Tantalum as a material of construction for the chemical processing industry – A critical survey

Materials selection is based on safety and economic considerations; the least expensive material securely withstanding service conditions for a required service time is chosen. For the integrity of equipment in the CPI chemical resistance is an essential factor. Of all metallic materials used for CPI equipment, tantalum is second to none regarding chemical inertness, comparing only to resistance properties of the nonmetals glass, fluoropolymers, and graphite. The price of tantalum, however, prohibits its broad application for construction. There are only two ways by which the demand for tantalum in this field can be promoted significantly. First, a major increase in the aggressivity of service conditions in process engineering caused by process development or modification. Second, cost reduction via tantalum price dilution by means of duplex systems application, utilizing the advantages of a less expensive base metal and a thin tantalum lining or coating. The more important systems of this type are discussed and evaluated regarding their potential of development.     

Hereditary macular dystrophies

BACKGROUND: Orthostatic hypotension is a common phenomenon in the elderly. Hormonal changes during orthostatic stress have been described in elderly normotensive people and in those with essential hypertension. However, the hormonal response in elderly people who have systolic hypertension during orthostasis has not yet been quantified. METHODS: In this study we investigated 14 non-diabetic men, aged 60 to 75 years, with untreated systolic hypertension who were subjected to 45 degrees passive head-up incline on a tilt table for 15 min. Their hormonal profile and hemodynamic changes were analyzed before and after the stress. RESULTS: In the supine position, plasma levels of norepinephrine, atrial natriuretic peptide and aldosterone were in the normal range, while the plasma renin activity was low. Immediately upon tilt the systolic blood pressure fell but it reverted to baseline values after 15 min of orthostasis. At that time the cardiac output decreased while the systemic vascular resistance and the plasma norepinephrine concentration rose. The atrial natriuretic peptide appeared to fall, and the renin-aldosterone level did not change. CONCLUSION: The physiologic response to orthostatic stress in elderly people with systolic hypertension is comparable to that of elderly normotensive people and those with essential hypertension, i.e. a decrease in cardiac output and an increase in plasma norepinephrine levels. The atrial natriuretic peptide appeared to fall appropriately. The response of the renin-aldosterone system mimicked that in elderly patients with low renin essential isolated hypertension. These observations may have a bearing on the management of elderly people with systolic hypertension who also have orthostatic symptoms; they may not require a different approach from that needed for others of the same age group.     

A scheduling decision aid in glass fiber manufacturing

A decision aid for scheduling production in glass fiber manufacturing industry is described. The methodology combines a linear programming (LP) optimization model with a heuristic model. The LP model determines production goals; the heuristic model then uses the LP output to incorporate system-specific constraints in developing processing sequences.     

When did a reduced speed limit show an effect? Exploratory identification of an intervention time

In a statistical analysis of accident data before and after a speed limit reduction, the time of the countermeasure is, of course, well known. Our understanding of the accident process may, however, be increased if we assume in a thought experiment that this time is unknown. We ask if the data themselves can tell us something about such a possible time. By means of time series of traffic accidents in Zurich before and after a speed limit reduction, different exploratory methods are presented to identify the "unknown" time of this measure. For most of the investigated series, the most likely time was found to lie in the three months before the true introduction. A possible explanation of this result may be that the media already informed the public before the countermeasure was actually introduced. This finding leads to an improved parsimonious intervention model which distinguishes between a possible "preintervention effect" and the usual "intervention effect."     

Evolutionary mechanism of conflict resolution

Conclusions Despite the accumulated evidence, many of the investigators as of quite recently have failed to understand that behavioral strategy or decision rules can be inherited and evolve and that they are subject to certain constraints that cannot be surmounted other than by natural selection. For example, in [9, p. 422] we read: The evolutionary pressure cannot act upon the relative contents of social interactions favoring certain individuals over others. The present study shows that the following scheme of conflict, which favors those individuals that conform to it with a better accuracy, can be evolutionary stable. On the basis of the information they receive, the partners estimate the role situation and the equilibrium pair of elementary strategies and use their strategies. If the role situations of the partners are coordinated, the partners cooperate in reducing the conflict and define its result according to AIS. If AIS are not coordinated, they cooperate in reducing the conflict if its expected loss for each is greater than the expected payoff; they escalate the against those that have a lesser set of elementary strategies but also against those that have a less accurate mechanism of AIS recognition. A poor accuracy of recognition mechanism would replace a strictly equilibrium ESS with a mixed strategy.From the point of view of behavioral control, the multilevel conflict model shows that generally for controlling the choices at a certain level actions of an equally high level are necessary. It is impossible, for example, to accomplish certain economic choices by using only informational actions.Translated from Kibernetika, No. 1, pp. 90–98, January–February, 1988.     

The dynamics of aging and rehabilitation following coronary bypass operation]

The dynamics of aging encompass the topics "aging of society" and "coping with chronic illness". Both are discussed using data from a qualitative study on return to work after coronary artery bypass surgery. Data from the retrospective substudy reveal four forms of aging as biographical development toward early retirement, old-age retirement, or related stages. It emerges that the manner of aging is less influenced by medical rehabilitation or medical history, and more by the patient's occupation and socio-economic status. Case reports are used to show that social class is a facilitation context, but not a determining force, regarding the choice between postoperative retirement or return to work. The final section briefly discusses whether the findings concerning the dynamics of aging of the cohort operated on in the late 1970s apply also to that of the cohort operated on in the late 1980s; this is addressed using some data from the prospective sub-study.     

Some techniques for solving linear equation systems with guarantee

Methods are described for solving a system of linear equations with error bounds. Rectangular and spherical intervals ofR ⁿ are used combined. The objective is to get guaranteed accuracy with a minimal effort of computing time.     

Effect of Phase-Selective Nanoscale Precipitates on the Bauschinger Effect in Austenitic–Ferritic Duplex Stainless Steels

Metallurgical and Materials Transactions A - The Bauschinger effect in austenitic–ferritic duplex stainless steel 1.4462 was investigated using tension–compression tests combined with...