20,373 results on '"Duncan, J"'
Search Results
2. Primitivity theorems for convolution algebras on McAlister monoids
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Crabb, M.J., Duncan, J., and McGregor, C.M.
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- 2022
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3. Surviving in the Hot Neptune Desert: The Discovery of the Ultra-Hot Neptune TOI-3261b
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Nabbie, Emma, Huang, Chelsea X., Burt, Jennifer A., Armstrong, David J., Mamajek, Eric E., Adibekyan, Vardan, Sousa, Sérgio G., Lopez, Eric D., Thorngren, Daniel P., Fernández, Jorge, Li, Gongjie, Jenkins, James S., Vines, Jose I., da Silva, João Gomes, Wittenmyer, Robert A., Bayliss, Daniel, Briceño, César, Collins, Karen A., Dumusque, Xavier, Horne, Keith D., Keniger, Marcelo F., Law, Nicholas, Lillo-Box, Jorge, Liu, Shang-Fei, Mann, Andrew W., Nielsen, Louise Dyregaard, Osborn, Ares, Relles, Howard M., Rodrigues, José J., Bell, Juan, Srdoc, Gregor, Stockdale, Chris, Strøm, Paul A., Gardner-Watkins, Cristilyn N., Wheatley, Peter J., Wright, Duncan J., Zhou, George, Ziegler, Carl, Ricker, George R., Seager, Sara, Vanderspek, Roland, Winn, Joshua W., Jenkins, Jon M., Fausnaugh, Michael, Kunimoto, Michelle, Osborn, Hugh P., Quinn, Samuel N., and Wohler, Bill
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Astrophysics - Earth and Planetary Astrophysics - Abstract
The recent discoveries of Neptune-sized ultra-short period planets (USPs) challenge existing planet formation theories. It is unclear whether these residents of the Hot Neptune Desert have similar origins to smaller, rocky USPs, or if this discrete population is evidence of a different formation pathway altogether. We report the discovery of TOI-3261b, an ultra-hot Neptune with an orbital period $P$ = 0.88 days. The host star is a $V = 13.2$ magnitude, slightly super-solar metallicity ([Fe/H] $\simeq$ 0.15), inactive K1.5 main sequence star at $d = 300$ pc. Using data from the Transiting Exoplanet Survey Satellite and the Las Cumbres Observatory Global Telescope, we find that TOI-3261b has a radius of $3.82_{-0.35}^{+0.42}$ $R_{\oplus}$. Moreover, radial velocities from ESPRESSO and HARPS reveal a mass of $30.3_{-2.4}^{+2.2}$ $M_{\oplus}$, more than twice the median mass of Neptune-sized planets on longer orbits. We investigate multiple mechanisms of mass loss that can reproduce the current-day properties of TOI-3261b, simulating the evolution of the planet via tidal stripping and photoevaporation. Thermal evolution models suggest that TOI-3261b should retain an envelope potentially enriched with volatiles constituting $\sim$5% of its total mass. This is the second highest envelope mass fraction among ultra-hot Neptunes discovered to date, making TOI-3261b an ideal candidate for atmospheric follow-up observations., Comment: 20 pages, 11 figures, accepted to AJ
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- 2024
4. HD 21520 b: a warm sub-Neptune transiting a bright G dwarf
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Nies, Molly, Mireles, Ismael, Bouchy, François, Dragomir, Diana, Nicholson, Belinda A., Eisner, Nora L., Sousa, Sergio G., Collins, Karen A., Howell, Steve B., Ziegler, Carl, Hellier, Coel, Addison, Brett, Ballard, Sarah, Bowler, Brendan P., Briceño, César, Clark, Catherine A., Conti, Dennis M., Dumusque, Xavier, Edwards, Billy, Gnilka, Crystal L., Hobson, Melissa, Horner, Jonathan, Kane, Stephen R., Kielkopf, John, Lavie, Baptiste, Law, Nicholas, Lendl, Monika, Littlefield, Colin, Liu, Huigen, Mann, Andrew W., Mengel, Matthew W., Oddo, Dominic, Okumura, Jack, Palle, Enric, Plavchan, Peter, Psaridi, Angelica, Santos, Nuno C., Schwarz, Richard P., Shporer, Avi, Wittenmyer, Robert A., Wright, Duncan J., Zhang, Hui, Watanabe, David, Medina, Jennifer V., Villaseñor, Joel, Ting, Eric B., Christiansen, Jessie L., Winn, Joshua N., Stassun, Keivan G., Seager, S., Latham, David W., and Ricker, George R.
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Astrophysics - Earth and Planetary Astrophysics - Abstract
We report the discovery and validation of HD 21520 b, a transiting planet found with TESS and orbiting a bright G dwarf (V=9.2, $T_{eff} = 5871 \pm 62$ K, $R_{\star} = 1.04\pm 0.02\, R_{\odot}$). HD 21520 b was originally alerted as a system (TOI-4320) consisting of two planet candidates with periods of 703.6 and 46.4 days. However, our analysis supports instead a single-planet system with an orbital period of $25.1292\pm0.0001$ days and radius of $2.70 \pm 0.09\, R_{\oplus}$. Three full transits in sectors 4, 30 and 31 match this period and have transit depths and durations in agreement with each other, as does a partial transit in sector 3. We also observe transits using CHEOPS and LCOGT. SOAR and Gemini high-resolution imaging do not indicate the presence of any nearby companions, and MINERVA-Australis and CORALIE radial velocities rule out an on-target spectroscopic binary. Additionally, we use ESPRESSO radial velocities to obtain a tentative mass measurement of $7.9^{+3.2}_{-3.0}\, M_{\oplus}$, with a 3-$\sigma$ upper limit of 17.7 $M_{\oplus}$. Due to the bright nature of its host and likely significant gas envelope of the planet, HD 21520 b is a promising candidate for further mass measurements and for atmospheric characterization., Comment: Submitted to MNRAS
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- 2024
5. Sensitivity-Improved Polarization Maps at 40 GHz with CLASS and WMAP data
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Shi, Rui, Appel, John W., Bennett, Charles L., Bustos, Ricardo, Chuss, David T., Dahal, Sumit, Couto, Jullianna Denes, Eimer, Joseph R., Essinger-Hileman, Thomas, Harrington, Kathleen, Iuliano, Jeffrey, Li, Yunyang, Marriage, Tobias A., Petroff, Matthew A., Rostem, Karwan, Song, Zeya, Valle, Deniz A. N., Watts, Duncan J., Weiland, Janet L., Wollack, Edward J., and Xu, Zhilei
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Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Improved polarization measurements at frequencies below 70 GHz with degree-level angular resolution are crucial for advancing our understanding of the Galactic synchrotron radiation and the potential polarized anomalous microwave emission and ultimately benefiting the detection of primordial $B$ modes. In this study, we present sensitivity-improved 40 GHz polarization maps obtained by combining the CLASS 40 GHz and WMAP $Q$-band data through a weighted average in the harmonic domain. The decision to include WMAP $Q$-band data stems from similarities in the bandpasses. Leveraging the accurate large-scale measurements from WMAP $Q$ band and the high-sensitivity information from CLASS 40 GHz band at intermediate scales, the noise level at $\ell\in[30, 100]$ is reduced by a factor of $2-3$ in the map space. A pixel domain analysis of the polarized synchrotron spectral index ($\beta_s$) using WMAP $K$ band and the combined maps (mean and 16/84th percentile across the $\beta_s$ map: $-3.08_{-0.20}^{+0.20}$) reveals a stronger preference for spatial variation (PTE for a uniform $\beta_s$ hypothesis smaller than 0.001) than the results obtained using WMAP $K$ and $Ka$ bands ($-3.08_{-0.14}^{+0.14}$). The cross-power spectra of the combined maps follow the same trend as other low-frequency data, and validation through simulations indicates negligible bias introduced by the combination method (sub-percent level in the power spectra). The products of this work are publicly available on $\mathtt{LAMBDA}$., Comment: 19 pages, 16 figures, 1 table, accepted for publication in ApJ
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- 2024
6. Spontaneous Intragastric Balloon Hyperinflation: Two Cases and Outcomes
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Flynn, Duncan J., Soltani, Amin K., and Singh, Amandeep
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- 2024
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7. Misunderstanding the harms of online misinformation
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Budak, Ceren, Nyhan, Brendan, Rothschild, David M., Thorson, Emily, and Watts, Duncan J.
