When engineers conduct research on groundwater, the water that flows beneath Earth's surface, they usually think of "large-scale" as one watershed -- an area of land where all of the water on it or ...

Patients treated four cluster headache episodes alternately with high-flow oxygen (inhaled oxygen at 100 percent, 12 L/min, delivered by face mask, for 15 minutes at the start of an attack) ...

crowded galaxy cluster known as Abell 1795. This smoothed Chandra X-ray Observatory image of the galaxy cluster A1795 shows a bright filament some 200,000 light years in length.