Discrete population balance models of random agglomeration and cleavage in polymer pyrolysis

The processes of random agglomeration and cleavage (both of which are important for the development of new models of polymer combustion, but are also applicable in a wide range of fields including atmospheric physics, radiation modelling and astrophysics) are analysed using population balance methods. The evolution of a discrete distribution of particles is considered within this framework, resulting in a set of ordinary differential equations for the individual particle concentrations. Exact solutions for these equations are derived, together with moment generating functions. Application of the discrete Laplace transform (analogous to the Z-transform) is found to be effective in these problems, providing both exact solutions for particle concentrations and moment generating functions. The combined agglomeration-cleavage problem is also considered. Unfortunately, it has been impossible to find an exact solution for the full problem, but a stable steady state has been identified and computed

Dynamics and transport near quantum-critical points

The physics of non-zero temperature dynamics and transport near quantum-critical points is discussed by a detailed study of the O(N)-symmetric, relativistic, quantum field theory of a N-component scalar field in $d$ spatial dimensions. A great deal of insight is gained from a simple, exact solution of the long-time dynamics for the N=1 d=1 case: this model describes the critical point of the Ising chain in a transverse field, and the dynamics in all the distinct, limiting, physical regions of its finite temperature phase diagram is obtained. The N=3, d=1 model describes insulating, gapped, spin chain compounds: the exact, low temperature value of the spin diffusivity is computed, and compared with NMR experiments. The N=3, d=2,3 models describe Heisenberg antiferromagnets with collinear N\'{e}el correlations, and experimental realizations of quantum-critical behavior in these systems are discussed. Finally, the N=2, d=2 model describes the superfluid-insulator transition in lattice boson systems: the frequency and temperature dependence of the the conductivity at the quantum-critical coupling is described and implications for experiments in two-dimensional thin films and inversion layers are noted.Comment: Lectures presented at the NATO Advanced Study Institute on "Dynamical properties of unconventional magnetic systems", Geilo, Norway, April 2-12, 1997, edited by A. Skjeltorp and D. Sherrington, Kluwer Academic, to be published. 46 page

Governing Uncertainty in a Secular Age: Rationalities of Violence, Theodicy and Torture

This article explores the problem of governing uncertainty in a secular age by focusing on the theological notion of ‘theodicy’ as the underlying rationale for the use of torture in the so-called ‘war on terror’. With God’s departure from the world, the problem of uncertainty acquires new salience as human beings can no longer explain tragic events as part of a transcendent order and must find immanent causes for the ‘evils’ that surround them. Taking a cue from Max Weber, I discuss how the problem of theodicy – how to reconcile the existence of God with the presence of evil in the world – does not disappear in the secular age but is mobilized through a Foucauldian biopolitical logic. Secular theodicy governs uncertainty through the production of economies of knowledge that rationalize processes of criminalization and securitization of entire groups and justify the use of violence. This process is particularly striking when analysing the use of torture in the so-called ‘war on terror’. Through a comparison with medieval practices and focusing on the cases of Guantanamo and Abu Ghraib, the article shows how secular torture is the product of a biopolitical theodicy aimed at governing uncertainty through the construction of the tortured as immanent evils who threaten our ‘good life’ and ‘deserve’ their treatment. Secular theodicy turns torture into an extreme form of governmentality of uncertainty in which the disciplining of conduct becomes the construction of subjectivities based on essentialist, stereotypical and racist – and for these very reasons, reassuring – economies of knowledge

Infrastructures of empire: towards a critical geopolitics of media and information studies

