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1
Ngueto, Yves Franklin, René Laprise et Oumarou Nikiéma. « A Detailed Limited-Area Atmospheric Energy Cycle for Climate and Weather Studies ». Atmosphere 15, no 1 (9 janvier 2024) : 87. http://dx.doi.org/10.3390/atmos15010087.
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Lorenz’ seminal work on global atmospheric energetics improved our understanding of the general circulation. With the advent of Regional Climate Models (RCMs), it is important to have a limited-area energetic budget available that is applicable for both weather and climate, analogous to Lorenz’ global atmospheric energetics. A regional-scale energetic budget is obtained in this study by applying Reynolds decomposition rules to quadratic forms of the kinetic energy K and the available enthalpy A, to obtain time mean and time deviation contributions. According to the employed definition, the time mean energy contributions are decomposed in a component associated with the time-averaged atmospheric state and a component due to the time-averaged statistics of transient eddies; these contributions are suitable for the study of the climate over a region of interest. Energy fluctuations (the deviations of instantaneous energies from their climate value) that are appropriate for weather studies are split into quadratic and linear contributions. The sum of all the contributions returns exactly to the total primitive kinetic energy and available enthalpy equations.
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Ohanian, Gabriel A. « The Role of Radio Loud Phase of Nuclear Activity in Galaxy Formation and Evolution ». Proceedings of the International Astronomical Union 9, S304 (octobre 2013) : 419–20. http://dx.doi.org/10.1017/s1743921314004487.
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AbstractKey questions, which arise when one tries to clear up a problem of formation and evolution of galaxies, is the question of energy: what is the energetic budget of AGN owing to form galaxies and provide its subsequent development? Hence, for understanding the formation and evolution of galaxies, it is important to estimate the energetic budget of AGN which we try to do involving radio loud phase of nuclear activity.
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Mahmoudabadi, Gita, Ron Milo et Rob Phillips. « Energetic cost of building a virus ». Proceedings of the National Academy of Sciences 114, no 22 (16 mai 2017) : E4324—E4333. http://dx.doi.org/10.1073/pnas.1701670114.
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Viruses are incapable of autonomous energy production. Although many experimental studies make it clear that viruses are parasitic entities that hijack the molecular resources of the host, a detailed estimate for the energetic cost of viral synthesis is largely lacking. To quantify the energetic cost of viruses to their hosts, we enumerated the costs associated with two very distinct but representative DNA and RNA viruses, namely, T4 and influenza. We found that, for these viruses, translation of viral proteins is the most energetically expensive process. Interestingly, the costs of building a T4 phage and a single influenza virus are nearly the same. Due to influenza’s higher burst size, however, the overall cost of a T4 phage infection is only 2–3% of the cost of an influenza infection. The costs of these infections relative to their host’s estimated energy budget during the infection reveal that a T4 infection consumes about a third of its host’s energy budget, whereas an influenza infection consumes only ≈ 1%. Building on our estimates for T4, we show how the energetic costs of double-stranded DNA phages scale with the capsid size, revealing that the dominant cost of building a virus can switch from translation to genome replication above a critical size. Last, using our predictions for the energetic cost of viruses, we provide estimates for the strengths of selection and genetic drift acting on newly incorporated genetic elements in viral genomes, under conditions of energy limitation.
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Egger, Joseph. « Mountain Forces and the Atmospheric Energy Budget ». Journal of the Atmospheric Sciences 68, no 11 (1 novembre 2011) : 2689–94. http://dx.doi.org/10.1175/2011jas3740.1.
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Abstract Although mountains are generally thought to exert forces on the atmosphere, the related transfers of energy between earth and atmosphere are not represented in standard energy equations of the atmosphere. It is shown that the axial rotation of the atmosphere must be included in the energy budget in order to resolve this issue. The energy transfer resulting from mountains turns out to be closely related to mountain torques. The energetic effects of a changing rotation of the earth are discussed, as well as those of friction torques and those of the nonspherical shape of the earth.
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Richardson, T. B., P. M. Forster, T. Andrews, O. Boucher, G. Faluvegi, D. Fläschner, Ø. Hodnebrog et al. « Drivers of Precipitation Change : An Energetic Understanding ». Journal of Climate 31, no 23 (décembre 2018) : 9641–57. http://dx.doi.org/10.1175/jcli-d-17-0240.1.
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The response of the hydrological cycle to climate forcings can be understood within the atmospheric energy budget framework. In this study precipitation and energy budget responses to five forcing agents are analyzed using 10 climate models from the Precipitation Driver Response Model Intercomparison Project (PDRMIP). Precipitation changes are split into a forcing-dependent fast response and a temperature-driven hydrological sensitivity. Globally, when normalized by top-of-atmosphere (TOA) forcing, fast precipitation changes are most sensitive to strongly absorbing drivers (CO2, black carbon). However, over land fast precipitation changes are most sensitive to weakly absorbing drivers (sulfate, solar) and are linked to rapid circulation changes. Despite this, land-mean fast responses to CO2 and black carbon exhibit more intermodel spread. Globally, the hydrological sensitivity is consistent across forcings, mainly associated with increased longwave cooling, which is highly correlated with intermodel spread. The land-mean hydrological sensitivity is weaker, consistent with limited moisture availability. The PDRMIP results are used to construct a simple model for land-mean and sea-mean precipitation change based on sea surface temperature change and TOA forcing. The model matches well with CMIP5 ensemble mean historical and future projections, and is used to understand the contributions of different drivers. During the twentieth century, temperature-driven intensification of land-mean precipitation has been masked by fast precipitation responses to anthropogenic sulfate and volcanic forcing, consistent with the small observed trend. However, as projected sulfate forcing decreases, and warming continues, land-mean precipitation is expected to increase more rapidly, and may become clearly observable by the mid-twenty-first century.
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Magris, Martina, et Cristina Tuni. « Enough for all : no mating effort adjustment to varying mate availability in a gift-giving spider ». Behavioral Ecology 30, no 5 (19 juin 2019) : 1461–68. http://dx.doi.org/10.1093/beheco/arz102.
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Males of a gift-giving spider do not modify their allocation to reproduction when mating opportunities vary. Due to their costly courtship via provision of food gifts to females, with high female availability males should reduce their reproductive investment per partner to avoid exhausting their energetic budget too early. Our findings suggest instead that males may be able to enlarge their total reproductive budget, possibly drawing resources from their food gifts by partially feeding on them.
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Marchand, Théo, Anne-Sophie Le Gal et Jean-Yves Georges. « Fine scale behaviour and time-budget in the cryptic ectotherm European pond turtle Emys orbicularis ». PLOS ONE 16, no 10 (15 octobre 2021) : e0256549. http://dx.doi.org/10.1371/journal.pone.0256549.
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For ectotherms, behaviour and associated energetic costs are directly related to thermal conditions. In the present context of global change, estimating time-budget for these species is relevant to assess and predict their capacity to adapt to near future. We tested the hypothesis that in ectotherms where reproduction is highly energy consuming, energy expenditure should vary throughout the breeding season with a maximum around nesting events. To test this hypothesis, we assessed the fine-scale behaviour, time-budget and estimated energetic costs in eight adult female European pond turtles Emys orbicularis equipped with data-loggers recording ambient temperature, pressure, light and the animals’ 3-axis acceleration. Deployments occurred over four months throughout the nesting season 2017 in semi-natural captive conditions in Alsace, France. All study turtles showed a clear daily pattern over the 24h cycle, with four distinct phases (referred to as Night, Morning, Midday and Evening), associated with different behaviours and activity levels. Before oviposition, turtles were mostly active during Morning, and activity was positively driven by ambient temperature. Activity levels doubled during the nesting period, mostly due to the increased activity in the Evening, when nesting events occurred. Throughout the active season, basking occurrence at Midday was related to air temperature but cloud coverage was an even more important factor. Our results are a first step in predicting the seasonal time and energy budgets of the European pond turtle, and demonstrate the usefulness of animal-borne accelerometers to study free living freshwater turtles over extended periods of time.
