362 research outputs found
Urban agriculture: a global analysis of the space constraint to meet urban vegetable demand
Urban agriculture (UA) has been drawing a lot of attention recently for several reasons: the majority of the world population has shifted from living in rural to urban areas; the environmental impact of agriculture is a matter of rising concern; and food insecurity, especially the accessibility of food, remains a major challenge. UA has often been proposed as a solution to some of these issues, for example by producing food in places where population density is highest, reducing transportation costs, connecting people directly to food systems and using urban areas efficiently. However, to date no study has examined how much food could actually be produced in urban areas at the global scale. Here we use a simple approach, based on different global-scale datasets, to assess to what extent UA is constrained by the existing amount of urban space. Our results suggest that UA would require roughly one third of the total global urban area to meet the global vegetable consumption of urban dwellers. This estimate does not consider how much urban area may actually be suitable and available for UA, which likely varies substantially around the world and according to the type of UA performed. Further, this global average value masks variations of more than two orders of magnitude among individual countries. The variations in the space required across countries derive mostly from variations in urban population density, and much less from variations in yields or per capita consumption. Overall, the space required is regrettably the highest where UA is most needed, i.e., in more food insecure countries. We also show that smaller urban clusters (i.e., <100 km2 each) together represent about two thirds of the global urban extent; thus UA discourse and policies should not focus on large cities exclusively, but should also target smaller urban areas that offer the greatest potential in terms of physical space
On the origin of the reactor antineutrino anomalies in light of a new summation model with parameterized transitions
We investigate the possible origins of the norm and shape reactor
antineutrino anomalies in the framework of a summation model (SM) where
transitions are simulated by a phenomenological Gamow-Teller
-decay strength model. The general trends of the discrepancies to the
Huber-Mueller model on the antineutrino side can be reproduced both in norm and
shape. From the exact electron-antineutrino correspondence of the SM model, we
predict similar distortions in the electron spectra, suggesting that biases on
the reference fission-electron spectra could be at the origin of the anomalies
Urban agriculture, civil interfaces and moving beyond difference: the experiences of plot holders in Dublin and Belfast
Recent literature suggests that a âshared politics of placeâ attained through joint activities fosters social integration and provides people with a means to practise co-operation [Baumann, G., 1996. Contesting culture: discourses of identity in multi-ethnic London. Cambridge: Cambridge University Press; Sanjek, R., 1998. The future of us all: race & neighbourhood policies in New York City. Ithaca, NY: Cornell University Press; Sennett, R., 2012. Together: the rituals, pleasures and politics of cooperation. UK: Penguin]. Such a âshared politics of placeâ is most likely to occur in the context of public space conceptualised broadly as âthe setting for everyday spatial behaviour of individuals and communities, emphasizing ordinary activities of citizensâ [Lownsbrough, H. and Beunderman, J., 2007. Equally spaced? Public space and interaction between diverse communities. London: Demos, p. 8]. Here we explore one element of such public space â urban agriculture sites â with a view to identifying the extent to which a âshared politics of placeâ can be created and nurtured among the cultivating citizenry. The paper draws on data collected on allotment gardening sites in two urban contexts: Dublin (Ireland) and Belfast (Northern Ireland) over the period 2009â2013. We demonstrate the centrality of allotment cultivation to the generation of solidarity, mutuality and trust among participating citizens. Individuals engaging in allotment gardening in both Dublin and Belfast create and sustain civil interfaces â dismantling barriers, exchanging knowledge, challenging stereotypes, generating empathy and getting on with the business of simply getting on with their lives. The modus operandi of allotment gardening is predicated on a willingness to disregard social and ethno-national categorisations while on site. This is not to deny that such differences exist and persist, but allotments offer a âspace of potentialâ where those differences are, at least for a time, rendered less salient
Faire campagne en ville : l'agriculture urbaine en Afrique de l'Est
Version anglaise disponible dans la BibliothÚque numérique du CRDI: Cities feeding people : an examination of urban agriculture in East Afric
Nuclear structure and reaction studies at SPIRAL
The SPIRAL facility at GANIL, operational since 2001, is described briefly.
