Carbonitriding of Clay: Relation between the Weight Loss and Crystalline Phases during Reaction

β'-Sialons are phases of the Si-Al-O-N system. The carbonitriding of clays and kaolins is a preparation method. The reaction mechanism of clay carbonitriding is verified by means of the relation among crystalline phases formed and the weight loss produced in the samples during the reaction. Two clays were previously mixed with carbon black and pressed into pellets, flowing through N₂ atmosphere, at five temperatures within the range 1335–1427°C. The phases formed (XRD)—mullite, SiC, β'A-sialon, and oxynitrides—were related to the weight loss measured in the pellet independently of reaction temperature and time. The β'A-sialon and the nitrogenous phases were formed from SiC and mullite. A z value decrease for β'A-sialon was observed during reaction progression.     

Thin conducting polypyrrole film on insulating surface and its applications

An electrically conductive plastic material was obtained by the polymerization of pyrrole on insulating polymeric materials and nylon cloth impregnated with the oxidant by vapour phase technique, resulting in a uniform, smooth and adherent coating of conducting polymer having a surface resistance ranging from 200 Ω/□ to 20 kΩ/□, which makes it suitable for applications as an antistatic material.     

The effect of physical exercise on the response to exertion in the elderly

BACKGROUND: A decrease in adaptation to exertion has been observed as age progresses. Although this decline may also be affected by factors such as health conditions and age, physical inactivity related to sedentary behaviour plays a dominant role. METHODS: In order to evaluate the influence of physical activity on cardiovascular response to exertion in the elderly, 4 groups of 22 subjects each were submitted to maximal electrocardiographic exercise test on a cycloergometer (multistage program with 30 Watts x 3 min. steps). All subjects were male. The composition of the groups was as follows: 1) veteran long distance runners (mean age: 71 +/- 5.4); 2) sedentary veterans (mean age: 69.8 +/- 3.9); 3) young long distance runners (mean age: 25.4 +/- 4.3); 4) sedentary young adults (mean age: 25.8 +/- 3.9). The endurance athletes, well fitted to competition, had been practicing sport activity for at least 3 years. RESULTS: Heart rate, arterial systolic and diastolic blood pressure were recorded; mean blood pressure and double product were calculated at baseline and at the climax of the stress test; furthermore, total and maximal watts were recorded. For each of the parameters, Student's t test for non-paired observations were used to evaluate statistical differences amongst the four groups. The most interesting result arises in the comparison between veteran long distance runners and sedentary young adults: between the two groups no statistically significant differences in workload, expressed as total watts (1649.55 +/- 296.32 vs 1650.00 +/- 446.32; p = NS) and maximal watts (175.91 +/- 19.19 vs 173.18 +/- 24.38; p = N.S.), were observed. On the contrary, highly significant differences in both total (p < 0.01) and maximal (p < 0.01) watts were noticed by comparing long distance runners and sedentary subjects of the same age. CONCLUSIONS: These data support the hypothesis that the progressive reduction in physical activity, which is usually observed in aging, is the major determinant of exercise deconditioning in the elderly.     

Sequential intraluminal endoscopic and laparoscopic treatment for bile duct stones associated with gallstones

BACKGROUND: On the basis of a flowchart including prior or current jaundice or pancreatitis, abnormal liver function, ultrasound or IV cholangiography, bile duct (BD) stones were suspected in 71/593 patients referred for gallstones. METHODS: When endoscopic retrograde cholangiography detected BD stones, endoscopic sphincterotomy (ES) and endoscopic BD clearance were attempted, followed by laparoscopic cholecystectomy (LC). BD stones were found in 44/71 patients. The sensitivity values of preoperative conditions were: 92% for IV cholangiography, 88% for abnormal liver function, 50% for ultrasound, and 37% for jaundice at admission. RESULTS: Endoscopic clearance succeeded in 37 patients and LC was completed in 33 patients. Conversion to open surgery (9%) was comparable with the rate in patients without BD stones. The median hospital stay for the sequential endoscopic and laparoscopic treatments was 13 days (range 4-54) or 22 days if open surgery was used. CONCLUSIONS: In conclusion, BD stones can be endoscopically cleared preoperatively in most patients without interfering with LC.     

