Banana-shaped molecules peculiarly oriented in a magnetic field: (2)H NMR spectroscopy and quantum mechanical calculations.

The orientational properties of the banana-shaped liquid crystal 4-chloro-1,3-phenylenebis{4-[4'-(10-undecenyloxy)]benzoyloxy} benzoate (ClPbis11BB) are reported in the nematic phase under the effect of an external magnetic field. A new hypothesis, which states that the central ring of the aromatic core is oriented perpendicularly to the external magnetic field, is proposed. In support of this hypothesis, a series of studies based on (2)H NMR spectroscopy, both in the bulk and in solution, are discussed. (2)H NMR measurements on three selectively deuterium-labelled isotopomers are presented, together with DFT results from B3LYP/cc-pvDz calculations performed on the aromatic core. The rather flat shape of the investigated intramolecular energy surface allows for several different conformations to be populated, the computed magnetic susceptibilities of which are consistent with the proposed hypothesis of peculiar orientation of banana-shaped molecules. Moreover, the orientation of the magnetic susceptibility tensor is shown to be strongly dependent on the internal conformation of the banana-shaped molecules.     

Analysis of dissolution profiles of iron,zinc, and manganese from complex dietary supplements by ion chromatography and chemometrics

Four commercially available formulations containing iron, zinc, and manganese were subjected to dissolution profile testing during 60 min and the dissolution was analyzed by ion chromatography. The obtained curves were analyzed directly by principal component analysis (PCA). The main trend (87.1% of variance) was connected with average dissolution percentage over the investigated time. The second component (11.2% of variance) is connected with shape of dissolution profile. All metals behave in the similar way and the differences were connected with excipients. An additional fit was completed on 12 kinetic models: first order kinetics (4 variants), Higuchi (2 variants), Hixson-Crowell (2 variants), Korsemeyer-Peppas, Logistic (2 variants), Peppas-Sahlin, Quadratic (2 variants), Weibull (3 variants), and Zero order kinetics (2 variants). The ranking of the fitting was performed by Akaike information criteria (AIC) values with additional PCA analysis on them, an approach presented in literature for the first time. The main trend (67.4% of variance) was connected with average fit. The second (14.8% of variance) is connected with differences of fitting ability to investigated dissolution curves. This methodology brought an overall look to trends and variances inside obtained data, both the profile shape and fitting ability to particular models.     

Synthesis and properties of a newly obtained sorbent based on silica gel coated with a polyaniline film as the stationary phase for non-suppressed ion chromatography

The new sorbent for non-suppressed ion chromatography based on silica gel coated with a film of polyaniline (PANI) was obtained in a process of in situ polymerization of aniline by oxidation with ammonium peroxydisulfate. Raman analyses performed using a Thermo Scientific DXR confocal Raman Microscope equipped with the Omnic 8 software from Thermo Fisher Scientific have proved a uniform distribution of PANI on the surface of chromatographic beads and in the pores of the particle.     

Computing stable loads for pallets

This paper describes an Integer Programming model for generating stable loading patterns for the Pallet Loading Problem under several stability criteria. The results obtained during evaluation show great improvement in the number of stable patterns in comparison with results reported earlier. Moreover, most of the solved cases also ensure optimality in terms of utilization of a pallet.     

Characterization of anomeric differences of ammonium-bound monomeric and dimeric complex ions of 1α- and 1β-azido-pentofuranosyl derivates by kinetic method

Relative stabilities (ΔG^c) of ammonium-bound monomers and dimers of anomeric β- -pentofuranosyl 1α- and 1β-azide derivates are determinate using the kinetic method by measuring relative rates of competitive collision-induced dissociations of dimeric [ANH₄B]⁺ and trimeric [A₂NH₄B]⁺ or [ANH₄B₂]⁺ cluster ions. Comparison between calculated ammonium affinities (AAs) and relative stabilities (ΔG^c) of ammonium-bound monomers shows qualitative correlations between both thermochemical quantities, but in two examples the activation barrier differences of competitive fragmentation channels cause a large disparity between both thermochemical data. Therefore, the most stable ammonium-bound monomers of the anomeric lα- and lβ-2,3,5-tri-O-benzyl-β- -arabino-pento-furanosyl azides possess the lowest ammonium affinities and the highest relative stabilities. Two different relative stabilities measured for the same ammonium-bound homo- or hetero-dimers indicate dissimilar activated barriers of trimers transition states for dimer formations. The activated barriers of trimers depend on the relative stabilities of ammonium-bound monomer within the trimeric cluster ions.     

Localized orbitals,electric field gradients and diamagnetic shielding in hydrogen bonded systems

Ab-initio localized molecular orbitals are used to evaluate the diamagnetic shieldings and the electric field gradients in hydrogen bonded systems.