196,527 research outputs found
Letter from Copenhagen to Stella Ruess, 1936
No full textLetter 1936 from Signe M. Anderzeg in Copenhagen, Denmark, to Stella K. Ruess in Los Angeles, California
Club picnic in the Ruess garden, August 1942, in Chinese costumes
No full textby E. M. G. Clark of a club picnic in the Ruess garden in August 1942. Probably the "Poetry and Music Club," wearing Chinese costumes
M. B. at home in Autumn 1933
No full textBlack and white photograph of a woman identified as "M. B." [a Browning], probably friend or relative of Christopher and Stella Ruess. the house in the background is identified as "grandfather\u27s house," located in Hyde Park, New York, in Autumn of 1933
Harold M. Dunning, Louise Marlow, Mary B. Gardels, Gerald Wyat, L. J. Masche, Chuck Konrad
No full textBlack and white photograph of ten adults and one boy, probably friends or associates of Christopher and Stella Ruess. On verso, six of them are identified as: Harold M. Dunning, Louise Marlow, Mary B. Gardels, Gerald Wyat, L. J. Masche, and Chuck Konrad
Nitrogen isotope ratios and fatty acid composition as indicators of animal diets in belowground systems
No full textThis study analyses trophic interactions between soil fungi, micro- and mesofauna in microcosm experiments. The trophic shift of N-15 and fatty acids (FAs) was investigated in different food chains, which comprised either two (fungi and grazers) or three (fungi, nematodes and Collembola) levels. Contrary to the widely accepted assumption of N-15 enrichment in trophic cascades the experiments revealed enrichment, depletion or no change in N-15 of consumers compared to their diet. Factors responsible for this pattern were suggested to be: (1) the main metabolic pathway used for N excretion in ammonotelic nematodes to be similar or depleted in the heavier isotope, and uricotelic Collembola mostly enriched in the heavier isotope; (2) a higher shift in N-15 with a high-protein diet (e.g. for predators); (3) compensation due to low-quality food altering the fractionation of N-15. Analysis of the lipid composition showed phospholipids to be generally unaffected and neutral lipids closely related to the FA pattern of the food source. Dietary routing of FAs into neutral lipids occurred, as evidenced by corresponding frequencies of FAs in host and consumer profiles. Additionally, several FAs were only detected in the grazer when present in the food source. Oleic acid showed a shift over three trophic levels, from fungi to nematodes to Collembola. The assimilation of dietary FAs resulted in a more diverse neutral lipid profile, i.e. animals higher in the food chain contained more individual FAs compared to animals lower in the food chain. The results indicate that monoenoic C18 and monoenoic C20 FAs have the potential to act as tools for the bioindication of feeding strategies in belowground systems. We suggest that primary consumers will have no or only trace amounts of monoenoic C20 acids in their neutral lipid profile, whereas consumers feeding on a eukaryote diet will show a considerably higher frequency
Feeding guilds in Collembola based on nitrogen stable isotope ratios
No full textIn soil a high number of species co-exist without extensive niche differentiation, which was assigned as ‘the enigma of soil animal species diversity’. In particular, the detritivores are regarded as food generalists. We have investigated nitrogen stable isotope ratios (15N/14N) of a major decomposer group, the Collembola, to evaluate trophic relationship and determine feeding guilds. Additionally, the δ15N values of potential food sources such as mosses, lichens and other plant derived material (bark, nuts, leaves) were analysed. The natural variation in nitrogen isotopes was assessed in 20 Collembola taxa from three deciduous forest stands. The δ15N signature formed a continuum from phycophages/herbivores to primary and secondary decomposers, reflecting a gradual shift from more detrital to more microbial diets. The δ15N gradient spanned over 9 δ units, which implies a wide range in food sources used. Assuming a shift in 15N of about 3 ‰ per trophic level, the results indicate a range of three trophic levels. These variations in 15N/14N ratios suggest that trophic niches of Collembola species differ and this likely contributes to Collembola species diversity
Isogeometric analysis for thin-walled composite structures
No full textThe conceptual ideas behind isogeometric analysis (IGA) are aimed at unifying computer aided design (CAD) and finite element analysis (FEA). Isogeometric analysis employs the non-uniform rational B-spline functions (NURBS) used for the geometric description of a structure to approximate its physical response in an isoparametric sense. Due to the tensor product property of multi-variate NURBS, it is difficult to represent complex topological shapes with a single NURBS patch. Multiple, often non-conforming patches are needed to tackle increasing complexity of the geometry. To further facilitate the modeling of complex shapes and geometric features trimming technology is widely used in CAD software, however, the trimmed domain is only visually unseen and the trimming features can not be utilized directly for the analysis. To overcome these difficulties, extra efforts are needed to make isogeometric methods adapted to engineering related cases. Thin-walled structures, such as plates and shells, excel in optimal load-carrying behavior and are of major importance in the design of aerospace components