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66 result(s) for "Triantafyllou, Athanasios"
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Green Transition and Electricity Sector Decarbonization: The Case of West Macedonia
During the last 50 years, the vast majority of European countries have relied on coal and imported carbon-containing fuels to meet their growing electricity demand. Coal is the only fossil fuel in significant reserves across Europe. However, the pressing threat of radical climate change and the looming depletion of fossil fuels necessitate a structural transformation from a conventional centralized fossil fuel-based electricity generation system to an innovative decentralized system based on zero carbon (green) energy resources. In this context, one important issue for communities operating coal-based Thermal Power Stations (TPS) nearing retirement is whether the European Union (EU) policy can ensure a socially just development of the coal mining areas during the coal phase-out. The objective is to avoid a decline in living standards and mass immigration. In response to the EU’s decarbonization policy, the Greek state has recently decided to retire the lignite-based West Macedonia TPS, which has been in operation since the 1970s. Since its establishment in August 1950, the (initially State-controlled) Greek Public Power Corporation (PPC) has undertaken the responsibility to operate the quarries and the six local TPS, offering approximately 25,000 direct and indirect jobs. Over the last 50 years, the extraction of lignite and the operation of the 4500 MWe TPS of West Macedonia has been the primary economic activity, accounting for nearly 45% of the entire Region’s GDP. While both the Greek state and the EU have prepared and presented plans to financially support local communities and encourage new private and public investments, local citizens remain anxious about their future. The present study investigates the attitude of young scientists towards the forthcoming radical changes linked to the green transition in seriously affected EU Regions, with a focus on West Macedonia. The proposed analysis in West Macedonia reveals the skepticism of young people regarding the speed of the green transition and concerns about significant migration and potential brain drain. On the other hand, the implementation of EU initiatives, including the involvement of young scientists in the planned new green energy-related activities, offers a promising alternative solution. This engagement can lead to the successful integration of local communities into the sustainable and green future envisioned by the EU.
Urban-Scale Computational Fluid Dynamics Simulations with Boundary Conditions from Similarity Theory and a Mesoscale Model
Mesoscale numerical weather prediction models usually provide information regarding environmental parameters near urban areas at a spatial resolution of the order of thousands or hundreds of meters, at best. If detailed information is required at the building scale, an urban-scale model is necessary. Proper definition of the boundary conditions for the urban-scale simulation is very demanding in terms of its compatibility with environmental conditions and numerical modeling. Here, steady-state computational fluid dynamics (CFD) microscale simulations of the wind and thermal environment are performed over an urban area of Kozani, Greece, using both the k-ε and k-ω SST turbulence models. For the boundary conditions, instead of interpolating vertical profiles from the mesoscale solution, which is obtained with the atmospheric pollution model (TAPM), a novel approach is proposed, relying on previously developed analytic expressions, based on the Monin Obuhkov similarity theory, and one-way coupling with minimal information from mesoscale indices (Vy = 10 m, Ty = 100 m, L*). The extra computational cost is negligible compared to direct interpolation from mesoscale data, and the methodology provides design phase flexibility, allowing for the representation of discrete urban-scale atmospheric conditions, as defined by the mesoscale indices. The results compared favorably with the common interpolation practice and with the following measurements obtained for the current study: SODAR for vertical profiles of wind speed and a meteorological temperature profiler for temperature. The significance of including the effects of diverse atmospheric conditions is manifested in the microscale simulations, through significant variations (~30%) in the critical building-related design parameters, such as the surface pressure distributions and local wind patterns.
Genetics and epigenetics of Pinus nigra populations with differential exposure to air pollution
Forest species in the course of their evolution have experienced several environmental challenges, which since historic times include anthropogenic pollution. The effects of pollution on the genetic and epigenetic diversity in black pine ( Pinus nigra ) forests were investigated in the Amyntaio – Ptolemais – Kozani Basin, which has been for decades the largest lignite mining and burning center of Greece, with a total installed generating capacity of about 4.5 GW, operating for more than 70 years and resulting in large amounts of primary air pollutant emissions, mainly SO 2 , NOx and PM10. P. nigra , a biomarker for air pollution and a keystone species of affected natural ecosystems, was examined in terms of phenology (cone and seed parameters), genetics (283 AFLP loci) and epigenetics (606 MSAP epiloci), using two populations (exposed to pollution and control) of the current (mature trees) and future (embryos) stand. It was found that cone, seed, as well as genetic diversity parameters, did not show statistically significant differences between the exposed population and the control. Nevertheless, statistically significant differences were detected at the population epigenetic level. Moreover, there was a further differentiation regarding the intergenerational comparison: while the epigenetic diversity does not substantially change in the two generations assessed in the control population, epigenetic diversity is significantly higher in the embryo population compared to the parental stand in the exposed population. This study sheds a light to genome dynamics in a forest tree population exposed to long term atmospheric pollution burden and stresses the importance of assessing both genetics and epigenetics in biomonitoring applications.
