• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 19
  • 16
  • 7
  • 5
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 69
  • 14
  • 8
  • 7
  • 6
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 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.
41

Stadium Squeeze: The Power and Politics of Housing the NFL in LA

Mullen, William M. 01 January 2012 (has links)
There are currently two proposals for an NFL stadium in the Los Angeles area. This thesis explains these proposals as a case study of an imbalanced political market in which concentrated gainers have an advantage over diffuse losers. Although there is little evidence that the economic benefits of a stadium will exceed the costs -- and much reason to worry that the costs will be large – developers have nonetheless gained considerable support in the political community. The pattern is a familiar one, but the thesis explains special features of this case: the excitement of professional football, the governmental fragmentation of the metropolitan area, and the relative shortage of local investigative journalism.
42

Numerical Analysis of Convective Storm Development over Maldives

Shareef, Ali January 2009 (has links)
In the Asian and other monsoon regions of the world most of the severe weather observed is local or mesoscale in nature. Forecasting convective storms or mesoscale systems in the monsoon regions, especially in the tropics, has always been a challenging task to operational meteorologists. Maldives Islands, being situated in the tropical Indian Ocean, are affected by monsoon depressions and tropical cyclones. Thunderstorms and the passage of squall lines are well known sources of heavy rainfall. However, due to the lack of professional people and necessary equipment the weather systems around these islands are seldom studied. Therefore the aim of this thesis is to investigate whether the small islands can create sufficient perturbations in the mesoscale environment to result in the development of convective systems. In this regard, two numerical models, Weather Research and Forecasting model (WRF version 2.2.1) and Regional Atmospheric Modelling System (RAMS version 6.0) were used in this study. Two experiments were performed using the WRF model. In the first experiment, a case study was investigated where the selected day experienced heavy rainfall and thunderstorms. In the second experiment, the same case study was used but with the topographical and surface properties removed in order to investigate the influence of the island in modifying the mesoscale environment. All the experiments were initialized using the re-analysis data from NECP. WRF was able to predict the large scale synoptic features with reasonable accuracy when compared to the observations. Development of the boundary layer and the downstream advection of the temperature anomaly generated by the island were well represented. However, the magnitude of the effects was shown to be weak, probably due to the influence of large scale synoptic features. Even though the model was able to predict the large scale features and some of the mesoscale features, it did not predict any storm development and underestimated the precipitation. Therefore, it was decided to idealize the storm development using the RAMS model. RAMS model was used in a two-dimensional framework. The model was initialized horizontally homogenous using a single sounding and six simulations were performed. The simulation results clearly depicted that the small island can generate its own circulation and influence the mesoscale environment. The daytime heating of the island and the downstream advection of the temperature anomaly in a moist unstable atmosphere could trigger a thunderstorm later in the day. The storm becomes mature approximately 40-80 km offshore. This also suggests that triggering of a storm on one side of an atoll could influence the islands on the downstream side. Sensitivity of storm development to the thermodynamics showed that even with an unstable atmosphere, enough moisture in the lower and mid-troposphere is needed to trigger the storm. Sensitivity to the change of SST showed that convective development was suppressed with a drop of 1 oC. However, this needs further investigation. Assessment of sensitivity to the size of the island showed that the time of triggering of the storm was later and the scale of influence was smaller with a smaller island.
43

