Hexagonal Boron Nitride Coated Carbon Nanotubes: Interlayer Polarization Improved Field Emission.

Coating of h-BN onto carbon nanotubes induces polarization at interfaces, and charges become localized at N and C atoms. Field emission of coated tubes is found to be highly stable, and current density fluctuates within 4%. Study further reveals that the electric field established between coatings and tubes facilitates charge transfer across interfaces and electrons are emitted through occupied and unoccupied bands of N and B atoms.

Clinical features of fatal asthma.

To characterize the clinical features of fatal asthma, we retrospectively analyzed the clinical characteristics of patients who died of an acute asthma attack in our hospital during a 15-year period from 1989 to 2003. Twelve patients had fatal asthma during this period, including eight who were dead on arrival in the emergency room (ER) and three who died within 1 hour of admission to the ER. Patients were categorized into three groups according to the clinical presentations during the fatal attack: (1) rapid (< 3 hours) decompensation in four patients; (2) gradual development of respiratory failure over several days in two patients; and (3) acute deterioration after unstable asthma lasting several days in six patients.