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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Descriptive Analysis of Ground Frost Patterns in Sweden (1991-2007)

Mellberg, Jenny January 2008 (has links)
No description available.
32

Managing Seasonality in Tourism : Challenges and Opportunities for the Tourism Industry in Húsavík, Iceland

Annisius, Daniel Chandrachur January 2014 (has links)
Seasonality is a common phenomenon in the tourism industry around the world. Húsavík, a town on the northern coast of Iceland, has experienced tremendous growth in tourism in recent years and is sometimes recognised as the „Whale Watching Capital of Europe‟. However, Húsavík faces extreme seasonality with high demand mainly during the summer months and limited or no demand at other times of the year. As is emphasised in the tourism literature and widely in practice, seasonality is frequently seen as a problem for the tourism industry which has to be tackled. Academic research has never before been done on seasonality in Húsavík and the aim of this thesis is to understand the nature of seasonality within the tourism industry in Húsavík and discover potential ways to reduce seasonality in Húsavík tourism. In order to fulfil the aim, qualitative semi-structured interviews were undertaken with six tourism managers in Húsavík to investigate their perceptions of seasonality and if and how it could be managed. The results confirmed that the peripheral location of the destination stimulates seasonality and it poses major economic challenges for tourism businesses in Húsavík. Managers would prefer a longer tourism season. Several recommendations were provided for how to reduce seasonality such as develop other attractions than whale watching, improve accessibility, focus marketing on seasons outside the summer, and offer winter packages for foreign and domestic tourists.
33

Foraging biology and habitat use of the southern African ice rat, Otomys sloggetti robertsi

Schwaibold, Ute Heidrun 15 November 2006 (has links)
Student Number : 9613963J - PhD thesis - School of Animal, Plant and Environmental Sciences - Faculty of Science / Animals living in cold environments show physiological, morphological and behavioural adaptations to low temperatures. The African ice rat, Otomys sloggetti robertsi, which is endemic to the southern African Drakensberg and Maluti mountains above 2000m, is an interesting exception since, unlike most alpine small mammals, it does not hibernate or display torpor and is physiologically poorly adapted to low temperatures. It is a strict herbivore, feeding on a low quality diet. Ice rats do show some morphological (e.g. short tails) and behavioural (e.g. communal huddling; constructing underground burrows) adaptations, but little else is known about their biology, particularly how they maximise energy gain to meet thermoregulatory requirements, especially during cold periods. Since feeding represents the primary method of energy gain in endotherms, I studied aspects of the foraging biology of ice rats, including gut structure, foraging patterns and habitat choice. The gut structure of O. s. robertsi is well adapted for a high fibre, herbivorous diet and shows broad similarities with those of its mesic- and arid-occurring relatives. However, O. s. robertsi showed increased dimensions of several foregut organs which may be adaptations for increased energy uptake and/or poor diet quality in alpine environments. Furthermore, females had a larger stomach as well as a longer caecum, small and large intestine in summer than in winter but the gut of males was unaffected; such sexual asymmetry may be related to increased energy requirements of females during pregnancy and lactation. Environmental influences on the aboveground behaviour of O. s. robertsi were investigated by recording the duration of behaviours as well as sequential transitions among behaviours. Ice rats spent most of their day foraging and basking, and much time was spent in their underground burrows. Seasonal comparisons revealed that ice rats spent significantly more time acquiring energy through foraging in winter, whereas they remained below ground for longer periods of time during the middle of the day in summer to escape extreme heat and solar radiation. To understand how low temperatures and predation influenced foraging patterns, the behaviour of ice rats was studied in summer and winter in a population where predators were minimal and in another population which experienced higher levels of predation. Ice rats are central place foragers that travel short distances to forage and display significant seasonal variation in their foraging patterns. In the absence of predation risk, ice rats generally returned to a central place with forage, even though returning to a burrow after foraging in winter was energetically costly. However, these costs must be weighed against the benefits of avoiding exposure to low temperatures by feeding under cover as well as the loss of collected food and possible injury associated with aggressive interactions with conspecifics. Under moderate predation pressure in both seasons, ice rats followed a central place foraging strategy to minimise predation risk, always returning to a burrow entrance with forage collected elsewhere. However, when no perceivable threat was observed, ice rats displayed ‘optimal’ foraging patterns in summer similar to those recorded in the absence of predation pressure and only returned to a burrow with forage as distance from that burrow increased, suggesting that ice rats display facultative foraging decision making in response to multiple environmental cues. The distribution of occupied ice rat burrows was correlated against several environmental factors to determine microhabitat requirements. Ice rat burrows were situated in close proximity to herbaceous and wetland plants, but away from woody vegetation, suggesting that habitat choice is related to the presence of food plants and reduction of shade, facilitating short travel distances during foraging as well as promoting basking. Despite the physiological shortcomings of ice rats, the gut structure, foraging behaviour, and habitat choice of the taxon are adapted for life in cold alpine habitats, most likely by maximising energy intake. Similarities in foraging behaviour and habitat use between O. s. robertsi with its closely-related arid-occurring relative Parotomys spp. suggest phylogenetic influences, but it is possibly more a reflection of similar phenotypic responses to the extreme habitats inhabited by these otomyines.
34