Numerical Analysis of Convective Storm Development over Maldives

Shareef, Ali January 2009 (has links)
In the Asian and other monsoon regions of the world most of the severe weather observed is local or mesoscale in nature. Forecasting convective storms or mesoscale systems in the monsoon regions, especially in the tropics, has always been a challenging task to operational meteorologists. Maldives Islands, being situated in the tropical Indian Ocean, are affected by monsoon depressions and tropical cyclones. Thunderstorms and the passage of squall lines are well known sources of heavy rainfall. However, due to the lack of professional people and necessary equipment the weather systems around these islands are seldom studied. Therefore the aim of this thesis is to investigate whether the small islands can create sufficient perturbations in the mesoscale environment to result in the development of convective systems. In this regard, two numerical models, Weather Research and Forecasting model (WRF version 2.2.1) and Regional Atmospheric Modelling System (RAMS version 6.0) were used in this study. Two experiments were performed using the WRF model. In the first experiment, a case study was investigated where the selected day experienced heavy rainfall and thunderstorms. In the second experiment, the same case study was used but with the topographical and surface properties removed in order to investigate the influence of the island in modifying the mesoscale environment. All the experiments were initialized using the re-analysis data from NECP. WRF was able to predict the large scale synoptic features with reasonable accuracy when compared to the observations. Development of the boundary layer and the downstream advection of the temperature anomaly generated by the island were well represented. However, the magnitude of the effects was shown to be weak, probably due to the influence of large scale synoptic features. Even though the model was able to predict the large scale features and some of the mesoscale features, it did not predict any storm development and underestimated the precipitation. Therefore, it was decided to idealize the storm development using the RAMS model. RAMS model was used in a two-dimensional framework. The model was initialized horizontally homogenous using a single sounding and six simulations were performed. The simulation results clearly depicted that the small island can generate its own circulation and influence the mesoscale environment. The daytime heating of the island and the downstream advection of the temperature anomaly in a moist unstable atmosphere could trigger a thunderstorm later in the day. The storm becomes mature approximately 40-80 km offshore. This also suggests that triggering of a storm on one side of an atoll could influence the islands on the downstream side. Sensitivity of storm development to the thermodynamics showed that even with an unstable atmosphere, enough moisture in the lower and mid-troposphere is needed to trigger the storm. Sensitivity to the change of SST showed that convective development was suppressed with a drop of 1 oC. However, this needs further investigation. Assessment of sensitivity to the size of the island showed that the time of triggering of the storm was later and the scale of influence was smaller with a smaller island.
44

I. Distribution of transforming growth factor beta 1, TGF receptor II and decorin in the sheep uterus shortly after breeding

Holásková, Ida, January 2007 (has links)
Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains ix, 144 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 126-144).
45

The Laird rams : warships in transition, 1862-1885

English, Andrew Ramsey January 2016 (has links)
The Laird rams, built from 1862-1865, reflected concepts of naval power in transition from the broadside of multiple guns, to the rotating turret with only a few very heavy pieces of ordnance. These two ironclads were experiments built around the two new offensive concepts for armoured warships at that time: the ram and the turret. These sister armourclads were a collection of innovative designs and compromises packed into smaller spaces. A result of the design leap forward was they suffered from too much, too soon, in too limited a hull area. The turret ships were designed and built rapidly for a Confederate Navy desperate for effective warships. As a result of this urgency, the pair of twin turreted armoured rams began as experimental warships and continued in that mode for the next thirty five years. They were armoured ships built in secrecy, then floated on the Mersey under the gaze of international scrutiny and suddenly purchased by Britain to avoid a war with the United States. Once purchased, they were largely forgotten. Historians rarely mention these two sister ironclads and if mentioned at all, they are given short shrift. Built with funds obtained in part through the Confederate Erlanger loan, these ironclads were constructed at Lairds shipyard in Birkenhead and represented an advanced concept of ironclad construction through new proposals involving turrets, the ram, heavy guns and tripod masts on an armoured ship, as advocated by Captain Cowper Coles, R.N. They proved too much of a leap in one design but when their roles caught up to the revised designs, the ships were modified to meet new requirements. After several mission and design changes they then performed to standard. This belated success occurred when the concept of the ideal armoured warship was in flux throughout the middle Victorian years.
46

Vyhodnocení reprodukčních a produkčních vlastností ovcí plemene suffolk ve vybraném chovu / Evaluation of reproduction and production traits of sheep breed suffolk in selected breeding

