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Jul 2009

Volume 77, Issue 7, pp. 581-672

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Publishing PER Articles in AJP and PRST-PER

Charles Henderson and Robert Beichner

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 581

Online Publication Date: Jun 2009

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Abstract Unavailable
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01.30.-y Physics literature and publications
01.40.Fk Research in physics education
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Resource Letter PBM-1: Physics of biomolecular machines

Debashish Chowdhury

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 583 | Cited 1 time

Online Publication Date: Jun 2009

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All living creatures are made of cells. The cell is the structural and functional unit of life. This Resource Letter serves as a guide to the literature on nano-machines, which drive not only intracellular movements but also motility of the cell. These machines are usually proteins or macromolecular assemblies that require appropriate fuel for their operations. Although, traditionally, these machines were subjects of investigation in biology and biochemistry, increasing use of the concepts and techniques of physics in recent years have contributed to the quantitative understanding of the fundamental principles underlying their operational mechanisms. The possibility of exploiting these principles for the design and control of artificial nanomachines has opened up a new frontier in the bottom-up approach to nanotechnology.
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01.30.Rr Surveys and tutorial papers; resource letters
87.00.00 Biological and medical physics

Analogy between one-dimensional chain models and graphene

A. Matulis and F. M. Peeters

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 595

Online Publication Date: Jun 2009

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The electron and hole spectrum in single and bilayer graphene is derived from known one-dimensional models, and the relation between the spectrum and symmetry of the lattice is shown.
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03.65.-w Quantum mechanics
73.00.00 Electronic structure and electrical properties of surfaces, interfaces, thin films, and low-dimensional structures

AC-driven Brownian motors: A Fokker-Planck treatment

S. Denisov, P. Hänggi, and J. L. Mateos

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 602 | Cited 5 times

Online Publication Date: Jun 2009

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We consider a model of AC-driven Brownian motors consisting of a classical particle which is placed in a potential that is periodic in space and time and which is coupled to a heat bath. The effects of fluctuations and dissipation are studied by a time-dependent Fokker-Planck equation. The approach lets us map the original stochastic problem onto a system of ordinary linear algebraic equations. The solution of the equations provides complete information about ratchet transport, avoiding the disadvantages of direct stochastic calculations such as long transients and large statistical fluctuations. The Fokker-Planck approach to dynamical ratchets opens the possibility for further generalizations.
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05.00.00 Statistical physics, thermodynamics, and nonlinear dynamical systems

What does it mean to modify or test Newton’s second law?

Shahen Hacyan

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 607 | Cited 1 time

Online Publication Date: Jun 2009

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Physicists in the 19th century concluded that Newton’s second law is not a real law of nature but a mere definition, because force cannot be measured directly but only through the acceleration it produces on a given mass. Although the debate seemed settled, it has been proposed in recent years that Newton’s second law could be modified, as if it were a real description of nature, to explain some intriguing aspects of galactic dynamics. Experiments have been performed claiming to test the validity of the second law. The aim of this article is to elucidate, without using the concept of force, what it means to modify or experimentally test Newtonian dynamics.
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47.00.00 Fluid dynamics

Harnessing celestial batteries

Antti Pulkkinen, Ari Viljanen, and Risto Pirjola

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 610

Online Publication Date: Jun 2009

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The harnessing of the electric power associated with space weather storms is discussed. A simple system based on a large-scale coil located at high latitudes is devised and the power output of the system for a sample storm is calculated. It is shown that independently of the resistances of the conductors used in the coil and the number of turns in the system the maximum output of the system is restricted to the 1–10 MW range, which is comparable to the maximum output of a single large wind turbine.
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89.30.-g Fossil fuels and nuclear power
94.00.00 Physics of the ionosphere and magnetosphere

Making sense of the Legendre transform

R. K. P. Zia, Edward F. Redish, and Susan R. McKay

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 614 | Cited 3 times

Online Publication Date: Jun 2009

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The Legendre transform is a powerful tool in theoretical physics and plays an important role in classical mechanics, statistical mechanics, and thermodynamics. In typical undergraduate and graduate courses the motivation and elegance of the method are often missing, unlike the treatments frequently enjoyed by Fourier transforms. We review and modify the presentation of Legendre transforms in a way that explicates the formal mathematics, resulting in manifestly symmetric equations, thereby clarifying the structure of the transform. We then discuss examples to motivate the transform as a way of choosing independent variables that are more easily controlled. We demonstrate how the Legendre transform arises naturally from statistical mechanics and show how the use of dimensionless thermodynamic potentials leads to more natural and symmetric relations.
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05.00.00 Statistical physics, thermodynamics, and nonlinear dynamical systems

