INVASIVE AQUATIC INVASION: THE SPREAD OF VARIABLE LEAF MILFOIL IN MAINE

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Invasive Aquatic Invasion: The Spread of Variable Leaf Milfoil in Maine

Variable leaf milfoil, Myriophyllum heterophyllum, has been present in Maine since 1970. We created an analysis area including seventeen infestation sites and all bodies of water within a forty mile buffer. We also eliminated all water locations with a size less than 7,101 km2, the size of the smallest infestation site, Shagg Pond. Within those specifications we randomly selected seventeen un-infested bodies of water and used them as our uncontaminated sample. We looked for relationships between presence and number of boat launches, and proximity to a populated area. Using the Mann-Whitney test, we compared the sample size of non-infested lakes to the infested lakes. We found there was no significant difference in all three variables on the infestation of variable leaf milfoil.

Competition of sicklepod, cassia obtusifolia l., densities on soybean, glycine max (l.) merr., at variable row distance

Competition studies with soybeans, Glycine max (L.) Merr. "Bragg." and sicklepod, Cassia obtusifolia L., were conducted at the Agricultural Research and Education Center of the University of Florida in Quincy, Florida. Two field experiments were established, one on May 22, 1975. and the other four weeks later, on June 19, 1975, to determine the competitive effects of various sicklepod densities and the influences of soybean row distances on weed dry matter, soybear plant characteristics, yield components and seed yield, and on soil nutrient content. Control, low, medium, and high sicklepod densities in the first experiment were O, 25,000, 53,000, and 77,000 p1ants/ha, respectively; while the second experiment presented control, low, medium, and high sicklepod densities of O, 36,000, 68,000, and 122,000 plants/ha, respectively. Three soybean row distance treatments were tested using a constant pattern of 90-, 60-, and 45-cm widths throughout the growing season. Three other treatments, evaluated in a variable patern, were initially seeded in 30-cm row widths. Five weeks after planting, an appropriate number of soybean rows were harvested from the 30"cm pattern to establish row distances of 90, 60, and 30-60 cm for the remainder of the season. ln the greenhouse a test was conducted to evaluate the effects af those variables on seed germination and seedling vigor for the next soybean generation. As a result of full-season sicklepod competition, soybean plants were less branched, set fewer leaves, and presented thinner stems as compared to the control. However, height of soybean plants was not affected by the presence of sicklepod. ln one of the two experiments, number of nodes decreased for soybeans under weed campetition. The yield components--number of pods; number of seeds, and seed yield per soybean plant--were all similarly reduced due to weed competition. Seeds per pod were decreased to a lesser extent. Soybean seed yields per unit area were significantly diminished by increasing levels af sicklepod ínfestation. While the control produced 3120 kg/ha, the sicklepod densities of 25,000, 53,000, and 77,000 plants/ha reduced seed yíelds 47, 65, and 73%, respectively. As soybean row distances decreased, number of branches, number of leaves, and stem diameter of soybeans decreased. However, the height of soybean plants increased with narrwing of row width. The components of seed yield--number of pods, number of seeds, and seed yield per soybean plant--diminished as row spacing was reduced. Maximum difference between row distances for these attributes was attained for soybean plants under weed-free conditions. Generally, as row width decreased, soybean seed yield per unit area increased. Specifically, soybear.s in 90-cm rows, either in constant or variable row pattern, yielded less than soybeans in 60- and 30-60-cm rows in the variable pattern. Soil contents of phosphorus, potassium, calcium, and magnesium were not affected by the various levels of sicklepod and soybean populalions. Neither the sicklepod densities nor the soybean row distances influenced seed germination and seedling vigor in the next soybean generation. Sicklepod was a strong competitor with soybeans at all density ranges investigated. Because sicklepod grows taller than soybeans during the reproductive stages of the crop, limited success can be reached by varying row spacing alone. However, this practice is considered an integral measure to complement other methods of sicklepod control. Compared to constant rows, the soybean cropping system using variable row spacings presents the choice of planting soybeans at close row spacings to provide early competition with weeds and the possibility of obtaining a forage crop after the first month of growth, without any decreases on the final seed yields.

