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8.7 Luminosity functions

Samples of galaxies can be biased due to the flux limit of the sample that is observed. This is the so called Malmquist bias.

Activity 9: Radio-quiet quasars

0 hours 20 minutes

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7.3 Polarization of electromagnetic radiation

So far we have described electromagnetic radiation in terms of its wavelength, frequency and speed. It has another, sometimes important, property: polarization. Figure 10 shows the electric and magnetic field in a plane-polarized electromagnetic wave. In any electromagnetic radiation, the electric an
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1.3.3 A breeding experiment: stage two

We now turn to the second stage of the breeding experiment, but this time we will follow the phenotypes and genotypes simultaneously. The purple (Gg) grains of the F1 generation are planted and when these have developed into mature F1 plants they produce male and female flowers. These F1 plants are crossed with each other, as shown in Figure 8. The fertilised ovules develop into grains borne on cobs, and these grains are the beginning of the second f
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References

National Audit Office (2001) Tackling obesity in England [online] Available from: www.nao.org.uk/publications/nao_reports/00-01/0001220.pdf (Accessed 20 April 2009).
Watkins, P. J.(2003) Diabetes and its Management, Oxford, Blackwell Publishing.
World Health Organization (1999) Definition, diagnosis and classification of diabetes mellitus and its complications
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5.2 Type 1 diabetes

Type 1 diabetes was previously called insulin-dependent diabetes. This is because in people with Type 1 diabetes their pancreas fails to produce insulin and they are dependent on taking insulin for their treatment. It would be useful to look back at Figure 5 to remind yourself of the actions of insulin. As we have already discuss
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3.8 Glucagon

Glucagon is another hormone produced by the pancreas.

Question: Can you recall which cells make glucagon?

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14 Unit questions and answers

Note: Question 1 is included in Section 3.

Question 2


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8 Managing the BSE/vCJD episode up to May 1990

BSE was formally recognised as a new disease in November 1986. However, this information was kept under ‘embargo’ at first while an initial epidemiological study – involving the collection of data from 200 herds – was started. The Ministry of Agriculture, Fisheries and Food (MAFF) was officially informed about BSE by the Chief Veterinary Officer (CVO) in June 1987. By December 1987, those responsible for analysing the data from the initial epidemiological study had concluded that the
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5.3 Heat production

Introduction

Mammals come in a bewildering variety of shapes and sizes and yet all of the 4700 or so species have some characteristics in common. Indeed, it's the existence of these common features that justifies the inclusion of all such diverse types within the single taxonomic group (or class) called the Mammalia.

This is the first in a series of units about studying mammals. To get the most from these units, you will need access to a copy of The Life of Mammals (2002) by David Attenboroug
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1.4.6 The signed area under a constant velocity–time graph

There is a simple feature of uniform velocity–time graphs that will be particularly useful to know about when we come to consider non-uniform motion in the next section. It concerns the relationship between the velocity–time graph and the change in position over a given time interval. Consider the following problem. A vehicle travels at a velocity vx = 12 m s−1 for 4 s. By how much does its position change over that interval?

The answer, fro
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1.3.5 A note on graph drawing

There will be many occasions throughout your study of physics when you will need to draw graphs. This subsection gives some important guidelines for this activity.

  1. Decide which is the independent variable and which the dependent variable. Plot the independent variable along the horizontal axis and the dependent variable along the vertical axis. This is purely a convention but is why, for instance, we usually plot the time
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1 2 From drop-towers to Oblivion – some applications of linear motion

We have all experienced that momentary feeling of lightness when an elevator begins its downward motion. It is almost as if our weight had suddenly been reduced or, conceivably, that the pull of the Earth's gravity had decreased for a moment. But imagine what it would be like if the lift cable had suddenly snapped and the lift, with you in it, had plummeted downward. Apart from stark terror, what else do you think you would experience during your fall? What would the physical experience
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Learning outcomes

After studying this unit you should be able to:

  • explain the meaning of all the newly defined (emboldened) terms introduced in this unit;

  • draw, analyse and interpret position–time, displacement–time, velocity–time and acceleration–time graphs. Where appropriate, you should also be able to relate those graphs one to another and to the functions or equations that describe them, particularly in the case of straight-line graphs;

  • find the derivati
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Acknowledgements

Video Materials

This extract is taken from S809 © 2005 The Open University.

All written material contained within this unit originated at the Open University.


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2.2.4 Film cassette and grid

As the X-rays pass through the patient some of them will be scattered and will therefore not follow the expected line through the patient. If these reach the detector they will blur the image. Some of the scattered radiation can be removed by a grid, usually oscillating, placed between the patient and the detector.

Analogue imaging systems use either film alone (rarely) or a combination of a film and fluorescent material (phosphor). The phosphor fluoresces and produces visible light whi
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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

The following appears in Introduction to Astrobiology (Planetary Science Book 2: ISBN 0-521-54621-4) which is published in ass
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2.3 Examining Europa's surface

It is all very well speculating about conditions in an ocean below Europa's ice, but what evidence is there that it actually exists? After all, tidal heating might not result in ice melting on a global scale, and current geophysical models of Europa's internal structure (e.g. Figure 14 in Section 1.5) cannot te
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Acknowledgements

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

T
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2 Who are the anthropoids?

As you know, the suborder Anthropoidea includes monkeys, apes and humans. You will be aware from reading LoM that taxonomists group monkeys according to the shape of their nose: Old World monkeys are catarrhines and New World monkeys are platyrrhines [p. 264]. In fact, apes and humans share many traits with Old World monkeys, so they too belong to the catarrhrines, whereas the New World monkeys are sufficiently distinct to be contained within a grouping of their own. DA also mentions other an
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