7,109 research outputs found
Development of Morphogen Gradient: The Role of Dimension and Discreteness
The fundamental processes of biological development are governed by multiple
signaling molecules that create non-uniform concentration profiles known as
morphogen gradients. It is widely believed that the establishment of morphogen
gradients is a result of complex processes that involve diffusion and
degradation of locally produced signaling molecules. We developed a
multi-dimensional discrete-state stochastic approach for investigating the
corresponding reaction-diffusion models. It provided a full analytical
description for stationary profiles and for important dynamic properties such
as local accumulation times, variances and mean first-passage times. The role
of discreteness in developing of morphogen gradients is analyzed by comparing
with available continuum descriptions. It is found that the continuum models
prediction about multiple time scales near the source region in two-dimensional
and three-dimensional systems is not supported in our analysis. Using ideas
that view the degradation process as an effective potential, the effect of
dimensionality on establishment of morphogen gradients is also discussed. In
addition, we investigated how these reaction-diffusion processes are modified
with changing the size of the source region
Theoretical Analysis of Dynamic Processes for Interacting Molecular Motors
Biological transport is supported by collective dynamics of enzymatic
molecules that are called motor proteins or molecular motors. Experiments
suggest that motor proteins interact locally via short-range potentials. We
investigate the fundamental role of these interactions by analyzing a new class
of totally asymmetric exclusion processes where interactions are accounted for
in a thermodynamically consistent fashion. Theoretical analysis that combines
various mean-field cal- culations and computer simulations suggests that
dynamic properties of molecular motors strongly depend on interactions, and
correlations are stronger for interacting motor proteins. Surprisingly, it is
found that there is an optimal strength of interactions (weak repulsion) that
leads to a maxi- mal particle flux. It is also argued that molecular motors
transport is more sensitive to attractive interactions. Applications of these
results for kinesin motor proteins are discussed
Gravitational Uncertainty and Black Hole Remnants
Possible existence of black holes remnants provides a suitable candidates for
dark matter. In this paper we study the possibility of existence for such
remnants. We consider quantum gravitational induced corrections of black hole's
entropy and temperature to investigate the possibility of such relics.
Observational scheme for detection of these remnants and their cosmological
constraints are discussed.Comment: 17 pages, 6 figure
On the Order of the Schur Multiplier of a Pair of Finite p-Groups
In 1998, G. Ellis defined the Schur multiplier of a pair of groups
and mentioned that this notion is a useful tool for studying pairs of groups.
In this paper, we characterize the structure of a pair of finite -groups
in terms of the order of the Schur multiplier of under some
conditions.Comment: 11 pages, to appear in Journal of Advanced Research in Pure
Mathematic
Does Resource Commercialization Induce Local Conservation? A Cautionary Tale From Southwestern Morocco
Ecotourism, bioprospecting and non-timber product marketing have been promoted recently as market-based instruments for environment protection, but without sound understanding of the resulting net conservation effects. We present evidence on the local conservation effects of recent argan oil commercialization in Morocco, which seems a promising case study in conservation through resource commercialization. Our empirical analysis shows, however, that resource commercialization is not creating strong net conservation incentives because assumptions implicit in the prevailing logic prove incorrect in this case. Generally, the experience of southwestern Morocco provides a cautionary tale about the assumed efficacy of conservation strategies founded on resource commercialization.Resource /Energy Economics and Policy,
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