Search results for: A. A. Politov

Items from 1 to 13 out of 13 results

article

Luminescence Spectroscopy as a Tool to Study the Amorphization of Indomethacin upon Co-Grinding with Polymers

A. A. Politov, T. P. Shakhtshneider, E. V. Boldyreva, V. V. Boldyrev

Doklady Physical Chemistry > 2018 > 480 > 2 > 77-80

The possibility of using luminescence spectroscopy to study even the early stages of the amorphization of active pharmaceutical ingredients (APIs) during their co-grinding with different polymers has been demonstrated using indomethacin as an example. Amorphization of an API is observed only on co-grinding with those polymers that have functional groups capable of interacting with the API to form...

article

Inhibition of organic mechanochemical synthesis by water vapor

I. A. Tumanov, A. A. L. Michalchuk, A. A. Politov, E. V. Boldyreva, more

Doklady Chemistry > 2017 > 472 > 1 > 17-19

The effect of water on the mechanochemical synthesis in the glycine–malonic acid system has been studied in different types of devices. Comparative studies of the hygroscopicity of the reagents and products made it possible to rationalize the inhibiting effect of water vapor and the difference in the reaction course in impact and shear devices and in devices providing both action modes. The importance...

article

Mechanochemical Neutralization of Hypericin in Hypericum perforatum Studied by Spectroluminescence

I. O. Lomovskii, A. A. Politov

Chemistry of Natural Compounds > 2014 > 50 > 2 > 247-250

The speciation of hypericin in plant raw material was determined. The solid-state mechanochemical reaction of hypericin in plant raw material with alkaline reagents was studied in order to produce a very soluble salt species.

article

On Mechanochemical Dimerization of Anthracene. Different Possible Reaction Pathways

V. M. Tapilin, N. N. Bulgakov, A. P. Chupakhin, A. A. Politov, more

Journal of Structural Chemistry > 2010 > 51 > 4 > 635-641

Calculations of the anthracene crystal structure, 10% isotropic compression of the anthracene crystal and its two dimers linked not through the central atoms of central rings are performed in the density functional theory approximation. Linear lattice parameters a, b, c, interatomic distances, and bond angles coincide with those determined by single crystal X-ray diffraction and previously calculated...

article

On the mechanism of mechanochemical dimerization of anthracene. Quantum-chemical calculation of the electronic structure of anthracene and its dimer

V. M. Tapilin, N. N. Bulgakov, A. P. Chupakhin, A. A. Politov

Journal of Structural Chemistry > 2008 > 49 > 4 > 581-586

The electronic structure of anthracene, its dimer, and intermediate structures composed of two anthracene molecules were calculated in the density functional theory. The calculated potential barrier to anthracene dimerization is ∼55 kcal/mol; the dissociation barrier is ∼45 kcal/mol. The pressure required for the reaction to reach the transition state and acting on the anthracene crystal is ∼60 kbar...

article

Isolation of lappaconitine from Aconitum septentrionale roots by adsorption

A. E. Goncharov, A. A. Politov, N. A. Pankrushina, O. I. Lomovskii

Chemistry of Natural Compounds > 2006 > 42 > 3 > 336-339

Extracts of Aconitum septentrionale Koelle roots obtained using chloroform, isopropanol, and ethanol were purified using chloroform and basic γ-Al₂O₃. Ballast materials were selectively adsorbed by γ-Al₂O₃, increasing the mass fraction of lappaconitine in the extract. The ethanol extract was purified most. The degree of lappaconitine extraction by chloroform was unaffected by the presence of γ-Al₂...

article

Directional chemical variations in diamonds showing octahedral following cuboid growth

D. A. Zedgenizov, B. Harte, Edinburgh Ion Microprobe Facility (EIMF), V. S. Shatsky, more

Contributions to Mineralogy and Petrology > 2006 > 151 > 1 > 45-57

A progression from cuboid to octahedral growth has been observed in 16 natural diamonds from Yakutian kimberlites. X-ray and cathodoluminescence topography have revealed that the change in morphology of diamonds with cloudy cuboid cores may occur without mixed-habit growth but via generation of numerous octahedral apices on cuboid surfaces and subsequent gradual transformation into regular octahedral...

