387 research outputs found
Temple of Sinawava, Zion National Park
No full textColor post card from Stella Ruess\u27s collection, showing the Temple of Sinawava in Zion National Park
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
Chemotherapy and radiation therapy in 4 dogs with muscle-invasive transitional cell carcinoma of the urinary tract
No full textFour dogs with T(2)N(0)M(0) transitional cell carcinoma of the lower urinary tract underwent multimodal treatment consisting of neoadjuvant chemotherapy, external-beam radiotherapy, and adjuvant chemotherapy. No significant toxicity was documented. All dogs showed clinical improvement and reduction of tumor volume based on computed tomography (CT)
On the structural design of imperfection sensitive laminated composite shell structures subjected to axial compression
No full textShell structures are used as primary structures of space launch vehicles. These structures are thin-walled and are thus prone to buckling when loaded in compression. Because of the imperfection sensitivity of these structures, small deviations of the real shell from the theoretically perfect shell may result in a tremendous decrease in load carrying capacity. For this reason, geometrical imperfections need to be taken into account. When designing unstiffened composite shells, the laminate stacking sequence influences both, the buckling load of the geometrically perfect shell and the imperfection sensitivity of the shell. Consequently, to derive laminate stacking sequences that maximize the buckling load of real shell structures, geometrical imperfections need to be taken into account already in an early design phase. In this paper, two laminate stacking sequences that were derived to maximize the buckling load of the geometrically perfect and imperfect shell structure are studied using stochastic methods. To this end, combination of non-rotational symmetric imperfections derived from measured data and variations of the ply orientation are studied in a stochastic analysis on basis of Monte Carlo simulations. The results of this study will be used to evaluate the influence of the stacking sequence as one of the essential properties dominating the structural response of geometrically imperfect laminate composite shell structures
Tree species diversity versus tree species identity: Driving forces in structuring forest food webs as indicated by soil nematodes
No full textPositive relationships between biodiversity and ecosystem functioning are reported in many studies. The underlying mechanisms are, however, only little understood, likely due to the focus on the aboveground system and neglecting species-specific traits. We used different clusters of tree species composition to investigate how tree species diversity and tree species identity affect belowground nematode communities. Since soil nematodes comprise different trophic groups and are strongly linked to the microbial community, results can provide insight on how soil food webs are structured. In addition, data on leaf litter and fine root biomass were included to account for different effects of aboveground and belowground resources. Clusters of three trees of one, two and three species were identified within a temperate deciduous forest. Target tree species were European beech (Fagus sylvatica), common ash (Fraxinus excelsior) and lime (Tilia cordata, T. platyphyllos) differing in physiology, leaf litter quality and type of mycorrhiza. Tree species identity strongly affected nematode trophic structure, whereas tree Species diversity had no impact. Ash beneficially affected bacterial-feeding nematodes, whereas fungal feeders were suppressed, likely caused by ash litter increasing soil pH. Fostering of the bacterial food chain by ash additionally could be related to rhizodeposition gaining importance after disappearance of high quality ash litter in spring, highlighting seasonal shifts in root and leaf litter-derived resources. The negative effect of ash on fungal-feeding nematodes is suggested to be due to the lack of ectomycorrhizal fungi as ash roots only form arbuscular mycorrhiza. In contrast, beech benefited fungal feeders and detrimentally affected bacterial feeders due to more acidic soil conditions that increase the competitive strength of fungi. Lime tended to negatively impact total nematode density but positively influenced plant-feeding nematodes. Generally, beech and ash strongly but opposingly influenced the trophic structure of nematode communities suggesting that changes in tree species identity result in major shifts in the channeling of energy through decomposer food webs. The results indicate that the structure of soil food webs varies markedly with tree species and point to the importance of basal resources, i.e., leaf litter and rhizodeposits. This suggests bottom-up forces mediated by individual tree species to control major decomposition pathways rather than tree diversity. (C) 2013 Elsevier Ltd. All rights reserved
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
