262,848 research outputs found
On the approximability of the L(h, k)-labelling problem on bipartite graphs (Extended abstract)
No full textGiven an undirected graph G, an L(h, k)-labelling of G assigns colors to vertices from the integer set {0,.. lambda(h,k)}, such that any two vertices v(i) and v(j) receive colors c(v(i)) and c(v(j)) satisfying the following conditions: i) if v(i) and v(j) are adjacent then vertical bar c(v(i)) - c(v(j))vertical bar >= h; ii) if v(i) and v(j) are at distance two then vertical bar c(v(i)) - c(v(j))vertical bar >= k. The aim of the L(h, k)-labelling problem is to minimize lambda(h,k)- In this paper we study the approximability of the L(h,k)-labelling problem on bipartite graphs and extend the results to s-partite and general graphs. Indeed, the decision version of this problem is known to be DIP-complete in general and, to our knowledge, there are no polynomial solutions, either exact or approximate, for bipartite graphs. Here, we state some results concerning the approximability of the L(h,k)-labelling problem for bipartite graphs, exploiting a novel technique, consisting in computing approximate vertex- and edge-colorings of auxiliary graphs to deduce an L(h, k)-labelling for the input bipartite graph. We derive an approximation algorithm with performance ratio bounded by (4)/D-3(2), where, D is equal to the minimum even value bounding the minimum of the maximum degrees of the two partitions. One of the above coloring algorithms is in fact an approximating edge-coloring algorithm for hypergraphs of maximum dimension d, i.e. the maximum edge cardinality, with performance ratio d. Furthermore, we consider a different approximation technique based on the reduction of the L(h, k)-labelling problem to the vertex-coloring of the square of a graph. Using this approach we derive an approximation algorithm with performance ratio bounded by min(h, 2k)root n + o(k root n), assuming h >= k. Hence, the first technique is competitive when D O(n(1/4)) These algorithms match with a result in [2] stating that L(1,1) labelling n-vertex bipartite graphs is hard to approximate within(n1/2-)epsilon, for any epsilon > 0, unless NP=ZPP. We then extend the latter approximation strategy to s-partite graphs, obtaining a (min(h, sk)root n + o(sk root n))-approximation ratio, and to general graphs deriving an (h root n + o(h root n))-approximation algorithm, assuming h >= k. Finally, we prove that the L(h, k)-labelling problem is not easier than coloring the square of a graph
ASMA BRONCHIALE E RINITE ALLERGICA: RUOLO DEL RECETTORE ST2 SUI LINFOCITI T HELPER 2
No full textAsma bronchiale e rinite allergica: ruolo del recettore ST2 sui linfociti T helper 2
Introduzione: Secondo recenti ricerche i linfociti T helper 2 (Th2) sono coinvolti nello stato infiammatorio cronico associato all'asma bronchiale e alla rinite allergica (1). Un ruolo importante nella patogenesi è stato attribuito alla produzione epiteliale di alcune nuove citochine, come l’IL-17A e l’IL-33 con il suo peculiare recettore ST2 espresso selettivamente sulle cellule Th2 (2,3). L’IL-17A e l’IL-33 sono implicate nell’indurre l’infiammazione Th2 dipendente della mucosa bronchiale e nasale innescando la produzione di altre citochine infiammatorie tra cui l’IL-31(4).
Materiali e Metodi: Campioni di plasma sono stati raccolti da pazienti con rinite allergica, da pazienti con comorbidità asma/rinite e da soggetti controllo, reclutati per lo studio in seguito ad anamnesi fisiopatologica, intervista preliminare, spirometria e Prick Test. Le concentrazioni plasmatiche dell’IL-31, dell’IL-33 e dell’IL-17A sono state misurate con dosaggio ELISA. Inoltre, l’IL-17A, l’IL-31 e il recettore ST2 sono stati acquisiti e valutati mediante analisi al citofluorimetro sui PBMC isolati dal sangue periferico di alcuni dei suddetti pazienti. Infine, si è proceduto alla valutazione dell’attività in vitro di uno steroide, il Beclometasone Dipropionato (BDP) (10−8M e 10−7M), sull’espressione delle citochine intracellulari IL-17A e IL-31 in associazione con il recettore ST2 in colture di PBMCs.
