The distinctive sensation of tannins on the tongue will be familiar (overfamiliar, perhaps?) to many arXivblog readers.

And if you’ve ever wondered what causes that mouth-puckering dryness, you now have an answer thanks to the dedicated and selfless work of Drazen Zanchi and colleagues at the Laboratoire de Physique Théorique et Hautes Energies in Paris.

Tannins are large molecules with aromatic rings and OH groups which naturally bind to each other and to proteins, while repelling water. So the presence of tannins causes proteins to aggregate together. From the biological point of view, that makes good sense. Tannins are part of plants’ defence systems against the proteins that bacteria, viruses and higher herbivores secrete when invading. It takes these proteins out of action be forcing them to aggrgegate together.

Zanchi says exactly this process is responsible for the mouthfeel of tannins. Tannins bind to salivary proteins in the mouth making them aggregate and this causes a rapid and immediate drop in the viscosity of saliva. That’s why your mouth feels dry as you gulp sip your favourite oak-matured cab before after work every day.

Obviously, the strength of this effect and the size of the aggregates that form determine the mouthfeel of the wine.

So feel free to raise a glass to Zanchi and his pals next time you get a chance (which shouldn’t be too long now). Not least because this effect may turn out to have other uses.

The team say that attaching tannins to a surface could force proteins to aggregate at that site. Sounds handy. And they’re convinced they have only scratched the surface of a rich, untapped and largely undiscovered chemistry of tannin behaviour.

Ref: http://arxiv.org/abs/0810.1136: Colloidal Stability of Tannins: Astringency, Wine Tasting and Beyond

Clathration of Volatiles in the Solar Nebula and Implications for the Origin of Titan’s atmosphere

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Cold fusion won’t go away and perhaps rightly so. Numerous groups have reported idiosyncratic behaviour of palladium hydrides sitting in heavy water when a current passes through them. Many of these experiments are said to be repeatable.

Of course, serious questions remain over what exactly is going on in these experiements. They may or may not involve fusion but either way, something interesting will have to be dreamt up to explain many of the results.

These days cold fusion goes by the name of LENR (low energy nuclear reactions). And Allan Widom from Northeastern University in Boston and a couple of mates have taken the trouble to spell out how they think the electroweak force may be behind one class of these reactions.

They say that the well known decay of a neutron into a proton and an electron is mediated by the electroweak force. And that the reaction can be reversed to turn electrons and protons into neutrons, a process that would also result in nuclear transmutation, which in turn my be responsible for the release of excess heat and of nuclear by-products. Both of these things are claimed to be seen in LENR experiments.

Surely it’s time we bury the hatchets on this one and start working out exactly what is going on in LENRs. No?

Ref: arxiv.org/abs/0810.0159: A Primer for Electro-Weak Induced Low Energy Nuclear Reactions

One of the outstanding mysteries of our Solar System is how Saturn’s rings formed.

We know they rings are made of water ice with very few contaminants. We know they are different to the rings around Jupiter, Neptune and Uranus which are much smaller and probably the result of the surface erosion of nearby moonlets.

But Saturn’s spectacular rings are different. They are far more massive, probably several times the mass of the Saturnian moon Mimas. So how did they get there?

There are three main theories, says Julien Salmon from the Université Paris Diderot in France and a couple of mates.

The first is that the rings are leftovers from the primordial cloud and never formed into a moon around Saturn. That seems unlikely say the researchers, because the rings have a different chemical composition to other Saturnian satellites which must have formed from the same cloud.

The next idea is that the rings formed when a comet collided with and destroyed an ancient Saturnian moon.

The final theory is that the rings formed when Saturn’s gravity captured one or more comets and tidal forces broke the comets apart.

These last two are much more difficult to tease apart because we know that about 4 billion years ago, the solar system was filled with comets which bombarded the planets and their moons. This period, known as the Late Heavy Bombardment, could have caused either scenario.

But a detailed analysis by Salmon and co cause them to lean towards the theory that a comet must have collided with an existing moon. Here’s why: if passing comets could be captured and torn apart by tidal forces, then all four gas giants ought to have Saturn-like rings. And Saturn’s ring system ought to be the smallest of the lot because of the planet’s low density and mass compared to Jupiter and its distance from the main body of comets compared to Uranus and Neptune.

