419 research outputs found
[External Resource] A treatise on the police of the metropolis: containing a detail of the various crimes and misdemeanors by which public and private property and security are, at present, injured and endangered: and suggesting remedies for their preve
No full textThe author examined the rise of crime in eighteenth-century London, which he contended threatened to undermine the British empire. Therefore, Colquhoun offered a variety of methods to try to curb the spread of crime including relying on an improved police force
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Catechol-based macrocyclic aromatic ether-sulfones: Synthesis, characterization and ring-opening polymerization
No full textCyclocondensation between 4,4`-bis(4-chlorobenzenesulfonyl)biphenyl and catechol, with subsequent chromatographic separation of the reaction products, led to the isolation of four novel ether-sulfone macrocycles (cyclic dimer, -trimer, -tetramer and -pentamer). Similarly, cyclocondensation of catechol with a novel seven-ring diketone/disulfone monomer allowed the isolation of the two new aromatic ether-ketone-sulfone macrocycles, a cyclic monomer and a cyclic dimer. Transannular shielding and deshielding effects in the cyclic monomer produce substantial chemical shift differences for chemically equivalent protons in the 1H NMR spectra of the cyclic monomer and -dimer. Fluoride-initiated ring-opening polymerization of the ether-sulfone cyclic trimer affords a novel, high-molecular weight poly(ether-sulfone)
Artistic biography as field theory: the case of Ithell Colquhoun - magician, surrealist, feminist
No full textRecent years have seen increased interest in the work of the British surrealist painter Ithell Colquhoun (1906–1988). This interest has been led by two constituencies: one feminist and the other esoteric. Both match dispositional characteristics of her work and address its significance within national and internal Surrealist movements. Rather than focus on feminist critiques or esoteric appraisals of Colquhoun, this article bases itself on the sociocultural aspects of her life and works. It builds on other studies from the author, which have employed the methodology developed by the French sociocultural theorist Pierre Bourdieu to the art “field.” Issues of research object construction are to the fore, together with analyses of the art and esoteric “fields” that involved Colquhoun. The article presents Colquhoun’s empirical biography (“habitus”), the networks she formed, and their relationship with the dominant “field” of cultural reproduction. Critical moments in her life trajectories are explored, detailing the breadth and focus of her influence with respect to the “Capitals”—“Social,” “Cultural,” and “Economic”—these levels of activities involved. Such analyses are set against exemplars from her painting as a way to compare the development of an esoteric aesthetic with her biographical experience. Issues of the artistic avant-gardes are also considered exemplified in her case. The article seeks to develop an understanding of the expressive impulse as it is manifested in transhistoric fields and the necessity of human creativity immanent within them
Synthesis and solution-state dynamics of donor-acceptor oligorotaxane foldamers
No full textWe describe in detail a strategy for creating foldamers in which interactions between mechanically interlocked components dictate the single-molecule assembly of a folded secondary structure. This unique folding motif is based on a flexible polyether dumbbell bearing 1,5-dioxynaphthalene (DNP) donors, which folds its way through a series of cyclobis(paraquat-p-phenylene) (CBPQT(4+)) acceptor rings in a serpentine fashion to enable extended donor-acceptor (D-A) stacking between DNP and the electron-poor 4,4'-bipyridinium (BIPY2+) units in CBPQT(4+). These oligorotaxanes can be prepared in a wide range of sizes, with molecular weights up to >15 000 Da, on account of novel one-pot reactions we developed to generate the necessary oligo-DNP precursors. The product distributions from the final kinetically controlled stoppering reactions are highly biased towards oligorotaxanes in which approximately half of the DNP units are encircled by rings, a fact which can be rationalized if the dominant solution-state structures of the pseudorotaxane precursors reflect the solid-state superstructures of analogous compounds, which express 50% recognition site occupancy because of their proclivity to pack into continuous D-A-D-A stacks. The presence of well-defined folded structures in solution have been confirmed by H-1 NMR spectroscopy in CD3CN. Moreover, we discovered an empirical selection rule forbidding CBPQT(4+) rings to occupy adjacent DNP sites, which elegantly explains both the product distributions and the H-1 NMR spectra. Depending on their adherence to this selection rule, all of the oligorotaxanes belong to one of three families: whereas 'Confused' oligorotaxanes adopt multiple translational isomers that satisfy the rule and 'Frustrated' species cannot obey it at all, members of the 'Happy' family each express only one rule-compliant 'Goldilocks' isomer. The NMR spectra of these oligorotaxanes also shed light on their dynamics; rapid 180 degrees rotations of DNP units cause pairs of heterotopic BIPY2+ protons in the accompanying CBPQT(4+) rings to exchange sites, giving rise to time-averaged signals. This process, which we term 'superrotation', will apply much more generally to other mechanically interlocked systems