Seasonal community dynamics of macroinvertebrates in an Arctic stream / Säsongsbunden samhällsstruktur hos makroevertebrater i ett vattendrag i Arktis

Jakobsson, Ellinor January 2019 (has links)
Arctic ecosystems are amongst the most vulnerable on Earth to ongoing climate change. While the responses to these changes are well studied on land, less is known about how aquatic communities may respond to a warmer arctic. For stream invertebrate communities, predicting such responses requires basic understanding of how and why different taxonomic groups fluctuate throughout the year. However, few studies have assessed the community dynamics of stream macroinvertebrates across seasons in the Arctic. In this project, I asked how macroinvertebrate community structure changes between months and across seasons in a small Arctic stream in northern Sweden. I expected that community change over time would reflect changes in the supply of organic matter (e.g., leaf litter and algae) to dominant consumers. A total of five transects were sampled for macroinvertebrates each month from July to April using Surber sampling. I used descriptive and multivariate analyses to evaluate changes in community structure between months and seasons. Marked differences in community composition were found between the seasons with detritivores (shredders) dominating the autumn months possibly reflecting input of birch litter and high abundances of grazers during and post winter, possibly reflecting primary production early in spring. Expected climate change effects in the Arctic include warmer temperatures and increases in the terrestrial plant productivity. My results suggest that these shifts could cause changes in stream community composition, driven by increases in deciduous litter inputs that promote shredders and/or by increases in primary production during spring that favour grazers and collector-gatherers, which feed on algae.
35

Estudo epidemiológico da dengue no período de 2000 a 2005 no Município de Guarulhos (SP) / Epidemiologic study of dengue in the period of 2000 to 2005 in the city of Guarulhos (SP)

