Radioactivity of honey from northern Poland

This work shows significant variations in the values of ²¹⁰Po in different analyzed Polish voivodeships. Statistical analysis of ²¹⁰Po activity concentrations in honey samples showed significant differences between place of honey collecting, kind of honey and morphological structure of plants from which bees collected nectar.

     

Direct Comparison of the Reactivity of Model Complexes for Compounds 0, I,and II in Oxygenation,Hydrogen‐Abstraction,and Hydride‐Transfer Processes

The iron(III) meso‐tetramesitylporphyrin complex is a good biomimetic to study the catalytic reactions of cytochrome P450. All of the three most discussed reactive intermediates concerning P450 catalysis (namely, Cpd 0, Cpd I, and Cpd II) can be selectively produced, identified, and stabilized for many minutes in solution at low temperature by choosing appropriate reaction conditions. In this way, their reactivity against various substrates was determined by utilizing low‐temperature rapid‐scan UV/Vis spectroscopy. Since all reactive intermediates are derived from a single model complex, the results of these kinetic measurements provide for the first time a full comparability of the determined rate constants for the three intermediates. The rate constants reveal a significant dependence of the reactivity on the type of reaction (e.g., oxygenation, hydrogen abstraction, or hydride transfer), which closely correlates with the chemical nature of Cpds 0, I, and II. The detailed knowledge of the reactivity of these intermediates provides a valuable tool to evaluate their particular role in biological systems.     

The self‐disproportionation of enantiomers (SDE): The effect of scaling down,potential problems versus prospective applications,possible new occurrences,and unrealized opportunities?

This commentary discusses an important, though not widely appreciated, chiral phenomenon of molecular chirality that effectively always occurs whenever nonracemic samples are subjected to practically any physicochemical process (e.g., force field, recrystallization, sublimation, even distillation, etc.) under totally achiral conditions external to the sample itself. The phenomenon is termed as the self‐disproportionation of enantiomers (SDE) and though ubiquitous, its presence may not always be readily apparent, or workers may be otherwise oblivious to its effects. In the particular case of chromatography, when the SDE is apparent, the enantiomeric excess (ee) of the chiral compound is observed to vary across an eluted peak, with anterior eluted portions either enantioenriched or enantiodepleted relative to the ee of the starting material, and conversely for the posterior eluted portions. Herein, we highlight various aspects of the SDE phenomenon as it pertains to chromatography and, in particular, the effect of scaling down chromatographic systems, the potential risk of problems that the SDE can cause, as well as opportunities for practical applications of the phenomenon, possible new occurrences of the SDE phenomenon to be searched for, and unrealized opportunities.     

Influence of SrO content on microstructure and crystallization of glazes in the SiO2–Al2O3–CaO–MgO–K2O system

The effect of the SrO addition on the microstructure and structure of the glazes from the SiO₂–Al₂O₃–CaO–MgO–K₂O system was investigated in this study. The results were obtained by testing the ability of the frits crystallization, the stability of the crystallizing phases during the single-step fast-firing cycle depending on their chemical composition and the effect of addition of strontium oxide. Differential scanning calorimetry (DSC) curves showed that all glazes crystallized, and diopside and anorthite were mainly identified as dominant phases in the obtained glazes, while the size and amount of each depended on the amount of SrO introduced. The thermal characteristic of the frits was carried out using DSC, and crystalline phases were determined by X-ray diffractometry. The glaze microstructure was investigated by scanning electron microscopy and transmission electron microscopy. Additional information on the microstructure of frits was derived from spectroscopic studies in the mid-infrared range.

     

Recommended Tests for the Self-Disproportionation of Enantiomers (SDE) to Ensure Accurate Reporting of the Stereochemical Outcome of Enantioselective Reactions

The purpose of this review is to highlight the necessity of conducting tests to gauge the magnitude of the self-disproportionation of enantiomers (SDE) phenomenon to ensure the veracity of reported enantiomeric excess (ee) values for scalemic samples obtained from enantioselective reactions, natural products isolation, etc. The SDE always occurs to some degree whenever any scalemic sample is subjected to physicochemical processes concomitant with the fractionation of the sample, thus leading to erroneous reporting of the true ee of the sample if due care is not taken to either preclude the effects of the SDE by measurement of the ee prior to the application of physicochemical processes, suppressing the SDE, or evaluating all obtained fractions of the sample. Or even avoiding fractionation altogether if possible. There is a clear necessity to conduct tests to assess the magnitude of the SDE for the processes applied to samples and the updated and improved recommendations described herein cover chromatography and processes involving gas-phase transformations such as evaporation or sublimation.     

