Posts Tagged ‘black’

Ferrofluid patterns and dancing art, fun with magnets

// April 29th, 2011 // 1 Comment » // How Things Work, Just for Fun, Science Art

Behold ferrofluid, nanoparticles of iron coated in a surfactant and suspended in a solution of oil or water.

The surfactant can be citric acid or soy lecithin, among other things, and is used to stop them sticking together

It’s like magnetic dust.

Put a magnet under some ferrofluid and the particles align themselves in patterns to show the field.

The magnetic attraction is so strong, the ferrofluid will stick to a magnet and then you’ll never get all the iron particles off it. They’re stuck for good.

To prevent that happening, people usually play with ferrofluid inside a sealed container.

And play it is, this stuff is fun.

Usually.

A friend of mine put a magnet above some ferrofluid with the lid off, and was abruptly COVERED in black gunk which stuck to him despite three showers. He wasn’t too happy, I think it smelled pretty bad. Hardcore.

Like most hardcore stuff, it’s been turned into kickass art. This video pretty well blew my mind.

Sachiko Kodama and Yasushi Miyajima created the piece, two ferrofluid sculptures which move synthetically to music. The two towers are iron cores of electromagnets sitting in a pool of ferrofluid. Etched with a helix pattern, the ferrofluid can move up the tower if the magnetic field is strong enough, stretching out in spikes as it goes.

The strength of the electromagnet is linked to metadata in the music controlling the voltage and AC pattern. To correct for the time delay, the electromagnet controls starts early so the maximum size of spikes coincides with beats of the music.

The result is a choreographed pattern that dances and winds like a living thing.

You can buy ferrofluid from Emovendo.

Hat tip to @DrSkySkull, who bought some ferrofluid as a classroom demo and supplied the picture at the top of the article.

Science that’s only skin deep

// December 3rd, 2010 // 2 Comments » // How Things Work, Recent Research, Science Communication, Sex and Reproduction

I’m a guest blogger for the RiAus, and this post also appeared on their fancy website. To tell the truth, I really wanted to call this post “Hormonally Yours” in homage to the Shakespeare Sisters (anyone?) but I’ll save it for another post.

Recently I was in Arnhem Land, visiting some Indigenous communities with a couple of friends. While I was there, I got pretty jealous of everybody’s darker skin. “It’s so well suited for Australia,” one of my friends lamented. “I should be in Norway or something.”

Pale skin like mine is not great for Australia. I tan pretty easily, but only after being burned bright red. While I was in the NT I slathered sunscreen religiously, but still managed to get a highly embarrassing burn on my lower back when I was building a sandcastle (an epic sand turtle, actually. Totally worth it.)

Anyway, enough about me and my weirdly tanned lower back (it’s been months! Why won’t it go away?) Let’s talk about Nina Jablonski, an anthropologist. In 2000 she suggested a new reason why skin colour varies so much. It’s not an adaptation to protect against skin cancer and sunburn, like I always thought it was.

It’s real job is to keep us highly fertile by maintaining a delicate balance between two key vitamins: Vitamin D and Folic acid.

Pica's skin tone matched her UVB exposure like her scarf matched her dress. Image by Monja Con Patines

Vitamin D is obtained through some foods, but mostly from drinking in sunshine. UV light turns cholesterol into Vitamin D, which then goes to either your liver or kidneys to be converted to an active form.

Once active it helps white blood cells like macrophages kill bacteria, and helps control levels of calcium and phosphate – important for building healthy bones.

Deficiency in Vitamin D causes rickets, a disease resulting in soft, easily broken bones and deformity which can lead to early death.

So getting enough UV (specifically UVB light) is important to not dying, and therefore having reproductive success later in life. It’s been backed up by Yuen, A. (Vitamin D: In the evolution of human skin colour DOI: 10.1016/j.mehy.2009.08.007)

Natural selection favours soaking up UV.

