Freeway Traffic Control - An adaptive control approach towards easy-to-implement Variable Speed Limit algorithms

Nowadays, the high demand for road transportation often reaches a point where it exceeds the capacity of freeway traffic networks, resulting in congestion. Freeway traffic congestion is a major social problem, as it is the reason for increased time delays, higher accident risk and environmental pollution. There is, therefore, the need for a sustainable solution that can be implemented on the existing road infrastructure. Freeway traffic control is considered as such a solution. It uses different control measures, in order to improve the performance of the freeway traffic network, by influencing the drivers’ behaviour.The Variable Speed Limits (VSLs) are a traffic control measure that aims to increase traffic safety, improve traffic flow and reduce the environmental pollution. Towards the improvement of the freeway traffic flow, easy-to-implement VSL control algorithms are used as mainline metering control approach.Two easy-to-implement VSL algorithms are reported, namely the Mainstream Traffic Flow Control (MTFC) and the Logic-Based control algorithm for Variable Speed Limits (LB-VSL). The algorithms are usually implemented in an non-adaptive framework. The main contribution of this thesis is that it proposes an adaptive framework for both algorithms, in which the critical density of the freeway traffic network at bottleneck’s location is estimated on-line. This estimated critical density is used to adjust the controllers’ parameters in real-time.Three different estimation methods for the bottleneck’s critical density are studied, namely the Parameter Estimation (Parameterschatter) method, the Simple Derivative Estimation (SDE) and the Kalman-Filter-based derivative Estimation (KFE) methods. All three methods focus on the real-time estimation of the derivative of the Fundamental Diagram (FD), in order to produce estimations of the critical density.A case study is performed to evaluate the performance of the three algorithms. A hypothetical 12 km long freeway stretch is used, which contains two VSLs installations and a lane-drop bottleneck. In the first part of the case study an accident scenario is studied, which decreases the critical density at the bottleneck’s location. The second part of the case study evaluates the three adaptive easy-to-implement VSL algorithms under the assumption of a decrease of the critical density across the whole network, due to bad weather conditions.Mechanical Engineering | Systems and Contro

Physiological and biochemical characterization of the metabolism of ascorbic acid in seeded and parthenocarpic cherry tomato fruits

