Letteratura scientifica selezionata sul tema "Spider flowers"
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Articoli di riviste sul tema "Spider flowers"
1
Rodríguez-Morales, Dulce, Helena Ajuria-Ibarra, Laura T. Hernández-Salazar, Víctor Rico-Gray, José G. García-Franco e Dinesh Rao. "Response of flower visitors to the morphology and color of crab spiders in a coastal environment of the Gulf of Mexico". Israel Journal of Ecology and Evolution 66, n. 1-2 (19 dicembre 2019): 32–40. http://dx.doi.org/10.1163/22244662-20191065.
Testo completoAbstract (sommario):
Abstract Predation is one of the main interactions between organisms and one of the primary selective agents for their survival. Both prey and predators have developed different strategies and characteristics that allow them to be conspicuous or go undetected. In sit and wait predators, their shape and appearance are important factors that allow them to remain undetected by their potential prey. Sit and wait predators such as crab spiders are difficult to identify when they sit on flowers or areas of flowers with colors similar to the color of their bodies. In this study, we aimed to determine if insects can recognize the morphology and color polymorphism of crab spiders by evaluating the response of flower visitors. We quantified the visits and approaches of floral visitors to the flowerheads of Palafoxia lindenii with spider morphology and color polymorphism treatments. Our results show that insects in general, and bees in particular, avoid visiting flowers with a real spider or a spider model and visit vacant flowers more frequently. In the case of the color polymorphism, insects approached flowerheads with spiders with a similar frequency independently of the color of the spiders, but did not visit them. Insects appeared to identify spiders through their morphological characteristics rather than their color characteristics, since flower visitors did not discriminate between the evaluated spider colors (white, lilac, and purple). This study emphasizes the differential response of different insect prey to the presence, color, and morphology of sit and wait predators.
2
Su, Qichen, Lin Qi, Wei Zhang, Yueli Yun, Yao Zhao e Yu Peng. "Biodiversity Survey of Flower-Visiting Spiders Based on Literature Review and Field Study". Environmental Entomology 49, n. 3 (13 aprile 2020): 673–82. http://dx.doi.org/10.1093/ee/nvaa022.
Testo completoAbstract (sommario):
Abstract Many arthropods exhibit flower-visiting behavior, including a variety of spider species. However, as spiders are assumed to be strictly predatory, flower-visiting spiders are an often neglected group. We conducted a systematic biodiversity study of flower-visiting spiders based on published papers and field surveys. Most previous studies have focused on the herbivorous behavior of flower-visiting spiders (nectivory or pollinivory) and their effects on host flowers (tritrophic interactions with flower-visiting insects). In our field survey, we utilized standard transect walks (active sampling) and colored pan traps (passive sampling) to investigate species occurrence, diurnal and seasonal variation, and flower color preference of flower-visiting spiders. From the transect walks, crab spider species were found to be the dominant flower-visiting spiders and, based on all spider species, juvenile visitors were significantly more common than adults. Furthermore, in terms of spider number and species richness, tulips were the preferred flower to visit. For the pan traps, wolf spiders were found to be the dominant spider species. No significant differences were observed in the number of spiders caught in different colored pans, suggesting that color may not be an important flower trait in regard to spider preference. To the best of our knowledge, this study is the first to propose the term ‘flower-visiting spiders’ and conduct a systematic investigation of their diversity. However, this is preliminary research and further studies are required, especially as biodiversity is often closely linked to survey sites and ecotopes.
3
Rodríguez-Gironés, Miguel A., e Olga M. Jiménez. "Encounters with predators fail to trigger predator avoidance in bumblebees, Bombus terrestris (Hymenoptera: Apidae)". Biological Journal of the Linnean Society 128, n. 4 (12 ottobre 2019): 901–8. http://dx.doi.org/10.1093/biolinnean/blz155.
Testo completoAbstract (sommario):
Abstract Many species must learn to identify their predators, but little is known about the effect of direct encounters on the development of predator avoidance. We asked whether bumblebees, Bombus terrestris, learn to avoid predators, whether learning depends on the conspicuousness of predators and whether bumblebees learn to identify predators or simply to avoid dangerous patches. To answer these questions, we allowed bumblebees to forage in an enclosed meadow of 15 artificial flowers containing a yellow female crab spider, Thomisus onustus. Flowers were yellow in half of the trials and white in the other half. Spiders could remain at the same flower throughout the experiment or swap flowers between bee foraging bouts. Of the 60 bees used in the experiment, eight were killed by the spiders and nine stopped foraging without finishing the trial. Death or refusal to forage typically occurred early in the trial. Regardless of the treatment, the probability of landing at the spider-harbouring flower increased with time. Previous encounters with heterospecific individuals can therefore be a poor source of information about their predatory nature.
4
Bjärtå, Anna, Anders Flykt e Örjan Sundin. "The Effect of Using Different Distractor Sets in Visual Search with Spiders and Snakes on Spider-Sensitive and Nonfearful Participants". Swiss Journal of Psychology 72, n. 4 (gennaio 2013): 171–79. http://dx.doi.org/10.1024/1421-0185/a000111.
Testo completoAbstract (sommario):
In two visual search experiments, we investigated the impact of distractor sets on fear-relevant stimuli by comparing a search set with spiders, snakes, flowers, and mushrooms to one with spiders, snakes, rabbits, and turtles. We found speeded responses to spider and snake targets when flowers and mushrooms, but not when rabbits and turtles served as distractors. In Experiment 2, we compared spider-sensitive to nonfearful participants. Spider-sensitive participants responded faster than nonfearful participants to spider targets when we used flowers and mushrooms as distractors, but not when we used rabbit and turtle distractors. These results indicate that behavioral responses to the visual search task not only depend on the individual’s relationship to the stimuli included in the search set, but also on the context in which the feared or fear-relevant objects are presented.
5
Anderson, Sarah Elizabeth, e Andrea Lucky. "Rusty Spider Wasp Tachypompilus ferrugineus". EDIS 2019, n. 5 (23 settembre 2019): 4. http://dx.doi.org/10.32473/edis-in1247-2019.
Testo completoAbstract (sommario):
The rusty spider wasp, Tachypompilus ferrugineus, is a large, reddish orange wasp with conspicuous iridescent blue to violet wings. Aptly named, the rusty spider wasp specializes in hunting large spiders which it paralyzes and provides for its offspring to consume. These eye-catching wasps can be seen perusing loose soil for spider burrows, nectaring at flowers, or dragging large spiders back to their nests.https://edis.ifas.ufl.edu/in1247
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Ings, Thomas C., e Lars Chittka. "Predator crypsis enhances behaviourally mediated indirect effects on plants by altering bumblebee foraging preferences". Proceedings of the Royal Society B: Biological Sciences 276, n. 1664 (4 marzo 2009): 2031–36. http://dx.doi.org/10.1098/rspb.2008.1748.
Testo completoAbstract (sommario):
Predators of pollinators can influence pollination services and plant fitness via both consumptive (reducing pollinator density) and non-consumptive (altering pollinator behaviour) effects. However, a better knowledge of the mechanisms underlying behaviourally mediated indirect effects of predators is necessary to properly understand their role in community dynamics. We used the tripartite relationship between bumblebees, predatory crab spiders and flowers to ask whether behaviourally mediated effects are localized to flowers harbouring predators, or whether bees extend their avoidance to entire plant species. In a tightly controlled laboratory environment, bumblebees ( Bombus terrestris ) were exposed to a random mixture of equally rewarding yellow and white artificial flowers, but foraging on yellow flowers was very risky: bees had a 25 per cent chance of receiving a simulated predation attempt by ‘robotic’ crab spiders. As bees learnt to avoid ‘dangerous’ flowers, their foraging preferences changed and they began to visit fewer yellow flowers than expected by chance. Bees avoided spider-free yellow flowers as well as dangerous yellow flowers when spiders were more difficult to detect (the colour of yellow spiders was indistinguishable from that of yellow flowers). Therefore, this interaction between bee learning and predator crypsis could lead flower species harbouring cryptic predators to suffer from reduced reproductive success.
