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"Oikonomou, Christina"
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Effects of Diet, Lifestyle, Chrononutrition and Alternative Dietary Interventions on Postprandial Glycemia and Insulin Resistance
by
Nychas, George
,
Papakonstantinou, Emilia
,
Dimitriadis, George D.
in
blood glucose
,
Blood Glucose - metabolism
,
Body fat
2022
As years progress, we are found more often in a postprandial than a postabsorptive state. Chrononutrition is an integral part of metabolism, pancreatic function, and hormone secretion. Eating most calories and carbohydrates at lunch time and early afternoon, avoiding late evening dinner, and keeping consistent number of daily meals and relative times of eating occasions seem to play a pivotal role for postprandial glycemia and insulin sensitivity. Sequence of meals and nutrients also play a significant role, as foods of low density such as vegetables, salads, or soups consumed first, followed by protein and then by starchy foods lead to ameliorated glycemic and insulin responses. There are several dietary schemes available, such as intermittent fasting regimes, which may improve glycemic and insulin responses. Weight loss is important for the treatment of insulin resistance, and it can be achieved by many approaches, such as low-fat, low-carbohydrate, Mediterranean-style diets, etc. Lifestyle interventions with small weight loss (7–10%), 150 min of weekly moderate intensity exercise and behavioral therapy approach can be highly effective in preventing and treating type 2 diabetes. Similarly, decreasing carbohydrates in meals also improves significantly glycemic and insulin responses, but the extent of this reduction should be individualized, patient-centered, and monitored. Alternative foods or ingredients, such as vinegar, yogurt, whey protein, peanuts and tree nuts should also be considered in ameliorating postprandial hyperglycemia and insulin resistance. This review aims to describe the available evidence about the effects of diet, chrononutrition, alternative dietary interventions and exercise on postprandial glycemia and insulin resistance.
Journal Article
Effects of the Mother’s Day Superstorm (10–11 May 2024) over the Global Ionosphere
by
Paul, Krishnendu Sekhar
,
Moses, Mefe
,
Oikonomou, Christina
in
Atmosphere, Upper
,
Constellations
,
COSMIC-2 RO
2025
The present study examines the global ionospheric response to the “Mother’s Day Superstorm” (10–11 May 2024), one of the most intense geomagnetic storms since 1957, with a minimum SYM-H index of −436 nT. Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) Radio Occultation (RO) data indicated an increase in the F2 layer maximum critical frequency (foF2) over midlatitude dayside regions, which was accompanied by a significant F-region uplift (hmF2 increase) on a global scale, even on the nightside during the main and recovery phases. At the same time, a decrease in foF2 was observed on the nightside. High southeastward and vertical drift velocities were observed in the nightside sector of the northern hemisphere with the dayside sector exhibiting upward and southwestward-to-northwestward drifts during the main and recovery phases of the storm. An intense upward drift (~170 m/s) in the southern hemisphere was registered with the poleward expansion of the Equatorial Ionization Anomaly (EIA) during the main phase. Swarm A data highlighted the EIA expansion from ~45°N to 60°S during the dayside main phase and from ~30°N to 40°S on the nightside during recovery.
Journal Article
Investigation of the Ionospheric Response on Mother’s Day 2024 Geomagnetic Superstorm over the European Sector
by
Bergeot, Nicolas
,
Paul, Krishnendu Sekhar
,
Chevalier, Jean-Marie
in
Auroral ionosphere
,
Coupling (molecular)
,
Electric fields
2025
The present study examines the negative ionospheric response over Europe during two geomagnetic storms on 10–13 May 2024, known as the Mother’s Day geomagnetic superstorm. The first storm, with a peak SYM-H value of −436 nT, occurred in the interval 10–11 May, while the second, less intense storm (SYM-H~−103 nT), followed in the interval 12–13 May. Using data from four European locations, temporal and spatial variations in ionospheric parameters (TEC, foF2, and hmF2) were analyzed to investigate the morphology of the strong negative response. Sharp electron density (Ne) depletion is associated with the equatorward displacement of the Midlatitude Ionospheric Trough (MIT), confirmed by Swarm satellite data. A key finding was the absence of foF2 and hmF2 values over all ionosonde stations during the recovery phase of the storms, likely due to the coupling between the Equatorial Ionization Anomaly (EIA) crests and the auroral ionosphere influenced by the intense uplift of the F layer. Relevant distinct features such as Large-scale Travelling Ionospheric Disturbance (LSTID) signatures and Spread F were also noted, particularly during the initial and main phase of the first storm over high midlatitude regions. Regional effects varied, with high European midlatitudes exhibiting different features compared to lower European latitude areas.