So Saturn’s rings must have been formed by a collision between a comet and moon, say Salmon and buddies. And it turns out that only  Saturn (and possibly Jupiter) could have had a moon at the relatively close distance that the rings have formed. (At that distance, moons around the other gas giants would not have been stable because of tidal forces.)

So that settles it: Saturn’s rings formed about 4 billions years ago when  a number of comets smashed apart one of its moons.

Well, not quite. There are still a number of important outstanding details. For instance,  moons and comets are known to contain relatively high fractions of silicates. And yet the rings contain very little silicates. Nobody has adequately explained where these silicates have gone.

And then there is the annoying evidence that the rings may be much younger than 4 billion years old because we can see some of them darkening at a rate which cannot have been going on for too long without turning the rings black.

Salmon and co say that on balance, the late heavy bombardment is your best bet if you wnat to plump for a mechanism that created the rings.

But there’s no need to be hasty– there’s more mileage in this mystery yet.

Ref: arxiv.org/abs/0809.5073: Did Saturn’s Rings Form During The Late Heavy Bombardment?

“Religions are sets of ideas, statements and prescriptions of whose validity and applicability individual humans can become convinced,” say Michael Doebeli  and Iaroslav Ispolatov at the University of Vancouver.

In other words, religions are memes, units of cultural inheritance just like songs, languages or political beliefs. Richard Dawkins proposed the idea that memes spread much in the same way that viruses do, using humans as hosts. Some get passed from person to person and can survive for many generations. Others die away and become rapidly extinct. The most successful adapt and thrive. Evolution acts on memes in the same way it acts on our genes.

That has given Doebeli and Ispolatov an idea: “We propose to model cultural diversification in religion using techniques from evolutionary theory to describe scenarios in which the reproducing units are religious memes.”

The model they use is relatively simple, including factors such as the rates of transmission of religious memes as well as the rate of loss,  but it generate some interesting results.

It predicts, for example, that new distinct religions should emerge as descendants of a single ancestor. Exactly this process has been observed many times in various religions such as the Catholic-Protestant split in the 16th century, and the ongoing fragmentation of a religious organisation in Papua New Guinea, which anthropologists are currently observing with interest.

This is an interesting piece of work and one that could lead to new detail in our  study of memes. Religious meme transmission rates are relatively easy to measure and change more quickly than other widespread memes such as languages. So there is plenty of data to play with.
But if ever an idea was likely to ruffle a few feathers, this is it. They’ll be spluttering over their coffee and donuts tomorrow morning in Dover, Pennsylvania.

Ref: arxiv.org/abs/0810.0296: A Model for the Evolutionary Diversification of Religions

Until now there has been no way to distinguish between this and the Born interpretation. This holds that each outcome of a measurement has a specific probability and that, while an ensemble of measurements will match that distribution, there is no way to determine the outcome of specific measurement.

Now Frank Tipler, a physicist at Tulane University in New Orleans says he has hit upon a way in which these interpretations must produce different experimental results.

His idea is to measure how quickly individual photons hitting a screen build into a pattern. According to the many worlds interpretation, this pattern should build more quickly, says Tipler.

And he points out that an experiment to test this idea would be easy to perform. Simply send photons through a double slit, onto a screen and measure where each one hits. Once the experiment is over, a simple mathematical test of the data tells you how quickly the pattern formed.

This experiment is almost trivial so we should find out pretty quickly which interpretation of quantum mechanics Tipler’s test tells us is right.

Then it boils down to whether you believe his reasoning.

(And not everybody does. When Tipler published his book The Physics of Immortality one reviewer described it as ” a masterpiece of pseudoscience”.)

Let’s hope this paper is received a little more positively than his books.