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- 2024
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8. The exciting potential and daunting challenge of using GPS human-mobility data for epidemic modeling
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Barreras, Francisco and Watts, Duncan J.
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- 2024
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9. The diminishing state of shared reality on US television news
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Hosseinmardi, Homa, Wolken, Samuel, Rothschild, David M., and Watts, Duncan J.
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Computer Science - Information Retrieval ,Computer Science - Computers and Society ,Physics - Physics and Society - Abstract
The potential for a large, diverse population to coexist peacefully is thought to depend on the existence of a ``shared reality:'' a public sphere in which participants are exposed to similar facts about similar topics. A generation ago, broadcast television news was widely considered to serve this function; however, since the rise of cable news in the 1990s, critics and scholars have worried that the corresponding fragmentation and segregation of audiences along partisan lines has caused this shared reality to be lost. Here we examine this concern using a unique combination of data sets tracking the production (since 2012) and consumption (since 2016) of television news content on the three largest cable and broadcast networks respectively. With regard to production, we find strong evidence for the ``loss of shared reality hypothesis:'' while broadcast continues to cover similar topics with similar language, cable news networks have become increasingly distinct, both from broadcast news and each other, diverging both in terms of content and language. With regard to consumption, we find more mixed evidence: while broadcast news has indeed declined in popularity, it remains the dominant source of news for roughly 50\% more Americans than does cable; moreover, its decline, while somewhat attributable to cable, appears driven more by a shift away from news consumption altogether than a growth in cable consumption. We conclude that shared reality on US television news is indeed diminishing, but is more robust than previously thought and is declining for somewhat different reasons.
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- 2023
10. CLASS Observations of Atmospheric Cloud Polarization at Millimeter Wavelengths
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Li, Yunyang, Appel, John W., Bennett, Charles L., Bustos, Ricardo, Chuss, David T., Cleary, Joseph, Couto, Jullianna Denes, Dahal, Sumit, Datta, Rahul, Dünner, Rolando, Eimer, Joseph R., Essinger-Hileman, Thomas, Harrington, Kathleen, Iuliano, Jeffrey, Marriage, Tobias A., Petroff, Matthew A., Reeves, Rodrigo A., Rostem, Karwan, Shi, Rui, Valle, Deniz A. N., Watts, Duncan J., Wolff, Oliver F., Wollack, Edward J., and Xu, Zhilei
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Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Cosmology and Nongalactic Astrophysics ,Physics - Atmospheric and Oceanic Physics - Abstract
The dynamic atmosphere imposes challenges to ground-based cosmic microwave background observation, especially for measurements on large angular scales. The hydrometeors in the atmosphere, mostly in the form of clouds, scatter the ambient thermal radiation and are known to be the main linearly polarized source in the atmosphere. This scattering-induced polarization is significantly enhanced for ice clouds due to the alignment of ice crystals under gravity, which are also the most common clouds seen at the millimeter-astronomy sites at high altitudes. This work presents a multifrequency study of cloud polarization observed by the Cosmology Large Angular Scale Surveyor (CLASS) experiment on Cerro Toco in the Atacama Desert of northern Chile, from 2016 to 2022, at the frequency bands centered around 40, 90, 150, and 220 GHz. Using a machine-learning-assisted cloud classifier, we made connections between the transient polarized emission found in all four frequencies with the clouds imaged by monitoring cameras at the observing site. The polarization angles of the cloud events are found to be mostly $90^\circ$ from the local meridian, which is consistent with the presence of horizontally aligned ice crystals. The 90 and 150 GHz polarization data are consistent with a power law with a spectral index of $3.90\pm0.06$, while an excess/deficit of polarization amplitude is found at 40/220 GHz compared with a Rayleigh scattering spectrum. These results are consistent with Rayleigh-scattering-dominated cloud polarization, with possible effects from supercooled water absorption and/or Mie scattering from a population of large cloud particles that contribute to the 220 GHz polarization., Comment: 16 pages, 14 figures, submitted to ApJ
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- 2023
11. Two mini-Neptunes Transiting the Adolescent K-star HIP 113103 Confirmed with TESS and CHEOPS
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Lowson, Nataliea, Zhou, George, Huang, Chelsea X., Wright, Duncan J., Edwards, Billy, Nabbie, Emma, Venner, Alex, Quinn, Samuel N., Collins, Karen A., Gillen, Edward, Battley, Matthew, Triaud, Amaury, Hellier, Coel, Seager, Sara, Winn, Joshua N., Jenkins, Jon M., Wohler, Bill, Shporer, Avi, Schwarz, Richard P., Murgas, Felipe, Pallé, Enric, Anderson, David R., West, Richard G., Wittenmyer, Robert A., Bowler, Brendan P., Horner, Jonathan, Kane, Stephen R., Kielkopf, John, Plavchan, Peter, Zhang, Hui, Fairnington, Tyler, Okumura, Jack, Mengel, Matthew W., and Addison, Brett C.