Journal Article
Occurrence features of intermediate descending layer and Sporadic E observed over the higher mid-latitude ionospheric station of Moscow
by
Panchenko, V. A
,
Leontiou, Theodoros
,
Oikonomou, Christina
in
Ionograms
,
Latitude
,
Morphology
2023
Nine years of ionograms from a higher mid-latitude ionospheric station (Moscow) are analyzed, by applying the ‘height–time–intensity’ (HTI) technique along with Spectrum (Lomb periodogram) analysis with the aim to investigate the daily and seasonal variability of sporadic E (Es) and intermediate descending layers (IDLs). Es and IDL traces are observed over Moscow, which are characterized by a 12-h periodicity prevailing throughout the year. Shorter periodicities in IDL and Es occurrence are also observed. A 6-h periodicity in Es and IDL dominates during November and December, while an 8-h periodicity is found mainly from October to February for IDL and in July for Es. These periodicities are primarily induced by the semi-, quarter- and terdiurnal thermospheric tides, respectively. Our results also establish the systematic and widespread manifestation of shorter-scale (4.8- and 4-h) periodicities observed mainly for IDL and less frequently for Es only during December and January, in the nine years considered, which is most probably linked to higher-order solar tides.
Journal Article
Hydrometeorological and Socio-Economic Impact Assessment of Stream Flooding in Southeast Mediterranean: The Case of Rafina Catchment (Attica, Greece)
2020
The CyFFORS (Cyprus Flood Forecasting System) project aims at increasing flood risk awareness and promoting preparedness against flooding by developing and validating a pilot flood forecasting system targeted over three river/stream basins in the Larnaca region, Cyprus, and Attica region, Greece. The present study demonstrates the analysis of flood-associated information, based on ground-based and ERA5 model reanalysis data, which is a necessary procedure prior to the development of the hydrometeorological modeling tool, in one of the study areas, namely in the Rafina catchment in Attica, Greece. The analysis focusses on 12 stream flood episodes that occurred in the period 2008–2014. The results show that most events were associated with a typical, for the study area, wet-season cyclonic activity. The detailed investigation of two case studies highlighted important spatiotemporal differences in the generation and development of rainfall, as well as in the flooding magnitude, which were related to specific characteristics of the synoptic-scale forcing, topography and soil moisture preconditioning. Moreover, highly correlated positive relationships were found between the observed maximum stream discharge and the duration and maximum total accumulation of precipitation. A strong positive correlation was also evident between the peak discharge and the flooding impacts, leading to the identification of preliminary discharge thresholds for impact-based warnings, which can be applied to the pilot CyFFORS forecasting system.
Journal Article
Investigation of Pre-Earthquake Ionospheric and Atmospheric Disturbances for Three Large Earthquakes in Mexico
by
Muslim, Buldan
,
Karagioras, Athanasios
,
Kourtidis, Konstantinos
in
19th century
,
Anomalies
,
Atmosphere
2021
The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and atmospheric disturbances by the application of different methodologies, with the ultimate aim to detect their possible link with the impending seismic event. Three large earthquakes in Mexico are selected (8.2 Mw, 7.1 Mw and 6.6 Mw during 8 and 19 September 2017 and 21 January 2016 respectively), while ionospheric variations during the entire year 2017 prior to 37 earthquakes are also examined. In particular, Total Electron Content (TEC) retrieved from Global Navigation Satellite System (GNSS) networks and Atmospheric Chemical Potential (ACP) variations extracted from an atmospheric model are analyzed by performing statistical and spectral analysis on TEC measurements with the aid of Global Ionospheric Maps (GIMs), Ionospheric Precursor Mask (IPM) methodology and time series and regional maps of ACP. It is found that both large and short scale ionospheric anomalies occurring from few hours to a few days prior to the seismic events may be linked to the forthcoming events and most of them are nearly concurrent with atmospheric anomalies happening during the same day. This analysis also highlights that even in low-latitude areas it is possible to discern pre-earthquake ionospheric disturbances possibly linked with the imminent seismic events.
Journal Article
Pre-Operational Application of a WRF-Hydro-Based Fluvial Flood Forecasting System in the Southeast Mediterranean
by
Giannaros, Christos
,
Galanaki, Elissavet
,
Giannaros, Theodore M.
in
Algorithms
,
Automation
,
Boundary conditions
2021
The Southeast Mediterranean (SEM) is characterized by increased vulnerability to river/stream flooding. However, impact-oriented, operational fluvial flood forecasting is far away from maturity in the region. The current paper presents the first attempt at introducing an operational impact-based warning system in the area, which is founded on the coupling of a state-of-the-art numerical weather prediction model with an advanced spatially-explicit hydrological model. The system’s modeling methodology and forecasting scheme are presented, as well as prototype results, which were derived under a pre-operational mode. Future developments and challenges needed to be addressed in terms of validating the system and increasing its efficiency are also discussed. This communication highlights that standard approaches used in operational weather forecasting in the SEM for providing flood-related information and alerts can, and should, be replaced by advanced coupled hydrometeorological systems, which can be implemented without a significant cost on the operational character of the provided services. This is of great importance in establishing effective early warning services for fluvial flooding in the region.