Computer monitor recycling: a case study

The total number of computer monitors being scrapped per year worldwide is predicted to rise to 30 million units by the year 2005. Monitors contain significant quantities of lead (in the solder and CRT glass) and polybrominated flame retardants, which are potentially hazardous if released to the environment. A recent study investigated the possibility of cost-effectively recycling monitors     

MODELING AND OPTIMIZATION FOR DESIGN UNDER PRODUCTION PLANNING CRITERIA IN MULTIPRODUCT DEHYDRATION PLANTS

The design problem of a multiproduct dehydration plant involving continuous conveyor-belt dryers utilised for the dehvdration of agricultural products over a fmite tim horizon, is presented. The peculiarities of the problem under demand-varying market patterns and time-variable market prices of raw materials are underlined. Limitations imposed by storage capacity, custormer orders, and constraints dictated by the process itself, are also taken into consideration. The overall problem is cast into a MINLP formulation involving the total annual cost of the plant as its objective function. This was infered by deducing the mathematical model of conveyor-belt dryers. Repeated evaluation of the total annual cost for various structures and operating points, allowed the determination of overall performance characteristic operational and structural curves. approximated by suitable mathematical expressions. A test case is presented in order to demonstrate the effectiveness of the proposed approach.     

THE LINEAR NORMALIZATION TECHNIQUE—AN ALTERNATIVE PROCEDURE FOR DETERMINING J-R CURVES FROM A SINGLE SPECIMEN TEST RECORD BASED ON LANDES' NORMALIZATION METHOD

An alternative approach for determining J-R curves from a single specimen test based on the normalization technique is proposed. The procedure requires only the load versus load-line displacement record and the final crack length in order to derive the J-R curve. The method has been applied to metal and polymers of various geometries and was verified by comparison with J-R curves obtained from potential drop and multiple specimen techniques.     

Rigid osteosynthesis with the AO plate and Phemister''s spongioplasty in secondary treatment of diaphyseal gunshot fractures

To clarify the histogenesis and differentiation potential of central neurocytoma, a pathological investigation of seven tumors from three patients was conducted using immunohistochemistry and ultrastructural analysis in addition to systematic in vitro studies. Six tumors were studied immunohistochemically and five were examined ultrastructurally. All cases that were immunostained were positive for synaptophysin in nuclear-free neuropil islands. In five tumors, a few tumor cells, in addition to reactive astrocytes, were positive for glial fibrillary acidic protein (GFAP). Vimentin staining was also positive in a few tumor cells of five specimens. Neurofilament staining was always negative. All cases for which ultrastructure was examined showed various synaptic abnormalities. Cultured cells were subdivided into three distinct tumor cell types: neuronal cells which stained for neurofilament proteins with neurosecretory granules; small flat undifferentiated cells with a high nuclear-cytoplasmic ratio and scant cytoplasmic organelles; and small round or multipolar astrocytic cells with 10-nm intermediate filaments which stained for GFAP. Our tissue culture studies disclosed that cultured neurocytoma cells form a cellular mosaic similar to subependymal plate layers that are composed of mitotically active cells, neurons and glia.     

Robust channel prediction technique for decision directed RAKEreceivers

The authors describe a robust channel prediction technique for a direct sequence spread spectrum (DS-SS) system in a fast fading environment. Coherent diversity reception is employed for improved performance. To estimate the channel response, an FIR type linear prediction filter is employed for each RAKE tap. The stability of the decision directed receiver is achieved through differential encoding of the data bits. It is demonstrated through simulations that the performance of the proposed decision directed receiver is better than a receiver which relies on a pilot signal