Transverse-integrated nodal di usion methods currently represent the standard in full core neutronic simulation. The primary shortcoming of this approach is the utilization of the quadratic transverse leakage approximation. This approach, although proven to work well for typical LWR problems, is not consistent with the formulation of nodal methods and can cause accuracy and convergence problems. In this work, an improved, consistent quadratic leakage approximation is formulated, which derives from the class of higher-order nodal methods developed some years ago. In this thesis a number of iteration schemes are developed around this consistent quadratic leakage approximation which yields accurate node average results in much improved calculational times. The most promising of these iteration schemes results from utilizing the consistent leakage approximation as a correction method to the standard quadratic leakage approximation. Numerical results are demonstrated on a set of benchmark problems and further applied to realistic reactor problems for particularly the SAFARI-1 reactor operating at Necsa, South Africa. The nal optimal solution strategy is packaged into a standalone module which may be simply coupled to existing nodal di usion codes, illustrated via coupling of the module to the OSCAR-4 code system developed at Necsa and utilized for the calculational support of a number of operating research reactors around the world. / Thesis(PhD (Reactor Science))--North-West University, Potchefstroom Campus, 2013

Transverse-integrated nodal di usion methods currently represent the standard in full core neutronic simulation. The primary shortcoming of this approach is the utilization of the quadratic transverse leakage approximation. This approach, although proven to work well for typical LWR problems, is not consistent with the formulation of nodal methods and can cause accuracy and convergence problems. In this work, an improved, consistent quadratic leakage approximation is formulated, which derives from the class of higher-order nodal methods developed some years ago. In this thesis a number of iteration schemes are developed around this consistent quadratic leakage approximation which yields accurate node average results in much improved calculational times. The most promising of these iteration schemes results from utilizing the consistent leakage approximation as a correction method to the standard quadratic leakage approximation. Numerical results are demonstrated on a set of benchmark problems and further applied to realistic reactor problems for particularly the SAFARI-1 reactor operating at Necsa, South Africa. The nal optimal solution strategy is packaged into a standalone module which may be simply coupled to existing nodal di usion codes, illustrated via coupling of the module to the OSCAR-4 code system developed at Necsa and utilized for the calculational support of a number of operating research reactors around the world. / Thesis(PhD (Reactor Science))--North-West University, Potchefstroom Campus, 2013

The present work aims for investigate the influence of electrospun Nylon 6,6 nanofibrous mat on the behavior of composite laminates. The main idea is that nanofibrous interleaved into particular ply-to-ply interfaces of a laminate can lead to significant improvements of mechanical properties and delamination/damage resistance. Experimental campaigns were performed to investigate how nanofibers affect both the static and dynamic behavior of the laminate in which they are interleaved. Fracture mechanics tests were initially performed on virgin and 8 different configuration of nanomodified specimens. The purposes of this first step of the work are to understand which geometrical parameters of the nanointerleave influence the behavior of the laminate and, to find the optimal architecture of the nanofibrous mat in order to obtain the best reinforcement. In particular, 3 morphological parameters are investigated: nanofibers diameter, nanofibers orientation and thickness of the reinforce. Two different values for each parameter have been used, and it leads to 8 different configurations of nanoreinforce. Acoustic Emission technique is also used to monitor the tests. Once the optimum configuration has been found, attention is focused on the mechanism of reinforce played by the nanofibers during static and dynamic tests. Low velocity impacts and free decay tests are performed to attest the effect of nanointerlayers and the reinforce mechanism during the dynamic loads. Bump tests are performed before and after the impact on virgin and two different nanomodified laminates configurations. The authors focused their attention on: vibrational behavior, low velocity impact response and post-impact vibration behavior of the nano-interleaved laminates with respect to the response of non-nanomodified ones. Experiments attest that nanofibers significantly strength the delamination resistance of the laminates and increase some mechanical properties. It is demonstrated that the nanofibers are capable to continue to carry on the loads even when the matrix around them is broken.

