Light is emitted from a quantum cascade laser when an electron falls from an excited energy level in a quantum well to a lower level. The quantum wells are defined by alternating layers of semiconductors with different energy gaps. When an appropriate voltage is applied to the device the electron then tunnels from this lower […]
Like ESA’s recent Hipparcos mission, FAME will use the parallax method to determine the stars’ positions: as the telescope and the Earth orbit the sun, the position of the stars will change slightly. The smaller the change, the further the star is from the Earth. FAME will also look in two directions at once to […]
As the highly energetic particles pass through conventional carbon-rich rocks, they would form carbon-60 molecules in their wake. The fact that these geological detectors have been “collecting data” for millions of years, combined with the stability of carbon-60 molecules, could give this geological approach to particle physics a “winning edge” according to Collar. Another bonus […]
Read article: Magnetic resonance sees the heart beat
Ultrasound is commonly used to look at the heart, but it is unsuitable for the 10-20% of the population that have breathing difficulties (emphysema) or who are medically obese. In both techniques, patients are given drugs to speed up their hearts and promote vigorous pumping. In a healthy heart both sides of the heart contract […]
The treaty will only come into effect if the 44 countries that have the capability to develop nuclear weapons ratify it. Although 26 countries, including France and the UK, have ratified the treaty, Russia, China and the US have not. “This decision is a serious blow to the entire system of agreements in the field […]
The Vienna team sent a collimated beam of carbon-60 molecules through a slit made of silicon nitride and detected the interference pattern by ionizing the molecules with a laser and then counting the ions. The slits in the diffraction grating were 50 nanometres wide and the grating had a period of 100 nanometres. The team […]
Prior to Zewail’s work chemists had thought that chemical reactions occurred on the same time scale as molecular vibrations — that is, on the femtosecond scale. In the late 1980s, Zewail developed a technique that could follow the motion of atoms and molecules on these time scales. A strong laser pulse was used to start […]
‘t Hooft and Veltman were both born in the Netherlands. In 1966 Veltman was appointed as professor of physics at the University of Utrecht, and ‘t Hooft became his PhD student in 1969. By 1971 ‘t Hooft had made several important breakthroughs in the theoretical effort to renormalize the electroweak interaction. Then using a computer […]
The material – 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA) – is non-magnetic at very low temperatures. The paramagnetic effect is strong at room temperature, but as the compound is cooled, it becomes diamagnetic below 230 K. However, it is heated again, it does not become paramagnetic until the temperature reaches is 305K. This is an unusually wide hysteresis loop […]
