Automated variance reduction for MCNP using deterministic methods.

In order to reduce the user's time and the computer time needed to solve deep penetration problems, an automated variance reduction capability has been developed for the MCNP Monte Carlo transport code. This new variance reduction capability developed for MCNP5 employs the PARTISN multigroup discrete ordinates code to generate mesh-based weight windows. The technique of using deterministic methods to generate importance maps has been widely used to increase the efficiency of deep penetration Monte Carlo calculations. The application of this method in MCNP uses the existing mesh-based weight window feature to translate the MCNP geometry into geometry suitable for PARTISN. The adjoint flux, which is calculated with PARTISN, is used to generate mesh-based weight windows for MCNP. Additionally, the MCNP source energy spectrum can be biased based on the adjoint energy spectrum at the source location. This method can also use angle-dependent weight windows.

Traumatic chronic subdural hematoma over 80 years. A preliminary prospective study.

Six very elderly patients (mean of age: 85 years with range from 80 to 95 years) with mean GCS = 12 and mean clinical grade = 2.5 affected by traumatic chronic subdural hematoma (CT mean maximum thickness = 2.8 +/- 0.46 cm with midline shift = 1.56 +/- 0.48 cm and absence of homolateral mesencefalic cistern in all case but one) underwent parietal or frontal craniectomy under temporalis muscle and 48-h closed subdural drain. There was no mortality as consequence of the operative procedure. In all the patients but one who died postoperatively from a preoperative midbrain infarction secondary to a transtentorial herniation, there was a progressive and slow clinical improvement in spite of residual markedly persistent fluid collection (CT mean maximum thickness 1.44 +/- 0.19 cm) with mass effect (CT mean midline shift = 0.5 +/- 0.17 cm) due to a some failure of the brain to re-expand. Impairment of hemodynamic reserve should be considered as important cause of failure of the brain re-expansion. Clinical and CT control within two months after discharge from hospital demonstrated further clinical improvement (mean GOS = 4.6) and resolution of subdural residual fluid collection. Basing on these results we recommend do not reoperate persistent subdural fluid collection if there is clinical improvement. The patient can be discharged from hospital or transferred to Geriatric Department where he can be clinically and CT evaluated. Only a clinical deterioration or an increase of residual subdural fluid collection provides clear indication to reoperative surgery.

Severe primary malnutrition in US children.

We studied 16 children aged 18 months or less who had severe primary protein-calorie malnutrition. All were admitted to one urban pediatric teaching hospital for treatment of failure to thrive between Jan 1, 1980, and Aug 30, 1984. The definitions of malnutrition were based on those of the Wellcome Trust. The patients had no evidence of medical causes for their conditions and grew rapidly when they were refed in the hospital. Eight were products of teenage pregnancies. Eleven patients were receiving public aid, and four had no third-party coverage. All were markedly below the fifth percentile in weight for length; their mean percentage of expected weight for age was 0.55. The mean hospital stay was 18.5 days. Severe primary protein-calorie malnutrition does exist in the United States. Thorough nutritional evaluation in children with failure to thrive is indicated, and malnutrition should be a reportable condition in the United States.

Should child abuse and neglect be considered when a child dies unexpectedly?

Deaths during two years at a pediatric teaching hospital were studied to develop guidelines for clinicians who must decide when to explore the possibility of child abuse or neglect when a child dies unexpectedly. Unexpected deaths were defined as deaths occurring before arrival at the hospital or within ten days of hospitalization in children past the first month of life and unrelated to any previously known congenital anomaly or medical condition. There were 43 such deaths during two years. The majority (27) were due to natural causes. However, nine deaths were related to suspected child abuse or neglect (SCAN) and in three of those cases evidence of injury was found only at autopsy. The SCAN cases were more often mistaken for medical illness than for uninflicted injury, indicating that autopsy and postmortem skeletal survey are warranted whenever a child dies unexpectedly. The two factors "dead on arrival" and "1 year of age or less" had a positive predictive value for SCAN of 89% and a negative predictive value of 94%. The two factors identify a high-risk group requiring at least hospital-based investigation into the possibility of abuse or neglect. Reporting for SCAN is warranted when unsuspected trauma is found post mortem, there is direct physical or social evidence of child abuse or neglect, or the child is in the high-risk group and hospital-based investigation falls to eliminate the possibility that maltreatment contributed to the child's death.