לוח שנה משולב

It is a well-known result from Hermann Weyl that if alpha is an irrational number in [0,1) then the number of visits of successive multiples of alpha modulo one in an interval contained in [0,1) is proportional to the size of the interval. In this talk we will revisit this problem, now looking at finer joint asymptotics of visits to several intervals with rational end points. We observe that the visit distribution can be modelled using random affine transformations

Primates live in environments characterized by continuous, complex cycles of social interactions, where the actions of any group member necessarily influences those of the other members. This raises the question of the extent to which adaptive behavior in social encounters involves specialized mechanisms to represent others’ intentions and affective states. In my talk, I will explore this topic at the behavioral level - asking whether monkeys take into account the welfare of their conspecific when making decisions- and at the brain level - asking what type of information about a social partner is encoded by single neurons in the amygdala and anterior insula. I will try yo argue that these two structures carry neuronal mechanisms for empathy and perspective taking.

Gut IgA production plays important an role in both shaping the composition of the gut commensal microbiota and in the protection from pathogens entering through the mucosa. While many recent studies have addressed interactions between the microbiota and IgA, fewer has studied in induction of IgA response, in particular at an antigen-specific level. Using cholera toxin conjugated to the well-known B cell hapten NP as an antigen we have followed antigen-specific gut IgA responses in vivo and compared them to response against antigens distributed systemically. In this seminar I will discuss the initiation of the response in the small intestine that differ from systemic responses in that B cells in PP invade pre-existing germinal centres (GC) rather than forming new GC. Furthermore, I will discuss the presence of subtypes of activated B cells in the PP during the response, where some B cells appear to migrate from the germinal centre, and how this allows for synchronization of the response between distinct PP along the gut. Finally, I will discuss the formation of life long B cell memory following oral immunization.

The knowledge of all correlation functions of a system is equivalent to solving the corresponding quantum many-body problem. If one can identify the relevant degrees of freedom, the knowledge of a finite set of correlation functions is in many cases sufficient to determine a sufficiently accurate solution of the corresponding field theory. Complete factorization is equivalent to identifying the relevant degrees of freedom where the Hamiltonian becomes diagonal. I will give examples how one can apply this powerful theoretical concept in experiment.

Work performed in collaboration with E.Demler (Harvard), Th. Gasenzer und J. Berges (Heidelberg). Supported by the Wittgenstein Prize, the Austrian Science Foundation (FWF): SFB FoQuS: F40-P10 and the EU: ERC-AdG QuantumRelax
[1] M. Gring et al., Science, 337, 1318 (2012);
[2] T. Langen et al., Science 348 207-211 (2015).
[3] T. Schweigler et al., Nature 545, 323 (2017), arXiv:1505.03126

Alternative splicing (AS) is a mechanism that increases transcriptomic and proteomic diversity by allowing the generation of multiple mRNA products from a single gene. A strong connection was established between AS and carcinogenesis. We recently developed a method that integrates all known physical interaction (protein-DNA, protein-RNA, protein-protein), gene expression and AS data to construct the largest map of transcriptomic and proteomic interactions leading to cancerous splicing aberrations defined to date and identify driver pathways therein. The method was already applied to colon adenocarcinoma and non-small-cell lung carcinoma. I will also talk about the link between chromatin organization and epigenetics markers and how they are related to the appearance of warm-blooded organisms and exon selection.

Neighboring neurons in motor cortex exhibit diverse selectivity during sensation, movement preparation, and movement execution. Neuronal selectivity could emerge from diverse mechanisms, including selective connectivity and nonlinear interactions of synaptic inputs in dendrites. We studied dendritic integration in the anterior motor cortex of mice performing a tactile discrimination task with a delayed response (Guo and Li et al., 2014). We constructed a two-photon microscope that allows rapid (~15 Hz) imaging of up to 300 µm of contiguous dendrite while resolving calcium transients in individual dendritic spines. Two galvanometers and a remote focusing mirror (Botcherby et al., 2008) steer 16 kHz lines (24 µm extent) produced by a resonant mirror arbitrarily in three dimensions. Pyramidal neurons were labeled sparsely with GCaMP6f in transgenic mice. We imaged spine and dendritic calcium transients, as well as somatic calcium transients associated with action potentials. We developed methods to computationally remove the influence of backpropagating action potentials (bAPs), which allowed us to quantify the selectivity of spines and dendritic segments during sensation, movement preparation, and movement execution. Nearby spines and dendritic segments share similar selectivity (length constant of signal correlation, ~30 µm). This clustering was more often seen in distal than in proximal dendrites. Using a measure of local autocorrelation, we also found that this reflects distinct “hotspot” locations on the dendrite where nearby dendrite and spines are co-active in time. Hotspot selectivity was correlated with the behavioral selectivity of somatic spikes, suggesting that these locations may have privileged influence over the output of the cell.