Passing by

This photo makes me melancholic.

EOS 300D, 28mm fixed lens, (45mm equiv.), f/8, 1/1600s, ISO 100.

A day in the lab: RS 232

Yes RS 232, the humble COM-port. You don't see it on modern computers anymore, USB has superceded it thank god. In the labs though, it is quite another story. Oscilloscopes, flow controllers, mass spectrometers, you name it, if it has been built in the last twenty years or so, and can be controlled by a PC, it will have a COM-port. Maybe a GPIB too, but you can count on the COM-port. And you don't throw perfectly good equipment out just because the standards have changed, not when an oscilloscope will cost you about twenty thousand Euro. Indeed, at the Vienna University of Technology they have an X-Ray flourescence spectrometer that is still faithfully controlled by a PDP-11 (or 12, not too sure)!

Also, RS 232 data transfer is real easy to understand and program, without difficult handshake rituals to go through. But sometimes you can still hit snags, like I did on Monday, when I wanted my student to start writing a program to controll our MKS Pressure controller. No luck, it just wouldn't answer. I checked syntax, the ports on both sides, the cable etc. all working, but no answer from the MKS. The next day I finally found the reason: MKS Instruments are a bunch of greedy bastards.

 The culprit.

You see, in the RS 232 standard, two machines communicate with each other: The DTE (Data Terminal Equipment , normally the PC) and the peripheral device, called DCE (Data Communications Equipment, because originally it was mainly used for modems). The DE-9 connector (your typical COM-port) has nine pins, but in the simplest communication only three are used: pin 5 for ground, pin three for transmitted data (TxD) and pin two for received data (RxD). The other pins can be used for handshake protocols and to speed up data transfer, but since we are transmitting only a couple of characters (close valve, etc.) we don't need to bother with those.

Now who is transmitting and who is receiving? Both of course, because I can ask the pressure controller to report the current pressure to me. But in the standard  it is specified that the DTE (PC) will transmit on pin three and receive on two, and the DCE will do it the other way round.

Now MKS Instruments (and they are in no way alone in this) thought: "Hey, we could make loads of money if we specify our controller as a DTE, so people will have to buy our "special" cable to use it with a PC! I bet nobody will figure that one out, and to make sure, let's hide this in a small footnote in the user's manual."

The cable you have to use to let two DTE's communicate with each other is no overprized "special" cable at all, it is called a crossed or Null-modem cable, older readers may remember it from way back when you would use it to let two PCs talk to each other. If you don't have one, you can make the cross by yourself with a solder iron and two sub-DE 9 connectors. So once I was getting desperate and sat down comparing the pinout in the Manual with the RS 232 specification, it took me about a minute to recognise the problem, and five minutes to solder up the solution:

And hey presto! it works. Take this, MKS! Take it with the day I wasted, and the bitterness of the tears my poor inconsolable student wept when he could not get his program to work.

Public Service Announcement

While it is true in general that the best-before dates are very conservative, and can be ignored in most cases, you are advised to proceed with caution in the case of eggs, especially when you add them to your ramen soup without properly boiling it.
Adding an egg (about 50 cubic centimeters) at fridge temperature to 250 ml of boiling water results in a temperature of 80 degrees centigrade - and the real temperature might even be lower if you add in a cold bowl and room temperature ramen. Not enough to kill any nasties living in the egg, which might upset your bowels.

And how was your weekend?

Fallen Angel

Literally. He (actually it I think, I seem to remember that Angels are supposed to be androgyn) probably got too chubby. Or else playing a flute while flying is the same as being on your cell while driving. But you have to grant it to it (that sounds weird), it is a persistent little bugger. Still fluting away!

Talon

I always, always, always get confused in Vo Vietnam, when they tell us to "laissez vos talons au sol", for example.

