Magnetic moments of the low-lying J(P)=1/2(-), 3/2(-) Lambda resonances within the framework of the chiral quark model

The magnetic moments of the low-lying spin-parity J(P) = 1/2(-), 3/2(-) Lambda resonances, like, for example, Lambda(1405) 1/2(-), Lambda(1520) 3/2(-), as well as their transition magnetic moments, are calculated using the chiral quark model. The results found are compared with those obtained from the nonrelativistic quark model and those of unitary chiral theories, where some of these states are generated through the dynamics of two hadron coupled channels and their unitarization.

Phage display identification of CD100 in human atherosclerotic plaque macrophages and foam cells

Atherosclerosis is a complex disease in which vessels develop plaques comprising dysfunctional endothelium, monocyte derived lipid laden foam cells and activated lymphocytes. Considering that humans and animal models of the disease develop quite distinct plaques, we used human plaques to search for proteins that could be used as markers of human atheromas. Phage display peptide libraries were probed to fresh human carotid plaques, and a bound phage homologous to plexin B1, a high affinity receptor for CD100, was identified. CD100 is a member of the semaphorin family expressed by most hematopoietic cells and particularly by activated T cells. CD100 expression was analyzed in human plaques and normal samples. CD100 mRNA and protein were analyzed in cultured monocytes, macrophages and foam cells. The effects of CD100 in oxLDL-induced foam cell formation and in CD36 mRNA abundance were evaluated. Human atherosclerotic plaques showed strong labeling of CD100/SEMA4D. CD100 expression was further demonstrated in peripheral blood monocytes and in in vitro differentiated macrophages and foam cells, with diminished CD100 transcript along the differentiation of these cells. Incubation of macrophages with CD100 led to a reduction in oxLDL-induced foam cell formation probably through a decrease of CD36 expression, suggesting for the first time an atheroprotective role for CD100 in the human disease. Given its differential expression in the numerous foam cells and macrophages of the plaques and its capacity to decrease oxLDL engulfment by macrophages we propose that CD100 may have a role in atherosclerotic plaque development, and may possibly be employed in targeted treatments of these atheromas.

Viruses in the marine environment: community dynamics, phage-host interactions and genomic structure

[EN] There are an estimated 1030 viruses in the world oceans, the majority of which are phages (viruses that infect bacteria). Extensive research has demonstrated the significant influence of marine phages on microbial abundance, community structure, genetic exchange and global biogeochemical cycles. In this thesis, we contribute to increase the knowledge about the ecological role of viruses in marine systems, but also we aimed to provide a better understanding about the interactions between phages and their hosts and the genetic pool and biogeography of some the isolated phages genomes.

Messung der Zerfallsasymmetrien der radiativen Hyperonzerfälle Xi 0 Lambda gamma und Xi 0 Sigma 0 gamma mit dem NA48/1-Experiment

