BER and outage probability of DPSK subcarrier intensity modulated free space optics in fully developed speckle.

In this paper a differential phase shift keying (DPSK) subcarrier intensity modulated (SIM) free space optical (FSO) link is considered in negative exponential atmospheric turbulence environment. To mitigate the scintillation effect, the selection combining spatial diversity scheme (SelC) is employed at the receiver. Bit error rate (BER) and outage probability (Pout) analysis are presented with and without the SelC spatial diversity. It is shown that at a BER of 10-6, a maximum diversity gain 25 dB is predicted. And about 60 dBm signal power is required to achieve an outage probability of 10-6, based on a threshold BER of 10-4

Atmospheric channel effects on terrestrial free space optical communication links

Abstract. This paper illustrates the challenges imposed by the atmospheric channel on the design of a terrestrial laser communication link. The power loss due to scattering effect is described using the Kim/Kruse scattering model while the effect and the penalty imposed by atmospheric turbulence is highlighted by considering the bit error rate (BER) of an On-Off Keying modulated link in an optical Poisson channel. The power loss due to thick fog can measure over 100 dB/km while snow and rain result in much lower attenuation. We show that non-uniformity in the atmospheric temperature also contributes to performance deterioration due to scintillation effect. At a BER of 10-4, for a channel with a turbulence strength of>0.1, the penalty imposed by turbulence induced fading is over 20 photoelectron counts in order to achieve the same level of performance as a channel with no fading. The work reported here is part of the EU COST actions and EU projects.

Modelling and analysis of FSO ground-to-train communications for straight and curved tracks

In this work, a free space optical (FSO) link for the ground-to-train communications is proposed. Analytical analysis is carried out for the case of the straight as well as curved rail tracks. We show that the transmitter divergence angle, the transmit power and the size of the concentration lens needs to increase for the curved section of the rail track compared to the straight track. We derive the analytical expression (11) for the received power level based on the link geometry for the cases of straight and curved tracks. The received power variation is compared for two cases showing a similar dynamic range. In the worst case scenario when the radius of curvature is 120 m, the transmit power at the optical base station (OBS) needs to increase by over 2 dB when the concentration lens radius is increased by 5 times. Analyses also show that received power increases with the radius of curvature. Finally, results are compared with the existing straight track model

Fourier domain optical coherence tomography system with balance detection

A Fourier domain optical coherence tomography system with two spectrometers in balance detection is assembled using each an InGaAs linear camera. Conditions and adjustments of spectrometer parameters are presented to ensure anti-phase channeled spectrum modulation across the two cameras for a majority of wavelengths within the optical source spectrum. By blocking the signal to one of the spectrometers, the setup was used to compare the conditions of operation of a single camera with that of a balanced configuration. Using multiple layer samples, balanced detection technique is compared with techniques applied to conventional single camera setups, based on sequential deduction of averaged spectra collected with different on/off settings for the sample or reference beams. In terms of reducing the autocorrelation terms and fixed pattern noise, it is concluded that balance detection performs better than single camera techniques, is more tolerant to movement, exhibits longer term stability and can operate dynamically in real time. The cameras used exhibit larger saturation power than the power threshold where excess photon noise exceeds shot noise. Therefore, conditions to adjust the two cameras to reduce the noise when used in a balanced configuration are presented. It is shown that balance detection can reduce the noise in real time operation, in comparison with single camera configurations. However, simple deduction of an average spectrum in single camera configurations delivers less noise than the balance detection

How do farmers research and learn? The example of organic farmers’ experiments and innovations: A research concept

Experimenting, adapting and innovating are central features of farmers’ activities all over the world. Farmers hold valuable knowledge about their environment, they actively do experiments, and have their own research traditions. The development of organic farming systems is continually evolving through the experiments and innovations of organic farmers. So far, there has been little attempt to study the nature, characteristics, and factors associated with the experimental processes of farmers in a systematic, comprehensive way. A current research project investigates learning processes of organic farmers in Austria, Cuba and Israel through researching the multifaceted experiments they conduct and the innovations they obtain as possible results. This paper presents the research concept of the project

A sztereoizoméria hatása peptidek térszerkezetére és bioaktivitására = The effect of stereoisomerism on the spatial structure and bioactivity of peptides

