165,541 research outputs found
A formação da taxa de câmbio no Brasil: Uma abordagem sobre a especulação e arbitragem no mercado de câmbio futuro
No full textTCC (graduação) - Universidade Federal de Santa Catarina. Centro Sócio-Econômico. Economia.Este trabalho apresenta a abordagem microestrutural sobre a especulação e a arbitragem no mercado de câmbio futuro para formação taxa de câmbio, baseando-se na literatura recente sobre o tema. Ao analisar os fatores microestruturais do mercado de câmbio futuro no Brasil constatou-se que as instituições financeiras, em especial os bancos, continuam agindo negativamente correlacionados com a taxa de câmbio e que a hipótese de que os investidores estrangeiros e institucionais são formadores de tendências ao apostar em ganhos especulativos no mercado de câmbio futuro deve ser considerada, bem como os ganhos de arbitragem realizados pelos bancos. Dessa forma essas operações de arbitragem constituem-se como canais de transmissão da pressão especulativa do mercado futuro para o mercado à vista, distanciando a formação da taxa de câmbio de seus fundamentos econômicos
Potential phytotoxic and shading effects of invasive Fallopia (Polygonaceae) taxa on the germination of dominant native species
No full textTwo species of the genus Fallopia (F. sachalinensis, F. japonica, Polygonaceae) native to Asia, and their hybrid (F. ×bohemica), belong to the most noxious plant invaders in Europe. They impact highly on invaded plant communities, resulting in extremely poor native species richness. The low number of native species in invaded communities points to the possible existence of mechanisms suppressing their germination. In this study we assessed, under laboratory conditions, whether there are phytotoxic effects of the three Fallopia congeners on seed germination of three target species: two native species commonly growing in habitats that are often invaded by Fallopia taxa (Urtica dioica, Calamagrostis epigejos), and Lepidium sativum, a species commonly used in allelopathic bioassays as a control. Since Fallopia taxa form dense stands with high cover, we included varying light conditions as an additional factor, to simulate the effects of shading by leaf canopy on germination. The effects of aqueous extracts (2.5%, 5.0%, and 0% as a control) from dry leaves and rhizomes of the Fallopia congeners on germination of the target species were thus studied under two light regimes, simulating full daylight (white light) and light filtered through canopy (green light), and in dark as a control regime. Rhizome extracts did not affect germination. Light treatments yielded inconclusive results, indicating that poor germination and establishment of species in invaded stands is unlikely to be caused by shading alone. However, we found a pronounced phytotoxic effect of leaf extracts of Fallopia taxa, more so at 5.0% than 2.5% extract concentration. Fallopia sachalinensis exerted the largest negative effect on the germination of Urtica dioica, F. ×bohemica on that of C. epigejos, and F. japonica had invariably the lowest inhibitory effect on all test species. The weak phytotoxic effect of F. japonica corresponds to the results of previous studies that found this species to be generally a weaker competitor than its two congeners. Although these results do not necessarily provide direct evidence for allelopathic effects in the field, we demonstrate the potential phytotoxic effect of invasive Fallopia taxa on the germination of native species. This suggests that allelopathy may play a role in the impact of Fallopia invasion on species diversity of invaded communities
Análise da estrutura a termo da taxa de juros Brasileira
No full textTCC (graduação) - Universidade Federal de Santa Catarina, Centro Sócio Econômico, Curso de Ciências Econômicas.Este trabalho testa a Teoria das Expectativas para a estrutura a termo da taxa de juros do Brasil entre o período de 1999 a 2011. Os testes foram realizados utilizando regressões com o método dos Mínimos Quadrados Ordinários (MQO) utilizando-se como base de dados os spreads das taxas de juros dos contratos swap DI x PRE para quatro diferentes maturidades, 30, 60, 90 e 120 dias. Os resultados indicam que a Teoria das Expectativas e rejeitada para todas as maturidades em teste. Possíveis causas dessa rejeição são apontadas como falhas inerentes da teoria e/ou falhas de mercado existentes no caso especifico brasileiro
Os impactos da política monetária na taxa de câmbio no Brasil
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Sócio-Econômico, Programa de Pós-Graduação em Economia, Florianópolis, 2015.O presente trabalho busca analisar os efeitos da política monetária sobre a taxa de câmbio, no período de 2004-2014, considerando o problema de endogeneidade da política monetária. É utilizado um modelo de variáveis instrumentais que estima os efeitos de uma variação na taxa de juros sobre a variação da taxa de câmbio. Para tratar do problema da endogeneidade da política monetária é empregado o método de identificação via heterocedasticidade. A principal vantagem deste método é que ele se baseia no comportamento estatístico das séries, não sendo necessário realizar suposições arbitrárias de identificação. Os resultados mostram que há uma relação positiva entre a taxa de juros e a taxa de câmbio durante todo período analisado e não só em momentos de elevação da taxa de juros.Abstract : This study aims to analyze the effects of monetary policy on the exchange rate during the period of 2004-2014, taking into account the endogeneity problem of monetary policy. It used a model of instrumental variables which estimates the effects of a change in the interest rate on a change in the exchange rate. To address the problem of endogeneity of monetary policy it is used the method of identification via heteroskedasticity. The main advantage is that this method is based on the statistical behavior of the series, it is not necessary to make arbitrary assumptions of identification. The results show that there is a positive relationship between the interest rate and the exchange rate throughout the period analyzed and not only in times of high interest rates
