Kojic acid derivatives as powerful chelators for iron(III) and aluminium(III)

Proceeding from a ligand constituted by two units of kojic acid linked by a methylene group, which proved a very promising chelator for excess iron(III) and aluminium(III) pathologies, two new ligands have been designed and synthesized: one by adding a vanillin molecule in the linker and the second by adding an o-vanillin molecule. Both these ligands, on the basis of complex formation studies presented here, show significant potential as therapeutic agents for iron and aluminium overload. Protonation constants of the pure ligands have been determined by potentiometry, and standard reaction heats by calorimetry. Hydrogen bonding plays an important role in the protonation reactions. The crystal structures of both ligands have furthermore been resolved. Complex formation equilibria for the iron complexes have been studied by combined potentiometry-spectrophotometry and those of aluminium by potentiometry alone. All complexes were found to contain two metal ions. NMR diffusion measurements hardly applied to complex formation equilibria and the results of density functional theory (DFT) calculations were powerful tools in confirming the proposed reaction model and in evaluating the relative stabilities of the products. Further support was given by NMR chemical shift measurements and electrospray mass spectrometry.     

N‐Fusion Approach in Construction of Contracted Carbaporphyrinoids: Formation of N‐Fused Telluraporphyrin

Insertion of PCl₃ into 5,10,15,20‐tetraaryl‐21‐telluraporphyrin leads to a phosphorus complex of N‐fused dihydrotelluraporphyrin with an inverted tellurophene ring. Its CNN coordination core places the macrocycle in the family of contracted carbaporphyrinoids. A cycle of direct transformations affords an elegant triangle of three mutually convertible N‐fused porphyrinoids, with distinct spectroscopic features: antiaromatic, nonaromatic and aromatic. The nonaromatic species has a dome shaped skeleton which forms in the solid state a ball and socket structure with C₆₀.     

Counting signed swallowtails of polynomial selfmaps of {\mathbb {R}^3}

For a generic \({f \in C^\infty({\mathbb {R}}^3,{\mathbb {R}}^3)}\), there is a discrete set of swallowtail critical points. At any swallowtail point p there exists a well-oriented coordinate system centred at p, and a coordinate system centred at f(p), such that locally f has the form \({f_\pm(x, y, z) = (\pm xy+x^2 z+x^4, y, z)}\), so one may associate with p a sign \({I(f, p) \in \{\pm 1\}}\). We shall show how to compute the number of swallowtail points having the positive/negative sign, in the case where \({f : {\mathbb {R}}^3 \rightarrow {\mathbb {R}}^3}\) is a polynomial mapping, in terms of signatures of quadratic forms.     

Minimum size transversals in uniform hypergraphs

A set of vertices in a hypergraph which meets all the edges is called a transversal. The transversal number τ(H)$\tau \left(H\right)$ of a hypergraph H$H$ is the minimum cardinality of a transversal in H$H$. A classical greedy algorithm for constructing a transversal of small size selects in each step a vertex which has the largest degree in the hypergraph formed by the edges not met yet. The analysis of this algorithm (by Chvátal and McDiarmid (1992)  [3]) gave some upper bounds for τ(H)$\tau \left(H\right)$ in a uniform hypergraph H$H$ with a given number of vertices and edges. We discuss a variation of this greedy algorithm. Analyzing this new algorithm, we obtain upper bounds for τ(H)$\tau \left(H\right)$ which improve the bounds by Chvátal and McDiarmid.     

The millimetre-wave rotational spectrum of phenylacetylene

The room-temperature rotational spectrum of phenylacetylene (C₆H₅CCH), was studied at frequencies up to 340 GHz. Extensive new measurements, covering rotational transitions with quantum number values up to J=140 and K_a=59, allowed determination of precise spectroscopic constants for the ground state and for the lowest two excited vibrational states, v₂₄=1 and v₃₆=1. The two excited states belong to the lowest B₁ and B₂ symmetry normal modes and their rotational transitions are very strongly perturbed by a-axis Coriolis resonance. A successful fit of the resonance is reported, resulting in and , in good agreement with results of ab initio computations.     

A local regularity of the complex Monge–Ampère equation

We prove a local regularity (and a corresponding a priori estimate) for plurisubharmonic solutions of the nondegenerate complex Monge–Ampère equation assuming that their W ^{2, p} -norm is under control for some p > n(n − 1). This condition is optimal. We use in particular some methods developed by Trudinger and an estimate for the complex Monge–Ampère equation due to Kołodziej.     

The imprints of superstatistics in multiparticle production processes

We provide an update of the overview of imprints of Tsallis nonextensive statistics seen in a multiparticle production processes. They reveal an ubiquitous presence of power law distributions of different variables characterized by the nonextensivity parameter q > 1. In nuclear collisions one additionally observes a q-dependence of the multiplicity fluctuations reflecting the finiteness of the hadronizing source. We present sum rules connecting parameters q obtained from an analysis of different observables, which allows us to combine different kinds of fluctuations seen in the data and analyze an ensemble in which the energy (E), temperature (T) and multiplicity (N) can all fluctuate. This results in a generalization of the so called Lindhard’s thermodynamic uncertainty relation. Finally, based on the example of nucleus-nucleus collisions (treated as a quasi-superposition of nucleon-nucleon collisions) we demonstrate that, for the standard Tsallis entropy with degree of nonextensivity q < 1, the corresponding standard Tsallis distribution is described by q′ = 2 − q > 1.     

Changes in the optical properties at phase transitions in TEA2MeCl4 (Me=Zn, Mn, Hg, Cu) crystals

Optical properties of TEA₂MeCl₄ crystals, where Me is a divalent metal ion, have been studied under polarization microscope in temperatures ranging from 200 to 300 K. Abrupt changes in the interference colours and strong cracking of the sample have been observed for all crystals except the TEA₂CuCl₄ one, for which only brightening of the plate image has been noted. The cracks are approximately parallel to the cleavage planes. These changes occur in two stages. The brightening of the images of the crystal samples may suggest the ferroelastic deformation in microregions. No classical ferroelastic domain structure has been observed in the low-temperature phase.     

Phase equilibria in the system FeVO4−Fe2WO6 in the solid state

A diagram of the phase equilibria established in the solid state in the system FeVO₄?Fe₂WO₆ was plotted on the basis of X-ray phase analysis and DTA. This system, one of the intersections of the three-component system Fe₂O₃?V₂O₅?WO₃, does not appear to be a real two-component system in the solid state.