Article
Chemistry, Physical
Paul Cavanaugh, Xudong Wang, Maria J. Bautista, Ilan Jen-La Plante, David F. Kelley
Summary: This paper investigates the mechanisms responsible for the larger Stokes shifts and photoluminescence (PL) line widths in InP-based quantum dots (QDs) compared to II-VI semiconductor QDs with comparable exciton energies. The Stokes shift is found to decrease with different semiconductors, with InP having the largest shift, followed by CdTe and CdSe. The size of the QDs and the deposition of a ZnSe shell also affect the Stokes shift. The spectral widths are controlled by homogeneous and inhomogeneous broadening, with size inhomogeneity and core-shell interface inhomogeneity being the two types of inhomogeneous broadening.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Kailai Lin, Dipti Jasrasaria, Jason J. Yoo, Moungi Bawendi, Hendrik Utzat, Eran Rabani
Summary: Single-molecule photoluminescence spectroscopy is used to study the exciton-phonon interactions in semiconductor nanocrystals. A detailed model is developed to explain the PL spectrum, taking into account excitonic effects, phonon dispersion relations, and exciton-phonon couplings. The model is validated with experimental measurements on CdSe/CdS nanocrystals, revealing the presence of a narrow zero-phonon line and acoustic phonon sidebands in the slightly asymmetric main peak at low temperatures. The dependence of the spectral line width on temperature is shown to be correlated with higher order exciton-phonon couplings.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Environmental Sciences
Sandra Vazquez-Martin, Thomas Kuhn, Salomon Eliasson
Summary: Meteorological forecast and climate models rely on understanding the microphysical properties of hydrometeors and ice crystals in clouds, including size, shape, mass, and fall speed. Shape is particularly important for its impact on ice particles' scattering properties and response to remote sensing techniques. Particle fall speed and mass are crucial for numerical forecast models and the representation of snow and ice clouds in climate models, influencing ice removal rates and connecting cloud microphysical properties to radiative properties.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2021)
Article
Nanoscience & Nanotechnology
Davis M. Welakuh, Prineha Narang
Summary: In this work, the researchers demonstrate that Fano interference phenomena can be realized in a multimode photonic environment by strong coupling to the electromagnetic continuum. They show that by effectively enhancing the light-matter coupling strength, transitions between Lorentzian and Fano line shapes can be achieved.
Article
Chemistry, Physical
Ruoqi Zhao, Joseph C. Shirley, Euihyun Lee, Adam Grofe, Hui Li, Carlos R. Baiz, Jiali Gao
Summary: This article discusses the difficulties in constructing a general-purpose vibrational map for methyl thiocyanate and the limitations of common vibrational mapping schemes. By comparing the results of quantum vibrational perturbation theory and molecular mechanical simulations with experimental results, an alternative and efficient modeling technique is proposed.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Optics
O. Ben Fathallah, L. Manceron, N. Dridi, M. Rotger, H. Aroui
Summary: In this study, broadening coefficients of methyl chloride were measured for N-2(-) and O-2 at specific wavenumber range using a high-resolution Fourier transform spectrometer. The experimental results showed an accuracy of around 7% and 17% for broadening and shift coefficients respectively, with comparisons made to previous measurements and semi-classical predictions.
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
(2021)
Article
Optics
C. Boulet, Q. Ma
Summary: Calculations of the widths and temperature dependence of transitions in CH3I in the v(5) and v(6) bands have been made using a modified semi-classical line shape formalism. The results show good agreement with available data and propose new experiments to further investigate inter-doublet mixing effects.
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
(2022)
Article
Materials Science, Multidisciplinary
V. A. Nepochatenko, A. V. Nepochatenko, U. S. Revytska, O. A. Strygina
Summary: A regression analysis was conducted to investigate the temperature dependence of the elasticity coefficients in the cubic phase of BaTiO3. Two functions were proposed with one or two critical temperatures (T-1 and T-2) in the region of phase transition and above the melting point. The study revealed that the effective elasticity coefficient has three minima, one near the phase transition, the second near the crystal melting temperature, and the third at 3502 ? where the bulk modulus of elasticity approaches zero.
