Αξιολόγηση μοντέλων πρόβλεψης Μηχανικής μάθησης με την χρήση των Χρονοσειρών του Bitcoin και του Ethereum

Το θέμα της μεταπτυχιακής εργασίας αφορά την αξιολόγηση μεθόδων μηχανικής μάθησης για την πρόβλεψη τιμών χρονοσειρών καθώς και η σύγκριση αυτών των προβλέψεων με διαφορετικές παραμέτρους. Λόγω της ταχείας ανάπτυξης της επιστήμης και της τεχνολογίας τα τελευταία χρόνια, οι μέθοδοι μηχανικής μάθησης προσφέρουν πολλές δυνατότητες σε πολλούς τομείς, όπως η πρόβλεψη μελλοντικών τιμών χρονοσειρών. Σκοπός αυτής της εργασίας είναι τόσο η θεωρητική όσον αφορά την βαθιά μάθηση όσο και το πρακτικό μέρος αποβλέπει στην αξιολόγηση των μοντέλων πρόβλεψης των δύο τύπων τεχνητών νευρωνικών δικτύων που επιλέχτηκαν. Το πρώτο μέρος της εργασίας περιλαμβάνει το απαιτούμενο θεωρητικό υπόβαθρο, όπως τα βασικά στοιχεία της Μηχανική Μάθησης, των τεχνητών νευρωνικών δικτύων, της βαθιάς μάθησης, των χρονοσειρών και έπειτα αναφέρονται οι βασικές ιδιότητες των κρυπτονομισμάτων. Το δεύτερο και πρακτικό μέρος της εργασίας ασχολείται με την αξιολόγηση των δύο τεχνητών νευρωνικών δικτύων που χρησιμοποιήθηκαν για την πρόβλεψη των τιμών δύο ευρέως γνωστών κρυπτονομισμάτων (Bitcoin, Ethereum). Εκπαιδεύοντας και χρησιμοποιώντας τα βαθιά νευρωνικά δίκτυα (DNN) και τα δίκτυα μακροπρόθεσμης μνήμης (LSTM), προβλέφθηκαν οι μελλοντικές τιμές των χρονοσειρών του Bitcoin και του Εthereum και αυτές οι προβλέψεις συγκρίθηκαν αλλάζοντας την τοπολογία των δικτύων. Ταυτόχρονα, οι προβλέψεις συγκρίνονται μεταξύ τούς λαμβάνοντας υπόψη τις διαφορετικές μεθόδους εκπαίδευσης (διαφόριση και μη διαφόριση χρονοσειρών) που χρησιμοποιήθηκαν. Τέλος, οι συγκρίσεις σχετικά με την απόδοση των μοντέλων πρόβλεψης γίνεται με βάση συγκεκριμένες μετρικές (RMSE,MSE,MAE κλπ.) και μέσω ενός συστήματος κατάταξης (Score Card) από το οποίο προκύπτουν χρήσιμα συμπεράσματα.The subject of this postgraduate thesis is the study of machine learning methods to predict time series prices of two cryptocurrencies and compare these predictions with different parameters. The aim of this study is to evaluate the reliability and the performance in terms of predictability of two types of Deep learning Artificial Neural Networks ( DNN and LSTM) with the use of time series. The first part of this thesis includes the required theoretical background, such as the basics of machine learning, artificial neural networks, deep learning, time series, and the fundamentals of cryptocurrencies. The second part which is the practical part of this study focuses on the evaluation of the prediction models and the methodology that was applied to train the two types of the artificial neural networks (DNN and LSTM) .The numerical experiments are conducted using two time series from Cryptocurrency space (Bitcoin and Ethereum). In addition, the reliability of the predictions of each artificial Neural Network was evaluated by taking into account the different training methods that were used. Finally, the comparison of the proposed models was made based on specific metrics and through a Ranking system

