In situ bioassay chambers and procedures for assessment of sediment toxicity with Chironomus riparius

The purpose of this study was to develop an in situ sediment bioassay chamber and respective procedures, suitable for performing toxicity bioassays with benthic invertebrates, using the midge Chironomus riparius. It was also our objective to compare the responses obtained under controlled conditions (laboratory 10-day larval growth and survival test) with those obtained in situ. Clean sand and a formulated sediment were incorporated in the in situ bioassay, along with local sediments, as a way of minimizing natural variability due to physicochemical differences among sediments or due to interactions with indigenous organisms. Recovery of organisms was good (80-100% in the control and reference site), indicating that the developed chamber and protocol were suitable for exposing and retrieving C. riparius in situ. Results also showed differences between responses obtained with formulated and natural sediment in situ, as well as between laboratory and in situ.http://www.sciencedirect.com/science/article/B6VB5-48N2VXR-2/1/4b92092a978e9882e296a0bf4236ff4

Biochemical and physiological modifications in tissues of Sardina pilchardus: spatial and temporal patterns as a baseline for biomonitoring studies

Sardina pilchardus is a marine species common in the North Atlantic Ocean, and is subjected to diffuse anthropogenic chemical contamination and seasonal fluctuations in biotic and abiotic parameters that may alter its physiology and condition. Biological material is easily available through commercial fisheries, which could facilitate its use as a bioindicator species. The aim of the present work was to address its potential inclusion in biomonitoring studies, considering a combinatory approach through the use of enzymatic biomarkers and somatic indices, by assessing spatial and temporal patterns in a metapopulation along the west coast of Portugal. Our results showed significant variability of the biochemical and physiological profile of the fish, mainly concordant between sampling sites. Large differences for most markers were found across periods of the year, showing the importance of seasonality, which was mostly related to the reproductive cycle. Hence, environmental scientists should acknowledge seasonality as a strong driving force for physiological adaptations, influencing biochemical markers that are normally used to identify effects of chemical contamination. The here-obtained set of data suggests that S. pilchardus may be successfully included in oceanic biomonitoring studies, when one considers that the contribution of seasonal factors may exceed the influence of eventual anthropogenic contamination

Exponential behavior of the interlayer exchange coupling across non-magnetic metallic superlattices

It is shown that the coupling between magnetic layers separated by non-magnetic metallic superlattices can decay exponentially as a function of the spacer thickness $N$, as opposed to the usual $N^{-2}$ decay. This effect is due to the lack of constructive contributions to the coupling from extended states across the spacer. The exponential behavior is obtained by properly choosing the distinct metals and the superlattice unit cell composition.Comment: To appear in Phys. Rev.

1/N Expansion in Correlated Graphene

We examine the 1/N expansion, where N is the number of two-component Dirac fermions, for Coulomb interactions in graphene with a gap of magnitude $\Delta = 2 m$. We find that for $N\alpha\gg1$, where $\alpha$ is graphene's "fine structure constant", there is a crossover as a function of distance $r$ from the usual 3D Coulomb law, $V(r) \sim 1/r$, to a 2D Coulomb interaction, $V(r) \sim \ln(N\alpha/mr)$, for $m^{-1} \ll r \ll m^{-1} N \alpha/6$. This effect reflects the weak "confinement" of the electric field in the graphene plane. The crossover also leads to unusual renormalization of the quasiparticle velocity and gap at low momenta. We also discuss the differences between the interaction potential in gapped graphene and usual QED for different coupling regimes.Comment: 7 pages, 2 figures; expanded presentation, references adde

Designing an Experimental and a Reference Robot to Test and Evaluate the Impact of Cultural Competence in Socially Assistive Robotics

The article focusses on the work performed in preparation for an experimental trial aimed at evaluating the impact of a culturally competent robot for care home assistance. Indeed, it has been estabilished that the user's cultural identity plays an important role during the interaction with a robotic system and cultural competence may be one of the key elements for increasing capabilities of socially assistive robots. Specifically, the paper describes part of the work carried out for the definition and implementation of two different robotic systems for the care of older adults: a culturally competent robot, that shows its awareness of the user's cultural identity, and a reference robot, non culturally competent, but with the same functionalities of the former. The design of both robots is here described in detail, together with the key elements that make a socially assistive robot culturally competent, which should be absent in the non-culturally competent counterpart. Examples of the experimental phase of the CARESSES project, with a fictional user are reported, giving a hint of the validness of the proposed approach

