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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Genus Bifidobacterium: taxonomy studies and gene expression analysis on folate pathway

Stenico, Verena <1983> 30 April 2014 (has links)
Folates (vitamin B9) are essential water soluble vitamins, whose deficiency in humans may contribute to the onset of several diseases, such as anaemia, cancer, cardiovascular diseases, neurological problems as well as defects in embryonic development. Human and other mammals are unable to synthesize ex novo folate obtaining it from exogenous sources, via intestinal absorption. Recently the gut microbiota has been identified as an important source of folates and the selection and use of folate producing microorganisms represents an innovative strategy to increase human folate levels. The aim of this thesis was to gain a fundamental understanding of folate metabolism in Bifidobacterium adolescentis. The work was subdivided in three main phases, also aimed to solve different problems encountered working with Bifidobacterium strains. First, a new identification method (based on PCR-RFLP of hsp60 gene) was specifically developed to identify Bifidobacterium strains. Secondly, Bifidobacterium adolescentis biodiversity was explored in order to recognize representing strains of this species to be screened for their folate production ability. Results showed that this species is characterized by a wide variability and support the idea that a possible new taxonomic re-organization would be required. Finally B. adolescentis folate metabolism was studied using a double approach. A quantitative analysis of folate content was complemented by the examination of expression levels of genes involved in folate related pathways. For the normalization process, required to increase the robustness of the qRT-PCR analysis, an appropriate set of reference genes was tested using two different algorithms. Results demonstrate that B.adolescentis strains may represent an endogenous source of natural folate and they could be used to fortify fermented dairy products. This bio-fortification strategy presents many advantages for the consumer, providing native folate forms more bio-available, and not implicated in the discussed controversy concerning the safety of high intake of synthetic folic acid.
2

Fine Mapping of qroot-yield-1.06, a QTL for Root, Plant Vigor and Yield in Maize

Martinez Ascanio, Ana Karine <1979> January 1900 (has links)
Root-yield-1.06 is a major QTL affecting root system architecture (RSA) and other agronomic traits in maize. The effect of this QTL has been evaluated with the development of near isogenic lines (NILs) differing at the QTL position. The objective of this study was to fine map qroot-yield-1.06 by marker-assisted searching for chromosome recombinants in the QTL interval and concurrent root phenotyping in both controlled and field conditions, through successive generations. Complementary approaches such as QTL meta-analysis and RNA-seq were deployed in order to help prioritizing candidate genes within the QTL target region. Using a selected group of genotypes, field based root analysis by ‘shovelomics’ enabled to accurately collect RSA information of adult maize plants. Shovelomics combined with software-assisted root imaging analysis proved to be an informative and relatively highly automated phenotyping protocol. A QTL interval mapping was conducted using a segregating population at the seedling stage grown in controlled environment. Results enabled to narrow down the QTL interval and to identify new polymorphic markers for MAS in field experiments. A collection of homozygous recombinant NILs was developed by screening segregating populations with markers flanking qroot-yield-1.06. A first set of lines from this collection was phenotyped based on the adapted shovelomics protocol. QTL analysis based on these data highlighted an interval of 1.3 Mb as completely linked with the target QTL but, a larger safer interval of 4.1 Mb was selected for further investigations. QTL meta-analysis allows to synthetize information on root QTLs and two mQTLs were identified in the qroot-yield-1.06 interval. Trascriptomics analysis based on RNA-seq data of the two contrasting QTL-NILs, confirmed alternative haplotypes at chromosome bin 1.06. qroot-yield-1.06 has now been delimited to a 4.1-Mb interval, and thanks to the availability of additional untested homozygous recombinant NILs, the potentially achievable mapping resolution at qroot-yield-1.06 is c. 50 kb.
3

The role of bifidobacteria in newborn health and the intestinal microbial balance

