Modeling stock markets through the reconstruction of market processes

Mestrado em EconomiaExistem duas maneira possíveis de interpretar a aparente natureza estocástica dos mercados financeiros: a Hipótese do mercado eficiente (HME) e um conjunto de factos estilizados que conduzem o comportamento dos mercados. Apresentamos evidência para alguns dos factos estilizados como a existência de um fenómeno de memória na volatilidade dos preços a curto prazo, um comportamento em lei de potência e dependências não lineares nos retornos. Considerando isto, construímos um modelo do mercado através de cadeias de Markov. Em seguida, desenvolvemos um algoritmo que pode ser generalizado para qualquer alfabeto de N símbolos e cadeia de Markov de comprimento K. Com esta ferramenta, somos capazes de mostrar que é, pelo menos, sempre melhor que um modelo completamente aleatório como o Passeio Aleatório. O código está escrito em MATLAB e é mantido no GitHub.There are two possible ways of interpreting the seemingly stochastic nature of financial markets: the Efficient Market Hypothesis (EMH) and a set of stylized facts that drive the behavior of the markets. We show evidence for some of the stylized facts such as memory-like phenomena in price volatility in the short term, a power-law behavior and non-linear dependencies on the returns. Given this, we construct a model of the market using Markov chains. Then, we develop an algorithm that can be generalized for any N-symbol alphabet and K-length Markov chain. Using this tool, we are able to show that it's, at least, always better than a completely random model such as a Random Walk. The code is written in MATLAB and maintained in GitHub.info:eu-repo/semantics/publishedVersio

Extensive Investigation on the Effect of Niobium Insertion on the Physical and Biological Properties of 45S5 Bioactive Glass for Dental Implant

Funding Information: This research was funded by FEDER funds through the COMPETE 2020 Program and National Funds through FCT—Portuguese Foundation for Science and Technology under the project LISBOA-01-0247-FEDER-039985/POCI-01-0247-FEDER-039985, LA/P/0037/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication—i3N, UIDP/04378/2020 and UIDB/04378/2020 of the Research Unit on Applied Molecular Biosciences—UCIBIO, and LA/P/0140/2020 of the Associate Laboratory Institute for Health and Bioeconomy—i4HB. S.K. Jakka acknowledges FCT—Fundaçao para a Ciência e a Tecnologia, Portugal, I.P., in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of article 23 of the Decree Law 57/2016 of 29 August, changed by Law 57/2017 of 19 July. Publisher Copyright: © 2023 by the authors.Dental implants have emerged as one of the most consistent and predictable treatments in the oral surgery field. However, the placement of the implant is sometimes associated with bacterial infection leading to its loss. In this work, we intend to solve this problem through the development of a biomaterial for implant coatings based on 45S5 Bioglass® modified with different amounts of niobium pentoxide (Nb2O5). The structural feature of the glasses, assessed by XRD and FTIR, did not change in spite of Nb2O5 incorporation. The Raman spectra reveal the Nb2O5 incorporation related to the appearance of NbO4 and NbO6 structural units. Since the electrical characteristics of these biomaterials influence their osseointegration ability, AC and DC electrical conductivity were studied by impedance spectroscopy, in the frequency range of 102–106 Hz and temperature range of 200–400 K. The cytotoxicity of glasses was evaluated using the osteosarcoma Saos-2 cells line. The in vitro bioactivity studies and the antibacterial tests against Gram-positive and Gram-negative bacteria revealed that the samples loaded with 2 mol% Nb2O5 had the highest bioactivity and greatest antibacterial effect. Overall, the results showed that the modified 45S5 bioactive glasses can be used as an antibacterial coating material for implants, with high bioactivity, being also non-cytotoxic to mammalian cells.publishersversionpublishe

Neuron-specific proteotoxicity of mutant ataxin-3 in C. elegans: rescue by the DAF-16 and HSF-1 pathways

