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3,605 results on '"SUTHERLAND, JOHN"'

53. Sulfidic Anion Concentrations on Early Earth for Surficial Origins-of-Life Chemistry

Author

Ranjan, Sukrit, Todd, Zoe R., Sutherland, John D., and Sasselov, Dimitar D.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

A key challenge in origin-of-life studies is understanding the environmental conditions on early Earth under which abiogenesis occurred. While some constraints do exist (e.g., zircon evidence for surface liquid water), relatively few constraints exist on the abundances of trace chemical species, which are relevant to assessing the plausibility and guiding the development of postulated prebiotic chemical pathways which depend on these species. In this work, we combine literature photochemistry models with simple equilibrium chemistry calculations to place constraints on the plausible range of concentrations of sulfidic anions (HS$^-$, HSO$_3^{-}$, SO$_3^{2-}$) available in surficial aquatic reservoirs on early Earth due to outgassing of SO$_2$ and H$_2$S and their dissolution into small shallow surface water reservoirs like lakes. We find that this mechanism could have supplied prebiotically relevant levels of SO$_2$-derived anions, but not H$_2$S-derived anions. Radiative transfer modelling suggests UV light would have remained abundant on the planet surface for all but the largest volcanic explosions. We apply our results to the case study of the proposed prebiotic reaction network of Patel et al. (2015), and discuss the implications for improving its prebiotic plausibility. In general, epochs of moderately high volcanism could have been especially conducive to cyanosulfidic prebiotic chemistry. Our work can be similarly applied to assess and improve the prebiotic plausibility of other postulated surficial prebiotic chemistries that are sensitive to sulfidic anions, and our methods adapted to study other atmospherically-derived trace species., Comment: Accepted to Astrobiology; comments welcome

Published
2018
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65. Prebiotic synthesis of dihydrouridine by photoreduction of uridine in formamide.

Author

Xu, Jianfeng, Janicki, Mikołaj J., Szabla, Rafał, and Sutherland, John D.

Subjects
FORMAMIDE, PHOTOREDUCTION, NUCLEOSIDES, URIDINE, RNA, PYRIMIDINES, TRANSFER RNA
Abstract

In this report, we show that a very common modification (especially in tRNA), dihydrouridine, was efficiently produced by photoreduction of the canonical pyrimidine ribonucleoside, uridine in formamide. Formamide not only acts as a solvent in this reaction, but also as the reductant. The other three components of the canonical alphabet (C, A, G) remained intact under the same conditions, suggesting that dihydrouridine might have coexisted with all four canonical RNA nucleosides (C, U, A, G) at the dawn of life. [ABSTRACT FROM AUTHOR]

Published
2024
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66. Manganese(II) promotes prebiotically plausible non-enzymatic RNA ligation reactions.

Author

Liu, Ziwei, Jiang, Clancy Zhijian, Bond, Andrew D., Tosca, Nicholas J., and Sutherland, John D.

Subjects
LIGATION reactions, RNA, MANGANESE, NON-coding RNA
Abstract

Using different prebiotically plausible activating reagents, the RNA ligation yield was significantly increased in the presence of Mn(II). The mechanism of the activation reaction has been investigated using 5′-AMP as an analogue. [ABSTRACT FROM AUTHOR]

Published
2024
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68. Techno-economic Assessment for Integrating Biosorption into Rare Earth Recovery Process

Author

Jin, Hongyue, Park, Dan M, Gupta, Mayank, Brewer, Aaron W, Ho, Lewis, Singer, Suzanne L, Bourcier, William L, Woods, Sam, Reed, David W, Lammers, Laura N, Sutherland, John W, and Jiao, Yongqin

Subjects
Chemical Engineering, Analytical Chemistry, Engineering, Chemical Sciences, Low-grade feedstock, Airlift bioreactor, Mineral recovery, TEA, Mining, Environmental Science and Management, Analytical chemistry, Chemical engineering
Abstract

The current uncertainty in the global supply of rare earth elements (REEs) necessitates the development of novel extraction technologies that utilize a variety of REE source materials. Herein, we examined the techno-economic performance of integrating a biosorption approach into a large-scale process for producing salable total rare earth oxides (TREOs) from various feedstocks. An airlift bioreactor is proposed to carry out a biosorption process mediated by bioengineered rare earth-adsorbing bacteria. Techno-economic assessments were compared for three distinctive categories of REE feedstocks requiring different pre-processing steps. Key parameters identified that affect profitability include REE concentration, composition of the feedstock, and costs of feedstock pretreatment and waste management. Among the 11 specific feedstocks investigated, coal ash from the Appalachian Basin was projected to be the most profitable, largely due to its high-value REE content. Its cost breakdown includes pre-processing (leaching primarily, 77.1%), biosorption (19.4%), and oxalic acid precipitation and TREO roasting (3.5%). Surprisingly, biosorption from the high-grade Bull Hill REE ore is less profitable due to high material cost and low production revenue. Overall, our results confirmed that the application of biosorption to low-grade feedstocks for REE recovery is economically viable.

