Influence of dry and wet cleaning on the properties of rapid thermal grown and deposited gate dielectrics

Various silicon surface cleaning processes for rapid thermal in-situ polysilicon/ oxide/silicon stacked gate structures have been evaluated. Metal-oxide-semiconductor capacitors were fabricated to assess the effects of cleaning on the quality of gate oxide structures produced by both rapid thermal oxidation (RTO) and rapid thermal chemical vapor deposition (RTCVD). Excellent electrical properties have been achieved for both RTO and RTCVD gate oxides formed on silicon wafers using either an ultraviole/zone (UV/O₃) treatment or a modified RCA clean. On the contrary, poor electrical properties have been observed for RTO and RTCVD gate oxides formed on silicon wafers using a high temperature bake in Ar, H₂, or high vacuum ambient. It has also been found that the electrical properties of the RTCVD gate oxides exhibit less dependence upon cleaning conditions than those of RTO gate oxides. This work demonstrates that initial surface condition prior to gate oxide formation plays an important role in determining the quality of RTO and RTCVD gate oxides.     

Neuromuscular disorders associated with failure to wean from the ventilator

OBJECTIVE: To determine, by retrospective chart analysis, the frequency, type and significance of neuromuscular disorders in patients whose clinical features suggested a neuromuscular cause of failure to wean. BACKGROUND: Failure to wean is a common and difficult problem in critical care units. While a neuromuscular cause may be suspected in some patients, the frequency and type has not been determined utilizing comprehensive electrophysiological studies of limbs and the respiratory system. Such knowledge may aid in patient management and prognosis. METHODS: The clinical setting was a critical care/trauma centre that admits 1500 patients per year, approximately 500 being on ventilators for longer than five days. We analyzed the hospital charts of 40 patients admitted to the unit during three years, whose respiratory assessment suggested a neuromuscular cause for failure to wean from the ventilator. To investigate this possibility, we performed electrophysiological studies of the limbs and also of the respiratory system by phrenic nerve conduction and needle electromyography of the chest wall and diaphragm. The results were compared to 25 healthy controls. RESULTS: 38 of 40 patients (95%) had a neuromuscular disorder: 25--critical illness polyneuropathy, 2--Guillain-Barré syndrome, 4--diabetic and critical illness polyneuropathy, 2--uremic and critical illness polyneuropathy, 10--an abnormality of central drive, 5--unilateral phrenic nerve palsy, 3--a neuromuscular transmission defect, and 5--a primary myopathy. Fifteen (38%) had a combination of disorders. Patients with more severe polyneuropathy took longer to wean, a mean of 136 versus 52 days (p = 0.007). The severity of the polyneuropathy had no effect on mortality. CONCLUSIONS: Electrophysiological studies of limbs and the respiratory system are together valuable in confirming the presence, and identifying the specific type of neuromuscular cause for difficulty in weaning from the ventilator. This information is important in patient management and prognosis.     

AIDS dementia complex with generalized myoclonus

Focal and segmental, but not generalized, myoclonus have been described with human immunodeficiency virus (HIV) infection. We describe three patients with generalized myoclonus and acquired immunodeficiency syndrome (AIDS) dementia complex. In each, myoclonus persisted until death, invariably after a course of a few months. In two patients, myoclonus was elicited by sudden auditory stimuli and resembled a startle response. This form of myoclonus may be subcortical in origin. We suggest that the AIDS dementia complex be included among the causes of myoclonic dementia.     

p53 antibodies in the saliva of patients with squamous cell carcinoma of the oral cavity

A significant age dependence of the risk of complete heart block complicating radiofrequency ablation of the AV nodal slow pathway was noticed, with no patients <45 years of age experiencing this complication.     

Molecular genetic diagnosis of von Hippel-Lindau disease in familial phaeochromocytoma

Inherited predisposition to phaeochromocytoma is seen in multiple endocrine neoplasia type 2 syndromes, von Hippel-Lindau (VHL) disease, and neuro-fibromatosis type 1. In addition familial phaeochromocytoma alone has been reported. To investigate the genetic basis for familial phaeochromocytoma alone, we screened three affected kindreds for mutations in the RET proto-oncogene and the VHL tumour suppressor gene. We did not detect MEN 2 associated RET mutations in any family, but missense VHL gene mutations (V155L and R238W) were identified in two kindreds with no clinical evidence of VHL disease. Patients with familial, multiple, or early onset phaeochromocytoma should be investigated for germline VHL and RET gene mutations as the molecular diagnosis of multisystem familial cancer syndromes enables appropriate counselling and screening to be provided.     

The influence of trend on estimates of accidents at junctions

While reliable estimates of expected accidents can be achieved by combining observed accidents and accident model predictions using an empirical Bayes approach, there are a number of obstacles to the widespread adoption of the method. This paper concentrates on problems associated with the available predictive models. Of particular concern is the effect on model predictions of accident trends over time resulting from, for instance, traffic growth or national road safety programmes. Since accident models invariably include traffic flow as an explanatory variable, the effects of flow changes can be included provided that account is taken of the nonlinear relationship between accidents and exposure. It is, however, common to assume that accident risk per unit of exposure is constant over time, whereas national data imply that accident risk is declining. In addition, there is a need, in practice, to rank and evaluate remedial sites in terms of the specific accident types or severities which might be targeted by treatment (for example, wet road accidents in the case of surface treatment). This then raises the question of whether the proportions of accidents of various types varies over time or with traffic flow and site characteristics. Generalized linear modelling was used to develop regression estimates of expected junction accidents (both in total and disaggregated by severity, road surface condition and lighting condition) which allow for the possibility of accident risk varying over time. Accident risk at the sample of some 500 junctions was shown to be declining annually by an average of 6%, with no significant difference in the value of trend between accident types. The factors which affected the proportions of accidents of various types included the method of junction control, speed limit and traffic flow.     

Rapid detection of Listeria monocytogenes in food using culture enrichment combined with real-time PCR

A rapid method for the detection of Listeria monocytogenes in foods combining culture enrichment and real-time PCR was compared to the ISO 11290-1 standard method. The culture enrichment component of the rapid method is based on the ISO standard and includes 24 h incubation in half-Fraser broth, 4 h incubation in Fraser broth followed by DNA extraction and real-time PCR detection of the ssrA gene of L. monocytogenes. An internal amplification control, which is co-amplified with the same primers as the L. monocytogenes DNA, was also included in the assay. The method has a limit of detection of 1–5 CFU/25 g food sample and can be performed in 2 working days compared to up to 7 days for the ISO standard. A variety of food samples from retail outlets and food processing plants (n = 175) and controls (n = 31) were tested using rapid and conventional methods. The rapid method was 99.44% specific, 96.15% sensitive and 99.03% accurate when compared to the standard method. This method has the potential to be used as an alternative to the standard method for food quality assurance providing rapid detection of L. monocytogenes in food.     

Finite element method applied to the supersonic flutter of circular cylindrical shells

The application of the finite element method to the supersonic flutter of circular cylindrical shells subjected to internal pressure and axial compression is presented. A circular cylindrical shell element is used. The element stiffness, mass and initial stiffness matrices are given. The element aerodynamic matrix is derived based on a first order high Mach number approximation to the linear potential flow theory. The eigenvalue problem is solved by the QR algorithm. Numerical results are presented and these are compared with analytical solutions and experimental data.