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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
191

Mezipodnikové srovnávání poskytovatelů telekomunikačních služeb v ČR a SR / Intercompany comparison of providers telecommunication services in Czech Republic and Slovakia

Dykast, Ondřej January 2007 (has links)
Diplomová práce se zabývá mezipodnikovým srovnáváním firem působících v oboru telekomunikací v České republice a na Slovensku v letech 2001 - 2005. Porovnávání podniků probíhá na základě nástrojů finanční analýzy. Samotné hodnocení je prováděno dle čtyřech základních metod mezipodnikového srovnávání a navíc pomocí grafické spider analýzy. V závěru jsou uvedené veškeré problémy, které musely být řešeny, a navrhnuté celkové pořadí firem za rok 2005.
192

Effects of Nitrogen and Potassium Fertilizer on Willamette Spider Mite (Eotetranychus willamettei) (Acari: Tetranychidae)

Geddes, Whitney Ann 01 June 2010 (has links)
The spider mite family (Tetranychidae) is a well known pest group in agriculture. Within this family, Willamette spider mite (Eotetranychus willamettei) causes physical harm and potential damage to grapevines (Vitis vinifera) along the central and north coast of California as well as Washington and Oregon. Willamette spider mite prefers cooler climates and feeds by puncturing the plant leaf tissue; therefore removing plant nutrients in the early stages of plant growth. Amending soils with fertilizer is a common cultural practice used in commercial vineyards, but no study has documented the interaction between the effects fertilizer concentrations have on Willamette spider mite. This project consisted of a field study (at Cambria Vineyards & Winery, Santa Maria, CA) and a laboratory study (at a California Polytechnic State University, San Luis Obispo campus greenhouse). The field study tested the effects potassium, nitrogen, and control (unfertilized) treatments had on Willamette spider mite on ‘Chardonnay’ grapes. Field results showed no significant difference among the three treatments, but suggest a response, given that mite density peaked highest in the potassium treatment and had a second high peak in the nitrogen treatment. In addition, egg density peaked highest in the potassium treatment. The lab study tested the effect four different nitrogen treatments had on Willamette spider mites. Treatments ranged from High N (1500 ppm N fertilizer), Med-High N (1500 ppm N fertilizer), Med–Low N (500 ppm N fertilizer), and Low N (0-50 ppm N fertilizer). Four parameters were tested: male and female days to maturation, male and female survivorship to adult, adult female longevity and oviposition. Longevity and oviposition lab results indicate that Willamette spider mite has a non-linear response to grape N concentration. Performance was better within the two medium treatments compared to High N and Low N treatments. Survivorship suggests the same as days to maturation although not statistically significant.
193

Spider Community Composition and Structure In A Shrub-Steppe Ecosystem: The Effects of Prey Availability and Shrub Architecture

Spears, Lori R. 01 May 2012 (has links)
Habitat structure is an important driver of many ecological patterns and processes, but few studies investigate whether habitat structure interacts with other environmental variables to affect community dynamics. The main objective of this study was to disentangle the relative importance of prey availability and shrub architecture on the distribution, abundance, and biodiversity of spiders of northern Utah, USA. We conducted field experiments which focused on: (1) describing the importance of these factors on spider community organization, (2) specifically evaluating whether prey availability mediates the relationship between shrub architecture and spider abundance and biodiversity, and (3) investigating spider and prey responses to manipulations of surrounding vegetation structures. For the first two experiments, big sagebrush shrubs were randomly assigned to six experimental treatments: two levels of prey attractant (shrubs were either baited or not baited) and three levels of foliage density (low, natural/control, or high). The purpose of manipulating both prey availability and shrub architecture was to delineate their significance to spiders. For the last experiment, changes in these factors were investigated at two different levels of spatial context (a single manipulated shrub surrounded by untreated shrubs vs. a manipulated shrub surrounded by a patch of similarly treated shrubs). We found both prey availability and shrub architecture directly influenced patterns of spider abundance and species richness and that spider species diversity and community composition varied in response to shrub architecture alone. Preferences of some spiders for certain shrub types likely reflect differences in foraging strategies or the substrate required to support different types of webs. We also demonstrate that spider response to shrub architecture is the result of multiple processes (i.e., a combination of direct and indirect effects via prey availability) and that surrounding vegetation structures affect spider abundances on shrubs. In addition, prey composition varied among different shrub foliage density treatments, but only when surrounding vegetation structures were also manipulated. More generally, this study suggests that ecological responses to habitat structure are in part mediated by associated variables and the significance of shrub architecture varies depending on the organisms examined and the spatial scale to which they respond most strongly.
194

Interaction Patterns and Web-Structures of Resonant Solitons of the Kadomtsev-Petviashvili Equation