combined-all-taxa-ML.phy
No full textCombined DNA and morphological data for all taxa of squamate stud
Taxa de câmbio e a fixação da política monetária no brasil pós-metas de inflação
No full textTCC (graduação) - Universidade Federal de Santa Catarina. Centro Sócio-Econômico. Economia.Este trabalho investiga as relações entre a fixação da política monetária e a taxa de câmbio no Brasil no período pós-metas de inflação. O modelo a ser estimado será a regra de Taylor foward-looking, incluindo a taxa de câmbio como variável instrumental e como argumento. A revisão bibliográfica proporcionará o embasamento teórico à inclusão da taxa de câmbio na regra de Taylor. As variáveis do modelo são: taxa Selic, o hiato do produto, a diferença da inflação observada para a meta e a taxa de câmbio real. Os resultados obtidos a partir de variáveis instrumentais mostraram que o Banco Central não está reagindo diretamente ao câmbio, mas sim de forma indireta, na medida em que as variações cambiais afetam o produto e a inflação e podem servir como indicador para a política monetária. Essa ultima conclusão obtemos a partir de uma análise de previsão
Mosquito Larvicidal Constituents from Lantana Viburnoides SP Viburnoides Var Kisi (A. rich) Verdc (Verbenaceae).
No full text\ud
\ud
Lantana viburnoides sp viburnoides var kisi is used in Tanzania ethnobotanically to repel mosquitoes as well as in traditional medicine for stomach ache relief. Bioassay-guided fractionation and subtraction bioassays of the dichloromethane extract of the root barks were carried out in order to identify the bioactive components for controlling Anopheles gambiae s.s. mosquito larvae. Twenty late III or early IV instar larvae of An. gambiae s.s. were exposed to various concentrations of the plant extracts, fractions, blends and pure compounds, and were assayed in the laboratory by using the protocol of WHO 1996. Mean mortalities were compared using Dunnett's test (p < 0.05) and lethal concentration calculated by Lackfit Inversel of the SAS programme. The crude extract (LC50 = 7.70 ppm in 72 h) and fractions exhibited different level of mosquito larvicidal activity with subtraction of some fractions resulting in activity enhancement. The active fractions contained furanonaphthaquinones regio-isomers (LC50 = 5.48-5.70 ppm in 72 h) and the lantadene triterpenoid camaric acid (LC50 = 6.19 ppm in 72 h) as active principles while the lupane triterpenoid betulinic acid (LC50 < 10 ppm in 72 h) was obtained from the least active fraction. Crude extracts and some fractions had higher or comparable larvicidal activity to the pure compounds. These results demonstrate that L. viburnoides sp viburnoides var kisi extracts may serve as larvicides for managing various mosquito habitats even in their semi-purified form. The isolated compounds can be used as distinct markers in the active extracts or plant materials belonging to the genus Lantana
Cytotaxonomical studies on some Crocus L. taxa in Turkey
No full textThe present study investigated the chromosome number and morphology of Crocus fleischeri Gay, C. pallasii Goldb subsp. pallasii, C. cancellatus Herbert subsp. lycius Mathew, C. pulchellus Herbert which are all belong to the Crocus L. taxa showing distribution in Western Anatolia in Turkey. Powder preparation was used as study method. Chromosome numbers and morphologies of the taxa were determined by examining the mitosis preparations. Furthermore, karyograms of taxa studied were made and examined in a detailed manner. In this study, it was found that the chromosome numbers of C. fleischeri, C. pallasii subsp. pallasii, C. cancellatus subsp. lycius and C. pulchellus were 2n = 20, 2n = 14, 2n = 16 and 2n = 12, respectively
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Leaf Micromorphology of Some Tanacetum L. (Asteraceae) Taxa in Turkey
No full textWOS: 000418818000003In this study we have examined leaf micromorphology of eight taxa of Tanacetum L. which are distributed in Turkey. The taxa are T. balsamita L. subsp. balsamita, T. balsamita L. subsp. balsamitoides, T. argenteum subsp. flabellifolium, T. argenteum subsp. argenteum, T. argenteum subsp. canum, T. depauperatum, T. haradjanii, T. tomentellum. Although the leaf characteristic has rather limited systematic value, the combination of some of these features could be systematically relevant, especially for the identification of species. According to our findings the leaves of eight taxa are amphistomatic and covering trichomes very frequent and unicellar. Our goal is contribute to taxonomy of Tanatcetum L. which has systematic problems
- …
