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Full-Text Articles in Physics
Planar Anchoring Strength And Pitch Measurements In Achiral And Chiral Chromonic Liquid Crystals Using 90-Degree Twist Cells, Christine K. Mcginn , '16, Laura I. Laderman , '15, N. Zimmermann, H.-S. Kitzerow, Peter J. Collings
Planar Anchoring Strength And Pitch Measurements In Achiral And Chiral Chromonic Liquid Crystals Using 90-Degree Twist Cells, Christine K. Mcginn , '16, Laura I. Laderman , '15, N. Zimmermann, H.-S. Kitzerow, Peter J. Collings
Physics & Astronomy Faculty Works
Chromonic liquid crystals are formed by molecules that spontaneously assemble into anisotropic structures in water. The ordering unit is therefore a molecular assembly instead of a molecule as in thermotropic liquid crystals. Although it has been known for a long time that certain dyes, drugs, and nucleic acids form chromonic liquid crystals, only recently has enough knowledge been gained on how to control their alignment so that studies of their fundamental liquid crystal properties can be performed. In this article, a simple method for producing planar alignment of the nematic phase in chromonic liquid crystals is described, and this in …
Aggregation, Pretransitional Behavior, And Optical Properties In The Isotropic Phase Of Lyotropic Chromonic Liquid Crystals Studied In High Magnetic Fields, T. Ostapenko, Y. A. Nastishin, Peter J. Collings, S. N. Sprunt, O D. Lavrentovich, J. T. Gleeson
Aggregation, Pretransitional Behavior, And Optical Properties In The Isotropic Phase Of Lyotropic Chromonic Liquid Crystals Studied In High Magnetic Fields, T. Ostapenko, Y. A. Nastishin, Peter J. Collings, S. N. Sprunt, O D. Lavrentovich, J. T. Gleeson
Physics & Astronomy Faculty Works
We report results on the high-field magneto-optical response of four aqueous, lyotropic, chromonic liquid crystal formulations in the isotropic phase. Measurements of the field-induced birefringence at temperatures above the isotropic-nematic coexistence region at high magnetic fields reveal qualitative differences in different materials; these differences can be attributed to the nature of aggregation and are discussed within the context of competing aggregation models. Extending these measurements to very high fields and large optical phase differences reveals the presence of an unexpected optical phenomenon: magnetic field-induced circular birefringence, measured in the Voigt geometry, in a system containing no molecularly chiral species. Possible …
Initial Interest, Goals, And Changes In Class Scores In Introductory Physics For Life Sciences, Catherine Hirshfeld Crouch, Panchompoo Wisittanawat , '13, K. Ann Renninger
Initial Interest, Goals, And Changes In Class Scores In Introductory Physics For Life Sciences, Catherine Hirshfeld Crouch, Panchompoo Wisittanawat , '13, K. Ann Renninger
Educational Studies Faculty Works
To examine the effect of extensive life science applications on student attitudes to learning physics, we analyzed CLASS data from life science students in introductory physics. We compare the same students' responses from the first semester, taught with a standard syllabus, to the second semester, taught with extensive life science applications (IPLS). Although first semester responses become less favorable (pre to post), IPLS responses show an increase in favorable and a decrease in unfavorable responses. This is noteworthy because improvement is rarely observed without direct attention to attitudes/beliefs, and suggests IPLS courses are one possible approach to improving attitudes. Finally, …
Observation Of A Relaxed Plasma State In A Quasi-Infinite Cylinder, Timothy G. Gray , '01, Michael R. Brown, Daniel R. Dandurand , '11
Observation Of A Relaxed Plasma State In A Quasi-Infinite Cylinder, Timothy G. Gray , '01, Michael R. Brown, Daniel R. Dandurand , '11
Physics & Astronomy Faculty Works
A helical relaxed plasma state is observed in a long cylindrical volume. The cylinder is long enough so that the predicted minimum energy state is a close approximation to the infinite cylinder solution. The plasma is injected at v >= 50 km/s by a coaxial magnetized plasma gun located at one end of the cylindrical volume. The relaxed state is rapidly attained in 1-2 axial Alfven times after initiation of the plasma. Magnetic data are favorably compared with an analytical model. Magnetic data exhibit broadband fluctuations of the measured axial modes during the formation period. The broadband activity rapidly decays …
Diffuse Optical Tomography In The Presence Of A Chest Wall, H. Y. Ban, D. R. Busch, S. Pathak, Frank Mosacatelli, M. Machida, J. C. Schotland, V. A. Markel, A. G. Yodh
Diffuse Optical Tomography In The Presence Of A Chest Wall, H. Y. Ban, D. R. Busch, S. Pathak, Frank Mosacatelli, M. Machida, J. C. Schotland, V. A. Markel, A. G. Yodh
Physics & Astronomy Faculty Works
Diffuse optical tomography (DOT) has been employed to derive spatial maps of physiologically important chromophores in the human breast, but the fidelity of these images is often compromised by boundary effects such as those due to the chest wall. We explore the image quality in fast, data-intensive analytic and algebraic linear DOT reconstructions of phantoms with subcentimeter target features and large absorptive regions mimicking the chest wall. Experiments demonstrate that the chest wall phantom can introduce severe image artifacts. We then show how these artifacts can be mitigated by exclusion of data affected by the chest wall. We also introduce …