49 research outputs found
Replicated shape variation between simple and complex habitats in two estuarine fishes
A replicated pattern of habitat-associated morphology among different lineages may represent adaptive convergence. Deviation from the replicated (shared) pattern of diversification reflects unique (e.g. species specific) effects resulting from site- or species-specific selection, intrinsic factors (e.g. G matrix differences) or chance historical events (e.g. genetic drift). For two distantly-related estuarine fishes [Lagodon rhomboides (Sparidae; Linnaeus) and Leiostomus xanthurus (Sciaenidae; Lacepede)], we examined shared and unique instances of body shape variation between seagrass (complex) and sand (simple) microhabitats at four sites. We found extensive shape variation between microhabitats for both species. As a shared response, both species from sand had subterminal snouts and long caudal peduncles, whereas those from seagrass had terminal snouts and deep bodies. Unique responses involved a greater difference in Lagodon rhomboides head shape between microhabitats compared to L. xanthurus. Patterns of shape variation fit ecomorphological predictions for foraging in the respective microhabitats (simple versus complex) because deep bodies are expected for fish that must negotiate complex habitats and subterminal snouts facilitate benthic foraging common in barren habitats. Parallel differentiation between microhabitats simultaneously suggests that individuals of each species use a particular microhabitat within estuaries for development and the differentiation in shape represents adaptive convergence. Spatial variation in the magnitude of shape differences between microhabitats was an unexpected finding and suggests that phenotypic variation operates at multiple scales within estuaries
Growth And The Growth Hormone-Insulin Like Growth Factor 1 Axis In Children With Chronic Inflammation:Current Evidence, Gaps In Knowledge And Future Directions
Growth failure is frequently encountered in children with chronic inflammatory conditions like juvenile idiopathic arthritis, inflammatory bowel disease and cystic fibrosis. Delayed puberty and attenuated pubertal growth spurt is often seen during adolescence. The underlying inflammatory state mediated by pro-inflammatory cytokines, prolonged use of glucocorticoid and suboptimal nutrition contribute to growth failure and pubertal abnormalities. These factors can impair growth by their effects on the growth hormone-insulin like growth factor axis and also directly at the level of the growth plate via alterations in chondrogenesis and local growth factor signaling. Recent studies on the impact of cytokines and glucocorticoid on the growth plate studies further advanced our understanding of growth failure in chronic disease and provided a biological rationale of growth promotion. Targeting cytokines using biologic therapy may lead to improvement of growth in some of these children but approximately one third continue to grow slowly. There is increasing evidence that the use of relatively high dose recombinant human growth hormone may lead to partial catch up growth in chronic inflammatory conditions, although long term follow-up data is currently limited. In this review, we comprehensively review the growth abnormalities in children with juvenile idiopathic arthritis, inflammatory bowel disease and cystic fibrosis, systemic abnormalities of the growth hormone-insulin like growth factor axis and growth plate perturbations. We also systematically reviewed all the current published studies of recombinant human growth hormone in these conditions and discuss the role of recombinant human insulin like growth factor-1
Variationelle Mehrfeldmodellierung der Entstehung und Evolution von Laminatmikrostruktur
The optimization of material properties and the design of new materials with tailored material behavior are among the greatest challenges in the field of computational continuum mechanics. Since the macroscopic material behavior of many technically relevant materials is very closely linked to their microstructure, a profound physical and mathematical understanding and a reliable computational prediction of the formation and evolution of this microstructure is the necessary basis for any optimization or material design. In this work, we focus on the physical and mathematical understanding and the modeling and simulation of laminate microstructure and use the modeling framework of gradient-extended standard-dissipative solids to construct a phase field model for martensitic laminate microstructure in two-variant martensitic CuAlNi and a gradient crystal plasticity model for laminate deformation microstructure in Copper with two active slip systems on the same slip plane. We derive rate- and incremental-variational as well as finite element formulations for the two models and carry out numerical simulations.
Basis for our modeling are the modeling framework of gradient-extended standard-dissipative solids on the one hand, and the continuum theory of non-material sharp interfaces with interface energy on the other hand, from which we derive the condition of kinematic compatibility, jump conditions in analogy to the balance equations and the dissipation postulate for the moving interface. We consider the variational origin of the formation of laminate microstructure and identify gradient-extended modeling approaches as the suitable choice for the modeling of the formation and dissipative evolution of laminate microstructure with interface energy.
Based on these considerations, we propose a phase field model for the formation and evolution of laminate microstructure in two-variant martensitic CuAlNi that is based on the variational smooth approximation of sharp topologies and contains a coherence-dependent interface energy. We show that an internal mixing approach for the bulk energy allows a clear separation of interface and bulk energy and that the model is capable of predicting the formation and dissipative evolution of martensitic laminate microstructure and size effects.
