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"Allers, Christopher R"
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Forgiveness in perspective
Amidst the cacophony of claims made about forgiveness, this book serves to aid in an effort to put \"forgiveness in perspective.\" Marieke Smit and Christopher R. Allers have collected here ten essays written by twelve authors from around the world and across the disciplinary spectrum including philosophers, practitioners, psychologists, literary theorists, and prison chaplains. All the essays offer a perspective on forgiveness and put forgiveness in perspective whether by tracing what forgiveness \"is,\" how this religious inheritance is worked out in our secularizing societies, how forgiveness works in our quotidian experience, or a particular manifestation in a particular context such as marriage, prison, or after an abortion, to name a few. The multi-disciplinary character of this book provides a multi-disciplinary appeal as well as a resource to enlarge one's own perspective on this perplexing, enigmatic, and wonderfully complex concept of forgiveness.
eBook
Taking Hannah Arendt to church: Toward a renewed appreciation of the mutuality between moral philosophy and religious life and culture
In this study, I consider the possibility of extending Hannah Arendt's critiques of conformity and behavior and her insights on thinking and moral philosophy to Christian life and culture. With Arendt, I argue that the possibility to refrain from perpetrating great evils made possible by uncritical conformity resides within the activity of thinking itself, as she defines it. Furthermore, I argue, again with Arendt, that refraining from such evils is a moral decision which finds its ultimate standard in the self. Although she culls many helpful insights from religious traditions, Arendt refrains from extending her moral philosophy into any realm in which religion is considered to be the valid standard of what constitutes moral behavior. Instead, I argue, against Arendt, that Christians can, and perhaps should, develop a more mature understanding of religion and a more “covenantal” understanding of their relationship with the divine.
Dissertation
Long-primed germinal centres with enduring affinity maturation and clonal migration
Germinal centres are the engines of antibody evolution. Here, using human immunodeficiency virus (HIV) Env protein immunogen priming in rhesus monkeys followed by a long period without further immunization, we demonstrate germinal centre B (B
GC
) cells that last for at least 6 months. A 186-fold increase in B
GC
cells was present by week 10 compared with conventional immunization. Single-cell transcriptional profiling showed that both light- and dark-zone germinal centre states were sustained. Antibody somatic hypermutation of B
GC
cells continued to accumulate throughout the 29-week priming period, with evidence of selective pressure. Env-binding B
GC
cells were still 49-fold above baseline at 29 weeks, which suggests that they could remain active for even longer periods of time. High titres of HIV-neutralizing antibodies were generated after a single booster immunization. Fully glycosylated HIV trimer protein is a complex antigen, posing considerable immunodominance challenges for B cells
1
,
2
. Memory B cells generated under these long priming conditions had higher levels of antibody somatic hypermutation, and both memory B cells and antibodies were more likely to recognize non-immunodominant epitopes. Numerous B
GC
cell lineage phylogenies spanning more than the 6-month germinal centre period were identified, demonstrating continuous germinal centre activity and selection for at least 191 days with no further antigen exposure. A long-prime, slow-delivery (12 days) immunization approach holds promise for difficult vaccine targets and suggests that patience can have great value for tuning of germinal centres to maximize antibody responses.
Using HIV Env protein immunogen priming in rhesus monkeys followed by a long period without further immunization, we demonstrate germinal centre B cells lasting at least 6 months, showing promise in regard to difficult vaccine targets.
Journal Article
Characterisation of a solvent-tolerant haloarchaeal (R)-selective transaminase isolated from a Triassic period salt mine
Transaminase enzymes (TAms) are becoming increasingly valuable in the chemist’s toolbox as a biocatalytic route to chiral amines. Despite high profile successes, the lack of (
R
)-selective TAms and robustness under harsh industrial conditions continue to prove problematic. Herein, we report the isolation of the first haloarchaeal TAm (BC61-TAm) to be characterised for the purposes of pharmaceutical biocatalysis. BC61-TAm is an (
R
)-selective enzyme, cloned from an extremely halophilic archaeon, isolated from a Triassic period salt mine. Produced using a
Haloferax volcanii
–based expression model, the resulting protein displays a classic halophilic activity profile, as well as thermotolerance (optimum 50 °C) and organic solvent tolerance. Molecular modelling predicts the putative active site residues of haloarchaeal TAms, with molecular dynamics simulations providing insights on the basis of BC61-TAm’s organic solvent tolerance. These results represent an exciting advance in the study of transaminases from extremophiles, providing a possible scaffold for future discovery of biocatalytic enzymes with robust properties.
