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Topic Review
Loopholes in Bell Test Experiments
In Bell test experiments, there may be problems of experimental design or set-up that affect the validity of the experimental findings. These problems are often referred to as "loopholes". See the article on Bell's theorem for the theoretical background to these experimental efforts (see also John Stewart Bell). The purpose of the experiment is to test whether nature is best described using a local hidden variable theory or by the quantum entanglement theory of quantum mechanics. The "detection efficiency", or "fair sampling" problem is the most prevalent loophole in optical experiments. Another loophole that has more often been addressed is that of communication, i.e. locality. There is also the "disjoint measurement" loophole which entails multiple samples used to obtain correlations as compared to "joint measurement" where a single sample is used to obtain all correlations used in an inequality. To date, no test has simultaneously closed all loopholes. Ronald Hanson of the Delft University of Technology claims the first Bell experiment that closes both the detection and the communication loopholes. (This was not an optical experiment in the sense discussed below; the entangled degrees of freedom were electron spins rather than photon polarization.) Nevertheless, correlations of classical optical fields also violate Bell's inequality. In some experiments there may be additional defects that make "local realist" explanations of Bell test violations possible; these are briefly described below. Many modern experiments are directed at detecting quantum entanglement rather than ruling out local hidden variable theories, and these tasks are different since the former accepts quantum mechanics at the outset (no entanglement without quantum mechanics). This is regularly done using Bell's theorem, but in this situation the theorem is used as an entanglement witness, a dividing line between entangled quantum states and separable quantum states, and is as such not as sensitive to the problems described here. In October 2015, scientists from the Kavli Institute of Nanoscience reported that the Quantum nonlocality phenomenon is supported at the 96% confidence level based on a "loophole-free Bell test" study. These results were confirmed by two studies with statistical significance over 5 standard deviations which were published in December 2015. However, Alain Aspect writes that No experiment can be said to be totally loophole-free.
  • 532
  • 10 Oct 2022
Topic Review
Nanocarbon-Iridium Oxide Nanostructured Hybrids
Nanostructuring nanocarbons with IrOx yields to material coatings with large charge capacities for neural electrostimulation, and large reproducibility in time, that carbons do not exhibit.
  • 530
  • 21 Jul 2021
Topic Review
Hinode
Hinode (/ˈhiːnoʊdeɪ/; Japanese: ひので, IPA: [çinode], Sunrise), formerly Solar-B, is a Japan Aerospace Exploration Agency Solar mission with United States and United Kingdom collaboration. It is the follow-up to the Yohkoh (Solar-A) mission and it was launched on the final flight of the M-V-7 rocket from Uchinoura Space Center, Japan on 22 September 2006 at 21:36 UTC (23 September, 06:36 JST). Initial orbit was perigee height 280 km, apogee height 686 km, inclination 98.3 degrees. Then the satellite maneuvered to the quasi-circular sun-synchronous orbit over the day/night terminator, which allows near-continuous observation of the Sun. On 28 October 2006, the probe's instruments captured their first images. The data from Hinode are being downloaded to the Norway , terrestrial Svalsat station, operated by Kongsberg a few kilometres west of Longyearbyen, Svalbard. From there, data was transmitted by Telenor through a fibre-optic network to mainland Norway at Harstad, and on to data users in North America, Europe and Japan.
  • 530
  • 15 Nov 2022
Topic Review
Solar Chemical
Solar chemical refers to a number of possible processes that harness solar energy by absorbing sunlight in a chemical reaction. The idea is conceptually similar to photosynthesis in plants, which converts solar energy into the chemical bonds of glucose molecules, but without using living organisms, which is why it is also called artificial photosynthesis. A promising approach is to use focused sunlight to provide the energy needed to split water into its constituent hydrogen and oxygen in the presence of a metallic catalyst such as zinc. This is normally done in a two-step process so that hydrogen and oxygen are not produced in the same chamber, which creates an explosion hazard. Another approach involves taking the hydrogen created in this process and combining it with carbon dioxide to create methane. The benefit of this approach is that there is an established infrastructure for transporting and burning methane for power generation, which is not true for hydrogen. One main drawback to both of these approaches is common to most methods of energy storage: adding an extra step between energy collection and electricity production drastically decreases the efficiency of the overall process.
