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For the in-orbit calibration and validation of the Aeolus products, ESA organized the Aeolus Tropical campaign, which will take place on June-July 2021 at Cape Verde region. During the campaign, Aeolus underfights will be performed with several aircrafts (by DLR, NASA, LATMOS, and the University of Nova Gorica (UNG)) and advanced ground-based instrumentation will be deployed in Mindelo island within ASKOS (https://askos.space.noa.gr/) experiment. ASKOS observations will provide an unprecedented dataset for the aerosol and wind conditions in the region, in order to provide reference values for the Cal/Val of the mission. Apart from the main aerosol Cal/Val objective of ASKOS, the foreseen synergistic activities will provide a wealth of information to address scientific questions posed by the participating groups on dust characterization, transportation and it’s impact of radiation and cloud formation.Here, we report on the status of the ASKOS preparations for the evaluation of the aerosol and cloud product, focusing on the instrumentation requirements and availability, as well as the engagement of the scientific community so far. ASKOS will deploy advanced ground-based and airborne remote sensing and in-situ instrumentation, including the full ACTRIS aerosol and cloud remote sensing/in-situ facilities and airborne in-situ sensors to be operated on drones and/or aircrafts. The main ground-based remote sensing instrumentation in Cape Verde will consist of sophisticated lidar systems, including the EVE lidar, a circular polarization system that is tailored to mimic the Aeolus measurement from ground, the multi-wavelength Polly-XT and the WALL-E prototype for detecting particle orientation. The instrumentation will also include sun-photometers such as AERONET-CIMEL, but also polarimeters to advance microphysical retrievals for non-spherical particles such as dust. Cloud remote sensors including a cloud radar and a microwave radiometer will operate in parallel along with meteorological radiosondes. In-situ sensors at surface and onboard UAVs and light aircrafts will be available. ASKOS will be fully supported by several operational modeling simulations for meteorological and atmospheric composition forecasting. ASKOS will remain open to contributions from other communities and research groups and more synergies will be pursued in the future.

Among all natural disasters, river floods are becoming increasingly frequent. They present high risk and their impact can be fairly destructive and of strong economic, health, and social importance. Key tools to avoid their catastrophic results are the Early Warning Systems (EWS). An EWS usually monitors various physical quantities through a specific hardware, and produce data which after certain processing can detect and estimate the level of the risk.In the current work we present the concept, the design, the application, and some preliminary data regarding a low cost imaging node, part of an EWS aimed for river floods. This EWS consists of various sensing nodes which are mainly equipped with water presence detectors, water level meters, water temperature sensors, along with the necessary networking capability. The novelty of this new node design is that it utilizes a VGA resolution camera which captures still images of a view of interest. The latter can be for example an implementation prone to defects in case of flood, such as a river basin level road crossing, or a bridge. The images can also provide constant monitoring of the river basin state, i.e. to detect the presence of any unwanted objects (waste or other natural & artificial bring materials). Through image processing the images can even provide some coarse data, i.e. water level measurements by utilizing vertical stripped rods within the field of view of the camera.The ability to have a camera usually counteracts the IoT characteristics of an electronic device. Nevertheless, in this design the IoT character of the node was not constrained. The nodes have extended power autonomy (several months via Li-Ion battery, optionally solar rechargeable), present a small size, each node is network independent using GSM and LoRaWAN technology. The data usage is minimized by uploading only 2 QVGA images per day in normal operation (can be increased to a maximum of 48 VGA images per day, if required). In case of risk detection the node also supports the actuation of a local warning sign.

The aim of this study was to determine the cognitive and behavioral effects of extra virgin olive oil total phenolic content (TPC) and Sideritis (SID) extracts in female mice, and identify the associated neurochemical changes in the hippocampus and the prefrontal cortex. All animals received intraperitoneal low or high doses of TPC, SID or vehicle treatment for 7 days and were subjected to the Open Field (OF), Novel Object Recognition (NOR) and Tail Suspension Test (TST). The prefrontal cortex and hippocampus were dissected for analysis of neurotransmitters and aminoacids with high performance liquid chromatography with electrochemical detection (HPLC-ED). Both TPC doses enhanced vertical activity and center entries in the OF, which could indicate an anxiolytic-like effect. In addition, TPC enhanced non-spatial working memory and, in high doses, exerted antidepressant effects. On the other hand, high SID doses remarkably decreased the animals&rsquo, overall activity. Locomotor and exploratory activities were closely associated with cortical increases in serotonin turnover induced by both treatments. Cognitive performance was linked to glutamate level changes. Furthermore, TPC reduced cortical taurine levels, while SID reduced cortical aspartate levels. TPC seems to have promising cognitive, anxiolytic and antidepressant effects, whereas SID has sedative effects in high doses. Both extracts act in the brain, but their specific actions and properties merit further exploration.