Mazzola, Giuseppe <1985> 08 May 2015 (has links)
Gut microbial acquisition during the early stage of life is an extremely important event since it affects the health status of the host. In this contest the healthy properties of the genus Bifidobacterium have a central function in newborns. The aim of this thesis was to explore the dynamics of the gut microbial colonization in newborns and to suggest possible strategies to maintain or restore a correct balance of gut bacterial population in infants. The first step of this work was to review the most recent studies on the use of probiotics and prebiotics in infants. Secondly, in order to prevent or treat intestinal disorders that may affect newborns, the capability of selected Bifidobacterium strains to reduce the amount of Enterobacteriaceae and against the infant pathogen Streptococcus agalactiae was evaluated in vitro. Furthermore, the ability of several commercial fibers to stimulate selectively the growth of bifidobacterial strains was checked. Finally, the gut microbial composition in the early stage of life in response to the intrapartum antibiotic prophylaxis (IAP) against group B Streptococcus was studied using q-PCR, DGGE and next generation sequencing. The results globally showed that Bifidobacterium breve B632 strain is the best candidate for the use in a synbiotic product coupled to a mixture of two selected prebiotic fibers (galactooligosaccharides and fructooligosaccharides) for gastrointestinal disorders in infants. Moreover, the early gut microbial composition was affected by IAP treatment with infants showing lower counts of Bifidobacterium spp. and Bacteroides spp. coupled to a decrement of biodiversity of bacteria, compared to control infants. These studies have shown that IAP could affect the early intestinal balance in infants and they have paved the way to the definition of new strategies alternative to antibiotic treatment to control GBS infection in pregnant women.
4

Genetic basis of variation for root traits and response to heat stress in durum wheat

Nazemi, Ghasemali <1976> 18 May 2015 (has links)
Durum wheat is the second most important wheat species worldwide and the most important crop in several Mediterranean countries including Italy. Durum wheat is primarily grown under rainfed conditions where episodes of drought and heat stress are major factors limiting grain yield. The research presented in this thesis aimed at the identification of traits and genes that underlie root system architecture (RSA) and tolerance to heat stress in durum wheat, in order to eventually contribute to the genetic improvement of this species. In the first two experiments we aimed at the identification of QTLs for root trait architecture at the seedling level by studying a bi-parental population of 176 recombinant inbred lines (from the cross Meridiano x Claudio) and a collection of 183 durum elite accessions. Forty-eight novel QTLs for RSA traits were identified in each of the two experiments, by means of linkage- and association mapping-based QTL analysis, respectively. Important QTLs controlling the angle of root growth in the seedling were identified. In a third experiment, we investigated the phenotypic variation of root anatomical traits by means of microscope-based analysis of root cross sections in 10 elite durum cultivars. The results showed the presence of sizeable genetic variation in aerenchyma-related traits, prompting for additional studies aimed at mapping the QTLs governing such variation and to test the role of aerenchyma in the adaptive response to abiotic stresses. In the fourth experiment, an association mapping experiment for cell membrane stability at the seedling stage (as a proxy trait for heat tolerance) was carried out by means of association mapping. A total of 34 QTLs (including five major ones), were detected. Our study provides information on QTLs for root architecture and heat tolerance which could potentially be considered in durum wheat breeding programs.
5

Atmospheric plasma processes for microbial inactivation: food applications and stress response in Listeria monocytogenes

Gozzi, Giorgia <1987> 29 May 2015 (has links)
This PhD thesis is focused on cold atmospheric plasma treatments (GP) for microbial inactivation in food applications. In fact GP represents a promising emerging technology alternative to the traditional methods for the decontamination of foods. The objectives of this work were to evaluate: - the effects of GP treatments on microbial inactivation in model systems and in real foods; - the stress response in L. monocytogenes following exposure to different GP treatments. As far as the first aspect, inactivation curves were obtained for some target pathogens, i.e. Listeria monocytogenes and Escherichia coli, by exposing microbial cells to GP generated with two different DBD equipments and processing conditions (exposure time, material of the electrodes). Concerning food applications, the effects of different GP treatments on the inactivation of natural microflora and Listeria monocytogenes, Salmonella Enteritidis and Escherichia coli on the surface of Fuji apples, soya sprouts and black pepper were evaluated. In particular the efficacy of the exposure to gas plasma was assessed immediately after treatments and during storage. Moreover, also possible changes in quality parameters such as colour, pH, Aw, moisture content, oxidation, polyphenol-oxidase activity, antioxidant activity were investigated. Since the lack of knowledge of cell targets of GP may limit its application, the possible mechanism of action of GP was studied against 2 strains of Listeria monocytogenes by evaluating modifications in the fatty acids of the cytoplasmic membrane (through GC/MS analysis) and metabolites detected by SPME-GC/MS and 1H-NMR analyses. Moreover, changes induced by different treatments on the expression of selected genes related to general stress response, virulence or to the metabolism were detected with Reverse Transcription-qPCR. In collaboration with the Scripps Research Institute (La Jolla, CA, USA) also proteomic profiles following gas plasma exposure were analysed through Multidimensional Protein Identification Technology (MudPIT) to evaluate possible changes in metabolic processes.
6

