Why business angels reject investment opportunities: Is it personal?

A major focus of research on business angels has examined their decision-making processes and investment criteria. As business angels reject most of the opportunities that they receive, this article explores the reasons informing such decisions. In view of angel heterogeneity, investment opportunities might be expected to be rejected for differing reasons. Two sources of data are used to examine this issue. Face-to-face interviews with 30 business angels in Scotland and Northern Ireland provided information on typical ‘deal killers’. This was complemented by an Internet survey of United Kingdom that attracted responses from 238 UK business angels. The findings confirm that the main reason for rejection relates to the entrepreneur/management team. However, angel characteristics do not explain the number of reasons given for opportunity rejection nor do they predict the reasons for rejecting investment opportunities. This could be related to the increasing trend for business angels to join organised groups which, in turn, leads to the development of a shared repertoire of investment approaches. We suggest the concept of ‘communities-of-practice’ as an explanation for this finding

Vortex-Antivortex Lattice in Ultra-Cold Fermi Gases

We discuss ultra-cold Fermi gases in two dimensions, which could be realized in a strongly confining one-dimensional optical lattice. We obtain the temperature versus effective interaction phase diagram for an s-wave superfluid and show that, below a certain critical temperature T_c, spontaneous vortex-antivortex pairs appear for all coupling strengths. In addition, we show that the evolution from weak to strong coupling is smooth, and that the system forms a square vortex-antivortex lattice at a lower critical temperature T_M.Comment: Submitted to Physical Review Letter

Two-Dimensional Bosonization from Variable Shifts in the Path Integral

A method to perform bosonization of a fermionic theory in (1+1) dimensions in a path integral framework is developed. The method relies exclusively on the path integral property of allowing variable shifts, and does not depend on the explicit form of Greens functions. Two examples, the Schwinger model and the massless Thirring model, are worked out.Comment: 4 page

Geography of AirBnb in Barcelona and Lisbon: A comparative study

Over the last decade, Airbnb has emerged as the most important actor in the short-term rental business worldwide. The spatial distribution of Airbnb accommodations in a city is highly sensitive to the location of different spatial, socioeconomic, demographic, and cultural factors, and therefore has the potential to increase existing and create spatial inequalities in host cities. Drawing from the data from the Inside Airbnb website, the 2011 census of population and housing, the municipal registers, and Open Street Maps, this article first measures and analyses the degree of penetration and spatial clustering (with LISA statistics) of Airbnb listings in Barcelona and Lisbon. Then, it explores the spatial, socioeconomic, demographic, and cultural determinants of the spatial clustering of accommodations offered on Airbnb in both cities. Finally, it examines the impact of the COVID-19 pandemic on the spread of Airbnb in both cities. Results show that Airbnb has penetrated deeply into the central residential areas and around major tourist attractions, and it is deepening spatial inequalities by benefitting mainly the upper income group of homeowners in these neighbourhoods. Lastly, the recent COVID-19 pandemics has curtailed the spread and changed the typology of accommodation offered on Airbnb.info:eu-repo/semantics/publishedVersio

Capacidade de troca de cátions das principais classes de solos da Amazônia, determinada a diferentes valores de pH.

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Efeito da inundação sobre as propriedades de um gleissolo salico sodico de várzea do rio dos Morcegos, no município de Primavera, PA.

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