Air pollution affects life quality and already has measurable impact on the human health and ecosystem change. It is widely accepted that in order invert the continually growing pollution, citizen awareness policies must be adopted and encouraged. Under this concept large data sets are collected using new measuring systems adopting low cost technologies. This tactic led to the need of evaluating low cost sensing systems in order to be able to collect valid measurements and been able to use them and provide as accurate information as possible. Many research teams are working on this topic studying various factors that affect measured quantities like the temperature and humidity are and propose new low-cost monitoring systems, aiming to developing a network over large geographic areas. This work presents a low cost, low energy consumption and high processing power monitoring station. The monitoring station incorporates Alphasense electrochemical sensors of measuring NO2 and O3 as well as NO2-B43F and OX-B431. In order to be able to design proper calibration and correction formulas temperature, humidity and barometric pressure are also measured and in this work the results of the above process are described. Results collected from two monitoring stations that were installed next to official measuring point of the National Observatory of Athens are presented herein for the NO2 and O3 quantities.

We report on the electric field variations during Saharan dust advection over two atmospheric remote stations in Greece, using synergistic observations of the vertical atmospheric electric field strength (Ez) at ground and the lidar-derived particle backscatter coefficient profiles. Both parameters were monitored for the first time with the simultaneous deployment of a ground-based field mill electrometer and a multiwavelength lidar system. The field mill timeseries are processed to extract the diurnal variations of the Global Electric Circuit and remove fast field perturbations due to peak lightning activity. In order to identify the influence of the elevated dust layers on the ground Ez, we extract a Localized Reference Electric Field from the timeseries that reflects the local fair weather activity. Then, we compare it with the reconstructed daily average behaviour of the electric field and the Saharan dust layers' evolution, as depicted by the lidar system. Reported cases of enhanced vertical electric field for detached pure dust layers suggest the presence of in-layer electric charges. Although higher dust loads are expected to result in electric field enhancement, episodic cases that reduce the electric field are also observed. To quantitatively approach our results, we examine the dependency of Ez against theoretical assumptions for the distribution of separated charges within the electrified dust layer. Electrically neutral dust is approximated by atmospheric conductivity reduction, while charge separation areas within electrically active dust layers are approximated as finite extent cylinders. This physical approximation constitutes a more realistic description of the distribution of charges, as opposed to infinite extent geometries, and allows for analytical solutions of the electric field strength, so that observed electric field variations during the monitored dust outbreaks can be explained.

River floods occupy a respectable percentage among all natural disasters, are presenting high risk, and usually cause great damage. Important tools in managing and preventing river floods are the Early Warning Systems (EWS), which are usually consisted both by a hardware infrastructure (sensors, communication network) and a relevant software infrastructure (data logging, signal processing, modeling, risk detection).In the current work we are presenting preliminary results from a novel, low-cost and low-power hardware system, part of a EWS aimed for river floods. The system consists of multiple sensing nodes, each to be strategically positioned at certain points along the route of river Evros, Greece. Each sensing node will bear a low-cost and high-quality ultrasonic water level sensor, along with an embedded microcomputer to control its functionality. An additional novelty of the proposed work is the design and utilization of a private low-power wide-area wireless network (LPWAN), taking advantage of IoT technologies and especially the LoRaWAN implementation. This way, the proposed system will have even lower power demands, together with greater expandability by allowing many nodes to be simultaneously connected and measuring, and having the ability to utilize crowd-sensing techniques. The power supply is battery based and autonomously recharged with the aid of small solar panel. Each node will measure the water level of the river, and upload the data to a cloud server at variable time intervals, depending on the actual water level variation and the system’s power consumption optimization.Future upgrades of the system will involve extra sensors, allowing the nodes to measure water quality parameters i.e. suspended solids, pH, etc. Although of secondary importance, these parameters might prove to be important in the development of the risk detection and alarm issuing algorithms.

