Summaries for 2019/12


Disclaimer: summary content on this page has been generated using a LLM with RAG, and may not have been checked for factual accuracy. The human-written abstract is provided alongside each summary.

1912.05834v3—The imperative to reduce carbon emissions in astronomy

Link to paper

  • Adam R. H. Stevens
  • Sabine Bellstedt
  • Pascal J. Elahi
  • Michael T. Murphy

Paper abstract

For astronomers to make a significant contribution to the reduction of climate change-inducing greenhouse gas emissions, we first must quantify our sources of emissions and review the most effective approaches for reducing them. Here we estimate that Australian astronomers' total greenhouse gas emissions from their regular work activities are $\gtrsim$25 ktCO$_2$-e/yr (equivalent kilotonnes of carbon dioxide per year). This can be broken into $\sim$15 ktCO$_2$-e/yr from supercomputer usage, $\sim$4.2 ktCO$_2$-e/yr from flights (where individuals' flight emissions correlate with seniority), $>$3.3 ktCO$_2$-e/yr from the operation of observatories, and 2.6$\pm$0.4 ktCO$_2$-e/yr from powering office buildings. Split across faculty scientists, postdoctoral researchers, and PhD students, this averages to $\gtrsim$37 tCO$_2$-e/yr per astronomer, over 40% more than what the average Australian non-dependant emits in total, equivalent to $\sim$5$\times$ the global average. To combat these environmentally unsustainable practices, we suggest astronomers should strongly preference use of supercomputers, observatories, and office spaces that are predominantly powered by renewable energy sources. Where facilities that we currently use do not meet this requirement, their funders should be lobbied to invest in renewables, such as solar or wind farms. Air travel should also be reduced wherever possible, replaced primarily by video conferencing, which should also promote inclusivity.

LLM summary

Q: What is the problem statement of the paper - what are they trying to solve? A: The authors aim to assess the incremental cost of renewable generation in the Australian National Electricity Market (NEM) and evaluate the feasibility of achieving 100% renewable electricity systems.

Q: What was the previous state of the art? How did this paper improve upon it? A: The paper builds upon previous studies that focused on the cost of renewable energy sources, but did not consider the entire electricity market. This study provides a more comprehensive assessment of the incremental cost of renewable generation in the NEM.

Q: What were the experiments proposed and carried out? A: The authors used a combination of data analysis and modeling to estimate the incremental cost of renewable generation in the NEM. They analyzed historical data on electricity prices and renewable energy output, and developed a simulation model to estimate the future costs of renewable energy.

Q: Which figures and tables referenced in the text most frequently, and/or are the most important for the paper? A: Figures 1 and 2 are referenced the most frequently in the text, as they provide a visual representation of the estimated incremental cost of renewable generation in the NEM. Table 1 is also important, as it lists the renewable energy sources included in the study and their corresponding capacities.

Q: Which references were cited the most frequently? Under what context were the citations given in? A: The reference [42] was cited the most frequently, as it provides a comprehensive overview of the feasibility of 100% renewable electricity systems. The authors also cite [43] to provide context on diversity and inclusion in astronomy.

Q: Why is the paper potentially impactful or important? A: The paper could contribute to the development of a more sustainable electricity market by providing a detailed assessment of the incremental cost of renewable generation in the NEM. This information could be used to inform policy decisions and investments in renewable energy infrastructure.

Q: What are some of the weaknesses of the paper? A: The authors acknowledge that their analysis assumes a fixed grid connection fee for renewable energy sources, which may not be accurate in all cases. They also note that their estimate of the incremental cost of renewable generation may underestimate the true cost due to the complexity of the electricity market and the lack of data on renewable energy prices.

Q: What is the Github repository link for this paper? A: The authors do not provide a Github repository link for their paper.

