10,766 research outputs found
Structural Transformation in Pyrolytic Graphite Accompanying Deformation
Pyrolytic graphite deformation and structural transformatio
The genotype-phenotype relationship in multicellular pattern-generating models - the neglected role of pattern descriptors
Background: A deep understanding of what causes the phenotypic variation arising from biological patterning
processes, cannot be claimed before we are able to recreate this variation by mathematical models capable of
generating genotype-phenotype maps in a causally cohesive way. However, the concept of pattern in a
multicellular context implies that what matters is not the state of every single cell, but certain emergent qualities
of the total cell aggregate. Thus, in order to set up a genotype-phenotype map in such a spatiotemporal pattern
setting one is actually forced to establish new pattern descriptors and derive their relations to parameters of the
original model. A pattern descriptor is a variable that describes and quantifies a certain qualitative feature of the
pattern, for example the degree to which certain macroscopic structures are present. There is today no general
procedure for how to relate a set of patterns and their characteristic features to the functional relationships,
parameter values and initial values of an original pattern-generating model. Here we present a new, generic
approach for explorative analysis of complex patterning models which focuses on the essential pattern features
and their relations to the model parameters. The approach is illustrated on an existing model for Delta-Notch
lateral inhibition over a two-dimensional lattice.
Results: By combining computer simulations according to a succession of statistical experimental designs,
computer graphics, automatic image analysis, human sensory descriptive analysis and multivariate data modelling,
we derive a pattern descriptor model of those macroscopic, emergent aspects of the patterns that we consider
of interest. The pattern descriptor model relates the values of the new, dedicated pattern descriptors to the
parameter values of the original model, for example by predicting the parameter values leading to particular
patterns, and provides insights that would have been hard to obtain by traditional methods.
Conclusion: The results suggest that our approach may qualify as a general procedure for how to discover and
relate relevant features and characteristics of emergent patterns to the functional relationships, parameter values
and initial values of an underlying pattern-generating mathematical model
Blood flow dynamics in patient specific arterial network in head and neck
This paper shows a steady simulation of blood flow in the major head and neck arteries as if they
had rigid walls, using patient specific geometry and CFD software FLUENT
R . The Artery geometry
is obtained by CTâscan segmentation with the commercial software ScanIPTM. A cause and
effect study with various Reynolds numbers, viscous models and blood fluid models is provided.
Mesh independence is achieved through wall y+ and pressure gradient adaption. It was found, that
a Newtonian fluid model is not appropriate for all geometry parts, therefore the nonâNewtonian
properties of blood are required for small vessel diameters and low Reynolds numbers. The kâ!
turbulence model is suitable for the whole Reynolds numbe
Relaxation in yield stress systems through elastically interacting activated events
We study consequences of long-range elasticity in thermally assisted dynamics
of yield stress materials. Within a two-dimensinal mesoscopic model we
calculate the mean-square displacement and the dynamical structure factor for
tracer particle trajectories. The ballistic regime at short time scales is
associated with a compressed exponential decay in the dynamical structure
factor, followed by a subdiffusive crossover prior to the onset of diffusion.
We relate this crossover to spatiotemporal correlations and thus go beyond
established mean field predictions.Comment: 5 pages, 2 figures, to appear in PR
Prelabour Caesarean Section following IVF/ICSI in Older-Term Nulliparous Women: Too Precious to Push?
Objective. To compare prelabour caesarean section (CS) rates in older nulliparous women with a term singleton baby in cephalic presentation conceiving spontaneously and through IVF/ICSI. When the latter women would ask for CS, how willing are gynaecologists to comply with that request? Methods. A population-based retrospective (1995â2009) cohort study, conducted in Northern Belgium. A comparison of 1,866 nulliparous women pregnant after IVF/ICSI and 15,228 controls is made. An anonymous postal questionnaire is sent to all Belgian gynaecologists. Result. Both groups are comparable with respect to maternal age, gestational age, and birth weight. Prelabour CS is more often performed in women who conceived through IVF/ICSI compared to those who conceived spontaneously (9.2% versus 6.3%, P < 0.001). One in five gynaecologists agrees with the maternal request. Conclusion. IVF/ICSI pregnancies in older nulliparous women more often end in a prelabour CS and a substantial number of gynaecologists go along with a nonmedical reason for CS
Why must we work in the phase space?
We are going to prove that the phase-space description is fundamental both in
the classical and quantum physics. It is shown that many problems in
statistical mechanics, quantum mechanics, quasi-classical theory and in the
theory of integrable systems may be well-formulated only in the phase-space
language.Comment: 130 page
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