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May 09

On the reality of the quantum state.

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By Matthew F. Pusey, Jonathan Barrett & Terry Rudolph in Nature Physics, 2012, doi:10.1038/nphys2309, Received 05 March 2012, Accepted 11 April 2012, Published online 06 May 2012.

Quantum states are the key mathematical objects in quantum theory. It is therefore surprising that physicists have been unable to agree on what a quantum state truly represents. One possibility is that a pure quantum state corresponds directly to reality. However, there is a long history of suggestions that a quantum state (even a pure state) represents only knowledge or information about some aspect of reality. Here we show that any model in which a quantum state represents mere information about an underlying physical state of the system, and in which systems that are prepared independently have independent physical states, must make predictions that contradict those of quantum theory.

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May 08

CUNY Energy Institute Battery System Could Reduce Buildings’ Electric Bills.

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Reported by Ellis Simon, in City College of New York News, May 4, 2012.

The CUNY Energy Institute, which has been developing innovative low-cost batteries that are safe, non-toxic, and reliable with fast discharge rates and high energy densities, announced that it has built an operating prototype zinc anode battery system. The Institute said large-scale commercialization of the battery would start later this year.

Zinc anode batteries offer an environmentally friendlier and less costly alternative to nickel cadmium batteries. In the longer term, they also could replace lead-acid batteries at the lower cost end of the market. However, the challenge of dendrite formation associated with zinc had to be addressed. Dendrites are crystalline structures that cause batteries to short out.

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May 01

What Is the Best Way of Stacking Apples?

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Reported by CNRS (Délégation Paris Michel-Ange) (2012, April 25) in ScienceDaily, May 1 2012.

When stacking apples on a market stall, fruit sellers “naturally” adopt a particular arrangement: a regular pyramid with a triangular base. A French-German team, which includes in particular the Laboratoire de Physique des Solides (Université Paris-Sud / CNRS), has demonstrated that this arrangement is favored for reasons of mechanical stability. This work, which is published on the Physical Review Letters (PRL) website, could contribute to the design of organized porous materials.

Take apples or marbles. The best way to stack them consists in erecting a pyramid layer by layer, which ensures the maximum number of spheres is fitted into the minimum amount of space. There are several arrangements for stacking such identical spheres (of the same volume) with the same, optimal density. Two, in particular, are well known: a structure known as face centered cubic (FCC), whose base is necessarily a triangle for the smallest possible pyramid, and a hexagonally close-packed (HCP) structure with a hexagonal base, also when constructing the smallest possible pyramid. The first arrangement consists of a periodic repetition of three different positions of layers: ABCABC…. In the second, two different positions of layers are periodically repeated: ABABAB…. As early as 1611, while studying the stacking of canon balls, the scientist Johannes Kepler proposed the FCC arrangement as being the most efficient. It is moreover the arrangement used by stall holders to stack their fruit and vegetables.

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Apr 30

Spin–orbital separation in the quasi-one-dimensional Mott insulator Sr2CuO3.

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By J. Schlappa, K. Wohlfeld, K. J. Zhou, M. Mourigal, M. W. Haverkort, V. N. Strocov, L. Hozoi, C. Monney, S. Nishimoto, S. Singh, A. Revcolevschi, J.-S. Caux, L. Patthey, H. M. Rønnow, J. van den Brink & T. Schmitt in Nature, 18 April 2012, doi:10.1038/nature10974

When viewed as an elementary particle, the electron has spin and charge. When binding to the atomic nucleus, it also acquires an angular momentum quantum number corresponding to the quantized atomic orbital it occupies. Even if electrons in solids form bands and delocalize from the nuclei, in Mott insulators they retain their three fundamental quantum numbers: spin, charge and orbital1. The hallmark of one-dimensional physics is a breaking up of the elementary electron into its separate degrees of freedom2. The separation of the electron into independent quasi-particles that carry either spin (spinons) or charge (holons) was first observed fifteen years ago3. Here we report observation of the separation of the orbital degree of freedom (orbiton) using resonant inelastic X-ray scattering on the one-dimensional Mott insulator Sr2CuO3. We resolve an orbiton separating itself from spinons and propagating through the lattice as a distinct quasi-particle with a substantial dispersion in energy over momentum, of about 0.2 electronvolts, over nearly one Brillouin zone.

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Mar 23

Microorganism mediated synthesis of reduced graphene oxide films.

