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71.
N. A. Yamnova Yu. K. Egorov-Tismenko N. V. Zubkova O. V. Dimitrova A. P. Kantor 《Crystallography Reports》2005,50(5):766-772
A calcium analog of strontioborite, namely, Ca[B8O11(OH)4], is synthesized under hydrothermal conditions (T = 270°C, P = 20 atm) within the framework of the study of the phase formation in the CaCl2 · Rb2CO3 · B2O3 system. The crystal structure of the synthetic calcium borate [a = 7.4480(5) Å, b = 8.2627(5) Å, c = 9.8102(6) Å, β = 108.331(1)°, V = 573.09(6) Å3, space group P21, Z = 2, ρcalcd = 2.15 g/cm3; Brucker SMART CCD automated diffractometer, 5506 reflections, λMoKα] is refined by the least-squares procedure in the anisotropic approximation of thermal atomic vibrations to R1 = 0.050. The calcium borate studied has a crystal structure identical to the structure of the natural strontium borate (strontioborite) Sr[B8O11(OH)4] and its calcium analog synthesized earlier. The crystal structure is built up of stacks consisting of skeleton layers (formed by boron-oxygen polyanions) and isolated strontium (calcium) polyhedra located in trigonal holes of the skeleton layers. Through channels that can contain H2O molecules are formed between the stacks. The structure refinement and analysis of the IR spectrum of the synthetic calcium analog of strontioborite do not confirm the previously proposed hypothesis that water molecules are involved in the channels of the structure. A comparative crystal chemical analysis of the calcium borate under investigation and its formula analog, namely, the lead borate Pb[B8O11(OH)4], is performed. 相似文献
72.
A. P. Kantor N. A. Yamnova Yu. K. Egorov-Tismenko O. V. Dimitrova 《Crystallography Reports》2004,49(6):936-941
When studying the phase formation in the CaO-Li2O-B2O3-H2O system, a new Ca,Li pentaborate was synthesized under hydrothermal conditions. The structure of a new compound with the crystallochemical formula CaLi4[B5O8(OH)2]2 (sp. gr. Pb2n, a = 8.807(7), b = 9.372(7), c = 8.265(6) Å, V = 682.2(9) Å3, Z = 2, dcalcd = 2.43 g/cm3, automated SYNTEX-\(P\bar 1\) diffractometer, 2690 reflections, 2θ/θ scan, λMo) is refined up to Rhkl = 0.0557 in the anisotropic approximation of atomic thermal vibrations with allowance for the localized H atoms. The structure of the Ca,Li pentaborate is formed by (010) open boron—oxygen layers formed by two independent [B5O8(OH)2]3? pentagroups, with each of them being formed by three B tetrahedra and two B triangles. The structure framework consists of the above boron—oxygen layers bound by isolated Li tetrahedra. The Ca cations are localized in the centers of eight-vertex polyhedra located in the [001] channels of the Li,B,O framework. Comparative crystallochemical analysis of the new Ca,Li pentaborate and Li pentaborate of the composition Li3[B5O8(OH)2]-II showed that the anionic matrices of both compounds are completely identical, whereas some of the cationic positions are different. 相似文献
73.
N. A. Yamnova Yu. K. Egorov-Tismenko N. V. Zubkova O. V. Dimitrova A. P. Kantor Ye Danian Xiong Ming 《Crystallography Reports》2003,48(4):557-562
A new representative of pentaborates with the composition Ca[B5O8(OH)] · H2O was synthesized under hydrothermal conditions within the framework of the study of phase formation in the CaCl2-Na2CO3-B2O3 system. The crystal structure of the new pentaborate was established (a = 6.5303(9) Å, b = 19.613(3) Å, c = 6.5303(9) Å, β = 119.207(2)°, V = 2513(2) Å3, sp. gr. P21/c, Z = 4, d calcd = 2.74 g/cm3, automated Brucker SMART CCD diffractometer, 6871 reflections, λMo radiation, anisotropic refinement by least-squares, R hkl = 0.076). The structure of calcium pentaborate is built by isolated B-Ca-B stacks parallel to the (010) plane. The central fragments of these stacks consists of nine-vertex Ca polyhedra. The Ca layers are located between loose B-O networks composed of [B 2 t B 3 Δ O8(OH)]2? pentaborate groups. The arrangement of the polyhedra around large cations in pentaborates with groups of two B tetrahedra and three B triangles was analyzed in terms of crystal chemistry. It is established that the structures of these compounds consist of large isolated polyhedra, columns, layers, and three-dimensional frameworks. 相似文献
74.
