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Showing papers by "Instituto Superior Técnico published in 2012"


Journal ArticleDOI
Sebastián F. Sánchez1, Robert C. Kennicutt2, A. Gil de Paz3, G. van de Ven4, José M. Vílchez1, Lutz Wisotzki5, C. J. Walcher5, D. Mast1, J. A. L. Aguerri1, J. A. L. Aguerri6, Sergio Albiol-Pérez7, Almudena Alonso-Herrero1, João Alves8, J. Bakos6, J. Bakos1, T. Bartakova9, Joss Bland-Hawthorn10, Alessandro Boselli11, D. J. Bomans12, África Castillo-Morales3, C. Cortijo-Ferrero1, A. de Lorenzo-Cáceres1, A. de Lorenzo-Cáceres6, A. del Olmo1, Ralf-Jürgen Dettmar12, Angeles I. Díaz13, Simon Ellis14, Simon Ellis10, Jesús Falcón-Barroso1, Jesús Falcón-Barroso6, Hector Flores15, Anna Gallazzi16, Begoña García-Lorenzo1, Begoña García-Lorenzo6, R. M. González Delgado1, Nicolas Gruel, Tim Haines17, C. Hao18, Bernd Husemann5, J. Iglesias-Páramo1, Knud Jahnke4, Benjamin D. Johnson19, Bruno Jungwiert20, Bruno Jungwiert21, Veselina Kalinova4, C. Kehrig5, D. Kupko5, Angel R. Lopez-Sanchez14, Angel R. Lopez-Sanchez22, Mariya Lyubenova4, R. A. Marino1, R. A. Marino3, E. Mármol-Queraltó1, E. Mármol-Queraltó3, I. Márquez1, J. Masegosa1, Sharon E. Meidt4, Jairo Méndez-Abreu6, Jairo Méndez-Abreu1, Ana Monreal-Ibero1, C. Montijo1, A. Mourao23, G. Palacios-Navarro7, Polychronis Papaderos24, Anna Pasquali25, Reynier Peletier, Enrique Pérez1, I. Pérez26, Andreas Quirrenbach, M. Relaño26, F. F. Rosales-Ortega13, F. F. Rosales-Ortega1, Martin Roth5, T. Ruiz-Lara26, Patricia Sanchez-Blazquez13, C. Sengupta1, R. Singh4, Vallery Stanishev23, Scott Trager27, Alexandre Vazdekis1, Alexandre Vazdekis6, Kerttu Viironen1, Vivienne Wild28, Stefano Zibetti16, Bodo L. Ziegler8 
TL;DR: The Calar Alto Legacy Integral Field Area (CALIFA) survey as discussed by the authors was designed to provide a first step in this direction by obtaining spatially resolved spectroscopic information of a diameter selected sample of similar to 600 galaxies in the Local Universe.
Abstract: The final product of galaxy evolution through cosmic time is the population of galaxies in the local universe. These galaxies are also those that can be studied in most detail, thus providing a stringent benchmark for our understanding of galaxy evolution. Through the huge success of spectroscopic single-fiber, statistical surveys of the Local Universe in the last decade, it has become clear, however, that an authoritative observational description of galaxies will involve measuring their spatially resolved properties over their full optical extent for a statistically significant sample. We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey, which has been designed to provide a first step in this direction. We summarize the survey goals and design, including sample selection and observational strategy. We also showcase the data taken during the first observing runs (June/July 2010) and outline the reduction pipeline, quality control schemes and general characteristics of the reduced data. This survey is obtaining spatially resolved spectroscopic information of a diameter selected sample of similar to 600 galaxies in the Local Universe (0.005 < z < 0.03). CALIFA has been designed to allow the building of two-dimensional maps of the following quantities: (a) stellar populations: ages and metallicities; (b) ionized gas: distribution, excitation mechanism and chemical abundances; and (c) kinematic properties: both from stellar and ionized gas components. CALIFA uses the PPAK integral field unit (IFU), with a hexagonal field-of-view of similar to 1.3 square', with a 100% covering factor by adopting a three-pointing dithering scheme. The optical wavelength range is covered from 3700 to 7000 angstrom, using two overlapping setups (V500 and V1200), with different resolutions: R similar to 850 and R similar to 1650, respectively. CALIFA is a legacy survey, intended for the community. The reduced data will be released, once the quality has been guaranteed. The analyzed data fulfill the expectations of the original observing proposal, on the basis of a set of quality checks and exploratory analysis: (i) the final datacubes reach a 3 sigma limiting surface brightness depth of similar to 23.0 mag/arcsec(2) for the V500 grating data (similar to 22.8 mag/arcsec(2) for V1200); (ii) about similar to 70% of the covered field-of-view is above this 3 sigma limit; (iii) the data have a blue-to-red relative flux calibration within a few percent in most of the wavelength range; (iv) the absolute flux calibration is accurate within similar to 8% with respect to SDSS; (v) the measured spectral resolution is similar to 85 km s(-1) for V1200 (similar to 150 km s(-1) for V500); (vi) the estimated accuracy of the wavelength calibration is similar to 5 km s(-1) for the V1200 data (similar to 10 km s(-1) for the V500 data); (vii) the aperture matched CALIFA and SDSS spectra are qualitatively and quantitatively similar. Finally, we show that we are able to carry out all measurements indicated above, recovering the properties of the stellar populations, the ionized gas and the kinematics of both components. The associated maps illustrate the spatial variation of these parameters across the field, reemphasizing the redshift dependence of single aperture spectroscopic measurements. We conclude from this first look at the data that CALIFA will be an important resource for archaeological studies of galaxies in the Local Universe.

