Objectives: To update surveillance data on antimicrobial susceptibility of Neisseria gonorrhoeae isolated in Greece with information for the years 2005 to 2008, and analyze changes occurred from the ...previous 4-year period. Methods: Annual antimicrobial susceptibility rates, susceptibility patterns, and serovars of 635 gonococci isolated in 2005 to 2008 were determined and compared to respective data concerning the gonococcal sample of 2001 to 2004. Genetic similarity of the isolates in phenotypic clusters was investigated by pulsed field gel electrophoresis. Epidemiologie information was also considered. Results: Despite a reduction in the isolation frequency of penicillinase-producing strains (3.9% vs. 11.6% in the previous period), the rates of resistance and intermediate susceptibility increased for penicillin, as well as for tetracycline, erythromycin, and chloramphenicol, leaving very small proportions of isolates sensitive to these agents (4.3%, 12.8%, 10.2%, and 3.6%, respectively). Resistance to fluoroquinolones increased from 11.3% in 2004 up to 63% in 2008, and strongly correlated with multidrug-resistant isolates of Bropyst serovar, accounting for 72.6% of the quinolone-resistant strains isolated during the last 4 years. All isolates were susceptible to spectinomycin and only 2 exceeded susceptibility breakpoints set for cefotaxime, exhibiting MICs 0.75 to 1μg/mL. These latter isolates, however, belonged to a cluster of strains with decreased susceptibility to cephalosporins (CDS, cefotaxime MICs ≥0.25 μg/mL) that emerged in late 2006 and increased in frequency up to 20.7% through 2008. Notably, CDS isolates were also quinolone-resistant and multiresistant, further contributing to the increasing rates of quinolone and multidrug resistance in the Greek gonococcal sample. Conclusions: Antimicrobial susceptibility figures of Neisseria gonorrhoeae in Greece are worsening due to changes in the synthesis of gonococcal population, resulting from high endemicity rates of multidrug-resistant strains.
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Loutsa is part of the municipality of Spata-Artemida and is located on the east coastline of Attica, between Raphina and Markopoulo (Fig. 8.1). The schematic marble figurine (Brauron Museum, ...Inventory number BE7102) was found in 2009 during a rescue excavation at a plot on Arkadias Street (OT 45-ITE 2η) in the Alyki area of Loutsa. Alyki, as may be deduced from the archaeological finds, has been inhabited since prehistoric times. About 1 km southeast of the plot on Arkadias Street, on the beach of Loutsa and more specifically on the peninsula where the seaside chapel of Agios Spyridon and Agios
H2 production via dehydrogenation of formic acid (HCOOH, FA), sodium formate (HCOONa, SF), or their mixtures, at near-ambient conditions, T < 100 °C, P = 1 bar, is intensively pursued, in the context ...of the most economically and environmentally eligible technologies. Herein we discuss molecular catalysts (ML), consisting of a metal center (M, e.g., Ru, Ir, Fe, Co) and an appropriate ligand (L), which exemplify highly efficient Turnover Numbers (TONs) and Turnover Frequencies (TOFs) in H2 production from FA/SF. Typically, many of these ML catalysts require the presence of a cofactor that promotes their optimal cycling. Thus, we distinguish the concept of such cofactors in additives vs. co-catalysts: When used at high concentrations, that is stoichiometric amounts vs. the substrate (HCOONa, SF), the cofactors are sacrificial additives. In contrast, co-catalysts are used at much lower concentrations, that is at stoichiometric amount vs. the catalyst. The first part of the present review article discusses the mechanistic key steps and key controversies in the literature, taking into account theoretical modeling data. Then, in the second part, the role of additives and co-catalysts as well as the role of the solvent and the eventual inhibitory role of H2O are discussed in connection to the main mechanistic steps. For completeness, photons used as activators of ML catalysts are also discussed in the context of co-catalysts. In the third part, we discuss examples of promising hybrid nanocatalysts, consisting of a molecular catalyst ML attached on the surface of a nanoparticle. In the same context, we discuss nanoparticulate co-catalysts and hybrid co-catalysts, consisting of catalyst attached on the surface of a nanoparticle, and their role in the performance of molecular catalysts ML.
