Multilayer Composites Based on PTFE Films and Fiberglass

Fibre Chemistry - The article is devoted to the development of two-layer composites with a fluoroplastic matrix and fiberglass reinforcing elements. The fluoroplastic matrix acts as a protective...     

Synthesis of carbon nanotubes by current annealing graphite paper

A new method for manufacturing multiwall carbon nanotubes by the current annealing in vacuum of the graphite paper saturated with Ni, Co, and Fe catalysts is designed. By using a scanning tunnel microscope, structural characteristics of the modified graphite paper are studied. Y- and V-shaped nanotubes are found.     

Observation of a half-quantum-flux periodicity pattern in an rf SQUID with small critical currents

We have found experimentally that rf SQUID's working in a nonhysteretic mode with small critical currents give exactly at resonance and at very low rf bias a triangular pattern with a period equal to half of one elementary quantum of magnetic flux. We discuss a possible explanation of this peculiar result.     

Synthesis,In Vitro,and Computational Studies of PTP1B Phosphatase Inhibitors Based on Oxovanadium(IV) and Dioxovanadium(V) Complexes

One of the main goals of recent bioinorganic chemistry studies has been to design and synthesize novel substances to treat human diseases. The promising compounds are metal-based and metal ion binding components such as vanadium-based compounds. The potential anticancer action of vanadium-based compounds is one of area of investigation in this field. In this study, we present five oxovanadium(IV) and dioxovanadium(V) complexes as potential PTP1B inhibitors with anticancer activity against the MCF-7 breast cancer cell line, the triple negative MDA-MB-231 breast cancer cell line, and the human keratinocyte HaCaT cell line. We observed that all tested compounds were effective inhibitors of PTP1B, which correlates with anticancer activity. [VO(dipic)(dmbipy)]·2 H₂O (Compound 4) and [VOO(dipic)](2-phepyH)·H₂O (Compound 5) possessed the greatest inhibitory effect, with IC₅₀ 185.4 ± 9.8 and 167.2 ± 8.0 nM, respectively. To obtain a better understanding of the relationship between the structure of the examined compounds and their activity, we performed a computer simulation of their binding inside the active site of PTP1B. We observed a stronger binding of complexes containing dipicolinic acid with PTP1B. Based on our simulations, we suggested that the studied complexes exert their activity by stabilizing the WPD-loop in an open position and limiting access to the P-loop.     

Hematites Precipitated in Alkaline Precursors: Comparison of Structural and Textural Properties for Methane Oxidation

Hematite (α-Fe₂O₃) catalysts prepared using the precipitation methods was found to be highly effective, and therefore, it was studied with methane (CH₄), showing an excellent stable performance below 500 °C. This study investigates hematite nanoparticles (NPs) obtained by precipitation in water from the precursor of ferric chloride hexahydrate using precipitating agents NaOH or NH₄OH at maintained pH 11 and calcined up to 500 °C for the catalytic oxidation of low concentrations of CH₄ (5% by volume in air) at 500 °C to compare their structural state in a CH₄ reducing environment. The conversion (%) of CH₄ values decreasing with time was discussed according to the course of different transformation of goethite and hydrohematites NPs precursors to magnetite and the structural state of the calcined hydrohematites. The phase composition, the size and morphology of nanocrystallites, thermal transformation of precipitates and the specific surface area of the NPs were characterized in detail by X-ray powder diffraction, transmission electron microscopy, infrared spectroscopy, thermal TG/DTA analysis and nitrogen physisorption measurements. The results support the finding that after goethite dehydration, transformation to hydrohematite due to structurally incorporated water and vacancies is different from hydrohematite α-Fe₂O₃. The surface area SBET of Fe₂O₃_NH-70 precipitate composed of protohematite was larger by about 53 m²/g in comparison with Fe₂O₃_Na-70 precipitate composed of goethite. The oxidation of methane was positively influenced by the hydrohematites of the smaller particle size and the largest lattice volume containing structurally incorporated water and vacancies.     

Synthesis,Characterization, and Application of Mesoporous Silica Functionalized with Alkyl‐Hydroperoxides

A variety of alkyl hydroperoxides such as tert‐butyl‐, tert‐octyl‐, 1‐cyclopentyl‐, 1‐cyclohexyl‐, 3,4‐disubstituted‐1‐cyclohexyl‐, n‐propyl, and n‐undecyl‐hydroperoxides have been functionalized onto ordered mesoporous silica, SBA‐15, from the corresponding covalently anchored synthons. All the tert‐hydroperoxides are prepared by autoxidation using molecular O₂ and an initiator, whereas other hydroperoxides are obtained by reaction with H₂O₂. For autoxidation, the use of a combination of an azoinitiator (AIBN) and N‐hydroxyphthalimide increased the hydroperoxide yield compared with using the azoinitiator alone. Synthons containing two or more tert‐ and sec‐hydrogens lead to higher peroxide yield compared to synthons with a single reactive site. Oxidation of Si–OH (silanol groups) with acidic H₂O₂ at low temperature produces Si–OOH. Reusability of these alkyl hydroperoxides is carried out by oxidation of alcohols obtained from the corresponding alkyl hydroperoxides using H₂O₂. Both the covalently anchored synthons and the resulting hydroperoxides are thoroughly characterized by powder X‐ray diffraction, ¹³C cross‐polarized magic angle spinning NMR, TG/DTA, Fourier transform IR spectroscopy, sorption, and surface area measurements. The quantification of the amount of alkyl hydroperoxide was carried out by iodometric titration using a thio solution. The hydroperoxides exhibit high activity for the epoxidation of styrene to styrene oxide and exhibit reasonably high efficiency for oxygen transfer.