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Castanet, G., P. Lavieille, F. Lemoine, M. Lebouché, A. Atthasit, Y. Biscos et G. Lavergne. « Energetic budget on an evaporating monodisperse droplet stream using combined optical methods ». International Journal of Heat and Mass Transfer 45, no 25 (décembre 2002) : 5053–67. http://dx.doi.org/10.1016/s0017-9310(02)00204-1.
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Frey, H. « Energetic Significance of Torpor and Other Energy-Conserving Mechanisms in Free-Living Sminthopsis-Crassicaudata (Marsupialia, Dasyuridae) ». Australian Journal of Zoology 39, no 6 (1991) : 689. http://dx.doi.org/10.1071/zo9910689.
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Factors influencing the use of energy-conserving mechanisms including torpor, as well as their energetic significance, were studied in free-living Sminthopsis crassicaudata at Werribee (Victoria) during winter 1981 and 1982. Possible correlations between behavioural or physiological condition of captured animals and climatic variables or food availability were investigated. Daily energy expenditure was calculated by combining time-budget analysis in the field (based on radio-tracking) with respirometric measurements of metabolic rates in captivity. The energy-conserving mechanisms used were torpor, reduced activity, basking, huddling in groups, use of nests, choice of a thermally favourable resting site and slightly lowered resting body temperature. Torpor and reduced activity only occurred after cold (< 6-degrees-C) and dry nights, when surface activity of prey was very low, leaving S. crassicaudata in a negative energy balance. Rainy nights increased the availability of prey (particularly slugs and earthworms), and the animals did not enter torpor. During the non-breeding season (April-June), the energy savings [compared with a reference budget (E(r)) where no energy-conserving mechanism is used] reached 20-25% of E(r) after rainy or mild and dry nights, the major contributors being huddling and use of a nest. After cold dry nights, the savings may reach 40-50% of E(r), primarily due to torpor and reduced activity. Various energy-conserving mechanisms were used, even in the absence of short-term energetic problems, resulting in spontaneous energy savings and a reduced depletion of food. More prey was then available at the onset of breeding (mid-July), when energy requirements increase noticeably, because of smaller group size, smaller nests and energy channelled into offspring. The adpative value of spontaneous energy savings is discussed and the overwintering energetics of S. crassicaudata are compared with those of some European shrews.
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Kessler, T. A., et T. R. Parsons. « Primary Production in a Tidally Energetic Fjord : Environmental Forcing of Vertical Phytoplankton Distribution ». Canadian Journal of Fisheries and Aquatic Sciences 46, no 12 (1 décembre 1989) : 2173–83. http://dx.doi.org/10.1139/f89-269.
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Time dependent changes in the vertical phytoplankton distribution, during two short-term intensive studies in a tidally energetic sill-fjord, were examined with the objective of identifying processes responsible for a seasonal dependence between biomass and stability in a 7-yr environmental data set for the region. Reconciling an apparent divergence between calculated chlorophyl a (Chla) and NO3− mass balances identified diapycnal mixing to be an important term in the NO3− budget, but not in the Chla budget. The balancing mixing rate required was consistent with a wind stress origin and inconsistent with a tidal origin. This calculation, combined with evidence that mixing events in the surface layer were generally more closely correlated with the wind than the tide was used to support a hypothesis relating the seasonal biomass–stability relationship to seasonally dependent tidal mixing in the surface layer.
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Blanckenhorn, Wolf U. « Energetic underpinnings of yellow dung fly mating success in the field ». Alpine Entomology 5 (22 juillet 2021) : 61–67. http://dx.doi.org/10.3897/alpento.5.68153.
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Foraging provides the basis for animal reproduction, but requires energy and time to be sustained, entailing a trade-off. Whereas females should maximize their time foraging for resources, males should minimize their foraging time by optimizing time budgets to maximize their access to mating partners. Mark-resight field studies are difficult and hence uncommon for small insects. Yellow dung flies (Scathophaga stercoraria L.) abound on pastures in cold-temperate regions across the northern hemisphere. Adult flies lick nectar from flowers for energy, but require small insect prey to produce eggs and sperm. Males wait for females around fresh cow dung, but at one point also need to replenish their energy and/or sperm reserves in the surrounding vegetation. Their foraging time budgets should depend on their body size, nutritional energy reserves, availability of sperm, competitor and female density. Marked male dung flies whose nutritional status was experimentally manipulated – water only (null control); water + sugar (energy replenishment); or water, sugar + Drosophila prey (energy and sperm replenishment) – were repeatedly observed on an experimental pasture for an entire day. Both nutrient types were expected to increase the mating success of especially large males. The total number of resighted males seen copulating was lowest for water-treated flies. Mating success was positively related to body size. The distance travelled between dung pats was greater for males fed sugar or prey and also increased with body size, while pat residence times decreased with size. No differences were found between the sugar- and prey-fed groups. Crucially however, there was no evidence in the field for a time budget or mating advantage of small males when nutrients were limited.
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Mann, G., et A. Warmuth. « Budget of energetic electrons during solar flares in the framework of magnetic reconnection ». Astronomy & ; Astrophysics 528 (9 mars 2011) : A104. http://dx.doi.org/10.1051/0004-6361/201014389.
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Uchida, Thomas K., Jennifer L. Hicks, Christopher L. Dembia et Scott L. Delp. « Stretching Your Energetic Budget : How Tendon Compliance Affects the Metabolic Cost of Running ». PLOS ONE 11, no 3 (1 mars 2016) : e0150378. http://dx.doi.org/10.1371/journal.pone.0150378.
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Trudel, Marc, Alain Tremblay, Roger Schetagne et Joseph B. Rasmussen. « Why are dwarf fish so small ? An energetic analysis of polymorphism in lake whitefish (Coregonus clupeaformis) ». Canadian Journal of Fisheries and Aquatic Sciences 58, no 2 (1 février 2001) : 394–405. http://dx.doi.org/10.1139/f00-252.
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Sympatric populations of dwarf lake whitefish (Coregonus clupeaformis) (DLW) and normal lake whitefish (NLW) commonly occur in north temperate and subarctic lakes. DLW have a much lower growth, mature earlier, and have a shorter life span than NLW. Furthermore, they are usually not found when cisco (Coregonus artedi) are present, possibly due to competitive exclusion. In this study, we compared the energy budget of DLW, NLW, and cisco using food consumption rates estimated with mass balance models of chemical tracers (i.e., mercury and radiocesium). These chemicals are globally distributed and can be readily detected in fish and their prey. Our analysis showed that the energy budget of DLW and cisco was similar. DLW and cisco consumed on average 4050% more food than NLW. The conversion efficiency of DLW and cisco was two to three times lower than that of NLW. These results suggest that DLW and cisco allocated a larger fraction of their energy budget to metabolism than NLW. Our analysis also suggests that the earlier maturation and shorter life span of DLW and cisco may be due to their higher metabolic rates.
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D’Angelo, Gianni, Francesco Palmieri et Antonio Robustelli. « Artificial neural networks for resources optimization in energetic environment ». Soft Computing 26, no 4 (21 janvier 2022) : 1779–92. http://dx.doi.org/10.1007/s00500-022-06757-x.
