Dissertations / Theses on the topic 'Effect of chemicals on weeds'
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1
Omami, Elizabeth Nabwile, of Western Sydney Hawkesbury University, of Agriculture Horticulture and Social Ecology Faculty, and School of Horticulture. "Amaranthus retroflexus seed dormancy and germination responses to environmental factors and chemical stimulants." THESIS_FAHSE_HOR_Omami_E.xml, 1993. http://handle.uws.edu.au:8081/1959.7/66.
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A large number of weed seeds in the soil persist because of seed dormancy, and depletion of the seed bank through manipulation of seed dormancy has been suggested as one of the goals in weed control. This study was designed to investigate some of the factors which control dormancy and germination in Amaranthus retroflexus seeds. Germination studies were conducted at different temperatures, and either in continuous white light or in the dark. Higher temperatures increased germination and, although light interacted with temperature, its effect on germination varied with the temperature. In an attempt to determine changes in dormancy during dry storage, two lots of seeds were stored dry at different temperatures. Loss in dormancy increased with an increase in storage temperature and duration, but the time required for maximum germination varied according to the seedlot. Seeds germinated to higher percentages at high temperatures, but storage at higher temperatures and for prolonged duration resulted in seeds gaining the ability to germinate at lower temperatures. Changes in dormancy under field conditions were also examined. Seeds were buried at different depths and for different durations and they all lost viability with time, but this loss was greater in surface-sown and shallowly buried seeds. Dormancy was broken during cold periods and induced as warmer periods progressed. The effects of chemical stimulants on dormancy and germination were investigated. The response of seeds to ethephon and nitrate were assessed at different temperatures either at continuous white light or in the dark. Germination increased with the concentration of the chemicals, and a greater response was observed at lower temperatures. The response to light varied depending on temperatureMaster of Science (Hons)
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Omami, Elizabeth Nabwile. "Amaranthus retroflexus seed dormancy and germination responses to environmental factors and chemical stimulants." Thesis, [S.l. : s.n.], 1993. http://handle.uws.edu.au:8081/1959.7/66.
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A large number of weed seeds in the soil persist because of seed dormancy, and depletion of the seed bank through manipulation of seed dormancy has been suggested as one of the goals in weed control. This study was designed to investigate some of the factors which control dormancy and germination in Amaranthus retroflexus seeds. Germination studies were conducted at different temperatures, and either in continuous white light or in the dark. Higher temperatures increased germination and, although light interacted with temperature, its effect on germination varied with the temperature. In an attempt to determine changes in dormancy during dry storage, two lots of seeds were stored dry at different temperatures. Loss in dormancy increased with an increase in storage temperature and duration, but the time required for maximum germination varied according to the seedlot. Seeds germinated to higher percentages at high temperatures, but storage at higher temperatures and for prolonged duration resulted in seeds gaining the ability to germinate at lower temperatures. Changes in dormancy under field conditions were also examined. Seeds were buried at different depths and for different durations and they all lost viability with time, but this loss was greater in surface-sown and shallowly buried seeds. Dormancy was broken during cold periods and induced as warmer periods progressed. The effects of chemical stimulants on dormancy and germination were investigated. The response of seeds to ethephon and nitrate were assessed at different temperatures either at continuous white light or in the dark. Germination increased with the concentration of the chemicals, and a greater response was observed at lower temperatures. The response to light varied depending on temperature
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Dodds, Darrin Matthew. "Adjuvant effects on herbicide absorption and translocation." Diss., Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-11022007-143506.
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Somireddy, Upender Reddy. "Effect of Herbicide-Organic Mulch Combinations on Weed Control and Herbicide Persistence." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1325255792.
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Filby, Amy Louisa. "Molecular effect pathways of endocrine disrupting chemicals in fish." Thesis, University of Exeter, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439828.
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Umeda, Kai. "Effect of Halosulfuron on Rotational Crops." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/214957.
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A field test was conducted to evaluate and determine the safety of halosulfuron on typical rotational crops such as lettuce, broccoli, spinach, onion, alfalfa, barley, field corn, and melons after an initial application on cantaloupes. Halosulfuron at 0.05 or 0.1 lb AI/A applied on cantaloupes did not detrimentally affect crop stand establishment, height, or whole plant fresh weights when alfalfa, barley, spinach, lettuce, onion, and broccoli were planted at approximately 4 to 5 MAT. Cantaloupes and field corn planted at 1 YAT were not affected in establishing a stand and in growing during the early season as height or vine lengths were measured. At 15 to 16 MAT, lettuce, onion, and broccoli were not affected in establishing a stand. Watermelon planted at 1 YAT exhibited slight stand reduction and crop injury with halosulfuron applied PREE. Alfalfa planted after PREE applications indicated slightly depressed height and yield compared to POST treatments and the untreated check. Spinach planted where POST applications were made on cantaloupes tended to show a slight reduction in fresh weight at 15 to 16 MAT. Halosulfuron does not appear to be a major deterrent to typical crop rotational schemes in the diverse desert agricultural systems.
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Umeda, K., and N. Lund. "Effect of Prowl and Prefar Herbicides on Onions." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/214935.
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Significant onion height reduction was observed when Prowl (pendimethalin) and Prefar (bensulide) herbicide combinations were applied preemergence (PREE). The onions resumed growth but the height was still slightly reduced later in the growing season compared to the handweeded check and the standard herbicide treatment, Dacthal (DCPA). The onion crop stand emerged initially but later in the season, a significant crop stand reduction was observed for the higher rate of Prowl at 0.5 lb AI/A plus Prefar. A lower rate of Prowl at 0.25 lb AI/A plus Prefar also caused a reduction of the onion stand compared to the handweeded check or Dacthal.
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Coberly, Samantha W. "The effect of household chemicals on deciduous and permanent tooth class." Thesis, Wichita State University, 2013. http://hdl.handle.net/10057/6807.
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Dental anthropology was wide ranging implications for the field of anthropology. Teeth have become important sources of data about the individual as well as possibly being able to identify them. One problem that can arise is the chemical destruction of teeth whether it be diagenesis in an archaeological context or deliberately in a forensic context. In terms of deliberate destruction of the body several household chemicals are cheap and easily assessable. The purpose of this research is to look at how six household chemicals affect both deciduous and permanent tooth classes. The six chemicals include, Vinegar (acetic acid), Bleach (sodium hypochlorite), Biz (Sodium per carbonate), Lye (Sodium Hydroxide) Ammonia and the control (tap water). The teeth were placed in jars containing the chemical for twenty-four hours. Every hour the weight and mesial/distal length were measured. Of the six chemicals, vinegar affected the teeth the most.Thesis (M.A.)--Wichita State University, Fairmount College of Liberal Arts and Sciences, Dept. of Anthropology
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Turan, Nahid. "The effect of plasticisers and related chemicals on sulphate supply enzymes." Thesis, University of Birmingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433746.
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Delacruz, C. Ligia. "The effect of natural toxicants and other chemicals on the kidney." Thesis, University of Surrey, 1988. http://epubs.surrey.ac.uk/847359/.