JANKOVSKÁ, Gabriela January 2014 (has links)
The aim of this theis is to evaluate reproducing and production qualities of sheep (suffolk race)in selected breding. Reproducing indicators were followed on the basis of calculated average values in sterility, death after delivery, pregnancy and fertility in percents. From the production indicators, average weight and fat width of rams and female lambs were followwed within the period of 100 days. The results were transformed into tables and diagrams. In this thesis ascertained information was also cetified by scattering analasis of F test on significance surface.
47

Efeitos de dieta contendo castanha de caju sobre o desenvolvimento ponderal, parÃmetros seminais e proteoma do plasma seminal de carneiros Morada Nova / Effects of cashew nut on growth, sÃmen parameters and seminal plasma proteome of Morada Nova rams

Emerson Pinto Moreira 26 February 2015 (has links)
nÃo hà / O presente estudo avaliou os efeitos da inclusÃo de 13% de farelo de castanha de caju (CNM) na dieta de carneiros Morada Nova nos parÃmetros seminais e proteÃnas do plasma seminal. Vinte carneiros foram distribuÃdos em dois grupos iguais: grupo castanha de caju (CNG) e grupo controle (COG). O CNG e COG receberam 13% e 0% de CNM na dieta durante 90 dias. Os grupos foram comparados para peso corporal, circunferÃncia escrotal, parÃmetros seminais e proteÃnas do plasma seminal, utilizando o MÃtodo de Shotgun Proteomics. Peso corporal e circunferÃncia escrotal aumentaram durante os 90 dias do perÃodo experimental em ambos grupos, porÃm nÃo existiu diferenÃa significativa entre CNG e COG. Contudo, apÃs 60 dias, o consumo de matÃria seca foi inferior no CNG (2,9  0,1; aos 90 dias) em relaÃÃo ao COG (3,4  0,1; aos 90 dias). Os parÃmetros seminais nÃo diferiram entre CNG e COG. A anÃlise shotgun proteomics identificou isoaspartil peptidase L asparaginase, gliceraldeÃdo 3 fosfato desidrogenase e prostaglandina H2 D isomerase com alta expressÃo no CNG quando comparado COG. Ao mesmo tempo, 12 proteÃnas do plasma seminal apresentaram baixa expressÃo no CNG, identificadas como beta galactosidase, caltrina, beta mannosidase, glutationa peroxidase, sorbitol desidrogenase, clusterina, albumina and serotransferrina. AlÃm disso, 20 proteÃnas detectadas no plasma seminal do COG foram ausentes no CNG e cinco proteÃnas foram presentes somente nos carneiros que receberam dieta hiperlipÃdica. Em conclusÃo, o presente estudo descreveu, pela primeira vez, os efeitos de uma dieta hiperlipÃdica nos parÃmetros do sÃmen fresco e do plasma seminal de carneiros. Enquanto os critÃrios seminais nÃo foram afetados, proteÃnas especÃficas do fluido seminal foram alteradas em decorrÃncia da dieta com castanha de caju. Visto os aspectos multifuncionais dessas proteÃnas, nÃs sugerimos que certos aspectos da fertilidades de carneiros podem ser alteradas se a castanha de caju for fornecida. / The present study was carried out to evaluate the effects of 13% of cashew nut meal (CNM) inclusion in the diet of Morada Nova rams on semen parameters and seminal plasma proteins. Twenty rams were distributed in two equal groups: cashew nut group (CNG) and control group (COG). The CNG and COG received 13% and 0% of CNM in the diet for 90 days. The groups were compared for live weight, scrotal circumference, seminal parameters and seminal plasma proteins, using shotgun proteomics. Body weight and scrotal circumference increased during the 90-day experimental period in both cashew nut-fed and control groups but with no differences between CNG and COG. However, after 60 days until 90 days, percentage of dry matter intake (% live weight) was inferior in CNG (2,9  0,1; at 90 days) group than COG (3,4  0,1; at 90 days). The sperm quality parameters were not different between CNG and COG.The shotgun proteomics analysis identified isoaspartyl peptidase L asparaginase, glyceraldehyde 3 phosphate dehydrogenase and prostaglandin H2 D isomerase with higher expression in the cashew nut group as compared to animals receiving the control diet. Conversely, 12 seminal plasma proteins had lower expression in the cashew nut group, identified as beta galactosidase, caltrin, beta mannosidase, glutathione peroxidase, sorbitol dehydrogenase, clusterin, albumin and serotransferrin. Moreover, 20 proteins detected in the seminal plasma of the control animals were absent in the cashew nut fed animals and five were present only in the rams receiving the high fat diet. In conclusion, the present study describes, for the first time, the effects of a high fat diet on parameters of the fresh semen and seminal plasma proteins of rams. While sperm criteria were not affected, specific seminal fluid proteins did change as the result of cashew nut feeding. Given the multifunctional aspects of such proteins, we suggest that certain aspects of the ram fertility can be altered if cashew nut is provided.
48

