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1.1 What is genetic testing?

When most people encounter genetic testing today, it is usually in a medical context. We may be referred by our GPs to a regional genetics unit, or we may approach our doctors, asking for genetic tests because we suspect something about our family history. In this unit we look at the issues and problems facing individuals and families when confronted with genetic testing.

The technologies that make genetic testing possible range from chemical tests for gene products in the blood,
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Introduction

This unit looks at three different uses of genetic testing: pre-natal diagnosis, childhood testing and adult testing. Such tests provide genetic information in the form of a predictive diagnosis, and as such are described as predictive tests. Pre-natal diagnosis uses techniques such as amniocentesis to test fetuses in the womb. For example, it is commonly offered to women over 35 to test for Down's syndrome. Childhood testing involves testing children for genetic diseases that may not
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Acknowledgements

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4.3 Type-II superconductors

For decades it was assumed that all superconductors, elements and alloys, behaved in similar ways, and that any differences could be attributed to impurities or defects in the materials. However, in 1957, Abrikosov predicted the existence of a different sort of superconductor, and Figure 23 shows direct evidence for the existence of what are now known as type-II superconductors. A comparison of Figures 23 and 22 indicates that the effect of an applied field on a type-II superconductor is rath
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3.3 The London equations

A simple but useful description of the electrodynamics of superconductivity was put forward by the brothers Fritz and Heinz London in 1935, shortly after the discovery that magnetic fields are expelled from superconductors. Their proposed equations are consistent with the Meissner effect and can be used with Maxwell's equations to predict how the magnetic field and surface current vary with distance from the surface of a superconductor.

In order to account for the Meissner effect, the L
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3.2 Magnetic field in a perfect conductor

When discussing the Meissner effect in Subsection 2.3, we argued qualitatively that a material that just had the property of zero resistance – a perfect conductor rather than a superconductor – would maintain a constant magnetic field in its interior, and would not expel any field that was present when the material became superconducting. We shall now show how that conclusion follows from an application of Maxwell's equations to a perfect conductor. We can then see what additional assumpt
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3.1 A two-fluid model

As was mentioned earlier, a substantial dose of quantum mechanics would be required to provide a full explanation of the properties of superconductors. This would take us too far away from electromagnetism, and we shall therefore restrict our discussion to aspects that can be discussed using classical concepts of electromagnetism.

We shall model the free electrons within a superconductor as two fluids. According to this two-fluid model, one fluid consists of ‘normal’ electron
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2.2 Persistent currents lead to constant magnetic flux

An important consequence of the persistent currents that flow in materials with zero resistance is that the magnetic flux that passes through a continuous loop of such a material remains constant. To see how this comes about, consider a ring of metal, enclosing a fixed area A, as shown in Figure 6a. An initial magnetic field B0 is applied perpendicular to the plane of the ring when the temperature is above the critical temperature of the material from which the rin
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2.1 Zero electrical resistance

In this section we shall discuss some of the most important electrical properties of superconductors, with discussion of magnetic properties to follow in the next section.

The most obvious characteristic of a superconductor is the complete disappearance of its electrical resistance below a temperature that is known as its critical temperature. Experiments have been carried out to attempt to detect whether there is any small residual resistance in the superconducting state. A sensitive t
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Acknowledgements

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2.9 End of section exercise

Portfolio exercise

After reading Section 2 you could conduct the following exercises as part of your evidence of achievement. You may like to discuss this activity with your supervisor.

  1. Write a reflective account of some of the skills you identify as important a
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2.1 Introduction

The most basic requirement of a PhD thesis is high-quality research. This outcome requires obvious intellectual skills related to knowledge and intelligence, but also less obvious skills such as planning and time management. A PhD project is a multi-year research programme, and the abilities to plan effectively, to coordinate activities and to manage your time and that of others are extremely important. The aim of this unit is to help you understand the planning and management skills that are
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1.9 Summary and conclusion: ‘take-away messages’

It helps to understand the PhD in context: the modern PhD is typically a three-year research training providing evidence of the ability to conduct and bring to fruition an independent programme of research. It requires rigour and an ability to enter the discourse, but its scope is limited and it does not require perfection. Models of study and models of dissertations vary for different universities, disciplines, and topics. The key is to understand what is appropriate for your particular prog
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1.8 The OU requirements

The criteria for an OU PhD (as stated in the Guidelines on Research Degree Examinations for Heads of Disciplines, Supervisors and Examination Panels, EX 10, revised January 1998) are that:

The thesis must be of good presentation style and show evidence of being a significant contribution knowledge and of the student's capacity to pursue further research without supervision. The thesis must contain
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1.4 Broadly typical phases of PhD research

A modern PhD can be viewed as having three key phases (very roughly, but not strictly, corresponding to the three years of a full-time degree), each of which contributes a necessary element of mastery:

  1. Orientation – mastering the literature and formulating a research problem and plan.

  2. Intensive research – gathering the evidence to support the thesis, whether empirical or theoretical.

  3. Entering t
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1.2 Different reasons for doing PhDs

Just as there are different views of what a PhD is or means, there are different reasons for undertaking a PhD, ranging from the pragmatic – acquiring a research credential for academia or for industry – to the idealistic – aspiring to deep scholarship. And students have many reasons in between, including things like curiosity, a drive to chase a long-held question, and the need to prove oneself. What's important here is not the reason for starting, but the compelling reason for finishi
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1.1 Thoughts on a PhD

Entering students often think of a PhD as a ‘magnum opus’, a brilliant research project culminating in a great work. This is rather a demanding model, and few students win Nobel Prizes as a result of their doctoral studies. More realistically, a PhD is research training leading to a research qualification. The PhD is a passport to a research career.

There are other views of a PhD, as well. Getting a PhD can be a ‘rite of passage’, prerequisite to admission into the academic ‘t
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2.5 Collecting quantitative data

How can you collect quantitative data that summarise the nature of a habitat when it is three-dimensional? How, in fact, do you collect quantitative data?

Multi-storied habitats where the components have a different scale are usually recorded storey by storey, but using much the same methodology. There are two standard ways of collecting data quantitatively. The first involves recording species present within a standard area such as 10 cm × 10 cm, 0.5 m × 0.5 m, 1 m × 1 m, or 10 m ×
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1.8.3 Explaining the observations

Having made and reviewed our observations, we are now in a position to interpret them – why are the rocks the way they are? The sedimentary strata that we see in Figure 16 were likely to have been deposited in essentially horizontal layers, so why is one set tilted and the other horizontal? To answer
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1.8.2 Interpretation of a geological exposure

We now want to make use of the observations obtained by sketching the exposure, and it is useful to start by briefly summarising the features seen. First of all, you probably noticed the large boulder in the foreground of Figure 16 (which has been attached below for ease of access). Where did this boul
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