Investigation of the SCC behaviour of alloy 2024 using the slow strain rate technique

The stress corrosion cracking (SCC) behaviour of 2024 plate in T351 and T851 tempers was investigated in short transverse direction performing accelerated tests under constant deformation, constant load and slow strain rate conditions. Corrosive media used were: aqueous 3.5% NaCl solution, an aqueous solution of 2% NaCl + 0.5% Na₂CrO₄ at pH 3 (according to LN 65666), an aqueous solution of 3% NaCl + 0.3% H₂O₂, and substitute ocean water according to ASTM D1141. Alternate immersion tests in 3.5% NaCl solution indicated the low SCC resistance of the alloy 2024-T351 as well as the improved SCC behaviour due to aging to T851 condition. Similar results were obtained from constant load tests under permanent immersion conditions in the acidified chloride-chromate solution, in 3% NaCl solution with peroxide, and in substitute ocean water, whereas no SCC failure was observed with specimens which were permanently immersed in 3.5% NaCl solution. Using the slow strain rate method, 3% NaCl + 0.3% H₂O₂ and substitute ocean water were found to be effective synthetic environments. The other two electrolytes did not promote severe stress corrosion cracking with alloy 2024-T351. The SCC behaviour of 2024-T851 was difficult to determine employing the slow strain rate technique. Large scatter in data, observed even in inert environment, and the low elongation of the aged material, exacerbated by a further degradation of ductility due to pitting and intergranular corrosion, precluded an evaluation.     

A detailed protocol for the measurement of TGF-beta1 in human blood samples

Bisphosphonates are compounds derived from pyrophosphate, a byproduct of cellular cleavage of adenosine triphosphate (ATP), and are resistant to alkaline phosphatase by virtue of replacement of oxygen by carbon. The high affinity of the P-C-P structure for hydroxyapatite accounts for deposition in bone. Modification of the two side chains of carbon alters the potency of the drugs. Of those that have either completed or are undergoing clinical trials, the order of increasing potency for inhibition of bone resorption is etidronate, clodronate, tiludronate, pamidronate, alendronate, residronate and ibandronate (potency range: 1 to 10,000). Less than 5% of bisphosphonates are absorbed and the half life is a few hours. The drugs must be given on an empty stomach because food and beverages interfere with gastrointestinal absorption. Of the absorbed fraction, as much as 60% is taken up by the skeleton and the remainder is excreted unchanged in the urine. Etidronate, tiludronate, residronate, and alendronate are given orally, clodronate intravenously, and pamidronate and ibandronate by either route. At lower concentrations, bisphosphonates inhibit osteoclatic bone resorption, whereas at higher concentrations they may inhibit mineralization and cause osteomalacia. Inhibition of mineralization diminishes with increasing potency. In postmenopausal women, etidronate and alendronate for 3 yr were shown to inhibit bone resorption, increase bone mineral density (BMD) of the lumbar spine and hip, and prevent fractures without producing osteomalacia. Bone formation also is reduced as a consequence of diminished bone resorption but reduction is less than the reduction of bone resorption. In higher doses bisphosphonates may cause upper gastrointestinal disturbances but in recommended doses they generally are well tolerated and have an excellent safety profile.     

An offset spline approximation for plane cubic splines

A plane cubic spline segment is given. We want to approximate its offset line by another cubic spline segment. Therefore we take the known curvatures and tangents at the end-points of the offset line and calculate the corresponding spline. Finally examples are given.     

Review of respiratory mechanics in animals. 3. Methodical and physiologic aspects of the use of the impulse oscilloresistometry system (OIS)

The impulse oscillometry system (IOS) which was originally developed for human medicine was found to be suitable for analysing respiratory mechanics in spontaneously breathing animals. This technique is non-invasive. METHODOLOGICAL ASPECTS: In order to use the IOS-technique in animals, a tightly fitting face mask is necessary. Furthermore, a flexible tube needs to be inserted into the measuring system. While the tube does not influence the measured results significantly, the face mask may affect the measurements. Therefore, its influence on the measured respiratory impedance must be taken into account. To prevent methodological errors, the head and body position of the animal should be standardised during the IOS-measurement. Since the methodological variability of the system is very small, the measuring results are highly reproducible. PHYSIOLOGICAL ASPECTS: In growing subjects, all parameters of respiratory mechanics depend on body weight. Since respiratory physiology is influenced by circadian rhythms, measurements of different days are only comparable when they have been done each day at the same hour. Comparing the respiratory impedance of different animals of similar age and body weight, a considerable inter-individual variability was observed. Due to the low level of physiological intra-individual variability, the method seems to be especially useful for studying influences on the respiratory system (i.e. pharmaceutics, therapeutics) in long-term studies using the same group of subjects.