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Active galaxies

Figure 10 shows the spectral energy distribution of an active galaxy.

Figure 10
Author(s): The Open University

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7.4 Emergency procedures

7.4.1 What do you do if a chemical catches on fire?

It is important to know which fire extinguisher is appropriate for the chemical you are using. The four commonly used extinguishers are carbon dioxide, dry powder, foam, and water.

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5.2 Cryogenic liquids and ionising radiation safety

5.2.1 Cryogenic liquids

There are a number of hazards associated with cryogenic liquids, the main one being that when accidentally released the liquid expands hugely to form a gas (600 times in the case of nitrogen). The formation of such a large volume of gas can lead to asphyxiation in confined areas.

The other main hazard is cold burns (frostbite).

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3.1 How do organisms take up iron?

Nearly all organisms are able to take up iron. However, only a handful of organisms have had their iron-uptake chemistry studied. The organism that has received most attention (other than human) is a single-cell, prokaryotic bacterium (found in the human large intestine and elsewhere), called Escherichia coli (abbreviated to E.coli), a high-resolution image of which is shown in Author(s): The Open University

3.4.2 Compaction and adhesion

Around the time of the 8- to 16-cell division, the conceptus undergoes a morphological (shape) change, called compaction, in which the cells fatten on each other, and the outlines of individual cells become hard to distinguish. This stage, sometimes referred to as a morula, from the Greek word for mulberry, is shown in Figure 17i. At this stage it is hard to see individual cells; in fact, unless the cells are separated by various laboratory treatments, it is not possible to see the two
Author(s): The Open University

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References

Huse, M. and Kuriyan, J. (2002) The conformational plasticity of protein kinases, Cell, 109, pp. 275–282.
Lipscomb, W. N., Reeke, G. N. Jr, Hartsuck, J. A., Quiocho, F. A. and Bethge, P. H. (1970) The structure of carboxypeptidase A. 8. Atomic interpretation at 0.2 nm resolution, a new study of the complex of glycyl-L-tyrosine with CPA, and mechanistic deductio
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7.3.1 Library-based methods for demonstrating an interaction between proteins

As well as the biochemical approaches to studying protein–protein interactions, there is a variety of qualitative methods for screening ‘libraries’ of cloned genes or gene fragments whose protein products might interact with a protein of interest. Such an approach has the advantage that the genes that encode those proteins that bind are available immediately for expression, facilitating subsequent analysis of the protein.

The two-hybrid system uses transcriptional activity
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7.3.1 Physical methods for demonstrating an interaction between proteins

To identify those unknown proteins in a complex mixture that interact with a particular protein of interest, protein affinity chromatography can be used (Figure 49a). This approach uses a ‘bait’ protein attached to a matrix. When this baited matrix material is then exposed to a mixture of proteins, only proteins that interact with the
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7.7 Radiation detection

In astronomy we detect the radiation from large numbers of electrons, rather than being able to distinguish the contributions of individual electrons. The electrons will have a range of velocities and of orientations with respect to the magnetic field, so the synchrotron spectrum we observe will be the sum of lots of individual spectra with varying values of
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Learning outcomes

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

  • recognise the terminology which is used to describe the properties and behaviour of active galactic nuclei (AGN);

  • manipulate numbers, algebraic symbols and mathematical functions in equations.


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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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3.8 Glucagon

Glucagon is another hormone produced by the pancreas.

Question: Can you recall which cells make glucagon?

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10 Managing the BSE/vCJD episode from March 1996

In March 1996, SEAC announced that the CJD Surveillance Unit had identified vCJD as a new human disease, the first death from which occurred in May 1995. SEAC concluded that, although there was no direct evidence of a link, the most likely explanation for vCJD was exposure to BSE before the SBO ban was introduced in 1989. At the time, the strongest evidence for the link was that vCJD was a new TSE in humans (the symptoms of which differed from previously known human TSEs) that had aris
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6 Is prion-like behaviour exceptional or the norm?

At the time of writing (2005), it is widely – but certainly not universally – accepted that TSEs are triggered by prions. Prions consist entirely and exclusively of PrP protein. In particular, they contain no nucleic acid – and hence no genetic information – at all. An animal may either produce its own disease-triggering PrPSc protein (in the case of inherited and probably some sporadic TSEs) or PrPSc protein from elsewhere might start a ‘chain reaction’ in w
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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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2.2.2 Collimator

The dimensions of the emerging X-ray beam can be altered by the collimator. This helps to ensure that only the region of interest is exposed to the X-rays.


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Introduction

Most contemporary evolutionary biologists study evolution experimentally using laboratory organisms such as Drosophila or natural systems in the wild. However, 18th and 19th century evolutionary biologists, including Darwin, emphasised the similarities between natural evolution and artificial ‘ improvement’ of livestock under domestication. They believed that studying domesticated animals and plants could illuminate the mechanisms of natural evolution. Indeed, Chapter 1 of On th
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2.6 End-of-unit questions

Question 1

What is the approximate wavelength range (in metres) of microwaves?

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