En Europe, 130 personnes périssent chaque année en avalanche, essentiellement lors de la pratique de sports de montagne. Cet article se focalise sur une innovation technique destinée à éviter ...l’ensevelissement lorsqu’une personne est emportée par une coulée : l’airbag d’avalanche. L’objectif est de réaliser un état des connaissances sur ce nouvel équipement, en privilégiant l’étude de son efficacité.
Le protocole de revue systématique mis en oeuvre, vérifiable et reproductible, donne accès aux données de recherche publiées ces vingt dernières années (1996–2016).
Dix-sept publications spécifiquement consacrées à la question ont été recensées. Une première période (1996–2002) est marquée par la mise en oeuvre d’expérimentations relativement fragiles (en termes de conditions comme d’échantillons), conduisant à des conclusions hâtives et flatteuses pour les fabricants d’airbags, notamment en termes de survie potentielle des victimes équipées (alors représentées par des mannequins). Bénéficiant d’informations fiabilisées sur les accidents d’avalanche impliquant des personnes équipées d’airbags, les publications postérieures à 2002, plus rigoureuses sur le plan de la méthode, fournissent des résultats plus précis qui confirment l’efficacité des airbags, tout en la relativisant sur plusieurs plans : diminution du « taux de survie » constaté, évocation croissante des situations et contextes particuliers pouvant altérer l’efficacité du dispositif (mise en avant d’effets pervers), précautions accrues dans l’interprétation des données.
Cette mise au point semble d’autant plus nécessaire que les chiffres avancés par les producteurs et les médias spécialisés constituent la principale influence poussant à investir dans un airbag. Au-delà de l’affinement progressif des études centrées sur l’efficacité des airbags, il reste à investiguer, parallèlement, l’influence de la possession d’un airbag sur le processus décisionnel sur le terrain.
In Europe, 130 people die every year in avalanches, mostly while practicing mountain sports. This paper focuses on a technical innovation aiming to avoid burial when a person is caught in an avalanche: the avalanche airbag. We undertook a literature review focused on the study of the effectiveness of such device.
A systematic review protocol has been implemented. It is reproducible and gave access to 17 publications dealing with this specific topic during the last twenty years (1996–2016).
A first period (1996–2002) is characterized by the implementation of relatively fragile experiments (in terms of conditions as well as samples), leading to hasty and flattering conclusions for airbag manufacturers, especially in terms of survival rates of the equipped victims (then represented by mannequins). Benefiting from reliable information on avalanche accidents involving people equipped with airbags, post-2002 publications, much more rigorous in terms of methods, provide more accurate results that both confirm the effectiveness of airbags, and relativize it on several levels: a decrease in the “survival rate”, a growing evocation of particular situations and contexts that could alter the effectiveness of the system, and increased precautions in the interpretation of data.
This synthesis seems all the more necessary as the figures put forward by the producers and the specialized media constitute the main influencing force to invest in an airbag. Beyond the gradual refining of studies centering on the effectiveness of airbags, the influence of the possession of an airbag on the decision-making process on the field remains to investigate.
The decisions that animals make are based on information gathered from their environment, and can have consequences for their fitness and survival. Such processes can be disrupted by environmental ...change. Hermit crabs find and select the gastropod shells they inhabit using chemical and visual cues, and tactile assessment. The choice of an optimal shell is important since it provides shelter against environmental extremes and protection against predators; inhabiting a suboptimal shell can also reduce fecundity. Hermit crabs are subject to cyclical reductions in the pH of the water in the intertidal rock pools that they inhabit, and such reductions may be further exacerbated by climate change. Reduced sea water pH, a consequence of ocean acidification and leaks from geological storage sites, has already been shown to disrupt the behaviour of marine animals. We investigated the effects of reduced sea water pH on the shell assessment and selection behaviour of the hermit crab
Pagurus bernhardus. Under highly reduced pH conditions (pH 6.8) crabs were less likely to change from a suboptimal to an optimal shell than those in untreated sea water; those that did change shells took longer to do so. Crabs in the reduced pH treatment also showed significantly lower antennular flicking rates (the ‘sniffing’ response in decapods) and reduced movement. Thus, a reduction in sea water pH disrupts the resource assessment and decision-making processes of these crabs, indicating that the ability to acquire a vital resource may be influenced by both naturally occurring environmental cycles and anthropogenically induced environmental change.
