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Boiling and freezing at the same time?

3/31/2014

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We think of freezing and boiling as opposites, things that happen at very different temperatures. However, under conditions of low air pressure the two can occur together, as we see in this video.
Substances can only be liquid in the presence of a gas to apply vapor pressure. If there is no pressure, or too little pressure, a substance will go straight from solid to gaseous phase as it warms. If you do this in an enclosed space the gas produced will build up, creating pressure as it does so, until a liquid phase is possible. If not enclosed, the gas will escape and the process can continue indefinitely.
 
The most familiar example is solid carbon dioxide, also known as dry ice. Liquid carbon dioxide needs much higher pressure than most other common substances. Under atmospheric pressure it will be a gas above -78.5C (-104.2F) and solid below that temperature. Take some solid carbon dioxide into a room and watch it go straight to gas (but careful, the extreme cold will “burn” you if you touch it).
 
The video above is what happens if a liquid is placed in conditions where the temperature is right at the point where it freezes and the gas pressure is removed. With no pressure it can't stay liquid, but it is right on the cusp between boiling and freezing, so it does a little of both.  Going from liquid to gas absorbs energy, while liquid to solid changes release it. This can keep the process in balance - if too much material boils the temperature will fall, shifting the balance in favor of freezing.
 
Some coverage has wrongly described the video as showing the triple point. However, at the triple point gas, liquid and solid can all survive indefinitely. What we are seeing is what would happen anywhere along the dotted lines to the left of the on the graph below to the left of the triple point.
 
We don't see this sort of thing often because if we performed such an experiment in a closed environment the boiling gas would build up pressure, allowing the remaining material to stay liquid. In the vidoe that is addressed by constantly drawing off the vapor.

Read more at http://www.iflscience.com/chemistry/watch-water-boil-and-freeze-same-time#JbmfsFp4mjwEYoXy.99

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Can we enhance our genes?

3/31/2014

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related videos

"smart genes?"
Cracking the genetic code
using gene therapy to "cure" disease
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Neurosurgeons successfully implant 3D printed skull

3/27/2014

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A 22-year-old woman from the Netherlands who suffers from a chronic bone disorder -- which has increased the thickness of her skull from 1.5cm to 5cm, causing reduced eyesight and severe headaches -- has had the top section of her skull removed and replaced with a 3D printed implant.

read more here
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No more stitches?

3/27/2014

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To supplement or even replace sutures, researchers have proposed applying sticky, biodegradable mats of polymer nanofibers onto surgical incisions to seal them and promote healing. But existing methods of depositing such mats aren’t compatible with living cells and tissues. Now, researchers have demonstrated that they can spray polymer nanofibers directly onto biological tissues using an airbrush from a hardware store
read more here

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How animals see the world

3/21/2014

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Some animals, including your pets, may be partially colorblind, and yet certain aspects of their vision are superior to your own. Living creatures’ visual perception of the surrounding world depends on how their eyes process light. Humans are trichromats—meaning that our eyes have three types of the photoreceptors known as cone cells, which are sensitive to the colors red, green, and blue. A different type of photoreceptors, called rods, detect small amounts of light; this allows us to see in the dark. Animals process light differently—some creatures have only two types of photoreceptors, which renders them partially colorblind, some have four, which enables them to see ultraviolet light, and others can detect polarized light, meaning light waves that are oscillating in the same plane.

“None of us can resist thinking that we can imagine what another animal is thinking,” says Thomas Cronin, a professor at the University of Maryland who studies visual physiology. But while guessing animals’ thoughts is a fantasy, looking at the world through their eyes is possible.

Click the link below to read the rest of this and also to use interactive sliders to see how animals see!

How animals see the world
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