Er, 'in a rule' should be 'in a room'.

In this context, I meant 'concurrency primitive' as a device used to keep two threads of a program synchronized.

That probably still doesn't make sense to non-coders, so I'll use a real-life analogy:

Imagine a bunch of people arguing in a rule. So that each person's voice can be heard, they make a rule: before someone can talk, they must be holding a 'magic stick'. No stick, no talk. In this way, only one person can be taking at a time.

The 'magic stick' is called a 'mutex' in programming-speak.

No idea how you'd visualise or illustrate something like that, but I'd be interested to see if it can be done :-)

#35, #36: Looking good. Definitely prefer the font from #35.
#37, #38, #39, #40: These look pretty good, but it's not the sort of style that I'm looking for. I'm thinking more conservative/technology-based. Also, no purple :-)
#41, #42, #44, #45: Wow, these look really slick. #41 is my favourite at the moment (colour scheme and layout are great), but the symbol - what does it mean? I need something that is recognizable - "lab beaker" or "sine wave" or "circuit board". I'm not sure how I'd describe the logo on #41. They look really, really nice though.
#46: I like the simple layout, but it's all a bit too cartoony. Try simplifying the symbol.
#47: Again, very cartoony.

More general advice: no more beakers :-) They don't fit the 'conservative, professional' look that I'm after.

Thanks everyone!

Eek, ASCII art didn't work out. Let me know if the above explanation makes no sense!

#27: Looks good!

#28: Yep, that's more like it. The two right-hand ones are the best, with the layout as specified in the brief.

#29, #30, #31, #32: All looking good! My favourite of the bunch is #32. The only suggestions I could make would be on the left-hand side of the logo, bring the horizontal line with the circle down to the centre-line of the text (in line with the right-hand horizontal line). It'd work out something like a heartbeat or sine wave, like:

_
| |
--| | |--
|_|

I'm also curious as to how it'd look with the font from #14, though I suspect that the current font is probably the best.

#33: See the comments for #17 - having the M in the logo symbol tends to be awkward. I'd prefer something abstract or technology based, possibly using the themes that I've mentioned above.

#34: I'm not sure what the symbol is meant to be, but again, taking something from the themes above should work well.

secondgig: Thanks, much appreciated.

Sean: I'd like the basic layout to be roughly as specified in the brief - symbol on the left, text on the right in a single row. I need a fairly distinctive symbol that can be used independently of the text.

#16: Nice idea. Probably don't emphasise the X so much - and again, symbol on the left, text on the right. Symbol needs to be distinctive. A heavier font would be good, too (easier to read).

#17, #18: Interesting, I like the concept. It took me a while to realise that the particle pattern was an 'm', so probably change to something more recognisable. Roughly a 1:1 aspect ratio would be better.

#19: Again, I like the idea, but the font seems a bit awkward. Also lose the HTML brackets and find a better symbol to stick out the front :-)

#21: I don't like the gothic font, but the symbol is good. Something more technical would look better. Also, a bit of shading/highlighting would really show this off nicely.

#22, #25: Definitely too cartoonish for my tastes. Sorry!

Probably the key piece of guidance I can give at this point is 'professional'. I don't want something that looks cartoonish or childish - I want to give a slick, professional, slightly conservative appearance.

Thanks again!

#11, #12: better. The symbols still have a lot of details; remember that they have to be recognisable on business cards.

#13, #14: These are great. Very professional-looking and simple. I like #13 better at the moment, but the symbol isn't particularly memorable. Maybe a waveform of some sort would work - heartbeat, decaying sine wave?

#15: I prefer #6 at the moment, but there's not much in it.

Thanks everyone!

Commentary so far:

#1: I'd prefer something a bit less 'traditional' and more 'modern' and 'high-tech'. High-tech is probably a good theme in general, actually.

#2, #3, #4: I like the general style, although the symbolic logo isn't particularly distinct. The colour scheme on #3 and #4 is good. As another general guideline, the symbol should probably be identifiable on the thumbnail view.

#6: Interesting idea, good to see something suggesting entirely new styling :-) This could work if the bubbling liquid was more distinct and didn't look so much like a party hat when viewed from afar.

#7: The font is good, but the symbol (M) is very much not in the style that I'm after. Less cartoony, more technology/conservative.

#8, #9, #10: Need it to be more sophisticated and conservative. Definitely less detail - those symbols aren't distinct even when zoomed.

Thanks for your submissions so far!