Article
Chemistry, Physical
Peter A. Knudsen, Kristine Niss, Nicholas P. Bailey
Summary: Experimental results on the structure of the ionic liquid show invariance along curves of equal electrical conductivity, with some variation with temperature. A study using molecular dynamics simulations indicates that there is substantial invariance of structure and dynamics along configurational adiabats, referred to as isodynes, within a certain density range.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Engineering, Electrical & Electronic
A. Chroneos, G. Ya Khadzhai, I. L. Goulatis, A. Mazepulin, M. Korobkov, R. V. Vovk
Summary: In this study, the influence of high hydrostatic pressure on the conductivity of praseodymium-doped single-crystal samples was investigated. It was found that high pressure resulted in phase separation in the crystals. The mechanisms of the resistive transition and the conductivity were analyzed.
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
(2022)
Article
Energy & Fuels
Mengyao Lyu, Jou Lin, John Krupczak, Donglu Shi
Summary: We have developed a spectral modulating nano system using Fe3O4@Cu2-XS nanoparticles and chlorophyllin, which can synergistically harvest and generate solar energy through photothermal, thermoelectric, and photovoltaic processes. The system utilizes a transparent photothermal spectral modulator (TPSM) to harvest solar light and separates it into different wavelengths. The infrared (IR) is used for photothermal heating of the thermoelectric module, while the UV/visible light is directed to the photovoltaic cell with reduced IR for enhanced power conversion efficiency. By implementing this system, the power conversion efficiency of the photovoltaic cell increased from 16.3% to 19.4%.
Article
Physics, Multidisciplinary
Peter Lunkenheimer, Alois Loidl, Birte Riechers, Alessio Zaccone, Konrad Samwer
Summary: The Lindemann criterion applies to the melting of crystals but not to glasses. There is a universal relationship between glass temperature and thermal expansion. The thermal expansion coefficient of glasses behaves differently from crystals, indicating a liquid-solid cross-over in glasses.
Article
Materials Science, Multidisciplinary
V. A. Nepochatenko, A. V. Nepochatenko, U. S. Revytska, O. A. Strygina
Summary: A regression analysis was conducted to investigate the temperature dependence of elastic compliance coefficients Sij in the tetragonal phase of BaTiO3. Two functions with critical temperatures were proposed, one for S44(t) and the other for the remaining coefficients Sij(t). The temperature dependence of elasticity tensor components Cij(t) in the tetragonal phase was calculated based on the obtained analytical relationships. Formulas for determining the effective coefficient of elasticity Cef and the effective coefficient of elastic compliance Sef were proposed. It was found that Cef exhibits minima near the structural phase transitions in BaTiO3.
Article
Biophysics
Yuxi Pang
Summary: This study aimed to demonstrate the importance of phase shift e0 in quantifying R-2 and R-2 in human brain white matter (WM). It was found that e0 is essential for better characterization of R-2 and R-2 orientation dependence profiles. The origin of e0 was shown to be related to the directional diffusivities from standard DTI. These findings have significant implications for interpreting prior R-2 and R-2 datasets and future research.
NMR IN BIOMEDICINE
(2023)
Article
Chemistry, Multidisciplinary
Brian M. Hays, Divita Gupta, Theo Guillaume, Omar Abdelkader Khedaoui, Ilsa R. Cooke, Franck Thibault, Francois Lique, Ian R. Sims
Summary: HCN and HNC, two molecules observed in the interstellar medium, have different collisional excitation properties and their abundance ratios correlate strongly with temperature.
Article
Environmental Sciences
Le Kuai, Nicholas C. Parazoo, Mingjie Shi, Charles E. Miller, Ian Baker, Anthony A. Bloom, Kevin Bowman, Meemong Lee, Zhao-Cheng Zeng, Roisin Commane, Stephen A. Montzka, Joe Berry, Colm Sweeney, John B. Miller, Yuk L. Yung
Summary: The northern high latitude is the second peak region of gross primary productivity other than the tropics, but both regions are highly uncertain. Optimized OCS fluxes suggest a stronger plant uptake OCS flux in the northern high latitude compared to GPP-based fluxes, and GPP-based fluxes underestimate the peak growing season. Additionally, early start of season in Alaska is consistent with previous studies. The optimized OCS-GPP for the northern high latitude is about 25% higher than the peak value.
