John A Milsom

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Scholarly Contributions

Chapters

• Burd, G. D., Tomanek, D. J., Blowers, P., Bolger, M. S., Cox, J., Elfring, L. K., Grubbs, E. A., Hunter, J., Johns, K. A., Lazos, L., Lysecky, R. L., Milsom, J. A., Novodvorsky, I., Pollard, J. R., Prather, E. E., Talanquer, V. A., Thamvichai, R., Tharp, H. S., & Wallace, C. (2015). Developing faculty cultures for evidence-based teaching practices in STEM: A progress report.. In Transforming Institutions: 21st Century Undergraduate STEM. West Lafayette, IN.: Purdue University Press.

Journals/Publications

• Milsom, J. A. (2023).

  Why are the Electric and Magnetic Fields in an Electromagnetic Wave Propagating through a Conductor not in Phase?

  . European Journal of Physics. doi:10.1088/1361-6404/aceadf
• Milsom, J. A. (2021).

  The Brachistochrone: An excellent problem for all levels of physics students

  . The Physics Teacher. https://doi.org/10.1119/5.0021274.
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  The classic brachistrochrone problem is standard material in intermediate mechanics. Many variations exist including some accessible to introductory students. While a quantitative solution isn't feasible in introductory classes, qualitative discussions can be very beneficial since kinematics, Newton's Laws, energy conservation and motion along curved trajectories all play a role. In this work, we describe an activity focusing on a qualitative understanding of the brachistochrone and examine the performance of freshmen, juniors and graduate students. The activity can be downloaded at this https URL .
• Milsom, J. A. (2021). The Brachistochrone: An excellent problem for all levels of physics students.. The Physics Teacher.
• Wallace, C. S., Prather, E. E., Milsom, J. A., Johns, K. A., & Manne, S. (2021). Students taught by a first-time instructor using active learning teaching strategies outperform students taught by a highly-regarded traditional instructor. Journal of College Science Teaching, 50(4), 48-57.
• Johns, K., Manne, S., Milsom, J. A., Prather, E. E., & Wallace, C. S. (2020).

  Students taught by a first-time instructor using active learning teaching strategies outperform students taught by a highly-regarded traditional instructor

