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4.2 The terrestrial carbon cycle

Figure 1.10 shows the rates of natural carbon exchange between the terrestrial system and the atmosphere.

2 Energy, work, power and efficiency

In everyday speech we often refer colloquially to the powerful politician, the energetic child, the working mother and the efficient administrator. We use these terms imprecisely, and often wrongly, compared with their scientific definitions.


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6.2 Do supermassive black holes really exist?

One outstanding feature of the black-hole model is that the black hole must be supermassive. Can one at least detect the presence of a massive central object?

  • How might a massive central object be detected using information from galactic rotation curves?

  • By measuring rotation speeds near the nucleus of the galaxy. The faster the rotation speeds, the greater the enclosed mass.

So the answer is yes. In NGC 4151
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3.2 Herbicide tolerance

As you discovered from Activity 1, herbicide tolerance is the trait most commonly incorporated into commercial GM plants. A crop can be made tolerant to herbicide by inserting a gene that causes plants to become unresponsive to the toxic chemical. Before considering how the genetic manipulation can be achieved, it is useful to understand a little about how herbicides act.

Many herbicides work by inhibiting a key plant enzyme necessary for growth (if you're not exactly sure what this mea
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Introduction

In this unit we will see that, despite having a high natural abundance, iron is in very short supply because of the insolubility of its oxides and hydroxides. A result of this is that organisms have developed methods for the uptake, transport and storage of iron. For example, iron storage in mammals, including humans, is achieved by ferritin, which stores iron as a hydrated iron(III) oxide – an example of biomineralisation.

This unit is from our archive and is an adapted extract from
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4.2 Reactor safety: the Chernobyl incident

By far the worst nuclear reactor accident took place on 26 April 1986 when one of four 1 GW reactors at Chernobyl in the Ukraine released a radioactive cloud over Europe (Figure 17). (See S278 video clips document.) The build-up to this accident has been related to a series of complex chemical reactions induced
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1.2 The origins of coal

If you examine a piece of coal, at first sight it appears black and rather homogenous. However, closer inspection generally shows a series of parallel bands up to a few millimetres thick. Most obvious are shiny bands that break into angular pieces if struck. Between them are layers of dull, relatively hard coal and thin weak layers of charcoal-like carbon. Coal splits easily along these weak layers, which crumble to give coal its characteristic dusty black coating.

Microscopic examinati
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Learning outcomes

By the end of this unit you should be able to:

  • explain how coal is formed;

  • explain how coal is found and extracted by either surface or underground mines;

  • discuss how geological problems and environmental issues surrounding extraction affect mining;

  • explain the reasons for the decline in the UK’s coal industry.


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7.4 Proteomics

Traditionally, the study of the biochemistry or structure of a protein necessitated its purification to a high degree. The development of protocols for cloning, manipulation and expression of genes greatly facilitated this kind of study, as will be clear to you from the previous section. In recent years, a number of high-throughput techniques have, to an extent, obviated traditional approaches and permit simultaneous analysis of all the expressed proteins in a cell or organism, known as the <
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8.4 Line spectra: line flux and equivalent width

In general, astronomical objects emit both continuous emission and lines superimposed on this continuous emission. The equivalent width is a useful way of describing the relative strength of a line compared to the continuous emission at nearby wavelengths. The flux level of the continuous spectrum is called the continuum level, and at an emission line the spectrum rises above this level, while at an absorption line the spectrum dips below this level, as Author(s): The Open University

7.5 Emission from spiralling electrons: synchrotron radiation

In the very first reading (Activity 1) we encountered the term ‘non-thermal’ describing the spectrum of light emitted from AGN. In this subsection we will learn more about the most important type of non-thermal radiation: synchrotron emission.

When a charged particle moves in the presence of a magnetic field it experiences a Lorentz force, which produces an acceleration whose direction is perpendicular to both the magnetic field line and the velocity of the particle,
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14 Unit questions and answers

Note: Question 1 is included in Section 3.

Question 2


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1.2 BSE

In December 1984, it was noticed that a cow on a Sussex farm was displaying head tremors and loss of coordination. The animal died in February 1985. The vet regarded this case as sufficiently serious for a post-mortem examination to be necessary. In September 1985, a government pathologist confirmed that the cause of its death was a type of disease known as a spongiform encephalopathy. Spongiform encephalopathies (i.e. ‘spongy brain diseases’) are so called because, on post-mortem
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6 Thermoregulation and mammalian fur

A coat of profuse mammalian body hair is commonly called fur. Fur provides insulation, which is a property that one first thinks of as useful for mammals to help retain body heat. Fur is a unique and fundamental feature of mammals, though not all living species possess it.

Question 12

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2.2.2 Collimator

The dimensions of the emerging X-ray beam can be altered by the collimator. This helps to ensure that only the region of interest is exposed to the X-rays.


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2.3.2 The crater Pwyll

You might also have noted that there are no obvious impact craters visible in Figure 16 (see Section 2.3.1). In fact there are a few. One is a bright spot, 15 km in diameter, surrounded by a dark halo of ejecta that occurs 10 mm from the top edge and 65 mm from the left-hand edge of the figure. Another is a s
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Learning outcomes

By the end of this unit you should be able to:

  • discuss processes upon and within, and internal structure of, differentiated icy bodies (primarily large satellites) in comparison with the terrestrial planets;

  • describe the conditions that may be required to originate and foster life in an icy body and discuss the likelihood of their having occurred;

  • recognise the moral and ethical issues of landing spacecraft on potential life-bearing worlds and appre
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3.2 Colour vision

DA stresses that colour vision is very important in primates, not only because colour is used ‘in sexual displays’ such as advertising a female's receptiveness to mating [p. 275], but also to identify ripe fruit [p.247] and to select nutritious leaves [p. 255]. This section discusses these points in more detail and explains how the visual system in primates is able to detect colour.

White light is composed of light of different wavelengths, from 300–800 nanometres (nm); 1 nm is on
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References

Durant, J., Bauer, M., Gaskell, G., Midden, C., Liakopoulos, M. and Scholten, L. (2000) ‘Two cultures of public understanding of science andtechnology in Europe’ in Dierkes, M. and Von Grote, C. (eds) Between Understanding and Trust: the Public, Science and Technology, Amsterdam: Harwood Academic Publishers.
Eurobarometer
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4.3 Phenotypic changes that appeared without being selected

As well as these behavioural changes, many of the selected foxes had unusual white markings (Figures 13c and d). The first colour change that the Russian investigators noted in their foxes was a white ‘star’ on the forehead similar to that of other domesticated mammals (Author(s): The Open University

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