Newtonian nonlinear hydrodynamics and magnetohydrodynamics

We use covariant methods to analyse the nonlinear evolution of self-gravitating, non-relativistic media. The formalism is first applied to imperfect fluids, aiming at the kinematic effects of viscosity, before extended to inhomogeneous magnetised environments. The nonlinear electrodynamic formulae are derived and successively applied to electrically resistive and to highly conductive fluids. By nature, the covariant equations isolate the magnetic effects on the kinematics and the dynamics of the medium, combining mathematical transparency and physical clarity. Employing the Newtonian analogue of the relativistic 1+3 covariant treatment, also facilitates the direct comparison with the earlier relativistic studies and helps to identify the differences in an unambiguous way. The purpose of this work is to set the framework and take a first step towards the detailed analytical study of complex nonlinear systems, like non-relativistic astrophysical plasmas and collapsing protogalactic clouds.Comment: Typos corrected, references added and updated (MNRAS in press

Characterization of Wind-Sea- and Swell-Induced Wave Energy along the Norwegian Coast

The necessity to reduce CO2 emissions in combination with the rising energy demand worldwide makes the extensive use of renewable energy sources increasingly important. To that end, countries with long coastlines, such as Norway, can exploit ocean wave energy to produce large amounts of power. In order to facilitate these efforts as well as to provide quantitative data on the wave energy potential of a specific area, it is essential to analyze the weather and climatic conditions detecting any variabilities. The complex physical processes and the atmosphere-wave synergetic effects make the investigation of temporal variability of wave energy a challenging issue. This work aims to shed new light on potential wave energy mapping, presenting a spatio-temporal assessment of swell- and wind-sea-induced energy flux in the Nordic Seas with a focus on the Norwegian coastline using the NORA10 hindcast for the period 1958–2017 (59 years). The results indicate high spatial and seasonal variability of the wave energy flux along the coast. The maximum wave energy flux is observed during winter, while the minimum is observed during summer. The highest coastal wave energy flux is observed in the Norwegian Sea. The majority of areas with dominant swell conditions (i.e., in the Norwegian Sea) are characterized by the highest coastal wave energy flux. The maximum values of wave energy flux in the North Sea are denoted in its northern parts in the intersection with the Norwegian Sea. In contrast to the Norwegian Sea, areas located in the North Sea and the Barents Sea show that wind sea is contributing more than swell to the total wave energy flux.publishedVersio

Hydro-meteorological risk assessment methods and management by nature-based solutions

Hydro-meteorological risk (HMR) management involves a range of methods, such as monitoring of uncertain climate, planning and prevention by technical countermeasures, risk assessment, preparedness for risk by early-warnings, spreading knowledge and awareness, response and recovery. To execute HMR management by risk assessment, many models and tools, ranging from conceptual to sophisticated/numerical methods are currently in use. However, there is still a gap in systematically classifying and documenting them in the field of disaster risk management. This paper discusses various methods used for HMR assessment and its management via potential nature-based solutions (NBS), which are actually lessons learnt from nature. We focused on three hydro-meteorological hazards (HMHs), floods, droughts and heatwaves, and their management by relevant NBS. Different methodologies related to the chosen HMHs are considered with respect to exposure, vulnerability and adaptation interaction of the elements at risk. Two widely used methods for flood risk assessment are fuzzy logic (e.g. fuzzy analytic hierarchy process) and probabilistic methodology (e.g. univariate and multivariate probability distributions). Different kinds of indices have been described in the literature to define drought risk, depending upon the type of drought and the purpose of evaluation. For heatwave risk estimation, mapping of the vulnerable property and population-based on geographical information system is a widely used methodology in addition to a number of computational, mathematical and statistical methods, such as principal component analysis, extreme value theorem, functional data analysis, the Ornstein–Uhlenbeck process and meta-analysis. NBS (blue, green and hybrid infrastructures) are promoted for HMR management. For example, marshes and wetlands in place of dams for flood and drought risk reduction, and green infrastructure for urban cooling and combating heatwaves, are potential NBS. More research is needed into risk assessment and management through NBS, to enhance its wider significance for sustainable living, building adaptations and resilience

The development of METAL-WRF Regional Model for the description of dust mineralogy in the atmosphere

