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3.5 Velocity-time and speed-time graphs

Just as we may plot the position-time graph or the displacement-time graph of a particular motion, so we may plot a velocity-time graph for that motion. By convention, velocity is plotted on the vertical axis (since velocity is the dependent variable) and time (the independent variable) is plotted on the horizontal axis. In the special case of uniform motion, the velocity-time graph takes a particularly simple form - it is just a horizontal line, i.e. the gradient is zero. Examples are
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6.4 Taking the image

Activity 14

Now watch this video clip of a patients lungs being imaged, called a VQ (ventilation quotient) scan. What are the two different types of acquisitions used called? What radioactive substance is used for each acq
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6.1 Introduction

Radionuclide imaging is a very valuable way of examining the function of an organ, as opposed to the more structural images obtained by other methods such as X-ray and CT.

The basic principles of radionuclide imaging are as follows:

  • a radioactive substance, usually combined with a biologically active compound, is injected into the patient;

  • this targets a particular organ or tissue type;

  • the radiation emitted i
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2.4 How thick is Europa's ice?

You learned in Section 1.4 that geophysical data show the 'icy' outer part of Europa to be about 100 km thick, but that the information is inadequate to distinguish between the extreme possibilities of solid ice all the way down to the bedrock and a floating sheet of ice supported above a liquid ocean (Author(s): The Open University

1.3 Unravelling the natures of the large satellites

Before the dawn of the space age, relatively little could be discovered about even the large satellites. Their orbits were well known, and from the subtle orbital perturbations caused by neighbouring satellites it was possible to deduce their masses. Measurements of their sizes enabled densities to be calculated to within about 20 per cent of the currently accepted values for the Galilean satellites, and with rather less certainty for the large satellites of the other giant planets. However,
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4 Germline gene therapy

Now that in vitro fertilization – bringing eggs and sperm together outside the prospective mother's body – is an established technology, the possibility exists that genes could be altered in eggs or sperm, or in a very early embryo. The obvious advantages of germline gene therapy are that the cells are accessible (because they are outside the body), so gene delivery is less of a problem than it tends to be with somatic cells; and the inserted gene (or genes) would be present
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Introduction

Following on from the advances made in diagnosing disorders using genetic testing, this course looks at the possibilities for genetic therapies. Two approaches to gene therapy are discussed: correcting genes involved in causing illness; and using genes to treat disorders. Before closing on a discussion of the issues around 'designer babies' somatic gene therapy and germline gene therapy are discussed.

This OpenLearn course provides a sample of Level 1 study in Author(s): The Open University

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1.3 Beyond visible light

During the twentieth century, astronomers extended their capabilities by developing telescopes and detectors that were sensitive to radio waves, microwaves, infrared and ultraviolet radiation, X-rays and gamma rays. All these forms of electromagnetic radiation, along with visible light, are emitted by the Sun.

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1.1 The Sun at visible wavelengths

The Sun is seen as a blindingly bright, yellow object in the sky. The part of the Sun that you normally see is called the photosphere (meaning 'sphere of light'); this is best thought of as the 'surface' of the Sun, although it is very different from the surface of a planet such as Earth. Its diameter is about 1.4 million kilometres, making the Sun's volume roughly one million times that of the Earth. The photosphere is not solid. Rather, it is a thin layer of hot gaseous material, abo
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1 Introducing cosmology

General relativity has a very different conceptual basis from that of Newtonian mechanics. Its success in accounting for the precession of Mercury's orbit, and the bending of light by massive objects like the Sun, gives us confidence that our picture of space and time should be Einstein's rather than Newton's. In this and the following courses, we turn our attention to the study of the large-scale structure of spacetime. We see how spacetime as a whole is curved by the gross distribution of m
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Keep on learning

Study another free course

There are more than 800 courses on OpenLearn for you to
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4.5 How wide were the oceans?

Once evidence has been found to prove the existence of an ancient ocean, is it possible to calculate its maximum width? Palaeomagnetic studies can give geologists an idea of the palaeolatitude (N–S) of the ocean but not its palaeolongtitude (E–W), so depending on its orientation, an indication of how wide it was may not be possible. However, an approximate indication of how wide the former oceans were can be obtained by examining the fossil faunal assemblages that are present (e.g.
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4.1 Introduction

In the theory of plate tectonics there are three main types of plate boundary, namely: constructive, destructive and conservative plate boundaries.

Figure 5
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3.5 Electrophysiological studies of language processing

Brain imaging and aphasic studies helped us localise the subparts of language processing within the brain. However, they have shed little light on how processing unfolds in real time. This is because contemporary brain imaging is quite poor at showing changes in activity through time in fine detail, so it is hard to pick up something that may be happening slightly before something else.

In Author(s): The Open University

12.8 More revision questions

Question 12

  • (a) If two tones are broadcast through headphones at an intensity of 100 dB SPL, which will sound louder, a 100 Hz tone or a 1000 Hz tone? Why?

  • (b) How lo
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12.1 Localisation of sound in the horizontal plane

While information about frequency and intensity is essential for interpreting sounds in our environment, sound localisation can be of critical importance for survival. For example, if you carelessly cross the street, your localisation of a car's horn may be all that saves you. Our current understanding of the mechanisms underlying sound localisation suggests that we use different techniques for locating sources in the horizontal plane and vertical plane.

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7.2.2 The ‘where’ pathway

The ‘where’ pathway involves the ventral cochlear nuclei, the superior olivary complex and the inferior colliculus. The superior olivary complex is composed of the lateral superior olive (LSO) and the medial superior olive (MSO).

The neurons in the superior olivary complex are the first brainstem neurons to receive strong inputs from both cochleae and are involved in sound localisation.

The MSO receives excitatory inputs from the cochlear nuclei on both sides and is tonotopica
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3.5.1 Hair cells transform mechanical energy into neural signals

The tectorial membrane runs parallel to the basilar membrane, so when the basilar membrane vibrates up and down in response to motion at the stapes, so does the tectorial membrane. However, as shown in Figure 14, the displacement of the membranes causes them to pivot about different hinging points and this creates a shearing force bet
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3.4 The organ of Corti and hair cells

We have established that the vibration patterns of the basilar membrane carry information about frequency, amplitude and time. The next step is to examine how this information is converted or coded into neural signals in the auditory nervous system. To do so, we must look at the organ of Corti in some detail since it is here that the auditory receptor cells that convert mechanical energy into a change in membrane polarisation are located.

As we saw in
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5.2.1 The GM Science Review

The review was undertaken by the GM Science Review Panel, chaired by the Government's Chief Scientific Adviser, Sir David King. Its role was to assess the evidence available in the peer-reviewed scientific literature. The panel produced two reports, the first in July 2003 and the second in January 2004. The main conclusions of these reports are listed below.

  • The risk to human health is very low.

  • There is little likelihood of such plan
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