Electrical processes can be a potential key player in the lifecycle of desert dust. The dust particles can be charged during their transport, either by the attachment of atmospheric ions or by particle to particle collisions (triboelectric effect). Measurements indicate that, on average, larger particles become positively charged while the smaller ones become negatively charged [Zhao, H. L., J. Electrostat, 55, 2002; Lacks, D.J., et al., Phys. Rev. Lett., 100, 188305, 2008; Merrison, J.P., Aeolian Res., 4, 2012; Shinbrot, T. and Herrmann, H.J., Nature, 451, 2008]. During dust transportation, the larger and mainly positively charged particles separate from the smaller negatively charged particles due to the gravitational sedimentation, which sorts the dust particles by size. This process develops vertical electric fields within the dust cloud, enhancing the pre-existing field due to the depletion of atmospheric conductivity by the presence of the dust layer [Gringel W. and Mulheisen. R., Beitr. Phys. Atmos., 51, 121–8, 1978]. Depending on its strength, the total electric field within the dust cloud can: (a) counteract the gravitational settling of large particles and (b) cause a preferential orientation of the non-spherical particles along the vertical direction affecting particle aerodynamics [Ulanowski, Z., et al., Atmos. Chem. Phys., 7, 2007]. Therefore, electrical processes may alter dust removal processes, and thus the evolution of particle size during transport, affecting dust-radiation-cloud interactions and the associated air quality [Sajani S.Z., et al., Occup. Environ. Med., 68(6), 2011], weather, and climate modeling [Mahowald, N., et al., Aeolian Res., 15, 2014].In the present work, we have developed a novel 3D Cartesian time-dependent model that takes into account several atmospheric processes, such as: (i) the ionization due to the galactic cosmic rays radiation, (ii) the ion-ion recombination, and (iii) the ion attachment to non spherical dust particles. The model is able to self-consistently calculate the time dynamics of the atmospheric conductivity, and the atmospheric electric field, under the presence of a distribution of stationary non spherical dust particles. Additionally, the total charge density, dust particle charge and dust particle orientation are also quantified. The new 3D electrification formalism allows the study of dust layers without imposing any symmetry and is valid for layers with any horizontal and vertical extend, as opposed to 1D models which are valid when the horizontal extend is much larger than the vertical, or to 2D models which assume a symmetry in the shape of the dust layer. The results are compared, in the limiting case that the horizontal extend is much larger than the vertical one, with those obtained from 1D models found in the past literature [e.g. Zhou, L., Tinsley, B.A., Adv. Space Res. 50, 2012]. Moreover, the effect of the studied electrification process is assessed through a comparison with recent and unique electric field measurements within lofted dust layers, as performed with the use of novel low cost atmospheric electricity sensors in an experimental campaign of the D-TECT ERC project, in Cyprus the past November.

This paper presents an in-house developed low-cost triggering design using wireless sensor network (WSN) nodes. A set of corresponding microelectromechanical system (MEMS) sensors (accelerometer and gyroscope) are used along with a radio transmission unit and a microprocessor. In conjunction with the WSN, terrestrial laser scanning (TLS) measurements are used. Specifically, the aim of this work is to introduce a low-cost WSN node with verified repeatability that will raise an initial signal for possible slope change which will be further verified by TLS measurements. The paper demonstrates the deployment of the developed design for a 3-month period in the Corinth Canal in Greece and presents indicative results.

Acoustic emission tests were conducted on prismatic Dionysos’ marble specimens subjected to compressive mechanical loading cycles. Two groups of acoustic emission time series were analyzed: one group comprised the number of counts per acoustic emission hit and a second group comprised the RA quantity (RA=rise time/amplitude). Both time series were studied during the load increase period. The investigation of prefailure indicators was carried out using an interdisciplinary approach: using two solid methods from different scientific areas (i.e. cardiology and seismology) we were able to detect failure indicators along before the final collapse. More specific, by means of multiresolution wavelet analysis for the study of temporal variation of the wavelet-coefficients’ standard deviation and natural time analysis using the variance ( κ1) of natural-time transformed time-series, a common pattern for both domains was discovered, clearly showing that it is feasible to estimate if the applied mechanical load has led the specimen in the nonlinear region (σ* > 70% σf) regarding the stress–strain behavior.

