A numerical integration scheme for special finite elements for the Helmholtz equation

The theory for integrating the element matrices for rectangular, triangular and quadrilateral finite elements for the solution of the Helmholtz equation for very short waves is presented. A numerical integration scheme is developed. Samples of Maple and Fortran code for the evaluation of integration abscissæ and weights are made available. The results are compared with those obtained using large numbers of Gauss–Legendre integration points for a range of testing wave problems. The results demonstrate that the method gives correct results, which gives confidence in the procedures, and show that large savings in computation time can be achieved. Copyright © 2002 John Wiley & Sons, Ltd.     

Improvement in Oxidation Resistance of Stainless Steel by Molten-Salt Electrodeposition of La

Improvement in the oxidation resistance of SUS304 stainless steel was accomplished by electrodeposition of La in a molten salt. The electrolysis of La was conducted using a potentiostatic-polarization method in an equimolar NaCl–KCl melt containing 3.5 mol. LaF ₃ at 1023 K. Observation of the specimen surface after polarization at –1.8 V (vs. Ag/Ag⁺ (0.1)) for 0.18 ks showed that La particles were uniformly dispersed on the surface. The oxidation resistance of the electrodeposited stainless steel was significantly improved as compared with the untreated stainless steel. The scale formed on the untreated stainless steel after oxidation was thick and consisted of Fe₂O₃ and Fe₃O₄, whereas the scale formed on the elecrodeposited stainless steel was extremely thin, and mainly consisted of Cr₂O₃.     

Untersuchung einer Axialturbinen-Stufe mit tangential gekrümmten Leitschaufeln - Teil I: Strömungsstruktur im Leitradkanal

By tangential curvature of the stacking line of the blade profiles guide vanes can be designed, which have on both ends an obtuse angle between suction side and sidewall. This configuration, according to literature, is capable of reducing the secondary loss. This type of vanes, because of the resulting radial components of the blade force, effects a radial displacement of the meridional stream-lines, a modification of the pressure distributions on the profiles and different flow outlet angles. Three-dimensional numerical simulations with the Navier-Stokes-solver Numeca have been made for a single stage axial turbine with different types of tangentially curved guide vanes. The effects of the blade curvature on the flow field and the blade forces have been investigated systematically and in detail.

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Zusammenfassung Durch eine tangentiale Krümmung der Auffädellinie der Profile lassen sich Leitschaufeln gestalten, die an beiden Schaufelenden einen stumpfen Winkel zwischen Saugseite und Seitenwand aufweisen, eine Konfiguration, die nach Aussage vieler Literaturstellen zu einer Reduktion der Sekundärverluste führt. Diese Schaufelform ergibt auch wegen der entstehenden radialen Komponenten der Schaufelkraft eine radiale Verschiebung der Meridian-Stromlinien, eine Veränderung der Profil-Druckverteilungen und veränderte Abströmwinkel. Es wurden dreidimensionale numerische Simulationsrechnungen mit dem Navier-Stokes-Löser Numeca für eine einstufige Axialturbinen-Stufe mit unterschiedlichen tangential gekrümmten Leitschaufeln durchgeführt. Die Auswirkungen der Leitschaufelkrümmung auf das Strömungsfeld und die Schaufelkräfte wurden systematisch im Detail untersucht.

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Die hier beschriebenen Ergebnisse wurden im Rahmen einer Dissertation erzielt, die vom Promotionsstipendium nach der Graduiertenförderung der Universität Hannover und vom Institut für Strömungsmaschinen gefördert wurde. Die Schaufeldaten und experimentellen Ergebnisse sind von Prof. Lapschin der TU St. Petersburg zur Verfügung gestellt     

Accumulation of Arsenic and Copper by Bryophytes Growing in an Aquatic Environment near Copper Mine Tailings

Bryophytes with high As accumulation affinity were identified in the aquatic environment. We surveyed a stream near copper mine tailings and then conducted laboratory experiments to confirm As accumulation in the bryophytes with high As affinity. We found that a moss, Scopelophila cataractae, accumulates As in addition to Cu in aquatic environments and confirmed it in laboratory experiments. The highest value for As in S. cataractae from the field survey was 1300 mg/kg dry weight at relatively low As concentrations in the stream water (0.005 mg/L). In addition, Brachythecium plumosum and Rhynchostegium riparioides may also be useful bryophytes for accumulation of Cu and As, though the mechanisms of As accumulation might differ between these two bryophytes and S. cataractae.     

Untersuchung einer Axialturbinen-Stufe mit tangential gekrümmten Leitschaufeln - Teil II: Modellierung für Throughflow-Rechenverfahren

Although today the reality-near flow simulation is possible with 3D Navier-Stokes-Codes also for several stages because of higher computer-performance, nevertheless the computation codes play yet an important role for several stages axialturbines on the basis of the assumption of a rotation-symmetrical flow, in particular for the design engineer in practice. In order to be able to compute such a computing code for the tangential leaned and curved bladings, compatible models of the radial force, models of loss and deflection for this code must be developed with rotational symmetry. With the 3D-numerical and experimental results, mathematical formulations were developed for the new deflection of flow models of this blades, that formally are compatible with the assumption of a rotation-symmetrical flow and with the existing codes.

