Unconditionally stable integration of Maxwell's equations

Numerical integration of Maxwell’s equations is often based on explicit methods accepting a stability step size restriction. In literature evidence is given that there is also a need for unconditionally stable methods, as exemplified by the successful alternating direction implicit – finite difference time domain scheme. In this paper, we discuss unconditionally stable integration for a general semidiscrete Maxwell system allowing non-Cartesian space grids as encountered in finite-element discretizations. Such grids exclude the alternating direction implicit approach. Particular attention is given to the second-order trapezoidal rule implemented with preconditioned conjugate gradient iteration and to second-order exponential integration using Krylov subspace iteration for evaluating the arising ϕ-functions. A three-space dimensional test problem is used for numerical assessment and comparison with an economical second-order implicit–explicit integrator

Numerical Integration of Damped Maxwell Equations

We study the numerical time integration of Maxwell's equations from electromagnetism. Following the method of lines approach we start from a general semi-discrete Maxwell system for which a number of time-integration methods are considered. These methods have in common an explicit treatment of the curl terms. Central in our investigation is the question how to efficiently raise the temporal convergence order beyond the standard order of two, in particular in the presence of an explicitly or implicitly treated damping term which models conduction

Garuda 5 (khyung lnga)

This article focuses on ethnographic work conducted at the Men-Tsee-Khang (Dharamsala, India) on Garuda 5 (khyung lnga), a commonly prescribed Tibetan medical formula. This medicine’s efficacy as a painkiller and activity against infection and inflammation is largely due to a particularly powerful plant, known as ‘virulent poison’ (btsan dug) as well as ‘the great medicine’ (sman chen), and identified as a subset of Aconitum species. Its effects, however, are potentially dangerous or even deadly. How can these poisonous plants be used in medicine and, conversely, when does a medicine become a poison? How can ostensibly the same substance be both harmful and helpful? The explanation requires a more nuanced picture than mere dose dependency. Attending to the broader ‘ecologies of potency’ in which these substances are locally enmeshed, in line with Sienna Craig’s Efficacy and the Social Ecologies of Tibetan Medicine (2012), provides fertile ground to better understand the effects of Garuda 5 and how potency is developed and directed in practice. I aim to unpack the spectrum between sman (medicine) and dug (poison) in Sowa Rigpa by elucidating some of the multiple dimensions which determine the activity of Garuda 5 as it is formulated and prescribed in India. I thus embrace the full spectrum of potency— the ‘good’ and the ‘bad,’ the ‘wanted’ and the ‘unwanted’—without presuming the universal validity of biomedical notions of toxicity and side effects

Total organic carbon in the Bowland-Hodder Unit of the southern Widmerpool Gulf: a discussion

This review of the article by Kenomore et al. (2017) on the total organic carbon (TOC) evaluation of the Bowland Shale Formation in the Widmerpool Gulf sub-basin (southern Pennine Basin, UK) reveals a number of deficiencies, rooted mostly in an inadequate appreciation of the local Carboniferous stratigraphy. Kenomore et al. use the ΔLog R, the ‘Passey’ method after Passey et al. (1990), to evaluate the TOC content in two boreholes in the Widmerpool Gulf: Rempstone 1 and Old Dalby 1. We show here that Kenomore and co-authors used maturity data, published by Andrews (2013), from different formations to calibrate their TOC models of the Bowland Shale Formation (Late Mississippian–Early Pennsylvanian); the Morridge Formation in Rempstone 1 and the Widmerpool Formation in Old Dalby 1. We contest that this gives viable TOC estimates for the Bowland Shale Formation and that because of the location of the boreholes these TOC models are not representative over the whole of the Widmerpool Gulf. The pyrite content of the mudstones in the Widmerpool Gulf also surpasses the threshold where it becomes an influence on geophysical well logs. Aside from these stratigraphic and lithologic issues, some methodological weaknesses were not adequately resolved by Kenomore and co-authors. No lithological information is available for the Rock-Eval samples used for the maturity calibration, which because of the interbedded nature of the source formations has implications for the modelling exercise. We recommend that more geochemical data from a larger array of boreholes covering a wider area, proximal and distal, of the basin are collected before any inferences on TOC are made. This is necessary in the complex Bowland Shale system where lithological changes occur on a centimetre scale and correlations between the different sub basins are not well understood

