Selective crystallization of indigo B by a modified sublimation method and its redetermined structure

Good-quality single crystals of the title compound, indigo B [systematic name: 2-(3-oxoindolin-2-yl­idene)indolin-3-one], C16H10N2O2, have been prepared with high selectivity by a sublimation process. The previous structure of indigo B [Süsse & Wolf (1980 ▶). Naturwissenschaften, 67, 453], which showed that the complete mol­ecule is generated by crystallographic inversion symmetry has been confirmed, but the present study reports more realistic geometrical parameters and modern standards of precision (e.g. σ for C—C bonds = 0.002–0.003 Å). Each mol­ecule features two intra­molecular N—H⋯O hydrogen bonds. In the crystal, mol­ecules are linked by strong face-to-face π–π stacking inter­actions involving both the six- and five-membered rings [centroid–centroid separations = 3.6290 (14) and 3.6506 (14) Å] and inter­molecular N—H⋯O hydrogen bonds

On Josephson effects in insulating spin systems

We discuss an experiment in which two magnetic insulators that both show a field-induced magnetic-ordering transition are weakly coupled to one another and are placed into an ex- ternal magnetic field. If the respective magnetic states can be interpreted as phase coherent Bose-Einstein condensates of magnetic bosonic quasiparticles, one expects the occurrence of Josephson effects. For two identical systems, the resulting d.c. Josephson effect formally represents a constant quasiparticle Josephson current across the weak link, which turns out to be unobservable in an experiment. For magnetic insulators with different critical fields, a spontaneous alternating quasiparticle current develops with a leading oscillation frequency {\omega}a.c. that is determined by the difference between the critical fields. As a result of the coupling, additional sidebands appear in the energy spectrum of the coupled device that would be absent without phase coherence. We discuss the primary conditions for such an effect to take place and conclude that its detection can be feasible for a proper choice of compounds with suitable and realistic material parameters.Comment: This version has been adapted to Elsevier style. The interpretation of the d.c. Josephson effect is more explicit. The role of the phase of the triplon-BEC-wavefunction is precisely defined to address a possible ambiguity with respect to the in-plane angle of the transverse magnetic moments. We include a remark in the conclusion on the possibility of an intrinsic Josephson effect in BaCuCi2O

Crystal structure of cobalt hydroxide carbonate Co2CO3(OH)2: density functional theory and X-ray diffraction investigation

The cobalt carbonate hydroxide Co2CO3(OH)2 is a technologically important solid which is used as precursor for the synthesis of cobalt oxides in a wide range of applications, and it also has relevance as a potential immobilizer of toxic element cobalt in the environment, but its detailed crystal structure is so far unknown. We have investigated the structure of Co2CO3(OH)2 using Density Functional Theory (DFT) simulations as well as Powder X-Ray Diffraction (PXRD) measurements on samples synthesized via deposition from aqueous solution. We consider two possible monoclinic phases, with closely related but symmetrically different crystal structures, based on those of the minerals malachite (Cu2CO3(OH)2) and rosasite (Cu1.5Zn0.5CO3(OH)2), as well as an orthorhombic phase that can be seen as a common parent structure for the two monoclinic phases, and a triclinic phase with the structure of the mineral kolwezite (Cu1.34Co0.66CO3(OH)2). Our DFT simulations predict that the rosasite-like and the malachite-like phases are two different local minima of the potential energy landscape for Co2CO3(OH)2, and are practically degenerate in energy, while the orthorhombic and triclinic structures are unstable and experience barrierless transformations to the malachite phase upon relaxation. The best fit to the PXRD data is obtained using a rosasite model (monoclinic with space group P1121/n and cell parameters a = 3.1408(4) Å, b = 12.2914(17) Å, c = 9.3311(16) Å, γ = 82.299(16)°). However, some features of the PXRD pattern are still not well accounted for by this refinement and the residual parameters are relatively poor. We discuss the relationship between the rosasite and malachite phases of Co2CO3(OH)2 and show that they can be seen as polytypes. Based on the similar calculated stability of these two polytypes, we speculate that some level of stacking disorder could account for the poor fit of our PXRD data. The possibility that Co2CO3(OH)2 could crystallize, under different growth conditions, as either rosasite or malachite, or even as a stacking-disordered phase intermediate between the two, requires further investigation

