Pages 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 9001 result(s) returned

How Far Can a Shirt See: The Birth of a Revolution in Fibers and Fabrics

Fibers and fabrics are among the earliest forms of human expression; these materials shield us from the environment and play an important role in defining who we are. Surprisingly, in sharp contrast to other areas of our existence, fibers have remained practically unchanged for thousands of years.

Can fibers become highly functional objects similar to computers and smartphones? Can they see, hear, sense, and communicate? Our research focuses on extending the f
Author(s): No creator set

License information
Related content

Acknowledgements

The content acknowledged below is Proprietary (see terms and conditions). This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence

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

Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

5 Summary

  1. Eutrophication is a process in which an ecosystem accumulates mineral nutrients. It can occur naturally, but is usually associated with human activity that releases nutrients into the environment.

  2. Anthropogenic eutrophication has caused a widespread loss of biodiversity in many systems. Recent attempts to reverse the process are proving difficult and expensive.

  3. Symptoms of eutrophication are most readily seen in aquatic sys
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

4.4 Reducing nutrient availability

Once nutrients are in an ecosystem, it is usually much harder and more expensive to remove them than tackle the eutrophication at source. The main methods available are:

  • precipitation (e.g. treatment with a solution of aluminium or ferrous salt to precipitate phosphates);

  • removal of nutrient-enriched sediments, for example by mud pumping; and

  • removal of biomass (e.g. harvesting of common reed) and using it for thatchi
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

2.4.1 Estuarine species

Nutrient runoff from the land is a major source of nutrients in estuarine habitats. Shallow-water estuaries are some of the most nutrient-rich ecosystems on Earth, due to coastal development and the effects of urbanization on nutrient runoff. Figure 2.19 shows some typical nitrogen pathways. Nitrogen loadings in rainfall are typically assimilated by plants or denitrified, but septic tanks tend to add nitrogen below the reach of plant roots, and if situated near the coast or rivers can lead to
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

1.1 Origin of the term ‘eutrophication’

The levels of nutrients present determine the trophic state of a water body, where trophic means ‘feeding’.

SAQ 1

Give another example of the adjective trophic be
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

6.1 Introduction

The biological functions of both DNA and RNA are dependent on complex, and sometimes transient, three-dimensional nucleoprotein structures. It is in such structures that the enzymatic manipulation of DNA in the essential biological processes such as DNA replication, transcription and recombination occur, and it is important to understand the interactions that drive these processes. Whether it is the activity of enzymes associated with DNA, such as DNA topoisomerases, or the packaging of DNA o
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

References

Bindon, J. R. and Baker, P. T. (1997) Bergmann's rule and the thrifty genotype. American Journal of Physical Anthropology, 104, 201–210.
Blundell, J. E., Stubbs, R. J., Hughes, D. A., Whybrow, S. and King, N. A. (2003) Cross talk between physical activity and appetite control: does physical activity stimulate appetite? Proceedings of the Nutrition Society, 62, 651–661.

Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

1.7 Summary of Section 1.2

  1. There is a need for a certain level of daily energy intake to allow the body to maintain its BMR, and to carry out work.

  2. Adenosine triphosphate (ATP) is the chemical currency of energy used by the body and is produced from the metabolism of food.

  3. The body mass index or BMI indicates whether an adult is a healthy weight for their height.

  4. Inadequate nutrition is a huge problem globally. Anorexia nervosa is one examp
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

1.6 Obesity treatment

Obesity treatment is only successful if weight is reduced and maintained to within a desired range. There are three approaches to obesity treatment: changing behaviour and diet is the most common approach although drugs and surgery can be used in some severe cases of obesity.

Behaviour and diet: it is important to be realistic about an obese patient's target weight as many patients have over-ambitious targets that they are unlikely to achieve. A severely obese patient probably ca
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

Learning outcomes

After studying this unit you should be able to:

  • list the six key nutrient groups and explain their role in a healthy diet;

  • understand and calculate body mass index (BMI), and use such calculations to predict desirable weight ranges for individuals;

  • explain the importance of a balanced diet in terms of energy intake;

  • explain how genetic and environmental variables may interact to produce variability in human body weight and adiposity b
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

4.1 Natural stores of carbon

The major natural stores of carbon (called ‘reservoirs’) are shown below in Figure 1.9.

7.3 The central engine

  • An object that fluctuates in brightness on a timescale Δt can have a radius no greater than RcΔt.

  • The point-like nature of AGNs and their rapid variability imply that the emitting region is smaller than the size of the Solar System.

  • The central engine of a typical AGN is believed to contain a supermassive black hole of mass ∼108M and Schwarzschild radius
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

7.2 Types of active galaxy

  • All active galaxies have a compact, energetic nucleus – an AGN.

  • Seyfert galaxies are spiral galaxies with bright, point-like nuclei which vary in brightness. They show excesses at far infrared and other wavelengths, and have strong, broad emission lines.

  • Quasars resemble very distant Seyfert galaxies with very luminous nuclei. They are variable. About 10% are strong radio sources thought to be powered by jets of material
    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

Radio-quiet AGNs

There has been a great deal of debate about whether there really are two different types of Seyfert or whether they can both be accounted for by the same model.

For example, suppose that you look at the model AGN in Figure 36a from a direction not too far from the rotation axis of the torus. You will see
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

4.1 Introduction: the active galactic nuclei (AGN)

From Section 3 you will have discovered that one thing all active galaxies have in common is a compact nucleus, the AGN, which is the source of their activity. In this section you will study the two properties of AGNs that make them so intriguing – their small size and high luminosity – and learn about the energy sou
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

6.1 Introduction

Reading 5 ends with a call for a move towards a more ‘deliberative democracy’ in which public engagement takes place in parallel with the development of new technologies, so that opportunities are provided for ongoing dialogue and influence between the two. To help to achieve this, the authors argue, ‘… now is the right time to start experi
Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

Learning outcomes

By the end of this unit you should:

  • have a greater awareness of science-based issues of public importance;

  • have greater insight into the phrase ‘the public understanding of science’

  • have a raised awareness of the ways in which the public can be consulted in relation to science policy issues;

  • be able to think of ways in which the public might in future become more engaged in decision-making about science that has social impact.


    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

5.2 Cryogenic liquids and ionising radiation safety

5.2.1 Cryogenic liquids

There are a number of hazards associated with cryogenic liquids, the main one being that when accidentally released the liquid expands hugely to form a gas (600 times in the case of nitrogen). The formation of such a large volume of gas can lead to asphyxiation in confined areas.

The other main hazard is cold burns (frostbite).

    Author(s): The Open University

    License information
    Related content

    Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

Acknowledgements

The content acknowledged below is Proprietary (see terms and conditions). This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence

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

Author(s): The Open University

License information
Related content

Except for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

Pages 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451