I'm watching the periphery of this, having just taught something about The Sixty-Five Space Groups a few days ago, but my impression is that you guys have too much time on your hands. If you'd like something really interesting (and perhaps useful) to spend your time on, let us know. We'll put you to work.
BS ________________________________________ From: CCP4 bulletin board [[email protected]] on behalf of Ian Tickle [[email protected]] Sent: Friday, May 02, 2014 7:42 PM To: [email protected] Subject: Re: [ccp4bb] Confusion about space group nomenclature Bernhard On 2 May 2014 21:51, Bernhard Rupp <[email protected]<mailto:[email protected]>> wrote: Nonetheless, this does not necessarily discredit my quest for a descriptive adjective, and the absence of such after this lively engagement might indicate that the question was not quite as illegitimate as it might have appeared even to the cognoscenti at first sight. Nonetheless, a toast to Sohncke! I second that, but while not intending in any way to belittle Sohncke's contribution to the subject, I would point out that Sohncke is a noun (of kind "proper noun") and most definitely not an adjective (of any kind). I say that because I have been working all along on the assumption that your quest was for an adjective (i.e. as you say above, a descriptor of a noun). In the English language at least, adjectives come in 5 different flavours: 1) attributive ("the good book"), 2) predicative ("this book is good"), 3) absolute ("this book, good though it is, won't win the Booker", 4) nounal adjective ("the good, the bad and the ugly"), and 5) postpositive (adjective follows noun: mostly archaic usage in English though common syntax in other languages). Of course nouns can also function as adjectives ("adjectival noun") but only in a very limited way. In particular nouns can only function as attributive adjectives ("a Sohncke space group"). You can't use a noun as a predicative adjective ("this space group is Sohncke" just doesn't sound right), or use an adjectival noun in any of the other 3 ways; it can only function as the attribute of another noun. A true adjective can be used in all 5 ways without breaking the syntactical rules, e.g. the attributive "a centrosymmetric space group" and the predicative "this space group is centrosymmetric" are both valid syntax (I hesitate to use the "e" word again having had it ruled totally out of contention). Exceedingly descriptive though it is, "chirality-preserving" is technically also not an adjective (it's an adjectival phrase), though of course that's no reason to rule it out. Some proper nouns (mostly names of mathematicians for some reason!) have been transformed into real adjectives (e.g. "Hessian" in honour of Ludwig Otto Hesse, "Wronskian" for Józef Hoene-Wronski, and several others). Sadly Sohncke is not one of those in common, or indeed any, usage in adjectival form (I would hesitate to suggest "Sohnckian" as the adjective derived from the proper noun). As an aside, strangely many of these name-derived adjectives have made the reverse journey and now double as true nouns themselves, having dropped the nouns to which they were originally attached. "Hessian" as a true noun (i.e. not even a nounal adjective) is of course now used in preference to and is a synonym for the original "Hessian matrix", "Wronskian" is used instead of "Wronskian determinant", etc. Enough of this drivel. You can tell it's the weekend, and that none of us have anything better to do ... Cheers -- Ian
