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4.3 Structural explanations I: biology

There is a long and uneven tradition of claims that the origins of crime and deviance are biological. In the nineteenth century it was claimed, for example, that brain sizes and skull shapes could explain criminal behaviour. This kind of crude biological determinism has long been discredited, but it gave way to a more subtle and notionally scientific model of genetic determinism.

In the early twentieth century advocates of eugenics claimed to have created the science of improving
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Rochester Castle J940480

ROCHESTER CASTLE, Kent. Aerial reconstruction drawing by Alan Sorrell showing the castle as it might have appeared in the fifteenth century.


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8.1 Balanced argument
Diagrams, mind-maps, tables, graphs, time lines, flow charts, sequence diagrams, decision trees: all can be used to organise thought. This unit will introduce you to a variety of thinking skills. Asking and answering questions is at the heart of high-quality thinking. Questions naturally arise from the desire to know and learn about things and may be the starting point for a journey of understanding.
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8 Analysis, argument and critical thinking
Diagrams, mind-maps, tables, graphs, time lines, flow charts, sequence diagrams, decision trees: all can be used to organise thought. This unit will introduce you to a variety of thinking skills. Asking and answering questions is at the heart of high-quality thinking. Questions naturally arise from the desire to know and learn about things and may be the starting point for a journey of understanding.
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Klartext 2010-11-11
På torsdagen handlade Klartext om den allvarliga krisen för partiet Socialdemokraterna. Professor Ulf Bjereld berättade vad han tror att krisen beror på. Klartext berättade också att den misstänkte våldtäkts-mannen i Örebro har erkänt alla de 7 överfall han är misstänkt för.
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GM, Ireland lift spirits
Summary of business headlines: GM shares rise in successful debut; Factory activity improves in November; Jobless benefits stabilize, but extension vote fails; Wall Street jumps 1.5 percent.
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Die Deutschen in Toulouse

Dans le cadre des interviews allemandes pour la rubrique VO sur Canal U, nous jetons aujourd'hui un regard sur « les Allemands à Toulouse ». Ils sont environ 10.000 à vivre dans l’agglomération toulousaine, la plupart d’entre eux à Pibrac, Blagnac, Colomiers et Tournefeuille.
Lorsqu’on parle de la « présence allemande » à Toulouse, on pense surtout à des entreprises telles que Airbus et EADS. Mais depuis les années 1960 un réseau allemand particulièrement dense et
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Telling the time
This unit helps you to acquire the basic language to find your way around a French town. You will learn how to understand and give directions, ask about accommodation, book a hotel room at the tourist information office and get information about what to see and do in the local area. You will visit some museums in Avignon and buy a film for your camera. This unit also deals with telling the time and making liaisons in speech. By the end of the unit, you will feel more confident understanding and
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Une brochure de détails d'hôtel
This unit helps you to acquire the basic language to find your way around a French town. You will learn how to understand and give directions, ask about accommodation, book a hotel room at the tourist information office and get information about what to see and do in the local area. You will visit some museums in Avignon and buy a film for your camera. This unit also deals with telling the time and making liaisons in speech. By the end of the unit, you will feel more confident understanding and
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Activités 26 et 27
This unit helps you to acquire the basic language to find your way around a French town. You will learn how to understand and give directions, ask about accommodation, book a hotel room at the tourist information office and get information about what to see and do in the local area. You will visit some museums in Avignon and buy a film for your camera. This unit also deals with telling the time and making liaisons in speech. By the end of the unit, you will feel more confident understanding and
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4.5.1 The copolymer equation

It can be shown that the rate of change of monomer concentration in any copolymerization is given by the equation

where [M1] and [M2] are the concentrations of monomers 1 and 2 at any instant and r1 and r2., are reactivity ratios. The reactivity ratios represent the rate at which one type of gr
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4.5 Copolymerization

The alloying of metals to improve their properties is widespread and although many polymers used today are relatively pure (e.g. polystyrene, nylon), an increasing number are mixtures of two or more polymers. As with metals, one reason for doing this is to increase the range of properties. The major practical problem, however, is that homopolymers blend together with difficulty and even where blends are possible, as in some thermoplastics, phase separation can occur readily.

This proble
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4.4 Step growth polymerization

Figure 41
Figure 41 Molecular mass distrib
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4.3.5 Co-ordination polymerization

While most free radical and ionic polymerizations are carried out homogeneously, there is another important class of reaction which is often performed with solid catalysts. These reactions, discovered in the mid-fifties, have revolutionized polymer manufacture by permitting much less severe polymerization conditions than with other systems and by allowing a greater degree of control of polymer structure. Ziegler-Natta catalysts, as they are called, will convert vinyl and diene monomers
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4.3.4 Ionic polymerization

Free radicals are indiscriminate in the compounds they attack, and their non-selective nature in polymerization reactions leads to problems such as chain branching and transfer which affect the structure of the polymer produced. Anionic polymerization overcomes many of these problems.

A typical commercial (but also see Box 8) anionic reaction is the polymerization of styrene using butyllithium, C4H9
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4.3.3 Termination and transfer

There are basically three ways in which chains terminate.

The first is known as coupling and occurs when two free radicals join together. This can be represented by the general equation

Such a mechanism significantly increases molecular mass, if it results in two polymer chains joining. This is the main mechanism which terminates the po
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4.3.2 Propagation

Once a small number of chains have been started, propagation involves successive addition of monomer units to achieve chain growth. At each step the free radical is regenerated as it reacts with the double bond. So in the case of styrene the propagation step is

The free radical can also add on in a different way to produce

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4.3.1 Initiation

Initiation is the mechanism which starts the polymerization process. Vinyl monomers are quite easily polymerized by a variety of activating methods. Styrene, for example, can be converted to solid polymer simply by heating, and ultraviolet light can have exactly the same effect. Usually, however, an activating agent is used. This is an unstable chemical which produces active species that attack the monomer. A good example is benzoyl peroxide which splits up when heated:

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4.3 Chain growth polymerization

Chain growth polymerization is basically a three-stage process, involving initiation of active molecules, their propagation and termination of the active chain ends.

4.2 Chain and step growth

There are two basic ways of making chains. The first is to activate a small number of monomer units M which then successively consume other monomers. This mechanism is known as chain growth and is shown schematically in Figure 36 (a), where a monomer unit is activated by initiator I and forms a chain very quickly. After 75 per cent of the monomer molecules have reacted in this case the degree of polymerization n =
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