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Topic Review
ΔT
In precise timekeeping, ΔT (Delta T, delta-T, deltaT, or DT) is a measure of the cumulative effect of the departure of the Earth's rotation period from the fixed-length day of atomic time. Formally it is the time difference obtained by subtracting Universal Time (UT, defined by the Earth's rotation) from Terrestrial Time (TT, independent of the Earth's rotation): ΔT = TT − UT. The value of ΔT for the start of 1902 was approximately zero; for 2002 it was about 64 seconds. So the Earth's rotations over that century took about 64 seconds longer than would be required for days of atomic time. As well as this long-term drift in the length of the day there are short-term fluctuations in the length of day (Δτ) which are dealt with separately.
  • 695
  • 01 Nov 2022
Topic Review
ZnO Nanostructures
Zinc oxide (ZnO) nanostructures are structures with at least one dimension on the nanometre scale, composed predominantly of zinc oxide. They may be combined with other composite substances to change the chemistry, structure or function of the nanostructures in order to be used in various technologies. Many different nanostructures can be synthesised from ZnO using relatively inexpensive and simple procedures. ZnO is a semiconductor material with a wide band gap energy of 3.3eV and has the potential to be widely used on the nanoscale. ZnO nanostructures have found uses in environmental, technological and biomedical purposes including ultrafast optical functions, dye-sensitised solar cells, lithium-ion batteries, biosensors, nanolasers and supercapacitors. Research is ongoing to synthesise more productive and successful nanostructures from ZnO and other composites. ZnO nanostructures is a rapidly growing research field, with over 5000 papers published during 2014-2019.
  • 479
  • 07 Nov 2022
Topic Review
Zisman Plot
The Zisman plot the graphical method of the Zisman theory or the Zisman method for characterizing the wettability of a solid surface , named for the American chemist and geophysicist, William Albert Zisman (1905–1986). It is a prominent Sessile drop technique used for characterizing liquid-surface interactions based on the contact angle of a single drop of liquid sitting on the solid surface.
  • 510
  • 24 Nov 2022
Biography
William C. Schwartz
William C. Schwartz (March 25, 1927 – July 23, 2000) was a civic leader in Central Florida and a pioneer in the laser industry. He was founder, President and Chairman of International Laser Systems, Inc., and later, Schwartz Electro-Optics, Inc., both based in Orlando, Florida. Schwartz was born in Lexington, Missouri. He attended Wentworth Military Academy in Lexington, then went on to earn a
  • 212
  • 08 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
  • 409
  • 08 Dec 2022
Biography
Willi A. Kalender
Willi A. Kalender (born 1 August 1949) is a German Medical Physicist and Professor and Chairman of the Institute of Medical Physics of the University of Erlangen-Nuremberg.[1] Kalender has produced several new technologies in the field of diagnostic radiology imaging. Kalender is a Fellow of the American Association of Physicists in Medicine (AAPM) and Honorary Fellow of the British Institute o
  • 391
  • 13 Dec 2022
Biography
Wilhelm Hanle
Wilhelm Hanle (13 January 1901 – 29 April 1993, Gießen) was a German experimental physicist. He is known for the Hanle effect. During World War II, he made contributions to the German nuclear energy project, also known as the Uranium Club. From 1941 until emeritus status in 1969, he was an ordinarius professor of experimental physics and held the chair of physics at the University of Giessen.
  • 355
  • 18 Nov 2022
Topic Review
White–Juday Warp-Field Interferometer
The White–Juday warp-field interferometer is an experiment designed to detect a microscopic instance of a warping of spacetime. If such a warp is detected, it is hoped that more research into creating an Alcubierre warp bubble will be inspired. A research team led by Harold "Sonny" White in collaboration with Dr. Richard Juday at the NASA Johnson Space Center and Dakota State University are conducting experiments, but results so far have been inconclusive.
  • 2.3K
  • 24 Nov 2022
Topic Review
Weight
In science and engineering, the weight of an object is the force acting on the object due to gravity. Some standard textbooks define weight as a vector quantity, the gravitational force acting on the object. Others define weight as a scalar quantity, the magnitude of the gravitational force. Others define it as the magnitude of the reaction force exerted on a body by mechanisms that keep it in place: the weight is the quantity that is measured by, for example, a spring scale. Thus, in a state of free fall, the weight would be zero. In this sense of weight, terrestrial objects can be weightless: ignoring air resistance, the famous apple falling from the tree, on its way to meet the ground near Isaac Newton, would be weightless. The unit of measurement for weight is that of force, which in the International System of Units (SI) is the newton. For example, an object with a mass of one kilogram has a weight of about 9.8 newtons on the surface of the Earth, and about one-sixth as much on the Moon. Although weight and mass are scientifically distinct quantities, the terms are often confused with each other in everyday use (i.e. comparing and converting force weight in pounds to mass in kilograms and vice versa). Further complications in elucidating the various concepts of weight have to do with the theory of relativity according to which gravity is modeled as a consequence of the curvature of spacetime. In the teaching community, a considerable debate has existed for over half a century on how to define weight for their students. The current situation is that a multiple set of concepts co-exist and find use in their various contexts.
  • 1.4K
  • 19 Oct 2022
Biography
Watt W. Webb
Watt W. Webb is known for his co-invention (with Winfried Denk and Jim Strickler) of Multiphoton microscopy in 1990. Professor Watt W. Webb’s undergraduate studies at MIT in Business and Engineering Administration for his SB degree in 1947 led him to engineering research and development at Union Carbide Corporation Research Laboratories until 1952, then back to MIT for his ScD in Metallurgy
  • 289
  • 12 Dec 2022
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