Bases for the management of the AM symbiosis in cropping systems of the prairie

Non-Peer Reviewe

Low temperature degradation behaviour of 10Ce-TZP/Al2O3 bioceramics obtained by microwave sintering technology

Zirconia is one of the most used ceramics, especially for biomedical applications, due to its exceptional mechanical properties. However, it is commonly known that its properties can be diminished owing to a low temperature degradation (LTD). This phenomenon consists on a spontaneous phase transformation, from tetragonal to monoclinic, under certain conditions, which is accelerated when the samples are exposed under high levels of humidity at a temperature range between 20-300 ºC. In addition to the fact that the monoclinic phase presents worse mechanical properties than the tetragonal one, there is a volume change of 4% between phases that gives rise to defects in the material as microcracks. Due to this reason, zirconia prostheses failed catastrophically inside the human body between 1999 and 2001 (1). Previous researches reveal that Al2O3 addition suppress the propagation of phase transformation (2). Thus, the aim of the present work is to study the hydrothermal ageing of zirconia doped with ceria and toughened with alumina (10Ce-TZP/Al2O3) composite, which has been sintered by microwave employing two different frequencies: 2.45 and 5.8 GHz. Microwave heating technology is based on the absorption of electromagnetic radiation by the material, which allows the sample to be heated. So far, most microwave heating equipments use 2.45 GHz; accordingly, the novelty of this study is to employ a frequency of 5.8 GHz and to investigate its effect on LTD. LTD is carried out in an autoclaved in steam at 120 ºC and 1.2 bar, because these conditions accelerate the hydrothermal aging process (3). In order to characterize the degraded samples, micro-Raman spectroscopy, AFM, nanoindentation technique and electronic microscopy have been performed. References 1. Norton, M. R., Yarlagadda, R., Anderson, G. H. J. Bone Joint Surg. Br., 2002, 84–B, 631–635. 2. Fabbri, P., Piconi, C., Burresi, E., Magnani, G., Mazzanti, F., Mingazzini, C. Dent. Mater., 2014. 3. Presenda, Á., Salvador, M. D., Moreno, R., Borrell, A. J. Am. Ceram. Soc., 2015, 98, 3680–3689

Movements, diving behaviour and diet of C-type killer whales (Orcinus orca) in the Ross Sea, Antarctica

The fish‐eating, type‐C ecotype, killer whale is a top predator in the Ross Sea, Antarctica. Increasing knowledge of this animal's foraging habitats, diet and movement patterns is listed amongst the research priorities adopted under the framework of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). To contribute to this goal, satellite transmitters were deployed on 10 type‐C killer whales and skin biopsies were obtained from seven individuals in Terra Nova Bay (Ross Sea) during austral summer (January-February) 2015. Hierarchical switching state-space models (hSSSM) were applied to Argos satellite tracking data to describe the movements of tagged whales, which were then paired with available diving data. Stable isotopes analyses were performed on the biopsy samples to describe the diet. A total of 8,803 Argos locations were available to fit the hSSSM. All whales engaged in potential foraging activity in localized areas along the Ross Sea coastline, followed by uninterrupted travel (i.e. migration) outside Antarctic waters, with no evidence of foraging activity. The pattern of deeper dives matched the occurrence of encamped behaviour indicated by the hSSSM results. The stable isotopes analysis indicated that Antarctic toothfish comprised the largest component (35%) of the prey biomass, raising concerns since this species is targeted by commercial fishery in the Ross Sea Region. These results provide new insights into the ecology of type‐C killer whales in the Ross Sea Region, underlining a potential threat from commercial fishing in the area. Considering the recent establishment of the Ross Sea Region Marine Protected Area, these findings will contribute to the required Research and Monitoring Programme of the Marine Protected Area and provide new empirical evidence to inform conservation measures in the existing Terra Nova Bay Antarctic Special Protected Are

Sliding wear behavior of WC-Co-Cr3C2-VC composites fabricated by conventional and non-conventional techniques

