THE ROLE OF NEUTRINOS IN BARYON ASYMMETRY OF THE UNIVERSE

Αστρονομικά δεδομένα και παρατηρήσεις υποδεικνύουν ότι το σύμπαν παρουσιάζει μία ασυμμετρία της ύλης ως προς την αντιύλη, γνωστή και ως βαρυονική ασυμμετρία του σύμπαντος, κάτι το οποίο αποτυπώνεται στη βιβλιογραφία στο λόγο της πυκνότητας βαρυονίων προς την πυκνότητα φωτονίων. Το μέγεθος του φαινομένου αυτού δεν μπορεί να εξηγηθεί στα πλαίσια του Καθιερωμένου Προτύπου (ΚΜ), με αποτέλεσμα να έχουν προταθεί πολλές ιδέες, με μία από αυτές να συνδέει τα νετρίνα, τα οποία στο ΚΜ θεωρούνται άμαζα. Η προσπάθεια επέκτασης του ΚΜ, μέσω της υπόθεσης ύπαρξης δεξιόστροφων Majorana νετρίνων, με σκοπό να εξηγηθεί η μάζα των νετρίνων, μπορεί να οδηγήσει στην επίλυση του προβλήματος της ασυμμετρίας μέσω ενός μοντέλου λεπτογένεσης. Στην παρούσα εργασία γίνεται η εισαγωγή στο πρόβλημα της βαρυονικής ασυμμετρίας με την αρχική αποτύπωση των απαραίτητων συνθηκών, γνωστών και ως συνθηκών Sakharov, κάτω από τις οποίες μία ασυμμετρία μπορεί να παραχθεί κατά τη διάρκεια εξέλιξης του σύμπαντος. Σκοπός της εργασίας είναι η εκτενής παρουσίαση ενός μοντέλου λεπτογένεσης που εμπλέκει ένα βαρύ Majorana νετρίνο, ένα λεπτόνιο και ένα σωματίδιο Higgs, με αποτέλεσμα την παραγωγή της ασυμμετρίας μέσω της επίλυσης των εξισώσεων Boltzmann. Επιπρόσθετα, γίνεται μια σύντομη ανασκόπηση στη θερμική ιστορία του σύμπαντος, καθώς επίσης και στο μηχανισμό της τραμπάλας ( seesaw mechanism ) που ενδεχομένως να είναι υπεύθυνος για την μικρή μάζα των νετρίνων του ΚΠ. Τέλος, στα τελευταία κεφάλαια εξετάζεται πως η ασυμμετρία στο λεπτονικό αριθμό μπορεί να μετατραπεί σε ασυμμετρία βαρυονίων, μέσω μεταβάσεων σφαλερονίων ( sphaleron ).Astronomical data and observations indicate that the universe exhibits a matter-antimatter asymmetry, also known as the Baryon Asymmetry of the Universe (BAU), which is reflected in the literature in terms of the baryon to photon density ratio. The magnitude of this phenomenon can not be explained in the context of the Standard Model (SM), and as a result, many ideas have been proposed so far, with one of them involving the neutrinos, which within the context of the SM are considered massless. The attempt to extend the SM through the hypothesis of the existence of right-handed Majorana neutrinos, in order to explain the mass of neutrinos, can lead to the solution of the BAU problem through a model of leptogenesis. In this thesis, the problem of BAU is introduced, starting with an initial depiction of the necessary conditions, also known as Sakharov conditions, under which an asymmetry can be generated during the evolution of the universe. The aim of this work is to present a model of leptogenesis involving a heavy Majorana neutrino, a lepton and a Higgs particle, resulting in the production of asymmetry by solving Boltzmann equations. In addition, we give a brief overview of the thermal history of the universe, as well as an account of the seesaw mechanism that may be responsible for the small SM neutrino mass. Finally, in the last chapters, we present how the asymmetry in the lepton number can be converted to baryon asymmetry, via sphaleron transitions

Performance and emissions of a series hybrid vehicle powered by a gasoline partially premixed combustion engine

