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261.
Chemisorption of oxygen on carbon produced by electrochemical reduction of poly(tetrafluoroethylene)
The electrochemical reduction of poly(tetrafluoroethylene) with lithium amalgam and washing the product with water yields a very reactive and pure carbonaceous substance which is capable of the chemisorption of oxygen from the gas phase or from aqueous solution at room temperature. The product was studied by infrared spectroscopy and electron paramagnetic resonance. Chemisorption of oxygen leads to the formation of IR-active C-O and C = O surface groups. The concentration of paramagnetic sites does not change after the chemisorption of oxygen; this is manifested only by a broadening of the EPR line. 相似文献
262.
Leonid V. Aseev Ludmila S. Koledinskaya Oksana S. Bychenko Irina V. Boni 《International journal of molecular sciences》2021,22(18)
The autogenous regulation of ribosomal protein (r-protein) synthesis plays a key role in maintaining the stoichiometry of ribosomal components in bacteria. In this work, taking the rpsO gene as a classic example, we addressed for the first time the in vivo regulation of r-protein synthesis in the mycobacteria M. smegmatis (Msm) and M. tuberculosis (Mtb). We used a strategy based on chromosomally integrated reporters under the control of the rpsO regulatory regions and the ectopic expression of Msm S15 to measure its impact on the reporter expression. Because the use of E. coli as a host appeared inefficient, a fluorescent reporter system was developed by inserting Msm or Mtb rpsO-egfp fusions into the Msm chromosome and expressing Msm S15 or E. coli S15 in trans from a novel replicative shuttle vector, pAMYC. The results of the eGFP expression measurements in Msm cells provided evidence that the rpsO gene in Msm and Mtb was feedback-regulated at the translation level. The mutagenic analysis showed that the folding of Msm rpsO 5′UTR in a pseudoknot appeared crucial for repression by both Msm S15 and E. coli S15, thus indicating a striking resemblance of the rpsO feedback control in mycobacteria and in E. coli. 相似文献
263.
Ivan Kelnar Ümitcan Bal Alexander Zhigunov Ludmila Kaprálková Ivan Fortelný Sabina Krejčíková Jana Kredatusová Jiří Dybal Miroslav Janata Mohammadreza Nofar 《应用聚合物科学杂志》2019,136(24):47660
Modification of microfibrillar composites (MFCs) by nanofillers shows important effects of its localization on performance. This work deals with control of migration/localization of amine-modified graphite nanoplatelets (GNPAs) in the HDPE/PA6 system through their in situ coupling. GNPA/HDPE linking also leads to complex morphology of PA6 fibers. Although such control of GNPA localization and migration in MFC is limited, marked variations of properties, including decrease with high draw ratio, occurs. This is in spite of the fact that structure and crystallinity are comparable with that of the polymer/GNPA adduct. The reason is a more pronounced negative effect of presence of the GNP adducts in the fiber surface layer on HDPE crystallinity, in comparison with neat GNP, that is, formation of “soft” interface. The negative effects were markedly eliminated by pre-blending and coupling of GNPA in both polymer phases. Results confirm more effective control of MFC performance by in situ coupling of GNPA with polymer components in comparison with a nonreactive system. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47660. 相似文献
264.
Sergei V. Voitekhovich Tatiyana V. Serebryanskaya Pavel N. Gaponik Ludmila S. Ivashkevich Alexander S. Lyakhov Oleg A. Ivashkevich 《Inorganic chemistry communications》2010,13(8):949-951
Tetrazol-2-ylacetic acid (2-TzaH) was found to react with CuCl2, PdCl2, and K2PtCl4 in water giving Cu(2-Tza)2, PdCl2(2-TzaH)2·2H2O and PtCl2(2-TzaH)2, correspondingly. Obtained complexes, being the first reported examples of coordination compounds derived from 2-TzaH, have been characterized by IR spectroscopy, thermal and X-ray diffraction methods. 2-TzaH was found to act as a monodentate ligand coordinated to the metal ion via N4 atom of heteroring in palladium complex and as tridentate bridging ligand coordinated via N4 atom and two oxygen atoms in copper complex. Cu(2-Tza)2 presents 2D coordination polymer, whereas PdCl2(2-TzaH)2·2H2O is molecular complex. 相似文献
265.
