23 November, 2009

A city in 140 symbols: Leeds

Leeds has a redbrick university built out of white bricks. But if you look for a good weather in Britain – better go to the south of France.

21 November, 2009

The Hirsch-bar index: leave your boss' name out of the authors list

I think you know what the Hirsch-index is: if you have n papers cited at least n times – then your h-index is n. For instance, if out of your 10 papers two were cited 4 times, and the rest three times, then your h-index is 3. The index was introduced by Jorge Hirsch in 2005, and became an accepted tool to rank scientists within about one year: community found it useful that a scientist's productivity may be described by a single number. However, the h-index does not take into account such important things as the number of co-authors and the self-citations.

Recently Jorge Hirsch himself wrote a preprint, where he proposed a new, ħ (hbar) - index, that is aimed to solve at least one of these problems, multiple co-athorship. Indeed, the "mass graves" (sorry), published by high-energy physicists and the institute policies to include everyone's name to any article, can unreasonably increase the Hirsch-index, with no extra work.

Some of the h-index terminology before describing the ħ-index. You have the h-index n, if n of your papers belong to the "h core". The paper belongs to the h-core if it was cited n times or more. Your co-authors will probably have other h cores, and a given paper may belong there or not.

ħ - index is defined in a similar way: you have the ħ - index m if m of your papers belong to the ħ-core. But, the paper belongs to the ħ-core if it was cited m times or more and it also belongs to the h-core of your co-authors. (Actually, the latter h should be also ħ, but since the index would be extremely difficult to compute in this case, Hirsch decided to relax the condition a bit)

In other words, only if the paper improves the h-index of all the authors, it will contribute to your ħ-index. Imagine that you have the h-index of 20, and you have a paper cited 25 times, co-authored by a student with a h-index of 5. Then, it will be included in your and the student's ħ-index, because it belongs to the h-cores of both of you. But, if you add a third author to this paper, say, a director of your institute with a h-index of 45, the paper will not count for any of you, because it doesn't belong to the director's h-core.

So, if you have 200 papers, cited 44 times each and co-authored by your director, who has the h-index of 45, none of them will count, and your ħ-index will be zero. Hirsch expects this to stimulate young scientists to work independently. However, he mentions, that the ħ-index will be definitely useless for postdocs, since they are used to include senior scientists in their papers.

I wonder whether it will be possible to eliminate self-citations at some point.

20 November, 2009

Theorists vs experimentalists again

Here is how I imagine the difference between experimental and theoretical particle physicists:

Left: Blind Reese can't spot the cheese. Right: Neither Phil can get a meal.

19 November, 2009

The LHC will be launched tomorrow

You may follow it online: here is a live display of the beam status. You may also follow CERN on twitter.

via cherstn (friends-only)

17 November, 2009

Another case of scientific fraud

The ETH Zürich research director Peter Chen decided to step down by the end of September after being accused of data falsifications:

"The institute made the announcement in a press release issued 21 September, saying 'there are suspicions that scientific data may have been falsified in two publications and a doctoral thesis in 1999 and 2000' while Chen was group leader. A panel of five chemists was formed earlier this year to investigate, confirming data had been falsified."

Chen will remain a full professor at ETH.

13 November, 2009

A city in 140 symbols: Frankfurt an der Oder

The Oder river separates Frankfurt from Polish town Słubice. Caravans of German smokers cross the bridge to buy cheap Polish cigarettes.

12 November, 2009

Who cites you is important: a new approach to ranking scientists

We are used to such metrics of a scientist's impact in a field like the number of papers published, how many times they are cited, and the h-index that the scientist has. These parameters are expected to rely on credit given to the researcher by the rest of community. However, they don't account for the important thing, namely who cites the published work.

In a paper recently published in Phys. Rev. E, Filippo Radicchi with colleagues propose a new ranking technique that captures this "who" issue: the citations coming from renowned scientists have more weight than those from less known researchers. The authors focused on physics and used the PROLA journal archive (1983-2006) as a testing ground for the methodology. The results show that the probability to win a major physics prize is more accurately predicted by their new method, than by the other metrics, such as citations count.

The only thing is probably missing here – the "negative" citations. The results may be cited as "doubtful" or "wrong" even by famous scientists, and the trustless paper will be scored higher. However, in the case of a scientist's rank, averaging over all his papers will probably make this contribution negligible.

Here is a website where you may figure out a rank of any scientist, based on his articles in physical review journals published before 2006. This piece of work was also highlighted in Physics.

09 November, 2009

Vitaly Ginzburg Dead at 93

Nobel Laureate Vitaly Ginzburg deceased yesterday due to heart failure. Apart from theoretical physics, he was renowned as an outspoken atheist and irreconcilable antagonist of religious obscurantism. Even being already seriously ill some two years ago, he wrote:

"...I'm 91 years old and suffer from an incurable blood disease, for that reason I cannot walk since about three years ago; I also have another difficulty that I don't feel like describing here. Passing through it would be probably much easier with a belief in God. But, until I'm in full possession of my faculties, I will never address to the mythic God. I would like to emphasise that the illness has no affect on my writings, and I ask my opponents to make no allowances for me..."