Institut für Theoretische Physik
Start / Aktuell
Juli  2015
Di
07.07.2015
Aquila + Bootes MPS
MPI für Sonnensystemforschung
11:00
Solar-Seminar

Sami K. Solanki
MPS

Polarisation in Astrophysics



Di
07.07.2015
Seminarraum A3.101
Theoretische Physik
14:15
Theoretisch-physikalisches Seminar

Matthias Kaminski
University of Alabama, Tuscaloosa

Quasinormal Modes of Electric and Magnetic Black Branes & Anisotropic Fluids Far From Equilibrium



Kontakt: S. Kehrein
Di
07.07.2015
SR 3, Institut für Theoretische Physik, A03.101
SFB 937
17:00
Seminar

Prof. Dr. Dieter Kube
UMG Göttingen, Abtl. Hämatologie und Onkologie

Cell migration and invasion of lymphoma cells in vitro and in xenograft models with particular focus to the role of Wnt signaling

Hodgkin’s lymphoma (HL) is characterized by a minority of malignant cells embedded in a background of reactive lymphoid stroma. Despite the identification of a complex network of deregulated pathways in HL, their influence on lymphoma migration, invasion, and the impact on the lymphoma microenvironment has not yet been investigated in detail.

Migration and invasion analysis have been carried out using the modified Boyden chamber assay, 3D-chemotaxis assays in combination with timelapse microscopy. For intervening signaling pathways chemical inhibitors, siRNA or corresponding overexpression plasmids for different ligands and pathway components have been used. A xenograft model for HL was established and evaluated using light microscopy, EM and micro-CT.

Comparing the migration rates of Non-Hodgkins Lymphoma and HLs, HL cells show the highest migration. Migration, invasion and adhesion of HL cells depend on autocrine signaling. The activity of this pathway in HLs is also important for lymphoma outgrowth and vascularization in a new xenograft model.

In this study the importance of a new pathway for HL cell migration, invasion, adhesion and the tumor outgrowth is shown as an important parameter of lymphoma progression.

Kontakt: Schmidt
Mi
08.07.2015
Aquila + Bootes MPS
MPI für Sonnensystemforschung
14:00
S3-Seminar

Zelia Ferret
IMPRS

Helioseismology of Subsurface Flows



Kontakt: Sonja Schuh
Mi
08.07.2015
Ludwig-Prandtl-Hörsaal, Am Faßberg 11, 37077 Göttingen
MPIDS
14:15
Kolloquium

Prof. Kurt Binder

Simulations of interfacial phenomena in soft
condensed matter and nanoscience

Computation of interfacial free energies between coexisting phases is a fundamental problem of statistical mechanics. The standard approach (van der Waals, Ginzburg-Landau etc.) assumes a continuation of the free energy of homogeneous states throughout the two-phase coexistence region. Beyond mean field, neither this continuation nor an "intrinsic" interfacial profile do exist! These problems are overcome by computer simulation. E.g., sampling the order parameter distribution function in the two-phase region yields the surface tension of both planar and curved interfaces, elucidating the problem of the "Tolman length". An alternative method analyses the capillary wave spectrum or the capillary wave-induced broadening of interfaces (examples include liquid-liquid and liquid-solid interfaces). Also methods to estimate the excess free energy due to walls and contact angles will be described. Then, an application showing ensemble inequivalence of systems under nanoconfinement will be discussed.

Kontakt: Marco Mazza
Mi
08.07.2015
Seminarraum 9, C.04.101
SFB 1073
14:15
SFB Seminar

Prof. Brian Benicewicz
University of South Carolina

Functionalization of nanoparticles by surface-initiated RAFT polymerization: Chemistry and applications

Reversible addition-fragmentation chain transfer (RAFT) polymerization has been applied to the controlled polymerization of various monomers under a broad range of conditions to prepare polymer materials with predetermined molecular weights, narrow polydispersities, and advanced architectures. The combination of the RAFT technique with polymer grafting techniques has been widely used as an approach to modify the surfaces of nanoparticles with a variety of functional polymers. In our work, we developed multiple approaches for attaching RAFT agents to the surface of nanoparticles with graft densities ranging from 0.01 to 0.8 chains/nm2. Using these surface-immobilized RAFT agents, styrenic, acrylate, and methacrylate monomers could be polymerized on the nanoparticle surfaces via surface-initiated RAFT polymerization in a controlled manner. The availability of the wide range of graft densities has allowed us to study the polymer chain behavior in both the brush and mushroom regions. This presentation will provide a general overview of the chemistry used to prepare polymer-grafted nanoparticles with precise control over the polymer chain variables, and a few select applications of grafted nanoparticles.

Mi
08.07.2015
Aquila + Bootes MPS
MPI für Sonnensystemforschung
14:30
S3-Seminar

Emanuele Papini
IMPRS

Linear Simulations of Acoustic Waves in Spotted Stars



Kontakt: Sonja Schuh
Mi
08.07.2015
Seminarraum Astrophysik (SR 17, F 05.104)
Astrophysik
16:15

