27 research outputs found
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A new validation scheme for the evaluation of multiparameter fields
On the basis of an extended cluster analysis algorithm, we present a new validation method for the evaluation of simulation experiments characterized by more than one parameter. This method allows the assessment of any parameter combination in space and time. As an example for the effectiveness of the algorithm, the results of two regional climate model runs and observational data have been tested and interpreted
Mutual Zonated Interactions of Wnt and Hh Signaling Are Orchestrating the Metabolism of the Adult Liver in Mice and Human
The Hedgehog (Hh) and Wnt/β-Catenin (Wnt) cascades are morphogen pathways whose pronounced influence on adult liver metabolism has been identified in recent years. How both pathways communicate and control liver metabolic functions are largely unknown. Detecting core components of Wnt and Hh signaling and mathematical modeling showed that both pathways in healthy liver act largely complementary to each other in the pericentral (Wnt) and the periportal zone (Hh) and communicate mainly by mutual repression. The Wnt/Hh module inversely controls the spatiotemporal operation of various liver metabolic pathways, as revealed by transcriptome, proteome, and metabolome analyses. Shifting the balance to Wnt (activation) or Hh (inhibition) causes pericentralization and periportalization of liver functions, respectively. Thus, homeostasis of the Wnt/Hh module is essential for maintaining proper liver metabolism and to avoid the development of certain metabolic diseases. With caution due to minor species-specific differences, these conclusions may hold for human liver as well
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Reliability of regional climate model simulations of extremes and of long-term climate
We present two case studies that demonstrate how a common evaluation methodology can be used to assess the reliability of regional climate model simulations from different fields of research. In Case I, we focused on the agricultural yield loss risk for maize in Northeastern Brazil during a drought linked to an El-Niño event. In Case II, the present-day regional climatic conditions in Europe for a 10-year period are simulated. To comprehensively evaluate the model results for both kinds of investigations, we developed a general methodology. On its basis, we elaborated and implemented modules to assess the quality of model results using both advanced visualization techniques and statistical algorithms. Besides univariate approaches for individual near-surface parameters, we used multivariate statistics to investigate multiple near-surface parameters of interest together. For the latter case, we defined generalized quality measures to quantify the model's accuracy. Furthermore, we elaborated a diagnosis tool applicable for atmospheric variables to assess the model's accuracy in representing the physical processes above the surface under various aspects. By means of this evaluation approach, it could be demonstrated in Case Study I that the accuracy of the applied regional climate model resides at the same level as that we found for another regional model and a global model. Excessive precipitation during the rainy season in coastal regions could be identified as a major contribution leading to this result. In Case Study II, we also identified the accuracy of the investigated mean characteristics for near-surface temperature and precipitation to be comparable to another regional model. In this case, an artificial modulation of the used initial and boundary data during preprocessing could be identified as the major source of error in the simulation. Altogether, the achieved results for the presented investigations indicate the potential of our methodology to be applied as a common test bed to different fields of research in regional climate modeling
Multiple-length-scale elastic instability mimics parametric resonance of nonlinear oscillators
Spatially confined rigid membranes reorganize their morphology in response to
the imposed constraints. A crumpled elastic sheet presents a complex pattern of
random folds focusing the deformation energy while compressing a membrane
resting on a soft foundation creates a regular pattern of sinusoidal wrinkles
with a broad distribution of energy. Here, we study the energy distribution for
highly confined membranes and show the emergence of a new morphological
instability triggered by a period-doubling bifurcation. A periodic
self-organized focalization of the deformation energy is observed provided an
up-down symmetry breaking, induced by the intrinsic nonlinearity of the
elasticity equations, occurs. The physical model, exhibiting an analogy with
parametric resonance in nonlinear oscillator, is a new theoretical toolkit to
understand the morphology of various confined systems, such as coated materials
or living tissues, e.g., wrinkled skin, internal structure of lungs, internal
elastica of an artery, brain convolutions or formation of fingerprints.
Moreover, it opens the way to new kind of microfabrication design of
multiperiodic or chaotic (aperiodic) surface topography via self-organization.Comment: Submitted for publicatio
Merkel cells and the individuality of friction ridge skin
There is no definite theory yet for the mechanism by which the pattern of epidermal ridges on fingers,
palms and soles forming friction ridge skin (FRS) patterns is created. For a long time growth forces in
the embryonal epidermis have been believed to be involved in FRS formation. More recent evidence
suggests that Merkel cells play an important part in this process as well. Here we suggest a model for
the formation of FRS patterns that links Merkel cells to the epidermal stress distribution. The Merkel
cells are modeled as agents in an agent based model that move anisotropically where the anisotropy is
created by the epidermal stress tensor. As a result ridge patterns are created with pattern defects as
they occur in real FRS patterns. As a consequence we suggest why the topology of FRS patterns is indeed
unique as the arrangement of pattern defects is sensitive to the initial configuration of Merkel cells
A model for fingerprint formation
The uniqueness of fingerprints (epidermal ridges) has been
recognized for over two thousand years. They have been studied
scientifically for more than two hundred years. Yet, in spite of
the accumulation of a wealth of empirical and experimental
knowledge, no widely accepted explanation for the development of
epidermal ridges on fingers, palms and soles has yet emerged.
Informed by an extensive literature study we suggest that
fingerprint patterns are created as the result of a buckling
instability in the basal cell layer of the fetal epidermis.
Analysis of the well-known von Karman equations informs us that
the buckling direction is perpendicular to the direction of
greatest stress in the basal layer. We propose that this stress
is induced by resistance of furrows and creases to the
differential growth of the basal layer and regression of the
volar pads during the time of ridge formation. These theories
have been tested by computer experiments. The results are in
close harmony with observations. Specifically, they are
consistent with the well-known observation that the pattern type
depends on the geometry of the fingertip surface when fingerprint
patterns are formed
Fingerprint Sample Synthesis
Fingerprint sample synthesis is the generation of images similar to human’s fingerprints, through parametric models that simulate the main characteristics of such biometric data and their modes of variation. The image synthesis is typically performed by a computer program that, starting from some input parameters, executes a sequence of algorithmic steps that finally produce a synthetic fingerprint image