Friday, 27 January 2012

When do babies learn about Surface Tension?

Discovering fluids dynamics.  These kids are all peeing while in the water.

A recent revicw of published literature from the past 30 years (wow that is a lot), Kristy vanMarle, together with Susan Hespos of Northwestern University, found evidence for an intuitive understanding of physics in infants as young as two months.  This is the earliest age at which testing can occur.

I have three young nieces, both my best friend and my girlfriend's brother had a babies recently so I am learning more about children. I find it interesting to really understand whether children can understand physical principles at such a young age.  Physics for me should be explored and understood when you are under 10 and can practice it in a real world setting and not when you are in a closed room at a University. 

Children most likely sense and potentially understand the difference of surface tension of different substances.  The study may confer this.  'By five months, they don't expect non-cohesive substances like sand or water to be solid...'. From all baths they receive they probably can understand that adding soap to the water helps to clean better,  the better wettability of cloth diapers vs. synthetic diapers, or clear difference in surface tension of breast milk vs. water.

Children have to learn by interacting with the world though, learning and experimenting about surface tension by interacting with different fluids.  'The majority of an adult’s everyday interactions with the world are automatic, the study author says - and it appears that babies have the same ability to form expectations, predicting the behavior of objects and substances with which they interact.'  However,. this has to be achieved through the 'natural interaction with the parent and objects in the world gives the child all the input that evolution has prepared the child to seek, accept and use to develop intuitive physics." 

Is your baby going to be a physicist that studies surface tension?     Let's hope so we need more of them.


P.S. When we move to the moon or mars we will have to deal with a new set of physics that are not intuitive on earth.  This will be interesting.

Monday, 23 January 2012

Twisting interfacial tension...

The understanding of science and surface tension in particular are one of those things where you think something as old as Benjamin Franklin (who conducted the first studies) would be understood to its fullest potential.  So I am always learning something new about surface science and surface tension in general.  I stumbled upon this that the Dogic group at Bradeis University in Massachusetts has demonstrated a demonstrated a new way of controlling interfacial tension using a change in chirality of a condensed membrane of rod-like bacteriophage virus fd.  By increasing the strength of chirality of the rods it both lowers the energy of the rods along the membrane’s edge and increases the frustration of untwisted rods in the bulk, lowering the interfacial tension  They published this in some unknown magazine called Nature (at least publish in Phys Letters). Here a link to the 2012 article.  (Read then watch these cool movies below)

Let's back up here and explain a few things.  Water has a surface tension of 72 dynes/cm2 which allows many things like water striders and even the ocassional son of God to walk on top of it.  Water also has an another interesting property when you add oil to it.  Oil and water as you have probably figured out do not mix.  Oil will create an interface with the water making a strong interfacial tension (cell membranes are also like this).  Adding soaps or detergents will adjust the surface tension and these soaps which are both hydrophobic and hydrophilic (amphipathic) will move to this interface between the oil and water.  This is basically how your detergents like Tide clean all the stains out of your clothes or SDS can detroy cell membranes.

The Dogic group has made it so that the membrane instead of an outside amphiphile changing the state of teh membrane they changed it using chirality.  Instead of lipid membrane they made a membrane of rod-liek bacteriophage virus fd.  This is a chiral molecule.  Think of your hands being mirror images but cannot superimpose on one another.  Since the rods have this property of chirality they tend to twist in a small angle with respect their neighbors.  When they increased the strength of the chirality it lowers the energy of the rod's along the membrane's edge thus lowering the interfacial tension. 

The interesting thing here is that they can change the microscopic shape of this membrane making it form from a flat two dimensional shape to a one-dimensional ribbon.  This is a fully reversible transition that you can see in the movies on youtube.  Twistier structures have more chiral strength.  In a lipid membrane the change in interfacial tension can be done chemically (by adding different lipids), mechanically or by changing the temperature but it is not always reversible and some degree of hysteresis may occur.

This movie depicts the reversible transition from a 2D membrane to a 1D twisted ribbon by the application of a stretching force imparted by optical tweezers. The diameter of the unstretched membrane is ~10microns.(text taken from youtube)

This movie shows the reversible transition of a 2D colloidal membrane composed of fd viruses into several connected 1D twisted ribbons, induced by increasing the strength of chiral interactions between the constituent virus particles. The duration of the movie is 11.9 minutes. The diameter of the membrane is ~10microns.(text taken from youtube)

Friday, 20 January 2012

Solving the Olive Oil Scandal?

I read this really cool piece by Adam Taylor from Business Insider entitled '21 Crazy Facts About the Corrupt Olive Oil Industry'.  If you love cooking as much as me you will be surprised by this article. Quality olive oil is difficult to find since there are so many cheap versions at local supermarkets.  Olive oil is tasted in spoonful quantities in early mornings in Greek homes I have heard.  You probably would not want to do this with the stuff you get at the local grocery store.

