Other reasons given are the intense concentration required and, for some, the adrenaline rush.

US Navy pilots practice low-level flying constantly, but the dangers remain, and the concentration required to precisely 250 feet above the water at.

Neither the music nor the concentration required to keep the vehicle on the road fully occupied his thoughts.

Mouth rinses containing fluoride in lower strengths are available over-the-counter; stronger concentrations require a doctor's prescription.

Concentration of adsorbate in the solution - low concentrations require longer immersion times and often create highly crystalline domains.

The effort and the concentration it required to walk helped to keep his mind off his body and its craving.

However, concentrations of gas burn and require precautions to avoid fires.

At the same time, concentration required shutting out peripheral stimuli, as he knew from experience.

Products which are capable of sterilising are either so noxious or corrosive in the concentration required that they cannot be used.

Smaller fragments and lower concentrations will require longer times to achieve the same recovery.