Post-Arthroplasty Spatiotemporal Gait Parameters in Patients with Hip Osteoarthritis or Developmental Dysplasia of the Hip: An Observational Study
Total hip arthroplasty (THA) is a preferred treatment for primary osteoarthritis (OA) or secondary degenerative arthropathy due to developmental hip dysplasia (DDH). Gait analysis is considered a gold standard for evaluating post-arthroplasty walking patterns. This study compared post-THA spatiotemporal gait parameters (SGPs) between OA and DDH patients and explored correlations with demographic and clinical variables. Thirty patients (15 per group) were recorded during gait and their SGPs were analyzed. Functionality was evaluated with the Oxford Hip Score (OHS). The OA patients were significantly older than DDH patients (p < 0.005). Significant and moderate to strong were the correlations between SGPs, age, and four items of the OHS concerning hip pain and activities of daily life (0.31 < Pearson’s r < 0.51 all p < 0.05). Following THA, both groups exhibited similar levels of the examined gait parameters. Post-arthroplasty SGPs and OHS correlations indicate limitations in certain activities. Given the absence of pre-operative data and the correlation between age and SGPs and OHS, ANCOVA testing revealed that age adjusts OHS and SGP values, while pre-operative diagnosis has no main effect. These findings indicate that hip OA or DDH do not affect postoperative SGPs and patients’ functionality. Future studies should examine both kinematic and kinetic data to better evaluate the post-THA gait patterns of OA and DDH patients.
The Acute and Chronic Effects of Resistance and Aerobic Exercise in Hemostatic Balance: A Brief Review
Hemostatic balance refers to the dynamic balance between blood clot formation (coagulation), blood clot dissolution (fibrinolysis), anticoagulation, and innate immunity. Although regular habitual exercise may lower the incidence of cardiovascular diseases (CVD) by improving an individual’s hemostatic profile at rest and during exertion, vigorous exercise may increase the risk of sudden cardiac death and venous thromboembolism (VTE). This literature review aims to investigate the hemostatic system’s acute and chronic adaptive responses to different types of exercise in healthy and patient populations. Compared to athletes, sedentary healthy individuals demonstrate similar post-exercise responses in platelet function and coagulatory and fibrinolytic potential. However, hemostatic adaptations of patients with chronic diseases in regular training is a promising field. Despite the increased risk of thrombotic events during an acute bout of vigorous exercise, regular exposure to high-intensity exercise might desensitize exercise-induced platelet aggregation, moderate coagulatory parameters, and up-regulate fibrinolytic potential via increasing tissue plasminogen activator (tPA) and decreasing plasminogen activator inhibitor (PAI-1) response. Future research might focus on combining different types of exercise, manipulating each training characteristic (frequency, intensity, time, and volume), or investigating the minimal exercise dosage required to maintain hemostatic balance, especially in patients with various health conditions.
Clinical Significance of the Static and Dynamic Q-angle
Q-angle represents the resultant force vector of the quadriceps and patellar tendons acting on the patella. An increased Q-angle has been considered a risk factor for many disorders and injuries. This literature review challenges the clinical value of static Q-angle and recommends a more dynamic movement evaluation for making clinical decisions. Although there are many articles about static Q-angle, few have assessed the value of dynamic Q-angle. We searched Scopus and PubMed (until September 2021) to identify and summarize English-language articles evaluating static and dynamic Q-angle, including articles for dynamic knee valgus (DKV) and frontal plane projection angle. We also used textbooks and articles from references to related articles. Although static Q-angle measurement is used systematically in clinical practice for critical clinical decisions, its interpretation and clinical translation present fundamental and intractable limitations. To date, it is acceptable that mechanisms that cause patellofemoral pain and athletic injuries have a stronger correlation with dynamic loading conditions. Dynamic Q-angle has the following three dynamic elements: frontal plane (hip adduction, knee abduction), transverse plane (hip internal rotation and tibia external rotation), and patella behavior. Measuring one out of three elements (frontal plane) illustrates only one-third of this concept. Static Q-angle lacks biomechanical meaning and utility for dynamic activities. Although DKV is accompanied by hip and tibia rotation, it remains a frontal plane measurement, which provides no information about the transverse plane and patella movement. However, given the acceptable reliability and the better differentiation capability, DKV assessment is recommended in clinical practice.
