Measurement and prediction of activity coefficients at infinite dilution (γ), vapor–liquid equilibria (VLE) and excess enthalpies (H) of binary systems with 1,1-dialkyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide using mod. UNIFAC (Dortmund)

Activity coefficients at infinite dilution (γ^∞), vapor–liquid equilibria (VLE) and excess enthalpies (H^E) were measured for alkanes and alkenes in the ionic liquids 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [BMPYR]⁺[BTI]⁻, 1-hexyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [HMPYR]⁺[BTI]⁻ and 1-octyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [OMPYR]⁺[BTI]⁻.     

C?F Activation at Rhodium Boryl Complexes: Formation of 2‐Fluoroalkyl‐1,3,2‐Dioxaborolanes by Catalytic Functionalization of Hexafluoropropene

Fluorinated building blocks by C? F bond cleavage : Catalytic C? F activation reactions that give novel dioxaborolanes have been developed (see scheme). The reactions proceed at room temperature, and catalytic intermediates are presumably rhodium hydride and boryl species.

     

Edge-reinforced random walk on one-dimensional periodic graphs

In the present paper, linearly edge-reinforced random walk is studied on a large class of one-dimensional periodic graphs satisfying a certain reflection symmetry. It is shown that the edge-reinforced random walk is recurrent. Estimates for the position of the random walker are given. The edge-reinforced random walk has a unique representation as a random walk in a random environment, where the random environment is given by random weights on the edges. It is shown that these weights decay exponentially in space. The distribution of the random weights equals the distribution of the asymptotic proportion of time spent by the edge-reinforced random walker on the edges of the graph. The results generalize work of the authors in Merkl and Rolles (Ann Probab 33(6):2051–2093, 2005; 35(1):115–140, 2007) and Rolles (Probab Theory Related Fields 135(2):216–264, 2006) to a large class of graphs and to periodic initial weights with a reflection symmetry.     

Tizanidine and tizanidine hydrochloride: on the correct tautomeric form of tizanidine

A crystallization series of tizanidine hydrochloride, used as a muscle relaxant for spasticity acting centrally as an α₂‐adrenergic agonist, yielded single crystals of the free base and the hydrochloride salt. The crystal structures of tizanidine [systematic name: 5‐chloro‐N‐(imidazolidin‐2‐ylidene)‐2,1,3‐benzothiadiazol‐4‐amine], C₉H₈ClN₅S, (I), and tizanidine hydrochloride {systematic name: 2‐[(5‐chloro‐2,1,3‐benzothiadiazol‐4‐yl)amino]imidazolidinium chloride}, C₉H₉ClN₅S⁺·Cl⁻, (II), have been determined. Tizanidine crystallizes with two almost identical molecules in the asymmetric unit (r.m.s. deviation = 0.179 Å for all non‐H atoms). The molecules are connected by N—H...N hydrogen bonds forming chains running along [21]. The present structure determination corrects the structure determination of tizanidine by John et al. [Acta Cryst. (2011), E 67 , o838–o839], which shows an incorrect tautomeric form. Tizanidine does not crystallize as the usually drawn 2‐amino–imidazoline tautomer, but as the 2‐imino–imidazolidine tautomer. This tautomer is present in solution as well, as shown by ¹H NMR analysis. In tizanidine hydrochloride, cations and anions are connected by N—H...Cl hydrogen bonds to form layers parallel to (100).     

Divide-and-price: A decomposition algorithm for solving large railway crew scheduling problems

The railway crew scheduling problem consists of generating crew duties to operate trains at minimal cost, while meeting all work regulations and operational requirements. Typically, a railway operation uses tens of thousands of train movements (trips) and requires thousands of crew members to be assigned to these trips. Despite the large size of the problem, crew schedules need to be generated in short time, because large parts of the train schedule are not finalized until few days before operation.     

Melt‐spun Eu8Ga16–xGe30+x Clathrates

Intermetallic clathrates are promising materials for thermoelectric applications. This is not only due to their low thermal and high electrical conductivities (“phonon glass – electron crystal”) but also due to the expectation that they are semiconductors and thus have large thermopower values. Band structure calculations of the stoichiometric compound Eu₈Ga₁₆Ge₃₀ indeed yield a semiconducting ground state. However, with conventional synthesis methods the exact 8:16:30 stoichiometry could not be reached. Herein we use the melt‐spinning technique to obtain Eu₈Ga_16–xGe_30+x samples with smaller x than previously realized. The quenching procedure and the results of the characterization of the quenched phases by X‐ray powder diffraction and electron microscopy are presented. The electrical resistivity shows that, in contrast to conventional synthesis procedures, semiconducting compounds can be produced.