Carcinoma polmonare non a piccole cellule T1aN0M0: Ruolo prognostico della Microvessel Density

Obiettivi. Valutare l’angiogenesi tumorale mediante la Microvessel density (MVD) come fattore predittivo di mortalità per tumore polmonare non a piccole cellule (NSCLC) pT1aN0M0 trattato chirurgicamente. Metodi. I dati demografici, clinici e istopatologici sono stati registrati per 82 pazienti (60 maschi, 22 femmine) sottoposti a resezione chirurgica in due diverse Chirurgie Toraciche tra gennaio 2002 e dicembre 2007 per tumori polmonari non a piccole cellule pT1AN0M0. La MVD è stata valutata mediante il conteggio visivo dei microvasi positivi alla colorazione immunoistochimica con anticorpo monoclonale anti-CD31 e definita come il numero medio di microvasi per 1 mm2 di campo ottico. Risultati. Sono state eseguite 59 lobectomie (72%) e 23 resezioni sublobari (28%). Reperti istopatologici: 43 adenocarcinomi (52%) e 39 neoplasie non- adenocarcinoma (48%) pT1aN0M0; MVD media: 161 (CD31/mm2); mediana: 148; range 50-365, cut-off=150. Una MVD elevata (> 150 CD31/mm2) è stata osservata in 40 pazienti (49%), una MVD ridotta ( ≤ 150 CD31/mm2 ) in 42 pazienti (51%). Sopravvivenze a 5 anni: 70 % e 95%, rispettivamente per il gruppo ad elevata MVD vs il gruppo a ridotta MVD con una p = 0,0041, statisticamente significativa. Il tipo di resezione chirurgica, il diametro del tumore, le principali comorbidità e l’istotipo nono sono stati fattori predittivi significativi di mortalità correlata alla malattia. La MVD è risultata essere superiore nel gruppo “Adenocarcinoma” (MVD mediana=180) rispetto al gruppo “Non-Adenocarcinoma (MVD mediana=125), con un test di Mann-Whitney statisticamente significativo (p < 0,0001). Nel gruppo “Adenocarcinoma” la sopravvivenza a 5 anni è stata del 66% e 93 %, rispettivamente per i pazienti con MVD elevata e ridotta (p = 0.043. Conclusioni. Il nostro studio ha mostrato che la Microvessel density valutata con la colorazione immunoistochimica per CD31 ha un valore prognostico rilevante nel carcinoma polmonare in stadio precoce pT1aN0M0.

Nano-fabrication of complex functional structures using non- conventional lithography

In Chapter 1 I will present a brief introduction on the state of art of nanotechnologies, nanofabrication techniques and unconventional lithography as a technique to fabricate the novel electronic device as resistive switch so-called memristor is shown. In Chapter 2 a detailed description of the main fabrication and characterization techniques employed in this work is reported. Chapter 3 parallel local oxidation lithography (pLOx) describes as a main technique to obtain accurate patterning process. All the effective parameters has been studied and the optimized condition observed to highly reproducible with excellent patterned nanostructures. The effect of negative bias, calls local reduction (LR) studied. Moreover, the use of AC bias shows faster patterning process respect to DC bias. In Chapter 4 (metal/ e-SiO2/ Si nanojunction) it is shown how the electrochemical oxide nanostructures by using pLOx can be used in the fabrication of novel devices call memristor. We demonstrate a new concept, based on conventional materials, where the lifetime problem is resolved by introducing a “regeneration” step, which restores the nano-memristor to its pristine condition by applying an appropriate voltage cycle. In Chapter 5 (Graphene/ e-SiO2/ Si), Graphene as a building block material is used as an electrode to selectively oxidize the silicon substrate by pLOx set up for the fabrication of novel resistive switch device. In Chapter 6 (surface architecture) I will show another application of pLOx in biotechnology is shown. So the surface functionalization combine with nano-patterning by pLOx used to design a new surface to accurately bind biomolecules with the possibility of studying those properties and more application in nano-bio device fabrication. So, in order to obtain biochips, electronic and optical/photonics devices Nano patterning of DNA used as scaffolds to fabricate small functional nano-components.