Kutatásom során tanulmányoztam a cisz-transz és L-D izomériának a peptidek térszerkezeti és konformációs tulajdonságaira, illetve bioaktivitására kifejtett hatásait. Az opioid peptidek összehasonlító konformáció-analízise alapján azonosítottam a sztereoizomerek karakterisztikus térszerkezeti sajátságait, illetve a peptidek közötti konformációs hasonlóságokat és különbségeket. A farmakofór elemek relatív térbeli elrendeződésének leírására használt módszer alkalmasnak bizonyult a sztereoizomerek egymástól való megkülönböztetésére, és a farmakofórok térbeli összefüggéseinek jellemzésére. Az antimikrobiális peptidek esetén meghatároztam a cisz-transz izomériának a sztereoizomerek konformációs tulajdonságainak kialakításában és a peptidek dinamikus viselkedésében betöltött szerepét. A bázikus aminosavakat tartalmazó alanin-alapú peptidekre vonatkozóan átfogóan feltérképeztük a folding folyamatokat, és a szimulációk alapján különböző módszerek alkalmazásával jellemeztük a hajtogatódási útvonalakat. Az antimikrobiális peptidek palindrom szekvenciái esetében elvégeztünk egy részletes térszerkezet-vizsgálatot, és azonosítottuk a peptidek jellegzetes térszerkezeti sajátságait. A peptid-micella/membrán rendszerek esetén tanulmányoztuk a sztereoizomer antimikrobiális peptidek micellához/membránhoz kötődésének folyamatát, illetve részletesen jellemeztük a sztereoizomerek micella- és membrán-kötött konformációit, valamint a peptidek és micellák/membránok között kialakuló kölcsönhatásokat. | In my project, the effects of cis-trans and L-D isomerisms on the structural and conformational properties, as well as on the bioactivity of peptides were studied. Based on the comparative conformational analysis of opioid peptides, the characteristic structural features of stereoisomers, as well as the conformational similarities and dissimilarities between the peptides were identified. The method, applied to describe the relative spatial arrangements of pharmacophore elements, proved to be suitable to distinguish the stereoisomers from one another, and to characterize the spatial relationships of pharmacophores. For the antimicrobial peptides, the role of cis-trans isomerism played in the formation of conformational properties of stereoisomers, and in the dynamic behaviour of peptides, was determined. The folding processes were comprehensively explored, regarding the alanine-based peptides containing basic amino acids, and based on the simulations, the folding pathways were characterized using various methods. A detailed structural investigation was performed on the palindromic sequences of antimicrobial peptides, and the typical structural features of peptides were identified. For the peptide-micelle/membrane systems, the binding processes of stereoisomeric antimicrobial peptides to micelle/membrane were studied, as well as the micelle- and membrane-bound conformations, and the interactions evolved between the peptides and micelles/membranes were characterized in detail

Investigation of punctured LDPC codes and time-diversity on free-space optical links

In this paper, we analyze the behavior of DVB-S2 un-punctured/punctured low-density parity-check (LDPC) coded on-off-keying (OOK) under atmospheric turbulence conditions by utilizing time diversity. A performance characterization between these schemes is evaluated, where punctured LDPC code provides a penalty of around 0.1 to 0.2 dB against unpunctured LDPC codes but still provides a coding gain of several dB against uncoded OOK. The combination of channel coding and a bit interleaver results in performance improvements in turbulence conditions. For example, such a system can achieve a coding gain of 16.7 dB in moderate turbulence conditions compared to uncoded OOK

Philippos Monotropos' Dioptra and its Social Milieu: Niketas Stethatos, Nikollaos III Grammatikos and the Persecution of Bogomilism

This article aims to investigate the social milieu of Philippos Monotropos, author of the Dioptra. Explicit evidence on Philippos is scarce, but the comparison with contemporary texts allows some conclusions. Indeed, the way that Philippos treats Bogomilism indicates connections with imperial and patriarchal circles. Moreover, numerous parallels between the Dioptra and the Poem on Fast Days written by Nikolaos III Grammatikos shows that the Patriarch knew and ap­preciated the Dioptra very soon after its composition. The hypothesis that Philip­pos belonged to an educated, urbane ecclesiastical milieu is in accordance with the assessment of the Dioptra as a simplistic epitome of Christian humanistic theology – contrary to previous views that overemphasised its ascetic element.

