News and Events

Eric Gibbs
Friday, February 14, 12:00 PM (C215 ESC, and online)
How physics shapes our understanding of molecular membrane biology and specific details on the structure and function of glycine receptors

 Biological membranes and the associated proteins are critical sites for physiology and medicine. They also are systems that manifest interesting properties that test our understanding of molecular physics. We are in an exciting era where these two paradigms and merging and presenting novel opportunities for scientific research and biomedical pursuits.  This colloquium will first present biological membranes from a biophysical perspective and survey various physical techniques to study them. I will then share results from my research on the molecular structure and function of the glycine receptor, a neurotransmitter-gated ion channel, using cryogenic electron microscopy (cryo-EM).

Thumbnail of Auroral Hummingbird over Norway
Is this the largest hummingbird ever? Although it may look like a popular fluttering nectarivore, what is pictured is actually a beautifully detailed and colorful aurora, complete with rays reminiscent of feathers. This aurora was so bright that it was visible to the unaided eye during blue hour -- just after sunset when the sky appears a darkening blue. However, the aurora only looked like a hummingbird through a sensitive camera able to pick up faint glows. As reds typically occurring higher in the Earth's atmosphere than the greens, the real 3D shape of this aurora would likely appear unfamiliar. Auroras are created when an explosion on the Sun causes high energy particles to flow into the Earth's atmosphere and excite atoms and molecules of nitrogen and oxygen. The featured image was captured about two weeks ago above Lyngseidt, Norway.
Mount Timpanogos with sky above
Temperature:34.2 F
Rel. Humidity: 48%
Pressure:29.96 Inches Hg
Image for Nathan Powers, Updated labs and AAPT lab committee work
Dr. Powers initiated the effort to update BYU’s physics undergraduate lab curriculum in 2015. The revamped curriculum, aimed at teaching students how to construct knowledge from experiments.
Image for BYU Women Represent at CUWiP 2024
21 women student attend conference at Montana State University, where students engaged in keynote speeches, panels, and research presentations.
Image for Dr. Stephens’ Sabbatical to University of Arizona
Dr. Stephens participated in a research project at the University of Arizona focused on studying brown dwarfs using the James Webb Space Telescope (JWST).

Selected Publications

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By E. Cunningham and R. L. Sandberg (et al.)
Abstract:

Shock-bubble interactions (SBIs) are important across a wide range of physical systems. In inertial confinement fusion, interactions between laser-driven shocks and micro-voids in both ablators and foam targets generate instabilities that are a major obstacle in achieving ignition. Experiments imaging the collapse of such voids at high energy densities (HED) are constrained by spatial and temporal resolution, making simulations a vital tool in understanding these systems. In this study, we benchmark several radiation and thermal transport models in the xRAGE hydrodynamic code against experimental images of a collapsing mesoscale void during the passage of a 300 GPa shock. We also quantitatively examine the role of transport physics in the evolution of the SBI. This allows us to understand the dynamics of the interaction at timescales shorter than experimental imaging framerates. We find that all radiation models examined reproduce empirical shock velocities within experimental error. Radiation transport is found to reduce shock pressures by providing an additional energy pathway in the ablation region, but this effect is small (similar to 1% of total shock pressure). Employing a flux-limited Spitzer model for heat conduction, we find that flux limiters between 0.03 and 0.10 produce agreement with experimental velocities, suggesting that the system is well-within the Spitzer regime. Higher heat conduction is found to lower temperatures in the ablated plasma and to prevent secondary shocks at the ablation front, resulting in weaker primary shocks. Finally, we confirm that the SBI-driven instabilities observed in the HED regime are baroclinically driven, as in the low energy case.

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By Henry D. Davis, James G. Harkness, Isa M. Kohls, Brian D. Jensen, Richard Vanfleet, Nathan B. Crane, and Robert C. Davis
Abstract:

High-temperature microfluidic devices (such as gas chromatography microcolumns) have traditionally been fabricated using photolithography, etching, and wafer bonding which allow for precise microscale features but lack the ability to form complex 3D designs. Metal additive manufacturing could enable higher complexity microfluidic designs if reliable methods for fabrication are developed, but forming small negative features is challenging-especially in powder-based processes. In this paper, the formation of sealed metal microchannels was demonstrated using stainless-steel binder jetting with bronze infiltration. To create small negative features, bronze infiltrant must fill the porous part produced by binder jetting without filling the negative features. This was achieved through sacrificial powder infiltration (SPI), wherein sacrificial powder reservoirs (pore size similar to 60 mu m) are used to control infiltrant pressure. With this pressure control, the infiltrant selectively filled the small pores between particles in the printed part (pore size similar to 3 mu m) while leaving printed microchannels (700 mu m and 930 mu m) empty. To develop the SPI method, a pore filling study was performed in this stainless-steel/bronze system with 370 mu m, 650 mu m, and 930 mu m microchannel segments. This study enabled SPI process design on these length scales by determining variations in pore filling across a sample and preferential filling between different sized pores.