1,143 citations


Journal ArticleDOI
TL;DR: A critical review provides a judicious assessment of the available literature on ionic-liquid-based Aqueous Biphasic Systems and addresses two of the main applications of ionic liquid-based ABS: extraction of biomolecules and other added-value compounds, and their use as alternative approaches for removing and recovering ionic liquids from aqueous media.
Abstract: During the past decade, ionic-liquid-based Aqueous Biphasic Systems (ABS) have been the focus of a significant amount of research. Based on a compilation and analysis of the data hitherto reported, this critical review provides a judicious assessment of the available literature on the subject. We evaluate the quality of the data and establish the main drawbacks found in the literature. We discuss the main issues which govern the phase behaviour of ionic-liquid-based ABS, and we highlight future challenges to the field. In particular, the effect of the ionic liquid structure and the various types of salting-out agents (inorganic or organic salts, amino acids and carbohydrates) on the phase equilibria of ABS is discussed, as well as the influence of secondary parameters such as temperature and pH. More recent approaches using ionic liquids as additives or as replacements for common salts in polymer-based ABS are also presented and discussed to emphasize the expanding number of aqueous two-phase systems that can actually be obtained. Finally, we address two of the main applications of ionic liquid-based ABS: extraction of biomolecules and other added-value compounds, and their use as alternative approaches for removing and recovering ionic liquids from aqueous media.

704 citations


Journal ArticleDOI
TL;DR: The plasmonic detection of single molecules in real time without the need for labelling or amplification is reported, and the binding of single proteins is detected by monitoring the plAsmon resonance of the nanorod with a sensitive photothermal assay.
Abstract: Existing methods for the optical detection of single molecules require the molecules to absorb light to produce fluorescence or direct absorption signals. This limits the range of species that can be detected, because most molecules are purely refractive. Metal nanoparticles or dielectric resonators can be used to detect non-absorbing molecules because local changes in the refractive index produce a resonance shift. However, current approaches only detect single molecules when the resonance shift is amplified by a highly polarizable label or by a localized precipitation reaction on the surface of a nanoparticle. Without such amplification, single-molecule events can only be identified in a statistical way. Here, we report the plasmonic detection of single molecules in real time without the need for labelling or amplification. Our sensor consists of a single gold nanorod coated with biotin receptors, and the binding of single proteins is detected by monitoring the plasmon resonance of the nanorod with a sensitive photothermal assay. The sensitivity of our device is ∼700 times higher than state-of-the-art plasmon sensors and is intrinsically limited by spectral diffusion of the surface plasmon resonance.

