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Category: particle physics – Page 567

Why is gravity so much weaker than the other fundamental forces? A small fridge magnet is enough to create an electromagnetic force greater than the gravitational pull exerted by planet Earth. One possibility is that we don’t feel the full effect of gravity because part of it spreads to extra dimensions. Though it may sound like science fiction, if extra dimensions exist, they could explain why the universe is expanding faster than expected, and why gravity is weaker than the other forces of nature.

In our everyday lives, we experience three spatial dimensions, and a fourth dimension of time. How could there be more? Einstein’s general theory of relativity tells us that space can expand, contract, and bend. Now if one dimension were to contract to a size smaller than an atom, it would be hidden from our view. But if we could look on a small enough scale, that hidden dimension might become visible again. Imagine a person walking on a tightrope. She can only move backward and forward; but not left and right, nor up and down, so she only sees one dimension. Ants living on a much smaller scale could move around the cable, in what would appear like an extra dimension to the tightrope-walker.

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Nice.

Abstract: Researchers have developed a way to use less platinum in chemical reactions commonly used in the clean energy, green chemicals, and automotive industries, according to a paper in Science.

Led by the University of New Mexico in collaboration with Washington State University, the researchers developed a unique approach for trapping platinum atoms that improves the efficiency and stability of the reactions.

Platinum is used as a catalyst in many clean energy processes, including in catalytic converters and fuel cells. The precious metal facilitates chemical reactions for many commonly used products and processes, such as converting poisonous carbon monoxide to less harmful carbon dioxide in catalytic converters.

Continue reading “Researchers improve catalyst efficiency for clean industries: Method reduces use of expensive platinum” | >

While there are several forms of ion propulsion, the version Brophy used on Dawn involves two grids, each about a foot wide and spaced half a millimeter apart. An electrical system powered by a solar array on the spacecraft passes a current through both grids, and the resulting voltage differential between the two is what accelerates the xenon particles as they pass through the grids. Each accelerating particle only provides a tiny amount of thrust — roughly equivalent to the pressure of a piece of paper lying in your hand — but in the airless and frictionless environment of space, a steady stream of that tiny thrust can build up to monumental speeds of about 24,000 miles-per-hour.

What Brophy and his coworkers aimed to do was build a grid and propulsion system that could pull this off, and demonstrate that the setup was durable enough to survive the whole mission. So before both Deep Space 1 and Dawn, they ran versions of the ion system here on Earth continuously for years to demonstrate their lifespan.

Finally, the Dawn mission became possible when Ceres and Vesta reached a once-every-17-years alignment, allowing the mission to visit them both. “That was really a great boon for space exploration to do the two largest asteroids in the asteroid belt with one mission,” Russell explains.

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Robots so small they can enter the bloodstream and perform surgeries are one step closer, a research team from Monash University has discovered.

Led by Dr Zhe Liu, the Monash Engineering team has focused on graphene oxide — which is a single atom thick — as an effective shape memory material.

Graphene has captured world scientific and industrial interest for its miracle properties, with potential applications across energy, medicine, and even biomedical nano-robots.

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“Nothing is impossible!” In line with this motto, physicists from the Quantum Dynamics Division of Professor Gerhard Rempe (director at the Max Planck Institute of Quantum Optics) managed to realise a quantum logic gate in which two light quanta are the main actors. The difficulty of such an endeavour is that photons usually do not interact at all but pass each other undisturbed. This makes them ideal for the transmission of quantum information, but less suited for its processing. The scientists overcame this steep hurdle by bringing an ancillary third particle into play: a single atom trapped inside an optical resonator that takes on the role of a mediator. “The distinct feature of our gate implementation is that the interaction between the photons is deterministic”, explains Dr. Stephan Ritter. “This is essential for future, more complex applications like scalable quantum computers or global quantum networks.”

In all modern computers, data processing is based on information being binary-coded and then processed using logical operations. This is done using so-called which assign predefined output values to each input via deterministic protocols. Likewise, for the information processing in computers, quantum logic gates are the key elements. To realise a universal quantum computer, it is necessary that every input quantum bit can cause a maximal change of the other quantum bits. The practical difficulty lies in the special nature of quantum information: in contrast to classical bits, it cannot be copied. Therefore, classical methods for error correction cannot be applied, and the gate must function for every single photon that carries information.

Because of the special importance of photons as information carriers – for example, for communicating quantum information in extended quantum networks – the realisation of a deterministic photon-photon gate has been a long-standing goal. One of several possibilities to encode photonic quantum bits is the use of polarisation states of single photons. Then the states “0” and “1” of a classical bit correspond to two orthogonal polarisation states. In the two-photon gate, the polarisation of each photon can influence the polarisation of the other photon. As in the classical logic gate it is specified beforehand which input polarisation leads to which output polarisation. For example, a linear polarisation of the second photon is rotated by 90° if the first one is in the logic state “1”, and remains unchanged if the first one is in “0”.

