Las Vegas Blooms in the Desert

Las Vegas is the most arid city in the United States, with less than 4 inches of precipitation per year. Yet it has has bloomed, swelling from a population of just 1,205 people in 1905 to 1.4 million by 2000. There are 5,000 new residents and 1,200 new homes a month. Groundwater alone could not supply the ever-increasing population.

In 1974, Las Vegas began pumping water from the Colorado River for the first time to supply its growing need. By 1985, a return flow credit system had been established, whereby for every liter of purified wastewater Las Vegas returned to the Colorado River, it could withdraw another liter of potable water. Las Vegas lies north of Hoover Dam and Lake Mead, and also several major cities. This makes the quality of Las Vegas’ treated water particularly important. Fortunately, the Southern Nevada Water Authority has gone to great lengths to ensure the water’s quality, and Las Vegas’ water treatment is in the 99th percentile nationwide.

Shane Snyder, who came to speak at Duke, is Research & Development Project Manager for the Southern Nevada Water Authority in Las Vegas. He has spent most of his career investigating pharmaceuticals and endocrine disruptors in water, even testifying before a Senate subcommittee about the risk of pharmaceuticals in water. Water contamination with these compounds is a major issue because many water purification systems are incapable of removing them. This is a major obstacle for water recycling efforts, because hormones and pharmaceuticals can have very adverse effects on humans and wildlife that ingest them.

However, Snyder has led the effort to remove hormones and pharmaceuticals from water, pioneering technologies for effectively removing these contaminants. During the lecture, Snyder discussed the effectiveness of treating water with UV radiation, chlorine, and ozone, among others. He noted that many pharmaceuticals and endocrine disruptors don't disappear with treatment, but transform into other products.

Snyder also recognized that water treatment can require a vast amount of energy. In fact, according to Snyder, 19% of California's energy grid is used to treat water.

“I believe that the future lies in making water treatment efficient and making sure that the public is confident that the water will not be harmful to them or their offspring,” Snyder said.

Putting Digital Meat on the Bones

Ever see one of those cop shows or National Geographic specials where a sculptor turns a tattered old skull into a realistic face?

Today's Visualization Friday Forum was a fascinating tour through the history and future of this exacting art with Andrea Stevenson Won, a medical illustrator and modeler from Raleigh who has done work on prosthetics and museum displays. (she hasn't solved any crimes yet, sorry)

Using intimate knowledge of facial anatomy and some average tissue thicknesses at various landmarks across the face, artists like Won can make an educated guess about a skull's former face. Eyebrows, hair, smirks, etc. get into art, and that's where it can quickly get misleading, she said.

Clay's out -- today it's all done digitally, allowing modelers to do three versions of the same skull, as seen here in this reconstruction of a woman who died in Illinois in the 1840s. Andrea also works with Duke's anaplastology clinic, helping make customized prosthetics for patients who are still very much alive.

Wells would have been proud

In 1897, H.G.Wells wrote a book called 'The Invisible Man'- the first time anyone tried to think rationally about invisibility. But that was just another sort of sci-fi fantasy. Around a century later, we are almost there.

Over the last few years, researchers at Duke and elsewhere have achieved remarkable developments in the effort to make things 'invisible'.

In 2006, researchers in the ECE department at Pratt School of Engineering, in collaboration with Imperial College of London, created a brilliant 'cloak' that deflects passing microwaves and behaves as if it were invisible. This was achieved using metamaterials, which in simple terms, can bend light the unexpected way. They can be modified to produce a negative refractive index. The metamaterials were specifically designed and arranged in circles to interact with electromagnetic waves in a way that natural elements cannot. This is the first breakthrough that highlights the uses of metamaterial technology over electromagnetic properties to create the effect of invisibility.

The following is a video of the working model of the first ever invisibility cloak at Duke, which hides a spherical metal cylinder from microwaves:

Even after this achievement, the researchers were not convinced. There were theories which said that the same theory of invisibility would work for 2-D acoustic cloaks, but not for 3-D, as electromagnetic and sound waves fail to be equivalent in 3 dimensions.

As Steven Cummer, Jeffrey N. Vinik Associate Professor of Electrical and Computer Engineering at Duke's Pratt School of Engineering, said 2 years later , "It was hard for me to imagine that something you could do with electromagnetic waves would be completely undoable for sound waves". So, in 2008, the same team devised a mechanism for another invisibility cloak, this time a 3 D acoustic cloak. Working on the same mathematical model they used 2 years earlier, the team proved that an object can be prevented from reflecting sound waves too.

Building upon all this work, scientists at University of California - Berkeley have conducted studies on metamaterials that can bend light the wrong way in 3 dimensions.

Even though we are far from a War of the Worlds or a Time Machine, in the case of an Invisible Man, there is not much longer we need to wait.