article

Directional chemical variations in diamonds showing octahedral following cuboid growth

D. A. Zedgenizov, B. Harte, Edinburgh Ion Microprobe Facility (EIMF), V. S. Shatsky, more

Contributions to Mineralogy and Petrology > 2006 > 151 > 2 > 243-244

The online version of the original article can be found at http://dx.doi.org/10.1007/s00410-005-0044-5

article

Mechanochemical interaction of Ca silicate and aluminosilicate minerals with carbon dioxide

A. M. Kalinkin, E. V. Kalinkina, A. A. Politov, V. N. Makarov, more

Journal of Materials Science > 2004 > 39 > 16-17 > 5393-5398

Processes induced by mechanical activation (MA) in a planetary ball mill of natural diopside CaMgSi₂O₆ and plagioclase (CaAl₂Si₂O₈)_0.745·(2NaAlSi₃O₈)_0.209·(2KAlSi₃O₈)_0.046 in CO₂ atmosphere have been studied. Plagioclase like diopside consumes CO₂ during MA in the form of distorted carbonate groups resulting in appearance of the double IR absorption band in 1400-1600 cm⁻¹ region corresponding to the...

article

Investigation into the Mechanism of Interaction of Calcium and Magnesium Silicates with Carbon Dioxide in the Course of Mechanical Activation

A. M. Kalinkin, V. V. Boldyrev, A. A. Politov, E. V. Kalinkina, more

Glass Physics and Chemistry > 2003 > 29 > 4 > 410-414

A prolonged grinding of diopside, akermanite, sphene, wollastonite, and enstatite is accompanied by absorption of CO₂ from the environment (carbonation) along with amorphization and hydration. The IR spectra of ground minerals contain bands of distorted carbonate groups due to absorption of carbon dioxide. If the mechanical activation is not attended by the distortion of the crystal lattice, the sorption...

article

Study of Mechanical Activation of Diopside in a CO₂ Atmosphere

A. M. Kalinkin, A. A. Politov, V. V. Boldyrev, E. V. Kalinkina, more

Journal of Materials Synthesis and Processing > 2002 > 10 > 1 > 61-67

Interaction of natural diopside CaMgSi₂O₆ with CO₂ during mechanical activation in a CO₂ atmosphere has been studied. It has been shown that, depending on the kind of mechanical activator used, two types of CO₂ sorption by diopside are possible. If grinding is not accompanied by crystal structure disordering, the sorption of CO₂ on the diopside surface is similar to the sorption on metal oxides in...

article

Mechanical Activation of Diopside in CO2

A. M. Kalinkin, A. A. Politov, V. V. Boldyrev, E. V. Kalinkina, more

Inorganic Materials > 2002 > 38 > 2 > 163-167

The mechanical activation (MA) of diopside in a controlled CO₂ atmosphere was studied using different grinding facilities. The results demonstrate that diopside may sorb CO₂ by two mechanisms, depending on the nature of the MA process. If grinding is not accompanied by structure breakdown, the sorption process is similar to that reported for metal oxides, and the adsorbate consists of undistorted...

article

Interface-Stabilized States of Silver Iodide in AgI–Al2O3 Composites

N. F. Uvarov, B. B. Bokhonov, A. A. Politov, P. Vaněk, more

Journal of Materials Synthesis and Processing > 2000 > 8 > 5-6 > 327-332

AgI–Al₂O₃ nanocomposites are investigated by high-resolution electron microscopy and luminescence spectroscopy. The results show that both crystalline and amorphous phases coexist in AgI–Al₂O₃ composites. At sufficiently high alumina content, almost all AgI occurs as amorphous spherical nanoparticles distributed uniformly on alumina surfaces. The amorphous phase exhibits unusual luminescence spectra...

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Chemistry of Natural Compounds (2)
Contributions to Mineralogy and Petrology (2)
Journal of Materials Synthesis and Processing (2)
Journal of Structural Chemistry (2)
Doklady Chemistry (1)
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Glass Physics and Chemistry (1)
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