Investigations of the Vicarious C‐Aminations of 5,7‐Dinitrobenzotriazole and 4,6‐Dinitrobenzotriazol‐3‐ium‐1‐oxide and Their Energetic Properties

This combined experimental and theoretical study details the vicarious nucleophilic substitution by amination of 5,7‐dinitrobenzotriazol ( 1 ) and 4,6‐dinitrobenzotriazole‐3‐ium‐1‐oxide ( 4 ) with trimethylhydrazinium iodide to afford the new corresponding one‐ and two‐time aminated compounds and investigations of its mechanism by EPR spectroscopy. The preferred position for the first amination is computed by spin density population and verified by X‐ray crystallography. The zwitterionic structure of 4 is investigated in solution by ¹H NMR spectroscopy and in solid state by X‐ray diffraction. Furthermore, the crystal structure of 1 is presented. The energetic behavior of the aminated products as well as the starting materials 1 and 4 was investigated, regarding sensitivities and performance.     

A switching for all strongly regular collinearity graphs from polar spaces

We describe a general construction of strongly regular graphs from the collinearity graph of a finite classical polar spaces of rank at least 3 over a finite field of order q. We show that these graphs are non-isomorphic to the collinearity graphs and have the same parameters. For most of these parameters, the collinearity graphs were the only known examples, and so many of our examples are new.     

A single-surface yield function for geomaterials

Summary The article outlines a seven-parametric yield function for geomaterials such as soils and rocks. Proceeding from a geometric representation in the principal stress space, the yield surface exhibits a closed shape, thus reflecting the sensitivity of the plastic response of this type of media to hydrostatic stresses. The yield function is able to describe the effects of primary yielding, as well as of isotropic and kinematic hardening. In addition the failure envelope contains an open cone when the number of material parameters is reduced from seven to five.Dedicated to F. G. Kollmann on the occasion of his 60th birthday     

Pyridazine based scorpionate ligand in a copper boratrane compound

Reaction of potassium tris(mercapto-tert-butylpyridazinyl)borate K[Tn(tBu)] with copper(II) chloride in dichloromethane at room temperature led to the diamagnetic copper boratrane compound [Cu{B(Pn(tBu))(3)}Cl] (Pn = pyridazine-3-thionyl) (1) under activation of the B-H bond and formation of a Cu-B dative bond. In contrast to this, stirring of the same ligand with copper(I) chloride in tetrahydrofuran (THF) gave the dimeric compound [Cu{Tn(tBu)}](2) (2) where one copper atom is coordinated by two sulfur atoms and one hydrogen atom of one ligand and one sulfur of the other ligand. Hereby, no activation of the B-H bond occurred but a 3-center-2-electron B-H···Cu bond is formed. The reaction of copper(II) chloride with K[Tn(tBu)] in water gave the same product 2, but a formal reduction of the metal center from Cu(II) to Cu(I) occurred. When adding tricyclohexyl phosphine to the reaction mixture of K[Tn(R)] (R = tBu, Me) and copper(I) chloride in MeOH, the distorted tetrahedral Cu complexes [Cu{Tn(R)}(PCy(3))] (R = tBu 3, Me 4) were formed. Compound 4 is exhibiting an "inverted" κ(3)-H,S,S, coordination mode. The copper boratrane 1 was further investigated by density functional theory (DFT) calculations for a better understanding of the M→B interaction involving the d(8) electron configuration of Cu.     

The stoichiometry of single nanoparticles of copper zinc tin selenide

Cu(2)ZnSnSe(4) nanoparticles have high potential to be used as ink for printable solar cells. Using transmission electron microscopy we show that these nanoparticles exhibit a broad range of chemical heterogeneity. These results are contrary to the interpretation of previous experimental work and will have considerable impact on the development of these nanoparticles.     

Electronic structure of pyridine-based SAMs on flat Au(111) surfaces: extended charge rearrangements and Fermi level pinning

Density functional theory calculations are used to investigate the electronic structure of pyridine-based self-assembled monolayers (SAMs) on an Au(111) surface. We find that, when using pyridine docking groups, the bonding-induced charge rearrangements are frequently found to extend well onto the molecular backbone. This is in contrast to previous observations for the chemisorption of other SAMs, e.g., organic thiolates on gold, and can be explained by a pinning of the lowest unoccupied states of the SAM at the metal Fermi-level. The details of the pinning process, especially the parts of the molecules most affected by the charge rearrangements, strongly depend on the length of the molecular backbone and the tail-group substituent. We also mention methodological shortcomings of conventional density functional theory that can impact the quantitative details regarding the circumstances under which pinning occurs and highlight a number of peculiarities associated with bond dipoles that arise from Fermi-level pinning.     

Column generation for vehicle routing problems with multiple synchronization constraints

Synchronization of workers and vehicles plays a major role in many industries such as logistics, healthcare or airport ground handling. In this paper, we focus on operational ground handling planning and model it as an archetype of vehicle routing problems with multiple synchronization constraints, coined as “abstract vehicle routing problem with worker and vehicle synchronization” (AVRPWVS). The AVRPWVS deals with routing workers to ground handling jobs such as unloading baggage or refuelling an aircraft, while meeting each job’s time window. Moreover, each job can be performed by a variable number of workers. As airports span vast distances and due to security regulations, workers use vehicles to travel between locations. Furthermore, each vehicle, moved by a driver, can carry several workers. We propose two mathematical multi-commodity flow formulations based on time-space networks to efficiently model five synchronization types including movement and load synchronization. Moreover, we develop a branch-and-price heuristic that employs both conventional variable branching and a novel variable fixing strategy. We demonstrate that the procedure achieves results close to the optimal solution in short time when compared to the two integer models.     

Influence of the retardation of the multiplexing element in a dual channel Q-switched laser

We present an experimental and numerical analysis, how deviations of the multiplexer-retardation influence the output power of a time-multiplexed dual channel laser. The laser has two different channels, each one with its own gain medium. The channels are time-multiplexed by a single crystal photo-elastic modulator. It enables to double the repetition rate and output power of the laser. However, as multiplexing is based on polarization-switching, the retardation of the modulator should be kept within certain limits. By experimental measurement and theoretical analysis, we determine the operational window within which the retardation should be kept to avoid additional losses into the resonator. The analysis was done for two configurations of the laser setup, namely with and without a quarter-wave plate.     

Collisional-Radiative Recombination in Argon Plasmas

On the basis of the realistic argon atom model consisting of 65 discrete effective levels numerical results for the collisional-radiative volume recombination, ionization and decay coefficients are obtained. The computations are carried out without any approximations of integral functions. The presented comparison of theoretical and experimental results for the decay coefficient shows that the values calculated by us are in much better agreement with experimental values than those obtained by Desai and Corcoran on the assumption that the argon atom is hydrogen-like.     

Mechanismus der elektronenstossinduzierten Äathylenabspaltung aus dem Ion [C9H11]+ aus 2,5-Dimethylbenzylbromid

By the investigation of ¹³C-labelled dimethylbenzylbromide, it has been shown that the [M – Br]⁺ ion isomerises to a dimethyltrophylium cation.