124,152 research outputs found
Health care associated pneumonia: a new clinical entity.
No full textFalcone M, Serra P, Licata G, Venditti M; Italian Society of Internal Medicine (SIMI). Health care associated pneumonia: a new clinical entity. Arch Intern Med.
2008 Jan 14;168(1):109-10. PubMed PMID: 18195203
Girolamo Serra storico
No full textAnalisi dell''opera storiografica di G. Serra alla luce delle sue idee politich
From batch to flow synthesis of purine ribonucleosides by enzymatic transglycosylation
No full textPurine nucleoside phosphorylases (PNPs, EC 2.4.2.1) catalyze the reversible phosphorolysis of the glycosydic bond of purine nucleosides; upon addition of a second nucleobase, these enzymes may transfer the glycosyl moiety to it, resulting in the chemo-, regio- and stereoselective formation of a new nucleoside (transglycosylation, Scheme 1). This chemoenzymatic process represents an advantageous alternative to conventional chemical strategies which are frequently hampered by several drawbacks such as multistep processes, need for protecting groups, low chemo-, regio- and stereoselectivity.
A PNP from Aeromonas hydrophila (AhPNP) has been recently characterized in terms of substrate specificity [1], also upon immobilization on the inner surface of a silica capillary coupled on-line with a chromatographic column [2].
Because of its wide substrate specificity, AhPNP was then exploited to catalyze the “one-pot, one-enzyme” transglycosylation of 7-methylguanosine iodide with a series of 6-substituted purines, resulting in a moderate to high conversion (18-65%) of the bases into a 23-compound library of 6-substituted purine-9-ribosides. Moreover, AhPNP was covalently immobilized (25 mg immobilized enzyme, 50% yield) in a pre-packed stainless steel column containing aminopropyl silica particles. The resulting AhPNP-IMER (Immobilized Enzyme Reactor) was coupled to a HPLC apparatus containing an analytical or a semi-preparative chromatographic column associated with a UV-visible detector. This system was used to synthesize five 6-substituted purine ribonucleosides at a mg scale by transglycosylation through a “flow-based” approach. Coupling of transglycosylation reaction and product separation resulted in a fast and efficient process (52-89% conversion) with minimized sample handling. To date, AhPNP-IMER completely retained its activity upon 50 reactions in 10 months.
[1] D. Ubiali, C. D. Serra, I. Serra, C. F. Morelli, M. Terreni, A. M. Albertini, P. Manitto, G. Speranza Adv. Synth. Catal. 2012, 354, 96-104
[2] E. Calleri, D. Ubiali, I. Serra, C. Temporini, G. Cattaneo, G. Speranza, C. F. Morelli, G. Massolini J. Chromatogr. B Analyt. Technol. Biomed. Life Sci. 2014, 968, 79-8
Nucleoside phosphorylases and deoxyribonucleoside kinases: the green side of nucleis acid chemistry
No full textBiocatalysis has become nowadays an important tool in synthetic organic chemistry. Biotransformations are chemo-, regio-, and stereoselective, occur under mild reaction conditions and are characterized by a reduced use of toxic reagents/solvents. One of the areas where biocatalyzed reactions have clearly shown their potential is nucleic acid chemistry. Enzymes of nucleic acid metabolism such as nucleoside phosphorylases (NPs, EC 2.4.2) and deoxyribonucleoside kinases (dNKs, EC 2.7.1) can be conveniently used as biocatalysts in the synthesis of nucleoside and nucleotide analogues.
NPs catalyze the reversible cleavage of the glycosidic bond of (deoxy)ribonucleosides in the presence of inorganic orthophosphate to generate the nucleobase and α-D-(deoxy)ribose-1-phosphate. If a second nucleobase is added to the reaction, the formation of a new nucleoside can result (transglycosylation). dNKs catalyze the regioselective transfer of a phosphate group from ATP to a nucleoside to give the corresponding nucleoside 5’-monophosphate. However, the bottleneck in the use of enzymes as biocatalysts is often their instability under experimental conditions, their cost and solubility in the reaction medium. These issues can be frequently overcome by immobilizing the enzyme on a solid support. Substrate specificity, immobilization and some synthetic applications of selected NPs1-3 and dNKs4 will be described.