Performance and evaluation of a coupled prognostic model TAPM over a mountainous complex terrain industrial area
Atmospheric modeling is considered an important tool with several applications such as prediction of air pollution levels, air quality management, and environmental impact assessment studies. Therefore, evaluation studies must be continuously made, in order to improve the accuracy and the approaches of the air quality models. In the present work, an attempt is made to examine the air pollution model (TAPM) efficiency in simulating the surface meteorology, as well as the SO2 concentrations in a mountainous complex terrain industrial area. Three configurations under different circumstances, firstly with default datasets, secondly with data assimilation, and thirdly with updated land use, ran in order to investigate the surface meteorology for a 3-year period (2009–2011) and one configuration applied to predict SO2 concentration levels for the year of 2011.The modeled hourly averaged meteorological and SO2 concentration values were statistically compared with those from five monitoring stations across the domain to evaluate the model’s performance. Statistical measures showed that the surface temperature and relative humidity are predicted well in all three simulations, with index of agreement (IOA) higher than 0.94 and 0.70 correspondingly, in all monitoring sites, while an overprediction of extreme low temperature values is noted, with mountain altitudes to have an important role. However, the results also showed that the model’s performance is related to the configuration regarding the wind. TAPM default dataset predicted better the wind variables in the center of the simulation than in the boundaries, while improvement in the boundary horizontal winds implied the performance of TAPM with updated land use. TAPM assimilation predicted the wind variables fairly good in the whole domain with IOA higher than 0.83 for the wind speed and higher than 0.85 for the horizontal wind components. Finally, the SO2 concentrations were assessed by the model with IOA varied from 0.37 to 0.57, mostly dependent on the grid/monitoring station of the simulated domain. The present study can be used, with relevant adaptations, as a user guideline for future conducting simulations in mountainous complex terrain.
Neurological and neurourological complications of electrical injuries
Electrical injury can affect any system and organ. Central nervous system (CNS) complications are especially well recognised, causing an increased risk of morbidity, while peripheral nervous system (PNS) complications, neurourological and cognitive and psychological abnormalities are less predictable after electrical injuries. PubMed was searched for English language clinical observational, retrospective, review and case studies published in the last 30 years using the key words: electrical injury, electrocution, complications, sequelae, neurological, cognitive, psychological, urological, neuropsychological, neurourological, neurogenic, and bladder. In this review, the broad spectrum of neurological, cognitive, psychological and neurourological consequences of electrical trauma are discussed, and clinical features characteristic of an underlying neurological, psychological or neurourological disorder are identified. The latest information about the most recently discovered forms of nervous system disorders secondary to electrical trauma, such as the presentation of neurological sequelae years after electrocution, in other words long-term sequelae, are presented. Unexpected central nervous system or muscular complications such as hydrocephalus, brain venous thrombosis, and amyotrophic lateral sclerosis are described. Common and uncommon neuropsychological syndromes after electrical trauma are defined. Neurourological sequelae secondary to spinal cord or brain trauma or as independent consequences of electrical shock are also highlighted.
The Impact of Supply and Demand Driven Oil Price Uncertainty on the Cost of Bank Loans
We study the effect of supply and demand-induced oil price uncertainty on the cost of debt for a sample of US loans credited during the 1990 to 2019 period. We estimate oil price uncertainty following Jurado et al.’s study, whereby oil price uncertainty is captured by forecasting the unpredictable fluctuations of oil prices. Interestingly, our findings reveal that oil price uncertainty induced by supply shocks increases cost of credit, while oil price uncertainty driven by demand shocks decreases the cost of bank loans. In further analysis, the positive association between supply induced oil price uncertainty and interest loan spread is more pronounced for major users of oil, while the negative effect of demand driven oil price uncertainty on the cost of bank loans is stronger for firms that belong to industries that produce oil. Overall, our findings feed into the emerging discussion of the differentiating effects of oil price uncertainty on micro-level outcomes and provide useful implications for both bankers and borrowing firms. JEL Classification: G20 - Financial Institutions and Services: General; Q41 - Energy: Demand and Supply; Prices; Q43 - Energy and the Macroeconomy
Application of Wearable Sensors Technology for Lumbar Spine Kinematic Measurements during Daily Activities following Microdiscectomy Due to Severe Sciatica
Background: The recurrence rate of lumbar spine microdiscectomies (rLSMs) is estimated to be 5–15%. Lumbar spine flexion (LSF) of more than 10° is mentioned as the most harmful load to the intervertebral disc that could lead to recurrence during the first six postoperative weeks. The purpose of this study is to quantify LSFs, following LSM, at the period of six weeks postoperatively. Methods: LSFs were recorded during the daily activities of 69 subjects for 24 h twice per week, using Inertial Measurement Units (IMU). Results: The mean number of more than 10 degrees of LSFs per hour were: 41.3/h during the 1st postoperative week (P.W.) (29.9% healthy subjects-H.S.), 2nd P.W. 60.1/h (43.5% H.S.), 3rd P.W. 74.2/h (53.7% H.S.), 4th P.W. 82.9/h (60% H.S.), 5th P.W. 97.3/h (70.4% H.S.) and 6th P.W. 105.5/h (76.4% H.S.). Conclusions: LSFs constitute important risk factors for rLDH. Our study records the lumbar spine kinematic pattern of such patients for the first time during their daily activities. Patients’ data report less sagittal plane movements than healthy subjects. In vitro studies should be carried out, replicating our results to identify if such a kinematic pattern could cause rLDH. Furthermore, IMU biofeedback capabilities could protect patients from such harmful movements.