Undressing Cherubino: Reassessing Gender and Sexuality in Mozart’s Le nozze di Figaro Although Le nozze di Figaro is one of Mozart’s most celebrated operas, we have not yet understood one crucial element. On the surface of the drama, the opera seems to be about class disruption: the Count is the head of the household, but it is his servants who run it. This plot is made evident to the audience, and it is the message that most critics draw from the work. However, there may be a second meaning below the surface that is, in fact, more subversive than the overt one. While class structures are questioned in the foreground, another more hidden narrative explores alternate depictions of femininity and sexuality. This covert meaning is arguably embodied in Cherubino. This character is portrayed as an adolescent boy despite the fact that the role calls for a female singer. Cherubino is understood to be male, and functions as one in the drama, but, as I will suggest, may in fact be conceived as female. As a pagegirl raging with sexual love for all the women in the palace, Cherubino may be seen embodying a prototype of femininity that is contrary to the heterosexual norms of the overt narrative. The first chapter of this thesis examines how both Pierre-Augustin Beaumarchais’ play Le mariage de Figaro and Mozart and Da Ponte’s operatic adaptation could point towards alternate depictions of women. The following two chapters survey the various ways an alternate gender identity for Cherubino can be expressed through features of the libretto (chapter 2) and the score (chapter 3). Drawing from my experience of performing Cherubino, the fourth and final chapter assesses the findings of the previous two and shows that while elements of the text and music may have characteristics that can be assigned gender attributes, neither can intrinsically embody masculinity or femininity. With this finding comes the understanding that who and what a character is is marked not by the outlines of libretto and score but by acts of musical performance.

Le sostanze perfluoralchiliche (PFAS), composti fluorurati ampiamente utilizzati negli ultimi anni in diverse applicazioni industriali e commerciali, sono ritrovati diffusamente nell’ambiente e in diverse specie animali. Recentemente i PFAS hanno destato preoccupazione anche per la salute umana. Il rischio di esposizione è principalmente legato alla dieta (i prodotti ittici sembrano essere gli alimenti più contaminati). Lo scopo di questo lavoro è stato quello di valutare la presenza del perfluorottanosulfonato (PFOS) e dell’acido perfluorottanoico (PFOA), in diverse matrici alimentari: latte vaccino commercialmente disponibile in Italia, latte materno italiano, diverse specie di pesce commercialmente disponibili in Italia e 140 branzini di diverse aree (principalmente Mediterraneo). I campioni di latte sono stati trattati con estrazione liquido-liquido seguita da due fasi di purificazione mediante cartucce SPE prima dell’iniezione nell’UPLC-MS/MS. L’analisi del latte vaccino ha evidenziato una contaminazione diffusa di PFOS, ma a basse concentrazioni (fino a 97 ng/L), mentre il PFOA è stato ritrovato raramente. In questo studio, in grado di individuare anche i livelli delle ultra-tracce, sono state osservate nel latte materno concentrazioni di 15-288 ng/L per il PFOS e di 24-241 ng/LPFOA. Le concentrazioni e le frequenze più alte, per entrambi i PFAS, sono stati ritrovate in campioni di latte forniti da donne primipare, suggerendo un rischio di esposizione per i primogeniti. Il metodo utilizzato per i campioni di pesce era basato su un’estrazione con solvente organico seguita da due fasi di purificazione: una con i sali e una con fase solida dispersiva. L’estratto, analizzato in UPLC-MS/MS, ha confermato la contaminazione di questa matrice a livelli significativi, ma anche l’alta variabilità delle concentrazioni misurate. Il monitoraggio monospecie ha mostrato una contaminazione rilevante (PFOS 11,1- > 10000 ng/L; PFOA < 9-487 ng/L), soprattutto nei branzini pescati, rispetto a quelli allevati. / Perfluoroalkyl substances (PFASs) are fully-fluorinated compounds widely employed for the production of different industrial and consumer applications. They have been frequently found in the environment and several animal species. These emerging contaminants have recently become of relevant concern for human health. The risk of exposure to PFASs is mainly related to diet; fish and other seafood seem to be the most contaminated foods. The aim of this work was to monitor the presence of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), the two most important and investigated PFASs, in various food matrices: cow milk commercially available in Italy, Italian breast milk, different species of fish commercially available in Italy and 140 sea basses collected from different areas (mainly Mediterranean Sea). Milk samples were treated with liquid-liquid extraction followed by two purification steps through SPE cartridges before UPLC-MS/MS analysis. The analysis of cow milk demonstrated that a contamination by PFOS was often present, but at low concentrations (up to 97 ng/L), and PFOA was rarely found. This study, capable to detect these contaminants at ultra-trace levels, has found concentrations for human milk in the range 15-288 ng/L for PFOS and 24-241 ng/L for PFOA. The highest concentrations and frequencies of both PFAS were found in milk samples provided by primiparous women, suggesting the higher risk of exposure for first-borns. The method used for fish samples was based on extraction with organic solvent followed by two purification steps: one with salts and one with dispersive solid phase. The extract analyzed by UPLC-MS/MS confirmed the contamination of this matrix at significant levels, but also the high variability of measured concentrations. The single species monitoring showed a relevant contamination (PFOS 11,1- > 10000 ng/L and PFOA < 9- 487 ng/L) in particular in fished basses compared to the reared ones.