669 citations


Journal ArticleDOI
TL;DR: In this paper, the authors analyze the perceptions of traditional agriculture in Europe and their influence in land management policies and argue that, contrary to the common perception, traditional agriculture practices were not environmentally friendly and that the standards of living of rural populations were low.
Abstract: For millennia, mankind has shaped landscapes, particularly through agriculture. In Europe, the age-old interaction between humans and ecosystems strongly influenced the cultural heritage. Yet European farmland is now being abandoned, especially in remote areas. The loss of the traditional agricultural landscapes and its consequences for biodiversity and ecosystem services is generating concerns in both the scientific community and the public. Here we ask to what extent farmland abandonment can be considered as an opportunity for rewilding ecosystems. We analyze the perceptions of traditional agriculture in Europe and their influence in land management policies. We argue that, contrary to the common perception, traditional agriculture practices were not environmentally friendly and that the standards of living of rural populations were low. We suggest that current policies to maintain extensive farming landscapes underestimate the human labor needed to sustain these landscapes and the recent and future dynamics of the socio-economic drivers behind abandonment. We examine the potential benefits for ecosystems and people from rewilding. We identify species that could benefit from land abandonment and forest regeneration and the ecosystem services that could be provided such as carbon sequestration and recreation. Finally, we discuss the challenges associated with rewilding, including the need to maintain open areas, the fire risks, and the conflicts between people and wildlife. Despite these challenges, we argue that rewilding should be recognized by policy-makers as one of the possible land management options in Europe, particularly on marginal areas.

624 citations


Journal ArticleDOI
TL;DR: In this paper, a review on the recycling of plastic waste as aggregate in cement mortar and concrete productions is presented, which is divided into four different sections along with introduction and conclusion sections.

465 citations


Journal ArticleDOI
TL;DR: Discovery of a laser–plasma acceleration mechanism that generates 20 MeV proton beams with a 1% spread is a promising step in the development of laser-driven proton accelerators.
Abstract: Laser-driven proton accelerators could enable more effective cancer treatment, but to fulfil this function proton beams with a higher energy and narrower energy spread will need to be produced. Discovery of a laser–plasma acceleration mechanism that generates 20 MeV proton beams with a 1% spread is a promising step.

402 citations


Journal ArticleDOI
TL;DR: This critical review analyses most of the surface tension data reported between 2001 and 2010 (187 references) and concludes that ionic liquids present characteristic surface behavior and distinctive trends of their surface tension versus temperature.
Abstract: Some of the most active scientific research fronts of the past decade are centered on ionic liquids These fluids present characteristic surface behavior and distinctive trends of their surface tension versus temperature One way to explore and understand their unique nature is to study their surface properties This critical review analyses most of the surface tension data reported between 2001 and 2010 (187 references)

360 citations


Proceedings ArticleDOI
05 Sep 2012
TL;DR: This paper presents an hybrid method for predicting human mobility on the basis of Hidden Markov Models, and reports on a series of experiments with a real-world location history dataset from the GeoLife project, showing that a prediction accuracy of 13.85% can be achieved when considering regions of roughly 1280 squared meters.
Abstract: The analysis of human location histories is currently getting an increasing attention, due to the widespread usage of geopositioning technologies such as the GPS, and also of online location-based services that allow users to share this information. Tasks such as the prediction of human movement can be addressed through the usage of these data, in turn offering support for more advanced applications, such as adaptive mobile services with proactive context-based functions. This paper presents an hybrid method for predicting human mobility on the basis of Hidden Markov Models (HMMs). The proposed approach clusters location histories according to their characteristics, and latter trains an HMM for each cluster. The usage of HMMs allows us to account with location characteristics as unobservable parameters, and also to account with the effects of each individual's previous actions. We report on a series of experiments with a real-world location history dataset from the GeoLife project, showing that a prediction accuracy of 13.85% can be achieved when considering regions of roughly 1280 squared meters.

335 citations


Proceedings ArticleDOI
13 Aug 2012
TL;DR: Odin, an SDN framework to introduce programmability in enterprise wireless local area networks (WLANs), builds on a light virtual AP abstraction that greatly simplifies client management and supports WPA2 Enterprise.
Abstract: We present Odin, an SDN framework to introduce programmability in enterprise wireless local area networks (WLANs). Enterprise WLANs need to support a wide range of services and functionalities. This includes authentication, authorization and accounting, policy, mobility and interference management, and load balancing. WLANs also exhibit unique challenges. In particular, access point (AP) association decisions are not made by the infrastructure, but by clients. In addition, the association state machine combined with the broadcast nature of the wireless medium requires keeping track of a large amount of state changes. To this end, Odin builds on a light virtual AP abstraction that greatly simplifies client management. Odin does not require any client side modifications and its design supports WPA2 Enterprise. With Odin, a network operator can implement enterprise WLAN services as network applications. A prototype implementation demonstrates Odin's feasibility.

330 citations


Journal ArticleDOI
TL;DR: The recent advances reported in the literature that could provide new avenues to the development of more efficient adhesives inspired in nature strategies are discussed.

