125,023 research outputs found
Gli 1,3-Dinitroalcani Come Immediati Precursori di Sistemi Aromatici
No full textI nitroalcani primari e secondari hanno da tempo dimostrato di essere una delle classi di composti più convenienti nella generazione di carbanioni stabilizzati e, quindi, nella formazione di nuovi legami C,C, semplici e doppi.1,2 Inoltre, la capacità della funzionalità nitro di poter contemporaneamente agire da forte gruppo elettron-attrattore e da ottimo gruppo uscente3 ha permesso, nel recente passato, di poter arrivare alla sintesi “one pot” di sistemi aromatici a partire da nitroalcani (Schema 1).
Continuando nello studio dell’applicazione dei nitroderivati nella sintesi di sistemi benzenici, abbiamo ora trovato che attraverso gli 1,3-dinitroalcani è possibile ottenere una serie di benzeni polialchilati e polifunzionalizzati, molto difficili da ottenere per altra via (Schema 2).
Risultati e condizioni di reazione verranno riportati.
1 G, Rosini In Comprehensive Organic Synthesis; B. M. Trost, Ed.; Pergamon: Oxford, 1991, Vol. 2, p. 321.
2 R. Ballini, G. Bosica, D. Fiorini, A. Palmieri, M. Petrini Chem. Rev. 2005, 105, 933.
3 R. Ballini, A. Rinaldi Tetrahedron Lett. 1994, 35, 9247.
4 (a) R. Ballini, L. Barboni, G. Bosica J. Org. Chem. 2000, 65, 6261. (b) R. Ballini, L. Barboni, G. Giarlo, D. Fiorini, A. Palmieri Chem. Commun. In press
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Multi-temporal analysis of geographical-hierarchical structures in Italy
No full textIn this paper, we propose a model to analyse the dynamic of the urban system looking at the national and local level at the same time; this work is a sketch of a wider project running by few years. The width of the objective suggested to adopt an elementary (meaningful) model of the city system; this is a necessary condition to span the temporal (fifty years) and geographical (all the country) dimensions as defined in our work
Le trasformazioni del territorio italiano tra il 1951 e il 2001
No full textIn questo lavoro, è presentata una ricognizione diacronica delle modificazioni del territorio dal punto di vista insediativo su tutto il territorio nazionale tra il 1951 e il 2001.
Il territorio è modellato in una struttura relazionale gerarchica i cui nodi – i comuni - attraggono e sono attratti localmente materializzando, ordinatamente, l’intreccio del sistema urbano. L’estensione spaziale e temporale ha comportato un grande sforzo di elaborazione e sistematizzazione della base dati tanto sul versante geografico che su quello alfanumerico.
Nel corso della ricerca, sono state definite e sperimentate molteplici opzioni di modellazione L’implementazione del modello individua le strutture gerarchico-geografiche locali su tutto il territorio nazionale Per la loro analisi, sono stati messi a punto una serie di indicatori sia di tipo statistico (consistenza demografica e spaziale, numerosità degli elementi, etc.) che di “forma” ( indice di complessità, indice di diramazione, lunghezza delle catene di elementi, numerosità dei nodi sub-apicali, etc.). Per gli indicatori di tipo statistico, ciascuna struttura locale è comparata alla distribuzione complessiva dei comuni a livello nazionale. Gli indicatori di forma sono invece visti nella loro composizione a livello di singola struttura. Ogni struttura locale è quindi descritta analiticamente tanto nella sua forma (grafo gerarchico-geografico ad ogni data di riferimento) tanto nelle singole variazioni della struttura stessa
La forma della città: luoghi di Roma da cambiare /conservare
No full textIl problema é la progressiva perdita di forma leggibile della città nata sulla base dei processi di accrescimento fisico del secondo dopoguerra e degli strumenti di pianificazione urbanistica da quel periodo utilizzati.
Una nuova consapevolezza del valore della forma urbana, intesa come contesto ed insieme esito di qualsiasi altra politica urbana, può esplicarsi in una strategia di (ri)progettazione morfologica metropolitana, un “progetto”, anche fisicamente inteso, di (ri)costruzione della leggibilità.
L’ipotesi é che la leggibilità della città metropolitana possa essere fondata sulla forma - fisica, percepita, e interpretabile – dello spazio delle reti e dei nodi più frequentati dal cittadino metropolitano.
