Periodic solutions of parabolic and telegraph equations with asymmetric nonlinearities

This paper is organized as follows: Introduction, In Section 2, we collect the notation and basic assumptions that we shall suppose fulfilled throughout this paper. Section 3 is devoted to second order nonlinear one-dimensional parabolic and (linearly) damped hyperbolic equations. We compare, in some sense, the nonlinearity g(x, u) with the Fuçik spectrum of the corresponding piecewise linear differential equations with homogeneous Dirichlet boundary conditions, and a resonance condition of Landesman-Lazer type with respect to the forcing term h(x, t). More specifically, we assume that (the asymptotic behavior of) u - ¹ g ( x , u) lies in a rectangle located in what we should call the Fucik -Landesman-Lazer "resolvent" set. In Section 4, we take up the case of second-order multi-dimensional equations, and we prove results on crossing at not necessarily simple (higher) eigenvalues. Finally, in Section 5 we indicate the conditions under which one can extend our results to higher-order multi-dimensional equations.info:eu-repo/semantics/publishedVersio

Measuring the orbit shrinkage rate of hot Jupiters due to tides

A tidal interaction between a star and a close-in exoplanet leads to shrinkage of the planetary orbit and eventual tidal disruption of the planet. Measuring the shrinkage of the orbits will allow for the tidal quality parameter of the star ($Q'_\star$) to be measured, which is an important parameter to obtain information about stellar interiors. We analyse data from TESS for two targets known to host close-in hot Jupiters, WASP-18 and WASP-19, to measure the current limits on orbital period variation and provide new constrains on $Q'_\star$. We modelled the transit shape using all the available TESS observations and fitted the individual transit times of each transit. We used previously published transit times together with our results to fit two models, a constant period model, and a quadratic orbital decay model, MCMC algorithms. We find period change rates of $(-0.11\pm0.21)\times10^{-10}$ for WASP-18b and $(-0.35\pm0.22)\times10^{-10}$ for WASP-19b and we do not find significant evidence of orbital decay in these targets. We obtain new lower limits for $Q'_\star$ of $(1.42\pm0.34)\times10^7$ in WASP-18 and $(1.26\pm0.10)\times10^6$ in WASP-19, corresponding to upper limits of the orbital decay rate of $-0.45\times10^{-10}$ and $-0.71\times10^{-10}$, respectively, with a 95% confidence level. We compare our results with other relevant targets for tidal decay studies. We find that the orbital decay rate in both WASP-18b and WASP-19b appears to be smaller than the measured orbital decay of WASP-12b. We show that the minimum value of $Q'_\star$ in WASP-18 is two orders of magnitude higher than that of WASP-12, while WASP-19 has a minimum value one order of magnitude higher, which is consistent with other similar targets. Further observations are required to constrain the orbital decay of WASP-18 and WASP-19.Comment: 10 pages plus 5-page appendix. To be published in Astronomy and Astrophysic

Digital health literacy and online information queries in Portuguese university students

Supplement to the European Journal of Public Health which contains the abstracts of presentations at the 14th European Public Health (EPH) Conference «Public health futures in a changing world», held online 10-12 November 2021. Section: 1.G. Workshop: COVID-HL: A global survey on digital health literacy in university students during the pandemicBackground Worldwide there is an overwhelming amount of information about COVID-19 circulating online, also named infodemic. Misinformation (the unintentional) and disinformation (the intentional) spreading of false information have proven to be very dangerous to public health. Hence, more than ever, people need skills for searching, evaluating and integrating information related to health in daily life, i.e., health literacy. Until now, little is known about the digital health literacy of university students and their information-seeking behaviour. Hence, this study aimed to analyse the associations between university students' digital health literacy and online information queries during the beginning of the COVID-19 pandemic (and infodemic) in Portugal. Methods A cross-sectional study of 3.084 Portuguese university students (75.7% females), with an average age of 24.2 (SD = 7.5), was conducted using an online survey. We used sociodemographic data (sex, age, subjective social status) and the digital health literacy questionnaire adapted to the specific COVID-19 context. Online information queries included the topics related to SARS-CoV-2 and COVID-19 searched by students. Logistic regression models were performed. Results Online information queries (e.g., individual measures to protect against infection, current spread of the virus, current situation assessments and recommendations) were associated with an increased odds of achieving sufficient digital health literacy. Conclusions Online information queries related to epidemiological and public health topics are significantly associated with digital health literacy in times of COVID-19. Further studies are needed, including programs that improve digital health literacy among university students and increase the availability of high-quality content information.publishersversionpublishe

Isolation of Hierridin B from a culturable Cyanobium sp. strain isolated from the Portuguese coast

Cyanobacteria are a genetically diverse group of phototrophic prokaryotes. On a secondary metabolite perspective, however, filamentous and benthic forms have been the major sources of compounds isolated from these organisms. Nevertheless, unicellular free-living, planktonic cyanobacteria also contain enzymatic machinery for secondary metabolite biosynthesis.info:eu-repo/semantics/publishedVersio

Isolation of bluish anthocyanin-derived pigments obtained from blueberry surplus using centrifugal partition chromatography

