Magnetically active vacancy related defects in irradiated GaN layers

We present the studies of magnetic properties of 2 MeV 4He+-irradiated GaN grown by metal-organic chemical-vapor deposition. Particle irradiation allowed controllable introduction of Ga-vacancy in the samples. The magnetic moments with concentrations changing between 4.3...8.3x10^17 cm^-3 showing superparamagnetic blocking at room temperature are observed. The appearance of clear hysteresis curve at T = 5 K with coercive field of about H_C = 270 Oe suggests that the formation of more complex Ga vacancy related defects is promoted with increasing Ga vacancy content. The small concentration of the observed magnetically-active defects with respect to the total Ga- vacancy concentration suggests that the presence of the oxygen/hydrogen-related vacancy complexes is the source of the observed magnetic moments.Comment: 3 pages, 3 figure

The Post-Anthropocene Diet: Navigating Future Diets for Sustainable Food Systems

This article examines how future diets could reduce the environmental impacts of food systems, and thus, enable movement into the post-Anthropocene. Such non-anthropocentric diets are proposed to address global food systems challenges inherent in the current geological epoch known as the Anthropocene—a period when human activity is the dominant cause of environmental change. Using non-anthropocentric indigenous worldviews and object-oriented ecosophy, the article discusses changes in ontologies around diets to consider choices made in the present for sustainable future food systems. This article conceptually addresses, how can pre-Anthropocene ontologies guide an exit of current approaches to diets? Considering temporality, what post-Anthropocene ontologies are possible in future diets for sustainable food systems? Through the ontological positions defining three distinct temporalities, considerations for guiding future diets in(to) the post-Anthropocene are proposed. Indigenous ontologies are presented as pre-Anthropocene examples that depict humans and non-humans in relational diets. Underlying Anthropocene ontologies define current unsustainable diets. These ontologies are described to present the context for the food systems challenges this article aims to address. A post-Anthropocene illustration then employs object-oriented ecosophy along with indigenous ontologies as theoretical foundations for shifting from the dominant neoliberal paradigm in current ontologies. Ontologically-based dietary guidelines for the post-Anthropocene diet present the ontological turns, consideration of temporality, and outline technological orientations proposed for sustainable future food systems. This is a novel attempt to integrate non-anthropocentric theories to suggest possible futures for human diets in order to exit the Anthropocene epoch. These non-anthropocentric ontologies demonstrate how temporal considerations and relational worldviews can be guidelines for transforming diets to address public health concerns, the environmental crisis, and socioeconomic challenges

Comparison of energy and greenhouse gas balances of biogas with other transport biofuel options based on domestic agricultural biomass in Finland

Biofuels have been promoted as a way to reduce greenhouse gas (GHG) emissions, but it is questionable whether they indeed do so. The study compared energy and GHG balances of transport biofuels produced in Finnish conditions. Energy and GHG balances were calculated from a life cycle perspective for biogas when timothy-clover and reed canary grass silages and green manure of an organic farm were used as a raw material. The results were compared with published data on barley-based ethanol, rape methyl ester (biodiesel) and biowaste-based biogas. The energy input for biogas was 22–37% of the output depending on the raw material. The GHG emissions from field-based biogas were 21–36% of emissions from fossil-based fuels. The largest energy input was used in the processing of the biofuels while most of the greenhouse gases were emitted during farming. The GHG emissions of the field-based biogas were emitted mainly from fuels of farming machinery, nitrous oxide (N2O) emissions of the soil and the production of ensiling additives. The energy efficiency was most sensitive to the methane yield, and GHG emissions to the N2O emissions. Biogas had clearly lower energy input and GHG emissions per unit energy output than domestic barley-based ethanol and biodiesel

Own or shared silage feeding place for dairy cows?

