267 research outputs found
Reaction-Diffusion Pattern in Shoot Apical Meristem of Plants
A fundamental question in developmental biology is how spatial patterns are
self-organized from homogeneous structures. In 1952, Turing proposed the
reaction-diffusion model in order to explain this issue. Experimental evidence
of reaction-diffusion patterns in living organisms was first provided by the
pigmentation pattern on the skin of fishes in 1995. However, whether or not this
mechanism plays an essential role in developmental events of living organisms
remains elusive. Here we show that a reaction-diffusion model can successfully
explain the shoot apical meristem (SAM) development of plants. SAM of plants
resides in the top of each shoot and consists of a central zone (CZ) and a
surrounding peripheral zone (PZ). SAM contains stem cells and continuously
produces new organs throughout the lifespan. Molecular genetic studies using
Arabidopsis thaliana revealed that the formation and
maintenance of the SAM are essentially regulated by the feedback interaction
between WUSHCEL (WUS) and CLAVATA (CLV). We developed a mathematical model of
the SAM based on a reaction-diffusion dynamics of the WUS-CLV interaction,
incorporating cell division and the spatial restriction of the dynamics. Our
model explains the various SAM patterns observed in plants, for example,
homeostatic control of SAM size in the wild type, enlarged or fasciated SAM in
clv mutants, and initiation of ectopic secondary meristems
from an initial flattened SAM in wus mutant. In addition, the
model is supported by comparing its prediction with the expression pattern of
WUS in the wus mutant. Furthermore, the
model can account for many experimental results including reorganization
processes caused by the CZ ablation and by incision through the meristem center.
We thus conclude that the reaction-diffusion dynamics is probably indispensable
for the SAM development of plants
High Metallicity of the X-Ray Gas up to the Virial Radius of a Binary Cluster of Galaxies: Evidence of Galactic Superwinds at High-Redshift
We present an analysis of a Suzaku observation of the link region between the
galaxy clusters A399 and A401. We obtained the metallicity of the intracluster
medium (ICM) up to the cluster virial radii for the first time. We determine
the metallicity where the virial radii of the two clusters cross each other (~2
Mpc away from their centers) and found that it is comparable to that in their
inner regions (~0.2 Zsun). It is unlikely that the uniformity of metallicity up
to the virial radii is due to mixing caused by a cluster collision. Since the
ram-pressure is too small to strip the interstellar medium of galaxies around
the virial radius of a cluster, the fairly high metallicity that we found there
indicates that the metals in the ICM are not transported from member galaxies
by ram-pressure stripping. Instead, the uniformity suggests that the
proto-cluster region was extensively polluted with metals by extremely powerful
outflows (superwinds) from galaxies before the clusters formed. We also
searched for the oxygen emission from the warm--hot intergalactic medium in
that region and obtained a strict upper limit of the hydrogen density
(nH<4.1x10^-5 cm^-3).Comment: Typo corrected. The published version is available on-line free of
charge by the end of 2008. http://pasj.asj.or.jp/v60/sp1/60s133/60s133.pd
Newton-Okounkov polytopes of Schubert varieties arising from cluster structures
The theory of Newton-Okounkov bodies is a generalization of that of Newton
polytopes for toric varieties, and it gives a systematic method of constructing
toric degenerations of projective varieties. In this paper, we study
Newton-Okounkov bodies of Schubert varieties from the theory of cluster
algebras. We construct Newton-Okounkov bodies using specific valuations which
generalize extended g-vectors in cluster theory, and discuss how these bodies
are related to string polytopes and Nakashima-Zelevinsky polytopes.Comment: 55 page
Isomorphisms among quantum Grothendieck rings and cluster algebras
We establish a cluster theoretical interpretation of the isomorphisms of
[F.-H.-O.-O., J. Reine Angew. Math., 2022] among quantum Grothendieck rings of
representations of quantum loop algebras. Consequently, we obtain a
quantization of the monoidal categorification theorem of
[Kashiwara-Kim-Oh-Park, arXiv:2103.10067]. We establish applications of these
new ingredients. First we solve long-standing problems for any non-simply-laced
quantum loop algebras: the positivity of -characters of all simple
modules, and the analog of Kazhdan-Lusztig conjecture for all reachable modules
(in the cluster monoidal categorification). We also establish the conjectural
quantum -systems for the -characters of Kirillov-Reshetikhin modules.
Eventually, we show that our isomorphisms arise from explicit birational
transformations of variables, which we call substitution formulas. This reveals
new non-trivial relations among -characters of simple modules.Comment: 60 page
Mathematical model studies of the comprehensive generation of major and minor phyllotactic patterns in plants with a predominant focus on orixate phyllotaxis
UTokyo FOCUS Press releases "Mathematics of leaves : Unusual Japanese plant inspires recalculation of equation used to model leaf arrangement patterns" https://www.u-tokyo.ac.jp/focus/en/press/z0508_00047.htm
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