Journal Article
New Candidate Extreme T Subdwarfs from the Backyard Worlds: Planet 9 Citizen Science Project
Schneider et al. (2020) presented the discovery of WISEA J041451.67-585456.7 and WISEA J181006.18-101000.5, which appear to be the first examples of extreme T-type subdwarfs (esdTs; metallicity <= -1 dex, T_eff <= 1400 K). Here we present new discoveries and follow-up of three T-type subdwarf candidates, with an eye toward expanding the sample of such objects with very low metallicity and extraordinarily high kinematics, properties that suggest membership in the Galactic halo. Keck/NIRES near-infrared spectroscopy of WISEA J155349.96+693355.2, a fast-moving object discovered by the Backyard Worlds: Planet 9 citizen science project, confirms that it is a mid-T subdwarf. With H_W2 = 22.3 mag, WISEA J155349.96+693355.2 has the largest W2 reduced proper motion among all spectroscopically confirmed L and T subdwarfs, suggesting that it may be kinematically extreme. Nevertheless, our modeling of the WISEA J155349.96+693355.2 near-infrared spectrum indicates that its metallicity is only mildly subsolar. In analyzing the J155349.96+693355.2 spectrum, we present a new grid of low-temperature, low-metallicity model atmosphere spectra. We also present the discoveries of two new esdT candidates, CWISE J073844.52-664334.6 and CWISE J221706.28-145437.6, based on their large motions and colors similar to those of the two known esdT objects. Finding more esdT examples is a critical step toward mapping out the spectral sequence and observational properties of this newly identified population.
Paper
The Field Substellar Mass Function Based on the Full-sky 20-pc Census of 525 L, T, and Y Dwarfs
We present final Spitzer trigonometric parallaxes for 361 L, T, and Y dwarfs. We combine these with prior studies to build a list of 525 known L, T, and Y dwarfs within 20 pc of the Sun, 38 of which are presented here for the first time. Using published photometry and spectroscopy as well as our own follow-up, we present an array of color-magnitude and color-color diagrams to further characterize census members, and we provide polynomial fits to the bulk trends. Using these characterizations, we assign each object a \\(T_{\\rm eff}\\) value and judge sample completeness over bins of \\(T_{\\rm eff}\\) and spectral type. Except for types \\(\\ge\\) T8 and \\(T_{\\rm eff} <\\) 600K, our census is statistically complete to the 20-pc limit. We compare our measured space densities to simulated density distributions and find that the best fit is a power law (\\(dN/dM \\propto M^{-\\alpha}\\)) with \\(\\alpha = 0.6{\\pm}0.1\\). We find that the evolutionary models of Saumon & Marley correctly predict the observed magnitude of the space density spike seen at 1200K \\(< T_{\\rm eff} <\\) 1350K, believed to be caused by an increase in the cooling timescale across the L/T transition. Defining the low-mass terminus using this sample requires a more statistically robust and complete sample of dwarfs \\(\\ge\\)Y0.5 and with \\(T_{\\rm eff} <\\) 400K. We conclude that such frigid objects must exist in substantial numbers, despite the fact that few have so far been identified, and we discuss possible reasons why they have largely eluded detection.
Paper
The Initial Mass Function Based on the Full-sky 20-pc Census of \\(\\sim\\)3,600 Stars and Brown Dwarfs
A complete accounting of nearby objects -- from the highest-mass white dwarf progenitors down to low-mass brown dwarfs -- is now possible, thanks to an almost complete set of trigonometric parallax determinations from Gaia, ground-based surveys, and Spitzer follow-up. We create a census of objects within a Sun-centered sphere of 20-pc radius and check published literature to decompose each binary or higher-order system into its separate components. The result is a volume-limited census of \\(\\sim\\)3,600 individual star formation products useful in measuring the initial mass function across the stellar (\\(<8 M_\\odot\\)) and substellar (\\(\\gtrsim 5 M_{Jup}\\)) regimes. Comparing our resulting initial mass function to previous measurements shows good agreement above 0.8\\(M_\\odot\\) and a divergence at lower masses. Our 20-pc space densities are best fit with a quadripartite power law, \\(\\xi(M) = dN/dM \\propto M^{-\\alpha}\\) with long-established values of \\(\\alpha = 2.3\\) at high masses (\\(0.55 < M < 8.00 M_\\odot\\)) and \\(\\alpha = 1.3\\) at intermediate masses (\\(0.22 < M < 0.55 M_\\odot\\)), but at lower masses we find \\(\\alpha = 0.25\\) for \\(0.05 < M <0.22 M_\\odot\\) and \\(\\alpha = 0.6\\) for \\(0.01 < M < 0.05 M_\\odot\\). This implies that the rate of production as a function of decreasing mass diminishes in the low-mass star/high-mass brown dwarf regime before increasing again in the low-mass brown dwarf regime. Correcting for completeness, we find a star to brown dwarf number ratio of, currently, 4:1, and an average mass per object of 0.41 \\(M_\\odot\\).
Paper