GLOBAL BIOGEOCHEMICAL CYCLES
(2022)
Article
Multidisciplinary Sciences
Daniel H. Cusworth, Andrew K. Thorpe, Alana K. Ayasse, David Stepp, Joseph Heckler, Gregory P. Asner, Charles E. Miller, Vineet Yadav, John W. Chapman, Michael L. Eastwood, Robert O. Green, Benjamin Hmiel, David R. Lyon, Riley M. Duren
Summary: Understanding, quantifying, and attributing methane emissions from facility to regional scales is crucial for effectively reducing methane emissions. This study deployed a tiered observing system to quantify and attribute methane emissions in multiple basins in the United States. The study found that point source emissions, which make up an average of 40% of the regional flux, exhibit a bimodal structure in emission timescales. With improved airborne and satellite observing capabilities in the future, tiered observing systems will be able to more comprehensively quantify and attribute methane emissions.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Environmental Sciences
Jeff Dozier, Edward H. Bair, Latha Baskaran, Philip G. Brodrick, Nimrod Carmon, Raymond F. Kokaly, Charles E. Miller, Kimberley R. Miner, Thomas H. Painter, David R. Thompson
Summary: The chemical and biological composition of Earth's land surface, as well as the physical structure and arrangement of surface materials, determine the intrinsic reflectance. Remote sensing data accuracy is sensitive to uncertainties in topographic properties, and global DEM products consistently underestimate solar angle cosine and shadows.
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
(2022)
Article
Environmental Sciences
Renato K. Braghiere, Joshua B. Fisher, Kimberley R. Miner, Charles E. Miller, John R. Worden, David S. Schimel, Christian Frankenberg
Summary: Estimating the impacts of climate change on the global carbon cycle relies on projections from Earth system models (ESMs). The new generation of increased complexity ESMs in the Intergovernmental Panel on Climate Change Sixth Assessment Report aims to improve future climate projections. In this study, CMIP5 and CMIP6 ensembles were benchmarked using ILAMB tool over the NASA Arctic-Boreal vulnerability experiment (ABoVE) region in North America, showing that CMIP6 has higher projected average net biome production (NBP) in 2100 compared to CMIP5, and better agreement with contemporary observed carbon cycle variables.
ENVIRONMENTAL RESEARCH LETTERS
(2023)
Article
Biodiversity Conservation
Donatella Zona, Peter M. Lafleur, Koen Hufkens, Beniamino Gioli, Barbara Bailey, George Burba, Eugenie S. Euskirchen, Jennifer D. Watts, Kyle A. Arndt, Mary Farina, John S. Kimball, Martin Heimann, Mathias Gockede, Martijn Pallandt, Torben R. Christensen, Mikhail Mastepanov, Efren Lopez-Blanco, Albertus J. Dolman, Roisin Commane, Charles E. Miller, Josh Hashemi, Lars Kutzbach, David Holl, Julia Boike, Christian Wille, Torsten Sachs, Aram Kalhori, Elyn R. Humphreys, Oliver Sonnentag, Gesa Meyer, Gabriel H. Gosselin, Philip Marsh, Walter C. Oechel
Summary: Long-term records of atmospheric CO2 concentration indicate a decrease in the positive effect of warming on carbon uptake in high-latitude regions since the 1990s. This study used data from permafrost tundra sites across the circumpolar Arctic to examine the temperature responses of ecosystem carbon fluxes and their relationship with soil moisture. The results suggest that reduced soil moisture during peak summer may limit plant productivity and carbon sequestration in tundra ecosystems.
