Q: I frequently see ads that ask for writing samples, along with the résumé and cover letter. I have hesitated to respond to these job ads because I’m not sure what kinds of things I should submit.

In quality control and chemistry, analytical samples are usually mixtures. Understanding the main compound’s assay and the number of impurities or other unwanted substances in the sample is essential ...

The usability of a contact lens largely depends on its design. Contact lenses need to be safe and convenient as they are in close contact with the eye and people may use them for extended periods of ...