Comparative Structural and Electrical Studies of V2O3 and V2—xNixO3 (0 < x < 0.75) Solid Solution

V₂O₃ room and low temperature structures have been refined using PXRD and Rietveld procedures. At 15 K, in addition to the umbrella like opening of V—O bonds associated to the typical large V—V distance through the face shared octahedra (V—V_fsh) we have observed three different V—V distances through the edge shared octahedra (V—V_edsh) : 2.985Å, 2.908Å, and 2.847Å. This splitting is a consequence of the rotation of V—V pairs in a plane itself rotated out of the ( ac ) one which appears to be the origin for the well‐known rhombohedral to monoclinic distortion. Ni for V substitutions drive to a V_2—xNi_xO₃ solid solution with a wide homogeneity range (0 < x < 0.75). Structure refinements on selected compositions show that at both room and 15 K temperatures the typical V₂O₃ corundum type is kept. At 300 K, the main Ni effect is a drastic decrease of the c parameter associated to a flattening of the octahedra but also to an increase of the M—M_fsh distance without rotation of the M—M pairs. This explains the absence of the monoclinic transition in the whole homogeneity and temperature ranges and shows clearly that a large M—M_fsh distance is not necessarily associated with the monoclinic form. Despite this large distance observed in the whole temperature range, the electric behavior exhibits a conductor to insulator transition. It is explained in terms of semi conduction via an electron hopping process between V³⁺ and V⁴⁺ cations which depends on Ni amounts. This last result implies also that a large M—M_fsh distance is not associated with an insulating behavior.     

ICP-MS Multi-Elemental Analysis of the Human Meninges Collected from Sudden Death Victims in South-Eastern Poland

Metals perform many important physiological functions in the human body. The distribution of elements in different tissues is not uniform. Moreover, some structures can be the site of an accumulation of essential or toxic metals, leading to multi-directional intracellular damage. In the nervous system, these disorders are especially dangerous. Metals dyshomeostasis has been linked to a variety of neurological disorders which end up leading to permanent injuries. The multi-elemental composition of the human brain is still the subject of numerous investigations and debates. In this study, for the first time, the meninges, i.e., the dura mater and the arachnoid, were examined for their elemental composition by means of inductively coupled plasma mass spectrometry (ICP-MS). Tissue samples were collected post mortem from those who died suddenly as a result of suicide (n = 20) or as a result of injuries after an accident (n = 20). The interactions between 51 elements in both groups showed mainly weak positive correlations, which dominated the arachnoid mater compared to the dura mater. The study showed differences in the distribution of some elements within the meninges in the studied groups. The significant differences concerned mainly metals from the lanthanide family (Ln), macroelements (Na, K, Ca, Mg), a few micronutrients (Co), and toxic cadmium (Cd). The performed evaluation of the elemental distribution in the human meninges sheds new light on the trace metals metabolism in the central nervous system, although we do not yet fully understand the role of the human meninges.     

Is human hair a proper 210Po and 210Pb monitor of their increased activity in the human body?

Journal of Radioanalytical and Nuclear Chemistry - The study focused on 210Po and 210Pb activity concentrations determination in human hair as well as investigation its utility as an easy and safe...     

A Multicoincidence Study of Fragmentation Dynamics in Collision of γ‐Aminobutyric Acid with Low‐Energy Ions

Fragmentation of the γ‐aminobutyric acid molecule (GABA, NH₂(CH₂)₃COOH) following collisions with slow O⁶⁺ ions (v≈0.3 a.u.) was studied in the gas phase by a combined experimental and theoretical approach. In the experiments, a multicoincidence detection method was used to deduce the charge state of the GABA molecule before fragmentation. This is essential to unambiguously unravel the different fragmentation pathways. It was found that the molecular cations resulting from the collisions hardly survive the interaction and that the main dissociation channels correspond to formation of NH₂CH₂⁺, HCNH⁺, CH₂CH₂⁺, and COOH⁺ fragments. State‐of‐the‐art quantum chemistry calculations allow different fragmentation mechanisms to be proposed from analysis of the relevant minima and transition states on the computed potential‐energy surface. For example, the weak contribution at [M?18]⁺, where M is the mass of the parent ion, can be interpreted as resulting from H₂O loss that follows molecular folding of the long carbon chain of the amino acid.