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Astrophysics - Earth and Planetary Astrophysics - Abstract
We report the discovery of two mini-Neptunes in near 2:1 resonance orbits ($P=7.610303$ d for HIP 113103 b and $P=14.245651$ d for HIP 113103 c) around the adolescent K-star HIP 113103 (TIC 121490076). The planet system was first identified from the TESS mission, and was confirmed via additional photometric and spectroscopic observations, including a $\sim$17.5 hour observation for the transits of both planets using ESA CHEOPS. We place $\leq4.5$ min and $\leq2.5$ min limits on the absence of transit timing variations over the three year photometric baseline, allowing further constraints on the orbital eccentricities of the system beyond that available from the photometric transit duration alone. With a planetary radius of $R_{p}=1.829^{+0.096}_{-0.067}\,R_{\oplus}$, HIP 113103 b resides within the radius gap, and this might provide invaluable information on the formation disparities between super-Earths and mini-Neptunes. Given the larger radius $R_{p}=2.40^{+0.10}_{-0.08}\,R_{\oplus}$ for HIP 113103 c, and close proximity of both planets to HIP 113103, it is likely that HIP 113103 b might have lost (or is still losing) its primordial atmosphere. We therefore present simulated atmospheric transmission spectra of both planets using JWST, HST, and Twinkle. It demonstrates a potential metallicity difference (due to differences in their evolution) would be a challenge to detect if the atmospheres are in chemical equilibrium. As one of the brightest multi sub-Neptune planet systems suitable for atmosphere follow up, HIP 113103 b and HIP 113103 c could provide insight on planetary evolution for the sub-Neptune K-star population., Comment: 18 pages, 12 figures, published in the Monthly Notices of the Royal Astronomical Society
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- 2023
12. CLASS Angular Power Spectra and Map-Component Analysis for 40 GHz Observations through 2022
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Eimer, Joseph R., Li, Yunyang, Brewer, Michael K., Shi, Rui, Ali, Aamir, Appel, John W., Bennett, Charles L., Bruno, Sarah Marie, Bustos, Ricardo, Chuss, David T., Cleary, Joseph, Dahal, Sumit, Datta, Rahul, Couto, Jullianna Denes, Denis, Kevin L., Dünner, Rolando, Essinger-Hileman, Thomas, Fluxá, Pedro, Hubmayer, Johannes, Harrington, Kathleen, Iuliano, Jeffrey, Karakla, John, Marriage, Tobias A., Núñez, Carolina, Parker, Lucas, Petroff, Matthew A., Reeves, Rodrigo A., Rostem, Karwan, Valle, Deniz A. N., Watts, Duncan J., Weiland, Janet L., Wollack, Edward J., Xu, Zhilei, and Zeng, Lingzhen
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Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Measurement of the largest angular scale ($\ell < 30$) features of the cosmic microwave background (CMB) polarization is a powerful way to constrain the optical depth to reionization and search for the signature of inflation through the detection of primordial $B$-modes. We present an analysis of maps covering 73.6\% of the sky made from the $40\,\mathrm{GHz}$ channel of the Cosmology Large Angular Scale Surveyor (CLASS) from 2016 August to 2022 May. Taking advantage of the measurement stability enabled by front-end polarization modulation and excellent conditions from the Atacama Desert, we show this channel achieves higher sensitivity than the analogous frequencies from satellite measurements in the range $10 < \ell < 100$. Simulations show the CLASS linear (circular) polarization maps have a white noise level of $125 \,(130)\,\mathrm{\mu K\, arcmin}$. We measure the Galaxy-masked $EE$ and $BB$ spectra of diffuse synchrotron radiation and compare to space-based measurements at similar frequencies. In combination with external data, we expand measurements of the spatial variations of the synchrotron spectral energy density (SED) to include new sky regions and measure the diffuse SED in the harmonic domain. We place a new upper limit on a background of circular polarization in the range $5 < \ell < 125$ with the first bin showing $D_\ell < 0.023$ $\mathrm{\mu K^2_{CMB}}$ at 95\% confidence. These results establish a new standard for recovery of the largest-scale CMB polarization from the ground and signal exciting possibilities when the higher sensitivity and higher-frequency CLASS channels are included in the analysis., Comment: 38 pages, 25 figures, 6 tables. Accepted to The Astrophysical Journal
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- 2023
13. Cosmology Large Angular Scale Surveyor (CLASS): 90 GHz Telescope Pointing, Beam Profile, Window Function, and Polarization Performance
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Datta, Rahul, Brewer, Michael K., Couto, Jullianna Denes, Eimer, Joseph, Li, Yunyang, Xu, Zhilei, Ali, Aamir, Appel, John W., Bennett, Charles L., Bustos, Ricardo, Chuss, David T., Cleary, Joseph, Dahal, Sumit, Espinoza, Francisco, Essinger-Hileman, Thomas, Fluxá, Pedro, Harrington, Kathleen, Helson, Kyle, Iuliano, Jeffrey, Karakla, John, Marriage, Tobias A., Novack, Sasha, Núñez, Carolina, Padilla, Ivan L., Parker, Lucas, Petroff, Matthew A., Reeves, Rodrigo, Rostem, Karwan, Shi, Rui, Valle, Deniz A. N., Watts, Duncan J., Weiland, Janet L., Wollack, Edward J., and Zeng, Lingzhen
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Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that observes the cosmic microwave background (CMB) over ~75% of the sky from the Atacama Desert, Chile, at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the large angular scale CMB polarization to constrain the tensor-to-scalar ratio and the optical depth to last scattering. This paper presents the optical characterization of the 90GHz telescope, which has been observing since July 2018. Observations of the Moon establish the pointing while dedicated observations of Jupiter are used for beam calibration. The standard deviations of the pointing error in azimuth, elevation, and boresight angle are 1.3, 2.1, and 2.0 arcminutes, respectively, over the first 3 years of observations. This corresponds to a pointing uncertainty ~7% of the beam's full width at half maximum (FWHM). The effective azimuthally-symmetrized instrument 1D beam estimated at 90 GHz has an FWHM of 0.620+/-0.003 deg and a solid angle of 138.7+/-0.6(stats.)+/-1.1(sys.) usr integrated to a radius of 4 deg. The corresponding beam window function drops to b_ell^2 = 0.93, 0.71, 0.14 at ell = 30, 100, 300, respectively. Far-sidelobes are studied using detector-centered intensity maps of the Moon and measured to be at a level of 10^-3 or below relative to the peak. The polarization angle of Tau A estimated from preliminary survey maps is 149.6+/-0.2(stats.) deg in equatorial coordinates. The instrumental temperature-to-polarization (T-to-P) leakage fraction, inferred from per-detector demodulated Jupiter scan data, has a monopole component at the level of 1.7 x 10^-3, a dipole component with an amplitude of 4.3 x 10^-3, with no evidence of quadrupolar leakage., Comment: 24 pages, 18 figures, submitted to ApJS
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- 2023
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14. Causally estimating the effect of YouTube's recommender system using counterfactual bots
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Hosseinmardi, Homa, Ghasemian, Amir, Rivera-Lanas, Miguel, Ribeiro, Manoel Horta, West, Robert, and Watts, Duncan J.