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Peira, Nathalie, Armita Golkar, Maria Larsson e Stefan Wiens. "What You Fear Will Appear". Experimental Psychology 57, n. 6 (1 gennaio 2010): 470–75. http://dx.doi.org/10.1027/1618-3169/a000058.
Testo completoAbstract (sommario):
Various experimental tasks suggest that fear guides attention. However, because these tasks often lack ecological validity, it is unclear to what extent results from these tasks can be generalized to real-life situations. In change detection tasks, a brief interruption of the visual input (i.e., a blank interval or a scene cut) often results in undetected changes in the scene. This setup resembles real-life viewing behavior and is used here to increase ecological validity of the attentional task without compromising control over the stimuli presented. Spider-fearful and nonfearful women detected schematic spiders and flowers that were added to one of two identical background pictures that alternated with a brief blank in between them (i.e., flicker paradigm). Results showed that spider-fearful women detected spiders (but not flowers) faster than did nonfearful women. Because spiders and flowers had similar low-level features, these findings suggest that fear guides attention on the basis of object features rather than simple low-level features.
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Jevremovic, Sladjana, Milana Trifunovic, Marija Nikolic, Angelina Subotic e Ljiljana Radojevic. "Clonal fidelity of chrysanthemum regenerated from long term cultures". Genetika 38, n. 3 (2006): 243–49. http://dx.doi.org/10.2298/gensr0603243j.
Testo completoAbstract (sommario):
Morphological characteristics of flowers of long term regenerated chrysanthemum, cv. "White Spider", after ten years of micropropagation are investigated. Shoot cultures are established and maintained more than ten years by stem segment culture on MS medium supplemented with BAP and NAA (1.0, 0.1 mgL-1, respectively). Rooting of shoots (100 %) has done on MS medium without hormones and it was very successful after ten years, as well as, after two or eight years of micropropagation. Acclimation of rooted chrysanthemum plantlets at greenhouse conditions was excellent and after appropriate photoperiod "in vitro" plants flowered 90.3 % and have the same flower color, shape and size as mother plants. Flower color changes of "in vitro" plants are observed during another flowering cycle one year after acclimatization. Observed variations of chrysanthemum flowers could be attributed to epigenetic factors.
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Meena, Narottam Kumar, Ram Pal, Rajendra Prasad Pant e Rajendra Prasad Medhi. "Seasonal Incidence of Mite and Infuence of Pesticidal Application on Orchid Flower Production". Journal of Plant Protection Research 53, n. 2 (1 aprile 2013): 124–27. http://dx.doi.org/10.2478/jppr-2013-0018.
Testo completoAbstract (sommario):
Abstract Investigations were carried out in 2010 to determine the influence of abiotic factors on the incidence of the two spotted spider mite; Tetranychus urticae Koch and to determine the influence of pesticides on orchid flower production. Initially, in January, the mite population was very low (1.0 mite/10 cm2 leaf area). The population gradually increased and peaked to 22.98 mites/10 cm2 leaf area in the first fortnight of May along with the rise in temperature and sunshine. Then, the population declined to a low level of 3.43 mites/10 cm2 leaf area in the first fortnight of December. Maximum and minimum temperatures had a significant positive correlation and sunshine had a non-significant positive correlation, whereas relative humidity and rainfall had a non-significant negative correlation with the mite population. Infestation of the two spotted spider mite was more severe in untreated conditions in comparison to the treated ones. The difference was due to various abiotic factors and natural pest infestation occurrence which drastically affected the flower quality and yield. In unprotected conditions, the number of flower spikes/plant (1.90±0.44 spikes), number of flowers/spike (7.35±1.04 flowers), spike length (42.59±5.69 cm), flower spike diameter (5.26±0.66 mm), and flower size (6.27±0.86 cm) was very low. In protected conditions, flower quality and yield were superior than in unprotected conditions i.e. number of flower spike/plant (2.92±0.57 spikes), number of flowers/spike (11.78±1.16 flowers), spike length (57.59±7.35 cm), diameter of flower spikes (9.09±1.01 mm), and flower size (6.73±1.16 cm).
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Diniz, Suzana, Everton Tizo-Pedroso, Denise Lange, Andréa Andrade Vilela, Danielle G. Justino, Fernanda Alves Martins, Erika Germanos, Rafael Arruda e Vanessa Stefani. "Might Heterostyly Underlie Spider Occurrence on Inflorescences? A Case Study ofPalicourea rigida(Rubiaceae), a Common Shrub from Brazilian Cerrado". Psyche: A Journal of Entomology 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/791395.
Testo completoAbstract (sommario):
We carried out a research on thePalicourea rigida(Rubiaceae) inflorescences, a distylous shrub of Brazilian Cerrado. Our objective was to compare the inflorescence architectural complexity and its quality in the two floral morphs and search for any relationship with spider occurrence. In order to assess the quality of inflorescence resources, we quantified the nectar volume and its sugar concentration and the number of fruits and flowers (intact and aborted) for both inflorescence morphs with and without spiders. For the architectural heterogeneity, we quantified floral structures and inflorescence levels of branching. Spider occurrence was higher in longistylous inflorescences than in brevistylous ones. The sampled spiders were classified into the guilds ambushers, jumpers, or orb-weavers. Ambushers, jumpers, and total richness were much higher among longistylous inflorescences. We found no difference between morphs neither in volume or nectar concentration nor in amount of fruits and flowers. However, longistylous inflorescences presented greater architectural heterogeneity than brevistylous ones. Therefore, we suggested that architectural heterogeneity is an important factor underlying the occurrence of cursorial spiders onP. rigidainflorescences, which possibly arose from the relationship between refuge availability and inflorescence architecture.
Tesi sul tema "Spider flowers"
1
Hoffmann, Nigel, of Western Sydney Hawkesbury University, of Health Humanities and Social Ecology Faculty e School of Social Ecology. "Goethe's notion of 'theory' : Goethean phenomenology as a new ecological discipline". THESIS_FHHSE_SEL_Hoffmann_N.xml, 1994. http://handle.uws.edu.au:8081/1959.7/234.
Testo completoAbstract (sommario):
Around two hundred years ago Goethe made the statement: ‘Let us not seek for something behind the phenomena – they themselves are the theory’. This would appear to be the antithesis of the claim of certain contemporary schools of epistemological thought, that a ‘theory’ is a construction of the human mind. Yet Goethe’s scientific aims are resonant with a present day ecological need: to find a form of ‘nature study’ which springs from a desire to care for things rather than merely to explain them, which can help to create a harmony between human and non-human nature. Goethe’s approach is phenomenological in that it seeks to uncover things ‘on their own terms’; it is integral in that it embraces both art and science. A Goethean methodology is used to study four Australian native plants: Grevillea buxifolia, Scaevola remosissima, Banksia integrifolia and Kunzea ambigua. It is suggested that Goethe’s way of ‘nature study’ fulfils the contemporary need for a participatory knowing which is responsible for the thing being researched, and various possibilities are indicated for further research and application – in the biological sciences and in disciplines such as architecture, landscape design and environmental education.Master of Science (Hons)
2
Brenner, Robert J. "Influence of Neonicotinoid Seed Treatment on Two Co-Occuring Arthropod Pests, Two-Spotted Spider Mite (Tetranychus urticae) and Western Flower Thrips (Frankliniella occidentalis)". Thesis, North Dakota State University, 2019. https://hdl.handle.net/10365/31549.
