Month: January 2012

Graphene is perhaps the thinnest material known. Essentially it is a single, isolated layer of the carbon allotrope graphite. In SpectroscopyNOW this week I discuss new research into how a single layer of graphene is transparent to water molecules in the sense that the water can “see” whatever is underneath without the graphene influence. More details on that and potential applications over on SN, but it was the coincidence of a paper by Geim and colleagues at Manchester, which I covered last week in Chemistry World that intrigued me. On the one hand water interacts with a metal coated with a single layer of graphene as if the graphene were not there, yet multiple layers of graphene oxide are impermeable to helium atoms but will let water pour through.

I asked the author of the single-layer work, Nikhil Koratkar of Rensselaer Polytechnic Institute in Troy, New York to compare and contrast his discovery with the Geim work:

“They appear to be working with a film which could be microns thick,” he told me. “The film is comprised of graphene oxide sheets that have aggregated to form a film. Now graphene oxide is very different from graphene. It is strongly hydrophilic and water spreads completely on graphene oxide. Given the fact that the film is an aggregate of graphene oxide sheets it will have a porous structure and hence it is not that surprising that water seeps through these pores. What is very interesting is that helium does not get through! Which means that the pores in the film are very small. Inspite of that water is able to force its way through these pores which is indeed interesting. In our system we have a single graphene (not graphene oxide) sheet and no pores. So there is no question of the water passing through the graphene.”

When you leave your body to medical science you might imagine some marvellous discovery among your organs and tissues that leads researchers to the wondrous discovery of a universal anticancer drug or something equally stupendous. In reality, it can be a much more mundane, especially for any women donating their mortal coil.

Researchers at Emory University have been testing two techniques for implanting silicone prosthetic breast implants into cadavers. Obviously, the implications of their work will be of relevance to living recipients, rather than the morticians. They have investigated whether the so-called Keller Funnel, which allows the implant to be inserted without the surgeon actually touching it, reduces potential contamination with skin or other bacteria. And, their results show that indeed it does. There’s a 27-fold reduction in transfer of a fluorescent paste smeared on the chest of the cadaver on to the implant surface compared with digital insertion.

Given that microbes such as MRSA could so easily be transferred with the implant using the digital insertion method it is perhaps time for surgeons to switch to this technique and so reduce infection, contracture, and the need for reparative surgery after implantation.

A more technical write-up appears in the 1st February issue of SpectroscopyNOW.

Incidentally, the only difference between industrial grade silicone gel and medical grade silicone gel is one of labelling and certification. As far as I know, surgeons have not been injecting women with the waterproofing material you use to seal around your bath.

The Alchemist learns how to manipulate tiny polystyrene beads with a set of micro-tweezers this week and spots the smoking gun in forensics using capillary-scale ion chromatography and suppressed conductivity. In the world of chemophobia has asked why parabens are still the focus of research into underarm hygiene and breast cancer despite the lack of evidence linking the two in any way. There is also an elemental discovery this week concerning that lowliest of metals, zinc, which may have activity in reducing the symptoms of the common cold. A venture that sounds truly alchemical sees research into burning ice heating up. Finally, a prize teacher.

From my fortnightly column The Alchemist.

On Christmas Day 2006, I posted a blog about how snowflakes are not all different and some of the science underlying the formation of snowflakes. The American Chemical Society had a nice infographic at the time showing the principles of snowflake formation (PDF here). There’s no snow around here, but this is Britain, the weather could change at any moment and although we don’t quite have the four seasons in one day they get in New Zealand, give it a day or two and a warm spell can become a cold snap almost overnight.

Snowflakes have at their heart a minute grain of dust that was once floating in a cloud, this speck of dust is the nucleation centre around which water vapour from the atmosphere can condense and if it is cold enough crystallise as ice. As with any crystallisation process it follows a symmetry intrinsic to the atoms or molecules from which the crystal is formed. In the case of water, the underlying symmetry is hexagonal symmetry. There’s more on this in the snow crystal primer.

