The NIST ytterbium-doped fiber laser used can provide up to 530 watts of laser output at a wavelength of 1.07 microns. At full power, they were able to deliver as much as 3.5 uN (0.35 mg) of force to the mirror. The experiments showed the expected linear relation between measured force and laser output.
It's just the way coffee is. Coffee is acidic. That's what probably upsets your stomach, especially if you're not eating or drinking other fluids throughout the day. People say that using coffee grounds are excellent for growing plants. BUT, they are only good for growing plants that are acidic soil loving plants.
While coffee is unlikely to cause diarrhea, that does not mean it's not a problem for you. At least one small study published in the journal Digestion in 2001 found that coffee was among the most common foods reported to cause symptoms -- including diarrhea -- in people with irritable bowel syndrome (IBS).