Showing papers by "University of the Aegean published in 2016"

A multi-decade record of high-quality fCO2 data in version 3 of the Surface Ocean CO2 Atlas (SOCAT)

Abstract: . The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.7 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.6 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "living data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014). Individual data set files, included in the synthesis product, can be downloaded here: doi:10.1594/PANGAEA.849770 . The gridded products are available here: doi:10.3334/CDIAC/OTG.SOCAT_V3_GRID .

Intrusion Detection in 802.11 Networks: Empirical Evaluation of Threats and a Public Dataset

Abstract: WiFi has become the de facto wireless technology for achieving short- to medium-range device connectivity. While early attempts to secure this technology have been proved inadequate in several respects, the current more robust security amendments will inevitably get outperformed in the future, too. In any case, several security vulnerabilities have been spotted in virtually any version of the protocol rendering the integration of external protection mechanisms a necessity. In this context, the contribution of this paper is multifold. First, it gathers, categorizes, thoroughly evaluates the most popular attacks on 802.11 and analyzes their signatures. Second, it offers a publicly available dataset containing a rich blend of normal and attack traffic against 802.11 networks. A quite extensive first-hand evaluation of this dataset using several machine learning algorithms and data features is also provided. Given that to the best of our knowledge the literature lacks such a rich and well-tailored dataset, it is anticipated that the results of the work at hand will offer a solid basis for intrusion detection in the current as well as next-generation wireless networks.

Projections of extreme storm surge levels along Europe

Abstract: Storm surges are an important coastal hazard component and it is unknown how they will evolve along Europe’s coastline in view of climate change. In the present contribution, the hydrodynamic model Delft3D-Flow was forced by surface wind and atmospheric pressure fields from a 8-member climate model ensemble in order to evaluate dynamics in storm surge levels (SSL) along the European coastline (1) for the baseline period 1970–2000; and (2) during this century under the Representative Concentration Pathways RCP4.5 and RCP8.5. Validation simulations, spanning from 2008 to 2014 and driven by ERA-Interim atmospheric forcing, indicated good predictive skill (0.06 m < RMSE < 0.29 m and 10 % < RMSE < 29 % for 110 tidal gauge stations across Europe). Peak-over-threshold extreme value analysis was applied to estimate SSL values for different return periods, and changes of future SSL were obtained from all models to obtain the final ensemble. Values for most scenarios and return periods indicate a projected increase in SSL at several locations along the North European coastline, which is more prominent for RCP8.5 and shows an increasing tendency towards the end of the century for both RCP4.5 and RCP8.5. Projected SSL changes along the European coastal areas south of 50°N show minimal change or even a small decrease, with the exception of RCP8.5 under which a moderate increase is projected towards the end of the century. The present findings indicate that the anticipated increase in extreme total water levels due to relative sea level rise (RSLR), can be further enforced by an increase of the extreme SSL, which can exceed 30 % of the RSLR, especially for the high return periods and pathway RCP8.5. This implies that the combined effect could increase even further anticipated impacts of climate change for certain European areas and highlights the necessity for timely coastal adaptation and protection measures. The dataset is publicly available under this link: http://data.jrc.ec.europa.eu/collection/LISCOAST .

Multi-hazard assessment in Europe under climate change

Abstract: While reported losses of climate-related hazards are at historically high levels, climate change is likely to enhance the risk posed by extreme weather events. Several regions are likely to be exposed to multiple climate hazards, yet their modeling in a joint scheme is still at the early stages. A multi-hazard framework to map exposure to multiple climate extremes in Europe along the twenty-first century is hereby presented. Using an ensemble of climate projections, changes in the frequency of heat and cold waves, river and coastal flooding, streamflow droughts, wildfires and windstorms are evaluated. Corresponding variations in expected annual exposure allow for a quantitative comparison of hazards described by different process characteristics and metrics. Projected changes in exposure depict important variations in hazard scenarios, especially those linked to rising temperatures, and spatial patterns largely modulated by local climate conditions. Results show that Europe will likely face a progressive increase in overall climate hazard with a prominent spatial gradient towards south-western regions mainly driven by the rise of heat waves, droughts and wildfires. Key hotspots emerge particularly along coastlines and in floodplains, often highly populated and economically pivotal, where floods and windstorms could be critical in combination with other climate hazards. Projected increases in exposure will be larger for very extreme events due to their pronounced changes in frequency. Results of this appraisal provide useful input for forthcoming European disaster risk and adaptation policy.