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Repeated administration of ochratoxin A (OTA) caused renal morphological dose-related changes, that were associated with proximal tubular and glomerular damage the latter showing oedema and prominent PAS staining suggestive of glomerular basement membrane thickening. On the other hand, the combined administration of repeated doses of OTA and aflatoxin B[1] (2. 5 mg and 100 ug per kg, respectively), appeared to have a synergistic effect, characterized by severe disruption of proximal tubules and general morphological derrangement of the glomerulus, involving intense and faint staining nuclei (suggestive of cell necrosis) and cytoplasmic vacuolation, which was not seen with either toxin alone. When clinical biochemical parameters were measured after repeated administration of a low dose of OTA, enzymuria, glucosuria, polyuria and proteinuria were observed, with glucose and alkaline phosphatase as the most sensitive parameters. Metabolic studies performed in vitro showed that isolated pig and rat glomeruli incorporate different amino acids linearly for several hours at different rates and perform oxidative metabolism of glucose and fatty acids to CO[2] also linearly. For pig glomeruli the order of amino acid incorporation was LEU >> PRO = HIS > LYS > GLY and for rat glomeruli it was TRP >> PHE > TYR = LEU > PRO > HIS. The same amino acids were incorporated in a similar way in rat tubules, but the incorporation rate is 10-fold lower. When de novo synthesis of protein by pig glomeruli exposed to different chemicals was assessed, using proline (PRO) as the precursor, adriamycin (ADR) and ethacrynic acid (ETA) inhibited protein synthesis more than 2-bromoethanamine (BEA) and streptomycin (STR), and much more than puromycin aminonucleoside (PAN). When isolated rat glomeruli were exposed to low concentrations of OTA, there was a generalized inhibition on de novo synthesis of protein from the six amino acids tested and the aromatic amino acids (TRP, TYR and PHE) were more sensitive to OTA effect than PRO. Low concentrations of OTA (10 - 100 uM) enhanced glomerular and tubular glucose metabolism to CO[2] and only high concentrations of the mycotoxin (1000 uM) caused significant inhibition of glomerular and proximal tubular linolenic acid metabolism.
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Howard, Samuel Clarence. "The effect of three holding tank chemicals on anaerobic wastewater treatment." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/45158.
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Sewage-holding tanks aboard recreational boats store human wastes, thereby preventing the direct discharge of wastewater to the aquatic environment. Water-conserving toilets and limited holding tank volumes produce a highly concentrated waste that must be periodically dumped to a wastewater treatment system. Prior to disposal, many boat operators add commercial preparations to control odors produced in their chemical toilets and holding tanks.
The objective of this study was to determine the effects of three holding-tank chemicals on anaerobic wastewater treatment. Specifically, septic-tank performance with respect to effluent total suspended solids (TSS) and chemical oxygen demand (COD) was evaluated. Potential drain-field failure was the concern that led to the selection of TSS and COD. Drain-field failure could result from high solids carry-over or from a high concentration of COD in the effluent which would promote excessive bio-mat growth and clog the system. Laboratory septic tanks were constructed and operated for this evaluation.
Methanol, paraformaldehyde and formaldehyde were each listed as an active ingredient in one of three chemical compounds used by recreational boat owners to deodorize sewage-holding tanks. septic-tank effluent TSS concentrations were not adversely effected by the shockloading with wastewater containing these chemicals. Concentrations expected to be achieved by dilution (20 and 50 percent of the recommended additive dose) resulted in septic-tank effluent COD within an acceptable range, which was determined by operation of a control system. Wastewaters containing these concentrations were not detrimental to the septic-tank treatment system. However, the full manufacturers' recommended dose of the odor control chemicals disrupted the system's ability to degrade COD. At full strength, the para formaldehyde and formaldehyde deodorants were particularly detrimental; no recovery occurred after the two-day shock-dose was completed.Master of Science
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Fillmore, Andrew Nathan. "Droplet Size Effect on Herbicide Used in Cereals to Control Dicotyledonous Weeds." Thesis, North Dakota State University, 2014. https://hdl.handle.net/10365/27419.
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Experiments were conducted to evaluate the effect of droplet size on the efficacy of translocated and non-translocated herbicides. Translocated and non-translocated herbicides provided similar control when comparing droplet size effect on efficacy. Medium and very coarse droplet sizes gave the greatest visible injury whereas coarse-sized gave the lowest visible injury assessments for most species. However, droplet size generally did not affect contact herbicide efficacy. Overall, droplet size was not a strong factor contributing to herbicide efficacy and often, differences were only between herbicides. Non-ionic surfactant solutions measured by a Sympatec droplet analysis system gave the highest percent of volume in droplets <150?m compared to other adjuvants. The lowest percent of volume in droplets <150?m was a 0.5x rate. A liquid herbicide formulation gave the largest percent of volume in droplets <150?m whereas an emulsifiable concentrate formulation was lowest. Percent volume in droplets <150?m was often related to the solution VMD.
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Hewitt, Cade Alan. "Effect of row spacing and seeding rate on grain sorghum tolerance of weeds." Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/19784.
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Master of ScienceDepartment of Agronomy
J. A. Dille
Weed control in grain sorghum has always presented a challenge to producers in the semi-arid Great Plains. Cultural control tactics such as narrowing of row spacings and increasing seeding rates can be effective control methods. The objective of this research was to determine the row spacing and seeding rates that maximizes yield while suppressing weeds. Grain sorghum row spacings of 25, 51, and 76-cm and seeding rates of 75,000, 100,000, 125,000, and 150,000 seeds ha[superscript]-1 were evaluated in Kansas at Beloit and Manhattan in 2013 and Beloit, Manhattan, and Hays in 2014. Grain sorghum growth and yield response were measured in response to natural weed communities. After evaluation, Beloit was considered a low weed pressure site while Manhattan and Hays were considered to be moderate and high weed pressure sites, respectively. Grain sorghum biomass was different while weed biomass was consistent across row spacings. Yield loss equations and profit functions were derived to determine the amount of grain yield and $ ha[superscript]-1 loss from each of the three locations. Yield and profit lost was greatest amongst weedy observations. Results indicated that grain sorghum grown on wide row spacings and seeding rates of 125,000 seeds ha[superscript]-1 out yielded all other treatments under a low weed pressure site (Beloit) and narrow row spacings out yielded wider spacings in moderate and high weed pressure sites (Manhattan and Hays). These results imply that a Kansas grain sorghum producer should evaluate potential weed pressure before determining a final row spacing and seeding rate.
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Sampson, D. L. "The effect of tillage systems on weed control and botanical composition in forage corn /." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63912.
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Mandal, Mili. "Amending subsoil with composted poultry litter effects on soil physical and chemical properties, turfgrass establishment and weed pressure /." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4196.
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Thesis (M.S.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains ix, 88 p. : ill. Includes abstract. Includes bibliographical references (p. 75-88).
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Li, Jing Adela, and 李晶. "Temperature-dependent toxic effects of selected chemicals on marine organisms." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/211051.
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Anthropogenically driven climate change not only results in rising of sea temperature but also leads to more frequent and longer-lasting cold and heat waves. Meanwhile, coastal marine ecosystems are constantly challenged by increasing threats of chemical pollution. Temperature and chemical stressors can jointly affect the livelihood of marine organisms, but their combined effects are still poorly understood. Therefore, this study aimed to investigate the effects of thermal stress and chemical exposure on the marine medaka Oryzias melastigma, copepod Tigriopus japonicus and rotifer Brachionus koreanus. The four selected chemical contaminants included copper sulphate pentahydrate (Cu), dichlorophenyltrichloroethane (DDT), triphenyltin chloride and copper pyrithione. It was hypothesized that marine organisms are more susceptible to chemical exposure at both cold and warm extremes.
In vivo acute ecotoxicity tests were conducted over a wide temperature range to ascertain the relationship between thermal stress and chemical toxicity. For O. melastigma larvae, the lowest toxicity occurred at an optimum temperature range; the chemical toxicity further increased with temperature increase or decrease from this optimum, and exacerbated at extremely low and high temperatures. For T. japonicus and B. koreanus, the chemical toxicity generally increased with increasing temperature. Such inter-species dissimilarities were possibly due to differences in the uptake route, detoxification mechanism, avoidance behaviour and physiological response between the fish and the copepod or rotifer.
Experiments were conducted to evaluate the temperature-dependent physiological and biochemical responses, and thermal tolerance of O. melastigma larvae. The growth in the fish larvae showed an inverse and negatively skewed V-shape relationship with temperature, with a significant reduction in performance at both low and high thermal extremes. A mismatch between demand and supply of oxygen and energy under extremely cold and warm conditions was probably the primary cause of growth inhibition and metabolic impairment, leading to a temporary adaptation by a shift to anaerobiosis and an induction of heat shock proteins (HSPs).
