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Topic Review
Rubens' Tube
A Rubens' tube, also known as a standing wave flame tube, or simply flame tube, is an antique physics apparatus for demonstrating acoustic standing waves in a tube. Invented by German physicist Heinrich Rubens in 1905, it graphically shows the relationship between sound waves and sound pressure, as a primitive oscilloscope. Today, it is used only occasionally, typically as a demonstration in physics education.
  • 585
  • 29 Nov 2022
Topic Review
Ultrafast Laser in Orthopedic Surgery
The potential of ultrafast lasers (pico- to femtosecond) in orthopedics-related procedures has been studied extensively for clinical adoption. As compared to conventional laser systems with continuous wave or longer wave pulse, ultrafast lasers provide advantages such as higher precision and minimal collateral thermal damages. Translation to surgical applications in the clinic has been restrained by limitations of material removal rate and pulse average power, whereas the use in surface texturing of implants has become more refined to greatly improve bioactivation and osteointegration within bone matrices.
  • 584
  • 07 May 2022
Topic Review
Line-Shaped-Illumination Two-Photon Microscopy
Line-shaped illumination is a useful configuration to obtain a multifocal pattern to be used in two-photon microscopy: the light beam emitted by the illuminating laser is first shaped by means of cylindrical lenses and then is focused inside the sample as a continuous line. The simultaneous excitation of several points in the specimen is expected to reduce the acquisition time with respect to the usual point-scanning two-photon microscopes, as a two-dimensional image is obtained by scanning the line along a single direction.
  • 583
  • 05 May 2022
Topic Review
Obsolete Polish Units of Measurement
The traditional Polish units of measurement included two uniform yet distinct systems of weights and measures, as well as a number of related systems borrowed from neighbouring states. The first attempt at standardisation came with the introduction of the Old Polish measurement [system], also dubbed the Warsaw system, introduced by a royal decree of December 6, 1764. The system was later replaced by the New Polish measurement [system] introduced on January 1, 1819. The traditional Polish systems of weights and measures were later replaced with those of surrounding nations (due to the Partitions of Poland), only to be replaced with metric system by the end of the 19th century (between 1872 and 1876).
  • 582
  • 14 Oct 2022
Topic Review
Chemical Reaction Rate
The reaction rate for a reactant or product in a particular reaction is defined as the amount of the chemical that is formed or removed (in moles or mass units) per unit time per unit volume. Knowledge of these rates is essential in, among other disciplines, chemical engineering and environmental engineering. Chemical kinetics is the part of physical chemistry which studies reaction rates.
  • 582
  • 28 Nov 2022
Topic Review
Magnetic Properties and Magnetocaloric Effect of Pr2Co7 Compound
The Pr2Co7 compound has interesting magnetic properties, such as a high Curie temperature TC and uniaxial magnetocrystalline anisotropy. It crystallizes in a hexagonal structure (2:7 H) of the Ce2Ni7 type and is stable at relatively low temperatures (Ta ≤ 1023 K), or it has a rhombohedral structure (2:7 R) of the Gd2Co7 type and is stable at high temperatures (Ta ≥ 1223 K). Studies of the magnetocaloric properties of the nanocrystalline Pr2Co7 compound have shown the existence of a large reversible magnetic entropy change (ΔSM) with a second-order magnetic transition. 
  • 581
  • 15 Jun 2023
Topic Review
Thermochemical Cycle
Thermochemical cycles combine solely heat sources (thermo) with chemical reactions to split water into its hydrogen and oxygen components. The term cycle is used because aside of water, hydrogen and oxygen, the chemical compounds used in these processes are continuously recycled. If work is partially used as an input, the resulting thermochemical cycle is defined as a hybrid one.
  • 581
  • 14 Oct 2022
Topic Review
Materials for Chemical Sensing
The ability to measure and monitor the concentration of specific chemical and/or gaseous species (i.e., “analytes”) is the main requirement in many fields, including industrial processes, medical applications, and workplace safety management. As a consequence, several kinds of sensors have been developed in the modern era according to some practical guidelines that regard the characteristics of the active (sensing) materials on which the sensor devices are based. These characteristics include the cost-effectiveness of the materials’ manufacturing, the sensitivity to analytes, the material stability, and the possibility of exploiting them for low-cost and portable devices. Consequently, many gas sensors employ well-defined transduction methods, the most popular being the oxidation (or reduction) of the analyte in an electrochemical reactor, optical techniques, and chemiresistive responses to gas adsorption. Many of the efforts devoted to improving these methods have been directed towards the use of certain classes of specific materials.
  • 579
  • 26 Aug 2022
Topic Review
List of Messier Objects
The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his "Catalogue des Nébuleuses et des Amas d'Étoiles" ("Catalogue of Nebulae and Star Clusters"). A preliminary version first appeared in Memoirs of the French Academy of Sciences in 1771, and the last item was added in 1966 by Kenneth Glyn Jones, based on Messier's observations. The first version of Messier's catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. In addition to his own discoveries, this version included objects previously observed by other astronomers, with only 17 of the 45 objects being Messier’s. By 1780 the catalog had increased to 80 objects. The final version of the catalogue containing 103 objects was published in 1781 in the Connaissance des Temps for the year 1784. However, due to what was thought for a long time to be the incorrect addition of Messier 102, the total number remained 102. Other astronomers, using side notes in Messier's texts, eventually filled out the list up to 110 objects. The catalogue consists of a diverse range of astronomical objects, ranging from star clusters, nebula and galaxies. Messier 1 is the supernova remnant of Crab Nebula and the great spiral Andromeda Galaxy is M 31. Many further inclusions followed in the next century when the first addition came from Nicolas Camille Flammarion in 1921, who added Messier 104 after finding Messier’s side note in his 1781 edition exemplar of the catalogue. M105 to M107 were added by Helen Sawyer Hogg in 1947, M108 and M109 by Owen Gingerich in 1960, and M110 by Kenneth Glyn Jones in 1967. Because Messier was interested in finding only comets, he created a list of non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as the Messier catalogue. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier number.
  • 579
  • 06 Dec 2022
Topic Review
Precise Optical Modulation
Optoelectronic devices which play important roles in high-speed optical fiber networks can offer effective measurement methods for optoelectronic devices including optical modulators and photodetectors. Precise optical signal modulation is required for measurement applications.
  • 579
  • 19 May 2021
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