Links for 21.12.08

• Politics, South Korea-style by LA Times - recent fight in the Korean parlament

• Physics Textbook by Dot Physics

• Essay: Fifty Years of Condensed Matter Physics

Links for 14.12.08

• Spot the math errors! - some false mathematical proofs. Can you see the mistake?

• Musicians condemn use of their songs as instruments of war by The Guardian - popular songs were used for tortures in Guantanamo. "Some prisoners have said it can be even worse than more traditional methods of physical torture, including waterboarding."

• Burlesque Matinée at the Max Planck Gesellschaft - A good answer to "why is it important to learn foreign languages?"

• Physicsworks - an interesting collection of physics-related links.

• World Lecture Hall - free online course materials from around the world.

You can find many more links I find interesting on my delicious webpage.

The worst ten technology predictions of all time

Were recently published by Mail Online, here they come:

1. BRITAIN DOESN'T NEED TELEPHONES

2. X-RAYS ARE A HOAX
3. THERE WILL NEVER BE A BIGGER PLANE (AND IT ONLY HELD TEN PEOPLE)
4. TV WON'T LAST
5 HOMES WILL BE CLEANED WITH NUCLEAR HOOVERS
6. LETTERS WILL BE DELIVERED BY ROCKET
7. COMPUTERS AREN'T FOR HOME USE
8. YOU'LL ONLY EVER NEED 640KB OF MEMORY
9. WE'LL KILL SPAM IN TWO YEARS
10. THE iPOD WILL BE KAPUT BY NEXT CHRISTMAS

I actually never heard of some of them...

Mendeley - some suggestions

As I mentioned before, I signed up to Mendeley, here is a link to my profile. In this post I just want to mention some improvements, that (I believe) will make Mendeley even more useful than it is now:

1) As I wrote earlier, the metadata transfer for arXiv preprints doesn't work properly.

2) On the one hand, all of us are used to publish arXiv preprints prior to publications, but one should not mix preprints and peer-review journal articles in the CV. Therefore, it will be great if the "preprint" option will be added as an article type.

3) Also, one may want to distinguish "conference proceedings" from "conference abstracts" (which may be also presented as posters).

4) A useful thing might be to add a list of conferences, visited by scientist, with a type of contribution (invited talk/oral presentation/poster) as an option.

5) Looks like a little bug: when I type my location, the list of suggestions appears. But, If I ignore this list and type "Berlin, Germany" by myself (which is exactly the same thing as given in the list), the following message occurs: "Sorry, we don't have details for the location you have entered. Please select one from the drop down list."

6) If I see a green cross near "add entry", I immediately want to click it. But it doesn't work, one has to click "add entry" itself.

I hope these issues may be fixed...

Mendeley

In comments to my recent post Jan Reichelt brought my attention to another academic collaboration tool, called Mendeley. The idea is a bit different from those of 2collab, and therefore one cannot directly compare these two things. While 2collab is a bookmarking tool, dealing with articles somewhere in the web, the heart of Mendeley is an online library, where you can upload and organize your .pdf files. You can also create your profile with CV and publication list, as well as join different groups. The online library can be synchronized with files on your computer using the offline tool, Mendeley desktop.

Surprisingly enough, Mendeley correctly reads almost all the metadata from .pdf's. However, it doesn't work correctly with arXiv preprints: what I had is the arXiv link read as an article title (e.g. arXiv:0809.3331), and the blank field of publication name (where the journal title should be). Hope that the authors can fix it soon.

Another point is that at the moment there are only very few users of such services as Mendeley and 2collab are. However, I believe that in the nearest future using "academic social networks" will be as usual as, for instance, having a personal webpage at institute website nowadays.

How much force does it take to stab somebody to death?

Here is a review of an absolutely crazy arXiv preprint:

"A number of groups have attempted to measure the forces necessary to penetrate skin but the results are difficult to apply to murder cases because of the sheer range of factors at work. The type and sharpness of the knife; the angle and speed at which it strikes; the strength of skin which varies with the age of the victim and the area of body involved; these are just a few of parameters that need to be taken into account.
...
They [the authors, by Misha] have developed a machine that measures the force required to penetrate skin–either the animal kind or an artificial human skin made of polyurethane, foam and soap. The surprise they’ve found is that the same knives from the same manufacturer can differ wildly in sharpness. And the force required for these knives to penetrate the skin can differ by more than 100 per cent."

This is definitely the strangest preprint I've ever seen...

2collab

I came across an interesting service - 2collab, a tool for scientific bookmarking, sharing and collaborating. It looks like an academic analogue of delicious. This project was started by Elsevier, and therefore any article from Elsevier journal may be immediately bookmarked using an "add 2collab" button at the journal website - and all the bibliographic data will be automatically transferred.  Unfortunately, at the moment no other journals have such buttons. Of course, one can bookmark absolutely any webpage, but in this case one should write up the bookmark description (title, etc.) by hands, which can take a while.

For this day, 2collab seems to be not very popular among the researchers, but I hope it will change soon.

An infinite number of mathematicians...

via

Links for 11.11.2008

• Flat bulb - is it really useful?
  
• Fixing Education Is Expensive - by Chad Orzel. How much do good teachers cost?
  

Links for 2.11.2008

• Fermilab Discovers... Something. Maybe. - some new physics from collision experiments?
  
• Demonstration of 3D - display
• How to survive grad school - an excellent post about great but hopeless projects you may be involved in

MIT students study the effectiveness of aluminium foil helmets

A relatively old, but extremely funny article:

Among a fringe community of paranoids, aluminum helmets serve as the protective measure of choice against invasive radio signals. We investigate the efficacy of three aluminum helmet designs on a sample group of four individuals. Using a $250,000 network analyser, we find that although on average all helmets attenuate invasive radio frequencies in either directions (either emanating from an outside source, or emanating from the cranium of the subject), certain frequencies are in fact greatly amplified. These amplified frequencies coincide with radio bands reserved for government use according to the Federal Communication Commission (FCC). Statistical evidence suggests the use of helmets may in fact enhance the government's invasive abilities. We speculate that the government may in fact have started the helmet craze for this reason.