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Computer Science - Social and Information Networks - Abstract
In recent years, critics of online platforms have raised concerns about the ability of recommendation algorithms to amplify problematic content, with potentially radicalizing consequences. However, attempts to evaluate the effect of recommenders have suffered from a lack of appropriate counterfactuals -- what a user would have viewed in the absence of algorithmic recommendations -- and hence cannot disentangle the effects of the algorithm from a user's intentions. Here we propose a method that we call ``counterfactual bots'' to causally estimate the role of algorithmic recommendations on the consumption of highly partisan content. By comparing bots that replicate real users' consumption patterns with ``counterfactual'' bots that follow rule-based trajectories, we show that, on average, relying exclusively on the recommender results in less partisan consumption, where the effect is most pronounced for heavy partisan consumers. Following a similar method, we also show that if partisan consumers switch to moderate content, YouTube's sidebar recommender ``forgets'' their partisan preference within roughly 30 videos regardless of their prior history, while homepage recommendations shift more gradually towards moderate content. Overall, our findings indicate that, at least since the algorithm changes that YouTube implemented in 2019, individual consumption patterns mostly reflect individual preferences, where algorithmic recommendations play, if anything, a moderating role.
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- 2023
15. 30 FIVE FEET AT A TIME
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Watts, Duncan J., primary
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- 2024
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16. The science of fake news
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Lazer, David M. J., Baum, Matthew A., Benkler, Yochai, Berinsky, Adam J., Greenhill, Kelly M., Menczer, Filippo, Metzger, Miriam J., Nyhan, Brendan, Pennycook, Gordon, Rothschild, David, Schudson, Michael, Sloman, Steven A., Sunstein, Cass R., Thorson, Emily A., Watts, Duncan J., and Zittrain, Jonathan L.
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Computer Science - Computers and Society - Abstract
Fake news emerged as an apparent global problem during the 2016 U.S. Presidential election. Addressing it requires a multidisciplinary effort to define the nature and extent of the problem, detect fake news in real time, and mitigate its potentially harmful effects. This will require a better understanding of how the Internet spreads content, how people process news, and how the two interact. We review the state of knowledge in these areas and discuss two broad potential mitigation strategies: better enabling individuals to identify fake news, and intervention within the platforms to reduce the attention given to fake news. The cooperation of Internet platforms (especially Facebook, Google, and Twitter) with researchers will be critical to understanding the scale of the issue and the effectiveness of possible interventions., Comment: This is the accepted version of the article, posted to comply with public access mandates. The final published version is available at https://doi.org/10.1126/science.aao2998
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- 2023
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17. Increasing control over biomineralization in conodont evolution
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Shirley, Bryan, Leonhard, Isabella, Murdock, Duncan J. E., Repetski, John, Świś, Przemysław, Bestmann, Michel, Trimby, Pat, Ohl, Markus, Plümper, Oliver, King, Helen E., and Jarochowska, Emilia
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- 2024
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18. Dormant origin firing promotes head-on transcription-replication conflicts at transcription termination sites in response to BRCA2 deficiency
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Goehring, Liana, Keegan, Sarah, Lahiri, Sudipta, Xia, Wenxin, Kong, Michael, Jimenez-Sainz, Judit, Gupta, Dipika, Drapkin, Ronny, Jensen, Ryan B., Smith, Duncan J., Rothenberg, Eli, Fenyö, David, and Huang, Tony T.
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- 2024
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19. Deciphering complexity in Pd–catalyzed cross-couplings
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Clarke, George E., Firth, James D., Ledingham, Lyndsay A., Horbaczewskyj, Chris S., Bourne, Richard A., Bray, Joshua T. W., Martin, Poppy L., Eastwood, Jonathan B., Campbell, Rebecca, Pagett, Alex, MacQuarrie, Duncan J., Slattery, John M., Lynam, Jason M., Whitwood, Adrian C., Milani, Jessica, Hart, Sam, Wilson, Julie, and Fairlamb, Ian J. S.
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- 2024
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20. Artificial Intelligence for Satellite Communication and Non-Terrestrial Networks: A Survey
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Fontanesi, G., Ortíz, F., Lagunas, E., Baeza, V. Monzon, Vázquez, M. Á., Vásquez-Peralvo, J. A., Minardi, M., Vu, H. N., Honnaiah, P. J., Lacoste, C., Drif, Y., Abdu, T. S., Eappen, G., Rehman, J., Garcés-Socorrás, L. M., Martins, W. A., Henarejos, P., Al-Hraishawi, H., Duncan, J. C. Merlano, Vu, T. X., and Chatzinotas, S.
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Electrical Engineering and Systems Science - Signal Processing - Abstract
This paper surveys the application and development of Artificial Intelligence (AI) in Satellite Communication (SatCom) and Non-Terrestrial Networks (NTN). We first present a comprehensive list of use cases, the relative challenges and the main AI tools capable of addressing those challenges. For each use case, we present the main motivation, a system description, the available non-AI solutions and the potential benefits and available works using AI. We also discuss the pros and cons of an on-board and on-ground AI-based architecture, and we revise the current commercial and research activities relevant to this topic. Next, we describe the state-of-the-art hardware solutions for developing ML in real satellite systems. Finally, we discuss the long-term developments of AI in the SatCom and NTN sectors and potential research directions. This paper provides a comprehensive and up-to-date overview of the opportunities and challenges offered by AI to improve the performance and efficiency of NTNs.