  . arXiv: Physics Education.
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  In this paper we put forth a model for physics course reform that uniquely uses proven, research-based active learning strategies to help students improve their physics knowledge and problem-solving skills. In this study, we compared the exam performance of students in two sections of the same introductory physics course. One section (the traditional section, N = 258) was taught by an instructor who is highly regarded for his lectures, but did not use any active learning teaching strategies. The other section (the reformed section, N = 217) was taught by an instructor who had never before taught a physics class but who was trained in physics and astronomy education research and who did use active learning teaching strategies. Students in the reformed section significantly outperformed students in the traditional section on common exam questions over the course of the semester, regardless of whether the question was conceptual or quantitative. This reform effort has been successful at improving students' learning and significantly increasing the department's use of active learning strategies at the introductory level and beyond.
• Milsom, J., & Chamberland, M. (2013). Mandevilla stans (Apocynaceae) new to the USA flora. Phytoneuron, 92, 1-6.
• Spiegel, D. S., Milsom, J. A., & Burrows, A. (2011). The Deuterium-burning Mass Limit for Brown Dwarfs and Giant Planets. The Astrophysical Journal, 727(1), 57. doi:10.1088/0004-637x/727/1/57
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  There is no universally acknowledged criterion to distinguish brown dwarfs from planets. Numerous studies have used or suggested a definition based on an object’s mass, taking the �13-Jupiter mass (MJ) limit for the ignition of deuterium. Here, we investigate various deuterium-burning masses for a range of models. We find that, while 13MJ is generally a reasonable rule of thumb, the deuterium fusion mass depends on the helium abundance, the initial deuterium abundance, the metallicity of the model, and on what fraction of an object’s initial deuterium abundance must combust in order for the object to qualify as having burned deuterium. Even though, for most proto-brown dwarf conditions, 50% of the initial deuterium will burn if the object’s mass is �(13.0±0.8)MJ, the full range of possibilities is significantly broader. For models ranging from zero-metallicity to more than three times solar metallicity, the deuterium burning mass ranges from �11.0 MJ (for 3-times solar metallicity, 10% of initial deuterium burned) to �16.3 MJ (for zero metallicity, 90% of initial deuterium burned). Subject headings: radiative transfer – stars: low-mass, brown dwarfs – stars: evolution
• Spiegel, D. S., Milsom, J. A., Ibgui, L., Hubeny, I., & Burrows, A. (2010). Models of Neptune-mass exoplanets: Emergent fluxes and albedos. The Astrophysical Journal, 709(1), 149-158. doi:10.1088/0004-637x/709/1/149
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  There are now many known exoplanets with Msin i within a factor of 2 of Neptune's, including the transiting planets GJ 436b and HAT-P-11b. Planets in this mass range are different from their more massive cousins in several ways that are relevant to their radiative properties and thermal structures. By analogy with Neptune and Uranus, they are likely to have metal abundances that are an order of magnitude or more greater than those of larger, more massive planets. This increases their opacity, decreases Rayleigh scattering, and changes their equation of state. Furthermore, their smaller radii mean that fluxes from these planets are roughly an order of magnitude lower than those of otherwise identical gas giant planets. Here, we compute a range of plausible radiative equilibrium models of GJ 436b and HAT-P-11b. In addition, we explore the dependence of generic Neptune-mass planets on a range of physical properties, including their distance from their host stars, their metallicity, the spectral type of their stars, the redistribution of heat in their atmospheres, and the possible presence of additional optical opacity in their upper atmospheres.
• Psaltis, D., Milsom, J. A., & Mao, S. A. (2009). SUPER-KEPLERIAN FREQUENCIES IN ACCRETION DISKS. IMPLICATIONS FOR MASS AND SPIN MEASUREMENTS OF COMPACT OBJECTS FROM X-RAY VARIABILITY STUDIES. The Astrophysical Journal, 703(1), 717-720. doi:10.1088/0004-637x/703/1/717
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  The detection of fast quasi-periodic variability from accreting black holes and neutron stars has been used to constrain their masses, radii, and spins. If the observed oscillations are linear modes in the accretion disks, then bounds can be placed on the properties of the central objects by assuming that these modes are locally sub-Keplerian. If, on the other hand, the observed oscillations correspond to nonlinear resonances between disk modes, then the properties of the central objects can be measured by assuming that the resonant modes are excited at the same radial annulus in the disk. In this paper, we use numerical simulations of vertically integrated, axisymmetric hydrodynamic accretion disks to provide examples of situations in which the assumptions implicit in both methods are not satisfied. We then discuss our results for the robustness of the mass and spin measurements of compact objects from variability studies.
• Sharp, C. M., Pasek, M. A., Milsom, J. A., Lunine, J. I., Lauretta, D. S., & Ciesla, F. J. (2005). Sulfur chemistry with time-varying oxygen abundance during Solar System formation. Icarus, 175(1), 1-14. doi:10.1016/j.icarus.2004.10.012