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AbstractResource Planning Optimization (RPO) is a common task that many companies need to face to get several benefits, like budget improvements and run-time analyses. However, even if it is often solved by using several software products and tools, the great success and validity of the Artificial Intelligence-based approaches, in many research fields, represent a huge opportunity to explore alternative solutions for solving optimization problems. To this purpose, the following paper aims to investigate the use of multiple Artificial Neural Networks (ANNs) for solving a RPO problem related to the scheduling of different Combined Heat & Power (CHP) generators. The experimental results, carried out by using data extracted by considering a real Microgrid system, have confirmed the effectiveness of the proposed approach.
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Mayer, Michael, Leopold Haimberger, John M. Edwards et Patrick Hyder. « Toward Consistent Diagnostics of the Coupled Atmosphere and Ocean Energy Budgets ». Journal of Climate 30, no 22 (novembre 2017) : 9225–46. http://dx.doi.org/10.1175/jcli-d-17-0137.1.
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The widely used diagnostic vertically integrated total energy budget equations of atmosphere and ocean contain inconsistencies that should no longer be disregarded. The neglect of enthalpy fluxes associated with precipitation and evaporation leads to a spurious dependence on reference temperature. This seemingly small inconsistency is amplified because enthalpy of water vapor implicitly included in lateral atmospheric energy transports usually is computed on the Kelvin scale, leading to inconsistencies that, although zero when globally averaged, attain values on the order of 20 W m−2 in the tropics. A more consistent energy budget framework is presented, which is independent of reference temperature and which takes full account of enthalpy fluxes associated with mass transfer through the surface. The latter include effects of snowfall and additional nonlatent contributions, which have a net cooling effect on the earth’s surface (−1.3 W m−2). In addition to these diagnostic issues, comparatively small inconsistencies in the energetic formulations of current weather and climate models are highlighted. Using the energy budget formulation presented here, instead of that commonly used, yields enhanced self-consistency of diagnosed atmospheric energy budgets and substantially improved spatial agreement between fields of net surface energy flux inferred from the divergence of lateral atmospheric energy transports in conjunction with satellite-based radiative fluxes and independent surface flux products. Results imply that previous estimates of radiative plus turbulent surface fluxes over the ocean, balancing the observed ocean warming, are biased low by ~1.3 W m−2. Moreover, previous studies seriously underestimated cross-equatorial atmospheric and oceanic energy transports. Overall, the presented framework allows for unambiguous coupled energy budget diagnostics and yields more reliable benchmark values for validation purposes.
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Gnanadesikan, Anand, Richard D. Slater, P. S. Swathi et Geoffrey K. Vallis. « The Energetics of Ocean Heat Transport ». Journal of Climate 18, no 14 (15 juillet 2005) : 2604–16. http://dx.doi.org/10.1175/jcli3436.1.
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Abstract A number of recent papers have argued that the mechanical energy budget of the ocean places constraints on how the thermohaline circulation is driven. These papers have been used to argue that climate models, which do not specifically account for the energy of mixing, potentially miss a very important feedback on climate change. This paper reexamines the question of what energetic arguments can teach us about the climate system and concludes that the relationship between energetics and climate is not straightforward. By analyzing the buoyancy transport equation, it is demonstrated that the large-scale transport of heat within the ocean requires an energy source of around 0.2 TW to accomplish vertical transport and around 0.4 TW (resulting from cabbeling) to accomplish horizontal transport. Within two general circulation models, this energy is almost entirely supplied by surface winds. It is also shown that there is no necessary relationship between heat transport and mechanical energy supply.
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Jouanno, Julien, et Julio Sheinbaum. « Heat Balance and Eddies in the Caribbean Upwelling System ». Journal of Physical Oceanography 43, no 5 (1 mai 2013) : 1004–14. http://dx.doi.org/10.1175/jpo-d-12-0140.1.
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Abstract The upper-ocean heat budget of the Caribbean upwelling system is investigated during the onset of the Atlantic warm pool (June–September) using high-resolution observations of sea surface temperature and a high-resolution (°) regional model. Vertical mixing is found to be the major cooling contribution to the mixed layer heat budget in the nearshore and offshore Colombia Basin. Numerical results show that intense mesoscale eddies in the Colombia Basin significantly shape the turbulent cooling and may participate in the maintenance of cooler temperature in this region compared to surrounding areas. Indeed, increased mixing at the base of the mixed layer occurs below energetic surface jets that form on the downstream side of the eddies. These jets generally flow offshore and may arise from the deformation of the surface mesoscale field. It is shown that significant contribution of horizontal advection to the mixed layer heat budget is limited to a radius of 300 km around the Guajira and Margarita upwelling zones.
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Rivero, A., et H. M. Ferguson. « The energetic budget ofAnopheles stephensiinfected withPlasmodium chabaudi : is energy depletion a mechanism for virulence ? » Proceedings of the Royal Society of London. Series B : Biological Sciences 270, no 1522 (7 juillet 2003) : 1365–71. http://dx.doi.org/10.1098/rspb.2003.2389.
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Safonova, Mariia, Vladimir Tabunshchik, Roman Gorbunov et Tatiana Gorbunova. « Heat Budget of Sub-Mediterranean Downy Oak Landscapes of Southeastern Crimea ». Forests 14, no 10 (22 septembre 2023) : 1927. http://dx.doi.org/10.3390/f14101927.
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This article presents the findings of a research endeavor focused on the diurnal and seasonal dynamics of heat balance and its constituent elements within an oak forest situated in the expanse of the Karadag Nature Reserve. Computed are the values corresponding to the elements of heat balance, encompassing radiation balance, latent heat fluxes corresponding to heat consumption for evaporation, turbulent heat exchange transpiring within the atmosphere, and heat flux coursing through the soil. The features of changes in the heat balance in two key areas are considered: in the zone of growth of the downy oak forest in an open area and in the forest itself. The study discloses patterns characterizing the apportionment of radiation balance into heat and energetic fluxes within the context of the downy oak landscapes native to the southeastern Crimea. Scrutiny of the data established that a substantial proportion of radiation balance finds application in propelling turbulent heat flux, while a minor share is channeled into processes of evaporation and soil heat flux. Evidenced is that the magnitudes of heat balance components, encompassing radiation balance, latent heat fluxes corresponding to heat consumption for evaporation, turbulent heat exchange transpiring within the atmosphere, and heat flux through the soil within the sub-canopy realm, undergo modifications contingent upon the seasons of the year and the vegetative phases of the downy oak forest. The correlation between air temperature and the constituents of heat balance is subject to analysis both within the confines of the territory in the zone of growth of the downy oak forest in an open area and in the forest itself. Manifest is the constancy of the influence exerted by forest vegetation upon heat balance; nevertheless, the degree of its impact is circumscribed by the cyclical dynamics of foliage upon the trees: a well-developed canopy serves to amplify the influence exerted upon the distribution of heat and energetic fluxes. This study of heat balance and its constituents assumes significance in engendering comprehension regarding the operation of downy oak landscapes that are situated on the periphery of their habitudinal range. Also, it helps to reveal deeper patterns of climate change in forest ecosystems.
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Esparza, Pablo, Sandra Castano-Solis, David Jiménez-Bermejo, Jesús Fraile Ardanuy et Manuel Merino. « Experimental Determination of the Energetic Performance of a Racing Motorcycle Battery-Pack ». Processes 8, no 11 (31 octobre 2020) : 1391. http://dx.doi.org/10.3390/pr8111391.
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This paper presents the evaluation of the energetic performance of the battery-pack from the motorcycle prototype EME 16E. This racing prototype was developed by a student team from the Universidad Politécnica de Madrid (UPM) to participate in the MotoStudent competition during 2015–2016. This study includes the sizing and assembly of the motorcycle’s battery-pack under strict regulations and a limited budget. The prototype was also tested under different performance conditions, such as laboratory tests and racing circuits. Experimental results show that the proposed battery-pack is capable of supplying the energy and power necessary to drive the motorcycle in all cases analyzed.