The link between biodiversity and ecosystem functioning is now well established, but the challenge remains to develop a mechanistic understanding of observed effects. Predator—prey interactions ...provide an opportunity to examine the role of resource partitioning, thought to be a principal mediator of biodiversity—function relationships. To date, interactions between multiple predators and their prey have typically been investigated in simplified agricultural systems with limited scope for resource partitioning. Thus there remains a dearth of studies examining the functional consequences of predator richness in diverse food webs. Here, we manipulated a species-rich intertidal food web, crossing predator diversity with total predator density, to simultaneously examine the independent and interactive effects of diversity and density on the efficiency of secondary resource capture. The effect of predator diversity was only detectable at high predator densities where competitive interactions between individual predators were magnified; the rate of resource capture within the species mixture more than doubled that of the best-performing single species. Direct observation of species-specific resource use in monoculture, as quantified by patterns of prey consumption, provided clear evidence that species occupied distinct functional niches, suggesting a mechanistic explanation of the observed diversity effect.
Submicrometer‐sized RDX and HMX crystals were produced by electrospray crystallization and submicrometer‐sized RDX crystals were produced by plasma‐assisted crystallization. Impact and friction ...sensitivity tests and ballistic impact chamber tests were performed to determine the product sensitivity. Rather than reflecting the quality of the particles, we found the sensitivity tests to be unreliable for submicrometer particles. The used impact test was not accurate enough, while in the friction and ballistic impact chamber tests the submicrometer‐sized crystals were distributed among the grooves of the porcelain plate or among the grains of the sandpaper used in these tests. These observations stress the need for revisiting the current standards used for determining the hazardous properties like friction and impact sensitivity of energetic materials in the case, where the sample consists of submicrometer‐sized crystals. Recommendations were suggested to develop new test methods that only use the interactions between the particles and therefore allow the application of sensitivity tests for submicrometer/nano‐sized energetic materials.
Early Taming of the Cat in Cyprus J. -D. Vigne; Guilaine, J.; Debue, K. ...
Science (American Association for the Advancement of Science),
04/2004, Letnik:
304, Številka:
5668
Journal Article
Recenzirano
It is generally accepted that cats were first domesticated in ancient Egypt at the latest by the 20th to 19th century B.C. However, similar finds from Cyprus suggest that origins of cat taming were ...earlier. A cat mandible at the early Neolithic site of Khirokitia, Cyprus, and more recently, from several other sites, show that cats were present on the island starting from approximately 9500 years ago.
The efficiency by which communities capture limiting resources may be related to the number of species or functional types competing therein. This is because species use different resources (i.e. ...complementarity effect) or because species-rich communities include species with extreme functional traits (positive selection effect). We conducted two manipulative studies to separate the effects of functional richness and functional identity on the feeding efficiency (i.e. filtration rate) of suspension-feeding invertebrates growing on vertical surfaces. In addition, one experiment tested whether the density of organisms influences the effect of functional diversity. Monocultures and complete mixtures of functional types were fed with a solution of microalgae of different sizes (6 μm–40 μm). Experiments conducted at two locations, Helgoland and Plymouth, showed that functional identity had far larger effects on filtration rate than richness. Mixtures did not outperform the average monoculture or the best-performing monoculture and this pattern was independent on density. The high efficiency of one of the functional types in consuming most microalgae could have minimised the resource complementarity. The loss or gain of particular species may therefore have a stronger impact on the functioning of epibenthic communities than richness per se.