Relações hospedeiro-parasita

Num ecossistema, é possível encontrar diversas relações entre os seres vivos aí presentes, incluindo relações em que um organismo é beneficiado às custas de outro. No caso das relações hospedeiro-parasita, verifica-se uma associação muito forte entre os dois organismos, sendo que os parasitas desempenham um papel ecológico e evolutivo muito relevante.Este trabalho foi financiado por fundos nacionais (através da Fundação para a Ciência e a Tecnologia) e pelo Fundo Europeu de Desenvolvimento Regional (através dos programas COMPETE2020 e PT2020) através do projeto de investigação FunG-Eye (POCI-01-0145-FEDER-029505)

Entanglement Dynamics after a Quench in Ising Field Theory: A Branch Point Twist Field Approach

We extend the branch point twist field approach for the calculation of entanglement entropies to time-dependent problems in 1+1-dimensional massive quantum field theories. We focus on the simplest example: a mass quench in the Ising field theory from initial mass m0 to final mass m. The main analytical results are obtained from a perturbative expansion of the twist field one-point function in the post-quench quasi-particle basis. The expected linear growth of the Rényi entropies at large times mt ≫ 1 emerges from a perturbative calculation at second order. We also show that the Rényi and von Neumann entropies, in infinite volume, contain subleading oscillatory contributions of frequency 2m and amplitude proportional to (mt)−3/2. The oscillatory terms are correctly predicted by an alternative perturbation series, in the pre-quench quasi-particle basis, which we also discuss. A comparison to lattice numerical calculations carried out on an Ising chain in the scaling limit shows very good agreement with the quantum field theory predictions. We also find evidence of clustering of twist field correlators which implies that the entanglement entropies are proportional to the number of subsystem boundary points

Simulation Mechanism with 2 Degrees of Freedom

This article discusses the historical analysis of the development of simulators applied to aviation. From the development with the application of the first necessity, at the beginning of the 20th century, to the nowadays technology. Today the technology is used in several fields, justifying the increasing business investment destined to the sector, such as training, recycling, development and entertainment. Its advantage, compared to the real model, is the lower cost and greater security. Some simulator mechanisms were studied in order to select one that meets practical USAge demands, and, in the end, a mechanism design is presented, aiming at the future construction and study of the different systems of a simulator in practice

Toxicity of the 3,4-methylenedioxymethamphetamine and its enantiomers to Daphnia magna after isolation by semipreparative chromatography

MDMA (3,4-methylenedioxymethamphetamine) is a chiral psychoactive recreational drug sold in illicit markets as racemate. Studies on the impact of MDMA on aquatic organisms are scarce. While enantioselectivity in toxicity in animals and humans has been reported, none is reported on aquatic organisms. This study aimed to investigate the ecotoxicological effects of MDMA and its enantiomers in Daphnia magna. For that, enantiomers (enantiomeric purity > 97%) were separated by liquid chromatography using a homemade semipreparative chiral column. Daphnids were exposed to three concentrations of (R,S)-MDMA (0.1, 1.0 and 10.0 µg L−1) and two concentrations of (R)- and (S)-enantiomers (0.1 and 1.0 µg L−1) over the course of 8 days. Morphophysiological responses were dependent on the substance form and daphnia development stage, and they were overall not affected by the (R)-enantiomer. Changes in swimming behaviour were observed for both the racemate and its enantiomers, but enantioselective effects were not observed. Reproductive or biochemical changes were not observed for enantiomers whereas a significant decrease in acetylcholinesterase and catalase activity was noted at the highest concentration of (R,S)-MDMA (10 µg L−1). Overall, this study showed that sub-chronic exposure to MDMA racemate and its enantiomers can interfere with morphophysiological and swimming behaviour of D. magna. In general, the (R)-enantiomer demonstrated less toxicity than the (S)-enantiomer.This work was financially supported by national funds through the FCT/MCTES (PIDDAC), under the project PTDC/CTA-AMB/6686/2020, and partially supported through the projects UIDB/04423/2020 and UIDP/04423/2020 (Group of Natural Products and Medicinal ChemistryCIIMAR)