Towards sample-efficient policy learning with DAC-ML

The sample-inefficiency problem in Artificial Intelligence refers to the inability of current Deep Reinforcement Learning models to optimize action policies within a small number of episodes. Recent studies have tried to overcome this limitation by adding memory systems and architectural biases to improve learning speed, such as in Episodic Reinforcement Learning. However, despite achieving incremental improvements, their performance is still not comparable to how humans learn behavioral policies. In this paper, we capitalize on the design principles of the Distributed Adaptive Control (DAC) theory of mind and brain to build a novel cognitive architecture (DAC-ML) that, by incorporating a hippocampus-inspired sequential memory system, can rapidly converge to effective action policies that maximize reward acquisition in a challenging foraging task

Immobilised cerium-doped zinc oxide as a photocatalyst for the degradation of antibiotics and the inactivation of antibiotic-resistant bacteria

The threat of antibiotic resistance to the wellbeing of societies is well established. Urban wastewater treatment plants (UWTPs) are recognised sources for antibiotic resistance dissemination in the environment. Herein a novel cerium-doped zinc oxide (Ce-ZnO) photocatalyst is compared to ZnO and the benchmark TiO 2 -P25 in the immobilised form on a metallic support, to evaluate a photocatalytic process as a possible tertiary treatment in UWTPs. The catalysts were compared for the removal of two antibiotics, trimethoprim (TMP) and sulfamethoxazole (SMX), and for the inactivation of Escherichia coli (E. coli) strain DH5-Alpha in isotonic sodium chloride solution and of autochthonous bacteria in real secondary wastewater. In real wastewater, E. coli and other coliforms were monitored, as well as the respective fractions resistant to ofloxacin and azithromycin. In parallel, Pseudomonas aeruginosa and the respective sub-population resistant to ofloxacin or ciprofloxacin were also monitored. Photocatalysis with both ZnO and Ce-ZnO was faster than using TiO 2 -P25 at degrading the antibiotics, with Ce-ZnO the fastest against SMX but slower than undoped ZnO in the removal of TMP. Ce-ZnO catalyst reuse in the immobilised form produced somewhat slower kinetics maintained >50% of the initial activity, even after five cycles of use. Approximately 3 log10 inactivation of E. coli in isotonic sodium chloride water was recorded with reproducible results. In the removal of autochthonous bacteria in real wastewater, Ce-ZnO performed better (more than 2 log values higher) than TiO 2 -P25. In all cases, E. coli and other coliforms, including their resistant subpopulations, were inactivated at a higher rate than P. aeruginosa. With short reaction times no evidence for enrichment of resistance was observed, yet with extended reaction times low levels of bacterial loads were not further inactivated. Overall, Ce-ZnO is an easy and cheap photocatalyst to produce and immobilise and the one that showed higher activity than the industry standard TiO2-P25 against the tested antibiotics and bacteria, including antibiotic-resistant bacteria

Gravitational instantons and black plane solutions in 4-d string theory

We consider gauged Wess-Zumino models based on the non compact group $SU(2,1)$. It is shown that by vector gauging the maximal compact subgroup $U(2)$ the resulting backgrounds obey the gravity-dilaton one loop string vacuum equations of motion in four dimensional euclidean space. The torsionless solution is then interpreted as a pseudo-instanton of the $d=4$ Liouville theory coupled to gravity. The presence of a traslational isometry in the model allows to get another string vacuum backgrounds by using target duality that we identify with those corresponding to the axial gauging. We also compute the exact backgrounds. Depending on the value of $k$, they may be interpreted as instantons connecting a highly singular big bang like universe with a static singular or regular black plane geometry.Comment: 29 page

Exact monopole instantons and cosmological solutions in string theory from abelian dimensional reduction

We compute the exact string vacuum backgrounds corresponding to the non-compact coset theory $SU(2,1)/SU(2)$. The conformal field theory defined by the level $k= 4$ results in a five dimensional singular solution that factorizes in an asymptotic region as the linear dilaton solution and a $S^3$ model. It presents two abelian compact isometries that allow to reinterpreting it from a four dimensional point of view as a stationary and magnetically charged space-time resembling in some aspects the Kerr-Newman solution of general relativity. The $k=\frac{13}{7}$ theory on the other hand describes a cosmological solution that interpolates between a singular phase at short times and a $S^1 \times S^2$ universe after some planckian times.Comment: 18 pages, section 5 replaced by 5 and 6, references added; to appear in Phys. Rev.

