4,430 research outputs found

    Log Skeletons: A Classification Approach to Process Discovery

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    To test the effectiveness of process discovery algorithms, a Process Discovery Contest (PDC) has been set up. This PDC uses a classification approach to measure this effectiveness: The better the discovered model can classify whether or not a new trace conforms to the event log, the better the discovery algorithm is supposed to be. Unfortunately, even the state-of-the-art fully-automated discovery algorithms score poorly on this classification. Even the best of these algorithms, the Inductive Miner, scored only 147 correct classified traces out of 200 traces on the PDC of 2017. This paper introduces the rule-based log skeleton model, which is closely related to the Declare constraint model, together with a way to classify traces using this model. This classification using log skeletons is shown to score better on the PDC of 2017 than state-of-the-art discovery algorithms: 194 out of 200. As a result, one can argue that the fully-automated algorithm to construct (or: discover) a log skeleton from an event log outperforms existing state-of-the-art fully-automated discovery algorithms.Comment: 16 pages with 9 figures, followed by an appendix of 14 pages with 17 figure

    Nieuwe virusstammen in pootaardappel

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    Het systeem waarmee het aardappelvirus Y in pootaardappelen beheerst werd, moet na twintig jaar trouwe dienst wellicht worden herzien. Onderzoekers van Plant Research International (PRI) ontdekten nieuwe, beter overdraagbare virusstamme

