Residents of Portland, Oregon, voted down, yet again, an effort to add fluoride to their tap water.

For the U.S. Navy and Northrop Grumman, it's shaping up to be a banner year in unmanned flight. While the carrier-based autonomous X-47B continues to hit milestones aboard the USS George H.W. Bush somewhere off the East Coast, out west in Palmdale, Calif., today the Navy flew its MQ-4C Triton maritime drone for the first time, marking the beginning of a sea change (pardon the pun) in the way the U.S. military patrols the oceans. The drone flew for 80 minutes and reached an altitude of 20,000 feet.

The colloquial medical advice "rub some dirt in it" appears to have some merit. Researchers at Arizona State University's Biodesign Institute have been experimenting with different clays, and it appears in research presented in the journal PLoS ONE that they've come across a family of antibacterial clays capable of killing pathogens ranging from E. coli to methicillin-resistant Staphylococcus aureus, otherwise known as hard-to-kill MRSA.

Monday's tornado in the Oklahoma City area killed at least 24 people and leveled a massive number of homes and businesses. The L.A. Times quoted weather officials as saying the twister "was at least in the same league" as the harrowing tornado that struck the same area in 1999, while one local meteorologist called it "the worst tornado in the history of the world."

A nanorose may not smell as sweet as an organic one, but the red petals on this micron-scale flower are unquestionably just as beautiful. At Harvard University, materials scientists have perfected an underwater chemical reaction that results in these gorgeous, self-assembling nanoflowers.

Here's a full-on "disk" shot of the planet, taken by NOAA's GOES-13 satellite. (Fun fact: NOAA is pronounced like the name "noah.") You can see the storm over the central part of the US.

A copy of the genetic code of an H7N9 avian flu-similar to, but not exactly the same as the flu that has killed 36 people in China-arrived in a lab in Boston Easter Sunday, 2011. By Saturday, scientists had made a vaccine against it, the Boston Globe reported.