Caltech’s Kenneth Libbrecht’s is the snowflake guru, here’s a video montage of his snow crystal gallery set to the tune of A Guy Called Gerald by Humanity (Borngraber & Struver Remix):

One question that puzzled me as a child is how each of the six arms “knows” to grow in the same way? Well, they’re growing under almost identical conditions so that might be expected, except, of course, that pretty drawings and diagrams aside, the six arms of snow crystals don’t actually grow symmetrically at all. At first glance they might look nice and symmetrical but under the microscope a single snow crystal will be seen to be far less than perfect in its symmetry. Symmetrical snow crystals are very rare except on Christmas cards. Speaking of which I abandoned my Christmas rant about octagonal and pentagonal snowflakes which are common in those pretty pictures but are physically impossible in the real world of snow because of symmetry constraints.

I’ve not yet seen the Aurora borealis, nor the Aurora australis, but they’re always on my mind. I am sure they’re amaaazing and wunderfuuul. This week a coronal mass ejection (CME) from the Sun stimulated the earth’s atmosphere and magnetic field to produce some marvellous lights that were even seen as far south as Northern England. There are plenty of photos on the web now and video footage is growing. Amateur astronomers have been gripped by the aurorae, apparently as have amateur astrologers looking for aura…

The aurorae are a natural light show in the sky, most commonly seen at high latitudes (Arctic and Antarctic). They are caused by the collision of energetic charged particles from the sun (the solar wind) at high altitudes (thermosphere). The northern lights are named for the Roman goddess of the dawn, Aurora, and the Greek name for the north wind, Boreas, after Pierre Gassendi, 1621.

“The northern lights are in my mind, They guide me back to you” – Renaissance

Photo: US Air Force photo by Senior Airman Joshua Strang. Eielson Air Force Base, Alaska, Aurora Borealis glowing above Bear Lake.

Sometimes an old viral video needs another airing. In this video from about three years ago, a mixture of corn starch poured into a speaker cone is vibrated at 30 Hz using a signal generator and the video shot at 30 frames per second (coincident timing with the speaker frequency).

Corn starch is a non-Newtonian fluid, which means it does not behave in a “classical” way, it undergoes shear thickening, which means it gets more viscous when a force is applied. You may have noticed it is much easier to stir it slowly than to try and stir it fast.

When the force applied is cyclic, as in the vibrations of the speaker cone, something very odd happens…weird tendrils form and crawl and collapse and regrow.

It’s also worth checking out the ferrofluid sculpture videos that show up when this Youtube clip finishes.

My gut feeling is that visceral manipulation is yet another sCAM practice based on falsehoods, an economy of truth, and, basically, lies. Science-based medicine gives us the low down:

“I think we can reasonably assume that any abdominal manipulation sufficient to disrupt adhesions would risk tissue damage and internal bleeding, but [visceral manipulation] is not likely to do that. As practiced, VM amounts to relaxation, suggestion, and gentle massage; so it is not likely to cause physical harm unless it replaces other, effective treatments. It’s more likely to cause harm to the wallet and to critical thinking.

From Science Based Medicine on VM

A stream of very viscous syrup falling from a nozzle on to a moving belt. At first, the speed of the belt is enough that the thread of syrup is just pulled out straight. However, as the belt is slowed down, the thread at first bifurcates to a meandering state, producing a sine wave and then to a “figure of eight” state and finally, it shifts to a coiling motion similar to what you would observe when drizzing syrup on to your pancakes, for instance. A wonderfully visual example of a Newtonian fluid in action.

There was a little confusion over whether or not the behaviour of the fluid is Newtonian or non-Newtonian. By definition, a Newtonian fluid is one in which the ratio of stress to strain rate is linear. Its graph would pass through the origin and the constant of proportionality is the fluid’s viscosity. A non-Newtonian fluid is any fluid that doesn’t follow that rule, by contrast. Examples include many salt solutions and molten polymers, ketchup (who knew?), custard, toothpaste, starch suspensions (check out cornstarch videos), paint, blood, and shampoo.

More here