Factorization and non-local 1/m b corrections in the decay B X s gamma

In this thesis, a systematic analysis of the bar B to X_sgamma photon spectrum in the endpoint region is presented. The endpoint region refers to a kinematic configuration of the final state, in which the photon has a large energy m_b-2E_gamma = O(Lambda_QCD), while the jet has a large energy but small invariant mass. Using methods of soft-collinear effective theory and heavy-quark effective theory, it is shown that the spectrum can be factorized into hard, jet, and soft functions, each encoding the dynamics at a certain scale. The relevant scales in the endpoint region are the heavy-quark mass m_b, the hadronic energy scale Lambda_QCD and an intermediate scale sqrt{Lambda_QCD m_b} associated with the invariant mass of the jet. It is found that the factorization formula contains two different types of contributions, distinguishable by the space-time structure of the underlying diagrams. On the one hand, there are the direct photon contributions which correspond to diagrams with the photon emitted directly from the weak vertex. The resolved photon contributions on the other hand arise at O(1/m_b) whenever the photon couples to light partons. In this work, these contributions will be explicitly defined in terms of convolutions of jet functions with subleading shape functions. While the direct photon contributions can be expressed in terms of a local operator product expansion, when the photon spectrum is integrated over a range larger than the endpoint region, the resolved photon contributions always remain non-local. Thus, they are responsible for a non-perturbative uncertainty on the partonic predictions. In this thesis, the effect of these uncertainties is estimated in two different phenomenological contexts. First, the hadronic uncertainties in the bar B to X_sgamma branching fraction, defined with a cut E_gamma > 1.6 GeV are discussed. It is found, that the resolved photon contributions give rise to an irreducible theory uncertainty of approximately 5 %. As a second application of the formalism, the influence of the long-distance effects on the direct CP asymmetry will be considered. It will be shown that these effects are dominant in the Standard Model and that a range of -0.6 < A_CP^SM < 2.8 % is possible for the asymmetry, if resolved photon contributions are taken into account.

Experimental assessment of environmental decay effects in masonry via non destructive diagnostic techniques and mechanical tests

Environmental decay in porous masonry materials, such as brick and mortar, is a widespread problem concerning both new and historic masonry structures. The decay mechanisms are quite complex dependng upon several interconnected parameters and from the interaction with the specific micro-climate. Materials undergo aesthetical and substantial changes in character but while many studies have been carried out, the mechanical aspect has been largely understudied while it bears true importance from the structural viewpoint. A quantitative assessment of the masonry material degradation and how it affects the load-bearing capacity of masonry structures appears missing. The research work carried out, limiting the attention to brick masonry addresses this issue through an experimental laboratory approach via different integrated testing procedures, both non-destructive and mechanical, together with monitoring methods. Attention was focused on transport of moisture and salts and on the damaging effects caused by the crystallization of two different salts, sodium chloride and sodium sulphate. Many series of masonry specimens, very different in size and purposes were used to track the damage process since its beginning and to monitor its evolution over a number of years Athe same time suitable testing techniques, non-destructive, mini-invasive, analytical, of monitoring, were validated for these purposes. The specimens were exposed to different aggressive agents (in terms of type of salt, of brine concentration, of artificial vs. open-air natural ageing, …), tested by different means (qualitative vs. quantitative, non destructive vs. mechanical testing, punctual vs. wide areas, …), and had different size (1-, 2-, 3-header thick walls, full-scale walls vs. small size specimens, brick columns and triplets vs. small walls, masonry specimens vs. single units of brick and mortar prisms, …). Different advanced testing methods and novel monitoring techniques were applied in an integrated holistic approach, for quantitative assessment of masonry health state.

Measurement of the e + e - pi + pi - pi + pi - cross section using initial state radiation at BABAR

