52 research outputs found
Soil profile modification and cotton production
Hardpan soils of the southeastern Coastal Plains were
mixed to depths up to 0.61 m in an attempt to alleviate
strength problems associated with a subsurface pan. It
was hypothesized that mixing the dense, coarse-textured
E Horizon with the less dense Ap and the relatively
clayey B horizon would increase the water-holding
capacity of the E and decrease its strength. Mixed
soil did have a higher amount of water held than the
unmixed E, increasing it from 5 to 7% at -200 kPa
matric potential. This would reduce its strength by
approximately 0.1 MPa allowing easier root penetration
whether the increased water is available for uptake or
not. Although seed cotton in the deeply-mixed
treatments outyielded the moldboard-plowed treatments
by 233 kg/ha in one year, they were outyielded by 132
kg/ha in another year. The decrease in strength and
the increases of retention as a result of the mixing
were small and infiltration was unchanged.
Furthermore, mixing of field samples was less
homogenous than lab samples. It is doubtful that the
level of improvement of cotton would warrant the effort
involved in the mixing operation.
Treatments at two sites were split into fertility
subplots. The only significant fertility difference
was between rates of N sidedressed when plants were
about 0.40 m tall. The 20 kg/ha rate outyielded the 67
kg/ha rate by up to 300 kg/ha presumably because the
higher rate encouraged vegetative growth and retarded
boll formation which in turn limited lint and seed
production. Interactions between tillage or mixing and
fertility were non-significant. Plants grew better in
the deeper disturbed soils in dryer years. Other crops
may respond more favorably to the mixing
Liquid 4He: contributions to first principles theory of quantized vortices, thermohydrodynamic properties, and the lambda transition
Liquid 4He has been studied extensively for almost a century, but there are
still a number of outstanding weak or missing links in our comprehension of it.
This paper reviews some of the principal paths taken in previous research and
then proceeds to fill gaps and create an integrated picture with more complete
understanding through first principles treatment of a realistic model that
starts with a microscopic, atomistic description of the liquid. Newly derived
results for vortex cores and thermohydrodynamic properties for a two-fluid
model are used to show that interacting quantized vortices may produce a lambda
anomaly in specific heat near the superfluid transition where flow properties
change. The nature of the order in the superfluid state is explained.
Experimental support for new calculations is exhibited, and a unique specific
heat experiment is proposed to test predictions of the theory. Relevance of the
theory to modern research in cosmology, astrophysics, and Bose-Einstein
condensates is discussed.Comment: 155 pages, 28 figure
Padrão geográfico de diversidade genética em populações naturais de Pau-rosa (Aniba rosaeodora), na Amazônia Central
Rosewood (Aniba rosaeodora Ducke, Lauraceae) is an Amazonian evergreen tree and a source of the purest linalool, the main component of its essential oil, which is very valuable in the international perfumery market. After decades of over-exploitation it is currently considered as threatened. We evaluated the genetic diversity and its distribution in four populations in Central Amazonia. Thirty-five reliable RAPD markers were generated, of which 32 were polymorphic (91.4%). Variation was higher within the populations (76.5%; p < 0.0001) and geographic distribution contributed to population differentiation (23.4%; p < 0.0001). The Amazon River had a small influence on gene flow (3.3%; p < 0.0001), but we identified evidence of gene flow across the river. There were significant differences in marker frequencies (p < 0.05), in agreement with the low gene flow (Nm = 2.02). The correlation between genetic distance and gene flow was - 0.95 (p = 0.06) and between geographic distance and gene flow was -0.78 (p = 0.12). There was a geographic cline of variability across an East-West axis, influenced as well by the Amazon River, suggesting the river could be a barrier to gene flow. Although threatened, these Rosewood populations retain high diversity, with the highest levels in the Manaus population, which has been protected for over 42 years in a Reserve.O Pau-rosa (Aniba rosaeodora Ducke, Lauraceae) é uma árvore amazônica fonte do mais puro linalol, o qual é o principal componente do seu óleo essencial e muito valioso no mercado internacional de perfumaria. Após várias décadas de intensa exploração, a espécie foi levada à categoria de ameaçada de extinção. Quatro populações naturais distribuídas na bacia Amazônia Central foram avaliadas quanto ao nível e a distribuição da diversidade genética. Trinta e cinco marcadores RAPD reprodutíveis foram gerados, dos quais 32 foram polimórficos (91,4%). A diversidade foi maior dentro das populações (76,5%; p < 0,0001) e a distribuição geográfica contribuiu para a diferenciação entre as populações (23,4%; p < 0,0001). A AMOVA indicou que pode haver uma influência parcial do Rio Amazonas no fluxo gênico (3,3%; p < 0,0001), mas foram identificadas evidências de fluxo gênico atravessando o rio. Houve diferenças significativas nas freqüências dos marcadores (p < 0,05) e o fluxo gênico estimado foi relativamente baixo (Nm = 2,02). A correlação entre a distância genética e o fluxo gênico foi de - 0,95 (p = 0,06) e para a distância geográfica e o fluxo gênico foi de - 0,78 (p = 0,12). Houve um padrão geográfico de variabilidade ao longo do eixo Leste - Oeste, influenciado também pelo Rio Amazonas, o que sugere que o rio poderia funcionar como uma barreira para o fluxo gênico. Apesar de ameaçadas, estas populações de Pau-rosa possuem alta diversidade, com o maior valor na população de Manaus, que vem sendo protegida por 42 anos em uma reserva
Soil profile modification and cotton production
Hardpan soils of the southeastern Coastal Plains were
mixed to depths up to 0.61 m in an attempt to alleviate
strength problems associated with a subsurface pan. It
was hypothesized that mixing the dense, coarse-textured
E Horizon with the less dense Ap and the relatively
clayey B horizon would increase the water-holding
capacity of the E and decrease its strength. Mixed
soil did have a higher amount of water held than the
unmixed E, increasing it from 5 to 7% at -200 kPa
matric potential. This would reduce its strength by
approximately 0.1 MPa allowing easier root penetration
whether the increased water is available for uptake or
not. Although seed cotton in the deeply-mixed
treatments outyielded the moldboard-plowed treatments
by 233 kg/ha in one year, they were outyielded by 132
kg/ha in another year. The decrease in strength and
the increases of retention as a result of the mixing
were small and infiltration was unchanged.
Furthermore, mixing of field samples was less
homogenous than lab samples. It is doubtful that the
level of improvement of cotton would warrant the effort
involved in the mixing operation.
Treatments at two sites were split into fertility
subplots. The only significant fertility difference
was between rates of N sidedressed when plants were
about 0.40 m tall. The 20 kg/ha rate outyielded the 67
kg/ha rate by up to 300 kg/ha presumably because the
higher rate encouraged vegetative growth and retarded
boll formation which in turn limited lint and seed
production. Interactions between tillage or mixing and
fertility were non-significant. Plants grew better in
the deeper disturbed soils in dryer years. Other crops
may respond more favorably to the mixing
- …