62 research outputs found
Periostin potently promotes metastatic growth of colon cancer by augmenting cell survival via the Akt/PKB pathway
Molecular mechanisms associated with tumor metastasis remain poorly understood. Here we report that acquired expression of periostin by colon cancer cells greatly promoted metastatic development of colon tumors. Periostin is overexpressed in more than 80% of human colon cancers examined with highest expression in metastatic tumors. Periostin expression dramatically enhanced metastatic growth of colon cancer by both preventing stress-induced apoptosis in the cancer cells and augmenting endothelial cell survival to promote angiogenesis. At the molecular level, periostin activated the Akt/PKB signaling pathway through the alpha(v)beta(3) integrins to increase cellular survival. These data demonstrated that the survival-promoting function is crucial for periostin to promote tumor metastasis of colon cancer
Angle resolved photoemission spectroscopy reveals spin charge separation in metallic MoSe2 grain boundary
Material line defects are one-dimensional structures but the search and proof of electron
behaviour consistent with the reduced dimension of such defects has been so far
unsuccessful. Here we show using angle resolved photoemission spectroscopy that
twin-grain boundaries in the layered semiconductor MoSe2 exhibit parabolic metallic bands.
The one-dimensional nature is evident from a charge density wave transition, whose
periodicity is given by kF/p, consistent with scanning tunnelling microscopy and angle
resolved photoemission measurements. Most importantly, we provide evidence for spin- and
charge-separation, the hallmark of one-dimensional quantum liquids. Our studies show that
the spectral line splits into distinctive spinon and holon excitations whose dispersions exactly
follow the energy-momentum dependence calculated by a Hubbard model with suitable
finite-range interactions. Our results also imply that quantum wires and junctions can be
isolated in line defects of other transition metal dichalcogenides, which may enable quantum
transport measurements and devices.The USF group acknowledges support from the National Science Foundation
(DMR-1204924). V.K., R.D. and M.-H. P. acknowledges support from the Army
Research Office (W911NF-15-1-0626) and thank Prof. Hari Srikanth for resistance
measurements in his laboratory. M.C.A., J.A. and C.C. thank enlightening exchanges
with Gabriel Kotliar and Zhi-Xun Shen. The Synchrotron SOLEIL is supported by the
Centre National de la Recherche Scientifique (CNRS) and the Commissariat a` l’Energie
Atomique et aux Energies Alternatives (CEA), France. T.Cˇ. and J.M.P.C. thank Eduardo
Castro, Hai-Qing Lin and Pedro D. Sacramento for illuminating discussions. The theory
group acknowledges the support from NSAF U1530401 and computational resources
from CSRC (Beijing), the Portuguese FCT through the Grant UID/FIS/04650/2013 and
the NSFC Grant 11650110443.info:eu-repo/semantics/publishedVersio
On the topological surface states of the intrinsic magnetic topological insulator Mn-Bi-Te family
We review recent progress in the electronic structure study of intrinsic
magnetic topological insulators (MnBiTe)(BiTe)
() family. Specifically, we focus on the ubiquitously (nearly)
gapless behavior of the topological surface state Dirac cone observed by
photoemission spectroscopy, even though a large Dirac gap is expected because
of surface ferromagnetic order. The dichotomy between experiment and theory
concerning this gap behavior is perhaps the most critical and puzzling question
in this frontier. We discuss various proposals accounting for the lack of
magnetic effect on the topological surface state Dirac cone, which are mainly
categorized into two pictures, magnetic reconfiguration, and topological
surface state redistribution. Band engineering towards opening a magnetic gap
of topological surface states provides great opportunities to realize quantized
topological transport and axion electrodynamics at higher temperatures
Smooth muscle phosphatase is regulated in vivo by exclusion of phosphorylation of threonine 696 of MYPT1 by phosphorylation of Serine 695 in response to cyclic nucleotides
Gapless surface Dirac cone in antiferromagnetic topological insulator MnBiTe
The recent discovered antiferromagnetic topological insulators in Mn-Bi-Te
family with intrinsic magnetic ordering have rapidly drawn broad interest since
its cleaved surface state is believed to be gapped, hosting the unprecedented
axion states with half-integer quantum Hall effect. Here, however, we show
unambiguously by using high-resolution angle-resolved photoemission