One of the most precisely measured quantities in particle physics is the magnetic moment of the muon, which describes its coupling to an external magnetic field. It is expressed in form of the anomalous magnetic moment of the muon a_mu=(g_mu-2)/2 and has been determined experimentally with a precision of 0.5 parts per million. The current direct measurement and the theoretical prediction of the standard model differ by more than 3.5 standard deviations. Concerning theory, the contribution of the QED and weak interaction to a_mu can be calculated with very high precision in a perturbative approach.rnAt low energies, however, perturbation theory cannot be used to determine the hadronic contribution a^had_mu. On the other hand, a^had_mu may be derived via a dispersion relation from the sum of measured cross sections of exclusive hadronic reactions. Decreasing the experimental uncertainty on these hadronic cross sections is of utmost importance for an improved standard model prediction of a_mu.rnrnIn addition to traditional energy scan experiments, the method of Initial State Radiation (ISR) is used to measure hadronic cross sections. This approach allows experiments at colliders running at a fixed centre-of-mass energy to access smaller effective energies by studying events which contain a high-energetic photon emitted from the initial electron or positron. Using the technique of ISR, the energy range from threshold up to 4.5GeV can be accessed at Babar.rnrnThe cross section e+e- -> pi+pi- contributes with approximately 70% to the hadronic part of the anomalous magnetic moment of the muon a_mu^had. This important channel has been measured with a precision of better than 1%. Therefore, the leading contribution to the uncertainty of a_mu^had at present stems from the invariant mass region between 1GeV and 2GeV. In this energy range, the channels e+e- -> pi+pi-pi+pi- and e+e- -> pi+pi-pi0pi0 dominate the inclusive hadronic cross section. The measurement of the process e+e- -> pi+pi-pi+pi- will be presented in this thesis. This channel has been previously measured by Babar based on 25% of the total dataset. The new analysis includes a more detailed study of the background contamination from other ISR and non-radiative background reactions. In addition, sophisticated studies of the track reconstruction as well as the photon efficiency difference between the data and the simulation of the Babar detector are performed. With these auxiliary studies, a reduction of the systematic uncertainty from 5.0% to 2.4% in the peak region was achieved.rnrnThe pi+pi-pi+pi- final state has a rich internal structure. Hints are seen for the intermediate states rho(770)^0 f_2(1270), rho(770)^0 f_0(980), as well as a_1(1260)pi. In addition, the branching ratios BR(jpsi -> pi+pi-pi+pi-) and BR(psitwos -> jpsi pi+pi-) are extracted.rn

Studio degli effetti della stimolazione transcranica a corrente diretta (tdcs) sui potenziali evocati visivi steady state

I potenziali evocati visivi steady state (ssVEPs) consistono in una perturbazione dell’attività elettrica cerebrale spontanea e insorgono in presenza di stimoli visivi come luci monocromatiche modulate sinusoidalmente. Nel tracciato EEG si instaurano oscillazioni di piccola ampiezza ad una frequenza pari a quella dello stimolo. L’analisi nel dominio delle frequenze permette di mettere in evidenza queste oscillazioni che si presentano con un picco ben distinto in corrispondenza della frequenza dello stimolo. L’obiettivo di questo lavoro è quello di capire se la stimolazione transcranica in corrente continua (tDCS) ha degli effetti a breve e a medio termine sui SSVEPs. Si è studiato gli effetti della stimolazione anodica utilizzando un montaggio di stimolazione extra-cefalico (anodo posizionato su Oz e catodo sul braccio destro). L’esperimento prevede il flickering a 3 frequenze di interesse (12, 15, 20 Hz) di 3 quadrati colorati (rosso e giallo) su sfondo nero. Sono state quindi messe a confronto 4 condizioni operative: baseline, stimolazione sham, stimolazione anodica, condizione Post Anodica.L’esperimento è stato sottoposto a 6 soggetti di età tra i 21 e i 51 anni. Il segnale è stato acquisito da due canali bipolari localizzati nella regione occipitale (O1-PO7 e O2-PO8). È stato effettuato un filtraggio tra 3-60 Hz e a 50 Hz. Si sono stimate le PSD normalizzate rispetto alla condizione di riposo in baseline e le potenze nell’intorno della frequenze di interesse (12,15,20 Hz). I dati chiaramente artefattuali sono stati scartati mediante un’analisi esplorativa. Da qui è stato deciso di non includere nella statistica la stimolazione anodica. L’analisi statistica considera tre aspetti: effetto stimolazione, effetto frequenza ed effetto colore. In alcune configurazioni la stimolazione post anodica si è rivelata significativamente differente con ranghi medi delle colonne inferiori alle altre stimolazioni. Non ci sono differenze significative tra le frequenze. Il colore giallo è risultato significativamente maggiore al colore rosso.

