| 1. |
- Chen, Qiuyu, et al.
(författare)
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Satellite observations of gravity wave momentum flux in the mesosphere and lower thermosphere (MLT) : feasibility and requirements
- 2022
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 15:23, s. 7071-7103
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Tidskriftsartikel (refereegranskat)abstract
- In the recent decade it became evident that we need to revise our picture of how gravity waves (GWs) reach the mesosphere and lower thermosphere (MLT). This has consequences for our understanding not just of the properties of the GWs themselves, but in particular of the global circulation in the MLT. Information on spectral distribution, direction, and zonal mean GW momentum flux is required to test the theoretical and modeling findings. In this study, we propose a constellation of two CubeSats for observing mesoscale GWs in the MLT region by means of temperature limb sounding in order to derive such constraints. Each CubeSat deploys a highly miniaturized spatial heterodyne interferometer (SHI) for the measurement of global oxygen atmospheric band emissions. From these emissions, the 3-D temperature structure can be inferred. We propose obtaining four independent observation tracks by splitting the interferograms in the center and thus gaining two observation tracks for each satellite. We present a feasibility study of this concept based on self-consistent, high-resolution global model data. This yields a full chain of end-to-end (E2E) simulations incorporating (1) orbit simulation, (2) airglow forward modeling, (3) tomographic temperature retrieval, (4) 3-D wave analysis, and (5) GW momentum flux (GWMF) calculation. The simulation performance is evaluated by comparing the retrieved zonal mean GWMF with that computed directly from the model wind data. A major question to be considered in our assessment is the minimum number of tracks required for the derivation of 3-D GW parameters. The main result from our simulations is that the GW polarization relations are still valid in the MLT region and can thus be employed for inferring GWMF from the 3-D temperature distributions. Based on the E2E simulations for gaining zonal mean climatologies of GW momentum flux, we demonstrate that our approach is robust and stable, given a four-track observation geometry and the expected instrument noise under nominal operation conditions. Using phase speed and direction spectra we show also that the properties of individual wave events are recovered when employing four tracks. Finally, we discuss the potential of the proposed observations to address current topics in the GW research. We outline for which investigations ancillary data are required to answer science questions.
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| 2. |
- Pfreundschuh, Simon, 1989, et al.
(författare)
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GPROF-NN: a neural-network-based implementation of the Goddard Profiling Algorithm
- 2022
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 15:17, s. 5033-5060
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Tidskriftsartikel (refereegranskat)abstract
- The Global Precipitation Measurement (GPM) mission measures global precipitation at a temporal resolution of a few hours to enable close monitoring of the global hydrological cycle. GPM achieves this by combining observations from a spaceborne precipitation radar, a constellation of passive microwave (PMW) sensors, and geostationary satellites. The Goddard Profiling Algorithm (GPROF) is used operationally to retrieve precipitation from all PMW sensors of the GPM constellation. Since the resulting precipitation rates serve as input for many of the level 3 retrieval products, GPROF constitutes an essential component of the GPM processing pipeline. This study investigates ways to improve GPROF using modern machine learning methods. We present two neuralnetwork-based, probabilistic implementations of GPROF: GPROF-NN 1D, which (just like the current GPROF implementation) processes pixels individually, and GPROF-NN 3D, which employs a convolutional neural network to incorporate structural information into the retrieval. The accuracy of the retrievals is evaluated using a test dataset consistent with the data used in the development of the GPROF and GPROF-NN retrievals. This allows for assessing the accuracy of the retrieval method isolated from the representativeness of the training data, which remains a major source of uncertainty in the development of precipitation retrievals. Despite using the same input information as GPROF, the GPROF-NN 1D retrieval improves the accuracy of the retrieved surface precipitation for the GPM Microwave Imager (GMI) from 0.079 to 0.059mmh 1 in terms of mean abso- lute error (MAE), from 76.1% to 69.5% in terms of symmetric mean absolute percentage error (SMAPE) and from 0 :797 to 0 :847 in terms of correlation. The improvements for the Microwave Humidity Sounder (MHS) are from 0.085 to 0.061mmh 1 in terms of MAE, from 81% to 70.1% for SMAPE, and from 0 :724 