290 citations


Journal ArticleDOI
TL;DR: In this article, the authors review the process that led to the development of one of the most widely used force fields in the area of ionic liquids modeling, analyze its subsequent expansions and alternative models, and consider future routes of improvement to overcome present limitations.
Abstract: In this account, we review the process that led to the development of one of the most widely used force fields in the area of ionic liquids modeling, analyze its subsequent expansions and alternative models, and consider future routes of improvement to overcome present limitations. This includes the description and discussion of (1) the rationale behind the generic and systematic character of the Canongia Lopes & Padua (CLP (2) the families of ionic liquids that have been (and continue to be) parameterized over the years and those that are the most challenging both in theoretical and applied terms; (3) the steps that lead to a correct parameterization of each type of ion and its homologous family, with special emphasis on the correct modeling of their flexibility and charge distribution; (4) the validation processes of the CLP and finally (5) the compromises that have to be attained when choosing between generic or specific force fields, coarse-grain or atomistic models, and polarizable or non-polarizable methods. The application of the CL&P and other force fields to the study of ionic liquids using quantum- and statistical-mechanics methods has led to the discovery and analysis of the unique nature of their liquid phases, that is, the notion that ionic liquids are nano-segregated fluids with structural and dynamic heterogeneities at the nanoscopic scale. This successful contribution of theoretical chemistry to the field of ionic liquids will also serve as a guide throughout the ensuing discussion.

Journal ArticleDOI
TL;DR: M Molecular epidemiology and surveillance of environmental samples are necessary to elucidate the public health hazards associated with exposure to environmental viruses and the human pathogenic viruses that are most relevant in this context are nonenveloped.
Abstract: Numerous viruses of human or animal origin can spread in the environment and infect people via water and food, mostly through ingestion and occasionally through skin contact. These viruses are released into the environment by various routes including water run-offs and aerosols. Furthermore, zoonotic viruses may infect humans exposed to contaminated surface waters. Foodstuffs of animal origin can be contaminated, and their consumption may cause human infection if the viruses are not inactivated during food processing. Molecular epidemiology and surveillance of environmental samples are necessary to elucidate the public health hazards associated with exposure to environmental viruses. Whereas monitoring of viral nucleic acids by PCR methods is relatively straightforward and well documented, detection of infectious virus particles is technically more demanding and not always possible (e.g. human norovirus or hepatitis E virus). The human pathogenic viruses that are most relevant in this context are nonenveloped and belong to the families of the Caliciviridae, Adenoviridae, Hepeviridae, Picornaviridae and Reoviridae. Sampling methods and strategies, first-choice detection methods and evaluation criteria are reviewed.

Journal ArticleDOI
TL;DR: The role of out-of-phase firing in neuronal clusters, the importance of strong excitatory AMPA-synaptic currents and recurrent inhibitory connectivity in combination with the fast time scales of IPSPs, ephaptic coupling and the contribution of interneuronal coupling through gap junctions are considered.

Journal ArticleDOI
TL;DR: These new results clearly show that guanidinium-, unlike the imidazolium- and phosphonium-based ILs, do not follow the trend of increasing toxicity with the increase in the alkyl chain length, and the introduction of oxygenated groups on theAlkyl chains leads to a decrease of the toxicity of guanIDinium and also imidrazolium compounds.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed the liquid-scintillator detector LENA (Low Energy Neutrino Astronomy) as a multipurpose neutrino observatory.

Journal ArticleDOI
TL;DR: In this paper, two types of latest generation superplasticisers were used that differ in terms of water reduction capacity and robustness, and the workability, density and compressive strength of each of the compositions analysed were then compared: a reference concrete, with no plasticisers, and concrete mixes with the super-plasticizers.

Journal ArticleDOI
TL;DR: In this paper, Zn-Al layered double hydroxides (LDHs) intercalated with nitrate anions are suggested as chloride nanotraps for organic polymeric coatings.

Journal ArticleDOI
TL;DR: In this paper, an approximately equimolar ratio TiVCrAlSi high entropy alloy coatings has been deposited by laser cladding on Ti-6Al-4V alloy.

Journal ArticleDOI
TL;DR: It is suggested that a standardized laboratory protocol for evaluating stone bioreceptivity and definition of a stone biOREceptivity index are required to enable creation of a database on the primary bioreCEPTivity of stone materials.

Journal ArticleDOI
01 Apr 2012-Energy
TL;DR: The European Strategy for Energy and Climate Change (ESCEECC) as discussed by the authors is an action plan that aims to achieve a 20% reduction in GHG (greenhouse gases) in developed countries by 2020 or 30% should there be an international agreement in the domain.

