12,209 research outputs found
NPA Hierarchy for Quantum Isomorphism and Homomorphism Indistinguishability
No full textMančinska and Roberson [FOCS'20] showed that two graphs are quantum isomorphic if and only if they are homomorphism indistinguishable over the class of planar graphs. Atserias et al. [JCTB'19] proved that quantum isomorphism is undecidable in general. The NPA hierarchy gives a sequence of semidefinite programming relaxations of quantum isomorphism. Recently, Roberson and Seppelt [ICALP'23] obtained a homomorphism indistinguishability characterization of the feasibility of each level of the Lasserre hierarchy of semidefinite programming relaxations of graph isomorphism. We prove a quantum analogue of this result by showing that each level of the NPA hierarchy of SDP relaxations for quantum isomorphism of graphs is equivalent to homomorphism indistinguishability over an appropriate class of planar graphs. By combining the convergence of the NPA hierarchy with the fact that the union of these graph classes is the set of all planar graphs, we are able to give a new proof of the result of Mančinska and Roberson [FOCS'20] that avoids the use of the theory of quantum groups. This homomorphism indistinguishability characterization also allows us to give a randomized polynomial-time algorithm deciding exact feasibility of each fixed level of the NPA hierarchy of SDP relaxations for quantum isomorphism
Lasserre Hierarchy for Graph Isomorphism and Homomorphism Indistinguishability
No full textWe show that feasibility of the level of the Lasserre semidefinite programming hierarchy for graph isomorphism can be expressed as a homomorphism indistinguishability relation. In other words, we define a class of graphs such that graphs and are not distinguished by the level of the Lasserre hierarchy if and only if they admit the same number of homomorphisms from any graph in . By analysing the treewidth of graphs in , we prove that the level of Sherali--Adams linear programming hierarchy is as strong as the level of Lasserre. Moreover, we show that this is best possible in the sense that cannot be lowered to for any . The same result holds for the Lasserre hierarchy with non-negativity constraints, which we similarly characterise in terms of homomorphism indistinguishability over a family of graphs. Additionally, we give characterisations of level- Lasserre with non-negativity constraints in terms of logical equivalence and via a graph colouring algorithm akin to the Weisfeiler--Leman algorithm. This provides a polynomial time algorithm for determining if two given graphs are distinguished by the level of the Lasserre hierarchy with non-negativity constraints.Full version. 36 pages, 6 figure
Evolution of cooperation among tumor cells
No full textThe evolution of cooperation has a well established theoretical framework based on game theory. This approach has made valuable contributions to a wide variety of disciplines, including political science, economics, and evolutionary biology. Existing cancer theory suggests that individual clones of cancer cells evolve independently from one another, acquiring all of the genetic traits or hallmarks necessary to form a malignant tumor. It is also now recognized that tumors are heterotypic, with cancer cells interacting with normal stromal cells within the issue microenvironment, including endothelial, stromal, and nerve cells. This tumor cell???stromal cell interaction in itself is a form of commensalism, because it has been demonstrated that these nonmalignant cells support and even enable tumor growth. Here, we add to this theory by regarding tumor cells as game players whose interactions help to determine their Darwinian fitness. We marshal evidence that tumor cells overcome certain host defenses by means of diffusible products. Our original contribution is to raise the possibility that two nearby cells can protect each other from a set of host defenses that neither could survive alone. Cooperation can evolve as byproduct mutualism among genetically diverse tumor cells. Our hypothesis supplements, but does not supplant, the traditional view of carcinogenesis in which one clonal population of cells develops all of the necessary genetic traits independently to form a tumor. Cooperation through the sharing of diffusible products raises new questions about tumorigenesis and has implications for understanding observed phenomena, designing new experiments, and developing new therapeutic approaches.Author manuscript. Published in final edited form as: Proc Natl Acad Sci U S A. 2006 September 5; 103(36): 13474-13479.The final published version of this article is located at: www.pnas.org/cgi/doi/10.1073/pnas.0606053103NIH U56 CA113004; to David E. AxelrodR.A. was supported by National Science Foundation (NSF) Grant SES-0240852. D.E.A. was supported by NSF Grant IIS-0312953, National Institutes of Health (NIH) Grant U56 CA113004, and New Jersey Commission on Cancer Research Grant 1076-CCR-SO. K.J.P. is an American Cancer Society Clinical Research Professor and is supported by NIH Grants CA69568, CA102872, and CA093900.NIH CA69568; to Kenneth J. PientaNIH CA102872; to Kenneth J. PientaNIH CA093900; to Kenneth J. PientaNSF SES-0240852; to Robert AxelrodNJ Commission on Cancer Research 1076-CCR-SO; to David E. AxelrodAlso available in PubMed Central. PMCID: PMC155738
Colon_Crypt_Model_041321.nlogo
No full textTitle: Colon_Crypt_Model_041321.nlogo
Research genre: Computer program
Creator: Axelrod, David E.