[EN] The present work aims are to study the dry sliding wear behavior of WC-12 wt.%Co materials, with or without addition of Cr3C2/VC grain growth inhibitors, and to sinter them by two different consolidation techniques: conventional sintering and spark plasma sintering (SPS). The dry sliding wear tests were performed on a tribometer with a ball-on-disc configuration using a WC-Co ball as a counterpart material with a normal contact load of 60 N, a sliding distance of 10000 m and a sliding speed of 0.1 m/s. The influence of the grain growth inhibitors and the consolidation techniques in sintered samples were related to the friction coefficient, wear rates and wear pattern damage. Samples sintered by non-conventional technique (SPS) show the best wear resistance and lower friction coefficient. The addition of inhibitors reduces the wear rates in materials consolidated by both techniques. The differences in the wear damage are related to microstructural parameters, mechanical properties and wear ratesThe work is supported financially by the Spanish Ministry of Science and Innovation by the project MAT2009-14144-C03-C02. L. Espinosa-Fernández, acknowledges the AECI program for the realization of the Ph.D in the ITM-UPV. A. Borrell, acknowledges the Spanish Ministry of Science and Innovation for her Juan de la Cierva contract (JCI-2011-10498)Espinosa-Fernández, L.; Borrell Tomás, MA.; Salvador Moya, MD.; Gutierrez-González, C. (2013). Sliding wear behavior of WC-Co-Cr3C2-VC composites fabricated by conventional and non-conventional techniques. Wear. 307:60-67. https://doi.org/10.1016/j.wear.2013.08.00S606730

Evidence of an efflux pump in Serratia marcescens

Spontaneous mutants resistant to fluoroquinolones were obtained by exposing Serratia marcescens NIMA (wild-type strain) to increasing concentrations of ciprofloxacin both in liquid and on solid media. Frequencies of mutation ranged from 10-7 to 10-9. Active expulsion of antibiotic was explored as a possible mechanism of resistance in mutants as well as changes in topoisomerase target genes. The role of extrusion mechanisms in determining the emergence of multidrug-resistant bacteria was also examined. Mutants resistant to high concentrations of fluoroquinolones had a single mutation in their gyrA QRDR sequences, whereas the moderate resistance in the rest of mutants was due to extrusion of the dru

Effect of microwave sintering on microstructure and mechanical properties in Y-TZP materials used for dental applications

The aim of this work is to study the application of microwave sintering to consolidate yttria-stabilized zirconia polycrystalline (Y-TZP) ceramics commonly applied in dentistry, so as to obtain highly dense materials and fine microstructure with shorter sintering cycles. Three Y-TZP materials are considered: two commercially available for dental applications and one laboratory studied powder. Microwave sintering was carried out at 1200 and 1300 degrees C for 10 min and conventional sintering at 1300 and 1400 degrees C for 2 h. Relative density, Vickers hardness and fracture toughness values for sintered samples were determined. Microwave sintering results, generally, in improved mechanical properties of the materials in terms of hardness and fracture toughness compared to conventional sintering and, in some cases, at lower sintering temperatures. A finer grain microstructure (final grain size < 250 min) was obtained with microwave sintering for both commercial materials. Fracture toughness values differ significantly between sintering techniques and chosen parameters. These results suggest that microwave heating can be employed to sinter Y-TZP commercial ceramics for dental applications obtaining improving the mechanical properties of the materials with a very important time and energy consumption reduction. Crown Copyright (C) 2015 Published by Elsevier Ltd and Techna Group S.r.l. All rights reserved.The authors would like to thank the financial support received from Universidad Politecnica de Valencia under Project 5P20120677 and Ministerio de Economia y Competitividad (MINECO) and co-funded by ERDF (European Regional Development Funds) through the Project (IEC2012-37532-C02-01). A. Borrell acknowledges the Spanish Ministry of Science and Innovation for her Juan de la Cierva Contract (JCI-2011-10498) and the Generalitat Valenciana for the financial support under Project GV/2014/009. A. Presenda acknowledges the Generalitat Valenciana for his Santiago Grisolia program scholarship (GRISOLLV2013/035). The authors would also like to acknowledge Prof. Dr. M. F. Sold from the Faculty of Medicine and Odontology at the Universidad de Valencia for supplying the commercial materials.Presenda, Á.; Salvador Moya, MD.; Penaranda-Foix, FL.; Moreno, R.; Borrell Tomás, MA. (2015). Effect of microwave sintering on microstructure and mechanical properties in Y-TZP materials used for dental applications. Ceramics International. 41(5, Part B):7125-7132. https://doi.org/10.1016/j.ceramint.2015.02.025S71257132415, Part

Improvement of microstructural properties of 3Y-TZP materials by conventional and non-conventional sintering techniques