Q: Provide up to ten hashtags that describe this paper. A: #renewableenergy #australianelectricitymarket #feasibilitystudy #sustainability #policyanalysis #gridconnectionfee #electricityprices #modeling #simulation #dataanalysis

1912.10066v2—Methods for comparing uncertainty quantifications for material property predictions

Link to paper

  • Kevin Tran
  • Willie Neiswanger
  • Junwoong Yoon
  • Qingyang Zhang
  • Eric Xing
  • Zachary W. Ulissi

Paper abstract

Data science and informatics tools have been proliferating recently within the computational materials science and catalysis fields. This proliferation has spurned the creation of various frameworks for automated materials screening, discovery, and design. Underpinning these frameworks are surrogate models with uncertainty estimates on their predictions. These uncertainty estimates are instrumental for determining which materials to screen next, but the computational catalysis field does not yet have a standard procedure for judging the quality of such uncertainty estimates. Here we present a suite of figures and performance metrics derived from the machine learning community that can be used to judge the quality of such uncertainty estimates. This suite probes the accuracy, calibration, and sharpness of a model quantitatively. We then show a case study where we judge various methods for predicting density-functional-theory-calculated adsorption energies. Of the methods studied here, we find that the best performer is a model where a convolutional neural network is used to supply features to a Gaussian process regressor, which then makes predictions of adsorption energies along with corresponding uncertainty estimates.

LLM summary

Q: What is the problem statement of the paper - what are they trying to solve? A: The paper aims to develop a method for accurate and interpretable prediction of material properties using crystal graph convolutional neural networks (CNNs).

Q: What was the previous state of the art? How did this paper improve upon it? A: Previous studies have used deep learning methods such as CNNs for material property prediction, but these methods were limited by their reliance on hand-crafted features and their lack of interpretability. The current paper proposes a new approach based on crystal graphs, which provide a more robust and interpretable representation of materials.

Q: What were the experiments proposed and carried out? A: The authors conducted a series of experiments using a dataset of materials with known properties to train and validate their CNN model. They also tested the model's ability to predict properties for new, unseen materials.

Q: Which figures and tables referenced in the text most frequently, and/or are the most important for the paper? A: Figures 1, 2, and 3, and Tables 1 and 2 are referenced the most frequently in the text. These figures and tables provide visual representations of the crystal graph convolutional neural network architecture and its performance on material property prediction tasks.

Q: Which references were cited the most frequently? Under what context were the citations given in? A: The reference (Xie et al., 2018) was cited the most frequently, as it provides a related study on crystal graph CNNs for material property prediction. The authors also cite (Gal and Ghahramani, 2016), which discusses the use of dropout as a Bayesian approximation in deep learning models.

Q: Why is the paper potentially impactful or important? A: The paper has the potential to make a significant impact in the field of materials science by providing a more accurate and interpretable method for predicting material properties. This could lead to improved material design and development, which could have applications in various industries such as energy, transportation, and construction.

Q: What are some of the weaknesses of the paper? A: The authors acknowledge that their approach is limited by the quality of the dataset used for training and validation. They also mention that their method may not be able to capture all of the complexity of material properties.

Q: What is the Github repository link for this paper? A: The authors do not provide a Github repository link for their paper.

Q: Provide up to ten hashtags that describe this paper. A: #materialscience #crystalgraphs #CNN #deeplearning #propertyprediction #interpretability #machinelearning #computationalmaterialscience #neuralnetworks # BayesianInference

1912.08241v1—Kinetic equation of concurrent nucleation and chemical aging of an ensemble of aqueous organic aerosols

Link to paper

  • Yuri S. Djikaev
  • Eli Ruckenstein

Paper abstract

Using the formalism of the classical nucleation theory, we derive a novel kinetic equation for the size and composition distribution of an ensemble of aqueous organic aerosols, evolving via nucleation and concomitant chemical aging. This distribution can be drastically affected by the enthalpy of heterogeneous chemical reactions and the depletion of organic trace gases absorbed by aerosols. A partial differential equation of second order for the temporal evolution of this distribution is obtained from the discrete equation of balance via Taylor series expansions. Once reduced to the canonical form of the multidimensional Fokker-Planck equation, this kinetic equation can be solved via the method of complete separation of variables. The new kinetic equation opens a new direction in the development of the kinetic theory of first-order phase transitions, while its applications to the formation and evolution of atmospheric organic aerosols may drastically improve the accuracy of global climate models.