Advanced Experimental Investigations on Cooling Concepts of Cavities for Megawatt-Class CW Gyrotrons
No full textThe ongoing research and development of high-power fusion gyrotrons demands for an effective cavity cooling system for optimum gyrotron operation. Since the last decade, fundamental experimental research of advanced cooling techniques using mini-channels for high-power gyrotron cavities is carried out at KIT. In this work, the latest improvements in the test set-up for the thermal-hydraulic investigation of a cavity cooling is described. In order to increase the overall accuracy in the experiments and to eliminate potential uncertainties a set of improvements of the test set-up are considered: a new flowmeter with flow rates that range up to 12 l/min and with improved measurements accuracy; faster thermocouples, with reaction times < 0.1 s. Additionally, following modifications are introduced: a coating of the inner surface of the copper cavity with a Nickel layer of 100 mu m thickness in order to increase the heat load using induction heating; 3D printing Additive Manufacturing (AM) of the mock-up in order to directly compare the cooling performances and to validate the 3D printing AM technique for this application; (3) installation and test of a new mock-dup with mini-channels and with Raschig rings for a direct comparison between the two cooling techniques. The obtained experimental results provide input to validate numerical models used for the cavity cooling optimization
Clifford T. Power
No full textBlack and white photograph of Clifford T. Power, American serviceman, in Paris, France, on May 10, 1945
Artificial groundwater recharge in forests : soil fauna and microbiology
No full textAt present, approximately half of the drinking water for the city of Basel (Switzerland) is obtained by an artificial groundwater recharge system in a former floodplain area called “Lange Erlen”. Generally, the use of groundwater for drinking water production may lower groundwater tables. Artificial groundwater recharge is a practice of directing and simultaneously purifying water into aquifers, thereby raising the groundwater table and guaranteeing sufficient drinking water sources. Water purification through artificial groundwater recharge is widespread. However, it more commonly involves areas without vegetation, i.e. slow sand filters, dunes or channels and is combined with long flooding periods. In contrast, at the “Lange Erlen”, forested areas are periodically flooded (max. 10 days) with water from the river Rhine. This routine is interrupted by longer regeneration periods. To date, water infiltration and purification processes have remained constant and satisfactory since the system has been established almost 100 years ago. However, detailed knowledge on the belowground processes that have been sustaining the water purification capacity of “Lange Erlen” is scarce.
Intensive flooding may detrimentally affect earthworm populations and result in clogging of the topsoil, which is a common problem in groundwater recharge systems. Earthworms are known to influence water infiltration and aeration of soils, but most of the existing knowledge relates to grasslands and little is known about the role of earthworms for water infiltration in forests. To better understand the “Lange Erlen” system in the shallow soil layer, earthworm populations, microbial parameters (substrate induced respiration, SIR) and water infiltration rates were studied at the recharge areas. The findings suggest that earthworms are an important factor of the long-term sustainability of this system (for the past ~100 years). The total earthworm
numbers and biomass in watered sites exceeded those of non-watered sites (+51% and +71%, respectively). Total earthworm numbers, numbers of endogeic (mineral forms) and epigeic (litter dwellers) earthworms, and numbers of two species (Lumbricus rubellus and Allolobophora chlorotica) significantly and positively correlated with water infiltration rates. Microbial biomass and activity was significantly enhanced in the top soil layer of the watered sites. The results imply that the flooding regime at the “Lange Erlen” favors earthworm populations which in turn prevent soil clogging, aerate the top soil layer, and stimulate microbial growth.
Groundwater quality is directly influenced by subsurface microbial, chemical and physical soil processes. However, most studies on microbial communities have been limited to the top soil layer. These studies disregarded deeper soil horizons although subsurface microorganisms are crucial for the degradation of natural organic compounds or contaminants and the maintenance of groundwater quality. Therefore, vertical soil profiles down to approximately 4 m of depth from two watered sites and one non-watered site were investigated for the structural (phospholipid fatty acids, PLFAs) and the functional (extracellular hydrolytic enzymes) microbial community composition. Furthermore, additional microbial (by SIR), physical and chemical soil parameters were obtained from the same soil samples.