Journal ArticleDOI
TL;DR: It is shown that monoenergetic ion beams can be accelerated by moderate Mach number collisionless, electrostatic shocks propagating in a long scale-length exponentially decaying plasma profile and that it is possible to generate ~200 MeV proton beams with state-of-the-art 100 TW class laser systems.
Abstract: We show that monoenergetic ion beams can be accelerated by moderate Mach number collisionless, electrostatic shocks propagating in a long scale-length exponentially decaying plasma profile. Strong plasma heating and density steepening produced by an intense laser pulse near the critical density can launch such shocks that propagate in the extended plasma at high velocities. The generation of a monoenergetic ion beam is possible due to the small and constant sheath electric field associated with the slowly decreasing density profile. The conditions for the acceleration of high-quality, energetic ion beams are identified through theory and multidimensional particle-in-cell simulations. The scaling of the ion energy with laser intensity shows that it is possible to generate $\ensuremath{\sim}200\text{ }\text{ }\mathrm{MeV}$ proton beams with state-of-the-art 100 TW class laser systems.

Journal ArticleDOI
TL;DR: In this article, a detailed treatment of nonperturbative solutions in string theory, and their relation to the large-order behavior of perturbation theory, making use of transseries and resurgent analysis, is presented.
Abstract: Nonperturbative eects in string theory are usually associated to D{branes. In many cases it can be explicitly shown that D{brane instantons control the large{order behavior of string perturbation theory, leading to the well{known (2g)! growth of the genus expansion. This paper presents a detailed treatment of nonperturbative solutions in string theory, and their relation to the large{order behavior of perturbation theory, making use of transseries and resurgent analysis. These are powerful techniques addressing general nonperturbative contributions within non{linear systems, which are developed at length herein as they apply to string theory. The cases of topological strings, the Painlev e I equation describing 2d quantum gravity, and the quartic matrix model, are explicitly addressed. These results generalize to minimal strings and general matrix models. It is shown that, in order to completely understand string theory at a fully nonperturbative level, new sectors are required beyond the standard D{brane sector.

Journal ArticleDOI
TL;DR: In this paper, the effects of incorporating two types of superplasticizer on the mechanical performance of concrete containing fine recycled aggregate were evaluated and the results of tests for splitting tensile strength, modulus of elasticity and abrasion resistance were presented.
Abstract: It is considered that using crushed recycled concrete as aggregate for concrete production is a viable alternative to dumping and would help to conserve abiotic resources. This use has fundamentally been based on the coarse fraction because the fine fraction is likely to degrade the performance of the resulting concrete. This paper presents results from a research work undertaken at Instituto Superior Tecnico (IST), Lisbon, Portugal, in which the effects of incorporating two types of superplasticizer on the mechanical performance of concrete containing fine recycled aggregate were evaluated. The purpose was to see if the addition of superplasticizer would offset the detrimental effects associated with the use of fine recycled concrete aggregate. The experimental programme is described and the results of tests for splitting tensile strength, modulus of elasticity and abrasion resistance are presented. The relative performance of concrete made with recycled aggregate was found to decrease. However, the same concrete with admixtures in general exhibited a better mechanical performance than the reference mixes without admixtures or with a less active superplasticizer. Therefore, it is argued that the mechanical performance of concrete made with fine recycled concrete aggregates can be as good as that of conventional concrete, if superplasticizers are used to reduce the water–cement ratio of the former concrete.

Journal ArticleDOI
TL;DR: In this article, a general method to study linear perturbations of slowly rotating black holes was proposed, which is valid for any perturbation field, and particularly advantageous when the field equations are not separable in the standard Teukolsky formalism.
Abstract: We discuss a general method to study linear perturbations of slowly rotating black holes which is valid for any perturbation field, and particularly advantageous when the field equations are not separable. As an illustration of the method we investigate massive vector (Proca) perturbations in the Kerr metric, which do not appear to be separable in the standard Teukolsky formalism. Working in a perturbative scheme, we discuss two important effects induced by rotation: a Zeeman-like shift of nonaxisymmetric quasinormal modes and bound states with different azimuthal number $m$, and the coupling between axial and polar modes with different multipolar index $\ensuremath{\ell}$. We explicitly compute the perturbation equations up to second order in rotation, but in principle the method can be extended to any order. Working at first order in rotation we show that polar and axial Proca modes can be computed by solving two decoupled sets of equations, and we derive a single master equation describing axial perturbations of spin $s=0$ and $s=\ifmmode\pm\else\textpm\fi{}1$. By extending the calculation to second order we can study the superradiant regime of Proca perturbations in a self-consistent way. For the first time we show that Proca fields around Kerr black holes exhibit a superradiant instability, which is significantly stronger than for massive scalar fields. Because of this instability, astrophysical observations of spinning black holes provide the tightest upper limit on the mass of the photon: ${m}_{\ensuremath{\gamma}}\ensuremath{\lesssim}4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\text{ }\text{ }\mathrm{eV}$ under our most conservative assumptions. Spin measurements for the largest black holes could reduce this bound to ${m}_{\ensuremath{\gamma}}\ensuremath{\lesssim}{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}$ or lower.

