752 research outputs found

    Partially Isometric Immersions and Free Maps

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    In this paper we investigate the existence of ``partially'' isometric immersions. These are maps f:M->R^q which, for a given Riemannian manifold M, are isometries on some sub-bundle H of TM. The concept of free maps, which is essential in the Nash--Gromov theory of isometric immersions, is replaced here by that of H-free maps, i.e. maps whose restriction to H is free. We prove, under suitable conditions on the dimension q of the Euclidean space, that H-free maps are generic and we provide, for the smallest possible value of q, explicit expressions for H-free maps in the following three settings: 1-dimensional distributions in R^2, Lagrangian distributions of completely integrable systems, Hamiltonian distributions of a particular kind of Poisson Bracket.Comment: 19 pages, 1 figur

    Preliminari alla ricomposizione dell’opera omnia di Antonio Simon Mossa: le fonti bibliografiche e l’archivio di famiglia

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    Il ritrovamento, nel 2007, dell’archivio personale di Antonio Simon Mossa ha aperto la strada a un approccio filologico verso una produzione assai più vasta di quanto generalmente ritenuto. Il confronto in atto tra il materiale restituito dall’archivio e la relativamente scarsa bibliografia finora edita si sta rivelando, a lavori ancora in corso, fondamentale punto di partenza per la ricomposizione di un’opera ampia, eclettica, estremamente frazionata e dispersa in una miriade di fonti, molte delle quali ancora da esplorare

    LivDet 2017 Fingerprint Liveness Detection Competition 2017

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    Fingerprint Presentation Attack Detection (FPAD) deals with distinguishing images coming from artificial replicas of the fingerprint characteristic, made up of materials like silicone, gelatine or latex, and images coming from alive fingerprints. Images are captured by modern scanners, typically relying on solid-state or optical technologies. Since from 2009, the Fingerprint Liveness Detection Competition (LivDet) aims to assess the performance of the state-of-the-art algorithms according to a rigorous experimental protocol and, at the same time, a simple overview of the basic achievements. The competition is open to all academics research centers and all companies that work in this field. The positive, increasing trend of the participants number, which supports the success of this initiative, is confirmed even this year: 17 algorithms were submitted to the competition, with a larger involvement of companies and academies. This means that the topic is relevant for both sides, and points out that a lot of work must be done in terms of fundamental and applied research.Comment: presented at ICB 201

    Balanced metrics on homogeneous vector bundles

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    Let E→ME\rightarrow M be a holomorphic vector bundle over a compact Kaehler manifold (M,ω)(M, \omega) and let E=E1⊕...⊕Em→ME=E_1\oplus... \oplus E_m\rightarrow M be its decomposition into irreducible factors. Suppose that each EjE_j admits a ω\omega-balanced metric in Donaldson-Wang terminology. In this paper we prove that EE admits a unique ω\omega-balanced metric if and only if rjNj=rkNk\frac{r_j}{N_j}=\frac{r_k}{N_k} for all j,k=1,...,mj, k=1, ..., m, where rjr_j denotes the rank of EjE_j and Nj=dim⁡H0(M,Ej)N_j=\dim H^0(M, E_j). We apply our result to the case of homogeneous vector bundles over a rational homogeneous variety (M,ω)(M, \omega) and we show the existence and rigidity of balanced Kaehler embedding from (M,ω)(M, \omega) into Grassmannians.Comment: 5 page

    Dieci partigiani ossesi nella Resistenza italiana

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    La ricostruzione delle vicende biografiche dei dieci partigiani originari di Ossi finora identificati, riproponendo implicitamente il tema del rapporto fra vicissitudini individuali ed eventi storici, si inserisce nel più ampio contesto del contributo della ricerca locale e settoriale alla storiografia della Resistenza. In tal senso l’articolo, sintesi introduttiva di una monografia in corso di pubblicazione, si propone come ulteriore tassello nel quadro degli studi tuttora in corso sul contributo dei sardi alla guerra di Liberazione

    Photophysics of pentacene-doped picene thin films

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    Here were report a study of picene nano-cristalline thin films doped with pentacene molecules. The thin films were grown by supersonic molecular beam deposition with a doping concentration that ranges between less than one molecules of pentacene every 104 picene molecules up to about one molecule of pentacene every 102 of picene. Morphology and opto-electronic properties of the films were studied as a function of the concentration of dopants. The optical response of the picene films, characterized by absorption, steady-state and time-resolved photoluminescence measurements, changes dramatically after the doping with pentacene. An efficient energy transfer from the picene host matrix to the pentacene guest molecules was observed giving rise to an intense photoluminescence coming out from pentacene. This efficient mechanism opens the possibility to exploit applications where the excitonic states of the guest component, pentacene, are of major interest such as MASER. The observed mechanism could also serve as prototypical system for the study of the photophysics of host guest systems based on different phenacenes and acenes.Comment: 15 pages, 6 figure

    Early increase in cyclin-D1 expression and accelerated entry of mouse hepatocytes into S phase after administration of the mitogen 1,4-bis[2-(3,5-dichloropyridyloxy)] benzene

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    We have previously demonstrated that hepatocyte proliferation induced by the mitogen 1,4-bis[2-(3,5-dichloropyridyloxyl)] benzene (TCPOBOP) is independent of changes in cytokines, immediate early genes, and transcription factors that are considered to be necessary for regeneration of the liver after partial hepatectomy (PH) or necrosis. To further investigate the differences between mitogen-induced mouse hepatocyte proliferation and liver regeneration after PH, we have measured the expression of cyclin D1, cyclin D3, cyclin E, and cyclin A and of the cyclin-dependent kinases CDK2, CDK4, and CDK6. The involvement of the cyclin-dependent kinase inhibitors p21 and p27 and of the oncosuppressor gene p53 was also examined at different times after stimulation of hepatocyte proliferation. Results showed that a single administration of TCPOBOP caused a very rapid increase in the levels of cyclin D1, a G1 protein, when compared with two thirds PH (8 hours versus 30 hours). The early increase in cyclin D1 protein levels was associated with a faster onset of increased expression of S-phase-associated cyclin A. (24 hours versus 36 hours with PH mice). Accordingly, measurement of bromodeoxyuridine (BrdU) incorporation revealed that, although approximately 8% of hepatocytes were BrdU-positive as early as 24 hours after TCPOBOP, no significant changes in BrdU incorporation were observed at the same time point after two thirds PH. The expression of other proteins involved in cell cycle control, such as cyclin-dependent kinases (CDK4, CDK2, CDK6), was also analyzed. Results showed that expression of CDK2 was induced. much more rapidly in TCPOBOP-treated mice (2 hours) than in mice subjected to PH (36 hours), A different pattern of expression in the two models of hepatocyte proliferation, although less dramatic, was also observed for CDK4 and CDK6. Expression of the CDK inhibitors p21 and p27 and the oncosuppressor gene p53 variably increased after two thirds PH, whereas basically no change in protein levels was found in TCPOBOP-treated mice. The results demonstrate that profound differences in many cell cycle-regulatory proteins exist between direct hyperplasia and compensatory regeneration. Cyclin D1 induction is one of the earlier events in hepatocyte proliferation induced by the primary mitogen TCPOBOP and suggests that a direct effect of the mitogen on this cyclin may be responsible for the rapid onset of DNA synthesis observed in TCPOBOP-induced hyperplasia
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