Mansho, Wilson 23 November 2006 (has links)
A cada ano a dengue tem preocupado cada vez mais os países e levado os sistemas de vigilância da saúde, nas diversas esferas, a adotar várias medidas para o seu controle, tendo em vista a iminência de uma grande epidemia de febre hemorrágica no mundo. Os estudos epidemiológicos ajudam esses sistemas de vigilância a melhorar e direcionar as ações preventivas para o controle da doença. O objetivo desse trabalho foi realizar um estudo epidemiológico dos casos notificados e confirmados de dengue, a partir do banco de dados do SINAN, nos anos de 2000 a 2005 no Município de Guarulhos (SP). Para se analisar a ocorrência da doença segundo variáveis sócio-demográficas (sexo, raça, faixa etária e a densidade demográfica de cada bairro) foi realizada uma análise estatística onde se observou as diferenças entre os casos do banco de dados e os indivíduos da população do município para cada variável. Para a variável sexo, não foram observadas diferenças estatísticas significativas entre as proporções para cada sexo na amostra e na população do município (P=0,28); para a variável raça, não foi observada diferença estatística significativa entre as proporções de indivíduos das raças parda e indígena (P>0,05), porém nas outras comparações entre as raças (branca, negra, amarela e ignorado), foram observadas diferenças estatísticas (P<0,05) em comparação com a população do Estado. Para as faixas etárias, não foram observadas diferenças estatísticas significativas nas categorias de 15-19 anos, 20-24 anos, 25-29 anos, 55-59 anos, 60-64 anos e 70-74 anos (P>0,05) em relação às proporções nas faixas etárias correspondentes na população do município. Por outro lado, nas outras faixas etárias (0-4, 5-9, 10-14, 30-34, 40-44, 45-49, 50-54, 75+ anos) foram observadas diferenças estatísticas significativas (P<0,05). Procurou-se relacionar o número mensal de casos, ano a ano, tanto com o índice de Breteau quanto com os dados meteorológicos de precipitação total mensal e a temperatura média compensada mensal, porém foi observada uma baixa correlação estatística entre os casos da doença e este índice e entre os casos e a temperatura média compensada mensal e a precipitação total mensal. Também foi realizada uma análise da série histórica dos casos, onde foi possível observar o aumento de casos nos anos de 2002 e 2003. Na análise de sazonalidade foi observado que, nos meses de fevereiro a maio, o número de casos supera a média anual, ficando abaixo da média nos meses de junho a janeiro. Os casos foram distribuídos nos mapas georreferenciados por bairros e por ano de incidência e foi possível observar o processo de endemização da doença, com casos espalhados no município em todos os anos do estudo. / Dengue is a disease that concerns health authorities in many countries and the surveillance systems are adopting measures to control it, once a great epidemic of hemorrhagic fever is expected to occur. Epidemiologic studies help these surveillance systems to improve and to manage preventive actions to control the disease. The objective of this research was to carry out an epidemiologic study of notified and confirmed cases of dengue, from the database of SINAN, corresponding to the years from 2000 to 2005 in the City of Guarulhos (SP). To analyze the occurrence of the illness according to social-demographic variables (sex, race, age and demographic density of each district), a statistical analysis was performed, and, for each variable, the differences between the cases of the data base and the individuals of the population of the city were observed. For the variable \"sex\", statistically significant differences between the proportions for each sex in the data base and in the city population were not observed (P=0.28); for the variable \"race\", a statistically significant difference was not observed between the proportions of individuals of the races \"medium brown\" and \"indigenous\" (P>0.05), however in the other comparisons between races (\"white\", \"black color\", \" yellow\" and \"ignored\"), statistically significant differences were observed (P<0.05). For age, statistically significant differences were not observed in the categories of 15-19 years, 20-24 years, 25-29 years, 55-59 years, 60-64 years and 70-74 years (P>0.05) when compared with the corresponding age intervals in the city population. However, in the other age intervals (0-4, 5-9, 10-14, 30-34, 40-44, 45-49, 50-54, 75+ years) statistically significant differences were observed (P<0.05). We assessed whether there was a relationship between the monthly number of cases, for each year, and the Breteau index, the meteorological data of monthly total precipitation and monthly compensated average temperature. Low correlation coefficients, however, were observed between the cases and the Breteau index and between the cases and the monthly compensated average temperature and the monthly total precipitation for each year. An analysis of the time series of cases was carried out, and it was possible to observe an increase in the number of cases in years 2002 and 2003. In the seasonal analysis it was observed that, from February to May, the number of cases surpasses the annual mean, and that the number of cases from June and January are below the mean. The cases were distributed in georeferenced maps by district and year of incidence and it was possible to observe the process of increasing endemicity of the illness, with cases spread throughout the city in every year of the study.
36

Análise da interação vitamina A e o ambiente em reprodutores suínos / Assessment of interaction between vitamin A and environment on boars

