Land-use change is prevalent across the Prairie Pothole Region (PPR) because of widespread agricultural expansion over the last century. Different land-use histories will affect the distributions of native vegetation and soil biogeochemistry of PPR wetlands. Furthermore, because native vegetation is partially required for wetland classification, supplementary methods are needed for proper wetland delineation. Accurate estimates of GHG emissions are required for correct climate change models; therefore proper investigation of contrasting land-use histories on GHG emissions is essential. This study focused on determining the effect that different land-use histories had on the expression of soil hydric features and magnetic susceptibility as well as examining interacting effects among contrasting land-use histories and biogeochemical controls of GHG emissions of PPR wetlands. To determine the differing effects of land-use histories on hydric soil indicators and magnetic susceptibility, fifteen ephemeral wetlands under differing land-uses (annually cultivated, restored grassland, seeded pasture and native grassland) were sampled to a depth of 1 m with samples collected every 10 cm. An upland pit was correspondingly sampled for each wetland. Soils were then analyzed for organic C, inorganic C, dithionite extractable Fe, particle size distributions, wet stable aggregate distributions and magnetic susceptibility at four different temperature treatments (room temperature, 100 °C, 300 °C and 500 °C). While some variables had observable difference among the land-uses (i.e. organic C, dithionite extractable Fe and magnetic susceptibility), the most pronounced differences were between the different pit positions (i.e. wetland pits vs. upland pits). The data was holistically analyzed through non-metric multidimensional scaling (NMDS) and position based differences were easily identified through this approach; however, only slight differences were present with respect to contrasting land-use histories. The controls of GHG emissions and their interactions were evaluated through two laboratory incubations (i.e. CH4 incubation and N2O incubation), with a factorial design using land-use history treatments as well as biogeochemical controls specific to each GHG (i.e. CH4: SO4- additions; N2O: water filled pore space [WFPS] treatments and NO3 - additions). Both incubations had the presence of interacting factors among the differing land-use histories. During the CH4 incubation, each land-use history responded oppositely to sulfate additions. During the N2O incubations, both WFPS treatments and NO3 - additions had additive effects on the emissions of N2O. Moreover, the presence of the interactions satisfied the objective of the incubation study. Overall it was determined that while land-use history significantly altered the response of GHG controls with respect to GHG emissions, it did not have strong effects in influencing hydric soil indicators and magnetic susceptibility values.

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No description available.

Thesis (M.S.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains viii, 46 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 43-45).

Thesis (Ph. D.)--Florida State University, 2006. / Advisor: Naresh Dalal, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed June 7, 2006). Document formatted into pages; contains xiv, 154 pages. Includes bibliographical references.

No description available.

<p> Magnetic susceptibility data indicate that Tb2Mo2O7 undergoes a spin glass transition at 25 K. The crystal structure is consistent with the fully ordered pyrochlore model. Short range order, involving ferromagnetic and antiferromagnetic correlations, is observed down to 8 K by neutron scattering. </p> <p> Sr2Cr03F and SrLaCr04 have the same magnetic structure. The neutron diffraction data are consistent with two different models. In both cases the magnetic cell is √2a and c and the magnetic moments lie out of the plane. However, in one model the in-plane projection is canted and in the other it is colinear. Sr2Cr03F has a Tc value of 132(2) K and a susceptibility maximum at 280 K. SrLaCr04 has a Tc value of approximately 200 K and a susceptibility maximum near 400 K. The critical· exponent β for Sr2Cr03F is 0.26(4). The (100) magnetic reflection of both SrLaCr04 and Sr2Cr03F shows short range order correlations above Tc. </p> / Thesis / Master of Science (MSc)

No / This report covers the application of magnetic survey, primarily using a magnetic susceptibility field instrument, at the historically attested site of KoBulawayo, Zimbabwe. The approximate position of the site was known before the geophysical survey took place; it was believed to comprise a Royal Enclosure, a surrounding open space possibly used as a military parade ground and the Commoner/Peripheral Settlement of Lobengula, King of the Ndebele. Occupation at the site was short lived and after only 11 years the capital of the Ndebele state was destroyed by fire in 1881. A pilot survey was undertaken in 1994 to assess the suitability of survey techniques. Consequently, a second, more extensive survey was carried out in late 1996 and early 1997 with the intention of delimiting the Royal Enclosure. Further periods of data collection took place later in 1997 and in 1998. This report describes the methods used and the interpretation of the geophysical results in the context of the understanding and management of this important historical site. Additionally, some of the results of the geophysical work have been tested by excavation and a discussion of the correlation between these data sets is also reported in this article.