Funding Information: This work was funded by Fundação para a Ciência e Tecnologia/Ministério da Ciência, Tecnologia e Ensino Superior (FCT/MCTES, Portugal) through national funds to iNOVA4Health (UIDB/04462/2020 and UIDP/04462/2020), the Associate Laboratory LS4FUTURE (LA/P/0087/2020) and Associated Laboratory for Sustainable Chemistry, Clean Processes, and Technologies LAQV (UIDB/50006/2020 and UIDP/50006/2020). Funding from INTERFACE Programme, through the Innovation, Technology and Circular Economy Fund (FITEC), is gratefully acknowledged. A.N.N. acknowledge FCT for the financial support received through SFRH/BD/144592/2019. J.O. acknowledge FCT her research contract (2022.00042.CEECIND/CP1724/CT0017). The authors also acknowledge Delícias do Tojal, CultiBaga, and Mirtilsul for kindly supplying the biomass. Funding Information: This work was funded by Fundação para a Ciência e Tecnologia/Ministério da Ciência, Tecnologia e Ensino Superior (FCT/MCTES, Portugal) through national funds to iNOVA4Health ( UIDB/04462/2020 and UIDP/04462/2020 ), the Associate Laboratory LS4FUTURE ( LA/P/0087/2020 ) and Associated Laboratory for Sustainable Chemistry, Clean Processes, and Technologies LAQV ( UIDB/50006/2020 and UIDP/50006/2020 ). Funding from INTERFACE Programme, through the Innovation, Technology and Circular Economy Fund ( FITEC ), is gratefully acknowledged. A.N.N. acknowledge FCT for the financial support received through SFRH/BD/144592/2019 . J.O. acknowledge FCT her research contract ( 2022.00042.CEECIND/CP1724/CT0017 ). The authors also acknowledge Delícias do Tojal, CultiBaga, and Mirtilsul for kindly supplying the biomass. Publisher Copyright: © 2023 The Author(s)Replacement of synthetic colorants with natural ones is a current marketing trend. Nevertheless, the naturally occurring blue color is rare compared to other colours. In this work, centrifugal partition chromatography (CPC) process was developed as a more efficient and sustainable alternative to reversed phase column chromatography (RP-CC) for the preparative-scale purification of portisins. The strategy began with the extraction of anthocyanins from blueberry surplus and hemi-synthesis of respective portisins. Then, the CPC method development started with the biphasic solvent system selection followed by the optimization of the operating parameters and ended up with a comparison with RP-CC. Aiming at maximizing the portisin content, process throughput, efficiency, and minimizing the environmental risk factor, the effect of sample load (100–500 mg/100 mL of column volume), mobile phase flow rate (10–20 mL/min), and rotation speed (1000–1600 rpm) was evaluated. The two-phase solvent system consisted of tert‑butyl‑methyl ether, n-butanol, acetonitrile, and water (volume ratio 2:2:1:5) acidified with 0.1 vol.% of HCl was selected. The best conditions were 464 mg of sample/100 mL of column volume, 20 mL/min of mobile phase flow rate, and 1600 rpm of rotation speed at reversed phase mode, allowing the purification of portisins by 5-fold. Compared to the RP-CC, the CPC process efficiency was 2.4 times higher, while the CPC process environmental risk factor was 5.5 times lower. Overall, this study suggests that CPC can be considered an effective, and sustainable alternative process for the preparative isolation of portisins. With this purification approach, the blueberry surplus has been valorized and a naturally derived product has been prepared, allowing its subsequent use as a natural blue colorant.publishersversionpublishe

Forcing and mixing processes in the Amazon estuary: A study case

The research area of this paper is located at the estuary of the Amazon River (Brazil), more precisely at the river mouth (parallels 00° 30'N and 1° 30'N and meridians 049° 00' W and 050° 00'W). This paper presents the results of air movement analysis on the surface atmospheric circulation over the Mouth of the Amazonas River, salinity and temperature measures as well as measurements of currents, carried out along a longitudinal section in the navigation canal region of the Northern Bar of the Amazon River (Barra Norte do Rio Amazonas) in June 2006, during the river flood season in the quadrature tide. This paper purports to contribute towards better interpreting the dynamics effect in hydrodynamic, meteorological and hydrographical parameters at the river mouth. The conclusion drawn from an examination of the issues and related research is that: a) the saline wedge-type stratification can be seen approximately 100km away from the mouth of the Amazon River during the end of the rainy season in the quadrature tide; b) probably, at Amazon estuary quadrature entrainment processes are predominant and are the ones responsible for increased salinity in surface layer, whereas turbulence scattering mixing is secondary to it. c) The large flow of fresh water from the Amazon River at the end of the rainy season implies the displacement of the front saline position over the internal Amazon continental platform. d) The tidal wave shows a positive asymmetry in the canal, with floods lasting less than the ebb tide. This asymmetry decreases towards the ocean, eventually becoming reversed in the presence of a saline wedge. The speeds, however, have a negative asymmetry, with more intense ebb tides, due to the river flow and is more evident by the existence of quadrature tides. e) The progressive behavior of the tidal wave in its propagation in the Northern Channel as well as the effect of morphology on the discharge were observed, with the canal configuration causing the first four anchoring points of the tide to propagate in a straight direction. f) The average climatology of the wind shearing vector shows that it is predominantly zonal over the Atlantic. g) The shearing intensification near the coastal area is according to the zonal wind intensification pattern. The Amazon estuary has unusual characteristics in relation to many established paradigms of estuarine physics; therefore, many more detailed studies are necessary to understand this system’s turbulent processes

Single-Objective Front Optimization: Application to RF Circuit Design

This paper proposes a new algorithm which promotes well distributed non-dominated fronts in the parameters space when a single- objective function is optimized. This algorithm is based on ǫ-dominance concept and maxmin sorting scheme. Besides that, the paper also presents the results of the algorithm when it is used in the automated synthesis of optimum performance CMOS radiofrequency and microwave binary-weighted differential switched capacitor arrays (RFDSCAs). The genetic synthesis tool optimizes a fitness function which is based on the performance parameter of the RFDSCAs. To validate the proposed design methodology, a CMOS RFDSCA is synthesized, using a 0.25 μm BiCMOS technology.N/