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By A. V. Mosenkov (et al.)
Abstract:

We present new three-dimensional (3D) interstellar extinction maps in the V and Gaia G filters within 2 kpc of the Sun, a 3D differential extinction (dust spatial distribution density) map along the lines of sight in the same space, a 3D map of variations in the ratio of the extinctions in the V and Gaia G filters within 800 pc of the Sun, and a 2D map of total Galactic extinction through the entire dust half-layer from the Sun to extragalactic space for Galactic latitudes |b|>13 degrees. The 3D maps have a transverse resolution from 3.6 to 11.6 pc and a radial resolution of 50 pc. The 2D map has an angular resolution of 6.1 arcmin. We have produced these maps based on the Gaia DR3 parallaxes and Gaia, Pan-STARRS1, SkyMapper, 2MASS, and WISE photometry for nearly 100 million stars. We have paid special attention to the space within 200 pc of the Sun and high Galactic latitudes as regions where the extinction estimates have had a large relative uncertainty so far. Our maps estimate the extinction within the Galactic dust layer from the Sun to an extended object or through the entire dust half-layer from the Sun to extragalactic space with a precision sigma(A(V))=0.06 mag. This gives a high relative precision of extinction estimates even at high Galactic latitudes, where, according to our estimates, the median total Galactic extinction through the entire dust half-layer from the Sun to extragalactic objects is AV=0.12 +/- 0.06 mag. We have shown that the presented maps are among the best ones in data amount, space size, resolution, precision, and other properties.

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Abstract:

Q-balls are non-topological solitons arising in scalar field theories. Solutions for rotating Q-balls (and the related boson stars) have been shown to exist when the angular momentum is equal to an integer multiple of the Q-ball charge Q. Here we consider the possibility of classically long-lived metastable rotating Q-balls with small angular momentum, even for large charge, for all scalar theories that support non-rotating Q-balls. This is relevant for rotating extensions of Q-balls and related solitons such as boson stars as it impacts their cosmological phenomenology.

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By Levi T. Moats and Kent L. Gee (et al.)
Abstract:

Migratory bird refuge soundscapes are seasonally dynamic due to changes in wildlife populations. Some of the most prominent acoustical events in a bird refuge are the morning and evening avian choruses, particularly during spring and early summer when breeding activity of birds is high. This event is acoustically dynamic, reacting to both biotic and abiotic drivers. One such driver is the presence of standing water. For this study, near-continuous spectral data were collected at the U.S. Federal Fish and Wildlife Services Bear River Migratory Bird Refuge. Although data fidelity can be compromised by wind and rain, changes in the avian chorus characteristics over time are observed. These changes over time are observed to correlate with times management at the refuge drained the wetland area surrounding the recording sites. Recording sites that were close to drained wetland units saw decreases in the average sound pressure level during the dawn chorus, sometimes on the order of 20 dB.

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By Aleksandr Mosenkov and Raymond Kelly (et al.)
Abstract:

Galaxy sizes correlate with many other important properties of galaxies, and the cosmic evolution of galaxy sizes is an important observational diagnostic for constraining galaxy evolution models. The effective radius is probably the most widely used indicator of galaxy size. We used the TNG50-SKIRT Atlas to investigate the wavelength dependence of the effective radius of galaxies at optical and near-infrared (NIR) wavelengths. We find that, on average, the effective radius in every band exceeds the stellar mass effective radius, and that this excess systematically decreases with increasing wavelength. The optical g-band (NIR K-s-band) effective radius is on average 58% (13%) larger than the stellar mass effective radius. Effective radii measured from dust-obscured images are systematically larger than those measured from dust-free images, although the effect is limited (8.7% in the g-band, 2.1% in the K-s-band). We find that stellar population gradients are the dominant factor (about 80%) in driving the wavelength dependence of the effective radius, and that differential dust attenuation is a secondary factor (20%). Comparing our results to recent observational data, we find offsets in the absolute values of the median effective radii, up to 50% for the population of blue galaxies. We find better agreement in the slope of the wavelength dependence of the effective radius, with red galaxies having a slightly steeper slope than green-blue galaxies. Comparing our effective radii with those of galaxies from the Siena Galaxy Atlas in separate bins in z-band absolute magnitude and g - z colour, we find excellent agreement for the reddest galaxies, but again significant offsets for the blue populations: up to 70% for galaxies around M-z = -21.5. This difference in median effective radius for the bluer galaxies is most probably due to intrinsic differences in the morphological structure of observed and TNG50 simulated galaxies. Finally, we find that the median effective radius in any broadband filter increases systematically with decreasing u - r colour and with increasing galaxy stellar mass, total SFR, sSFR, and dust-to-stellar-mass ratio. For the slope of the wavelength dependence of R-e, however, there does not seem to be a systematic, monotonic correlation with any of these global properties.