936 resultados para Small World Graphs


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Let G be a graph on n vertices with maximum degree ?. We use the Lovasz local lemma to show the following two results about colourings ? of the edges of the complete graph Kn. If for each vertex v of Kn the colouring ? assigns each colour to at most (n - 2)/(22.4?2) edges emanating from v, then there is a copy of G in Kn which is properly edge-coloured by ?. This improves on a result of Alon, Jiang, Miller, and Pritikin [Random Struct. Algorithms 23(4), 409433, 2003]. On the other hand, if ? assigns each colour to at most n/(51?2) edges of Kn, then there is a copy of G in Kn such that each edge of G receives a different colour from ?. This proves a conjecture of Frieze and Krivelevich [Electron. J. Comb. 15(1), R59, 2008]. Our proofs rely on a framework developed by Lu and Szekely [Electron. J. Comb. 14(1), R63, 2007] for applying the local lemma to random injections. In order to improve the constants in our results we use a version of the local lemma due to Bissacot, Fernandez, Procacci, and Scoppola [preprint, arXiv:0910.1824]. (c) 2011 Wiley Periodicals, Inc. Random Struct. Alg., 40, 425436, 2012

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The addition of a capped mini-exon [spliced leader (SL)] through trans-splicing is essential for the maturation of RNA polymerase (pol) II-transcribed polycistronic pre-mRNAs in all members of the Trypanosomatidae family. This process is an inter-molecular splicing reaction that follows the same basic rules of cis-splicing reactions. In this study, we demonstrated that mini-exons were added to precursor ribosomal RNA (pre-rRNA) are transcribed by RNA pol I, including the 5' external transcribed spacer (ETS) region. Additionally, we detected the SL-5' ETS molecule using three distinct methods and located the acceptor site between two known 5' ETS rRNA processing sites (A' and A1) in four different trypanosomatids. Moreover, we detected a polyadenylated 5' ETS upstream of the trans-splicing acceptor site, which also occurs in pre-mRNA trans-splicing. After treatment with an indirect trans-splicing inhibitor (sinefungin), we observed SL-5' ETS decay. However, treatment with 5-fluorouracil (a precursor of RNA synthesis that inhibits the degradation of pre-rRNA) led to the accumulation of SL-5' ETS, suggesting that the molecule may play a role in rRNA degradation. The detection of trans-splicing in these molecules may indicate broad RNA-joining properties, regardless of the polymerase used for transcription.

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The seroprevalence of pestivirus infections in small ruminants and new world camelids in Switzerland was determined. In 5'059 sera of sheep from 382 herds, 503 sera of goats from 54 herds and 109 sera of alpacas and lamas from 53 herds, population prevalences of 16.1% (sheep), 25.4% (goats) and 4.6% (new world camelids), respectively, were found. In order to determine the source of infection, the serological reactions were further characterized by cross-neutralization against two pestiviruses representing the genotypes BVDV (Bovine Virus Diarrhea Virus)-1 and BDV (Border Disease Virus)-1. Based on the ratio of respective antibody titres, 56.1% of the infections in sheep were induced by a BDV-1, 12.9% by a BVDV-1 and 31.0% by an unresolved pestivirus. In goats, the corresponding proportions were 23.4%, 10.2% and 66.4%, respectively. In Alpacas and Lamas, the source of infection of 1 animal was BDV-1 and that of 4 seropositive animals remained unresolved. In view of the phylogenetic relationship between pestiviruses, the unresolved source of infection is most probably attributable to other pestivirus genotypes circulating in small ruminants and new world camelids. Due to the predominance of pestiviral genotypes other than BVDV-1, the risk of transmission of BVDV from persistently infected small ruminants and new world camelids to cattle appears to be moderate, apart from close direct contact in mixed animal husbandry, communal pasturing and grazing in the Alps.

