University of Thessaly
Recent publications
Structural identification and damage detection can be generalized as the simultaneous estimation of input forces, physical parameters, and dynamical states. Although Kalman-type filters are efficient tools to address this problem, the calibration of noise covariance matrices is cumbersome. For instance, calibration of input noise covariance matrix in augmented or dual Kalman filters is a critical task since a slight variation in its value can adversely affect estimations. The present study develops a Bayesian Expectation-Maximization (BEM) methodology for the uncertainty quantification and propagation in coupled input-state-parameter-noise identification problems. It also proposes the incorporation of input dummy observations for stabilizing low-frequency components of the latent states and mitigating potential drifts. In this respect, the covariance matrix of the dummy observations is also calibrated based on the measured data. Additionally, an explicit formulation is provided to study the theoretical observability of the Bayesian estimators, which helps characterize the minimum sensor requirements. Ultimately, the BEM is tested and verified through numerical and experimental examples, wherein sensor configurations, multiple input forces, and abrupt stiffness changes are investigated. It is confirmed that the BEM provides accurate estimations of states, input, and parameters while characterizing the degree of belief in these estimations based on the posterior uncertainties driven by applying a Bayesian perspective.
In this research, we design an open, easy-to-use robotics platform for education applications, focused on primary education. Our platform is statistically evaluated and is modular, expandable, and scalable in terms of supporting the development of new modules. Our proposed platform, in contrast to other commercial ones, is easy to use, cheap, and modular. Additionally, we present initial results regarding the evaluation of the usage of the proposed robotic structure under the technology acceptance model (TAM) in terms of easiness of usage. According to the results, the proposed open educational robotic platform shows a positive effect toward its usage by active teachers.
Background Recent multicenter studies identified COVID-19 as a risk factor for invasive pulmonary aspergillosis (IPA). However, no large multicenter study has compared the incidence of IPA between COVID-19 and influenza patients. Objectives To determine the incidence of putative IPA in critically ill SARS-CoV-2 patients, compared with influenza patients. Methods This study was a planned ancillary analysis of the coVAPid multicenter retrospective European cohort. Consecutive adult patients requiring invasive mechanical ventilation for > 48 h for SARS-CoV-2 pneumonia or influenza pneumonia were included. The 28-day cumulative incidence of putative IPA, based on Blot definition, was the primary outcome. IPA incidence was estimated using the Kalbfleisch and Prentice method, considering extubation (dead or alive) within 28 days as competing event. Results A total of 1047 patients were included (566 in the SARS-CoV-2 group and 481 in the influenza group). The incidence of putative IPA was lower in SARS-CoV-2 pneumonia group (14, 2.5%) than in influenza pneumonia group (29, 6%), adjusted cause-specific hazard ratio (cHR) 3.29 (95% CI 1.53–7.02, p = 0.0006). When putative IPA and Aspergillus respiratory tract colonization were combined, the incidence was also significantly lower in the SARS-CoV-2 group, as compared to influenza group (4.1% vs. 10.2%), adjusted cHR 3.21 (95% CI 1.88–5.46, p < 0.0001). In the whole study population, putative IPA was associated with significant increase in 28-day mortality rate, and length of ICU stay, compared with colonized patients, or those with no IPA or Aspergillus colonization. Conclusions Overall, the incidence of putative IPA was low. Its incidence was significantly lower in patients with SARS-CoV-2 pneumonia than in those with influenza pneumonia. Clinical trial registration The study was registered at ClinicalTrials.gov, number NCT04359693 .
Objective The study of the circadian clock and its mechanisms is easily facilitated through clock resetting in cell culture. Among the various established synchronizers of the circadian clock in cell culture (temperature, serum shock, glucocorticoids), the artificial glucocorticoid Dexamethasone (DEX) is the most widely used. DEX treatment as a protocol to reset the circadian clock in culture gives simple readout with minimal laboratory requirements. Even though there are many studies regarding clock resetting in culture using DEX, reference points or expression patterns of core clock genes and their protein products are scarce and sometimes contradict other works with similar methodology. We synchronise a cell line of human origin with DEX to be used for studies on circadian rhythms. Results We treat HEK 293T cells with DEX and describe the patterns of mRNA and proteins of core clock regulators, while making a clear point on how CLOCK is less than an ideal molecule to help monitor rhythms in this cell line.
