Brandon Johnson

Purdue University West Lafayette

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H. J. Melosh

Purdue University West Lafayette

M. T. Zuber

Massachusetts Institute of Technology

J. M. Soderblom

Massachusetts Institute of Technology

A. M. Freed

Purdue University West Lafayette

J. C. Andrews‐Hanna

University of Arizona

G. S. Collins

Imperial College London

M. A. Wieczorek

Centre National de la Recherche Scientifique

H. J. Melosh

Purdue University West Lafayette

T. J. Bowling

Southwest Research Institute

D. M. Blair

Brown University

Cooperative Institutions

Planetary Science Institute

Jet Propulsion Laboratory

California Institute of Technology

Goddard Space Flight Center

University of Arizona

Purdue University West Lafayette

Massachusetts Institute of Technology

Southwest Research Institute

Brown University

Commonwealth Scientific and Industrial Research Organisation

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Detecting Nasopharyngeal Reflux: A Novel pH Probe Technique

Annals of Otology Rhinology & Laryngology (2012)

Joseph D. Brunworth Rishi Garg Hossein Mahboubi Brandon Johnson Hamid R. Djalilian

Objectives: We sought to ascertain the normal pH values in the aerosolized environment of the nasopharynx in healthy subjects and utilize a novel pH probe that allows measuring acidity in a nonliquid environment. Methods: Between November 2009 and February 2011, healthy volunteers without a history of reflux or eustachian tube dysfunction were enrolled in the prospective study. A total of 20 subjects had a Dx–pH Measurement System Probe (Respiratory Technology Corp) placed near the torus tubarius. The pH probe records the pH throughout the 24-hour study. A pH below 5.5 while the subject was upright or below 5.0 while the subject was supine was used as a criterion to determine a reflux event. Recording was stopped during meals. Results: For normal individuals with no history of reflux or eustachian tube dysfunction, the pH values obtained from the nasopharynx ranged from 6.10 to 7.92. The average pH was 7.03 (SD, 0.67). Eight subjects (40%) had at least 1 reflux event during the 24-hour pH study. Conclusions: By utilizing a novel self-condensing pH probe, we were able to perform a 24-hour pH study in the nasopharynx of 20 healthy individuals. In our study, the average pH for individuals without symptomatic reflux or eustachian tube dysfunction was 7.03. Interestingly, 8 control subjects had at least 1 episode of pH below 5.5 while awake or below 5.0 while asleep, which was considered to be a reflux event in our study.

Supine position

Eustachian tube

Esophageal pH monitoring

pH meter

10.1177/000348941212100701

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Citations (16)

An endogenic origin of cerean organics

Earth and Planetary Science Letters (2020)

T. J. Bowling Brandon Johnson S. Marchi M. C. De Sanctis Julie Castillo‐Rogez

Hypervelocity

Dwarf planet

10.1016/j.epsl.2020.116069

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Citations (17)

Modeling the Formation of Selk Impact Crater on Titan: Implications for Dragonfly

The Planetary Science Journal (2023)

Shigeru Wakita Brandon Johnson J. M. Soderblom Jahnavi Shah C. D. Neish

Abstract Selk crater is an ∼80 km diameter impact crater on the Saturnian icy satellite Titan. Melt pools associated with impact craters like Selk provide environments where liquid water and organics can mix and produce biomolecules like amino acids. It is partly for this reason that the Selk region has been selected as the area that NASA’s Dragonfly mission will explore and address one of its primary goals: to search for biological signatures on Titan. Here we simulate Selk-sized impact craters on Titan to better understand the formation of Selk and its melt pool. We consider several structures for the icy target material by changing the thickness of the methane clathrate layer, which has a substantial effect on the target thermal structure and crater formation. Our numerical results show that a 4 km diameter impactor produces a Selk-sized crater when 5–15 km thick methane clathrate layers are considered. We confirm the production of melt pools in these cases and find that the melt volumes are similar regardless of methane clathrate layer thickness. The distribution of the melted material, however, is sensitive to the thickness of the methane clathrate layer. In the case of a 10–15 km thick methane clathrate layer, the melt pool appears as a torus-like shape that is a few kilometers deep, and as a shallower layer in the case of a 5 km thick clathrate layer. Melt pools of this thickness may take tens of thousands of years to freeze, allowing more time for complex organics to form.

Clathrate hydrate

10.3847/psj/acbe40

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Citations (8)

Jetting during oblique impacts of spherical impactors

Icarus (2021)

Shigeru Wakita Brandon Johnson C. A. Denton T. M. Davison

Impact structure

Impact energy

10.1016/j.icarus.2021.114365

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Citations (15)

FIG_4B.fig

Harvard Dataverse (2018)

Brandon Johnson

Matlab .fig file containing data in Fig 4B

10.7910/dvn/jucvxw/ai8dfv

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Replication Data for: Controls on the formation of lunar multiring basins FIG_5C.fig

Harvard Dataverse (2018)

Brandon Johnson

Matlab .fig file containing data in Fig 5C

Replication

10.7910/dvn/jucvxw/0mq2yk

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Replication Data for: Controls on the formation of lunar multiring basins 52crst_40imp_13kpkm.dat

Harvard Dataverse (2018)

Brandon Johnson

iSALE Jdata file for a 52 km thick crust, 40 km diameter impactor, 13 K/km thermal gradient, and 1300 K roll over temperature

Replication

10.7910/dvn/jucvxw/2dxsbx

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Citations (0)

Replication Data for: Controls on the formation of lunar multiring basins FIG_1.fig

Harvard Dataverse (2018)

Brandon Johnson

Matlab .fig file containing data in Fig 1

Replication

10.7910/dvn/jucvxw/ylpgva

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Effect of Impact Velocity and Angle on Deformational Heating and Postimpact Temperature

Journal of Geophysical Research Planets (2022)

Shigeru Wakita Hidenori Genda Kosuke Kurosawa T. M. Davison Brandon Johnson

Abstract The record of impact‐induced shock heating in meteorites is an important key for understanding the collisional history of the solar system. Material strength is important for impact heating, but the effect of impact angle and impact velocity on shear heating remains poorly understood. Here, we report three‐dimensional oblique impact simulations, which confirm the enhanced heating due to material strength and explore the effects of impact angle and impact velocity. We find that oblique impacts with an impact angle that is steeper than 45‐degrees produce a similar amount of heated mass as vertical impacts. On the other hand, grazing impacts produce less heated mass and smaller heated regions compared to impacts at steeper angles. We derive an empirical formula of the heated mass, as a function of the impact angle and velocity. This formula can be used to estimate the impact conditions (velocity and angle) that occurred and caused Ar loss in the meteoritic parent bodies. Furthermore, our results indicate that grazing impacts at higher impact velocities could generate a similar amount of heated material as vertical impacts at lower velocities. As the heated material produced by grazing impacts has experienced lower pressure than the material heated by vertical impacts, our results imply that grazing impacts may produce weakly shock‐heated meteorites.

Impact pressure

10.1029/2022je007266

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Citations (7)

Impact spherules as a record of an ancient heavy bombardment of Earth

Nature (2012)

Brandon Johnson H. J. Melosh

Chronology

10.1038/nature10982

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Citations (124)