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Seminario DFI: Mechanics and Dynamics of Plant Cell Division Imprimir

Expositor: Jacques Dumais

Facultad de Ingeniería y Ciencias

Universidad Adolfo Ibáñez

Viña del Mar


Viernes 9 de noviembre, 16 h

Av. Blanco Encalada 2008, 3er piso

sala de seminarios

 

The division of eukaryotic cells involves the assembly of complex cytoskeletal

structures to exert the forces required for chromosome segregation and

cytokinesis. In plants, tensional forces within the cytoskeleton appear to

constrain cells to divide according to a small number of area minimizing

configurations. We have shown that the probability of observing a particular

division configuration increases inversely with its relative area according to an

exponential probability distribution known as the Gibbs measure. The distribution

is universal up to experimental accuracy with a unique constant that applies for

all plants studied irrespective of the shape and size of their cells. Using a

maximum entropy formulation, we were able to demonstrate that the empirically

derived division rule is predicted by the dynamics of the tense cytoskeletal

elements controlling the positioning of the division plane. Finally, by framing this

division rule as a dynamical system we were able to identify several attractors

that are predictive of characteristic cell patterns observed in plants. Plant cell

division thus offers a remarkable example of how simple mechanical interactions

at the subcellular level can lead to subtle behaviors at the cellular or multicellular

levels.

 

Seminarios Anteriores

SEMINARIO DFI: The Cosmic History of Black Hole Growth Imprimir

Expositor:

Ezequiel Treister

Departamento de Astronomia

Universidad de Concepcion

 

Viernes 26 de Octubre, 16 h

Blanco Encalada 2008, 3er piso

Sala de Seminarios

 

Abstract: It is now clear that supermassive black holes (M>1e6 Msun) live in the center of most (all) galaxies, including our own Milky Way. Furthermore, it is  now clear that the energy released during the growth of this black hole is a critical ingredient in understanding galaxy formation and evolution. In this  talk, I will show what we know about how, when and where these supermassive black holes are acquiring their masses. In particular, I will focus on the effects of obscuration, as it is now clear that the majority of this black hole growth is hidden from our view by large amounts of gas and dust. I will present observational evidence for the link between major galaxy mergers and black hole growth. Future data obtained combining observations with the ALMA radio telescope and NuSTAR X-ray observatory will allow us to finally understand the physical details of this connection.

 

 
SEMINARIO DFI: Control of nanosystems in solids for spintronics, and high sensitivity and high spati Imprimir

Expositor:

Jerónimo Maze

Departamento de Física, PUC


Viernes 12 de Octubre, 16 h

Blanco Encalada 2008, 3er piso 

Sala de Seminarios

 

 

Abstract: 

Defects in solids have received much attention from the scientific community as they have enabled not only the exploration of novel metrology techniques to investigate our world at the nanoscale in biology and material science, but also the realization of new systems with robust characteristics for spintronics and quantum information. As an example, defects in solids such as the nitrogen-vacancy center in diamond can sense magnetic fields with unprecedented combination of sensitivity and spatial resolution. Using quantum coherence, they can detect a single electronic, and even a single nuclear spins 10 nm away. In this talk I will introduce to the basic properties of defects in solids and explain how their internal electronic and spin degrees of freedom can be exploited to enable spintronics and metrology applications such as multiple single-shot qubit measurements, single spin detection at room temperature and creation of new diamond-based fluorescent markers for biological labeling. 

 
SEMINARIO DFI: Non-linear transport in Kondo-correlated quantum dots: a dual fermion perturbation th Imprimir

Expositor: Enrique Muñoz Tavera

Expositor: Enrique Muñoz Tavera

Departamento de Física

P. Universidad Católica de Chile

 

Viernes 5 de octubre, 16 h

Av. Blanco Encalada 2008, tercer piso

Sala de seminarios

 

The non-linear conductance of semiconductor hetero-structures and single molecule devices exhibiting Kondo physics has recently attracted attention. We address the observed sample dependence across various systems by considering additional electronic contributions present in the effective low-energy model underlying these experiments. To this end, we develop a novel perturbation theory in terms of dual fermions on the Keldysh contour. We analyze the role of particle-hole asymmetry on the transport coefficients. Our approach systematically extends the work of Yamada and Yosida and others to the particle-hole asymmetric Anderson model out of equilibrium. It correctly describes the strong coupling physics and satisfies current conservation. Our approach is also extended to obtain analytical expressions for other transport coefficients, such as the thermal conductance and Seebeck coefficient beyond linear response.

 

(1)  E. Muñoz, C. J. Bolech and S. Kirchner. "Universal out-of-equilibrium transport in Kondo correlated quantum dots: renormalized dual fermions on the Keldysh contour". Phys. Rev. Lett. (2012, with referees).

 

(2)  S. Kirchner, F. Zamani and E. Muñoz, "Nonlinear thermoelectric response of quantum dots: renormalized dual fermions out of equilibrium".  Chapter 10 in "New Materials for Thermoelectric Applications: Theory and Experiment". Springer (2012). V. Zlatic’ and A. Hewson (eds.), ISBN:9789400749832.


 
SEMINARIO DFI: Waves on a foam surface: propagation of subshear and supershear pulses. Imprimir

Expositor:

Guillaume Lagubeau

Física No Lineal, USACh

 

Viernes 28 de Septiembre, 16 h

Av. Blanco Encalada 2008, tercer piso

Sala de Seminarios

 

Liquid foams consist in a concentrated dispersion of gas bubbles in a continuous liquid phase. The dynamical properties of such a mixture, studied by rheologists over the last 30 years, are now well characterized, although not fully understood. Acoustics as a way to probe foam fast dynamics is a developing tool, that has to face the challenge of the strong dissipation occurring in this medium and therefore requires highly accurate measurement methods. Taking advantage of the precision of a space-time resolved profilometry technique we present here the first foam study using surface acoustics.

Subsequently, we observe two kinds of surfaces waves: the well known anelastic Rayleigh wave and a supershear surface wave that can be identified with another solution of Rayleigh’s secular equation.

 

 

 
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