Temperatures at both cold and warm extremes increased toxicities of DDT and Cu to O. melastigma larvae, resulting in restricted growth and interrupted oxygen consumption rate. The fish larvae modulated their metabolic pathway and produced stress proteins (i.e., HSPs and metallothioneins) for adaptation to the combined stress. However, such responses were disrupted by combinations of thermal extremes, in particular high temperature, and high chemical concentration. Most importantly, both DDT and Cu exposure significantly reduced the thermal tolerance of the fish larvae.
The interacting effect of temperature and Cu was also investigated on T. japonicus. The results showed that their combined effect could significantly reduce the survival, lengthen the developmental time and change the sex ratio of the copepod. Transcriptions of several stress-related genes (i.e., glutathione reductase, glutathione S-transferases and HSPs) in the adult T. japonicus were significantly affected by the joint-effect of temperature and Cu exposure, implying that these genes played essential roles in protecting the cellular integrity against the stresses.
This study advanced the understanding on the temperature-dependent toxicity of chemical contaminants to marine organisms, and provided valuable information and empirical models for deriving water quality criteria of chemical contaminants at various temperatures.published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy
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Reed, Susan, of Western Sydney Hawkesbury University, and of Science Technology and Environment College. "Development of method to assess skin contact to chemicals." THESIS_CSTE_XXX_Reed_S.xml, 2001. http://handle.uws.edu.au:8081/1959.7/611.
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Chemical exposure of the skin has become a route of entry of some chemicals into the body and has come under major review in recent times. This research aims to develop a method of estimating skin exposure that is both reliable and non-prohibitive in cost. This involved the design and testing of skin patches adaptable for monitoring skin exposure to chemicals using several different types of absorbents which could be easily worn against skin. The final design of the patch used either activated charcoal or tenax as the absorbing medium. The patches were then desorbed with a solvent in order to analyse the chemicals. The results of the study showed that many skin exposures do not have a direct relationship with inhalation exposures, which is important because currently there are no estimates of the levels of skin exposures that may have potential long term health effects. The patch has proved successful for detecting the presence and determining the amount of chemicals that come in contact with the skin. Charcoal patches have the widest application, but are not suitable for all situations and tenax should be used on these occasions.Doctor of Philosophy (PhD)
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Quinn, Amie L., and University of Lethbridge Faculty of Arts and Science. "The impacts of agricultural chemicals and temperature on the physiological stress response in fish." Thesis, Lethbridge, Alta. : University of Lethbirdge, Faculty of Arts and Science, 2007, 2007. http://hdl.handle.net/10133/676.
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Fish are exposed to multiple stressors in their environment. The interactive
effects of pesticide exposure and increased temperature on the physiological stress
response were investigated in a comparative field study with cold-water (whitefish,
Prosopium williamsoni) and cool-water (sucker, Catostomus) fish from the Oldman
River, Alberta, Canada, and in a laboratory study with rainbow trout, Oncorhynchus
mykiss. Physiogical stress indicators were measured, and exposure to pesticides was
estimated using acetylcholinesterase (AChE) inhibition. Species-specific differences in
AChE activities and responses of the physiological stress axis were detected in whitefish
and suckers, suggesting that whitefish are a more sensitive species to temperature and
pesticide stress. In vivo Dimethoate exposure inhibited AChE activity in various tissues
and disrupted the physiogical stress response. Commercial Dimethoate, in vitro, caused a
decrease in viability and cortisol secretion while pure grade Dimethoate did not. The
results from this study can be used in predictions of fish vulnerability to stress.ix, 137 leaves : ill. ; 29 cm.
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Tomic, Tjasa. "Functionalised cellulosic materials for hydrolysis free reactive dyeing and the fixation of effect chemicals." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498845.
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Esquerdo, Julio Cesar Dalla Mora. "Adaptação de um pulverizador convencional para a aplicação localizada de defensivos agrícolas." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/11/11148/tde-05072002-090630/.
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Os defensivos constituem grande parte do custo total dos insumos utilizados na produção agrícola. O alto consumo de defensivos reduz a lucratividade e aumenta os riscos de contaminação ao ambiente. Uma das alternativas que vêm sendo propostas para a redução da quantidade de defensivos utilizada na produção agrícola é o chamado "gerenciamento localizado das culturas", através do uso dos conceitos da Agricultura de Precisão. Máquinas destinadas à aplicação localizada de defensivos líquidos em doses e produtos variáveis já estão presentes no mercado; entretanto, seu alto custo inicial e alta capacidade operacional inviabilizam sua aquisição em propriedades de menor porte. No presente trabalho, um pulverizador convencional foi adaptado com válvulas solenóides para promover a aplicação do defensivo na estratégia "liga-desliga", utilizando uma dose fixa. Um programa computacional foi desenvolvido para executar o controle independente sobre cada uma das válvulas solenóides presentes nas duas seções de barra do pulverizador, em função das informações de um mapa de prescrição, contendo as coordenadas dos locais onde a aplicação deveria ocorrer. Um DGPS foi conectado ao sistema para informar a localização do trator no campo. O sistema foi submetido a um teste em condições reais de controle de plantas daninhas, as quais foram previamente georreferenciadas através do caminhamento do contorno das infestações. Os resultados mostraram que a adaptação realizada, assim como o sistema de controle desenvolvido, permitiram o controle localizado das infestações, resultando na redução da quantidade de herbicida aplicada, em comparação ao tratamento convencional.Agrochemicals constitute a great part of the total cost of inputs used in the crops production. The high consumption of agrochemicals reduces the profitability and increases the risks of environmental contaminations. One of the alternatives that have been proposed to reduce the amount of chemicals used in the crop production is the site-specific management, using the Precision Agricultures concepts. Machines used for site-specific application of liquid agrochemicals using variable rates and products are already in the market; however, its high initial cost and operational capacity make its acquisition unfeasible for small farms. In this work, a conventional sprayer was adapted with solenoid valves to allow the site-specific application using the "on/off" strategy, and a fixed rate. A computer program was developed to control each solenoid valve installed at the two sections of the boom, according to the information of a prescription map, containing the position of the points where the application should be done. A DGPS was connected to the system to inform the tractors position in the field. The system was tested in a real condition of weed control. The perimeter of the weed patches was previously georeferenced. The results showed that the developed system was able to achieve the patch application using fixed rates, resulting in a significant economy of herbicides, when compared with the conventional treatment, over the total area.
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Thomas, Dean Timothy. "Selective grazing by sheep to improve the control of weeds of crops." University of Western Australia. School of Animal Biology, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0041.
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[Truncated abstract] With the rapid development of multiple herbicide resistant weeds in crops, it is likely that an important role now exists for new grazing management strategies in farming systems to provide an integrated approach to weed management. In this thesis we examined the general hypothesis that sowing a legume of low preference by sheep relative to the target weeds of crops would improve the control of those weeds in a grazed pasture. To test this general hypothesis, legumes of low preference by Merino sheep were identified and a series of experiments conducted to determine the effect on pasture composition when these less preferred legumes were incorporated into a grazed pasture. We found a learned response that altered forage preference by sheep was important in determining the effectiveness of grazing to reduce seed set by weeds of crops. Investigations on this aspect of the grazing behaviour of sheep were a key part of this thesis. The short-term relative preference of Merino hoggets among 15 pasture legumes, 4 grain legumes and annual ryegrass was determined by offering adjacent monocultures of each of the forage genotypes to the sheep. The relative preference of the hoggets for each of the 20 forages was determined at three phases of plant growth from estimates of the amount of forage consumed. Sheep showed a low selective preference for Vetch (Vicia sativa L.), chickpea (Cicer arietinum L.), biserrula (Biserrula pelecinus L.), lotus (Lotus ornithopodioides L.) and snail medic (Medicago scutellata L.) cvs. Kelson and Sava at the vegetative phase of plant growth. An indoor method was also developed to test the relative preference of sheep among forages growing in pots. Using this method chickpea and snail medic, but not biserrula, were found to have a low relative preference by sheep at the vegetative phase.
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Čepulienė, Rita. "Dynamics of accumulation of allelochemical compounds in oilseed rape and effect on agricultural crops and weeds." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20141230_175312-56329.
