3.5.1 Final arousal Emergence can be viewed as the final step in the series of periodic arousals. Instead of re-entering hibernation, the animal maintains the euthermic condition. The cue for maintaining this final arousal is probably not temperature, as some species emerge when T
a is well below zero. It is also difficult to see how arousal could be affected by daylength, since the hibernating animal is usually underground in a cavity or a burrow. Perhaps fat or food stores reach a minimum lev
4.5.4 Phosphorus Phosphorus is recognised as a potential poison for automotive catalysts. The phosphorus level in fuel is generally very low (2×10−5 g l−1), but it is present in higher concentrations in engine oils (1.2 g l−1). Phosphorus derived from the engine oil is believed to react with the alumina support, and also to reduce the activity of the noble metal component. This deactivation is particularly important for Pd, with which phosphorus may form an all
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
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 All materials included in this unit are derived from content originated at the Open University.
3.7 Vitamin C (ascorbic acid) What is the condition that results from vitamin C deficiency and what are its symptoms? You will probably remember from the start of this 3.6 Vitamin B Vitamin B, often called the vitamin B complex, consists of a whole range of different compounds, some of which have similar functions and work together. However, unlike the families of compounds forming vitamins E and K, the B vitamins are sufficiently different from one another to be given individual names or numbers, and to be listed separately on many food labels. Except for vitamin B12, the body can only store limited amounts of B vitamins and because they are all water-soluble 1.5 Some chemistry involving esters Esters are produced by the reaction of a carboxylic acid with an alcohol and result from the formation of a new bond (Reaction 2.1). For example, ethyl butanoate, the major constituent of artificial pineapple flavouring, is made from the reaction of butanoic acid with ethanol.
There is a certain l 1.4.3 Aspirin Compare the structure of aspirin, 2.8, with that of salicylic acid, 2.7. What similarities and differences can you see?
Author(s): 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 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: All other materials included in this unit are derived from content originated at the Open University. 3.3 Producing a scientific paper: science communication as knowledge production and exchange As with all other communication, the production of science communication does not exist in a social vacuum. It involves norms and conventions that science communicators learn as part of the process of becoming a scientist. As you have seen, in taking on this social role scientists are both motivated and constrained in how they communicate, depending on the content and context of the communication. Indeed, part of the remit of this course is to develop your skills as scientists, to ensure that Optional reading If you are interested in considering the role of the internet on science communication practices, you may find the following references are of interest: Wulf (1999), Rzepa (1999) and Rowland (1999a). So far, you have been asked to reflect on your experiences of science communication both as a receiver and as a producer. You have also considered a definition for communication in terms of different types of media, noting how this influences the context for science communication (e.g. ‘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 1.7 Interlude Now that we have covered the features found in igneous, sedimentary and metamorphic rocks, and seen how these features can be explained by the processes that formed the rocks, here is a useful point at which to have a break before continuing with the next section. Before returning, you might like to see for yourself what types of rock you can find in your area. Can you identify their texture, or spot any fossils? Surfaces that haven't been obscured by grime or lichens are by far the best, as 3.1.2. After reading this article: The chapter by Teesson et al. (2002) will have presented you with a clearly written initial orientation to addiction. The article introduced addiction at several different levels of explanation in what the authors term a ‘biopsy chosocial model’ (p. 47). Such an integrated model is at the heart of the app 3.1.1 Before reading this article: Take some time to think about what ‘addiction’ means to you – how chemical and non-chemical substances can be abused and how they can lead to dependent behaviour that can affect individuals and the society in which they live. Write down your ideas. This short exercise may be useful to establish 1.2.3 The physiological and behavioural levels Anticipation of winter If organisms are to survive winter, they must be well prepared for cold weather and sometimes for reduced supply of food. Physiological changes such as shedding leaves and building up fat reserves, and behaviours such as hoarding food, must be completed before winter begins. In order to be prepared, organisms need to anticipate the onset of winter, which is done in two ways, each of which has its own associated physiological mechanisms. First, they could re 1.2 Response to winter: understanding at different levels Winter in a temperate region poses a number of environmental problems for organisms. Most obviously, average temperatures are lower than at other times of year and there are frequent frosts. Frost is highly significant for living organisms because water forms such a large proportion of their body tissues; for the great majority of organisms, freezing of their tissues leads to death. Secondly, because, as shown in Table 1.1, many adult organisms die, go into hiding or migrate in winter, many o 1.8 Primordial nucleosynthesis Time: 100 s to 1000 s Temperature: 109 K to 3 × 108 K Energy: 300 keV to 100 keV As the temperature continued to decrease, protons and neutrons were able to combine to make light nuclei. This marked the beginning of the period referred to as the era of primordial nucleosynthesis (which literally means ‘making nuclei’). The first such reaction to become energetically favoured was that of a single proton and neutron comb 1.6 The quark-lepton era (contd) The next stage of the story is to look at how and when the original mixture of all types of quark and lepton that were present when the Universe was 10−11 s old, gave rise to the Universe today, which seems to be dominated by protons, neutrons and electrons.
Activity 14
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Question 8