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- 2023
21. Microwave Observations of Venus with CLASS
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Dahal, Sumit, Brewer, Michael K., Akins, Alex B., Appel, John W., Bennett, Charles L., Bustos, Ricardo, Cleary, Joseph, Couto, Jullianna D., Datta, Rahul, Eimer, Joseph, Essinger-Hileman, Thomas, Iuliano, Jeffrey, Li, Yunyang, Marriage, Tobias A., Núñez, Carolina, Petroff, Matthew A., Reeves, Rodrigo, Rostem, Karwan, Shi, Rui, Valle, Deniz A. N., Watts, Duncan J., Weiland, Janet L., Wollack, Edward J., and Xu, Zhilei
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Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
We report on the disk-averaged absolute brightness temperatures of Venus measured at four microwave frequency bands with the Cosmology Large Angular Scale Surveyor (CLASS). We measure temperatures of 432.3 $\pm$ 2.8 K, 355.6 $\pm$ 1.3 K, 317.9 $\pm$ 1.7 K, and 294.7 $\pm$ 1.9 K for frequency bands centered at 38.8, 93.7, 147.9, and 217.5 GHz, respectively. We do not observe any dependence of the measured brightness temperatures on solar illumination for all four frequency bands. A joint analysis of our measurements with lower frequency Very Large Array (VLA) observations suggests relatively warmer ($\sim$ 7 K higher) mean atmospheric temperatures and lower abundances of microwave continuum absorbers than those inferred from prior radio occultation measurements., Comment: 10 pages, 3 figures, published in PSJ
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- 2023
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22. Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS
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Psaridi, Angelica, Bouchy, François, Lendl, Monika, Akinsanmi, Babatunde, Stassun, Keivan G., Smalley, Barry, Armstrong, David J., Howard, Saburo, Ulmer-Moll, Solène, Grieves, Nolan, Barkaoui, Khalid, Rodriguez, Joseph E., Bryant, Edward M., Suárez, Olga, Guillot, Tristan, Evans, Phil, Attia, Omar, Wittenmyer, Robert A., Yee, Samuel W., Collins, Karen A., Zhou, George, Galland, Franck, Parc, Léna, Udry, Stéphane, Figueira, Pedro, Ziegler, Carl, Mordasini, Christoph, Winn, Joshua N., Seager, Sara, Jenkins, Jon M., Twicken, Joseph D., Brahm, Rafael, Jones, Matías I., Abe, Lyu, Addison, Brett, Briceño, César, Briegal, Joshua T., Collins, Kevin I., Daylan, Tansu, Eigmüller, Phillip, Furesz, Gabor, Guerrero, Natalia M., Hagelberg, Janis, Heitzmann, Alexis, Hounsell, Rebekah, Huang, Chelsea X., Krenn, Andreas, Law, Nicholas M., Mann, Andrew W., McCormac, James, Mékarnia, Djamel, Mounzer, Dany, Nielsen, Louise D., Osborn, Ares, Reinarz, Yared, Sefako, Ramotholo R., Steiner, Michal, Strøm, Paul A., Triaud, Amaury H. M. J., Vanderspek, Roland, Vanzi, Leonardo, Vines, Jose I., Watson, Christopher A., Wright, Duncan J., and Zapata, Abner
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Astrophysics - Earth and Planetary Astrophysics - Abstract
While the sample of confirmed exoplanets continues to increase, the population of transiting exoplanets around early-type stars is still limited. These planets allow us to investigate the planet properties and formation pathways over a wide range of stellar masses and study the impact of high irradiation on hot Jupiters orbiting such stars. We report the discovery of TOI-615b, TOI-622b, and TOI-2641b, three Saturn-mass planets transiting main sequence, F-type stars. The planets were identified by the Transiting Exoplanet Survey Satellite (TESS) and confirmed with complementary ground-based and radial velocity observations. TOI-615b is a highly irradiated ($\sim$1277 $F_{\oplus}$) and bloated Saturn-mass planet (1.69$^{+0.05}_{-0.06}$$R_{Jup}$ and 0.43$^{+0.09}_{-0.08}$$M_{Jup}$) in a 4.66 day orbit transiting a 6850 K star. TOI-622b has a radius of 0.82$^{+0.03}_{-0.03}$$R_{Jup}$ and a mass of 0.30$^{+0.07}_{-0.08}$~$M_{Jup}$ in a 6.40 day orbit. Despite its high insolation flux ($\sim$600 $F_{\oplus}$), TOI-622b does not show any evidence of radius inflation. TOI-2641b is a 0.39$^{+0.02}_{-0.04}$$M_{Jup}$ planet in a 4.88 day orbit with a grazing transit (b = 1.04$^{+0.05}_{-0.06 }$) that results in a poorly constrained radius of 1.61$^{+0.46}_{-0.64}$$R_{Jup}$. Additionally, TOI-615b is considered attractive for atmospheric studies via transmission spectroscopy with ground-based spectrographs and $\textit{JWST}$. Future atmospheric and spin-orbit alignment observations are essential since they can provide information on the atmospheric composition, formation and migration of exoplanets across various stellar types., Comment: 16 pages, 17 figures, submitted to A&A
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- 2023
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23. Increasing control over biomineralization in conodont evolution
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Bryan Shirley, Isabella Leonhard, Duncan J. E. Murdock, John Repetski, Przemysław Świś, Michel Bestmann, Pat Trimby, Markus Ohl, Oliver Plümper, Helen E. King, and Emilia Jarochowska
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Science - Abstract
Abstract Vertebrates use the phosphate mineral apatite in their skeletons, which allowed them to develop tissues such as enamel, characterized by an outstanding combination of hardness and elasticity. It has been hypothesized that the evolution of the earliest vertebrate skeletal tissues, found in the teeth of the extinct group of conodonts, was driven by adaptation to dental function. We test this hypothesis quantitatively and demonstrate that the crystallographic order increased throughout the early evolution of conodont teeth in parallel with morphological adaptation to food processing. With the c-axes of apatite crystals oriented perpendicular to the functional feeding surfaces, the strongest resistance to uniaxial compressional stress is conferred along the long axes of denticles. Our results support increasing control over biomineralization in the first skeletonized vertebrates and allow us to test models of functional morphology and material properties across conodont dental diversity.
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- 2024
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24. Dormant origin firing promotes head-on transcription-replication conflicts at transcription termination sites in response to BRCA2 deficiency
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Liana Goehring, Sarah Keegan, Sudipta Lahiri, Wenxin Xia, Michael Kong, Judit Jimenez-Sainz, Dipika Gupta, Ronny Drapkin, Ryan B. Jensen, Duncan J. Smith, Eli Rothenberg, David Fenyö, and Tony T. Huang
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Science - Abstract
Abstract BRCA2 is a tumor suppressor protein responsible for safeguarding the cellular genome from replication stress and genotoxicity, but the specific mechanism(s) by which this is achieved to prevent early oncogenesis remains unclear. Here, we provide evidence that BRCA2 acts as a critical suppressor of head-on transcription-replication conflicts (HO-TRCs). Using Okazaki-fragment sequencing (Ok-seq) and computational analysis, we identified origins (dormant origins) that are activated near the transcription termination sites (TTS) of highly expressed, long genes in response to replication stress. Dormant origins are a source for HO-TRCs, and drug treatments that inhibit dormant origin firing led to a reduction in HO-TRCs, R-loop formation, and DNA damage. Using super-resolution microscopy, we showed that HO-TRC events track with elongating RNA polymerase II, but not with transcription initiation. Importantly, RNase H2 is recruited to sites of HO-TRCs in a BRCA2-dependent manner to help alleviate toxic R-loops associated with HO-TRCs. Collectively, our results provide a mechanistic basis for how BRCA2 shields against genomic instability by preventing HO-TRCs through both direct and indirect means occurring at predetermined genomic sites based on the pre-cancer transcriptome.