Martins, Simone Maria Massami Kitamura 14 December 2006 (has links)
Os objetivos do estudo foram: (a) avaliar a influência da suplementação de vitamina A na dieta de cachaços nos parâmetros seminais: volume, motilidade, vigor espermático, pH, concentração espermática, número total de espermatozóides, percentual de espermatozóides vivos e anormalidades morfológicas ao longo do ano; (b) averiguar a variabilidade das características, em animais suplementados com vitamina A na dieta, frente às variações da temperatura nas estações do ano. A pesquisa foi desenvolvida no Laboratório de Pesquisa em Suínos, da FMVZ-USP, utilizando-se 10 machos de linhagem híbrida e distribuídos em dois tratamentos, controle (nível de 25.000 UI de vitamina A/animal/dia) e suplementado com a vitamina A (nível de 40.000 UI de vitamina A/animal/dia). O delineamento foi inteiramente casualizado, com medidas repetidas no tempo, sendo os dados analisados utilizando o programa estatístico Statistical Analysis System (SAS). As probabilidades de interações com o tempo foram determinadas pelo teste de Greenhouse-Geisser Epsilon, considerando o nível de significância de 5%. Em relação aos efeitos da vitamina A durante o período de 1 ano, verificou-se que não houve diferença entre os tratamentos para os parâmetros seminais, não encontrando-se efeito de interação tempo e tratamento. Detectou-se efeito de tempo para os parâmetros pH, concentração espermática, número total de espermatozóides, percentual de espermatozóides vivos e anormalidades morfológicas. Já na averiguação da variabilidade também não foi constatado efeito de tratamento, porém houve efeito de estação do ano para todos os parâmetros e de temperatura para o percentual de espermatozóides vivos, pH e anormalidades morfológicas, não sendo verificado efeito para os demais parâmetros. Inferiuse com o estudo que, dada à condição metabólica diferencial dos animais híbridas, novas averiguações devem ser perseguidas para a relação nutrição e reprodução, uma vez que, os efeitos positivos da suplementação da vitamina A na espermatogênese foram evidenciados, principalmente nas características que mais se relacionam com a formação da célula espermática, as anormalidades morfológicas, percentual de espermatozóides vivos e número total de espermatozóides no ejaculado. / The objectives of the study were: (a) to evaluate the effect of vitamin A supplementation on boars? diet considering the parameters: volume, motility, spermatic vigor, seminal pH, spermatic concentration, total number of spermatozoa, percentage of living sperm cells and morphologic abnormalities during one year; (b) to investigate the variability founded against the temperature and seasons of the year on vitamin A supplemented animals seminal parameters. The research was developed in the Laboratory of Research in Swines, the FMVZUSP, using 10 boars of hybrid lineages. Two treatments were used having the control (level of 25.000 UI of vitamin A/animal/day) and vitamin A supplemented group (level of 40.000 UI of vitamin A/animal/day). The statistical design was random, with repeated measured in time. The analyzed data used was the statistical program Statistical Analysis System (SAS). The probabilities of the interactions in time were determined by Greenhouse-Geisser Epsilon test, considering the significant level 5%. None of the evaluated parameters was significantly different and no detected interaction in time was found treatment. In relation to the effects of the vitamin A on supplementation in one year period it wasn?t have differences among treatments on seminal parameters, and also there wasn?t interaction in time and at treatment, however for pH, spermatic concentration, total number of spermatozoa, percentage of living sperm cells and morphologic abnormalities it was detected effect on time. In relation to the variability there wasn?t treatment effect, however there was for all the parameters studied effect of the season. The effect of temperature was only for the percentage of living sperm cells, pH and morphologic abnormalities. It was concluded that at a given metabolic condition of the hybrid animals, new ascertainments must be inquired for the relation nutrition and reproduction, a time that, the positive effect of the suplementation of the vitamin in spermatogenesis had been evidenced, mainly in the characteristics that more become related with the formation of the espermática cell.
37

A comunidade de anuros do folhiço da Serra das Torres, sul do Espírito Santo, no sudeste do Brasil: A sazonalidade afeta os parâmetros da comunidade? / The leaf-litter frog community of an Atlantic Rainforest area at Serra das Torres, southern Espírito Santo State, Brazil: the seasonality affects the parameters of the community?