Five key attributes can increase marine protected areas performance for small-scale fisheries management.

Abstract: Marine protected areas (MPAs) have largely proven to be effective tools for conserving marine ecosystem, while socio-economic benefits generated by MPAs to fisheries are still under debate. Many MPAs embed a no-take zone, aiming to preserve natural populations and ecosystems, within a buffer zone where potentially sustainable activities are allowed. Small-scale fisheries (SSF) within buffer zones can be highly beneficial by promoting local socio-economies. However, guidelines to successfully manage SSFs within MPAs, ensuring both conservation and fisheries goals, and reaching a win-win scenario, are largely unavailable. From the peer-reviewed literature, grey-literature and interviews, we assembled a unique database of ecological, social and economic attributes of SSF in 25 Mediterranean MPAs. Using random forest with Boruta algorithm we identified a set of attributes determining successful SSFs management within MPAs. We show that fish stocks are healthier, fishermen incomes are higher and the social acceptance of management practices is fostered if five attributes are present (i.e. high MPA enforcement, presence of a management plan, fishermen engagement in MPA management, fishermen representative in the MPA board, and promotion of sustainable fishing). These findings are pivotal to Mediterranean coastal communities so they can achieve conservation goals while allowing for profitable exploitation of fisheries resources.

Developments in large-scale coastal flood hazard mapping

Abstract: . Coastal flooding related to marine extreme events has severe socioeconomic impacts, and even though the latter are projected to increase under the changing climate, there is a clear deficit of information and predictive capacity related to coastal flood mapping. The present contribution reports on efforts towards a new methodology for mapping coastal flood hazard at European scale, combining (i) the contribution of waves to the total water level; (ii) improved inundation modeling; and (iii) an open, physics-based framework which can be constantly upgraded, whenever new and more accurate data become available. Four inundation approaches of gradually increasing complexity and computational costs were evaluated in terms of their applicability to large-scale coastal flooding mapping: static inundation (SM); a semi-dynamic method, considering the water volume discharge over the dykes (VD); the flood intensity index approach (Iw); and the model LISFLOOD-FP (LFP). A validation test performed against observed flood extents during the Xynthia storm event showed that SM and VD can lead to an overestimation of flood extents by 232 and 209 %, while Iw and LFP showed satisfactory predictive skill. Application at pan-European scale for the present-day 100-year event confirmed that static approaches can overestimate flood extents by 56 % compared to LFP; however, Iw can deliver results of reasonable accuracy in cases when reduced computational costs are a priority. Moreover, omitting the wave contribution in the extreme total water level (TWL) can result in a ∼ 60 % underestimation of the flooded area. The present findings have implications for impact assessment studies, since combination of the estimated inundation maps with population exposure maps revealed differences in the estimated number of people affected within the 20–70 % range.

A Survey on Buffer-Aided Relay Selection

Abstract: Relays receive and retransmit signals between one or more sources and one or more destinations. Cooperative relaying is a novel technique for wireless communications that increases throughput and extends the coverage of networks. The task of relay selection serves as a building block to realize cooperative relaying. Recently, relays with buffers have been incorporated into cooperative relaying providing extra degrees of freedom in selection, thus improving various performance metrics, such as outage probability, power reduction, and throughput, at the expense of tolerating an increase in packet delay. In this survey, we review and classify various buffer-aided relay selection policies and discuss their importance through applications. The classification is mainly based on the following aspects: 1) duplexing capabilities, 2) channel state information (CSI), 3) transmission strategies, 4) relay mode, and 5) performance metrics. Relay selection policies for enhanced physical-layer security and cognitive communications with reduced interference are also discussed. Then, a framework for modeling such algorithms is presented based on Markov Chain theory. In addition, performance evaluation is conducted for various buffer-aided relay selection algorithms. To provide a broad perspective on the role of buffer-aided relay selection, various issues relevant to fifth-generation (5G) networks are discussed. Finally, we draw conclusion and discuss current challenges, possible future directions, and emerging technologies.