The present document is a deliverable of the hackAIR project, funded by the European Commission under the Horizon 2020 programme.The current document summarizes the updates performed in the provided methodologies according to the user needs and the modifications implemented in the relevant methodologies based on the findings from their application in real-life conditions.

The present document is a deliverable of the hackAIR project, funded by the European Commission under the Horizon 2020 programme.The current report is the second version of the design guidelines for the hackAIR open sensor fabrication that describes the implementation details of three open hardware solutions along with an initial version of user guidelines for the construction of each one.

This paper presents a new method for assessing the three-point-bending (3PB) strength of mortar beams in a non-destructive manner, based on neural network (NN) models. The models are based on the radial basis function (RBF) architecture and the fuzzy means algorithm is employed for training, in order to boost the prediction accuracy. Data for training the models were collected based on a series of experiments, where the cement mortar beams were subjected to various bending mechanical loads and the resulting pressure stimulated currents (PSCs) were recorded. The input variables to the NN models were then calculated by describing the PSC relaxation process through a generalization of Boltzmannn-Gibbs statistical physics, known as non-extensive statistical physics (NESP). The NN predictions were evaluated using k-fold cross-validation and new data that were kept independent from training; it can be seen that the proposed method can successfully form the basis of a non-destructive tool for assessing the bending strength. A comparison with a different NN architecture confirms the superiority of the proposed approach.

The purpose of this study is to demonstrate the use of wavelet transform (WT) as the common processing tool for earthquake’s rapid magnitude determination and epicentral estimation. The goal is to use the same set of wavelet coefficients that characterize the seismogram (and especially its P-wave portion) to use one technique (WT) for double use (magnitude and location estimation). Wavelet magnitude estimation (WME) is used to derive a scaling relation between earthquake’s magnitude and wavelet coefficients for South Aegean using data from 469 events with magnitudes from 3.8 to 6.9. The performance of the proposed relation was evaluated using data from 40 additional events with magnitude from 3.8 to 6.2. In addition, the epicentral estimation is achieved by a new proposed method (wavelet epicentral estimation—WEpE) which is based on the combination of wavelet azimuth estimation and two stations’ sub array method. Following the performance investigation of WEpE method, we present results and simulations with real data from characteristic events that occurred in South Aegean. Both methods can be run in parallel, providing in this way a suitable core of a regional earthquake early warning system in South Aegean.

In the present work, the installation and the technology applied for the operation of the Hellenic Seismological Network of Crete (HSNC), located in the front of the Hellenic Arc, are presented. The topology, the communication modes (wire and satellite) along with data collection and processing methodologies applied leads to the operation of a new seismological infrastructure in South Aegean, one of the most seismically active regions in Europe.

Although air pollution is one of the most significant environmental factors posing a threat to human health worldwide, air quality data are scarce or not easily accessible in most European countries. The current work aims to develop a centralized air quality data hub that enables citizens to contribute to air quality monitoring. In this work, data from official air quality monitoring stations are combined with air pollution estimates from sky-depicting photos and from low-cost sensing devices that citizens build on their own so that citizens receive improved information about the quality of the air they breathe. Additionally, a data fusion algorithm merges air quality information from various sources to provide information in areas where no air quality measurements exist.

The experimental set-up described in Part I of the present short two-papers series is used for the implementation of non-standardized structural tests with specimens simulating interconnected epistyles of the Parthenon Temple on the Acropolis of Athens. The aim of the study is two folded: To quantify the response of the connections when they are subjected to shear forces and also to assess comparatively the experimental data pumped with the aid of the Acoustic Emission and Pressure Stimulated Currents techniques from the interior of the specimens. It is concluded that the experimental set-up restricts in a satisfactory manner parasitic bending and torsional moments although they are not completely eliminated due to the inherent asymmetries of the specimens’ geometry. It is also proven that the data of these innovative techniques are in good qualitative and quantitative agreement with the respective ones recorded with the aid of both traditional and modern sensing techniques pumping data from the outer surface of the specimens. Moreover it is concluded that the Pressure Stimulated Currents technique could be a safe fracture predictor.

