Solved: the mathematics of sinking stout bubbles

Researchers at the University of Limerick have, they say, solved the riddle of why bubbles of Guinness (or other stouts) seem to sink rather than rise.

You know, the Cascade.

The key, apparently, is the pint glass itself.

Over the last ten years or so, physicists have begun to pick this problem apart. Most recently they’ve shown that it is not the bubbles that sink but the liquid, which circulates in a way that is downwards near the glass walls and upwards in the interior.  As long as the downward flow of the liquid is faster than the upward motion of the bubbles, they will appear to sink.

But that still leaves a puzzle: why does the liquid circulate in this way?

Today, a dedicated team of Irish mathematicians reveal the answer. Eugene Benilov, Cathal Cummins and William Lee at the University of Limerick say the final piece in this puzzle is the shape of the glass, which has a crucial influence over the circulatory patterns in the liquid.

Irish Mathematicians Solve The Guinness Sinking Bubble Problem

There is even a video (downloadable from the article) which shows the phenomenon in action.

The article at The Physics arXiv blog closes with this line: We’ll be following future developments closely.

As will we all.

Research: Guinness doesn’t travel well

Whatever you might feel about Guinness, I’m sure you’ve heard it said that it doesn’t “travel well”. (There’s a joke floating around the intarwebz about this being said in a pub across the street from the St. James Gate brewery.)

Well, some researchers set out to see if this is actually true. Their conclusion?

Guinness tastes best close to home.

Their research is in the Journal of Food Science. From the Abstract:

This study aimed to test the much-pronounced but poorly supported theory that “Guinness does not travel well.” A total of 4 researchers from 4 different countries of origin traveled around the world for 12 mo to collect data on the enjoyment of Guinness and related factors. The main outcome was measured on a Visual Analogue Scale (VAS) from 0 (enjoyed it not at all) to 100 (enjoyed it very much). A total of 103 tastings were recorded (42 in Ireland, 61 elsewhere) in 71 different pubs spread over 33 cities and 14 countries. The enjoyment of Guinness consumed in Ireland was rated higher (74 mm VAS) than outside Ireland (57 mm; P < 0.001). This difference remained statistically significant after adjusting for researcher, pub ambience, Guinness appearance, and the sensory measures mouthfeel, flavor, and aftertaste. This study is the first to provide scientific evidence that Guinness does not travel well and that the enjoyment of Guinness (for our group of nonexpert tasters) was higher when in Ireland. Results, however, are subject to further verification because of limitations in the study design.

You’ll need to pay to get the whole study (or be a researcher that subscribes to the Wiley Online Library).

I’d like to volunteer to help them with that “further verification”.

(via Ars Technica)

Proof that Guinness bubbles go the wrong way

Telegraph: Bubbles in Guinness ‘go down not up’ say scientists

Guinness, in the best Irish tradition, does things differently. The bubbles in a freshly poured pint appear to be cascading down the side of the glass – yet the creamy top which is the drink’s trademark remains.

Members of the Royal Society of Chemistry set out to investigate the puzzle over the course of one lunchtime.

Scientists used a super-fast camera that could zoom in and magnify the bubbles 10 times.

The study showed that the more visible outlying bubbles in a pint of Guinness did move downwards, as a result of circulation flow and drag.

At the centre of the glass, the bubbles were free to rise rapidly, pulling the surrounding liquid with them and setting up a circulating current.

Flowing outwards from the surface, the frothy ”head”, the current hit the glass edge and was pushed down. Bubbles held back by dragging on the side of the glass were caught in the circulation and forced to go with the flow – the wrong way, for a bubble.

(Follow the link for the full article)

I have only one thing to say: Cascade!

Beer hydrates better after exercise than water

I guess I’m out of excuses for not exercising.

Researchers in Spain have discovered that beer after a workout re-hydrates the body better than plain water.

It’s Better To Drink Beer After Exercise Than Water

Professor Manuel Garzon, a member of Granada’s medical faculty, made the finding after tests on 25 students over several months. Researchers believe that it is the sugars, salts, and bubbles in a beer that may help people absorb fluids more quickly.

