Imaging the atomic structure and local chemistry of platelets in natural type Ia diamond.

In the past decades, many efforts have been devoted to characterizing {001} platelet defects in type Ia diamond. It is known that N is concentrated at the defect core. However, an accurate description of the atomic structure of the defect and the role that N plays in it is still unknown. Here, by using aberration-corrected transmission electron microscopy and electron energy-loss spectroscopy we have determined the atomic arrangement within platelet defects in a natural type Ia diamond and matched it to a prevalent theoretical model. The platelet has an anisotropic atomic structure with a zigzag ordering of defect pairs along the defect line. The electron energy-loss near-edge fine structure of both carbon K- and nitrogen K-edges obtained from the platelet core is consistent with a trigonal bonding arrangement at interstitial sites. The experimental observations support an interstitial aggregate mode of formation for platelet defects in natural diamond.

The amended legislation on procedure-related deaths--an advance in patient care?

Deaths during or after a surgical procedure may be considered medico-legal and subjected to medico-legal autopsy and inquest. We define death in medical terms and discuss the implications of the provisions of the Amended Health Professions Act of 1974 and its recent amendment. Problems with the old and new definitions of such deaths and whether the amendment provides additional patient protection for the patient are considered. We challenge the South African law-makers to review the all-inclusive terminology in relation to such deaths.

Transcranial brainstem stab injuries: a retrospective analysis of 17 patients.

OBJECTIVE: Transcranial stab injuries remain a frequent cause of emergent neurosurgical admissions to neurosurgical units in South Africa. Brainstem stabs are an uncommon, yet often fatal, form of brain injury. METHODS: A retrospective audit of 597 patients with transcranial stab injuries admitted to our unit over a 12-year period (January 1987 to December 1998) identified 17 patients (2.85%) with brainstem stab injuries. The computed tomographic scans of all patients were analyzed, and a detailed autopsy examination of the skull and its contents was performed in all patients who died. Stepwise linear regression analysis was used to formulate a predictive model of outcome for the entire series of 597 patients. RESULTS: The majority of the patients were males (16 patients), and the study group had a mean age of 28.65 +/- 9.59 years and a mean Glasgow Coma Scale score of 8.59 +/- 2.76. Knives (82%) were the most common instruments of penetration. Cerebral angiography identified 3 patients with vascular abnormalities, and autopsy revealed an additional 4 patients with vascular injury. Emergency ventriculostomy was performed in 10 patients for obstructive hydrocephalus. Four of the 17 patients survived (76.5% mortality). Factors significantly predictive of outcome in patients with transcranial stab injuries were the Glasgow Coma Scale score (F = 43.7), the occurrence of intraventricular hemorrhage (F = 22.8), the type of associated lesion (intracranial bleed, vascular abnormality, or brain abscess) (F = 5.9), and the number of operations (F = 3.2). CONCLUSION: The Glasgow Coma Scale score is the most significant predictor of outcome in low-velocity transcranial stab injuries. Brainstem stab injuries have a great propensity for vascular damage. Survivors are incapacitated by severe, fixed neurological deficits.