4,216 research outputs found
Introduction to the Theory of Stellar Evolution
No full textStars form from the collapse and fragmentation of molecular clouds. After this first stage of formation and evolution as a pre-main-sequence object, a star begins its life in the main sequence stage through the ignition of Hydrogen in its core. From here after, the life of a star is simply described as the evolution of a gaseous mass through well defined stages of equilibrium between gravitational energy and the energy produced by the nuclear reactions in its interior. Depending on its initial mass, heavier and heavier chemical elements are processed in the stellar core up to iron for the most massive stars. Finally, the star will end its life by simply cooling down as a white dwarf or exploding as a supernova, depending once again on its initial mass. In this introductory chapter, we briefly review the most important aspects concerning the evolution and nucleosynthesis of single stars, form the early stage of its formation to the final stages and death
A new race, 704, of Plasmopara helianthi pathogen of sunflower downy mildew in Italy
No full textDuring 2006, surveys on approximately 92 ha of Umbrian (central Italy) sunflower fields were carried out for monitoring distribution and race variability of the pathogen. Twelve fields planted with commercial hybrids were surveyed. Downy mildew was only observed in five fields, with 2 to 3% of disease incidence. Pathogen inocula were directly recovered from infected leaves by brushing the fungal structures or after infected leaves were incubated in a humid chamber at 18 to 20°C in the dark for 24 to 48 h. After increasing initial inocula on the suscpetible cv. Ala, race identification of four isolates was determined by the reaction of three standard sets of nine differential sunflower lines using a triplet code. The isolates were also evaluated for their sensitivity to metalaxyl-M (Apron XL 31.8%) used at the Italian registered rate (1.05 g of a.i. per kg of seed). Three isolates were characterized as race 700 and one as a mixture of races 700 and 704. To our knowledge, this is the first report of race 704 in Italy. All field isolates were also metalaxyl-M sensitive as already reported in other European countries
Miscanthus rhizome rot: A potential threat for the establishment and the development of biomass cultivations
No full textLittle is known about diseases of miscanthus, one of the most important possible bioenergy crops in the world. In 2007, in an experimental field located near Perugia (Central Italy), the failure of the establishment of a miscanthus crop was observed a few days after rhizome transplanting. Previous phytopathological studies revealed the presence of three pathogenic fungal species (Fusarium avenaceum, Fusarium oxysporum and Mucor hiemalis) causing miscanthus rhizome rot (MRR). In the present study, the incidence and the severity of the disease caused by the mentioned pathogens were assessed and their effect on some miscanthus growth parameters, as indicators of rhizome viability and quality, was determined. Two different inoculation methods (rhizome immersion in conidial suspension and rhizome planting into a contaminated soil) were also evaluated. All fungal species, in single and mixed inoculation, produced MRR and a significant reduction of the number of roots per rhizome and root and shoot length decrease was also observed. Although all the species were pathogenic, significant differences in virulence between the two inoculation methods and between pathogens were observed, with F. avenaceum and M. hiemalis being more virulent than F. oxysporum in both types of inoculations. These results suggest that the three pathogens colonized the rhizomes in the soil of origin and/or during their storage, resulting in the failure of the crop after plantation. Therefore, the commercialization of certified miscanthus rhizomes should be strongly recommended in order to obtain healthy miscanthus cultivations and to avoid the transmission of soil-borne pathogens between different areas. © 2012 Elsevier Ltd
PRELIMINARY RESULTS ON THE TRANSLOCATION OF DON TO THE HEAD OF SOFT WHEAT FOLLOWING INFECTION OF THE STEM BASE BY F. CULMORUM
No full textPresence of mycotoxigenic fungi and mycotoxins in wheat grain in Umbria (Central Italy).
No full textReport on the Workshop ''Ecology of Blue Straggler Stars''
No full textThe last workshop dedicated to blue straggler stars (BSS) took place 20 years ago and there have been a great number of subsequent developments since in both observations and theory. The wide range of BSS topics covered at the workshop are briefly summarised; the published proceedings will form the first book on the subject
Un'inedita sestina del Trecento (tra le rime di Niccolò Beccari)
No full textNell'ambiente letterario della Padova di Francesco da Carrara il Vecchio, in cui intorno al Petrarca (giunto ai suoi ultimi anni) si raccoglieva un laboratorio particolarmente motivato ad una pur ardua e precoce imitazione del maestro (con la partecipazione di rimatori come Giovanni Dondi e Francesco di Vannozzo), questo contributo delinea per la prima volta il ruolo svolto da Niccolò Beccari, fratello del più conosciuto Antonio da Ferrara. Noto finora quasi esclusivamente per le sue "Regulae singulares" (quattro epistole latine di argomento politico), Niccolò Beccari fu infatti, nei tre anni trascorsi a Padova (1370-72) un entusiasta ammiratore del Petrarca, che tentò di imitare nella composizione di alcuni sonetti (di cui otto pervenutici), ma soprattutto cimentandosi nel difficile e molto petrarchesco genere lirico della “sestina”, ancora assai raro a questa altezza cronologica. Lo studio pubblica criticamente e analizza non solo questo inedito, interessante componimento, ma l’intera produzione lirica di Niccolò Beccari pervenutaci, in minima parte già disponibile a stampa.In the literary environment of the Padua of Francesco da Carrara the Elder, in which around the Petrarca (in his last years) a workshop was gathered that was particularly motivated by a difficult and precocious imitation of the master (with the participation of versifiers such as Giovanni Dondi and Francesco di Vannozzo), this contribution outlines for the first time the role played by Niccolò Beccari, brother of the most famous Antonio da Ferrara. Known so far almost exclusively for his "Regulae singulares" (four Latin epistles of political argument), Niccolò Beccari was in fact, in the three years spent in Padua (1370-72) an enthusiastic admirer of Petrarch, who tried to imitate in the composition of some sonnets (of which eight have survived), but above all by experimenting with the difficult and very Petrarchist lyrical genre of the "sestina", still very rare at this chronological height. The study critically publishes and analyzes not only this unpublished, interesting composition, but the entire lyric production of Niccolò Beccari, which we have received, in a small part already available to the press
Le «buone letture». 2. Giovanni Casati
No full textIl saggio è costituito da due parti, la prima delle quali, dedicata alla fondazione della Federazione italiana delle biblioteche circolanti cattoliche, è stata pubblicata nel precedente numero dei «Nuovi Annali», XXVII (2013), pp. 137-163. In questa seconda parte viene delineata la figura intellettuale di Giovanni Casati, che diresse la «Rivista di letture» dal 1912 al 1944, trasformando il periodico della Federazione in una rivista impegnata nella divulgazione della cultura cattolica. A questo impegno militante Casati fece corrispondere un intenso programma editoriale, che trovò espressione nella pubblicazione di saggi letterari, di manuali e opere repertoriali.The study consists of two parts; the first is dedicated to the history of the Federazione italiana delle biblioteche circolanti cattoliche since its foundation (1904) up to 1912 and was published in the previous volume of the «Nuovi Annali », XXVII (2013), pp. 137-163. In this second part, the author outlines the intellectual figure of Giovanni Casati, who directed the «Rivista di letture» from 1912 to 1944, transforming the magazine of the Federation in a journal engaged in the spreading of Catholic culture. To this militant engagement Casati matched an intense publishing program, which found its expression in the publication of literary essays, manuals and reference works
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