Showing papers by "Instituto Superior Técnico published in 2003"
Vanderbilt University1, Association of Universities for Research in Astronomy2, Lawrence Berkeley National Laboratory3, Stockholm University4, Pierre-and-Marie-Curie University5, Colorado College6, University of California, Berkeley7, American Astronomical Society8, University of Tokyo9, California Institute of Technology10, Instituto Superior Técnico11, Space Telescope Science Institute12, University of Oxford13, European Southern Observatory14, University of Barcelona15, École Polytechnique16, University of Texas at Austin17, Durham University18, University of Cambridge19
TL;DR: In this paper, a set of high-redshift supernovae were used to confirm previous supernova evidence for an accelerating universe, and the supernova results were combined with independent flat-universe measurements of the mass density from CMB and galaxy redshift distortion data, they provided a measurement of $w=-1.05^{+0.15}-0.09$ if w is assumed to be constant in time.
Abstract: We report measurements of $\Omega_M$, $\Omega_\Lambda$, and w from eleven supernovae at z=0.36-0.86 with high-quality lightcurves measured using WFPC-2 on the HST. This is an independent set of high-redshift supernovae that confirms previous supernova evidence for an accelerating Universe. Combined with earlier Supernova Cosmology Project data, the new supernovae yield a flat-universe measurement of the mass density $\Omega_M=0.25^{+0.07}_{-0.06}$ (statistical) $\pm0.04$ (identified systematics), or equivalently, a cosmological constant of $\Omega_\Lambda=0.75^{+0.06}_{-0.07}$ (statistical) $\pm0.04$ (identified systematics). When the supernova results are combined with independent flat-universe measurements of $\Omega_M$ from CMB and galaxy redshift distortion data, they provide a measurement of $w=-1.05^{+0.15}_{-0.20}$ (statistical) $\pm0.09$ (identified systematic), if w is assumed to be constant in time. The new data offer greatly improved color measurements of the high-redshift supernovae, and hence improved host-galaxy extinction estimates. These extinction measurements show no anomalous negative E(B-V) at high redshift. The precision of the measurements is such that it is possible to perform a host-galaxy extinction correction directly for individual supernovae without any assumptions or priors on the parent E(B-V) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with $P(\Omega_\Lambda>0)>0.99$, a result consistent with previous and current supernova analyses which rely upon the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution.
1,687 citations
TL;DR: In this paper, it was shown that there exist composite media that exhibit strong spatial dispersion even in the very large wavelength limit, where the description of this medium by means of a local dispersive uniaxial dielectric tensor is not complete.
Abstract: It is found that there exist composite media that exhibit strong spatial dispersion even in the very large wavelength limit. This follows from the study of lattices of ideally conducting parallel thin wires (wire media). In fact, our analysis reveals that the description of this medium by means of a local dispersive uniaxial dielectric tensor is not complete, leading to unphysical results for the propagation of electromagnetic waves at any frequencies. Since nonlocal constitutive relations have been usually considered in the past as a second-order approximation, meaningful in the short-wavelength limit, the aforementioned result presents a relevant theoretical interest. In addition, since such wire media have been recently used as a constituent of some discrete artificial media (or metamaterials), the reported results open the question of the relevance of the spatial dispersion in the characterization of these artificial media.
583 citations
TL;DR: An overview of recent developments on the use of microorganisms for steroid production is presented in order to increase the efficiency of the existing processes as well as to identify new potentially useful bioconversions.
500 citations
TL;DR: In this paper, the integrability problem of Lie algebroids is solved by two computable obstructions, i.e., local Lie groupoids and the smoothness of the Poisson sigma model.
Abstract: In this paper we present the solution to a longstanding problem of differential geometry: Lie’s third theorem for Lie algebroids. We show that the integrability problem is controlled by two computable obstructions. As applications we derive, explain and improve the known integrability results, we establish integrability by local Lie groupoids, we clarify the smoothness of the Poisson sigma-model for Poisson manifolds, and we describe other geometrical applications.
491 citations
TL;DR: In this article, the authors present an overview on the state-of-the-art of the most important aspects of the corrosion process initiated by chlorides, its development and monitoring techniques.
