Analysis and Fate of Toxic Glycoalkaloids from Solanum tuberosum in the Terrestrial Environment

Many plants and microorganisms produce toxins and there has been an increased interest in the fate of natural toxins in the terrestrial environment within the last decade. Several natural toxins have been detected in the soil or in surface, drainage, or soil water. The presence of natural toxins in the terrestrial environment is of concern, because they may have unintended effects on various organisms or because they may contaminate valuable drinking water resources. One of the most important crops in the world, the potato plant, produces the two toxic glycoalkaloids, α-chaconine and α-solanine. These compounds are present in all parts of the potato plant, and previous studies indicate that they may be relatively persistent in the terrestrial environment. Potato plants are often grown on sandy soils under heavy irrigation; both conditions increase the risk of leaching. Hence, the potato glycoalkaloids could possible be a risk in the terrestrial environment. The aim of the Ph.D. work presented here was to investigate the fate of the potato glycoalkaloids, αchaconine and α-solanine, in the soil and groundwater environment. As a part of the project, a sensitive and specific analysis method using liquid chromatography-electrospray ionization time-offlight mass spectrometry (LC-ESI-MS-TOF) was developed in order to be able to detect the glycoalkaloids in environmental samples. The fate of the two glycoalkaloids in the environment was investigated in both laboratory and field studies. In the laboratory, degradation of the glycoalkaloids was studied in soil and groundwater; the latter enabled identification of formed degradation products. A conventional potato field was used in a field study, where the glycoalkaloid content was followed in plants, soil, and groundwater during one year. The present Ph.D. thesis consists of an introductory section and four manuscripts. One of the manuscripts is already published. The introduction section consists of three major parts. The first part is a literature review of potato glycoalkaloids in general, with focus on the aspects relevant for their environmental fate. The second part comprises the analytical work. A review of the many methods, which are or have been used for determination of the glycoalkaloids, is given. Further, the analytical methods used in the present work are discussed in detail. The fate of the potato glycoalkaloids in the environment is discussed in the last part, and this section is primarily based on the results obtained in the present work. The fate studies are related to similar fate studies of other natural compounds. Manuscript I describes the development of a sensitive LC-TOF-MS method for determination of the two potato glycoalkaloids and their common aglycone, solanidine, in environmental samples. The development included optimization of a new HPLC method and optimization of the response by the TOF-MS. Additionally, the fragmentation patterns of the compounds were presented. The performance of the method was evaluated with respect to linearity, precision, and detection limits. The obtained detection limits were in the range 2.2-4.7 µg/L. The work showed the LC-TOF-MS to be a powerful tool for quantitative studies of glycoalkaloids including identification of unknown metabolites. Manuscript II is a lab degradation study of α-chaconine and α-solanine in groundwater sampled from the field location at Fladerne Bæk, Denmark. The degradation of the glycoalkaloids and the formation of metabolites were followed by LC-MS. The degradation was shown to be primarily microbial and proceeded as a cleavage of the three carbohydrate units. The metabolites, β1-solanine, γ-solanine, and solanidine were formed from α-solanine, while β-chaconine, γ-chaconine, and solanidine were detected from α-chaconine. This is the first report of the formation of β1-solanine by microbial degradation. The metabolite, solanidine, was also degraded, but no further metabolites could be detected. Thus, this study shows that indigenous groundwater microorganisms are capable of degrading the glycoalkaloids. Manuscript III is a comprehensive field study. The glycoalkaloid content in potato plants, soil, and groundwater from a potato field was followed during a growth season and the following winter. The field location was a sandy soil from Fladerne Bæk, Denmark used for potato growing. In the plants, the maximum glycoalkaloid concentration of 22 g/kg dry weight was found in June. The total plant amount of glycoalkaloids was at maximum in July (25 kg/ha), after which it decreased during plant senescence to below 0.63 kg/ha in October. In the upper soil, glycoalkaloids were found in concentrations of up to 2.8 mg/kg dry weight. The highest soil load was estimated to be 0.6 kg/ha in September. Glycoalkaloids were still present in the soil in March, despite no further transfer from the plants during winter. Hence, the dissipation in the soil was slow during winter. The amount of glycoalkaloids found in the soil accounted for only a minor fraction of the amount present in the plants. The investigation also showed degradation of the glycoalkaloids in the potato plant during decay. Thus, the major dissipation route for the glycoalkaloids was proposed to be degradation within the plant material. No traces of glycoalkaloids were detected in the groundwater sampled from 2-4 m below the potato field during the growth season. From these results, the leaching potential of the glycoalkaloids is evaluated to be low. In Manuscript IV, the degradation of the potato glycoalkaloid, α-solanine, was followed in three agricultural soils, including soil from Fladerne Bæk. Similar degradation pattern was found in all soils, where a fast initial degradation was followed by a slower phase. The pattern was well described by a sum of two first-order expressions. Half-lives ranging from 1.8-4.1 days were found for the three topsoils at 15 ºC, but residuals were still detected by the end of the experiment after 42 days. For the Fladerne Bæk soil, the degradation was additionally followed at 5 ºC in both top- and subsoil and here half-lives of similar lengths ranging from 4.7-8.7 days were found. Overall, fast degradation was found in both top- and subsoil even at low temperatures, and from these results, the risk of glycoalkaloid leaching to the groundwater appears to be limited