The Arab Uprisings of 2011 can be seen as a turning point for media and information studies scholars, many of whom newly discovered the region as a site for theories of digital media and social transformation. This work has argued that digital media technologies fuel or transform political change through new networked publics, new forms of connective action cultivating liberal democratic values. These works have, surprisingly, little to say about the United States and other Western colonial powers’ legacy of occupation, ongoing violence and strategic interests in the region. It is as if the Arab Spring was a vindication for the universal appeal of Western liberal democracy delivered through the gift of the Internet, social media as manifestation of the ‘technologies of freedom’ long promised by Cold War. We propose an alternate trajectory in terms of reorienting discussions of media and information infrastructures as embedded within the resurgence of idealized liberal democratic norms in the wake of the end of the Cold War. We look at the demise of the media and empire debates and ‘the rise of the BRICS’ (Brazil, Russia, India, China, South Africa) as modes of intra-imperial competition that complicate earlier Eurocentric narratives media and empire. We then outline the individual contributions for the special collection of essays

Lectin-like bacteriocins from pseudomonas spp. utilise D-rhamnose containing lipopolysaccharide as a cellular receptor

Lectin-like bacteriocins consist of tandem monocot mannose-binding domains and display a genus-specific killing activity. Here we show that pyocin L1, a novel member of this family from Pseudomonas aeruginosa, targets susceptible strains of this species through recognition of the common polysaccharide antigen (CPA) of P. aeruginosa lipopolysaccharide that is predominantly a homopolymer of d-rhamnose. Structural and biophysical analyses show that recognition of CPA occurs through the C-terminal carbohydrate-binding domain of pyocin L1 and that this interaction is a prerequisite for bactericidal activity. Further to this, we show that the previously described lectin-like bacteriocin putidacin L1 shows a similar carbohydrate-binding specificity, indicating that oligosaccharides containing d-rhamnose and not d-mannose, as was previously thought, are the physiologically relevant ligands for this group of bacteriocins. The widespread inclusion of d-rhamnose in the lipopolysaccharide of members of the genus Pseudomonas explains the unusual genus-specific activity of the lectin-like bacteriocins

Structural basis of PROTAC cooperative recognition for selective protein degradation

Inducing macromolecular interactions with small molecules to activate cellular signaling is a challenging goal. PROTACs (proteolysis-targeting chimeras) are bifunctional molecules that recruit a target protein in proximity to an E3 ubiquitin ligase to trigger protein degradation. Structural elucidation of the key ternary ligase-PROTAC-target species and its impact on target degradation selectivity remain elusive. We solved the crystal structure of Brd4 degrader MZ1 in complex with human VHL and the Brd4 bromodomain (Brd4BD2). The ligand folds into itself to allow formation of specific intermolecular interactions in the ternary complex. Isothermal titration calorimetry studies, supported by surface mutagenesis and proximity assays, are consistent with pronounced cooperative formation of ternary complexes with Brd4BD2. Structure-based-designed compound AT1 exhibits highly selective depletion of Brd4 in cells. Our results elucidate how PROTAC-induced de novo contacts dictate preferential recruitment of a target protein into a stable and cooperative complex with an E3 ligase for selective degradation

Exploring the Trypanosoma brucei Hsp83 Potential as a Target for Structure Guided Drug Design

Human African trypanosomiasis is a neglected parasitic disease that is fatal if untreated. The current drugs available to eliminate the causative agent Trypanosoma brucei have multiple liabilities, including toxicity, increasing problems due to treatment failure and limited efficacy. There are two approaches to discover novel antimicrobial drugs--whole-cell screening and target-based discovery. In the latter case, there is a need to identify and validate novel drug targets in Trypanosoma parasites. The heat shock proteins (Hsp), while best known as cancer targets with a number of drug candidates in clinical development, are a family of emerging targets for infectious diseases. In this paper, we report the exploration of T. brucei Hsp83--a homolog of human Hsp90--as a drug target using multiple biophysical and biochemical techniques. Our approach included the characterization of the chemical sensitivity of the parasitic chaperone against a library of known Hsp90 inhibitors by means of differential scanning fluorimetry (DSF). Several compounds identified by this screening procedure were further studied using isothermal titration calorimetry (ITC) and X-ray crystallography, as well as tested in parasite growth inhibitions assays. These experiments led us to the identification of a benzamide derivative compound capable of interacting with TbHsp83 more strongly than with its human homologs and structural rationalization of this selectivity. The results highlight the opportunities created by subtle structural differences to develop new series of compounds to selectively target the Trypanosoma brucei chaperone and effectively kill the sleeping sickness parasite

