A per diem plan must be a qualified per diem plan in order for the per diem payments to be paid tax-free. Failure to properly administer a per diem plan that is intended to be qualified will have adverse tax implications for both employees and the employer.
A tracheoesophageal fistula (TEF, or TOF; see spelling differences) is an abnormal connection (fistula) between the esophagus and the trachea. TEF is a common congenital abnormality, but when occurring late in life is usually the sequela of surgical procedures such as a laryngectomy.
I dislike the term EMF (Electromotive force) as it is very confusing. Electromotive force, also called emf (denoted $\mathcal{E}$ and measured in volts), is the voltage developed by any source of electrical energy such as a battery or dynamo. Which means that all EMF are voltages but not all voltages are EMF. A voltage is only an EMF if it is a source of energy.