La presenza di micotossine nelle materie prime desta grande preoccupazione a causa delle importanti implicazioni nella sicurezza di alimenti e mangimi. Lo scopo di questo lavoro è stato quello di mettere a punto e validare una metodica analitica rapida e semplice, in cromatografia liquida ad ultra prestazione accoppiata a spettrometria di massa-tandem (UPLC-MS/MS), per la determinazione simultanea di differenti micotossine: aflatossine (B1, B2, G1, G2), ocratossina A, fumonisine (B1, B2), deossinivalenolo e zearalenone in matrici biologiche. Il metodo sviluppato per l’analisi di campioni di mangime secco per cani ha mostrato prestazioni adeguate ed è stato applicato a 49 campioni reperibili in commercio, al fine di valutare la sua efficacia e di ottenere alcuni dati preliminari sulla contaminazione da micotossine in alimenti per cani disponibili sul mercato italiano. Lo studio ha evidenziato una percentuale alta di campioni positivi, contenenti principalmente fumonisine, deossinivalenolo e ocratossina A; tutti i tenori si sono dimostrati inferiori al limite di legge previsto (Racc. CE 576/2006). Una seconda metodica è stata messa a punto e validata per l’identificazione e la quantificazione micotossine in campioni di formaggio; per questa matrice è stata inserita anche l’aflatossina M1, specifica dei prodotti lattiero - caseari. Le differenti proprietà chimico-fisiche degli analiti e la complessità della matrice hanno implicato alcune difficoltà nello sviluppo della metodica. Tuttavia, il metodo validato si è mostrato rapido, semplice ed affidabile ed è stato applicato a diversi tipi di formaggi per verificarne la versatilità. I risultati preliminari hanno mostrato l’assenza di contaminazione da parte delle micotossine in oggetto. Entrambi i metodi si sono dimostrati utili per il monitoraggio di contaminanti in matrici complesse ad oggi ancora poco studiate. / The occurrence of mycotoxins contamination in various crops is of major concern as it has major implications for food and feed safety. The aim of the study was the set up and the validation of fast and simple methods by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UPLC–MS/MS) for the simultaneous determination of different mycotoxins: aflatoxins (B1, B2, G1, G2), ochratoxin A, fumonisins (FB1, FB2), deoxynivalenol and zearalenone in biological matrices. A method was developed for the analysis of samples of dried pet-food; the method showed appropriate performances and was applied to 49 commercial samples in order to test its efficacy and gain some preliminary data about mycotoxins contamination in dog food available in the Italian market. The results have shown a quite high percentage of positive samples, mainly contaminated by fumonisin, deoxynivalenol and ochratoxin A. All the observed values were below the limits specified by regulations (Rec. CE 2006/576). A second method was set up and validated for the identification and quantification of mycotoxins in cheese samples; for this matrix it was included also the aflatoxin M1, which is specific of dairy products. Different chemical-physical properties of the analytes and the complex composition of the matrix led to some difficulties to the development of the method. Finally, the method validated has proved to be rapid, simple and reliable and was applied to different types of cheeses to prove its versatility. Preliminary results have shown the absence of all mycotoxins detected. Both methods are useful tools for the monitoring of mycotoxins contamination in unconventional matrices, not subjected to wide studies until now.

A major weakness of composite materials is that low-velocity impact, introduced accidentally during manufacture, operation or maintenance of the aircraft, may result in delaminations between the plies. Therefore, the first part of this study is focused on mechanics of curved laminates under impact. For this aim, the effect of preloading on impact response of curved composite laminates is considered. By applying the preload, the stress through the thickness and curvature of the laminates increased. The results showed that all impact parameters are varied significantly. For understanding the contribution rate of preloading and pre-stress on the obtained results another test is designed. The interesting phenomenon is that the preloading can decrease the damaged area when the curvature of the both specimens is the same. Finally the effect of curvature type, concave and convex, is investigated under impact loading. In the second part, a new composition of nanofibrous mats are developed to improve the efficiency of curved laminates under impact loading. Therefore, at first some fracture tests are conducted to consider the effect of Nylon 6,6, PCL, and their mixture on mode I and mode II fracture toughness. For this goal, nanofibers are electrospun and interleaved between mid-plane of laminate composite to conduct mode I and mode II tests. The results shows that efficiency of Nylon 6,6 is better than PCL in mode II, while the effect of PCL on fracture toughness of mode I is more. By mixing these nanofibers the shortage of the individual nanofibers is compensated and so the Nylon 6,6/PCL nanofibers could increased mode I and II fracture toughness. Then all these nanofibers are used between all layers of composite layers to investigate their effect on damaged area. The results showed that PCL could decrease the damaged area about 25% and Nylon 6,6 and mixed nanofibers about 50%.

