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21.
Mihaylov M Chakarova K Hadjiivanov K Marie O Daturi M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(25):11821-11828
Different carbonyls are formed after CO adsorption at ambient temperature on a Pt-Na-mordenite (Pt-Na-MOR) sample. Pt(3+)(CO)(2) dicarbonyls (nu(s) at 2205 cm(-1) and nu(as) at 2167 cm(-1)) are decomposed without formation of monocarbonyls. The respective mixed-ligand species, Pt(3+)((12)CO)((13)CO), formed after (12)CO-(13)CO coadsorption, display bands at 2192 and 2131 cm(-1), in excellent agreement with the theoretically calculated values. Pt(2+)-CO species absorb at 2145 cm(-1) and are not able to accept a second CO molecule. Pt(+)-CO carbonyls are characterized by a band at 2111 cm(-1). Under CO equilibrium pressure, these species are converted into dicarbonyls (nu(s) at 2135 cm(-1) and nu(as) at 2101 cm(-1)). The respective mixed-ligand species, Pt(+)((12)CO)((13)CO), manifest bands at 2123 and 2069 cm(-1), in good agreement again with the theory. Different carbonyls of metallic platinum are observed below 2100 cm(-)(1). In addition, weakly adsorbed CO was registered as Na(+)-CO complexes (2177 and 2165 cm(-1)) and Na(+)-OC-Na(+) species (2138 cm(-1)). It was found that during desorption of CO platinum was reduced, ultimately to metal. However, heating in a NO + O(2) mixture leads to reoxidation of the metal particles and restoration of the initial state of the sample. 相似文献
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Hydroxyapatite-poly(d,l-lactide) Nanografts. Synthesis and Characterization as Bone Cement Additives
Kristina L. Goranova Anne Kathrine Kattenhj Sloth Overgaard Ivan Gitsov 《Molecules (Basel, Switzerland)》2021,26(2)
This paper reports the creation of hydroxyapatite/polyester nanografts by “graft-from” polymerization of d,l-lactide with [Ca5(OH)(PO4)3]2 as the initiator and tin(II)-2-ethylhexanoate as the catalyst. Model polymerizations were performed with cyclooctanol as initiator to confirm the grafting on the surface of the hydroxyapatite nanocrystals. Polymers with the highest molecular mass (Mn) between 4250 Da (cyclooctanol) and 6100 Da (hydroxyapatite) were produced. In both cases the molecular mass distributions of the polymers formed were monomodal. The materials obtained were characterized by size-exclusion chromatography, NMR and FT-IR spectroscopy, and thermal methods. Their suitability as additives for commercial bone cement (Simplex P Speedset, Stryker Orthopaedics) has been confirmed by thermal analysis techniques and mechanical testing. The results obtained show that addition of the hydroxyapatite/ polyester nanografts improved both thermal and mechanical properties of the bone cement. 相似文献
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The reversible formation of a selenenylsulfide linkage in mammalian thioredoxin reductase was identified as having a key role in its activity. Identification of selenenylsulfide and/or diselenide linkages is therefore critical to the determination of the structure and function of selenoproteins. A selenopeptide, (298)SGSAITUQCAENLPSLCSUQGLFAEEK(324) (U=selenocysteine), was isolated from a tryptic digest of rat selenoprotein P. Its two cysteine residues and two selenocysteine (Sec) residues were determined to be present in oxidized form by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The selenopeptide was subjected to partial reduction by dithiothreitol with immediate alkylation by iodoacetamide. This process was monitored by MALDI-TOFMS to determine the number of alkylations that had taken place. The partially reduced and alkylated peptides were then analyzed by nano-electrospray ionization tandem mass spectrometry and the results indicated that selenenylsulfide linkages Sec304-Cys314 and Cys306-Sec316 were present. It is concluded that selenoprotein P contains these two selenenylsulfide bonds. 相似文献
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Kristina D. Radosavljević Jelena D. Lović Dušan Ž. Mijin Slobodan D. Petrović Milka B. Jadranin Aleksandar R. Mladenović Milka L. Avramov Ivić 《Chemical Papers》2017,71(7):1217-1224
The electrodegradation of azithromycin was studied by its indirect oxidation using dimensionally stable Ti/RuO2 anode as catalyst in the electrolyte containing methanol, 0.05 M NaHCO3, sodium chloride and deionized water. The optimal conditions for galvanostatic electrodegradation for the azithromycin concentration of 0.472 mg cm?3 were found to be NaCl concentration of 7 mg cm?3 and the applied current of 300 mA. The differential pulse voltammetry using glassy carbon electrode was performed for the first time in the above-mentioned content of electrolyte for the nine concentration of azithromycin (0.075–0.675 mg cm?3) giving the limits of azithromycin detection and of quantification as: LOD 0.044 mg cm?3 and LOQ 0.145 mg cm?3. The calibration curve was constructed enabling the electrolyte analysis during its electrodegradation process. The electrolyte was analyzed by high-performance liquid chromatography and electrospray ionization time-of-flight mass spectrometry. The electrooxidation products were identified and after 180 min there was no azithromycin in the electrolyte while TOC analysis showed that 79% of azithromycin was mineralized. The proposed degradation scheme is presented. 相似文献
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Truemper configurations (thetas, pyramids, prisms, and wheels) have played an important role in the study of complex hereditary graph classes (eg, the class of perfect graphs and the class of even-hole-free graphs), appearing both as excluded configurations, and as configurations around which graphs can be decomposed. In this paper, we study the structure of graphs that contain (as induced subgraphs) no Truemper configurations other than (possibly) universal wheels and twin wheels. We also study several subclasses of this class. We use our structural results to analyze the complexity of the recognition, maximum weight clique, maximum weight stable set, and optimal vertex coloring problems for these classes. Furthermore, we obtain polynomial -bounding functions for these classes. 相似文献