All matter has a specific magnetic signal , due to their magnetic properties. These range from a high susceptibility to become magnetised (ferrimagnetic) to a low ability to be magnetised (diamagnetic). Magnetic susceptibility measures the degree to which a substance can be magnetised, and this can be used to identi fy minerals within material and used as an indicator for processes Le., erosion. Therefore magnetic susceptibility has been widely used to investigate soil related research as the values obtained correspond with the types of magnetic mineral s in the soil, mainly the iron oxides such as magnetite and maghaemite (higher MS), and haematite and goethite (lower MS). Thus MS acts as a signature for different types of soils allowing them to be categorised. The amount of magnetic minerals present in the soil is largely dependent on soil processes active in the profile and external factors, such as parent material. Soil processes influence the type or amount of magnetic mineral in the soil, or the strength of the magnetic signal. Lower MS values are associated with horizons that have undergone gleying, eluviation, leaching and reductive weathering. Higher MS values are found in horizons that have undergone illuviation, and hydrolytic and oxidative weathering. Diamagnetic materials, such as calcium carbonate, decrease the magnetic susceptibility by diluting the magnetic signal. The relationship between MS and iron in soil is influenced by both external factors such as parent material ; climate; topography; land use history of the area and time. Similarly these factors significantly contribute to soil genesis and are highly interactive. Parent materials that are igneous are found to form soil with higher magnetic susceptibility, and sedimentary and metamorphic rocks form less magnetic soils. However, it has also been found that materials such as slate are related to soil with high susceptibility, which is argued to result from more rapid weathering and the release of iron in the ionic form. Climate has a direct affect on the soil processes that drive magnetic susceptibility, thus in warm tropical climates magnetic susceptibility is expected to have higher values . Topography has been shown to alter magnetic susceptibility values , and generall y the top and foot of the slope have higher values than the slopes. Land-use history influences magnetic susceptibility as cultivation is likely to disturb the soil causing magnetic susceptibility values to be lower due to mixing of the upper and lower soil layers. Time relates to the age of the soil and older soil either has large magnetic susceptibility values due to more prolonged pedogenesis, or the magnetic particles have weathered out of the profile and magnetic susceptibility is lowered. Past research has found topsoil to have higher frequency dependent magnetic susceptibility than lower soil horizons. Frequency dependent magnetic susceptibility measures fine-grained ferrimagnetic particles with grain sizes between 0.013 and O.027f.lm. Two measurements at low and high frequency (0.46 and 46 kHz respectively) are used to calculate frequency dependent magnetic susceptibility. These are measured using a Bartington MS2B sensor and certain measures need to be taken in order to obtain an accurate measurements of magnetic susceptibility. Frequency dependent magnetic susceptibility values are influenced by factors including burning, organic matter and pedogenesis. However, the nature of contribution of these is still highly debated. Many South African soils are considered to be old soils and the amount of magnetic minerals in these is unknown. It has been found that magnetic minerals such as maghaemite have been depleted due to erosion cycles. Very little research has been undertaken regarding the applicability of magnetic susceptibility for South African soils as most of the research on magnetic susceptibility in soils has been carried out in countries of the northern hemisphere, where soil materials are much younger than in South Africa. The ability of frequency dependent magnetic susceptibility to differentiate between topsoil and subsoil allows it to be used as a method of assessing topsoil erosion. Topsoil erosion has a detrimental effect on the environment and it is vital a rapid field indicator is developed to assess erosion in order to curb the process. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.

Este trabalho tem como objetivo desenvolver uma técnica de calculo que permita diagonalizar Hamiltonianos de mais de uma impureza e adaptá-la ao calculo de suas propriedades termodinamicas. Esta técnica é uma extensão do método de grupo de renormalização, originalmente desenvolvido por Wilson para calcular propriedades termodinâmicas do modelo Kondo de uma impureza. O procedimento baseia-se na discretização logarítmica da banda de condução do metal hospedeiro, definida por um parâmetro de discretização &#923, que permite que se projete o Hamiltoniano em uma base quântica finita, na qual o mesmo possa ser diagonalizado numericamente. O tempo do custo computacional do calculo diminui exponencialmente à medida que &#923 cresce, tornando melhor trabalharmos com valores grandes de &#923. O grande problema em usarmos &#923 grande e que aparecem oscilações nas curvas das propriedades termodinâmicas. Neste trabalho apresentamos o método generalizado que elimina essas oscilações. Inicialmente, testamos o método no modelo de Anderson sem correlação de uma impureza para o cálculo da suscetibilidade magnética do sistema, com resultado satisfatório. Na seqüência, para verificar a potencialidade do método, diagonalizamos o Hamiltoniano de Falicov, Kimball e Ramirez (sem spin) do modelo de duas impurezas e calculamos a suscetibilidade de carga da impureza. A motivação para esse cálculo e a equivalência existente entre o Hamiltoniano de Vigman e Finkelshtein e o Hamiltoniano Kondo, para o modelo de uma impureza. No caso de duas impurezas o nosso calculo demonstra que a interação RKKY destrói essa equivalência, ainda que qualitativamente as curvas da suscetibilidade de carga neste modelo reproduzam as de suscetibilidade magnética do modelo Kondo. / This thesis develops an extension of the numerical renormalization - group method. The extended procedure is capable of computing the temperature dependence of the magnetic susceptibility for two-impurity models of dilute magnetic alloys. The renormalization-group approach was devised by Wilson to calculate the thermodynamical properties for the one-impurity Kondo model. The numerical procedure is based on a logarithmic discretization of the conduction band of the metallic host, which is defined by a dimensionless parameter &#923 &#62 1, equal to the ratio of two sucessive discrete energies. Once the conduction Hamiltonian is discretized, the model Hamiltonian reduces to a discrete series that can be diagonalized numerically. The computational cost of the diagonalization diminishes exponentially with 1/ ln &#923, which makes it attractive to work with large &#923. unfortunately, the thermodynamical averages computed with Wilson\'s original version of the numerical renormalization group method and large &#923, computed as function of the temperature, display artificial oscilations with period ln &#923 and amplitude proportional to e-&#9602/ln&#923. By contrast, the generalized procedure in this work produces thermal dependences that converge so rapidly to the continuum (&#923 + 1) limit that curves computed with &#923=10 are virtually identical with those calculated with &#923=3 in the original procedure. As an illustration, we have diagonalized a two-impurity version of the (spinless) Falicov-Kimball-Ramirez Hamiltonian and calculated its charge susceptibility. This application was motivated by the well-established equivalence between the single-impurity (spinless) Vigman-Finkelshtein and Kondo models. In the case of two impurities, our work shows tha the RKKY interaction destroys the equivalence between the two models. Nonetheless, the charge susceptibility curves for the two-impurity Falicov-Kimball-Ramirez model show the qualitative features of the magnetic susceptibility for the two-impurity Kondo model.