A simple method for Bragg diffraction in volume holographic gratings

Alexander Heifetz, John T. Shen, and M. S. Shahriar

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 623

Online Publication Date: Jun 2009

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We discuss a simple beam interference approximation method for deriving the angular selectivity of diffraction in weakly modulated volume holographic gratings. The results obtained using the multiple beam interference model agree qualitatively with the results obtained from a physical optics treatment of the coupled-wave theory for volume holographic gratings.
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42.00.00 Optics

Reinventing college physics for biologists: Explicating an epistemological curriculum

Edward F. Redish and David Hammer

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 629 | Cited 5 times

Online Publication Date: Jun 2009

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The University of Maryland Physics Education Research Group has done a five-year project to rethink, observe, and reform introductory algebra-based (college) physics, which primarily serves life-science majors. We refocused the class on helping the students learn to think scientifically—to build coherence, think in terms of mechanisms, and to follow the implications of assumptions. We designed the course to tap into students’ productive conceptual and epistemological resources, based on a theoretical framework from research on learning. The reformed class retains its traditional structure in terms of time and instructional personnel, but we modified existing best-practices curricular materials. We provided class-controlled spaces for student collaboration, which allowed us to observe and record students learning directly. We also scanned all written homework and examinations and administered pre-post conceptual and epistemological surveys. The reformed class enhanced the strong gains on pre-post conceptual tests produced by the best-practices materials while obtaining unprecedented pre-post gains on epistemological surveys instead of the traditional losses.
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01.40.Fk Research in physics education

Are we asking the right questions? Validating clicker question sequences by student interviews

Lin Ding, Neville W. Reay, Albert Lee, and Lei Bao

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 643 | Cited 2 times

Online Publication Date: Jun 2009

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When answering physics questions, students often have different perspectives than do physics experts. Sometimes this difference does not mean students possess misconceptions, but might indicate that the questions need to be revised. We conducted student interviews to identify and resolve validity issues that stem from the different perspectives of students and question designers. After interviews with 35 student volunteers, we selected 14 verbal and detail-oriented individuals for repeated interviews. Instead of using interviews for soliciting and confirming students’ incorrect answers, we conducted interviews as a “student consultation” process that revealed validity issues missed by physics experts. A four-stage response model was used to examine student verbal reports, and validity issues corresponding to each of the response stages were uncovered.
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01.40.Fk Research in physics education
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Exploring gender differences with different gain calculations in astronomy and biology

Shannon D. Willoughby and Anneke Metz

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 651

Online Publication Date: Jun 2009

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To investigate differences in learning gains by gender, we collected data in large introductory astronomy and biology courses. Male astronomy students had significantly higher pre- and post-test scores than female students on the astronomy diagnostic test. Male students also had significantly higher pretest and somewhat higher post-test scores than female students on a survey instrument designed for an introductory biology course. For both courses, males had higher learning gains than female students only when the normalized gain measure was utilized. No differences were found with any other measures, including other gain calculations, overall course grades, or individual exams. Implications for using different learning gain measures in science classrooms, as well as for research on learning differences by gender are discussed.
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01.40.Fk Research in physics education

A study of pre- and inservice physics teachers’ understanding of photoelectric phenomenon as part of the development of a research-based quantum physics course

Mervi A. Asikainen and Pekka E. Hirvonen

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 658 | Cited 2 times

Online Publication Date: Jun 2009

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We describe the development of a research-based quantum physics course for physics teachers. A case study approach is used to study the effect of the course on preservice and inservice teachers’ understanding of the photoelectric effect. Results offer new insights into the learning of the photoelectric effect by providing a detailed description of the participant understanding. The learning outcomes achieved indicate that the instructional approach and the teaching–learning procedure used in the course can help preservice and inservice teachers attain an in-depth understanding of key quantum physics concepts.
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01.40.Fk Research in physics education
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Low-cost coincidence-counting electronics for undergraduate quantum optics

D. Branning, S. Bhandari, and M. Beck

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 667 | Cited 8 times

Online Publication Date: Jun 2009

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Coincidence counting is a necessary ingredient for quantum optics experiments at the undergraduate level, but cost has created an entry barrier for many schools. We present a design of a coincidence-counting module that replaces the traditional method based on time-to-amplitude conversion and pulse-height analysis. Our module accepts inputs from up to four detectors, has a coincidence-time window of less than 10 ns, and has a throughput of more than triple that of the traditional method. The cost of our coincidence-counting module is less than 5% of the cost of the traditional method.
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01.50.Pa Laboratory experiments and apparatus
42.00.00 Optics
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Fermilab: Physics, the Frontier, and Megascience

Lillian Hoddeson, Adrienne W. Kolb, Catherine Westfall, and Gabor Domokos, Reviewer, Reviewer

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 671

Online Publication Date: Jun 2009

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Abstract Unavailable
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01.65.+g History of science
01.30.Vv Book reviews

BOOKS RECEIVED

American Journal of Physics -- July 2009 -- Volume 77, Issue 7, pp. 672

Online Publication Date: Jun 2009

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