The auxin treatment in tomato plants is often been used to overcome problems in fruit seting caused by low temperatures. In order to evaluate the effects of this agronomical practice on the fruit physiology and on the dietary value of "cherry" tomato fruits, in the first section of this study, the concentration of free and total ascorbic acid had been evaluated in developing seeded and parthenocarpic fruits. Moreover, the expression of the gene and the immunolocalization of galactono-1,4 lactone dehydrogenase and the expression of GDP-mannose 3 ,5 -epimerase gene, two key enzymes in ascorbic acid biosynthesis, had been also studied. The immunolocalization signal was stronger in vascular bundles and in the embryos of seeded fruits. The results of this section suggested that even differences had been found in the gene expression of ascorbate biosynthesis and in the immunolocalization of galactono 1,4 lactone dehydrogenase, no significant differences in ascorbic acid had been found between seeded and parthenocarpic fruits induced by auxin. In the second section, the metabolism of ascorbic acid was examined in seeded and parthenocarpic fruits. For this purpose, the activity of ascorbate peroxidase and of dehydroascorbate reductase, the expression of all characterized genes of ascorbic acid metabolism, as well as the immunolocalization of ascorbate peroxidase, were all examined in developing cherry tomato fruits, both parthenocarpic and seeded. Significant differences were found in the expression of the isoenzymes 5 and 7 of ascorbate peroxidase, in the expression of cytosolic monodehydro ascorbate reductase and on the plastidial glutathione reductase. The activity of ascorbate peroxidase was higher in the maturing parthenocarpic fruits. However, no major differences were found in dehydroascorbate reductace activity. The immunolocalization signal of ascorbate peroxidase was heavy in the embryos. The results of this section suggested that induced parhenocarpy caused some differences in ascorbic acid metabolism. In the third part of this study the behavior concerning ascorbate biosynthesis and metabolism of seeded and parthenocarpic fruits was studied under temperatures simulating the conditions those of popular postharvest treatments for five days. Almost all genes were up-regulated during cold storage in 5oC and 10oC. Reduced and total ascorbate was considerable lower and ascorbate peroxidase was higher in fruits stored next to plants under the same conditions to the red ripe fruits, especially in seeded fruits. These results indicate that while fruits stored in low temperatures were probably stressed and exhibeted lower Ascorbate levels. However, the fruits stored next to plants suffered heavier losses of ascorbate fact that indicates that also in this case the fruits were significantly stresed.Στην τομάτα, η παρθενοκαρπία προκαλείται συχνά με την επίδραση αυξινών για να ξεπεραστούν τα εμπόδια της γονιμοποίησης που προκαλούνται από τις χαμηλές θερμοκρασίες. Για να εκτιμηθούν τα αποτελέσματα της αγρονομικής αυτής πρακτικής στη φυσιολογία του καρπού και τη διαιτητική αξία της τομάτας τύπου “cherry” στην πρώτη ενότητα αυτής της διατριβής προσδιορίστηκε η συγκέντρωση του ανηγμένου και ολικού ασκορβικού οξέος σε παρθενοκαρπικούς και ένσπερμους καρπούς. Επιπλέον ανοσοεντοπίστηκε η αφυδρογονάση της γαλακτονολακτόνης και μελετήθηκε η έκφραση των γονιδίων της αφυδρογονάσης της γαλακτονολακτόνης, και της επιμεράσης της GDP-μαννόζης, δύο ενζύμων κλειδιών της βιοσύνθεσης του ασκορβικού οξέος τόσο στους ένσπερμους όσο και στους παρθενοκαρπικούς καρπούς. Το σήμα εντοπισμού της αφυδρογονάσης της γαλακτονολακτόνης ήταν εντονότερο στις σπερματικές βλάστες και στα ώριμα έμβρυα των ένσπερμων καρπών. Τα αποτελέσματά αυτής της ενότητας προτείνουν ότι αν και υπήρχαν διαφορές στην έκφραση των γονιδίων της βιοσύνθεσης του ασκορβικού καθώς και στον ανοσοεντοπισμό της αφυδρογονάσης της γαλακτονολακτόνης, αυτές δεν προκάλεσαν σημαντικές διαφορές στη συγκέντρωση του ασκορβικού οξέος των καρπών μεταξύ ένσπερμων και παρθενοκαρπικών καρπών που παρήχθησαν με την εφαρμογή της αυξίνης.Στη δεύτερη ενότητα εξετάστηκε ο μεταβολισμός του ασκορβικού οξέος σε παρθενοκαρπικούς και ένσπερμους καρπούς. Για το σκοπό αυτό εξετάστηκε η δραστικότητα της υπεροξειδάσης και της ρεδουκτάσης του δεϋδροασκορβικού οξέος, ανοσοεντοπίστηκε η υπεροξειδάση του ασκορβικού και μελετήθηκε η έκφραση όλων των γνωστών γονιδίων που σχετίζονται με την οξείδωση και την αναγωγή του ασκορβικού οξέος κατά την ανάπτυξη και ωρίμανση των καρπών. Σημαντικές διαφορές εντοπίστηκαν κυρίως στην έκφραση των γονιδίων των ισοενζύμων 5 και 7 της υπεροξειδάσης του ασκορβικού οξέος, του κυτοπλασματικού ισοενζύμου της ρεδουκτάσης του μονοδεϋδρο ασκορβικού οξέος και του πλαστιδιακού ισοενζύμου της ρεδουκτάσης της γλουταθειόνης. Η δραστικότητα της υπεροξειδάσης του ασκορβικού οξέως ήταν ελαφρώς αυξημένη στους παρθενοκαρπικούς καρπούς κατά την ωρίμανση του καρπού ενώ η δραστικότητα της ρεδουκτάσης του δεϋδροασκορβικού οξέος δεν παρουσίασε σημαντικές διαφορές στις δύο μεταχειρίσεις. Το σήμα του εντοπισμού της υπεροξειδάσης του ασκορβικού οξέος ήταν εντονότερο στις σπερματικές βλάστες και στα αναπτυσσόμενα έμβρυα. Τα παραπάνω αποτελέσματα οδηγούν στο συμπέρασμα ότι οι ένσπερμοι και παρθενοκαρπικοί καρποί, παρουσίασαν κάποιες διαφορές στο μεταβολισμό του ασκορβικού οξέος.Στην τρίτη ενότητα μελετήθηκε η συμπεριφορά των καρπών σε συνθήκες παρόμοιες με διαδεδομένους μετασυλλεκτικούς χειρισμούς, αναφορικά με τη βιοσύνθεση και το μεταβολισμό του ασκορβικού οξέος σε ένσπερμους και παρθενοκαρπικούς καρπούς. Οι χειρισμοί αφορούσαν, αποκομένους καρπούς που διατηρήθηκαν στις ίδιες συνθήκες με τα φυτά, ή και αποθήκευση τους στους 5 oC ή 10 oC για χρονικό διάστημα πέντε ημερών. Η έκφραση όλων σχεδόν των γονιδίων που μελετήθηκαν ήταν αυξημένη στους καρπούς που αποθηκεύτηκαν σε χαμηλές θερμοκρασίες 5oC και 10oC. Στους αποκομένους καρπούς που τοποθετήθηκαν δίπλα στα φυτά, το ανηγμένο και το ολικό ασκορβικό οξύ ήταν σημαντικά χαμηλότερο ενώ η δραστικότητα της υπεροξειδάσης του ασκορβικού οξέος ήταν αυξημένη ιδίως στους ένσπερμους καρπούς. Τα παραπάνω ευρήματα καταδεικνύουν ότι ενω οι καρποί που αποθηκεύτηκαν σε χαμηλές θερμοκρασίες πιθανά υπέστησαν καταπόνηση και απώλεσαν κάποια ποσότητα ασκορβικού οξέως. Η απώλεια ασκορβικού οξέος ήταν σημαντικότερη στους καρπούς που αποθηκεύτηκαν δίπλα στα φυτά γεγονός που υποδηλώνει και σε αυτή τη περίπτωση υπήρχε σημαντική καταπόνηση των καρπών