spectroscopy that a gapless Dirac cone at the (0001) surface of MnBiTe
exists between the bulk band gap. Such unexpected surface state remains
unchanged across the bulk N\'eel temperature, and is even robust against severe
surface degradation, indicating additional topological protection. Through
symmetry analysis and - calculations we consider
different types of surface reconstruction of the magnetic moments as possible
origins giving rise to such linear dispersion. Our results reveal that the
intrinsic magnetic topological insulator hosts a rich platform to realize
various topological phases such as topological crystalline insulator and
time-reversal-preserved topological insulator, by tuning the magnetic
configurations.Comment: 9 pages, 4 figures. To appear in Phys. Rev. X. See Version 1 for the
supplementary fil
Dichotomy of Electronic Structure and Superconductivity between Single-Layer and Double-Layer FeSe/SrTiO3 Films
The latest discovery of possible high temperature superconductivity in the
single-layer FeSe film grown on a SrTiO3 substrate, together with the
observation of its unique electronic structure and nodeless superconducting
gap, has generated much attention. Initial work also found that, while the
single-layer FeSe/SrTiO3 film exhibits a clear signature of superconductivity,
the double-layer FeSe/SrTiO3 film shows an insulating behavior. Such a dramatic
difference between the single-layer and double-layer FeSe/SrTiO3 films is
surprising and the underlying origin remains unclear. Here we report our
comparative study between the single-layer and double-layer FeSe/SrTiO3 films
by performing a systematic angle-resolved photoemission study on the samples
annealed in vacuum. We find that, like the single-layer FeSe/SrTiO3 film, the
as-prepared double-layer FeSe/SrTiO3 film is insulating and possibly magnetic,
thus establishing a universal existence of the magnetic phase in the
FeSe/SrTiO3 films. In particular, the double-layer FeSe/SrTiO3 film shows a
quite different doping behavior from the single-layer film in that it is hard
to get doped and remains in the insulating state under an extensive annealing
condition. The difference originates from the much reduced doping efficiency in
the bottom FeSe layer of the double-layer FeSe/SrTiO3 film from the FeSe-SrTiO3
interface. These observations provide key insights in understanding the origin
of superconductivity and the doping mechanism in the FeSe/SrTiO3 films. The
property disparity between the single-layer and double-layer FeSe/SrTiO3 films
may facilitate to fabricate electronic devices by making superconducting and
insulating components on the same substrate under the same condition.Comment: 19 pages, 4 figure
Distinct Topological Surface States on the Two Terminations of MnBiTe
The recent discovered intrinsic magnetic topological insulator MnBi2Te4 have
been met with unusual success in hosting emergent phenomena such as the quantum
anomalous Hall effect and the axion insulator states. However, the surface-bulk
correspondence of the Mn-Bi-Te family, composed by the superlattice-like
MnBi2Te4/(Bi2Te3)n (n = 0, 1, 2, 3 ...) layered structure, remains intriguing
but elusive. Here, by using scanning tunneling microscopy (STM) and
angle-resolved photoemission spectroscopy (ARPES) techniques, we unambiguously
assign the two distinct surface states of MnBi4Te7 (n = 1) to the
quintuple-layer (QL) Bi2Te3 termination and the septuple-layer (SL) MnBi2Te4
termination, respectively. A comparison of the experimental observations with
theoretical calculations reveals the diverging topological behaviors,
especially the hybridization effect between magnetic and nonmagnetic layers, on
the two terminations: a gap on the QL termination originating from the
topological surface states of the QL hybridizing with the bands of the beneath
SL, and a gapless Dirac-cone band structure on the SL termination with
time-reversal symmetry. The quasi-particle interference patterns further
confirm the topological nature of the surface states for both terminations,
continuing far above the Fermi energy. The QL termination carries a
spin-helical Dirac state with hexagonal warping, while at the SL termination, a
strongly canted helical state from the surface lies between a pair of
Rashba-split states from its neighboring layer. Our work elucidates an
unprecedented hybridization effect between the building blocks of the
topological surface states, and also reveals the termination-dependent
time-reversal symmetry breaking in a magnetic topological insulator, rendering
an ideal platform to realize the half-integer quantum Hall effect and relevant
quantum phenomena.Comment: 22 Pages, 4 Figure
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