Decay of distance autocorrelation and Lyapunov exponents

This work presents numerical evidences that for discrete dynamical systems with one positive Lyapunov exponent the decay of the distance autocorrelation is always related to the Lyapunov exponent. Distinct decay laws for the distance autocorrelation are observed for different systems, namely exponential decays for the quadratic map, logarithmic for the H\'enon map and power-law for the conservative standard map. In all these cases the decay exponent is close to the positive Lyapunov exponent. For hyperbolic conservative systems, the power-law decay of the distance autocorrelation tends to be guided by the smallest Lyapunov exponent.Comment: 7 pages, 8 figure

Refinement of the daily precipitation simulated by the CMIP5 models over the north of the Northeast of Brazil

The ability of the Artificial Neural Network (ANN) and the Multiple Linear Regression (MLR) in reproducing the area-average observed daily precipitation during the rainy season (Feb-Mar-Apr) over the north of the Northeast of Brazil (NEB) is examined. For the present climate of Dec-Jan-Feb from 1963 to 2003 period these statistical models are developed and validated using the observed daily precipitation and simulated from the historical outputs of 4 models of the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The simulations from all the models during DJF and FMA seasons show an anomalous intensification of the ITCZ and southward displacement in comparison with the climatology. Correlations of 0.54, 0.66 and 0.66 are found between the simulated daily precipitation of the CCSM4, GFDL_ESM2M and MIROC_ESM models during DJF season and the observed values during FMA season. Only the CCSM4 model displays a slightly reasonable agreement with the observations. A comparison between the statistical downscaling using the nonlinear (ANN) and linear model (MLR) to identify the one most suitable for the analysis of daily precipitation was made. The ANN technique provides more ability to predict the present climate when compared to MLR technique. Based on this result, we examined the accuracy of the ANN model in project the changes for the future climate period from 2055 to 2095 over the same study region. For instance, a comparison between the daily precipitation changes projected indirectly from the ANN during Feb-Mar-Apr with those projected directly from the CMIP5 models forced by RCP 8.5 scenario is made. The results suggest that ANN model weights the CMIP5 projections according to the each model ability in simulating the present climate (and its variability). In others, the ANN model is a potentially promising approach to use as a complementary tool to improvement of the seasonal numerical simulations

Anti-bacterial activity of Annona muricata Linnaeus extracts: a systematic review

Current analysis systematically reviews data available in the literature on the anti-bacterial activity of Annona muricata extracts (AME) against Staphylococcus aureus and Escherichia coli. Search was undertaken at four electronic databases and studies’ quality were assessed. Results were summarized and Minimum Inhibitory Concentration (MIC) of AME (versus antimicrobial control) against S. aureus and E. coli was the main datum analyzed. The initial database search yielded 2,433 results. We selected 14 studies and four were used for meta-analysis. The MIC ranged between 156 μg/mL and 1,024 μg/mL against S. aureus and between 256 μg/mL and 1,024 μg/mL against E. coli. The different strains of E. coli studied were more sensitive to AME than those of S. aureus. The differences mean concentrations and standard deviations between AME and antimicrobials were 101.91 and 946.05 for E. coli, and 388.90 and 970.61 for S. aureus respectively. The heterogeneity of data is highlighted. Different methodologies were used, several studies didn’t include antibiotics as control, antibiotics were different and various concentrations of extracts were tested. Studies showed possibilities of the plant under analysis as a source of new phytochemical compounds against microorganisms.info:eu-repo/semantics/publishedVersio

