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Full-Text Articles in Physics
Optimization Of Detergent-Mediated Reconstitution Of Influenza A M2 Protein Into Proteoliposomes, Catherine Hirshfeld Crouch, Margaret H. Bost , '17, Tae H. Kim , '14, Bryan M. Green , '16, Douglas Stuart Arbuckle , '17, Carl H. Grossman, Kathleen P. Howard
Optimization Of Detergent-Mediated Reconstitution Of Influenza A M2 Protein Into Proteoliposomes, Catherine Hirshfeld Crouch, Margaret H. Bost , '17, Tae H. Kim , '14, Bryan M. Green , '16, Douglas Stuart Arbuckle , '17, Carl H. Grossman, Kathleen P. Howard
Physics & Astronomy Faculty Works
We report the optimization of detergent-mediated reconstitution of an integral membrane-bound protein, full-length influenza M2 protein, by direct insertion into detergent-saturated liposomes. Detergent-mediated reconstitution is an important method for preparing proteoliposomes for studying membrane proteins, and must be optimized for each combination of protein and membrane constituents used. The purpose of the reconstitution was to prepare samples for site-directed spin-labeling electron paramagnetic resonance (SDSL-EPR) studies. Our goals in optimizing the protocol were to minimize the amount of detergent used, reduce overall proteoliposome preparation time, and confirm the removal of all detergent. The liposomes were comprised of (1-palmitoyl-2-oleyl-sn-glycero-phosphocholine (POPC) and 1-palmitoyl-2-oleyl-sn-glycero-3-[phospho-rac-(1-glycerol)] …
Cosmological Implications Of Ultralight Axionlike Fields, V. Poulin, Tristan L. Smith, D. Grin, R. Karwal, M. Kamionkowski
Cosmological Implications Of Ultralight Axionlike Fields, V. Poulin, Tristan L. Smith, D. Grin, R. Karwal, M. Kamionkowski
Physics & Astronomy Faculty Works
Cosmological observations are used to test for imprints of an ultralight axionlike field (ULA), with a range of potentials V(ϕ)∝[1−cos(ϕ/f)]ⁿ set by the axion-field value ϕ and decay constant f. Scalar field dynamics dictate that the field is initially frozen and then begins to oscillate around its minimum when the Hubble parameter drops below some critical value. For n=1, once dynamical, the axion energy density dilutes as matter; for n=2 it dilutes as radiation and for n=3 it dilutes faster than radiation. Both the homogeneous evolution of the ULA and the dynamics of its linear perturbations are included, using an …
Brownian Dynamics Of Particles “Dressed” By Chiral Director Configurations In Lyotropic Chromonic Liquid Crystals, A. Martinez, Peter J. Collings, A. G. Yodh
Brownian Dynamics Of Particles “Dressed” By Chiral Director Configurations In Lyotropic Chromonic Liquid Crystals, A. Martinez, Peter J. Collings, A. G. Yodh
Physics & Astronomy Faculty Works
We study Brownian dynamics of colloidal spheres, with planar anchoring conditions, suspended in the nematic phase of the lyotropic chromonic liquid crystal disodium chromoglycate (DSCG). Unlike typical liquid crystals, the unusually small twist elastic modulus of DSCG permits two energetically distinct helical distortions (twisted tails) of the nematic director to “dress” the suspended spheres. Video microscopy is used to characterize the helical distortions versus particle size and to measure particle mean-square displacements. Diffusion coefficients parallel and perpendicular to the far-field director, and their anisotropy ratio, are different for the two twisted tail configurations. Moreover, the crossover from subdiffusive to diffusive …
Sources Of Student Engagement In Introductory Physics For Life Sciences, Benjamin D. Geller , '01, C. Turpen, Catherine Hirshfeld Crouch
Sources Of Student Engagement In Introductory Physics For Life Sciences, Benjamin D. Geller , '01, C. Turpen, Catherine Hirshfeld Crouch
Physics & Astronomy Faculty Works
We explore the sources of student engagement with curricular content in an Introductory Physics for Life Science (IPLS) course at Swarthmore College. Do IPLS students find some life-science contexts more interesting than others, and, if so, what are the sources of these differences? We draw on three sources of student data to answer this question: (1) quantitative survey data illustrating how interested students were in particular contexts from the curriculum, (2) qualitative survey data in which students describe the source of their interest in these particular contexts, and (3) interview data in which students reflect on the contexts that were …
