The composites xTiO 2 -(1-x)SiO 2 (x = 0.1, 0.5, 0.9) were obtained by coprecipitation from solutions of alkoxides: tetraethoxysilane (TEOS) and titanium tetraisopropoxide (TIPT). Intermolecular interaction of the components of the composite is apparent in the IR absorption spectra in the 928-952 cm -1 region, and is connected with bending vibrations of the Si-O-Ti bond.Introduction. Composites based on titanium and silicon dioxides have begun to be used relatively recently as catalysts and photocatalysts for various processes, protective coatings, components of glasses with low linear thermal expansion coefficient, and waveguide materials [1][2][3][4][5][6][7]. The method for obtaining the composite determines the nature and extent of interactions between components. For mechanical mixing of the individual phases, weak van der Waals interaction occurs. Thorough mixing of the components at the molecular level when obtaining the composite by sol-gel or coprecipitation methods leads to a substantial change in the properties of the end product: the appearance of new catalytically active centers, a shift in the onset of crystallization for the titanium-containing component toward higher temperatures, and accordingly an increase in the thermal stability of the structural and adsorption characteristics of the composite [7]. Formation of Si-O-Ti bonds at the TiO 2 -SiO 2 interface leads to an appreciable change in the electronic structure of the titanium atoms in the composite [8,9]. One possible method for estimating the interaction between components is IR spectroscopy. The absorption band observed in the 910-960 cm -1 region is due to characteristic vibrations of the Si-OH and Si-O-Ti bonds. Its position depends on the chemical composition of the sample and the resolution of the instrument [10,11]. We know that for exhaustive dehydration of SiO 2 , the band in the 940-950 cm -1 region, due to bending vibrations of the Si-OH bond, disappears in the absorption spectra. After appropriate heat treatment of the composite, absorption in this region will be due only to bending vibrations of the Si-O-Ti bond and thus it becomes possible to study the nature and extent of intermolecular interaction between titanium and silicon oxides by IR spectroscopy, which was the subject of this work.The Experiment. The composite was obtained by the coprecipitation method. For this purpose, the specified amounts of tetraethoxysilane (TEOS) and titanium tetraisopropoxide (TIPT) were mixed with isopropyl alcohol, then a solution of water (or ammonium hydroxide) in alcohol was added dropwise with vigorous stirring. The suspension was stirred for 1 h, the residue was separated by filtration and washed with water until the organic components were no longer present. The samples were dried at 120 o C for 5 h and calcined at 350 o C and 650 o C for 3 h. The individual titanium and silicon oxides were obtained under similar conditions. Table 1 gives the conditions for obtaining powders of the individual titanium and silicon oxides and the composit...

IMPORTANCEThe cyclin-dependent kinase 4 and 6 inhibitor palbociclib in combination with letrozole has become a standard first-line treatment for patients with endocrine-sensitive, hormone receptor-positive, ERBB2-negative advanced breast cancer. Meanwhile, the antiestrogen fulvestrant was shown to be superior to anastrozole in the absence of cyclin-dependent kinase 4 and 6 inhibition for this patient population. OBJECTIVE To assess whether fulvestrant is superior to letrozole when combined with palbociclib in the first-line scenario. DESIGN, SETTING, AND PARTICIPANTSIn this international, randomized, open-label, phase 2 clinical study conducted from July 30, 2015, to January 8, 2018, patients with hormone receptor-positive, ERBB2-negative advanced breast cancer with no prior therapy in the metastatic setting and endocrine-sensitive criteria were recruited from 47 centers in 7 countries. Data were analyzed from February 11 to May 15, 2020.INTERVENTIONS Patients were randomly assigned (1:1 ratio) to receive palbociclib with either fulvestrant or letrozole. Stratification factors were type of disease presentation (de novo vs recurrent) and the presence of visceral involvement (yes vs no). MAIN OUTCOMES AND MEASURESThe primary end point was investigator-assessed progression-free survival determined by Response Evaluation Criteria in Solid Tumors, version 1.1.RESULTS A total of 486 women (median age, 63 years [range, 25-90 years]; 3 Asian women [0.6%]; 4 Black women [0.8%]; 461 White women [94.9%]; 18 women of unknown race [3.7%]) were randomized (243 to fulvestrant-palbociclib and 243 to letrozole-palbociclib). Median investigator-assessed progression-free survival was 27.9 months (95% CI, 24.2-33.1 months) in the fulvestrant-palbociclib group vs 32.8 months (95% CI, 25.8-35.9 months) in the letrozole-palbociclib group (hazard ratio, 1.13; 95% CI, 0.89-1.45; P = .32). This result was consistent across the stratification factors. No significant differences were observed in objective response rate (46.5% vs 50.2%) and 3-year overall survival rate (79.4% vs 77.1%) for fulvestrant-palbociclib and letrozole-palbociclib, respectively. Grade 3-4 adverse events were comparable among treatment groups, and no new safety signals were identified. No treatment-related deaths were reported. CONCLUSIONS AND RELEVANCEAlthough fulvestrant-palbociclib demonstrated significant antitumor activity, this randomized clinical trial failed to identify an improvement in progression-free survival with this regimen over letrozole-palbociclib in patients with endocrine-sensitive, hormone receptor-positive, ERBB2-negative advanced breast cancer.

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