1,720,964 research outputs found
L’analisi univariata e multivariata per lo studio dei caratteri morfometrici di bozzoli e larve diapausanti di Neodryinus typyhlocybae (Ashmead) (Hymenoptera: Dryinidae)
No full textResearch and management oriented sampling plans for vine plant inhabiting Scaphoideus titanus Grape leafhopper nymphs
No full textThis paper summarizes the methodology used for describing the spatial distribution of the
grape leafhopper Scaphoideus titanus in a vineyard located in Southern Switzerland and presents
sampling plans for research and management purposes. The sampling technique consisted of repeated
visual counts of S. titanus nymphs. In general, a vineyard is a highly structured environment whose
influence on spatial distributions is studied by analyses of variance and quantified by regression
models developed in a stratified and multi-stage sampling universe. First, a regression model was
applied to the relationship between the proportion of infested trunk shoot leaves and the mean density
of trunk shoot leaves. This allowed the translation of a critical density for entering the vineyard in an
adaptive management (AM) program into a critical proportion. A sequential binomial sampling plan
was developed to efficiently decide whether a vineyard should be included into the AM program or
not. Second, the spatial distribution in the entire vine plant canopy was analysed. Since there were
significant differences between densities on trunk shoots and productive shoots, two different
sampling plans were designed. However, there were no significant differences between other strata
(parts of the vineyard, leaf position within shoots), so that they were disregarded in sampling plan
design. The mean crowding – mean regression model, with the intercept set to 0, indicated aggregated
distributions at the vineyard, shoot type and shoot levels. On the basis of this statistics, enumerative
and sequential sampling plans are proposed and implemented in the AM framework. The here
presented sampling techniques are advantageous over the previously used beating tray method and the
sampling plans are useful for research and management purpose
Multiannual infestation patterns of grapevine plant canopy inhabiting Scaphoideus titanus Ball leafhoppers
No full textThis paper summarizes the procedures for designing, parametrizing and validating a model
representing five years infestation patterns of Scaphoideus titanus populations in grapevine plant
canopies, on the basis of temperature influences. The development of S. titanus comprises nymphs,
adults, diapausing eggs and post diapausing eggs. The basic elements of the model are temperaturedependent
i) stochastic development of the four “life stages”, ii) developmental and senescence rates,
and stage-specific survivorships, and iii) reproduction. The phenology model is based on a timevarying
delay with attrition and operates on a time step length of 1 hour. It is initialized by
proportional entries of hatching eggs resulting from a Weibull frequency distribution. Temperature
effects on the survivorship of non-diapausing life stages are modelled via attrition and on fecundity
rates via input into the diapausing egg stage. Diapausing eggs, however, do not suffer from adverse
temperature conditions. If the temperature is between 0°C and the lower developmental threshold all
life stages except the diapausing eggs suffer from an additional temperature dependent mortality. The
model is validated with observations made during five years in a Southern Switzerland (located at
Contone) vineyard. The model predictions are in agreement with the observations. The successfully
validated model will be inserted into an Adaptive Management system aiming at rationalizing pest
management and learning how the pest population system work
Multiannual infestation patterns of grapevine plant inhabiting Scaphoideus titanus (Hemiptera: Cicadellidae) leafhoppers
No full textThe Nearctic leafhopper Scaphoideus titanus Ball (Hemiptera: Cicadellidae) was accidentally introduced in Europe, where it became the vector of the ‘Candidatus Phytoplasma vitis’ phytoplasma causing the ‘Flavescence dore ́e’ disease of grapevine plants. A time-varying distributed delay model, simulating the successive occurrences of egg hatching, nymph presence, and adult emergence, is extended here to represent multi-generation infestation patterns of grapevine plants inhabited by eggs, nymphs, and adults. The model extension includes intrinsic mortality, mortality caused by plant dormancy, and low temperatures, development of diapausing and postdiapausing eggs, fecundity rates, and adult longevity. Field observations and published data were used to estimate parameters. The model was validated with five years canopy infestation data from five vineyards not subjected to insecticide treatments and found to have satisfactory explicative and predictive qualities. The model output is most sensitive to a 10% variation in the upper threshold and in the shape parameters of the survivorship function and least sensitive to a 10% variation in the shape parameters of the development function and the survivorship level. Recommendations are made to take into account other factors than temperature and plant phenology and include a wider geographical area in further model development.La cicadelle ne ́arctique Scaphoideus titanus Ball (Hemiptera: Cicadellidae) a e ́te ́ introduite
accidentellement en Europe dans les anne ́es ‘50, ou` elle est devenue le vecteur du ) Candidatus
Phytoplasma vitis * responsable de la maladie de Flavescence dore ́e de la vigne. Un mode`le de
de ́lai distribue ́ dans le temps (time-varying distributed delay model), simulant les e ́ve`nements
successifs des e ́closions, de la pre ́sence des stades juve ́niles et de l’e ́mergence des adultes, a e ́te ́
e ́tendu pour repre ́senter les niveaux d’infestation multi-ge ́ne ́rationnels de la vigne colonise ́e par des
œufs, des nymphes et des adultes. L’extension du mode`le inclut la mortalite ́ intrinse`que, la mortalite ́
cause ́e par la dormance de la plante et les basses tempe ́ratures, le de ́veloppement des œufs
diapausants et post-diapausants, les taux de fe ́condite ́ et la longe ́vite ́ des adultes. Les observations
au champ et les donne ́es publie ́es ont servi de base pour l’estimation des parame`tres du mode`le.
Le mode`le a e ́te ́ valide ́ avec les donne ́es de cinq anne ́es d’infestation de la haie foliaire de cinq
vignobles sans traitements insecticides et il a montre ́ des qualite ́s explicatives et pre ́dictives
satisfaisantes. Le re ́sultat du mode`le est plus sensible a` une variation de 10% dans le seuil supe ́rieur
et dans les parame`tres de forme de la fonction de survie et moins sensible a` une variation de
10% dans les parame`tres de forme de la fonction de de ́veloppement et du niveau de survie.
Des recommandations sont faites pour prendre en compte d’autres facteurs que la tempe ́rature
et la phe ́nologie de la plante et inclure un plus large e ́ventail de zones ge ́ographiques pour un
de ́veloppement ulte ́rieur du mode`le
Marrying research and management activities: adaptive management of Grape leafhopper Scaphoideus titanus
No full textThis paper deals with the study and management of the Grape leafhopper Scaphoideus
titanus Ball, vector of the Candidatus Phytoplasma vitis pathogen, in vineyards located in Southern
Switzerland. S. titanus is an invasive species of North American origin that became a component of a
complex population system and an object of a complex population management set-up. Uncertainities
have been recorded in three areas: uncertainty about the observations and measurements, uncertainty
about the underlying behavior of the system and uncertainty about the environment. For dealing with
complex problems high in uncertainty, an adaptive management (AM) strategy is developed and
implemented. Progress is reported in the area of technology selection for measuring infestation levels
and temperature profiles (i), the quantitative analytical tools have been advanced as to obtain a better
insight into the dynamics of the population system (ii) and the timing of insecticide applications and
monitoring operations (iii), the ground has been solidified for the design and implementation of an
integrated population and disease transmission system (iv). The detailed presentation of the
methodologies and the results of different component studies by Rigamonti et al. (2011a; 2011b;
2013), Prevostini et al. (2013) and Trivellone et al. (2011) allows focusing on AM design,
implementation and preliminary achievements. The AM framework was concluded to be adequate for
dealing with high uncertainties associated with the complexities of the S. titanus population system
and the design and implementation of an IPM progra
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
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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