N. A. Yamnova Yu. K. Egorov-Tismenko O. V. Dimitrova A. P. Kantor 《Crystallography Reports》2002,47(4):566-573
In the process of studying the phase formation in the Li2CO3-CaO-B2O3-NaCl system, new Ca,Na, Li-carbonate-borate has been synthesized under hydrothermal conditions. The crystal structure of carbonate-borate with the crystallochemical formula Ca4(Ca0.7Na0.3)3(Na0.7□ 0.3)Li5[B 12 t B 10 Δ O36(O,OH)6](CO3)(OH) · (OH,H2O) was refined to R hkl = 0.0716 by the least squares method in the isotropic approximation of atomic thermal vibrations without the preliminary knowledge of the chemical composition and the formula (sp. gr. R3, a rh = 13.05(2) Å, α = 40.32(7)]°, V = 838(2) Å3, a h = 8.99(2), c h = 35.91(2) Å, V = 2513(2) Å3, Z = 3, d calcd = 2.62 g/cm3, Syntex P $\bar 1$ diffractometer, 3459 reflections, 2θ-θ method, λMo). The structure has a new boron-oxygen radical [B 12 t B 10 Δ O36(O,OH)6] ∞∞ 15? , a double layer of nine-membered [B 6 t B 3 Δ O15(O,OH)3]7.5?-rings bound by BO3-triangles, and twelve-membered [B 6 t B 6 Δ O19.5(O,OH)3]7.5? rings. This allows one to relate this compound to megaborates with complex boron-oxygen radicals. The structure is built from two types of blocks consisting of Ca,Na,B-and Li,B-polyhedra alternating along the c-axis, which explains the perfect cleavage of the crystals along the (0001) plane. 相似文献
75.
E. L. Belokoneva Yu. K. Kabalov A. G. Al-Ama O. V. Dimitrova V. S. Kurazhkovskaya S. Yu. Stefanovich 《Crystallography Reports》2002,47(1):17-23
Anhydrous oxygen-and lead-deficient lead borate of the composition Pb 0.9 (I) Pb 0.6 (II) [BO2.25]2 = 2Pb0.75[BO2.25] (sp. gr. P312) has been obtained by the hydrothermal synthesis. New acentric borate possesses optical nonlinearity comparable with the optical nonlinearity of α-quartz. The crystal structure of new borate is determined and refined by two X-ray diffraction methods—the single crystal diffractometry and the full-profile analysis. All the positions in the structure, except for those of the boron atom in the triangular coordination, are occupied only partly; one of the two lead positions is split. It is established that new borate is closely related to calcium carbonates—aragonite, calcite, and paralstonite. With an increase of the temperature, new borate undergoes the reversible phase transition into the centrosymmetric, most probably, aragonite-like phase. 相似文献
76.
Krassimira Yoncheva Niko Benbassat Maya M. Zaharieva Lyudmila Dimitrova Alexander Kroumov Ivanka Spassova Daniela Kovacheva Hristo M. Najdenski 《Molecules (Basel, Switzerland)》2021,26(22)
Oregano oil (OrO) possesses well-pronounced antimicrobial properties but its application is limited due to low water solubility and possible instability. The aim of this study was to evaluate the possibility to incorporate OrO in an aqueous dispersion of chitosan—alginate nanoparticles and how this will affect its antimicrobial activity. The encapsulation of OrO was performed by emulsification and consequent electrostatic gelation of both polysaccharides. OrO-loaded nanoparticles (OrO-NP) have small size (320 nm) and negative charge (−25 mV). The data from FTIR spectroscopy and XRD analyses reveal successful encapsulation of the oil into the nanoparticles. The results of thermogravimetry suggest improved thermal stability of the encapsulated oil. The minimal inhibitory concentrations of OrO-NP determined on a panel of Gram-positive and Gram-negative pathogens (ISO 20776-1:2006) are 4–32-fold lower than those of OrO. OrO-NP inhibit the respiratory activity of the bacteria (MTT assay) to a lower extent than OrO; however, the minimal bactericidal concentrations still remain significantly lower. OrO-NP exhibit significantly lower in vitro cytotoxicity than pure OrO on the HaCaT cell line as determined by ISO 10993-5:2009. The irritation test (ISO 10993-10) shows no signs of irritation or edema on the application site. In conclusion, the nanodelivery system of oregano oil possesses strong antimicrobial activity and is promising for development of food additives. 相似文献
77.