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Damiani, Alessandro, Bernd Funke, Manuel López Puertas, Michelle L. Santee, Raul R. Cordero et Shingo Watanabe. « Energetic particle precipitation : A major driver of the ozone budget in the Antarctic upper stratosphere ». Geophysical Research Letters 43, no 7 (9 avril 2016) : 3554–62. http://dx.doi.org/10.1002/2016gl068279.
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Villafranca, Natalie, Isabella Changsut, Sofia Diaz de Villegas, Haley Womack et Lauren E. Fuess. « Characterization of trade-offs between immunity and reproduction in the coral species Astrangia poculata ». PeerJ 11 (4 décembre 2023) : e16586. http://dx.doi.org/10.7717/peerj.16586.
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Background Living organisms face ubiquitous pathogenic threats and have consequently evolved immune systems to protect against potential invaders. However, many components of the immune system are physiologically costly to maintain and engage, often drawing resources away from other organismal processes such as growth and reproduction. Evidence from a diversity of systems has demonstrated that organisms use complex resource allocation mechanisms to manage competing needs and optimize fitness. However, understanding of resource allocation patterns is limited across taxa. Cnidarians, which include ecologically important organisms like hard corals, have been historically understudied in the context of resource allocations. Improving understanding of resource allocation-associated trade-offs in cnidarians is critical for understanding future ecological dynamics in the face of rapid environmental change. Methods Here, we characterize trade-offs between constitutive immunity and reproduction in the facultatively symbiotic coral Astrangia poculata. Male colonies underwent ex situ spawning and sperm density was quantified. We then examined the effects of variable symbiont density and energetic budget on physiological traits, including immune activity and reproductive investment. Furthermore, we tested for potential trade-offs between immune activity and reproductive investment. Results We found limited associations between energetic budget and immune metrics; melanin production was significantly positively associated with carbohydrate concentration. However, we failed to document any associations between immunity and reproductive output which would be indicative of trade-offs, possibly due to experimental limitations. Our results provide a preliminary framework for future studies investigating immune trade-offs in cnidarians.
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Magomedov, M. R. D. « Trophic-Energetic Bases of Functioning and Stability of Natural Populations of Herbivorous Mammals ». Известия Российской академии наук. Серия биологическая, no 7 (1 mai 2023) : 54–69. http://dx.doi.org/10.31857/s1026347023600188.
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Using the example of various groups of herbivorous mammals, it is shown that the spatial, seasonal and long-term dynamics of energy resources directly affects the level of their consumption by animals, determines changes in the intensity of reproduction, mortality and migration processes, and, ultimately, the state and stability of populations. The supply of nutrients and energy is initially limited, that determines certain forms of ecological processes according to the hierarchy of components of the energy budget. The energy balance of the organism acts as a universal integral indicator of the effectiveness of the adaptation capabilities of the organism to environmental factors at every moment of its life cycle.
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Liu, Yushuo, Chee Kent Lim, Zhiyong Shen, Patrick K. H. Lee et Theodora Nah. « Effects of pH and light exposure on the survival of bacteria and their ability to biodegrade organic compounds in clouds : implications for microbial activity in acidic cloud water ». Atmospheric Chemistry and Physics 23, no 2 (31 janvier 2023) : 1731–47. http://dx.doi.org/10.5194/acp-23-1731-2023.
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Abstract. Recent studies have reported that interactions between live bacteria and organic matter can potentially affect the carbon budget in clouds, which has important atmospheric and climate implications. However, bacteria in clouds are subject to a variety of atmospheric stressors, which can adversely affect their survival and energetic metabolism and, consequently, their ability to biodegrade organic compounds. At present, the effects of cloud water pH and solar radiation on bacteria are not well understood. In this study, we investigated how cloud water pH (pH 3 to 6) and exposure to solar radiation impact the survival and energetic metabolism of two Enterobacter bacterial strains that were isolated from ambient air collected in Hong Kong and their ability to biodegrade organic acids. Experiments were conducted using simulated sunlight (wavelength from 320 to 700 nm) and microcosms comprised of artificial cloud water that mimicked the pH and chemical composition of cloud water in Hong Kong, South China. Our results showed that the energetic metabolism and survival of both strains depended on the pH. Low survival rates were observed for both strains at pH<4, regardless of whether the strains were exposed to simulated sunlight. At pH 4 to 5, the energetic metabolism and survival of both strains were negatively impacted only when they were exposed to simulated sunlight. Organic compounds such as lipids and peptides were detected during exposure to simulated sunlight at pH 4 to 5. In contrast, there were minimal effects on the energetic metabolism and the survival of both strains when they were exposed to simulated sunlight at pH>5. The biodegradation of organic acids was found to depend on the presence (or absence) of simulated sunlight and the pH of the artificial cloud water medium. Overall, this study provides new insights into how two common atmospheric stressors, cloud water pH and exposure to solar radiation, can influence the survival and energetic metabolism of bacteria, and consequently the roles that they play in cloud processes.
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Danylevsky, V. « Estimations of the aerosols direct radiative effects in the atmosphere over Kyiv from the AERONET sun-photometer measurements in 2008–2019 ». Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, no 60 (2019) : 38–45. http://dx.doi.org/10.17721/btsnua.2019.60.38-45.
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The article describes briefly the problem of the aerosols influence on the energetic budget of the Earth whole climate system and of the atmosphere particularly. The literary sources comprising such estimations are analyzed and aerosols basic properties are presented which are necessary to determine the quantitative estimations of the aerosols climatology effects. Basic terms and definitions are stated that are using to estimate the influence of the external and internal agents of the climate system on its energy budget. Basic features of the algorithms used to compute the co-called radiative forcing from data of the sun-photometer international network AERONET briefly described. The estimations of the aerosols radiative forcing obtained from measurements with the sun-photometer at the Kyiv AERONET site starting from 2008 are presented. Also the comparison of the Kyiv aerosol RF data to the aerosol RF data at some others urban regions of the globe are presented.
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Demas, Gregory E., Vladimir Chefer, Mark I. Talan et Randy J. Nelson. « Metabolic costs of mounting an antigen-stimulated immune response in adult and aged C57BL/6J mice ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 273, no 5 (1 novembre 1997) : R1631—R1637. http://dx.doi.org/10.1152/ajpregu.1997.273.5.r1631.
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Animals must balance their energy budget despite seasonal changes in both energy availability and physiological expenditures. Immunity, in addition to growth, thermoregulation, and cellular maintenance, requires substantial energy to maintain function, although few studies have directly tested the energetic cost of immunity. The present study assessed the metabolic costs of an antibody response. Adult and aged male C5BL/6J mice were implanted with either empty Silastic capsules or capsules filled with melatonin and injected with either saline or keyhole limpet hemocyanin (KLH). O2 consumption was monitored periodically throughout antibody production using indirect calorimetry. KLH-injected mice mounted significant immunoglobulin G (IgG) responses and consumed more O2 compared with animals injected with saline. Melatonin treatment increased O2 consumption in mice injected with saline but suppressed the increased metabolic rate associated with an immune response in KLH-injected animals. Melatonin had no effect on immune response to KLH. Adult and aged mice did not differ in antibody response or metabolic activity. Aged mice appear unable to maintain sufficient heat production despite comparable O2 production to adult mice. These results suggest that mounting an immune response requires significant energy and therefore requires using resources that could otherwise be allocated to other physiological processes. Energetic trade-offs are likely when energy demands are high (e.g., during winter, pregnancy, or lactation). Melatonin appears to play an adaptive role in coordinating reproductive, immunologic, and energetic processes.