The g-factor of the electron bound in 28 Si 13+ : the most stringent test of bound-state quantum electrodynamics

This thesis describes the ultra-precise determination of the g-factor of the electron bound to hydrogenlike 28Si13+. The experiment is based on the simultaneous determination of the cyclotron- and Larmor frequency of a single ion, which is stored in a triple Penning-trap setup. The continuous Stern-Gerlach effect is used to couple the spin of the bound electron to the motional frequencies of the ion via a magnetic bottle, which allows the non-destructive determination of the spin state. To this end, a highly sensitive, cryogenic detection system was developed, which allowed the direct, non-destructive detection of the eigenfrequencies with the required precision.rnThe development of a novel, phase sensitive detection technique finally allowed the determination of the g-factor with a relative accuracy of 40 ppt, which was previously inconceivable. The comparison of the hereby determined value with the value predicted by quantumelectrodynamics (QED) allows the verification of the validity of this fundamental theory under the extreme conditions of the strong binding potential of a highly charged ion. The exact agreement of theory and experiment is an impressive demonstration of the exactness of QED. The experimental possibilities created in this work will allow in the near future not only further tests of theory, but also the determination of the mass of the electron with a precision that exceeds the current literature value by more than an order of magnitude.

Structure, Dynamics and Reactivity in the Organic Solid State: Anthracene Derivatives and Charge Transfer Crystals

The work presented in this thesis tackles some important points concerning the collective properties of two typical categories of molecular crystals, i.e., anthracene derivatives and charge transfer crystals. Anthracene derivatives have constituted the class of materials from which systematical investigations of crystal-to-crystal photodimerization reactions started, developed and have been the subject of a new awakening in the recent years. In this work some of these compounds, namely, 9-cyanoanthacene, 9-anthacenecarboxylic acid and 9-methylanthracene, have been selected as model systems for a phenomenological approach to some key properties of the solid state, investigated by spectroscopic methods. The present results show that, on the basis of the solid state organization and the chemical nature of each compound, photo-reaction dynamics and kinetics display distinctive behaviors, which allows for a classification of the various processes in topochemical, non topochemical, reversible or topophysical. The second part of the thesis was focused on charge transfer crystals, binary systems formed by stoichiometric combinations of the charge donating perylene (D) and the charge accepting tetracyano-quinodimethane (A), this latter also in its fluorinated derivatives. The work was focused on the growth of single crystals, some of which not yet reported in the literature, by PVT technique. Structural and spectroscopic characterizations have been performed, with the aim of determining the degree of charge transfer between donor and acceptor in the co-crystals. An interesting outcome of the systematic search performed in this work is the definition of the experimental conditions which drive the crystal growth of the binary systems either towards the low (1:1) or the high ratio (3:1 or 3:2) stoichiometries.

Chiral properties of two-flavour QCD at zero and non-zero temperature

Lattice Quantum Chromodynamics (LQCD) is the preferred tool for obtaining non-perturbative results from QCD in the low-energy regime. It has by nowrnentered the era in which high precision calculations for a number of phenomenologically relevant observables at the physical point, with dynamical quark degrees of freedom and controlled systematics, become feasible. Despite these successes there are still quantities where control of systematic effects is insufficient. The subject of this thesis is the exploration of the potential of todays state-of-the-art simulation algorithms for non-perturbativelyrn$\mathcal{O}(a)$-improved Wilson fermions to produce reliable results in thernchiral regime and at the physical point both for zero and non-zero temperature. Important in this context is the control over the chiral extrapolation. Thisrnthesis is concerned with two particular topics, namely the computation of hadronic form factors at zero temperature, and the properties of the phaserntransition in the chiral limit of two-flavour QCD.rnrnThe electromagnetic iso-vector form factor of the pion provides a platform to study systematic effects and the chiral extrapolation for observables connected to the structure of mesons (and baryons). Mesonic form factors are computationally simpler than their baryonic counterparts but share most of the systematic effects. This thesis contains a comprehensive study of the form factor in the regime of low momentum transfer $q^2$, where the form factor is connected to the charge radius of the pion. A particular emphasis is on the region very close to $q^2=0$ which has not been explored so far, neither in experiment nor in LQCD. The results for the form factor close the gap between the smallest spacelike $q^2$-value available so far and $q^2=0$, and reach an unprecedented accuracy at full control over the main systematic effects. This enables the model-independent extraction of the pion charge radius. The results for the form factor and the charge radius are used to test chiral perturbation theory ($\chi$PT) and are thereby extrapolated to the physical point and the continuum. The final result in units of the hadronic radius $r_0$ is rn$$ \left\langle r_\pi^2 \right\rangle^{\rm phys}/r_0^2 = 1.87 \: \left(^{+12}_{-10}\right)\left(^{+\:4}_{-15}\right) \quad \textnormal{or} \quad \left\langle r_\pi^2 \right\rangle^{\rm phys} = 0.473 \: \left(^{+30}_{-26}\right)\left(^{+10}_{-38}\right)(10) \: \textnormal{fm} \;, $$rn which agrees well with the results from other measurements in LQCD and experiment. Note, that this is the first continuum extrapolated result for the charge radius from LQCD which has been extracted from measurements of the form factor in the region of small $q^2$.rnrnThe order of the phase transition in the chiral limit of two-flavour QCD and the associated transition temperature are the last unkown features of the phase diagram at zero chemical potential. The two possible scenarios are a second order transition in the $O(4)$-universality class or a first order transition. Since direct simulations in the chiral limit are not possible the transition can only be investigated by simulating at non-zero quark mass with a subsequent chiral extrapolation, guided by the universal scaling in the vicinity of the critical point. The thesis presents the setup and first results from a study on this topic. The study provides the ideal platform to test the potential and limits of todays simulation algorithms at finite temperature. The results from a first scan at a constant zero-temperature pion mass of about 290~MeV are promising, and it appears that simulations down to physical quark masses are feasible. Of particular relevance for the order of the chiral transition is the strength of the anomalous breaking of the $U_A(1)$ symmetry at the transition point. It can be studied by looking at the degeneracies of the correlation functions in scalar and pseudoscalar channels. For the temperature scan reported in this thesis the breaking is still pronounced in the transition region and the symmetry becomes effectively restored only above $1.16\:T_C$. The thesis also provides an extensive outline of research perspectives and includes a generalisation of the standard multi-histogram method to explicitly $\beta$-dependent fermion actions.

