--- _id: '7186' abstract: - lang: eng text: "Tissue morphogenesis in developmental or physiological processes is regulated by molecular\r\nand mechanical signals. While the molecular signaling cascades are increasingly well\r\ndescribed, the mechanical signals affecting tissue shape changes have only recently been\r\nstudied in greater detail. To gain more insight into the mechanochemical and biophysical\r\nbasis of an epithelial spreading process (epiboly) in early zebrafish development, we studied\r\ncell-cell junction formation and actomyosin network dynamics at the boundary between\r\nsurface layer epithelial cells (EVL) and the yolk syncytial layer (YSL). During zebrafish epiboly,\r\nthe cell mass sitting on top of the yolk cell spreads to engulf the yolk cell by the end of\r\ngastrulation. It has been previously shown that an actomyosin ring residing within the YSL\r\npulls on the EVL tissue through a cable-constriction and a flow-friction motor, thereby\r\ndragging the tissue vegetal wards. Pulling forces are likely transmitted from the YSL\r\nactomyosin ring to EVL cells; however, the nature and formation of the junctional structure\r\nmediating this process has not been well described so far. Therefore, our main aim was to\r\ndetermine the nature, dynamics and potential function of the EVL-YSL junction during this\r\nepithelial tissue spreading. Specifically, we show that the EVL-YSL junction is a\r\nmechanosensitive structure, predominantly made of tight junction (TJ) proteins. The process\r\nof TJ mechanosensation depends on the retrograde flow of non-junctional, phase-separated\r\nZonula Occludens-1 (ZO-1) protein clusters towards the EVL-YSL boundary. Interestingly, we\r\ncould demonstrate that ZO-1 is present in a non-junctional pool on the surface of the yolk\r\ncell, and ZO-1 undergoes a phase separation process that likely renders the protein\r\nresponsive to flows. These flows are directed towards the junction and mediate proper\r\ntension-dependent recruitment of ZO-1. Upon reaching the EVL-YSL junction ZO-1 gets\r\nincorporated into the junctional pool mediated through its direct actin-binding domain.\r\nWhen the non-junctional pool and/or ZO-1 direct actin binding is absent, TJs fail in their\r\nproper mechanosensitive responses resulting in slower tissue spreading. We could further\r\ndemonstrate that depletion of ZO proteins within the YSL results in diminished actomyosin\r\nring formation. This suggests that a mechanochemical feedback loop is at work during\r\nzebrafish epiboly: ZO proteins help in proper actomyosin ring formation and actomyosin\r\ncontractility and flows positively influence ZO-1 junctional recruitment. Finally, such a\r\nmesoscale polarization process mediated through the flow of phase-separated protein\r\nclusters might have implications for other processes such as immunological synapse\r\nformation, C. elegans zygote polarization and wound healing." acknowledged_ssus: - _id: Bio - _id: LifeSc - _id: EM-Fac - _id: SSU alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Cornelia full_name: Schwayer, Cornelia id: 3436488C-F248-11E8-B48F-1D18A9856A87 last_name: Schwayer orcid: 0000-0001-5130-2226 citation: ama: Schwayer C. Mechanosensation of tight junctions depends on ZO-1 phase separation and flow. 2019. doi:10.15479/AT:ISTA:7186 apa: Schwayer, C. (2019). Mechanosensation of tight junctions depends on ZO-1 phase separation and flow. Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:7186 chicago: Schwayer, Cornelia. “Mechanosensation of Tight Junctions Depends on ZO-1 Phase Separation and Flow.” Institute of Science and Technology Austria, 2019. https://doi.org/10.15479/AT:ISTA:7186. ieee: C. Schwayer, “Mechanosensation of tight junctions depends on ZO-1 phase separation and flow,” Institute of Science and Technology Austria, 2019. ista: Schwayer C. 2019. Mechanosensation of tight junctions depends on ZO-1 phase separation and flow. Institute of Science and Technology Austria. mla: Schwayer, Cornelia. Mechanosensation of Tight Junctions Depends on ZO-1 Phase Separation and Flow. Institute of Science and Technology Austria, 2019, doi:10.15479/AT:ISTA:7186. short: C. Schwayer, Mechanosensation of Tight Junctions Depends on ZO-1 Phase Separation and Flow, Institute of Science and Technology Austria, 2019. date_created: 2019-12-16T14:26:14Z date_published: 2019-12-16T00:00:00Z date_updated: 2023-09-07T12:56:42Z day: '16' ddc: - '570' degree_awarded: PhD department: - _id: CaHe doi: 10.15479/AT:ISTA:7186 file: - access_level: closed checksum: 585583c1c875c5d9525703a539668a7c content_type: application/zip creator: cschwayer date_created: 2019-12-19T15:18:11Z date_updated: 2020-07-14T12:47:52Z file_id: '7194' file_name: DocumentSourceFiles.zip file_size: 19431292 relation: source_file - access_level: open_access checksum: 9b9b24351514948d27cec659e632e2cd content_type: application/pdf creator: cschwayer date_created: 2019-12-19T15:19:21Z date_updated: 2020-07-14T12:47:52Z file_id: '7195' file_name: Thesis_CS_final.pdf file_size: 19226428 relation: main_file file_date_updated: 2020-07-14T12:47:52Z has_accepted_license: '1' language: - iso: eng month: '12' oa: 1 oa_version: Published Version page: '107' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '1096' relation: dissertation_contains status: public - id: '7001' relation: part_of_dissertation status: public status: public supervisor: - first_name: Carl-Philipp J full_name: Heisenberg, Carl-Philipp J id: 39427864-F248-11E8-B48F-1D18A9856A87 last_name: Heisenberg orcid: 0000-0002-0912-4566 title: Mechanosensation of tight junctions depends on ZO-1 phase separation and flow type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2019' ... --- _id: '6681' abstract: - lang: eng text: "The first part of the thesis considers the computational aspects of the homotopy groups πd(X) of a topological space X. It is well known that there is no algorithm to decide whether the fundamental group π1(X) of a given finite simplicial complex X is trivial. On the other hand, there are several algorithms that, given a finite simplicial complex X that is simply connected (i.e., with π1(X) trivial), compute the higher homotopy group πd(X) for any given d ≥ 2.\r\nHowever, these algorithms come with a caveat: They compute the isomorphism type of πd(X), d ≥ 2 as an abstract finitely generated abelian group given by generators and relations, but they work with very implicit representations of the elements of πd(X). We present an algorithm that, given a simply connected space X, computes πd(X) and represents its elements as simplicial maps from suitable triangulations of the d-sphere Sd to X. For fixed d, the algorithm runs in time exponential in size(X), the number of simplices of X. Moreover, we prove that this is optimal: For every fixed d ≥ 2,\r\nwe construct a family of simply connected spaces X such that for any simplicial map representing a generator of πd(X), the size of the triangulation of S d on which the map is defined, is exponential in size(X).\r\nIn the second part of the thesis, we prove that the following question is algorithmically undecidable for d < ⌊3(k+1)/2⌋, k ≥ 5 and (k, d) ̸= (5, 7), which covers essentially everything outside the meta-stable range: Given a finite simplicial complex K of dimension k, decide whether there exists a piecewise-linear (i.e., linear on an arbitrarily fine subdivision of K) embedding f : K ↪→ Rd of K into a d-dimensional Euclidean space." alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Stephan Y full_name: Zhechev, Stephan Y id: 3AA52972-F248-11E8-B48F-1D18A9856A87 last_name: Zhechev citation: ama: Zhechev SY. Algorithmic aspects of homotopy theory and embeddability. 