Energy Systems Optimization on Agricultural Sector / Ottimizzazione di Sistemi Energetici nel Settore Agricolo

Malagnino, Remo Alessio <1986> January 1900 (has links)
Come molti altri settori produttivi, anche l'agricoltura deve affrontare una crescente dipendenza energetica da elettricità, petrolio e gas naturale. Tuttavia, l'agricoltura può rispondere direttamente a tali richieste ricorrendo alle fonti di energia rinnovabili (FER), come il solare fotovoltaico (PV) e gli impianti biogas/biometano (BP). Questi sistemi sono stati fortemente incentivati in passato. Gli attuali sistemi d’incentivazione prevedono invece sussidi commisurati alle caratteristiche aziendali come stalle, fienili, disponibilità di biomasse, ecc. Per questi motivi, per quanto riguarda il settore FV, è necessario utilizzare modelli analitici affidabili per valutare l’orientamento e la tecnologia migliore, in particolare per generatori integrati architettonicamente. Per la produzione di biometano, gli impianti di piccole dimensioni risultano quelli maggiormente incentivati previa alimentazione con sottoprodotti agro-industriali. Tuttavia, le loro performance dipendono fortemente dalla tecnologia d’upgrading. Pertanto, le prospettive economiche offerte da questi sistemi RES sono legate alla scelta della tecnologia da impiegare e non più esclusivamente al semplice dimensionamento. Su questa base, l'obiettivo principale di questo lavoro è stato lo sviluppo di strumenti di supporto decisionali (DSSS) per l'ottimizzazione energetica d’impianti FV e BP. Un primo studio si è focalizzato sull’analisi prestazionale per singolo componente e globale d’impianti FV installati in un’azienda agricola. Inoltre, una procedura analitica di ottimizzazione dei parametri d’impianto è stata definita per massimizzare il rendimento elettrico di un generatore integrato architettonicamente rispetto ad un’installazione a terra. Attraverso una serie d’informazioni tecnico-economiche di tecnologie di upgrading, un secondo studio è stato condotto con l'obiettivo di sviluppare un DSS per valutare la marginalità sul reddito aziendale data dall’installazione on-farm di un impianto BP collegato alla rete del gas naturale. I risultati dei due studi hanno dimostrato come questi DSS possono essere utili strumenti per valutare preventivamente le diverse potenzialità offerte da impianti FV e BP in base alle caratteristiche di un’azienda agricola. / Like many other productive sectors, even agriculture must tackle an increasing energy dependency on electricity, petroleum and natural gas. Nevertheless, agriculture can directly respond to such request thanks to renewable energy systems (RES) like solar photovoltaic (PV) and biogas/biomethane (BP) plants. These systems have been strongly incentivized in the past. On the contrary, current incentive schemes provide feed-in-tariffs proportionate to farming characteristics as stables, barns, biomass availability, etc. For this reason, as regards the PV sector, it is required to use reliable analytical models for assessing the best orientation and technology, in particular for architecturally integrated generators. For the biomethane production, small-medium plants have stronger incentives in particular using agro-food by-products as feed. However, their performances are strongly dependent on biomethane upgrading technology. Thus, the economic prospective offered by these RES systems are substantially tied to technology choice optimization and no longer solely in simple sizing. On this basis, the main goal of this work is to develop Decision Support Tools (DSSs) for energy optimization both for PV and BP plants. A first study was focused on the analysis of PV plants installed in the same farm. The aim is to examine the impact each plant component has on the PV generator global efficiency and define an analytical procedure for technical parameters optimization in order to maximize the electric yield of an architectonically integrated plant compared to a ground-mounted one. Based on the economic and efficiency features of a biomethane upgrading technology set, a second study was carried out with the aim to design a DSS to assess enterprise-wide profit margins resulting from the on-farm BP plant installation linked to the natural gas grid. The results of the two studies have shown how these DSSs can be useful tools for choosing PV and BP technologies based on farm characteristics.
7