Time-distance analysis of the emerging active region NOAA 10790

We investigate the emergence of Active Region NOAA 10790 by means of time – distance helioseismology. Shallow regions of increased sound speed at the location of increased magnetic activity are observed, with regions becoming deeper at the locations of sunspot pores. We also see a long-lasting region of decreased sound speed located underneath the region of the flux emergence, possibly relating to a temperature perturbation due to magnetic quenching of eddy diffusivity, or to a dense flux tube. We detect and track an object in the subsurface layers of the Sun characterised by increased sound speed which could be related to emerging magnetic-flux and thus obtain a provisional estimate of the speed of emergence of around 1 km s−1

The role of credit ratings on capital structure and its speed of adjustment: an international study

Using an international dataset, we examine the role of issuers’ credit ratings in explaining corporate leverage and the speed with which firms adjust toward their optimal level of leverage. We find that, in countries with a more market-oriented financial system, the impact of credit ratings on firms’ capital structure is more significant and that firms with a poorer credit rating adjust more rapidly. Furthermore, our results show some striking differences in the speed of adjusting capital structure between firms rated as speculative and investment grade, with the former adjusting much more rapidly. As hypothesized, those differences are statistically significant only for firms based in a more market-oriented economy

Predictive ability of logistic regression, auto-logistic regression and neural network models in empirical land-use change modeling: a case study

The objective of this study is to compare the abilities of logistic, auto-logistic and artificial neural network (ANN) models for quantifying the relationships between land uses and their drivers. In addition, the application of the results obtained by the three techniques is tested in a dynamic land-use change model (CLUE-s) for the Paochiao watershed region in Taiwan. Relative operating characteristic curves (ROCs), kappa statistics, multiple resolution validation and landscape metrics were used to assess the ability of the three techniques in estimating the relationship between driving factors and land use and its subsequent application in land-use change models. The validation results illustrate that for this case study ANNs constitute a powerful alternative for the use of logistic regression in empirical modeling of spatial land-use change processes. ANNs provide in this case a better fit between driving factors and land-use pattern. In addition, auto-logistic regression performs better than logistic regression and nearly as well as ANNs. Auto-logistic regression and ANNs are considered especially useful when the performance of more conventional models is not satisfactory or the underlying data relationships are unknown. The results indicate that an evaluation of alternative techniques to specify relationships between driving factors and land use can improve the performance of land-use change models

Singular solutions of fully nonlinear elliptic equations and applications

We study the properties of solutions of fully nonlinear, positively homogeneous elliptic equations near boundary points of Lipschitz domains at which the solution may be singular. We show that these equations have two positive solutions in each cone of $\mathbb{R}^n$, and the solutions are unique in an appropriate sense. We introduce a new method for analyzing the behavior of solutions near certain Lipschitz boundary points, which permits us to classify isolated boundary singularities of solutions which are bounded from either above or below. We also obtain a sharp Phragm\'en-Lindel\"of result as well as a principle of positive singularities in certain Lipschitz domains.Comment: 41 pages, 2 figure

Time--Distance Helioseismology Data Analysis Pipeline for Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory (SDO/HMI) and Its Initial Results