[EN] This work evaluates the performance and emissions of the series hybrid vehicle concept powered by a gasoline partially premixed internal combustion engine. To do so, experimental data was collected from a Volvo VED-D4 Euro 6 four-cylinder compression ignition engine running under gasoline partially premixed combustion. Two series hybrid vehicle models were developed in GT-Power (R), which were fed with the experimental data to evaluate the potential of the hybrid concept. First of all, the battery charging strategy of the hybrid vehicles was optimized in terms of number of power levels and operating conditions. For this, a design of experiments was performed in GT-Power (R), which enabled to obtain a predictive model of the performance and emissions. The predictive model was used to obtain the optimized NOx-fuel consumption Pareto frontiers for each charging strategy proposed. Finally, the GT-Power (R) vehicle models were run with the optimal operating conditions (selected from each Pareto) in both the new European driving cycle and worldwide harmonized light vehicles test cycle. The results show that the hybrid powertrain running with partially premixed combustion is able to achieve similar or better performance than the commercial diesel vehicle with low engine-out emissions. Moreover, comparing the results from both vehicles, it was confirmed that the hybridization results in better improvements when applied to urban traffic than for highway conditions where the power request is higher and the potential for regenerative braking is reduced.The authors gratefully acknowledge FEDER and Spanish Ministerio de Economia y Competitividad for partially supporting this research through TRANCO project (TRA2017-87694-R). The authors also gratefully acknowledge the KCFP Engine Research Center (Swedish Energy Agency grant number 22485-4) for partial support of this research.García Martínez, A.; Monsalve-Serrano, J.; Lago-Sari, R.; Dimitrakopoulos, N.; Turnér, M.; Tunestål, P. (2019). Performance and emissions of a series hybrid vehicle powered by a gasoline partially premixed combustion engine. Applied Thermal Engineering. 150:564-575. https://doi.org/10.1016/j.applthermaleng.2019.01.035S56457515

The seed germination properties of two hyperaccumulator plant species with the potential for Ni agromining

The aim of this study is to investigate the effect of different nickel concentrations and light in combination with storage conditions and storage time on the seed germination ability of two serpentine-endemic nickel hyperaccumulating species (Bornmuellera emarginata and B. tymphaea). The seeds of both species were collected from natural populations in the Pindus Mountain range, Greece in early July and stored in a refrigerator (4°C) and in laboratory conditions (22°C). The seeds were exposed to a range of nickel concentrations typical of non-ultramafic ‒ ultramafic gradient in two light environments (12 h photoperiod and continuous darkness). The nickel concentration only had a significant effect on B. emarginata, decreasing its seed germination rate with increasing Ni concentrations. The storage temperature significantly affected the germination percentage of both species and it was higher at 4°C compared to 22°C. A higher germination rate (> 60%) was observed for 5‒8-month-old seeds, but both species generally showed significantly higher germination rates in the tests conducted seven months after seed ripening in the field. A higher germination rate was observed in a 12-hour photoperiod than in continuous darkness only for B. tymphaea. This study provides guidelines on the germination capacity of two obligate nickel hyperaccumulators with a potential for use in agromining systems

Characterization of substantia nigra neurogenesis in homeostasis and dopaminergic degeneration: beneficial effects of the microneurotrophin BNN-20

Background Loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) underlines much of the pathology of Parkinson’s disease (PD), but the existence of an endogenous neurogenic system that could be targeted as a therapeutic strategy has been controversial. BNN-20 is a synthetic, BDNF-mimicking, microneurotrophin that we previously showed to exhibit a pleiotropic neuroprotective effect on the dopaminergic neurons of the SNpc in the “weaver” mouse model of PD. Here, we assessed its potential effects on neurogenesis. Methods We quantified total numbers of dopaminergic neurons in the SNpc of wild-type and “weaver” mice, with or without administration of BNN-20, and we employed BrdU labelling and intracerebroventricular injections of DiI to evaluate the existence of dopaminergic neurogenesis in the SNpc and to assess the origin of newborn dopaminergic neurons. The in vivo experiments were complemented by in vitro proliferation/differentiation assays of adult neural stem cells (NSCs) isolated from the substantia nigra and the subependymal zone (SEZ) stem cell niche to further characterize the effects of BNN-20. Results Our analysis revealed the existence of a low-rate turnover of dopaminergic neurons in the normal SNpc and showed, using three independent lines of experiments (stereologic cell counts, BrdU and DiI tracing), that the administration of BNN-20 leads to increased neurogenesis in the SNpc and to partial reversal of dopaminergic cell loss. The newly born dopaminergic neurons, that are partially originated from the SEZ, follow the typical nigral maturation pathway, expressing the transcription factor FoxA2. Importantly, the pro-cytogenic effects of BNN-20 were very strong in the SNpc, but were absent in other brain areas such as the cortex or the stem cell niche of the hippocampus. Moreover, although the in vitro assays showed that BNN-20 enhances the differentiation of NSCs towards glia and neurons, its in vivo administration stimulated only neurogenesis. Conclusions Our results demonstrate the existence of a neurogenic system in the SNpc that can be manipulated in order to regenerate the depleted dopaminergic cell population in the “weaver” PD mouse model. Microneurotrophin BNN-20 emerges as an excellent candidate for future PD cell replacement therapies, due to its area-specific, pro-neurogenic effects