ExpressÃo de proteÃnas do plasma seminal em carneiros das raÃas santa ines e morada nova: associaÃÃoes com parÃmetros seminais , influencia de fontes de proteÃnas e de nitrogÃnio nÃo proteico nas dietas. / Expression of seminal plasma proteins in Santa InÃs and Morada Nova rams: associations with semen parameters and influence of protein sources and non-protein nitrogen in the diets.

Marco Antonio de MagalhÃes Rodrigues 30 September 2011 (has links)
FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / O Nordeste brasileiro possui aproximadamente quase metade do rebanho ovino brasileiro, estimado em vinte milhÃes de animais. Das raÃas aqui criadas, destacam-se as raÃas Santa InÃs e Morada Nova que tÃm bom desenvolvimento corporal, ganho de peso e boa adaptaÃÃo ao clima tropical. Recentemente mostrou-se o perfil protÃico de carneiros maduros atravÃs das tÃcnicas de eletroforese bidimensional associada à espectrometria de massa, onde vÃrias proteÃnas foram identificadas, entre elas as RSVPs 14 e 22 kDa, pertencentes à famÃlia das BSPs e as bodesinas â 1 e 2, que fazem parte da famÃlia das espermadesinas, bem como as alteraÃÃes que sofre o perfil protÃico do plasma seminal dos animais durante o desenvolvimento reprodutivo, simultaneamente a mudanÃas nos parÃmetros de motilidade e concentraÃÃo espermÃtica, embora a associaÃÃo entre a expressÃo protÃica dessas proteÃnas com parÃmetros reprodutivos e medidas testiculares ainda nÃo tenham sido feitas no nordeste do Brasil. Amostras de sÃmen foram coletadas de 21 carneiros adultos Santa InÃs e 11 da raÃa Morada Nova com normalidade reprodutiva e idade mÃdia de dois anos. O plasma seminal foi obtido atravÃs da centrifugaÃÃo e submetido à eletroforese bidimensional, sendo os spots que diferiram estatisticamente entre os grupos de animais de alta (G1) e baixa motilidade (G2) foram digeridos com tripsina e submetidos a espectometria de massa e pesquisa em banco de dados para identificaÃÃo. Os gÃis foram corados com Cromassie coloidal, digitalizados e analisados no aplicativo PDQuest e as quantidades dos spots estimados quantitativamente. Avaliaram-se, entÃo, associaÃÃes estatÃsticas entre estas variÃveis e os parÃmetros reprodutivos como, circunferÃncia escrotal (CE), percentual de cÃlulas mÃveis (PEM) e total de defeitos espermÃticos maiores (TDM) dos animais Santa InÃs e CircunferÃncia escrotal (CE), Motilidade Individual Progressiva (MIP), Percentual de cÃlulas mÃveis (PEM), ConcentraÃÃo espermÃtica (CONC) e Motilidade Massal (MM) para os animais Morada Nova. Em mÃdia foram detectados 236Â7,65 spots por gel, de acordo com o pareamento gerado pelo aplicativo PDQuest para a raÃa Santa InÃs e 261 15,09 spots por gel do plasma seminal dos animais Morada Nova, variando entre 182 e 375 spots por gel. Para a raÃa Santa InÃs um total de 63 spots foi identificado consistentemente em todos os gÃis, o que representou 41,5% da intensidade todos os spots detectados. Para os animais Morada Nova, um total de 98 spots foram detectados de forma consistente em todos os gÃis. A intensidade desses spots somou 60,82% da intensidade de todos os spots mostrados no gel master. Foi observado a grande expressÃo de proteÃnas de baixo peso molecular (14,5 a 18,4 kDa) e pI variando de 4,2 a 5,9.para a raÃa Santa InÃs. Do total mÃdio de 236 spots encontrados, treze spots apresentaram diferenÃa significativa (p<0,05) entre animais de alta e baixa motilidade, sendo dez spots mais intensos em animais de alta motilidade e trÃs em animais de baixa motilidade. ApÃs digestÃo dos spots e identificaÃÃo por espectometria de massa esses spots foram identificados como as proteÃnas Arilsulfatase A e Zinco alfa 2 glicoproteÃna, mais intensas no G1 e RSVP-22 e Bodesina-2 com maior expressÃo no grupo G2. Para a raÃa Morada Nova , quatro spots apresentaram diferenÃa significativa (p<0,05) para o parÃmetro percentual de cÃlulas mÃveis (PEM). ApÃs digestÃo dos spots e identificaÃÃo por MALDI-Tof-Tof, foram identificadas as proteÃnas RSVP-14, RSVP-22, ProteÃna &#945;-1 do complexo-t e aldose