On the Papapetrou field in vacuum

In this paper we study the electromagnetic fields generated by a Killing vector field in vacuum space-times (Papapetrou fields). The motivation of this work is to provide new tools for the resolution of Maxwell's equations as well as for the search, characterization, and study of exact solutions of Einstein's equations. The first part of this paper is devoted to an algebraic study in which we give an explicit and covariant procedure to construct the principal null directions of a Papapetrou field. In the second part, we focus on the main differential properties of the principal directions, studying when they are geodesic, and in that case we compute their associated optical scalars. With this information we get the conditions that a principal direction of the Papapetrou field must satisfy in order to be aligned with a multiple principal direction of the Weyl tensor in the case of algebraically special vacuum space-times. Finally, we illustrate this study using the Kerr, Kasner and pp waves space-times.Comment: 24 pages, LaTeX2e, IOP style. To appear in Classical and Quantum Gravit

Beyond variegation: the territorialisation of states, communities and developers in large-scale developments in Johannesburg, Shanghai and London

Large-scale urban development projects are a significant format of urban expansion and renewal across the globe. As generators of governance innovation and indicators of the future city in each urban context, large-scale development projects have been interpreted within frameworks of “variegations” of wider circulating processes, such as neoliberalisation or financialisation. However, such projects often entail significant state support and investment, are strongly linked to a wide variety of transnational investors and developers and are frequently highly contested in their local environments. Thus, each project comes to fruition in a distinctive regulatory context, often as an exception to the norm, and each emerges through complex interactions over a long period of time amongst an array of actors. We therefore seek to broaden the discussion from an analytical focus on variegated globalised processes to consider three large-scale urban development projects (in Shanghai, Johannesburg and London) as distinctive (transcalar) territorialisations. Using an innovative comparative approach we outline the grounds for a systematic analytical conversation across mega-urban development projects in very different contexts. Initially, comparability rests on the shared features of large-scale developments – that they are multi-jurisdictional, involve long time scales, and bring significant financing challenges. Comparing three development projects we are able to interrogate, rather than take for granted, how wider processes, circulating practices, transcalar actors, and territorial regulatory formations composed specific urban outcomes in each case. Thinking across these diverse cases provides grounds for rebuilding understandings of urban development politics

Probation, credibility and justice

This paper explores the difficulties that arise for probation agencies or those that deliver community sanctions in developing and maintaining their credibility in prevailing ‘late-modern’ social conditions. It begins by questioning the limits of the pursuit and promise of ‘public protection’ as a source of credibility, and then proceeds to examine the emergence of an alternative strategy – based principally on reparation and ‘payback’ – in Scotland, arguing that these Scottish developments have much to say to the emerging debates in England and Wales (and elsewhere) about the ‘rehabilitation revolution’ and the proper use of imprisonment. The paper provides a critical account of the development and meaning of the Scottish version of ‘payback’, linking it to some important philosophical and empirical studies that may help to steer the development of payback away from a ‘merely punitive’ drift. In the conclusion, I argue that probation agencies and services need to engage much more deeply and urgently with their roles as justice services, rather than as ‘mere’ crime reduction agencies

Adding Chinese herbal medicine to probiotics for irritable bowel syndrome-diarrhea: A systematic review and meta-analysis of randomized controlled trials

© 2020 Beijing University of Chinese Medicine Objective: This study assessed whether Chinese herbal medicine (CHM) combined with probiotics/synbiotics for irritable bowel syndrome - diarrhea (IBS-D) was more effective and safer than probiotics/synbiotics alone. Methods: Ten databases were searched for randomized control trials (RCTs) of IBS-D as diagnosed by Manning or Rome criteria. Trials comparing probiotics and probiotics with CHM were included. The Cochrane risk of bias (ROB) was evaluated for each trial. RevMan 5.3 was used to conduct a meta-analysis. Results: Twenty-six RCTs were included (25 Chinese, 1 English), involving 2045 participants. Meta-analysis was conducted on two outcomes: overall symptom improvement and relapse. CHM combined with live Bifidobacterium and Lactobacillus preparations reduced relapse rate (RR 0.28, 95%CI 0.15–0.52, 3 trials, n = 205) compared with probiotics alone. The subgroup analysis showed the benefit of CHM prescriptions based on soothing liver and invigorating spleen (1.28, 1.14–1.44, 3, 244), invigorating spleen and resolving dampness (1.20, 1.03–1.41, 2, 128), or warming and invigorating spleen and kidney formulae (1.27, 1.09–1.46, 2, 210) combined with triple Bifidobacterium preparations than the same probiotics alone which improved overall symptoms for IBS-D. There was unclear bias in almost domains of ROB. Most studies had a high risk of bias due to lack of blinding of investigator and participants, and selective reporting. Conclusions: This study showed that CHM combined with probiotics may reduce relapse rate by 72%, and improve overall symptoms of IBS-D (as diagnosed by Rome II and III) compared to probiotics alone. From the limited subgroup analysis, only soothing liver and invigorating spleen formulae, represented by Tongxie Yaofang, added to triple Bifidobacterium preparations may be superior to the single preparations in terms of overall symptoms. However, due to the poor methodological quality and small sample size of the trials, these findings must be interpreted with caution

Coherent X-ray Scattering from Manganite Charge and Orbital Domains

We report coherent x-ray scattering studies of charge and orbital domains in manganite systems. The experiments were carried out on LaMnO_3 and Pr_{0.6}Ca_{0.4}MnO_3, with the incident photon energy tuned near the Mn K edge. At room temperature, the orbital speckle pattern of LaMnO_3 was observed to be constant over a timescale of at least minutes, which is indicative of static orbital domains on this timescale. For Pr_{0.6}Ca_{0.4}MnO_3, both charge and orbital speckle patterns were observed. The observation of the latter rules out the presence of fast orbital fluctuations, while long time series data-- on the order of several minutes-- were suggestive of slow dynamic behavior. In contrast, the charge order speckle patterns were static.Comment: 6 pages, 4 figure

Consequences of a Killing symmetry in spacetime's local structure

In this paper we discuss the consequences of a Killing symmetry on the local geometrical structure of four-dimensional spacetimes. We have adopted the point of view introduced in recent works where the exterior derivative of the Killing plays a fundamental role. Then, we study some issues related with this approach and clarify why in many circumstances its use has advantages with respect to other approaches. We also extend the formalism developed in the case of vacuum spacetimes to the general case of an arbitrary energy-momentum content. Finally, we illustrate our framework with the case of spacetimes with a gravitating electromagnetic field.Comment: 20 pages, LaTeX2e, IOP style. Revised version accepted for publication in Classical and Quantum Gravit

Modeling electrolytically top gated graphene

We investigate doping of a single-layer graphene in the presence of electrolytic top gating. The interfacial phenomena is modeled using a modified Poisson-Boltzmann equation for an aqueous solution of simple salt. We demonstrate both the sensitivity of graphene's doping levels to the salt concentration and the importance of quantum capacitance that arises due to the smallness of the Debye screening length in the electrolyte.Comment: 7 pages, including 4 figures, submitted to Nanoscale Research Letters for a special issue related to the NGC 2009 conference (http://asdn.net/ngc2009/index.shtml