Studio e ottimizzazione di alcuni parametri nell'ambito della radiografia a doppia energia

La tecnica radiografica si presta a molteplici applicazioni in svariati campi dell'attività umana: fra i più rilevanti ci sono senz'altro le applicazioni mediche, che permetto indagini non invasive e, attraverso programmi di screening, diagnosi precoci. La natura integrale della misura radiografica comporta pero' alcuni limiti, che sono in grossa parte superabili con l'utilizzo della tecnica a doppia energia, che sfrutta due immagini radiografiche acquisite in corrispondenza di due diverse energie della radiazione incidente per estrapolare ulteriori informazioni sui materiali che compongono il campione. Una particolare implementazione di questa tecnica, proposta da Alvarez e Macovsky sfruttando l'espressione approssimata del coefficiente di attenuazione lineare per energie nel range utilizzato in medicina, prevede la rappresentazione di un dato spessore di un qualsiasi materiale 'xi' come somma di spessori 'equivalenti' di due materiali 'alpha' e 'beta' scelti come base. Questo permette quindi di ottenere due campioni dei materiali 'alpha' e 'beta' che, sovrapposti, presentino le stesse proprieta' di attenuazione del campione originale, indipendentemente dall'energia della radiazione incidente. Il vantaggio di tale procedura consiste poi nel poter sintetizzare, con opportune combinazioni lineari dei due campioni di base, immagini con interessanti proprieta': Per trarre il massimo vantaggio da questo tipo di elaborazioni appare inoltre chiaramente vantaggioso poter lavorare con immagini digitali: benche' un'immagine digitale si possa ottenere dalle tradizionali lastre radiografiche, sono gia' in commercio molti sistemi che ne permettono un'acquisizione diretta, approccio che garantisce una lunga serie di vantaggi sia a livello di gestione che di qualita'. In particolare i sensori digitali, oltre a presentare una maggior flessibilita' di utilizzo, danno la possibilita', rispetto alle tecniche tradizionali, di ottenere un piu' ampio range dinamico e una risposta lineare. Scopo di questo lavoro di tesi e' quello di verificare l'impatto di alcune variabili sui risultati ottenuti dall'applicazione della tecnica a doppia energia nel campo mammografico, evidenziando eventuali parametri critici e aprendo la strada per una sua ottimizzazione: in particolare abbiamo verificato la sensibilita' dei risultati al contrasto intrinseco dei campioni, ai fasci utilizzati per ottenere le immagini originali, e alla base scelta per la scomposizione. Dopo una breve introduzione ai principi della radiografia tradizionale e digitale, con una piccola digressione sui parametri di qualita' (Capitolo 1), si descrive la teoria della tecnica dual energy e il suo adattamento all'utilizzo di fasci policromatici, mettendone in luce gli aspetti di rilievo dal punto di vista applicativo e proponendo alcune varianti sia teoriche che di implementazione (Capitolo 2). Successivamente (Capitolo 3) si descrive l'apparto utilizzato per le acquisizioni, con particolare riguardo per il sistema digitale a conteggio di singolo fotone. Infine (Capitolo 4) si espongono i risultati ottenuti, su immagini di fantocci di diverso spessore appositamente preparati, usando tre diversi fasci per l'immagine ad alta energia e quattro diverse basi per la scomposizione. I valori ottenuti mostrano come ci sia una forte dipendenza della qualita' delle immagini dalla distribuzione in energia dei fasci utilizzati. Non altrettanto si puo' dire per le basi scelte per la scomposizione: in particolare sembra che l'utilizzo di una base generica, non legata a materiali reali e senza le conseguenti necessita' di procedure di calibrazione, possa dare risultati di poco inferiori a quelli delle altre basi. Questo suggerisce che la specifica implementazione da noi utilizzata, sebbene lasci intravedere possibili margini di miglioramento dei risultati introducendo parametri sui quali si puo' lavorare per compensare alcune difficolta' sperimentali, non e' ancora sufficientemente matura da risultare vantaggiosa al confronto di procedure piu' semplici. Appare comunque chiaro dalle misure effettuate che la tecnica dual energy è estremamente potente, e permette gia' adesso di ottenere risultati di tutto riguardo su alcune tipologie di immagine e per alcuni scopi. Il lavoro si conclude con l'esposizione dei risultati ottenuti applicando la tecnica ad una serie di campioni autoptici, alcuni dei quali presentano patologie. L'applicazione di questa tecnica puo' portare grandi vantaggi nel campo mammografico: i tessuti adiposo e ghiandolare presenti nella mammella formano infatti sull'immagine un pattern irregolare che contribuisce a ridurre la visibilita' di eventuali patologie da parte del medico. Riuscire ad annullare il contrasto tra i due tessuti sani promette di aumentare notevolmente la visibilita' di particolari di interesse medico, e con essa la capacita' di formulare diagnosi precoci, fondamentali per poter sperare nel successo di eventuali terapie

