Kriechverhalten einiger warmfester Stähle unter rechteckzyklisch veränderter Spannung oder Temperatur

Untersuchung des Kriechverhaltens warmfester Stähle unter rechteckzyklisch veränderter Spannung oder Temperatur bis zu 30 000 h Beanspruchungsdauer an je einer Schmelze der Stähle 10 CrMo 9 10, X 22 CrMo 12 1 und X 6 CrNiMo 17 13. Vergleich des gemessenen Kriechverlaufes mit dem nach der Lebensdaueranteil regel, der Dehnungsverfestigungsregel und der Energieverfestigungsregel berechneten Kriechverlauf.     

Familial occurrence of a del(Xp-) chromosome: pitfall in karyotype/phenotype correlation

PURPOSE: To examine the attitudes of physicians practicing in New Mexico toward gay and lesbian medical students, house officers, and physician colleagues. METHOD: In May 1996, the authors mailed a questionnaire with demographic and attitude questions to 1,949 non-federally employed physicians practicing in New Mexico. The questionnaire consisted of questions dealing with medical school admission, residency training, and referrals to colleagues. The response rate was 53.6%. RESULTS: Of all the responding physicians, 4.3% would refuse medical school admission to applicants known to be gay or lesbian. Respondents were most opposed to gay and lesbian physicians' seeking residency training in obstetrics and gynecology (10.1%), and least opposed to their seeking residency training in radiology (4.3%). Disclosure of homosexual orientation would also threaten referrals to gay and lesbian obstetrician-gynecologists (11.4%) more than to gay or lesbian physicians in other specialties. CONCLUSION: Physicians' attitudes toward gay and lesbian medical students, house officers, and physician colleagues seem to have improved considerably from those reported previously in the literature. However, gay men and lesbians in medicine continue to face opposition in their medical training and in their pursuit of specialty practice.     

Temperature oscillation calorimetry in stirred tank reactors with variable heat transfer

A new method for applying reaction calorimetry to stirred tank reactors with variable heat transfer is presented. Sinusoidal temperature oscillations are induced by an electrical heater placed either in the reactor or in the jacket in order to decouple the chemical heat production from the variable heat transfer during reaction. Multiplication of the reactor heat balance by periodic functions and integration yields the overall heat transfer. Temperature oscillation calorimetry was successfully applied to the free radical polymerization of methyl methacrylate in ethyl acetate which shows a strong decrease in heat transfer.     

Zur Kinetik der stabilisierten Fällungs-polymerisation eines Kationischen Monomeren in wäßrigen Natriumchlorid-Lösungen

The stabilized free-radical precipitation polymerization of the cationic monomer N-(2-methacryloyloxyethyl)-N,N-dimethylbenzylammonium chloride (MADAMBQ) in aqueous solutions of sodium chloride was studied by reaction calorimetry. Poly(ethylene oxide) was used as stabilizer. The rate of polymerization reaches its maximum immediately after initiation and remains nearly constant up to 50 % conversion followed by a decrease that could be described by a first order kinetics. The particles formed are approximately 1 to 30 μm in diameter and are stable over a period of several months. A model based on the theory of homogeneous particle nucleation is suggested to describe the kinetic course of polymerization, taking into account the rate of polymerization in both phases. With the assumption that the concentration of monomer in the phases is determined by a Nernst distribution law, the kinetics of the early stage of polymerization can be modelled reasonably well. The solution polymerization and the unstabilized precipitation polymerization of MADAMBQ was also studied.     

Korrosionsuntersuchungen zur Entwicklung von Dekontaminationslösungen für Nuklearanlagen – Teil III: Das Korrosionsverhalten ferritischer Baustähle mit unterschiedlichen Kohlenstoffgehalten in Ameisensäure-Formaldehyd-Lösungen ohne und mit Inhibierung

Investigation of corrosion in the development of decontamination solutions for nuclear systems – Part III: The corrosion behaviour of ferritic steels with different carbon contents in formic acid-formaldehyde solutions with and without inhibitors In decontamination solutions of the type formic acid-formaldehyde, ferritic steels undergo heavy pitting corrosion or shallow pitting corrosion. The addition of formaldehyde to formic acid solutions scarcely influences the temperature dependency of the corrosion rates, the solution specific corrosion rates, however, increase with increasing carbon content of the steels. The high corrosion rates, especially of the steel 21 CrMoV 5 11, can be reduced by about two orders of magnitude by adding inhibitors as thiourea, ethyl thiourea, and phenyl thiourea to the formic acid-form-aldehyde solutions, but pitting corrosion is unavoidable.     

Flow fields in electromagnetic stirring of rectangular strands with linear inductors: Part II. computation of flow fields in billets, blooms, and slabs of steel

The model presented in Part I of this series of papers is used to compute flow velocities in the longitudinal stirring of steel blooms and billets, and in the horizontal stirring of steel slabs. In longitudinal stirring of blooms and billets the reverse flow is on the side of the strand opposite to the inductor. The effects of penetration depth of the electromagnetic force, of the force itself, of the length of the stirrer, and of the width of the liquid core were determined. In horizontal stirring of slabs the reverse flow takes place outside of the stirrer region, forming the so-called butterfly stirring pattern. The characteristics of this flow field depend to a considerable extent on the width of the stirrer. The effects of stirrer width, of thickness of the liquid core, of force and of width of the slab were elucidated. The maximum velocities in both types of stirring are represented as simple formulae. Formerly with Institut für Allgemeine Metallurgie, Technische Universit?t Clausthal     

Malnutrition and mortality during recent famines in Ethiopia: implications for food aid and rehabilitation

The 1972-73 and 1984-85 famines varied significantly among different populations within famine areas at the regional, community and household levels. Political and social factors were crucial in this pattern. Evidence from both pastoral and farming areas indicates that the development of community-based resources may be less disruptive socially and economically and result in less morbidity and mortality than dependence on relief shelters. Areas needing further study are identified.     

Rotational electromagnetic stirring in continuous casting of round strands

A model is presented to compute the three-dimensional flow field in rotational electromagnetic stirring of round strands. The model involves the solution of the Maxwell equations, the Navier-Stokes equations, and the transport equations for the turbulence characteristicsk andε. For the limiting case of one-dimensional stirring, the computations were checked with experiments using mercury as the fluid. Several sets of computations were carried out to determine the influence of stirrer position, stirrer length, and electromagnetic parameters on the flow field in continuous casting of steel strands.     

Effect of bottom stirring and post stirring on the oxygen distribution between metal and slag at the end of the LD process

Studies concerning the effect of stirring and post-stirring on the oxygen distribution at the end of the LD process show that a post-stirring phase following the end of the blow establishes an oxygen distribution close to equilibrium. The sub-lance tests performed at 90% of the oxygen throughput show in comparison with the post-stirring phase a distinct oxygen deficiency, while the blow end-point measurements show an excess of oxygen.