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  Abstract Chemical models of solar nebula chemistry are presented which show the influence of progressive water depletion from the inner solar nebula. The main focus of this work is the equilibrium distribution of S resulting from this process. Under canonical solar nebula conditions, H2S is the dominant S-bearing species in the gas phase and troilite (FeS) is the primary reservoir for S after condensation. As water vapor diffuses out to its condensation front, the equilibrium distribution of S changes significantly. With the removal of water vapor, SiS becomes the most abundant S-bearing gas and MgS and CaS compete with FeS as the main sulfide reservoir. These results allow us to argue that some of the minerals in the enstatite chondrites formed through the heterogeneities associated with the nebular ice condensation front, and that the sulfur abundance in Jupiter reflects a depletion in H2S that is the result of inner nebula sulfur chemistry under varying oxygen abundance.
• Sharp, C. M., Ram, R. S., Milsom, J. A., Dulick, M., Burrows, A., Bernath, P. F., Bauschlicher, J. C., & Bauschlicher, C. W. (2005). Spectroscopic constants, abundances, and opacities of the TiH molecule. The Astrophysical Journal, 624(2), 988-1002. doi:10.1086/429366
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  Using previous measurements and quantum chemical calculations to derive the molecular properties of the TiH molecule, we obtain new values for its rovibrational constants, thermochemical data, spectral line lists, line strengths, and absorption opacities. Furthermore, we calculate the abundance of TiH in M and L dwarf atmospheres and conclude that it is much higher than previously thought. We find that the TiH/TiO ratio increases strongly with decreasing metallicity, and at high temperatures can exceed unity. We suggest that, particularly for subdwarf L and M dwarfs, spectral features of TiH near ~0.52 and 0.94 μm and in the H band may be more easily measurable than heretofore thought. The recent possible identification in the L subdwarf 2MASS J0532 of the 0.94 μm feature of TiH is in keeping with this expectation. We speculate that looking for TiH in other dwarfs and subdwarfs will shed light on the distinctive titanium chemistry of the atmospheres of substellar-mass objects and the dimmest stars.
• Sudarsky, D., Milsom, J. A., Lunine, J. I., Cooper, C. S., & Burrows, A. (2003). Erratum: ``Modeling the Formation of Clouds in Brown Dwarf Atmospheres'' ( ApJ, 586, 1320 [2003] ). The Astrophysical Journal, 595(1), 573-573. doi:10.1086/377199
• Sudarsky, D., Milsom, J. A., Lunine, J. I., Cooper, C. S., & Burrows, A. (2003). Modeling the Formation of Clouds in Brown Dwarf Atmospheres. The Astrophysical Journal, 586(2), 1320-1337. doi:10.1086/367763
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  Because the opacity of clouds in substellar mass object (SMO) atmospheres depends on the composition and distribution of particle sizes within the cloud, a credible cloud model is essential for accurately modeling SMO spectra and colors. We present a one-dimensional model of cloud particle formation and subsequent growth based on a consideration of basic cloud microphysics. We apply this microphysical cloud model to a set of synthetic brown dwarf atmospheres spanning a broad range of surface gravities and effective temperatures (gsurf ¼ 1:78 � 10 3 3 � 10 5 cm s � 2 and Teff ¼ 600 1600 K) to obtain plausible particle sizes for several abundant species (Fe, Mg2SiO4, and Ca2Al2SiO7). At the base of the clouds, where the particles are largest, the particle sizes thus computed range from � 5 to over 300 lm in radius over the full range of atmospheric conditions considered. We show that average particle sizes decrease significantly with increasing brown dwarf surface gravity. We also find that brown dwarfs with higher effective temperatures have characteristically larger cloud particles than those with lower effective temperatures. We therefore conclude that it is unrealistic when modeling SMO spectra to apply a single particle size distribution to the entire class of objects. Subject headings: stars: atmospheres — stars: low-mass, brown dwarfs
• Burgasser, A. J., Sudarsky, D., Milsom, J. A., Liebert, J., Kirkpatrick, J. D., Hubeny, I., Burrows, A., & Burgasser, A. J. (2002). Theoretical Spectral Models of T Dwarfs at Short Wavelengths and Their Comparison with Data. The Astrophysical Journal, 573(1), 394-417. doi:10.1086/340584
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  We have generated new, self-consistent spectral and atmosphere models for the effective temperature range 600-1300 K thought to encompass the known T dwarfs. For the first time, theoretical models are compared with a family of measured T dwarf spectra at wavelengths shortward of ~1.0 μm. By defining spectral indices and standard colors in the optical and very near-infrared, we explore the theoretical systematics with Teff, gravity, and metallicity. We conclude that the short-wavelength range is rich in diagnostics that complement those in the near-infrared now used for spectral subtyping. We also conclude that the wings of the Na D and K I (7700 A) resonance lines and aggressive rainout of heavy metals (with the resulting enhancement of the sodium and potassium abundances at altitude) are required to fit the new data shortward of 1.0 μm. Furthermore, we find that the water bands weaken with increasing gravity, that modest decreases in metallicity enhance the effect in the optical of the sodium and potassium lines, and that at low values of Teff, in a reversal of the normal pattern, optical spectra become bluer with further decreases in Teff. Moreover, we conclude that T dwarf subtype is not a function of Teff alone but that it is a nontrivial function of gravity and metallicity as well. As do Marley and coworkers in their 2002 work, we see evidence in early T dwarf atmospheres of a residual effect of clouds. With cloudless models, we obtain spectral fits to the two late T dwarfs with known parallaxes, but a residual effect of clouds on the emergent spectra of even late T dwarfs cannot yet be discounted. However, our focus is not on detailed fits to individual objects but on the interpretation of the overall spectral and color trends of the entire class of T dwarfs, as seen at shorter wavelengths.
• Burrows, A., & Milsom, J. A. (2002).