The subjects in the study were asked to run on a treadmill at temperatures of 104F (40C) until they were close to exhaustion. Once they had reached the point of giving up, researchers measured their hydration levels, motor skills, and concentration ability.

Half of the subjects were given two half pints of Spanish lager to drink, and the other half were given just water.

Garzon said that the rehydration effection in those who were given beer was “slightly better” than those who were given only water. He also believes that the carbon dioxide in beer helps quench thirst more quickly, and that beer’s carbohydrates replace calories lost during physical exertion.

(via Uncle Jack)

Alcohol can prevent erectile dysfunction

What would happen if all the commercials they show during NFL games got mixed together? My current vision is of macro-brewed American light lager and pickup trucks helping old guys get it up.

Well, that may be partly true. A new study out of Australia suggests that moderate drinking may reduce the incidence of ED.

NewScientist: Alcohol stops men being a flop in bed

There is good evidence that excessive drinking can hinder sexual performance after a night out – a phenomenon sometimes called “brewer’s droop”. [We call it "whisky dick" - Ed.] The effect has been noted for many years: “[Drink] provokes the desire, but it takes away the performance,” Shakespeare reminds us in Macbeth.

But over longer periods, moderate drinking doesn’t seem to be linked to erectile dysfunction, says Kew-Kim Chew, an epidemiologist at the University of West Australia in Nedlands, whose team conducted an anonymous postal survey of 1770 West Australian men.

After accounting for differences due to age, smoking and heart disease – all risk factors for ED – Chew and colleagues found that drinkers experienced rates of impotence 25% to 30% below those of teetotallers.

I wonder if this plays into the psychosis of Neo-Prohibitionists?

(via Boing Boing)

Update: Of course, this article is going to be the target of comment spammers for time immemorial.

Genetics can make you an angry drunk

A new study links a high-activity monoamine oxidase A (MAOA) gene with violent behavior, triggered by alcohol.

This genetic sparkplug has already been linked to violent behavior, but alcohol seems to bring out the worst in otherwise not-so-violent people.

Alcohol and a polymorphism of the monoamine oxidase A gene predict impulsive violence

“People react quite differently to acute alcohol exposure,” [Roope Tikkanen, a researcher in the department of psychiatry at Helsinki University Central Hospital and corresponding author for the study said]. “Most individuals become relaxed and talkative, while some – particularly persons who are introverted while sober – become expansively extroverted and aggressive. A dramatic change from a normally introverted personality to extroverted aggressiveness and uncontrolled behaviors under the influence of alcohol was formerly called ‘pathological intoxication’ in Finland.”

Regarding the decline in impulsive-aggressive behavior with aging among high-activity MAOA offenders, Tikkanen hypothesized that it may be due to a correction of low central serotonin levels in the central nervous system.

Tikkanen cautioned against genetic testing for individuals who may be worried for one reason or another about their risk. “Even though whole genome scans will one day be affordable, the average person probably has very many factors that differ from the violent offenders in the study,” he said. “For instance, the average Finnish consumption is two drinks a day or 10 kg pure alcohol per year, whereas the upper 10 percent of violent offenders drink approximately one 0.75 liter bottle of liquor a day or around 100 kg pure alcohol a year.”

I think I know a few of them. They may have already reproduced, though.

No word on any genetic causes for weepy drunks, sloppy drunks, or beer goggles. I expect to hear from a representative of Mothers Against Defective DNA any day now.

The study will be published in the March issue of Alcoholism: Clinical & Experimental Research

(via Geeks are Sexy)

Heavy drinking damages eyesight

No, this isn’t about that old expression about being “blind drunk” or about “beer goggles”. No, a group of Australian scientists have linked heavy drinking to increased risk of age-related macular degeneration (AMD).

AMD is when sight in the center of the visual field fades, and “heavy drinking” is defined as more than four alcoholic drinks per day. Beer was cited in particular.

The Daily Telegraph: Four beers a day can make you blind

Smoking and genetics have been linked to the condition but Dr Elaine Chong from the Royal Victorian Eye and Ear Hospital decided to study the diet and eye health of almost 7000 people over a period of time to determine the contribution of alcohol.

