NYCadAdept's New Writeups

hexadecimal (idea)

2002-08-28T20:38:47Z

On a seven segment display the hexadecimal characters can be displayed thusly:

 _      _   _       _   _   _   _   _   _              _   _ 
| |  |  _|  _| |_| |_  |_    | |_| |_| |_| |_   _  _| |_  |_ 
|_|  | |_   _|   |  _| |_|   | |_|  _| | | |_| |_ |_| |_  |

Simple enough, eh?

I once ran across a microcomputer training manual, (If memory serves, it was distributed by Ampex.) that claimed the correct way to display the hexadecimal characters was as follows:

 _      _   _       _   _   _   _   _              _        
| |  |  _|  _| |_| |_  |_    | |_| |_| |_   _  _| |_ |_|   |
|_|  | |_   _|   |  _| |_|   | |_| | | |_| |_ |_| |  | | |_|

The explanation was that this eliminated the possibility of confusion when viewing an inverted display. I dismissed this as unique and amusing lore, until I encountered a customized Control Data Corporation, FDS disk drive.…

Control Data Corporation (thing)

2002-08-28T19:50:56Z

Founded in 1957 by William Norris, and Seymore Cray. CDC built some of the first `super computers'; among them, the CDC 6600 and CDC 7600. They were also players in academic computing and peripherals. In the 1960's CDC diversified into data processing and financial services. Cray left the company in 1972 and founded Cray Research the next year. Norris retired from the company in 1986. In 1992 after considerable financial difficulties the company was renamed Ceridian Corporation,and spun-off its computer business as Control Data Systems,Inc.

There is a good history of CDC at: http://www.digitalcentury.com/encyclo/update/cdc.html

Dermabond (thing)

2001-12-26T18:13:22Z

Dermabond is the Johnson & Johnson brand name for 2-Octyl Cyanoacrylate, a topical skin adhesive. It can be used to close surgical incisions, and wounds where there is little tension on the skin. It is an excellent replacement for sutures or staples in some circumstances.

Dermabond comes in a single application ampul and is applied over the wound, in two or three coats, while the incision is held closed. It will dry to a flexible seal in about a minute

Some of the advantages of using this method to close wounds are:

Affords good closure in awkward areas. (i.e. sides of fingers, etc.)
Forms waterproof seal over wound.
Quickly applied and less painful than sutures. (This is of particular value when the patient is a child.)
Does not require follow-up by a medical professional for removal.

Disadvantages:

Limited resistance to

…

Cassini gap (thing)

2001-06-14T00:38:31Z

Gap in the rings of Saturn produced by the instability of nearby orbit; caused by the 2:1 orbital resonance with the moon Mimas.

orbital resonance (idea)

2001-06-14T00:28:35Z

The ratio between the orbital periods of two bodies. Expressed as a dimensionless ratio > 1. Alternately: The inverse of the ratio the orbital frequencies. Whole number orbital resonances with large bodies are often unstable, owing to undue gravitational influences. In the asteroid belt there are gaps corresponding to certain whole number orbital resonances with Jupiter: i.e. 2:1, 3:1, 5:2, 7:2. The Cassini gap appears in the rings of Saturn, produced by an orbital resonances of 2:1 with the inner moon Mimas. As Grzcyrgba points out, the nearly 2:1 orbital resonance between Europa and Io is responsible for the tremendous tidal forces that cause Io's volcanism.

Trojan asteroids (thing)

2001-06-13T22:37:32Z

A group of a few thousand asteroids that travel in roughly the same orbit as Jupiter. They occupy the L4 and L5 Lagrange points of the Sun-Jupiter system. As such, they have a 1:1 orbital resonance with Jupiter. The L4 and L5 Lagrange points are stable, meaning that any body occupying these points will tend to return if disturbed by a small enough impulse. The name Trojan, refers to the fact that all these asteroids are named after heroes from the Iliad: Achilles, Hector, Odysseus, etc.