6.1 Basic isotropy As we have said, the photons in the 3 K background have been practically free from interaction with anything since about 4 × 105 years after the instant of the big bang. The present angular distribution of the microwave radiation – the way in which it is spread across the sky – is therefore almost the same as it was then. The spectrum we find today depends on the temperatures at that time – for the intensity of the radiation in a particular region of the early Unive
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12.7 Summary of Section 12 For precise localisation of a sound source, binaural cues are required. Two types of binaural cue are used to localise non-continuous sounds in the horizontal plane: interaural time differences, which are most efficient for low-frequency sounds (20–1500 Hz) and interaural intensity cues, which are important for high-frequency sounds (1500–20 000 Hz). The frequency responses in the superior olive reflect these differences. The medial superior olive includes neurons that are responsiv
11.3 Frequency selectivity In preceding sections we examined two ways in which the auditory system may code frequency information: the place theory and phase locking. In this section we will look at the psychophysical evidence for place coding on the basilar membrane by examining the ability of the auditory system to resolve the components of sinusoidal waves in a complex sound – a phenomenon known as frequency selectivity. The perception of a sound depends not only on its own frequency and intensity but also o
5.4 Inspiratory drive The supply of oxygen to tissues such as the heart, liver and WAT is, under euthermic conditions, invariably linked to and dependent upon local blood flow and pulmonary function. However, as we have already seen, under conditions in which blood flow is reduced to a trickle, the control of energy supply switches to local adaptations in the capillaries and tissue cells, including the oxygen affinity of erythrocyte haemoglobin, the supply and metabolism of respiratory fuels and the rate of protei
3.2 Small babies Development continues in the womb until birth, which, in humans, is about 38 weeks after conception. (The often quoted duration of pregnancy of 40 weeks is based on pregnancy beginning on the first day of the last menstrual period.) The duration of the period of development before birth, called gestation, is highly variable. It is not possible to determine its full range in the UK, because medical intervention usually prevents pregnancies going beyond about two weeks after the due date, or te
Learning outcomes After studying this Unit you should know: that certain minerals are required in the body and that some minerals form essential structural components of tissues; that sodium, potassium, calcium and chloride ions are important in maintaining the correct composition of cells and of the tissue fluids around them (homeostasis); that some minerals are essential components of important molecules such as hormones and enzymes; that the correct
1.7.1 Enzymes: nature's catalysts It will probably come as no surprise to you that chemical reactions, including the conversion of arachidonic acid into prostaglandin, do not occur instantaneously and the rate at which they take place can be very variable. Some reactions are over in a flash, such as the burning of gunpowder, and others take months, such as rust formation on a car. All chemical reactions can be speeded up by increasing the temperature of the reactants. In the laboratory one often ‘cooks’ reaction mixtures
2.1 The heart of spectroscopy: dispersing light Telescopes may simply be used to collect the light from an astronomical object in order to measure its position, brightness or spatial distribution. However, it is often far more instructive to examine the spectrum of light from an object such as a star or galaxy, namely the distribution of light intensity as a function of wavelength. The spectrum of a light source may be revealed in several ways, all of which involve making light of different wavelengths travel in different dire
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
10 ‘Science for all?’ A look at some contexts The following statement is from the science National Curriculum in England published in 2000. Science stimulates and excites pupils’ curiosity about phenomena and events in the world around them. It also satisfies this curiosity with knowledge. Because science links direct practical experience with ideas, it can engage learners at many levels. Scientific meth 4 Key players in law enforcement If a law is broken, who has the responsibility for ensuring that the individual or company who has broken the law is ‘brought to justice’? 1.1 ‘Company law’ Before embarking on this unit, it is important to take some time to think about the implications of its title: Company law in context. In particular, what constitutes ‘company law’, and what is the context in which we are thinking about it? At this point, you might like to pause for a moment and contemplate what this phrase means to you. In particular, what do you understand by the concept of a ‘company’? At first, this may seem like a ludicrously straightforward question. 3.1 Have I done the right calculation? Once you have done a calculation, with or without the aid of a calculator, it is important that you pause for a moment to check your calculation. You need to ask yourself some questions. Have I done the right calculation in the right order? Have I given due consideration to units of measurement? Is my answer reasonable? Did I make a rough estimate to act as a check? Your calculation wil 2.7 Powers and roots There are several symbols for powers and roots: for instance, 24 means ‘2 to the power 4’. An alternative to 24 is 2 4.8 General equation of a conic You have already met the parabola, ellipse and hyperbola. So far, you have considered the equation of a conic only when it is in standard form; that is, when the centre of the conic (if it has a centre) is at the origin, and the axes of the conic are parallel to the x- and y-axes. However, most of the conics that arise in calculations are not in standard form. We have seen that any circle can be described by an equation of the form 4.5.1 Surfaces with holes Using this result, we can obtain the Euler characteristic of a surface with any number of holes by successively inserting the holes one at a time. For example, since a closed disc has Euler characteristic 1, it follows that a closed disc with 1 hole has Euler characteristic 0, a disc with 2 holes has Euler characteristic −1, and so on. Using the Straighten and Crop Tools 2012 Valpo Christmas with Dining Services & Facilities Management One Minute Romanian - flyer
The importance of science
Activity 5: Who enforces the law?
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