Ref: arxiv.org/abs/0809.4422: Testing Many-Worlds Quantum Theory By Measuring Pattern Convergence Rates

Vai is a language spoken by 150,000 people in western Africa, specifically in Liberia and Sierra Leone. The language is noteworthy because its uses a remarkable system of sounds. Speakers must be able to pronounce seven oral vowels, five nasal vowels and 31 consonants all of which come in various combinations. In its written form, Vai has 229 characters.

So perhaps it wouldn’t be surprising if Vai had some interesting statistical characteristics not shared by other languages. If so, that might give some insight into the language’s unique history and evolution. This week, Charles Riley at Yale University and a few pals make exactly that claim.

Their analysis focuses on the the written form of Vai and the complexity of the characters in its alphabet. The complexity of a character is a measure of how difficult it is to draw. For example, the letter ‘O’ consists of two arches connected by two line sections which, using the strange arithmetic of character complexity, gives it a complexity of 8. The letter ‘X’ which is two straight lines that cross, has a complexity of 7.

By contrast, most characters in Vai have a complexity of more than 20 and one letter has a complexity of 48.

In all languages analysed to date, the complexity of characters is governed by an overarching rule which is that it is uniformly distributed. That means that there should be roughly equal numbers of characters with similar complexities. That’s true whether the language be Latin, Cyrillic and Runic scripts.

But Vai turns out to be different, says Riley and co. The complexity of the Vai alphabet is a better fit to a Poisson distribution rather than a uniform distribution.

So does that mean there is something special about Vai that sets it apart from other languages?

Maybe. The authors say non-uniform complexity is probably the result of the way the language was first written down in the mid-19th century. Riley and co suggest that this may have been influenced by a Cherokee native American who lived in an American mission in the area at the time.

Cherokee was famously first written down by a tribesman named Sequoyah who had seen western script without knowing what it mean. He then wrote out a similar looking script in which each sign represented a Cherokee syllable.

The clear, if improbably, implication by Riley and pals is that Vai was written down in the same way.

There are two problems with this analysis. First, as far as I know, Cherokee has not been subjected to this kind of analysis. If it has a uniform distribution, this idea is scuppered.

Second, what the authors fail to take into account is that although the alphabet has 229 characters, there is a large amount of redundancy and only 100 or so are in common usage.

When the analysis is redone using only these common characters, I wouldn’t mind betting that a uniform distribution of complexity emerges.

Which means that Riley and co have a little work to do before they take their analysis of Vai any further down this little backwater of linguistics

Ref: arxiv.org/abs/0810.0200: Distribution of Complexities in the Vai script

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A Statistical Approach to Modeling Indian Classical Music Performance

The first step in such an endeavour is work out to look for, which the goal that Lisa Kaltenegger at the Harvard-Smithsonian Center for Astrophysics in Cambridge  and Franck Selsis at the Laboratoire d’Astrophysique de Bordeaux in France have set themselves.

“The spectrum of the planet can contain signatures of atmospheric species that are important for habitability, like CO2 and H2O, or resulting from biological activity (O3, CH4, and N2O),” they say.  “The presence or absence of these spectral features will indicate similarities or differences with the atmospheres of terrestrial planets.”

But  just how similar is a question of some controversy. In one of the most fascinating papers of all time, Carl Sagan and friends analyzed a spectrum of the Earth taken by the Galileo probe, searching for signatures of life. They concluded that the large amount of O2 and the simultaneous presence of CH4 traces are strongly suggestive of biology.

But a more detailed study of this parameter space is necessary and not just from a theoretical point of view, conclude Kaltenegger and Selsis.

And time is short. With over 300 giant exoplanets already detected it is only a matter of time, maybe only months, before astrobiologists will have their first alien test case to analyse.

Ref: arxiv.org/abs/0809.4042: Atmospheric Modeling: Setting Biomarkers in Context

Conducting polymers just keep getting better. This week, Sayani Majumdar at Åbo Akademi University in Finland and pals say they’ve used using an inkjet printer to print a plastic circuit onto a plastic substrate that clearly shows magnetoresistance at room temperature.

That means they can print plastic microchips capable of sensing magnetic fields.  Cool, huh?

Ref: arxiv.org/abs/0809.3864: Towards Printed Magnetic Sensors Based on Organic Diodes