The microbial biomass did not differ between watered sites and the non-watered site, however considerable fractions of the microbial biomass (25-42% by PLFA and 42-58% by SIR) were located in 40-340 cm depth at all sites. The microbial activity (CO2 emission) and the specific respiration (qCO2) were highest at the watered sites. The microbial community structure differed significantly between watered and non-watered sites (predominantly below 100 cm depth), whereas the functional structure (based on the relative enzyme pattern) differed significantly between all sites. The latter finding could probably be explained by different soil structures in each soil
profile rather than by flooding. Proportions of the bacterial PLFAs 16:1ω5, 16:1ω7, cy17:0 and 18:1ω9t, and the long chained PLFAs 22:1ω9 and 24:1ω9 were more prominent at the watered sites, whereas branched, saturated PLFAs (iso/anteiso) dominated at the non-watered site. The PLFA community indices indicated stress response and higher nutrient availability due to flooding. The analysis of extracellular soil enzymes revealed that acid phosphatase showed highest absolute activities at all field sites throughout the soil depth transect and was followed by L-leucine aminopeptidase and β-glucosidase. Combining the structural and the functional diversity of the microbial community in one analysis revealed significant correlations between the PLFA pattern and specific enzymes activities in the non-watered site. However, at the watered sites these relationships were not detected and the same factors appeared uncoupled from each other.
Overall, this implies that adding labile nutrients (i.e. DOC or DON by flooding) to a soil where other nutrients are limiting microbial growth (i.e. P as indicated by acid phosphatase) increases microbial activity but not biomass. This in turn results in waste respiration by overflow metabolism. Additionally, slight nutrient leaching (e.g. nitrate) into the groundwater is observed due to P-limiting conditions.
No differences in absolute and specific enzyme activities between watered sites and the non-watered site indicated complex organic matter input at the recharge sites to be impeded by flooding water pretreatment. In conclusion, water recharge processes resulted in a microbial community adapted to resource and environmental conditions, which was predominantly located in the upper (100-220 cm depth) and partly in the lower vadose zone (220-280 cm depth). Given a better understanding, the system may be more widely adopted and used to provide sufficient and reliable drinking water to the city of Basel
Identification of novel CD8+ T-cell-epitopes from the tumor antigen Cytokeratin 7
No full textGroße Fortschritte in der Tumorimmunologie über die letzten ein bis zwei Dekaden ermöglichen die Erwägung der Krebsimmuntherapie als ernsthafte Ergänzung des onkologischen Behandlungsspektrums für unterschiedlichste Malignomentitäten. Trotz vieler Rückschläge und weiter bestehender Herausforderungen sind doch einige Ansätze – vor allem Antikörper – schon klinisch etabliert. Aktive Immunisierungen befinden sich noch in klinischen Studien, die bisher, auch für das Pankreaskarzinom, unterschiedlichen Vakzinationen generell Sicherheit und in einigen Patienten Induktion von Immunantworten attestieren, welche nicht selten mit verlängertem Überleben korrelieren.
Motivation zu vorliegender Arbeit nährte sich aus dem Los eines chirurgisch und chemotherapeutisch erschöpfend therapierten noch sehr jungen Patienten mit histologisch atypischem, duktalem Pankreaskarzinom, für den ein Heilversuch per Tumorimpfung gewagt worden war. Die Immunhistochemie des malignen Gewebes empfahl das stark überexprimierte Zytokeratin 7 (CK7) als zusätzliches Tumorantigen. Nun sollten aus diesem Protein neue CD8+ T-Zell-Epitope identifiziert werden um sie als Peptide zur Vakzinierung zur Verfügung stellen zu können. Einer in silico-Prädiktion anhand des Vorhersagetools „SYFPEITHI“ von HLA-A*0201- bzw. HLA-B*5101-restringierten, wahrscheinlichen Epitopen folgte eine in vitro-Verifikation dieser Peptide: Aus Monozyten erzeugte, mit synthetischem Peptid beladene dendritische Zellen gesunder Spender fungierten als aktivierende, professionelle antigenpräsentierende Zellen für eine gesuchte, naive, peptidspezifische CD8+ T-Zelle im Lymphozytenpool des identischen Spenders. Nach repetitiver Stimulation und Proliferation erfolgte die Analyse der Kultur auf eine distinkte spezifische Population über intrazelluläre IFNgamma-Färbung. Zum Nachweis der endogenen Prozessierung und Präsentation der untersuchten Epitopkandidaten sowie der zytotoxischen Kapazität der erzeugten Effektorpopulation waren Tumorzelllyseexperimente geplant.