Testo completoAbstract (sommario):
Insecticidal neonicotinoid seed treatments in agriculture is a common insect pest management strategy. Seed treatments have systemic and residual toxicity, which are effective against target insect pests. However, effects on other arthropod pests is less straightforward. We evaluated the effects of a neonicotinoid seed treatment, thiamethoxam, on two soybean pests, herbivorous two-spotted spider mites (Tetranychus urticae Koch) and an omnivore and facultative predator of spider mite eggs, western flower thrips (Frankliniella occidentalis Pergande). We used greenhouse and laboratory experiments to evaluate thiamethoxam soybean seed treatments on spider mite densities and thrips omnivorous feeding behavior. Our results suggest seed treatment may encourage spider mite reproduction and influence thrips herbivory over egg predation when both resources are available. Implications of this study highlight the use of thiamethoxam soybean seed treatment as a potential contributor to increased spider mite populations, thrips reduced role as spider mite predator, and increased role as herbivorous pest.
3
Feszty, Daniel. "Numerical simulation and analysis of high-speed unsteady spiked body flows". Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368552.
Testo completo
4
Chen, Yan. "Nitrogen and phosphorus fertilization of ivy geranium (Pelargonium peltatum) and impatiens (Impatiens wallerana) affects population levels of twospotted spider mite (Tetranychus urticae) and western flower thrips (Frankliniella occidentalis) /". Search for this dissertation online, 2003. http://wwwlib.umi.com/cr/ksu/main.
Testo completo
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Strandmark, Alma. "Baltic shore-lands facing climate change". Doctoral thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-141794.
Testo completoAbstract (sommario):
This thesis provides new insight concerning drivers behind differences in arthropod diversity and abundance in Baltic shore ecosystems and how the arthropod communities might be affected when the conditions in the Baltic Sea are altered due to climate change. The focus has been on climate related changes that are unique for coastal ecosystems, especially sea level rise and changes in the inflow of marine nutrients. As sea levels rise, features in coastal landscapes will be altered, islands and habitats will be flooded and diminished, and structural connectivity within the island landscape will therefore change. This thesis shows that arthropod diversity within the two arthropod groups, spiders and beetles, increases with island size but also that diversity is positively influenced by a high number of islands in the surroundings. A changed distribution and occurrence of marine species, due to climate change or eutrophication, can also affect terrestrial organisms on the shore. In the Baltic Sea the new conditions following climate change will decrease the prevalence of bladder-wrack and benefit filamentous algae. Algal deposits on shores reflect the marine species composition and a decreased prevalence of bladder-wrack in the Baltic Sea will also be visible on the shores. This thesis shows that a lower proportion of bladder-wrack in the algal deposits will decrease the diversity and abundance of arthropods in these deposits. Changes in the marine environment may also affect the inflow of insects with aquatic life stages and terrestrial adult stages. On Baltic shores, prey species with aquatic life stages, especially chironomids, constitute a large proportion of the diet of the terrestrial predatory group, wolf spiders. In freshwater system, the inflow of chironomids is known to decrease with elevated water temperatures if this is true in the Baltic Sea prey availability of wolf spiders would decrease. This thesis supports the importance of chironomids as a prey for coastal wolf spiders, but also shows that the diet varies over season with dominance of terrestrial prey in early summer shifting to a dominance of marine prey in late summer and autumn. This seasonal variation is primarily due to a gradual increase in the consumption of chironomids over season. Climate change has the potential to alter the biogeographical conditions in coastal landscapes as well as the density and quality of marine nutrient inflow. Sea level rise will diminish and flood islands and this thesis shows that a moderate sea level rise of 0.5 meters would make the total number of islands in the outer part of Stockholm archipelago decrease with about 25 %. Sea level rise could thus have consequences for arthropod diversity in Baltic shore meadows in the near future. The combined effects of sea level rise and changed prevalence of marine species in the Baltic Sea will affect the abundance and diversity of arthropods substantially. The abundance and diversity of spiders and beetles will decrease on shores that today have a high occurrence of bladder-wrack and prey availability for coastal predators might decrease due to a decreased inflow of chironomids. Changes in the arthropod communities could have consequences also further up in the food chain, such as for shore birds feeding on these arthropods.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.
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Cho, Moonsung [Verfasser], Peter [Akademischer Betreuer] Neubauer, Ingo [Akademischer Betreuer] Rechenberg, Klaus [Akademischer Betreuer] Affeld, Peter [Gutachter] Neubauer, Ingo [Gutachter] Rechenberg, Ulrich [Gutachter] Kertzer e Bournazou Mariano Nicolas [Gutachter] Cruz. "Suspension of a point-mass-loaded filament in non-uniform flows : the ballooning flight of spiders / Moonsung Cho ; Gutachter: Peter Neubauer, Ingo Rechenberg, Ulrich Kertzer, Mariano Nicolas Cruz Bournazou ; Peter Neubauer, Ingo Rechenberg, Klaus Affeld". Berlin : Technische Universität Berlin, 2020. http://d-nb.info/1210572273/34.
Testo completo
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黃啟嘉. "An Analysis of the Homosexual Movies by Zero Chou : Take《Splendid Float》、《Spider Lilies》and《Drifting Flowers》as examples". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/2wcy8h.
Testo completoAbstract (sommario):
碩士臺北市立大學
視覺藝術學系視覺藝術教學碩士學位班
102
Taiwan lesbian’s movies have been improved a lot since 2000. No matter in topics or plots, they have been directed in diverse and cultural ways. One of them, Cho Mei-Ling, who directed lesbian trilogies, presented various aspects of unique customs and cultures in Taiwan. This study researches in how Taiwan lesbians came through, how they lived, and what they thought. Especially, that is from the objectives of Cho Mei-Ling who announced herself a lesbian in public. According to the accomplishing moment, the lesbian trilogies of Zero Chou are “Splendid Float,” “Spider Lilies,” and “Drifting Flowers.” First of all, this study analyses the director’s personal profiles. The director Chou had taken documental films in the early period. Those films concern this island of emotions, people, and the society. Second, discuss about the lives of lesbians. After that, Chou commenced to document lesbians and continued to put her efforts in lesbian creations. In this study, the lesbian trilogies are investigated separately. In “Splendid Float,” analyze the sex role-play in Drag Queen and discuss on Queer Gaze. In the second film ”Spider Lilies,” it is discussed by the role of Takeko about the representation of lesbian T character and the diversified bodily desires. In addition, the social resistence and the relationships among lesbians are discussed in this study. In “Drifting Flower,” not only talk over butch’s representation, femme’s self-identification, but also the care between elder lesbians. Last but not least, these three movies are placed in correlational comparisons, also compared with other chinese lesbian movies. Consequently, the different representing ways by Chou Mei-Ling and other directors are researched deeply here. Based on nowaday reflections, which respect diverse sex characters, lesbian films will stand out toward a brilliant direction in the future.
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Hoffmann, Nigel. "Goethe's notion of 'theory' : Goethean phenomenology as a new ecological discipline". Thesis, 1994. http://handle.uws.edu.au:8081/1959.7/234.
Testo completoAbstract (sommario):
Around two hundred years ago Goethe made the statement: ‘Let us not seek for something behind the phenomena – they themselves are the theory’. This would appear to be the antithesis of the claim of certain contemporary schools of epistemological thought, that a ‘theory’ is a construction of the human mind. Yet Goethe’s scientific aims are resonant with a present day ecological need: to find a form of ‘nature study’ which springs from a desire to care for things rather than merely to explain them, which can help to create a harmony between human and non-human nature. Goethe’s approach is phenomenological in that it seeks to uncover things ‘on their own terms’; it is integral in that it embraces both art and science. A Goethean methodology is used to study four Australian native plants: Grevillea buxifolia, Scaevola remosissima, Banksia integrifolia and Kunzea ambigua. It is suggested that Goethe’s way of ‘nature study’ fulfils the contemporary need for a participatory knowing which is responsible for the thing being researched, and various possibilities are indicated for further research and application – in the biological sciences and in disciplines such as architecture, landscape design and environmental education.