3 mol% Y2O3-stabilized zirconia nanopowders were fabricated using various sintering techniques; conventional sintering (CS) and non-conventional sintering such as microwave (MW) and pulsed electric current-assisted-sintering (PECS) at 1300 °C and 1400 °C. A considerable difference in the densification behaviour between conventional and non-conventional sintered specimens was observed. The MW materials attain a bulk density 99.4% theoretical density (t.d.) at 1300 °C, while the CS materials attain only 92.5% t.d. and PECS 98.7% t.d. Detailed microstructural evaluation indicated that a low temperature densification leading to finer grain sizes (135 nm) could be achieved by PECS followed by MW with an average sintered grain size of 188 nm and CS 225 nm. It is believed that the high heating rate and effective particle packing are responsible for the improvements in these properties. © 2011 Published by Elsevier Ltd and Techna Group S.r.l. All rights reserved.This work has been carried out with programme to support research and development of the Polytechnic University of Valencia (U.P.V) under multidisciplinary projects PAID-05-09 and PAID-05-10. A. Borrell, acknowledges the Spanish Ministry of Science and Innovation for her FPI Ph.D. grant and the people from Institute Technological of Materials (ITM) of the U.P.V for helping us with the microwave experiments during a stay in 2010-2011. Felipe L. Pefiaranda-Foix wants to thank the Generalitat Valenciana for the grant obtained in the frame of the Program BEST/2010, because some results of this paper have been possible with this help.Borrell Tomás, MA.; Salvador Moya, MD.; Rayón Encinas, E.; Penaranda-Foix, FL. (2012). Improvement of microstructural properties of 3Y-TZP materials by conventional and non-conventional sintering techniques. Ceramics International. 38(1):39-43. https://doi.org/10.1016/j.ceramint.2011.06.035S394338

Fin whales as bioindicators of multi-decadal change in carbon and oxygen stable isotope shifts in the North Atlantic

Global changes, and particularly the massive release of CO2 to the atmosphere and subsequent global warming, have altered the baselines of carbon and oxygen stable isotopic ratios. Temporal shifts in these baselines can be advantageously monitored through cetacean skin samples because these animals are highly mobile and therefore integrate in their tissues the heterogeneity of local environmental signals. In this study, we examine variation of delta C-13 and delta O-18 values in the skin of fin whales sampled over three decades in two different North Atlantic feeding grounds: west Iceland and northwest Spain. These locations are situated about 2700 km apart and thus represent a wide latitudinal range within the North Atlantic Ocean. The delta C-13 decrease in both areas is attributed to the burning of fossil fuels and increased deforestation worldwide, the so-called Suess effect. The dissimilarity in the magnitude of the shift between the two areas is coincidental with previous information on local shifts and lies within the ranges of variation observed. delta O-18 values experienced a minimal, yet significant change in fin whales from W Iceland (a decline of - 0.44 parts per thousand between 1986 and 2013) but not in those from NW Spain. This is in concordance with a higher rise in temperatures in the former area than in the latter. The study validates the use of cetacean skin to monitor temporal and geographical shifts in stable isotopic values and alerts that, when applying this tool to ecological research, comparisons between sample sets should take into account temporal and latitudinal scales

Microwave Sintering of zirconia materials: Mechanical and microstructural properties

Commercially, 3mol% Y2O3-stabilized tetragonal zirconia (7090nm) compacts were fabricated using a conventional and a nonconventional sintering technique; microwave heating in a resonant mono-mode cavity at 2.45GHz, at temperatures in the 11001400 degrees C range. A considerable difference in the densification behavior between conventional (CS) and microwave (MW) sintered materials was observed. The MW materials attain a full density of 99.9% of the theoretical density (t.d.) at 1400 degrees C/10min, whereas the CS reach only 98.0% t.d. at the same temperature and 1h of dwelling time. Therefore, the MW materials exhibit superior Vickers hardness values (16.0GPa) when compared with CS (13.4GPa).This work has been carried out under program to support research and development of the Polytechnic University of Valencia (U.P.V) under multidisciplinary projects, PAID-05-09 and PAID-05-10. A. Borrell acknowledges the Spanish Ministry of Science and Innovation for her FPI Ph.D. grant and the people from Institute Technological of Materials (ITM) of the U.P.V for helping us with the microwave experiments during a stay in 2010-2011. Felipe L. Penaranda-Foix thanks the Generalitat Valenciana for the grant in the frame of the Program BEST/2010 because some results of this paper have been possible with this help.Borrell Tomás, MA.; Salvador Moya, MD.; Penaranda-Foix, FL.; Catalá Civera, JM. (2012). Microwave Sintering of zirconia materials: Mechanical and microstructural properties. International Journal of Applied Ceramic Technology. 10(2):313-320. https://doi.org/10.1111/j.1744-7402.2011.02741.xS313320102Deville, S., Gremillard, L., Chevalier, J., & Fantozzi, G. (2005). A critical comparison of methods for the determination of the aging sensitivity in biomedical grade yttria-stabilized zirconia. 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