Analisi statistica di parametri di utilizzo di trattrici agricole / Statistical analysis of agricultural tractors's use parameters

Perozzi, Daniela <1986> January 1900 (has links)
Negli ultimi anni le continue esigenze di mercato hanno spinto gli agricoltori a richiedere trattrici sempre più evolute e altamente specializzate al fine di limitare i costi e massimizzare le rese produttive. Per questo motivo i progettisti hanno dovuto sviluppare delle metodologie per definire con precisione il profilo di utilizzo delle macchine, al fine di ridefinire i test per la validazione finale dei componenti delle trattrici. Uno dei componenti più costosi è la trasmissione, in quanto è costituita da diversi automatismi e pertanto, in questa tesi, è stato descritto un piano sperimentale atto all’acquisizione di dati da trattrici utilizzate da clienti, con l’obiettivo di monitorare l’utilizzo delle trasmissioni. In una prima analisi sono state identificate relazioni statistiche del diverso utilizzo delle trasmissioni delle trattrici in funzione dell’area geografica di vendita e della potenza massima del motore. Sono state poi stimate le distribuzioni ed i parametri del tempo di neutro, delle gamme e retromarce, al fine di integrare le limitazioni riscontrate dalle analisi di correlazione cliente sulle trattrici. E’ stato riscontrato che la vita lavorativa di una trattrice è caratterizzata dal utilizzo del neutro e della gamma media per oltre il 75%. Non sono state evidenziate differenze significative tra i valori del 5° percentile della distribuzione del Neutro per l’intero campione rispetto a quelli calcolati per i gruppi, i quali sono stati formati in funzione dei fattori area geografica e intervalli di potenza massima motore. La gamma media, oltre ad essere la gamma più utilizzata, risulta essere influenzata dai fattori presi in esame, in particolare per le trattrici di potenza pari a A kW. / In the lasts years, the continuous demands of agricultural market, have prompted farmers of having more advanced and highly specialized tractors. This in order to limit the costs and maximize the working yields. Designers have, for the previous reasons, developed methods on the definition of machine usage profile, in order to re-define the final validation tests of tractor components. Considering that the most expensive components is the transmission, because it is constituted by various automatic functions, in this thesis it has been described an experimental acquisition data plan from tractors used by customers, to monitor the transmissions. First of all, there were identified statistical relations of the different tractor’s transmissions usage considering sale geographical areas and the maximum engine power. Therefore, there have been estimated distributions and parameters for neutral time, ranges and reverse gears, to supplement the limitations of customers correlation analysis about tractors. It has been verified that the tractor’s life time is characterized by the usage of the neutral and intermediate range for more than 75%. No significant differences were found between the values of the 5° percentile of the neutral gear distribution for the entire sample, compared to those calculated for the groups. These groups were formed considering the geographical area and maximum engine power ranges factors. The intermediate range, besides being the most used, is influenced by the considered factors, in particular for tractors with A kW of maximum engine power.
8