9
Shuttleworth, Adam. "Ecology and evolution of the specialized hemipepsis-wasp (Hymenoptera : Pompilidae) pollination guild in South Africa". Thesis, 2011. http://hdl.handle.net/10413/10107.
Testo completoAbstract (sommario):
Pollinators are believed to have played a key role in the radiation of flowering plants. The Grant-Stebbins model of pollinator-mediated speciation, in which evolutionary shifts between pollinators
result in phenotypic diversification and enforce reproductive isolation, is one of the most compelling
hypotheses for the rapid diversification of angiosperms. A key principle in this model is that plant
pollination systems tend towards specialization, resulting in convergent suites of floral traits
(syndromes) associated with particular types of pollinators. However, the expectation of pollination
system specialization is not always supported by ecological data and has also been questioned on
theoretical grounds. In this thesis, I examine pollination by Hemipepsis spider-hunting wasps
(Hymenoptera, Pompilidae, Pepsinae) and use this system to address questions about levels and
proximal mechanisms of floral specialization, floral shifts and convergent evolution of floral traits.
Specialized pollination by Hemipepsis wasps is a newly described pollination system within the
angiosperms. I document pollination by these wasps for the first time in 15 South African grassland
plant species, including two species of Eucomis (Hyacinthaceae) and 13 asclepiads (Apocynaceae:
Asclepiadoideae). In one of the asclepiads, Xysmalobium undulatum, I describe a bimodal pollination
system involving both Hemipepsis wasps and a cetoniine beetle. I also describe an unusual and
potentially antagonistic pollination mechanism whereby wasps are systematically dismembered
during the insertion of pollinia in the two asclepiads Pachycarpus asperifolius and P. appendiculatus.
I have used these and previous case studies to establish the existence of a new pollination guild,
consisting of at least 21 plant species (across 10 genera and three families), that are reliant on four
functionally similar species of Hemipepsis wasp for pollination. Plants in the guild are distributed
throughout the moist grasslands of eastern South Africa and flower from September through until early May, peaking in December/January.
The Hemipepsis-wasp pollination guild is characterized by high levels of functional
specialization (17 of the 21 known guild members are pollinated exclusively by Hemipepsis wasps),
despite the absence of morphological adaptations to prevent non-pollinating insects from accessing
nectar. I used field and laboratory based experiments to explore the function of floral traits in
enforcing specialization. These showed that Hemipepsis wasps primarily use scent, rather than visual
cues, to locate flowers, but I was unable to firmly identify specific compounds responsible for the
attraction of these wasps (compounds that elicited antennal responses in preliminary GC-EAD experiments did not attract wasps in bioassays). The chemical composition of the floral scents of guild
members was examined for 71 individuals representing 14 species in addition to previous studies, and
found to comprise complex blends of volatiles (usually containing between 30 and 50 compounds),
typically dominated by aliphatics and monoterpenes with small amounts of aromatics. I also showed
that the floral colours of guild members are similar to background vegetation, suggesting that floral
colours are adapted for crypsis to avoid detection by non-pollinating insects. Palatability choice experiments with honeybees showed that non-pollinating insects find the nectars of at least three of
the asclepiad guild members distasteful. Plants in this guild thus appear to achieve specialization
through biochemical filters (scent as an attractant and differentially palatable nectar) and cryptic coloration.
Pollinator-mediated convergence in floral traits is the fundamental basis for pollination
syndromes, but has seldom been rigorously analyzed. Flowers in the Hemipepsis-wasp pollination
guild share several qualitative traits, including dull greenish- or brownish-white colour, often with
purple blotches, exposed sucrose dominant nectar with a relatively high sugar concentration (typically
over 50% sugar by weight) and a sweet/spicy fragrance to the human nose. To test for convergent
evolution in guild members, I compared scent, nectar and colour traits of guild members to those of
congeners with different pollinators. Although traits often differed between guild members and their
congeners, I found little evidence for overall convergence in floral scent profiles and nectar
properties, but floral colours in the guild were significantly closer to the colour of background
vegetation than those of congeners. At this stage, the lack of knowledge about specific floral volatiles
that influence Hemipepsis-wasp behaviour and secondary nectar constituents that limit non-pollinator
visits makes it difficult to identify the extent of biochemical convergent evolution within the guild.
The directions and functional traits involved in evolutionary transitions between pollination by
Hemipepsis wasps and other vectors are currently difficult to ascertain as there is limited phylogenetic
data for the plant families concerned. In the genus Eucomis, fly and Hemipepsis-wasp pollinated
species are very similar in floral morphology and colour, but differ strongly in floral scent. Using
manipulative field experiments in conjunction with detailed analyses of colour, scent and
morphology, I was able to show that a shift between wasp and fly pollination could be induced simply
by manipulating oligosulphides in the scent emission from inflorescences. When considered in
combination with other experiments highlighting the importance of scent as a pollinator attractant for
all guild members, this suggests that scent properties may have played a key role in the evolutionary
transitions between pollination by Hemipepsis wasps and other vectors.
This research has established that pollination by Hemipepsis spider-hunting wasps is more
geographically and phylogenetically widespread than was previously known, and has confirmed that
these wasps are important and consistent pollinators in southern African grassland ecosystems. I have
shown that a distinct guild of plants is specialized for pollination by these wasps. The high levels of
specialization within this guild highlight the effectiveness of biochemical filters and cryptic coloration
in limiting the spectrum of flower visitors. The major challenge ahead will be to identify the floral
volatiles that attract Hemipepsis wasps and the non-sugar constituents that make the nectars of some
guild members differentially palatable. These would both contribute greatly to our understanding of
floral specialization and the mechanisms involved in the radiation of the angiosperms.Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
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Зазуляк, Тарас Григорович, e Taras Hryhorovych Zazulyak. "Оптимізація конструкції станини фрезерного верстата методом комп’ютерного моделювання". Master's thesis, 2021. http://elartu.tntu.edu.ua/handle/lib/35230.
Testo completoAbstract (sommario):
The purpose and objectives of the master's work - to obtain a new design of the body (frame) of the milling machine with subsequent theoretical study of its rigidity, namely 3D-models of the milling machine to obtain the maximum deviation and its comparison with analytical calculations.
Objectives of the study:
- perform analysis of the layout of milling machines;
- to model a column (bed) of the milling machine;
- set restrictions on surfaces that must remain unchanged;
- to analyze the method of calculating the stiffness of milling machines;
- conduct a theoretical study using CAD Fusion 360, Autodesk Inventor 2021;
- compare the results of deviations of the column of the milling machine obtained by ITU with analytical calculations;
The object of research is the frame of a milling machine. The subject of research is the optimization of the frame shape. Research methods. Theoretical research is based on ITU, the use of the module of generative design, morphological analysis.
General conclusions:
1. An information search on the use and implementation of modern design methods such as topological optimization and generative design. It is proved that these methods are efficient and metal-saving, but currently energy-intensive. Use in aeronautics, transport and architecture prove their prospects for implementation in the near future;
2. The analysis of the layout of the milling machine and the optimization of its design proved its functionality. Using the topological optimization module in Inventor 2021 it was possible to reduce the weight of the product to 1834 kg with sufficient rigidity of the frame.
3. The consoleless arrangement of the machine is suitable for processing of heavy details and weighing up to 1500 kg that is especially actual in arrangement of machines with ChPK.
4. Theoretical calculations and computer simulations coincided with an error of up to 10%. The analysis of the stress-strain state showed the maximum deflection of the column at the upper point of 0.0055 mm;
5. Modeling of the column of the milling machine showed that neither the partitions nor their shape do not significantly affect the rigidity of the column. Which is confirmed by theoretical and experimental studies.