The historical origins of corruption in the developing world: a comparative analysis of East Asia

A new approach has emerged in the literature on corruption in the developing world that breaks with the assumption that corruption is driven by individualistic self-interest and, instead, conceptualizes corruption as an informal system of norms and practices. While this emerging neo-institutionalist approach has done much to further our understanding of corruption in the developing world, one key question has received relatively little attention: how do we explain differences in the institutionalization of corruption between developing countries? The paper here addresses this question through a systematic comparison of seven developing and newly industrialized countries in East Asia. The argument that emerges through this analysis is that historical sequencing mattered: countries in which the "political marketplace" had gone through a process of concentration before universal suffrage was introduced are now marked by less harmful types of corruption than countries where mass voting rights where rolled out in a context of fragmented political marketplaces. The paper concludes by demonstrating that this argument can be generalized to the developing world as a whole

British Torture in the 'War on Terror'

Despite longstanding allegations of UK involvement in prisoner abuse during counterterrorism operations as part of the US-led ‘war on terror’, a consistent narrative emanating from British government officials is that Britain neither uses, condones nor facilitates torture or other cruel, inhuman, degrading treatment and punishment. We argue that such denials are untenable. We have established beyond reasonable doubt that Britain has been deeply involved in post-9/11 prisoner abuse, and we can now provide the most detailed account to date of the depth of this involvement. We argue that it is possible to identify a peculiarly British approach to torture in the ‘war on terror’, which is particularly well-suited to sustaining a narrative of denial. To explain the nature of UK involvement, we argue that it can be best understood within the context of how law and sovereign power have come to operate during the ‘war on terror’. We turn here to the work of Judith Butler, and explore the role of Britain as a ‘petty sovereign’, operating under the state of exception established by the US Executive. UK authorities have not themselves suspended the rule of law so overtly, and indeed have repeatedly insisted on their commitment to it. They have nevertheless been able to construct a rhetorical, legal and policy ‘scaffold’ that has enabled them to demonstrate at least procedural adherence to human rights norms, while at the same time allowing UK officials to acquiesce in the arbitrary exercise of sovereignty over individuals who are denied any access to appropriate representation or redress in compliance with the rule of law

Comparative assessment of multiple COVID-19 serological technologies supports continued evaluation of point-of-care lateral flow assays in hospital and community healthcare settings

There is a clear requirement for an accurate SARS-CoV-2 antibody test, both as a complement to existing diagnostic capabilities and for determining community seroprevalence. We therefore evaluated the performance of a variety of antibody testing technologies and their potential use as diagnostic tools. Highly specific in-house ELISAs were developed for the detection of anti-spike (S), -receptor binding domain (RBD) and -nucleocapsid (N) antibodies and used for the cross-comparison of ten commercial serological assays-a chemiluminescence-based platform, two ELISAs and seven colloidal gold lateral flow immunoassays (LFIAs)-on an identical panel of 110 SARS-CoV-2-positive samples and 50 pre-pandemic negatives. There was a wide variation in the performance of the different platforms, with specificity ranging from 82% to 100%, and overall sensitivity from 60.9% to 87.3%. However, the head-to-head comparison of multiple sero-diagnostic assays on identical sample sets revealed that performance is highly dependent on the time of sampling, with sensitivities of over 95% seen in several tests when assessing samples from more than 20 days post onset of symptoms. Furthermore, these analyses identified clear outlying samples that were negative in all tests, but were later shown to be from individuals with mildest disease presentation. Rigorous comparison of antibody testing platforms will inform the deployment of point-of-care technologies in healthcare settings and their use in the monitoring of SARS-CoV-2 infections