Background Mean circulatory filling pressure (Pmcf) provides information on stressed volume and is crucial for maintaining venous return. This study investigated the Pmcf and other determinants of venous return in dysrhythmic and asphyxial circulatory shock and arrest. Methods Twenty Landrace/Large-White piglets were allocated into two groups of 10 animals each. In the dysrhythmic group, ventricular fibrillation was induced with a 9 V cadmium battery, while in the asphyxia group, cardiac arrest was induced by stopping and disconnecting the ventilator and clamping the tracheal tube at the end of exhalation. Mean circulatory filling pressure was calculated using the equilibrium mean right atrial pressure at 5–7.5 s after the onset of cardiac arrest and then every 10 s until 1 min post-arrest. Successful resuscitation was defined as return of spontaneous circulation (ROSC) with a MAP of at least 60 mmHg for a minimum of 5 min. Results After the onset of asphyxia, a ΔPmca increase of 0.004 mmHg, 0.01 mmHg, and 1.26 mmHg was observed for each mmHg decrease in PaO 2 , each mmHg increase in PaCO 2, and each unit decrease in pH, respectively. Mean Pmcf value in the ventricular fibrillation and asphyxia group was 14.81 ± 0.5 mmHg and 16.04 ± 0.6 mmHg ( p < 0.001) and decreased by 0.031 mmHg and 0.013 mmHg ( p < 0.001), respectively, for every additional second passing after the onset of cardiac arrest. With the exception of the 5–7.5 s time interval, post-cardiac arrest right atrial pressure was significantly higher in the asphyxia group. Mean circulatory filling pressure at 5 to 7.5 s after cardiac arrest predicted ROSC in both groups, with a cut-off value of 16 mmHg (AUC = 0.905, p < 0.001). Conclusion Mean circulatory filling pressure was higher in hypoxic hypercapnic conditions and decreased at a lower rate after cardiac arrest compared to normoxemic and normocapnic state. A Pmcf cut-off point of 16 mmHg at 5–7.5 s after cardiac arrest can highly predict ROSC.
Background Flexibility is an important component of physical fitness for competitive and recreational athletes. It is generally suggested that flexibility training should start from childhood (6–11 years of age) to optimize joint range of motion (ROM) increases; however, evidence is limited and inconsistent. Objective To examine whether there is a difference in the effect of stretching training on flexibility during childhood (6–11 years of age) and adolescence (12–18 years of age). Design Systematic review and meta-analysis. Methods We searched PubMed Central, Web of Science, Scopus, Embase, and SPORTDiscus, to conduct this systematic review. Randomized controlled trials and non-randomized controlled trials were eligible. No language and date of publication restrictions were applied. Risk of bias was assessed using Cochrane RoB2 and ROBINS-I tools. Meta-analyses were conducted via an inverse variance random-effects model. GRADE analysis was used to assess the methodological quality of the studies. Results From the 2713 records retrieved 28 studies were included in the meta-analysis ( n = 1936 participants). Risk of bias was low in 56.9% of all criteria. Confidence in cumulative evidence was moderate. We found that stretching was effective in increasing ROM in both children (SMD = 1.09; 95% CI = 0.77–1.41; Z = 6.65; p < 0.001; I ² = 79%) and adolescents (SMD = 0.90; 95% CI = 0.70–1.10; Z = 8.88; p < 0.001; I ² = 81%), with no differences between children and adolescents in ROM improvements ( p = 0.32; I ² = 0%). However, when stretching volume load was considered, children exhibited greater increases in ROM with higher than lower stretching volumes (SMD = 1.21; 95% CI = 0.82–1.60; Z = 6.09; p < 0.001; I ² = 82% and SMD = 0.62; 95% CI = 0.29–0.95; Z = 3.65; p < 0.001; I ² = 0%, respectively; subgroup difference: p = 0.02; I ² = 80.5%), while adolescents responded equally to higher and lower stretching volume loads (SMD = 0.90; 95% CI = 0.47–1.33; Z = 4.08; p < 0.001; I ² = 83%, and SMD = 0.90; 95% CI = 0.69–1.12; Z = 8.18; p < 0.001; I ² = 79%, respectively; subgroup difference: p = 0.98; I ² = 0%). Conclusions Systematic stretching training increases ROM during both childhood and adolescence. However, larger ROM gains may be induced in childhood than in adolescence when higher stretching volume loads are applied, while adolescents respond equally to high and low stretching volume loads. Registration: INPLASY, registration number: INPLASY202190032; https://inplasy.com/inplasy-2021-9-0032/
Increasingly fierce competition in energy industry for alternative fuels has raised demand for fuel storage stations to be one of the pivots towards sustainable urban freight transportation. For zero-emission hydrogen-powered vehicles, these demands focus mostly on storage capacity and refueling-station location selection to maximize freight forwarding efficiency in major urban regions. This research proposes a Decision Support System (DSS) for hydrogen storage station location selection based on Intuitionistic Hesitant Fuzzy (IHF) methodologies. An ensemble of four methods were analyzed and applied for the use case of Larissa city urban region, central Greece. Fifteen evaluation criteria were imposed by experts from the transportation department and the local competent authorities, spanning to hydrogen infrastructure, socioeconomics and fleet and road network. Scenarios such as energy efficiency, pollution prevention and public acceptance in conjunction to the risk and safety considerations play a critical role in the process. All qualitative indicators were represented by triangular intuitionistic fuzzy numbers. The ensemble produced the same ranking indicating the Steiner point locations of the imposed communication tree on the road network as the most preferable scenario. (https://authors.elsevier.com/a/1feFv1H%7Ec%7EHttj)
