1,720,976 research outputs found
Partial Temporal Vertex Cover with Bounded Activity Intervals
No full textDifferent variants of Vertex Cover have recently garnered attention in the context of temporal graphs. One of these variants is motivated by the need to summarize timeline activities in social networks. Here, the activities of individual vertices, representing users, are characterized by time intervals. In this paper, we explore a scenario where the temporal span of each vertex’s activity interval is bounded by an integer l, and the objective is to maximize the number of (temporal) edges that are covered. We establish the APX-hardness of this problem and the NP-hardness of the corresponding decision problem, even under the restricted condition where the temporal domain comprises only two timestamps and each edge appears at most once. Subsequently, we delve into the parameterized complexity of the problem, offering two fixed-parameter algorithms parameterized by: (i) the number k of temporal edges covered by the solution, and (ii) the number h of temporal edges not covered by the solution. Finally, we present a polynomial-time approximation algorithm achieving a factor of 3/
Computing Bend-Minimum Orthogonal Drawings of Plane Series–Parallel Graphs in Linear Time
No full textA planar orthogonal drawing of a planar 4-graph G (i.e., a planar graph with vertex-degree at most four) is a crossing-free drawing that maps each vertex of G to a distinct point of the plane and each edge of G to a polygonal chain consisting of horizontal and vertical segments. A longstanding open question in Graph Drawing, dating back over 30 years, is whether there exists a linear-time algorithm to compute an orthogonal drawing of a plane 4-graph with the minimum number of bends. The term “plane” indicates that the input graph comes together with a planar embedding, which must be preserved by the drawing (i.e., the drawing must have the same set of faces as the input graph). In this paper we positively answer the question above for the widely-studied class of series–parallel graphs. Our linear-time algorithm is based on a characterization of the planar series–parallel graphs that admit an orthogonal drawing without bends. This characterization is given in terms of the orthogonal spirality that each type of triconnected component of the graph can take; the orthogonal spirality of a component measures how much that component is “rolled-up” in an orthogonal drawing of the graph
Epidemia di influenza aviaria nella regione Veneto: analisi dei costi degli interventi di controllo.
No full textLe epidemie di influenza aviaria, oltre a rappresentare un grave problema di carattere
sanitario, hanno causato ingenti danni economici a tutto il settore avicolo, compromettendo
l'economia di interi comparti produttivi. Inoltre, il pagamento dei danni diretti, che è a
carico della sanità pubblica, ha pesato in modo rilevante sui bilanci dello Stato. Dal 1997 al
2005 l'Italia è stata interessata da continue epidemie di influenza aviaria ad alta (HPAI) e
bassa (LPAI) patogenicità. Durante l'epidemia HPAI del 1999-2000 si sono verificati 413
focolai, per la maggior parte localizzati nelle aree a elevata densità zootecnica di Veneto e
Lombardia. L'elevata mortalità e gli abbattimenti dei gruppi di volatili infetti e sospetti
infetti, hanno portato all'eliminazione di 16 milioni di animali, determinando una notevole
perdita economica (più di 111 milioni di euro di danni diretti, circa 500 milioni
considerando anche i danni indiretti). Dopo l'epidemia HPAI, varie ondate epidemiche di
LPAI si sono verificate a partire dal 2000 fino al 2005. Per contenere la diffusione
dell'infezione ed eradicare la malattia, sono state adottate misure di controllo (abbattimento
dei gruppi infetti, macellazione controllata, misure di restrizione) e prevenzione (blocco
accasamenti, misure di biosicurezza). Inoltre, a partire da metà novembre del 2000, è stato
attuato un programma di vaccinazione di emergenza (PVE), approvato dalla Commissione
Europea (Decisione 2000/721/CE), per le specie avicole considerate maggiormente a
rischio e localizzate nelle aree densamente popolate di Veneto e Lombardia. Due campagne
vaccinali, la prima dal 2000 al 2002 e la seconda dal 2002 al 2006 (Decisione
2002/975/CE), hanno permesso di contenere l'infezione (l'ultima epidemia verificatasi
nella primavera del 2005 in provincia di Brescia ha visto coinvolti solo 15 allevamenti).