    Bold or cautious : behavioural characteristics and dominance in great tits

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    Social dominance affects territory acquisition, reproduction and survival in many species. It plays a major role in the life of an individual, and has important consequences for its fitness. Several factors that can influence dominance relationships between individuals have been well studied, such as differences between rivals in size, weight, fighting experience, prior residence, and resource value. Individual behavioural characteristics can also influence dominance. Studies of domesticated and laboratory animals show that individual animals can be characterised by their aggressiveness, as measured in standardised tests, and that aggressive individuals are generally dominant over non-aggressive ones. These behavioural characteristics have a genetic basis, and are not only reflected in aggressiveness but also in a whole range of other behaviours, such as exploration or nest building. Based on these behavioural characteristics, different types of animals can be distinguished. So far, behavioural characteristics have mainly been studied in mammals, not in birds. Moreover, the effect of such behavioural characteristics on social dominance has received little attention in studies of natural populations. This thesis aims to take a first step by studying the existence of consistent individual behavioural characteristics and their effect on social dominance in the great tit (Parus major).If behavioural characteristics are really individual traits, or in other words 'consistent', they should already exist early in life, before any dominance relationship develops. In that phase of life, exploration and foraging are the main activities of great tits. Indeed, during the first 18 weeks of their life, hand-reared young male great tits, collected from a natural population, could be characterised by their exploratory behaviour (chapter 2). In repeated tests, they showed consistent reactions to a strange object in their home cage, even with different objects and after an interval of some weeks. This extended to other exploratory behaviour. Birds that approached a strange object quickly, were also fast to explore an aviary with which they were unfamiliar. Accordingly, birds that approached a strange object more slowly, took more time to explore thoroughly the unfamiliar aviary. These behavioural differences were also reflected in the strength of foraging habits, built up during a training in which food was always offered in the same place. After a change in the location of food, the fast and superficial explorers (FE) would stick to their habit, and keep going to the place where the food used to be. The slow and thorough explorers (SE) soon changed their behaviour and stopped going to the usual feeding place. They seemed to remain alert and to pay more attention to stimuli in the known environment than the fast, superficial explorers.The juveniles could also be characterised by their aggressive behaviour in experimental pair-wise confrontations (chapter 3). FE started more fights and won more often than SE, also when possible effects on dominance of other factors such as weight and size were taken into account. For FE clearly the first blow was half the battle. For natural populations, the relevance of these findings could still be small, since dominance relationships normally develop in a flock of juveniles, resulting in a more complex social hierarchy. Therefore groups of birds were observed in aviaries, which probably better resemble natural conditions (chapter 4). In all observed groups, a stable hierarchy only established after a dynamic phase of several days, in which many reversals in dominance relations occurred. During the first day in the aviary, the situation was similar to that observed in the tests with pair-wise confrontations. FE initiated more fights than SE and won more often, again after correction for factors such as weight and size. Surprisingly though, once the hierarchy had stabilised, SE were on average dominant over FE; SE had higher ranks than FE in the hierarchy.Apparently, the same behavioural characteristics result in different dominance relationships under different circumstances. Further observations supported and specified this conclusion. Other studies have shown that familiarity with the environment increases chances of becoming dominant. The birds in the groups had been unfamiliar with the aviary before being put together. The SE initiated fewer fights than FE and initiated their first fight more often in the place where they had spent most time. This suggested that SE made more use of their knowledge of the environment than FE, who were more focused on fights. Their more thorough manner of exploring may gradually have led to a better, or more detailed, knowledge of the environment in SE, which in turn may increase their chances of winning. In this way, the initial advantage that FE had by giving the first blow, could be reversed by the alertness and increasing spatial knowledge of SE. Such a gradual process could not happen in groups of birds that were first separately familiarised with the aviary before being put together (chapter 5). In those groups, all birds had a good knowledge of the environment and FE and SE did not show the differences in their behaviour that they showed in the unfamiliar aviaries. In these familiar aviaries, FE won on average over SE, both on the first day and after stabilisation of the hierarchy. These results suggest that SE may be best adapted to new or unstable and changing environments, while FE may do better in familiar and stable ones.The presence and behaviour of flock mates in the groups also modified dominance relations of FE and SE (chapters 4, 5). Several studies have shown that previous experience in a fight influences the outcome of a subsequent fight. FE and SE differed in their fighting behaviour and reaction to previous fights. FE seemed to take more risks in their fighting behaviour. In all groups, they attacked quickly and won from SE on the first day. But if FE lost severely, they needed more time to recover before starting a new fight, which strongly suggests that they had problems in coping with the defeat. The more cautious SE needed less time to recover and seemed not only to make more use in their fights of information about their physical, but also about their social, environment. They would take advantage of the vulnerability of a FE that had just lost from a third bird, by starting a fight with that loser. In this way, a FE with a high rank that lost severely from a FE with an even higher rank, could subsequently also lose from SE and fall in hierarchy to the lowest positions. This resulted in a stable hierarchy in which fast explorers had either high or low ranks, while slow explorers had middle ranks. This characteristic dominance pattern was found in all observed groups. In the groups in unfamiliar aviaries, only a small proportion of the FE had extreme high ranks, while a large proportion had extreme low ranks. In the groups in familiar aviaries it was the other way round. Hence, familiarity with the environment only influenced the proportion of FE in highest or lowest places, resulting in different average dominance of FE and SE in the two experimental situations. Such average dominance is therefore not the most sensitive way to describe dominance relations in a stable hierarchy.The last chapter (6) discusses whether the behavioural characteristics reflect two different, but equally successful, behavioural strategies to cope with environmental challenges, and what their consequences could be for foraging success, territoriality and survival in different natural situations. This could be the starting point for future studies.In conclusion, the results of this study show that juvenile male great tits show consistent individual differences in exploratory behaviour. These differences extend to fighting behaviour, which is consistent over different social situations. These behavioural characteristics predict dominance, the outcome depending on familiarity with the environment and behaviour of possible flock mates.</p

    Nucleotide sequence and genomic organization of an ophiovirus associated with lettuce big-vein disease

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    The complete nucleotide sequence of an ophiovirus associated with lettuce big-vein disease has been elucidated. The genome consisted of four RNA molecules of approximately 7ò8, 1ò7, 1ò5 and 1ò4 kb. Virus particles were shown to contain nearly equimolar amounts of RNA molecules of both polarities. The 5'- and 3'-terminal ends of the RNA molecules are largely, but not perfectly, complementary to each other. The virus genome contains seven open reading frames. Database searches with the putative viral products revealed homologies with the RNA-dependent RNA polymerases of rhabdoviruses and Ranunculus white mottle virus, and the capsid protein of Citrus psorosis virus. The gene encoding the viral polymerase appears to be located on the RNA segment 1, while the nucleocapsid protein is encoded by the RNA3. No significant sequence similarities were observed with other viral proteins. In spite of the morphological resemblance with species in the genus Tenuivirus, the ophioviruses appear not to be evolutionary closely related to this genus nor any other viral genus

