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Topic Review
Composition (Objects)
Compositional objects are wholes instantiated by collections of parts. If an ontology wishes to permit the inclusion of compositional objects it must define which collections of objects are to be considered parts composing a whole. Mereology, the study of relationships between parts and their wholes, provides specifications on how parts must relate to one another in order to compose a whole.
  • 299
  • 04 Nov 2022
Topic Review
Silicon-Based Avalanche Photodiodes in Medical Imaging
Avalanche photodiodes have emerged as a promising technology with significant potential for various medical applications. Avalanche photodiodes offer distinct advantages over traditional photodetectors, including a higher responsivity, faster response times, and superior signal-to-noise ratios. These characteristics make avalanche photodiodes particularly suitable for medical-imaging modalities that require a high detection efficiency, excellent timing resolution, and enhanced spatial resolution.
  • 298
  • 13 Dec 2023
Topic Review
Pavo
Pavo, Latin for "peacock," is a small but distinct constellation in the southern sky. Representing the majestic bird from ancient mythology, Pavo is notable for its compact arrangement of stars and its proximity to the south celestial pole, making it a prominent feature of the southern hemisphere's night sky.
  • 295
  • 15 Mar 2024
Topic Review
Micro-Raman Spectroscopy for Graphene Characterization
There has been growing interest in combining the unique properties of graphene-based materials with silver nanostructures, aiming for their utilization in the fields of plasmonics and metamaterials applications. Silver nanoparticles and nanostructures, with localized surface plasmonic resonance spanning from the visible to the near-infrared range, find utility in various applications, particularly in surface-enhanced Raman scattering (SERS). Materials based on graphene, for instance, graphene oxide (GO) and reduced graphene oxide (RGO), have demonstrated their potential as SERS substrates by generating strong chemical enhancement.
  • 294
  • 16 Oct 2023
Topic Review
Timeline of Physical Chemistry
The timeline of physical chemistry lists the sequence of physical chemistry theories and discoveries in chronological order.
  • 293
  • 21 Nov 2022
Topic Review
Crater
Crater, Latin for "cup" or "bowl," is a small and inconspicuous constellation located in the southern celestial hemisphere. Positioned near the prominent constellation Hydra, Crater represents a celestial cup often associated with the mythological story of the Greek god Apollo and his daily ritual of sun-chariot driving.
  • 291
  • 08 Mar 2024
Topic Review
Detection System for DDoS Attacks
Distributed Denial of Service (DDoS) attacks, advanced persistent threats, and malware actively compromise the availability and security of Internet services. A DDoS attack is a vindictive attempt from numerous frameworks to make PC/network assets inaccessible to its expected clients, more often than not, by blocking/interrupting services associated with the organization of the network/Internet.
  • 291
  • 29 Dec 2023
Topic Review
Osmium-167
Osmium (76Os) has seven naturally occurring isotopes, five of which are stable: 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other natural isotopes, 184Os, and 186Os, have extremely long half-life (1.12×1013 years and 2×1015 years, respectively) and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re (half-life 4.56×1010 years) and is most often measured in an 187Os/188Os ratio. This ratio, as well as the 187Re/188Os ratio, have been used extensively in dating terrestrial as well as meteoric rocks. It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. However, the most notable application of Os in dating has been in conjunction with iridium, to analyze the layer of shocked quartz along the Cretaceous–Paleogene boundary that marks the extinction of the dinosaurs 66 million years ago. There are also 30 artificial radioisotopes, the longest-lived of which is 194Os with a half-life of six years; all others have half-lives under 94 days. There are also nine known nuclear isomers, the longest-lived of which is 191mOs with a half-life of 13.10 hours. All isotopes and nuclear isomers of osmium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.
  • 291
  • 15 Nov 2022
Topic Review
Northern Light (Spacecraft)
Northern Light was a concept mission for a robotic mission to Mars that would consist of a lander and a rover, being studied by a consortium of Canadian universities, companies and organisations. The primary contractor for the spacecraft was Thoth Technology Inc. The spacecraft would consist of four parts: an apogee kick engine to provide orbital injection for a cruise vehicle that carries the Northern Light lander and the Beaver Rover to a direct rendezvous with Mars using a Hohmann transfer orbit. Atmospheric entry would be achieved by a heat shield, parachute and airbag deployment system. The lander would transfer the rover to the Martian surface. Once deployed on the Martian surface, the lander contacts Earth directly to the 46 m parabolic antenna located at the Algonquin Radio Observatory. The Beaver Rover was proposed to have a maximum range of 1000 metres (0.62 mile) from the landing site. It would have operated under battery, utilizing tools and sensors to investigate surface rocks that may contain the presence of photosynthetic life.
  • 290
  • 03 Nov 2022
Topic Review
Nuclear Clock
A nuclear clock or nuclear optical clock is a notional clock that would use the frequency of a nuclear transition as its reference frequency, in the same manner as an atomic clock uses the frequency of an electronic transition in an atom's shell. Such a clock is expected to be more accurate than the best current atomic clocks by a factor of about 10, with an achievable accuracy approaching the 10−19 level. The only nuclear state suitable for the development of a nuclear clock using existing technology is thorium-229m, a nuclear isomer of thorium-229 and the lowest-energy nuclear isomer known. With an energy of about 8 eV, the corresponding ground-state transition is expected to be in the vacuum ultraviolet wavelength region around 150 nm, which would make it accessible to laser excitation.
  • 289
  • 11 Oct 2022
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