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Cliffe, Rebecca N., Judy A. Avey-Arroyo, Francisco J. Arroyo, Mark D. Holton et Rory P. Wilson. « Mitigating the squash effect : sloths breathe easily upside down ». Biology Letters 10, no 4 (avril 2014) : 20140172. http://dx.doi.org/10.1098/rsbl.2014.0172.
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Sloths are mammals renowned for spending a large proportion of time hanging inverted. In this position, the weight of the abdominal contents is expected to act on the lungs and increase the energetic costs of inspiration. Here, we show that three-fingered sloths Bradypus variegatus possess unique fibrinous adhesions that anchor the abdominal organs, particularly the liver and glandular stomach, to the lower ribs. The key locations of these adhesions, close to the diaphragm, prevent the weight of the abdominal contents from acting on the lungs when the sloth is inverted. Using ventilation rate and body orientation data collected from captive and wild sloths, we use an energetics-based model to estimate that these small adhesions could reduce the energy expenditure of a sloth at any time it is fully inverted by almost 13%. Given body angle preferences for individual sloths in our study over time, this equates to mean energy saving of 0.8–1.5% across individuals (with individual values ranging between 0.01 and 8.6%) per day. Given the sloth's reduced metabolic rate compared with other mammals and extremely low energy diet, these seemingly innocuous adhesions are likely to be important in the animal's energy budget and survival.
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Chen, Jinqiang, et Simona Bordoni. « Orographic Effects of the Tibetan Plateau on the East Asian Summer Monsoon : An Energetic Perspective ». Journal of Climate 27, no 8 (10 avril 2014) : 3052–72. http://dx.doi.org/10.1175/jcli-d-13-00479.1.
Texte intégralRésumé :
Abstract This paper investigates the dynamical processes through which the Tibetan Plateau (TP) influences the East Asian summer monsoon (EASM) within the framework of the moist static energy (MSE) budget, using both observations and atmospheric general circulation model (AGCM) simulations. The focus is on the most prominent feature of the EASM, the so-called meiyu–baiu (MB), which is characterized by a well-defined, southwest–northeast elongated quasi-stationary rainfall band, spanning from eastern China to Japan and into the northwestern Pacific Ocean between mid-June and mid-July. Observational analyses of the MSE budget of the MB front indicate that horizontal advection of moist enthalpy, and primarily of dry enthalpy, sustains the front in a region of otherwise negative net energy input into the atmospheric column. A decomposition of the horizontal dry enthalpy advection into mean, transient, and stationary eddy fluxes identifies the longitudinal thermal gradient due to zonal asymmetries and the meridional stationary eddy velocity as the most influential factors determining the pattern of horizontal moist enthalpy advection. Numerical simulations in which the TP is either retained or removed show that the TP influences the stationary enthalpy flux, and hence the MB front, primarily by changing the meridional stationary eddy velocity, with reinforced southerly wind over the MB region and northerly wind to its north. Changes in the longitudinal thermal gradient are mainly confined to the near downstream of the TP, with the resulting changes in zonal warm air advection having a lesser impact on the rainfall in the extended MB region.
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Thiébaut, Maxime, Jean-François Filipot, Christophe Maisondieu, Guillaume Damblans, Rui Duarte, Eloi Droniou et Sylvain Guillou. « Assessing the turbulent kinetic energy budget in an energetic tidal flow from measurements of coupled ADCPs ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 378, no 2178 (27 juillet 2020) : 20190496. http://dx.doi.org/10.1098/rsta.2019.0496.
Texte intégralRésumé :
Two coupled four-beam acoustic Doppler current profilers were used to provide simultaneous and independent measurements of the turbulent kinetic energy (TKE) dissipation rate ε and the TKE production rate P over a 36 h long period at a highly energetic tidal energy site in the Alderney Race. The eight-beam arrangement enabled the evaluation of the six components of the Reynolds stress tensor which allows for an improved estimation of the TKE production rate. Depth-time series of ε, P and the Reynolds stresses are provided. The comparison between ε and P was performed by calculating individual ratios of ε corresponding to P . The depth-averaged ratio ε / P averaged over whole flood and ebb tide were found to be 2.2 and 2.8 respectively, indicating that TKE dissipation exceeds TKE production. It is shown that the term of diffusive transport of TKE is significant. As a result, non-local transport is important to the TKE budget and the common assumption of a local balance, i.e. a balance between production and dissipation, is not valid at the measurement site. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.
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FORAY, VINCENT, PIERRE-FRANCOIS PELISSON, MARIE-CLAUDE BEL-VENNER, EMMANUEL DESOUHANT, SAMUEL VENNER, FREDERIC MENU, DAVID GIRON et BENJAMIN REY. « A handbook for uncovering the complete energetic budget in insects : the van Handel's method (1985) revisited ». Physiological Entomology 37, no 3 (12 mars 2012) : 295–302. http://dx.doi.org/10.1111/j.1365-3032.2012.00831.x.
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Dyck, Markus G., et Ermias Kebreab. « Estimating the Energetic Contribution of Polar Bear (Ursus maritimus) Summer Diets to the Total Energy Budget ». Journal of Mammalogy 90, no 3 (2 juin 2009) : 585–93. http://dx.doi.org/10.1644/08-mamm-a-103r2.1.
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Schwemmer, Teresa G., Roger M. Nisbet et Janet A. Nye. « Attributing hypoxia responses of early life Menidia menidia to energetic mechanisms with Dynamic Energy Budget theory ». Ecological Modelling 498 (décembre 2024) : 110889. http://dx.doi.org/10.1016/j.ecolmodel.2024.110889.
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Lill, A. « Behavioral Energetics of Overwintering in the Rifleman, Acanthisitta-Chloris ». Australian Journal of Zoology 39, no 6 (1991) : 643. http://dx.doi.org/10.1071/zo9910643.
Texte intégralRésumé :
The role of behavioural adjustments in meeting increased daily energy requirements in winter was investigated in rifleman, Acanthisitta chloris, inhabiting lowland forest in South I., New Zealand, by comparing their population density, time-activity budget and foraging behaviour in autumn and winter. Rifleman foraged for 83% of daytime in both seasons. The combined effects on the birds' winter energy budget of increased thermoregulation costs and the shorter daylength for foraging were at least partly offset by an estimated 23-29% decrease in the amount of energy expended daily on activity and a 78% increment in prey caught per day. The reduced energy expenditure on activity resulted from rifleman spending less time on expensive flying and more time roosting. The increase in prey capture rate may have stemmed from a 35% seasonal reduction in the birds' population density and reduced prey mobility at lower ambient temperatures. Marked sexual size dimorphism was not reflected in gender differences in activity budgeting or prey capture rate, but the sexes differed in their relative use of foraging substrates. Rifleman showed few seasonal changes in daily activity rhythm or microhabitat use. The behavioural energetic overwintering tactics of rifleman are compared with those of other Australasian and north temperate zone land-birds.
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Sherwood, Graham D., Joseph B. Rasmussen, David J. Rowan, Julie Brodeur et Alice Hontela. « Bioenergetic costs of heavy metal exposure in yellow perch (Perca flavescens) : in situ estimates with a radiotracer (137Cs) technique ». Canadian Journal of Fisheries and Aquatic Sciences 57, no 2 (1 février 2000) : 441–50. http://dx.doi.org/10.1139/f99-268.
