4.7 Jets

You have seen that two kinds of active galaxies - quasars and radio galaxies - are often seen to possess narrow features called jets projecting up to several hundred kiloparsecs from their nuclei. If these are indeed streams of energetic particles flowing from the central engine, how do they fit with the accretion disc model? How could the jets be produced?

The answers to these questions are not fully resolved, but there are some aspects of the model of the central engine which probably
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Veterans History Project Congressional Staff Briefing
Staff of the Veterans History Project make their annual briefing to Congressional staff. Speakers included Betsy Peterson, Bob Patrick, Patrick Burns, Florence Champagne, Lloyd Lenhart and Lisa Taylor. For transcript, captions, and more information, visit http://www.loc.gov/today/cyberlc/feature_wdesc.php?rec=6324
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2.2 Persistent currents lead to constant magnetic flux

An important consequence of the persistent currents that flow in materials with zero resistance is that the magnetic flux that passes through a continuous loop of such a material remains constant. To see how this comes about, consider a ring of metal, enclosing a fixed area A, as shown in Figure 6a. An initial magnetic field B0 is applied perpendicular to the plane of the ring when the temperature is above the critical temperature of the material from which the rin
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The Organ of Corti
Situated in the spiral-shaped cochlea of the inner ear is the organ of Corti. Only one inch long if uncoiled, it bears about twenty-five thousand sound receptor cells with hairlike projections arranged in rows on the basilar membrane. Diagrams show detailed structure of the organ of Corti. Grades 5-12. 1 min.
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Free Hugs Campaign
Free hugs campaign. Good for service-learning classes. (03:40)
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School activities: Evolutionary tree of mammals
This introduction to the evolution of mammals considers Darwin's observations on mammals and how he noticed that species fell into natural groups. This free course, School activities: Evolutionary tree of mammals, looks at evidence from fossils and DNA to examine which mammals are most closely related to whales. First published on Fri, 2
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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
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The Diversity of Countries and Economies across the World
OpenStax College
By the end of this section, you will be able to: Analyze GDP per capita as a measure of the diversity of international standards of living Identify what classifies a […]

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FORMGRIP closed cell aluminium foam
Additions such as SiC are made to molten aluminium or aluminium alloy to modify the melt viscosity and make it suitable for foaming. 1 to 3 wt% of pre-oxidised titanium hydride is then added to the melt which is solidified to form a precursor which can be foamed in a controlled manner by a subsequent heat treatment. The resulting foam has a relatively fine and uniform cell structure.
Author(s): DoITPoMS, University of Cambridge,Dr V Gergely, De

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Coarse open celled aluminium foam produced by infiltration of sintered salt (FOAM-U-LIKE)
FOAM-U-LIKE (Foaming of aluminium metal using lightly interconnected kevelled elements) is a very inexpensive route for the production of coarse open celled foams. It allows a reasonable degree of control over cell size and shape, and results in relatively uniform morphology. The interconnectivity of pores can be controlled by varying the degree of sintering of the precursor. In this case, grains of 1-4mm diameter have been sintered at 600 degrees C for just 10 minutes, giving rise to lightly
Author(s): DoITPoMS, University of Cambridge,J A Curran, Depa

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5 Biomass conversion of solar energy

Photosynthesis in the geological past was responsible for all fossil fuel reserves, but its products are buried about 2000 times more slowly than we use them at present. The total carbon content of all biomass growing on land is estimated to be 5.6 × 1014 kg and, as Figure 10 shows, about one-fifth of this mass is renewed each year. Figure 6 shows how modern plant biomass is distributed across the continents. Clearly, biological conversion of solar energy to a chemical form in com
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Acknowledgements

Grateful acknowledgement is made to the following sources for permission to reproduce material in this course:

Couse image: Mike in Flickr made available under Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence.

The content acknowledg
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Tissue engineering and stem cell technology
A lecture, "Tissue engineering and stem cell technology" given by Prof ZhanFeng Cui, University of Oxford, at the 10th OIBC Spring Symposium, held jointly with the Department for Continuing Education, at St Edward's School, Oxford, on 4 March 2009. Visit http://media.conted.ox.ac.uk/oibc2 to view the full presentation from Prof ZhanFeng Cui, including his slides.
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2.4.2 Saltmarshes

Marsh plant primary production is generally nitrogen limited, so saltmarsh vegetation responds readily to the artificial eutrophication that is now so common in nearshore waters. Eutrophication causes marked changes in plant communities in saltmarshes, just as it does in freshwater aquatic and terrestrial systems. Biomass production increases markedly as levels of eutrophication increase. Increases in the nitrogen content of plants cause dramatic changes in populations of marsh plant consumer
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2.3 A closer look at ethical issues

Science can define what is practicable, what can be done, but it cannot determine which developments it is right to pursue; this is largely an ethical judgement. One sensible approach in making an ethical assessment is to try to weigh up the benefits of a technology against its potential to do harm. Deciding whether GM technology is acceptable, in ethical terms, then involves a judgement about the plausibility and moral weight of competing sets of claims. Individuals may make widely different
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An introduction to software development
Software development is the practice of organising the design and construction of software, the beating heart of much technology fundamental to our personal and professional life. This free introductory course, An introduction to software development, discusses the engineering nature of software development, its challenges and some fundamental practices which have developed to meet them. Software development is a fast-moving discipline and as a software development professional you must be
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Stem Cell Therapies are no More Drugs Than Soufflés are Fast Food
Stemcell discoveries make great news stories, but their actual translation into routine clinical practice is still a major hurdle. Is it reasonable to expect the big pharmaceutical companies to manufacture these living therapies or is the paradigm shift from today’s drugs to ‘living cells as therapies’ overwhelming? Would McDonald’s ever put delicate soufflés on their fast-food menus? This lecture will use examples from current cell and tissue-engineered clinical therapies to illustrate
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1.3 Coal-forming environments today

Coal formation begins with preservation of waterlogged plant remains to produce peat and then slow compression as the peat is buried. About 10 m of peat will compress down to form about 1 m of coal; clearly large amounts of plant debris must be available for preservation. Even so, for a significant thickness of peat to accumulate there must be a balance between the growth of plants and the decay of underlying dead material to form peat (a process known as humification).

Su
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3.3 Business operations: a transformation process

The view that operations is the set of processes responsible for producing the organisation's intended outputs from an appropriate range of resource inputs can be represented very simply, as in Figure 2.

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7.2 The professional engineer

It has been suggested that there are four main criteria that identify a profession:

Custody of a clearly definable and valuable body of knowledge and understanding associated with a long period of training.

A strong unitary organization which ensures that the profession generally speaks with 'one voice'.

Clearly defined and rigorous entry standards, backed up by a requirement to register with the profession
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