X-ray from the Scotch tape

A funny article in Nature:

Relative motion between two contacting surfaces can produce visible light, called triboluminescence. This concentration of diffuse mechanical energy into electromagnetic radiation has previously been observed to extend even to X-ray energies. Here we report that peeling common adhesive tape in a moderate vacuum produces radio and visible emission, along with nanosecond, 100-mW X-ray pulses that are correlated with stick–slip peeling events. For the observed 15-keV peak in X-ray energy, various models give a competing picture of the discharge process, with the length of the gap between the separating faces of the tape being 30 or 300 m at the moment of emission. The intensity of X-ray triboluminescence allowed us to use it as a source for X-ray imaging. The limits on energies and flash widths that can be achieved are beyond current theories of tribology.

Happy Mole Day!

It turned out that today (10/23 in American notation) is a Mole Day...

Scholarpedia

Surprisingly enough there is a peer-reviewed alternative to Wikipedia, called Scholarpedia. The authors pretend that 

"...Scholarpedia articles could be cited, articles are not frozen and outdated, but dynamic, subject to an ongoing process of improvement moderated by their curators."

So it is supposed to be better than Wiki, due to the peer-review system, and better than any printed issues, because they cannot be changed.

I wonder whether Scholarpedia will really become a source of "articles that could be cited".

A popular article about Zeno effect

Some time ago we were asked to write a little popular article in the Oktober issue of the Czech journal Chemické Listy, in occasion to the 80th birthday of Prof. Rudolf Zahradnik. For a long time he was a president of Czech academy of sciences, and about ten years ago was even asked to be a Czech president candidate, but refused.

Finally, we came up with an article about quantum Zeno effect, called "Kvantový Zenonův jev aneb co nesejde z oči, nezestárne", which sounds in English as "Quantum Zeno effect, or who's kept in sight, won't age".

This is the first article by myself, which I do not really understand, because it was translated and published in Czech.

Links for 19.10.2008

Useful:

• Springer Online Reference Works - online encyclopedia of math
• Advanced physics forums

Interesting:

• Why LaTeX is like Latin - by Paul Goldberg. "LaTeX, like Latin, does not prevent one from writing down a statement that is incorrect. ... But it does help to prevent vagueness."
• Essay: Fifty Years of Atomic, Molecular and Optical Physics in Physical Review Letters - by Serge Haroche.
• The complete work of Charles Darwin online
• Old scientists never clean out their refrigerators - the story of the Miller-Urey experiment
• Website of Michio Kaku, and his opinion about the last Nobel Prize.

Blogs:

• How you can save the world - an interesting blog, written by many well-known contributors, string theorist Michio Kaku among them.

Funny:

• Iran minister admits holding fake Oxford degree
  
• 'Punch drunk' pony rescued from swimming pool
  

The most specialized journal I ever seen

Today I came across a journal called "Platinum metals review", which is present in our labrary,but isn't indexed by Web of Science, though.

The simpler the better

Abstruse Goose

The crisis and life

www.phdcomics.com

Links for 12.10.08

• Chemical Portal - an excellent collection of useful tools and tables
  
• The collapse of peer-review - from the economist's point of view
• What's Interesting About AMO Physics - by Chad Orzel
  
• APS now leaves copyright with authors for derivative works - "When you submit an article to an APS journal, we ask you to sign our copyright form. It transfers copyright for the article to APS, but keeps certain rights for you, the author. We have recently changed the form to add the right to make ‘‘derivative works’’ that reuse parts of the article in a new work."

For this day

Echte Männer essen keinen Honig, sie kauen Bienen.

Nobel Prize in physics 2008

I am completely ignorant in the field of particle physics, but here is an excellent essay about the science behind the today's prize.

The teacher's day

Today is a Teacher's day in Russia (also in Pakistan and Philippines :-), and www.google.ru looks like this:

The date is chosen to coincide with the World Teacher's Day, defined by UNESCO.

The 2008 Ig Nobel Prize Winners

Since I'm a physicist, I present physics the first:

PHYSICS PRIZE. Dorian Raymer of the Ocean Observatories Initiative at Scripps Institution of Oceanography, USA, and Douglas Smith of the University of California, San Diego, USA, for proving mathematically that heaps of string or hair or almost anything else will inevitably tangle themselves up in knots.

But, my favorite one is a chemical one:

CHEMISTRY PRIZE. Sharee A. Umpierre of the University of Puerto Rico, Joseph A. Hill of The Fertility Centers of New England (USA), Deborah J. Anderson of Boston University School of Medicine and Harvard Medical School (USA), for discovering that Coca-Cola is an effective spermicide, and to Chuang-Ye Hong of Taipei Medical University (Taiwan), C.C. Shieh, P. Wu, and B.N. Chiang (all of Taiwan) for discovering that it is not.

here are other prizes

Brown sharpie

Another funny mathematical cartoon

A terrific Nature cover

I wonder whether this is an "accidental degeneracy", or there is some hidden symmetry in it...

Bloggers given new Ten Commandments by church leaders

Christian bloggers have been given a new set of 'Ten Commandments' aimed at delivering them from the temptations of online arguments. Here it is:

1) You shall not put your blog before your integrity.
2) You shall not make an idol of your blog.
3) You shall not misuse your screen name by using your anonymity to sin.
4) Remember the Sabbath day by taking one day off a week from your blog.
5) Honour your fellow-bloggers above yourselves and do not give undue significance to their mistakes.
6) You shall not murder someone else's honour, reputation or feelings.
7) You shall not use the web to commit or permit adultery in your mind.
8) You shall not steal another person's content.
9) You shall not give false testimony against your fellow-blogger.
10) You shall not covet your neighbour's blog ranking. Be content with your own content.

Links for 28.09.08

• Sergey Brin's blog
• Survivor: theoretical physics - some thoughts about career.
• How long should an astronomical paper be to increase its Impact? - an interesting preprint.

Links for 14.09.08

Scientific:

• Webcam at LHC - want to know what's going on there?
• Frequently asked questions in mathematics - by Alex López-Ortiz.
• Mathematical constants - by Steven R. Finch.
• NIST digital library of mathematical functions
• Theoretical computer science cheat sheet - a .pdf file there.

Interesting:

• Google launches the digitalization of old papers
• Has the Large Hadron Collider destroyed the earth yet?
  

The Monte-Carlo method

I was actually not aware of the fact that the Monte-Carlo method of integration was proposed by Stan Ulam working on Manhattan project at Los Alamos. I also like his aphorism, which I came across of here:

"My late friend Stan Ulam used to remark that his life was sharply divided into two halves. In the first half, he was always the youngest person in the group; in the second half, he was always the oldest. There was no transitional period."