Texte intégralRésumé :
While the flow of energy is understood to determine the growth of organisms and the productivity of ecosystems, little is known about the sublethal effect of pollutants on the energetic efficiency of wild populations. We used field estimates of fish growth coupled to in situ estimates of food consumption rates obtained from the mass balance of a globally dispersed, trophically transferred radiotracer (137Cs) to demonstrate the bioenergetic impairment of yellow perch (Perca flavescens) from lakes polluted by heavy metals (Cd, Cu, and Zn). Annual growth increment relative to the total energy budget (conversion efficiency) was about three times lower in cortisol-impaired yellow perch from metal-polluted lakes relative to yellow perch from reference lakes (4.2% compared with 10.8%), suggesting that fish exposed to pollutants experienced greater total energetic costs. In addition, metal-polluted lakes were dominated by adult yellow perch populations and simplified prey bases, suggesting that effects are occurring at multiple levels of biological organization. Our in situ bioenergetic approach to toxicity assessment provides a measurable and ecologically relevant endpoint for assessing the sublethal effects of pollutants on fish communities.
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Grutter, Alexandra S., Jennifer G. Rumney, Tane Sinclair-Taylor, Peter Waldie et Craig E. Franklin. « Fish mucous cocoons : the ‘mosquito nets’ of the sea ». Biology Letters 7, no 2 (17 novembre 2010) : 292–94. http://dx.doi.org/10.1098/rsbl.2010.0916.
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Mucus performs numerous protective functions in vertebrates, and in fishes may defend them against harmful organisms, although often the evidence is contradictory. The function of the mucous cocoons that many parrotfishes and wrasses sleep in, while long used as a classical example of antipredator behaviour, remains unresolved. Ectoparasitic gnathiid isopods (Gnathiidae), which feed on the blood of fish, are removed by cleaner fish during the day; however, it is unclear how parrotfish and wrasse avoid gnathiid attacks at night. To test the novel hypothesis that mucous cocoons protect against gnathiids, we exposed the coral reef parrotfish Chlorurus sordidus (Scaridae) with and without cocoons to gnathiids overnight and measured the energetic content of cocoons. Fish without mucous cocoons were attacked more by gnathiids than fish with cocoons. The energetic content of mucous cocoons was estimated as 2.5 per cent of the fish's daily energy budget fish. Therefore, mucous cocoons protected against attacks by gnathiids, acting like mosquito nets in humans, a function of cocoons and an efficient physiological adaptation for preventing parasite infestation that is not used by any other animal.
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Smith, Richard W., Dominic F. Houlihan, Göran E. Nilsson et Julie Alexandre. « Tissue-specific changes in RNA synthesis in vivo during anoxia in crucian carp ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 277, no 3 (1 septembre 1999) : R690—R697. http://dx.doi.org/10.1152/ajpregu.1999.277.3.r690.
Texte intégralRésumé :
The overall energy budget for protein synthesis (i.e., transcription plus translation) is thought to consist of fixed and variable components, with RNA synthesis accounting for the former and protein synthesis the latter. During anoxia, the downregulation of protein synthesis (i.e., the variable component), to reduce energetic demand, is an important aspect of survival in crucian carp. The present study examines RNA synthesis during anoxia by labeling with [3H]uridine. A novel synthesis rate calculation is presented, which allows for the tissue-specific salvage of uridine, with synthesis rates finally expressed relative to DNA. After 48 h anoxia, the decline (29%) in brain RNA synthesis and increases in the heart and liver (132 and 871%, respectively) support known RNA functions during hypoxic/anoxic survival. This study provides evidence that, in an anoxia-tolerant species, survival mechanisms involving RNA are able to operate because tissue-specific restructuring of the RNA synthesis process enables fixed synthesis costs to be maintained; this may be as vital to survival as exploiting the variable energetic demand of protein synthesis.
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Su, Zhan, Andrew P. Ingersoll, Andrew L. Stewart et Andrew F. Thompson. « Ocean Convective Available Potential Energy. Part II : Energetics of Thermobaric Convection and Thermobaric Cabbeling ». Journal of Physical Oceanography 46, no 4 (avril 2016) : 1097–115. http://dx.doi.org/10.1175/jpo-d-14-0156.1.
Texte intégralRésumé :
AbstractThe energetics of thermobaricity- and cabbeling-powered deep convection occurring in oceans with cold freshwater overlying warm salty water are investigated here. These quasi-two-layer profiles are widely observed in wintertime polar oceans. The key diagnostic is the ocean convective available potential energy (OCAPE), a concept introduced in a companion piece to this paper (Part I). For an isolated ocean column, OCAPE arises from thermobaricity and is the maximum potential energy (PE) that can be converted into kinetic energy (KE) under adiabatic vertical parcel rearrangements. This study explores the KE budget of convection using two-dimensional numerical simulations and analytical estimates. The authors find that OCAPE is a principal source for KE. However, the complete conversion of OCAPE to KE is inhibited by diabatic processes. Further, this study finds that diabatic processes produce three other distinct contributions to the KE budget: (i) a sink of KE due to the reduction of stratification by vertical mixing, which raises water column’s center of mass and thus acts to convert KE to PE; (ii) a source of KE due to cabbeling-induced shrinking of the water column’s volume when water masses with different temperatures are mixed, which lowers the water column’s center of mass and thus acts to convert PE into KE; and (iii) a reduced production of KE due to diabatic energy conversion of the KE convertible part of the PE to the KE inconvertible part of the PE. Under some simplifying assumptions, the authors also propose a theory to estimate the maximum depth of convection from an energetic perspective. This study provides a potential basis for improving the convection parameterization in ocean models.
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Vialatte, A., M. Barthélemy et J. Lilensten. « Impact of Energetic Electron Precipitation on the Upper Atmosphere : Nitric Monoxide ». Open Atmospheric Science Journal 11, no 1 (27 juillet 2017) : 88–104. http://dx.doi.org/10.2174/1874282301711010088.
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Background:Nitric oxide concentration in the upper atmosphere is known to be highly dependent on the solar activity. It can be transported to the stratosphere by the atmospheric circulation. In the stratosphere it is responsible for the destruction of ozone and consequently stratospheric heating rates are affected. This is one of the mechanisms by which solar variability has been suspected to drive variability in the energetic budget of the Earth climate. Therefore, it is essential to know every physical and chemical processes leading to the production or to a destruction of nitric oxide.Aim:The aim of this work is to calculate the production rate of NO+and some of the NO electronic states created by electron impact on NO at night in the auroral zone using an electron transport code.Conclusion:We study this variability under different precipitation conditions and taking into account the variability of the neutral atmosphere with the geomagnetic and solar activity. We find that the energetic electron precipitation has a very small effect on the absolute value of the NO+and NO* production rates. In order to help further research to consider the effect of NO+and NO*, we provide a table of all the production rates in a medium solar and geomagnetic activity case.
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Hochet, Antoine, Thierry Huck, Olivier Arzel, Florian Sévellec et Alain Colin de Verdière. « Energy Transfers between Multidecadal and Turbulent Variability ». Journal of Climate 35, no 4 (15 février 2022) : 1157–78. http://dx.doi.org/10.1175/jcli-d-21-0136.1.
Texte intégralRésumé :
Abstract One of the proposed mechanisms to explain the multidecadal variability observed in sea surface temperature of the North Atlantic Ocean consists of a large-scale low-frequency internal mode spontaneously developing because of the large-scale baroclinic instability of the time-mean circulation. Even though this mode has been extensively studied in terms of the buoyancy variance budget, its energetic properties remain poorly known. Here we perform the full mechanical energy budget including available potential energy (APE) and kinetic energy (KE) of this internal mode and decompose the budget into three frequency bands: mean, low frequency (LF) associated with the large-scale mode, and high frequency (HF) associated with mesoscale eddy turbulence. This decomposition allows us to diagnose the energy fluxes between the different reservoirs and to understand the sources and sinks. Because of the large scale of the mode, most of its energy is contained in the APE. In our configuration, the only source of LF APE is the transfer from mean APE to LF APE that is attributed to the large-scale baroclinic instability. In return the sinks of LF APE are the parameterized diffusion, the flux toward HF APE, and, to a much lesser extent, the flux toward LF KE. The presence of an additional wind stress component weakens multidecadal oscillations and modifies the energy fluxes between the different energy reservoirs. The KE transfer appears to only have a minor influence on the multidecadal mode relative to the other energy sources involving APE, in all experiments. These results highlight the utility of the full APE–KE budget.
