2,150 research outputs found
Bone growth as the main determinant of mouse digit tip regeneration after amputation
Regeneration is classically demonstrated in mammals using mice digit tip. In this study, we compared different amputation plans and show that distally amputated digits regrow with morphology close to normal but fail to regrow the fat pad. Proximally amputated digits do not regrow the phalangeal bone, but the remaining structures (nail, skin and connective tissue), all with intrinsic regenerative capacity, re-establishing integrity indistinguishably in distally and proximally amputated digits. Thus, we suggest that the bone growth promoted by signals and progenitor cells not removed by distal amputations is responsible for the re-establishment of a drastically different final morphology after distal or proximal digit tip amputations. Despite challenging the use of mouse digit tip as a model system for limb regeneration in mammals, these findings evidence a main role of bone growth in digit tip regeneration and suggest that mechanisms that promote joint structures formation should be the main goal of regenerative medicine for limb and digit regrowth9CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP460664/2014-02012/09602-0; 2019/09870-
Antibonding Ground state of Adatom Molecules in Bulk Dirac Semimetals
The ground state of the diatomic molecules in nature is inevitably bonding,
and its first excited state is antibonding. We demonstrate theoretically that,
for a pair of distant adatoms placed buried in three-dimensional-Dirac
semimetals, this natural order of the states can be reversed and an antibonding
ground state occurs at the lowest energy of the so-called bound states in the
continuum. We propose an experimental protocol with the use of a scanning
tunneling microscope tip to visualize the topographic map of the local density
of states on the surface of the system to reveal the emerging physics
Catching the Bound States in the Continuum of a Phantom Atom in Graphene
We explore theoretically the formation of bound states in the continuum
(BICs) in graphene hosting two collinear adatoms situated at different sides of
the sheet and at the center of the hexagonal cell, where a phantom atom of a
fictitious lattice emulates the six carbons of the cell. We verify that in this
configuration the local density of states (LDOS) near the Dirac points exhibits
two characteristic features: i) the cubic dependence on energy instead of the
linear one for graphene as found in New J. Phys. 16, 013045 (2014) and ii)
formation of BICs as aftermath of a Fano destructive interference assisted by
the Coulomb correlations in the adatoms. For the geometry where adatoms are
collinear to carbon atoms, we report absence of BICs
Holocentric Karyotype Evolution inRhynchosporaIs Marked by Intense Numerical, Structural, and Genome Size Changes
Quantum phase transition triggering magnetic BICs in graphene
Graphene hosting a pair of collinear adatoms in the phantom atom
configuration has pseudogap with cubic scaling on energy,
which leads to the appearance of
spin-degenerate bound states in the continuum (BICs) [Phys. Rev. B 92, 045409
(2015)]. In the case when adatoms are locally coupled to a single carbon atom
the pseudogap scales linearly with energy, which prevents the formation of
BICs. In this Letter, we explore the effects of non-local coupling
characterized by the Fano factor of interference tunable by changing
the slope of the Dirac cones in the graphene band-structure. We demonstrate
that three distinct regimes can be identified: i) for (critical
point) a mixed pseudogap appears
yielding a phase with spin-degenerate BICs; ii) near when
the system undergoes a quantum phase
transition in which the new phase is characterized by magnetic BICs and iii) at
a second critical value the cubic scaling of the pseudogap with
energy characteristic to the phantom atom
configuration is restored and the phase with non-magnetic BICs is recovered.
The phase with magnetic BICs can be described in terms of an effective
intrinsic exchange field of ferromagnetic nature between the adatoms mediated
by graphene monolayer. We thus propose a new type of quantum phase transition
resulting from the competition between the states characterized by
spin-degenerate and magnetic BICs
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