Il riferimento ad un paradigma formale di tipo reticolare/nodale, i cui elementi sono assunti come luoghi e oggetti urbani da progettare sostiene le ipotesi di applicabilità ed efficienza della strategia, per l’aderenza alle politiche di intervento correnti (nodi e reti sono oggetto di trasformazione a motivo delle loro funzioni di servizio ai flussi di spostamento), e per la fattibilità economica (l’intorno di reti e nodi è il luogo di massimizzazione dell’investimento)
Hierarchical analysis and aggregation of territorial units for more detailed levels in the “NUTS” classification
No full textAt the beginning of the 1970s, the Commission set up the “Nomenclature of Statistical Territorial Units” (NUTS) as a single, coherent system for dividing up the European Union's territory in order to produce regional statistics for the Community. Since in Italy the LAU level 1 has not yet been defined, a committee established by National Statistical Institute (ISTAT) is studying a possible delimitation. This work is set in this background, reporting only one of several diverse hypothesis developed within the committee. A set of common principles for LAU1 have been defined, deriving them from the NUTS Regulation. Consequently, likewise to NUTS, territorial units specific to certain fields of activity have been excluded, while this branch of still running experiments aims to define units of a full general nature. The expected result is the identification of a number of “settlements systems”, where the underlying law is some kind of general relationship existing between communes. So, it has been adopted a very general model of aggregation, applied to municipalities. The model considers two kinds of constraints for the aggregation: i) a hierarchical ranking of settlements, and ii) the relations between settlements, in the geographical space domain. With these constraints, an aggregative algorithm is defined, whose meaning will result by the specific variables that are used: i) to establish the settlements hierarchy, and ii) to evaluate the spatial distribution of settlements
Systems Biology Analysis of the Endocannabinoid System Reveals a Scale-free Network with Distinct Roles for Anandamide and 2-Arachidonoylglycerol
No full textAbstract We represented the endocannabinoid system (ECS) as a biological network, where ECS molecules are the nodes (123) and their interactions the links (189). ECS network follows a scale-free topology, which confers robustness against random damage, easy navigability, and controllability. Network topological parameters, such as clustering coefficient (i.e., how the nodes form clusters) of 0.0009, network diameter (the longest shortest path among all pairs of nodes) of 12, averaged number of neighbors (the mean number of connections per node) of 3.073, and characteristic path length (the expected distance between two connected nodes) of 4.715, suggested that molecular messages are transferred through the ECS network quickly and specifically. Interestingly, 75% of nodes are located on, or are active at the level of, the cell membrane. The hubs of ECS network are anandamide (AEA) and 2-arachidonoylglycerol (2-AG), which have also the highest value of betweeness centrality, and their removal causes network collapse into multiple disconnected components. Importantly, AEA is a ubiquitous player while 2-AG plays more restricted actions. Instead, the product of their degradation, arachidonic acid, and their hydrolyzing enzyme, fatty acid amide hydrolase, FAAH, have a marginal impact on ECS network, indeed their removal did not significantly affect its topology
Urban planning as project management: a limited rationality model
No full textWe consider program proposals as separate projects and use an incremental decision process (incremental functional formulation) backed by methods of optimisation through incremental and interactive decision processes which have been developed in operations research. These methods fit the ill-structured problems in planning better than the conventional optimisation methods. We'll conclude showing one of the possible concrete applications of our model to a real-life case, where one of the main results was a suggested expense of € 4 millions leading to the 90% of the result possible with the cost of € 10 millions (but with just a 40% expenditure)
Rheediinosides A and B, two antiproliferative and antioxidant triterpene saponins from Entada rheedii
No full textTwo triterpenoid saponins have been isolated from the seed kernels of Entada rheedii. Their structures
have been established using 1D- and 2D-NMR and mass spectrometry as 3-O-b-D-xylopyranosyl-
(1 -3)-O-a-L-arabinopyranosyl-(1 -6)-2-acetylamino-2-deoxy-b-D-glucopyranosylentagenic acid 28-
O-b-apiofuranosyl-(1-3)-b-D-xylopyranosyl-(1 -2)-b-D-glucopyranoside (Rheediinoside A, 1) and
3-O-b-D-glucopyranosyl-(1 -3)-O-[b-D-xylopyranosyl-(1-3)-a-L-arabinopyranosyl-(1 -6)]-2-acetylamino-
2-deoxy-b-D-glucopyranosylentagenic acid 28-O-b-apiofuranosyl-(1-3)-b-D-xylopyranosyl-
(1-2)-b-D-glucopyranoside (Rheediinoside B, 2). Compounds 1 and 2 were tested for their antiproliferative
activity against T98G, A431, PC3 and B16-F1 cell lines, and further for their antioxidant properties.
Moderate cytotoxic potency and antioxidant properties were found for these compounds whereas Rheediinoside
B was in all assays more active than Rheediinoside A
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