Data frequency and forecast performance for stock markets: A deep learning approach for DAX index

[EN] Due to non-stationary, high volatility, and complex nonlinear patterns of stock market fluctuation, it is demanding to predict the stock price accurately. Nowadays, hybrid and ensemble models based on machine learning and economics replicate several patterns learned from the time series. This paper analyses the SARIMAX models in a classical approach and using AutoML algorithms from the Darts library. Second, a deep learning procedure predicts the DAX index stock prices. In particular, LSTM (Long Short-Term Memory) and BiLSTM recurrent neural networks (with and without stacking), with optimised hyperparameters architecture by KerasTuner, in the context of different time-frequency data (with and without mixed frequencies) are implemented. Nowadays great interest in multi-step-ahead stock price index forecasting by using different time frequencies (daily, one-minute, five-minute, and ten-minute granularity), focusing on raising intraday stock market prices. The results show that the BiLSTM model forecast outperforms the benchmark models –the random walk and SARIMAX - and slightly improves LSTM. More specifically, the average reduction error rate by BiLSTM is 14-17% compared to SARIMAX. According to the scientific literature, we also obtained that high-frequency data improve the forecast accuracy by 3-4% compared with daily data since we have some insights about volatility driving forces.Mendes, DA.; Ferreira, N.; Mendes, V. (2023). Data frequency and forecast performance for stock markets: A deep learning approach for DAX index. Editorial Universitat Politècnica de València. 39-40. http://hdl.handle.net/10251/201760394

First- and second-order phase transitions in Ising models on small world networks, simulations and comparison with an effective field theory

We perform simulations of random Ising models defined over small-world networks and we check the validity and the level of approximation of a recently proposed effective field theory. Simulations confirm a rich scenario with the presence of multicritical points with first- or second-order phase transitions. In particular, for second-order phase transitions, independent of the dimension d_0 of the underlying lattice, the exact predictions of the theory in the paramagnetic regions, such as the location of critical surfaces and correlation functions, are verified. Quite interestingly, we verify that the Edwards-Anderson model with d_0=2 is not thermodynamically stable under graph noise.Comment: 12 pages, 12 figures, 1 tabl

Calcifilaxia: Revisão da Literatura a Propósito de 2 Casos Clínicos

Calciphylaxis is a rare and devastating obliterative vasculopathy, leading to ischemia and subcutaneous necrosis. In most cases it affects patients with renal disease and is associated with high morbidity and mortality. We present two case reports followed recently in our department, and a literature review on this topic. Case one refers to an 80 -year -old Caucasian woman with chronic kidney disease stage 5 and primary hyperparathyroidism with secondary brown tumour and calciphylaxis. Case two refers to a 59 -year -old Caucasian woman admitted with severe nephrotic syndrome associated with amyloidosis, that developed a catastrophic picture of calciphylaxis, ending in the patient’s death. There is a critical need to understand the pathogenesis of calciphylaxis. Its comprehension is the only way to improve the survival of these patients, and may help to elucidate the pathophysiology of vascular calcification in general. Educating physicians in the prevention and early detection of calciphylaxis is crucial. Only by increasing the knowledge about risk factors, pathophysiology, response to treatment and outcome, will we be able to improve prophylaxis and therapy of patients with calciphylaxis, decreasing the high mortality of this entity

Seismic vulnerability assessment of the old city centre of Seixal, Portugal

The seismic vulnerability assessment of old traditional masonry building stocks, in a seismic risk mitigation perspective, is truly essential not only for buildings with recognized historical and patrimonial value, but also, in relation to regular buildings. In this sense, this paper approaches the issue of the seismic vulnerability assessment of masonry buildings through the application of a simplified methodology to building stock of the old city centre of Seixal, Portugal. This methodology is based on a vulnerability index, suitable in the evaluation of damage and in the creation of large scale loss scenarios (economical and human). Over 500 buildings were evaluated in accordance with the referred methodology and the results obtained were then integrated into a Geographical Information System tool. The integration of this kind of vulnerability and loss results into a GIS tool allows that city councils or regional authorities make their decisions based on a global view of the site under analysis, which led to more accurate and faster decisions either in terms of risk mitigation strategies or rehabilitation plans. This tool can also assumes great importance in the construction of safety and rescue plans

Vulnerability assessment of urban building stock: a hierarchic approach

In the last decades the evaluation of the seismic risk are of rising concern, considered essential in the activity and definition of strategy planning and urban management. The evaluation of the seismic vulnerability of the existent building stock in the perspective of the seismic risk mitigation should not be placed only in relation to the isolated buildings of relevant historical and cultural importance, but also, in relation to the agglomerate of buildings in urban centres. The chronological construction process frequently results in characteristic heterogeneity of masonry and wall connection quality. In addition, buildings do not constitute independent units given that they share the mid-walls with adjacent buildings and the façade walls are aligned. This way, as post-seismic observations proved, buildings do not have an independent structural behaviour, but they interact amongst themselves, mainly for horizontal actions and so the structural performance should be studied at the level of the aggregate and not only for each isolated building. In most cases, for masonry structures there is no need for sophisticated dynamic analyses for seismic resistance verification or vulnerability assessment. This is even more relevant when an assessment at the level of a city centre is pursued. In this work, the results of evaluation of the vulnerability will be presented in accordance to three proposed methodologies based on a vulnerability index that consequently allows the evaluation of damage and creation of loss scenarios (economical and human) not only at the level of the building and its façade walls but also at the level of the aggregates. It will be discussed and evaluated the application of the referred methodologies and its integration in an SIG platform

Mead production: Fermentative performance of yeasts entrapped in different concentrations of alginate