Magnetothermodynamics: Measurements Of The Thermodynamic Properties In A Relaxed Magnetohydrodynamic Plasma, M. Kaur, Luke J. Barbano , '18, Emma M. Suen-Lewis , '18, Jaron E. Shrock , '18, A. D. Light, D. A. Schaffner, Michael R. Brown, S. Woodruff, T. Meyer
Magnetothermodynamics: Measurements Of The Thermodynamic Properties In A Relaxed Magnetohydrodynamic Plasma, M. Kaur, Luke J. Barbano , '18, Emma M. Suen-Lewis , '18, Jaron E. Shrock , '18, A. D. Light, D. A. Schaffner, Michael R. Brown, S. Woodruff, T. Meyer
Physics & Astronomy Faculty Works
We have explored the thermodynamics of compressed magnetized plasmas in laboratory experiments and we call these studies ‘magnetothermodynamics’. The experiments are carried out in the Swarthmore Spheromak eXperiment device. In this device, a magnetized plasma source is located at one end and at the other end, a closed conducting can is installed. We generate parcels of magnetized plasma and observe their compression against the end wall of the conducting cylinder. The plasma parameters such as plasma density, temperature and magnetic field are measured during compression using HeNe laser interferometry, ion Doppler spectroscopy and a linear dot{B} probe array, respectively. To …
Measuring The Equations Of State In A Relaxed Magnetohydrodynamic Plasma, M. Kaur, Luke J. Barbano , '18, Emma M. Suen-Lewis , '18, Jaron E. Shrock , '18, A. D. Light, Michael R. Brown
Measuring The Equations Of State In A Relaxed Magnetohydrodynamic Plasma, M. Kaur, Luke J. Barbano , '18, Emma M. Suen-Lewis , '18, Jaron E. Shrock , '18, A. D. Light, Michael R. Brown
Physics & Astronomy Faculty Works
We report measurements of the equations of state of a fully relaxed magnetohydrodynamic (MHD) laboratory plasma. Parcels of magnetized plasma, called Taylor states, are formed in a coaxial magnetized plasma gun, and are allowed to relax and drift into a closed flux conserving volume. Density, ion temperature, and magnetic field are measured as a function of time as the Taylor states compress and heat. The theoretically predicted MHD and double adiabatic equations of state are compared to experimental measurements. We find that the MHD equation of state is inconsistent with our data.
Life Science Students’ Attitudes, Interest, And Performance In Introductory Physics For Life Sciences: An Exploratory Study, Catherine Hirshfeld Crouch, Panchompoo Wisittanawat , '13, Ming Cai , '11
Life Science Students’ Attitudes, Interest, And Performance In Introductory Physics For Life Sciences: An Exploratory Study, Catherine Hirshfeld Crouch, Panchompoo Wisittanawat , '13, Ming Cai , '11
Educational Studies Faculty Works
In response to national calls for improved physical sciences education for students pursuing careers in the life sciences and medicine, reformed introductory physics for life sciences (IPLS) courses are being developed. This exploratory study is among the first to assess the effect of an IPLS course on students’ attitudes, interest, and performance. The IPLS course studied was the second semester of introductory physics, following a standard first semester course, allowing the outcomes of the same students in a standard course and in an IPLS course to be compared. In the IPLS course, each physics topic was introduced and elaborated in …
Temperature And Lifetime Measurements In The Ssx Wind Tunnel, M. Kaur, Kaitlin D. Gelber , '20, A. D. Light, Michael R. Brown
Temperature And Lifetime Measurements In The Ssx Wind Tunnel, M. Kaur, Kaitlin D. Gelber , '20, A. D. Light, Michael R. Brown
Physics & Astronomy Faculty Works
We describe ion and electron temperature measurements in the Swarthmore Spheromak Experiment (SSX) MHD wind tunnel with the goal of understanding limitations on the lifetime of our Taylor-state plasma. A simple model based on the equilibrium eigenvalue and Spitzer resistivity predicted the lifetime satisfactorily during the first phase of the plasma evolution. We measured an average Tₑ along a chord by taking the ratio of the CIII97.7 nm to CIV155 nm line intensities using a vacuum ultraviolet (VUV) monochromator. We also recorded local measurements of Tₑ and nₑ using a double Langmuir probe in order to inform our interpretation of …