“We found that higher levels of alcohol, more than four standard drinks a day, was associated with a three-fold increase in end-stage AMD in men,” Dr Chong said.

Beer drinking, in particular, carried a six-fold increased risk. Quantities of wine and spirits drunk were too low to evaluate their risk.

The same link was not see [sic] in women, possibly because they were less likely to drink heavily, she said.

No mention of beer’s benefits, of course. Not that I’m suggesting that it’s a health drink. Something else to look forward to in my twilight years. Not that I’m that heavy a drinker, though.

As with all things: moderation.

Engineering a cancer-fighting beer

Resveratrol is getting a lot of press lately. It is the miracle compound which apparently allows the French to enjoy a cuisine loaded with saturated fats and yet avoid heart disease. Its cancer-fighting properties have also been documented.

Some researchers at Rice University are trying to genetically engineer some brewing yeast in order to create beer loaded with resveratrol.

ComputerWorld: University researchers developing cancer-fighting beer

[University of] Wisconsin researchers had noted that adding small doses of resveratrol to the diet of middle-aged mice significantly slows their aging and keeps their hearts healthy. And they added that giving high doses to invertebrates extends their life spans, and high doses also stave off premature death in mice fed a high-fat diet.

[Taylor] Stevenson said that the Rice research group, most of the members of which aren’t old enough to legally drink alcoholic beverages, came up with the idea of adding resveratrol to beer during a casual conversation about potential projects to undertake. “The idea is that it may have greater effects [in beer than in wine],” he added. “The amount of red wine you’d need to drink to get the same results they get with rats in labs is about half a bottle a day.”

He explained that the amount of resveratrol in wine varies from bottle to bottle, since it depends on growing conditions for the grapes and other variables. The researchers felt they could design a beer with higher and more consistent concentrations of the cancer-fighting chemical.

(via Scribal Terror (via Wired (via ComputerWorld)))

Better living through chemistry: fresh(er) beer

Over on ZDnet’s Emerging Tech blog, there’s an article about some scientists in Venezuela who have discovered the chemical compounds that contribute to the “the decline in fresh flavor that occurs as beer ages”.

Secrets of a fresh beer

So the researchers tried to manipulate this Maillard reaction by adding the drug aminoguanidine and a chemical called 1,2-diaminobenzene (1,2-DAB) to the beer. “Over 105 days they detected the appearance of 11 different alpha-dicarbonyls, some of which increased in concentration continuously as the beer aged. This left the team wondering if these highly reactive alpha-dicarbonyls were the ones involved in forming the off-flavours, and what compounds were formed when they reacted with the rest of the beer.”

Of course, they only tested this on a pilsner, and they don’t quite know what’s going on. Obviously, no one is thinking about cellaring beer or even anything “bigger” than a ubiquitous light lager.

Frankly, I’d rather try to stick to actually fresh beer than to have something loaded with chemicals. No preservatives in my beer, thankyouverymuch.

Beer goggles explained

It’s an effect most of us have encountered at one time or another. The hour is late, someone new is looking mighty attractive to you, and then when you sober up you wonder “what the hell was I thinking?”

We call them “ten to two” girls (or guys). You know, they start looking really good at about ten minutes to 2 AM.

Can this phenomenon be expressed in a mathematical formula? Apparently so.

Researchers at Manchester University say while beauty is in the eye of the beer-holder, the amount of alcohol consumed is not the only factor.

Additional factors include the level of light in the pub or club, the drinker’s own eyesight and the room’s smokiness.

The distance between two people is also a factor.

beer goggles equation

  • An = number of units of alcohol consumed
  • S = smokiness of the room (graded from 0-10, where 0 clear air; 10 extremely smoky)
  • L = luminance of ‘person of interest’ (candelas per square meter; typically 1 pitch black; 150 as seen in normal room lighting)
  • Vo = Snellen visual acuity (6/6 normal; 6/12 just meets driving standard)
  • d = distance from ‘person of interest’ (meters; 0.5 to 3 meters)

BBC News: ‘Beer goggles’ effect explained

(via Mental Floss)

Speaking of beer goggles, this music video illustrates the phenomenon rather well. NSFW.


http://www.youtube.com/watch?v=n4BA6F5SfTM