31 January, 2010

Two quotes from Paul Dirac's letters

I certainly loose it if I don't write it up somewhere. These two quotes picked from letters to Manci Balázs, entirely describe Dirac's childhood:

i) 'I did not know of anyone who liked someone else – I thought it did not happen outside novels', 7 March 1936

ii) 'I found it to be the best policy as a child [...] to make my happiness depend only on myself and not on other people', 9 April 1935

Take care,


30 January, 2010

The Gunning-Fog index

Nature publishing group has a science blogroll with a bit of statistics for each blog, here is how it looks like for mine:
  • Ranked 18 in science (377 overall)
  • 2 post(s) per week (on average)
  • 65 post(s) collected so far
  • 7,032 words per post (on average)
  • 14% complex words (on average)
  • Readability by Flesch-Kincaid : best understood by university graduates
  • Readability by Gunning-Fog : 146.0
  • On 0 blogroll(s)
  • 2 links to other science blogs
  • 0 links from other science blogs
The first thing that crossed my mind was "what the hell this Gunning-Fog index is?". If you follow the link you get that "The Gunning-Fog index [...] is a rough estimate of the number of years of formal education that a person requires in order to understand the text on a first reading."

So, basically an average person needs to study for 146 years to get a rough idea what I'm writing about, while a well understandable text should have the index below 12. First I thought that this is due to appalling English I'm used to, but if you read further you'll see that there is nothing to do with that. The Gunning-Fox index comes from analysis of the average sentence length and the average number of syllables in words.

I never thought those indexes even exist. I promise, I promise to keep sentences shorter... )

Take care,


In fifty words or less

In his book “Indiscrete thoughts” famous Italian-born American mathematician Gian-Carlo Rota mentions that Stan Ulam was used to say “Whatever is worth saying can be stated in fifty words or less”.

Well, these days he would probably adjust it a bit:

“Whatever is worth saying can be stated in 140 symbols or less”


29 January, 2010

True random numbers: linguistics may be of help

I'm completely ignorant in computer science, but even I know that it's tough to get true random numbers. The problem is that any software-based algorithm generates "pseudo-random" numbers, that is there is still some regularity in a row of those, and the sequence will repeat itself after a while.

People are used to get the real randomness from the outside, like picking up the thermal noise of the sound card, the displacements of mouse (that are supposed to be random), or even monitoring the atmosphere. But, there is at least one challenging method to get true random numbers out of the software part.

Let's take a block of English text (say, a .pdf of a paper), written by a native Russian speaker. What is to do, is to analyze the articles "a" and "the" over there. If the correct article is used, we have "1", if not – "0". In such a way, we get a truly random sequence of 1's and 0's, and we can generate true random base-10 numbers out of it.

Is there anyone who wants to give it a try? )

Take care,


A bug in Mathematica: Clebsch-Gordan coefficients

A technical issue for those of you using Wolfram Mathematica. Apparently there is a bug in the function furnishing Clebsch-Gordan coefficients, check it out:

These two inputs are equivalent, but the outputs are different somehow. Actually, this Clebsch-Gordan coefficient is zero, because the angular momentum j=9/2 cannot give a projection of m=0. In general, for a coefficient to be nonzero all the (j+m)'s should be nonnegative integer numbers.

The ClebschGordan[] function in Mathematica is used to test all the conditions of existence, such as the triangle rule, but as we see it fails when it comes to substitutions of parameters.

I dropped a message to the Wolfram support team, and they promised to do their best to figure out where the problem comes from. I hope to hear from them soon and I'll keep you posted about it.

Take care,


22 January, 2010

arxiv.org seeks donations

Keeping it short, the arxiv.org preprints server faced serious problems after significant budget cuts for Cornell university library. The annual budget is as large as $400,000 and the library will provide only 15% of it. The rest is expected to be donated by top 200 heavy user institutions, allowing to keep both submission and downloading of preprints free of charge. Here is the arXiv support FAQ.

21 January, 2010

Fake structures published in Acta Crystallographica

Stop press from the wonderful world of scientific misconduct:

"Regrettably, this editorial is to alert readers and authors of Acta Crystallographica Section E and the wider scientific community to the fact that we have recently uncovered evidence for an extensive series of scientific frauds involving papers published in the journal, principally during 2007. Although several thousands of structures published in Acta Crystallographica Section E every year will continue to reflect results of serious scientific work, the extent of these problems is significant with at least 70 structures demonstrated to be falsified and meanwhile acknowledged by the authors as such...

...The falsified structures have many features in common: in each case, a bona fide set of intensity data, usually on a compound whose structure had been correctly determined and reported in the literature, was used to produce a number of papers, with the authors changing one or more atoms in the structure to produce what appeared to be a genuine structure determination of a new compound. The worst example generated no fewer than 18 supposedly original structures from a single common set of data. There is nothing to suggest that the authors of the original papers describing the real structures are in any way aware of, or complicit in, this fraud...

...The initial set of falsified structures arises from two groups. The correspondence authors are Dr H. Zhong and Professor T. Liu, both from Jinggangshan University, Jian, China. The co-authors on these papers included other workers from Jinggangshan University together with authors from different institutions in China. Both these correspondence authors and all co-authors have signed forms agreeing to the retraction of 41 papers published by Dr Zhong and 29 by Professor Liu. Details of these retractions appear elsewhere in this issue of the journal. Having found these problems with articles from Jinggangshan University, all submissions from this University to Acta Crystallographica Sections E or C have now been identified and are being checked for authenticity. Preliminary results indicate that further retractions will result from this exercise."

Huh, this way they will end up with checking every single submitted structure by hands soon...