Saccharomyces and Non-Saccharomyces Starter Yeasts

This chapter describes the importance of yeast in beer fermentation. Initially, the differences between Saccharomyces cerevisiae and Saccharomyces pastorianus in the production of “ale” and “lager” beers are analyzed. Then, the relationships between beer nutrients and yeast growth are discussed, with special emphasis on the production of the flavor compounds. The impact of the wort composition on flocculation is also discussed. Furthermore, conventional approaches to starter yeast selection and the development of genetically modified microorganisms are analyzed. Recent discoveries relating to the use of S. cerevisiae strains isolated from different food matrices (i.e., bread and wine) and the potential for the use of non-Saccharomyces starter strains in beer production are discussed. A detailed review of the selection of starter strains for the production of specialty beers then follows, such as for gluten-free beers and biologically aged beers. Yeast recovery from top-cropping and bottom-cropping systems and the methodologies and issues in yeast propagation in the laboratory and brewery (i.e., re-pitching) are also analyzed. Finally, the available commercial preparations of starter yeast and the methods to evaluate yeast viability prior to inoculation of the must are analyzed

Upper limits to surface force disturbances on LISA proof masses and the possibility of observing galactic binaries

We report on the measurement of parasitic surface force noise on a hollow replica of a LISA (Laser Interferometer Space Antenna for the observation of gravitational waves) proof mass surrounded by a faithful representation of its in flight surroundings, namely the capacitive sensor used to detect proof-mass motion. Parasitic forces are detected through the corresponding torque exerted on the proof mass and measured with a torsion pendulum in the frequency range 0.1 30 mHz. The sensor electrodes, electrode housing and associated readout electronics have the same nominal design as for the flight hardware, including 4 mm gaps around the proof mass along the sensitive laser interferometry axis. We show that the measured upper limit for surface forces would allow detection of a number of galactic binaries signals with signal to noise ratio up to approximately 40 for 1 year integration. We also discuss how the flight test under development, LISA Pathfinder, will substantially improve this limit, approaching the performance required for LISA.Comment: 3 Figures. Submitted to Physical Review Letter

Overview of Advanced LIGO Adaptive Optics

This is an overview of the adaptive optics used in Advanced LIGO (aLIGO), known as the thermal compensation system (TCS). The thermal compensation system was designed to minimize thermally-induced spatial distortions in the interferometer optical modes and to provide some correction for static curvature errors in the core optics of aLIGO. The TCS is comprised of ring heater actuators, spatially tunable CO$_{2}$ laser projectors and Hartmann wavefront sensors. The system meets the requirements of correcting for nominal distortion in Advanced LIGO to a maximum residual error of 5.4nm, weighted across the laser beam, for up to 125W of laser input power into the interferometer

Sub-Femto- g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2±0.1  fm s−2/Hz, or (0.54±0.01)×10−15  g/Hz, with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8±0.3)  fm/Hz, about 2 orders of magnitude better than requirements. At f≤0.5  mHz we observe a low-frequency tail that stays below 12  fm s−2/Hz down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.CNES 1316634/CNRS 103747UnivEarthS Labex program/ANR-10-LABX-0023UnivEarthS Labex program/ANR-11-IDEX-0005-02DLRFederal Ministry for Economic Affairs and Energy/FKZ 50OQ0501Federal Ministry for Economic Affairs and Energy/FKZ 50OQ1601Agenzia Spaziale ItalianaInstituto Nazionale di Fisica NucleareAYA2010-15709 (MICINN)ESP2013-47637-P (MINECO)ESP2015-67234-P (MINECO)Fundacion General CSICSwiss Space Office (SSO)Swiss National Science FoundationUnited Kingdom Space Agency (UKSA)University of GlasgowUniversity of BirminghamImperial CollegeScottish Universities Physics Alliance (SUPA)U.S. National Aeronautics and Space Administration (NASA

The advanced LIGO input optics

The advanced LIGO gravitational wave detectors are nearing their design sensitivity and should begin taking meaningful astrophysical data in the fall of 2015. These resonant optical interferometers will have unprecedented sensitivity to the strains caused by passing gravitational waves. The input optics play a significant part in allowing these devices to reach such sensitivities. Residing between the pre-stabilized laser and the main interferometer, the input optics subsystem is tasked with preparing the laser beam for interferometry at the sub-attometer level while operating at continuous wave input power levels ranging from 100 mW to 150 W. These extreme operating conditions required every major component to be custom designed. These designs draw heavily on the experience and understanding gained during the operation of Initial LIGO and Enhanced LIGO. In this article, we report on how the components of the input optics were designed to meet their stringent requirements and present measurements showing how well they have lived up to their design

