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2008 February 01

Logic Elements
New p5 Herschel technology

reduced p5 fountain for Lx73 Herschel conduit
Scot Ellison's smaller p5 fountain
for the p5 73-step Herschel conduit
Scot Ellison's search for a smaller p5 oscillator to support the 73-step Herschel conduit was successful, back in May of last year -- though he says that even smaller, perhaps asymmetrical, sparkers are likely to exist.

This smaller p5 fountain is included in an updated version of Hersrch, Karel Suhajda's Herschel-track search and construction program.

adjustable p5 conduit and period doubler
Adjustable p5 tandem-glider conduit
Another p5 Herschel conduit that showed up in 2007 was an adjustable diagonal track in which two gliders to travel an arbitrary distance diagonally between a transmitter and a receiver, similar to Paul Callahan's stable "tandem glider" circuits. It's constructed from known pieces: a stable converter that produces two gliders on the same lane from an input Herschel, and a p5 "doubler" that produces one output glider and/or Herschel from each pair of input gliders.

The circuit's p5 limitation is somewhat mitigated by its reversibility -- there are two mirror-image ways to receive the two gliders, whereas most tandem gliders need either a left- or right-handed receiver. (Some pairs of gliders with two-cell separation, usually produced with the assistance of a boojum reflector, can be received ambidextrously by standard receivers -- but this significantly alters the timing of the circuit.)

Depending on the position of the block, either of the two gliders can be chosen to trigger the Herschel output, while the other one resets the circuit. The circuit can also be hooked up to any glider output of a Herschel track for use as a period doubling fanout device, or a two-state track switch (two circuits on two glider outputs with alternating block positions).

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2007 December 17

Discovery
New 180-degree glider reflector, period 4 and up

2007-12-16-reflector-pN.rle
p6, p7, p8, and p22 versions of Noam Elkies'
spark-assisted glider reflection reaction,
with a previously-known p15 'kickback simulator'
included at the far right for timing comparisons.
From patterns by Jason Summers, 5-6 October 2007.
Noam Elkies responded to the challenge of finding a period-4 glider reflector by designing a new type of 180-degree reflector based on a spark-assisted block reconstruction. Jason Summers built a faster version at p22 (upper right), which produces a glider on the same path two ticks earlier.

The original reflection reaction can work at higher periods; variants are shown at right with p6, p7, and p8 sparks. The reflection path is the same as a kickback reaction, but the timing is different. By comparison, a pentadecathlon-based kickback emulator (far right) is four ticks faster -- or four ticks slower, since timing can be adjusted mod 8 by changing the reflector's location.

2007-12-16-Lx134-p8-and-p4.rle
Lx134 conduit, p8 and p4 versions -- recovery times 172 and 292
Reflector by Noam Elkies, 15 Nov 2007, improved by David Eppstein
David Eppstein contributed a p4 oscillator that could accomplish the same catalysis as the p22 oscillator above; improved versions are shown in the period 4 and period 8 reflectors at right, cleaning up the extra debris in an Lx134 conduit.

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2007 March 03

Logic Elements
New Herschel Conduit Discoveries

2007-03-03-H-to-Boat.rle
Herschel-controlled glider demultiplexer
Brice Due, 23 August 2006
Last August, Brice Due ran some interesting searches with Paul Callahan's catalyst search program, ptbsearch. His first discovery was a compact 'demultiplexer' -- a Herschel-to-boat converter where the boat can be used to reflect a glider. Unlike previously known Herschel-to-boat converters, the glider has a clear path through the circuit if the boat is not present:

2007-03-03-Herschel-F171.rle
F171 Herschel conduit discovered by Brice Due on 31 Aug 2006
The next discovery was a previously unknown F171 Herschel conduit -- the first new addition to the elemental Herschel conduit list in almost eight years:

2007-03-03-HtoG22NWpath18.rle
glider #22: Brice Due, 2 September 2006
Another unrelated ptbsearch discovery was a Herschel-to-glider converter, #22, with a new output lane:

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2005 November 26

Logic Elements
New P7 sparker

weak P7 sparker

P7 oscillator with a weak spark (glider deletion due to David Eppstein)

Toward the end of October, Scot Ellison published a new oscillator with a weak P7 spark:

Though no uses have been found for this particular pattern as yet, oscillators that can delete gliders can sometimes be useful for specialized signal processing. One example is in low-period Herschel conduits. The FNG (first natural glider) released by a moving Herschel is often the key factor determining the allowable "compression" of a circuit: a second Herschel can't pass through most conduits until after the glider from the previous Herschel has gotten out of the way. In some cases, an oscillator can "reach in" slightly and delete a glider more quickly, or in a tighter space, than a still-life eater can manage.