The mechanical response of marble epistyles interconnected to each other by means of metallic connectors when subjected to shear loading is studied experimentally. The study is motivated by the need of the scientific group of the Athenian Acropolis to substitute damaged ancient connections by new ones. In this direction “I”-shaped titanium connectors are placed in the grooves sculptured by ancient stonemasons in the marble blocks and the empty space is then filled by a suitable cement-based material. Guided by the experience gathered from the inspection of failed connections, which clearly indicates that failure starts at the interior of the “titanium-mortar-marble” complex, along the material interfaces, an experimental protocol was improvised, aiming at pumping data from the interior of the interconnected epistyles. For this to be accomplished innovative sensing techniques like pressure stimulated currents, digital image correlation and acoustic emission were used in conjunction with traditional ones. In the first part of this short two-paper series the experimental set-up, the materials and the specimens’ geometry are described.

On January 26 and February 3, 2014, Cephalonia Island (Ionian Sea, Greece) was struck by two strong, shallow earthquakes (moment magnitudes Mw6.1 and Mw6.0, respectively) that ruptured two sub-parallel, strike-slip faults, with right-lateral kinematics. The scope of the present work is to investigate the complex correlations of the earthquake activity that preceded the Mw6.1 event in the broader area of the Cephalonia Island and identify possible indications of critical stages in the evolution of the earthquake generation process. We apply the recently introduced methods of Multiresolution Wavelet Analysis (MRWA) and Natural Time (NT) analysis and for the first time we combine their results in a joint approach that may lead to universal principles in describing the evolution of the earthquake activity as it approaches a major event. In particular, the initial application of MRWA on the inter-event time series indicates a time marker 12 days prior to the major event. By using this time as the initiation point of the NT analysis, the critical stage of seismicity, where the κ 1 parameter reaches the critical value of κ 1 = 0.070, is approached few days before the occurrence of the Mw6.1 earthquake.

Specimens of polymer matrix — ceramic TiO2 filler composites were prepared. The contribution of the filler content on the electrical conductivity and energy storage properties of the samples was examined. I–V and Isothermal Polarization/Depolarization Current (IPC/IDC) measurements were conducted. Dc conductivity values directly calculated from the I–V curves exhibited excellent agreement with corresponding values derived from the IPC/IDC recordings. Standard models were employed for fitting the IPC/IDC data. In specific, the short and the very long depolarization times were fitted by use of power laws of different slopes, while the intermediate depolarization times were fitted as a sum of three exponential decays. The present study reveals a strong dependence of the depolarization and polarization processes, as well as of the dc conductivity, on the filler concentration.

We report on experimental measurements of the refractive index of twelve organic solvents at five different wavelengths (450, 532, 632.8, 964 and 1,551 nm) and a temperature of 300 K. Based on these new data visible to near-infrared dispersion relations are constructed. Group-velocity dispersion (GVD) is theoretically calculated. Zero- and negative-GVD situations are identified for two common solvents in near-infrared wavelengths. Via comparison with refractive index data available in bibliography, estimated values of thermo-optic coefficients are also presented.

The application of mechanical loading on cement-based materials generates weak electrical currents due to the formation and propagation of microfractures. This paper introduces the simultaneous recording of electrical signal emissions know as Pressure Stimulated Currents (PSCs) and Acoustic Emissions (AEs) detected in cement mortar beams of rectangular cross-section subjected to mechanical loading using the Three Point Bending tests. The rate of the applied load during the experiments was constant up to the fracture of the specimen. The characteristics of the AE and PSC were put in contrast in order to better understand the evolution of the microfracture processes up to fracture. Specifically, the recorded PSC and AE were studied in terms of their time series, cumulative energy along with AE rate and AE interevent times that may provide information about the upcoming specimen fracture. Moreover, non-extensive statistical physics modeling was attempted in terms of studying the Tsallis entropy. Specifically, the entropic index q was calculated and its dependence on the applied mechanical load was investigated.

