Notes from the biomass

Even amongst programmers, the semicolon has a hard time. Newer languages in the C-tree such as Python and Ruby have no use for it and mirror its unfortunate demise in the literature and journalism. Its wikipedia entry is already shorter than the ampersand’s if you need hard evidence.
I like the semicolon; when I started writing papers, I tried to squeeze at least one in every piece of work. The few that survived the review of my peers were usually removed by the editors of the journals. I almost forgot about it and was touched when I discovered it again brushing up my touch typing skills (lower row, middle finger on a German keyboard).
Now, the NYT reports the re-emergence of the written-off punctuation mark in the subway. There is hope and nothing will hold me back to inflict it on my readership. Brace for impact!

Everyone is using tiling arrays these days but the quality of results is still hard to judge even for the most experienced people in the field. Designs differ in type of the oligo density, oligo length, selection algorithms and experimental procedures. On top of that, several analysis procedures claim to be superior over each other. Eight groups performed independent evaluations of tiling arrays for the human genome from the major vendors (Affymetrix, NimbleGen and Agilent) and report their findings in Genome Research, on February 7th, 2008. As the scientists had no knowledge about the PCR products that were spiked in the sample, this is an blind evaluation and thus much more powerful than the typical validations using real time PCR.

The overall results are a sobering: only 50% of the sequences selected were consistently detected at10% FDR. This is not to be taken literally as the majority of the missed samples were present in low numbers only (1.25 to 4 fold) and we do not have good data for the true fold changes in these experiments.

All three vendors supported this study and employ a good number of the authors. In that light, it is no surprise that the study does not report major quality differences between the chips. They do report that Affymetrix arrays require more repetitions to reach the same quality of the results but are of lower price (conveniently tabulated in the paper). No method performs well in the low concentration regime, although Agilent and Nimblegen arrays look a little better at it. I certainly don’t want to imply that the affiliations biased the results of this study (this is the internet after all). On the contrary, this is a very useful collaboration between chip vendors and technology leaders in academia. But read it before the next sales person in the chip business knocks on your door or you want to build trust in a particular data set.

Lars Juhl Jensen is one of the most prolific people in computational biology. A fellow scientist once said enviously: “The worst thing about him is that he is even a nice guy”. (I don’t find that particularly bad but there you go.) Lars has recently decided to post the crumbs that fall from his notebook in his blog “Buried treasure”, which you should add to your feed reader if you are but barely interested in bioinformatics.

[via Konrad]

Giving good presentations is easy. I have read all about it, practiced it many times and even won a presentation contest against half of the info elite of Berlin (n=10, once). Surprisingly, I occasionally find myself in front of an audience stuttering and apparently inept to close a single sentence appropriately. I appear to be utterly unprepared even when this is the seventh time I tell my little story about bugs and yeasts. As presenting ones work will be a regular activity of the rest of my life, I’ve been asking myself what to do about it for some time and found a little trick that has done me well often (n=3).

Listening to colleagues or seeing a scientist at conferences again and again, it seems that many people’s presentation skills vary dramatically by time, too; hence the hope that this post will reach others could put it to use.

It’s no secret: You need to start your delivery on the strong end, not only is it the first impression that your audience gets of you (or your colleagues of your new idea). Often enough, I find my grip only halfway through the slides. Even more importantly, sentences flow easily if the first three of five are on target. However, those are often the hardest and one typically starts presenting after sitting silently in an auditorium for hours or following up on the good ideas that you had while preparing the talk.

Therefore, I am trying to get a flying start whenever I can by grabbing an unsuspecting subject that doesn’t talk back too much and start an abbreviated presentation one-to-one without the slides just outside the lecture theater or seminar room. Science conferences typically have a session chair that you can finally put to use if there’s a coffee break before your talk but you can just as well coerce an interested student into receiving an advance on your presentation. You just need to reset the presentation but instead of having waited anxiously at the start of your talk, you have practised, have your head in the subject or vice versa and you will have remembered how to make audible sounds with your mouth. The transition were rather smooth and its an good way to beat the stage fright. Just keep talking.

Next: The importance of regular posts for the success of your blog.