Jane Célia Ferreira de Oliveira 28 February 2011 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente estudo trás informações acerca da comunidade de anfíbios anuros do folhiço nas florestas que compõem a região da Serra das Torres, sul do Espírito Santo, sudeste do Brasil. Foram utilizados métodos de parcelas 4 x 4 m para obter os primeiros dados de sazonalidade na composição, massa e densidade no estado do Espírito Santo. Amostragens de campo foram realizadas durante as estações seca e de chuvas, no período de junho de 2009 a dezembro de 2010. Foram registrados 348 indivíduos com média de 1,0 0,1 ind/parcela, em 14 espécies associadas ao folhiço do chão da floresta. As curvas de rarefação e do coletor apresentaram assíntotas tendendo a estabilizarem. A densidade de anuros na área estudada foi de 6,59 ind/100 m e a biomassa total 413,9 g. Brachycephalus didactylus foi a espécie com maior densidade (3,8 ind/100 m) e a maior abundância (100 indivíduos ou 40,6% da comunidade geral), entretanto, apresentou biomassa relativamente baixa (16,8 g) quando comparada às demais espécies como Haddadus binotatus (239,6 g ou 57,2% da biomassa total da comunidade). Não foi registrada nenhuma variação sazonal em relação à densidade ou biomassa na comunidade. A umidade relativa do ar e a profundidade do folhiço foram fatores ambientais significativos para a abundância de indivíduos, enquanto a temperatura e a presença de rochas ou árvores no interior das parcelas não foram importantes na estruturação da comunidade daquela área. Este estudo aumenta a distribuição geográfica de Brachycephalus didactylus, Zachaenus parvulus, Physalaemus crombiei, Ischnocnema cf. bolbodactyla, Ischnocnema gr. lactea e Leptodactylus cf. bokermanni. / We studied the leaf-litter frog community of the forests of Serra das Torres, southern Espírito Santo, southeastern Brazil. We used methods 4 x 4 m plots for the first data on seasonality in the composition, mass and density in the state of Espirito Santo. We field sampling during the dry and rainy season, from June 2009 to December 2010. We recorded 348 individuals with an average of 1.0 0.1 ind / plot, and 14 species associated with leaf litter on the forest floor. Rarefaction curves and the collector had asymptotes tended to stabilize. The density of frogs in the study area was 6.59 ind/100 m and total biomass 413.9 g. Brachycephalus didactylus was the species with the highest density (3.8 ind/100 m) and greater abundance (100 individuals or 40.6% of the general community), however, had relatively low biomass (16.8 g) when compared to other species as Haddadus binotatus (239.6 g or 57.2% of the total biomass of the community). We register no seasonal variation in relation to the density or biomass in the community. The relative humidity and leaf litter depth environmental factors were significant for abundance, while the temperature and the presence of rocks or trees within the plots were not important in structuring the community in that area. This study adds to the geographic distribution of Brachycephalus didactylus, Zachaenus parvulus, Physalaemus crombiei, Ischnocnema cf. bolbodactyla, Ischnocnema gr. lactea and Leptodactylus cf. bokermanni.
38

Diversidade e hábitos alimentares de peixes de riachos afluentes do rio Teles Pires, drenagem do rio Tapajós, Bacia Amazônica /

