Δημιουργία υπολογιστικού εργαλείου για την Μοντελοποίηση Υβριδικών FSO/MMW συστημάτων και την προσομοίωσή των επιδόσεων τους στο MATLAB

Η διαρκής απαίτηση για μεγαλύτερες ταχύτητες ευρυζωνικότητας, έχει οδηγήσει τα τελευταία χρόνια σε μεγάλο ερευνητικό ενδιαφέρον στις ασύρματες οπτικές ζεύξεις (FSO), οι οποίες έχουν άμεση εφαρμογή σε backhaul και last mile δίκτυα. Τα FSO είναι μια πολλά υποσχόμενη τεχνολογία λόγω των πλεονεκτημάτων που υποστηρίζει όπως: το τεράστιο εύρος ζώνης, ο χρόνος εγκαταστάτης, η απουσία παρεμβολών και η αυξημένη ασφάλεια είναι μερικά από αυτά. Ωστόσο οι επιδόσεις των FSO επηρεάζονται από καιρικά φαινόμενα όπως: η ομίχλη, το χιόνι, η βροχή και το φαινόμενο της τύρβης. Εξ αιτίας αυτού προτείνεται το Υβριδικό σύστημα FSO/MMW στο οποίο το Χιλιοστομετρικό (MMW) σύστημα λειτουργεί ως εφεδρικό ώστε να βελτιωθεί η διαθεσιμότητα του συστήματος. Σε αυτή τη διπλωματική εργασία παρουσιάζουμε αρχικά τις υπάρχουσες τεχνολογίες που έχουν εφαρμογή στο τηλεπικοινωνιακό backhaul και στο πρόβλημα του τελευταίου μιλίου ενώ εστιάζουμε στο Υβριδικό σύστημα. Στη συνέχεια μελετάμε το ατμοσφαιρικό κανάλι στο οποίο λειτουργεί το σύστημά μας. Τόσο το FSO όσο και το MMW επηρεάζονται από την ατμόσφαιρά της οποίας τα συστατικά (μόρια, αερολύματα) προκαλούν φαινόμενα απορρόφησης και σκέδασης με αποτέλεσμα την εξασθένηση του σήματος μαζί με την γεωμετρική του διάδοση. Ο βέλτιστος τρόπος να περιγράψουμε όλες τις απώλειες που επηρεάζουν το σύστημά μας (FSO,MMW) είναι να αναλύσουμε το ισοζύγιο ισχύος για την κάθε τεχνολογία χωριστά και έτσι να εκτιμήσουμε το τελικό σήμα που φθάνει στο δέκτη. Σε μια προσπάθεια να γίνει ποιο ρεαλιστικό το εγχείρημα αυτό σχεδιάσαμε ένα υπολογιστικό εργαλείο με γραφικό περιβάλλον στο Matlab. Ο βασικός κορμός αυτού του εργαλείου περιέχει πολλές συναρτήσεις ,κάθε μία από αυτές αντιστοιχεί σε μία εξασθένηση που επηρεάζει το σύστημά μας. Σε αυτό το εργαλείο ο χρήστης εισάγει τις παραμέτρους του συστήματος που μελετά και πραγματοποιεί τις προσομοιώσεις του σε γραφικό περιβάλλον. Για να βελτιώσουμε περαιτέρω τις επιδόσεις του συστήματος, συνδυάσαμε αυτές τις τεχνολογίες ως ένα Υβριδικό FSO/MMW σύστημα όπου ως παράμετρο διασύνδεσης αυτών των δύο χρησιμοποιήσαμε το link margin όπου και υπολογίζεται κάθε φορά. Μεταξύ των δύο συστημάτων το FSO υπερέχει σε σχέση με το MMW λόγω των πλεονεκτημάτων του, έτσι στη συνέχεια εστιάζουμε στις επιδόσεις του FSO ώστε να μελετήσουμε περαιτέρω την απόδοση του σε κανάλι με τυρβώδη ροή. Το φαινόμενο αυτό έχει ως συνέπεια τους σπινθηρισμούς της δέσμης στο δέκτη. Οι διακυμάνσεις αυτές του σήματος μέσω των σπινθηρισμών μελετώνται με στοχαστικές μεθόδους. Στην μελέτη μας χρησιμοποιούμε τις lognormal και γαμμα-γαμμα κατανομές για ασθενής και μέτρια έως ισχυρή τύρβη. Για το σκοπό αυτό αναβαθμίσαμε το tool μας ώστε να μελετήσουμε τις επιδόσεις όπως η πιθανότητα διακοπής και η μέση χωρητικότητα του FSO συστήματος. Από τα αποτελέσματα των προσομοιώσεων μας συμπεραίνουμε ότι το FSO σύστημα επηρεάζεται έντονα από την ομίχλη, το χιόνι, την τύρβη ενώ σε έντονη βροχόπτωση τόσο το FSO όσο και το MMW έχουν αρκετές απώλειες με αποτέλεσμα το σύστημα να οδηγείται σε απώλεια ζεύξης. Ωστόσο τα FSO συστήματα εξαιτίας του τεράστιου εύρους ζώνης που διαθέτει η οπτική τεχνολογία προσφέρει πολύ υψηλή χωρητικότητα σε τηλεπικοινωνιακά συστήματα ακόμα και σε κανάλι με