Secret History of Quantum Physics

An interesting post by Chad Orzel, about the great discoveries made during vacations:

"Erwin Schrödinger famously discovered the equation that bears his name while on a skiing holiday in 1925. He was accompanied on this vacation by one of his many girlfriends, but which of them went on the fateful trip has been lost to history-- Schrödinger kept exceedingly detailed diaries, but the volume covering the relevant period has been lost."

I'm eager to know, who was his girlfriend...

Ten Lessons I wish I had been Taught

I came across these advices of Gian-Carlo Rota in the blog of Alexandre Borovik. Among them there is the following one:

"6) Do not worry about your mistakes.
Once more let me begin with Hilbert. When the Germans were planning to publish Hilbert’s collected papers and to present him with a set on the occasion of one of his later birthdays, they realized that they could not publish the papers in their original versions because they were full of errors, some of them quite serious. Thereupon they hired a young unemployed mathematician, Olga Taussky-Todd, to go over Hilbert’s papers and correct all mistakes. Olga labored for three years; it turned out that all mistake scould be corrected without any major changes in the statement of the theorems. There was one exception, a paper Hilbert wrote in his old age, which could not be fixed; it was a purported proof of the continuum hypothesis, you will find it in a volume of the Mathematische Annalen of the early thirties. At last, on Hilbert’s birthday, a freshly printed set of Hilbert’s collected papers was presented to the Geheimrat. Hilbert leafed through them carefully and did not notice anything."

Fermat's last theorem

I was often thinking about "whether Fermat really had a proof of his famous theorem":

Theorem. There are no positive integers x, y, z, and n > 2 such that x^n + y^n = z^n.

Today I found an answer in the mathematical FAQ:

"Did Fermat prove this theorem? No he did not. Fermat claimed to have found a proof of the theorem at an early stage in his career. Much later he spent time and effort proving the cases n = 4 and n = 5. Had he had a proof to his theorem earlier, there would have been no need for him to study specific cases."

This is followed by an interesting discussion about different mistakes that Fermat may have done (see section 3.1.4 of FAQ).

But, anyway, Pierre de Fermat never had his theorem proven.

Wolfram support

I was surprised by fast and friendly support that Wolfram offers to Mathematica users. The last two days I was bothering with a problem, which occurs when you try to calculate an alternating sum consisting of big numbers - the precision was not high enough and I always obtained a "noisy" curve instead of the smooth one. I played with accuracy and precision, but nothing helped. Finally, I've sent my notebook to Wolfram support, and have got an answer within a few hours, with a correct notebook attached. Now it seems to work - it is a bit tricky, though. 

The LHC switches on this morning

Sincerely, I don't want to contribute in the worldwide discussion about the "black hole consisting of antimatter" (c) which will destroy the Universe, but there is a nice picture from Google today:

How to learn any language?

Some time ago I came across a very interesting website by a Swiss amateur linguist François Micheloud. He presents an interesting table for those people who want to learn a foreign language, but don't know from which one to start (or which should be the next). François compares difficulty, popularity, transparency, the number of countries speaking the language etc. For instance he rates Russian to be the easiest languages among the "languages usually considered as hard".

Links for 07.09.2008

Scientific:

• Free mathematics textbooks online
• Abramowitz and Stegun: Handbook of Mathematical Functions - an online version of famous reference.
• Data paparazzi - about writing papers based on a snapshot of a data slide made at a conference.
• How to be a good teaching assistant - some advices
• 20 Things I Have Learned as a College Professor
• Why Assistant Professors Should Earn More Than the Tenured
• Do numbers have personalities? - The Herald article about John Baez' opinion on this.
• Plush subatomic particles - terrific toys for particle physicists, there is a Higgs boson and dark matter.
• Quantum minigolf - essentially the same thing as minigolf, but with quantum particles
• Physicists periodic table - by Timmothy Stowe.

Useful stuff:

• Scribd - a "YouTube for documents", supports a variety of formats.
• Chrome - a new browser from Google. Only for Windows yet.
• FriendFeed - probably everyone knows this, but I came across it only today. Using friendfeed.com you can share everything you produce in one place. It supports blog, youtube, google reader, picasa, and probably everything else you may need. My account there is lemeshko.

Other:

• Urban Legends - an interesting collection.
• Deadjournal - a livejournal for emokids.

Why is mercury liquid?

The answer is clearly presented here. I find very interesting that mercury does not crystallizes at the room temperature not only due to the filled atomic shells (the Hg configuration is [Xe] 4f14 5d10 6s2), but also because of relativistic effects, which decrease the radius of the 6s orbital.

Mercury is a liquid at room temperature because the "relativistic contraction" of its atomic orbitals makes it behave chemically almost like a noble gas, not wanting to share electrons with other atoms, even other mercury atoms! Note that mercury is monatomic in the gas phase, just like a noble gas. Of course this should not be pushed too far; mercury is not a noble gas. There are enough outer-electron interactions for mercury to remain a liquid (radon, 22 amu heavier, is a gas), to conduct electricity, and to participate in ordinary chemical reactions...

Citations for 07.09.2008

Probably it might be a good idea to make something like bash.org, but for aphorisms and interesting citations... Here there are a few I came across this week:

• Young man, in mathematics you don't understand things. You just get used to them. John von Neumann

• There are three rules for writing the novel. Unfortunately, no one knows what they are.  W. Somerset Maugham

•  Teach the Students You Have - not the ones you wish you had. If you get annoyed at students for being insufficiently prepared, or not as smart as you, you'll become a grumpy old fart, just like some of the lousy teachers you had. John Baez

The Most Alien-Looking Place on Earth

An article about a unique island, with a lot of pictures...

Imagine waking up on the Socotra Island and taking a good look around you (let's say your buddies pulled a prank on you and delivered you there, and lets also assume that you don't have any hangover from abuse of any substances). After a yelp of disbelief, you'd be inclined to think you were transported to another planet - or traveled to another era of Earth's history.

The second would be closer to the truth for this island, which is part of a group of 4 islands, has been geographically isolated from mainland Africa for the last 6 or 7 million years. Like the Galapagos Islands, this island is teeming with 700 endemic species of flora and fauna, a full 1/3 of which are found nowhere else on Earth.

I was laughing very loud...

Sociologists want to be psychologists, because if you understand the brain you can understand society.

Psychologists want to be biologists, because if you understand life you can understand the brain.