to 0 :804 in terms of correlation. Comparable improvements are found for the retrieved hydrometeor profiles and their column integrals, as well as the detection of precipitation. Moreover, the ability of the retrievals to resolve small-scale variability is improved by more than 40% for GMI and 29% for MHS. The GPROFNN 3D retrieval further improves the MAE to 0.043mmh 1; the SMAPE to 48.67 %; and the correlation to 0:897 for GMI and 0.043mmh 1, 63.42 %, and 0:83 for MHS. Application of the retrievals to GMI observations of Hurricane Harvey shows moderate improvements when compared to co-located GPM-combined and ground-based radar measurements indicating that the improvements at least partially carry over to assessment against independent measurements. Similar retrievals for MHS do not show equally clear improvements, leaving the validation against independent measurements for future investigation. Both GPROF-NN algorithms make use of the same input and output data as the original GPROF algorithm and thus may replace the current implementation in a future update of the GPM processing pipeline. Despite their superior accuracy, the single-core runtime required for the operational processing of an orbit of observations is lower than that of GPROF. The GPROF-NN algorithms promise to be a simple and cost-efficient way to increase the accuracy of the PMW precipitation retrievals of the GPM constellation and thus improve the monitoring of the global hydrological cycle.
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| 3. |
- Andappan, Murugaiah, et al.
(författare)
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Arylboronic acids as versatile coupling partners in fast microwave promoted oxidative Heck chemistry
- 2003
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Ingår i: Molecular diversity. - 1381-1991 .- 1573-501X. ; 7:2-4, s. 97-106
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Tidskriftsartikel (refereegranskat)abstract
- The useful and selective reactivity of arylboronic acids makes them favourite building blocks for many modern organic chemistry applications like the metal-mediated formation of C-C, C-O, C-N, and C-S bonds. This report describes oxidative Heck coupling reactions of arylboronic acids and olefins, which were conveniently and rapidly (5-30 min) carried out under air with temperature-controlled microwave heating. Different reaction conditions were investigated with regard to both microwave heating capability and chemical productivity. Copper(II) acetate was identified as a microwave compatible reoxidant of Pd(0). The scope and limitations of this high-speed chemistry protocol with diverse olefins and organoboronic acids are discussed.
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| 4. |
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| 5. |
- Chinnadurai, Raj Kumar, et al.
(författare)
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Pharmacoinformatic approach to identify potential phytochemicals against SARS-CoV-2 spike receptor-binding domain in native and variants of concern
- 2022
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Ingår i: Molecular diversity. - : Springer Nature. - 1381-1991 .- 1573-501X.
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Tidskriftsartikel (refereegranskat)abstract
- Severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) pathogenesis is initiated by the binding of SARS-CoV-2 spike (S) protein with the angiotensin-converting enzyme 2 receptor (ACE2R) on the host cell surface. The receptor-binding domain (RBD) of the S protein mediates the binding and is more prone to mutations resulting in the generation of different variants. Recently, molecules with the potential to inhibit the interaction of S protein with ACE2R have been of interest due to their therapeutic value. In this context, the present work was performed to identify potential RBD binders from the Indian medicinal plant's phytochemical database through virtual screening, molecular docking, and molecular dynamic simulation. Briefly, 1578 compounds filtered from 9596 phytochemicals were chosen for screening against the RBD of the native SARS-CoV-2 S protein. Based on the binding energy, the top 30 compounds were selected and re-docked individually against the native and five variants of concern (VOCs: alpha, beta, gamma, delta, and omicron) of SARS-CoV-2. Four phytochemicals, namely withanolide F, serotobenine, orobanchol, and gibberellin A51, were found to be potential RBD binders in native and all SARS-CoV-2 VOCs. Among the four, withanolide F exhibited lower binding energy (− 10.84 to − 8.56 kcal/mol) and better ligand efficiency (− 0.3 to − 0.25) against all forms of RBD and hence was subjected to a 100 ns MD simulation which confirmed its stringent binding to the RBDs in native and VOCs. The study prioritizes withanolide F as a prospective COVID-19 (Coronavirus disease) therapeutic agent based on the observations. It warrants deeper investigations into the four promising leads for understanding their precise therapeutic value. Graphical abstract: [Figure not available: see fulltext.].