Risultati: È stato osservato che i livelli plasmatici di IL-17A, IL-31 e IL-33 sono aumentati in maniera statisticamente significativa sia nei pazienti con rinite allergica che nei pazienti con comorbidità asma/rinite rispetto ai controlli. I dati ottenuti dall'analisi al citofluorimetro hanno rivelato incrementi statisticamente significativi di espressione delle citochine intracellulari IL-17A e IL-31 in ognuno dei gruppi di pazienti allergici rispetto al gruppo controllo. Allo stesso tempo, i livelli di espressione del recettore ST2 sulle cellule degli stessi pazienti sono risultati considerevolmente più bassi rispetto ai controlli. Infine, è stato osservato che il BDP riduce significativamente i livelli intracellulari di IL-17A e di IL-31 nei PBMCs di questi pazienti in confronto alla baseline e che, per quanto riguarda invece l’espressione del recettore ST2 sulla membrana delle cellule T, è stato riscontrato un aumento dose-dipendente, che diventa significativo alla concentrazione di BDP 10-7M.
Conclusioni: In base ai dati sperimentali ottenuti, si è potuto quindi concludere che esiste una correlazione tra l’aumento di IL-17A, l’attivazione dell’asse IL-33/ST2 e l’incremento di IL-31 nell’asma bronchiale e nella rinite allergica e che queste tre nuove citochine potrebbero quindi rappresentare dei validi biomarcatori valutabili per la patogenesi e per la diagnosi di asma e rinite. Infine, i risultati di questo studio hanno supportato il potenziale approccio terapeutico mediante l’impiego di BDP nel controllo dell’infiammazione locale e sistemica, generata dalla risposta immunitaria Th2- e Th17-mediata, in pazienti con malattie infiammatorie allergiche delle vie aeree.
1. Saenz SA et al. IL25 elicits a multipotent progenitor cell population that promotes T(H)2 cytikine responses. Nature. 2010;464(7293):1362-6.
2. Glück J. et al. Serum IL-33 but not ST2 level is elevated in intermittent allergic rhinitis and is a marker of the disease severity. Inflamm. Res. 2012;61:547-550.
3. Kamekura R. et al. The role of IL-33 and its receptor ST2 in human nasal epithelium with allergic rhinitis. Clin. Exp.Allergy. 2012;42(2):218-228.
4. Okano M. et al. Characterization of pollen antigen-induced IL-31 production by PBMCs in patients with allergic rhinitis. JACI. 2010;127(1):277-9.Bronchial Asthma and Allergic Rhinitis: Role of ST2 receptor on T helper 2 lymphocytes.
Introduction: T helper 2 (Th2) lymphocytes play an important role in the chronic inflammatory process concerning bronchial asthma and allergic rhinitis (1), regulating the production of some new cytokines, IL-17A and IL-33 with ST2 receptor, selectively expressed on the Th2 cells surface (2, 3), by the airway epithelium. IL-17A and IL-33 are involved in the Th2 cells-mediate induction of the bronchial and nasal mucosa inflammation, triggering the production of more inflammatory cytokines, including IL-31 (4).
Materials and Methods: Plasma samples from allergic rhinitis, both asthma and rhinitis patients and control subjects were collected. These subjects were recruited for this study following pathophysiological history, preliminary interview, spirometry and Prick Test. Plasma concentrations of IL-31, IL-33 and IL-17A were measured by ELISA. Also, IL-17A, IL-31 and ST2 receptor were evaluated by flow cytometric analysis on peripheral blood mononuclear cells (PBMC) of some of these patients. After all, the in vitro activity of a steroidal drug, Beclomethasone Dipropionate (BDP) (10−8M e 10−7M), was evaluated on the intracellular cytokines IL-17A and IL-31 expression, together with ST2 receptor levels in PBMCs cultures.
Results: IL-17A, IL-31 e IL-33 plasma levels were significantly higher in patients with allergic rhinitis and in those with both asthma and rhinitis than in control subjects. Flow cytometer data show that the expression of the intracellular cytokines IL-31 and IL-17A were increased in all patients categories compared to controls. At the same time, ST2 receptor expression levels, on T cells surface of these same patients, were significantly lower than those in control subjects. Finally, has been observed that BDP substantially decreases intracellular levels of IL-17A and IL-31 cytokines in PBMCs of these patients compared to baseline. Rather, the ST2 receptor surface expression was increased in a dose-dependent manner and, significantly, at BDP concentration 10-7M.
Conclusions: In the present study, the experimental data suggest that there is a correlation between higher levels of IL-17A, activation of IL-33/ST2 axis and increased concentration of IL-31 in bronchial asthma and allergic rhinitis and that these three new cytokines could therefore represent valid biomarkers evaluable in the pathogenesis and diagnosis of both diseases. At last, the results of this study supported the potential therapeutic approach by BDP in local and systemic inflammation control, of Th2 and Th17 immune response, in patients with inflammatory diseases of allergic airways.