Lost in protest, found in segregation: Divided cities in the light of the 2015 “Οχι” referendum in Greece

Abstract: The referendum held in Greece on the 5th of July 2015 about the rejection of the conditions for a new loan sought by European Commission, European Central Bank and International Monetary Fund, become an event of great symbolic importance to national and even continental scale, although its precise scope and meaning were to a large extent loose. Participation to vote was rather high (62.5% of the electorate) and the electorate spoke widely in favour of the ‘no’ (61.3%). The concentration of ‘no’ and ‘yes’ votes followed a polarized distribution in the urban area of Athens. The present study analyzes the geographical distribution of ‘no’ votes at the municipal scale in the metropolitan region of Athens testing for the influence of the local socioeconomic context considering 67 indicators explored through the use of multivariate statistics. The polarization of the referendum vote reflects territorial disparities observed at both urban scale (distinguishing urban districts east, north and south of Athens from those situated west of Athens) and metropolitan scale (based on the urban-rural gradient). The percentage of ‘no’ votes at the municipal scale was correlated negatively with average per-capita declared income. Concentration of farmers and tourism activities, population growth rate and the enforcement of a municipal master plan were additional predictors of the spatial variability of ‘no’ votes. Going beyond the traditional division between ‘left’ and ‘right’ urban neighbourhoods, the spatial distribution of ’no’ votes in Athens reflects socioeconomic disparities consolidated during recession.

Introducing touchstroke: keystroke-based authentication system for smartphones

Abstract: Keystroke dynamics is a well-investigated behavioural biometric based on the way and rhythm in which someone interacts with a keyboard or keypad when typing characters. This paper explores the potential of this modality but for touchscreen-equipped smartphones. The main research question posed is whether 'touchstroking' can be effective in building the biometric profile of a user, in terms of typing pattern, for future authentication. To reach this goal, we implemented a touchstroke system in the Android platform and executed different scenarios under disparate methodologies to estimate its effectiveness in authenticating the end-user. Apart from typical classification features used in legacy keystroke systems, we introduce two novel ones, namely, speed and distance. From the experiments, it can be argued that touchstroke dynamics can be quite competitive, at least when compared to similar results obtained from keystroke evaluation studies. As far as we are aware of, this is the first time this newly arisen behavioural trait is put into focus. Copyright © 2014 John Wiley & Sons, Ltd.

Monitoring sensitivity to land degradation and desertification with the environmentally sensitive area index: The case of lesvos island

Abstract: In Europe, the most susceptible areas to land degradation and desertification (LDD) are found in the Mediterranean region. The present study focuses on the island of Lesvos (Greece) and maps the environmental sensitivity of the island to LDD between the years 1990 and 2000. Sensitivity is estimated with a modification of the MEDALUS Environmentally Sensitive Area Index (ESAI) approach, employing 21 quantitative parameters divided in five main quality indices: climate, vegetation, soils, groundwater and socio-economic quality. Parameterisation of these indices is achieved via remote sensing and ancillary data in a Geographical Information System (GIS). Results show that ~85% of the island is fragile or critically sensitive in both epochs. Fragile areas are on the increase, covering an estimated 72% of the island in 1990 and 77% in 2000, whereas critically sensitive areas decrease from 214 to 113 km2. By modifying the ESAI to include 10 additional parameters related to soil erosion, groundwater quality, demographic and grazing pressure, and by applying the modified ESAI in two—rather than one—periods, this study was able to identify that, contrary to previous belief, critically sensitive areas are also found in the eastern side of the island mainly due to human-related factors. It is concluded that the proposed methodology is a useful tool for regional scale trend analyses of environmental sensitivity and the identification of LDD hot spots in Mediterranean environments. Copyright © 2014 John Wiley & Sons, Ltd.