References
1. Ubiali, D.; Serra, C.D.; Serra, I.; Morelli, C.F.; Terreni, M.; Albertini, A.M.; Manitto, P.; Speranza, G. Adv. Synth. Catal., 2012, 354, 96.
2. Ubiali, D.; Morelli, C.F.; Rabuffetti, M.; Cattaneo, G.; Serra, I.; Bavaro, T.; Albertini, A.M.; Speranza, G. Curr. Org. Chem., 2015, 19, 2220.
3. Calleri, E.; Cattaneo, G.; Rabuffetti, M.; Serra, I.; Bavaro, T.; Massolini, G.; Speranza, G.; Ubiali, D. Adv. Synth. Catal., 2015, 357, 2520.
4. Serra, I.; Conti, S.; Piškur, J.; Clausen, A.R.; Munch-Petersen, B.; Terreni, M.; Ubiali, D. Adv. Synth. Catal., 2014, 356, 563
On the mechanism involved in the behavioural supersensitivity to DA-agonists induced by chronic antidepressants.
No full textParque Estadual da Serra do Tabuleiro (PEST): história e conflito sócio-ambiental (1975-2007)
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas. Programa de Pós-graduação em HistóriaEsta dissertação trata do Parque Estadual da Serra do Tabuleiro (PEST), em Santa Catarina/Brasil, e da história de alguns de seus conflitos sócio-ambientais. O PEST está inserido no bioma da Mata Atlântica, qualificado como um dos principais parques de conservação do Brasil, pois seu território abriga vários ecossistemas, tais como Restinga, Araucária, Floresta Pluvial Atlântica, Matinha Nebular, Campos de Altitude e Mangues. A Fundação do Meio Ambiente de Santa Catarina (FATMA), ao longo de sua história como autarquia, tem construído um discurso que busca nomear o PEST como #santuário da biodiversidade. Mas essa área de preservação permanente tem ainda habitantes e seu interior, que vêm sendo retirados ou impedidos de exercerem suas atividades econômicas tradicionais, o que gera inúmeros conflitos e discursos resistentes. Nesse sentido é que o enfoque dado à pesquisa buscou compreender e discutir a formação das Unidades de Conservação (UCs) e suas implicações sociopolíticas na região total do PEST. This dissertation concerns the Serra do Tabuleiro State Park (Parque Estadual da Serra do Tabuleiro - PEST), in the Santa Catarina state, Brazil, and the history of some of its social-environmental conflicts. The STSP is inserted in the Atlantic Forest bioma and it is considered one of the main conservation units in Brazil, for its territory hosts many different ecosystems such as Restinga vegetations, Araucaria pine forests, Atlantic Rainforests, Cloud forests, Altitude fields, and Mangue vegetations. The Santa Catarina State Environment Foundation (Fundação do Meio Ambiente de Santa Catarina # FATMA) has been developing the concept of the STSP as #the sanctuary of biodiversity#, though this permanent conservation unit is inhabited in its countryside; these people have been removed or their economical activities have been obstructed, which has generated countless conflicts. This research has focused on the formation of the Conservation Units (CUs) and the sociopolitical implications within the PEST area
Il contributo degli Enti locali alla riduzione dei gas serra
No full textIl primo testo che nel 2004, prima dell'applicazione del Protocollo di Kyoto per la riduzione dei gas serra, ha definito il ruolo sempre più attivo degli Enti locali rispetto alla più importante sfida ambientale di questo secolo: i cambiamenti climatici e le emissioni inquinanti. Politiche e azioni dei Comuni italiani in termini di efficienza energetica, fonti rinnovabili, mobilità sostenibile. Questo studio - frutto della collaborazione tra ANCI e Kyoto Club, ha messo in evidenza le attività svolte nel decennio 1994 - 2004, ed il ruolo dei Comuni e delle Province
How to choose the best iterative strategy for symmetric Toeplitz systems