The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI) provides continuous full-disk observations of solar oscillations. We develop a data-analysis pipeline based on the time-distance helioseismology method to measure acoustic travel times using HMI Doppler-shift observations, and infer solar interior properties by inverting these measurements. The pipeline is used for routine production of near-real-time full-disk maps of subsurface wave-speed perturbations and horizontal flow velocities for depths ranging from 0 to 20 Mm, every eight hours. In addition, Carrington synoptic maps for the subsurface properties are made from these full-disk maps. The pipeline can also be used for selected target areas and time periods. We explain details of the pipeline organization and procedures, including processing of the HMI Doppler observations, measurements of the travel times, inversions, and constructions of the full-disk and synoptic maps. Some initial results from the pipeline, including full-disk flow maps, sunspot subsurface flow fields, and the interior rotation and meridional flow speeds, are presented.Comment: Accepted by Solar Physics topical issue 'Solar Dynamics Observatory

Slow relaxations and history dependence of the transport properties of layered superconductors

We study numerically the time evolution of the transport properties of layered superconductors after different preparations. We show that, in accordance with recent experiments in BSCCO performed in the second peak region of the phase diagram (Portier et al, 2001), the relaxation strongly depends on the initial conditions and is extremely slow. We investigate the dependence on the pinning center density and the perturbation applied. We compare the measurements to recent findings in tapped granular matter and we interpret our results with a rather simple picture.Comment: 4 pages, 4 fig

Green manure in coffee systems in the region of Zona da Mata, Minas Gerais: characteristics and kinetics of carbon and nitrogen mineralization.

The use of green manure may contribute to reduce soil erosion and increase the soil organic matter content and N availability in coffee plantations in the Zona da Mata, State of Minas Gerais, in Southeastern Brazil. The potential of four legumes (A. pintoi, C. mucunoides, S. aterrimum and S. guianensis)to produce above-ground biomass, accumulate nutrients and mineralize N was studied in two coffee plantations of subsistence farmers under different climate conditions. The biomass production of C. mucunoides was influenced by the shade of the coffee plantation.C. mucunoides tended to mineralize more N than the other legumes due to the low polyphenol content and polyphenol/N ratio. In the first year, the crop establishment of A. pintoi in the area took longer than of the other legumes, resulting in lower biomass production and N2 fixation. In the long term, cellulose was the main factor controlling N mineralization. The biochemical characteristics, nutrient accumulation and biomass production of the legumes were greatly influenced by the altitude and position of the area relative to the sun

An efficient adaptive multigrid algorithm for predicting thin film flow on surfaces containing localised topographic features

Gravity-driven continuous thin film flow over a plane, containing well-defined single and grouped topographic features, is modelled as a Stokes flow using lubrication theory. The associated time dependent, nonlinear, coupled set of governing equations are solved using a Full Approximation Storage (FAS) Multigrid algorithm by employing automatic mesh adaptivity, the power efficiency and accuracy of which is demonstrated by comparing the results with corresponding global fine-mesh solutions.. These show that automatic grid refinement effectively restricts the use of find grids to regions of rapid flow development which, for flow over the topographies considered, includes the topography itself, the upstream Capillary ridge, downstream sure region, and the characteristic bow wave. It is shown that for the accurate solution of such flow problems, adaptive Multigridding offers increased flexibility together with a significant reduction in memory requirement. This is further demonstrated by solving the problem of transient flow over a trench topography, generated by a sinusoidally varying inlet condition

Avalanche Dynamics in Evolution, Growth, and Depinning Models

The dynamics of complex systems in nature often occurs in terms of punctuations, or avalanches, rather than following a smooth, gradual path. A comprehensive theory of avalanche dynamics in models of growth, interface depinning, and evolution is presented. Specifically, we include the Bak-Sneppen evolution model, the Sneppen interface depinning model, the Zaitsev flux creep model, invasion percolation, and several other depinning models into a unified treatment encompassing a large class of far from equilibrium processes. The formation of fractal structures, the appearance of $1/f$ noise, diffusion with anomalous Hurst exponents, Levy flights, and punctuated equilibria can all be related to the same underlying avalanche dynamics. This dynamics can be represented as a fractal in $d$ spatial plus one temporal dimension. We develop a scaling theory that relates many of the critical exponents in this broad category of extremal models, representing different universality classes, to two basic exponents characterizing the fractal attractor. The exact equations and the derived set of scaling relations are consistent with numerical simulations of the above mentioned models.Comment: 27 pages in revtex, no figures included. Figures or hard copy of the manuscript supplied on reques