Penny stayed under foliage at noon to protect her folic acid. Image by Monja Con Patines

Folic acid is obtained in leafy vegetables and fortified cereals. Rather than being made by UV, the light can destroy folic acid by literally breaking it apart. (Jablonski, N. The evolution of human skin coloration DOI: 10.1006/jhev.2000.0403)

Critical for DNA synthesis, folic acid is essential during pregnancy when a lot of new cells are being made.

Folic acid prevents against 70% of neural tube defects in embryos. Its destruction by UV is bad news.

Natural selection favours avoiding UV.

So there’s an ideal amount of UV light that needs to get through the skin – enough to produce Vitamin D, but not too much to destroy all the folic acid. Getting the balance right for the environment you’re in means higher fertility, which drives natural selection

This is what Nina Jablonski thinks caused the evolution of skin colour through the sepia spectrum we see today. Dark skin, with high melanin, stops more UV light. That’s exactly what you want if you live in a place with a lot of sun, like places near the equator. Light skin lets more UV in, which is great if you live somewhere overcast and not very high on UV.

Understanding how your skin colour (NOT your race) influences these two vitamins is important in being healthy. It’s more important now than ever, because we humans travel a LOT.

Sadly, Australia is pretty high in UV and I am pretty white. Thank god for sunscreen.

Things are rarely that simple though, and I imagine there’s a few different things going on that connect UV light to skin colour.

On Tuesday the RiAus is holding an event called Skin Deep: Exploring human ancestry. They’ll be showing a preview of a new SBS documentary about skin colour scientific research, as well as results from the Genographic Project. Basically they took DNA samples from a lot of volunteers and some national identities, and now they’re giving us the goss on who’s related to who’s secret love child.

I’ll be there, I’d love to see you (though seats are limited.) I’ll be the one tweeting in the corner. Follow me @CaptainSkellett

Would love to hear from anyone who took part in the Genographic Project, and anyone who didn’t. Who would you most like to be related to? For me it’s David Attenborough, then I can dream of inheriting his voice.

Gold nanoparticles make plants glow in the dark

// November 8th, 2010 // 1 Comment » // How Things Work, Recent Research, The Realm of Bizzare

Image by Yellowcloud

Imagine if instead of having sensor lights to illuminate a garden path, you could line it with light-emitting plants. You could stroll along bio-luminescent flower beds, dancing in dappled moonlight and delighting in eerily lit peace, free from the shackles of electricity.

It could be possible with sea urchin shaped gold nanoparticles. Seriously, every time I turn on my computer the world gets more random. Sea urchins, I ask you. In any event, they’re called nano-sea-urchins.

Taiwanese researchers made a solution of gold nano-sea-urchins and dipped into it an aquatic plant, Bacopa caroliniana or blue waterhyssop. The nanoparticles moved into the plant over a day or so, and stayed there for about a month.

When exposed to UV light, the nanoparticles produced blue-violet light which encouraged the chlorophyll inside the plant to make red light. The result? An awesome glowing plant, just add UV.

It’s exciting stuff, there are a lot of excellent uses for light emitting things that work inside plants or animals. If the particles could be attached to a drug we could track exactly where the drug goes over the course of a treatment. You could attach it to proteins and find out where they are located inside a plant. Or you could just have a sweet glow in the dark plant in your house or garden.

Of course, you still need to have that UV source. But what’s wrong with having black light in your house or garden? Just think of the possibilities… You could drink tonic water every day, that stuff glows blue in black light because of the quinine.

Also, if you’ve ever wondered if black light can cause sunburn (as I recently have) here’s the low down. Black light is made of UV light which is close in wavelength to visible light, so it’s quite low energy. This counts as UVA, not UVB which causes most sunburns. Large amounts of UVA (such as those found in tanning beds) can cause skin cancer or premature aging, but the small amount contained in black lights is unlikely to do much damage.

ResearchBlogging.orgSu, Y., Tu, S., Tseng, S., Chang, Y., Chang, S., & Zhang, W. (2010). Influence of surface plasmon resonance on the emission intermittency of photoluminescence from gold nano-sea-urchins Nanoscale DOI: 10.1039/C0NR00330A

Hat tip to New Scientist






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