Abstract: One of the most important causes for reinforcing steel corrosion is the presence of chloride ions. They cause localised breakdown of the passive film that initially forms on steel as a result of the alkaline nature of the pore solution in concrete. The harmful chloride ions can be originated from the use of contaminated mix constituents or from the surrounding environment. The determination of a critical level, above which serious problems can occur, has been one of the main goals of investigation. Unfortunately, it is difficult to establish such a value since the chloride level is influenced by several factors. Thus, after concrete contamination, it is of fundamental importance to follow the activity of chlorides and the state of the reinforcing rebars. In this respect, the use of electrochemical techniques such as polarisation resistance, electrochemical impedance, galvanostatic pulse and potential measurements have shown to be powerful tools. Nevertheless, the interpretation of the results becomes sometimes a difficult task. A large number of authors have dedicated several studies to the interpretation of such measurements and a highly dispersed number of interpretations can be found in literature. The aim of this paper is to present an overview on the state-of-the-art of the most important aspects of the corrosion process initiated by chlorides, its development and monitoring techniques.
429 citations
TL;DR: In this paper, four microalgae (Botryococcus braunii, Chlorella vulgaris, Dunaliella salina, Arthrospira maxima) were subject to supercritical CO 2 extraction in a flow apparatus at temperatures between 313.1 and 333.1 K and pressures up to 35.0 MPa.
425 citations
TL;DR: In this paper, the authors presented the first 3D fully kinetic electromagnetic relativistic particle-in-cell simulations of the collision of two interpenetrating plasma shells. But the simulation was performed using the OSIRIS parallel code.
Abstract: We present the first three-dimensional fully kinetic electromagnetic relativistic particle-in-cell simulations of the collision of two interpenetrating plasma shells The highly accurate plasma-kinetic particle-in-cell (with the total of 108 particles) parallel code OSIRIS has been used Our simulations show (1) the generation of long-lived near-equipartition (electro)magnetic fields, (2) nonthermal particle acceleration, and (3) short-scale to long-scale magnetic field evolution, in the collision region Our results provide new insights into the magnetic field generation and particle acceleration in relativistic and subrelativistic colliding streams of particles, which are present in gamma-ray bursters, supernova remnants, relativistic jets, pulsar winds, etc
402 citations
TL;DR: In this article, the authors analyzed spherically symmetric and static traversable Morris-Thorne wormholes in the presence of a generic cosmological constant (ensuremath{Lambda}$).
Abstract: First, the ideas introduced in the wormhole research field since the work of Morris and Thorne are reviewed, namely, the issues of energy conditions, wormhole construction, stability, time machines and astrophysical signatures. Then, spherically symmetric and static traversable Morris-Thorne wormholes in the presence of a generic cosmological constant $\ensuremath{\Lambda}$ are analyzed. A matching of an interior solution to the unique exterior vacuum solution is done using directly the Einstein equations. The structure as well as several physical properties and characteristics of traversable wormholes due to the effects of the cosmological term are studied. Interesting equations appear in the process of matching. For instance, one finds that for asymptotically flat and anti\char21{}de Sitter spacetimes the surface tangential pressure $\mathcal{P}$ of the thin shell, at the boundary of the interior and exterior solutions, is always strictly positive, whereas for de Sitter spacetime it can take either sign as one would expect, being negative (tension) for relatively high $\ensuremath{\Lambda}$ and high wormhole radius, positive for relatively high mass and small wormhole radius, and zero in between. Finally, some specific solutions with $\ensuremath{\Lambda},$ based on the Morris-Thorne solutions, are provided.
283 citations
01 Jan 2003
TL;DR: This review addresses the applications of peroxidases, especially HRP, in the environmental and health care sectors, and in the pharmaceutical, chemical and biotechnological industries.
Abstract: Peroxidases have conquered a prominent position in biotechnology and associated research areas (enzymology, biochemistry, medicine, genetics, physiology, histo- and cytochem- istry). They are one of the most extensively studied groups of enzymes and the literature is rich in research papers dating back from the 19th century. Nevertheless, peroxidases continue to be widely studied, with more than 2000 articles already published in 2002 (according to the Institute for Scientific Information). The importance of peroxidases is emphasised by their wide distribution among living organisms and by their multiple physiological roles. They have been divided into three superfamilies according to their source and mode of action: plant peroxidases, animal peroxidases and catalases. Among all peroxidases, horseradish peroxidase (HRP) has received a special attention and will be the focus of this review. A brief description of the three super-families is included in the first section of this review. In the second section, a comprehensive description of the present state of knowledge of the structure and catalytic action of HRP is presented. The physiological role of peroxidases in higher plants is described in the third section. And finally, the fourth section addresses the applications of peroxidases, especially HRP, in the environmental and health care sectors, and in the pharmaceutical, chemical and biotechnological industries.