Emmanuel Richaud Xavier Colin Carole Monchy‐Leroy Ludmila Audouin Jacques Verdu 《Polymer International》2011,60(3):371-381
The radiochemical degradation of bisphenol A polysulfone was investigated under a γ‐ray dose rate of 24 kGy h?1 up to 30.7 MGy total absorbed dose at 60 °C using gel permeation chromatography, sol–gel analysis, glass transition and rheometry measurements, and oxidation profile measurements by microscopy coupled with Fourier transform infrared analysis in attenuated total reflectance mode. Thin (200 µm) and thick (2 mm) samples were compared. Thin samples undergo mainly chain scissions whereas thick ones undergo mainly crosslinking. The thickness of oxidized layers and, radiochemical yields for chain scissions, crosslinking, oxygen absorption and radical formation were tentatively determined from experimental data in order to determine the influence of oxidative processes on radiochemical ageing and to establish the nature of the crosslinking reactions. Copyright © 2010 Society of Chemical Industry 相似文献
266.
Marina I. Nikolaeva Tatiana B. Mikenas Mikhail A. Matsko Ludmila G. Echevskaya Vladimir A. Zakharov 《应用聚合物科学杂志》2010,115(4):2432-2439
Experimental data on the molecular weight distribution (MWD) of polyethylene (PE) produced over a broad number of Ziegler‐Natta catalysts differing in composition and preparation procedure are presented. These catalysts include nonsupported TiCl3 catalyst, four types of supported titanium‐magnesium catalysts (TMC) differing in the content of titanium and the presence of various modifiers in the composition of the support, and a supported catalyst containing VCl4 as an active component instead of TiCl4. The studied catalysts produce PE with different molecular weights within a broad range of polydispersity (Mw/Mn = 2.8–16) under the same polymerization conditions. The heterogeneity of active sites of these catalysts was studied by deconvolution of experimental MWD curves into Flory components assuming a correlation between the number of Flory components and the number of active site types. Five Flory components were found for PE produced over nonsupported TiCl3 catalysts (Mw/Mn = 6.8), and three–four Flory components were found for PE produced over TMC of different composition. A minimal number of Flory components (three) was found for PE samples (Mw/Mn values from 2.8 to 3.3) produced over TMC with a very low titanium content (0.07 wt %) and TMC modified with dibutylphtalate. It was shown that five Flory components are sufficient to fit the experimental MWD curve for bimodal PE (Mw/Mn = 16) produced over VMC. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
267.
Galina A Polotskaya Alexandra Yu Pulyalina Valeriia A Rostovtseva Alexander M Toikka Natalia N Saprykina Ludmila V Vinogradova 《Polymer International》2016,65(4):407-414
Star‐shaped macromolecules with six arms of polystyrene grafted onto a fullerene C60 core, or fullerene‐containing polystyrene (FPS), were used for the modification of poly(phenylene oxide) (PPO) and the preparation of a dense thin‐film membrane. The membrane structure was studied using scanning electron microscopy. The effect of FPS modifier on membrane density and mass transfer of methanol and ethylene glycol through the membrane was studied. Sorption and pervaporation tests were used to determine degree of sorption, diffusion coefficients, flux through the membrane and separation factor. In the pervaporation of a methanol–ethylene glycol mixture over the concentration range of 10–30 wt% methanol in the feed, all membranes showed high affinity to methanol. The separation factor reached a maximum at 5 wt% FPS in the membrane. The PPO/FPS membranes exhibit the best separation properties when the feed is enriched with ethylene glycol. © 2016 Society of Chemical Industry 相似文献
268.