Cast iron still remains the most common material for the manufacture of body parts, with the effective use of other modern vibration-insulating materials. This can be explained by the cost and performance of manufacturing technologyМета і завдання магістерської роботи - отримання нової конструкції корпусу (станини) фрезерного верстата з подальшим теоретичним дослідженням її жорсткості, а саме 3D-моделі фрезерного верстата для отримання максимальної величини відхилення і її порівняння з аналітичним розрахунками. Завдання дослідження: - виконати аналіз компонувань фрезерних верстатів; - змоделювати колону (станину) фрезерного верстата; - задати обмеження поверхонь, які повинні залишитися незмінними; - провести аналіз методики розрахунку жорсткості фрезерних верстатів; - провести теоретичне дослідження з використанням САПР Fusion 360, Autodesk Inventor 2021; - порівняти результати відхилень колони фрезерного верстату отриманого МСЕ з аналітичними розрахунками; Об’єкт дослідження – станина фрезерного верстату. Предмет дослідження – оптимізація форми станини. Методи дослідження. Проведення теоретичних досліджень ґрунтується на МСЕ, використання модуля генеративного проектування, морфологічного аналізу. Загальні висновки: 1. Проведено інформаційний пошук стосовно використання і впровадження сучасних методів проектування таких як топологічна оптимізація та генеративне проектування. Доведено, що ці способи є ефективними і металоощадливими, проте на даний час – енерговитратними. Використання в аеронавтиці, транспорті та архітектурі доводять їх перспективність впровадження в близькому майбутньому; 2. Проведений аналіз компонування фрезерного верстата і оптимізація його конструкції довела свою функціональність. Використовуючи модуль топологічної оптимізації в Inventor 2021 вдалося зменшити масу виробу до 1834 кг при достатній жорсткості станини. 3. Безконсольне компонування верстату підходить для оброблення важких деталей і вагою до 1500 кг, що особливо актуально в компонуванні верстатів з ЧПК. 4. Теоретичні розрахунки і комп’ютерне моделювання співпали з похибкою до 10%. Проведений аналіз напружено-деформованого стану показав максимальний прогин колони у верхній точці 0,0055 мм; 5. Моделювання колони фрезерного верстата показало, що ні перегородки, ні їх форма не суттєво впливають на жорсткість колони. Що підтверджено теоретичними та експериментальними дослідженнями. 6. Чавун досі залишається найпоширенішим матеріалом для виготовлення корпусних деталей, по при ефективне використання інших сучасних віброізолюючих матеріалів. Це можна пояснити вартістю і відпрацьованістю технології виготовлення.
Вступ...7 1. Аналітичний розділ...8 1.1.Огляд та аналіз проблематики дипломної роботи...8 1.2.Інформаційно-патентний пошук...9 1.3.Висновки по розділу, постановка мети та задач дослідження...26 2.Дослідно-проектний розділ...28 2.1.Вибір рухів по забезпеченню виробничого циклу на верстаті...28 2.2.Обґрунтування структурно-кінематичної схеми верстата....30 2.3.Обґрунтування модулів верстата (МК,ТМ)...31 2.4.Аналіз типів базових компонувань...34 2.4.1.Вибір верстатів-аналогів...34 2.4.2.Вибір оптимальної схеми компонування...34 2.5.Опис та обґрунтування конструкції станини на основі аналогу....37 2.6.Принцип роботи та технологічні розрахунки...41 2.6.1.Силові та міцнісні розрахунки станини...41 2.6.2.Розрахунок безступеневого приводу...47 2.7.Висновки по розділу...51 3.Науково-дослідний розділ...52 3.1.Методика та план проведення наукових досліджень...52 3.2.Розробка моделі об‘єкта досліджень...52 3.4.Обговорення та аналіз отриманих результатів* (*оприлюднені результати досліджень подаються в додатках)...59 3.5.Висновки за результатами наукового дослідження...60 4.Охорона праці та безпека в надзвичайних ситуаціях....61 4.1.Охорона праці при роботі на металообробних верстатах...61 4.1.1.Додаткові вимоги безпеки...62 4.2.Безпека в надзвичайних ситуаціях....64 4.2.1.Техногенні небезпеки....64 4.2.2.Аварії з викидом радіоактивних речовин у навколишнє середовище...65 ЗАГАЛЬНІ ВИСНОВКИ...67 ПЕРЕЛІК ПОСИЛАНЬ....71 ДОДАТКИ...61
Libri sul tema "Spider flowers"
1
Hughes, Ted. Flowers and insects: Some birds and a pair of spiders. New York: Knopf, 1986.
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1922-, Baskin Leonard, a cura di. Flowers and insects: Some birds and a pair of spiders. London: Faber and Faber, 1986.
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Predator upon a flower: Life history and fitness in a crab spider. Cambridge, MA: Harvard University Press, 2007.
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4
Lizzie, Orme, a cura di. The country book of herbs & spices. London: Tiger, 1994.
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Sheen, Joanna. The country book of herbs & spices. London: Anaya, 1993.
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Press, Favorite Recipes, a cura di. Flights of fancy: A cookbook of fanciful recipes for artful living : edible flowers & herb recipes. Seaside, Fla: Festival Promotions, 1994.
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Leeson, Christine. Just for you! Wilton, CT: Tiger Tales, 2004.
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Creasy, Rosalind. Rosalind Creasy 's recipes from the garden. North Clarendon, Vt: Tuttle Pub., 2008.
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Symposium on Seed Research in Horticulture (4th 1988 Angers, France). Symposium on Seed Research in Horticulture: Flowers, vegetables, medicinal and aromatic plants and spices : Angers, France, September 5-9, 1988. [Wageningen, Netherlands]: International Society for Horticultural Science, 1989.
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Herbs for weddings & other celebrations: A treasury of recipes, gifts, & decorations. Pownal, Vt: Storey Communications, 1993.
Cerca il testo completoCapitoli di libri sul tema "Spider flowers"
1
Kaul, Veenu, e Shveta Saroop. "Bioactive Compounds of Asian Spider Flower (Cleome viscosa Linn.)". In Reference Series in Phytochemistry, 121–39. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-57415-4_8.
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Kaul, Veenu, e Shveta Saroop. "Bioactive Compounds of Asian Spider Flower (Cleome viscosa Linn.)". In Reference Series in Phytochemistry, 1–19. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44578-2_8-1.
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Pallini, Angelo, Arne Janssen e Maurice W. Sabelis. "Do western flower thrips avoid plants infested with spider mites? Interactions between potential competitors". In Ecology and Evolution of the Acari, 375–80. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-017-1343-6_27.
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González, Daniel, Rex Friesen, Thomas F. Leigh, T. Wilson e M. Waggoner. "Naturally-Occurring Biological Control: Western Flower Thrips Impact on Spider Mites in California Cotton". In Thrips Biology and Management, 317–23. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4899-1409-5_48.
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Hancock, James F. "Silk route connections." In Spices, scents and silk: catalysts of world trade, 94–106. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789249743.0008.
Testo completoAbstract (sommario):
Abstract This chapter elaborates the landscape of political power and Silk trade in the Middle East. It consists of eleven subchapters which are about the empires of the Middle East, Roman intrusions into the Middle East, Palmyra as the greatest of the Middle Eastern trading centres, the power of Zenobia, Kushans take the centre of the silk routes, Kushan Connections, Parthia's control of the Terminus, Sasanians taking over, ebbs and flows of the silk route, plague that slowed the trade, and lastly, silk trade after 400 ce.
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Morgan, Lynette. "Background and history of hydroponics and protected cultivation." In Hydroponics and protected cultivation: a practical guide, 1–10. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789244830.0001.
Testo completoAbstract (sommario):
Abstract Along with new types of protected cropping structures, materials and technology, the range and diversity of hydroponic crops grown are also expanding. While the greenhouse mainstays of nursery plants, tomatoes, capsicum, cucumber, salad vegetables and herbs will continue to expand in volume, newer, speciality and niche market crops are growing in popularity. These include new cut flower species, potted plants and ornamental crops, and a growing trend in the commercial production of medicinal herbs using high-technology methods such as aeroponics. Exotic culinary herbs such as wasabi, dwarf fruiting trees and spices such as ginger and vanilla are now grown commercially in protected cropping structures, while many home gardeners continue to take up hydroponics and protected cropping as both a hobby and a means of growing produce. Protected cropping and hydroponic methods will further their expansion into hostile climates which never previously allowed the production of food.