Godoi, Divina Sueide de. January 2008 (has links)
Orientador: Francisco Langeani Neto / Banca: Lilian Casatti / Banca: Carlos Alberto Vicentini / Banca: Sirlei Terezinha Bennemann / Banca: Luiz Henrique Florindo / Resumo: Com o objetivo de estudar a diversidade dos peixes de dois afluentes do rio Teles Pires, foram realizadas expedições bimestrais entre outubro de 2005 e dezembro de 2006. Para amostragem da ictiofauna dos afluentes, foram cercados 75m de cada trecho com rede de arrasto; a coleta foi feita através de redes de arrasto manuais, puçás e peneiras. O esforço de coleta aplicado a cada variante metodológica foi de 40 minutos. No total foram coletados 3362 exemplares, pertencentes a 5 ordens, 26 famílias, 65 gêneros e 106 espécies. A ordem Characiformes, foi a mais representativa. As famílias mais abundantes numericamente foram Characidae e Cichlidae, em ambos os rios e períodos analisados. Para a jusante do rio Taxidermista e do rio Verde Paraíso ocorreu maior diversidade na seca, decaindo na cheia. A menor diversidade encontrada foi no período da seca à montante do rio Taxidermista. Para o rio Taxidermista, ocorreu uma pequena similaridade em todo o período de coletas, entre os dois trechos, 0,1 na cheia e 0,3 na seca. Já para o rio Verde Paraíso, houve maior similaridade entre os dois trechos, sendo que a maior foi no período da seca (0,80) e a menor na cheia (0,72). Para o Taxidermista os resultados dos cálculos da constância de ocorrência indicaram 2 espécies constantes entre os trechos a montante e a jusante no período da cheia e para o período da seca, 5. No Rio Verde Paraíso no período da cheia, 9 espécies foram consideradas constantes entre a montante e a jusante e 22 no período da seca. / Abstract: With the objective to study the diversity of fishes in two affluents from River Teles Pires there were realized bimonthly expeditions between October of 2005 and December of 2006. For samples of the ichthyofauna from the affluents, there were encompassed 75 meters from each river with dragging net; gathering was done with puca and sieves. The applied effort of gathering with each methodological variant was of 40 minutes. In total, there were collected 3362 samples, from 5 orders, 26 families, 65 genders and 106 species. The order Characiformes was the most representative. The most present in numbers were the families Characidae and Cichlidae, in both rivers and periods analyzed. For the downstream of the river Taxidermista and of the river Verde Paraíso occurred more diversity in drought, decreasing in flood. The minor diversity found was in the drought period in transom of the river Taxidermista. For river Taxidermista, occurred a small similarity in all collecting period, among the two stretch, 0,1 in flood and 0,3 in drought. For the river Verde Paraíso, there was a greater similarity among the two stretches, as for the greater in the drought period (0,80) and the smallest in flood (0,72). For the Taxidermista the results of the calculations of the constant occurrence pointed two constant species between the stretches the transom and the downstream in seasons of flood and for the drought, 5. In the river Verde Paraíso in the flood season, 9 species were considered constant between the transom and downstream and 22 in the season of drought. / Doutor
39

Indu??o da ovula??o em ?guas durante o per?odo de transi??o primaveril / Ovulation induction in mares during the spring transition period