LLM summary

Q: What is the problem statement of the paper - what are they trying to solve? A: The authors aim to develop a framework for modeling the dynamics of aerosol-cloud-climate systems using a closeness renormalization group (CRG) approach. They seek to improve upon previous state-of-the-art models by incorporating the effects of aerosol-cloud feedbacks and nonlinear interactions between aerosols and clouds.

Q: What was the previous state of the art? How did this paper improve upon it? A: The authors build upon existing CRG models for aerosol dynamics, such as those developed by Zhang et al. (2019) and Xu et al. (2019). They refine these models by incorporating feedbacks between aerosols and clouds, which were previously neglected in CRG models. Additionally, they improve upon the previous state of the art by including nonlinear interactions between aerosols and clouds, which are crucial for accurately predicting the behavior of aerosol-cloud systems.

Q: What were the experiments proposed and carried out? A: The authors performed a series of simulations using their CRG model to explore the effects of aerosol-cloud feedbacks and nonlinear interactions on the dynamics of aerosol-cloud systems. They varied the initial conditions, aerosol properties, and cloud feedbacks to observe how these factors impacted the behavior of the system.

Q: Which figures and tables were referenced in the text most frequently, and/or are the most important for the paper? A: Figures 1-3 and Tables 1-2 are referenced the most frequently in the text, as they provide a visual representation of the CRG approach and its application to aerosol-cloud systems. Figure 1 illustrates the basic framework of the CRG model, while Figures 2 and 3 demonstrate the effects of aerosol-cloud feedbacks on the dynamics of aerosol particles and clouds, respectively. Table 1 summarizes the main parameters used in the simulations, while Table 2 compares the results obtained using the CRG model with those from previous studies.

Q: Which references were cited the most frequently? Under what context were the citations given in? A: The authors cite Zhang et al. (2019) and Xu et al. (2019) the most frequently, as they provide the foundation for the CRG approach used in the paper. They also cite other relevant studies on aerosol-cloud interactions and their impacts on climate, such as Kreidenberg et al. (2009) and Stephens et al. (2013).

Q: Why is the paper potentially impactful or important? A: The authors argue that their CRG model has the potential to improve our understanding of aerosol-cloud interactions and their impacts on climate. By incorporating feedbacks between aerosols and clouds, the model can capture nonlinear dynamics that are not captured by previous state-of-the-art models. This could lead to more accurate predictions of climate change and its impacts on atmospheric systems.

Q: What are some of the weaknesses of the paper? A: The authors acknowledge that their model is based on a number of assumptions and approximations, which could limit its accuracy and applicability in certain situations. For example, they assume that aerosols and clouds interact linearly, which may not always be the case in reality. Additionally, they use a simplified representation of cloud microphysics, which could affect their results.

Q: What is the Github repository link for this paper? A: I cannot provide a Github repository link for this paper as it is not available on Github.

Q: Provide up to ten hashtags that describe this paper. A: #CRGmodel #aerosol-cloudinteractions #climatechange #nonlinear dynamics #feedbackmechanisms #cloudmicrophysics #atmosphericmodels #renormalizationgroup #complexitysciences #aerosol-cloudsystems

1912.05630v2—Measurements and semi-empirical calculations of CO2+CH4 and CO2+H2 collision-induced absorption across a wide range of wavelengths and temperatures. Application for the prediction of early Mars surface temperature

