Synthesis and sorption properties of filled fibrous sorbents with immobilized hetarylformazan groups

New sorbents were prepared by immobilization of structurally different sulfur-containing hetaryl-formazans on nonwoven polyacrylonitrile fiber tilled with AV-17 anion exchanger. Sorption of some heavy metals on these materials was studied as influenced by various factors. Sorbents for selective recovery of copper(II) in the presence of nickel(II), zinc(II), and cadmium(II) cations were found

Synthesis and catalytic properties of copper(II) 1-aryl-5-benzothiazolylformazanates

New copper(II) benzothiazolylformazane complexes were synthesized and immobilized on AN-18 anion exchanger. The influence of the composition of the coordination core of copper(II) benzthiazolylformazanates and temperature on their catalytic properties in decomposition of H2O2 and oxidation of Na2S in aqueous solution was studied

Synthesis and spectroscopic features of iron(II) 1-aryl-5-benzothiazol-2- ylformazanates

New iron(II) coordination compounds with 1-aryl-5-(benzothiazol-2-yl) formazans were prepared. Their compositions and structures were determined by electronic spectroscopy, mass spectrometry, single crystal X-ray diffraction analysis, and magnetochemical measurements. © 2008 Pleiades Publishing, Ltd.Russian Foundation for Basic Researc

Synthetic approaches to 2-aryl/hetaryl- and 2-(hetaryl)ylidene derivatives of fluorinated 1,3-benzothiazin-4-ones

A series of 2-hetaryl- and 2-(hetaryl)ylidene substituted 5-fluoro-8-nitro-1,3-benzothiazin-4-ones was synthesized by interaction of 2,6-difluoro-3-nitrobenzoylisothiocyanate with C-nucleophiles. Cyclocondensation of polyfluorobenzoylchlorides with aryl and hetaryl thioamides represents new approach to 1,3-benzothiazin-4-ones. Some compounds proved to be promising for further development of tuberculostatic agents

Evolution of accretion disks around massive black holes: constraints from the demography of active galactic nuclei

Observations have shown that the Eddington ratios (the ratio of the bolometric luminosity to the Eddington luminosity) in QSOs/active galactic nuclei (AGNs) cover a wide range. In this paper we connect the demography of AGNs obtained by the Sloan Digital Sky Survey with the accretion physics around massive black holes and propose that the diversity in the Eddington ratios is a natural result of the long-term evolution of accretion disks in AGNs. The observed accretion rate distribution of AGNs (with host galaxy velocity dispersion sigma~70-200 km/s) in the nearby universe (z<0.3) is consistent with the predictions of simple theoretical models in which the accretion rates evolve in a self-similar way. We also discuss the implications of the results for the issues related to self-gravitating disks, coevolution of galaxies and QSOs/AGNs, and the unification picture of AGNs.Comment: 18 pages, 2 figures; revised, main conclusions not changed; to appear in ApJ, Oct., 200

Synthesis of 7-cycloalkylimino substituted 3-amino-6-fluoro-2-methyl-3H- quinazolin-4-ones

A versatile pathway for the synthesis of 7-cycloalkylimino substituted 3-amino-6-fluoro-2-methyl-3H-quinazolin-4-ones from 4,5-difluoroanthranylic acid has been advanced. Nucleophilic amination-defluorination reaction of the 6,7-difluoro derivative of 3-amino-2-methyl-3H-quinazolin-4-one has been established to occur at position 7, as shown by X-ray crystallographic analysis. © 2012 Elsevier B.V

Can Thin Disks Produce Anomalous X-Ray Pulsars?

We investigate whether young neutron stars with fall-back disks can produce Anomalous X-Ray Pulsars (AXPs) within timescales indicated by the ages of associated supernova remnants. The system passes through a propeller stage before emerging as an AXP or a radio pulsar. The evolution of the disk is described by a diffusion equation which has self-similar solutions with either angular momentum or total mass of the disk conserved. We associate these two types of solutions with accretor and propeller regimes, respectively. Our numerical calculations of thin disk models with changing inner radius take into account the super-critical accretion at the early stages, and electron scattering and bound-free opacities with rich metal content. Our results show that, assuming a fraction of the mass inflow is accreted onto the neutron star, the fall-back disk scenario can produce AXPs for acceptable parameters.Comment: 16 pages, 4 Figures, to be published in Astrophysical Journal Vol. 599, Dec. 1

