Turbulence structure of open channel flows over permeable and impermeable beds : A comparative study

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The Coupling of Yang-Mills to Extended Objects

The coupling of Yang-Mills fields to the heterotic string in bosonic formulation is generalized to extended objects of higher dimension (p-branes). For odd p, the Bianchi identities obeyed by the field strengths of the (p+1)-forms receive Chern-Simons corrections which, in the case of the 5-brane, are consistent with an earlier conjecture based on string/5-brane duality.Comment: 14 Page

Interplay among unstable modes in films over permeable walls

The stability of open-channel flows (or film flows) has been extensively investigated for the case of impermeable smooth walls. In contrast, despite its relevance in many geophysical and industrial flows, the case that considers a permeable rather than an impermeable wall is almost unexplored. In the present work, a linear stability analysis of a film falling over a permeable and inclined wall is developed and discussed. The focus is on the mutual interaction between three modes of instability, namely, the well-known free-surface and hydrodynamic (i.e. shear) modes, which are commonly observed in open-channel flows over impermeable walls, plus a new one associated with the flow within the permeable wall (i.e. the porous mode). The flow in this porous region is modelled by the volume-averaged Navier-Stokes equations and, at the wall interface, the surface and subsurface flow are coupled through a stress-jump condition, which allows one to obtain a continuous velocity profile throughout the whole flow domain. The generalized eigenvalue problem is then solved via a novel spectral Galerkin method, and the whole spectrum of eigenvalues is presented and physically interpreted. The results show that, in order to perform an analysis with a full coupling between surface and subsurface flow, the convective terms in the volume-averaged equations have to be retained. In previous studies, this aspect has never been considered. For each kind of instability, the critical Reynolds number (${\mathit{Re}}_{c}$) is reported for a wide range of bed slopes ($\theta$) and permeabilities ($\sigma$). The results show that the free-surface mode follows the behaviour that was theoretically predicted by Benjamin and Yih for impermeable walls and is independent of wall permeability. In contrast, the shear mode shows a high dependence on $\sigma$: at $\sigma = 0$ the behaviour of ${\mathit{Re}}_{c} (\theta )$ recovers the well-known non-monotonic behaviour of the impermeable-wall case, with a minimum at \theta \sim 0. 05\textdegree . However, with an increase in wall permeability, ${\mathit{Re}}_{c}$ gradually decreases and eventually recovers a monotonic decreasing behaviour. At high values of $\sigma$, the porous mode of instability also occurs. A physical interpretation of the results is presented on the basis of the interplay between the free-surface-induced perturbation of pressure, the increment of straining due to shear with the increase in slope, and the shear stress condition at the free surface. Finally, the paper investigates the extent to which Squire's theorem is applicable to the problem presented herei

On coalgebras with internal moves

In the first part of the paper we recall the coalgebraic approach to handling the so-called invisible transitions that appear in different state-based systems semantics. We claim that these transitions are always part of the unit of a certain monad. Hence, coalgebras with internal moves are exactly coalgebras over a monadic type. The rest of the paper is devoted to supporting our claim by studying two important behavioural equivalences for state-based systems with internal moves, namely: weak bisimulation and trace semantics. We continue our research on weak bisimulations for coalgebras over order enriched monads. The key notions used in this paper and proposed by us in our previous work are the notions of an order saturation monad and a saturator. A saturator operator can be intuitively understood as a reflexive, transitive closure operator. There are two approaches towards defining saturators for coalgebras with internal moves. Here, we give necessary conditions for them to yield the same notion of weak bisimulation. Finally, we propose a definition of trace semantics for coalgebras with silent moves via a uniform fixed point operator. We compare strong and weak bisimilation together with trace semantics for coalgebras with internal steps.Comment: Article: 23 pages, Appendix: 3 page

Features and drivers of citizen participation: Insights from participatory budgeting in three European cities

Participatory budgeting (PB) is a relatively novel approach to the allocation of funds which allows ordinary citizens to become directly involved in how local government money is spent. This study identifies and examines the features and drivers of PB that incentivize citizen participation and the co-production of public services. Our analysis takes a fresh approach by setting PB initiatives in an innovative frame combining a paradigm of ‘ideal’ types of PB and their diachronic constituent phases. The results provide insights for both scholars and policy makers on the key features and drivers of citizen participation through PB. © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group

Anticoagulant treatment in patients with pulmonary arterial hypertension associated with systemic sclerosis: More shadows than lights

Pulmonary arterial hypertension is a chronic and progressive disease characterized by elevated pulmonary artery pressure and pulmonary vascular resistance leading to heart failure and premature death. Pulmonary arterial hypertension is characterized by proliferative and obstructive lesions in the distal pulmonary arteries and some descriptions include also thrombotic lesions. Despite this, in an era when multiple effective pulmonary arterial hypertension therapies are available, the role of anticoagulation in the treatment of pulmonary arterial hypertension remains uncertain. In particular, anticoagulant treatment in pulmonary arterial hypertension associated with connective tissue disease seems to be associated with unfavorable risk to benefit ratio due to an increased rate of bleeding from the gastrointestinal tract. However, anticoagulation may be required in conditions with increased thrombophilia like in the presence of lupus anticoagulant phenomenon or in the presence of anticardiolipin antibodies

Algebraic characterization of the Wess-Zumino consistency conditions in gauge theories

A new way of solving the descent equations corresponding to the Wess-Zumino consistency conditions is presented. The method relies on the introduction of an operator $\delta$ which allows to decompose the exterior space-time derivative $d$ as a $BRS$ commutator. The case of the Yang-Mills theories is treated in detail.Comment: 16 pages, UGVA-DPT 1992/08-781 to appear in Comm. Math. Phy