14,488 research outputs found
Coupled Reversible and Irreversible Bistable Switches Underlying TGF-\beta-induced Epithelial to Mesenchymal Transition
Epithelial to mesenchymal transition (EMT) plays important roles in embryonic
development, tissue regeneration and cancer metastasis. While several feedback
loops have been shown to regulate EMT, it remains elusive how they coordinately
modulate EMT response to TGF-\beta treatment. We construct a mathematical model
for the core regulatory network controlling TGF-\beta-induced EMT. Through
deterministic analyses and stochastic simulations, we show that EMT is a
sequential two-step program that an epithelial cell first transits to partial
EMT then to the mesenchymal state, depending on the strength and duration of
TGF-\beta stimulation. Mechanistically the system is governed by coupled
reversible and irreversible bistable switches. The SNAIL1/miR-34 double
negative feedback loop is responsible for the reversible switch and regulates
the initiation of EMT, while the ZEB/miR-200 feedback loop is accountable for
the irreversible switch and controls the establishment of the mesenchymal
state. Furthermore, an autocrine TGF-\beta/miR-200 feedback loop makes the
second switch irreversible, modulating the maintenance of EMT. Such coupled
bistable switches are robust to parameter variation and molecular noise. We
provide a mechanistic explanation on multiple experimental observations. The
model makes several explicit predictions on hysteretic dynamic behaviors,
system response to pulsed stimulation and various perturbations, which can be
straightforwardly tested.Comment: 32 pages, 8 figures, accepted by Biophysical Journa
Unusual Compression Behavior of Columbite TiO2 via First-Principles Calculations
The physical mechanisms behind the reduction of the bulk modulus of a
high-pressure cubic TiO2 phase are confirmed by first-principles calculations.
An unusual and abrupt change occurs in the dependence of energy on pressure at
43 GPa, indicating a pressure-induced phase transition from columbite TiO2 to a
newly-identified modified fluorite TiO2 with a Pca21 symmetry. Oxygen atom
displacement in Pca21 TiO2 unexpectedly reduces the bulk modulus by 34%
relative to fluorite TiO2. This discovering provides a direct evidence for
understanding the compressive properties of such groups of homologous materialsComment: [email protected] or [email protected]
Infinite critical boson non-Fermi liquid on heterostructure interfaces
We study the emergence of non-Fermi liquid on heterostructure interfaces
where there exists an infinite number of critical boson modes accounting for
the magnetic fluctuations in two spatial dimensions. The interfacial
Dzyaloshinskii-Moriya interaction naturally arises in magnetic interactions due
to the absence of inversion symmetry, resulting in a degenerate contour for the
low-energy bosonic modes in the momentum space which simultaneously becomes
critical near the magnetic phase transition. The itinerant electrons are
scattered by the critical boson contour via the Yukawa coupling. When the boson
contour is much smaller than the Fermi surface, it is shown that, there exists
a regime with a dynamic critical exponent z=3 while the boson contour still
controls the low-energy magnetic fluctuations. Using a self-consistent
renormalization calculation for this regime, we uncover a prominent non-Fermi
liquid behavior in the resistivity with a characteristic temperature scaling
power. These findings open up new avenues for understanding boson-fermion
interactions and the novel fermionic quantum criticality.Comment: 17 pages(with Appendix), 7 figure
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