Blogs / Discoblog

Murderers desperate to get rid of evidence might want to consider using bleach to wash away stains. But not just any bleach will do. When old-school chlorine-based bleach is splashed all over blood-stained clothing, even if the clothes are washed ten times, DNA is still detected.

So for the criminal aspiring for perfection, here’s the secret you’ll need to know: It’s the oxygen-producing detergents that will get rid of any incriminating evidence for good.

Researchers at the University of Valencia tested oxygen bleach on blood-stained clothing for two hours and found that it destroys all DNA evidence. Forensic tests such as luminal tests rely on the ability of blood to uptake oxygen: A protein in the blood called hemoglobin (responsible for transporting oxygen throughout the body) reacts with hydrogen peroxide and gives a positive test result.

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Vampirism isn’t just for bats and Edward Cullen anymore. Some ordinary insects are also beginning to covet human blood, sweat, and tears, because these fluids contain valuable salt that is hard to find in their natural environment. Surprisingly, many species are even preferring salt to energy-rich sugar.

The idea that salt attracted bugs first dawned on a team of sweaty scientists studying insects in Peruvian forests. Puzzled by the swarms of tiny bees attacking them, the scientists soon realized that the bees were trying to get a taste of their sweat. Animals need salt to activate nerves and muscles, and to maintain water balance in their cells.

Intrigued, the scientists littered the forest floor with hundreds of vials filled with either sugar or salt and counted the ant species they baited. They found that ant species living within 100 kilometers of the oceans (with easy access to salt) chose sugar over salt. But ant species living farther inland had a noticeable preference for salt. Reporting in the Proceedings of the National Academy of Sciences, the scientists say the salt cravings were only seen in vegetarian ants, since carnivorous ants can get enough salt from the bodies of their prey.

Which brings us to the vampire moths.

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Centrifuges are a pain to carry around. They also cost hundreds of dollars and need to be plugged in. All of which means that medical facilities in poor rural areas often go without this essential piece of diagnostic equipment that’s used to separate blood plasma for detecting infectious diseases.

Now, Harvard scientists have developed a portable, manually-operated centrifuge that does the job, and it only costs $2.50. To top it all off, it’s even dishwasher safe.

The scientists purchased an ordinary eggbeater from a local grocery store, removed one of the rotor blades, and taped a thin plastic tube containing blood to the remaining blade. Spinning the handle of the eggbeater at a comfortably brisk pace can fling the tube of blood round and round at a rotational speed of 1200RPM. That’s enough to separate blood cells from blood plasma, the clear liquid part of blood used to run cholesterol assays or to screen for diseases such as Hepatitis B and cysticercosis. Right now, infectious diseases cause up to half of all deaths in developing countries.

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