Echo-Doppler angle determination for noninvasive transmitral blood velocity calculations in normal and porcine bioprosthetic mitral valves

Doppler incident angle (DA) determination is a critical factor in the noninvasive attempt to measure transmitral blood velocity (TMBV) and to estimate volumetric flow. The error in TMBV varies with the cosine of DA. Using an echo-Doppler duplex scanner (DS), we studied transmitral flow velocities in 10 normal subjects (Group I) and 10 asymptomatic patients with procine mitral valve (PMV) bioprostheses. A 3-MHz scanhead with three medium focused rotating transducers was positioned at the left ventricular apex, and standard apical four-chamber views of the heart were obtained. The position of the Doppler sample volume (SV) was adjusted within the valve orifice until the maximal power of the Doppler audio spectra reflecting TMBV was recorded by a spectral analyzer. At this location of the SV, images were recorded and protractors were used to estimate DA. DA ranged from 10 to 40 degrees (x = 22.5 degrees +/- 10.8 degrees) in Group I and from 0 to 15 degrees (x = 4.5 degrees +/- 5.0 degrees) in Group II. Mean values of DA in Groups I and II were significantly different (p less than 0.01). We conclude: (1) in normal subjects, DA measured from the apex into the MV varies significantly and thus may compromise the accuracy of TMBV measurements; (2) the truncated funnel shape of the stent of the PMV bioprosthesis allows a DA less than 15 degrees and thus a smaller error in TMBV calculations.     

Zur Berechnung einseitigmagnetischer Zugkräfte in Drehfeldmaschienen

Übersicht Bei dem herkömmlichen Berechnungsverfahren für die einseitig magnetischen zugkräfte in Drehfeldmaschinen geht man von den Maxwell'schen Zugspannungen aus, die auf einen exzentrischen Läufer wirken. Der zeitlich konstante einseitig magnetische Zug ergibt sich aus parametrisch erregten Luftspaltfeldern, welche durch Leitwertschwankungen der Polpaarzahl eins entstehen. Die alteinative Ermittlung der Zugkräfte aus der magnetischen Energie des Luftspaltfeldes zeigt, daß Leitwertrehwellen der Polpaarzahl eins keinen Beitrag liefern. In dem Aufsatz wird der scheinbare Widerspruch zwischen den beiden Berechnungsverfahren aufgeklärt. Sowohl die Behandlung in mathematisch geschlossener Form als auch die Anwendung der Drehfeldtheorie ergeben, daß neben den bisher bekannten Gleichkräften bei Läuferexzentrizitäten zusätzliche Wechselkräfte entstehen, deren Frequenz bei statischen Exzentrizitäten gleich der doppelten Netzfrequenz und bei dynamischen Exzentrizitäten gleich der doppelten Schlupffrequenz ist. Die Amplituden der Wechselkräfte hängen von Polzahl und Größe der Verlagerung ab; bei zweipoligen Maschinen liegen sie in der Größenordnung von 50% der Gleichkräfte. Die Kräfte werden für Sperisung der Maschine aus einem starren Netz und mit konstanten Strom berechnet. Bei kleinen Exzentrizitäten sind die Unterschiede gering. Die bisher nicht beachteten einseitig magnetischen Wechselkräfte wurden an zwei Maschinen auch experimentell nachgewiesen. Um die fundamentalen Wirkungsmechanismen offen zu legen, wurden in der Arbeit Eisensättigung und Läuferrückwirkung vernachlässigt und nur der Grund-Strombelag berücksichtigt.

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About the calculation of unbalanced magnetic pull in induction-and synchronous machines

Contents Unbalanced magnetic pull (u.m.p.) in induction and synchronous machines is usually calculated by integrating the mechanical tension on the eccentric rotor around its surface. The invariant u.m.p. follows from parametric magnetic fields in the air-gap caused by a 2-pole-oscillation of the magnetic resistance. Whe deriving the u.m.p. from the magnetic energy it bcomes evident that the energy of the parametric waves is always zero. The apparent discrepancy between the

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Prof. Dr.-Ing. Dr. ir. h. c. H. Jordan, Prof. Dr.-Ing. H.O. Seinsch, Dipl.-Ing. R.-D. Chroeder, Institut für Elektrische Maschinen und Antriebe der Universität Hannover     

High-accuracy magnetic position encoder concept

Position sensors based on the detection of magnetic flux densities by Hall sensors or magnetoresistors are used in automotive applications for crankshaft and camshaft position sensing, which are needed for engine control. This paper identifies the limitations of traditional designs, which introduce an angular error between the position signal pulse and the actual location of the corresponding triggering feature on the sensor target wheel. It proposes a solution ensuring that the position signal pulse coincides with a point of symmetry in the triggering target wheel feature, thus eliminating the angular error. Two interesting implementations are described in this paper. One of them is analyzed in full detail, and a methodology for its design is provided. In particular, specific design rules are derived which link some of the design parameters to relevant dimensional specifications. These rules are established on the basis of a geometrical method developed for this particular type of problem which necessitates the calculation of flux densities in a few specific locations, namely, where the sensing elements are located. The overall approach, including these design rules, is validated by finite-element analysis, as well as by experimental data     