In English, talon means first and foremost the claws of a raptor, but it can be used figuratively for the grasping fingers of a greedy archmage as well (I might be slightly influenced by my favourite genre here). This, however, is far removed from the origin of the word - in fact, the French talon (heel) is much closer to the original meaning of the latin root  talus, i.e. ankle.  Since I know the instructors are talking about our feet, I immediatly assume talon->fingers->toes, and get it wrong (incidentally, the toes are called orteilles in French, a word that is much too long and onomatopoaeic unpleasing).

To clear up the confusion, I turned to my new favourite resource, the Oxford English Dictionary (oh sweet manna of definitions, oh ambrosia of etymology - thank you EPFL for buying access!), which says about the english talon:

talon, n.

  I. 1. a. The ‘heel’ or hinder part of the foot of certain quadrupeds, as swine and deer, or of the hoof of a horse. Obs. 

  b. The hallux or hinder claw of a bird. Obs. 

  2. pl. The claws (or less usually in sing. any claw) of a bird or beast. a. spec. The powerful claws of a bird of prey, or of a dragon, griffin, etc. 

  b. The claws (or in sing. any claw) of a wild beast, of an insect, etc. 

  c. Allusively applied to the grasping fingers or hands of human beings. (Cf. CLAW.)

[ME. a. OF. talon heel of a man, or of a shoe, hinder part of the foot of a quadruped = Pr. talo, Sp. talon, Pg. talo, It. talone heel, heel-piece:late pop. L. or Com. Romanic talo, talon-em heel, deriv. form of talus ankle. With the forms talant, talent, cf. ancient, margent, parchment, peasant, tyrant, etc.: see -ANT3. The sense-development shows the stages: ankle; heel of man (of a shoe, etc.); heel or hinder part of the foot of a beast; hinder claw of a bird of prey; any claw (usually in pl. the claws) of a bird, a dragon, an ungulate beast, an insect, etc. The extension to a bird of prey, and subsequent stages, are peculiar to English.] 

Well, there you go. Ankle -> heel -> hindclaw -> raptor claw -> any claw -> fingers. Obvious.

For completeness sake here the french definition of the Larousse (to which the EPFL also provides access. Oh joy, oh... etc.)

talon:nom masculin

(latin populaire talo, -onis, du latin classique talus)

Partie postérieure et inférieure du pied de l'homme, dont le squelette est le calcanéum.

Support placé sous l'emboîtage pour donner à une chaussure son aplomb : Chaussures à talons hauts.

Partie d'un bas, d'un collant, d'une chaussette qui correspond au talon : Bas à talons renforcés.

Extrémité inférieure ou postérieure de certains objets : Le talon d'un ski.

Extrémité d'un aliment qu'on débite en tranches : Talon de jambon.

Partie non détachable d'une feuille de carnet à souches, d'un chéquier.

Être, marcher sur les talons de quelqu'un, le suivre de très près ; l'imiter.

Le talon d'Achille, la seule partie vulnérable de son corps ; le point faible de quelqu'un.

Tourner, montrer les talons, s'enfuir.

There you have it. The point? There is supposed to be a point to my blog-entries?

Propaganda

I've been interested in propaganda posters of the last century lately, in particular the ones from the Soviet Union. I really like their stark style, and their clear black-and-white messages. How much more refreshing than those stupid heads of politicians grinning down on us from contemporary election placards!

To the right you see a typical poster of the House Elf Liberation Front. That was before the ascendency of Comrade Dobby of course, when the HELF was still an underground movement.