Reutova O. V. Belokoneva E. L. Dimitrova O. V. Volkov A. S. 《Crystallography Reports》2020,65(3):428-432
Crystallography Reports - Crystals of new iodate Na3Fe[IO3]6 were prepared by the hydrothermal synthesis (the unit cell parameters a = 6.6886(2) Å, b = 6.7756(3) Å, c = 10.1396(6) Å,... 相似文献
78.
Rozalina Dimitrova Lionel Catalan Dimiter Alexandrov Aicheng Chen 《Electroanalysis》2008,20(7):789-796
The response of potentiometric anion selective electrodes employing undoped GaN or In0.2Ga0.8N films as sensing element to detect various anions was investigated in solutions of KF, KNO3, KCl, HOC6H4COONa, KSCN, CH3COOK, KClO4 and KBr salts. The calibration plots for the GaN and In0.2Ga0.8N semiconductor electrodes contained linear regions extending over four decades of activity change in most solutions. The structure of the GaN and In0.2Ga0.8N semiconductor electrode/ electrolyte interface was studied through electrochemical impedance spectroscopy. Analogous equivalent circuits modeling the GaN or In0.2Ga0.8N electrode/electrolyte interface were proposed and their parameters were calculated. The space charge layer of the GaN and In0.2Ga0.8N semiconductors dominated the impedance of the electrochemical system at high frequencies (>10 kHz), whereas at low frequencies (<10 kHz), the impedance was controlled by the diffusion of electroactive species across the layer of adsorbed ions at the surface of the electrode. Results imply a strong dependence of the electrodes performance on the adsorption capacity of tested anions. 相似文献
79.
M. P. Nemeryuk V. D. Dimitrova O. S. Anisimova A. L. Sedov N. P. Solov'eva V. F. Traven 《Chemistry of Heterocyclic Compounds》2005,41(10):1255-1266
Reaction between the N,N′-diisopropylidene and N,N′-diacetyl derivatives of malonic acid dihydrazide and 3-acyl(3-cyano, 3-ethoxycarbonyl)coumarins
under the conditions of the Michael reaction lead to the formation of N′-isopropylidene and N′-acetyl derivatives of coumarin-3-carboxylic
acid hydrazide. Ethoxycarbonylacethydrazide reacts in an analogous manner. Special features have been studied of the interaction
of malonic acid amide derivatives with unsubstituted coumarin and with coumarins containing electron-withdrawing groupings
in position 3 of the ring.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1502–1514, October, 2005. 相似文献
80.
Neronov A Mazgalova J Cholakova M Dimitrova M Deligiozova I Kovatcheva S Nikolova E 《Cryo letters》2005,26(2):131-136
The aim of the present study was to elaborate an optimal method for cryopreservation of human donor cornea for transplantation and to follow the morphological changes in the structure of the endothelial cell layer using scanning electron microscopy (SEM). Sixteen groups, with four donor cornea each, were cryopreserved at cooling rates of 1 degree C per min and 5 degree C per min. Four cryoprotectants (glycerol, dimethyl sulfoxide, 1,2-propanediol, polyethylene glycol-400) in two concentrations (5% and 10% v/v) were prepared on the bases of medium Optisol GS supplied with 20% v/v human serum albumin. Four additional human cornea were used as controls. Endothelial cell recovery of the cornea after thawing and 24 hours culture, was calculated as a percent of the preserved recovered cells. Sufficient recovery of the endothelial cell layer, making the cornea suitable for transplantation was obtained using the cryoprotectants dimethyl sulfoxide and especially polyethylene glycol-400. 相似文献