2019. doi:10.15479/AT:ISTA:6681 apa: Zhechev, S. Y. (2019). Algorithmic aspects of homotopy theory and embeddability. Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:6681 chicago: Zhechev, Stephan Y. “Algorithmic Aspects of Homotopy Theory and Embeddability.” Institute of Science and Technology Austria, 2019. https://doi.org/10.15479/AT:ISTA:6681. ieee: S. Y. Zhechev, “Algorithmic aspects of homotopy theory and embeddability,” Institute of Science and Technology Austria, 2019. ista: Zhechev SY. 2019. Algorithmic aspects of homotopy theory and embeddability. Institute of Science and Technology Austria. mla: Zhechev, Stephan Y. Algorithmic Aspects of Homotopy Theory and Embeddability. Institute of Science and Technology Austria, 2019, doi:10.15479/AT:ISTA:6681. short: S.Y. Zhechev, Algorithmic Aspects of Homotopy Theory and Embeddability, Institute of Science and Technology Austria, 2019. date_created: 2019-07-26T11:14:34Z date_published: 2019-08-08T00:00:00Z date_updated: 2023-09-07T13:10:36Z day: '08' ddc: - '514' degree_awarded: PhD department: - _id: UlWa doi: 10.15479/AT:ISTA:6681 file: - access_level: open_access checksum: 3231e7cbfca3b5687366f84f0a57a0c0 content_type: application/pdf creator: szhechev date_created: 2019-08-07T13:02:50Z date_updated: 2020-07-14T12:47:37Z file_id: '6771' file_name: Stephan_Zhechev_thesis.pdf file_size: 1464227 relation: main_file - access_level: closed checksum: 85d65eb27b4377a9e332ee37a70f08b6 content_type: application/octet-stream creator: szhechev date_created: 2019-08-07T13:03:22Z date_updated: 2020-07-14T12:47:37Z file_id: '6772' file_name: Stephan_Zhechev_thesis.tex file_size: 303988 relation: source_file - access_level: closed checksum: 86b374d264ca2dd53e712728e253ee75 content_type: application/zip creator: szhechev date_created: 2019-08-07T13:03:34Z date_updated: 2020-07-14T12:47:37Z file_id: '6773' file_name: supplementary_material.zip file_size: 1087004 relation: supplementary_material file_date_updated: 2020-07-14T12:47:37Z has_accepted_license: '1' language: - iso: eng license: https://creativecommons.org/licenses/by/4.0/ month: '08' oa: 1 oa_version: Published Version page: '104' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '6774' relation: part_of_dissertation status: public status: public supervisor: - first_name: Uli full_name: Wagner, Uli id: 36690CA2-F248-11E8-B48F-1D18A9856A87 last_name: Wagner orcid: 0000-0002-1494-0568 title: Algorithmic aspects of homotopy theory and embeddability tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2019' ... --- _id: '8182' abstract: - lang: eng text: "Suppose that $n\\neq p^k$ and $n\\neq 2p^k$ for all $k$ and all primes $p$. We prove that for any Hausdorff compactum $X$ with a free action of the symmetric group $\\mathfrak S_n$ there exists an $\\mathfrak S_n$-equivariant map $X \\to\r\n{\\mathbb R}^n$ whose image avoids the diagonal $\\{(x,x\\dots,x)\\in {\\mathbb R}^n|x\\in {\\mathbb R}\\}$.\r\n Previously, the special cases of this statement for certain $X$ were usually proved using the equivartiant obstruction theory. Such calculations are difficult and may become infeasible past the first (primary) obstruction. We\r\ntake a different approach which allows us to prove the vanishing of all obstructions simultaneously. The essential step in the proof is classifying the possible degrees of $\\mathfrak S_n$-equivariant maps from the boundary\r\n$\\partial\\Delta^{n-1}$ of $(n-1)$-simplex to itself. Existence of equivariant maps between spaces is important for many questions arising from discrete mathematics and geometry, such as Kneser's conjecture, the Square Peg conjecture, the Splitting Necklace problem, and the Topological Tverberg conjecture, etc. We demonstrate the utility of our result applying it to