Biologists want to be chemists, because if you understand matter you understand life.

Chemists want to be physicists, because if you understand the universe you understand matter.

Physicists want to be God.

God wants to be a mathematician.


Found here.

Terence Tao

A 33 years old professor of math from University of California, 2006 Fields medal winner Terence Tao has a blog. It is extremely interesting as a whole, but here are some links to Terry's advices: Advices on career, On writing papers, Talk to your advisor, Take the initiative, and tons of references to older posts therein.

How to write consistently boring scientific literature

An excellent article about writing, which is accessible at Scribd (youtube for docs).

A Scandinavian professor has told me an interesting story. The first English manuscript prepared by one of his PhD students had been written in a personal style, slightly verbose but with a humoristic tone and thoughtful side-tracks. There was absolutely no chance, however, that it would meet the strict demands of brevity, clarity and impersonality of a standard article. With great difficulty, this student eventually learned the standard style of producing technical, boring and impersonal scientific writing, thus enabling him to write and defend his thesis successfully (Fig. 1).

Dunning-Kruger effect

Today I came across some interesting stuff:

The Dunning-Kruger effect is the phenomenon wherein people who have little knowledge (or skill) tend to think they know more (or have more skill) than they do, while others who have much more knowledge tend to think that they know less. Dunning and Kruger were awarded a 2000 Ig Nobel prize for their work.

Why the h-index is little use

Two interesting posts by Michael Nilsen about the Hirsch index: the first and the second. Michael notes that the h-index can be calculated to a good approximation from the formula:

h ~ sqrt(T) / 2,

where T is the total number of citations. Therefore it provides no new information beyond the total number of citations, and can not be properly regarded as a new measure of impact at all. Earlier I wrote a little post about Hirsch index (in Russian).

Einstein Versus the Physical Review

A nice story from Physics Today. When Einstein moved to the US, he began to publish his work in American journals, but was not used to the peer-review procedure. After submitting his work "Do gravitational waves exist?" (with Rosen as coauthor) to Physical Review, Einstein received a critically reviewed manuscript with a comment of editor that it "would be great to have [Einstein's] reaction to the various comments and criticisms the referee has made". He was shocked by it and withdrew the article with the following letter to the editor:

Dear Sir,
We (Mr. Rosen and I) had sent you our manuscript for publication and had not authorized you to show it to specialists before it is printed. I see no reason to address the—in any case erroneous—comments of your anonymous expert. On the basis of this incident I prefer to publish the paper elsewhere.
Respectfully,
P.S. Mr. Rosen, who has left for the Soviet Union, has authorized me to represent him in this matter.

The paper was finally published in Journal of the Franklin Institute in Philadelphia.

Abstruse Goose - another terrific comics

Here it is.

Academic reader

One of the Michael Nilsen's projects is the so-called Academic reader. After a first look I was curious about its difference from standard RSS-readers, like Google Reader for instance. A bit later I found a little post about it:

"In the existing site, the main difference between the Academic Reader and RSS readers like the Google Reader is that we have a variety of ways of searching and browsing older papers. This means the Academic Reader allows you to both (1) keep abreast of your current reading, and (2) look back into the past, discovering older papers and so on. RSS readers typically focus on just the first of these problems."

Since a new tool contains all metadata from journal archives, it looks like a hybrid of an RSS-reader with some offline library like (my favorite) Papers.

"Work. Finish. Publish."

This was an advice of Michael Faraday to his younger colleague William Crookes. The second statement, "finish", is probably the most difficult part. Here it does not mean "stop collecting the experimental data", or "switch off the computer and do no extra calculations" (...since we have enough for a paper). It is really hard to came up with some closed-form investigation, with an exciting story you have nothing to add to. Most likely, if this is done, the third step, "to publish", needs only a bit of routine work...

Six rules for rewriting by Michael Nilsen

Very helpful post by one of the pioneers of quantum computation, Michael Nilsen. Here are the ideas which I find the most interesting:

1) Every sentence should grab the reader and propel them forward: Academics are wont to ignore this rule, believing the reader should be willing to endure any pain for a sufficient payoff. Of course, academics aren’t paid per reader. Good bloggers and journalists know better.

2) Use the strongest appropriate verb: Identify the verb in every sentence, and ask if you can improve it, perhaps eliminating adjectives and adverbs in the process. This is simple and mechanical, but often yields great improvements with little effort.

3) Beware of nominalization: A common way we weaken verbs is by turning them into nouns, and then combining them with weaker verbs. This bad habit is called nominalization. Contrast the wishy-washy “I conducted an investigation of rules for rewriting” with the more direct “I investigated rules for rewriting”. In the first sentence I have nominalized the strong verb “investigated” so that it becomes the noun “investigation”, and then combined it with the weaker verb “conducted”.

Probably we can generalize these rules as:

"Avoid the official, bureaucratic language in your articles. Surprisingly, science can be easily understood as an interesting story, without useless overcomplications."

Brian Green about string theory

No, this is not another rap (take a look at his hands, yo). These are very clear and understandable explanations of "what the string theory is" by Brian Greene:

via Greg Laden's blog

Astrobiology rap

not so cool as the one about LHC, but anyway



via Dynamics of cats.

Obituaries in store

It is of no surprise that newsmakers prepare the obituaries ahead of time. Two days ago the Bloomberg financial newswire accidentally published one for Steve Jobs, a CEO of Apple corp. The obituary was retracted after a while, but not fast enough, so it was copied by gawker.com, and published there. The most interesting part are comments for Bloomberg reporters and lists of contact persons, who probably can give interviews in case of Jobs' death.

A similar case was recently described by Tatiana Tolstaya: ten years ago living in the US, she received a call from The New York Times with an offer to write an obituary to Solzhenitsyn. She said "no". Now, when Solzhenitsyn have died, we know who agreed to do this - Michael T. Kaufman.

Ambitions

"Keep away from people who try to belittle your ambitions. Small people always do that, but the really great make you feel that you, too, can become great."

Mark Twain

There are thousands of his aphorisms here.

LHC Rap

The best popular lecture I have ever seen...

Knol

Сегодня Google Scholar известил меня о том, что появился новый проект от Google, называется Knol. Кноль - это единица знаний, от слова knowledge. В общем, каждый желающий приглашается туда написать статью о том, что он знает. На данный момент, я не совсем понимаю цель этого проекта... Разве что, при должном пиаре, он может составить альтернативу Википедии. Отличия, безусловно, есть: отправить статью может кто угодно, редактировать её просто так нельзя, но можно послать еще одну, от своего имени. Короче говоря, время покажет.