A Deadenylase Assay by Size-Exclusion Chromatography

The shortening of the 3′-end poly(A) tail, also called deadenylation, is crucial to the regulation of mRNA processing, transportation, translation and degradation. The deadenylation process is achieved by deadenylases, which specifically catalyze the removal of the poly(A) tail at the 3′-end of eukaryotic mRNAs and release 5′-AMP as the product. To achieve their physiological functions, all deadenylases have numerous binding partners that may regulate their catalytic properties or recruit them into various protein complexes. To study the effects of various partners, it is important to develop new deadenylase assay that can be applied either in vivo or in vitro. In this research, we developed the deadenylase assay by the size-exclusion chromatography (SEC) method. The SEC analysis indicated that the poly(A) or oligo(A) substrate and the product AMP could be successfully separated and quantified. The enzymatic parameters of deadenylase could be obtained by quantifying the AMP generation. When using the commercial poly(A) as the substrate, a biphasic catalytic process was observed, which might correlate to the two distinct states of poly(A) in the commercial samples. Different lots of commercial poly(A) had dissimilar size distributions and were dissimilar in response to the degradation of deadenylase. The deadenylation pattern, processive or distributive, could also be investigated using the SEC assay by monitoring the status of the substrate and the generation kinetics of AMP and A2. The SEC assay was applicable to both simple samples using the purified enzyme and complex enzyme reaction conditions such as using protein mixtures or crude cell extracts as samples. The influence of solutes with absorption at 254 nm could be successfully eliminated by constructing the different SEC profiles

Dissimilar Roles of the Four Conserved Acidic Residues in the Thermal Stability of Poly(A)-Specific Ribonuclease

Divalent metal ions are essential for the efficient catalysis and structural stability of many nucleotidyl-transfer enzymes. Poly(A)-specific ribonuclease (PARN) belongs to the DEDD superfamily of 3′-exonucleases, and the active site of PARN contains four conserved acidic amino acid residues that coordinate two Mg2+ ions. In this research, we studied the roles of these four acidic residues in PARN thermal stability by mutational analysis. It was found that Mg2+ significantly decreased the rate but increased the aggregate size of the 54 kDa wild-type PARN in a concentration-dependent manner. All of the four mutants decreased PARN thermal aggregation, while the aggregation kinetics of the mutants exhibited dissimilar Mg2+-dependent behavior. A comparison of the kinetic parameters indicated that Asp28 was the most crucial one to the binding of the two Mg2+ ions, while metal B might be more important in PARN structural stability. The spectroscopic and aggregation results also suggested that the alterations in the active site structure by metal binding or mutations might lead to a global conformational change of the PARN molecule

From Bio-Prospecting to Field Assessment: The Case of Carvacrol Rich Essential Oil as a Potent Mosquito Larvicidal and Repellent Agent

Contemporary legislation tends to increase limitation on the use of all synthetic pesticides, promoting bio-pesticides as a safer alternative. Bio-prospecting efforts for bio-pesticides provide results, which rarely reach the industry. Present essay elaborates on our efforts to chart the path from the laboratory bench to field assessment. Eight Mediterranean wild gathered foods provided the essential oils that were assessed as mosquito control agents against the Asian tiger mosquito (Aedes albopictus). Three Lamiaceae essential oils, derived from Satureja thymbra, Origanum onites, and Thymbra spicata presented carvacrol as principal component. All exhibited DEET-like repellent performance and total larvae mortality defining the carvacrol rich essential oil (CREO) as a promising mosquito control agent. A commercial variety of Origanum vulgare ssp. hirtum, was selected as CREO source and subjected to dose-response and eco-toxicity studies. We have found significant larvicidal (LC90 of 58,747 mg/L), and repellent (0.2 μL/cm2) properties, but also severe toxicity (LC90 of 12,806 mg/L) against Macrocyclops albidus. This last figure was the limit for the larvicidal field assessment; while for the repellent evaluation was used double the minimum indication (0.4 μL/cm2). CREO was tested per se as larvicidal agent, and emulsified for both repellent and larvicidal field activity. The emulsified CREO's spatial repellent assessment showed maximum efficacy of 86% in day 1 that gradually declined in the following 2 days (81%, 69%). Both emulsified and crude CREO proved to be efficient larvicidal agents, with crude CREO (3 weeks) overrunning slightly the emulsified (2 weeks) in terms of endurance. Conclusively, CREO in its emulsified form may be considered as a promising mosquito larvicidal and repellent agent, applicable in both precautionary and emergency response measures

Involvement of the nuclear cap-binding protein complex in alternative splicing in Arabidopsis thaliana

The nuclear cap-binding protein complex (CBC) participates in 5′ splice site selection of introns that are proximal to the mRNA cap. However, it is not known whether CBC has a role in alternative splicing. Using an RT–PCR alternative splicing panel, we analysed 435 alternative splicing events in Arabidopsis thaliana genes, encoding mainly transcription factors, splicing factors and stress-related proteins. Splicing profiles were determined in wild type plants, the cbp20 and cbp80(abh1) single mutants and the cbp20/80 double mutant. The alternative splicing events included alternative 5′ and 3′ splice site selection, exon skipping and intron retention. Significant changes in the ratios of alternative splicing isoforms were found in 101 genes. Of these, 41% were common to all three CBC mutants and 15% were observed only in the double mutant. The cbp80(abh1) and cbp20/80 mutants had many more changes in alternative splicing in common than did cbp20 and cbp20/80 suggesting that CBP80 plays a more significant role in alternative splicing than CBP20, probably being a platform for interactions with other splicing factors. Cap-binding proteins and the CBC are therefore directly involved in alternative splicing of some Arabidopsis genes and in most cases influenced alternative splicing of the first intron, particularly at the 5′ splice site

