1,722,832 research outputs found
Structural and electronic properties of hybrid perovskites for high-efficiency thin-film photovoltaics from first-principles
No full textThe performance of perovskite solar cells recently exceeded 15% solar-to-electricity conversion efficiency for small-area devices. The fundamental properties of the active absorber layers, hybrid organic-inorganic perovskites formed from mixing metal and organic halides [e. g., (NH4)PbI3 and (CH3NH3)PbI3], are largely unknown. The materials are semiconductors with direct band gaps at the boundary of the first Brillouin zone. The calculated dielectric constants and band gaps show an orientation dependence, with a low barrier for rotation of the organic cations. Due to the electric dipole of the methylammonium cation, a photoferroic effect may be accessible, which could enhance carrier collection. (C) 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License
Thermodynamic Origin of Photoinstability in the CH3NH3Pb(I1-xBrx)(3) Hybrid Halide Perovskite Alloy
No full textThe formation of solid-solutions of iodide, bromide, and chloride provides the means to control the structure, band gap, and stability of hybrid halide perovskite semiconductors for photovoltaic applications. We report a computational investigation of the CH3NH3PbI3/CH3NH3PbBr3 alloy from density functional theory with a thermodynamic analysis performed within the generalized quasi-chemical approximation. We construct the phase diagram and identify a large miscibility gap, with a critical temperature of 343 K. The observed photoinstability in some mixed halide solar cells is explained by the thermodynamics of alloy formation, where an initially homogeneous solution is subject to spinodal decomposition with I and Br-rich phases, which is further complicated by a wide metastable region defined by the binodal line
Primi risultati dell’uso delle fototrappole per valutare la distribuzione, i ritmi di attività e il comportamento alimentare degli ungulati nella Tenuta di Castelporziano
No full textIs horn length crucial for Alpine chamois?
No full textAnimal weapons are one of the most studied morphological traits, particularly in Artiodactyla. Since in polygynous species males with larger weapons tend to be more successful in gaining access to females, researchers have traditionally focused on horn size. However, in species with limited horn size, weapon size has been assumed to have a reduced or null effect on life history traits. We examined the effect of intrinsic and extrinsic factors on the length of the second and third segments of Alpine chamois horns (Rupicapra rupicapra) in a population living in a poor environment. Our aim was to test how environmental conditions affected weapon growth and whether compensatory growth occurred. We showed that horn length was isometric to body size, although male horns grew more quickly. Ecological factors such as snow and forage availability affected weapon length, though mildly. No sign of compensatory growth was detected. We inferred that chamois mainly use horns as armament in intrasexual interactions. However, horn length was not a key element since horn growth remained isometric, at least under suboptimal ecological conditions. In species without extreme weapons, the handicap caused by longer horns is likely not compensated by an increase in individual fitness
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The effects of recreational activities on wild mammals
No full textAn increasing number of people practise nature-based recreational activities, generating great economic resources, which can become a threat to wildlife species, because wild animals may perceive human presence as a predation risk. Many studies have investigated the effects induced in wild mammals by nature-based recreation. Despite that, a thorough overview of the literature focused on this topic is lacking. We conducted a broad bibliographic search, reviewed 209 articles, and identified 672 case studies about the effect of recreational activities on terrestrial mammals. We hypothesised behavioural metrics, disturbance sources and protocols of data collection affect the probability of detecting the effect of recreational activities. We highlighted this research topic is affected by huge bias both on a taxonomical and geographical level. Studies were mostly carried out in North America or Europe and almost 90 % of them focused on Cetartiodactyla, Carnivora, and Rodentia. Nevertheless, trends in publication rates suggest that these biases are declining. Using multiple regression, we examined the study designs to understand which features were linked with a higher probability of detecting a disturbance. Although studies measuring physiological responses are scarce in the literature, these seem to be more likely to detect disturbances than behavioural ones. Studies implemented on individually recognisable animals are associated with a higher likelihood of detecting the effects of the disturbance. Harnessing this knowledge, future studies could generate a better understanding of the effects of recreational activities. Adopting suitable study protocols is essential for efficiently managing economic resources in scientific research and can help define better conservation strategies
Livestock displace European mouflon from optimal foraging sites
