Nelson, Philip
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Publication Beyond Conformal Field Theory(1990-06-01) Nelson, Philip CThis is an account of some recent work done with H. S. La [1] [2], based ultimately on the work of Fischler and Susskind [3] and Polchinski [4].Publication Introduction to Sigma Model Anomalies, in Symposium on Anomalies, Geometry, and Topology(1985-03-01) Nelson, Philip CTalk presented at the Symposium on Anomalies, Topology, and Geometry, Argonne National Laboratory, March, 1985.Publication Teaching Biological Physics(2005-03-01) Goldstein, Raymond E; Nelson, Philip C; Powers, Thomas RPublication New Measurements of DNA Twist Elasticity(1998-05-01) Nelson, Philip CThe symmetries of the DNA double helix require a new term in its linear response to stress: the coupling between twist and stretch. Recent experiments with torsionally constrained single molecules give the first direct measurement of this new material parameter. We extract its value from a recent experiment. Finally, we sketch the effect of constrained twist on entropic elasticity of DNA arising from the connection between Link, Twist, and Writhe.Publication Analytic Structure of Two Dimensional Quantum Field Theory(1986-08-01) Nelson, Philip CTalk presented at the Conference on Mathematical Aspects of String Theory at La Jolla, California in August 1986.Publication Spontaneous Expulsion of Giant Lipid Vesicles Induced by Laser Tweezers(1997) Moroz, J David; Nelson, Philip C; Bar-Ziv, Roy; Moses, ElishaIrradiation of a giant unilamellar lipid bilayer vesicle with a focused laser spot leads to a tense pressurized state which persists indefinitely after laser shutoff. If the vesicle contains another object it can then be gently and continuously expelled from the tense outer vesicle. Remarkably, the inner object can be almost as large as the parent vesicle; its volume is replaced during the exit process. We offer a qualitative theoretical model to explain these and related phenomena. The main hypothesis is that the laser trap pulls in lipid and ejects it in the form of submicron objects, whose osmotic activity then drives the expulsion.Publication Hidden Symmetry in Topological Gravity(1991) Distler, Jacques; Nelson, Philip CTalk presented by P.N. at “Mathematics and Physics of Strings,” Berkeley and “Topology and Geometry in Theoretical Physics,” Turku (Finland), 1991.Publication Activities and Classroom Demonstrations in Biological Physics: A resource document(2018-07-30) Nelson, Philip C; Berner, WilliamWe give detailed recipes for a number of classroom demonstrations relevant to biological physics instruction. We developed them mainly for use in 2nd-3rd year undergraduate Physics courses. But you can (and we do) use them for primary school, through high school, up to PhD candidates. You adapt the words for each audience, but a phenomenon is a phenomenon. We also outline a 1-hour introduction to Python for undergraduate scientific computing. Finally we document some outcomes from courses taught at U Pennsylvania using these resources and others cited here. This material was presented at a workshop at the AAPT meeting in July 2018.Publication A Student’s Guide to Matlab for Physical Modeling(2018-08-14) Nelson, Philip C; Dodson, TomThis tutorial aims to help you teach yourself enough of the Matlab programming language to get started on physical modeling, and particularly the problems appearing in Physical Models of Living Systems (Nelson, 2015). This is not an official publication of The MathWorks, Inc. We attempt to maintain it, but no claim is made that every suggestion made here will work properly with future versions of Matlab. This is a free online document. Code listings that appear in this document, errata, and more can be found online via http://www.physics.upenn.edu/biophys/PMLS/Student ; code can also be accessed by following the links that appear in the far left margins of this document. A companion to this tutorial covers similar techniques, but with the Python programming language (Kinder & Nelson, 2018).Publication The Ætiology of Sigma Model Anomalies(1985-03-01) Moore, Gregory; Nelson, Philip CCertain nonlinear sigma models with fermions are ill-defined due to an anomaly which exhibits characteristics of both the nonabelian gauge theory anomaly and the SU(2) anomaly. The simplest way to diagnose the anomaly involves consideration of the global topology of the theory. We review the mathematical methods needed for this analysis and apply them to several supersymmetric sigma models. Some of these are found to be anomalous.