Structural manipulation of pyrochlores: Thermal evolution of metastable Gd2(Ti1−yZry)2O7 powders prepared by mechanical milling

The structural and microstructural characteristics of metastable Gd₂(Ti_1−yZr_y)₂O₇ powders prepared by mechanical milling have been studied by a combination of XRD and Raman spectroscopy. Irrespective of their Zr content, as-prepared powder phases present an anion-deficient fluorite-type of structure as opposed to the pyrochlore equilibrium configuration obtained for the same solid solution by other synthetic routes. These fluorites are stable versus thermal activation, at least up to temperatures of 800 °C. For the Ti-rich compositions, thermal treatments at higher temperatures facilitate the rearrangement of the cation and anion substructures and the relaxation of mechanochemically induced defects whereas for compositions with high Zr content, the fluorite crystal structure is retained even at temperatures as high as 1200 °C. Interestingly enough, transient pyrochlores showing a very unusual cation distribution were observed during the thermally induced defect-recovery process.     

Discretization of the thermal excitation in highly excited matter

In this paper the thermal energy diffusion for quantum particles is described. The quantum heat transport equation is obtained. It is shown that, for a short-time thermal excitation (of the order of the relaxation time), the excited matter response is quantized on the different levels (atomic, nuclear, quark) with quantum thermal energy equalE ^atomic 9 eV,E ^nuclear 7 MeV, andE ^quark 139 MeV.     

Solvated electron in liquid methanol. An example of a statistical species in chemistry

The methods of analysis of the statistical ensembles of trapping sites, before and after electron localization, for electrons in disordered media are surveyed. The review covers the computer-search methods for pre-existing traps in polar matrices, random field theory of disordered polar matrices and the path integral simulations of solvated electron. The common picture provided by all these methods is emphasized: the solvated electron is a unique in chemistry statistical species characterized by statistical distributions of the structural parameters, energy states, reactivity, etc. The numerical examples are provided by the simulations of the trapping sites and the solvated electron in liquid methanol.     

Note on vertex degrees of planar graphs

In this note the second moment of the vertex degree sequence of planar graphs is considered. We prove that

• 1 If G is an outerplanar graph of order n ? 3 then

• 2 If G is a planar graph of order n ? 4 then

where d₁,…,d_n is the vertex degree sequence of G. We exhibit all graphs for which these upper bounds are attained.     

2‐Methoxynaphthylnaphthoquinone and its solvate: synthesis and structure–properties relationship

Because of their unique visual optic and electronic properties, substituted quinones are commonly used as dyes and pigments; nevertheless, a theoretic background of relationship between the structures and optical properties of such compounds seems to be still undeveloped. Two crystalline forms of 2‐methoxynaphth‐1‐yl‐naphthoquinone (MNQ) have been synthesized and characterized by means X‐ray, NMR, UV–VIS, as well as, MS spectroscopy. The interpretation of intriguing optical properties of two crystalline forms of MNQ, based on detailed spectral and structural characterization, as well as, DFT and MP2 computations clearly connects the conformation of the molecules with their optical and electronic properties. Thus, flatter conformation, stabilized by crystal net force, favours the intense electron density transition from auxochrome to chromophore moiety (which corresponds excitation from HOMO to LUMO), as well as, favours the π‐stacking interaction, that eventually results in colour enhancement. At the same time, small molecules of solvents included into the crystal net allow molecules of arylnaphthoquinones to adopt less rigid conformation what has a dramatic optical outcome. Copyright © 2013 John Wiley & Sons, Ltd.     

Radon in well waters in the Kraków area

The method and the results of radon concentration measurements in water samples are presented. Since May 2000, measurements of radon concentration in well waters in the Kraków area have been carried out--both in urban wells (depth above 50 meters) and in other private wells (depth of several meters). The ionisation chamber AlphaGUARD PQ 2000PRO along with the additional special equipment AquaKIT were used for determination of radon concentration in water samples. A total of 45 wells were examined for radon concentration in water--19 urban wells, 21 private ones (from Nowa Huta, Ojcowska, Wola Justowska area--parts of Kraków) and 5 mineral water sources. Wola Justowska is a region where tectonics faults occur and radon can easily migrate from deep basement structure. All the obtained values of radon concentration are below 12 Bq/l. These preliminary results do not show a direct correlation between geological structure and radon concentration in water samples. However, further investigation is needed and is planned to be undertaken.     

Rapid two-step synthesis of mitrin from heparosan: a replacement for heparin

We have engineered a two-step enzymatic synthesis of Mitrin which is a more potent and homogeneous anticoagulant than the current animal-derived heparin. This engineered heparin may have advantages of being free from animal-derived pathogens and may also have reduced side effects such as heparin induced thrombocytopenia. This approach can also be extended to tailor heparin-based drugs with improved therapeutic characteristics to treat other disorders or infections in which heparin-like molecules play a major role.     

Reaction field effects on the electronic structure of carbon radical and ionic centers

We examine solvent effects on carbon radical and ionic centers of HCXY by including a self-consistent reaction-field into the AM 1 and MNDO electronic structure models to mimic dielectric effects. We find that such concepts as merostability are principally solvent effects, and that, as expected, molecules with large dipoles or with charge assymmetry are stabilized more by solvent than those with atoms that are more electrically neutral. Of some importance in this study is the finding that conformation is also dependent on solvation and that change in geometry must be considered if an accurate estimate is to be made of energy differences such as those examined in the calculations of merostabilization.     

Microstructure of nickel nanoparticles embedded in carbon films: case study on annealing effect by micromorphology analysis

The presented study is aimed at analyzing the surface texture of amorphous hydrogenated carbon layers containing nickel nanoparticles (Ni‐NPs@a‐C:H) within their structure, which were deposited by Radio Frequency (RF) sputtering and RF‐Plasma Enhanced Chemical Vapor Deposition (RF‐PECVD) methods on glass substrates. Prepared films were then used as research material following their annealing at two different temperatures of 250 °C and 350 °C in an inert argon atmosphere. Series of height samples were taken with the help of atomic force microscopy (AFM) operating in a non‐contact mode and examined in order to determine their fractal characteristics. Raw AFM data were first plane‐fitted to remove the surface bow exhibiting the so‐called residual surface, and then numerically processed to calculate the Areal Autocorrelation Function (AACF), which was later used to compute the Structure Function (SF). The log–log plots of the latter served for calculation of fractal properties of surfaces under investigation, including fractal dimension D, and pseudo‐topothesy K. The analysis of 3‐D surface texture helps to understand their essential characteristics and their implications as well as graphical models and their implementation in computer simulation. Copyright © 2016 John Wiley & Sons, Ltd.