891 resultados para prey capture
Resumo:
Ocean acidification is the suite of chemical changes to the carbonate system of seawater as a consequence of anthropogenic carbon dioxide (CO2) emissions. Despite a growing body of evidences demonstrating the negative effects of ocean acidification on marine species, the consequences at the ecosystem level are still unclear. One factor limiting our ability to upscale from species to ecosystem is the poor mechanistic understanding of the functional consequences of the observed effects on organisms. This is particularly true in the context of species interactions. The aim of this work was to investigate the functional consequence of the exposure of a prey (the mussel Brachidontes pharaonis) to ocean acidification for both the prey and its predator (the crab Eriphia verrucosa). Mussels exposed to pH 7.5 for >4 weeks showed significant decreases in condition index and in mechanical properties (65% decrease in maximum breaking load) as compared with mussels acclimated to pH 8.0. This translated into negative consequences for the mussel in presence of the predator crab. The crab feeding efficiency increased through a significant 27% decrease in prey handling time when offered mussels acclimated to the lowest pH. The predator was also negatively impacted by the acclimation of the prey, probably as a consequence of a decreased food quality. When fed with prey acclimated under decreased pH for 3 months, crab assimilation efficiency significantly decreased by 30% and its growth rate was 5 times slower as compared with crab fed with mussels acclimated under high pH. Our results highlight the important to consider physiological endpoints in the context of species interactions.
Resumo:
Microzooplankton (the 20 to 200 µm size class of zooplankton) is recognised as an important part of marine pelagic ecosystems. In terms of biomass and abundance pelagic ciliates are one of the important groups of organism in microzooplankton. However, their rates - grazing and growth - , feeding behaviour and prey preferences are poorly known and understood. A set of data was assembled in order to derive a better understanding of pelagic ciliates rates, in response to parameters such as prey concentration, prey type (size and species), temperature and their own size. With these objectives, literature was searched for laboratory experiments with information on one or more of these parameters effect studied. The criteria for selection and inclusion in the database included: (i) controlled laboratory experiment with a known ciliates feeding on a known prey; (ii) presence of ancillary information about experimental conditions, used organisms - cell volume, cell dimensions, and carbon content. Rates and ancillary information were measured in units that meet the experimenter need, creating a need to harmonize the data units after collection. In addition different units can link to different mechanisms (carbon to nutritive quality of the prey, volume to size limits). As a result, grazing rates are thus available as pg C/(ciliate*h), µm**3/(ciliate*h) and prey cell/(ciliate*h); clearance rate was calculated if not given and growth rate is expressed as the growth rate per day.
Resumo:
The neutron capture (n,gamma) cross-section for 27-Co-58 theoretically presents a single resonance for 9 eV. However, after plotting the processed library, a discontinuity is made clear as the cross section plummets down to cero in a small range of energy where the peak of the resonance would be expected.
Resumo:
Coal is the most plentiful and evenly distributed fossil fuel worldwide. Based on current production, it is estimated that the reserves will last approximately 130 years. Its use worldwide has been increasing, mainly due to consumption by emerging countries. CO2 emissions generated by combustion and the repercussions of such on climate change support the view that it could no longer be used. CO2 capture may be the solution to continue using it, which would cater for the growing energy demand worldwide. The aim of this study is to compare different processes concerning CO2 capture that may be economically viable, ultimately showing that coal, a fossil energy source widely distributed around the world, can, as a result of using different CO2 capture processes, be used as a clean source of electricity. Hence, in places where geological hurdles may render the costs of CO2 storage considerably higher, since it might have to travel far, coal may be used for other purposes, thus valorising CO2 within the industrial sector. This research is focused on the technical and economic comparison of the most relevant CO2 capture projects designed in Spain using different existing technologies. The oxyfuel project in Ciuden (Leon, Spain), the IGCC Elcogas, precombustion CO2-capture project (Puertollano, Spain) and the postcombustion project in Carboneras (Almeria, Spain) will be analyzed in order to assess the options available to valorise captured CO2. Valorising captured CO2 may be an adequate solution in areas where, although CO2 capture is still possible, storage is not equally so, thus generating a further benefit. The possible uses of CO2 will be assessed in vegetable growing greenhouses, harnessing CO2 in vegetable life cycles. This will also be used in growing algae for subsequent biodiesel production. Both CO2 capture and valorising will eventually lead to the clean use of coal, which will thus enhance the level of self-supply, aiding the development of electric vehicles, which require large amounts of electricity, as well as improve the level of energy autonomy in countries around the world. Another type of fuel, biodiesel, will also be obtained, without this affecting international food prices.
Resumo:
Climate change conference was hold in Copenhagen in 2009, global warming became the worldwide focus once again. China as a developing country has paid more attention for this environmental problem. In China, a large part of carbon dioxide is emitted to the atmosphere from combustion of fossil fuels in power plants. How to control emission of the greenhouse gas into atmosphere is becoming an urgent concern. Among numerous methods, CO2 capture is the hope to limit the amount of CO2 emitted into the air. The well-established method for CO2 capture is to remove CO2 by absorption into solutions in conventional equipment. Absorbents used for CO2 and H2S capture are important choice for CO2 capture technology. It is related to the cost and efficiency of plant directly and is essential to investigate the proposed CO2 and H2S absorbents.
Resumo:
onceptual design phase is partially supported by product lifecycle management/computer-aided design (PLM/CAD) systems causing discontinuity of the design information flow: customer needs — functional requirements — key characteristics — design parameters (DPs) — geometric DPs. Aiming to address this issue, it is proposed a knowledge-based approach is proposed to integrate quality function deployment, failure mode and effects analysis, and axiomatic design into a commercial PLM/CAD system. A case study, main subject of this article, was carried out to validate the proposed process, to evaluate, by a pilot development, how the commercial PLM/CAD modules and application programming interface could support the information flow, and based on the pilot scheme results to propose a full development framework.