PARP-1 and Ku compete for repair of DNA double strand breaks by distinct NHEJ pathways

Poly(ADP-ribose)polymerase 1 (PARP-1) recognizes DNA strand interruptions in vivo and triggers its own modification as well as that of other proteins by the sequential addition of ADP-ribose to form polymers. This modification causes a release of PARP-1 from DNA ends and initiates a variety of responses including DNA repair. While PARP-1 has been firmly implicated in base excision and single strand break repair, its role in the repair of DNA double strand breaks (DSBs) remains unclear. Here, we show that PARP-1, probably together with DNA ligase III, operates in an alternative pathway of non-homologous end joining (NHEJ) that functions as backup to the classical pathway of NHEJ that utilizes DNA-PKcs, Ku, DNA ligase IV, XRCC4, XLF/Cernunnos and Artemis. PARP-1 binds to DNA ends in direct competition with Ku. However, in irradiated cells the higher affinity of Ku for DSBs and an excessive number of other forms of competing DNA lesions limit its contribution to DSB repair. When essential components of the classical pathway of NHEJ are absent, PARP-1 is recruited for DSB repair, particularly in the absence of Ku and non-DSB lesions. This form of DSB repair is sensitive to PARP-1 inhibitors. The results define the function of PARP-1 in DSB repair and characterize a candidate pathway responsible for joining errors causing genomic instability and cancer

A Raman spectroscopic study of M2+M3+ sulfate minerals, romerite Fe2+Fe23+ (SO4)4.14H2O and botryogen Mg2+Fe3+ (SO4)2(OH).7H2O

The mixed valency (M2+M3+) sulphate minerals, römerite Fe2+Fe23+(SO4)4•14H2O and botryogen Mg2+Fe3+(SO4)2(OH).7H2O have been studied by Raman spectroscopy. The Raman spectra of the two types of crystals proved very similar but not identical. The observation of two symmetric stretching modes confirmed the presence of the two non-equivalent sulphate units in the römerite structure. The observation of multiple bands in the antisymmetric stretching region and in the bending regions proves the symmetry of the sulphate anion is significantly reduced in the römerite structure. The number of Raman bands related to the (SO4)2- symmetric and antisymmetric vibrations support the X-ray single crystal structure conclusion that two symmetrically distinct S6+ are present in the structure of botryogen. Römerite is a mineral of environmental significance as it is commonly found in tailings and dumps

Fund manager compensation and the impact on fund performance

Fund managers earn large bonuses while the value added by them seems doubtful, particularly in light of the low persistence of superior fund performance. Thus, the amount of bonuses and their design is questionable. The aim of this thesis is to determine how fund manager compensation impacts fund performance. The empirical part of this thesis uses a hand-collected data set of compensation structures of fund managers from U.S. domestic equity funds as well as return and benchmark data from several data providers. Fund performance is measured using four different performance measures each net- and gross-of-fees. The results show that compensation linked to the fund performance relative to a benchmark significantly increases fund performance. Other compensation forms like long-term incentive plans, compensation linked to firm profitability or other benefits do not significantly impact fund performance and may even have a negative effect on performance i.e. in the case of qualitative compensation elements. Although the results of this thesis are limited and not robust in all cases, the incentive effect of performance-based compensation gives a clear indication of the importance of incentives for managers

Remarks on the method of coordinatewise search

summary:In der vorliegenden Arbeit wird das Verfahren der koordinatenweisen Suche mit Hilfe der Intervallarithmetik realisiert. Dadurch ist es möglich, bei speziellen nichtlinearen Optimierungsproblemen alle auftretenden Fehlerarten zu erfaßen, einschliesslich eingangsbedingter Fehler. Vor- und Nachteile werden erläutert sowie Testbeispiele angegeben