GLOBAL CHANGE BIOLOGY
(2022)
Article
Biodiversity Conservation
Jennifer D. Watts, Mary Farina, John S. Kimball, Luke D. Schiferl, Zhihua Liu, Kyle A. Arndt, Donatella Zona, Ashley Ballantyne, Eugenie S. Euskirchen, Frans-Jan W. Parmentier, Manuel Helbig, Oliver Sonnentag, Torbern Tagesson, Janne Rinne, Hiroki Ikawa, Masahito Ueyama, Hideki Kobayashi, Torsten Sachs, Daniel F. Nadeau, John Kochendorfer, Marcin Jackowicz-Korczynski, Anna Virkkala, Mika Aurela, Roisin Commane, Brendan Byrne, Leah Birch, Matthew S. Johnson, Nima Madani, Brendan Rogers, Jinyang Du, Arthur Endsley, Kathleen Savage, Ben Poulter, Zhen Zhang, Lori M. Bruhwiler, Charles E. Miller, Scott Goetz, Walter C. Oechel
Summary: Arctic-boreal landscapes are experiencing significant warming, moisture changes, and fire disturbance, which affects the carbon budget in the region. This study provides new estimates of carbon fluxes and methane emissions based on satellite data and model simulations, showing a net carbon sink in the Arctic-boreal zone. However, accounting for additional emissions from aquatic bodies and fire shifts some areas to carbon sources, highlighting the need for integrated assessments to monitor the vulnerability of these ecosystems to climate change.
GLOBAL CHANGE BIOLOGY
(2023)
Article
Optics
Keeyoon Sung, Edward H. Wishnow, Brian J. Drouin, Laurent Manceron, Marine Verseils, D. Chris Benner, Conor A. Nixon
Summary: Laboratory measurements were conducted on the pure rotational transitions of hydrogen deuteride (HD) at low pressures and temperatures. The obtained spectroscopic line parameters were compared to previous measurements, showing a significant difference in linewidths. This research is important for understanding the atmospheres of giant gaseous planets.
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
(2023)
Article
Geosciences, Multidisciplinary
Andrew L. Mullen, Jennifer D. Watts, Brendan M. Rogers, Mark L. Carroll, Clayton D. Elder, Jonas Noomah, Zachary Williams, Jordan A. Caraballo-Vega, Allison Bredder, Eliza Rickenbaugh, Eric Levenson, Sarah W. Cooley, Jacqueline K. Y. Hung, Greg Fiske, Stefano Potter, Yili Yang, Charles E. Miller, Susan M. Natali, Thomas A. Douglas, Ethan D. Kyzivat
Summary: Small water bodies, such as ponds, have a significant impact on Earth System processes, but detecting and monitoring them using satellite imagery has been challenging. A new approach using high-resolution optical satellite imagery and deep learning methods allows for mapping seasonal changes in pond and lake areas. This method has various applications including assessing water resources, land cover change, wildlife management, and biogeochemical modeling.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Geosciences, Multidisciplinary
C. Bertin, D. Carroll, D. Menemenlis, S. Dutkiewicz, H. Zhang, A. Matsuoka, S. Tank, M. Manizza, C. E. Miller, M. Babin, A. Mangin, V. Le Fouest
Summary: Arctic warming changes the fluxes of nutrients and organic matter from land to sea, affecting air-sea carbon exchange. Using a biogeochemical model, this study examines the role of Mackenzie River discharge in modulating air-sea CO2 fluxes in the southeastern Beaufort Sea from 2000 to 2019. The discharge of six chemical constituents leads to a net CO2 outgassing of 0.13 TgC yr(-1) and a decrease in the coastal carbon sink due to riverine dissolved organic and inorganic carbon. The results indicate that the Mackenzie River influences the capacity of the southeastern Beaufort Sea to act as a sink or source of atmospheric CO2. Accurate representation of land-to-sea biogeochemical coupling is crucial for understanding the Arctic coastal ocean response to the rapidly changing environment.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Environmental Sciences
Dedi Yang, Bailey D. Morrison, Wouter Hanston, Andrew McMahon, Latha Baskaran, Daniel. J. Hayes, Charles E. Miller, Shawn P. Serbin
Summary: This study demonstrates the feasibility of using UAS imagery and hyperspectral airborne instrument to map the composition of Arctic vegetation. The results show that high-resolution UAS imagery can effectively map Arctic plant functional types, and the fractional cover of each type can be accurately estimated from AVIRIS-NG imagery using partial least squares regression models.
