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1.5 Obesity

At the time of writing (2004) 20% of the adult population of the UK is classified as obese. The number of obese children has doubled since 1982, 10% of six year olds and 17% of fifteen year olds are now classified as obese. As shown in Table 4, obesity is recognized when the BMI exceeds 30 and occurs quite simply wh
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1.1 The components of a balanced diet

A balanced diet contains six key nutrient groups that are required in appropriate amounts for health. These groups are outlined below.

  • Proteins are involved in growth, repair and general maintenance of the body.

  • Carbohydrates are usually the main energy source for the body.

  • Lipids or fats are a rich source of energy, key components of cell membranes and signalling molecules, and as myelin they insulate neurons (nerve cells
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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.

3 Sources of energy from the natural environment

The natural environment itself is bathed in energy from other sources. Standing on a cliff top on a bright spring day you can feel the warmth of the Sun and the freshness of the breeze and hear the crashing of breaking waves below. All these energetic processes can be compared in terms of Author(s): The Open University

7.4 Models of active galaxies

  • The standard model of an AGN consists of an accreting supermassive black hole (the engine) surrounded by a broad-line region contained within a torus of infrared emitting dust and a narrow-line region.

  • Unified models attempt to explain the range of AGNs on the assumption that they differ only in luminosity and the angle at which they are viewed.

  • One type of model attempts to unify radio-quiet AGNs. Type 1 Seyferts and type
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7.2 Types of active galaxy

  • All active galaxies have a compact, energetic nucleus - an AGN.

  • Seyfert galaxies are spiral galaxies with bright, point-like nuclei which vary in brightness. They show excesses at far infrared and other wavelengths, and have strong, broad emission lines.

  • Quasars resemble very distant Seyfert galaxies with very luminous nuclei. They are variable. About 10% are strong radio sources thought to be powered by jets of material mo
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Radio-quiet AGNs

There has been a great deal of debate about whether there really are two different types of Seyfert or whether they can both be accounted for by the same model.

For example, suppose that you look at the model AGN in Figure 36a from a direction not too far from the rotation axis of the torus. You will see
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5.2 The obscuring torus

If an AGN consisted solely of the central engine, observers would see X-rays and ultraviolet radiation from the hot accretion disc (accounting for the 'the big blue bump' in Figure 17) and, apart from the jets, very little else. To account for the strong infrared emission from many AGNs, the model includes a t
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4.1 Introduction: the active galactic nuclei (AGN)

From Section 3 you will have discovered that one thing all active galaxies have in common is a compact nucleus, the AGN, which is the source of their activity. In this section you will study the two properties of AGNs that make them so intriguing - their small size and high luminosity - and learn about the energy source
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Learning outcomes

After studying this course, you should be able to:

  • demonstrate a greater awareness of science-based issues of public importance

  • demonstrate a greater insight into the phrase ‘the public understanding of science’

  • demonstrate a raised awareness of the ways in which the public can be consulted in relation to science policy issues

  • think of ways in which the public might in future become more engaged in decision-making about science th
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7.2 Information sources

7.2.1 How do I find the information required to carry out COSHH risk assessments?

The best source of information is the material safety data sheet (MSDS). By law (CHIP3) this should accompany any chemical that is purchased. However, if this is not available, or the chemical is old, then copies can be obtained from the manufacturer's website or information can sometimes be found in the
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5.2 Cryogenic liquids and ionising radiation safety

5.2.1 Cryogenic liquids

There are a number of hazards associated with cryogenic liquids, the main one being that when accidentally released the liquid expands hugely to form a gas (600 times in the case of nitrogen). The formation of such a large volume of gas can lead to asphyxiation in confined areas.

The other main hazard is cold burns (frostbite).

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Acknowledgements

Course image: Žarko Šušnjar in Flickr made available under Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence.

The content acknowledged below is Proprietary, used under licence and not subject to Creative Commons licensing. See Author(s): The Open University

A strategy for ridding the world of VAD?

In July 2000, Time magazine announced that a potential solution to VAD had been found - 'Golden Rice' (Figure 8). This was a variety of rice that had been genetically modified to introduce β-carotene into the endosperm (part of the grain of the rice). The name arises from the fact that the otherwise white grains of rice are given a golden colour by the presence of carotenoid compounds.

The announcement came at the height of the global controversy over genetically modified crops.
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2.2 Using A. tumefaciens to genetically modify plant cells

Genetic engineers have capitalised on the fact that part of the DNA from the Ti plasmid of A. tumefaciens is integrated into the plant genome during the infection process. Ti plasmids can be isolated and a foreign gene spliced in at an appropriate point, making it possible to transfer the novel gene into the plant.

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1 Hydropower

Hydroelectric energy is ultimately solar energy converted through evaporation of water, movement of air masses and precipitation to gravitational potential energy and then to the kinetic energy of water flowing down a slope. That energy was harnessed for centuries through the use of water wheels to drive mills, forges and textile works, before being supplanted by coal-fired steam energy. Electricity generation using water turbines, although first centred on constricted streams, has increasing
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2.1 The problems of iron uptake

Iron has a high natural abundance. It is the second most abundant metallic element by mass in the Earth's crust (7.1 per cent).

Activity 1

What are the main oxidation states of iron?

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3.8 Review

In this unit we have looked at some of the factors which infuence a couple's decision to have a child. For people who choose not to do so, at least for some part of their lives, a range of contraceptive practices is available. We have looked at the biological processes involved in producing gametes, and at the precise sequence of events necessary to produce a healthy, fertilized egg. We have seen how this egg develops, first as a pre-programmed, free-living embryo, then becomes buried within
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3.6.1 Identifying the pregnacy

Our description of the developing embryo has, so to speak, detached it from its mother. But we should remember that on the other end of the placenta is a woman whose reaction to her pregnancy may lie almost anywhere in the scale of human emotion, and whose behaviour during her pregnancy will have an enormous effect on its outcome. This section attempts to look at the pregnancy from the mother's point of view. Of course, it cannot possibly be applicable to all women in all pregna
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3.1 Pre-implantation and assymetric division

Let us now return to the Fallopian tube, where a fertilized egg is assembling its chromosomes prior to commencing a series of mitotic divisions which will eventually give rise to the millions of cells that make up the human body. Obviously these millions of cells do not just exist as an amorphous mass: they are differentiated into many different types of cell, and they are organized into recognizable, discrete structures: tissues and organs. This is accomplished by a coordinated sequen
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