No full textIn the last decade many efficient iterative solvers for n × n symmetric (also Hermitian or generic) Toeplitz systems have been devised [R. H. Chan and G. Strang, SIAM J. Sci. Stat. Comput., 10 (1989), pp. 104-119; T. F. Chan, SIAM J. Sci. Stat. Comput., 9 (1988), pp. 766-771; D. Bini and F. Di Benedetto, Proceedings, 2nd SPAA Conference, 1990, pp. 220-223; D. Bini and P. Favati, SIAM J. Matrix Anal. Appl., 14 (1993), pp. 500-507; T. Huckle, SIAM J. Matrix Anal. Appl., 13 (1992), pp. 767-777; F. Di Benedetto, G. Fiorentino, and S. Serra, Comput. Math. Appl., 26 (1993), pp. 35-45; S. Serra, SIAM J. Matrix Anal. Appl., 17 (1996), pp. 1007-1019; G. Fiorentino and S. Serra, Calcolo, 28 (1991), pp. 283-305; S. Serra, SIAM J. Matrix Anal. Appl., 20 (1998), pp. 31-44]. In all these methods it is assumed that the considered systems have the form An(f)x = b where the symbol f, the generating function, is an L1 function and the entries of An(f) along the kth diagonal coincide with the kth Fourier coefficient of f. The proof of convergence and sometimes even the definition of these solvers are derived by using some symbolic or analytic properties of f, while this function is often unknown in real applications. In this paper, by means of the knowledge of the coefficients of An(f) only, we propose and discuss an algorithm to economically determine the minimal features of f allowing us to choose and define the best iterative strategy. As a consequence of the analysis of the proposed procedure, we find some results on the structure of "quasi algebra" of the set {An(f)}f∈L1. Finally, we exhibit several numerical experiments which confirm the effectiveness of the proposed idea
Block generalized locally Toeplitz sequences: theory and applications in the multidimensional case. ETNA - Electronic Transactions on Numerical Analysis
No full textIn computational mathematics, when dealing with a large linear discrete problem (e.g., a linear system) arising from thenumerical discretization of a partial differential equation (PDE), knowledge of the spectral distribution of the associated matrix has proved to beuseful information for designing/analyzing appropriate solvers–-especially, preconditioned Krylov and multigrid solvers–-for the considered problem.Actually, this spectral information is of interest also in itself as long as the eigenvalues of the aforementioned matrix represent physical quantities of interest,which is the case for several problems from engineering and applied sciences (e.g., the study of natural vibration frequencies in an elastic material).The theory of multilevel generalized locally Toeplitz (GLT) sequences is a powerful apparatus for computing the asymptotic spectral distribution of matrices arising from virtually any kind of numerical discretization of PDEs. Indeed, when the mesh-fineness parameter tends to infinity, these matrices give rise to asequence , which often turns out to be a multilevel GLT sequence or one of its “relatives”, i.e., a multilevel block GLT sequence or a (multilevel) reduced GLTsequence. In particular, multilevel block GLT sequences are encountered in the discretization of systems of PDEs as well as in the higher-order finite element or discontinuousGalerkin approximation of scalar/vectorial PDEs.In this work, we systematically develop the theory of multilevel block GLT sequences as an extension of the theories of (unilevel) GLT sequences[Garoni and Serra-Capizzano, Generalized Locally Toeplitz Sequences: Theory and Applications. Vol. I., Springer, Cham, 2017],multilevel GLT sequences[Garoni and Serra-Capizzano, Generalized Locally Toeplitz Sequences: Theory and Applications. Vol. II., Springer, Cham, 2018],and block GLT sequences[Barbarino, Garoni, and Serra-Capizzano, Electron. Trans. Numer. Anal., 53 (2020), pp. 28–112].We also present several emblematic applications of this theory in the context of PDE discretizations
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