Mapping the impact of alien species on marine ecosystems: the Mediterranean Sea case study

Abstract: Aim To develop a standardized, quantitative method for mapping cumulative impacts of invasive alien species on marine ecosystems. Location The methodology is applied in the Mediterranean Sea but is widely applicable. Methods A conservative additive model was developed to account for the Cumulative IMPacts of invasive ALien species (CIMPAL) on marine ecosystems. According to this model, cumulative impact scores are estimated on the basis of the distributions of invasive species and ecosystems, and both the reported magnitude of ecological impacts and the strength of such evidence. In the Mediterranean Sea case study, the magnitude of impact was estimated for every combination of 60 invasive species and 13 habitats, for every 10 × 10 km cell of the basin. Invasive species were ranked based on their contribution to the cumulative impact score across the Mediterranean. Results The CIMPAL index showed strong spatial heterogeneity. Spatial patterns varied depending on the pathway of initial introduction of the invasive species in the Mediterranean Sea. Species introduced by shipping gave the highest impact scores and impacted a much larger area than those introduced by aquaculture and the Suez Canal. Overall, invasive macroalgae had the highest impact among all taxonomic groups. These results represent the current best estimate of the spatial variation in impacts of invasive alien species on ecosystems, in the Mediterranean Sea. Main Conclusions A framework for mapping cumulative impacts of invasive alien species was developed. The application of this framework in the Mediterranean Sea provided a baseline that can be built upon with future improved information. Such analysis allows the identification of hotspots of highly impacted areas, and prioritization of sites, pathways and species for management actions.

Novel Glycerol-Based Natural Eutectic Mixtures and Their Efficiency in the Ultrasound-Assisted Extraction of Antioxidant Polyphenols from Agri-Food Waste Biomass

Abstract: Several abundant agri-food wastes, including lemon peels, olive leaves, onion solid wastes, red grape pomace, spent filter coffee and wheat bran, were used to test the efficiency of some novel glycerol-based natural eutectic mixtures to extract polyphenolic compounds. Extractions were performed under specified ultrasonication conditions and the eutectic mixtures, tested as 90 % (v/v) aqueous solutions, were glycerol:choline chloride, glycerol:sodium acetate and glycerol:sodium–potassium tartrate:water, with corresponding molar ratios of 3:1, 3:1 and 5:1:4. The latter two mixtures are reported for the first time. Water and 60 % (v/v) aqueous ethanol were also used as control solvents. The results obtained evidenced that glycerol:choline chloride exhibited high efficiency, which was comparable or even surpassed that of aqueous ethanol, but in some instances the same was observed for glycerol:sodium acetate too. In general, glycerol:sodium–potassium tartrate:water displayed lower efficiency in extracting polyphenols. The data also suggested that extracts with high polyphenol concentration may also possess higher antiradical activity and reducing power. The findings of this study were interpreted on the ground of assumptions regarding the polarity of the eutectic mixtures tested.

A taxonomy of open government data research areas and topics

Abstract: The opening of government data, in order to have both social and economic value generated from them, has attracted the attention and interest of both researchers and practitioners from various disciplines, such as information systems, management sciences, political and social sciences, and law. Despite the rapid growth of this multidisciplinary research domain, which has led to the emergence and continuous evolution of technologies and management approaches for open government data (OGD), a detailed analysis of the specific areas and topics of this research is still missing. In this article, a detailed taxonomy of research areas and corresponding research topics of the OGD domain is presented: it includes four main research areas (ODG management and policies, infrastructures, interoperability and usage and value), which are further analyzed into 35 research topics. An important advantage of this taxonomy, beyond its high level of detail, is that it has been developed through extraction and a combi...