The risk of developing neurodegenerative diseases increases with age. Although many of the molecular pathways regulating proteotoxic stress and longevity are well characterized, their contribution to disease susceptibility remains unclear. In this study, we describe a new Caenorhabditis elegans model of Machado–Joseph disease pathogenesis. Pan-neuronal expression of mutant ATXN3 leads to a polyQ-length dependent, neuron subtype-specific aggregation and neuronal dysfunction. Analysis of different neurons revealed a pattern of dorsal nerve cord and sensory neuron susceptibility to mutant ataxin-3 that was distinct from the aggregation and toxicity profiles of polyQ-alone proteins. This reveals that the sequences flanking the polyQ-stretch in ATXN3 have a dominant influence on cell-intrinsic neuronal factors that modulate polyQ-mediated athogenesis. Aging influences the ATXN3 phenotypes which can be suppressed by the nregulation of the insulin/insulin growth factor-1-like signaling pathway and activation of heat shock factor-1.This work was supported by grants from Fundacão Ciência eTecnologia (FCT) to P.M. (PTDC/SAU-GMG/64076/2006, PTDC/SAU-GMG/112617/2009, SFRH/BD/27258/2006 to A.T.C., UMINHO/BI/052/2010 to A.J. and SFRH/BD/51059/2010 to A.N.C.), from the National Ataxia Foundation to PM and from the National Institutes of Health (NIGMS, NIA and NINDS) to R.M. This work was also granted by the Hospital San Rafael (Coruna) with the Rafael Hervada prize on Biomedical Research (2010)

Uso de drogas e o aumento das infecções sexualmente transmissíveis: uma revisão sistemática: Drug use and the increase in sexually transmitted infections: a systematic review

Populações de usuários de drogas têm sido associadas a epidemias de infecções ou Infecções Sexualmente Transmissíveis, especialmente a infecção pelo HIV (que está associada a drogas injetáveis, uso de equipamentos contaminados para drogas injetáveis e sexo inseguro). A droga mais associada às DSTs é a cocaína fumável de base livre (crack), devido ao aumento dos comportamentos sexuais de risco. Diante disso, o presente estudo teve como objetivo compreender o impacto do uso de drogas no aumento das infecções sexualmente transmissíveis. Para isso, adotou-se como metodologia a revisão sistemática de literatura, realizando buscas nas bases de dados Scielo, Pubmed e BVS/Medline a partir do uso de descritores DeCS/MeSH e aplicação de critérios de inclusão e exclusão. A partir da análise e interpretação dos dados, concluiu-se que que pessoas que fazem uso abusivo de drogas lícitas ou ilícitas, sejam elas mulheres, homens, adolescentes, jovens, adultos, idosos, em situação de rua ou não, tendem a desenvolver comportamentos vulneráveis que pode resultar em IST. Somado a isso, enquanto comportamento de risco, tem-se a preferência por não usar preservativo, seja em relações sexuais com pessoas monogâmicas como com dois ou mais parceiros. Nesses casos, tanto o uso exacerbado de drogas como a falta de informação sobre comportamento sexual demonstram-se insuficientes

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

ATLANTIC EPIPHYTES: a data set of vascular and non-vascular epiphyte plants and lichens from the Atlantic Forest

Epiphytes are hyper-diverse and one of the frequently undervalued life forms in plant surveys and biodiversity inventories. Epiphytes of the Atlantic Forest, one of the most endangered ecosystems in the world, have high endemism and radiated recently in the Pliocene. We aimed to (1) compile an extensive Atlantic Forest data set on vascular, non-vascular plants (including hemiepiphytes), and lichen epiphyte species occurrence and abundance; (2) describe the epiphyte distribution in the Atlantic Forest, in order to indicate future sampling efforts. Our work presents the first epiphyte data set with information on abundance and occurrence of epiphyte phorophyte species. All data compiled here come from three main sources provided by the authors: published sources (comprising peer-reviewed articles, books, and theses), unpublished data, and herbarium data. We compiled a data set composed of 2,095 species, from 89,270 holo/hemiepiphyte records, in the Atlantic Forest of Brazil, Argentina, Paraguay, and Uruguay, recorded from 1824 to early 2018. Most of the records were from qualitative data (occurrence only, 88%), well distributed throughout the Atlantic Forest. For quantitative records, the most common sampling method was individual trees (71%), followed by plot sampling (19%), and transect sampling (10%). Angiosperms (81%) were the most frequently registered group, and Bromeliaceae and Orchidaceae were the families with the greatest number of records (27,272 and 21,945, respectively). Ferns and Lycophytes presented fewer records than Angiosperms, and Polypodiaceae were the most recorded family, and more concentrated in the Southern and Southeastern regions. Data on non-vascular plants and lichens were scarce, with a few disjunct records concentrated in the Northeastern region of the Atlantic Forest. For all non-vascular plant records, Lejeuneaceae, a family of liverworts, was the most recorded family. We hope that our effort to organize scattered epiphyte data help advance the knowledge of epiphyte ecology, as well as our understanding of macroecological and biogeographical patterns in the Atlantic Forest. No copyright restrictions are associated with the data set. Please cite this Ecology Data Paper if the data are used in publication and teaching events. © 2019 The Authors. Ecology © 2019 The Ecological Society of Americ