DUTRA, Gabriel Almeida 31 March 2016 (has links)
Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2017-08-18T12:40:09Z No. of bitstreams: 1 2016 - Gabriel Almeida Dutra.pdf: 941212 bytes, checksum: 83615886b763ec9a1fb70714c85ae122 (MD5) / Made available in DSpace on 2017-08-18T12:40:09Z (GMT). No. of bitstreams: 1 2016 - Gabriel Almeida Dutra.pdf: 941212 bytes, checksum: 83615886b763ec9a1fb70714c85ae122 (MD5) Previous issue date: 2016-03-31 / CAPES / The anticipation of the breeding season has been the subject of great interest in front of their economic impact. In order to advance the first ovulation and anticipate the reproductive phase of the mares, this study aimed to evaluate if the transvaginal follicle aspiration technique guided by ultrasound during spring transition period, was able to induce cyclicity in mares. The experiment was conducted in Animal Reproduction area of DRAA / IZ / UFRRJ, located at Serop?dica-Rj, during spring transition period (August-September) and early reproductive period (October) 2015. Selected mares were randomly distributed into three groups: Group 1 Control (G1, n = 9), without hormonal treatment; Group 2 P4 + PGF2? (G2, n = 9), 1500 mg of long-acting progesterone, intramuscularly (IM), and seven days later, 7.5 mg Dinoprost (PGF2?), IM and Group 3 transvaginal follicular aspiration + PGF2? (G3, n = 9), greater follicle aspirated (>25mm) and seven days later, 7.5 mg Dinoprost (PGF2?), IM. Prior to the beginning of the experiment, all mares were evaluated by ultrasonography, and the criteria for the study was absence of corpora lutea as well as the presence of ovarian follicles larger than 25 mm. Subsequent to this evaluation, the reproductive activity was monitored every 48 hours until the second ovulation of each mare. When evaluated the number of mares ovulating within 16 days after initiation of treatment, it was observed that the groups G2 and G3 were significantly more effective (P = 0.0031) in the first ovulation of the breeding season, when compared to G1. In G1, 16 days after the start of treatment, no animal ovulated. In G2 and G3 eigh (88.9%) and six (66.7%) mares ovulated respectively. The mares were evaluated until the second subsequent ovulation treatment. All mares ovulated normally, showing that none of them returned to the transitional period and the average number of days between the first and second ovulation did not differ between the groups (P> 0.05). The results of this study allow us to conclude that follicular aspiration technique during spring transition period associated with the administration of 7.5 mg of PGF2? seven days later, was able to induce cyclicity in XI mares. This treatment was effective as the conventional protocol P4 + PGF2?, thus possible to use it in routine reproductive centers. However, more studies are needed to evaluate its effectiveness during the early spring transition period, as well as its association with ovulation inducers. / A antecipa??o da esta??o reprodutiva tem sido assunto de grande interesse frente ao seu impacto econ?mico. A fim de adiantar a primeira ovula??o e antecipar a fase reprodutiva das ?guas, o presente estudo teve como objetivo avaliar se a t?cnica de aspira??o folicular transvaginal guiada por ultrassom durante o per?odo de transi??o primaveril foi capaz de induzir a ciclicidade em ?guas. O experimento foi realizado na ?rea de Reprodu??o Animal do DRAA/IZ/UFRRJ, localizado no munic?pio de Serop?dica-RJ, durante o per?odo de transi??o primaveril (agosto-setembro) e in?cio do per?odo reprodutivo (outubro) de 2015. Foram selecionadas 27 ?guas da ra?a Mangalarga Marchador, entre 5-12 anos, pesando entre 350- 450 kg e com hist?rico de atividade reprodutiva normal. As ?guas selecionadas foram distribu?das aleatoriamente em tr?s grupos: Grupo 1- Controle (G1; n=9), sem tratamento hormonal; Grupo 2- P4 + PGF2? (G2; n=9), 1500mg de progesterona de longa a??o, por via intramuscular (IM), e sete dias ap?s, 7,5 mg de Dinoprost (PGF2?), IM e Grupo 3- Aspira??o folicular transvaginal + PGF2? (G3; n=9), maior fol?culo aspirado (>25mm) e sete dias ap?s, 7,5 mg de PGF2?, IM. Previamente ao in?cio do experimento, todas as ?guas foram avaliadas por meio da ultrassonografia, sendo crit?rio para o estudo a aus?ncia de corpo l?teo, bem como a presen?a de fol?culos ovarianos >25mm. Posteriormente a esta avalia??o, a atividade reprodutiva foi monitorada a cada 48 horas at? o momento da segunda ovula??o de cada ?gua. Quando avaliado o n?mero de ?guas que ovularam em at? 16 dias ap?s o in?cio do tratamento, observou-se que os grupos G2 e G3 foram mais eficientes (P=0,0031) em acelerar a primeira ovula??o da esta??o reprodutiva, quando comparados ao grupo G1. No grupo G1, ap?s 16 dias do in?cio do tratamento, nenhum animal ovulou. Nos grupos G2 e G3 oito (88,9%) e seis (66,7%) ?guas ovularam, respectivamente. Analisando o n?mero m?dio de dias a partir do tratamento at? a primeira ovula??o, os grupos tratados (G2 e G3) foram mais eficientes que o IX grupo controle na antecipa??o da primeira ovula??o (P<0,001). Em rela??o aos grupos tratados, n?o houve diferen?a (P>0,05) entre eles. Foi poss?vel verificar que os grupos G2 e G3 apresentaram uma antecipa??o da primeira ovula??o em rela??o ao controle em m?dia de 12,2 e 8,9 dias, respectivamente. As ?guas foram acompanhadas at? a segunda ovula??o subsequente ao tratamento. Todas ovularam normalmente, demonstrando que nenhuma delas retornou ao per?odo de transi??o e que a m?dia de dias entre a primeira e a segunda ovula??o, n?o diferiu entre os grupos (P>0,05). Os resultados do presente estudo nos permitem concluir que a t?cnica de aspira??o folicular durante o per?odo de transi??o primaveril, associado ? administra??o de 7,5 mg de PGF2? sete dias mais tarde, foi capaz de induzir a ciclicidade em ?guas. Este tratamento mostrou-se t?o eficaz quanto o protocolo convencional de P4 + PGF2?, sendo vi?vel utiliza-lo na rotina de centros reprodutivos. No entanto, mais estudos s?o necess?rios a fim de avaliar sua efic?cia em fol?culos com di?metros menores no per?odo de transi??o primaveril, assim como sua associa??o aos indutores de ovula??o.
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On seasonality and cointegration