Tippabhotla, Anupama 08 July 2005 (has links)
In this thesis, the interaction pattern for a class of soliton solutions of the Kadomtsev- Petviashvili (KP) equation (−4ut + uxxx + 6uux )x + 3uyy = 0 is analyzed. The complete asymptotic properties of the soliton solutions for y → ±∞ are determined. The resonance characteristic of two sub-classes of the soliton solutions, in which N- incoming line solitons for y → −∞ interact to form N+ outgoing line solitons for y → ∞, is described. These two specific sub-classes of (N-,N+)-soliton solutions are the following: 1) [(2, 3), (2, 4), (2, 5)], 2) [(3, 2), (3, 3), (3, 4)]. The intermediate solitons and the interaction regions of the above soliton solutions are determined, and their various interaction patterns are explored. Maple and Mathematica are used to get the 3 dimensional plots and contour plots of the soliton solutions to show their interaction patterns. Finally, the spider-web-structures of the discussed solitons of the KP equation are displayed.
195

Effects of an nC24 agricultural mineral oil on tritrophic interactions between French bean (Phaseolus vulgaris L.), two-spotted mite (Tetranychus urticae Koch) and its predator, Phytoseiulus persimilis Athias-Henriot.

Xue, Yingen, University of Western Sydney, College of Health and Science, School of Natural Sciences January 2007 (has links)
A comprehensive evaluation of the effects of an nC24 agricultural mineral oil (AMO) on tritrophic interactions between French bean Phaseolus vulgaris cv. Redlands Pioneer [Fabales : Fabaceae ], two spotted mite (TSM) Tetranychus urticea Koch [Acari: Tetranychidea] and the predatory mite Phytoseiulus persimilus Atheus-Henriot [Acari: Phytoseiidae] was conducted under laboratory conditions. / Doctor of Philosophy (PhD)
196

Olfactory sensitivity of spider monkeys (Ateles geoffroyi) for six structurally related aromatic aldehydes

Kjelmand, Luna January 2009 (has links)
<p>For many years, primates have been considered to be animals with a poorly developed sense of smell. However, in recent years several studies have shown that at least some primate species have a high olfactory sensitivity for a variety of odorants. The present study used a two-choice instrumental conditioning paradigm to test the olfactory sensitivity for six aromatic aldehydes in four spider monkeys (Ateles geoffroyi). With helional, cyclamal,canthoxal and lilial all animals discriminated concentrations below 1 ppm from the odorless solvent, with single individuals even scoring better. With 3-phenyl-propionic aldehyde all animals detected concentrations below 2 ppb, and with bourgeonal even below 0.3 ppb. The detection thresholds of the odorants changed systematically with molecular structure. Addition of a dioxo or methoxy group to the benzene ring led to an increase in threshold values,while the absence of a methyl group close to the aldehyde moiety was linked to a low threshold value for the odorant. The study shows that spider monkeys have a well developed olfactory sensitivity for aromatic aldehydes.</p>
197

Client-side threats and a honeyclient-based defense mechanism, Honeyscout

Clementson, Christian January 2009 (has links)
<p>Client-side computers connected to the Internet today are exposed to a lot malicious activity. Browsing the web can easily result in malware infection even if the user only visits well known and trusted sites. Attackers use website vulnerabilities and ad-networks to expose their malicious code to a large user base. The continuing trend of the attackers seems to be botnet construction that collects large amounts of data which could be a serious threat to company secrets and personal integrity. Meanwhile security researches are using a technology known as honeypots/honeyclients to find and analyze new malware. This thesis takes the concept of honeyclients and combines it with a proxy and database software to construct a new kind of real time defense mechanism usable in live environments. The concept is given the name Honeyscout and it analyzes any content before it reaches the user by using visited sites as a starting point for further crawling, blacklisting any malicious content found. A proof-of-concept honeyscout has been developed using the honeyclient Monkey-Spider by Ali Ikinci as a base. Results from the evaluation shows that the concept has potential as an effective and user-friendly defense technology. There are however large needs to further optimize and speed up the crawling process.</p>
198

