The Limits of Scribal Creativity: Rewriting the \u3cem\u3eCook’s Tale\u3c/em\u3e in Bodley 686

Geoffrey Chaucer’s Canterbury Tales exhibits elements of both completeness and incompleteness as a work of literature. Written in England starting c. 1387, the text presents a collection of tales told by characters of diverse backgrounds, combining poetry and prose to form a sequence of stories. With some exceptions, the tales themselves appear to be contained and complete, but the collection in its entirety “still bears signs of a work in progress.”1 In the General Prologue, the host of the Tabard Inn proposes the structure for the tales told by the travelers on their pilgrimage from London to Canterbury, giving the text its frame. According to the rules outlined by the host, each of the travelers is to tell two tales on the way to Canterbury and two on the way back. The tales that actually appear in the sequence number far fewer than the proposed amount—the clearest sign of the incompleteness inherent in the text

Spontaneous formation of persistent square pattern in a driven superfluid

The emergence of patterns from simple physical laws belongs to the most striking topics in natural science. In particular, the spontaneous formation of structures from an initially homogeneous state can eventually lead to stable, non-homogeneous states of matter. Here we report on the spontaneous formation of square lattice patterns in a rotationally symmetric and driven Bose-Einstein condensate, confined in a two-dimensional box potential with absorptive boundaries. The drive is realized by globally modulating the two-particle interaction periodically in time. After a primary phase of randomly oriented stripes that emerge as a consequence of the Faraday instability, we observe the subsequent formation of persistent square lattice patterns in the highly occupied regime, where phonon-phonon interactions become relevant. We show theoretically that this state can be understood as an attractive fixed point of coupled nonlinear amplitude equations. Establishing the existence of this fixed point opens the perspective for engineering new, highly correlated states of matter in driven superfluids.Comment: 9 pages, 5 figure

Square Pattern Formation as Stable Fixed Point in Driven Two-Dimensional Bose-Einstein Condensates

We investigate pattern formation in two-dimensional Bose-Einstein condensates (BECs) caused by temporal periodic modulation of the interatomic interaction. Temporal modulation of the interaction causes the so-called Faraday instability in the condensate, which we show generically leads to a stable square grid density pattern. We take the amplitudes in each of the two directions spanning the two-dimensional density pattern as order parameters in pattern formation and derive a set of simultaneous time evolution equations for those order parameters from the Gross--Pitaevskii (GP) equation with a time-periodic interaction. We identify the fixed points of the time evolution and show by stability analysis that the inhomogeneous density exhibits a square grid pattern as a stable fixed point.Comment: 7 pages, 3 figures. Supplemental material: 9 page

Simple Viscous Flows: from Boundary Layers to the Renormalization Group

The seemingly simple problem of determining the drag on a body moving through a very viscous fluid has, for over 150 years, been a source of theoretical confusion, mathematical paradoxes, and experimental artifacts, primarily arising from the complex boundary layer structure of the flow near the body and at infinity. We review the extensive experimental and theoretical literature on this problem, with special emphasis on the logical relationship between different approaches. The survey begins with the developments of matched asymptotic expansions, and concludes with a discussion of perturbative renormalization group techniques, adapted from quantum field theory to differential equations. The renormalization group calculations lead to a new prediction for the drag coefficient, one which can both reproduce and surpass the results of matched asymptotics

Re-sensitization of Mycobacterium smegmatis to Rifampicin Using CRISPR Interference Demonstrates Its Utility for the Study of Non-essential Drug Resistance Traits

© 2021 Faulkner, Cox, Goh, van Bohemen, Gibson, Liebster, Wren, Willcocks and Kendall. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). https://creativecommons.org/licenses/by/4.0/A greater understanding of the genes involved in antibiotic resistance in Mycobacterium tuberculosis (Mtb) is necessary for the design of improved therapies. Clustered regularly interspaced short palindromic repeat interference (CRISPRi) has been previously utilized in mycobacteria to identify novel drug targets by the demonstration of gene essentiality. The work presented here shows that it can also be usefully applied to the study of non-essential genes involved in antibiotic resistance. The expression of an ADP-ribosyltransferase (Arr) involved in rifampicin resistance in Mycobacterium smegmatis was silenced using CRISPRi and the impact on rifampicin susceptibility was measured. Gene silencing resulted in a decrease in the minimum inhibitory concentration (MIC) similar to that previously reported in an arr deletion mutant. There is contradictory evidence for the toxicity of Streptococcus pyogenes dCas9 (dCas9 Spy) in the literature. In this study the expression of dCas9 Spy in M. smegmatis showed no impact on viability. Silencing was achieved with concentrations of the aTc inducer lower than previously described and with shorter induction times. Finally, designing small guide RNAs (sgRNAs) that target transcription initiation, or the early stages of elongation had the most impact on rifampicin susceptibility. This study demonstrates that CRISPRi based gene silencing can be as impactful as gene deletion for the study of non-essential genes and further contributes to the knowledge on the design and induction of sgRNAs for CRISPRi. This approach can be applied to other non-essential antimicrobial resistance genes such as drug efflux pumps.Peer reviewe

The use of aldolase enzymes for stereospecific carbon-carbon bond formation

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