Development of resistance to insecticides and fumigants in several stored product insect pests is of global concern as failure of routine treatment protocols is on the rise, causing serious economic implications. A series of trials in commercial flour and rice mills were conducted to evaluate the effectiveness of heat treatment against two major pest species, as an alternative to fumigant phosphine that has been under serious threat from resistance development in key pest species. Adults and immatures of both susceptible and phosphine-resistant strains of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) were included in the study. The target temperature for the treatment was 50 • C and the treatment lasted for 16-36 h, depending on the building size. Vials containing test insect cohorts along with their preferred diets were placed at predetermined locations within the trial sites. Wireless sensors were also placed next to test insect vials to record and monitor course of temperature change during the treatment. The adult mortality assessment of test insects was carried out immediately after the termination of each trial. Thereafter, the treated vials containing the diet and immature insect life-stages were shifted to a controlled environment cabinet and maintained at 25 • C and 65% relative humidity for 65 d when the progeny mortalities were assessed. Our results showed that heat treatment had caused very high adult (in most cases 100%) and suppressed progeny mortality in both T. castaneum and S. oryzae in all trials, irrespective of their susceptibility status to phosphine. The current study suggests that heat treatment in rice/flour mills holds potentials to be used as an alternative treatment to phosphine, especially to control phosphine resistant strains.
Full-fat and defatted superworm Zophobas morio larvae meals were used in a feeding trial of 540 gilthead seabream, Sparus aurata, juveniles (3.4 g initial weight) in order to assess their immunomodulatory effects. Six isonitrogenous (52 %) and isoenergetic (21 MJ/Kg) diets were formulated where the fishmeal of the control diet was replaced by full-fat Z. morio meal at 5 % and 10 % (FF5 and FF10) or defatted Z. morio meal at 10, 20 or 30 % (LF10, LF20 and LF30). Fish were kept in 18 glass tanks (125 L) within a closed recirculation seawater system and fed to satiation twice a day, 6 days per week for 100 days. LF20 significantly increased the percentage of neutrophils compared to a control fish-fed fishmeal (FM)-based diet. The dietary Z. morio meal immunomodulated the fish as expressed through an increased complement-associated bacterial killing (FF5 and FF10), nitric oxide production (LF30), and a tendency for an increased activity of lysozyme (FF5, LF20 and LF30) and of myeloperoxidase (FF5 and LF20), while trypsin inhibition was significantly suppressed by dietary FF5 and all 3 LF-containing diets compared to control FM-fed fish. These findings suggest that dietary Z. morio can immunomodulate gilthead seabream but further infectious challenge studies will have to be performed to determine if these effects are translated into an increased resistance to diseases.
This paper develops a Hierarchical Bayesian Modeling (HBM) framework for uncertainty quantification of Finite Element (FE) models based on modal information. This framework uses an existing Fast Fourier Transform (FFT) approach to identify experimental modal parameters from time-history data and employs a class of maximum-entropy probability distributions to account for the mismatch between the modal parameters. It also considers a parameterized probability distribution for capturing the variability of structural parameters across multiple data sets. In this framework, the computation is addressed through Expectation-Maximization (EM) strategies, empowered by Laplace approximations. As a result, a new rationale is introduced for assigning optimal weights to the modal properties when updating structural parameters. According to this framework, the modal features’ weights are equal to the inverse of the aggregate uncertainty, comprised of the identification and prediction uncertainties. The proposed framework is coherent in modeling the entire process of inferring structural parameters from response-only measurements and is comprehensive in accounting for different sources of uncertainty, including the variability of both modal and structural parameters over multiple data sets, as well as their identification uncertainties. Numerical and experimental examples are employed to demonstrate the HBM framework, wherein the environmental and operational conditions are almost constant. It is observed that the variability of parameters across data sets remains the dominant source of uncertainty while being much larger than the identification uncertainties.