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| 6. |
- Datta, Gopal K., et al.
(författare)
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A rapid microwave protocol for Heck vinylation of aryl chlorides under air
- 2003
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Ingår i: Molecular diversity. - 1381-1991 .- 1573-501X. ; 7:2-4, s. 107-114
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Tidskriftsartikel (refereegranskat)abstract
- In modern high-throughput chemistry, the overall workflow is a crucial factor and much work is devoted to speeding up the process of chemistry development. Since automated microwave-based synthesizers are known to streamline the compound production and to accelerate slow organic transformations, this technology was implemented for Heck reactions with sluggish aryl chlorides. Furthermore, homogeneous palladium-catalyzed Heck vinylations of aryl chlorides can be performed under air under optimized conditions. Based on this finding, controlled microwave heating was utilized to accelerate model reactions down to 30 min employing a mixture of ionic liquid and 1,4-dioxane as solvent.
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| 7. |
- Emtenäs, Hans, et al.
(författare)
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Efficient Microwave Assisted Synthesis of Optically Active Bicyclic 2-Pyridinones via Δ2-Thiazolines
- 2003
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Ingår i: Molecular diversity. - : Springer Netherlands. - 1381-1991 .- 1573-501X. ; :2-4, s. 165-169
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Tidskriftsartikel (refereegranskat)abstract
- A new efficient synthesis of optically active bicyclic 2-pyridiones has been developed using microwave irradiation. The synthesis is a two-step procedure via 2-thiazolines, which only requires a 3 + 2 min reaction time compared to 2 days when using conventional heating. The optimized conditions proved to be suitable for the synthesis of a small library in excellent yields and with limited racemizations.
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| 8. |
- Eriksson, Lennart, et al.
(författare)
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Megavariate analysis of environmental QSAR data. Part I--a basic framework founded on principal component analysis (PCA), partial least squares (PLS), and statistical molecular design (SMD)
- 2006
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Ingår i: Molecular Diversity. - : Springer Science and Business Media LLC. - 1381-1991 .- 1573-501X. ; 10:2, s. 169-86
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Tidskriftsartikel (refereegranskat)abstract
- This paper introduces principal component analysis (PCA), partial least squares projections to latent structures (PLS), and statistical molecular design (SMD) as useful tools in deriving multi- and megavariate quantitative structure-activity relationship (QSAR) models. Two QSAR data sets from the fields of environmental toxicology and environmental chemistry are worked out in detail, showing the benefits of PCA, PLS and SMD. PCA is useful when overviewing a data set and exploring relationships among compounds and relationships among variables. PLS is the regression extension of PCA and is used for establishing QSARs. SMD is essential for selecting informative training and test sets of compounds for QSAR calibration and validation.
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| 9. |
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| 10. |
- Gottfries, Johan, et al.
(författare)
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Extensions to amino acid description
- 2010
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Ingår i: Molecular diversity. - : Springer Science and Business Media LLC. - 1381-1991 .- 1573-501X. ; 14:4, s. 709-718
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Tidskriftsartikel (refereegranskat)abstract
- A new set of amino acid descriptor scales was recently introduced. The new scales relate to amino acid side chain (i) rigidity and (ii) flexibility. These two properties were found to be orthogonal to each other. In this study, (i) the understanding of their meaning is improved, (ii) their utility further corroborated, and (iii) the scope of their applicability is broadened. Notably, the rigidity and flexibility scales are benchmarked against previous amino acid description precedence and found to contribute (1) new information, and (2) direct interpretation. The suggested description extensions were tested using empirical data from peptide description and in quantitative structure-activity relationships (QSAR).
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