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Understanding how super-massive black holes form and grow in the early Universe has become a major challenge1,2since it was discovered that luminous quasars existed only 700 million years after the Big Bang3,4. Simulations indicate an evolutionary sequence of dust-reddened quasars emerging from heavily dust-obscured starbursts that then transition to unobscured luminous quasars by expelling gas and dust5. Although the last phase has been identified out to a redshift of 7.6 (ref. 6), a transitioning quasar has not been found at similar redshifts owing to their faintness at optical and near-infrared wavelengths. Here we report observations of an ultraviolet compact object, GNz7q, associated with a dust-enshrouded starburst at a redshift of 7.1899 ± 0.0005. The host galaxy is more luminous in dust emission than any other known object at this epoch, forming 1,600 solar masses of stars per year within a central radius of 480 parsec. A red point source in the far-ultraviolet is identified in deep, high-resolution imaging and slitless spectroscopy. GNz7q is extremely faint in X-rays, which indicates the emergence of a uniquely ultraviolet compact star-forming region or a Compton-thick super-Eddington black-hole accretion disk at the dusty starburst core. In the latter case, the observed properties are consistent with predictions from cosmological simulations7and suggest that GNz7q is an antecedent to unobscured luminous quasars at later epochs.

Abstract: Bipolar expansion of the Ohno potential as a method of calculating two-center Coulomb integrals that appear in the NDDO approximation is generalized to one-center two-electron integrals. A unified semiempirical scheme is suggested for estimating two-electron interactions in molecules. This scheme can be readily extended to arbitrary Slater basis sets (including the s,p,d-orbitals) and involves no a priori data on the valent states of atoms. In this work, the scheme is employed to extend the semiempirical PM3 method to the s,p,d-basis set. The efficiency of the method is proven by test calculations of 24 chromium compounds (π-complexes, carbonyls, isocyanides, etc.).

Abstract: This paper deals with the problems of extending semiempirical MNDO methods to compounds with d-elements. The problem is solved by estimating two-center two-electron integrals (TTI) with the Ono potential modeling interaction between two electrons in a molecule. A scheme for calculating TTI is suggested which uses the expansion of the Ono potential in a series of pairwise products of spherical harmonics centered on two atoms in the molecule. The scheme is stable and efficient for calculations in arbitrary Slater basis sets (including the s,p,d-basis set) and seems to be useful for development of NDDO methods.

1.The SCF MO LCAO method with the MINDO/3 valence approximation and the nonempirical STO-3G and 4-31G methods were used to calculate the potential energy hypersurface of the intramolecular rearrangement of dimethyl(methylperoxy)borane. We found that the reaction takes place by a congruent mechanism with an unsymmetrical transition state similar to bicyclobutane.2.The calculated data indicate the existence of two organoboron peroxide conformations different in structure: an open form analogous to the structure of organic peroxides, and a cyclic form with intramolecular coordination of the boron-oxygen bond.

p-Cymene and p-cyclopropyltoluene and their radical-cations were calculated by the LCAO-MO SCF method in the MINDO/3 valence approximation. It was shown that the radical-cations are stabilized through s,p conjugation of the methyl groups.

1.Results of USM are governed both by the location of actual defects and by microstructure through the forging cross section.2.Pulses observed from the remains of boundaries in overheated structure [1] and a simultaneous reduction in the number BES are apparently caused by a change in the angle of reflection of untrasonic (US) waves at the pearlite-ferrite boundary with partial energy dissipation [3].3."Grey whiskers" observed in each forging without obvious defects are differentiated with sufficient reliability from actual defects by controlling the power of the ultrasonic signal and receiver sensitivity for the US defectoscope under conditions when the remains of overheated structure boundaries are absent from the microstructure.

1.The basic reason for total or partial nonsounding for large forgings during ultrasonic inspection is the presence of coarse grains grown during heating castings after forging (reheated structure) which is not refined due to improper heat treatment.2.After carrying out normalization and tempering properly, large forgings have a fine-grained microstructure (grain size Nos. 5–8) with good sounding (not less than four bottom echo signals).