The mineralogical composition of airborne dust particles is an important but often neglected parameter for several physiochemical processes, such as atmospheric radiative transfer and ocean biochemistry. We present the development of the METAL-WRF module for the simulation of the composition of desert dust minerals in atmospheric aerosols. The new development is based on the GOCART-AFWA dust module of WRF-Chem. A new wet deposition scheme has been implemented in the dust module alongside the existing dry deposition scheme. The new model includes separate prognostic fields for nine (9) minerals: illite, kaolinite, smectite, calcite, quartz, feldspar, hematite, gypsum, and phosphorus, derived from the GMINER30 database and also iron derived from the FERRUM30 database. Two regional model sensitivity studies are presented for dust events that occurred in August and December 2017, which include a comparison of the model versus elemental dust composition measurements performed in the North Atlantic (at Izaña Observatory, Tenerife Island) and in the eastern Mediterranean (at Agia Marina Xyliatos station, Cyprus Island). The results indicate the important role of dust minerals, as dominant aerosols, for the greater region of North Africa, South Europe, the North Atlantic, and the Middle East, including the dry and wet depositions away from desert sources. Overall, METAL-WRF was found to be capable of reproducing the relative abundances of the different dust minerals in the atmosphere. In particular, the concentration of iron (Fe), which is an important element for ocean biochemistry and solar absorption, was modeled in good agreement with the corresponding measurements at Izaña Observatory (22% overestimation) and at Agia Marina Xyliatos site (4% overestimation). Further model developments, including the implementation of newer surface mineralogical datasets, e.g., from the NASA-EMIT satellite mission, can be implemented in the model to improve its accuracy.This study was supported by the Hellenic Foundation for Research and Innovation project Mineralogy of Dust Emissions and Impacts on Environment and Health (MegDeth - HFRI no. 703). Part of this study was conducted within the framing of the AERO-EXTREME (PID2021-125669NB-I00) project funded by the State Research Agency/Agencia Estatal de Investigación of Spain and the European Regional Development Funds

Putative antimicrobial peptides within bacterial proteomes affect bacterial predominance: a network analysis perspective

The predominance of bacterial taxa in the gut, was examined in view of the putative antimicrobial peptide sequences (AMPs) within their proteomes. The working assumption was that compatible bacteria would share homology and thus immunity to their putative AMPs, while competing taxa would have dissimilarities in their proteome-hidden AMPs. A network–based method (“Bacterial Wars”) was developed to handle sequence similarities of predicted AMPs among UniProt-derived protein sequences from different bacterial taxa, while a resulting parameter (“Die” score) suggested which taxa would prevail in a defined microbiome. T he working hypothesis was examined by correlating the calculated Die scores, to the abundance of bacterial taxa from gut microbiomes from different states of health and disease. Eleven publicly available 16S rRNA datasets and a dataset from a full shotgun metagenomics served for the analysis. The overall conclusion was that AMPs encrypted within bacterial proteomes affected the predominance of bacterial taxa in chemospheres

Polarisation of Major Histocompatibility Complex II Host Genotype with Pathogenesis of European Brown Hare Syndrome Virus.

A study was conducted in order to determine the occurrence of European Brown Hare Syndrome virus (EBHSV) in Denmark and possible relation between disease pathogenesis and Major Histocompatibility Complex (MHC) host genotype. Liver samples were examined from 170 brown hares (hunted, found sick or dead), collected between 2004 and 2009. Macroscopical and histopathological findings consistent with EBHS were detected in 24 (14.1%) hares; 35 (20.6%) had liver lesions not typical of the syndrome, 50 (29.4%) had lesions in other tissues and 61 (35.9%) had no lesions. Sixty five (38.2%) of 170 samples were found to be EBHSV-positive (RT-PCR, VP60 gene). In order to investigate associations between viral pathogenesis and host genotype, variation within the exon 2 DQA gene of MHC was assessed. DQA exon 2 analysis revealed the occurrence of seven different alleles in Denmark. Consistent with other populations examined so far in Europe, observed heterozygosity of DQA (H o = 0.1180) was lower than expected (H e = 0.5835). The overall variation for both nucleotide and amino acid differences (2.9% and 14.9%, respectively) were lower in Denmark than those assessed in other European countries (8.3% and 16.9%, respectively). Within the peptide binding region codons the number of nonsynonymous substitutions (dN) was much higher than synonymous substitutions (dS), which would be expected for MHC alleles under balancing selection. Allele frequencies did not significantly differ between EBHSV-positive and -negative hares. However, allele Leeu-DQA*30 was detected in significantly higher (P = 0.000006) frequency among the positive hares found dead with severe histopathological lesions than among those found sick or apparently healthy. In contrast, the latter group was characterized by a higher frequency of the allele Leeu-DQA*14 as well as the proportion of heterozygous individuals (P = 0.000006 and P = 0.027). These data reveal a polarisation between EBHSV pathogenesis and MHC class II genotype within the European brown hare in Denmark

On the management of nature-based solutions in open-air laboratories: new insights and future perspectives

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Use of wild bird surveillance, human case data and GIS spatial analysis for predicting spatial distributions of West Nile Virus in Greece