ισχυρά επίπεδα τύρβης όπου και εξετάσαμε.The growing demand on broadband applications has lead recently to strong interest in research and the development of high data rate wireless optical communications systems or Free Space Optics (FSO), which have direct application on backhaul and last mile problems. FSO has been very attractive, because it supports huge bandwidth, low installation time, no interference and high safety communications. However, its performance is strongly affected by weather conditions such as fog, snow rain and turbulence phenomenon. For these reasons, the Hybrid FSO/MMW system has proposed with the millimeter wave (MMW) system as a backup to improve system availability. In this academic thesis, first of all, we present all the existing technologies for the backhaul and last mile applications and we focus on the Hybrid FSO/MMW which is the scope of this thesis. Subsequently we discuss the atmospheric channel in which the Hybrid system operation takes place. Not only the FSO system operation but also the MMW system are affected by atmospheric weather phenomena which cause absorption and scattering from both molecular and aerosols particles. In this capital, we analyse all the losses that involve the atmospheric channel in our system as well as the geometric looses of these systems. The best way to describe all these looses that affect our Hybrid FSO/MMW system is to study and compute all link budget parameters to estimate the final received signal. Thus we designed a computation tool, which has a Graphical User Interface (GUI) on Matlab. This tool is consisted of a main program which controls other functions and starts the simulation to obtain the final received power for these two technologies (FSO and MMW). To improve the System performance, we combine these technologies as a Hybrid System. For the switching mode of the Hybrid System we use the link margin performance parameter which is estimated for each specific weather phenomenon. It is obvious that between these two systems, FSO is more changelings and more competitive thus we focus on FSO performance to study further the efficiency of this technology. Another weather effect that we study is the atmospheric turbulence which causes the scintillation effect that induces rapid fluctuations of the FSO optical receiver’s side. These fluctuations can be studied accurately with statistical methods. For this study we use either the lognormal or the gamma–gamma distribution for weak or moderate to strong turbulence conditions, respectively. So we design another version of computation tool to estimate the FSO average capacity and the outage probability performance metrics, as functions of the link’s parameters and the transmitted power. Finally from our simulation results we conclude that on Hybrid system the FSO is strongly affected by fog, snow and especially on strong rain the FSO such as the WWM have so many looses that lead to system outage. The turbulence effect is another weather phenomenon that has influence on FSO operation. However, it can been seen that, due to the extremely large bandwidth of the optical channel on a FSO system, the channels capacity is high enough in order to support high fidelity communications, even for large attenuation values, strong atmospheric turbulence effect and long link lengths