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Researcher Tim Burgess added atoms of zinc to lasers one hundredth the diameter of a human hair and made of gallium arsenide — a material used extensively in smartphones and other electronic devices.

The impurities led to a 100 times improvement in the amount of light from the lasers.

“Normally you wouldn’t even bother looking for light from nanocrystals of gallium arsenide — we were initially adding zinc simply to improve the electrical conductivity,” said Mr Burgess, a PhD student in the ANU Research School of Physics and Engineering.

Continue reading “A little impurity makes nanolasers shine” | >

Bowtie-shaped nanoparticles made of silver may help bring the dream of quantum computing and quantum information processing closer to reality. These nanostructures, created at the Weizmann Institute of Science and described recently in Nature Communications, greatly simplify the experimental conditions for studying quantum phenomena and may one day be developed into crucial components of quantum devices.

The research team led by Prof. Gilad Haran of Weizmann’s Chemical Physics Department — postdoctoral fellow Dr. Kotni Santhosh, Dr. Ora Bitton of Chemical Research Support and Prof. Lev Chuntonov of the Technion-Israel Institute of Technology — manufactured two-dimensional bowtie-shaped silver nanoparticles with a minuscule gap of about 20 nanometers (billionths of a meter) in the center. The researchers then dipped the “bowties” in a solution containing quantum dots, tiny semiconductor particles that can absorb and emit light, each measuring six to eight nanometers across. In the course of the dipping, some of the quantum dots became trapped in the bowtie gaps.

Under exposure to light, the trapped dots became “coupled” with the bowties — a scientific term referring to the formation of a mixed state, in which a photon in the bowtie is shared, so to speak, with the quantum dot. The coupling was sufficiently strong to be observed even when the gaps contained a single quantum dot, as opposed to several. The bowtie nanoparticles could thus be prompted to switch from one state to another: from a state without coupling to quantum dots, before exposure to light, to the mixed state characterized by strong coupling, following such exposure.

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A team of researchers led by professor Jean-Christophe Marine (VIB-KU Leuven) has identified NEAT1, a non-coding RNA, as a potential therapeutic target in the fight against cancer. In collaboration with the Cédric Blanpain lab (ULB), VIB researchers have shown that NEAT1 plays an important role in the survival of highly dividing cells — and in particular of cancer cells. These findings can help develop new drugs that target NEAT1, in order to kill cancer cells more effectively.

As a non-coding RNA, NEAT1 is not translated into a protein. It does however contribute to the formation of so-called ‘paraspeckles’, subnuclear particles that can be found in the cell nuclei of cancer cells. The function of these particles has remained obscure. Although highly conserved through evolution, NEAT1 appears to be dispensable for normal embryonic development and adult life as mice lacking NEAT1 are viable and healthy.

Guarding the genome

PhD student Carmen Adriaens (VIB-KU Leuven): “In our study, we have found that the expression of NEAT1 in the cell nucleus is regulated by p53. This protein plays an important role in protecting people against cancer and is known as ‘the guardian of the genome’. When a cell is stressed or damaged, p53 will upregulate the expression of NEAT1, which leads to the formation of paraspeckles. This has two possible outcomes: the cell can either go into transient cell cycle arrest, giving it time to deal with the stress and repair the damage before continuing cell division. If the stress or damage is too high, however, p53 will instruct the cell to commit suicide and die.”

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Not only could they transform quantum computing, they’re a candidate for dark matter.

A team of Chinese physicists from Shanghai’s Jiaotong University have proof beyond a reasonable doubt of the existence of the Majorana fermion — a special particle that could potentially revolutionize quantum computing.

“The search for this particle is for condensed-matter physicists what the Higgs boson search was for high-energy particle physicists,” said Leonid Rokhinson, an associate professor of physics at Purdue University, who was the first to detect the signature of the fermion in 2012 but was not involved in this study, in a 2012 press release. “It is a very peculiar object because it is a fermion yet it is its own antiparticle with zero mass and zero charge.”

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Physicists working with the Large Hadron Collider beauty experiment (LHCb) have discovered what appears to be an entire family of new particles that our current physics models can’t explain.

The existence of these new forms of matter, known as tetraquarks, challenges our current understanding of the role they play inside the protons and neutrons that make up atoms — the fundamental building blocks of everything we know and love in the Universe.

“We looked at every known particle and process to make sure these four structures couldn’t be explained by any pre-existing physics,” one of the team, Thomas Britton from Syracuse University, told Sarah Charley at Symmetry. “It was like baking a six-dimensional cake with 98 ingredients and no recipe — just a picture of a cake.”

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