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Research objective. The study was aimed to identify the dynamics of accumulation of phenolic compounds and glucosinolates in oilseed rape and the effect of different morphological parts of oilseed rape on agricultural plants and weeds. The goals of the studies. The following goals were set in order to reach the aim of the studies: 1. To identify the dynamics of accumulation of phenolic compounds in oilseed rapeduring vegetation. 2. To analyse composition of allelochemical compounds of different morphological parts of rape residues after harvesting and ascertain quantitative and qualitative changes of these compounds in rape residues that decomposed in the soil for a different period. 3. To ascertain the effect of different morphological parts of oilseed rape that remain immediately after harvesting on the germination, shoot height and root length of agricultural plants and weeds. 4. To ascertain the effect of different morphological parts of oilseed rape that decomposed in the soil for a different period on the germination, growth of shoots and roots of agricultural plants and weeds.Tyrimų tikslas. Nustatyti fenolinių junginių ir gliukozinolatų kaupimosi rapsuose dinamiką bei rapsų skirtingų morfologinių dalių liekanų poveikį žemės ūkio augalams ir piktžolėms. Tyrimų uždaviniai: 1. Nustatyti fenolinių junginių kaupimosi dinamiką rapsuose vegetacijos metu. 2. Ištirti alelocheminių junginių sudėtį rapsų skirtingų morfologinių dalių liekanose po derliaus nuėmimo ir nustatyti jų kiekybinius ir kokybinius pokyčius skirtingą laiką dirvoje irusiose rapsų liekanose. 3. Nustatyti rapsų atskirų morfologinių dalių, liekančių iškart po derliaus nuėmimo, poveikį žemes ūkio augalų ir piktžolių sėklų dygimui, daigų aukščiui ir šaknų ilgiui. 4. Nustatyti skirtingą laiką dirvoje irusių rapsų morfologinių dalių poveikį žemės ūkio augalų ir piktžolių sėklų dygimui, daigų bei šaknų augimui.
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Worsham, Jessica Nicole. "5-HT3 Receptor Ligands and Their Effect on Psychomotor Stimulants." VCU Scholars Compass, 2008. http://scholarscompass.vcu.edu/etd/1054.
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Drug abuse and addiction are considered to be a result, at least in part, of the rewarding effects produced by increasing dopamine levels. 5-HT3 serotonin receptors have been shown to indirectly affect dopamine levels. Therefore, the effect of the 5-HT3 receptor partial agonist, MD-354, on the actions of psychomotor stimulants was analyzed in mouse locomotor activity assays to determine whether MD-354 is working through a 5-HT3 receptor agonist or antagonist mode of action. Studies with (+)amphetamine and (+)methamphetamine in combination with MD-354 indicated MD-354 is either devoid of action or is behaving similar to the 5-HT3 receptor antagonist, ondansetron. This effect could be occurring centrally; however peripheral effects can not be discounted. In combination with cocaine, MD-354 behaved similar to the 5-HT3 receptor agonist, SR 57227A, known to act both centrally and peripherally. This difference between central and peripheral effects could account for the different modes of action observed with MD-354. Studies also involved synthesis of potentially brain-penetrant carbamate analogs of MD-354, and QSAR to assist in validating a 5-HT3 receptor agonist pharmacophore.
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Nongauza, Sinethemba Aubrey. "An investigation of the effect of co-solvents on the hydrothermal liquefaction of microalgae biomass." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/21667.
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The study introduces and demonstrates the viability of the continuous flow reactor (CFR) system for the production of bio-crude oil (BCO) from wet microalgae. Preliminary experiments conducted in the CFR system in hot compressed water (HCW) were successful in converting wet microalgae into liquid BCO. However, the synthesis and aggregation of high boiling point (HBP) components of BCO and the accumulation of char in the tubular piping of CFR system were identified as the limiting factor to the viability of the system. The aggregation of HBP components and the accumulation of char result to system blockage which prevents the continuous flow of the liquefaction product mixture in the CFR system. Inhibiting the reactions leading to the formation of HBP components and char will improve the performance of the CFR system. Therefore, the study seeks to incorporate co-solvents in the liquefaction reaction media in an attempt to inhibit or minimize the prevalence of HBP components of BCO. As such, different co-solvents were screened for their influence on improving the quality of BCO with respect to its boiling point profile (BPP), initial and final boiling point, as well as the amount of char recovered from each experiment. Only one co-solvent was chosen for further exploration in the CFR system. Batch liquefaction reactor’s (BLR) made up of stainless steel were used to carry out the co-solvent screening experiments. These experiments were carried out at a constant temperature (280 °C), pressure (75 bar), and co-solvent concentration (10 wt.%), at varying residence times. Solvent extraction with dichloromethane (DCM) was performed on the liquefaction product mixture to separate the products, viz. BCO, char and water soluble components. The extracted BCO was analysed through simulated distillation (SimDis) to obtain the BPP. The BPP properties of the BCO samples, from different liquefaction media, and the amount of char recovered were highly influenced by the addition of a co-solvent. The final boiling point (FBP) of tetralin, heptane, and n-octanol BCO products were significantly reduced to below 500 °C for all tested residence times except at 20 minutes. The residence time also proved to be influential in the processing of wet microalgae. n-Octanol was selected as the optimal performing co-solvent and was used for the continuous liquefaction of wet microalgae in the CFR system. The CFR system was modified by adding a co-solvent feed line into the continuous system since n-octanol was insoluble in water. The n-octanol pump was set at different flow rates, 0.2, 0.3, and 0.4 g/min, which resulted in a concentration of about 10 wt.% in the reactor feed. The concentration of n-octanol had a significant influence on the BPP of BCO components. The FBP’s were reduced with an increase in n-octanol concentration. The initial boiling point (IBP) of n-octanol BCO was increased to just above 100 °C which was required for the stability of the BCO product. The components of BCO were identified by GCMS. n-Octanol also proved to affect the composition of the BCO with respect to its components. HCW BCO components were significantly different from those identified from n-octanol BCO. A second co-solvent (tetralin) was used to prove whether the difference on the components of BCO was affected by n-octanol. The results proved that indeed the addition of different solvents in liquefaction reaction media favours the formation of different components. The amount of char formed was also reduced when using a co-solvent. A decrease in the oxygen/nitrogen compounds was also observed in the presence of a co-solvent, thus improving BCO properties.
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DiTommaso, Antonio. "Effect of the fungal pathogen, Colletotrichum coccodes (Wallr.) Hughes, on growth, reproduction and competitive ability of velvetleaf (Abutilon theophrasti Medik.)." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29012.
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Field and growth bench experiments were performed to assess the effect of a selective fungal pathogen of Abutilon theophrasti (velvetleaf) on various aspects of intra- and interspecific competition between this vigorous agricultural weed and soybean (Glycine max). In the absence of the foliar pathogen, Colletotrichum coccodes, A. theophrasti and soybean responded differently to the presence of conspecies or to individuals of the other species. In pure stand, the deleterious effects of intraspecific competition on reproductive output were substantially greater for A. theophrasti than for soybean, especially at lower monoculture densities. In mixtures, however, A. theophrasti reproductive performance was markedly higher than at equivalent monoculture densities, particularly at the lower mixture densities. Soybean reproduction at these lower mixture densities (10 to 20 plants m$ sp{-2}$) was severely curtailed compared with reproductive output at equivalent pure stand densities. A. theophrasti reproductive output was limited more by the presence of conspecies than by the presence of soybean, whereas the opposite trend was observed for soybean. In pure stand, application of C. coccodes had limited impact on either A. theophrasti or soybean yield. However, application of the fungal pathogen in A. theophrasti monocultures caused significant (30-44%) aboveground biomass reductions within five weeks of inoculation, in two of the three years in one field study. Eight weeks following C. coccodes inoculation, A. theophrasti biomass within inoculated monoculture plots did not differ significantly from biomass within uninoculated control plots, although height hierarchies were significantly more developed. In mixtures, C. coccodes applications caused reductions in A. theophrasti growth and reproduction when provided with an adequate dew period. Alternatively, soybean yield losses within inoculated mixture plots were generally lower than for uninoculated control plots, althoug
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Li, Yuhong, and n/a. "Effect of alcohol exposure in early gestation on brain development." University of Otago. Department of Anatomy & Structural Biology, 2007. http://adt.otago.ac.nz./public/adt-NZDU20070502.100319.
