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Topic Review
Surface-Extended X-Ray Absorption Fine Structure
Surface-extended X-ray absorption fine structure (SEXAFS) is the surface-sensitive equivalent of the EXAFS technique. This technique involves the illumination of the sample by high-intensity X-ray beams from a synchrotron and monitoring their photoabsorption by detecting in the intensity of Auger electrons as a function of the incident photon energy. Surface sensitivity is achieved by the interpretation of data depending on the intensity of the Auger electrons (which have an escape depth of ~1–2 nm) instead of looking at the relative absorption of the X-rays as in the parent method, EXAFS. The photon energies are tuned through the characteristic energy for the onset of core level excitation for surface atoms. The core holes thus created can then be filled by nonradiative decay of a higher-lying electron and communication of energy to yet another electron, which can then escape from the surface (Auger emission). The photoabsorption can therefore be monitored by direct detection of these Auger electrons to the total photoelectron yield. The absorption coefficient versus incident photon energy contains oscillations which are due to the interference of the backscattered Auger electrons with the outward propagating waves. The period of this oscillations depends on the type of the backscattering atom and its distance from the central atom. Thus, this technique enables the investigation of interatomic distances for adsorbates and their coordination chemistry. This technique benefits from long range order not being required, which sometimes becomes a limitation in the other conventional techniques like LEED (about 10 nm). This method also largely eliminates the background from the signal. It also benefits because it can probe different species in the sample by just tuning the X-ray photon energy to the absorption edge of that species. Joachim Stöhr played a major role in the initial development of this technique.
  • 510
  • 24 Oct 2022
Topic Review
Physical Phenomenology
After a brief digression on the current landscape of theoretical physics and on some open questions pertaining to coherence with experimental results, still to be settled, it is shown that the properties of the deformed Minkowski space lead to a plurality of potential physical phenomena that should occur, provided that the resulting formalisms can be considered as useful models for the description of some aspects of physical reality. 
  • 510
  • 27 Apr 2021
Biography
Joseph Larmor
Sir Joseph Larmor FRS FRSE DCL LLD[1] (11 July 1857 – 19 May 1942) was an Irish[2] physicist and mathematician who made innovations in the understanding of electricity, dynamics, thermodynamics, and the electron theory of matter. His most influential work was Aether and Matter, a theoretical physics book published in 1900. He was born in Magheragall in County Antrim the son of Hugh Larmor,
  • 510
  • 02 Dec 2022
Topic Review
Ion-Mobility Spectrometry
Ion mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized molecules in the gas phase based on their mobility in a carrier buffer gas. Though heavily employed for military or security purposes, such as detecting drugs and explosives, the technique also has many laboratory analytical applications, including the analysis of both small and large biomolecules. IMS instruments are extremely sensitive stand-alone devices, but are often coupled with mass spectrometry, gas chromatography or high-performance liquid chromatography in order to achieve a multi-dimensional separation. They come in various sizes, ranging from a few millimeters to several meters depending on the specific application, and are capable of operating under a broad range of conditions. IMS instruments such as microscale high-field asymmetric-waveform ion-mobility spectrometry can be palm-portable for use in a range of applications including volatile organic compound (VOC) monitoring, biological sample analysis, medical diagnosis and food quality monitoring. Systems operated at higher pressure (i.e. atmospheric conditions, 1 atm or 1013 hPa) are often accompanied by elevated temperature (above 100 °C), while lower pressure systems (1-20 hPa) do not require heating.
  • 509
  • 30 Nov 2022
Topic Review
Traditional Chinese Timekeeping
The traditional Chinese time systems refers to the time standards for divisions of the day used in China until the introduction of the Shixian calendar in 1628 at the beginning of the Qing dynasty.
  • 508
  • 30 Oct 2022
Topic Review
Soyuz TMA-03M
Soyuz TMA-03M was a spaceflight to the International Space Station (ISS). It launched on 21 December 2011 from Site One at the Baikonur Cosmodrome, Kazakhstan, carrying three members of Expedition 30 to the ISS. TMA-03M was the 112th flight of a Russian Soyuz spacecraft, since the first in 1967, and the third flight of the modernised Soyuz-TMA-M version. The docking with the International Space Station took place at 19:19 Moscow Time on 23 December, three minutes ahead of schedule. The crew were Oleg Kononenko (Russia , commander), André Kuipers (the Netherlands) and Donald Pettit (United States ). The Soyuz remained aboard the space station for the Expedition 30 increment to serve as an emergency escape vehicle if needed. The capsule used in the mission can be seen at the Space Expo visitors center at the European Space Research and Technology Centre in Noordwijk, Netherlands.
  • 508
  • 05 Dec 2022
Biography
William Allis
William Phelps Allis (November 15, 1901 in Menton, France – March 5, 1999 in Cambridge, Massachusetts) was an American theoretical physicist specializing in electrical discharges in gases.[1] He was the grandson of Edward P. Allis,[2] founder of the E.P. Allis Company, which became Allis-Chalmers. Allis majored in school and received his S.B. in 1923 and S.M. in 1924 from the Massachusetts
  • 509
  • 08 Dec 2022
Topic Review
PENG-Based Non-Invasive Medical Sensors
Piezoelectric nanogenerators (PENGs) not only are able to harvest mechanical energy from the ambient environment or body and convert mechanical signals into electricity but can also inform people about pathophysiological changes and communicate this information using electrical signals, thus acting as medical sensors to provide personalized medical solutions to patients.
  • 507
  • 19 Jan 2023
Topic Review
Miles-Phillips Mechanism
In physical oceanography and fluid mechanics, the Miles-Phillips mechanism describes the generation of wind waves from a flat surface by the use of two distinct mechanisms. Both mechanisms are applied on the gravity-capillary waves and have in common that waves are generated by a resonance phenomenon. The Miles mechanism is based on the hypothesis that waves arise as an instability of the sea-atmosphere system. The Phillips mechanism assumes that turbulent eddies in the atmospheric boundary layer induce pressure fluctuations at the sea surface.
  • 508
  • 13 Oct 2022
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.
  • 506
  • 15 Nov 2022
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