Seminars 2017
Seminar
Tuesday, May 9
TightBinding Model Realized with Coupled Acoustic
Resonators
Hong Kong University of Science and Technology
Abstract
Tightbinding model is a simple yet powerful method
that can be used to study electronic band structures in
solidstate physics. The method considers only the
hopping, or the coupling, among the most adjacent
atomic wavefunctions. In this talk, I will show that
tightbinding model can be faithfully reproduced by
using coupled acoustic resonators. Based on such a
convenient platform, we are able to experimentally
investigate novel physics that arises therein. Two
examples will be discussed. As the first example, we
consider a 4by4 nonHermitian matrix, and study the
complex behaviors of the eigenfrequencies, including
formation and coalescence of multiple exceptional
points upon the variation of system parameters [1].
Second, we construct a SuSchriefferHeeger (SSH)
dimerized chain using the similar acoustic cavities.
Band inversion, together with a change in (quantized)
Zak phase can be realized. An interface system can be
constructed using two SSH chains with different Zak
phases. By coupling two of such interface systems
together; we obtain a new system with a fivesite unit
cell. For such a system, a specific separation of the
5by5 Hamiltonian into a topological subspace and a
nontopological subspace can be found. By tuning the
system parameters, the topological interface state,
which exists in the topological subspace, can be
embedded into a band continuum, which resides in the
nontopological subspace. This gives rise to a new type
of bound states in the continuum [2].
[1] Ding, K., Ma, G., Xiao, M., Zhang, Z.Q. and
Chan, C. T. Emergence, coalescence, and topological
properties of multiple exceptional points and their
experimental realization. Phys. Rev. X 6, 021007
(2016).
The seminar will take place at 13:00 in classroom
2.1.C19 (Edificio Sabatini) Universidad Carlos III
Seminar
Wednesday, May 3
Identification of cancer related genes using a
comprehensive map of human gene expression
UC3M
Abstract
The development of highthroughput techniques for gene
expression profiling over the last two decades has
rapidly led to the accumulation of vast amounts of
datasets, which are available in public repositories.
This has enabled largescale metaanalyses of combined
data to provide new biological insights, including the
identification of new cancer genes. We compiled a human
gene expression dataset from over 40000 microarrays.
After strict quality control and data normalisation the
data was quantified in an expression matrix of ~20,000
genes and ~28,000 samples, where we identified groups
like normal tissues, neoplasmic tissues, cell lines and
incompletely differentiated cells. Several unsupervised
analyses of the data confirmed a global structure of
the gene expression, which was consistent with earlier
analyses, but with more details revealed due to the
increased resolution. We suggested a suitable
mixedeffects linear model for gene expression, which
was used to further investigate it in solid tissue
tumours, and to compare these with the respective
healthy solid tissues. Our analysis identified 1285
genes with a systematic expression change in cancer.
The list was significantly enriched with known cancer
genes from large, peerreviewed databases, whereas the
remaining ones were proposed as new cancer gene
candidates.
The seminar will take place at 13:00 in classroom
2.1.C19 (Edificio Sabatini) Universidad Carlos III
Seminar
Tuesday, April 4
Application of thermal boundary conditions at the
microscale: A means for flow generation and control
Faculty of Aerospace Engineering at the Technion
(Israel)
Abstract
In marked difference from incompressible fluid flows,
microscale gas flows commonly couple the dynamic and
thermodynamic fluid descriptions, through the
combination of bulkflow evolution and external
boundary conditions. Yet, while the thermal boundary
conditions have a significant effect on the generated
flows, traditional studies on rarefied gas systems have
been limited to gassurface interactions where the
surfaces temperatures are prescribed. Such an
assumption, however, seems of little practical value,
as the surface temperature at any experimental setup
can only be imposed indirectly through a direct
prescription of the boundary heatflux. To examine this
observation, the present work demonstrates the impact
of replacing an isothermal surface condition with a
heatflux condition in a variety of onedimensional and
unsteady microflow setups. These include gasflow
animation problems, acoustic wave propagation, and
active flow control applications. Possible extensions
to higherdimension configurations, including
sheardriven flows and hydrodynamic instability
problems, are also reviewed.
The seminar will take place at 11:00 in classroom
2.1.C19 (Edificio Sabatini) Universidad Carlos III
Seminar
Wednesday, March 15
Acoustic wave propagation in granular media: rotation
and nonlinearities
UC3M
Abstract
Granular materials are considered as a complex media
when elastic waves propagates in the bulk. This
complexity comes from their microinhomogeneous
character and from the highly nonlinear behavior of the
contact between the particles. Compared to the
classical elastic solids, one major difference is due
to the importance of the rotational degrees of freedom
of each particle for the description of the elastic
behavior of the media. In this work, the effects of the
rotational degrees of freedom are shown through
theoretical predictions, numerical simulations and
experimental results. Nonlinear wave propagation
phenomena also happen in granular materials. Two
examples are presented. The first one is the asymmetry
of the nonlinear wave generation in a granular crystal
submitted to gravity. The second one is the study of
one single contact sphereplane as a nonlinear
resonator.
The seminar will take place at 13:00 in classroom
2.1.C19 (Edificio Sabatini) Universidad Carlos III


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