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Fetal alcohol spectrum disorders (FASD), caused by maternal alcohol consumption during pregnancy, has been extensively studied in the human. Animal studies show that alcohol exposure during very early development may result in severe brain damage, often incompatible with a postnatal life. However, for surviving offspring it is unknown whether they suffer long term brain damage. The final assembly of the mature brain results from a controlled balance between proliferation of glial and neuronal precursors and programmed cell death. The overall aim of the current study was to use a physiologically relevant mouse model to assess the acute and long-term effects of binge alcohol exposure on the early embryo, to simulate human pregnancy at the third week of gestation when pregnancy may be undetected.
A number of paradigms were used to assess the acute dose-response effect, the blood alcohol concentration (BAC) profile and the extent of cell death following alcohol exposure on gestational day (G) 7.5. The exposure paradigms were single binge IG6.5, IG4.5, IP4.5, or an extended binge IG4.5+, IG3.0+. Two control groups were Con6.5 and Con4.5+. Acute cell death was determined using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), activated caspase-3 staining, and transmission electron microscopy. Cell proliferation was investigated using S-phase immuno-labeling, bromodeoxyuridine (BrdU) birthdating and immuno-detection (BrdU/anti-BrdU). The long-term effects were investigated at G18.5 and postnatal day (PN) 60. Unbiased stereological methods were used to assess the effect of ethanol exposure at G7.5 on neocortical volume, cell number and density of neurons, glial cells, and capillary cells at PN60.
The first principal finding of the present study was that binge ethanol exposure during gastrulation resulted in acute apoptotic cell death in the ectoderm of the mouse embryo. Cell death was dependent on both peak BAC and the duration of elevated BAC. Significant increased cell death (TUNEL labeling) was observed in groups IG6.5 (9.43 � 2.08%) and IG4.5+ (8.97 � 2.12%) compared with control groups Con6.5 (2.14 � 0.09%) and Con4.5+ (2.81 � 0.36%). There was no significant increased cell death in ethanol exposed groups IG4.5 (3.43 � 0.45%), IP4.5 (3.68 � 0.67%), or IG3.0+ (1.72 � 0.24%). TEM analysis revealed that cell death exhibited characteristics of the apoptotic pathway.
The second principal finding of the present study was that binge ethanol exposure during gastrulation resulted in acute arrested proliferation in the ectoderm of the mouse embryo. The S-phase proliferation was significantly decreased within the whole ectoderm in the ethanol exposed group IG6.5 (45.58 � 2.34%) compared with control group Con6.5 (62.08 � 3.11%).
The third principal finding of the present study was that binge ethanol exposure during gastrulation induced the long term effect of laminate disorganization in the neocortex. The incidence of abnormal lamination was 87.5% in IG6.5 compared with 16.7% in IG3.0+ and 14.3% in Con6.5. Although ethanol exposure increased embryonic reabsorption, decreased litter size, and increased abnormal offspring, neocortical volume, and the total number of neurons, glial cells, and capillary cells was not affected. The total number (10⁶) of neurons, glial cells, and endothelial cells respectively was 12.221 � 0.436, 4.865 � 0.167, and 2.874 � 0.234 in IG6.5; 11.987 � 0.416, 4.942 � 0.133, and 2.922 � 0.130 in IG3.0+; and 11.806 � 0.368, 5.166 � 0.267, and 3.284 � 0.217 in controls, at PN60.
These results provide important information pertinent to fetal outcome for those women who drink heavily in early pregnancy. The results also demonstrate the importance of the pattern of ethanol exposure and blood alcohol concentration in determining the magnitude of ethanol�s teratogenic impact. Ethanol exposure on G7.5 that resulted in a high transient BAC, induced disorganized neocortical lamination, indicative of a permanent structural change. This disruption may result in altered neocortical function and requires further investigation.
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Gaongalelwe, Motlhasedi Olebile. "Effect of delayed sowing and increased crop density on weed emergence and competition with wheat." Title page, table of contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09AFM/09afmg2118.pdf.
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Chan, Sai Yen Victor, and 陳世欽. "Effect of homocysteine on nitric oxide production in cardiomyocytes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31970321.
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Montambault, François. "The use of Hoe-39866 as a potato-top desiccant /." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61703.
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Weyand, Eric Henry. "The metabolic fate of benzo [a] pyrene in vivo." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/77786.
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[³H]-B[a]P absorption, distribution, metabolism, excretion and macromolecular binding in male Sprague-Dawley rats were investigated following administration by intratracheal instillation through a cannula. [³H]- radioactivity in various organs was determined at timed intervals between 5 and 360 min. Elimination of radioactivity from lungs was biphasic with half-lives of 5 and 116 min. Radioactivity in liver increased rapidly, reaching a maximum of 21% of the dose within 10 min after installation and decreasing thereafter, until less than 5% of the dose was detected at 360 min. Radioactivity in intestinal contents accounted for 45% of the dose 360 min after installation. Carcass accounted for 15-30% of the dose within the time intervals investigated. Toxicokinetic parameters to describe B[a]P disposition following intratracheal administration were similar to those following intravenous injection of B[a]P. HPLC was used to identify various types of metabolites in lungs, liver, and intestinal contents at selected times after B[a]P instillation. Notably, quinones were at highest concentrations in both lung and liver 5 min after installation, accounting for 12 and 7% of organic extractable material, respectively. Covalent binding of B[a]P metabolites to DNA, RNA, and protein at 6 hrs after installation was also quantified for lung and liver. There was extensive binding of metabolites to RNA while much lesser amounts of metabolites were associated with protein and DNA in both organs. Six B[a]P:DNA adducts were detected in lung, while only three such adducts were detected in liver.
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Biliary excretion of B[a]P was investigated in SpragueDawley rats, Gunn rats, hamsters, and guinea pigs following instillation of [³H]-B[a]P. [³H]-B[a]P was administered at concentrations ranging from 6 ng to 380 μg and biliary radioactivity was monitored for 6 hrs. In addition, tissue distribution of radioactivity was determined. Species differences in biliary excretion of B[a]P and/or metabolites were detected. Rats and guinea pigs, but not hamsters, exhibited differences in biliary excretion of low and high doses of B[a]P. Phase II metabolites of B[a]P in bile were quantified for all species. The majority of these metabolites were glucuronides and thio-ether conjugates. Enterohepatic circulation of B[a]P biliary metabolites was investigated in Sprague-Dawley rats.Ph. D.
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Reed, Susan. "Development of method to assess skin contact to chemicals." Thesis, View thesis View thesis, 2001. http://handle.uws.edu.au:8081/1959.7/611.
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Chemical exposure of the skin has become a route of entry of some chemicals into the body and has come under major review in recent times. This research aims to develop a method of estimating skin exposure that is both reliable and non-prohibitive in cost. This involved the design and testing of skin patches adaptable for monitoring skin exposure to chemicals using several different types of absorbents which could be easily worn against skin. The final design of the patch used either activated charcoal or tenax as the absorbing medium. The patches were then desorbed with a solvent in order to analyse the chemicals. The results of the study showed that many skin exposures do not have a direct relationship with inhalation exposures, which is important because currently there are no estimates of the levels of skin exposures that may have potential long term health effects. The patch has proved successful for detecting the presence and determining the amount of chemicals that come in contact with the skin. Charcoal patches have the widest application, but are not suitable for all situations and tenax should be used on these occasions.
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Pline, Wendy Ann. "Effect of Temperature and Chemical Additives on the Efficacy of the Herbicides Glufosinate and Glyphosate in Weed Management of Liberty-Link and Roundup-Ready Soybeans." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/31699.
