1,721,088 research outputs found
Effect of synthetic and functionalized waxes on bituminous binders: From the glassy state to the intermediate viscoelastic domain
No full textA 50/70 bitumen was modified with five different commercial waxes, including Fischer-Tropsch, Montan
and functionalized waxes. Thermal and morphological properties were investigated through Differential
Scanning Calorimetry (DSC) and polarized optical microscopy (POM). Dynamic and continuous rheological
tests were carried out to analyse the mechanical response of wax-modified bitumens (WMB).
Theories behind possible mechanisms of asphalt/wax interaction are discussed. The entire frequency/
temperature domain was divided into two macro-regions. The first one covers the glassy state, with independent
waxy structures, where the bitumen mainly determines the mechanical response. The second
macro region develops along the intermediate viscoelastic domain and propagates towards high temperatures/
low frequencies. Within this domain, all WMB exhibits a complex mechanical response, with gellike
characteristics, thus suggesting the existence of physical networks and interconnections between
contiguous wax crystalline segments
Vulcanization accelerators as alternative to elemental sulfur to produce storage stable SBS modified asphalt
No full textStorage stability is one of the main problems of polymer modified asphalts and the use of elemental sulfur
is probably the most effective solution, even if not free from inconveniences. Here ten commercially
available vulcanization accelerators were tested as potential alternative to sulfur and added to asphalts
modified with SBS. Mixing asphalt and polymer at 180 C, out of the 10 products two gave performance
comparable to sulfur, while some of the other additives became effective only at mixing temperature of
210 C and a few did not work at all. A qualitative correlation between the thermal stability and the effectiveness
of the additives was attempted through the thermogravimetric analysis
Reproduction and health status in swordfish (Xiphias gladius) and Atlantic Bluefin Tuna (Thunnus thynnus) Mediterranean stock for management of sustainable fishing
Full text linkIl pesce spada (Xiphias gladius) e il tonno rosso dell'Atlantico (Thunnus thynnus) sono grandi specie epipelagiche, capaci di movimenti a lunga distanza come evidenziato da programmi di tagging, sia convenzionali che elettronici, e sono un'importante risorsa ittica. Nel Mar Mediterraneo, la Commissione internazionale per la conservazione dei tunnidi dell'Atlantico (ICCAT) è l’RFMO di riferimento. L'ICCAT ha stabilito un piano pluriennale per la ricostituzione dello stock mediterraneo di pesce spada e di tonno rosso dell'Atlantico, che stabilisce norme per la conservazione, la gestione e il controllo per ottenere biomassa corrispondente al rendimento massimo sostenibile. La valutazione dello stato di salute, della struttura della popolazione e delle dinamiche riproduttive è alla base della biologia della conservazione del pesce spada e del tonno rosso. Nella gestione della pesca, l'applicazione di approcci multidisciplinari (ad esempio, l'analisi istologica, gli approcci genomici e trascrittomici e l'analisi della variabilità genetica si sono dimostrati una soluzione efficace per determinare la struttura genetica della popolazione e lo stato di salute degli stock ittici. In questo progetto di dottorato, sono stati applicati molteplici approcci per comprendere meglio e far luce sulla salute e sullo stato riproduttivo di Xiphias gladius e Thunnus thynnus in Mediterraneo e sostenere un processo decisionale basato sulla scienza nel contesto della gestione della pesca. Gli obiettivi sono indicati per ciascun capitolo come segue: 1. A window of vulnerability: chronic environmental stress does not impair reproduction in the swordfish Xiphias gladius • Obiettivi: i) valutare il cross-talk tra metabolismo, risposta allo stress, sistema immunitario e riproduzione in femmine immature e mature mediante analisi trascrittomica; ii) identificare una variazione dello stato di salute relativa alla maturità sessuale e alla dimensione del pesce mediante analisi istologica 2. Oogenesis impairment in Swordfish (Xiphias gladius) caught in Central Adriatic Sea: differences between mature and immature females • Obiettivi: i) valutare lo stato di salute del fegato e della gonade delle femmine immature e mature catturate nell'Adriatico centrale durante la stagione estiva e autunnale; ii) valutare le alterazioni che potrebbero colpire la gonade delle femmine immature e mature; iii) determinare il range di dimensioni sbarcate nell'Adriatico centrale 3. ddRAD genotyping reveals new insight into the genetic structure and diversity, fitness and evolutionary potential of Atlantic and Mediterranean swordfish stocks • Obiettivi: i) approfondire la struttura e la diversità genetica a livello genomico dei tre stock di pesce spada, l'Atlantico settentrionale, l'Atlantico meridionale e il Mediterraneo; ii) valutare l'idoneità degli stock e il potenziale evolutivo per rispondere ai cambiamenti ambientali; iii) confermare gli attuali confini territoriali degli stock e il grado di mixing 4. Histological investigation on reproductive biology of the Atlantic bluefin tuna (Thunnus thynnus) in the Central Adriatic Sea: differences between males and females • Obiettivi: i) valutare lo stato gonadico dei maschi e delle femmine catturati nel Mar Adriatico Centrale da febbraio a novembre; ii) valutare le alterazioni che potrebbero interessare le gonadi di maschi e femmine; iii) determinare il range di dimensioni sbarcate nell'Adriatico centrale.Swordfish (Xiphias gladius) and Atlantic bluefin tuna (Thunnus thynnus) are a large epipelagic species capable of long-distance movements as evidenced by both conventional and electronic tagging programs and are an important fisheries resource. In the Mediterranean Sea, the International Commission for the Conservation of Atlantic Tunas (ICCAT) is the reference RFMO. ICCAT established a multiannual plan for the recovery of Mediterranean swordfish and Atlantic blue fin tuna stock, laying down rules for the conservation, management, and control to achieve biomass corresponding to maximum sustainable