Current water-filtering technology is costly, but MIT scientists are testing a simpler and cheaper method that uses wood from white pine trees.

Removing all the dangerous bacteria from drinking water would have enormous health benefits for people around the world.

The technologies exist for doing that, but there’s a problem: cost.

Now a scientist at the Massachusetts Institute of Technology thinks he’s on to a much less expensive way to clean up water.

MIT’s Rohit Karnik is a mechanical engineer who works on water technologies. He says it’s relatively easy to make membranes that can filter the bacteria out of water. But making membranes cheaply, he says, is not so easy.

One day a few years ago, he was at a meeting on plants and water flow when a light bulb went off in his head. Why not, he thought, use the xylem tissue in plants for water filtration?

Now if you remember your high school biology, you’ll know that xylem is the stuff in plants that transports water in the form of sap from the roots to the leaves.

“And the way the water is moved is by evaporation from the leaves,” says Karnik.

It’s somewhat like what happens when you put a straw into a glass of liquid. Evaporation from the leaves has the same effect as sucking on the straw.

Pulling water up to the leaves this way creates a problem for the plant, but also an opportunity for an inventor.

The plant’s problem is something called cavitation, or the growth of air bubbles, which makes it harder for water to reach the leaves. But Karnik says xylem has a way of getting rid of these bubbles.

“The xylem has membranes with pores and other mechanisms by which bubbles are prevented from easily spreading and flowing in the xylem tissue,” he says.

And it turns out these same pores that are so good at filtering out air bubbles are just the right size for filtering out nasty bacteria.

To prove it worked, he created a simple setup in his lab. He peeled the bark off a pine branch and took the sapwood underneath containing the xylem into a tube. He then sent a stream of water containing tiny particles through the tube and showed that the wood filter removed them.

“We also flowed in bacteria and showed we could filter out bacteria using the xylem,” he says. Karnik estimates the xylem removed 99.9 percent of the bacteria.

But Robert Jackson, an environmental expert at Stanford University, points out that at least as it stands now, the system doesn’t do a good enough job at filtering out bacteria. He wrote in an email that filtering out almost all of the nasty bacteria is certainly helpful, “but when you can have hundreds of thousands, even millions, of them in a drop of water, you don’t want to rely on something with 99 percent efficiency.”

“In a survival or short-term situation this could work,” he wrote. “As a longer-term or global solution to the billion people on Earth without access to clean water, call me skeptical.”

Graphing in “Right Place Right Time” – How I Met Your Mother

Marshall Loves Data Visualizations.

And who can blame him?

Studies repeatedly point to the importance of data visualization in helping us understand and remember information. Think of your own experience – have you ever tried to understand a difficult concept without the use of a visual? Have there been times when a visual was essential to your understanding of the information?

Can you think of an instance where you remembered a concept or idea because of the visual that accompanied it?

Not only does data visualization aid in understanding and remembering, but most of us just like visuals over text alone – kind of like Marshall.

The Power of the Visual

Check out this short video by Column Five on the power of data visualizaton. It shows how simple techniques, like the use of color, orientation and animation can make data pop.

As useful and necessary as graphics are, it is not enough to just plop them into a document. Here are the steps you must take to correctly incorporate a graphic into your work.

Step 1: Label, number and title every graphic. In technical writing, all graphics are either “tables” or “figures” – “tables” are, well, tables (duh) and “figures” are everything else. The graphics should be numbered according to when they appear in your document (“Figure 1, Figure 2″ – or “Table 1, 2″ etc.). Also, every graphic should have an informative title that helps the reader understand the content.

Step 2: Place the graphic in the right spot. Usually, this means as close as possible to the text that refers to it. If the graphic is not directly relevant, OR if the graphic is so large that it interrupts the flow of your document, place it in the appendix (and reference it in the text).

Step 3: Introduce and explain every graphic. Don’t make your reader do all the interpretive work – explain what your graphic is doing and what the content means. Use legends, arrows, captions – anything that will help your reader understand. Also reference every graphic in the text – either before the graphic appears or, if you are wrapping text, next to the graphic. Avoid referencing a graphic for the first time after the graphic has already appeared.

Step 4: Document your graphics. If you didn’t create the graphic yourself (and your company doesn’t already own it), be sure cite the source. If you are publishing your work and the graphic is protected by copyright, you will have to get permission and possibly pay a fee. Most style guides recommend you cite the source in both a references section and in the caption of the graphic itself.

Step 4: Make your graphic stand out. Most graphics stand out anyway, but consider adding rules or boxes or additional spaces to distinguish your graphic from the text. If you are writing a document with several types of graphics, consider using colored screens or filters to separate the, say, marginal glosses from the charts and graphs.

Step 5: Make it easy to find your graphics. If your document includes 4 or more graphics, consider including a list of illustrations (just after your table of contents).

If you are looking for examples, our Technical Definition and Description student samples incorporate most, if not all, of these steps. Plus – you can always use our textbook as an example!