Nel presente lavoro vengono analizzati i costi sostenuti per l'estinzione dei focolai (158
aziende coinvolte e danni diretti per più di 54 milioni di euro), i danni indiretti a essa
collegati e i costi relativi alla campagna di vaccinazione, nella Regione Veneto dal 1999 al
2006 (fine del PVE). L'analisi economica effettuata, considerando gli indennizzi per la
distruzione di animali, uova, mangimi e altre spese connesse, riferiti all'epidemia HPAI, ha
evidenziato che i costi a carico del sistema sanitario nazionale (L 218/88), sono
sensibilmente più onerosi rispetto a quelli sostenuti per attuare il programma di
vaccinazione 2002/06, che ha interessato 513 aziende nell'area a maggior rischio di
infezione e a più alta densità di popolazione avicola (DPPA) a livello nazionale
Culture chevaleresque et Quatrième Croisade: quelques réflexions sur les motivations des croisés
No full textG. ORTALI, G. RAVEGNANI et P. SCHREINER (eds)International audienc
Epidemiology of Avian pathogenic Escherichia coli (APEC) in a finisching male turkey farm: longitudinal survey of three consecutive production cycles.
No full textThe purpose of this study was to investigate the epidemiology of APEC (Avian Pathogenic Escherichia coli), in a finishing male turkey commercial farm, conducting longitudinal surveys of three consecutive production cycles. The diversity and the distribution of APEC strains during the production cycles were examined using microbiological and molecular techniques. APEC isolates were serotyped, assessed for the presence of virulence-associated genes (pathogenic potential – pathotype) and for resistance to antibiotics (resistotype). Random Amplified Polymorphic DNA (RAPD) was applied to analyse their genetic relationship. Strains of high genetic homology were grouped into the same RAPD cluster (RAPD type).
Sampling included, when colisepticemic or articular lesions were observed, viscera and joints from day one until 14 weeks.
In the first cycle, APEC O78 was the most prevalent serotype with all isolates sharing the same resistotype and pathotype. Seven of them were included in the same RAPD cluster indicating high genetic similarity. In this cycle, APEC O111 was detected and this represents, to our knowledge,
In the second cycle, APEC O2 isolates predominated at the beginning, while O78 strains appeared later until the end of the survey. APEC O2 were classified in two resistotypes, same pathotype and RAPD type. APEC 078 belonged to three resistotypes, same pathotype and three RAPD types. APEC O78 strains, differently from serotype O2, were detected from both colisepticemic viscera (such as brain, pericardium, lungs) and joints. The articular tropism of this serotype is unique as it was observed only in APEC O78 strains of this cycle and of the previous one. Moreover, RAPD molecular studies identified a specific articular O78 cluster, including two strains, which was different from other RAPD clusters including O78 and O2 colisepticemic strains
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Characterization and antimicrobial resistance analysis of avian pathogenic Escherichia coli isolated from Italian turkey flocks
No full textThis study investigated the occurrence of avian pathogenic Escherichia coli (APEC) in a finishing turkey commercial farm, carrying out longitudinal surveys involving 3 consecutive flocks. The diversity and the distribution of the E. coli strains detected during colisepticemia outbreaks were examined. The strains were isolated, serogrouped, assessed for the presence of virulence-associated genes, typed by random amplification of polymorphic DNA (RAPD), and antimicrobial resistance analysis was then carried out. Escherichia coli O78 and O2 were predominantly found. Moreover, based on the somatic antigens used in the study, strains were recovered that were nontypeable. On one occasion, an E. coli O111 strain was found in turkeys. The E. coli isolates differed in terms of antibiotic resistance and RAPD profile. All strains possessed the virulence genes that enabled them to be considered APEC. Strains not only differed between flocks, but also within the same flock. These findings point out the importance of addressing colibacillosis therapy on the basis of a sensitivity test
Avian Metapneumovirus, Hemorrhagic Enteritis Virus and Avian Pathogenic Escherichia coli (APEC) interaction in a finishing turkey farm subjected to colibacillosis-associated mortality
No full textThe spectrum of pathogens responsible for colibacillosis-associated mortality is investigated by longitudinal surveys performed in three consecutive production cycles of a finishing toms farm. The surveys mainly focus on the interaction between Avian Metapneumovirus (AMPV), Haemorrhagic Enteritis Virus (HEV) and Avian Pathogenic Escherichia Coli (APEC). Rhino-pharyngeal swabs, cloacal swabs and blood samples were weekly collected for AMPV and HEV PCR detection, and antibody response evaluation, until birds were 14-weeks-old. Mortality was reported and dead birds were examined post mortem. When colibacillosis was suspected, microbiological tests were performed from selected organs. All detected E. coli strains were serotyped and assessed for the presence of virulence-associated genes. In the first cycle, colisepticaemia associated mortality was recorded at week 4, due to AMPV and APEC O78. Late high O78 or O2 APEC associated mortality was observed respectively in the second and third cycle; these outbreaks were correlated to both HEV and AMPV infections
Culture chevaleresque et Quatrième Croisade: quelques réflexions sur les motivations des croisés
No full textG. ORTALI, G. RAVEGNANI et P. SCHREINER (eds)International audienc
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