C–H activation through late transition metal cyclometallation. Addressing selectivity and reactivity problems.

The ligand-directed C—H activation relies on a coordinating donor atom being in proximity to the C—H bond activated. Cyclometallation of 2-(1-naphthyl)-pyridine – a substrate containing both γ- and δ-positions in proximity to the directing nitrogen atom – was studied. Cycloruthenation and cyclopalladation result in γ-substitution and formation of the corresponding 5-membered metallacycles, which is in agreement with published regioselectivities of the corresponding catalytic reactions. Simultaneously, cycloauration and cycloborylation result in δ-substitution and formation of the corresponding 6-membered metallacycles. X-ray structures of all the metallacycles are presented. Deuterium labelling studies show that the cyclopalladation and cycloauration are irreversible, while the cycloruthenation is reversible and happens in both γ- and δ-positions. Attempts to synthesise bimetallic palladium complexes, consisting of two (2-phenyl-pyridine) palladium fragments connected via bridging ligands, resulted predominantly in the formation of monometallic species. While 1,8-naphthyridine and 7-aza-indole bind to palladium in an L-fashion with only one of the two nitrogen atoms, N-piperidine dithiocarbamic acid binds with both sulfur atoms in a chelating, rather than a bridging fashion. 3,3-Dimethylglutaric acid acts as a bridging ligand. X-ray structures of naphthyridine and dithiocarbamate complexes are presented. No increase in the reactivity is observed, when 1,8-naphthyridine, 7-aza-indole and N-piperidine dithiocarbamic acid were used as additives in palladium-catalysed acetoxylation and bromination of 2-phenyl-pyridine. Oxidative anion metathesis was employed as a method of synthesis of organic salts. Trimethylsulfoxonium iodide salts can be converted to tetrafluoroborate, hexafluorophosphate, trifluoroacetate, tosylate and bis-triflimide salts in the presence of hydrogen peroxide and the corresponding acids. The scope of cations, suitable for this reaction also includes N-alkylpyridinium and quaternary phosphonium salts. N-acetoxypyridinium chloride was employed as an oxidant in the palladium-catalysed C—H functionalisation of 2-aryl-pyridine resulting in the formation of the corresponding chloro-derivative. Trimethylsulfoxonium tetrafluoroborate, hexafluorophosphate and tosylate are unreactive as oxidants towards 2-(phenyl)-pyridine palladium acetate. Cyclopalladation of PCP pincer ligands with aromatic and aliphatic backbones by (PhCN)2PdCl2 was shown to proceed at temperatures as low as -62⁰C. The initial interaction results in the formation of a mixture of coordinated species, only some of which react further to form metallacyclic pincer compounds. The formation of pre-cyclometallation intermediates is kinetically disfavoured. However, C—H activation is fast and not rate-limiting in case of neither sp2 nor sp3 C—H bonds

Development of ways of increase of ore-heating electric furnaces for production of ferroalloys efficiency

Ways of increase of ore-heating electric furnaces, used for production of ferroalloys, efficiency are considered. The advanced system of automatic control of the ore-heating furnace providing improvement of technical and economic indicators of technological process and adaptability to quality of burden stocks is offered

Research of Reliable Power Supply Schemes for OOO Gazprom Production Yamburg Gas Field

In article the analysis of substation electric part for the enterprises an oil and gas complex power supply is carried out: structure and switchgear schemes, uninterrupted reserve sources structure. Recommendations for power supply reliability are made

Using Static Polynomial Load Models in "Rastrwin" Software Package for Power System Studies

Polynomial load model practical application has some specificity. Per unit static load model dependence on node rated voltage value is demonstrated in this paper. The assigned rated voltage values of load nodes with polynomial characteristics are to be invariant to avoid calculation complementary error appearance. If rated voltage correction is necessary condition, for example to obtain calculation convergence, the active and reactive power drawn under rated voltage and polynomial coefficients must be corrected too. Correcting calculation expressions are presented in the paper

Estimating Accuracy of Experimentally Obtained Power System Zip Load Models

Experimentally obtained ZIP load models are used for the power system analysis. Estimating accuracy of such models is presented in this paper. The dependence of ZIP load model error on the range in which voltage changes during the experiment, the number of measured values of voltage and power, standard deviation of the load change random process have been obtained using the computing experiment. The results could be used to estimate the accuracy of ZIP load models or to design the experiment to determine ZIP load models with prescribed accuracy

Testis-specific glyceraldehyde-3-phosphate dehydrogenase: origin and evolution

<p>Abstract</p> <p>Background</p> <p>Glyceraldehyde-3-phosphate dehydrogenase (GAPD) catalyses one of the glycolytic reactions and is also involved in a number of non-glycolytic processes, such as endocytosis, DNA excision repair, and induction of apoptosis. Mammals are known to possess two homologous GAPD isoenzymes: GAPD-1, a well-studied protein found in all somatic cells, and GAPD-2, which is expressed solely in testis. GAPD-2 supplies energy required for the movement of spermatozoa and is tightly bound to the sperm tail cytoskeleton by the additional N-terminal proline-rich domain absent in GAPD-1. In this study we investigate the evolutionary history of GAPD and gain some insights into specialization of GAPD-2 as a testis-specific protein.</p> <p>Results</p> <p>A dataset of GAPD sequences was assembled from public databases and used for phylogeny reconstruction by means of the Bayesian method. Since resolution in some clades of the obtained tree was too low, syntenic analysis was carried out to define the evolutionary history of GAPD more precisely. The performed selection tests showed that selective pressure varies across lineages and isoenzymes, as well as across different regions of the same sequences.</p> <p>Conclusions</p> <p>The obtained results suggest that GAPD-1 and GAPD-2 emerged after duplication during the early evolution of chordates. GAPD-2 was subsequently lost by most lineages except lizards, mammals, as well as cartilaginous and bony fishes. In reptilians and mammals, GAPD-2 specialized to a testis-specific protein and acquired the novel N-terminal proline-rich domain anchoring the protein in the sperm tail cytoskeleton. This domain is likely to have originated by exonization of a microsatellite genomic region. Recognition of the proline-rich domain by cytoskeletal proteins seems to be unspecific. Besides testis, GAPD-2 of lizards was also found in some regenerating tissues, but it lacks the proline-rich domain due to tissue-specific alternative splicing.</p

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M&gt;70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0&lt;e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Using Static Polynomial Load Models in “Rastrwin” Software Package for Power System Studies

Polynomial load model practical application has some specificity. Per unit static load model dependence on node rated voltage value is demonstrated in this paper. The assigned rated voltage values of load nodes with polynomial characteristics are to be invariant to avoid calculation complementary error appearance. If rated voltage correction is necessary condition, for example to obtain calculation convergence, the active and reactive power drawn under rated voltage and polynomial coefficients must be corrected too. Correcting calculation expressions are presented in the paper