"Рисунок человека"

Статья о диагностике умственного и психического развития по тому, как рисуют человечков. Мой любимый вот этот:

Fundamental physical constants

Online reference on constants, units and uncertainty from National Institute of Standards and Technology.

AMO physics refbook

Some useful stuff - Collection оf atomic, molecular and optical physics formulae by Andrei Derevianko, University of Nevada.

Коллекция плохого английского

Интересная подборочка на Engrish.com. Хотя, скорее всего, такое читать вредно.

via Vasya Vasin

Jacek Yerka paintings

Сайт известного художника Яцека Йерки, много его картин. Вот одна из них, "Mistery Garden":

Крикатуры Херлуфа Бидструпа

Здесь много веселых картинок от известного датского коммуниста-крикатуриста. Вот эта, например, называется "Культ личности":

via жена

Paul Richard Halmos «How to write mathematics»

Русский перевод статьи изветсного математика Пауля Халмоша "Как писать математические тексты".

Нашел через Словоманию.

Доктор, мой гамильтониан неэрмитов, я буду жить?

Сегодня наткнулся на любопытную прошлогоднюю статью 

Carl M Bender, Making sense of non-Hermitian Hamiltonians, Rep. Prog. Phys. 70, 947 (2007).

В ней автор задается вопросом - является ли необходимым условием при построении квантовой механики эрмитовость гамильтониана? Бендер предлагает взамен эрмитовости ввести другое условие, симметрию относительно отражения пространства-времени (PT-symmetry). Если гамильтониан PT-симметричен, его собственные значения будут действительны. Это работает, если PT-симметрия гамильтониана не нарушается, то есть собственные значения H являются собственными значениями оператора PT. В качестве примеров приводятся такие неэрмитовые гамильтонианы, как, например, H=p^2+ix^3 или H=p^2-x^4, собственные значения которых действительны и положительны. Действительность собственных значений не является достаточным условием для постоения теории, нужно еще добиться положительной нормы векторов и унитарности оператора эволюции. Автор показывает, что все это можно сделать, работая с PT-инвариантными гамальтонианами.

В общем, предлагается строить квантовую механику, опираясь именно на PT-инвариантность в качестве одной из аксиом, вместо "математического" требования эрмитовости.

P.S. На самом деле, данная статья - обзор того, что сделано за последние 10 лет, и автор в ней уже ничего не "предлагает". :) Но, поскольку основные результаты и были получены Карлом Бендером, то я позволил себе написать так, как будто действие происходит в реальном времени.

Glenn Gould

Оказывается, на Youtube полно всего интересного, в том числе много записей гениального канадского пианиста Glenn Gould. Вот он, например, играет Баха:

A new journal from APS

Американское физическое общество запустило новый проект - журнал под незамысловатым названием "Physics". В нем будут публиковаться популярные обзоры выдающихся работ, опубликованных в Physical Review. Публикации будут трех видов: Synopsis - краткая, в несколько строчек, новость об открытии; Viewpoint - короткое описание работы, как я понимаю, что-то типа Nature: News&Views; и Trends - описание развития какой-то популярной области науки. Отличие Trends от Reviews of Modern Physics в том, что они написаны популярным языком, и не претендуют на исчерпывающий научный обзор работ.

Нашел через Игоря Иванова

Igor Falecki

Барабанщик-вундеркинд из Польши. На этом видео ему 4 года:



На Youtube очень много роликов с ним, вот ссылка на его сайт.

О мелочах, влияющих на цитирования

Наткнулся на два интересных препринта J. P. Dietrich, о том, как влияет позиция препринта в ежедневной рассылке arxiv.org на количестыо цитирований, полученных статьей:

1) The Importance of Being First: Position Dependent Citation Rates on arXiv:astro-ph

2) Disentangling Visibility and Self-Promotion Bias in the arXiv:astro-ph Positional Citation Effect

Автор выяснил, что препринты, находящиеся в конце ежедневной рассылки в среднем получают в два раза меньше ссылок, чем работы из первых строчек. В первом препринте Дитриха этот факт был обнородован, но было еще не понятно, в чем причина такой разницы, в "случайном попадании в топ" или намеренной отправкой препринта в течение короткого времени после дедлайна, чтобы статья появилась в верхних строчках рассылки. Дело в том, что опытные авторы, которые много публикуются и цитируются, часто поступают именно таким образом. Во втором препринте Dietrich (проанализировав log - файлы сервера arxiv.org, которые ему любезно предоставили) приходит к выводу, что играют роль оба фактора.

Словомания

Очень интересный блог о словах, языках и прочей популярной лингвистике.

Первая статья

Вышла моя первая статья на новом месте

Mikhail Lemeshko and Bretislav Friedrich, An analytic model of rotationally inelastic collisions of polar molecules in electric fields, J. Chem. Phys. 129, 024301 (2008)

Её можно скачать без подписки - общество Макса Планка оплатило свободный доступ.

Письма рядового домой. Армия как она есть.

Журнал, который ведет солдат российской армии через своих друзей. Очень познавательно.

Презентация о презентациях

Death by Powerpoint (and how to fight it) by Alexei Kapterev

Отличная критика того, что обычно показывается на семинарах и конференциях. Как обычно, правила очень просты, но большинство почему-то их игнорирует...

Cris Moore's Gallery

Web-page about the 3-body and n-body problems, with interesting pictures.

И снова о берлинском акценте

Бог, как говорится, шельму метит. Недавно я писал о том, как мечтаю наконец-то услышать настоящий берлинский акцент. И услышал. У нас были двухдневный курсы первой помощи, где тётенька доктор обладала типичным берлинским прононсом. То есть, например, вместо "alles gar nicht gut gemacht", она говорила "allet jar nischt jut jemascht" - и это было ужасно. За два дня я ничего не понял из ее рассказов, хотя обычный немецкий на слух понимаю. Просто сидел и втыкал. Не дай бог никому пережить такое.

The world factbook

Описания всех стран на сайте ЦРУ, очень информативно, только факты, без особой пропаганды.

Нашел через сайт Студии Лебедева.

“SO WHAT WILL YOU DO IF STRING THEORY IS WRONG?”

