Oliver Heaviside's Electromagnetic Theory

The year 2018 marks the 125th anniversary of the first of three published volumes on electromagnetic theory by the eminent Victorian electrical engineer, physicist and mathematician, Oliver Heaviside FRS. This commemorative issue of Philosophical Transactions of the Royal Society A celebrates the publication of this work by collecting papers on a broad spectrum across the field of electromagnetic theory, including innovative research papers interspersed between historical perspectives and relevant reviews. Heaviside was a remarkable man, an original thinker with brilliant mathematical powers and physical insight who made many significant contributions in his fields of interest, though he is remembered primarily for his ‘step function’, commonly used today in many branches of physics, mathematics and engineering. Here, we celebrate the man and his work by illustrating his major contributions and highlighting his great success in solving some of the great telegraphic engineering problems of the Victorian era, in part due to his development and detailed understanding of the governing electromagnetic theory. We celebrate his Electromagnetic theory: three volumes of insights, techniques and understanding from mathematical, physical and engineering perspectives—as dictated by J. C. Maxwell FRS, but interpreted, reformulated and expanded by Heaviside to advance the art and science of electrical engineering beyond all expectations. This article is part of the theme issue ‘Celebrating 125 years of Oliver Heaviside's ‘Electromagnetic Theory’’

The Effect of Defoliation Interval on Regrowth of Tall Fescue

Herbage yield, persistence and quality optimise when defoliation interval is based on physiological indicators, such as leaf regrowth stage. Examples include ryegrass (Fulkerson & Donaghy, 2001), cocksfoot (Rawnsley et al., 2002), prairie grass (Fulkerson et al., 2000) and kikuyu (Reeves et al., 1996). Yield, persistence and quality optimise because leaf regrowth stage relates closely to plant energy reserves, which generally peak as the number of live leaves/tiller maximise. More frequent defoliation than the optimum reduces energy reserves and leads to a smaller root system, fewer tillers and retarded growth rate (Fulkerson & Donaghy, 2001). Based on plant physiological development, the optimum defoliation interval for tall fescue has not been defined

On the Spatial Distribution of Hard X-Rays from Solar Flare Loops

The aim of this paper is to investigate the spatial structure of the impulsive phase hard X-ray emission from solar flares. This work is motivated by the YOHKOH and the forthcoming HESSI observations. Summarizing past results, it is shown that the transport effects can account for the observations by inhomogeneous loops where there is a strong field convergence and/or density enhancement at the top of the flaring loop. Scattering by plasma turbulence at the acceleration site or pancake type pitch angle distribution of the accelerated electrons can also give rise to enhanced emission at the loop tops. These could be a natural consequence of acceleration by plasma waves. This paper considers a general case of stochastic scattering and acceleration that leads to an isotropic pitch angle distribution and an enhanced emission from the loop tops or the acceleration site. Following the formalism developed in earlier papers the strength and the spectrum of the radiation expected from the acceleration site and the foot points are evaluated and their dependence on the parameters describing the acceleration process and the flare plasma are determined. The theoretical ratio of these two intensities and relative values of their spectral indices are compared with the YOHKOH observations, demonstrating that the above mentioned parameters can be constrained with such observations. It is shown that future high spatial and spectral resolution observations, for example those expected from HESSI, can begin to distinguish between different models and constrain their parameters.Comment: 37 pages with 20 figures. Accepted for publication in ApJ http://www.astronomy.stanford.ed

Cobimetinib and trametinib inhibit platelet MEK but do not cause platelet dysfunction

The MEK inhibitors cobimetinib and trametinib are used in combination with BRAF inhibitors to treat metastatic melanoma but increase rates of hemorrhage relative to BRAF inhibitors alone. Platelets express several members of the MAPK signalling cascade including MEK1 and MEK2 and ERK1 and ERK2 but their role in platelet function and haemostasis is ambiguous as previous reports have been contradictory. It is therefore unclear if MEK inhibitors might be causing platelet dysfunction and contributing to increased hemorrhage. In the present study we performed pharmacological characterisation of cobimetinib and trametinib in vitro to investigate potential for MEK inhibitors to cause platelet dysfunction. We report that whilst both cobimetinib and trametinib are potent inhibitors of platelet MEK activity, treatment with trametinib did not alter platelet function. Treatment with cobimetinib results in inhibition of platelet aggregation, integrin activation, alpha-granule secretion and adhesion but only at suprapharmacological concentrations. We identified that the inhibitory effects of high concentrations of cobimetinib are associated with off-target inhibition on Akt and PKC. Neither inhibitor caused any alteration in thrombus formation on collagen under flow conditions in vitro. Our findings demonstrate that platelets are able to function normally when MEK activity is fully inhibited, indicating MEK activity is dispensable for normal platelet function. We conclude that the MEK inhibitors cobimetinib and trametinib do not induce platelet dysfunction and are therefore unlikely to contribute to increased incidence of bleeding reported during MEK inhibitor therapy