Prey-stage preference in phytoseiid mites

Blackwood, J. Scott 31 October 2003 (has links)
Knowledge of how individual organisms behave in their environment can provide a greater understanding of population dynamics. In a predator-prey system, the choices made by predators when foraging for prey are important aspects of behavior. Particularly in the case of a stage-structured prey population, how the predator selects prey stages once a prey patch has been located can have implications for prey population growth, predator development and fecundity, and predator-prey system dynamics. Predaceous mites of the family Phytoseiidae are important biological control agents of Tetranychus spider mites in agricultural settings worldwide. Phytoseiid species range from specialists that require Tetranychus spider mite prey in order to develop and reproduce to generalist omnivores. In studies with 13 phytoseiid species, specialized species tended to prefer T. urticae eggs as prey or have no prey-stage preference while more generalist species tended to have no prey-stage preference or prey more often on mobile immatures. Further testing with a subset of these species suggested variability among species with regard to genetic and environmental influences on prey-stage preference. The specialist Phytoseiulus persimilis also preferred to forage and oviposit in patches containing egg-biased stage distributions rather than in adjacent mobile immature-biased patches. No benefits to offspring developing in either type of patch were found in terms of developmental time or subsequent adult fecundity. However, the results of both manipulative experiments and nonlinear population models indicated potential benefits of egg-biased predation in terms of current adult female fecundity, a less severe impact of predation on the prey population, and an increased number of predator descendents during the predator-prey interaction. Considering both subjective factors and discriminant analyses, prey-stage preference performed well as an indicator for the ecological classification of phytoseiid species. The classifications of four phytoseiid species occurring on apple in central and eastern Oregon, USA, were evaluated accordingly. / Graduation date: 2004
199

Biological control of spider mites (Acari: Tetranychidae) on grape emphasizing regional aspects

Prischmann, Deirdre A. 06 July 2000 (has links)
During summer of 1998 and 1999, 34 and 10 vineyard sites, respectively, were sampled to assess spider mite pests and associated biological control by phytoseiid mites. Vineyards studied spanned five major valleys in western Oregon where grape production occurs. Leaf samples were taken from site perimeters and centers. One leaf was taken every ten meters of border length, five meters inward from the border to prevent wind-biased or extreme edge effects, while 20 leaves were taken at regular intervals from centers. Variables recorded at each site were: plant age, grape variety, chemical spray information and local vegetation occurring in proximity to vineyards. Sites were categorized as either agricultural or riparian based on what surrounding vegetation type was in the majority. Several parametric and non-parametric tests were used to analyze data, including multiple linear regressions using a computer-based genetic algorithm in conjunction with the AIC criterion to pre-select a subset of explanatory variables. Typhlodromus pyri was the predominant phytoseiid mite and Tetranychus urticae was the most abundant tetranychid mite sampled. High levels of T. urticae were found when predator densities were very low, and low levels of T. urticae occurred when predator densities were moderate or high. Phytoseiid densities were highest in June and July, while T. urticae densities were highest from August to September. The latter's densities were significantly higher in vineyards surrounded primarily by agriculture, while phytoseiid densities were not significantly different between the two categories. Predatory phytoseiids had significantly higher densities on vineyard edges, while T. urticae densities were higher in vineyard centers. Caneberry, cherry and grape habitats appeared to be sources of predator immigration, while no vegetation type consistently served as a short-range or nearby immigration source for spider mites. Due to insufficient data, pesticide information was not included in multiple linear regression models, although certain chemicals used in vineyards can potentially impact mite populations. Impacts of surrounding vegetation type, grape variety, regional location, plant age, and presence of other mites on phytoseiid and T. urticae densities are discussed. / Graduation date: 2001
200

Within and between plant dispersal and distributions of adult females and immatures of Neoseiulus californicus and N. fallacis (Acari: Phytoseiidae) in bean and apple plant systems

Pratt, Paul D. (Paul David), 1970- 21 April 1997 (has links)
Intra- and interplant movement and dispersal of the predator mites Neoseiulus californicus (McGregor) and Neoseiulus fallacis (Garman) were studied on both lima bean (Phaseolus lunatus L.) and apple (Malus pumila Miller) branch plant systems that were seeded with excess numbers of the spider mite Tetranychus urticae Koch. Individuals of either predator were randomly selected from colonies of well-fed, mixed-age adult females and moved to test plants. When tested separately in each plant system, median leaf positions of N. californicus from the point of release were greater than those of N. fallacis at 1-8 d. A fan placed in front of a common source unit (1x3m) containing T. urticae and near equal densities of both predaceous mites, provided continuous air (wind) to 3 isolated receiver units located 2.5, 5, and 7.5 m downwind. Receiver units consisted of continuous bean foliage with excess T. urticae, but no predators. Wind speeds at the source and each receiver unit averaged 2.2, 0.9, 0.4, and 0.03 m/s respectively. As predators eliminated prey, N. fallacis dispersed earlier at higher prey densities and further downwind than N. californicus, but cumulative densities of each predator in all receiver units were alike after 20 d. Results of both plant movement studies supported the hypothesis that N. californicus has dispersal traits more like those of a generalist predator of spider mites than does N. fallacis. Spatial patterns of dispersal and biological control of pest mites are discussed in relation to predation types within the Phytoseiidae. / Graduation date: 1997

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