178,953 research outputs found
PGPDT: Parallel Gradient Projection-based Decomposition Technique
No full textGPDT is a C++ software designed to train large-scale Support Vector Machines (SVMs) for binary classification in both scalar and distributed memory parallel environments [1,3,5,6]. It uses a popular problem decomposition technique to split the SVM quadratic programming (QP) problem into a sequence of smaller QP subproblems, each one being solved by a suitable gradient projection method (GPM). The currently implemented GPMs are the Generalized Variable Projection Method (GVPM) [2] and the Dai-Fletcher method (DFGPM) [4]. [1] G. Zanghirati, L. Zanni, A Parallel Solver for Large Quadratic Programs in Training Support Vector Machines, Parallel Computing 29 (2003), 535-551.[2] T. Serafini, G. Zanghirati, L. Zanni, Gradient Projection Methods for Large Quadratic Programs and Applications in Training Support Vector Machines, Optim. Meth. Soft. 20 (2005), 353-378.[3] T. Serafini, L. Zanni, On the Working Set Selection in Gradient Projection-based Decomposition Techniques for Support Vector Machines, Optim. Meth. Soft. 20 (2005), 583-596.[4] Y.H. Dai, R. Fletcher, New Algorithms for Singly Linearly Constrained Quadratic Programming Problems Subject to Lower and Upper Bounds, Math. Prog. 106(3) (2006), 403-421. [5] L. Zanni, An Improved Gradient Projection-based Decomposition Technique for Support Vector Machines, Computational Management Science 3(2) (2006), 131-145.[6] L. Zanni, T. Serafini, G. Zanghirati, Parallel Software for Training Large Scale Support Vector Machines on Multiprocessor Systems, JMLR 7(Jul), 1467-1492, 2006
TRANSGLUTAMINASES IN SENESCENCE AND PROGRAMMED CELL DEATH OF LEAVES AND PETALS: THEIR SIMILARITIES TO ANIMAL TRANSGLUTAMINASES
No full textFree polyamines (PAs) have a contrasting role in the delay of senescence in animals, whereas in plants its protective effect is better established, eventhough the molecular mechanism is not clarified. We hypothesised that PAs can be conjugated to specific proteins by catalysis of Ca++-dependent transglutaminases (TGases). TGases are involved in PCD in animals, whereas few data are available in plants. Plants utilized were: Nicotiana tabacum corolla, models of short-lived flowers and Lactuca sativa leaves, commercially utilised for food purposes. Many morphological and physiological parameters were examined.
The supply of spermine (SM) to excised flowers or entire plant efficiently delayed senescence and PCD in petals or leaves respectively. SM caused an increase also of putrescine (PU) and spermidine (SD) levels. Only in senescent plants a new TGase band was immunodetected and, in concomitance, high molecular mass and other protein bands were PA-modified. During senescence mainly mono-, bis-PU and bis-SD catalysis increased. This data suggests that the protective effect of PAs could be mediated by TGase. SM effect on the retention of leaf proteins and chlorophylls was analysed in Valeriana young and senescent plants. Most of chlorophyll is bound to the antennae of light-harvesting complexes (LHC), known preferential thylakoid TGase substrates under light2. In Valeriana LHC enriched fractions, different TGase isoforms, immunologically related to TGases of animal origin, were co-purified. PA conjugation to both photosystems was light-stimulated.
The capacity of plants to express animal TGases and the similarities in the TGase sequences and activity in animals and plants have also been explored. Rat TGase (DP1 ORF) introduced into mature rice embryos by bombardment was expressed by the plant. It is Ca2+-dependent and active in in vitro assay, showing that plants could produce functional mammalian TGases3. Thylakoid TGase recognises animal substrates as well as animal TGases plant substrates, but only the plant TGase/plant substrate catalysis is light regulated2.
As in both the investigated senescence models any TGase has been fully-purified until now, another approach was undertaken. On the basis of the identification of a TGase-like domain in an A. thaliana gene, AtPng1p, we have cloned its codifying sequence on E. coli and purified the over-expressed recombinant protein. All biochemical assays showed a clear Ca++, pH, and DTT dependent TGase activity. This TGase was immunodetected by three antibodies raised against animal TGases. Data and bio-informatic analysis also suggest a possible protease activity for this first plant sequenced TGase4.
1 D Serafini-Fracassini, S Del Duca, F Monti, F Poli, G Sacchetti, AM Bregoli, S Biondi and M Della Mea (2002) -Transglutaminase activity during senescence and programmed cell death in the corolla of tobacco (Nicotian a tabacum) flowers. Cell Death and Diff. 9 (3) 309-321.