Geographic distribution of the V1016G knockdown resistance mutation in aedes albopictus. A warning bell for Europe

Background: Colonization of large part of Europe by the Asian tiger mosquito Aedes albopictus is causing autochthonous transmission of chikungunya and dengue exotic arboviruses. While pyrethroids are recommended only to reduce/limit transmission, they are widely implemented to reduce biting nuisance and to control agricultural pests, increasing the risk of insurgence of resistance mechanisms. Worryingly, pyrethroid resistance (with mortality < 70%) was recently reported in Ae. albopictus populations from Italy and Spain and associated with the V1016G point mutation in the voltage-sensitive sodium channel gene conferring knockdown resistance (kdr). Genotyping pyrethroid resistance-associated kdr mutations in field mosquito samples represents a powerful approach to detect early signs of resistance without the need for carrying out phenotypic bioassays which require availability of live mosquitoes, dedicated facilities and appropriate expertise.Methods: Here we report results on the PCR-genotyping of the V1016G mutation in 2530 Ae. albopictus specimens from 69 sampling sites in 19 European countries.Results: The mutation was identified in 12 sites from nine countries (with allele frequencies ranging from 1 to 8%), mostly distributed in two geographical clusters. The western cluster includes Mediterranean coastal sites from Italy, France and Malta as well as single sites from both Spain and Switzerland. The eastern cluster includes sites on both sides of the Black Sea in Bulgaria, Turkey and Georgia as well as one site from Romania. These results are consistent with genomic data showing high connectivity and close genetic relationship among West European populations and a major barrier to gene flow between West European and Balkan populations.Conclusions: The results of this first effort to map kdr mutations in Ae. albopictus on a continental scale show a widespread presence of the V1016G allele in Europe, although at lower frequencies than those previously reported from Italy. This represents a wake-up call for mosquito surveillance programs in Europe to include PCR-genotyping of pyrethroid resistance alleles, as well as phenotypic resistance assessments, in their routine activities

Feasibility, acceptability, and effectiveness of non-pharmaceutical interventions against infectious diseases among crisis-affected populations: a scoping review

BACKGROUND: Colonization of large part of Europe by the Asian tiger mosquito Aedes albopictus is causing autochthonous transmission of chikungunya and dengue exotic arboviruses. While pyrethroids are recommended only to reduce/limit transmission, they are widely implemented to reduce biting nuisance and to control agricultural pests, increasing the risk of insurgence of resistance mechanisms. Worryingly, pyrethroid resistance (with mortality < 70%) was recently reported in Ae. albopictus populations from Italy and Spain and associated with the V1016G point mutation in the voltage-sensitive sodium channel gene conferring knockdown resistance (kdr). Genotyping pyrethroid resistance-associated kdr mutations in field mosquito samples represents a powerful approach to detect early signs of resistance without the need for carrying out phenotypic bioassays which require availability of live mosquitoes, dedicated facilities and appropriate expertise. METHODS: Here we report results on the PCR-genotyping of the V1016G mutation in 2530 Ae. albopictus specimens from 69 sampling sites in 19 European countries. RESULTS: The mutation was identified in 12 sites from nine countries (with allele frequencies ranging from 1 to 8%), mostly distributed in two geographical clusters. The western cluster includes Mediterranean coastal sites from Italy, France and Malta as well as single sites from both Spain and Switzerland. The eastern cluster includes sites on both sides of the Black Sea in Bulgaria, Turkey and Georgia as well as one site from Romania. These results are consistent with genomic data showing high connectivity and close genetic relationship among West European populations and a major barrier to gene flow between West European and Balkan populations. CONCLUSIONS: The results of this first effort to map kdr mutations in Ae. albopictus on a continental scale show a widespread presence of the V1016G allele in Europe, although at lower frequencies than those previously reported from Italy. This represents a wake-up call for mosquito surveillance programs in Europe to include PCR-genotyping of pyrethroid resistance alleles, as well as phenotypic resistance assessments, in their routine activities