Terahertz array beamforming using low-voltage graphene-modulators

The terahertz band (0.1-10 THz) is a vastly un-used segment of the spectrum, set to be used by future 6G communications, for its super high transmission speeds. Not only that, but radiation in the below infra-red band is also finding more uses in various applications, such as sensing and medical, where THz may enable innovative solutions. However, technology for this part of the spectrum is still in its infant stages of development. From emitters, to re-ceivers, signal generators, antennas, the devices aren’t yet matured or even realized. In this work we present a 4x2 antenna array, whose diagram is controlled via graphene modulators, designed having in mind a fabrication process available for 8 inch wafers. Chemical potentials of 0.1 to 0.4 eV are used, which corresponds to maximum bias tensions of 5 V, that should be more easily implemented with conventional electronics. This allows a comprehensive dia-gram control, reaching 360 degrees of reach in Phi, and at least 15 degrees in theta (Figure 1). Theoretically, a plasmonic array with graphene modulators could use graphene radiators to achieve incredible size reduction. In practice, graphene will not have enough efficiency to serve as a useful radiator, and metallic radiators should serve as the main emitting elements (Figure 2). This means a compromise between array dimensions and radiation efficiency, as the metallic elements do not support the plas-monic phenomenon at 1 THz. Additionally, graphene on-chip electronics implementation in the micro and nanometer range presents sev-eral other challenges. Adding additional gra-phene elements besides the modulators may also not be feasible with current available fabri-cation processes and measuring capabilities, or even in a functional sense. Some planned-for-fabrication devices are pre-sented. Their architecture was designed to facil-itate measurements in probe-less THz meas-urement ranges. The fabrication masks are ready, and the devices should be relatively sim-ple to fabricate

2D electronics based on graphene field effect transistors: tutorial for modelling and simulation

This paper provides modeling and simulation insights into field-effect transistors based on graphene (GFET), focusing on the devices’ architecture with regards to the position of the gate (top-gated graphene transistors, back-gated graphene transistors, and top-/back-gated graphene transistors), substrate (silicon, silicon carbide, and quartz/glass), and the graphene growth (CVD, CVD on SiC, and mechanical exfoliation). These aspects are explored and discussed in order to facilitate the selection of the appropriate topology for system-level design, based on the most common topologies. Since most of the GFET models reported in the literature are complex and hard to understand, a model of a GFET was implemented and made available in MATLAB, Verilog in Cadence, and VHDL-AMS in Simplorer—useful tools for circuit designers with different backgrounds. A tutorial is presented, enabling the researchers to easily implement the model to predict the performance of their devices. In short, this paper aims to provide the initial knowledge and tools for researchers willing to use GFETs in their designs at the system level, who are looking to implement an initial setup that allows the inclusion of the performance of GFETs.This research was funded by PTDC/EEI-TEL/29670/2017—(POCI-01-0145-FEDER-029670); co-financed by the European Regional Development Fund (ERDF), and through COMPETE 2020, by grant SFRH/BD/137529/2018

A comprehensive review on photoacoustic-based devices for biomedical applications

The photoacoustic effect is an emerging technology that has sparked significant interest in the research field since an acoustic wave can be produced simply by the incidence of light on a material or tissue. This phenomenon has been extensively investigated, not only to perform photoacoustic imaging but also to develop highly miniaturized ultrasound probes that can provide biologically meaningful information. Therefore, this review aims to outline the materials and their fabrication process that can be employed as photoacoustic targets, both biological and non-biological, and report the main components’ features to achieve a certain performance. When designing a device, it is of utmost importance to model it at an early stage for a deeper understanding and to ease the optimization process. As such, throughout this article, the different methods already implemented to model the photoacoustic effect are introduced, as well as the advantages and drawbacks inherent in each approach. However, some remaining challenges are still faced when developing such a system regarding its fabrication, modeling, and characterization, which are also discussed.This work was supported by Fundação para a Ciência e Tecnologia national funds, under the national support to R&D units grant, through the reference project UIDB/04436/2020 and UIDP/04436/2020

Attitudes toward Credit and Finances among College Students in Brazil and the United States

Although research on credit card debt in developed countries has identified predictors of debt among college students, it is unknown whether these same predictors apply in emerging markets, such as Brazil. To examine this issue, a total of 1257 college students, 814 from Brazil and 443 from the United States, participated in a study exploring the utility of a theory of planned behavior as a predictor of credit card debtand student loans among college students, as well as perceived financial well-being. Compared to the Brazilian participants, the American sample was more financially self-confident, reported better financial well-being, and was more likely to believe that credit cards are negative. Similar predictors of financial well-being emerged in the samples. Specifically, parenting practices related to money and better self-reported delay of gratification are related to more positive financial attitudes and lower levels of debt. Although the debt to income ratio among card holders was similar, Brazilian students held more credit cards than American students. Greater delay of gratification was related to lower levels of student loans in the United States, but there were no significant predictors of student loans in Brazil