As in Adam's article here are the interesting facts laid out:
1. Olive oil is more expensive than other oils but easy to fake
2.The fake industry is as long and counterfeit as the real olive oil industry (merchants mixed oil with lard to make more profit
3. Sounds like Roman's were drinking the stuff because they consumed up to 50 litres per yer per capita
4. Roman's took the fake olive oil more seriously than we currently do (this is surprising since we have great technology to help prevent faking and to make better quality olive oil)
5. Roman's must have passed on the tradition to their future descendants because olive oil faking is done today and has ties to the mafia.  The main character of the Godfather novel Vito Corleone was based on real life olive oil mafioso Joe Profaci.
6.Once of the world's largest dealer in olive oil Domenico Ribatti was sentenced to 13 years in prison in the 90's for counterfeit olive oil.  That is as many years as drug dealers.
7. Thank you Italy & Greece!  87 % of misappropriated EU subsidies have gone to Italy.  Greece is probably also a haven for this kind of activity.
8.  Thanks to great chef's like David Rocco spreading the word of awesome food made with olive oil.  This oil's consumption has gone up 37% in Southern Europe and 100% in North America.
9. See number 5-7.  Organized crime loves this because food counterfeiting has less charges about half as much penalty than drug dealing....
10.but with profits about the same as cocaine trafficking.  I wonder if they have trained dogs for detecting counterfeit olive oil
11. Italy cops found one ring with 100,000 liters of olive oil equal to 8 million euros.
12 Gangs are getting smarter by using chemical methods to evade chemical testing.  I wonder what these are?    Taste testing is much harder to fool.
13. 787 olive oil producers were investigated in Italy with 205 being charged with different crimes from faulty labels to full on counterfeiting.
14. In 2007 only 4% of olive oil leaving Italy was pure Italian olive oil so this is possibly the reason they can sell three times as much as they produce. 
15.What is an extra virgin?  Extra Virgin olive oil is one withas oleic acid, of not more than 0.8 grams per 100 grams and a peroxide value of less than 20 milliequivalent O2. It must be produced entirely by mechanical means without the use of any solvents, and under temperatures that will not degrade the oil (less than 86°F, 30°C).
16. FDA and probably other bodies do not check so thoroughly so many people can die from this.  Many people did die in Spain from poor oil.

Tom Mueller is also wrote about the scandal of olive oil in the New Yorker and a really great book that I am dying to read

So can measuring the surface tension or interfacial tension help to stop the corruption?  Are more expensive instruments needed?

This is as far as I have gone in my research.  Still looking for answers.

Castor oil surface tension 36.4 dynes/cm interfacial tension15.4 dynes/cm
Olive oil (surface tension 32.0 dynes/cm interfacial tension 17 dynes/cm

Wednesday, 4 January 2012

Why Renewable Surfactants are a Great Idea

Thinking what kind of carbohydrate surfactant is going down the drain.



Much of the thinking I do is done in the shower.  Maybe it is the early morning and without an iphone there is nothing more to do in the shower but think.  It could also be the water pounding on my head stimulating brain waves.  I do not know.  This morning I was thinking about all the soap and detergent from the shampoo I was washing down the drain.  Is this good for the environment and why has nobody come up with something better to clean ourselves and everything else that is dirty?

 Pouring detergents down the sink is not good for the environment.  Most detergents after WWII are made using petroleum.  Most detergents companies tell you to use way more soap than needed. A lot of energy is input to making these products from extracting the oil from the ground to refining the products to fit the needs for a given product takes a lot of energy.  Also the petroleum is getting more expensive and ties a country politically to other countries.  (Tethered by the detergents).  Shell is a huge producer of surfactants and the chemistry behind producing their surfactants have already been developed but the chemistry might not be all that green.

So with all the research and dollars generated by surfactant companies why have they not done a better job at making renewable detergents before it goes down the drain.  Companies like P&G have made better surfactants but more leaps forward need to be achieved in order decrease our dependence on petroleum surfactants.  O-linked carbohydrate surfactants have come as a result of this.  A startup called P2 Science hope to achieve more green chemistry to develop high performance carbohydrate surfactants called C-glycosides.  What is that? 

Carbohydrate-based surfactants represent an increasingly important class of nonionic surfactants with low toxicity.  Tween is an example of this (you might see this on some of the products you are using).  One problem exists with these: the linkage linking the sugar to the rest where a long alkyl chain or a cyclic residue can be placed (to achieve the desired CMC and detergent effect) is an unstable O-linkage which limits their use in products.  Carbohydrate-based surfactants or C-glycoside developed by P2 Science and Yale's Patrick Foley are more stable and can be tuned to have desirable effects to reduce the surface tension.