Today I came across an interesting letter by Moataz Emam, published in The American Journal of Physics. Here is the main idea:

"...So even if someone shows that the universe cannot be based on string theory, I suspect that people will continue to work on it. It might no longer be considered physics, nor will mathematicians consider it to be pure mathematics. I can imagine that string theory in that case may become its own new discipline; that is, a mathematical science that is devoted to the study of the structure of physical theory and the development of computational tools to be used in the real world. The theory would be studied by physicists and mathematicians who might no longer consider themselves either. They will continue to derive beautiful mathematical formulas and feed them to the mathematicians next door. They also might, every once in a while, point out interesting and important properties concerning the nature of a physical theory which might guide the physicists exploring the actual theory of everything over in the next building..."

UPD: There is a preprint of this article in arXiv.

Unbreakable spaces

In the post How to make sure your paper will be rejected Daniel Lemire mentions that the paper will be definitely not accepted if "The authors have obviously never heard of unbreakable spaces." I absolutely agree with such a point, and always use a tilde in LaTeX when typing names, references, etc. However, such a rule is often violated by journals themselves. For instance, today I've got the authors' proofs of our article, accepted for publication in Jounal of Chemical Physics, where all my unbreakable spaces were broken. Afterwards I've had a look to recent articles in Physical Review and some other journals - their publishing staff also seems to be happy with breaking "Fig. 1" into two parts...

Writing papers

Here I provide a few links that I found interesting:

1) Write good papers by Daniel Lemire:

2) How to maximize citations by Peter Turney

3) Hints for New PhD students on How to Write Papers by Shahn Majid

I'm gratefut to Daniel for such a point:
"...A good abstract answers the question why should I read this paper?, it does not summarize the paper..."

Снова об эффекте Зенона

Игорь Иванов оставил два интересных комментария к моему достаточно старому посту про эффект Зенона. Я стал лучше понимать.

Ссылки

Как следует из предыдущего поста, я решил добавлять на сайдбар блоги и сайты, которые я регулярно смотрю. Добавил блог Игоря Иванова "Что интересного происходит в науке", который я читаю давно, и несколько раз на него ссылался здесь и здесь (может и еще где-то).

Свободные исследователи

Относительно недвано нашел отличный научно-популярный блог Свободные исследователи, который ведет Алексей Тимошенко. Очень рекомендую, добавил ссылку в сайдбар.

Два форума

1) хороший математический форум - Dr. Math, via Roman Krems' webpage

2) англоязычный форум о Берлине, via Vasya Vasin

The Disadvantages of an Elite Education

An exciting article by William Deresiewicz:

"Our best universities have forgotten that the reason they exist is to make minds, not careers"

via Daniel Lemire's blog

Daniel also picks up a cool phrase: "It’s no coincidence that our current president [Bush], the apotheosis of entitled mediocrity, went to Yale."

Top 10 Scientists Killed or Injured by Their Experiments

Such a strange top-10 list was published at listverse.com:

"Man owes a great debt to the scientists on this list; all of them died or were injured in their pursuit of knowledge. The advances they have all made to science are extraordinary and many of them paved the way for some of man’s greatest discoveries and inventions."

Русская версия доступна здесь.

The "purity" of science

via Daniel Lemire's blog

Harpstars at YouTube

Оказывается, некоторые гармошечные знаменитости стали выкладывать свои уроки на YouTube. Например, Adam Gussow:




Или Jason Ricci

Ещё одна картинка о французских забастовках

-Но Вы же не можете бастовать, Вы же безработный!
- Я тренеруюсь на случай, если найду работу...

Ne plus jamais travailler

И еще одна любимая:


"Никогда больше не работать"

"La majorité c'est vous" par René Maltête

Одна из моих любимых фотографий:


"Большинство - это вы"

На сайте René Maltête куча веселых и интересных работ.

One-page round-number handbook of physics

Это гениально:
Edward Purcell, Am. J. Phys 51, 11 (1983).

Acoustical and physical dynamics of the diatonic harmonica

Интересная научная статья о физике диатонической гармошки:
H. T. Banson, J. F. Antaki, Q. C. Beery, J. Acoust. Soc. Am. 103 (4), 2134 (1998)

"The harmonica is arguably the most widely played instrument in the world, yet there is a surprising paucity of published studies of its acoustics or physical dynamics. The typical diatonic harmonica and the physical forces involved in its natural function are described, and simple observations of the harp’s functions are reported. The speaking of the reeds, naturally, when producing a bend, and when speaking as an overblow or overdraw is discussed and investigated by simple stopping of the reeds, by videostroboscopic analysis, and by recording vibration of the reeds with displacement gauges. The reeds of the ten hole harmonica can be made to vibrate at varying frequencies depending on the size and shape of the player’s vocal tract. Three different modes of speaking from each hole and its pair of reeds are revealed and studied: first, naturally in a closing mode, either blown or drawn; second, as a bend, either blown or drawn, with pitch in the interval between the two notes in the hole; and third, as an overblow or overdraw in an opening mode with a pitch outside the interval between the two natural notes of the hole. This dynamic interaction allows the player to speak with the instrument perhaps as with no other."

Three brain rules to improve your presentations.

В принципе, это очевидные вещи, но далеко не все их соблюдают:

"1) Exercise - Making your body a lean, clean, aerobic machine, besides giving you time to think, ensures that your brain gets the oxygen it needs. It also gives you some empathy for the poor schlubs that must sit through your lecture, inert brains encased in a desk. Make their time worth it.

2) The 10 minute rule – Your audience fades after 10 minutes. If you have to lecture for 50 minutes, conscientiously change-up every 10 minutes or so. Turn on the lights, show a blank screen and tell a story, have your audience stand up and stretch, anything to reset the 10-minute boredom clock.

3) Pictures beat text – We remember a good image far longer than a string of text. During your talks, show images, speak words. If you need blocks of text for your talk, use handouts."

отсюда

О Берлинском акценте

Сегодня я написал пост в сообщество ru_berlin о типично Берлинском произношении ("икь" вместо "ихь", "гюнстикь" вместо "гюнстих" итд). Вопрос был в том, где водятся люди с таким произношением - за 9 месяцев я их ни разу не встречал, более того, повсюду это ужасное, режущее ухо "ищщььь" .Вот что мне ответили:

"Дело в том, что до объединения на западе от берлинского диалекта в школах отучали, а на востоке и сами учителя не брезговали. Так что ищите в любом восточном районе, который ещё не забит приезжими из других федеральных земель."

