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Onderzoek naar het kiemgetal en de aard van de microflora van snijbloemstengels en naar de invloed van deze microflora op het vaasleven van vers geoogste snijbloemen
No full textFactors affecting the vase life of Rosa cultivar "Sonia" : microbiological and scanning electron microscopic investigations = Factoren die van invloed zijn op het vaasleven van Rosa cultivar "Sonia" : microbiologisch en raster electronenmicroscopisch onderzoek
No full textThe papers compiled in this thesis comprise a series of successively executed investigations into the role of micro-organisms in xylem plugging, and disturbance of the water relations and the vase life of cut flowers. For this purpose Rosahybrida cultivar 'Sonia' (the hybrid tea-rose Rosa cultivar 'Sweet Promise') was selected.Chapter 1 comprises an introduction into the economic importance of cut flowers and the capability of cut flowers for post harvest life. In addition, a brief review is given of literature on physiological and microbiological factors which can influence the vase life of cut flowers. Gaps in our knowledge of the mechanisms leading to vascular blockage of cut flowers are discussed. An outline is given of: (1) the selection of a greenhouse Rosa cultivar as plant material to study, (2) the experimental methods applied, (3) the results of preliminary investigations, and (4) the microbiological factors investigated.Chapter 2 shows that stems of freshly cut flowers contain a wide variety and low numbers of microbial species. The initial microbial load on stems of Rosa flowers was found to be much lower than those on Chrysanthemum and Gerbera stems. Their distribution on the flower stem is not homogeneous.The stem flora, predominantly Enterobacter , Bacillus and fungal species, lost its dominance in the vase fluid. The vase water showed an initial predominance of Pseudomonas species which do not require organic growth factors. In the course of the vase life Enterobacter and Bacillus species became dominant. These bacterial genera require organic nutrients and special growth factors for their multiplication.Fungal growth was shown at a later stage, mainly in vase fluids of Chrysanthemum and Gerbera flowers, which have a much longer vase life and a higher initial number of fungi on their stems than Rosa flower stems.Chapters 3, 4 and 5 demonstrate that the extent of infiltration of viable microbial cells into the xylem vessel system of Rosa and Gerbera cut flowers depends upon the number of microbial cells per ml initially added to the vase fluid, the shape and the size of the individual microbial cells and the width of the xylem vessels.Scanning Electron Microscopic (SEM) observations as well as the assessment of the number of bacteria Infiltrated into Rosa xylem vessels showed in addition that: (1) the number of bacteria which infiltrated into xylem vessels increased with time and, (2) this number increased with increasing numbers of bacteria initially added to the vase fluid, (3) this number decreased with increasing distance between cutting point and sampling point, (4) only a minor part of the bacterial and fungal cells suspended in the vase fluid was able to infiltrate into the xylem vessels of the flowers, a major part of the microbial cells remained attached to the cut surface, (5) even low numbers of infiltrated microbial cells caused a significantly decreased conductivity of stem segments, (6) a similar water conductivity decreasing phenomenon of stem segments was observed when low numbers of heat- inactivated microbial cells or low concentrations of microbial EPS (exopolysaccharides) were added to the vase fluid, as shown in Chapters 5 and 6.Chapter 7 does show that purified microbial pectic enzymes added to the vase fluid of Rosa flowers cause a rapidly decreasing uptake of vase water, promoting desiccation of the flower petals and leaves. This phenomenon may have been due to enzymatic degradation of the pectin-linked structures of the xylem vessels as observed in SEM preparations. The SEM figures show: (1) degradation of the xylem vessel wall structure, (2) loose particles in the vessels, (3) released spiral vessels, and (4) injury of vessel pits.The consequences for the ornamental value of the roses of vessel plugging and flower desiccation were easy to assess by means of macroscopic observations. Since pectic enzymes in extremely low concentrations exert a dramatic effect on cut flowers, it is likely that some of the products of the enzymatic activity elicit specific responses in the flowers, further affecting their vase life.Chapter 8 covers the results of an electron microscopic study, using cryoSEM techniques and X-ray microanalysis to demonstrate the effects of aluminium sulphate added to the vase fluid of Rosa flowers on the ability of bacteria e.g. Bacillus subtilis cells to infiltrate into the xylem vessels of the Rosa flowers. The biocidal activity of aluminium sulphate added to the vase fluid was negligible. Aluminium sulphate probably acts as a flocculating agent, in which bacterial cells are embedded. Indeed, Al 3+ions react easily with inorganic and organic anionic substances e.g. Bacillus subtilis cell wall peptides, substances of wounded stem cells and stem cell wall compounds of cut Rosa flowers. The Bacillus /aluminium complexes contribute to the formation of flocky deposits which adhere onto the cut surface and the adjacent open xylem vessel wall of the roses. The flocculated material may form a filter bed at the cut surface of the flower stem, hardly decreasing the water uptake, but strongly obstructing the embedded Bacillus calls to enter the vascular system of the roses, as clearly shown by cryoSEM figures
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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