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Zusammenfassung Obwohl heuzutage die realitätsnahe Strömungssimulation mit 3D Navier-Stokes-Lösern auch für mehr als eine Stufe möglich ist, spielen für vielstufige Axialturbinen Rechenprogramme auf der Basis der vereinfachenden Annahme einer rotationssymmetrischen Strömung immer noch eine große Rolle, insbesondere für den Auslegungsingenieur in der Praxis. Um ein solches Rechenverfahren für tangential geneigte und gekrümmte Beschaufelungen anwenden zu können, müssen mit der Rotationssymmetrie kompatible Modelle der Radialkraft, Umlenk- und Verlustmodelle für dieses Verfahren entwickelt werden. Mithilfe der Ergebnisse aus den 3D-Berechnungen sowie den experimentellen Daten sind vereinfachte mathematische Formulierungen für die Auswirkungen dieser Beschaufelungen auf Umlenkungen in der Strömung für das vorhandene rotationssymmetrische Rechenverfahren neu entwickelt worden.

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Die hier beschriebenen Ergebnisse wurden im Rahmen einer Dissertation erzielt, die vom Promotionsstipendium nach der Graduiertenförderung der Universität Hannover und vom Institut für Strömungsmaschinen gefördert wurde. Die Schaufeldaten und experimentellen Ergebnisse sind von Prof. Lapschin der TU St. Petersburg zur Verfügung gestellt.     

Suppression by carotenoids of microtenoids of microcystin-induced morphological changes in mouse hepatocytes

Microcystin-LR is a liver tumor promoter in the okadaic acid class, a group of potent inhibitors of protein phosphatases 1 and 2A. Because of inhibition of protein phosphatases, microcystin-LR induces hyperphosphorylation of cellular proteins, including cytoskeletal proteins—cytokeratins 8 and 18—and causes morphological changes in mouse hepatocytes in primary culture. We studied the effects of carotenoids to antagonize microcystin-LR-induced morphological changes in hepatocytes. β-Carotene (100 nM to 100 μM), suppressed the morphological changes induced by 100 nM microcystin-LR in a dose-dependent manner. Other carotenoids tested exerted similar suppressive effects, although retinoids, such as all-trans retinol, all-trans retinoic acid, and 9-cis retinoic acid, were only weakly suppressive. The relative potency of the suppression correlated significantly with the number of conjugated double bonds in thetrans configuration. β-Carotene strongly suppressed the hyperphosphorylation of cellular proteins induced by microcystin-LR without significant changes in the basal phosphorylation level. Other antioxidants, such as α-tocopherol, did not protect the cells against microcystin-LR. Taken together, the antagonistic effects of carotenoids against microcystin-LR are difficult to explain by their antioxidant or provitamin A activities. Suppression of the hyperphosphorylation of cellular proteins may be a novel mechanism by which carotenoids inhibit tumor promotion.     

Experimentelle Untersuchung der Strömungsphänomene des Rotating Stall und des Pumpens bei mehrstufigen,hochbelasteten Axialverdichtern

Ohne Zusammenfassung     

Mechanism of the fatigue life increment due to dynamic strain ageing during hold time

The effect of hold time on the low-cycle fatigue behaviour of AlSl 4140 steel at 303 to 473 K was investigated in air and argon gas. All tests were conducted under a constant total strain amplitude of 0.5, 0.65, 1.0, 1.3 and 1.6×10^–2 with zero mean level. Experimental results show that dynamic strain ageing is occurring during the hold time period and that piled-up dislocations near the carbides are locked by the Cottrell atmosphere. Formation of the Cottrell atmosphere around dislocations near the carbides induces the redistribution of carbon or carbides in the matrix. These randomly dispersed grown up carbides behave like the increased number of dislocation pile-up sites from which fatigue cracks may initiate. Therefore, as the hold time is applied in fatigue cycles under constant strain amplitude the dislocation density at each site will be lowered to retard the fatigue damage or improve the fatigue life.     

Recall, retention, and Ritalin.

Studied the effects of Ritalin on 2-hr story recall, 2-day story retention, and 2-day changes on screening tests of achievement in 16 male and 4 female primary-grade underachieving children. Ss were of average intelligence and free of both demonstrable neurological impairment and major psychological problems. Comparisons of drug and no-drug responses showed a significant positive drug effect on 2-hr story recall but not on 2-day story retention. A significant positive drug effect was also observed on achievement test scores after only 2 days when practice effects were discounted. The short time precluded skill acquisition. These findings indicate that immediate drug-attributable gains in scholastic performance cannot be equated with ultimate gains in scholastic achievement. Immediate drug-induced increments in test performance could be mistaken for long-term drug effects on achievement if baseline measures are obtained before drug administration. Both baseline and ultimate functioning should be determined following drug administration. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)