Гезельшаст - от слова "шастать". А немцев в войну звали "Фрецами".

На сайте университета, где я раньше учился, опубликовали данные о трудоустройстве выпускников 2007 года. Интересно, что за бездари оформляют этот сайт? Название института, где я работаю написано с двумя (!) ошибками...

О юной_деве

Забавно, что в немецком языке "девственник" и "девственница" обозначаются одним и тем же словом женского рода - die Jungfrau.

Учитесь хорошо, детки

Российским студентам подняли стипендию с 900 до 1100 рублей.

Несколько полезных статей об академической карьере

1) Duncan A. Forbes "So you want to be a professional astronomer!"

2) Ronald T. Azuma "A graduate school survival guide: "So long, and thanks for the Ph.D.!" "

3) Marie desJardins "How to Be a Good Graduate Student"

Архив акцентов мира

Все таки, это гениально

The speech accent archive

via Igor Efimov

Об ошибках в переводах Корана

Компот вместо 72 девственниц from BBCRussian.com

"...В отличие от довольно выхолощенного описания христианского рая с его кущами, нектаром и амброзией, мусульманам обещан рай, в котором их якобы ждут чувственные удовольствия, в том числе 72 девственницы, или "ясноглазые гурии", которые встречают правоверного и становятся его женами, сохраняя при этом девственность.....
...........
.... Люксенберг подвергает в своей книге подробному анализу множество таких мест в Коране. Среди прочего выяснилось, что очень многие неясности вызваны неточным переводом с арамейского на арабский. В частности, корень "гур" в слове "гурия", или девственница, означает на сирийском диалекте арамейского языка "белый изюм". А вместо "ясноглазой" следует читать "кристально-чистый". Иными словами, праведникам обещали вовсе не девственниц, а напиток из изюма, правда, никогда не иссякающий. Для многих мусульман, особенно тех из них, кто готовит себя к судьбе шахида или мученика, это открытие может стать самым глубоким разочарованием в жизни - легко ли расстаться с надеждой на ласки 72 гурий в обмен на обещание... бесконечного компота."

О выборах президента РАН

Интересный пост Игоря Ефимова, и его же комментарий там:

"Ну эти выборы - вообще бессмыслица. Это похоже на выборы председателя карточного клуба в доме престарелых."

Назад к основам

Как известно, уравнение Шрёдингера описывает плавное изменение, или эволюцию, волновой функции со временем. Однако коллапс волновой функции, происходящий в результате измерения (Йохан фон Нойман называл это редукцией волнового пакета) уравнению Шрёдингера не подчиняется. В кратце, если состояние частицы описывается суперпозицией стостояний |1> и |2>:
то при измерении мы всегда получим либо |1>, либо |2> - то есть волновая функция "схлопывается" до одного состояния.

Оказвается, некоторое время назад были попытки как-то феноменологически видоизменить уравнение Шрёдингера, чтобы оно учитывало коллапс волновой функции, см. например работу S.L. Adler "Weisskopf-Wigner decay theory for the energy-driven stochastic Schrödinger equation", Phys. Rev. D 67, 025007 (2003).

Однако экспериментальное наблюдение квантового эффекта Зенона существенно ограничивает спекулятивные попытки дописать в уравнение Шрёдингера дополнительные члены, учитывающие коллапс.

Вкратце, эффект Зенона заключается в том, что если постоянно наблюдать за нестабильной частицей (скажем, ядром, которое может испустить электрон) - она не распадется. Здесь нет никакой магии: рассмотрим записанную выше суперпозицию состояний, где |1> - состояние частицы внутри ядра, |2> - вне его. Считаем, что в начальный момент времени частица находится чисто в состоянии |1>. Дальше, со временем система эволюционирует и при измерении мы обнаружим частицу либо в состоянии |1>, либо в состоянии |2>. То есть, если детектор не регистрирует вылетевшей частицы - это автоматически означает, что волновая функция снова схлопнулась до состояния |1> и все начинается сначала. Если производить измерения достаточно часто, то система просто будет не успевать эволюционировать, и мы будем постоянно схлопывать волновую функцию частицы, "запирая" ее внутри ядра. Если измерение непрерывное, то ядро вообще никогда не распадется.
Также существенен тот факт, что в начале распада вероятность обнаружить систему в состоянии |2> растет медленно, пропорционально квадрату времени - системе еще труднее успеть эволюционировать до того, как очередное измерение схлопнет волновую функцию.

Указанные выше эксперименты проводились не с ядрами, а с возбужденными состояниями атомов, см. работы Itano et al. Phys. Rev. A 41, 2295 - 2300 (1990) и Streed et al. Phys. Rev. Lett. 97, 260402 (2006). Более того, было показано, что наблюдение эффекта Зенона в радиоактивных распадах принципиально невозможно. Однако это очень простой, наглядный и теоретически корректный пример.

Прошу прощения, если этот пост получился несколько сумбурным - возможно, как-нибудь я напишу об эффекте Зенона (и об анти-эффекте Зенона!) подробнее...

Very true

Забавный пост Week-old cappucinos taste bad в Daniel Lemire's blog

"I am not a neat guy. I tend to drop coffee cups on my desk and I never look back. What I learned this year is that if you leave a cup of cappucino for a week on your desk, then drink a shot of it by mistake while staring at your computer screen, you are left with a terrible taste in your mouth for the rest of the day. However, day-old cappucinos are ok.

There is a lesson here kids: do not leave projects without attention for weeks at a time. You will get a bad taste once you go back to it later."

Еще один препринт

Мы немного развили предыдущую модель на случай рассеяния в лазерном поле и позавчера отправили статью в International Journal of Mass Spectrometry, вот препринт на arxiv.org:

Mikhail Lemeshko, Bretislav Friedrich, "The effect of a nonresonant radiative field on low-energy rotationally inelastic $\text{Na}^{+} + \text{N}_2$ collisions"

The American Journal of Chinese Medicine

Забавно, но такой журнал действительно существует:

The American Journal of Chinese Medicine, which is defined in its broadest sense possible, publishes original articles and essays relating to traditional or ethnomedicine of all cultures. Areas of particular interest include:

1. Basic scientific and clinical research in indigenous medical techniques, therapeutic procedures, medicinal plants, and traditional medical theories and concepts;
2. Multidisciplinary study of medical practice and health care, especially from historical, cultural, public health, and socioeconomic perspectives;
3. International policy implications of comparative studies of medicine in all cultures, including such issues as health in developing countries, affordability and transferability of health-care techniques and concepts;
4. Translating scholarly ancient texts or modern publications on ethnomedicine.