Emissione non termica in ammassi di galassie in relazione con la massa del sistema

L'oggetto di studio di questa tesi e' l'analisi degli ammassi di galassie (galaxy clusters) e delle loro proprieta', attraverso un introduttiva analisi morfologica e dinamica, considerazioni sulle proprieta' termiche (con caratteristiche collegate direttamente dalla temperatura), ed infine l'ispezione dei meccanismi che generano le emissioni non termiche e le loro sorgenti. Cercheremo delle relazioni fra le une e le altre. In particolare studieremo specifiche conformazioni del mezzo intergalattico (ICM, intracluster medium) all'interno degli ammassi, quali Aloni, Relitti e Mini Aloni, attraverso le radiazioni che essi sprigionano nella banda dei raggi X e onde radio. Le prime osservazioni sugli ammassi di galassie sono state effettuate gia' alla fine del '700 da Charles Messier, che, al fine di esaminare il cielo alla ricerca di comete, forni un catalogo di 110 oggetti cosmici che, pur apparendo nebulosi per via della limitatezza di risoluzione dei telescopi di allora, non erano sicuramente comete. Fra questi oggetti vi erano anche ammassi di galassie. I primi studi approfonditi si ebbero soltanto con il rapido incremento tecnologico del XX secolo che permise di capire che quelle formazioni confuse altro non erano che agglomerati di galassie. Telescopi piu' grandi, e poi interferometri, radiotelescopi osservazioni agli X hanno sostanzialmente aperto il mondo dell'astrofisica. In particolare Abell stabili' nel primo dopoguerra il primo catalogo di ammassi su determinazione morfologica. Altri astronomi ampliarono poi i parametri di classificazione basandosi su caratteristiche ottiche e meccaniche. Le analisi piu' recenti infine basano le loro conclusioni sullo studio delle bande non ottiche dello spettro, principalmente i raggi X e onde Radio.

Outcomes feto-neonatali dell'infezione non primaria da Cytomegalovirus

OBIETTIVI: Valutazione del rischio di trasmissione verticale e delle conseguenze dell’infezione congenita da cytomegalovirus (CMV) in caso di infezione non primaria versus l’outcome delle gravidanze complicate da infezione primaria. MATERIALI E METODI: Studio retrospettivo di coorte di gravide con infezione recente da CMV diagnosticata c/o il nostro centro negli anni 2000-2013. Le pazienti sono state suddivise in 2 gruppi in base al risultato delle indagini sierologiche (avidità IgG e immunoblot): il primo con profilo sierologico compatibile con infezione non primaria e l'altro compatibile con infezione primaria da CMV. Sono stati confrontati il rischio di trasmissione e di infezione congenita sintomatica nei due gruppi. RISULTATI: Il follow-up è risultato disponibile in 1122 casi di cui 182 con infezione materna non-primaria e 940 con infezione primaria materna. L’infezione congenita è stata diagnosticata in 7 (3.86%) feti/neonati nei casi di infezione non primaria e in 217 (23%) feti/neonati nei casi di infezione primaria (p<0.001). Tra gli infetti, erano sintomatici 43 (19,8%) e 3 (42,8%) rispettivamente nell’infezione primaria e non primaria. COMMENTO: La preesistente immunità materna offre una protezione contro la trasmissione intrauterina nell’infezione da CMV ma non protegge dalla malattia congenita sintomatica.

