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Aktuelle Veranstaltungen

 

Kolloquium

Thema:

DNA Origami Tools for Plasmonics, Superresolution and Sensing

Datum:

03.07.17

Uhrzeit:

16:15

Ort:

H6

Vortragender:

Prof. Dr. Philip Tinnefeld

TU Braunschweig

Inhalt:

In recent years, DNA nanotechnology has matured to enable robust production of complex nanostuctures and hybrid materials. We have combined DNA nanotechnology with sensitive optical detection to create functional single-molecule devices that enable new applications in single-molecule biophysics. Starting with superresolution nanorulers [1], a single-molecule mirage [2] and energy transfer switches [3] we developed DNA origami nano-adapters for targeted placement of single molecules in zeromode waveguides used for DNA sequencing [4]. Furthermore, a plasmonic fluorescence amplifier [5] is used for sensitive biosensing and single-molecule detection on low-tec detection devices such as a smartphone. Finally, we present a new molecular force spectroscopy employing DNA origami force clamps that work autonomously without any physical connection to the macroscopic world [6]. We used the conformer switching of a Holliday junction as a benchmark and studied the TATA-binding protein–induced bending of a DNA duplex under tension. The observed suppression of bending above 10 piconewtons provides further evidence of mechanosensitivity in gene regulation.
[1] Schmied, J.J. et al. DNA origami-based standards for quantitative fluorescence microscopy. Nature protocols 9, 1367-1391 (2014).
[2] Raab, M., Vietz, C., Stefani, F.D., Acuna, G.P. \& Tinnefeld, P. Shifting molecular localization by plasmonic coupling in a single-molecule mirage. Nature communications 8, 13966 (2017).
[3] Stein, I.H., Steinhauer, C. \& Tinnefeld, P. Single-Molecule Four-Color FRET Visualizes Energy-Transfer Paths on DNA Origami. J Am Chem Soc 133, 4193-4195 (2011).
[4] Pibiri, E., Holzmeister, P., Lalkens, B., Acuna, G.P. \& Tinnefeld, P. Single-molecule positioning in zeromode waveguides by DNA origami nanoadapters. Nano letters 14, 3499-3503 (2014).
[5] Acuna, G.P. et al. Fluorescence enhancement at docking sites of DNA-directed self-assembled nanoantennas. Science 338, 506-510 (2012).
[6] Nickels, P.C. et al. Molecular force spectroscopy with a DNA origami-based nanoscopic force clamp. Science 354, 305-307 (2016).

Ansprechpartner:

T. Huser

Kolloquium Mathematische Physik

Thema:

Random field of gradients - Critical Phenomena and Scaling limits

Datum:

02.06.17

Uhrzeit:

16:15

Ort:

V2-210/216

Vortragender:

Stefan Adams

University of Warwick

Inhalt:

Random fields of gradients are families of highly correlated random variables arising in the studies of e.g. random surfaces & interfaces and discrete Gaussian Free Fields (GFFs), random geometry, field theory, and elasticity theory. Recently their study has attained a lot of attention. There are several reasons for that. On one hand, these are approximations of critical systems and natural models for a macroscopic description of elastic systems as well as, in a different setting, for fluctuating phase interfaces. In addition, over continuum, the level lines of the GFF are connected to Schramm's SLE (an active field of modern mathematics for understanding critical phenomena) and the fields are natural space-time analog of Brownian motions and as such a simple random object of widespread application and great intrinsic beauty. Gradient fields are likely to be an universal class of models combining probability, analysis and physics in the study of critical phenomena, and these mass-less fields are also a starting point for many constructions in field theory. A more recent connection are mathematical models for the Cauchy-Born rule of materials, i.e., a microscopic approach to nonlinear elasticity. The latter class of models requires that interaction energies are non-convex functions of the gradients. Open problems over the last decades include unicity of Gibbs measures and strict convexity of the free energy as well as scaling limits to the Gaussian Free Field and the decay behaviour of two-point correlation functions. After giving a broad introduction to this recently active field of research we present in the talk Gaussian decay of correlations and the scaling to the Gaussian Free Field for a class of mass-less fields with non-convex interaction using a recent renormalisation group approach.

Ansprechpartner:

M. Baake

Seminar Hochenergiephysik

Thema:

Relativistic wide-angle galaxy bispectrum on the light-cone: All-sky analysis

Datum:

18.07.17

Uhrzeit:

14:15

Ort:

D6-135

Vortragender:

Daniele Bertacca

Argelander Institut für Astronomie, Bonn

Inhalt:

Given the important role that the galaxy bispectrum has recently acquired in cosmology and the scale and precision of forthcoming galaxy clustering observations, it is timely to derive the full expression of the large-scale bispectrum going beyond approximated treatments which neglect integrated terms or higher-order bias terms or use the Limber approximation. On cosmological scales, relativistic effects that arise from observing on the past light-cone alter the observed galaxy number counts, therefore leaving their imprints on N-point correlators at all orders. Working in spherical Bessel coordinates, in this talk I will show that it is possible to derive a compact expression for the power spectrum and bispectrum that encompasses all the physical effects at first and second order, including integrated (along the line of sight) terms.

Ansprechpartner:

D. Schwarz

Seminar Kondensierte Materie

Thema:

Connecting Spin Hamiltonians from DFT Calculations to Experiment

Datum:

06.04.17

Uhrzeit:

14:15

Ort:

D5-153

Vortragender:

Shadan Ghassemi

TU Berlin

Inhalt:

Ansprechpartner:

Jürgen Schnack

Seminar Mathematische Physik

Thema:

Non-orthogonality of eigenvectors from the Haagerup-Larsen theorem

Datum:

01.06.17

Uhrzeit:

17:00

Ort:

D5-153

Vortragender:

Wojciech Tarnowski

Jagiellonian University Krakow

Inhalt:

Biunitarily invariant ensembles have been thoroughly studied in recent years from the point of view of statistics of eigenvalues. An enhanced symmetry of the probability distribution function allows us to expect that all spectral properties will be determined by the singular values only. Indeed, for large matrices, a mapping between one-point densities is known as the Haagerup-Larsen theorem. Recently, this mapping has been extended to all k-point functions (Kieburg-Kösters). During my talk, I will present a recent extension of the Haagerup-Larsen theorem, which gives a simple mapping between the radial spectral cumulative distribution function and a certain one-point eigenvector correlation function, built out of (non-orthogonal) left- and right eigenvectors. I will discuss also its relation with the stability of the spectrum.

Ansprechpartner:

Gernot Akemann

Seminar AG Zufallsmatrizen

Thema:

Matrix product ensembles of Hermite-type

Datum:

21.06.17

Uhrzeit:

16:00

Ort:

V3-201

Vortragender:

Dang-Zheng Liu

Institute of Science and Technology Austria & University of Science and Technology of China

Inhalt:

We investigate spectral properties of a Hermitised random matrix product which, contrary to previous product ensembles, allows for eigenvalues on the full real line. We find an explicit expression of the joint probability density function as a bi-orthogonal ensemble. As an interesting example, we focus on the product of GUE and LUE matrices and provide explicit expressions both for the bi-orthogonal functions and the correlation kernel. Then a new double-side kernel is found at the origin, which is slightly different from the Bessel kernel. This talk is based on joint work with P. J. Forrester and J. R. Ipsen.

Ansprechpartner:

Gernot Akemann



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  • | Letzte Änderung: 23.11.2011
  •  Olaf Kaczmarek
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