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The IUPAC numerical multiplier is a system of prefixes used in chemistry to indicate the number of atoms or groups in a molecule.
In the following prefixes, a final vowel is normally dropped before a root that begins with a vowel, with the exceptions of bi-, which is extended to bis-before a vowel; among the other monosyllables, du-, di-, dvi-, and tri-, never vary.
Pentaerythritol tetranitrate (PETN), also known as PENT, pentyl, PENTA (ПЕНТА, primarily in Russian), TEN (tetraeritrit nitrate), corpent, or penthrite (or, rarely and primarily in German, as nitropenta), is an explosive material. It is the nitrate ester of pentaerythritol, and is structurally very similar to nitroglycerin.
Pentation is the next hyperoperation (infinite sequence of arithmetic operations, based on the previous one each time) after tetration and before hexation. It is defined as iterated (repeated) tetration (assuming right-associativity).
The "k" is the unit prefix for kilo-or thousand with the suffix "yr" simply an abbreviation for "year". Occasionally, the "k" is shown in upper case , as in "100 Kyr"; this is an incorrect usage. "kyr" itself is often considered incorrect, with some preferring to use "ky".
"SNL50: The Anniversary Special" aired on Sunday to celebrate 50 years of "Saturday Night Live." The star-studded event featured live performances, sketches, and references to current events.
Pentaerythritol was first reported in 1891 by German chemist Bernhard Tollens and his student P. Wigand. [5] It may be prepared via a base-catalyzed multiple-addition reaction between acetaldehyde and 3 equivalents of formaldehyde to give pentaerythrose (CAS: 3818-32-4), followed by a Cannizzaro reaction with a fourth equivalent of formaldehyde to give the final product plus formate ion.
The University of Hawaii's asteroid impact alert system captured the motion of asteroid 2024 YR4 over the course of one hour on December 27. - ATLAS/University of Hawaii/NASA/AP