2 M. Della Mea, A. Di Sandro, L. Dondini, S. Del Duca, F.Vantini, C.Bergamini, R. Bassi and D. Serafini-Fracassini - A Zea mays 39 kDa thylakoidal transglutaminase catalyses the modification by polyamines of light harvesting complex II in a light-dependent way. Planta, in press. DOI 10.1007/s00425-004-1278-6
Asymptotic behaviour in age dependent population dynamics with spatial spread
No full textTh paper investigates a model of age-dependent population growth with spatial diffusion. The model equations are the linear McKendrick equations with an added diffusion term. These are reduced to an abstract Volterra integral equation by means of a semigroup approach. Using Laplace transform techniques, the authors then derive an asymptotic expression for the solution for large time
When form is substance. Castles of Puglia and the art of building
No full textOn the basis of first-hand architectural surveys based on an integrated approach (topographical, aero- photogrammetric,digitalterrestrialphotogrammetric,3Dlaseracquisitions),bothat small and large scales, this contribution intends to draw attention to the reality of fortified buildings that, due to the richness of their palimpsests and the singularity of their transformations, can serve as research laboratories and reference points for all others.In addition to increasing historical research,the aim is also to provide new arguments for the reasons of conservation. When they have not disappeared or been violated by incon- gruous interventions, the heritage of Apulia's fortified factories is in fact in a precarious condition, if not in a state of ruin, thus requiring new ways of protection and reconnection with the reference landscapes
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Inhibition of pollen tube growth is controlled by the inhibition of a novel extracellular transglutaminase activity: is transglutaminase involved in the subsequent pollen self-incompatibility PCD events?
No full textPlant sexual reproduction involves the interaction between male and female gametophytes, which still remains an enigma, and requires the Ca2+-dependent growth of pollen tube (male gametophyte).
We report the detection of the first extracellular plant TGase and demonstration that its extracellular protein crosslinking activity is essential for pollen germination. Transglutaminases (TGase or TG) are Ca2+-dependent widespread enzymes able to post-translationally modify proteins by forming bridges between protein-bound glutaminyl residues and -lysines or polyamines (1). TGases are also involved in apoptosis: for instance, crosslinking by TG2 facilitates the phagocytic clearance of dead cells (1). The research on plant TGases lags much more behind that in mammalian cells, however TGase is also involved in flower PCD (2).
In our model, extracellular inhibition of transamidating activity either by a monoclonal anti-TGase antibody or irreversible site directed inhibitors blocked pollen tube growth. TGase, immunolocalised on the pollen tube surface, was also capable of crosslinking labelled amines and the H6-Xpr-GFP substrate into extracellular proteins in immediate contact with the pollen tube. Contribution of TGase-mediated crosslinking in the pollen tube wall formation was confirmed also by the immunodetection of (-glutamyl)lysine crosslinks. These findings suggest that the enzyme functions in the attachment of the pollen tube to the female style and in the stabilisation of the pollen tube wall. Plant cell wall has been described as a cellular compartment important in cell communication. A well-documented case of this sort is the rejection of self-pollen in the self-incompatiblility (SI) reaction. SI-specific events involved in a PCD signalling pathway are subsequent to inhibition of pollen tube growth. As the extracellular matrix (ECM) is a key regulator of gametophyte communication, ongoing work is focusing on the putative involvement of the extracellular pollen TGase in the SI events that follows the inhibition of incompatible pollen tube growth.
1. Lorand L and Graham R M. (2003). Transglutaminases: crosslinking enzymes with pleiotropic functions. Nature Reviews Molecular Cell Biology Vol. 4, February 2003.
2. Serafini-Fracassini D, Del Duca S, Monti F, Poli F, Sacchetti G, Bregoli AM, Biondi S, Della Mea M. (2002). Transglutaminase activity during senescence and programmed cell death in the corolla of tobacco (Nicotiana tabacum) flowers.Cell Death Differ.: 9(3):309-21
Conservare per sopravvivere: l’eredità di Mauro Civita (1933-2003) (paragrafo "Palinsesti architettonici. Il cantiere di restauro come luogo di comprensione della fabbrica e banco di prova per il progetto", pp. 22-31)
No full text"Preserving to survive" is the title of the text published by Mauro Civita in Granada, in 1984, as a collection of his Conversations in Baeza: lessons held in September of the previous year at the Universidad Internacional "Antonio Machado" of Baeza, which are placed in the broad framework of international relations that the Apulian professor and architect was establishing in those years, both in the fields of teaching and scientific research. The conversations are actually communications on the restoration of factories and historic centers, especially in Puglia, which provide Civita with the opportunity to collect in the title a work program established by him between the "G. D'Annunzio" University of Chieti and Pescara , where he taught for eighteen years starting in 1977, and UNAM, the National Autonomous University of Mexico City, which gave him the opportunity to successfully deal with a culture that was distant but only geographically, assumed as a counterpoint and food of an experience that to this day the Abruzzo