Electric techniques for the assessment of quality parameters of foodstuffs

Iaccheri, Eleonora <1985> 27 May 2015 (has links)
In food industry, quality assurance requires low cost methods for the rapid assessment of the parameters that affect product stability. Foodstuffs are complex in their structure, mainly composed by gaseous, liquid and solid phases which often coexist in the same product. Special attention is given to water, concerned as natural component of the major food product or as added ingredient of a production process. Particularly water is structurally present in the matrix and not completely available. In this way, water can be present in foodstuff in many different states: as water of crystallization, bound to protein or starch molecules, entrapped in biopolymer networks or adsorbed on solid surfaces of porous food particles. The traditional technique for the assessment of food quality give reliable information but are destructive, time consuming and unsuitable for on line application. The techniques proposed answer to the limited disposition of time and could be able to characterize the main compositional parameters. Dielectric interaction response is mainly related to water and could be useful not only to provide information on the total content but also on the degree of mobility of this ubiquitous molecule in different complex food matrix. In this way the proposal of this thesis is to answer at this need. Dielectric and electric tool can be used for the scope and led us to describe the complex food matrix and predict food characteristic. The thesis is structured in three main part, in the first one some theoretical tools are recalled to well assess the food parameter involved in the quality definition and the techniques able to reply at the problem emerged. The second part explains the research conducted and the experimental plans are illustrated in detail. Finally the last section is left for rapid method easily implementable in an industrial process.
9

Bifidobacteria Ecology of non-Human Primates: Characterization of Novel Species with Unexpected Functionalities for Probiotic Applications and a Co-Evolutionary Host-Microbe Analysis

Michelini, Samanta <1987> January 1900 (has links)
Bifidobacterium spp. are known as probiotic strains and recently new features emphasize their importance for human health, as EPSs and folate production. The relationship between Bifidobacterium spp. and their hosts is unknown, but probably links to peculiarities in the bifidobacterial cell-wall structures or to bifidobacterial ability to metabolize substrates from the host diet. Recently, a richness and diversity of bifidobacteria was observed in Callithrix jacchus and Saguinus midas, introducing the existence of a storehouse in primate guts. Several techniques were developed to deepen the microbial diversity, mainly based on the PCR. The RFLP-PCR of 16S rRNA gene represents a fast tool to distinguish human or animal origin bifidobacteria, useful in “Microbial Source Tracking” and probiotic selection. The project aim was the exploration of the bifidobacterial occurrence and diversity in evolutionary primate hosts to improve the knowledge about bifidobacteria distribution in non-human primates, and to identify bifidobacteria with new probiotic features (EPSs and folate production). 17 subjects from Strepsirrhini, Eulemur macaco, Eulemur rubriventer, Hapalemur alaotrensis and Lemur catta, and from Simiiformes, the New World Monkeys Callithrix jaccus, Pithecia pithecia, Saguinus oedipus and Saguinus imperator, and the Old World Monkeys, Chlorocebo aethiops and Macaca Sylvanus, were studied. Strains tested for probiotics traits, acid and bile tolerance, revealed B. aesculapii, B. myosotis and B. spp. MRM_8.19 strains as the most resistance. The folate production on strains from ring-tailed lemur and common marmoset revealed autotrophy only in strains from common marmoset. The distribution of microbial communities in non-human primates from 8 babies of common marmosets, golden faced saki and Barbary macaques and 11 adults of ring-tail lemurs, black lemurs, red-bellied lemur, Alaotran bamboo lemur, Barbary macaques, grivet, cotton top-tamarin and emperor tamarin, was carried out using ARDRA and rep-PCR. Results revealed a richness in both abundance and diversity of Bifidobacterium in primates.
10

Evolución del derecho peruano desde 1968 : el caso agrario

Pásara, Luis 05 October 2016 (has links)
En los últimos años, dentro de numerosos trabajos teóricos se ha venido en recusar la aproximación tradicional al derecho como objeto de estudio. La vieja polémica entre quienes conceptualizaban el derecho como un orden derivado de otro superior y quienes tomaban el orden jurídico y formal como un hecho dado e indiscutilble, es decir, la secular discusión entre jusnaturalistas y positivistas, ha sido superada por nuevos enfoques del derecho que vinculan determinadas aproximaciones teóricas tributarias del realismo escandinavo y norteamericano y de la escuela sociológica con los crecientes análisis empíricos del derecho en la reali dad, visto con los instrument:os proporcionados por las ciencias sociales. Es necesario ubicar en esta perspectiva el presente trabajo para hacer explicito su enfoque. / Tesis

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