Design of graphene-based TiO2 photocatalysts - A review

There is a recent increase in the interest of de- signing high-performance photocatalysts using graphene- based materials. This review gathers some important aspects of graphene–TiO 2 , graphene oxide–TiO 2 , and reduced gra- phene oxide–TiO 2 composites, which are of especial rele- vance as next generation photocatalysts. The methods used for the preparation of these materials, the associated mech- anistic fundamentals, and the application of graphene-based composites on the photocatalytic degradation of pollutants are reviewed. Some structural, textural, and chemical prop- erties of these materials and other photo-assisted applica- tions, such as hydrogen production from water splitting and dye-sensitized solar cells, are also briefly includedFinancial support for this work was provided by the European Commission (Clean Water—grant agreement no 227017) and by Fundação para a Ciência e a Tecnologia (FCT) and FEDER under Program COMPETE, project FCOMP-01-0124-FEDER-022706 (Ref. FCT Pest-C/EQB/LA0020/2011) and FCOMP-01-0124-FEDER- 008442 (Ref. NANO/NTec-CA/0046/2007). Clean Water is a Collab- orative Project co-funded by the Research DG of the European Com- mission within the joint RTD activities of the Environment and NMP Thematic Priorities. SMT and AMTS acknowledge financial support from SFRH/BPD/74239/2010 and POCI/N010/2006, respectively

Haemocompatibility of iron oxide nanoparticles synthesized for theranostic applications: a high-sensitivity microfluidic tool

The poor heating efficiency of the most reported magnetic nanoparticles (MNPs), allied to the lack of comprehensive biocompatibility and haemodynamic studies, hampers the spread of multifunctional nanoparticles as the next generation of therapeutic bio-agents in medicine. The present work reports the synthesis and characterization, with special focus on biological/toxicological compatibility, of superparamagnetic nanoparticles with diameter around 18 nm, suitable for theranostic applications (i.e. simultaneous diagnosis and therapy of cancer). Envisioning more insights into the complex nanoparticle-red blood cells (RBCs) membrane interaction, the deformability of the human RBCs in contact with magnetic nanoparticles (MNPs) was assessed for the first time with a microfluidic extensional approach, and used as an indicator of haematological disorders in comparison with a conventional haematological test, i.e. the haemolysis analysis. Microfluidic results highlight the potential of this microfluidic tool over traditional haemolysis analysis, by detecting small increments in the rigidity of the blood cells, when traditional haemotoxicology analysis showed no significant alteration (haemolysis rates lower than 2 %). The detected rigidity has been predicted to be due to the wrapping of small MNPs by the bilayer membrane of the RBCs, which is directly related to MNPs size, shape and composition. The proposed microfluidic tool adds a new dimension into the field of nanomedicine, allowing to be applied as a highsensitivity technique capable of bringing a better understanding of the biological impact of nanoparticles developed for clinical applications.This work was financially supported by: Project POCI-01-0145-FEDER-006984 – Associate Laboratory J Nanopart Res (2016) 18:194 Page 15 of 17 194 123 LSRE-LCM funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalizac¸a˜o (POCI) – and by national funds through FCT - Fundac¸a˜o para a Cieˆncia e a Tecnologia. R.O.R. acknowledges the Ph.D. scholarship SFRH/BD/97658/2013 Granted by FCT. A.M.T.S acknowledges the FCT Investigator 2013 Programme (IF/01501/ 2013), with financing from the European Social Fund and the Human Potential Operational Programme. M.B. would like to thank ERDF (European Regional Development Fund) under grant PO Norte CCDR-N/ON.2 Programme. J.G. also thanks the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 600375.info:eu-repo/semantics/publishedVersio

Performance of polycarbonate, cellulose nitrate and polyethersulfone filtering membranes for culture-independent microbiota analysis of clean waters