Foodborne diseases impact human health and economies worldwide in terms of health care and productivity loss. Prevention is necessary and methods to detect, isolate and quantify foodborne pathogens play a fundamental role, changing continuously to face microorganisms and food production evolution. Official methods are mainly based on microorganisms growth in different media and their isolation on selective agars followed by confirmation of presumptive colonies through biochemical and serological test. A complete identification requires form 7 to 10 days. Over the last decades, new molecular techniques based on antibodies and nucleic acids allow a more accurate typing and a faster detection and quantification. The present thesis aims to apply molecular techniques to improve official methods performances regarding two pathogens: Shiga-like Toxin-producing Escherichia coli (STEC) and Listeria monocytogenes. In 2011, a new strain of STEC belonging to the serogroup O104 provoked a large outbreak. Therefore, the development of a method to detect and isolate STEC O104 is demanded. The first objective of this work is the detection, isolation and identification of STEC O104 in sprouts artificially contaminated. Multiplex PCR assays and antibodies anti-O104 incorporated in reagents for immunomagnetic separation and latex agglutination were employed. Contamination levels of less than 1 CFU/g were detected. Multiplex PCR assays permitted a rapid screening of enriched food samples and identification of isolated colonies. Immunomagnetic separation and latex agglutination allowed a high sensitivity and rapid identification of O104 antigen, respectively. The development of a rapid method to detect and quantify Listeria monocytogenes, a high-risk pathogen, is the second objective. Detection of 1 CFU/ml and quantification of 10–1,000 CFU/ml in raw milk were achieved by a sample pretreatment step and quantitative PCR in about 3h. L. monocytogenes growth in raw milk was also evaluated.

Textual repetitions abound in verses of the Seven Penitential Psalms of Lassus and this research attempts to discover their function. A total of one hundred and thirty-two verses were analyzed. The results of this investigation exhibit numerous mathematical figures underlying the entire work's structure, and the influence of repetitions is conspicuous in each figure's organization. Moreover, this study shows, in a smaller measure, the mutual influence between form and text expression. A detailed method of calculation is also provided which may eventually be applied to other works of the repertoire of the sixteenth century.

Xylella fastidiosa is an important bacterial plant pathogen that colonizes the xylem of hundreds of plant species. X. fastidiosa cause Pierce's disease in grapevine by occlusion of the xylem by extensive bacterial colonization, extracellular polysaccharides and the formation of a biofilm. These traits are mediated in a cell-density manner by a cell-to-cell signaling system that transduces a diffusible signaling factor (DSF). This dissertation demonstrates that PD1994, PD1617 and RpfG regulate important traits for bacterial virulence such as cell-cell signaling, biofilm formation and cell aggregation. X. fastidiosa strains harboring mutations in pd1994 (which encodes for a defective GGDEF- EAL-domain protein) and in pd1617 (which encodes for a EAL-domain protein) have increased growth rate, increased biofilm formation, increased plant colonization and decreased cell aggregation. Gene expression analysis of the pd1994 mutant strain showed overexpression of rpfF, which is a DSF synthase, suggesting that PD1994 regulates DSF signaling by repressing rpfF expression. Additionally, the pd1994mutant showed overexpression of pd1617 and rpfG (with EAL and HD-GYP domains respectively, that may be responsible for c-di-GMP turnover), which suggested that this mutant may have low c-di-GMP levels and that PD1994 regulates c-di-GMP turnover by repression of RpfG activity and PD1617 gene expression. X. fastidiosa harboring a mutation on rpfG exhibited decreased biofilm formation while it had no effect in growth or cell aggregation. Together, these results suggest that PD1994, PD1617 and RpfG regulate the DSF regulatory network by controlling the turnover of the second messenger c-di-GMP.