Der radiative Zerfall eines Hyperons in ein leichteres Hyperon und ein Photon erlaubt eine Untersuchung der Struktur der elektroschwachen Wechselwirkung von Hadronen. Dazu wird die Zerfallsasymmetrie $alpha$ betrachtet. Sie beschreibt die Verteilung des Tochterhyperons bezüglich der Polarisation $vec{P}$ des Mutterhyperons mit $dN / d cos(Theta) propto 1 + alpha |vec{P}| cos(Theta)$, wobei $Theta$ der Winkel zwischen $vec{P}$ und dem Impuls des Tochterhyperons ist. Von besonderem Interesse ist der radiative Zerfall $Xi^0 to Lambda gamma$, für den alle Rechnungen auf Quarkniveau eine positive Asymmetrie vorhersagen, wohingegen bisher eine negative Asymmetrie von $alpha_{Lambda gamma} = -0,73 +- 0,17$ gemessen wurde. Ziel dieser Arbeit war es, die bisherigen Messungen zu überprüfen und die Asymmetrie mit einer deutlich höheren Präzision zu bestimmen. Ferner wurden die Zerfallsasymmetrie des radiativen Zerfalls $Xi^0 to Sigma^0 gamma$ ermittelt und zum Test der angewandten Analysemethode der gut bekannte Zerfall $Xi^0 to Lambda pi^0$ herangezogen. Während der Datennahme im Jahr 2002 zeichnete das NA48/1-Experiment am CERN gezielt seltene $K_S$- und Hyperonzerfälle auf. Damit konnte der weltweit größte Datensatz an $Xi^0$-Zerfällen gewonnen werden, aus dem etwa 52.000 $Xi^0 to Lambda gamma$-Zerfälle, 15.000 $Xi^0 to Sigma^0 gamma$-Zerfälle und 4 Mill. $Xi^0 to Lambda pi^0$-Zerfälle mit nur geringem Untergrund extrahiert wurden. Ebenso wurden die entsprechenden $antiXi$-Zerfälle mit etwa einem Zehntel der obigen Ereigniszahlen registriert. Die Bestimmung der Zerfallsasymmetrien erfolgte durch den Vergleich der gemessene Daten mit einer detaillierten Detektorsimulation und führte zu den folgenden Resultaten dieser Arbeit: $alpha_{Lambda gamma} = -0,701 +- 0,019_{stat} +- 0,064_{sys}$, $alpha_{Sigma^0 gamma} = -0,683 +- 0,032_{stat} +- 0,077_{sys}$, $alpha_{Lambda pi^0} = -0,439 +- 0,002_{stat} +- 0,056_{sys}$, $alpha_{antiLambda gamma} = 0,772 +- 0,064_{stat} +- 0,066_{sys}$, $alpha_{antiSigma^0 gamma} = 0,811 +- 0,103_{stat} +- 0,135_{sys}$, $alpha_{antiLambda pi^0} = 0,451 +- 0,005_{stat} +- 0,057_{sys}$. Somit konnte die Unsicherheit der $Xi^0 to Lambda gamma$-Zerfallsasymmetrie auf etwa ein Drittel reduziert werden. Ihr negatives Vorzeichen und damit der Widerspruch zu den Vorhersagen der Quarkmodellrechnungen ist so zweifelsfrei bestätigt. Mit den zum ersten Mal gemessenen $antiXi$-Asymmetrien konnten zusätzlich Grenzen auf eine mögliche CP-Verletzung in den $Xi^0$-Zerfällen, die $alpha_{Xi^0} neq -alpha_{antiXi}$ zur Folge hätte, bestimmt werden.

Feasibility study of performing high precision gamma spectroscopy of lambda lambda hypernuclei in the PANDA experiment