  Deuterium Burning and Lithium Burning in Brown Dwarfs

  . AAS.
• Sharp, C. M., Ram, R. S., Milsom, J. A., Burrows, A., & Bernath, P. F. (2002). New CrH Opacities for the Study of L and Brown Dwarf Atmospheres. The Astrophysical Journal, 577(2), 986-992. doi:10.1086/342242
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  In this paper, we calculate new line lists and opacities for the 12 bands of the A 6þ X 6þ transitions of the CrH molecule. Identified in objects of the new L dwarf spectroscopic class (many of which are brown dwarfs), as well as in sunspots, the CrH molecule plays an important role in the diagnosis of low-temperature atmospheres. As a tentative first application of these opacities, we employ our new theoretical CrH data in an atmospheres code to obtain a CrH/H2 number ratio for the skin of the L5 dwarf 2MASSI J1507038� 151648 of �ð 2 4 Þ� 10 � 9 , in rough agreement with chemical equilibrium expectations. Since in previous compilations the oscillator strength was off by more than an order of magnitude, this agreement represents a modest advance. However, in order to fit the CrH abundance in the L dwarf spectral class, silicate clouds need to be incorporated into the model. Given that this subject is still in a primitive stage of development, one should view any spectral model in the L dwarf range as merely tentative. Nevertheless, a necessary first step in L dwarf modeling is a reliable CrH opacity algorithm, and this is what we have here attempted to provide. Subject headings: astrochemistry — infrared: stars — molecular data — stars: atmospheres — stars: fundamental parameters — stars: low-mass, brown dwarfs
• Burgasser, A. J., Burrows, A., Hubeny, I., Kirkpatrick, J. D., Liebert, J., Milsom, J. A., Sudarsky, D., Burgasser, A. J., Burrows, A., Hubeny, I., Kirkpatrick, J. D., Liebert, J., Milsom, J. A., & Sudarsky, D. (2001).

  Theoretical Spectral Models of T Dwarfs at Short Wavelengths

  . Astrophysical Journal.
• Milsom, J. A., & Taam, R. E. (1997).

  Two-dimensional studies of inertial-acoustic oscillations in black hole accretion discs

  . Monthly Notices of the Royal Astronomical Society. doi:10.1093/mnras/286.2.358
• Milsom, J. A., & Taam, R. E. (1996).

  Variability of black hole accretion discs: effects of local and global inertial-acoustic oscillations

  . Monthly Notices of the Royal Astronomical Society. doi:10.1093/mnras/283.3.919
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  The non-linear time-dependent evolution of inertial-acoustic oscillations in black hole accretion discs has been investigated as a function of mass accretion rate, Ṁ/ṀEdd, black hole mass, M, and viscosity, v. The results indicate qualitatively distinct behaviour in three regimes. In particular, for Ṁ ≳ 0.25ṀEdd the disc is stable to inertial-acoustic oscillations. For 0.01MEdd ≲ Ṁ ≲ 0.25 ṀEdd, a global oscillation occurs at the maximum epicyclic frequency, and local oscillations at the local epicyclic frequencies are also present. At accretion rates lower than ∼0.01 ≲ṀEdd, the disc exhibits local oscillations at all radii with no global oscillation. The disc luminosity power spectra are characterized by power-law slopes of between 0.80 and 1.95, with the flattest spectra corresponding to the lowest accretion rates. In each regime the luminosity oscillation amplitudes are largest for large viscosities (rms variations always ≲ 1 per cent), and the oscillations vanish if the viscosity is sufficiently small. Constant-viscosity models and α-viscosity models were used, and these yield qualitatively similar results. The locations of the transitions between these three regimes are approximately independent of M. Unless disc coronae or multidimensional effects reduce the amplitude of these oscillations, observations of these oscillations should be possible with the X-ray Timing Explorer (XTE).
• Chen, X., Milsom, J. A., & Taam, R. E. (1994).