Published
2017

73. Election by lot and the democratic diarchy

Author

Sutherland, John Keith Bell, Castiglione, Dario, and Mitchell, Lynette

Subjects
320, Democratic Theory, Sortition, Selection by Lot, Representation, Athenian democracy
Abstract

This thesis argues that ‘democracy’ can better be understood in terms of a conceptual diarchy of ‘isonomia’ (equal political rights) and ‘isegoria’ (equal speech rights), rather than the conventional diarchy of ‘will’ and ‘opinion’ that originated in the era of absolute monarchy. As the proposed diarchy has its origin in classical Greece, the thesis starts with a brief overview of the institutional changes in sixth-, fifth- and fourth-century Athenian democracy that implemented the distinction in different ways, and examines some of its dysfunctions. The particular aspect of Athenian democracy under focus is sortition – the random selection of citizens for public office – viewed in antiquity as democratic, whereas election was viewed as an aristocratic or oligarchic selection mechanism. The thesis takes issue with Bernard Manin’s claim that the ‘triumph of election’ was on account of the natural right theory of consent, arguing that sortition-based proxy representation is a better way of indicating (hypothetical) consent than preference election. The thesis then seeks to clarify the concept(s) of representation – essential to the implementation of the democratic diarchy in modern large-scale societies – and to study how the diarchy has been reincarnated in modern representative democracies, along with an examination of the pathologies thereof. Consideration is given as to what the deliberative style of assemblies selected by lot should be, alongside evaluation of the epistemic potential of cognitive diversity and the ‘wisdom of crowds’. Given the need for both isonomia and isegoria to assume a representative form in large modern states, Michael Saward’s Representative Claim is adopted as a theoretical model to extend the reach of political representation beyond elections. The thesis concludes with tentative proposals as to how the fourth-century reforms (delegation of the final lawmaking decision to randomly-selected nomothetic courts) might be used as a template for modern institutions to resolve some of the problems of mass democracy.

Published
2017

80. Initial experience with 3D isotropic high-resolution 3 T MR arthrography of the wrist

Author

Sutherland, John K, Nozaki, Taiki, Kaneko, Yasuhito, J. Yu, Hon, Rafijah, Gregory, Hitt, David, and Yoshioka, Hiroshi

Subjects
Biomedical and Clinical Sciences, Clinical Sciences, Bioengineering, Biomedical Imaging, Clinical Research, Neurological, Adolescent, Adult, Arthrography, Female, Humans, Imaging, Three-Dimensional, Magnetic Resonance Imaging, Male, Middle Aged, Retrospective Studies, Wrist, Young Adult, Musculoskeletal MRI, 3D MR imaging, MR arthrography, Wrist MRI, Orthopedics, Clinical sciences, Allied health and rehabilitation science, Sports science and exercise
Abstract

BackgroundOur study was performed to evaluate the image quality of 3 T MR wrist arthrograms with attention to ulnar wrist structures, comparing image quality of isotropic 3D proton density fat suppressed turbo spin echo (PDFS TSE) sequence versus standard 2D 3 T sequences as well as comparison with 1.5 T MR arthrograms.MethodsEleven consecutive 3 T MR wrist arthrograms were performed and the following sequences evaluated: 3D isotropic PDFS, repetition time/echo time (TR/TE) 1400/28.3 ms, voxel size 0.35x0.35x0.35 mm, acquisition time 5 min; 2D coronal sequences with slice thickness 2 mm: T1 fat suppressed turbo spin echo (T1FS TSE) (TR/TE 600/20 ms); proton density (PD) TSE (TR/TE 3499/27 ms). A 1.5 T group of 18 studies with standard sequences were evaluated for comparison. All MR imaging followed fluoroscopically guided intra-articular injection of dilute gadolinium contrast. Qualitative assessment related to delineation of anatomic structures between 1.5 T and 3 T MR arthrograms was carried out using Mann-Whitney test and the differences in delineation of anatomic structures among each sequence in 3 T group were analyzed with Wilcoxon signed-rank test. Quantitative assessment of mean relative signal intensity (SI) and relative contrast measurements was performed using Wilcoxon signed-rank test.ResultsMean qualitative scores for 3 T sequences were significantly higher than 1.5 T (p

Published
2016

83. Reuse

Author

Ortegon, Katherine, Nies, Loring, Sutherland, John W, Dewulf, Wim, Section editor, Chatti, Sami, editor, Laperrière, Luc, editor, Reinhart, Gunther, editor, and Tolio, Tullio, editor

Published
2019
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