Cubic phase content and structure of BN films from an X-ray absorption study.

X-ray absorption near-edge structure (XANES) was used to study the cubic boron nitride (c-BN) content in the BN films deposited on various substrates by different physical vapor deposition or plasma-enhanced chemical vapor deposition methods. By fitting the XANES curves of thin-film samples using standard spectra of pure c-BN and sp(2)-bonded BN in the films with suitable weight factors, the c-BN contents at the film's surface region and across the film's thickness have been determined quantitatively. The results agree well with the previous transmission electron microscopic observations. The method is proved to be independent of the optical properties of thin film and provides a possibility to evaluate the cubic content of BN films accurately.

Intubation conditions with low dose rocuronium under sevoflurane induction for children.

BACKGROUND: During short surgical procedures and when there is a need to avoid the use of anticholinesterase at the end of surgery, the use of a smaller intubation dose of neuromuscular blocking drug is preferred. The aim of this study was to evaluate tracheal intubation conditions using smaller doses of rocuronium for children under sevoflurane induction. METHODS: Eighty American Society of Anesthesiologists classification physical status I or II children were enrolled. After mask induction with sevoflurane with nitrous oxide for 3 minutes, 0.3 mg/kg of rocuronium was given. Intubation was performed 60 or 90 seconds thereafter. Study group A included children aged 1 to 3 years and 90 seconds between rocuronium injection and intubation. Group B included children aged 1 to 3 years who had 60 seconds between rocuronium injection and intubation. Group C included children aged 4 to 6 years who had 90 seconds between rocuronium injection and intubation. Group D included children aged 4 to 6 years who had 60 seconds between rocuronium injection and intubation. Intubation conditions were judged based on the scoring of ease of jaw opening and laryngoscopy, position of the vocal cords, and degree of straining after tracheal intubation. RESULTS: All 80 children underwent successful tracheal intubation without laryngospasm or any complications. Intubation conditions were judged as optimal in all children in group A, 95% in group B, 80% in group C, and 65% in group D. CONCLUSIONS: A total of 0.3 mg/kg of rocuronium was sufficient for tracheal intubation for children 1 to 6 years old under sevoflurane induction. To guarantee optimal intubation conditions for elder children, allow 90 seconds waiting time after rocuronium administration was recommended.

Studying the growth of cubic boron nitride on amorphous tetrahedral carbon interlayers.

The growth of cubic boron nitride (cBN) films on bare silicon and amorphous tetrahedral carbon (ta-C) layers prepared on silicon substrates was studied. The cBN films were prepared by radio frequency magnetron sputter deposition at approximately 870 degrees C. The original ta-C interlayers were graphitized and restructured under high temperature and possibly under ion bombardment during BN deposition. The majority of graphitic basal planes were nearly perpendicular to the surface of silicon substrates. The BN films grown on these restructured carbon layers were deposited with higher content of cubic phase and did not show delamination signs. Turbostratic BN (tBN) basal planes extended carbon basal planes and their edges served as cBN nucleation sites. The cBN films grown on textured ta-C interlayers were insensitive to the ambient environment. The residual sp(3)-bonded carbon phase confined in the interlayers probably acts as a diffusion barrier preventing the oxidation of dangling bonds near BN interface and thus precludes weakening the interface as a result of volume expansion. The carbon interlayers also improve the crystallinity of the oriented tBN because they are continuation of carbon graphitic basal planes so that the volume fraction of nitrogen-void (N-void) defects in the sp(2)-bonded BN intermediate layers is reduced. The strong sp(3)-bonded carbon matrix could thereto withstand large compressive stress and facilitates deposition of thicker cBN films.