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- 2024
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25. Deciphering complexity in Pd–catalyzed cross-couplings
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George E. Clarke, James D. Firth, Lyndsay A. Ledingham, Chris S. Horbaczewskyj, Richard A. Bourne, Joshua T. W. Bray, Poppy L. Martin, Jonathan B. Eastwood, Rebecca Campbell, Alex Pagett, Duncan J. MacQuarrie, John M. Slattery, Jason M. Lynam, Adrian C. Whitwood, Jessica Milani, Sam Hart, Julie Wilson, and Ian J. S. Fairlamb
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Science - Abstract
Abstract Understanding complex reaction systems is critical in chemistry. While synthetic methods for selective formation of products are sought after, oftentimes it is the full reaction signature, i.e., complete profile of products/side-products, that informs mechanistic rationale and accelerates discovery chemistry. Here, we report a methodology using high-throughput experimentation and multivariate data analysis to examine the full signature of one of the most complicated chemical reactions catalyzed by palladium known in the chemical literature. A model Pd-catalyzed reaction was selected involving functionalization of 2-bromo-N-phenylbenzamide and multiple bond activation pathways. Principal component analysis, correspondence analysis and heatmaps with hierarchical clustering reveal the factors contributing to the variance in product distributions and show associations between solvents and reaction products. Using robust data from experiments performed with eight solvents, for four different reaction times at five different temperatures, we correlate side-products to a major dominant N-phenyl phenanthridinone product, and many other side products.
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- 2024
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26. Multi-epoch detections of the extended atmosphere and transmission spectra of KELT-9b with a 1.5 m telescope
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Lowson, Nataliea, Zhou, George, Wright, Duncan J., Huang, Chelsea X., Mendonca, Joao M., Cabot, Samuel H. C., Pudmenzky, Christa, Wittenmyer, Robert A., Latham, David W., Bieryla, Allyson, Esquerdo, Gilbert A., Berlind, Perry, and Calkins, Michael L.
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Astrophysics - Earth and Planetary Astrophysics - Abstract
Irradiated Jovian atmospheres are complex, dynamic, and can undergo temporal variations due to the close proximity of their parent stars. Of the Jovian planets that have been catalogued to date, KELT-9b is the hottest Gas Giant known, with an equilibrium temperature of 4050 K. We probe the temporal variability of transmission spectroscopic signatures from KELT-9b via a set of archival multi-year ground-based transit observations, performed with the TRES facility on the 1.5 m reflector at the Fred Lawrence Whipple Observatory. Our observations confirm past detections of Fe I, Fe II and Mg I over multiple epochs, in addition to excess absorption at H-alpha, which is an indicator for ongoing mass-loss. From our multi-year dataset, the H-alpha light curve consistently deviates from a standard transit, and follows a 'W' shape that is deeper near ingress and egress, and shallower mid-transit. To search for and quantify any seasonal variations that may be present, we parameterise a 'cometary tail' model to fit for the H-alpha transit. We find no detectable variations between the different observed epochs. Though a 'cometary tail' describes the H-alpha flux variations well, we note that such a scenario requires a high density of neutral hydrogen in the n = 2 excited state far beyond the planetary atmosphere. Other scenarios, such as centre-to-limb variations larger than that expected from 1-D atmosphere models, may also contribute to the observed H-alpha transit shape. These multi-epoch observations highlight the capabilities of small telescopes to provide temporal monitoring of the dynamics of exoplanet atmospheres., Comment: 19 pages, 11 figures, accepted for publication in AJ
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- 2023
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27. On-sky performance of new 90 GHz detectors for the Cosmology Large Angular Scale Surveyor (CLASS)
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Núñez, Carolina, Appel, John W., Brewer, Michael K., Bruno, Sarah Marie, Datta, Rahul, Bennett, Charles L., Bustos, Ricardo, Chuss, David T., Dahal, Sumit, Denis, Kevin L., Eimer, Joseph, Essinger-Hileman, Thomas, Helson, Kyle, Marriage, Tobias, Pérez, Carolina Morales, Padilla, Ivan L., Petroff, Matthew A., Rostem, Karwan, Watts, Duncan J., Wollack, Edward J., and Xu, Zhilei
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Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Cosmology and Nongalactic Astrophysics ,Physics - Instrumentation and Detectors - Abstract
The Cosmology Large Angular Scale Surveyor (CLASS) is a polarization-sensitive telescope array located at an altitude of 5,200 m in the Chilean Atacama Desert and designed to measure the polarized Cosmic Microwave Background (CMB) over large angular scales. The CLASS array is currently observing with three telescopes covering four frequency bands: one at 40 GHz (Q); one at 90 GHz (W1); and one dichroic system at 150/220 GHz (HF). During the austral winter of 2022, we upgraded the first 90 GHz telescope (W1) by replacing four of the seven focal plane modules. These new modules contain detector wafers with an updated design, aimed at improving the optical efficiency and detector stability. We present a description of the design changes and measurements of on-sky optical efficiencies derived from observations of Jupiter., Comment: 5 pages, 3 figures, to appear in the IEEE Transactions on Applied Superconductivity. arXiv admin note: text overlap with arXiv:2208.05006
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- 2023
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28. Cellular senescence in the pathogenesis of pulmonary arterial hypertension: the good, the bad and the uncertain
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Elmira Safaie Qamsari and Duncan J. Stewart
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endothelial cells ,senescence ,PAH ,pulmonary hypertension ,senotherapeutic ,pulmonary arterial hypertension ,Immunologic diseases. Allergy ,RC581-607 - Abstract
Senescence refers to a cellular state marked by irreversible cell cycle arrest and the secretion of pro-inflammatory and tissue-remodeling factors. The senescence associated secretory phenotype (SASP) impacts the tissue microenvironment and provides cues for the immune system to eliminate senescent cells (SCs). Cellular senescence has a dual nature; it can be beneficial during embryonic development, tissue repair, and tumor suppression, but it can also be detrimental in the context of chronic stress, persistent tissue injury, together with an impairment in SC clearance. Recently, the accumulation of SCs has been implicated in the pathogenesis of pulmonary arterial hypertension (PAH), a progressive condition affecting the pre-capillary pulmonary arterial bed. PAH is characterized by endothelial cell (EC) injury, inflammation, and proliferative arterial remodeling, which leads to right heart failure and premature mortality. While vasodilator therapies can improve symptoms, there are currently no approved treatments capable of reversing the obliterative arterial remodeling. Ongoing endothelial injury and dysfunction is central to the development of PAH, perpetuated by hemodynamic perturbation leading to pathological intimal shear stress. The precise role of senescent ECs in PAH remains unclear. Cellular senescence may facilitate endothelial repair, particularly in the early stages of disease. However, in more advanced disease the accumulation of senescent ECs may promote vascular inflammation and occlusive arterial remodeling. In this review, we will examine the evidence that supports a role of endothelial cell senescence to the pathogenesis of PAH. Furthermore, we will compare and discuss the apparent contradictory outcomes with the use of interventions targeting cellular senescence in the context of experimental models of pulmonary hypertension. Finally, we will attempt to propose a framework for the understanding of the complex interplay between EC injury, senescence, inflammation and arterial remodeling, which can guide further research in this area and the development of effective therapeutic strategies.