one such question, a specific instance of envy-free division problem." article_number: '1910.12628' article_processing_charge: No author: - first_name: Sergey full_name: Avvakumov, Sergey id: 3827DAC8-F248-11E8-B48F-1D18A9856A87 last_name: Avvakumov - first_name: Sergey full_name: Kudrya, Sergey id: ecf01965-d252-11ea-95a5-8ada5f6c6a67 last_name: Kudrya citation: ama: Avvakumov S, Kudrya S. Vanishing of all equivariant obstructions and the mapping degree. arXiv. apa: Avvakumov, S., & Kudrya, S. (n.d.). Vanishing of all equivariant obstructions and the mapping degree. arXiv. arXiv. chicago: Avvakumov, Sergey, and Sergey Kudrya. “Vanishing of All Equivariant Obstructions and the Mapping Degree.” ArXiv. arXiv, n.d. ieee: S. Avvakumov and S. Kudrya, “Vanishing of all equivariant obstructions and the mapping degree,” arXiv. arXiv. ista: Avvakumov S, Kudrya S. Vanishing of all equivariant obstructions and the mapping degree. arXiv, 1910.12628. mla: Avvakumov, Sergey, and Sergey Kudrya. “Vanishing of All Equivariant Obstructions and the Mapping Degree.” ArXiv, 1910.12628, arXiv. short: S. Avvakumov, S. Kudrya, ArXiv (n.d.). date_created: 2020-07-30T10:45:08Z date_published: 2019-10-28T00:00:00Z date_updated: 2023-09-07T13:12:17Z day: '28' department: - _id: UlWa external_id: arxiv: - '1910.12628' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1910.12628 month: '10' oa: 1 oa_version: Preprint project: - _id: 26611F5C-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: P31312 name: Algorithms for Embeddings and Homotopy Theory publication: arXiv publication_status: submitted publisher: arXiv related_material: record: - id: '11446' relation: later_version status: public - id: '8156' relation: dissertation_contains status: public status: public title: Vanishing of all equivariant obstructions and the mapping degree type: preprint user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 year: '2019' ... --- _id: '8185' abstract: - lang: eng text: "In this paper we study envy-free division problems. The classical approach to some of such problems, used by David Gale, reduces to considering continuous maps of a simplex to itself and finding sufficient conditions when this map hits the center of the simplex. The mere continuity is not sufficient for such a conclusion, the usual assumption (for example, in the Knaster--Kuratowski--Mazurkiewicz and the Gale theorem) is a certain boundary condition.\r\n We follow Erel Segal-Halevi, Fr\\'ed\\'eric Meunier, and Shira Zerbib, and replace the boundary condition by another assumption, which has the economic meaning of possibility for a player to prefer an empty part in the segment\r\npartition problem. We solve the problem positively when $n$, the number of players that divide the segment, is a prime power, and we provide counterexamples for every $n$ which is not a prime power. We also provide counterexamples relevant to a wider class of fair or envy-free partition problems when $n$ is odd and not a prime power." article_number: '1907.11183' article_processing_charge: No author: - first_name: Sergey full_name: Avvakumov, Sergey id: 3827DAC8-F248-11E8-B48F-1D18A9856A87 last_name: Avvakumov - first_name: Roman full_name: Karasev, Roman last_name: Karasev citation: ama: Avvakumov S, Karasev R. Envy-free division using mapping degree. arXiv. doi:10.48550/arXiv.1907.11183 apa: Avvakumov, S., & Karasev, R. (n.d.). Envy-free division using mapping degree. arXiv. https://doi.org/10.48550/arXiv.1907.11183 chicago: Avvakumov, Sergey, and Roman Karasev. “Envy-Free Division Using Mapping Degree.” ArXiv, n.d. https://doi.org/10.48550/arXiv.1907.11183. ieee: S. Avvakumov and R. Karasev, “Envy-free division using mapping degree,” arXiv. . ista: Avvakumov S, Karasev R. Envy-free division using mapping degree. arXiv, 1907.11183. mla: Avvakumov, Sergey, and