Stellar activity features such as spots and plages can create complications in determining planetary parameters through spectroscopic and photometric observations. The overlap of a transiting planet and stellar spots/plages can produce anomalies in the transit light-curves that may lead to inaccurate estimation of the transit duration, depth and timing. We found that spot anomalies can lead to the transit duration be 4%, overestimated or underestimated, which can affect the planet orbital inclination estimation. The anomalies can also produce transit timing variations (TTV) with significant amplitudes of 200 seconds. Such a large TTV is similar to that induced by an Earth-mass planet on a transiting Jupiter in a three-day orbit. The transmission spectroscopy method, which is based on the measurements of the variations of planet-to-star radius ratio as a function of wavelength, is a powerful technique to study the atmospheric properties of transiting planets. Results of our simulations indicated that transit anomalies can lead to a significant underestimation or overestimation of the planet-to-star radius ratio as a function of wavelength. At short wavelengths, the effect can reach to difference of up to 10% in the planet-to-star radius ratio, mimicking the signature of Rayleigh scattering in the planetary atmosphere. Application of our calculations to HD 189733b and GJ 3470b transmission spectroscopy measurements and especially the reported excess in their planet-to-star radius ratio in the bluer part of the spectra, which were interpreted as the signature of blue sky, can exactly be reproduced by assuming that the planet occults a plage on the surface of these stars.

Kontakt: Dreizler
Do
09.07.2015
Ludwig Prandtl Lecture Hall AI Building, Am Faßberg 11, 37077 Göttingen
Nichtlineare Dynamik
10:15
Seminar: MPI für Dynamik und Selbstorganisation - Institut für Nichtlineare Dynamik, Universität Göttingen - Bernstein Focus Neurotechnology / Bernstein Center for Computational Neuroscience

Prof. Dr. Leonid Bunimovich
School of Mathematics, Georgia Institute of Technology, Atlanta, USA

1st lecture

ISOSPECTRAL TRANSFORMATIONS of NETWORKS

We will describe a new theory that allows to reduce, compress and enlarge networks while keeping all the information about its spectrum as well as eigenvectors. This technique allows to uncover various types of hierarchies ("scalings") within a network, the roles of nodes with respect to various characteristics, etc. Some applications to stability of dynamical networks will be discussed as well.

Only basic knowledge of linear algebra is required.

Do
09.07.2015
Seminarraum Astrophysik (SR 17, F 05.104)
Astrophysik
14:15

I will review what we have learned from studies with VLT/FLAMES about the importance of atomic diffusion in shaping the surface abundances of late-type stars. After 10+ years, we can conclude that, not unexpectedly, atomic diffusion does modify surface abundances of (especially metal-poor) dwarfs and turn-off stars, with consequences for isochrone-based age determinations and studies of Galactic chemical evolution. Furthermore, atomic diffusion drastically alleviates the cosmological lithium-7 discrepancy (Korn et al. 2006, Nature).

Kontakt: Husser
Do
09.07.2015
Sitzungssaal Mathematik
Theoretische Physik
15:15
Graduiertenkolleg 1493

Christian Becker
Uni Potsdam

TBA



Kontakt: K.-H. Rehren
Fr
10.07.2015
Ludwig Prandtl Lecture Hall AI Building, Am Faßberg 11, 37077 Göttingen
Nichtlineare Dynamik
14:15
Seminar: MPI für Dynamik und Selbstorganisation - Institut für Nichtlineare Dynamik, Universität Göttingen - Bernstein Focus Neurotechnology / Bernstein Center for Computational Neuroscience

Prof. Dr. Leonid Bunimovich
School of Mathematics, Georgia Institute of Technology, Atlanta, USA

2nd lecture

ISOSPECTRAL TRANSFORMATIONS of NETWORKS

We will describe a new theory that allows to reduce, compress and enlarge networks while keeping all the information about its spectrum as well as eigenvectors. This technique allows to uncover various types of hierarchies ("scalings") within a network, the roles of nodes with respect to various characteristics, etc. Some applications to stability of dynamical networks will be discussed as well.

Only basic knowledge of linear algebra is required.

So
12.07.2015
Astrophysik
00:00



Kontakt: S. Dreizler
Mo
13.07.2015
SR4 oder Sitzungszimmer Mathematik
Theoretische Physik
14:15



Kontakt: K.-H. Rehren
Mo
13.07.2015
Ludwig Prandtl Lecture Hall AI Building, Am Faßberg 11, 37077 Göttingen
Nichtlineare Dynamik
17:15
Seminar: MPI für Dynamik und Selbstorganisation - Institut für Nichtlineare Dynamik, Universität Göttingen - Bernstein Focus Neurotechnology / Bernstein Center for Computational Neuroscience

Dr. Joseph Lizier
School of Civil Engineering, The University of Sydney, Australia

What is "information dynamics" and what can it tell us?

The space-time dynamics of interactions in complex systems, artificial life, neural data, etc., are often described using terminology of information processing or computation, in particular with reference to information being stored, transfered and modified in these systems. In this talk, I describe a framework -- information dynamics -- that we have used to quantify each of these operations on information, and their dynamics in space and time. Not only does this framework quantitatively align with natural qualitative descriptions of these systems, it provides multiple complementary perspectives on how, where and why a system is exhibiting complexity. We will review various applications of this framework at a high level, describing what it can and indeed has revealed in these domains. In particular, using applications to cellular automata, flocking models and neural images, we show that the space-time dynamics of information storage, transfer and modification directly reveal how distributed computation is implemented in a system, highlighting information processing hot-spots and emergent computational structures such as information cascades. Next, via applications to several models of dynamical networks, RoboCup football data as well as human brain images, we demonstrate how information dynamics relates the structure of complex networks to their function, and how it can invert such analysis to infer structure from dynamics. Finally, we explore maximisations in capacity for these operations on information as a system approaches criticality (e.g. using the Ising model), and the extent to which they may be used to guide self-organisation.


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