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The introduction of herbicide resistant crops offers producers many more options for weed control systems. These crops allow environmentally safe, non-selective herbicides to be used as selective herbicides, broadening the spectrum of weeds controlled, while not harming the crop. As these crops are very new on the market, investigation of their performance under various environmental conditions as well as in various weed control programs is needed. Liberty-link ® soybeans are resistant to the herbicide glufosinate, because of the incorporation of a gene encoding phosphinothricin acetyl-transferase (pat), which is able to detoxify glufosinate. Roundup-Ready ® soybeans are transformed with an altered, non-sensitive form of 5-enolpyruvylshikimate- 3-phosphate synthase (EPSPS), which confers glyphosate resistance. Field and greenhouse studies were conducted to determine the efficacy of glufosinate and glyphosate on annual and perennial weeds. Also to determine whether the use of ammonium sulfate (AMS) or pelargonic acid (PA), a 9-carbon fatty acid, as additives of glufosinate or glyphosate would increase their efficacy, while maintaining their safety on the transgenic soybeans. Three annual weeds: common lambsquarters, giant foxtail, sicklepod, as well as two perennial weeds: common milkweed and horsenettle were included in studies. Uptake, translocation, and metabolism of 14C-glufosinate + AMS or PA, were studied in the five weeds in order to determine the basis for their differential weed sensitivity to glufosinate, and the effect of the two additives. The effect of temperature on Liberty-Link ® and Roundup-Ready ® soybeans after application of glufosinate or glyphosate was investigated. Injury was quantified by measuring chlorophyll content of herbicide treated soybean trifoliolates. Uptake, translocation, and metabolism studies of 14C-glufosinate and 14C-glyphosate in transgenic soybeans were conducted to determine the potential cause for the observed temperature-dependent sensitivity. Since glufosinate is a synthetic analog of a naturally occurring bacterial toxin, it was tested for possible bactericidal activity on the soybean pathogen Pseudomonas syringae. Greenhouse and field-studies showed that the 5 weeds responded differently to glufosinate and glyphosate. Common milkweed was the most tolerant to glufosinate and common lambsquarters to glyphosate while giant foxtail was the most sensitive species to both herbicides. Some interactions between AMS or PA and glufosinate or glyphosate were also observed. Uptake and translocation studies showed that AMS increased the uptake of 14C-glufosinate in some weeds, whereas PA had only minimal effects on absorption and translocation of glufosinate. Metabolism of glufosinate was detected only in common lambsquarters. A rate dependent loss of chlorophyll in Liberty-Link ® soybeans treated with glufosinate was observed that was greater at 15° C than at 25° or 35° C. Metabolism studies showed a decrease in the rate of glufosinate metabolism 3 hours after treatment in Liberty-Link ® soybeans grown at 15° C versus 25° C. Conversely, chlorophyll loss in glyphosate-treated Roundup-Ready soybeans was greater at 35° C than at 15° or 25° C. Translocation studies showed a significantly greater percentage of absorbed 14C-glyphosate translocated to developing meristems at 35° C than at 15° C in Roundup-Ready® soybeans. Glufosinate concentrations of 1 mM and higher significantly inhibited the growth of Pseudomonas syringae (L-529) in liquid media cultures. Typical field use rates of glufosinate also reduced the number of live P. syringae on Liberty-Link® soybean leaves. Overall, the results of this research show that annual and perennial weeds differ in their sensitivity to glufosinate and glyphosate. Additives such as AMS and PA may enhance the efficacy of glufosinate on perennial weed species, and glyphosate in most weeds. Differences in weed sensitivity to herbicides and effects of additives can in most cases be explained by differences in absorption or metabolism. Variable temperatures may affect the engineered resistance of transgenic soybeans to the herbicides glufosinate and glyphosate. The herbicide glufosinate has some bacteriocidal activity on P. syringae. Nomenclature: Glufosinate, 2-amino-4-(hydroxymethylphosphinyl) butanoic acid; Glyphosate, N-(phosphonomethyl)glycine; PA, pelargonic acid (nanoic acid); AMS, ammonium sulfate; giant foxtail, Setaria faberi Herrm.; common lambsquarters,
Chenopodium album L.; sicklepod, Cassia obtusifolia L.; horsenettle, Solanum carolinense L.; common milkweed, Ascleipias syriaca L. pat, phosphinothricin acetyl transferase; EPSPS, 5-enolpyruvylshikimate-3-phosphate synthase.Master of Science
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Hankins, S. D. "The effect of precipitation on the performance of foliage-applied herbicides for the control of broad-leaved weeds." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379852.
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Casa, Maria V. "Accumulation of Emerging Chemicals in Southern Hemisphere Humpback Whales (Megaptera novaeangliae) and Species-specific Chemical Effect Assessment." Thesis, Griffith University, 2022. http://hdl.handle.net/10072/411890.
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Millions of hazardous chemicals are synthesized each year. Their release often represents a risk for the environment and biota. As part of a broader effort to investigate the accumulation and effect of emerging chemicals of concern in the Antarctic sea-ice ecosystem, this thesis focuses upon exposure and effect assessment in southern hemisphere (SH) humpback whales (Megaptera novaeangliae). Cetaceans traditionally represent ideal targets for exposure assessment to Persistent Organic Pollutants (POPs), that is chemicals identified as persistent, bioaccumulative, toxic and capable of long-range environmental transport. Their extended life span and high proportion of body fat render cetaceans susceptible to accumulation of elevated burdens. Southern hemisphere humpback whales feed almost exclusively on Antarctic krill (Euphasia superba) and thus represent second order consumers of the Antarctic sea-ice ecosystem. Exposure assessment consisted of targeted analysis of short-chain chlorinated paraffins (SCCPs) included under the Stockholm Convention (SC) in 2017, and brominated structures listed in 2009 as well as novel, naturally occurring brominated structures, already detected at lower trophic levels of the Antarctic sea-ice ecosystem. SCCPs were targeted in stranded specimens and were detected in 77.7 % of samples, representing the first detection of SCCPs in any mysticetes or any Antarctic foraging marine mammal.Blubber samples from free-swimming and stranded specimens were dedicated to the analysis of the modern category of POPs, polybromodiphenilethers (PBDEs), and a naturally occurring brominated compound, 2,4,6-tribromoanysole (TBA), the chemical structure of which closely resembles PBDEs, flagging the possibility of similar toxic action. Humpback whale PBDEs profiles were dominated by tetra- and penta- congeners, supporting a single previous study on PBDE accumulation in Southern hemisphere humpback whales feeding in the Antarctic Peninsula region. Further, the detection of decaBDE adds support for the local emissions or particle bound transport to Antarctica. PBDE congeners were detected in all samples analysed, whilst TBA was 88 detected in 80% of samples. Upon establishing accumulation of three novel chemical groups in the Antarctic sea-ice ecosystem, species-specific effect assessment was performed through cytotoxicity assessment implementing the newly established immortalized humpback whale fibroblast cell line (HuWaTERT). Two endpoints were targeted, namely membrane integrity and metabolic activity following 24h exposure to an SCCP cocktail, BDE-47, BDE-99, TBA. Each assay also incorporated the assay reference chemical, p,p’-DDE. The four chemicals did not show a dose-dependent response comparable to the one produced by the reference chemical. Whilst p,p’-DDE induced a decrease of both metabolic activity and membrane integrity, the cell response to BDE-99 indicated a positive, or potentially hermetic relationship with regards to the metabolic activity, warranting further investigation of underlying mechanisms.The final thesis chapter explores the unique potential of HuWaTERT for the generation of induced pluripotent stem cells (iPSCs). The main objective of this work was to generate a source of a number of different cell lines from the iPSCs, that could be applied for a more tailored approach to in-vitro chemical effect evaluation to fill the gap currently existing in the field of cetacean toxicology. The re-generation trial involved the use of the Sendai virus, which induces the de-differentiation mechanism in HuWaTERT to become iPSCs without integrating into the cell genome. After successfully generating a number of iPC colonies, the cells ultimately did not thrive, likely due to a fungal infection. Overall, this thesis combines both chemical exposure and effect assessment of novel chemical groups, for unique insight into chemical accumulation and impact in the Antarctic sea-ice ecosystem. The work provides new information regarding the range of chemicals that Antarctic consumers are exposed to, a reflection of hemispheric chemical usage and local input, and also contributes invaluable species-specific in vitro toxicity assessment data, which represents a critical research gap for cetacean chemical impact assessment.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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Dwyer, Suzanne. "Effects of Neonatal Clomipramine Treatment on Photic and Non-Photic Circadian Phase Shifting in Rats." Fogler Library, University of Maine, 2000. http://www.library.umaine.edu/theses/pdf/DwyerSM2000.pdf.