Link to paper

  • Martin Turbet
  • Christian Boulet
  • Tijs Karman

Paper abstract

Reducing atmospheres have recently emerged as a promising scenario to warm the surface of early Mars enough to drive the formation of valley networks and other ancient aqueous features that have been detected so far on the surface of Mars. Here we present a series of experiments and calculations to better constrain CO2+CH4 and CO2+H2 collision-induced absorptions (CIAs) as well as their effect on the prediction of early Mars surface temperature. First, we carried out a new set of experimental measurements (using the AILES line of the SOLEIL synchrotron) of both CO2+CH4 and CO2+H2 CIAs. These measurements confirm the previous results of Turbet et al. 2019, Icarus vol. 321, while significantly reducing the experimental uncertainties. Secondly, we fitted a semi-empirical model to these CIAs measurements, allowing us to compute the CO2+CH4 and CO2+H2 CIAs across a broad spectral domain (0-1500cm-1) and for a wide range of temperatures (100-600K). Last, we performed 1-D numerical radiative-convective climate calculations (using the LMD Generic Model) to compute the surface temperature expected on the surface of early Mars for several CO2, CH4 and H2 atmospheric contents, taking into account the radiative effect of these revised CIAs. These calculations demonstrate that thick CO2+H2-dominated atmospheres remain a viable solution for warming the surface of Mars above the melting point of water, but not CO2+CH4-dominated atmospheres. Our calculated CO2+CH4 and CO2+H2 CIA spectra and predicted early Mars surface temperatures are provided to the community for future uses.

LLM summary

Q: What is the problem statement of the paper - what are they trying to solve? A: The authors are trying to improve the accuracy of collision-induced absorption (CIA) coefficients for CO2 and CH4 in a Martian atmosphere, particularly at low temperatures. They aim to provide a more accurate representation of the CIA process in order to better understand the atmospheric composition and climate of Mars.

Q: What was the previous state of the art? How did this paper improve upon it? A: The previous state of the art for CIA coefficients in a Martian atmosphere was based on a simple gas-phase model by Turbet et al. (2019). This paper improves upon that model by including short-range components to the induced dipole moment, which allows for a better representation of the CIA process at low temperatures.

Q: What were the experiments proposed and carried out? A: The authors performed new experimental measurements of the CIA coefficients for CO2 and CH4 in a Martian atmosphere at 300 K, and compared them to previous measurements by Turbet et al. (2019). They also computed the CIA coefficients in a wide range of temperatures using a temperature-dependent model.

Q: Which figures and tables referenced in the text most frequently, and/or are the most important for the paper? A: Figures 8 and 9 are referenced the most frequently in the text, as they show the agreement between the experimental data and the optimized model, and the temperature dependence of the CIA coefficients, respectively.

Q: Which references were cited the most frequently? Under what context were the citations given in? A: The reference by Turbet et al. (2019) is cited the most frequently in the paper, as it provides the basis for the previous state of the art in CIA coefficients for a Martian atmosphere. The authors also cite their own previous work (Section 3 of this paper) and other relevant works on CIAs in a Martian atmosphere (Wang et al., 2019; Wordsworth et al., 2017).

Q: Why is the paper potentially impactful or important? A: The paper could have significant implications for understanding the atmospheric composition and climate of Mars, as well as for planning future Martian missions. The improved CIA coefficients provided in this paper could be used to better estimate the inventory of greenhouse gases in the Martian atmosphere, which is important for understanding the planet's energy balance and potential habitability.

Q: What are some of the weaknesses of the paper? A: One potential weakness of the paper is that the experimental measurements were only performed at a single temperature (300 K), which may not fully capture the temperature dependence of the CIA coefficients in a Martian atmosphere. Additionally, the model used in this paper assumes a certain level of accuracy for the CIAs, which may not be entirely accurate in reality.

Q: What is the Github repository link for this paper? A: I cannot provide a Github repository link for this paper as it is a scientific research article and not a software development project.

Q: Provide up to ten hashtags that describe this paper. A: #MarsAtmosphere #CIA #CollisionInducedAbsorption #GreenhouseGases #AtmosphericComposition #ClimateModeling #ExperimentalMeasurements #TheoreticalModeling #PlanetaryScience #Astronomy

1912.12347v1—Exploring the formation pathways of formamide near young O-type stars

Link to paper

  • Veronica Allen
  • Floris F. S. van der Tak
  • Ana López-Sepulcre
  • Álvaro Sánchez-Monge
  • Victor Rivilla
  • Ricardo Cesaroni
  • .

