7 Some philosophical issues In this unit we have considered global issues that have implications for our health and the health of future generations. This places our own lives in a different context and also indicates the uncertainties that surround the future. Whilst some environmental changes have very direct health consequences, we should not forget the indirect benefits that accrue from a healthy planet. The principle that ‘we should hand on to the next generation an environment no less rich than the one we
6 Population growth Earlier it was stated that three factors check population growth. These are predation, disease and insufficient food supply. For much of our history, our ancestors’ numbers were indeed limited by wars, disease and famine. The world population remained relatively stable until around 300 years ago. Then at the beginning of the 19th century (100 years after population growth started its geometric increase), the demographer Thomas Malthus predicted that population growth would outstrip food pro
5.5 Indoor pollutants Before leaving air pollution you might reflect that many of us spend most of our time indoors where the air quality can differ from that outside the building. In what ways will the air be different inside a building? 5.3 Global warming Media attention has been such that it would be hard to have missed the fact that global warming is considered to be a ‘bad thing’. Why should this be so? What is so wrong with being a bit warmer? Anyway, is global warming really occurring and, if it is, what are the causal factors responsible for it? Let us deal with this last question first. As we sit on a beach in summer, or in a sunny window seat in winter, we are aware of the Earth being warmed by the Sun. In fact the Earth is w 6.2 The hierarchy of human needs A second approach is to look at the human needs and wants from a more theoretical perspective. One such model was developed in the 1950s and 1960s by Abraham Maslow. Although it exists in many variants it is generally known as Maslow's hierarchy of human needs. In the most common interpretations it places the fundamental material needs of survival, such as food, shelter and safety at the base of a triangle, rising through social needs of belonging in human society, to 4.4 Discussion In this second case study, I have described two different trends in energy use by cold appliances over the last few decades. On the one hand the efficiency with which appliances use electrical energy has improved but, in spite of this, their consumption of electricity has increased significantly in recent decades. Since 2000 consumption has started to decline, probably as a result of the introduction of minimum energy standards. The trend will only continue if we demand and use the most energ 3.2 The agreement to protect the ozone layer After a decade of controversy about the possible effects of CFCs, in 1985 British scientists discovered over the Antarctic a quite unexpected ‘hole’ in the ozone layer which was the size of the USA. This helped to galvanise the international community into action (though some who took part in the negotiations claim it played little part). By 1987 the first international agreement to control substances damaging to the ozone layer, the Montreal Protocol, was established. Interestingl 1 Introductory advice There are two ways to approach this Introduction. The first is the more natural one: to read it straight through to get a general feel for its style and content, and to see whether you are going to find the unit and the issues it raises interesting; in short, to get an overview. There is nothing wrong with this at all. You will find as you read through it, though, that the Introduction covers a wide range of topics. In part this is because the unit authors takes a broad vi 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 Grateful acknowledgement is made to the following sources for permission to reproduce material within this book. 3.1 (4A) Exploring dynamic relationships using sign graphs Here is where things start getting really interesting in terms of system dynamics! So far, most of your modelling work has been pretty static, with a limited sense of how things change over time. In fact, the behaviour of complex systems is rarely stable. Sometimes change is exponential (e.g. the growth of the World Wide Web); sometimes systems crash and burn (e.g. extinction of populations); but often systems demonstrate repetitive patterns of behaviour (e.g. economic boom and bust cycles). 3.1 (2A): Exploring the global implications of different mindsets In this activity the aim is to investigate the implications of different mindsets with regards to the future unfolding of events on a global scale. So far, you have focused your attention on exploring your personal cognitive 3.3 Thermal stresses When the temperature of an object increases (say, by ΔT) it expands. According to the linear model of thermal expansion the length increase is described by What if there is a temperature change, but some constraint prevents the proper thermal size changes? The constraint 5.5 Copyright – what you need to know An original piece of work, whether it is text, music, pictures, sound recordings, web pages, etc., is protected by copyright law and may often have an accompanying symbol (©) and/or legal statement. In the UK it is the Copyright, Designs and Patents Act 1988 which regulates this. In most circumstances, works protected by copyright can be used in whole or in part only with the permission of the owner. In some cases this permission results in a fee. However, the UK legislation incl 3.1 Introduction You can find a lot of information about technology on the internet. To find this information you might choose to use: search engines and subject gateways; books and electronic books; databases; journals; encyclopedias; patents; news sources. 5.6.3 Conformation and crystallinity If there are key connections between the chain configuration and crystallisation, you might also expect some more subtle effects from rotation about chain bonds. After all, polymer chains must be able to twist into the regular conformation demanded for crystal structures (Figure 57(a)). And what influence will rotation have on 4.5 Copolymerization The alloying of metals to improve their properties is widespread and although many polymers used today are relatively pure (e.g. polystyrene, nylon), an increasing number are mixtures of two or more polymers. As with metals, one reason for doing this is to increase the range of properties. The major practical problem, however, is that homopolymers blend together with difficulty and even where blends are possible, as in some thermoplastics, phase separation can occur readily. This proble 4.3.3 Termination and transfer There are basically three ways in which chains terminate. The first is known as coupling and occurs when two free radicals join together. This can be represented by the general equation Such a mechanism significantly increases molecular mass, if it results in 4.3 Chain growth polymerization Chain growth polymerization is basically a three-stage process, involving initiation of active molecules, their propagation and termination of the active chain ends. 3.3.2 Benzene, toluene and xylene In addition to benzene itself, the catalytic reformer also produces ethylbenzene, toluene and the isomeric xylenes directly. The demand for ethylbenzene is always great as a source of styrene monomer, but toluene does not find great use apart from a relatively small application in polyurethane. This is why most toluene is de-alkylated to increase overall benzene production. A similar problem exists with the xylenes:
Stage 2: Analysis of the existing situation (where are we now?) Having defined and agreed on the problem, it is necessary to decide on the system in which you consider it plays a part. In practice the two stages are closely linked and the analysis of the existing system nearly always means a redefinition or refinement of the problem or opportunity. Identifying and defining the problem and the system or systems that relate to it are critical for the success of subsequent analysis.
Question 30
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