1,721,086 research outputs found
Inanna e Dumuzi, al di là del tempo e dello spazio. Tradizioni cultuali e letterarie
Full text linkIl presente lavoro intende analizzare le evidenze testuali relative alle figure divine di Inanna e Dumuzi. Attraverso lo studio approfondito della tradizione letteraria di periodo paleo-babilonese (ca 2000-1600 a.C.) in lingua sumerica, è stato possibile delineare la natura del rapporto che unisce le vicende dei due personaggi mitici. La ricerca si è concentrata non solo sulle composizioni d’amore aventi in oggetto proprio la nascita e lo sviluppo del sentimento che coinvolge i due giovani dei, ma anche sulle tradizioni mitiche che che riguardano il periodo di formazione dell’identità delle due singole figure. L’analisi condotta ha permesso di individuare i caratteri principali delle due personalità divine, che fino ad oggi, specialmente nel caso di Dumuzi, erano state oggetto di una vivace discussione nel campo assiriologico. In virtù del particolare rapporto di omologia funzionale tra il dio Dumuzi ed la figura del sovrano nella letteratura sumerica di periodo paleo-babilonese, si è deciso di tenere in considerazione anche quelle composizioni che testimoniassero un legame privilegiato tra un personaggio di rango reale e la dea Inanna; ciò ha permesso di delineare con maggiore chiarezza le sfere di competenza e di tutela dei due personaggi divini in rapporto all’istituzione regale.
La presente ricerca ha beneficiato di un approccio multidisciplinare che ha permesso di unire la metodologia storico-religiosa a quella assiriologica, al fine di ancorare saldamente il panorama letterario in oggetto al contesto storico di provenienza e di utilizzo.
L’uso di un approccio che predilige la contestualizzazione storica del materiale non solo ha fatto sì che si ottenesse un’analisi puntuale della documentazione, ma ha anche permesso di evitare generalizzazioni diacroniche sulle figure oggetto della ricerca.
In definitiva, lo studio ha permesso una rivalutazione della natura dei personaggi divini di Inanna e Dumuzi nel contesto letterario paleo-babilonese, sia per quanto riguarda le caratteristiche delle singole figure che nel loro rapporto di interdipendenza, con particolare riferimento alla costruzione di un’ideologia regale legittimata dalla sfera divina
Thermodynamics of the interaction of α-cyclodextrin with α,ω-dicarboxylic acids in aqueous solutions. A calorimetric study at 25°C
No full textThe interaction in water of α-cyclodextrin with α,ω-dicarboxylic acids from C5 to C11 has been studied calorimetrically at 25°C in phosphate buffer at pH 11.3 and 1.3. When a complex forms, calorimetry enables the calculation of both enthalpy and association constant, from which the free energy and the entropy of the process can be obtained. At pH 11.3, 1 : 1 complexes are formed, the association occurring through the interaction of the charged carboxylate groups with the hydroxyl groups on the exterior of the dextrin. The alkyl chain should point toward the interior of the cavity. This 'capping' mechanism relies on the impossibility of the carboxylate group to reside within the cavity. At pH 1.3, the values of the association constants do not follow a regular trend with increasing alkyl chain length. Evidences are presented for a variation of the stoichiometry of association for longer chain substances. A 2 : 1 stoichiometry would be possible because of the ability of the uncharged carboxyl group to be included in the cavity. The forces involved in the association process are discussed in the light of the analysis of the signs and values of the thermodynamic parameters. © 1997 Elsevier Science B.V
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Role of the functional group in the formation of the complexes between α-cyclodextrin and alkanols or monocarboxylic acids in aqueous solutions. A calorimetric study at 25 °C
No full textThe interaction of α-cyclodextrin with 1-alkanols, monocarboxylic acids and α,ω-diols has been studied calorimetrically at 25 °C in water, in phosphoric acid, pH 1.3, and in phosphate buffer, pH 11.3. When a complex is formed, calorimetry enables the calculation of both the enthalpy and the association constant, from which the free energy and the entropy of the process can be obtained. Inclusion complexes are formed by 1-alkanols and monocarboxylic acids. For alkanols, a model is proposed to explain the unusual trend of the association constants at increasing alkyl chain length. The association occurs through the insertion of the guest's alkyl chain into the host's cavity. However, for terms longer than C6, two forms of the guest can exist, each one associating to αCD with a different constant and enthalpy. α,ω-Diols associate through a mechanism which involves prevailingly the exterior of α-cyclodextrin. For terms longer than C7, another mechanism is proposed which provides the inclusion of the alkyl chain, with the hydroxyl groups both laying outside the cavity. The main role played by the different functional groups, and the forces involved in the association process are discussed in the light of the analysis of the signs and values of the thermodynamic parameters obtained