redutase, sendo todas mais intensas em animais de alta motilidade (G1). Em um segundo estudo, foi avaliada a influÃncia de diferentes fontes de proteÃna da dieta (farelo de soja, feno de folha de leucena e torta de algodÃo) e de nitrogÃnio nÃo- protÃico (urÃia) sobre o peso corporal, desenvolvimento testicular e qualidade espermÃtica dos animais estudados, bem como a expressÃo de proteÃnas no plasma seminal dos animais potencialmente relacionadas Ãs dietas. Foram utilizados 20 cordeiros da raÃa Morada Nova com idade variando entre 24 e 39 semanas. Para os critÃrios de desenvolvimento testicular (cirrcunferÃncia escrotal, espessura testicular, largura testicular e comprimento testicular) nÃo houve diferenÃa significativa (p<0,05). ao final do perÃodo experimental Animais alimentados com torta de algodÃo tiveram um aumento significativo do peso corporal (p<0,05), quando comparado com feno de leucena. No mesmo perÃodo, o peso corporal dos animais alimentados com feno de leucena, soja e urÃia foi semelhante. DiferenÃas entre os tratamentos (p <0,05) foram observadas apenas para motilidade progressiva individual e defeitos totais. O sÃmen dos animais alimentados com dietas contendo feno de leucena apresentou baixa motilidade progressiva individual quando comparados aqueles alimentados com dietas contendo farelo de soja. No entanto, animais alimentados com dietas contendo torta de algodÃo e urÃia tinham valores semelhantes para a motilidade progressiva. Quando os defeitos totais foram analisados, houve uma diferenÃa significativa entre os grupos de feno de leucena e urÃia. Foi detectado uma quantidade de 246,6  13,9, 236,0  12,4, 261,2  20,2 e 243,8  20,5 spots por gel nos grupos de farelo de soja, feno de folhas de leucena, torta de algodÃo e urÃia, respectivamente. NÃo houve diferenÃas significativas no nÃmero de spots por gel, entre os grupos. DiferenÃas significativas (p <0,05) foram observadas nas intensidades de doze spots dos mapas protÃicos. Foi observado um aumento da expressÃo do spot S8707 (62,8 kDa, pI 6,9 ) em animais alimentados com feno de folhas de leucena, quando comparados Ãqueles alimentados com farelo de soja, bem como correlaÃÃo negativa com a motilidade progressiva individual (MPI). Estas observaÃÃes indicam que fatores presentes no feno de folhas de leucena promovem um aumento na expressÃo da proteÃna (S8707), o que provavelmente provoca alteraÃÃes deletÃrias no mecanismo que controla a motilidade progressiva da cÃlula espermÃtica, jà que neste grupo observou-se valores mais baixos para MPI. / The Brazilian Northeast has about almost half of Brazilian sheep livestock, estimated at twenty million animals. The races created here, Santa Ines and Morada Nova stand out because they have good physical development, weight gain and good adaptation to the tropical climate. Recently showed the protein profile of mature rams through the techniques of two-dimensional electrophoresis associated with mass spectrometry, which several proteins have been identified, including those RSVPs 14 and 22 kDa, belonging to the family of BSPs and bodesinas - 1 and 2, that are part of the family of espermadesinas as well as the changes suffered by the protein profile of seminal plasma of animals during reproductive development, while changes in the parameters of sperm concentration and motility, although the association between the protein expression of these proteins with reproductive parameters testicular and measures have not yet been made in northeastern Brazil. Semen samples were collected from twenty-one adult sheep Santa Ines and eleven Morada Nova with normal reproductive and mean age of two years and seminal plasma was obtained by centrifugation and subjected to two-dimensional electrophoresis, and the spots that differed significantly between the groups of animals from high (G1) and low motility (G2) were digested with trypsin and subjected to mass spectrometry and research database for identification. The gels were stained with colloidal Cromassie, scanned and analyzed with PDQuest application