Effects of manufacturing defects on the mechanical properties of carbon fibre reinforced polyethersulphone laminates

The effects of defects on the mechanical properties of carbon fibre reinforced polyethersulphone laminates have been measured. The defects studied were cut fibre plies, omission of polymer films and local delamination produced by the inclusion of foreign matter. Of these it was found that only cut plies had a significant detrimental effect on the strength of a laminate. For specimens with two cut plies, the failure stress, tensile, flexural and compressive in the remaining continuous plies was the same as in the defect-free material, provided that the cut plies were widely separated. However the failure stresses were 15–18% lower in the continuous plies in the specimens containing two cut plies which were more closely spaced and in specimens containing four cut plies.     

Elevated serum levels of soluble CD30 in patients with atopic dermatitis (AD)

The immunopathology of AD is still unclear, but evidence for an immune response polarized towards Th2 activity has been provided. The CD30 molecule belongs to the tumour necrosis factor (TNF) receptor family and is expressed on activated T cells with a sustained expression in Th2 cells. This molecule also exists in a soluble form (sCD30). Elevated serum levels of sCD30 have been found in patients with Hodgkin's disease, chronic hepatitis B infection and HIV infection. Studies were undertaken to compare the serum levels of sCD30 in patients with AD (n=49) and healthy non-atopic controls (n=94). The presence of sCD30 was analysed with ELISA. A significantly higher concentration of sCD30 was noted in AD patients, median sCD30 level 29 U/ml (range 1-708 U/ml), compared with healthy non-atopic controls (P<0.001), where the median level was 11 U/ml with a range of 1-1042 U/ml. No correlation was found between sCD30 levels and total serum IgE, or between the AD patients' SCORAD values and concentration of sCD30. sCD30 levels were also analysed in 20 AD patients, which during ketoconazole treatment had improved their clinical scores and reduced their serum IgE and eosinophil cationic protein levels. However, no significant decrease in sCD30 levels was noted after treatment. The results show that patients with AD have elevated levels of sCD30, but without correlation to total serum IgE or disease activity.     

A method for dynamic measurement of the resistance to dry heat exchange by footwear

Five different types of cold protective footwear have been tested with regard to their resistance to dry heat loss (i.e. the insulation) with a new electrically heated foot model. The model is able to simulate 'walking' movements in order to provide a more realistic simulation of wear conditions. Thermal insulation of shoes with and without a steel toe cap was the same. The insulating properties during simulated walking movements were 10-25% lower compared with static conditions. For two of the shoe models a significantly lower insulation value for the sole area was obtained when adding a weight of 30 kg. A significant difference could also be found between the insulation values of two different sizes of one of the models. Measurements with the standard method (EN 344) correlated well with the local insulation value of the sole part of the thermal foot. Correlation with the insulation value for the whole shoe was much less, variation was bigger and ranking in terms of cold protection differed between methods. The electrically heated foot model appears to provide a reproducible, accurate and more realistic method for measuring the insulation properties of shoes than EN 344.     

A planar integrated RCD snubber/voltage clamp

In order to reduce the cost, size, and weight of power electronic systems, it has become necessary to integrate electromagnetic structures, which until now have been constructed with discrete components. This approach not only reduces the component count, but also gives much greater control over parasitic elements. In this article, the authors describe an electromagnetically integrated resistor-capacitor-diode (RCD) snubber/voltage clamp that uses a planar construction technique. The design and construction are described and the performance is verified experimentally. Some advantages of the integrated component over its discrete counterpart are also given     

Bestimmung der Abtragungsraten von Zirconium,Tantal und der Legierung Tantal-40Niob in fluoridhaltiger azeotroper Salpetersäure mit Hilfe der Radiotracer-Methode

The radiotracer technique as a means to investigate the corrosion of zirconium, tantalum, and a Ta-40Nb alloy in fluoride containing azeotropic nitric acid Zirconium and tantalum as well as the tantalum 40% niobium alloy are of considerable technical importance due to their high corrosion resistance against numerous corrosive media. With respect to corrosion testing in analytically pure azeotropic nitric acid in the temperature range between 20 and 121°C, corrosion rates were determined for zirconium: 7 · 10^?6 to 5 · 10^?4 mm/y, for tantalum: 10^?8 to 4 · 10^?6 mm/y, and for the Ta-40Nb alloy: 2 · 10^?7 to 8 · 10^?6 mm/y [1]. These corrosion rates will be markedly increased by adding small amounts of fluorides or by fluoride impurities. The radiotracer method after neutron activation was applied to determine the corrosion rates in azeotropic fluoride containing nitric acid. Even minute additions of fluorides strongly affect the corrosion resistance of zirconium. In the range between 0.15 and 10 ppm F^? and at a temperature of 108°C, corrosion rates between 5.3 · 10^?3 and 3.1 mm/y were measured. It was impossible to establish a limit for the fluoride concentration, below which the corrosion rate of zirconium will not be adversely influenced. The corrosion rates of tantalum and the Ta-40Nb alloy are considerably increasing above a fluoride concentration of 10 ppm. The highest corrosion rates measured were between 8.4 · 10^?3 mm/y at 50°C/280 ppm F^? and 1.4 · 10^?2 mm/y at 110°C/320 ppm F^?. Within the range of this investigation, the corrosion resistance of tantalum was higher than that of the Ta-40Nb alloy by one order of magnitude. The corrosion resistance of zirconium and tantalum was not influenced by any treatment of the samples before testing.     