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- 2024
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29. Key quality parameter comparison of mesenchymal stem cell product cryopreserved in different cryopreservation solutions for clinical applications
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Yuan Tan, Mahmoud Salkhordeh, Aidan B. P. Murray, Luciana Souza-Moreira, Duncan J. Stewart, and Shirley H. J. Mei
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mesenchymal stem cells ,cryopreservation ,stability ,cell therapy ,final cell products ,quality ,Biotechnology ,TP248.13-248.65 - Abstract
IntroductionCryopreservation is a critical process of cell products for achieving a commercial viability through wide scale adoption. By preserving cells in a lower temperature, cryopreservation enables a product to be off-the-shelf and ready for infusion. An optimized cryopreservation strategy can maintain the viability, phenotype, and potency of thawed mesenchymal stromal/stem cells (MSCs) while being regulatory compliant. We compared three clinical-ready formulations with one research cryopreservation solutions and evaluated key quality parameters of post thawed MSCs.Method and resultMSCs were cryopreserved at 3, 6, and 9 million cells/mL (M/mL) in four different cryopreservation solutions: NutriFreez (10% dimethyl sulfoxide [DMSO]), Plasmalyte A (PLA)/5% human albumin (HA)/10% DMSO (PHD10), CryoStor CS5 (5% DMSO), and CryoStor CS10 (10% DMSO). To establish post thaw viability, cells were evaluated with no dilution of DMSO (from 3 M/mL), 1:1 dilution (from 6 M/mL), or 1:2 dilution (from 9 M/mL) with PLA/5% HA, to achieve uniform concentration at 3 M/mL. Cell viability was measured at 0-, 2-, 4-, and 6-h post thaw with Trypan blue exclusion and Annexin V/PI staining. Dilution (1:2) of final cell products from 9M/mL resulted in an improvement of cell viability over 6 h but showed a trend of decreased recovery. MSCs cryopreserved in solutions with 10% DMSO displayed comparable viabilities and recoveries up to 6 h after thawing, whereas a decreasing trend was noted in cell viability and recovery with CS5. Cells from all groups exhibited surface marker characteristics of MSCs. We further evaluated cell proliferation after 6-day recovery in culture. While cells cryopreserved in NutriFreez and PHD10 presented similar cell growth post thaw, MSCs cryopreserved in CS5 and CS10 at 3 M/mL and 6M/mL showed 10-fold less proliferative capacity. No significant differences were observed between MSCs cryopreserved in NutriFreez and PHD10 in their potency to inhibit T cell proliferation and improve monocytic phagocytosis.ConclusionMSCs can be cryopreserved up to 9 M/mL without losing notable viability and recovery, while exhibiting comparable post thaw potency with NutriFreez and PHD10. These results highlight the importance of key parameter testing for selecting the optimal cryopreservation solution for MSC-based therapy.
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- 2024
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30. 6. Esther Seligson: Nostalgia for the Unknown
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Duncan, J. Ann
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- 2010
31. 4. Carlos Montemayor: Transience and Transcendence
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Duncan, J. Ann
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- 2010
32. 8. Jesus Gardea: Dust Storms in a Desert Bowl
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Duncan, J. Ann
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- 2010
33. 5. Humberto Guzman: Texts and Pretexts
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Duncan, J. Ann
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- 2010
34. 7. Antonio Delgado: Patterns and Language
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Duncan, J. Ann
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- 2010
35. 10. Conclusion
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Duncan, J. Ann
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- 2010
36. 3. Jose-Emilio Pacheco: The Truth of Fiction
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Duncan, J. Ann
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- 2010
37. Index
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Duncan, J. Ann
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- 2010
38. 9. Further innovations, 1970-1982: Huerta, Puga, Azuela, Samperio, Ruiz, Campbell, Hiriart
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Duncan, J. Ann
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- 2010
39. Bibliography
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Duncan, J. Ann
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- 2010
40. Notes
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Duncan, J. Ann
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- 2010
41. Cover
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Duncan, J. Ann
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- 2010
42. Half-Title Page, Title Page, Copyright, Dedication
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Duncan, J. Ann
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- 2010
43. 1. Introduction
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Duncan, J. Ann
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- 2010
44. 2. Innovations in the 1960s: Del Paso, Elizondo, Monterroso, Sainz, Agustin, Garcia Ponce, Lenero, Monsivais
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Duncan, J. Ann
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- 2010
45. Acknowledgments & Textual Note
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Duncan, J. Ann
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- 2010
46. Series Titles
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Duncan, J. Ann
- Published
- 2010
47. A dense mini-Neptune orbiting the bright young star HD 18599
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Vines, Jose I., Jenkins, James S., Berdiñas, Zaira, Soto, Maritza G., Díaz, Matías R., Alves, Douglas R., Tuomi, Mikko, Wittenmyer, Robert A., de Leon, Jerome Pitogo, Peña, Pablo, Lissauer, Jack J., Ballard, Sarah, Bedding, Timothy, Bowler, Brendan P., Horner, Jonathan, Jones, Hugh R. A., Kane, Stephen R., Kielkopf, John, Plavchan, Peter, Shporer, Avi, Tinney, C. G., Wright, Hui Zhang Duncan J., Addison, Brett, Mengel, Matthew W., Okumura, Jack, and Samadi-Ghadim, Anya
- Subjects
Astrophysics - Earth and Planetary Astrophysics - Abstract
Very little is known about the young planet population because the detection of small planets orbiting young stars is obscured by the effects of stellar activity and fast rotation which mask planets within radial velocity and transit data sets. The few planets that have been discovered in young clusters generally orbit stars too faint for any detailed follow-up analysis. Here we present the characterization of a new mini-Neptune planet orbiting the bright (V=9) and nearby K2 dwarf star, HD 18599. The planet candidate was originally detected in TESS light curves from Sectors 2, 3, 29, and 30, with an orbital period of 4.138~days. We then used HARPS and FEROS radial velocities, to find the companion mass to be 25.5$\pm$4.6~M$_\oplus$. When we combine this with the measured radius from TESS, of 2.70$\pm$0.05~R$_\oplus$, we find a high planetary density of 7.1$\pm$1.4~g cm$^{-3}$. The planet exists on the edge of the Neptune Desert and is the first young planet (300 Myr) of its type to inhabit this region. Structure models argue for a bulk composition to consist of 23% H$_2$O and 77% Rock and Iron. Future follow-up with large ground- and space-based telescopes can enable us to begin to understand in detail the characteristics of young Neptunes in the galaxy., Comment: Accepted in MNRAS
- Published
- 2022
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48. Cosmology Large Angular Scale Surveyor (CLASS): Pointing Stability and Beam Measurements at 90, 150, and 220 GHz
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Datta, Rahul, Brewer, Michael K., Couto, Jullianna D., Eimer, Joseph R., Li, Yunyang, Xu, Zhilei, Appel, John W., Bustos, Ricardo, Chuss, David T., Cleary, Joseph, Dahal, Sumit, Essinger-Hileman, Thomas, Iuliano, Jeffrey, Marriage, Tobias A., Núñez, Carolina, Petroff, Matthew A., Rostem, Karwan, Watts, Duncan J., and Wollack, Edward J.