Ascorbate metabolism in vegetative and reproductive organs of "cherry" tomato

Ascorbate metabolism is an essential procedure for all plant cells that plays important roles in several physiological processes such as plant development and reactive oxygen species detoxification. To shed more light on ascorbate metabolism in certain organs of tomato plants, we performed a detailed compartmentalized analysis of ascorbate concentration, ascorbate peroxidase/dehydroascorbate reductase enzyme activities and transcript accumulation of genes related to ascorbate metabolism. Our results showed higher level of ascorbate concentration and ascorbate peroxidase and dehydroascorbate reductase activities in young leaves and shoot tips, while min. ascorbate concentration was recorded in root tips. The study of the expression of the genes involved in ascorbate metabolism revealed that several genes followed similar patterns. However, APX3 gene expression was considerably higher in reproductive organs, while plastidial APX6 and DHAR2 genes transcripts were barely detectable in root tips. Organ-specific expression of genes involved in ascorbate metabolism suggests that different isoenzymes have a specific role in regulation of the redox status of some of the organs in tomato plants

Low temperature storage affects the ascorbic acid metabolism of cherry tomato fruits

Tomato fruits are an important source of l-Ascorbic acid, which is an essential compound of human diet. The effect of the widespread practice of cold storing (5-10 °C) tomato fruits was monitored to determine its impact on the concentration and redox status of l-Ascorbic acid. Total l-Ascorbic acid levels were well maintained in both attached fruits and cold treated fruits, while in other treatments its levels were considerably reduced. However, low temperature storage conditions enhanced the expression of most genes coding for enzymes involved in l-Ascorbic acid biosynthesis and redox reactions. The findings suggest that the transcriptional up-regulation under chilling stress conditions of most genes coding for l-Ascorbic acid biosynthetic genes galactono-1,4-lactone dehydrogenase, GDP-d-mannose 3,5-epimerase but also for the isoenzymes of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase enzyme, glutathione reductase that are strongly correlated to the l-Ascorbic redox status. Moreover, fruits stored at 10 °C exhibited higher levels of transcript accumulation of MDHAR2, DHAR1, DHAR2, GR1 and GR2 genes, pointing to a better ability to manage chilling stress in comparison to fruits stored at 5 °C

Glutamate dehydrogenase is differentially regulated in seeded and parthenocarpic tomato fruits during crop development and postharvest storage