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By Y. Tanizawa, Y. Okamoto, K. Tsuzuki, Y. Nagao, N. Yoshida, R. Tero, S. Iwasa, A. Hiraishi, Y. Suda, H. Takikawa, R. Numano, H. Okada, R. Ishikawa and A. Sandhu, in J. Phys.: Conf. Ser. 352 012011 doi:10.1088/1742-6596/352/1/012011

Abstract: The wide-ranging industrial application of graphene and related compounds has led researchers to devise methods for the synthesis of high quality graphene. We recently reported on the chemical synthesis, patterning, and doping of graphene films by the chemical exfoliation of graphite into graphene oxide (GO) with subsequent chemical reduction into graphene films [1, 2]. Here, we describe a hybrid approach for the synthesis of reduced graphene sheets, where chemically derived GO was reduced by microorganisms extracted from a riverside near the University. Our procedure enabled the production of ~100 μm sized reduced graphene sheets, which showed excellent Raman spectra associated with high quality reduced graphene. We give a detailed account of the relationship between the type of microorganisms and the properties of the resulting reduced graphene.

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Mar 22

A camera that peers around corners.

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Reported by Caroline McCall, MIT News Office, March 2012.

A new imaging system could use opaque walls, doors or floors as ‘mirrors’ to gather information about scenes outside its line of sight.

In December, MIT Media Lab researchers caused a stir by releasing a slow-motion video of a burst of light traveling the length of a plastic bottle. But the experimental setup that enabled that video was designed for a much different application: a camera that can see around corners.

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Mar 21

How the Alphabet of Data Processing Is Growing: Flying ‘Qubits’ Generated.

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Reported by Science Daily, 21 March 2012.

Electron one-way street. In this dual channel, electrons (blue) move on defined, parallel paths. Only one single electron fits through at a time. By means of tunnel coupling, the electron can switch back and forth between the channels, thus occupying two different states, which are denoted by “arrow up” and “arrow down”. The electron virtually flies in both tracks at the same time, its two states overlap. (Credit: © Andreas Wieck)

The alphabet of data processing could include more elements than the “0” and “1” in future. An international research team has achieved a new kind of bit with single electrons, called quantum bits, or qubits. With them, considerably more than two states can be defined. So far, quantum bits have only existed in relatively large vacuum chambers. The team has now generated them in semiconductors. They have put an effect in practice, which the RUB physicist Prof. Dr. Andreas Wieck had already theoretically predicted 22 years ago. This represents another step along the path to quantum computing.

Together with colleagues from Grenoble and Tokyo, Wieck from the Chair of Applied Solid State Physics reports on the results in the journal Nature Nanotechnology.

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Mar 19

Who Wouldn’t Pay a Penny for a Sports Car?

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Reported by Megan Fellman, in Northwestern University News, 16 March 2012.

Who wouldn’t pay a penny for a sports car? That’s the mentality some popular online auctions take advantage of — the opportunity to get an expensive item for very little money.

In a study of hundreds of lowest unique bid auctions, Northwestern University researchers asked a different question: Who wins these auctions, the strategic gambler or the lucky one? The answer is the lucky. But, ironically, it’s a lucky person using a winning strategy.

The researchers found that all players intuitively use the right strategy, and that turns the auction into a game of pure chance. The findings, published by the journal PLoS One, provide insight into playing the stock market, real estate market and other gambles.

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Mar 18

Princeton scientists identify neural activity sequences that help form memory, decision-making.

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Reported by Catherine Zandonella, in Princeton University News-Stories,  14 March 2012.

Princeton University researchers have used a novel virtual reality and brain imaging system to detect a form of neural activity underlying how the brain forms short-term memories that are used in making decisions.

By following the brain activity of mice as they navigated a virtual reality maze, the researchers found that populations of neurons fire in distinctive sequences when the brain is holding a memory. Previous research centered on the idea that populations of neurons fire together with similar patterns to each other during the memory period.

The study was performed in the laboratory of David Tank, who is Princeton’s Henry L. Hillman Professor in Molecular Biology and co-director of the Princeton Neuroscience Institute. Both Tank and Christopher Harvey, who was first author on the paper and a postdoctoral researcher at the time of the experiments, said they were surprised to discover the sequential firing of neurons. The study was published online on March 14 in the journal Nature. Continue reading »

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Mar 16

Researchers develop graphene supercapacitor holding promise for portable electronics.

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Reported by Jennifer Marcus, in UCLA Newsroom, 15 March 2012.

Electrochemical capacitors (ECs), also known as supercapacitors or ultracapacitors, differ from regular capacitors that you would find in your TV or computer in that they store sustantially higher amounts of charges. They have garnered attention as energy storage devices as they charge and discharge faster than batteries, yet they are still limited by low energy densities, only a fraction of the energy density of batteries. An EC that combines the power performance of capacitors with the high energy density of batteries would represent a significant advance in energy storage technology. This requires new electrodes that not only maintain high conductivity but also provide higher and more accessible surface area than conventional ECs that use activated carbon electrodes. Continue reading »
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