Predicting bee community responses to land-use changes : Effects of geographic and taxonomic biases

Abstract: Land-use change and intensification threaten bee populations worldwide, imperilling pollination services. Global models are needed to better characterise, project, and mitigate bees' responses to these human impacts. The available data are, however, geographically and taxonomically unrepresentative; most data are from North America and Western Europe, overrepresenting bumblebees and raising concerns that model results may not be generalizable to other regions and taxa. To assess whether the geographic and taxonomic biases of data could undermine effectiveness of models for conservation policy, we have collated from the published literature a global dataset of bee diversity at sites facing land-use change and intensification, and assess whether bee responses to these pressures vary across 11 regions (Western, Northern, Eastern and Southern Europe; North, Central and South America; Australia and New Zealand; South East Asia; Middle and Southern Africa) and between bumblebees and other bees. Our analyses highlight strong regionally-based responses of total abundance, species richness and Simpson's diversity to land use, caused by variation in the sensitivity of species and potentially in the nature of threats. These results suggest that global extrapolation of models based on geographically and taxonomically restricted data may underestimate the true uncertainty, increasing the risk of ecological surprises.

Being ‘there’: At the front line of the ‘European refugee crisis’ - part 1

Abstract: In the course of 2015, Skala Sykamnias, a fishing village and tourist idyll on the northern coast of Lesbos, by accident of its geographical location, has turned into the informal gate into Europe for more than 200.000 refugees. In this article the author analyses the massive flows of people and things that transverse his fieldwork site from different directions: the great diversity of actors enacting what are often dissonant ideals and strategies, the several theatres of operation and reception ‘structures’, both frontline and back stage, and the debates that revolve around humanitarian action in the region. The local community is falling apart whilst to the incoming it represents the gateway to freedom. It is becoming a mini theatre of conflicts that echoes wider debates on the political future of Europe.

Search for squarks and gluinos in events with an isolated lepton, jets, and missing transverse momentum at s=13 TeV with the ATLAS detector

Abstract: The results of a search for gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton--proton collision data at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV are presented. The dataset used was recorded in 2015 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 3.2 fb$^{-1}$. Six signal selections are defined that best exploit the signal characteristics. The data agree with the Standard Model background expectation in all six signal selections, and the largest deviation is a 2.1 standard deviation excess. The results are interpreted in a simplified model where pair-produced gluinos decay via the lightest chargino to the lightest neutralino. In this model, gluinos are excluded up to masses of approximately 1.6 TeV depending on the mass spectrum of the simplified model, thus surpassing the limits of previous searches.

Biomass-burning impact on CCN number, hygroscopicity and cloud formation during summertime in the eastern Mediterranean

