1,720,965 research outputs found
Application of nanoparticles in cryopreservation of bleeding heart
No full textBiodiversity protection is important for systematics research, species evolution understanding, and breeding programs. Cryopreservation, i.e. maintenance of biological material at a cryogenic temperature of liquid nitrogen (-196oC), is considered the most effective long-term storage method. Nonetheless, this technology is still developing and requires more research. Application of nanoparticles (NPs) may greatly improve the effectiveness of cryopreservation protocols and ought to be carefully explored.The popularity of nanoparticles (i.e. particles of a maximum size = 100 nm) is continuously increasing. They are commonly applied in medicine, pharmacy, cosmetology, and plant protection. To date, however, there has been no research on the application of NPs in plant cryopreservation. Moreover, there is a lack of comprehensive research demonstrating the influence of nanoparticles on living organisms.The aim of the project was to broaden the scope of knowledge about the effect of various NPs on the in vitro and ex vitro development of plants, particularly concerning cryobiology studies.The scientific hypothesis assumed that silver (AgNPs), gold (AuNPs), and zinc oxide (ZnONPs) nanoparticles can penetrate plant tissues, enhance the pace of cooling and rewarming during a cryopreservation procedure, and consequently, minimize the lethal ice-formation effects. Moreover, the addition of NPs into the protective bead matrix may positively affect the regrowth of explants and the biosynthesis of primary and/or secondary metabolites after rewarming.Two cultivars of Lamprocapnos spectabilis – a vegetatively propagated species of great ornamental, medicinal, and economic value were used in the experiments.Shoot tips of in vitro-derived plants were cryopreserved with the previously optimised encapsulation-vitrification protocol. Silver or gold nanoparticles at various concentrations were added either into the preculture medium (1st step of the cryopreservation procedure) or to the protective bead matrix during encapsulation (2nd step of the protocol). The control included plants recovered from cryopreserved explants 1) non-treated with nanoparticles and 2) treated with colloid dispersion medium without NPs.After storage and rewarming, the influence of NPs on the cryopreservation efficiency was determined. This included evaluation of the recovery rate of explants and their morphogenetic response; i.e. number of shoots, leaves, and roots produced. Transmission electron microscopy (TEM) allowed to detect the presence of NPs in the cells, as well as to assess their structural integrity. Based on the spectrophotometric analyses of phenolic compounds concentration and antioxidant enzymes activity in shoots, the level of defence reaction against reactive oxygen species, resulting from NPs application, was evaluated. During the in vitro cultivation period, it was demonstrated, whether NPs cause alternations in the DNA sequence with the use of RAPD and SCoT molecular markers. The cytogenetic stability of the LN-derived plant material was evaluated using flow cytometry.After acclimatisation to ex vitro glasshouse conditions, the biochemical stability of plants was assessed. The influence of NPs on the content of photosynthetic pigments and secondary metabolites (carotenoids and flavonoids) in the NP-treated and untreated control leaves and stems was monitored. HPLC chromatography was used to study the phenolic profile of plants. The fluorescence parameters of chlorophyll gave insights into stress reactions. The detailed phenotype analysis of plants at this stage was included. By those means, it was possible to evaluate the widely understood stability of plants at various developmental stages.The results of the study suggest that different types and concentrations of nanoparticles, such as gold, silver and zinc oxide, have different effects on cryopreservation efficiency and further growth and physiological activity of plants, which highlights their specific effects in the context of different plant cultivars. The proper use of nanoparticles in cryopreservation protocols can significantly improve explant survival rates and their regenerative potential, which is crucial for the protection of genetic resources, as well as enable the modulation of plant secondary metabolism to achieve the desired production effects. However, the use of NPs in suboptimal conditions may have an adverse effect on the plants.</p
Time-dependent modulation of genetic stability and phytochemical profiles in chrysanthemum leaves and inflorescences by iron oxide nanoparticles and IAA auxin
No full textThis research studied the impact of bare iron oxide nanoparticles (Fe3O4 NPs), citrate-stabilized iron oxide nanoparticles (Fe3O4CA NPs), and indole-3-acetic acid (IAA) on the genetic stability and metabolic activity of Chrysanthemum × morifolium (Ramat.) Hemsl. plants obtained from synthetic seeds. For this purpose, axillary buds of chrysanthemum ‘Richmond’ were embedded in 3% calcium alginate supplemented with NPs and IAA, either singularly or in combination. Next, the synthetic seeds were stored at 4 oC in the dark (for eight weeks) on an agar-water medium and then transferred to room temperature for 30 or 60 days. Next, the germinated seeds were transplanted to the greenhouse until the plants were fully flowering. The content of total polyphenols was determined in the leaves and inflorescences of the plants. Moreover, the content of anthocyanins was measured in the inflorescences. RAPD markers were used to assess the genetic stability of plants. It was found that NPs and IAA significantly affected the content of total polyphenols (TCP) in the leaves of chrysanthemum. Most treatments stimulated the accumulation of these compounds but in a time-dependent manner. No decline in the value of this parameter was reported compared with the untreated control. Conversely, Fe3O4NPs and IAA + Fe3O4CA NPs stimulated the biosynthesis of polyphenols and anthocyanins in the inflorescences after 30 days of treatment, however, a decline in the content of these compounds was reported after 60 days in most experimental objects, except for Fe3O4CA NPs and IAA + Fe3O4CA NPs. The inflorescences of plants treated with nanoparticles usually exhibited a larger diameter than the control, but only after a shorter exposure to the analyzed factors. In contrast, prolonged treatment resulted in the opposite effect. The genetic uniformity of the plants was confirmed with 2160 RAPD markers.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
IMPROVEMENT OF Chrysanthemum × grandiflorum (Ramat.) Kitam. ENCAPSULATION-DEHYDRATION CRYOPRESERVATION PROTOCOL
Full text linkTo optimize the protocol, the shoot tips of Chrysanthemum × grandiflorum (Ramat.) Kitam. radiomutants have been cryopreserved using the encapsulationdehydration technique, following different approaches. In the experiment the influence of abscisic acid – ABA (0; 10; 20 and 30 μM), sucrose concentration (0.09; 0.25 and 0.5 M) and temperature (5ºC or 22ºC) during preculture were tested. Furthermore two dehydration methods, gradual and one-step, were considered. Since the best results were reported with 10 μM ABA + 0.09 M sucrose at room temperature and gradual dehydration, only this combination was selected for the next desiccation-adjustment step. From the time of air desiccation under laminar air-flow applied (0; 1; 2; 3; 4 and 5 hours), 3 hours providedthe best results. Due to the growth inhibition on the hormone-free medium, the addition of plant growth regulators during that phase was also tested, confirming the need to apply cytokinins into the medium
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
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