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Hage, Hassan, Emmanouil Seferis, Vahid Hashemi e Frank Mantwill. "SMC4PEP: Stochastic Model Checking of Product Engineering Processes". In Fundamental Approaches to Software Engineering, 155–62. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99429-7_9.
Testo completoAbstract (sommario):
AbstractProduct Engineering Processes (PEPs) are used for describing complex product developments in big enterprises such as automotive and avionics industries. The Business Process Model Notation (BPMN) is a widely used language to encode interactions among several participants in such PEPs. In this paper, we present SMC4PEPl as a tool to convert graphical representations of a business process using the BPMN standard to an equivalent discrete-time stochastic control process called Markov Decision Process (MDP). To this aim, we first follow the approach described in an earlier investigation to generate a semantically equivalent business process which is more capable of handling the PEP complexity. In particular, the interaction between different levels of abstraction is realized by events rather than direct message flows. Afterwards, SMC4PEPl converts the generated process to an MDP model described by the syntax of the probabilistic model checking tool PRISM. As such, SMC4PEPl provides a framework for automatic verification and validation of business processes in particular with respect to requirements from legal standards such as Automotive SPICE. Moreover, our experimental results confirm a faster verification routine due to smaller MDP models generated from the alternative event-based BPMN models.
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"Mulberrys, sauce and spider-orchids". In Flowers of the Forest, 182–84. Princeton University Press, 2010. http://dx.doi.org/10.1515/9780691237602-045.
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Willmer, Pat. "Pollination by Bees". In Pollination and Floral Ecology. Princeton University Press, 2011. http://dx.doi.org/10.23943/princeton/9780691128610.003.0018.
Testo completoAbstract (sommario):
This chapter considers pollination by bees, or melittophily. The bee flower syndrome involves flowers that have medium to long corolla tubes, often pendant, usually zygomorphic (i.e., bilaterally symmetrical rather than radial), commonly with a landing platform with complex texture or ridging so that a bee can hang on easily, and often arranged in spiked inflorescences. The flowers typically open in the early morning and offer their main rewards before midday, although a few are particularly rewarding in the evenings. The chapter begins with a discussion of the bee’s feeding apparatus and feeding methods, along with sensory systems and bee perception of flowers. It then examines the effects of sociality on bees’ flower-visiting patterns as well as behavior and learning in flower-visiting bees. Finally, it analyzes six melittophily types namely: solitary bees, carpenter bees, euglossine bees, bumblebees, stingless bees, and honeybees.
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"Xysticus emertoni, a Cohabiting Crab Spider". In Predator upon a Flower, 304–18. Harvard University Press, 2007. http://dx.doi.org/10.2307/j.ctv23dxd2z.14.
Testo completoAtti di convegni sul tema "Spider flowers"
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Otte, Eileen, Christina Alpmann e Cornelia Denz. "Tailored vectorial light fields: flower, spider web and hybrid structures". In SPIE Technologies and Applications of Structured Light, a cura di Takashige Omatsu. SPIE, 2017. http://dx.doi.org/10.1117/12.2274935.
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Welti, Ellen. "Crab spiders (Thomisidae) attract insect flower-visitors without UV signaling". In 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.113748.
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Grudzinski, J. J., R. Fischer, R. L. Talaga, V. Guarino, A. Pla-Dalmau, J. E. Fagan e C. Grozis. "Evaluation of Mechanical Properties at the Knit Line Interface in a Complex Multi-Cell PVC Extrusion". In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-40217.
Testo completoAbstract (sommario):
In order to form internal cells in PVC extrusions, the die requires an insert or internal member that the material flows past. These inserts are supported to the outer die structure by so-called spiders that pass through to the outer wall of the extrusion die. The extruded material must separate and then recombine as it passes over the spider. The material must then form a bond at this interface shortly before exiting the die. These interfaces are referred to as knit-lines. In a recent project involving a large and complex PVC extrusion, difficulty was encountered in developing these knit lines within the webs of the extrusions. Upon visual inspection, these interfaces appeared to be without bond over portions of the cross section. However, mechanical testing in the worst knits revealed that bonding had occurred with the knit providing 85% of the bulk material strength although without supporting any significant ductility. At the same time, knits at different parts of the extrusions showed ductility comparable with the base material. Altering the process variables showed a means for improvement in the webs but this was limited by other constraints. In this work we describe the character of the knitlines and the resulting mechanical properties along with the testing methodology.
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YAMAUCHI, MASAFUMI, KOZO FUJII, YOSHIAKI TAMURA e FUMIO HIGASHINO. "Numerical investigation of supersonic flows around a spiked blunt-body". In 31st Aerospace Sciences Meeting. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1993. http://dx.doi.org/10.2514/6.1993-887.
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Kish, Laszlo B. "Stochastic Resonance in interacting flows of cars and neural spikes". In Unsolved problems of noise and fluctuations. AIP, 2000. http://dx.doi.org/10.1063/1.59973.
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Feszty, D., K. Badcock e B. Richards. "Numerical simulation of the hysteresis phenomenon in high-speed spiked body flows". In 38th Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2000. http://dx.doi.org/10.2514/6.2000-141.
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Post, Madison J., e Richard E. Cupp. "The Effects of CO2 Gain-Switched Spikes on Estimating Lidar Doppler Shifts". In Coherent Laser Radar. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/clr.1991.mb2.
Testo completoAbstract (sommario):
We reported earlier1 that, despite having achieved single-mode output from the TEA laser in NOAA’s pulsed Doppler lidar, we could not estimate Doppler shifts to accuracies better than 100 kHz rms, or about 0.6 m s–1 using a complex pulse-pair algorithm. Inaccuracies of this magnitude are acceptable for mesoscale or terrain-induced flows, but they limit the usefulness of the lidar in studying convective flows and turbulent transfers, where accuracies near 0.1 m s–1 are required.
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Im, Hong-Sik, Xiangying Chen e Ge-Cheng Zha. "Detached Eddy Simulation of Unsteady Stall Flows of a Full Annulus Transonic Rotor". In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23465.
Testo completoAbstract (sommario):
This paper uses the advanced Delayed-Detached Eddy Simulation (DDES) of turbulence to simulate rotating stall inception of NASA Rotor 67. The rotor is a low-aspect-ratio transonic axial-flow fan with a tip speed of 429 m/s and a pressure ratio of 1.63. A full annulus simulation was employed with the time accurate compressible Navier-Stokes code in order to accurately capture the the formation of long-length disturbance and a short-length inception (spike). The validation for all numerical methods used in this study was accomplished by the comparisons of the CFD solutions with the test data in advance of unsteady simulations. Self-induced rotating stall development is simulated holding the same back pressure at the near stall experiment without any throttling. Spike type rotating stall occurs and rotates at roughly 50% of rotor speed counter to the rotation. After spike onset, rotating stall fully develops approximately within 2 rotor revolutions. Two distinct characteristics that can advance the mechanism of spike type rotating stall are observed. First, the passage shock is fully detached from rotor and decays during the spike inception. Consequently the shifted sonic line at the upstream of rotor allows stalling flow to propagate to the neighboring passage. Second, the trailing edge back flow contributes to the build up of a fully developed stall cell by pushing tip clearance flow toward blade leading edge and inducing tip spillage flow. Tip vortex originated from the leading edge dies out during spike inception as the swirl angle of incoming tip flow decreases, while in the unstalled passages it develops without breakdown. DDES challenge for the complete blade row reflects well the sequence of rotating stall and its unsteady behavior.
