A dose of watermelon a day could help keep high blood pressure at bay. Scientists say the fruit contains compounds that widen blood vessels and may cut risk of heart attack and stroke:

"Watermelon is an edible source of L-citrulline -- a compound vital in the production of nitric oxide, a gas that widens blood vessels. Researchers in the U.S. gave a group of volunteers a daily dose of 6g, or slightly more than a teaspoonful, of L-citrulline extracted from watermelons.

"All of those taking part had pre-hypertension, or borderline high blood pressure. After six weeks, readings had improved in all nine participants, with none experiencing any side-effects."

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A new study says tests actually help students learn. The act of retrieving information improves memory, so researchers recommend taking practice tests while studying for an exam:

"The study, published in the Oct. 15 issue of the journal Science, suggests that rather than dread tests, students should embrace them.

"'It'd be great to have more tests in the classroom, but also to get students to test themselves more often when they're studying,' said study author Mary Pyc, a postdoctoral fellow at Washington University in St. Louis who completed the work as a graduate student at Kent State University in Ohio. Although many people view tests as a way to mark and grade students' progress, research has found that the act of retrieving information from memory actually makes remembering it easier. In other words, tests improve learning."

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Doctors say mouth-to-mouth resuscitation isn't always necessary when giving CPR. Performing chest compressions by themselves could increase a heart attack patient's chance of survival by 20 percent:

"U.S. researchers say giving mouth-to-mouth actually interrupts time which should be spent on chest compressions to keep blood flowing round the body. If patients are only given chest compressions, survival rates increase by a fifth, they found.

"Dr. Peter Nagele, of Washington University School of Medicine, in St Louis, said: 'Our findings support the idea that emergency medical services dispatch should instruct bystanders to focus on chest-compression-only CPR in adults with out-of-hospital cardiac arrest.'"

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