Век учись #2

В общеобразовательных целях привожу распределение температуры в атмосфере. Стыдно, но я не знал, что она так меняется:

Adopted from Plane, "Atmospheric chemistry of meteoric metals", Chem. Rev. 103, 4963 (2003).

Об атмосфере или век живи - век учись

Один из научных проектов, в которых я участвую, связан с рассеянием ионов на молекулах в лазерном поле. В ходе поиска литературы, я наткнулся на кучу статей о ион-молекулярных реакциях в верхних слоях атмосферы, из которых узнал много нового. Оказывается, из-за трения о воздух метеориты испаряют в атмосферу атомы и ионы таких веществ, как железо, натрий, магний, алюминий, никель и кальций - этому посвещен достаточно недавний обзор Plane, "Atmospheric chemistry of meteoric metals", Chem. Rev. 103, 4963 (2003).

Металлы, попадающие в атмосферу, иногда вызывают забавные явления. Например, долгое время считалось непонятным, откуда берутся так называемые sporadic sodium layers в верхних слоях мезосферы (на высоте 90-100 км). Эти объекты ни что иное, как тонкие, но плотные слои натрия, спонтанно появляющиеся и исчезающие в течение нескольких минут. Не смотря на их маленькую толщину - ширина распределения на половине высоты (FWHM) всего 1-2 км - эти слои простираются до 1000 км в ширину, вот картинка распределения из статьи Gardner, Farad. Diss. 100, 431 (1995):

Видно, что пиковая концентрация натрия намного превосходит фоновую, которая появляется вследствие испарения нейтрального натрия с метеороидов.

Известно кроме атомарного натрия с метеоров испаряются и ионы Na+, которые могут рекомбинировать в чистый Na. Однако, все не так просто, как кажется, поскольку радиациаонный захват электрона атомом натрия,

очень медленный процесс. Другая возможность, нейтрализация через "третье тело",

более вероятна, но тоже очень медленна. Здесь M - чаще всего атом He или Ar.

Гораздо вероятнее случается рекомбинация, происходящая через промежуточный слабосвязанный комплекс NaX+:

где X - один из атмосферных лигандов, например N2, O2, или CO2.
Затем этот комплекс распадается:

Однако по-прежнему не ясно, почему натрий кластеризуется а таком тонком слое? В работах Cox, Plane J.Chem.Soc.Far.Trans. 93, 2619 (1997); Cox, Plane J.Geoph.Res. 103, 6349 (1998) была проведена серия лабораторных эксперментов и их анализ с помощью простых моделей и все по -видимому прояснилось. Попробую кратко описать их результаты.

Нейтрализация иона натрия начинается с его реакции с атмосферным азотом:

Это самая вероятная реакция в верхней мезосфере/нижней термосфере из-за высокой концентрации молекул N2. Однако, из-за слабой связи между Na+ и N2, происходит обмен лигандами, при котором N2 заменяется на CO2 или на H2O, вот так:

Далее, кластерные ионы распадаются, образуя атомы Na.

С другой стороны, комплекс NaN2+ может обменяться лигандом с атомным кислородом, образуя ион NaO+, который затем реагирует с другим атомом O, и в результате получается опять ион Na+:

то есть все остается как и было.

Отсюда можно сделать вывод, что вероятность образования нейтрального натрия будет зависеть от концентрации CO2 по отношению к концентрации O. Оказывается, что выше 100 км это отношение составляет 1:80 и доминирует реакция с атомарным кислородом - нейтрализации не происходит. При понижении высоты, концентрация CO2 растет (на высоте 95 км отношение концентраций CO2:O уже 1:20), и, следовательно, образуется атомарный натрий.
Более того, в вышеупомянутых работах было получено, что время нейтрализации иона Na+ меняется от более чем одного дня (!) выше 100 км, до нескольких минут на высоте 90 км.

Об образовании атмосферных слоев натрия неплохо написано в статье Collins et al. "A study of the role of ion-molecule chemistry in the formation of sporadic sodium layers", J. Atm. Sol.-Ter.Phys 64, 845 (2002).

On the dead-born child's life

Совместное заседание попечительских советов Сибирского и Южного федеральных университетов. (стенограмма).

Избранный Президент Российской Федерации. Официальный сайт
24 апреля 2008 года, Москва, Кремль

Общество Маркса-Планка

Оказывается, при крещении Максу Планку было дано имя Marx (в дальнейшей жизни ученый никогда не подписывался им), вот небольшая заметка об этом:

Der Streit ums "r". Wie hieß Max Planck wirklich?

"Einen Tag nach dem Geburtstag des Namenspatrons der Max-Planck-Gesellschaft bewegt ein Fund im Kieler Kirchenarchiv die Gemüter. Laut des Taufeintrags im Kirchenbuch der St.-Nikolai-Gemeinde soll der Physiknobelpreisträger mit Rufnamen nicht Max, sondern Marx geheißen haben. Wir fragten Dr. Lorenz Beck, Direktor des Archivs der Max-Planck-Gesellschaft."

Забавно, что Marx является достаточно распространенной немецкой фамилией, но как имя встречается редко - мои немецкие коллеги признались, что не встречали такого.

Первые результаты

Вчера отослали первую статью в Journal of Chemical Physics, заодно поместили препринт на arxiv.org, вот он:

Mikhail Lemeshko and Bretislav Friedrich, "An analytic model of rotationally inelastic collisions of polar molecules in electric fields".

О пложении жуков

Гуляя на выходных несколько раз наблюдали большие скопления плодящихся жуков-солдатиков на бордюрах:Первый раз видел такое. Интересно, что бы это значило?

Это действительно захватывающе

В своем блоге Игорь Иванов написал заметку "Дарвиновская эволюция на чипе" о новом эксперименте по управлению эволюцией. Это не какое-нибудь там компьютерное моделирование, а непосредственное наблюдение эволюции коротких молекул РНК, прямо в стакане, причем, процесс контролируется компьютером. Не имеет смысла пересказывать пост Игоря, рекомендую его всем прочесть. Мне кажется, такие эксперименты способны восхитить даже очень далекого от науки человека...