Primary prevention of malignant melanoma in the Stockholm Cancer Prevention Programme

The relation between intracoronary thrombus and endothelin-1 (ET-1) was studied. In a canine model, acute myocardial infarction (MI) was induced by coronary occlusive thrombus produced at a mock atheromatous plaque. Blood samples were collected from the aorta (A) and coronary vein (V). Twenty-eight open-chest dogs divided into three groups were studied. Group I (n = 15): acute MI was induced by coronary occlusive thrombus, and thrombolysis was obtained by urokinase two hours after MI. Group II (n = 8): nonocclusive thrombus was produced without inducing MI. Group III (n = 5): coronary artery was ligated for two hours and reperfused by release of ligation. In Group I, ET-1 was significantly increased after MI in A and V, and ET-1 in V was significantly more elevated than in A during thrombolysis, suggesting ET-1 production in the coronary vessels by thrombolysis. In Group II, ET-1 increased slightly during thrombus formation, but there was no difference in A and V. In Group III, ET-1 was elevated significantly after MI without A and V difference. These results indicate that there is no detectable ET-1 production with coronary thrombus formation, whereas coronary ET-1 production is detected during thrombolysis, most probably because resolved thrombus releases a more potent stimulus to ET-1 production.     

Non-invasive assessment of magnitude and dispersion of atrial cycle length during chronic atrial fibrillation in man

AIMS: Atrial fibrillation cycle lengths can be assessed from right precordial ECG leads and the unipolar oesophageal ECG using a non-invasive method called Frequency Analysis of Fibrillatory ECG. The purpose of this report is to present the results from application of this method in a large group of patients with long-term atrial fibrillation and to examine the differences between patients with 'coarse' and 'fine' atrial fibrillation. METHODS AND RESULTS: Simultaneous 15 min recordings from V1, V2 and an oesophageal lead at a position behind the posterior atrium were obtained in 28 patients, aged 41 to 78 years, with long-term (> 1 month) atrial fibrillation. In each lead, using the time averaging technique, the QRST complexes were suppressed. Thereafter, the frequency distribution of the residual ECG was estimated by means of Fast Fourier Transform. In the 3-12 Hz range of each lead, the dominant atrial cycle length, the power maximum and the spectral width were calculated. In 26 patients (93%), frequency spectra in the 3-12 Hz range could be obtained. The dominant atrial cycle length ranged from 120 to 175 ms, mean 150+/-16 (SD) ms in V1, and from 120 to 190 ms, mean 150+/-16 in an oesophageal lead (ns). The absolute difference in the dominant atrial cycle length between V1 and the oesophageal lead was 10.4+/-7.7 ms. There was no significant difference in the dominant atrial cycle length in V1 between patients with coarse and fine atrial fibrillation. The power maximum in V1 was significantly greater in patients with coarse compared to fine atrial fibrillation (P=0.01). The spectral widths ranged from 10 to 55 ms and demonstrated significantly higher mean values in lead V2 compared to V1 (P=0.001). Compared to V1, the mean values tended to be smaller in the oesophageal lead (P=0.05). CONCLUSIONS: Using the Frequency Analysis of Fibrillatory ECG method, the dominant atrial cycle length, power maximum and spectral width can be estimated from the frequency spectra in the majority of patients with atrial fibrillation. Spatial dispersion of the dominant atrial cycle length occurs in some patients and may be an important proarrhythmic marker. The distinction between coarse and fine atrial fibrillation cannot be used as a marker of the atrial cycle length.     

Identification of domains involved in superantigenicity of streptococcal pyrogenic exotoxin F (SpeF)

Coronary artery angioplasty or bypass is being performed for increasing numbers of patients in their seventh, eighth, ninth and even tenth decades of life. Because of the cost involved, justification for performing these procedures in the elderly has become a topic of daily discussion among those responsible for funding healthcare. Both silent and overt coronary artery disease (CAD) are more common in the population over 65 years of age. Because CAD in the elderly often presents in an atypical manner, diagnosis of the disease is frequently delayed. Partly because of the delayed diagnosis and partly because of cost considerations, coronary arterial bypass (CABG) is more often performed as an emergency procedure in the elderly with the results that both operative mortality and costs are increased over those observed in a younger population. Nevertheless, it is clear that performance of coronary revascularization procedures in the elderly can both prolong life and improve the quality of life beyond what can be achieved using alternative methods of treatment. Greater efforts directed toward detection of ischemic heart disease in the these patients and earlier, elective surgery could significantly reduce both the mortality and disability associated with CAD in the elderly.