  The vertical structure and stability of accretion disks surrounding black holes and neutron stars

  . The Astrophysical Journal. doi:10.1086/173680
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  The structure and stability of the inner regions of accretion disks surrounding neutron stars and black holes have been investigated. Within the framework of the alpha viscosity prescription for optically thick disks, we assume the viscous stress scales with gas pressure only, and the alpha parameter, which is less than or equal to unity, is formulated as alpha(sub 0)(h/r)(exp n), where h is the local scale height and n and alpha(sub 0) are constants. We neglect advective energy transport associated with radial motions and construct the vertical structure of the disks by assuming a Keplerian rotation law and local hydrostatic and thermal equilibrium. The vertical structures have been calculated with and without convective energy transport, and it has been demonstrated that convection is important especially for mass accretion rates, M-dot, greater than about 0.1 times the Eddington value, M-dot(sub Edd). Although the efficiency of convection is not high, convection significantly modifies the vertical structure of the disk (as compared with a purely radiative model) and leads to lower temperatures at a given M-dot. The results show that the disk can be locally unstable and that for n greater than or = 0.75, an S-shaped relation can exist between M-dot and the column density, sigma, at a given radius. While the lower stable branch (derivative of M-dot/derivative of sigma greater than 0) and middle unstable branch (derivative of M-dot/derivative of sigma less than 0) represent structures for which the gas and radiation pressure dominate respectively, the stable upper branch (derivative of M-dot/derivative of sigma greater than 0) is a consequence of the saturation of alpha. This saturation of alpha can occur for large alpha(sub 0) and at M-dot less than or = M-dot(sub Edd). The instability is found to occur at higher mass accretion rates for neutron stars than for black holes. In particular, the disk is locally unstable for M-dot greater than or = 0.5 M-dot(sub Edd) for neutron stars and for M-dot greater than or = M-dot(sub Edd) for black holes for a viscosity prescription characterized by n = 1 and alpha(sub 0) = 10.
• Fee, R. S., Fee, R. S., Milsom, J. A., Milsom, J. A., Maroncelli, M., & Maroncelli, M. (1991).

  Inhomogeneous decay kinetics and apparent solvent relaxation at low temperatures

  . Journal of Physical Chemistry. doi:10.1021/j100166a048
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  ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInhomogeneous decay kinetics and apparent solvent relaxation at low temperaturesRichard S. Fee, John A. Milsom, and Mark MaroncelliCite this: J. Phys. Chem. 1991, 95, 13, 5170–5181Publication Date (Print):June 1, 1991Publication History Published online1 May 2002Published inissue 1 June 1991https://doi.org/10.1021/j100166a048RIGHTS & PERMISSIONSArticle Views206Altmetric-Citations54LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

Presentations

• Milsom, J. A. (2021, winter). Analyzing the Brachistrochrone in a Freshmen Class?. Winter 2021 meeting of the American Association of Physics Teachers. Virtual: American Association of Physics Teachers.
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  Gave a talk title "Analyzing the Brachistrochrone in a Freshmen Class? at the winter 2021 AAPT meeting.
• Milsom, J. A. (2020, summer). Untold secrets of the slowly charging capacitor.. Summer 2020 meeting of the American Assocation of Physics Teachers. Virtual: American Association of Physics Teachers.
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  Gave a talk titled "Untold secrets of the slowly charging capacitor" at the summer 2020 AAPT meeting.
• Milsom, J. A. (2019, winter). Computational physics in our curriculum. Winter 2019 American Association of Physics Teachers meeting. Houston: American Association of Physics Teacher.
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  Gave a talk on "Computational physics in our curriculum" at the National January 2019 AAPT meeting.