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
2.3 From ear to phoneme: the phonological problem The phonological problem is the problem of knowing which units (words, calls) are being uttered. The speech signal is a pattern of sound, and sound consists of patterns of minute vibrations in the air. Sounds vary in their frequency distribution. The sound of a flute playing is relatively harmonic. This means that the energy of the sound is concentrated at certain frequencies of vibration. A plot of the energy of a sound against the frequency at which that energy occurs is called a spe
11.3.1 A masking experiment The procedure for a masking experiment is shown in Figure 38. First, the threshold for hearing is determined across a range of frequencies (Figure 38a). Then, a masking stimulus is presente
7.2.1 The ‘what’ pathway The main nucleus involved in the ‘what’ pathway is the cochlear nucleus which has three main components, each of which is tonotopically organised; cells with progressively higher characteristic frequencies are arrayed in an orderly progression along one axis (Figure 29). The cochlear nuclei contain neurons of several types, each of which
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
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. 1.2 The main classes of stars The main classes of stars are shown in Figure 5. The main sequence is ‘main’ in the sense that about 90% of stars fall into this class, and ‘sequence’ in the sense that it is a long, thin region that trails across the H–R diagram, covering a very wide range of temperatures and luminosities. The Sun i 2.3 Behavioural strategies of evaders Small animals, classified as evaders, include desert amphibians and reptiles, and also mammals, rodents and insectivores. The term ‘evaders’ refers to the animals’ behaviour, which helps to prevent overheating of the body on hot sunny days, and avoids the need for cooling by evaporative water loss, which is not feasible for small animals living in an arid habitat. Evaders make use of microenvironments such as shady rock crevices, underground burrows and shade cast by plants, for behavio 1 Hibernation and torpor: An introduction
This unit examines hibernation, a special form of adaptation that animals can make to the ecological demands of remaining in a chosen habitat in winter. Hibernation is a state which enables energy-efficient survival when ambient temperatures are so low that foraging or simply maintaining normal core body temperature and basal metabolic rate are either energetically too costly or impossible. Polar endotherms can maintain a high T
b even when living actively at sub-zero 4.5.5 Sulfur Deactivation The presence of sulfur in the exhaust gas mixture causes a reduction in the activity of the three-way catalyst, particularly for the water-gas shift and steam reforming reactions – processes that are important mechanisms for the removal of CO and hydrocarbons under fuel-rich conditions. Sulfur also decreases the efficiency of NOx removal. The deleterious effect of exposure to SO2 on the catalytic activity of a commercial monolithic cata Learning outcomes Having read this unit you should be able to: discuss how the gas mixture expelled from the engine, and the conversion performance of the three-way catalytic converter, depend on the air/fuel (A/F) ratio; list the chemical reactions whereby the three-way catalyst removes carbon monoxide (CO), hydrocarbons and oxides of nitrogen (NOx) from petrol vehicle exhausts; interpret the results of experimental studies (involving activity test 9.2 Antisocial behaviour disease The psychological arena is hugely complex because there are additional issues of responsibility and treatment. Briefly, society takes a more lenient attitude towards the behaviour of someone who is ill (diseased) compared to someone who is well. The diseased person is not fully responsible for their actions (‘They can't help it’). Therefore any individual with antisocial (aggressive) behaviour who is diagnosed as having a disease is largely absolved of blame. Having a disease, means, at l 8.1 Genes and behaviour In the preceding sections many different proteins have been mentioned. These proteins are the receptors, signals, channels, enzymes, transporters, structural components and transcription factors that enable the nervous system to grow and function. Other proteins (e.g. the actin in muscles) are involved in making limbs move and sense organs function. Any and all behaviour is dependent on these proteins. And as each of these myriad proteins is the product of a gene, it follows that any and all 7.1 Neuron proliferation There is a huge proliferation of neurons in early life. Even whilst that proliferation continues, some cells, e.g. neuroblasts, stop being able to divide. At some later stage the proliferation itself virtually ceases. It follows that cells switch from being able to divide, to being unable to divide, and that they switch at the appropriate time: the process of cell proliferation is controlled. The details of the control of proliferation are not yet understood and are not considered here. But o 5.1 The nervous system Development has so far mostly been assessed in terms of the gross performance, the overt behaviour, of the organism. Relationships have been established between certain environmental events and certain behaviours. In the next three sections, Sections 5 to 7, there is a major shift in emphasis, from considering behaviour to considering the structure of the nervous system. Essentially, this is doing no more than stepping down a level to look at what is going on inside the organism, in particula 1.1 Introduction This unit addresses the question of how the differences between individuals, especially in behaviour, arise during development. Development, the transformation of the single cell, the zygote, into an adult organism with billions of cells, numerous organs and an intricate, functioning nervous system, is one of the most remarkable feats of living systems. The process begins when an egg cell, or ovum, is fertilised by a sperm, or spermatozoon. The resultant single cell, the zygote, divides to pr 4.2 Major minerals The major mineral elements, defined here as those where 25 g or more is present in the body, are listed in Table 4. 1.1.1 Inheritance of characters Imagine you have found some old family photograph albums which span many generations. What are the distinctive family features, or characters, that demonstrate the relatedness of individuals? In other words, what characters do they have in common? For example, they might have brown eyes, a white forelock in their hair, ears that are closely attached to the head, that is, without lobes. But you will also notice the striking differences between related individuals. For example, they may differ Acknowledgements The content acknowledged below is Proprietary (see terms and conditions) and is used under licence. Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: Figure 1 Science Photo Library; Figure 8a This photograph has been provided by Railway Technical Research Institute in Japan; Figure 22 Proceedings of the Royal Society A248 464. The Royal Society; F Optional reading If you are interested in investigating the issues raised by the House of Lords Select Committee report in more detail, you will find a copy of the full report on the web at: http://www.publications.parliament.uk/pa/ld199900/ldselect/ldsctech/38/3801.htm The following references also discuss issues related to key findings from this report: Irwin and Michael (2003, particularly pp. 19–40), Miller (2001) and Gibbons (1999). This overall picture places demands on you as a co
Table 4 The major mineral elements required by the body. The recommended intak
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