Thermodynamic Properties of Aqueous Micellar Solutions of 1-Methyl-4-Octyl-Pyridinium Halides
No full textApparent and partial molar enthalpies at 298K and Gibbs free energies at 313K of aqueous solutions of the cationic surfactants 1-methyl-4-octylpyridinium chloride, bromide and iodide (OMPC, OMPB, OMPI, respectively) have been measured as a function of concentration. The changes in enthalpies upon micellization have been obtained from the experimental data by using a pseudo phase transition approach. The data reported here are a further contribution in defining the effect of the counter ion on the energetics of surfactant solutions and confirm the validity of the group contribution approach also for the counter ion. The effect of the counter ion on the trends of apparent and partial molar enthalpies is strong and inversely proportional to the radius of the hydrated counter ion.
The change in structure between the compounds in which the alkyl chain is bound directly to the pyridine nitrogen and
those having the tail in position 4, significantly affects the value of the cmc, showing that the latter are more hydrophobic, but scarcely affects the enthalpic properties of the solutions
Thermodynamic Properties of the Aqueous Solution of Potassium Salts of Some 4-((alkylcarbonyl)amino)-2-hydroxybenzoic Acids at 298 and 313 K
No full textTo understand the aggregation behavior of surface-active ligands with a salycilic polar head, we undertook a systematic study of some classes of anionic surfactants where the presence and the position of the –OH and the carboxylic group differ. This paper reports the dilution heats at 298 and 313 K of aqueous solutions of potassium 4-((alkylcarbonyl)amino)-2-hydroxybenzoate (KPAS-Cn where n stands for the number of carbon atoms in the chain) in KOH at 0.1 m, measured as a function of concentration. From the experimental data, apparent and partial molar enthalpies vs concentration were obtained. By using a pseudo-phase-transition approach, the enthalpy changes upon micelle formation (DHm) and assuming that in the restricted range of temperature examined heat capacities are constant, the heat capacity changes have been obtained. Micelle formation enthalpies are seen to be additive with a group contribution
for the methylene group of −1.5±0.1 kJ mol−1 per group
at 298 K and −2.3±0.1 kJ mol−1 per group at 313 K, comparable with that obtained for similar anionic compounds in the same experimental conditions and for N-alkylnicotinamide chlorides (cationic surfactants). The –CH2– group contribution to the micelle formation heat capacities is−53±1JK−1 mol−1.
Aqueous micellar solutions of some N-alkylnicotinamide and N-alkylpyridinium halide surfactants: apparent and partial molar enthalpies
No full textIn order to acquire thermodn. data for aq. solns. of functionalized surfactants, and to study the effect of the amidic group in the polar head and of the counterion, the enthalpies of diln. at 25° of N-alkylnicotinamide chlorides (alkyl chain length 7.9 or 10 carbon atoms), N-alkylpyridinium chlorides (alkyl chain length 8, 10, or 12 atoms), N-octylpyridinium bromide and N-decylpyridinium bromide were measured by means of a flow microcalorimeter. From the exptl. data, apparent and partial molar relative enthalpies as function of the molaity of the surfactant were derived. The amidic group in the nicotinamide compds. greatly enhances the hydrophobicity relative to the pyridinium compds. For cationic surfactants with the same alkyl chain, the trends of the molar enthalpies vs. concn. can be explained in terms of charge localization on the polar head. For the compds. under investigation, enthalpic data are not able to show phase transitions in the micellar region, but they confirm the role of the counterion in the energetics of micellar soln. The thermodn. functions of micellization were evaluated on the basis of the pseudo-phase transition model by graphical extrapolation
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