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Kajiura, Lovaye J., et C. David Rollo. « A mass budget for transgenic "Supermice" engineered with extra rat growth hormone genes : evidence for energetic limitation ». Canadian Journal of Zoology 72, no 6 (1 juin 1994) : 1010–17. http://dx.doi.org/10.1139/z94-137.
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Genetically engineered "Supermice" (Mus musculus, transgenic strain Tg[MT-1,rGH],Bri2) possess multiple copies of rat growth hormone genes yielding growth rates 220% that of normal mice. To discover how Supermice alter their acquisition and allocation of resources under elevated costs of growth, a resource allocation study was conducted on forty 50-day-old normal and transgenic male mice. Individual dry mass budgets were used to compare rates of growth, consumption, faecal deposition, digestive assimilation, and respiration over 11-day intervals. The mean body mass of transgenic mice was 153% that of normal animals during this period. Surprisingly, on a mass-specific basis, Supermice consumed 6% less food despite their higher investment in growth (normal: 0.50 ± 0.01 mg food/mg dry body mass per day; Supermice: 0.47 ± 0.01 mg food/mg dry body mass per day). Assimilation efficiency was also slightly lower in Supermice (64.1%) than in normal animals (66.7%). Enhanced growth was achieved entirely through improved conversion efficiencies. Gross and net production efficiencies of Supermice were 227 and 244% those of controls, respectively. Such increased efficiencies appeared to be the result of diverting resources from processes such as behaviour, longevity assurance, and other respiratory demands. Evidence for such trade-offs supports the "principle of allocation," a key assumption for theories of life-history evolution.
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RIVERO, A., P. AGNEW, S. BEDHOMME, C. SIDOBRE et Y. MICHALAKIS. « Resource depletion in Aedes aegypti mosquitoes infected by the microsporidia Vavraia culicis ». Parasitology 134, no 10 (18 juillet 2007) : 1355–62. http://dx.doi.org/10.1017/s0031182007002703.
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SUMMARYParasitic infection is often associated with changes in host life-history traits, such as host development. Many of these life-history changes are ultimately thought to be the result of a depletion or reallocation of the host's resources driven either by the host (to minimize the effects of infection) or by the parasite (to maximize its growth rate). In this paper we investigate the energetic budget of Aedes aegypti mosquito larvae infected by Vavraia culicis, a microsporidian parasite that transmits horizontally between larvae, and which has been previously shown to reduce the probability of pupation of its host. Our results show that infected larvae have significantly less lipids, sugars and glycogen than uninfected larvae. These differences in resources were not due to differences in larval energy intake (feeding rate) or expenditure (metabolic rate). We conclude that the lower energetic resources of infected mosquitoes are the result of the high metabolic demands that microsporidian parasites impose on their hosts. Given the fitness advantages for the parasite of maintaining the host in a larval stage, we discuss whether resource depletion may also be a parasite mechanism to prevent the pupation of the larvae and thus maximize its own transmission.
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Yakovenko, Sergey. « Budget of Equations for Reynolds Stresses in a Turbulent Patch Arising from Internal Wave Breaking ». Siberian Journal of Physics 7, no 4 (1 décembre 2012) : 87–95. http://dx.doi.org/10.54362/1818-7919-2012-7-4-87-95.
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Results of the direct numerical simulations are used to obtain statistical moments in a quasi-steady turbulent patch arising in a stably stratified flow above an obstacle after internal wave breaking. Temporal evolution and spatial behavior of the Reynolds-stress tensor components and budgets of the Reynolds-stress transport equations have been studied. Such an analysis is helpful to explore the turbulent patch and its energetic characteristics by means of statistical moments, to examine closure hypotheses in turbulence models, and to evaluate geophysically important quantites. In particular, the calculated global value of the mixing efficiency is about 0.2 as in oceanic applications. Moreover, simple algebraic relations are proposed between the turbulent kinetic energy and its dissipation rate. In the Reynolds stress tensor equation, the pressure-strain correlation term provides the redistribution of the normal stress components according to the linear returnto-isotropy approximation, whereas the dissipation tensor roughly follows the local-isotropy assumption
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Keogh, Stephanie, Gerald Mills et Rowan Fealy. « The energy budget of the urban surface : two locations in Dublin ». Irish Geography 45, no 1 (11 avril 2014) : 1–23. http://dx.doi.org/10.55650/igj.2012.6.
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Urban areas generate distinctive climates that are revealed in the statistics of wind, temperature, humidity and so on. These properties are the result of energy exchanges between the atmosphere and underlying urban surface, which is the focus of physical climatology studies. These exchanges form an energy budget (EB), which includes radiation exchanges (both solar and terrestrial), the turbulent fluxes of sensible and latent heat and the energy transferred to the substrate by conduction. An evaluation of these exchanges and their spatial variation is essential to explaining the effect that cities have on climate at all scales. However, observing these exchanges is difficult and requires both sensitive equipment and careful placement to ensure representative readings. This paper presents some initial results on the EB over two urban surfaces in Dublin, one a densely built urban site near the city centre and the other a mature, well vegetated, suburban site. The results demonstrate the effects of different urban surface features on surface-air exchanges. The objective hysteresis model is also employed to evaluate the energy balance residual. Results show good agreement between modelled and residual values. Although there have been studies on Dublin’s urban climate, most notably its urban heat island (UHI), there has been no prior study of the energetic processes responsible for this local climate change. This research programme, for which initial results are presented in this paper, is one of the few studies globally that will maintain long-term measurements (five years) of urban EBs.
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Kotrschal, Alexander, Alberto Corral-Lopez et Niclas Kolm. « Large brains, short life : selection on brain size impacts intrinsic lifespan ». Biology Letters 15, no 5 (15 mai 2019) : 20190137. http://dx.doi.org/10.1098/rsbl.2019.0137.
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The relationship between brain size and ageing is a paradox. The cognitive benefits of large brains should protect from extrinsic mortality and thus indirectly select for slower ageing. However, the substantial energetic cost of neural tissue may also impact the energetic budget of large-brained organisms, causing less investment in somatic maintenance and thereby faster ageing. While the positive association between brain size and survival in the wild is well established, no studies exist on the direct effects of brain size on ageing. Here we test how brain size influences intrinsic ageing in guppy ( Poecilia reticulata ) brain size selection lines with 12% difference in relative brain size. Measuring survival under benign conditions, we find that large-brained animals live 22% shorter than small-brained animals and the effect is similar in both males and females. Our results suggest a trade-off between investment into brain size and somatic maintenance. This implies that the link between brain size and ageing is contingent on the mechanism of mortality, and selection for positive correlations between brain size and ageing should occur mainly under cognition-driven survival benefits from increased brain size. We show that accelerated ageing can be a cost of evolving a larger brain.
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Oleinik, Phelype, Eduardo de Paula Kirinus, Cristiano Fragassa, Wiliam Marques et Juliana Costi. « Energetic Potential Assessment of Wind-Driven Waves on the South-Southeastern Brazilian Shelf ». Journal of Marine Science and Engineering 7, no 2 (23 janvier 2019) : 25. http://dx.doi.org/10.3390/jmse7020025.