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Amoako, Daniel Kwasi. "Cyclopiazonic acid changes the mode of excitation-contraction couplingin acetylcholine-stimulated bovine tracheal smooth muscle." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B3121387X.
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Yeung, Chiu Wai. "Neurotoxicological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on cultured neurons." HKBU Institutional Repository, 2004. http://repository.hkbu.edu.hk/etd_ra/529.
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Chidgey, Laura Louise. "An integrated approach to unravel the effect pathways of endocrine disrupting chemicals on the developing zebrafish, Danio rerio." Thesis, University of Exeter, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496171.
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Over the last two decades, a wide range of chemicals in the aquatic environment have been shown to elicit disruptive effects on the endocrine system and, in turn, alter physiological function. However, the underlying mechanisms for these effects remain largely elusive. In this thesis, a molecular approach (using DNA microarrays and RTPCR) was employed to investigate the mechanistic basis for estrogenic disruption in ling the zebrafish (Danio rerio) as a model species.
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Sandoval, Mojica Andres Felipe. "Antifeedant effect of commercial chemicals and plant extracts against Schistocerca americana (Orthoptera: Acrididae) and Diaprepes abbreviatus (Coleoptera: Curculionidae)." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024748.
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Seggio, Joseph A. "Chronic Ethanol Modulated Photic and Non-photic Phase Responses in Syrian Hamster and C57BL/6J Inbred Mouse." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/SeggioJA2009.pdf.
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Wei, Juntong. "Mass spectrometry-based metabolomics to unveil the polybrominated diphenyl ether-47 induced alteration in breast carcinoma." HKBU Institutional Repository, 2019. https://repository.hkbu.edu.hk/etd_oa/661.
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Based on the findings from breast cancer cells and nude mouse assays, we noticed that fatty acid metabolism was influenced by BDE-47 exposure. To have a comprehensive understanding of the impact, we performed targeted metabolomics analysis of fatty acids. Short-chain fatty acids (SCFAs) and hydroxylated short-chain fatty acids (OH-SCFAs) are crucial intermediates related to a variety of diseases, such as bowel disease, cardiovascular disease, renal disease and cancer. We developed a global profiling method to screen SCFAs and OH-SCFAs by tagging these analytes with d0/d6-N, N-dimethyl-6,7-dihydro-5H-pyrrolo[3,4-d] pyrimidine-2-amine (d0/d6-DHPP) and UHPLC-MS/MS in parallel reaction monitoring (PRM) mode. The derivatization procedure was simple and rapid. The targeted compounds could be derivatized within three minutes under mild condition and analyzed without the need of further purification. The derivatization significantly improved the chromatographic performance and mass spectrometry response. The d6-DHPP tagged standards were used as internal standards, which remarkably reduced the matrix effects. The use of high resolution PRM mode made it possible to identify unknown SCFA and OH-SCFA species. The developed method was successfully applied to the analysis of mouse feces, serum, and liver tissue samples harvested from the breast cancer nude mice that had been exposed to BDE-47. By using the developed method, 40 analytes (10 SCFAs and 30 OH-SCFAs) were characterized. Semi-quantitative analysis indicated that the exposure of BDE-47 to the mice altered the SCFA and OH-SCFA metabolism, especially in the high dose group. In addition, medium- and long-chain fatty acids (MLFAs) are essential energy sources in cells and possess vital biological functions. Characteristics of MLFAs in biosamples can contribute to the understanding of biological process and the discovery of potential biomarkers for relevant diseases. However, there are obstacles of the MLFAs determination because of the poor ionization efficiency in mass spectrometry and structural similarity. Herein, a derivatization strategy was developed by labeling with d0-DHPP and detecting with UHPLC-MS/MS in multiple reaction monitoring (MRM) mode. The parallel isotope labeled internal standards were generated by tagging d6-DHPP to MLFAs. The simple and rapid derivatization procedure and mild reaction conditions greatly reduced the potential of MLFA degradation. With the methodology, the chromatography performance was greatly improved, and the mass spectrum response was enhanced up to 1, 600 folds. Finally, the developed derivatization method was applied to serum samples to analyze the alteration of MLFAs induced by BDE-47 exposure in breast cancer nude mice. The semi-quantitative results demonstrated that the BDE-47 exposure significantly influenced the MLFA metabolism. Together, mass spectrometry-based targeted and nontargeted metabolomics of in vitro and in vivo studies suggested that BDE-47 impacted multiple metabolic pathways and was positively associated with breast tumor growth in mice. This study might further our understanding of the health risks of BDE-47 to breast cancer.;Polybrominated diphenyl ethers (PBDEs) are commonly used to prevent the development of fire in various factory products. Due to the adverse effects on human health and bio-accumulation capacity, PBDEs are considered as one kind of persistent organic pollutants. 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) is one of the most frequently detected PBDE congeners in humans. Although numerous studies have shown the close connection between BDE-47 and human health, few reports were related to breast carcinoma. In vivo study of the association between BDE-47 and breast cancer was also scarce. In this study, both in vitro and in vivo experiments were conducted to explore the influence of BDE-47 to breast cancer. Firstly, we performed the in vitro study by exposing different concentrations of BDE-47 (5, 10 µM) to MCF-7 breast cancer cells. Nontargeted metabolomics analysis was conducted by using ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC-MS). Results showed that the toxicity to MCF-7 cells gradually increased when the concentration of BDE-47 exceeded 1 µM in the medium. Pyrimidine metabolism, purine metabolism and pentose phosphate pathway (PPP) were the most influenced metabolic pathways, and the metabolites in the three metabolic pathways were significantly downregulated. Moreover, the increase of reactive oxygen species was detected by using the 2',7'-dichlorodihydrofluorescein diacetate staining assay. Results suggested that the BDE-47 induced oxidative stress by downregulating the NADPH generation in PPP. The pyrimidine metabolism and purine metabolism might be downregulated by the downregulation of mRNA transcripts. Therefore, BDE-47 could induce oxidative stress in breast cancer cells by inhibiting PPP and disordering the metabolism of the entire cell subsequently. Secondly, we constructed a breast cancer nude mouse model, performed in vivo exposure of BDE-47 to the mice, and conducted mass spectrometry-based metabolomics and lipidomics analysis to investigate the metabolic changes in mice. Results showed that the tumor sizes were positively associated with the dosage of BDE-47. Metabolomics and lipidomics profiling analysis indicated that BDE-47 induced significant alterations of metabolic pathways in livers, including glutathione metabolism, ascorbate and aldarate metabolism, and lipids metabolism, etc. The upregulations of phosphatidylcholines and phosphatidylethanolamines suggested the membrane remodeling, and the downregulations of Lyso-phosphatidylcholines and Lyso-phosphatidylethanolamines might be associated with the tumor growth. Targeted metabolomics analysis revealed that BDE-47 inhibited fatty acid β-oxidation (FAO) and induced incomplete FAO. The inhibition of FAO and downregulation of PPARγ would contribute to inflammation, which could promote tumor growth. In addition, BDE-47 elevated the expression of the cytokines TNFRSF12A, TNF-α, IL-1β and IL-6, and lowered the cytokines SOCS3 and the nuclear receptor PPARα. The changes of cytokines and receptor may contribute to the tumor growth of mice.
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Lau, Wai Kit Jaeger. "Developmental expression of N-methyl-D-aspartate and gamma-aminobutyric acid receptors in the rat basal ganglia." HKBU Institutional Repository, 2004. http://repository.hkbu.edu.hk/etd_ra/535.
