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Learning outcomes

By the end of this unit you should:

  • have a greater awareness of science-based issues of public importance;

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

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

  • be able to think of ways in which the public might in future become more engaged in decision-making about science that has social impact.


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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

The content acknowledged below is Proprietary (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 in this unit:

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5 Summary

At the time of writing (2006) a relatively small number of types of GM crop have been grown globally, in a limited number of countries. The take-up of these crops has been relatively high in countries like the USA and Canada, but very much lower in Europe. However, there is a very rapid increase in the growth of GM crops in developing countries.

The technique most commonly used to introduce new genetic material into dicots has involved the use of a modified soil bacterium, Agrobacter
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4.1 Vitamin A deficiency

Vitamin A, more properly known as retinol, is an important chemical intermediate in a number of biochemical processes in mammals. It is involved in vision, and is found in the rod cells of the retina of the eye. These cells are particularly important in seeing at low light levels, and night blindness is a symptom of vitamin A deficiency (VAD). Vitamin A is also involved in the proper functioning of the immune system. Children suffering from VAD are prone to serious infections, and often die f
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2.1 Crown gall disease: genetic engineering in nature

A. tumefaciens causes crown gall disease in a wide range of dicotyledonous plants. (Dicotyledonous plants, are also known as dicots, have broad leaves with branching veins. An example would be a broad leaved tree like an oak. Narrow leaved plants with parallel grains such as grasses are known as monocotyledonous plant or monocots.) The infection normally occurs at the site of a wound in the plant. The disease gains its name from the large tumour-like swellings, or galls, that o
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Learning outcomes

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

  • explain the principles that underlie the ability of hydropower to deliver useable energy;

  • outline the technologies that are used to harness hydropower;

  • discuss the positive and negative aspects of hydropower in relation to natural and human aspects of the environment.


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3.2 Removal of iron

Before leaving enterobactin to look at iron transport and storage in humans, it is worth asking the question: how does E. coli remove the iron from such a stable complex as the iron(III)–enterobactin once it has been absorbed?

The answer to this question can be found if we look back to reaction 38. The rigid, three-dimensional structure of the triserine ring of enterobactin is the main reason why enterobactin is such an effective ligand. If the structure of the ring is destroye
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1 How do organisms acquire iron?

Metals are an essential part of biological chemistry. Of all the trace elements, iron is the most important, especially as it is present in many essential enzymes and proteins. But how do organisms acquire the iron from their surroundings? Clearly, organisms need to absorb iron biochemically before it can be used in proteins. Also, some method of replacing lost iron quickly is needed: for instance, how is blood replaced once it has been lost through a cut? This prompts the question: what bioc
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4.5 Gamete production in women

It is time now to turn to the question of how female gametes – eggs – are made. There are substantial differences between sperm and eggs, and consequently their production pathways are very different.

Q Can you give one similar
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3.6 Summary of Section 3

  1. Many people wish to limit the number of their offspring, and so resort to contraceptive measures.

  2. Chemical contraceptives interrupt the production of gametes, or prevent implantation.

  3. Mechanical or barrier contraceptives prevent egg and sperm from meeting and, in the case of IUDs, prevent implantation.

  4. Surgical methods of contraception involve physical alteration of the reproductive tract so as to prevent e
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1.3.5 Natural methods of contraception

Many people with particular religious beliefs are fundamentally opposed to the use of artificial methods of contraception. In the developing world, where, as you saw above, the population is frequently increasing at an unsustainable rate, this is a particular problem. For Muslims and Roman Catholics (and others), who may nonetheless wish to limit their families, the preferred option is to use natural family planning methods. The most commonplace method, which involves estimating the ‘fertil
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Introduction

This unit is from our archive and it is an adapted extract from Human Biology and Health (SK220) which is no longer in presentation. If you wish to study formally at The Open University, you may wish to explore the courses we offer in this curriculum area .

This unit looks at the human being in the context of an individual life cycle, examining some of the processes that
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Acknowledgements

Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit:

This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence. See Terms and Conditions.

Figures

Figure 1 Copyright ©
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3.3 Dams

To economize on constructional materials and costs, it is desirable to build a dam at a narrow part of a valley so that the dam can be kept as short as possible. The quantity of constructional materials needed to build dams, and their cost, can be enormous. The Aswan High Dam, built during the 1960s, cost £400 million for a 1.2 km dam. Though shorter than the Aswan High Dam, the longest dam in Britain, the Kielder Dam in Northumberland (Author(s): The Open University

3.1 Introduction

The simplest and oldest way of storing surface water is in reservoirs and this has been done for thousands of years. Most reservoirs are still built to increase water supplies, but some are also built for other purposes, especially for generating hydroelectric power and for protection against floods. The Tennessee River in the United States, for example, has reservoirs to trap and store water that would otherwise cause floods, the water being released when the height of the river falls to saf
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Learning outcomes

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

  • list the types of springs, and how each type relates to a different geological setting;

  • use hydrographs to distinguish overland flow and interflow from baseflow, and make inferences about the climate of an area;

  • expain how various changes in land use in a river catchment will change the hydrograph of a river;

  • distinguish the different types of reservoir construction, and decide whether a
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Introduction

We have seen that where precipitation reaches the ground, some runs off the surface into streams and rivers and some of it infiltrates, passing through the soil. Water that reaches the water table to become groundwater may eventually re-emerge at the surface as springs where the water table intersects the surface. Almost all streams and rivers have springs or seepages as their ultimate source, or are fed by them at various points along their courses.

This unit is from our archive and is
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5 Porosity

The amount of water that a rock can store depends on its porosity, which is the proportion of the volume of the rock that consists of pores:

The principal factors that control porosity are grain size and shape, the degree of sorting (a well-sorted sediment has a narrow
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Introduction

Many people have the impression that underground water occupies vast caverns, such as those in the Derbyshire Peak District, flowing from one cavern to another along underground rivers. This is a common misconception: underground caverns are fairly rare, but huge quantities of water exist underground, within rocks. This is because many rocks contain pores, spaces that come in all shapes and sizes. In sediments, and consequently sedimentary rocks, there are often pores between grains which can
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