Structure characteristics and valence state study for La 1−x K x TiO 3 synthesized under high-pressure and high-temperature

Abstract By using a high-pressure and high-temperature method, perovskite oxides of the type La 1−x K x TiO 3 (x = 0.30, 0.35, 0.40, 0.45, 0.50) with mixed valence state were synthesized. This new synthesis route has several advantages. XRD analysis shows a cubic cell for the samples. XPS of the surface and EPR measurements indicate that the Ti ions have a mixed valence of 3+ and 4+ and that A-cation vacancies exist in the samples. As x increases, the amount of Ti 3+ ions and A-cation vacancies decreases. The valence state of the Ti ions can be altered by changing both pressure and temperature

Methanocella conradii sp. nov., a Thermophilic, Obligate Hydrogenotrophic Methanogen, Isolated from Chinese Rice Field Soil

BACKGROUND: Methanocellales contributes significantly to anthropogenic methane emissions that cause global warming, but few pure cultures for Methanocellales are available to permit subsequent laboratory studies (physiology, biochemistry, etc.). METHODOLOGY/PRINCIPAL FINDINGS: By combining anaerobic culture and molecular techniques, a novel thermophilic methanogen, strain HZ254(T) was isolated from a Chinese rice field soil located in Hangzhou, China. The phylogenetic analyses of both the 16S rRNA gene and mcrA gene (encoding the α subunit of methyl-coenzyme M reductase) confirmed its affiliation with Methanocellales, and Methanocella paludicola SANAE(T) was the most closely related species. Cells were non-motile rods, albeit with a flagellum, 1.4-2.8 µm long and by 0.2-0.3 µm in width. They grew at 37-60 °C (optimally at 55 °C) and salinity of 0-5 g NaCl l(-1) (optimally at 0-1 g NaCl l(-1)). The pH range for growth was 6.4-7.2 (optimum 6.8). Under the optimum growth condition, the doubling time was 6.5-7.8 h, which is the shortest ever observed in Methanocellales. Strain HZ254(T) utilized H(2)/CO(2) but not formate for growth and methane production. The DNA G+C content of this organism was 52.7 mol%. The sequence identities of 16S rRNA gene and mcrA gene between strain HZ254(T) and SANAE(T) were 95.0 and 87.5% respectively, and the genome based Average Nucleotide Identity value between them was 74.8%. These two strains differed in phenotypic features with regard to substrate utilization, possession of a flagellum, doubling time (under optimal conditions), NaCl and temperature ranges. Taking account of the phenotypic and phylogenetic characteristics, we propose strain HZ254(T) as a representative of a novel species, Methanocella conradii sp. nov. The type strain is HZ254(T) ( = CGMCC 1.5162(T) = JCM 17849(T) = DSM 24694(T)). CONCLUSIONS/SIGNIFICANCE: Strain HZ254(T) could potentially serve as an excellent laboratory model for studying Methanocellales due to its fast growth and consistent cultivability

Rational A/B Site Ion Doping to Design Efficient and Stable Pr0.5Ba0.4Ca0.1Fe1-xCoxO3-δ Perovskites as Zinc–Air Batteries Cathode

The development of robust and efficient electrocatalysts for use in fuel cells and metal–air batteries has garnered a great deal of interest due to the quest for clean and renewable energy sources. In this paper, a promising Co-doped Pr0.5Ba0.4Ca0.1Fe1-xCoxO3-δ (x = 0, 0.2, 0.4, 0.6, 0.8; denoted as PBCFC-x, x = 0, 2, 4, 6, 8) with enhanced durability and electrocatalytic ORR/OER activity for zinc–air battery cathode catalysts is presented. Particularly, PBCFC-6 exhibits the best bifunctional catalytic activity in alkaline media among several materials, according to research using the RDE. The zinc–air battery with PBCFC-6 as the cathode catalyst delivered the smallest discharge–charge voltage difference at the current density of 10 mA·cm−2 and only increased by 0.031 V after 220 cycles (220 h), demonstrating its superior bifunctional catalytic activity and durability. The optimized electrochemical performance of both OER and ORR as well as stability in zinc–air batteries might result from the higher electrical conductivity, increasing concentration of adsorbed oxygen, and the greater proportion of Fe4+ (t2g3eg1) with optimal electron occupancy, owing to the partial replacement of Fe with Co

Comparative characteristics of strain HZ254^T and <i>Methanocella paludicola</i> SANAE^T and <i>Methanocella arvoryzae</i> MRE50^T.

