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Articles 1 - 7 of 7
Full-Text Articles in Physics
Distributions Of Long-Lived Radioactive Nuclei Provided By Star-Forming Environments, Marco Fatuzzo, Fred Adams
Distributions Of Long-Lived Radioactive Nuclei Provided By Star-Forming Environments, Marco Fatuzzo, Fred Adams
Faculty Scholarship
Radioactive nuclei play an important role in planetary evolution by providing an internal heat source, which affects planetary structure and helps facilitate plate tectonics. A minimum level of nuclear activity is thought to be necessary—but not sufficient—for planets to be habitable. Extending previous work that focused on short-lived nuclei, this paper considers the delivery of long-lived radioactive nuclei to circumstellar disks in star forming regions. Although the long-lived nuclear species are always present, their abundances can be enhanced through multiple mechanisms. Most stars form in embedded cluster environments, so that disks can be enriched directly by intercepting ejecta from supernovae …
Student Understanding Of The Boltzmann Factor, Trevor I. Smith, Donald B. Mountcastle, John R. Thompson
Student Understanding Of The Boltzmann Factor, Trevor I. Smith, Donald B. Mountcastle, John R. Thompson
Physics and Astronomy Faculty Scholarship
We present results of our investigation into student understanding of the physical significance and utility of the Boltzmann factor in several simple models. We identify various justifications, both correct and incorrect, that students use when answering written questions that require application of the Boltzmann factor. Results from written data as well as teaching interviews suggest that many students can neither recognize situations in which the Boltzmann factor is applicable nor articulate the physical significance of the Boltzmann factor as an expression for multiplicity, a fundamental quantity of statistical mechanics. The specific student difficulties seen in the written data led us …
Identifying Student Difficulties With Heat Engines, Entropy, And The Carnot Cycle, Trevor I. Smith, Warren M. Christensen, Donald B. Mountcastle, John R. Thompson
Identifying Student Difficulties With Heat Engines, Entropy, And The Carnot Cycle, Trevor I. Smith, Warren M. Christensen, Donald B. Mountcastle, John R. Thompson
Physics and Astronomy Faculty Scholarship
We report on several specific student difficulties regarding the second law of thermodynamics in the context of heat engines within upper-division undergraduate thermal physics courses. Data come from ungraded written surveys, graded homework assignments, and videotaped classroom observations of tutorial activities. Written data show that students in these courses do not clearly articulate the connection between the Carnot cycle and the second law after lecture instruction. This result is consistent both within and across student populations. Observation data provide evidence for myriad difficulties related to entropy and heat engines, including students’ struggles in reasoning about situations that are physically impossible …
Temperature Dependent Surface Reconstruction Of Freely Suspended Films Of 4-N-Heptyloxybenzylidene-4-N-Heptylaniline, Daniel E. Martinez Zambrano
Temperature Dependent Surface Reconstruction Of Freely Suspended Films Of 4-N-Heptyloxybenzylidene-4-N-Heptylaniline, Daniel E. Martinez Zambrano
Lawrence University Honors Projects
Surfaces of freely suspended thick films of 4-n-heptyloxybenzylidene-4-n-heptylaniline (7O.7) in the crystalline-B phase have been imaged using non-contact mode atomic force microscopy. Steps are observed on the surface of the film with a height of 3.0 +/- 0.1 nm corresponding to the upright molecular length of 7O.7. In addition, we find that the step width varies with temperature between 56 and 59 degrees C. The steps are many times wider than the molecular length, suggesting that the steps are not on the surface but instead originate from edge dislocations in the interior. Using a strain model for liquid crystalline layers …
Time-Frequency Analysis Reveals Pairwise Interactions In Insect Swarms, James G. Puckett, Rui Ni, Nicholas T. Ouellette
Time-Frequency Analysis Reveals Pairwise Interactions In Insect Swarms, James G. Puckett, Rui Ni, Nicholas T. Ouellette
Physics and Astronomy Faculty Publications
The macroscopic emergent behavior of social animal groups is a classic example of dynamical self-organization, and is thought to arise from the local interactions between individuals. Determining these interactions from empirical data sets of real animal groups, however, is challenging. Using multicamera imaging and tracking, we studied the motion of individual flying midges in laboratory mating swarms. By performing a time-frequency analysis of the midge trajectories, we show that the midge behavior can be segmented into two distinct modes: one that is independent and composed of low-frequency maneuvers, and one that consists of higher-frequency nearly harmonic oscillations conducted in synchrony …
Discrete Excitation Spectrum Of A Classical Harmonic Oscillator In Zero-Point Radiation, Wayne Cheng-Wei Huang, Herman Batelaan
Discrete Excitation Spectrum Of A Classical Harmonic Oscillator In Zero-Point Radiation, Wayne Cheng-Wei Huang, Herman Batelaan
Department of Physics and Astronomy: Faculty Publications
We report that upon excitation by a single pulse, a classical harmonic oscillator immersed in the classical electromagnetic zero-point radiation exhibits a discrete harmonic spectrum in agreement with that of its quantum counterpart. This result is interesting in view of the fact that the vacuum field is needed in the classical calculation to obtain the agreement.
Charged Particle Dynamics In The Magnetic Field Of A Long Straight Current-Carrying Wire, M. Fatuzzo, A. Prentice, T. Toepker
Charged Particle Dynamics In The Magnetic Field Of A Long Straight Current-Carrying Wire, M. Fatuzzo, A. Prentice, T. Toepker
Faculty Scholarship
The article discusses the concept behind motion of a charged particle in a non-uniform filed of a wire carrying current. Topics discussed include possible types of motion in a current carrying field, vector analysis of velocity and magnetic field of the particle and Coupled differential equations.