279 citations
TL;DR: In this paper, a series of numerical simulations on a simple beam are made in order to compare various damage detection methods based on mode shape changes and a generalisation of these methods to the whole frequency ranges of measurement is proposed.
275 citations
TL;DR: The proposed algorithm is compatible with the link adaptation mechanisms implemented in commercial WLANs, as it limits the amount of time during which the stations control the wireless medium and follows a delay-earliest-due-date algorithm.
Abstract: This article presents a scheduling algorithm for the IEEE 802.11e hybrid coordination function under definition by the IEEE 802.11e task group. HCF can be used to provide IP quality of service guarantees in IEEE802.11e infrastructure WLANs. The enhanced distributed coordination function is mainly used for data transmission without QoS guarantees, but can also be used to decrease the transmission delay of QoS-sensitive traffic. Scheduling of queued packets follows a delay-earliest-due-date algorithm. The proposed algorithm is compatible with the link adaptation mechanisms implemented in commercial WLANs, as it limits the amount of time during which the stations control the wireless medium. The performance of the algorithm is evaluated through computer simulation and compared with the reference scheduler presented by the IEEE 802.11e task group.
09 Dec 2003
TL;DR: In this paper, a nonlinear adaptive control law is proposed to steer a wheeled robot of unicycle type along a desired spatial path by controlling explicitly the rate of progression of a "virtual target" to be tracked along the path.
Abstract: This paper derives a new type of control law to steer the dynamic model of a wheeled robot of unicycle type along a desired spatial path. The methodology adopted for path following control deals explicitly with vehicle dynamics and plant parameter uncertainty. Furthermore, it overcomes stringent initial condition constraints that are present in a number of path following control strategies described in the literature. This is done by controlling explicitly the rate of progression of a "virtual target" to be tracked along the path, thus bypassing the problems that arise when the position of the virtual target is simply defined by the projection of the actual vehicle on that path. The nonlinear adaptive control law proposed yields convergence of the (closed loop system) path following error trajectories to zero. Controller design relies on Lyapunov theory and backstepping techniques. Simulation results illustrate the performance of the control system proposed.
TL;DR: In this paper, the dependence of the location of the cosmic microwave background radiation peaks on the parameters of the generalized Chaplygin gas model was studied, and it was shown that observational data arising from Archeops, BOOMERANG, supernova and high-redshift observations allow constraining significantly the parameter space of the model.
Abstract: We study the dependence of the location of the cosmic microwave background radiation peaks on the parameters of the generalized Chaplygin gas model, whose equation of state is given by $p=\ensuremath{-}A/{\ensuremath{\rho}}^{\ensuremath{\alpha}},$ where A is a positive constant and $0l\ensuremath{\alpha}l~1.$ We find, in particular, that observational data arising from Archeops, BOOMERANG, supernova and high-redshift observations allow constraining significantly the parameter space of the model. Our analysis indicates that the emerging model is clearly distinguishable from the $\ensuremath{\alpha}=1$ Chaplygin case and the $\ensuremath{\Lambda}\mathrm{CDM}$ model.
TL;DR: The generalized Chaplygin gas (GCG) model as mentioned in this paper explains the recent accelerated expansion of the Universe via an exotic background fluid whose equation of state is given by p =− A / ρ α, where A is a positive constant and 0 α ⩽1.
TL;DR: AFM is progressively becoming a usual benchtop technique and overcomes materials science applications, showing that 17 years after its invention, AFM has completely crossed the limits of its traditional areas of application.
TL;DR: The very recently observed D(*)(sJ)(2317)(+) meson is described as a quasibound scalar csmacr; state in a unitarized meson model, owing its existence to the strong 3P0 Okubo-Zweig-Iizuka-allowed coupling to the nearby S-wave DK threshold.