yield. The evaluation of health status, population structure and reproductive dynamics underlies conservation biology of swordfish and Atlantic bluefin tuna. In fisheries management, the application of multidisciplinary approaches (e.g., histological analysis, genomic and transcriptomic approaches and genetic variation analysis has proven as an effective solution to determine the genetic structure of population and health status of fish stocks. In this PhD project, multiple approaches were applied to better understand and to shed light on the health and reproductive status Xiphias gladius and Thunnus thynnus Mediterranean stock and support a science-based decision-making process in the context of fishery management. The detailed objectives are provided for each chapter as follows: 1. A window of vulnerability: chronic environmental stress does not impair reproduction in the swordfish Xiphias gladius • Aims: i) evaluate the cross-talk among metabolism, stress response, immune system and reproduction in immature and mature females by transcriptomic analysis; ii) identified a variation of health status related to sexual maturity and fish size by histological analysis 2. Oogenesis impairment in Swordfish (Xiphias gladius) caught in Central Adriatic Sea: differences between mature and immature females • Aims: i) evaluate the health of liver and ovary of immature and mature females caught in central Adriatic Sea during the summer and autumn seasons; ii) evaluate the alterations that could affected the ovaries of immature and mature females; iii) determine the range sizes landed in central Adriatic sea 3. ddRAD genotyping reveals new insight into the genetic structure and diversity, fitness and evolutionary potential of Atlantic and Mediterranean swordfish stocks • Aims: i) gain deeper insights into the genetic structure and genetic diversity at genomic level of the three swordfish stocks, the North Atlantic, the South Atlantic and the Mediterranean; ii) assess the stocks fitness and evolutionary potential to respond to environmental changes; iii) confirm the current spatial stock boundaries and degree of mixture 4. Histological investigation on reproductive biology of the Atlantic bluefin tuna (Thunnus thynnus) in the Central Adriatic Sea: differences between males and females • Aims: i) evaluate the gonadal status of males and females caught in Central Adriatic Sea from February to November; ii) evaluate the alterations that could affected the ovaries and testis; iii) determine the range sizes landed in central Adriatic se
XRD study of intercalation in statically annealed composites of ethylene copolymers and organically modified montmorillonites. 2. One-tailed organoclays
Full text linkEthylene copolymers with different polar comonomers, such as vinyl acetate, methyl acrylate, glycidyl methacrylate, and maleic anhydride, were used for the preparation of polymer/clay nanocomposites by statically annealing their mechanical mixtures with different commercial or home-made organically modified montmorillonites containing only one long alkyl tail. The nanostructure of the products was monitored by X-ray
diffraction, and the dispersion of the silicate particles within the polymer matrix was qualitatively evaluated through microscopic analyses. The effect of the preparation conditions on the structure and the morphology of the composites was also addressed through the characterization of selected samples with similar composition prepared by melt compounding. In agreement with the findings reported in a previous paper for the
composites filled with two-tailed organoclays, intercalation of the copolymer chains within the tighter galleries of the one-tailed clays occurs easily, independent of the application of a mechanical stress. However, the shear-driven break-up of the intercalated clay particles into smaller platelets (exfoliation) seems more hindered. A collapse of the organoclay interlayer spacing was only observed clearly for a commercial one-tailed organoclay – Cloisite® 30B – whereas the same effect was almost negligible for a home-made organoclay with similar structure
Thermal Behaviour of Polymer/Cellulose Fibre Composites. Effect of Chemical Modification and Interfacial Interactions,
No full textCoupling of chiral 1-bromo-1,2-dienes with zinc-based cuprates: a new procedure for the regio and stereoselective synthesis of functionalized acetylenic compounds
No full textZinc alkylcyanocuprates (Knochel reagents) are found to be active in the cross-coupling reaction with allenic bromides affording acetylenic products with a high regio and stereoselective 1,3-anti substitution. The coupling process, which has been successfully extended to functionalized cuprates, can also be performed with alkylzinc chlorides in the presence of catalytic amounts of cuprous salts
STRUCTURE AND MORPHOLOGY OF NYLON 6-CLOISITE® 30B COMPOSITES. EFFECTS OF THE PREPARATION CONDITIONS
No full textA revised relationship between molecular weight and reduced angular frequency in δ-method applied to unmodified petroleum bitumens
No full textThe δ-method has been developed to estimate molecular weight distributions of bitumens from phase-angle master curves. The method uses a correlation between the cross-over frequency(ωC) and the molecular weight
(MW) that was developed from average MW measured by vapour pressure
osmometry. This study proposes a revised correlation whose parameters
have been calculated from Gel Permeation Chromatography (GPC), which
can be conducted at a low level of dilution preserving the interactions in the
bitumen bulk. Furthermore, data from the GPC allow the optimisation of the
parameters considering the entire MW distribution (MWD), thus improving
the predictive capability of the method. Three unmodified petroleum bitumens at different levels of ageing and three rheological models were used
in the optimisation. Two groups of parameters were identified; one for hard
(e.g. Pen 35-50) and another one for soft-medium bitumens (e.g. Pen 50–70
or Pen 70-100). The apparent-MWDs (A-MWDs) calculated with the new
parameters show improved correlation with the respective distributions
and average molecular weight from GPC
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