and the automotive engineering. Isogeometric analysis is an ideal candidate for the modeling and simulation of shell structures, especially for rotation-free Kirchhoff-Love type shells, which profit from the exact description of the geometry and from the higher continuity properties of NURBS. Furthermore, it favorably supports continuity requirements for flexible through-the-thickness design of laminate composites. Laminated composite materials are increasingly used in the aerospace industry this asks for reliable and computationally efficient lamina theories. The classical lamination theory belongs to the class of equivalent-single-layer methods (ESL), it is computationally efficient but often fails to capture the 3D stress state accurately. The demand for an accurate 3D stress state within laminates is mainly driven by the need to identify and to evaluate potential damage of lamina structures. While a full 3D layerwise (LW) model is computationally expensive, a combined approach considering both concepts, ESL and LW, seems to be a natural choice to tackle the computational costs of increasing model size and model complexity. In this thesis, a layerwise method for laminated composite structures is proposed in the framework of isogeometric analysis. A highly accurate prediction of the state of stress for thick and moderately thick laminate composite shells including transverse normal and shear stresses is demonstrated. The layerwise theory is successfully extended to linear buckling analysis of delaminated composites where a contact formulation is added to eliminate physically inadmissible buckling states which may result from overlapping plies. Furthermore, a Nitsche type formulation is introduced to enforce both weakly, essential boundary conditions and multi-patch coupling constraints for trimmed and non-conforming isogeometric rotation-free Kirchhoff-Love shell patches. The proposed formulation is variationally consistent and excels in a high level of stability and accuracy. A built-in stabilization, used to ensure coercivity of the formulation, prevents ill-conditioning of the physical problem. The inherent trimming problem is tackled with a fictitious domain extension for the trimming domain following the principles of the finite cell method to facilitate the workflow for geometrically complex structures in engineering practice. Computational efficiency is significantly increased with a blended coupling, taking continuum-like shell elements and thin shells elements, according to the theory of Kirchhoff-Love, into account. The blended approach provides access to the full 3D state of stress within selected subdomains while preserving the computational efficiency of the overall analysis.Aerospace Structures and Computational MechanicsAerospace Engineerin
Burial mound of Gorm the Old
No full textPhoto of the Burial mound of Gorm the Old, Denmark\u27s first historic king. Photo probably taken in 1936 by a daughter of Signe M. Anderzeg in Copenhagen, Denmark, who sent them to Stella K. Ruess
Unequal Waters: Flood Risk and Indigenous Coping Capacity in Coastal Virginia
No full textHere we investigate coping capacity of indigenous communities in Coastal Virginia by creating a Coping Capacity Index. Indigenous communities, including those along the East Coast of the United States, face increased vulnerability to flooding due to a combination of socio-economic, environmental, and historical factors. These findings provide insights towards implementing both larger policy solutions and local community-based flood hazard mitigation strategies to improve resiliency in coastal Virginia, while simultaneously establishing a structure for similar assessments in other regions
Topology optimization using the Finite Cell Method
No full textThe ongoing demand for better performing designs, has resulted in an increase in the complexity of topology optimization problems. Traditionally, the majority of the corresponding computational cost comes from solving the analysis equations using linear finite elements (FE). In this thesis a topology optimization method is presented, that is based on the finite cell method (FCM). This higher-order fictitious domain method is, due to its decoupled geometry-, integration-, and analysis-mesh well suited for large-scale topology optimization, and reducing its corresponding computational cost. The use of a decoupled density and analysis mesh greatly reduced the computational cost of topology optimization compared to linear FEM. Especially in 3D topology optimization examples, the computational cost has been decreased by more than a factor 10, while maintaining a high-resolution in the density field. The use of a larger length-scale can reduce the computational cost even more, which is especially beneficial for robust topology optimization. It is identified that the choice of the analysis system completely depends on the complexity of the optimization problem. Simple optimization problems showed great increase in computational efficiency using relatively low polynomial degree (p= 1, 2, 3), combined with more density elements per finite cell. For more difficult topology optimization examples, such as problems were the boundary conditions have to be enforced in the weak sense, or stress-constrained topology optimization, a more accurate analysis system is required, hence a larger polynomial degree should be used.Mechanics, Aerospace Structures & MaterialsAerospace Engineerin
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