Search results for "rare"
showing 10 items of 2778 documents
Preparation and characterisation of TiO2 (anatase) supported on TiO2 (rutile) catalysts employed for 4-nitrophenol photodegradation in aqueous medium…
1999
Abstract In this paper the preparation of two sets of polycrystalline photocatalysts prepared by supporting TiO2 (anatase) on TiO2 (rutile) or Al2O3 is reported. The powders were prepared by a wet impregnation method using titanium(IV) isopropylate. The impregnation was followed by thermal treatment and this procedure was repeated several times in order to obtain samples with progressively increasing amounts of TiO2 (anatase). The photocatalytic activity of all of the specimens was tested by carrying out the 4-nitrophenol photodegradation, used as a “probe” reaction, in aqueous medium and in different kinds of batch photoreactors. The solids were characterised by X-ray diffraction (XRD), sp…
Preparation characterization and photocatalytic activity of polycrystalline ZnO/TiO2 systems. 2. Surface, bulk characterization, and 4-nitrophenol ph…
2001
Electron spin resonance spectroscopy (ESR), Fourier transform infrared spectroscopy (FTIR), and monitoring of pyridine (py) and boric acid trimethyl ester (BATE) adsorption for determining surface acidity and basicity, respectively, were used to carry out further characterization of mixed ZnO/TiO2 polycrystalline solids prepared by different methods. Moreover, the powders were tested in a batch photoreactor for a probe reaction, i.e., 4-nitrophenol photodegradation in aqueous medium. ESR results indicated the presence of signals attributable to Zn+ species in ZnO/TiO2 (anatase) solids, while in ZnO/TiO2 (rutile) samples the presence of zinc induced only the formation of signals probably due…
Photocatalytic oxidation of gaseous toluene on anatase TiO2 catalyst: Mechanistic aspects and FT-IR investigation
1999
Abstract Photo-oxidation of toluene has been carried out in gas–solid regime by using polycrystalline anatase TiO2 as the catalyst. The reacting gaseous mixture was toluene, air and water in various molar ratios. A pyrex fixed-bed continuous photoreactor irradiated by a medium pressure Hg lamp was used for performing the photoreactivity experiments. The main oxidation product was benzaldehyde but benzene, benzyl alcohol and traces of benzoic acid, phenol and unidentified compounds were also detected. The molar conversion to benzaldehyde with respect to the initial amount of toluene was ca. 20% in the best experimental conditions. Benzene was produced only as a transient product during the f…
Pēc 5 mirkļiem 100 gadi: bibliotēku dārgumi : izstādes buklets
2014
Reto izdevumu un manuskriptu izstāde BIBLIOTĒKU DĀRGUMI ir Latvijas Universitātes Bibliotēkas un Latvijas Universitātes Akadēmiskās bibliotēkas veltījums Latvijas Universitātei 95. gadadienā
A rare case of Prinzmetal angina 3 days after coronary artery stenting with a second-generation drug-eluting stent
2015
Non previsto.
Hyperbranched Polyglycerol-Based Lipids via Oxyanionic Polymerization: Toward Multifunctional Stealth Liposomes
2010
We describe the synthesis of linear-hyperbranched lipids for liposome preparation based on linear poly(ethylene glycol) (PEG) and hyperbranched polyglycerol (PG). Molecular weights were adjusted to values around 3000 g/mol with varying degrees of polymerization of the linear and the branched segments in analogy to PEG-based stealth lipids; polydispersities were generally low and below 1.3. The hydrophobic anchors were introduced into the lipid structures as initiators for the anionic polymerization of ethylene oxide and are either based on cholesterol or on different aliphatic glyceryl ethers. Complete incorporation of the apolar initiators was evidenced by MALDI-ToF analysis at all stages …
The Crucial Role of Polyatomic Anions in Molecular Architecture: Structural And Magnetic Versatility of Five Nickel(II) Complexes Derived from A N,N,…
2009
Five new nickel(II) complexes [Ni(2)L(2)(N(3))(2)(H(2)O)(2)] (1), [Ni(2)L(2)(NO(3))(2)] (2), [Ni(2)L(2)(O(2)CPh)(CH(3)OH)(2)]ClO(4).0.5CH(3)OH (3), [Ni(3)L(2)(O(2)CPh)(4)] (4), and [Ni(2)L(2)(NO(2))(2)](n) (5) have been synthesized by using a tridentate Schiff base ligand, HL (2-[(3-Methylamino-propylimino)-methyl]-phenol), and the polyatomic monoanions N(3)(-), NO(3)(-), PhCOO(-), or NO(2)(-). The complexes have been structurally and magnetically characterized. The structural analysis reveals that in all five complexes, the Ni(II) ions possess a distorted octahedral geometry. Complexes 1 and 2 are dinuclear with di-mu-1,1-azido and di-mu(2)-phenoxo bridges, respectively. Complex 3 is also …
Dynamics of F-center annihilation in thermochemically reduced MgO single crystals
2001
Optical absorption measurements were used to monitor the thermal annihilation of oxygen vacancies (F-centers) in thermochemically reduced MgO crystals. The annihilation characteristics were sample-dependent and varied strongly with the F-center concentration. Different mechanisms for the destruction of F centers are suggested depending on their concentration.
Synthesis, characterization and the first crystal structure of the Zn(II) complex of 4,6-O-ethylidine-N-(2-hydroxybenzylidene)-β-D-glucopyranosylamine
2001
4,6-O-Ethylidine-N-(2-hydroxybenzylidene)-β-D-glucopyranosylamine (H3L1) and N-(5-bromo-2-hydroxybenzylidene-4,6-O-ethylidine-β-D-glucopyranosylamine (H3L2) molecules possessing a–C-1–N=C(H)–moiety for metal-ion binding were synthesized by condensing the 4,6–O–ethylidene–β–D–glucopyranosylamine with salicylaldehyde or 5–bromosalicylaldehyde. Complexes of these ligands with Zn(II) were isolated and characterized using elemental analysis, FTIR, UV–Vis absorption, NMR spectroscopic and FAB mass spectrometric techniques. The structure of the Zn(II) complex derived from H3L1 was established for the first time by a single-crystal X-ray diffraction study. The anomeric nature of the saccharide moie…
Lanthanides Revealing Anthropogenic Impact within a Stratigraphic Sequence
2014
Difficulties to differentiate between anthropogenic and natural processes in the formation of archaeological deposits are crucial for a correct interpretation not only of the actions involved in the development of archaeological sites, but also of their occupation-abandonment dynamics and the understanding of their spatial behaviors and relationship with the environment. We have carried out lanthanides (rare earth elements “REE”) analysis to distinguish anthropogenic from natural stratigraphic units in sediments using the advantage of the high sensibility, precision, and accuracy of ICP-MS measurements. In the Neolithic site of Mas d’Is (Alacant, Spain), we have applied REE analysis in a hu…