En Europe, 130 personnes périssent chaque année en avalanche, essentiellement lors de la pratique de sports de montagne. Cet article se focalise sur une innovation technique destinée à éviter ...l'ensevelissement lorsqu'une personne est emportée par une coulée~: l'airbag d'avalanche. L'objectif est de réaliser un état des connaissances sur ce nouvel équipement, en privilégiant l'étude de son efficacité. Méthodes Le protocole de revue systématique mis en oeuvre, vérifiable et reproductible, donne accès aux données de recherche publiées ces vingt dernières années (1996-2016). Résultats Dix-sept publications spécifiquement consacrées à la question ont été recensées. Une première période (1996-2002) est marquée par la mise en oeuvre d'expérimentations relativement fragiles (en termes de conditions comme d'échantillons), conduisant à des conclusions hâtives et flatteuses pour les fabricants d'airbags, notamment en termes de survie potentielle des victimes équipées (alors représentées par des mannequins). Bénéficiant d'informations fiabilisées sur les accidents d'avalanche impliquant des personnes équipées d'airbags, les publications postérieures à 2002, plus rigoureuses sur le plan de la méthode, fournissent des résultats plus précis qui confirment l'efficacité des airbags, tout en la relativisant sur plusieurs plans: diminution du 'taux de survie' constaté, évocation croissante des situations et contextes particuliers pouvant altérer l'efficacité du dispositif (mise en avant d'effets pervers), précautions accrues dans l'interprétation des données. Conclusion Cette mise au point semble d'autant plus nécessaire que les chiffres avancés par les producteurs et les médias spécialisés constituent la principale influence poussant à investir dans un airbag. Au-delà de l'affinement progressif des études centrées sur l'efficacité des airbags, il reste à investiguer, parallèlement, l'influence de la possession d'un airbag sur le processus décisionnel sur le terrain. Summary Background In Europe, 130 people die every year in avalanches, mostly while practicing mountain sports. This paper focuses on a technical innovation aiming to avoid burial when a person is caught in an avalanche: the avalanche airbag. We undertook a literature review focused on the study of the effectiveness of such device. Methods A systematic review protocol has been implemented. It is reproducible and gave access to 17 publications dealing with this specific topic during the last twenty years (1996-2016). Results A first period (1996\textendash2002) is characterized by the implementation of relatively fragile experiments (in terms of conditions as well as samples), leading to hasty and flattering conclusions for airbag manufacturers, especially in terms of survival rates of the equipped victims (then represented by mannequins). Benefiting from reliable information on avalanche accidents involving people equipped with airbags, post-2002 publications, much more rigorous in terms of methods, provide more accurate results that both confirm the effectiveness of airbags, and relativize it on several levels: a decrease in the 'survival rate', a growing evocation of particular situations and contexts that could alter the effectiveness of the system, and increased precautions in the interpretation of data. Conclusion This synthesis seems all the more necessary as the figures put forward by the producers and the specialized media constitute the main influencing force to invest in an airbag. Beyond the gradual refining of studies centering on the effectiveness of airbags, the influence of the possession of an airbag on the decision-making process on the field remains to investigate.
A stochastic magnetic boundary, produced by an applied edge resonant magnetic perturbation, is used to suppress most large edge-localized modes (ELMs) in high confinement (H-mode) plasmas. The ...resulting H mode displays rapid, small oscillations with a bursty character modulated by a coherent 130 Hz envelope. The H mode transport barrier and core confinement are unaffected by the stochastic boundary, despite a threefold drop in the toroidal rotation. These results demonstrate that stochastic boundaries are compatible with H modes and may be attractive for ELM control in next-step fusion tokamaks.
•Most conservation projects failed so far in conserving the Common hamster Cricetus cricetus.•The effects of litter size and timing of harvest on population growth and persistence were ...evaluated.•Farming practices have been intensified and have become an important threat to this species.•The timing of harvest determines the total reproductive output of a population.•Conservation projects should focus on delaying harvest of cereals until September.
The Common hamster Cricetus cricetus was an agricultural pest in large parts of Europe less than 50years ago. Currently the species is highly threatened or locally extinct and acknowledged as an important and even iconic species for nature conservation in farmland areas in Western Europe. The species was listed in the European habitats directive in 1992 to prevent a further decline, but the Common hamster is still declining in most parts of its European range despite large conservation efforts. Only a few local conservation successes have been reported so far. These disappointing conservation results raise the question: why is it so difficult to conserve this former pest species?
Farming practices have been intensified in Europe and this has resulted in a more efficient way of harvesting cereals in combination with a strong reduction of spring sown cereals in favour of winter sown cereals. It is possible that these changes have become an important threat for survival of populations of this species. We developed both a deterministic and a stochastic population model for a better understanding of the current way of harvesting on the population ecology of this species and evaluated the effects of using different litter sizes on population growth and persistence. Our results suggest that under the current efficient harvest of cereals in Europe, it is highly unlikely that females of the Common hamster produce enough offspring for a sustainable population. Conservation projects for this species should focus on creating cereal fields which are not harvested until the end of August, as lack of cover is a major cause of high predation rates.
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