Sequence-Modification in Copoly(ester-Imide)s: A Catalytic/supramolecular Approach to Writing/reading Copolymer Sequence-Information
No full textCatalytic
ester-interchange reactions, analogous to mutation and recombination, allow new
sequence-information to be written, statistically, into NDI-based
poly(ester-imide) chains. Thus, insertion of the cyclic ester cyclopentadecanolide
("exaltolide") into an NDI-based homopolymer, and quantitative
sequence-exchange between two different homopoly(ester-imide)s, are catalysed
by di-n-butyl tin(IV) oxide. Emerging sequences are
identified at the triplet and quintet levels by 1H NMR analysis,
using supramolecular complexation of pyrene-d10
at the NDI residues to amplify the separation of resonances associated with
different sequences. In such systems, pyrene is able to act as a
"reader-molecule" by generating different levels of ring-current
shielding from the different patterns of supramolecular binding to all the NDI-centred
sequences of a given length
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Sequence-modification in copoly(ester-imide)s: a catalytic/supramolecular approach to the evolution and reading of copolymer sequence-information
No full textCatalytic ester-interchange reactions, analogous to mutation and recombination, allow new sequence-information to be written, statistically, into NDI-based poly(ester-imide) chains. Thus, both insertion of the cyclic ester cyclopentadecanolide ("exaltolide") into an NDI-based homopolymer, and quantitative sequence-exchange between two different homopoly(ester-imide)s, are catalysed by di-n-butyl tin(IV) oxide. Emerging sequences are identified at the triplet and quintet levels using supramolecular complexation of pyrene-d10 at the NDI residues to amplify the separation of 1H NMR resonances associated with different sequences. In such systems, pyrene is able to act as a "reader-molecule" by generating different levels of ring-current shielding from the different patterns of supramolecular binding to all the NDI-centred sequences of a given length
Jüri Okas’ ‘specific objects’: diverging discourses in Estonian Art in the 1970s.
No full textPreviously in the University eprints HAIRST pilot service at http://eprints.st-andrews.ac.uk/archive/00000367/Article 3 of 6 in issue devoted to the visual culture of the Scandinavian and Baltic region.This article will look at the early works of Estonian architect and artist Jüri Okas and will try to work between diverging languages and interpretations, reading works by Okas against the background of Anglo-american conceptualism and minimalism of the same period. The first part of the paper will analyse a print by Jüri Okas that paraphrases works by the American artist Donald Judd and will try to show how Okas’ concept of minimalism differed from the Western one and the reasons behind it. The second part of the paper will focus on a conceptual book by Jüri Okas, consisting of a series of photographs of everyday and banal architectural objects, and compare it to Rober Venturi’s book on Complexity and Contradiction in Architecture. Finally, a comparison will be made with works of Robert Smithson in the context of concepts of waste, excess and the remainders of industrial civilisationPostprin
Numerical representations of AB-type copolymer complexes: Analysis of 1H NMR chemical shift patterns in terms of a Smith-Cantor set
No full textWhen considering the possibility of storing information in the sequence of monomer residues within an AB-type copolymer chain, it is constructive to model that sequence as a string of ones and zeros. The local (intramolecular) environment around a given monomer residue within the chain can then be represented by another string of integers, which we denote as a code, obtained by summing pairs of digits at equivalent positions, in both directions, from that monomer residue’s position. The code can include only the integers 0, 1 and 2, and in principle it can represent a number in any base b, higher than 2 (i.e. it cannot be a binary number). Whereas in base b = 3 the resulting set of codes includes all numbers (because only digits 0, 1 and 2 are required for ternary representations), in any base b > 3 the codes define a limited set of numbers comprising a type of fractal we term a last-fraction Smith-Cantor set. Experimentally, the 1H NMR spectrum of a random, AB-type co(polyester-imide) shows, on complexation with the ring-current-shielding molecule pyrene, a pattern of chemical shifts approximating very closely to the fourth-quarter Smith-Cantor set (i.e. b = 4). It is demonstrated that this pattern results from the binding of pyrene to single diimide residues under conditions of fast-exchange on the NMR timescale. Other co(polyimide) complexes show a related 1H NMR pattern, but one now corresponding to a specific sub-set of the same fractal. We show that this sub-set corresponds to codes based on a “stop-at-zero” limitation, whereby digits in the initial string are disregarded (i.e. set to zero) for code-generating purposes if they occur beyond a zero, when viewed from the central “1”. This limitation is found to arise in copolymer systems where the shielding molecule binds by intercalation between pairs of adjacent diimide residues. The present numerical approach provides a complete, unifying theory to account for the emergence of fractal character in the 1H NMR spectra of AB-type copolymer complexes
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