431 research outputs found
G-Protein coupled receptor signalling in pluripotent stem cell-derived cardiovascular cells: Implications for disease modelling
Human pluripotent stem cell derivatives show promise as an in vitro platform to study a range of human cardiovascular diseases. A better understanding of the biology of stem cells and their cardiovascular derivatives will help to understand the strengths and limitations of this new model system. G-protein coupled receptors (GPCRs) are key regulators of stem cell maintenance and differentiation and have an important role in cardiovascular cell signaling. In this review, we will therefore describe the state of knowledge concerning the regulatory role of GPCRs in both the generation and function of pluripotent stem cell derived-cardiomyocytes, -endothelial, and -vascular smooth muscle cells. We will consider how far the in vitro disease models recapitulate authentic GPCR signaling and provide a useful basis for discovery of disease mechanisms or design of therapeutic strategies
The Lorentz group and its finite field analogues: local isomorphism and approximation
Finite Lorentz groups acting on 4-dimensional vector spaces coordinatized by
finite fields with a prime number of elements are represented as homomorphic
images of countable, rational subgroups of the Lorentz group acting on real
4-dimensional space-time. Bounded subsets of the real Lorentz group are
retractable with arbitrary accuracy to finite subsets of such rational
subgroups. These finite retracts correspond, via local isomorphisms, to
well-behaved subsets of Lorentz groups over finite fields. This establishes a
relationship of approximation between the real Lorentz group and Lorentz groups
over very large finite fields
CD-independent subsets in meet-distributive lattices
A subset of a finite lattice is CD-independent if the meet of any two
incomparable elements of equals 0. In 2009, Cz\'edli, Hartmann and Schmidt
proved that any two maximal CD-independent subsets of a finite distributive
lattice have the same number of elements. In this paper, we prove that if
is a finite meet-distributive lattice, then the size of every CD-independent
subset of is at most the number of atoms of plus the length of . If,
in addition, there is no three-element antichain of meet-irreducible elements,
then we give a recursive description of maximal CD-independent subsets.
Finally, to give an application of CD-independent subsets, we give a new
approach to count islands on a rectangular board.Comment: 14 pages, 4 figure
A catalogue of observed geo-effective CME/ICME characteristics
One of the goals of Space Weather studies is to achieve a better
understanding of impulsive phenomena, such as Coronal Mass Ejections (CMEs), in
order to improve our ability to forecast them and mitigate the risk to our
technologically driven society. The essential part of achieving this goal is to
assess the performance of forecasting models. To this end, the quality and
availability of suitable data are of paramount importance. In this work, we
have merged already publicly available data of CMEs from both in-situ and
remote instrumentation in order to build a database of CME properties. To
evaluate the accuracy of such a database and confirm the relationship between
in-situ and remote observations, we have employed the drag-based model (DBM)
due to its simplicity and inexpensive cost of computational resources. In this
study, we have also explored the parameter space for the drag parameter and
solar wind speed using a Monte Carlo approach to evaluate how well the DBM
determines the propagation of CMEs for the events in the dataset. The dataset
of geoeffective CMEs constructed as a result of this work provides validation
of the initial hypothesis about DBM, and solar wind speed and also yields
further insight into CME features like arrival time, arrival speed, lift-off
time, etc. Using a data-driven approach, this procedure allows us to present a
homogeneous, reliable, and robust dataset for the investigation of CME
propagation. On the other hand, possible CME events are identified where DBM
approximation is not valid due to model limitations and higher uncertainties in
the input parameters, those events require more thorough investigation
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