Löf, Mårten January 2001 (has links)
This thesis, which consists of four essays, focus on seasonal and periodic cointegration models. These models are tools to describe changing seasonality.Essay 1 "Forecasting performance of seasonal cointegration models", with Johan Lyhagen. Forecasts from two different seasonal cointegration specifications are compared in an empirical forecasting example and in a Monte Carlo study. One of the two specifications include a certain parameter restriction at the annual frequency, wheras the other specification is more general. In the empirical forecasting example we also include a standard cointegration model based on first differences and seasonal dummies and analyze the effects of restricting or not restricting seasonal dummies in the seasonal cointegration models. While the Monte Carlo results favor the general specification, and definitely so if larger sample sizes are considered, we do not find such clear cut evidence in the empirical example.Essay 2 "On forecasting cointegrated seasonal time series", with Philip Hans Franses. In this essay we analyze periodic and seasonal cointegration models for bivariate quarterly observed time series in an empirical forecasting study. We include both single equation and multiple equations methods for those two classes of models. A VAR model in first differences, with and without cointegration restrictions, and a VAR model in annual differences are also included in the analysis, where they serve as benchmark models. Our empirical results indicate that the VAR model in first differences without cointegration is best if one-step ahead forecasts are considered. For longer forecast horizons however, the VAR model in annual differences is better. When comparing periodic versus seasonal cointegration models, we find that the seasonal cointegration models tend to yield better forecasts. Essay 3 "Size and power of the likelihood ratio test for seasonal cointegration in small samples: A Monte Carlo study", This essay investigates the small sample size and power properties of the likelihood ratio test in the seasonal error correction model. Two specifications of the model at the annual frequency are analyzed. One is more restricted (RS), designed for the particular case of 'synchronous cointegration', whereas the other specification is general (GS). The results indicate that RS has poor size properties in cases where non-synchronous cointegration clearly should play a role. There is a risk of finding 'evidence' of too many cointegrating vectors at the annual frequency when using RS. On the other hand, if the restriction is almost satisfied, the general specification looses power at least for small sample sizes, while tests in RS have good properties. Essay 4 "On seasonal error correction when the processes include different numbers of unit roots", with Johan Lyhagen. We propose a seasonal error correction model (SECM) for quarterly data which includes variables with different numbers of unit roots and thus needs to be transformed in different ways in order to yield stationarity. A Monte Carlo simulation is carried out to investigate the consequences of specifying a SECM with all variables in annual diffrerences in this situation. The SECM in annual differences is compared to the correctly specified model. Pre-testing for unit roots using two different approaches, and where the models are specified according to the unit root test results, is also considered. The results indicate that, in practice, a cointegration model where all variables are transformed with the annual difference filter is more robust than one obtained by pre-testing for a smaller number of unit roots. / Diss. Stockholm : Handelshögsk., 2001 [4], iv s., s. 1-23: sammanfattning, s. 25-110, [5] s.: 4 uppsatser

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