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4 Inside the atom

Before going on to see how atoms can link (bond) with each other, you need to look at atoms in a little more detail. Doubtless they are not like blocks of Lego! So what are they like?

In fact, every atom has a complex internal structure. Given the extremely small size of an atom, you may find it difficult to visualise any smaller bits inside it. However, you may already be familiar with some of the effects of one of these components – electrons. It is easy to do an experiment t
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7 Sedimentation and tectonics at a mid-Ordovician to Silurian active margin

The document attached below includes the seventh section of Mountain building in Scotland. In this section, you will find the following subsections:

  • 7.1 Introduction

  • 7.2 Mid-Ordovician to Silurian sedimentation in the Midland Valley Terrane

    • 7.2.1 Ordivician sedimentation

    • 7.2.2 Silurian sedimentiation

    • 7.2.3 Summary of Section 7.2

  • 7
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Learning outcomes

When you have studied this unit you should be able to:

  • describe the geological history of the Scottish Highlands;

  • give examples of igneous, metamorphic and structurally complex rocks.


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11.5 Summary of sections 8 to 11

In these sections we have described some of the quantitative relationships between the physical dimensions of simple sounds and their subjective psychological dimensions. The physical dimension of intensity, or pressure amplitude, given in decibels (dB), directly affects loudness. Frequency of pressure changes, in hertz (Hz), mainly determines pitch.

The lowest threshold value and hence the maximal sensitivity for humans is in the region of 3000 Hz.

The quantitative relationship b
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11.3 Frequency selectivity

In preceding sections we examined two ways in which the auditory system may code frequency information: the place theory and phase locking. In this section we will look at the psychophysical evidence for place coding on the basilar membrane by examining the ability of the auditory system to resolve the components of sinusoidal waves in a complex sound – a phenomenon known as frequency selectivity.

The perception of a sound depends not only on its own frequency and intensity but also o
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9.1 Introduction

Psychophysics is the oldest field of the science of psychology. It stems from attempts in the nineteenth century to measure and quantify sensation. It attempts to quantify the relationship between a stimulus and the sensation it evokes, usually for the purpose of understanding the process of perception. Historically, psychophysics has centred around three general approaches. The first involves measuring the smallest value of some stimulus that a listener can detect – a measure of sensitivit
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7.2 Coding of information in the higher auditory centres

We have seen that in the cochlear nerve, information about sound intensity is coded for in two ways: the firing rates of neurons and the number of neurons active. These two mechanisms of coding signal intensity are found throughout the auditory pathway and are believed to be the neural correlates of perceived loudness. The tonotopic organisation of the auditory nerve is also preserved throughout the auditory pathway; there are tonotopic maps within each of the auditory nerve relay nuclei, the
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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 betw
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3.1 Introduction

The inner ear (Figure 3) can be divided into three parts: the semicircular canals, the vestibule and the cochlea, all of which are located in the temporal bone. The semicircular canals and the vestibule affect the sense of balance and are not concerned with hearing. However, the cochlea, and what goes on inside it, provides
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2.1 Structure and function of the outer and middle ear

Figure 1 is a diagram of the human ear. The outer ear consists of the visible part of the ear or pinna, the external auditory canal (meatus), and the tympanic membrane (tympanum) or eardrum. The human pinna is formed primarily of cartilage and is attached to the head by muscles and ligaments. The deep central portion of the
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Learning outcomes

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

  • distinguish between the major anatomical components of the outer, middle and inner ear;

  • describe the function of the outer, middle and inner ear;

  • describe the structure of the cochlea;

  • describe the structural arrangements of the organ of Corti and the function of the basilar membrane;

  • explain the difference between the four coding mechanisms used in order to transmit inform
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2.5 The uncertain Universe

Despite the impact of relativity, the greatest source of change in the scientific world-view in the twentieth century has undoubtedly been the development of quantum physics. This is the branch of physics that is mainly concerned with microscopic entities such as atoms and molecules, and their constituents. It is by far the most quantitatively accurate part of science, routinely providing predictions that are correct to just a few parts in a million. Quantum physics is also of enormous
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2.3.1 Thermodynamics and entropy

The first half of the nineteenth century was a period of great economic and industrial growth. The steam engine, invented in the previous century, was becoming increasingly common in locomotives, mines and factories; power was becoming available on demand. A major priority for engineers was to produce more efficient engines, in order to deliver more useful power for less expenditure on fuel. Thermodynamics emerged as a study of the basic principles determining energy flows and the effi
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5.1 Introduction

The first genetically modified organisms (GMOs) were created in the early 1970s, but for much of the 1980s biotechnology was a phenomenon confined to the laboratory. In 1988, ‘vegetarian cheese’, the first food product created using GMOs, was introduced in the UK. This cheese was produced using chymosin, an enzyme derived from genetically modified bacteria, rather than the traditional animal product (rennet). Chymosin derived from GMOs is now used to produce 90% of the hard cheeses
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4.3 Assessing GM foods: substantial equivalence is introduced

In the early 1990s, biotechnology companies were preparing to market the first food products derived from GM crops. This provided a challenge to legislators. There were no precedents to guide them as to how to approve or ban novel food products. The methods used to approve pharmaceuticals, summarised above (Section 3.1), did not seem to transfer easily to whole food products.

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4.1 Introduction

Pusztai and his team were attempting to develop suitable tests to assess the safety of GM potatoes. Typically, testing the safety of GM food involves comparing its composition and/or its effects with that of the conventionally produced food it most closely resembles. We have seen that such comparisons were at the heart of Pusztai's work.

The comparison of GM and conventional crops and food has led to the so-called principle of substantial equivalence, which has been used extensiv
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2.1 Introduction

There are at least three broad and overlapping areas of concern about GM crops. First, there is a concern that GM products might be detrimental to human health. These include concerns that:

  • The use of antibiotic marker genes might increase bacterial resistance to antibiotics. These concerns have led to the development of alternative selectable marker genes.

  • New proteins manufactured in GM crops might provoke unwanted allergic response
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2.4 The effect of interstellar dust

Let's now consider the dust. Photoexcitation (by absorption of photons) and collisional excitation (by atoms/molecules) occur in the atoms and molecules that constitute the surface of a dust grain. Much of this energy is shared throughout the grain, raising its temperature until thermal radiation from the grain balances the energy absorbed. An alternative fate for an incident photon is to be scattered (Figure 15), a process that is very efficient at certain wavelengths. Figure 20 illustrates
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Learning outcomes

After studying this unit you should be able to:

  • describe and comment on the main features of a Hertzsprung-Russell diagram of stars in general, and of stars in a cluster;

  • outline a broad model of stellar evolution based on the observed properties of large numbers of stars, and describe how stars of different initial mass might evolve;

  • describe the effects of interstellar material on starlight, and outline some of the processes by which such material
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5 Integrating across species

Populations of related species occupy similar niches in different environments. A big question for environmental physiologists is whether differences in biochemistry and physiology between related species living in different environments derive from physiological acclimatisation (sometimes referred to as phenotypic flexibility), phenotypic plasticity or evolutionary adaptation.

Recall from Section 3.3 how hoopoe larks, wild-captured from the Arabian desert and kept at T a
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