7.8 Example 2 and questions Example 2 Show that the synchrotron spectrum produced by a power-law distribution of electron energies N(E) dE = N0E−s dE, is described by You may use the approximation that all the power
7.6 Producing synchroton radiation in a laboratory Synchrotron radiation can, of course, be produced in a laboratory by arranging for electrons to be deflected by a magnetic field. Figure 13 shows a beam of synchrotron radiation produced at the European Synchrotron Radiation Facility (Author(s):
6.1 Introduction Approximately 150 million people worldwide have diabetes, of which 90 per cent have Type 2 diabetes. The incidence of the condition is rapidly increasing. In western countries about 10 per cent of people over the age of 65 years have diabetes. In the UK it is thought that there are between 765 000 and 1 million people with undiagnosed Type 2 diabetes, that is, 29–36 per cent of the total with diabetes (Watkins, 2003). These undiagnosed numbers are based on population samples where everyone
8 Managing the BSE/vCJD episode up to May 1990 BSE was formally recognised as a new disease in November 1986. However, this information was kept under ‘embargo’ at first while an initial epidemiological study – involving the collection of data from 200 herds – was started. The Ministry of Agriculture, Fisheries and Food (MAFF) was officially informed about BSE by the Chief Veterinary Officer (CVO) in June 1987. By December 1987, those responsible for analysing the data from the initial epidemiological study had concluded that the
4 The emergence of vCJD We now turn our attention to vCJD. If vCJD really is ‘the human form of BSE’ (as it is often described), how is it likely to have crossed the species barrier from cattle to humans? 3 The origin and spread of BSE In the light of the above discussion about prions, what is the most probable explanation for the spread of BSE among cattle? The cattle presumabl 2 The biology of prions The increasing interest in kuru during the 1950s and 1960s had the effect of stimulating research into TSEs in humans and other animals. Summarise, in general terms, the possible causes of disease in animals. 1.5 BSE and risks to human health: vCJD Given this background, it is not surprising that the possibility that BSE in cattle might pose a health risk to humans was given serious consideration from a very early stage in the outbreak. Various precautionary measures intended to eradicate BSE in cattle and also to prevent any possibility of transmission of the disease to humans were introduced. We will discuss these in more detail later in the unit. At the same time, the public was repeatedly assured by both officials (e.g. the C 1.1 Unit overview BSE and vCJD are important in their own right, having had major impacts on the lives of many people. Some people have died of vCJD and their deaths will have profoundly affected those who knew them. Large numbers of cattle have died either directly or indirectly because of BSE and this has had enormous economic effects on the agriculture and food industries. As a result, many practices in these industries are profoundly different from those of two decades ago. Although fundamental research in Introduction The Open University course S250 Science in context looks at a range of science-based topics of current or recent importance to public debates about science. It does this by examining the scientific facts and concepts that underpin such areas as genetic modification, medicinal plants and climate change, and in doing so aims to forefront a number of themes that we feel are of value in gaining greater insight into these types of controversies. At the points in the text where one or more o 1.4.2 Constant velocity and the gradient of the position–time graph Two things you will almost certainly want to know about any particle undergoing uniform motion are ‘how fast is it travelling?’ and ‘in which direction is it moving?’ The physical quantity that provides both these items of information is the particle's velocity. This is defined as the rate of change of the particle's position with respect to time, and has a constant value for each case of uniform motion along a line. 1.4.1 Describing uniform motion
Uniform motion along a line is the very special kind of motion that occurs when an object moves with unvarying speed in a fixed direction. During a fixed period of time, such as one second, an object in uniform motion will always cover the same distance, no matter when the period begins. This is the kind of motion associated with traffic-free motoring along straight roads, with uninterrupted train journeys along straight tracks, and with unhindered straight and level flying (provided 1.3.5 A note on graph drawing There will be many occasions throughout your study of physics when you will need to draw graphs. This subsection gives some important guidelines for this activity.
Decide which is the independent variable and which the dependent variable. Plot the independent variable along the horizontal axis and the dependent variable along the vertical axis. This is purely a convention but is why, for instance, we usually plot the time 1.3.4 Displacement–time graphs Learning outcomes By the end of this unit you should be able to: explain the underlying scientific principles of the major medical imaging techniques; explain the mode of operation of the major medical imaging techniques; understand the advantages and disadvantages of the major imaging techniques. Acknowledgements Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence The following appears in Introduction to Astrobiology (Planetary Science Book 2: ISBN 0-521-54621-4) which is published in ass 4 Unit summary Many of the large icy bodies in the outer Solar System are internally differentiated. Thanks largely to tidal heating, some, especially Europa, are likely to have an ocean sandwiched between the icy exterior and the rocky core. Others may have had such an ocean in the past. Wherever water rests on warm rock, water must percolate into it and become heated. This will cause hydrothermal convection to begin. Hot, chemical-rich water will emerge 2.4 How thick is Europa's ice? You learned in Section 1.4 that geophysical data show the ‘icy’ outer part of Europa to be about 100 km thick, but that the information is inadequate to distinguish between the extreme possibilities of solid ice all the way down to the bedrock and a floating sheet of ice supported above a liquid ocean (Author(s): 2.3.4 More surface disruption Now let's examine some detailed images of the region of Europa's northern hemisphere that was indicated on Figure 17 (see Section 2.3.2). A medium resolution image is shown in Figure 21, and higher resolution images from within this area are shown in Author(s): 1.4 The discovery of tidal heating The Voyager fly-bys of the Jupiter system convinced planetary scientists that former preconceptions about ‘dead’ globes were wrong – even before Voyager 1 had got as far as Saturn, the mission had enabled them to identify a new heating mechanism to explain the discrepancies. The ease with which this revolution in thought was brought about was thanks to some of the Voyager images of Io, Jupiter's innermost Galilean satellite. Io is only a fraction larger and denser than the Moon, and so
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