The interplay between dopants and oxygen vacancies in the magnetism of V-doped TiO2

Density functional theory calculations indicate that the incorporation of V into Ti lattice positions of rutile TiO2 leads to magnetic V4+ species, but the extension and sign of the coupling between dopant moments confirm that ferromagnetic order cannot be reached via low-concentration doping in the non-defective oxide. Oxygen vacancies can introduce additional magnetic centres, and we show here that one of the effects of vanadium doping is to reduce the formation energies of these defects. In the presence of both V dopants and O vacancies all the spins tend to align with the same orientation. We conclude that V doping favours the ferromagnetic behaviour of TiO2 not only by introducing spins associated with the dopant centres but also by increasing the concentration of oxygen vacancies with respect to the pure oxide.Comment: 11 pages, including 1 table and 3 figures. To appear in the Journal of Physics Condensed Matter (special issue on Semiconducting Oxides

Globalization and land-use transitions in Latin America

Current socioeconomic drivers of land-use change associated with globalization are producing two contrasting land-use trends in Latin America. Increasing global food demand (particularly in Southeast Asia) accelerates deforestation in areas suitable for modern agriculture (e.g., soybean), severely threatening ecosystems, such as Amazonian rain forests, dry forests, and subtropical grasslands. Additionally, in the coming decades, demand for biofuels may become an emerging threat. In contrast, high yields in modern agricultural systems and rural–urban migration coupled with remittances promote the abandonment of marginal agricultural lands, thus favoring ecosystem recovery on mountains, deserts, and areas of poor soils, while improving human well-being. The potential switch from production in traditional extensive grazing areas to intensive modern agriculture provides opportunities to significantly increase food production while sparing land for nature conservation. This combination of emerging threats and opportunities requires changes in the way the conservation of Latin American ecosystems is approached. Land-use efficiency should be analyzed beyond the local-based paradigm that drives most conservation programs, and focus on large geographic scales involving long-distance fluxes of products, information, and people in order to maximize both agricultural production and the conservation of environmental services.Fil: Grau, Hector Ricardo. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Mitchell, Aide. Universidad de Puerto Rico; Puerto Ric

VO2: A Novel View from Band Theory

New calculations for vanadium dioxide, one of the most controversely discussed materials for decades, reveal that band theory as based on density functional theory is well capable of correctly describing the electronic and magnetic properties of the metallic as well as both the insulating M1 and M2 phases. Considerable progress in the understanding of the physics of VO2 is achieved by the use of the recently developed hybrid functionals, which include part of the electron-electron interaction exactly and thereby improve on the weaknesses of semilocal exchange functionals as provided by the local density and generalized gradient approximations. Much better agreement with photoemission data as compared to previous calculations is found and a consistent description of the rutile-type early transition-metal dioxides is achieved.Comment: 5 pages, 4 figure

Validation Report: outcome stories for CIAT-CCAFS projects in Colombia during 2014

In November 2014, I engaged with five Colombian government staff to validate two Outcome Stories prepared by CIAT staff describing governmental changes that CIAT science had influenced. The first Story described how the Ministry of Agriculture and Rural Development (MADR)1 and the Ministry of Environment and Sustainable Development (MADS) prioritized mitigation actions for the agriculture and livestock sector. CIAT’s contribution was its scientific collaboration in 2013 and 2014 with the Colombian government to identify appropriate mitigation measures for the agricultural sector and establish the evidence base for the Colombian Low Emission Development Strategy (LEDS). The second Story described how the Colombian National Planning Department (DNP) developed detailed sector level adaptation plans in part as a result of CIAT researchers’ measurement of the economic impacts of climate change in the water, biodiversity and livestock sector. The purpose of the validation was to both verify and enrich the understanding of the influence of CIAT research in decision-making at the policy level

Validation Report: outcome stories for CIAT-CCAFS projects in Colombia during 2014

In November 2014, I engaged with five Colombian government staff to validate two Outcome Stories prepared by CIAT staff describing governmental changes that CIAT science had influenced. The first Story described how the Ministry of Agriculture and Rural Development (MADR)1 and the Ministry of Environment and Sustainable Development (MADS) prioritized mitigation actions for the agriculture and livestock sector. CIAT’s contribution was its scientific collaboration in 2013 and 2014 with the Colombian government to identify appropriate mitigation measures for the agricultural sector and establish the evidence base for the Colombian Low Emission Development Strategy (LEDS). The second Story described how the Colombian National Planning Department (DNP) developed detailed sector level adaptation plans in part as a result of CIAT researchers’ measurement of the economic impacts of climate change in the water, biodiversity and livestock sector. The purpose of the validation was to both verify and enrich the understanding of the influence of CIAT research in decision-making at the policy level

Mechanical properties of compacted graphite cast iron with different microstructures

Tensile strength, fracture toughness and impact properties were evaluated in compacted graphite (CG) cast iron with ferritic, pearlitic and ausferritic microstructures. Ultimate tensile strengths for the ferritic and pearlitic samples were 337 and 632 MPa respectively. The austempered samples showed a significant increment in the strength and recording values between 675 and 943 MPa. The fracture toughness test revealed that the stress–intensity factor KIC was 34.0 MPa m1/2 for the ferritic CG iron, 39.7 MPa m1/2 for the pearlitic and between 51.0 and 58.0 MPa m1/2 for the austempered irons. On the other hand, CG iron with ferritic matrix exhibited the best impact properties with absorbed energy of 33.3 J. The absorbed energy of the pearlitic CG iron was the lowest, 14.3 J, while the austempered samples showed values between 17.2 and 28.4 J. Complementing these results, the critical crack size was also analysed