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Nishioka, Takahiro, Toshio Kanno e Hiroshi Hayami. "Characteristics of End-Wall Flow at Spike and Modal Stall Inceptions in a Variable-Pitch Axial-Flow Fan". In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27738.
Testo completoAbstract (sommario):
The flow mechanisms for spike and modal stall inceptions in a low-speed axial-flow fan with a relatively large tip clearance were studied. The pressure and velocity fluctuations were measured to clarify the influences of blade loading, end-wall flow, and tip-leakage flow on stall inception at two stagger-angle settings for the rotor blade, which are the design and small stagger-angle settings. A rotating instability was observed near the maximum pressure-rise point at both design and small stagger-angle settings. This instability was induced by the interaction between the incoming flow, tip-leakage flow, and end-wall backflow. The stall inception patterns were a spike type at the design stagger-angle setting and a modal type at the small stagger-angle setting. At the design stagger-angle setting, the interface between the incoming flow, tip-leakage flow, and end-wall backflow became parallel to the rotor leading edge plane and reached the pressure side of adjacent blade. The interaction between these flows generated the large end-wall blockage in the rotor blade passage, and this blockage developed leading edge separation on the overloaded rotor blade at the tip. The leading edge separation that developed then grew into a spike, which traveled upstream of the rotor. At the small stagger-angle setting, the rotating instability and modal disturbance were also induced by the interaction between the incoming flow, tip-leakage flow, and end-wall backflow. However, the interface between the tip-leakage flow and end-wall backflow surrounded the suction surface of the rotor blade at the tip and neither became parallel to the leading edge plane nor reached the pressure side of the adjacent blade even though the rotor blade at the tip had stalled. Spikes did not therefore appear. The modal disturbance periodically decreased the inlet velocity and induced a long length-scale stall cell including a spike. It is concluded from these results that the stall inception patterns, which were characterized by the interaction between the incoming flow, tip-leakage flow, and end-wall backflow, depended on the stagger-angle settings for the rotor blades.
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Zhang, J., F. Lin, J. Chen e C. Nie. "The Flow Mechanism of How Distorted Flows Deteriorate Stability of an Axial Flow Compressor". In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27628.
Testo completoAbstract (sommario):
The stalling behavior in a single-stage low-speed axial compressor under inlet distortion is investigated. A blade-passage-scale flow mechanism is proposed to explain the stability deterioration caused by inlet distortion for the tested compressor exhibiting spike stall inception. In contrast to the existing understanding of inlet distortion based on system scale dynamics, the main elements of this flow mechanism are the unsteady behavior of tip leakage vortices (TLV) under inlet distortion; its effect on the initiation of spike flow disturbances, and its interaction with distorted sectors. Rotating inlet distortion (RID) is used as a tool because RID makes it possible to directly compare the flows between distorted and clean flow sectors with fixed measurement stations on the casing, and the fact that the stationary inlet distortion is only a special case of RID makes the results generic. The tests demonstrate that the blade loading in the distorted sector is heavier than that in the non-distorted sector, causing the TLV in the distorted sector move closer to the leading edge of the rotor blade and thus be the first to initiate the spike-like disturbance. The unsteady CFD simulation further confirms that such a disturbance corresponds to a vortex spinning out of the leading edge of the blades. However, the initiation of this spike-like disturbance doesn’t necessarily trigger the full stall immediately. The tracking of the disturbances indicates that most of such spike-like disturbances will be smeared by non-distorted sector and the growth of the spike-like disturbances actually relate closely to how and how often the path of the propagating disturbances come across the path of the rotating distorted sector. The proposed blade-passage-scale flow mechanism also offers an alternative explanation to the “resonance” phenomenon in rotating inlet distortion research, which was explained with excitation-and-response theory for compressors that exhibit modal stall inception.
Rapporti di organizzazioni sul tema "Spider flowers"
1
Philosoph-Hadas, Sonia, Peter Kaufman, Shimon Meir e Abraham Halevy. Signal Transduction Pathway of Hormonal Action in Control and Regulation of the Gravitropic Response of Cut Flowering Stems during Storage and Transport. United States Department of Agriculture, ottobre 1999. http://dx.doi.org/10.32747/1999.7695838.bard.
Testo completoAbstract (sommario):
Original objectives: The basic goal of the present project was to increase our understanding of the cellular mechanisms operating during the gravitropic response of cut flowers, for solving their bending problem without affecting flower quality. Thus, several elements operating at the 3 levels o the gravity-induced signal transduction pathway, were proposed to be examined in snapdragon stems according to the following research goals: 1) Signaling: characterize the signal transduction pathway leading to the gravitropic response, regarding the involvement of [Ca2+]cyt as a mediator of IAA movement and sensitivity to auxin. 2) Transduction by plant hormones: a) Examine the involvement of auxin in the gravitropic response of flower stems with regard to: possible participation of auxin binding protein (ABP), auxin redistribution, auxin mechanism of action (activation of H+-ATPase) mediation by changes in [Ca2+]cyt and possible regulation of auxin-induced Ca2+ action b: calmodulin-activated or Ca2+-activated protein kinases (PK). b) Examine the involvement of ethylene in the gravitropic response of flower stems with regard to auxin-induced ethylene production and sensitivity of the tissue to ethylene. 3) Response: examine the effect of gravistimulation on invertase (associated with growth and elongation) activity and invertase gene expression. 4) Commercial practice: develop practical and simple treatments to prevent bending of cut flowers grown for export. Revisions: 1) Model systems: in addition to snapdragon (Antirrhinum majus L.), 3 other model shoe systems, consisting of oat (Avena sativa) pulvini, Ornithogalun 'Nova' cut flowers and Arabidopsis thaliana inflorescence, were targeted to confirm a more general mechanism for shoot gravitropism. 2 Research topics: the involvement of ABP, auxin action, PK and invertase in the gravitropic response of snapdragon stems could not be demonstrated. Alternatively, the involvement in the gravity signaling cascade of several other physiological mediators apart of [Ca2+]cyt such as: IP3, protein phosphorylation and actin cytoskeleton, was shown. Additional topics introduced: starch statolith reorientation, differential expression of early auxin responsive genes, and differential shoot growth. Background to the topic: The gravitropic bending response of flowering shoots occurring upon their horizontal placement during shipment exhibits a major horticultural problem. In spite of extensive studies in various aboveground organs, the gravitropic response was hardly investigated in flowering shoots. Being a complex multistep process that requires the participation of various cellular components acting in succession or in parallel, analysis of the negative gravitropic response of shoot includes investigation of signal transduction elements and various regulatory physiological mediators. Major achievements: 1) A correlative role for starch statoliths as gravireceptors in flowering shoot was initially established. 2) Differentially phosphorylated proteins and IP3 levels across the oat shoe pulvini, as well as a differential appearance of 2 early auxin-responsive genes in snapdragon stems were all detected within 5-30 minutes following gravistimulation. 3) Unlike in roots, involvement of actin cytoskeleton in early events of the gravitropic response of snapdragon shoots was established. 4) An asymmetric IAA distribution, followed by an asymmetric ethylene production across snapdragon stems was found following gravistimulation. 5) The gravity-induced differential growth in shoots of snapdragon was derived from initial shrinkage of the upper stem side and a subsequent elongation o the lower stem side. 6) Shoot bending could be successfully inhibited by Ca2+ antagonists (that serve as a basis for practical treatments), kinase and phosphatase inhibitors and actin-cytoskeleton modulators. All these agents did not affect vertical growth. The essential characterization of these key events and their sequence led us to the conclusion that blocking gravity perception may be the most powerful means to inhibit bending without hampering shoot and flower growth after harvest. Implications, scientific and agriculture: The innovative results of this project have provided some new insight in the basic understanding of gravitropism in flower stalks, that partially filled the gap in our knowledge, and established useful means for its control. Additionally, our analysis has advanced the understanding of important and fundamental physiological processes involved, thereby leading to new ideas for agriculture. Gravitropism has an important impact on agriculture, particularly for controlling the bending of various important agricultural products with economic value. So far, no safe control of the undesired bending problem of flower stalks has been established. Our results show for the first time that shoot bending of cut flowers can be inhibited without adverse effects by controlling the gravity perception step with Ca2+ antagonists and cytoskeleton modulators. Such a practical benefit resulting from this project is of great economic value for the floriculture industry.