Non Invasive Tools for Early Detection of Autism Spectrum Disorders

Autism Spectrum Disorders (ASDs) describe a set of neurodevelopmental disorders. ASD represents a significant public health problem. Currently, ASDs are not diagnosed before the 2nd year of life but an early identification of ASDs would be crucial as interventions are much more effective than specific therapies starting in later childhood. To this aim, cheap an contact-less automatic approaches recently aroused great clinical interest. Among them, the cry and the movements of the newborn, both involving the central nervous system, are proposed as possible indicators of neurological disorders. This PhD work is a first step towards solving this challenging problem. An integrated system is presented enabling the recording of audio (crying) and video (movements) data of the newborn, their automatic analysis with innovative techniques for the extraction of clinically relevant parameters and their classification with data mining techniques. New robust algorithms were developed for the selection of the voiced parts of the cry signal, the estimation of acoustic parameters based on the wavelet transform and the analysis of the infant’s general movements (GMs) through a new body model for segmentation and 2D reconstruction. In addition to a thorough literature review this thesis presents the state of the art on these topics that shows that no studies exist concerning normative ranges for newborn infant cry in the first 6 months of life nor the correlation between cry and movements. Through the new automatic methods a population of control infants (“low-risk”, LR) was compared to a group of “high-risk” (HR) infants, i.e. siblings of children already diagnosed with ASD. A subset of LR infants clinically diagnosed as newborns with Typical Development (TD) and one affected by ASD were compared. The results show that the selected acoustic parameters allow good differentiation between the two groups. This result provides new perspectives both diagnostic and therapeutic.

The gas mass fraction and the dynamical state in x-ray luminous clusters of galaxies at low redshift

Gli ammassi di galassie sono le strutture gravitazionalmente legate con le più profonde buche di potenziale, pertanto è previsto che questi contengano una frazione di barioni non molto diversa da quella cosmologica. Con l’introduzione di modelli sempre più accurati di fisica barionica all’interno di simulazioni idrodinamiche è stato possibile predire la percentuale cosmica di barioni presente negli ammassi di galassie. Unendo questi modelli previsionali con misure della frazione di gas in ammassi e informazioni sulla densità di barioni dell’Universo si può ottenere una stima della densità di materia cosmica Ωm. L'obiettivo di questo lavoro di Tesi è la stima di Ωm a partire dalla frazione di gas osservata in questi sistemi. Questo lavoro era stato già fatto in precedenza, ma tenendo in considerazione solo gli ammassi più massivi e dinamicamente rilassati. Usando parametri che caratterizzano la morfologia della distribuzione di brillanza superficiale nei raggi X, abbiamo classificato i nostri oggetti come rilassati o disturbati, laddove presentassero evidenze di recenti attività di interazione. Abbiamo dunque valutato l’impatto degli oggetti disturbati sulla stima del parametro cosmologico Ωm, computando il Chi2 tra la frazione di massa barionica nell’Universo e quella da noi ricavata. Infine abbiamo investigato una relazione tra il valore della frazione di gas degli ammassi rilassati e quello dei disturbati, in modo da correggere quindi questi ultimi, riportandoli nei dintorni del valore medio per i rilassati e usarli per ampliare il campione e porre un vincolo più stringente su Ωm. Anche con il limitato campione a nostra disposizione, è stato possibile porre un vincolo più stretto su Ωm, utilizzando un maggior numero di oggetti e riducendo così l’errore statistico.