Abstract: The very recently observed ${D}_{sJ}^{*}(2317{)}^{+}$ meson is described as a quasibound scalar $c\overline{s}$ state in a unitarized meson model, owing its existence to the strong $^{3}P_{0}$ Okubo-Zweig-Iizuka\char21{}allowed coupling to the nearby $S$-wave $DK$ threshold. By the same mechanism, a scalar ${D}_{0}^{*}(2100\char21{}2300)$ resonance is predicted above the $D\ensuremath{\pi}$ threshold. These scalars are the charmed cousins of the light scalar nonet ${f}_{0}(600)$, ${f}_{0}(980)$, ${K}_{0}^{*}(800)$, and ${a}_{0}(980)$, reproduced by the same model. The standard $c\overline{n}$ and $c\overline{s}$ charmed scalars ${D}_{0}$ and ${D}_{s0}$, cousins of the scalar nonet ${f}_{0}(1370)$, ${f}_{0}(1500)$, ${K}_{0}^{*}(1430)$, and ${a}_{0}(1450)$, are predicted to lie at about 2.64 and 2.79 GeV, respectively, both with a width of some 200 MeV.
TL;DR: In this paper, the effect of electric charge in compact stars was studied and the authors concluded that the electric fields have to be huge to have any appreciable effect on the phenomenology of the compact stars, which implies that the total charge is Coulomb.
Abstract: We study the effect of electric charge in compact stars assuming that the charge distribution is proportional to the mass density. The pressure and the density of the matter inside the stars are large, and the gravitational field is intense. This indicates that electric charge and a strong electric field can also be present. The relativistic hydrostatic equilibrium equation, i.e., the Tolman-Oppenheimer-Volkoff equation, is modified in order to include electric charge. We perform a detailed numerical study of the effect of electric charge using a polytropic equation of state. We conclude that in order to see any appreciable effect on the phenomenology of the compact stars, the electric fields have to be huge $(\ensuremath{\sim}{10}^{21}$ V/m), which implies that the total charge is $Q\ensuremath{\sim}{10}^{20}$ Coulomb. From the local effect of the forces experienced on a single charged particle, it is expected that each individual charged particle is quickly ejected from the star. This in turn produces a huge force imbalance, and the gravitational force overwhelms the repulsive Coulomb and fluid pressure forces. The star can then collapse to form a charged black hole before all the charge leaves the system.
TL;DR: In this paper, the authors present a thorough analysis of the quasinormal behavior associated with the decay of scalar, electromagnetic, and gravitational perturbations of Schwarzschild black holes in anti-de Sitter (AdS) spacetimes.
Abstract: We present a thorough analysis of the quasinormal (QN) behavior associated with the decay of scalar, electromagnetic, and gravitational perturbations of Schwarzschild black holes in anti--de Sitter (AdS) spacetimes. As is known, the AdS QN spectrum crucially depends on the relative size of the black hole to the AdS radius. There are three different types of behavior depending on whether the black hole is large, intermediate, or small. The results of previous works, concerning lower overtones for large black holes, are completed here by obtaining higher overtones for all three black hole regimes. There are two major conclusions that one can draw from this work: First, asymptotically for high overtones, all the modes are evenly spaced, and this holds for all three types of regime, large, intermediate, and small black holes, independently of l, where l is the quantum number characterizing the angular distribution; second, the spacing between modes is apparently universal in that it does not depend on the field; i.e., scalar, electromagnetic, and gravitational QN modes all have the same spacing for high overtones. We are also able to prove why scalar and gravitational perturbations are isospectral, asymptotically for high overtones, by introducing appropriate superpartner potentials.
TL;DR: In this paper, the performance improvement of conventional electrical discharge machining with a powder-mixed dielectric was evaluated through quality surface indicators and process time measurements, over a set of different processing areas.
Abstract: Electrical discharge machining (EDM) is a technological process with a large industrial implementation. Its use is particularly intense when very complex shapes on hard materials with a high geometrical and dimensional accuracy are required. However, the technological capability of the process has limited its application when the specification of the part surface quality imposes polished and mirror-like characteristics. The addition of powder particles in suspension in the dielectric modifies some process variables and creates the conditions to achieve a high surface quality in large areas. This paper presents a new research work aiming to study the performance improvement of conventional EDM when used with a powder-mixed dielectric. A silicon powder was used and the improvement is assessed through quality surface indicators and process time measurements, over a set of different processing areas. The results show the positive influence of the silicon powder in the reduction of the operating time, required to achieve a specific surface quality, and in the decrease of the surface roughness, allowing the generation of mirror-like surfaces.
