The compound Poisson limit ruling periodic extreme behaviour of non-uniformly hyperbolic dynamics

We prove that the distributional limit of the normalised number of returns to small neighbourhoods of periodic points of non-uniformly hyperbolic dynamical systems is compound Poisson. The returns to small balls around a fixed point in the phase space correspond to the occurrence of rare events, or exceedances of high thresholds, so that there is a connection between the laws of Return Times Statistics and Extreme Value Laws. The fact that the fixed point in the phase space is a repelling periodic point implies that there is a tendency for the exceedances to appear in clusters whose average sizes is given by the Extremal Index, which depends on the expansion of the system at the periodic point. We recall that for generic points, the exceedances, in the limit, are singular and occur at Poisson times. However, around periodic points, the picture is different: the respective point processes of exceedances converge to a compound Poisson process, so instead of single exceedances, we have entire clusters of exceedances occurring at Poisson times with a geometric distribution ruling its multiplicity. The systems to which our results apply include: general piecewise expanding maps of the interval (Rychlik maps), maps with indifferent fixed points (Manneville-Pomeau maps) and Benedicks-Carleson quadratic maps.Comment: To appear in Communications in Mathematical Physic

The influence of light and culture media on the growth of the red seaweed Gracilaria gracilis (Rhodophyta, Gracilariales) under laboratory conditions

info:eu-repo/semantics/publishedVersio

Structure-antifouling activity relationship and molecular targets of bio-inspired(Thio)xanthones

The development of alternative ecological and effective antifouling technologies is still challenging. Synthesis of nature-inspired compounds has been exploited, given the potential to assure commercial supplies of potential ecofriendly antifouling agents. In this direction, the antifouling activity of a series of nineteen synthetic small molecules, with chemical similarities with natural products, were exploited in this work. Six (4, 5, 7, 10, 15 and 17) of the tested xanthones showed in vivo activity toward the settlement of Mytilus galloprovincialis larvae (EC50: 3.53–28.60 µM) and low toxicity to this macrofouling species (LC50 > 500 µM and LC50/EC50: 17.42–141.64), and two of them (7 and 10) showed no general marine ecotoxicity (<10% of Artemia salina mortality) after 48 h of exposure. Regarding the mechanism of action in mussel larvae, the best performance compounds 4 and 5 might be acting by the inhibition of acetylcholinesterase activity (in vitro and in silico studies), while 7 and 10 showed specific targets (proteomic studies) directly related with the mussel adhesive structure (byssal threads), given by the alterations in the expression of Mytilus collagen proteins (PreCols) and proximal thread proteins (TMPs). A quantitative structure-activity relationship (QSAR) model was built with predictive capacity to enable speeding the design of new potential active compounds.This research was supported by national funds through FCT - Foundation for Science and Technology within the scope of UIDB/04423/2020 and UIDP/04423/2020 and under the project PTDC/AAG-TEC/0739/2014 (reference POCI-01-0145-FEDER-016793) supported through national funds provided by FCT and ERDF - European Regional Development Fund through the COMPETE - Programa Operacional Factores de Competitividade (POFC) programme and RIDTI - Reforçar a Investigação, o Desenvolvimento Tecnológico e a Inovação (project 9471) and the project NASCEM PTDC/BTA-BTA/31422/2017 (POCI-01-0145-FEDER-031422) also financed by FCT, COMPETE2020 and PORTUGAL2020

Influence of nanoencapsulated lutein on acetylcholinesterase activity: In vitro determination, kinetic parameters, and in silico docking simulations

Lutein is a bioactive found in dark leafy vegetables that may be used as a nutraceutical agent in foodstuff and an inhibitor of key enzymes of the human body such as those involved in the cholinergic system. However, its high hydrophobicity leads to low bioavailability and must be overcome if lutein is to be added in foods. The objective of this study was to evaluate the influence of nanoencapsulated lutein in the activity of the acetylcholinesterase enzyme. The in vitro study was carried out using water in order to evaluate the impact of encapsulation on the hydrophilicity of lutein. In vitro assays showed that lutein, both free and nanoencapsulated, presented a mixedtype inhibition behavior, and encapsulated lutein was able to inhibit acetylcholinesterase activity even in an aqueous medium. Inhibition was also showed by the in silico docking results which show that lutein interacted with the pocket region of the enzyme.info:eu-repo/semantics/publishedVersio

Non-perturbative effective field theory for two-leg antiferromagnetic spin ladders

We study the long wavelength limit of a spin 1/2 Heisenberg antiferromagnetic two-leg ladder, treating the interchain coupling in a non-perturbative way. We perform a mean field analysis and then include exactly the fluctuations. This allows for a discussion of the phase diagram of the system and provides an effective field theory for the low energy excitations. The coset fermionic Lagrangian obtained corresponds to a perturbed SU(4)_1/U(1) Conformal Field Theory (CFT). This effective theory is naturally embedded in a SU(2)_2 x Z_2 CFT, where perturbations are easily identified in terms of conformal operators in the two sectors. Crossed and zig-zag ladders are also discussed using the same approach.Comment: 14 pages LaTeX, 5 PostScript figures included using epsfig.sty; minor corrections and a few references adde

Quem somos nós? Ou perfis da comunidade profissional arqueológica no Brasil: primeiras aproximações

WHO ARE WE? OR A PROFILE OF THE ARCHAEOLOGICAL PROFESSIONAL COMMUNITY IN BRAZIL: FIRST APPROACHESIn the last twenty years, archeological academic-scientific training has grown exponen-tially in Brazil, culminating in the recognition of the profession in 2018. However, little is known about the demographic profiles of people working in the area, as well as of students in the process of training, in undergraduate and graduate levels. By updating some data from previous studies, in this manuscript we present the results of an initial survey on the professional profile in Brazilian archeology, which includes information on the trajectory of education, gender, nationality and re-search themes. This initiative allows us to outline the challenges of inclusion and representativeness in the exercise of the profession, whose reflections will assist us in the conceiving of practical measures for a change in this situation in the future.Archaeology of the AmericasArchaeological Heritage Managemen