Comparative advantage, heterogeneous firms and variable mark-ups

We develop a model of comparative advantage with monopolistic competition, that incorporates heterogeneous firms and endogenous mark-ups. We analyse how these features vary across countries with different factor endowments, and across markets of different size. In this model we can obtain trade gains via two channels. First, when we open the economy, most productive firms start to export their product, then, they demand more producing factors and wages rises, thus, those firms that are less productive will be forced to stop to produce. Second channel is via endogenous mark-ups, when we open the economy, the competition gets ``tougher'', then, mark-ups falls, thus, those firms that are less productive will stop to produce. We also show that comparative advantage works as a ``third channel'' of trade gains, because, all trade gains results are magnified in comparative advantage industry of both countries. We also make a numerical exercise to see how endogenous variables of the model vary when trade costs fall.

Asymptotic efficiency in an instrumental variable model

Esta dissertação se propõe ao estudo de inferência usando estimação por método generalizado dos momentos (GMM) baseado no uso de instrumentos. A motivação para o estudo está no fato de que sob identificação fraca dos parâmetros, a inferência tradicional pode levar a resultados enganosos. Dessa forma, é feita uma revisão dos mais usuais testes para superar tal problema e uma apresentação dos arcabouços propostos por Moreira (2002) e Moreira & Moreira (2013), e Kleibergen (2005). Com isso, o trabalho concilia as estatísticas utilizadas por eles para realizar inferência e reescreve o teste score proposto em Kleibergen (2005) utilizando as estatísticas de Moreira & Moreira (2013), e é obtido usando a teoria assintótica em Newey & McFadden (1984) a estatística do teste score ótimo. Além disso, mostra-se a equivalência entre a abordagem por GMM e a que usa sistema de equações e verossimilhança para abordar o problema de identificação fraca.

Distinctively variable sequence-based nuclear DNA markers for multilocus phylogeography of the soybean- and rice-infecting fungal pathogen Rhizoctonia solani AG-1 IA

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chronic restraint or variable stresses differently affect the behavior, corticosterone secretion and body weight in rats

Organisms are constantly subjected to stressful stimuli that affect numerous physiological processes and activate the hypothalamo-pituitary-adrenal (HPA) axis, increasing the release of glucocorticoids. Exposure to chronic stress is known to alter basic mechanisms of the stress response. The purpose of the present study was to compare the effect of two different stress paradigms (chronic restraint or variable stress) on behavioral and corticosterone release to a subsequent exposure to stressors. Considering that the HPA axis might respond differently when it is challenged with a novel or a familiar stressor we investigated the changes in the corticosterone levels following the exposure to two stressors: restraint (familiar stress) or forced novelty (novel stress). The changes in the behavioral response were evaluated by measuring the locomotor response to a novel environment. In addition, we examined changes in body, adrenals, and thymus weights in response to the chronic paradigms. Our results showed that exposure to chronic variable stress increased basal plasma corticosterone levels and that both, chronic restraint and variable stresses, promote higher corticosterone levels in response to a novel environment, but not to a challenge restraint stress, as compared to the control (non-stressed) group. Exposure to chronic restraint leads to increased novelty-induced locomotor activity. Furthermore, only the exposure to variable stress reduced body weights. In conclusion, the present results provide additional evidence on how chronic stress affects the organism physiology and point to the importance of the chronic paradigm and challenge stress on the behavioral and hormonal adaptations induced by chronic stress. (c) 2006 Elsevier B.V. All rights reserved.

Behavioral and neuroendocrine effects of the exposure to chronic restraint or variable stress in early adolescent rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vortices in a mesoscopic superconducting disk of variable thickness

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vortex dynamics in mesoscopic superconducting square of variable surface

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Two-branes with variable tension model and the effective Newtonian constant

It is shown that, in the two brane time variation model framework, if the hidden brane tension varies according to the phenomenological Eotvos law, the visible brane tension behavior is such that its time derivative is negative in the past and positive after a specific time of cosmological evolution. This behavior is interpreted in terms of a useful mechanical system analog and its relation with the variation of the Newtonian (effective) gravitational constant is explored.

Black string corrections in variable tension braneworld scenarios

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)