The electrochemical reduction of CO2 into fine chemicals, assisted with renewable energy, is the most instant approach for balancing the atmospheric CO2 level, as well as for storing solar energy as chemical energy. Due to their easy synthesis and good performance, metal oxides are attractive as electrocatalysts for the CO2 reduction reaction (CO2RR). In this review article, we concise the recent advances in the product efficiency of CO2RR for metal oxide electrocatalysts. It is here worth noticing that, overlooking the metal sites of metal oxide-based catalysts, we only considered the M−O (metal–oxygen bond) active sites for discussion. Further, recent strategies, such as advanced morphologies development and interface and vacancy defect engineering, used to improve the CO2RR performance, are also overviewed. By covering the critical role of catalysts (M−O) structure in efficiency and stability, this review also provides some future aspects for the design and development of efficient metal oxide-based electrocatalysts for CO2RR.
Transport infrastructure is the backbone of the economy and society, while at the same time is exposed to multiple hazards. Previous natural disasters, including earthquakes, had a significant impact on transport networks with severe consequences for the users and supply chain. In this context, the resilience assessment of critical assets such as tunnels is of paramount importance for increasing safety and maintaining their functionality in seismic-prone areas. This study presents a practical resilience assessment framework for tunnels subjected to earthquakes. The proposed framework combines fragility and restoration functions, for assessing the robustness of tunnels exposed to different seismic scenarios, and the rapidity of the recovery considering different damage levels. The framework is applied to circular tunnels in alluvial deposits. A life-cycle resilience index is estimated, and the effects of soil conditions, tunnel burial depths, construction quality, and aging of the tunnel lining, on the resilience quantifications are examined and assessed. This effort contributes to the resilience-based design and management of tunnels and underground transport networks, and hence, facilitates decision-making and efficient allocation of resources by consultants, operators, and stakeholders.
This study examined whether emotional intelligence (EI) contributes to teachers' (N = 221) responses to vignettes portraying student peer conflicts characterizable as indirect bullying. They rated these vignettes (and others portraying direct bullying) on perceived seriousness, self-efficacy for intervening, and likelihood of intervening. EI was a positive predictor of seriousness of indirect bullying and self-efficacy, these two variables mediating the effect of EI on likelihood of intervening. However, the effect of EI was relatively small. Teachers also perceived indirect bullying as less serious than direct bullying, and felt less self-efficacious and less likely to intervene. Implications for teacher professional education are discussed.
The purpose of this research study is to investigate, with the use of panel cointegration methodology, the existence of a stationary long-run relationship between private capital formation and total government spending in Eurozone countries since the introduction of the euro as currency. Our findings indicate a positive but not complete (one to one) long run relationship on average. This positive relationship is smaller for the PIGS countries relevant to other Eurozone members and it is significantly reduced over time, implying economic asymmetries among Euro Area countries. An interesting finding of the performed analysis is that Greece, one of the panel countries, presents the fastest long-run adjustment process but its existence significantly reduces the magnitude of the overall average long-run coefficient. Therefore, the implementation of common European policies across all countries is expected to be a difficult task for the policy makers.
Background Iodine is an essential trace element, which is important for human metabolism, growth and mental development. Iodine deficiency may still occur in Europe and the use of iodised salt is an effective measure to enhance iodine intake. Knowledge and awareness about the importance of iodine in nutrition and health can have a positive impact on the use of iodised salt. Therefore, the aim of this study was to assess the knowledge about and use of iodised salt among university students in two European countries. Method Data from two countries (Germany and Greece) were extracted from a multi-centre cross-sectional survey, conducted among non-nutrition science/non-medical students from October 2018 to April 2019. Results Among the 359 participants in Germany (35% females, median age: 22 years) and the 403 participants in Greece (51% females, median age: 21 years), 41% and 37%, respectively, reported use of iodised salt at home. Users and non-users did not differ by age, gender and Body Mass Index or general interest in nutrition in both cohorts. However, those who had a better knowledge about iodine and (iodised) salt or had previously attended nutrition classes were more likely to report iodised salt usage. Conclusion The results suggest that strengthening the imparting of nutritional information and additional education of young adults are needed and may improve knowledge about and usage of iodised salt.