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The purpose of this research project was to investigate two distinct types of research questions – one theoretical, the other empirical: (1) What would justice mean in the context of the international trade regime? (2.Using the small developing states of the Commonwealth Caribbean as a case study, what do Commonwealth Caribbean trade negotiators mean when they appeal to justice? Regarding the first question, Iris Young's framework which focuses on the achievement of social justice in a domestic context by acknowledging social differences such as those based on race and gender, was adopted and its relevance argued in the international context of interstate trade negotiation so as to validate the notion of (size, location, and governance capacity) difference in this latter context. The point of departure is that while states are typically treated as equals in international law – as are individuals in liberal political theory – there are significant differences between states which warrant different treatment in the international arena. The study found that this re-formulation of justice which takes account of such differences between states, allows for more adequate policy responses than those offered by the presumption of equal treatment. Regarding the second question, this theoretical perspective was used to analyze the understandings of justice from which Commonwealth Caribbean trade negotiators proceed. Interpretive and ethnographic methods, including participant observation, interviews, field notes, and textual analysis, were employed to analyze their understandings of justice. The study found that these negotiators perceive such justice as being justice to difference because of the distinct characteristics of small developing states which combine to constrain their participation in the international trading system; based on this perception, they seek rules and outcomes in the multilateral trade regime which are sensitive to such different characteristics; and while these issues were examined in a specific region, its findings are relevant for other regions consisting of small developing states, such as those in the ACP group.

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This article uses small states scholarship to map North Korea’s evolution from a post-colonial small state to a system-influencing state due to its nuclear weapons programme. The framework allows for contributions to: (1) The DPRK literature which in some parts has suggested the future collapse of the state, (2) The small states literature that suggests they can only survive if they integrate larger political and/or economic units, (3) The mainstream IR literature and its dominant realist streak that considers great powers and their will as the main drivers in contemporary world politics.

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Kepler-454 (KOI-273) is a relatively bright (V = 11.69 mag), Sun-like star that hosts a transiting planet candidate in a 10.6 day orbit. From spectroscopy, we estimate the stellar temperature to be 5687 ± 50 K, its metallicity to be [m/H] = 0.32 ± 0.08, and the projected rotational velocity to be v sin i <2.4 km s-1. We combine these values with a study of the asteroseismic frequencies from short cadence Kepler data to estimate the stellar mass to be , the radius to be 1.066 ± 0.012 Ro, and the age to be Gyr. We estimate the radius of the 10.6 day planet as 2.37 ± 0.13 R. Using 63 radial velocity observations obtained with the HARPS-N spectrograph on the Telescopio Nazionale Galileo and 36 observations made with the HIRES spectrograph at the Keck Observatory, we measure the mass of this planet to be 6.8 ± 1.4 M. We also detect two additional non-transiting companions, a planet with a minimum mass of 4.46 ± 0.12 MJ in a nearly circular 524 day orbit and a massive companion with a period >10 years and mass >12.1 MJ. The 12 exoplanets with radii ⊕ and precise mass measurements appear to fall into two populations, with those ⊕ following an Earth-like composition curve and larger planets requiring a significant fraction of volatiles. With a density of 2.76 ± 0.73 g cm-3, Kepler-454b lies near the mass transition between these two populations and requires the presence of volatiles and/or H/He gas.

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Previous research examining players of Massively-Multiplayer Online Games (MMOGs) suggests that players form meaningful relationships with each other. Other research indicates that people may derive social support from online sources and this social support has been associated with greater wellbeing. This study used an online survey of players (N = 206) of the MMOG “World of Warcraft” (WoW) to examine if social support can be derived from MMOGs, and to examine its relationship with negative psychological symptoms. Players of WoW were found to derive social support from playing and a positive relationship was found between game engagement and levels of in-game social support. Higher levels of in-game social support were associated with fewer negative psychological symptoms, although this effect was not maintained after accounting for social support derived from the offline sources. Additionally, a small subsample of players (N = 21) were identified that played for between 44 and 82 hours per week (M = 63.33). These players had significantly lower levels of offline social support and higher levels of negative symptoms compared to the rest of the sample. This study provides evidence that social support can be derived from MMOGs and the associated potential to promote well being, but also highlights the potential harm from spending excessive hours playing.