A photophysical study of excited state dynamics in donor-acceptor copolymer photovoltaic blends

This thesis deals with the investigation of charge generation and recombination processes in three different polymer:fullerene photovoltaic blends by means of ultrafast time-resolved optical spectroscopy. The first donor polymer, namely poly[N-11"-henicosanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT), is a mid-bandgap polymer, the other two materials are the low-bandgap donor polymers poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole) (PCPDTBT) and poly[(4,4'-bis(2-ethylhexyl)dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl] (PSBTBT). Despite their broader absorption, the low-bandgap polymers do not show enhanced photovoltaic efficiencies compared to the mid-bandgap system.rnrnTransient absorption spectroscopy revealed that energetic disorder plays an important role in the photophysics of PCDTBT, and that in a blend with PCBM geminate losses are small. The photophysics of the low-bandgap system PCPDTBT were strongly altered by adding a high boiling point cosolvent to the polymer:fullerene blend due to a partial demixing of the materials. We observed an increase in device performance together with a reduction of geminate recombination upon addition of the cosolvent. By applying model-free multi-variate curve resolution to the spectroscopic data, we found that fast non-geminate recombination due to polymer triplet state formation is a limiting loss channel in the low-bandgap material system PCPDTBT, whereas in PSBTBT triplet formation has a smaller impact on device performance, and thus higher efficiencies are obtained.rn

Excited-state dynamics in donor-acceptor systems for energy conversion

In dieser Arbeit werden die Dynamiken angeregter Zustände in Donor-Akzeptorsystemen für Energieumwandlungsprozesse mit ultraschneller zeitaufgelöster optischer Spektroskopie behandelt. Der Hauptteil dieser Arbeit legt den Fokus auf die Erforschung der Photophysik organischer Solarzellen, deren aktive Schichten aus diketopyrrolopyrrole (DPP) basierten Polymeren mit kleiner Bandlücke als Elektronendonatoren und Fullerenen als Elektronenakzeptoren bestehen. rnEin zweiter Teil widmet sich der Erforschung von künstlichen primären Photosynthesereaktionszentren, basierend auf Porphyrinen, Quinonen und Ferrocenen, die jeweils als Lichtsammeleinheit, Elektronenakzeptor beziehungsweise als Elektronendonatoren eingesetzt werden, um langlebige ladungsgetrennte Zustände zu erzeugen.rnrnZeitaufgelöste Photolumineszenzspektroskopie und transiente Absorptionsspektroskopie haben gezeigt, dass Singulettexzitonenlebenszeiten in den Polymeren PTDPP-TT und PFDPP-TT Polymeren kurz sind (< 20 ps) und dass in Mischungen der Polymere mit PC71BM geminale Rekombination von gebundenen Ladungstransferzuständen ein Hauptverlustkanal ist. Zudem wurde in beiden Systemen schnelle nichtgeminale Rekombination freier Ladungen zu Triplettzuständen auf dem Polymer beobachtet. Für das Donor-Akzeptor System PDPP5T:PC71BM wurde nachgewiesen, dass die Zugabe eines Lösungsmittels mit hohem Siedepunkt, und zwar ortho-Dichlorbenzol, die Morphologie der aktiven Schicht stark beeinflusst und die Solarzelleneffizienz verbessert. Der Grund hierfür ist, dass die Donator- und Akzeptormaterialien besser durchmischt sind und sich Perkolationswege zu den Elektroden ausgebildet haben, was zu einer verbesserten Ladungsträgergeneration und Extraktion führt. Schnelle Bildung des Triplettzustands wurde in beiden PDPP5T:PC71BM Systemen beobachtet, da der Triplettzustand des Polymers über Laungstransferzustände mit Triplettcharakter populiert werden kann. "Multivariate curve resolution" (MCR) Analyse hat eine starke Intensitätsabhängigkeit gezeigt, was auf nichtgeminale Ladungsträgerrekombination in den Triplettzustand hinweist.rnrnIn den künstlichen primären Photosynthesereaktionszentren hat transiente Absorptionsspektroskopie bestätigt, dass photoinduzierter Ladungstransfer in Quinon-Porphyrin (Q-P) und Porphyrin-Ferrocen (P-Fc) Diaden sowie in Quinon-Porphyrin-Ferrocen (Q-P-Fc) Triaden effizient ist. Es wurde jedoch auch gezeigt, dass in den P-Fc unf Q-P-Fc Systemen die ladungsgetrennten Zustände in den Triplettzustand der jeweiligen Porphyrine rekombinieren. Der ladungsgetrennte Zustand konnte in der Q-P Diade durch Zugabe einer Lewissäure signifikant stabilisiert werden.