The diverse physics program using the re-accelerated (1.2 to 25 MeV/u) beams
ranging from He to Kr and the instrumentation specially developed for their
exploitation are presented. Results of these studies, using both direct and
compound processes, addressing various questions related to the existence of
exotic states of nuclear matter, evolution of new "magic numbers", tunnelling
of exotic nuclei, neutron correlations, exotic pathways in astrophysical sites
and characterization of the continuum are discussed. The future prospects for
the facility and the path towards SPIRAL2, a next generation ISOL facility, are
also briefly presented.Comment: 48 pages, 27 figures. Accepted for publication in Journal of Physics
spectroscopy of Ne and Na
Expérience GANILThe spectroscopy of Ne and Na was studied from the reaction of Ne with a deuterium target in inverse kinematics at 9.7 MeV/nucleon. The selectivity of the (d,p),(d,t), and (d,n) transfer reactions provides new spectroscopic information on low-lying states. The validity of the sd shell-model space for these nuclei is discussed
Shell Gap Reduction In Exotic N = 17 Nuclei
An experimental spectroscopic investigation of some neutron rich Mg and Al isotopes around the shell closure N=20 has been performed. The delayed neutron and spectra, following the -decay of Mg and Al have been measured using the delayed neutron detector array TONNERRE coupled with high efficiency EXOGAM clover detectors, a LEPS detector and eight low-energy neutron detectors. A detailed analysis of such spectra allows one to construct the level schemes of their daughters, ^{32,33)Al and Si. The resulting spectroscopic information will provide stringent tests of large scale shell model calculations including np - nh excitations aimed at the understanding of the structural effects occurring in this region
Differential effects of testosterone, dihydrotestosterone and estradiol on carotenoid deposition in an avian sexually selected signal
Recent studies have demonstrated that carotenoid-based traits are under the control of testosterone (T) by up-regulation of carotenoid carriers (lipoproteins) and/or tissue-specific uptake of carotenoids. T can be converted to dihydrotestosterone (DHT) and estradiol (E2), and variation in conversion rate may partly explain some contradictory findings in the literature. Moreover, most studies on the effect of T on sexual signals have focused on the male sex only, while in many species females show the same signal, albeit to a lesser extent. We studied the effects of T, DHT, and E2 treatment in male and female diamond doves Geopelia cuneata in which both sexes have an enlarged red eye ring, which is more pronounced in males. We first showed that this periorbital ring contains very high concentration of carotenoids, of which most are lutein esters. Both T and DHT were effective in enhancing hue, UV-chroma and size in both sexes, while E2 was ineffective. However, E2 dramatically increased the concentration of circulating lipoproteins. We conclude that in both sexes both color and size of the secondary sexual trait are androgen dependent. The action of androgens is independent of lipoproteins regulation. Potential mechanisms and their consequences for trade-off are discussed
Summit of the N=40 Island of Inversion: precision mass measurements and ab initio calculations of neutron-rich chromium isotopes
Mass measurements continue to provide invaluable information for elucidating
nuclear structure and scenarios of astrophysical interest. The transition
region between the and proton shell closures is particularly
interesting due to the onset and evolution of nuclear deformation as nuclei
become more neutron rich. This provides a critical testing ground for emerging
ab-initio nuclear structure models. Here, we present high-precision mass
measurements of neutron-rich chromium isotopes using the sensitive
electrostatic Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS)
at TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) facility. Our
high-precision mass measurements of Cr confirm previous results,
and the improved precision in measurements of Cr refine the mass
surface beyond N=40. With the ab initio in-medium similarity renormalization
group, we examine the trends in collectivity in chromium isotopes and give a
complete picture of the N=40 island of inversion from calcium to nickel.Comment: 12 pages, 7 figure
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