We studied behaviour, silage eating and milk production of cows when every animal had an own silage feeding place and when the feeding place was shared with two other cows

Low energy electron beam induced vacancy activation in GaN

Experimental evidence on low energy electron beam induced point defect activation in GaN grown by metal-organic vapor phase epitaxy(MOVPE) is presented. The GaN samples are irradiated with a 5–20 keV electron beam of a scanning electron microscope and investigated by photoluminescence and positron annihilation spectroscopy measurements. The degradation of the band-to-band luminescence of the irradiatedGaN films is associated with the activation of point defects. The activated defects were identified as in-grown Ga-vacancies. We propose that MOVPE-GaN contains a significant concentration of passive VGa-H n complexes that can be activated by H removal during low energy electron irradiation.Peer reviewe

Meat substitutes : Resource demands and environmental footprints

FThe modern food system is characterized with high environmental impact, which is in many cases associated with increased rates of animal production and overconsumption. The adoption of alternatives to meat proteins (insects, plants, mycoprotein, microalgae, cultured meat, etc.) might potentially influence the environmental impact and human health in a positive or negative way but could also trigger indirect impacts with higher consumption rates. Current review provides a condensed analysis on potential environmental impacts, resource consumption rates and unintended trade-offs associated with integration of alternative proteins in complex global food system in the form of meat substitutes. We focus on emissions of greenhouse gases, land use, non-renewable energy use and water footprint highlighted for both ingredients used for meat substitutes and ready products. The benefits and limitations of meat substitution are highlighted in relation to a weight and protein content. The analysis of the recent research literature allowed us to define issues, that require the attention of future studies.Peer reviewe

Holistic environmental assessment of High Nature Value farming systems in Europe

Many life cycle assessment (LCA) studies comparing environmental impacts of different beef production systems are incomplete as they exclude biodiversity impacts and soil carbon stock changes. This study aims to assess the environmental impact of ruminant production on semi-natural grasslands or so-called high nature value (HNV) farms at the European level. We collected data for 24 HNV farms in Europe (in Finland, Estonia and France). The studied farms are extensive beef, sheep and goat production systems. We used LCA to assess the potential environmental impact of HNV farms according to global warming potential (GWP100), eutrophication, fossil fuels and water use, by using the Solagro carbon calculator and OpenLCA software. Results showed that HNV farming systems have the potential to maintain unique biodiversity, act as carbon sinks, reduce greenhouse gas emissions and reduce nutrient losses and water use while producing animal-derived food. There were significant differences between HNV farms among countries in their greenhouse gas emissions at the farm level (tCO2eq ha-1) and N inputs (kg N ha-1). Better regional understanding of the environmental impact performance of HNV farming systems in relation to sustainable ruminant production will be achieved as the undergoing study progresses.Peer reviewe

Self-compensation in semiconductors: The Zn vacancy in Ga-doped ZnO

Self-compensation, the tendency of a crystal to lower its energy by forming point defects to counter the effects of a dopant, is here quantitatively proven. Based on a new theoretical formalism and several different experimental techniques, we demonstrate that the addition of 1.4 × 10 exp 21-cm exp −3 Ga donors in ZnO causes the lattice to form 1.7 × 10 exp 20-cm exp −3 Zn-vacancy acceptors. The calculated VZn formation energy of 0.2 eV is consistent with predictions from density functional theory. Our formalism is of general validity and can be used to investigate self-compensation in any degenerate semiconductor material.Peer reviewe

SPECTROSCOPY OF DEFECTS IN NEUTRON IRRADIATED AMMONO-THERMAL GaN BY COMBINING PHOTOIONIZATION, PHOTOLUMINESCENCE AND POSITRON ANNIHILATION TECHNIQUES

In this work, pulsed photoionization as well as photoluminescence and positron annihilation spectroscopy were combined to detect different species of defects. The GaN crystals, grown by the ammono-thermal method, doped with Mn as well as Mg impurities and irradiated with different fluences of reactor neutrons, were examined to clarify the role of the technological and radiation defects. The evolution of the prevailing photoactive centres was examined by pulsed photoionization spectroscopy. Positron annihilation spectroscopy was applied to reveal vacancy-type defects.Peer reviewe