Demineralized and disinfected waters may have very low microbial loads, requiring that large volumes of water are filtered to recover enough biomass for further analysis. Extended filtration periods, often interrupted by clogging, are a major limiting factor to concentrate samples' microbiota for further examination, besides hindering the work pace. In this study, we investigated the performance of three types of filtering membranes - polycarbonate (PC), cellulose nitrate (CN), and polyethersulfone (PES) with 0.22 μm pore size for culture-independent microbiological analysis (quantitative PCR of seven housekeeping and integrase genes) of tap water, recirculating tap water in a bottle washing loop, and of demineralized water. Compared to PC membranes, CN or PES required lower filtration periods, although had slightly lower DNA extraction yields. However, genes abundance per volume of water was, in general, not significantly different. The exception was observed for bottle washing water in which PC membranes supported significantly higher quantification values than PES membranes. These differences were lower than ∼0.5 log-units and did not hamper the distinction of the types of water based on genes profile. Also, the type of membrane did not significantly affect the profile of the bacterial community determined for tap and demineralized water. A major conclusion is that CN membranes, cheaper, allowing shorter filtration periods, and producing results that are not significantly different from those obtained with PC or PES, can be a good alternative to analyze waters with low biomass loads.info:eu-repo/semantics/publishedVersio

Secure neighbor discovery in wireless sensor networks using range-free localization techniques

Si una red inalámbrica de sensores se implementa en un entorno hostil, las limitaciones intrínsecas a los nodos conllevan muchos problemas de seguridad. En este artículo se aborda un ataque particular a los protocolos de localización y descubrimiento de vecinos, llevada a cabo por dos nodos que actúan en connivencia y establecen un "agujero de gusano" para tratar de engañar a un nodo aislado, haciéndole creer que se encuentra en la vecindad de un conjunto de nodos locales. Para contrarrestar este tipo de amenazas, se presenta un marco de actuación genéricamente denominado "detection of wormhole attacks using range-free methods" (DWARF) dentro del cual derivamos dos estrategias para de detección de agujeros de gusano: el primer enfoque (DWARFLoc) realiza conjuntamente la localización y la detección de ataques, mientras que el otro (DWARFTest) valida la posición estimada por el nodo una vez finalizado el protocolo de localización. Las simulaciones muestran que ambas estrategias son eficaces en la detección de ataques tipo "agujero de gusano", y sus prestaciones se comparan con las de un test convencional basado en la razón de verosimilitudes

Hybrid plasma simulations of a magnetically shielded Hall thruste

Numerical simulations of a magnetically shielded Hall effect thruster with a centrally mounted cathode are performed with an axisymmetric hybrid particle-in-cell/fluid code and are partially validated with experimental data. A full description of the plasma discharge inside the thruster chamber and in the near plume is presented and discussed, with the aim of highlighting those features most dependent on the magnetic configuration and the central cathode. Compared to traditional magnetic configurations, the acceleration region is mainly outside the thruster, whereas high plasma densities and low temperatures are found inside the thruster. Thus, magnetic shielding does not decrease plasma currents to the walls, but reduces significantly the energy fluxes, yielding low heat loads and practically no wall erosion. The injection of neutrals at the central cathode generates a secondary plasma plume that merges with the main one and facilitates much the drift of elec- trons toward the chamber. Once inside, the magnetic topology is efficient in channeling electron current away from lateral walls. Current and power balances are analyzed to assess performances in detail.This work has been supported by the EDDA project, funded by the European Union’s Horizon 2020 Research and Innovation Program, under Grant Agreement No. 87047

The Sound Emission Board of the KM3NeT Acoustic Positioning System

We describe the sound emission board proposed for installation in the acoustic positioning system of the future KM3NeT underwater neutrino telescope. The KM3NeT European consortium aims to build a multi-cubic kilometre underwater neutrino telescope in the deep Mediterranean Sea. In this kind of telescope the mechanical structures holding the optical sensors, which detect the Cherenkov radiation produced by muons emanating from neutrino interactions, are not completely rigid and can move up to dozens of meters in undersea currents. Knowledge of the position of the optical sensors to an accuracy of about 10 cm is needed for adequate muon track reconstruction. A positioning system based on the acoustic triangulation of sound transit time differences between fixed seabed emitters and receiving hydrophones attached to the kilometre-scale vertical flexible structures carrying the optical sensors is being developed. In this paper, we describe the sound emission board developed in the framework of KM3NeT project, which is totally adapted to the chosen FFR SX30 ultrasonic transducer and fulfils the requirements imposed by the collaboration in terms of cost, high reliability, low power consumption, high acoustic emission power for short signals, low intrinsic noise and capacity to use arbitrary signals in emission mode.Comment: 9 pages, 4 figure