Resumo:
Tethered spacecraft missions to the Jovian system suit the use of electrodynamic tethers because: 1) magnetic stresses are 100 times greater than at the Earth; 2) the stationary orbit is one-third the relative distance for Earth; and 3) moon Io is a nearby giant plasma source. The (bare) tether is a reinforced aluminum foil with tens of kilometer length L and a fraction of millimeter thickness h, which collects electrons as an efficient Langmuir probe and can tap Jupiter’s rotational energy for both propulsion and power. In this paper, the critical capture operation is explicitly formulated in terms of orbit geometry and established magnetic and thermal plasma models. The design parameters L and h and capture perijove radius rp face opposite criteria independent of tape width. Efficient capture requires a low rp and a high L 3/2/h ratio. However, combined bounds on tether bowing and tether tensile stress, arising from a spin made necessary by the low Jovian gravity gradient, require a high rp and a low L 5/2/h ratio. Bounds on tether temperature again require a high rp and a low L 3/8/(tether emissivity)1/4 ratio. Optimal design values are discussed.
Resumo:
An electrodynamic bare-tether mission to Jupiter,following the capture of a spacecraft (SC) into an equatorial highly elliptical orbit with perijove at about 1.3 times the Jovian radius, is discussed. Repeated applications of the propellantless Lorentz drag on a spinning tether, at the perijove vicinity, can progressively lower the apojove at constant perijove, for a tour of Galilean moons. Electrical energy is generated and stored as the SC moves from an orbit at 1 : 1 resonance with a moon, down to resonance with the next moon; switching tether current off, stored power is then used as the SC makes a number of flybys of each moon. Radiation dose is calculated throughout the mission,during capture, flybys and moves between moons. The tour mission is limited by both power needs and accumulated dose. The three-stage apojove lowering down to Ganymede, Io, and Europa resonances would total less than 14 weeks, while 4 Ganymede, 20 Europa, and 16 Io flybys would add up to 18 weeks, with the entire mission taking just over seven months and the accumulated radiation dose keeping under 3 Mrad (Si) at 10-mm Al shield thickness.
Resumo:
In the C02 capture from power generation, the energy penalties for the capture are one of the main challenges. Nowadays, the post-combustion methods have energy penalties 10wer than the oxy combustion and pre-combustion technologies. One of the main disadvantages of the post combustion method is the fact that the capture ofC02at atmospheric pressure requires quite big equipment for the high flow rates of flue gas, and the 10w partial pressure of the CO2generates an important 10ss of energy. The A1lam cyc1e presented for NETPOWER gives high efficiencies in the power production and 10w energy penalties. A simulation of this cyc1e is made together with a simulation of power plants with pre-combustion and post-combustion capture and without capture for natural gas and forcoa1. The simulations give 10wer efficiencies than the proposed for NETPOWER For natural gas the efficiency is 52% instead of the 59% presented, and 33% instead of51% in the case of using coal as fuel. Are brought to light problems in the CO2compressor due the high flow ofC02that is compressed unti1300 bar to be recyc1ed into the combustor.
Resumo:
Three separate scenarios of an electrodynamic tether mission at Jupiter following capture of a spacecraft (SC) into an equatorial, highly elliptical orbit around the planet, with perijove at about 1.5 times the Jovian radius, are discussed. Repeated application of Lorentz drag on the spinning tether, at the perijove vicinity, can progressively lower the apojove. One mission involves the tethered-SC rapidly and frequently visiting Galilean moons; elliptical orbits with apojove down at the Ganymede, Europa, and Io orbits are in 2:5, 4:9, and 1:2 resonances with the respective moons. About 20 slow flybys of Io would take place before the accumulated radiation dose exceeds 3 Mrad (Si) at 10 mm Al shield thickness, with a total duration of 5 months after capture (4 months for lowering the apojove to Io and one month for the flybys). The respective number of flybys for Ganymede would be 10 with a total duration of about 9 months. An alternative mission would have the SC acquire a low circular orbit around Jupiter, below the radiation belts, and manoeuvre to get an optimal altitude, with no major radiation effects, in less than 5 months after capture. In a third mission, repeated thrusting at the apojove vicinity, once down at the Io torus, would raise the perijove itself to the torus to acquire a low circular orbit around Io in about 4 months, for a total of 8 months after capture; this corresponds, however, to over 100 apojove passes with an accumulated dose, of about 8.5 Mrad (Si), that poses a critical issue.
Resumo:
Versatile and accurate motion capture systems, with the required properties to be integrated within both clinical and domiciliary environments, would represent a significant advance in following the progress of the patients as well as in allowing the incorporation of new data exploitation and analysis methods to enhance the functional neurorehabilitation therapeutic processes. Besides, these systems would permit the later development of new applications focused on the automatization of the therapeutic tasks in order to increase the therapist/patient ratio, thus decreasing the costs [1]. However, current motion capture systems are not still ready to work within uncontrolled environments.
Resumo:
The aim of this research is to obtain the absorption rate of CO2 into aqueous solution of N,N- di methyl ethanolamine and into aqueous solution of Triethylene diamine and to demonstrate the importance of absorption of CO2 in nowadays by discussing global warming and greenhouse effect. It is also discussed the current situation of China focusing in the latest steps this country has recently made. In the experimental part of this work, the two tertiary amine solutions will absorb CO2 in a Lewis type cell, measuring the pressure change during the reactions take place. The temperature will be between 35 degree and 70 degree Celsius. The results of both solutions, concentrations of 0.5 and 1.0 mol per liter, are discussed and a single value of the rate constant is given for the first time along with some others parameters.