Characterization of substantia nigra neurogenesis in homeostasis and dopaminergic degeneration: beneficial effects of the microneurotrophin BNN-20.

BACKGROUND: Loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) underlines much of the pathology of Parkinson's disease (PD), but the existence of an endogenous neurogenic system that could be targeted as a therapeutic strategy has been controversial. BNN-20 is a synthetic, BDNF-mimicking, microneurotrophin that we previously showed to exhibit a pleiotropic neuroprotective effect on the dopaminergic neurons of the SNpc in the "weaver" mouse model of PD. Here, we assessed its potential effects on neurogenesis. METHODS: We quantified total numbers of dopaminergic neurons in the SNpc of wild-type and "weaver" mice, with or without administration of BNN-20, and we employed BrdU labelling and intracerebroventricular injections of DiI to evaluate the existence of dopaminergic neurogenesis in the SNpc and to assess the origin of newborn dopaminergic neurons. The in vivo experiments were complemented by in vitro proliferation/differentiation assays of adult neural stem cells (NSCs) isolated from the substantia nigra and the subependymal zone (SEZ) stem cell niche to further characterize the effects of BNN-20. RESULTS: Our analysis revealed the existence of a low-rate turnover of dopaminergic neurons in the normal SNpc and showed, using three independent lines of experiments (stereologic cell counts, BrdU and DiI tracing), that the administration of BNN-20 leads to increased neurogenesis in the SNpc and to partial reversal of dopaminergic cell loss. The newly born dopaminergic neurons, that are partially originated from the SEZ, follow the typical nigral maturation pathway, expressing the transcription factor FoxA2. Importantly, the pro-cytogenic effects of BNN-20 were very strong in the SNpc, but were absent in other brain areas such as the cortex or the stem cell niche of the hippocampus. Moreover, although the in vitro assays showed that BNN-20 enhances the differentiation of NSCs towards glia and neurons, its in vivo administration stimulated only neurogenesis. CONCLUSIONS: Our results demonstrate the existence of a neurogenic system in the SNpc that can be manipulated in order to regenerate the depleted dopaminergic cell population in the "weaver" PD mouse model. Microneurotrophin BNN-20 emerges as an excellent candidate for future PD cell replacement therapies, due to its area-specific, pro-neurogenic effects

Prevalence of hepatitis B and C markers in high-risk hospitalised patients in Crete: a five-year observational study