Heat stress causes extensive losses in the dairy sector, due to negative effects on milk production and reproduction. Cows have evolved a series of protective mechanisms, (physiological, biochemical, behavioral) to cope with the thermostressing environments, which have allowed the preservation of productive and reproductive potential of specific animals during summer; these animals are considered thermotolerant and could be used to design programs of selective breeding. These programs, targeting to the generations of a population of heat resistant animals, would increase the frequency of the desired phenotypes, tackling the financial losses on one hand and reducing the carbon footprints of the dairy sector on the other. The development of genomics techniques has enabled the genome wide variant calling, to detect SNPs associated with the desired phenotypes. In this study, we used a comparative genomics approach to to detect genetic variation associated with thermotolerance and to design molecular markers for characterizing the animals as tolerant/sensitive. A total of 40 cows from each group were split in 4 sequencing pools and a Whole Genome Sequencing approach was used. Results and conclusion: Genome‐wide genetic variation between groups was characterized and enrichment analysis revealed specific pathways which participate in the adaptive mechanisms of thermotolerance, implicated into systemic and cellular responses, including the immune system functionality, Heat Stress and Unfolded Protein Response. The markers made a promising set of results, as specific SNPs in 5 genes encoding for Heat Shock Proteins were significantly associated with thermotolerance.
A steady supply of hosts at the susceptible stage for parasitism is a major component of mass rearing parasitoids for biological control programs. Here we describe the effects of storing 5th instar Plodia interpunctella larvae in dormancy on subsequent host development in the context of host colony maintenance and effects of the duration of host dormancy on the development of Habrobracon hebetor parasitoids reared from dormant hosts. We induced dormancy with a combination of short daylength (12L:12D) and lower temperature (15°C), conditions known to induce diapause in this species, and held 5th instar larvae of P. interpunctella for a series of dormancy durations ranging from 15 to 105 days. Extended storage of dormant 5th instar larvae had no significant impacts on survival, development, or reproductive potential of P. interpunctella , reinforcing that dormant hosts have a substantial shelf life. This ability to store hosts in dormancy for more than 3 months at a time without strong negative consequences reinforces the promise of using dormancy to maintain host colonies. The proportion of hosts parasitized by H. hebetor did not vary significantly between non-dormant host larvae and dormant host larvae stored for periods as long as 105 days. Concordant with a prior study, H. hebetor adult progeny production from dormant host larvae was higher than the number of progeny produced on non-dormant host larvae. There were no differences in size, sex ratio, or reproductive output of parasitoids reared on dormant hosts compared to non-dormant hosts stored for up to 105 days. Larval development times of H. hebetor were however longer when reared on dormant hosts compared to non-dormant hosts. Our results agree with other studies showing using dormant hosts can improve parasitoid mass rearing, and we show benefits for parasitoid rearing even after 3 months of host dormancy.
MicroRNAs represent major regulatory components of the disease epigenome and they constitute powerful biomarkers for the accurate diagnosis and prognosis of various diseases, including cancers. The advent of high-throughput technologies facilitated the generation of a vast amount of miRNA-cancer association data. Computational approaches have been utilized widely to effectively analyze and interpret these data towards the identification of miRNA signatures for diverse types of cancers. Herein, a novel computational workflow was applied to discover core sets of miRNA interactions for the major groups of neoplastic diseases by employing network-based methods. To this end, miRNA-cancer association data from four comprehensive publicly available resources were utilized for constructing miRNA-centered networks for each major group of neoplasms. The corresponding miRNA-miRNA interactions were inferred based on shared functionally related target genes. The topological attributes of the generated networks were investigated in order to detect clusters of highly interconnected miRNAs that form core modules in each network. Those modules that exhibited the highest degree of mutual exclusivity were selected from each graph. In this way, neoplasm-specific miRNA modules were identified that could represent potential signatures for the corresponding diseases.
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5,825 members
Michalis Savelonas
  • Department of Computer Science and Biomedical Informatics
Alexandros Papachatzis
  • Agriculture Agrotechnology
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Argonafton & Filellinon, 38221, Volos, Greece
Head of institution
Prof. Zissis Mamuris, University Rector
Website
http://www.uth.gr/
Phone
+30-24210-74000