Hypernuclear physics is currently attracting renewed interest, due tornthe important role of hypernuclei spectroscopy rn(hyperon-hyperon and hyperon-nucleon interactions) rnas a unique toolrnto describe the baryon-baryon interactions in a unified way and to rnunderstand the origin of their short-range.rnrnHypernuclear research will be one of the main topics addressed by the {sc PANDA} experimentrnat the planned Facility for Antiproton and Ion Research {sc FAIR}.rnThanks to the use of stored $overline{p}$ beams, copiousrnproduction of double $Lambda$ hypernuclei is expected at thern{sc PANDA} experiment, which will enable high precision $gamma$rnspectroscopy of such nuclei for the first time.rnAt {sc PANDA} excited states of $Xi^-$ hypernuclei will be usedrnas a basis for the formation of double $Lambda$ hypernuclei.rnFor their detection, a devoted hypernuclear detector setup is planned. This setup consists ofrna primary nuclear target for the production of $Xi^{-}+overline{Xi}$ pairs, a secondary active targetrnfor the hypernuclei formation and the identification of associated decay products and a germanium array detector to perform $gamma$ spectroscopy.rnrnIn the present work, the feasibility of performing high precision $gamma$rnspectroscopy of double $Lambda$ hypernuclei at the {sc PANDA} experiment has been studiedrnby means of a Monte Carlo simulation. For this issue, the designing and simulation of the devoted detector setup as well as of the mechanism to produce double $Lambda$ hypernuclei have been optimizedrntogether with the performance of the whole system. rnIn addition, the production yields of double hypernuclei in excitedrnparticle stable states have been evaluated within a statistical decay model.rnrnA strategy for the unique assignment of various newly observed $gamma$-transitions rnto specific double hypernuclei has been successfully implemented by combining the predicted energy spectra rnof each target with the measurement of two pion momenta from the subsequent weak decays of a double hypernucleus.rn% Indeed, based on these Monte Carlo simulation, the analysis of the statistical decay of $^{13}_{Lambda{}Lambda}$B has been performed. rn% As result, three $gamma$-transitions associated to the double hypernuclei $^{11}_{Lambda{}Lambda}$Bern% and to the single hyperfragments $^{4}_{Lambda}$H and $^{9}_{Lambda}$Be, have been well identified.rnrnFor the background handling a method based on time measurement has also been implemented.rnHowever, the percentage of tagged events related to the production of $Xi^{-}+overline{Xi}$ pairs, variesrnbetween 20% and 30% of the total number of produced events of this type. As a consequence, further considerations have to be made to increase the tagging efficiency by a factor of 2.rnrnThe contribution of the background reactions to the radiation damage on the germanium detectorsrnhas also been studied within the simulation. Additionally, a test to check the degradation of the energyrnresolution of the germanium detectors in the presence of a magnetic field has also been performed.rnNo significant degradation of the energy resolution or in the electronics was observed. A correlationrnbetween rise time and the pulse shape has been used to correct the measured energy. rnrnBased on the present results, one can say that the performance of $gamma$ spectroscopy of double $Lambda$ hypernuclei at the {sc PANDA} experiment seems feasible.rnA further improvement of the statistics is needed for the background rejection studies. Moreover, a more realistic layout of the hypernuclear detectors has been suggested using the results of these studies to accomplish a better balance between the physical and the technical requirements.rn

Measurement of the unpolarized K+ Lambda and K+ Sigma 0 electroproduction cross-section off the proton with KAOS-spectrometer

The new stage of the Mainz Microtron, MAMI, at the Institute for Nuclear Physics of the Johannes Gutenberg-University, operational since 2007, allows open strangeness experiments to be performed. Covering the lack of electroproduction data at very low Q2, p(e,K+)Lambda and p(e,K+)Sigma0, reactions have been studied at Q^2 = 0.036(GeV/c)^2 andrnQ^2 = 0.05(GeV=c)^2 in a large angular range. Cross-section at W=1.75rnGeV will be given in angular bins and compared with the predictions of Saclay-Lyon and Kaon Maid isobaric models. We conclude that the original Kaon-Maid model, which has large longitudinal couplings of the photon to nucleon resonances, is unphysical. Extensive studies for the suitability of silicon photomultipliers as read out devices for a scintillating fiber tracking detector, with potential applications in both positive and negative arms of the spectrometer, will be presented as well.

Measurement of CP asymmetries in $\lambda^0_b \to pk^-$ and $\lambda^0_b \to p \pi^-$ decays at LHCb

The LHCb experiment has been designed to perform precision measurements in the flavour physics sector at the Large Hadron Collider (LHC) located at CERN. After the recent observation of CP violation in the decay of the Bs0 meson to a charged pion-kaon pair at LHCb, it is interesting to see whether the same quark-level transition in Λ0b baryon decays gives rise to large CP-violating effects. Such decay processes involve both tree and penguin Feynman diagrams and could be sensitive probes for physics beyond the Standard Model. The measurement of the CP-violating observable defined as ∆ACP = ACP(Λ0b → pK−)−ACP(Λ0b →pπ−),where ACP(Λ0b →pK−) and ACP(Λ0b →pπ−) are the direct CP asymmetries in Λ0b → pK− and Λ0b → pπ− decays, is presented for the first time using LHCb data. The procedure followed to optimize the event selection, to calibrate particle identification, to parametrise the various components of the invariant mass spectra, and to compute corrections due to the production asymmetry of the initial state and the detection asymmetries of the final states, is discussed in detail. Using the full 2011 and 2012 data sets of pp collisions collected with the LHCb detector, corresponding to an integrated luminosity of about 3 fb−1, the value ∆ACP = (0.8 ± 2.1 ± 0.2)% is obtained. The first uncertainty is statistical and the second corresponds to one of the dominant systematic effects. As the result is compatible with zero, no evidence of CP violation is found. This is the most precise measurement of CP violation in the decays of baryons containing the b quark to date. Once the analysis will be completed with an exhaustive study of systematic uncertainties, the results will be published by the LHCb Collaboration.