Roman Karasev. “Envy-Free Division Using Mapping Degree.” ArXiv, 1907.11183, doi:10.48550/arXiv.1907.11183. short: S. Avvakumov, R. Karasev, ArXiv (n.d.). date_created: 2020-07-30T10:45:51Z date_published: 2019-07-25T00:00:00Z date_updated: 2023-09-07T13:12:17Z day: '25' department: - _id: UlWa doi: 10.48550/arXiv.1907.11183 external_id: arxiv: - '1907.11183' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1907.11183 month: '07' oa: 1 oa_version: Preprint project: - _id: 26611F5C-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: P31312 name: Algorithms for Embeddings and Homotopy Theory publication: arXiv publication_status: submitted related_material: link: - relation: later_version url: https://doi.org/10.1112/mtk.12059 record: - id: '8156' relation: dissertation_contains status: public status: public title: Envy-free division using mapping degree type: preprint user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 year: '2019' ... --- _id: '7524' abstract: - lang: eng text: "We prove a lower bound for the free energy (per unit volume) of the two-dimensional Bose gas in the thermodynamic limit. We show that the free energy at density $\\rho$ and inverse temperature $\\beta$ differs from the one of the non-interacting system by the correction term $4 \\pi \\rho^2 |\\ln a^2 \\rho|^{-1} (2 - [1 - \\beta_{\\mathrm{c}}/\\beta]_+^2)$. Here $a$ is the scattering length of the interaction potential, $[\\cdot]_+ = \\max\\{ 0, \\cdot \\}$ and $\\beta_{\\mathrm{c}}$ is the inverse Berezinskii--Kosterlitz--Thouless critical temperature for superfluidity. The result is valid in the dilute limit\r\n$a^2\\rho \\ll 1$ and if $\\beta \\rho \\gtrsim 1$." article_processing_charge: No author: - first_name: Andreas full_name: Deuchert, Andreas id: 4DA65CD0-F248-11E8-B48F-1D18A9856A87 last_name: Deuchert orcid: 0000-0003-3146-6746 - first_name: Simon full_name: Mayer, Simon id: 30C4630A-F248-11E8-B48F-1D18A9856A87 last_name: Mayer - first_name: Robert full_name: Seiringer, Robert id: 4AFD0470-F248-11E8-B48F-1D18A9856A87 last_name: Seiringer orcid: 0000-0002-6781-0521 citation: ama: Deuchert A, Mayer S, Seiringer R. The free energy of the two-dimensional dilute Bose gas. I. Lower bound. arXiv:191003372. apa: Deuchert, A., Mayer, S., & Seiringer, R. (n.d.). The free energy of the two-dimensional dilute Bose gas. I. Lower bound. arXiv:1910.03372. ArXiv. chicago: Deuchert, Andreas, Simon Mayer, and Robert Seiringer. “The Free Energy of the Two-Dimensional Dilute Bose Gas. I. Lower Bound.” ArXiv:1910.03372. ArXiv, n.d. ieee: A. Deuchert, S. Mayer, and R. Seiringer, “The free energy of the two-dimensional dilute Bose gas. I. Lower bound,” arXiv:1910.03372. ArXiv. ista: Deuchert A, Mayer S, Seiringer R. The free energy of the two-dimensional dilute Bose gas. I. Lower bound. arXiv:1910.03372, . mla: Deuchert, Andreas, et al. “The Free Energy of the Two-Dimensional Dilute Bose Gas. I. Lower Bound.” ArXiv:1910.03372, ArXiv. short: A. Deuchert, S. Mayer, R. Seiringer, ArXiv:1910.03372 (n.d.). date_created: 2020-02-26T08:46:40Z date_published: 2019-10-08T00:00:00Z date_updated: 2023-09-07T13:12:41Z day: '08' department: - _id: RoSe ec_funded: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1910.03372 month: '10' oa: 1 oa_version: Preprint page: '61' project: - _id: 25C6DC12-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '694227' name: Analysis of quantum many-body systems publication: arXiv:1910.03372 publication_status: draft publisher: ArXiv related_material: record: - id: '7790' relation: later_version status: public - id: '7514' relation: dissertation_contains status: public scopus_import: 1 status: public title: The free energy of the two-dimensional dilute Bose gas. I. Lower bound type: preprint user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 year: '2019' ...