Challenging the Biomedical Notion of ‘Active Substance’

Sowa Rigpa (Tibetan medicine) has been practiced across vast regions of Central and South Asia for centuries. In this medical tradition, it is common practice to dynamically adapt the mainly herbal formulas according to the regional flora and local conditions, and to use local variants of ingredients. Consequently, one Tibetan ingredient name within a specific formula can signify a variety of therapeutically fitting botanical items, which appear quite different from the perspective of modern taxonomy. This has led many researchers to understand the botanical plasticity of Tibetan medical formulas as misidentifications. We develop an alternative approach, exploring the advantages of this plasticity as a necessary practice to fulfill economic and therapeutic needs. This perspective piece questions the biomedical paradigm of single ‘active substances,’ since botanically unrelated plants with different chemical compositions can be similarly therapeutically effective. From a systems biology perspective, network pharmacology lets us understand the correspondence of illness and medicine as a semiotic process in which herbal formulations act via their ‘pleiotropic signatures’: complex webs of signal pathways that connect and act on multiple levels of organization in the body

Another face of Lorenz-Mie scattering: monodisperse distributions of spheres produce Lissajous-like patterns

The complete scattering matrix S of spheres was measured with a flow cytometer. The experimental equipment allows simultaneous detection of two scattering-matrix elements for every sphere in the distribution. Two-parameter scatterplots withx andy coordinates determined by the Sll + Sij and S11 - Sij values are measured. Samples of spheres with very narrow size distributions (< 1%) were analyzed with a FlowCytometer, and they produced unexpected two-parameter scatterplots. Instead of compact distributions we observed Lissajous-like loops. Simulation of the scatterplots, using Lorenz-Mie theory, shows that these loops are due not to experimental errors but to true Lorenz-Mie scattering. It is shown that the loops originate from the sensitivity of the scattered field on the radius of the spheres. This paper demonstrates that the interpretation of rare events and hidden features in flow cytometry needs reconsideration

Characteristics of direct human impacts on the rivers Karun and Dez in lowland south-west Iran and their interactions with earth surface movements

Two of the primary external factors influencing the variability of major river systems, over river reach scales, are human activities and tectonics. Based on the rivers Karun and Dez in south-west Iran, this paper presents an analysis of the geomorphological responses of these major rivers to ancient human modifications and tectonics. Direct human modifications can be distinguished by both modern constructions and ancient remnants of former constructions that can leave a subtle legacy in a suite of river characteristics. For example, the ruins of major dams are characterised by a legacy of channel widening to 100's up to c. 1000 m within upstream zones that can stretch to channel distances of many kilometres upstream of former dam sites, whilst the legacy of major, ancient, anthropogenic river channel straightening can also be distinguished by very low channel sinuosities over long lengths of the river course. Tectonic movements in the region are mainly associated with young and emerging folds with NW–SE and N–S trends and with a long structural lineament oriented E–W. These earth surface movements can be shown to interact with both modern and ancient human impacts over similar timescales, with the types of modification and earth surface motion being distinguishable. This paper examines the geomorphological evidence and outlines the processes involved in the evolution of these interactions through time. The analysis shows how interactions between earth surface movements and major dams are slight, especially after ancient dam collapse. By contrast, interactions between earth surface movements and major anthropogenic river channel straightening are shown to be a key factor in the persistence of long, near-straight river courses. Additionally, it is suggested that artificial river development, with very limited river channel lateral migration, may promote incision across an active fold at unusually long distances from the fold “core” and may promote markedly increased sinuosity across a structural lineament