This study attempts a comparative evaluation of chromatic dispersion equations in 61 crystalline solids. Based on previously published data, it is demonstrated that the extended-Cauchy equation (which in the past has been mainly used with glasses) outperforms Sellmeier models and other alternative approaches in the cases of 43 crystals, including BBO, BiBO, KTP, etc. Accumulated Cauchy coefficients for these 43 materials are presented. Performance characteristics of the extended-Cauchy model are related to specific experimental conditions, such as the number of available refractive index data, as well as the spectral location and bandwidth of measurement. The number of Cauchy coefficients required for reaching practically maximum fitting accuracy is determined. It is shown that typically, extended-Cauchy equations constructed by use of only five experimental data may be used for precise modeling of two-octave spanning spectral bandwidths.

This paper discusses the experimental results of concurrently measured Electrical and Acoustic Emissions in order to evaluate the mechanical health status of cement mortar beams subjected to three-point bending mechanical tests. In particular, the Electrical Resistance and the Electrical Current emissions are recorded concurrent with Acoustic Emissions and the experimental results are discussed under the concept of crack initiation and propagation processes. For the first time, the electrodes that are used for conducting the measurements are placed in the bulk of the specimen, near the tensile zone, during its preparation. The damage evolution is examined by monitoring the fractional change of the Electrical Resistance and the variation of the Electrical Current in combination with the Acoustic Emission recordings.

The main goal of an earthquake early warning system (EEWS) is to estimate the magnitude of an underway rupture from the first few seconds in order to allow hazard assessment and mitigation before destructive events occur. This letter investigates the application of a wavelet-based algorithm for local magnitude estimation in the South Aegean Sea (focusing on Crete Island) which is covered by a sparse seismological network. A relation between the first few seconds of the first-arriving energy at the surface, the P wave, and the local magnitude of the earthquake has been developed for the area of interest. Results show that the errors produced by the proposed method present less scattering than relevant magnitude rapid estimation methods. It is the first time that such a method is applied in a sparse seismological network since all the previous studies took place in high-density networks. This fact expands the applicability of EEWS and also provides an alternative magnitude estimator for the currently developed EEWS.

The electrical signals emitted during the application of uniaxial compressive mechanical stress upon cement mortar specimens are observed and discussed in this paper. This work discusses the electrical signals that are detected when the specimens are excited by a stepwise uniaxial stress increase from a low level (σ L ) to a higher level (σ H ) at a fast or slow rate and consequently remain at a high pressure regime for a long time. When maintaining constant mechanical stress for a long time, creep phenomena are evident in the specimen and the corresponding electrical emissions are recorded and analyzed. The characteristics of the electrical signal give clear information regarding the breaking stress (σ F ) of the material. The electrical emission recordings are of great interest when the applied σ H is located in the vicinity of the failure stress; the emitted electrical current increases greatly due to the sequential formation and propagation of cracks that occurs in this stress region. Thus, by correlating the strain rate variations to the electrical emissions this methodology can be used to predict failure due to compressive stress in cement mortars.

We applied multiresolution wavelet analysis to the sequence of times between earthquakes occurred between 1970 and 2003 in the southern Aegean area, one of the most seismically active area in the Mediterranean. We observed a twofold features in the wavelet-coefficient standard deviation σwav: (i) at low scales it decreases in correspondence with the occurrence of the strongest earthquake, mainly due to the aftershock activation mechanism; (ii) at high scales it is characterized by oscillating behaviour, which is a typical background seismicity.

It is already known that when a mechanical loading is applied to cement-based specimens weak electrical currents are generated. Their existence is attributed to the creation of cracks and the eventual evolution of the cracks’ network in the bulk of the specimen. This work introduces the simultaneous recording of electrical signal emissions at both the tension and the compression region of cement mortar beams of rectangular cross-section that were subjected to mechanical loading using the Three-Point-Bending technique. During the experiments the behavior of the electrical signal was studied during four sequential load stages: (1) Abrupt load increase up to the vicinity of 3 PB strength, (2) maintaining the high load level for relatively long time, (3) abrupt load decrease to a low load level (i.e. 50 % of the 3 PB strength approximately), (4) maintaining the low load level for relatively long time. The electrical signal analysis was conducted using non extensive statistical physics (NESP) and specifically the Tsallis entropy model studying the values of its q-parameter. The aim of this work was to study the electrical signal relaxation process that follows the change of the mechanical load and the law that describes this relaxation with respect to the mechanical status of the specimen using statistical physics analysis.