Date Created: 2021
Extent: 1 digital file (393 KB)
Intended Audience: Science
Description: Computer program that simulates and plots the dynamics of stem cells, transient amplifying cells, differentiated cells, and mutant cells in normal human colon crypts and early colon cancer. It has been calibrated with measurements of human biopsy specimens. Includes graphical user interface, detailed information text, and annotated code. Experiments can be run from the GUI without knowledge of coding, or from the Behavior Space Tool using example code or modified code. It has been used to simulate human colon cancer initiation, therapy, and prevention. Different chemotherapy or prevention intermittent dose schedules can be input. Chemotherapy of heterogeneous and drug resistant early colon cancers can be simulated. Circadian cell proliferation can be selected to investigate chronomodulated chemotherapy dose schedules. Simulated output can be saved in spreadsheet format, or as images of plots of cell numbers as function of time.
The model was developed in the application NetLogo version 5.3.1, and revisions made to also run in NetLogo version 6.2.0. The model will not run on the Web version of NetLogo. NetLogo is a multi-agent programmable modeling environment. It is authored by Uri Wilenski and developed at The Center for Connected Learning (CCL) and Computer-Based Modeling. It is multi-platform (Mac, Windows, or Linux) open source application.
NetLogo version 6.2.0, can be downloaded at http://ccl.northwestern.edu/netlogo/download.shtml. To download the computer program click on the red link “NLOGO" to the left.
Earlier versions of the model and its use have been described in the following publications: Theoret Biol Med Model. 2013;10:66-89. Cancer Chemother Pharmcol 2017;79:889-898. Converg Sci Phys Oncol 2017;3:035004. Cancer Inform 2019;18:1-8. JCO Clin Cancer Inform 2020;4:514-520. A forthcoming publication will describe results of circadian-timed chemotherapy.
Research Domain: Science
Subjects: Chronotherapy: Circadian: Colorectal cancer: Chemotherapy: Agent-based model
Rights statement: The author owns the copyright to this work
Disputatio philosophica de dependentia creaturae a Deo in esse, fieri, et operari
No full textquam auspice Deo , sub praesidio Dn. Ioh. Rod. Ottii ... amico examini subiicit David Holzhalbius author & respondens ...Diss. Hohe Schule Zürich, 169
NPA Hierarchy for Quantum Isomorphism and Homomorphism Indistinguishability
No full textMan\v{c}inska and Roberson~[FOCS'20] showed that two graphs are quantum
isomorphic if and only if they are homomorphism indistinguishable over the
class of planar graphs. Atserias et al.~[JCTB'19] proved that quantum
isomorphism is undecidable in general. The NPA hierarchy gives a sequence of
semidefinite programming relaxations of quantum isomorphism. Recently, Roberson
and Seppelt~[ICALP'23] obtained a homomorphism indistinguishability
characterization of the feasibility of each level of the Lasserre hierarchy of
semidefinite programming relaxations of graph isomorphism. We prove a quantum
analogue of this result by showing that each level of the NPA hierarchy of SDP
relaxations for quantum isomorphism of graphs is equivalent to homomorphism
indistinguishability over an appropriate class of planar graphs. By combining
the convergence of the NPA hierarchy with the fact that the union of these
graph classes is the set of all planar graphs, we are able to give a new proof
of the result of Man\v{c}inska and Roberson~[FOCS'20] that avoids the use of
the theory of quantum groups. This homomorphism indistinguishability
characterization also allows us to give a randomized polynomial-time algorithm
deciding exact feasibility of each fixed level of the NPA hierarchy of SDP
relaxations for quantum isomorphism.Comment: 34 Pages, 5 Figure
E-book : Industrial Transformation In The Developing World (author: Michael T. Rock & David P. Angel)
No full textArsip Kuliah Online 2010: E-book : Industrial Transformation In The Developing World (author: Michael T. Rock & David P. Angel
E-book : "industrial Transformations In The Developing World (author: Michael T. Rock & David. P Angel)
No full textArsip Kuliah Online 2010: E-book : "industrial Transformations In The Developing World (author: Michael T. Rock & David. P Angel
Landsat MSS classification of fire fuel types in Wood Buffalo National Park, northern Canada
No full textJ1: Global Ecology & Biogeography Letters; M3: Article; Milne, David Franklin, Steven E. Wilson, Bradley A. Ghitter, Geoff Heathcott, Mark McCaffrey, Thomas M. Ow, Charlotte F. Y.; Source Information: Mar1994, Vol. 4 Issue 2, p33; Subject Term: FOREST fires; Author-Supplied Keyword: Canada (Wood Buffalo National Park); Author-Supplied Keyword: Forest fire; Author-Supplied Keyword: Fuel type classification; Author-Supplied Keyword: Landsat data; Number of Pages: 0p; Document Type: Articl
David Audretsch: A Source of Inspiration, a Co-author, and a Friend
No full textIn this chapter, Enrico Santarelli discusses the profound impact that David had on his career. Beginning with a conference in Budapest, Santarelli and David bocame close friends and colleagues. They went on to collaborate on many papers and projects, several of which Santarelli highlights below
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