May thermal imaging be useful in cyclist endurance tests?

Thermovision is a completely non-invasive and easy-to-perform method of imaging, and it is becoming useful not only in different modalities of clinical medicine, but also in sports medicine. However, it seems that thermal imaging may also find some use in training. That is why the aim of these studies is to compare temperature parameters with data obtained from specialist equipment, which uses monitoring to choose organism parameters during the endurance test and also to determine the efficiency level. In this study, we also try to estimate body metabolism, using a modified formula of Kleiber’s law. We describe how metabolism changes during efficiency tests and compare these changes with parameters checked by an ergospirometer. All studies were performed by thermovision camera (Flir Systems E60). Results of the study showed that thermal imaging may be useful in sports medicine as a helpful method in efficiency evaluation. We obtained a high correlation between the standard parameters used in efficiency tests and the parameters derived from thermal imaging, which may suggest the possibility of using thermovision as an additional method in the planning of training cycles, and its effects.     

Coexistence of the relaxor-like and ferroelectric behavior in K1-xLixTaO3

ABSTRACT

The results of low-temperature linear and nonlinear susceptibilities, polarization measurements and the dc electric field dependence of the dielectric properties of the lithium-doped potassium tantalate K_1-xLi_xTaO₃, x = 0.034 (KLT-3.4%Li) solid solution are presented. The coexistence of the relaxor-like and ferroelectric behavior and different mechanisms leading to either of them are discussed. The observed ferroelectric phase transition is of the first-order type with temperature hysteresis. This transition is due to the off-center motions of Ta ions in the octahedral environment of oxygen ions. Clusters of Li⁺ ions produce a relaxor-like behavior and random electric field. This field reduces the depolarization field and allows off-center motions of Ta ions and an appearance of spontaneous polarization.     

Design of thiolate rich metal binding sites within a peptidic framework

A de novo protein design strategy provides a powerful tool to elucidate how heavy metals interact with proteins.Cysteine derivatives of the TRI peptide family (Ac-G(LKALEEK)4G-NH2) have been shown to bind heavy metals in an unusual trigonal geometry. Our present objective was to design binding sites in R-helical scaffolds that are able to form higher coordination number complexes with Cd(II) and Hg(II). Herein, we evaluate the binding of Cd(II) and Hg(II) to double cysteine substituted TRI peptides lacking intervening leucines between sulfurs in the heptads. We compare a -Cysd-X-X-X-Cysa- binding motif found in TRIL12CL16C to the more common -Cysa-X-X-Cysd- sequence of native proteins found in TRIL9CL12C. Compared to TRI, these substitutions destabilize the helical aggregates,leading to mixtures of two- and three-stranded bundles. The three-stranded coiled coils are stabilized by the addition of metals. TRIL9CL12C forms distorted tetrahedral complexes with both Cd(II) and Hg(II), as supported by UV-vis,CD, 113Cd NMR, 199Hg NMR and 111mCd PAC spectroscopy. Additionally, these signatures are very similar to those found for heavy metal substituted rubredoxin. These results suggest that in terms of Hg(II) binding, TRIL9CL12Ccan be considered as a good mimic of the metallochaperone HAH1, that has previously been shown to form protein dimers. TRIL12CL16C has limited ability to generate homoleptic tetrahedral complexes (Cd(SR)42-). These type of complexes were identified only for Hg(II). However, the spectroscopic signatures suggest a different geometry around the metal ion, demonstrating that effective metal sequestration into the hydrophobic interior of the bundle requires more than simply adding two sulfur residues in adjacent layers of the peptide core. Thus, proper design of metal binding sites must also consider the orientation of cysteine sidechains in a vs d positions of the heptads.     