Journal Article
Multi-station investigation of spread F over Europe during low to high solar activity
by
Paul, Krishnendu Sekhar
,
Paul, Ashik
,
Belehaki, Anna
in
Dependence
,
effects of solar activity over spread F occurrence
,
Electric fields
2018
Spread F is an ionospheric phenomenon which has been reported and analyzed extensively over equatorial regions on the basis of the Rayleigh-Taylor (R-T) instability. It has also been investigated over midlatitude regions, mostly over the Southern Hemisphere with its generation attributed to the Perkins instability mechanism. Over midlatitudes it has also been correlated with geomagnetic storms through the excitation of travelling ionospheric disturbances (TIDs) and subsequent F region uplifts. The present study deals with the occurrence rate of nighttime spread F events and their diurnal, seasonal and solar cycle variation observed over three stations in the European longitude sector namely Nicosia (geographic Lat: 35.29 °N, Long: 33.38 °E geographic: geomagnetic Lat: 29.38 °N), Athens (geographic Lat: 37.98 °N, Long: 23.73 °E geographic: geomagnetic Lat: 34.61 °N) and Pruhonice (geographic Lat: 50.05 °N, Long: 14.41 °E geographic: geomagnetic Lat: 47.7 °N) during 2009, 2015 and 2016 encompassing periods of low, medium and high solar activity, respectively. The latitudinal and longitudinal variation of spread F occurrence was examined by considering different instability triggering mechanisms and precursors which past literature identified as critical to the generation of spread F events. The main findings of this investigation is an inverse solar cycle and annual temporal dependence of the spread F occurrence rate and a different dominant spread F type between low and high European midlatitudes.
Journal Article
Identification of two rate-limiting steps in the degradation of partially folded immunoglobulin light chains
by
Melendez-Suchi, Chris
,
Flory, Ashley R.
,
Hayes, Candace A.
in
Amino acids
,
Antibodies
,
Antigens
2022
Antibody monomers are produced from two immunoglobulin heavy chains and two light chains that are folded and assembled in the endoplasmic reticulum This process is assisted and monitored by components of the endoplasmic reticulum quality control machinery; an outcome made more fraught by the unusual genetic machinations employed to produce a seemingly unlimited antibody repertoire. Proper functioning of the adaptive immune system is as dependent on the success of this operation, as it is on the ability to identify and degrade those molecules that fail to reach their native state. In this study, two rate-limiting steps were identified in the degradation of a non-secreted κ light chain. Both focus on the constant domain (C L ), which has evolved to fold rapidly and very stably to serve as a catalyst for the folding of the heavy chain C H 1 domain. The first hurdle is the reduction of the disulfide bond in the C L domain, which is required for retrotranslocation to the cytosol. In spite of being reduced, the C L domain retains structure, giving rise to the second rate-limiting step, the unfolding of this domain at the proteasome, which results in a stalled degradation intermediate.
Journal Article
Investigation of ionospheric TEC precursors related to the M7.8 Nepal and M8.3 Chile earthquakes in 2015 based on spectral and statistical analysis
by
Muslim, Buldan
,
Oikonomou, Christina
,
Haralambous, Haris
in
Anomalies
,
Civil Engineering
,
Earth and Environmental Science
2016
Ionospheric total electron content (TEC) variations prior to 2 large earthquakes in Nepal (
M
= 7.8) and Chile (
M
= 8.3) in 2015 were analyzed using measurements from global navigation satellite system network with the aim to detect possible ionospheric anomalies associated to these seismic events and describe their main features, by applying statistical and spectral analysis. It was shown that abnormal TEC variations appeared few days up to few hours before the events lasting up to 8 h, whereas intensified TEC wave-like oscillations with periods 20 and 2–5 min were also identified that could be linked to the impending earthquakes. An unusual modification of the equatorial ionospheric anomaly 5 days before the main shock was also detected. Spectral analysis on TEC satellite measurements proved an effective method for the discrimination between seismically induced ionospheric waves and those of different origin such as the solar terminator transition and geomagnetic storms.
Journal Article