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Zero-Acreage Farming (ZAF) recently developed as a novel land-use form and is aimed at addressing food security and sustainable urban development. While it is often lauded as a sustainable land-use form with potential to improve resource consumption and urban sustainability, little research into the spatial and technological requirements of this land-use form is available. This study undertakes a comparative analysis of ZAF and ground-based urban agriculture (UA) farms in diverse countries to differentiate their technical and spatial implementation parameters and uncover ZAF-specific characteristics and their implementation feasibility in rapidly developing cities. This qualitative study uses semi-structured interviews, triangulated with observational studies, to document ZAF and UA farms in South Africa, Belgium, the Netherlands and Singapore. The findings reveal UA as highly flexible, modular landuse forms while, contrastingly, the technological focus of ZAF farms often results in monofunctional and inflexible once implemented, isolated, and non-contextual solutions. While ZAF farms are appropriate to improve livelihoods and food security in dense urban contexts, the study highlights trends that must be addressed to promote the implementation of ZAF in poorer rapidly developing cities. [ABSTRACT FROM AUTHOR]

The growth of Sn on Si(557) has been studied by M. Jäger et al. (article no. 1900152) in order to elucidate the possibility to form defined nanowires. For low Sn-coverage, the surface structure consists of ca. 3 nm wide (111) terraces covered with the Sn structure separated by triple steps, similar to Ag/Si(557). The cover image shows a 3D rendered scanning tunneling microscope image of such Sn-nanowires grown on vicinal Si(111). [Extracted from the article]

In this study, the growth of Sn on Si(557) surfaces by means of scanning tunneling microscopy, low energy electron diffraction and angle resolved photoemission is analyzed. Depending on the Sn submonolayer coverage, various Sn‐nanowires are identified. For Sn‐coverages above 0.5 ML, (3×3)‐ and (23×23)‐reconstructions are found. In particular, these phases cover extended (111)‐areas, thus leading to an inhomogeneous refacetting of the Si(557) surface. The (223)‐facets between the mini‐(111) terraces reveal structures, which resemble a ×2 reconstruction along edges. The initial step structure of the Si(557) surface is maintained for Sn‐coverages below 0.5 ML, showing the α‐Sn phase on 3 nm wide (111)‐terraces. In contrast to the 2D Mott state of α‐Sn/Si(111), this confinement seems to quench the correlated electronic phase yielding metallic surface states at 40 K, in accordance with photoemission. [ABSTRACT FROM AUTHOR]