Two-photon quantum walks in an elliptical direct-write waveguide array

Integrated optics provides an ideal test bed for the emulation of quantum systems via continuous-time quantum walks. Here we study the evolution of two-photon states in an elliptic array of waveguides. We characterise the photonic chip via coherent-light tomography and use the results to predict distinct differences between temporally indistinguishable and distinguishable two-photon inputs which we then compare with experimental observations. Our work highlights the feasibility for emulation of coherent quantum phenomena in three-dimensional waveguide structures.Comment: 8 pages, 7 figure

Functional and community-level soil microbial responses to zinc addition may depend on test system biocomplexity.

The effect of zinc on soil nitrification and composition of the microbial community in soil was investigated using a full factorial experiment with five zinc concentrations and four levels of biological complexity (microbes only, microbes and earthworms (Eisenia fetida), microbes and Italian ryegrass (Lolium multiflorum var. Macho), and microbes, ryegrass and earthworms). After 6 weeks of exposure, the activity of soil nitrifying bacteria was measured and the microbial community structure was characterized by phospholipid fatty acid (PLFA) analysis. Soil nitrification and several PLFA markers were significantly influenced by either zinc addition and/or the presence of earthworms or ryegrass, and one of the most pronounced changes was the increase of fungi and decrease of bacteria with increasing concentrations of zinc. Of particular interest, however, was the potential interaction between the presence of plants and/or earthworms and the effect of zinc, which the factorial study design allowed us to explore. Such an effect was observed in two cases: Earthworms reduced the positive effect of zinc on the fungal biomass (ANOVA, p = 0.03), and the effect of earthworms on the soil nitrification activity depended on zinc concentration (ANOVA, p < 0.05). The effect of earthworm presence was not very large, but it does show that multispecies tests might give information about metal toxicity or bioavailability that cannot be predicted from single-species tests. © 2006 Elsevier Ltd. All rights reserved

Smart-sustainability:A new urban fix?

\u3cp\u3eUrban policy increasingly positions smart urban development as a transformative approach to deliver sustainability. In this paper, we question the transformative credentials of smartness and argue that it is better understood as a partial fix for the economic, environmental and social challenges faced by cities. Drawing on the urban sustainability and smart city literatures, we develop the concept of the urban smart-sustainability fix. This concept focuses on how smart-sustainable city initiatives selectively integrate digital and environmental agendas via entrepreneurial forms of urban governance. We develop this concept by examining how the urban smart-sustainability fix is constructed in the European Commission's flagship smart cities and communities lighthouse projects, focusing on the Triangulum initiative. Our research reveals three elements of the urban smart-sustainability fix: (1) the spatial development of smart-sustainable districts; (2) the digitisation of urban infrastructure to reveal hidden processes; and, (3) collaborative experimentation with low-carbon and digital technologies. We argue that this has produced urban districts that are attempting to reduce their carbon emissions while promoting green economic growth. The main aim of the urban smart-sustainability fix is to make the urban realm more manageable resulting in amplification, rather than transformation, of the dominant ecological modernisation agenda of sustainable development.\u3c/p\u3

Recycling of biogas digestates in plant production: NPK fertilizer value and risk of leaching

Abstract Purpose The main purposes of the study were to assess the NPK fertilizer value of biogas digestates in different soils and to evaluate the risk of unwanted nutrient leaching. Methods The fertilizer value of digestates from anaerobic digesters was investigated in a greenhouse pot experiment with wheat in three different soils; silt, loam and sand. The digestates were based on different feedstock and had a low, dry matter content. The fertilizing effect of digestates was compared to mineral fertilizer and manure. To investigate the fate of excess nutrients in soil after the growing season, the pots were leached after harvest. A complementary soil column leaching experiment without plants was carried out in the laboratory. Results The concentration of ammonium in digestates provided a good indicator of the nitrogen fertilizer value of the digestates. In the silt and loam, the ammonium N fraction in digestates had a fertilizer replacement value equal to that of mineral fertilizer N, whereas the replacement value was higher in the nutrient poor sandy soil. Digestates often have a ratio between nitrogen, phosphorus and potassium which is not favourable for plant growth. However, the suboptimal balance did not result in reduced plant growth or unwanted leaching from soil. Conclusions The results show that digestates from biogas production based on fundamentally different feedstock are promising as NPK fertilizers. The N fertilization can simply be based on the digestate NH4 + concentration and, at least for wheat production, considerable variation in the concentrations of K and P can be tolerated

Continuous- and discrete-time quantum walks with non-classical two-photon inputs

We present two-photon continuous- and discrete-time quantum walks, respectively implemented in an integrated coupled waveguide array and a polarization-based beam-displacer network. We observe distinctly non-classical signatures, constituting progress towards quantum simulation capabilities