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•Catalyst concentration determines the catalytic cycle since it can affect the speciation of monomeric/dimeric species formed.•The involvement of dimeric MnIV-MnIII transients, has ...been invoked as active catalytic intermediate.
The oxidative evolution of Mn-catalysts via transient high-oxidation state, MnIII or MnIV, intermediates is often assumed in literature, however a direct in-situ evidence for cycling between high-oxidation states of Mn is scarce. Moreover, the involvement of dimeric MnIV-MnIII transients, has been invoked as active catalytic intermediate. Herein, we present a study by Dual-Mode EPR and Low-Temperature UV–Vis spectroscopies, on the monitoring of cycling of MnII, MnIII, MnIV states formed by a MnL catalytic system. It is found that, while starting as monomeric, the MnL catalyst, is capable to form in-situ stable oxo-bridged Mn-Mn dimers which are catalytically/redox-active.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Palladium is among the most versatile noble-metal atoms that, when dispersed on solid supports, can be stabilized in 0, +1, +2, +3 redox states. Moreover, despite its noble-metal character, Pd shows ...a considerable degree of chemical reactivity. In Pd Nanoparticles (NPs), atomic {Pdn+-X} states, where n = 0, 1, 2, 3, and X = atom or hydride, can play key roles in catalytic processes. Pd-oxygen moieties can be stabilized at nanointerfaces of Pd in contact with metal-oxides. These {Pdn+-X}s can be either isolated Pd atoms dispersed on the support, or, more interestingly, atomic states of Pd occurring on the Pd NPs. The present review focuses on the role of such {Pdn+-X} states in catalytic processes related to energy storage or energy conversion, with specific focus on photocatalysis, H2 production reaction (HRR), oxygen reduction reaction (ORR), and water-splitting. Synthesis of atomic {Pdn+-X} states and their detection methodology is among the current challenges. Herein, the chemistry of {Pdn+-X} states on Pd- metal oxide interfaces, methods of detection, and identification are discussed. The implication of {Pdn+-X} in transient catalytic intermediates is reviewed. Finally, the role of {Pdn+-X} in photo electrocatalytic processes is critically discussed.
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A flame spray pyrolysis (FSP) method has been developed, for controlled doping of BiVO4 nanoparticles with W and Zr in tandem with the oxygen vacancies (Vo) of the BiVO4 lattice. Based on XPS and ...Raman data, we show that the nanolattice of W-BiVO4 and Zr-BiO4 can be controlled to achieve optimal O2 evolution from H2O photocatalysis. A synergistic effect is found between the W- and Zr-doping level in correlation with the Vo-concentration. FSP- made W-BiVO4 show optimal photocatalytic O2-production from H2O, up to 1020 μmol/(g × h) for 5%W-BiVO4, while the best performing Zr-doped achieved 970 μmol/(g × h) for 5%Zr-BiVO4. Higher W-or Zr-doping resulted in deterioration in photocatalytic O2-production from H2O. Thus, engineering of FSP-made BiVO4 nanoparticles by precise control of the lattice and doping-level, allows significant enhancement of the photocatalytic O2-evolution efficiency. Technology-wise, the present work demonstrates that flame spray pyrolysis as an inherently scalable technology, allows precise control of the BiVO4 nanolattice, to achieve significant improvement of its photocatalytic efficiency.
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•A non-heme Fe catalyst with a low- and a high-spin component.•Detection of the LS-FeIII−OOH transient with EPR & low-T UV–Vis.•Arrhenius Ea is low i.e. 18.5 kJ/mol for the formation ...of the LS-FeIII−OOH transient.•Low Ea explains fast kinetics and efficiency for alkene oxidation by LFeIII/H2O2.
The oxidative catalytic evolution of a highly efficient non-heme Fe catalyst (LFeIII) was studied using EPR and Low-Temperature UV–Vis spectroscopies. The key transient-intermediates of the Fe center were monitored during the catalytic cycle, in the presence of H2O2. The EPR data show that this non-heme Fe catalyst can evolve via either High-Spin or Low-Spin states of the Fe center, with only the Low-Spin path being catalytically efficient. The key transient, intermediate LFeIII-OOH in the Low-Spin path has also been monitored with Low-Temperature UV–Vis. Arrhenius analysis allowed determination of the energy barrier Ea = 18.5 ± 6.2 kJ/mole for the Low-Spin path.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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