Mathematical Musings

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Quick book recommendation
2007-07-26 18:46:00
This summer, I've got an undergraduate research bursary at our university's Systems Biology centre, which is wierd as I always viewed myself of more of a pure mathematician, but is absolutely fascinating.I have jumped in at the deep end, however (my supervisor seems to think I know a lot more than I really do and maybe hasn't realised I haven't done any serious integration/differentiation or ODEs stuff since the first year...).What I'm actually doing is looking at the response of Neurons to different types of presynaptic noise, which I am slowly learning more about. In particular, noise is random (well, duh) and so all of the models I end up with have Stochastic Differential Equations, which are typically quite unpleasant. For those interested, the toy models I'm playing with end up with Brownian motion in a harmonic potential.So the book I'm recommending is:Paul and Baschnagel, "Stochastic Processes, From Physics to Finance"Don't let the reference to finance put you off - I...
More About: Book , Quick , Recommendation , Dati

Fun with xorg.conf
2007-07-06 00:53:00
So I've finally got my ALPS / Synaptics touchpad working along with a compose key on debian (the ALPS touchpad comes with, among many other laptops, the Dell Inspiron 500m which I own).The touchpadFor the touchpad, I need to thank this walkthrough along with this forum thread.Before anything will work, you need to make sure that the evdev module is being compiled in your kernel (it wasn't) and is being loaded (that bit worked for free for me, but one comment on the above forum post suggested you needed to add it to /etc/modules). You can find the option under Device Drivers/Input Device Support/Event Interface in the kernel config (e.g. make menuconfig)Now you need to edit your xorg.conf (found in /etc/X11). There are three things that you need to do:Load the synaptics moduleAdd a new input device to ServerLayoutDeclare the input deviceIn order to load the synaptics module, add a line saying: Load "synaptics"to the "Module" section. Mine now looks like:Section "Module" ...
More About: Xorg

Backing up your home to DVD with debian
2007-06-13 14:13:00
I've finally got a DVD writer (external - it's a laptop) and it works quite amazingly well: no setup issues at all!Now, the whole point of the exercise was that my Dell is getting a little dodgy (you have to press down hard around the power button to flex the PCB below in order to get it to boot!) and I wanted to back up my documents, sourcecode, emails etc. in case the worst should befall my poor old laptop. But I had a German exam the next day, and while I was burning the DVD I should also be revising!In general, burning a data DVD on linux is easy. You get a copy of mkisofs and growisofs (on debian, this is easy: apt-get install dvd+rw-tools mkisofs). Then you call mkisofs on a directory tree to create an iso image (put it in /tmp!) and growisofs to write the lot to your DVD (I got the instructions hereAhah, but not so fast! I wanted to do my home directory whilst xfce, claws-mail, firefox and probably a whole load of other processes were writing tiddly little bits to all my hi...
More About: Home , Debian , Backing

Ical subscriptions with orage
2007-06-07 02:34:00
Orage looks to be an exciting program for my new Xfce desktop, but what good's a calendar if it can't subscribe to ical feeds from the internet?! Fortunately, I'm supposed to be revising at the moment, so have had an urge to hack code together...And so we present a simple shell script to download .ics files periodically from the internet to your filesystem. The one nifty feature is that if the internet's down, this won't blat the current copies as using wget blindly would, which should be useful with my laptop.There are probably more sophisticated systems, but I was going for the 25 minute job option. Firstly, we need a list of feeds - mine looked something like this:## Lines must be either urls, blank, or start with a #.# UK holidayshttp://ical.mac.com/ical/UK32Holi days.ics# NASA Space Missionshttp://ical.mac.com/tonyfarley/Sp aceMissions.ics# Astronomical Eventshttp://hewgill.com/astrocal/astroca l.icsThe lines beginning with hashes really are comments - they get stripped by th...
More About: Subs , Subscriptions

Tree display program (update)
2007-05-13 17:27:00
Well, I handed in a rather inconclusive version of the essay I mentioned. It and the program used to generate the trees are both here.I'd love it if anyone found the program useful - and anyone's more than welcome to do anything with the code, although I'd appreciate a heads-up out of interest. Enjoy!
More About: Display , Update , Tree , Program , Gram

Copying UTF into Emacs
2007-05-13 16:28:00
It's been annoying me for ages, but I never really got UTF copy/paste working right in Emacs. Finally (procrastinating from German revision) I found a solution that works for copying from Firefox at least.The solution is detailed here and I'm eternally grateful. Basically, just put the following code somewhere in your .emacs:(setq x-select-request-type '(UTF8_STRING COMPOUND_TEXT TEXT STRING))And, voila, umlauts (like ö) and I presume strange characters from other languages will appear in all their glory!

Leptonica 1.43 in debian
2007-04-08 19:56:00
What a load of effort! I've been developing a program using leptonica recently, using the debian package without thinking. Irritatingly, however, debian is at version 1.37 and upstream is at 1.43.The good news is that the debian diff still works - to get a quick and dirty install (which is all I'm interested in!) do the following:Download the debian diff from this page.Patch a copy of the current source (from here) using the command:patch from within the directory into which you extracted leptonica.Make the "debian/rules" file executable:chmod 0755 debian/rulesEdit the "debian/docs" file and remove the line with library-notes.txt (it no longer exists in the package)cd into the debian directory and run the commanddch -v 1.44-1(The dch program is part of the devscripts package)Finally, make sure a copy of the original 1.43 tar.gz is in the parent directory with the name leptonlib_1.43.orig.tar.gz and call debuild from the main source directory. Hopefully, it should compile and you'...
More About: Debian , Toni

Tree display program
2007-03-30 22:57:00
I've been writing away at a compulsory second year essay for what seems ages now. In particular, this one's about Goodstein's Theorem. When it's done (which will definitely be before the deadline in 3 weeks' time), I'll see what I can do about posting a version.However, for now, I've been working on a bit in the proof of the theorem. What you need to do is express a number in hereditary base-n notation which is explained on the Wikipedia article I just linked to. Now suppose you draw a rooted finite tree in the following way (let's express 93 in base 2).First note that:Now build a tree one level of branches at a time. In the first level, is a branch for each term in the expansion above. Then a child of each node has children that are the terms in the exponent of that child... It'll make more sense with a picture:I hope :)So what I wrote was a program that would generate that sort of picture because I needed some in the essay and couldn't find something on the internet to d...
More About: Display , Tree , Program , Gram

Latex in Posts
2007-03-30 21:42:00
So the question is whether as posted here will actually work. OK. So I'm impressed :)Now can it work with ScribeFire? I fear not...
More About: Posts , Latex