© 2014 Elsevier B.V. Cherry tomatoes are more susceptible than larger fruit varieties to producing auxin-induced parthenocarpic fruits indistinguishable from seeded fruits in most organoleptic characteristics. In this study, the effects of auxin-induced parthenocarpy and of the short-term cold storage on the expression of GDH genes, one of the main regulatory enzymes of nitrogen metabolism, were examined. Seeded and parthenocarpic fruits exhibited differences in the pattern of expression of the genes coding for α- and β-subunits of GDH during fruit development. Short-term cold storage at 5. °C significantly increased transcript accumulation of GDH genes, while storage at 10. °C for five days mostly caused a reduction in the expression of the genes in both fruit types. Finally, no significant differences between the two fruit types were detected in the localization of GDH protein and GDH enzyme activity

The Cypriot indigenous grapevine germplasm is a multi-clonal varietal mixture

The article was funded by the “CUT Open Access Author Fund”Cypriot vineyards are considered as one among the earliest niches of viticulture and a pivotal hub for the domestication and dissemination of grapevine. The millennial presence of Vitis spp. in this Eastern Mediterranean island has given rise to a plethora of biotypes that have not been adequately characterized, despite their unique attributes and stress tolerance. This ancient germplasm also has an additional value since it survived the phylloxera outbreak; hence, it possesses a large amount of genetic diversity that has been unnoticed. In order to provide useful insights to the lineage of Cypriot vineyards, a two-year-spanning collection of centennial grapevine cultivars mostly regarded to belong to four indigenous variety clusters (“Mavro”, “Xynisteri”, “Maratheftiko”, and “Veriko”) was initiated. There were 164 accessions across the broader Commandaria wine zone sampled and characterized using a universal microsatellite primer set. Genetic analysis indicated that considered indigenous Cypriot germplasm has a polyclonal structure with a high level of heterozygosity. Moreover, several lineages or unexplored varieties may exist, since a larger than considered number of discrete genotypes was discovered. Furthermore, it was established that grapevine lineages in Cyprus were shaped across eras via clonal, as well as, sexual propagation. The special attributes of the Cypriot landscape are discussed

l-Ascorbic acid metabolism in parthenocarpic and seeded cherry tomatoes

The auxin treatment in tomato plants during anthesis has been extensively used for setting fruits in adverse climatic conditions (e.g., low temperatures and inadequate light), which is well known that reduces pollen availability and fertility. Since auxin application may affect fruit composition and quality, we examined l-ascorbic acid metabolism in seeded fruit (set by natural pollination) and parthenocarpic fruit (set by auxin) in cherry tomato cv. Conchita. Specifically, we studied the oxidized and total ascorbic acid contents, the expression of all characterized genes of l-ascorbic acid metabolism, the activity of ascorbate peroxidase and dehydroascorbate reductase and the immunolocalization of ascorbate peroxidase. Differences were detected between seeded and parthenocarpic fruits, in the expression of some of the genes of ascorbic acid metabolism. However, strong presence of l-ascorbic acid peroxidase protein was detected on the developing seeds. Our data indicate that induced parthenocarpy in auxin treated plants has a significant influence in ascorbic acid metabolism comparing to seeded tomato fruits. © 2013 Springer Science+Business Media Dordrecht

Seeded and Parthenocarpic Cherry Tomato Fruits Exhibit Similar Sucrose, Glucose, and Fructose Levels, Despite Dissimilarities in UGPase and SPS Gene Expression and Enzyme Activity

© 2014, Springer Science+Business Media New York. Farmers often resort to the production of auxin-induced parthenocarpic tomato fruits to overcome the adverse climatic conditions which are unfavorable for sufficient fertilization and to lengthen the production period. Even though this practice improves the out-of-season yield, it often undermines fruit quality. In the current study, we examined the effect of induced parthenocarpy in cherry tomato cv. Conchita on the concentration of the main sugars, and on the expression, the activity and the localization of UDP-glucose pyrophosphorylase (UGPase) and sucrose phosphate synthase (SPS), enzymes that are actively involved in sucrose metabolism. Minor differences were detected in sugar levels of seeded and parthenocarpic fruits, whereas considerable variances were found in transcript accumulation and enzyme activities of both UGPase and SPS. Moreover, both proteins were present in the developing seeds. Our data indicate that although induced parthenocarpy significantly influences sucrose metabolism, it has a negligible effect on sugar levels