1,4-Phenylene-bis-((1-methyl-1H-pyrazol-5-yl)borinic 8-oxyquinolinate) as a photoredox catalyst in the atom transfer radical addition of iodoperfluoroalkanes to alkenyl groups bearing organoboron compounds

The key photocatalytic properties of a transition-metal-free heteroleptic complex derived from 1,4-phenyldiboronic acid were evaluated. This compound was utilized in the atom transfer radical addition of iodoperfluoroalkanes to a series of alkenyl group bearing organoboron compounds. The products of these reactions retained the BC bond, and Suzuki-Miyaura coupling of one product gave biphenyl derivatives. The X-ray analysis of one of the obtained perfluoroalkylated boronic acids revealed the presence of open star-shaped channels.     

Stereoselective synthesis of amides possessing a vinylsilicon functionality via a ruthenium catalyzed silylative coupling reaction

An effective stereoselective synthesis of E-N-2-(silyl)vinylamides via silylative coupling of vinyl amides such as N-vinylpyrrolidinone, N-vinylphthalimide, and N-vinylformamide with vinyltrisubstituted silanes catalyzed by [RuH(Cl)(CO)(PCy₃)₂] I is described.     

New Acyclic Dimers of Cholic Acid with Oxamide and Hydrazide Spacers

Three new acyclic dimers of cholic acid with oxamide and isomeric hydrazide (N,N′-diacylhydrazine) spacers were obtained. The oxamide spacers bind two identical steroidal subunits through position 3 (head-to-head dimer) or position 23 (tail-to-tail dimer). In the case of a third dimer the hydrazine moiety binds two molecules of cholic acid through position 24 (tail-to-tail dimer).     

A criterion for high-cycle fatigue life and fatigue limit prediction in biaxial loading conditions

This paper presents a criterion for high-cycle fatigue life and fatigue strength estimation under periodic proportional and non-proportional cyclic loading. The criterion is based on the mean and maximum values of the second invariant of the stress deviator. Important elements of the criterion are: function of the non-proportionality of fatigue loading and the materials parameter that expresses the materials sensitivity to non-proportional loading. The methods for the materials parameters determination uses three S–N curves: tension–compression, torsion, and any non-proportional loading proposed. The criterion has been verified using experimental data, and the results are included in the paper. These results should be considered as promising. The paper also includes a proposal for multiaxial fatigue models classification due to the approach for the nonproportionality of loading.     

Quantum Evolution beyond the Markovian Semigroup — Generalizing the Stenholm–Barnett Approach

We provide conditions for the memory kernel governing the time-nonlocal quantum master equation which guarantee that the corresponding dynamical map is completely positive and trace-preserving. This approach gives rise to the new parametrization of dynamical maps in terms of two completely positive maps – so-called legitimate pair. In fact, these new parameterizations are a natural generalization of Markovian semigroup. Interestingly our class contains recently studied models like semi-Markov evolution and collision models.     

Variations of plutonium isotopic ratios in Antarctic ecosystems

The aim of the article was to verify the hypothesis concerning the diversification of plutonium sources in the natural environment of Antarctica. Plutonium activity and atom ratios were analyzed in two groups of biological samples: terrestrial and marine. Both isotopic ratios in the terrestrial set were consistent with global radioactive fallout ratios. The average activity ratio in the marine ecosystem was lower than global radioactive fallout. At the same time mass ratio values in this group turned out to be surprisingly varied. Analysis of the results showed statistically significant differences between the marine and terrestrial ecosystems.     

Monitoring Hydrogenation Reactions using Benchtop 2D NMR with Extraordinary Sensitivity and Spectral Resolution

Low-field benchtop nuclear magnetic resonance (BT-NMR) spectrometers with Halbach magnets are being increasingly used in science and industry as cost-efficient tools for the monitoring of chemical reactions, including hydrogenation. However, their use of low-field magnets limits both resolution and sensitivity. In this paper, we show that it is possible to alleviate these two problems through the combination of parahydrogen-induced polarization (PHIP) and fast correlation spectroscopy with time-resolved non-uniform sampling (TR-NUS). PHIP can enhance NMR signals so that substrates are easily detectable on BT-NMR spectrometers. The interleaved acquisition of one- and two-dimensional spectra with TR-NUS provides unique insight into the consecutive moments of hydrogenation reactions, with a spectral resolution unachievable in a standard approach. We illustrate the potential of the technique with two examples: the hydrogenation of ethylphenyl propiolate and the hydrogenation of a mixture of two substrates – ethylphenyl propiolate and ethyl 2-butynoate.