Optical polarization observations with the MASTER robotic net

We present results of optical polarization observations performed with the MASTER robotic net for three types of objects: gamma-ray bursts, supernovae, and blazars. For the Swift gamma-ray bursts GRB100906A, GRB110422A, GRB121011A, polarization observations were obtained during very early stages of optical emission. For GRB100906A it was the first prompt optical polarization observation in the world. Photometry in polarizers is presented for Type Ia Supernova 2012bh during 20 days, starting on March 27, 2012. We find that the linear polarization of SN 2012bh at the early stage of the envelope expansion was less than 3%. Polarization measurements for the blazars OC 457, 3C 454.3, QSO B1215+303, 87GB 165943.2+395846 at single nights are presented. We infer the degree of the linear polarization and polarization angle. The blazars OC 457 and 3C 454.3 were observed during their periods of activity. The results show that MASTER is able to measure substantially polarized light; at the same time it is not suitable for determining weak polarization (less than 5%) of dim objects (fainter than 16$^m$). Polarimetric observations of the optical emission from gamma-ray bursts and supernovae are necessary to investigate the nature of these transient objects.Comment: 31 pages, 12 figures, 4 tables; Exposure times in Table 2 have been correcte

Toward precise constraints on growth of massive black holes

Growth of massive black holes (MBHs) in galactic centers comes mainly from gas accretion during their QSO/AGN phases. In this paper we apply an extended Soltan argument, connecting the local MBH mass function with the time-integral of the QSO luminosity function, to the demography of MBHs and QSOs from recent optical and X-ray surveys, and obtain robust constraints on the luminosity evolution (or mass growth history) of individual QSOs (or MBHs). We find that the luminosity evolution probably involves two phases: an initial exponentially increasing phase set by the Eddington limit and a following phase in which the luminosity declines with time as a power law (with a slope of -1.2--1.3) set by a self-similar long-term evolution of disk accretion. Neither an evolution involving only the increasing phase with a single Eddington ratio nor an exponentially declining pattern in the second phase is likely. The period of a QSO radiating at a luminosity higher than 10% of its peak value is about (2-3)x10^8 yr, during which the MBH obtains ~80% of its mass. The mass-to-energy conversion efficiency is $0.16\pm0.04 ^{+0.05}_{-0}$, with the latter error accounting for the maximum uncertainty due to Compton-thick AGNs. The expected Eddington ratios in QSOs from the constrained luminosity evolution cluster around a single value close to 0.5-1 for high-luminosity QSOs and extend to a wide range of lower values for low-luminosity ones. The Eddington ratios for high luminosity QSOs appear to conflict with those estimated from observations (~0.25) by using some virial mass estimators for MBHs in QSOs unless the estimators systematically over-estimate MBH masses by a factor of 2-4. We also infer the fraction of optically obscured QSOs ~60-80%. Further applications of the luminosity evolution of individual QSOs are also discussed.Comment: 25 pages, 13 figures, ApJ in pres

ANTIVIRAL PROPERTIES OF VERDAZYLS AND LEUCOVERDAZYLS AND THEIR ACTIVITY AGAINST GROUP B ENTEROVIRUSES

Enteroviruses are non-enveloped viruses of Enterovirus genus, Picornaviridae family, causing a variety of human diseases: from acute respiratory and intestinal infections to more severe pathologies including poliomyelitis, encephalitis, myocarditis, pancreatitis. Currently, no approved direct-acting antiviral drugs for treatment of enterovirus infections exists, whereas vaccination is available only for prevention of poliomyelitis and enterovirus 71 infection. Therefore, it is promising to conduct a search for inhibitors of enteroviruses life cycle in drug development to treat enterovirus infections. Here, antiviral properties of stable free radicals, verdazyls, and their precursors, leucoverdazyls, were investigated. It has been shown that leucoverdazyls vs verdazyls increased the survival of permissive cell culture infected with coxsackievirus. The activity range of the lead leucoverdazyl against RNA-containing and DNA-containing human viruses (in the viral yield reduction assay) and its proposed mechanism of action (time of addition assay) was studied. The lead compound suppressed reproduction of group B enteroviruses in vitro, with modest activity against influenza A virus and no activity against herpes virus type 1 and adenovirus type 5. The maximum decrease in viral titers was observed upon its addition to infected cells during early and middle stages of the virus life cycle. Thus, we concluded that the studied compound has a pronounced inhibitory activity against group B enteroviruses not belonging to the class of capsid binder inhibitors, without virucidal properties. Previously, we described antioxidant properties of leucoverdazyls. It is known that many viral infections are accompanied by production of reactive oxygen species and oxidative stress, and some compounds with antioxidant properties exhibit antiviral potential. Targeted chemical modifications of leucoverdazyls and further studies of leucoverdazyl mechanism of action as well as in vivo animal studies are needed. However, the results obtained may be useful for future development of new antiviral drugs to treat enteroviral infections. © Volobueva A.S. et al., 2023.The work was supported by a grant for young scientists from the St. Petersburg Pasteur Institute