and quantity of the spots quantitatively estimated. Evaluated, then, statistical associations between these variables and the reproductive parameters scrotal circumference (EC), percentage of motile cells (PEM) and total sperm defects (MDD) of the animals Santa InÃs and scrotal circumference (EC) motility individual rogressive (MIP), percentage of motile cells (PEM), Sperm concentration (CONC) and Massal motility (MM) for the animails Morada Nova. Were detected on average 236  7.65 spots per gel, according to the pairing generated by PDQuest application to the Santa Ines and 261  15.09 spots per gel in the seminal plasma of animals Morada Nova, ranging between 182 and 375 spots gel. For Santa InÃs a total of 63 spots were identified consistently in all gels, which represented 41.5% of all spots detected intensity. For Morada Nova animails, a total of 98 spots were detected consistently in all gels. The intensity of these spots amounted to 60.82% of the intensity of all spots shown on the master gel was observed a great expression of proteins of low molecular weight (14.5 to 18.4 kDa) and pI ranging from 4.2 to 5, 9. to Santa Ines. The average total of 236 spots found thirteen spots showed significant difference (p <0.05) between animals of high and low motility, being more intense ten spots in animals with high motility and three in animals with low motility. After digestion of spots and identification by mass spectrometry these spots were identified as proteins Arylsulfatase A and zinc alpha 2 glycoprotein more intense in G1and RSVP-22 and Bodesina with higher expression in G2. For the Morada Nova race, four spots showed significant difference (p <0.05) for the parameter percentage of motile cells (PEM). After digestion of spots and identification by MALDI-TOF-TOF, we identified as proteins, RSVP-14, RSVP-22, a protein &#945;-1 of t-complex and aldose reductase, which are all more intense in animals with high motility (G1). In a second study, evaluated the influence of different sources of dietary protein (soybean meal, leucaena leaf hay and cottonseed meal) and non-protein nitrogen (urea) on body weight, testicular development and sperm quality of the animals studied and protein expression in the seminal plasma of the animals potentially related to the diets. We used 20 Morada Nova lambs aged between 24 and 39 weeks. For the testicular development criteria (cirrcunferÃncia scrotal, testicular thickness, width and length testicular testicular) no significant difference (p <0.05) was observed at the end of experiment. Animals fed cottonseed meal had a significant increase in body weight (p <0.05) compared with Leucaena hay. In the same period, the body weight of animals fed leucaena hay, soybeans and urea was similar. Differences between treatments (p <0.05) were observed only for individual progressive motility and total defects. The semen of animals fed diets containing leucaena showed low motility individual when compared with those fed diets containing soybean meal. However, animals fed diets containing cottonseed meal and urea had similar values for progressive motility. When the total defects were analyzed, there was a significant difference between groups of leucaena hay and urea. Detected an amount of 246.6  13.9, 236.0  12.4, 261.2  20.2 and 243.8  20.5 spots per gel in groups of soybean meal, leucaena leaf hay, cottonseed meal and urea, respectively. No significant differences in the number of spots per gel, in both groups. Significant differences (p <0.05) were observed in the intensities of twelve spots in the proteic maps . An increased expression of spot S8707 (62.8 kDa, pI 6.9) in animals fed with hay and leaves of leucaena compared to those fed soybean meal, and a negative correlation with individual motility (MPI .) These observations indicate that factors present in hay sheets leucaena promote an increase in protein expression (S8707), the likely cause deleterious changes in the mechanism controlling the motility of sperm cells, as observed in this group lowest for MPI.
49