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Philosoph-Hadas, Sonia, Peter B. Kaufman, Shimon Meir e Abraham H. Halevy. Inhibition of the Gravitropic Shoot Bending in Stored Cut Flowers Through Control of Their Graviperception: Involvement of the Cytoskeleton and Cytosolic Calcium. United States Department of Agriculture, dicembre 2005. http://dx.doi.org/10.32747/2005.7586533.bard.
Testo completoAbstract (sommario):
Original objectives: The basic goal of the present project was to study the mechanism involved in shoot graviperception and early transduction, in order to determine the sequence of events operating in this process. This will enable to control the entire process of gravity-induced differential growth without affecting vertical growth processes essential for development. Thus, several new postulated interactions, operating at the perception and early transduction stages of the signaling cascade leading to auxin-mediated bending, were proposed to be examined in snapdragon spikes and oat shoot pulvini, according to the following research goals: 1) Establish the role of amyloplasts as gravireceptors in shoots; 2) Investigate gravity-induced changes in the integrity of shoot actin cytoskeleton (CK); 3) Study the cellular interactions among actin CK, statoliths and cell membranes (endoplasmic reticulum - ER, plasma membrane - PM) during shoot graviperception; 4) Examine mediation of graviperception by modulations of cytosolic calcium - [Ca2+]cyt, and other second messengers (protein phosphorylation, inositol 1,4,5-trisphosphate - IP3). Revisions: 1) Model system: in addition to snapdragon (Antirrhinum majus L.) spikes and oat (Avena sativa) shoot pulvini, the model system of maize (Zea mays) primary roots was targeted to confirm a more general mechanism for graviperception. 2) Research topic: brassinolide, which were not included in the original plan, were examined for their regulatory role in gravity perception and signal transduction in roots, in relation to auxin and ethylene. Background to the topic: The negative gravitropic response of shoots is a complex multi-step process that requires the participation of various cellular components acting in succession or in parallel. Most of the long-lasting studies regarding the link between graviperception and cellular components were focused mainly on roots, and there are relatively few reports on shoot graviperception. Our previous project has successfully characterized several key events occurring during shoot bending of cut flowers and oat pulvini, including amyloplast displacement, hormonal interactions and differential growth analysis. Based on this evidence, the present project has focused on studying the initial graviperception process in flowering stems and cereal shoots. Major conclusions and achievements: 1) The actin and not the microtubule (MT) CK is involved in the graviperception of snapdragon shoots. 2) Gravisensing, exhibited by amyloplast displacement, and early transduction events (auxin redistribution) in the gravitropic response of snapdragon spikes are mediated by the acto-myosin complex. 3) MTs are involved in stem directional growth, which occurs during gravitropism of cut snapdragon spikes, but they are not necessary for the gravity-induced differential growth. 4) The role of amyloplasts as gravisensors in the shoot endodermis was demonstrated for both plant systems. 5) A gravity-induced increase in IP.
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Beirne, John, e Eric Sugandi. Risk-Off Shocks and Spillovers in Safe Havens. Asian Development Bank Institute, novembre 2022. http://dx.doi.org/10.56506/guux7790.
Testo completoAbstract (sommario):
We examine real and financial spillovers to safe haven financial flow destinations due to risk-off shocks in global financial markets. Using country-specific structural vector autoregression models over the period 1990 to 2021, we show that dynamics for Japan appear to be different to those of Switzerland and the United States in four main ways. First, in response to risk-off episodes over the estimation period, the yen real effective exchange rate appreciates sharply and significantly, with the effect persisting over time. Second, no significant effects on portfolio flows to Japan are found, in spite of the exchange rate effects, suggesting a rapid adjustment of financial markets to shifts in equilibrium exchange rates. Third, negative real spillovers from risk-off shocks appear to only apply to Japan with exchange rate appreciation exacerbating declines in GDP growth. Fourth, risk-off shocks do not have a statistically significant effect on domestic economic policy uncertainty in Japan, which may be related to the strong expectations priced in of overseas portfolio holdings repatriated back to Japan. Our findings have important implications for policy makers in safe haven destinations in managing domestic financial vulnerabilities associated with risk-off episodes.
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Swanson, David, e Celia Hampton-Miller. Drained lakes in Bering Land Bridge National Preserve: Vegetation succession and impacts on loon habitat. National Park Service, gennaio 2023. http://dx.doi.org/10.36967/2296593.
Testo completoAbstract (sommario):
The northern coastal plain of Bering Land Bridge National Preserve (BELA) lost lakes at an alarming rate over the first two decades of this century, including four lakes over 100 ha in size in 2018-2019 alone. To understand the effects of these lake drainages, we sampled vegetation of these lakes in 2019 (a reconnaissance visit) and 2021 (for the installation of permanent vegetation monitoring plots). We used these data to summarize the changes that occurred in the first three years after drainage, and to create vegetation maps from 3-m resolution satellite images coinciding with the visit dates. We used time series of these satellite images to study the rate of drainage and vegetation colonization on the lakes. We analyzed our existing data from older drained lake basins (estimated to be more than 200 years since drainage) and reviewed the literature on vegetation change in drained lakes to understand the vegetation changes that are likely in the future. Finally, we used a model of lake occupancy by loons developed by Mizel et al. (2021) to predict the effect of the 2018-2019 lake drainages on available loon habitat, using both our detailed maps of the four sampled drained lakes, and also data on all drained lakes over most of northern BELA derived from Landsat satellite images. Our results show that the four study lakes drained early in the summer, before the end of June, in 2018 (3 lakes) and 2019 (one lake). A combination of record warm weather and heavy snowfall made 2018 and 2019 especially favorable for lake drainage: thaw subsidence probably enlarged existing drainage outlet channels from the lakes, and large amounts of spring snowmelt runoff deepened the outlet channels by thermal erosion (the combination of thaw and erosion). Drainage exposed moist loamy sediment on the lake bottoms that was rapidly colonized by plants. Substantial vegetation cover developed by late summer in the same year as lake drainage in one lake, in the first post-drainage summer in a second lake, and during the 2nd year after drainage in the remaining two lakes. The first vegetation communities to develop consisted of just one or two dominant species, notably Eleocharis acicularis (spike rush), Equisetum arvense (horsetail), and/or Tephroseris palustris (mastodon flower). Other important early species were Arctophila fulva (pendant grass) and Rorippa palustris (yellow cress). By year 3, the communities had become more diverse, with significant cover by taller wetland graminoid species, including A. fulva, Eriophorum scheuchzeri, and Carex aquatilis. Frozen soil was observed in most locations on the lakes in July of 2021, suggesting that permafrost was forming on the lake bottoms. Comparison of the three-year trends in vegetation change with data from older lake basins suggest that ultimately most lake basins will develop wet tundra communities dominated by Carex aquatilis and mosses, with various low shrub species on acid, peat-dominated soils and permafrost; however, this process should take several centuries. The loon habitat model suggests that drainage essentially eliminated the potential habitat for Yellow-billed Loons on the four study lakes, because the residuals ponds were too small for Yellow-billed Loons to take flight from. A total of 17 lakes drained in northern BELA in 2018-2019. As a result, the potential Yellow-billed Loon nesting habitat in northern BELA probably decreased by approximately 2%, while habitat for Pacific Loons decreased less, by about 0.6%. Habitat for the more abundant Red-throated Loons probably increased slightly as a result of lake drainage, because of their ability to use the small residual ponds created by lake drainage.