of pyrrolo[1,2-a]quinoxalines. The formation of this and other byproducts was investigated in more detail. The new and herein described heteroleptic complexes were fully characterized and compared among each other. In all examined cases crystallographic studies showed a meridional geometry mostly with a preferred stereochemical configuration. NMR analysis also clearly showed the meridional geometry in solution. Radical cations of the type of one iridium center cyclometalated with two ligands were observed to be typical in ESI-mass spectrometry. The emission maxima of the complexes could be varied in the range of 605 to 664 nm by the substitution pattern of the ligands. A selection of metal complexes was inserted with outmost success in OLEDs and showed a high efficiency and a remarkable stability

Pyrrolo[1,2‑<i>a</i>]quinoxalines: Novel Synthesis via Annulation of 2‑Alkylquinoxalines

In an attempt to synthesize a novel homoleptic complex <b>3</b> from 2-methyl-3-phenylquinoxaline <b>1</b> and Ir(acac)₃ for application as a triplet emitter in OLEDs (organic light-emitting diodes) no cyclometalation was observed. Instead, an annulation to 1-methyl-4-phenylpyrrolo[1,2-<i>a</i>]quinoxaline <b>2</b> was observed. Since pyrroloquinoxalines are potentially bioactive and few paths for their synthesis are known, selected reactions and conditions were investigated, suggesting Ir(acac)₃ as catalyst and proving glycerol to be a reactant

Pyrrolo[1,2‑<i>a</i>]quinoxalines: Novel Synthesis via Annulation of 2‑Alkylquinoxalines

In an attempt to synthesize a novel homoleptic complex <b>3</b> from 2-methyl-3-phenylquinoxaline <b>1</b> and Ir(acac)₃ for application as a triplet emitter in OLEDs (organic light-emitting diodes) no cyclometalation was observed. Instead, an annulation to 1-methyl-4-phenylpyrrolo[1,2-<i>a</i>]quinoxaline <b>2</b> was observed. Since pyrroloquinoxalines are potentially bioactive and few paths for their synthesis are known, selected reactions and conditions were investigated, suggesting Ir(acac)₃ as catalyst and proving glycerol to be a reactant