Suppression of inward-rectifying K+ channels KAT1 and AKT2 by dominant negative point mutations in the KAT1 alpha-subunit

Na(+)-glucose transport and transepithelial permeability were investigated during symptomatic acute cryptosporidiosis in newborn rats. The infection resulted in a significant (P < 0.01) decrease in the ileal short-circuit current and a nonsignificant fall in the transepithelial potential difference and conductance. In glucose-stimulated conditions, the rise in ileal short-circuit current and transepithelial permeability were significantly lower in Cryptosporidium parvum-infected rats than in controls (delta Isc = 3.24 +/- 1.21 microA.cm-2 vs delta Isc = 5.09 +/- 2.23 microA.cm-2 in infected and control animals, respectively; P < 0.001; delta PD = -0.35 +/- 0.13 mV vs delta PD = -0.44 +/- 0.14 mV for infected and control animals, respectively; P < 0.01). Electrical parameters were not affected by addition of the cyclooxygenase inhibitor indomethacin in either Cryptosporidium-infected newborn rats or controls. Horseradish peroxidase and mannitol flux studies demonstrated a significant decrease (P < 0.05) in transepithelial molecular permeability in infected enterocyte rats, HRP flux = 380, range 68-5570 ng.cm-2, and mannitol flux = 1.06, range, 0.34-1.44%.cm-2.min-1, compared with controls rats, HRP flux = 4446 range, 1121-124,363 ng.cm-2, and mannitol flux = 1.99, range, 0.57-5.09%.cm-2.min-1; P < 0.05. These effects could originate from C. parvum-induced alteration of intracellular trafficking of pinocytosis vesicles and therefore account for the decrease in permeability to solute and macromolecules, together with impaired transcellular nutrient transport, in suckling rats.     

Neural network analysis of combined conventional and experimental prognostic markers in prostate cancer: a pilot study

Radiolabeling permits the detection of trace amounts of zwitterionic detergent remaining in extracted hydrophobic or membrane proteins. To develop a sensitive and specific assay for its presence, the commonly used zwitterionic membrane protein detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (Chaps) was synthesized in a tritiated form. Synthesis via 7-ketodeoxycholic acid gave [7-3H]Chaps in 53% yield with a specific activity of 0.85 mCi/mmol. A novel solvent extraction system for cholic acid obviated the need for chromatographic isolation of this intermediate. The protocol can be readily modified to yield [7-3H]Chaps of higher specific activity. [7-3H]Chaps was used to monitor the efficiency of various strategies for detergent removal from concentrated bacterial culture supernatants containing 0.2% (w/v) Chaps. Dialysis removed 95% of Chaps and the addition of detergent-affinity beads to the dialysis buffer resulted in 97% removal of Chaps. Gel-filtration chromatography removed 99.9% of Chaps, while a detergent-affinity bead chromatography column removed 99.99%. Overall, gel-filtration chromatography was the most convenient and economical method for the one-step removal of the zwittergent from complex biological mixtures.     

Validation of 19F-magnetic resonance determination of myocardial blood volume

Site-specific regeneration of the liver after 70% partial hepatectomy was investigated noninvasively in terms of protein synthesis using PET with L-[methyl-11C]methionine in a living animal. Protein synthesis in rat liver at 24 hr after partial hepatectomy did not occur uniformly in the whole liver but intensely in the middle part of the regenerating organ in comparison with the other parts. The activity was significantly low at the posterior aspect of the liver. On the other hand, site-specific protein synthesis was not observed in normal liver. These results were confirmed by bioimaging analyzer system (BAS) analysis, an invasive method that indicates radioactivities of precise intrahepatic sites. DNA synthesis in regenerating liver was also monitored with [2-14C]thymidine and analyzed by BAS 24 hr after 70% hepatectomy. Site-specific DNA synthesis in regenerating liver corresponding to the protein synthesis was also observed by BAS analysis. These results indicate that liver regeneration occurs intensely in the middle part of the liver and that PET enables noninvasive in vivo biochemical analysis.     

Hydrocarbon-soluble alkylaniline/formaldehyde oligomers as corrosion inhibitors

Hydrocarbon-soluble oligomers were prepared by the acid-catalyzed condensation of alkylanilines with formaldehyde. Highest molecular weight oligomers (MW ～ 6000) were obtained from alkylanilines prepared by the Friedel-Crafts alkylation of aniline with α-olefins. By NMR, it was shown that the oligomers contain structures corresponding to methylene-linked aromatic rings and methylene linked to both an aromatic ring and a nitrogen atom. The oligomers exhibit very good initial inhibition of metal corrosion in aqueous environment; and the inhibition is more persistent than that observed with monomeric analogs.