Furthermore, we propose a gradient crystal plasticity model for Copper with two active slip systems on the same slip plane that allows a prediction of both the formation and evolution of plastic laminate microstructure and incorporates the effect of geometrically necessary dislocations (GNDs). The model contains a biquadratic non-convex latent hardening function and a gradient contribution based on the dislocation density tensor. The evolution equations of the plastic slips and the accumulated plastic slips are obtained by use of a rate regularization that makes use of the approximation of |x| as a*ln(cosh(x/a)) for a<<1. The model is shown to be capable of predicting the formation and evolution of deformation laminate microstructure together with length-scale effects related to GNDs.Die Optimierung von Materialeigenschaften und die Entwicklung neuer Materialien mit maĂ geschneiderten Eigenschaften zĂ€hlen zu den gröà ten Herausforderungen im Bereich der computerorientierten Kontinuumsmechanik. Da das makroskopische Materialverhalten vieler technisch relevanter Materialien eng mit ihrer Mikrostruktur verbunden ist, sind ein fundiertes physikalisches und mathematisches VerstĂ€ndnis sowie eine zuverlĂ€ssige numerische Vorhersage der Entstehung und Evolution von Mikrostrukturen die nötige Basis fĂŒr jegliche Art von Optimierung und Materialentwicklung. Diese Arbeit befasst sich speziell mit den physikalischen und mathematischen Grundlagen und der Modellierung und Simulation von Laminatmikrostruktur. Im Rahmen der Materialklasse der gradientenerweiterten standarddissipativen Festkörper formulieren wir ein Phasenfeldmodell fĂŒr Laminatmikrostruktur in martensitischem CuAlNi mit zwei martensitischen Varianten sowie ein gradientenerweitertes KristallplastizitĂ€tsmodell fĂŒr plastische Laminatmikrostruktur in Kupfer mit zwei aktiven Gleitsystemen auf derselben Gleitebene. FĂŒr die Modelle werden ratenbasiert und inkrementell variationelle Prinzipe sowie Finite Element Formulierungen hergeleitet und zur Betrachtung numerischer Beispiele verwendet.
Basis fĂŒr die Modellierung ist auf der einen Seite der Modellierungsrahmen der Materialklasse der gradientenerweiterten standarddissipativen Festkörper und auf der anderen Seite die Kontinuumsmechanik scharfer nichtmaterieller GrenzflĂ€chen mit GrenzflĂ€chen-energie, mit deren Hilfe wir die Bedingung der kinematischen KompatibilitĂ€t, die Sprungbedingungen in Analogie zu den Bilanzgleichungen sowie das Dissipationspostulat der GrenzflĂ€che herleiten. Wir betrachten den variationellen Ursprung von Laminatmikrostrukturen und identifizieren gradientenerweiterte AnsĂ€tze als den am Besten geeigneten Weg zu deren Modellierung unter Einbeziehung von GrenzflĂ€chenenergie und Dissipation.
Ausgehend von diesen Ăberlegungen entwickeln wir ein Phasenfeldmodell fĂŒr die Enstehung und Evolution von Laminatmikrostruktur in martensitischem CuAlNi mit zwei martensitischen Varianten, das auf der variationellen und glatten Approximation scharfer GrenzflĂ€chen basiert und eine kohĂ€renzabhĂ€ngige GrenzflĂ€chenenergie beinhalten. Wir zeigen, dass ein innerer Mischungsansatz der elastischen Energie eine saubere Trennung zwischen GrenzflĂ€chen- und elastischer Energie erlaubt und dass das Modell die Enstehung und dissipative Evolution von martensitischer Laminatmikrostruktur vorhersagen kann.
Des Weiteren konstruieren wir ein gradientenerweitertes KristallplastizitĂ€tsmodell fĂŒr plastische Laminatmikrostruktur in Kupfer mit zwei aktiven Gleitsystemen auf derselben Gleitebene, das die Vorhersage sowohl der Enstehung und Evolution von Laminatmikrostruktur als auch des Effekts von geometrisch notwendigen Versetzungen erlaubt. Das Modell beinhaltet eine biquadratische Funktion fĂŒr latente Verfestigung und einen Gradiententerm, der auf dem Versetzungsdichtetensor basiert. Die Evolutionsgleichungen fĂŒr die plastischen Gleitungen und die akkumulierten plastischen Gleitungen basieren auf Ratenregularisierungen mit Hilfe der Approximation von |x| als a*ln(cosh(x/a)) fĂŒr a<<1. Wir zeigen die FĂ€higkeit unseres Modells, die Enstehung und Entwicklung von Laminatmikrostruktur zusammen mit LĂ€ngenskaleneffekten aufgrund geometrisch notwendiger Versetzungen vorherzusagen
A chip card for patients with diabetes.
DIABCARD provides the specification for the core of a Chip Card Based Medical Information System (CCMIS) for the treatment of patients with chronic diseases. It will provide an instrument for assessing health care services, improve the links between health care providers and set up communication between the different levels of health care. It will therefore improve the quality of care and thus the life of patients with chronic diseases. DIABCARD concentrates on diabetes at the moment, the concept of the diabetes chip card will, however, be extendable to other chronic diseases.DIABCARD provides the specification for the core of a Chip Card Based Medical Information System (CCMIS) for the treatment of patients with chronic diseases. It will provide an instrument for assessing health care services, improve the links between health care providers and set up communication between the different levels of health care. It will therefore improve the quality of care and thus the life of patients with chronic diseases. DIABCARD concentrates on diabetes at the moment, the concept of the diabetes chip card will, however, be extendable to other chronic diseases