Searches for direct pair production of scalar tau leptons in events with two hadronically decaying tau leptons with the ATLAS detector in LHC run 2

The Standard Model of particle physics has so far not been contradicted by evidence from experiments. There are, however, several indications that a more fundamental underlying theory is necessary at higher energy scales. At the Large Hadron Collider the possible presence of new physics can be probed in proton-proton collisions at an unprecedented center-of-mass energy of 13 TeV. Some of the most promising extensions to the Standard Model are suggested by supersymmetric models, which predict an entirely new particle spectrum connected to the Standard Model particle content via a fermion-boson symmetry. In this thesis, two approaches for the search for the supersymmetric partner particle to the Standard Model τ -lepton (stau or τ ̃) with 139 fb−1 of data taken by the ATLAS detector at the LHC are presented. The considered collision events should contain two hadronically decaying τ -leptons and missing transverse momentum. The first approach is an analysis based on cuts on kinematic variables, which – in the absence of a supersymmetric signal in data – could exclude stau masses between 120 GeV and 390 GeV at 95% CL for a nearly massless lightest supersymmetric particle (LSP). It was also possible to exclude pair production of the supersymmetric partner of the left-handed τ -lepton ( ̃τL ) for stau masses between 155 GeV and 310 GeV at 95% CL. For the supersymmetric partner of the right-handed τ -lepton it was not possible to reach exclusion sensitivity separately from τ ̃ L production. The second search aims to improve the sensitivity of the first iteration of the analysis by using boosted decision trees and a shape fit. The expected exclusion sensitivity ranges from stau masses of 80 GeV to 430 GeV for the combined scenarios of τ ̃ L and τ ̃ R production. For the separate τ ̃ L pair production, the expected exclusion range covers stau masses from 100 GeV to 350 GeV. Furthermore, for a range of stau masses between 120 GeV and 230 GeV exclusion sensitivity could also be achieved for separate τ ̃ R pair production.Bis heute konnte aus experimentellen Befunden kein Widerspruch zum Standardmodell der Teilchenphysik abgeleitet werden. Es gibt jedoch einige Hinweise für die Existenz einer fundamentaleren zugrundeliegenden Theorie bei höheren Energieskalen. Am Large Hadron Collider kann das mögliche Auftreten von neuer Physik in Proton-Proton Kollisionen bei zuvor unerreichten Schwerpunktsenergien von derzeit 13 TeV erforscht werden. Einige der vielversprechendsten Erweiterungen des Standardmodells sind supersymmetrische Modelle, die ein gänzlich neues Spektrum von Teilchen vorhersagen. Diese werden durch eine Symmetrie von Fermionen und Bosonen mit den Teilchen des Standardmodells in Verbindung gebracht. In dieser Dissertation werden zwei Ansätze für die Suche nach dem supersymmetrischen Partnerteilchen des τ -Leptons im Standardmodell (Stau oder τ ̃) mit 139 fb−1 an Daten vorgestellt, die durch den ATLAS-Detektor am LHC aufgezeichnet wurden. Die selektierten Kollisionsereignisse beinhalten zwei hadronisch zerfallende τ -Leptonen, sowie fehlenden transversalen Impuls. Der erste Ansatz besteht in einer Analyse, die auf Schnitten auf kinematische Variablen basiert. Im Zuge dieser Analyse konnten – in Abwesenheit eines signifikanten Überschusses in den Daten – Staumassen zwischen 120 GeV und 390 GeV mit einem beinahe masselosen leichtesten supersymmetrischen Teilchen (LSP) bei 95% Konfidenzniveau ausgeschlossen werden. Des Weiteren war es möglich, die Paarproduktion des supersymmetrischen Partners des linkshändigen τ -Leptons ( ̃τL ) gesondert im Staumassen-Bereich von 155 GeV bis 310 GeV auf einem Konfidenzniveau von 95% auszuschließen. Für den supersymmetrischen Partner des rechtshändigen τ -Leptons ( ̃τR ) konnte keine Sensitivität erreicht werden, die einen Ausschluss von Staumassen unabhängig von der Paarproduktion von τ ̃ L -Teilchen ermöglicht hätte. Die zweite Suche hat zum Ziel, die Sensitivität der ersten Analyse zu verbessern, indem Boosted Decision Trees und ein Multi-Bin-Fit verwendet werden. Die erwartete Ausschluss-Sensitivität für Staumassen reicht von 80 GeV bis 430 GeV für die kombinierte τ ̃ L - und τ ̃ R -Paarproduktion. Für die gesonderte Produktion von τ ̃ L-Paaren wird ein Ausschluss von Staumassen zwischen 100 GeV und 350 GeV erwartet. Weiterhin konnte auch für eine Spanne von Staumassen zwischen 120 GeV und 230 GeV für gesonderte τ ̃ R-Produktion eine erwartete Sensitivität erreicht werden, die einen Ausschluss dieser Massen ermöglichen kann