Effect of Defoliation Interval on Regrowth of Leaves and Roots, and Tiller Number of Cocksfoot Plants

The key to defoliation management for optimal production and persistence of pasture lies in the use of a physiological basis for defoliation interval (specific to plant type), as opposed to a regime based on time or the height of herbage. The full expansion of a particular number of leaves/tiller is a useful plant-related indicator of optimal defoliation timing. Leaf regrowth stage (\u27leaf stage\u27) reflects the stage of plant recovery from defoliation as regards plant energy levels (Fulkerson & Donaghy, 2001). The level of water-soluble carbohydrate (WSC) reserves in grass tiller bases influences the rate of regrowth after defoliation, affecting the rate of shoot growth, root growth and tillering. This study was aimed to determine the influence of leaf stage based defoliation interval on regrowth of leaves and root, and on tiller number of \u27Kara\u27 cocksfoot plants up to 24 days after defoliation

The Nutritional Value of Cocksfoot (\u3ci\u3eDactylis glomerata L.) and Perennial Ryegrass (\u3ci\u3eLolium perenne L.\u3c/i\u3e) Under Leaf-Stage Based Defoliation Management

The perception that cocksfoot is of lower nutritional value and less productive than perennial ryegrass is largely the result of studies in which management was based on perennial ryegrass (to the detriment of cocksfoot) or involved defoliation of both species at the same time (Greenhalgh & Reid, 1969; Johnson & Thomson, 1996). Maintaining plants in a vegetative state through species-specific management is essential to retain the high quality and productivity of cocksfoot. Defoliation at or before 4-5 fully expanded live leaves per tiller is recommended as the ideal physiological regrowth stage for defoliation of cocksfoot, resulting in metabolisable energy (ME) levels in excess of 11MJ/kg dry matter (DM) (Rawnsley et al., 2002). The aim of the current study was to provide an objective comparison of the nutritional value of cocksfoot and perennial ryegrass grown in dryland conditions under a management regime based on the physiological status of each grass species

The influence of riparian woodland on the spatial and temporal variability of stream water temperatures in an upland salmon stream

International audienceThe spatio-temporal variability of stream water temperatures was investigated at six locations on the Girnock Burn (30km2 catchment), Cairngorms, Scotland over three hydrological years between 1998 and 2002. The key site-specific factors affecting the hydrology and climatology of the sampling points were investigated as a basis for physical process inference. Particular emphasis was placed on assessing the effects of riparian forest in the lower catchment versus the heather moorland riparian zones that are spatially dominant in the upper catchment. The findings were related to river heat budget studies that provided process detail. Gross changes in stream temperature were affected by the annual cycle of incoming solar radiation and seasonal changes in hydrological and climatological conditions. Inter-annual variation in these controlling variables resulted in inter-annual variability in thermal regime. However, more subtle inter-site differences reflected the impact of site-specific characteristics on various components of the river energy budget. Inter-site variability was most apparent at shorter time scales, during the summer months and for higher stream temperatures. Riparian woodland in the lower catchment had a substantial impact on thermal regime, reducing diel variability (over a period of 24 hours) and temperature extremes. Observed inter-site differences are likely to have a substantial effect on freshwater ecology in general and salmonid fish in particular. Keywords: temperature, thermal regime, forest, salmon, hydrology, Girnock Burn, Cairngor

Validation of a non-contact technique for torque measurements in wind turbines using an enhanced transient FSV approach

In-service turbine monitoring is essential for maximizing the wind energy contribution to the global energy budget. Measurement of turbine shaft torque under transient wind conditions is fundamental to develop reliable condition monitoring techniques. Contact based measurements bring their own disadvantages and non-contactless measurements have many potential advantages. However, their performance needs to be validated against standard methods. This paper focuses on the development of an enhanced transient Feature Selective Validation (FSV) techniques to undertake this analysis with an emphasis on transient data processing. The nature of FSV makes it a natural technique to consider for this problem space. Open questions have existed as to how transients should be dealt with in FSV. This paper overcomes the limitations of previous approaches for step-function transient comparison and presents analytical methods to ensure the transient feature itself is considered, irrespective of how much pre- and post- transient data happens to be included