REMOTE SENSING OF ENVIRONMENT
(2023)
Article
Astronomy & Astrophysics
Brendan L. Steffens, Conor A. Nixon, Keeyoon Sung, Patrick G. J. Irwin, Nicholas A. Lombardo, Eric Pereira
Summary: Researchers used infrared spectroscopic observations to search for signals of n-butane in Titan's atmosphere. Although no firm detection was made, they obtained new upper limits on the abundance of this gas, which will constrain future photochemical modeling of Titan's C-4 chemistry.
PLANETARY SCIENCE JOURNAL
(2022)
Article
Meteorology & Atmospheric Sciences
Broghan M. Erland, Cristen Adams, Andrea Darlington, Mackenzie L. Smith, Andrew K. Thorpe, Gregory R. Wentworth, Steve Conley, John Liggio, Shao-Meng Li, Charles E. Miller, John A. Gamon
Summary: To combat global warming, Canada has committed to reducing greenhouse gases (GHGs) to 40%-45% below 2005 emission levels by 2025. This study compares two airborne mass-balance box-flight algorithms and finds that they produce similar estimates under ideal conditions. However, the algorithms may disagree under non-ideal conditions. The study also highlights the importance of increased sampling to understand the variability of emissions.
ATMOSPHERIC MEASUREMENT TECHNIQUES
(2022)
Article
Ecology
Brendan Byrne, Junjie Liu, Yonghong Yi, Abhishek Chatterjee, Sourish Basu, Rui Cheng, Russell Doughty, Frederic Chevallier, Kevin W. Bowman, Nicholas C. Parazoo, David Crisp, Xing Li, Jingfeng Xiao, Stephen Sitch, Bertrand Guenet, Feng Deng, Matthew S. Johnson, Sajeev Philip, Patrick C. McGuire, Charles E. Miller
Summary: This study reveals strong seasonal variations of CO2 exchange in the northeastern region of Eurasia during the 2015-2019 period, which differ from current global vegetation models' predictions. The significant and spatially extensive early cold season CO2 efflux in the permafrost-rich region of northeast Eurasia is highlighted in this study.
Article
Environmental Sciences
Colm Sweeney, Abhishek Chatterjee, Sonja Wolter, Kathryn McKain, Robert Bogue, Stephen Conley, Tim Newberger, Lei Hu, Lesley Ott, Benjamin Poulter, Luke Schiferl, Brad Weir, Zhen Zhang, Charles E. Miller
Summary: Accurate estimation of carbon-climate feedbacks requires evaluation of surface flux models at regional scales. The Arctic Carbon Atmospheric Profiles (Arctic-CAP) project demonstrates the usefulness of the altitude-integrated enhancement (AIE) as a bulk quantity for model evaluation. Six airborne profiling surveys were conducted in Alaska and northwestern Canada as part of NASA's Arctic-Boreal Vulnerability Experiment (ABoVE), comparing aircraft observations to a global simulation using the Goddard Earth Observing System (GEOS) modeling system. The comparison highlights the accuracy of the modeled surface fluxes but indicates the need for further study of fine-scale flux features captured in CO observations.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2022)
Review
Environmental Sciences
Kimberley R. Miner, Merritt R. Turetsky, Edward Malina, Annett Bartsch, Johanna Tamminen, A. David McGuire, Andreas Fix, Colm Sweeney, Clayton D. Elder, Charles E. Miller
Summary: Arctic permafrost stores a significant amount of carbon, which could be released due to anthropogenic warming, affecting climate. Abrupt thaw and thermokarst could rapidly release a substantial amount of carbon to the atmosphere, and future methane emissions could increase due to expanding anoxic conditions. Wildfires in the Arctic could also lead to unpredictable carbon flux. More detailed monitoring can provide a better understanding of Arctic's future carbon emissions and their impact on the Earth system.
NATURE REVIEWS EARTH & ENVIRONMENT
(2022)