Mead is an alcoholic drink known since ancient times, produced by yeast fermenting diluted honey. However, the production of mead has suffered in recent years, partially owing to the lack of scientific progress in this field. In this study, two strains of Saccharomyces cerevisiae, QA23 and ICVD47, were immobilized in 2 or 4% (w/v) alginate beads to assess the most effective alginate concentration for yeast immobilization to produce mead. Neither of the alginate concentrations was able to prevent cell leakage from the beads. The fermentation length was 120h for both yeast strains. In all cases, at the end of the fermentation, the number of cells entrapped in the beads was higher than the number of free cells, and the total 4% alginate bead wet weight was significantly higher than the 2% alginate bead wet weight. In addition, the evaluation of mead quality showed that the yeast strain had significantly more influence on the physicochemical characteristics than the alginate concentration. Although the yeasts immobilized in the two alginate concentrations were able to perform the fermentation, further research is needed in order to understand the evolution of the yeast population inside the beads throughout the fermentative process.The research presented in this paper was partially funded by the Fundação para a Ciência e Tecnologia, and by the PTDC project (contract PTDC/AGR-ALI/68284/2006). A.P.P. is the recipient of a PhD grant from FCT (SFRH/BD/45820/2008).info:eu-repo/semantics/publishedVersio

Do shame and perfectionistic self-presentation explain the link between early affiliative memories and eating psychopathology?

This study explored a model examining the impact that early affiliative memories (with family and peers) presents on eating psychopathology, and whether this link is carried by the mechanisms of external shame and body image-related perfectionistic self-presentation. This study’s sample comprised 480 female college students, who completed the self-report measures of interest. Path analyses’ results revealed that this model accounted for 48% of disordered eating’s variance. Furthermore, results showed that 26% of external shame was explained by early memories of warmth and safeness, and that 19% of body image-related perfectionistic self-presentation was explained by the lack of recall of these affiliative memories, through increased levels of external shame. These findings seem to suggest that the lack of these positive memories is associated with higher levels of shame (feelings of inferiority and unattractiveness), and with higher tendencies to adopt body image-related perfectionistic strategies, that seem to explain excessive eating concern and rigid control of one’s eating behaviours. This study offers important insights for future research and for the development of intervention programs, by revealing the importance of assessing and targeting shame and perfectionistic strategies and suggesting the importance of promoting adaptive emotion regulation strategies to deal with adverse memories

A BWM approach to determinants of sustainable entrepreneurship in small and medium-sized enterprises

Small and medium-sized enterprises (SMEs) constitute an extremely large percentage of most nations’ businesses. These companies are also expressing growing concerns about sustainability and its strategic integration into operations. However, SMEs have been prevented from making investments in sustainability by the absence of a holistic view of this topic, an overemphasis on an economic perspective, and the consequent devaluation of environmental and social perspectives. In this context, greater importance needs to be given to investigating SME sustainability and building a transparent, holistic, and realistic business model. The present study combines cognitive mapping and the best worst method (BWM) to identify determinants of sustainable entrepreneurship in SMEs. These techniques were applied in two meetings with a panel of specialists with knowledge about and experience in this subject matter. The insights obtained during the two panel meetings allowed the proposed process-oriented approach to assist decision-makers in analyzing a sample of SMEs and selecting the ones that best match the following clusters of decision criteria: (1) entrepreneur profile; (2) firm internal characteristics; (3) economic factors; (4) other external factors; and (5) market. The results were validated by four representatives of the Portuguese Institute for Small and Medium-sized Enterprises and Innovation (Instituto de Apoio às Pequenas e Médias Empresas e à Inovação (IAPMEI) in Portuguese). The study’s contributions and limitations are also discussed.info:eu-repo/semantics/publishedVersio

Impact of inoculum size on mead aroma compounds formation by wine strains of S. cerevisiae

Mead is a traditional drink, containing 8-18% (v/v) of ethanol, which results from the alcoholic fermentation of diluted honey performed by yeasts. It has been reported that mead fermentation is a time-consuming process, and an important objective of mead makers is to reduce the fermentation time without decreasing the quality of the end product. A significant time can be saved in the fermentation process by increasing the pitching rate, i.e., the amount of suspended yeast cells added to a batch fermenter. However, an increase in the inoculum size could also have deleterious side effects on the flavour profile of the final beverage. Therefore, the aim of this study was to investigate the impact of the inoculum size of two commercial winemaking strains of Saccharomyces cerevisiae (Lalvin QA23 and Lalvin ICV D47) on the mead volatile aromatic compound production. Honey must was prepared according to the recipe developed by our team, supplemented with potassium tartrate, pH adjusted to 3.7 with malic acid and the nitrogen concentration adjusted to 267 mg/L with diammonium phosphate. The appropriate amounts of inoculum were pitched into the honey-must to obtain five different pitching rates. Mead produced was analysed for major volatile compounds by GC-FID and for minor volatile compounds by GC-MS. A total of twenty-seven fermentative aroma compounds including alcohols, esters, volatile phenols, volatile fatty acids and carbonyl compounds were identified and quantified in meads. It was observed quantitative differences in aroma profiles, confirming the contribution of both yeast strain and inoculum size on the sensory characteristics of meads. Of the twenty-seven volatile compounds quantified, fourteen could contribute to mead aroma and flavour because their concentrations rose above their respective thresholds. In general, the formation of these compounds was particularly pronounced at low pitching rates. The esters ethyl hexanoate, ethyl octanoate and isoamyl acetate were the most powerful odorants detected in all meads. In addition to this quantitative analysis of the impact of strain selection and inoculum size on mead aroma, a complementary sensorial evaluation of the meads would yield further useful information for mead producers