Ketan Kuperkar Ludmila Abezgauz Kamlesh Prasad P. Bahadur 《Journal of surfactants and detergents》2010,13(3):293-303
Self-assembly of cetyltrimethylammonium bromide (CTAB) in aqueous solution, in the presence of two inorganic salts viz, NaNO3 and NaClO3 was investigated by steady-state fluorescence, electrical conductance, surface tension, viscosity, dynamic light scattering (DLS) and cryogenic transmission microscopy (cryo-TEM). The counterions located at short enough distances to CTA+ micellar surface experience a very strong electrostatic attraction and thus become condensed. This counterion condensation plays a significant role in deciding the effective charge on the micelle, their screening interaction and structural transition of the micelles. In the present work, the probable mechanism of the salts' action in aqueous solution of CTAB is explained. The critical micelle concentration (CMC), area per molecule (Å2), micelle hydrodynamic diameter (D h ), and aggregation number (N agg) of CTAB micelles in the absence and presence of the salts are reported. The addition of both salts followed the lyotropic series and showed a remarkable decrease in CMC. A detailed investigation of the structural transitions from spherical to rod or even to entangled wormlike structures is presented from cryoTEM. 相似文献
269.
Boris A. Katsnelson Larisa I. Privalova Vladimir B. Gurvich Oleg H. Makeyev Vladimir Ya. Shur Yakov B. Beikin Marina P. Sutunkova Ekaterina P. Kireyeva Ilzira A. Minigalieva Nadezhda V. Loginova Marina S. Vasilyeva Artem V. Korotkov Eugene A. Shuman Larisa A. Vlasova Ekaterina V. Shishkina Anastasia E. Tyurnina Roman V. Kozin Irene E. Valamina Svetlana V. Pichugova Ludmila G. Tulakina 《International journal of molecular sciences》2013,14(2):2449-2483
Stable suspensions of nanogold (NG) and nanosilver (NS) with mean particle diameter 50 and 49 nm, respectively, were prepared by laser ablation of metals in water. To assess rat’s pulmonary phagocytosis response to a single intratracheal instillation of these suspensions, we used optical, transmission electron, and semi-contact atomic force microscopy. NG and NS were also repeatedly injected intraperitoneally into rats at a dose of 10 mg/kg (0.5 mg per mL of deionized water) three times a week, up to 20 injections. A group of rats was thus injected with NS after oral administration of a “bioprotective complex” (BPC) comprised of pectin, multivitamins, some amino acids, calcium, selenium, and omega-3 PUFA. After the termination of the injections, many functional and biochemical indices and histopathological features of the spleen, kidneys and liver were evaluated for signs of toxicity, and accumulation of NG or NS in these organs was measured. From the same rats, we obtained cell suspensions of different tissues for performing the RAPD test. It was demonstrated that, although both nanometals were adversely bioactive in all respects considered in this study, NS was more noxious as compared with NG, and that the BPC tested by us attenuated both the toxicity and genotoxicity of NS. 相似文献
270.
It is generally assumed that short-chain organoclays are better sorbents for non-ionic organic compounds than are the long-chain organoclays. We believe that the above statement is correct only for relatively hydrophilic or slightly hydrophobic compounds and that the opposite should be true for highly hydrophobic compounds, namely, that long-chain organoclays are expected to be superior to the short-chain analogs for sorption of highly hydrophobic materials.To verify our hypothesis, the sorption of six compounds with a range of log Kow values from 2.5 to 6 was studied on tetramethyltriammonium-(TMA) and octadecyltrimethylammonium-(ODTMA) bentonite, representing short- and long-chain organoclays, respectively. Compounds with low or medium hydrophobicities (log Kow 2.5–3.8) were more strongly sorbed on the short-chain organoclay, whereas the more hydrophobic compounds (log Kow 5.2–6.1) were better sorbed on the long-chain organoclay, in agreement with our hypothesis.The efficacy of organoclays in removing organic pollutants from the effluent of a pesticide producing plant was evaluated. Pesticide sorption from the wastewater was studied on both types of organoclays. It was found that both organoclays were able to remove organic pollutants from industrial wastewater, but solute uptake by short-chain organoclays was strongly depressed by competition, while long-chain organoclays were only slightly affected, if at all, by the presence of competing solutes in the industrial wastewater. 相似文献