A Gene Regulatory Network Subcircuit Drives a Dynamic Pattern of Gene Expression

Early specification of endomesodermal territories in the sea urchin embryo depends on a moving torus of regulatory gene expression. We show how this dynamic patterning function is encoded in a gene regulatory network (GRN) subcircuit that includes the otx, wnt8, and blimp1 genes, the cis-regulatory control systems of which have all been experimentally defined. A cis-regulatory reconstruction experiment revealed that blimp1 autorepression accounts for progressive extinction of expression in the center of the torus, whereas its outward expansion follows reception of the Wnt8 ligand by adjacent cells. GRN circuitry thus controls not only static spatial assignment in development but also dynamic regulatory patterning

Identification of glucose transporters in Aspergillus nidulans

o characterize the mechanisms involved in glucose transport, in the filamentous fungus Aspergillus nidulans, we have identified four glucose transporter encoding genes hxtB-E. We evaluated the ability of hxtB-E to functionally complement the Saccharomyces cerevisiae EBY.VW4000 strain that is unable to grow on glucose, fructose, mannose or galactose as single carbon source. In S. cerevisiae HxtB-E were targeted to the plasma membrane. The expression of HxtB, HxtC and HxtE was able to restore growth on glucose, fructose, mannose or galactose, indicating that these transporters accept multiple sugars as a substrate through an energy dependent process. A tenfold excess of unlabeled maltose, galactose, fructose, and mannose were able to inhibit glucose uptake to different levels (50 to 80 %) in these s. cerevisiae complemented strains. Moreover, experiments with cyanide-m-chlorophenylhydrazone (CCCP), strongly suggest that hxtB, -C, and –E mediate glucose transport via active proton symport. The A. nidulans ΔhxtB, ΔhxtC or ΔhxtE null mutants showed ~2.5-fold reduction in the affinity for glucose, while ΔhxtB and -C also showed a 2-fold reduction in the capacity for glucose uptake. The ΔhxtD mutant had a 7.8-fold reduction in affinity, but a 3-fold increase in the capacity for glucose uptake. However, only the ΔhxtB mutant strain showed a detectable decreased rate of glucose consumption at low concentrations and an increased resistance to 2-deoxyglucose.The authors would like to thank the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo and Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, Brazil for financial support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Regulation of Plant Developmental Processes by a Novel Splicing Factor

Serine/arginine-rich (SR) proteins play important roles in constitutive and alternative splicing and other aspects of mRNA metabolism. We have previously isolated a unique plant SR protein (SR45) with atypical domain organization. However, the biological and molecular functions of this novel SR protein are not known. Here, we report biological and molecular functions of this protein. Using an in vitro splicing complementation assay, we showed that SR45 functions as an essential splicing factor. Furthermore, the alternative splicing pattern of transcripts of several other SR genes was altered in a mutant, sr45-1, suggesting that the observed phenotypic abnormalities in sr45-1 are likely due to altered levels of SR protein isoforms, which in turn modulate splicing of other pre-mRNAs. sr45-1 exhibited developmental abnormalities, including delayed flowering, narrow leaves and altered number of petals and stamens. The late flowering phenotype was observed under both long days and short days and was rescued by vernalization. FLC, a key flowering repressor, is up-regulated in sr45-1 demonstrating that SR45 influences the autonomous flowering pathway. Changes in the alternative splicing of SR genes and the phenotypic defects in the mutant were rescued by SR45 cDNA, further confirming that the observed defects in the mutant are due to the lack of SR45. These results indicate that SR45 is a novel plant-specific splicing factor that plays a crucial role in regulating developmental processes

The Role of NOTCH1 Haploinsufficiency in Calcific Aortic Valve Disease

The mechanisms by which transcription factor haploinsufficiency alters the epigenetic and transcriptional landscape in human cells to cause disease are unknown. Here, I utilized human induced pluripotent stem cell (iPSC)-derived endothelial cells (ECs) to show that heterozygous nonsense mutations in NOTCH1 (N1) that cause calcific aortic valve disease (CAVD) disrupt the epigenetic architecture resulting in derepression of latent pro-osteogenic and -inflammatory gene networks. Hemodynamic shear stress, which protects valves from calcification in vivo, activated anti-osteogenic and anti-inflammatory networks in N1+/+, but not N1+/-, iPSC-derived ECs. N1 haploinsufficiency altered H3K27ac at N1-bound enhancers, dysregulating downstream transcription of over 1000 genes involved in osteogenesis, inflammation, and oxidative stress. Computational predictions of the disrupted N1-dependent gene network revealed regulatory nodes that when modulated restored the network toward the N1+/+ state. My results highlight how alterations in transcription factor dosage affect gene networks leading to human disease and reveal nodes for potential therapeutic intervention.This iPSC model of CAVD provides a platform for screening for small molecules that target central regulatory nodes to alleviate the gene network dysregulation in N1 haploinsufficient cells. However, the lack of an in vivo animal model of CAVD caused by N1 haploinsufficiency severely limits safety and efficacy testing of potential therapeutics. Diseases caused by gene haploinsufficiency in humans commonly lack a phenotype in mice heterozygous for the orthologous factor. Since CAVD is an age-dependent disease, I generated N1+/- mice lacking telomerase activity and showed that telomere shortening reveals heart valve disease in N1+/- mice. Furthermore, N1 haploinsufficiency promoted proliferation that accelerated telomere shortening, potentially past the critical threshold at which valve disease ensues. Gene dysregulation in AVs of N1 haploinsufficient mice with shortened telomeres involved downregulation of osteoclast factors and upregulation of pro-calcific regulatory nodes paralleling gene network alterations in the human iPSC disease model. Concordance between the murine and human models supports that this model may represent an ideal in vivo setting in which to test therapeutics aimed at preventing or delaying the progression of CAVD

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Dissertation (PhD) -- Universiteit van Stellenbosch, 1971.Full text to be digitised and attached to bibliographic record