TL;DR: This talk discusses MPEG-21's parts, achievements, ongoing activities, and opportunities for new technologies.
Abstract: MPEG-21 is an open standards-based framework for multimedia delivery and consumption. It aims to enable the use of multimedia resources across a wide range of networks and devices. We discuss MPEG-21's parts, achievements, ongoing activities, and opportunities for new technologies.
TL;DR: In this article, the removal of heavy metal from solutions using biosorption in cork powder is described, along with the effect of different variables, such as the solid-liquid ratio, temperature and pH on the removal efficiency of the metals.
TL;DR: In this paper, the problem of computing the energy-momentum tensor tensor at retarded time was studied in D-dimensional flat spacetimes with the help of retarded D-dimensions of Green's functions.
Abstract: Gravitational wave solutions to Einstein's equations and their generation are examined in D-dimensional flat spacetimes. First the plane wave solutions are analyzed; then the wave generation is studied with the solution for the metric tensor being obtained with the help of retarded D-dimensional Green's functions. Because of the difficulties in handling the wave tails in odd dimensions we concentrate our study on even dimensions. We compute the metric quantities in the wave zone in terms of the energy-momentum tensor at retarded time. Some special cases of interest are studied. First we study the slow motion approximation, where the D-dimensional quadrupole formula is deduced. Within the quadrupole approximation, we consider two cases of interest: a particle in circular orbit and a particle falling radially into a higher dimensional Schwarzschild black hole. Then we turn our attention to the gravitational radiation emitted during collisions lasting zero seconds, i.e., hard collisions. We compute the gravitational energy radiated during the collision of two point particles, in terms of a cutoff frequency. In the case in which at least one of the particles is a black hole, we argue that this cutoff frequency should be close to the lowest gravitational quasinormal frequency. In this context, we compute the scalar quasinormal frequencies of higher dimensional Schwarzschild black holes. Finally, as an interesting new application of this formalism, we compute the gravitational energy release during the quantum process of black hole pair creation. These results might be important in light of the recent proposal that there may exist extra dimensions in the Universe, one consequence of which may be black hole creation at the Large Hadron Collider at CERN.
TL;DR: In this article, an exact expression for the quasinormal modes of scalar, electromagnetic, and gravitational perturbations of a near extremal Schwarzschild-de Sitter black hole was presented.
Abstract: We present an exact expression for the quasinormal modes of scalar, electromagnetic, and gravitational perturbations of a near extremal Schwarzschild--de Sitter black hole and we show that is why a previous approximation holds exactly in this near extremal regime. In particular, our results give the asymptotic behavior of the quasinormal frequencies for highly damped modes, which has recently attracted much attention due to the proposed identification of its real part with the Barbero-Immirzi parameter.
TL;DR: In this article, the state-of-the-art on constructed wetlands for treatment of specific organic compounds, to the present the lack of knowledge, and to derive future research needs.
Abstract: Constructed wetlands (wetland treatment systems) are wetlands designed to improve water quality. They use the same processes that occur in natural wetlands but have the flexibility of being constructed. As in natural wetlands vegetation, soil and hydrology are the major components. Different soil types and plant species are used in constructed wetlands. Regarding hydrology surface flow and subsurface flow constructed wetlands are the main types. Subsurface flow constructed wetlands are further subdivided into horizontal or vertical flow. Many constructed wetlands deal with domestic wastewater where BOD and COD (Biochemical and Chemical Oxygen Demand respectively) are used as a sum parameter for organic matter. However, also special organic compounds can be removed. The objectives are to summarise the state-of-the-art on constructed wetlands for treatment of specific organic compounds, to the present the lack of knowledge, and to derive future research needs. Case studies in combination with a literature review are used to summarise the available knowledge on removal processes for specific organic compounds. Case studies are presented for the treatment of wastewaters contaminated with aromatic organic compounds, and sulphonated anthraquinones, olive mill wastewater, landfill leachate, and groundwater contaminated with hydrocarbons, cyanides, chlorinated volatile organics, and explosives. In general the removal efficiency for organic contaminants is high in all presented studies. Constructed wetlands are an effective and low cost way to treat water polluted with organic compounds. There is a lack of knowledge on the detailed removal pathways for most of the contaminants. Removal rates as well as optimal plant species are substance-specific, and also typically not available. If a constructed wetland provides different environmental conditions and uses different plant species the treatment efficiency can be improved. There is a great need to lighten the black box ‘constructed wetland’ to obtain performance data for both microbial activity and the contribution of the plants to the overall removal process. Also genetic modified plants should be considered to enhance the treatment performance of constructed wetlands for specific compounds.