BACKGROUND: So far the prevalence of viral hepatitis infection in hospitalized patients has not been extensively studied. Therefore we conducted the present five-year observational study to evaluate the prevalence of HBV and HCV infection in high-risk hospitalized patients of Crete, the largest Greek island, Due to the homogeneous population, epidemiological studies can be accurately done. METHODS: The study was carried out in two out of four District General Hospitals, and in the University Hospital of the island. Markers for HBV and HCV were studied and statistically evaluated according to age, sex and geographical area, in a well-defined hospitalized population. RESULTS: The total prevalence of HBsAg and anti-HCV in the three prefectures during the five-year study is 2.66% and 4.75% respectively. Overall the relative risks were higher in males than females for each hepatitis marker (p < 0.001). Higher prevalence of HBcAb was found in the 41–60 years age group for both sexes (males 36.17%, females 27.38%). Peak HBsAg prevalence was found in the age group of 21–40 and 41–60 years for males (5.4%) and females (3.09%) respectively. Anti-HCV prevalence increases with age reaching the highest prevalence in the age group of 41–60 years for males (7.19%) and in the 61–90 years age group for females (7.16%). For both sexes significant differences between the three locations were identified. For HBsAg a higher prevalence in Heraklion (3.96%) compared to Chania (2.30%, males: p < 0.0001, females: p < 0.05) and Rethymnon (1.45%, males: p < 0.01, females: p < 0.0001) was detected. For HCV a significantly higher prevalence in Heraklion (6.54%) compared to Chania (2.39%, males: p < 0.001, females: p < 0.001) but not in Rethymnon (5.15%, NS). A lower prevalence rate of HBcAb in Heraklion compared to Chania (20.07% versus 23.05%, males: p < 0.001, females: p < 0.001) was found. CONCLUSIONS: These results were possibly overestimated, but nevertheless reflect the situation of the general population within the island as shown by our previous publications in other study groups. Moreover they contribute to the mapping of viral hepatitis prevalence in a geographical area of Southern Europe and may be helpful in planning public health interventional strategies

Predicting species dominance shifts across elevation gradients in mountain forests in Greece under a warmer and drier climate

The Mediterranean Basin is expected to face warmer and drier conditions in the future, following projected increases in temperature and declines in precipitation. The aim of this study is to explore how forests dominated by Abies borisii-regis, Abies cephalonica, Fagus sylvatica, Pinus nigra and Quercus frainetto will respond under such conditions. We combined an individual-based model (GREFOS), with a novel tree ring data set in order to constrain tree diameter growth and to account for inter- and intraspecific growth variability. We used wood density data to infer tree longevity, taking into account inter- and intraspecific variability. The model was applied at three 500-m-wide elevation gradients at Taygetos in Peloponnese, at Agrafa on Southern Pindos and at Valia Kalda on Northern Pindos in Greece. Simulations adequately represented species distribution and abundance across the elevation gradients under current climate. We subsequently used the model to estimate species and functional trait shifts under warmer and drier future conditions based on the IPCC A1B scenario. In all three sites, a retreat of less drought-tolerant species and an upward shift of more drought-tolerant species were simulated. These shifts were also associated with changes in two key functional traits, in particular maximum radial growth rate and wood density. Drought-tolerant species presented an increase in their average maximal growth and decrease in their average wood density, in contrast to less drought-tolerant species

Achaiki Iatriki : official publication of the medical society of western Greece and Peloponnesus

In the current issue, the editorial by Cauchi et al. argues for eco-friendly measures in endoscopy and emphasies the role of healthcare providers in reducing waste. The editorial adeptly employs the three Rs (Reduce, Reuse, Recycle) framework to tackle waste management, offering practical solutions. The editorial by Milionis et al. focuses on the reverse cascade screening for paediatric familial hypercholesterolaemia (FH), which is an upcoming tool for public health. Advantages, practices, and challenges regarding FH are thoroughly discussed. Lastly, the editorial by Fousekis et al. presents the main aspects of a chronic immune-mediated cutaneous disease, dermatitis herpetiformis (DH), which constitutes an extraintestinal manifestation of celiac disease, including its diagnosis, pathogenesis, and management. Moreover, this issue includes three review articles. The review article by Krontira et al. discusses the evolving data on the epidemiology, diagnostic approach and appropriate management of foreign body and caustic substance ingestion, based on updated guidelines published by gastroenterological and endoscopic societies. The review by Halliasos et al. provides data on the clinical presentation, diagnosis, and management of metastatic acute spinal cord compression, focusing on the importance of a multidisciplinary team approach, including spine surgeons, radiation oncologists, medical oncologists, palliative care clinicians, physiotherapists, and psychologists. Lastly, the review by Schinas et al. outlines the potential of immune modulation in the treatment of infections and the need for individualised approaches in the modern world of personalised medicine by examining some of the key strategies and immune-based therapies being developed to combat infectious diseases.peer-reviewe