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Lam, Wai Chi Rebecca. "Expression of metabotropic glutamate receptors in the rat striatum during postnatal development." HKBU Institutional Repository, 2003. http://repository.hkbu.edu.hk/etd_ra/528.
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Alm, Therese. "Characterization of retention chemicals and their effect on the paper forming process on machine PM4, Billerud Korsnäs Gävle Mill." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-93424.
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In the papermaking industries spots in the finished product is a recurring problem. Billerud Korsnäs have in earlier studies identified poorly optimized retention systems as one of the reasons for these spots. Poorly optimized retention systems will allow for detrimental substances to flow freely in the system, which may cause agglomeration into larger particles that could end up as darker spots in the finished product. The aim of this thesis is to investigate a number of retention systems, consisting of a retention polymer and retention microparticles, and characterize the polymers.The retention aid systems task is to flocculate fibres, fines and fillers along with the colloidal material to improve process parameters. To investigate the retention systems three different retention polymers with different charge densities have been investigated alongside one microparticle. The parameters investigated in this thesis were the retention systems effect on drainage time, turbidity, charge demand and zeta potential. Pulp and white water from PM4 was used to imitate mill conditions.The results showed that the drainage time and turbidity was most effected by the retention aid systems. The polymer with the highest charge yielded the best results. Only minor effects could be detected on charge demand and Zeta potential.
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Belayneh, Teferi Yeshitela. "Effect of cultural practices and selected chemicals on flowering and fruit production in some mango (Mangifera indica L.) cultivars." Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-01142005-085139.
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Castillo-Ruiz, Priscila. "Plant activation of different chemicals by tobacco and brassica cell cultures, using the plant cellmicrobe coincubation assay." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39239.
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In this study, the ability of various chemicals to be biotransformed into mutagens by plant cells was investigated. Two thiocarbamate herbicides, diallate and triallate, the sulfonylurea herbicide chlorsulfuron, and the aniline derivative m-phenylenediamine were tested for their ability to revert Salmonella typhimurium (strains TA100 and TA98) in the presence and absence of Nicotiana tabacum (TX1) cell cultures in liquid suspension. Chlorsulfuron and m-phenylenediamine were also tested in the presence and absence of Brassica napus cv. 'Topas' cells. Diallate was found to be activated by TX1 cells into a mutagen that induces base-pair substitution mutations. In the presence of the TX1 plant cell line, chlorsulfuron significantly increased the number of mutations on the strain TA98 of Salmonella. Tobacco TX1 cells did not activate triallate into a mutagen. m-Phenylenediamine was activated into a mutagen by TX1 and Brassica cells as detected by Salmonella TA98. This aniline derivative, in the absence of plant cells and at concentrations higher than 20 $ mu$ Moles/plate, was also able to significantly increase the number of TA98 revertants as compared to the control plants. Finally, Brassica napus cells activated chlorsulfuron into a mutagen that induces frameshift mutations.
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Poon, Ming-see Angela, and 潘明施. "Binding of 2[125I]iodomelatonin in the guinea pig spleen: evidence for a direct action of melatonin on themammalian immune system." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1994. http://hub.hku.hk/bib/B31233855.
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Allison, Edwin. "Effects of seed adjuvants on germination and development of onions." Thesis, Cape Technikon, 2001. http://hdl.handle.net/20.500.11838/2000.
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Thesis (MTech (Agriculture))--Cape Technikon, 2001.Onion seeds (cultivar Caledon Globe), and soil into which the seedlings were planted, were treated with various adjuvants including fungicides, a seed disinfectant and a soil sterilant, as well as soil-applied growth stimulants to determine the effect of these on germination of seed, the growth of plants and the storage life of onions obtained. Three sets of germination trials were undertaken in petri dishes, and sets of seed was also sown in deep seed trays. A trial planting was made and the crop graded and stored. Seed was also sown in pots in soil obtained from a commercial undertaking where poor germination had been obtained. A portion of this soil was pasteurised and a portion inoculated with Fusarium spp. Growth of these seedlings was then followed by re-sowing in the same pots using seed of additional cultivars.
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Sartini. "The effect of inoculum density, virulency, and carrier systems of phoma sp. on biological control of giant foxtail (setaria faberi hermm.)." Virtual Press, 1995. http://liblink.bsu.edu/uhtbin/catkey/955092.
Full textAbstract:
The effect of spore titer, virulency, and carrier systems on biological control of giant foxtail (Setaria faberi hermm.) with a species of Phoma isolated from this weed wereinvestigated. The lowest concentration of Phoma conidia which significantly affected (lowered) growth of giant foxtail was 1x106 conidia/ml. In conducting Koch's postulates, all but one (FF2) of the Phoma, isolates tested infected giant foxtail. Isolates FF1 and FF9 were the most virulent against giant foxtail. No correlation was apparent between virulency and fungus germination rate. No visible difference occurred with in vitro germination rates of spores incubated upon pea vsr water agar media; nutrient rich vs. nutrient poor media, respectively. These results suggest that Phoma spores already contain sufficient nutrients required for infection of foxtail. A definitive answer as to the effect of carrier system (e.g. surfactant, sticker, spreader, etc.) on efficacy of Phoma to infect foxtail could not be determined from results obtained, based upon statistical analysis of variance (ANOVA) for the single experiment performed. Several of the surfactant treatments (e.g. Silwet 77 and 408) did produce significant biomass losses against foxtail due to the phytotoxicity of the carrier system alone, and not reflective of fungal (Phoma) infection. Inoculation of foxtail plants with a conidial suspension amended with carriers of either Tween 20 (0.05%-0.1%) or methylcellulose (0.1%) should optimize chances for sufficient infection resulting in biological control of this weed.Department of Biology
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Shubat, Pamela Jane. "Monocrotaline toxicity and pulmonary arteries." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184533.
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Monocrotaline is a pyrrolizidine alkaloid found in plants implicated in livestock and human poisoning. Laboratory rats given monocrotaline develop pulmonary hypertension and right heart hypertrophy in the weeks following administration of the chemical. Lung weight increases and right heart hypertrophy correlate with increased pulmonary artery pressure. Rats which consumed monocrotaline drinking water (20 mg/l) for only 4 days developed significant increases in lung and heart weights 14 days after exposure began. This exposure was equivalent to a dose of 15 mg/kg. Other treatment combinations of time (0-10 days exposure) and monocrotaline concentration (5-60 mg/l in drinking water) were tested. The accumulative dose calculated for each of the treatment combinations which produced toxicity was in the range of 15 to 20 mg/kg. Monocrotaline injury appears to be cumulative, but organ weight increases reverse once exposure is stopped. As pulmonary hypertension develops and pulmonary arteries hypertrophy, the force with which isolated pulmonary artery segments contract decreases. This is a loss of efficacy rather than potency to the contracting agents KCl, norepinephrine, and 5-hydroxytryptamine. Relaxation of arteries under conditions of potassium-return (a measure of Na⁺/K⁺ ATPase activity) was also altered by monocrotaline treatment. In vivo monocrotaline treatment had little effect on the force of K⁺-return relaxation. However, the rate at which arteries relaxed was significantly decreased following 4 days ingestion of monocrotaline drinking water (20 mg/l). In vitro ouabain treatment and endothelial injury also decreased the rate of K⁺-return relaxation. Another Na⁺/K⁺ ATPase activity, ⁸⁶Rb⁺ uptake, was decreased following monocrotaline treatment only when 5-hydroxytryptamine was present and only uptake associated with the endothelium was affected. These studies utilized a very low exposure to monocrotaline (4 days ingestion of 20 mg/l monocrotaline drinking water or 15 mg/kg) to produce toxicity in rats. Monocrotaline-induced toxicity measured 20 days after treatment included right heart and lung hypertrophy and decreased contractions of isolated pulmonary arteries. Monocrotaline treatment decreased the rate of Na⁺/K⁺ ATPase-dependent relaxation of isolated pulmonary arteries 4 days after treatment began.