1,720,989 research outputs found
Quibus verbis uti posset : alcune considerazioni su Prisciano e la tradizione progimnasmatica latina tardoantica
No full textPersio e il suicidio di Catone : sulle tracce di un esercizio scolastico antico (Pers. III 44-47)
No full textTiberio Claudio Donato e i "progymnasmata"
Get PDFIl contributo analizza la presenza e l'utilizzo dei progymnasmata, ed in particolare del locus communis, nelle Interpretationes Vergilianae di Tiberio Claudio Donato. Il caso di Donato mostra chiaramente come l’educazione retorica (veicolata non solo con l’insegnamento dei precetti astratti, ma anche e soprattutto attraverso la proposizione di concrete fattispecie di esercitazione scolastica) rappresentasse, in antico, uno strumento utile per scrivere (o riscrivere) un testo, per leggere ed interpretare le opere altrui e, in definitiva, per pensare il mondo
Prova latente e "normalizzazione" dei lemmi : problemi filologici nelle "Interpretationes Vergilianae" di Tiberio Claudio Donato
No full textIl contributo si propone di analizzare i due principali problemi filologici che contraddistinguono il testo delle Interpretationes Vergilianae di Tiberio Claudio Donato: (1)la relazione stemmatia tra i principali testimoni manoscritti, ed in particolare tra L (Laur. 45.15) e R (Reg. Lat. 1484); (2) il rapporto tra le note di commento e i lemmi virgiliani, che sono stati sottoposti ad un processo di "normalizzazione" sulla bse della tradizione diretta dell'Eneide. In entrambi i casi, le opinioni di H. Georgii, l'ultimo editore dell'opera (Lipsiae 1905-1906), necessitano di essere - almeno in gran parte - riviste
L'insegnamento dei 'progymnasmata' nell'opera di Emporio retore
No full textIl contributo è finalizzato ad offrire un'analisi complessiva dei quattro capitoletti retorici trasmessi sotto il nome del retore Emporio, che rappresentano una delle pochissime testimonianze superstiti dell'insegnamento degli esercizi preliminari (progymnasmata) nelle scuole latine durante il periodo tardoantico. Il confronto con le fonti parallele consente di mettere in evidenza la presenza di numerosi elementi tradizionali, accanto ad alcune particolarità che trovano un corrispettivo preciso solo nei commentari al manuale di Aftonio di epoca bizantina (Giovanni di Sardi, Giovanni Dossapatre)
I picnic siciliani della valle del Tempio
Get PDFRiflessione su una serie di workshop internazionali di progettazione architettonica e paesaggistic
Cadmium-induced sulfate uptake in maize roots
No full textThe effect of cadmium (Cd) on high-affinity sulfate transport of maize (Zea mays) roots was studied and related to the changes in the levels of sulfate and nonprotein thiols during Cd-induced phytochelatin (PC) biosynthesis. Ten micromolar CdCl2 in the nutrient solution induced a 100% increase in sulfate uptake by roots. This was not observed either for potassium or phosphate uptake, suggesting a specific effect of Cd2+ on sulfate transport. The higher sulfate uptake was not dependent on a change in the proton motive force that energizes it. In fact, in Cd-treated plants, the transmembrane electric potential difference of root cortical cells was only slightly more negative than in the controls, the external pH did not change, and the activity of the plasma membrane H+-ATPase did not increase. Kinetics analysis showed that in the range of the high-affinity sulfate transport systems, 10 to 250 μM, Cd exposure did not influence the Km value (about 20 μM), whereas it doubled the Vmax value with respect to the control. Northern-blot analysis showed that Cd-induced sulfate uptake was related to a higher level of mRNA encoding for a putative high-affinity sulfate transporter in roots. Cd-induced sulfate uptake was associated to both a decrease in the contents of sulfate and glutathione and synthesis of a large amount of PCs. These results suggest
that Cd-induced sulfate uptake depends on a pretranslational regulation of the high-affinity sulfate transporter gene and that this response is necessary for sustaining the higher sulfur demand during PC biosynthesis
Ca2+-dependent phosphorylation regulates the plasma membrane H+-ATPase activity of maize (Zea mays L.) roots
No full textPhosphorylation/dephosphorylation of the plasma-membrane H+-ATPase (EC 3.6.1.35) could act as a regulatory mechanism to control its activity. In this work, a plasmalemma-enriched fraction from maize roots and a partially purified H+-ATPase were used to investigate the effects of Ca2+ and calmodulin on the H+-ATPase activity and on its phosphorylation status. Both the hydrolytic and the proton-pumping activities were reduced approximately 50% by micromolar Ca2+ concentrations while calmodulin did not show any effect either alone or in the presence of Ca2+. The lack of effect of calmodulin antagonists indicated that calmodulin was not involved in this response. The addition of staurosporine, a kinase inhibitor, abolished the inhibitory effect of Ca2+. Phosphorylation of plasma membrane and partially purified H+-ATPase showed the same behavior. In the presence of Ca2+ a polypeptide of 100 kDa was phosphorylated. This polypeptide cross-reacted with antibodies raised against the H+-ATPase of maize roots. The autoradiogram of the immunodetected protein clearly showed that this polypeptide, which corresponds to the H+-ATPase, was phosphorylated. Additional clear evidence comes from the immunoprecipitation experiments: the data obtained show that the H+-ATPase activity is indeed influenced by its state of phosphorylation
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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