University preserves among its most precious legacies, and which is the support of the same collection of essays in this volume. Undoubtedly Mauro Civita was an important witness of the history of restoration in Italy and in the world, also by virtue of his bond with Roberto Pane (1897-1987) and a relationship of continuity with respect to them that goes from the end of the seventies until the death of the Neapolitan master."Conservare per sopravvivere" è il titolo del testo pubblicato da Mauro Civita a Granada, nel 1984, a raccolta delle sue Conversazioni in Baeza: lezioni tenute nel settembre dell'anno prima alla Universidad Internacional "Antonio Machado" di Baeza, che si collocano nell'ampio quadro dei rapporti internazionali che il professore e architetto pugliese andava stabilendo in quegli anni, sia nell'ambito della didattica che della ricerca scientifica. Le conversazioni sono in realtà comunicazioni sui restauri di fabbriche e centri storici, soprattutto pugliesi, che forniscono a Civita l'opportunità di raccogliere nel titolo un programma di lavoro da lui stabilito tra l'Università "G. D'Annunzio" di Chieti e Pescara, dove insegna per diciotto anni a partire dal 1977, e la UNAM, L'Università Nazionale autonoma di Città del Messico, che gli dà l'occasione di confrontarsi, con successo, con una cultura lontana ma solo geograficamente, assunta a contrappunto e alimento di un'esperienza che a tutt'oggi l'Ateneo abruzzese conserva tra le sue più preziose eredità, e che è il sostegno della stessa raccolta di saggi del presente volume. Senz'altro Mauro Civita è stato un testimone importante della storia del restauro in Italia e nl mondo, anche in virtù del suo legame con Roberto Pane (1897-1987) e di un rapporto di continuità rispetto a questi che va dalla fine degli anni Settanta fino alla morte del maestro napoletano
Interpreting the mechanism of action of polyamines: twenty years of plant transglutaminases
No full textThe post-translational modification of proteins by polyamines forming inter- or intra-molecular cross-links has been the main transglutaminase (TGase) reaction studied in plants. Plant transglutaminases have been studied in our laboratory since 1987 in investigations aimed at interpreting some of the molecular mechanisms by which polyamines affect plant growth, differentiation, reaction to stresses, PCD. Transglutaminase activity is ubiquitous: it has been detected in algae and in angiosperms in different organs and sub-cellular compartments: chloroplasts, cytosol, microsomal fraction, cell walls (1).
Possible roles concern the structural modification of specific proteins. In the cytosol, they modify actin and tubulin, also influencing motor proteins, thus exerting a role on cell growth and cell structure (2). In chloroplasts, transglutaminases appear to stabilise the photosynthetic complexes and Rubisco, being regulated by light and other factors, and possibly exerting a positive effect on photosynthesis and photoprotection (1). Recent reports suggest an involvement in construction/organisation of the cell wall and extracellular matrix in relationship with fertilisation and a possible role of pollen extracellular TGase in cross-allergenicity. Other roles appear to be related to stresses, senescence and programmed cell death, including the hypersensitive reaction caused by TMV virus. The cross recognition of substrates between plant and animal enzymes suggest both similarities and differences. Proofs of their catalytic activity are: 1. their ability to produce glutamyl-polyamine derivatives, 2. their recognition by animal transglutaminase antibodies, 3. biochemical features such as calcium- and GTP-dependency, etc. 4. Inhibition by specific inhibitors of animal transglutaminases. However, many of their fundamental physiological properties still remain elusive. The few plant transglutaminases sequenced so far have little sequence homology with the best-known animal enzymes, except for the catalytic triad; however, they share a possible structural homology (3). Specificity and similarity with animal transglutaminases are discussed in the light of their biochemical characteristics and functional roles.
1. Serafini-Fracassini D and Del Duca S (2008) Tranglutaminases: widespread cross-linking enzymes in plants. Ann. Bot. 102, 145-152. DOI 10.1093/aob/mcn075. 2. Del Duca S. et al. (2008) Effects of post-translational modifications catalyzed by pollen transglutaminase on the functional properties of microtubules and actin filaments. Biochem. J., 418 3,651-664. 3. Serafini-Fracassini D, et al. (2008) Plant and animal transglutaminases: do similar functions imply similar structures? Amino Acids 36 (4) 643-657, DOI: 10.1007/s00726-008-0131-9
FUNDING: MUR-PRIN, Interaction mechanisms for protein mediators of flower incompatibility in fertilisation of fruit trees,to D.S-F;“Crossallergenicity”, Progetto Strategico d’Ateneo 2006 to D.S-F
Comment on Competition between coherent emission and broadband spontaneous emission in the quantum free electron laser : Phys. Plasmas 20, 033106 (2013)
No full textWe point out that in the equation for the electron distribution evolution during Thomson/Compton or undulator radiation used in the paper: “Competition between coherent emission and broadband spontaneous emission in the quantum free electron laser” by G. R. M. Robb and R. Bonifacio [Phys. Plasmas 20, 033106 (2013)], the weight function should be the distribution of the number of emitted photons and not the photon energy distribution. Nevertheless, the considerations expressed in this comment do not alter the conclusions drawn in the paper in object
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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