frankieleon / CC BY 2.0 Large numbers of people with learning disabilities and no record of severe mental illness are being prescribed strong psychotropic drugs, possibly as a means of subduing and controlling uncooperative patients, research shows.
A UCSF-led team has developed a technique to build tiny models of human tissues, called organoids, more precisely than ever before using a process that turns human cells into a biological equivalent of LEGO bricks.
Rising sea temperatures attributed to global climate change could drive many marine creatures away from the equator, but their move towards the poles promises to put them in peril in habitats that are...
A team of scientists has successfully measured particles of light being “squeezed”, in an experiment that had been written off in physics textbooks as impossible to observe.
Squeezing is a strange phenomenon of quantum physics. It creates a very specific form of light which is “low-noise” and is potentially useful in technology designed to pick up faint signals, such as the detection of gravitational waves.
The standard approach to squeezing light involves firing an intense laser beam at a material, usually a non-linear crystal, which produces the desired effect.
For more than 30 years, however, a theory has existed about another possible technique. This involves exciting a single atom with just a tiny amount of light. The theory states that the light scattered by this atom should, similarly, be squeezed.
Unfortunately, although the mathematical basis for this method – known as squeezing of resonance fluorescence – was drawn up in 1981, the experiment to observe it was so difficult that one established quantum physics textbook despairingly concludes: “It seems hopeless to measure it”.
So it has proven – until now. In the journal Nature, a team of physicists report that they have successfully demonstrated the squeezing of individual light particles, or photons, using an artificially constructed atom, known as a semiconductor quantum dot. Thanks to the enhanced optical properties of this system and the technique used to make the measurements, they were able to observe the light as it was scattered, and proved that it had indeed been squeezed.
Professor Mete Atature, from the Cavendish Laboratory, Department of Physics, and a Fellow of St John’s College at the University of Cambridge, led the research. He said: “It’s one of those cases of a fundamental question that theorists came up with, but which, after years of trying, people basically concluded it is impossible to see for real – if it’s there at all.”
“We managed to do it because we now have artificial atoms with optical properties that are superior to natural atoms. That meant we were able to reach the necessary conditions to observe this fundamental property of photons and prove that this odd phenomenon of squeezing really exists at the level of a single photon. It’s a very bizarre effect that goes completely against our senses and expectations about what photons should do.”
The best way to study the subatomic particles that make up the most fundamental building blocks of our universe is, of course, to smash them into each other with as much energy as possible. And now physicists at SLAC National Accelerator Laboratory say they’ve found a better way to do that.
Researchers at SLAC’s Facility for Advanced Accelerator Experimental Tests (FACET) are especially interested in what happens when they crash high-energy beams of electrons into beams of positrons, their antimatter opposites. To answer the next generation of questions about these particles, however, physicists would need particle accelerators six miles long or more, with current accelerator technology.
That’s why FACET researchers developed a way to increase the energy of a particle beam in a shorter distance, so physicists could study electrons and positrons with smaller accelerators. It works like this: when physicists fire a concentrated group of electrons into an ionized gas, or plasma, the electrons create a wake. That wake can help accelerate a second group of electrons, travelling behind the first group, because they get to basically surf on a wave of plasma.
The technique, called plasma wakefield acceleration, works well for electrons, but it’s harder to accelerate positrons this way. Usually, the second group of positrons loses its shape or slows down when its hits the wake, rather than surfing the plasma wave and going faster. Researchers at FACET found a way to fire a single, carefully shaped group of positrons so that the front of the group creates a wake that helps accelerate the tail of the group and focus its shape.
It works well, according to the researchers, who published the results of their experiments in the journal Nature. “In this stable state, about 1 billion positrons gained 5 billion electronvolts of energy over a short distance of only 1.3 meters,” said lead author Sébastien Corde, of France’s Ecole Polytechnique, in a statement. That means the particle colliders of the future could be much smaller, with higher energy collisions, than today’s colliders.
At the moment, FACET is the only facility that can accelerate positrons this way. Particle colliders are expensive, so it’s not likely that research facilities will be building new colliders to take advantage of the wakefield acceleration method anytime soon, but some may upgrade their existing accelerators. “It’s conceivable to boost the performance of linear accelerators by adding a very short plasma accelerator at the end,” said Corde, “That would multiply the accelerator’s energy without making the entire structure significantly longer.”
When Stanley B. Prusiner, a UCSF neurologist, first proposed that inert proteins he called prions could somehow fold into strange shapes and infect humans with rare diseases of the brain, his idea 30 years ago was widely dismissed as nonsense.
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