1.2 Summary of Section 1.1 A balanced diet consists of six main nutrient groups; proteins, carbohydrates, lipids, vitamins, minerals and water. Dietary reference values (DRVs) comprise a range and an estimated average of recommended daily intake levels for nutrients and energy for males and females at different stages of their life.
6.1 Concentrating energy As far as human needs are concerned, there is a marked difference between ‘dilute’ and ‘concentrated’ energy. Water vapour in the atmosphere, for example, has considerable
6.1 Introduction The active galaxy model is very attractive. Indeed, it is so attractive that it is easy to overlook the many problems that remain. We will now consider some of the outstanding questions about the origin and evolution of active galaxies, focusing on two questions: do supermassive black holes really exist? And where are active galaxies now?
7 Final thoughts We deliberately chose a wide range of different initiatives to explore, to reflect the broad range of initiatives underway. And yet, as you have seen, there are common threads that run though all our examples, such as the representativeness of ‘public’ opinion and how outcomes input into policy making. A key issue that Reading 5 highlighted was
4.2 The science behind Golden Rice Modifying crops to produce the Bt toxin (Section 3.1) was, in some ways, relatively simple. The toxin is a single protein and can therefore be produced as a result of the insertion of a single gene into the plant's genome. Similarly, introducing herbicide tolerance (Section 3.2) typically involves modifying the action of a single enzyme, and therefore modification again involves the insertion of a single gene. β-carotene is not a protein. It is a hydrocarbon, i.e. a compound containing
2.3 From infected cells to transgenic plants Unlike the ‘natural’ infection process, where only the cells at the site of the crown gall are affected by the inserted T-DNA, scientists wanted to introduce new genes into all the cells of the plant. Fortunately, most plant cells are totipotent, which means that any cell from any part of the plant is capable of dividing into cells that can form any or all of the plant's tissues. This means that, using appropriate growth hormones and other tissue culture techniques, a single infect
2 The future of hydropower Hydroelectric power generators produce no emissions — except indirectly during their construction — and the water used is renewable. Generation can be started and stopped almost instantaneously, simply by opening or closing the inlets to the turbines. The generating technology is well-established. Other positive aspects of hydroelectric schemes are river regulation, and provision of irrigation and drinking water supplies, fisheries and recreational facilities. These advantages have
2.2 Summary of iron chemistry Try to summarise the main points of iron chemistry for yourself, and then compare it with the list below. From a bioinorganic point of view, we can conclude that despite the high natural abundance of iron, it is in scarce supply in water. The more stable form of iron in oxygenated water is iron(III). The low concentration of Fe3+ in water is because of the extreme insolubility of Fe(OH)3.
4 The future of direct solar energy use The immense global energy flux from the Sun makes it the prime candidate for future sustainable energy production. Both solar thermal energy and solar PV conversion involve technologies that can be deployed on personal through community to regional scales, using both simple and advanced technologies. You have probably seen solar PV panels that power automatic roadside weather stations and other low-drain communications systems. The panels require low maintenance and usually charge batteries t
1.5 The physics and chemistry of coal formation Coal is a type of sediment made up mainly of lithified plant remains. But how does spongy, rotting plant debris become a hard seam of coal? As discussed earlier, plant material growing in mires dies, and then rots under anoxic conditions to form peat (by the process of humification). With time, the mire becomes covered with layers of sediment, the weight of which squeezes water and gas out of the pore spaces and compacts the vegetation. As subsidence allows deposition of further mireâ€
2.2 Traffic in the endoplasmic reticulum and the Golgi network The ER extends as a network of membranous tubes and sheets throughout the cytoplasm and is the site of synthesis of proteins ultimately destined for the Golgi apparatus, endosomes, lysosomes, the plasma membrane, secretory vesicles and beyond. In animal cells, the Golgi apparatus is usually a single structure located near the nucleus of the cell, consisting of between four and ten flattened cisternae, which are designated the cis, medial or trans Golgi network, depending on thei
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
5 The epidemiology of vCJD In 1990, six years before the probable link between BSE and vCJD was established, the CJD Surveillance Unit was set up in Edinburgh. All suspected TSEs in humans have to be referred to this Unit, which maintains the UK's official data on all forms of these diseases. Figure 10 is a plot of the number of cases refe
5.3 Heat production There are two graphs in this section, Figure 2 and Author(s): 1.1 The description of motion The concepts that have been developed to allow the description of motion – concepts such as speed, velocity and acceleration – are now so much a part of everyday language that we rarely think about them. Just consider the number of times each day you have to describe some aspect of motion or understand an instruction about motion; obey a speed limit or work out a journey time. We may take the description of motion for granted, but the concepts involved are so fundamen 2.3.1 The general view
Figure 16 shows a Voyager 2 image of a large region of Europa. Examine this image carefully, in order to answer Question 4. 6.2 Opting out This last section of the unit contains, I think, some of the most challenging science that you have met so far. Take it slowly, translating all the abbreviations in your head as you come to them (read BAT as ‘brown adipose tissue’, for example) and looking carefully at the graph in Author(s): 4.2 Evidence for a big bang Having interpreted the redshift as indicating a recessional speed proportional to distance, one may extrapolate into the future to predict how the positions of the galaxies will evolve with time. One can also run the sequence backwards, so to speak, to discuss what their positions were in the past. Clearly, at former times the galaxies were closer to each other. But not only that. Because of the proportional relationship between speed and distance (Equation 6), at a certain time in the 1.6.3 Litres and kilograms The two physical units of measurement that you will probably come across most often in your workplace concern volumes of liquids and weight measurements. It's important to get a feeling for what various factors of ten look like, so that you can spot when there seems to be a mistake in a value that you've calculated or have been given by someone else. The litre is the main unit of measurement for liquid volumes (written as liter in America), but what does a litre of fluid look like? What 12.5 Localisation of sound in the vertical plane Much of our ability to localise sound in the vertical plane is due to the shape of the outer ear, in particular the pinna. The pinnae provide a monaural cue to localisation. The bumps and ridges on the pinnae produce reflections, and delays between the direct path and the reflected path make vertical localisation possible. Vertical localisation is seriously impaired if the convolutions of the pinnae are covered.