Study of 3 Lambda H and 4 Lambda H in the reaction of 6 Li + 12 C at 2 A GeV

Die Produktion von Hyperkernen wurde in peripheren Schwerionenreaktionen untersucht, bei denen eine Kohlenstofffolie mit $^6$Li Projektilen mit einer Strahlenergie von $2 A$~GeV bestrahlt wurde. Es konnten klare Signale f{"{u}}r $Lambda$, $^3_{Lambda}$H, $^4_{Lambda}$H in deren jeweiligen invarianten Massenverteilungen aus Mesonenzerfall beobachtet werden.rnrnIn dieser Arbeit wird eine unabh{"{a}}ngige Datenauswertung vorgelegt, die eine Verifizierung fr"{u}herer Ergebnisse der HypHI Kollaboration zum Ziel hatte. Zu diesem Zweck wurde eine neue Track-Rekonstruktion, basierend auf einem Kalman-Filter-Ansatz, und zwei unterschiedliche Algorithmen zur Rekonstruktion sekund"{a}rer Vertices entwickelt.rn%-Rekonstruktionsalgorithmen .rnrnDie invarianten Massen des $Lambda$-Hyperon und der $^3_{Lambda}$H- und $^4_{Lambda}$H-Hyperkerne wurden mit $1109.6 pm 0.4$, $2981.0 pm 0.3$ und $3898.1 pm 0.7$~MeV$/c^2$ und statistischen Signifikanzen von $9.8sigma$, $12.8sigma$ beziehungsweise $7.3sigma$ bestimmt. Die in dieser Arbeit erhaltenen Ergebnisse stimmen mit der fr{"{u}}heren Auswertung {"{u}}berein.rnrnDas Ausbeutenverh{"{a}}ltnis der beiden Hyperkerne wurde als $N(^3_{Lambda}$H)/$N(^4_{Lambda}$H)$ sim 3$ bestimmt. Das deutet darauf hin, dass der Produktionsmechanismus f{"{u}}r Hyperkerne in Schwerionen-induzierten Reaktionen im Projektil-Rapidit{"{a}}tsbereich nicht allein durch einen Koaleszenzmechanismus beschrieben werden kann, sondern dass auch sekund{"{a}}re Pion-/Kaon-induzierte Reaktionen und Fermi-Aufbruch involviert sind.rn

The finite lambda calculus

In questa tesi si descrive il lambda calcolo finito, un'istanza del lambda calcolo con tipi finiti. Si studia la metateoria e la complessità della riduzione.

Phage therapy: A software system for phage quantification and kinetic model inference.

