search
Wednesday, 2020 February 12, 16:57 — prose

a sense of place?

I read Jack Vance’s memoir, of which many pages say “We went to Ireland / Tahiti / Kashmir . . . found a pleasant cottage and stayed there for a couple of months, cranking out stories.” It would be pleasant to know what was written where! Perhaps Jack himself did not remember. But it is impossible not to imagine that “The Moon Moth” was conceived on the houseboat in Kashmir.

Thursday, 2019 November 28, 19:51 — mathematics

it’s in the literature

On a truncated icosahedron / buckyball / Telstar-style soccer ball, consider two adjacent hexagons and the two pentagons that are adjacent to both. These four faces can be removed, rotated by a right angle, and reattached, causing only a small change to the overall shape. Most fullerenes have at least one such patch.

If I ever get around to making more printable models of fullerenes, I would omit those that can be changed, by the above twist, into one of higher symmetry. I have a pretty good idea of how I’d go about listing the fullerenes and finding their siblings; but I do not have a grip on distinguishing symmetry groups of the same order – e.g., that of the regular tetrahedron versus that of a hexagonal prism – and a subgroup of one may not be a subgroup of the other.

So I got out An Atlas of Fullerenes in the hope of understanding how they did it – and happened to open to a chapter I had not looked at before, which covers the Stone-Wales transformation (for so it is named) and lists, up to C50 (15 hexagons), which fullerenes change with which.

The 812 smallest fullerenes are thus cut to 72 in 47 families. The biggest of these families has six remaining members, four with C2v symmetry (one axis of twofold rotation, and a reflection plane containing that axis) and two with C3 symmetry (chiral with one threefold axis). Their symmetry numbers are 4 and 3 respectively, but as C3 is not a subgroup of C2v I keep them all.

Surprisingly the ten families of C50 include two with no nontrivial symmetry at all.

Wednesday, 2019 July 24, 09:24 — merch

I ain’t Zazzling any more

You probably haven’t noticed the absence of a link in the upper left, “buy 2D printed objects”, which went to my catalogue on Zazzle: shirts, mugs, posters. ( . . more . . )

Tuesday, 2019 June 4, 17:11 — blogdom, me!me!me!, neep-neep

all the world’s a wiki

I toy with the thought of converting this here website to MediaWiki (which my host supports), as I am more efficient at editing there than at writing raw HTML in vi.

The wiki’s first articles would be:

  • Two-dimensional design
    • Hyperbolic tilings
    • Arrangements of the color gamut in the plane
    • Curve-fitting
  • Three-dimensional design
    • Ray-tracing
    • Solid printing
  • Posthuman speculation
  • Political speculation
  • Linguistics
    • Diachronics
    • Writing
    • Conlang

I’d continue to report new thoughts here, and then integrate them into appropriate articles. I wonder whether MediaWiki and WordPress play well together. I’m not aware of any personal website that combines blog with wiki, but it seems unlikely that nobody does it.

And now I wonder whether a wiki on my home box would help me keep track of the little files I write as notes on this topic or that, and the PDFs that I download to read someday, and the

Friday, 2019 April 26, 19:45 — general

BJ

Mom died today.

She was a better friend to more people than I’ll ever be.

Sunday, 2019 March 10, 21:15 — merch

a token creation

I got a notice from Zazzle that if I don’t post at least one new product in every fifteen months they’re going to charge me a Non-Contributing Account Fee. So here’s one. I can spin more variations on this theme until the cows come home.

Wednesday, 2019 February 27, 13:57 — me!me!me!, medicine

vision imperfect

This morning I saw a series of flashes (both bright and dark) in my left eye, along a peripheral arc. They’ve stopped for now but I also have some new floaters. I have a recurring urge to clean off the spectacles I’m not wearing!

« Previous PageNext Page »