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Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
The Cosmology Large Angular Scale Surveyor (CLASS) telescope array surveys 75% of the sky from the Atacama desert in Chile at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the largest-angular-scale CMB polarization with the aim of constraining the tensor-to-scalar ratio, measuring the optical depth to reionization to near the cosmic variance limit, and more. The CLASS Q-band (40 GHz), W-band (90 GHz), and dichroic high frequency (150/220 GHz) telescopes have been observing since June 2016, May 2018, and September 2019, respectively. On-sky optical characterization of the 40 GHz instrument has been published. Here, we present preliminary on-sky measurements of the beams at 90, 150, and 220 GHz, and pointing stability of the 90 and 150/220 GHz telescopes. The average 90, 150, and 220 GHz beams measured from dedicated observations of Jupiter have full width at half maximum (FWHM) of 0.615+/-0.019 deg, 0.378+/-0.005 deg, and 0.266+/-0.008 deg, respectively. Telescope pointing variations are within a few percent of the beam FWHM., Comment: Submitted to Proc. SPIE Astronomical Telescopes and Instrumentation (2022)
- Published
- 2022
49. Design and characterization of new 90 GHz detectors for the Cosmology Large Angular Scale Surveyor (CLASS)
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Núñez, Carolina, Appel, John W., Bruno, Sarah Marie, Datta, Rahul, Ali, Aamir, Bennett, Charles L., Dahal, Sumit, Couto, Jullianna Denes, Denis, Kevin L., Eimer, Joseph, Espinoza, Francisco, Essinger-Hileman, Tom, Helson, Kyle, Iuliano, Jeffrey, Marriage, Tobias A., Pérez, Carolina Morales, Valle, Deniz Augusto Nunes, Petroff, Matthew A., Rostem, Karwan, Shi, Rui, Watts, Duncan J., Wollack, Edward J., and Xu, Zhilei
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Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
The Cosmology Large Angular Scale Surveyor (CLASS) is a polarization-sensitive telescope array located at an altitude of 5,200 m in the Chilean Atacama Desert. CLASS is designed to measure "E-mode" (even parity) and "B-mode" (odd parity) polarization patterns in the Cosmic Microwave Background (CMB) over large angular scales with the aim of improving our understanding of inflation, reionization, and dark matter. CLASS is currently observing with three telescopes covering four frequency bands: one at 40 GHz (Q); one at 90 GHz (W1); and one dichroic system at 150/220 GHz (G). In these proceedings, we discuss the updated design and in-lab characterization of new 90 GHz detectors. The new detectors include design changes to the transition-edge sensor (TES) bolometer architecture, which aim to improve stability and optical efficiency. We assembled and tested four new detector wafers, to replace four modules of the W1 focal plane. These detectors were installed into the W1 telescope, and will achieve first light in the austral winter of 2022. We present electrothermal parameters and bandpass measurements from in-lab dark and optical testing. From in-lab dark tests, we also measure a median NEP of 12.3 $\mathrm{aW\sqrt{s}}$ across all four wafers about the CLASS signal band, which is below the expected photon NEP of 32 $\mathrm{aW\sqrt{s}}$ from the field. We therefore expect the new detectors to be photon noise limited., Comment: 10 pages, 6 figures, to appear in Proc. SPIE Astronomical Telescopes and Instrumentation 2022
- Published
- 2022
50. Construction of a Large Diameter Reflective Half-Wave Plate Modulator for Millimeter Wave Applications
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Eimer, Joseph R., Brewer, Michael K., Chuss, David T., Karakla, John, Shi, Rui, Appel, John W., Bennett, Charles L., Cleary, Joseph, Dahal, Sumit, Datta, Rahul, Essinger-Hileman, Thomas, Marriage, Tobias A., Núñez, Carolina, Petroff, Matthew A., Watts, Duncan J., Wollack, Edward J., and Xu, Zhilei
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
Polarization modulation is a powerful technique to increase the stability of measurements by enabling the distinction of a polarized signal from dominant slow system drifts and unpolarized foregrounds. Furthermore, when placed as close to the sky as possible, modulation can reduce systematic errors from instrument polarization. In this work, we introduce the design and preliminary drive system laboratory performance of a new 60 cm diameter reflective half-wave plate (RHWP) polarization modulator. The wave plate consists of a wire array situated in front of a flat mirror. Using \mbox{50 $\mu$m} diameter wires with \mbox{175 $\mu$m} spacing, the wave plate will be suitable for operation in the millimeter wavelength range with flatness of the wires and parallelism to the mirror held to a small fraction of a wavelength. The presented design targets the 77--108 GHz range. Modulation is performed by a rotation of the wave plate with a custom rotary drive utilizing an actively controlled servo motor., Comment: 13 pages, 7 figures, to appear in Proc. SPIE Astronomical Telescopes and Instrumentation 2022
- Published
- 2022
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