Journal ArticleDOI
TL;DR: This paper presents Electre Tri-nC, a new sorting method which takes into account several reference actions for characterizing each category and is composed of two joint rules.

Journal ArticleDOI
TL;DR: These methods use low-complexity relevance and redundancy criteria, applicable to supervised, semi-supervised, and unsupervised learning, being able to act as pre-processors for computationally intensive methods to focus their attention on smaller subsets of promising features.

Journal ArticleDOI
TL;DR: In this paper, the anti-corrosion properties of water-based epoxy coatings loaded with pH sensitive particles, acting as feedback active containers for corrosion inhibitors and applied on the aluminium alloy AA2024-T3.

Journal ArticleDOI
TL;DR: Laser-induced ultrafast demagnetization in [Co/Pd](30) multilayer films is studied, which, for the first time, achieves a spatial resolution better than 100 nm by using femtosecond soft X-ray pulses.
Abstract: Femtosecond magnetization phenomena have been challenging our understanding for over a decade Most experiments have relied on infrared femtosecond lasers, limiting the spatial resolution to a few micrometres With the advent of femtosecond X-ray sources, nanometric resolution can now be reached, which matches key length scales in femtomagnetism such as the travelling length of excited 'hot' electrons on a femtosecond timescale Here we study laser-induced ultrafast demagnetization in [Co/Pd]30 multilayer films, which, for the first time, achieves a spatial resolution better than 100 nm by using femtosecond soft X-ray pulses This allows us to follow the femtosecond demagnetization process in a magnetic system consisting of alternating nanometric domains of opposite magnetization No modification of the magnetic structure is observed, but, in comparison with uniformly magnetized systems of similar composition, we find a significantly faster demagnetization time We argue that this may be caused by direct transfer of spin angular momentum between neighbouring domains

Book ChapterDOI
01 Jan 2012
TL;DR: This chapter presents the POMDP model by focusing on the differences with fully observable MDPs, and it is shown how optimal policies for POM DPs can be represented.
Abstract: For reinforcement learning in environments in which an agent has access to a reliable state signal, methods based on the Markov decision process (MDP) have had many successes. In many problem domains, however, an agent suffers from limited sensing capabilities that preclude it from recovering a Markovian state signal from its perceptions. Extending the MDP framework, partially observable Markov decision processes (POMDPs) allow for principled decision making under conditions of uncertain sensing. In this chapter we present the POMDP model by focusing on the differences with fully observable MDPs, and we show how optimal policies for POMDPs can be represented. Next, we give a review of model-based techniques for policy computation, followed by an overview of the available model-free methods for POMDPs. We conclude by highlighting recent trends in POMDP reinforcement learning.

Journal ArticleDOI
TL;DR: The formation of nonrelativistic collisionless shocks in the laboratory with ultrahigh intensity lasers is studied via ab initio multidimensional particle-in-cell simulations, illustrating that the Weibel instability plays a crucial role in the generation of strong subequipartition magnetic fields that isotropize the incoming flow and lead to the formation of a collisionless shock, similar to what occurs in astrophysical scenarios.
Abstract: The formation of nonrelativistic collisionless shocks in the laboratory with ultrahigh intensity lasers is studied via ab initio multidimensional particle-in-cell simulations. The microphysics behind shock formation and dissipation and the detailed shock structure are analyzed, illustrating that the Weibel instability plays a crucial role in the generation of strong subequipartition magnetic fields that isotropize the incoming flow and lead to the formation of a collisionless shock, similar to what occurs in astrophysical scenarios. The possibility of generating such collisionless shocks in the laboratory opens the way to the direct study of the physics associated with astrophysical shocks.