Epidemiology of early blight on potatoes in South Africa

Van der Waals, Jacquie E. (Jacqueline Elise) 11 May 2005 (has links)
Early blight (Alternaria solani Sorauer)is a major foliar disease of potatoes in most growing regions of the world and is underestimated in South Africa. This project studies the epidemiology and control of the disease in South Africa. A decision support system (DSS) for early blight in South Africa was developed and evaluated in field trials. This early blight DSS is the first such system to be developed in South Africa and once incorporated with the late blight model, will represent innovative technology for use in the South African potato industry. Trends in weather variables and concentrations of airborne conidia of A. solani were monitored. Distinct seasonal variation was noted. Peaks in spore concentration coincided with periods favourable for spore formation and dispersal; most notable was diurnal periodicity and interrupted wetting periods. The results obtained from these measurements will be useful in improving early blight DSSs for southern Africa. Isolates of A. solani from various potato-growing regions in South Africa were characterized using virulence, vegetative compatibility (VC) and random amplified microsatellite (RAMS) primers. Neither the virulence assays nor VC tests sufficiently characterised the population. Analysis of RAMS profiles revealed 27% genetic diversity among the isolates. This value is similar to diversity values obtained by previous authors studying A. solani, however, it is relatively high for an asexually reproducing fungus. There was no evidence for geographical clustering of isolates, indicating that isolates are widespread across South Africa. A survey on control practices and grower perceptions of early blight in South Africa was conducted using a questionnaire. These questionnaires were distributed to growers from 10 potato-growing regions in South Africa. Results highlighted the most popular control methods and cultivars in the South African potato industry. The majority of respondents indicated that they would use an accurate, cost-effective early blight DSS, and that more research is necessary on early blight in South Africa. A survey on control practices and grower perceptions of early blight in South Africa was conducted using a questionnaire. These questionnaires were distributed to growers from 10 potato-growing regions in South Africa. Results highlighted the most popular control methods and cultivars in the South African potato industry. The majority of respondents indicated that they would use an accurate, cost-effective early blight DSS, and that more research is necessary on early blight in South Africa. Estimated crop losses ranged from 1% - 60%, with an average of approximately 20%. This is the first comprehensive epidemiological study to be conducted on early blight in South Africa and has highlighted the need for further research. / Thesis (DPhil (Plant Pathology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted
50

The effects of isolation and restraint stress, and cortisol, on the responsiveness of the anterior pituitary to gonadotrophin-releasing hormone in rams and ewes

Stackpole, Catherine Amelia January 2004 (has links)
Abstract not available

Page generated in 0.0297 seconds