No full textThe conflict between free-ranging livestock and wildlife is a serious conservation concern across rural communities worldwide. Livestock may affect wild herbivores via direct competition for resources due to spatial and diet overlap or via behavioural interference. It is imperative that we disentangle the effects of livestock on wildlife behaviour to obtain an empirical basis able to stir management and conservation decisions. Here, we studied the effect of livestock presence on the habitat selection in a free-ranging European mouflon (Ovis aries musimon) population in Sardinia, where the species is under strict protection. We collected spatial data on mouflon and livestock during two consecutive years to investigate whether the mouflon selection of key feeding grassland sites was negatively impacted by the livestock presence. We found that mouflon preferably selected grassland, and its selection significantly increased when grass was of better quality (greener). We showed that livestock presence led to the displacement of mouflon from such preferred feeding sites, an effect clearly exacerbated by livestock proximity. We indeed found that the selection of grassland by mouflon dropped significantly when the distance between livestock and mouflon was below ~ 650 m, providing a useful management threshold indication. Livestock presence in close proximity displaced mouflon to sub-optimal habitat, and its effects may have negative impact on the population dynamic of this species which is already characterized by low female productivity within harsh Mediterranean environment. Our results give clear management indications aimed at better managing livestock grazing within natural areas to ultimately improve wildlife conservation
Territorial behaviour of male roe deer: a telemetry study of spatial behaviour and activity levels
No full textThe roe deer (Capreolus capreolus) is considered a special case of territorial ungulate. This study aimed to contribute to the knowledge of male roe deer territoriality by exploring its spatial use and activity patterns. We divided the territorial period (March- August) into three two-month sampling periods and found that the home range (HR) size of 13 radio-collared males averaged from 47.9 ± 14.5 ha to 109.7 ± 31.9 ha. We classified the spatial behaviour of eight out of the 13 males into three groups and concluded that HR size variation alone did not explain the potential territorial status. Nevertheless, it was indicative of their territorial status when considered along with the bucks’ age, spatial movements and activity levels. The activity levels of July-August were significantly lower than the activity levels of March-April. HR size variation of the males monitored significantly contributed to explain the variations in their activity levels. Old bucks were significantly less active than other males, especially during July-August. To sum up, we found an indication of an influence of spatial profiles on activity levels, though a larger sample will be needed in order to better understand differences in age and territorial status, and inter-individual differences in activity
Behavioural syndromes going wild: individual risk-taking behaviours of free-ranging wild boar
No full textBehavioural syndromes theory predicts animals will exhibit sets of correlated risk-taking behaviours, with individuals displaying a constant willingness to take risks across different situations. Because this phenomenon has mostly been investigated under artificial experimental conditions, we aimed to establish whether wild animals spontaneously exhibit correlated risk-taking behaviours. We merged a large data set of spatial positions from 43 wild boar, Sus scrofa, with the spatial distribution of risks, modelling their risk-induced resource selection. Elaborating these data by means of a resource selection analysis (step selection functions) and focusing only on periods when individuals were active represents an innovative approach to the study of spontaneous risk-taking behaviour exhibited across different situations. We sampled wild boar from two populations in southern Europe living in extremely different environmental conditions (mountainous versus Mediterranean area). We used model coefficients and parameters as quantitative measures of four different risk-taking behaviours (human avoidance, site fidelity, selection for covered habitat and mobility), for both the population and the individual level. A risk-taking syndrome was detected within both populations, with wild boar clustering in two groups sharing homogeneous sets of risk-taking behaviours. Contrary to the theoretical expectation which predicted individual use of consistent strategies, we observed a compensation among pairs of risk-taking behaviours, with individuals that could be considered risk avoiders on account of strong site fidelity and human avoidance being risk prone in terms of a low selection for covered habitats and a high mobility. Our results suggest that wild animals may adaptively exhibit strategies trading off different risk-taking behaviours. The similarities of risk-taking strategies in the two monitored populations suggested that the observed syndrome was not shaped by biotic or abiotic factors, but rather unintentionally caused by humans.(c) 2022 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved
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