Signal scaling in cascade digital filters

Scaling of filter variables is central to fixed-point implementation of digital filters. A simple method of scaling based on scaling constants of individual sections of a cascade digital filter is presented. The proposed method saves much computational labor in the implementation of higher-order digital filters. Maximal amplitude expressions of second-order filter transfer functions are also presented.This work was supported by the Department of Science and Technology, Government of India, under Grant No. D.O.No.III-5(17)/85-ET.     

Inflammation, pravastatin, and the risk of coronary events after myocardial infarction in patients with average cholesterol levels. Cholesterol and Recurrent Events (CARE) Investigators

BACKGROUND: Idiopathic bile acid malabsorption is a poorly recognized cause of chronic diarrhoea. The SeHCAT (75Selenium HomotauroCholic Acid Test) can accurately diagnose this condition. AIM: To identify patients with idiopathic bile acid malabsorption, to describe their clinical features, both qualitatively and quantitatively, and to assess the response to cholestyramine. METHOD: Idiopathic bile acid malabsorption was considered in all patients complaining of chronic diarrhoea. They were included in the study if their SeHCATs were positive (< 15% retention) and secondary causes of bile acid malabsorption were excluded. The response to therapy with cholestyramine was assessed. RESULTS: Nine patients were diagnosed with idiopathic bile acid malabsorption (median SeHCAT retention 8%, range 3-12.6). Their median daily faecal weight was 285 g (range 85-676) and median faecal fat output was 17 mmol/24 h (range 8.3-38.8). Six patients had an immediate response to cholestyramine. There was a marked reduction in stool frequency (median stool frequency pre-treatment 5/day vs. 2/day post-treatment, P = 0.03). Five patients had large volume diarrhoea (faecal weight > 200 g/day) and three had steatorrhoea. CONCLUSIONS: Idiopathic bile acid malabsorption, once suspected, especially by documenting true 'large volume' watery diarrhoea or steatorrhoea, is easily diagnosed and response to therapy is often very good. There is often a previous history of gastrointestinal infection and this condition should be considered in patients with chronic diarrhoea of undetermined origin, especially before they are labelled as having irritable bowel syndrome.     

Rheological studies on Streptomyces fradiae ScF-5 in submerged fermentation

Studies on the rheology of Streptomyces fradiae ScF-5 in a 10-dm³ submerged fermenter for the production of intracellular glucose isomerase revealed that the apparent viscosity of the broth increased with increase in cell density up to 24 h and then declined while the density of the broth remained constant. The plot of shear stress versus shear rate at various fermentation periods showed the applicability of the Casson model. The yield stress and consistency index were found to increase gradually then decrease subsequently. In contrast, the flow behaviour index was less than unity and remained constant throughout the fermentation. The results contrast with the findings of other workers on the Newtonian and non-Newtonian character of fermentation broths and the applicability of the power law model to such systems.     

Self diffusion studies on cobalt thin films

The study of lateral diffusion in thin metallic films is important from the application point of view, especially in electromigration reliability studies. Lateral self diffusion in cobalt thin films is studied using a non-destructive tracer scanning method. Neutron irradiation is employed to make a well-defined radioactive (⁶⁰Co) region in the middle of a continuous cobalt thin film stripe of width 3 mm. The experimental data are fitted to the appropriate solution of the diffusion equations by means of a non-linear least square fitting procedure using a computer. The diffusion experiments are conducted in the temperature range 300–600°C in argon atmosphere. This thin film data are compared with the diffusion data available on bulk cobalt. The activation energy for surface diffusion obtained (0·14 eV) is very much smaller than the reported activation energy for grain boundary diffusion in cobalt.