Images Dated 9th May 2003

Col. MRI scan of a brain with multiple sclerosis

Multiple sclerosis. Coloured magnetic resonance image (MRI) scan of an axial section through the brain of a patient with multiple sclerosis (MS). The cerebral hemispheres are seen here. Grey matter is on the cerebral outer edges; white matter is found deeper in the brain. Lesions caused by MS are seen at left and lower left (red/yellow). They are due to destruction of myelin sheaths around nerve fibres. Progressive destruction of myelin in the brain and spinal cord produces such symptoms as unsteady gait, tremor, speech defects, paralysis and incontinence. MS is thought to be an autoimmune disorder

© Science Photo Library

Artwork showing a mechanism for gamma-ray bursts

Gamma-ray burst. Artwork showing a possible mechanism for gamma-ray bursts, extremely powerful bursts of gamma radiation that flare and then disappear in a matter of seconds. The small body seen at centre represents a neutron star or a black hole - end product of the supernova explosion which marks the death of a massive star. In the explosion a tremendous amount of energy is channelled into two narrow beams. According to this theory, the gamma-ray burst is seen only when one of the two beams points towards the Earth. Other models for gamma-ray bursts involve the collision between two neutron stars or two black holes

© NASA/SCIENCE PHOTO LIBRARY

The Hoover Dam, Colorado River

Hydroelectric dam. The dam of a hydroelectric power station. Electricity generated by hydro- electric stations is relatively cheap and involves little impact on the environment. The formation of the holding lake behind the dam, however, may have an impact on the local ecosystem. In addition to the cost benefit, hydroelectric power may be generated at a moment's notice, simply requiring that flood gates be raised. As such, hydroelectric power stations are commonly used during peak demand times. This is Hoover Dam on the Colorado River. It is the highest concrete dam in the USA and impounds Lake Meade. Its hydroelectric power capacity is 1300 megawatts

© David Parker/Science Photo Library