    Sequence analysis and genomic organization of Aphid lethal paralysis virus: a new member of the family Dicistroviridae

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    The complete nucleotide sequence of the genomic RNA of an aphid-infecting virus, Aphid lethal paralysis virus (ALPV), has been determined. The genome is 9812 nt in length and contains two long open reading frames (ORFs), which are separated by an intergenic region of 163 nt. The first ORF (5' ORF) is preceded by an untranslated leader sequence of 506 nt, while an untranslated region of 571 nt follows the second ORF (3' ORF). The deduced amino acid sequences of the 5' ORF and 3' ORF products respectively showed similarity to the non-structural and structural proteins of members of the newly recognized genus Cripavirus (family Dicistroviridae). On the basis of the observed sequence similarities and identical genome organization, it is proposed that ALPV belongs to this genus. Phylogenetic analysis showed that ALPV is most closely related to Rhopalosiphum padi virus, and groups in a cluster with Drosophila C virus and Cricket paralysis virus, while the other members of this genus are more distantly related. Infectivity experiments showed that ALPV can not only infect aphid species but is also able to infect the whitefly Trialeurodes vaporariorum, extending its host range to another family of the order Hemipter

    Linking science to technology: using bibliographic references in patents to build linkage schemes.

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    In this paper, we develop and discuss a method to design a linkage scheme that links the systems of science and technology through the use of patent citation data. After conceptually embedding the linkage scheme in the current literature on science-technology interactions and associations, the methodology and algorithms used to decelop the linkage scheme are discussed in detail. The method is subsequently tested on and applied to subsets of USPTO patents. The results point to highly skewed citation distributions, enabling us to discern between those fields of technology that are highly science-interactive and those fields where technology develoment is highly independent from the scientific literature base.Science; Patents; Systems; Data; Algorithms; Distribution;

    The control of PVY in Dutch seed potato culture

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    Over the recent years Potato virus Y presents a growing problem in Dutch seed potato culture. In recent years a significant % of seed potato lots was de-classified due to PVY infections. This apparent increase in PVY infections was unexpected since no increase in field symptoms were observed and the numbers of aphids caught in the yellow water traps and high suction traps showed a clear decline over the last 10 years http://www.aab.org.uk/images/VIRO_CONF_PROG.pd

    Task Elimination may Actually Increase Throughput Time

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    The well-known Task Elimination redesign principle suggests to remove unnecessary tasks from a process to improve on time and cost. Although there seems to be a general consensus that removing work can only improve the throughput time of the process, this paper shows that this is not necessarily the case by providing an example that uses plain M/M/c activities. This paper also shows that the Task Automation and Parallelism redesign principles may also lead to longer throughput times. Finally, apart from these negative results, the paper also show under which assumption these redesign principles indeed can only improve the throughput time

    Tomato marchitez virus, a new plant picorna-like virus from tomato related to tomato torrado virus

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    A new virus was isolated from a tomato plant from the state of Sinaloa in Mexico. This plant showed symptoms locally known as `marchitez disease¿: severe leaf necrosis, beginning at the base of the leaflets, and necrotic rings on the fruits. A virus was isolated from the infected plant consisting of isometric particles with a diameter of approximately 28¿nm. The viral genome consists of two (+)ssRNA molecules of 7221 (RNA1) and 4898¿nts (RNA2). The viral capsid contains three coat proteins of 35, 26 and 24¿kDa, respectively. The abovementioned characteristics: symptoms, morphology, number and size of coat proteins, and number of RNAs are similar to those of the previously described tomato torrado virus (ToTV). Sequence analysis of the entire viral genome shows that this new virus is related to, but distinct from, ToTV and that these members of two obviously new virus species belong to the recently proposed plant virus genus Torradovirus. For this new virus, the name tomato marchitez virus (ToMarV) is proposed
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