The Advanced LIGO Input Optics

The advanced LIGO gravitational wave detectors are nearing their design sensitivity and should begin taking meaningful astrophysical data in the fall of 2015. These resonant optical interferometers will have unprecedented sensitivity to the strains caused by passing gravitational waves. The input optics play a significant part in allowing these devices to reach such sensitivities. Residing between the pre-stabilized laser and the main interferometer, the input optics subsystem is tasked with preparing the laser beam for interferometry at the sub-attometer level while operating at continuous wave input power levels ranging from 100 mW to 150 W. These extreme operating conditions required every major component to be custom designed. These designs draw heavily on the experience and understanding gained during the operation of Initial LIGO and Enhanced LIGO. In this article, we report on how the components of the input optics were designed to meet their stringent requirements and present measurements showing how well they have lived up to their design

Acute Delta Hepatitis in Italy spanning three decades (1991–2019): Evidence for the effectiveness of the hepatitis B vaccination campaign

Updated incidence data of acute Delta virus hepatitis (HDV) are lacking worldwide. Our aim was to evaluate incidence of and risk factors for acute HDV in Italy after the introduction of the compulsory vaccination against hepatitis B virus (HBV) in 1991. Data were obtained from the National Surveillance System of acute viral hepatitis (SEIEVA). Independent predictors of HDV were assessed by logistic-regression analysis. The incidence of acute HDV per 1-million population declined from 3.2 cases in 1987 to 0.04 in 2019, parallel to that of acute HBV per 100,000 from 10.0 to 0.39 cases during the same period. The median age of cases increased from 27 years in the decade 1991-1999 to 44 years in the decade 2010-2019 (p < .001). Over the same period, the male/female ratio decreased from 3.8 to 2.1, the proportion of coinfections increased from 55% to 75% (p = .003) and that of HBsAg positive acute hepatitis tested for by IgM anti-HDV linearly decreased from 50.1% to 34.1% (p < .001). People born abroad accounted for 24.6% of cases in 2004-2010 and 32.1% in 2011-2019. In the period 2010-2019, risky sexual behaviour (O.R. 4.2; 95%CI: 1.4-12.8) was the sole independent predictor of acute HDV; conversely intravenous drug use was no longer associated (O.R. 1.25; 95%CI: 0.15-10.22) with this. In conclusion, HBV vaccination was an effective measure to control acute HDV. Intravenous drug use is no longer an efficient mode of HDV spread. Testing for IgM-anti HDV is a grey area requiring alert. Acute HDV in foreigners should be monitored in the years to come

Uniparental markers in Italy reveal a sex-biased genetic structure and different historical strata

University of Adelaide Genographic Consortium contributers: Christina J. Adler, Alan Cooper, Clio S. I. Der Sarkissian, Wolfgang Haak.Located in the center of the Mediterranean landscape and with an extensive coastal line, the territory of what is today Italy has played an important role in the history of human settlements and movements of Southern Europe and the Mediterranean Basin. Populated since Paleolithic times, the complexity of human movements during the Neolithic, the Metal Ages and the most recent history of the two last millennia (involving the overlapping of different cultural and demic strata) has shaped the pattern of the modern Italian genetic structure. With the aim of disentangling this pattern and understanding which processes more importantly shaped the distribution of diversity, we have analyzed the uniparentally-inherited markers in ~900 individuals from an extensive sampling across the Italian peninsula, Sardinia and Sicily. Spatial PCAs and DAPCs revealed a sex-biased pattern indicating different demographic histories for males and females. Besides the genetic outlier position of Sardinians, a North West–South East Y-chromosome structure is found in continental Italy. Such structure is in agreement with recent archeological syntheses indicating two independent and parallel processes of Neolithisation. In addition, date estimates pinpoint the importance of the cultural and demographic events during the late Neolithic and Metal Ages. On the other hand, mitochondrial diversity is distributed more homogeneously in agreement with older population events that might be related to the presence of an Italian Refugium during the last glacial period in Europe.Alessio Boattini, Begoña Martinez-Cruz, Stefania Sarno, Christine Harmant, Antonella Useli, Paula Sanz, Daniele Yang-Yao, Jeremy Manry, Graziella Ciani, Donata Luiselli, Lluis Quintana- Murci, David Comas, Davide Pettener, the Genographic Consortiu