25 Aug 2003
TL;DR: It is concluded that path vector protocols can be made to converge to widest or widest-shortest paths, but that the composite metric of IGRP (Interior Gateway Protocol), for example, does not guarantee convergence to optimal paths.
Abstract: Path vector protocols are currently in the limelight, mainly because the inter-domain routing protocol of the Internet, BGP (Border Gateway Protocol), belongs to this class. In this paper, we cast the operation of path vector protocols into a broad algebraic framework and relate the convergence of the protocol, and the characteristics of the paths to which it converges, with the monotonicity and isotonicity properties of its path compositional operation. Here, monotonicity means that the weight of a path cannot decrease when it is extended, and isotonicity means that the relationship between the weights of any two paths with the same origin is preserved when both are extended to the same node. We show that path vector protocols can be made to converge for every network if and only if the algebra is monotone, and that the resulting paths selected by the nodes are optimal if and only if the algebra is isotone as well.Many practical conclusions can be drawn from instances of the generic algebra. For performance-oriented routing, typical in intra-domain routing, we conclude that path vector protocols can be made to converge to widest or widest-shortest paths, but that the composite metric of IGRP (Interior Gateway Protocol), for example, does not guarantee convergence to optimal paths. For policy-based routing, typical in inter-domain routing, we formulate existing guidelines as instances of the generic algebra and we propose new ones. We also show how a particular instance of the algebra yields a sufficient condition for signaling correctness of internal BGP.
TL;DR: In this paper, the effects of surface-active contaminants on mass transfer coefficients k L a and k L were studied in two different bubble contactors and a theoretical interpretation was proposed based on modelling the kinetics of single bubble contamination, followed by sudden surface transition from mobile to rigid condition, in accordance with the stagnant cap model.
TL;DR: In this article, the results of a study of the application of two adhesives with different stiffnesses along the overlap length in single lap joints were presented, and the results showed measurable increase in strength of the bi-adhesive bonded joints compared with those in which single adhesive were used over the full length of the bondline.
TL;DR: In this article, the relation between leptogenesis and CP violation at low energies is analyzed in detail in the framework of the minimal seesaw mechanism, without loss of generality, in a weak basis where both the charged lepton and the right-handed Majorana mass matrices are diagonal and real.
Abstract: The relation between leptogenesis and CP violation at low energies is analyzed in detail in the framework of the minimal seesaw mechanism. Working, without loss of generality, in a weak basis where both the charged lepton and the right-handed Majorana mass matrices are diagonal and real, we consider a convenient generic parametrization of the Dirac neutrino Yukawa coupling matrix and identify the necessary condition which has to be satisfied in order to establish a direct link between leptogenesis and CP violation at low energies. In the context of the LMA solution of the solar neutrino problem, we present minimal scenarios which allow for the full determination of the cosmological baryon asymmetry and the strength of CP violation in neutrino oscillations. Some specific realizations of these minimal scenarios are considered. The question of the relative sign between the baryon asymmetry and CP violation at low energies is also discussed.
TL;DR: In this article, solvent extraction is investigated as a promising alternative for the recovery of iron from leach solutions, which is usually carried out by precipitation as jarosite, goethite or hematite.
TL;DR: In this paper, tomato skins and their mixtures with seeds were submitted to supercritical CO2 extraction using a flow apparatus at pressures of 250 and 300 bar and temperatures of 60 and 80 °C.
Abstract: Tomato skins and their mixtures with seeds were submitted to supercritical CO2 extraction using a flow apparatus at pressures of 250 and 300 bar and temperatures of 60 and 80 °C Two different mean particle sizes (80 and 345 μm) were used at two solvent flow rates (0792 and 135 kg/h) The yields of lipids, lycopene, and β-carotene obtained by supercritical fluid extraction were compared with those obtained by conventional organic solvent extraction Supercritical fluid extraction from tomato skins at 300 bar and 80 °C allowed the recovery of 80% of the lycopene and 88% of the β-carotene, using about 130 g of CO2 per gram of matrix at the lower flow rate of CO2