Von den acht bzw. zehn HLA-A*0201- bzw. HLA-B*5101-restringierten vorhergesagten Kandidaten erwiesen sich in neunzehn verschiedenen untersuchten Leukozytenspenden jeweils zwei als immunogen und konnten distinkte peptidspezifisch IFNgamma-produzierende CD8+-T-Zellpopulationen, teilweise in mehreren, unterschiedlichen Spenden induzieren: RLAGDGVGAV, CK7 402-411 und TLNETELTEL, CK7 227-236 (HLA-A*0201-restringiert) sowie DGVDAVNI, CK7 406-413 und TAAENEFVV, CK7 188-198 (HLA-B*5101-restringiert) sind somit als hochkarätige Epitopkandidaten identifiziert. Lediglich der Nachweis ihrer natürlichen Prozession und Präsentation steht noch aus. Die Zytotoxizitätsexperimente konnten bisher aufgrund leider erfolgloser – obwohl umfangreicher – HLA-Transfektionsbemühungen einer potentiell geeigneten Zielzelle, der Pankreaskarzinomzelllinie Capan-1, noch nicht angeschlossen werden.
Zukünftige Zytotoxizitäts-assays und die Evaluation der spontanen in vivo-Relevanz dieser vier Epitopkandidaten in Patienten mit Zytokeratin 7 überexprimierenden Tumoren sollten diese Lücke jedoch schließen können und den Weg zum Einsatz als Vakzine bei Pankreaskarzinomen aber auch anderen Entitäten bereiten.
Bedauerlicherweise konnte unser Patient nicht mehr wie erwünscht von der Impfung profitieren.Marked progress over the past two decades in tumor immunology supplies rationale for sincere consideration of immunotherapy as complementary approach in treatment for diverse tumor entities. In spite of numerous defeats and many persisting challenges, some strategies like monoclonal antibodies are already established in clinical routine. Up to now still object of (pre-)clinical studies are active immunizations: Diverse protocols including several for treatment of pancreatic carcinoma generally attest safety and in some cases and patients also show induction of a specific immune response which not rarely correlates with improved survival.
Motivation for the reported work had its source in the fate of a still quite young patient suffering from a histologically rare and atypical pancreatic adenocarcinoma. Surgery and chemotherapy had approached their limits and complementary active immunization was hopefully embraced as a last resort. Immunohistochemistry of the specimen recommended the highly overexpressed intermediate filament Cytokeratin 7 (CK7) as additional tumor antigen and vaccination target. Aim of the present study was the identification of novel CD8+ T-cell-epitopes emerging from this protein, providing immunogen peptides for vaccination: Following in silico prediction with the SYFPEITHI-tool, in vitro verification of highly likely HLA-A*0201- and HLA-B*5101-restricted epitopes was aspired. Monocyte-derived, synthetic peptide pulsed Dendritic Cells from healthy donors functioned as activating professional Antigen Presenting Cells for the wanted naive and peptide-specific CD8+ T-cell in the PBMC-lymphocyte-pool of the identic donor. After priming, repetitive stimulation and proliferation, cultures were analyzed for distinct specific populations, mainly by IFNgamma- Intracellular Cytokine Staining. Tumor cell lysis assays were planned for proof of endogenous processing and presentation of the studied epitope candidates as well as the generated effector-populations' cytotoxic capacity.
Out of eight and ten HLA-A*0201- and HLA-B*5101-restricted predicted candidates respectively, in nineteen leukocyte donations two in each case proved immunogenicity and were able to induce distinct peptide-specific IFNgamma-producing CD8+-T-cell-populations: Hence RLAGDGVGAV, CK7 402-411 and TLNETELTEL, CK7 227-236 (HLA-A*0201-restricted) as well as DGVDAVNI, CK7 406-413 and TAAENEFVV, CK7 188-198 (HLA-B*5101-restricted) are now identified as epitopes. Simply proof of natural processing and presentation is pending. Because of - up to this point - unsuccessful endeavors to HLA-transfect the CK7-overexpressing pancreatic carcinoma cell line Capan-1, cytotoxicity assays could not yet be performed.
Future tumor cell killing-experiments and evaluation of spontaneous in vivo responses to these four epitopes in patients with CK7-overexpressing tumors should bridge this gap and path the way to an application as vaccine in pancreatic carcinoma as well as in a variety of different entities.
Regrettably our patient could not profit any more from the desired vaccination
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