Non-invasive surface analysis of ancient bronze arrowheads with scanning electron microscopy and X-ray powder diffractometry

In this research, surfaces of eight ancient metal arrowheads were investigated regarding chemical composition, homogeneity, and products of corrosion. To perform that, two nondestructive techniques were applied: Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray powder diffractometry (XRPD). Importantly, both methods did not require sampling, cutting, nor significant cleaning of the historical artifacts, which made the measurements not only nondestructive but noninvasive too. SEM-EDS measurements provided information on the morphology and elemental composition of the surfaces of the studied objects as well as the distribution of chemical elements on the surfaces and supported crystalline phase analysis. It was revealed that the arrowheads were cast of tin bronze, but some of them contained high amounts of lead and admixtures of antimony and arsenic while copper and tin oxides and lead carbonates were found as the major corrosion products. In some cases, distribution of elements in the surface exhibited serious nonhomogeneity, probably resulting from limited solubility of the casting metals and degradation processes. Based on the obtained results, authenticity and declared provenience of the arrowheads were assessed in reference to the characteristics of similar objects described in literature.     

Copper(II) 2,2-Bis(Hydroxymethyl)Propionate Coordination Compounds with Hexamethylenetetramine: From Mononuclear Complex to One-Dimensional Coordination Polymer

Three new copper coordination compounds derived from 2,2-bis(hydroxymethyl)propionic acid (dmpa) and hexamethylenetetramine (hmta) were obtained and their crystal structures were determined. The stoichiometry of the reagents applied in the syntheses reflects the metal to ligand molar ratio in the formed solid products. Due to the multiple coordination modes of the used ligands, wide structural diversity was achieved among synthesized compounds, i.e., mononuclear [Cu(dmp)₂(hmta)₂(H₂O)] (1), dinuclear [Cu₂(dmp)₄(hmta)₂] (2), and 1D coordination polymer [Cu₂(dmp)₄(hmta)]_n (3). Their supramolecular structures are governed by O—H•••O and O—H•••N hydrogen bonds. The compounds were characterized in terms of absorption (UV-Vis and IR) and thermal properties. The relationships between structural features and properties were discussed in detail. Owing to discrepancies in the coordination mode of a dmp ligand, bidentate chelating in 1, and bidentate bridging in 2 and 3, there is a noticeable change in the position of the bands corresponding to the stretching vibrations of the carboxylate group in the IR spectra. The differences in the structures of the compounds are also reflected in the nature and position of the UV-Vis absorption maxima, which are located at lower wavelengths for 1.     

The impact of sterol structure on the interactions with sphingomyelin in mixed langmuir monolayers

In this work, the Langmuir monolayer technique was applied to study the interactions between sphingomyelin and various sterols differing in the structure of the side chain (cholesterol, beta-sitosterol, stigmasterol). The mean area per molecule and the excess free energy of mixing values were analyzed in the context of sterol-induced condensing effect and interactions between molecules in the mixed monolayers. Moreover, the compression modulus values were calculated and widely discussed from the point of view of the ordering effect of sterols. It was found that all of the sterols investigated form the most stable monolayers with sphingomyelin at 2:1 sphingomyelin:sterol proportion and the strongest interactions exist between molecules in cholesterol-containing films. Moreover, cholesterol provokes the strongest area condensation and reveals the highest ordering properties, while plant sterols were found to differ only slightly with regards to their ordering properties. Additionally, the ordering effect of the sterols on dipalmitoylphosphatidylcholine (DPPC) films was analyzed and compared to that on sphingomyelin films.     

Quick prediction of the retention of solutes in 13 thin layer chromatographic screening systems on silica gel by classification and regression trees

The use of classification and regression trees (CART) was studied in a quantitative structure-retention relationship (QSRR) context to predict the retention in 13 thin layer chromatographic screening systems on a silica gel, where large datasets of interlaboratory determined retention are available. The response (dependent variable) was the rate mobility (RM) factor, while a set of atomic contributions and functional substituent counts was used as an explanatory dataset. The trees were investigated against optimal complexity (number of the leaves) by external validation and internal crossvalidation. Their predictive performance is slightly lower than full atomic contribution model, but the main advantage is the simplicity. The retention prediction with the proposed trees can be done without computer or even pocket calculator.