  • 529
  • 22 Nov 2022
Topic Review
Two-Dimensional Nanostructures as Surface-Enhanced Raman Scattering Substrates
Two-dimensional nanostructures (2DNS) attract tremendous interest and have emerged as potential materials for a variety of applications, including biomolecule sensing, due to their high surface-to-volume ratio, tuneable optical and electronic properties. Advancements in the engineering of 2DNS and associated technologies have opened up new opportunities. Surface-enhanced Raman scattering (SERS) is a rapid, highly sensitive, non-destructive analytical technique with exceptional signal amplification potential. Several structurally and chemically engineered 2DNS with added advantages (e.g., π–π* interaction), over plasmonic SERS substrates, have been developed specifically towards biomolecule sensing in a complex matrix, such as biological fluids. 
  • 527
  • 11 Jan 2023
Topic Review
GEO600
GEO600 is a gravitational wave detector located near Sarstedt in the South of Hanover, Germany. It is designed and operated by scientists from the Max Planck Institute for Gravitational Physics, Max Planck Institute of Quantum Optics and the Leibniz Universität Hannover, along with University of Glasgow, University of Birmingham and Cardiff University in the United Kingdom, and is funded by the Max Planck Society and the Science and Technology Facilities Council (STFC). GEO600 is part of a worldwide network of gravitational wave detectors. This instrument, and its sister interferometric detectors, when operational, are some of the most sensitive gravitational wave detectors ever designed. They are designed to detect relative changes in distance of the order of 10−21, about the size of a single atom compared to the distance from the Sun to the Earth. GEO600 is capable of detecting gravitational waves in the frequency range 50 Hz to 1.5 kHz. Construction on the project began in 1995.
  • 523
  • 03 Nov 2022
Topic Review
Soyuz TMA-20
Soyuz TMA-20 was a human spaceflight to the International Space Station (ISS) and was part of the Soyuz programme. It lifted off from the Baikonur Cosmodrome in Kazakhstan on December 15, 2010, and docked with the ISS two days later. The three-person crew of Soyuz TMA-20 – Dmitri Kondratyev, Catherine Coleman and Paolo Nespoli – represented the ISS partner organizations of Roscosmos, NASA and the European Space Agency (ESA). Soyuz TMA-20's crew represented half of the members of Expedition 27; the other three members of the expedition arrived at the station on board Soyuz TMA-21 on April 6, 2011. The COSPAR ID of Soyuz TMA-20 was 2010-067A. It is ISS flight 25S. On May 24, 2011, after spending 159 days in space, the Soyuz TMA-20 descent module landed safely in Zhezkazgan, Kazakhstan, carrying Kondratyev, Coleman and Nespoli.
  • 523
  • 17 Nov 2022
Topic Review
Effects in Molecular Nanomagnets
Molecular magnets, in principle, have a similar hierarchy. Starting from single-molecule magnets (SMM)and single-chain magnets (SCM), more complex structures are also possible. In general, molecular nanomagnets can be built without the aforementioned magnetic elements; however, highly interesting molecular nanomagnets can be created by adding Mn12, Fe8, Mn4, or other metallic elements.
  • 520
  • 26 Aug 2021
Topic Review
Soyuz T-15
Soyuz T-15 (Russian: Союз T-15, Union T-15) was a crewed mission to the Mir and Salyut 7 space stations and was part of the Soyuz programme. It marked the final flight of the Soyuz-T spacecraft, the third generation Soyuz spacecraft, which had been in service for seven years from 1979 to 1986. This mission marked the first time that a spacecraft visited, and docked with, two space stations in the same mission.
  • 519
  • 17 Oct 2022
Topic Review Peer Reviewed
Development of the Concept of Space up to Newton
The concept of space, ubiquitous among all humans from birth, has changed profoundly in the course of the history of Western civilization, the only one to be considered here. An important contribution to this change was the theoretical elaborations of the philosophers of nature and mathematicians, started in Ancient Greece. Here, the process is considered up to Newton, when the concept of space for physicists, who then replaced the traditional philosophers of nature, took on a connotation that remained substantially undisputed for two centuries—that of absolute space. 
  • 523
  • 18 Oct 2022
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