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 ...

Among preterm infants, males have a greater incidence of respiratory distress and death than do females born at the same gestational age, likely due to sex-related differences in lung maturation. Our ...