1. Saenz S.A. et al. IL25 elicits a multipotent progenitor cell population that promotes T(H)2 cytokine responses. Nature. 2010;464(7293):1362-6.
2. Glück J. et al. Serum IL-33 but not ST2 level is elevated in intermittent allergic rhinitis and is a marker of the disease severity. Inflamm. Res. 2012;61:547-550.
3. Kamekura R. et al. The role of IL-33 and its receptor ST2 in human nasal epithelium with allergic rhinitis. Clin. Exp.Allergy. 2012;42(2):218-228.
4. Okano M. et al. Characterization of pollen antigen-induced IL-31 production by PBMCs in patients with allergic rhinitis. JACI. 2010;127(1):277-9
Teoria dei giochi
No full textLa Teoria dei Giochi è la scienza matematica che analizza situa zioni di conflitto e ne ricerca soluzioni competitive e cooperative. Studia le decisioni individuali in situazioni in cui vi sono interazioni tra diversi soggetti. È una disciplina relativamente nuova, formalizzata all’inizio del secolo scorso, e recentemente venuta all’attenzione del grande pubblico grazie anche alla pubblicazione di diversi saggi divulgativi e non, ma soprattutto per la realizzazione di film e citazioni in telefilm ad ampia diffusione che ne hanno descritto, seppur in maniera informale e romanzata, alcuni aspetti più caratteristici e intriganti.
Gli strumenti della Teoria dei Giochi permettono di analizzare le eventuali situazioni di equilibrio e la loro bontà rispetto a una soluzione ottima dal punto di vista sociale. Le sue applicazioni e interazioni sono molteplici: dall’economia e finanza, alle strategie militari; dalla politica alla sociologia, dalla psicologia all’informatica, dalla biologia allo sport.
In questo breve lavoro si intende descriverne i princìpi fondamentali e fornirne alcuni esempi tra i più significativi, senza pretendere di entrare nei dettagli matematici sottostanti che, pur di per sé decisamente interessanti, sono al di là dello scopo di questo articolo.
Per concludere, si analizzerà un altro aspetto della Teoria dei Giochi riguardante il Mechanism Design che si occupa di progettare meccanismi che conducano i giocatori di un gioco a fare delle scelte che siano in accordo con il concetto di soluzione prefissata. In questo contesto, mostreremo come qualunque sistema di voto non sia equo e possa essere manipolato, essendo il solo sistema non manipolabile la dittatura.
o il solo sistema non manipolabile la dittatura
Area requirement of Proximity Drawings
No full textIn this paper we investigate the area requirement of proximity drawings and we prove an exponential lower bound. Our main contribution is to show the existence of a class of Gabriel-drawable graphs that require exponential area for any Gabriel drawing and any resolution rule. The result is further extended to an infinite class of proximity drawings
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
Area requirement of Gabriel drawings
No full textIn this paper we investigate the area requirement of proximity drawings and we prove an exponential lower bound. Our main contribution is to show the existence of a class of Gabriel-drawable graphs that require exponential area for any Gabriel drawing and any resolution rule. The result is further extended to an infinite class of proximity drawings
A comparison between nonlinear cantilever and buckled beam for energy harvesting
No full textNonlinear dynamics has become one of the key aspect to improve the efficiency of kinetic energy harvesters working in the real environment. Different methods based on the exploitation of the dynamical features of stochastic nonlinear oscillators using bi-stable piezoelectric cantilevers or buckled beams have been proposed in the past years. Such methods are shown to outperform standard linear oscillators and to overcome some of the most severe limitations of present approaches once applied to ambient vibrations. This work presents simulation results comparing the two methods. The same piezoelectric element subjected to a fixed vibrating body in a cantilever or bridge configuration has been simulated. The kinetic excitation considered is a zero mean exponentially correlated gaussian noise with different amplitudes. The piezoelectric oscillator output response has been obtained as a function of a nonlinear parameter. This work is intended to help designing the most performing energy harvester for real world applications starting from the same piezoelectric element
Protecting Animals 36: Author Witi Ihimaera
No full textIn this very special episode of Knowing Animals I am joined by beloved New Zealand author Witi Ihimaera. Witi has written many books featuring nonhuman animals. He offers us a non-colonial lens through which to think about the human/nonhuman relationship
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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