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Global electric energy demand is constantly growing, consequently leading towards the usage of renewable energy sources reducing pollution and increasing sustainability. The ocean is a poorly explored renewable energy source; thus, to evaluate the Brazilian wave energy budget, this study investigated the mean behaviour of the wave power rate on the south-southeastern Brazilian Shelf as well as analysed the temporal variability of the wave power rate at the most energetic locations near the coast. Three locations were examined, namely Laguna, Ilhabela and Farol Island, based on the criteria of high means and small standard deviations. The mean wave power rate was approximately 9 . 08 k W / m on Laguna, 10 . 01 k W / m on Ilhabela and 15 . 93 k W / m on Farol Island. The standard deviation identified in the three locations reached values of 6 . 47 k W / m on Laguna, 7 . 59 k W / m on Ilhabela and 13 . 51 k W / m on Farol Island. Temporal variability analysis was conducted through wavelet analysis. The results show a dominant yearly cycle with a background presence of synoptic cycles, with little deviation between the locations. The El Niño southern oscillation plays a minor role on the energy spectrum of Laguna and does not have a significant influence on Ilhabela and Farol Island.
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HILLSTRÖM, Lars, et Juan Moreno. « Variation in Time and Energy Budgets of Breeding Wheatears ». Behaviour 120, no 1-2 (1992) : 11–39. http://dx.doi.org/10.1163/156853992x00183.
Texte intégralRésumé :
AbstractWe examined the sources of variation in time allocation of males and females of the wheatear (Oenanthe oenanthe) on the island of Öland, South Sweden, throughout the breeding season. We quantified rates of prey capture attempts and specified foraging methods used. From respirometric measurements of basal metabolic rate and temperature-dependent metabolism on captive wheatears, and after having made certain assumptions abour the costs of different activities, we estimated the energy budgets of both sexes during the different reproductive phases. Males and females differed in their time allocation and foraging rates during prelaying, laying, and incubation, but not while feeding grown nestlings. During prelaying and laying, females foraged at higher rates than males; they also perched less often, gleaned more on the ground, and flew less. Although incubation was the least costly phase for females because of their low activity, high foraging rates yet indicated that this phase may represent an energetic bottleneck as a result of restrictions on foraging time. After incubation, females switched from foraging mostly on the ground during early breeding phases to hunting from elevated perches during later breeding phases. The shift in foraging behavior corresponds to the drastic changes in time allocation. Relatively high daily energy expenditures (DEE) by brooding females coupled with low foraging rates may explain the observed posthatching body mass losses. In both sexes, high required energy acquisition rates when feeding large nestlings indicate that parent wheatears then may encounter another energetic bottleneck. Postfledging was the least costly phase because, compared with the period of feeding nestlings, there were reduced thermostatic costs and a marked drop in flight time. Males and females had similar DEEs during prelaying, laying and nestling feeding, but females had lower needs during incubation. The elective components of energy budgets during nestling feeding, as well as the estimated sum of the elective components throughout the season, were 12% higher for males than for females. The elective components of the energy budgets varied more than the obligatory components (basal + thermoregulation), especially in females, and were more important in determining the variation of DEE throughout the breeding season. A validation study with doubly labeled water indicated that the energy budget model used was accurate enough for comparisons between sexes or breeding phases, but not for measuring individual variation.
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Nascimento, Janaina F., Rodolpho O. O. Souza, Mayke B. Alencar, Sabrina Marsiccobetre, Ana M. Murillo, Flávia S. Damasceno, Richard B. M. M. Girard et al. « How much (ATP) does it cost to build a trypanosome ? A theoretical study on the quantity of ATP needed to maintain and duplicate a bloodstream-form Trypanosoma brucei cell ». PLOS Pathogens 19, no 7 (27 juillet 2023) : e1011522. http://dx.doi.org/10.1371/journal.ppat.1011522.
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ATP hydrolysis is required for the synthesis, transport and polymerization of monomers for macromolecules as well as for the assembly of the latter into cellular structures. Other cellular processes not directly related to synthesis of biomass, such as maintenance of membrane potential and cellular shape, also require ATP. The unicellular flagellated parasite Trypanosoma brucei has a complex digenetic life cycle. The primary energy source for this parasite in its bloodstream form (BSF) is glucose, which is abundant in the host’s bloodstream. Here, we made a detailed estimation of the energy budget during the BSF cell cycle. As glycolysis is the source of most produced ATP, we calculated that a single parasite produces 6.0 x 1011 molecules of ATP/cell cycle. Total biomass production (which involves biomass maintenance and duplication) accounts for ~63% of the total energy budget, while the total biomass duplication accounts for the remaining ~37% of the ATP consumption, with in both cases translation being the most expensive process. These values allowed us to estimate a theoretical YATP of 10.1 (g biomass)/mole ATP and a theoretical YATPmax of 28.6 (g biomass)/mole ATP. Flagellar motility, variant surface glycoprotein recycling, transport and maintenance of transmembrane potential account for less than 30% of the consumed ATP. Finally, there is still ~5.5% available in the budget that is being used for other cellular processes of as yet unknown cost. These data put a new perspective on the assumptions about the relative energetic weight of the processes a BSF trypanosome undergoes during its cell cycle.
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Cressler, Clayton E., William A. Nelson, Troy Day et Edward McCauley. « Starvation reveals the cause of infection-induced castration and gigantism ». Proceedings of the Royal Society B : Biological Sciences 281, no 1792 (7 octobre 2014) : 20141087. http://dx.doi.org/10.1098/rspb.2014.1087.
Texte intégralRésumé :
Parasites often induce life-history changes in their hosts. In many cases, these infection-induced life-history changes are driven by changes in the pattern of energy allocation and utilization within the host. Because these processes will affect both host and parasite fitness, it can be challenging to determine who benefits from them. Determining the causes and consequences of infection-induced life-history changes requires the ability to experimentally manipulate life history and a framework for connecting life history to host and parasite fitness. Here, we combine a novel starvation manipulation with energy budget models to provide new insights into castration and gigantism in the Daphnia magna – Pasteuria ramosa host–parasite system. Our results show that starvation primarily affects investment in reproduction, and increasing starvation stress reduces gigantism and parasite fitness without affecting castration. These results are consistent with an energetic structure where the parasite uses growth energy as a resource. This finding gives us new understanding of the role of castration and gigantism in this system, and how life-history variation will affect infection outcome and epidemiological dynamics. The approach of combining targeted life-history manipulations with energy budget models can be adapted to understand life-history changes in other disease systems.
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Cabrera-Martínez, Lucia V., L. Gerardo Herrera M. et Ariovaldo P. Cruz-Neto. « The energetic cost of mounting an immune response for Pallas’s long-tongued bat (Glossophaga soricina) ». PeerJ 6 (5 juin 2018) : e4627. http://dx.doi.org/10.7717/peerj.4627.
Texte intégralRésumé :
The acute phase response (APR) is the first line of defense of the vertebrate immune system against pathogens. Mounting an immune response is believed to be energetically costly but direct measures of metabolic rate during immune challenges contradict this assumption. The energetic cost of APR for birds is higher than for rodents, suggesting that this response is less expensive for mammals. However, the particularly large increase in metabolic rate after APR activation for a piscivorous bat (Myotis vivesi) suggests that immune response might be unusually costly for bats. Here we quantified the energetic cost and body mass change associated with APR for the nectarivorous Pallas’s long-tongued bat (Glossophaga soricina). Activation of the APR resulted in a short-term decrease in body mass and an increase in resting metabolic rate (RMR) with a total energy cost of only 2% of the total energy expenditure estimated for G. soricina. This increase in RMR was far from the large increase measured for piscivorous bats; rather, it was similar to the highest values reported for birds. Overall, our results suggest that the costs of APR for bats may vary interspecifically. Measurement of the energy cost of vertebrate immune response is limited to a few species and further work is warranted to evaluate its significance for an animal’s energy budget.