West Nile Virus (WNV) is the causative agent of a vector-borne, zoonotic disease with a worldwide distribution. Recent expansion and introduction of WNV into new areas, including southern Europe, has been associated with severe disease in humans and equids, and has increased concerns regarding the need to prevent and control future WNV outbreaks. Since 2010, 524 confirmed human cases of the disease have been reported in Greece with greater than 10% mortality. Infected mosquitoes, wild birds, equids, and chickens have been detected and associated with human disease. The aim of our study was to establish a monitoring system with wild birds and reported human cases data using Geographical Information System (GIS). Potential distribution of WNV was modelled by combining wild bird serological surveillance data with environmental factors (e.g. elevation, slope, land use, vegetation density, temperature, precipitation indices, and population density). Local factors including areas of low altitude and proximity to water were important predictors of appearance of both human and wild bird cases (Odds Ratio = 1,001 95%CI = 0,723–1,386). Using GIS analysis, the identified risk factors were applied across Greece identifying the northern part of Greece (Macedonia, Thrace) western Greece and a number of Greek islands as being at highest risk of future outbreaks. The results of the analysis were evaluated and confirmed using the 161 reported human cases of the 2012 outbreak predicting correctly (Odds = 130/31 = 4,194 95%CI = 2,841–6,189) and more areas were identified for potential dispersion in the following years. Our approach verified that WNV risk can be modelled in a fast cost-effective way indicating high risk areas where prevention measures should be implemented in order to reduce the disease incidence

Development of algorithms for the calculation of the feedback of naturally produced particles of radiative transfer and energy balance

The scope of this thesis is to study the processes that govern dust production, transport and deposition of desert dust particles, the development of parameterizations for calculating the radiative impacts of dust on limited area models and finally the application of the system to the Mediterranean Area. The algorithms developed redefine the areas that can act as desert dust sources and improve the description of the physical processes that have to do with the dust cycle in the atmosphere. Also a new radiative transfer algorithm, RRTMG, has been modified to work in the framework of the SKIRON model for the purpose of quantifying the direct radiative feedback of mineral dust. The first and foremost effect of dust is the reduction of the incoming solar radiation through scattering and absorption. During the day the amount of energy absorbed by the dust cloud increases the heating rates of the atmospheric layer. On the contrary during the night dust particles emit longwave radiation towards the adjacent layers increasing their temperature. Also the outgoing radiation is trapped between surface and dust layer which causes heating in the lower troposphere. The dust feedback on radiation has a profound effect on the model performance on temperature, wind speed and precipitation. The introduction of dust feedbacks improves the representation of the atmosphere by the model.Σκοπός της παρούσας διατριβής είναι η μελέτη των μηχανισμών παραγωγής και μεταφοράς σωματιδίων εδαφικής σκόνης, η ανάπτυξη νέων μηχανισμών περιγραφής της επίδρασης της σκόνης στο ενεργειακό ισοζύγιο σε μοντέλα ατμοσφαιρικής κυκλοφορίας και η εφαρμογή των παραπάνω στην ευρύτερη περιοχή της Μεσογείου. Οι αλγόριθμοι που αναπτύχθηκαν στο πλαίσιο της διατριβής επαναπροσδιορίζουν τις περιοχές που λειτουργούν σαν πηγές σωματιδίων σκόνης φυσικής προέλευσης και βελτιώνουν τις διεργασίες παραγωγής, μεταφοράς και εναπόθεσης. Παράλληλα αναπτύχθηκαν κατάλληλοι αλγόριθμοι για την προσαρμογή του νέου μοντέλου ακτινοβολίας RRTMG στο σύστημα SKIRON με τελικό στόχο την ποσοτικοποίηση των άμεσων επιδράσεων της σκόνης στο ενεργειακό ισοζύγιο. Η ύπαρξη σωματιδίων φυσικής προέλευσης στην ατμόσφαιρα ελαττώνει το ποσοστό της εισερχόμενης ηλιακής ακτινοβολίας στο έδαφος μέσω σκέδασης και απορρόφησης. Κατά τη διάρκεια της ημέρας το ποσοστό της ενέργειας που απορροφάται από το νέφος σκόνης θερμαίνει το στρώμα της ατμόσφαιρας στο οποίο βρίσκεται. Αντίθετα κατά τη διάρκεια της νύχτας ακτινοβολεί θερμαίνοντας τα υποκείμενα και παρακείμενα στρώματα της ατμόσφαιρας, ενώ ψύχεται το ίδιο. Παράλληλα το στρώμα της σκόνης παγιδεύει την εξερχόμενη υπέρυθρη ακτινοβολία από το έδαφος, θερμαίνοντας τα επιφανειακά στρώματα. Η επίδραση της σκόνης έχει εμφανείς επιδράσεις και στην απόδοση του μοντέλου, όσον αφορά στην αναπαράσταση της θερμοκρασίας, της ταχύτητας του ανέμου και την κατανομή της βροχόπτωσης. Η εισαγωγή της ανάδρασης της σκόνης σύστημα επιτρέπει ικανοποιητικότερη αναπαράσταση των φαινομένων