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2.2.2 Precision

Measuring the same sample should give the same result every time if the equipment is precise. In practice, the information displayed by a measuring device can depend on several factors (such as temperature and humidity) and can drift slightly over time. Nevertheless, during the time it takes to complete a measurement sequence, all measurements ought to remain within a specified, small margin of error, often marked on the equipment. We will see later on, in Author(s): The Open University

2.1.1 Accuracy

The way to ensure that equipment is accurate is to use a series of known standards against which to calibrate the equipment. Calibrating should be done at least each day and sometimes more frequently (such as before using the equipment to measure unknown samples). Many types of measuring equipment go through an automatic calibration when they are switched on, but others require the user to provide a series of known calibration standards.


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1.10 Subtraction of decimal numbers

Subtraction of numbers can be used to answer questions such as ‘what's the difference between two values?’ or ‘if something has decreased by a certain amount, what's its new value?’ Subtraction can also be thought of as undoing the process of addition. For instance, instead of saying ‘£10 take away £7.85 leaves how much?’ you could say, ‘what do I have to add to £7.85 to get back to £10?’

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1.9 Addition of decimal numbers

If we add 109.8 ml of one liquid to 6.5 ml of another liquid, what would be the total volume of liquid in ml?

To compare 109.8 with 6.5, you need to remember that

Place the two numbers in a grid on top of each other and make sure that columns representing the same magnitude line up wit
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1.8.1 Study Note 4

If you have difficulty with this section, you might find it helpful to investigate some of the Government schemes aimed at improving maths skills. More information about such schemes can be found at http://www.direct.gov.uk/en/EducationAndLearning/AdultLearning/ImprovingYourSkills/index.htm (accessed 5 March 2008).

Box 3: The basics
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3.6 Moon38: Apollo 12 station 5

Two of the frames show Al Bean carrying the Apollo Lunar Surface Experiments Package (ALSEP) packages out from the Lunar Module. (QuickTime, 500KB, note: this may take some time to download depending on your connection speed)

Introduction

This unit is an adapted extract from the course Biological psychology: exploring the brain (SD226)

This unit looks at how language is understood, which includes hearing and how sounds and words are interpreted by the brain. It takes an interdisciplinary approach and should be of wide general interest.


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3 Orogenies in the Proterozoic

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

  • 3.1 Introduction

  • 3.2 Palaeoproterozoic rifting, sedimentation and magmatism

  • 3.3 The Palaeoproterozoic Laxfordian Orogeny

    • 3.3.1 Assembly of the Lewisian Complex

    • 3.3.2 Formation of Proterozoic crust


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1 Introduction

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

  • Table of contents

  • 1.1 Setting the scene

  • 1.2 Recognizing ancient mountains

  • 1.3 Orogeny through geological time

    • 1.3.1 Geological time: a brief note

    • 1.3.2 Disentangling the cont
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Acknowledgements

Except for third party materials and otherwise stated (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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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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6.1 Firing-rate hypothesis

Information about stimulus intensity is encoded in two ways: the firing rates of neurons and the number of active neurons.

Intensity is assumed to be encoded by an increase in discharge rate of action potentials within the auditory system. As the stimulus gets more intense, the basilar membrane vibrates at a greater amplitude causing the membrane potential of activated hair cells to be more depolarised and this causes the nerve fibres that synapse onto the hair cells to fire at a greate
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3.5.2 Mechanical force directly opens and closes transduction channels

It is believed that tip links aid in causing ‘channels’ to open and close near the top of the hair cell (Figure 16). Tip links are filamentous connections between two stereocilia. Each tip link is a fine fibre obliquely joining the distal end of one stereocilium to the side of the longest adjacent process. It is thought that each l
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3 Appendix: Some highlights of physics

c. 624 BC Birth of Thales of Miletus: traditionally ‘the first physicist’.
384 BC Birth of Aristotle: author of Physics.
1543 Nicolaus Copernicus' De Revolutionibus Orbium Celestium.
1600 William Gilbert's De Magnete describing the behaviour of
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2.4.1 The second generation of GM crops

Much of the present-day debate about GM plants centres around the existing range of GM crops, most of which have been engineered for herbicide tolerance or insect resistance (covered in unit S250_1 Gene manipulation in plants). One of the implications of this narrow commercial focus is that the benefit that such crops would bring, other than to those multinational companies that produce them, is by no means clear. Weighing up their value on some form of ethical scales might be unlikely
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1.5 Star clusters and stellar evolution

Detailed observations of star clusters suggest that they occur because the stars in them form at about the same time. Moreover, the compositions of the stars are similar. Isolated stars (including isolated binary stars) result from the later partial or complete dispersal of a cluster.

The crucial points for us here are that all the stars in a cluster formed at about the same time, and all have similar compositions.

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Acknowledgements

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All other materials included in this unit are derived from content originated at the Open University.

1. Join the 200,000 studen
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1.3 The aspirin story

As long ago as 400 BC the physician Hippocrates, from the island of Kos (now a popular Greek holiday destination) prescribed a concoction made from willow leaves to help relieve the pain of childbirth. Ever since then (and probably even before) herbal remedies based on the leaves or bark of willow trees have been used for the alleviation of pain and fever. In the 1840s the chemists of the day were able to extract the substance salicin from the bark of willow trees by treating it with boiling
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1.1 Why does it hurt?

The relief or avoidance of pain must be one of the major driving forces behind medical research. In this unit we start the discussion about relief of pain.

When we experience the sensation of pain it is likely that something is happening that the brain needs to know about, so it can direct us to whatever damage-limiting action is needed. We hurt because we have genes that constructed a body able to feel pain.

Without such a mechanism it is likely that life would be much shorter, w
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3.4 Science communication and citizenship: getting involved

This section began with a brief review of the current context for science communication, noting the calls for greater dialogue and consultation between science and society. This is important for a number of reasons, as illustrated by the following simplified examples. It has been argued that we are currently living (in the UK) in an ‘information age’ and that we rely on a ‘knowledge-based economy’ for economic prosperity. To these ends a common argument put forward by Western governme
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