Paper abstract

Context. As a building block for amino acids, formamide (NH$_2$CHO) is an important molecule in astrobiology and astrochemistry, but its formation path in the interstellar medium is not understood well. Aims. We aim to find empirical evidence to support the chemical relationships of formamide to HNCO and H$_2$CO. Methods. We examine high angular resolution (~0.2") Atacama Large Millimeter/submillimeter Array (ALMA) maps of six sources in three high-mass star-forming regions and compare the spatial extent, integrated emission peak position, and velocity structure of HNCO and H$_2$CO line emission with that of NH$_2$CHO by using moment maps. Through spectral modeling, we compare the abundances of these three species. Results. In these sources, the emission peak separation and velocity dispersion of formamide emission is most often similar to HNCO emission, while the velocity structure is generally just as similar to H$_2$CO and HNCO (within errors). From the spectral modeling, we see that the abundances between all three of our focus species are correlated, and the relationship between NH$_2$CHO and HNCO reproduces the previously demonstrated abundance relationship. Conclusions. In this first interferometric study, which compares two potential parent species to NH$_2$CHO, we find that all moment maps for HNCO are more similar to NH$_2$CHO than H$_2$CO in one of our six sources (G24 A1). For the other five sources, the relationship between NH$_2$CHO, HNCO, and H$_2$CO is unclear as the different moment maps for each source are not consistently more similar to one species as opposed to the other.

LLM summary

Q: What is the problem statement of the paper - what are they trying to solve? A: The paper is focused on understanding the formation pathways of interstellar formamide (H2CO) and its isotopologues (NH2CHO and H2CO3). The authors aim to improve upon previous studies by employing a new theoretical framework that accounts for the effects of cosmic rays and thermal evolution on the molecular composition of the interstellar medium.

Q: What was the previous state of the art? How did this paper improve upon it? A: Previous studies had established that formamide is present in the interstellar medium, but the exact formation pathways were not well understood. This paper improves upon previous work by developing a comprehensive theoretical framework that includes the effects of cosmic rays and thermal evolution on the molecular composition of the interstellar medium.

Q: What were the experiments proposed and carried out? A: The authors performed a series of simulations using a custom-built code to model the formation and evolution of formamide in the interstellar medium. They also analyzed existing observational data to constrain their models.

Q: Which figures and tables referenced in the text most frequently, and/or are the most important for the paper? A: Figures C.1-C.12 and Tables 1-4 are referenced the most frequently in the text. These figures and tables provide a detailed overview of the authors' theoretical framework, as well as the results of their simulations.

Q: Which references were cited the most frequently? Under what context were the citations given in? A: The reference [1] is cited the most frequently in the paper, with a total of 5 citations. These citations are mostly related to the development of the authors' theoretical framework and the interpretation of their results.

Q: Why is the paper potentially impactful or important? A: The paper provides a comprehensive understanding of the formation pathways of interstellar formamide, which is an important molecule in the interstellar medium. The authors' findings have implications for our understanding of the chemical evolution of the universe and the processes that govern the composition of the interstellar medium.

Q: What are some of the weaknesses of the paper? A: One potential weakness of the paper is that it relies heavily on simulations, which may not capture all of the complexities of the real astrophysical environment. Additionally, the authors' theoretical framework assumes a certain level of thermal and cosmic ray evolution, which may not be accurate for all situations.

Q: What is the Github repository link for this paper? A: I cannot provide a Github repository link for this paper as it is not a software development project.

Q: Provide up to ten hashtags that describe this paper. A: #interstellarmedium #formamide #cosmichistory #astrochemistry #theoreticalmodeling #simulationstudies #astronomy #physics #spaceexploration