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A portable, advanced sensor based on infrared spectroscopy in a hollow fiber matched to a silicon-micromachined fast gas chromatography column can analyze illegal stimulants and precursors with nanogram-level sensitivity. [2] Raman spectroscopy has been successfully tested to detect explosives and their precursors. [3]
Drug precursors, also referred to as precursor chemicals or simply precursors, are substances used to manufacture illicit drugs. Most precursors also have legitimate commercial uses and are legally used in a wide variety of industrial processes and consumer products, such as medicines, flavourings, and fragrances.
Precursors in the Halo series, an extremely advanced race that preceded and were destroyed by The Forerunners; Precursor, a 1999 novel set in C. J. Cherryh's Foreigner universe; Precursors, a fictional race (now extinct) of ancient beings in the board game Cosmic Encounter; Precursors, a fictional alien race in the Star Control video game series
In chemistry, a precursor is a compound that contributes in a chemical reaction and produces another compound, or a chemical substance that gives rise to another more significant chemical product. Since several years metal-organic compounds are widely used as molecular precursors for the chemical vapor deposition process (MOCVD).
Protein precursors are often used by an organism when the subsequent protein is potentially harmful, but needs to be available on short notice and/or in large quantities. Enzyme precursors are called zymogens or proenzymes. Examples are enzymes of the digestive tract in humans. Some protein precursors are secreted from the cell.
Precursors were first theoretically predicted in 1914 by Arnold Sommerfeld for the case of electromagnetic radiation propagating through a neutral dielectric in a region of normal dispersion. [6] Sommerfeld's work was expanded in the following years by Léon Brillouin, who applied the saddle point approximation to compute the integrals involved ...
The concept has been applied to those who would find precursors of Darwin in the early nineteenth century, [3] and to those who would find anticipations of modern science in ancient cultures from the Near East to Mesoamerica. [4] Precursorism has recently been identified as a significant factor in some studies of the work of Islamic scientists. [5]
These precursors react with the surface of a material one at a time in a sequential, self-limiting, manner. A thin film is slowly deposited through repeated exposure to separate precursors. ALD is a key process in fabricating semiconductor devices , and part of the set of tools for synthesizing nanomaterials .