Abstract: . This study investigates the concentration, cloud condensation nuclei (CCN) activity and hygroscopic properties of particles influenced by biomass burning in the eastern Mediterranean and their impacts on cloud droplet formation. Air masses sampled were subject to a range of atmospheric processing (several hours up to 3 days). Values of the hygroscopicity parameter, κ, were derived from CCN measurements and a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA). An Aerosol Chemical Speciation Monitor (ACSM) was also used to determine the chemical composition and mass concentration of non-refractory components of the submicron aerosol fraction. During fire events, the increased organic content (and lower inorganic fraction) of the aerosol decreases the values of κ, for all particle sizes. Particle sizes smaller than 80 nm exhibited considerable chemical dispersion (where hygroscopicity varied up to 100 % for particles of same size); larger particles, however, exhibited considerably less dispersion owing to the effects of condensational growth and cloud processing. ACSM measurements indicate that the bulk composition reflects the hygroscopicity and chemical nature of the largest particles (having a diameter of ∼ 100 nm at dry conditions) sampled. Based on positive matrix factorization (PMF) analysis of the organic ACSM spectra, CCN concentrations follow a similar trend as the biomass-burning organic aerosol (BBOA) component, with the former being enhanced between 65 and 150 % (for supersaturations ranging between 0.2 and 0.7 %) with the arrival of the smoke plumes. Using multilinear regression of the PMF factors (BBOA, OOA-BB and OOA) and the observed hygroscopicity parameter, the inferred hygroscopicity of the oxygenated organic aerosol components is determined. We find that the transformation of freshly emitted biomass burning (BBOA) to more oxidized organic aerosol (OOA-BB) can result in a 2-fold increase of the inferred organic hygroscopicity; about 10 % of the total aerosol hygroscopicity is related to the two biomass-burning components (BBOA and OOA-BB), which in turn contribute almost 35 % to the fine-particle organic water of the aerosol. Observation-derived calculations of the cloud droplet concentrations that develop for typical boundary layer cloud conditions suggest that biomass burning increases droplet number, on average by 8.5 %. The strongly sublinear response of clouds to biomass-burning (BB) influences is a result of strong competition of CCN for water vapor, which results in very low maximum supersaturation (0.08 % on average). Attributing droplet number variations to the total aerosol number and the chemical composition variations shows that the importance of chemical composition increases with distance, contributing up to 25 % of the total droplet variability. Therefore, although BB may strongly elevate CCN numbers, the impact on droplet number is limited by water vapor availability and depends on the aerosol particle concentration levels associated with the background.

New Mediterranean Biodiversity Records (July 2016)

Abstract: This contribution forms part of a series of collective articles published regularly in Mediterranean Marine Science that report on new biodiversity records from the Mediterranean basin. The current article presents 51 geographically distinct records for 21 taxa belonging to 6 Phyla, extending from the western Mediterranean to the Levantine. The new records, per country, are as follows: Spain: the cryptogenic calcareous sponge Paraleucilla magna is reported from a new location in the Alicante region. Algeria: the rare Atlanto-Mediterranean bivalve Cardium indicum is reported from Annaba. Tunisia: new distribution records for the Indo-Pacific lionfish Pterois miles from Zembra Island and Cape Bon. Italy: the ark clam Anadara transversa is reported from mussel cultures in the Gulf of Naples, while the amphipod Caprella scaura and the isopods Paracerceis sculpta and Paranthura japonica are reported as associated to the –also allochthonous–bryozoan Amathia verticillata in the Adriatic Sea; in the latter region, the cosmopolitan Atlantic tripletail Lobotes surinamensis is also reported, a rare finding for the Mediterranean. Slovenia: a new record of the non-indigenous nudibranch Polycera hedgpethi in the Adriatic. Greece: several new reports of the introduced scleractinian Oculina patagonica, the fangtooth moray Enchelycore anatina , the blunthead puffer Sphoeroides pachygaster (all Atlantic), and the lionfish Pterois miles (Indo-Pacific) suggest their ongoing establishment in the Aegean Sea; the deepest bathymetric record of the invasive alga Caulerpa cylindracea in the Mediterranean Sea is also registered in the Kyklades, at depths exceeding 70 m. Turkey: new distribution records for two non indigenous crustaceans, the blue crab Callinectes sapidus (Atlantic origin) and the moon crab Matuta victor (Indo-Pacific origin) from the Bay of Izmir and Antalya, respectively; in the latter region, the Red Sea goatfish Parupeneus forsskali , is also reported. Lebanon: an array of records of 5 alien and one native Mediterranean species is reported by citizen-scientists; the Pacific jellyfish Phyllorhiza punctata and the Indo-Pacific teleosteans Tylerius spinosissimus , Ostracion cubicus , and Lutjanus argentimaculatus are reported from the Lebanese coast, the latter notably being the second record for the species in the Mediterranean Sea since 1977; the native sand snake-eel Ophisurus serpens , rare in the eastern Mediterranean, is reported for the first time from Lebanon, this being its easternmost distribution range; finally, a substantial number of sightings of the lionfish Pterois miles further confirm the current establishment of this lessepsian species in the Levantine.