Papers by Kostas Kourtidis
Faculty of Physics, Saint Petersburg State University, Saint Petersburg, Russia, National Researc... more Faculty of Physics, Saint Petersburg State University, Saint Petersburg, Russia, National Research Nuclear University MEPhI, Moscow, Russia, Deptment of Electronic and Electrical Engineering, University of Bath, Bath, United Kingdom, Deptment of Environmental Engineering, Democritus University of Thrace, Xanthi, Greece, Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia
<p>In the lightning channel pressures can be of the order of 100 atm and hence in the produ... more <p>In the lightning channel pressures can be of the order of 100 atm and hence in the produced thunder, sound pressure levels (SPL) can be very high. Additionally, the thunder frequency spectra have peaks for peal and claps at around 100 Hz and around 50 Hz for rumble sounds, with intracloud lightning having peaks at even fewer Hz. These low frequencies are ideal for acoustically induced orthokinetic agglomeration of droplets. Thunder occurs in cloud environments where not only large numbers of droplets are present, but additionally the shockwave front expands at supersonic velocities in excess of 60 km/s and hence could cause also modulations of droplet size distributions through e.g. vibrational breakup. We present calculations for the two mechanisms above (orthokinetic agglomeration and vibrational breakup) for typical cloud droplet sizes and concentrations. In thunderstorm conditions, it is found that acoustic orthokinetic agglomeration of droplets can be very effective and can produce very rapidly changes in the mean cloud droplet diameter. Also, it is found that the critical Weber number, over which breakup occurs, is easily exceeded in thunderstorm environments and may lead to droplet and ice nuclei breakup. We note that these processes need further study to assess how they could interfere with the lightning generation process itself, through charge redistribution in the modified droplet size distribution spectra.&#160;</p>
Fresenius Environmental Bulletin, 1997
Results and Discussion To study the response of PG to thunderstorm distance, the area of interest... more Results and Discussion To study the response of PG to thunderstorm distance, the area of interest, centered over the EFM site, was divided into six circular rings (0 – 30 km, interval: 5km). Then, the PG values at the moments of lightning occurrence within each ring were selected. Here, lightning data act as indicators of the existence of a thunderstorm and give information about its distance from EFM. Finally, for each circular ring, PG values were distributed in 1 kV m-1 bins.
International Journal of Biometeorology, 2020
International Journal of Biometeorology, 2020
We present an analysis of the impact of circulation weather types (CT) on a factor that might inf... more We present an analysis of the impact of circulation weather types (CT) on a factor that might influence biological systems and the human condition, the electric state of the atmosphere. We present results on the influence of CT to the magnitude, the direction (positive or negative), the fluctuation magnitude, and the short-term peaks of the atmospheric electric field (potential gradient, PG), using data from a station in Greece. CTs with high vorticity centers over Greece are associated with high positive and negative excursions of the PG, higher PG variability, and rain events. CTs with thinner 850–500 hPa layer are associated with higher daily mean values of fair-weather PG. We also examine the influence of CT on the frequency and amplitude of the naturally occurring extremely low-frequency electric field fluctuations known as Schumann resonances (SR) using data from a station in Hungary. The first and second mode SR frequencies are increased during CTs associated with higher 500 ...
International Journal of Biometeorology, 2020
The term neurodegenerative diseases include a long list of diseases affecting the nervous system ... more The term neurodegenerative diseases include a long list of diseases affecting the nervous system that are characterized by the degeneration of different neurological structures. Among them, Alzheimer disease (AD), Parkinson disease (PD), and amyotrophic lateral sclerosis (ALS) are the most representative ones. The vast majority of cases are sporadic and results from the interaction of genes and environmental factors in genetically predisposed individuals. Among environmental conditions, electromagnetic field exposure has begun to be assessed as a potential risk factor for neurodegeneration. In this review, we discuss the existing literature regarding electromagnetic fields and neurodegenerative diseases. Epidemiological studies in AD, PD, and ALS have shown discordant results; thus, a clear correlation between electromagnetic exposure and neurodegeneration has not been demonstrated. In addition, we discuss the role of electromagnetic radiation as a potential non-invasive therapeutic strategy for some neurodegenerative diseases, particularly for PD and AD.
Frontiers in Environmental Science, 2019
Issue 1, 2013
Estimates of the amount of secondary organic aerosol formed in the atmosphere from the degradatio... more Estimates of the amount of secondary organic aerosol formed in the atmosphere from the degradation of traffic C6-C12 hydrocarbon emissions in the city of Athens are presented. Around 1.26 tn of organic aerosol is estimated to be produced during a six hours air pollution episode from the aromatic hydrocarbons, the other NMHC groups contributing an additional 0.2 tn. The main contributor to the SOA production is m-xylene. It accounts, together with toluene, for around 50% of the produced organic aerosol. The main aerosol products that are expected to form from the Athens NMHC traffic mixture are nitrophenols. Due to predominant wind flow to the S-SE direction in the area, a portion of these aerosols is likely to contribute to the SOA burden of the marine atmosphere over SE Mediterranean. These results are also relevant to ozone abatement strategies involving species-specific NMHC reductions and affecting fine particulate composition and concentrations.
Issue 1, 2013
Although noise is a very common nuisance in Greek cities, information on actual noise levels in s... more Although noise is a very common nuisance in Greek cities, information on actual noise levels in streets is sparse. Here, noise measurements at five main streets of Thessaloniki, Greece for about five weeks are presented. Ten minute, one hour and daily average noise levels were calculated. Traffic noise levels were significant in every examined street during the study. In all streets, the diurnal variation of noise levels and traffic volume exhibited significant correlation, with r2 up to 0.92. Noise measurements at two heights in one street showed a difference of around 14 db between the 1st and the 8th floor. The noise levels difference between working days and weekends was around 1-2 dB during daytime, but it changed sign during the late night hours. The latter can be attributed to night-life recreational traffic during weekends. Noise levels from 7:00 to 24:00 were around 63-66 dB in the 1st and 2nd floors of all four streets where measurements were made at these floors. In these...
Atmospheric Chemistry and Physics, 2018
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Papers by Kostas Kourtidis