One of the most serious problems of the modern medicine is the growing emergence of antibiotic resistance among pathogenic bacteria. In this circumstance, different and innovative approaches for treating infections caused by multidrug-resistant bacteria are imperatively required. Bacteriophage Therapy is one among the fascinating approaches to be taken into account. This consists of the use of bacteriophages, viruses that infect bacteria, in order to defeat specific bacterial pathogens. Phage therapy is not an innovative idea, indeed, it was widely used around the world in the 1930s and 1940s, in order to treat various infection diseases, and it is still used in Eastern Europe and the former Soviet Union. Nevertheless, Western scientists mostly lost interest in further use and study of phage therapy and abandoned it after the discovery and the spread of antibiotics. The advancement of scientific knowledge of the last years, together with the encouraging results from recent animal studies using phages to treat bacterial infections, and above all the urgent need for novel and effective antimicrobials, have given a prompt for additional rigorous researches in this field. In particular, in the laboratory of synthetic biology of the department of Life Sciences at the University of Warwick, a novel approach was adopted, starting from the original concept of phage therapy, in order to study a concrete alternative to antibiotics. The innovative idea of the project consists in the development of experimental methodologies, which allow to engineer a programmable synthetic phage system using a combination of directed evolution, automation and microfluidics. The main aim is to make “the therapeutics of tomorrow individualized, specific, and self-regulated” (Jaramillo, 2015). In this context, one of the most important key points is the Bacteriophage Quantification. Therefore, in this research work, a mathematical model describing complex dynamics occurring in biological systems involving continuous growth of bacteriophages, modulated by the performance of the host organisms, was implemented as algorithms into a working software using MATLAB. The developed program is able to predict different unknown concentrations of phages much faster than the classical overnight Plaque Assay. What is more, it gives a meaning and an explanation to the obtained data, making inference about the parameter set of the model, that are representative of the bacteriophage-host interaction.

Elaborazione di Big Data: un’applicazione dello Speed Layer di Lambda Architecture

I Big Data hanno forgiato nuove tecnologie che migliorano la qualità della vita utilizzando la combinazione di rappresentazioni eterogenee di dati in varie discipline. Occorre, quindi, un sistema realtime in grado di computare i dati in tempo reale. Tale sistema viene denominato speed layer, come si evince dal nome si è pensato a garantire che i nuovi dati siano restituiti dalle query funcions con la rapidità in cui essi arrivano. Il lavoro di tesi verte sulla realizzazione di un’architettura che si rifaccia allo Speed Layer della Lambda Architecture e che sia in grado di ricevere dati metereologici pubblicati su una coda MQTT, elaborarli in tempo reale e memorizzarli in un database per renderli disponibili ai Data Scientist. L’ambiente di programmazione utilizzato è JAVA, il progetto è stato installato sulla piattaforma Hortonworks che si basa sul framework Hadoop e sul sistema di computazione Storm, che permette di lavorare con flussi di dati illimitati, effettuando l’elaborazione in tempo reale. A differenza dei tradizionali approcci di stream-processing con reti di code e workers, Storm è fault-tolerance e scalabile. Gli sforzi dedicati al suo sviluppo da parte della Apache Software Foundation, il crescente utilizzo in ambito di produzione di importanti aziende, il supporto da parte delle compagnie di cloud hosting sono segnali che questa tecnologia prenderà sempre più piede come soluzione per la gestione di computazioni distribuite orientate agli eventi. Per poter memorizzare e analizzare queste moli di dati, che da sempre hanno costituito una problematica non superabile con i database tradizionali, è stato utilizzato un database non relazionale: HBase.

DARPins recognizing the tumor-associated antigen EpCAM selected by phage and ribosome display and engineered for multivalency

Designed Ankyrin Repeat Proteins (DARPins) represent a novel class of binding molecules. Their favorable biophysical properties such as high affinity, stability and expression yields make them ideal candidates for tumor targeting. Here, we describe the selection of DARPins specific for the tumor-associated antigen epithelial cell adhesion molecule (EpCAM), an approved therapeutic target on solid tumors. We selected DARPins from combinatorial libraries by both phage display and ribosome display and compared their binding on tumor cells. By further rounds of random mutagenesis and ribosome display selection, binders with picomolar affinity were obtained that were entirely monomeric and could be expressed at high yields in the cytoplasm of Escherichia coli. One of the binders, denoted Ec1, bound to EpCAM with picomolar affinity (K(d)=68 pM), and another selected DARPin (Ac2) recognized a different epitope on EpCAM. Through the use of a variety of bivalent and tetravalent arrangements with these DARPins, the off-rate on cells was further improved by up to 47-fold. All EpCAM-specific DARPins were efficiently internalized by receptor-mediated endocytosis, which is essential for intracellular delivery of anticancer agents to tumor cells. Thus, using EpCAM as a target, we provide evidence that DARPins can be conveniently selected and rationally engineered to high-affinity binders of various formats for tumor targeting.