Obscure Units, how I hate you

Caution: Research Rant Ahead!I wish I had a time-machine. I would go back in time to 1660, travel to London (maybe the other way round, in fact), burst into the founding of the Royal Society and beat the snot out of them, until they agreed to use the SI and nothing but the SI for all existing and future units, forevermore and until the end of time, but at least until 2009.
For weeks I have intermittently tried to calculate a theoretical breakdown curve, without much success. One of the difficulties (after you have written a program to solve the stupid transcendental equation that laughingly calls itself "breakdown condition") is finding values for the diffusion coefficients, Townsend coefficients and electron mobility in the literature, particulary for the high electrical fields I am using. All those values depend on the electric field over the concentration of your neutral gas, E/N, which is Volts times square metres in good, sensible SI units. But noo, nobody likes using those. Instead, you find Vcm^2, V/(cm torr), V/(m torr), V/(cm mbar), V/(m bar) and my personal favourite, Townsend (Td), which is Vcm^2 x 10^(-17).
Converting all those units is a pain in the ass in and of itself, but the problem is excasperated in that I was using the wonderful little Boltzmann equation solver BOLSIG to calculate my coefficients, and only now found out that BOLSIG expects Townsends, not Vcm^2 as an input. Typical example of garbage in, garbage out - I got diffusion coefficients that were for values 14 orders of  magnitude smaller than I was looking for.

Anyway, this is now resolved, so behold the diffusion coefficients (times N) for argon, from 10 to 10000 (grmbl) Townsend.

Emoticons

Emoticons, I have found, make you a lazy writer.

I don't use many different emoticons, in fact, I only use three:

:)    ;)   :(

But recently I have found myself sprinkling them in my emails and comments with abandon. They are useful - you can indicate a sarcastic sentence with a quick ;), or lighten up a criticism with a :). But you cannot always use emoticons (Dear prospective employer ;), I...), and then there is the pesky parantheses problem.Also, since you can't expect people to know the more obscure ones :-{>, you limit yourself. Furthermore, I think I (and everyone else, are you listening, youtube-commenters? [Commenter - obsolete, or so the OED tells me. Commentator is the word.]) should be able to communicate sufficiently well by writing to impart the more complex emotions without resorting to crutches.  How, I ask myself, can you develop your writing skills when you are making no effort, you idiot ;)?

To be sure, emoticons have their uses, when you are working with a character-limit for example. But I am trying to wean myself off.

Seriously ;)

Drawing

After doing nothing for a long time - I let myself become discouraged by the voltage-measurement disaster - I am now drawing again. I have lessons each Monday evening at a small art-studio called Cordeb'Art, a block from where I live.

Interesting stuff (who knew how much it helps to study and draw anatomy?).

See more drawings (well, more like sketches, really) on the panel on the right, or go directly to my Deviant-Art account.

Flu/cress

Ugh, at home fighting of the flu - hence the lack of posts lately. It might be an Alien flu from Giger's museum!

Can't understand why though, I have been eating all my vitamins. Even some home-grown ones: Cress. My mother used to grow it every winter, and we'd have it on some buttered bread in the evening. Mmmh.

It's very easy to grow: Just some tissues or toiletpaper on a plate, sprinkle the seeds on it and keep wet. In about five to seven days the little plants are thumb-high, and then it is time to harvest them with scissors. Excellent in a salad, or on your bread!

Update:

This is the garden cress, Lepidium sativum.

Giger in Gruyères

Today I spontaneously hopped into my car and drove to Gruyères, which is only about forty minutes from Lausanne. The reason why I did this was not a sudden hankering for the excellent Gruyère cheese, or the fondue made thereof, but rather to visit the HR Giger museum, him of Alien-fame.



The museum is rather excellent, well worth a visit. Unforunately you are not allowed to take any photos, so you'll have to visit yourself. See the entrance to the right, though:

 
Most funny was the "Adult" section, nearly at the entrance. Not in and of itself, but rather the fact that it exists. Most of Giger's works are at least sexually suggestive (not  to mention weird, weird, weird), so it seems like they tried to keep it family-friendly at first. But at some point they must have realised the futility, because as you penentrate (ha!) deeper into the museum, the exhibited works are far "worse" than the stuff in the adult section. I think the curator just gave up...

But Gruyère has other attractions as well: The old town is rather lovely

and there is an amazing Savoyen-style castle:

 And then there is the Giger-Bar:

 where you can slurp your intestine-cocktail of choice, Alien-style!


All in all it was a very nice trip - I think the  countryside might be awesome as well, only the weather conspired against me and shrouded everything in fog & snow.