<p>Data for strain HZ254^T is from this study, and strain SANAE^T and MRE50^T were retrieved from Sakai <i>et al.</i>, 2008 and 2010.</p>*<p>The data in parentheses were determined by HPLC, other data were taken from genome information <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035279#pone.0035279-Erkel1" target="_blank">[2]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035279#pone.0035279-L1" target="_blank">[23]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035279#pone.0035279-Sakai4" target="_blank">[24]</a>.</p>†<p>pH for HZ254^T and other strains were determined at 55°C and 25°C, respectively. Abbreviations, −, negative; +, positive; N.A., not applicable.</p

T-RFLP patterns based on 16S rRNA genes for enrichment cultures of strain HZ254^T along with successive transfers.

<p>The analysis was performed using Ar109f/915r primer set and <i>TaqI</i> restriction enzymes <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035279#pone.0035279-Peng1" target="_blank">[14]</a>. T-RFLP fingerprints were normalized to a total of 100 relative fluorescence units (RFU), and T-RF peaks with RFU less than 1 were discarded. The 254-bp T-RF was affiliated with <i>Methanocellales</i> (RC-I) as determined by cloning and sequencing of 16S rRNA genes, and the T-RF length calculated from the sequence was actually 258-bp (data not shown). All other T-RF peaks could be assigned correspondingly to <i>Methanomicrobiales</i> (Mm), <i>Methanobacteriales</i> (Mb), <i>Methanosarcinaceae</i> (Msr)/Crenarchaeotal group 1.1b (G1.1b), <i>Methanosaetaceae</i> (Msa) and RC-I/<i>Methanomicrobiales</i> (Mm), according to our previous studies in the same soil <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035279#pone.0035279-Peng1" target="_blank">[14]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035279#pone.0035279-Yuan1" target="_blank">[34]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035279#pone.0035279-Wu1" target="_blank">[35]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035279#pone.0035279-Yuan2" target="_blank">[36]</a>, respectively. The pre-incubation samples were sampled after 24 hours of incubation, and all other samples were sampled after that methane production ceased and/or hydrogen could not be detected in the headspace. After the 13^th transfer, the archaeal community was still frequently monitored by T-RFLP analysis along with subsequent transfers, but the 254-bp was always the sole T-RF product.</p

Dynamics of the Methanogenic Archaeal Community during Plant Residue Decomposition in an Anoxic Rice Field Soil ▿

Incorporation of plant residues strongly enhances the methane production and emission from flooded rice fields. Temperature and residue type are important factors that regulate residue decomposition and CH4 production. However, the response of the methanogenic archaeal community to these factors in rice field soil is not well understood. In the present experiment, the structure of the archaeal community was determined during the decomposition of rice root and straw residues in anoxic rice field soil incubated at three temperatures (15°C, 30°C, and 45°C). More CH4 was produced in the straw treatment than root treatment. Increasing the temperature from 15°C to 45°C enhanced CH4 production. Terminal restriction fragment length polymorphism analyses in combination with cloning and sequencing of 16S rRNA genes showed that Methanosarcinaceae developed early in the incubations, whereas Methanosaetaceae became more abundant in the later stages. Methanosarcinaceae and Methanosaetaceae seemed to be better adapted at 15°C and 30°C, respectively, while the thermophilic Methanobacteriales and rice cluster I methanogens were significantly enhanced at 45°C. Straw residues promoted the growth of Methanosarcinaceae, whereas the root residues favored Methanosaetaceae. In conclusion, our study revealed a highly dynamic structure of the methanogenic archaeal community during plant residue decomposition. The in situ concentration of acetate (and possibly of H2) seems to be the key factor that regulates the shift of methanogenic community

Can Fallback Accretion on the Magnetar Model Power the X-Ray Flares Simultaneously Observed with Gamma Rays of Gamma-Ray Bursts?

The prompt emission, X-ray plateau, and X-ray flares of gamma-ray bursts (GRBs) are thought to be from internal dissipation, and the magnetar as the central engine with propeller fallback accretion is proposed to interpret the observed phenomena of GRBs. In this paper, by systematically searching for X-ray emission observed by Swift/X-ray Telescope, we find that seven robust GRBs include both X-ray flares and plateau emissions with measured redshift. More interestingly, the X-ray flares/bumps for those seven GRBs are simultaneously observed in the gamma-ray band. By adopting the propeller fallback accretion model to fit the observed data, it is found that the free parameters of two GRBs (140512A and 180329B) can be constrained very well, while in the other five cases, more or less, they are not all sufficiently constrained. On the other hand, this requires the conversion efficiency of the propeller to be two or three times higher than that of the spindown dipole radiation of the magnetar. If this is the case, it is contradictory to the expectation from the propeller model: namely, a dirtier ejecta should be less efficient in producing gamma-ray emissions. Our results hint that at least the magnetar central engine with propeller fallback accretion model cannot interpret very well both the GRB X-ray flares simultaneously observed in the gamma-ray band and the X-ray flares of GRBs with a high Lorentz factor