Development of a so-called hour method for analysis of plutonium in soil samples

A short overview of HPLC column packings is presented. The properties of chromatographic carriers and the possibilities to combine the solid matrices with organic polymeric stationary phases are elucidated in detail. The latest achievements and anticipated future developments in the area are outlined.     

Ambivalent role of metal chlorides in ring opening reactions of 2H-azirines: synthesis of imidazoles,pyrroles and pyrrolinones

2H-Azirines were found to react with imines, enaminones and enaminoesters in the presence of metal salts. Imidazoles, pyrroles and new pyrrolinones derivatives are isolated in good overall yields. The role of metal salts was investigated as they can act as Lewis acids or electron donors. Mechanisms are proposed suggesting that imidazoles arise from addition of azirine to imines via radical or ionic mechanism; pyrroles and pyrrolinones are obtained from azirines with enamino derivatives when the salt acts as a Lewis acid. In the latter case the properties of the metallic compound influence the reaction regioselectivity.     

Pyrazolo[3,4-d][1,2,3]triazolo[1,5-a]pyrimidine: a new ring system through Dimroth rearrangement

Derivatives of the new ring system pyrazolo[3,4-d][1,2,3]triazolo[1,5-a]pyrimidine were synthesized from the corresponding angular isomers, through a Dimroth rearrangement, in quantitative yields. Preliminary computational studies demonstrated that this class of compounds could be a good candidate as DNA intercalating agents.     

A Click Chemistry Approach to Developing Molecularly Targeted DNA Scissors

Nucleic acid click chemistry was used to prepare a family of chemically modified triplex forming oligonucleotides (TFOs) for application as a new gene-targeted technology. Azide-bearing phenanthrene ligands—designed to promote triplex stability and copper binding—were ‘clicked’ to alkyne-modified parallel TFOs. Using this approach, a library of TFO hybrids was prepared and shown to effectively target purine-rich genetic elements in vitro. Several of the hybrids provide significant stabilisation toward melting in parallel triplexes (>20 °C) and DNA damage can be triggered upon copper binding in the presence of added reductant. Therefore, the TFO and ‘clicked’ ligands work synergistically to provide sequence-selectivity to the copper cutting unit which, in turn, confers high stabilisation to the DNA triplex. To extend the boundaries of this hybrid system further, a click chemistry-based di-copper binding ligand was developed to accommodate designer ancillary ligands such as DPQ and DPPZ. When this ligand was inserted into a TFO, a dramatic improvement in targeted oxidative cleavage is afforded.     

Parameter Analysis of Multiscale Two-Dimensional Fuzzy and Dispersion Entropy Measures Using Machine Learning Classification

Two-dimensional fuzzy entropy, dispersion entropy, and their multiscale extensions (MFuzzyEn2D and MDispEn2D, respectively) have shown promising results for image classifications. However, these results rely on the selection of key parameters that may largely influence the entropy values obtained. Yet, the optimal choice for these parameters has not been studied thoroughly. We propose a study on the impact of these parameters in image classification. For this purpose, the entropy-based algorithms are applied to a variety of images from different datasets, each containing multiple image classes. Several parameter combinations are used to obtain the entropy values. These entropy values are then applied to a range of machine learning classifiers and the algorithm parameters are analyzed based on the classification results. By using specific parameters, we show that both MFuzzyEn2D and MDispEn2D approach state-of-the-art in terms of image classification for multiple image types. They lead to an average maximum accuracy of more than 95% for all the datasets tested. Moreover, MFuzzyEn2D results in a better classification performance than that extracted by MDispEn2D as a majority. Furthermore, the choice of classifier does not have a significant impact on the classification of the extracted features by both entropy algorithms. The results open new perspectives for these entropy-based measures in textural analysis.     

Study of the absorption edge of SnO2 nanoparticles embedded in silica films

Silica thin films with embedded SnO₂ nanoparticles have been grown on transparent substrates by the sol–gel method. Tin dioxide crystals with cassiterite structure are semiconductors with a wide band gap of ~ 3.6 eV. Optical absorption spectroscopy in the near ultraviolet–visible range has been exploited to probe nanostructuring features of such nanocrystals. The results show that the sintering conditions modify crystallite mean size and enable the occurrence of quantum confinement effects. The outcome is in accordance with transmission electron microscopy data conducted on analogous bulk samples.     

Pyrrolo[3,2-c][1,2,5]benzotriazocine: A new ring system

A nucleophilic substitution reaction in the pyrrole series, achieved by a neutral nucleophile, led to the key intermediate 7 which by reduction and successive diazotization afforded the new ring system pyrrolo[3,2-c][1,2,5]benzotriazocine 9 in good yield.