Stability Studies for Photovoltaic Integration using Power Hardware-in-the-Loop Experiments

The electrical power network is gradually migrating from a centralized generation approach to a decentralized generation with high shares of renewable energy sources (RES). However, power systems with low shares of synchronous generation and consequently low total system inertia, are vulnerable to power imbalances. Such systems can experience frequency stability problems, such as high frequency excursions and higher rates of change of frequency even under small disturbances. This phenomenon is intensified when the grid under investigation has low or no interconnections (islanded) and thus the challenge for stable operation becomes more significant for the operators. This work focuses on how the frequency stability is affected when a photovoltaic (PV) inverter is integrated into a real non-interconnected distribution grid in Cyprus. In order to capture the realistic interactions of this integration, stability experiments in a hardware-in-the-loop (HIL) environment are performed with the aim to provide insightful results for the grid operator.Comment: The 12th Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion (MEDPOWER 2020

Ekspresija i obrada somatostatina u gušterači u razvoju i u duktalnom adenokarcinomu gušterače

Somatostatin is a gastrointestinal peptide hormone that inhibits growth of pancreatic cancer as reported by an increasing body of evidence. Yet this is not always the case. To clarify the controversy we aimed to identify the expression of somatostatin in developing human embryonic pancreatic tissue and pancreatic adenocarcinoma given that somatostatin positive cells were shown either into primitive pancreatic ductal epithelium or into pancreatic carcinoma. Tissue sections representing pancreatic fetal specimens (n=15) and ductal pancreatic adenocarcinoma specimens (n=15) were assessed using immunohistochemical methods for somatostatin expression. Normal primitive exocrine ductal epithelium and endocrine epithelium showed a definite, statistically significant, higher expression of somatostatin over neoplastic pancreatic tissue of mixed (ductal-endocrine) and pure ductal type (p1=0.021, p2=0.001, p3<0.0001and p4=0.003 respectively) during the 8th to the 10th week. No statistically significantly different expression of somatostatin in the mantle zone of the islets over neoplastic tissue of mixed (p5=0.16) and pureductal type (p6=0.65), from the 13th to the 24th week was demonstrated. Pancreatic cancer cells can express somatostatin in a model that reproduces the normal expression of the peptide by d-cells during embryonal organogenesis. Therapy aimed at pancreatic cancer must be targeted to somatostatin and analogues as a potential adjuvant novel option.Somatostatin je probavni peptidni hormon koji suzbija rast raka gušterače, za što postoji sve više dokaza. No to se ne događa uvijek. Cilj studije bio je utvrditi ekspresiju somatostatina u ljudskom embrijskom tkivu gušterače u razvoju i u adenokarcinomu gušterače, s tim da su na somatostatin pozitivne stanice dokazane ili u primitivnom duktalnom epitelu gušterače ili u karcinomu gušterače. Tkivni isječci koji su predstavljali uzorke fetalne gušterače (n=15) i uzorke adenokarcinoma gušterače (n=15) ispitani su pomoću imunohistokemijskih metoda za ekspresiju somatostatina. Normalan primitivni egzokrini duktalni epitel i endokrini epitel pokazao je konačnu, statistički značajno višu ekspresiju somatostatina iznad neoplastičnog tkiva gušterače miješanog (duktalno-endokrinog) i čistog duktalnog tipa (p1=0,021, P2=0,001, p3<0,0001 odnosno p4=0,003) tijekom 8. do 10. tjedna. Nije dokazana statistički značajno različita ekspresija somatostatina u ovojnom sloju (mantle zone, mantle layer) otočića iznadneoplastičnog tkiva miješanog (p5=0,16) i čistog duktalnog tipa (p6=0,65) od 13. do 24. tjedna. Dakle, stanice raka gušterače mogu izražavati somatostatin na naein koji ponavlja normalnu d-staničnu ekspresiju peptida za vrijeme embrijske organogeneze. Liječenje zbog raka gušterače usmjereno na somatostatin i njegove analoge moglo bi predstavljati novu mogućnosti adjuvantne terapije

Pyruvate: immunonutritional effects on neutrophil intracellular amino or alpha-keto acid profiles and reactive oxygen species production

For the first time the immunonutritional role of pyruvate on neutrophils (PMN), free α-keto and amino acid profiles, important reactive oxygen species (ROS) produced [superoxide anion (O2−), hydrogen peroxide (H2O2)] as well as released myeloperoxidase (MPO) acitivity has been investigated. Exogenous pyruvate significantly increased PMN pyruvate, α-ketoglutarate, asparagine, glutamine, aspartate, glutamate, arginine, citrulline, alanine, glycine and serine in a dose as well as duration of exposure dependent manner. Moreover, increases in O2− formation, H2O2-generation and MPO acitivity in parallel with intracellular pyruvate changes have also been detected. Regarding the interesting findings presented here we believe, that pyruvate fulfils considerably the criteria for a potent immunonutritional molecule in the regulation of the PMN dynamic α-keto and amino acid pools. Moreover it also plays an important role in parallel modulation of the granulocyte-dependent innate immune regulation. Although further research is necessary to clarify pyruvate’s sole therapeutical role in critically ill patients’ immunonutrition, the first scientific successes seem to be very promising

The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats

The Mediterranean Sea is a marine biodiversity hot spot. Here we combined an extensive literature analysis with expert opinions to update publicly available estimates of major taxa in this marine ecosystem and to revise and update several species lists. We also assessed overall spatial and temporal patterns of species diversity and identified major changes and threats. Our results listed approximately 17,000 marine species occurring in the Mediterranean Sea. However, our estimates of marine diversity are still incomplete as yet—undescribed species will be added in the future. Diversity for microbes is substantially underestimated, and the deep-sea areas and portions of the southern and eastern region are still poorly known. In addition, the invasion of alien species is a crucial factor that will continue to change the biodiversity of the Mediterranean, mainly in its eastern basin that can spread rapidly northwards and westwards due to the warming of the Mediterranean Sea. Spatial patterns showed a general decrease in biodiversity from northwestern to southeastern regions following a gradient of production, with some exceptions and caution due to gaps in our knowledge of the biota along the southern and eastern rims. Biodiversity was also generally higher in coastal areas and continental shelves, and decreases with depth. Temporal trends indicated that overexploitation and habitat loss have been the main human drivers of historical changes in biodiversity. At present, habitat loss and degradation, followed by fishing impacts, pollution, climate change, eutrophication, and the establishment of alien species are the most important threats and affect the greatest number of taxonomic groups. All these impacts are expected to grow in importance in the future, especially climate change and habitat degradation. The spatial identification of hot spots highlighted the ecological importance of most of the western Mediterranean shelves (and in particular, the Strait of Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well

Smart Photovoltaic Energy Systems for a Sustainable Future

This book is the result of a concerted effort to shed scientific light on the timely theme of “Smart Photovoltaic Energy Systems for a Sustainable Future” [...